dSED: A database tool for modeling sediment early diagenesis

NASA Astrophysics Data System (ADS)

Katsev, S.; Rancourt, D. G.; L'Heureux, I.

2003-04-01

Sediment early diagenesis reaction transport models (RTMs) are becoming powerful tools in providing kinetic descriptions of the metal and nutrient diagenetic cycling in marine, lacustrine, estuarine, and other aquatic sediments, as well as of exchanges with the water column. Whereas there exist several good database/program combinations for thermodynamic equilibrium calculations in aqueous systems, at present there exist no database tools for classification and analysis of the kinetic data essential to RTM development. We present a database tool that is intended to serve as an online resource for information about chemical reactions, solid phase and solute reactants, sorption reactions, transport mechanisms, and kinetic and equilibrium parameters that are relevant to sediment diagenesis processes. The list of reactive substances includes but is not limited to organic matter, Fe and Mn oxides and oxyhydroxides, sulfides and sulfates, calcium, iron, and manganese carbonates, phosphorus-bearing minerals, and silicates. Aqueous phases include dissolved carbon dioxide, oxygen, methane, hydrogen sulfide, sulfate, nitrate, phosphate, some organic compounds, and dissolved metal species. A number of filters allow extracting information according to user-specified criteria, e.g., about a class of substances contributing to the cycling of iron. The database also includes bibliographic information about published diagenetic models and the reactions and processes that they consider. At the time of preparing this abstract, dSED contained 128 reactions and 12 pre-defined filters. dSED is maintained by the Lake Sediment Structure and Evolution (LSSE) group at the University of Ottawa (www.science.uottawa.ca/LSSE/dSED) and we invite input from the geochemical community.

The Effect of Early Diagenesis on the 238U/235U Ratio of Platform Carbonates.

NASA Astrophysics Data System (ADS)

Tissot, F.; Chen, C.; Go, B. M.; Naziemiec, M.; Healy, G.; Swart, P. K.; Dauphas, N.

2017-12-01

In the past 15 years, the so-called non-traditional stable isotopes systems (e.g., Mg, Fe, Mo, U) have emerged as powerful tracers of both high-T and low-T geochemical processes (e.g., [1]). Of particular interest for paleoredox studies is the ratio of "stable" isotopes of U (238U/235U), which has the potential to track the global extent of oceanic anoxia (e.g., [2, 3]). Indeed, in the modern ocean, U exists in two main oxidation states, soluble U6+ and insoluble U4+, and has a mean residence time of 400 kyr ([4]), much longer than the global ocean mixing time (1-2 kyr). As such the salinity-normalized ocean is homogeneous with regards to both U concentrations and isotopes (δ238USW = -0.392±0.005 ‰, [2]). The value of δ238USW at any given time is therefore the balance between U input to the ocean, mainly from rivers, and U removal, mostly into biogenic carbonates, anoxic/euxinic sediments and suboxic/hypoxic sediments (e.g., [2, 5]). Because the 238U/235U ratio of the past ocean cannot be measured directly, it has to be estimated from the measurement of the 238U/235U ratio of a sedimentary rock and assuming a constant fractionation factor. Carbonates appear as a promising record since they span most of Earth's history, and the δ238U values of modern primary carbonate precipitates and well-preserved fossil aragonitic coral up to 600 ka are indistinguishable from that of seawater (e.g., [2, 6, 7]). Yet, the effect of secondary processes on the δ238U values of non-coral carbonates, which represent the bulk of the rock record, has only been studied in a handful of shallow samples (down to 40cm, [6]) and remains poorly understood. To investigate the effect of early diagenesis on the 238U/235U ratio of carbonates on the 30kyr to 1Myr timescale, we measured δ13C, δ18O, and δ238U in samples from a 220m long drill core from the Bahamas carbonate platform. In order to separate lattice bound U from secondary U we developed a leaching protocol applicable to carbonate

Patterns of metal distribution in hypersaline microbialites during early diagenesis: Implications for the fossil record.

PubMed

Sforna, M C; Daye, M; Philippot, P; Somogyi, A; van Zuilen, M A; Medjoubi, K; Gérard, E; Jamme, F; Dupraz, C; Braissant, O; Glunk, C; Visscher, P T

2017-03-01

The use of metals as biosignatures in the fossil stromatolite record requires understanding of the processes controlling the initial metal(loid) incorporation and diagenetic preservation in living microbialites. Here, we report the distribution of metals and the organic fraction within the lithifying microbialite of the hypersaline Big Pond Lake (Bahamas). Using synchrotron-based X-ray microfluorescence, confocal, and biphoton microscopies at different scales (cm-μm) in combination with traditional geochemical analyses, we show that the initial cation sorption at the surface of an active microbialite is governed by passive binding to the organic matrix, resulting in a homogeneous metal distribution. During early diagenesis, the metabolic activity in deeper microbialite layers slows down and the distribution of the metals becomes progressively heterogeneous, resulting from remobilization and concentration as metal(loid)-enriched sulfides, which are aligned with the lamination of the microbialite. In addition, we were able to identify globules containing significant Mn, Cu, Zn, and As enrichments potentially produced through microbial activity. The similarity of the metal(loid) distributions observed in the Big Pond microbialite to those observed in the Archean stromatolites of Tumbiana provides the foundation for a conceptual model of the evolution of the metal distribution through initial growth, early diagenesis, and fossilization of a microbialite, with a potential application to the fossil record. © 2016 John Wiley & Sons Ltd.

Early diagenesis of travertine deposits from the Tibetan Plateau - implications for 230Th/234U dating and palaeoenvironmental reconstruction

NASA Astrophysics Data System (ADS)

Wang, Zhijun; Meyer, Michael; Hoffmann, Dirk; Spötl, Christoph; Aldenderfer, Mark; Sanders, Diethard

2014-05-01

Travertine is calcium carbonate precipitated from hydrothermal springs. These terrestrial carbonate deposits can be used as high-resolution archives for reconstructing palaeoclimatic and palaeoenvironmental change and are also suitable for uranium-series disequilibrium (230Th/234U) dating. In many instances such spring deposits are associated with archaeological remains (e.g. stone artifacts and other traces of prehistoric human activity) and are therefore of interest for palaeoclimatologists and archaeologists alike. However, travertines are often affected by early diagenesis that can impact on the closed-system U-series behavior and on their geochemical signature. Hence, careful evaluation of the travertine microfabrics is required before these types of hot spring deposits can be accurately dated and used for paleoenviromental reconstruction. The Tibetan plateau hosts numerous hydrothermal spring deposits that occur along neotectonic faults. In this study, samples were collected from two archaeological travertine sites, i.e. Chusang and Tirthapuri, located in southern and western Tibet, respectively. Microscopic analysis of thin sections reveals a wide variety of crystal fabrics, including micrite, microspar and sparite, the latter can be composed of columnar or mosaic crystals, respectively. Areas where dendritic crystals are preserved are identified in our micrographs as well. Many of the Chusang and Tirthapuri travertine samples are porous. Drusy sparite is rimming most of the pore walls and a complex succession of secondary calcite phases precipitated in these pore spaces as well. The different generations of pore cement comprise micrite and sparite that can be laminated or fibrous in character and show sometimes evidence of an aragonite precursor. Detrital material like quartz, feldspar and other grains as well as humic and fulvic acids have been washed into the travertine pores too. Based on our microscopic analysis a complex growth history can be

Chemical remagnetization and clay diagenesis: testing the hypothesis in the Cretaceous sedimentary rocks of northwestern Montana

NASA Astrophysics Data System (ADS)

Gill, J. D.; Elmore, R. D.; Engel, M. H.

Although the migration of fluids is a likely agent of remagnetization for some chemical remanent magnetizations (CRMs), widespread CRMs, which occur in rocks that have not been altered by externally derived fluids, need to explained by another mechanism. We are testing clay diagenesis as a remagnetization mechanism for such CRMs by comparing results from Mesozoic strata in the disturbed belt of Montana where the rocks contain ordered illite/smectite that formed by moderate heating as a result of thrust loading, with equivalent strata on the adjacent Sweetgrass Arch which contain unaltered smectite-rich clay mineral assemblages. The results indicate that the magnetization in the rocks in the Sweetgrass Arch is weak and dominated by a modern viscous component. In contrast, the disturbed belt rocks have higher magnetic intensities and contain a prefolding or early synfolding, reversed tertiary magnetization that is interpreted to be a CRM residing in magnetite and perhaps pyrrhotite. A presence-absence test and the timing of acquisition for the CRM suggest that magnetite authigenesis could be related to the smectite-to-illite conversion.

Impact of diagenesis on the environmental magnetic record from a Holocene sedimentary sequence from the Chukchi-Alaskan margin, Arctic Ocean

NASA Astrophysics Data System (ADS)

Brachfeld, Stefanie; Barletta, Francesco; St-Onge, Guillaume; Darby, Dennis; Ortiz, Joseph D.

2009-07-01

We present a high-resolution Holocene sedimentary record of environmental variability from the eastern Chukchi Sea. An ice-rafted debris bearing silty-clay marks the deglacial to post-glacial Holocene transition at this site and is dated at 9.7 ka. An interval of oscillating magnetic parameters from 9.5 to 8.7 ka coincides with the Holocene Thermal Maximum in the western Arctic, and is manifested at the study area as pulses of fine-grained magnetite input every 180-230 years, possibly from increased river discharge or stronger currents flowing over the core site. The magnetic mineral assemblage is very uniform over the last 8.2 ka and consists of a mixture of magnetite, titanomagnetite, and a magnetic phase that we tentatively identify as the magnetic iron sulfide greigite. The amount of magnetic iron sulfides increases up through the Holocene, a trend that is controlled by the amount of marine organic matter available to fuel bacterial sulfate reduction. The median destructive field of the Natural Remanent Magnetization (MDF NRM) displays centennial to millennial scale cycles with significant variance at periods of 900-1300 and 1700-2700 years, with intervals of high MDF NRM values coinciding with indicators of greater sea ice cover [McKay, J., de Vernal, A., Hillaire-Marcel, C., Not, C., Polyak, L., Darby, D., 2008. Holocene fluctuations in Arctic sea-ice cover: Dinocyst-based reconstructions for the eastern Chukchi Sea. Can. J. Earth Sci. 45, 1399-1415]. The MDF NRM is controlled by the variable abundance of iron sulfides formed during early diagenesis. We interpret intervals of high MDF NRM values as times of stronger water column stratification, during which the pyritization process was interrupted by the lack of marine organic matter and lack of reactive iron. Intervals of low MDF NRM values, which coincide with indicators of reduced sea ice cover, are interpreted as times of stronger vertical mixing of the water column, which allows fresh marine organic

Sedimentary facies and depositional environments of early Mesozoic Newark Supergroup basins, eastern North America

USGS Publications Warehouse

Smoot, J.P.

1991-01-01

The early Mesozoic Newark Supergroup consists of continental sedimentary rocks and basalt flows that occupy a NE-trending belt of elongate basins exposed in eastern North America. The basins were filled over a period of 30-40 m.y. spanning the Late Triassic to Early Jurassic, prior to the opening of the north Atlantic Ocean. The sedimentary rocks are here divided into four principal lithofacies. The alluvial-fan facies includes deposits dominated by: (1) debris flows; (2) shallow braided streams; (3) deeper braided streams (with trough crossbeds); or (4) intense bioturbation or hyperconcentrated flows (tabular, unstratified muddy sandstone). The fluvial facies include deposits of: (1) shallow, ephemeral braided streams; (2) deeper, flashflooding, braided streams (with poor sorting and crossbeds); (3) perennial braided rivers; (4) meandering rivers; (5) meandering streams (with high suspended loads); (6) overbank areas or local flood-plain lakes; or (7) local streams and/or colluvium. The lacustrine facies includes deposits of: (1) deep perennial lakes; (2) shallow perennial lakes; (3) shallow ephemeral lakes; (4) playa dry mudflats; (5) salt-encrusted saline mudflats; or (6) vegetated mudflats. The lake margin clastic facies includes deposits of: (1) birdfoot deltas; (2) stacked Gilbert-type deltas; (3) sheet deltas; (4) wave-reworked alluvial fans; or (5) wave-sorted sand sheets. Coal deposits are present in the lake margin clastic and the lacustrine facies of Carnian age (Late Triassic) only in basins of south-central Virginia and North and South Carolina. Eolian deposits are known only from the basins in Nova Scotia and Connecticut. Evaporites (and their pseudomorphs) occur mainly in the northern basins as deposits of saline soils and less commonly of saline lakes, and some evaporite and alkaline minerals present in the Mesozoic rocks may be a result of later diagenesis. These relationships suggest climatic variations across paleolatitudes, more humid to the

Early diagenesis of organic matter in a Sawgrass peat from the Everglades, Florida

USGS Publications Warehouse

Orem, W.H.; Hatcher, P.G.

1987-01-01

The transformation of plant biopolymers to humic substances in peats during early diagenesis is a critical but poorly understood step in the formation of coal. This paper presents results concerning the structural interrelationships among various fractions of the organic matter in peat and the dissolved organic matter in the pore water from a site in The Everglades, relying primarily on elemental analysis and 13C nuclear magnetic resonance for structural elucidation. Our goal was to obtaine some insight into the sequence of steps involved in the formation of humic substances. Results show that the major change occurring in the whole peat during diagenesis is loss of carbohydrates. The components of the peat which are more resistant to microbial degradation become concentrated in the humin fraction. This resistant fraction of the organic matter includes aliphatic and aromatic components. The aromatic components are thought to be derived from lignin while the aliphatic moieties may represent decomposed algal remains. The carbohydrates lost from the whole peat appear to be concentrated in the fulvic acids and the dissolved organic matter in the pore water. The humic acids consist predominantly of aromatic and aliphatic structures, and may represent partially degraded lignin-like structures and aliphatic compounds from algae. The data presented here suggest that humic and fulvic acids are the partially degraded fractions of the peat while the humin contains the resistant or preserved portion of the organic matter. The proposition that humic substances are formed by the condensation of amino acids and sugars is not supported by the results of this study. ?? 1987.

Archean sedimentary styles and early crustal evolution

NASA Technical Reports Server (NTRS)

Lowe, D. R.

1986-01-01

The distinctions between and implications of early and late Archean sedimentary styles are presented. Early Archean greenstone belts, such as the Barberton of South Africa and those in the eastern Pilbar Block of Australia are characterized by fresh or slightly reworked pyroclastic debris, orthochemical sediments such as carbonates, evaporites, and silica, and biogenic deposits including cherts and stromatolitic units. Terrigenous deposits are rare, and it is suggested that early Archean sediments were deposited on shallow simatic platforms, with little or no components derived from sialic sources. In contrast, late Archean greenstone belts in the Canadian Shield and the Yilgarn Block of Australia contain coarse terrigenous clastic rocks including conglomerate, sandstone, and shale derived largely from sialic basement. Deposition appears to have taken place in deepwater, tectonically unstable environments. These observations are interpreted to indicate that the early Archean greenstone belts formed as anorogenic, shallow water, simatic platforms, with little or no underlying or adjacent continental crust, an environment similar to modern oceanic islands formed over hot spots.

Diagenesis of conifer needles in a coastal marine environment

NASA Astrophysics Data System (ADS)

Hedges, John I.; Weliky, K.

1989-10-01

Physically intact fir, hemlock and cedar needles were isolated from different horizons of a sediment core from a coastal marine bay (Dabob Bay, Washington State, U.S.A.) and from nearby trees and forest litter. Green fir, hemlock and cedar needles were all characterized by glucose-rich aldose mixtures (~30% of tissue carbon), the production of vanillyl and cinnamyl CuO-derived phenols (~8% of tissue carbon) and the presence of both pinitol and myo-inositol (1-2% of tissue carbon). Needles from forest litter were enriched in lignin phenols and non-glucose aldoses and depleted in glucose and cyclitols. The sediment core contained an average of 10 mg/1 of physically intact fir, hemlock and cedar needles, which occurred in similar relative abundances and accounted for less than 1% of the total nonwoody gymnosperm tissue. Compared to the green and litter counterparts, all sedimentary needles were greatly depleted in cyclitols, glucose and p-coumaric acid and enriched in vanillyl phenol precursors. The degree of elevation of vanillyl phenol yield from the degraded needles was used to estimate minimal carbon losses from the samples, which ranged from near 40% for needle litter to almost 70% for the deepest (~100 years old) sedimentary fir/hemlock samples. Although downcore increases in carbon loss and refractory organic components indicated in situ diagenesis, the bulk of overall degradation occurred either on land or during the first 10-20 years after deposition. Atomic C/N ratios of degraded needles were lower than for green counterparts, but nitrogen was lost overall. These relative changes indicate the following stability series: vanillyl phenols > N > ferulic acid, p-hydroxy phenols, most aldoses and bulk tissue > glucose and p-coumaric acid > cyclitols (near 100% loss). Vanillic acid to vanillin ratios, (Ad/Al)v, of the green fir and hemlock needles were unusually high (0.36-0.38) and decreased downcore. Diagenesis also decreased the cinnamyl/vanillyl phenol ratio

Reactive transport and mass balance modeling of the Stimson sedimentary formation and altered fracture zones constrain diagenetic conditions at Gale crater, Mars

NASA Astrophysics Data System (ADS)

Hausrath, E. M.; Ming, D. W.; Peretyazhko, T. S.; Rampe, E. B.

2018-06-01

On a planet as cold and dry as present-day Mars, evidence of multiple aqueous episodes offers an intriguing view into very different past environments. Fluvial, lacustrine, and eolian depositional environments are being investigated by the Mars Science Laboratory Curiosity in Gale crater, Mars. Geochemical and mineralogical observations of these sedimentary rocks suggest diagenetic processes affected the sediments. Here, we analyze diagenesis of the Stimson formation eolian parent material, which caused loss of olivine and formation of magnetite. Additional, later alteration in fracture zones resulted in preferential dissolution of pyroxene and precipitation of secondary amorphous silica and Ca sulfate. The ability to compare the unaltered parent material with the reacted material allows constraints to be placed on the characteristics of the altering solutions. In this work we use a combination of a mass balance approach calculating the fraction of a mobile element lost or gained, τ, with fundamental geochemical kinetics and thermodynamics in the reactive transport code CrunchFlow to examine the characteristics of multiple stages of aqueous alteration at Gale crater, Mars. Our model results indicate that early diagenesis of the Stimson sedimentary formation is consistent with leaching of an eolian deposit by a near-neutral solution, and that formation of the altered fracture zones is consistent with a very acidic, high sulfate solution containing Ca, P and Si. These results indicate a range of past aqueous conditions occurring at Gale crater, Mars, with important implications for past martian climate and environments.

DOE workshop: Sedimentary systems, aqueous and organic geochemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1993-07-01

A DOE workshop on sedimentary systems, aqueous and organic geochemistry was held July 15-16, 1993 at Lawrence Berkeley Laboratory. Papers were organized into several sections: Fundamental Properties, containing papers on the thermodynamics of brines, minerals and aqueous electrolyte solutions; Geochemical Transport, covering 3-D imaging of drill core samples, hydrothermal geochemistry, chemical interactions in hydrocarbon reservoirs, fluid flow model application, among others; Rock-Water Interactions, with presentations on stable isotope systematics of fluid/rock interaction, fluid flow and petotectonic evolution, grain boundary transport, sulfur incorporation, tracers in geologic reservoirs, geothermal controls on oil-reservoir evolution, and mineral hydrolysis kinetics; Organic Geochemistry covered new methodsmore » for constraining time of hydrocarbon migration, kinetic models of petroleum formation, mudstones in burial diagenesis, compound-specific carbon isotope analysis of petroleums, stability of natural gas, sulfur in sedimentary organic matter, organic geochemistry of deep ocean sediments, direct speciation of metal by optical spectroscopies; and lastly, Sedimentary Systems, covering sequence stratigraphy, seismic reflectors and diagenetic changes in carbonates, geochemistry and origin of regional dolomites, and evidence of large comet or asteroid impacts at extinction boundaries.« less

Does burial diagenesis reset pristine isotopic compositions in paleosol carbonates?

NASA Astrophysics Data System (ADS)

Bera, M. K.; Sarkar, A.; Tandon, S. K.; Samanta, A.; Sanyal, P.

2010-11-01

Sedimentological study of early Oligocene continental carbonates from the fluvial Dagshai Formation of the Himalayan foreland basin, India resulted in the recognition of four different types namely, soil, palustrine, pedogenically modified palustrine and groundwater carbonates. Stable oxygen and carbon isotopic ( δ18O and δ13C) analyses of fabric selective carbonate microsamples show that although the pristine isotopic compositions are largely altered during deep-burial diagenesis, complete isotopic homogenization does not occur. δ18O and δ13C analyses of ~ 200 calcrete and palustrine carbonates from different stratigraphic horizons and comparison with δ18O of more robust bioapatite (fossil vertebrate tooth) phase show that dense micrites (~ > 70% carbonate) invariably preserve the pristine δ18O value (mean) of ~ - 9.8‰, while altered carbonates show much lower δ18O value ~ - 13.8‰. Such inhomogeneity causes large intra-sample and intra-soil profile variability as high as > 5‰, suggesting that soils behave like a closed system where diagenetic overprinting occurs in local domains. A simple fluid-rock interaction model suggests active participation of clay minerals to enhance the effect of fluid-rock ratio in local domains during diagenesis. This places an upper limit of 70% micrite concentration above which the effect of diagenetic alteration is minimal. Careful sampling of dense micritic part of the soil carbonate nodules, therefore, does provide pristine isotopic composition and it is inappropriate, as proposed recently, to reject the paleoclimatic potential of all paleosol carbonates affected by burial diagenesis. Based on pristine δ13C value of - 8.8 ± 0.2‰ in soil carbonates an atmospheric CO 2 concentration between ~ 764 and ~ 306 ppmv is estimated for the early Oligocene (~ 31 Ma) Dagshai time. These data show excellent agreement between two independent proxy records (viz. soil carbonate and marine alkenone) and support early Oligocene

Experimental evidence for an effect of early-diagenetic interaction between labile and refractory marine sedimentary organic matter on nitrogen dynamics

NASA Astrophysics Data System (ADS)

Turnewitsch, Robert; Domeyer, Bettina; Graf, Gerhard

2007-05-01

In most natural sedimentary systems labile and refractory organic material (OM) occur concomitantly. Little, however, is known on how different kinds of OM interact and how such interactions affect early diagenesis in sediments. In a simple sediment experiment, we investigated how interactions of OM substrates of different degradability affect benthic nitrogen (N) dynamics. Temporal evolution of a set of selected biogeochemical parameters was monitored in sandy sediment over 116 days in three experimental set-ups spiked with labile OM (tissue of Mytilus edulis), refractory OM (mostly aged Zostera marina and macroalgae), and a 1:1 mixture of labile and refractory OM. The initial amounts of particulate organic carbon (POC) were identical in the three set-ups. To check for non-linear interactions between labile and refractory OM, the evolution of the mixture system was compared with the evolution of the simple sum of the labile and refractory systems, divided by two. The sum system is the experimental control where labile and refractory OM are virtually combined but not allowed to interact. During the first 30 days there was evidence for net dissolved-inorganic-nitrogen (DIN) production followed by net DIN consumption. (Here 'DIN' is the sum of ammonium, nitrite and nitrate.) After ˜ 30 days a quasi steady state was reached. Non-linear interactions between the two types of OM were reflected by three main differences between the early-diagenetic evolutions of nitrogen dynamics of the mixture and sum (control) systems: (1) In the mixture system the phases of net DIN production and consumption commenced more rapidly and were more intense. (2) The mixture system was shifted towards a more oxidised state of DIN products [as indicated by increased (nitrite + nitrate)/(ammonium) ratios]. (3) There was some evidence that more OM, POC and particulate nitrogen were preserved in the mixture system. That is, in the mixture system more particulate OM was preserved while a higher

Mesozoic clay diagenesis in the Appalachian Plateau

NASA Astrophysics Data System (ADS)

Boles, A.; Mulch, A.; van der Pluijm, B.

2017-12-01

Integrated investigation of authigenic clays in the Appalachian Plateau of the northeastern US Midcontinent using X-ray goniometry, Rietveld-method based illite polytype analysis, and 40Ar/39Ar geochronology yields novel insights about the structural diagenetic history of the North American sedimentary cover sequence. Texture analysis by High Resolution X-ray Texture Goniometry records the presence of a bedding-parallel diagenetic fabric, corresponding to a burial depth of 2-5 km. New development of polytype modeling using BGMN®, a quantitative X-ray powder diffraction forward modeling and whole-pattern matching program matches mineralic characteristic of illite at those depths and reduces uncertainty estimates in age analysis. Based on dating size fractions, the diagenetic age is constrained to 225-250 Ma (Triassic) by four authigenic illite samples, reflecting protracted, regional diagenesis in the area. Preliminary H isotopic analysis points to a surface-derived diagenetic fluid with δD values ranging from -48 to -72‰ (in the range of predicted Pangea meteoric fluid), with a dependence on proximity to the Appalachian Mountains that may reflect a rain shadow effect.

Early diagenesis and authigenic mineral formation in mobile muds of the Changjiang Estuary and adjacent shelf

NASA Astrophysics Data System (ADS)

Zhao, Bin; Yao, Peng; Bianchi, Thomas S.; Xu, Yahong; Liu, Hui; Mi, Tiezhu; Zhang, Xiao-Hua; Liu, Jiwen; Yu, Zhigang

2017-08-01

Large-river delta-front estuaries (LDEs) and their adjacent shelf margins are sites of dynamic diagenetic processes that play a significant role in coastal biogeochemical cycling. In this study, we used dissolved inorganic carbon (DIC), redox sensitive elements (Fe2 + and Mn2 +), dissolved inorganic nitrogen (DIN) nutrients (NH4+, NO3-, and NO2-), major cations and anions (K+, Ca2 +, Mg2 +, SO42 -, and Cl-) in bottom-water and sediment pore-waters, to investigate the early chemical diagenesis and authigenic mineral formation in mobile-mud deposits of the Changjiang Estuary and adjacent inner shelf of the East China Sea (ECS). Vertical profiles of DIC and NH4+ in pore-waters had similar trends at most sites, showing a significant increase with depth near the Changjiang Estuary and being relatively constant at offshore sites. Higher pore-water DIC and NH4+ concentrations were observed in nearshore sites in winter, which were likely attributed to exposure of deeper deposits by winter coastal erosion. Nitrification was observed at most sites, and AOB (ammonia-oxidizing bacteria) played a leading role in ammonia oxidation in the study areas. The nitrification-denitrification was likely important in contributing to the loss of DIN in offshore sites during summer. Large inputs of organic carbon (OC) and terrestrial materials from Changjiang River resulted in intense sulfate reduction and Fe and Mn reduction in nearshore sites. Lower C/N and C/S ratios coupled with an apparent decrease in pore-water Ca2 + and Mg2+ concentrations with depth near the Changjiang Estuary, which indicated that authigenic carbonate formation occurs in these sediments. Decreases in K+ and Mg2 + with depth reflected that reverse weathering was an important process of authigenic mineral formation in these sediments. We conclude that adsorption process, seasonal erosion-redeposition, and summer hypoxic conditions of bottom-waters may play an important role in early diagenesis processes and

Early diagenesis of recently deposited organic matter: a 9-yr time-series study of a flood deposit

NASA Astrophysics Data System (ADS)

Tesi, T.; Goñi, M. A.; Langone, L.; Wheatcroft, R. A.; Miserocchi, S.; Bertotti, L.

2012-04-01

Because the preservation of organic carbon (OC) in river-dominated margins accounts for a significant fraction of OC burial in the ocean, biochemical studies must find novel ways to explicitly address the non-steadiness of these settings. In this study, we approached this issue by collecting event-beds soon after their emplacement (event-response sampling) and following their evolution with time (time-series analysis). In Fall 2000, the Po River (Italy) experienced a 100-yr return period flood that resulted in a thick deposit in the adjacent prodelta. Cores collected in the central prodelta after the flood event and over the following 9 years (8 sediment cores), allowed characterization of the event-strata in their initial state and documentation of their subsequent evolution. The characterization of sedimentary organic matter (OM) collected soon after the flood deposit emplacement and the description of its subsequent evolution with time provided extraordinary opportunity to investigate the reactivity of OM on a 9-yr time scale. Our analysis included the evaluation of the whole spectrum of CuO reaction products such as lignin phenols, p-hydroxy benzenes, benzoic acids, cutin-derived products, dicarboxylic acids, and fatty acids, as well as bulk organic carbon, nitrogen and carbon stable isotopes. Sedimentological characteristics were investigated using x-radiographs and sediment texture analyses whereas the evolution of sedimentary OM was evaluated via inventories of bulk elements and biomarkers. Remineralization of organic nitrogen and organic carbon occurred at similar rates (% change ~-17%) indicating that the overall elemental composition of sedimentary OM remained stable with time. This steadiness was confirmed by lack of temporal changes of the OC/TN ratio. Despite the steady OC/TN ratio, changes in δ13C revealed preferential loss of isotopically enriched organic material. Biomarker inventories indicated selective degradation during diagenesis, consistent

Preservation of overmature, ancient, sedimentary organic matter in carbonate concretions during outcrop weathering.

PubMed

Loyd, S J

2017-01-01

Concretions are preferentially cemented zones within sediments and sedimentary rocks. Cementation can result from relatively early diagenetic processes that include degradation of sedimentary organic compounds or methane as indicated by significantly 13 C-depleted or enriched carbon isotope compositions. As minerals fill pore space, reduced permeability may promote preservation of sediment components from degradation during subsequent diagenesis, burial heating and outcrop weathering. Discrete and macroscopic organic remains, macro and microfossils, magnetic grains, and sedimentary structures can be preferentially preserved within concretions. Here, Cretaceous carbonate concretions of the Holz Shale are shown to contain relatively high carbonate-free total organic carbon (TOC) contents (up to ~18.5 wt%) compared to the surrounding host rock (with <2.1 wt%). TOC increases with total inorganic carbon (TIC) content, a metric of the degree of cementation. Pyrite contents within concretions generally correlate with organic carbon contents. Concretion carbonate carbon isotope compositions (δ 13 C carb ) range from -22.5 to -3.4‰ (VPDB) and do not correlate strongly with TOC. Organic carbon isotope compositions (δ 13 C org ) of concretions and host rock are similar. Thermal maturity data indicate that both host and concretion organic matter are overmature and have evolved beyond the oil window maturity stage. Although the organic matter in general has experienced significant oxidative weathering, concretion interiors exhibit lower oxygen indices relative to the host. These results suggest that carbonate concretions can preferentially preserve overmature, ancient, sedimentary organic matter during outcrop weathering, despite evidence for organic matter degradation genetic mechanisms. As a result, concretions may provide an optimal proxy target for characterization of more primary organic carbon concentrations and chemical compositions. In addition, these findings

Impact of silica diagenesis on the porosity of fine-grained strata: An analysis of Cenozoic mudstones from the North Sea

NASA Astrophysics Data System (ADS)

Wrona, Thilo; Taylor, Kevin G.; Jackson, Christopher A.-L.; Huuse, Mads; Najorka, Jens; Pan, Indranil

2017-04-01

Silica diagenesis has the potential to drastically change the physical and fluid flow properties of its host strata and therefore plays a key role in the development of sedimentary basins. The specific processes involved in silica diagenesis are, however, still poorly explained by existing models. This knowledge gap is addressed by investigating the effect of silica diagenesis on the porosity of Cenozoic mudstones of the North Viking Graben, northern North Sea through a multiple linear regression analysis. First, we identify and quantify the mineralogy of these rocks by scanning electron microscopy and X-ray diffraction, respectively. Mineral contents and host rock porosity data inferred from wireline data of two exploration wells are then analyzed by multiple linear regressions. This robust statistical analysis reveals that biogenic opal-A is a significant control and authigenic opal-CT is a minor influence on the porosity of these rocks. These results suggest that the initial porosity of siliceous mudstones increases with biogenic opal-A production during deposition and that the porosity reduction during opal-A/CT transformation results from opal-A dissolution. These findings advance our understanding of compaction, dewatering, and lithification of siliceous sediments and rocks. Moreover, this study provides a recipe for the derivation of the key controls (e.g., composition) on a rock property (e.g., porosity) that can be applied to a variety of problems in rock physics.

Magnetic Diagenesis in the Gas Hydrate System

NASA Astrophysics Data System (ADS)

Enkin, R. J.; Hamilton, T. S.; Esteban, L.

2009-05-01

Natural gas hydrate is a methane-bearing form of ice which occurs in permafrost and continental slope settings. Geochemical processes associated with gas hydrate formation lead to the growth of iron sulphides which have a geophysically measurable magnetic signature. Detailed magnetic investigation and complementary petrological observations were undertaken on unconsolidated sediments from three gas hydrate (GH) settings: permafrost in fluvial-deltaic silts and sands in the Western Canadian Arctic (Japex et al. Mallik 5L-38 in 2002); diamictons and hemipelagics in the Cascadia accretionary wedge west of Vancouver Island (IODP Exp.311 in 2006); and marine sands and hemipelagics from the Bay of Bengal (NGHP Exp.01 in 2007). These magnetic measurements provide stratigraphic profiles which reveal fine scale variations in lithology, magnetic grain size, and paleo-pore fluid geochemistry. The highest magnetic susceptibility values are observed in strata which preserve high initial concentrations of detrital magnetite, such as glacial deposits. The lowest values of magnetic susceptibility are observed where iron has been reduced to paramagnetic pyrite, formed in settings with high methane and sulphate flux such as at methane vents. Enhanced values of magnetic susceptibility characterize the introduction of the ferrimagnetic iron sulphide minerals greigite and smythite. These magnetic minerals are mostly found immediately adjacent to the sedimentary horizons which host the gas hydrate and their textures and compositions indicate rapid disequilibrium crystallization. The observed diagenesis result from the unique physical and geochemical properties of the environment where gas hydrates form: methane is available to fuel microbiological activity and the freezing which accompanied GH crystallization quickly removed pure water, froze the sediments into an impermeable solid and expelled more concentrated brines into the adjacent less permeable strata to the point of inducing

Twenty years of sedimentary change and diagenesis, Qatar Peninsula, Arabian Gulf

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shinn, E.A.

Re-examination in February 1986 of areas studied by the author in 1966 and 1967 revealed rapid rates of sedimentation and diagenesis along the east coast of the Qatar Peninsula. At Ras Um Sa on the north-east side of Qatar, a series of chenier-like beaches and curved spits is building southward under the influence of longshore currents. Beach and spit growth increasingly protects the shoreline and allows tidal flats to form in their lee. As these spits accrete, they become armored on their lagoonal side by beachrock formation. In the last 20 years a spit approximately 1/2 km long has grown,more » and beachrock has already armored its recurved lagoonal side. At Umm Said on the southeast side of Qatar, seawardly accreting barchan dunes composed of quartz sand have built a 40-km long, 10-km wide sabkha as thick as 30 m. Aerial and ground photographs show that certain dunes near the seaward edge of the sabkha have migrated into the sea and have contributed to shoreline accretion. The observed rate of dune migration suggests that within approximately 100 years the remaining quartz sands will be depleted and blown into the sea because there is no replenishment of the dune field. Subsequently, the area will revert to one of carbonate deposition. Fine-grained dolomite is presently precipitating in interstitial brines in the landwardmost portions of this unusual sabkha. In the geologic record, such a deposit would be an anomalous, porous and permeable, cross-bedded, linear, 30-m thick, dolomite-cemented sandstone body encased in carbonate sediments. A modern model such as the one at Umm Said can provide useful clues for determining the origin of similar deposits in ancient rocks.« less

Twenty years of sedimentary change and diagenesis, Qatar Peninsula, Arabian Gulf

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shinn, E.A.

Re-examination in February 1986 of areas studied by the author in 1966 and 1967 revealed rapid rates of sedimentation and diagenesis along the east coast of the Qatar Peninsula. At Ras UmSa on the northeast side of Qatar, a series of chenier-like beaches and curved spits is building southward under the influence of longshore currents. Beach and spit growth increasingly protects the shoreline and allows tidal flats to form in their lee. As these spits accrete, they become armored on their lagoonal side by beachrock formation. In the last 20 years a spit approximately 1/2 km long has grown, andmore » beachrock has already armored its recurved lagoonal side. At Umm Said on the southeast side of Qatar, seawardly accreting barchan dunes composed of quartz sand have built a 40-km long, 10-km wide sabkha as thick as 30 m. Aerial and ground photographs show that certain dunes near the seaward edge of the sabkha have migrated into the sea and have contributed to shoreline accretion. The observed rate of dune migration suggests that within approximately 100 years the remaining quartz sands are depleted and blown into the sea because there is no replenishment of the dune field. Subsequently, the area reverts to one of carbonate deposition. Fine-grained dolomite is presently precipitating in interstitial brines in the landwardmost portions of this unusual sabkha. In the geologic record, such a deposit would be an anomalous, porous and permeable, cross-bedded, linear, 30-m thick, dolomite-cemented sandstones body encased in carbonate sediments. A modern model such as the one at Umm Said can provide useful clues for determining the origin of similar deposits in ancient rocks.« less

Impact of Diagenesis on Biosignature Preservation Potential in Playa Lake Evaporites in Verde Formation, Arizona: Implications for Mars Exploration

NASA Astrophysics Data System (ADS)

Shkolyar, S.; Farmer, J. D.

2015-12-01

Major priorities for Mars science include assessing the preservation potential and impact of diagenesis on biosignature preservation in aqueous sedimentary environments. We address these priorities with field and lab studies of playa evaporites of the Verde Formation (upper Pliocene) in Arizona. Evaporites studied include bottom-nucleated halite and displacive growth gypsum in magnesite-rich mudstone. These lithotypes are potential analogs for ancient lacustrine habitable environments on Mars. This study aimed to understand organic matter preservation potential under different diagenetic histories. Methods combined outcrop-scale field observations and lab analyses, including: (1) thin-section petrography to understand diagenetic processes and paragenesis; (2) X-ray powder diffraction to obtain bulk mineralogy; (3) Raman spectroscopy to identify and place phases (and kerogenous fossil remains) within a microtextural context; (4) Total Organic Carbon (TOC) analyses to estimate weight percentages of preserved organic carbon for each subfacies endmember; and (5) electron microprobe to create 2D kerogen maps semi-quantifying kerogen preservation in each subfacies. Results revealed complex diagenetic histories for each evaporite subfacies and pathways for organic matter preservation. Secondary gypsum grew displacively within primary playa lake mudstones during early diagenesis. Mudstones then experienced cementation by Mg-carbonates. Displacive-growth gypsum was sometimes dissolved, forming crystal molds. These molds were later either infilled by secondary sulfates or recrystallized to gypsum pseudomorphs with minor phases present (i.e., glauberite). These observations helped define taphonomic models for organic matter preservation in each subfacies. This work has the potential to inform in situ target identification, sampling strategies, and data interpretations for future Mars Sample Return missions (e.g., sample caching strategies for NASA's Mars 2020 mission).

Paleomagnetic and oxygen isotopic evidence for long term diagenesis in radiolarian chert, Pindos Mountains, Greece

NASA Astrophysics Data System (ADS)

Baltuck, Miriam

1987-02-01

Paleomagnetics was used in an attempt to improve chronostratigraphy in the Middle and Upper Jurassic radiolarian chert and siliceous mudstone of the Pindos Zone, Greece. Remanent magnetism studies showed strong magnetic intensity but scattered orientation. Orientation of some pressure solution features in the radiolarities indicates their formation under horizontal pressure, a condition which in Pindos geologic history would only have occurred during early Cretaceous or Cenozoic tectonics, indicating very late diagenesis in these parts of the section. From time of deposition to later time at which diagenesis can be documented, the Earth's magnetic field would have reversed many times. Remagnetization during solution-precipitation steps of silica diagenesis could complicate the rock magnetics. Oxygen isotopic and major element analyses of radiolarite lithologies show a systematic variation of rate of silica diagenesis in different host lithologies, thus solution-precipitation would occur at widely differing times throughout the section lithologies. If the dissolution of the silica cement were physically to free magnetic material from an earlier orientation, the result could be a partial shift toward alignment with the ambient magnetic field. Alternatively, complete reorientation of particles could have occurred at varying times in different parts of the section as a function of host lithology. During the northward movement and clockwise rotation of the Apulian subplate (including Pindos) these different lithologies could completely reorient during different stages of silica diagenesis, locking the orientation of iron magnetic moments into alignment with the ambient magnetic field at time of precipitation to result in a strong intensity but scattered orientation of Pindos rock magnetics.

The Rio Tinto Basin, Spain: Mineralogy, Sedimentary Geobiology, and Implications for Interpretation of Outcrop Rocks at Meridiani Planum, Mars

NASA Technical Reports Server (NTRS)

Fernandez-Remolar, David C.; Morris, Richard V.; Gruener, John E.; Amils, Ricardo; Knoll, Andrew H.

2005-01-01

Exploration by the NASA rover Opportunity has revealed sulfate- and hematite-rich sedimentary rocks exposed in craters and other surface features of Meridiani Planum, Mars. Modern, Holocene, and Plio-Pleistocene deposits of the Rio Tinto, southwestern Spain, provide at least a partial environmental analog to Meridiani Planum rocks, facilitating our understanding of Meridiani mineral precipitation and diagenesis, while informing considerations of martian astrobiology. Oxidation, thought to be biologically mediated, of pyritic ore bodies by groundwaters in the source area of the Rio Tinto generates headwaters enriched in sulfuric acid and ferric iron. Seasonal evaporation of river water drives precipitation of hydronium jarosite and schwertmannite, while (Mg,Al,Fe(sup 3+))-copiapite, coquimbite, gypsum, and other sulfate minerals precipitate nearby as efflorescences where locally variable source waters are brought to the surface by capillary action. During the wet season, hydrolysis of sulfate salts results in the precipitation of nanophase goethite. Holocene and Plio-Pleistocene terraces show increasing goethite crystallinity and then replacement of goethite with hematite through time. Hematite in Meridiani spherules also formed during diagenesis, although whether these replaced precursor goethite or precipitated directly from groundwaters is not known. The retention of jarosite and other soluble sulfate salts suggests that water limited the diagenesis of Meridiani rocks. Diverse prokaryotic and eukaryotic microorganisms inhabit acidic and seasonally dry Rio Tinto environments. Organic matter does not persist in Rio Tinto sediments, but biosignatures imparted to sedimentary rocks as macroscopic textures of coated microbial streamers, surface blisters formed by biogenic gas, and microfossils preserved as casts and molds in iron oxides help to shape strategies for astrobiological investigation of Meridiani outcrops.

Compositional variations and differential diagenesis in Miocene turbidites from the western coast of Mallorca (Balearic Islands, Spain)

NASA Astrophysics Data System (ADS)

Felder, Sonja; Westphal, Hildegard; Munnecke, Axel; Mateu Vicens, Guillem

2010-05-01

Compositional variations and differential diagenesis in Miocene turbidites from the western coast of Mallorca (Balearic Islands, Spain) Sonja Felder (1), Hildegard Westphal (1), Axel Munnecke (2), Guillem Mateu Vicens (1,3) (1) MARUM and Department of Geosciences, Universität Bremen, Leobener Straße, 28359 Bremen, Germany (2) GeoZentrum Nordbayern, Universität Erlangen-Nürnberg, Loewenichstr. 28, 91054 Erlangen, Germany (3) Dipartimento di Scienze della Terra, Università di Roma "La Sapienza", Ple Aldo 7 Moro, 5. I-00185 Roma, Italy Cyclic alternations of limestone and marl beds crop out along the western coast of the Island of Mallorca. This Miocene succession is traditionally interpreted to represent more weathering-resistant turbidites interlayered by softer hemipelagic background sediment. However, the cementation patterns that dominate the appearance of the outcrop do not always consistently follow sedimentary layering; locally the cemented beds are systematically oblique to the sedimentary layers. Compositional studies demonstrate that differences in non-carbonate fraction, carbonate concentration and fossil content (e.g. foraminiferal assemblages) trace sedimentary bedding, regardless the diagenetic style. Limestone versus marl lithology, in contrast, is defined by the diagenetic style, tight cementation by calcite cements in the limestones versus low porosity and compaction in the marls. The reason for this striking pattern of diagenetic bedding cross-cutting sedimentary layers is assumed to be related to tectonic fracturing, opening pathways for diagenetic fluids. This example cautions the straight-forward interpretation of limestone-marl alternations as direct witnesses of environmental or climatic variations.

Provenance and diagenesis of the evaporite-bearing Burns formation, Meridiani Planum, Mars

USGS Publications Warehouse

McLennan, S.M.; Bell, J.F.; Calvin, W.M.; Christensen, P.R.; Clark, B. C.; de Souza, P.A.; Farmer, J.; Farrand, W. H.; Fike, D.A.; Gellert, Ralf; Ghosh, A.; Glotch, T.D.; Grotzinger, J.P.; Hahn, B.; Herkenhoff, K. E.; Hurowitz, J.A.; Johnson, J. R.; Johnson, S.S.; Jolliff, B.; Klingelhofer, G.; Knoll, A.H.; Learner, Z.; Malin, M.C.; McSween, H.Y.; Pocock, J.; Ruff, S.W.; Soderblom, L.A.; Squyres, S. W.; Tosca, N.J.; Watters, W.A.; Wyatt, M.B.; Yen, A.

2005-01-01

Impure reworked evaporitic sandstones, preserved on Meridiani Planum, Mars, are mixtures of roughly equal amounts of altered siliciclastic debris, of basaltic provenance (40 ?? 10% by mass), and chemical constituents, dominated by evaporitic minerals (jarosite, Mg-, Ca-sulfates ?? chlorides ?? Fe-, Na-sulfates), hematite and possibly secondary silica (60 ?? 10%). These chemical constituents and their relative abundances are not an equilibrium evaporite assemblage and to a substantial degree have been reworked by aeolian and subaqueous transport. Ultimately they formed by evaporation of acidic waters derived from interaction with olivine-bearing basalts and subsequent diagenetic alteration. The rocks experienced an extended diagenetic history, with at least two and up to four distinct episodes of cementation, including stratigraphically restricted zones of recrystallization and secondary porosity, non-randomly distributed, highly spherical millimeter-scale hematitic concretions, millimeter-scale crystal molds, interpreted to have resulted from dissolution of a highly soluble evaporite mineral, elongate to sheet-like vugs and evidence for minor synsedimentary deformation (convolute and contorted bedding, possible teepee structures or salt ridge features). Other features that may be diagenetic, but more likely are associated with relatively recent meteorite impact, are meter-scale fracture patterns, veins and polygonal fractures on rock surfaces that cut across bedding. Crystallization of minerals that originally filled the molds, early cement and sediment deformation occurred syndepositionally or during early diagenesis. All other diagenetic features are consistent with formation during later diagenesis in the phreatic (fluid saturated) zone or capillary fringe of a groundwater table under near isotropic hydrological conditions such as those expected during periodic groundwater recharge. Textural evidence suggests that rapidly formed hematitic concretions post

Provenance and diagenesis of the evaporite-bearing Burns formation, Meridiani Planum, Mars

NASA Astrophysics Data System (ADS)

McLennan, S. M.; Bell, J. F.; Calvin, W. M.; Christensen, P. R.; Clark, B. C.; de Souza, P. A.; Farmer, J.; Farrand, W. H.; Fike, D. A.; Gellert, R.; Ghosh, A.; Glotch, T. D.; Grotzinger, J. P.; Hahn, B.; Herkenhoff, K. E.; Hurowitz, J. A.; Johnson, J. R.; Johnson, S. S.; Jolliff, B.; Klingelhöfer, G.; Knoll, A. H.; Learner, Z.; Malin, M. C.; McSween, H. Y.; Pocock, J.; Ruff, S. W.; Soderblom, L. A.; Squyres, S. W.; Tosca, N. J.; Watters, W. A.; Wyatt, M. B.; Yen, A.

2005-11-01

Impure reworked evaporitic sandstones, preserved on Meridiani Planum, Mars, are mixtures of roughly equal amounts of altered siliciclastic debris, of basaltic provenance (40 ± 10% by mass), and chemical constituents, dominated by evaporitic minerals (jarosite, Mg-, Ca-sulfates ± chlorides ± Fe-, Na-sulfates), hematite and possibly secondary silica (60 ± 10%). These chemical constituents and their relative abundances are not an equilibrium evaporite assemblage and to a substantial degree have been reworked by aeolian and subaqueous transport. Ultimately they formed by evaporation of acidic waters derived from interaction with olivine-bearing basalts and subsequent diagenetic alteration. The rocks experienced an extended diagenetic history, with at least two and up to four distinct episodes of cementation, including stratigraphically restricted zones of recrystallization and secondary porosity, non-randomly distributed, highly spherical millimeter-scale hematitic concretions, millimeter-scale crystal molds, interpreted to have resulted from dissolution of a highly soluble evaporite mineral, elongate to sheet-like vugs and evidence for minor synsedimentary deformation (convolute and contorted bedding, possible teepee structures or salt ridge features). Other features that may be diagenetic, but more likely are associated with relatively recent meteorite impact, are meter-scale fracture patterns, veins and polygonal fractures on rock surfaces that cut across bedding. Crystallization of minerals that originally filled the molds, early cement and sediment deformation occurred syndepositionally or during early diagenesis. All other diagenetic features are consistent with formation during later diagenesis in the phreatic (fluid saturated) zone or capillary fringe of a groundwater table under near isotropic hydrological conditions such as those expected during periodic groundwater recharge. Textural evidence suggests that rapidly formed hematitic concretions post

Diagenesis and porosity evolution of tight sand reservoirs in Carboniferous Benxi Formation, Southeast Ordos Basin

NASA Astrophysics Data System (ADS)

Hu, Peng; Yu, Xinghe; Shan, Xin; Su, Dongxu; Wang, Jiao; Li, Yalong; Shi, Xin; Xu, Liqiang

2016-04-01

The Ordos Basin, situated in west-central China, is one of the oldest and most important fossil-fuel energy base, which contains large reserves of coal, oil and natural gas. The Upper Palaeozoic strata are widely distributed with rich gas-bearing and large natural gas resources, whose potential is tremendous. Recent years have witnessed a great tight gas exploration improvement of the Upper Paleozoic in Southeastern Ordos basin. The Carboniferous Benxi Formation, mainly buried more than 2,500m, is the key target strata for hydrocarbon exploration, which was deposited in a barrier island and tidal flat environment. The sandy bars and flats are the favorable sedimentary microfacies. With an integrated approach of thin-section petrophysics, constant velocity mercury injection test, scanning electron microscopy and X-ray diffractometry, diagenesis and porosity evolution of tight sand reservoirs of Benxi Formation were analyzed in detail. The result shows that the main lithology of sandstone in this area is dominated by moderately to well sorted quartz sandstone. The average porosity and permeability is 4.72% and 1.22mD. The reservoirs of Benxi Formation holds a variety of pore types and the pore throats, with obvious heterogeneity and poor connection. Based on the capillary pressure curve morphological characteristics and parameters, combined with thin section and phycical property data, the reservoir pore structure of Benxi Formation can be divided into 4 types, including mid pore mid throat type(I), mid pore fine throat type(II), small pore fine throat type(III) and micro pro micro throat type(Ⅳ). The reservoirs primarily fall in B-subsate of middle diagenesis and late diagenesis, which mainly undergo compaction, cmentation, dissolution and fracturing process. Employing the empirical formula of different sorting for unconsolideated sandstone porosity, the initial sandstone porosity is 38.32% on average. Quantitative evaluation of the increase and decrease of

Fine-grained rutile in the Gulf of Maine: Diagenetic origin, source rocks, and sedimentary environment of deposition

USGS Publications Warehouse

Valentine, P.C.; Commeau, J.A.

1990-01-01

The Gulf of Maine, an embayment of the New England margin, is floored by shallow, glacially scoured basins that are partly filled with late Pleistocene and Holocene silt and clay containing 0.7 to 1.0 wt percent TiO2 chiefly in the form of silt-size rutile. Much of the rutile in the Gulf of Maine mud probably formed diagenetically in poorly cemented Carboniferous and Triassic coarse-grained sedimentary rocks of Nova Scotia and New Brunswick after the dissolution of titanium-rich detrital minerals (ilmenite, ilmenomagnetite). The diagenesis of rutile in coarse sedimentary rocks (especially arkose and graywacke) followed by erosion, segregation, and deposition (and including recycling of fine-grained rutile from shales) can serve as a model for predicting and prospecting for unconsolidated deposits of fine-grained TiO2. -from Authors

Accumulation of sedimentary photosynthetic pigments characterized by pyropheophorbide a and steryl chlorin esters (SCEs) in a shallow eutrophic coastal lake (Lake Hamana, Japan)

NASA Astrophysics Data System (ADS)

Itoh, Nobuyasu; Tani, Yukinori; Soma, Yuko; Soma, Mitsuyuki

2007-01-01

We investigated the factors controlling the composition of sedimentary photosynthetic pigments in Lake Hamana (Japan), a shallow (12 m), brackish, holomictic lake, by analyzing photosynthetic pigments and the sterol composition of steryl esters of pyropheophorbide a (steryl chlorin esters, SCEs) in the water column and surface sediments. The mean annual composition of carotenoids in the water was quite different from that in the surface sediments. We evaluated the relative accumulation efficiency of individual pigments in the sediments by comparing ratios of individual pigment concentrations relative to total chlorophyll a (TChl- a) in sediment to those in the water column. The relative accumulation efficiencies decreased in the following order: lutein > diatoxanthin > β,β-carotene > zeaxanthin > β,ɛ-carotene > alloxanthin ≫ fucoxanthin. The ratio of total pyro-derivatives of chlorophyll a, formed through the grazing of algae by zooplankton, to TChl- a in the surface sediments was much higher (0.24-0.33) than that in the water column, which was less than 0.03 even in the deepest water (10 m). The summed concentration of pyropheophytin a and SCEs (TPyphe- a) showed positive and significant relationships ( r2 > 0.56, n = 7) with residual carotenoids in sediments. These results suggest that incorporation of algal pigments in fecal pellets through grazing by zooplankton enhances pigment preservation during early diagenesis at the sediment surface. Moreover, sedimentary carotenoid compositions were consistent with the sterol compositions of sedimentary SCE fractions. Selective grazing by zooplankton was thus a primary factor determining the composition of sedimentary carotenoids in this lake.

Organic sulphur in macromolecular sedimentary organic matter: I. Structure and origin of sulphur-containing moieties in kerogen, asphaltenes and coal as revealed by flash pyrolysis

NASA Astrophysics Data System (ADS)

Sinninghe Damsté, Jaap S.; Eglinton, Timothy I.; De Leeuw, Jan W.; Schenck, P. A.

1989-04-01

The distributions of sulphur-containing compounds generated by flash pyrolysis of macromolecular sedimentary organic matter (kerogen, coal, asphaltenes) were studied by gas chromatography in combination with Sselective flame photometric detection or mass spectrometry. The abundance of S-containing pyrolysis products in the pyrolysates relative to other products was highly variable depending on the sample but the types of products were generally similar, being mainly composed of "gaseous" compounds ( e.g., hydrogen sulphide) and low molecular weight alkylthiophenes and alkylbenzothiophenes. The distribution patterns of the alkylated thiophenes were dominated by a limited number of all theoretically possible isomers. The alkyl substitution patterns of the dominant isomers bear a strong similarity to those of the organic S compounds present in the GC-amenable fractions of bitumens and immature oils. Therefore, it is suggested that these S-containing pyrolysis products are formed by pyrolysis of related thiophenic and benzothiophenic moieties present in the macromolecular sedimentary substances. Specific examples include those with linear alkyl, iso and anteiso alkyl, isoprenoid alkyl and steroidal carbon skeletons. The presence of higher molecular weight alkylthiophenes and alkylbenzothiophenes with these same carbon skeletons in pyrolysates of S-rich kerogens provided further evidence for the presence of these S-containing moieties. It is likely that these moieties have been formed by abiogenic S incorporation into sedimentary organic matter during early diagenesis.

Modeling the effects of diagenesis on carbonate clumped-isotope values in deep- and shallow-water settings

NASA Astrophysics Data System (ADS)

Stolper, Daniel A.; Eiler, John M.; Higgins, John A.

2018-04-01

The measurement of multiply isotopically substituted ('clumped isotope') carbonate groups provides a way to reconstruct past mineral formation temperatures. However, dissolution-reprecipitation (i.e., recrystallization) reactions, which commonly occur during sedimentary burial, can alter a sample's clumped-isotope composition such that it partially or wholly reflects deeper burial temperatures. Here we derive a quantitative model of diagenesis to explore how diagenesis alters carbonate clumped-isotope values. We apply the model to a new dataset from deep-sea sediments taken from Ocean Drilling Project site 807 in the equatorial Pacific. This dataset is used to ground truth the model. We demonstrate that the use of the model with accompanying carbonate clumped-isotope and carbonate δ18O values provides new constraints on both the diagenetic history of deep-sea settings as well as past equatorial sea-surface temperatures. Specifically, the combination of the diagenetic model and data support previous work that indicates equatorial sea-surface temperatures were warmer in the Paleogene as compared to today. We then explore whether the model is applicable to shallow-water settings commonly preserved in the rock record. Using a previously published dataset from the Bahamas, we demonstrate that the model captures the main trends of the data as a function of burial depth and thus appears applicable to a range of depositional settings.

Geochemical characteristics and early diagenesis of recent carbonate mound sediments in the Gulf of Cadiz

NASA Astrophysics Data System (ADS)

Hamaekers, Helen; Foubert, Anneleen; Wienberg, Claudia; Hebbeln, Dierk; Swennen, Rudy

2010-05-01

investigate the influence of early diagenesis. Along with the dating that has been performed, the obtained geochemical data give an overview of the extent to which palaeo-environmental conditions and diagenesis have influenced the carbonate mound sediments in the Gulf of Cádiz. References Foubert, A., Depreiter, D., Beck, T., Maignien, L., Pannemans, B., Frank, N., Blamart, D., Henriet, J.P., 2008. Carbonate mounds in a mud volcano province off north-west Morocco: Key to processes and controls. Marine Geology, 248, 74-96. Wienberg, C., Hebbeln, D., Fink, H.G., Mienis, F., Dorschel, B., Vertino, A., López Correa, M., Freiwald, A., 2009. Scleractinian cold-water corals in the Gulf of Cádiz - First clues about their spatial and temporal distribution, Deep-Sea Research I, 56, 1873-1893.

Use of variations in unit cell length, reflectance and hardness for determining the origin of Fe disulphides in sedimentary rocks

NASA Astrophysics Data System (ADS)

Dill, H. G.; Eberhard, E.; Hartmann, B.

1997-01-01

Fe disulphides are common opaque accessories in sedimentary rocks. Both marcasite and pyrite may shed some light on the depositional environment and help determine the diagenesis of their host rocks. Quantitative ore microscopy (reflectance measurements, Vickers hardness numbers) and X-ray diffraction methods, supplemented with scanning electron microscopy and chemical analyses, were applied to pyrite (and some marcasite) hosted by sedimentary rocks spanning the interval from the Devonian to the Pliocene, and formed in various marine and continental environments. Quantitative ore microscopy of pyrites of sedimentary origin does not seem to be an efficient tool for analyzing the environment owing to the inhomogeneous nature of sulphide aggregates when viewed under the ore microscope, and the variable amounts of minor elements (e.g., As, Ni, and Co) that control the reflectance values (RV) and Vickers hardness numbers (VHN) of the host sulphides. However, such parameters as crystal habit and unit cell length of pyrite, which correlate with FeS x, are useful for environmental analysis. The redox conditions and the presence of organic remains during formation are the main factors determining these crystallographic parameters. Differences in these parameters from those of pure, ideal FeS 2 can be related to substitution of, e.g., wustite in the pyrite lattice, reflecting moderate oxidation (i.e. in the microenvironment). As far as crystal habit and length of the cell edge are concerned, late stage diagenesis is obviously less important than the microenvironment attending initial formation. The environment of deposition (i.e. the macroenvironment) of pyrite-bearing rocks has no influence on the crystal morphology or the length of the unit cell of Fe disulphide. X-ray diffraction measurements demonstrate that this method provides useful evidence on the microenvironment of sulphide precipitation around a single, equant pyrite, as well as around pyritized fossils.

Early Diagenesis of Subseafloor Sandy Sediments Closely Related to Gas Hydrate Occurrences and Their Provenances in the Eastern Margin of Japan Sea

NASA Astrophysics Data System (ADS)

Uchida, T.; Sakai, H.; Horiuchi, S.; Matsumoto, R.

2015-12-01

remarked that physical diagenesis proceeds first due to mechanical compaction, whereas chemical diagenesis advances very slowly in early diagenesis. This study was performed as a part of the MH21 Research Consortium on methane hydrate in Japan and the METI project entitled "FY2014 promoting research and development on methane hydrate."

Diagenesis of clay mineral assemblages in the Shikoku Basin: Inputs to the Nankai Trough megathrust and seismogenic zone

NASA Astrophysics Data System (ADS)

Underwood, M.; Guo, J.; Song, C.

2012-12-01

One of the essential components of the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is to document the composition and diagenetic alteration of sedimentary inputs to the subduction zone of SW Japan. Two sites were drilled seaward of the trench during IODP Expeditions 322 and 333 to demonstrate how those subduction inputs have been influenced by the basement topography of Shikoku Basin. Site C0011 was drilled on the NW flank of Kashinosaki Knoll, and Site C0012 is located near the seamount's summit. The lithostratigraphy expands and condenses from site to site, but the clay mineral assemblages are nearly identical when comparisons are made among coeval units. The early history of sedimentation (middle to late Miocene) was dominated by expandable clay minerals of the smectite group. Contents of smectite in strata older than 5.3 Ma typically exceed 65% of the clay-size fraction, and there are dozens of bentonite layers (altered volcanic ash) interbedded with the hemipelagic mudstones and turbidites. Those percentages amount to >45 wt-% smectite in the bulk mudstone. Volcanic sources for the Miocene clay probably included the ancestral Izu-Bonin island arc, the Izu-Honshu collision zone, and anomalous near-trench magma bodies in the Outer Zone of Honshu and Shikoku Island. As sedimentation progressed into the Pliocene and Pleistocene, mud supplies to the Shikoku Basin shifted increasingly to detrital illite and chlorite eroded from the uplifted accretionary complex (Outer Zone). At Site C0011, the younger hemipelagic-pyroclastic facies (upper Shikoku Basin) contains an average of 43% smectite, 36% illite, and 18% kaolinite + chlorite in the clay-size fraction. At Site C0012, comparable values are S = 51%, I = 32%, and K+C = 14%. XRD results show no evidence of smectite-to-illite diagenesis seaward of the trench, although it is important to note that Site C0011 was abandoned before reaching basaltic basement. We can predict the extent of smectite

Sequence-stratigraphic controls on sandstone diagenesis: An example from the Williams Fork formation, Piceance Basin, Colorado

NASA Astrophysics Data System (ADS)

Aboktef, Adel

This study documents the distribution of diagenetic alterations in Williams Fork fluvial sandstones, assess sequence stratigraphic controls on diagenetic features, and addresses diagenetic impacts on porosity. Petrographic point counts of 220 thin sections from six wells forms the database. The near absence of potassium feldspar and volcanic rock fragments in the lower Williams Fork interval and increasing plagioclase content upward represent changes in sediment provenance rather than stratigraphic variability in diagenesis. The lower Williams Fork sands are from sedimentary sources whereas middle and upper Williams Fork sands include input from magmatic arcs and basement uplifts. Compaction, early and late cementation, dissolution, and replacement by calcite or clay minerals combined to alter Williams Fork sandstones. Infiltration of clays occurred prior to any burial. Chlorite, quartz, non-ferroan calcite, compaction and dissolution features, and kaolinite formed during eo-diagenesis at <70°C. More quartz, compaction and dissolution features, plus albite, illite, mixed-layer illite/smectite, ferroan calcite, and dolomite formed in the meso-diagenetic realm (>70°C). Four of these features show spatial variability with respect to systems tracts. Infiltrated clays are concentrated in lowstand systems tracts (LST) and highstand systems tracts (HST) because accommodation space rose slow or fell during deposition of those sands, which led to prolonged sand body exposure on floodplain and ample opportunities for downward percolation of mud during flood events. Concentration of pseudomatrix (mud intraclasts) in HST and LST deposits resulted from floodplain erosion when base-level fell with decreasing accommodation space. Authigenic chlorite formed in the HST and transgressive systems tracts (TST) of the upper half of the Williams Fork Formation because volcanic clasts are abundant in that interval. Quartz overgrowths are more likely to exceed 7% in TST deposits for

Diagenesis and porosity preservation in Eocene microporous limestones, South Florida, USA

NASA Astrophysics Data System (ADS)

Maliva, Robert G.; Missimer, Thomas M.; Clayton, Edward A.; Dickson, J. A. D.

2009-05-01

Microporous limestones may contain immobile, capillary-bound (irreducible) water that is only in diffusional contact with mobile pore waters or in some reservoirs may contain producible hydrocarbons. The preservation and distribution of microporosity impact both subsurface fluid flow and solute transport. The diagenesis of microporous limestones has received relatively little attention because their very fine grains and cements are not amenable to standard analytical methods. The Ocala Limestone (Upper Eocene) and upper Avon Park Formation (Middle Eocene) in South Florida contain microporous micritic limestones (mudstones to packstones) that are at an intermediate stage of diagenesis. The limestones have been exposed to the active near-surface environment, but have not yet reached a burial depth sufficient for intense chemical compaction and associated porosity reduction. Nuclear magnetic resonance (NMR) logging allowed for the quantification of total porosity, pore-size distribution, and permeability. The Ocala Limestone and Avon Park Formation have different predominant microfacies and porosity size distributions, but yet both retain total porosities predominantly between 35% and 37%. Estimated microporosities range mostly between 12% and 45%. The mudstones and wackestones of the Ocala Limestone have significantly lower permeabilities (mostly 3 to 12 md) than the wackestones to grainstones of the Avon Park Formation (commonly in the 100 to 3000 md range), which have more mixed and overall coarser pore sizes. Computer modeling using carbon and oxygen stable data indicates that the studied microporous limestones underwent only a low degree of chemical diagenetic alteration, despite likely experiencing episodes of freshwater flushing associated with post-depositional sea-level lowstands. The Ocala Limestone and Avon Park Formation limestones illustrate the general concept that total porosity is often largely preserved through early diagenesis (although may undergo

Sedimentary petrography of the Early Proterozoic Pretoria Group, Transvaal Sequence, South Africa: implications for tectonic setting

NASA Astrophysics Data System (ADS)

Schreiber, U. M.; Eriksson, P. G.; van der Neut, M.; Snyman, C. P.

1992-11-01

Sandstone petrography, geochemistry and petrotectonic assemblages of the predominantly clastic sedimentary rocks of the Early Proterozoic Pretoria Group, Transvaal Sequence, point to relatively stable cratonic conditions at the beginning of sedimentation, interrupted by minor rifting events. Basement uplift and a second period of rifting occurred towards the end of Pretoria Group deposition, which was followed by the intrusion of mafic sill swarms and the emplacement of the Bushveld Complex in the Kaapvaal Craton at about 2050 Ma, the latter indicating increased extensional tectonism, and incipient continental rifting. An overall intracratonic lacustrine tectonic setting for the Pretoria Group is supported by periods of subaerial volcanic activity and palaeosol formation, rapid sedimentary facies changes, significant arkosic sandstones, the presence of non-glacial varves and a highly variable mudrock geochemistry.

Classification scheme for sedimentary and igneous rocks in Gale crater, Mars

NASA Astrophysics Data System (ADS)

Mangold, N.; Schmidt, M. E.; Fisk, M. R.; Forni, O.; McLennan, S. M.; Ming, D. W.; Sautter, V.; Sumner, D.; Williams, A. J.; Clegg, S. M.; Cousin, A.; Gasnault, O.; Gellert, R.; Grotzinger, J. P.; Wiens, R. C.

2017-03-01

Rocks analyzed by the Curiosity rover in Gale crater include a variety of clastic sedimentary rocks and igneous float rocks transported by fluvial and impact processes. To facilitate the discussion of the range of lithologies, we present in this article a petrological classification framework adapting terrestrial classification schemes to Mars compositions (such as Fe abundances typically higher than for comparable lithologies on Earth), to specific Curiosity observations (such as common alkali-rich rocks), and to the capabilities of the rover instruments. Mineralogy was acquired only locally for a few drilled rocks, and so it does not suffice as a systematic classification tool, in contrast to classical terrestrial rock classification. The core of this classification involves (1) the characterization of rock texture as sedimentary, igneous or undefined according to grain/crystal sizes and shapes using imaging from the ChemCam Remote Micro-Imager (RMI), Mars Hand Lens Imager (MAHLI) and Mastcam instruments, and (2) the assignment of geochemical modifiers based on the abundances of Fe, Si, alkali, and S determined by the Alpha Particle X-ray Spectrometer (APXS) and ChemCam instruments. The aims are to help understand Gale crater geology by highlighting the various categories of rocks analyzed by the rover. Several implications are proposed from the cross-comparisons of rocks of various texture and composition, for instance between in place outcrops and float rocks. All outcrops analyzed by the rover are sedimentary; no igneous outcrops have been observed. However, some igneous rocks are clasts in conglomerates, suggesting that part of them are derived from the crater rim. The compositions of in-place sedimentary rocks contrast significantly with the compositions of igneous float rocks. While some of the differences between sedimentary rocks and igneous floats may be related to physical sorting and diagenesis of the sediments, some of the sedimentary rocks (e

Classification scheme for sedimentary and igneous rocks in Gale crater, Mars

DOE PAGES

Mangold, Nicolas; Schmidt, Mariek E.; Fisk, Martin R.; ...

2016-11-05

Rocks analyzed by the Curiosity rover in Gale crater include a variety of clastic sedimentary rocks and igneous float rocks transported by fluvial and impact processes. Here, to facilitate the discussion of the range of lithologies, we present in this article a petrological classification framework adapting terrestrial classification schemes to Mars compositions (such as Fe abundances typically higher than for comparable lithologies on Earth), to specific Curiosity observations (such as common alkali-rich rocks), and to the capabilities of the rover instruments. Mineralogy was acquired only locally for a few drilled rocks, and so it does not suffice as a systematicmore » classification tool, in contrast to classical terrestrial rock classification. The core of this classification involves (1) the characterization of rock texture as sedimentary, igneous or undefined according to grain/crystal sizes and shapes using imaging from the ChemCam Remote Micro-Imager (RMI), Mars Hand Lens Imager (MAHLI) and Mastcam instruments, and (2) the assignment of geochemical modifiers based on the abundances of Fe, Si, alkali, and S determined by the Alpha Particle X-ray Spectrometer (APXS) and ChemCam instruments. The aims are to help understand Gale crater geology by highlighting the various categories of rocks analyzed by the rover. Several implications are proposed from the cross-comparisons of rocks of various texture and composition, for instance between in place outcrops and float rocks. All outcrops analyzed by the rover are sedimentary; no igneous outcrops have been observed. However, some igneous rocks are clasts in conglomerates, suggesting that part of them are derived from the crater rim. The compositions of in-place sedimentary rocks contrast significantly with the compositions of igneous float rocks. While some of the differences between sedimentary rocks and igneous floats may be related to physical sorting and diagenesis of the sediments, some of the sedimentary

Classification scheme for sedimentary and igneous rocks in Gale crater, Mars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mangold, Nicolas; Schmidt, Mariek E.; Fisk, Martin R.

Rocks analyzed by the Curiosity rover in Gale crater include a variety of clastic sedimentary rocks and igneous float rocks transported by fluvial and impact processes. Here, to facilitate the discussion of the range of lithologies, we present in this article a petrological classification framework adapting terrestrial classification schemes to Mars compositions (such as Fe abundances typically higher than for comparable lithologies on Earth), to specific Curiosity observations (such as common alkali-rich rocks), and to the capabilities of the rover instruments. Mineralogy was acquired only locally for a few drilled rocks, and so it does not suffice as a systematicmore » classification tool, in contrast to classical terrestrial rock classification. The core of this classification involves (1) the characterization of rock texture as sedimentary, igneous or undefined according to grain/crystal sizes and shapes using imaging from the ChemCam Remote Micro-Imager (RMI), Mars Hand Lens Imager (MAHLI) and Mastcam instruments, and (2) the assignment of geochemical modifiers based on the abundances of Fe, Si, alkali, and S determined by the Alpha Particle X-ray Spectrometer (APXS) and ChemCam instruments. The aims are to help understand Gale crater geology by highlighting the various categories of rocks analyzed by the rover. Several implications are proposed from the cross-comparisons of rocks of various texture and composition, for instance between in place outcrops and float rocks. All outcrops analyzed by the rover are sedimentary; no igneous outcrops have been observed. However, some igneous rocks are clasts in conglomerates, suggesting that part of them are derived from the crater rim. The compositions of in-place sedimentary rocks contrast significantly with the compositions of igneous float rocks. While some of the differences between sedimentary rocks and igneous floats may be related to physical sorting and diagenesis of the sediments, some of the sedimentary

Biostratigraphic and chemostratigraphic correlation of Neoproterozoic sedimentary successions: upper Tindir Group, northwestern Canada, as a test case

NASA Technical Reports Server (NTRS)

Kaufman, A. J.; Knoll, A. H.; Awramik, S. M.

1992-01-01

Recent advances in Proterozoic micropaleontology and sedimentary isotope geochemistry suggest that improved interbasinal correlation of Neoproterozoic (1000-540 Ma) successions is possible. Because widely varying interpretations of its age have been suggested and no reliable radiometric dates or paleomagnetic data are available, the upper Tindir Group of northwestern Canada provides an opportunity to test this hypothesis. The age of these strata is of paleontological importance because silicified carbonates near the top of the group contain disc-shaped-scale microfossils that may provide insights into the early evolution of biomineralization. A reinterpretation of upper Tindir microfossil assemblages suggests a late Riphean age. Although diagenesis and contact metamorphism have altered the isotopic compositions of some carbonates, least altered samples indicate that delta 13C of contemporaneous seawater was at least +4.7%, typical of Neoproterozoic, but not Cambrian, carbonates. Strontium isotopic compositions of the least altered samples yield values of approximately 0.7065, which can be uniquely correlated with late Riphean seawater. Together, micropaleontology and the isotopic tracers of C and Sr constrain the upper Tindir carbonates and their unique fossils to be late Riphean, likely between 620 and 780 Ma.

A Volcanic Environment for Bedrock Diagenesis at Meridiani Planum, Mars

NASA Astrophysics Data System (ADS)

Hynek, B. M.; McCollom, T. M.

2005-12-01

Exposed bedrocks at Meridiani Planum on Mars display chemical and mineralogical evidence suggesting interaction with liquid water. Based on the observed bedding morphology, crystal vugs, varying Br:Cl ratios, as well as high abundances of hematite and sulfate minerals, the rocks have been interpreted by the Mars Exploration Rover (MER) team as sedimentary/evaporite deposits. However, the composition of the Meridiani bedrocks indicates that the formation model advocated by the MER team is not plausible. If the sulfates were attributable to precipitation of salts from an evaporating brine the rocks would be enriched in a balancing cation (e.g., Ca, Mg, or Fe) but this is not observed. Ratios of cations including Fe, Mg, Ca, and Na to (Si + Al) in the rocks are nearly identical to the basaltic martian meteorite Shergotty, and also very similar to unweathered basaltic rocks at Meridiani and Gusev Crater. The compositional data strongly suggest that the Meridiani rocks represent typical martian basalt with a sulfur component added. Here, we propose an alternative model for diagenesis of Meridiani bedrock that involves deposition of volcanic ash followed by reaction with condensed SO2- and H2O-bearing vapors in a solfatara-like setting. We suggest that volcanic deposition may account for the textures observed in Meridiani rocks since morphologic bedding features including sorted grains, planar bedding, low-angle cross-stratification, festoon bedding, and ripple lamination are common in base surge deposits of ash on Earth. The lath-shaped vugs may be the remains of ferrous sulfates (or mixed Fe-Mg-Ca sulfates) formed in the early stages of alteration that became unstable during oxidation. Widely varying Br:Cl ratios are also common in solfatara environments on Earth. In this scenario, most of the alteration of the rocks likely occurred at high temperatures (~100° C or higher), possibly soon after the volcaniclastic deposits were emplaced and still retained their original

Chemical diagenesis, porosity reduction, and rock strength, IODP Site U1480: Influences on great earthquakes at shallow depths

NASA Astrophysics Data System (ADS)

Song, Insun; Milliken, Kitty; Dugan, Brandon; Bourlange, Sylvain; Colson, Tobias; Frederik, Marina; Jeppson, Tamara; Kuranaga, Mebae; Nair, Nisha; Henstock, Timothy

2017-04-01

International Ocean Discovery Program (IODP) Expedition 362 drilled two sites, U1480 and U1481, on the Indian oceanic plate ˜250 km west of the Sunda subduction zone to a maximum depth of 1500 meters below seafloor (mbsf). One of the primary objectives was to understand the mechanism of great earthquakes such as the 2004 Sumatra earthquake (Mw 9.0) which showed unexpectedly shallow megathrust slip by establishing the initial and evolving properties of the North Sumatran incoming sedimentary section. Core sampling and logging from the complete sedimentary section at U1480 indicates a distinct change in sedimentation rate from a slowly deposited pelagic system to a rapidly deposited submarine fan system at late Miocene. Following burial, sediments of the Nicobar Fan underwent compaction leading to porosity reduction from 66±9% near seafloor to ˜30% at the base of the sampled Nicobar Fan section (˜1250 mbsf), representing a normal consolidation behavior. Rock strength gradually increases with depth as the sediments are mechanically compacted. Below the fan (1250-1415 mbsf), the pelagic sediments are composed of tuffaceous, calcareous, and siliceous sediments/rocks and their porosity is dependent upon lithology more than upon depth. Tuffaceous materials exhibit high porosity ranging from ˜30-60%, even higher than that of overlying layers. However, porosity of most calcareous samples is lower than 20% at the same depth. The large variation in porosity depends on the degree of cementation, which in turn is controlled by grain assemblage composition and environmental conditions such as slow sedimentation rates and locally high temperatures related to igneous activity as documented by local igneous intrusives and extrusives. The minor cementation in tuffaceous sandy sediments has retained high porosity, but strengthened their skeleton so as to bear the overburden. The low porosity in calcareous rocks is considered to come from extensive cementation rather than

Sulfur diagenesis in marine sediments

NASA Technical Reports Server (NTRS)

Goldhaber, M.

1985-01-01

Bacterial sulfate reduction occurs in all marine sediments that contain organic matter. Aqueous sulfide (HS-, H2S), one of the initial products of bacterial sulfide reduction, is extremely reactive with iron bearing minerals: sulfur is fixed into sediments as iron sulfide (first FeS and then Fe2S2). A working definition is given of sulfur diagenesis in marine sediments. Controls and consequences of sulfate reduction rates in marine sediments are examined.

Mineralogy of Fluvio-Lacustrine Sediments Investigated by Curiosity during the Prime Mission: Implications for Diagenesis

NASA Astrophysics Data System (ADS)

Rampe, E. B.; Morris, R. V.; Bish, D. L.; Vaniman, D. T.; Bristow, T.; Chipera, S.; Blake, D. F.; Ming, D. W.; Farmer, J.; Morrison, S. M.; Treiman, A. H.; Achilles, C.; Crisp, J.; Des Marais, D. J.; Downs, R. T.; Morookian, J. M.; Sarrazin, P.; Spanovich, N.; Yen, A.

2014-12-01

The Mars Science Laboratory rover Curiosity investigated sedimentary rocks that were deposited in a diversity of fluvio-lacustrine settings. The entire science payload was employed to characterize the mineralogy and chemistry of the Sheepbed mudstone at Yellowknife Bay and the Windjana sandstone at the Kimberley. Data from the CheMin instrument, a transmission X-ray diffractometer, were used to determine the quantitative mineralogy of both samples. The Sheepbed mudstone contains detrital basaltic minerals, calcium sulfates, iron oxides or hydroxides, iron sulfides, trioctahedral smectite, and amorphous material. The mineral assemblage and chemical data from APXS suggest that the trioctahedral smectite and magnetite formed authigenically as a result of alteration of olivine. The apparent lack of higher-grade phyllosilicates (e.g., illite and chlorite) and the presence of anhydrite indicate diagenesis at ~50-80 ºC. The mineralogy of the Windjana sandstone is different than the Sheepbed mudstone. Windjana contains significant abundances of K-feldspar, low- and high-Ca pyroxenes, magnetite, phyllosilicates, and amorphous material. At least two distinct phyllosilicate phases exist: a 10 Å phase and a component that is expanded with a peak at ~11.8 Å. The identity of the expanded phase is currently unknown, but could be a smectite with interlayer H2O, and the 10 Å phase could be illite or collapsed smectite. Further work is necessary to characterize the phyllosilicates, but the presence of illite could suggest that Windjana experienced burial diagenesis. Candidates for the cementing agents include fine-grained phyllosilicates, Fe-oxides, and/or amorphous material. Interpretations of CheMin data from the Windjana sandstone are ongoing at the time of writing, but we will present an estimate of the composition of the amorphous material from mass balance calculations using the APXS bulk chemistry and quantitative mineralogy from CheMin.

Mineralogy of Fluvio-Lacustrine Sediments Investigated by Curiosity During the Prime Mission: Implications for Diagenesis

NASA Technical Reports Server (NTRS)

Rampe, Elizabeth B.; Morris, R. V.; Bish, D. L.; Vaniman, D. T.; Bristow, T. F.; Chipera, S. J.; Blake, D. F.; Ming, D. W.; Farmer, J. D.; Morrison, S. M.;

Significance of hypoburrow nodule formation associated with large biogenic sedimentary structures in open-marine bay siliciclastics of the Upper Eocene Birket Qarun Formation, Wadi El-Hitan, Fayum, Egypt

NASA Astrophysics Data System (ADS)

Abdel-Fattah, Zaki A.; Gingras, Murray K.; Pemberton, S. George

Unusually large biogenic sedimentary structures from the shallow quiescent-marine siliciclastics of the Upper Eocene Birket Qarun Formation in the Fayum area of Egypt display pronounced concretion formation around the trace fossils. The structures are massive, and vary morphologically, forming branched pillars (up to dm-scale), vertical (up to 180 cm height) amphora-like masses, and 3-D box-work "maze". Bioturbation, mainly Thalassinoides attributable to the Glossifungites ichnofacies, mediated and modified the physical and chemical microenvironments influencing early diagenesis; i.e., burrows promote the precipitation of pervasive calcite-dominated cement. The inferred paragenesis, combined with the negative (light) carbon and oxygen stable-isotopic values of the bulk calcite (δ 13C PDB from -0.94 to -4.98‰ and δ 18O PDB from -4.63 to -7.22‰) and bulk dolomite (δ 13C PDB from -2.05 to -8.23‰ and δ 18O PDB from -1.41 to -11.20‰), imply that the pore-water carbon was derived directly from seawater and dissolution of metastable carbonate, which was mediated by bacterial decomposition of organic matter and mixing of meteoric ground water. Thereby, the carbonate cement precipitated mostly under eodiagenetic conditions near the sediment/water interface (<~3 m in depth). The distribution of these structures is confined to parasequence-bounding flooding surfaces (generally expressed as transgressive surfaces of erosion). Notably, sedimentological, ichnological and paragenetic data can be related to stratigraphic evolution such that geochemical and textural evidence is distinctly associated with (1) early cementation of the host sandstone during highstands of relative sea level, (2) the formation of firmgrounds during low relative sea level, (3) the development of a Glossifungites-demarcated discontinuity during initial relative sea-level rise, and (4) continued cementation with rising relative sea level. This was followed by burial diagenesis, evidence for

Inverse modeling of geochemical and mechanical compaction in sedimentary basins

NASA Astrophysics Data System (ADS)

Colombo, Ivo; Porta, Giovanni Michele; Guadagnini, Alberto

2015-04-01

We study key phenomena driving the feedback between sediment compaction processes and fluid flow in stratified sedimentary basins formed through lithification of sand and clay sediments after deposition. Processes we consider are mechanic compaction of the host rock and the geochemical compaction due to quartz cementation in sandstones. Key objectives of our study include (i) the quantification of the influence of the uncertainty of the model input parameters on the model output and (ii) the application of an inverse modeling technique to field scale data. Proper accounting of the feedback between sediment compaction processes and fluid flow in the subsurface is key to quantify a wide set of environmentally and industrially relevant phenomena. These include, e.g., compaction-driven brine and/or saltwater flow at deep locations and its influence on (a) tracer concentrations observed in shallow sediments, (b) build up of fluid overpressure, (c) hydrocarbon generation and migration, (d) subsidence due to groundwater and/or hydrocarbons withdrawal, and (e) formation of ore deposits. Main processes driving the diagenesis of sediments after deposition are mechanical compaction due to overburden and precipitation/dissolution associated with reactive transport. The natural evolution of sedimentary basins is characterized by geological time scales, thus preventing direct and exhaustive measurement of the system dynamical changes. The outputs of compaction models are plagued by uncertainty because of the incomplete knowledge of the models and parameters governing diagenesis. Development of robust methodologies for inverse modeling and parameter estimation under uncertainty is therefore crucial to the quantification of natural compaction phenomena. We employ a numerical methodology based on three building blocks: (i) space-time discretization of the compaction process; (ii) representation of target output variables through a Polynomial Chaos Expansion (PCE); and (iii) model

Magnetic history of Early and Middle Ordovician sedimentary sequence, northern Estonia

NASA Astrophysics Data System (ADS)

Plado, J.; Preeden, U.; Pesonen, L. J.; Mertanen, S.; Puura, V.

2010-01-01

Alternating field and thermal demagnetization of lime- and dolostones from the Lower and Middle Ordovician (Floian to Darriwilian stages) subhorizontally bedded sequences in NW and NE Estonia reveal two characteristic magnetization components (named P and S). The intermediate-coercivity (demagnetized at 30-60 mT, up to 300-350°C) reversed polarity component P (mean of Floian Stage: Dref = 147.8 +/- 10.8°, Iref = 65.8 +/- 5.4° combined mean of Dapingian and Darriwilian stages: Dref = 166.0 +/- 8.4°, Iref = 56.1 +/- 6.5°) is regarded as the primary remanence of early diagenetic (chemical) origin. On the Baltica's apparent polar wander path (APWP), the palaeopoles (Floian: Plat = 25.0°N, Plon = 50.8°E, K = 52.7, A95 = 7.2° Dapingian and Darriwilian: Plat = 11.4°N, Plon = 39.1°E, K = 33.8, A95 = 6.7°) are placed on the Lower and Middle Ordovician segment. The poles indicate that Estonia was located at southerly latitudes, decreasing with time (Floian: ~48°S Dapingian and Darriwilian: ~37°S), when the remanence was acquired. A high-coercivity and high-unblocking-temperature component S (mean of samples: Dref = 33.7 +/- 6.3°, Iref = 51.9 +/- 5.7°) that is regarded as a secondary remanence has both normal and reversed polarities. On the European APWP, its palaeopole (Plat = 52.5°N, Plon = 157.9°E, K = 38.9, A95 = 5.3°) gives middle to late Permian age. According to mineralogical (SEM and optical microscopy) and rock magnetic (three-component induced remnant magnetization) studies, component P is carried by magnetite (coexisting with glauconite) and component S by haematite. Magnetite is of chemical origin, formed in the course of early diagenesis and/or dolomitization. During the Permian continental period haematite, the carrier of component S, was likely precipitated from oxidizing meteoric fluids in the already existing or simultaneously formed pore space between the dolomite crystals.

Permo-Carboniferous sedimentary basins related to the distribution of planetary cryptoblemes

USGS Publications Warehouse

Windolph, J.F.

1997-01-01

Massive/high velocity solar, galactic, and cosmic debris impacting the Earths surface may account for the enormous energy required for the formation of Permo-Carboniferous sedimentary basins and related mountain building orogenies. Analysis of satellite immagry, sea floor sonar, geophysical data, and geotectonic fabrics show a strong correlation throughout geologic time between sedimentary basin origin and planetary cryptoblemes. Cryptoblemes are subtile, multi-ringed, radial centric impact shock signatures covering the entire terrestrial surface and ocean floors, having a geometry and distribution strikingly similar to the surfaces of the lunar planetary bodies in the solar system. Investigations of Permo-Carboniferous basins show an intensely overprinted pattern of cryptoblemes coinciding with partial obliteration and elliptical compression of pre-existing basins and accompanying shock patterns. Large distorted cryptoblemes may incorporate thin skin deformation, localized sediment diagenesis, regional metamorphism, and juxtaposed exotic terrains. These data, related to basin morphogenic symmetry, suggest that large episodic impact events are the primary cause of tectonogenic features, geologic boundary formation and mass extinction episodes on the planet Earth. Plate tectonics may be only a slow moving, low energy secondary effect defined and set in motion by megacosmic accretion events. Permo-Carboniferous sediments of note are preserved or accumulated in relatively small rectangular to arcuate rift valleys and synclinal down warps, such as the Narraganset basin of Massachusetts, USA, and Paganzo basin in Argentina, S.A. These deposits and depocenters may originate from dynamic reinforcement/cancellation impact effects, as can be seen in the Basin Range of Nevada and Utah, USA. Large circular to oval sedimentary basins commonly include internal ring structures indicating post depositional subsidence and rebound adjustments with growth faulting, notable in the

Quantification of diagenesis in Cenozoic sharks: Elemental and mineralogical changes

NASA Astrophysics Data System (ADS)

Labs-Hochstein, Joann; MacFadden, Bruce J.

2006-10-01

Diagenesis of bone during fossilization is pervasive, however, the extent of this process varies with depositional environment. This study quantifies diagenesis of shark vertebral centra through analysis of a suite of physical and chemical characters including crystallinty index (CI), carbonate content, and elemental concentrations. Although shark skeletons are initially cartilaginous, the soft cartilage of the vertebral centra is replaced with carbonate hydroxyapatite during growth. Nine vertebral centra are analyzed from lamnoid (Lamnoidea) sharks ranging in age from the cretaceous to recent using Fourier transform infrared spectroscopy (FT-IR) and inductively coupled plasma mass spectrometry (ICPMS). The variables CI, carbonate content, rare earth element (REE) concentrations, Ca/P, Ba/Ca, Sr/Ba, (La/Yb) N, (La/Y) N, (La/Yb) N vs. (La/Sm) N, La/Yb, and Ce anomalies elucidate the diagenetic and depositional environments of the seven fossil vertebral centra. The two extant centra demonstrate the initial, unaltered end-member conditions for these variables. Two fossil vertebral centra ( Carcharodon megalodon and Isurus hastalis) demonstrate a strong terrestrial influence during diagenesis (distinctive flattening of shale-normalized REE patterns) that masked the seawater signal. Three centra ( Carcharodon auriculatus, Carcharodon angustidens, and Creotxyrhina mantelli) have indications of some terrestrial influx evident by some flattening of the REE patterns relative to seawater. The terrestrial influence in these five shark centra ( C. megalodon, I. hastalis, C. auriculatus, C. angustidens and C. mantelli) are interpreted to represent a primarily nearshore habitat for these species. In contrast, the two Otodus obliquus centra have REE patterns that represent the original seawater signal and have no indications of terrigenous input. These results indicate that fossil shark vertebral centra have the potential to understand diagenesis and reconstruct

Jellyfish Lake, Palau: early diagenesis of organic matter in sediments of an anoxic marine lake

USGS Publications Warehouse

Orem, W.H.; Burnett, W.C.; Landing, W.M.; Lyons, W.B.; Showers, W.

1991-01-01

The major postdepositional change in the sedimentary organic matter is carbohydrate biodegradation. Lignin and aliphatic substances are preserved in the sediments. Dissolved organic matter in pore waters is primarily composed of carbohydrates, reflecting the degradation of sedimentary carbohydrates. Rate constants for organic carbon degradation and sulfate reduction in sediments of the lake are about 10?? lower than in other anoxic sediments. This may reflect the vascular plant source and partly degraded nature of the organic matter reaching the sediments of the lake. -from Authors

Petrology, sedimentology, and diagenesis of hemipelagic limestone and tuffaceous turbidities in the Aksitero Formation, central Luzon, Philippines

USGS Publications Warehouse

Garrison, Robert E.; Espiritu, E.; Horan, L.J.; Mack, L.E.

1979-01-01

The Aksitero Formation of central Luzon is an upper Eocene and lower Oligocene sequence of evenly bedded hemipelagic limestone with a few thin interlayers of tuffaceous turbidites. The limestone consists chiefly of planktonic foraminifers and calcareous nannofossils, with up to 30 percent of noncarbonate components, chiefly volcaniclastic debris. The tuff layers are graded beds. Composed mainly of glass shards, pumice fragments, crystals, and fine-grained volcanic rock fragments. Hydrocarbons migrated into the pores of the tuffaceous layers early during diagenesis but they were subsequently flushed out and only bitumen remains, chiefly as thin coatings on grains and wthin pumice vesicles. Later during diagenesis, zeolites (mordenite and c1inoptilolite) and secondary calcite preferentially replaced glass shards and pumice fragments. Deposition of the Aksitero Formation probably occurred at depths of at least 1,000 meters within a subsiding basin adjacent to an active island arc system. Submarine ash eruptions of silicic composition caused volcaniclastic turbidity currents that occasionally reached the basin floor. The more proximal facies of these volcaniclastic deposits may be prospective for hydrocarbons.

Mineral Trends in Early Hesperian Lacustrine Mudstone at Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Rampe, E. B.; Ming, D. W.; Grotzinger, J. P.; Morris, R. V.; Blake, D. F.; Vaniman, D. T.; Bristow, T. F.; Morrison, S. M.; Yen, A. S.; Chipera, S. J.;

Deep burial dolomitization driven by plate collision: Evidence from strontium-isotopes of Jurassic Arab IV dolomites from offshore Qatar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vahrenkamp, V.C.; Taylor, S.R.

