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Sample records for sedimentary biomarker record

  1. Biomass Burning, Long-Range Atmospheric Transport and the Sedimentary Record of Plant Wax Biomarkers

    NASA Astrophysics Data System (ADS)

    Weber, J. C.; Conte, M. H.

    2007-12-01

    Sedimentary distributions of plant leaf wax molecular and isotopic composition can provide detailed information about past terrestrial ecosystem structure and its variability in response to climatic forcing. However, in many locales (e.g. marine sediments, high elevation lakes), sedimentary plant waxes are derived primarily from atmospheric deposition rather than from local fluvial input or direct runoff. Thus, an understanding of wax atmospheric transport and deposition is essential for accurate interpretation of the sedimentary signal. In this talk we synthesize results from our studies of wax aerosol composition and atmospheric transport at strategically located sites (Northern Alaska, Maine, Florida, Bermuda, Barbados, French Guiana) that sample continental air masses passing over major terrestrial ecosystems (tundra, North American boreal, temperate and southern pine forests, North African desert grasslands, Amazon rain forest). Wax aerosols in boundary layer air masses reflect a large regionally integrated source signal. Over the North Atlantic, the long-range atmospheric transport of plant waxes is essentially uncorrelated with episodes of high African dust transport. Rather, the highest plant wax aerosol concentrations are clearly associated with continental air masses that are laden with smoke from biomass burning, which enhances long-range transport both by the process of steam distillation of wax and other easily volatilized compounds off living (moisture-rich) vegetation in the advancing front of the fire and by deep atmospheric convection, which efficiently injects re- condensed particles into the lower troposphere where they can be most efficiently transported by high altitude winds. The direct linkage between enhanced long-range atmospheric transport of plant waxes and biomass burning suggests that the wax sedimentary record in localities dominated by atmospheric input strongly co-varies with climate-driven changes in fire frequency and is

  2. Biomarker characterization of the record of the OAE1a (early Aptian) in Betic and Cantabrian basins (Spain)-Sedimentary implications

    NASA Astrophysics Data System (ADS)

    Quijano, María. Luisa; Castro, José Manuel; Pancost, Richard D.; de Gea, Ginés. A.; Najarro, María.; Aguado, Roque; Rosales, Idoia; Martín-Chivelet, Javier

    2010-05-01

    Molecular analyses of sedimentary organic matter are powerful tools in assessing the origin of organic matter and its thermal maturity as well as constraining ancient environmental conditions, such as as marine productivity, anoxia in bottom waters or the photic zone and sea surface temperatures. This communication presents the study of four sections recording the OAE1a (early Aptian) in Spain, which are located in two broad basins respectively located in the South and the North of Iberia: the Southern Iberian Palaeomargin (Carbonero - CAB, La Frontera - XF and Cau - CAU sections) and the Cantabrian Basin (Puente Nansa - PN section). These sections represent depositional settings ranging from platform (CAU, PN) to pelagic environments (CAB, XF). C-isotope profiles and biostratigraphic data are used to define the interval corresponding to the OAE 1a. Here we focus on the biomarker composition of the organic-rich facies, and the integration of these data with the sedimentology, stratigraphy and paleogeography. The study has been based mainly upon the analysis of samples with Gas Chromatography-Mass Spectrometry (GCMS). Four main groups of compounds are present in all sections: n-alkanes, isoprenoids, hopanes and steranes. n-Alkanes and isoprenoids (pristane and phytane) are dominant in most samples. To facilitate interpretation of these distributions, we have calculated the TAR (terrestrial aquatic ratio derived from the ratio of long to short chain compounds) and also the OEP (odd over even predominance of n-alkanes). The ratio of pristane to phytane and various isoprenoid/n-alkanes ratios have also been calculated. The hopanes are represented by a range of C27 to C35 components, with the specific isomers varying amongst the sections due to differences in thermal maturity. Steranes occur as a range of C27, C28 and C29 isomers, whereas diasteranes only occur in the most thermally mature section (CAB). Other compounds of interest include gammacerane and dinosterane

  3. Technical Note: n-Alkane lipid biomarkers in loess: post-sedimentary or syn-sedimentary?

    NASA Astrophysics Data System (ADS)

    Zech, M.; Kreutzer, S.; Goslar, T.; Meszner, S.; Krause, T.; Faust, D.; Fuchs, M.

    2012-07-01

    There is an ongoing discussion whether n-alkane biomarkers - and organic matter (OM) from loess in general - reflect a syn-sedimentary paleoenvironmental and paleoclimate signal or whether they are significantly a post-sedimentary feature contaminated by root-derived OM. We present first radiocarbon data for the n-alkane fraction of lipid extracts and for the first time luminescence ages for the Middle to Late Weichselian loess-paleosol sequence of Gleina in Saxony, Germany. Comparison of these biomarker ages with sedimentation ages as assessed by optically stimulated luminescence (OSL) dating shows that one n-alkane sample features a syn-sedimentary age (14C: 29.2 ± 1.4 kyr cal BP versus OSL: 27.3 ± 3.0 kyr). By contrast, the 14C ages derived from the other n-alkane samples are clearly younger (20.3 ± 0.7 kyr cal BP, 22.1 ± 0.7 kyr cal BP and 29.8 ± 1.4 kyr cal BP) than the corresponding OSL ages (26.6 ± 3.1 kyr, 32.0 ± 3.5 kyr and 45.6 ± 5.3 kyr). This finding suggests that a post-sedimentary n-alkane contamination presumably by roots has occurred. In order to estimate the post-sedimentary n-alkane contamination more quantitatively, we applied a 14C mass balance calculation based on the measured pMC (percent modern carbon) values, the calculated syn-sedimentary pMC values and pMC values suspected to reflect likely time points of post-sedimentary contamination (current, modern, 3 kyr, 6 kyr and 9 kyr). Accordingly, current and modern root-contamination would account for up to 7%, a 3 kyr old root-contamination for up to 10%, and an Early and Middle Holocene root-contamination for up to 20% of the total sedimentary n-alkane pool. We acknowledge and encourage that these first radiocarbon results need further confirmation both from other loess-paleosol sequences and for different biomarkers, e.g. carboxylic acids or alcohols as further lipid biomarkers.

  4. n-Alkane lipid biomarkers in loess: post-sedimentary or syn-sedimentary?

    NASA Astrophysics Data System (ADS)

    Zech, Michael; Kreutzer, Sebastian; Goslar, Tomasz; Meszner, Sascha; Krause, Tobias; Faust, Dominik; Fuchs, Markus

    2013-04-01

    There is an ongoing discussion whether n-alkane biomarkers - and organic matter (OM) from loess in general - reflect a syn-sedimentary paleoenvironmental and paleoclimate signal or whether they are significantly a post-sedimentary feature contaminated by root-derived OM (Zech et al., 2012, 2013; Wiesenberg and Gocke, 2013). We present first radiocarbon data for the n-alkane fraction of lipid extracts and for the first time luminescence ages for the Middle to Late Weichselian loess-paleosol sequence of Gleina in Saxony, Germany. Comparison of these biomarker ages with sedimentation ages as assessed by optically stimulated luminescence (OSL) dating shows that one n-alkane sample features a syn-sedimentary age (14C: 29.2 ± 1.4 kyr calBP versus OSL: 27.3 ± 3.0 kyr). By contrast, the 14C ages derived from the other n-alkane samples are clearly younger (20.3 ± 0.7 kyr calBP, 22.1 ± 0.7 kyr calBP and 29.8 ± 1.4 kyr calBP) than the corresponding OSL ages (26.6 ± 3.1 kyr, 32.0 ± 3.5 kyr and 45.6 ± 5.3 kyr). This finding suggests that a post-sedimentary n-alkane contamination presumably by roots has occurred. In order to estimate the post-sedimentary n-alkane contamination more quantitatively, we applied a 14C mass balance calculation based on the measured pMC (percent modern carbon) values, the calculated syn-sedimentary pMC values and pMC values suspected to reflect likely time points of post-sedimentary contamination (modern, last decades, 3 kyr, 6 kyr and 9 kyr). Accordingly, modern and last decadal root-contamination would account for up to 7%, a 3 kyr old root-contamination for up to 10%, and an Early and Middle Holocene root-contamination for up to 20% of the total sedimentary n-alkane pool. We acknowledge and encourage that these first radiocarbon results need further confirmation both from other loess-paleosol sequences and for different biomarkers, e.g. carboxylic acids or alcohols as further lipid biomarkers. Zech, M., Kreutzer, S., Goslar, T., Meszner, S

  5. Temporal Trends in Syngenetic Lipid Biomarker Signals from Proterozoic Sedimentary Organic Matter

    NASA Astrophysics Data System (ADS)

    Love, G. D.; Li, C.; Summons, R. E.

    2008-12-01

    The development of continuous-flow catalytic hydropyrolysis (HyPy) for reproducible recovery of biomarker lipid skeletons covalently-bound within kerogen has proved to be an important analytical breakthrough for ancient lipid biomarker research. The parallel analyses of free (solvent-extractable) and kerogen-bound biomarkers affords more confidence that we have correctly identified syngenetic compounds. Combining HyPy with detailed biomarker product analyzes using metastable reaction monitoring-gas chromatography mass spectrometry (MRM-GC-MS) allows detection of a large suite of biomarker compounds which are usually too low in abundance to be analyzed in detail using conventional GC-MS. Here we compare free and bound lipid biomarker records generated from Paleoproterozoic (ca. 1.7 Ga) to Late Ediacaran age (ca. 542 Ma) strata from marine basins from North and South China, Australia and Oman. Fundamental changes in eukaryotic community structure are evident after the Sturtian glaciation (ca. 713 Ma) from distinctive sterane distributions. In particular, radiations in basal animals (sponges) and chlorophyte microalgae are first apparent in Huqf sedimentary rocks from South Oman Salt Basin. Marine microbial communities were not globally homogenous in contemporaneous Proterozoic settings from comparison of biomarker profiles and this could reflect differences in ocean chemistry, affecting nutrient supply, from basin to basin.

  6. The Hidden Watershed's Journals: the Informational Characteristics of Biomarkers in Sedimentary Deposits

    NASA Astrophysics Data System (ADS)

    Guerrero, F. J.; Hatten, J. A.

    2014-12-01

    The historical reconstruction of past environmental changes in watersheds is essential to understand watershed response to disturbances and how those diturbances could affect the provision of valuable goods like water. That reconstruction requires the interpretation of natural records, mainly associated to sedimentary deposits that store detailed information in the form of specific biogenic molecules (i.e. biomarkers). In forested watersheds terrestrial vegetation is an important source of biomarkers like those associated to Lignin, a complex organic polymer used by plants to provide physical support in its tissues. Through litter inputs Lignin is deposited in soils and then is transported to sedimentary environments by rivers (e.g. floodplains, lake bottoms), serving as a source of information about vegetation changes in watersheds. In spite of the critical character of the information extracted from biomarkers in sedimentary records, the very concept of information is still used in a metaphorical sense, even though it was formally defined more than 60 years ago and has been applied extensively in ecology (e.g. Shannon's diversity index). Furthermore, sophisticated techniques are being used to deliver more complex molecular data that require examination and validation as indicators for watershed historical reconstructions. My research aims to explore the applicability of some information metrics (i.e. diversity indices, information coefficients) to a diverse molecular set derived from the chemical depolymerization of lignin deposited in floodplains and lake sediments in different basins. This approach attempts to assess the informational characteristics of Lignin as an indicator of natural/human-induced perturbations in forested watersheds. The formal assessment of the informational characteristics of natural records could have a profound impact not only in our methodological approaches but also in our philosophical view about information and communication in

  7. Continental Growth and the Sedimentary Record

    NASA Astrophysics Data System (ADS)

    Dhuime, B.; Hawkesworth, C. J.; Robinson, R. A. J.; Cawood, P. A.

    2014-12-01

    Detrital sedimentary rocks provide average samples of the continental crust formed at different times and in different places. Some materials are more susceptible to erosion and/or to preservation bias than others, and one issue is to understand how the compositions of a range of source rocks are then recorded in the sediments. Here we considered two different approaches to model the growth of the continental crust: (i) The variation of Nd isotopes in continental shales with different deposition ages, which requires a correction of the bias induced by preferential erosion of younger rocks through an erosion parameter usually referred to as 'K'. The determination of K, and the extent to which it varies in different erosion systems, thus have fundamental implications for the models of continental growth based on radiogenic isotopes in continental sediments. (ii) The variations in U-Pb, Hf and O isotopes in detrital zircons, from 'modern' sediments sampled worldwide. In this approach, O isotopes are used to screen 'hybrid' Hf model ages (i.e. ages resulting from mixing processes of crustal material from different ages) from Hf model ages that represent actual crust formation ages. These two approaches independently suggest that the continental crust has been generated continuously, but with a marked decrease in the continental growth rate at ~3 Ga. The >4 Ga to ~3 Ga period is characterised by relatively high net rates of continental growth (~3.0 km3.a-1), which are similar to the rates at which new crust is generated, and destroyed, at the present time. Net growth rates are much lower since 3 Ga (~0.8 km3.a-1), which may be attributed to higher rates of destruction of continental crust. The inflexion in the continental growth curve at ~3 Ga indicates a change in the way the crust was generated and preserved. This change may be linked to onset of subduction-driven plate tectonics and discrete subduction zones.

  8. Historical eutrophication in the Changjiang and Mississippi delta-front estuaries: Stable sedimentary chloropigments as biomarkers

    NASA Astrophysics Data System (ADS)

    Zhao, Jun; Bianchi, Thomas S.; Li, Xinxin; Allison, Mead A.; Yao, Peng; Yu, Zhigang

    2012-09-01

    Eutrophication is one of the most significant ecological problems in large-river delta-front estuaries (LDEs) around the world. We used TOC, TN, δ13C, δ15N and three stable sedimentary chloropigments (pyropheophytin-a [pPHtin-a], sterol chlorin esters [SCEs] and carotenol chlorin esters [CCEs]) as geochemical proxies to examine historical trends of eutrophication over the last few decades in the Changjiang and Mississippi LDEs. Concentrations of sedimentary pPHtin-a, SCEs and CCEs increased from 15, 12 and 120 nmol g-1 OC in 1960s to 51, 32 and 256 nmol g-1 OC in 1990s on the inner shelf of the East China Sea, respectively, and from 57, 69 and 31 nmol g-1 OC in 1950s to 70, 90 and 44 nmol g-1 OC in 2000s in the Mississippi Canyon, respectively. Riverine loading of DIN flux to LDE increased from (261±109)×106 kg yr-1 in pre-1980 to (1385±209)×106 kg yr-1 in post-1990 in the Changjiang LDE, while nitrate flux increased from (322±89)×106 kg yr-1 in the 1950s to 1960s to (589±123)×106 kg yr-1 in the 1970s, and DIN flux kept relatively stable in (963±250)×106 kg yr-1 from the 1980s to 2000s in the Mississippi LDE. This work reveals that the stable sedimentary chloropigments in accumulating sediments on the inner shelf are suitable biomarkers for examining past changes in eutrophication in the Changjiang and Mississippi LDE ecosystems. The historical record of riverine nutrient inputs as related to changes in the watershed (e.g., fertilizers and manure) is well-correlated with down-core concentrations of stable pheopigment biomarkers in sediments at both LDEs. These results support the coupling between enhanced phytoplankton abundance and increasing anthropogenic nutrients input to the inner shelves of these LDEs.

  9. Leaf wax biomarkers in transit record river catchment composition

    NASA Astrophysics Data System (ADS)

    Ponton, Camilo; West, A. Joshua; Feakins, Sarah J.; Galy, Valier

    2014-09-01

    Rivers carry organic molecules derived from terrestrial vegetation to sedimentary deposits in lakes and oceans, storing information about past climate and erosion, as well as representing a component of the carbon cycle. It is anticipated that sourcing of organic matter may not be uniform across catchments with substantial environmental variability in topography, vegetation zones, and climate. Here we analyze plant leaf wax biomarkers in transit in the Madre de Dios River (Peru), which drains a forested catchment across 4.5 km of elevation from the tropical montane forests of the Andes down into the rainforests of Amazonia. We find that the hydrogen isotopic composition of leaf wax molecules (specifically the C28 n-alkanoic acid) carried by this tropical mountain river largely records the elevation gradient defined by the isotopic composition of precipitation, and this supports the general interpretation of these biomarkers as proxy recorders of catchment conditions. However, we also find that leaf wax isotopic composition varies with river flow regime over storm and seasonal timescales, which could in some cases be quantitatively significant relative to changes in the isotopic composition of precipitation in the past. Our results inform on the sourcing and transport of material by a major tributary of the Amazon River and contribute to the spatial interpretation of sedimentary records of past climate using the leaf wax proxy.

  10. Decoupled sedimentary records of combustion: Causes and implications

    NASA Astrophysics Data System (ADS)

    Hanke, Ulrich M.; Eglinton, Timothy I.; Braun, Ana L. L.; Reddy, Christopher M.; Wiedemeier, Daniel B.; Schmidt, Michael W. I.

    2016-05-01

    Pyrogenic carbon (PyC) is a collective term for carbon-rich residues comprised of a continuum of products arising from biomass burning and fossil-fuel combustion. PyC is ubiquitous in the environment where it can be transported by wind and water before being deposited in aquatic sediments. We compare results from four different methods used to trace PyC that were applied to a high-temporal resolution sedimentary record in order to constrain changes in PyC concentrations and fluxes over the past ~250 years. We find markedly discordant records for different PyC tracers, particularly during the preindustrial age, implying different origins and modes of supply of sedimentary PyC. In addition to providing new insights into the composition of sedimentary combustion products, this study reveals that elucidation of past combustion processes and development of accurate budgets of PyC production and deposition on local to regional scales requires careful consideration of both source characteristics and transport processes.

  11. Organic chemical and biomarker analyses of terrestrial archives - is all what we measure of sedimentary origin?

    NASA Astrophysics Data System (ADS)

    Wiesenberg, G. L.; Gocke, M.

    2012-12-01

    Organic chemical analyses of sedimentary organic matter have been widely used in the past. In terrestrial archives total carbon, organic carbon (Corg) and carbonatic carbon (Ccarb) and their stable isotope composition (δ13C) were established for source assessment of sedimentary matter covering source area (Ccarb) and source vegetation (Corg). Furthermore, radiocarbon dating (Δ14C) was found useful to date sedimentary archives covering the past 50 ka. In addition, the application of biomarkers was tried in sedimentary archives like loess-paleosol sequences to trace source vegetation in more detail. Among others, several alkane molecular proxies have been introduced and adopted in order to assess the contribution of tree and grass vegetation to sedimentary organic matter. Furthermore, other biomarkers like alcohols, fatty acids and others were introduced into the investigation of terrestrial archives. However, studies of the recent 10 years clearly indicate that overprint of sedimentary matter is very likely for terrestrial archives and that caution should be paid, when interpreting chemical results. While secondary carbonate formation is a well known feature covering e.g. loess dolls, pseudomycelia and rhizoliths, commonly these features are not mentioned correctly in a paleoenvironmental context. Nevertheless, they provide unique opportunities for the reassessment of potential contamination of sedimentary organic matter. Especially rhizoliths as calcified root remains can impressively cut vertically through several pairs of sediments and paleosols. While some authors still suggest their formation during sedimentation, we could clearly show different ages of sediments and rhizoliths from the same depth. While some of these root features are easy to see during field campaigns, others are not. This is e.g. observed for biopores in the vicinity of rhizoliths. They can have diameters <0.1 mm and are associated with former fine roots, which must not necessarily be

  12. Sedimentary Records of the Paleohurricane Activity in the Bahamas

    NASA Astrophysics Data System (ADS)

    Wallace, E. J.; Donnelly, J. P.; Wiman, C.; Cashman, M.

    2015-12-01

    Hurricanes pose a threat to human lives and can cause significant destruction of coastal areas. This threat has become more pronounced with recent rises in sea level and coastal populations. Currently, there is a large degree of uncertainty surrounding future changes in tropical cyclone activity. This is due to the limitations of climate models as well as the scarcity and unreliability of the current observational record. With so much uncertainty surrounding the current projections of hurricane activity, it is crucial to establish a longer and more accurate historical record. This study uses sediment cores extracted from blueholes in the Bahamas to develop a record of intense hurricane landfalls in the region dating back more than a millennia. The collected cores were sectioned, split, and scanned on an X-ray fluorescence scanner to obtain a high resolution core profile of the sediments' elemental composition and to identify potential sedimentary structures. Age control of the samples was determined using radiocarbon dating, coarse fraction was measured every centimeter, and hurricane event bed frequency was established for each core. We assess the statistical significance of the patterns observed in the sedimentary record using a coupled ocean-atmosphere hurricane model to simulate storms representative of modern climatology. Cores extracted from two blue holes near South Andros Island provide approximately a 1600 year and a 600 year record respectively, with sedimentation rates exceeding 1 cm/year. Both records contain coarse grained event deposits that correlate with known historical intense hurricane strikes in the Bahamas within age uncertainties. The 1600 year record confirms previous hurricane reconstructions from the Caribbean indicating higher tropical cyclone activity from 500 to 1400 CE. In addition, these new high-resolution records indicate elevated intense hurricane activity in the 17th and 18th centuries CE, when activity is also elevated in lower

  13. Compound-specific nitrogen isotopes of equatorial Pacific sedimentary record

    NASA Astrophysics Data System (ADS)

    Sauthoff, W.; Ravelo, A. C.; Mccarthy, M. D.

    2014-12-01

    Compound specific nitrogen isotopic analysis of amino acids (δ15N-AA) is a technique that is widely used in regional ecology and food web studies, with newly expanding applications in organic geochemistry. However, its applicability to marine sediment has been minimally examined. This study is one of the first δ15N-AA applications into the paleorecord of marine sediment. We explore how δ15N-AA measurements provide insights into past changes in water column N cycling and N utilization, and into post-depositional processes that impact sedimentary N. This is possible because δ15N-AA investigates the molecular-level basis of the bulk sedimentary δ15N signal, revealing possible diagenetic alteration of sedimentary organic matter. Our goal was is to investigate the extent of alteration (vs. preservation) of individual sedimentary amino acid δ15N values from surface nitrate δ15N across a wide range of depositional environments. The δ15N of bulk sediment differs from that of the surface nitrate δ15N signal because of water column processes or more often because of alteration of the signal during initial sedimentation. To investigate this alteration we compare δ15N-AA to bulk δ15N measurements in a suite of equatorial Pacific core tops (378-4360 m below sea level) across contrasting oceanographic and sedimentary depositional conditions (e.g. high vs. low productivity, hypoxic vs. oxic bottom waters). To examine down core diagenetic alteration of the sediment record, we present δ15N-AA and bulk δ15N of selected deeper depths to observe 1) if diagenetic shift is coherently resolved by both types of measurements and 2) if select individual δ15N-AA values remain representative of the surface organic δ15N signal. We hypothesize that compound specific analysis (δ15N-AA) will provide a molecular level assessment of mechanism for diagenetic changes in bulk organic δ15N values while also preserving detailed information about planktonic ecosystem structure.

  14. A full lipid biomarker based record from Lake Challa, Tanzania

    NASA Astrophysics Data System (ADS)

    Blaga, C. I.; de Leeuw, J. W.; Verschuren, D.; Sinninghe Damsté1, J. S.

    2012-04-01

    The climate of the regions surrounding the Indian Ocean - East Africa, Arabian and Indian peninsulas - is strongly dominated by the dynamics of the seasonal monsoon. To understand the long and short term driving forces behind the natural climatic variability in this region it is highly important to reconstruct climatic changes in the past and, thereby, predict future changes taking into account also anthropogenic activities. Most low latitude locations lack continuous, highly resolved continental records with good age control. From the few existing records acquired from tropical glacier ice, cave stalagmites and fossil diatoms a thorough understanding of the climatic variations reflected (rainfall and drought or temperature and its effect on precipitation) is scanty. Chemically stratified crater lakes accumulate high-quality climate-proxy records as shown in very recent studies done on the continuous and finely laminated sediment record of Lake Challa situated on the lower East slope of Mt. Kilimanjaro (Verschuren et al. 2009; Wolff et al. 2011). The unique location of this lake in equatorial East Africa implies that the climate variability is influenced by the Indian Ocean and not by the Atlantic due to the Congo Air Boundary (Thierney et al. 2011). The objective of this study is to fully explore the biomarker content of the Lake Challa sedimentary record already characterized by an excellent time resolution and chronology. Various normal chain lipids (n-alkanes, n-fatty acids, n-alcohols), sterols, long-chain diols, triterpenoids and glycolipids in sedimentary organic matter, were determined in their solvent-extractable (free) and saponification-released forms (bound). The changing composition of organic matter content from the investigated lake is used as a framework to trace palaeo-humidity, terrestrial input, algal input, temperature in sediment traps and underlying sediments of Lake Challa to further our palaeo-environmental knowledge based on GDGT's and

  15. Biomarker Records Associated with Mass Extinction Events

    NASA Astrophysics Data System (ADS)

    Whiteside, Jessica H.; Grice, Kliti

    2016-06-01

    The history of life on Earth is punctuated by a series of mass extinction episodes that vary widely in their magnitude, duration, and cause. Biomarkers are a powerful tool for the reconstruction of historical environmental conditions and can therefore provide insights into the cause and responses to ancient extinction events. In examining the five largest mass extinctions in the geological record, investigators have used biomarkers to elucidate key processes such as eutrophy, euxinia, ocean acidification, changes in hydrological balance, and changes in atmospheric CO2. By using these molecular fossils to understand how Earth and its ecosystems have responded to unusual environmental activity during these extinctions, models can be made to predict how Earth will respond to future changes in its climate.

  16. Multi-biomarker Characterization of Sedimentary Organic Carbon along the Mullica River, NJ

    NASA Astrophysics Data System (ADS)

    Medeiros, P. M.; Sikes, E. L.

    2007-05-01

    Located in southeastern New Jersey, the Mullica River is approximately 90 km long, extending from the Indian Mills headwaters, through the Pinelands National Reserve to the Great Bay Estuary. The land cover vegetation of the Mullica River watershed (~ 1700 km2) encompasses pine-oak forests (50%) predominantly in the Pinelands followed by wetlands (36%) especially towards the estuary, representing one of the most pristine areas in the state. Sources and potential transformations of sedimentary organic carbon along the Mullica River were assessed using a natural multi-biomarker approach. Sediment samples were collected from the Pinelands to the bay and analyzed as silylated total extracts by gas chromatography-mass spectrometry. The primary biomarker classes found in the samples included n-alkanoic acids, n-alkanols, phytosterols, triterpenoids and saccharides. In general, sediment extracts composition reflected changes in the characteristic main cover vegetation along the river. The major biomarker contributions in the Pinelands sediments were phytosterols (sitosterol, stigmasterol, campesterol), their reduced products (i.e., stigmastanol, campestanol) and triterpenoids (β-amyrin, oleanoic acid) derived from higher plants detritus, followed by n-alkanoic acids and n- alkanols from epicuticular plant wax. Diterpenoids, mainly dehydroabietic acid (a biomarker for conifers), as well as the monosaccharide glucose and the fatty acids 16:0, 16:1, 18:0, 18:1, 18:2 (ubiquitous in biota) were important organic tracers observed in these sediments. The higher plants biomarkers tended to decrease downstream to trace levels in the bay extracts. An exception was the triterpenoid taraxerol (previously identified as a mangrove biomarker) derived mainly from the salt marsh vegetation draining the Great Bay. The higher abundances of the low molecular weight fatty acids (< C19) observed in the estuarine sediments are likely derived from marine phytoplanktonic inputs.

  17. Antarctic Cenozoic climate history from sedimentary records: ANDRILL and beyond.

    PubMed

    McKay, R M; Barrett, P J; Levy, R S; Naish, T R; Golledge, N R; Pyne, A

    2016-01-28

    Mounting evidence from models and geological data implies that the Antarctic Ice Sheet may behave in an unstable manner and retreat rapidly in response to a warming climate, which is a key factor motivating efforts to improve estimates of Antarctic ice volume contributions to future sea-level rise. Here, we review Antarctic cooling history since peak temperatures of the Middle Eocene Climatic Optimum (approx. 50 Ma) to provide a framework for future initiatives to recover sediment cores from subglacial lakes and sedimentary basins in Antarctica's continental interior. While the existing inventory of cores has yielded important insights into the biotic and climatic evolution of Antarctica, strata have numerous and often lengthy time breaks, providing a framework of 'snapshots' through time. Further cores, and more work on existing cores, are needed to reconcile Antarctic records with the more continuous 'far-field' records documenting the evolution of global ice volume and deep-sea temperature. To achieve this, we argue for an integrated portfolio of drilling and coring missions that encompasses existing methodologies using ship- and sea-ice-/ice-shelf-based drilling platforms as well as recently developed seafloor-based drilling and subglacial access systems. We conclude by reviewing key technological issues that will need to be overcome. PMID:26667911

  18. Effect of phosphorous concentrations on sedimentary distributions and isotopic composition of algal lipid biomarkers in lakes from central Switzerland

    NASA Astrophysics Data System (ADS)

    Ladd, N.; Dubois, N.; Schubert, C. J.

    2015-12-01

    Lakes in the Swiss central plateau experienced increasing anthropogenic phosphorous loading throughout much of the 20th century. Since the 1980s concerted remediation efforts on the part of the Swiss government have significantly reduced P concentrations in most lakes and reversed previous eutrophication. However, P concentrations remain elevated above their preindustrial levels in many sites. High quality monitoring of lake nutrient levels since the 1950s, along with several lakes of wide-ranging P concentrations in close proximity, make central Switzerland an ideal location for studying the ways in which nutrient loading affects the organic composition of lacustrine sediments. Results of such studies can be used to develop proxies of eutrophication in sites where fewer historical data exist, and to reconstruct historical P concentrations in local lakes from the time before record keeping began. We analyzed the distributions of algal lipid biomarkers from surface sediment and sediment traps collected in the spring of 2015 from ten lakes with variable P concentrations in central Switzerland. Sedimentary lipid distributions from these lakes confirm that biomarkers associated with algal and cyanobacterial sources are more abundant in the sediment of lakes with greater P loading. The dry sedimentary concentrations of biomarkers such as brassicasterol (primarily diatom source) and diplopterol (cyanobacteria source), as well as the less source specific short-chain n-alkanols, linearly increase from 0.3 - 1.9 μg/g as total phosphorous in the upper water column increases by 1 μg/L over a range of 7 - 50 μg/L. We also present preliminary hydrogen isotope data from these biomarkers. Hydrogen isotopes of algal lipids primarily reflect the source water in which the algae grew, and this relationship has been developed as a paleohydrologic proxy. However, laboratory cultures of marine algae demonstrate that they discriminate more against 2H under nutrient replete conditions

  19. Is modern climate variability reflected in compund specific hydrogen isotope ratios of sedimentary biomarkers?

    NASA Astrophysics Data System (ADS)

    Sachse, D.; Radke, J.; Gleixner, G.