The use of strontium-isotope ratios of dolomites to constrain timing and mechanism of diagenesis has been investigated on Jurassic Arab IV dolomites from offshore Qatar. Reservoir quality is determined by two types of dolomites, which were differentiated geochemically (cathodoluminescence, fluid inclusions, and carbon and oxygen stable isotopes): (1) stratigraphically concordant sucrosic dolomites with high porosity formed during early near-surface diagenesis (Jurassic) and (2) stratigraphically discordant cylindrical bodies of massive, porosity-destroying dolomites formed late during deep burial diagenesis (Eocene-Pliocene). Detailed Sr-isotope analysis of dolomites from the Arab IV confirms an Early Jurassic age of the sucrosic, high porosity dolomites ({sup 87}Sr/{supmore » 86}SR = 0.70707 for NBS 987 = 0.71024) with magnesium and strontium being derived from Jurassic seawater. Late Tertiary compressional orogeny of the Zagros belt to the north is proposed to have caused large-scale squeezing of fluids from the pore system of sedimentary rocks. A regional deep fluid flow system developed dissolving infra-Cambrian evaporites upflow and causing large-scale deep burial dolomitization downflow.« less

Syn- and post-sedimentary controls on clay mineral assemblages in a tectonically active basin, Andean Argentinean foreland

NASA Astrophysics Data System (ADS)

Do Campo, Margarita; Nieto, Fernando; del Papa, Cecilia; Hongn, Fernando

2014-07-01

In the northern part of the Calchaquí Valley (NW Argentina), Palaeogene Andean foreland sediments are represented by a 1400-metre-thick continental succession (QLC: Quebrada de Los Colorados Formation) consisting of claystones, siltstones, sandstones, and conglomerates representing sedimentation in fluvial-alluvial plains and alluvial fan settings. To understand the main syn- and postsedimentary variables controlling the clay mineral assemblages of this succession, we have studied the fine-grained clastic sediments by X-ray diffraction and electron microscopy, along with a detailed sedimentary facies analysis, for two representative sections. In the northern section, the whole succession was sampled and analysed by XRD, whereas in the second section, a control point 15 km to the south, only the basal levels were analysed. The XRD study revealed a strong contrast in clay mineral assemblages between these two sections as well as with sections in the central Calchaquí Valley studied previously. In the northernmost part of the study area, a complete evolution from smectite at the top to R3 illite/smectite mixed-layers plus authigenic kaolinite at the bottom, through R1-type mixed-layers in between, has been recognized, indicating the attainment of late diagenesis. In contrast, the clay mineral assemblages of equivalent foreland sediments cropping out only 15 km to the south contain abundant smectite and micas, subordinate kaolinite and chlorite, and no I/S mixed-layers to the bottom of the sequence. Early diagenetic conditions were also inferred in a previous study for equivalent sediments of the QLC Formation cropping out to the south, in the central Calchaquí Valley, as smectite occurs in basal strata. Burial depths of approximately 3000 m were estimated for the QLC Formation in the central and northern Calchaquí Valley; in addition, an intermediate to slightly low geothermal gradient can be considered likely for both areas as foreland basins are regarded as

Rare earth elements and neodymium isotopes in sedimentary organic matter

NASA Astrophysics Data System (ADS)

Freslon, Nicolas; Bayon, Germain; Toucanne, Samuel; Bermell, Sylvain; Bollinger, Claire; Chéron, Sandrine; Etoubleau, Joel; Germain, Yoan; Khripounoff, Alexis; Ponzevera, Emmanuel; Rouget, Marie-Laure

2014-09-01

(inferred from the analysis of local surface seawater). A notable exception is the case of organic matter (OM) fractions leached from cold seep sediment samples, which sometimes exhibit εNd values markedly different from both terrigenous and surface seawater signatures. This suggests that a significant fraction of organic compounds in these sediments may be derived from chemosynthetic processes, recycling pore water REE characterized by a distinct isotopic composition. Overall, our results confirm that organic matter probably plays an important role in the oceanic REE budget, through direct scavenging and remineralization within the water column. Both the high REE abundances and the shape of shale-normalized patterns for leached SOM also suggest that OM degradation in sub-surface marine sediments during early diagenesis could control, to a large extent, the distribution of REE in pore waters. Benthic fluxes of organic-bound REE could hence substantially contribute to the exchange processes between particulates and seawater that take place at ocean margins. Neodymium isotopes could provide useful information for tracing the origin (terrestrial versus marine) and geographical provenance of organic matter, with potential applications in paleoceanography. In particular, future studies should further investigate the potential of Nd isotopes in organic compounds preserved in sedimentary records for reconstructing past variations of surface ocean circulation.

Preservation of carbonate clumped isotopes in sedimentary paleoclimate archives

NASA Astrophysics Data System (ADS)

Henkes, G. A.; Passey, B. H.; Grossman, E. L.; Shenton, B.; Perez-Huerta, A.

2014-12-01

Carbonate clumped isotope thermometry is increasingly used to reconstruct paleotemperatures of ancient terrestrial environments. One promising application is elucidating paleoelevation from carbonate archives such as paleosols, lacustrine marls, and fossil freshwater shells. Unlike conventional stable isotope approaches (e.g., mineral δ18O or δD), clumped isotope thermometry is independent of the isotopic composition of the precipitating waters and can therefore be used to reconstruct elevation by both the temperature-altitude relationship and the rainfall δ18O-altitude relationship. However, interpretation of clumped isotope data is not without its own complications. Like conventional stable isotopes, clumped isotope paleotemperatures can be effectively reset to warmer values by dissolution/reprecipitation-type diagenesis during sedimentary burial. It is also known that carbonate clumped isotope bonds (i.e., 13C-18O) are susceptible to 'reordering' in the solid mineral lattice at warmer burial temperatures, with laboratory studies of natural carbonates indicating activation of this phenomenon at temperatures as low as 100 °C over geologic timescales. A challenge in applying carbonate clumped isotope thermometry to natural samples is now evaluating terrestrial archives with respect to both types of alteration: 'open-system' alteration and 'closed-system' bond reordering. In this talk we will review our experimental efforts to constrain the kinetics of clumped isotope reordering, with relevance to low-temperature carbonates like fossil shells and early diagenetic minerals, and present new laboratory data that further inform our theoretical framework for the mechanism(s) of 13C-18O bond reordering. Together with traditional analytical and petrographic screening for recrystallization, empirical and laboratory studies of carbonate clumped isotope reordering represent the next steps in evaluating isotopic records of paleoclimate, paleobiology, and paleoelevation

Glacioeustasy, meteoric diagenesis, and the carbon cycle during the Middle Carboniferous

NASA Astrophysics Data System (ADS)

Dyer, Blake; Maloof, Adam C.; Higgins, John A.

2015-10-01

Middle Carboniferous carbonates in the western U.S. have undergone Pleistocene Bahamas-style meteoric diagenesis that may be associated with expanding late Paleozoic ice sheets. Fourteen stratigraphic sections from carbonate platforms illustrate the regional distribution and variable intensity of physical and chemical diagenesis just below the Middle Carboniferous unconformity. These sections contain top-negative carbon isotope excursions that terminate in regional exposure surfaces that are associated with some combination of karst towers, desiccation cracks, fabric destructive recrystallization, or extensive root systems. The timing of the diagenesis is synchronous with similarly scaled top-negative carbon isotope excursions observed by others in England, Kazakhstan, and China. The mass flux of negative carbon required to generate similar isotopic profiles across the areal extent of Middle Carboniferous platform carbonates is a significant component of the global carbon cycle. We present a simple carbon box model to illustrate that the δ13C of dissolved inorganic carbon in the ocean could be elevated by ˜1.4‰ as isotopically light carbon from the weathering of terrestrial organic matter reacts with exposed platforms before reaching the ocean and atmosphere. These results represent an improvement on global biogeochemical models that have struggled to provide a congruent solution to the high δ13C of the late Paleozoic icehouse.

Archean sedimentary systems and crustal evolution

NASA Technical Reports Server (NTRS)

Lowe, D. R.

1985-01-01

Current knowledge of preserved Archean sedimentary rocks suggests that they accumulated in at least three major depositional settings. These are represented generally by sedimentary units: (1) in early Archean, pre-3.0 Ga old greenstone belts, (2) on late Archean sialic cratons, and (3) in late Archean, post-3.0 Ga old greenstone belts. Research suggests that the Archean was characterized by at least two distinctive and largely diachronous styles of crustal evolution. Thick, stable early Archean simatic platforms, perhaps analogous to modern oceanic islands formed over hot spots, underwent a single cycle of cratonization to form stable continental blocks in the early Archean. Later formed Archean continents show a two stage evolution. The initial stage is reflected in the existence of older sialic material, perhaps representing incompletely cratonized areas or microcontinents of as yet unknown origin. During the second stage, late Archean greenstone belts, perhaps analogous to modern magmatic arcs or back arc basins, developed upon or adjacent to these older sialic blocks. The formation of this generation of Archean continents was largely complete by the end of the Archean. These results suggest that Archean greenstone belts may represent a considerable range of sedimentological and tectonic settings.

Diagenesis in coastal carbonates related to Pleistocene sea level, Bermuda Platform

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vollbrecht, R.; Meischner, D.

1996-01-01

Pleistocene glacioeustatic sea-level oscillation on the stable Bermuda Platform is expressed in a succession of shallow-water carbonates interrupted by lowstand unconformities. In Bermuda, the maximum highstands of the last 400,000 yr ranged within 10 m around the present level. Coastal carbonates of various highstands are exposed along the present shoreline. These carbonates were penetrated by meteoric and marine pore waters during lowstands and highstands following on deposition. Two representative Pleistocene shoreline sections were studied to see whether early diagenesis has recorded these pore-water changes. The sediments of both sections show multiple generations of cement. Optical and scanning electron microscopy, cathodoluminescencemore » microscopy, X-ray diffraction, microprobe studies and stable-isotope analyses were used to determine the diagenetic environments involved. Regardless of the degree of substrate cementation, freshwater alteration was mainly vadose whereas marine cementation was either phreatic or vadose or both. Early diagenetic oscillation is easier recorded in coastal successions than in lagoonal sediments, mainly because marine cementation is more active nearshore.Because the coastal environment is prone to wave destruction, the potential for preserving these diagenetic features is usually low. Data published on tectonically unstable areas suggest that early diagenetic oscillation may characterize stable coastlines.« less

Early diagenesis and organic matter preservation--A molecular stable isotope perspective

DOE Office of Scientific and Technical Information (OSTI.GOV)

Macko, S.A.; Engel, M.H.; Qian, Y.

1992-01-01

Through new developments in stable isotope capability, gas chromatography coupled to a stable isotope ratio mass spectrometer (GC/IRMS), the molecular pathways of the diagenetic reactions can be observed on the components themselves. The authors report the results of laboratory-controlled degradation experiments of fresh organic substrates. Isotopically resolvable materials were used. Seagrass showed slight enrichments in [delta]N-15 with little change in [delta]C-13 following four weeks of decomposition. During that period the identifiable amino acid content decreased by approx. 50% for each amino acid. Mixtures of marine sediment with the same seagrass showed enrichments in nitrogen with associated depletions in carbon isotopicmore » compositions over the same time span. Control experiments on the sediments without added fresh seagrass showed no change in isotopic content. These changes are attributed to hydrolysis, deamination and decarboxylation reactions. Isotopic fractionations of similar size and direction have been observed in laboratory studies on peptide hydrolysis and natural samples of particulate organic materials. At the molecular level, using GC/IRMS, certain amino acids are seen to decrease in C-13 content while others become increasingly enriched in C-13. Similar reactions are seen in carbohydrates. The molecular isotope approach indicates that the process of diagenesis and preservation is significantly more complex than simple breakdown and loss. A large portion of the organic matter eventually preserved in organic-rich deposits can be attributed to new production in the deposit.« less

Chemistry and texture of the rocks at Rocknest, Gale Crater: Evidence for sedimentary origin and diagenetic alteration

USGS Publications Warehouse

Blaney, Diana L.; Wiens, R.C.; Maurice, S.; Clegg, S.M.; Anderson, Ryan; Kah, L.C.; Le Mouélic, S.; Ollila, A.; Bridges, N.; Tokar, R.; Berger, G.; Bridges, J.C.; Cousin, A.; Clark, B.; Dyar, M.D.; King, P.L.; Lanza, N.; Mangold, N.; Meslin, P.-Y.; Newsom, H.; Schroder, S.; Rowland, S.; Johnson, J.; Edgar, L.; Gasnault, O.; Forni, O.; Schmidt, M.; Goetz, W.; Stack, K.; Sumner, D.; Fisk, M.; Madsen, M.B.

2014-01-01

A suite of eight rocks analyzed by the Curiosity Rover while it was stopped at the Rocknest sand ripple shows the greatest chemical divergence of any potentially sedimentary rocks analyzed in the early part of the mission. Relative to average Martian soil and to the stratigraphically lower units encountered as part of the Yellowknife Bay formation, these rocks are significantly depleted in MgO, with a mean of 1.3 wt %, and high in Fe, averaging over 20 wt % FeOT, with values between 15 and 26 wt % FeOT. The variable iron and low magnesium and rock texture make it unlikely that these are igneous rocks. Rock surface textures range from rough to smooth, can be pitted or grooved, and show various degrees of wind erosion. Some rocks display poorly defined layering while others seem to show possible fractures. Narrow vertical voids are present in Rocknest 3, one of the rocks showing the strongest layering. Rocks in the vicinity of Rocknest may have undergone some diagenesis similar to other rocks in the Yellowknife Bay Formation as indicated by the presence of soluble calcium phases. The most reasonable scenario is that fine-grained sediments, potentially a mixture of feldspar-rich rocks from Bradbury Rise and normal Martian soil, were lithified together by an iron-rich cement.

Sedimentary rocks of the coast of Liberia

USGS Publications Warehouse

White, Richard William

1969-01-01

Two basins containing sedimentary rocks o# probable Cretaceous age have been recognized near the coast of Liberia in the area between Monrovia and Buchanan; geophysical evidence suggests that similar though larger basins exist on the adjacent continental shelf. The oldest sedimentary unit recognized, the Paynesville Sandstone of possible early to middle Paleozoic age, is intruded by dikes and sills of diabase of early Jurassic age and lies unconformably on crystalline rocks of late Precambrian age. Dips in the Paynesville Sandstone define a structural basin centered south of Roberts International Airport (formerly called Roberts Field) about 25 miles east of Monrovla. Wackes and conglomerates of Cretaceous age, herein named the Farmington River Formation, unconformably overlie the Paynesville Sandstone and constitute the sedimentary fill in the Roberts basin. The Bassa basin lies to the southeast of the Roberts basin and is separated from it by an upwarp of crystalline rocks. The basin is occupied by wackes and conglomerates of the Farmington River Formation, which apparently lie directly on the crystalline basement. Both basins are bounded on the northeast by northwest-trending dip-slip faults. The best potential for petroleum deposits that exists in Liberia is beneath the adjacent continental shelf and slope. Geophysical exploration and drilling will be required to evaluate this potential.

Diffusion-reaction modelling of early diagenesis of sediments affected by acid mine drainage.

NASA Astrophysics Data System (ADS)

Torres, E.; Ayora, C.; Arias, J. L.; Garcia Robledo, E.; Papaspyrou, S.; Corzo, A.

2012-04-01

The Sancho Reservoir (SW Spain) is a monomictic water reservoir affected by acid mine drainage. It has a pH of ~4, with high sulfate (200 ppm) and heavy metal concentrations in the water column. The reservoir develops reducing conditions at the bottom during the stratification period. A laboratory experiment was carried out to study the effect of this oxygen variation on the early diagenesis processes and the cycling of metals. Sediment cores and bottom water were collected during the stratification period and brought to the laboratory. The cores were maintained in an aquarium bubbled with nitrogen gas to maintain hypoxic conditions (~10 µmol O2 L-1) for 1 day. Then, oxic conditions were induced by bubbling with air and maintained for 50 days. Finally, hypoxia was re-established for 10 days. Triplicate cores were sliced in a anaerobic glove box at each stage. Pore water was extracted by centrifugation and: Eh, pH, DO, DOC, sulfate, Fe and trace metals were analyzed. The sediment was freeze-dried and a sequential extraction protocol was applied to determine the exchangeable, AVS, Fe-(oxy)hydroxides, Fe-oxides, organic matter, pyrite sulfur and residual phase iron fractions. Organic carbon and total C, N, H and S were also analyzed in the sediment. A reactive diffusion model has been used to obtain the rates of biogeochemical reactions by fitting to the experimental data. During hypoxic conditions sulfate and Fe-(oxy)hydroxides are reduced, due to the anaerobic oxidation of organic matter, at the very first few cm, releasing sulfide and Fe(II) which precipitate as iron sulfide. When oxygen diffuses in the sediment, sulfate-reduction and the sulfide peaks are displaced deeper into the sediment. Oxygen penetration depth and its consumption rates in the sediment increase quickly, resulting in the reoxidation of the iron sulfides that had precipitated during hypoxic conditions. Sulfide and Fe(II) are released and are again oxidized to Fe(III) and sulfate respectively

Black shale - Its deposition and diagenesis.

USGS Publications Warehouse

Tourtelot, H.A.

1979-01-01

Black shale is a dark-colored mudrock containing organic matter that may have generated hydrocarbons in the subsurface or that may yield hydrocarbons by pyrolysis. Many black shale units are enriched in metals severalfold above expected amounts in ordinary shale. Some black shale units have served as host rocks for syngenetic metal deposits.Black shales have formed throughout the Earth's history and in all parts of the world. This suggests that geologic processes and not geologic settings are the controlling factors in the accumulation of black shale. Geologic processes are those of deposition by which the raw materials of black shale are accumulated and those of diagenesis in response to increasing depth of burial.Depositional processes involve a range of relationships among such factors as organic productivity, clastic sedimentation rate, and the intensity of oxidation by which organic matter is destroyed. If enough organic material is present to exhaust the oxygen in the environment, black shale results.Diagenetic processes involve chemical reactions controlled by the nature of the components and by the pressure and temperature regimens that continuing burial imposes. For a thickness of a few meters beneath the surface, sulfate is reduced and sulfide minerals may be deposited. Fermentation reactions in the next several hundred meters result in biogenic methane, followed successively at greater depths by decarboxylation reactions and thermal maturation that form additional hydrocarbons. Suites of newly formed minerals are characteristic for each of the zones of diagenesis.

Extreme Hafnium Values in Archean Banded Iron Formations: Evidence for Sedimentary Lu/Hf Fractionation at 3.2 Ga or Diagenesis?

NASA Astrophysics Data System (ADS)

Foster, I. S.; Agranier, A.; Heubeck, C. E.; Köhler, I.; Homann, M.; Tripati, A. K.; Nonnotte, P.; Ponzevera, E.; Lalonde, S.

2017-12-01

The emergence of continental crust above sea level in the early Precambrian would have created the first terrestrial habitats, and initiated atmosphere-driven weathering of the continents, yet the history of continental emergence is largely unknown[1]. Precambrian chemical sediments, specifically Banded Iron Formation (BIF), appear to have sampled the Hf-Nd isotope composition of ancient seawater, and may preserve a historical record of the emergence of the continental landmass[2] via Lu/Hf fractionation induced by subaerial differential weathering[3,4]. However, paired Hf-Nd isotope data are available for only one BIF to date, indicating appreciable emerged continental landmass ca. 2.7 Ga[2]. Our work extends this record back into the Eo- and Meso-Archean using samples of 3.8 Ga BIF from Isua, Greenland, and 3.2 Ga BIF from the Moodies Group, S. Africa. Isua samples appear to have been altered by amphibolite-grade metamorphism, however Moodies Group samples appear primary, having experienced significantly lower metamorphic grades. Moodies samples appear to retain their primary seawater signatures, however, their range of ˜Hf(i) values, from -54.6 to +40.7, is among the most extreme ever reported. Such extreme values may be indicative of one of several possibilities: unusual and intense sedimentary Lu/Hf fractionation during the Mesoarchean relative to today, sampling of a continuum of compositions from two sources with distinct Hf-compositions, or the result of early diagenetic processes occurring soon after the deposition of the Moodies Group BIF. These results suggest that interpretation of ˜Hf and ˜Nd data from BIF is not as straightforward as previously suggested[2], and positive ˜Hf values are not necessarily indicative of emerged continental crust. [1] Flament et al. (2013), Precambrian Research, 229, 177-188. [2] Veihmann et al. (2014), Geology, 42, 115-118. [3] Bayon et al. (2006), Geology, 34, 433-436. [4] Vervoort et al. (2011), Geochimica et

The impact of sedimentary coatings on the diagenetic Nd flux

NASA Astrophysics Data System (ADS)

Abbott, April N.; Haley, Brian A.; McManus, James

2016-09-01

Because ocean circulation impacts global heat transport, understanding the relationship between deep ocean circulation and climate is important for predicting the ocean's role in climate change. A common approach to reconstruct ocean circulation patterns employs the neodymium isotope compositions of authigenic phases recovered from marine sediments. In this approach, mild chemical extractions of these phases is thought to yield information regarding the εNd of the bottom waters that are in contact with the underlying sediment package. However, recent pore fluid studies present evidence for neodymium cycling within the upper portions of the marine sediment package that drives a significant benthic flux of neodymium to the ocean. This internal sedimentary cycling has the potential to obfuscate any relationship between the neodymium signature recovered from the authigenic coating and the overlying neodymium signature of the seawater. For this manuscript, we present sedimentary leach results from three sites on the Oregon margin in the northeast Pacific Ocean. Our goal is to examine the potential mechanisms controlling the exchange of Nd between the sedimentary package and the overlying water column, as well as the relationship between the εNd composition of authigenic sedimentary coatings and that of the pore fluid. In our comparison of the neodymium concentrations and isotope compositions from the total sediment, sediment leachates, and pore fluid we find that the leachable components account for about half of the total solid-phase Nd, therefore representing a significant reservoir of reactive Nd within the sediment package. Based on these and other data, we propose that sediment diagenesis determines the εNd of the pore fluid, which in turn controls the εNd of the bottom water. Consistent with this notion, despite having 1 to 2 orders of magnitude greater Nd concentration than the bottom water, the pore fluid is still <0.001% of the total Nd reservoir in the

Mutual Dependence Between Sedimentary Organic Carbon and Infaunal Macrobenthos Resolved by Mechanistic Modeling

NASA Astrophysics Data System (ADS)

Zhang, Wenyan; Wirtz, Kai

2017-10-01

The mutual dependence between sedimentary total organic carbon (TOC) and infaunal macrobenthos is here quantified by a mechanistic model. The model describes (i) the vertical distribution of infaunal macrobenthic biomass resulting from a trade-off between nutritional benefit (quantity and quality of TOC) and the costs of burial (respiration) and mortality, and (ii) the variable vertical distribution of TOC being in turn shaped by bioturbation of local macrobenthos. In contrast to conventional approaches, our model emphasizes variations of bioturbation both spatially and temporally depending on local food resources and macrobenthic biomass. Our implementation of the dynamic interaction between TOC and infaunal macrobenthos is able to capture a temporal benthic response to both depositional and erosional environments and provides improved estimates of the material exchange flux at the sediment-water interface. Applications to literature data for the North Sea demonstrate the robustness and accuracy of the model and its potential as an analysis tool for the status of TOC and macrobenthos in marine sediments. Results indicate that the vertical distribution of infaunal biomass is shaped by both the quantity and the quality of OC, while the community structure is determined only by the quality of OC. Bioturbation intensity may differ by 1 order of magnitude over different seasons owing to variations in the OC input, resulting in a significant modulation on the distribution of OC. Our relatively simple implementation may further improve models of early diagenesis and marine food web dynamics by mechanistically connecting the vertical distribution of both TOC and macrobenthic biomass.

The potential for free and mixed convection in sedimentary basins

USGS Publications Warehouse

Raffensperger, Jeff P.; Vlassopoulos, D.

1999-01-01

Free thermal convection and mixed convection are considered as potential mechanisms for mass and heat transport in sedimentary basins. Mixed convection occurs when horizontal flows (forced convection) are superimposed on thermally driven flows. In cross section, mixed convection is characterized by convection cells that migrate laterally in the direction of forced convective flow. Two-dimensional finite-element simulations of variable-density groundwater flow and heat transport in a horizontal porous layer were performed to determine critical mean Rayleigh numbers for the onset of free convection, using both isothermal and semi-conductive boundaries. Additional simulations imposed a varying lateral fluid flux on the free-convection pattern. Results from these experiments indicate that forced convection becomes dominant, completely eliminating buoyancy-driven circulation, when the total forced-convection fluid flux exceeds the total flux possible due to free convection. Calculations of the thermal rock alteration index (RAI=q????T) delineate the patterns of potential diagenesis produced by fluid movement through temperature gradients. Free convection produces a distinct pattern of alternating positive and negative RAIs, whereas mixed convection produces a simpler layering of positive and negative values and in general less diagenetic alteration. ?? Springer-Verlag.

Geochemistry of approximately 1.9 Ga sedimentary rocks from northeastern Labrador, Canada

NASA Technical Reports Server (NTRS)

Hayashi, K. I.; Fujisawa, H.; Holland, H. D.; Ohmoto, H.

1997-01-01

source for most sedimentary rocks of the Ramah Group, except for black shales of the Nullataktok Formation. The black shales were apparently derived from Provenance II that was comprised mostly of felsic rocks with SiO2 contents approximately 65 wt%. Comparing the compositions of the Ramah Group sedimentary rocks and their source rocks, we have recognized that several major elements, especially Ca and Mg, were lost almost entirely from the source rocks during weathering and sedimentation. Sodium and potassium were also leached almost entirely during the weathering of the source rocks. However, significant amounts of Na were added to the black shales and K to all the rock types during diagenesis and/or regional metamorphism. The intensity of weathering of source rocks for the Ramah Group sediments was much higher than that of typical Phanerozoic sediments, possibly because of a higher PCO2 in the Proterozoic atmosphere. Compared to the source rock values, the Fe3+/Ti ratios of many of the graywackes and gray shales of the Ramah Group are higher, the Fe2+/Ti ratios are lower, and the sigma Fe/Ti ratios are the same. Such characteristics of the Fe geochemistry indicate that these sedimentary rocks are comprised of soils formed by weathering of source rocks under an oxygen-rich atmosphere. The atmosphere about 1.9 Ga was, therefore, oxygen rich. Typical black shales of Phanerozoic age exhibit positive correlations between the organic C contents and the concentrations of S, U, and Mo, because these elements are enriched in oxygenated seawater and are removed from seawater by organic matter in sediments. However, such correlations are not found in the Ramah Group sediments. Black shales of the Ramah Group contain 1.7-2.8 wt% organic C, but are extremely depleted in sigma Fe (<1 wt% as FeO), S (<0.3 wt%), U (approximately l ppm), Mo (<5 ppm), Ni (<2 ppm), and Co (approximately 0 ppm). This lack of correlation, however, does not imply that the approximately 1.9 Ga atmosphere

The organic geochemistry of black sedimentary barite: significance and implications of trapped fatty acids

USGS Publications Warehouse

Miller, R.E.; Brobst, D.A.; Beck, P.C.

1977-01-01

Fatty acids isolated in sedimentary black barite (BaSO4) from Arkansas and Nevada were identified by gas chromatography-mass spectroscopy. The dominant or major fatty acids found in these beds of barite are C16:0, C18:0, and C18:1. The occurrence and distribution of these acids in this type of rock may serve as "molecular fingerprints" of microbial biogeochemical processes. The organic matter and associated microorganisms are shown to be trapped within the finely crystalline barite, thus forming a closed system for microbial diagenesis. Important differences that occur in the distribution of the lesser or minor fatty acids probably result from: (1) the nature of the progenitor organic detritus in the environment of barite deposition: and (2) the subsequent degree of microbiological alteration of the parent organic debris swept into and trapped in the depositional environment. Three general models of sedimentary environments are proposed in which anoxic conditions may prevail and where barium sulfate (BaSO4) may precipitate: (1) in a silled basin with semi-restricted circulation; (2) on an outer continental shelf where the slope is encroached upon by water of the oxygen minimum layer; (3) on a low-energy, inner shelf or semi-restricted embayment impinged by a wedge of anoxic water. The major geochemical and geological parameters which are believed to be the significant factors controlling the formation and high grade of these organic-rich, black bedded barites are: (1) a unique source of barium-rich fluid that only contains trace amounts of other elements; (2) the presence of an anoxic bottom environment within the depositional basin; (3) a reflux source of sulfate ion; (4) an adequate source of organic matter. The results of this study may serve as guidelines for future exploration in similar, untested sedimentary basins, especially those with rocks of middle Paleozoic age. ?? 1977.

Spatial, temporal and geographic considerations of the problem of rock varnish diagenesis

NASA Astrophysics Data System (ADS)

Dorn, Ronald I.; Krinsley, David

2011-07-01

The rock varnish literature hosts an abundance of prima facie contradictory empirical data. Past and perhaps future empirical contradictions, however, can be resolved by theoretical considerations of different spatial and temporal scales of varnish diagenesis, as well as the geomorphic position of different types of varnishes. For example, twentieth-century contamination by lead and other heavy metals has led to claims of accumulation rates in the last century far more rapid than prior published empirical studies. A consideration of spatial scales resolves this contradiction; nanoscale processes allow migration of lead into varnish deposited well before the twentieth century time of heavy metal pollution. Evidence of nanometer-scale disequilibrium in three samples led to claims that varnish cannot be used in paleoclimatic research; these data rest in contrast to replicable patterns in varnish deposition observed by Dr. Tanzhuo Liu and others in over ten thousand micro-sedimentary basins. This contraction can be resolved by understanding that the types of varnishes studied differ and that processes differ substantially between the nanoscale and the micron scale. A lack of evidence of Mn-oxidizers in genetic analyses contrasts with culturing studies and in situ evidence of Mn-enhancement by bacteria. This contradiction has a likely resolution in vastly different temporal scales; DNA material analyzed may be no older than 200 years, but in situ fossilized remains of bacteria may be preserved for thousands of years recording palaeoecological conditions favoring growth of Mn-enhancing bacteria.

Texture-specific Si isotope variations in Barberton Greenstone Belt cherts record low temperature fractionations in early Archean seawater

NASA Astrophysics Data System (ADS)

Stefurak, Elizabeth J. T.; Fischer, Woodward W.; Lowe, Donald R.

2015-02-01

Sedimentary cherts are unusually abundant in early Archean (pre-3.0 Ga) sequences, suggesting a silica cycle that was profoundly different than the modern system. Previously applied for the purpose of paleothermometry, Si isotopes in ancient cherts can offer broader insight into mass fluxes and mechanisms associated with silica concentration, precipitation, diagenesis, and metamorphism. Early Archean cherts contain a rich suite of sedimentological and petrographic textures that document a history of silica deposition, cementation, silicification, and recrystallization. To add a new layer of insight into the chemistry of early cherts, we have used wavelength-dispersive spectroscopy and then secondary ion mass spectrometry (SIMS) to produce elemental and Si and O isotope ratio data from banded black-and-white cherts from the Onverwacht Group of the Barberton Greenstone Belt, South Africa. This geochemical data is then interpreted in the framework of depositional and diagenetic timing of silica precipitation provided by geological observations. SIMS allows the comparison of Si and O isotope ratios of distinct silica phases, including black carbonaceous chert beds and bands (many including well-defined sedimentary grains), white relatively pure chert bands including primary silica granules, early cavity-filling cements, and later quartz-filled veins. Including all chert types and textures analyzed, the δ30Si dataset spans a range from -4.78‰ to +3.74‰, with overall mean 0.20‰, median 0.51‰, and standard deviation 1.30‰ (n = 1087). Most samples have broadly similar δ30Si distributions, but systematic texture-specific δ30Si differences are observed between white chert bands (mean +0.60‰, n = 750), which contain textures that represent primary and earliest diagenetic silica phases, and later cavity-filling cements (mean -1.41‰, n = 198). We observed variations at a ∼100 μm scale indicating a lack of Si isotope homogenization at this scale during

Assessing the potential of amino acid 13C patterns as a carbon source tracer in marine sediments: effects of algal growth conditions and sedimentary diagenesis

NASA Astrophysics Data System (ADS)

Larsen, T.; Bach, L. T.; Salvatteci, R.; Wang, Y. V.; Andersen, N.; Ventura, M.; McCarthy, M. D.

2015-08-01

Burial of organic carbon in marine sediments has a profound influence in marine biogeochemical cycles and provides a sink for greenhouse gases such as CO2 and CH4. However, tracing organic carbon from primary production sources as well as its transformations in the sediment record remains challenging. Here we examine a novel but growing tool for tracing the biosynthetic origin of amino acid carbon skeletons, based on naturally occurring stable carbon isotope patterns in individual amino acids (δ13CAA). We focus on two important aspects for δ13CAA utility in sedimentary paleoarchives: first, the fidelity of source diagnostic of algal δ13CAA patterns across different oceanographic growth conditions, and second, the ability of δ13CAA patterns to record the degree of subsequent microbial amino acid synthesis after sedimentary burial. Using the marine diatom Thalassiosira weissflogii, we tested under controlled conditions how δ13CAA patterns respond to changing environmental conditions, including light, salinity, temperature, and pH. Our findings show that while differing oceanic growth conditions can change macromolecular cellular composition, δ13CAA isotopic patterns remain largely invariant. These results emphasize that δ13CAA patterns should accurately record biosynthetic sources across widely disparate oceanographic conditions. We also explored how δ13CAA patterns change as a function of age, total nitrogen and organic carbon content after burial, in a marine sediment core from a coastal upwelling area off Peru. Based on the four most informative amino acids for distinguishing between diatom and bacterial sources (i.e., isoleucine, lysine, leucine and tyrosine), bacterially derived amino acids ranged from 10 to 15 % in the sediment layers from the last 5000 years, and up to 35 % during the last glacial period. The greater bacterial contributions in older sediments indicate that bacterial activity and amino acid resynthesis progressed, approximately as a

Numerical modelling of fluid-rock interactions: Lessons learnt from carbonate rocks diagenesis studies

NASA Astrophysics Data System (ADS)

Nader, Fadi; Bachaud, Pierre; Michel, Anthony

2015-04-01

Quantitative assessment of fluid-rock interactions and their impact on carbonate host-rocks has recently become a very attractive research topic within academic and industrial realms. Today, a common operational workflow that aims at predicting the relevant diagenetic processes on the host rocks (i.e. fluid-rock interactions) consists of three main stages: i) constructing a conceptual diagenesis model including inferred preferential fluids pathways; ii) quantifying the resulted diagenetic phases (e.g. depositing cements, dissolved and recrystallized minerals); and iii) numerical modelling of diagenetic processes. Most of the concepts of diagenetic processes operate at the larger, basin-scale, however, the description of the diagenetic phases (products of such processes) and their association with the overall petrophysical evolution of sedimentary rocks remain at reservoir (and even outcrop/ well core) scale. Conceptual models of diagenetic processes are thereafter constructed based on studying surface-exposed rocks and well cores (e.g. petrography, geochemistry, fluid inclusions). We are able to quantify the diagenetic products with various evolving techniques and on varying scales (e.g. point-counting, 2D and 3D image analysis, XRD, micro-CT and pore network models). Geochemical modelling makes use of thermodynamic and kinetic rules as well as data-bases to simulate chemical reactions and fluid-rock interactions. This can be through a 0D model, whereby a certain process is tested (e.g. the likelihood of a certain chemical reaction to operate under specific conditions). Results relate to the fluids and mineral phases involved in the chemical reactions. They could be used as arguments to support or refute proposed outcomes of fluid-rock interactions. Coupling geochemical modelling with transport (reactive transport model; 1D, 2D and 3D) is another possibility, attractive as it provides forward simulations of diagenetic processes and resulting phases. This

Prediction of sedimentary facies of x-oilfield in northwest of China by geostatistical inversion

NASA Astrophysics Data System (ADS)

Lei, Zhao; Ling, Ke; Tingting, He

2017-03-01

In the early stage of oilfield development, there are only a few wells and well spacing can reach several kilometers. for the alluvial fans and other heterogeneous reservoirs, information from wells alone is not sufficient to derive detailed reservoir information. In this paper, the method of calculating sand thickness through geostatistics inversion is studied, and quantitative relationships between each sedimentary micro-facies are analyzed by combining with single well sedimentary facies. Further, the sedimentary facies plane distribution based on seismic inversion is obtained by combining with sedimentary model, providing the geological basis for the next exploration and deployment.

The Early Toarcian Oceanic Anoxic Event and its sedimentary record in Switzerland

NASA Astrophysics Data System (ADS)

Fantasia, Alicia; Föllmi, Karl B.; Adatte, Thierry; Spangenberg, Jorge E.; Montero-Serrano, Jean-Carlos

2015-04-01

In the Jurassic period, the Early Toarcian Oceanic Anoxic Event (T-OAE), about 183 Ma ago, was a global perturbation of paleoclimatic and paleoenvironmental conditions. This episode was associated with a crisis in marine carbonate accumulation, climate warming, an increase in sea level, ocean acidification, enhanced continental weathering, whereas organic-rich sediments are noticeable for example in the Atlantic and in the Tethys. This episode is associated with a negative carbon excursion, which is recorded both in marine and terrestrial environments. The cause(s) of this environmental crisis remain(s) still controversial. Nevertheless, the development of negative δ13C excursions is commonly interpreted as due to the injection of isotopically-light carbon associated with gas hydrate dissociation, the thermal metamorphism of carbon-rich sediments and input of thermogenic and volcanogenic carbon related to the formation of the Karoo-Ferrar basaltic province in southern Gondwana (Hesselbo et al., 2000, 2007; Beerling et al., 2002; Cohen et al., 2004, 2007; McElwain et al., 2005, Beerling and Brentnall, 2007; Svensen et al., 2007; Hermoso et al., 2009, 2012; Mazzini et al., 2010). Several studies of the T-OAE have been conducted on sediments in central and northwest Europe, but only few data are available concerning the Swiss sedimentary records. Therefore, we focused on two sections in the Jura Plateau (canton Aargau): the Rietheim section (Montero-Serrano et al., submitted) and the Gipf section (current study). A multidisciplinary approach has been chosen and the tools to be used are based on sedimentological observations (sedimentary condensation, etc.), biostratigraphy, mineralogy (bulk-rock composition), facies and microfacies analysis (presence or absence of benthos), clay-mineralogy composition (climatic conditions), major and trace-element analyses (productivity, redox conditions, etc.), phosphorus (trophic levels, anoxia), carbon isotopes and organic

Middle to Upper Jurassic sedimentary sequences and marine biota of the early Indian Ocean (Southwest Madagascar): some biostratigraphic, palaeoecologic and palaeobiogeographic conclusions

NASA Astrophysics Data System (ADS)

Mette, Wolfgang

2004-03-01

As part of an intradisciplinary project which was concerned with the early rifting processes between Madagascar and East Africa, the Middle to Upper Jurassic sedimentary sequences of the Morondava Basin in Southwest Madagascar has been investigated with respect to biostratigraphy, sedimentary facies and palaeoecology. The transgressive sedimentary sections in the Bajocian and Callovian-Oxfordian yield rich macro- and microfossil assemblages which improved the biostratigraphic framework and gave some important information about the palaeoenvironments. Palaeogeographic distribution patterns of the Bajocian ostracod Paradoxorhyncha are suggestive of a migration along the southern shores of Gondwana between Madagascar, Australia and South America. The Callovian ostracods show strong affinities to the Indian faunas, indicating existence of a free migration route for shallow marine benthic organisms between Madagascar and India. Significant faunal differences between Madagascar and Tanzania suggest a physical or environmental migration barrier between Madagascar and East Africa during the Callovian to Kimmeridgian interval. The Upper Jurassic ostracods from the northern and eastern margin of Gondwana show a very high degree of endemism and they can be assigned to two faunal provinces in North Gondwana (Arabia, Near East, North Africa) and South Gondwana (India, Madagascar, East Africa).

Shoreline deposits and diagenesis resulting from two Late Pleistocene highstands near +5 and +6 metres, Durban, South Africa

USGS Publications Warehouse

Cooper, J.A.G.; Flores, R.M.

1991-01-01

In exposures of Pleistocene rocks on the east coast of South Africa, eight sedimentary facies were distinguished on the basis of petrology, grain size, internal structures and field relationships. These are interpreted as deposits of surf zone, breaker zone, swash zone, backbeach, boulder beach and dune environments. Three phases of deposition and diagenesis are recognized. As a result of the stabilising effect of pre-existing coastal facies, the deposits from successive sea level stands are stacked vertically in a narrow coast-normal strip. Early cementation prevented erosion of the deposits during subsequent transgressions. Deposition of subsequent facies took place on an existing coastal dune (Facies 1). A terrace was cut into this dune at a sea level 4.5 to 5 m above present. At this sea level, clastic shoreline sediments were deposited which make up the main sedimentary sequence exposed (Facies 2-7). The steep swash zone, coarse grain size, and comparison with modern conditions in the study area indicate clastic deposition on a high-energy, wave-dominated, microtidal coastline. Vertical stacking of progressively shallower water facies indicates progradation associated with slightly regressive conditions, prior to stranding of the succession above sea level. During a subsequent transgression to 5.5 or 6 m above present sea level, a second terrace was cut across the existing facies, which by then were partly lithified. A boulder beach (Facies 8) deposited on this terrace is indicative of high wave energy and a rocky coastline, formed by existing cemented coastal facies. Comparison with dated deposits from other parts of the South African coast suggest a Late Pleistocene age for Facies 2-8. Deposition was terminated by subsequent regression and continuing low sea levels during the remainder of the Pleistocene. Cementation of the facies took place almost entirely by carbonate precipitation. The presence of isopachous fibrous cements suggests early cementation of

Fluid-flow, diagenesis and generation of secondary porosity-permeability in the Cretaceous Jandaira Formation, Brazil - an analogue of karstified carbonate reservoirs

NASA Astrophysics Data System (ADS)

Bezerra, F. H.; Cazarin, C. L.; Srivastava, N. K.

2017-12-01

This study investigates the diagenetic processes that generated secondary porosity-permeability in carbonates. Our study area is the Jandaira Formation, a post-rift unit, 50-700 m thick, which occurs over an area of 70 x 260 km in the Potiguar Basin, Equatorial margin of Brazil. The Jandaira Formation formed in the Turonian-Campanian and is the major exposed Cretaceous carbonate platform in the eastern continental margin of South America. Little folding and nearly flat-lying layers characterize this unit. We used a multidisciplinary approach, which included drone imagery, petrographic, petrophysical, petrological, and structural studies. Our results indicate that several levels of dissolution occurred in mudstone, grainstone, and wackestone facies along faults, fractures, and bedding planes. Fracture and faults provided vertical leaching pathways and sedimentary bedding provided horizontal pathways of increased secondary porosity and permeability. Dissolution resulted in a multi-scale karst system that could reach voids 5 m wide and 1 km long. Dissolution mostly affect the dolomitized sedimentary facies in the form of vugular, moldic, interparticular, and intercrystalline porosity. It also generated a new modified facies that we defined as karstified facies. Dissolution increased permeability in carbonate rocks from primary values of 0.0-0.94 mD to as much as 1370.11 mD. Micritization, lixiviation of evaporites, meteoric water infiltration and dolomitization during late diagenesis could have triggered dissolution processes. The Jandaira Formation serves as an analog of fractured and karstified carbonate reservoirs, where faults, joints, and bedding acted as pathways of high permeability.

Seismic Characterization of Silica Diagenesis in the Northwestern Pacific

NASA Astrophysics Data System (ADS)

Greene, J. A.; Lizarralde, D.; Tominaga, M.; Tivey, M.

2017-12-01

We use seismic reflection data to investigate the silica diagenesis that converted siliceous ooze into the widespread chert/porcellanite layer in the northwestern Pacific. In particular, we investigate whether this process is currently ongoing in the oldest lithosphere of the Pacific. We present images of seismic reflection data collected during the R/V Thomas G. Thompson cruise TN272 and processed using a velocity model constructed from concurrently collected sonobuoy refraction data, applying a normal moveout correction and stack, post-stack Kirchhoff time migration, and predictive gap deconvolution. We compare our seismic observations of the chert/porcellanite layer with nearby drill holes and analogous studies of silica diagenesis around the world. In the processed seismic data, we identify a previously unobserved short-wavelength depth variation to a prominent reflector representing the top of the chert/porcellanite layer, with a vertical change in this horizon of 20 m. This short-wavelength character is in contrast to the flat, seafloor parallel character more typical of the regional chert/porcellanite reflector and may be indicative of the active transformation of siliceous ooze to chert/porcellanite. Drill results in the northwestern Pacific document little to no siliceous ooze above the chert/porcellanite layer; however, they have extremely low recovery rates that could have failed to sample this sediment. No folding or reflector offsets indicative of faulting are observed above or below the short-wave character of the chert/porcellanite reflector, suggesting a structural origin is unlikely, nor are the surrounding reflectors disturbed, as would be expected if these features were caused by fluid expulsion. Instead, the short-wavelength depth variation in the chert/porcellanite layer may be the result of differential advancement of the silica diagenetic front where the siliceous ooze to chert/porcellanite reaction locally occurs in shallower sediments, as

Tectonic Impact on the Sedimentary Magnetic Record in Active Margin Settings

NASA Astrophysics Data System (ADS)

Riedinger, N.; Torres, M. E.; Solomon, E. A.

2017-12-01

difference in the magnetic susceptibility records at the two sites can be linked to in situ diagenesis potentially caused by differences in their histories of subsidence and uplift. This highlights the importance of understanding both the tectonic and digenetic history of sedimentary settings prior the application of proxy tools such as magnetic susceptibility.

Experimental Approaches to Understanding Surficial Processes on Mars: The Stony Brook Experience 2000-2016

NASA Astrophysics Data System (ADS)

McLennan, S. M.; Dehouck, E.; Hurowitz, J.; Lindsley, D. H.; Schoonen, M. A.; Tosca, N. J.; Zhao, Y. Y. S.

2016-12-01

Starting with Pathfinder and Global Surveyor, recent missions to Mars have provided great opportunity for low-temperature experimental geochemistry investigations of the Martian sedimentary record by providing geochemical and mineralogical data that can be used as meaningful tests for experiments. These missions have documented a long-lived, complex and dynamic sedimentary rock cycle, including "source-to-sink" sedimentary systems and global paleoenvironmental transitions through time. We designed and constructed an experimental facility, beginning in 2000, specifically to evaluate surficial processes on Mars. Our experimental philosophy has been to (1) keep apparatus simple and flexible, and if feasible maintain sample access during experiments; (2) use starting materials (minerals, rocks) close to known Mars compositions (often requiring synthesis); (3) address sedimentary processes supported by geological investigations at Mars; (4) begin with experiments at standard conditions so they are best supported by thermodynamics; (5) support experiments with thermodynamic-kinetic-mass balance modeling in both design and interpretation, and by high quality chemical, mineralogical and textural lab analyses; (6) interpret results in the context of measurements made at Mars. Although eliciting much comment in proposal and manuscript reviews, we have not attempted to slavishly maintain "Mars conditions", doing so only to the degree required by variables being tested in any given experiments. Among the problems we have addressed are (1) Amazonian alteration of rock surfaces; (2) Noachian-Hesperian chemical weathering; (3) epithermal alteration of `evolved' igneous rocks; (4) mineral surface chemical reactivity from aeolian abrasion; (5) evaporation of mafic brines; (6) early diagenesis of sedimentary iron mineralogy; (7) trace element and halogen behavior during chemical weathering and diagenesis; (8) photochemical influences on halogen distribution and speciation; (9) post

The 2.1 Ga old Francevillian biota: biogenicity, taphonomy and biodiversity.

PubMed

El Albani, Abderrazak; Bengtson, Stefan; Canfield, Donald E; Riboulleau, Armelle; Rollion Bard, Claire; Macchiarelli, Roberto; Ngombi Pemba, Lauriss; Hammarlund, Emma; Meunier, Alain; Moubiya Mouele, Idalina; Benzerara, Karim; Bernard, Sylvain; Boulvais, Philippe; Chaussidon, Marc; Cesari, Christian; Fontaine, Claude; Chi-Fru, Ernest; Garcia Ruiz, Juan Manuel; Gauthier-Lafaye, François; Mazurier, Arnaud; Pierson-Wickmann, Anne Catherine; Rouxel, Olivier; Trentesaux, Alain; Vecoli, Marco; Versteegh, Gerard J M; White, Lee; Whitehouse, Martin; Bekker, Andrey

2014-01-01

The Paleoproterozoic Era witnessed crucial steps in the evolution of Earth's surface environments following the first appreciable rise of free atmospheric oxygen concentrations ∼2.3 to 2.1 Ga ago, and concomitant shallow ocean oxygenation. While most sedimentary successions deposited during this time interval have experienced thermal overprinting from burial diagenesis and metamorphism, the ca. 2.1 Ga black shales of the Francevillian B Formation (FB2) cropping out in southeastern Gabon have not. The Francevillian Formation contains centimeter-sized structures interpreted as organized and spatially discrete populations of colonial organisms living in an oxygenated marine ecosystem. Here, new material from the FB2 black shales is presented and analyzed to further explore its biogenicity and taphonomy. Our extended record comprises variably sized, shaped, and structured pyritized macrofossils of lobate, elongated, and rod-shaped morphologies as well as abundant non-pyritized disk-shaped macrofossils and organic-walled acritarchs. Combined microtomography, geochemistry, and sedimentary analysis suggest a biota fossilized during early diagenesis. The emergence of this biota follows a rise in atmospheric oxygen, which is consistent with the idea that surface oxygenation allowed the evolution and ecological expansion of complex megascopic life.

Prolonged carbonate diagenesis under an evolving late cenozoic climate; Nullarbor Plain, southern Australia

NASA Astrophysics Data System (ADS)

Miller, Cody R.; James, Noel P.; Bone, Yvonne

2012-06-01

The Nullarbor Plain in southern Australia, the largest areal karst on the globe, is a ~ 240,000 km2 uplifted succession of Cenozoic marine carbonates whose surface has been exposed for 14 to 15 m.y. The middle Miocene Nullarbor Limestone forms the upper surface of the plain and hosts a complex and prolonged record of meteoric diagenesis. Such a complete record offers unique insights into the effects of climate, tectonics, sea level, topography, and hydrology on the style and placement of numerous diagenetic events in flat low lying carbonate plains. Alteration took place during three broad phases comprising eight stages that are interpreted to have formed against a background of dramatic climate change. Middle Miocene phase one diagenesis took place under a humid climate and resulted in rapid mineral equilibration, calcite cementation, extensive karst development, and finally widespread lacustrine and palustrine sedimentation. Resultant palustrine sediments, especially terrestrial ooids, are now preserved at the surface and in underlying karst cavities. Latest middle Miocene to middle Pliocene phase two diagenesis occurred during a prolonged period (~ 8 m.y.) of temperate climate and resulted in initial deep cave dissolution during low sea levels and later shallow cave development in the course of a high sea level. Onset of a somewhat more arid climate in the latest Pliocene led to the development of the modern desolate landscape of the Plain. This final phase of diagenesis involved creation of solution pits filled with black limestone pebbles, open and closed dolines with associated colluvium fill, and pervasive pedogenic calcrete. The Nullarbor Plain demonstrates that low lying carbonate plains can have low surficial erosion rates, precisely record relative sea level positions, be able to have extensive caves with extended periods of arrested calcite precipitation, and finally host extensive terrestrial ooid deposits. The importance of this comprehensive

Microbial Paleontology, Mineralogy and Geochemistry of Modern and Ancient Thermal Spring Deposits and Their Recognition on the Early Earth and Mars"

NASA Technical Reports Server (NTRS)

Farmer, Jack D.

2004-01-01

The vision of this project was to improve our understanding of the processes by which microbiological information is captured and preserved in rapidly mineralizing sedimentary environments. Specifically, the research focused on the ways in which microbial mats and biofilms influence the sedimentology, geochemistry and paleontology of modem hydrothermal spring deposits in Yellowstone national Park and their ancient analogs. Toward that goal, we sought to understand how the preservation of fossil biosignatures is affected by 1) taphonomy- the natural degradation processes that affect an organism from the time of its death, until its discovery as a fossil and 2) diagenesis- longer-term, post-depositional processes, including cementation and matrix recrystallization, which collectively affect the mineral matrix that contains fossil biosignature information. Early objectives of this project included the development of observational frameworks (facies models) and methods (highly-integrated, interdisciplinary approaches) that could be used to explore for hydrothermal deposits in ancient terranes on Earth, and eventually on Mars.

Phosphorus cycling in the Early Aptian

NASA Astrophysics Data System (ADS)

Oakes, R.; Dittrich, M.; Wortmann, U. G.

2012-12-01

Phosphorus is an essential nutrient for living organisms. It is vital for the formation of ATP, the energy store in cells, and is needed for DNA synthesis. Seawater phosphorus concentration therefore plays a critical role in controlling marine productivity on geological timescales. The majority of research on the P cycle focuses on modern lacustrine and marine settings. This follows the necessity to gain a further understanding on the effects of agricultural fertilisers on nutrient cycling; in particular on the mechanisms which lead to eutrophication. These studies use sequential extraction to determine the speciation of P. The results suggest that bottom sediments can act as both a source and a sink of phosphorus; the role they assume depends on range of factors including bottom water oxygen concentrations, sedimentation rate and the concentration of iron. This study applies a sequential extraction method developed in modern sediments to sediments from the Early Cretaceous, specifically the Early Aptian. During this time, globally synchronous oceanic anoxic events (OAE's) appear in the rock record. It has been suggested that these events represent an increase in marine productivity combined with bottom water anoxia. Our study investigates whether the speciation of sedimentary phosphorus can be used to reconstruct P cycling at this time. Our samples are taken from pre-, syn- and post-OAE1a but are not from the organic matter rich layers. Our results show that the original fractions of phosphorus have been altered during diagenesis with the majority of phosphorus now being preserved as either apatite (Ca-P) or phosphorus in organic matter (Porg). The dominance of Ca-P is expected as it is thought that redox-sensitive forms of P undergo 'sink switching' during diagenesis and are preserved as Ca-P. The high concentration of Porg however, differs from previous studies which generally find that Ca-P or iron (oxyhydr)oxide associated phosphorus (Fe-P) are dominant

Stable Carbon and Nitrogen Isotopes in a Peat Profile Are Influenced by Early Stage Diagenesis and Changes in Atmospheric CO(2) and N Deposition.

PubMed

Esmeijer-Liu, Alice J; Kürschner, Wolfram M; Lotter, André F; Verhoeven, Jos T A; Goslar, Tomasz

2012-06-01

In this study, we test whether the δ(13)C and δ(15)N in a peat profile are, respectively, linked to the recent dilution of atmospheric δ(13)CO(2) caused by increased fossil fuel combustion and changes in atmospheric δ(15)N deposition. We analysed bulk peat and Sphagnum fuscum branch C and N concentrations and bulk peat, S. fuscum branch and Andromeda polifolia leaf δ(13)C and δ(15)N from a 30-cm hummock-like peat profile from an Aapa mire in northern Finland. Statistically significant correlations were found between the dilution of atmospheric δ(13)CO(2) and bulk peat δ(13)C, as well as between historically increasing wet N deposition and bulk peat δ(15)N. However, these correlations may be affected by early stage kinetic fractionation during decomposition and possibly other processes. We conclude that bulk peat stable carbon and nitrogen isotope ratios may reflect the dilution of atmospheric δ(13)CO(2) and the changes in δ(15)N deposition, but probably also reflect the effects of early stage kinetic fractionation during diagenesis. This needs to be taken into account when interpreting palaeodata. There is a need for further studies of δ(15)N profiles in sufficiently old dated cores from sites with different rates of decomposition: These would facilitate more reliable separation of depositional δ(15)N from patterns caused by other processes. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11270-011-1001-8) contains supplementary material, which is available to authorized users.

The formation of magnetite in the early Archean oceans

NASA Astrophysics Data System (ADS)

Li, Yi-Liang; Konhauser, Kurt O.; Zhai, Mingguo

2017-05-01

Banded iron formations (BIFs) are iron- and silica-rich chemical sedimentary rocks that were deposited throughout much of the Precambrian. The biological oxidation of dissolved Fe(II) led to the precipitation of a ferric oxyhydroxide phase, such as ferrihydrite, in the marine photic zone. Upon burial, ferrihydrite was either transformed into hematite through dehydration or it was reduced to magnetite via biological or abiological Fe(III) reduction coupled to the oxidation of buried microbial biomass. However, it has always been intriguing as to why the oldest BIFs are characteristically magnetite-rich, while BIFs formed after the Neoarchean are dominated by hematite. Here, we propose that some magnetite in early Archean BIF could have precipitated directly from seawater through the reaction of settling ferrihydrite and hot, Fe(II)-rich hydrothermal fluids that existed in the deeper waters. We conducted experiments that showed the reaction of Fe(II) with biogenic ferric iron mats under strict anoxic conditions lead to the formation of a metastable green rust phase that within hours transformed into magnetite. Our model further posits that with the progressive cooling and oxidation of the Earth's oceans, the above reaction shuts off, and magnetite was subsequently restricted to reactions associated with diagenesis and metamorphism.

Sedimentary characteristics and depositional model of a Paleocene-Eocene salt lake in the Jiangling Depression, China

NASA Astrophysics Data System (ADS)

Yu, Xiaocan; Wang, Chunlian; Liu, Chenglin; Zhang, Zhaochong; Xu, Haiming; Huang, Hua; Xie, Tengxiao; Li, Haonan; Liu, Jinlei

2015-11-01

We studied the sedimentary characteristics of a Paleocene-Eocene salt lake in the Jiangling Depression through field core observation, thin section identification, scanning electron microscopy, and X-ray diffraction analysis. On the basis of sedimentary characteristics we have summarized the petrological and mineralogical characteristics of the salt lake and proposed 9 types of grade IV salt rhythms. The deposition shows a desalting to salting order of halite-argillaceous-mudstone-mud dolostonemud anhydrock-glauberite-halite. The relationship among grade IV rhythms, water salinity and climate fluctuations was analyzed. Based on the analysis of the relationship between boron content and mudstone color and by combining the mineralogy and sedimentary environment characteristics, we propose that the early and late Paleocene Shashi Formation in the Jiangling Depression was a paleolacustrine depositional environment with a high salt content, which is a representation of the shallow water salt lake depositional model. The middle Paleocene Shashi Formation and the early Eocene Xingouzui Formation were salt and brackish sedimentary environments with low salt content in a deep paleolake, which represents a deep salt lake depositional model.

Co-diagenesis of iron and phosphorus in hydrothermal sediments from the southern East Pacific Rise: Implications for the evaluation of paleoseawater phosphate concentrations

NASA Astrophysics Data System (ADS)

Poulton, Simon W.; Canfield, Donald E.

2006-12-01

We present a detailed study of the co-diagenesis of Fe and P in hydrothermal plume fallout sediments from ˜19°S on the southern East Pacific Rise. Three distal sediment cores from 340-1130 km from the ridge crest, collected during DSDP Leg 92, were analysed for solid phase Fe and P associations using sequential chemical extraction techniques. The sediments at all sites are enriched in hydrothermal Fe (oxyhydr)oxides, but during diagenesis a large proportion of the primary ferrihydrite precipitates are transformed to the more stable mineral form of goethite and to a lesser extent to clay minerals, resulting in the release to solution of scavenged P. However, a significant proportion of this P is retained within the sediment, by incorporation into secondary goethite, by precipitation as authigenic apatite, and by readsorption to Fe (oxyhydr)oxides. Molar P/Fe ratios for these sediments are significantly lower than those measured in plume particles from more northern localities along the southern East Pacific Rise, and show a distinct downcore decrease to a depth of ˜12 m. Molar P/Fe ratios are then relatively constant to a depth of ˜35 m. The Fe and P speciation data indicate that diagenetic modification of the sediments is largely complete by a depth of 2.5 m, and thus depth trends in molar P/Fe ratios can not solely be explained by losses of P from the sediment by diffusion to the overlying water column during early diagenesis. Instead, these sediments are likely recording changes in dissolved P concentrations off the SEPR, possibly as a result of redistribution of nutrients in response to changes in oceanic circulation over the last 10 million years. Furthermore, the relatively low molar P/Fe ratios observed throughout these sediments are not necessarily solely due to losses of scavenged P by diffusion to the overlying water column during diagenesis, but may also reflect post-depositional oxidation of pyrite originating from the volatile-rich vents of the

Neoproterozoic-Early Paleozoic Peri-Pacific Accretionary Evolution of the Mongolian Collage System: Insights From Geochemical and U-Pb Zircon Data From the Ordovician Sedimentary Wedge in the Mongolian Altai

NASA Astrophysics Data System (ADS)

Jiang, Y. D.; Schulmann, K.; Kröner, A.; Sun, M.; Lexa, O.; Janoušek, V.; Buriánek, D.; Yuan, C.; Hanžl, P.

2017-11-01

Neoproterozoic to early Paleozoic accretionary processes of the Central Asian Orogenic Belt have been evaluated so far mainly using the geology of ophiolites and/or magmatic arcs. Thus, the knowledge of the nature and evolution of associated sedimentary prisms remains fragmentary. We carried out an integrated geological, geochemical, and zircon U-Pb geochronological study on a giant Ordovician metasedimentary succession of the Mongolian Altai Mountains. This succession is characterized by dominant terrigenous components mixed with volcanogenic material. It is chemically immature, compositionally analogous to graywacke, and marked by significant input of felsic to intermediate arc components, pointing to an active continental margin depositional setting. Detrital zircon U-Pb ages suggest a source dominated by products of early Paleozoic magmatism prevailing during the Cambrian-Ordovician and culminating at circa 500 Ma. We propose that the Ordovician succession forms an "Altai sedimentary wedge," the evolution of which can be linked to the geodynamics of the margins of the Mongolian Precambrian Zavhan-Baydrag blocks. This involved subduction reversal from southward subduction of a passive continental margin (Early Cambrian) to the development of the "Ikh-Mongol Magmatic Arc System" and the giant Altai sedimentary wedge above a north dipping subduction zone (Late Cambrian-Ordovician). Such a dynamic process resembles the tectonic evolution of the peri-Pacific accretionary Terra Australis Orogen. A new model reconciling the Baikalian metamorphic belt along the southern Siberian Craton with peri-Pacific Altai accretionary systems fringing the Mongolian microcontinents is proposed to explain the Cambro-Ordovician geodynamic evolution of the Mongolian collage system.

On diagenesis, dolomitisation and mineralisation in the Irish Zn-Pb orefield

NASA Astrophysics Data System (ADS)

Wilkinson, Jamie J.

2003-12-01

Marine calcite cementation and lithification of Carboniferous carbonate sediments hosting Zn-Pb mineralisation in the Irish orefield occurred at or near the seafloor. A relatively early, fine-grained, grey replacive dolomite, preferentially developed in micrite, is widely developed in the Waulsortian Limestone Formation, the main host to mineralisation, and is pervasive in the southeastern Midlands in proximity to the Leinster Massif. This dolomite formed after the first four main stages of calcite cementation but probably also developed within tens of metres of the seafloor as evidenced by incorporation of clasts of dolomite in intraformational sedimentary breccias. Later, coarse-grained white dolomite preferentially replaced coarser components of the Waulsortian Limestone and infilled residual vuggy porosity. Whilst some of this coarse dolomite may be related to the fine replacive dolomite event, a common spatial association with fault zones, coupled with primary fluid inclusion data, suggest that a significant proportion of this phase precipitated during the onset of fault-controlled subsidence and widespread hydrothermal circulation within the Irish Midlands area. Fluids up to ~250 °C and 10-15 wt% NaCl equivalent, sourced from a Lower Palaeozoic basement-equilibrated fluid reservoir, infiltrated the carbonate sequence via faults and fractures. The more localised development of dolomite-cemented breccias (white matrix breccias) that are frequently associated spatially with mineralisation was a consequence of the increased focusing of these hydrothermal fluids. Ore formation was broadly synchronous with development of the white dolomite breccias but only happened where mixing occurred between the hydrothermal ore-fluids and localised, near-surface reservoirs of low-temperature, H2S-rich brine. In the Waulsortian, this process led to the precipitation of a distinctive black dolomite that forms a broad halo to massive sulphides. Although ore-stage sulphides

Diagenesis of Upper Carboniferous rocks in the Ouachita foreland shelf in mid-continent USA: an overview of widespread effects of a Variscan-equivalent orogeny

USGS Publications Warehouse

Walton, A.W.; Wojcik, K.M.; Goldstein, R.H.; Barker, C.E.

1995-01-01

Diagenesis of Upper Carboniferous foreland shelf rocks in southeastern Kansas took place at temperatures as high as 100-150?? C at a depth of less than 2 km. High temperatures are the result of the long distance (hundreds of kilometers) advection of groundwater related to collisional orogeny in the Ouachita tectonic belt to the south. Orogenic activity in the Ouachita area was broadly Late Carboniferous, equivalent to the Variscan activity of Europe. Mississippi Valley-type Pb-Zn deposits and oil and gas fields in the US midcontinent and elsewhere are commonly attributed to regional groundwater flow resulting from such collisional events. This paper describes the diagenesis and thermal effects in sandstone and limestone of Upper Carboniferous siliciclastic and limestone-shale cyclothems, the purported confining layer of a supposed regional aquifer. Diagenesis took place in early, intermediate, and late stages. Many intermediate and late stage events in the sandstones have equivalents in the limestones, suggesting that the causes were regional. The sandstone paragenesis includes siderite cement (early stage), quartz overgrowths (intermediate stage), dissolution of feldspar and carbonates, followed by minor Fe calcite, pore-filling kaolinite and sub-poikilotopic Ca ankerite (late stage). The limestone paragenesis includes calcite cement (early stage); megaquartz, chalcedony, and Fe calcite spar (intermediate stage); and dissolution, Ca-Fe dolomite and kaolinite (late stage). The Rm value of vitrinite shows a regional average of 0.6-0.7%; Rock-Eval TmaX suggests a comparable degree of organic maturity. The Th of aqueous fluid inclusions in late stage Ca-Fe-Mg carbonates ranges from 90 to 160?? and Tmice indicates very saline water (>200000 ppm NaCl equivalent); ??18O suggests that the water is of basinal origin. Local warm spots have higher Rm, Tmax, and Th. The results constrain numerical models of regional fluid migration, which is widely viewed as an artesian flow

Diagenesis, not biogenesis: Two late Roman skeletal examples.

PubMed

Zapata, J; Pérez-Sirvent, C; Martínez-Sánchez, M J; Tovar, P

2006-10-01

Bone element analysis of two Late Roman populations from coastal south-eastern Spain suggests significant diagenesis. Trace element levels, in particular elevated Sr, Pb, Al, Mn, and the Ca/P ratio indicate post-mortem changes in the composition of the bones, preventing use of the data for dietary reconstructions, as well as for the investigation of the different individuals' health conditions, or of links between diet, health and skeletal indicators of growth stress. Such diagenetic biases are more widespread than usually recognized; paleodietary and paleoenvironmental inferences derived from the chemistry of archaeological bones need to be critically assessed.

Major Perspectives of The Dfg-research Programm (schwerpunktprogramm) Dynamics of Sedimentary Systems Under Varying Stress Conditions By Example of The Central European Basin-system

NASA Astrophysics Data System (ADS)

Bayer, U.; Littke, R.; Gajewski, D.; Brink, H.-J.

In 2001 a major research program "Dynamics of Sedimentary Systems under Varying Stress Conditions" has been established by the German Science Foundation (DFG). The programme effectively will start early in 2002 and in some sense provides a continuation of the EUROPROBE project TESZ. However, it will focus mainly on post-Paleozoic processes. The following sub-themes for this programme capture a wide range of areas of interest, calling for interdisciplinary research: 1. Structure and evolution of the crust. This topic will be based on the three- dimensional structural interpretation, pre-stack migration, and modelling of geophysi- cal data such as seismic, gravimetric, magnetic, and magnetotelluric data. The deriva- tion of interval velocities and the prediction of lateral inhomogeneities will be essential for the interpretation of rheological properties on one hand and historical geodynamic processes on the other. 2. Basin dynamics in space and time. Methods of basin anal- ysis, seismic stratigraphy,sedimentology, sequence- and event stratigraphy should be used in combination with subsidence analysis and basin modelling to interpret facies distributions within the evolving accomodation space of a sedimentary basin. An ad- vanced interpretation of seismic lines using new modelling tools is of key interest to extract facies patterns and related petrophysical properties for the three dimensional space of a sedimentary basin. 3. Fluid- and salt dynamics. Salt dynamics is related to the recent and historic stress fields of a basin and greatly governs the sedimentation and erosion processes at the surface. In addition, the rheology of the upper crust and the temperature field within sedimentary basins greatly depends on salt doming. Fluid dynamics is coupled to the temperature and pressure field, but depends also on the permeability of sedimentary rocks which varies by more than 15 orders of magnitude. The origin of non-hydrocarbon gases (CO2, N2, H2S), each dominating

Sedimentary modeling and analysis of petroleum system of the upper Tertiary sequences in southern Ulleung sedimentary Basin, East Sea (Sea of Japan)

NASA Astrophysics Data System (ADS)

Cheong, D.; Kim, D.; Kim, Y.

2010-12-01

The block 6-1 located in the southwestern margin of the Ulleung basin, East Sea (Sea of Japan) is an area where recently produces commercial natural gas and condensate. A total of 17 exploratory wells have been drilled, and also many seismic explorations have been carried out since early 1970s. Among the wells and seismic sections, the Gorae 1 well and a seismic section through the Gorae 1-2 well were chosen for this simulation work. Then, a 2-D graphic simulation using SEDPAK elucidates the evolution, burial history and diagenesis of the sedimentary sequence. The study area is a suitable place for modeling a petroleum system and evaluating hydrocarbon potential of reservoir. Shale as a source rock is about 3500m deep from sea floor, and sandstones interbedded with thin mud layers are distributed as potential reservoir rocks from 3,500m to 2,000m deep. On top of that, shales cover as seal rocks and overburden rocks upto 900m deep. Input data(sea level, sediment supply, subsidence rate, etc) for the simulation was taken from several previous published papers including the well and seismic data, and the thermal maturity of the sediment was calculated from known thermal gradient data. In this study area, gas and condensate have been found and commercially produced, and the result of the simulation also shows that there is a gas window between 4000m and 6000m deep, so that three possible interpretations can be inferred from the simulation result. First, oil has already moved and gone to the southeastern area along uplifting zones. Or second, oil has never been generated because organic matter is kerogen type 3, and or finally, generated oil has been converted into gas by thermally overcooking. SEDPAK has an advantage that it provides the timing and depth information of generated oil and gas with TTI values even though it has a limit which itself can not perform geochemical modeling to analyze thermal maturity level of source rocks. Based on the result of our simulation

Curiosity Rover's CheMin Instrument Investigates Mineralogy of Gale Crater and Implications for Diagenesis

NASA Astrophysics Data System (ADS)

Fendrich, Kim; Rampe, Elizabeth; Vaniman, David; Bish, David; Blake, David; Treiman, Allan; Ming, Doug; Morris, Richard; Bristow, Tom; Cavanagh, Patrick; Downs, Robert; Morrison, Shaunna; Chipera, Steve; Achilles, Cherie; Farmer, Jack; Sarrazin, Philippe; Crisp, Joy; Morookian, John Michael; Yen, Albert; Gellert, Ralf

2015-04-01

within the phyllosilicates differs between the two samples, which implies localized diagenesis. The Windjana sandstone at the Kimberley location differs from the Sheepbed mudstone in that it contains more pyroxene and magnetite and abundant K-feldspar, as well as phyllosilicates and amorphous material. These phases may represent potassium-rich basaltic provenance or aqueous alteration by potassium-bearing fluids. While the Confidence Hills sample is still in the preliminary stages of evaluation, major crystalline phases observed in this fine-grained sedimentary rock include plagioclase, pyroxene, K-feldspar and phyllosilicates; hematite, rare in all previous samples, is notably abundant and jarosite is present. The findings suggest localized mobilization of iron-bearing fluids and acidic conditions. The more oxidized assemblage of Confidence Hills marks the transition into the lower strata of Mount Sharp.

Combining Textural Techniques to Explore Effects of Diagenesis and Low-grade Metamorphism on Iron Mineralogy and Iron Speciation

NASA Astrophysics Data System (ADS)

Slotznick, S. P.; Webb, S.; Eiler, J. M.; Kirschvink, J. L.; Fischer, W. W.

2016-12-01

Iron chemistry and mineralogy in the sedimentary rocks provide a valuable tool for studying paleoenvironmental conditions due to the fact that iron atoms can take on either the +II or +III valence state under geological redox conditions. One method utilizing this redox chemistry is `iron speciation', a bulk chemical sequential extraction technique that maps proportions of iron species to redox conditions empirically calibrated from modern sediments. However, all Precambrian and many Phanerozoic rocks have experienced post-depositional processes; it is vital to explore their effects on iron mineralogy and speciation. We combined light and electron microscopy, magnetic microscopy, (synchrotron-based) microprobe x-ray spectroscopy, and rock magnetic measurements in order to deconvolve secondary overprints from primary phases and provide quantitative measurement of iron minerals. These techniques were applied to excellently-preserved shale and siltstone samples of the 1.4 Ga lower Belt Supergroup, Montana and Idaho, USA, spanning a metamorphic gradient from sub-biotite to garnet zone. Previously measured Silurian-Devonian shales, sandstones, and carbonates in Maine and Vermont, USA spanning from the chlorite to kyanite zone provided additional well-constrained, quantitative data for comparison and to extend our analysis. In all of the studied samples, pyrrhotite formation occurred at the sub-biotite or sub-chlorite zone. Pyrrhotite was interpreted to form from pyrite and/or other iron phases based on lithology; these reactions can affect the paleoredox proxy. Iron carbonates can also severely influence iron speciation results since they often form in anoxic pore fluids during diagenesis; textural analyses of the Belt Supergroup samples highlighted that iron-bearing carbonates were early diagenetic cements or later diagenetic overprints. The inclusion of iron from diagenetic minerals during iron speciation analyses will skew results by providing a view of pore

Aqueous geochemistry and diagenesis in the eastern Snake River Plain aquifer system, Idaho

USGS Publications Warehouse

Wood, Warren W.; Low, Walton H.

1986-01-01

Water budget and isotopic analyses of water in the eastern Snake River Plain aquifer system confirm that most, if not all, of the water is local meteoric in origin. Solute mass-balance arguments suggest that ∼5 × 109 moles of calcite and 2.6 × 109 moles of silica are precipitated annually in the aquifer. Isotopic evaluations of calcite and petrographic observation of silica support the low-temperature origin of these deposits. Approximately 2.8 × 109 moles of chloride, 4.5 × 109 moles of sodium, 1.4 × 109 moles of sulfate, and 2 × 109 moles of magnesium are removed annually from the aquifer framework by solution. Proposed weathering reactions are shown to be consistent with mass balance, carbon isotopes, observed mineralogy, and chemical thermodynamics. Large quantities of sodium, chloride, and sulfate are being removed from the system relative to their abundances in the rock. Sedimentary interbeds, which are estimated to compose <10% of the aquifer volume, may yield as much as 20% of the solutes generated within the aquifer. Weathering rate of the aquifer framework of the eastern Snake River Plain is 14 (Mg/km2)/yr or less than half the average of the North American continent. This contrasts with the rate for the eastern Snake River basin, 34 (Mg/km2)/yr, which is almost identical to the average for the North American continent. Identification and quantification of reactions controlling solute concentrations in ground water in the eastern plain indicate that the aquifer is not an “inert bathtub” that simply stores and transmits water and solutes but is undergoing active diagenesis and is both a source and sink for solutes.

Extreme diagenesis displayed by Pliocene-Pleistocene Calcareous Nannofossils in IODP Hole 1396A, adjacent to Montserrat Island in the Lesser Antilles

NASA Astrophysics Data System (ADS)

Aljahdali, M. H.; Behzad, A.; Missimer, T. M.; Wise, S. W.; Scientists, E.

2013-12-01

Adjacent to Montserrat Island in the Lesser Antilles of the Caribbean Sea, Integrated Ocean Drilling Program (IODP) Site 1396 recovered lower Pliocene to Pleistocene calcareous nannofossil assemblages (CN11 to CN15) that range between common to abundant and display a variety of preservations. High-resolution Scanning Electron Microscopy (SEM) observation of calcareous nannofossil assemblages in selected samples from Hole 1396A, shows severe diagenesis (overgrowth and/or dissolution) even near the top of the sequence. The nannofossil assemblages in this relatively shallow basin (e.g., 800 m) reveal abnormal diagenesis for such young specimens that are quite similar to the heavy overgrowths and dissolution generally seen only in older deposits (e.g., Cretaceous). Our hypothesis is that volcanic activity in the region probably induced this extreme diagenesis. A more detailed examination of these samples should provide a better understanding of the progression of carbonate diagenesis in this basin. The nannofossil biostratigraphy and magnetostratigraphy at Site 1396 also suggest lower sedimentation rates in the Pleistocene than in the Pliocene. A comparison site (ODP Leg 165 Site 1000) in the Caribbean Sea also shows a similar sedimentation-rate pattern. This we interpret as a regional event caused by the closure of the Central American Seaway.

Hydrogeologic framework of fractured sedimentary rock, Newark Basin, New Jersey

USGS Publications Warehouse

Lacombe, Pierre J.; Burton, William C.

2010-01-01

The hydrogeologic framework of fractured sedimentary bedrock at the former Naval Air Warfare Center (NAWC), Trenton, New Jersey, a trichloroethylene (TCE)-contaminated site in the Newark Basin, is developed using an understanding of the geologic history of the strata, gamma-ray logs, and rock cores. NAWC is the newest field research site established as part of the U.S. Geological Survey Toxic Substances Hydrology Program, Department of Defense (DoD) Strategic Environmental Research and Development Program, and DoD Environmental Security Technology Certification Program to investigate contaminant remediation in fractured rock. Sedimentary bedrock at the NAWC research site comprises the Skunk Hollow, Byram, and Ewing Creek Members of the Lockatong Formation and Raven Rock Member of the Stockton Formation. Muds of the Lockatong Formation that were deposited in Van Houten cycles during the Triassic have lithified to form the bedrock that is typical of much of the Newark Basin. Four lithotypes formed from the sediments include black, carbon-rich laminated mudstone, dark-gray laminated mudstone, light-gray massive mudstone, and red massive mudstone. Diagenesis, tectonic compression, off-loading, and weathering have altered the rocks to give some strata greater hydraulic conductivity than other strata. Each stratum in the Lockatong Formation is 0.3 to 8 m thick, strikes N65 degrees E, and dips 25 degrees to 70 degrees NW. The black, carbon-rich laminated mudstone tends to fracture easily, has a relatively high hydraulic conductivity and is associated with high natural gamma-ray count rates. The dark-gray laminated mudstone is less fractured and has a lower hydraulic conductivity than the black carbon-rich laminated mudstone. The light-gray and the red massive mudstones are highly indurated and tend to have the least fractures and a low hydraulic conductivity. The differences in gamma-ray count rates for different mudstones allow gamma-ray logs to be used to correlate and

Hg concentrations from Late Triassic and Early Jurassic sedimentary rocks: first order similarities and second order depositional and diagenetic controls

NASA Astrophysics Data System (ADS)

Yager, J. A.; West, A. J.; Bergquist, B. A.; Thibodeau, A. M.; Corsetti, F. A.; Berelson, W.; Bottjer, D. J.; Rosas, S.

2016-12-01

Mercury concentrations in sediments have recently gained prominence as a potential tool for identifying large igneous province (LIP) volcanism in sedimentary records. LIP volcanism coincides with several mass extinctions during the Phanerozoic, but it is often difficult to directly tie LIP activity with the record of extinction in marine successions. Here, we build on mercury concentration data reported by Thibodeau et al. (Nature Communications, 7:11147, 2016) from the Late Triassic and Early Jurassic of New York Canyon, Nevada, USA. Increases in Hg concentrations in that record were attributed to Central Atlantic Magmatic Province (CAMP) activity in association with the end-Triassic mass extinction. We expand the measured section from New York Canyon and report new mercury concentrations from Levanto, Peru, where dated ash beds provide a discrete chronology, as well as St. Audrie's Bay, UK, a well-studied succession. We correlate these records using carbon isotopes and ammonites and find similarities in the onset of elevated Hg concentrations and Hg/TOC in association with changes in C isotopes. We also find second order patterns that differ between sections and may have depositional and diagenetic controls. We will discuss these changes within a sedimentological framework to further understand the controls on Hg concentrations in sedimentary records and their implications for past volcanism.

Hypolyminetic Oxygen Depletion And Dynamics of P Binding Forms: Insights From Modeling Sediment Early Diagenesis Coupled With Automatic Parameter Estimation

NASA Astrophysics Data System (ADS)

Shafei, Babak; Schmid, Martin; Müller, Beat; Chwalek, Thomas

2014-05-01

Sediment diagenesis can significantly impact on lake water quality through depleting hypolimnion oxygen and acting as a sink or source of nutrients and contaminants. In this study, we apply MATsedLAB, a sediment diagenesis module developed in MATLAB [1, 2] to quantify benthic oxygen consumption and biogeochemical cycling of phosphate (P) in lacustrine sediments of Lake Baldegg, located in central Switzerland. MATsedLAB provides an access to the advanced computational and visualization capabilities of the interactive programming environment of MATLAB. It allows for a flexible definition of non steady-state boundary conditions at the sediment-water interface (SWI), the model parameters as well as transport and biogeochemical reactions. The model has been extended to facilitate the model-independent parameter estimation and uncertainty analysis using the software package, PEST. Lake Baldegg represents an interesting case where sediment-water interactions control P loading in an eutrophic lake. It is of 5.2 km2 surface area and has been artificially aerated since 1982. Between 1960 and 1980, low oxygen concentrations and meromictic condition were established as a result of high productivity. Here, we use the cores for the measurements of anions and cations which were collected in April and June 2012 respectively from the deepest location (66 m), by Torres et al. (2013) to calibrate the developed model [3]. Depth profiles of thirty three species were simulated by including thirty mixed kinetic-equilibrium biogeochemical processes as well as imposing the fluxes of organic and inorganic matters along with solute concentrations at the SWI as dynamic boundary conditions. The diffusive transport in the boundary layer (DBL) above the SWI was included as the supply of O2 to the sediment surface can be diffusion-limited, and applying a constant O2 concentration at the sediment surface may overestimate O2 consumption. Benthic oxygen consumption was calculated as a function of

Early Diagenesis of Trace Elements in Modern Fjord Sediments of the High Arctic

NASA Astrophysics Data System (ADS)

Herbert, L.; Riedinger, N.; Aller, R. C.; Jørgensen, B. B.; Wehrmann, L.

2017-12-01

Marine sediments are critical repositories for elements that are only available at trace concentrations in seawater, such as Fe, Mn, Co, Ni, As, Mo, and U. The behavior of these trace elements in the sediment is governed by a dynamic interplay of diagenetic reactions involving organic carbon, Fe and Mn oxides, and sulfur phases. In the Arctic fjords of Svalbard, glacial meltwater delivers large amounts of reactive Fe and Mn oxides to the sediment, while organic carbon is deposited episodically and diluted by lithogenic material. These conditions result in pronounced Fe and Mn cycling, which in turn drives other diagenetic processes such as rapid sulfide oxidation. These conditions make the Svalbard fjords ideal sites for investigating trace element diagenesis because they allow resolution of the interconnections between Fe and Mn dynamics and trace element cycling. In August 2016, we collected sediment cores from three Svalbard fjords and analyzed trace elements in the pore water and solid sediment over the top meter. Initial results reveal the dynamic nature of these fjords, which are dominated by non-steady state processes and episodic events such as meltwater pulses and phytoplankton blooms. Within this system, the distribution of As appears to be strongly linked to the Fe cycle, while Co and Ni follow Mn; thus, these three elements may be released from the sediment through diffusion and bioturbation along with Fe and Mn. The pore water profiles of U and Mo indicate removal processes that are independent from Fe or Mn, and which are rather unexpected given the apparent diagenetic conditions. Our results will help elucidate the processes controlling trace element cycling in a dynamic, glacially impacted environment and will ultimately contribute to our understanding of the role of fjords in the biogeochemical cycling of trace elements in a rapidly changing Arctic Ocean.

Carbonate and silicate cementation of siliciclastic sediments of the New Jersey shelf (IODP Expedition 313): relation with organic matter diagenesis and submarine groundwater discharge

NASA Astrophysics Data System (ADS)

Pierre, Catherine; Blanc-Valleron, Marie-Madeleine; Boudouma, Omar; Lofi, Johanna

2017-12-01

The New Jersey continental shelf extends 150 km off the shoreline. During IODP Expedition 313, siliciclastic deposits of late Eocene to late Pleistocene age were drilled down to 631, 669 and 755 m below seafloor at sites 27A, 28A and 29A respectively in very shallow waters (33.5 to 36 m depth). Pore water salinities display multilayered brackish-salty-brine units 10 to 170 m thick, where low-salinity water is preferentially stored in fine-grained sediments. The sharp boundaries of these buried aquifers are often marked by cemented layers a few centimetres thick. The mineralogy and scanning electron microscope observations of these layers show two phases of cementation by authigenic minerals: (1) the early carbonate cement is frequently associated with pyrite, and (2) the late silicate cement infills the residual porosity. The isotopic compositions of the carbonate cements vary widely: -2.4 < δ18O ‰ VPDB < +2.8; -15.1 < δ13C ‰ VPDB < +15.6. The δ18O values indicate that the carbonate cements precipitated with pore waters comprising variable mixtures of seawater and 18O-depleted fresh water originating from submarine groundwater discharge. The δ13C values of the carbonate cements are related to organic matter diagenesis, providing 13C-depleted dissolved inorganic carbon during bacterial sulphate reduction and anaerobic oxidation of methane, and 13C-rich dissolved inorganic carbon during methanogenesis. The diagenetic cementation processes included chemical weathering of reactive silicate minerals by the CO2-rich pore waters issued from organic matter diagenesis that released bicarbonate, cations and dissolved silica, which were further precipitated as carbonate and silicate cements. The estimated range of temperature (18±4 °C) during carbonate precipitation is consistent with carbonate cementation at moderate burial depths; however, silicate cementation occurred later during diagenesis at deeper burial depths.

Calcified proteins in the sedimentary environment.

NASA Technical Reports Server (NTRS)

Mitterer, R. M.

1972-01-01

Amino acid diagenesis is considered in relatively young fossil mollusk shells which are capable of preserving some of their original organic constituents. The rate of change of amino acid content in fossils is related to time and diagenetic temperature. Thus, the amino acid content provides information relating to the approximate ages of shells. Pleistocene temperatures and sea level changes in Florida are discussed, along with stratification correlation.

Trace elements and REE geochemistry of Middle Devonian carbonate mounds (Maïder Basin, Eastern Anti-Atlas, Morocco): Implications for early diagenetic processes

NASA Astrophysics Data System (ADS)

Franchi, Fulvio; Turetta, Clara; Cavalazzi, Barbara; Corami, Fabiana; Barbieri, Roberto

2016-08-01

Trace and rare earth elements (REEs) have proven their utility as tools for assessing the genesis and early diagenesis of widespread geological bodies such as carbonate mounds, whose genetic processes are not yet fully understood. Carbonates from the Middle Devonian conical mud mounds of the Maïder Basin (eastern Anti-Atlas, Morocco) have been analysed for their REE and trace element distribution. Collectively, the carbonates from the Maïder Basin mud mounds appear to display coherent REE patterns. Three different geochemical patterns, possibly related with three different diagenetic events, include: i) dyke fills with a normal marine REE pattern probably precipitated in equilibrium with seawater, ii) mound micrite with a particular enrichment of overall REE contents and variable Ce anomaly probably related to variation of pH, increase of alkalinity or dissolution/remineralization of organic matter during early diagenesis, and iii) haematite-rich vein fills precipitated from venting fluids of probable hydrothermal origin. Our results reinforce the hypothesis that these mounds were probably affected by an early diagenesis induced by microbial activity and triggered by abundance of dispersed organic matter, whilst venting may have affected the mounds during a later diagenetic phase.

The formation of magnetite in the early Archean oceans

NASA Astrophysics Data System (ADS)

Li, Y. L.

2017-12-01

Banded iron formations are iron- and silica-rich chemical sedimentary rocks that were deposited throughout much of the Precambrian. It is generally accepted that biological oxidation of dissolved Fe(II) led to the precipitation of a ferric oxyhydroxide phase, such as ferrihydrite, in the marine photic zone. Upon burial, ferrihydrite was either transformed into hematite through dehydration or it was reduced to magnetite via biological or abiological Fe(III) reduction coupled to the oxidation of buried microbial biomass. However, it has always been intriguing as to why the oldest BIFs are characteristically magnetite-rich, while BIFs formed after the Neoarchean are dominated by hematite. Here, we propose that some magnetite in early Archean BIF could have precipitated directly from seawater through the reaction of settling ferrihydrite and hot, Fe(II)-rich hydrothermal fluids that vented directly into the photic zone. We conducted experiments that showed the reaction of Fe(II) with biogenic ferric iron mats under strict anoxic conditions led to the formation of a metastable green rust phase that within hours transformed into magnetite at relatively high temperatures. At lower temperatures magnetite does not form. Our model further posits that with the progressive cooling of the Earth's oceans through Archean, the above reaction shut off, and magnetite was subsequently restricted to reactions associated with diagenesis and metamorphism.

Rock magnetic and geochemical proxies for iron mineral diagenesis in a tropical lake: Lago Verde, Los Tuxtlas, East Central Mexico

NASA Astrophysics Data System (ADS)

Ortega, Beatriz; Caballero, Margarita; Lozano, Socorro; Vilaclara, Gloria; Rodríguez, Alejandro

2006-10-01

Magnetic and non-magnetic mineral analyses were conducted on a lacustrine sequence from Lago Verde in the tropical coast along the Gulf of Mexico that covers the last 2000 years. The site witnessed the transformation of the environment since the early Olmec societies until forest clearance in the last century. Through these analyses we investigated the processes that affected the magnetic mineralogy in order to construct a model of past environmental changes, and compare this model with the archeological record and inferred climatic changes in the northern hemisphere of tropical America. Volcanic activity has played a major influence on sediment magnetic properties, as a purveyor of Ti-magnetites/Ti-maghemites, and as a factor of instability in the environment. Anoxic reductive conditions are evident in most of Lago Verde's sedimentary record. Direct observations of magnetic minerals and ratios of geochemical (Fe, Ti), and ferrimagnetic ( χf) and paramagnetic ( χp) susceptibility ( χ) data, are used as parameters for magnetite dissolution ( χp/ χ, Fe/ χf), and precipitation ( χf/Ti) of magnetic minerals. Intense volcanic activity and anoxia are recorded before A.D. 20, leading to the formation of framboidal pyrite. Increased erosion, higher evaporation rates, lower lake levels, anoxia and reductive diagenesis in non-sulphidic conditions are inferred for laminated sediments between A.D. 20-850. This deposit matches the period of historical crisis and multiyear droughts that contributed to the collapse of the Maya civilization. Dissolution of magnetite, a high organic content and framboidal pyrite point to anoxic, sulphidic conditions and higher lake levels after A.D. 850. Higher lake levels in Lago Verde broadly coincide with the increased precipitation documented during the Medieval Warm Period (A.D. 950-1350) in the northern tropical and subtropical regions of the American continent. For the Little Ice Age (A.D. 1400-1800), the relatively moist conditions

Gold deposition by sulfidation of ferrous Fe in the lacustrine sediments of the Pueblo Viejo district (Dominican Republic): The effect of Fe-C-S diagenesis on later hydrothermal mineralization in a Maar-Diatreme complex

USGS Publications Warehouse

Kettler, R.M.; Rye, R.O.; Kesler, S.E.; Meyers, P.A.; Polanco, J.; Russell, N.

1992-01-01

The Pueblo Viejo district, located in the Cordillera Central of the Dominican Republic, contains large Au-Ag deposits associated with acid-sulfate alteration within spilites, conglomerates and carbonaceous sedimentary rocks that were deposited in a maar-diatreme complex. Much of the Au mineralization occurs in pyritic, carbonaceous siltstones of the Pueblo Viejo Maar-Diatreme Member of the Cretaceous Los Ranchos Formation. Pyrite is the only Fe-bearing phase in mineralized rock, whereas siderite is the dominant Fe-bearing phase in siltstones distal to mineralization. Disseminated pyrite occurs as framboids, cubes, pyritohedra, concretions and cement. Early framboids occur throughout the district. Au occurs as inclusions in later non-framboid disseminated pyrite (NFDP); an occurrence that is interpreted to be indicative of contemporaneous deposition. Pyrite framboids exhibit a wide range of ??34Scdt-values (-17.5 to +4.8???) and are interpreted to have formed during biogenic reduction of pore-water sulfate. The NFDP yield restricted ??34Scdt-values ( x ?? = -5.2???, s = ??2.4???, n = 43) similar to those obtained from later vein pyrite ( x ?? = -6.4???, s = ??1.5???, n = 12). Alunite and barite have ??34S-values ranging from +18.8 to +21.6???. The interpretation that the NFDP, vein pyrite, alunite and barite, and possibly even the framboidal pyrite share a common source of igneous sulfur is supported by the ??34S data. Siderite occurs as concretions and cement, contains abundant Mg (Fe0.75Mg0.19Mn0.03Ca0.02CO3) and has ??13Cpdb- and ??18Osmow-values ranging from -2.5 to +1.1%. and +14.6 to +19.5???, respectively. These data are consistent with the interpretation that the siderite formed in lacustrine sediments and that the carbonate in the siderite is probably methanogenic, although contributions from oxidation of organic matter during biogenic sulfate reduction, thermal decarboxylation of organic matter, or magmatic vapor cannot be ruled out. Disseminated Au

Sedimentary and Enhanced Geothermal Systems | Geothermal Technologies |

Science.gov Websites

NREL Sedimentary and Enhanced Geothermal Systems Sedimentary and Enhanced Geothermal Systems To innovative technologies, such as sedimentary and enhanced geothermal systems (EGS). Photo of a geothermal power plant in Imperial California. Capabilities To advance EGS and sedimentary geothermal systems, NREL

Glacial to interglacial surface nutrient variations of Bering Deep Basins recorded by δ13C and δ15N of sedimentary organic matter

NASA Astrophysics Data System (ADS)

Nakatsuka, Takeshi; Watanabe, Kazuki; Handa, Nobuhiko; Matsumoto, Eiji; Wada, Eitaro

1995-12-01

Stable carbon and nitrogen isotopic ratios (δ13C and δ15N) of organic matter were measured in three sediment cores from deep basins of the Bering Sea to investigate past changes in surface nutrient conditions. For surface water reconstructions, hemipelagic layers in the cores were distinguished from turbidite layers (on the basis of their sedimentary structures and 14C ages) and analyzed for isotopic studies. Although δ13C profiles may have been affected by diagenesis, both δ15N and δ13C values showed common positive anomalies during the last deglaciation. We explain these anomalies as reflecting suppressed vertical mixing and low nutrient concentrations in surface waters caused by injection of meltwater from alpine glaciers around the Bering Sea. Appendix tables are available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington , DC 20009. Document P95-003; $2.50. Payment must accompany order.

The beginning of the Buntsandstein cycle (Early-Middle Triassic) in the Catalan Ranges, NE Spain: Sedimentary and palaeogeographic implications

NASA Astrophysics Data System (ADS)

Galán-Abellán, Belén; López-Gómez, José; Barrenechea, José F.; Marzo, Mariano; De la Horra, Raúl; Arche, Alfredo

2013-10-01

The Early-Middle Triassic siliciclastic deposits of the Catalan Ranges, NE Spain, are dominated by aeolian sediments indicating a predominance of arid climate during this time span, in sharp contrast with the coeval fluvial sediments found in the Castilian Branch of the Iberian Ranges, 300 km to the SW. The NE-SW-oriented Catalan Basin evolved during the Middle-Late Permian as the result of widespread extension in the Iberian plate. This rift basin was bounded by the Pyrenees, Ebro and Montalbán-Oropesa highs. The Permian-Early Triassic-age sediments of the Catalan Basin were deposited in three isolated subbasins (Montseny, Garraf, Prades), separated by intrabasinal highs, but linked by transversal NW-SE oriented faults. The three subbasins show evidence of diachronic evolution with different subsidence rates and differences in their sedimentary records. The Buntsandstein sedimentary cycle started in the late Early Triassic (Smithian-Spathian) in the central and southern domains (Garraf and Prades), with conglomerates of alluvial fan origin followed by fluvial and aeolian sandstones. Source area of the fluvial sediments was nearby Paleozoic highs to the north and west, in contrast with the far-away source areas of the fluvial sediments in the Iberian Ranges, to the SW. These fluvial systems were interacting with migrating aeolian dune fields located towards the S, which developed in the shadow areas behind the barriers formed by the Paleozoic highs. These highs were separating the subbasins under arid and semi-arid climate conditions. The dominating winds came from the east where the westernmost coast of the Tethys Sea was located, and periods of water run-off and fields of aeolian dunes development alternated. Some of the fluvial systems were probably evaporating as they were mixed into the interdune areas, never reaching the sea. From the end of the Smithian to the Spathian, the Catalan Basin and neighbour peri-Tethys basins of the present-day southern France

Early rifting deposition: examples from carbonate sequences of Sardinia (Cambrian) and Tuscany (Triassic-Jurassic), Italy: an analogous tectono-sedimentary and climatic context

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cocozza, T.; Gandin, A.

Lower Cambrian Ceroide Limestone (Sardinia) and Lower Jurassic Massiccio Limestone (Tuscany) belong to sequences deposited in analogous tectono-sedimentary context: the former linked to the Caledonian Sardic Phase, the latter to the Alpine Orogeny. Both units consist of massive pure limestone characterized by marginal and lagoonal sequences repeatedly interfingering in the same geological structure. This distribution indicates a morphology of the platforms composed of banks (marginal facies) and shallow basins (lagoonal facies) comparable with a Bahamian complex. Dolomitization affects patchily the massive limestone bodies, and karstic features, breccias, and sedimentary dikes occur at their upper boundary. Both units overlie early dolomitemore » and evaporites (sabkha facies) containing siliciclastic intercalations in their lower and/or upper part and are unconformably covered by open-shelf red (hematitic), nodular limestone Ammonitico Rosso facies). The sedimentary evolution of the two sequences appears to have been controlled by synsedimentary tectonics whose major effects are the end of the terrigenous input, the bank-and-basin morphology of the platform, the irregular distribution of the dolomitization, and the nodular fabric of the overlying facies. The end of the Bahamian-type system is marked by the karstification of the emerged blocks and is followed by their differential sinking and burial under red-nodular facies. From a geodynamic viewpoint, sequences composed of Bahamian-like platform carbonates followed by Ammonitico Rosso facies imply deposition along continental margins subjected to block-faulting during an extensional regime connected with the beginning of continental rifting. Moreover, the variation from sabkha to Bahamian conditions suggests the drifting of the continent from arid to humid, tropical areas.« less

Correlative microscopy of the constituents of a dinosaur rib fossil and hosting mudstone: Implications on diagenesis and fossil preservation.

PubMed

Kim, Jung-Kyun; Kwon, Yong-Eun; Lee, Sang-Gil; Kim, Chang-Yeon; Kim, Jin-Gyu; Huh, Min; Lee, Eunji; Kim, Youn-Joong

2017-01-01

We have applied correlative microscopy to identify the key constituents of a dorsal rib fossil from Koreanosaurus boseongensis and its hosting mudstone discovered at the rich fossil site in Boseong, South Korea, to investigate the factors that likely contributed to diagenesis and the preservation of fossil bone. Calcite and illite were the commonly occurring phases in the rib bone, hosting mudstone, and the boundary region in-between. The boundary region may have contributed to bone preservation once it fully formed by acting as a protective shell. Fluorapatite crystals in the rib bone matrix signified diagenetic alteration of the original bioapatite crystals. While calcite predominantly occupied vascular channels and cracks, platy illite crystals widely occupied miniscule pores throughout the bone matrix. Thorough transmission electron microscopy (TEM) study of illite within the bone matrix indicated the solid-state transformation of 1M to 2M without composition change, which was more evident from the lateral variation of 1M to 2M within the same layer. The high level of lattice disordering of 2M illite suggested an early stage of 1M to 2M transformation. Thus, the diagenetic alteration of both apatite and illite crystals within the bone matrix may have increased its overall density, as the preferred orientation of apatite crystals from moderate to strong degrees was evident despite the poor preservation of osteohistological features. The combined effects of rapid burial, formation of a boundary region, and diagenesis of illite and apatite within the bone matrix may have contributed to the rib bone preservation.

The effects of diagenesis and dolomitization on Ca and Mg isotopes in marine platform carbonates: Implications for the geochemical cycles of Ca and Mg

NASA Astrophysics Data System (ADS)

Fantle, Matthew S.; Higgins, John

2014-10-01

The Ca, Mg, O, and C isotopic and trace elemental compositions of marine limestones and dolostones from ODP Site 1196A, which range in depth (∼58 to 627 mbsf) and in depositional age (∼5 and 23 Ma), are presented. The objectives of the study are to explore the potential for non-traditional isotope systems to fingerprint diagenesis, to quantify the extent to which geochemical proxies are altered during diagenesis, and to investigate the importance of diagenesis within the global Ca and Mg geochemical cycles. The data suggest that Ca, which has a relatively high solid to fluid mass ratio, can be isotopically altered during diagenesis. In addition, the alteration of Ca correlates with the alteration of Mg in such a way that both can serve as useful tools for deciphering diagenesis in ancient rocks. Bulk carbonate δ44Ca values vary between 0.60 and 1.31‰ (SRM-915a scale); the average limestone δ44Ca is 0.97 ± 0.24‰ (1SD), identical within error to the average dolostone (1.03 ± 0.15 1SD ‰). Magnesium isotopic compositions (δ26Mg, DSM-3 scale) range between -2.59‰ and -3.91‰, and limestones (-3.60 ± 0.25‰) and dolostones (-2.68 ± 0.07‰) are isotopically distinct. Carbon isotopic compositions (δ13C, PDB scale) vary between 0.86‰ and 2.47‰, with average limestone (1.96 ± 0.31‰) marginally offset relative to average dolostone (1.68 ± 0.57‰). The oxygen isotopic compositions (δ18O, PDB scale) of limestones (-1.22 ± 0.94‰) are substantially lower than the dolostones measured (2.72 ± 1.07‰). The isotopic data from 1196A suggest distinct and coherent trends in isotopic and elemental compositions that are interpreted in terms of diagenetic trajectories. Numerical modeling supports the contention that such trends can be interpreted as diagenetic, and suggests that the appropriate distribution coefficient (KMg) associated with limestone diagenesis is ∼1 to 5 × 10-3, distinctly lower than those values (>0.015) reported in laboratory

Seasonal variation of early diagenesis and greenhouse gas production in coastal sediments of Cadiz Bay: Influence of anthropogenic activities

NASA Astrophysics Data System (ADS)

Burgos, Macarena; Ortega, Teodora; Bohórquez, Julio; Corzo, Alfonso; Rabouille, Christophe; Forja, Jesús M.

2018-01-01

Greenhouse gas production in coastal sediments is closely associated with the early diagenesis processes of organic matter and nutrients. Discharges from anthropogenic activities, particularly agriculture, fish farming and waste-water treatment plants supply large amounts of organic matter and inorganic nutrients that affect mineralization processes. Three coastal systems of Cadiz Bay (SW Spain) (Guadalete River, Rio San Pedro Creek and Sancti Petri Channel) were chosen to determine the seasonal variation of organic matter mineralization. Two sampling stations were selected in each system; one in the outer part, close to the bay, and another more inland, close to a discharge point of effluent related to anthropogenic activities. Seasonal variation revealed that metabolic reactions were driven by the annual change of temperature in the outer station of the systems. In contrast, these reactions depended on the amount of organic matter reaching the sediments in the outermost part of the systems, which was higher during winter. Oxygen is consumed in the first 0.5 cm indicating that suboxic and anoxic processes, such as denitrification, sulfate reduction and methanogenesis are important in these sediments. Sulfate reduction seems to account for most of the mineralization of organic matter at the marine stations, while methanogenesis is the main pathway at the sole freshwater station of this study, located inside the estuary of the Guadalete River, because of the lack of sulfate as electron acceptor. Results point to denitrification being the principal process of N2O formation. Diffusive fluxes varied between 2.6 and 160 mmol m-2 d-1 for dissolved inorganic carbon (DIC); 0.9 and 164.3 mmol m-2 d-1 for TA; 0.8 and 17.4 μmol m-2 d-1 for N2O; and 0.1 μmol and 13.1 mmol m-2 d-1 for CH4, indicating that these sediments act as a source of greenhouse gases to the water column.

Origin and diagenetic transformations of C 25 and C 30 highly branched isoprenoid sulphur compounds: Further evidence for the formation of organically bound sulphur during early diagenesis

NASA Astrophysics Data System (ADS)

Kohnen, M. E. L.; Damsté, J. S. Slnninghe; Kock-van Dalen, A. C.; Haven, H. L. Ten; Rullkötter, J.; De Leeuw, J. W.

1990-11-01

A number of C 25 and C 30 highly branched isoprenoid (HBI) sulphur compounds (E.G., thiolanes, 1-oxo-thiolanes, thiophenes, and benzo[ b]thiophenes) with 2,6,10,14-tetramethyl-7-(3-methylpentyl)pentadecane and 2,6,10,14,18-pentamethyl-7-(3-methylpentyl)nonadecane carbon skeletons were identified in sediments, ranging from Holocene to Upper Cretaceous. These identifications are based on mass spectral characterisation, desulphurisation, and, in some cases, by comparison of mass spectral and relative retention time data with those of authentic standards. The presence of unsaturated C 25 and C 30 HBI thiolanes in a Recent sediment from the Black Sea (age 3-6 × 10 3 a) strongly supports their formation during early diagenesis. The co-occurrence of HBI polyenes (C 25 and C 30) and unsaturated HBI thiolanes (C 25 and C 30) possessing two double bonds less than the corresponding HBI polyenes, in this Recent sediment, testifies to the formation of unsaturated HBI thiolanes by a reaction of inorganic sulphur species with double bonds of the HBI polyenes. Furthermore, a diagenetic scheme for HBI sulphur compounds is proposed based on the identification of HBI sulphur compounds in sediment samples with different maturity levels.

Upper Cretaceous Shannon Sandstone Reservoirs, Powder River Basin, Wyoming: Evidence for organic acid diagenesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hansley, P.L.; Nuccio, V.F.

Comparison of the petrology of shallow and deep oil reservoirs in the Upper Cretaceous Shannon Sandstone Beds of the Steele Member of the Cody Shale strongly suggests that organic acids have had a more significant impact on the diagenetic alteration of aluminosilicate grains and carbonate cements in the deep reservoirs than in the shallow reservoirs. In shallow reservoirs, detrital grains exhibit minor dissolution, sparse and small overgrowths, and secondary porosity created by dissolution of early calcite cement. However, deeper sandstones are characterized by extensive dissolution of detrital K-feldspar and detrital glauconite grains, and precipitation of abundant, large quartz and feldsparmore » overgrowths. Throughout the Shannon and Steele, dissolution of glauconite and degradation of kerogen were probably aided by clay mineral/organic catalysis, which caused simultaneous reduction of iron and oxidation of kerogen. This process resulted in release of ferrous iron and organic acids and was promoted in the deep reservoirs by higher formation temperatures accounting for more extensive dissolution of aluminosilicate grains. Carbonic acid produced from the dissolution of early calcite cement, decarboxylation of organic matter, and influx of meteoric water after Laramide uplift produced additional dissolution of cements and grains. Dissolution by organic acids and complexing by organic acid anions, however, best explain the intensity of diagenesis and absence of dissolution products in secondary pores and on etched surfaces of framework grains in deep reservoirs.« less

A Multi-proxy Approach to Understanding the Diagenesis of Carbonates in Pennsylvanian Mudrocks in the Midland Basin

NASA Astrophysics Data System (ADS)

Reis, A.; McGlue, M. M.; Waite, L.; Erhardt, A. M.

2017-12-01

Diagenetic processes influenced by changing climate, eustatic fluctuations, and porewater evolution led to the formation and alteration of carbonate layers in the Pennsylvanian Wolfcamp D Formation of the Midland Basin. Preliminary evidence from bulk geochemistry, oxygen and carbon stable isotopes, and petrographic analysis of the carbonates recovered from two drill cores indicate multiple generations of diagenesis. High Mg calcite and dolomite layers predominantly occur in the fine grained intervals of both cores. Whereas there are less carbonate layers in the central basin core, more of the layers underwent diagenesis compared to the carbonates in the southern core. δ13CPDB values ranging from -6‰ to -4‰ and the presence of framboidal pyrite indicate initial dolomite precipitation occurring in the zone of bacterial sulfate reduction. Later stages alteration occurred following the burial diagenesis of clay, releasing Mg2+ and Fe2+ into the pore waters allowing ferroan dolomite rims to precipitate on the precursor iron-poor dolomite rhombs. δ13CPDB and δ18OPDBvalues from altered beds in the southern core show a positive 4-6‰ offset from the central basin beds. Petrographic analysis of the carbonate intervals shows a larger allochem size, and lower pyrite abundance in the southern core. These differences can be associated with a shorter source-to-sink distance and less frequent bottom water anoxia, leading to reduced rates of sulfate reduction. One possibility we will explore is if increased circulation due to the proximity of the southern core to the Sheffield Channel could stabilize the bottom water conditions in this region of the basin. In addition to dolomite precipitation and replacement, scanning electron microscopy reveals the replacement of silica cements by calcite, suggesting an increase in porewater pH during or following sulfate reduction coinciding with pyrite formation. Changing bottom water chemistry tied to fluctuations in sea-level through

Testing and Validation Studies of the NSMII-Benthic Sediment Diagenesis Module

DTIC Science & Technology

2016-07-01

NSMII analytical vs. numerical solutions of sediment methane ............................ 27 3.2.4 Comparisons of the diagenesis rates of three sediment...26 Figure 12. Comparisons of NSMII analytical vs. numerical solutions of sediment methane : (a) layer 2’s CH4, (b...oxygen demand mg-O2 L-1 0-10 CH4 Methane mg-O2 L-1 On/Off HxS Total dissolved sulfides mg-O2 L-1 On/Off DO Dissolved oxygen mg-O2 L-1 On BSi

Humic acids contribution to sedimentary organic matter on a shallow continental shelf (northern Adriatic Sea)

NASA Astrophysics Data System (ADS)

Giani, M.; Rampazzo, F.; Berto, D.

2010-12-01

The shallow northern Adriatic Sea receives large river runoff, predominantly from the Po River, which is the main allochthonous source of nutrients and organic matter. The origin and quality of organic matter deposited in the sediments can influence the degradation processes and oxygen consumption in the bottom waters as well as the fate of many pollutants. Therefore the humic acids (HA) were quantified in surface and sub-surface sediments collected in an area of the north-western Adriatic platform south of Po River. HA showed to have a relevant contribution to sedimentary organic matter. HA content in sediments were positively correlated with the organic carbon concentration and negatively with redox potential and pH, particularly in sub-surface reduced sediments, suggesting their important role in the diagenetic processes taking place in anoxic conditions. Elemental composition of HA extracted from surface and sub-surface sediments showed a wide range of variation of the C org/N ratios which could be due to a mixed (terrestrial and marine) origin and/or an elevated bacteria degradation of nitrogen during diagenesis processes in sediments. The spectroscopic ratios A 2/A 4 and A 4/A 6 of HA confirmed a mixed origin with a high degree of condensation of the HA extracted from sediments.

Diagenesis in subrecent marine sediments in the Eastern Scheldt, Southwest Netherlands

NASA Astrophysics Data System (ADS)

Oenema, O.

The diagenesis in fine-grained sediments from a 300 to 400-years-old Dunkirk deposit, exposed on the intertidal flat, was studied at a site in the Eastern Scheldt. A new in situ pore water sampling technique that allowed repeated sampling at exactly the same place was used to monitor the seasonal fluctuations in interstitial water composition. Concentrations of organic carbon (1.5 to 2%), nitrogen (C/N = 19), phosphorus (500 μg·g -1) and manganese (250 μg·g -1) in the subrecent anoxic sediments were low, probably because they had already been depleted during earlier stages of diagenesis. Rates of organic carbon mineralization by sulphate reduction (0.1 Mole·m -2·y -1) and rates of nutrient regeneration were 1 to 2 orders of magnitude lower than in recent fine-grained sediments elsewhere in the Eastern Scheldt. Pore water NH 4+ and ΣPO 4 concentrations were controlled by mineralization, uptake by Zostera noltii and sediment-seawater exchange. During the summer the uptake exceeded the mineralization rate at 0 to 5 cm. Mineralization and diffusional processes dominated the changes in the NH 4+ and ΣPO 4 profiles in the other seasons. Dissolved manganese and iron concentrations showed a typical subsurface maximum at 0 to 3 cm, and low (<5 μMole) concentrations below this depth. Dissolved iron concentrations were probably controlled by the solubility of iron sulphides, and manganese probably by the solubility of Mn, Ca-carbonate.

Zinc and germanium in the sedimentary rocks of Gale Crater on Mars indicate hydrothermal enrichment followed by diagenetic fractionation

NASA Astrophysics Data System (ADS)

Berger, Jeff A.; Schmidt, Mariek E.; Gellert, Ralf; Boyd, Nicholas I.; Desouza, Elstan D.; Flemming, Roberta L.; Izawa, Matthew R. M.; Ming, Douglas W.; Perrett, Glynis M.; Rampe, Elizabeth B.; Thompson, Lucy M.; VanBommel, Scott J. V.; Yen, Albert S.

2017-08-01

Zinc and germanium enrichments have been discovered in sedimentary rocks in Gale Crater, Mars, by the Alpha Particle X-ray Spectrometer on the rover Curiosity. Concentrations of Zn (910 ± 840 ppm) and Ge (65 ± 58 ppm) are tens to hundreds of times greater than in Martian meteorites and estimates for average silicate Mars. Enrichments occur in diverse rocks including minimally to extensively altered basaltic and alkalic sedimentary rocks. The magnitude of the enrichments indicates hydrothermal fluids, but Curiosity has not discovered unambiguous hydrothermal mineral assemblages. We propose that Zn- and Ge-rich hydrothermal deposits in the source region were dispersed in siliciclastic sediments during transport into the crater. Subsequent diagenetic mobilization and fractionation of Zn and Ge is evident in a Zn-rich sandstone (Windjana; Zn 4000 ppm, Ge 85 ppm) and associated Cl-rich vein (Stephen; Zn 8000 ppm, Ge 60 ppm), in Ge-rich veins (Garden City; Zn 2200 ppm, Ge 650 ppm), and in silica-rich alteration haloes leached of Zn (30-200 ppm). In moderately to highly altered silica-rich rocks, Ge remained immobile relative to leached elements (Fe, Mn, Mg, and Ca), consistent with fluid interaction at pH ≪ 7. In contrast, crosscutting Ge-rich veins at Garden City suggest aqueous mobilization as Ge-F complexes at pH < 2.5. Multiple jarosite detections by the CheMin X-ray diffractometer and variable Zn concentrations indicate diagenesis of lower Mount Sharp bedrock under acidic conditions. The enrichment and fractionation of Zn and Ge constrains fluid events affecting Gale sediments and can aid in unraveling fluid histories as Curiosity's traverse continues.

Restore the change process of Longmaxi shale pore structure during the diagenesis by the potassium and the magnesium

NASA Astrophysics Data System (ADS)

Zhou, W.

2016-12-01

The pore structure of Longmaxi shale was changing during the diagenetic process, mainly caused by the illitization and serpentinzation. The evolution of shale pore structure mainly relates to the element migration. Based on the result of electron microprobe analyser (EMPA), it is possible to find the distribution of element in shale directly and to distinguish the destroyed primary pore structure as element will remain in the migration way. The migration of potassium in Longmaxi shale mainly happened during early diagenesis phase to middle diagenesis phase (Geothermal temperature: 60°-140°). During the illitization, potassium mainly came from potassium feldspar, migrated though the connected pore structure and reacted with smectite. Illite and illite/smectite in Longmaxi shale distribute continuously in 10micron-level flocculent formation, which means that primary connective pore structure in Longmaxi shale has a same scale. The concentration of potassium has an obvious gradient that potassium content in middle of flocculation of Illite/smectite is about 6.8% and 4.8% in the boundary parts (Fig.). In addition, as SiO2 was generated during the illitization, which makes Longmaxi shale very compacted. The migration of magnesium in Longmaxi shale happened during low temperature serpentinization (Geothermal temperature: 140°-350°). Magnesium mainly came from dolomite and migrated in primary pores. According to the result of EMPA, it can be recognized that the migration path of magnesium is much simpler than potassium, which is caused as serpentinization do not have much reaction with clay minerals around (Fig.). Serpentine jams the primary pores of Longmaxi shale too. As reaction temperature of serpentinization is higher than illitization and serpentine is inserts in illite/smectite, the formation process of Longmaxi shale pore structure can be mainly divided into two phases: geothermal temperature˜140° and˜140°.

To what extent can intracrater layered deposits that lack clear sedimentary textures be used to infer depositional environments?

NASA Astrophysics Data System (ADS)

Cadieux, Sarah B.; Kah, Linda C.

2015-03-01

Craters within Arabia Terra, Mars, contain hundreds of meters of layered strata showing systematic alternation between slope- and cliff-forming units, suggesting either rhythmic deposition of distinct lithologies or similar lithologies that experienced differential cementation. On Earth, rhythmically deposited strata can be examined in terms of stratal packaging, wherein the interplay of tectonics, sediment deposition, and base level (i.e., the position above which sediment accumulation is expected to be temporary) result in changes in the amount of space available for sediment accumulation. These predictable patterns of sediment deposition can be used to infer changes in basin accommodation regardless of the mechanism of deposition (e.g. fluvial, lacustrine, or aeolian). Here, we analyze sedimentary deposits from three craters (Becquerel Crater, Danielson Crater, Crater A) in Arabia Terra. Each crater contains layered deposits that are clearly observed in orbital images. Although orbital images are insufficient to specifically determine the origin of sedimentary deposits, depositional couplets can be interpreted in terms of potential accommodation space available for deposition, and changes in the distribution of couplet thickness through stratigraphy can be interpreted in terms of changing base level and the production of new accommodation space. Differences in stratal packaging in these three craters suggest varying relationships between sedimentary influx, sedimentary base level, and concomitant changes in accommodation space. Previous groundwater upwelling models hypothesize that layered sedimentary deposits were deposited under warm climate conditions of early Mars. Here, we use observed stacking patterns to propose a model for deposition under cold climate conditions, wherein episodic melting of ground ice could raise local base level, stabilize sediment deposition, and result in differential cementation of accumulated strata. Such analysis demonstrates that

P-wave velocity anisotropy related to sealed fractures reactivation tracing the structural diagenesis in carbonates

NASA Astrophysics Data System (ADS)

Matonti, C.; Guglielmi, Y.; Viseur, S.; Garambois, S.; Marié, L.

2017-05-01

Fracture properties are important in carbonate reservoir characterization, as they are responsible for a large part of the fluid transfer properties at all scales. It is especially true in tight rocks where the matrix transfer properties only slightly contribute to the fluid flow. Open fractures are known to strongly affect seismic velocities, amplitudes and anisotropy. Here, we explore the impact of fracture evolution on the geophysical signature and directional Vp anisotropy of fractured carbonates through diagenesis. For that purpose, we studied a meter-scale, parallelepiped quarry block of limestone using a detailed structural and diagenetic characterization, and numerous Vp measurements. The block is affected by two en-échelon fracture clusters, both being formed in opening mode (mode 1) and cemented, but only one being reactivated in shear. We compared the diagenetic evolution of the fractures, which are almost all 100% filled with successive calcite cements, with the P-wave velocities measured across this meter-scale block of carbonate, which recorded the tectonic and diagenetic changes of a South Provence sedimentary basin. We found that a directional Vp anisotropy magnitude as high as 8-16% correlates with the reactivated fractures' cluster dip angle, which is explained by the complex filling sequence and softer material present inside the fractures that have been reactivated during the basin's tectonic inversion. We show that although a late karstification phase preferentially affected these reactivated fractures, it only amplified the pre-existing anisotropy due to tectonic shear. We conclude that Vp anisotropy measurements may help to identify the fracture sealing/opening processes associated with polyphased tectonic history, the anisotropy being independent of the current stress-state. This case shows that velocity anisotropies induced by fractures resulted here from a cause that is different from how these features have often been interpreted

A Guide to Oceanic Sedimentary Layering.

DTIC Science & Technology

1983-07-28

Profiling," J. Geophys. Res. 73, 2597-2614. L3 Lee, H. J., 1980. "Physical Properties of Northeast Pacific Sedi- ments Related to Sedimentary Environment and...7i -AI33 060 A GUIDE TO OCEANIC SEDIMENTARY LAYERING(U) TEXAS UNIV 1/i AT AUSTIN APPLIED RESEARCH LABS C B BENNETT ET AL, 28 JUL 83 RRL-TR-83-25...Copy No. 3 A GUIDE TO OCEANIC SEDIMENTARY LAYERING Christopher B. Bennett J. Mark Daniels APPLIED RESEARCH LABORATORIES THE UNIVERSITY OF TEXAS AT

Mineralogical and isotopic record of biotic and abiotic diagenesis of the Callovian-Oxfordian clayey formation of Bure (France)

NASA Astrophysics Data System (ADS)

Lerouge, C.; Grangeon, S.; Gaucher, E. C.; Tournassat, C.; Agrinier, P.; Guerrot, C.; Widory, D.; Fléhoc, C.; Wille, G.; Ramboz, C.; Vinsot, A.; Buschaert, S.

2011-05-01

The Callovian-Oxfordian (COx) clayey unit is being studied in the Eastern part of the Paris Basin at depths between 400 and 500 m depth to assess of its suitability for nuclear waste disposal. The present study combines new mineralogical and isotopic data to describe the sedimentary history of the COx unit. Petrologic study provided evidence of the following diagenetic mineral sequence: (1) framboidal pyrite and micritic calcite, (2) iron-rich euhedral carbonates (ankerite, sideroplesite) and glauconite (3) limpid calcite and dolomite and celestite infilling residual porosity in bioclasts and cracks, (4) chalcedony, (5) quartz/calcite. Pyrite in bioturbations shows a wide range of δ 34S (-38‰ to +34.5‰), providing evidence of bacterial sulphate reduction processes in changing sedimentation conditions. The most negative values (-38‰ to -22‰), measured in the lower part of the COx unit indicate precipitation of pyrite in a marine environment with a continuous sulphate supply. The most positive pyrite δ 34S values (-14‰ up to +34.5‰) in the upper part of the COx unit indicate pyrite precipitation in a closed system. Celestite δ 34S values reflect the last evolutionary stage of the system when bacterial activity ended; however its deposition cannot be possible without sulphate supply due to carbonate bioclast dissolution. The 87Sr/ 86Sr ratio of celestite (0.706872-0.707040) is consistent with deposition from Jurassic marine-derived waters. Carbon and oxygen isotopic compositions of bulk calcite and dolomite are consistent with marine carbonates. Siderite, only present in the maximum clay zone, has chemical composition and δ 18O consistent with a marine environment. Its δ 13C is however lower than those of marine carbonates, suggesting a contribution of 13C-depleted carbon from degradation of organic matter. δ 18O values of diagenetic chalcedony range between +27‰ and +31‰, suggesting precipitation from marine-derived pore waters. Late calcite

Assessing the potential of amino acid δ13C patterns as a carbon source tracer in marine sediments: effects of algal growth conditions and sedimentary diagenesis

NASA Astrophysics Data System (ADS)

Larsen, T.; Bach, L. T.; Salvatteci, R.; Wang, Y. V.; Andersen, N.; Ventura, M.; McCarthy, M. D.

2015-01-01

Burial of organic carbon in marine sediments has a profound influence in marine biogeochemical cycles, and provides a sink for greenhouse gases such as CO2 and CH4. However, tracing organic carbon from primary production sources as well as its transformations in the sediment record remains challenging. Here we examine a novel but growing tool for tracing biosynthetic origin of amino acid carbon skeletons, based on natural occurring stable carbon isotope patterns in individual amino acids (δ13CAA). We focus on two important aspects for δ13CAA utility in sedimentary paleoarchives: first, the fidelity of source diagnostic of algal δ13CAA patterns across different oceanographic growth conditions; and second, the ability of δ13CAA patterns to record the degree of subsequent microbial amino acid synthesis after sedimentary burial. Using the marine diatom Thalassiosira weissflogii, we tested under controlled conditions how δ13CAA patterns respond to changing environmental conditions, including light, salinity, temperature, and pH. Our findings show that while differing oceanic growth conditions can change macromolecular cellular composition, δ13CAA isotopic patterns remain largely invariant. These results underscore that δ13CAA patterns should accurately record biosynthetic sources across widely disparate oceanographic conditions. We also explored how δ13CAA patterns change as a function of age, total nitrogen and organic carbon content after burial, in a marine sediment core from a coastal upwelling area off Peru. Based on the four most informative amino acids for distinguishing between diatom and bacterial sources (i.e. isoleucine, lysine, leucine and tyrosine), bacterial derived amino acids ranged from 10-15% in the sediment layers from the last 5000 years to 35% during the last glacial period. The larger bacterial fractions in older sediments indicate that bacterial activity and amino acid resynthesis progressed, approximately as a function of sediment age, to

Evidence and age estimation of mass wasting at the distal lobe of the Congo deep-sea fan

NASA Astrophysics Data System (ADS)

Croguennec, Claire; Ruffine, Livio; Dennielou, Bernard; Baudin, François; Caprais, Jean-Claude; Guyader, Vivien; Bayon, Germain; Brandily, Christophe; Le Bruchec, Julie; Bollinger, Claire; Germain, Yoan; Droz, Laurence; Babonneau, Nathalie; Rabouille, Christophe

2017-08-01

On continental margins, sulfate reduction occurs within the sedimentary column. It is coupled with the degradation of organic matter and the anaerobic oxidation of methane. These processes may be significantly disturbed by sedimentary events, leading to transient state profiles for the involved chemical species. Yet, little is known about the impact of turbidity currents and mass wasting on the migration of chemical species and the redox reactions in which they are involved. Due to its connection to the River, the Congo deep-sea fan continuously receives huge amount of organic matter-rich sediments primarily transported by turbidity currents, which impact on the development of the associated ecosystems (Rabouille et al., 2017). Thus, it is well suited to better understand causal relationships between sedimentary events and fluid flow path, with consequences on the zonation of early diagenesis sequences. Here, we combined sedimentological observations with geochemical analyses of pore-water and sediment samples to explore how sedimentary instabilities affected the migration of methane and the distribution of organic matter within the sedimentary column. The results unveiled mass wasting processes affecting recent turbiditic and pelagic deposits, and are interpreted as being slides/ slumps and debrites. Two slides were responsible for the exhumation of an organic matter-rich sedimentary block of more than 5 m thick and the movement of a methane-rich sedimentary block, while turbidity currents enable the intercalation of sandy intervals within a pelagic clay layer. The youngest slide promoted the development of two Sulfate Methane Transition Zones (SMTZ), and may have possibly triggered a lateral migration of methane. Numerical simulation of the sulfate profile indicates that the youngest sedimentary event has occurred around a century ago. Our study emphasizes that turbidity currents and sedimentary instabilities can significantly affect the transport paths and the

The Case for Scientific Drilling of Precambrian Sedimentary Sequences: A Mission to Early Earth

NASA Astrophysics Data System (ADS)

Buick, R.; Anbar, A. D.; Mojzsis, S. J.; Kaufman, A. J.; Kieft, T. L.; Lyons, T. W.; Humayun, M.

2001-12-01

Research into the emergence and early evolution of life, particularly in relation to environmental conditions, has intensified in the past decade. The field is energized by controversy (e.g., over the history of atmospheric composition, ocean redox, climate and biochemical pathways) and by the application of new biogeochemical tools (e.g., ion probe in situ stable isotope studies; improved geochronological techniques; non-mass-dependent stable isotope effects; stable metal isotope systematics; advances in organic geochemistry/biomarkers). The past decade has also seen improved understanding of old tools (notably, S isotopes), and new perspectives on evolution and on microbial interaction with the environment borne of the genomics revolution. Recent papers demonstrate the potential for innovative research when such developments are integrated, as well as the limitations of present knowledge. The chief limiting factor is not lack of scientists or advanced techniques, but availability of fresh samples from suitable successions. Where classic Precambrian stratigraphy exists, suitable rocks are rarely exposed due to interaction with the oxidizing atmosphere, occurrence of flat-lying strata or sedimentary cover. Available drill-cores are concentrated around ore bodies, and hence are inherently altered or not environmentally representative. Stratigraphic drilling using clean diamond drilling techniques, targeted in accord with scientific priorities, could provide samples of unmatched quality across the most interesting stratigraphic intervals. Diamond drilling is a proven, inexpensive technology for accessing subsurface material. The time is ripe to use this technology to secure the materials needed for further advances. The Mission to Early Earth (MtEE) Focus Group of the NASA Astrobiology Institute is developing a case for the acquisition, curation and distribution of suitable samples, with a special focus on diamond drilling. A communal activity is envisioned, modeled

Examining the association of DDX compounds to sedimentary organic matter

NASA Astrophysics Data System (ADS)

Weathers, N.; Rowlett, K.; Geng, Z.; Morrison, A.; White, H. K.

2016-02-01

The association of hydrophobic organic contaminants (HOCs) with sedimentary organic matter (OM) influences their mobility and bioavailability in the environment. Determining whether these associations result from mechanisms such as sorption, chemical binding or encapsulation is critical for predicting their long-term fate. The pesticide DDT (dichlorodiphenyltrichloroethane) has been previously observed to form bound residues with sedimentary OM although the mechanisms of this association are yet to be fully explored. DDT, which was sprayed ubiquitously in the 1950s and early 1960s, can still be found in the environment today along with its three major metabolites, DDE, DDD and DDMU (collectively known as DDX compounds), and therefore presents a unique opportunity to further explore its long-term associations with OM. To this end, a sediment core from a salt marsh in Dover, Delaware known to contain DDX compounds was collected. A maximum concentration of DDX compounds was found at sediment depths corresponding to the time of the widespread usage of DDT. An initial solvent extraction with toluene provided data on the loosely associated DDX fraction followed by subsequent treatments with sulfuric acid and saponification to release DDX that was encapsulated or bound to the sedimentary matrix. Determining the physical disposition of DDX compounds that persist in sediments for several decades is integral to determining the extent to which they are mobile, bioavailable or sequestered in the marsh.

Sedimentary manganese metallogenesis in response to the evolution of the Earth system

NASA Astrophysics Data System (ADS)

Roy, Supriya

2006-08-01

The concentration of manganese in solution and its precipitation in inorganic systems are primarily redox-controlled, guided by several Earth processes most of which were tectonically induced. The Early Archean atmosphere-hydrosphere system was extremely O 2-deficient. Thus, the very high mantle heat flux producing superplumes, severe outgassing and high-temperature hydrothermal activity introduced substantial Mn 2+ in anoxic oceans but prevented its precipitation. During the Late Archean, centered at ca. 2.75 Ga, the introduction of Photosystem II and decrease of the oxygen sinks led to a limited buildup of surface O 2-content locally, initiating modest deposition of manganese in shallow basin-margin oxygenated niches (e.g., deposits in India and Brazil). Rapid burial of organic matter, decline of reduced gases from a progressively oxygenated mantle and a net increase in photosynthetic oxygen marked the Archean-Proterozoic transition. Concurrently, a massive drawdown of atmospheric CO 2 owing to increased weathering rates on the tectonically expanded freeboard of the assembled supercontinents caused Paleoproterozoic glaciations (2.45-2.22 Ga). The spectacular sedimentary manganese deposits (at ca. 2.4 Ga) of Transvaal Supergroup, South Africa, were formed by oxidation of hydrothermally derived Mn 2+ transferred from a stratified ocean to the continental shelf by transgression. Episodes of increased burial rate of organic matter during ca. 2.4 and 2.06 Ga are correlatable to ocean stratification and further rise of oxygen in the atmosphere. Black shale-hosted Mn carbonate deposits in the Birimian sequence (ca. 2.3-2.0 Ga), West Africa, its equivalents in South America and those in the Francevillian sequence (ca. 2.2-2.1 Ga), Gabon are correlatable to this period. Tectonically forced doming-up, attenuation and substantial increase in freeboard areas prompted increased silicate weathering and atmospheric CO 2 drawdown causing glaciation on the Neoproterozoic Rodinia

Clastic sedimentary rocks of the Michipicoten Volcanic-sedimentary belt, Wawa, Ontario

NASA Technical Reports Server (NTRS)

Ojakangas, R. W.

1983-01-01

The Wawa area, part of the Michipicoten greenstone belt, contains rock assemblages representative of volcanic sedimentary accumulations elsewhere on the shield. Three mafic to felsic metavolcanic sequences and cogenetic granitic rocks range in age from 2749 + or - 2Ma to 2696 + or - 2Ma. Metasedimentary rocks occur between the metavolcanic sequences. The total thickness of the supracrustal rocks may be 10,000 m. Most rocks have been metamorphosed under greenschist conditions. The belt has been studied earlier and is currently being remapped by Sage. The sedimentrologic work has been briefly summarized; two mainfacies associations of clastic sedimentary rocks are present - a Resedimented (Turbidite) Facies Association and a Nonmarine (Alluvial Fan Fluvial) Facies Association.

Polygenetic Karsted Hardground Omission Surfaces in Lower Silurian Neritic Limestones: a Signature of Early Paleozoic Calcite Seas

NASA Astrophysics Data System (ADS)

James, Noel P.; Desrochers, André; Kyser, Kurt T.

2015-04-01

Exquisitely preserved and well-exposed rocky paleoshoreline omission surfaces in Lower Silurian Chicotte Formation limestones on Anticosti Island, Quebec, are interpreted to be the product of combined marine and meteoric diagenesis. The different omission features include; 1) planar erosional bedding tops, 2) scalloped erosional surfaces, 3) knobs, ridges, and swales at bedding contacts, and 4) paleoscarps. An interpretation is proposed that relates specific omission surface styles to different diagenetic-depositional processes that took place in separate terrestrial-peritidal-shallow neritic zones. Such processes were linked to fluctuations in relative sea level with specific zones of diagenesis such as; 1) karst corrosion, 2) peritidal erosion, 3) subtidal seawater flushing and cementation, and 4) shallow subtidal deposition. Most surfaces are interpreted to have been the result of initial extensive shallow-water synsedimentary lithification that were, as sea level fell, altered by exposure and subaerial corrosion, only to be buried by sediments as sea level rose again. This succession was repeated several times resulting in a suite of recurring polyphase omission surfaces through many meters of stratigraphic section. Synsedimentary cloudy marine cements are well preserved and are thus interpreted to have been calcitic originally. Aragonite components are rare and thought to have to have been dissolved just below the Silurian seafloor. Large molluscs that survived such seafloor removal were nonetheless leached and the resultant megamoulds were filled with synsedimentary calcite cement. These Silurian inner neritic-strandline omission surfaces are temporally unique. They are part of a suite of marine omission surfaces that are mostly found in early Paleozoic neritic carbonate sedimentary rocks. These karsted hardgrounds formed during a calcite-sea time of elevated marine carbonate saturation and extensive marine cement precipitation. The contemporaneous greenhouse

Impact of Diagenesis on Biosignature Preservation Potential in Playa Lake Evaporites of the Verde Formation, Arizona: Implications for Mars Exploration

NASA Astrophysics Data System (ADS)

Shkolyar, S.; Farmer, J. D.

2016-05-01

We studied evaporite subfacies in the Verde Fmn., AZ. We identified diagenetic pathways and assessed how diagenesis affected biosignature preservation potential (BPP) in each. Results revealed eight pathways, each with diverse impacts on BPP.

QEMSCAN+LAICPMS: a new tool for petrochronology and sedimentary provenance analysis

NASA Astrophysics Data System (ADS)

Vermeesch, Pieter; Rittner, Martin; Omma, Jenny

2017-04-01

Only a relatively small number of rock-forming minerals contain sufficiently high concentrations of naturally occurring radioactive parent isotopes and sufficiently low background concentrations of the corresponding daughter isotopes to be suitable for geochronology. The first step in most geochronological studies is to extract these datable minerals from the host rock using a combination of magnetic and density separation techniques, a process that is tedious and time consuming. We here present a new method to avoid mineral separation by coupling a QEMSCAN electron microscope to an LA-ICP-MS instrument. Given a polished hand specimen, a petrographic thin section, or a grain mount, the QEMSCAN+LAICPMS method produces chemical and mineralogical maps from which the X-Y coordinates of the datable mineral are extracted. These coordinates are subsequently passed on to the laser ablation system for isotopic and, hence, geochronological analysis. QEMSCAN+LAICPMS can be applied to a wide range of problems in igneous, metamorphic and sedimentary geology, as is illustrated with three case studies. In the first case study, a 3 × 4 cm slab of polished granite from the L'Erée pluton in Guernsey is scanned for zircon. This yields 23 U-Pb ages resulting in a concordia age of 615 ± 2 Ma. The second case study re-investigates a paragneiss from an ultra-high pressure terrane in the Qaidam Basin (Qinghai, China) that was previously analysed by conventional petrography, electron microscopy and SIMS zircon U-Pb analysis. In this example, the QEMSCAN revealed 107 small (20 μm) metamorphic zircons that were analysed by LA-ICP-MS to constrain the 430 Ma age of peak metamorphism. The third and final case study investigates the mineralogy and geochronology of sedimentary rocks of the Ordovician Sarah Formation (Saudi Arabia). We analysed 44 outcrop samples and a further 35 subsurface samples, resulting in a dataset comprising 10,000 detrital zircon U-Pb ages and 79 heavy mineral

Diagenetic history of late Oligocene-early Miocene carbonates in East Sabah, Malaysia

NASA Astrophysics Data System (ADS)

Zainal Abidin, N. S.; Raymond, R. R.; Bashah, N. S. I.

2017-10-01

Limestones are particularly susceptible to drastic early diagenesis modifications, mainly cementation and dissolution. During the early Miocene, a major tectonic deformation has caused a widespread of uplift in Sabah. This has resulted change in depositional environment from deep to shallow marine, which favours the deposition of Gomantong Limestone. This study aims to investigate the diagenetic history of Gomantong Limestone in East Sabah. Thorough understanding of the diagenetic processes may provide data to unravel the tectonic activities which affected the reservoir quality of the carbonates. Combining the data from comprehensive petrographic analysis, and Scanning Electron Microscopy (SEM) of 30 samples, two main cements type were identified. These are microcrystalline cement and Mg-calcite cement of granular and blocky mosaics which are dominantly seen in all samples. The sequence of diagenesis events are determined as (1) micritization; (2) grain scale compaction; (3) cementation (pore-filling); (4) mechanical compaction and cementation infilling fractures and (5) chemical compaction. These diagenetic events are interpreted as reflection of changes in diagenetic environment from shallow marine to deep burial. The massive cementation in the Gomantong Limestone has resulted into a poor reservoir quality.

Diagenesis in tephra-rich sediments from the Lesser Antilles Volcanic Arc: Pore fluid constraints

NASA Astrophysics Data System (ADS)

Murray, Natalie A.; McManus, James; Palmer, Martin R.; Haley, Brian; Manners, Hayley

2018-05-01

We present sediment pore fluid and sediment solid phase results obtained during IODP Expedition 340 from seven sites located within the Grenada Basin of the southern Lesser Antilles Volcanic Arc region. These sites are generally characterized as being low in organic carbon content and rich in calcium carbonate and volcanogenic material. In addition to the typical reactions related to organic matter diagenesis, pore fluid chemistry indicates that the diagenetic reactions fall within two broad categories; (1) reactions related to chemical exchange with volcanogenic material and (2) reactions related to carbonate dissolution, precipitation, or recrystallization. For locations dominated by reaction with volcanogenic material, these sites exhibit increases in dissolved Ca with coeval decreases in Mg. We interpret this behavior as being driven by sediment-water exchange reactions from the alteration of volcanic material that is dispersed throughout the sediment package, which likely result in formation of Mg-rich secondary authigenic clays. In contrast to this behavior, sediment sequences that exhibit decreases in Ca, Mg, Mn, and Sr with depth suggest that carbonate precipitation is an active diagenetic process affecting solute distributions. The distributions of pore fluid 87Sr/86Sr reflect these competitive diagenetic reactions between volcanic material and carbonate, which are inferred by the major cation distributions. From one site where we have solid phase 87Sr/86Sr (site U1396), the carbonate fraction is found to be generally consistent with the contemporaneous seawater isotope values. However, the 87Sr/86Sr of the non-carbonate fraction ranges from 0.7074 to 0.7052, and these values likely represent a mixture of local arc volcanic sources and trans-Atlantic eolian sources. Even at this site where there is clear evidence for diagenesis of volcanogenic material, carbonate diagenesis appears to buffer pore fluid 87Sr/86Sr from the larger changes that might be

Early diagenetic dolomitization and dedolomitization of Late Jurassic and earliest Cretaceous platform carbonates: A case study from the Jura Mountains (NW Switzerland, E France)

NASA Astrophysics Data System (ADS)

Rameil, Niels

2008-12-01

Early diagenetic dolomitization is a common feature in cyclic shallow-water carbonates throughout the geologic record. After their generation, dolomites may be subject to dedolomitization (re-calcification of dolomites), e.g. by contact with meteoric water during emersion. These patterns of dolomitization and subsequent dedolomitization frequently play a key role in unravelling the development and history of a carbonate platform. On the basis of excellent outcrops, detailed logging and sampling and integrating sedimentological work, high-resolution sequence stratigraphic interpretations, and isotope analyses (O, C), conceptual models on early diagenetic dolomitization and dedolomitization and their underlying mechanisms were developed for the Upper Jurassic / Lower Cretaceous Jura platform in north-western Switzerland and eastern France. Three different types of early diagenetic dolomites and two types of dedolomites were observed. Each is defined by a distinct petrographic/isotopic signature and a distinct spatial distribution pattern. Different types of dolomites are interpreted to have been formed by different mechanisms, such as shallow seepage reflux, evaporation on tidal flats, and microbially mediated selective dolomitization of burrows. Depending on the type of dolomite, sea water with normal marine to slightly enhanced salinities is proposed as dolomitizing fluid. Based on the data obtained, the main volume of dolomite was precipitated by a reflux mechanism that was switched on and off by high-frequency sea-level changes. It appears, however, that more than one dolomitization mechanism was active (pene)contemporaneously or several processes alternated in time. During early diagenesis, percolating meteoric waters obviously played an important role in the dedolomitization of carbonate rocks that underlie exposure surfaces. Cyclostratigraphic interpretation of the sedimentary succession allows for estimates on the timing of early diagenetic (de

Isotopic Evidence for Platform Exposure and Diagenesis in the Miocene: Implications for South-East Asian Platform Evolution.

NASA Astrophysics Data System (ADS)

Prince, K.; Laya, J. C.; Betzler, C.; Eberli, G. P.; Zarikian, C.; Swart, P. K.; Blättler, C. L.; Reolid, J.; Reijmer, J.

2017-12-01

The Maldives record nearly continuous carbonate deposition from the Eocene to the Holocene, and its stable tectonic regime and lack of clastic input make it an ideal example for understanding the depositional and diagenetic dynamics of isolated carbonate platforms. The Kardiva platform ultimately drowned, but the amplitude and frequency of sea-level changes in the Miocene make it likely that subaerial exposure occurred during its evolution. Abundant moldic porosity has been interpreted as meteoric diagenesis, but stable isotope evidence to support this has not been reported. Using bulk stable isotope analyses and petrographic methods, we sought to identify evidence of meteoric diagenesis by investigating the variations in grains, cements, porosity, δ13C, and δ18O at IODP Sites U1645, U1469, and U1470. Within the platform, grain distribution is variable with algae, benthic foraminifera, and corals representing the most abundant grain types. Cement abundance generally increases while porosity decreases with depth, with some variability. δ18O and δ13C range from -7.0‰ to 3.2‰ and -7‰ to 2.5‰, respectively. Petrography and isotope values show evidence for subaerial exposure and alteration by meteoric fluids, with a cross-plot of δ13C and δ18O showing the characteristic inverted "J" trend associated with dissolution and precipitation reactions mediated by meteoric fluids, resulting in more negative values. These results are compared to isotopic values for unaltered red algae and corals to account for the possibility of vital effects, but vital effects alone do not yield such low values. This evidence for meteoric diagenesis of the Kardiva Platform indicates variation between wet and dry periods, and also potential high-amplitude sea-level fluctuations during the Miocene in the Indo-Pacific region.

Role of microbial processes in linking sandstone diagenesis with organic-rich clays

USGS Publications Warehouse

McMahon, P.B.; Chapelle, F.H.; Falls, W.F.; Bradley, P.M.

1992-01-01

Shows that the processes of microbial organic-acid production (via fermentation) in clays and microbial organic-acid consumption (via sulfate reduction) in sands effectively link organic-rich clays to sandstone diagenesis in the Black Creek Formation of South Carolina. Diagenetic processes have resulted in the formation of 10 volume percent calcite cement, 0.1 volume percent authigenic pyrite, and 1.5 volume percent secondary porosity in Black Creek sands. However, the distribution of these diagenetic processes is not uniform, resulting in net destruction of porosity in some parts of the sand and net porosity enchancement in other parts. -from Authors

Sedimentary facies and depositional history of the Swan Islands, Honduras

NASA Astrophysics Data System (ADS)

Ivey, Marvin L.; Breyer, John A.; Britton, Joseph C.

1980-10-01

Swan Island is a Honduran possession in the western Caribbean, located on the southeastern side of the Cayman Trench. Two sedimentary assemblages are found on the island: an older bedded sequence of mid-Tertiary age (Aquitanian or Burdigalian) and a younger sedimentary sequence of Late Pleistocene age. The older sequence is composed of a series of calcarenites, calcilutites, and siliciclastic mudstones; capping these are cliff-forming reefal carbonates of the younger sequence. The rocks of the older bedded sequence accumulated in deep water. Sedimentation consisted of a constant rain of pyroclastic debris interrupted by the episodic introduction of upslope carbonate material by turbidity currents. Uplift and deformation of this sequence was initiated sometime after the Early Miocene. By the Late Pleistocene, uplift had brought the rocks into water depths conducive to coral growth. Pleistocene sedimentation on the island was controlled by the interaction between tectonic uplift and eustatic sea-level changes. The primary controlling force on the tectonic history of the island is its proximity to the boundary between the North American and Caribbean plates.

Diagenesis of the Oligocene-Miocene rocks of the Upper Floridan and Intermediate aquifer systems by meteoric and mixing-zone waters in southwest Florida

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weedman, S.D.; McCartan, L.

1993-03-01

Optical and SEM of samples from 6 cores of Oligocene and Miocene rocks that compose portions of the Florida and Intermediate aquifers and the intervening semiconfining unit documents meteoric and mixing-zone (seawater and fresh carbonate ground water) diagenesis inferred to have occurred over several cycles of sea level change. Dolomite, limestone, sandstone, and claystone of the Suwannee Formation and the Arcadia Formation (Hawthorn Group) were examined. Core samples from time-equivalent strata in two E--W transects in Manatee, Hardee, Highlands, Sarasota, and DeSoto Counties are estimated to be 16--33 Ma on the basis of [sup 87]Sr/[sup 86]Sr ratios from unaltered molluskmore » shells and by molluscan biostratigraphy. Lithostratigraphic correlations are based on examination of 19 cores, 62 thin sections, 60 geophysical logs, and mineralogy determined by X-ray diffraction. Diagenetic indicators that the authors tracked petrographically include shell micritization, shell dissolution, equant and (or) fibrous CaCO[sub 3] cement, neomorphism, dolomite, etched phosphate grains, echinoderm fragment syntaxial overgrowths, and amorphous silica pore lining. Infiltration of meteoric water caused dissolution of carbonate minerals, especially aragonite, and precipitation of equant calcite crystals in voids of dissolved fossils and in pore spaces between grains. The silica was precipitated as pore linings in zones having soil textures. Observed replacement of calcite by limpid dolomite is consistent with modeling predictions of mixing-zone diagenesis. Etched crystals of limpid dolomite may indicate freshwater dissolution of a mixing-zone precipitate. Mapping of regional unconformities revealed pronounced thickening and thinning of some units. Evidence of meteoric water diagenesis is observed in the upper 600 ft of the transects examined. Evidence of mixing-zone diagenesis is observed at varying depths, but appears to increase in abundance and thickness toward the west.« less

Microbial shaping of sedimentary wrinkle structures

NASA Astrophysics Data System (ADS)

Mariotti, G.; Pruss, S. B.; Perron, J. T.; Bosak, T.

2014-10-01

Wrinkle structures on sandy bed surfaces were present in some of the earliest sedimentary environments, but are rare in modern environments. These enigmatic millimetre- to centimetre-scale ridges or pits are particularly common in sediments that harbour trace fossils and imprints of early animals, and appeared in the aftermath of some large mass extinctions. Wrinkle structures have been interpreted as possible remnants of microbial mats, but the formation mechanism and associated palaeoenvironmental and palaeoecological implications of these structures remain debated. Here we show that microbial aggregates can form wrinkle structures on a bed of bare sand in wave tank experiments. Waves with a small orbital amplitude at the bed surface do not move sand grains directly. However, they move millimetre-size, light microbial fragments and thereby produce linear sand ridges and rounded scour pits at the wavelengths observed in nature within hours. We conclude that wrinkle structures are morphological biosignatures that form at the sediment-water interface in wave-dominated environments, and not beneath microbial mats as previously thought. During early animal evolution, grazing by eukaryotic organisms may have temporarily increased the abundance of microbial fragments and thus the production of wrinkle structures.

Miocene Antarctic ice dynamics in the Ross Embayment (Western Ross Sea, Antarctica): Insights from provenance analyses of sedimentary clasts in the AND-2A drill core

NASA Astrophysics Data System (ADS)

Cornamusini, Gianluca; Talarico, Franco M.

2016-11-01

A detailed study of gravel-size sedimentary clasts in the ANDRILL-2A (AND-2A) drill core reveals distinct changes in provenance and allows reconstructions to be produced of the paleo ice flow in the McMurdo Sound region (Ross Sea) from the Early Miocene to the Holocene. The sedimentary clasts in AND-2A are divided into seven distinct petrofacies. A comparison of these with potential source rocks from the Transantarctic Mountains and the coastal Southern Victoria Land suggests that the majority of the sedimentary clasts were derived from formations within the Devonian-Triassic Beacon Supergroup. The siliciclastic-carbonate petrofacies are similar to the fossiliferous erratics found in the Quaternary Moraine in the southern McMurdo Sound and were probably sourced from Eocene strata that are currently hidden beneath the Ross Ice Shelf. Intraformational clasts were almost certainly reworked from diamictite and mudstone sequences that were originally deposited proximal to the drill site. The distribution of sedimentary gravel clasts in AND-2A suggests that sedimentary sequences in the drill core were deposited under two main glacial scenarios: 1) a highly dynamic ice sheet that did not extend beyond the coastal margin and produced abundant debris-rich icebergs from outlet glaciers in the central Transantarctic Mountains and South Victoria Land; 2) and an ice sheet that extended well beyond the coastal margin and periodically advanced across the Ross Embayment. Glacial scenario 1 dominated the early to mid-Miocene (between ca. 1000 and 225 mbsf in AND-2A) and scenario 2 the early Miocene (between ca. 1138 and 1000 mbsf) and late Neogene to Holocene (above ca. 225 mbsf). This study augments previous research on the clast provenance and highlights the added value that sedimentary clasts offer in terms of reconstructing past glacial conditions from Antarctic drill core records.

The South China - Indochina collision: a perspective from sedimentary basins analysis

NASA Astrophysics Data System (ADS)

Rossignol, Camille; Bourquin, Sylvie; Hallot, Erwan; Poujol, Marc; Roger, Françoise; Dabard, Marie-Pierre; Martini, Rossana; Villeneuve, Michel; Cornée, Jean-Jacques; Peyrotty, Giovan

2017-04-01

Sedimentary basins, through the sedimentary successions and the nature of the deposits, reflect the geology of the area from which the sediments were derived and thus provide valuable record of hinterland tectonism. As the collision between the South China and the Indochina blocks (i.e., the Indosinian orogeny) is still the object of a number of controversies regarding, for instance, its timing and the polarity of the subduction, the sedimentary basins associated with this mountain belt are likely to provide clues to reconstruct its geodynamic evolution. However, both the Sam Nua Basin (located to the south of the inner zones of the Indosinian orogeny and the Song Ma ophiolites) and the Song Da Basin (located to the north of the inner zones), northern Vietnam, are still lacking important information regarding the depositional environments and the ages of the main formations that they contain. Using sedimentological and dating analyses (foraminifers biostratigraphy and U-Pb dating on detrital zircon), we provide a new stratigraphic framework for these basins and propose a geodynamic evolution of the present-day northern Vietnam. During the Early Triassic, the Sam Nua Basin was mainly supplied by volcaniclastic sediments originating from an active volcanic activity. Geochemical investigations, combined with sedimentological and structural analyses, support an arc-related setting for this magmatism. This magmatic arc resulted from the subduction of a south dipping oceanic slab that once separated the South China from the Indochina blocks. During the Middle to the Late Triassic, the Sam Nua Basin underwent erosion that lead to the formation of a major unconformity, termed the Indosinian unconformity. This unconformity is interpreted to result from the erosion of the Indosinian mountain belt, built after the continental collision between the South China and the Indochina blocks. Later, during the Late Triassic, the Sam Nua Basin experienced the deposition of very coarse

Magnetic Mineral diagenesis in changing water environments in the Black Sea since ˜41.6 ka

NASA Astrophysics Data System (ADS)

Liu, Jiabo; Nowaczyk, Norbert; Frank, Ute; Arz, Helge

2017-04-01

Magnetic mineral diagenesis plays a key role in the global iron cycle. To understand the authigenic magnetic mineral formation by diagenesis is also fundamentally important for the interpretation of environmental magnetic as well as paleomagnetic signals. Core MSM33-55-1, recovered from the SW Black Sea, was subjected to rock-magnetic and SEM studies. The results demonstrate that four different magnetic mineral assemblages associated to specific water conditions can be observed. Between ˜41.6 ka and ˜19 ka, magnetite and greigite are alternatively in dominance in the sediment. Due to low organic matter input during the late MIS 3 and the last glacial maximum (LGM), oxygenated bottom water in the Black Sea was favourable for preserving detrital magnetite. Greigite in this interval have irregular shapes and assemble in spots, which were formed in a micro environment with limited sulfate availability. Between ˜19 ka and ˜16.5 ka, black layers were deposited as a result of organic matter accumulation induced by productivity blooming and riverine discharge soaring after the LGM. Hence less oxygenated bottom water conditions developed, and more fine grained greigite was formed. After melt-water pulse (MWP) events (˜16.5 ka), both primary productivity and the sea level were continuously rising until ˜8.3 ka, leading to the depletion of oxygen in bottom water. In addition to greigite, pyrite was also formed and gradually in dominance as approaching the Holocene. The influx of salt water masses from the Mediterranean Sea after ˜8.3 ka contributed to the establishment of the anoxic Black Sea, which resulted in the formation of ubiquitous frambiods of pyrite. Additionally, bacterial magnetic minerals are likely present in the sediment younger than ˜8.3 ka as indicated by rock magnetic results. In this paper, four different magnetic mineral assemblages, reflecting gradual changes from an oxic to an anoix Black Sea, were identified, yielding insights into the relation

Influence of Diagenesis on Bioavailable Phosphorus in Lake Mendota, USA

NASA Astrophysics Data System (ADS)

Hoffman, A.; Armstrong, D.; Lathrop, R.; Penn, M.

2013-12-01

Phosphorus (P) is a major driver of productivity in many freshwater systems and in excess P can cause a variety of deleterious effects. Lake Mendota, located in Madison, Wisconsin (USA), is a eutrophic calcareous lake that is influenced by both urban and agricultural sources. As measures have been implemented to control point and non-point source pollution, internal sources, including release by sediments, has become more important. We collected multiple sediment cores from seven depositional basins to determine how diagenesis is influencing the bioavailability of sediment P. Cores were sliced in 1-cm intervals and analyzed for total P (TP), various P fractions, total metals, and multiple stable isotopes. While the average amount of total P that was bioavailable was 64.8%, the range noted was 39.2% to 88.6%. Spatial differences existed among the cores when comparing TP and bioavailable P among the cores. Depth profiles elucidated temporal differences as occasional increases in TP with depth were noted. These increases were found to contain a higher percent of bioavailable P. This variation was explored to determine if it resulted from differences in source material, for example inorganic P formed by diagenesis of organic P (algal derived) rather than soil P from external inputs. Saturation index modeling using MINEQL+ suggests that phosphorus concentrations in Lake Mendota pore waters are influenced by precipitation of vivianite (Fe3(PO4)2●8H2O) and certain calcium phosphates. However, hydroxyl apatite (Ca5(PO4)3(OH)), was highly supersaturated, indicating that precipitation of hydroxyl apatite is hindered and not important in controlling phosphate concentrations in these sediments. Yet even more important than precipitation reactions, adsorption/desorption characteristics of P seem to play a major role in P bioavailability. Sediment 210Pb and 137Cs activity profiles indicate differences exist among sedimentation rates for the various depositional sites in Lake

Impact of diagenesis and low grade metamorphosis on Triassic sabkha dolomite δ26Mg

NASA Astrophysics Data System (ADS)

Immenhauser, A.; Geske, A.; Richter, D.; Buhl, D.; Niedermayr, A.

2012-12-01

Dolomite is a common rock forming mineral in the geological record but its value as archive of ancient seawater δ26Mg signatures and their variations in time are at present underexplored. Unknown factors include the sensitivity of δ26Mg ratio to processes in the diagenetic and low grade metamorphic domain. Here, we document and discusses the first detailed δ26Mg data set from early diagenetic and burial dolomites. Samples come from the Upper Triassic Hauptdolomit (Dolomia Principale; The Dolomites, Italy) and include coeval dolmicrites that underwent differential burial diagenesis in a temperature range between about 100 and more than 350°C. As indicated by dolmicrite 87/86Sr ratios, sabkha calcian D1 dolomites precipitated from evaporated seawater and stabilized at an early diagenetic stage to D2 dolomites analysed here. With increasing burial temperature, dolomite δ26Mg ratio scatter in the data set decreases with increasing Mg/Ca ratio and degree of order. Specifically, δ26Mg ratio variability is reduced from ~0.7‰ at burial temperatures beneath 100°C to about ~0.2‰ at temperatures in excess of 350°C, respectively, with mean δ26Mg values ranging constantly near -1.9‰. This suggests that, at least for the rock buffered system investigated here, dolmicrite δ26Mg proxy data are conservative and preserve near pristine values even at elevated burial temperatures. At present, the main element of uncertainty is the Mg-isotope fractionation factor between (evaporated) seawater and dolomite. A possible solution to this problem includes the compilation of a data from modern sabkha environments including pore water and calcian dolomite δ26Mg isotope signatures.

Deep Magnetic Diagenesis in Sediments: Progressive and Punctuated Processes.

NASA Astrophysics Data System (ADS)

Musgrave, R. J.; Kars, M. A. C.; Vega, M. E.

2017-12-01

Magnetic diagenesis in the tuffaceous muds, mudstones and volcaniclastic rocks cored at IODP Site U1437 is a product of progressive processes that continue throughout the 1800-m-thick sequence, punctuated by superimposed features corresponding to a series of influxes of fluids and concentrations of hydrocarbons. XRD, visual examination and SEM images indicate the presence of both magnetite and the magnetic sulfide greigite. Inferences from high values of saturation isothermal remanence normalised by magnetic susceptibility (SIRM/χ), distribution of hysteresis data near a diagenetic greigite curve on a Day plot, and 'humping' of low-temperature cycles of SIRM suggest that detrital magnetite and diagenetic greigite are both significant contributors to the magnetic assemblage, with greigite constituting a higher proportion in shallower samples. Progressive magnetic diagenesis is expressed as a continuing background decrease in SIRM/χ. FORC curves indicate an initial diagenetic growth of one or more higher-coercivity phases, followed downhole by increasing loss of all but low-coercivity material. The downhole pattern is consistent with progressive loss of fine-grained magnetite, initial authigenesis of greigite, and progressive pyritisation of the greigite. Some coarse-grained samples from the base of the sequence buck the trend, exhibiting SD behavior probably related to surviving magnetite inclusions in silicates. Shipboard fluid analysis revealed a complex profile of interstitial-water geochemistry, marked by several fluid influxes, including inputs of sulfate-rich water at about 275 and 460 meters below seafloor (mbsf). Methane concentrations, mostly low, markedly increase in the interval between 750 and 1460 mbsf, and ethane appears below an inferred fault at 1104 mbsf. Each of these fluid events is marked by offsets in the rock magnetic parameters SIRM/χ, S-0.3T, and DJH, representing repeated phases of late diagenetic growth of greigite in response to

Quantitative characterisation of sedimentary grains

NASA Astrophysics Data System (ADS)

Tunwal, Mohit; Mulchrone, Kieran F.; Meere, Patrick A.

2016-04-01

Analysis of sedimentary texture helps in determining the formation, transportation and deposition processes of sedimentary rocks. Grain size analysis is traditionally quantitative, whereas grain shape analysis is largely qualitative. A semi-automated approach to quantitatively analyse shape and size of sand sized sedimentary grains is presented. Grain boundaries are manually traced from thin section microphotographs in the case of lithified samples and are automatically identified in the case of loose sediments. Shape and size paramters can then be estimated using a software package written on the Mathematica platform. While automated methodology already exists for loose sediment analysis, the available techniques for the case of lithified samples are limited to cases of high definition thin section microphotographs showing clear contrast between framework grains and matrix. Along with the size of grain, shape parameters such as roundness, angularity, circularity, irregularity and fractal dimension are measured. A new grain shape parameter developed using Fourier descriptors has also been developed. To test this new approach theoretical examples were analysed and produce high quality results supporting the accuracy of the algorithm. Furthermore sandstone samples from known aeolian and fluvial environments from the Dingle Basin, County Kerry, Ireland were collected and analysed. Modern loose sediments from glacial till from County Cork, Ireland and aeolian sediments from Rajasthan, India have also been collected and analysed. A graphical summary of the data is presented and allows for quantitative distinction between samples extracted from different sedimentary environments.

Sedimentary Rocks of Aram Chaos

NASA Technical Reports Server (NTRS)

2004-01-01

4 February 2004 Aram Chaos is a large meteor impact crater that was nearly filled with sediment. Over time, this sediment was hardened to form sedimentary rock. Today, much of the eastern half of the crater has exposures of light-toned sedimentary rock, such as the outcrops shown in this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image. The picture is located near 2.0oN, 20.3oW, and covers an area 3 km (1.9 mi) wide. Sunlight illuminates the scene from the left.

Supercomputer analysis of sedimentary basins.

PubMed

Bethke, C M; Altaner, S P; Harrison, W J; Upson, C

1988-01-15

Geological processes of fluid transport and chemical reaction in sedimentary basins have formed many of the earth's energy and mineral resources. These processes can be analyzed on natural time and distance scales with the use of supercomputers. Numerical experiments are presented that give insights to the factors controlling subsurface pressures, temperatures, and reactions; the origin of ores; and the distribution and quality of hydrocarbon reservoirs. The results show that numerical analysis combined with stratigraphic, sea level, and plate tectonic histories provides a powerful tool for studying the evolution of sedimentary basins over geologic time.

Formation of Mg-aluminosilicates During Early Diagenesis of Carbonate Sediments in the Volcanic Crater Lake of Dziani Dzaha (Mayotte - Indian Ocean)

NASA Astrophysics Data System (ADS)

Milesi, V. P.; Jezequel, D.; Debure, M.; Marty, N.; Guyot, F. J.; Claret, F.; Virgone, A.; Gaucher, E.; Ader, M.

2017-12-01

Authigenic clays are increasingly reported in ancient carbonate rocks, but their origin remains poorly understood, strongly limiting paleoenvironmental interpretations. To tackle this issue, the carbonate sediments of the volcanic crater lake Dziani Dzaha are studied and reactive transport modeling is performed to assess the processes originating carbonate sediments associated with Mg-rich silicates during early diagenesis. The Dziani Dzaha is characterized by CO2-rich gases bubbling in three different locations, a high primary productivity leading to organic carbon contents of up to 30wt.% in the sediment, an alkalinity of 0.26 molal in the water column and pH values of 9 to 9.5. Characterization of bulk samples and clay fraction (<2µm) from the first meter of sediment with X-ray powder diffraction and X-ray fluorescence spectrometry indicates aragonite and hydromagnesite in surface sediment. The contents of hydromagnesite and organic matter decrease at depth while saponite, a Mg- and Al-rich trioctahedral smectite, accumulates to reach up to 25wt.% of mineral phases. Concurrently, chemical analyses of pore waters show a decrease of pH values from 9 to 8.3. Modeling of these diagenetic evolutions is performed with the reactive transport code Crunchflow, taking into account the sediment burial. High pH values combined with the alteration of alkaline feldspars and clinopyroxenes from the volcanic catchment allow supersaturation of lake waters relative to aragonite, hydromagnesite and saponite. Kinetic limitations in the formation of saponite explain its accumulation at depth. Production of CO2 associated with organic matter mineralization accounts for the pH decrease of pore waters, which induces hydromagnesite destabilisation leaving behind a saponite-aragonite mineral assemblage. The main driving force for the observed sequence is the intense primary productivity partly fueled by inputs of CO2-rich volcanic gases, which generates high pH, promoting the formation

Diagenesis and fracture development in the Bakken Formation, Williston Basin; implications for reservoir quality in the middle member

USGS Publications Warehouse

Pitman, Janet K.; Price, Leigh C.; LeFever, Julie A.

2001-01-01

The middle member of the Bakken Formation is an attractive petroleum exploration target in the deeper part of the Williston Basin because it is favorably positioned with respect to source and seal units. Progressive rates of burial and minor uplift and erosion of this member led to a stable thermal regime and, consequently, minor variations in diagenesis across much of the basin. The simple diagenetic history recorded in sandstones and siltstones in the middle member can, in part, be attributed to the closed, low-permeability nature of the Bakken petroleum system during most of its burial history. Most diagenesis ceased in the middle member when oil entered the sandstones and siltstones in the Late Cretaceous. Most oil in the Bakken Formation resides in open, horizontal fractures in the middle member. Core analysis reveals that sandstones and siltstones associated with thick mature shales typically have a greater density of fractures than sandstones and siltstones associated with thin mature shales. Fractures were caused by superlithostatic pressures that formed in response to increased fluid volumes in the source rocks during hydrocarbon generation

The effects of burial diagenesis on multiscale porosity in the St. Peter Sandstone: An imaging, small-angle, and ultra-small-angle neutron scattering analysis

DOE PAGES

Anovitz, Lawrence M.; Freiburg, Jared T.; Wasbrough, Matthew; ...

2017-11-06

To examine the effects of burial diagenesis on heirarchical pore structures in sandstone and compare those with the effects of overgrowth formation, we obtained samples of St. Peter Sandstone from drill cores obtained in the Illinois and Michigan Basins. The multiscale pore structure of rocks in sedimentary reservoirs and the mineralogy associated with those pores are critical factors for estimating reservoir properties, including fluid mass in place, permeability, and capillary pressures, as well as geochemical interactions between the rock and the fluid. The combination of small- and ultra-small-angle neutron scattering with backscattered electron or X ray-computed tomographic imaging, or both,more » provided a means by which pore structures were quantified at scales ranging from aproximately 1 nm to 1 cm—seven orders of magnitude. Larger scale (>10 µm) porosity showed the expected logarithmic decrease in porosity with depth, although there was significant variation in each sample group. However, small- and ultra-small-angle neutron scattering data showed that the proportion of small-scale porosity increased with depth. Porosity distributions were not continuous, but consisted of a series of log normal-like distributions at several distinct scales within these rocks. Fractal dimensions at larger scales decreased (surfaces smoothed) with increasing depth, and those at smaller scales increased (surfaces roughened) and pores become more isolated (higher lacunarity). Furthermore, data suggest that changes in pore-size distributions are controlled by both physical (compaction) and chemical effects (precipitation, cementation, dissolution).« less

The effects of burial diagenesis on multiscale porosity in the St. Peter Sandstone: An imaging, small-angle, and ultra-small-angle neutron scattering analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anovitz, Lawrence M.; Freiburg, Jared T.; Wasbrough, Matthew

To examine the effects of burial diagenesis on heirarchical pore structures in sandstone and compare those with the effects of overgrowth formation, we obtained samples of St. Peter Sandstone from drill cores obtained in the Illinois and Michigan Basins. The multiscale pore structure of rocks in sedimentary reservoirs and the mineralogy associated with those pores are critical factors for estimating reservoir properties, including fluid mass in place, permeability, and capillary pressures, as well as geochemical interactions between the rock and the fluid. The combination of small- and ultra-small-angle neutron scattering with backscattered electron or X ray-computed tomographic imaging, or both,more » provided a means by which pore structures were quantified at scales ranging from aproximately 1 nm to 1 cm—seven orders of magnitude. Larger scale (>10 µm) porosity showed the expected logarithmic decrease in porosity with depth, although there was significant variation in each sample group. However, small- and ultra-small-angle neutron scattering data showed that the proportion of small-scale porosity increased with depth. Porosity distributions were not continuous, but consisted of a series of log normal-like distributions at several distinct scales within these rocks. Fractal dimensions at larger scales decreased (surfaces smoothed) with increasing depth, and those at smaller scales increased (surfaces roughened) and pores become more isolated (higher lacunarity). Furthermore, data suggest that changes in pore-size distributions are controlled by both physical (compaction) and chemical effects (precipitation, cementation, dissolution).« less

Sedimentary Geology Context and Challenges for Cyberinfrastructure Data Management

NASA Astrophysics Data System (ADS)

Chan, M. A.; Budd, D. A.

2014-12-01

A cyberinfrastructure data management system for sedimentary geology is crucial to multiple facets of interdisciplinary Earth science research, as sedimentary systems form the deep-time framework for many geoscience communities. The breadth and depth of the sedimentary field spans research on the processes that form, shape and affect the Earth's sedimentary crust and distribute resources such as hydrocarbons, coal, and water. The sedimentary record is used by Earth scientists to explore questions such as the continental crust evolution, dynamics of Earth's past climates and oceans, evolution of the biosphere, and the human interface with Earth surface processes. Major challenges to a data management system for sedimentary geology are the volume and diversity of field, analytical, and experimental data, along with many types of physical objects. Objects include rock samples, biological specimens, cores, and photographs. Field data runs the gamut from discrete location and spatial orientation to vertical records of bed thickness, textures, color, sedimentary structures, and grain types. Ex situ information can include geochemistry, mineralogy, petrophysics, chronologic, and paleobiologic data. All data types cover multiple order-of-magnitude scales, often requiring correlation of the multiple scales with varying degrees of resolution. The stratigraphic framework needs dimensional context with locality, time, space, and depth relationships. A significant challenge is that physical objects represent discrete values at specific points, but measured stratigraphic sections are continuous. In many cases, field data is not easily quantified, and determining uncertainty can be difficult. Despite many possible hurdles, the sedimentary community is anxious to embrace geoinformatic resources that can provide better tools to integrate the many data types, create better search capabilities, and equip our communities to conduct high-impact science at unprecedented levels.

Sedimentary response to halfgraben dipslope faults evolution -Billefjorden Trough, Svalbard.

NASA Astrophysics Data System (ADS)

Smyrak-Sikora, Aleksandra; Kristensen, Jakob B.; Braathen, Alvar; Johannessen, Erik P.; Olaussen, Snorre; Sandal, Geir; Stemmerik, Lars

2017-04-01

Fault growth and linkage into larger segments has profound effect on the sedimentary architecture of rift basins. The uplifted Billefjorden Through located in central Spitsbergen is an excellent example of half-graben basin development. Detailed sedimentological and structural investigations supported by helicopter and ground base lidar scans along with photogrammetry analysis have been used to improve our understanding of the sedimentary response to faulting and along strike variations in footwall uplift and hanging wall subsidence. The early syn-rift basin fill, the Serpukhovian to Bashkirian Hultberget Formation and the Bashkirian Ebbaelven Member consists of fluvial to deltaic sandstones with minor marine incursions. During this early stage tens to hundred- meters-scale syn-tectonic faults disrupted the dipslope, and created local hanging wall depocentres where sediments were arrested. Changes in fluvial drainage pattern, development of small lacustrine basins along the faults, and the sharp based boundaries of some facies associations are interpreted as response to activity along these, mostly antithetic faults. The basin fill of the late syn-rift stage is composed of shallow marine to tidal mixed evaporite -carbonate facies in the hanging wall i.e. the Bashkirian Trikolorfjellet Member and the Moscovian Minkenfjellet Formation. These sediments interfinger with thick alluvial fan deposits outpouring from relay ramps on the master fault i.e. drainage from the footwall. The carbonate-evaporite cycles deposited on the hanging wall responded to both the eustatic sea level variations and tectonic movements in the rift basin. Intra-basinal footwall uplift of the dipslope controlled development of an internal unconformity and resulted in dissolution of the gypsum to produce stratiform breccia. In contrast thick gypsum-rich subbasins are preserved locally in hanging wall positions where they were protected from the erosion. The syn rift basin fill is capped by post

Deciphering the impact of diagenesis overprint on negative δ13C excursions using rock magnetism: Case study of Ediacaran carbonates, Yangjiaping section, South China

NASA Astrophysics Data System (ADS)

Macouin, Mélina; Ader, Magali; Moreau, Marie-Gabrielle; Poitou, Charles; Yang, Zhenyu; Sun, Zhimming

2012-10-01

Rock magnetism is used here to investigate the genesis of one of the puzzling negative carbon isotopic excursions of the Neoproterozoic in the Yangtze platform (South China). A detailed characterization of the magnetic mineralogy, which includes low-temperature and high-field magnetometry and classical magnetic measurement (ARM, IRM, susceptibility), was therefore performed along upper Doushantuo and lower Dengying Formations outcropping in the Yangjiaping section. The derived magnetic parameters show variations that can be interpreted as variations in magnetic grains size and in oxide contents. They show that the magnetic content is significantly reduced in samples presenting negative δ13Ccalcite values. We interpret this as a result of magnetite dissolution and secondary carbonate precipitation during early diagenesis bacterial sulfate reduction. Combined with C and O isotopic data, paleomagnetic techniques thus show that the upper Doushantuo-lower Dengying negative excursion of the Yangjiaping section is largely due to diagenesis, although the preservation of a genuine δ13C excursion of lower magnitude from +7‰ down to 0‰, instead of down to -9‰ as usually considered, cannot be ruled out. A corrected δ13Ccarbonate chemostratigraphic curve is therefore proposed. The unambiguous identification of a strong diagenetic component for this excursion casts doubts on the primary nature of other potentially time equivalent negative excursions of the Yangtze platform and thus to its correlation to negative excursions in other cratons (i.e. Shuram excursion). More generally, this study illustrates the potential of magnetic mineralogy characterization, a low cost, time efficient and non-destructive technique, as screening tool for diagenetic overprints of δ13C and δ18O.

Polygon/Cracked Sedimentary Rock

NASA Technical Reports Server (NTRS)

2004-01-01

4 December 2004 Exposures of sedimentary rock are quite common on the surface of Mars. Less common, but found in many craters in the regions north and northwest of the giant basin, Hellas, are sedimentary rocks with distinct polygonal cracks in them. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an example from the floor of an unnamed crater near 21.0oS, 311.9oW. Such cracks might have formed by desiccation as an ancient lake dried up, or they might be related to ground ice freeze/thaw cycles or some other stresses placed on the original sediment or the rock after it became lithified. The 300 meter scale bar is about 328 yards long. The scene is illuminated by sunlight from the upper left.

Factors influencing the biogeochemistry of sedimentary carbon and phosphorus in the Sacramento-San Joaquin Delta

USGS Publications Warehouse

Nilsen, E.B.; Delaney, M.L.

2005-01-01

This study characterizes organic carbon (Corganic) and phosphorus (P) geochemistry in surface sediments of the Sacramento-San Joaquin Delta, California. Sediment cores were collected from five sites on a sample transect from the edge of the San Francisco Bay eastward to the freshwater Consumnes River. The top 8 cm of each core were analyzed (in 1-cm intervals) for Corganic, four P fractions, and redox-sensitive trace metals (uranium and manganese). Sedimentary Corganic concentrations and Corganic:P ratios decreased, while reactive P concentrations increased moving inland in the Delta. The fraction of total P represented by organic P increased inland, while that of authigenic P was higher bayward than inland reflecting increased diagenetic alteration of organic matter toward the bayward end of the transect. The redox indicator metals are consistent with decreasing sedimentary suboxia inland. The distribution of P fractions and C:P ratios reflect the presence of relatively labile organic matter in upstream surface sediments. Sediment C and P geochemistry is influenced by site-specific particulate organic matter sources, the sorptive power of the sedimentary material present, physical forcing, and early diagenetic transformations presumably driven by Corganic oxidation. ?? 2005 Estuarine Research Federation.

Tissue Microarray Analysis Applied to Bone Diagenesis

PubMed Central

Mello, Rafael Barrios; Silva, Maria Regina Regis; Alves, Maria Teresa Seixas; Evison, Martin Paul; Guimarães, Marco Aurelio; Francisco, Rafaella Arrabaca; Astolphi, Rafael Dias; Iwamura, Edna Sadayo Miazato

2017-01-01

Taphonomic processes affecting bone post mortem are important in forensic, archaeological and palaeontological investigations. In this study, the application of tissue microarray (TMA) analysis to a sample of femoral bone specimens from 20 exhumed individuals of known period of burial and age at death is described. TMA allows multiplexing of subsamples, permitting standardized comparative analysis of adjacent sections in 3-D and of representative cross-sections of a large number of specimens. Standard hematoxylin and eosin, periodic acid-Schiff and silver methenamine, and picrosirius red staining, and CD31 and CD34 immunohistochemistry were applied to TMA sections. Osteocyte and osteocyte lacuna counts, percent bone matrix loss, and fungal spheroid element counts could be measured and collagen fibre bundles observed in all specimens. Decalcification with 7% nitric acid proceeded more rapidly than with 0.5 M EDTA and may offer better preservation of histological and cellular structure. No endothelial cells could be detected using CD31 and CD34 immunohistochemistry. Correlation between osteocytes per lacuna and age at death may reflect reported age-related responses to microdamage. Methodological limitations and caveats, and results of the TMA analysis of post mortem diagenesis in bone are discussed, and implications for DNA survival and recovery considered. PMID:28051148

A study of uranium favorability of Cenozoic sedimentary rocks, Basin and Range Province, Arizona: Part I, General geology and chronology of pre-late Miocene Cenozoic sedimentary rocks

USGS Publications Warehouse

Scarborough, Robert Bryan; Wilt, Jan Carol

1979-01-01

This study focuses attention on Cenozoic sedimentary rocks in the Basin and Range Province of Arizona. The known occurrences of uranium and anomalous radioactivity in these rocks are associated with sediments that accumulated in a low energy environment characterized by fine-grained clastics, including important tuffaceous materials, and carbonate rocks. Most uranium occurrences, in these rocks appear to be stratabound. Emphasis was placed on those sedimentary materials that pre-date the late Cenozoic Basin and Range disturbance. They are deformed and crop out on pedimented range blocks and along the province interface with the Transition Zone. Three tentative age groups are recognized: Group I - Oligocene, pre-22 m.y., Group II - early Miocene - 22 m.y. - 16 m.y., and Group III - middle Miocene - 16 m.y. to 13--10 m.y. Regionally, these three groups contain both coarse to fine-grained red clastics and low energy lighter colored 'lacustrine' phases. Each of the three groups has been the object of uranium exploration. Group II, the early Miocene strata, embraces the Anderson Mine - Artillery region host rocks and also the New River - Cave Creek early Miocene beds-along the boundary with the Transition Zone. These three groups of rocks have been tectonically deformed to the extent that original basins of deposition cannot yet be reconstructed. However, they were considerably more extensive in size than the late Cenozoic basins the origin of which deformed the former. Group II rocks are judged to be of prime interest because of: (1) the development and preservation of organic matter in varying lithologies, (2) apparent contemporaneity with silicic volcanic centers, (3) influence of Precambrian crystalline rocks, and (4) relative outcrop continuity near the stable Transition Zone. The Transition Zone, especially along its boundary with the Basin and Range Province, needs additional geologic investigation, especially as regards the depositional continuity of Group II

Sedimentary records on the subduction-accretion history of the Russian Altai, northwestern Central Asian Orogenic Belt

NASA Astrophysics Data System (ADS)

Chen, Ming; Sun, Min

2017-04-01

The Russian Altai, comprising the northern segment of the Altai-Mongolian terrane (AM) in the south, the Gorny Altai terrane (GA) in the north and the intervening Charysh-Terekta-Ulagan-Sayan suture zone, is a key area of the northwestern Central Asian Orogenic Belt (CAOB). A combined geochemical and detrital zircon study was conducted on the (meta-)sedimentary sequences from the Russian Altai to reveal the tectono-magmatic history of these two terranes and their amalgamation history, which in turn place constraints on the accretionary orogenesis and crustal growth in the CAOB. The Cambrian-Ordovician meta-sedimentary rocks from the northern AM are dominated by immature sediments possibly sourced from intermediate-felsic igneous rocks. Geochemical data show that the sediments were likely deposited in a continental arc-related setting. Zircons separated from these rocks are mainly 566-475 Ma and 1015-600 Ma old, comparable to the magmatic records of the Tuva-Mongolian terrane and surrounding island arcs in the western Mongolia. The similar source nature, provenance and depositional setting of these rocks to the counterparts from the Chinese Altai (i.e., the southern AM) imply that the whole AM possibly represents a coherent accretionary prism of the western Mongolia in the early Paleozoic rather than a Precambrian continental block with passive marginal deposition as previously thought. In contrast, the Cambrian to Silurian (meta-)sedimentary rocks from the GA are characterized by a unitary zircon population with ages of 640-470 Ma, which were potentially sourced from the Kuznetsk-Altai intra-oceanic island arc in the east of this terrane. The low abundance of 640-540 Ma zircons (5%) may attest that this arc was under a primitive stage in the late Neoproterozoic, when mafic igneous rocks dominated. However, the voluminous 530-470 Ma zircons (95%) suggest that this arc possibly evolved toward a mature one in the Cambrian to early Ordovician with increasing amount of

Chemical variations in Yellowknife Bay formation sedimentary rocks analyzed by ChemCam on board the Curiosity rover on Mars

USGS Publications Warehouse

Mangold, Nicolas; Forni, Olivier; Dromart, G.; Stack, K.M.; Wiens, Roger C.; Gasnault, Olivier; Sumner, Dawn Y.; Nachon, Marion; Meslin, Pierre-Yves; Anderson, Ryan B.; Barraclough, Bruce; Bell, J.F.; Berger, G.; Blaney, D.L.; Bridges, J.C.; Calef, F.; Clark, Brian R.; Clegg, Samuel M.; Cousin, Agnes; Edgar, L.; Edgett, Kenneth S.; Ehlmann, B.L.; Fabre, Cecile; Fisk, M.; Grotzinger, John P.; Gupta, S.C.; Herkenhoff, Kenneth E.; Hurowitz, J.A.; Johnson, J. R.; Kah, Linda C.; Lanza, Nina L.; Lasue, Jeremie; Le Mouélic, S.; Lewin, Eric; Malin, Michael; McLennan, Scott M.; Maurice, S.; Melikechi, Noureddine; Mezzacappa, Alissa; Milliken, Ralph E.; Newsome, H.L.; Ollila, A.; Rowland, Scott K.; Sautter, Violaine; Schmidt, M.E.; Schroder, S.; D'Uston, C.; Vaniman, Dave; Williams, R.A.

2015-01-01

The Yellowknife Bay formation represents a ~5 m thick stratigraphic section of lithified fluvial and lacustrine sediments analyzed by the Curiosity rover in Gale crater, Mars. Previous works have mainly focused on the mudstones that were drilled by the rover at two locations. The present study focuses on the sedimentary rocks stratigraphically above the mudstones by studying their chemical variations in parallel with rock textures. Results show that differences in composition correlate with textures and both manifest subtle but significant variations through the stratigraphic column. Though the chemistry of the sediments does not vary much in the lower part of the stratigraphy, the variations in alkali elements indicate variations in the source material and/or physical sorting, as shown by the identification of alkali feldspars. The sandstones contain similar relative proportions of hydrogen to the mudstones below, suggesting the presence of hydrous minerals that may have contributed to their cementation. Slight variations in magnesium correlate with changes in textures suggesting that diagenesis through cementation and dissolution modified the initial rock composition and texture simultaneously. The upper part of the stratigraphy (~1 m thick) displays rocks with different compositions suggesting a strong change in the depositional system. The presence of float rocks with similar compositions found along the rover traverse suggests that some of these outcrops extend further away in the nearby hummocky plains.

Aptian-Albian boundary in Central Southern Atlas of Tunisia: New tectono-sedimentary facts

NASA Astrophysics Data System (ADS)

Ghanmi, Mohamed Abdelhamid; Barhoumi, Amine; Ghanmi, Mohamed; Zargouni, Fouad

2017-08-01

The Aptian-Albian boundary preserves one of the most important events in Central-Southern Atlas of Tunisia, which belongs to the Southern Tethyan margin. A major sedimentary break was recorded between Early Aptian and Albian series in Bouhedma-Boudouaou Mountains. This major hiatus probably linked to the ''Austrian phase'' and to the Aptian and Albian ''Crisis'' testify a period of major tectonic events. In this paper, field observations on the Mid-Cretaceous stratigraphy combined with seismic profile interpretation were used for the first time to characterize the Aptian-Albian boundary in Central-Southern Atlas of Tunisia. Our new results reveal that Aptian-Albian boundary marks a critical interval not only in Maknassy-Mezzouna orogenic system but also in the Tunisian Atlas. Furthermore, Aptian-Albian series outcrop is marked by the important sedimentary gaps as well as a dramatic thickness change from West to East and predominately from North to South. This is linked to the extensional tectonic features which characterize all the Central-Southern Atlas of Tunisia.

Evolution of the Toarcian (Early Jurassic) carbon-cycle and global climatic controls on local sedimentary processes (Cardigan Bay Basin, UK)

NASA Astrophysics Data System (ADS)

Xu, Weimu; Ruhl, Micha; Jenkyns, Hugh C.; Leng, Melanie J.; Huggett, Jennifer M.; Minisini, Daniel; Ullmann, Clemens V.; Riding, James B.; Weijers, Johan W. H.; Storm, Marisa S.; Percival, Lawrence M. E.; Tosca, Nicholas J.; Idiz, Erdem F.; Tegelaar, Erik W.; Hesselbo, Stephen P.