    2003-04-01

    Compound specific hydrogen isotope ratios are emerging as a new palaeoclimatic and palaeohydrological proxy. First reconstructions of palaeoclimate using D/H ratios from n-alkanes are available (Andersen et al. 2001, Sauer et al. 2001, Sachse et al. 2003). However, a systematic approach comparing recent sedimentary biomarkers with climate data is still lacking. We are establishing an ecosystem study of small, ground water fed lakes with known limnology. Nearly all lakes are close to a long-term climate-monitoring site (CARBOEUROPE flux tower site, IAEA precipitation monitoring) delivering ecophysiological and climatic data as temperature, precipitation, evapotranspiration etc. Water, primary biomass, plant, soil and sediment were sampled from lakes and the surrounding ecosystem along a climatic and isotopic gradient in meteoric waters from northern Finland (deltaD: -130 permil vs. VSMOW) to southern Italy (deltaD: -30 permil vs. VSMOW, IAEA 2001). Biomarkers were extracted from the samples to test if climatic variability is reflected in their D/H ratios. First results of the factors influencing the hydrogen isotope composition of sedimentary biomarkers and their use as palaeoclimatic and palaeohydrological proxy will be presented. Andersen N, Paul HA, Bernasconi SM, McKenzie JA, Behrens A, Schaeffer P, Albrecht P (2001) Large and rapid climate variability during the Messinian salinity crisis: Evidence from deuterium concentrations of individual biomarkers. Geology 29:799-802 IAEA (2001) GNIP Maps and Animations. International Atomic Energy Agency, Vienna. Accessible at http://isohis.iaea.org Sachse D, Radke J, Gaupp R, Schwark L, Lüniger G, Gleixner G (2003) Reconstruction of palaeohydrological conditions in a lagoon during the 2nd Zechstein cycle through simultaneous use of deltaD values of individual n-alkanes and delta18O and delta13C values of carbonates. International Journal of Earth Sciences, submitted Sauer PE, Eglington TI, Hayes JM, Schimmelman A

  20. Western Tibet relief evolution, insight from sedimentary record and thermochronology

    NASA Astrophysics Data System (ADS)

    Mahéo, Gweltaz; Gourbet, Loraine; Hervé Leloup, Philippe; Sorrel, Philippe; Shuster, David L.; Paquette, Jean-Louis; Quillévéré, Frédéric

    2014-05-01

    The Tibetan plateau is defined as a low relief high elevation zone, resulting from India-Asia convergence. However, its morphology is relatively heterogeneous. Especially the western Tibetan plateau is characterized by a strong relief, numerous peaks higher than 6000 m.a.s.l. and large (up to 10 km), deep (1-2 km) valleys. We investigate the origin of this particular morphology, coupling geomorphologic studies with sedimentary records and (U-Th)/He thermochronometry. The western Tibet Tertiary sedimentation is mostly characterized by conglomerates, red sandstone and siltstones related with alluvial fan deposits. Zircon U-Pb dating of interbedded trachyte flows implies that deposition started before 25 Ma and was still ongoing at 20 Ma. These continental, detrital deposits are filling wide open valleys during probable arid climatic conditions. Such valleys are thus interpreted as inherited basins, paleovalleys, formed before detrital sedimentation i.e. at ~25 Ma. Moreover, rare marine sediments were observed below the detrital deposits. Foraminifera suggest an Oligocene age, which implies that the paleovalleys already existed during the Oligocene, and that the emersion of the Western Tibetan Plateau occurred between the Oligocene and 25 Ma. This emersion thus occurred much later than the India-Asia collision (~50-45Ma) but is compatible with the onset of the main thickening phase of the Indian plate. The orientation of the inherited valley axis appears to be that of active strike slip faults that induced eastward extrusion of Western Tibet. This suggests that such extrusion was already active at the time of sedimentation (both marine and continental). Thus extrusion was also active during the plateau emersion at Oligocene time. The morphology of the valleys, and their sedimentary infilling, suggest that a significant relief, similar to present-day one (about 1000-2000m between valleys floor and surrounding peaks) already existed at the time of sedimentation. This

  1. 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)

  2. Manganese mineralogy and diagenesis in the sedimentary rock record

    NASA Astrophysics Data System (ADS)

    Johnson, Jena E.; Webb, Samuel M.; Ma, Chi; Fischer, Woodward W.

    2016-01-01

    Oxidation of manganese (II) to manganese (III,IV) demands oxidants with very high redox potentials; consequently, manganese oxides are both excellent proxies for molecular oxygen and highly favorable electron acceptors when oxygen is absent. The first of these features results in manganese-enriched sedimentary rocks (manganese deposits, commonly Mn ore deposits), which generally correspond to the availability of molecular oxygen in Earth surface environments. And yet because manganese reduction is promoted by a variety of chemical species, these ancient manganese deposits are often significantly more reduced than modern environmental manganese-rich sediments. We document the impacts of manganese reduction and the mineral phases that form stable manganese deposits from seven sedimentary examples spanning from modern surface environments to rocks over 2 billion years old. Integrating redox and coordination information from synchrotron X-ray absorption spectroscopy and X-ray microprobe imaging with scanning electron microscopy and energy and wavelength-dispersive spectroscopy, we find that unlike the Mn(IV)-dominated modern manganese deposits, three manganese minerals dominate these representative ancient deposits: kutnohorite (CaMn(CO3)2), rhodochrosite (MnCO3), and braunite (Mn(III)6Mn(II)O8SiO4). Pairing these mineral and textural observations with previous studies of manganese geochemistry, we develop a paragenetic model of post-depositional manganese mineralization with kutnohorite and calcian rhodochrosite as the earliest diagenetic mineral phases, rhodochrosite and braunite forming secondarily, and later alteration forming Mn-silicates.

  3. A conceptual model for interpreting δ18O and δD biomarker records from terrestrial archives

    NASA Astrophysics Data System (ADS)

    Zech, Michael; Tuthorn, Mario; Detsch, Florian; Rozanski, Kazimierz; Zech, Roland; Zöller, Ludwig; Zech, Wolfgang; Glaser, Bruno

    2013-04-01

    The natural abundances of stable oxygen (18O/16O) and hydrogen isotopes (D/H) are valuable proxies for reconstructing paleoclimate history on global as well as on regional scale. While stable isotope analyses of sedimentary leaf wax-derived n-alkanes enables establishing δD biomarker records, we recently developed a method based on compound-specific δ18O analyses of hemicellulose sugars (Zech and Glaser, 2009), which now additionally allows establishing δ18O biomarker records from soil/sedimentary organic matter of terrestrial archives. Here we present a conceptual model for interpreting combined δ18O and δD biomarker records (Zech et al., submitted). Based on this model, we suggest that both δ18O and δD biomarker records primarily reflect the isotopic composition of paleoprecipitation modified by evaporative isotope enrichment of leaf water during transpiration. Considering biosynthetic fractionation factors allows reconstructing from combined δ18O and δD biomarker records the leaf water isotopic composition and the deuterium excess of the leaf water. The deuterium excess may serve as proxy for evaporative enrichment and allows reconstructing relative humidity using a Craig-Gordon model. Furthermore, the model allows calculating δ18O of the plant source water (δ18Osource water), which can be assumed to primarily reflect δ18O of paleoprecipitation. Hence, paleoclimatic conclusions in terms of temperature can be drawn in high latitude study areas and precipitation amount can be reconstructed in monsoon regions. Zech, M., Glaser, B., 2009. Compound-specific δ18O analyses of neutral sugars in soils using GC-Py-IRMS: problems, possible solutions and a first application. Rapid Commun. Mass Spectrom. 23, 3522-3532. Zech et al., 2013. A 220 ka terrestrial δ18O and deuterium excess biomarker record from an eolian permafrost paleosol sequence, NE-Siberia. Submitted to Chemical Geology.

  4. Strong influence of the littoral zone on sedimentary lipid biomarkers in a meromictic lake.

    PubMed

    Bovee, R J; Pearson, A

    2014-11-01

    Planktonic sulfur bacteria growing in zones of photic zone euxinia (PZE) are important primary producers in stratified, sulfur-rich environments. The potential for export and burial of microbial biomass from anoxic photic zones remains relatively understudied, despite being of fundamental importance to interpreting the geologic record of bulk total organic carbon (TOC) and individual lipid biomarkers. Here we report the relative concentrations and carbon isotope ratios of lipid biomarkers from the water column and sediments of meromictic Mahoney Lake. The data show that organic matter in the central basin sediments is indistinguishable from material at the lake shoreline in both its lipid and carbon isotopic compositions. However, this material is not consistent with either the lipid profile or carbon isotope composition of biomass obtained directly from the region of PZE. Due to the strong density stratification and the intensive carbon and sulfur recycling pathways in the water column, there appears to be minimal direct export of the sulfur-oxidizing planktonic community to depth. The results instead suggest that basinal sediments are sourced via the littoral environment, a system that integrates an indigenous shoreline microbial community, the degraded remains of laterally rafted biomass from the PZE community, and detrital remains of terrigenous higher plants. Material from the lake margins appears to travel downslope, traverse the strong density gradient, and become deposited in the deep basin; its final composition may be largely heterotrophic in origin. This suggests an important role for clastic and/or authigenic minerals in aiding the burial of terrigenous and mat-derived organic matter in euxinic systems. Downslope or mineral-aided transport of anoxygenic, photoautotrophic microbial mats may have been a significant sedimentation process in early Earth history. PMID:25201322

  5. The role of springs and sedimentary volcanism in Martian Geological Record

    NASA Astrophysics Data System (ADS)

    Pio Rossi, Angelo; Pondrelli, Monica

    Mars has a rich and complex sedimentary record. It is believed to be largely Noachian, but its age is poorly constrained, mostly due to the heavy erosion and modification of the deposits. Layered Light-Toned Deposits (LTDs) are prominent among them, and they crop out in sev-eral discrete locations on Mars. The range of genetic models for these deposits is extremely wide (also including non-sedimentary mechanisms). Regardless their actual origin, there is a very good chance that these deposits have possibly recorded past climatic and environmental conditions. We concentrated our analysis in Arabia Terra, where several craters are hosting thick (up to few km) stacks of layered sedimentary-looking rocks, such as Becquerel and Crom-melin. Although clear indications of allogenic signals are present in the sedimentary record, there are evidences for both depositional and structural features suggestive of internal dynamic control. These include: evidence of local sources, structural control on LTDs occurrence and development, synsedimentary deformation and (soft?) sediment expulsion. We interpret, at least partially LTDs in Arabia Terra as the result of groundwater emergence and spring-based deposition, which likely occurred along with other processes, such as climatically controlled variable eolian input. Therefore Martian LTDs might retain a precious record of both allogenic and autogenic effects.

  6. Marine sedimentary record of Meltwater Pulse 1a along the NW Barents Sea continental margin

    NASA Astrophysics Data System (ADS)

    Giulia Lucchi, Renata; Sagnotti, Leonardo; Camerlenghi, Angelo; Macrì, Patrizia; Rebesco, Michele; Pedrosa, Maria Teresa; Giorgetti, Giovanna

    2016-04-01

    The upper continental slope of the Storfjorden-Kveithola Trough Mouth Fans (NW Barents Sea) contains a several m-thick late Pleistocene sequence of plumites composed of laminated mud interbedded with sand/silt layers. Radiocarbon ages revealed that deposition occurred during about 130 years at a very high sedimentation rate of 3.4 cm a-1, at about 7 km from the present shelf break. Palaeomagnetic and rock magnetic analyses confirm the existence of a prominent, short-living sedimentary event. The plumites appear laterally continuous and were correlated with the sedimentary sequences described west of Svalbard and neighbouring glacial depositional systems representing a major event at regional scale appointed to correspond to the deep-sea sedimentary record of Meltwater Pulse-1a. We also present new sedimentological and geochemical insights, and multi-beam data adding information on the palaeoenvironmental characteristics during MWP-1a and ice sheet decay in the NW Barents Sea.

  7. Paleosecular variation during the PCRS based on a new database of sedimentary and volcanic records

    NASA Astrophysics Data System (ADS)

    Haldan, M. M.; Langereis, C. G.; Evans, M. E.

    2007-12-01

    We present a paleosecular variation study using a generalised global paleomagnetic sedimentary and volcanic database. We made use of all available (and suitable) - published and some new- sedimentary and volcanic paleomagnetic records corresponding to the Permo-Carboniferous Reversed Superchron (PCRS) interval to reanalyse all data. We focused on records with a sufficient number of samples, and acquired - whenever possible - the original data, or - as a second choice - parametrised published site means. Analysis of these paleomagnetic data in terms of latitude variation of the scatter of the virtual geomagnetic poles (VGPs) suggests that careful data selection is required and that some of the older studies may need to be redone using more modern methods, both in terms of sampling and laboratory treatment. In addition, high (southern and especially northern hemisphere) latitudes are notably lacking in published records. The transitional data is removed using a variable VGP cut-off angle which varies with latitude. We use also our extended sedimentary records from Permian red beds from the Lodève and Dôme de Barrot basins (S. France), a new detailed paleomagnetic study of the Permian volcanics in the Oslo graben (Norway), as well as new data from Carboniferous-Permian sediments from the Donbas basin (Ukraine). We compare our results with those from published paleosecular variation models and with recent (re)analyses of VGP scatter during different periods of the geological archive.

  8. Assessment of the sources of sedimentary organic matter in the Bohai Sea and the northern Yellow Sea using biomarker proxies

    NASA Astrophysics Data System (ADS)

    Xing, Lei; Hou, Di; Wang, Xinchen; Li, Li; Zhao, Meixun

    2016-07-01

    To evaluate the applicability of source proxies and to assess the sources of sedimentary organic matter in the Bohai Sea (BS) and the northern Yellow Sea (NYS), we analyzed total organic carbon (TOC), total nitrogen (TN), δ13C of TOC, n-alkanes, phytoplankton biomarkers, and glycerol dialkyl glycerol tetraethers (GDGTs) including branched GDGTs (brGDGTs) in 60 surface sediment samples covering the BS and the NYS. Spatial distribution comparison and principal component analysis indicate that with the exception of brGDGTs, terrestrial biomarkers have different spatial distribution pattern from marine biomarkers, suggesting that the sources control the distributions of these biomarkers in spite of hydrodynamic forcing. Significantly positive correlation (R2 = 0.5) between TOC normalized brGDGTs content and TOC normalized crenarchaeol content suggested in situ production of brGDGTs in the BS and the NYS. The δ13C values, TMBR [terrestrial and marine biomarker ratio: (C27 + C29 + C31n-alkanes)/[(C27 + C29 + C31n-alkanes) + (brassicasterol + dinosterol + alkenones)] ] and BIT (branched isoprenoid tetratether index) proxy indicated high terrestrial organic matter (TOM) input near the Huanghe River Estuary, while TOC/TON did not reveal similar distribution pattern. Quantitative estimates of TOM using a binary model revealed much higher TOM percentage from δ13C (avg. 58%) and TMBR (avg. 31%) than from BIT (avg. 7.4%). Our results suggest that, owing to significant in situ production of brGDGTs, the BIT is not a good proxy for indicating soil OM contribution in marine sediments from the BS and the NYS.

  9. 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.

  10. Searching for tsunamis evidences on the Algarve (Southern Portugal) continental shelf sedimentary record

    NASA Astrophysics Data System (ADS)

    Drago, Teresa; Silva, Pedro; Lopes, Ana; Magalhães, Vitor; Roque, Cristina; Rodrigues, Ana Isabel; Noiva, João; Terrinha, Pedro; Mena, Anxo; Francés, Guillermo; Kopf, Achim; Völker, David; Omira, Rachid; Baptista, Maria Ana

    2016-04-01

    Tsunami hazard assessment is important in order to prevent and/or minimize its effects, which is only possible if a complete and long record dataset of past events is available, allowing the estimation of their recurrence intervals. The knowledge of past tsunami events are based on instrumental, historical and geological records. Although instrumental and historical records are reliable sources they are limited in time. Geological records can give a much more extended reconstruction overview of thousand years, which can provide a good estimation of tsunami return periods. Most of the existing studies have been conducted onshore and only a few were based on offshore sedimentary record. These last ones, have the advantage to provide a more continuous and almost undisturbed records but the identification of tsunami sediments in marine environment require a multi-proxy approach in order to better identify the allochtonous layers/deposits and to differentiate them from storm deposits. In the context of ASTARTE project (FP7), five gravity and piston cores on the southern Portuguese continental shelf collected in 2008 and 2014 were studied. The methodology included XRF, MSCL, sedimentological and magnetic analyses. Preliminary results show some identifiable layers that may related with allochthonous sedimentary material, compatible with a genesis resulting from tsunami backwash sediment transport and deposition. Acknowledgments - Publication supported by project FCT UID/GEO/50019/2013 - Instituto Dom Luiz.

  11. Isotopic Equilibration Between Sulfide and Organic Matter: Implications for Records of Sedimentary δ34S.

    NASA Astrophysics Data System (ADS)

    Raven, M. R.; Sessions, A. L.; Adkins, J. F.; Fischer, W. W.

    2015-12-01

    Records of the sulfur-isotopic composition of sedimentary pyrite have been used to constrain the evolutionary timing of major metabolic pathways, the size of the marine sulfate reservoir, and the redox balance of the planet. It remains a major challenge, however, to explain the enormous range of pyrite δ34S values in the literature and their typical ~10‰ offset relative to sedimentary organic S. We investigate the development of pyrite and organic S records in Santa Barbara Basin, which has suboxic bottom water and high (≥4 wt%) organic matter burial. Concentration and δ34S profiles of major sulfur species (sulfate, sulfide, elemental S, proto-kerogen, pyrite, and extractable organic matter) suggest the occurrence of S-isotope exchange between porewater sulfide and organic S, so we conducted laboratory experiments to test organic S exchangeability with 34S-labelled sulfide-polysulfide solutions. We found that both extractable and proto-kerogen organic matter incorporated significant amounts of label within days, supporting the feasibility of equilibration between sulfide and organic matter in the environment. Unlike organic S, pyrite δ34S values in Santa Barbara Basin sediments are up to 30‰ lower than those for porewater sulfide. We hypothesize that this strongly 34S-depleted pyrite reflects the immediate products of bacterial sulfate reduction at organic-rich structures like microbial biofilms or aggregates and suggest that this δ34S difference between porewater sulfide and pyrite may be a more common than previously recognized. Pyrite δ34S values are not necessarily reflective of porewater sulfide δ34S, suggesting that this common assumption should be revisited. Sedimentary pyrite and organic S are potentially powerful and complementary archives of environmental information. To meaningfully interpret these records, it is essential that we take into account the complex processes affecting sedimentary pyrite and organic sulfur δ34S in modern sediments.

  12. The application of fossil resin biomarkers to oil-source correlation in some Australian sedimentary basins

    SciTech Connect

    Alexander, R.; Larcher, A.V.; Kagi, R.I. ); Price, P.L. )

    1989-03-01

    Suites of aromatic and saturated compounds which are indicative of plant resins from Araucariaceae have been identified in widely distributed sediments of Jurassic age from the Eromanga Basin. Similar biomarker assemblages have been shown not to be present in sediments of Permian age from the Cooper Basin. Some crude oils contained in reservoirs of Jurassic to Cretaceous age have been shown to contain the biomarker assemblage characteristic of the sediments of Jurassic age and, therefore, appear to have been derived from sediments within the Eromanga Basin. Other crude oils in reservoirs of this age, together with all crude oils from reservoirs of Permian age do not contain the biomarker signature of the sediments of Jurassic age, and are therefore presumed to have been derived from the Permian sediments within the Eromanga Basin. Other crude oils in reservoirs of this age, together with all crude oils from reservoirs of Permian age do not contain the biomarker signature of the sediments of Jurassic age, and are therefore presumed to have been derived from the Permian sediments of the Cooper Basin.

  13. Reconstructing Earthquake-Driven Erosion in the Southern Alps, New Zealand using the Sedimentary Record

    NASA Astrophysics Data System (ADS)

    Howarth, J. D.; Fitzsimons, S.; Norris, R.; Jacobsen, G.; Strong, D.

    2011-12-01

    Studies of active mountain belts have concluded that large earthquakes are significant drivers of erosion. However, relatively few studies have directly quantified the volume of earthquake-driven erosion because these events occur infrequently and are rarely recorded using instrumental measures of erosion such as suspended sediment yield from rivers. Deposits in sedimentary basins adjacent to mountain belts afford the possibility of developing records of mountain building processes that capture the impact of large earthquakes. This paper reports a study of erosion and depositional processes over multiple seismic cycles that are preserved in a small lake in South Westland, New Zealand. The sedimentology of three 6m cores was investigated using high resolution grain-size, TOC and C:N ratios to identify the sedimentary record of co-seismic mass wasting in Lake Paringa. The co-seismic sedimentary signature consists of megaturbidites that exhibit complexly graded fine sandy bases, overlain by normally graded silts and a clayey silt cap. High resolution radiocarbon dating shows that the megaturbidites record the 1717 AD (Mw > 7.9), 1620 AD (Mw > 7.6) and 1430 AD (Mw >7.9) Alpine Fault earthquakes; and two additional Alpine Fault earthquakes between 1166-1061 AD and 868-449 AD. The co-seismic sedimentation is followed by a sequence of normally graded turbidites that are interpreted as the sedimentary product of increased post-seismic erosion. The post-seismic turbidite sequences are overlain by sediments deposited in quiescent depositional conditions. Together these two phases of deposition represent sedimentation over a complete seismic cycle and provide the basis for reconstructing erosion driven by Alpine Fault earthquakes. Over the last ca. 1200 years five ruptures of the Alpine Fault have contributed nearly half of the total erosion in the catchments that drain into Lake Paringa. These new insights into sedimentary responses to co- and post- seismic disturbance open

  14. Quantitative bounds on morphodynamics and implications for reading the sedimentary record.

    PubMed

    Ganti, Vamsi; Lamb, Michael P; McElroy, Brandon

    2014-01-01

    Sedimentary rocks are the archives of environmental conditions and ancient planetary surface processes that led to their formation. Reconstructions of Earth's past surface behaviour from the physical sedimentary record remain controversial, however, in part because we lack a quantitative framework to deconvolve internal dynamics of sediment-transport systems from environmental signal preservation. Internal dynamics of landscapes--a consequence of the coupling between bed topography, sediment transport and flow dynamics (morphodynamics)--result in regular and quasiperiodic landforms that abound on the Earth and other planets. Here, using theory and a data compilation of morphodynamic landforms that span a wide range of terrestrial, marine and planetary depositional systems, we show that the advection length for settling sediment sets bounds on the scales over which internal landscape dynamics operate. These bounds provide a universal palaeohydraulic reconstruction tool on planetary surfaces and allow for quantitative identification of depositional systems that may preserve tectonic, climatic and anthropogenic signals. PMID:24576990

  15. Linking the Fe-, Mo-, and Cr isotope records with the multiple S isotope record of Archean sedimentary rocks

    NASA Astrophysics Data System (ADS)

    Ohmoto, H.; Watanabe, Y.

    2011-12-01

    Researchers have interpreted the isotopic data of redox sensitive elements (e.g., Fe, Mo and Cr) in Archean- and Proterozoic-aged sedimentary rocks within a framework of an atmospheric O2 evolution model that relied on an interpretation of the multiple sulfur isotopic record of sedimentary rocks. The current paradigm is that the anomalous isotopic fractionations of sulfur (AIF-S, or MIF-S) in sedimentary rocks were created by the UV photolysis of volcanic SO2 in an O2-poor (i.e., pO2 < 1 ppm) atmosphere, and that the rise of atmospheric pO2 to > 1 ppm occurred at ~2.45 Ga. However, this paradigm has recently encountered the following serious problems: (1) UV photolysis of SO2 by a broad-band UV lamp, which simulates the UV spectra of the sun light, produced the δ34S-Δ33S values for the S0 and SO4 that are significantly different from >90% of data on natural samples. (2) Many Archean-age sedimentary rocks do not exhibit AIF-S signatures. (3) Strong AIF-S signatures are typically found in organic C- and pyrite rich Archean-age black shales that were altered by submarine hydrothermal fluids during the early diagenetic stage of the rocks. (4) H2S, rather than SO2, was probably the dominant S-bearing volcanic gas on an anoxic Earth. Yet, UV photolysis of H2S does not generate AIF-S. (5) Some post-2.0 Ga natural samples were found to possess strong AIF-S signatures, such as sulfates in air pollutants that were produced by coal burning in an oxygen-rich atmosphere. Lasaga et al. (2008) demonstrated theoretically that chemisorption reactions between some solid surfaces and S-bearing aqueous (or gaseous) species, such as between organic matter and aqueous sulfate, may generate AIF-S. Watanabe et al. (2009; in prep.) demonstrated experimentally that reactions between simple amino acid crystals and sulfate under hydrothermal conditions produced AIF-S signatures that matched with more than 90% of data on natural samples. These studies, as well as the observed correlations

  16. Biomarker records of Holocene climate variations in Asian interior

    NASA Astrophysics Data System (ADS)

    Song, M.; Liu, Z.; Liu, W.; Zhao, C.; Li, S.; He, Y.

    2012-12-01

    Understanding Holocene climate fluctuation may provide clues to projection of future climate change. Lake sediments in the arid central Asia (ACA), as an archive of past climate information, keep attracting considerable interest. We have retrieved several sediment cores from Lake Manas, an endorheic lake in Zunggar desert, Xinjiang Province, China. Biomarker proxies including alkenone Uk'37, %C37:4 and C37 concentration (C37 Conc), and physical proxies including density and magnetic susceptibility (MS) have been analyzed. We have found substantial climatic and environmental changes during the late Holocene. Density, MS and Uk'37 values are high during Medieval Warm Period (MWP) and C37 Conc is very low. During the Little Ice Age, density and MS decrease, Uk'37 values drop to near 0.1, C37 Conc is increased by 2 to 3 magnitude. Thus, warm and dry conditions dominated MWP while cold and wet conditions dominated LIA, a typical "Westerly" pattern which is opposite to the hydrological variation in Asian monsoonal regions. Biomarker records' correlation with solar irradiance (SI), the North Atlantic Oscillation (NAO), the 1000year ACA Moisture Index (ACAM), and the North Hemisphere Temperature (NHT) suggests SI as one of the forcing factor on temperature fluctuation and cold and wet LIA possibly resulting from westerly-jet shift, negative NAO oscillation and the lower evaporation induced by the decrease of temperature. Biomarker records for the whole Holocene will be also presented.

  17. What is the tectono-sedimentary record of hyper-extended, magma-poor rifted margins ?

    NASA Astrophysics Data System (ADS)

    Masini, Emmanuel; Manatschal, Gianreto; Mohn, Geoffroy; Lafont, François; Jammes, Suzon; Geoffroy, Laurent; Robin, Cécile

    2010-05-01

    The tectono-sedimentary record of hyper-extended, deep-water rifted margins is yet poorly understood due to the limited access to direct observations. The study of fossil analogues shows that the major change from low strain (e.g. North Sea) to high-strain rift systems is controlled by the occurrence of low-angle detachment systems associated with extensional allochthons. In such systems classical syn- to post-rift sedimentary models cannot be directly applied because the depositional geometries, the creation of space as well as the relation to potential sources are different. In our study we investigate the tectono-sedimentary record of high strain, hyper-extended deep-water rifted margins. We studied a present-day and two fossil hyper-extended rift systems, which preserve detachment systems that control the syn- to post-rift sedimentary record. The three examples are: (1) The SE Alpine Tethys (AT) rifted margin preserved in SE Switzerland. (2) The Mauléon basin in the Western Pyrenees (WP) (3) The southeastern termination of the Baja California peninsula in the Gulf of California (GC) representing a subactual system. For all three examples rift related detachment structures and their relations to pre-, syn-, and post-rift sediments can be mapped. Despite of the different plate kinematic settings (orthogonal (AT), segmented (WP), transtensional (GC)), sediment supply (starved (AT) vs. rich (WP, GC), and facies (marine (AT, WP) vs. subareal (GC)), the overall tectono-sedimentary evolution shows strong similarities and can be described as following. The detachment faulting is recorded by the generation of extensional allochthons derived from the delamination of the former hanging-wall. These syn-tectonic sediments show the progressive switch from hanging-wall to footwall derived lithologies. The sourcing change reflects the exhumation and formation of top-basement detachment systems. Sediments related to this stage represent poorly organized locally-derived tectono-sedimentary

  18. Recording of climate and diagenesis through sedimentary DNA and fossil pigments at Laguna Potrok Aike, Argentina

    NASA Astrophysics Data System (ADS)

    Vuillemin, Aurèle; Ariztegui, Daniel; Leavitt, Peter R.; Bunting, Lynda; The Pasado Science Team

    2016-04-01

    Aquatic sediments record past climatic conditions while providing a wide range of ecological niches for microorganisms. In theory, benthic microbial community composition should depend on environmental features and geochemical conditions of surrounding sediments, as well as ontogeny of the subsurface environment as sediment degraded. In principle, DNA in sediments should be composed of ancient and extant microbial elements persisting at different degrees of preservation, although to date few studies have quantified the relative influence of each factor in regulating final composition of total sedimentary DNA assemblage. Here geomicrobiological and phylogenetic analyses of a Patagonian maar lake were used to indicate that the different sedimentary microbial assemblages derive from specific lacustrine regimes during defined climatic periods. Two climatic intervals (Mid-Holocene, 5 ka BP; Last Glacial Maximum, 25 ka BP) whose sediments harbored active microbial populations were sampled for a comparative environmental study based on fossil pigments and 16S rRNA gene sequences. The genetic assemblage recovered from the Holocene record revealed a microbial community displaying metabolic complementarities that allowed prolonged degradation of organic matter to methane. The series of Archaea identified throughout the Holocene record indicated an age-related stratification of these populations brought on by environmental selection during early diagenesis. These characteristics were associated with sediments resulting from endorheic lake conditions and stable pelagic regime, high evaporative stress and concomitant high algal productivity. In contrast, sulphate-reducing bacteria and lithotrophic Archaea were predominant in sediments dated from the Last Glacial Maximum, in which pelagic clays alternated with fine volcanic material characteristic of a lake level highstand and freshwater conditions, but reduced water column productivity. Comparison of sedimentary DNA composition

  19. A sugar biomarker proxy for assessing terrestrial versus aquatic sedimentary input

    NASA Astrophysics Data System (ADS)

    Hepp, Johannes; Rabus, Max; Laforsch, Christian; Anhäuser, Tobias; Glaser, Bruno; Zech, Michael

    2016-04-01

    Lake sediments are valuable, often continuous and potentially high resolution archives for studying past climate changes. Thereby, one of the crucial questions is often whether the origin of the organic matter in lake sediments is allochthonous (terrestrial) or autochthonous (aquatic). Here we present patterns of neutral sugars of various plants and algae species to answer the question whether the deoxyhexoses (fucose, rhamnose) to pentoses (arabinose, xylose) ratio can serve as a proxy for aquatic versus terrestrial sedimentary lake input, respectively. Our sugar pattern results show that the fucose + rhamnose content plotted against arabinose and xylose in a ternary diagram can be used to distinguish between algae and other (namely aquatic plants, emergent plant, and terrestrial plants) sugar sources. This finding is confirmed by a compilation with sugar data from the literature. Mosses plot within the range of algae. Although the (fucose + rhamnose)/(arabinose + xylose) ratio yields some overlapping between algae and soil/litter samples, we recommend this ratio, particularly when applied within a multiproxy approach, as promising proxy for distinguishing between aquatic vs. terrestrial organic matter in sedimentary archives. Regarding the sugar concentrations of the investigated samples, emergent plants show the highest values as well as the highest variability. Mosses, aquatic plants and algae yield lower sugar concentrations comparable to those of terrestrial plants.

  20. Ecosystem development following deglaciation: A new sedimentary record from Devils Lake, Wisconsin, USA

    NASA Astrophysics Data System (ADS)

    Williams, Joseph J.; McLauchlan, Kendra K.; Mueller, Joshua R.; Mellicant, Emily M.; Myrbo, Amy E.; Lascu, Ioan

    2015-10-01

    Processes and rates of ecosystem development can be reconstructed using lacustrine sedimentary sequences, but this approach often requires records that contain the start of primary succession. Most lakes in the upper Midwestern U.S. were formed by glaciers at the end of the last Ice Age approximately 11,700 cal yr BP. Devils Lake, Wisconsin is a rare example of a lake from this region whose sediments extend into the Pleistocene and may include the Last Glacial Maximum. Sediment magnetic, geochemical, pollen, and charcoal records were generated from a 10 m core whose basal sediments may be 28,000 years old. Together with a previously published pollen record, these proxies combine to reveal a history of long-term climatic, vegetative and geologic change during the late Pleistocene to Holocene. We identify six sedimentary units that indicate a series of consecutive events rather than a predictable trajectory of ecosystem development at the site. Productivity in the lake was low during the late Pleistocene and increased during the Holocene, as reflected by the sediment lithology, which shows a sudden shift from glacial vivianite-rich and organic-poor clastic-dominated sediments to Holocene diatomaceous sapropels. Several important processes initiated around 17,000 cal yr BP, including the onset of organic matter accumulation and fire in the terrestrial ecosystem. However, the post-glacial landscape was not devoid of vegetation because pollen assemblages indicate that terrestrial vegetation, likely a spruce tundra, survived near the site. A switch to a hardwood forest period during the Holocene also led to a change in the fire regime, with increased frequency of burning. Aquatic ecosystem productivity lagged terrestrial ecosystem productivity throughout the record. Nutrient cycling (as recorded by sedimentary δ15N) was variable but not directional, and appeared to be correlated with climate conditions early in the record, and terrestrial ecosystem processes later in

  1. [Over one hundred year sedimentary record of polycyclic aromatic hydrocarbons in the Andaman Sea, Malaysia].

    PubMed

    Wu, Yu-Ling; Wang, Xin-Hong; Li, Yong-Yu; Hong, Hua-Sheng; Li, He-Yang; Yin, Ming-Duan

    2009-09-15

    Polycyclic aromatic hydrocarbons (PAHs) in a sediment core collected from Langkawi Island of the Andaman Sea, Malaysia were determined by GC/MS, the vertical variations of concentration and distributions of PAHs were investigated. In combining with 210Pb-dating, the PAHs sedimentary record in the last 100 years was reconstructed and their possible sources were also discussed. The sigmaPAH concentration ranged from 13.2-60.1 ng x g(-1) in the whole sedimentary section (0-56 cm) with the dominant compounds of phenanthrene, naphthalene and perylene. The sediments contaminated to a lesser extent comparing with the surrounding waters. Before the 1920s, the concentrations of PAHs were considered to be the background level, which was implied from the natural inputs. The historical records of PAHs in the core showed that two distinct peaks which represented the input time of 1960s and 1980s, respectively, inferred that there were some relatively dramatically land-based inputs, and human activities leaded a clear impact to these waters during these periods. Furthermore, PAHs diagnostic ratios indicated that PAHs in the core sediments were mainly of pyrolytic origin (combustion), accompanied with minor petroleum origin. These were related with agriculture, industry, ocean import and export, and shipping activities in the surrounding regions. Meanwhile as the vital communication line, the marine transportation of the Strait of Malacca had influenced the environmental quality of the Andaman Sea. Meanwhile, based on the sedimentary record, PAHs concentrations were found to correlate positively with humanism activities and socioeconomic development (Gross Domestic Production) in the surrounding regions. PMID:19927796

  2. Early maize (Zea mays L.) cultivation in Mexico: Dating sedimentary pollen records and its implications

    PubMed Central

    Sluyter, Andrew; Dominguez, Gabriela

    2006-01-01

    A sedimentary pollen sequence from the coastal plain of Veracruz, Mexico, demonstrates maize cultivation by 5,000 years ago, refining understanding of the geography of early maize cultivation. Methodological issues related to bioturbation involved in dating that record combine with its similarity to a pollen sequence from the coastal plain of Tabasco, Mexico, to suggest that the inception of maize cultivation in that record occurred as much as 1,000–2,000 years more recently than the previously accepted 7,000 years ago. Our analysis thereby has substantive, theoretical, and methodological implications for understanding the complex process of maize domestication. Substantively, it demonstrates that the earliest securely dated evidence of maize comes from macrofossils excavated near Oaxaca and Tehuacán, Mexico, and not from the coastal plain along the southern Gulf of Mexico. Theoretically, that evidence best supports the hypothesis that people in the Southern Highlands domesticated this important crop plant. Methodologically, sedimentary pollen and other microfossil sequences can make valuable contributions to reconstructing the geography of early maize cultivation, but we must acknowledge the limits to precision that bioturbation in coastal lagoons imposes on the dating of such records. PMID:16418287

  3. Neogene biomarker record of vegetation change in eastern Africa

    PubMed Central

    Polissar, Pratigya J.; Jackson, Kevin E.; deMenocal, Peter B.

    2016-01-01

    The evolution of C4 grassland ecosystems in eastern Africa has been intensely studied because of the potential influence of vegetation on mammalian evolution, including that of our own lineage, hominins. Although a handful of sparse vegetation records exists from middle and early Miocene terrestrial fossil sites, there is no comprehensive record of vegetation through the Neogene. Here we present a vegetation record spanning the Neogene and Quaternary Periods that documents the appearance and subsequent expansion of C4 grasslands in eastern Africa. Carbon isotope ratios from terrestrial plant wax biomarkers deposited in marine sediments indicate constant C3 vegetation from ∼24 Ma to 10 Ma, when C4 grasses first appeared. From this time forward, C4 vegetation increases monotonically to present, with a coherent signal between marine core sites located in the Somali Basin and the Red Sea. The response of mammalian herbivores to the appearance of C4 grasses at 10 Ma is immediate, as evidenced from existing records of mammalian diets from isotopic analyses of tooth enamel. The expansion of C4 vegetation in eastern Africa is broadly mirrored by increasing proportions of C4-based foods in hominin diets, beginning at 3.8 Ma in Australopithecus and, slightly later, Kenyanthropus. This continues into the late Pleistocene in Paranthropus, whereas Homo maintains a flexible diet. The biomarker vegetation record suggests the increase in open, C4 grassland ecosystems over the last 10 Ma may have operated as a selection pressure for traits and behaviors in Homo such as bipedalism, flexible diets, and complex social structure. PMID:27274042

  4. Neogene biomarker record of vegetation change in eastern Africa.

    PubMed

    Uno, Kevin T; Polissar, Pratigya J; Jackson, Kevin E; deMenocal, Peter B

    2016-06-01

    The evolution of C4 grassland ecosystems in eastern Africa has been intensely studied because of the potential influence of vegetation on mammalian evolution, including that of our own lineage, hominins. Although a handful of sparse vegetation records exists from middle and early Miocene terrestrial fossil sites, there is no comprehensive record of vegetation through the Neogene. Here we present a vegetation record spanning the Neogene and Quaternary Periods that documents the appearance and subsequent expansion of C4 grasslands in eastern Africa. Carbon isotope ratios from terrestrial plant wax biomarkers deposited in marine sediments indicate constant C3 vegetation from ∼24 Ma to 10 Ma, when C4 grasses first appeared. From this time forward, C4 vegetation increases monotonically to present, with a coherent signal between marine core sites located in the Somali Basin and the Red Sea. The response of mammalian herbivores to the appearance of C4 grasses at 10 Ma is immediate, as evidenced from existing records of mammalian diets from isotopic analyses of tooth enamel. The expansion of C4 vegetation in eastern Africa is broadly mirrored by increasing proportions of C4-based foods in hominin diets, beginning at 3.8 Ma in Australopithecus and, slightly later, Kenyanthropus This continues into the late Pleistocene in Paranthropus, whereas Homo maintains a flexible diet. The biomarker vegetation record suggests the increase in open, C4 grassland ecosystems over the last 10 Ma may have operated as a selection pressure for traits and behaviors in Homo such as bipedalism, flexible diets, and complex social structure. PMID:27274042

  5. Microbially-induced sedimentary structures (MISS) as record of storm action in supratidal modern estuarine setting

    NASA Astrophysics Data System (ADS)

    Cuadrado, Diana G.; Bournod, Constanza N.; Pan, Jerónimo; Carmona, Noelia B.

    2013-10-01

    One of the aims of tidal sedimentology in recent years is to find signatures in the stratigraphic record that help in recognizing basic ancient tidal processes. The present study was carried out on the supratidal zone of the middle Bahía Blanca estuary which is colonized by extensive microbial mats. The purpose of the study was to relate the tidal and wave energy with the microbially-induced sedimentary structures (MISS) present in the tidal flat. The energy reaching the area was quantified by tidal and wave records, while MISS were simultaneously recognized and described after a strong storm event. The MISS and the microsequences of sediments in vertical cross-sections of the tidal flat were considered as tidal signatures over a supratidal zone, when high-tide in severe energy conditions can reach the zone. This paper contributes to the understanding of physical sedimentary parameters that control the modification of microbial structures in modern siliciclastic regimes and that, in turn, can aid in the reconstruction of ancient hydraulic settings.

  6. Sedimentary biomarker and isotopic indicators of the paleoclimatic history of the Walker Lake basin, western Nevada

    USGS Publications Warehouse

    Meyers, P.A.; Benson, L.V.

    1988-01-01

    Walker Lake, a terminal saline lake in western Nevada, has experienced major fluctuations in its water level due to changes in the regional climate during Quaternary times. As part of a paleo-climatological study of western Nevada, we have investigated organic matter ??13C and C/N values and lipid biomarker contents of sediments deposited at various periods over the past 150 thousand years of lake history. Surficial sediments from two cross-lake transects contain mostly lake-derived organic matter. Diagenetic losses of organic matter are evident in deeper sediments, and the proportion of aquatic and terrigenous organic materials changes in response to variations in preservational factors. Source identification of organic matter is complicated by the probability that Walker Lake has experienced desiccation at various times in its history which impacts the degree of preservation of organic substances. ?? 1988.

  7. The last millenia sedimentary record of Lake Esponja, Northern Chilean Patagonia

    NASA Astrophysics Data System (ADS)

    Fagel, Nathalie; Araneda, Alberto; Alvarez, Denisse; Perfetti-Bolaño, Alessandra; Billy, Isabelle; Martinez, Philippe; Schmidt, Sabine; Urrutia, Roberto

    2016-04-01

    We evaluate the climate and environmental variability of Northern Chilean Patagonia during the Last Millennia, using a multi-proxy analysis of a sediment core from Lago Esponja (45°09'S, 72°08'W). The lake is located in the region of Aysen del General Carlos Ibanez del Campo, in NW Patagonia. The study focuses on a multiproxy analysis of sedimentary records. The longest core (150 cm long) was collected in 2014 at 40 m depth. The sediment, which is composed of light brown organic-rich clayey silt, was analyzed for sedimentology (grain size, magnetic susceptibility organic matter and biogenic silica content), mineralogy (X-ray diffraction) and geochemistry (elemental and isotopic analyses of C and N, XRF core-scaner at 1 mm resolution). The radiocarbon ages, measured on 3 macro-remains, demonstrate that the core covers the last 6.700 years. The sedimentation rate ranges between 0.1 mm/yr in the lower section (100-150 cm) and 0.4 mm/yr in the upper meter. Visual descriptions and Scopix radiographies show that the sediment record is finely laminated except a massive decimetric coarser and darker layer corresponding to a tephra (estimated age 700AD±50). Magnetic susceptibility (confirmed by scopix radiographies) highlights the presence of 8 additional millimetric tephra layers. The biogenic silica content of the sediment is low (mean 5%). Diatom assemblage is dominated by benthic and acidophilous species, with high saprobic values. None marked changes were observed regarding the dynamic of the lake. The high organic matter content (mean 15%) and its high C/N ratio (12.7) throughout the core indicate inputs of allochtonous and terrestrial organic matter. Such parameters present high sediment variability also marked by changes in the chemical composition. The laminations reflect changes in the allochtonous sedimentary inputs, with high terrestrial inputs during wetter conditions in relation with the Westerlies. The sedimentary records of Lago Esponja will be compared

  8. Sedimentary nitrogen isotopic ratio as a recorder for surface ocean nitrate utilization

    SciTech Connect

    Altabet, M.A.; Francois, R. )

    1994-03-01

    The availability of nutrients in the near surface ocean is an important control on primary production, whose variability over geologic time may have altered major biogeochemical cycles. Ocean models have suggested a specific link between glacial/interglacial variations in atmospheric CO2 concentrations and changes in nutrient concentration at the surface of high latitude seas. Isotope ratios have been used to evaluate nutrients in the ocean surface. To test the fidelity with which surface generated isotopic signals are recorded in deep-sea sediments, this study focused on equatorial Pacific ocean and the southern ocean. In both regions large gradients in near surface NO3 concentration and depletion dominate any local temporal variation. Corresponding gradients were found in Nitrogen 15 and compared to sedimentary values. Results indicate that strong near surface N15 gradients are indeed recorded in underlying surface sediments. 55 refs., 10 figs., 1 tab.

  9. Estimating C3 vs. C4 vegetation cover from sedimentary records - a surface sediment test from Cameroon, Western Central Africa

    NASA Astrophysics Data System (ADS)

    Garcin, Y.; Schefuss, E.; Schwab-Lavrič, V.; Gleixner, G.; Todou, G.; Séné, O.; Onana, J.; Achoundong, G.; Sachse, D.

    2012-12-01

    Carbon isotope fractionation associated with higher plant photosynthesis differs between the Calvin-Benson (C3) and Hatch-Slack (C4) cycles. It is possible to identify both C3 and C4 plants by measuring their δ13C values: C3 plants are depleted in δ13C compared with C4 plants. Higher plant lipid biomarkers, such as long-chain n-alkanes, which inherit the δ13C values representative of the carbon fixation pathway, are often used to reconstruct past vegetation cover (C3 vs. C4) for the African continent quantitatively. The percentage of C3 and C4 vegetation contribution to sedimentary n-alkanes can be determined by applying simple mixing models that assume two end-member δ13C values for both vegetation types. Here, we present a new dataset of δ13C values of n-alkanes from modern C3 and C4 plants and lake surface sediments with the aim to test the accuracy of these binary mixing models to infer C3 and C4 vegetation compositions from sedimentary records. Samples were collected in Cameroon across a natural gradient, which accommodates a wide range of climates and vegetation classes. Our results indicate that while the mean δ13C values of C4 plants remains relatively stable along the studied gradient (n-C29 alkane = -20±2‰), the mean δ13C values of C3 plants show larger variations (n-C29 alkane = -37±4‰). The latter observation can be attributed to environmental variables such as the relative humidity: n-C29 alkanes from C3 plants growing under high relative humidity (80%) had mean δ13C values of -40‰ while at low relative humidity (45%) they reached up to -31‰. These results suggest that δ13C values of C3 plants are not independent of environmental conditions, which likely reflects known physiological responses of leaves such as the decrease in stomatal conductance and increase in water use efficiency under drier conditions. The large variability of δ13C values of C3 plants across this transect further suggests that assigning an end-member value for C

  10. Sources of sedimentary biomarkers and proxies with potential paleoenvironmental significance for the Baltic Sea

    NASA Astrophysics Data System (ADS)

    Kaiser, Jérôme; Arz, Helge W.

    2016-07-01

    The Baltic Sea is a shallow, semi-enclosed and intra-continental shelf sea characterized by anoxic bottom waters in the deepest basins, allowing for the preservation of sedimentary organic matter. In the present study, the most abundant, naturally-occurring lipids in surface sediments from the entire Baltic Sea and the Skagerrak area were identified and their potential sources were assigned. Together with long-chain n-alkanes derived from land plant leaf waxes, diploptene and branched glycerol dialkyl glycerol tetraethers (GDGTs) are of allochthonous origin, while isoprenoid GDGTs, hydroxylated isoprenoid GDGTs (OH-GDGTs), n-C25:1, n-C27:1 and n-C29:1 alkenes are autochthonous lipids. The isoprenoid and OH-GDGTs are probably derived from Thaumarchaeota and the long-chain n-alkenes from phototrophic organisms. Significant correlations were found between indexes based on isoprenoid and OH-GDGTs and Baltic Sea surface and bottom temperatures. The calibrations obtained for surface temperature have statistically similar slopes, but different intercepts than calibrations established for the Nordic Seas. The branched and isoprenoid tetraether index can be used to estimate the percentage of soil (terrestrial) organic matter in the sediments of the Baltic Sea. High values of the Paq' ratio (defined here as the ratio of odd numbered n-C23 and n-C25 over n-C23 to n-C29 alkanes) in the northern Baltic Sea originate from the presence of both Sphagnum mosses in the drainage basin and submerged macrophytes, such as Potamogeton sp. and Myriophyllum sp., in the freshwater to brackish water of the coastal areas. The Paq' ratio may thus reflect fluctuations in the regional expansion of freshwater to brackish coastal environments in the Baltic Sea.

  11. Alteration of immature sedimentary rocks on Earth and Mars: Recording aqueous and surface-atmosphere processes

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    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. However, 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 previous 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 Fe3+ 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. Our 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.

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

    SciTech Connect

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

    2015-03-05

    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 previous 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 Fe3+ 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.

  13. Sedimentary earthquake records in the İzmit Gulf, Sea of Marmara, Turkey

    NASA Astrophysics Data System (ADS)

    Çağatay, M. N.; Erel, L.; Bellucci, L. G.; Polonia, A.; Gasperini, L.; Eriş, K. K.; Sancar, Ü.; Biltekin, D.; Uçarkuş, G.; Ülgen, U. B.; Damcı, E.

    2012-12-01

    Sedimentary earthquake records of the last 2400 a, including that of the devastating 17 August 1999 İzmit earthquake (Mw = 7.4), were studied in cores from the 210 m-deep central Karamürsel Basin of the İzmit Gulf in the eastern Sea of Marmara, using laser grain-size, physical properties, stable O and C isotopes and XRF Core Scanner analyses, and dated by radionuclide and radiocarbon methods. The earthquake records are represented by turbidite-homogenite mass-flow units (THU) that commonly contain a basal coarse layer, a middle laminated silt layer and an overlying homogeneous mud layer. The coarse basal part has a sharp and sometimes scoured lower boundary, and includes multiple coarse (sand/silt) layers or laminae showing normal size grading. Multiple coarse layers and occasional bi-directional cross-bedding suggest deposition from a bed-load during water column oscillations, or seiche effect. The grain-size characteristics of the overlaying laminated silt and the homogeneous mud units indicate deposition from weak oscillating currents and homogeneous suspension, respectively. High Mn value just below the base of THUs suggests diagenetic enrichment at oxic/anoxic redox boundary before the mass-flow event. Sharp decrease in Mn with very low values within the THUs suggests transient redox conditions following the mass-flow. Variable geochemical compositions of the basal coarse layers indicate different sediment sources for different THUs. Eight sedimentary earthquake records observed in the last 2400 a in the İzmit Gulf can be confidently correlated with the historical earthquakes of 1999, 1509 AD (Ms = 7.2), 1296 AD (I = VII), 865 AD (I = VIII), 740 AD (I = VIII), 268 AD (I = VIII), 358 AD (I = IX), and 427 BC. This gives an earthquake recurrence time of ca. 300 a, with the interval between consecutive events ranging from 90 to 695 a.

  14. Sedimentary record of Earthquakes and Tsunamis in the Central Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Polonia, A.; Romano, S.; Vaiani, S. C.; Gasparotto, G.; Gasperini, L.; Nelson, C. H.

    2014-12-01

    The Ionian Sea is a landlocked basin where convergence between Africa and Eurasia produced the emplacement of two opposite verging subduction/rollback systems (i.e. the Calabrian and the Hellenic Arcs). It is one of the most seismically active regions in the Mediterranean Sea and has been struck repeatedly by destructive historical earthquakes, often associated with tsunamis. Slab tearing in a pre-collisional setting is reflected in dynamic topography with high uplift rates of the coastal mountain belts, accompanied with a great sediment discharge to the continental margins. This increases the susceptibility to mass failures implying a strong interplay between active tectonics, seismic shaking, mass flows and tsunami generation.We investigated the effects of historic earthquakes on abyssal marine sedimentation through the analysis of the turbidite record in tectonically controlled basins. Holocene resedimented units in the deep Ionian Sea represent more than 90% of the total thickness of the sedimentary record. We dated the most recent turbidite sequences using different radiometric methods and the results suggest that turbidite emplacement was triggered by major historic earthquakes and tsunamis recorded in the region (i.e. AD 365 Crete and AD 1169, 1693 and 1908 Italian earthquakes).Textural, micropaleontological, geochemical and mineralogical signatures reveal that turbidite beds are stacked sandy units, which have different compositions suggesting coeval multiple failures. They are characterized by organic-rich sandy layers, containing a mixture of lithic clasts, plant fragments and displaced benthic foraminifera derived from several sources and bathymetric ranges. Structure and composition of each turbidite unit, combined with geochemical and isotopic analysis on organic carbon, are being refined to unravel the relative contribution of seismic shaking and tsunami wave loading on mass flow processes generation.Turbidites may be considered as the sedimentary

  15. Recording of climate and diagenesis through fossil pigments and sedimentary DNA at Laguna Potrok Aike, Argentina

    NASA Astrophysics Data System (ADS)

    Vuillemin, A.; Ariztegui, D.; Leavitt, P. R.; Bunting, L.; Pasado Science Team

    2015-11-01

    Aquatic sediments record past climatic conditions while providing a wide range of ecological niches for microorganisms. Although marine sedimentary microbial assemblages are often defined by their surrounding geochemical conditions, the influence of environmental features upon microbial development and post-depositional survival remains largely unknown in the lacustrine realm. Due to long-term microbial activity, the composition of environmental DNA can be expected to evolve with sediment depth and over time and therefore should reflect both ancient and extant microbial populations, but this hypothesis has rarely been tested using a multiproxy approach. Here geomicrobiological and phylogenetic analyses of a Patagonian maar lake were used to indicate that the different sedimentary microbial assemblages derive from specific lacustrine regimes during defined climatic periods. Two well defined climatic intervals whose sediments harboured active microbial populations and measurable ATP were sampled for a comparative environmental study based on fossil pigments and 16S rRNA gene sequences. Bacterial and archaeal 16S rRNA gene sequences recovered from the Holocene record revealed a microbial community adapted to subsaline conditions actively producing methane during organic matter degradation. These characteristics were associated with sediments resulting from endorheic lake conditions with high evaporative stress and concomitant high algal productivity. Moreover, archaeal clone libraries established throughout the Holocene record indicate an age-related stratification of these populations, consistent with a gradual use of organic substrates after deposition. In contrast, sulphate-reducing bacteria and lithotrophic Archaea were predominant in sediments dated from the Last Glacial Maximum, in which pelagic clays alternated with fine volcanic material characteristic of a lake level highstand and freshwater conditions, but reduced water column productivity. These patterns

  16. Recurrent giant earthquakes in South-Central Chile revealed by lacustrine sedimentary records

    NASA Astrophysics Data System (ADS)

    Moernaut, J.; de Batist, M. A.; Heirman, K.; van Daele, M.; Brümmer, R.; Pino, M.; Urrutia, R.; Wolff, C.; Brauer, A.; Roberts, S.; Kilian, R.

    2009-12-01

    event deposits provide key quantitative information about local earthquake intensity. For example, deposits associated with the giant earthquakes of 1575 and 1960 earthquakes are well-defined in all records, but event deposits associated with the smaller 1737 and 1837 earthquakes are more fragmentary. In summary, we found up to 25 paleoseismic ‘events’ with a sedimentary signature comparable with that of the giant 1960 earthquake. Our data enables reliable recurrence rates for ‘giant’ seismic events to be calculated, and will help improve earthquake hazard assessments for this part of Chile.

  17. 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.

  18. Diversity of recent tsunami impact, sedimentary record, and hazards from local to distal environments.

    NASA Astrophysics Data System (ADS)

    Richmond, B. M.; Gelfenbaum, G. R.; Jaffe, B. E.; Szczucinski, W.

    2014-12-01

    One of the goals of paleotsunami research is to define the frequency and magnitude of past tsunamis in order to better understand the hazards posed to coastal communities and ecosystems. Field observations and mapping in the aftermath of several recent tsunamis has greatly improved our understanding of the diversity of tsunami impacts in different environments, the variability observed in the sedimentary record of tsunamis, and the change in these characteristics along the tsunami path from the near- to far-field. Recent tsunamis originating in the Indian Ocean (2004), South Pacific (2009), Chile (2010), and Japan (2011) have affected both local and distant coastlines across a wide range of coastal environments and morphologies. Coral reefs, beaches, dunes, coastal plains with wetlands and/or beach ridge complexes, and rocky embayed coasts have been examined for depositional patterns and evidence of erosion, landscape and vegetation change, and, at a number of sites, impacts to the built environment. We summarize deposit variability, including thickness, stratification, and composition, in an effort to document the wide range of observed deposit features. We observed evidence where vegetation can modify the tsunami flow characteristics. Our field efforts did not focus on impacts to coastal structures, but observations during the course of our work can be applied to improve hazard assessment and recognition of vulnerable areas. Tsunami magnitude, deposits, and hazards are most pronounced near the source and tend to decline with distance, although local factors can modify this trend significantly. For example, general trends in the decrease of tsunami height, inundation, and run-up with distance from the source often exhibit local anomalies where interactions between the tsunami characteristics and local physiography, such as slope and orientation of the coast, create complex interactions that may greatly modify general trends. Efforts to relate the sedimentary

  19. The Upstream and Downstream impact of Milankovitch cycles in continental nonmarine sedimentary records

    NASA Astrophysics Data System (ADS)

    Valero, Luis; Garcés, Miguel; Huerta, Pedro; Cabrera, Lluís

    2016-04-01

    Discerning the effects of climate in the stratigraphic record is crucial for the comprehension of past climate changes. The signature of climate in sedimentary sequences is often assessed by the identification of Milankovitch cycles, as they can be recognized due to their (quasi) periodic behaviour. The integration of diverse stratigraphic disciplines is required in order to understand the different processes involved in the expression of the orbital cycles in the sedimentary records. New advances in Stratigraphy disclose the different variables that affect the sedimentation along the sediment routing systems. These variables can be summarized as the relationship between accommodation and sediment supply (AS/SS), because they account for the shifts of the total mass balance of a basin. Based in these indicators we propose a synthetic model for the understanding of the expression of climate in continental basins. Sedimentation in internally drained lake basins is particularly sensitive to net precipitation/evaporation variations. Rapid base level oscillations modify the AS/SS ratio sufficiently as to mask possible sediment flux variations associated to the changing discharge. On the other hand, basins lacking a central lacustrine system do not experience climatically-driven accommodation changes, and thus are more sensitive to archive sediment pulses. Small basins lacking carbonate facies are the ideal candidates to archive the impact of orbital forcing in the landscapes, as their small-scale sediment transfer systems are unable to buffer the upstream signal. Sedimentation models that include the relationship between accommodation and sediment supply, the effects of density and type of vegetation, and its coupled response with climate are needed to enhance their reliability.

  20. Intraoceanic Arc Tectonic and Sedimentary Processes: Translation from Modern Activity to Ancient Records

    NASA Astrophysics Data System (ADS)

    Draut, A. E.; Clift, P. D.

    2013-12-01

    Records of ancient intraoceanic arc activity, now preserved in continental suture zones, are used to reconstruct paleogeography, plate motion, collision and accretion events, and to understand how continental crust is formed, recycled, and maintained through time. However, interpreting tectonic and sedimentary records after arc-continent collision is complicated by preservation of evidence for some processes and loss of evidence for others. We examine what is lost, and what is preserved, in the translation from modern processes to the ancient record of oceanic subduction zones. Composition of accreted arc terranes differs as a function of arc-continent collision geometry. ';Forward-facing' collision can accrete an oceanic arc onto either a passive or an active continental margin, with the arc facing the continent and colliding trench- and forearc-side first. In ';backward-facing' collision, involving two subduction zones with similar polarity, the arc collides backarc-first with an active continental margin. The preservation of evidence for contemporary sedimentary and tectonic arc processes in the geologic record depends greatly on how well the various parts of the arc survive collision and orogeny in each case. Preservation of arc terranes likely is biased towards those that were in tectonic accretion for tens of millions of years before collision, rather than tectonic erosion. The prevalence of tectonic erosion in modern oceanic subduction zones implies that valuable records of arc processes are commonly destroyed even before collision with a continent. Arc systems are most likely to undergo tectonic accretion shortly before forward-facing collision with a continent, and thus most forearc and accretionary-prism material in ancient arc terranes likely is temporally biased toward the final stages of arc activity, when sediment flux to the trench was greatest. Collision geometry and tectonic erosion vs. accretion are important controls on the ultimate survival of

  1. Differential preservation in the geologic record of intraoceanic arc sedimentary and tectonic processes

    NASA Astrophysics Data System (ADS)

    Draut, Amy E.; Clift, Peter D.

    2013-01-01

    Records of ancient intraoceanic arc activity, now preserved in continental suture zones, are commonly used to reconstruct paleogeography and plate motion, and to understand how continental crust is formed, recycled, and maintained through time. However, interpreting tectonic and sedimentary records from ancient terranes after arc-continent collision is complicated by preferential preservation of evidence for some arc processes and loss of evidence for others. In this synthesis we examine what is lost, and what is preserved, in the translation from modern processes to the ancient record of intraoceanic arcs. Composition of accreted arc terranes differs as a function of arc-continent collision geometry. 'Forward-facing' collision can accrete an oceanic arc on to either a passive or an active continental margin, with the arc facing the continent and colliding trench- and forearc-side first. In a 'backward-facing' collision, involving two subduction zones with similar polarity, the arc collides backarc-first with an active continental margin. The preservation of evidence for contemporary sedimentary and tectonic arc processes in the geologic record depends greatly on how well the various parts of the arc survive collision and orogeny in each case. Preservation of arc terranes likely is biased towards those that were in a state of tectonic accretion for tens of millions of years before collision, rather than tectonic erosion. The prevalence of tectonic erosion in modern intraoceanic arcs implies that valuable records of arc processes are commonly destroyed even before the arc collides with a continent. Arc systems are most likely to undergo tectonic accretion shortly before forward-facing collision with a continent, and thus most forearc and accretionary-prism material in ancient arc terranes likely is temporally biased toward the final stages of arc activity, when sediment flux to the trench was greatest and tectonic accretion prevailed. Collision geometry and tectonic

  2. Sedimentary record of Warta river floods in summer 2010 and winter 2011 nearby Poznan, W Poland

    NASA Astrophysics Data System (ADS)

    Skolasińska, Katarzyna; Szczuciński, Witold; Mitręga, Marta; Rotnicka, Joanna; Jagodziński, Robert; Lorenc, Stanisław

    2013-04-01

    The Warta River valley nearby Poznań (W Poland) represents a meandering lowland river changed during the last 150 years by hydro-engineering works. Floods represent a major natural hazard in the region. However, historical records are not complete - particularly for former rural areas. Thus, sedimentary record may potentially offer additional insights into the flooding history. The big floods in the summer 2010 (the largest during the last 31 years) and winter 2011 offered opportunity to study their sedimentary record. The particular purposes were to identify sedimentary characteristics of summer and winter floods, interpret various phases of particular floods in the record, and assess impact of early post-depositional changes of the flood deposits. The surveys were conducted in six areas just after the floods and were repeated after several months, one and two years. The deposits spatial extent, thickness, surface bedforms and sediment type were assessed in the field. Sediment samples were further investigated for grain size distribution, organic matter content, roundness and sand grains surface features (SEM). The sandy flood deposits mostly build natural levee, side bars (<5 m from the channel bank) or crevasse splays (<40 m). They were up to 10-15 cm thick for the summer and 30-35 cm for the winter flood. The sands were mostly fine grained, well sorted and fine skewed. Their structures were massive with rare cases of climbing ripple lamination and planar cross laminations (only in crevasse splays). Vertical grain size changes in levee deposits revealed pensymmetric and/or reverse grading interpreted as effect of changing velocity during the rising water level. The sand grains were similar to the river channel sands and dominated by polished and sub-rounded quartz grains with preserved dissolution and dulled surface microfeatures. Further from the channel bank (few to few hundreds of meters) only discontinuous up to few mm thick organic rich mud layer was left

  3. 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

  4. A Global Record of Surface Earth Oxygenation from Sedimentary V/Sc

    NASA Astrophysics Data System (ADS)

    Keller, C. B.; Schoene, B.; Johnston, D. T.