2018-02-01

The late Early Jurassic Toarcian Stage represents the warmest interval of the Jurassic Period, with an abrupt rise in global temperatures of up to ∼7 °C in mid-latitudes at the onset of the early Toarcian Oceanic Anoxic Event (T-OAE; ∼183 Ma). The T-OAE, which has been extensively studied in marine and continental successions from both hemispheres, was marked by the widespread expansion of anoxic and euxinic waters, geographically extensive deposition of organic-rich black shales, and climatic and environmental perturbations. Climatic and environmental processes following the T-OAE are, however, poorly known, largely due to a lack of study of stratigraphically well-constrained and complete sedimentary archives. Here, we present integrated geochemical and physical proxy data (high-resolution carbon-isotope data (δ13 C), bulk and molecular organic geochemistry, inorganic petrology, mineral characterisation, and major- and trace-element concentrations) from the biostratigraphically complete and expanded entire Toarcian succession in the Llanbedr (Mochras Farm) Borehole, Cardigan Bay Basin, Wales, UK. With these data, we (1) construct the first high-resolution biostratigraphically calibrated chemostratigraphic reference record for nearly the complete Toarcian Stage, (2) establish palaeoceanographic and depositional conditions in the Cardigan Bay Basin, (3) show that the T-OAE in the hemipelagic Cardigan Bay Basin was marked by the occurrence of gravity-flow deposits that were likely linked to globally enhanced sediment fluxes to continental margins and deeper marine (shelf) basins, and (4) explore how early Toarcian (tenuicostatum and serpentinum zones) siderite formation in the Cardigan Bay Basin may have been linked to low global oceanic sulphate concentrations and elevated supply of iron (Fe) from the hinterland, in response to climatically induced changes in hydrological cycling, global weathering rates and large-scale sulphide and evaporite deposition.

Are polygonal faults the keystone for better understanding the timing of fluid migration in sedimentary basins?

NASA Astrophysics Data System (ADS)

Gay, Aurélien

2017-06-01

The initial sediment lithification starts with complex interactions involving minerals, surface water, decomposing organic matter and living organisms. This is the eogenesis domain (0 to 2 km below the seafloor) in which the sediments are subject to physical, chemical and mechanical transformations defining the early fabric of rocks. This interval is intensively prospected for its energy/mining resources (hydrocarbons, metal deposits, geothermal energy). In most basins worldwide it is composed of very fine-grained sediments and it is supposed to play the role of a seal for fluids migration. However, it is affected by polygonal faulting due to a volume loss during burial by contraction of clay sediments with a high smectite content. This process is of high interest for fractured reservoirs and/or cover integrity but it is not well constrained giving an uncertainty as this interval can either promote the migration of deeper fluids and the mineralized fluids intensifies diagenesis in the fracture planes, rendering this interval all the more impermeable. The next challenge will be to define where, when and how does this polygonal fault interval occur and this can only be done by understanding the behavior of clay grains and fluids during early burial.

Mongolian Oil Shale, hosted in Mesozoic Sedimentary Basins

NASA Astrophysics Data System (ADS)

Bat-Orshikh, E.; Lee, I.; Norov, B.; Batsaikhan, M.

2016-12-01

Mongolia contains several Mesozoic sedimentary basins, which filled >2000 m thick non-marine successions. Late Triassic-Middle Jurassic foreland basins were formed under compression tectonic conditions, whereas Late Jurassic-Early Cretaceous rift valleys were formed through extension tectonics. Also, large areas of China were affected by these tectonic events. The sedimentary basins in China host prolific petroleum and oil shale resources. Similarly, Mongolian basins contain hundreds meter thick oil shale as well as oil fields. However, petroleum system and oil shale geology of Mongolia remain not well known due to lack of survey. Mongolian oil shale deposits and occurrences, hosted in Middle Jurassic and Lower Cretaceous units, are classified into thirteen oil shale-bearing basins, of which oil shale resources were estimated to be 787 Bt. Jurassic oil shale has been identified in central Mongolia, while Lower Cretaceous oil shale is distributed in eastern Mongolia. Lithologically, Jurassic and Cretaceous oil shale-bearing units (up to 700 m thick) are similar, composed mainly of alternating beds of oil shale, dolomotic marl, siltstone and sandstone, representing lacustrine facies. Both Jurassic and Cretaceous oil shales are characterized by Type I kerogen with high TOC contents, up to 35.6% and low sulfur contents ranging from 0.1% to 1.5%. Moreover, S2 values of oil shales are up to 146 kg/t. The numbers indicate that the oil shales are high quality, oil prone source rocks. The Tmax values of samples range from 410 to 447, suggesting immature to early oil window maturity levels. PI values are consistent with this interpretation, ranging from 0.01 to 0.03. According to bulk geochemistry data, Jurassic and Cretaceous oil shales are identical, high quality petroleum source rocks. However, previous studies indicate that known oil fields in Eastern Mongolia were originated from Lower Cretaceous oil shales. Thus, further detailed studies on Jurassic oil shale and its

Sedimentary Cover of the Central Arctic

NASA Astrophysics Data System (ADS)

Kireev, Artem; Poselov, Viktor; Butsenko, Viktor; Smirnov, Oleg

2017-04-01

Partial revised Submission of the Russian Federation for establishment of the OLCS (outer limit of the continental shelf) in the Arctic Ocean is made to include in the extended continental shelf of the Russian Federation, in accordance with article 76 of the Convention, the seabed and its subsoil in the central Arctic Ocean which is natural prolongation of the Russian land territory. To submit partial revised Submission in 2016, in 2005 - 2014 the Russian organizations carried out a wide range of geophysical studies, so that today over 23000 km of MCS lines, over hundreds of wide-angle reflection/refraction seismic sonobuoy soundings and 4000 km of deep seismic sounding are accomplished. All of these MCS and seismic soundings data were used to establish the seismic stratigraphy model of the Arctic region. Stratigraphy model of the sedimentary cover was successively determined for the Cenozoic and pre-Cenozoic parts of the section and was based on correlation of the Russian MCS data and seismic data documented by existing boreholes. Interpretation of the Cenozoic part of the sedimentary cover was based on correlation of the Russian MCS data and AWI91090 section calibrated by ACEX-2004 boreholes on the Lomonosov Ridge for Amerasia basin and by correlation of onlap contacts onto oceanic crust with defined magnetic anomalies for Eurasia basin, while interpretation of the Pre-Cenozoic part of the sedimentary cover was based on correlation with MCS and boreholes data from Chukchi sea shelf. Six main unconformities were traced: regional unconformity (RU), Eocene unconformity (EoU) (for Eurasia basin only), post-Campanian unconformity (pCU), Brookian (BU - base of the Lower Brookian unit), Lower Cretaceous (LCU) and Jurassic (JU - top of the Upper Ellesmerian unit). The final step in our research was to estimate the total thickness of the sedimentary cover of the Arctic Ocean and adjacent Eurasian shelf using top of acoustic basement correlation data and bathymetry data

Greigite formed in early Pleistocene lacustrine sediments from the Heqing Basin, southwest China, and its paleoenvironmental implications

NASA Astrophysics Data System (ADS)

Qiang, Xiaoke; Xu, Xinwen; Zhao, Hui; Fu, Chaofeng

2018-05-01

The ferrimagnetic iron sulfide greigite (Fe3S4) occurs widely in sulfidic lacustrine and marine sedimentary environments. Knowledge of its formation and persistence is important for both magnetostratigraphic and paleoenvironmental studies. Although the formation mechanism of greigite has been widely demonstrated, the sedimentary environments associated with greigite formation in lakes, especially on relatively long timescales, are poorly understood. A long and continuous sequence of Pleistocene lacustrine sediments was recovered in the Heqing drill core from southwestern China, which provides an outstanding record of continental climate and environment. Integrated magnetic, geochemical, and paleoclimatic analysis of the lacustrine sequence provides an opportunity to improve our understanding of the environmental controls on greigite formation. Rock magnetic and scanning electron microscope analyses of selected samples from the core reveal that greigite is present in the lower part of the core (part 1, 665.8-372.5 m). Greigite occurs throughout this interval and is the dominant magnetic mineral, irrespective of the climatic state. The magnetic susceptibility (χ) record, which is mainly controlled by the concentration of greigite, matches well with variations in the Indian Summer Monsoon (ISM) index and total organic carbon (TOC) content, with no significant time lag. This indicates that the greigite formed during early diagenesis. In greigite-bearing intervals, with the χ increase, Bc value increase and tends to be stable at about 50 mT. Therefore, we suggest that χ values could estimate the variation of greigite concentration approximately in the Heqing core. Greigite favored more abundant in terrigenous-rich and organic-poor layers associated with weak summer monsoon which are characterized by high χ values, high Fe content, high Rb/Sr ratio and low TOC content. Greigite enhancement can be explained by variations in terrigenous inputs. Our studies demonstrate

Early Archaean collapse basins, a habitat for early bacterial life.

NASA Astrophysics Data System (ADS)

Nijman, W.

For a better definition of the sedimentary environment in which early life may have flourished during the early Archaean, understanding of the basin geometry in terms of shape, depth, and fill is a prerequisite. The basin fill is the easiest to approach, namely from the well exposed, low-grade metamorphic 3.4 - 3.5 Ga rock successions in the greenstone belts of the east Pilbara (Coppin Gap Greenstone Belt and North Pole Dome) in West Australia and of the Barberton Greenstone Belt (Buck Ridge volcano-sedimentary complex) in South Africa. They consist of mafic to ultramafic volcanic rocks, largely pillow basalts, with distinct intercalations of intermediate to felsic intrusive and volcanic rocks and of silicious sediments. The, partly volcaniclastic, silicious sediments of the Buck Ridge and North Pole volcano-sedimentary complexes form a regressive-transgressive sequence. They were deposited close to base level, and experienced occasional emersion. Both North Pole Chert and the chert of the Kittys Gap volcano-sedimentary complex in the Coppin Gap Greenstone Belt preserve the flat-and-channel architecture of a shallow tidal environment. Thickness and facies distribution appear to be genetically linked to systems, i.e. arrays, of syn-depositionally active, extensional faults. Structures at the rear, front and bottoms of these fault arrays, and the fault vergence from the basin margin towards the centre characterize the basins as due to surficial crustal collapse. Observations in the Pilbara craton point to a non-linear plan view and persistence for the basin-defining fault patterns over up to 50 Ma, during which several of these fault arrays became superposed. The faults linked high-crustal level felsic intrusions within the overall mafic rock suite via porphyry pipes, black chert veins and inferred hydrothermal circulations with the overlying felsic lavas, and more importantly, with the cherty sediments. Where such veins surfaced, high-energy breccias, and in the

Diagenesis of an 'overmature' gas reservoir: The Spiro sand of the Arkoma Basin, USA

USGS Publications Warehouse

Spotl, C.; Houseknecht, D.W.; Burns, S.J.

1996-01-01

The Spiro sand is a laterally extensive thin sandstone of earliest Atokan (Pennsylvanian) age that forms a major natural gas reservoir in the western Arkoma Basin, Oklahoma. Petrographic analysis reveals a variety of diagenetic alterations, the majority of which occurred during moderate to deep burial. Early diagenetic processes include calcite cementation and the formation of Fe-clay mineral peloids and coatings around quartz framework grains. These clays, which underwent transformation to well-crystallized chamosite [polytype Ib(?? = 90??)] on burial, are particularly abundant in medium-grained channel sandstones, whereas illitic clays are predominant in fine-grained interchannel sandstones. Subsequent to mechanical compaction, saddle ankerite precipitated in the reservoir at temperatures in excess of 70??C. Crude oil collected in favourable structural locations during and after ankeritization. Whereas hydrocarbons apparently halted inorganic diagenesis in oil-saturated zones, cementation continued in the underlying water-saturated zones. As reservoir temperatures increased further, hydrocarbons were cracked and a solid pyrobitumen residue remained in the reservoir. At temperatures exceeding ???140-150??C, non-syntaxial quartz cement, ferroan calcite and traces of dickite(?) locally reduced the reservoir quality. Local secondary porosity was created by carbonate cement dissolution. This alteration post-dated hydrocarbon emplacement and is probably related to late-stage infiltration of freshwater along 'leaky' faults. The study shows that the Spiro sandstone locally retained excellent porosities despite deep burial and thermal conditions that correspond to the zone of incipient very low grade metamorphism.

Petrology and diagenetic history of the upper shale member of the Late Devonian-Early Mississippian Bakken Formation, Williston Basin, North Dakota

USGS Publications Warehouse

Neil S. Fishman,; Sven O. Egenhoff,; Boehlke, Adam; Lowers, Heather A.

2015-01-01

The organic-rich upper shale member of the upper Devonian–lower Mississippian Bakken Formation (Williston Basin, North Dakota, USA) has undergone significant diagenetic alteration, irrespective of catagenesis related to hydrocarbon generation. Alteration includes precipitation of numerous cements, replacement of both detrital and authigenic minerals, multiple episodes of fracturing, and compaction. Quartz authigenesis occurred throughout much of the member, and is represented by multiple generations of microcrystalline quartz. Chalcedonic quartz fills radiolarian microfossils and is present in the matrix. Sulfide minerals include pyrite and sphalerite. Carbonate diagenesis is volumetrically minor and includes thin dolomite overgrowths and calcite cement. At least two generations of fractures are observed. Based on the authigenic minerals and their relative timing of formation, the evolution of pore waters can be postulated. Dolomite and calcite resulted from early postdepositional aerobic oxidation of some of the abundant organic material in the formation. Following aerobic oxidation, conditions became anoxic and sulfide minerals precipitated. Transformation of the originally opaline tests of radiolaria resulted in precipitation of quartz, and quartz authigenesis is most common in more distal parts of the depositional basin where radiolaria were abundant. Because quartz authigenesis is related to the distribution of radiolaria, there is a link between diagenesis and depositional environment. Furthermore, much of the diagenesis in the upper shale member preceded hydrocarbon generation, so early postdepositional processes were responsible for occlusion of significant original porosity in the member. Thus, diagenetic mineral precipitation was at least partly responsible for the limited ability of these mudstones to provide porosity for storage of hydrocarbons.

Eolian Dust and the Origin of Sedimentary Chert

USGS Publications Warehouse

Cecil, C. Blaine

2004-01-01

This paper proposes an alternative model for the primary source of silica contained in bedded sedimentary chert. The proposed model is derived from three principal observations as follows: (1) eolian processes in warm-arid climates produce copious amounts of highly reactive fine-grained quartz particles (dust), (2) eolian processes in warm-arid climates export enormous quantities of quartzose dust to marine environments, and (3) bedded sedimentary cherts generally occur in marine strata that were deposited in warm-arid paleoclimates where dust was a potential source of silica. An empirical integration of these observations suggests that eolian dust best explains both the primary and predominant source of silica for most bedded sedimentary cherts.

Multiple sources and extensive degradation of terrestrial sedimentary organic matter across an energetic, wide continental shelf

NASA Astrophysics Data System (ADS)

Zhu, Chun; Wagner, Thomas; Pan, Jian-Ming; Pancost, Richard D.

2011-08-01

The fate of organic carbon in marine sediments is closely linked to atmospheric CO2 concentrations and thus to climate variability over geological time scales. The East China Sea (ECS) is characterized not only by massive terrestrial organic matter (TOM) inputs from the Yangtze (Changjiang) River but also by a shallow (<130 m) and broad (>500 km) continental shelf with widespread relict sands, such that it is distinct from other continental margins. We examine the diagenesis of sedimentary TOM and the impacts of relict sands on TOM in the ECS. The results reveal that bulk δ13Corg values correlate with terrestrial biomarker concentrations in muddy and accumulative areas; in contrast, depleted δ13Corg values around -24.5‰ co-occur with almost absent terrestrial biomarkers in sandy/erosional areas. We suggest that mixing of contemporary TOM and marine OM dominates in the muddy/accumulative shelf areas, whereas a putative relict OM, associated with relict sands, appears to be significant in many sandy/erosional shelf areas. Given the global occurrence of relict sands, a persistent amount of relict OC (e.g., 0.1%) may complicate TOM budget calculations. In addition, our observations reveal that TOM is extensively partitioned and degraded in the estuary and continues to be partitioned and degraded during the along-shore and across-shelf transport, which is reflected by decreases in terrestrial biomarker concentrations and increases in degradation indices. This study highlights the unique and dynamic role of shallow and wide continental shelves with massive relict sands on TOM cycling.

Pre-lithification tectonic foliation development in a clastic sedimentary rock sequence from SW Ireland

NASA Astrophysics Data System (ADS)

Meere, Patrick; Mulchrone, Kieran; McCarthy, David

2017-04-01

The current orthodoxy regarding the development of regionally developed penetrative tectonic cleavage fabrics in sedimentary rocks is that it postdates lithification of those rocks. It is well established that fabric development under these circumstances is achieved by a combination of grain rigid body rotation, crystal-plastic deformation and pressure solution. The latter is believed to be the primary mechanism responsible for the domainal nature of cleavage development commonly observed in low grade metamorphic rocks. While there have been advocates for the development of tectonic cleavages before host rock lithification these are currently viewed as essentially local aberrations without regional significance. In this study we combine new field observations with strain analysis, element mapping and modelling to characterise Acadian (>50%) crustal shortening in a Devonian clastic sedimentary sequence from the Dingle Peninsula of south west Ireland. Fabrics in these rocks reflect significant levels of tectonic shortening are a product of grain translation, rigid body rotation and repacking of intra- and extra-formational clasts during deformation of an unconsolidated clastic sedimentary sequence. There is an absence of the expected domainal cleavage structure and intra-clast deformation expected with conventional cleavage formation. This study requires geologists to consider the possibility such a mechanism contributing to tectonic strain in a wide range of geological settings and to look again at field evidence that indicates early sediment mobility during deformation.

Geochemistry of Fine-grained Sediments and Sedimentary Rocks

NASA Astrophysics Data System (ADS)

Sageman, B. B.; Lyons, T. W.

2003-12-01

The nature of detrital sedimentary (siliciclastic) rocks is determined by geological processes that occur in the four main Earth surface environments encountered over the sediment's history from source to final sink: (i) the site of sediment production (provenance), where interactions among bedrock geology, tectonic uplift, and climate control weathering and erosion processes; (ii) the transport path, where the medium of transport, gradient, and distance to the depositional basin may modify the texture and composition of weathered material; (iii) the site of deposition, where a suite of physical, chemical, and biological processes control the nature of sediment accumulation and early burial modification; and (iv) the conditions of later burial, where diagenetic processes may further alter the texture and composition of buried sediments. Many of these geological processes leave characteristic geochemical signatures, making detrital sedimentary rocks one of the most important archives of geochemical data available for reconstructions of ancient Earth surface environments. Although documentation of geochemical data has long been a part of the study of sedimentation (e.g., Twenhofel, 1926, 1950; Pettijohn, 1949; Trask, 1955), the development and application of geochemical methods specific to sedimentary geological problems blossomed in the period following the Second World War ( Degens, 1965; Garrels and Mackenzie, 1971) and culminated in recent years, as reflected by the publication of various texts on marine geochemistry (e.g., Chester, 1990, 2000), biogeochemistry (e.g., Schlesinger, 1991; Libes, 1992), and organic geochemistry (e.g., Tissot and Welte, 1984; Engel and Macko, 1993).Coincident with the growth of these subdisciplines a new focus has emerged in the geological sciences broadly represented under the title of "Earth System Science" (e.g., Kump et al., 1999). Geochemistry has played the central role in this revolution (e.g., Berner, 1980; Garrels and Lerman

Origin and Evolution of The Early- Silurian Land Vascular Plants: Evidence From Biomarkers

NASA Astrophysics Data System (ADS)

Jin, R.

2016-12-01

Origin and early evolution of land vascular plants, is one of the most intriguing hotspots in the life science research. During the 1970s and 1980s,Pinnatiramosus qianensis was found in early-Silurian strata in guizhou of south China.43 years have passed. But so far, the biological characteristics and belonging of the age of this unique plant have been debated again and again, up in the air.Biomarkers have a good stability in the process of organic evolution, no more or less changed, so they have a special `function of mark'. While biomarkers can provide information about organic matter of hydrocarbon source rock (the source), the period of deposition and burial (diagenesis) environmental conditions, and many other aspects of information.This paper obtained the sedimentary environment, source of organic matter input and other relevant information, through extracting and analyzing biomarkers of the 26 samples in the late Ordovician to early Silurian strata in NorthGuizhou areas. According to the results, Pr/Ph of late Ordovician Meitan Fm-early Silurian Hanjiadian Fm is high.It manifests more pristane, characterized by reductive environment. At the bottom of the Hanjiadian Fm, Pr/Ph has a volatility.Some huge environmental changes may have taken place in the corresponding period. N-alkanes do not have parity advantage or has even carbon advantage slightly.The peak carbon is mainly in low carbon number.(C21 + C22)/(C28 + C29) is high.Aquatic organisms is a major source of organic matter during this period,C21-/C22+ is low.This may be caused by the relatively serious loss of light hydrocarbon during the separation of components. In the Hanjiadian Fm,information of C29/C27 sterane ratios and oleanane index showed a trend of rising at the same time, indicating that during this period, there was a gradual increase input in the number of higher plants.The stable carbon isotope of saturated hydrocarbon and aromatic hydrocarbon in the Hanjiadian Fm also gradually become

Alteration of immature sedimentary rocks on Earth and Mars. Recording Aqueous and Surface-atmosphere Processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cannon, Kenneth M.; Mustard, John F.; Salvatore, Mark R.

The rock alteration and rind formation in analog environments like Antarctica may provide clues to rock alteration and therefore paleoclimates on Mars. Clastic sedimentary rocks derived from basaltic sources have been studied in situ by martian rovers and are likely abundant on the surface of Mars. Moreover, how such rock types undergo alteration when exposed to different environmental conditions is poorly understood compared with alteration of intact basaltic flows. Here we characterize alteration in the chemically immature Carapace Sandstone from Antarctica, a terrestrial analog for martian sedimentary rocks. We employ a variety of measurements similar to those used on previousmore » and current Mars missions. Laboratory techniques included bulk chemistry, powder X-ray diffraction (XRD), hyperspectral imaging and X-ray absorption spectroscopy. Through these methods we find that primary basaltic material in the Carapace Sandstone is pervasively altered to hydrated clay minerals and palagonite as a result of water–rock interaction. A thick orange rind is forming in current Antarctic conditions, superimposing this previous aqueous alteration signature. The rind exhibits a higher reflectance at visible-near infrared wavelengths than the rock interior, with an enhanced ferric absorption edge likely due to an increase in Fe 3+ of existing phases or the formation of minor iron (oxy)hydroxides. This alteration sequence in the Carapace Sandstone results from decreased water–rock interaction over time, and weathering in a cold, dry environment, mimicking a similar transition early in martian history. This transition may be recorded in sedimentary rocks on Mars through a similar superimposition mechanism, capturing past climate changes at the hand sample scale. These results also suggest that basalt-derived sediments could have sourced significant volumes of hydrated minerals on early Mars due to their greater permeability compared with intact igneous rocks.« less

Occurrence of Tourmaline in Metasedimentary Rocks of the Isua Supracrustal Belt, Greenland: Implications for Ribose Stabilization in Hadean Marine Sediments.

PubMed

Mishima, Shinpei; Ohtomo, Yoko; Kakegawa, Takeshi

2016-06-01

Abiotic formation of RNA was important for the emergence of terrestrial life, but the acknowledged difficulties of generating and stabilizing ribose have often raised questions regarding how the first RNA might have formed. Previous researchers have proposed that borate could have stabilized ribose; however, the availability of borate on the early Earth has been the subject of intense debate. In order to examine whether borate was available on the early Earth, this study examined metasedimentary rocks from the Isua Supracrustal Belt. Garnet, biotite, and quartz comprise the major constituents of the examined rocks. Field relationships and the chemical compositions of the examined rocks suggest sedimentary origin. The present study found that garnet crystals contain a number of inclusions of tourmaline (a type of borosilicate mineral). All tourmaline crystals are Fe-rich and categorized as schorl. Both garnet and tourmaline often contain graphite inclusions and this close association of tourmaline with garnet and graphite has not been recognized previously. Garnet-biotite and graphite geothermometers suggest that the tourmaline in garnet experienced peak metamorphic conditions (~500 °C and 5 kbar). The mineralogical characteristics of the tourmaline and the whole rock composition indicate that the tourmaline formed authigenically in the sediment during diagenesis and/or early metamorphism. Clay minerals in modern sediments have the capability to adsorb and concentrate borate, which could lead to boron enrichment during diagenesis, followed by tourmaline formation under metamorphic conditions. Clay minerals, deposited on the early Archean seafloor, were the precursors of the garnet and biotite in the examined samples. The studied tourmaline crystals were most likely formed in the same way as modern tourmaline in marine sediments. Therefore, boron enrichment by clays must have been possible even during the early Archean. Thus, similar enrichment could have been

The early diagenetic and PETROphysical behaviour of recent cold-water CARbonate mounds in Deep Environments (PETROCARDE)

NASA Astrophysics Data System (ADS)

Foubert, Anneleen; Pirlet, Hans; Thierens, Mieke; de Mol, Ben; Henriet, Jean-Pierre; Swennen, Rudy

2010-05-01

Sub-recent cold-water carbonate mounds localized in deeper slope settings on the Atlantic continental margins cannot be any longer neglected in the study of carbonate systems. They clearly play a major role in the dynamics of mixed siliciclastic-carbonate and/or carbonate-dominated continental slopes. Carbonate accumulation rates of cold-water carbonate mounds are about 4 to 12 % of the carbonate accumulation rates of tropical shallow-water reefs but exceed the carbonate accumulation rates of their slope settings by a factor of 4 to 12 (Titschack et al., 2009). These findings emphasize the importance of these carbonate factories as carbonate niches on the continental margins. The primary environmental architecture of such carbonate bodies is well-characterized. However, despite proven evidences of early diagenesis overprinting the primary environmental record (e.g. aragonite dissolution) (Foubert & Henriet, 2009), the extent of early diagenetic and biogeochemical processes shaping the petrophysical nature of mounds is until now not yet fully understood. Understanding (1) the functioning of a carbonate mound as biogeochemical reactor triggering early diagenetic processes and (2) the impact of early diagenesis on the petrophysical behaviour of a carbonate mound in space and through time are necessary (vital) for the reliable prediction of potential late diagenetic processes. Approaching the fossil carbonate mound record, through a profound study of recent carbonate bodies is innovative and will help to better understand processes observed in the fossil mound world (such as cementation, brecciation, fracturing, etc…). In this study, the 155-m high Challenger mound (Porcupine Seabight, SW of Ireland), drilled during IODP Expedition 307 aboard the R/V Joides Resolution (Foubert & Henriet, 2009), and mounds from the Gulf of Cadiz (Moroccan margin) will be discussed in terms of early diagenetic processes and petrophysical behaviour. Early differential diagenesis

EGS in sedimentary basins: sensitivity of early-flowback tracer signals to induced-fracture parameters

NASA Astrophysics Data System (ADS)

Karmakar, Shyamal; Ghergut, Julia; Sauter, Martin

2015-04-01

-effective aperture, in a water fracture (WF), or - fracture thickness and porosity, for a gel-proppant fracture (GPF). We find that parameter determination from SW early signals can significantly be improved by concomitantly using a number of solute tracers with different transport and retardation behaviour. We considered tracers of different sorptivity to proppant coatings, and to matrix rock surfaces, for GPF, as well as contrasting-diffusivity or -sorptivity tracers, for WF. An advantage of this SW approach is that it requires only small chaser volumes (few times the fracture volume), not relying on advective penetration into the rock matrix. Thus, selected tracer species are to be injected during the very last stage of the fracturing process, when fracture sizes and thus target parameters are supposed to attain more or less stable values. We illustrate the application of these tracer test design principles using hydro- and lithostratigraphy data from the Geothermal Research Platform at Groß Schönebeck [4], targeting a multi-layer reservoir (sedimentary and crystalline formations in 4-5 km depth) in the NE-German Sedimentary Basin. Acknowledgments: This work benefited from long-term support from Baker Hughes (Celle) and from the Lower-Saxonian Science and Culture Ministry (MWK Niedersachsen) within the applied research project gebo (Geothermal Energy and High-Performance Drilling, 2009-2014). The first author gratefully acknowledges continued financial support from the DAAD (German Academic Exchange Service) to pursuing Ph. D. work. References: [1] http://www.sciencedirect.com/science/article/pii/S1876610214017391 [2] http://www.geothermal-energy.org/cpdb/record_detail.php?id=7215 [3] http://www.geothermal-energy.org/cpdb/record_detail.php?id=19034 [4] http://www.gfz-potsdam.de/en/scientific-services/laboratories/gross-schoenebeck/

Pedo-sedimentary record of human-environment interaction in ditches and waterlogged depressions on tableland (roman and early medieval period) : micromorphological cases studies from Marne-la-Vallée area (Paris Basin, France)

NASA Astrophysics Data System (ADS)

Cammas, C.; Blanchard, J.; Broutin, P.; Berga, A.

2012-04-01

On lœss derived soils located on the Stampien plateau from the Paris Basin (France), archaeological anthroposols and ancient cultivated soils are only preserved in very few places. Recent archaeological excavations showed the presence of a pattern of roman ditches and waterlogged depressions (« mares ») under the actual cultivated horizon (Ap). This presence strongly suggests extensive past agricultural practices and water management. An original system of ditches was found Near Marne-la-Vallée (France). It is composed of two parts, one being large ditches characterized by flat bottom and sometimes water layered deposits, called « fossés collecteurs » by the archaeologists, and the orher being smaller ditches with colluvial deposits. Our objectives was to use archaeological and micromorphological studies in order to study i) the agricultural function of these ditches and depressions, ii) their evolution with time. Observations conducted on the infilling of a « fossé collecteur » at Bussy-Saint-Georges suggest that it was not part of a drainage system, but that it was a linear water controlled system, with a ramp in one part, and a basin or a tank in another, and that it was used for others anthropic activities. In the same area, a large waterlogged depression was studied, and micromorphological analysis helped to elucidate its pedo-sedimentary formation processes. At the bottom, massive silty clayey matrix retained water. Thin layers composed of silt and clay (indicating low energy flows and decantation), sometimes impregnated and hardened by iron, alternated with silty deposit (indicating higher ernergy water layered deposits). The thin, non porous and iron impregnated crusts helped to raise the depression level, as well as, most likely the water table during roman period, maintaining waterlogging conditions. At the beginning of the early medival period, a slightly peaty event was discriminated. Higher in the profile, in more redoxic conditions

Chronostratigraphy in karst records from the Epipaleolithic to the Mid/Early Neolithic (c. 13.0-6.0 cal ka BP) in the Catalan Coastal Ranges of NE Iberia: environmental changes, sedimentary processes and human activity

NASA Astrophysics Data System (ADS)

Bergadà, M. Mercè; Cervelló, Josep M.; Edo, Manel; Cebrià, Artur; Oms, F. Xavier; Martínez, Pablo; Antolín, Ferran; Morales, Juan Ignacio; Pedro, Mireia

2018-03-01

The stratigraphic, sedimentary and palaeoenvironmental features reflected in cavities in the Catalan Coastal Ranges of NE Iberia (Can Sadurní and Guineu caves) characterize the periods of pronounced climatic and human complexity that occurred c. 13.0-6.0 cal ka BP. This includes the stages of the Younger Dryas and Mid/Early Holocene, the latter being one of the periods of so-called Rapid Climatic Changes (RCCs). These caves, like others in Mediterranean contexts, are the result of an old duct originating in the saturated zone of the karst system and open to the outside; recording a succession of different detrital and anthropic episodes of the Epipaleolithic, Mesolithic and Neolithic communities. From this study it can be seen that paleoclimatic events do not always present clear signals in the karst records, especially c. 12.7-7.4 cal ka BP, corresponding to the Epipaleolithic and Mesolithic. It is characterized by a stratigraphic discontinuity in which there are phases with predominantly detrital sedimentation alternating with hiatus intervals. Detrital sedimentation formed by fine material colluvium with gravitational movements or solifluction processes in fresh and humid conditions. It appears in the following chronological intervals: 12.7-12.2 cal ka BP, 11.5/11.1-10.7/10.4 cal ka BP and 8.2-8.0 cal ka BP (less humid). Hiatus phases are represented in the rest of the sequence up to c. 7.4 cal ka BP. From the sedimentary point of view these stages of hiatus are indicative of phases of stability or lack of episodes with seasonal contrasts; a fact that would cause interruptions to detrital deposition in the interior of the caves. In contrast, in the period c. 7.4 to 6.0 cal ka BP, attributed to the Middle and Early Neolithic, there is a certain stratigraphic continuity. From the sedimentary point of view it is distinguished by a variability of processes that responds to accumulative episodes of short duration characteristic of morphogenesis of the slopes in an

Sedimentary exhalative (sedex) zinc-lead-silver deposit model

USGS Publications Warehouse

Emsbo, Poul; Seal, Robert R.; Breit, George N.; Diehl, Sharon F.; Shah, Anjana K.

2016-10-28

This report draws on previous syntheses and basic research studies of sedimentary exhalative (sedex) deposits to arrive at the defining criteria, both descriptive and genetic, for sedex-type deposits. Studies of the tectonic, sedimentary, and fluid evolution of modern and ancient sedimentary basins have also been used to select defining criteria. The focus here is on the geologic characteristics of sedex deposit-hosting basins that contain greater than 10 million metric tons of zinc and lead. The enormous size of sedex deposits strongly suggests that basin-scale geologic processes are involved in their formation. It follows that mass balance constraints of basinal processes can provide a conceptual underpinning for the evaluation of potential ore-forming mechanisms and the identification of geologic indicators for ore potential in specific sedimentary basins. Empirical data and a genetic understanding of the physicochemical, geologic, and mass balance conditions required for each of these elements are used to establish a hierarchy of quantifiable geologic criteria that can be used in U.S. Geological Survey national assessments.  In addition, this report also provides a comprehensive evaluation of environmental considerations associated with the mining of sedex deposits.

Early metal pollution in southwestern Europe: the former littoral lagoon of El Almarjal (Cartagena mining district, S.E. Spain).A sedimentary archive more than 8000 years old.

PubMed

Manteca, José-Ignacio; Ros-Sala, Milagros; Ramallo-Asensio, Sebastián; Navarro-Hervás, Francisca; Rodríguez-Estrella, Tomás; Cerezo-Andreo, Felipe; Ortiz-Menéndez, José-Eugenio; de-Torres, Trinidad; Martínez-Andreu, Miguel

2017-04-01

A borehole drilling campaign has allowed the study of a former littoral lagoon located next to the harbour city of Cartagena in South-East Spain (close to the Sierra de Cartagena polymetallic ore deposits). This lagoon, which developed during the Holocene, was first a shallow sedimentary marine environment and later evolved into a swampy semi-endorheic basin named "Almarjal" (after the Arab term from the fourteenth century). The lagoon eventually dried out and at present forms part of the substratum of the modern sector of the city urban area. The basin representative sediments are sapropelic black silty facies forming a continuous sedimentary archive, accounting for more than 8000 years of depositional phenomena. The geochemical study of these sediments, together with their absolute calibrated dating by 14 C, allows definition of successive stages of mining and metallurgical activities in the area. In turn, this information provides a more comprehensive perspective regarding metal pollution, particularly lead contamination during different periods of the Recent Prehistory and the Classical Age. The results indicate that the beginning of contamination by lead and other heavy metals occurred as early as 4500 years ago, when the Final Chalcolithic period was taking place in the South-East of the Iberian Peninsula. This finding provides further insights regarding the debate on the origins of lead mining and metallurgy in SE Spain.

Diagenesis of fossil coral skeletons: Correlation between trace elements, textures, and 234U /238U

NASA Astrophysics Data System (ADS)

Bar-Matthews, M.; Wasserburg, G. J.; Chen, J. H.

1993-01-01

A comparative study of Pleistocene fossil coral skeletons and of modern coral skeletons was carried out using petrographie and trace element analyses on a suite of Pleistocene samples that had previously been studied for 234U, 230Th, and U- 230Th ages ( CHEN et al. 1991). Evidence of a range of diagenetic changes can be recognized by optical (OM) and scanning electron microscopy (SEM). The normal texture exhibited by modern corals under OM consists of fine needles of aragonite forming a radial-fibrous pattern around a central dark line (center of calcification). This pattern can also be seen in many fossil corals. In most cases, the central dark line partially disappears during diagenesis, the radialfibrous pattern is obscured, and there is a distinct coarsening of the radial fabric of aragonite to unoriented platy or equant aragonite crystals. SEM images show diagenetic textures ranging from dense structureless images of the coralline matrix, with sharp boundaries at the septa walls, to the development of (1) a patchy distribution of dissolution micropores partially filled with aragonite fibers in the matrix, (2)aragonite needles coming from selvages in the septa walls which radiate into the septa voids. Using an electron microprobe and SEM, concentrations of Na, S, Sr, and Mg were measured. No other trace elements were detected. Na, S, and Mg contents of the matrix, the fibrous micropores, and radiating needles are highly variable and well correlated. High concentrations of Na, S, and Mg were found in modern living corals with lower concentrations in fossil corals and fibrous micropores, and the lowest value in the radiating needles. The reason for the correlations of Na, S, and Mg and crystal chemistry and the response to diagenesis of these trace elements is not understood. The average concentrations of Na, S, and Mg for each sample, when plotted against the whole coral initial δ 234U, are generally correlated ( CHEN et al., 1991). As all these diagenetic

Revised interpretations of stable C and O patterns in carbonate rocks resulting from meteoric diagenesis

NASA Astrophysics Data System (ADS)

Swart, Peter K.; Oehlert, Amanda M.

2018-02-01

A positive correlation between the δ13C and δ18O values of carbonate rocks is a screening tool widely used to identify the overprint of meteoric diagenesis on the original isotopic composition of a sample. In particular, it has been suggested that systematic change from negative to positive δ13C and δ18O values with increasing depth in the core is an indicator of alteration within the zone of mixing between meteoric and marine waters. In this paper, we propose that such covariance is not generated within the traditionally defined mixing zone, and that positive correlations between δ13C and δ18O values in marine carbonates are not necessarily indicators of meteoric alteration. This new interpretation is based on data collected from the shallow sub-surface of the Bahamas, a region unequivocally influenced by meteoric waters to depths of at least 200 m below the current sediment-water interface. The classic interpretation of the diagenetic environments, based on changes in the δ13C and δ18O values, would suggest the maximum penetration of freshwater occurs between 65 and 100 m below seafloor. Below these depths, a strong positive covariation between the δ13C and δ18O values exists, and would traditionally be defined as the mixing zone. However, based upon known changes in sea level, the penetration of the freshwater lens extends significantly below this limit. We contend that the zone showing covariance of δ13C and δ18O values is actually altered within the freshwater lens, and not the mixing zone as previously proposed. The co-varying trend in δ13C and δ18O values is the result of diagenetic processes occurring at the interface between vadose and phreatic zones. Significantly greater rates of recrystallization and neomorphism are driven by the increased rates of oxidation of organic matter at this transition with progressively less alteration occurring with increasing depth. As sea level oscillates, the position of this interface moves through the

Tectonostratigraphic reconstruction Cretaceous volcano-sedimentary in the northwestern Andes: from extensional tectonics to arc accretion.

NASA Astrophysics Data System (ADS)

Zapata, S.; Patino, A. M.; Cardona, A.; Mejia, D.; Leon, S.; Jaramillo, J. S.; Valencia, V.; Parra, M.; Hincapie, S.

2014-12-01

Active continental margins characterized by continuous convergence experienced overimposed tectonic configurations that allowed the formation of volcanic arcs, back arc basins, transtensional divergent tectonics or the accretion of exotic volcanic terranes. Such record, particularly the extensional phases, can be partially destroyed and obscure by multiple deformational events, the accretion of exotic terranes and strike slip fragmentation along the margin. The tectonic evolution of the northern Andes during the Mesozoic is the result of post Pangea extension followed by the installation of a long-lived Jurassic volcanic arc (209 - 136 ma) that apparently stops between 136 Ma and 110 Ma. The Quebradagrande Complex has been define as a single Lower Cretaceous volcano-sedimentary unit exposed in the western flank of the Central Cordillera of the Colombian Andes that growth after the Late Jurassic to Early Cretaceous magmatic hiatus. The origin of this unit have been related either to an oceanic volcanic arc or a marginal basin environment. The existence of such contrasting models reflect the regional perspective followed in published studies and the paucity of detail analysis of the volcano-sedimentary sequences.We integrate multiple approaches including structural mapping, stratigraphy, geochemistry, U-Pb provenance and geochronology to improve the understanding of this unit and track the earlier phases of accumulation that are mask on the overimposed tectonic history. Our preliminary results suggest the existence of different volcano-sedimentary units that accumulated between 100 Ma and 82 Ma.The older Lower Cretaceous sequences was deposited over Triassic metamorphic continental crust and include a upward basin deepening record characterized by thick fan delta conglomerates, followed by distal turbidites and a syn-sedimentary volcanic record at 100 ma. The other sequence include a 85 - 82 Ma fringing arc that was also formed close to the continental margin or

Discriminating between natural and anthropogenic features of the sedimentary record in the coastal Beaufort Sea

NASA Astrophysics Data System (ADS)

Trefry, J. H.; Trocine, R. P.; Fox, A. L.; Fox, S. L.; Durell, G.; Kasper, J.

2016-02-01

The coastal Beaufort Sea is at a crossroads with respect to the impacts of human activities. Accurate discrimination of regional and global anthropogenic impacts, versus those due to natural physical and biogeochemical processes, is an important tool for managing environmental issues in the Arctic. We have investigated several natural and anthropogenic features in age-dated sediment cores from the coastal Beaufort Sea. For example, Hg enrichment (by 20 to >50% or +20 to 40 ng/g) was identified in some surface sediments using Hg/Al ratios in cores from nearshore, outer shelf and slope environments. Nearshore Hg anomalies, although quite limited in number, have been linked to drilling fluids deposited during oil and gas exploration in the 1980s. In contrast, similar offshore Hg anomalies are likely due to natural sediment diagenesis as previously noted by others in the deeper Arctic Ocean. We also found Ba enrichment in surface sediments that can be best explained by the deposition of natural, Ba-rich suspended particles from the Colville River; yet, Ba enrichment can sometimes be explained by the presence of drilling fluids in sediments near historic drilling sites. Human induced diagenetic changes are likely to follow current increases in river runoff and coastal erosion. Higher deposition rates for sediment and organic carbon in the coastal Beaufort Sea may create future anomalies for As, Cd and other metals. For example, metal anomalies can presently be found in older subsurface sediments where a layer of carbon-rich sediment was previously deposited. Correct identification of natural versus anthropogenic forcing factors that lead to distinct diagenetic features in the sedimentary record will help us to identify problem areas and make informed regulatory decisions.

Schiaparelli Sedimentary Rocks

NASA Technical Reports Server (NTRS)

2003-01-01

MGS MOC Release No. MOC2-403, 26 June 2003

Some of the most important high resolution imaging results of the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) experiment center on discoveries about the presence and nature of the sedimentary rock record on Mars. This old meteor impact crater in northwestern Schiaparelli Basin exhibits a spectacular view of layered, sedimentary rock. The 2.3 kilometer (1.4 miles) wide crater may have once been completely filled with sediment; the material was later eroded to its present form. Dozens of layers of similar thickness and physical properties are now expressed in a wedding cake-like stack in the middle of the crater. Sunlight illuminating the scene from the left shows that the circle, or mesa top, at the middle of the crater stands higher than the other stair-stepped layers. The uniform physical properties and bedding of these layers might indicate that they were originally deposited in a lake (it is possible that the crater was at the bottom of a much larger lake, filling Schiaparelli Basin); alternatively, the layers were deposited by settling out of the atmosphere in a dry environment. This picture was acquired on June 3, 2003, and is located near 0.9oS, 346.2oW.

Reducing Risk in Horizontal Directional Drilling (HDD) in Soft Sedimentary Environments

NASA Astrophysics Data System (ADS)

Yarbrough, L. D.; Skonberg, E.

2017-12-01

This is a focus on the applied outcome of geologic reports and the scale of near surface geologic process which affect the success of horizontal directional drilling (HDD) operations. Often there is too little data to fully characterize the subsurface along the drilled hole. Adding uncertainty is the exploration borehole is typically vertical while the drill path orientation of the HDD is not. The stratigraphic principle of original horizontality is heavily relied upon when interpreting the geology of the drill path and for good reason because of the depositional processes involved. However, the scale of secondary sedimentary processes, specifically zones of induration and their potential effects on the HDD can be at a scale or frequency that is not properly sampled during the geotechnical investigation. This lack of direct evidence could lead geologists and designers not to include these low-frequency phenomena in their risk analysis. For HDD planning and design, the industry routinely generalizes the earth materials to be encountered as soft or hard. This use of inexact, colloquial phrasing paints a picture of the a nearly homogeneous drilling site. Even though a majority of the site can be characterized as a low-strength or high-strength material, the diagenesis of sediments can include zones with wide-ranging strengths that can negatively impact the rate of penetration, the ability to steer and bore hole stability. In this generalization, soft is a majority of low strength or unconsolidated material (sands, silts, and clays). This does not preclude concretions and other indurated lenticular features that are widespread in the Gulf Coast states. This investigation reviews several formations commonly encountered during medium to large diameter (>10 inches) HDD operations. The Bashi formation with surface exposures in Mississippi and Alabama; the Wilcox Group in southern Mississippi and central Louisiana; the Cook Mountain Formation; the Hatchetigbee formation and

Provenance, diagenesis, tectonic setting and reservoir quality of the sandstones of the Kareem Formation, Gulf of Suez, Egypt

NASA Astrophysics Data System (ADS)

Zaid, Samir M.

2013-09-01

The Middle Miocene Kareem sandstones are important oil reservoirs in the southwestern part of the Gulf of Suez basin, Egypt. However, their diagenesis and provenance and their impact on reservoir quality, are virtually unknown. Samples from the Zeit Bay Oil Field, and the East Zeit Oil Field represent the Lower Kareem (Rahmi Member) and the Upper Kareem (Shagar Member), were studied using a combination of petrographic, mineralogical and geochemical techniques. The Lower Rahmi sandstones have an average framework composition of Q95F3.4R1.6, and 90% of the quartz grains are monocrystalline. By contrast, the Upper Shagar sandstones are only slightly less quartzose with an average framework composition of Q76F21R3 and 82% of the quartz grains are monocrystalline. The Kareem sandstones are mostly quartzarenite with subordinate subarkose and arkose. Petrographical and geochemical data of sandstones indicate that they were derived from granitic and metamorphic terrains as the main source rock with a subordinate quartzose recycled sedimentary rocks and deposited in a passive continental margin of a syn rift basin. The sandstones of the Kareem Formation show upward decrease in maturity. Petrographic study revealed that dolomite is the dominant cement and generally occurs as fine to medium rhombs pore occluding phase and locally as a grain replacive phase. Authigenic quartz occurs as small euhedral crystals, locally as large pyramidal crystals in the primary pores. Authigenic anhydrites typically occur as poikilotopic rhombs or elongate laths infilling pores but also as vein filling cement. The kaolinite is a by-product of feldspar leaching in the presence of acidic fluid produced during the maturation of organic matter in the adjacent Miocene rocks. Diagenetic features include compaction; dolomite, silica and anhydrite cementation with minor iron-oxide, illite, kaolinite and pyrite cements; dissolution of feldspars, rock fragments. Silica dissolution, grain replacement and

Salt-dome-related diagenesis of Miocene sediment, Black Bayou field, Cameron Parish, Louisiana

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leger, W.R.

1988-09-01

The Black Bayou field is associated with a salt dome that pierces Miocene sediment and rises to within 900 ft (275 m) of the surface. The Louisiana Gulf Coast regional geothermal gradient is locally affected by the salt dome. The gradient increases to values greater than the regional gradient, 1.26/degrees/F/100 ft (23/degrees/C/km), near the dome. Local effects of the salt dome on clastic diagenesis have been determined by studying sandstone samples adjacent to and away from the salt dome within Miocene sediment. Sample depths range from 4155 to 6145 ft (1266 to 1873 m). Distances of samples from the edgemore » of the dome range from 82 to 820 ft (25 to 250 m).« less

Tertiary sedimentary history and structure of the Valencia trough (western Mediterranean)

NASA Astrophysics Data System (ADS)

Maillard, A.; Mauffret, A.; Watts, A. B.; Torné, M.; Pascal, G.; Buhl, P.; Pinet, B.

1992-03-01

We present here main results of the Common Depth Point (CDP) data acquired during the Valsis 2 Cruise in 1988 in the Valencia trough. The profiles are tied in with industrial well data and this correlation allows the sedimentary and structural history of the region to be deduced. The Valsis Cruise seismic profiles have been supplemented by a very dense grid of industrial seismic lines and these data permit us to establish an accurate depth to basement map. The formation of the initial grabens, coeval with those of the Gulf of Lions, is related to the Early Miocene opening of the northwestern Mediterranean basin and the Barcelona graben is filled by the same sedimentary layers, including evaporites, as that of the Provençal region. Nevertheless, the Valencia-Catalan grabens have been reactivated by young extensional tectonics which could be a consequence of the convergence of Africa relative to Europe. The Valencia trough is segmented by transfer faults which trend NW-SE. These faults, which have a more accentuated structural expression than the Valencia and Catalonia grabens, may act as transform faults separating the individual Balearic Islands. The transfer faults are in strike with volcanic ridges which have been sampled during the DSDP Leg 13. The dense seismic grid allows us to delineate several widespread volcanic features in the Valencia trough which have been active from the Early Miocene to the Pleistocene. However, we note that the volcanic features are mainly Miocene in age whereas the recent volcanism is restricted to a narrow zone (Columbretes Islands). The compressional tectonics which deformed the Balearic Islands does not appear to extend far towards the North. We delineate the compressional front north of Ibiza, but we failed to determine any thrust or fold north of Mallorca, whereas an extensional tectonics is evident.

Inclination Shallowing in the Permian/Triassic Boundary Sedimentary Sections of the East European Platform: the New Paleomagnetic Pole and its Significance for GAD Hypothesis

NASA Astrophysics Data System (ADS)

Veselovskiy, R. V.; Fetisova, A. M.; Balabanov, Y.

2017-12-01

One of the key challenges which are traditionally encountered in studying the paleomagnetism of terrigenous sedimentary strata is the necessity to allow for the effect of shallowing of paleomagnetic inclinations which takes place under the compaction of the sediment at the early stages of diagenesis and most clearly manifests itself in the case of midlatitude sedimentation. Traditionally, estimating the coefficient of inclination flattening (f) implies routine re-deposition experiments and studying their magnetic anisotropy (Kodama, 2012), which is not possible in every standard paleomagnetic laboratory. The Elongation-Inclination (E/I) statistical method for estimating the coefficient of inclination shallowing, which was recently suggested in (Tauxe and Kent, 2004), does not require the investigation of the rock material in a specially equipped laboratory but toughens the requirements on the paleomagnetic data and, primarily, regarding the volume of the data, which significantly restricts the possibilities of the post factum estimation and correction for inclination shallowing. We present the results of the paleomagnetic reinvestigation of the some key sections of the Upper Permian and Lower Triassic rocks located on the East European Platform. The obtained paleomagnetic data allowed us to estimate the coefficient of inclination shallowing by the E/I method and calculate a new P-Tr paleomagnetic pole for Europe. The absence of a statistically significant difference between the mean Siberian, European and North American Permian-Triassic paleomagnetic poles allow us to conclude that 252 Ma the configuration of the Earth's magnetic field was predominantly dipole. We believe that the assumption of the non-dipolarity of the geomagnetic field at the Permian-Triassic boundary, which has been repeatedly discussed in recent decades (Van der Voo and Torsvik, 2001; Bazhenov and Shatsillo, 2010; Veselovskiy and Pavlov, 2006), arose due to the failure to take into account the

Synchronisation of sedimentary records using tephra: A postglacial tephrochronological model for the Chilean Lake District

NASA Astrophysics Data System (ADS)

Fontijn, Karen; Rawson, Harriet; Van Daele, Maarten; Moernaut, Jasper; Abarzúa, Ana M.; Heirman, Katrien; Bertrand, Sébastien; Pyle, David M.; Mather, Tamsin A.; De Batist, Marc; Naranjo, Jose-Antonio; Moreno, Hugo

2016-04-01

Well-characterised tephra horizons deposited in various sedimentary environments provide a means of synchronising sedimentary archives. The use of tephra as a chronological tool is however still widely underutilised in southern Chile and Argentina. In this study we develop a postglacial tephrochronological model for the Chilean Lake District (ca. 38 to 42°S) by integrating terrestrial and lacustrine records. Tephra deposits preserved in lake sediments record discrete events even if they do not correspond to primary fallout. By combining terrestrial with lacustrine records we obtain the most complete tephrostratigraphic record for the area to date. We present glass geochemical and chronological data for key marker horizons that may be used to synchronise sedimentary archives used for palaeoenvironmental, palaeoclimatological and palaeoseismological purposes. Most volcanoes in the studied segment of the Southern Volcanic Zone, between Llaima and Calbuco, have produced at least one regional marker deposit resulting from a large explosive eruption (magnitude ≥ 4), some of which now have a significantly improved age estimate (e.g., the 10.5 ka Llaima Pumice eruption from Llaima volcano). Others, including several units from Puyehue-Cordón Caulle, are newly described here. We also find tephra related to the Cha1 eruption from Chaitén volcano in lake sediments up to 400 km north from source. Several clear marker horizons are now identified that should help refine age model reconstructions for various sedimentary archives. Our chronological model suggests three distinct phases of eruptive activity impacting the area, with an early-to-mid-Holocene period of relative quiescence. Extending our tephrochronological framework further south into Patagonia will allow a more detailed evaluation of the controls on the occurrence and magnitude of explosive eruptions throughout the postglacial.

Geochemistry of Late Cretaceous phosphorites in Egypt: Implication for their genesis and diagenesis

NASA Astrophysics Data System (ADS)

Baioumy, H. M.; Tada, R.; Gharaie, M. H. M.

2007-09-01

Phosphorite deposits in Egypt, known as the Duwi Formation, are a part of the Middle East to North Africa phosphogenic province of Late Cretaceous to Paleogene age. Phosphatic grains in these deposites are classified into phosphatic mudclasts and phosphatic bioclasts. Phosphatic bioclasts are subdivided into fish bone fragments and shark tooth fragments. All phosphatic grains are composed of francolite. Chemical mapping of the phosphatic grains using Electron Probe Microanalysis (EPMA) indicated that the phosphatic mudclasts are homogeneous in their chemical composition and no concentric texture nor chemical zoning are observed. Some of the bone fragments show Fe and S zoning. No significant difference in chemical composition is observed between the phosphatic mudclasts and bioclasts. Acid-insoluble residues of the phosphorites show lower values of the Chemical Index of Alteration (CIA) compared to the associated rocks. Structural CO 2 contents in the francolites range from 3.32% to 7.21% with an average of 5.3%. The δ13C PDB values range from -4.04‰ to -8.7‰, while the δ18O PDB values range from -4.3‰ to -10.3‰. The compositional homogeneity of the mudclasts, Fe and S zoning in some of the bone fragments and the difference in the Chemical Index of Alteration between the acid-insoluble residues of the phosphorites and the associated rocks suggest that the phosphatic grains in the Duwi Formation are derived from pre-existing authigenic phosphorites, which reworked and concentrated afterward. Negative δ13C values of structural CO 2 suggest that the CO 2 was derived from degradation of organic matter. Low δ18O values of structural CO 2 can be attributed to the influence of meteoric water. Higher CO 2, SO 3 and F contents compared to the recent authigenic phosphorites and negative δ13C and δ18O values of structural CO 2 indicate that diagenesis plays an important role in the modification of the chemical composition of phosphatic grains and that the

Sedimentary controls on modern sand grain coat formation

NASA Astrophysics Data System (ADS)

Dowey, Patrick J.; Worden, Richard H.; Utley, James; Hodgson, David M.

2017-05-01

Coated sand grains can influence reservoir quality evolution during sandstone diagenesis. Porosity can be reduced and fluid flow restricted where grain coats encroach into pore space. Conversely pore-lining grain coats can restrict the growth of pore-filling quartz cement in deeply buried sandstones, and thus can result in unusually high porosity in deeply buried sandstones. Being able to predict the distribution of coated sand grains within petroleum reservoirs is thus important to help find good reservoir quality. Here we report a modern analogue study of 12 sediment cores from the Anllóns Estuary, Galicia, NW Spain, collected from a range of sub-environments, to help develop an understanding of the occurrence and distribution of coated grains. The cores were described for grain size, bioturbation and sedimentary structures, and then sub-sampled for electron and light microscopy, laser granulometry, and X-ray diffraction analysis. The Anllóns Estuary is sand-dominated with intertidal sand flats and saltmarsh environments at the margins; there is a shallowing/fining-upwards trend in the estuary-fill succession. Grain coats are present in nearly every sample analysed; they are between 1 μm and 100 μm thick and typically lack internal organisation. The extent of grain coat coverage can exceed 25% in some samples with coverage highest in the top 20 cm of cores. Samples from muddy intertidal flat and the muddy saltmarsh environments, close to the margins of the estuary, have the highest coat coverage (mean coat coverage of 20.2% and 21.3%, respectively). The lowest mean coat coverage occurs in the sandy saltmarsh (10.4%), beyond the upper tidal limit and sandy intertidal flat environments (8.4%), close to the main estuary channel. Mean coat coverage correlates with the concentration of clay fraction. The primary controls on the distribution of fine-grained sediment, and therefore grain coat distribution, are primary sediment transport and deposition processes that

Research into Surface Wave Phenomena in Sedimentary Basins.

DTIC Science & Technology

1981-12-31

150 km of the southerly extension of the Overthrust Belt, 350 km of the Green River Basin paralleling the Uinta Mountains and 150 km across the Front...WEIDLINGER ASSOCIATES O300 SAND HiLL ROAD BUILDING 4, SUITE 245 MENLO PARK, CALIFORNIA 9462 RESEARCH INTO SURFACE WAVE PHENOMENA IN SEDIMENTARY BASINS BY...PARK, CALIFORNIA 94025 ! I RESEARCH INTO SURFACE WAVE PHENOMENA IN SEDIMENTARY BASINS I Dy G.L. Wojcik J. Isenberg F. Ma E. Richardson Prepared for

Early Cretaceous stratigraphy, paleontology, and sedimentary tectonics in Paris overthrust foredeep (western Wyoming and southeastern Idaho) compared with Quaternary features of indo-gangetic plain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dorr, J.A. Jr.

1983-08-01

Fluviatile clastics of the nonmarine, early Cretaceous Gannett and Wayan groups were deposited on wet alluvial megafans and on intervening interfan piedmont slopes which declined eastward into more poorly drained lowlands from a western highland source area uplifted episodically by movements of the Paris overthrust. Lacustrine episodes of deposition intercalated Peterson and Draney limestones with Gannett fluvial clastics. Westward marine transgressions (Skull Creek, Mowry) intercalated mixed lacustrine and brackish facies (Smiths and Cokedale formations) into Wayan fluviatile clastics. Newly discovered fossil vertebrate and invertebrate materials (all fragmentary but identifiable) include: Gannett Group - large reptiles including turtles; Thomas Fork Formationmore » - freshwater gastropods and unionid pelecypods, gastroliths, two types of turtles, large reptilian fragments (dinosaur), and abundant dinosaur eggshell fragments; Wayan Formation - perennially aquatic snails, turtles, unidentifiable large reptiles, two types of crocodilians, an iguanodontid dinosaur (Tenontosaurus), an ankylosaurian dinosaur, a large ornithopod dinosaur, gastroliths, abundant and ubiquitous dinosaur eggshell fragments (numerous types and sizes), and miscellaneous unidentifiable small vertebrate bone fragments. A census of analogous modern reptile reproductive behaviors supports the conclusion that the Wayan, and probably also the Gannett, alluvial fan environments were used as upland breeding grounds by dinosaurs and perhaps other reptiles. Comparison of these Early Cretaceous data with observations on the tectonic setting, sedimentology, and biology of the Quaternary indo-gangetic plain suggests many close analogies between the two sedimentary tectonic settings.« less

Sedimentary Geochemistry of Martian Samples from the Pathfinder Mission

NASA Technical Reports Server (NTRS)

McLennan, Scott M.

2001-01-01

The purpose of this research project was to evaluate the APXS data collected on soils and rocks at the Pathfinder site in terms of sedimentary geochemistry. Below are described the major findings of this research: (1) An influential model to explain the chemical variation among Pathfinder soils and rocks is a two component mixing model where rocks of fairly uniform composition mix with soil of uniform composition; (2) The very strong positive correlation between MgO and SO, points to a control by a MgSO4 mineral however, spectroscopic data continue to suggest that Fe-sulfates, notably schwertmannite and jarosite, may be important components; (3) In an attempt to better understand the causes of complexities in mixing relationships, the possible influence of sedimentary transport has been evaluated; (4) Another aspect of this research has been to examine the possibility of sedimentary silica being a significant phase on Mars; and (5) On Earth, the geochemistry of sedimentary rocks has been used to constrain the chemical composition of the continental crust and an important part of this research was to evaluate this approach for Mars.

Flexure and faulting of sedimentary host rocks during growth of igneous domes, Henry Mountains, Utah

USGS Publications Warehouse

Jackson, M.D.; Pollard, D.D.

1990-01-01

A sequence of sedimentary rocks about 4 km thick was bent, stretched and uplifted during the growth of three igneous domes in the southern Henry Mountains. Mount Holmes, Mount Ellsworth and Mount Hillers are all about 12 km in diameter, but the amplitudes of their domes are about 1.2, 1.85 and 3.0 km, respectively. These mountains record successive stages in the inflation of near-surface diorite intrusions that are probably laccolithic in origin. The host rocks deformed along networks of outcrop-scale faults, or deformation bands, marked by crushed grains, consolidation of the porous sandstone and small displacements of sedimentary beds. Zones of deformation bands oriented parallel to the beds and formation contacts subdivided the overburden into thin mechanical layers that slipped over one another during doming. Measurements of outcrop-scale fault populations at the three mountains reveal a network of faults that strikes at high angles to sedimentary beds which themselves strike tangentially about the domes. These faults have normal and reverse components of slip that accommodated bending and stretching strains within the strata. An early stage of this deformation is displayed at Mount Holmes, where states of stress computed from three fault samples correlate with the theoretical distribution of stresses resulting from bending of thin, circular, elastic plates. Field observations and analysis of frictional driving stresses acting on horizontal planes above an opening-mode dislocation, as well as the paleostress analysis of faulting, indicate that bedding-plane slip and layer flexure were important components of the early deformation. As the amplitude of doming increased, radial and circumferential stretching of the strata and rotation of the older faults in the steepening limbs of the domes increased the complexity of the fault patterns. Steeply-dipping, map-scale faults with dip-slip displacements indicate a late-stage jostling of major blocks over the central

Sulphur and oxygen sequestration of n-C37 and n-C38 unsaturated ketones in an immature kerogen and the release of their carbon skeletons during early stages of thermal maturation

USGS Publications Warehouse

Koopmans, M.P.; Schaeffer-Reiss, C.; De Leeuw, J. W.; Lewan, M.D.; Maxwell, J.R.; Schaeffer, P.; Sinninghe, Damste J.S.

1997-01-01

Sedimentary rock from the Gessoso-solfifera Formation (Messinian) in the Vena del Gesso Basin (northern Italy) containing immature (Ro = 0.25%) S-rich organic matter was artificially matured by hydrous pyrolysis at temperatures from 160 to 330??C for 72 h to study the diagenetic fate of n-C37 and n-C38 di-and tri-unsaturated methyl and ethyl ketones (alkenones) biosynthesised by several prymnesiophyte algae. During early diagenesis, the alkenones are incorporated into the kerogen by both sulphur and oxygen cross-linking as indicated by chemical degradation experiments with the kerogen of the unheated sample. Heating at temperatures between 160 and 260??C, which still represents early stages of thermal maturation, produces large amounts (up to 1 mg/g TOC) of S-bound, O-bound, and both S-and O-bound n-C37 and n-C38 skeletons, saturated n-C37 and n-C38 methyl, ethyl, and mid-chain ketones, C37 and C38 mid-chain 2,5-di-n-alkylthiophenes, C37 and C38 1,2-di-n-alkylbenzenes, and C37 and C38 n-alkanes. With increasing thermal maturation, three forms of the n-C37 and n-C38 skeletons are relatively stable (saturated hydrocarbons, 1,2-di-n-alkylbenzenes and saturated ketones), whereas the S-and O-bound skeletons are relatively labile. These results suggest that in natural situations saturated ketones with an n-C37 and n-C38 skeleton can be expected as well as the corresponding hydrocarbons. Copyright ?? 1997 Elsevier Science Ltd.

Sulphur and oxygen sequestration of n-C 37 and n-C 38 unsaturated ketones in an immature kerogen and the release of their carbon skeletons during early stages of thermal maturation

NASA Astrophysics Data System (ADS)

Koopmans, Martin P.; Schaeffer-Reiss, Christine; de Leeuw, Jan W.; Lewan, Michael D.; Maxwell, James R.; Schaeffer, Philippe; Sinninghe Damsté, Jaap S.

1997-06-01

Sedimentary rock from the Gessoso-solfifera Formation (Messinian) in the Vena del Gesso Basin (northern Italy) containing immature ( Ro = 0.25%) S-rich organic matter was artificially matured by hydrous pyrolysis at temperatures from 160 to 330°C for 72 h to study the diagenetic fate of n-C 37 and n-C 38 di- and tri-unsaturated methyl and ethyl ketones (alkenones) biosynthesised by several prymnesiophyte algae. During early diagenesis, the alkenones are incorporated into the kerogen by both sulphur and oxygen cross-linking as indicated by chemical degradation experiments with the kerogen of the unheated sample. Heating at temperatures between 160 and 260°C, which still represents early stages of thermal maturation, produces large amounts (up to 1 mg/g TOC) of S-bound, O-bound, and both S- and O-bound n-C 37 and n-C 38 skeletons, saturated n-C 37 and n-C38 methyl, ethyl, and mid-chain ketones, C 37 and C 38 mid-chain 2,5-di- n-alkylthiophenes, C 37 and C 38 1,2-di- n-alkylbenzenes, and C 37 and C 38n-alkanes. With increasing thermal maturation, three forms of the n-C 37 and n-C 38 skeletons are relatively stable (saturated hydrocarbons, 1,2-di- n-alkylbenzenes and saturated ketones), whereas the S- and O-bound skeletons are relatively labile. These results suggest that in natural situations saturated ketones with an n-C 37 and n-C 38 skeleton can be expected as well as the corresponding hydrocarbons.

Cryptic Carbonate Alteration in Orogenic Sedimentary Basins: Saving the Signal

NASA Astrophysics Data System (ADS)

Ingalls, M.; Rowley, D. B.; Colman, A. S.; Currie, B.; Snell, K. E.

2017-12-01

The clumped isotope thermometer (T(Δ47)) is arguably one of the most important tools introduced to the fields of paleoclimatology and tectonics in the past decade. However, we measure clumped isotope abundances in natural materials collected from sedimentary basins, many of which have experienced complex thermal and fluid interaction histories. Throughout the history of an authigenic mineral—from precipitation to exhumation—there are multiple opportunities to overprint isotopic signatures and obscure the essential fingerprint of primary environmental conditions. Therefore, we must critically assess the presence or absence of textural and isotopic alteration after original mineral formation. We investigate Paleocene shallow marine carbonates from the Xigaze forearc (S. Tibet) that yield demonstrably non-marine δ18Oc values (-12 to -21‰ VPDB), significant cm-scale variation in clumped isotope values (0.456 to 0.721‰, or 80 to 20°C), and have experienced temperatures >150°C for longer than 10 My based on ages of partial resetting of zircon He. δ18Oc values require complete oxygen isotopic exchange during fluid-buffered diagenesis, but display little visible evidence of recrystallization. Further, within the constraints of the Xigaze forearc time-temperature history, we explain the intrasample Δ47 variation by a combination of the two known mechanisms of Δ47 alteration: (1) water-rock recrystallization and (2) solid-state reordering. The definitively altered marine carbonates pass the same optical screening tests for secondary mineralization traditionally used when employing δ18Oc or Δ47 as proxies for ancient Earth conditions, suggesting that alteration occurred on a spatial scale irresolvable by standard techniques. Therefore, higher spatial resolution detection of carbonate alteration is required to prevent incorrect or incomplete interpretation of carbonate isotopic values. We employ a suite of isotopic (δ18O, δ13C, Δ47, U/Pb), geochemical (EBSD

Isotopic inferences of ancient biochemistries - Carbon, sulfur, hydrogen, and nitrogen

NASA Technical Reports Server (NTRS)

Schidlowski, M.; Hayes, J. M.; Kaplan, I. R.

1983-01-01

In processes of biological incorporation and subsequent biochemical processing sizable isotope effects occur as a result of both thermodynamic and kinetic fractionations which take place during metabolic and biosynthetic reactions. In this chapter a review is provided of earlier work and recent studies on isotope fractionations in the biogeochemical cycles of carbon, sulfur, hydrogen, and nitrogen. Attention is given to the biochemistry of carbon isotope fractionation, carbon isotope fractionation in extant plants and microorganisms, isotope fractionation in the terrestrial carbon cycle, the effects of diagenesis and metamorphism on the isotopic composition of sedimentary carbon, the isotopic composition of sedimentary carbon through time, implications of the sedimentary carbon isotope record, the biochemistry of sulfur isotope fractionation, pathways of the biogeochemical cycle of nitrogen, and the D/H ratio in naturally occurring materials.

Sedimentary Processes on Earth, Mars, Titan, and Venus

NASA Astrophysics Data System (ADS)

Grotzinger, J. P.; Hayes, A. G.; Lamb, M. P.; McLennan, S. M.

The production, transport and deposition of sediment occur to varying degrees on Earth, Mars, Venus, and Titan. These sedimentary processes are significantly influenced by climate that affects production of sediment in source regions (weathering), and the mode by which that sediment is transported (wind vs. water). Other, more geological, factors determine where sediments are deposited (topography and tectonics). Fluvial and marine processes dominate Earth both today and in its geologic past, aeolian processes dominate modern Mars although in its past fluvial processes also were important, Venus knows only aeolian processes, and Titan shows evidence of both fluvial and aeolian processes. Earth and Mars also feature vast deposits of sedimentary rocks, spanning billions of years of planetary history. These ancient rocks preserve the long-term record of the evolution of surface environments, including variations in climate state. On Mars, sedimentary rocks record the transition from wetter, neutral-pH weathering, to brine-dominated low-pH weathering, to its dry current state.

Impact of stylolitization on diagenesis of a Lower Cretaceous carbonate reservoir from a giant oilfield, Abu Dhabi, United Arab Emirates

NASA Astrophysics Data System (ADS)

Paganoni, Matteo; Al Harthi, Amena; Morad, Daniel; Morad, Sadoon; Ceriani, Andrea; Mansurbeg, Howri; Al Suwaidi, Aisha; Al-Aasm, Ihsan S.; Ehrenberg, Stephen N.; Sirat, Manhal

2016-04-01

Bed-parallel stylolites are a widespread diagenetic feature in Lower Cretaceous limestone reservoirs, Abu Dhabi, United Arab Emirates (UAE). Diagenetic calcite, dolomite, kaolin and small amounts of pyrite, fluorite, anhydrite and sphalerite occur along and in the vicinity of the stylolites. Petrographic observations, negative δ18OVPDB, fluid inclusion microthermometry, and enrichment in 87Sr suggest that these cements have precipitated from hot basinal brines, which migrated along the stylolites and genetically related microfractures (tension gashes). Fluid migration was presumably related to lateral tectonic compression events related to the foreland basin formation. The low solubility of Al3 + in formation waters suggests that kaolin precipitation was linked to derivation of organic acids during organic matter maturation, probably in siliciclastic source rocks. The mass released from stylolitization was presumably re-precipitated as macro- and microcrystalline calcite cement in the host limestones. The flanks of the oilfield (water zone) display more frequent presence and higher amplitude of stylolites, lower porosity and permeability, higher homogenization temperatures and more radiogenic composition of carbonates compared to the crest (oil zone). This indicates that oil emplacement retards diagenesis. This study demonstrates that stylolitization plays a crucial role in fluid flow and diagenesis of carbonate reservoirs during basin evolution.

Building a Bridge to Deep Time: Sedimentary Systems Across Timescales

NASA Astrophysics Data System (ADS)

Romans, B.; Castelltort, S.; Covault, J. A.; Walsh, J. P.

2013-12-01

It is increasingly important to understand the complex and interdependent processes associated with sediment production, transport, and deposition at timescales relevant to civilization (annual to millennial). However, predicting the response of sedimentary systems to global environmental change across a range of timescales remains a significant challenge. For example, a significant increase in global average temperature at the Paleocene-Eocene boundary (55.8 Ma) is interpreted to have occurred over millennial timescales; however, the specific response of sedimentary systems (e.g., timing and magnitude of sediment flux variability in river systems) to that forcing is debated. Thus, using such environmental perturbations recorded in sedimentary archives as analogs for ongoing/future global change requires improved approaches to bridging across time. Additionally, the ability to bridge timescales is critical for addressing other questions about sedimentary system behavior, including signal propagation and signal versus ';noise' in the record. The geologic record provides information that can be used to develop a comprehensive understanding of process-response behavior at multiple timescales. The geomorphic ';snapshot' of present-day erosional and depositional landscapes can be examined to reconstruct the history of processes that created the observable configurations. Direct measurement and monitoring of active processes are used to constrain conceptual and numerical models and develop sedimentary system theory. But real-time observations of active Earth-surface processes are limited to the very recent, and how such processes integrate over longer timescales to transform into strata remains unknown. At longer timescales (>106 yr), the stratigraphic record is the only vestige of ancient sedimentary systems. Stratigraphic successions contain a complex record of sediment deposition and preservation, as well as the detrital material that originated in long since denuded

Sedimentary and Paleoceanographic Responses to the South China Sea Basin Evolution

NASA Astrophysics Data System (ADS)

Jian, Z.; Liu, Z.; Jin, H.; Larsen, H. C.; Alvarez Zarikian, C. A.; Stock, J. M.; Sun, Z.; Klaus, A.

2017-12-01

As the largest marginal sea of the western Pacific, the South China Sea (SCS) has experienced a complete Wilson cycle, which had inevitably exerted a profound impact on the sedimentary environment and ocean circulation. Based on the results of four ODP/IODP expeditions to the SCS since 1999, together with other research data in this region, this study aims to explore the sedimentary and paleoceanographic responses to the tectonic events and basin evolution in the SCS. The early history of the SCS from land to deep sea was revealed by foraminiferal fauna: (1) The SCS evolved from continental shelf to an upper bathyal environment around the Oligocene/Eocene boundary, and significantly deepened at the turn of Oligocene/Miocene; (2) The early Oligocene SCS was deep but its shelf was narrow, evidenced by the Para-Tethys type deep-sea agglutinated benthic foraminifers and abundant transported shallow-water species at ODP Site 1148. Along with the SCS basin formation and the development of this semi-closed basin, the deep-sea benthic foraminiferal δ13C decreased when the Antarctic ice sheet began to reestablish at 14 Ma, the Indonesian Seaway and the southern SCS deep-water channel were closed at 10 Ma, the Luzon arc collided with Taiwan at 6.5 Ma, and the Bashi Strait was restricted at 1.2 Ma. Nd isotopes of shark teeth at ODP Site 1148 also support these inferences. An early to middle Miocene succession of red clay was found at all sites deeper than 3500 m water depth, which may be correlated to a basin-wide event related to deep circulation of oxygenated water from the western Pacific. After the earliest late Miocene carbonate crash, the red clay disappeared while the large carbonate platforms were drowned and remarkably shrank in the SCS. Late Miocene sediments display a succession of hemi-pelagic and turbidite deposits, indicating that the deep basin entered its modern state below the CCD. Frequent turbidites ended when Pliocene growth of deep-sea manganese

Origins of chromite and magnetite in sedimentary rocks deposited in a shallow water environment in the 3.2 Ga Moodies Group, South Africa

NASA Astrophysics Data System (ADS)

Otake, T.; Sakamoto, Y.; Itoh, S.; Yurimoto, H.; Kakegawa, T.

2012-12-01

*Otake, T. totake@eng.hokudai.ac.jp Div. of Sustainable Resources Engineering, Hokkaido Univ., Sapporo, Japan Sakamoto, Y. yu.sakamoto12@gmail.com Dep. of Earth Science, Tohoku Univ., Sendai, Japan Itoh, S. sitoh@ep.sci.hokudai.ac.jp Dep. of Natural History Sciences, Hokkaido Univ., Sapporo, Japan Yurimoto. H. yuri@ep.sci.hokudai.ac.jp Dep. of Natural History Sciences, Hokkaido Univ., Sapporo, Japan Kakegawa, T. kakegawa@m.tohoku.ac.jp Dep. of Earth Science, Tohoku Univ., Sendai, Japan Geochemical data from ferruginous chemical sedimentary rocks (e.g., Banded Iron Formation: BIF) have been used to reconstruct the surface environments of early Earth. However, only a few studies have investigated the geochemical characteristics of BIFs deposited in a shallow water environment during the Archean, which may have differed from those deposited in a deep water environment. Therefore, we investigated geological, petrographic and geochemical characteristics of ferruginous rocks deposited in a shallow water environment in the Moodies group, in the Barberton Greenstone Belt, South Africa. We obtained ferruginous rock samples in the Moodies group from both an outcrop and underground gold mine, and compared the characteristics of these samples. The 70 sedimentary rock samples were divided into groups based on the dominant Fe minerals they contain: Hematite-rich jaspilite (HM group), Magnetite-rich iron formation/shale/sandstone (MT group), and Siderite-rich sandstone (SD group). Samples in the HM group are predominantly composed of fine-grained quartz (< 20 μm) and hematite (< 5 μm), which are interpreted to be chemical precipitates. Samples in the MT group contain quartz, magnetite, siderite, ankerite, chlorite, biotite and chromite. The grain size of magnetite is much larger (20-150 μm) than that of hematite in the HM group. The magnetite is interpreted as a secondary mineral transformed from hematite during early diagenesis. Results of in situ oxygen isotope analysis by

Evidence for persistent flow and aqueous sedimentation on early Mars.

PubMed

Malin, Michael C; Edgett, Kenneth S

2003-12-12

Landforms representative of sedimentary processes and environments that occurred early in martian history have been recognized in Mars Global Surveyor Mars Orbiter Camera and Mars Odyssey Thermal Emission Imaging System images. Evidence of distributary, channelized flow (in particular, flow that lasted long enough to foster meandering) and the resulting deposition of a fan-shaped apron of debris indicate persistent flow conditions and formation of at least some large intracrater layered sedimentary sequences within fluvial, and potentially lacustrine, environments.

Siderite concretions: indicators of early diagenesis in the Gammon shale (Cretaceous).

USGS Publications Warehouse

Gautier, D.L.

1982-01-01

The Gammon member of the Pierre shale of the northern Great Plains, USA, contains abundant siderite concretions. The relative depth and time of siderite precipitation can be inferred from the structure, mineralogy and isotopic composition of these concretions. Concretions that formed at shallow depths, early in the history of the sediment, contain a high percentage (75-85%) of carbonate, preserve uncompacted structures and have oxygen isotopic ratios similar to that of sea-water. In contrast, concretions that formed later and/or at greater depths have lower carbonate content and lower 18O/16O ratios. Concretions in rapidly deposited sediments formed at shallow depths (<10 m), and those in sediments that accumulated slowly formed at greater depths. These differences agree with the fossil evidence. Siderite did not form until nearly all the dissolved sulphur had been reduced and precipitated as pyrite; the excess organic matter produced methane at about the same time.-H.R.B.

Amino acid distribution in meteorites: diagenesis, extraction methods, and standard metrics in the search for extraterrestrial biosignatures.

PubMed

McDonald, Gene D; Storrie-Lombardi, Michael C

2006-02-01

The relative abundance of the protein amino acids has been previously investigated as a potential marker for biogenicity in meteoritic samples. However, these investigations were executed without a quantitative metric to evaluate distribution variations, and they did not account for the possibility of interdisciplinary systematic error arising from inter-laboratory differences in extraction and detection techniques. Principal component analysis (PCA), hierarchical cluster analysis (HCA), and stochastic probabilistic artificial neural networks (ANNs) were used to compare the distributions for nine protein amino acids previously reported for the Murchison carbonaceous chondrite, Mars meteorites (ALH84001, Nakhla, and EETA79001), prebiotic synthesis experiments, and terrestrial biota and sediments. These techniques allowed us (1) to identify a shift in terrestrial amino acid distributions secondary to diagenesis; (2) to detect differences in terrestrial distributions that may be systematic differences between extraction and analysis techniques in biological and geological laboratories; and (3) to determine that distributions in meteoritic samples appear more similar to prebiotic chemistry samples than they do to the terrestrial unaltered or diagenetic samples. Both diagenesis and putative interdisciplinary differences in analysis complicate interpretation of meteoritic amino acid distributions. We propose that the analysis of future samples from such diverse sources as meteoritic influx, sample return missions, and in situ exploration of Mars would be less ambiguous with adoption of standardized assay techniques, systematic inclusion of assay standards, and the use of a quantitative, probabilistic metric. We present here one such metric determined by sequential feature extraction and normalization (PCA), information-driven automated exploration of classification possibilities (HCA), and prediction of classification accuracy (ANNs).

The potassic sedimentary rocks in Gale Crater, Mars, as seen by ChemCam on board Curiosity: Potassic Sedimentary Rocks, Gale Crater

DOE PAGES

Le Deit, L.; Mangold, N.; Forni, O.; ...

2016-05-13

The Mars Science Laboratory rover Curiosity encountered potassium-rich clastic sedimentary rocks at two sites in Gale Crater, the waypoints Cooperstown and Kimberley. These rocks include several distinct meters thick sedimentary outcrops ranging from fine sandstone to conglomerate, interpreted to record an ancient fluvial or fluvio-deltaic depositional system. Furthermore, from ChemCam Laser-Induced Breakdown Spectroscopy (LIBS) chemical analyses, this suite of sedimentary rocks has an overall mean K 2O abundance that is more than 5 times higher than that of the average Martian crust. The combined analysis of ChemCam data with stratigraphic and geographic locations then reveals that the mean K 2Omore » abundance increases upward through the stratigraphic section. Chemical analyses across each unit can be represented as mixtures of several distinct chemical components, i.e., mineral phases, including K-bearing minerals, mafic silicates, Fe-oxides, and Fe-hydroxide/oxyhydroxides. Possible K-bearing minerals include alkali feldspar (including anorthoclase and sanidine) and K-bearing phyllosilicate such as illite. Mixtures of different source rocks, including a potassium-rich rock located on the rim and walls of Gale Crater, are the likely origin of observed chemical variations within each unit. Physical sorting may have also played a role in the enrichment in K in the Kimberley formation. The occurrence of these potassic sedimentary rocks provides additional evidence for the chemical diversity of the crust exposed at Gale Crater.« less

The potassic sedimentary rocks in Gale Crater, Mars, as seen by ChemCam on board Curiosity: Potassic Sedimentary Rocks, Gale Crater

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le Deit, L.; Mangold, N.; Forni, O.

The Mars Science Laboratory rover Curiosity encountered potassium-rich clastic sedimentary rocks at two sites in Gale Crater, the waypoints Cooperstown and Kimberley. These rocks include several distinct meters thick sedimentary outcrops ranging from fine sandstone to conglomerate, interpreted to record an ancient fluvial or fluvio-deltaic depositional system. Furthermore, from ChemCam Laser-Induced Breakdown Spectroscopy (LIBS) chemical analyses, this suite of sedimentary rocks has an overall mean K 2O abundance that is more than 5 times higher than that of the average Martian crust. The combined analysis of ChemCam data with stratigraphic and geographic locations then reveals that the mean K 2Omore » abundance increases upward through the stratigraphic section. Chemical analyses across each unit can be represented as mixtures of several distinct chemical components, i.e., mineral phases, including K-bearing minerals, mafic silicates, Fe-oxides, and Fe-hydroxide/oxyhydroxides. Possible K-bearing minerals include alkali feldspar (including anorthoclase and sanidine) and K-bearing phyllosilicate such as illite. Mixtures of different source rocks, including a potassium-rich rock located on the rim and walls of Gale Crater, are the likely origin of observed chemical variations within each unit. Physical sorting may have also played a role in the enrichment in K in the Kimberley formation. The occurrence of these potassic sedimentary rocks provides additional evidence for the chemical diversity of the crust exposed at Gale Crater.« less

The Zambezi sedimentary system (coastal plain - deep sea fan): a record of the vertical movements of the Mozambican margin since Cretaceous times.

NASA Astrophysics Data System (ADS)

Ponte, Jean Pierre; Robin, Cecile; Guillocheau, Francois; Baby, Guillaume; Dall'Asta, Massimo; Popescu, Speranta; Suc, Jean Pierre; Droz, Laurence; Rabineau, Marina; Moulin, Maryline

2016-04-01

The Mozambique margin is an oblique to transform margin which feeds one of the largest African turbiditic system, the Zambezi deep-sea fan (1800 km length and 400 km wide; Droz and Mougenot., AAPG Bull., 1987). The Zambezi sedimentary system is characterized by (1) a changing catchment area through time with evidences of river captures (Thomas and Shaw, J. Afr. Earth. Sci, 1988) and (2) a delta, storing more than 12 km of sediment, with no gravitary tectonics. The aim of this study is to carry out a source to sink study along the Zambezi sedimentary system and to analyse the margin evolution (vertical movements, climate change) since Early Cretaceous times. The used data are seismic lines (industrial and academic) and petroleum wells (with access to the cuttings). Our first objective was to perform a new biochronostratigraphic framework based on nannofossils, foraminifers, pollen and spores on the cuttings of three industrial wells. The second target was to recognize the different steps of the growth of the Zambezi sedimentary systems. Four main phases were identified: • Late Jurassic (?) - early Late Cretaceous: from Neocomian to Aptian times, the high of the clinoforms is getting higher, with the first occurrence of contouritic ridges during Aptian times. • Late Cretaceous - Early Paleocene: a major drop of relative sea-level occurred as a consequence of the South African Plateau uplift. The occurrence of two depocenters suggests siliciclastic supplies from the Bushveld and from the North Mozambique domain. • Early Paleocene - Eocene: growth of carbonate platforms and large contouritic ridges. • Oligocene - Present-day: birth of the modern Zambezi Delta, with quite low siliciclastic supply during Oligocene times, increasing during Miocene times. As previously expected (Droz and Mougenot) some sediments of the so-called Zambezi fans are coming from a feeder located east of the Davie Ridge. This study was founded by TOTAL and IFREMER in the frame of the

Early Diagenetic Changes of Sediment Pore Properties Beneath the Seafloor and Their Contributions to Gas Hydrate Concentration in the Eastern Margin of Japan Sea

NASA Astrophysics Data System (ADS)

Uchida, T.; Horiuchi, S.; Kato, Y.; Matsumoto, R.

2014-12-01

Recently many of the chimney-shape gas hydrate concentrated beneath the seafloor have been confirmed off Shimane and off Akita as well as off Joetsu in the eastern margin of Japan Sea, which are quite different from the occurrences of pore space hydrate filling the intergranular pore system of sands recognized in Nankai Trough, Mallik and other sites. Sediment samples below the seafloor were retrieved in 2010 up to 40 m long at the Umitaka Spur, Joetsu Channel, Toyama Trough, Japan Basin, Nishi Tsugaru and Okushiri Ridge areas. Small amounts of sandy sediment have been retrieved as thin intercalations in Pleistocene and Holocene muddy layers transported approximately around 3 to 30 ka according to the tephra ages, where supplying sediments might have not been abundant due to sea level fluctuation during the Pleistocene ice age. It is important to clarify the relationship between burial depths and absolute porosities of the argillaceous sediments in relation to early diagenesis. Macroscopic observations and descriptions, measurements of porosity and permeability, SEM (scanning electron microscope) observations, and X-ray diffraction analyses have been performed. They consist of silt- to clay-grained particles, and they sometimes contain very fine- to medium-grained thin sandy layers. Average porosities of these fine-grained sediments are 50 % in all study areas, which quickly reduce from 60% to less than 50% within 10 meters and gradually decrease to the depth. However, mean pore sizes in the Nishi Tsugaru are around 1000 nm while 100 nm in the other areas, which tend to decrease with depth. It is suggested that repacking of the muddy particles gradually advances by mechanical compaction, which may crucially influence permeability. They usually contain much opal-A, quartz, feldspar, illite and smectite that do not change definitely with depth. By optical and microscopic observations, diatom tests, foraminifers and framboidal pyrites are commonly observed, and, in

Sedimentary Signs of a Martian Lakebed

NASA Image and Video Library

2014-12-08

This evenly layered rock photographed by the Mast Camera Mastcam on NASA Curiosity Mars Rover on Aug. 7, 2014, shows a pattern typical of a lake-floor sedimentary deposit not far from where flowing water entered a lake.

A volcanic environment for bedrock diagenesis at Meridiani Planum on Mars.

PubMed

McCollom, Thomas M; Hynek, Brian M

2005-12-22

Exposed bedrocks at Meridiani Planum on Mars display chemical and mineralogical evidence suggesting interaction with liquid water. On the basis of morphological observations as well as high abundances of haematite and sulphate minerals, the rocks have been interpreted as sediments that were deposited in a shallow body of briny water with subsequent evaporation leaving behind the sulphate minerals. The iron-sulphur mineralization at Meridiani has also been inferred to be analogous to that produced during oxidative weathering of metal sulphide minerals, such as occurs at acid mine drainage sites. Neither of these interpretations, however, is consistent with the chemical composition of the rocks. Here we propose an alternative model for diagenesis of Meridiani bedrock that involves deposition of volcanic ash followed by reaction with condensed sulphur dioxide- and water-bearing vapours emitted from fumaroles. This scenario does not require prolonged interaction with a standing body of surface water and may have occurred at high temperatures. Consequently, the model invokes an environment considerably less favourable for biological activity on Mars than previously proposed interpretations.

Diagenesis and reservoir quality of Bhuban sandstones (Neogene), Titas Gas Field, Bengal Basin, Bangladesh

NASA Astrophysics Data System (ADS)

Aminul Islam, M.

2009-06-01

This study deals with the diagenesis and reservoir quality of sandstones of the Bhuban Formation located at the Titas Gas Field of Bengal Basin. Petrographic study including XRD, CL, SEM and BSE image analysis and quantitative determination of reservoir properties were carried out for this study. The sandstones are fine to medium-grained, moderately well to well sorted subfeldspathic arenites with subordinate feldspathic and lithic arenites. The diagenetic processes include clay infiltration, compaction and cementation (quartz overgrowth, chlorite, kaolinite, calcite and minor amount of pyrite, dolomite and K-feldspar overgrowth). Quartz is the dominant pore occluding cement and generally occurred as small euhedral crystals, locally as large pyramidal crystals in the primary pores. Pressure solution derived from grain contact is the main contributor of quartz overgrowths. Chlorite occurs as pore-lining and pore filling cement. In some cases, chlorite helps to retain porosity by preventing quartz overgrowth. In some restricted depth interval, pore-occlusion by calcite cement is very much intense. Kaolinite locally developed as vermiform and accelerated the minor porosity loss due to pore-occlusion. Kaolinite/chlorite enhances ineffective microporosity. Kaolinite is a by-product of feldspar leaching in the presence of acidic fluid produced during the maturation of organic matter in the adjacent Miocene or deeper Oligocene source rocks. The relation between diagenesis and reservoir quality is as follows: the initial porosity was decreased by compaction and cementation and then increased by leaching of the metastable grains and dissolution of cement. Good quality reservoir rocks were deposited in fluvial environment and hence quality of reservoir rocks is also environment selective. Porosity and permeability data exhibit good inverse correlation with cement. However, some data points indicate multiple controls on permeability. Reservoir quality is thus controlled by

Diagenesis and clay mineral formation at Gale Crater, Mars

PubMed Central

Bridges, J C; Schwenzer, S P; Leveille, R; Westall, F; Wiens, R C; Mangold, N; Bristow, T; Edwards, P; Berger, G

2015-01-01

The Mars Science Laboratory rover Curiosity found host rocks of basaltic composition and alteration assemblages containing clay minerals at Yellowknife Bay, Gale Crater. On the basis of the observed host rock and alteration minerals, we present results of equilibrium thermochemical modeling of the Sheepbed mudstones of Yellowknife Bay in order to constrain the formation conditions of its secondary mineral assemblage. Building on conclusions from sedimentary observations by the Mars Science Laboratory team, we assume diagenetic, in situ alteration. The modeling shows that the mineral assemblage formed by the reaction of a CO2-poor and oxidizing, dilute aqueous solution (Gale Portage Water) in an open system with the Fe-rich basaltic-composition sedimentary rocks at 10–50°C and water/rock ratio (mass of rock reacted with the starting fluid) of 100–1000, pH of ∽7.5–12. Model alteration assemblages predominantly contain phyllosilicates (Fe-smectite, chlorite), the bulk composition of a mixture of which is close to that of saponite inferred from Chemistry and Mineralogy data and to that of saponite observed in the nakhlite Martian meteorites and terrestrial analogues. To match the observed clay mineral chemistry, inhomogeneous dissolution dominated by the amorphous phase and olivine is required. We therefore deduce a dissolving composition of approximately 70% amorphous material, with 20% olivine, and 10% whole rock component. PMID:26213668

Diagenesis and clay mineral formation at Gale Crater, Mars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bridges, J. C.; Schwenzer, S. P.; Leveille, R.

The Mars Science Laboratory rover Curiosity found host rocks of basaltic composition and alteration assemblages containing clay minerals at Yellowknife Bay, Gale Crater. On the basis of the observed host rock and alteration minerals, we present results of equilibrium thermochemical modeling of the Sheepbed mudstones of Yellowknife Bay in order to constrain the formation conditions of its secondary mineral assemblage. Building on conclusions from sedimentary observations by the Mars Science Laboratory team, we assume diagenetic, in situ alteration. The modeling shows that the mineral assemblage formed by the reaction of a CO₂-poor and oxidizing, dilute aqueous solution (Gale Portage Water)more » in an open system with the Fe-rich basaltic-composition sedimentary rocks at 10–50°C and water/rock ratio (mass of rock reacted with the starting fluid) of 100–1000, pH of ~7.5–12. Model alteration assemblages predominantly contain phyllosilicates (Fe-smectite, chlorite), the bulk composition of a mixture of which is close to that of saponite inferred from Chemistry and Mineralogy data and to that of saponite observed in the nakhlite Martian meteorites and terrestrial analogues. To match the observed clay mineral chemistry, inhomogeneous dissolution dominated by the amorphous phase and olivine is required. We therefore deduce a dissolving composition of approximately 70% amorphous material, with 20% olivine, and 10% whole rock component.« less

Diagenesis and clay mineral formation at Gale Crater, Mars

DOE PAGES

Bridges, J. C.; Schwenzer, S. P.; Leveille, R.; ...