    2015-12-01

    One of the simplest methods to investigate changes in oxidation potential in geologic environments is to examine a pair of otherwise similar elements with dramatically different redox chemistry. The first-row transition metals Sc and V represent one such pair, with generally similar mass, radius, and ionization energies up to the trivalent redox state. However, as a d3 transition metal, Sc is limited to a maximum oxidation state of 3+, while d5 vanadium may be further oxidized to form tetravalent and pentavalent ions. Due to the greater incompatibility of pentavalent (relative to trivalent) metal cations in silicate melts, V/Sc ratio has been applied to the silicate rock record as a tracer of magma redox - indicating roughly constant mantle oxygen fugacity over Earth history1,2. As a result, the solid earth represents a boundary condition with constant V/Sc observed over geologic time1. However, oxidation state also affects the weathering, solubility, and coordination behaviour of V and Sc, resulting in a potential redox signal in the sedimentary V/Sc record. We apply the weighted bootstrap resampling approach of [2] to a geochemical dataset of ~87,000 sedimentary whole-rock analyses from the EarthChem portal3. The resulting trends reveal a 4 Gyr record of V/Sc redox chemistry, with the great oxidation event represented as an upward step ca. 2.5 Ga, and Phanerozoic variation suggestive of low oxygen in the early Paleozoic, increasing to twin maxima circa 270 Ma and 130 Ma, remarkably similar to that predicted by the COPSE model4, and broadly congruent with the Phanerozoic biochar record5. Li, Z.-X. A. & Lee, C.-T. A. EPSL 228, 483-493 (2004). Keller, C. B. & Schoene, B. Nature 485, 490-493 (2012). EarthChem Bergman, N. M. Am. J. Science 304, 397-437 (2004). Glasspool, I. J. & Scott, A. C. Nat. Geosci. 3, 627-630 (2010).

  5. A Lower Rhine flood chronology based on the sedimentary record of an abandoned channel fill

    NASA Astrophysics Data System (ADS)

    Toonen, W. H. J.; Winkels, T. G.; Prins, M. A.; de Groot, L. V.; Bunnik, F. P. M.; Cohen, K. M.

    2012-04-01

    The Bienener Altrhein is an abandoned channel of the Lower Rhine (Germany). Following a late 16th century abandonment event, the channel was disconnected from the main stream and the oxbow lake gradually filled with 8 meters of flood deposits. This process still continues today. During annual floods, a limited proportion of overbank discharge is routed across the oxbow lake. Large floods produce individual flood layers, which are visually recognized in the sedimentary sequence. Based on the sedimentary characteristics of these event layers, we created a ~450-year flood chronology for the Lower Rhine. Laser-diffraction grain size measurements were used to assess relative flood magnitudes for individual flood event layers. Continuous sampling at a ~2 cm interval provided a high-resolution record, resolving the record at an annual scale. Standard descriptive techniques (e.g., mean grain size, 95th percentile, % sand) and the more advanced 'end member modelling' were applied to zoom in on the coarse particle bins in the grain size distributions, which are indicative of higher flow velocities. The most recent part of the record was equated to modern discharge measurements. This allows to establish relations between deposited grain size characteristics in the abandoned channel and flood magnitudes in the main river. This relation can also be applied on flood event layers from previous centuries, for which only water level measurements and historical descriptions exist. This makes this method relevant to expand data series used in flood frequency analysis from 100 years to more than 400 years. To date event-layers in the rapidly accumulated sequence, we created an age-depth model that uses organic content variations to tune sedimentation rates between the known basal and top ages. No suitable identifiable organic material for radiocarbon dating was found in the cores. Instead, palynological results (introduction of agricultural species) and palaeomagnetic secular

  6. Reconstructing Past Depositional and Diagenetic Processes through Quantitative Stratigraphic Analysis of the Martian Sedimentary Rock Record

    NASA Astrophysics Data System (ADS)

    Stack, Kathryn M.

    High-resolution orbital and in situ observations acquired of the Martian surface during the past two decades provide the opportunity to study the rock record of Mars at an unprecedented level of detail. This dissertation consists of four studies whose common goal is to establish new standards for the quantitative analysis of visible and near-infrared data from the surface of Mars. Through the compilation of global image inventories, application of stratigraphic and sedimentologic statistical methods, and use of laboratory analogs, this dissertation provides insight into the history of past depositional and diagenetic processes on Mars. The first study presents a global inventory of stratified deposits observed in images from the High Resolution Image Science Experiment (HiRISE) camera on-board the Mars Reconnaissance Orbiter. This work uses the widespread coverage of high-resolution orbital images to make global-scale observations about the processes controlling sediment transport and deposition on Mars. The next chapter presents a study of bed thickness distributions in Martian sedimentary deposits, showing how statistical methods can be used to establish quantitative criteria for evaluating the depositional history of stratified deposits observed in orbital images. The third study tests the ability of spectral mixing models to obtain quantitative mineral abundances from near-infrared reflectance spectra of clay and sulfate mixtures in the laboratory for application to the analysis of orbital spectra of sedimentary deposits on Mars. The final study employs a statistical analysis of the size, shape, and distribution of nodules observed by the Mars Science Laboratory Curiosity rover team in the Sheepbed mudstone at Yellowknife Bay in Gale crater. This analysis is used to evaluate hypotheses for nodule formation and to gain insight into the diagenetic history of an ancient habitable environment on Mars.

  7. Historical reconstruction of anthropogenic mercury input from sedimentary records: Yeongsan Estuary, South Korea

    NASA Astrophysics Data System (ADS)

    Williams, Joshua; Dellapenna, Timothy; Louchouarn, Patrick; Lee, Guan-hong

    2015-12-01

    The rapid economic growth of the Republic of Korea (S. Korea) within the last half-century has resulted in a pronounced increase in anthropogenic Hg emission from coal combustion, oil refining, cement production, and waste incineration. The record of increasing atmospheric sources have been investigated with a historical reconstruction of Hg accumulation in 30 sediment cores collected from the Yeongsan Estuary. Within the last several decades, this region has undergone severe anthropogenic alteration, including the construction of an estuarine dam forming the Yeongsan Lake, and installation of numerous seawalls that eliminated vast tidal flats and restricted estuarine circulation. Total mercury concentrations (T-Hg) measured in sediments deposited after 1980 (23.2 ± 9.6 ng g-1; n = 273), were significantly higher than those reported for pre-industrial sediments (i.e. background values: 8.6 ± 2.7 ng g-1; n = 274). An extensive survey of surface samples show that T-Hg concentrations are highest above the dam, with a gradient to lower values further offshore. The concomitant timing of enrichment of T-Hg within the sedimentary record and increased National emissions in Korea suggests that regional sources dominate the input to the Yeongsan Estuary. This indicates that with sufficient regional historic emission data, T-Hg might be utilized as a geochronologic tool to aid in corroborating traditional radioisotopic methods.

  8. The magnetic and mineralogical signature of the Deccan volcanism in the sedimentary record: a review

    NASA Astrophysics Data System (ADS)

    Font, Eric

    2016-04-01

    The contribution of the Deccan Traps volcanism in the Cretaceous-Palaeogene (KPg) crisis is still a matter of debate. The main limitation is the lack of mass extinction proxies within the Deccan lava flows, making hard the correlation of the onset of Deccan volcanism in India with the mass extinction recorded in the global marine record. An alternative is to investigate the magnetic and mineral assemblages of remote marine section. Iron oxides are very sensitive to changes in redox conditions, and thus can be possibly used as markers of paleoenvironmental changes driven by Deccan volcanism. This is the case in the Basque-Cantabric basin (Bidart, Zumaya) and the western margin of the Tethys (Gubbio), where an interval of low magnetic susceptibility (MS) containing akaganeite features in the last 50 cm just below the KPg boundary. The low MS interval originated from the loss of detrital and biogenic magnetites, features consistent with reductive iron oxide dissolution possibly linked to environmental acidification (acid rain and acidification of surficial waters). These insights provide new and promising benchmarks of the sedimentary imprint of the Deccan-induced paleoclimatic and paleoenvironmental changes. More importantly, the fact that the hypothesised Deccan perturbations occurred some 50 cm (~30,000 y.r.) before the KPg boundary suggest that Deccan volcanism may have contribute significantly to the KPg mass extinction. Keywords: Deccan, reductive iron oxide dissolution, akaganeite, KPg boundary, mass extinction Funded by IDL (FCT UID/GEO/50019/2013)

  9. Is it possible to use "twin cores" as a unique sedimentary record? An experimental design based on sediment color

    NASA Astrophysics Data System (ADS)

    Veiga-Pires, C.; Mestre, N. C.

    2009-01-01

    Sedimentary cores are widely used for studying Quaternary records. However, the amount of sediment that is available is proportional to the diameter of the core, which is rarely bigger than 15 cm. One way to obtain more sediment is to use two cores retrieved from almost the same location and use them as if they represent a unique sedimentary record. In the present work, an experimental design has been applied to verify if "twin cores" from an estuary can be considered as representing the same sedimentary record with twice the amount of sediment to study. Because sediment can be characterized based on its color, the variables used as replicates in the experimental design are the three Lab CIE colors acquired with a X-Rite Colortron spectrophotometer. Sediment cores were retrieved from the upper saltmarsh of Gilão River's estuary, southern Portugal. Twin cores, with in between distances of 50 cm, 100 cm and 200 cm, from two different sites were analysed. Results from a nested ANOVA show that even for the closest twin cores (50 cm apart) there is at least one color variable that shows significant variations between the profiles of both cores. These results clearly show that "twin cores" cannot be used as a unique sedimentary record without any previous testing, at least in such transitional regions.

  10. Reassessment of some Holocene Sedimentary Paleomagnetic Records with Implications for Geomagnetic Field Models

    NASA Astrophysics Data System (ADS)

    Brown, M. C.; Korte, M. C.; Constable, C.; Berner, N.; Hayn, M.; Holschneider, M.

    2012-12-01

    Temporally continuous global spherical harmonic models of the Holocene geomagnetic field (e.g., CALS3k.4 and CALS10k.1b) rely on compilations of published sedimentary paleomagnetic records for their construction. In current models all data are initially included regardless of their quality and only extreme outliers are rejected during the fitting procedure. Encouragingly, they can extract globally and regionally consistent signals from the data; however, low quality paleomagnetic data and erroneous age models may distort geomagnetic field structures generated by the models. One particularly interesting non-dipolar feature observed in CALS3k.4 and CALS10k.1b is an undulation of the magnetic equator and associated paired flux patches at the core-mantle boundary under southeast Asia and northern Australasia. We re-examine and reconstruct a number of previously published records that influence this region. Although these records were suitably analyzed for the original aims of the specific studies, for global modeling it is desirable to treat data consistently wherever possible. Four problems commonly plague reconstructions: 1) the data used for modeling are often a smoothed composite from multiple cores, rather than horizon-level inclination, declination or relative intensity data from individual cores; 2) varied methods for correlation and smoothing lead to uneven data consistency; 3) advances in radiocarbon dating have resulted in changes to the calibration curve for atmospheric radiocarbon leading to possible offsets in time series across studies; and 4) age-depth models often do not fully consider the uncertainty distribution of the radiocarbon mixing profile and calibration process, producing implausible results. Reconstruction of a composite record is only possible when an author provides raw core data. This involves two key steps: re-correlation of data between cores and creation of a new age-depth model. In both cases we ultimately attempt a uniform approach

  11. Sedimentary organic and inorganic records of eutrophication and hypoxia in and off the Changjiang Estuary over the last century.

    PubMed

    Zhao, Jun; Feng, Xuwen; Shi, Xiaolai; Bai, Youcheng; Yu, Xiaoguo; Shi, Xuefa; Zhang, Weiyan; Zhang, Rongping

    2015-10-15

    Organic and inorganic sedimentary parameters in and off the Changjiang Estuary have been analyzed to reconstruct historical trends in eutrophication and hypoxia over the last century. The lipid biomarker concentrations in the Changjiang Estuary mud area (CEMA) indicated eutrophication accelerated after the 1970s. Meanwhile, Mo/Al indicated hypoxia has increased since 1960s. Eutrophication and hypoxia in the CEMA are primarily a result of the dramatically increased load of terrestrial nutrients from the Changjiang to the East China Sea. The lipid biomarker concentrations in the southwest Cheju Island mud area (SCIMA) showed primary production is controlled mainly by changes in regional climate and marine current. No significant hypoxia occurred in the SCIMA over the past century as indicated by Mo/Al. Therefore, geochemical indicators of eutrophication and hypoxia revealed different patterns between the CEMA and SCIMA, suggesting the role of river-derived nutrients in sustaining eutrophication and hypoxia in the CEMA since the 1960s. PMID:26233303

  12. Structural and sedimentary records of the Oligocene revolution in the Western Alpine arc

    NASA Astrophysics Data System (ADS)

    Dumont, T.; Schwartz, S.; Guillot, S.; Simon-Labric, T.; Tricart, P.; Jourdan, S.

    2012-05-01

    The northwestwards-directed Eocene propagation of the Western Alpine orogen is linked with (1) compressional structures in the basement and the Mesozoic sedimentary cover of the European foreland, well preserved in the External Zone (or Dauphiné Zone) of the Western Alps and (2) tectono-sedimentary features associated with the displacement of the early Tertiary foreland basin. Three major shortening episodes are identified: a pre-Priabonian deformation D1 (N-S shortening), supposedly linked with the Pyrenean-Provence orogeny, and two Alpine shortening events D2 (N- to NW-directed) and D3 (W-directed). The change from D2 to D3, which occurred during early Oligocene time in the Dauphiné zone, is demonstrated by a high obliquity between the trends of the D3 folds and thrusts, which follow the arcuate orogen, and of the D2 structures which are crosscut by them. This change is also recorded in the evolution of the Alpine foreland basins: the flexural basin propagating NW-wards from Eocene to earliest Oligocene shows thin-skinned compressional deformation, with syn-depositional basin-floor tilting and submarine removal of the basin infill above active structures. Locally, a steep submarine slope scar is overlain by kilometric-scale blocks slided NW-wards from the orogenic wedge. The deformations of the basin floor and the associated sedimentary and erosional features are kinematically consistent with D2 in the Dauphiné foreland. Since ˜32 Ma, the previously subsiding areas were uplifted and the syntectonic sedimentation shifted westwards. Simultaneously, the paleo-accretionary prism, which developed during the previous, continental subduction stage, was rapidly exhumed during the Oligocene collision stage due to westward indentation by the Adriatic lithosphere, which likely enhanced the relief and erosion rate. The proposed palinspastic restoration takes into account this two-stage evolution, with important northward transport of the distal passive margin fragments

  13. Ultra-high-resolution paleoenvironmental records via direct laser-based analysis of lipid biomarkers in sediment core samples

    PubMed Central

    Wörmer, Lars; Elvert, Marcus; Fuchser, Jens; Lipp, Julius Sebastian; Buttigieg, Pier Luigi; Zabel, Matthias; Hinrichs, Kai-Uwe

    2014-01-01

    Marine microorganisms adapt to their habitat by structural modification of their membrane lipids. This concept is the basis of numerous molecular proxies used for paleoenvironmental reconstruction. Archaeal tetraether lipids from ubiquitous marine planktonic archaea are particularly abundant, well preserved in the sedimentary record and used in several molecular proxies. We here introduce the direct, extraction-free analysis of these compounds in intact sediment core sections using laser desorption ionization (LDI) coupled to Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). LDI FTICR-MS can detect the target lipids in single submillimeter-sized spots on sediment sections, equivalent to a sample mass in the nanogram range, and could thus pave the way for biomarker-based reconstruction of past environments and ecosystems at subannual to decadal resolution. We demonstrate that ratios of selected archaeal tetraethers acquired by LDI FTICR-MS are highly correlated with values obtained by conventional liquid chromatography/MS protocols. The ratio of the major archaeal lipids, caldarchaeol and crenarchaeol, analyzed in a 6.2-cm intact section of Mediterranean sapropel S1 at 250-µm resolution (∼4-y temporal resolution), provides an unprecedented view of the fine-scale patchiness of sedimentary biomarker distributions and the processes involved in proxy signal formation. Temporal variations of this lipid ratio indicate a strong influence of the ∼200-y de Vries solar cycle on reconstructed sea surface temperatures with possible amplitudes of several degrees, and suggest signal amplification by a complex interplay of ecological and environmental factors. Laser-based biomarker analysis of geological samples has the potential to revolutionize molecular stratigraphic studies of paleoenvironments. PMID:25331871

  14. Sedimentary record of anthropogenic and biogenic polycyclic aromatic hydrocarbons in San Francisco Bay, California

    USGS Publications Warehouse

    Pereira, W.E.; Hostettler, F.D.; Luoma, S.N.; VanGeen, A.; Fuller, C.C.; Anima, R.J.

    1999-01-01

    Dated sediment cores collected from Richardson and San Pablo Bays in San Francisco Bay were used to reconstruct a history of polycyclic aromatic hydrocarbon (PAH) contamination. The sedimentary record of PAHs in Richardson Bay shows that anthropogenic inputs have increased since the turn of the century, presumably as a result of increasing urbanization and industrialization around the Bay Area. Concentrations range from about 0.04-6.3 ??g g-1. The dominant origin of the PAHs contributing to this modern contamination is from combustion processes. Depth profiles in San Pablo Bay indicate higher concentrations of PAHs since the 1950s than during the late 1800s, also presumably resulting from an increase in urbanization and industrialization. Total PAHs in San Pablo Bay range from about 0.04-1.3 ??g g-1. The ratios of methylphenanthrenes/phenanthrene and (methylfluoranthenes + methylpyrenes)/fluoranthene were sensitive indicators of anthropogenic influences in the estuary. Variations in the ratio of 1,7-dimethylphenanthrene/2,6-dimethylphenanthrene indicate a gradual replacement of wood by fossil-fuel as the main combustion source of PAHs in. San Francisco Bay sediments. The profile of perylene may be an indicator of eroding peat from marshlands.

  15. Sedimentary Records of Harmful Bloom-Producing Dinoflagellates from Alvarado Lagoon (Southwestern Gulf of Mexico)

    NASA Astrophysics Data System (ADS)

    Limoges, A.; Mertens, K. N.; ruiz-Fernandez, A. C.; Sánchez Cabeza, J. A.; de Vernal, A.

    2014-12-01

    Organic-walled dinoflagellate cyst assemblages were studied from a sediment core collected in Alvarado Lagoon (southwestern Gulf of Mexico) in order to evaluate their use as tracers of toxic algal blooms. The sedimentary record spans the last ~560 years (CE) and shows high abundances of Polysphaeridium zoharyi, the cyst of the dinoflagellate Pyrodinium bahamense, which is known to cause toxic blooms. Cyst fluxes in the sediment of the Alvarado lagoon suggest frequent blooms of Pyrodinium bahamense in the past hundreds of years. Moreover, the high concentrations of the cysts (~ 4000 cysts g-1) in the "modern" surface sediment reveal that the area is susceptible to be affected by future blooms, especially during seasons of heavy rain and wind, when cysts are resuspended in the water column. The dinoflagellate cyst bank in sediment deserves special attention as it may constitute a source for the export of cells in adjacent regions. The cyst of other harmful dinoflagellates have been recovered in the sediment. They notably include those of the benthic dinoflagellate Bysmatrum subsalsum, which is here reported for the first time.

  16. Sedimentary processes in High Arctic lakes (Cape Bounty, Melville Island, Canada): What do sediments really record?

    NASA Astrophysics Data System (ADS)

    Normandeau, Alexandre; Lamoureux, Scott; Lajeunesse, Patrick; Francus, Pierre

    2016-04-01

    Lacustrine sedimentary sequences can hold a substantial amount of information regarding paleoenvironments, hydroclimate variability and extreme events, providing critical insights into past climate change. The study of lacustrine sediments is often limited to the analysis of sediment cores from which past changes are inferred. However, studies have provided evidence that the accumulation of sediments in lacustrine basins and their distribution can be affected by a wide range of internal and external forcing mechanisms. It is therefore crucial to have a good knowledge of the factors controlling the transport and distribution of sediments in lakes prior to investigating paleoenvironmental archives. To address this knowledge gap, the Cape Bounty Arctic Watershed Observatory (CBAWO), located on southern Melville Island in the Canadian High Arctic, was initiated in 2003 as a long term monitoring site with the aim of understanding the controls over sediment transport within similar paired watersheds and lakes. The East and West lakes have been monitored each year since 2003 to document the role of hydro-climate variability on water column processes and sediment deposition. Moorings recording water electrical conductivity, temperature, density, dissolved oxygen and turbidity, as well as sediment traps were deployed during the active hydrological period (generally May-July). These data were analyzed in combination with hydrological and climatic data from the watersheds. Additionally, a high-resolution bathymetric and sub-bottom survey was completed in 2015 and allowed imaging the lake floor and sub-surface in great detail. This combination of process and lake morphological data are unique in the Arctic. The morphostratigraphic analysis reveals two highly disturbed lake floors, being widely affected by subaqueous mass movements that were triggered during the last 2000 years. Backscatter intensity maps and the presence of bedforms on each delta foresets indicate that

  17. Sedimentary record of the 2013 Typhoon Haiyan in Leyte Gulf, Philippines

    NASA Astrophysics Data System (ADS)

    Soria, Janneli Lea; Switzer, Adam; Pilarczyk, Jessica; Siringan, Fernando; Angelique Doctor, Ma.; Khan, Nicole; Fritz, Hermann; Ramos, Riovie; Ildefonso, Sorvigenaleon; Garcia, Mikko

    2016-04-01

    Overwash associated with the 5 to 8 m storm surge of Typhoon Haiyan has left washover sediments inland, surrounding the northwestern shores of Leyte Gulf. The Typhoon Haiyan sediments represent a modern sedimentary record of a high impact landfalling typhoon, and now form the platform for reconstructing pre-historical storm surge events in the Philippines. Long-term storm surge records provide foundation to understanding coastal responses and assessing future coastal risk, but data in tropical settings is still limited. In this study, we mapped the thickness and extent of the Typhoon Haiyan deposit, and document the textural and compositional variations along four transects in two contrasting coastal environments. On the mixed siliciclastic-carbonate coast of Basey, the Typhoon Haiyan deposit is beige, poorly-sorted, silt to fine sand. The sediments deposited proximal to the coast were predominantly carbonate-rich, fine sand. Farther inland the sediments were predominantly silt containing less carbonate. In contrast, on the silicilastic coast of Tanauan, the Typhoon Haiyan deposit is predominantly gray, moderately- to well-sorted, fine to coarse sand. The generally coarse-grained and well-sorted Typhoon Haiyan deposit contained limited amount of carbonate and organic matter, and was most probably scoured from the beach. Post-typhoon satellite images, exposed coconut roots, and erosion scarps consistently indicate extensive beach erosion. Grasses were completely buried with the Typhoon Haiyan sediment indicating rapid deposition with little or no erosion on the back beach environments. Given that storm surge conditions were similar in these two sites, the significant differences in sediment grainsize, sorting, and composition can be likely attributed to local factors including variations in near-shore bathymetry and sediment source.

  18. Holocene Sedimentary Record of Unusual Primary Productivity, Dalton Polynya, Sabrina Coast, East Antarctica

    NASA Astrophysics Data System (ADS)

    Leventer, A.; Armand, L.; Redovian, M.; Domack, E. W.; Shevenell, A.; Smith, C.; Lavoie, C.; Orsi, A. H.; Huber, B. A.; Gulick, S. P. S.; Fernandez-Vasquez, R. A.

    2014-12-01

    Cruise NBP14-02 surveyed the previously unstudied Moscow University Ice Shelf region, East Antarctica, an area of concern due to recent changes in the glacial system. Using 3.5 kHz sub-bottom geophysical data, we targeted a mid-shelf site with an expanded Holocene sedimentary section, recovering ~ 10 meters of Holocene diatom-rich sediments characterized by an unusual floral assemblage that records the strong and consistent presence of open ocean diatoms. The sedimentary assemblage is dominated by ~50% Fragilariopsis kerguelensis, with a diagnostic contribution of Thalassiosira lentiginosa and Thalassiosira oliverana, species typical of the open Southern Ocean, suggesting southward inflow onto the shelf. A lesser contribution of Fragilariopsis curta indicates the influence of sea ice associated productivity within the polynya. Strong easterly winds and the blocking of sea ice transport into the region by the Dalton Iceberg Tongue to the east appear to be important factors in polynya development and maintenance; sea ice melt within the polynya likely contributes a diatom seed population. Chaetoceros is notably absent, likely due to the polynya opening later in the season (January) and the absence of a typical spring bloom. Unusual Thalassiothrix antarctica layers, up to 15 centimeters thick and comprised of tightly matted valves with a newspaper-like texture, are evident down core. This shade-adapted species can live at depth, maximizing access to nutrients, and is thought to be an under-recognized contributor to oceanic primary productivity due to the patchy subsurface nature of blooms. Thalassiothrix, and other species with a similar thread-like morphology, are often associated with oceanic frontal zones and may be responsible for episodic but significant carbon and silica flux to the sea floor. Temporal variability in the occurrence of Thalassiothrix layers in this Holocene sediment sequence may reflect past changes in the relative proximity and/or strength of

  19. The geomorphic and sedimentary record of past subglacial water outbursts, Sabrina Coast, East Antarctica

    NASA Astrophysics Data System (ADS)

    Fernandez-Vasquez, R. A.; Domack, E. W.; Lavoie, C.; Gulick, S. P. S.; Saustrup, S., Sr.; Frederick, B.; Leventer, A.; Shevenell, A.; Blankenship, D. D.

    2014-12-01

    The drainage basin of Totten Glacier (TG) comprises nearly one-eighth of the East Antarctic Ice Sheet and contains an estimated ice volume equivalent to 6.9 m of eustatic sea level rise, a value greater than the entire West Antarctic Ice Sheet. Adjacent, and partially covering the area presently corresponding to TG drainage basin, is the Aurora Subglacial Basin, a deep trough that reaches more than 1 km below sea level where geophysical data suggest the existence of numerous subglacial water bodies. Such water bodies maintain zero basal shear stress relatively to the overlying ice. It is theorized that subglacial outburst would decrease the shear stress at the bottom of marine ice sheets near the margin, inducing ice acceleration, thinning and ultimately contributing to the collapse of the ice sheet. In this contribution we present part of the preliminary results of the first geological and geophysical marine survey (NBP1402) to the inner continental shelf off the Sabrina Coast in the Totten Glacier/Moscow University Ice Shelf area, East Antarctica. We describe a set of subglacial features that we interpret as representing the sedimentary and geomorphic record of past subglacial water outbursts. These features, which we refer as "feather moraines", were imaged by high-resolution multichannel seismic (MCS) and CHIRP data to consist of a stack of subglacial sediments separated by erosional unconformities, and were shown in the swath bathymetry to consist of feather-like areas exhibiting cross and cut relationships between different sets, with distinct step-wise borders on the downstream side. They are superimposed on megascale glacial lineations (MSGL) and are elongated in generally the same direction as the MSGLs. The upstream side of the feather moraines coincides with the initiation of the MSGL and an area of drumlins near the limit of the glacial sediments and the outcropping of bedrock. A network of channels carved in bedrock just south of the feather moraines

  20. Geochemical Modeling of Evaporation Processes on Mars: Insight From the Sedimentary Record at Meridiani Planum

    NASA Astrophysics Data System (ADS)

    Tosca, N. J.; McLennan, S. M.

    2004-12-01

    The Opportunity rover's analysis of an impure evaporite component present in the Martian sedimentary record reveals a unique geochemical system. The evaporation of basaltic weathering fluids is a process which is rare on Earth, but is likely to have played a major role in the formation of sedimentary rocks at Meridiani Planum. Adequately modeling the evaporation processes in this system must involve adding additional components to current thermodynamic models, namely Fe(II) and Fe(III). The goals of this study are to: (1) develop a thermodynamic database suitable for modeling evaporation of basaltic weathering fluids in the Meridiani system and (2) to apply the model to experimental fluid data obtained in our laboratory from weathering synthetic Martian basalt, which will allow for the testing of hypotheses related to the geochemical evolution of the Meridiani site. The evaporation of these fluids is simulated using an expanded version of the Harvie-Moller-Weare model which employs Pitzer's ion interaction approach in calculating activity coefficients in high ionic strength solutions. This model has been expanded using recent data to include Fe(II) and Fe(III). Although a full set of experimentally-derived data allowing the inclusion of Fe(III) into such models is not yet available, an adequate set of interaction parameters was built, based on viable assumptions and substitutions using analog data (e.g., Al3+, Ga3+, Cr3+). The accuracy of the thermodynamic model in predicting Fe(II) and Fe(III) activities in a multi-component system can be assessed. This is accomplished by comparing calculated Eh values (proportional to aFe2+/aFe3+) to those measured in the field from high ionic strength acid mine waters containing all of the relevant components of the model. The agreement between calculated and observed values suggests that the model calculations are adequate for reaction path calculations. New thermodynamic data for several Fe(II) and/or Fe(III) containing

  1. Eutrophication signals in the sedimentary record of dinoflagellate cysts in coastal waters

    NASA Astrophysics Data System (ADS)

    Dale, Barrie

    2009-01-01

    A brief review is presented of the current status of eutrophication signals from the sedimentary records of dinoflagellate cysts in coastal waters, particularly of NW Europe. There is a dearth of the multi-decadal time series data from plankton needed to document eutrophication, and the cysts may provide an alternative source of information. Two different eutrophication signals have been described so far from cyst records: 1) from the Oslofjord, comprising a marked increase in total cyst concentrations (interpreted as probably reflecting increased phytoplankton productivity), with Lingulodinium polyedrum cysts accounting for most of the increase (interpreted as a species particularly benefiting from added nutrients from cultural eutrophication in late summer when nutrients otherwise may be limiting); and 2) the heterotroph signal, from several other Norwegian fjords and Tokyo Bay, Japan, involving both cases of increased cyst concentrations and others with no particular increase, but with a marked proportional increase in cysts of heterotrophic species (interpreted as reflecting increased diatoms and possibly other prey for the heterotrophic dinoflagellates and/or more unfavourable conditions for autotrophs, e.g. from shading). These signals should be used critically, and there is a particular need to distinguish between eutrophication signals and climate signals that may be co-occurring at a given time. Work by various authors has generally supported the concept of these cyst-based signals since they were first published, including both further records from cored sediments from other parts of the world and studies relating cyst distributions in surface sediments to gradients of pollution and nutrients from sewage discharge. Recent, unpublished work by Dale and Sætre, linked cyst signals in cored sediments to the timing of collapse of local fisheries at different times within the past fifty years in four fjord systems along the Norwegian Skagerrak coast

  2. Classification of Modern and Old Río Tinto Sedimentary Deposits Through the Biomolecular Record Using a Life Marker Biochip: Implications for Detecting Life on Mars

    NASA Astrophysics Data System (ADS)

    Parro, Victor; Fernández-Remolar, David; Rodríguez-Manfredi, José A.; Cruz-Gil, Patricia; Rivas, Luis A.; Ruiz-Bermejo, Marta; Moreno-Paz, Mercedes; García-Villadangos, Miriam; Gómez-Ortiz, David; Blanco-López, Yolanda; Menor-Salván, César; Prieto-Ballesteros, Olga; Gómez-Elvira, Javier

    2011-01-01

    The particular mineralogy formed in the acidic conditions of the Río Tinto has proven to be a first-order analogue for the acid-sulfate aqueous environments of Mars. Therefore, studies about the formation and preservation of biosignatures in the Río Tinto will provide insights into equivalent processes on Mars. We characterized the biomolecular patterns recorded in samples of modern and old fluvial sediments along a segment of the river by means of an antibody microarray containing more than 200 antibodies (LDCHIP200, for Life Detector Chip) against whole microorganisms, universal biomolecules, or environmental extracts. Samples containing 0.3-0.5g of solid material were automatically analyzed in situ by the Signs Of LIfe Detector instrument (SOLID2), and the results were corroborated by extensive analysis in the laboratory. Positive antigen-antibody reactions indicated the presence of microbial strains or high-molecular-weight biopolymers that originated from them. The LDCHIP200 results were quantified and subjected to a multivariate analysis for immunoprofiling. We associated similar immunopatterns, and biomolecular markers, to samples with similar sedimentary age. Phyllosilicate-rich samples from modern fluvial sediments gave strong positive reactions with antibodies against bacteria of the genus Acidithiobacillus and against biochemical extracts from Río Tinto sediments and biofilms. These samples contained high amounts of sugars (mostly polysaccharides) with monosaccharides like glucose, rhamnose, fucose, and so on. By contrast, the older deposits, which are a mix of clastic sands and evaporites, showed only a few positives with LDCHIP200, consistent with lower protein and sugar content. We conclude that LDCHIP200 results can establish a correlation between microenvironments, diagenetic stages, and age with the biomarker profile associated with a sample. Our results would help in the search for putative martian biomarkers in acidic deposits with similar

  3. 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

  4. Sedimentary Record of the Last two Interglacials in the Terrestrial Canadian Arctic (Pingualuit Crater Lake, Nunavik)

    NASA Astrophysics Data System (ADS)

    St-Onge, G.; Guyard, H.; Pienitz, R.; Hausmann, S.; Francus, P.; Salonen, V.; Luoto, T.; Black, J.; Lamothe, M.; Zolitschka, B.; Larocque, I.

    2009-05-01

    The Pingualuit crater lake (Nunavik, Canada) resulted from a meteoritic impact that occurred ca. 1.4 million years ago. Due to its unique morphometry (depth and shape), the lake bottom may have escaped glacial erosion. Based on a punctual seismic profile acquired using a 12 kHz Knudsen echosounder and using both gravity and piston corers, we recovered the uppermost 8.5 m of sediments. High-resolution physical (CAT- Scan, Multi Sensor Core Logger, diffuse spectral reflectance), geochemical (ITRAX core scanner, carbon and nitrogen contents, δ13C of the organic matter) and magnetic (magnetic susceptibility, natural, anhysteretic, isothermal and saturation isothermal remanent magnetizations) analyses were performed. Two main lithofacies were clearly identified by the different measurements and likely represent successive interglacial/glacial cycles. Most of the sediment consists of light grey silts containing several angular rock fragments, that is characterized by very low organic carbon content, relatively high density and magnetic susceptibility values, suggesting a deposition during glacial conditions. Interbedded between this facies are at least two decimetre-thick, organic-rich and finely laminated intervals likely representing ice free periods. The presence of diatoms, chrysophytes and chironomid head capsules in smear and microscope slides from these two intervals supports this hypothesis. In addition, preliminary Infrared Stimulated Luminescence (IRSL) measurements indicate that the upper organic-rich layer has an age coeval with the last interglacial (Oxygen Isotope Stage 5), while the age of the lower organic-rich layer is consistent with an older interglacial, likely the Oxygen Isotope Stage 7. The sedimentary infill thus constitutes a unique long-term terrestrial record of environmental and climatic conditions in the Canadian Arctic. Furthermore, because these sediments escaped glacial erosion, it suggests the presence of a subglacial lake during the last

  5. Sedimentary record of sub-glacial outburst floods at Laurentian Fan

    NASA Astrophysics Data System (ADS)

    Leng, Wei; von Dobeneck, Tilo

    2016-04-01

    Large-scale glacial meltwater discharge could be widely recognized off the eastern Canadian continental margin. At Laurentian Fan, sub-glacial outburst floods eroded Permian-Carboniferous redbeds at Gulf of St. Lawrence and then delivered the reddish sediments by Laurentian Channel. Sedimentary record from four gravity cores (GeoB18514-2, 18515-1, 18516-2 and 18517-1) at the SW slope of the Grand Banks of Newfoundland revealed the major depositional processes since Heinrich event 2 (ca. 22 ka). In the cores, the upper thick Holocene olive-grey silty mud units overly IRD-rich Heinrich 1 layer, five reddish units are distinguished in the lower part. Reddish units get proportionally thinner along the SW slope at higher and more distal positions; instead, separating olive-grey layers get thicker with height and distance. Reddish and olive grey units have sharp boundaries and no signs of erosion. Mean grain size changes abruptly from coarse in grey layers to fine in reddish layers, terrigenous elements (as Al, K, Ti, Fe) and clays (Al/Si) are highly elevated in reddish layers and low in Heinrich layers, which are instead enriched in detrital continental carbonates. Both Heinrich layers and reddish layers have enhanced magnetic susceptibility, but Heinrich layer have higher ferromagnetic (SIRM) content (mafic rocks), while reddish layers have more hematite (HIRM). These five reddish layers differ from event to event, which seems to reflect different mixing ratios of event-related and background sedimentation. This mixing will allow estimating event-specific sedimentation rates. Using mixing ratio combined with 14C dating data could contribute to estimate the sedimentation rate and duration of outburst floods, which could help to build ice sheet retreat history and find the connection with paleoclimate changes.

  6. Penultimate and last glacial cycles in the western Bering Sea: evidence from micropaleontological and sedimentary records

    NASA Astrophysics Data System (ADS)

    Ovsepyan, Ekaterina; Ivanova, Elena; Murdmaa, Ivar

    2014-05-01

    The short- and long-term variability of sea-surface bioproductivity, intermediate-water oxygenation, sea ice conditions and bottom current velocities are inferred from the high-resolution multi-proxy study based on benthic (BF) and planktonic (PF) foraminiferal assemblages and sedimentary record of the 18m-long Core SO201-2-85KL (western Bering Sea). Early MIS 6 is characterized by a very low seasonal bioproductivity, moderate bottom-water oxygenation, and expanded seasonal sea ice conditions, as documented by the abundant phytodetritus species Alabaminella weddelensis, Islandiella norcrossi and Epistominella arctica, suboxic group of BF, and high accumulation rates of gravel grains, respectively. Middle MIS 6 is represented by intercalation of green diatomaceous ooze and grey clayey silt layers with sharp peaks of BF abundance in green interbeds. These spikes might result either from short-term events of enhanced sea surface bioproductivity or from lateral BF transport by intensified bottom currents, as it is demonstrated by high-amplitude variations of the clay/silt ratio. Rather high seasonal productivity and northward migration of the sea ice margin are reconstructed for the late MIS 6 that is also characterized by a slight increase in the Northern Hemisphere summer insolation. Strong dissolution of calcareous microfossils is revealed for MIS 5.5-5.1 when the Bering Strait was open. Dissolution might be caused by an excess of carbon dioxide in the bottom-water due to an abundant organic matter decay and/or to an influence of the old CO2-rich deep water. MIS 4 - early Termination I is characterized by a dominance of glacial benthic foraminiferal assemblages that implies low bioproductivity conditions. A prevalence of suboxic BF group suggests moderate bottom-water oxygenation. Sea ice rafting occurred in the western Bering Sea during MIS 4 - early Termination I but the drifted ice was not so dense as during MIS 6. The well-known productivity spikes at B

  7. Subducted sedimentary serpentinite mélanges: Record of multiple burial-exhumation cycles and subduction erosion

    NASA Astrophysics Data System (ADS)

    Wakabayashi, John

    2012-09-01

    Serpentinite matrix mélanges give insight into large-scale convergent plate margin processes, particularly because of the derivation of the serpentinite from oceanic mantle. Similar to shale-matrix mélanges, a field geologist may easily recognize the sedimentary origins of little-deformed serpentinite matrix mélanges, but mélanges within accretionary prisms have undergone significant deformation and recrystallization of matrix. Serpentinite mélanges of the Franciscan subduction complex of California have a seemingly intact and foliated matrix. Such exposures contrast sharply with the granular undeformed sedimentary serpentinite mélanges of the coeval Great Valley Group (GVG) forearc basin deposits that depositionally overlie Coast Range Ophiolite (that structurally overlies the Franciscan). Nonetheless, Franciscan serpentinite mélanges display evidence of sedimentary origins, including sedimentary breccia composed of exotic block material (Tolay Ridge), sedimentary serpentinite breccia (Panoche Pass Road), basal serpentinite conglomerate with exotic clasts (Sunol Regional Wilderness), and serpentinite sandstones and conglomerates, including a basal conglomerate overlying coherent metagraywacke (Tiburon Peninsula). These examples record two burial-exhumation cycles to blueschist facies depths. In addition, a mélange/breccia in the Panoche Pass area may have components that record three burial-exhumation cycles to blueschist (or greater) depth. Exhumation rates for various cycles ranged from about 1.2 to 10 mm/year. The Tiburon Peninsula serpentinite mélange occupies the structurally highest horizon in the Franciscan of the San Francisco Bay area, and regional field relationships indicate deposition at ca. 100 Ma. Apparently, about 65 Ma of subduction erosion/non accretion followed initiation of Franciscan subduction in this region. The oldest Franciscan serpentinite mélanges are at least 35 Ma younger than sedimentary serpentinites of the GVG. Subduction

  8. Some geochemical features of Caledonian volcanism recorded in sedimentary rocks of the East Baltic area

    NASA Astrophysics Data System (ADS)

    Soesoo, Alvar; Kiipli, Tarmo; Kallaste, Toivo

    2013-04-01

    The Caledonian rocks have formed as a result of a multitude of magmatic and tectonic processes. All these major processes have generated a set of volcanic and magmatic products. While products of intrusive magmatism can still be well recognised in Caledonian mountains, some of the volcanic products can be found in a wide area of the Baltica paleocontinent. The best record of the ancient explosive volcanism can be traced in sedimentary sections adjacent to tectonically active areas. The aim of this study is to describe geochemical evolution of the volcanism near the Baltica plate using bulk geochemistry and phenocryst compositions of the Caledonian volcanic ashes stored in the Lower Palaeozoic sections of the Eastern Baltica. The bentonite samples were collected from several drill cores from Estonia, Latvia and Lithuania. Thickness of the ash beds varies mostly between 0.1 and 10 cm, rarely reaching 20-70 cm. Constructed isopach schemes indicate increase of thickness of ash beds towards the northwest and west. Original sanidine composition in ca 400 samples and biotite from 13 ash beds were analysed from grain fraction of bentonites using X-ray diffractometry. Stratigraphical distribution of volcanic ash beds in the East Baltic area can be subdivided into four major intervals separated by intervals with less frequent signs of volcanism. The above intervals show characteristic geochemical signatures. Over 175 thin altered volcanic ash beds have been recognised by authors in the East Baltic sedimentary sections from the Upper Ordovician (ca. 458 Ma) to the Upper Silurian (ca. 421 Ma). There separate ash units may correspond to distinct volcanic eruptions in Caledonides. Volcanic ashes which reached the East Baltic area fall into four time periods (time intervals distinguished by micro-paleontological methods): (1) Sandbian with main sources at the margins of the Avalonian microcontinent; (2) Katian with sources at the margin of the Baltica in Iapetus Palaeo

  9. The recent marine sedimentary record of Baranof Island, Southeast Alaska - implications for paleoclimate reconstructions

    NASA Astrophysics Data System (ADS)

    Addison, J. A.; Finney, B. P.; Jaeger, J. M.; Stoner, J. S.; Norris, R. D.; Hangsterfer, A.

    2011-12-01

    -thick laminae; (ii) a potentially seismogenic turbidite; (iii) a fluvial hypopycnal deposit; and (iv) a subsurface bioturbated horizon. The contrasting natures of these two multicores collected from adjacent fjords argue for strong local controls on sedimentation (e.g. sill depth, fluvial discharge, and productivity). Preliminary analysis of the clr Br data (a proxy for organic carbon) from EW0408-32MC shows striking similarities to both the winter anomaly pattern of the North Pacific Index (NPI), as well as a modeled net primary productivity summer anomaly dataset. Both the NPI and Pacific marine productivity are known to vary due to dynamics associated with the Pacific Decadal Oscillation, suggesting that the recent sedimentary record of Baranof Island is a faithful recorder of regional climate signals.

  10. Annual and Longer Sedimentary Rhythms of the Organic Rock Record of Titan's Circumpolar Seas and Lakes

    NASA Astrophysics Data System (ADS)

    Kargel, J. S.; Tan, S. P.; Marion, G. M.; Jennings, D. E.; Mastrogiuseppe, M.; Adidharma, H.

    2014-12-01

    Seasonality and phase equilibrium in Titan's lakes and seas will result in predictable sedimentary processes, deposits, and landforms. Calculated using CRYOCHEM, liquids on Titan should exhibit a counter-intuitive behavior where density increases with temperature but decreases with pressure, unless the temperature falls below 89.6 K. For warmer temperatures, the surface liquid of seas should flow toward the hottest spot; return flow may occur beneath the surface. Methane-rich liquid flowing southward from one interconnected northern sea to another will evaporate methane and concentrate ethane and other heavy hydrocarbons. In the north polar and circumpolar regions, a south-flowing river entering a sea from cold northerly uplands will inject a buoyant plume of low-density methane-rich liquid into the sea, unless the liquid at the inlet is heavily charged with dense solid phases or unless the lake is colder than 89.6 K. Generally north of (colder than) the seasonally shifting 89.6K transition (possible during the winter precisely when river discharges are high), a different behavior exists, whereby cold and methane-rich liquid forms denser liquids and flows across the bottom of the sea—possibly forming sub-sea channels as observed at Ligeia Mare. If the river carries clastic sediment denser than the methane liquid, the solids will undergo Stokes settling of the coarser fractions during periods of high river discharge, leaving the finest clastic fraction to undergo slow pelagic sedimentation throughout the year. From late spring to late summer, methane undergoes net evaporation from the sea, and solid organics that were saturated during the winter are likely to precipitate once warm weather starts. Hence, varves in Titan's seas are apt to consist of annual cycles of (1) winter: coarse clastics, (2) all dry season: fine-grained clastics, and (3) summer: evaporites. As Titan undergoes 'Milankovic' type variations in rotational obliquity and Saturn's orbital

  11. The circum-Antarctic sedimentary record; a dowsing rod for Antarctic ice in the Eocene

    NASA Astrophysics Data System (ADS)

    Scher, H.

    2012-12-01

    Arguments for short-lived Antarctic glacial events during the Eocene (55-34 Ma) are compelling, however the paleoceanographic proxy records upon which these arguments are based (e.g., benthic δ18O, eustatic sea level, deep sea carbonate deposition) are global signals in which the role of Antarctic ice volume variability is ambiguous. That is to say, the proxy response to ice volume may be masked other processes. As a result broad correlations between proxies for ice volume are lacking during suspected Eocene glacial events. I will present a more direct approach for detecting Antarctic ice sheets in the Eocene; utilizing provenance information derived from the radiogenic isotopic composition of the terrigenous component of marine sediments near Antarctica. The method relies on knowledge that marine sediments represent a mixture derived from different basement terrains with different isotopic fingerprints. A key issue when using sedimentary deposits to characterize continental sediment sources is to deconvolve different sources from the mixed signal of the bulk sample. The pioneering work of Roy et al. (2007) and van de Flierdt et al. (2007) represents a major advance in Antarctic provenance studies. It is now known that the isotopic composition of neodymium (Nd) and hafnium (Hf) in modern circum-Antarctic sediments are distributed in a pattern that mimics the basement age of sediment sources around Antarctica. For this study I selected two Ocean Drilling Program (ODP) sites on southern Kerguelen Plateau (ODP Sites 738 and 748) because of their proximity to Prydz Bay, where Precambrian sediment sources contribute to extremely nonradiogenic isotopic signatures in modern sediments in the Prydz Bay region. New detrital Nd isotope records from these sediment cores reveal an Nd isotope excursion at the Bartonian/Priabonian boundary (ca. 37 Ma) that coincides with a 0.5 ‰ increase in benthic foram δ18O values. Detrital sediment ɛNd values are around -12 in intervals

  12. Foreland sedimentary record of Andean mountain building during advancing and retreating subduction

    NASA Astrophysics Data System (ADS)

    Horton, Brian K.

    2016-04-01

    As in many ocean-continent (Andean-type) convergent margins, the South American foreland has long-lived (>50-100 Myr) sedimentary records spanning not only protracted crustal shortening, but also periods of neutral to extensional stress conditions. A regional synthesis of Andean basin histories is complemented by new results from the Mesozoic Neuquén basin system and succeeding Cenozoic foreland system of west-central Argentina (34-36°S) showing (1) a Late Cretaceous shift from backarc extension to retroarc contraction and (2) an anomalous mid-Cenozoic (~40-20 Ma) phase of sustained nondeposition. New detrital zircon U-Pb geochronological results from Jurassic through Neogene clastic deposits constrain exhumation of the evolving Andean magmatic arc, retroarc thrust belt, foreland basement uplifts, and distal eastern craton. Abrupt changes in sediment provenance and distal-to-proximal depositional conditions can be reconciled with a complex Mesozoic-Cenozoic history of extension, post-extensional thermal subsidence, punctuated tectonic inversion involving thick- and thin-skinned shortening, alternating phases of erosion and rapid accumulation, and overlapping igneous activity. U-Pb age distributions define the depositional ages of several Cenozoic stratigraphic units and reveal a major late middle Eocene-earliest Miocene (~40-20 Ma) hiatus in the Malargüe foreland basin. This boundary marks an abrupt shift in depositional conditions and sediment sources, from Paleocene-middle Eocene distal fluviolacustrine deposition of sediments from far western volcanic sources (Andean magmatic arc) and subordinate eastern cratonic basement (Permian-Triassic Choiyoi igneous complex) to Miocene-Quaternary proximal fluvial and alluvial-fan deposition of sediments recycled from emerging western sources (Malargüe fold-thrust belt) of Mesozoic basin fill originally derived from basement and magmatic arc sources. Neogene eastward advance of the fold-thrust belt involved thick

  13. North Atlantic Holocene climate evolution recorded by high-resolution terrestrial and marine biomarker records

    NASA Astrophysics Data System (ADS)

    Moossen, Heiko; Bendle, James; Seki, Osamu; Quillmann, Ursula; Kawamura, Kimitaka

    2015-12-01

    Holocene climatic change is driven by a plethora of forcing mechanisms acting on different time scales, including: insolation, internal ocean (e.g. Atlantic Meridional Overturning Circulation; AMOC) and atmospheric (e.g. North Atlantic Oscillation; NAO) variability. However, it is unclear how these driving mechanisms interact with each other. Here we present five, biomarker based, paleoclimate records (air-, sea surface temperature and precipitation), from a fjordic sediment core, revealing North Atlantic terrestrial and marine climate in unprecedented detail. The Early Holocene (10.7-7.8 kyrs BP) is characterised by relatively high air temperatures while SSTs are dampened by melt water events, and relatively low precipitation. The Middle Holocene (7.8-3.2 kyrs BP) is characterised by peak SSTs, declining air temperatures and high precipitation. A pronounced marine thermal maximum occurs between ∼7-5.5 kyrs BP, 3000 years after the terrestrial thermal maximum, driven by melt water cessation and an accelerating AMOC. The neoglacial cooling, between 5.8 and 3.2 kyrs BP leads into the late Holocene. We demonstrate that an observed modern link between Icelandic precipitation variability during different NAO phases, may have existed from ∼7.5 kyrs BP. A simultaneous decoupling of both air, and sea surface temperature records from declining insolation at ∼3.2 kyrs BP may indicate a threshold, after which internal feedback mechanisms, namely the NAO evolved to be the primary drivers of Icelandic climate on centennial time-scales.

  14. A study of the record of ancient sedimentary rocks on Mars using MER, HiRISE and CRISM images

    NASA Astrophysics Data System (ADS)

    Metz, Joannah M.

    2010-11-01

    Many processes that operate on a planetary surface have the potential to create sedimentary deposits which when preserved as rocks can provide clues that allow past environmental conditions to be reconstructed. This work combines several studies using data from the Mars Exploration Rover and Mars Reconnaissance Orbiter spacecraft to examine the structure and sedimentology of the sedimentary rock record of Mars. The first study supports the dune-interdune model proposed for the formation of the deposits at the Opportunity landing site in Meridiani Planum and provides evidence that liquid water was involved to a greater extent in the formation of outcrops in Erebus crater. The next study identifies two depositional fan complexes on the floor of southwestern Melas Chasma and suggests that they may be sublacustrine in origin, which suggests the former presence of a significant body of water stable for at least 100 to 10,000 years. Furthermore, the basin containing the fans may be a complete source-to-sink system. The third study examines the geomorphic channel patterns present on analogue terrestrial submarine fans and deltas. The last study characterizes the extent and styles of deformation of sedimentary rocks in Valles Marineris and finds that subaerial or subaqueous gravitational slumping or sliding and soft-sediment deformation are potential mechanisms that may have caused the deformation.

  15. Late paleozoic tectonic amalgamation of northwestern China. Sedimentary record of the northern Tarim, northwestern Turpan, and southern Junggar basins

    SciTech Connect

    Carroll, A.R.; Graham, S.A.; Hendrix, M.S.; Ying, D.; Zhou, D.

    1995-05-01

    This study focuses on areas adjacent to the Tian Shan (shan is Chinese for mountains) in Xinjiang Uygur Autonomous Region, northwestern China, and provides new field data on Carboniferous and Permian outcrop exposures of sedimentary rocks of the southern Junggar, northwestern Turpan, and northern Tarim basins that bear directly on the history of late Paleozoic tectonic amalgamation. We present here a multifaceted sedimentary basin analysis, including sedimentary facies, paleocurrent, and sandstone provenance analyses, and reconstructions of late Paleozoic basin subsidence. These data provide a unique record not only of the basins themselves, but also of the evolution of the adjacent orogenic belts. This study is based on fieldwork during the summers of 1987, 1988, 1991, and 1992 by workers from Stanford University, the Chinese Academy of Geological Sciences, and the Xinjiang Bureau of Geology and Mineral Resources. Although reconnaissance in nature, the data presented here provide a basis for evaluating alternative hypotheses for the evolution of northwestern China and provide a starting point for more comprehensive future studies. 72 refs., 18 figs., 1 tab.

  16. Archaean Crustal Growth, Proterozoic Terrane Amalgamation and the Pan-African Orogeny, as Recorded in the NE African Sedimentary Record.

    NASA Astrophysics Data System (ADS)

    Najman, Y.; Fielding, L.; Millar, I.; Butterworth, P.; Andò, S.; Padoan, M.; Barfod, D. N.; Kneller, B. C.

    2015-12-01

    The cratons of Central Africa are formed of various blocks of Archaean and Palaeoproterozoic crust, flanked or truncated by Palaeoproterozoic to Mesoproterozoic orogenic belts. The geology of east Africa has largely been shaped by the events of the Pan-African Orogeny when east and west Gondwana collided to form 'Greater Gondwana' at the end of the Neoproterozoic. The Pan-African orogeny in NE Africa involved the collision of Archaean cratons and the Saharan Metacraton with the Arabian Nubian Shield, a terrane comprising Neoproterozoic juvenile oceanic island arcs. Phanerozoic cover sedimentary rocks, eroded from the Pan-African orogenies, blanket much of NE Africa. Detrital data from these Phanerozoic cover sedimentary rocks, and modern rivers draining both the cover the basement, provide a wealth of information on basement evolution, of particular relevance for regions where the basement itself is poorly exposed due to ancient or modern sedimentary cover. From samples collected in Uganda, Ethiopia, Sudan and Egypt, we provide combined U-Pb and Hf-isotope zircon, U-Pb rutile and Ar-Ar mica datasets, heavy mineral analyses, and bulk trace element data, from Archaean basement, Phanerozoic cover and modern river sediment from the Nile and its tributaries to document the evolution of the North African crust. The data document early crust-forming events in the Congo Craton and Sahara Metacraton, phased development of the Arabian Nubian Shield culminating in the Neoproterozoic assembly of Gondwana during the Pan African Orogeny, and the orogen's subsequent erosion, with deposition of voluminous Phanerozoic cover.

  17. Quasi-periodic bedding in the sedimentary rock record of mars

    USGS Publications Warehouse

    Lewis, K.W.; Aharonson, O.; Grotzinger, J.P.; Kirk, R.L.; McEwen, A.S.; Suer, T.-A.

    2008-01-01

    Widespread sedimentary rocks on Mars preserve evidence of surface conditions different from the modern cold and dry environment, although it is unknown how long conditions favorable to deposition persisted. We used 1-meter stereo topographic maps to demonstrate the presence of rhythmic bedding at several outcrops in the Arabia Terra region. Repeating beds are ???10 meters thick, and one site contains hundreds of meters of strata bundled into larger units at a ???10:1 thickness ratio. This repetition likely points to cyclicity in environmental conditions, possibly as a result of astronomical forcing. If deposition were forced by orbital variation, the rocks may have been deposited over tens of millions of years.

  18. First seismic survey of Lake Saint-Jean (Québec, Canada): sedimentary record of the last deglaciation

    NASA Astrophysics Data System (ADS)

    Nutz, Alexis; Schuster, Mathieu; Ghienne, Jean-François; Raphaël, Certain; Nicolas, Robin; Claude, Roquin; Frédéric, Bouchette; Cousineau Pierre, A.

    2015-04-01

    complexity. It is notably worth noting that the transition from glacial to post-glacial periods is well marked by an abrupt change in depositional dynamics. In addition, this work highlights an original lacustrine sedimentary system which is not straightforward notably because of the importance of erosion, by-pass and intermittent deposition over most of the lakefloor. As it deals with both glacial environments and lake systems, this works is of interest for all those concerned by the geological record of both the transition from glacial to post-glacial periods and the lacustrine environments.

  19. Age and sedimentary record of inland eolian sediments in Lithuania, NE European Sand Belt

    NASA Astrophysics Data System (ADS)

    Kalińska-Nartiša, Edyta; Thiel, Christine; Nartišs, Māris; Buylaert, Jan-Pieter; Murray, Andrew S.

    2015-07-01

    We present a study based on four inland eolian locations in Eastern, Central and Southeastern Lithuania belonging to the northeastern part of the 'European Sand Belt' (ESB). Although there have been several previous studies of the ESB, this north-eastern extension has not been investigated before in any detail. The sedimentary structural-textural features are investigated and a chronology was derived using optically stimulated luminescence on both quartz and feldspar. The sedimentary structures and the rounding and surface characteristics of the quartz grains argue for a predominance of eolian transport. Additionally, some structural alternations and a significant contribution of non-eolian grains are interpreted as inherited local glacial/glaciofluvial-bearing lithologies. Three main (glaciolacustrine-) eolian phases are distinguished based on the position in the landscape and the luminescence ages: (1) An older eolian series around 15 to 16 ka, possibly correlated with the cold GS-2a event according to the GRIP stratigraphy, and (2) a younger eolian series around 14.0 ka, possibly representing the GI-1d and 1c events. The older eolian series is underlain by (3) a glaciolacustrine-eolian series for which the period of deposition remains uncertain due to the significant discrepancy between the ages based on quartz and feldspar.

  20. The Oligocene Creede Formation, Colorado: The sedimentary record of a deep lake within a resurgent caldera

    SciTech Connect

    Larsen, D.; Smith, G.A. . Dept. of Earth and Planetary Sciences)

    1993-04-01

    The Oligocene Creede Formation is the sedimentary fill of the Creede caldera in the Tertiary San Juan volcanic field in southern Colorado. Scientific drill core and outcrop studies of Creede strata allow an evaluation of the post-collapse sedimentary environments present within a caldera. Although the Creede Formation is structurally disrupted, correlation of fallout tuffs in exposed strata to those in the cores has clarified stratigraphic relationships. Following ash-fallout from the caldera-forming eruption, up to 121 meters of coarse grained debris-flow strata and rockfall debris with interstratified basinward ephemeral lake deposits were deposited. The presence of pseudomorphs after ikaite and up-section increase in carbonate facies suggest that the lake water was somewhat alkaline and cold (near freezing), and evolved chemically with time. A late-stage drop in lake level combined with integration of basin-feeding drainages and decreased subsidence lead to basinward progradation of coarser deltaic and lacustrine fan deposits. Sedimentation patterns suggest that subsidence occurred largely in the northern half of the caldera, and decreased late in the lake's history allowing the basin to fill with sediment.

  1. Inevitability of low-latitude melting on Mars: implications for the sedimentary record

    NASA Astrophysics Data System (ADS)

    Kite, E. S.; Manga, M.; Halevy, I.

    2010-12-01

    The recently published MOC-NA database of sedimentary rock locations shows an extraordinary concentration of sedimentary rocks near the equator - 64% at <10° latitude (59% when Valles Marineris is excluded). These rocks overwhelmingly date from the late Noachian to the middle Hesperian, when many sulfate-bearing deposits formed. With the reasonable assumption that liquid water is required for lithification, we hypothesize that liquid water only occurred near the equator during this era. As an initial test of this hypothesis, we model melting on Early Mars assuming a weak greenhouse effect similar to today. Combining the Laskar group's chaotic diffusion parameterization of orbital evolution with simple assumptions about ice stability, we show that melting under a weak greenhouse is most likely when (1) obliquity is high, (2) eccentricity is moderately high, (3) at equinox, (4) when the longitude of perihelion corresponds to equinox, and (5) at the equator. We compare discharge results from a snowpack Energy Balance Model to published discharge constraints at three Early Mars locations - SW Melas, Gale-Aeolis-Zephyria, and Meridiani. If these discharges cannot be reproduced under a weak greenhouse similar to today, then a stronger Early Mars greenhouse effect is required to explain these observations. We show how the fraction of a precession cycle during which melting occurs - the 'stratigraphic wet fraction' - can be used to set a lower bound on the strength of the Early Mars greenhouse effect. The stratigraphic wet fraction can be measured by MSL at Gale.

  2. Holocene-aged sedimentary records of environmental changes and early agriculture in the lower Yangtze, China

    NASA Astrophysics Data System (ADS)

    Atahan, P.; Itzstein-Davey, F.; Taylor, D.; Dodson, J.; Qin, J.; Zheng, H.; Brooks, A.

    2008-03-01

    Sedimentary evidence from a total of 21 AMS 14C dates and 192 pollen and charcoal and 181 phytolith samples from three study sites in the archaeologically rich lower Yangtze in China provides an indication of interactions between early agriculturalists and generally highly dynamic environmental conditions. Results suggest that environmental changes influenced agricultural development, and attest the localised environmental impacts of incipient agriculture. Evidence of human activity, in the form of indicators of deforestation and possibly food production, is apparent by ca 7000 BP (early Neolithic or Majiabang). Clearer evidence of human activity dates to ca 4700 BP (late Neolithic or Liangzhu). Extensive, profound and apparently widespread human impacts do not appear until the Eastern Zhou (Iron Age, ca 2800-2200 BP), however, which in the lower Yangtze was a period associated with technological advances in agriculture, increased urbanisation and relatively stable hydro-geomorphological conditions.

  3. A deep-time perspective of land-ocean linkages in the sedimentary record.

    PubMed

    Romans, Brian W; Graham, Stephan A

    2013-01-01

    It is increasingly important to understand and predict how marine environments respond to changes in climate and sea level and to variability in sediment flux from rivers. The dynamics of these factors occur over several orders of temporal magnitude and, under favorable geologic conditions, contribute to long-lived sediment accumulation. Thus, stratigraphic successions along continental margins are archives of these environmental changes and can be used to reconstruct land-ocean linkages, which provide important context for shorter-term and future modifications to this critical zone. Here, we discuss an integrated approach to the analysis of deep-time sediment archives (>10(6) years) that considers the entire system, from eroding catchments where sediment is produced to subsiding basins where sediment accumulates. This holistic approach is presented within the framework of fundamental concepts about sedimentary-basin analysis and stratigraphic characterization through a combination of foundational literature and studies that represent the state of the art. PMID:22809187

  4. The Sedimentary Record of an Intraoceanic Magmatic Arc, from Inception through Maturation to Abandonment: IODP Expedition 351, Site U1438

    NASA Astrophysics Data System (ADS)

    Marsaglia, K. M.; Barth, A. P.; Brandl, P. A.; Hickey-Vargas, R.; Jiang, F.; Kanayama, K.; Kusano, Y.; Li, H.; McCarthy, A.; Meffre, S.; Savov, I. P.; Tepley, F. J., III; Yogodzinski, G. M.