2015-01-18

The Mars Science Laboratory rover Curiosity found host rocks of basaltic composition and alteration assemblages containing clay minerals at Yellowknife Bay, Gale Crater. On the basis of the observed host rock and alteration minerals, we present results of equilibrium thermochemical modeling of the Sheepbed mudstones of Yellowknife Bay in order to constrain the formation conditions of its secondary mineral assemblage. Building on conclusions from sedimentary observations by the Mars Science Laboratory team, we assume diagenetic, in situ alteration. The modeling shows that the mineral assemblage formed by the reaction of a CO₂-poor and oxidizing, dilute aqueous solution (Gale Portage Water)more » in an open system with the Fe-rich basaltic-composition sedimentary rocks at 10–50°C and water/rock ratio (mass of rock reacted with the starting fluid) of 100–1000, pH of ~7.5–12. Model alteration assemblages predominantly contain phyllosilicates (Fe-smectite, chlorite), the bulk composition of a mixture of which is close to that of saponite inferred from Chemistry and Mineralogy data and to that of saponite observed in the nakhlite Martian meteorites and terrestrial analogues. To match the observed clay mineral chemistry, inhomogeneous dissolution dominated by the amorphous phase and olivine is required. We therefore deduce a dissolving composition of approximately 70% amorphous material, with 20% olivine, and 10% whole rock component.« less

Sedimentary Record of the Back-Arc Basins of South-Central Mexico: an Evolution from Extensional Basin to Carbonate Platform.

NASA Astrophysics Data System (ADS)

Sierra-Rojas, M. I.; Molina-Garza, R. S.; Lawton, T. F.

2015-12-01

The Lower Cretaceous depositional systems of southwestern Oaxaquia, in south-central Mexico, were controlled by tectonic processes related to the instauration of a continental arc and the accretion of the Guerrero arc to mainland Mexico. The Atzompa Formation refers to a succession of conglomerate, sandstone, siltstone, and limestone that crop out in southwestern Mexico with Early Cretaceous fauna and detrital zircon maximum depositional ages. The sedimentary record shows a transition from early fluvial/alluvial to shallow marine depositional environments. The first stage corresponds to juvenile fluvial/alluvial setting followed by a deep lacustrine depositional environment, suggesting the early stages of an extensional basin. The second stage is characterized by anabranched deposits of axial fluvial systems flowing to the NE-SE, showing deposition during a period of rapid subsidence. The third and final stage is made of tidal deposits followed, in turn, by abrupt marine flooding of the basin and development of a Barremian-Aptian carbonate ramp. We interpret the Tentzo basin as a response to crustal extension in a back-arc setting, with high rates of sedimentation in the early stages of the basin (3-4 mm/m.y), slower rates during the development of starved fluvial to tidal systems and carbonate ramps, and at the top of the Atzompa Formation an abrupt deepening of the basin due to flexural subsidence related to terrane docking and attendant thrusting to the west. These events were recorded in the back-arc region of a continental convergent margin (Zicapa arc) where syn-sedimentary magmatism is indicated by Early Cretaceous detrital and volcanic clasts from alluvial fan facies west of the basin. Finally, and as a response to the accretion of the Guerrero superterrane to Oaxaquia during the Aptian, a carbonate platform facing toward the Gulf of Mexico was established in central to eastern Oaxaquia.

Molecular evidence for lignin degradation in sulfate-reducing mangrove sediments (Amazônia, Brazil)

NASA Astrophysics Data System (ADS)

Dittmar, Thorsten; Lara, Rubén José

2001-05-01

- Molecular lignin analyses have become a powerful quantitative approach for estimating flux and fate of vascular plant organic matter in coastal and marine environments. The use of a specific molecular biomarker requires detailed knowledge of its decomposition rates relative to the associated organic matter and its structural diagenetic changes. To gain insight into the poorly known processes of anaerobic lignin diagenesis, molecular analyses were performed in the sulfate-reducing sediment of a north Brazilian mangrove. Organic matter in samples representing different diagenetic stages (i.e., fresh litter, a sediment core, and percolating water) was characterized by alkaline CuO oxidation for lignin composition, element (C, N), and stable carbon isotope analyses. On the basis of these results and on a balance model, long-term in situ decomposition rates of lignin in sulfate-reducing sediments were estimated for the first time. The half-life ( T1/2) of lignin derived from mangrove leaf litter (mainly Rhizophora mangle) was ˜150 yr in the upper 1.5 m of the sediment. Associated organic carbon from leaf tissue was depleted to ˜75% within weeks, followed by a slow mineralization in the sediment ( T1/2 ≈ 300 yr). Unlike the known pathways of lignin diagenesis, even highly degraded lignin did not show any alterations of the propyl or methoxyl side chains, as evident from stable acid to aldehyde ratios and the proportion of methoxylated phenols (vanillyl and syringyl phenols). Aromatic ring cleavage is probably the principal mechanism for lignin decay in the studied environment. Cinnamyl phenols were highly abundant in mangrove leaves and were rapidly depleted during early diagenesis. Thus, the cinnamyl to vanillyl ratio could be used as a tracer for early diagenesis even under the sulfate-reducing conditions. Syringyl phenols were removed from dissolved organic matter in interstitial water, probably by sorption onto the sediment. Suspended organic matter in a

Evidence from carbon isotope measurements for diverse origins of sedimentary hydrocarbons

NASA Technical Reports Server (NTRS)

Freeman, K. H.; Hayes, J. M.; Trendel, J. M.; Albrecht, P.

1990-01-01

The organic matter found in sedimentary rocks must derive from many sources; not only from ancient primary producers but also from consumers and secondary producers. In all of these organisms, isotope effects can affect the abundance and distribution of 13C in metabolites. Here, by using an improved form of a previously described technique in which the effluent of a gas chromatograph is continuously analysed isotopically, we report evidence of the diverse origins of sedimentary organic matter. The record of 13C abundances in sedimentary carbonate and total organic carbon can be interpreted in terms of variations in the global carbon cycle. Our results demonstrate, however, that isotope variations within sedimentary organic mixtures substantially exceed those observed between samples of total organic carbon. Resolution of isotope variations at the molecular level offers a new and convenient means of refining views both of localized palaeoenvironments and of control mechanisms within the global carbon cycle.

Paleoclimatic and Paleoceanographic Holocene Sedimentary Records in the Gulf of California - Eastern Pacific Ocean Interhemispheric Connections

NASA Astrophysics Data System (ADS)

Perez-Cruz, L.; Urrutia-Fucugauchi, J.

2009-05-01

Initial results of a study on the distribution, thickness and stratigraphy of the sedimentary sequences in the Gulf of California are presented. The Gulf is an elongated narrow young oceanic basin bordered by the Baja California peninsula and mainland Mexico. The Gulf extends over 1200 km across the Tropic of Cancer from the tropical to the temperate zones, surrounded by arid and semi-arid regions, including the Sonora-Mojave Desert. Paleoceanographic conditions are dominated by water exchange at the Gulf mouth and water masses changes along the Gulf. Tectonic basins reach down in excess of 3000 m depths and get shallower to the north. Here we focus on the Holocene sediment sequences in the southern sector, which contains several marginal and central anoxic basins that constitute rich archives of paleoclimatic and paleoenvironmental evolution for the past 3.6 Ma. In the mouth area, main sources of sediments are silicic volcanic and intrusive rocks in the Baja peninsula and mainland, including Los Cabos and Puerto Vallarta batholiths. Fine-grained eolian dusts, pluvial and biogenic sediments are present in the sediment cores in the Gulf basins such as La Paz, Alfonso, Carmen, Pescadero and Guaymas basins. Turbiditic currents and tephra deposits also occur in the cores. Paleoclimatic records show the influences of regional processes, including the ENSO and PDO signals marked by drought and increased precipitation phases. Relative distribution and thickness of sediments at the mouth of the Gulf correlate with bathymetry and location with respect to spreading center, transform faults and margins of the peninsula and mainland Mexico. Rock magnetic core scans and mineralogy at few locations are available, which allow inferences on sediment sources, transport and deposition processes, diagenesis, paleoceanographic and paleoclimatic evolution for the Holocene.

Constraining the Texture and Composition of Pore-Filling Cements at Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Siebach, K. L.; Grotzinger, J. P.; McLennan, S. M.; Hurowitz, J. A.; Ming, D. W.; Vaniman, D. T.; Rampe, E. B.; Blaney, D. L.; Kah, L. C.

2015-01-01

The Mars Science Laboratory (MSL) rover Curiosity has encountered a wide variety of sedimentary rocks deposited in fluvio-lacuestrine sequences at the base of Gale Crater. The presence of sedimentary rocks requires that initial sediments underwent diagenesis and were lithified. Lithification involves sediment compaction, cementation, and re-crystallization (or authigenic) processes. Analysis of the texture and composition of the cement can reveal the environmental conditions when the cements were deposited, enabling better understanding of early environments present within Gale Crater. The first step in lithification is sediment compaction. The Gale crater sediments do not show evidence for extensive compaction prior to cementation; the Sheepbed mudstone in Yellowknife Bay (YKB) has preserved void spaces ("hollow nodules"), indicating that sediments were cemented around the hollow prior to compaction, and conglomerates show imbrication, indicating minimal grain reorganization prior to lithification. Furthermore, assuming the maximum burial depth of these sediments is equivalent to the depth of Gale Crater, the sediments were never under more than 1 kb of pressure, and assuming a 15 C/km thermal gradient in the late Noachian, the maximum temperature of diagenesis would have been approximately 75 C. This is comparable to shallow burial diagenetic conditions on Earth. The cementation and recrystallization components of lithification are closely intertwined. Cementation describes the precipitation of minerals between grains from pore fluids, and recrystallization (or authigenesis) is when the original sedimentary mineral grains are altered into secondary minerals. The presence of authigenic smectites and magnetite in the YKB formation suggests that some recrystallization has taken place. The relatively high percentage of XRD-amorphous material (25-40%) detected by CheMin suggests that this recrystallization may be limited in scope, and therefore may not contribute

Frontiers in Sedimentary Geology: Microstructure of Fine-Grained Sediments from Mud to Shale

DTIC Science & Technology

1990-01-01

observations at the East Pacific cal Society of America Bulletin. v. 92. p. 212-218. Rise , 8°45’ N , and some interpretations. In: Rosendahl. BR.. R...in the basin east of Shatski Rise . Scale = t Pm. Burial diagenesis processes involve (I) postdepositional/mech- enables the investigator to determine...commonly used in the field. 50N Figure 15.1. Map of the eastern equatorial North Pacific Ocean showing the Results kation of Site H The East Pacific Rise

Impact of dia- and catagenesis on sulphur and oxygen sequestration of biomarkers as revealed by artificial maturation of an immature sedimentary rock

USGS Publications Warehouse

Koopmans, M.P.; De Leeuw, J. W.; Lewan, M.D.; Sinninghe, Damste J.S.

1996-01-01

Hydrous pyrolysis of an immature (R(a)??? 0.25%) sulphur-rich marl from the Gessoso-solfifera Formation (Messinian) in the Vena del Gesso Basin was carried out at 160C ??? T ???330 C for 72 h, to study the effect of progressive diagenesis and early catagenesis on the abundance and distribution of sulphur-containing and sulphur- and oxygen-linked carbon skeletons in low-molecular-weight and highmolecular-weight fractions (e.g. kerogen). To this end, compounds in the saturated hydrocarbon fraction, monoaromatic hydrocarbon fraction, polyaromatic hydrocarbon fraction, alkylsulphide fraction and ketone fraction were quantified, as well as compounds released after desulphurisation of the polar fraction and HI/LiAIH4 treatment of the desulphurised polar fraction. Sulphur-bound phytane and (20R)-5??,14??,17??(H) and (20R)-5??,14??,17??(H) C27 C29 steranes in the polar fraction become less abundant with increasing maturation temperature, whereas the amount of their corresponding hydrocarbons increases in the saturated hydrocarbon fraction. Carbon skeletons that are bound in the kerogen by multiple bonds (e.g. C38 n-alkane and isorenieratane) are first released into the polar fraction, and then as free hydrocarbons. These changes occur at relatively low levels of thermal maturity (R(a) <0.6%), as evidenced by the 'immature' values of biomarker maturity parameters such as the ????/(????+ ???? + ????) C35 hopane ratio and the 22S/(22S + 22R)-17??,21??(H) C35 hopane ratio. Sulphur- and oxygen-bound moieties, present in the polar fraction, are not stable with increasing thermal maturation. However, alkylthiophenes, ketones. 1,2-di-n-alkylbenzenes and free n-alkanes seem to be stable thermal degradation products of these sulphur- and oxygen-bound moieties. Thus, apart from free n-alkanes, which are abundantly present in more mature sedimentary rocks and crude oils, alkylthiophenes, 1,2-di-n-alkylbenzenes and ketones can also be expected to occur. The positions of the thiophene

Kinetically Controlled Alteration of the Chemical Record During Diagenesis: An Experimental Study on Hydrothermal Carbonate Replacement

NASA Astrophysics Data System (ADS)

Mueller, T.; Dohmen, R.; Jonas, L.; Immenhauser, A.

2016-12-01

The geological record stored in the geochemical composition of carbonates provides a direct source of information on the Earth systems. However, the robustness and accuracy of these key records can be compromised by post-depositional alteration of sediments, such as dolomitization during diagenesis or low temperature metamorphism. Hence, knowledge on the mechanisms and rates of these processes hold the key to evaluate the robustness of proxies or to evaluate the extent of geochemical alteration. Previously, we presented experimental results of hydrothermal alteration of single calcite crystals and aragonitic coral fragments leading to replacement of the original carbonate by a Ca-Mg carbonate phase of variable composition. The experiments revealed the formation of a multiphase reaction rim with multiple replacement fronts [1]. Here, the reaction rate as well as composition of the reaction products is controlled by element transport in the pore fluid. In this study we focus on the reaction path of the replacement reaction and its effect on the recorded Mg-isotope composition. XRD diffraction patterns suggest the initial precipitation of non-ordered protodolomite that is subsequently continuously recrystallizing over the duration of the experiments to form an ordered, albeit non-stoichiometric dolomite. These observations are in agreement with Mg-isotope composition measured of the bulk reaction rim showing a systematic evolution over time that cannot be explained by simple Rayleigh or equilibrium fractionation. We interpret these findings as additional, but delayed reaction fronts affecting the microstructure and chemical composition of the newly formed carbonate rim that are essentially decoupled from the initial replacement front. Our results highlight the need to quantitatively understand alteration processes during diagenesis in order to accurately interpret the preserved geochemical record stored in element and isotope ratios of carbonates. [1] Jonas L

Distribution and tectonic implications of Cretaceous-Quaternary sedimentary facies in Solomon Islands

NASA Astrophysics Data System (ADS)

Turner, C. C.; Hughes, G. W.

1982-08-01

Sedimentary rocks of the Solomon Islands-Bougainville Arc are described in terms of nine widespread facies. Four facies associations are recognised by grouping facies which developed in broadly similar sedimentary environments. A marine pelagic association of Early Cretaceous to Miocene rocks comprises three facies. Facies Al: Early Cretaceous siliceous mudstone, found only on Malaita, is interpreted as deep marine siliceous ooze. Facies A2: Early Cretaceous to Eocene limestone with chert, overlies the siliceous mudstone facies, and is widespread in the central and eastern Solomons. It represents lithified calcareous ooze. Facies A3: Oligocene to Miocene calcisiltite with thin tuffaceous beds, overlies Facies A2 in most areas, and also occurs in the western Solomons. This represents similar, but less lithified calcareous ooze, and the deposits of periodic andesitic volcanism. An open marine detrital association of Oligocene to Recent age occurs throughout the Solomons. This comprises two facies. Facies B1 is variably calcareous siltstone, of hemipelagic origin; and Facies B2 consists of volcanogenic clastic deposits, laid down from submarine mass flows. A third association, of shallow marine carbonates, ranges in age from Late Oligocene to Recent. Facies C1 is biohermal limestone, and Facies C2 is biostromal calcarenite. The fourth association comprises areally restricted Pliocene to Recent paralic detrital deposits. Facies D1 includes nearshore clastic sediments, and Facies D2 comprises alluvial sands and gravels. Pre-Oligocene pelagic sediments were deposited contemporaneously with, and subsequent to, the extrusion of oceanic tholeiite. Island arc volcanism commenced along the length of the Solomons during the Oligocene, and greatly influenced sedimentation. Thick volcaniclastic sequences were deposited from submarine mass flows, and shallow marine carbonates accumulated locally. Fine grained graded tuffaceous beds within the marine pelagic association are

Sedimentary textures formed by aqueous processes, Erebus crater Meridiani Planum, Mars

USGS Publications Warehouse

Grotzinger, J.; Bell, J.; Herkenhoff, K.; Johnson, J.; Knoll, A.; McCartney, E.; McLennan, S.; Metz, J.; Moore, J.; Squyres, S.; Sullivan, R.; Ahronson, O.; Arvidson, R.; Joliff, B.; Golombek, M.; Lewis, K.; Parker, T.; Soderblom, J.

2006-01-01

New observations at Erebus crater (Olympia outcrop) by the Mars Exploration Rover Opportunity between sols 671 and 735 (a sol is a martian day) indicate that a diverse suite of primary and penecontemporaneous sedimentary structures is preserved in sulfate-rich bedrock. Centimeter-scale trough (festoon) cross-lamination is abundant, and is better expressed and thicker than previously described examples. Postdepositional shrinkage cracks in the same outcrop are interpreted to have formed in response to desiccation. Considered collectively, this suite of sedimentary structures provides strong support for the involvement of liquid water during accumulation of sedimentary rocks at Meridiani Planum. ?? 2006 Geological Society of America.

Petrography and geochemistry of Cenozoic sedimentary sequences of the southern Samar Island, Philippines: Clues to the unroofing history of an ancient subduction zone

NASA Astrophysics Data System (ADS)

Pacle, Nichole Anthony D.; Dimalanta, Carla B.; Ramos, Noelynna T.; Payot, Betchaida D.; Faustino-Eslava, Decibel V.; Queaño, Karlo L.; Yumul, Graciano P.

2017-07-01

The Cenozoic sedimentary sequences of southern Samar Island in eastern Philippines were examined to understand the unroofing history of an ancient arc terrane. Petrographic and geochemical data revealed varying degrees of inputs from the ophiolite basement and differences in modal compositions. The sedimentary units are mostly made up of lithic fragments. The Late Oligocene to Early Miocene Daram Formation contains more chert and volcanic fragments whereas the late Middle Miocene to Early Pliocene Catbalogan Formation is dominantly composed of ultramafic components. These variances are correspondingly reflected in the geochemical signatures of these two sedimentary formations. The Catbalogan Formation clastic rocks have higher volatile-free MgO and Fe2O3 values (average: 8.4% for both oxides) compared to the Daram Formation samples (average: 5.1 and 6.3%, respectively). Geochemical variations are also reflected in the Co, Cr and Ni values: the Catbalogan Formation samples reflect higher concentrations (Co: 15-57 ppm; Cr: 231-1094 ppm; Ni: 84-484 ppm) compared to the Daram Formation samples (Co: 24-32 ppm; Cr: 234-418 ppm; Ni: 212-323 ppm). These observations suggest that the Daram Formation eroded and transported more of the crustal portions of the ophiolite, while the younger Catbalogan Formation represents a later exhumation and subsequent erosion of the ultramafic section. An oceanic island arc (OIA) setting is proposed for the two formations based on several tectonic discrimination diagrams (e.g., Th-La-Sc, La vs. Th). The OIA signature is further supported by their smooth chondrite-normalized rare earth element (REE) patterns with no obvious Eu anomaly as well as LREE enrichment which are typical of sediments deposited in OIA setting. Based on the dominantly ophiolitic provenance of the Daram and Catbalogan formations, the post-emplacement history of the nearby Samar Ophiolite is constrained during the Late Oligocene to Early Pliocene period.

Diagenetic effects on magnetic minerals in a Holocene lacustrine sediment core from Huguangyan maar lake, southeast China

NASA Astrophysics Data System (ADS)

Wu, Xudong; Wang, Yong; Bian, Liu; Shen, Ji

2016-09-01

strong Asian summer monsoon intensity during the early Holocene are accountable for intensive diagenesis in the lowermost subsection. Complete erasing of detrital magnetic input signal at certain positions of the lowermost subsection, and considerable formation of authigenic siderite indicate that palaeomagnetic records of the studied core have been significantly compromised. The studied core has relatively higher TOC content, lower detrital matter content, calmer sedimentary environments, and less DO available at its water-sediment interface than the cores retrieved at relatively shallower water depths, which all contribute to its relatively stronger diagenesis. Progressive thickening of the upper two subsections with increasing water depth is owing to progressive increase in sedimentation rate with increasing water depth, which is the key factor in determining the thickness of each diagenetic subsection of cores from HGY. It would be better that lake sediments for palaeomagnetic investigations collected at a water depth shallower than the depth of its thermocline.

Sedimentary rock-hosted Au deposits of the Dian-Qian-Gui area, Guizhou, and Yunnan Provinces, and Guangxi District, China

USGS Publications Warehouse

Peters, S.G.; Jiazhan, H.; Zhiping, L.; Chenggui, J.

2007-01-01

Sedimentary rock-hosted Au deposits in the Dian-Qian-Gui area in southwest China are hosted in Paleozoic and early Mesozoic sedimentary rocks along the southwest margin of the Yangtze (South China) Precambrian craton. Most deposits have characteristics similar to Carlin-type Au deposits and are spatially associated, on a regional scale, with deposits of coal, Sb, barite, As, Tl, and Hg. Sedimentary rock-hosted Au deposits are disseminated stratabound and(or) structurally controlled. The deposits have many similar characteristics, particularly mineralogy, geochemistry, host rock, and structural control. Most deposits are associated with structural domes, stratabound breccia bodies, unconformity surfaces or intense brittle-ductile deformation zones, such as the Youjiang fault system. Typical characteristics include impure carbonate rock or calcareous and carbonaceous host rock that contains disseminated pyrite, marcasite, and arsenopyrite-usually with ??m-sized Au, commonly in As-rich rims of pyrite and in disseminations. Late realgar, orpiment, stibnite, and Hg minerals are spatially associated with earlier forming sulfide minerals. Minor base-metal sulfides, such as galena, sphalerite, chalcopyrite, and Pb-Sb-As-sulphosalts also are present. The rocks locally are silicified and altered to sericite-clay (illite). Rocks and(or) stream-sediment geochemical signatures typically include elevated concentrations of As, Sb, Hg, Tl, and Ba. A general lack of igneous rocks in the Dian-Qian-Gui area implies non-pluton-related, ore forming processes. Some deposits contain evidence that sources of the metal may have originated in carbonaceous parts of the sedimentary pile or other sedimentary or volcanic horizons. This genetic process may be associated with formation and mobilization of petroleum and Hg in the region and may also be related to As-, Au-, and Tl-bearing coal horizons. Many deposits also contain textures and features indicative of strong structural control by

Early diagenetic processes of saline meromictic Lake Kai-ike, southwest Japan: III. Sulfur speciation and isotopes

NASA Astrophysics Data System (ADS)

Sakai, N.; Yamaguchi, K. E.; Oguri, K.

2014-12-01

Lake Kai-ike is a saline meromictic lake located along the coast of Kami-Koshiki Island. The lake is isolated from ocean by a gravel bar, through which seawater infiltrates by tidal pumping. The lake is permanently redox (density)-stratified with a mid-depth development of photic zone anoxia and a dense community of photosynthetic bacteria pinkish "bacterial plate". The early diagenesis of sulfur in sediments overlain by an anoxic water body was investigated using a sediment core (KAI4) from the lake. We determined abundance of various S-bearing species (i.e., Cr-reducible sulfide (= pyrite S: Spy), acid-volatile sulfide (AVS), sulfate sulfur (SSO4), elemental sulfur (S0), and organic sulfur) by an improved sequential extraction method. Here we focus on drastic and rapid changes on sulfur biogeochemistry found in the uppermost 5cm layer. With increasing depth, abundance of Spy increased but that of SSO4 and δ34S value of Spy (δ34Spy) decreased. These results suggest progressive formation of bacteriogenic pyrite. The δ34S values of SSO4 (δ34SSO4) ranged from 25.1 ‰ (at sediment surface) to 3.8 ‰ in the uppermost 5 cm layer. This δ34SSO4 decrease in the top 5 cm sediment suggests that SSO4 in the surface sediment inherits SO42- with elevated δ34S values (higher than typical seawater δ34S value of 21‰) in the water column, which is due to extensive bacterial sulfate reduction with preferential removal of low-δ34S sulfur as sulfide. In the lower part of the uppermost 5 cm layer, SO42- formed by oxidation of S0, AVS, and/or Spy with low-δ34S values by SO42--bearing seawater introduced by infiltration through the gravel bar. Increasing δ34Spy values with increasing depth suggest near complete consumption of SO42- by active bacterial sulfate reduction, and this process could be explained by Rayleigh distillation model. Early diagenesis of sulfur does occur in whole section of 25cm-long KAI4 core that accumulated for the last ~60 years (Yamaguchi et al

Sedimentary environment and facies of St Lucia Estuary Mouth, Zululand, South Africa

NASA Astrophysics Data System (ADS)

Wright, C. I.; Mason, T. R.

The St. Lucia Estuary is situated on the subtropical, predominantly microtidal Zululand coast. Modern sedimentary environments within the estuary fall into three categories: (1) barrier environments; (2) abandoned channel environments; and (3) estuarine/lagoonal environments. The barrier-associated environment includes tidal inlet channel, inlet beach face, flood-tidal delta, ebb-tidal delta, spit, backspit and aeolian dune facies. The abandoned channel environment comprises washover fan, tidal creek tidal creek delta and back-barrier lagoon facies. The estuarine/lagoonal environment includes subtidal estuarine channel, side-attached bar, channel margin, mangrove fringe and channel island facies. Each sedimentary facies is characterised by sedimentary and biogenic structures, grain-size and sedimentary processes. Vertical facies sequences produced by inlet channel migration and lagoonal infilling are sufficiently distinct to be recognized in the geological record and are typical of a prograding shoreline.

The problem of genesis and systematic of sedimentary units of hydrocarbon reservoirs

NASA Astrophysics Data System (ADS)

Zhilina, E. N.; Chernova, O. S.

2017-12-01

The problem of identifying and ranking sedimentation, facies associations and their constituent parts - lithogenetic types of sedimentary rocks was considered. As a basis for paleo-sedimentary modelling, the author has developed a classification for terrigenous natural reservoirs,that for the first time links separate sedimentological units into a single hierarchical system. Hierarchy ranking levels are based on a compilation of global knowledge and experience in sediment geology, sedimentological study and systematization, and data from deep-well coresrepresentingJurassichydrocarbon-bearing formationsof the southeastern margin of the Western Siberian sedimentary basin.

Formation of Ocean Sedimentary Rocks as Active Planets and Life-Like Systems

NASA Astrophysics Data System (ADS)

Miura, Y.

2017-10-01

Wet shocked rocks are discarded globally and enriched elements in ocean-sedimentary rocks, which is strong indicator of ocean water of other planets. Ocean-sedimentary rocks are strong indicator of water planets and possible exo-life on planet Mars.

Reaction capacity characterization of shallow sedimentary deposits in geologically different regions of the Netherlands.

PubMed

Griffioen, Jasper; Klein, Janneke; van Gaans, Pauline F M

2012-01-01

Quantitative insight into the reaction capacity of porous media is necessary to assess the buffering capacity of the subsurface against contaminant input via groundwater recharge. Here, reaction capacity is to be considered as a series of geochemical characteristics that control acid/base conditions, redox conditions and sorption intensity. Using existing geochemical analyses, a statistical regional assessment of the reaction capacity was performed for two geologically different areas in the Netherlands. The first area is dominated by Pleistocene aquifer sediments only, in the second area a heterogeneous Holocene confining layer is found on top of the Pleistocene aquifer sediments. Within both areas, two or more regions can be distinguished that have a distinctly different geological build-up of the shallow subsurface. The reactive compounds considered were pyrite, reactive Fe other than pyrite, sedimentary organic matter, carbonate and clay content. This characterization was complemented by the analysis of a dataset of samples newly collected, from two regions within the Pleistocene area, where the sedimentary facies of samples was additionally distinguished. The statistical assessment per area was executed at the levels of region, geological formation and lithology class. For both areas, significant differences in reaction capacities were observed between: 1. different lithology classes within a geological formation in a single region, 2. identical geological formations in different regions and 3. various geological formations within a single region. Here, the reaction capacity is not only controlled by lithostratigraphy, but also by post-depositional diagenesis and paleohydrology. Correlation coefficients among the reactive compounds were generally higher for sand than for clay, but insufficiently high to allow good estimation of reactive compounds from each other. For the sandy Pleistocene aquifer sediments, the content of reactive compounds was frequently

Perspectives on geochemical proxies: The impact of model and parameter selection on the quantification of carbonate recrystallization rates

NASA Astrophysics Data System (ADS)

Huber, Christian; Druhan, Jennifer L.; Fantle, Matthew S.

2017-11-01

Diagenetic reactions in marine sediments, such as the recrystallization of carbonates, can impact the accuracy of paleo-environmental and paleo-climatic reconstructions by geochemical proxies. The extent to which the recrystallization of carbonates affects the chemistry of sedimentary archives depends on the reaction rate, extent of isotopic disequilibrium, and duration of reaction. The reaction rate, which is obviously critical, can be constrained by the elemental and isotopic compositions of pore fluids. Such constraints are affected by assumptions regarding the temperature in the sedimentary column relative to the temperature of formation, the burial rate, pore fluid advection, the composition of the sediments (carbonate-rich versus siliciclastic), and the porosity of the sediment column. In this study, we use a steady-state analytical solution to the diagenetic equations to constrain depth-dependent reaction rates (and extents of recrystallization) based on the Ca isotopic compositions of pore fluids in sedimentary columns at multiple ocean drilling sites (Sites 807, 984, 1170, and 1171), which encompass a diverse range of sedimentary compositions and conditions. We find that carbonates in siliciclastic sediments are generally less altered by diagenesis than their carbonate-rich counterparts. The discrepancy in recrystallization rates between siliciclastic and carbonate-rich sedimentary sections is, however, significantly smaller than previously estimated, suggesting that siliciclastic archives are not immune to diagenetic effects. While we find that diagenesis can decouple contemporaneous proxies of sea surface temperature (Mg/Ca and δ18O), our calculations also reveal that δ18O-based temperature estimates are more robust in siliciclastic sections relative to carbonate-rich sections. Sensitivity tests of the calculated extent of recrystallization suggest that uncertainties in porosity and burial rate are generally the greatest sources of error to proxy

A New Unusual Ice-induced Sedimentary Structure: the Silt Mushroom

PubMed Central

Jianhua, Zhong; Liangtian, Ni; Ningliang, Sun; Chuang, Liu; Bing, Hao; Mengchun, Cao; xin, Chen; Ke, Luo; Shengxin, Liu; Leitong, Huang; Guanqun, Yang; Shaojie, Wang; Feifei, Su; Xuejing, He; Yanqiu, Xue

2016-01-01

Upon channel bars or point bars within the lows of the Yellow River, a new sedimentary structure, named ‘silt mushroom’, has been observed. The process of their formation is interpreted to be via the ice process. The name, the silt mushroom comes from their figurative form. This is because they look somewhat similar to mushroom’s in size and shape; being in the range of 1 to 10 cm in diameter, with the medium 3–5 cm, and on average 10 cm in height, occuring generally in groups, and occasionally in isolation in relatively soft silt. They develop in the transition from winter to spring, and are convincingly related to ice processes. Ice-induced silt mushrooms are best examined in association with the many other newly discovered ice-induced sedimentary structures (over 20 kinds). Clearly, up to now, ice processes have been significantly underestimated. With the substantial discovery of the ice-induced silt mushroom, it opens up new questions. This is because its structure mirrors the same sedimentary structures found in rocks, questioning their genesis, and sedimentary environment analysis. This achievement is significant not only in sedimentology, but also in palaeogeography, palaeoclimate, geological engineering, hydraulics and fluviology. PMID:27833155

Inferred Early Permian Arc Rifting in Bogda Mountain, Southernmost of the Central Asia Orogenic Belt: Evidence from a Peperite Bearing Volcano-Sedimentary Succession

NASA Astrophysics Data System (ADS)

Memtimin, M.; Guo, Z.

2017-12-01

Late Paleozoic tectonic history, especially Carboniferous-Permian periods, of the Central Asia Orogenic Belt (CAOB) is considered to be the turning point for the termination of terrane amalgamation and closure of the Paleoasian Ocean. However, the debate about the paleoenvironment and tectonic setting of the region during the period is still not resolved. In this study, we report a set of volcano-sedimentary sequence in the Bogda Mountain of the southernmost of CAOB, which is associated with contemporaneous subaqueous emplacement of and interaction between mafic lava and carbonate sediments. The succession contains four distinct facies including closely packed pillow basalts, pillow basalts with interstitial materials, hyaloclastites and peperites. We discuss their formation and emplacement mechanism, interaction between hot magma-water/unconsolidated sediments and thermal metamorphism during the interaction. Textural features of the sequence, especially hyaloclastites and peperites, provide clear evidence for in situ autofragmentation of lava flows, synvolcanic sedimentation of carbonates, fuel coolant interaction when hot magma bulldozed into wet unconsolidated sediments, and represent autochthonous origin of the succession. Lateral transition of the lithofacies indicate a progressively deepening subaqueous environment, resembling a stepwise evolution from early stage of volcanic intrusion with lower lava flux in shallower water level to increasingly subsiding basin with more lava flux in greater depth. Previous studies determined that the mafic magma was intruded around the Carboniferous-Permian boundary ( 300Ma), and geochemical studies showed the magma was originated from dry depleted mantle with little crustal contamination. Nevertheless, the succession was thought to be fault related allochthones formation which was transferred in as part of a Carboniferous intraplate arc. Combining our findings with the previous study results, we propose a new model to

What controls diffuse fractures in platform carbonates? Insights from Provence (France) and Apulia (Italy)

NASA Astrophysics Data System (ADS)

Lavenu, Arthur P. C.; Lamarche, Juliette

2018-03-01

Fractures are widespread in rocks and regional opening-mode arrays are commonly ascribed to major tectonic events. However, fractures occur in otherwise undeformed rocks. Some of these are early-developed features independent of tectonics and forming a background network at regional scale. To overcome this lack of understanding, two hydrocarbon reservoir analogues from platform carbonates have been targeted: the Provence (SE France), and the Apulian platform (SE Italy). In both areas, an early fracturing stage has been observed, made of high-angle-to-bedding opening-mode fractures, and bed-parallel stylolites. These features developed synchronously during the first burial stages and prior to major tectonic events. The fracture sets are not genetically related to the present-day layering. Contrarily, fractures developed in a brittle media where facies transitions were not sharp and did not act as mechanical discontinuities. Carbonate facies distribution and early diagenetic imprint constrained the mechanical stratigraphy when fractures occurred. In addition, we observed that fractures related to late tectonic inversion were partly inhibited. Indeed, rock mechanical properties change through time. Characterizing the temporal evolution of carbonate rocks has revealed that diagenesis and sedimentary facies are the prime actors for brittleness and mechanical layering in carbonates.

Structural and sedimentary evolution of the Malay Basin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ismail, M.T.; Rudolph, K.W.; Abdullah, S.A.

1994-07-01

The Malay Basin is a back-arc basin that formed via Eocene ( ) through Oligocene extension. This early extensional episode is characterized by large east-west and northwest-southeast-trending normal fault systems with associated block rotation. Extensional subbasins are filled with a thick succession of alluvial and fluvial sediments that show increasing lacustrine influence toward the central basin dep. In the early Miocene, the basin entered a passive sag phase in which depositional relief decreased, and there is the first evidence of widespread marine influence. Lower Miocene sediments consist of cyclic offshore marine, tidal-estuarine, and coastal plain fluvial sediments with very widemore » facies tracts. The middle Miocene is dominated by increasing compressional inversion, in which preexisting extensional lows were folded into east-west anticlines. This compression continues well into the Pliocene-Pleistocene, especially in the northwest portion of the basin and is accompanied by an increase in basin-wide subsidence. There is significant thinning over the crest of the growing anticlines and an angular unconformity near the top of the middle Miocene in the southeast portion of the basin. Middle Miocene sedimentary facies are similar to those seen in the lower Miocene, but are influenced by the contemporaneous compressional folding and normal faulting. Based on this study, there is no evidence of through-going wrench-fault deformation in the Malay Basin. Instead, localized strike-slip faulting is a subsidiary phenomenon associated with the extensional and compressional tectonic episodes.« less

In-situ Detection of Squalane in Sedimentary Organic Matter Using Monoclonal Antibodies

NASA Astrophysics Data System (ADS)

Bailey, J. V.; Corsetti, F. A.; Moldowan, J. M.; Fago, F.; Caron, D.

2008-12-01

Sedimentary geolipids can serve as powerful tools for reconstructing ancient ecosystems, but only if investigators can demonstrate that the hydrocarbons are indigenous to their host rocks. The association of molecules with primary sedimentary fabrics could indicate a syngenetic relationship. However, traditional biomarker analyses require extraction from large quantities of powdered rock, confounding detailed spatial correlations. Biological studies commonly use antibodies as extremely sensitive molecular probes. When coupled with fluorescent labels, antibodies allow for the visual localization of molecules. Here we show that monoclonal antibodies that bind specifically to geolipid compounds can be used for in situ detection and labeling of such compounds in mineral-bound organic macerals. Monoclonal antibodies to squalene, produced for human health studies, also react with the geolipid, squalane. We show that squalene antibodies do not react with other common sedimentary hydrocarbons. We also show that squalane antibodies bind specifically to isolated organic-rich lamina in Eocene-age, squalane-containing rocks. These results suggest that squalane is confined to discrete organo-sedimentary fabrics within those rocks, providing evidence for its syngeneity. The chemical similarity of squalane to other sedimentary hydrocarbons hints at the potential for developing monoclonal antibodies to a variety of biomarkers that could then be localized in rocks, sediments, and extant cells.

Testing the survival of microfossils in an artificial martian sedimentary meteorite: the STONE 6 Experiment

NASA Astrophysics Data System (ADS)

Foucher, Frédéric; Westall, Frances; Brandstaetter, Franz; Demets, Rene; Parnell, John; Cockell, Charles; Edwards, Howell; Jean-Michel, B.; Brack, André; Kurat, Gero

Conditions on early Mars during the Noachian (-4.5 to -3.5 Ga) were possibly suitable for the emergence of life [1,3] even though water bodies were probably not permanent and could have been destroyed by frequent impacts. Since Mars does not appear to have had plate tectonics, the remains of this hypothetic life could be found within Noachian sediments. In addition to proving the existence of extraterrestrial life, such a discovery would be very helpful for studies related to the origin and early evolution of life on Earth. Indeed, although life most likely appeared on Earth before 4 Ga ago, no suitable (i.e. well-preserved) rocks containing traces of life older than 3.5 billion years exist; older rocks are either too metamorphosed or have been destroyed by plate tectonics. Because of the harsh conditions on Noachian Mars compared to those of the early Earth, the martian organisms are likely to have remained in a very primitive state of evolution and will thus be very difficult to observe in situ. One way to investigate potential traces of life in martian rocks would be to study sedimentary meteorites from Mars. However, all the 54 martian meteorites found so far are volcanic rocks [4]. Is this because sedimentary rocks do not survive the original impact to escape Mars, or the stresses of entry into the Earth's atmosphere? In order to test the latter effects, a series of experiments were devised to test the survivability of different types of sediments during Earth atmosphere entry, the STONE experiments. In particular, the present experiment STONE 6 tested a Noachian sedimentary analogue that consisted of a 3.45 Ga-old silicified volcanic sand containing ancient traces of life [5]. The volcanic sand (chert) from the Pilbara, Australia, containing organic microfossils [6] was embedded in the heat shield of a FOTON space capsule that underwent atmospheric entry on the 26th September, 2007. After landing, the first observation was the white colour of the fusion crust

Tectono-sedimentary constraints to the Oligocene-to-Miocene evolution of the Peloritani thrust belt (NE Sicily)

NASA Astrophysics Data System (ADS)

Giunta, G.; Nigro, F.

1999-12-01

The Peloritani thrust belt belongs to the southern sector of the Calabrian Arc and is formed by a set of south-verging tectonic units, including crystalline basement and sedimentary cover (from the top: Aspromonte U.; Mela U.; Mandanici U.; Fondachelli U.; Longi-Taormina U.), piled up starting from Late Oligocene. At least two main terrigenous clastic formations lie with complicated relationships on top of the previous units: the Frazzanò Fm (Oligocene) and the Stilo-Capo d'Orlando Fm (Late Oligocene?-Early Miocene), as syn-to-post-tectonic deposits. These clastic deposits have different characteristics, in space and time, representing or flysch-like sequences involved in several thrust events (Frazzanò Fm) or molassic-like sequences (Stilo-Capo d'Orlando Fm), which unconformably overlie the tectonic units. In the present paper we describe a kinematic model of the progressive foreland migration of the Peloritani thrust belt, starting from Oligocene, carrying piggy-back basins and incorporating foredeep deposits, recognised in the Frazzanò-Stilo-Capo d'Orlando terrigenous successions. In general, the facies and structural observations on the overall Oligo-Miocene clastic sequences, outcropping in the Western Peloritani Mts, indicate: (a) the distal character of the Frazzanò Fm; (b) a complex group of terrigenous facies of the Stilo-Capo d'Orlando Fm, with lateral-to-vertical organisation, characterised by a distal-to-proximal-to-distal facies trend; (c) facies analogies of the basal portions of the Stilo-Capo d'Orlando Fm with the Frazzanò Fm; (d) the involvement of the Frazzanò Fm in lowermost and more external thrusting, and of the basal (Late Oligocene?) distal Stilo-Capo d'Orlando facies in the higher and inner thrusting during the early stages of deformation; (e) the involvement of the proximal Stilo-Capo d'Orlando facies in the tectonic edifice during the Early Miocene deformation; (f) the generally unconformable stratigraphical contacts of the higher

Sedimentary evolution of the Pliocene and Pleistocene Ebro margin, northeastern Spain

USGS Publications Warehouse

Alonso, B.; Field, M.E.; Gardner, J.V.; Maldonado, A.

1990-01-01

The Pliocene and Pleistocene deposits of the Spanish Ebro margin overlie a regional unconformity and contain a major disconformity. These unconformities, named Reflector M and Reflector G, mark the bases of two seismic sequences. Except for close to the upper boundary where a few small channel deposits are recognized, the lower sequence lacks channels. The upper sequence contains nine channel-levee complexes as well as base-of-slope aprons that represent the proximal part of the Valencia turbidite system. Diverse geometries and variations in seismic units distinguish shelf, slope, base-of-slope and basin-floor facies. Four events characterize the late Miocene to Pleistocene evolution of the Ebro margin: (a) formation of a paleodrainage system and an extensive erosion-to-depositional surface during the latest Miocene (Messinian), (b) deposition of hemipelagic units during the early Pliocene, (c) development of canyons during the late Pliocene to early Pleistocene, and (d) deposition of slope wedges, channel-levee complexes, and base-of-slope aprons alternating with hemipelagic deposition during the Pleistocene. Sea-level fluctuations influenced the evolution of the sedimentary sequences of the Ebro margin, but the major control was the sediment supply from the Ebro River. ?? 1990.

Distributions, Early Diagenesis, and Spatial Characteristics of Amino Acids in Sediments of Multi-Polluted Rivers: A Case Study in the Haihe River Basin, China.

PubMed

Zhao, Yu; Shan, Baoqing; Tang, Wenzhong; Zhang, Hong; Rong, Nan; Ding, Yuekui

2016-02-19

The Haihe River Basin, which is one of the most water-scarce and polluted river basins in China, has abnormally high nitrogen levels. In this study, total hydrolyzable amino acids (THAAs) were measured in surface sediment and sediment core samples in the Haihe River Basin to determine if amino acids were potential sources of ammonium, organic nitrogen, and organic carbon. The rivers were found to be in a state of hypoxia and contain abnormally high levels of ammonium and organic nitrogen. Additionally, NH₃-N was the predominant form of inorganic nitrogen in the surface sediments, while organic nitrogen accounted for 92.53% of sedimentary nitrogen. THAAs-C accounted for 14.92% of the total organic carbon, while THAAs-N accounted for more than 49.59% of organic nitrogen and 45.68% of total nitrogen. The major fraction of THAAs were protein amino acids. Three sediment cores of the most heavily polluted rivers also showed high levels of THAAs. Evaluation of the degradation index (DI) of sedimentary organic matter in sediments evaluated based on the THAAs revealed that most positive DI values were found in the downstream portion of the Ziya River Watershed. Additionally, the DI of surface sediment was correlated with THAAs (r² = 0.763, p < 0.001), as was the DI of sediment cores (r² = 0.773, p < 0.001). Overall, amino acids in sediments were found to be an important potential source of ammonium, organic nitrogen, and organic carbon.

Distributions, Early Diagenesis, and Spatial Characteristics of Amino Acids in Sediments of Multi-Polluted Rivers: A Case Study in the Haihe River Basin, China

PubMed Central

Zhao, Yu; Shan, Baoqing; Tang, Wenzhong; Zhang, Hong; Rong, Nan; Ding, Yuekui

2016-01-01

The Haihe River Basin, which is one of the most water-scarce and polluted river basins in China, has abnormally high nitrogen levels. In this study, total hydrolyzable amino acids (THAAs) were measured in surface sediment and sediment core samples in the Haihe River Basin to determine if amino acids were potential sources of ammonium, organic nitrogen, and organic carbon. The rivers were found to be in a state of hypoxia and contain abnormally high levels of ammonium and organic nitrogen. Additionally, NH3-N was the predominant form of inorganic nitrogen in the surface sediments, while organic nitrogen accounted for 92.53% of sedimentary nitrogen. THAAs-C accounted for 14.92% of the total organic carbon, while THAAs-N accounted for more than 49.59% of organic nitrogen and 45.68% of total nitrogen. The major fraction of THAAs were protein amino acids. Three sediment cores of the most heavily polluted rivers also showed high levels of THAAs. Evaluation of the degradation index (DI) of sedimentary organic matter in sediments evaluated based on the THAAs revealed that most positive DI values were found in the downstream portion of the Ziya River Watershed. Additionally, the DI of surface sediment was correlated with THAAs (r2 = 0.763, p < 0.001), as was the DI of sediment cores (r2 = 0.773, p < 0.001). Overall, amino acids in sediments were found to be an important potential source of ammonium, organic nitrogen, and organic carbon. PMID:26907310

Alteration of Sedimentary Clasts in Martian Meteorite Northwest Africa 7034

NASA Technical Reports Server (NTRS)

McCubbin, F. M.; Tartese, R.; Santos, A. R.; Domokos, G.; Muttik, N.; Szabo, T.; Vazquez, J.; Boyce, J. W.; Keller, L. P.; Jerolmack, D. J.;

Diagenesis of fossil coral skeletons: Correlation between trace elements, textures, and [sup 234]U/[sup 238]U

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bar-Matthews, M.; Wasserburg, G.J.; Chen, J.H.

1993-01-01

A comparative study of Pleistocene fossil coral skeletons and of modern coral skeletons was carried out using petrographic and trace element analyses on a suite of Pleistocene samples that had previously been studied from [sup 234]U, [sup 230]Th, and U-[sup 230]Th ages (Chen et al. 1991). Evidence of a range of diagenetic changes can be recognized by optical (OM) and scanning electron microscopy (SEM). Using an electron microprobe and SEM, concentrations of Na, S, Sr, and Mg were measured. No other trace elements were detected. Na, S, and Mg contents of the matrix, the fibrous micropores, and radiating needles aremore » highly variable and well correlated. High concentrations of Na, S, and Mg were found in modern living corals with lower concentrations in fossil corals and fibrous micropores, and the lowest value in the radiating needles. The reason for the correlations of Na, S, and Mg and crystal chemistry and the response to diagenesis of these trace elements is not understood. The average concentrations of Na, S, and Mg for each sample, when plotted against the whole coral initial [delta][sup 234]U, are generally correlated (Chen et al., 1991). As all these diagenetic changes involve the recystallization and deposition of aragonite, the authors infer that the geologic site of diagenesis both for forming the secondary aragonitic phases and for the enhancement of the [sup 234]U content in the fossil corals was the marine environment. It is possible that the textural and Na, S, and Mg trace element contents of fossil corals be used to ascertain the reliability of fossil coral skeletons for U-[sup 230]Th dating. The basic problem of identifying a priori unaltered coral skeletons for [sup 230]Th dating is not yet resolved. 64 refs., 16 figs., 5 tabs.« less

Heterotrophic Archaea dominate sedimentary subsurface ecosystems off Peru

PubMed Central

Biddle, Jennifer F.; Lipp, Julius S.; Lever, Mark A.; Lloyd, Karen G.; Sørensen, Ketil B.; Anderson, Rika; Fredricks, Helen F.; Elvert, Marcus; Kelly, Timothy J.; Schrag, Daniel P.; Sogin, Mitchell L.; Brenchley, Jean E.; Teske, Andreas; House, Christopher H.; Hinrichs, Kai-Uwe

2006-01-01

Studies of deeply buried, sedimentary microbial communities and associated biogeochemical processes during Ocean Drilling Program Leg 201 showed elevated prokaryotic cell numbers in sediment layers where methane is consumed anaerobically at the expense of sulfate. Here, we show that extractable archaeal rRNA, selecting only for active community members in these ecosystems, is dominated by sequences of uncultivated Archaea affiliated with the Marine Benthic Group B and the Miscellaneous Crenarchaeotal Group, whereas known methanotrophic Archaea are not detectable. Carbon flow reconstructions based on stable isotopic compositions of whole archaeal cells, intact archaeal membrane lipids, and other sedimentary carbon pools indicate that these Archaea assimilate sedimentary organic compounds other than methane even though methanotrophy accounts for a major fraction of carbon cycled in these ecosystems. Oxidation of methane by members of Marine Benthic Group B and the Miscellaneous Crenarchaeotal Group without assimilation of methane–carbon provides a plausible explanation. Maintenance energies of these subsurface communities appear to be orders of magnitude lower than minimum values known from laboratory observations, and ecosystem-level carbon budgets suggest that community turnover times are on the order of 100–2,000 years. Our study provides clues about the metabolic functionality of two cosmopolitan groups of uncultured Archaea. PMID:16505362

Neodymium and strontium isotopic dating of diagenesis and low-grade metamorphism of argillaceous sediments

NASA Astrophysics Data System (ADS)

Schaltegger, Urs; Stille, Peter; Rais, Naoual; Piqué, Alain; Clauer, Norbert

1994-03-01

The behaviour of the Rb-Sr and Sm-Nd isotopic systems with increasing degree of Hercynian metamorphic overprint was studied along a transect in Cambrian shales of northwestern Morocco. Clay fractions of < 0.2 to 2-6 μm size from five samples were investigated, representing a range from nonmetamorphic to epizonal metamorphic conditions. The samples were washed in cold l N HC1 prior to digestion to separate soluble/exchangeable Rb, Sr, Sm, and Nd from amounts of these elements fixed in the crystallographic sites of the minerals and to analyze both components separately. The results reveal that the Rb-Sr isotopic system is dominated by Sr hosted by clay mineral phases (both detrital and authigenic illite and chlorite) and carbonate-hosted soluble Sr. Isotopic homogenization of Sr occurred during Hercynian metamorphism, yielding ages between 309 and 349 Ma. The Sm-Nd isotopic system, on the other hand, is dominated by cogenetic apatite and Fe oxide/ hydroxide, both having high contents of leachable REEs. The leachates yield a Sm-Nd isochron age of 523 ± 72 Ma, indicating diagenetic equilibrium between apatite and Fe-oxide/hydroxide. Fine-grained clay fractions of < 0.2 μm size plot onto this reference line, suggesting isotopic equilibrium with the leachates. Size fractions > 0.2 μm show inheritance of a detrital Nd component. The study demonstrates that the diagenesis of the investigated argillaceous sediments can be dated by the Sm-Nd chronometer in authigenic cement phases. The isotopic system of these minerals (apatite, Fe hydroxide/oxide) was homogenized during authigenic mineral growth in a sediment that was flushed by diagenetic fluids and had abundant primary or secondary interconnected pore space. The Hercynian metamorphic overprint caused partial isotopic rehomogenization of the adsorbed and clay-hosted portion of the Sr as well as of the carbonate-hosted Sr. The Sm-Nd system in the cement phases survived this metamorphism. This results in decoupling of

Sedimentary Rocks of Aram Chaos

NASA Technical Reports Server (NTRS)

2004-01-01

10 May 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows outcroppings of light-toned, layered, sedimentary rock within Aram Chaos, an ancient, partly-filled impact crater located near 3.2oN, 19.9oW. This 1.5 meters (5 feet) per pixel picture is illuminated by sunlight from the left and covers an area about 3 km (1.9 mi) across.

Diagenesis Along Fractures in an Eolian Sandstone, Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Ming, D. W.; Yen, A. S.; Rampe, E. B.; Grotzinger, J. P.; Blake, D. F.; Bristow, T. F.; Chipera, S. J.; Downs, R.; Morris, R. V.; Morrison, S. M.;

Radiographic analysis of sedimentary structures and depositional histories in Apollo 15 cores

NASA Technical Reports Server (NTRS)

Coch, N. K.

1977-01-01

Radiographs of the Apollo 15 deepdrill drive tubes were analyzed on an SDS electronic enhancer to determine sedimentary structures in the core samples. The data obtained were compared with all other Apollo mission radiographs and used to make inferences on the character of sedimentary depositional processes on the lunar surface.

Variety of Sedimentary Process and Distribution of Tsunami Deposits in Laboratory Experiments

NASA Astrophysics Data System (ADS)

Yamaguchi, N.; Sekiguchi, T.

2017-12-01

As an indicator of the history and magnitude of paleotsunami events, tsunami deposits have received considerable attention. To improve the identification and interpretation of paleotsunami deposits, an understanding of sedimentary process and distribution of tsunami deposits is crucial. Recent detailed surveys of onshore tsunami deposits including the 2004 Indian Ocean tsunami and the 2011 Tohoku-oki tsunami have revealed that terrestrial topography causes a variety of their features and distributions. Therefore, a better understanding of possible sedimentary process and distribution on such influential topographies is required. Flume experiments, in which sedimentary conditions can be easily controlled, can provide insights into the effects of terrestrial topography as well as tsunami magnitude on the feature of tsunami deposits. In this presentation, we report laboratory experiments that focused on terrestrial topography including a water body (e.g. coastal lake) on a coastal lowland and a cliff. In both cases, the results suggested relationship between the distribution of tsunami deposits and the hydraulic condition of the tsunami flow associated with the terrestrial topography. These experiments suggest that influential topography would enhance the variability in thickness of tsunami deposits, and thus, in reconstructions of paleotsunami events using sedimentary records, we should take into account such anomalous distribution of tsunami deposits. Further examination of the temporal sequence of sedimentary process in laboratory tsunamis may improve interpretation and estimation of paleotsunami events.

STEPPE: Supporting collaborative research and education on Earth's deep-time sedimentary crust.

NASA Astrophysics Data System (ADS)

Smith, D. M.

2014-12-01

STEPPE—Sedimentary geology, Time, Environment, Paleontology, Paleoclimate, and Energy—is a National Science Foundation supported consortium whose mission is to promote multidisciplinary research and education on Earth's deep-time sedimentary crust. Deep-time sedimentary crust research includes many specialty areas—biology, geography, ecology, paleontology, sedimentary geology, stratigraphy, geochronology, paleoclimatology, sedimentary geochemistry, and more. In fact, the diversity of disciplines and size of the community (roughly one-third of Earth-science faculty in US universities) itself has been a barrier to the formation of collaborative, multidisciplinary teams in the past. STEPPE has been working to support new research synergies and the development of infrastructure that will encourage the community to think about the big problems that need to be solved and facilitate the formation of collaborative research teams to tackle these problems. Toward this end, STEPPE is providing opportunities for workshops, working groups and professional development training sessions, web-hosting and database services and an online collaboration platform that facilitates interaction among participants, the sharing of documentation and workflows and an ability to push news and reports to group participants and beyond using social media tools. As such, STEPPE is working to provide an interactive space that will serve as both a gathering place and clearinghouse for information, allowing for broader integration of research and education across all STEPPE-related sub disciplines.

A 2.7 Myr record of sedimentary processes on a high-latitude continental slope: 3D seismic evidence from the mid-Norwegian margin

NASA Astrophysics Data System (ADS)

Montelli, A.; Dowdeswell, J. A.; Ottesen, D.; Johansen, S. E.

2017-12-01

An extensive three-dimensional seismic dataset is used to investigate the sedimentary processes and morphological evolution of the mid-Norwegian continental slope through the Quaternary. These data reveal hundreds of buried landforms, including channels and debris flows of variable morphology, as well as gullies, iceberg ploughmarks, slide scars and sediment waves. Slide scars, turbidity currents and debris flows comprise slope systems controlled by local slope morphology, showing the spatial variability of high-latitude sedimentation. Channels dominate the Early Pleistocene ( 2.7-0.8 Ma) morphological record of the mid-Norwegian slope. During Early Plesitocene, glacimarine sedimentation on the slope was influenced by dense bottom-water flow and turbidity currents. Glacigenic debris-flows appear within the Middle-Late Pleistocene ( 0.8-0 Ma) succession. Their abundance increases on Late Pleistocene palaeo-surfaces, marking a paleo-environmental change characterised by decreasing role for channelized turbidity currents and dense water flows. This transition coincides with the gradual shift to full-glacial ice-sheet conditions marked by the appearance of the first erosive fast-flowing ice streams and an associated increase in sediment flux to the shelf edge, emphasizing first-order climate control on the temporal variability of high-latitude sedimentary slope records.

The role of Mesozoic sedimentary basin tapers on the formation of Cenozoic crustal shortening structures and foredeep in the western Sichuan Basin, China

NASA Astrophysics Data System (ADS)

Wang, M.

2017-12-01

The foreland basin records important clues of tectonic and sedimentary process of mountain-building, thus to explore its dynamic mechanism on the formation is an important issue of the mountain-basin interaction. The Longmen Shan fold-and-thrust belt and its adjacent Sichuan basin located in the eastern margin of Tibetan Plateau, are one of the most-concerned regions of studying modern mountain-building and seismic process, and are also a natural laboratory of studying the dynamics of the formation and development of foreland basin. However, it still need further explore on the mechanics of the development of the Cenozoic foreland basin and thrust-belts in the western Sichuan Basin. The Longmen Shan thrust belt has experienced multi-stages of tectonics evolution, foreland basin formation and topography growth since Late Triassic, and whether the early formed basin architecture and large Mesozoic sedimentary basin taper can influence the formation and development of the Cenozoic foreland basin and thrust belts? To solve these issues, this project aim to focus on the Cenozoic foreland basin and internal crustal shortening structures in the western Sichuan basin, on the basis of growth critical wedge taper theory. We will reconstruct the shape of multi-phases of sedimentary basin tapers, the temporal-spatial distribution of crustal shortening and thrusting sequences, and analyze the control mechanism of Mesozoic sedimentary basin taper on the formation of Cenozoic foreland basins, and final explore the interaction between the tectonics geomorphology, stress field and dynamic propagation of foreland basin.

Atmospheric methane from organic carbon mobilization in sedimentary basins — The sleeping giant?

NASA Astrophysics Data System (ADS)

Kroeger, K. F.; di Primio, R.; Horsfield, B.

2011-08-01

The mass of organic carbon in sedimentary basins amounts to a staggering 10 16 t, dwarfing the mass contained in coal, oil, gas and all living systems by ten thousand-fold. The evolution of this giant mass during subsidence and uplift, via chemical, physical and biological processes, not only controls fossil energy resource occurrence worldwide, but also has the capacity for driving global climate: only a tiny change in the degree of leakage, particularly if focused through the hydrate cycle, can result in globally significant greenhouse gas emissions. To date, neither climate models nor atmospheric CO 2 budget estimates have quantitatively included methane from thermal or microbial cracking of sedimentary organic matter deep in sedimentary basins. Recent estimates of average low latitude Eocene surface temperatures beyond 30 °C require extreme levels of atmospheric CO 2. Methane degassing from sedimentary basins may be a mechanism to explain increases of atmospheric CO 2 to values as much as 20 times higher than pre-industrial values. Increased natural gas emission could have been set in motion either by global tectonic processes such as pulses of activity in the global alpine fold belt, leading to increased basin subsidence and maturation rates in the prolific Jurassic and Cretaceous organic-rich sediments, or by increased magmatic activity such as observed in the northern Atlantic around the Paleocene-Eocene boundary. Increased natural gas emission would have led to global warming that was accentuated by long lasting positive feedback effects through temperature transfer from the surface into sedimentary basins. Massive gas hydrate dissociation may have been an additional positive feedback factor during hyperthermals superimposed on long term warming, such as the Paleocene-Eocene Thermal Maximum (PETM). As geologic sources may have contributed over one third of global atmospheric methane in pre-industrial time, variability in methane flux from sedimentary

Diagenesis of the Machar Field (British North Sea) chalk: Evidence for decoupling of diagenesis in fractures and the host rock

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maliva, R.G.; Dickson, J.A.D.; Smalley, P.C.

1995-01-02

The Chalk Group (Cretaceous/Tertiary) in the Machar Field (British North Sea) contains both fracture-filling and microcrystalline calcite cements. Modeling of fluid-rock interaction using data on light stable isotopes obtained by whole rock analyses and laser ablation analyses of calcite cements reveal that the fracture and matrix diagenetic systems were largely decoupled. The calcium and carbonate of the fracture-filling calcite cements were derived largely from the adjacent chalk matrix. The fracture diagenetic system had a high water-rock ratio, which maintained a relatively stable water {delta}{sup 18}O ratio during calcite dissolution and precipitation. The chalk matrix, on the contrary, had a lowmore » molar water-rock ratio during recrystallization, which resulted in increases in the pore-water {delta}{sup 18}O value during recrystallization at elevated temperatures. This evolution of the pore-water {delta}{sup 18}O value is manifested by highly variable cement {delta}{sup 18}O values. The present-day formation waters of the Machar Field have {sup 87}Sr/{sup 86}Sr ratios significantly higher than the whole rock and fracture-filling cement calcite values, evidence that the chemical composition of the formation waters is not representative of that of the pore waters during chalk recrystallization. Little diagenesis is therefore now occurring in the Machar Field. The diagenetic systems of the chalk matrix and fractures both had a high degree of openness with respect to carbon, because of the introduction of organically derived bicarbonate rather than advection of water through the chalk. The bulk of calcite cementation in fractures and the recrystallization and cementation of the chalk matrix occurred at temperatures in the 80--100 C range, at or just below the present-day reservoir temperature of 97 C.« less

The Pliocene Horcón Formation, Central Chile: a case study of earthquake-induced landslide susceptibility

NASA Astrophysics Data System (ADS)

Valdivia, D.; Elgueta, S.; Hodgkin, A.; Marquardt, C.; del Valle, F.; Yáñez Morroni, G.

2017-12-01

Stability slope analysis is typically focused on modeling using cohesion and friction angle parameters but in earthquake-induced landslides, susceptibility is correlated more to lithological and stratigraphic parameters. In sedimentary deposits whose cohesion and diagenesis are very low, the risk of landslides increases. The Horcón Formation, which crops out continuously along cliffs in Central Chile between 32.5° and 33°S, is a Miocene-Pliocene well preserved, horizontally stratified unit composed of marine strata which overlies Paleozoic-Mesozoic igneous basement. During the Quaternary, the sequence was tectonically uplifted 80 meters and covered by unconsolidated eolian deposits. Given that Seismotectonic and Barrier-Asperity models suggest the occurrence of a forthcoming megathrust earthquake in a segment which includes this area, the Horcón Formation constitutes a good case study to characterize the susceptibility of this type of sediment for mass movements triggered by earthquakes. Field mapping, stratigraphic and sedimentological studies, including petrographic analyses to determine lithological composition and paragenesis of diagenetic events, have been carried out along with limited gravimetric profiling and CPTU drill tests. High resolution digital elevation modeling has also been applied. This work has led to the recognition of a shallow marine lithofacies association composed of weakly lithified fossiliferous and bioturbated medium to fine grained litharenite, mudstone, and fine conglomerate. The low grade of diagenesis in the sedimentary deposits was in response to a short period of burial and a subsequent accelerated uplift evidenced along the coast of Chile during the Quaternary. We have generated a predictive model of landslide susceptibility for the Horcón Formation and for the overlying Quaternary eolian deposits incorporating variables such as composition and diagenesis of lithofacies, slope, structures, weathering and landcover. The model

Application of MSS/LANDSAT images to the structural study of recent sedimentary areas: Campos Sedimentary Basin, Rio de Janeiro, Brazil

NASA Technical Reports Server (NTRS)

Parada, N. D. J. (Principal Investigator); Barbosa, M. P.

1983-01-01

Visual and computer aided interpretation of MSS/LANDSAT data identified linear and circular features which represent the ""reflexes'' of the crystalline basement structures in the Cenozoic sediments of the emergent part of the Campos Sedimentary Basin.

Nitrogen isotopes from terrestrial organic matter as a new paleoclimatic proxy for pre-quaternary time

NASA Astrophysics Data System (ADS)

Tramoy, romain; Schnyder, johann; thuy Nguyen Tu, thanh; Yans, johan; Storme, jean yves; Sebilo, mathieu; Derenne, sylvie; Jacob, jérémy; Baudin, françois

2014-05-01

Taskomirsay, Kazakhstan. This succession is rich in dispersed OM and wood fragments allowing accurate N isotopes measurements. Preliminary results on δ13Corg and palynology suggest that the Pliensbachian/Toarcian transition is recorded at the top of the sedimentary succession. This transition has been studied for a long time since it is characterized by one of the most important global environmental and climatic change of the Phanerozoic time ( Jenkyns, 1988; Hermoso et al., 2012). We are therefore testing the paleoclimatic "proxy" potential of δ15Norg for this time interval by comparing the δ15Norg signal with other indicators more classically used for paleoclimate studies. We have also investigated the influence of differences in organic sources and of early diagenesis on the δ15Norg variations.

Velocity Models of the Sedimentary Cover and Acoustic Basement, Central Arctic

NASA Astrophysics Data System (ADS)

Bezumov, D. V.; Butsenko, V.

2017-12-01

As the part of the Russian Federation Application on the Extension of the outer limit of the continental shelf in the Arctic Ocean to the Commission for the limits of the continental shelf the regional 2D seismic reflection and sonobuoy data was obtained in 2011, 2012 and 2014 years. Structure and thickness of the sedimentary cover and acoustic basement of the Central Arctic ocean can be refined due to this data. "VNIIOkeangeologia" created a methodology for matching 2D velocity model of the sedimentary cover based on vertical velocity spectrum calculated from wide-angle reflection sonobuoy data and the results of ray tracing of reflected and refracted waves. Matched 2D velocity models of the sedimentary cover in the Russian part of the Arctic Ocean were computed along several seismic profiles (see Figure). Figure comments: a) vertical velocity spectrum calculated from wide-angle reflection sonobuoy data. RMS velocity curve was picked in accordance with interpreted MCS section. Interval velocities within sedimentary units are shown. Interval velocities from Seiswide model are shown in brackets.b) interpreted sonobuoy record with overlapping of time-distance curves calculated by ray-tracing modelling.c) final depth velocity model specified by means of Seiswide software.

Global Drainage Patterns to Modern Terrestrial Sedimentary Basins and its Influence on Large River Systems

NASA Astrophysics Data System (ADS)

Nyberg, B.; Helland-Hansen, W.

2017-12-01

Long-term preservation of alluvial sediments is dependent on the hydrological processes that deposit sediments solely within an area that has available accomodation space and net subsidence know as a sedimentary basin. An understanding of the river processes contributing to terrestrial sedimentary basins is essential to fundamentally constrain and quantify controls on the modern terrestrial sink. Furthermore, the terrestrial source to sink controls place constraints on the entire coastal, shelf and deep marine sediment routing systems. In addition, the geographical importance of modern terrestrial sedimentary basins for agriculture and human settlements has resulted in significant upstream anthropogenic catchment modification for irrigation and energy needs. Yet to our knowledge, a global catchment model depicting the drainage patterns to modern terrestrial sedimentary basins has previously not been established that may be used to address these challenging issues. Here we present a new database of 180,737 global catchments that show the surface drainage patterns to modern terrestrial sedimentary basins. This is achieved by using high resolution river networks derived from digital elevation models in relation to newly acquired maps on global modern sedimentary basins to identify terrestrial sinks. The results show that active tectonic regimes are typically characterized by larger terrestrial sedimentary basins, numerous smaller source catchments and a high source to sink relief ratio. To the contrary passive margins drain catchments to smaller terrestrial sedimentary basins, are composed of fewer source catchments that are relatively larger and a lower source to sink relief ratio. The different geomorphological characteristics of source catchments by tectonic setting influence the spatial and temporal patterns of fluvial architecture within sedimentary basins and the anthropogenic methods of exploiting those rivers. The new digital database resource is aimed to help

Coastal sedimentary research examines critical issues of national and global priority

USGS Publications Warehouse

Fletcher, Chip; Anderson, John; Crook, Keith A.W.; Kaminsky, George; Larcombe, Piers; Murray-Wallace, Colin V.; Sansone, Frank; Scott, David B.; Riggs, Stan; Sallenger, Asbury; Shennan, Ian; Thieler, E. Robert; Wehmiller, John F.

2000-01-01

An international conference was held recently in Honolulu, Hawaii, to examine and plan for coastal sedimentary research in the United States and globally. Participants agreed that sedimentary coastal environments constitute a critical national and global resource that suffers widespread degradation due to human impacts. Moreover, human population growth and inappropriate development in the coastal zone are escalating public asset losses due to coastal hazards and placing large numbers of communities at growing risk (Figure 1).

Correlation between magnetic susceptibility and mineral species along NWA-1 well, southern Tunisia: An overlap of the depositional environment, the climate, and the diagenesis

NASA Astrophysics Data System (ADS)

Mefteh, Samir; Essefi, Elhoucine; Yaich, Chokri; Jamoussi, Fakher; Medhioub, Mounir

2015-03-01

In order to distinguish the effects of diagenesis, the climate and the depositional environment, the magnetic properties were correlated with some minerals along the NWA-1 well, which crosses the southern subsurface from Cretaceous to Silurian successions. The MS along NWA-1 well shows major picks probably indicating a dramatic change of geochemical and mineralogical composition. Minor picks may be attributed to diagenetic transformations affecting some minerals. The mineralogical analysis shows the presence of illite, kaolinite with some traces of chlorite and smectite. Quartz, calcite, white feldspar, anorthite, dolomite, gypsum and pyrite are identified as associated minerals. The PCA of the different minerals and the magnetic susceptibility shows three different heterogeneous populations. In these populations, the traditional classification of magnetic minerals is not respected. For instance, diamagnetic minerals are positively correlated with MS. This correlation is through indirect causal relation extrapolating the temperature caused by the burial diagenesis. The aim is not totally reached because the handicap is twofold. The XRD diffraction is not able to identify the low amounts of magnetic minerals and the primary mineralogy and magnetic properties are radically modified by post-depositional processes. At the productive well of NWA-1, this overlap is further complicated by hydrocarbons, low grade metamorphism and remagnetization modifying the original magnetic signal.

Compaction and sedimentary basin analysis on Mars

NASA Astrophysics Data System (ADS)

Gabasova, Leila R.; Kite, Edwin S.

2018-03-01

Many of the sedimentary basins of Mars show patterns of faults and off-horizontal layers that, if correctly understood, could serve as a key to basin history. Sediment compaction is a possible cause of these patterns. We quantified the possible role of differential sediment compaction for two Martian sedimentary basins: the sediment fill of Gunjur crater (which shows concentric graben), and the sediment fill of Gale crater (which shows outward-dipping layers). We assume that basement topography for these craters is similar to the present-day topography of complex craters that lack sediment infill. For Gunjur, we find that differential compaction produces maximum strains consistent with the locations of observed graben. For Gale, we were able to approximately reproduce the observed layer orientations measured from orbiter image-based digital terrain models, but only with a >3 km-thick donut-shaped past overburden. It is not immediately obvious what geologic processes could produce this shape.

Shaler: in situ analysis of a fluvial sedimentary deposit on Mars

USGS Publications Warehouse

Edgar, Lauren; Gupta, Sanjeev; Rubin, David M.; Lewis, Kevin W.; Kocurek, Gary A.; Anderson, Ryan; Bell, James F.; Dromart, Gilles; Edgett, Kenneth S.; Grotzinger, John P.; Hardgrove, Craig; Kah, Linda C.; LeVeille, Richard A.; Malin, Michael C.; Mangold, Nicholas; Milliken, Ralph E.; Minitti, Michelle; Palucis, Marisa C.; Rice, Melissa; Rowland, Scott K.; Schieber, Juergen; Stack, Kathryn M.; Sumner, Dawn Y.; Wiens, Roger C.; Williams, Rebecca M.E.; Williams, Amy J.

2018-01-01

This paper characterizes the detailed sedimentology of a fluvial sandbody on Mars for the first time, and interprets its depositional processes and palaeoenvironmental setting. Despite numerous orbital observations of fluvial landforms on the surface of Mars, ground-based characterization of the sedimentology of such fluvial deposits has not previously been possible. Results from the NASA Mars Science Laboratory Curiosity rover provide an opportunity to reconstruct at fine scale the sedimentary architecture and palaeomorphology of a fluvial environment on Mars. This work describes the grain size, texture, and sedimentary facies of the Shaler outcrop, reconstructs the bedding architecture, and analyses cross-stratification to determine palaeocurrents. On the basis of bedset geometry and inclination, grain-size distribution, and bedform migration direction, this study concludes that the Shaler outcrop likely records the accretion of a fluvial barform. The majority of the outcrop consists of large-scale trough cross-bedding of coarse sand and granules. Palaeocurrent analyses and bedform reconstruction indicate that the beds were deposited by bedforms that migrated towards the northeast, across the surface of a bar that migrated southeast. Stacked cosets of dune cross-bedding suggest aggradation of multiple bedforms, which provides evidence for short periods of sustained flow during Shaler deposition. However, local evidence for aeolian reworking and the presence of potential desiccation cracks within the outcrop suggests that fluvial deposition may have been intermittent. The uppermost strata at Shaler are distinct in terms of texture and chemistry, and are inferred to record deposition from a different sediment dispersal system with a contrasting provenance. The outcrop as a whole is a testament to the availability of liquid water on the surface of Mars in its early history.

Pre-lithification tectonic foliation development in a clastic sedimentary sequence

NASA Astrophysics Data System (ADS)

Meere, Patrick; Mulchrone, Kieran; McCarthy, David; Timmermann, Martin; Dewey, John

2016-04-01

The current view regarding the timing of regionally developed penetrative tectonic fabrics in sedimentary rocks is that their development postdates lithification of those rocks. In this case fabric development is achieved by a number of deformation mechanisms including grain rigid body rotation, crystal-plastic deformation and pressure solution (wet diffusion). The latter is believed to be the primary mechanism responsible for shortening and the domainal structure of cleavage development commonly observed in low grade metamorphic rocks. In this study we combine field observations with strain analysis and modelling to fully characterise considerable (>50%) mid-Devonian Acadian crustal shortening in a Devonian clastic sedimentary sequence from south west Ireland. Despite these high levels of shortening and associated penetrative tectonic fabric there is a marked absence of the expected domainal cleavage structure and intra-clast deformation, which are expected with this level of deformation. In contrast to the expected deformation processes associated with conventional cleavage development, fabrics in these rocks are a product of translation, rigid body rotation and repacking of extra-formational clasts during deformation of an un-lithified clastic sedimentary sequence.

Sedimentary records of metal contamination and eutrophication in Jinhae-Masan Bay, Korea.

PubMed

Lim, Dhong-il; Jung, Hoi Soo; Kim, Kyung Tae; Shin, Hyeon Ho; Jung, Seung Won

2012-11-01

Historical environmental pollution in a semi-enclosed coastal bay was investigated using high-resolution sedimentary records for C(org), N(tot), CaCO(3,) δ(13)C, and δ(15)N signatures, and trace metals. A temporal increase in organic matter might have been attributable to enhanced primary marine productivity, presumably caused by increased anthropogenic nutrient inputs in the semi-enclosed, eutrophic system. Metal accumulation occurred in three stages: a preindustrial stage before the 1930s with natural concentrations of metals, an industrialization stage (1940s-1970s) with the highest concentrations, and a postindustrial stage (post 1970s) with stable or decreasing concentrations. However, Hg exhibited a different accumulation history, with concentrations increasing in the early 1900s and accelerating after the 1920s, probably in response to coal burning. Copyright © 2012 Elsevier Ltd. All rights reserved.

Estimating tectonic history through basin simulation-enhanced seismic inversion: Geoinformatics for sedimentary basins

USGS Publications Warehouse

Tandon, K.; Tuncay, K.; Hubbard, K.; Comer, J.; Ortoleva, P.

2004-01-01

A data assimilation approach is demonstrated whereby seismic inversion is both automated and enhanced using a comprehensive numerical sedimentary basin simulator to study the physics and chemistry of sedimentary basin processes in response to geothermal gradient in much greater detail than previously attempted. The approach not only reduces costs by integrating the basin analysis and seismic inversion activities to understand the sedimentary basin evolution with respect to geodynamic parameters-but the technique also has the potential for serving as a geoinfomatics platform for understanding various physical and chemical processes operating at different scales within a sedimentary basin. Tectonic history has a first-order effect on the physical and chemical processes that govern the evolution of sedimentary basins. We demonstrate how such tectonic parameters may be estimated by minimizing the difference between observed seismic reflection data and synthetic ones constructed from the output of a reaction, transport, mechanical (RTM) basin model. We demonstrate the method by reconstructing the geothermal gradient. As thermal history strongly affects the rate of RTM processes operating in a sedimentary basin, variations in geothermal gradient history alter the present-day fluid pressure, effective stress, porosity, fracture statistics and hydrocarbon distribution. All these properties, in turn, affect the mechanical wave velocity and sediment density profiles for a sedimentary basin. The present-day state of the sedimentary basin is imaged by reflection seismology data to a high degree of resolution, but it does not give any indication of the processes that contributed to the evolution of the basin or causes for heterogeneities within the basin that are being imaged. Using texture and fluid properties predicted by our Basin RTM simulator, we generate synthetic seismograms. Linear correlation using power spectra as an error measure and an efficient quadratic

Modern sedimentary environments in Boston Harbor, Massachusetts

USGS Publications Warehouse

Knebel, H.J.; Rendigs, R. R.; Bothner, Michael H.

1991-01-01

Analyses of sidescan-sonar records supplemented by available bathymetric, sedimentary, subbottom, and bottom-current data reveal the distributions of the following three categories of sedimentary environments within the glaciated, topographically complex Boston Harbor estuary in Massachusetts. 1) Environments of erosion appear on the sonographs either as patterns with isolated strong reflections or as uniform patterns of strong reflectivity. These patterns define outcrops of bedrock or till and coarse lag deposits that are being scoured and winnowed by tidal- and wave-induced currents. Erosional areas are located primarily along mainland and insular shores, within large channels that have strong tidal currents, atop submerged ridges and knolls, and across much of the harbor entrance. 2) Environments of deposition are depicted on the sidescan-sonar records as smooth, featureless surfaces that have low to moderate reflectivity. Depositional environments are found predominantly over shallow subtidal flats and in broad bathymetric lows where tidal currents are weak. Sediments within depositional areas are organic-rich sandy and clayey silts that are accumulating at rates ranging from 0.01 to 0.11 g/cm 2 /yr or 4000 to 46,100 metric tons/yr. The cumulative mass of modern mud in harbor depocenters is 24.3 million metric tons. 3) Environments of sediment reworking constitute areas affected by a combination of erosional and depositional processes. They are characterized on the sonographs by mosaics of light and dark patches produced by relatively subtle and gradational changes in reflectivity. Reworked sediments have diverse grain sizes that overlap and are transitional between those of the other two sedimentary environments, and they are indicative of highly variable bottom currents.

Fluvial geomorphic elements in modern sedimentary basins and their potential preservation in the rock record: A review

NASA Astrophysics Data System (ADS)

Weissmann, G. S.; Hartley, A. J.; Scuderi, L. A.; Nichols, G. J.; Owen, A.; Wright, S.; Felicia, A. L.; Holland, F.; Anaya, F. M. L.

2015-12-01

Since tectonic subsidence in sedimentary basins provides the potential for long-term facies preservation into the sedimentary record, analysis of geomorphic elements in modern continental sedimentary basins is required to understand facies relationships in sedimentary rocks. We use a database of over 700 modern sedimentary basins to characterize the fluvial geomorphology of sedimentary basins. Geomorphic elements were delineated in 10 representative sedimentary basins, focusing primarily on fluvial environments. Elements identified include distributive fluvial systems (DFS), tributive fluvial systems that occur between large DFS or in an axial position in the basin, lacustrine/playa, and eolian environments. The DFS elements include large DFS (> 30 km in length), small DFS (< 30 km in length), coalesced DFS in bajada or piedmont plains, and incised DFS. Our results indicate that over 88% of fluvial deposits in the evaluated sedimentary basins are present as DFS, with tributary systems covering a small portion (1-12%) of the basin. These geomorphic elements are commonly arranged hierarchically, with the largest transverse rivers forming large DFS and smaller transverse streams depositing smaller DFS in the areas between the larger DFS. These smaller streams commonly converge between the large DFS, forming a tributary system. Ultimately, most transverse rivers become tributary to the axial system in the sedimentary basin, with the axial system being confined between transverse DFS entering the basin from opposite sides of the basin, or a transverse DFS and the edge of the sedimentary basin. If axial systems are not confined by transverse DFS, they will form a DFS. Many of the world's largest rivers are located in the axial position of some sedimentary basins. Assuming uniformitarianism, sedimentary basins from the past most likely had a similar configuration of geomorphic elements. Facies distributions in tributary positions and those on DFS appear to display

14th-16th century Danube floods and long-term water-level changes reflected in archaeological-sedimentary evidence - in comparison with documentary evidence

NASA Astrophysics Data System (ADS)

Kiss, Andrea; Laszlovszky, József

2014-05-01

In the present paper an overview of published and unpublished results of archaeological and sedimentary investigations, predominantly reflect on 14th-16th-century changes, are provided and compared to documentary information on flood events and long-term changes. Long-term changes in flood behaviour and average water-level conditions had long-term detectable impacts on sedimentation and fluvio-morphological processes. Moreover, the available archaeological evidence might also provide information on the reaction of the society, in the form of changes in settlement organisation, building structures and processes. At present, information is mainly available concerning the 16th, and partly to the 14th-15th centuries. Medium and short term evidence mainly corresponds to the main flood peaks or even to single catastrophic flood events. Such processes may be identified in archaeological evidence concerning the second half of the 14th, early 15th centuries; while most of the cases listed above were connected to the flood peak (and/or generally increasing water-level conditions) of the late 15th and early 16th centuries. In other cases connections between sedimentary/archaeological evidence and the mid- and late 16th-century high flood-frequency period were presumed. Documentary evidence referring to the same period suggests that higher flood frequency and intensity periods occurred in the early and mid 16th century; a probably more prolonged flood rich period took place in the second half of the 16th century, with a peak in the late 1560s-early 1570s and maybe with another at the end of the 16th century. Earlier flood peaks in documentary evidence were detected on the Danube at the turn of the 14th-15th centuries and in the last decades of the 15th century, continuing in the early 16th century.

Microfacies and diagenesis of the reefal limestone, Callovian Tuwaiq Mountain Limestone Formation, central Saudi Arabia

NASA Astrophysics Data System (ADS)

EL-Sorogy, Abdelbaset S.; Almadani, Sattam A.; Al-Dabbagh, Mohammad E.

2016-03-01

In order to document the microfacies and diagenesis of the reefal limestone in the uppermost part of the Callovian Tuwaiq Mountain Limestone Formation at Khashm Al-Qaddiyah area, central Saudi Arabia, scleractinian corals and rock samples were collected and thin sections were prepared. Coral framestone, coral floatstone, pelloidal packstone, bioclastic packstone, bioclastic wacke/packstone, algal wackestone and bioclastic foraminiferal wacke/packstone were the recorded microfacies types. Cementation, recrystallization, silicification and dolomitization are the main diagenetic alterations affected the aragonitic skeletons of scleractinian corals. All coral skeletons were recrystallized, while some ones were dolomitized and silicified. Microfacies types, as well as the fossil content of sclearctinian corals, bivalves, gastropods, brachiopods and foraminifera indicated a deposition in environments ranging from shelf lagoon with open circulation in quiet water below wave base to shallow reef flank and organic build up for the uppermost reefal part of the Tuwaiq Formation in the study area.

Ancient sedimentary structures in the <3.7 Ga Gillespie Lake Member, Mars, that resemble macroscopic morphology, spatial associations, and temporal succession in terrestrial microbialites.

PubMed

Noffke, Nora

2015-02-01

Sandstone beds of the <3.7 Ga Gillespie Lake Member on Mars have been interpreted as evidence of an ancient playa lake environment. On Earth, such environments have been sites of colonization by microbial mats from the early Archean to the present time. Terrestrial microbial mats in playa lake environments form microbialites known as microbially induced sedimentary structures (MISS). On Mars, three lithofacies of the Gillespie Lake Member sandstone display centimeter- to meter-scale structures similar in macroscopic morphology to terrestrial MISS that include "erosional remnants and pockets," "mat chips," "roll-ups," "desiccation cracks," and "gas domes." The microbially induced sedimentary-like structures identified in Curiosity rover mission images do not have a random distribution. Rather, they were found to be arranged in spatial associations and temporal successions that indicate they changed over time. On Earth, if such MISS occurred with this type of spatial association and temporal succession, they would be interpreted as having recorded the growth of a microbially dominated ecosystem that thrived in pools that later dried completely: erosional pockets, mat chips, and roll-ups resulted from water eroding an ancient microbial mat-covered sedimentary surface; during the course of subsequent water recess, channels would have cut deep into the microbial mats, leaving erosional remnants behind; desiccation cracks and gas domes would have occurred during a final period of subaerial exposure of the microbial mats. In this paper, the similarities of the macroscopic morphologies, spatial associations, and temporal succession of sedimentary structures on Mars to MISS preserved on Earth has led to the following hypothesis: The sedimentary structures in the <3.7 Ga Gillespie Lake Member on Mars are ancient MISS produced by interactions between microbial mats and their environment. Proposed here is a strategy for detecting, identifying, confirming, and differentiating

Arctic Ocean Sedimentary Cover Structure, Based on 2D MCS Seismic Data.

NASA Astrophysics Data System (ADS)

Kireev, A.; Kaminsky, V.; Poselov, V.; Poselova, L.; Kaminsky, D.

2016-12-01

In 2016 the Russian Federation has submitted its partial revised Submission for establishment of the OLCS (outer limit of the continental shelf) in the Arctic Ocean. In order to prepare the Submission, in 2005 - 2014 the Russian organizations carried out a wide range of geological and geophysical studies, so that today over 23000 km of MCS lines and 4000 km of deep seismic sounding are accomplished. For correct time/depth conversion of seismic sections obtained with a short streamer in difficult ice conditions wide-angle reflection/refraction seismic sonobuoy soundings were used. All of these seismic data were used to refine the stratigraphy model, to identify sedimentary complexes and to estimate the total thickness of the sedimentary cover. Seismic stratigraphy model was successively determined for the Cenozoic and pre-Cenozoic parts of the sedimentary section and was based on correlation of the Russian MCS data and seismic data documented by boreholes. Cenozoic part of the sedimentary cover is based on correlation of the Russian MCS data and AWI91090 section calibrated by ACEX-2004 boreholes on the Lomonosov Ridge for Amerasia basin and by correlation of onlap contacts onto oceanic crust with defined magnetic anomalies for Eurasia basin. Pre-Cenozoic part of the sedimentary cover is based on tracing major unconformities from boreholes on the Chukchi shelf (Crackerjack, Klondike, Popcorn) to the North-Chuckchi Trough and further to the Mendeleev Rise as well as to the Vilkitsky Trough and the adjacent Podvodnikov Basin. Six main unconformities were traced: regional unconformity (RU), Eocene unconformity (EoU) (for Eurasia basin only), post-Campanian unconformity (pCU), Brookian (BU - base of the Lower Brookian unit), Lower Cretaceous (LCU) and Jurassic (JU - top of the Upper Ellesmerian unit). The final step in our research was to generalize all seismic surveys (top of acoustic basement correlation data) and bathymetry data in the sedimentary cover thickness map

Depositional environment, sand provenance, and diagenesis of the Basal Salina Formation (lower Eocene), northwestern Peru

NASA Astrophysics Data System (ADS)

Marsaglia, K. M.; Carozzi, A. V.

The Basal Salina Formation is a lower Eocene transgressive sequence consisting of interbedded shales, siltstones, and conglomeratic sandstones. This formation occurs in the Talara basin of northwestern Peru and is one of a series of complexly faulted hydrocarbon-producing formations within this extensional forearc basin. These sediments were probably deposited in a fan-delta complex that developed along the ancestral Amotape Mountains during the early Eocene. Most of the sediment was derived from the low-grade metamorphic and plutonic rocks that comprise the Amotape Mountains, and their sedimentary cover. Detrital modes of these sandstones reflect the complex tectonic history of the area, rather than the overall forearc setting. Unlike most forearc sediments, these are highly quartzose, with only minor percentages of volcanic detritus. This sand is variably indurated and cemented by chlorite, quartz, calcite, and kaolinite. Clay-mineral matrix assemblages show gradational changes with depth, from primarily detrital kaolinite to diagenetic chlorite and mixed-layered illite/smectite. Basal Salina sandstones exhibit a paragenetic sequence that may be tied to early meteoric influx or late-stage influx of thermally driven brines associated with hydrocarbon migration. Much of the porosity is secondary, resulting from a first-stage dissolution of silicic constituents (volcanic lithic fragments, feldspar, and fibrous quartz) and a later dissolution of surrounding carbonate cement. Types of pores include skeletal grains, grain molds, elongate pores, and fracture porosity. Measured porosity values range up to 24% and coarser samples tend to be more porous. Permeability is enhanced by fractures and deterred by clay-mineral cements and alteration residues.

Sedimentary particulate iron: the missing micronutrients ?

NASA Astrophysics Data System (ADS)

Beghoura, Houda; Gorgues, Thomas; Aumont, Olivier; Planquette, Hélène

2017-04-01

Iron is known to regulate the marine primary production and to impact the structure of ecosystems. Indeed, iron is the limiting nutrient for the phytoplankton growth over about 30% of the global ocean. However, the nature of the external sources of iron to the ocean and their quantification remain uncertain. Among these external sources, the sediment sources have been recently shown to be underestimated. Besides, since the operationally defined dissolved iron (which is the sum of truly dissolved and colloidal iron) was traditionally assumed to be the only form available to phytoplankton and bacteria, most studies have focused on the supply of dissolved iron to the ocean, the role of the particulate fraction of iron being largely ignored. This traditional view has been recently challenged, noticeably, by observational evidences. Indeed, in situ observations have shown that large amounts of particulate iron are being resuspended from continental margins to the open ocean thanks to fine grained particles' transport over long distances. A fraction of this particulate iron may dissolve and thereby fuel the phytoplankton growth. The magnitude of the sedimentary sources of particulate iron and the releasing processes affecting this iron phase are not yet well constrained or quantified. As a consequence, the role of sedimentary particulate iron in the biogeochemical cycles is still unclear despite its potentially major widespread importance. Here, we propose a modeling exercise to assess the first order impacts of this newly considered particulate sedimentary iron on global ocean biogeochemistry. We designed global experiments with a coupled dynamical-biogeochemical model (NEMO-PISCES). First, a control simulation that includes only a sediment source of iron in the dissolved phase has been run. Then, this control simulation is being compared with simulations, in which we include a sediment source of iron in both phases (dissolved as well as particulate). Those latter

Sedimentary Mounds on Mars: Tracing Present-day Formation Processes into the Past

NASA Technical Reports Server (NTRS)

Niles, P. B.; Michalski, J.; Edwards, C. S.

2014-01-01

High resolution photography and spectroscopy of the martian surface (MOC, HiRISE) from orbit has revolutionized our view of Mars with one and revealed spectacular views of finely layered sedimentary materials throughout the globe [1]. Some of these sedimentary deposits are 'mound' shaped and lie inside of craters (Fig 1). Crater mound deposits are found throughout the equatorial region, as well as ice-rich deposits found in craters in the north and south polar region [2-4]. Despite their wide geographical extent and varying volatile content, the 'mound' deposits have a large number of geomorphic and structural similarities that suggest they formed via equivalent processes. Thus, modern depositional processes of ice and dust can serve as an invaluable analog for interpreting the genesis of ancient sedimentary mound deposits.

Sedimentary Rocks and Methane - Southwest Arabia Terra

NASA Technical Reports Server (NTRS)

Allen, Carlton C.; Oehler, Dorothy Z.; Venechuk, Elizabeth M.

2006-01-01

We propose to land the Mars Science Laboratory in southwest Arabia Terra to study two key aspects of martian history the extensive record of sedimentary rocks and the continuing release of methane. The results of this exploration will directly address the MSL Scientific Objectives regarding biological potential, geology and geochemistry, and past habitability.

Control and distribution of uranium in coral reefs during diagenesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gvirtzman, G.; Friedman, G.M.; Miller, D.S.