    2014-12-01

    International Ocean Discovery Program (IODP) Expedition 351 recovered an unprecedented ~1.4-km thick volcaniclastic sedimentary record documenting the initiation and subsequent evolution of the Izu-Bonin-Mariana (IBM) intra-oceanic arc-basin system. The oldest sedimentary rocks in the 50 m above igneous basement may correspond to the time of subduction initiation to the east. They are lithologically complex, consisting of a mix of variably tuffaceous mudstone, sandstone and breccia-conglomerate with some basaltic andesite passing upsection into 50 m of reddish-brown, radiolarian-bearing hemipelagic mudstone with thin volcaniclastic siltstone to sandstone beds. Coarser volcaniclastic rocks (andesitic average whole rock composition) then dominate the overlying section from 1360 to 160 mbsf. Variably graded tuffaceous sandstone to conglomerate and breccia beds range from a few cm to 9 m in thickness and exhibit a wide range of bedding contact relationships and sedimentary structures, including partial to complete Bouma sequences. Gravel to silt-sized volcaniclastic sediment was likely delivered to the site by gravity flows ranging from low- to high-concentration turbidity currents to debris flows. The depositional setting was ~ 50 km from the main arc front (Palau-Kyushu Ridge, PKR), so these may represent very distal apron to fan deposits. The sharp decline in coarse volcanic sediment supply and switch to hemipelagic mud accumulation at ~160mbsf is coincident with the C. 25 Ma transformation of the KPR to a remnant arc by backarc spreading in the adjacent Shikoku Basin and the eastward migration of magmatic arc activity to the IBM.

  5. Annual biomarker record for export production in the central Arabian Sea

    NASA Astrophysics Data System (ADS)

    Prahl, Fredrick G.; Dymond, Jack; Sparrow, Margaret A.

    The record for plankton biomarkers in sediment trap samples from a one-year experiment in the central Arabian Sea (AS4: 15°59'N 61°30'E) shows variations that reflect changing biological conditions in surface waters. Particulate fluxes of C 37-39 alkenones, highly branched C 25 isoprenoids (HBI), dinosterol, nC 28 12-hydroxy fatty acid, 24-ethylcholesterol, and a C 30-34 series of pentacyclic triterpanols all displayed distinct maxima at the start and stop of the Northeast (NE) and Southwest (SW) Monsoons. Surface mixing conditions changed rapidly at these times, altering light and nutrient availability, thereby triggering these biomarker signals of export production. Temporal offsets noted in individual biomarker concentrations (per g total organic carbon) at the start of the SW Monsoon suggest succession occurs in the phytoplankton community contributing to organic matter export. Comparable offsets were neither apparent at the start of the less dynamic NE Monsoon nor at the end of the NE or SW Monsoons. Broad concentration maxima for HBI also were observed at the beginning and end of the time-series during the relatively quiescent Fall Intermonsoon period when such features were conspicuously absent for other biomarkers. HBI are reputed biomarkers of Rhizoselenia and Haslea spp., two recognized dominants of diatom biomass in the Arabian Sea. These peaks in biomarker concentration could reflect either changes in the relative proportion of specific organisms that contribute to the upper ocean productivity or enhanced preservation of the biomarkers during times of high export production. In either case, the biomarker record in sediment traps reflects important changes in the biological condition of the upper ocean. All biomarkers except HBI were measurable in surface sediments deposited beneath the trap site. Comparison with concentrations in average sediment trap particles showed each was sensitive to significant (˜99%) degradation, displaying depletion factors

  6. A century long sedimentary record of anthropogenic lead (Pb), Pb isotopes and other trace metals in Singapore.

    PubMed

    Chen, Mengli; Boyle, Edward A; Switzer, Adam D; Gouramanis, Chris

    2016-06-01

    Reconstructing the history of metal deposition in Singapore lake sediments contributes to understanding the anthropogenic and natural metal deposition in the data-sparse Southeast Asia. To this end, we present a sedimentary record of Pb, Pb isotopes and eleven other metals (Ag, As, Ba, Cd, Co, Cr, Cu, Ni, Tl, U and Zn) from a well-dated sediment core collected near the depocenter of MacRitchie Reservoir in central Singapore. Before the 1900s, the sedimentary Pb concentration was less than 2 mg/kg for both soil and sediment, with a corresponding (206)Pb/(207)Pb of ∼1.20. The Pb concentration increased to 55 mg/kg in the 1990s, and correspondingly the (206)Pb/(207)Pb decreased to less than 1.14. The (206)Pb/(207)Pb in the core top sediment is concordant with the (206)Pb/(207)Pb signal of aerosols in Singapore and other Southeast Asian cities, suggesting that Pb in the reservoir sediment was mainly from atmospheric deposition. Using the Pb concentration in the topmost layer of sediment, the estimated atmospheric Pb flux in Singapore today is ∼1.6 × 10(-2) g/m(2) yr. The concentrations of eleven other metals preserved in the sediment were also determined. A principal component analysis showed that most of the metals exhibit an increasing trend towards 1990s with a local concentration peak in the mid-20(th) century. PMID:26967352

  7. Sedimentary and microbial record of the Middle/Late Ordovician phosphogenetic episode in the northern Holy Cross Mountains, Poland

    NASA Astrophysics Data System (ADS)

    Trela, Wiesław

    2008-01-01

    Numerous phosphorite beds and phosphatic nodules occur in the upper Middle and lower Upper Ordovician carbonate-shale succession of the Bukowiany Formation outcropping in the northern Holy Cross Mountains, central Poland. The vertical stacking pattern of this succession indicates that phosphatic and accompanying strata reflect a conformable sedimentary succession accumulated during a rise of relative sea level. The base of the Bukowiany Formation is marked by a conspicuous phosphorite horizon revealing a low net sediment accumulation rate reflecting a switch into a mesotrophic ecological system. This horizon was produced by reworking and redeposition of pristine phosphate sediment (e.g. by currents activity) during the late Darriwilian transgression. The overlying sedimentary record appears to reflect nucleation of the phosphate phase in the sediment-water interface and its subsequent burial by the accompanying sediment. The phosphatized tiny stromatolites and nodules preserved within the Bukowiany Formation indicate that benthic microbial communities played an important role in redistribution and concentration of phosphate during deposition of this succession.

  8. Geophysical borehole logging for control of driller's records: hydrogeological case study from Voltaian sedimentary rocks in northern Ghana

    NASA Astrophysics Data System (ADS)

    Agyekum, William; Klitten, Kurt; Armah, Thomas; Banoeng-Yakubo, Bruce; Amartey, Edmund Okoe

    2013-06-01

    The low borehole yielding potential and the high drilling failure rate of the Voltaian sedimentary rocks of Northern Ghana have been of concern to many local hydrogeologists and international donors. Consequently, several donor-supported projects have been instituted within the last few years with the view to study the hydrogeological characteristics of this `difficult' rock system. One such project is the geophysical borehole logging of 13 boreholes drilled into the Voltaian sedimentary rocks of Northern Ghana to enhance detailed hydrogeological assessment. Natural gamma detectors embedded in the five exploratory logging tools employed for the study ensured depth control by comparing their individual gamma log signatures. The combined gamma and formation resistivity/conductivity response logs provided more detailed lithological information than were shown in the driller's/geologist's logs. Significant discrepancies between the logging results and the reported drilled depths, construction depths, and screen settings were observed in seven of the thirteen investigated boreholes. Thus, the reliability of driller's borehole records seems questionable, which will hamper hydrogeological studies and the mapping of groundwater resources. Further, it may be supposed that the productivity of most wells in Ghana is compromised by poor depth control of screen placement.

  9. Tracing late Quaternary tropical wetland dynamics in the Congo catchment using microbial biomarker records from deep sea fan sediments

    NASA Astrophysics Data System (ADS)

    Spencer-Jones, Charlotte Louise; Schefuβ, Enno; Wagner, Thomas; Handley, Luke; Talbot, Helen Marie

    2014-05-01

    Methane is a climatically active gas with a global warming potential 72 time that of CO2 over 20 years. Release of methane into the atmosphere has been suggested as a potential source of warming in palaeoclimate studies. This has implications for future climate as increased global temperatures could destabilise sources of sedimentary methane releasing it to the atmosphere. It is therefore important to establish the possible sinks of methane that could attenuate methane emissions. We present a high resolution record from the Congo deep sea fan (ODP 1075) of amino-bacteriohopanepolyols (amino-BHPs). The methanotrophic source of aminopentol, a biomarker for aerobic methane oxidation (AMO), in ODP 1075 is supported by compound specific δ13C isotope values of -41‰ for aminopentol precursors. High resolution intervals of isotope stages 10 to 13 (~500 to ~400 kyrs BP) confirm aminopentol to vary on glacial-interglacial timescales. High concentrations of amino-BHPs are recorded during warm, interglacial stages 11 and 13 with low concentrations of amino-BHPs during cold, glacial stages 10 and 12. This increase in AMO intensity (as suggested by aminopentol concentrations) during stages 11 and 13 is likely an imported signature from the Congo hinterland. Sediments analysed for amino-BHPs from floodplain wetlands show similar biomarker signatures as the marine sediments, suggesting a common source. Wetlands are important and widespread sub-environments in all large tropical river catchments. Their extent responds to fluctuations in humidity, which changes at glacial-interglacial and shorter time scales in response to the level of humidity. Humidity in the interior of tropical Africa has been shown to be driven by fluctuations in the difference in sea surface temperature (SST) between the subtropical and tropical South Atlantic (Schefuss et al., 2004). D-SST profiles based on UK 37 from the Angola (ODP 1082) and Congo basins (ODP 1077, Geob 1082) show an inverse relationship

  10. Sedimentary record of Pleistocene paleodoline evolution in the Ebro basin (NE Spain)

    NASA Astrophysics Data System (ADS)

    Luzón, A.; Pérez, A.; Soriano, M. A.; Pocoví, A.

    2008-03-01

    Pleistocene fluvial deposits of the Ebro River, in NE Spain, are widely affected by faults, fractures and tilting of beds. Based on the lithological, geometrical and textural features of these deposits, seven architectural elements have been differentiated. Gravel Bars (GB), Gravel-filled Channels (CH), Sheets and Channel-fill Sands (SB), are the most common elements and, together with less frequent Overbank Fines (FF), characterize a gravel-dominated braided fluvial system. Gravel Lobes (GL) that draw progressive unconformities and are laterally related to U-shaped or basin-form mud deposits, Sediment Gravity Flow deposits (SG), and Sands with Slumps and Convolute Bedding (SGS), are not typical architectural elements of braided fluvial environments and they are interpreted in this work as related to syn-sedimentary deformation. Our research proves that deformation is due to dissolution of the underlying Tertiary evaporites with genesis of dolines. The development of these karst structures involved both subsidence and sudden collapses that affected previous fluvial sediments. Small depressions (dolines) generated that were progressively filled by syn-sedimentary deformed detrital deposits. A model for the evolution of the doline fills is purposed that envisages several stages: 1) gravitational processes caused remobilisation of previous fluvial gravels that were dragged to the created depression, 2) flooding of the depression and development of a backswamp area that was progressively filled by fine sediments and gravel lobes as a consequence of the overflow of nearby channels, 3) gravel lobes draw progressive unconformities revealing several subsidence episodes related to dissolution, dragging and compaction, 4) non-deformed fluvial facies at the top of the series mark the end of the karstification influence. OSL (Optically Stimulated Luminiscence) ages, the first from the terraces of the Ebro River, demonstrate that karst has developed in this area at least since

  11. Aliphatic biomarkers and their signal from two hydrogeochemically differing sedimentary environments of the Tertiary Krepoljin Coal Basin (Serbia)

    NASA Astrophysics Data System (ADS)

    Dević, Gordana J.; Popovic, Zoran

    2010-05-01

    The sediments of the coal-bearing series of the Tertiary Krepoljin Brown Coal Basin have been investigated and presented in this manuscript. The samples of the intercalated mixed sediments (pieces of coal in clays, sandstones and shales) originate from two hydrogeochemically differing sedimentary environments: the illite-montmorillonitic (IM), and the calcitic (Ct) environment. The characteristics of the early diagenetic processes which influenced the composition of the organic matter of this sediment were assessed by the statistical correlation analysis and multivariate principal component analysis. The precursor material of higher plants gymnosperms had a significant influence on the overall organic matter of mixed sediments in both hydrochemical environments. A weak effect of N/C ratios on the specific diagenetic transformations of hopanoid molecules is noticed in the samples of the calcite environment. Sterane maturation transformations are not marked as significant for the samples of mixed sediments by the component analysis. The samples of I-M environments show a strong inhibitory effect on the processes of diastereoisomerization.

  12. Contrasting glacial/interglacial regimes in the western Arctic Ocean as exemplified by a sedimentary record from the Mendeleev Ridge

    USGS Publications Warehouse

    Polyak, L.; Curry, W.B.; Darby, D.A.; Bischof, J.; Cronin, T. M.

    2004-01-01

    Distinct cyclicity in lithology and microfaunal distribution in sediment cores from the Mendeleev Ridge in the western Arctic Ocean (water depths ca. 1. 5 km) reflects contrasting glacial/interglacial sedimentary patterns. We conclude that during major glaciations extremely thick pack ice or ice shelves covered the western Arctic Ocean and its circulation was restricted in comparison with interglacial, modern-type conditions. Glacier collapse events are marked in sediment cores by increased contents of ice-rafted debris, notably by spikes of detrital carbonates and iron oxide grains from the Canadian Arctic Archipelago. Composition of foraminiferal calcite ?? 18O and ??13C also shows strong cyclicity indicating changes in freshwater balance and/or ventilation rates of the Arctic Ocean. Light stable isotopic spikes characterize deglacial events such as the last deglaciation at ca. 12 14C kyr BP. The prolonged period with low ??18O and ??13C values and elevated contents of iron oxide grains from the Canadian Archipelago in the lower part of the Mendeleev Ridge record is interpreted to signify the pooling of freshwater in the Amerasia Basin, possibly in relation to an extended glaciation in arctic North America. Unique benthic foraminiferal events provide a means for an independent stratigraphic correlation of sedimentary records from the Mendeleev Ridge and other mid-depth locations throughout the Arctic Ocean such as the Northwind and Lomonosov Ridges. This correlation demonstrates the disparity of existing age models and underscores the need to establish a definitive chronostratigraphy for Arctic Ocean sediments. ?? 2003 Elsevier B.V. All rights reserved.

  13. Repeated fault rupture recorded by paleoenvironmental changes in a wetland sedimentary sequence ponded against the Alpine Fault, New Zealand

    NASA Astrophysics Data System (ADS)

    Clark, K.; Berryman, K. R.; Cochran, U. A.; Bartholomew, T.; Turner, G. M.

    2010-12-01

    cycles were repeated 18 times at Hokuri Creek. Evidence that fault rupture was responsible for the cyclical paleoenvironmental changes at Hokuri Creek include: the average time period for each organic- and clastic-rich couplet to be deposited approximately equals the long-term average Alpine Fault recurrence interval, and the most recent events recorded at Hokuri correlate to an earthquake dated in paleoseismic trenches 100 km along strike; fault rupture is the only mechanism that can create accommodation space for 18 m of sediment to accumulate, and the sedimentary units can be traced from the outcrop to the fault trace and show tectonic deformation. The record of 18 fault rupture events at Hokuri Creek is one of the longest records of surface ruptures on a major plate boundary fault. High-resolution dating and statistical treatment of the radiocarbon data (Biasi et al., this meeting) has resulted in major advances in understanding the long-term behaviour of the Alpine Fault (Berryman et al., this meeting).

  14. Sedimentary Record of syn- and Post-Glacial Climate Change Along the Former LGM ice Terminus, Flathead Lake, Montana

    NASA Astrophysics Data System (ADS)

    Hendrix, M. S.; Hofmann, M.; Moore, J. N.; Sperazza, M.

    2006-12-01

    Located west of the continental divide at the former LGM terminal position of the Flathead Lobe of the Cordilleran Ice Sheet, Flathead Lake (Montana) contains a well preserved record of syn- and post-glacial Quaternary sedimentation. We have studied this record through a combination of geologic mapping around the lake margins, 3.5 kHz and lower frequency seismic reflection profiling of lake sediments, and coring of the lake floor. The oldest part of the Quaternary sedimentary record comprises ice-contact till exposed along the lake basin margins and imaged in deep seismic reflection profiles. Sedimentary facies and geomorphology of the terminal moraine suggest that the Flathead Lobe flowed into a major proglacial lake, probably glacial Lake Missoula. The oldest core sediments recovered from the lake basin consist of a series of clay-rich glacial varves that thin- and fine-upward. These are overlain by a series of anomalously coarse silt beds, each containing a sharp base, upward fining grain size, and lakewide distribution. Depositional age of these beds is constrained as between 14,150±150 cal. Yr BP (14C date on a pine needle below the beds) and 13,180±120 cal. Yr BP (Glacier Peak tephra above the beds). We interpret the silt beds to reflect pulses of sediment delivered to the Flathead Lake basin by high discharge flood events associated with rapid retreat of the Flathead Lobe and possible rapid release of proglacial melt water from upstream tributary valleys dammed by the Flathead Lobe. The transition of Flathead Lake from a proglacial lake to the modern oligotrophic lake system took place shortly after deposition of the Glacier Peak tephra. Interestingly, none of our 8 deep piston cores display an obvious Younger Dryas sedimentologic signal. Holocene core records, combined with information from 3.5 kHz seismic data, indicate periods of significant lake level fluctuation that are likely climate-driven. Of these, the most significant lake drawdown immediately

  15. Reconstruction of past glacier calving and oceanographic variability in Southeast Greenland from marine sedimentary records

    NASA Astrophysics Data System (ADS)

    Andresen, C. S.; Hansen, M. J.; Seidenkrantz, M.; Kuijpers, A.; Noergaard-Pedersen, N.

    2011-12-01

    The Greenland ice sheet is one of the most significant water contributors to the rising global sea level, and therefore there are concerns about its long term stability. However, prediction of its contribution to global sea-level rise is complicated by lack of knowledge about mechanisms behind ice sheet change. In particular ice streams and their interaction with components of the atmospheric and oceanic climate system needs further investigation in order to make realistic models of future sea level rise. Previous studies indicate a link between acceleration of fast-flowing outlet glaciers and temperature rise in near-by (subsurface) ocean waters on short-term timescales (Holland et al. 2008) and longer-term timescales (Andresen et al. 2011) by Jakobshavn Glacier in West Greenland. The SEDIMICE project ('Linking sediments with ice-sheet response and glacier retreat in Southeast Greenland') investigates past outlet glacier fluctuations in Southeast Greenland in the region from Sermilik Fjord by Helheim Glacier to Bernstorffs Fjord further south. The aim is to extend the knowledge from observational time series further back in time by analysing sediment cores retrieved from fjords by outlet glaciers and from the shelf. The sediment cores are dated and the past iceberg rafting is reconstructed on the basis of sediment grain size (IRD, ice rafted debris from icebergs). We also aim at investigating the palaeoceanographic conditions from the content of biomarkers and analysis of benthic foraminifera content can be used to reconstruct subsurface water variability on the shelf. These studies allow us to evaluate the latest 4000-5000 years - and in details the latest c. 100 years - of interaction between oceanographic variability and glacier calving.

  16. Dynamics of the anoxygenic phototrophic community in meromictic Fayetteville Green Lake (NY) and the associated sedimentary pigment record

    NASA Astrophysics Data System (ADS)

    Meyer, K. M.; Fulton, J. M.; Hunter, S.; Macalady, J. L.; Kump, L.; Freeman, K. H.

    2012-12-01

    Photosynthetic pigments and their diagenetic products in marine sedimentary rocks hold important clues about recent and ancient variability in the Earth's surface environment. The chemical relicts of carotenoids from anoxygenic sulfur bacteria are of particular interest to geoscientists because of their potential to signal episodes of marine photic-zone euxinia such as those proposed for extended periods in the Proterozoic as well as brief intervals during the Phanerozoic. It is therefore critical to constrain the environmental and physiological factors that influence carotenoid production and preservation in modern environments. Our work in redox stratified, microbially dominated Fayetteville Green Lake (New York) has spanned the past decade and included seasonal (2005-2006) and monthly (2011) pigment monitoring in the water column, as well as a coupled pigment and nucleic acid clone library analyses from planktonic and benthic samples in 2006. Populations of photosynthetic bacteria in the water column are dynamic on monthly and annual scales. In 2011, purple sulfur bacteria (PSB) and green sulfur bacteria (GSB) were most abundant in spring and fall, respectively, responding to environmental conditions. PSB are diverse both at the chemocline and in benthic mats below oxygenated shallow waters, with different PSB species inhabiting the two environments. Okenone (from PSB) is an abundant carotenoid in both the chemocline waters and in benthic mats. GSB and their primary pigment Bchl e are also represented in and below the chemocline. However, the water column and sediments contain only trace concentrations of the GSB carotenoid isorenieratene, with concentrations relative to Bchl e being at least two orders of magnitude lower than we have observed in other meromictic lakes. Sediments deposited over the past ~550 years also reveal decadal to centennial scale variability in pigment production in the water column, possibly associated with hypothesized climatic and

  17. Sedimentary organic biomarkers suggest detrimental effects of PAHs on estuarine microbial biomass during the 20th century in San Francisco Bay, CA, USA.

    PubMed

    Nilsen, Elena B; Rosenbauer, Robert J; Fuller, Christopher C; Jaffe, Bruce J

    2015-01-01

    Hydrocarbon contaminants are ubiquitous in urban aquatic ecosystems, and the ability of some microbial strains to degrade certain polycyclic aromatic hydrocarbons (PAHs) is well established. However, detrimental effects of petroleum hydrocarbon contamination on nondegrader microbial populations and photosynthetic organisms have not often been considered. In the current study, fatty acid methyl ester (FAME) biomarkers in the sediment record were used to assess historical impacts of petroleum contamination on microbial and/or algal biomass in South San Francisco Bay, CA, USA. Profiles of saturated, branched, and monounsaturated fatty acids had similar concentrations and patterns downcore. Total PAHs in a sediment core were on average greater than 20× higher above ∼200 cm than below, which corresponds roughly to the year 1900. Isomer ratios were consistent with a predominant petroleum combustion source for PAHs. Several individual PAHs exceeded sediment quality screening values. Negative correlations between petroleum contaminants and microbial and algal biomarkers - along with high trans/cis ratios of unsaturated FA, and principle component analysis of the PAH and fatty acid records - suggest a negative impacts of petroleum contamination, appearing early in the 20th century, on microbial and/or algal ecology at the site. PMID:25303655

  18. Sedimentary and chemostratigraphic record of climatic cycles in Lower Pliensbachian marl-limestone platform successions of Asturias (North Spain)

    NASA Astrophysics Data System (ADS)

    Bádenas, Beatriz; Aurell, Marc; Armendáriz, Maider; Rosales, Idoia; García-Ramos, José Carlos; Piñuela, Laura

    2012-12-01

    A combined sedimentological, lithological and chemostratigraphical (Mg/Ca, δ13C, δ18O) analysis of the Lower Pliensbachian marl-limestone platform successions exposed along the Asturias coastline (northern Spain) has resulted in the characterization of high-frequency cycles. The highest-order sedimentary cycles (i.e. elementary cycles) are centimeter- to deciemeter-thick alternations of bioclastic and muddy laminated/burrowed facies, which do not match the marl-limestone couplets. They encompass three sedimentary stages: deposition from storm-density currents (bioclastic facies), dominant lateral advection of continental terrigenous mud accumulated on to an oxygen-deficient seafloor (laminated facies), and recovery of bottom oxygenation involving the burrowing of laminated sediments (burrowed facies). The close match between the number of elementary cycles recorded during the Jamesoni Subzone in Asturias and Yorkshire (Northern England) gives support to the idea of the influence of a regional climatic factor (i.e. millennial-scale cyclicity). Decimeter- to meter-scale cycles formed by bundles of elementary cycles are thought to record orbitally driven climatic changes (precession or obliquity, depending on the time calibration considered). Lower hemicycles of bundles are dominated by marls/calcareous mudstones, with decreasing burrowing and eventual preservation of laminated facies. They formed during humid periods, which controlled an increase in freshwater and terrigenous input to the platform and quasi-estuarine circulation promoting bottom-anoxia. Upper hemicycles of bundles are dominated by burrowed and bioclastic limestones, thought to be formed under arid conditions with anti-estuarine circulation and an increase of shallow carbonate production and offshore resedimentation. Chemostratigraphic data from belemnites recorded in the muddy laminated and burrowed facies indicate that significant concomitant shifts in δ13C and δ18O occurred during the lower

  19. Integrating satellite observations and modern climate measurements with the recent sedimentary record: An example from Southeast Alaska

    NASA Astrophysics Data System (ADS)

    Addison, Jason A.; Finney, Bruce P.; Jaeger, John M.; Stoner, Joseph S.; Norris, Richard D.; Hangsterfer, Alexandra

    2013-07-01

    Assessments of climate change over time scales that exceed the last 100 years require robust integration of high-quality instrument records with high-resolution paleoclimate proxy data. In this study, we show that the recent biogenic sediments accumulating in two temperate ice-free fjords in Southeast Alaska preserve evidence of North Pacific Ocean climate variability as recorded by both instrument networks and satellite observations. Multicore samples EW0408-32MC and EW0408-43MC were investigated with 137Cs and excess 210Pb geochronometry, three-dimensional computed tomography, high-resolution scanning XRF geochemistry, and organic stable isotope analyses. EW0408-32MC (57.162°N, 135.357°W, 146 m depth) is a moderately bioturbated continuous record that spans AD ˜1930-2004. EW0408-43MC (56.965°N, 135.268°W, 91 m depth) is composed of laminated diatom oozes, a turbidite, and a hypopycnal plume (river flood) deposit. A discontinuous event-based varve chronology indicates 43MC spans AD ˜1940-1981. Decadal-scale fluctuations in sedimentary Br/Cl ratios accurately reflect changes in marine organic matter accumulation that display the same temporal pattern as that of the Pacific Decadal Oscillation. An estimated Sitka summer productivity parameter calibrated using SeaWiFS satellite observations support these relationships. The correlation of North Pacific climate regime states, primary productivity, and sediment geochemistry indicate the accumulation of biogenic sediment in Southeast Alaska temperate fjords can be used as a sensitive recorder of past productivity variability, and by inference, past climate conditions in the high-latitude Gulf of Alaska.

  20. Linking Holocene sedimentary and water column records from Fiordland, New Zealand to westerly wind variability

    NASA Astrophysics Data System (ADS)

    Hinojosa, J.; Moy, C. M.; Wilson, G. S.; Stirling, C.

    2012-12-01

    The strength and latitudinal position of the Southern Hemisphere westerly winds play a fundamental role in the global carbon cycle by regulating Southern Ocean CO2 flux. Modeling studies predict that when the winds are centered over the Antarctic Circumpolar Current, carbon-rich deepwater is upwelled, enhancing CO2 outgassing to the atmosphere. When the winds shift north, atmospheric CO2 is entrained in downwelling intermediate waters, causing uptake processes to dominate. Resolving past westerly wind variability is crucial for evaluating the how the winds influence the the Southern Ocean CO2 sink along geologic timescales, yet broadly distributed paleoclimate records currently limit our ability to do so. We have begun a research program that aims to develop high-resolution records of the westerly winds throughout the Holocene using sediment cores from Fiordland, New Zealand. Fiordland is one of two regions globally that intersects the northern reach of the modern wind field maximum and there is a strong relationship between the strength of the overlying winds and the amount of precipitation falling at interannual timescales. The New Zealand fjords offer high sedimentation rate (>1mm/yr) in sub-oxic to anoxic basins that can yield high-resolution sediment records of climate, environmental, and hydrographic change. In April 2012, we collected seismic data, surface sediment, water column samples, and multiple piston cores from Doutbful Sound, Dagg Sound, Dusky Sound, and Preservation Inlet with the University of Otago research vessel Polaris II. We characterized the physical oceanography of the fjords with multiple CTD casts and measured dissolved oxygen concentrations to determine the extent of anoxia within selected sub-basins. We also characterized the relative input of marine and terrestrial sources using carbon and nitrogen concentration and isotope variations and macrofossil identification. From this preliminary work, and our understanding of regional climate

  1. A 220 ka terrestrial δ18O and deuterium excess biomarker record from an eolian permafrost paleosol sequence, NE-Siberia

    NASA Astrophysics Data System (ADS)

    Tuthorn, Mario; Zech, Michael; Detsch, Florian; Rozanski, Kazimierz; Zech, Roland; Zöller, Ludwig; Zech, Wolfgang; Glaser, Bruno

    2013-04-01

    The natural abundances of stable oxygen (18O/16O) and hydrogen isotopes (D/H) are valuable proxies of climate changes in the past. Yet, to date no continuous δ18O and only few δD records are available from loess-paleosol sequences. Taking advantage of a recently developed method based on compound-specific δ18O analyzes of hemicellulose sugar biomarkers in soils (Zech and Glaser, 2009), we here present a first terrestrial δ18O biomarker record from an eolian permafrost paleosol sequence in NE-Siberia that covers the last ~220 ka. The δ18O values of the hemicellulose biomarkers arabinose and xylose range from 22.5 to 32.8‰ and from 21.3 to 31.9‰, respectively, and reveal systematic glacial - interglacial shifts. The modern topsoil and the interglacial paleosols exhibit more positive δ18O values, whereas the glacial paleosols are characterized by more negative δ18O values. This is in agreement with the δD record obtained for sedimentary n-alkane leaf wax biomarkers. We present a conceptual model for interpreting the combined δ18O and δD biomarker record. Based on this model, we suggest that both our δ18O and the δD record primarily reflect the temperature-controlled isotopic composition of paleoprecipitation modified by evaporative isotope enrichment of leaf water during transpiration. Considering fractionation factors during sugar and n-alkane biomarker biosynthesis allows reconstructing the leaf water isotopic composition and the deuterium excess of the leaf water. The deuterium excess may serve as proxy for evaporative enrichment and allows calculating relative humidity using a Craig-Gordon model. Accordingly, relative humidity in NE-Siberia was higher during marine isotope stage (MIS) 6 compared to MIS 2, 4 and 5d and thus could help explaining the much larger extent of the Late Saalian glaciation compared to the Weichselian glaciations. Using the Craig-Gordon model, we also calculated δ18O of the plant source water (δ18Osource water), which can

  2. Ecosystem disturbances in Central European spruce forests: a multi-proxy integration of dendroecology and sedimentary records

    NASA Astrophysics Data System (ADS)

    Clear, Jennifer; Chiverrell, Richard; Kunes, Petr; Svoboda, Miroslav; Boyle, John

    2016-04-01

    Disturbance dynamics in forest ecosystems shows signs of perturbation in the light of changing climate regimes with the frequency and intensity of events (e.g. pathogens in North America and Central Europe) amplified, becoming more frequent and severe. The montane Norway spruce (Picea abies) dominated forests of Central Europe are a niche habitat and environment; situated outside their natural boreal distribution (e.g. Fenno-Scandinavia). These communities are at or near their ecological limits and are vulnerable to both short term disturbances (e.g. fire, windstorm and pathogens) and longer-term environmental change (e.g. climate induced stress and changing disturbance patterns). Researches have linked negative impacts on spruce forest with both wind disturbance (wind-throw) and outbreaks of spruce bark beetle (Ips typographus), and there is growing evidence for co-association with wind damage enhancing pathogenic outbreaks. Examples include: in the Bohemian Forest (Czech Republic) the mid-1990s spruce bark beetle outbreak and the 2007 windstorm and subsequent bark beetle outbreak. In the High Tatra Mountains (Slovakia) there is a further co-association of forest disturbance with windstorms (2004 and 2014) and an ongoing bark beetle outbreak. The scale and severity of these recent outbreaks of spruce bark beetle are unprecedented in the historical forest records. Here, findings from ongoing research developing and integrating data from dendroecological, sedimentary palaeoecological and geochemical time series to develop a longer-term perspective on forest dynamics in these regions. Tree-ring series from plots or forest stands (>500) are used alongside lake (5) and forest hollow (3) sediments from the Czech and Slovak Republics to explore the local, regional and biogeographical scale of forest disturbances. Dendroecological data showing tree-ring gap recruitment and post-suppression growth release highlight frequent disturbance events focused on tree or forest

  3. High Resolution Environmental Magnetic Study of a Holocene Sedimentary Record from Zaca Lake, Ca

    NASA Astrophysics Data System (ADS)

    Platzman, E. S.; Lund, S.; Kirby, M. E.; Feakins, S. J.

    2012-12-01

    Magnetic studies of Holocene lake sediments recovered from Zaca lake have yielded a 3000-year high resolution record of environmental variability and paleolimnology. Zaca lake is a small oligomictic lake ~12m deep situated 730 m above sea level in the steep canyons of the San Rafael mountains, NW of Santa Barbara. Throughout much of the year Zaca lake is anaerobic below 7m. Hydrogen sulfide, fed into the lake via runoff and local sulphur springs, is present throughout the hypolimnion with concentrations sometime exceeding 30 mg/ l. During the summer months when the lake is stratified, light colored carbonate rich microlaminae are formed; and often during the winter months when the lake overturns, killing the anaerobic bacteria, black microlamina rich in iron sulfide are deposited on the lake floor, creating a stratigraphy reflecting patterns of environmental variability on annual to millennial scales. Samples for magnetic analysis were obtained from 8.5 m of core recovered from the central region of Zaca lake. Ages, constrained using radiocarbon chronostratigraphy, yielded sedimentation rates of 2-10 mm/yr with an average rate of 3 mm per yr over the 3000 yr interval. Parameters reflecting decadal scale variability in magnetic concentration (susceptibility, ARM, SIRM) and grainsize (ARM/Chi) were measured every 2 cm. Additional rock magnetic tests, including thermal demagnetization of three component IRM, were applied at selected intervals to constrain the magnetic mineralogy. These data were combined with analyses of clastic grain size, % calcium carbonate and % organics to create a multiproxy record of environmental variability. Results show that Zaca lake has had a complex depositional history. Anthropogenic effects associated with European colonization are present in the upper meters. Most notable, however, is a dramatic shift in the magnetic parameters and mineralogy between the upper and lower half of the core (circa 1300 ybp) indicating a shift in regime

  4. Selective preservation of organic matter in marine environments; processes and impact on the sedimentary record

    NASA Astrophysics Data System (ADS)

    Zonneveld, K. A. F.; Versteegh, G. J. M.; Kasten, S.; Eglinton, T. I.; Emeis, K.-C.; Huguet, C.; Koch, B. P.; de Lange, G. J.; de Leeuw, J. W.; Middelburg, J. J.; Mollenhauer, G.; Prahl, F. G.; Rethemeyer, J.; Wakeham, S. G.

    2010-02-01

    The present paper is the result of a workshop sponsored by the DFG Research Center/Cluster of Excellence MARUM "The Ocean in the Earth System", the International Graduate College EUROPROX, and the Alfred Wegener Institute for Polar and Marine Research. The workshop brought together specialists on organic matter degradation and on proxy-based environmental reconstruction. The paper deals with the main theme of the workshop, understanding the impact of selective degradation/preservation of organic matter (OM) in marine sediments on the interpretation of the fossil record. Special attention is paid to (A) the influence of the molecular composition of OM in relation to the biological and physical depositional environment, including new methods for determining complex organic biomolecules, (B) the impact of selective OM preservation on the interpretation of proxies for marine palaeoceanographic and palaeoclimatic reconstruction, and (C) past marine productivity and selective preservation in sediments. It appears that most of the factors influencing OM preservation have been identified, but many of the mechanisms by which they operate are partly, or even fragmentarily, understood. Some factors have not even been taken carefully into consideration. This incomplete understanding of OM breakdown hampers proper assessment of the present and past carbon cycle as well as the interpretation of OM based proxies and proxies affected by OM breakdown. To arrive at better proxy-based reconstructions "deformation functions" are needed, taking into account the transport and diagenesis-related molecular and atomic modifications following proxy formation. Some emerging proxies for OM degradation may shed light on such deformation functions. The use of palynomorph concentrations and selective changes in assemblage composition as models for production and preservation of OM may correct for bias due to selective degradation. Such quantitative assessment of OM degradation may lead to more

  5. Late Devonian sedimentary record of the Paleotethys Ocean - The Mae Sariang section, northwestern Thailand

    NASA Astrophysics Data System (ADS)

    Königshof, P.; Savage, N. M.; Lutat, P.; Sardsud, A.; Dopieralska, J.; Belka, Z.; Racki, G.

    2012-06-01

    An 11 m thick condensed sequence of Late Devonian limestones in northwestern Thailand exhibits faunal associations and sedimentological-/microfacies data which are indicative of a pelagic facies setting. The entire long-ranging section is completely free from clastic input. Similar successions are known worldwide in a few sections only. The Mae Sariang section is characterised by low sedimentation rates as recognised by a number of hardgrounds, neptunian dikes and Fe/Mn crusts. The succession comprises a number of pelagic faunal elements e.g. conodonts, cephalopods and pelagic ostracodes. The fauna records rare macrofossils and the faunal diversity is low. The very condensed section ranges from the Late rhenana to praesulcata conodont biozones, but contains some global events as undoubtedly shown by biostratigraphical and carbon-isotope results (including major Kellwasser and Hangenberg biotic crises). In terms of plate tectonics this important succession most probably belongs to the Inthanon Zone comprising remnants of the Paleotethys Ocean.

  6. Biospheric traumas caused by large impacts and predicted relics in the sedimentary record

    NASA Technical Reports Server (NTRS)

    Prinn, R. G.; Fegley, B., Jr.

    1988-01-01

    When a large asteroid or comet impacts the Earth the supersonic plume ejected on impact causes severe shock heating and chemical reprocessing of the proximal atmosphere. The resultant NO is converted rapidly to NO2, foliage damage due to exposure to NO2 and HNO3, toxicosis resulting from massive mobilization of soil trace metals, and faunal asphyxiation due to exposure to NO2. One class of relic evidence for the above effects arises because extinction of species caused by these chemically induced traumas would be selective. A second class of relic evidence arises because the acid rain will cause massive weathering of continental rocks and soils characterized by large ratios of the relatively insoluble metals, to the more soluble metals. This weathering would be best recorded in fossils in unperturbed deltaic, neritic, or limnetic sediments and for metals with very long oceanic residence times in deep ocean sediments as well. This evidence is discussed.

  7. Climate Forcing on the Sedimentary Pb Isotope Record of the Equatorial Atlantic

    NASA Astrophysics Data System (ADS)

    Abouchami, W.; Zabel, M.

    2001-12-01

    The forcing mechanism for the radiogenic isotopes variations recorded in marine sediments over the past few million years remains debatable and a causal link between isotope tracers and climate is difficult to ascertain. We report evidence for a climate control on Pb sources to the Equatorial Atlantic using high precision Pb triple spike data (Galer, 1999) on two sediments cores covering the last six Marine Isotope Stages ( ~200 ka). Core GeoB1523-1 (3° 49,9'N, 41° 37.3'W, 3292m) is located on the Ceará Rise (West Atlantic) close to the Amazon mouth and core GeoB2910-1 (4° 50.7'N, 21° 03.2'W, 2703m) on the Sierra Leone Rise (East Atlantic) on the downwind trajectory of the boreal winter Saharan dust plume. These cores are ideally situated for monitoring climate-related Pb isotopic variations, since they have been shown to record past variations in terrigenous fluxes in response to Earth's orbital changes (Zabel et al., 1999; Rühlemann et al., 2001). Pb isotope data were obtained on bulk sediments which, given the two orders of magnitude difference in Pb contents of detritus ( ~10ppm) and carbonate (1-10ppb), will essentially reflect the composition of the terrigenous fraction. Pb isotope ratios display periodic fluctuations over the last ~200 ka in both cores and are quite distinct in the two basins. The east Atlantic core exhibits higher 207Pb/204Pb and 208Pb/204Pb but lower 206Pb/204Pb than the west Atlantic core. The Pb isotope signal is cyclical and closely follows the \\delta 18O record, interglacial periods being systematically more radiogenic than glacial periods. This pattern is observed in both cores, although changes in the western Atlantic seem to lead those in the eastern Atlantic. In Pb isotope space, the west Atlantic data form a unique Pb isotope array that is quite distinct from the east Atlantic where two trends are found. This clearly demonstrates that the Pb sources feeding the two basins are different. Furthermore, the persistence of a

  8. A potential relationship between molybdenum speciation and its isotopic signature in sedimentary records: New insights from old shales

    NASA Astrophysics Data System (ADS)

    Chappaz, A.; Reinhard, C.

    2015-12-01

    Molybdenum has emerged as a powerful paleo-indicator of sulfidic conditions in studies of the evolution of Earth's early oxygenation, either by examining patterns of Mo enrichment and/or the δ98Mo isotopic signature in sedimentary records. However, the processes leading to Mo incorporation in sulfidic sediments are still unknown, limiting its use as a proxy. The Mount McRae Shale, deposited ~2.5 billion years ago (Ga) in the Hamersley Basin, Western Australia, provides a unique opportunity to examine Earth surface conditions during the Archean just prior to the Great Oxidation Event, and an important example of the deep time application of Mo geochemistry. Trace element [1] and iron speciation [2] data measured in the upper shale interval indicate deposition under euxinic conditions and significant aqueous transport of redox-sensitive trace elements. δ98Mo measured in the upper euxinic interval of the Mt. McRae Shale ranges from 0.99 to 1.86 ‰ [3]. These heavy δ98Mo values have been attributed to the effects of oxidative weathering and adsorption of Mo to oxide mineral surfaces. To further explore the implications of these data and to identify possible mechanisms controlling Mo burial, we analyzed samples from the upper euxinic shale using XANES and EXAFS. First, our data suggest an association between Mo and organic matter implying that metamorphic processes have not altered this interval. Perhaps more surprisingly, we find a strong relationship between Mo speciation and δ98Mo isotopic signature (r2 = 0.90). We suggest an alternative mechanism for explaining the Mo isotope systematics of the upper Mt. McRae Shale involving Mo reduction. If correct, our results add new interpretive texture to sedimentary Mo isotope records and imply a primary role for speciation in the Mo isotope composition of sulfidic marine environments. [1] Anbar et al., 2007. Science 317, 1903-1906 [2] Reinhard et al. 2009. Science 326, 713-716 [3] Duan et al. 2010. GCA 74, 6655-6668

  9. A continental shelf sedimentary record of Little Ice Age to modern glacial dynamics: Bering Glacier, Alaska

    NASA Astrophysics Data System (ADS)

    Jaeger, John M.; Kramer, Branden

    2014-09-01

    The Bering Glacier System is the world's largest surging temperate glacier with seven events occurring over the past century under a range of north Pacific climatic conditions. Onshore records reveal changes in glacial termini positions and evidence of late Holocene glacial advances, but the Little Ice Age (LIA) record of potential glacial surging and associated flooding has not been examined. A 13.6 m-long jumbo core collected on the adjacent continental shelf reveals a 600-yr-long record of sedimentation associated with changing glacifluvial discharge. The chronology is based on 210Pb geochronology and five radiocarbon dates, and the core can be separated into three distinct lithologic units based on the examination of X-radiographs and physical properties: (1) an uppermost unit dating from ∼125 cal yr BP to the present characterized by bioturbated mud interbedded with laminated, thick (5-20 cm) low-bulk density clay-rich beds; (2) a middle unit dating from ∼120-400 cal yr BP that includes numerous interlaminated-to-interbedded low- and high-bulk density beds with infrequent evidence of bioturbation; thick laminated clay-rich beds are rare; (3) a lowermost unit that predates ∼400 cal yr BP and is composed of rare laminated beds grading down into mottled to massive mud. In each of these units, the laminated lithofacies from this mid-shelf location indicates both flood deposition and likely sediment transport in the wave-current bottom-boundary layer. The thick low-density, clay-rich beds in the uppermost unit correlate with historic outburst floods associated with known surge events. Based on previous terrestrial studies, the terminus was at its Holocene Neoglacial maximum extent close to the modern coastline at some point in the middle to late stages of the LIA in southern Alaska (100-350 cal yr BP). During the LIA, preservation of bioturbated intervals is rare while laminated intervals are common. This style of interbedding indicates frequent (<10 yr

  10. It's getting hot here - The Middle Eocene Climatic Optimum (MECO) in a terrestrial sedimentary record

    NASA Astrophysics Data System (ADS)

    Methner, K.; Wacker, U.; Fiebig, J.; Chamberlain, C.; Mulch, A.

    2013-12-01

    The Middle Eocene Climatic Optimum (MECO) represents an enigmatic global warming event during Cenozoic cooling that has been discovered in ocean drill cores from varying latitudes and oceanic basins. It is marked by a rapid negative shift in oxygen isotope ratios of foraminiferal calcite and thought to reflect the combined effects of freshwater input as well as an increase in sea surface and bottom water temperatures by up to 5 to 6 °C. MECO is therefore a temperature extreme during already warm Eocene climate. This makes the MECO to one of the hottest phases during Earth's climate history, yet it is largely unknown how MECO affected temperatures in the continental interiors as well as their rainfall and vegetation dynamics. Here, we present stable isotope (δ18O, δ13C) and clumped isotope temperature (Δ47) records from a middle Eocene (ca. 42.0 to 40.0 Ma) mammal fossil locality in southwestern Montana, USA. The sampled section (Upper Dell Beds, Sage Creek Basin) comprises about 60 m of stacked paleosols that were correlated to Chron C18r by paleomagnetics and biostratigraphy. δ18O values of pedogenic carbonate range from -12 to -18 per mil (SMOW) and to first-order follows the marine δ18O pattern. Low δ18O values coincide with peak-MECO conditions and show a relatively rapid ca. 5°C increase in soil temperatures reaching peak temperatures of ~27°C at the climax of MECO. Immediately after the MECO event temperatures drop rapidly by about 8°C. To our knowledge this is the first terrestrial MECO paleotemperature record that further provides insight into the precipitation dynamics deep within the North American continent during this early Cenozoic hyperthermal. Paleosol Δ47 temperatures are highly reproducible within and across individual soil sequences and provide a realistic temperature estimate prior, during and after the MECO event. The combined δ18O and Δ47 data therefore provide important insight into the isotopic evolution of precipitation and mean

  11. Sedimentary records of hydroxylated and methoxylated polybrominated diphenyl ethers in the southern Yellow Sea.

    PubMed

    Fan, Ying; Lan, Jing; Zhao, Zongshan; Zhao, Meixun

    2014-07-15

    Although hydroxylated (OH-) and methoxylated (MeO-) polybrominated diphenyl ethers (PBDEs) have caused much concern in recent years, few reports had discussed on their input history. In this study, we measured the contents of nine MeO-BDEs, ten OH-BDEs, and total organic carbon (TOC) of two sediment cores from the southern Yellow Sea. 6-MeO-BDE-47, 2'-MeO-BDE-68, 6-OH-BDE-47, and 2'-OH-BDE-68 were the predominant congeners in HH12, while only 2'-OH-BDE-68 and 6-OH-BDE-47 were frequently detected in core HH11. The records showed that OH-/MeO-BDEs in both cores had increased rapidly since the 1950s. Their existence was detected at the bottom layers (∼1800 s) prior to the production of PBDEs (1960s), thus OH-/MeO-BDEs originate from natural origins rather than artificial PBDEs. Comparisons between TOC and OH-/MeO-BDEs indicated that TOC is a potential factor affecting the accumulation of OH-/MeO-BDEs in marine environments. Similar trends and significant correlations between OH-BDEs and MeO-BDEs suggest their common origins or interconversion. PMID:24910183

  12. Evolution of salt structures, East Texas Diapir Province, Part 1: Sedimentary record of Halokinesis

    SciTech Connect

    Seni, S.J.; Jackson, M.P.A.

    1983-08-01

    Post-Aptian (post-112Ma) strata in the East Texas basin were strongly influenced by halokinesis and therefore record the evolution of associated salt structures. Domeinduced changes in patterns of sandstone distribution, depositional facies, and reef growth indicate that thickness variations in strata surrounding domes were caused by syndepositional processes rather than by tectonic distortion. Salt domes in the East Texas basin exhibit three stages of growth: pillow, diapir, and post-diapir, each of which affected surrounding strata differently. Pillow growth caused broad uplift of strata over the crest of the pillows; the resulting topographic swell influenced depositional trends and was susceptible to erosion. Fluvial channel systems bypassed pillow crests and stacked vertically in primary peripheral sinks on the updip flanks of the pillows. Diapir growth was characterized by expanded sections of shelf and deltaic strata in secondary peripheral sinks around the diapirs. Lower Cretaceous reefs on topographic saddles between secondary peripheral sinks now host major oil production at Fairway field. Post-diapir crestal uplifts and peripheral subsidence affected smaller areas than did equivalent processes during pillow or diapir stages. Documented facies variations over and around domes at different stages of growth enable prediction of subtle facies-controlled hydrocarbon traps. Facies-controlled traps are likely to be the only undiscovered ones remaining in mature petroliferous basins such as the East Texas basin.

  13. Evolution of salt structures, East Texas diapir province, part 1: sedimentary record of halokinesis

    SciTech Connect

    Seni, S.J.; Jackson M.P.A.

    1983-08-01

    Post-Aptian (post-112 Ma) strata in the East Texas basin were strongly influenced by halokinesis and therefore record the evolution of associated salt structures. Dome-induced changes in patterns of sandstone distribution, depositional facies, and reef growth indicate that thickness variations in strata surrounding domes were caused by syndepositional processes rather than by tectonic distortion. Salt domes in the East Texas basin exhibit three stages of growth: pillow, diapir, and post-diapir, each of which affected surrounding strata differently. Pillow growth caused broad uplift of strata over the crest of the pillows; the resulting topographic swell influenced depositional trends and was susceptible to erosion. Fluvial channel systems bypassed pillow crests and stacked vertically in primary peripheral sinks on the updip flanks of the pillows. Diapir growth was characterized by expanded sections of shelf and deltaic strata in secondary peripheral sinks around the diapirs. Lower Cretaceous reefs on topographic saddles between secondary peripheral sinks now host major oil production at Fairway field. Post-diapir crestal uplifts and peripheral subsidence affected smaller areas than did equivalent processes during pillow or diapir stages. Documented facies variations over and around domes at different stages of growth enable prediction of subtle facies-controlled hydrocarbon traps. Facies-controlled traps are likely to be the only undiscovered ones remaining in mature petroliferous basins such as the East Texas basin.

  14. Linking the MIF-S Record of Sedimentary Rocks to the Thermal and Biological Evolutions of the Earth

    NASA Astrophysics Data System (ADS)

    Ohmoto, H.; Watanabe, Y.; Lasaga, A. C.

    2006-05-01

    Many recent geoscientists have accepted that the record of mass independent fractionation of sulfur isotopes (MIF-S) is a smoking gun for the dramatic change from an anoxic (pO2 < 10-5 PAL) to oxic (pO2 > 10-5 PAL) atmosphere ~2.4 Ga ago, based on the acceptance of two dogmas: (I) atmospheric photochemical reactions are the only mechanisms to create MIF-S, and (II) only rocks older than 2.4 Ga in age bear MIF-S signatures. We question the validity of these dogmas because of the following recent discoveries: (1) the presence of MIF-S in some rocks younger than 1.7 Ga; (2) the absence of MIF-S in many rocks older than 2.7 Ga; (3) a systematic geochemical signature coincident with strong MIF-S in shales; (4) large MIFs in the isotopes of many elements (e.g., U, Cr, Mg) accompanying redox reactions, which are attributed to nuclear field shift effect (i.e., nuclear size and shape effects); (5) MIF-S in the H2S generated from the reduction of sulfate by simple amino acids in our experiments at 150-200°C, while a lack of sulfate reduction by more complex amino acids occurred (Watanabe et al., preceeding paper); and (6) agreements in the Δ33 S(sulfide)- Δ33 S(sulfate) relationships predicted from the nuclear field shift theory with those observed in (a) geologic samples, (b) photochemical experimental products, and (c) reaction products in our amino acids - sulfate experiments. The above discoveries suggest the following three possible reasons for a MIF-S signature in a sedimentary rock: (i) an anoxic atmosphere, (ii) a regional explosive volcanic event, or (iii) unique diagenetic reactions (e.g., sulfate reduction by amino acids) in organic-rich sediments. If (i) was the case, it would imply a yo-yo atmosphere, where the atmospheric pO2 fluctuated from anoxic to oxic, during the Archean. However, we suggest the combinations of (ii) and (iii) were the main reasons for MIF-S signatures in sedimentary rocks for the following reasons: (a) reactive amino acids were probably

  15. Records of sedimentary dynamics in the continental shelf and upper slope between Aveiro-Espinho (N Portugal)

    NASA Astrophysics Data System (ADS)

    Martins, Virgínia; Abrantes, Isabel; Grangeia, Carlos; Martins, Paula; Nagai, Renata; Sousa, Sílvia H. M.; Laut, Lazaro L. M.; Dias, João M. Alveirinho; Dias, João M.; da Silva, Eduardo Ferreira; Rocha, Fernando

    2012-08-01

    The sedimentary unconsolidated cover of the Aveiro-Espinho continental shelf and upper slope (NW Portugal) records a complex interplay of processes including wave energy and currents, fluvial input, sediment transport alongshore and cross-shelf, geological and oceanographic processes and sediment sources and sinks. In order to study this record, a set of surface sediment samples was studied. Sediment grain size and composition, as well as the mineralogical composition (by XRD) of the fine (< 63 μm) and clay (< 2 μm) fractions and benthic microfaunal (foraminifera) data were analysed. Cluster analysis applied to the sedimentological data (grain size, sediment composition and mineralogy) allowed the establishment of three main zones corresponding to the: inner-, mid- and outer-shelf/upper slope. On the inner-shelf, the sedimentary coverture is composed of siliciclastic fine to very fine sand, essentially comprising modern (immature) terrigenous particles. The sediment grain size, as well as mineralogical and microfaunal composition, denote the high energetic conditions of this sector in which the alongshore transport of sand is predominantly southward and occurs mostly during the spring-summer oceanographic regime, when the main river providing sediments to this area, the River Douro, undergoes periods of drought. This effect may emphasize the erosive character of this coastal sector at present, since the Ria de Aveiro provides the shelf with few sediments. On the mid-shelf, an alongshore siliciclastic band of coarse sand and gravel can be found between the 40 m and 60 m isobaths. This gravelly deposit includes relic sediments deposited during lower sea-level stands. This structure stays on the surface due to the high bottom energy, which promotes the remobilization of the fine-grained sediments, and/or events of sediments bypassing. Benthic foraminifera density and "Benthic Foraminifera High Productivity" (BFHP) proxy values are in general low, which is consistent

  16. Glacial to Holocene climate changes in the SE Pacific. The Raraku Lake sedimentary record (Easter Island, 27°S)

    NASA Astrophysics Data System (ADS)

    Sáez, Alberto; Valero-Garcés, Blas L.; Giralt, Santiago; Moreno, Ana; Bao, Roberto; Pueyo, Juan J.; Hernández, Armand; Casas, David

    2009-12-01

    Easter Island (SE Pacific, 27°S) provides a unique opportunity to reconstruct past climate changes in the South Pacific region based on terrestrial archives. Although the general climate evolution of the south Pacific since the Last Glacial Maximum (LGM) is coherent with terrestrial records in southern South America and Polynesia, the details of the dynamics of the shifting Westerlies, the South Pacific Convergence Zone and the South Pacific Anticyclone during the glacial-interglacial transition and the Holocene, and the large scale controls on precipitation in tropical and extratropical regions remain elusive. Here we present a high-resolution reconstruction of lake dynamics, watershed processes and paleohydrology for the last 34 000 cal yrs BP based on a sedimentological and geochemical multiproxy study of 8 cores from the Raraku Lake sediments constrained by 22 AMS radiocarbon dates. This multicore strategy has reconstructed the sedimentary architecture of the lake infilling and provided a stratigraphic framework to integrate and correlate previous core and vegetation studies conducted in the lake. High lake levels and clastic input dominated sedimentation in Raraku Lake between 34 and 28 cal kyr BP. Sedimentological and geochemical evidences support previously reported pollen data showing a relatively open forest and a cold and relatively humid climate during the Glacial period. Between 28 and 17.3 cal kyr BP, including the LGM period, colder conditions contributed to a reduction of the tree coverage in the island. The coherent climate patterns in subtropical and mid latitudes of Chile and Eastern Island for the LGM (more humid conditions) suggest stronger influence of the Antarctic circumpolar current and an enhancement of the Westerlies. The end of Glacial Period occurred at 17.3 cal kyr BP and was characterized by a sharp decrease in lake level conducive to the development of major flood events and erosion of littoral sediments. Deglaciation (Termination

  17. Sedimentary Records of Non-Aroclor and Aroclor PCB mixtures in the Great Lakes

    PubMed Central

    HU, DINGFEI; MARTINEZ, ANDRES; HORNBUCKLE, KERI C.

    2012-01-01

    Three sediment cores from Lake Ontario, Lake Erie and Indiana Harbor Ship Canal were collected, segmented and analyzed for Aroclor and non-Aroclor polychlorinated biphenyl congeners (PCBs). PCBs associated with the commercially produced Aroclor mixtures 1248 and 1254 dominate the sediment signal and the sum of all congeners (ΣPCB) peaks in concentration and accumulation around 1970 in the Great Lakes. This trend is very similar to Aroclor production history. In the Indiana Harbor Ship Canal, PCBs appear around 1935 and remain at very high levels between 1940 and 1980, probably reflecting the history of use at the nearby steel mill. In contrast, the non-Aroclor PCBs in the Lake Ontario and IHSC sediment cores, including PCB11 and heavily chlorinated congeners PCB206, 207, 208 and 209 reach a peak in the 1950s, decline and peak again in the 1970s or in the early 1980s. All five congeners have been previously measured in commercial paint pigment. PCB11 was found to peak about 5 years later than ΣPCBs, and is probably associated with the production or use history of diarylide yellow pigments. The temporal distribution profiles of these non-Aroclor PCBs are well correlated with the production history of paint pigments and dyes. Although it is well known that the production of Aroclor PCBs is preserved in Great Lakes sediments, this study is the first to show that production of non-Aroclors are also preserved in the sediments as a record of long term trends in environmental exposure. PMID:23538476

  18. Sedimentary Records of Non-Aroclor and Aroclor PCB mixtures in the Great Lakes.

    PubMed

    Hu, Dingfei; Martinez, Andres; Hornbuckle, Keri C

    2011-06-01

    Three sediment cores from Lake Ontario, Lake Erie and Indiana Harbor Ship Canal were collected, segmented and analyzed for Aroclor and non-Aroclor polychlorinated biphenyl congeners (PCBs). PCBs associated with the commercially produced Aroclor mixtures 1248 and 1254 dominate the sediment signal and the sum of all congeners (ΣPCB) peaks in concentration and accumulation around 1970 in the Great Lakes. This trend is very similar to Aroclor production history. In the Indiana Harbor Ship Canal, PCBs appear around 1935 and remain at very high levels between 1940 and 1980, probably reflecting the history of use at the nearby steel mill. In contrast, the non-Aroclor PCBs in the Lake Ontario and IHSC sediment cores, including PCB11 and heavily chlorinated congeners PCB206, 207, 208 and 209 reach a peak in the 1950s, decline and peak again in the 1970s or in the early 1980s. All five congeners have been previously measured in commercial paint pigment. PCB11 was found to peak about 5 years later than ΣPCBs, and is probably associated with the production or use history of diarylide yellow pigments. The temporal distribution profiles of these non-Aroclor PCBs are well correlated with the production history of paint pigments and dyes. Although it is well known that the production of Aroclor PCBs is preserved in Great Lakes sediments, this study is the first to show that production of non-Aroclors are also preserved in the sediments as a record of long term trends in environmental exposure. PMID:23538476

  19. The sedimentary records of Holocene environmental changes from the Central High of the Sea of Marmara

    NASA Astrophysics Data System (ADS)

    Filikci, Betul; Çağatay, Namık; Kadir Eriş, Kürşad; Akyol, Mustafa; Yalamaz, Burak; Uçarkuş, Gülsen; Henry, Pierre

    2015-04-01

    The Sea of Marmara (SoM) is located between the Aegean Sea and the Black Sea, to which it is connected via the Istanbul (Bosphorus) and Canakkale (Dardanelles) straits having sill depths of 65 and 35 m, respectively. It has a two-way water mass exchange with a permanent pycnocline located at 20-25 m water depth. With the objective of determining Holocene paleoenvironmental changes, we studied a 8.36 m-long piston core recovered from the Central High of the SoM at a water depth of 835 m, using multiproxy analyses such as total organic and inorganic carbon, high resolution µ-XRF core scanner analysis, grain size, magnetic susceptibility and density. A 2 cm-thick tephra layer with high K and Zr and relatively low magnetic susceptibility occurs at 2.1 meter below sea floor (mbsf), which is correlated with the Avellino (Somma-Vesuvius, Italy) eruption dated at 3.9 ka BP, according to the previous studies. Using this age and assuming a uniform sedimentation rate, the base of the core dates back to ca 8 ka BP. The core includes organic-rich (sapropelic) sediments with 1.5 % to 2.2%) in its top 3.5 m and bottom 1 m. Sapropelic layers are olive green and in part laminated, and contain occasional reddish brown spots and laminae formed by oxidation of iron monosulphides. The core also contains some few mm- to cm-thick sandy-silty mass-flow units below 2.4 mbsf, some of which could have been triggered by the earthquake activity on the Central High segment of the North Anatolian Fault, just a few km away from the core location. Variations in Ca-Ti ratio suggest millennial-scale climatic changes during the Holocene. Keywords: Sea of Marmara, Holocene paleoenvironmental records, tephra, turbidites, TOC analysis, XRF analysis, physical properties.

  20. Ancestral Rocky Mountian Tectonics: A Sedimentary Record of Ancestral Front Range and Uncompahgre Exhumation

    NASA Astrophysics Data System (ADS)

    Smith, T. M.; Saylor, J. E.; Lapen, T. J.

    2015-12-01

    The Ancestral Rocky Mountains (ARM) encompass multiple crustal provinces with characteristic crystallization ages across the central and western US. Two driving mechanisms have been proposed to explain ARM deformation. (1) Ouachita-Marathon collision SE of the ARM uplifts has been linked to an E-to-W sequence of uplift and is consistent with proposed disruption of a larger Paradox-Central Colorado Trough Basin by exhumation of the Uncompahgre Uplift. Initial exhumation of the Amarillo-Wichita Uplift to the east would provide a unique ~530 Ma signal absent from source areas to the SW, and result in initial exhumation of the Ancestral Front Range. (2) Alternatively, deformation due to flat slab subduction along a hypothesized plate boundary to the SW suggests a SW-to-NE younging of exhumation. This hypothesis suggests a SW-derived Grenville signature, and would trigger uplift of the Uncompahgre first. We analyzed depositional environments, sediment dispersal patterns, and sediment and basement zircon U-Pb and (U-Th)/He ages in 3 locations in the Paradox Basin and Central Colorado Trough (CCT). The Paradox Basin exhibits an up-section transition in fluvial style that suggests a decrease in overbank stability and increased lateral migration. Similarly, the CCT records a long-term progradation of depositional environments from marginal marine to fluvial, indicating that sediment supply in both basins outpaced accommodation. Preliminary provenance results indicate little to no input from the Amarillo-Wichita uplift in either basin despite uniformly westward sediment dispersal systems in both basins. Results also show that the Uncompahgre Uplift was the source for sediment throughout Paradox Basin deposition. These observations are inconsistent with the predictions of scenario 1 above. Rather, they suggest either a synchronous response to tectonic stress across the ARM provinces or an SW-to-NE pattern of deformation.