1973-12-01

The concentration of about 2 ppM of uranium in the aragonitic skeletons of modern scleractinian corals which we studied is a constant value, regardless of occurrence, anatomy, or taxonomy. The presence of cement of aragonite or high- magnesian calcite usually raises the concentration of bulk samples to about 3 ppM. Modern corals may contain up to 50% of cementing minerals. Organisms, such as corals and coralline algae, while secreting their skeleton, discriminate against the uptake of uranium, whereas the uptake of uranium by mineral cements is less restrained. Aragonite cement contains about 3.6 ppM and highmagnesian calcite cement 2.6 ppMmore » uranium. During leaching by freshwater, the aragonite of the skeletons of corals dissolves out. This creates hollow molds which fill with drusy low-magnesian calcite. In emergent reefs from the shores of the Red Sea which display the ellects of progressive diagenesis this calcite is enriched in uranium (3.9 ppM) beyond that found in marine cements. Second-generation calcite, which fills original voids in the corals from the emergent reefs, contains a lower level of uranium concent ration (1.3 ppM). The level of concentration of uranium in low-magnesian calcite of diagenetically altered corals is a function of the availability of uranium in meteoric waters. In aragonite as well as in high- and low-magnesian calcite uranium replaces calcium or occupies lattice vacancies in the crystal lattice. (auth)« less

Microbially Induced Sedimentary Structures Recording an Ancient Ecosystem in the ca. 3.48 Billion-Year-Old Dresser Formation, Pilbara, Western Australia

PubMed Central

Christian, Daniel; Wacey, David; Hazen, Robert M.

2013-01-01

Abstract Microbially induced sedimentary structures (MISS) result from the response of microbial mats to physical sediment dynamics. MISS are cosmopolitan and found in many modern environments, including shelves, tidal flats, lagoons, riverine shores, lakes, interdune areas, and sabkhas. The structures record highly diverse communities of microbial mats and have been reported from numerous intervals in the geological record up to 3.2 billion years (Ga) old. This contribution describes a suite of MISS from some of the oldest well-preserved sedimentary rocks in the geological record, the early Archean (ca. 3.48 Ga) Dresser Formation, Western Australia. Outcrop mapping at the meter to millimeter scale defined five sub-environments characteristic of an ancient coastal sabkha. These sub-environments contain associations of distinct macroscopic and microscopic MISS. Macroscopic MISS include polygonal oscillation cracks and gas domes, erosional remnants and pockets, and mat chips. Microscopic MISS comprise tufts, sinoidal structures, and laminae fabrics; the microscopic laminae are composed of primary carbonaceous matter, pyrite, and hematite, plus trapped and bound grains. Identical suites of MISS occur in equivalent environmental settings through the entire subsequent history of Earth including the present time. This work extends the geological record of MISS by almost 300 million years. Complex mat-forming microbial communities likely existed almost 3.5 billion years ago. Key Words: Archean—Biofilms—Microbial mats—Early Earth—Evolution. Astrobiology 13, 1103–1124. PMID:24205812

Sedimentary record of late Paleozoic to Recent tectonism in central Asia — analysis of subsurface data from the Turan and south Kazak domains

NASA Astrophysics Data System (ADS)

Thomas, J. C.; Cobbold, P. R.; Shein, V. S.; Le Douaran, S.

1999-11-01

The Turan and south Kazak domains (TSK) are in central Asia, between the Caspian Sea and the Tien Shan. The area is covered by sediments, deposited since the Late Permian during a series of tectonic events closely related to the history of two oceanic domains, Paleotethys and Neotethys. Sedimentary basins on the TSK therefore provide constraints on the tectonic development of the southern margin of Eurasia since the Late Permian. Our study is based on structure-contour maps and isopach maps of five key stratigraphic markers, of Late Permian to Tertiary age. Isopach maps help locate major faults and delimit sedimentary basins, providing information on vertical motions and, in some instances, horizontal motions. Subsidence associated with extension appears to have dominated the TSK, from the Late Permian to the Eocene. The extension may have been of back-arc type in southern Eurasia, next to the active margin, where the Paleotethys and Neotethys successively subducted toward the north. Here, sedimentary basins are both wide and deep (up to 15 km). During the Mesozoic, two compressional events of regional significance occurred in association with accretion of continental blocks at the southern margin of Eurasia. The first one, at the end of the Triassic, led to strong selective inversion of basins over the Turan domain. The second one, during the Late Jurassic-Early Cretaceous, had weaker effects. Since the Oligocene, following collision of both India and Arabia with Eurasia, inversion has become more generalized and compressional basins have formed on the TSK. Throughout the entire history of development of the TSK, from the Late Permian to the Tertiary, structures of Paleozoic and early Mesozoic age have exerted a strong control on sedimentation and especially on the location of depocenters. The south Kazak domain has registered little subsidence, in comparison with the Turan domain, where some basins have become very deep.

Nature and tectonic implications of uneven sedimentary filling of the South China Sea oceanic basin

NASA Astrophysics Data System (ADS)

Yin, Shaoru; Li, Jiabiao; Ding, Weiwei; Fang, Yinxia

2017-04-01

The IODP Expedition 349 in 2014, for the first time, illustrated significant differences of sediment rate and lithology in the central South China Sea (SCS) oceanic basin. Based on seismic reflection profiles tied to IODP349 drilling data, we investigated characteristics of sedimentary filling of the whole SCS oceanic basin, and examined their implications for tectonics. Results show that sediments fill the SCS oceanic basin mainly in three depositional patterns. Firstly, during the Oligocene to middle Miocene, sediments amassed almost solely and then connected like a band parallel to the continent in a low average sediment rate (<10 m/Myr) in the northern oceanic basin. These sediments were deposited mainly in the form of submarine fans and mass transport deposits. Sediments were predominately supplied by the Red and Pearl Rivers and the Dongsha Islands. The sedimentary characteristics likely reflect the latest early Miocene end of seafloor spreading of the SCS and the first-phase rapid uplift of the Tibetan Plateau. Secondly, during the late Miocene, deposition mainly occurred in the Northwest Sub-basin and extended southeastward with a middle average sediment rate ( 30 m/Myr). Sediments were mostly transported by the Red River and Xisha Trough and deposited in the form of submarine fans. The abnormal increase of sediment rate in the Northwest Sub-basin reflects late Miocene slip reversal of the Red River Fault. Finally, since the Pliocene, sediments gradually propagated northeastward in the Southwestern Sub-basin, and accumulated rapidly in the southeastern and northeastern basin, especially in the northern Manila Trench during the Quaternary, in an average sediment rate about 60-80 m/Myr. These sediments were transported mainly by submarine canyons and settled in the form of submarine fans and canyon-overbank deposition. Sediments came from four major sources, including Taiwan, Dongsha Islands, Mekong River, and northern Palawan. The Pliocene to Quaternary

Sedimentary history and mass flow structures of Chryse and Acidalia Planitiae, Mars

USGS Publications Warehouse

Tanaka, K.L.

1997-01-01

Geologic mapping and crater counting in Chryse and Acidalia Planitiae (GAP) reveal five major sedimentary deposits of Hesperian to Early Amazonian age, including (1) a mass flow deposited during the Early Hesperian near Deuteronilus Mensae (northeast of the map region) that may have resulted from the carving of Kasei Valles, >3000 km southwest of the exposed part of the deposit; (2) knobby plains material consisting of channel (likely; from Simud and Tiu Valles and possibly Ares and Shalbatana Valles) and mass-wasting deposits in central and eastern CAP; (3) material largely from Maja and Ares Valles emplaced in at least western and southern CAP (outcrops in southern Chryse Planitia developed thermokarst); (4) a thin mass flow covering much of southern Chryse Planitia that emanated from Simud and Tiu Valles; and (5) a thick, extensive (perhaps >3500 km across) mass flow deposit in central and northern CAP derived from accumulation and backflow of the preceding thin mass flow or perhaps melting of polar deposits. Other possible deposits may not be recognizable owing to burial by younger materials or a lack of morphologic signature. Various associated landforms appear to be consistent with the mass flow interpretations, including lobate and linear scarps along deposit edges, fractures related to desiccation of thick sediments, troughs, and ridges near the edges of the deposit indicative of secondary mass movement and deformation, pitted domes and fissure-fed flows possibly formed by sedimentary (mud) eruptions, and longitudinal channel grooves perhaps formed by roller vortices. No convincing evidence for paleoshorelines or stagnant ice sheets is found in CAP. These findings suggest that mass flow and hyperconcentrated flooding may have been the predominant processes of outflow-channel dissection in CAP. Elsewhere in the northern plains, similar landforms are prevalent. The mass flow interpretation does not require either multiple episodes of extraordinarily high

Specific Heat Capacities of Martian Sedimentary Analogs at Low Temperatures

NASA Astrophysics Data System (ADS)

Vu, T. H.; Piqueux, S.; Choukroun, M.; Christensen, P. R.; Glotch, T. D.; Edwards, C. S.

2017-12-01

Data returned from Martian missions have revealed a wide diversity of surface mineralogies, especially in geological structures interpreted to be sedimentary or altered by liquid water. These terrains are of great interest because of their potential to document the environment at a time when life may have appeared. Intriguingly, Martian sedimentary rocks show distinctly low thermal inertia values (300-700 J.m-2.K-1.s-1/2, indicative of a combination of low thermal conductivity, specific heat, and density) that are difficult to reconcile with their bedrock morphologies (where hundreds of magmatic bedrock occurrences have been mapped with thermal inertia values >> 1200 J.m-2.K-1.s-1/2). While low thermal conductivity and density values are sometimes invoked to lower the thermal inertia of massive bedrock, both are not sufficient to lower values below 1200 J.m-2.K-1.s-1/2, far above the numbers reported in the literature for Martian sedimentary/altered rocks. In addition, our limited knowledge of the specific heat of geological materials and their temperature dependency, especially below room temperature, have prevented accurate thermal modeling and impeded interpretation of the thermal inertia data. In this work, we have addressed that knowledge gap by conducting experimental measurements of the specific heat capacities of geological materials relevant to Martian sedimentary rocks at temperatures between 100 and 350 K. The results show that variation of the specific heat with temperature, while appreciable to some extent, is rather small and is unlikely to contribute significantly in the lowering of thermal inertia values. Therefore, thermal conductivity is the parameter that has the most potential in explaining this phenomenon. Such scenario could be possible if the sedimentary rocks are finely layered with poor thermal contact between each internal bed. As the density of most geological materials is well-known, the obtained specific heat data can be used to

Neogene marine sedimentary record of the Gulf of Alaska: from the glaciers to the distal submarine fan systems

NASA Astrophysics Data System (ADS)

Ridgway, K. D.; Bahlburg, H.; Childress, L. B.; Cowan, E. A.; Forwick, M.; Moy, C. M.; Müller, J.; Ribeiro, F.; Gupta, S.; Gulick, S. P.; Jaeger, J. M.

2013-12-01

facies as representing deposition of coarse-grained detritus originating from sedimentary gravity flows followed by longer periods of hemipelagic deposition. The first clear record of glacial sediment input in the distal submarine fan environment is late Pliocene - early Pleistocene muddy diamict beds that probably are the products of ice-rafting. This unit is about 30 m in thickness. The overlying 260 m of the core are mainly dark gray mud with thin beds of volcanic ash and sand/silt beds. Lonestones are common and are mainly argillite and metasiltstone clasts suggesting at least a component of sediment derivation from onshore metamorphosed parts of the Mesozoic accretionary prism. In general, the overall Neogene sedimentary record in both the proximal and distal marine settings appears to be similar but requires a sediment link between the proximal strata deposited on the Yakutat microplate and the Surveyor fan system deposited on the Pacific Plate.

Excess europium content in Precambrian sedimentary rocks and continental evolution

NASA Technical Reports Server (NTRS)

Jakes, P.; Taylor, S. R.

1974-01-01

It is proposed that the europium excess in Precambrian sedimentary rocks, relative to those of younger age, is derived from volcanic rocks of ancient island arcs, which were the source materials for the sediments. Precambrian sedimentary rocks and present-day volcanic rocks of island arcs have similar REE patterns, total REE abundances, and excess Eu, relative to the North American shale composite. The present upper crustal REE pattern, as exemplified by that of sediments, is depleted in Eu, relative to chondrites. This depletion is considered to be a consequence of development of a granodioritic upper crust by partial melting in the lower crust, which selectively retains europium.

Elastic and viscoelastic model of the stress history of sedimentary rocks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warpinski, N.R.

A model has been developed to calculate the elastic and viscoelastic stresses which develop in rocks at depth due to burial, uplift and diagenesis. This model includes the effect of the overburden load, tectonic or geometric strains, thermal strains, varying material properties, pore pressure variations, and viscoeleastic relaxation. Calculations for some simple examples are given to show the contributions of the individual stress components due to gravity, tectonics, thermal effects and pore pressure. A complete stress history for Mesaverde rocks in the Piceance basin is calculated based on available burial history, thermal history and expected pore pressure, material property andmore » tectonic strain variations through time. These calculations show the importance of including material property changes and viscoelastic effects. 15 refs., 48 figs.« less

Sedimentary condensation and authigenesis

NASA Astrophysics Data System (ADS)

Föllmi, Karl

2016-04-01

Most marine authigenic minerals form in sediments, which are subjected to condensation. Condensation processes lead to the formation of well individualized, extremely thin (< 1m) beds, which were accumulated during extremely long time periods (> 100ky), and which experienced authigenesis and the precipitation of glaucony, verdine, phosphate, iron and manganese oxyhydroxides, iron sulfide, carbonate and/or silica. They usually show complex internal stratigraphies, which result from an interplay of sediment accumulation, halts in sedimentation, sediment winnowing, erosion, reworking and bypass. They may include amalgamated faunas of different origin and age. Hardgrounds may be part of condensed beds and may embody strongly condensed beds by themselves. Sedimentary condensation is the result of a hydrodynamically active depositional regime, in which sediment accumulation, winnowing, erosion, reworking and bypass are processes, which alternate as a function of changes in the location and intensity of currents, and/or as the result of episodic high-energy events engendered by storms and gravity flow. Sedimentary condensation has been and still is a widespread phenomenon in past and present-day oceans. The present-day distribution of glaucony and verdine-rich sediments on shelves and upper slopes, phosphate-rich sediments and phosphorite on outer shelves and upper slopes, ferromanganese crusts on slopes, seamounts and submarine plateaus, and ferromanganese nodules on abyssal seafloors is a good indication of the importance of condensation processes today. In the past, we may add the occurrence of oolitic ironstone, carbonate hardgrounds, and eventually also silica layers in banded iron formations as indicators of the importance of condensation processes. Besides their economic value, condensed sediments are useful both as a carrier of geochemical proxies of paleoceanographic and paleoenvironmental change, as well as the product of episodes of paleoceanographic and

Sedimentary sequence evolution in a Foredeep basin: Eastern Venezuela

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bejarano, C.; Funes, D.; Sarzalho, S.

1996-08-01

Well log-seismic sequence stratigraphy analysis in the Eastern Venezuela Foreland Basin leads to study of the evolution of sedimentary sequences onto the Cretaceous-Paleocene passive margin. This basin comprises two different foredeep sub-basins: The Guarico subbasin to the west, older, and the Maturin sub-basin to the east, younger. A foredeep switching between these two sub-basins is observed at 12.5 m.y. Seismic interpretation and well log sections across the study area show sedimentary sequences with transgressive sands and coastal onlaps to the east-southeast for the Guarico sub-basin, as well as truncations below the switching sequence (12.5 m.y.), and the Maturin sub-basin showsmore » apparent coastal onlaps to the west-northwest, as well as a marine onlap (deeper water) in the west, where it starts to establish. Sequence stratigraphy analysis of these sequences with well logs allowed the study of the evolution of stratigraphic section from Paleocene to middle Miocene (68.0-12.0 m.y.). On the basis of well log patterns, the sequences were divided in regressive-transgressive-regressive sedimentary cycles caused by changes in relative sea level. Facies distributions were analyzed and the sequences were divided into simple sequences or sub- sequences of a greater frequencies than third order depositional sequences.« less

Active hematite concretion formation in modern acid saline lake sediments, Lake Brown, Western Australia

NASA Astrophysics Data System (ADS)

Bowen, Brenda Beitler; Benison, K. C.; Oboh-Ikuenobe, F. E.; Story, S.; Mormile, M. R.

2008-04-01

Concretions can provide valuable records of diagenesis and fluid-sediment interactions, however, reconstruction of ancient concretion-forming conditions can be difficult. Observation of modern hematite concretion growth in a natural sedimentary setting provides a rare glimpse of conditions at the time of formation. Spheroidal hematite-cemented concretions are actively precipitating in shallow subsurface sediments at Lake Brown in Western Australia. Lake Brown is a hypersaline (total dissolved solids up to 23%) and acidic (pH ˜ 4) ephemeral lake. The concretion host sediments were deposited between ˜ 1 and 3 ka, based on dating of stratigraphically higher and lower beds. These age constraints indicate that the diagenetic concretions formed < 3 ka, and field observations suggest that some are currently forming. These modern concretions from Lake Brown provide an example of very early diagenetic formation in acid and saline conditions that may be analogous to past conditions on Mars. Previously, the hematite concretions in the Burns formation on Mars have been interpreted as late stage diagenetic products, requiring long geologic time scales and multiple fluid flow events to form. In contrast, the Lake Brown concretions support the possibility of similar syndepositional to very early diagenetic concretion precipitation on Mars.

Sulfurized carbohydrates: an important sedimentary sink for organic carbon?

NASA Astrophysics Data System (ADS)

Sinninghe Damsté, Jaap S.; Kok, Marika D.; Köster, Jürgen; Schouten, Stefan

1998-12-01

In contrast to the general belief that carbohydrate carbon (C CHO) is preferentially degraded and is not extensively preserved in the sedimentary record, it is shown here that C CHO forms a large fraction of the organic matter (OM) of the total organic carbon (TOC)-rich upper Jurassic Kimmeridge Clay Formation as a result of early diagenetic sulfurization, a previously unrecognized pathway of OM preservation. This is evident from both changes in the molecular composition of the insoluble OM and from δ 13C TOC shifts of 6‰ with varying C CHO contents. Furthermore, experiments simulating the natural sulfurization of the C CHO-rich alga Phaeocystis spp. demonstrated that sulfurization can indeed lead to a substantial preservation of C CHO with a molecular fingerprint identical to that of the Kimmeridge Clay and many other Recent and ancient marine OM-rich sediments. These results imply that preservation of C CHO can exert a fundamental control on δ 13C TOC in OM-rich sediments, complicating the interpretation of δ 13C TOC records with regard to estimating terrestrial versus aquatic OM fractions, reconstruction of past atmospheric CO 2 levels and global carbon budget models.

Imaging the Moho beneath Sedimentary Basins: A Comparative Study of Virtual Deep Seismic Sounding (VDSS) and P Wave Receiver Functions (PRF)

NASA Astrophysics Data System (ADS)

Liu, T.; Klemperer, S. L.; Yu, C.; Ning, J.

2017-12-01

In the past decades, P wave receiver functions (PRF) have been routinely used to image the Moho, although it is well known that PRFs are susceptible to contamination from sedimentary multiples. Recently, Virtual Deep Seismic Sounding (VDSS) emerged as a novel method to image the Moho. However, despite successful applications of VDSS on multiple datasets from different areas, how sedimentary basins affect the waveforms of post-critical SsPmp, the Moho reflection phase used in VDSS, is not widely understood. Here, motivated by a dataset collected in the Ordos plateau, which shows distinct effects of sedimentary basins on SsPmp and Pms waveforms, we use synthetic seismograms to study the effects of sedimentary basins on SsPmp and Pms, the phases used in VDSS and PRF respectively. The results show that when the sedimentary thickness is on the same order of magnitude as the dominant wavelength of the incident S wave, SsPmp amplitude decreases significantly with S velocity of the sedimentary layer, whereas increasing sedimentary thickness has little effect in SsPmp amplitude. Our explanation is that the low S velocity layer at the virtual source reduces the incident angle of S wave at the free surface, thus decreases the S-to-P reflection coefficient at the virtual source. In addition, transmission loss associated with the bottom of sedimentary basins also contributes to reducing SsPmp amplitude. This explains not only our observations from the Ordos plateau, but also observations from other areas where post-critical SsPmp is expected to be observable, but instead is too weak to be identified. As for Pms, we observe that increasing sedimentary thickness and decreasing sedimentary velocities both can cause interference between sedimentary multiples and Pms, rendering the Moho depths inferred from Pms arrival times unreliable. The reason is that although Pms amplitude does not vary with sedimentary thickness or velocities, as sedimentary velocities decrease and thickness

Sedimentary features of the Blackhawk formation (Cretaceous) at Sunnyside, Carbon County, Utah

USGS Publications Warehouse

Maberry, John O.

1968-01-01

The Blackhawk Formation at Sunnyside, Utah, was deposited along the western margin of the Western Interior Cretaceous sea during southeastward withdrawal of the sea. Sand was the dominant type of land-derived sediment deposited in the Sunnyside district during the regressive phases. Sand bodies prograded seaward in response to changing sediment supply from a source west of Sunnyside. Where conditions were favorable for the accumulation of vegetable material, peat deposits formed and were later changed to bituminous Coal by diagenesis. Studies of the coal bed show that the coals were formed from accumulation of small, low-growing plants and plant debris that was transported into the area of accumulation. Remains of large plants in the coals are rare. Trace fossils, which are tracks, trails and burrows formed by organisms and preserved in the rock, are extremely abundant in the Blackhawk rocks. These biogenic sedimentary structures are common in Cretaceous deposits throughout the western United States. Trace fossil distribution in the rocks is controlled by the depositional environment preferred by their creators. A study of the trace fossils of a. locality allows a more precise determination of the conditions during deposition of the sediments. Water depth, bottom conditions, salinity, current velocity and amount of suspended nutrients in the water are some of the environmental factors that may be reconstructed by studying trace fossils. The Blackhawk Formation at Sunnyside comprises the members, the Kenilworth Member and the Sunnyside Member. Field studies show that the formation may be further subdivided in the Sunnyside district., according to the precepts of units of mappable thickness and similar lithologic characteristics. The Blackhawk pinches out eastward and north. ward into the Mancos Shale, and names for submembers become meaningless. Names are of value in the region of interest, however, because of the prominence of the named units. Coal mining is the

Characteristics of sedimentary structures in coarse-grained alluvial rivers

NASA Astrophysics Data System (ADS)

Ackerley, David; Powell, Mark

2013-04-01

The characteristics of coarse-grained alluvial surfaces have important implications for the estimation of flow resistance, entrainment thresholds and sediment transport rates in gravel-bed rivers. This area of research has, thus, demanded attention from geomorphologists, sedimentologists, and river engineers. The majority of research has focused towards understanding the characteristics and adjustments in surface grain size. Bed stability, however, is not ultimately defined by particle size but how grains are arranged within the bed surface. For example, by the organisation of particles into a variety of grain and form scale sedimentary structures and bedforms (e.g. imbrication; pebble clusters, stone nets, transverse ribs). While it is widely acknowledged sedimentary structuring must be considered within estimates of flow resistance and sediment transport, relatively little is known about the structural properties of water-worked river gravels. As a consequence, we remain woefully ignorant of this important aspect of gravel-bed river sedimentology. The aim of this poster is to present some preliminary results of a study designed to characterise the morphodynamics of sedimentary structures in coarse-grained alluvial rivers and their implications upon entrainment thresholds and sediment transport rates. The poster focuses on investigating the variability in grain and form scale sedimentary structuring across a number of field sites. Representative patches of three gravel bars on the Rivers Wharfe, Manifold and Afon Elan, UK, have been surveyed using a Leica HDS 3000 Terrestrial Laser Scanner. The resultant raw point-cloud data, recorded at a 4mm resolution, has been registered, filtered, and interpolated to produce highly detailed 2½D digital elevation models of gravel-bed surface topography. These surfaces have been analysed using a number of structural parameters including bed elevation probability distribution function statistics (standard deviation, skewness

Subcritical water extraction of organic matter from sedimentary rocks.

PubMed

Luong, Duy; Sephton, Mark A; Watson, Jonathan S

2015-06-16

Subcritical water extraction of organic matter containing sedimentary rocks at 300°C and 1500 psi produces extracts comparable to conventional solvent extraction. Subcritical water extraction of previously solvent extracted samples confirms that high molecular weight organic matter (kerogen) degradation is not occurring and that only low molecular weight organic matter (free compounds) are being accessed in analogy to solvent extraction procedures. The sedimentary rocks chosen for extraction span the classic geochemical organic matter types. A type I organic matter-containing sedimentary rock produces n-alkanes and isoprenoidal hydrocarbons at 300°C and 1500 psi that indicate an algal source for the organic matter. Extraction of a rock containing type II organic matter at the same temperature and pressure produces aliphatic hydrocarbons but also aromatic compounds reflecting the increased contributions from terrestrial organic matter in this sample. A type III organic matter-containing sample produces a range of non-polar and polar compounds including polycyclic aromatic hydrocarbons and oxygenated aromatic compounds at 300°C and 1500 psi reflecting a dominantly terrestrial origin for the organic materials. Although extraction at 300°C and 1500 psi produces extracts that are comparable to solvent extraction, lower temperature steps display differences related to organic solubility. The type I organic matter produces no products below 300°C and 1500 psi, reflecting its dominantly aliphatic character, while type II and type III organic matter contribute some polar components to the lower temperature steps, reflecting the chemical heterogeneity of their organic inventory. The separation of polar and non-polar organic compounds by using different temperatures provides the potential for selective extraction that may obviate the need for subsequent preparative chromatography steps. Our results indicate that subcritical water extraction can act as a suitable

Chemical composition of sedimentary rocks in California and Hawaii

USGS Publications Warehouse

Hill, Thelma P.

1981-01-01

A compilation of published chemical analyses of sedimentary rocks of the United States was undertaken by the U.S. Geological Survey in 1952 to make available scattered data that are needed for a wide range of economic and scientific uses. About 20,000-25,000 chemical analyses of sedimentary rocks in the United States have been published. This report brings together 2,312 of these analyses from California and Hawaii. The samples are arranged by general lithologic characteristics and locality. Indexes of stratigraphy, rock name, commercial uses, and minor elements are provided. The sedimentary rocks are classified into groups and into categories according to the chemical analyses. The groups (A through F2) are defined by a system similar to that proposed by Brian Mason in 1952, in which the main parameters are the three major components of sedimentary rocks: (1) uncombined silica, (2) clay (R203 ? 3Si02 ? nH20), and (3) calcium-magnesium carbonate. The categories are based on the degree of admixture of these three major components with other components, such as sulfate, phos- phate, and iron oxide. Common-rock, mixed-rock, and special-rock categories apply to rocks consisting of 85 percent or more, 50-84 percent, and less than 49 percent, respectively, of the three major components combined. Maps show distribution of sample localities by States; triangular diagrams show the lithologic characteristics and classification groups. Cumulative-frequency curves of each constituent in each classification group of the common-rock and mixed-rock categories are also included. The numerous analyses may not adequately represent the geochemical nature of the rock types and formations of the region because of sampling bias. Maps showing distribution of sample localities indicate that many of the localities are in areas where, for economic or other reasons, special problems attracted interest. Most of the analyzed rocks tended to be fairly simple in composition - mainly mixtures of

Facies architecture of a Triassic rift-related Silicic Volcano-Sedimentary succession in the Tethyan realm, Peonias subzone, Vardar (Axios) Zone, northern Greece; Regional implications

NASA Astrophysics Data System (ADS)

Asvesta, Argyro; Dimitriadis, Sarantis

2010-06-01

In northern Greece, along the western edge of the Paleozoic Vertiscos terrane (Serbomacedonian massif) and within the Peonias subzone - the eastern part of the Vardar (Axios) Zone - a Silicic Volcano-Sedimentary (SVS) succession of Permo(?)-Skythian to Mid Triassic age records the development of a faulted continental margin and the formation of rhyolitic volcanoes along a continental shelf fringed by neritic carbonate accumulations. It represents the early rifting extensional stages that eventually led to the opening of the main oceanic basin in the western part of the Vardar (Axios) Zone (the Almopias Oceanic Basin). Even though the SVS succession is deformed, altered, extensively silicified and metamorphosed in the low greenschist facies, primary textures, original contacts and facies relationships are recognized in some places allowing clues for the facies architecture and the depositional environment. Volcanic and sedimentary facies analysis has been carried out at Nea Santa and Kolchida rhyolitic volcanic centres. Pyroclastic facies, mostly composed of gas-supported lapilli tuffs and locally intercalated accretionary lapilli tuffs, built the early cones which were then overridden by rhyolitic aphyric and minor K-feldspar-phyric lava flows. The characteristics of facies, especially the presence of accretionary lapilli, imply subaerial to coastal emplacement at this early stage. The mature and final stages of volcanism are mostly represented by quartz-feldspar porphyry intrusions that probably occupied the vents. At Nea Santa area, the presence of resedimented hyaloclastite facies indicates subaqueous emplacement of rhyolitic lavas and/or lobes. Moreover, quartz-feldspar-phyric sills and a partly extrusive dome featuring peperites at their margins are inferred to have intruded unconsolidated, wet carbonate sediments of the overlying Triassic Neritic Carbonate Formation, in a shallow submarine environment. The dome had probably reached above wave-base as is

Scotland's forgotten carbon: a national assessment of mid-latitude fjord sedimentary carbon stocks

NASA Astrophysics Data System (ADS)

Smeaton, Craig; Austin, William E. N.; Davies, Althea L.; Baltzer, Agnes; Howe, John A.; Baxter, John M.

2017-12-01

Fjords are recognised as hotspots for the burial and long-term storage of carbon (C) and potentially provide a significant climate regulation service over multiple timescales. Understanding the magnitude of marine sedimentary C stores and the processes which govern their development is fundamental to understanding the role of the coastal ocean in the global C cycle. In this study, we use the mid-latitude fjords of Scotland as a natural laboratory to further develop methods to quantify these marine sedimentary C stores on both the individual fjord and national scale. Targeted geophysical and geochemical analysis has allowed the quantification of sedimentary C stocks for a number of mid-latitude fjords and, coupled with upscaling techniques based on fjord classification, has generated the first full national sedimentary C inventory for a fjordic system. The sediments within these mid-latitude fjords hold 640.7 ± 46 Mt of C split between 295.6 ± 52 and 345.1 ± 39 Mt of organic and inorganic C, respectively. When compared, these marine mid-latitude sedimentary C stores are of similar magnitude to their terrestrial equivalents, with the exception of the Scottish peatlands, which hold significantly more C. However, when area-normalised comparisons are made, these mid-latitude fjords are significantly more effective as C stores than their terrestrial counterparts, including Scottish peatlands. The C held within Scotland's coastal marine sediments has been largely overlooked as a significant component of the nation's natural capital; such coastal C stores are likely to be key to understanding and constraining improved global C budgets.

Phorbin steryl esters in Black Sea sediment traps and sediments: A preliminary evaluation of their paleooceanographic potential

NASA Astrophysics Data System (ADS)

King, Linda L.; Repeta, Daniel J.

1994-10-01

The distributions of pyropheophorbide- a steryl esters in one-year deployments of sediment traps at two locations in the Black Sea are described. In nearly all our trap samples, phorbin steryl esters (PSEs) contribute a significant portion of the total phorbin flux. The relative abundances of sterols esterified to pyropheophorbide- a varied throughout the year, and we suggest these changes result from the observed seasonal variation of phytoplankton species in the overlying water column. The distribution of free sterols in a one-year composite sediment trap sample closely approximates the distribution of sterols derived from the hydrolysis of sedimentary PSEs collected at an adjacent site. From these results, we suggest that the distribution of sedimentary PSE sterols provides a record of sterol deposition to the sediment-water interface. Esterification of sterols to pyropheophorbide- a apparently prevents the preferential removal of 4-desmethyl sterols relative to 4-methyl sterols, and the reduction of stenols to stanols during degradation. Analysis of PSEs in a gravity core covering the last 8-10 Kyr shows that the abundance and distribution of PSEs change with downcore variations in sedimentology. Detailed analysis of PSEs in sediments may, therefore, provide a means to evaluate paleooceanographic changes in phytoplankton community structure and sterol early diagenesis. The synthesis, NMR, CI-MS, and visible spectroscopic properties of four abundant PSEs found in the Black Sea are also described.

APPLICATIONS OF CATHODOLUMINESCENCE OF QUARTZ AND FELDSPAR TO SEDIMENTARY PETROLOGY.

USGS Publications Warehouse

Ruppert, Leslie F.

1987-01-01

Cathodoluminescence (CL), the emission of visible light during electron bombardment, was first used in sandstone petrology in the mid-1960's. CL techniques are especially useful for determining the origin and source of quartz and feldspar, two of the most common constituents in clastic rocks. CL properties of both minerals are dependent on their temperature of crystallization, duration of cooling, and/or history of deformation. Detrital quartz and feldspar are typically derived from igneous and metamorphic sources and luminesce in the visible range whereas authigenic quartz and feldspar form at low temperatures and do not luminesce. Quantification of luminescent and non-luminescent quartz and feldspar with the scanning electron microscope, electron microprobe, or a commercial CL device can allow for the determination of origin, diagenesis, and source of clastic rocks when used in conjunction with field and other petrographic analyses.

The Sedimentary Architecture of the Hatton Basin from New 2D Seismic Reflection and Gravity Data

NASA Astrophysics Data System (ADS)

Bérdi, L.; Prada, M.; O'Reilly, B.; Haughton, P.; Shannon, P.; Martínez-Loriente, S.

2017-12-01

The Hatton Basin is located at the western European Atlantic Margin, approximately 600 km west of Scotland and Ireland. It is bounded by the Rockall Bank to the east and by the Hatton High to the west. Little is known about its structure and evolution within the context of the North Atlantic opening. Here we present a preliminary interpretation of the large-scale sedimentary structure of the Hatton basin from new 2D regional long-streamer seismic reflection data and DSDP information. Gravity data and previous knowledge on the crustal structure of the basin are used to investigate its formation processes.First interpretations of the seismic data suggest the presence of three megasequences referred to as Ha (Early Pliocene to Holocene), Hb (Late Eocene to Late Miocene) and Hc (Paleocene to middle Eocene), which are bounded by regional unconformities C10 (intra-Early Pliocene), C30 (intra-Late Eocene) and C40 (base Cenozoic) respectively. The C20 (intra-Early Miocene) surface is absent in the basin but is locally identified to the south of the study area. The mapped regional reflectors are recognized throughout the European North Atlantic.Below the Cenozoic succession, the presence of Mesozoic and/or older rocks in the basin is proposed based on the seismic character of the reflectors and the apparent rotated fault blocks. In the lowest Cenozoic megasequence (Hc), a prograding sedimentary wedge system was identified at the basin margins that implies a relative sea level fall during this period. In Late Paleocene‒Early Eocene times, the basin was affected by extensive magmatism that resulted in the emplacement of volcanic intrusives and extrusives of basaltic origin. The deposition of megasequence Hb was controlled by strong bottom current activity as a consequence of rapid subsidence and deep marine conditions. The transition from sequence Hb to Ha is marked by the C10 unconformity, which records the late Cenozoic uplift and erosion of Ireland and Britain

Palynostratigraphy of the Erkovtsy field of brown coal (the Zeya-Bureya sedimentary basin)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kezina, T.V.; Litvinenko, N.D.

2007-08-15

The Erkovtsy brown coal field in the northwestern Zeya-Bureya sedimentary basin (129-130{sup o}E, 46-47{sup o}N) is structurally confined to southern flank of the Mesozoic-Cenozoic Belogor'e depression. The verified stratigraphic scheme of the coalfield sedimentary sequence is substantiated by palynological data on core samples from 18 boreholes sampled in the course of detailed prospecting and by paleobotanical analysis of sections in the Yuzhnyi sector of the coalfield (data of 1998 by M.A. Akhmetiev and S.P. Manchester). Sections of the Erkovtsy, Arkhara-Boguchan, and Raichikha brown-coal mines are correlated. Stratigraphic subdivisions distinguished in the studied sedimentary succession are the middle and upper Tsagayanmore » subformations (the latter incorporating the Kivda Beds), Raichikha, Mukhino, Buzuli, and Sazanka formations.« less

Sedimentary architecture of the Shaler outcrop, Gale Crater, Mars: paleoenvironmental and sediment transport implications

NASA Astrophysics Data System (ADS)

Gupta, S.; Edgar, L. A.; Rubin, D. M.; Lewis, K. W.; Kocurek, G.; Anderson, R. B.; Bell, J. F.; Dromart, G.; Edgett, K. S.; Grotzinger, J. P.; Hardgrove, C. J.; Kah, L. C.; Leveille, R. J.; Malin, M.; Mangold, N.; Milliken, R.; Minitti, M. E.; Muller, J.; Rice, M. S.; Rowland, S. K.; Schieber, J.; Stack, K.; Sumner, D. Y.; Team, M.

2013-12-01

Sedimentary rocks are archives of ancient depositional processes and environments on planetary surfaces. Reconstructing such processes and environments requires observations of sedimentary structures and architecture (the large-scale geometry and organisation of sedimentary bedsets). We report the analysis of the distinct Shaler outcrop, a prominent stratified unit located between the Bathurst Inlet outcrop and the floor of Yellowknife bay. The Shaler outcrop is an ~1 m thick stratal unit that spans approximately 30 m outcrop in length, and was examined by Curiosity on sols 120-121 and more recently on sols 309-324. Detailed stereo observations of the outcrop across most of its entire lateral extent were made using Navigation and Mast Cameras. These data permit detailed analysis of stratal geometries, distribution of sedimentary structures, and broad grain size trends. Overall the Shaler outcrop comprises a heterogeneous assemblage of interstratified platy sandstones separated by recessive, likely finer-grained beds. Coarser-grained beds are characterised by decimeter-scale trough cross-bedding. The north-eastern section of the outcrop shows greater abundance of interstratified sandstones and finer-grained beds. The southwestern section is characterised by darker bedsets that are likely coarser grained interstratified with finer-grained sandstones. The darker bedsets appear to comprise stacked trough-cross stratified bedsets. Finer-grained recessive intervals are not apparent in this section. The presence and scale of trough cross-stratification indicates that sediment was transported by the migration of sinuous crested dunes. Bedding geometries indicate sub-critical angles of climb. We examine the large-scale bedset architecture to evaluate the original depositional geometry of the Shaler sedimentary system, and consider its plausible depositional processes and paleoenvironmental setting. Finally, we consider its relationship to the sedimentary succession exposed

Geology, Geochemistry and Geophysics of Sedimentary Rock-Hosted Au Deposits in P.R. China

USGS Publications Warehouse

Peters, Stephen G.

2002-01-01

This is the second report concerning results of a joint project between the U.S. Geological Survey and the Tianjin Geological Academy to study sedimentary rock-hosted Au deposits in P.R. China. Since the 1980s, Chinese geologists have devoted a large-scale exploration and research effort to the deposits. As a result, there are more than 20 million oz of proven Au reserves in sedimentary rock-hosted Au deposits in P.R. China. Additional estimated and inferred resources are present in over 160 deposits and occurrences, which are undergoing exploration. This makes China second to Nevada in contained ounces of Au in Carlin-type deposits. It is likely that many of the Carlin-type Au ore districts in China, when fully developed, could have resource potential comparable to the multi-1,000-tonne Au resource in northern Nevada. The six chapters of this report describe sedimentary rock-hosted Au deposits that were visited during the project. Chapters 1 and 2 provide an overview of sedimentary rock-hosted Au deposits and Carlin-type Au deposits and also provide a working classification for the sedimentary rock-hosted Au deposits. Chapters 3, 4, and 5 provide descriptions that were compiled from the literature in China in three main areas: the Dian-Qian-Gui, the Qinling fold belt, and Middle-Lower Yangtze River areas. Chapter 6 contains a weights-of-evidence (WofE), GIS-based mineral assessment of sedimentary rock-hosted Au deposits in the Qinling fold belt and Dian-Qian-Gui areas. Appendices contain scanned aeromagnetic (Appendix I) and gravity (Appendix II) geophysical maps of south and central China. Data tables of the deposits (Appendix III) also are available in the first report as an interactive database at http://geopubs.wr.usgs.gov/open-file/of98-466/. Geochemical analysis of ore samples from the deposits visited are contained in Appendix IV.

Sedimentary structures and stratal geometries at the foothills of Mount Sharp: their role in paleoenvironmental interpretation

NASA Astrophysics Data System (ADS)

Gupta, S.; Rubin, D. M.; Sumner, D. Y.; Grotzinger, J. P.; Lewis, K. W.; Stack, K.; Kah, L. C.; Banham, S.; Edgett, K. S.

2015-12-01

The Mars Science Laboratory Curiosity rover has been exploring sedimentary rocks at the foothills of Mount Sharp since August 2014. Robust interpretation of the paleoenvironmental contexts requires detailed facies analysis of these rocks including analysis and interpretation of sedimentary structures and sediment body geometries. Here, we describe some of the detailed sedimentary structures and sedimentary geometries observed by Curiosity between the Pahrump_Hills field site and its current location at Marias Pass. The Pahrump Hills sedimentary section comprises a succession dominated by finely laminated mudstones of the Murray formation that are interpreted to have been deposited in an ancient lake within Gale crater. Toward the top of the Pahump Hills succession, we observe the appearance of coarser-grained sandstones that are interstratified within the lacustrine mudstones. These sandstones that include Whale Rock and Newspaper Rock show lenticular geometries, and are pervasively cross-stratified. These features indicate that currents eroded shallow scours in the lake beds that were then infilled by deposition from migrating subaqueous dunes. The paleoenvironmental setting may represent either a gullied delta front setting or one in which lake level fall caused fluvial erosion and infilling of the shallow scours. Since leaving Pahrump_Hills, Curiosity has imaged extensive exposures of strata that are partly correlative with and stratigraphically overlie the uppermost part of the Pahrump section. Isolated cross-bedded sandstones and possible interstratified conglomerates beds occur within Murray formation mudstones. Capping sandstones with a likely variety of environmental contexts overlie mudstones. Where imaged in detail, sedimentary structures, such as trough-cross bedding and possible eolian pinstriping, provide constraints on plausible sedimentary processes and bounds on depositional setting.

Extensional Tectonics and Sedimentary Architecture Using 3-D Seismic Data: An Example from Hydrocarbon-Bearing Mumbai Offshore Basin, West Coast of India

NASA Astrophysics Data System (ADS)

Mukhopadhyay, D. K.; Bhowmick, P. K.; Mishra, P.

2016-12-01

In offshore sedimentary basins, analysis of 3-D seismic data tied with well log data can be used to deduce robust isopach and structure contour maps of different stratigraphic formations. The isopach maps give depocenters whereas structure contour maps give structural relief at a specific time. Combination of these two types of data helps us decipher horst-graben structures, sedimentary basin architecture and tectono-stratigraphic relations through Tertiary time. Restoration of structural cross sections with back-stripping of successively older stratigraphic layers leads to better understand tectono-sedimentary evolution of a basin. The Mumbai (or Bombay) Offshore Basin is the largest basin off the west coast of India and includes Bombay High giant oil/gas field. Although this field was discovered in 1974 and still producing, the basin architecture vis-à-vis structural evolution are not well documented. We take the approach briefly outlined above to study in detail three large hydrocarbon-bearing structures located within the offshore basin. The Cretaceous Deccan basalt forms the basement and hosts prodigal thickness (> 8 km at some localities) of Tertiary sedimentary formations.A two stage deformation is envisaged. At the first stage horst and graben structures formed due to approximately E-W extensional tectonics. This is most spectacularly seen at the basement top level. The faults associated with this extension strike NNW. At the second stage of deformation a set of ENE-striking cross faults have developed leading to the formation of transpressional structures at places. High rate of early sedimentation obliterated horst-graben architecture to large extent. An interesting aspect emerges is that the all the large-scale structures have rather low structural relief. However, the areal extent of such structures are very large. Consequently, these structures hold commercial quantities of oil/gas.

Tectono-sedimentary events and geodynamic evolution of the Mesozoic and Cenozoic basins of the Alpine Margin, Gulf of Tunis, north-eastern Tunisia offshore

NASA Astrophysics Data System (ADS)

Melki, Fetheddine; Zouaghi, Taher; Chelbi, Mohamed Ben; Bédir, Mourad; Zargouni, Fouad

2010-09-01

The structural pattern, tectono-sedimentary framework and geodynamic evolution for Mesozoic and Cenozoic deep structures of the Gulf of Tunis (north-eastern Tunisia) are proposed using petroleum well data and a 2-D seismic interpretation. The structural system of the study area is marked by two sets of faults that control the Mesozoic subsidence and inversions during the Paleogene and Neogene times: (i) a NE-SW striking set associated with folds and faults, which have a reverse component; and (ii) a NW-SE striking set active during the Tertiary extension episodes and delineating grabens and subsiding synclines. In order to better characterize the tectono-sedimentary evolution of the Gulf of Tunis structures, seismic data interpretations are compared to stratigraphic and structural data from wells and neighbouring outcrops. The Atlas and external Tell belonged to the southernmost Tethyan margin record a geodynamic evolution including: (i) rifting periods of subsidence and Tethyan oceanic accretions from Triassic until Early Cretaceous: we recognized high subsiding zones (Raja and Carthage domains), less subsiding zones (Gamart domain) and a completely emerged area (Raouad domain); (ii) compressive events during the Cenozoic with relaxation periods of the Oligocene-Aquitanian and Messinian-Early Pliocene. The NW-SE Late Eocene and Tortonian compressive events caused local inversions with sealed and eroded folded structures. During Middle to Late Miocene and Early Pliocene, we have identified depocentre structures corresponding to half-grabens and synclines in the Carthage and Karkouane domains. The north-south contractional events at the end of Early Pliocene and Late Pliocene periods are associated with significant inversion of subsidence and synsedimentary folded structures. Structuring and major tectonic events, recognized in the Gulf of Tunis, are linked to the common geodynamic evolution of the north African and western Mediterranean basins.

Seismic Stratigraphy of the Mariana Forearc Sedimentary Basin

NASA Astrophysics Data System (ADS)

Chapp, E.; Taylor, B.; Oakley, A.; Moore, G.

2005-12-01

A grid of seismic reflection profiles across the Mariana forearc between 14N-18N reveals a sedimentary basin between the Oligocene-Miocene frontal arc and the Eocene outer forearc highs. We identify and correlate several seismic stratigraphic units and use them to constrain the local and regional tectonics, which vary significantly from north to south. Four major sediment packages are distinguished in the southern forearc basin. The oldest unit, U-4, is conformable to arcward-tilted, rotated fault blocks formed during early extension, possibly associated with early Oligocene rifting prior to Parece Vela Basin spreading. Onlap relationships between the oldest sedimentary units indicate that deposition occurred before, during and after block rotation. On one profile, the U-4 sequence is deformed above a blind thrust fault in an otherwise extensional environment. Sediments that comprise the third unit, U-3, thin trenchward and onlap onto U-4. U-2 sediments onlap both sides of the basin and are characterized by nearly uniform thicknesses across the southern section. They currently dip trenchward, but are bypassed and onlapped arcward by thin recent deposits, U-1, on the three southern lines, suggesting recent relative subsidence of the outer forearc. The onset of this subsidence (during deposition of the upper strata of U-2) may have generated slope instability that triggered a large submarine slump off the frontal arc high into the forearc basin ENE of Saipan. The seismic stratigraphic units reveal both pre- and post-slump depositional boundaries including a possible post-slump debris apron around the perimeter of the toe thrust. The central region (near 16N), absent of the large rotated basement fault blocks found in the south, is characterized by high-angle normal faults that offset the seafloor by as much as 200 m. The upper section of U-4 is visible in isolated sections, but the coherency of the oldest layers is lost. Because a clear basement reflection is not

Optimization of Well Configuration for a Sedimentary Enhanced Geothermal Reservoir

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Mengnan; Cho, JaeKyoung; Zerpa, Luis E.

The extraction of geothermal energy in the form of hot water from sedimentary rock formations could expand the current geothermal energy resources toward new regions. From previous work, we observed that sedimentary geothermal reservoirs with relatively low permeability would require the application of enhancement techniques (e.g., well hydraulic stimulation) to achieve commercial production/injection rates. In this paper we extend our previous work to develop a methodology to determine the optimum well configuration that maximizes the hydraulic performance of the geothermal system. The geothermal systems considered consist of one vertical well doublet system with hydraulic fractures, and three horizontal well configurationsmore » with open-hole completion, longitudinal fractures and transverse fractures, respectively. A commercial thermal reservoir simulation is used to evaluate the geothermal reservoir performance using as design parameters the well spacing and the length of the horizontal wells. The results obtained from the numerical simulations are used to build a response surface model based on the multiple linear regression method. The optimum configuration of the sedimentary geothermal systems is obtained from the analysis of the response surface model. The proposed methodology is applied to a case study based on a reservoir model of the Lyons sandstone formation, located in the Wattenberg field, Denver-Julesburg basin, Colorado.« less

A Hydrothermal-Sedimentary Context for the Origin of Life

PubMed Central

Hickman-Lewis, K.; Hinman, N.; Gautret, P.; Campbell, K.A.; Bréhéret, J.G.; Foucher, F.; Hubert, A.; Sorieul, S.; Dass, A.V.; Kee, T.P.; Georgelin, T.; Brack, A.

2018-01-01

Abstract Critical to the origin of life are the ingredients of life, of course, but also the physical and chemical conditions in which prebiotic chemical reactions can take place. These factors place constraints on the types of Hadean environment in which life could have emerged. Many locations, ranging from hydrothermal vents and pumice rafts, through volcanic-hosted splash pools to continental springs and rivers, have been proposed for the emergence of life on Earth, each with respective advantages and certain disadvantages. However, there is another, hitherto unrecognized environment that, on the Hadean Earth (4.5–4.0 Ga), would have been more important than any other in terms of spatial and temporal scale: the sedimentary layer between oceanic crust and seawater. Using as an example sediments from the 3.5–3.33 Ga Barberton Greenstone Belt, South Africa, analogous at least on a local scale to those of the Hadean eon, we document constant permeation of the porous, carbonaceous, and reactive sedimentary layer by hydrothermal fluids emanating from the crust. This partially UV-protected, subaqueous sedimentary environment, characterized by physical and chemical gradients, represented a widespread system of miniature chemical reactors in which the production and complexification of prebiotic molecules could have led to the origin of life. Key Words: Origin of life—Hadean environment—Mineral surface reactions—Hydrothermal fluids—Archean volcanic sediments. Astrobiology 18, 259–293. PMID:29489386

Impact of raking and bioturbation-mediated ecological manipulation on sediment-water phosphorus diagenesis: a mesocosm study supported with radioactive signature.

PubMed

Biswas, Jayanta K; Hazra, Saumen; Majumdar, Jayjit; Mandal, Sushil K; Shaheen, Sabry M; Sarkar, Santosh K; Meissner, Ralph; Meers, Erik; Rinklebe, Jörg

2017-12-01

The study examined the impact of raking and fish bioturbation on modulating phosphorus (P) concentrations in the water and sediment under different trophic conditions. An outdoor experiment was set to monitor physicochemical and microbiological parameters of water and sediment influencing P diagenesis. A pilot study with radioactive 32 P was also performed under the agency of raking and bacteria (Bacillus sp.). Raking was more effective in release of P under unfertilized conditions by significantly enhancing orthophosphate (35%) and soluble reactive phosphate (31.8%) over respective controls. Bioturbation increased total and available P in sediments significantly as compared to control. The rates of increase were higher in the unfertilized conditions (17.6-28.4% for total P and 12.2 to 23.2% for available P) than the fertilized ones (6.5-12.4% for total P and 9.1 to 15% for available P). The combined effects of raking and bioturbation on orthophosphate and soluble reactive phosphate were also stronger under unfertilized state (54.5 and 81.8%) than fertilized ones (50 and 70%). The tracer signature showed that coupled action of introduced bacteria and repeated raking resulted in 59.2, 23 and 16% higher counts of radioactive P than the treatments receiving raking once, repeated raking and bacteria inoculation, respectively. Raking alone or in sync with bioturbation exerted pronounced impact on P diagenesis through induction of coupled mineralization and nutrient release. It has significant implication for performing regular raking of fish-farm sediments and manipulation of bottom-grazing fish to regulate mineralization of organic matter and release of obnoxious gases from the system. Further, they synergistically can enhance the buffering capacity against organic overload and help to maintain aquatic ecosystem health.

Sources and distribution of sedimentary organic matter along the Andong salt marsh, Hangzhou Bay

NASA Astrophysics Data System (ADS)

Yuan, Hong-Wei; Chen, Jian-Fang; Ye, Ying; Lou, Zhang-Hua; Jin, Ai-Min; Chen, Xue-Gang; Jiang, Zong-Pei; Lin, Yu-Shih; Chen, Chen-Tung Arthur; Loh, Pei Sun

2017-10-01

Lignin oxidation products, δ13C values, C/N ratios and particle size were used to investigate the sources, distribution and chemical stability of sedimentary organic matter (OM) along the Andong salt marsh located in the southwestern end of Hangzhou Bay, China. Terrestrial OM was highest at the upper marshes and decreased closer to the sea, and the distribution of sedimentary total organic carbon (TOC) was influenced mostly by particle size. Terrestrial OM with a C3 signature was the predominant source of sedimentary OM in the Spartina alterniflora-dominated salt marsh system. This means that aside from contributions from the local marsh plants, the Andong salt marsh received input mostly from the Qiantang River and the Changjiang Estuary. Transect C, which was situated nearer to the Qiantang River mouth, was most likely influenced by input from the Qiantang River. Likewise, a nearby creek could be transporting materials from Hangzhou Bay into Transect A (farther east than Transect C), as Transect A showed a signal resembling that of the Changjiang Estuary. The predominance of terrestrial OM in the Andong salt marsh despite overall reductions in sedimentary and terrestrial OM input from the rivers is most likely due to increased contributions of sedimentary and terrestrial OM from erosion. This study shows that lower salt marsh accretion due to the presence of reservoirs upstream may be counterbalanced by increased erosion from the surrounding coastal areas.

Raman spectral, elemental, crystallinity, and oxygen-isotope variations in conodont apatite during diagenesis

NASA Astrophysics Data System (ADS)

Zhang, Lei; Cao, Ling; Zhao, Laishi; Algeo, Thomas J.; Chen, Zhong-Qiang; Li, Zhihong; Lv, Zhengyi; Wang, Xiangdong

2017-08-01

Conodont apatite has long been used in paleoenvironmental studies, often with minimal evaluation of the influence of diagenesis on measured elemental and isotopic signals. In this study, we evaluate diagenetic influences on conodonts using an integrated set of analytical techniques. A total of 92 points in 19 coniform conodonts from Ordovician marine units of South China were analyzed by micro-laser Raman spectroscopy (M-LRS), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), high-resolution X-ray microdiffraction (HXRD), and secondary ion mass spectrometry (SIMS). Each conodont element was analyzed along its full length, including the albid crown, hyaline crown, and basal body, in either a whole specimen (i.e., reflecting the composition of its outer layer) or a split specimen (i.e., reflecting the composition of its interior). In the conodonts of this study, the outer surfaces consist of hydroxyfluorapatite and the interiors of strontian hydroxyfluorapatite. Ionic substitutions resulted in characteristic Raman spectral shifts in the position (SS1) and width (SS2) of the ν1-PO43- stretching band. Although multiple elements were enriched (Sr2+, Mg2+) and depleted (Fe3+, Mn2+, Ca2+) during diagenesis, geochemical modeling constraints and known Raman spectral patterns suggest that Sr uptake was the dominant influence on diagenetic redshifts of SS1. All study specimens show lower SS2 values than modern bioapatite and synthetic apatite, suggesting that band width decreases with time in ancient bioapatite, possibly through an annealing process that produces larger, more uniform crystal domains. Most specimens consist mainly of amorphous or poorly crystalline apatite, which is inferred to represent the original microstructure of conodonts. In a subset of specimens, some tissues (especially albid crown) exhibit an increased degree of crystallinity developed through aggrading neomorphism. However, no systematic relationship was observed between

Geochemical and multi-isotopic (87Sr/86Sr, 143Nd/144Nd, 238U/235U) perspectives of sediment sources, depositional conditions, and diagenesis of the Marcellus Shale, Appalachian Basin, USA

NASA Astrophysics Data System (ADS)

Phan, Thai T.; Gardiner, James B.; Capo, Rosemary C.; Stewart, Brian W.

2018-02-01

We investigate sediment sources, depositional conditions and diagenetic processes affecting the Middle Devonian Marcellus Shale in the Appalachian Basin, eastern USA, a major target of natural gas exploration. Multiple proxies, including trace metal contents, rare earth elements (REE), the Sm-Nd and Rb-Sr isotope systems, and U isotopes were applied to whole rock digestions and sequentially extracted fractions of the Marcellus shale and adjacent units from two locations in the Appalachian Basin. The narrow range of εNd values (from -7.8 to -6.4 at 390 Ma) is consistent with derivation of the clastic sedimentary component of the Marcellus Shale from a well-mixed source of fluvial and eolian material of the Grenville orogenic belt, and indicate minimal post-depositional alteration of the Sm-Nd system. While silicate minerals host >80% of the REE in the shale, data from sequentially extracted fractions reflect post-depositional modifications at the mineralogical scale, which is not observed in whole rock REE patterns. Limestone units thought to have formed under open ocean (oxic) conditions have δ238U values and REE patterns consistent with modern seawater. The δ238U values in whole rock shale and authigenic phases are greater than those of modern seawater and the upper crust. The δ238U values of reduced phases (the oxidizable fraction consisting of organics and sulfide minerals) are ∼0.6‰ greater than that of modern seawater. Bulk shale and carbonate cement extracted from the shale have similar δ238U values, and are greater than δ238U values of adjacent limestone units. We suggest these trends are due to the accumulation of chemically and, more likely, biologically reduced U from anoxic to euxinic bottom water as well as the influence of diagenetic reactions between pore fluids and surrounding sediment and organic matter during diagenesis and catagenesis.

Chemistry of decomposition of freshwater wetland sedimentary organic material during ramped pyrolysis

NASA Astrophysics Data System (ADS)

Williams, E. K.; Rosenheim, B. E.

2011-12-01

Ramped pyrolysis methodology, such as that used in the programmed-temperature pyrolysis/combustion system (PTP/CS), improves radiocarbon analysis of geologic materials devoid of authigenic carbonate compounds and with low concentrations of extractable authochthonous organic molecules. The approach has improved sediment chronology in organic-rich sediments proximal to Antarctic ice shelves (Rosenheim et al., 2008) and constrained the carbon sequestration potential of suspended sediments in the lower Mississippi River (Roe et al., in review). Although ramped pyrolysis allows for separation of sedimentary organic material based upon relative reactivity, chemical information (i.e. chemical composition of pyrolysis products) is lost during the in-line combustion of pyrolysis products. A first order approximation of ramped pyrolysis/combustion system CO2 evolution, employing a simple Gaussian decomposition routine, has been useful (Rosenheim et al., 2008), but improvements may be possible. First, without prior compound-specific extractions, the molecular composition of sedimentary organic matter is unknown and/or unidentifiable. Second, even if determined as constituents of sedimentary organic material, many organic compounds have unknown or variable decomposition temperatures. Third, mixtures of organic compounds may result in significant chemistry within the pyrolysis reactor, prior to introduction of oxygen along the flow path. Gaussian decomposition of the reaction rate may be too simple to fully explain the combination of these factors. To relate both the radiocarbon age over different temperature intervals and the pyrolysis reaction thermograph (temperature (°C) vs. CO2 evolved (μmol)) obtained from PTP/CS to chemical composition of sedimentary organic material, we present a modeling framework developed based upon the ramped pyrolysis decomposition of simple mixtures of organic compounds (i.e. cellulose, lignin, plant fatty acids, etc.) often found in sedimentary

Early Triassic environmental dynamics and microbial development during the Smithian-Spathian transition (Lower Weber Canyon, Utah, USA)

NASA Astrophysics Data System (ADS)

Grosjean, Anne-Sabine; Vennin, Emmanuelle; Olivier, Nicolas; Caravaca, Gwénaël; Thomazo, Christophe; Fara, Emmanuel; Escarguel, Gilles; Bylund, Kevin G.; Jenks, James F.; Stephen, Daniel A.; Brayard, Arnaud

2018-01-01

The Early Triassic biotic recovery following the end-Permian mass extinction is well documented in the Smithian-Spathian Thaynes Group of the western USA basin. This sedimentary succession is commonly interpreted as recording harsh conditions of various shallow marine environments where microbial structures flourished. However, recent studies questioned the relevance of the classical view of long-lasting deleterious post-crisis conditions and suggested a rapid diversification of some marine ecosystems during the Early Triassic. Using field and microfacies analyses, we investigate a well-preserved Early Triassic marine sedimentary succession in Lower Weber Canyon (Utah, USA). The identification of microbial structures and their depositional settings provide insights on factors controlling their morphologies and distribution. The Lower Weber Canyon sediments record the vertical evolution of depositional environments from a middle Smithian microbial and dolosiliciclastic peritidal system to a late Smithian-early Spathian bioclastic, muddy mid ramp. The microbial deposits are interpreted as Microbially Induced Sedimentary Structures (MISS) that developed either (1) in a subtidal mid ramp where microbial wrinkles and chips are associated with megaripples characterizing hydrodynamic conditions of lower flow regime, or (2) in protected areas of inter- to subtidal inner ramp where they formed laminae and domal structures. Integrated with other published data, our investigations highlight that the distribution of these microbial structures was influenced by the combined effects of bathymetry, hydrodynamic conditions, lithology of the substrat physico-chemical characteristics of the depositional environment and by the regional relative sea-level fluctuations. Thus, we suggest that local environmental factors and basin dynamics primarily controlled the modalities of microbial development and preservation during the Early Triassic in the western USA basin.

Tectonics of Chukchi Sea Shelf sedimentary basins and its influence on petroleum systems

NASA Astrophysics Data System (ADS)

Agasheva, Mariia; Antonina, Stoupakova; Anna, Suslova; Yury, Karpov

2016-04-01

The Chukchi Sea Shelf placed in the East Arctic offshore of Russia between East Siberian Sea Shelf and North Slope Alaska. The Chukchi margin is considered as high petroleum potential play. The major problem is absence of core material from drilling wells in Russian part of Chukchi Shelf, hence strong complex geological and geophysical analyses such as seismic stratigraphy interpretation should be provided. In addition, similarity to North Slope and Beaufort Basins (North Chukchi) and Hope Basin (South Chukchi) allow to infer the resembling sedimentary succession and petroleum systems. The Chukchi Sea Shelf include North and South Chukchi Basins, which are separated by Wrangel-Herald Arch and characterized by different opening time. The North Chukchi basin is formed as a general part of Canada Basin opened in Early Cretaceous. The South Chukchi Basin is characterized by a transtensional origin of the basin, this deformation related to motion on the Kobuk Fault [1]. Because seismic reflections follow chronostratigraphic correlations, it is possible to achieve stratigraphic interpretation. The main seismic horizons were indicated as: PU, JU, LCU, BU, mBU marking each regional unconformities. Reconstruction of main tectonic events of basin is important for building correct geological model. Since there are no drilling wells in the North and South Chukchi basins, source rocks could not be proven. Referring to the North Chukchi basin, source rocks equivalents of Lower Cretaceous Pebble Shale Formation, Lower Jurassic Kingdak shales and Upper Triassic Shublik Formation (North Slope) is possible exhibited [2]. In the South Chukchi, it is possible that Cretaceous source rocks could be mature for hydrocarbon generation. Erosions and uplifts that could effect on hydrocarbon preservation was substantially in Lower Jurassic and Early Cretaceous periods. Most of the structures may be connected with fault and stratigraphy traps. The structure formed at Wrangel-Herald Arch to

Sedimentary Facies Mapping Based on Tidal Channel Network and Topographic Features

NASA Astrophysics Data System (ADS)

Ryu, J. H.; Lee, Y. K.; Kim, K.; Kim, B.

2015-12-01

Tidal flats on the west coast of Korea suffer intensive changes in their surface sedimentary facies as a result of the influence of natural and artificial changes. Spatial relationships between surface sedimentary facies distribution and benthic environments were estimated for the open-type Ganghwa tidal flat and semi closed-type Hwangdo tidal flat, Korea. In this study, we standardized the surface sedimentary facies and tidal channel index of the channel density, distance, thickness and order. To extract tidal channel information, we used remotely sensed data, such as those from the Korea Multi-Purpose Satellite (KOMPSAT)-2, KOMPSAT-3, and aerial photographs. Surface sedimentary facies maps were generated based on field data using an interpolation method.The tidal channels in each sediment facies had relatively constant meandering patterns, but the density and complexity were distinguishable. The second fractal dimension was 1.7-1.8 in the mud flat, about 1.4 in the mixed flat, and about 1.3 in the sand flat. The channel density was 0.03-0.06 m/m2 in the mud flat and less than 0.02 m/m2 in the mixed and sand flat areas of the two test areas. Low values of the tidal channel index, which indicated a simple pattern of tidal channel distribution, were identified at areas having low elevation and coarse-grained sediments. By contrast, high values of the tidal channel index, which indicated a dendritic pattern of tidal channel distribution, were identified at areas having high elevation and fine-grained sediments. Surface sediment classification based on remotely sensed data must circumspectly consider an effective critical grain size, water content, local topography, and intertidal structures.

Geoengineering Research for a Deep Underground Science and Engineering Laboratory in Sedimentary Rock

NASA Astrophysics Data System (ADS)

Mauldon, M.

2004-12-01

A process to identify world-class research for a Deep Underground Science and Engineering Laboratory (DUSEL) in the USA has been initiated by NSF. While allowing physicists to study, inter alia, dark matter and dark energy, this laboratory will create unprecedented opportunities for biologists to study deep life, geoscientists to study crustal processes and geoengineers to study the behavior of rock, fluids and underground cavities at depth, on time scales of decades. A substantial portion of the nation's future infrastructure is likely to be sited underground because of energy costs, urban crowding and vulnerability of critical surface facilities. Economic and safe development of subsurface space will require an improved ability to engineer the geologic environment. Because of the prevalence of sedimentary rock in the upper continental crust, much of this subterranean infrastructure will be hosted in sedimentary rock. Sedimentary rocks are fundamentally anisotropic due to lithology and bedding, and to discontinuities ranging from microcracks to faults. Fractures, faults and bedding planes create structural defects and hydraulic pathways over a wide range of scales. Through experimentation, observation and monitoring in a sedimentary rock DUSEL, in conjunction with high performance computational models and visualization tools, we will explore the mechanical and hydraulic characteristics of layered rock. DUSEL will permit long-term experiments on 100 m blocks of rock in situ, accessed via peripheral tunnels. Rock volumes will be loaded to failure and monitored for post-peak behavior. The response of large rock bodies to stress relief-driven, time-dependent strain will be monitored over decades. Large block experiments will be aimed at measurement of fluid flow and particle/colloid transport, in situ mining (incl. mining with microbes), remediation technologies, fracture enhancement for resource extraction and large scale long-term rock mass response to induced

Shaler: in situ analysis of a fluvial sedimentary deposit on Mars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edgar, Lauren A.; Gupta, Sanjeev; Rubin, David M.

This article characterizes the detailed sedimentology of a fluvial sandbody on Mars for the first time and interprets its depositional processes and palaeoenvironmental setting. Despite numerous orbital observations of fluvial landforms on the surface of Mars, ground-based characterization of the sedimentology of such fluvial deposits has not previously been possible. Results from the NASA Mars Science Laboratory Curiosity rover provide an opportunity to reconstruct at fine scale the sedimentary architecture and palaeomorphology of a fluvial environment on Mars. This work describes the grain size, texture and sedimentary facies of the Shaler outcrop, reconstructs the bedding architecture, and analyses cross-stratification tomore » determine palaeocurrents. On the basis of bedset geometry and inclination, grain-size distribution and bedform migration direction, this study concludes that the Shaler outcrop probably records the accretion of a fluvial barform. The majority of the outcrop consists of large-scale trough cross-bedding of coarse sand and granules. Palaeocurrent analyses and bedform reconstruction indicate that the beds were deposited by bedforms that migrated towards the north-east, across the surface of a bar that migrated south-east. Stacked cosets of dune cross-bedding suggest aggradation of multiple bedforms, which provides evidence for short periods of sustained flow during Shaler deposition. However, local evidence for aeolian reworking and the presence of potential desiccation cracks within the outcrop suggest that fluvial deposition may have been intermittent. The uppermost strata at Shaler are distinct in terms of texture and chemistry and are inferred to record deposition from a different sediment dispersal system with a contrasting provenance. The outcrop as a whole is a testament to the availability of liquid water on the surface of Mars in its early history.« less

Shaler: in situ analysis of a fluvial sedimentary deposit on Mars

DOE PAGES

Edgar, Lauren A.; Gupta, Sanjeev; Rubin, David M.; ...

2017-03-09

This article characterizes the detailed sedimentology of a fluvial sandbody on Mars for the first time and interprets its depositional processes and palaeoenvironmental setting. Despite numerous orbital observations of fluvial landforms on the surface of Mars, ground-based characterization of the sedimentology of such fluvial deposits has not previously been possible. Results from the NASA Mars Science Laboratory Curiosity rover provide an opportunity to reconstruct at fine scale the sedimentary architecture and palaeomorphology of a fluvial environment on Mars. This work describes the grain size, texture and sedimentary facies of the Shaler outcrop, reconstructs the bedding architecture, and analyses cross-stratification tomore » determine palaeocurrents. On the basis of bedset geometry and inclination, grain-size distribution and bedform migration direction, this study concludes that the Shaler outcrop probably records the accretion of a fluvial barform. The majority of the outcrop consists of large-scale trough cross-bedding of coarse sand and granules. Palaeocurrent analyses and bedform reconstruction indicate that the beds were deposited by bedforms that migrated towards the north-east, across the surface of a bar that migrated south-east. Stacked cosets of dune cross-bedding suggest aggradation of multiple bedforms, which provides evidence for short periods of sustained flow during Shaler deposition. However, local evidence for aeolian reworking and the presence of potential desiccation cracks within the outcrop suggest that fluvial deposition may have been intermittent. The uppermost strata at Shaler are distinct in terms of texture and chemistry and are inferred to record deposition from a different sediment dispersal system with a contrasting provenance. The outcrop as a whole is a testament to the availability of liquid water on the surface of Mars in its early history.« less

Mineral remains of early life on Earth? On Mars?

USGS Publications Warehouse

Iberall, Robbins E.; Iberall, A.S.

1991-01-01

The oldest sedimentary rocks on Earth, the 3.8-Ga Isua Iron-Formation in southwestern Greenland, are metamorphosed past the point where organic-walled fossils would remain. Acid residues and thin sections of these rocks reveal ferric microstructures that have filamentous, hollow rod, and spherical shapes not characteristic of crystalline minerals. Instead, they resemble ferric-coated remains of bacteria. Because there are no earlier sedimentary rocks to study on Earth, it may be necessary to expand the search elsewhere in the solar system for clues to any biotic precursors or other types of early life. A study of morphologies of iron oxide minerals collected in the southern highlands during a Mars sample return mission may therefore help to fill in important gaps in the history of Earth's earliest biosphere. -from Authors

Sedimentary Flux to Passive Margins From Inversion of Drainage Patterns: Examples from Africa

NASA Astrophysics Data System (ADS)

Lodhia, Bhavik Harish; Roberts, Gareth G.; Fraser, Alastair

2017-04-01

We show that inversion of more than 14000 rivers from the African continent provides information about Cenozoic uplift and sedimentary flux to its passive margins. We test predicted sedimentary flux using a dense two-dimensional seismic dataset offshore northwest Africa. First, six biostratigraphically dated horizons were mapped (seabed, 5.6 Ma, 23.8 Ma, 58.40 Ma, 89.4 Ma and basement) across the Mauritanian margin and used to construct isopachs. Check-shot data were used to convert time to depth and to determine best-fitting compaction parameters. Observed solid sedimentary fluxes are ˜2x103 km3 /Ma between 58.4 and 23.8 Ma, ˜4x103 km3 /Ma between 23.8 and 5.6 Ma, and ˜28x103 km3 /Ma between 5.6 and 0 Ma. Compaction errors were propagated into our history of sedimentary flux. Secondly, we inverted our drainage inventory to explore the relationship between uplift and erosion onshore and our measured flux. The stream power erosional model was calibrated using independent observations of marine terrace elevations and ages. We integrate incision rates along best-fitting theoretical river profiles to predict sedimentary flux at mouths of the rivers draining northwest Africa (e.g. Senegal). Calculated Neogene uplift and erosion is staged. Our predicted history of sedimentary flux increases in three stages towards the present-day, which agrees with the offshore measurements. Finally, using our inverse approach we systematically tested different erosional scenarios. We find that sedimentary flux to Africa's passive margins is controlled up the history of uplift and erosional processes play a moderating role. Predicted fluxes are indistinguishable if precipitation rate varies with a period less than ˜ 1 Ma or drainage area varies by less than 50%. To investigate the geodynamic setting of the Mauritanian margin we backstripped eight commercial wells that penetrate Neogene stratigraphy. Wells in the central part of the Mauritania basin include 500-800 m of Neogene water

The origin and fate of 4-methyl steroid hydrocarbons. I. Diagenesis of 4-methyl sterenes

NASA Astrophysics Data System (ADS)

Wolff, George A.; Lamb, Neil A.; Maxwell, James R.

1986-03-01

Treatment of 4-methylcholest-4-ene under mild acid conditions at low temperatures gives chemical evidence for certain features seen in the distributions of sedimentary 4-methyl steroid hydrocarbons, and further indicates that many low temperature diagenetic reactions of steroids are explicable in terms of acid catalysed rearrangements. Specifically, the results provide: (i) Indirect evidence that the 4-ene skeleton is a key intermediate in the dehydration of 4-methyl stanols in sediments. (ii) An explanation for the distribution of 4-methyl sterenes and A-nor sterenes in the lacustrine Messel shale (Eocene). (iii) An explanation for the presence of 4β-methyl steranes in relatively immature sedimentary rocks, despite the precursor stanols having the 4α-methyl configuration. With increasing maturity in the Paris Basin shales (Lower Toarcian), the less stable 4β-methyl steranes decrease gradually in abundance relative to their 4α-methyl counterparts, at a rate fairly similar to the change in pristane stereochemistry.

3D mechanical stratigraphy of a deformed multi-layer: Linking sedimentary architecture and strain partitioning

NASA Astrophysics Data System (ADS)

Cawood, Adam J.; Bond, Clare E.

2018-01-01

Stratigraphic influence on structural style and strain distribution in deformed sedimentary sequences is well established, in models of 2D mechanical stratigraphy. In this study we attempt to refine existing models of stratigraphic-structure interaction by examining outcrop scale 3D variations in sedimentary architecture and the effects on subsequent deformation. At Monkstone Point, Pembrokeshire, SW Wales, digital mapping and virtual scanline data from a high resolution virtual outcrop have been combined with field observations, sedimentary logs and thin section analysis. Results show that significant variation in strain partitioning is controlled by changes, at a scale of tens of metres, in sedimentary architecture within Upper Carboniferous fluvio-deltaic deposits. Coupled vs uncoupled deformation of the sequence is defined by the composition and lateral continuity of mechanical units and unit interfaces. Where the sedimentary sequence is characterized by gradational changes in composition and grain size, we find that deformation structures are best characterized by patterns of distributed strain. In contrast, distinct compositional changes vertically and in laterally equivalent deposits results in highly partitioned deformation and strain. The mechanical stratigraphy of the study area is inherently 3D in nature, due to lateral and vertical compositional variability. Consideration should be given to 3D variations in mechanical stratigraphy, such as those outlined here, when predicting subsurface deformation in multi-layers.

Sea-floor morphology and sedimentary environments in western Block Island Sound, offshore of Fishers Island, New York

USGS Publications Warehouse

McMullen, Katherine Y.; Poppe, Lawrence J.; Danforth, William W.; Blackwood, Dann S.; Winner, William G.; Parker, Castle E.

2015-01-01

Multibeam-bathymetric and sidescan-sonar data, collected by the National Oceanic and Atmospheric Administration in a 114-square-kilometer area of Block Island Sound, southeast of Fishers Island, New York, are combined with sediment samples and bottom photography collected by the U.S. Geological Survey from 36 stations in this area in order to interpret sea-floor features and sedimentary environments. These interpretations and datasets provide base maps for studies on benthic ecology and resource management. The geologic features and sedimentary environments on the sea floor are products of the area’s glacial history and modern processes. These features include bedrock, drumlins, boulders, cobbles, large current-scoured bathymetric depressions, obstacle marks, and glaciolacustrine sediments found in high-energy sedimentary environments of erosion or nondeposition; and sand waves and megaripples in sedimentary environments characterized by coarse-grained bedload transport. Trawl marks are preserved in lower energy environments of sorting and reworking. This report releases the multibeam-bathymetric, sidescan-sonar, sediment, and photographic data and interpretations of the features and sedimentary environments in Block Island Sound, offshore Fishers Island.

Sedimentary Environment Changes between Tsunami Events in the Central Fukushima Prefecture, Japan

NASA Astrophysics Data System (ADS)

Kusumoto, S.; Goto, T.; Satake, K.; Sugai, T.; Yoneda, M.; Omori, T.; Ozaki, H.

2016-12-01

Many tsunami deposits were found in the Tohoku region, Japan from recent and past tsunamis. Study of tsunami deposits is particularly important in the central to southern Fukushima Prefecture, which is the southern limit of the distributions of tsunami deposits of the 869 Jogan, 1454 Kyotoku and 1611 Keicho-Sanriku earthquakes. Previous studies reported that there were at least five tsunami deposits (EV1-EV5) consisted of fine-middle sand and the sedimentary environment was inner-bay or lagoon for the past 2,600 years (Goto and Aoyama, 2005; JpGU, Oikawa et al., 2011; JpGU, Oota and Hoyanagi, 2014; GSJ, Kusumoto et al., 2016; JpGU). However, the sedimentary environment changes between or across historical tsunamis have not been examined. In this study, we try to estimate the sedimentary environment changes using Total Organic Carbon (TOC), Total Nitrogen (TN) concentrations and organic Carbon-to-Nitrogen (C/N) ratio. We took 13 geological core samples of length 2.0-2.5 m at 11 locations 0.6-2.7 km from the coast. The deposits consisted of silt and massive sand with graded beddings, laminas and rip-up clasts. For samples, we performed grain-size analysis, radiocarbon age measurement and CN elemental analysis. We found three interesting characteristics. First, grain size of ordinary deposits between EV4 and EV5 tend to fine upward slightly. It suggests that tidal current became gradually weak. Second, C/N ratio is about 5-10 at every depth, meaning that organic material source was phytoplankton or zooplankton (Müller, 1977; GCA). Finally, TOC and TN concentrations slowly increase between EV4 and EV5, and they rapidly decrease across EV3 and EV4. Their slow increases correspond to sedimentary environment change from anaerobic to aerobic, whereas rapid decreases correspond to sedimentary environment change from aerobic to anaerobic. These characteristics might indicate development of sand bar between tsunami events and sudden collapse of sand bar by historical

In-situ Micro-structural Studies of Gas Hydrate Formation in Sedimentary Matrices

NASA Astrophysics Data System (ADS)

Kuhs, Werner F.; Chaouachi, Marwen; Falenty, Andrzej; Sell, Kathleen; Schwarz, Jens-Oliver; Wolf, Martin; Enzmann, Frieder; Kersten, Michael; Haberthür, David

2015-04-01

The formation process of gas hydrates in sedimentary matrices is of crucial importance for the physical and transport properties of the resulting aggregates. This process has never been observed in-situ with sub-micron resolution. Here, we report on synchrotron-based micro-tomographic studies by which the nucleation and growth processes of gas hydrate were observed in different sedimentary matrices (natural quartz, glass beds with different surface properties, with and without admixtures of kaolinite and montmorillonite) at varying water saturation. The nucleation sites can be easily identified and the growth pattern is clearly established. In under-saturated sediments the nucleation starts at the water-gas interface and proceeds from there to form predominantly isometric single crystals of 10-20μm size. Using a newly developed synchrotron-based method we have determined the crystallite size distributions (CSD) of the gas hydrate in the sedimentary matrix confirming in a quantitative and statistically relevant manner the impressions from the tomographic reconstructions. It is noteworthy that the CSDs from synthetic hydrates are distinctly smaller than those of natural gas hydrates [1], which suggest that coarsening processes take place in the sedimentary matrix after the initial hydrate formation. Understanding the processes of formation and coarsening may eventually permit the determination of the age of gas hydrates in sedimentary matrices [2], which are largely unknown at present. Furthermore, the full micro-structural picture and its evolution will enable quantitative digital rock physics modeling to reveal poroelastic properties and in this way to support the exploration and exploitation of gas hydrate resources in the future. [1] Klapp S.A., Hemes S., Klein H., Bohrmann G., McDonald I., Kuhs W.F. Grain size measurements of natural gas hydrates. Marine Geology 2010; 274(1-4):85-94. [2] Klapp S.A., Klein H, Kuhs W.F. First determination of gas hydrate

New Insights into the Provenance of the Southern Junggar Basin in the Jurassic from Heavy Mineral Analysis and Sedimentary Characteristics

NASA Astrophysics Data System (ADS)

Zhou, T. Q.; Wu, C.; Zhu, W.

2017-12-01

Being a vital component of foreland basin of Central-western China, Southern Junggar Basin has observed solid evidences of oil and gas in recent years without a considerable advancement. The key reason behind this is the lack of systematic study on sedimentary provenance analysis of the Southern Junggar basin. Three parts of the Southern Junggar basin, including the western segment (Sikeshu Sag), the central segment (Qigu Fault-Fold Belt) and the eastern segment (Fukang Fault Zone), possess varied provenance systems, giving rise to difficulties for oil-gas exploration. In this study, 3468 heavy minerals data as well as the sedimentary environment analysis of 10 profiles and 7 boreholes were used to investigate the provenances of the deposits in the southern Junggar basin . Based on this research, it reveals that: Sikeshu sag initially shaped the foreland basin prototype in the Triassic and its provenance area of the sediments from the Sikeshu sag has primarily been situated in zhongguai uplift-chepaizi uplift depositional systems located in the northwestern margin of the Junggar Basin. From the early Jurassic, the key sources were likely to be late Carboniferous to early Permain post-collisional volcanic rocks from the North Tian Shan block to Centrao Tian Shan. In the Xishanyao formation, Abundant lithic metamorphic, epidote and garnet that suggests the source rocks were possibly late Carboniferous subduction-related arc volcanic rocks of the Central Tian Shan. In the Toutunhe formation, Bogda Mountains began uplifting and gradually becoming the major provenance. Moreover, the sedimentary boundaries of Junggar basin have also shifted towards the North Tian Shan again. In the late Jurassic, the conglomerates of the Kalazha formation directly overlie the fine-grained red beds of Qigu formation, which throw light on the rapid tectonic uplift of the North Tian Shan. In the eastern segment, meandering river delta and shore-lacustrine environments were fully developed

Hydrogeologic framework of sedimentary deposits in six structural basins, Yakima River basin, Washington

USGS Publications Warehouse

Jones, M.A.; Vaccaro, J.J.; Watkins, A.M.

2006-01-01

The hydrogeologic framework was delineated for the ground-water flow system of the sedimentary deposits in six structural basins in the Yakima River Basin, Washington. The six basins delineated, from north to south are: Roslyn, Kittitas, Selah, Yakima, Toppenish, and Benton. Extent and thicknesses of the hydrogeologic units and total basin sediment thickness were mapped for each basin. Interpretations were based on information from about 4,700 well records using geochemical, geophysical, geologist's or driller's logs, and from the surficial geology and previously constructed maps and well interpretations. The sedimentary deposits were thickest in the Kittitas Basin reaching a depth of greater than 2,000 ft, followed by successively thinner sedimentary deposits in the Selah basin with about 1,900 ft, Yakima Basin with about 1,800 ft, Toppenish Basin with about 1,200 ft, Benton basin with about 870 ft and Roslyn Basin with about 700 ft.

A process-sedimentary framework for characterizing recent and ancient sabkhas

USGS Publications Warehouse

Handford, C.R.

1981-01-01

The discovery of sabkha environments during the 1960's, marked the beginning of Recent evaporite sedimentological studies and their perception as models for facies analysis. However, variation among Recent sabkhas, though recognized by the geologic community, has not been duly addressed, which has resulted in overuse of the Trucial Coast model in comparative sedimentological studies. Knowledge of the dominant physical processes which determine sabkha morphology, and of the sedimentary response to those processes, can lead to a fundamental understanding of a sabkha's origin and of how it differs from other sabkhas. Physical processes thought to be most important (besides evaporation) include those operative under: (1) marine-; (2) fluvial-lacustrine-; and (3) eolian-dominated conditions. Dominance of one or more of these in the proper settings give rise to marine coastal sabkhas, continental playas, and interdune sabkhas. Sedimentary responses to dominant physical processes lead to the development of sabkhas consisting of a combination of either: (1) terrigenous clastics; (2) carbonate-sulfate (anhydrite-gypsum) minerals; or (3) soluble salts (halite, sylvite, polyhalite, etc.). Sediment characterization can also allow discrimination of the range or compositional variety in, for example, coastal sabkhas. Where applied to the stratigraphic record, this classification system may help unravel the sedimentary history of an ancient sabkha system, and a determination of the dominant physical processes that ruled its development. ?? 1981.

Contribution of NAD 2D-NMR in liquid crystals to the determination of hydrogen isotope profile of methyl groups in miliacin

NASA Astrophysics Data System (ADS)

Berdagué, Philippe; Lesot, Philippe; Jacob, Jérémy; Terwilliger, Valery J.; Le Milbeau, Claude

2016-01-01

The hydrogen isotopic composition (δD or (D/H) value) of molecular biomarkers preserved in sedimentary archives is increasingly used to provide clues about the evolution of past climatic conditions. The rationale is that intact biomarkers retain isotopic information related to the climatic conditions that prevailed at the time of their synthesis. Some of these biomarkers may be degraded during diagenesis, however. The extent to which these degradations alter the original δD value of the source biomarker is presently debated and the capacity to resolve this question by determination of compound-specific δD values alone is limited. The ;bulk; or ;global; δD value of any molecule is in fact a composite of δD values at each site within this molecule (δDi or (D/H)i with i = number of hydrogen/deuterium atoms in the considered molecule). Determination of this site-specific δDi value in biomarkers could not only yield outstanding paleoenvironmental information but also help forecast the impacts of diagenesis and define essential steps in biosynthetic pathways. This task is analytically challenging. Here, we examined the capabilities of natural abundance deuterium 2D-NMR (NAD 2D-NMR) using homopolypeptide liquid crystals as an NMR solvent to: (i) analyze the NAD spectra of biomakers; (ii) determine the site-specific distribution of hydrogen in the nine methyl groups (δDMei with i = 23-31) of miliacin, a pentacyclic triterpene of the amyrin family and key biomarker for broomcorn millet in sedimentary archives. Relative (D/H)Mei values were established by anisotropic NAD 2D-NMR. Then absolute δDMei values were obtained by determining δDMei value of the methoxy group of miliacin using two independent approaches: isotropic NAD NMR (SNIF-NMR™) and GC-irMS. The resulting isotope profile for miliacin shows, for the first time, large variations in δDMei values that can directly be explained by biosynthetic processes. This approach has also the potential to permit

Developing a Trace Element Biosignature for Early Earth and Mars

NASA Astrophysics Data System (ADS)

Gangidine, A.; Czaja, A. D.; Havig, J.

2018-04-01

Due to metamorphism and diagenesis, determining the biogenicity of ancient fossils is difficult and often contentious. Using trace element concentrations, we propose a novel biosignature independent from organic and morphological preservation.

Geothermal resources of California sedimentary basins

USGS Publications Warehouse

Williams, C.F.; Grubb, F.V.; Galanis, S.P.

2004-01-01

The 2004 Department of Energy (DOE) Strategic Plan for geothermal energy calls for expanding the geothermal resource base of the United States to 40,000 MW of electric power generating potential. This will require advances in technologies for exploiting unconventional geothermal resources, including Enhanced Geothermal Systems (EGS) and geopressured geothermal. An investigation of thermal conditions in California sedimentary basins through new temperature and heat flow measurements reveals significant geothermal potential in some areas. In many of the basins, the combined cooling effects of recent tectonic and sedimentary processes result in relatively low (<60 mW/m2) heat flow and geothermal gradients. For example, temperatures in the upper 3 km of San Joaquin, Sacramento and Ventura basins are typically less than 125??C and do not reach 200??c by 5 km. By contrast, in the Cuyama, Santa Maria and western Los Angeles basins, heat flow exceeds 80 mW/m2 and temperatures near or above 200??C occur at 4 to 5 km depth, which represents thermal conditions equivalent to or hotter than those encountered at the Soultz EGS geothermal site in Europe. Although the extractable geothermal energy contained in these basins is not large relative to the major California producing geothermal fields at The Geysers or Salton Sea, the collocation in the Los Angeles basin of a substantial petroleum extraction infrastructure and a major metropolitan area may make it attractive for eventual geothermal development as EGS technology matures.

Non-steady state diagenesis of organic and inorganic sulfur in lake sediments

NASA Astrophysics Data System (ADS)

Couture, Raoul-Marie; Fischer, Rachele; Van Cappellen, Philippe; Gobeil, Charles

2016-12-01

Sulfur controls the fate of many geochemical elements in lake sediments, including iron, phosphorus and environmentally important trace elements. We measured the speciation of pore-water and sediment-bound sulfur (aqueous sulfate and sulfides, elemental sulfur, iron monosulfide, pyrite, organic sulfur) and supporting geochemical variables (carbon, oxygen, iron) in the sediments of a perennially oxygenated and a seasonally anoxic basin of an oligotrophic lake in Québec, using a combination of pore-water analyses, sequential extractions and X-ray absorption near edge structure. A non-steady state early diagenetic model was developed and calibrated against this extensive dataset to help unravel the pathways and quantify the rates of S transformations. Results suggest that the main source of S to the sediments is the settling of organic ester-sulfate (R-O-SO3-H). Hydrolysis of these compounds provides an additional source of sulfate for anaerobic microbial oxidation of sedimentary organic matter, releasing sulfide to the pore-water. Reduced solid-bound S species accumulate as thiols (R-SH) and iron sulfides in the perennially oxygenated and seasonally anoxic basin, respectively. The model-estimated rate constant for R-SH formation is lower than previously estimated for this particular lacustrine site, but similar to that proposed for marine shelf sediments. The solid sediment S profiles, however, carry the imprint of the time-dependent sulfate input to the lake. Iron sulfide enrichments formed during past decades of elevated atmospheric SO4 deposition are presently dissolving. In the sediments of the perennially oxygenated basin this reaction hampers the build-up of Fe(III) (oxy)hydroxide near the sediment-water interface.

[Distribution Characteristics of Sedimentary Pigments in the Changjiang Estuary and Zhe-Min Coast and its Implications].

PubMed

Li, Dong; Yao, Peng; Zhao, Bin; Wang, Jin-peng; Pan, Hui-hui

2015-08-01

Compositions and contents of sedimentary pigments were examined using high performance liquid chromatography in order to discuss the spatial distributions of phytoplankton primary production, phytoplankton functional type and the preservation efficiency of phytoplankton pigments and their influencing factors. The results showed that: chloropigments [Chlorins, including chlorophyll-a (Chl-a) and pheopigments (Pheo-a), such as pheophytin-a (PHtin-a), pheophorbide-a (PHide-a), pPheophytin-a (pPHtin-a), sterol chlorin esters (SCEs) and carotenol chlorin esters (CCEs)] were the major type of sedimentary pigments. The nutrients inputs from Changjiang Diluted Water and upwelling in the Zhe-Min coastal mud area were the major cause for the patchy distribution with high sedimentary chloropigment contents. Carotenoid contents showed no trending changes and exhibited high values in the Changjiang Estuary and Zhe-Min Coasts. Based on the relative proportions of each diagnostic carotenoid to the total diagnostic carotenoids in the sediments, the relative contributions of diatoms, dinoflagellates, prymnesiophytes, prasinophytes, cryptophytes and cyanobacterias in the phytoplankton fuctional types were 48.8% +/- 17.4%, 10.7% +/- 11.5%, 8.1% +/- 7.2%, 18.6% +/- 8.2%, 9.4% +/- 6.4% and 4.3% +/- 3.2%, respectively. The preference for external environmental conditions (e.g., nutrient level and water salinity) was the main cause for the decreasing trends of diatoms and dinoflagellates proportions and the increasing trends of prasinophytes, cryptophytes and cyanobacterias seawards. Based on the spatial distribution of Chl-a/Pheo-a ratios, the higher preservation efficiencies of sedimentary pigments in the coastal regions (e.g., outer edge of maximum turbidity zone in the Changjiang Estuary, mouth of the Hangzhou Bay and upwelling region in the Zhe-Min Coast) were mainly due to the higher sedimentation rate and seasonal occurrences of hypoxia in bottom water, and these regions with

Late Pleistocene dune-sourced alluvial fans in coastal settings: Sedimentary facies and related processes (Mallorca, Western Mediterranean)

NASA Astrophysics Data System (ADS)

Pomar, F.; del Valle, L.; Fornós, J. J.; Gómez-Pujol, L.

2018-05-01

Aeolian-alluvial sedimentary interaction results in the formation of deposits characterized by typical alluvial sedimentary structures, but is composed of conspicuous amounts of aeolian sediments. The literature on this topic is limited and most works relate more with continental aeolian dunes or fluvial dune interference with fan bodies. Furthermore, there is a lack of examples of aeolian-alluvial sedimentary interference in coastal settings. In the western Mediterranean, there are many Pleistocene alluvial fan deposits built up partly by sediment originating from coastal dunes dismantled by alluvial streams. Very often, these deposits show a continuous sedimentary sequence through which we can derive the contribution and predominance of coastal, alluvial-colluvial and aeolian processes and their controls on landscape formation. This is an outstanding feature within coastal systems since it shows marine sediments reworked and integrated within coastal dune fields by aeolian transport, and the latter built up into alluvial fan bodies. In this sense, aeolian-alluvial interaction is the geomorphic-sedimentary expression of the coexistence and overlapping of alluvial and aeolian environments resulting in deposits sharing sedimentary features from both environments. The aim of this paper is to unravel the contribution of coastal dunes in the construction of alluvial fans bodies and identify the main sedimentary facies that constitute these deposits, as well as their climatic controls. For this reason, Es Caló fan (northern Mallorca) has been selected due to its well-exposed deposits exhibiting the alternation of aeolian, alluvial and colluvial deposits. Sedimentological and stratigraphic analyses based on 33 logs and complementary analyses demonstrate that most of the facies constituting the fan body are made up completely of marine bioclastic sands. These deposits record an alluvial fan sedimentary environment characterized by sediments inputs that do not proceed

Discriminating sediment archives and sedimentary processes in the arid endorheic Ejina Basin, NW China using a robust geochemical approach

NASA Astrophysics Data System (ADS)

Yu, Kaifeng; Hartmann, Kai; Nottebaum, Veit; Stauch, Georg; Lu, Huayu; Zeeden, Christian; Yi, Shuangwen; Wünnemann, Bernd; Lehmkuhl, Frank

2016-04-01

, aeolian sand input, whereas pedogenesis and diagenesis exert only limited influences. Hence, this study demonstrates a practical geochemical strategy supplemented by grain size and mineralogical data, to discriminate sediment archives and thereafter enhance our ability to offer more intriguing information about the sedimentary processes in the arid central Asia.

Sedimentary record of erg migration

NASA Astrophysics Data System (ADS)

Porter, M. L.

1986-06-01

The sedimentary record of erg (eolian sand sea) migration consists of an idealized threefold division of sand-sea facies sequences. The basal division, here termed the fore-erg, is composed of a hierarchy of eolian sand bodies contained within sediments of the flanking depositional environment. These sand bodies consist of eolian strata deposited by small dune complexes, zibars, and sand sheets. The fore-erg represents the downwind, leading edge of the erg and records the onset of eolian sedimentation. Basin subsidence coupled with erg migration places the medial division, termed the central erg, over the fore-erg strata. The central erg, represented by a thick accumulation of large-scale, cross-stratified sandstone, is the product of large draa complexes. Eolian influence on regional sedimentation patterns is greatest in the central erg, and most of the sand transported and deposited in the erg is contained within this region. Reduction in sand supply and continued erg migration will cover the central-erg deposits with a veneer of back-erg deposits. This upper division of the erg facies sequence resembles closely the fore-erg region. Similar types of eolian strata are present and organized in sand bodies encased in sediments of the upwind flanking depositional environment(s). Back-erg deposits may be thin due to limited eolian influence on sedimentation or incomplete erg migration, or they may be completely absent because of great susceptibility to postdepositional erosion. Tectonic, climatic, and eustatic influences on sand-sea deposition will produce distinctive variations or modifications of the idealized erg facies sequence. The resulting variants in the sedimentary record of erg migration are illustrated with ancient examples from western North America, Europe, southern Africa, and South America.

Microbially mediated carbon cycling as a control on the δ 13C of sedimentary carbon in eutrophic Lake Mendota (USA): new models for interpreting isotopic excursions in the sedimentary record

NASA Astrophysics Data System (ADS)

Hollander, David J.; Smith, Michael A.

2001-12-01

An isotopic study of various carbon phases in eutrophic Lake Mendota (Wisconsin, USA) indicates that the δ13C composition of sedimentary organic and inorganic carbon has become more negative in response to increasing microbially mediated carbon cycling and processes associated with the intensification of seasonal and long-term eutrophication. Progressive increases in the contributions of isotopically depleted chemoautotrophic and methanotrophic biomass (reflected in the -40 to -90‰ values of hopanols and FAMES), attributed to seasonal and long-term increases in production and expansion of the anaerobic water mass, accounts for carbon isotopic trends towards depleted δ13C values observed in both seasonal varves and over the past 100 years. Changes in the intensities of certain microbial processes are also evident in the sedimentary geochemical record. During the period of most intense cultural eutrophication, when the oxic-anoxic interface was located close to the surface, methanogenesis/methanotrophy and the oxidation of biogenic methane increased to the extent that significant quantities of 13C-depleted CO2 were added into the epilimnion. This depleted CO2 was subsequently utilized by phytoplankton and incorporated into CaCO3 during biogenically induced calcite precipitation. A comparative study between eutrophic Lakes Mendota and Greifen, further indicate that the extent of nutrient loading in the epilimnion determines whether the δ13C record of sedimentary organic carbon reflects intensification of microbial processes in the hypolimnion and sediments, or changes in the primary productivity in the photic zone. From this comparison, a series of eutrophication models are developed to describe progressive transitions through thresholds of microbial and eukaryotic productivity and their influence on the δ13C record of sedimentary carbon. With increasing eutrophication, the models initially predict a negative and then a subsequent positive carbon isotopic

Sedimentary noise and sea levels linked to land-ocean water exchange and obliquity forcing.

PubMed

Li, Mingsong; Hinnov, Linda A; Huang, Chunju; Ogg, James G

2018-03-08

In ancient hothouses lacking ice sheets, the origins of large, million-year (myr)-scale sea-level oscillations remain a mystery, challenging current models of sea-level change. To address this mystery, we develop a sedimentary noise model for sea-level changes that simultaneously estimates geologic time and sea level from astronomically forced marginal marine stratigraphy. The noise model involves two complementary approaches: dynamic noise after orbital tuning (DYNOT) and lag-1 autocorrelation coefficient (ρ 1 ). Noise modeling of Lower Triassic marine slope stratigraphy in South China reveal evidence for global sea-level variations in the Early Triassic hothouse that are anti-phased with continental water storage variations in the Germanic Basin. This supports the hypothesis that long-period (1-2 myr) astronomically forced water mass exchange between land and ocean reservoirs is a missing link for reconciling geological records and models for sea-level change during non-glacial periods.

Copper Deposits in Sedimentary and Volcanogenic Rocks

USGS Publications Warehouse

Tourtelot, Elizabeth B.; Vine, James David

1976-01-01

Copper deposits occur in sedimentary and volcanogenic rocks within a wide variety of geologic environments where there may be little or no evidence of hydrothermal alteration. Some deposits may be hypogene and have a deep-seated source for the ore fluids, but because of rapid cooling and dilution during syngenetic deposition on the ocean floor, the resulting deposits are not associated with hydrothermal alteration. Many of these deposits are formed at or near major tectonic features on the Earth's crust, including plate boundaries, rift valleys, and island arcs. The resulting ore bodies may be stratabound and either massive or disseminated. Other deposits form in rocks deposited in shallow-marine, deltaic, and nonmarine environments by the movement and reaction of interstratal brines whose metal content is derived from buried sedimentary and volcanic rocks. Some of the world's largest copper deposits were probably formed in this manner. This process we regard as diagenetic, but some would regard it as syngenetic, if the ore metals are derived from disseminated metal in the host-rock sequence, and others would regard the process as epigenetic, if there is demonstrable evidence of ore cutting across bedding. Because the oxidation associated with diagenetic red beds releases copper to ground-water solutions, red rocks and copper deposits are commonly associated. However, the ultimate size, shape, and mineral zoning of a deposit result from local conditions at the site of deposition - a logjam in fluvial channel sandstone may result in an irregular tabular body of limited size; a petroleum-water interface in an oil pool may result in a copper deposit limited by the size and shape of the petroleum reservoir; a persistent thin bed of black shale may result in a copper deposit the size and shape of that single bed. The process of supergene enrichment has been largely overlooked in descriptions of copper deposits in sedimentary rocks. However, supergene processes may be

Origin and time-space distribution of hydrothermal systems in east-central Australian sedimentary basins: Constraints from illite geochronology and isotope geochemistry.

NASA Astrophysics Data System (ADS)

Uysal, I. Tonguç

2016-04-01

Some well-known precious mineral deposits and hydrocarbon resources occur extensively in east-central Australian sedimentary Basins. The metal occurrences are abundant in northwestern and eastern part of Queensland, whereas no significant deposits are known in large areas further south, which may, however, be hidden beneath the Jurassic-Cretaceous sedimentary basins. Important hydrocarbon resources exist within the Jurassic-Cretaceous sedimentary rocks at relatively shallow depths, of which the distribution represent zones of high paleo-geothermal gradients. This study examines the time-space distribution in relation to the regional tectonic history of concealed metal deposits and areas of high paleo-geothermal gradient leading to hydrocarbon maturation. To this end, authigenic illitic clay minerals representing various locations and stratigraphic depths in east-central Australia were investigated, of which the Rb-Sr and Ar-Ar geochronology and stable isotope geochemistry assist in delineating zones of hydrothermal systems responsible for hydro-carbon maturation/migration and potentially ore deposition. The Late Carboniferous - Early Permian crustal extension that affected large areas of eastern Australia and led to the epithermal mineralisations (e.g., the Drummond Basin) is also recorded in northern South Australia and southwest Queensland. A Late Triassic - Early Jurassic tectonic event being responsible for coal maturation and gas generation in the Bowen Basin and the epithermal mineralisation in the North Arm goldfield in SE Queensland likewise affected the areas much further west in Queensland. Some illites from the basement in outback Queensland and fault gouges from the Demon Fault in NE New South Wales yield younger Rb-Sr and Ar-Ar ages indicating the effect of hydrothermal processes as a result of a Middle-Upper Jurassic tectonic event. The majority of illite samples from the crystalline basement rocks, Permian Cooper Basin, and Jurassic

Sedimentary Carbon Stocks: A National Assessment of Scotland's Fjords.

NASA Astrophysics Data System (ADS)

Smeaton, Craig; Austin, William; Davies, Althea; Howe, John

2017-04-01

Coastal sediments have been shown to be globally significant repositories for carbon (C) with an estimated 126.2 Tg of C being buried annually (Duarte et al. 2005). Though it is clear these areas are important for the long-term storage of C the actual quantity of C held within coastal sediment remains largely unaccounted for. The first step to understanding the role the coastal ocean plays in the global C cycle is to quantify the C held within these coastal sediments. Of the different coastal environment fjords have been shown to be hotspots for C burial with approximately 11 % of the annual global marine carbon sequestration occurring within fjordic environments (Smith et al. 2015). Through the development of a joint geophysical and geochemical methodology we estimated that the sediment in a mid-latitude fjord holds 26.9 ± 0.5 Mt of C (Smeaton et al., 2016), with these results suggesting that Scottish mid-latitude fjords could be a significant unaccounted store of C equivalent to their terrestrial counterparts (i.e. peatlands). Through the application of the joint geophysical and geochemical methodology developed by Smeaton et al (2016) to a number of other mid-latitude fjords, we will create detailed estimations of the sedimentary C stored at these individual sites. Using these detailed C stock estimations in conjunction with upscaling techniques we will establish the first national estimation of fjordic sedimentary C stocks. The data produced will allow for the sedimentary C stocks to be compared to other national C stocks, such as the Scottish peatlands (Chapman et al. 2009) and forestry (Forestry Commission, 2016). Alongside quantifying this large unaccounted for store of C in the coastal ocean this work also lays foundations for future work to understand the role of the coastal ocean in the global C cycle. Duarte, C. M., Middelburg, J. J., and Caraco, N.: Major role of marine vegetation on the oceanic carbon cycle, Biogeosciences, 2, 1-8, doi:10.5194/bg-2

Using Aluminum Foil to Record Structures in Sedimentary Rock.

ERIC Educational Resources Information Center

Metz, Robert

1982-01-01

Aluminum foil can be used to make impressions of structures preserved in sedimentary rock. The impressions can be projected onto a screen, photographed, or a Plaster of Paris model can be made from them. Impressions of ripple marks, mudcracks, and raindrop impressions are provided in photographs illustrating the technique. (Author/JN)

Sea-floor morphology and sedimentary environments in southern Narragansett Bay, Rhode Island

USGS Publications Warehouse

McMullen, Katherine Y.; Poppe, Lawrence J.; Blackwood, Dann S.; Nardi, Matthew J.; Andring, Matthew A.

2015-09-09

Multibeam echosounder data collected by the National Oceanic and Atmospheric Administration along with sediment samples and still and video photography of the sea floor collected by the U.S. Geological Survey were used to interpret sea-floor features and sedimentary environments in southern Narragansett Bay, Rhode Island, as part of a long-term effort to map the sea floor along the northeastern coast of the United States. Sea-floor features include rocky areas and scour depressions in high-energy environments characterized by erosion or nondeposition, and sand waves and megaripples in environments characterized by coarse-grained bedload transport. Two shipwrecks are also located in the study area. Much of the sea floor is relatively featureless within the resolution of the multibeam data; sedimentary environments in these areas are characterized by processes associated with sorting and reworking. This report releases bathymetric data from the multibeam echosounder, grain-size analyses of sediment samples, and photographs of the sea floor and interpretations of the sea-floor features and sedimentary environments. It provides base maps that can be used for resource management and studies of topics such as benthic ecology, contaminant inventories, and sediment transport.

Amorphous silica maturation in chemically weathered clastic sediments

NASA Astrophysics Data System (ADS)

Liesegang, Moritz; Milke, Ralf; Berthold, Christoph

2018-03-01

A detailed understanding of silica postdepositional transformation mechanisms is fundamental for its use as a palaeobiologic and palaeoenvironmental archive. Amorphous silica (opal-A) is an important biomineral, an alteration product of silicate rocks on the surface of Earth and Mars, and a precursor material for stable silica phases. During diagenesis, amorphous silica gradually and gradationally transforms to opal-CT, opal-C, and eventually quartz. Here we demonstrate the early-stage maturation of several million year old opal-A from deeply weathered Early Cretaceous and Ordovician sedimentary rocks of the Great Artesian Basin (central Australia). X-ray diffraction, scanning electron microscopy, and electron probe microanalyses show that the mineralogical maturation of the nanosphere material is decoupled from its chemical properties and begins significantly earlier than micromorphology suggests. Non-destructive and locally highly resolved X-ray microdiffraction (μ-XRD2) reveals an almost linear positive correlation between the main peak position (3.97 to 4.06 Å) and a new asymmetry parameter, AP. Heating experiments and calculated diffractograms indicate that nucleation and growth of tridymite-rich nanodomains induce systematic peak shifts and symmetry variations in diffraction patterns of morphologically juvenile opal-A. Our results show that the asymmetry parameter traces the early-stage maturation of amorphous silica, and that the mineralogical opal-A/CT stage extends to smaller d-spacings and larger FWHM values than previously suggested.

An evaluation of multiband photography for rock discrimination. [sedimentary rocks of Front Range, Colorado

NASA Technical Reports Server (NTRS)

Lee, K. (Principal Investigator); Raines, G. L.

1974-01-01

The author has identified the following significant results. With the advent of ERTS and Skylab satellites, multiband imagery and photography have become readily available to geologists. The ability of multiband photography to discriminate sedimentary rocks was examined. More than 8600 in situ measurements of band reflectance of the sedimentary rocks of the Front Range, Colorado, were acquired. Statistical analysis of these measurements showed that: (1) measurements from one site can be used at another site 100 miles away; (2) there is basically only one spectral reflectance curve for these rocks, with constant amplitude differences between the curves; and (3) the natural variation is so large that at least 150 measurements per formation are required to select best filters. These conclusions are supported by subjective tests with aerial multiband photography. The designed multiband photography concept for rock discrimination is not a practical method of improving sedimentary rock discrimination capabilities.

Mantle convective support, drainage patterns and sedimentary flux: Examples from the West Africa passive margin

NASA Astrophysics Data System (ADS)

Lodhia, B. H.; Roberts, G. G.; Fraser, A.; Goes, S. D. B.; Fishwick, S.; Jarvis, J.

2017-12-01

Sedimentary flux measurements, regional subsidence patterns, inversion of drainage patterns, tomographic models and simple isostatic calculations are combined to constrain the history of sub-plate support of North West Africa. Backstripping of 8 commercial wells and mapping of 53,000 line-km of 2D seismic reflection data show that rapid ( 0.03 mm a-1) Neogene-Recent subsidence occurred in a 500 x 500 km region offshore Mauritania. 0.4-0.8 km of water-loaded subsidence occurred in the center of the basin during the last 23 Ma. Salt withdrawal, thin-skinned tectonics, glacio-eustasy and flexure of the lithosphere due to the emplacement of Cape Verde cannot explain the timing or magnitude of this phase of subsidence. Instead, conversion of shear wave velocities into temperature and simple isostatic calculations indicate that asthenospheric temperatures determine bathymetry from Cape Verde to West Africa. Our results indicate that asthenospheric flow from Cape Verde to Mauritania generated a bathymetric gradient of 1/300 at a wavelength of 103 km during the last 23 Ma. We explore the relationship between uplift and erosion onshore and measured solid sedimentary flux offshore. First, the history of sedimentary flux to the margin was determined by depth-converting and decompacting biostratigraphically-dated isopachs. Compaction and velocity errors, determined using check-shot data, were propagated into calculated sedimentary flux history. Solid-sedimentary flux rates of 0.2-0.1+0.2 ×103 km3 /Ma between 23.8-5.6 Ma, and 1.9-1.4+2.0 ×103 km3 /Ma from 5.6-0 Ma are observed. Secondly, a calibrated stream power erosional model was used to invert 14700 river profiles for a history of regional uplift rate. Incision rates were integrated along best-fitting theoretical river profiles to predict sedimentary flux at mouths of the rivers draining NW Africa. Our predicted history of sedimentary flux increases in two stages towards the present-day, in agreement with our offshore

Use of laboratory simulated pyrolysis in tracing the history of sedimentary organic matter

NASA Technical Reports Server (NTRS)

Kaplan, I. R.; Tannenbaum, E.; Huizinga, B. E.

1986-01-01

Results from laboratory simulated pyrolyses experiments show that in addition to depth of burial, preservation of kerogen, and hence any morphologic structure in it, is also dependent on the mineral matrix with which it is associated. In the presence of clay minerals, and especially under dry conditions, extractable lipids released during kerogen decomposition are more rapidly destroyed than in the presence of calcite or chert matrices. The result is production of gas, polar bitumen and pyrobitumen and destruction of biomarkers. During such an early reorganization of the kerogen, the biomarker constituents can be destroyed, or unrecognizably altered. The above process of organic residues maturation appears to be inhibited in the presence of water and is significantly reduced where kerogen is hosted in limestones, dolomites or cherts. These minerals have been characteristically found to be the most reliable in yielding morphological fossils and small quantities of extractable bitumen in Archean and Proterozoic rocks. To understand the validity of chemical and morphological fossils, in the early geologic record, it will be necessary to understand the process of kerogen in sedimentary rocks. To test the role of various minerals on the preservation process, kerogen extracted from a variety of rocks has been heated together with montmorillonite, illite and calcite. The kinetics of the process has been monitored and the products quantitatively identified.

Pore water colloid properties in argillaceous sedimentary rocks.

PubMed

Degueldre, Claude; Cloet, Veerle

2016-11-01

The focus of this work is to evaluate the colloid nature, concentration and size distribution in the pore water of Opalinus Clay and other sedimentary host rocks identified for a potential radioactive waste repository in Switzerland. Because colloids could not be measured in representative undisturbed porewater of these host rocks, predictive modelling based on data from field and laboratory studies is applied. This approach allowed estimating the nature, concentration and size distributions of the colloids in the pore water of these host rocks. As a result of field campaigns, groundwater colloid concentrations are investigated on the basis of their size distribution quantified experimentally using single particle counting techniques. The colloid properties are estimated considering data gained from analogue hydrogeochemical systems ranging from mylonite features in crystalline fissures to sedimentary formations. The colloid concentrations were analysed as a function of the alkaline and alkaline earth element concentrations. Laboratory batch results on clay colloid generation from compacted pellets in quasi-stagnant water are also reported. Experiments with colloids in batch containers indicate that the size distribution of a colloidal suspension evolves toward a common particle size distribution independently of initial conditions. The final suspension size distribution was found to be a function of the attachment factor of the colloids. Finally, calculations were performed using a novel colloid distribution model based on colloid generation, aggregation and sedimentation rates to predict under in-situ conditions what makes colloid concentrations and size distributions batch- or fracture-size dependent. The data presented so far are compared with the field and laboratory data. The colloid occurrence, stability and mobility have been evaluated for the water of the considered potential host rocks. In the pore water of the considered sedimentary host rocks, the clay

Space Station Views of African Sedimentary Basins-Analogs for Subsurface Patterns

NASA Technical Reports Server (NTRS)

Wilkinson, M. Justin

2007-01-01

Views of African sedimentary basins from the International Space Station (ISS) is presented. The images from ISS include: 1) Inland deltas; 2) Prediction; 3) Significance; 4) Exploration applications; and 5) Coastal megafans

Diachronous evolution of volcano-sedimentary basins north of the Congo craton: Insights from U Pb ion microprobe dating of zircons from the Poli, Lom and Yaoundé Groups (Cameroon)

NASA Astrophysics Data System (ADS)

Toteu, Sadrack Félix; Penaye, Joseph; Deloule, Etienne; Van Schmus, William Randall; Tchameni, Rigobert

2006-04-01

Ion microprobe U-Pb dating of zircons from Neoproterozoic volcano-sedimentary sequences in Cameroon north of the Congo craton is presented. For the Poli basin, the depositional age is constrained between 700-665 Ma; detrital sources comprise ca. 920, 830, 780 and 736 Ma magmatic zircons. In the Lom basin, the depositional age is constrained between 613 and 600 Ma, and detrital sources include Archaean to Palaeoproterozoic, late Mesoproterozoic to early Neoproterozoic (1100-950 Ma), and Neoproterozoic (735, 644 and 613 Ma) zircons. The Yaoundé Group is probably younger than 625 Ma, and detrital sources include Palaeoproterozoic and Neoproterozoic zircons. The depositional age of the Mahan metavolcano-sedimentary sequence is post-820 Ma, and detrital sources include late Mesoproterozoic (1070 Ma) and early Neoproterozoic volcanic rocks (824 Ma). The following conclusions can be made from these data. (1) The three basins evolved during the Pan-African event but are significantly different in age and tectonic setting; the Poli is a pre- to syn-collisional basin developed upon, or in the vicinity of young magmatic arcs; the Lom basin is post-collisional and intracontinental and developed on old crust; the tectono-metamorphic evolution of the Yaoundé Group resulted from rapid tectonic burial and subsequent collision between the Congo craton and the Adamawa-Yade block. (2) Late Mesoproterozoic to early Neoproterozoic inheritance reflects the presence of magmatic event(s) of this age in west-central Africa.

The sedimentary record of India-Asia collision: an evaluation of new and existing constraints

NASA Astrophysics Data System (ADS)

Najman, Yani; Henderson, Alex; Boudagher-Fadel, Marcelle; Godin, Laurent; Parrish, Randy; Bown, Paul; Garzanti, Eduardo; Horstwood, Matt; Jenks, Dan

2010-05-01

The age and degree of diachroneity of India-Asia collision is critical to construction of models of orogenesis and to understanding the causes of spatial variations in Himalayan evolution along strike. The age of collision is quoted between ~65-34 Ma (Jaeger et al 1989; Aitchison et al 2007) and the degree of dichroneity is considered negligible (Searle et al 1997) to substantial (Rowley 1998). Such discrepancy is, to some extent, the result of the different definitions and methods used to define the collision. Here, we evaluate constraints from the sedimentary record preserved in the suture zone and Tethyan Himalaya where a minimum age to collision has been constrained by determining 1) the timing of cessation of marine facies, 2) first evidence of Asian detritus deposited on the Indian plate and 3) first evidence of mixed Indian-Asian detritus in the sedimentary record. Extensive previous work has been carried out on the Indus molasse of the Indus Suture zone in Ladakh, India. Here, cessation of marine facies is dated at 50.5 Ma (Green et al. 2008), with the underlying Chogdo Formation considered to show first evidence of mixed Indian and Asian provenance, and be the oldest Formation of Asian-derived provenance to lie in sedimentary contact with the underlying Indian plate (Clift et al 2001, 2002), thus constraining collision at >50.5 Ma. However, our new mapping and provenance analyses on these rocks show that there is no unequivocal evidence of Indian-derived material in the Chogdo Formation, nor that the Chogdo Formation lies in sedimentary contact with the underlying Indian plate (Henderson et al., in review). Thus we question the timing of Indian-Asian collision based on these evidences. South of the suture zone in India and Tibet, we carried out similar investigations of the youngest Tethyan strata. In Ladakh, Indian plate passive margin limestones of the Paleocene Dibling Fm are overlain by the youngest marine facies of the region, the marine Kong Fm and

An astrobiological perspective on Meridiani Planum

USGS Publications Warehouse

Knoll, A.H.; Carr, M.; Clark, B.; Des Marais, D.J.; Farmer, J.D.; Fischer, W.W.; Grotzinger, J.P.; McLennan, S.M.; Malin, M.; Schroder, C.; Squyres, S.; Tosca, N.J.; Wdowiak, T.

2005-01-01

Sedimentary rocks exposed in the Meridiani Planum region of Mars record aqueous and eolian deposition in ancient dune and interdune playa-like environments that were arid, acidic, and oxidizing. On Earth, microbial populations have repeatedly adapted to low pH and both episodic and chronic water limitation, suggesting that, to a first approximation, the Meridiani plain may have been habitable during at least part of the interval when deposition and early diagenesis took place. On the other hand, the environmental conditions inferred for Meridiani deposition would have posed a challenge for prebiotic chemical reactions thought to have played a role in the origin of life on Earth. Orbital observations suggest that the combination of sulfate minerals and hematite found in Meridiani rocks may be unusual on the martian surface; however, there is reason to believe that acidity, aridity, and oxidizing conditions were broadly distributed on ancient Mars. When these conditions were established and how much environmental heterogeneity existed on early Mars remain to be determined. Because sulfates and iron oxides can preserve detailed geochemical records of environmental history as well as chemical, textural and microfossil signatures of biological activity, Meridiani Planum is an attractive candidate for Mars sample return. ?? 2005 Elsevier B.V. All rights reserved.

From the ocean to a salt marsh: towards understanding iron reduction processes with FORC-PCA.

NASA Astrophysics Data System (ADS)

Muraszko, J. R.; Lascu, I.; Collins, S. M.; Harrison, R. J.

2017-12-01

Biogenic magnetic minerals are a high fidelity recorder of climate change. Their sensitivity to sedimentary redox conditions and bottom water ventilation have the potential to provide useful insights into past diagenetic conditions. However, the mechanisms controlling preservation and dissolution of magnetosomes are not fully understood, thus undermining the reliability of the paleomagnetic records in marine environments. Recovering information about the diagenetic past of the sediment is a crucial challenge; specifically, the biogenic components need to be identified and unmixed from the bulk magnetic signal. We address the issue in this study by applying Principal Component Analysis on First Order Reversal Curve diagrams (FORC-PCA) in case studies of cores obtained from the Iberian Margin and the sedimentologically active coastal salt marshes of Norfolk. We demonstrate the applicability of FORC-PCA as a new environmental proxy, yielding a high resolution temporal marine record of environmental changes reflected in magnetic composition over the last 194 kyr. The strongest variations are observed in the microbially derived components, the bulk properties of the sediment being controlled by a low coercivity SP-SD component which is generally anticorrelated with the magnetosome signal. Supported by TEM studies, we suggest the prevalence of clusters of nano-particles of magnetite associated with iron reduction. To further investigate the mechanisms controlling these processes, the active sedimentary environment of Norfolk was chosen as a case study of early diagenesis controlled by strong vertical geochemical gradients.

Phorbin steryl esters in Black Sea sediment traps and sediments: A preliminary evaluation of their paleooceanographic potential

DOE Office of Scientific and Technical Information (OSTI.GOV)

King, L.L.; Repeta, D.J.

1994-10-01

The distributions of pyropheophorbide-a steryl esters in one-year deployments of sediment traps at two locations in the Black Sea are described. In nearly all trap samples, phorbin steryl esters (PSEs) contribute a significant portion of the total phorbin flux. The relative abundances of sterols esterified to pyropheophorbide-a varied throughout the year, and the authors suggest these changes result from the observed seasonal variation of phytoplankton species in the overlying water column. The distribution of free sterols in a one-year composite sediment trap sample closely approximates the distribution of sterols derived from the hydrolysis of sedimentary PSEs collected at an adjacentmore » site. From these results, they suggest that the distribution of sedimentary PSE sterols provides a record of sterol deposition to the sediment-water interface. Esterification of sterols to pyropheophorbide-a apparently prevents the preferential removal of 4-desmethyl sterols relative to 4-methyl sterols, and the reduction of stenols to stanols during degradation. Analysis of PSEs in a gravity core covering the last 8-10 Kyr shows that the abundance and distribution of PSEs change with downcore variations in sedimentology. Detailed analysis of PSEs in sediments may, therefore, provide a means to evaluate paleooceanographic changes in phytoplankton community structure and sterol early diagenesis. The synthesis, NMR, CI-MS, and visible spectroscopic properties of four abundance PSEs found in the Black Sea are also described.« less

Restoration of original 3D sedimentary geometries in deformed basin fill supporting reservoir characterization

NASA Astrophysics Data System (ADS)

Back, S.

2009-04-01

A large progradational clastic system centred on Brunei Darussalam has been present on the NW Borneo margin since the early middle Miocene. This system has many sedimentary and structural similarities with major deltaic provinces such as the Niger and Nile. It differs from these systems by being affected in the hinterland by contemporaneous compressional tectonics. Uplift partially forced strong progradation of the clastic system, but also folded older deltaic units. Erosion and the exhumation of folded strata in the area of the Jerudong Anticline resulted in the exposure of large-scale prograding clinoforms and syn-sedimentary deltaic faults of middle Miocene age along a natural cross-section of several tens of kilometres in extent. Westward of the key outcrop sites on the Jerudong Anticline, the middle Miocene deltaic units are overlain by late Miocene, Pliocene and Quaternary clastics up to 3 kilometres thick. Both, the middle Miocene target units of this study as well as the late Miocene to recent overburden are recorded in the subsurface of the Belait Syncline on regional 2D seismic lines (total line length around 1400 km) and at 7 well locations. In this study, we integrate the available geophysical subsurface information with existing structural, sedimentological and geomorphological field data of the "classic" Jerudong Anticline exposures (e.g., Back et al. 2001, Morley et al. 2003, Back et al. 2005) into a static 3D surface-subsurface model that provides quantitative constraints on the structural and stratigraphic architecture of the Miocene Belait delta and the overlying units in three dimensions, supporting basin-scale as well as reservoir-scale analysis of the subsurface rock volume. Additionally, we use the static surface-subsurface model as input for a tectonic retro-deformation of the study area, in which the 3D paleo-relief of the middle Miocene Belait delta is restored by unfolding and fault balancing (Back et al. 2008). This kinematic

Shallow-seated explosions in the construction of the Motukorea tuff ring (Auckland, New Zealand): Evidence from lithic and sedimentary characteristics

NASA Astrophysics Data System (ADS)

Agustín-Flores, Javier; Németh, Károly; Cronin, Shane J.; Lindsay, Jan M.; Kereszturi, Gábor

2015-10-01

At least 52 eruption centres are scattered within the 360 km2 Auckland Volcanic Field (AVF). Motukorea, now an island in the Waitemata Harbour, is one of 39 AVF volcanoes that experienced a phreatomagmatic explosive phase, before a magmatic phase. The volcano erupted through a 200-300 m-thick, consolidated, mudstone/sandstone sequence of the Miocene Waitemata Group, which overlies the Waipapa Terrane greywacke basement. Detailed field descriptions of the sedimentary characteristics of the early phreatomagmatic deposits were carried out, along with examination of lithics. The ejecta ring deposit comprises 55 to 60 vol.% lithics, of which Waitemata Group fragments constitute approximately 90 vol.%, whereas < 10 vol.% are Waipapa fragments, suggesting a dominance of shallow fragmentation. The sedimentary characteristics of the stratigraphic sequence at Motukorea suggest a dominance of wet surges at the beginning of the eruption with progression into drier sequences upwards. This is reflected in increasing inter-bedded juvenile-pyroclast-dominated fall deposits up-sequence. These characteristics are attributed to the changing hydrogeological conditions within the diatreme and the host rocks. These findings shed light on the eruption dynamics of phreatomagmatic eruptions through consolidated rocks in the AVF and enable the depiction of a scenario of future eruptions within the field in similar substrates.

JOINTS AND SYN-SEDIMENTARY FAULTS NETWORKS IN MARINE CLAYS AND MUDSTONES. Importance for Radwaste storage

NASA Astrophysics Data System (ADS)

Arnould, M.

2009-12-01

There is a number of marine clays, mudstones, marls, 100 to 200 m thick, showing smectites, mixed layers illite/smectite, with a small percentage of organic matter and sulphides with a variable clay, silt, and carbonate content. I published (Arnould , 2006) examples from Lower Cambrian to Miocene in age and from the Baltic shore to Spain in Europe. Observations were made mostly in quarries and pits down to more than 40 m and in underground research laboratories (URL). Only visible on fresh cuts amongst a variety of fissures there is always a network of joints. Schematically one family is the bedding (horizontal) the two others are normal to the bedding and orthogonal between them. The orientations of vertical joints are different from the orientations of pits and quarries’s walls. The networks are intrinsic. It was first well described by Skempton & al (1969) in Eocene London Clay. Joints are matt in texture, clean, without filling or cement. The order of magnitude of their linear dimensions is decimeter to meter. It is necessary to start from the original sediment: mud. Deposited in flakes mud has a bee’s nest microscopic structure. Each nest is full of water. Hence mud may have a water content up to 300%, reported to its dry weight. Paradoxically mud is impervious. As proposed by Cosgrove (2001) progressive but discontinuous hydraulic fracturing could be the origin of vertical joints, with drainage upwards and compaction of the sediment. Geological observations show that ioints are formed during the sedimentation process. There is also a world literature concluding at the necessary early fracturing of mudstones and marls hosts of sand dykes. Very few faults are identified in field observations and on exploration logs. But it is obvious that drainage and compaction of mud over thousands square kilometers induced differential settlements with many syn-sedimentary non tectonic faults constituting another discontinuity network. These faults inside the same

An extraterrestrial trigger for the Early Cretaceous massive volcanism? Evidence from the paleo-Tethys Ocean.

PubMed

Tejada, M L G; Ravizza, G; Suzuki, K; Paquay, F S

2012-01-01

The Early Cretaceous Greater Ontong Java Event in the Pacific Ocean may have covered ca. 1% of the Earth's surface with volcanism. It has puzzled scientists trying to explain its origin by several mechanisms possible on Earth, leading others to propose an extraterrestrial trigger to explain this event. A large oceanic extraterrestrial impact causing such voluminous volcanism may have traces of its distal ejecta in sedimentary rocks around the basin, including the paleo-Tethys Ocean which was then contiguous with the Pacific Ocean. The contemporaneous marine sequence at central Italy, containing the sedimentary expression of a global oceanic anoxic event (OAE1a), may have recorded such ocurrence as indicated by two stratigraphic intervals with (187)Os/(188)Os indicative of meteoritic influence. Here we show, for the first time, that platinum group element abundances and inter-element ratios in this paleo-Tethyan marine sequence provide no evidence for an extraterrestrial trigger for the Early Cretaceous massive volcanism.

An extraterrestrial trigger for the Early Cretaceous massive volcanism? Evidence from the paleo-Tethys Ocean

PubMed Central

Tejada, M. L. G.; Ravizza, G.; Suzuki, K.; Paquay, F. S.

2012-01-01

The Early Cretaceous Greater Ontong Java Event in the Pacific Ocean may have covered ca. 1% of the Earth's surface with volcanism. It has puzzled scientists trying to explain its origin by several mechanisms possible on Earth, leading others to propose an extraterrestrial trigger to explain this event. A large oceanic extraterrestrial impact causing such voluminous volcanism may have traces of its distal ejecta in sedimentary rocks around the basin, including the paleo-Tethys Ocean which was then contiguous with the Pacific Ocean. The contemporaneous marine sequence at central Italy, containing the sedimentary expression of a global oceanic anoxic event (OAE1a), may have recorded such ocurrence as indicated by two stratigraphic intervals with 187Os/188Os indicative of meteoritic influence. Here we show, for the first time, that platinum group element abundances and inter-element ratios in this paleo-Tethyan marine sequence provide no evidence for an extraterrestrial trigger for the Early Cretaceous massive volcanism. PMID:22355780

Mechanism for Burgess Shale-type preservation

PubMed Central

Gaines, Robert R.; Hammarlund, Emma U.; Hou, Xianguang; Qi, Changshi; Gabbott, Sarah E.; Zhao, Yuanlong; Peng, Jin; Canfield, Donald E.

2012-01-01

Exceptionally preserved fossil biotas of the Burgess Shale and a handful of other similar Cambrian deposits provide rare but critical insights into the early diversification of animals. The extraordinary preservation of labile tissues in these geographically widespread but temporally restricted soft-bodied fossil assemblages has remained enigmatic since Walcott’s initial discovery in 1909. Here, we demonstrate the mechanism of Burgess Shale-type preservation using sedimentologic and geochemical data from the Chengjiang, Burgess Shale, and five other principal Burgess Shale-type deposits. Sulfur isotope evidence from sedimentary pyrites reveals that the exquisite fossilization of organic remains as carbonaceous compressions resulted from early inhibition of microbial activity in the sediments by means of oxidant deprivation. Low sulfate concentrations in the global ocean and low-oxygen bottom water conditions at the sites of deposition resulted in reduced oxidant availability. Subsequently, rapid entombment of fossils in fine-grained sediments and early sealing of sediments by pervasive carbonate cements at bed tops restricted oxidant flux into the sediments. A permeability barrier, provided by bed-capping cements that were emplaced at the seafloor, is a feature that is shared among Burgess Shale-type deposits, and resulted from the unusually high alkalinity of Cambrian oceans. Thus, Burgess Shale-type preservation of soft-bodied fossil assemblages worldwide was promoted by unique aspects of early Paleozoic seawater chemistry that strongly impacted sediment diagenesis, providing a fundamentally unique record of the immediate aftermath of the “Cambrian explosion.” PMID:22392974

Corrosion of heavy minerals during weathering and diagenesis: A catalog for optical analysis

NASA Astrophysics Data System (ADS)

Andò, Sergio; Garzanti, Eduardo; Padoan, Marta; Limonta, Mara

2012-12-01

A practical classification of surface textures observed on detrital grains in sands and sandstones is proposed, in order to enhance data reproducibility among operators and to implement the use of high-resolution heavy-mineral data in studies of sediment-generation, provenance, and diagenesis. Five stages of progressive weathering (unweathered, corroded, etched, deeply etched, skeletal) are recognized for diverse detrital minerals. Archetypal grains displaying increasing degrees of corrosion are illustrated in numerous color tables for visual comparison. This catalog, specifically devised to systematically collect valuable information for paleoclimatic or diagenetic interpretation during routine grain-counting under the microscope, is here shown to represent a useful subsidiary tool to reveal the different degrees of weathering for diverse minerals in modern sands of equatorial Africa, and to identify post-depositional modifications of detrital assemblages in buried orogenic sediments of the Bengal Basin. The data thus obtained need to be interpreted by carefully considering the concentration of heavy minerals in each sample, which provides the fundamental clue to quantify the degree of heavy-mineral depletion caused by either pre-depositional or post-depositional processes. The scrutiny of dissolution effects has applications in the study of the chemical properties of minerals and of diagenetic evolution, helping us to understand the development of secondary porosity and to assess the potential of water and hydrocarbon reservoirs.

A multi-proxy study of sedimentary humic substances in the salt marsh of the Changjiang Estuary, China

NASA Astrophysics Data System (ADS)

Zhang, Yaoling; Du, Jinzhou; Zhao, Xin; Wu, Wangsuo; Peng, Bo; Zhang, Jing

2014-12-01

To better understand the origin, composition, and reactivity of sedimentary humic substances (HSs) in salt marshes in the Changjiang Estuary, HS samples were isolated from a sediment core that was collected from the Eastern Chongming salt marsh. Chemical and spectroscopic methods were used to analyze the features of these HSs. The results indicate that the studied HSs in the salt marsh sediments are mainly terrestrial-derived and that the sedimentary organic matter (SOM) in the top layer may contain more organic matter from marine sources and/or autochthonous materials due to the dramatic decreasing of the sediment supply as a result of damming. The degradation of labile carbohydrates and proteins and the preservation of refractory lignin components dominate the early diagenetic reactions of SOM in the salt marsh area. The average contents of the carboxylic groups in FAs and HAs are 11.64 ± 1.08 and 7.13 ± 0.16 meq/gC, and those of phenolic groups are 1.95 ± 0.13 and 2.40 ± 0.44 meq/gC, respectively. The content of carboxylic groups increased with increasing depth, while there were no obvious changes in the content of phenolic groups. The average concentration of total proton-binding sites is approximately 12.5 μmol/g sediment for the studied HSs. These values may provide insight into the migration and fate of HS-bound contaminants in sediments and the overlying sea water in the salt marsh areas of the Changjiang Estuary.

Climatic pacing of Mediterranean fire histories from lake sedimentary microcharcoal

NASA Astrophysics Data System (ADS)

Turner, R.; Roberts, N.; Jones, M. D.

2008-10-01

The microcharcoal content (particles < 180 µm) of overlapping sedimentary sequences from two crater lake basins in central Turkey are used to reconstruct the regional fire history of the East Mediterranean oak-grass parkland zone from the Last Glacial Maximum to the present-day. These results are correlated with stable isotope and pollen data from the same cores in order to assess the changing role of climate, vegetation and human activity in landscape burning. This indicates that climatically-induced variation in biomass availability was the main factor controlling the timing of regional fire activity during the Last Glacial-Interglacial climatic transition, and again during Mid-Holocene times, with fire frequency and magnitude increasing during wetter climatic phases. Spectral analysis of the Holocene part of the record from Eski Acıgöl indicates significant cyclicity with a periodicity of ~ 1500 years that may be linked with large-scale climate forcing. Although proto-agricultural societies were established in this region as early as 10,000 years ago, it is only during the last two to three millennia that the pacing of wildfire cycles appears to have become decoupled from climate and linked instead to human-induced changes in land cover and fuel load availability.

Siderite deposits in northern Italy: Early Permian to Early Triassic hydrothermalism in the Southern Alps

NASA Astrophysics Data System (ADS)

Martin, Silvana; Toffolo, Luca; Moroni, Marilena; Montorfano, Carlo; Secco, Luciano; Agnini, Claudia; Nimis, Paolo; Tumiati, Simone

2017-07-01

We present a minero-petrographic, geochemical and geochronological study of siderite orebodies from different localities of the Southern Alps (northern Italy). Siderite occurs as veins cutting the Variscan basement and the overlying Lower Permian volcano-sedimentary cover (Collio Fm.), and as both veins and conformable stratabound orebodies in the Upper Permian (Verrucano Lombardo and Bellerophon Fms.) and Lower Triassic (Servino and Werfen Fms.) sedimentary sequences of the Lombardian and the Venetian Alps. All types of deposits show similar major- and rare-earth (REE)-element patterns, suggesting a common iron-mineralizing event. The compositions of coexisting siderite, Fe-rich dolomite and calcite suggest formation from hydrothermal fluids at relatively high temperature conditions (≥ 250 °C). Geochemical modelling, supported by REE analyses and by literature and new δ13C and δ18O isotopic data, suggests that fluids responsible for the formation of siderite in the Variscan basement and in the overlying Lower Permian cover were derived from dominant fresh water, which leached Fe and C from volcanic rocks (mainly rhyolites/rhyodacites) and organic carbon-bearing continental sediments. On the basis of U-Th-Pb microchemical dating of uraninite associated with siderite in the Val Vedello and Novazza deposits (Lombardian Alps), the onset of hydrothermalism is constrained to 275 ± 13 Ma (Early-Mid Permian), i.e., it was virtually contemporaneous to the plutonism and the volcanic-sedimentary cycle reported in the same area (Orobic Basin). The youngest iron-mineralizing event is represented by siderite veins and conformable orebodies hosted in Lower Triassic shallow-marine carbonatic successions. In this case, the siderite-forming fluids contained a seawater component, interacted with the underlying Permian successions and eventually replaced the marine carbonates at temperatures of ≥ 250 °C. The absence of siderite in younger rocks suggests an Early Triassic

Marine and Lacustrine Organic-rich Sedimentary Unit Time Markers: Implications from Rhenium-Osmium Geochronology

NASA Astrophysics Data System (ADS)

Selby, D.

2011-12-01

Geochronology is fundamental to understand the age, rates and durations of Earth processes. This concerned Arthur Holmes who, for much of his career, attempted to define a geological time scale. This is a topic still important to Earth Scientists today, specifically the chronostratigraphy of sedimentary rocks. Here I explore the Re-Os geochronology of marine and lacustrine sedimentary rocks and its application to yield absolute time constraints for stratigraphy. The past decade has seen the pioneering research of Re-Os organic-rich sedimentary rock geochronology blossom into a tool that can now to be used to accurately and precisely determine depositional ages of organic-rich rock units that have experienced up to low grade greenschist metamorphism. This direct dating of sedimentary rocks is critical where volcanic horizons are absent. As a result, this tool has been applied to timescale calibration, basin correlation, formation duration and the timing of key Earth events (e.g., Neoproterozoic glaciations). The application of Re-Os chronometer to the Devonian-Mississippian boundary contained within the Exshaw Formation, Canada, determined an age of 361.3 ± 2.4 Ma. This age is in accord with U-Pb dates of interbedded tuff horizons and also U-Pb zircon date for the type Devonian-Mississippian Hasselbachtal section, Germany. The agreement of the biostratigraphic and U-Pb constraints of the Exshaw Formation with the Re-Os date illustrated the potential of the Re-Os chronometer to yield age determinations for sedimentary packages, especially in the absence of interbedd tuff horizons and biozones. A Re-Os date for the proposed type section of the Oxfordian-Kimmeridgian boundary, Staffin Bay, Isle of Skye, U.K., gave an age of 154.1 ± 2.2 Ma. This Re-Os age presents a 45 % (1.8 Ma) improvement in precision for the basal Kimmeridgian. It also demonstrated that the duration of the Kimmeridgian is nominally 3.3 Ma and thus is 1.6 Ma shorter than previously indicated. In

The Effect of Sedimentary Basins on Through-Passing Short-Period Surface Waves

NASA Astrophysics Data System (ADS)

Feng, L.; Ritzwoller, M. H.

2017-12-01

Surface waves propagating through sedimentary basins undergo elastic wave field complications that include multiple scattering, amplification, the formation of secondary wave fronts, and subsequent wave front healing. Unless these effects are accounted for accurately, they may introduce systematic bias to estimates of source characteristics, the inference of the anelastic structure of the Earth, and ground motion predictions for hazard assessment. Most studies of the effects of basins on surface waves have centered on waves inside the basins. In contrast, we investigate wave field effects downstream from sedimentary basins, with particular emphasis on continental basins and propagation paths, elastic structural heterogeneity, and Rayleigh waves at 10 s period. Based on wave field simulations through a recent 3D crustal and upper mantle model of East Asia, we demonstrate significant Rayleigh wave amplification downstream from sedimentary basins in eastern China such that Ms measurements obtained on the simulated wave field vary by more than a magnitude unit. We show that surface wave amplification caused by basins results predominantly from elastic focusing and that amplification effects produced through 3D basin models are reproduced using 2D membrane wave simulations through an appropriately defined phase velocity map. The principal characteristics of elastic focusing in both 2D and 3D simulations include (1) retardation of the wave front inside the basins; (2) deflection of the wave propagation direction; (3) formation of a high amplitude lineation directly downstream from the basin bracketed by two low amplitude zones; and (4) formation of a secondary wave front. Finally, by comparing the impact of elastic focusing with anelastic attenuation, we argue that on-continent sedimentary basins are expected to affect surface wave amplitudes more strongly through elastic focusing than through the anelastic attenuation.

Provenance of Carboniferous sedimentary rocks in the northern margin of Dabie Mountains, central China and the tectonic significance: constraints from trace elements, mineral chemistry and SHRIMP dating of zircons

NASA Astrophysics Data System (ADS)

Li, Renwei; Li, Shuangying; Jin, Fuquan; Wan, Yusheng; Zhang, Shukun

2004-04-01

A suite of slightly metamorphosed Carboniferous sedimentary strata occurs in the northern margin of the Dabie Mountains, central China. It consists, in ascending order, of the upper Huayuanqiang Formation (C 1), the Yangshan Formation (C 1), the Daorenchong Formation (C 1-2), the most widely distributed Huyoufang Formation (C 2) and the Yangxiaozhuang Formation (C 2). The provenance of the Carboniferous sedimentary rocks is constrained by the integration of trace elements, detrital mineral chemistry and sensitive high resolution ion microprobe (SHRIMP) dating of detrital zircons, which can help to understand the connection between the provenance and the Paleozoic tectonic evolution of the Qinling-Dabie Orogen. The trace element compositions indicate that the source terrain was probably a continental island arc. Detrital tourmalines were mainly derived from aluminous and Al-poor metapelites and metapsammites, and some are sourced from Li-poor granitoids, pegmatites and aplites. Detrital garnets, found only in the uppermost Huyoufang Formation, are almandine and Mn-almandine garnets, indicating probable sources mainly from garnetiferous schists, and partly from granitoid rocks. The detrital white K-micas are muscovitic in the Huayuanqiang, Daorenchong and Huyoufang Formations, and phengitic with Si contents (p.f.u.) from 3.20 up to max. 3.47-3.53 in the uppermost Huyoufang and the Yangxiaozhuang Formations, a meta-sedimentary source. Major components in the detrital zircon age structure for the Huyoufang Formation range from 506 to 363 Ma, centering on ˜400 and ˜480 Ma, which is characteristic of the Qinling and Erlangping Groups in the Qinling and Tongbai Mountains, central China. Evidently, the major source of the Carboniferous sedimentary rocks in the northern margin of Dabie Mountains was from the southern margin of the Sino-Korean Craton represented by the Qinling and Erlangping Groups. The source area was an island-arc system during the Early Paleozoic that

Aeolian sedimentary processes at the Bagnold Dunes, Mars: Implications for modern dune dynamics and sedimentary structures in the aeolian stratigraphic record of Mars

NASA Astrophysics Data System (ADS)

Ewing, Ryan C.; Bridges, Nathan T.; Sullivan, Rob; Lapotre, Mathieu G. A.; Fischer, Woodward W.; Lamb, Mike P.; Rubin, David M.; Lewis, Kevin W.; Gupta, Sanjeev

2016-04-01

Wind-blown sand dunes are ubiquitous on the surface of Mars and are a recognized component of the martian stratigraphic record. Our current knowledge of the aeolian sedimentary processes that determine dune morphology, drive dune dynamics, and create aeolian cross-stratification are based upon orbital studies of ripple and dune morphodynamics, rover observations of stratification on Mars, Earth analogs, and experimental and theoretical studies of sand movement under Martian conditions. In-situ observations of sand dunes (informally called the Bagnold Dunes) by Curiosity Rover in Gale Crater, Mars provide the first opportunity to make observations of dunes from the grain-to-dune scale thereby filling the gap in knowledge between theory and orbital observations and refining our understanding of the martian aeolian stratigraphic record. We use the suite of cameras on Curiosity, including Navigation Camera (Navcam), Mast Camera (Mastcam) and Mars Hand Lens Imager (MAHLI), to make observations of the Bagnold Dunes. Measurements of sedimentary structures are made where stereo images are available. Observations indicate that structures generated by gravity-driven processes on the dune lee slopes, such as grainflow and grainfall, are similar to the suite of aeolian sedimentary structures observed on Earth and should be present and recognizable in Mars' aeolian stratigraphic record. Structures formed by traction-driven processes deviate significantly from those found on Earth. The dune hosts centimeter-scale wind ripples and large, meter-scale ripples, which are not found on Earth. The large ripples migrate across the depositional, lee slopes of the dune, which implies that these structures should be present in Mars' stratigraphic record and may appear similar to compound-dune stratification.The Mars Science Laboratory Curiosity Rover Team is acknowledged for their support of this work.

Life Detection on the Early Earth

NASA Technical Reports Server (NTRS)

Runnegar, B.

2004-01-01

Finding evidence for first the existence, and then the nature of life on the early Earth or early Mars requires both the recognition of subtle biosignatures and the elimination of false positives. The history of the search for fossils in increasingly older Precambrian strata illustrates these difficulties very clearly, and new observational and theoretical approaches are both needed and being developed. At the microscopic level of investigation, three-dimensional morphological characterization coupled with in situ chemical (isotopic, elemental, structural) analysis is the desirable first step. Geological context is paramount, as has been demonstrated by the controversies over AH84001, the Greenland graphites, and the Apex chert microfossils . At larger scales, the nature of sedimentary bedforms and the structures they display becomes crucial, and here the methods of condensed matter physics prove most useful in discriminating between biological and non-biological constructions. Ultimately, a combination of geochemical, morphological, and contextural evidence may be required for certain life detection on the early Earth or elsewhere.

Early pleistocene sediments at Great Blakenham, Suffolk, England

NASA Astrophysics Data System (ADS)

Gibbard, P. L.; Allen, P.; Field, M. H.; Hallam, D. F.

Detailed investigation of a fine sediment sequence, the College Farm Silty Clay Member, that overlies the Creeting Sands (Early Pleistocene) in Suffolk, is presented. The sedimentary sequence is thought to represent a freshwater pool accumulation in a small coastal embayment. Palaeobotanical investigation of the sediment indicates that it accumulated during the late temperate substage of a temperate (interglacial) event. The occurrence of Tsuga pollen, associated with abundant remains of the water fern Azolla tegeliensis indicate that the deposits are of Early Pleistocene age and are correlated with a later part of the Antian-Bramertonian Stage. Correlation with Tiglian TO substage in The Netherlands' sequence is most likely. The sediments' normal palaeomagnetic polarity reinforces the biostratigraphical correlation.

Stratigraphy, correlation, depositional setting, and geophysical characteristics of the Oligocene Snowshoe Mountain Tuff and Creede Formation in two cored boreholes

USGS Publications Warehouse

Larsen, Daniel; Nelson, Philip H.

2000-01-01

Core descriptions and geophysical logs from two boreholes (CCM-1 and CCM-2) in the Oligocene Snowshoe Mountain Tuff and Creede Formation, south-central Colorado, are used to interpret sedimentary and volcanic facies associations and their physical properties. The seven facies association include a mixed sequence of intracaldera ash-flow tuffs and breccias, alluvial and lake margin deposits, and tuffaceous lake beds. These deposits represent volcanic units related to caldera collapse and emplacement of the Snowshoe Mountain Tuff, and sediments and pyroclastic material deposited in the newly formed caldera basin, Early sedimentation is interpreted to have been rapid, and to have occurred in volcaniclastic fan environments at CCM-1 and in a variery of volcaniclastic fan, braided stream shallow lacustrine, and mudflat environments at CCM-2. After an initial period of lake-level rise, suspension settling, turbidite, and debris-flow sedimentation occurred in lacustrine slope and basin environments below wave base. Carbonate sedimentation was initially sporadic, but more continuous in the latter part of the recorded lake history (after the H fallout tuff). Sublacustrine-fan deposition occurred at CCM-1 after a pronounced lake-level fall and subsequent rise that preceded the H tuff. Variations in density, neutron, gamma-ray, sonic, and electrical properties of deposits penetrated oin the two holes reflect variations in lithology, porosity, and alteration. Trends in the geophysical properties of the lacustrine strata are linked to downhole changes in authigenic mineralology and a decrease in porosity interpreted to have resulted primarily from diagenesis. Lithological and geophysical characteristics provide a basis for correlation of the cores; however, mineralogical methods of correlation are hampered by the degree of diagenesis and alteration.

Sedimentary laminations in the Isheyevo (CH/CBb) carbonaceous chondrite formed by gentle impact-plume sweep-up

NASA Astrophysics Data System (ADS)

Garvie, Laurence A. J.; Knauth, L. Paul; Morris, Melissa A.

2017-08-01

meteorite provides evidence of gentle layer-by-layer accretion in the early Solar System, and also extends the terrestrial sedimentary source-to-sink paradigm to a near vacuum environment where neither fluvial nor aeolian processes operate.

Quantifying the impact of early calcite cementation on the reservoir quality of carbonate rocks: A 3D process-based model

NASA Astrophysics Data System (ADS)

Hosa, Aleksandra; Wood, Rachel

2017-06-01

The reservoir properties of carbonate rocks are controlled by both deposition and diagenesis. The latter includes the early precipitation of calcite cements, which can exert a strong control on the evolution of subsequent diagenetic pathways. We quantify the impact of early marine cement growth in grainstones on evolving pore space by examining trends in the relationship between cementation and permeability using a 3D process-based model (Calcite3D). The model assumes varying proportions of polycrystalline and monocrystalline grain types, upon which we grow isopachous and syntaxial calcite cement types, respectively. We model two syntaxial cement shapes, compact and elongated, that approximate the geometries of typical rhombohedral calcite forms. Results demonstrate the effect of cement competition: an increasing proportion of monocrystalline grains creates stronger competition and a reduction in the impact of individual grains on final calcite cement volume and porosity. Isopachous cement is effective in closing pore throats and limiting permeability. We also show that the impact of syntaxial cement on porosity occlusion and therefore flow is highly dependent on monocrystalline grain location and the orientation of crystal axes. This demonstrates the importance of diagenetic overprint in controlling the evolution of rock properties, but also that this process can be essentially random. We also show that diagenesis alone can create notable heterogeneity in the permeability of carbonates. While Calcite3D is successful in modelling realistic changes in cement volumes and pore space morphology, modelled permeabilities (0.01 -30D) are above the range reported in reservoir grainstones due to the very high permeability of the initial synthetic sediment deposit (58.9D). Poroperm data generated by Calcite3D, however, exhibits a linear relationship between the logarithms of porosity and permeability with a high coefficient of determination, as observed in natural media.

Sedimentary processes and depositional environments of the Horn River Shale in British Columbia, Canada

NASA Astrophysics Data System (ADS)

Yoon, Seok-Hoon; Koh, Chang-Seong; Joe, Young-Jin; Woo, Ju-Hwan; Lee, Hyun-Suk

2017-04-01

The Horn River Basin in the northeastern British Columbia, Canada, is one of the largest unconventional gas accumulations in North America. It consists mainly of Devonian shales (Horn River Formation) and is stratigraphically divided into three members, the Muskwa, Otterpark and Evie in descending order. This study focuses on sedimentary processes and depositional environments of the Horn River shale based on sedimentary facies analysis aided by well-log mineralogy (ECS) and total organic carbon (TOC) data. The shale formation consists dominantly of siliceous minerals (quartz, feldspar and mica) and subordinate clay mineral and carbonate materials, and TOC ranging from 1.0 to 7.6%. Based on sedimentary structures and micro texture, three sedimentary facies were classified: homogeneous mudstone (HM), indistinctly laminated mudstone (ILM), and planar laminated mudstone (PLM). Integrated interpretation of the sedimentary facies, lithology and TOC suggests that depositional environment of the Horn River shale was an anoxic quiescent basin plain and base-of-slope off carbonate platform or reef. In this deeper marine setting, organic-rich facies HM and ILM, dominant in the Muskwa (the upper part of the Horn River Formation) and Evie (the lower part of the Horn River Formation) members, may have been emplaced by pelagic to hemipelagic sedimentation on the anoxic sea floor with infrequent effects of low-density gravity flows (turbidity currents or nepheloid flows). In the other hand, facies PLM typifying the Otterpark Member (the middle part of the Horn River Formation) suggests more frequent inflow of bottom-hugging turbidity currents punctuating the hemipelagic settling of the background sedimentation process. The stratigraphic change of sedimentary facies and TOC content in the Horn River Formation is most appropriately interpreted to have been caused by the relative sea-level change, that is, lower TOC and frequent signal of turbidity current during the sea

Geothermal reservoir simulation of hot sedimentary aquifer system using FEFLOW®

NASA Astrophysics Data System (ADS)

Nur Hidayat, Hardi; Gala Permana, Maximillian

2017-12-01

The study presents the simulation of hot sedimentary aquifer for geothermal utilization. Hot sedimentary aquifer (HSA) is a conduction-dominated hydrothermal play type utilizing deep aquifer, which is heated by near normal heat flow. One of the examples of HSA is Bavarian Molasse Basin in South Germany. This system typically uses doublet wells: an injection and production well. The simulation was run for 3650 days of simulation time. The technical feasibility and performance are analysed in regards to the extracted energy from this concept. Several parameters are compared to determine the model performance. Parameters such as reservoir characteristics, temperature information and well information are defined. Several assumptions are also defined to simplify the simulation process. The main results of the simulation are heat period budget or total extracted heat energy, and heat rate budget or heat production rate. Qualitative approaches for sensitivity analysis are conducted by using five parameters in which assigned lower and higher value scenarios.

Prediction of hydrocarbons in sedimentary basins

USGS Publications Warehouse

Harff, J.E.; Davis, J.C.; Eiserbeck, W.

1993-01-01

To estimate the undiscovered hydrocarbon potential of sedimentary basins, quantitative play assessments specific for each location in a region may be obtained using geostatistical methods combined with the theory of classification of geological objects, a methodology referred to as regionalization. The technique relies on process modeling and measured borehole data as well as probabilistic methods to exploit the relationship between geology (the "predictor") and known hydrocarbon productivity (the "target") to define prospective stratigraphic intervals within a basin. It is demonstrated in case studies from the oil-producing region of the western Kansas Pennsylvanian Shelf and the gas-bearing Rotliegend sediments of the Northeast German Basin. ?? 1993 International Association for Mathematical Geology.

Timing of porosity destruction related to pressure-solution in limestones

NASA Astrophysics Data System (ADS)

Beaudoin, Nicolas; Koehn, Daniel; Aharonov, Einat; Boyce, Adrian; Billi, Andrea; Hamilton, Andrea

2017-04-01

Among effects that affect sedimentary rocks during diagenesis, pressure-solution has a very strong impact on the physical properties of rocks such as porosity and permeability. Intergranular pressure-solution results in rough or wavy surfaces called stylolites, which are very common in sedimentary basins, especially in limestone. According to the opening of the system, dissolved material can precipitate locally, leading to the destruction of the porosity around the stylolite. That can namely occur during the development of sedimentary stylolites, when no fracture of fault can allow dissolved material to flow away before precipitating again. This contribution aims at unravelling the depth at which the material dissolved during compaction precipitated in the open porosity, adding new data to discuss when pressure-solution starts to be an efficient mechanism of deformation in limestone during strata burial in sedimentary basins. We report the results of the study of cements that fill the fractures developed at the tips of stylolites in a sample of dolostone from the Jurassic Calcare Massiccio formation, coming from the Umbria-Marche area (Italy). The fractures developed from stylolite-induced stress, and the filling cements' oxygen and carbon isotopic values range between 10.6‰ to -6.1‰ PDB and -8.2‰ to -0.6‰ PDB, respectively. Considering a closed system, we use fractionation equations to convert δ18O values into temperature, which shows that the material put in solution during pressure-solution precipitated at a temperature ranging from 18°C to 39°C. Temperature range and geothermal gradient estimates suggest that the mechanism of pressure-solution actually was primarily active at depth as low as 1 km. In the studied sample, up to 18% of the original volume has been dissolved on stylolites, and that volume loss would have occurred in the first 2 km of the burial history. This natural example feeds the growing body of evidence that stylolites can start

Finite-strain analysis of Metavolcano-sedimentary rocks at Gabel El Mayet area, Central Eastern Desert, Egypt

NASA Astrophysics Data System (ADS)

Kassem, Osama M. K.; Abd El Rahim, Said H.

2010-09-01

Finite strain was estimated in the metavolcano-sedimentary rocks, which surround by serpentinites of Gabel El Mayet area. Finite strain shows a relationship to nappe contacts between the metavolcano-sedimentary rocks and serpentinite and sheds light on the nature of the subhorizontal foliation typical for the Gable Mayet shear zone. We used the Rf/ ϕ and Fry methods on feldspar porphyroclasts and mafic grains from 10 metasedimentary and six metavolcanic samples in Gabel El Mayet region. Our finite-strain data show that the metavolcano-sedimentary rocks were moderately deformed and axial ratios in the XZ section range from 1.9 to 3.9. The long axes of the finite-strain ellipsoids trend W/WNW in the north and W/WSW in the south of the Gabel El Mayet shear zone. Furthermore, the short axes are subvertical to a subhorizontal foliation. The strain magnitudes increase towards the tectonic contacts between the metavolcano-sedimentary rocks and serpentinite. The data indicate oblate strain symmetry in the metavolcano-sedimentary rocks. Hence, our strain data also indicate flattening strain. We assume that the metasedimentary and metavolcanics rocks have similar deformation behaviour. The fact that finite strain accumulated during the metamorphism indicates that the nappe contacts formed during the accumulation of finite strain and thus during thrusting. We conclude that the nappe contacts formed during progressive thrusting under brittle to semi-brittle deformation conditions by simple shear and involved a component of vertical shortening, which caused the subhorizontal foliation in the Gabel El Mayet shear zone.

Case study of a sabkha sedimentary environment: Mallahat al Bariquah, Libya

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krason, J.

1987-05-01

The importance of the sabkha sedimentary environment for formation and/or accumulation of hydrocarbons, salts, and various metalliferous mineral deposits has been recognized by many geologists. A sabkha in which sedimentation and the formation of salt deposits and hydrocarbons is in progress is located along the Mediterranean Sea coast, in northwestern Libya and northeastern Tunisia. The sabkha Mallahat al Bariquah was drilled in a regular grid at 1-km spacing; 63 holes have been completed. The sabkha and its vicinity were geologically mapped (1:20,000). Several hundred core and loose rock samples were thoroughly examined with regard to the lithology, mineralogy, paleontology, andmore » chemical composition. The chemistry of brine from each drill hole and solar pan was determined. Three 24-hour pumping tests were performed, and the hydrogeological conditions of the sabkha were analyzed in detail. Economically valuable bedded salt reserves of 170,800,000 MT of NaCl were discovered and proven. Additionally, over 30 million MT of potassium, magnesium, and sodium salts including bromides are recoverable from the brine. Although marine-coastal sabkhas are common, the extensive scope of this study is unique. Mallahat al Bariquah sabkha is not unique with regard to its geographic, climatic, or sedimentary environments. Therefore, Mallahat al Bariquah can be considered as a model applicable in exploration for and study of similar sedimentary environments in other geographic regions and older geologic epochs.« less

Geochemistry and origin of regional dolomites

NASA Astrophysics Data System (ADS)

Hanson, G. N.; Meyers, W. J.

1989-12-01

The major goal of the carbonate research program at Stony Brook is to better understand the conditions and processes leading to regional diagenesis of carbonate rocks. Our research focuses on studies of ancient, massive dolostones, but we are also studying limestone diagenesis for its own importance, and as it relates to dolomitization. Our approach has been to carry out a very detailed petrographic and geochemical case study to the Mississippian Burlington-Keokuk Fms. of Iowa, Illinois and Missouri, and to develop this as a testing ground for new geochemical and modelling techniques, and for testing various models for regional dolomitization in epicontinental carbonates. The ideas and techniques developed in our Burlington-Keokuk studies are being expanded and applied to carbonate sequences of other ages (Devonian to Neogene), and other tectono-sedimentary settings. The emphasis of this report will be on new developments and results on the Burlington-Keokuk studies and on our diagenetic studies of other strata. Recent research on Burlington-Keokuk rocks include development and application of boron isotopes and the U--Th--Pb system to dolomite studies, investigations of porosity and permeability in the dolostones. Projects on other strata include dolomitization and limestones diagenesis of Devonian carbonates of Alberta and Western Australia, Miocene reefal carbonates of Spain, Neogene carbonates of Curacao and Bonaire, Waulsortian limestones of Ireland, modelling of trace elements and stable isotopes, and experimental growth of calcites to investigate crystallographic controls of trace element incorporation.

Production and early preservation of lipid biomarkers in iron hot springs.

PubMed

Parenteau, Mary N; Jahnke, Linda L; Farmer, Jack D; Cady, Sherry L

2014-06-01

The bicarbonate-buffered anoxic vent waters at Chocolate Pots hot springs in Yellowstone National Park are 51-54°C, pH 5.5-6.0, and are very high in dissolved Fe(II) at 5.8-5.9 mg/L. The aqueous Fe(II) is oxidized by a combination of biotic and abiotic mechanisms and precipitated as primary siliceous nanophase iron oxyhydroxides (ferrihydrite). Four distinct prokaryotic photosynthetic microbial mat types grow on top of these iron deposits. Lipids were used to characterize the community composition of the microbial mats, link source organisms to geologically significant biomarkers, and investigate how iron mineralization degrades the lipid signature of the community. The phospholipid and glycolipid fatty acid profiles of the highest-temperature mats indicate that they are dominated by cyanobacteria and green nonsulfur filamentous anoxygenic phototrophs (FAPs). Diagnostic lipid biomarkers of the cyanobacteria include midchain branched mono- and dimethylalkanes and, most notably, 2-methylbacteriohopanepolyol. Diagnostic lipid biomarkers of the FAPs (Chloroflexus and Roseiflexus spp.) include wax esters and a long-chain tri-unsaturated alkene. Surprisingly, the lipid biomarkers resisted the earliest stages of microbial degradation and diagenesis to survive in the iron oxides beneath the mats. Understanding the potential of particular sedimentary environments to capture and preserve fossil biosignatures is of vital importance in the selection of the best landing sites for future astrobiological missions to Mars. This study explores the nature of organic degradation processes in moderately thermal Fe(II)-rich groundwater springs--environmental conditions that have been previously identified as highly relevant for Mars exploration.

Potential Cement Phases in Sedimentary Rocks Drilled by Curiosity at Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Rampe, E. B.; Morris, R. V.; Bish, D. L.; Chipera, S. J.; Ming, D. W.; Blake, D. F.; Vaniman, D. T.; Bristow, T. F.; Cavanagh, P.; Farmer, J. D.;

Microbially induced sedimentary structures recording an ancient ecosystem in the ca. 3.48 billion-year-old Dresser Formation, Pilbara, Western Australia.

PubMed

Noffke, Nora; Christian, Daniel; Wacey, David; Hazen, Robert M

2013-12-01

Microbially induced sedimentary structures (MISS) result from the response of microbial mats to physical sediment dynamics. MISS are cosmopolitan and found in many modern environments, including shelves, tidal flats, lagoons, riverine shores, lakes, interdune areas, and sabkhas. The structures record highly diverse communities of microbial mats and have been reported from numerous intervals in the geological record up to 3.2 billion years (Ga) old. This contribution describes a suite of MISS from some of the oldest well-preserved sedimentary rocks in the geological record, the early Archean (ca. 3.48 Ga) Dresser Formation, Western Australia. Outcrop mapping at the meter to millimeter scale defined five sub-environments characteristic of an ancient coastal sabkha. These sub-environments contain associations of distinct macroscopic and microscopic MISS. Macroscopic MISS include polygonal oscillation cracks and gas domes, erosional remnants and pockets, and mat chips. Microscopic MISS comprise tufts, sinoidal structures, and laminae fabrics; the microscopic laminae are composed of primary carbonaceous matter, pyrite, and hematite, plus trapped and bound grains. Identical suites of MISS occur in equivalent environmental settings through the entire subsequent history of Earth including the present time. This work extends the geological record of MISS by almost 300 million years. Complex mat-forming microbial communities likely existed almost 3.5 billion years ago.

Evolution of fore-arc and back-arc sedimentary basins with focus on the Japan subduction system and its analogues

NASA Astrophysics Data System (ADS)

Sato, Hiroshi; Ishiyama, Tatsuya; Matenco, Liviu; Nader, Fadi Henri

2017-07-01

The International Lithosphere Program (ILP) seeks to elucidate the nature, dynamics, origin and evolution of the lithosphere through international, multidisciplinary geoscience research projects and coordinating committees (Cloetingh and Negendank, 2010). The focus of the Task Force VI Sedimentary Basins activities is to foster collaborations between academia, research institutes and industry in all domains relevant for the understanding of sedimentary basins, from regional to nano-scale, from the deep earth to near surface processes (e.g., Roure et al., 2010, 2013). In this activity, it is important to develop and validate novel concepts of sedimentary basin evolution and topography building by incorporating geological/geophysical datasets and methodologies applied to worldwide natural laboratories (Cloetingh et al., 2011; Cloetingh and Willett, 2013; Matenco and Andriessen, 2013). The Task Force aims to understand and predict the processes that control the formation and evolution of the coupled orogens and sedimentary basins system through integration of field studies, analytical techniques and numerical/analogue modelling. At the same time, the Task Force aims to promote research in the domain of sedimentary basins evolution and quantitative tectonics for the study of mountain building and the subsequent extensional collapse, and their quantitative implications for vertical motions on different temporal and spatial scales (Gibson et al., 2015; Matenco et al., 2016; Roure, 2008; Seranne et al., 2015). The implications of tectonics on basin fluids (fluid-flow and rock-fluid interactions) are important to understand and predict geo-resources (e.g., Nader, 2016). Important is to initiate innovative research lines in linking the evolution of sedimentary systems by integrating cross-disciplinary expertise with a focus on integrated sedimentary basins and orogenic evolution. The key is to strengthen the synergy between academic research and applied industry in large

A burial diagenesis origin for the Ediacaran Shuram-Wonoka carbon isotope anomaly

NASA Astrophysics Data System (ADS)

Derry, Louis A.

2010-05-01

Marked negative δ 13C excursions in Ediacaran-age carbonate sediments have been identified in several sections globally, but are not recognized in all sections of similar age. The presence of δ 13C carb values as low as -12‰ has been interpreted as recording fundamentally different processes in the global carbon cycle than those recognized today. The δ 13C carb anomalies are strongly correlated with δ 18O carb values but are not represented in δ 13C org records. While no primary depositional processes have been identified that can produce the correlated δ 18O-δ 13C arrays, simulations show that fluid-rock interaction with high- pCO 2 fluids is capable of producing such arrays at geologically reasonable pCO 2 and water-rock ratios. Variations in the Mg/Ca ratio and sulfate concentration of the altering fluid determine the extent of dolomite vs. calcite and anhydrite in the resulting mineral assemblage. Incorporation of an initially aragonitic mineralogy demonstrates that high Sr, low Mn/Sr and modest alteration of 87Sr/ 86Sr in ancient carbonates are all compatible with a burial diagenesis mechanism for generation of the δ 13C anomalies, and do not necessarily imply preservation of primary values. The profound Ediacaran negative δ 13C anomalies can be adequately explained by well-understood diagenetic processes, conflated with the difficulty of correlating Precambrian sections independently of chemostratigraphy. They are not a record of primary seawater variations and need not have independent stratigraphic significance.

The potassic sedimentary rocks in Gale Crater, Mars, as seen by ChemCam Onboard Curiosity

USGS Publications Warehouse

Le Deit, Laetitia; Mangold, Nicolas; Forni, Olivier; Cousin, Agnes; Lasue, Jeremie; Schröder, Susanne; Wiens, Roger C.; Sumner, Dawn Y.; Fabre, Cecile; Stack, Katherine M.; Anderson, Ryan; Blaney, Diana L.; Clegg, Samuel M.; Dromart, Gilles; Fisk, Martin; Gasnault, Olivier; Grotzinger, John P.; Gupta, Sanjeev; Lanza, Nina; Le Mouélic, Stephane; Maurice, Sylvestre; McLennan, Scott M.; Meslin, Pierre-Yves; Nachon, Marion; Newsom, Horton E.; Payre, Valerie; Rapin, William; Rice, Melissa; Sautter, Violaine; Treiman, Alan H.

2016-01-01

The Mars Science Laboratory rover Curiosity encountered potassium-rich clastic sedimentary rocks at two sites in Gale Crater, the waypoints Cooperstown and Kimberley. These rocks include several distinct meters thick sedimentary outcrops ranging from fine sandstone to conglomerate, interpreted to record an ancient fluvial or fluvio-deltaic depositional system. From ChemCam Laser-Induced Breakdown Spectroscopy (LIBS) chemical analyses, this suite of sedimentary rocks has an overall mean K2O abundance that is more than 5 times higher than that of the average Martian crust. The combined analysis of ChemCam data with stratigraphic and geographic locations reveals that the mean K2O abundance increases upward through the stratigraphic section. Chemical analyses across each unit can be represented as mixtures of several distinct chemical components, i.e., mineral phases, including K-bearing minerals, mafic silicates, Fe-oxides, and Fe-hydroxide/oxyhydroxides. Possible K-bearing minerals include alkali feldspar (including anorthoclase and sanidine) and K-bearing phyllosilicate such as illite. Mixtures of different source rocks, including a potassium-rich rock located on the rim and walls of Gale Crater, are the likely origin of observed chemical variations within each unit. Physical sorting may have also played a role in the enrichment in K in the Kimberley formation. The occurrence of these potassic sedimentary rocks provides additional evidence for the chemical diversity of the crust exposed at Gale Crater.

Raised Ridges in the Sheepbed Member as Evidence for Early Subaqueous Diagenesis at Yellowknife Bay, Gale Crater, Mars

NASA Astrophysics Data System (ADS)

Siebach, K. L.; Grotzinger, J. P.; Kah, L. C.; Stack, K.; Leveille, R. J.; Sumner, D. Y.; Edgar, L. A.; Team, M.

2013-12-01

Spatially restricted clusters of erosion-resistant, ridged fracture fills have been found throughout the fine-grained clay-rich Sheepbed member of the Yellowknife Bay Formation where the Mars Science Laboratory rover recently drilled. These 'raised ridge' features are characterized by 1-6 mm thick fractures filled with 2-4 subparallel resistant ridges. The ridges have been mapped throughout the Sheepbed member on Mastcam mosaics from sols 137 to 194 and are shown to be constrained to relatively dense, spatially localized clusters within the unit. The ridges have highly variable attitudes, ranging in dip from vertical to sub-horizontal, and striking in all directions, indicating that the original fractures formed in a mechanically isotropic setting. The fractures are generally short (<50 cm), have spindle-shaped terminations, and do not form regular polygons. The individual ridges are approximately a millimeter across and separated by at least a millimeter of less-resistant material. Based on the geometry of these features and lateral fabric variability within the unit, these are interpreted as early diagenetic synaeresis cracks, likely formed by gas expansion prior to final lithification of the Sheepbed member. Based on the isopachous nature of both the resistant and less-resistant fracture fills, the fracture-filling also occurred subaqueously, in the phreatic zone, and was likely a very early diagenetic process. This is supported by the observation that later diagenetic features, including light-toned sulfate-rich veins, cross-cut raised ridges. Investigation into the characteristics and distribution of these features, and comparison with synaeresis cracks on Earth, provide insight into the formation of the Sheepbed member and early aqueous and diagenetic processes in Gale Crater.

Controls on Cyclic Formation of Quaternary Early Diagenetic Dolomite

NASA Astrophysics Data System (ADS)

McCormack, J.; Bontognali, T. R. R.; Immenhauser, A.; Kwiecien, O.

2018-04-01

The origin of sedimentary dolomite and the factors that control its formation within the geological record remain speculative. In most models, dolomite formation is linked to evaporative conditions, high water temperature, increasing Mg/Ca ratio, increasing alkalinity, and high amounts of biomass. Here we challenge these archetypal views, by documenting a case example of Quaternary dolomite which formed in Lake Van at constantly low temperature (<4°C) and without direct control of the latter conditions. Dolomite occurs within highstand sediments related to suborbital climate variability (Dansgaard-Oeschger cycles). We propose that dolomite precipitation is a product of a microbially influenced process, triggered by ecological stress, resulting from reventilation of the water-sediment interface. Independently from the validity of this hypothesis, our results call for a reevaluation of the paleoenvironmental conditions often invoked for early diagenetic dolomite-rich intervals within sedimentary sequences and for caution when interpreting time series of subrecent lacustrine carbonates.

Isotopic and elemental chemistry of sedimentary pyrite: A combined analytical and statistical approach to a novel planetary biosignature

NASA Astrophysics Data System (ADS)

Figueroa, M. C.; Gregory, D. D.; Lyons, T. W.; Williford, K. H.

2017-12-01

Life processes affect trace element abundances in pyrite such that sedimentary and hydrothermal pyrite have significantly different trace element signatures. Thus, we propose that these biogeochemical data could be used to identify pyrite that formed biogenetically either early in our planet's history or on other planets, particularly Mars. The potential for this approach is elevated because pyrite is common in diverse sedimentary settings, and its trace element content can be preserved despite secondary overprints up to greenschist facies, thus minimizing the concerns about remobilization that can plague traditional whole rock studies. We are also including in-situ sulfur isotope analysis to further refine our understanding of the complex signatures of ancient pyrite. Sulfur isotope data can point straightforwardly to the involvement of life, because pyrite in sediments is inextricably linked to bacterial sulfate reduction and its diagnostic isotopic expressions. In addition to analyzing pyrite of known biological origin formed in the modern and ancient oceans under a range of conditions, we are building a data set for pyrite formed by hydrothermal and metamorphic processes to minimize the risk of false positives in life detection. We have used Random Forests (RF), a machine learning statistical technique with proven efficiency for classifying large geological datasets, to classify pyrite into biotic and abiotic end members. Coupling the trace element and sulfur isotope data from our analyses with a large existing dataset from diverse settings has yielded 4500 analyses with 18 different variables. Our initial results reveal the promise of the RF approach, correctly identifying biogenic pyrite 97 percent of the time. We will continue to couple new in-situ S-isotope and trace element analyses of biogenic pyrite grains from modern and ancient environments, using cutting-edge microanalytical techniques, with new data from high temperature settings. Our ultimately goal

Sedimentary Petrography and Facies Analysis at the Shaler Outcrop, Gale Crater, Mars

NASA Astrophysics Data System (ADS)

Edgar, L. A.; Gupta, S.; Rubin, D. M.; Lewis, K. W.; Kocurek, G.; Anderson, R. B.; Bell, J. F.; Dromart, G.; Edgett, K. S.; Grotzinger, J. P.; Hardgrove, C. J.; Kah, L. C.; Leveille, R. J.; Malin, M.; Mangold, N.; Milliken, R.; Minitti, M. E.; Rice, M. S.; Rowland, S. K.; Schieber, J.; Stack, K.; Sumner, D. Y.; Team, M.

2013-12-01

The Mars Science Laboratory Curiosity rover has recently completed an investigation of a large fluvial deposit known informally as the Shaler outcrop (~1 m thick). Curiosity acquired data at the Shaler outcrop during sols 120-121 and 309-324. The Shaler outcrop is comprised of cross-bedded coarse-grained sandstones and recessive finer-grained intervals. Shaler is distinguished from the surrounding units by the presence of resistant beds exhibiting decimeter scale trough cross-bedding. Observations using the Mast Cameras, Mars Hand Lens Imager (MAHLI) and ChemCam Remote Micro Imager (RMI) enable the recognition of several distinct facies. MAHLI images were acquired on five distinct rock targets, and RMI images were acquired at 33 different locations. On the basis of grain size, erosional resistance, color, and sedimentary structures, we identify four facies: 1) resistant cross-stratified facies, 2) smooth, fine-grained cross-stratified facies, 3) dark gray, pitted facies, and 4) recessive, vertically fractured facies. Panoramic Mastcam observations reveal facies distributions and associations, and show cross-bedded facies that are similar to those observed at the Rocknest and Bathurst_Inlet locations. MAHLI and RMI images are used to determine the grain size, sorting, rounding and sedimentary fabric of the different facies. High-resolution images also reveal small-scale diagenetic features and sedimentary structures that are used to reconstruct the depositional and diagenetic history.

CUTS FOR MTR EXCAVATION ILLUSTRATE SEDIMENTARY MANTLE OF SOIL AND ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

CUTS FOR MTR EXCAVATION ILLUSTRATE SEDIMENTARY MANTLE OF SOIL AND GRAVEL OVERLAYING LAVA ROCK FIFTY FEET BELOW. SAGEBRUSH HAS BEEN SCOURED FROM REST OF SITE. CAMERA PROBABLY FACES SOUTHWEST. INL NEGATIVE NO. 67. Unknown Photographer, 6/4/1950 - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

Overpressure generation by load transfer following shale framework weakening due to smectite diagenesis

USGS Publications Warehouse

Lahann, R.W.; Swarbrick, R.E.

2011-01-01

Basin model studies which have addressed the importance of smectite conversion to illite as a source of overpressure in the Gulf of Mexico have principally relied on a single-shale compaction model and treated the smectite reaction as only a fluid-source term. Recent fluid pressure interpretation and shale petrology studies indicate that conversion of bound water to mobile water, dissolution of load-bearing grains, and increased preferred orientation change the compaction properties of the shale. This results in substantial changes in effective stress and fluid pressure. The resulting fluid pressure can be 1500-3000psi higher than pressures interpreted from models based on shallow compaction trends. Shale diagenesis changes the mineralogy, volume, and orientation of the load-bearing grains in the shale as well as the volume of bound water. This process creates a weaker (more compactable) grain framework. When these changes occur without fluid export from the shale, some of the stress is transferred from the grains onto the fluid. Observed relationships between shale density and calculated effective stress in Gulf of Mexico shelf wells confirm these changes in shale properties with depth. Further, the density-effective stress changes cannot be explained by fluid-expansion or fluid-source processes or by prediagenesis compaction, but are consistent with a dynamic diagenetic modification of the shale mineralogy, texture, and compaction properties during burial. These findings support the incorporation of diagenetic modification of compaction properties as part of the fluid pressure interpretation process. ?? 2011 Blackwell Publishing Ltd.

Early Archean stromatolites: Paleoenvironmental setting and controls on formation

NASA Technical Reports Server (NTRS)

Lowe, D. R.

1991-01-01

The earliest record of terrestrial life is contained in thin, silicified sedimentary layers within enormously thick, predominantly volcanic sequences in South Africa and Western Australia. This record includes bacteria-like microfossils, laminated carbonaceous structures resembling flat bacterial mats and stromatolites, and a morphologically diverse assemblage of carbonaceous particles. These structures and particles and their host sediments provide the only direct source of information on the morphology, paleoecology, and biogeochemistry of early life; the nature of interactions between organisms and surface systems on the early earth; and possible settings within which life might have evolved. The three known occurrences of 3.5 to 3.2 billion-year-old stromalites were evaluated in terms of depositional setting and biogenicity.

Long-term sedimentary recycling of rare sulphur isotope anomalies.

PubMed

Reinhard, Christopher T; Planavsky, Noah J; Lyons, Timothy W

2013-05-02

The accumulation of substantial quantities of O2 in the atmosphere has come to control the chemistry and ecological structure of Earth's surface. Non-mass-dependent (NMD) sulphur isotope anomalies in the rock record are the central tool used to reconstruct the redox history of the early atmosphere. The generation and initial delivery of these anomalies to marine sediments requires low partial pressures of atmospheric O2 (p(O2); refs 2, 3), and the disappearance of NMD anomalies from the rock record 2.32 billion years ago is thought to have signalled a departure from persistently low atmospheric oxygen levels (less than about 10(-5) times the present atmospheric level) during approximately the first two billion years of Earth's history. Here we present a model study designed to describe the long-term surface recycling of crustal NMD anomalies, and show that the record of this geochemical signal is likely to display a 'crustal memory effect' following increases in atmospheric p(O2) above this threshold. Once NMD anomalies have been buried in the upper crust they are extremely resistant to removal, and can be erased only through successive cycles of weathering, dilution and burial on an oxygenated Earth surface. This recycling results in the residual incorporation of NMD anomalies into the sedimentary record long after synchronous atmospheric generation of the isotopic signal has ceased, with dynamic and measurable signals probably surviving for as long as 10-100 million years subsequent to an increase in atmospheric p(O2) to more than 10(-5) times the present atmospheric level. Our results can reconcile geochemical evidence for oxygen production and transient accumulation with the maintenance of NMD anomalies on the early Earth, and suggest that future work should investigate the notion that temporally continuous generation of new NMD sulphur isotope anomalies in the atmosphere was likely to have ceased long before their ultimate disappearance from the rock record.

Organic sedimentary deposits in Titan's dry lakebeds: Probable evaporite

USGS Publications Warehouse

Barnes, J.W.; Bow, J.; Schwartz, J.; Brown, R.H.; Soderblom, J.M.; Hayes, A.G.; Vixie, G.; Le, Mouelic S.; Rodriguez, S.; Sotin, Christophe; Jaumann, R.; Stephan, K.; Soderblom, L.A.; Clark, R.N.; Buratti, B.J.; Baines, K.H.; Nicholson, P.D.

2011-01-01

We report the discovery of organic sedimentary deposits at the bottom of dry lakebeds near Titan's north pole in observations from the Cassini Visual and Infrared Mapping Spectrometer (VIMS). We show evidence that the deposits are evaporitic, making Titan just the third known planetary body with evaporitic processes after Earth and Mars, and is the first that uses a solvent other than water. ?? 2011 Elsevier Inc.

Tectonic evolution of the northern African margin in Tunisia from paleostress data and sedimentary record

NASA Astrophysics Data System (ADS)

Bouaziz, Samir; Barrier, Eric; Soussi, Mohamed; Turki, Mohamed M.; Zouari, Hédi

2002-11-01

A reconstruction of the tectonic evolution of the northern African margin in Tunisia since the Late Permian combining paleostress, tectonic stratigraphic and sedimentary approaches allows the characterization of several major periods corresponding to consistent stress patterns. The extension lasting from the Late Permian to the Middle Triassic is contemporaneous of the rifting related to the break up of Pangea. During Liassic times, regional extensional tectonics originated the dislocation of the initial continental platform. In northern Tunisia, the evolution of the Liassic NE-SW rifting led during Dogger times to the North African passive continental margin, whereas in southern Tunisia, a N-S extension, associated with E-W trending subsiding basins, lasted from the Jurassic until the Early Cretaceous. After an Upper Aptian-Early Albian transpressional event, NE-SW to ENE-WSW trending extensions prevailed during Late Cretaceous in relationship with the general tectonic evolution of the northeastern African plate. The inversions started in the Late Maastrichtian-Paleocene in northern Tunisia, probably as a consequence of the Africa-Eurasia convergence. Two major NW-SE trending compressions occurred in the Late Eocene and in the Middle-Late Miocene alternating with extensional periods in the Eocene, Oligocene, Early-Middle Miocene and Pliocene. The latter compressional event led to the complete inversion of the basins of the northwestern African plate, originating the Maghrebide chain. Such a study, supported by a high density of paleostress data and including complementary structural and stratigraphic approaches, provides a reliable way of determining the regional tectonic evolution.

Isolation of Geobacter species from diverse sedimentary environments

USGS Publications Warehouse

Coaxes, J.D.; Phillips, E.J.P.; Lonergan, D.J.; Jenter, H.; Lovley, D.R.

1996-01-01

In an attempt to better understand the microorganisms responsible for Fe(III) reduction in sedimentary environments, Fe(III)-reducing microorganisms were enriched for and isolated from freshwater aquatic sediments, a pristine deep aquifer, and a petroleum-contaminated shallow aquifer. Enrichments were initiated with acetate or toluene as the electron donor and Fe(III) as the electron acceptor. Isolations were made with acetate or benzoate. Five new strains which could obtain energy for growth by dissimilatory Fe(III) reduction were isolated. All five isolates are gram- negative strict anaerobes which grow with acetate as the electron donor and Fe(III) as the electron acceptor. Analysis of the 16S rRNA sequence of the isolated organisms demonstrated that they all belonged to the genus Geobacter in the delta subdivision of the Proteobacteria. Unlike the type strain, Geobacter metallireducens, three of the five isolates could use H2 as an electron donor fur Fe(III) reduction. The deep subsurface isolate is the first Fe(III) reducer shown to completely oxidize lactate to carbon dioxide, while one of the freshwater sediment isolates is only the second Fe(III) reducer known that can oxidize toluene. The isolation of these organisms demonstrates that Geobacter species are widely distributed in a diversity of sedimentary environments in which Fe(III) reduction is an important process.

Permanganate diffusion and reaction in sedimentary rocks.

PubMed

Huang, Qiuyuan; Dong, Hailiang; Towne, Rachael M; Fischer, Timothy B; Schaefer, Charles E

2014-04-01

In situ chemical oxidation using permanganate has frequently been used to treat chlorinated solvents in fractured bedrock aquifers. However, in systems where matrix back-diffusion is an important process, the ability of the oxidant to migrate and treat target contaminants within the rock matrix will likely determine the overall effectiveness of this remedial approach. In this study, a series of diffusion experiments were performed to measure the permanganate diffusion and reaction in four different types of sedimentary rocks (dark gray mudstone, light gray mudstone, red sandstone, and tan sandstone). Results showed that, within the experimental time frame (~2 months), oxidant migration into the rock was limited to distances less than 500 μm. The observed diffusivities for permanganate into the rock matrices ranged from 5.3 × 10(-13) to 1.3 × 10(-11) cm(2)/s. These values were reasonably predicted by accounting for both the rock oxidant demand and the effective diffusivity of the rock. Various Mn minerals formed as surface coatings from reduction of permanganate coupled with oxidation of total organic carbon (TOC), and the nature of the formed Mn minerals was dependent upon the rock type. Post-treatment tracer testing showed that these Mn mineral coatings had a negligible impact on diffusion through the rock. Overall, our results showed that the extent of permanganate diffusion and reaction depended on rock properties, including porosity, mineralogy, and organic carbon. These results have important implications for our understanding of long-term organic contaminant remediation in sedimentary rocks using permanganate. Copyright © 2014 Elsevier B.V. All rights reserved.

Net Flux of Sedimentary Carbon to the Mantle During the Cenozoic

NASA Astrophysics Data System (ADS)

Clift, P. D.

2017-12-01

Quantification of the long-term cycling of carbon from the mantle to the surface remains contentious despite its importance in governing the climate and biosphere of Earth. Sedimentary carbon represents a significant part of the budget and can be recycled to the mantle if it reaches subduction zones and is not preserved in an accretionary prism. By estimating rates of sediment supply and accretion and taking into account carbonate and carbon contents it appears that 60 Mt/yr is presently being subducted below forearcs. 80% is in the form of carbonate, significantly more than previously estimated. Sedimentary carbon represents around two thirds of the total carbon input at the trenches, the rest being in the igneous crust. An additional 7 Mt/yr is averaged over the Cenozoic as a result of passive margin subduction during continental collision. My revised budget puts the input and output budgets within the range of uncertainties, compared to the previous deficit. Degassing from arc volcanoes and in forearcs totals 55 Mt/yr. A net flux to the mantle is probable. The efficiency of carbon subduction is largely controlled by the carbonate contents of the sediment column, and is partly linked to the latitude of the trench. Accretionary margins are the biggest suppliers of carbon to the mantle wedge, especially Java, Sumatra, Andaman-Burma and Makran because the offscraping is inefficient and the thickness of the trench sediment and trench length are both large. The Western Pacific trenches are negligible sinks of sedimentary carbon.

Stratigraphic Sedimentary Environmental Change of the Mount Bruce Supergroup, Beasley River Area, Southern Pilbara, Western Australia

NASA Astrophysics Data System (ADS)

Komure, M.; Kiyokawa, S.; Ikehara, M.; Tsutsumi, Y.; Horie, K.

2005-12-01

The Mount Bruce Supergroup is deposited from Late Archaean to Early Proterozoic in the Pilbara craton, Western Australia. It is filed the information of the period that changes from the Late Archean to the Early Proterozoic, and is the key sequences which could reconstruct the sedimentary environment because of its low metamorphic grade. The evidence of early Proterozoic global ice age as the glacial sediment is reported in this uppermost group (Martin 1999). In this study, we focus the lithological changes of the Mount Bruce Supergroup at the Beasley River - Rocklea Dome area in the Southern Pilbara. Along the Beasley River, this supergroup distributes more than 10000m thick with 5 billion years sequences, and is divided into three groups. The Fortescue Group is identified with the flood basalt to the Shallow marine or the non-marine sediment, the middle Hamersley Group rich in the banded iron formation and the acidic volcanic rock and the upper Turee Creek Group mainly of the Shallow marine sediment. Here we focused origin of the sandstone in each group, especially in the Meteorite Bore Member of Turee Creek Formation which is identified as the early snowball earth events. At the matrix of the diamictite of the Meteorite Bore Member, Origin of diamictite matrix in the Turee Creek Group sediment by the U-Pb detrital zircon geochronology by CHIME and SHRIMP2. The zircon ages points between 2.7Ga and 2.4Ga. In addtion from this matrix, TOC value indicate 0.1-0.05%, the delta 13 C value is -30--20 par mil. These evidence suggested that the organic activity might take place at during ice age.

Inversion of the Erlian Basin (NE China) in the early Late Cretaceous: Implications for the collision of the Okhotomorsk Block with East Asia

NASA Astrophysics Data System (ADS)

Guo, Zhi-Xin; Shi, Yuan-Peng; Yang, Yong-Tai; Jiang, Shuan-Qi; Li, Lin-Bo; Zhao, Zhi-Gang

2018-04-01

A significant transition in tectonic regime from extension to compression occurred throughout East Asia during the mid-Cretaceous and has stimulated much attention. However, the timing and driving mechanisms of the transition remain disputed. The Erlian Basin, a giant late Mesozoic intracontinental petroliferous basin located in the Inner Mongolia, Northeast China, contains important sedimentary and structural records related to the mid-Cretaceous compressional event. The stratigraphical, sedimentological and structural analyses reveal that a NW-SE compressional inversion occurred in the Erlian Basin between the depositions of the Lower Cretaceous Saihan and Upper Cretaceous Erlian formations, causing intense folding of the Saihan Formation and underlying strata, and the northwestward migration of the depocenters of the Erlian Formation. Based on the newly obtained detrital zircon U-Pb data and previously published paleomagnetism- and fossil-based ages, the Saihan and Erlian formations are suggested as latest Aptian-Albian and post-early Cenomanian in age, respectively, implying that the inversion in the Erlian Basin occurred in the early Late Cretaceous (Cenomanian time). Apatite fission-track thermochronological data record an early Late Cretaceous cooling/exhuming event in the basin, corresponding well with the aforementioned sedimentary, structural and chronological analyses. Combining with the tectono-sedimentary evolutions of the neighboring basins of the Erlian Basin, we suggest that the early Late Cretaceous inversional event in the Erlian Basin and the large scale tectonic transition in East Asia shared the common driving mechanism, probably resulting from the Okhotomorsk Block-East Asia collisional event at about 100-89 Ma.

Early diagenesis of lignin-associated phenolics in the salt marsh grass Spartina alterniflora

NASA Astrophysics Data System (ADS)

Haddad, R. I.; Newell, S. Y.; Martens, C. S.; Fallon, R. D.

1992-10-01

The predepositional stability of lignin in the salt marsh cordgrass Spartina alterniflora was examined in two different degradation studies: one was a traditional litterbag study carried out using post-senescent brown leaves in a North Carolina marsh creek, and the other was a study in which senescing, standing plants were tagged and allowed to undergo in situ degradation in a Sapelo Island, Georgia, salt marsh. Based on results from lignin oxidation product (LOP) analysis of leaves, lignin in the S. alterniflora was shown to be significantly degraded in both studies, with 13 ± 2% and 25 ± 12% of the total lignin mass loss occurring over the 496-day litterbag and 146-day tagged studies, respectively. A comparison of the results from both studies suggests that most of the calculated lignin loss (> 90%) occurs early in the degradation history of the plant, with a significant portion occurring while the plant is still standing in the salt marsh. Further detailed evaluation of this loss demonstrates that selective lignin degradation occurs in S. alterniflora, deriving from the preferential loss of labile lignin moieties. The most labile component, trans-ferulic acid, accounted for 57% and 82% of the total lignin loss in the litterbag and tagged studies, respectively, based on normalization to syringyl-phenol concentrations. Comparison of these two data sets supports the following approximate lignin stability sequence for S. alterniflora:S ≅ Ca ≅ V > P > Fa. Based on measured changes in both the lignin mass loss and the LOP acid/aldehyde ratio, as well as evidence suggesting that degradation occurred under oxic conditions, it is proposed that aromatic ring cleavage was the predominant mechanism of lignin degradation in both studies. In light of these results and those from other recent lignin degradation studies, we discuss the geochemical consequences regarding the usefulness of lignin oxidation products as quantitative tracers of vascular plant-derived organic

Diagenetic effects of compaction on reservoir properties: The case of early callovian ``Dalle Nacrée'' formation (Paris basin, France)

NASA Astrophysics Data System (ADS)

Nader, Fadi H.; Champenois, France; Barbier, Mickaël; Adelinet, Mathilde; Rosenberg, Elisabeth; Houel, Pascal; Delmas, Jocelyne; Swennen, Rudy

2016-11-01

The impact of compaction diagenesis on reservoir properties is addressed by means of observations made on five boreholes with different burial histories of the Early Callovian ;Dalle Nacrée; Formation in the Paris Basin. Petrographic analyses were carried out in order to investigate the rock-texture, pore space type and volume, micro-fabrics, and cement phases. Based on the acquired data, a chronologically ordered sequence of diagenetic events (paragenesis) for each borehole was reconstructed taking the burial history into account. Point counting and a segmentation algorithm (Matlab) were used to quantify porosity, as well as the amounts of grain constituents and cement phases on scanned images of studied thin sections. In addition, four key samples were analyzed by 3D imaging using microfocus X-ray computer tomography. Basin margin grainstones display a different burial diagenesis when compared to basin centre grainstones and wackestones. The former have been affected by considerable cementation (especially by blocky calcite) prior to effective burial, in contrast to the basin centre lithologies where burial and compaction prevailed with relatively less cementation. Fracturing and bed-parallel stylolitization, observed especially in basinal wackestone facies also invoke higher levels of mechanical and chemical compaction than observed in basin marginal equivalents. Compaction fluids may have migrated at the time of burial from the basin centre towards its margins, affecting hence the reservoir properties of similar rock textures and facies and resulting in cross-basin spatial diagenetic heterogeneities.

Isotopic and chemical studies of early crustal metasedimentary rocks

NASA Technical Reports Server (NTRS)

Jacobsen, Stein B.

1988-01-01

The aim, within the bounds of the Early Crustal Genesis Project, was the isotopic and chemical study of selected early crustal meta-sedimentary rocks. Western Australia was chosen as the first field area to examine, as the Yilgarn and Pilbara Blocks comprise one of the largest and most varied Precambrian terranes. Furthermore, the Western Gneiss Terrane (on the western flank of the Yilgarn Block) and the Pilbara Block are both non-greenstone in character; these types of terrane were relatively neglected, but are of great significance in the understanding of early crustal meta-sediments. The meta-sediments of aluminous or peraluminous character, commonly also enriched in Mg and/or Fe relative to the more common pelitic meta-sediments, and at many locations, deficient in one or more of the elements Ca, N, and K, were initially chosen.

Exhumation and stress history in the sedimentary cover during Laramide thick-skinned tectonics assessed by stylolite roughness analysis.

NASA Astrophysics Data System (ADS)

Beaudoin, Nicolas; Lacombe, Olivier; David, Marie-Eléonore; Koehn, Daniel; Coltier, Robin

2017-04-01

Basement-involvement in shortening in forelands has a strong impact on the overlying sedimentary cover. The basement influences namely the geometry of folds and structures, the stress evolution and the nature and pathways for fluid migrations. However, these influences are poorly documented in context where the basement/cover interface is shallow (<6 km). This contribution presents the reconstruction of paleostress and vertical burial history of the Palaeozoic sedimentary strata affected by the Sevier-Laramide deformation at the front of the Rocky Mountains, in the Bighorn Basin (Wyoming, USA). Stylolite populations have been considered as part of an extensive microstructure investigation including also fractures, striated microfaults and calcite twins in key major structures such as the Sheep Mountain Anticline, the Rattlesnake Mountain Anticline, and the Bighorn Mountains Arch. Stylolite recognized in the field are clearly related to successive stages of deformation of the sedimentary cover, including fold development. We further apply a newly developed roughness analysis of pressure-solution stylolites which grant access (1) to the magnitude of the vertical principal stress, hence the maximum burial depth of the strata based on sedimentary stylolites, (2) to the principal stress orientations and regimes based on tectonic stylolites and (3) ultimately to the complete stress tensor when sedimentary and tectonic stylolites can be considered coeval. This approach was then coupled to mechanical properties of main competent formations exposed in the basin. Results of stylolite paleopiezometry, compared and combined to existing paleostress estimates from calcite twins and to exhumation reconstruction from low-temperature thermochronology, unravel the potential of the method to refine the structural history at the structure- and basin-scale. On top of the advances this case study adds to the methodology, the quantified reconstruction of stress-exhumation evolution in

Petrochronology in constraining early Archean Earth processes and environments: Barberton greenstone belt, South Africa

NASA Astrophysics Data System (ADS)

Grosch, Eugene

2017-04-01

Analytical and petrological software developments over the past decade have seen rapid innovation in high-spatial resolution petrological techniques, for example, laser-ablation ICP-MS, secondary ion microprobe (SIMS, nano-SIMS), thermodynamic modelling and electron microprobe microscale mapping techniques (e.g. XMapTools). This presentation will focus on the application of petrochronology to ca. 3.55 to 3.33 billion-year-old metavolcanic and sedimentary rocks of the Onverwacht Group, shedding light on the earliest geologic evolution of the Paleoarchean Barberton greenstone belt (BGB) of South Africa. The field, scientific drilling and petrological research conducted over the past 8 years, aims to illustrate how: (a) LA-ICP-MS and SIMS U-Pb detrital zircon geochronology has helped identify the earliest tectono-sedimentary basin and sediment sources in the BGB, as well as reconstructing geodynamic processes as early as ca. 3.432 billion-years ago; (b) in-situ SIMS multiple sulphur isotope analysis of sulphides across various early Archean rock units help to reconstruct atmospheric, surface and subsurface environments on early Archean Earth and (c) the earliest candidate textural traces for subsurface microbial life can be investigated by in-situ LA-ICP-MS U-Pb dating of titanite, micro-XANES Fe-speciation analysis and metamorphic microscale mapping. Collectively, petrochronology combined with high-resolution field mapping studies, is a powerful multi-disciplinary approach towards deciphering petrogenetic and geodynamic processes preserved in the Paleoarchean Barberton greenstone belt of South Africa, with implications for early Archean Earth evolution.

Late Jurassic-Early Cretaceous radiolarian age constraints from the sedimentary cover of the Amasia ophiolite (NW Armenia), at the junction between the Izmir-Ankara-Erzinçan and Sevan-Hakari suture zones

NASA Astrophysics Data System (ADS)

Danelian, T.; Asatryan, G.; Galoyan, Gh.; Sahakyan, L.; Stepanyan, J.

2016-01-01

The Amasia ophiolite, situated at the northernmost corner of Armenia, is part of the Sevan-Hakari suture zone which links with the Izmir-Ankara-Erzinçan suture zone in northern Turkey. Three new radiolarian assemblages have been extracted from siliceous sedimentary rocks that accumulated on the Amasia ophiolite in an oceanic setting. Two of these assemblages were extracted from red-brownish bedded cherts overlying basaltic lavas; one of these is likely to be middle Oxfordian to early Kimmeridgian in age, while the second correlates with the Berriasian. Similar time-equivalent lava-chert sequences have been dated recently using radiolarians from the Stepanavan, Vedi and Sevan ophiolite units, where they are considered to relate to submarine volcanic activity in the back-arc marginal basin in which the Armenian ophiolites were formed. The third radiolarian assemblage, of late Barremian age, was extracted from a more than 15-m-thick volcaniclastic-chert sequence. The related volcanic activity is likely to have been subaerial and probably relates to the formation of an oceanic volcanic plateau; no Cretaceous subaerial volcanism has been previously recorded in the Lesser Caucasus area.

Sedimentary architecture and chronostratigraphy of a late Quaternary incised-valley fill: A case study of the late Middle and Late Pleistocene Rhine system in the Netherlands

NASA Astrophysics Data System (ADS)

Peeters, J.; Busschers, F. S.; Stouthamer, E.; Bosch, J. H. A.; Van den Berg, M. W.; Wallinga, J.; Versendaal, A. J.; Bunnik, F. P. M.; Middelkoop, H.

2016-01-01

This paper describes the sedimentary architecture, chronostratigraphy and palaeogeography of the late Middle and Late Pleistocene (Marine Isotope Stage/MIS 6-2) incised Rhine-valley fill in the central Netherlands based on six geological transects, luminescence dating, biostratigraphical data and a 3D geological model. The incised-valley fill consists of a ca. 50 m thick and 10-20 km wide sand-dominated succession and includes a well-developed sequence dating from the Last Interglacial: known as the Eemian in northwest Europe. The lower part of the valley fill contains coarse-grained fluvio-glacial and fluvial Rhine sediments that were deposited under Late Saalian (MIS 6) cold-climatic periglacial conditions and during the transition into the warm Eemian interglacial (MIS 5e-d). This unit is overlain by fine-grained fresh-water flood-basin deposits, which are transgressed by a fine-grained estuarine unit that formed during marine high-stand. This ca. 10 m thick sequence reflects gradual drowning of the Eemian interglacial fluvial Rhine system and transformation into an estuary due to relative sea-level rise. The chronological data suggests a delay in timing of regional Eemian interglacial transgression and sea-level high-stand of several thousand years, when compared to eustatic sea-level. As a result of this glacio-isostatic controlled delay, formation of the interglacial lower deltaic system took only place for a relative short period of time: progradation was therefore limited. During the cooler Weichselian Early Glacial period (MIS 5d-a) deposition of deltaic sediments continued and extensive westward progradation of the Rhine system occurred. Major parts of the Eemian and Weichselian Early Glacial deposits were eroded and buried as a result of sea-level lowering and climate cooling during the early Middle Weichselian (MIS 4-3). Near complete sedimentary preservation occurred along the margins of the incised valley allowing the detailed reconstruction presented

Mid-depth sedimentary oxygenation variation in the western Pacific since the last glacial period: geochemical evidence from the Okinawa Trough

NASA Astrophysics Data System (ADS)

Zou, J. J.; Shi, X.; Zhu, A.

2017-12-01

In this study, we investigate a suite of sediment geochemical proxies (total organic carbon and carbonate contents, carbon to nitrogen ratio, aluminum and redox-sensitive elements) to reconstruct the history of sedimentary oxygenation in the northern Okinawa Trough (OT) over the last 50 thousand years (ka). Our data support the presence of oxygen-deficient deep waters during the late deglacial and Preboreal phases (15‒9.5 ka), but oxygenated water column during the Heinrich Stadial 1 (HS1) and the Last Glacial Maximum (LGM). In contrast, increased sedimentary oxygenations are evident during the late glacial period and since 8.5 ka. Fluctuations of sedimentary oxygenation were widespread and apparently coherent over the entire North Pacific basin, reflecting broad effects of North Pacific Intermediate Water (NPIW) ventilation and export productivity. Intensified Kuroshio, however, improved the sedimentary oxygenation since 8.5 ka. We found the correspondence between changes in deglacial sedimentary oxygenation in the OT and Atlantic Meridional Overturning Circulation through the NPIW ventilation. The mechanism behind Atlantic-Pacific ventilation seesaw seems to be attributed to the perturbation of sea ice formation in high latitude North Pacific through atmospheric teleconnection.

Sedimentary facies and gas accumulation model of Lower Shihezi Formation in Shenguhao area, northern Ordos basin, China

NASA Astrophysics Data System (ADS)

Lin, Weibing; Chen, Lin; Lu, Yongchao; Zhao, Shuai

2017-04-01

The Lower Shihezi formation of lower Permian series in Shenguhao develops the highest gas abundance of upper Paleozoic in China, which has already commercially produced on a large scale. The structural location of Shenguhao belongs to the transition zone of Yimeng uplift and Yishan slope of northern Ordos basin, China. Based on the data of core, well logging and seismic, the sedimentary facies and gas accumulation model have been studied in this paper. Sedimentary facies analysis shows that the braided delta is the major facies type developed in this area during the period of Lower Shihezi formation. The braided delta can be further divided into two microfacies, distributary channel and flood plain. The distributary channel sandbody develops the characteristics of scour surface, trough cross beddings and normal grading sequences. Its seismic reflection structure is with the shape of flat top and concave bottom. Its gamma-ray logging curve is mainly in a box or bell shape. The flood plain is mainly composed of thick mudstones. Its seismic reflection structure is with the shape of parallel or sub-parallel sheet. Its gamma-ray logging curve is mainly in a linear tooth shape. On the whole, the distribution of sandbody is characterized by large thickness, wide area and good continuity. Based on the analysis of the sea level change and the restoration of the ancient landform in the period of Lower Shihezi formation, the sea level relative change and morphology of ancient landform have been considered as the main controlling factors for the development and distribution of sedimentary facies. The topography was with big topographic relief, and the sea level was relatively low in the early stage of Low Shihezi formation. The sandbody distributed chiefly along the landform depressions. The sandbody mainly developed in the pattern of multiple vertical superpositions with thick layer. In the later stage, landform gradually converted to be flat, and strata tended to be gentle

Evaluation of carbonate diagenesis: A comparative study of minor elements, trace elements, and rare-earth elements (REE + Y) between Pleistocene corals and matrices from Grand Cayman, British West Indies

NASA Astrophysics Data System (ADS)

Li, Rong; Jones, Brian

2014-12-01

On Grand Cayman, the Pleistocene Ironshore Formation consists of six unconformity-bounded units of limestones that have been partially or completely altered to calcite by post-depositional meteoric diagenesis. In order to examine the diagenetic history from the perspective of geochemical elements, the concentrations of minor element (Sr, Na, Mg), trace elements (Ba, Fe, Mn, Al, Si), and rare-earth elements (REE) and yttrium (Y) were determined for 105 corals and 84 matrices collected from the Rogers Wreck Point (RWP), Western Onshore area (WO), and offshore George Town (GT) areas. With the transformation of aragonite to calcite, the Sr, Na, and Ba values decreased, but Mg increased, which are indicative of diagenetic alteration in an open water system. Due to intrinsic "vital effects" and the extrinsic diagenetic environment, the variations of Sr, Na, Ba, and Mg concentrations between Acropora and Montastrea from the GT area are different to those of their counterparts from RWP and WO. The signatures of Sr, Na, Ba, and Mg are in good agreement with the diagenetic history as determined from petrographic and stable isotopic criteria. The REE + Y (REY) concentrations (ΣREY) are higher in the matrices (0.2-6.9 ppm, average 2.6 ppm) than in the associated corals (0.1-5.4 ppm, average 0.6 ppm). Shale-normalized REY patterns of the Pleistocene Ironshore Formation are similar to those of oxygenated seawater, which are characterized by (1) light REE depletion relative to heavy REE (average DySN/SmSN = 1.7, n = 35), (2) positive La anomalies (average Pr/Pr* = 1.17, n = 53), and (3) negative Ce anomalies (average Ce/Ce* = 0.49, n = 53). The preserved seawater-like REY distribution pattern, the lack of correlation between ΣREY and mineralogy, and the lack of correlation between ΣREY and diagenesis-sensitive stable oxygen isotope (δ18O) indicate that meteoric diagenesis did not have a major impact on the REY distribution patterns. The matrices and corals in the GT area

Impacts of flocculation on the distribution and diagenesis of iron in boreal estuarine sediments

NASA Astrophysics Data System (ADS)

Jilbert, Tom; Asmala, Eero; Schröder, Christian; Tiihonen, Rosa; Myllykangas, Jukka-Pekka; Virtasalo, Joonas J.; Kotilainen, Aarno; Peltola, Pasi; Ekholm, Päivi; Hietanen, Susanna

2018-03-01

Iron (Fe) plays a key role in sedimentary diagenetic processes in coastal systems, participating in various redox reactions and influencing the burial of organic carbon. Large amounts of Fe enter the marine environment from boreal river catchments associated with dissolved organic matter (DOM) and as colloidal Fe oxyhydroxides, principally ferrihydrite. However, the fate of this Fe pool in estuarine sediments has not been extensively studied. Here we show that flocculation processes along a salinity gradient in an estuary of the northern Baltic Sea efficiently transfer Fe and OM from the dissolved phase into particulate material that accumulates in the sediments. Flocculation of Fe and OM is partially decoupled. This is likely due to the presence of discrete colloidal ferrihydrite in the freshwater Fe pool, which responds differently from DOM to estuarine mixing. Further decoupling of Fe from OM occurs during sedimentation. While we observe a clear decline with distance offshore in the proportion of terrestrial material in the sedimentary particulate organic matter (POM) pool, the distribution of flocculated Fe in sediments is modulated by focusing effects. Labile Fe phases are most abundant at a deep site in the inner basin of the estuary, consistent with input from flocculation and subsequent focusing. The majority of the labile Fe pool is present as Fe (II), including both acid-volatile sulfur (AVS)-bound Fe and unsulfidized phases. The ubiquitous presence of unsulfidized Fe (II) throughout the sediment column suggests Fe (II)-OM complexes derived from reduction of flocculated Fe (III)-OM, while other Fe (II) phases are likely derived from the reduction of flocculated ferrihydrite. Depth-integrated rates of Fe (II) accumulation (AVS-Fe + unsulfidized Fe (II) + pyrite) for the period 1970-2015 are greater in the inner basin of the estuary with respect to a site further offshore, confirming higher rates of Fe reduction in near-shore areas. Mössbauer 57Fe

Riverine Carbon and the Sedimentary Record on the Continental Shelves

DTIC Science & Technology

2004-09-30

Riverine Carbon and the Sedimentary Record on the Continental Shelves Stefano Miserocchi Istituto Scienze Marine, Sezione Geologia Marina...formerly Istituto di Geologia Marina) Consiglio Nazionale delle Ricerche Via Gobetti, 101 40129 Bologna, Italy phone: +39 (051) 6398880 Fax. +39 (051... Geologia Marina,,(formerly Istituto di Geologia Marina),Consiglio Nazionale delle Ricerche,,Via Gobetti, 101,40129 Bologna, Italy, , 8. PERFORMING

Hydrodynamic Controls on Muddy Sedimentary Fabric Development on Low-Gradient Shelves: Atchafalaya Chenier Plain Subaqueous Delta

NASA Astrophysics Data System (ADS)

Denommee, K.; Bentley, S. J.; Harazim, D.; Macquaker, J.

2016-02-01

Short sediment cores and geophysical data collected on the Southwest Louisiana Chenier Plain inner shelf have been studied in order to examine the sedimentary products of current-wave-enhanced sediment gravity flows (CWESGFs), a type of sediment gravity flow where the driving energy required to transport sediment across low-gradient settings is augmented by the near-bed orbital velocity of surface gravity wave and near-bed currents. Sedimentary fabrics observed on the SWLA shelf document the following flow evolution: (1) the erosion of the underlying substrate in response to wave-generated shear stresses in the bottom boundary layer, followed by (2) the deposition of ripple a crossbeded unit during wave-mediated oscillatory motions in low-viscosity suspension; (3) the deposition of subtle intercalated laminae during laminar flow at higher suspended sediment concentrations; followed by the deposition of (4) normally graded sediments during the waning phases of the flow. Significantly, the sedimentary fabrics deposited by CWESGFs on SWLA shelf show diagnostic variations from CWESGF-generated sedimentary fabrics observed on the Eel and Amazon shelves. Differences between the observed sedimentary fabrics are hypothesized to result from variations in the relative contribution of near-bed currents, wave orbital velocities, and bed slope (gravity) to the driving energy of the CWESGF, and as such can be catalogued as diagnostic recognition criteria using a prismatic ternary diagram where current-, wave-, and gravity-dominated end members form the vertices of a triangle, and wave period forms the prism axis. In this framework forcing mechanisms can be represented quantitatively, based on wave period and the relative contribution of each of the CWESGF velocity terms. This framework can be used to explore relationships between hydrodynamics and CWESGF fabrics, providing geologists with a tool with which to better recognize the depositional products of CWESGFs in the rock

Seasonal variations and sources of sedimentary organic carbon in Tokyo Bay.

PubMed

Kubo, Atsushi; Kanda, Jota

2017-01-30

Total organic carbon (TOC), total nitrogen (TN) contents, their stable C and N isotope ratio (δ 13 C and δ 15 N), and chlorophyll a ([Chl a] sed ) of surface sediments were investigated monthly to identify the seasonal variations and sources of organic matter in Tokyo Bay. The sedimentary TOC (TOC sed ) and TN (TN sed ) contents, and the sedimentary δ 13 C and δ 15 N (δ 13 C sed and δ 15 N sed ) values were higher in summer than other seasons. The seasonal variations were controlled by high primary production in the water column and hypoxic water in the bottom water during summer. The fraction of terrestrial and marine derived organic matter was estimated by Bayesian mixing model using stable isotope data and TOC/TN ratio. Surface sediments in Tokyo Bay are dominated by marine derived organic matter, which accounts for about 69±5% of TOC sed . Copyright © 2016 Elsevier Ltd. All rights reserved.

Evidence for only minor contributions from bacteria to sedimentary organic carbon

NASA Technical Reports Server (NTRS)

Hartgers, W. A.; Sinninghe Damste, J. S.; Requejo, A. G.; Allan, J.; Hayes, J. M.; de Leeuw, J. W.

1994-01-01

Because their molecular signatures are often prominent in extracts of sediments, bacteria are thought to be important contributors to petroleum source beds. It has been shown recently, however, that abundances of biomarkers do not always reflect relative contributions to sedimentary organic carbon (Corg). The contribution of photosynthetic green sulphur bacteria to sediments can be assessed effectively because the diagenetic products of distinctive carotenoids from these organisms occur widely and their biomass is isotopically labelled, being enriched in 13C. We show here that, although sediments and oils from the Western Canada and Williston basins contain prominent biomarkers of photosynthetic bacteria, the absence of 13C enrichment in the total Corg requires that the bacterial contribution is in fact minimal. Although the importance of bacterial reworking of sedimentary debris cannot be doubted, we argue that our findings, when considered in conjunction with those from other settings, suggest that bacterial biomass may commonly represent only a minor component of total Corg in carbonaceous rocks.

Accumulation and diagenesis of chlorinated hydrocarbons in lacustrine sediments

USGS Publications Warehouse

Elsenreich, S.J.; Capel, P.D.; Robbins, J.A.; Bourbonniere, R.

1989-01-01

Two sediment cores were taken from the Rochester Basin of eastern Lake Ontario and analyzed for the radionuclides 210Pb and 137Cs and several high molecular weight chlorinated hydrocarbons (CHs). The two sites are geographically proximate but differ in sedimentation rate, permitting sedimentation-dependent processes to be factored out. The 210Pb chronology showed a mixed depth of 3-5 cm and an intrinsic time resolution of 11-14 years. Vertically integrated numbers of deposit-feeding oligochaete worms and burrowing organisms are insufficient to homogenize the sediment on the time scale of CH inputs, which are non steady state. U.S. production and sales of polychlorinated biphenyls (PCBs), DDT, Mirex, and hexachlorobenzene (HCB), as determinants of the shape of the input function, adequately predict the overall shape and, in many cases, details in the sedimentary profile. Sediment focusing factors (FF) inferred from 137Cs and 210Pb inventories averaged 1.17 and 1.74 for cores E-30 and G-32, respectively. This permitted CH accumulation rates to be corrected for focusing. Apparent molecular diffusion coefficients modeled for many of the CHs were about (1-3) ?? 10-9 cm2/s.

Areal distribution of sedimentary facies determined from seismic facies analysis and models of modern depositional systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seramur, K.C.; Powell, R.D.; Carpenter, P.J.

1988-02-01

Seismic facies analysis was applied to 3.5-kHz single-channel analog reflection profiles of the sediment fill within Muir Inlet, Glacier Bay, southeast Alaska. Nine sedimentary facies have been interpreted from seven seismic facies identified on the profiles. The interpretations are based on reflection characteristics and structural features of the seismic facies. The following reflection characteristics and structural features are used: reflector spacing, amplitude and continuity of reflections, internal reflection configurations, attitude of reflection terminations at a facies boundary, body geometry of a facies, and the architectural associations of seismic facies within each basin. The depositional systems are reconstructed by determining themore » paleotopography, bedding patterns, sedimentary facies, and modes of deposition within the basin. Muir Inlet is a recently deglaciated fjord for which successive glacier terminus positions and consequent rates of glacial retreat are known. In this environment the depositional processes and sediment characteristics vary with distance from a glacier terminus, such that during a retreat a record of these variations is preserved in the aggrading sediment fill. Sedimentary facies within the basins of lower Muir Inlet are correlated with observed depositional processes near the present glacier terminus in the upper inlet. The areal distribution of sedimentary facies within the basins is interpreted using the seismic facies architecture and inferences from known sediment characteristics proximal to present glacier termini.« less

Sedimentary Deposits within Ius Chasma

NASA Image and Video Library

2015-07-15

Sedimentary deposits are common within Valles Marineris. Most larger chasmata contain kilometer-thick light-toned layered deposits composed of sulfates. However, some of the chasmata, like Ius Chasma shown in this image from NASA Mars Reconnaissance Orbiter, lack these deposits or have much thinner deposits. The light-toned deposits in Ius Chasma are observed both along the floor and inner wallrock materials. Some of the light-toned deposits appear to post-date formation of the chasma floor, whereas other deposits appear to lie beneath wallrock materials, indicating they are older. By examining the stratigraphy using digital terrain models and 3D images, it should be possible to decipher the relative ages of the different geologic units. CRISM data may also provide insight into the mineralogy, which will tell scientists about the aqueous conditions that emplaced the light-toned deposits. http://photojournal.jpl.nasa.gov/catalog/PIA19855

Bottom-trawling along submarine canyons impacts deep sedimentary regimes

PubMed Central

Paradis, Sarah; Puig, Pere; Masqué, Pere; Juan-Díaz, Xènia; Martín, Jacobo; Palanques, Albert

2017-01-01

Many studies highlight that fish trawling activities cause seafloor erosion, but the assessment of the remobilization of surface sediments and its relocation is still not well documented. These impacts were examined along the flanks and axes of three headless submarine canyons incised on the Barcelona continental margin, where trawling fleets have been operating for decades. Trawled grounds along canyon flanks presented eroded and highly reworked surface sediments resulting from the passage of heavy trawling gear. Sedimentation rates on the upper canyon axes tripled and quadrupled its natural (i.e. pre-industrialization) values after a substantial increase in total horsepower of the operating trawling fleets between 1960 s and 1970 s. These impacts affected the upper canyon reaches next to fishing grounds, where sediment resuspended by trawling can be transported towards the canyon axes. This study highlights that bottom trawling has the capacity to alter natural sedimentary environments by promoting sediment-starved canyon flanks, and by enhancing sedimentation rates along the contiguous axes, independently of canyons’ morphology. Considering the global mechanisation and offshore expansion of bottom trawling fisheries since the mid-20th century, these sedimentary alterations may occur in many trawled canyons worldwide, with further ecological impacts on the trophic status of these non-resilient benthic communities. PMID:28233856

Bottom-trawling along submarine canyons impacts deep sedimentary regimes

NASA Astrophysics Data System (ADS)

Paradis, Sarah; Puig, Pere; Masqué, Pere; Juan-Díaz, Xènia; Martín, Jacobo; Palanques, Albert

2017-02-01

Many studies highlight that fish trawling activities cause seafloor erosion, but the assessment of the remobilization of surface sediments and its relocation is still not well documented. These impacts were examined along the flanks and axes of three headless submarine canyons incised on the Barcelona continental margin, where trawling fleets have been operating for decades. Trawled grounds along canyon flanks presented eroded and highly reworked surface sediments resulting from the passage of heavy trawling gear. Sedimentation rates on the upper canyon axes tripled and quadrupled its natural (i.e. pre-industrialization) values after a substantial increase in total horsepower of the operating trawling fleets between 1960 s and 1970 s. These impacts affected the upper canyon reaches next to fishing grounds, where sediment resuspended by trawling can be transported towards the canyon axes. This study highlights that bottom trawling has the capacity to alter natural sedimentary environments by promoting sediment-starved canyon flanks, and by enhancing sedimentation rates along the contiguous axes, independently of canyons’ morphology. Considering the global mechanisation and offshore expansion of bottom trawling fisheries since the mid-20th century, these sedimentary alterations may occur in many trawled canyons worldwide, with further ecological impacts on the trophic status of these non-resilient benthic communities.

Bottom-trawling along submarine canyons impacts deep sedimentary regimes.

PubMed

Paradis, Sarah; Puig, Pere; Masqué, Pere; Juan-Díaz, Xènia; Martín, Jacobo; Palanques, Albert

2017-02-24

Many studies highlight that fish trawling activities cause seafloor erosion, but the assessment of the remobilization of surface sediments and its relocation is still not well documented. These impacts were examined along the flanks and axes of three headless submarine canyons incised on the Barcelona continental margin, where trawling fleets have been operating for decades. Trawled grounds along canyon flanks presented eroded and highly reworked surface sediments resulting from the passage of heavy trawling gear. Sedimentation rates on the upper canyon axes tripled and quadrupled its natural (i.e. pre-industrialization) values after a substantial increase in total horsepower of the operating trawling fleets between 1960 s and 1970 s. These impacts affected the upper canyon reaches next to fishing grounds, where sediment resuspended by trawling can be transported towards the canyon axes. This study highlights that bottom trawling has the capacity to alter natural sedimentary environments by promoting sediment-starved canyon flanks, and by enhancing sedimentation rates along the contiguous axes, independently of canyons' morphology. Considering the global mechanisation and offshore expansion of bottom trawling fisheries since the mid-20 th century, these sedimentary alterations may occur in many trawled canyons worldwide, with further ecological impacts on the trophic status of these non-resilient benthic communities.

Characteristics of depositional environment and evolution of Upper Cretaceous Mishrif Formation, Halfaya Oil field, Iraq based on sedimentary microfacies analysis

NASA Astrophysics Data System (ADS)

Zhong, Yuan; Zhou, Lu; Tan, Xiucheng; Guo, Rui; Zhao, Limin; Li, Fei; Jin, Zhimin; Chen, Yantao

2018-04-01

As one of the most important carbonate targets in the Middle East, Upper Cretaceous Mishrif Formation has been highlighted for a long time. Although consensus has been reached on the overall sedimentary background, disputes still exist in understanding the sedimentary environment changes among sub-regions due to relatively limited research, rare outcrop, and incomplete drilled core, which hinders the analysis on sedimentary environment and thus the horizontal and vertical correlation. In this study, taking the Halfaya Oil Field as an example, the sedimentary microfacies analysis method was introduced to comprehensively characterize the cored interval of Mishrif Formation, including Single Layers MC1-1 to MA2. A total of 11 sedimentary microfacies are identified through system identification of sedimentary microfacies and environmental analysis, with reference to the standard microfacies classification in the rimmed carbonate platform. Then three kinds of environments are identified through microfacies assemblage analysis, namely restricted platform, open platform, and platform margin. Systematic analyses indicate that the deposits are mainly developed in the open platform and platform margin. Meanwhile, rock-electricity interpretation model is established according to the electricity response to cored intervals, and is then employed to interpret the uncored intervals, which finally helps build the sedimentary evolution pattern through horizontal and vertical correlation. It is proposed that the Single Layers MC1-1 to MB2-3 were deposited in the open platform featured by low water level, including sub-environments of low-energy shoal within platform and inter-shoal sea; Single Layers MB2-2 to MB1-2B were deposited in the open platform and platform margin, including sub-environments of high-energy shoal on the platform margin, low-energy shoal within platform, inter-shoal sea, and open sea; and Single Layers MB1-2A to MA2 were again deposited in the open platform

Workshop on the Early Earth: The Interval from Accretion to the Older Archean

NASA Technical Reports Server (NTRS)

Burke, K. (Editor); Ashwal, L. D. (Editor)

1985-01-01

Presentation abstracts are compiled which address various issues in Earth developmental processes in the first one hundred million years. The session topics included: accretion of the Earth (processes accompanying immediately following the accretion, including core formation); impact records and other information from planets and the Moon relevant to early Earth history; isotopic patterns of the oldest rocks; and igneous, sedimentary, and metamorphic petrology of the oldest rocks.

Geothermal prospection in the Greater Geneva Basin (Switzerland and France). Impact of diagenesis on reservoir properties of the Upper Jurassic carbonate sediments

NASA Astrophysics Data System (ADS)

Makhloufi, Yasin; Rusillon, Elme; Brentini, Maud; Clerc, Nicolas; Meyer, Michel; Samankassou, Elias

2017-04-01

Diagenesis of carbonate rocks is known to affect the petrophysical properties (porosity, permeability) of the host rock. Assessing the diagenetic history of the rock is thus essential when evaluating any reservoir exploitation project. The Canton of Geneva (Switzerland) is currently exploring the opportunities for geothermal energy exploitation in the Great Geneva Basin (GGB) sub-surface. In this context, a structural analysis of the basin (Clerc et al., 2016) associated with reservoir appraisal (Brentini et al., 2017) and rock-typing of reservoir bodies of potential interest were conducted (Rusillon et al., 2017). Other geothermal exploitation projects elsewhere (e.g. Bavaria, south Germany, Paris Basin, France) showed that dolomitized carbonate rocks have good reservoir properties and are suitable for geothermal energy production. The objectives of this work are to (1) describe and characterize the dolomitized bodies in the GGB and especially their diagenetic history and (2) quantify the reservoir properties of those bodies (porosity, permeability). Currently, our study focuses on the Upper Jurassic sedimentary bodies of the GGB. Field and well data show that the dolomitization is not ubiquitous in the GGB. Results from the petrographical analyses of the Kimmeridgian cores (Humilly-2) and of field analogues (Jura, Saleve and Vuache mountains) display complex diagenetic histories, dependent of the study sites. The paragenesis exhibits several stages of interparticular calcite cementation as well as different stages of dolomitization and/or dedolomitization. Those processes seem to follow constrained path of fluid migrations through burial, faulting or exhumation during the basin's history. These complex diagenetic histories affected the petrophysical and microstructural properties via porogenesis (conservation of initial porosity, moldic porosity) and/or poronecrosis events. The best reservoir properties appear to be recorded in patch reef and peri

Thermal evolution of sedimentary basins in Alaska

USGS Publications Warehouse

Johnsson, Mark J.; Howell, D.G.

1996-01-01

The complex tectonic collage of Alaska is reflected in the conjunction of rocks of widely varying thermal maturity. Indicators of the level of thermal maturity of rocks exposed at the surface, such as vitrinite reflectance and conodont color alteration index, can help constrain the tectonic evolution of such complex regions and, when combined with petrographic, modern heat flow, thermogeochronologic, and isotopic data, allow for the detailed evaluation of a region?s burial and uplift history. We have collected and assembled nearly 10,000 vitrinite-reflectance and conodont-color-alteration index values from the literature, previous U.S. Geological Survey investigations, and our own studies in Alaska. This database allows for the first synthesis of thermal maturity on a broadly regional scale. Post-accretionary sedimentary basins in Alaska show wide variability in terms of thermal maturity. The Tertiary interior basins, as well as some of the forearc and backarc basins associated with the Aleutian Arc, are presently at their greatest depth of burial, with immature rocks exposed at the surface. Other basins, such as some backarc basins on the Alaska Peninsula, show higher thermal maturities, indicating modest uplift, perhaps in conjunction with higher geothermal gradients related to the arc itself. Cretaceous ?flysch? basins, such as the Yukon-Koyukuk basin, are at much higher thermal maturity, reflecting great amounts of uplift perhaps associated with compressional regimes generated through terrane accretion. Many sedimentary basins in Alaska, such as the Yukon-Koyukuk and Colville basins, show higher thermal maturity at basin margins, perhaps reflecting greater uplift of the margins in response to isostatic unloading, owing to erosion of the hinterland adjacent to the basin or to compressional stresses adjacent to basin margins.

Identification of remagnetization processes in Paleozoic sedimentary rocks of the northeast Rhenish Massif in Germany by K-Ar dating and REE tracing of authigenic illite and Fe oxides

NASA Astrophysics Data System (ADS)

Zwing, A.; Clauer, N.; Liewig, N.; Bachtadse, V.

2009-06-01

This study combines mineralogical, chemical (rare earth elemental (REE)) and isotopic (K-Ar) data of clay minerals as well as chemical compositions (major and REE) of Fe oxide leachates from remagnetized Palaeozoic sedimentary rocks from NE Rhenish Massif in Germany, for which the causes of remagnetization are not yet clear. The dominant carrier of the syntectonic, pervasive Carboniferous magnetization is magnetite. The Middle Devonian clastic rocks record an illitization event at 348 ± 7 Ma probably connected to a major magmatic event in the Mid-German Crystalline Rise, whereas a second illitization episode at 324 ± 3 Ma is coeval to the northward migrating deformation through the Rhenish Massif, being only detected in Upper Devonian and Lower Carboniferous rocks. The age of that younger illitization is not significantly different from that of the remagnetization, which, however, is not restricted to the upper part of the orogenic belt, but affects also the Middle Devonian strata. The REE patterns of the Fe-enriched leachates support two mineralization episodes with varied oxidation-reduction conditions outlined by varied Eu and Ce anomalies. This is not compatible with a unique, pervasive migration of orogenic fluids on a regional scale to explain the remagnetization in the studied region. While clay diagenesis and remagnetization are time-equivalent in Upper Devonian and Lower Carboniferous rocks, they are not so in Middle Devonian rocks. Transformation of smectite into illite cannot, therefore, account for the growth of associated authigenic magnetite, which must have been triggered by a different process. Since remagnetization and deformation ages are similar, the mechanism could relate to local physical conditions such as pressure solution and changing pore fluid pressure due to tectonic stress as well as to chemical conditions such as changing composition of the pore fluids.

Extreme events in the sedimentary record of maar Lake Pavin: Implications for natural hazards assessment in the French Massif Central

NASA Astrophysics Data System (ADS)

Chassiot, Léo; Chapron, Emmanuel; Di Giovanni, Christian; Albéric, Patrick; Lajeunesse, Patrick; Lehours, Anne-Catherine; Meybeck, Michel

2016-06-01

A set of sedimentary cores, high resolution swath bathymetry and subbottom profiler data provides new insights on sedimentary processes in meromictic maar Lake Pavin, France. Three sedimentary environments (i.e., littoral, plateau and basin) have been identified in the lake from sediment composition using bulk organic geochemistry and the analysis of hydroacoustic images. Various forms of rapidly deposited layers (RDLs) have been identified and radiocarbon dated. An up to date stratigraphy of sedimentary events matching coeval RDLs across the lake is presented and illustrates a wide range of natural hazards linked to Lake Pavin during the last 2000 years. In AD 600, a sudden lake outburst triggered a slump deposit along with a 9 m lake-level drop that drove shifts in sedimentary organic matter composition. Outside the lake, outburst flood deposits have been described downstream and provide sedimentary evidence for this event. The lake-level drop also favored the generation of gravity reworking processes, as shown by (1) a regional earthquake-triggered large slope failure on the plateau connected to a mass-wasting deposit in the basin dated to AD 1300, and (2) a succession of turbidites in AD 1825 and AD 1860 contemporaneous to two historic earthquakes, suggesting that this lake is sensitive to earthquakes with a minimum epicentral intensity of V. Finally, past observations of lake water color changes in AD 1783 and AD 1936, similar to reports in other meromictic lakes, match iron-rich deposits identified in maar lake sediments and suggest that Lake Pavin could have undergone limnic eruptions.

An Aquatic Journey toward Aeolis Mons (Mount Sharp): Sedimentary Rock Evidence observed by Mars Science Laboratory

NASA Astrophysics Data System (ADS)

Gupta, Sanjeev; Edgar, Lauren; Williams, Rebecca; Rubin, David; Yingst, Aileen; Lewis, Kevin; Kocurek, Gary; Anderson, Ryan; Dromart, Gilles; Edgett, Ken; Hardgrove, Craig; Kah, Linda; Mangold, Nicolas; Milliken, Ralph; Minitti, Michelle; Palucis, Marisa; Rice, Melissa; Stack, Katie; Sumner, Dawn; Williford, Ken

2014-05-01

Since leaving Yellowknife Bay (summer 2013), Mars Science Laboratory Curiosity has investigated a number of key outcrops as it traverses along the Rapid Transit Route toward the entry point to begin its investigations of the extensive rock outcrops at the base of Mount Sharp. Rover observations are characterizing the variability of lithologies and sedimentary facies along the traverse and establishing stratigraphic relationships with the aim of reconstructing depositional processes and palaeoenvironments. Here, we report on sedimentological and stratigraphic observations based on images from the Mastcam and MAHLI instruments at Shaler and the Darwin waypoint. The informally named Shaler outcrop, which forms part of the Glenelg member of the Yellowknife Bay formation [1] is remarkable for the preservation of a rich suite of sedimentary structures and architecture, and was investigated on sols 120-121 and 309-324. The outcrop forms a pebbly sandstone body that is ~0.7 m thick and extends for up to 20 m. Shaler is largely characterized by pebbly sandstone facies showing well-developed decimeter-scale trough cross-stratification. Bedding geometries indicate sub-critical angles of climb, resulting in preservation of only the lee slope deposits. The grain size, and the presence and scale of cross-stratification imply sediment transport and deposition by unidirectional currents in a fluvial sedimentary environment. Curiosity investigated the informally named Darwin waypoint between sols 390 and 401, making detailed Mastcam and MAHLI observations at two separate locations. The Darwin outcrop comprises light-toned sandstone beds separated by darker pebbly sandstones. MAHLI observations permit differentiation of distinct sedimentary facies. The Altar Mountain facies is a poorly sorted pebbly sandstone that is rich in fine pebbles. Pebbles are sub-angular to sub-rounded in shape and show no preferred orientation or fabric. Pebbles and sand grains show clast-to-clast contacts

Average sedimentary rock rare Earth element patterns and crustal evolution: Some observations and implications from the 3800 Ma ISUA supracrustal belt, West Greenland

NASA Technical Reports Server (NTRS)

Dymek, R. F.; Boak, J. L.; Gromet, L. P.

1983-01-01

Rare earth element (REE) data is given on a set of clastic metasediments from the 3800 Ma Isua Supracrustal belt, West Greenland. Each of two units from the same sedimentary sequence has a distinctive REE pattern, but the average of these rocks bears a very strong resemblance to the REE pattern for the North American Shale Composite (NASC), and departs considerably from previous estimates of REE patterns in Archaean sediments. The possibility that the source area for the Isua sediments resembled that of the NASC is regarded as highly unlikely. However, REE patterns like that in the NASC may be produced by sedimentary recycling of material yielding patterns such as are found at Isua. The results lead to the following tentative conclusions: (1) The REE patterns for Isua Seq. B MBG indicate the existence of crustal materials with fractionated REE and negative Eu anomalies at 3800 Ma, (2) The average Seq. B REE pattern resembles that of the North American Shale Composite (NASC), (3) If the Seq. B average is truly representative of its crustal sources, then this early crust could have been extensively differentiated. In this regard, a proper understanding of the NASC pattern, and its relationship to post-Archaean crustal REE reservoirs, is essential, (4) The Isua results may represent a local effect.

Identification and geochemical significance of sulphurized fatty acids in sedimentary organic matter from the Lorca Basin, SE Spain

NASA Astrophysics Data System (ADS)

Russell, Marie; Hartgers, Walter A.; Grimalt, Joan O.

2000-11-01

The presence of free sulphurized fatty acids in various sediment types (carbonates, marls, organic-rich shales) of the Messinian of the Lorca Basin, SE Spain, is reported. These compounds are found in the majority, but not all, of the samples from this basin which also contain sulphur-bound hydrocarbons. They constitute mixtures of C 16-C 26 linear fatty acids predominated by the C 18 homologues with thiophene, thiolane, and thiane rings attached at various chain positions, with the most abundant isomers being those with ring substitution at position C-9. The dominance of these isomers points to an early sulphurization process involving octadec-9,12-dienoic acid and/or octadeca-9-enoic acid, major lipid constituents of algae. In general, the alkylthiophene fatty acids are more abundant than the alkylthiolane or alkylthiane fatty acids. The presence of the sulphur moiety and structural identification was confirmed by GC-HRMS and by desulphurization of the fatty acid fraction. Desulphurization also showed that a portion of the sulphur containing fatty acids is intermolecularly bound to the polymeric organic matter. The samples exhibiting higher proportions of macromolecularly bound fatty acids were also those showing higher abundances of alkylthiolane or alkylthiane fatty acids. The identification of these compounds shows that the original algal lipids, including the fatty acid pool, can be effectively preserved in sedimentary samples by sulphurization. However, sulphur-bonding only occurs by addition to the unsaturated carbons. Thus, only unsaturated fatty acids are preserved, constituting a major bias in terms of the original sedimentary distributions.

Continental Drilling to Explore Earth's Sedimentary, Paleobiological, and Biogeochemical Record

NASA Astrophysics Data System (ADS)

Cohen, Andrew; Soreghan, Gerilyn

2013-07-01

A workshop to promote research using continental scientific drilling to explore the Earth's sedimentary, paleobiological, and biogeochemical record was held in Norman, Okla. The workshop, funded by the U.S. National Science Foundation (NSF), was intended to encourage U.S.-based scientists to take advantage of the exceptional capacity of unweathered, continuous sediment cores to serve as archives of the Earth's history.

Effects of Hypoxia on Sedimentary Nitrogen Cycling in the Pensacola Bay Estuary

EPA Science Inventory

Eutrophic-induced hypoxic events pose a serious threat to estuaries in coastal systems. Hypoxic events are becoming more intense and widespread with changes in land use and increased anthropogenic pressures. Microbial communities involved in sedimentary nitrogen (N) cycling may h...

Primary arsenic(V) preserved in 3.26 billion-year-old shallow marine cherts of the Fig Tree Group demonstrates a complete Paleoarchean arsenic cycle driven by photosynthetic bacteria

NASA Astrophysics Data System (ADS)

Myers, K. D.; Tice, M. M.; Bostick, B. C.

2016-12-01

Microbial arsenic (As) redox cycling is hypothesized to have been widespread in oxygen-free Archean environments, yet our understanding of Archean As cycles is hindered by a poor sedimentary record of As. Concentrations of up to 1.6 wt % As were discovered in chert clasts of a fan delta conglomerate sourced from shallow-water coastal environments in the 3.26-3.23 Ga Fig Tree Group of the Barberton Greenstone Belt, South Africa. Arsenic is associated at the outcrop-scale with Fe-bearing conglomerate pebbles and underlying banded ferruginous cherts, whereas low-Fe chert clasts, underlying low-Fe banded black and white cherts, bedded barites, and overlying ash deposits lack As. Bulk As and Fe K-edge X-ray absorption spectroscopy and 1-100 μm scale μ-X-ray fluorescence mapping were used to determine the abundance, oxidation state, and mineralogy of As in relation to sedimentary textures and bulk Fe mineralogy. Arsenic concentration is strongly linked to lithology: hematite (Fe2O3)-rich pebbles contain higher Fe:As ratios ( 10:1-100:1) than sideritic pebbles with little to no Fe2O3 (Fe:As 1:1-10:1). Arsenopyrite (FeAsS), orpiment (As2S3), As(III), and As(V) line pre-erosional textures and early dewatering structures. Significantly, As(V) is associated with hematite, pyrite, and siderite but not with products of recent oxidative weathering such as goethite. These results are best explained by As(V) adsorption to Fe-oxide phases during deposition or very early diagenesis, prior to silicification. Microbially-mediated SO42- and As(V) reduction led to As2S3 precipitation, known to occur in modern reducing and arsenic-bearing aquifers. Later metamorphic alteration of As2S3 led to partial replacement, likely isomorphously, with FeAsS. The presence of minerals formed during different stages of As(V) reduction associated with early sedimentary textures show that a complete biogeochemical As redox cycle was possible by 3.2 Ga. The As(V)/As(III) pair has a more positive

Geochemistry of shale and sedimentary pyrite as a proxy for gold fertility in the Selwyn basin area, Yukon

NASA Astrophysics Data System (ADS)

Sack, Patrick J.; Large, Ross R.; Gregory, Daniel D.

2018-01-01

Selwyn basin area strata contain sedimentary pyrite with Au above background levels when analyzed by laser ablation-inductively coupled mass spectrometry. Hyland Group rocks contain framboidal pyrite contents of 670 ppb Au, 1223 ppm As, and 5.3 ppm Te; the mean of all types of sedimentary pyrite in the Hyland Group is 391 ppb Au, 1489 ppm As, and 3.8 ppm Te. These levels are similar to sedimentary pyrite in host lithologies from major orogenic gold districts in New Zealand and Australia. Comparison of whole rock and pyrite data show that rocks deposited in continental slope settings with significant terrigenous input contain pyrite that is consistently enriched in Au, As, Te, Co, and Cu. Although data are limited, whole rock samples of stratigraphic units containing Au-rich pyrite also contain high Au, indicating that most of the Au is within sedimentary pyrite. Based on geologic characteristics and comparison of pyrite chemistry data with whole rock chemistry, Selwyn basin area strata have the necessary ingredients to form orogenic gold deposits: Au-enriched source rocks, metamorphic conditions permissive of forming a metamorphic ore fluid, and abundant structural preparation for channeling fluids and depositing ore.

Rare earth, major, and trace element composition of Monterey and DSDP chert and associated host sediment: Assessing the influence of chemical fractionation during diagenesis

USGS Publications Warehouse

Murray, R.W.; Buchholtz ten Brink, Marilyn R.; Gerlach, David C.; Russ III, G. Price; Jones, David L.

1992-01-01

Chert and associated host sediments from Monterey Formation and Deep Sea Drilling Project (DSDP) sequences were analyzed in order to assess chemical behavior during diagenesis of biogenic sediments. The primary compositional contrast between chert and host sediment is a greater absolute SiO2 concentration in chert, often with final SiO2 ≥ 98 wt%. This contrast in SiO2 (and SiAl">SiAl) potentially reflects precursor sediment heterogeneity, diagenetic chemical fractionation, or both. SiO2 concentrations and SiAl">SiAl ratios in chert are far greater than in modern siliceous oozes, however and often exceed values in acid-cleaned diatom tests. Compositional contrasts between chert and host sediment are also orders-of-magnitude greater than between multiple samples of the host sediment. Calculations based on the initial composition of adjacent host, observed porosity reductions from host to chert and a postulated influx of pure SiO2, construct a chert composition which is essentially identical to observed SiO2 values in chert. Thus, precursor heterogeneity does not seem to be the dominant factor influencing the current chert composition for the key elements of interest. In order to assess the extent of chemical fractionation during diagenesis, we approximate the precursor composition by analyzing host sediments adjacent to the chert.The SiO2 concentration contrast seems caused by biogenic SiO2 dissolution and transport from the local adjacent host sediment and subsequent SiO2reprecipitation in the chert. Along with SiO2, other elements are often added (with respect to Al) to Monterey and DSDP chert during silicification, although absolute concentrations decrease. The two Monterey quartz chert nodules investigated, in contrast to the opal-CT and quartz chert lenses, formed primarily by extreme removal of carbonate and phosphate, thereby increasing relative SiO2 concentrations. DSDP chert formed by both carbonate/phosphate dissolution and SiO2 addition from

Silicic volcanism on Mars evidenced by tridymite in high-SiO2 sedimentary rock at Gale crater

NASA Astrophysics Data System (ADS)

Morris, Richard V.; Vaniman, David T.; Blake, David F.; Gellert, Ralf; Chipera, Steve J.; Rampe, Elizabeth B.; Ming, Douglas W.; Morrison, Shaunna M.; Downs, Robert T.; Treiman, Allan H.; Yen, Albert S.; Grotzinger, John P.; Achilles, Cherie N.; Bristow, Thomas F.; Crisp, Joy A.; Des Marais, David J.; Farmer, Jack D.; Fendrich, Kim V.; Frydenvang, Jens; Graff, Trevor G.; Morookian, John-Michael; Stolper, Edward M.; Schwenzer, Susanne P.

2016-06-01

Tridymite, a low-pressure, high-temperature (>870 °C) SiO2 polymorph, was detected in a drill sample of laminated mudstone (Buckskin) at Marias Pass in Gale crater, Mars, by the Chemistry and Mineralogy X-ray diffraction instrument onboard the Mars Science Laboratory rover Curiosity. The tridymitic mudstone has ˜40 wt.% crystalline and ˜60 wt.% X-ray amorphous material and a bulk composition with ˜74 wt.% SiO2 (Alpha Particle X-Ray Spectrometer analysis). Plagioclase (˜17 wt.% of bulk sample), tridymite (˜14 wt.%), sanidine (˜3 wt.%), cation-deficient magnetite (˜3 wt.%), cristobalite (˜2 wt.%), and anhydrite (˜1 wt.%) are the mudstone crystalline minerals. Amorphous material is silica-rich (˜39 wt.% opal-A and/or high-SiO2 glass and opal-CT), volatile-bearing (16 wt.% mixed cation sulfates, phosphates, and chlorides-perchlorates-chlorates), and has minor TiO2 and Fe2O3T oxides (˜5 wt.%). Rietveld refinement yielded a monoclinic structural model for a well-crystalline tridymite, consistent with high formation temperatures. Terrestrial tridymite is commonly associated with silicic volcanism, and detritus from such volcanism in a “Lake Gale” catchment environment can account for Buckskin's tridymite, cristobalite, feldspar, and any residual high-SiO2 glass. These cogenetic detrital phases are possibly sourced from the Gale crater wall/rim/central peak. Opaline silica could form during diagenesis from high-SiO2 glass, as amorphous precipitated silica, or as a residue of acidic leaching in the sediment source region or at Marias Pass. The amorphous mixed-cation salts and oxides and possibly the crystalline magnetite (otherwise detrital) are primary precipitates and/or their diagenesis products derived from multiple infiltrations of aqueous solutions having variable compositions, temperatures, and acidities. Anhydrite is post lithification fracture/vein fill.

Silicic volcanism on Mars evidenced by tridymite in high-SiO2 sedimentary rock at Gale crater

PubMed Central

Morris, Richard V.; Vaniman, David T.; Blake, David F.; Gellert, Ralf; Chipera, Steve J.; Rampe, Elizabeth B.; Ming, Douglas W.; Morrison, Shaunna M.; Downs, Robert T.; Treiman, Allan H.; Yen, Albert S.; Grotzinger, John P.; Achilles, Cherie N.; Bristow, Thomas F.; Crisp, Joy A.; Des Marais, David J.; Farmer, Jack D.; Fendrich, Kim V.; Graff, Trevor G.; Morookian, John-Michael; Stolper, Edward M.; Schwenzer, Susanne P.

2016-01-01

Tridymite, a low-pressure, high-temperature (>870 °C) SiO2 polymorph, was detected in a drill sample of laminated mudstone (Buckskin) at Marias Pass in Gale crater, Mars, by the Chemistry and Mineralogy X-ray diffraction instrument onboard the Mars Science Laboratory rover Curiosity. The tridymitic mudstone has ∼40 wt.% crystalline and ∼60 wt.% X-ray amorphous material and a bulk composition with ∼74 wt.% SiO2 (Alpha Particle X-Ray Spectrometer analysis). Plagioclase (∼17 wt.% of bulk sample), tridymite (∼14 wt.%), sanidine (∼3 wt.%), cation-deficient magnetite (∼3 wt.%), cristobalite (∼2 wt.%), and anhydrite (∼1 wt.%) are the mudstone crystalline minerals. Amorphous material is silica-rich (∼39 wt.% opal-A and/or high-SiO2 glass and opal-CT), volatile-bearing (16 wt.% mixed cation sulfates, phosphates, and chlorides−perchlorates−chlorates), and has minor TiO2 and Fe2O3T oxides (∼5 wt.%). Rietveld refinement yielded a monoclinic structural model for a well-crystalline tridymite, consistent with high formation temperatures. Terrestrial tridymite is commonly associated with silicic volcanism, and detritus from such volcanism in a “Lake Gale” catchment environment can account for Buckskin’s tridymite, cristobalite, feldspar, and any residual high-SiO2 glass. These cogenetic detrital phases are possibly sourced from the Gale crater wall/rim/central peak. Opaline silica could form during diagenesis from high-SiO2 glass, as amorphous precipitated silica, or as a residue of acidic leaching in the sediment source region or at Marias Pass. The amorphous mixed-cation salts and oxides and possibly the crystalline magnetite (otherwise detrital) are primary precipitates and/or their diagenesis products derived from multiple infiltrations of aqueous solutions having variable compositions, temperatures, and acidities. Anhydrite is post lithification fracture/vein fill. PMID:27298370

Sulfur-binding in recent environments: II. Speciation of sulfur and iron and implications for the occurrence of organo-sulfur compounds

NASA Astrophysics Data System (ADS)

Hartgers, Walter A.; Lòpez, Jordi F.; Sinninghe Damsté, Jaap S.; Reiss, Christine; Maxwell, James R.; Grimalt, Joan O.

1997-11-01

Speciation of iron and sulfur species was determined for two recent sediments (La Trinitat and Lake Cisó) which were deposited in environments with a high biological productivity and sulfate-reducing activity. In sediments from calcite ponds of La Trinitat an excess of reactive iron species (iron monosulfides, iron hydroxides) results in a depletion of reactive sulfur which is accompanied by a virtual absence of organo-sulfur compounds, both in low (LMW) and high molecular-weight (HMW) fractions. Small amounts of phytanyl and highly branched isoprenoid (HBI) thiophenes in the extract demonstrate that these molecules exhibit a higher reactivity towards reduced sulfur species as compared to detrital iron. Euxinic sediments from Lake Cisó are characterised by an excess of reduced sulfur species which can rapidly trap reactive iron. High concentrations of H 2S results in the formation of organo-sulfur compounds which were encountered in both LMW and HMW fractions. The major part of the organic sulfur is bound to the carbohydrate portion of woody tissues, whose presence was revealed by a specific alkylthiophene distribution in the flash pyrolysate and by Li/EtNH 2 desulfurisation of the kerogen which resulted in the solubilisation of the sulfur-enriched hemicellulose fraction. Relatively high amounts of sulfurised C 25 HBI compounds in the sediment extract of Lake Cisó reflect the incorporation of sulfur into algal derived organic matter upon early diagenesis. The combined approach of the speciation of iron and sulfur species and the molecular analysis of sedimentary fractions demonstrates that abiotic sulfur binding to organic matter occurs at the earliest stages of diagenesis under specific depositional conditions (anoxic, stratified water column) in which an excess of reduced sulfur species relative to the amount of reactive iron is a controlling factor.

Production and Early Preservation of Lipid Biomarkers in Iron Hot Springs

PubMed Central

Jahnke, Linda L.; Farmer, Jack D.; Cady, Sherry L.

2014-01-01

Abstract The bicarbonate-buffered anoxic vent waters at Chocolate Pots hot springs in Yellowstone National Park are 51–54°C, pH 5.5–6.0, and are very high in dissolved Fe(II) at 5.8–5.9 mg/L. The aqueous Fe(II) is oxidized by a combination of biotic and abiotic mechanisms and precipitated as primary siliceous nanophase iron oxyhydroxides (ferrihydrite). Four distinct prokaryotic photosynthetic microbial mat types grow on top of these iron deposits. Lipids were used to characterize the community composition of the microbial mats, link source organisms to geologically significant biomarkers, and investigate how iron mineralization degrades the lipid signature of the community. The phospholipid and glycolipid fatty acid profiles of the highest-temperature mats indicate that they are dominated by cyanobacteria and green nonsulfur filamentous anoxygenic phototrophs (FAPs). Diagnostic lipid biomarkers of the cyanobacteria include midchain branched mono- and dimethylalkanes and, most notably, 2-methylbacteriohopanepolyol. Diagnostic lipid biomarkers of the FAPs (Chloroflexus and Roseiflexus spp.) include wax esters and a long-chain tri-unsaturated alkene. Surprisingly, the lipid biomarkers resisted the earliest stages of microbial degradation and diagenesis to survive in the iron oxides beneath the mats. Understanding the potential of particular sedimentary environments to capture and preserve fossil biosignatures is of vital importance in the selection of the best landing sites for future astrobiological missions to Mars. This study explores the nature of organic degradation processes in moderately thermal Fe(II)-rich groundwater springs—environmental conditions that have been previously identified as highly relevant for Mars exploration. Key Words: Lipid biomarkers—Photosynthesis—Iron—Hot springs—Mars. Astrobiology 14, 502–521. PMID:24886100

Production and Early Preservation of Lipid Biomarkers in Iron Hot Springs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parenteau, Mary N.; Jahnke, Linda L.; Farmer, Jack D.

2014-06-01

The bicarbonate-buffered anoxic vent waters at Chocolate Pots hot springs in Yellowstone National Park are 51–54°C, pH 5.5–6.0, and are very high in dissolved Fe(II) at 5.8–5.9 mg/L. The aqueous Fe(II) is oxidized by a combination of biotic and abiotic mechanisms and precipitated as primary siliceous nanophase iron oxyhydroxides (ferrihydrite). Four distinct prokaryotic photosynthetic microbial mat types grow on top of these iron deposits. Lipids were used to characterize the community composition of the microbial mats, link source organisms to geologically significant biomarkers, and investigate how iron mineralization degrades the lipid signature of the community. The phospholipid and glycolipid fattymore » acid profiles of the highest-temperature mats indicate that they are dominated by cyanobacteria and green nonsulfur filamentous anoxygenic phototrophs (FAPs). Diagnostic lipid biomarkers of the cyanobacteria include midchain branched mono- and dimethylalkanes and, most notably, 2-methylbacteriohopanepolyol. Diagnostic lipid biomarkers of the FAPs (Chloroflexus and Roseiflexus spp.) include wax esters and a long-chain tri-unsaturated alkene. Surprisingly, the lipid biomarkers resisted the earliest stages of microbial degradation and diagenesis to survive in the iron oxides beneath the mats. Understanding the potential of particular sedimentary environments to capture and preserve fossil biosignatures is of vital importance in the selection of the best landing sites for future astrobiological missions to Mars. Finally, this study explores the nature of organic degradation processes in moderately thermal Fe(II)-rich groundwater springs—environmental conditions that have been previously identified as highly relevant for Mars exploration.« less

Questioning the Sedimentary Paradigm for Granites

NASA Astrophysics Data System (ADS)

Glazner, A. F.; Bartley, J. M.; Coleman, D. S.; Boudreau, A.; Walker, J. D.

2007-12-01

A critical question regarding volcano-pluton links is whether plutons are samples of magma that passed through on its way to eruption, or residues left behind after volcanic rocks were extracted. A persistent theme of recent work on granites sensu lato is that many are sedimentary accumulations of crystals that lost significant volumes of magmatic liquid. This view is based on observations of structures that clearly seem to reflect deposition on a magma chamber floor (e.g., flows of chilled mafic magma into silicic magma) and on the inference that many other structures, such as modal layering, truncated layering, and crystal accumulations, reflect crystal sedimentation on such chamber floors. There are significant physical and geochemical reasons to question this view, based on observations in the Sierra Nevada of California and similar results from other batholiths. First, few granites show the enrichments in Ba, Sr, and relative Eu that feldspar accumulation should produce. Second, sedimentary features such as graded bedding and cross-bedding form in highly turbulent flows, but turbulence is unachievable in viscous silicic liquids, where velocities on the order of 104 m/s would be required to induce turbulence in a liquid with η=104 Pa s. Third, tabular modally layered domains commonly cut surrounding modal layering on both sides, and orientations of modal layering and of the troughs of "ladder dikes" commonly scatter widely within hectare-sized areas; it is difficult to reconcile these features with gravity-driven settling. Fourth, accumulations of K-feldspar megacrysts are typically inferred to be depositional, but this is precluded by crystallization of most K- feldspar after rheologic lock-up occurs. Finally, accumulations of K-feldspar and hornblende are typically packed too tightly to be depositional. With analogy to layered mafic intrusions, many features attributed to crystal sedimentation in granites may be better explained by crystal aging and other in

Geochemistry and origin of regional dolomites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanson, G.N.; Meyers, W.J.

1989-12-01

The major goal of the carbonate research program at Stony Brook is to better understand the conditions and processes leading to regional diagenesis of carbonate rocks. Our research focuses on studies of ancient, massive dolostones, but we are also studying limestone diagenesis for its own importance, and as it relates to dolomitization. Our approach has been to carry out a very detailed petrographic and geochemical case study to the Mississippian Burlington-Keokuk Fms. of Iowa, Illinois and Missouri, and to develop this as a testing ground for new geochemical and modelling techniques, and for testing various models for regional dolomitization inmore » epicontinental carbonates. The ideas and techniques developed in our Burlington-Keokuk studies are being expanded and applied to carbonate sequences of other ages (Devonian to Neogene), and other tectono-sedimentary settings. The emphasis of this report will be on new developments and results on the Burlington-Keokuk studies and on our diagenetic studies of other strata. Recent research on Burlington-Keokuk rocks include development and application of boron isotopes and the U--Th--Pb system to dolomite studies, investigations of porosity and permeability in the dolostones. Projects on other strata include dolomitization and limestones diagenesis of Devonian carbonates of Alberta and Western Australia, Miocene reefal carbonates of Spain, Neogene carbonates of Curacao and Bonaire, Waulsortian limestones of Ireland, modelling of trace elements and stable isotopes, and experimental growth of calcites to investigate crystallographic controls of trace element incorporation. 118 refs., 46 figs.« less

Deformation style of the Mesozoic sedimentary rocks in southern Thailand

NASA Astrophysics Data System (ADS)

Kanjanapayont, Pitsanupong

2014-10-01

Mesozoic sedimentary rocks in southern Thailand are widespread from NNE-SSW and N-S in Chumphon and Trang provinces. The Mesozoic stratigraphic units are the marine Triassic Sai Bon Formation and the non-marine Jurassic-Cretaceous Thung Yai Group, the latter subdivided into Khlong Min, Lam Thap, Sam Chom, and Phun Phin Formations. These units overlie Permian carbonate rocks with an angular unconformity, and are overlain unconformably by Cenozoic units and the Quaternary sediments. The Mesozoic rocks have been folded to form two huge first-ordered syncline or synclinoria, the Chumphon and Surat Thani-Krabi-Trang synclinoria. These synclinoria are elongated in NNE-SSW to N-S direction, and incorporate asymmetric lower-order parasitic folds. The folds have moderately to steeply dipping eastward limbs and more gently dipping westward limbs. These folds were transected by brittle fractures in four major directions. These geologic structures indicate WNW-ESE to E-W contraction with top-to-the-east simple shear at some time before the deposition of the Cenozoic sedimentary units. No major deformation has affected the rocks subsequently, apart from the formation of the fault-controlled Cenozoic basins.

Magnetic fabrics in tectonically inverted sedimentary basins: a review

NASA Astrophysics Data System (ADS)

García-Lasanta, Cristina; Román-Berdiel, Teresa; Casas-Sainz, Antonio; Oliva-Urcia, Belén; Soto, Ruth; Izquierdo-Llavall, Esther

2017-04-01

Magnetic fabric studies in sedimentary rocks were firstly focused on strongly deformed tectonic contexts, such as fold-and-thrust belts. As measurement techniques were improved by the introduction of high-resolution equipments (e.g. KLY3-S and more recent Kappabridge susceptometers from AGICO Inc., Czech Republic), more complex tectonic contexts could be subjected to anisotropy of magnetic susceptibility (AMS) analyses in order to describe the relationship between tectonic conditions and the orientation and shape of the resultant magnetic ellipsoids. One of the most common complex tectonic frames involving deformed sedimentary rocks are inverted extensional basins. In the last decade, multiple AMS studies revealed that the magnetic fabric associated with the extensional stage (i.e. a primary magnetic fabric) can be preserved despite the occurrence of subsequent deformational processes. In these cases, magnetic fabrics may provide valuable information about the geometry and kinematics of the extensional episode (i.e. magnetic ellipsoids with their minimum susceptibility axis oriented perpendicular to the deposit plane and magnetic lineation oriented parallel to the extension direction). On the other hand, several of these studies have also determined how the subsequent compressional stage can modify the primary extensional fabric in some cases, particularly in areas subjected to more intense deformation (with development of compression-related cleavage). In this contribution we present a compilation of AMS studies developed in sedimentary basins that underwent different degree of tectonic inversion during their history, in order to describe the relationship of this degree of deformation and the degree of imprint that tectonic conditions have in the previous magnetic ellipsoid (primary extension-related geometry). The inverted basins included in this synthesis are located in the Iberian Peninsula and show: i) weak deformation (W Castilian Branch and Maestrazgo basin

Non-marine carbonate facies, facies models and palaeogeographies of the Purbeck Formation (Late Jurassic to Early Cretaceous) of Dorset (Southern England).

NASA Astrophysics Data System (ADS)

Gallois, Arnaud; Bosence, Dan; Burgess, Peter

2015-04-01

Non-marine carbonates are relatively poorly understood compared with their more abundant marine counterparts. Sedimentary facies and basin architecture are controlled by a range of environmental parameters such as climate, hydrology and tectonic setting but facies models are few and limited in their predictive value. Following the discovery of extensive Early Cretaceous, non-marine carbonate hydrocarbon reservoirs in the South Atlantic, the interest of understanding such complex deposits has increased during recent years. This study is developing a new depositional model for non-marine carbonates in a semi-arid climate setting in an extensional basin; the Purbeck Formation (Upper Jurassic - Lower Cretaceous) in Dorset (Southern England). Outcrop study coupled with subsurface data analysis and petrographic study (sedimentology and early diagenesis) aims to constrain and improve published models of depositional settings. Facies models for brackish water and hypersaline water conditions of these lacustrine to palustrine carbonates deposited in the syn-rift phase of the Wessex Basin will be presented. Particular attention focusses on the factors that control the accumulation of in-situ microbialite mounds that occur within bedded inter-mound packstones-grainstones in the lower Purbeck. The microbialite mounds are located in three units (locally known as the Skull Cap, the Hard Cap and the Soft Cap) separated by three fossil soils (locally known as the Basal, the Lower and the Great Dirt Beds) respectively within three shallowing upward lacustrine sequences. These complex microbialite mounds (up to 4m high), are composed of tabular small-scale mounds (flat and long, up to 50cm high) divided into four subfacies. Many of these small-scale mounds developed around trees and branches which are preserved as moulds (or silicified wood) which are surrounded by a burrowed mudstone-wackestone collar. Subsequently a thrombolite framework developed on the upper part only within

Magnetic resonance imaging analyses of varved marine sedimentary records of the Gulf of California

NASA Astrophysics Data System (ADS)

Briskin, Madeleine; Robins, Jon; Riedel, William R.; Booker, Ron

1986-08-01

Nuclear Magnetic Resonance Imaging used for the first time to analyze marine sedimentary records of the Gulf of California is a remarkable improvement over the more conventional X-ray technique in the identification of organic rich layers. Analytical results indicate that NMRI differentiates clearly between organic rich (light) and organic poor (dark) deposits. It also provides a fine resolution of sedimentary structures, laminae and stratigraphic subtleties. It may be made to yield a three-dimensional stratigraphy; the procedure is nondestructive. The organic vs. inorganic resolution provided by NMRI technology complemented by X-ray when needed should facilitate future studies of paleoceanographic, paleoclimatic and biogeochemical cycles recorded in the vast deposits of marine clays.

Extensional deformation of the Guadalquivir Basin: rate of WSW-ward tectonic displacement from Upper Tortonian sedimentary rocks

NASA Astrophysics Data System (ADS)

Roldán, Francisco J.; Azañón, Jose Miguel; Rodríguez-Fernández, Jose; María Mateos, Rosa

2016-04-01

The Guadalquivir Basin (Upper Tortonian-Quaternary sedimentary infilling) has been considered the foreland basin of the Betic Orogen built up during its collision with the Sudiberian margin. The basin is currently restricted to its westernmost sector, in the Cadiz Gulf, because the Neogene-Quaternary uplift of the Betic Cordillera has produced the emersion of their central and eastern parts. The upper Tortonian chronostratigraphic unit is the oldest one and it was indistinctly deposited on the South Iberian paleomargin and the External units from the Betic Cordillera. However, these rocks are undeformed on the Sudiberian paleomargin while they are deeply affected by brittle deformation on the External Betic Zone. Outcrops of Upper Tortonian sedimentary rocks on External Betic Zone are severely fragmented showing allocthonous characters with regard to those located on the Sudiberian paleomargin. This post- Upper Tortonian deformation is not well known in the External Zones of the Cordillera where the most prominent feature is the ubiquity of a highly deformed tecto-sedimentary unit outcropping at the basement of the Guadalquivir sedimentary infilling. This tecto-sedimentary unit belongs to the Mass Wasting Extensional Complex (Rodríguez-Fernández, 2014) formed during the collision and westward migration of the Internal Zone of the Betic Cordillera (15-8,5 Ma). In the present work, we show an ensemble of tectonic, geophysical and cartographic data in order to characterize the post-Upper Tortonian deformation. For this, seismic reflection profiles have been interpreted with the help of hidrocarbon boreholes to define the thickness of the Upper Tortonian sedimentary sequence. All these data provide an estimation of the geometrical and kinematic characteristics of the extensional faults, direction of movement and rate of displacement of these rocks during Messinian/Pliocene times. References Rodríguez-Fernández, J., Roldan, F. J., J.M. Azañón y Garcia-Cortes, A

Radiolarian biochronology of upper Anisian to upper Ladinian (Middle Triassic) blocks and tectonic slices of volcano-sedimentary successions in the Mersin Mélange, southern Turkey: New insights for the evolution of Neotethys

NASA Astrophysics Data System (ADS)

Tekin, U. Kagan; Bedi, Yavuz; Okuyucu, Cengiz; Göncüoglu, M. Cemal; Sayit, Kaan

2016-12-01

The Mersin Ophiolitic Complex located in southern Turkey comprises two main structural units; the Mersin Mélange, and a well-developed ophiolite succession with its metamorphic sole. The Mersin Mélange is a sedimentary complex including blocks and tectonic slices of oceanic litosphere and continental crust in different sizes. Based on different fossil groups (Radiolaria, Conodonta, Foraminifera and Ammonoidea), the age of these blocks ranges from Early Carboniferous to early Late Cretaceous. Detailed fieldwork in the central part of the Mersin Mélange resulted in identification of a number of peculiar blocks of thick basaltic pillow-and massive lava sequences alternating with pelagic-clastic sediments and radiolarian cherts. The oldest ages obtained from the radiolarian assemblages from the pelagic sediments transitional to the volcano-sedimentary succession in some blocks are middle to late Late Anisian. These pelagic sediments are overlain by thick sandstones of latest Anisian to middle Early Ladinian age. In some blocks, sandstones are overlain by clastic and pelagic sediments with lower Upper to middle Upper Ladinian radiolarian fauna. Considering the litho- and biostratigraphical data from Middle Triassic successions in several blocks in the Mersin Mélange, it is concluded that they correspond mainly to the blocks/slices of the Beysehir-Hoyran Nappes, which were originated from the southern margin of the Neotethyan Izmir-Ankara Ocean. As the pre-Upper Anisian basic volcanics are geochemically evaluated as back-arc basalts, this new age finding suggest that a segment of the Izmir-Ankara branch of the Neotethys was already open prior to Middle Triassic and was the site of intraoceanic subduction.

Origin, evolution and sedimentary processes associated with a late Miocene submarine landslide, southeast Spain

NASA Astrophysics Data System (ADS)

Sola, F.; Puga-Bernabéu, Á.; Aguirre, J.; Braga, J. C.

2018-02-01

A submarine landslide, the Alhama de Almería Slide, influenced late Tortonian and early Messinian (late Miocene) sedimentary processes in the vicinity of Alhama de Almería in southeast Spain. Its 220-m-high headscarp and deposits are now subaerially exposed. The landslide occurred at the northern slope of the antecedent relief of the present-day Sierra de Gádor mountain range. This is a large antiform trending east-west to east-northeast-west-southwest, which has been uplifting since the late Miocene due to convergence of the African and Eurasian plates. During the Tortonian, this relief was an island separated from the Iberian Peninsula mainland by the Alpujarra corridor, a small and narrow intermontane basin of the Betic Cordillera in the western Mediterranean Sea. The materials involved in the slope failure were Triassic dolostones and phyllites from the metamorphic Alpujárride Complex and Tortonian marine conglomerates, sandstones, and marls that formed an initial sedimentary cover on the basement rocks. Coherent large masses of metamorphic rocks and Miocene deposits at the base of the headscarp distally change to chaotic deposits of blocks of different lithologies embedded in upper Tortonian marine marls, and high-strength cohesive debrites. During downslope sliding, coherent carbonate blocks brecciated due to their greater strength. Phyllites disintegrated, forming a cohesive matrix that engulfed and/or sustained the carbonate blocks. Resedimented, channelized breccias were formed by continuing clast collision, bed fragmentation, and disaggregation of the failed mass. The conditions leading to rock/sediment failure were favoured by steep slopes and weak planes at the contact between the basement carbonates and phyllites. Displacement of collapsed rocks created a canyon-like depression at the southeast edge of the landslide. This depression funnelled sediment gravity flows that were generated upslope, promoting local thick accumulations of sediments during

Early Tertiary Anaconda metamorphic core complex, southwestern Montana

USGS Publications Warehouse

O'Neill, J. M.; Lonn, J.D.; Lageson, D.R.; Kunk, Michael J.

2004-01-01

A sinuous zone of gently southeast-dipping low-angle Tertiary normal faults is exposed for 100 km along the eastern margins of the Anaconda and Flint Creek ranges in southwest Montana. Faults in the zone variously place Mesoproterozoic through Paleozoic sedimentary rocks on younger Tertiary granitic rocks or on sedimentary rocks older than the overlying detached rocks. Lower plate rocks are lineated and mylonitic at the main fault and, below the mylonitic front, are cut by mylonitic mesoscopic to microscopic shear zones. The upper plate consists of an imbricate stack of younger-on-older sedimentary rocks that are locally mylonitic at the main, lowermost detachment fault but are characteristically strongly brecciated or broken. Kinematic indicators in the lineated mylonite indicate tectonic transport to the east-southeast. Syntectonic sedimentary breccia and coarse conglomerate derived solely from upper plate rocks were deposited locally on top of hanging-wall rocks in low-lying areas between fault blocks and breccia zones. Muscovite occurs locally as mica fish in mylonitic quartzites at or near the main detachment. The 40Ar/39Ar age spectrum obtained from muscovite in one mylonitic quartzite yielded an age of 47.2 + 0.14 Ma, interpreted to be the age of mylonitization. The fault zone is interpreted as a detachment fault that bounds a metamorphic core complex, here termed the Anaconda metamorphic core complex, similar in age and character to the Bitterroot mylonite that bounds the Bitterroot metamorphic core complex along the Idaho-Montana state line 100 km to the west. The Bitterroot and Anaconda core complexes are likely components of a continuous, tectonically integrated system. Recognition of this core complex expands the region of known early Tertiary brittle-ductile crustal extension eastward into areas of profound Late Cretaceous contractile deformation characterized by complex structural interactions between the overthrust belt and Laramide basement uplifts

Textural Maturity Analysis and Sedimentary Environment Discrimination Based on Grain Shape Data

NASA Astrophysics Data System (ADS)

Tunwal, M.; Mulchrone, K. F.; Meere, P. A.

2017-12-01

Morphological analysis of clastic sedimentary grains is an important source of information regarding the processes involved in their formation, transportation and deposition. However, a standardised approach for quantitative grain shape analysis is generally lacking. In this contribution we report on a study where fully automated image analysis techniques were applied to loose sediment samples collected from glacial, aeolian, beach and fluvial environments. A range of shape parameters are evaluated for their usefulness in textural characterisation of populations of grains. The utility of grain shape data in ranking textural maturity of samples within a given sedimentary environment is evaluated. Furthermore, discrimination of sedimentary environment on the basis of grain shape information is explored. The data gathered demonstrates a clear progression in textural maturity in terms of roundness, angularity, irregularity, fractal dimension, convexity, solidity and rectangularity. Textural maturity can be readily categorised using automated grain shape parameter analysis. However, absolute discrimination between different depositional environments on the basis of shape parameters alone is less certain. For example, the aeolian environment is quite distinct whereas fluvial, glacial and beach samples are inherently variable and tend to overlap each other in terms of textural maturity. This is most likely due to a collection of similar processes and sources operating within these environments. This study strongly demonstrates the merit of quantitative population-based shape parameter analysis of texture and indicates that it can play a key role in characterising both loose and consolidated sediments. This project is funded by the Irish Petroleum Infrastructure Programme (www.pip.ie)

Sedimentary denitrification: Isotope fractionation and its impact on water column nitrate isotopes

NASA Astrophysics Data System (ADS)

Dähnke, K.; Thamdrup, B.

2012-04-01

The global marine nitrogen cycle is constrained by one major source and two processes that act as nitrogen sinks: nitrogen fixation on the one side and denitrification or anammox on the other. These processes with their respective isotope effecst set the marine nitrate 15N-isotope value to a relatively constant average of 5 per mil. This value can be used to better assess the magnitude of these source and sink terms, but the underlying assumption at present is that sedimentary denitrification, a process responsible for approximately one third of global nitrogen removal, has little to no isotope effect on the water column. We tested this hypothesis in sediment incubations, measuring net denitrification and nitrogen and oxygen stable isotope fractionation in surface sediments from the coastal Baltic Sea (Boknis Eck, Northern Germany). We found tremendously high denitrification rates, and regardless of current paradigms assuming little fractionation during sediment denitrification, we measured fractionation factors of 19 per mil for nitrogen and 11 per mil for oxygen in nitrate. These results potentially challenge the current view of fractionation during sedimentary denitrification and imply that nitrogen budget calculation may need to consider this variability. Furthermore, the ratio of fractionation factors for nitrogen and oxygen is distinct from the 1 : 1 ratio otherwise found in marine systems, and suggests that isotope kinetics of sedimentary denitrification might be entirely different from water column denitrification. Acknowledgements: This work was funded by the German Research Foundation (DFG) and in parts by the Danish National Research Foundation.

Application of Fourier transform infrared spectroscopy to silica diagenesis: The opal-A to opal-CT transformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rice, S.B.; Freund, H.; Huang, W.L.

An important goal in silica diagenesis research is to understand the kinetics of opal transformation from noncrystalline opal-A to the disordered silica polymorph opal-CT. Because the conventional technique for monitoring the transformation, powder X-ray diffraction (XRD), is applicable only to phases with long-range order, the authors used Fourier transform infrared spectroscopy (FTIR) to monitor the transformation. They applied this technique, combined with XRD and TEM, to experimental run products and natural opals from the Monterey Formation and from siliceous deposits in the western Pacific Ocean. Using a ratio of two infrared absorption intensities ({omega} = I{sub 472 cm{sup {minus}1}}/I{sub 500more » cm{sup {minus}1}}), the relative proportions of opal-A and opal-CT can be determined. The progress of the transformation is marked by changes in slope of {omega} vs. depth or time when a sufficient stratigraphic profile is available. There are three stages in the opal-A to opal-CT reaction: (1) opal-A dissolution; (2) opal-CT precipitation, whose end point is marked by completion of opal-A dissolution; and (3) opal-CT ordering, during which tridymite stacking is eliminated in favor of crystobalite stacking.« less

Comprehensive assessment of precursors, diagenesis, and reactivity to water treatment of dissolved and colloidal organic matter

USGS Publications Warehouse

Leenheer, J.A.

2004-01-01

A comprehensive isolation, fractionation, and characterization research approach was developed for dissolved and colloidal organic matter (DOM) in water, and it was applied to various surface- and groundwaters to assess DOM precursors, DOM diagenesis, and DOM reactivity to water treatment processes. Major precursors for natural DOM are amino sugars, condensed tannins, and terpenoids. Amino sugar colloids derived from bacterial cell walls are incompletely removed by drinking water treatment and foul reverse osmosis membranes, but are nearly quantitatively removed by soil/aquifer treatment. When chlorinated, amino sugars produce low yields of regulated disinfection by-products (DBFs) but they produce significant chlorine demand that is likely caused by chlorination of free amino groups. Condensed tannins are major precursors for "blackwater" DOM such as that found in the Suwannee River. This DOM produces high yields of DBPs upon chorination, and is efficiently removed by coagulation/flocculation treatment. Terpenoid-derived DOM appears to be biologically refractory, infiltrates readily into groundwater with little removal by soil/aquifer treatment, gives low DBF-yields upon chlorination and is poorly removed by coagulation/flocculation treatments. Peptides derived from proteins are major components of the base DOM fraction (10% or less of the mass of DOM), and this fraction produces large yields of haloacetonitriles upon chorination.

Sedimentary geology of the middle Carboniferous of the Donbas region (Dniepr-Donets Basin, Ukraine).

PubMed

van Hinsbergen, Douwe J J; Abels, Hemmo A; Bosch, Wolter; Boekhout, Flora; Kitchka, Alexander; Hamers, Maartje; van der Meer, Douwe G; Geluk, Mark; Stephenson, Randell A

2015-03-20

The Paleozoic Dniepr-Donets Basin in Belarus, Ukraine, and Russia forms a major hydrocarbon province. Although well- and seismic data have established a 20 km thick stratigraphy, field-studies of its sediments are scarce. The inverted Donbas segment (Ukraine) exposes the middle Carboniferous part of the basin's stratigraphy. Here, we provide detailed sedimentological data from 13 sections that cover 1.5 of the total of 5 km of the Bashkirian and Moscovian stages and assess the paleoenvironment and paleo-current directions. Middle Carboniferous deposition occurred in a shelf environment, with coal deposition, subordinate fluvial facies, and abundant lower and middle shoreface facies, comprising an intercalated package of potential source and reservoir rocks. Sedimentary facies indicate a paleodepth range from below storm wave base to near-coastal swamp environments. Sedimentation and subsidence were hence in pace, with subtle facies changes likely representing relative sea-level changes. Paleocurrent directions are remarkably consistently southeastward in time and space in the different sedimentary facies across the Donbas Fold Belt, illustrating a dominant sedimentary infill along the basin axis, with little basin margin influence. This suggests that the middle Carboniferous stratigraphy of the Dniepr-Donets basin to the northwest probably contains significant amounts of fluvial sandstones, important for assessing hydrocarbon reservoir potential.

Sedimentary geology of the middle Carboniferous of the Donbas region (Dniepr-Donets basin, Ukraine)

PubMed Central

van Hinsbergen, Douwe J. J.; Abels, Hemmo A.; Bosch, Wolter; Boekhout, Flora; Kitchka, Alexander; Hamers, Maartje; van der Meer, Douwe G.; Geluk, Mark; Stephenson, Randell A.

2015-01-01

The Paleozoic Dniepr-Donets Basin in Belarus, Ukraine, and Russia forms a major hydrocarbon province. Although well- and seismic data have established a 20 km thick stratigraphy, field-studies of its sediments are scarce. The inverted Donbas segment (Ukraine) exposes the middle Carboniferous part of the basin's stratigraphy. Here, we provide detailed sedimentological data from 13 sections that cover 1.5 of the total of 5 km of the Bashkirian and Moscovian stages and assess the paleoenvironment and paleo-current directions. Middle Carboniferous deposition occurred in a shelf environment, with coal deposition, subordinate fluvial facies, and abundant lower and middle shoreface facies, comprising an intercalated package of potential source and reservoir rocks. Sedimentary facies indicate a paleodepth range from below storm wave base to near-coastal swamp environments. Sedimentation and subsidence were hence in pace, with subtle facies changes likely representing relative sea-level changes. Paleocurrent directions are remarkably consistently southeastward in time and space in the different sedimentary facies across the Donbas Fold Belt, illustrating a dominant sedimentary infill along the basin axis, with little basin margin influence. This suggests that the middle Carboniferous stratigraphy of the Dniepr-Donets basin to the northwest probably contains significant amounts of fluvial sandstones, important for assessing hydrocarbon reservoir potential. PMID:25791400