  1. 3. Mercury pollution in the Lot River system (France): fluxes and sedimentary record.

    NASA Astrophysics Data System (ADS)

    Schäfer, J.; Blanc, G.; Audry, S.; Bossy, C.; Vu Duc, L.; Lissalde, J.-P.

    2003-04-01

    We present first data on Hg concentrations and fluxes in the Lot River system (southwest France), known for its historic Zn and Cd pollution affecting seafood production in the Gironde Estuary. Present day Hg fluxes (1999-2000) were estimated from daily measured discharge and SPM concentrations and concentrations of particulate and dissolved Hg in monthly collected samples. The data show that Hg is essentially (up to 98 %) transported in the particulate phase. Particulate Hg concentrations in SPM show a distinct decrease between 1992 and 1999 but, since then, tend to increase in magnitude and variability. The evolution of Hg fluxes in the Lot River in 1992, 1994, 1995 and 1998-2001 reflect hydrological variations and the decrease of direct Hg inputs from the point source at the Riou-Mort River, draining a small watershed polluted by former mining and ore treatment. However, the data also indicate important Hg remobilization from the sediment by dredging due to lock construction along the Lot River. Mercury concentrations in sediment cores from a dam lake downstream of the Riou-Mort watershed are up to 30 mg.kg-1, i.e. more than 300-fold higher than geochemical background measured in the same riverbed upstream the confluence with the Riou-Mort River. In the sediment cores Hg from the Lot River dam lakes Hg concentration profiles are comparable to those of Cd and Zn. This indicates common sources and transport. Element ratios (e.g. Cd/Zn) in the sediment reflect SPM values and suggest an important Hg stock (7 t) in these sediments. Historic (˜40 years) Hg records in the sediment cores dated by using 137Cs activities and Cd-concentrations (e.g. Chernobyl accident and accidental Cd pollution in 1986) confirm the decreasing Hg level in SPM since the early nineties. Nevertheless Hg concentrations in the upper sediment and SPM remain high compared to background values from reference sites in the upper Lot River system.

  2. A Qualitative and Quantitative Comparison of Sedimentary Palynomorphs, Lipid Biomarkers and Fossil DNA: Which Tool Provides the Most Detailed Paleoecological and Paleoenvironmental Information?

    NASA Astrophysics Data System (ADS)

    Boere, A. C.; Abbas, B.; Rijpstra, W. I.; Volkman, J. K.; Sinninghe Damsté, J. S.; Coolen, M. J.

    2007-12-01

    In recent years, it was shown that Holocene planktonic taxa could be identified at the species-level based on their preserved fossil genetic signatures (fossil DNA) in either cold and/or sulfidic lacustrine and marine settings. Many of those species are not known to leave morphologically recognizable remains and thus most likely would have escaped microscopic determination and enumeration. In addition, fossil DNA analysis also revealed past planktonic taxa for which no specific lipid biomarkers are known. However, the best, and yet unexplored, approach to validate fossil DNA as paleoenvironmental tool would be based on a direct qualitative and quantitative comparison of each of the above described proxies. In an up to 2700-year-old record of undisturbed sulfidic sediments from the Small Meromictic Basin in Ellis Fjord, Antarctica, we compared the quantitative and qualitative distribution of fossil ribosomal DNA of phototrophic algae like diatoms, dinoflagellates and past chemocline bacteria (green sulfur bacteria) with the distribution of their fossil lipid biomarkers: highly branched isoprenoids, dinosterol and carotenoids. For dinoflagellates, we performed a comparative microscopic (palynological) analysis of fossil dinocysts whereas comparative diatom microfossil data was available from the literature. We will discuss important new insights about the cell-specific fate of fossil DNA and the additional paleoenvironmental information which was revealed from the fossil DNA analysis.

  3. Mountain Lake, Presidio National Park, San Francisco: Paleoenvironment, heavy metal contamination, sedimentary record rescue, remediation, and public outreach

    NASA Astrophysics Data System (ADS)

    Myrbo, A.; Rodysill, J. R.; Jones, K.; Reidy, L. M.

    2014-12-01

    determine whether people lived at the tip of the SF peninsula as early as 2000 BP. In October 2014 the Presidio Trust opened a Heritage Gallery that interprets the cultural and natural history of the park for the public. The Mountain Lake sedimentary record is an important component of this exhibit, which includes an epoxy-embedded core from the lake.

  4. Deformation within the Pisco Basin sedimentary record (southern Peru): Stratabound orthogonal vein sets and their impact on fault development

    NASA Astrophysics Data System (ADS)

    Rustichelli, Andrea; Di Celma, Claudio; Tondi, Emanuele; Bianucci, Giovanni

    2016-01-01

    This outcrop-based study reports diffuse joints and veins, normal to strike-slip fault zones and minor folds that developed, from Miocene to Quaternary, within the clastic to siliceous sedimentary record of the forearc Pisco Basin of southern Peru. Patterns, orientations, dimensional parameters and other outcrop-scale characteristics of the various deformation features are illustrated and their genetic mechanisms and timing of development are inferred. These new structural data and interpretations allow a better constraint of the structural style and evolution of the Pisco Basin, and can represent useful guidelines for characterizing the outcrop-scale deformation affecting similar forearc basins along the Peruvian coast. Major results of this study are that the development of the documented deformation features, their patterns, dimensional parameters and kinematics seem influenced by local perturbations of the paleostress field by mechanic processes partly independent of plate tectonics forces. These processes include strain localization on both pre-existing and progressively forming new structural discontinuities, and cyclic switches of the horizontal, principal stress axes σ2 and σ3. In particular, we discuss how different normal fault patterns, from sub-parallel to multidirectional/polygonal, could form in a same deformation phase in response of the local σ2/σ3 magnitude ratio, as an evolution of stratabound, mutually orthogonal vein sets.

  5. A Pleistocene palaeovegetation record from plant wax biomarkers from the Nachukui Formation, West Turkana, Kenya.

    PubMed

    Uno, Kevin T; Polissar, Pratigya J; Kahle, Emma; Feibel, Craig; Harmand, Sonia; Roche, Hélène; deMenocal, Peter B

    2016-07-01

    Reconstructing vegetation at hominin fossil sites provides us critical information about hominin palaeoenvironments and the potential role of climate in their evolution. Here we reconstruct vegetation from carbon isotopes of plant wax biomarkers in sediments of the Nachukui Formation in the Turkana Basin. Plant wax biomarkers were extracted from samples from a wide range of lithologies that include fluvial-lacustrine sediments and palaeosols, and therefore provide a record of vegetation from diverse depositional environments. Carbon isotope ratios from biomarkers indicate a highly dynamic vegetation structure (ca 5-100% C4 vegetation) from 2.3 to 1.7 Ma, with an overall shift towards more C4 vegetation on the landscape after about 2.1 Ma. The biomarker isotope data indicate ca 25-30% more C4 vegetation on the landscape than carbon isotope data of pedogenic carbonates from the same sequence. Our data show that the environments of early Paranthropus and Homo in this part of the Turkana Basin were primarily mixed C3-C4 to C4-dominated ecosystems. The proportion of C4-based foods in the diet of Paranthropus increases through time, broadly paralleling the increase in C4 vegetation on the landscape, whereas the diet of Homo remains unchanged. Biomarker isotope data associated with the Kokiselei archaeological site complex, which includes the site where the oldest Acheulean stone tools to date were recovered, indicate 61-97% C4 vegetation on the landscape.This article is part of the themed issue 'Major transitions in human evolution'. PMID:27298466

  6. Climate variability from the Florida Bay sedimentary record: Possible teleconnections to ENSO, PNA and CNP

    USGS Publications Warehouse

    Cronin, T. M.; Dwyer, G.S.; Schwede, S.B.; Vann, C.D.; Dowsett, H.

    2002-01-01

    We analyzed decadal and interannual climate variability in South Florida since 1880 using geochemical and faunal paleosalinity indicators from isotopically dated sediment cores at Russell Bank in Florida Bay (FB). Using the relative abundance of 2 ostracode species and the Mg/Ca ratios in Loxoconcha matagordensis shells to reconstruct paleosalinity, we found evidence for cyclic oscillations in the salinity of central FB. During this time salinity fluctuated from as low as ???18 parts per thousand (ppt) to as high as ???57 ppt. Time series analyses suggest, in addition to a 5.6 yr Mg/Ca based salinity periodicity, there are 3 other modes of variability in paleosalinity indicators: 6-7, 8-9, and 13-14 yr periods which occur in all paleo-proxies. To search for factors that might cause salinity to vary in FB, we compared the Russell Bank paleosalinity record to South Florida winter rainfall, the Southern Oscillation Index (SOI), winter North Atlantic Oscillation (NAO), and the winter Pacific North American (PNA) index, and a surrogate for the PNA in the winter season, the Central North Pacific (CNP) index. SOI and PNA/CNP appear to be associated with South Florida winter precipitation. Time series analyses of SOI and winter rainfall for the period 1910-1999 suggest ???5, 6-7, 8-9 and 13-14 yr cycles. The 6-7 yr and 13-14 yr cycles correspond to those observed in the faunal and geochemical time series from Russell Bank. The main periods of the CNP index are 5-6 and 13-15 yr, which are similar to those observed in FB paleosalinity. Cross-spectral analyses show that winter rainfall and salinity are coherent at 5.6 yr with a salinity lag of ???1.6 mo. These results suggest that regional rainfall variability influences FB salinity over interannual and decadal timescales and that much of this variability may have its origin in climate variability in the Pacific Ocean/atmosphere system.

  7. Marine Sedimentary Record of the Gulf of Tehuantepec in the Late Quaternary: paleoceanographic and paleoclimatic implications

    NASA Astrophysics Data System (ADS)

    Pavón-Moreno, J. A.; Pérez-Cruz, L.; Urrutia-Fucugauchi, J.; Monreal-Gómez, M. A.

    2012-04-01

    The aim of this study is reconstruct the paleoceanographic and paleoclimatic conditions in the northern Gulf of Tehuantepec, through the use of geochemical and magnetic proxies. The sediment core MD02-2523 was collected using a giant piston corer during the oceanographic campaign MD126 (IMAGES VIII - MONA) in the Gulf of Tehuantepec, on June 2002 aboard the R/V "Marion Dufresne". The core was collected at 202 m depth and it has an 18.19 m length. Age control is established from AMS radiocarbon dating on four samples from the first 700 cm, which were converted to calendar years by applying a reservoir correction of 456 yr (ΔR 162±50) with the CALIB 6.1.0 radiocarbon program. This provides an initial age control for the core from 900 to 47,000 cal yr BP. A linear age model extends the record to ~120,000 cal yr BP, with a mean sedimentation rate of about 0.15 mm/ yr. Sediments in the core are composed mostly of silty clays, with some horizons containing fossil fragments presented as disarticulated bivalve shells with average sizes of 1 cm, as well as foraminifera and nannofossils. At different depths we observed cream to white ash layers, with thicknesses ranging from 2 to 10 cm. For this study, mineral magnetic and XRF analyses were carried out along the core. For mineral magnetic analyses, standard 2.2 × 2.2 × 2.2 cm samples were taken throughout the core split. The low-field magnetic susceptibility was measured in all samples at low and high frequencies (0.465 kHz and 4.65 kHz) with the MS2 Bartington susceptibility instrument equipped with the MS2B dual-frequency sensor. For the geochemical study, samples were taken every ~2 cm and elemental chemical concentration was measured using an X-ray fluorescence analyzer (Niton XL3t GOLDD). Magnetic susceptibility shows a cyclic pattern with peaks along the core indicating apparent increases in the amount of magnetic minerals. The peaks could be associated to (about 20 ka) precession cycles. Magnetic susceptibility

  8. Sedimentary record of a fluctuating ice margin from the Pennsylvanian of western Gondwana: Paraná Basin, southern Brazil

    NASA Astrophysics Data System (ADS)

    Vesely, Fernando F.; Trzaskos, Barbara; Kipper, Felipe; Assine, Mario Luis; Souza, Paulo A.

    2015-08-01

    The Paraná Basin is a key locality in the context of the Late Paleozoic Ice Age (LPIA) because of its location east of the Andean proto-margin of Gondwana and west of contiguous interior basins today found in western Africa. In this paper we document the sedimentary record associated with an ice margin that reached the eastern border of the Paraná Basin during the Pennsylvanian, with the aim of interpreting the depositional environments and discussing paleogeographic implications. The examined stratigraphic succession is divided in four stacked facies associations that record an upward transition from subglacial to glaciomarine environments. Deposition took place during deglaciation but was punctuated by minor readvances of the ice margin that deformed the sediment pile. Tillites, well-preserved landforms of subglacial erosion and glaciotectonic deformational structures indicate that the ice flowed to the north and northwest and that the ice margin did not advance far throughout the basin during the glacial maximum. Consequently, time-equivalent glacial deposits that crop out in other localities of eastern Paraná Basin are better explained by assuming multiple smaller ice lobes instead of one single large glacier. These ice lobes flowed from an ice cap covering uplifted lands now located in western Namibia, where glacial deposits are younger and occur confined within paleovalleys cut onto the Precambrian basement. This conclusion corroborates the idea of a topographically-controlled ice-spreading center in southwestern Africa and does not support the view of a large polar ice sheet controlling deposition in the Paraná Basin during the LPIA.

  9. New insights into the Glacial to Holocene climatic evolution of Southern Patagonia from lacustrine lipid biomarker isotope records

    NASA Astrophysics Data System (ADS)

    Hockun, K.; Mollenhauer, G.; Sachse, D.; Schefuß, E.

    2015-12-01

    Southern Patagonia is a key region for paleoclimatic reconstructions in the Southern Hemisphere as it is the only landmass located in the Southern Hemisphere westerly wind (SHW) belt. Within the framework of the ICDP drilling campaign PASADO ("Potrok Aike Maar Lake Sediment Archive Drilling Project"), a high resolution sediment record was recovered from Laguna Potrok Aike (LPTA, 51°58´S, 70°23´W). In order to identify the sources of organic matter contributions to the sedimentary archive, we investigated long-chain n-alkanes as tracers for terrestrial and aquatic plants. We analysed n-alkane distributions and their compound-specific hydrogen (δD) and stable carbon (δ13C) isotopic composition in various sample types such as soils, dust, aquatic and terrestrial plants and lake surface sediments. Based on two different model approaches, one using the n-alkane distributions and the other the compound-specific isotope values, we traced the origin of mid- (n-C23) and long- (n-C29) chain n-alkanes into modern lake sediments. Both models yield similar results: around 70% of the n-C23 originates from aquatic plants and more than 80% of the n-C29 is delivered from dust and terrestrial plants to the sediment. These results provide the basis for a robust paleo-environmental reconstruction of the lipid biomarker isotope records from LPTA. Compound-specific δD and δ13C records for the last 55,000 years from the PASADO core are interpreted in the framework of these findings. Here, δD of the n-C23 alkane serves as proxy for lake water isotopic changes driven by the precipitation-evaporation balance, moisture sources and water column stratification. In contrast, we interpret changes in δD of the n-C29 alkane to reflect dust source area changes and therefore, the intensity of the SHW. A 50‰ shift in the δD record of the n-C23 alkane between 10.000 to 8.000 years age indicates a major hydrological change affecting the lake level while isotopic changes in the n-C29 alkane

  10. Unsteady diagenetic processes and sulfur biogeochemistry in tropical deltaic muds: Implications for oceanic isotope cycles and the sedimentary record

    NASA Astrophysics Data System (ADS)

    Aller, Robert C.; Madrid, Vanessa; Chistoserdov, Andrei; Aller, Josephine Y.; Heilbrun, Christina

    2010-08-01

    Sedimentary S cycling is usually conceptualized and interpreted within the context of steadily accreting (1-D) transport-reaction regimes. Unsteady processes, however, are common in many sedimentary systems and can result in dramatically different S reaction balances and diagenetic products than steady conditions. Globally important common examples include tropical deltaic topset and inner shelf muds such as those extending from the Amazon River ˜1600 km along the Guianas coast of South America. These deposits are characterized by episodic reworking of the surface seabed over vertical depths of ˜0.1-3 m. Reworked surface sediments act as unsteady, suboxic batch reactors, unconformably overlying relict anoxic, often methanic deposits, and have diagenetic properties largely decoupled from net accumulation of sediment. Despite well-oxygenated water and an abundant reactive organic matter supply, physical disturbance inhibits macrofauna, and benthic communities are dominated by microbial biomass across immense areas. In the surficial suboxic layer, molecular biological analyses, tracer experiments, sediment C/S/Fe compositions, and δ 34S, δ 18O of pore water SO42- indicate close coupling of anaerobic C, S, and Fe cycles. δ 18O- SO42- can increase by 2-3‰ during anaerobic recycling without net change in δ 34S- SO42-, demonstrating SO42- reduction coupled to complete anaerobic reoxidation to SO42- and a δ 18O- SO42- reduction + reoxidation fractionation factor⩾12‰ (summed magnitudes). S reoxidation must be coupled to Fe-oxide reduction, contributing to high dissolved Fe 2+ (˜1 mM) and Fe mobilization-export. The reworking of Amazon-Guianas shelf muds alone may isotopically alter δ 18O- SO42- equivalent in mass to⩾25% of the annual riverine delivery of SO42- to the global ocean. Unsteady conditions result in preservation of unusually heavy δ 34S isotopic compositions of residual Cr reducible S, ranging from 0‰ to >30‰ in physically reworked deposits

  11. The supra-detachment tectono-sedimentary record of rifted margins: the example of the Los Barriles Basin, SE Baja California Sur.

    NASA Astrophysics Data System (ADS)

    Masini, Emmanuel; Robin, Cécile; Geoffroy, Laurent; Strzerzynski, Pierre

    2010-05-01

    The study of rifted margins have shown that the main controlling structures are changing from classical high-angle faults to low-angle detachment fault dominated extension when the crust thins to less than 10 km, which is the case in hyper-extended, magma-poor rifted margins. While the stratigraphic record related to classical high-angle faulting is well constrained, little is known about the tectono-sedimentary evolution of hyper-extended rift systems. A major question remains, how supra-detachment tectono-sedimentary systems are recorded in the stratigraphic record? This remains largely unexplored and must be better constrained by observations. In our poster, we present preliminary results from our study of a rift basin floored by a low-angle detachment system exposed at the southeastern edge of the Baja California Peninsula in the so-called Los Barriles area in the Gulf of California. This area represents one of the best examples of an active transtensional rift system from which the tectono-sedimentary evolution of the rift to drift transition can be studied in the field. The syn-tectonic sedimentary sequence is floored by a detachment fault and is limited oceanward by an extensional allochthon. The syn- to post-tectonic stratigraphy can be summarized into 4 main formations: (1) The Pescadero fluvial fm. (no available ages) evolves upsection from poorly organized polymictic in components and faulted breccias to more granitic and stratified conglomerates. It overlies the extensional allochthon and is tilted continentwards. The channel incisions show EW paleoflows and the upper Pescadero fm. is transitional to the following Refugio fm. (2) The overlying Refugio fm. (Lower Pliocene) occurs as thick marine sandy deposits within the basin axis, is granitic in composition and has average paleocurrents directions trending N-S. The upper part of the fm. is transitional to the following Barriles fm. (3) The Barriles fm. (Upper Miocene - Lower Pleistocene) occurs as very

  12. Historical reconstruction of atmospheric lead pollution in central Yunnan province, southwest China: an analysis based on lacustrine sedimentary records.

    PubMed

    Liu, Enfeng; Zhang, Enlou; Li, Kai; Nath, Bibhash; Li, Yanling; Shen, Ji

    2013-12-01

    Atmospheric lead (Pb) pollution during the last century in central Yunnan province, one of the largest non-ferrous metal production centers in China, was reconstructed using sediment cores collected from Fuxian and Qingshui Lakes. Lead concentrations and isotopic ratios ((207)Pb/(206)Pb and (208)Pb/(206)Pb) were measured in sediment cores from both lakes. The operationally defined chemical fractions of Pb in sediment core from Fuxian Lake were determined by the optimized BCR procedure. The chronology of the cores was reconstructed using (210)Pb and (137)Cs dating methods. Similar three-phase variations in isotopic ratios and enrichment factors of Pb were observed in the sediment cores from both lakes. Before the 1950s, the sediment data showed low (207)Pb/(206)Pb and (208)Pb/(206)Pb ratios and enrichment factors (EFs=~1), indicating that the sedimentary Pb was predominantly of lithogenic origin. However, these indices were increased gradually between the 1950s and the mid-1980s, implying an atmospheric Pb deposition. The EFs and isotopic ratios of Pb reached their peak during recent years, indicating aggravating atmospheric Pb pollution. The average anthropogenic Pb fluxes since the mid-1980s were estimated to be 0.032 and 0.053 g m(-2) year(-1) recorded in Fuxian and Qingshui cores, respectively. The anthropogenic Pb was primarily concentrated in the reducible fraction. Combining the results of Pb isotopic compositions and chemical speciations in the sediment cores and in potential sources, we deduced that recent aggravating atmospheric Pb pollution in central Yunnan province should primarily be attributed to regional emissions from non-ferrous metal production industries. PMID:23729030

  13. 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

  14. Sedimentary record of the obduction of the Samail ophiolite in northern Oman: the Muti Formation in the Sail Hatat window

    NASA Astrophysics Data System (ADS)

    Ducassou, Céline; Robin, Cecile; Poujol, Marc; Al-Rahbi, Basim; Estournes, Guilhem

    2016-04-01

    palaeocurrents, petrological determinations and geochronological analyses (LA-ICPMS) on detrital zircons have been performed in order to identify the source areas. In both studied areas, the sedimentary series are characterised by mainly carbonated slope to basin deposits. The more distal deposits identified are in the easternmost part (Quryat area). Episodes of terrigenous input are recorded in both areas and palaeocurrents indicate a source area located toward the south, in agreement with the dating obtained on detrital zircons, yielding a dominant population at ca. 800 Ma. These results suggest that the Proterozoic basement was being eroded during the sedimentation of the Muti Formation in the Sail Hatat window and an episode of uplift of the Huqf High is therefore inferred. These results allow to discuss the evolution of the north-easternmost part of the Arabian platform during the first steps of the obduction.

  15. Reconstructing Late Pleistocene air temperature variability based on branched GDGTs in the sedimentary record of Llangorse Lake (Wales)

    NASA Astrophysics Data System (ADS)

    Maas, David; Hoek, Wim; Peterse, Francien; Akkerman, Keechy; Macleod, Alison; Palmer, Adrian; Lowe, John

    2015-04-01

    This study aims to provide a temperature reconstruction of the Lateglacial sediments of Llangorse Lake. A new temperature proxy is used, based on the occurrence of different membrane lipids of soil bacteria (de Jonge et al., 2014). Application of this proxy on lacustrine environments is difficult because of in situ (water column) production and co-elution of isomers. Pollen analysis provides a palynological record that can be used for biostratigraphical correlation to other records. Llangorse Lake lies in a glacial basin just northeast of the Brecon Beacons in Powys, South Wales. The lake is located upstream in the Afon Llynfi valley, at the edge of the watershed of the River Wye. The lake consists of two semi-separated basins with a maximum water depth of 7.5 m, arranged in an L-shape with a surface area of roughly 1.5 km2. Previous studies have focused on the Holocene development of the lake and its surrounding environment (Jones et al., 1985). This study focuses on the deglacial record that appeared to be present in the basal part of the sequence. The lake was cored in the September, 2014 with a manual operated 3 m piston corer from a small coring platform. Overlapping cores were taken to form a continuous 12 m core, spanning the Holocene and the Lateglacial sediments. Six adjacent Lateglacial core segments from the southern basin of Llangorse lake were scanned for their major element composition using XRF scanning at 5 mm resolution to discern changes in sediment origin. Furthermore, loss on ignition (LOI) analysis was used to determine the changes in organic content of the sediments. Subsamples of the Lateglacial sedimentary record were analyzed for the occurrence of different bacterial membrane lipids (brGDGTs: branched glycerol dialkyl glycerol tetraethers) by means of HPLC-MS (high performance liquid chromatography and mass spectrometry) using two silica columns to achieve proper separation of isomers (de Jonge et al., 2013). Air temperatures are

  16. 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.

  17. A first Late Glacial and Early Holocene coupled 18O and 2H biomarker isotope record from Gemuendener Maar, Germany

    NASA Astrophysics Data System (ADS)

    Zech, Michael; Bromm, Tobias; Hepp, Johannes; Benesch, Marianne; Sirocko, Frank; Glaser, Bruno; Zech, Roland

    2015-04-01

    During the last years, we developed a method for compound-specific d18O analyses of hemicellulose-derived sugars from plants, soils and sediment archives (Zech and Glaser, 2009; Zech et al., 2014). The coupling of respective d18O sugar results with d2H alkane results from paleosol and sediment climate archives proved to be a valuable innovative approach towards quantitative paleoclimate reconstruction (Hepp et al., 2014; Zech et al., 2013). Here we present a first coupled d18O sugar and d2H alkane biomarker record obtained for Late Glacial and Early Holocene sediments from the Gemuendener Maar in the Eifel, Germany. The d18O sugar biomarker record resembles the d18O ice core records of Greenland. The coupling with the d2H alkane biomarker results allows drawing further more quantitative paleocimate information in terms of (i) paleohumidity and (ii) d18O of paleoprecipitation.

  18. On the Syn-glacial Sedimentary Record of Snowball Earth: Tales of Three Ice-mass Types

    NASA Astrophysics Data System (ADS)

    Hoffman, P. F.; Maloof, A. C.; Halverson, G. P.

    2004-05-01

    We sketch a conceptual model of the glacial history of a snowball Earth, based on new field studies of Marinoan (c640 Ma), Sturtian (c710 Ma) and Huronian (c2.4 Ga) syn-glacial deposits, and informed by sea-ice dynamics modeling. If the oceans froze over from pole to pole, sea ice would thicken and flow glacially towards the Equator, maintained in dynamic steady state by sublimation-precipitation and melting-freezing (Goodman & Pierrehumbert, 2003). Flowage thickens tropical sea ice (and thins extratropical sea ice) relative to adjacent landfast sea ice, where ice thickness is set by one-dimensional thermal diffusion. The latter, called 'sikussak' on Greenland fjords, would occur on rimmed shelves, silled basins and inland seas that are physically protected from invasion by sea glaciers. Such areas have high preservation potential in the geological record and their stratigraphic development through a snowball cycle (CO2 hysteresis loop) ought to reflect an interplay between three distinct ice-mass types: (1) sea glaciers, (2) sikussak, and (3) grounded ice domes. The snowball stage begins when sea glaciers invade the tropics and sikussak prevents calving from outlet glaciers and associated shelf ice. The snowball onset might easily be mistaken for a glacial termination in the sedimentary record. Suspended sediment discharged from wet-base grounded ice may accumulate beneath the sikussak, producing deposits previously interpreted as interstadial or non-glacial. Despite tropical sea ice c450 m thick (GP2003), sea glacier movement ensures a perpetual habitat for photoautotrophy in grounding-line crack systems. After greenhouse forcing raises tropical sea-surface temperature to the melting point, sikussak is replaced by 'oases' of open water, but the tropical ocean remains ice covered due to sea glacial inflow from higher latitudes. If evolved snowball seawater is anoxic and charged with dissolved iron, banded iron-formation will precipitate in snowball oases due to

  19. Biomarker records and paleoenvironment of the central Arctic Ocean during Paleogene times

    NASA Astrophysics Data System (ADS)

    Weller, P.; Stein, R.

    2007-12-01

    During IODP Expedition 302 (Arctic Coring Expedition - ACEX), a more than 200 m thick sequence of Paleogene organic-carbon (OC)-rich (black shale-type) sediments has been drilled. Here, we present new biomarker data determined in ACEX sediment samples to decipher processes controlling OC accumulation and their paleo- environmental significance during periods of extreme global warmth and proposed increased freshwater discharge in the early Cenozoic. Specific source-related biomarkers including n-alkanes, fatty acids, isoprenoids, carotenoids, steranes/sterenes, hopanes/hopenes, hopanoic acids, aromatic terpenoids, benzohopanes, long- chain alkenones and organic sulfur compounds show a high variable of compounds, derived from marine, terrestrial and bacterial origin. Based on the biomarker data, the terrestrial OC supply was significantly enriched during the late Paleocene and part of the earliest Eocene, whereas n-alkanes and n-fatty acids in samples from the PETM and Elmo events as well as the middle Eocene indicate increased aquatic contributions. For the latter, an anoxic environment similar to the modern Black Sea, and moderate primary productivity are proposed. The occurrence of C37-alkenenones, which were first determined in the middle part of the Azolla Freshwater Event (about 49 Ma), suggests that significant amounts of the OC is of marine origin during in middle Eocene. During the Eocene, a prominant cooling and onset of first significant IRD deposition near 45.4 Ma were recorded in the terrigenous coarse fraction of the ACEX sequence, related to iceberg and/or sea-ice transport (K. St. John, Paleoceanography, in press). This cooling trend is also reflected in the alkenone SST, showing a temperature decrease of about 10°C between about 49 and 44 Ma.

  20. The Holocene Sedimentary Record of Climate Change from Gualas Glacier, Golfo Elefantes, Northern Patagonia (46.5°S)

    NASA Astrophysics Data System (ADS)

    Fernandez-Vasquez, R. A.; Anderson, J. B.; Bertrand, S.; Wellner, J. S.

    2010-12-01

    Gualas Glacier is an outlet glacier of the Northern Patagonian Icefield (NPI), one of the largest temperate ice bodies on Earth. NPI is nourished by moisture from the Pacific Ocean, which is transported by the southern hemisphere Westerlies and results in year-round precipitation. This system also creates a strong West to East gradient due to the rain shadow effect of the Andes (Warren, 1993). Most glaciers of the NPI, including Gualas Glacier, are currently receding from their historical maximum position, which was reached during the northern hemisphere Little Ice Age (LIA) (Harrison and Winchester, 2000). However, virtually nothing is known about the Holocene behavior of NPI outlet glaciers prior to the LIA, although it is generally assumed that they followed the pattern of Neoglacial advances described for the Southern Patagonian Icefield (SPI) by Mercer (1965, 1968, 1976). The lack of data in this sensitive area of the Patagonian Andes, the only continental cordillera in the Southern Hemisphere that intersects the entire Westerly Wind Belt, limits our understanding of climate processes that relate mid-latitude circulation patterns with low and high latitudes as well as the inter-hemispheric coupling of climate changes. We present the results of a marine geological survey at Golfo Elefantes, the depositional basin of Gualas Glacier. The dataset includes swath bathymetry, single channel seismic data and sediment cores analyses. The studied sedimentary record spans, with some hiatuses, at least the last 10.5 Ka. No evidences of ice proximal or till deposits were found in the area, and seismic records show no evidence of basin-wide erosional hiatuses. This implies that the arcuate terminal moraines that occur along the edges of Golfo Elefantes, which have been suggested to represent Neoglacial advances of Gualas Glacier, were instead formed during the waning stages of the local LGM (Late Pleistocene) after ~12.6 ka according to paleogeographical reconstructions

  1. 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

  2. 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. PMID:24205812

  3. Tectonic Processes Along the Southeastern Margin of Alaska - The Neogene Sedimentary Record: Yakataga Formation, St. Elias Mountains

    NASA Astrophysics Data System (ADS)

    Witmer, J. W.; Ridgway, K. D.; Brennan, P. R.; Arnaud, E.; Pavlis, T.

    2008-12-01

    Neogene collision of the Yakutat microplate with the southern Alaskan continental margin is associated with extreme rates of exhumation and erosion of the St. Elias Mountains. The exhumation and the concurrent development of temperate glaciers are recorded in the ~5000 m of sedimentary strata of the Yakataga Formation. We present new data from measured stratigraphic sections that document along-strike and temporal changes within the Yakataga Formation along this collisional margin during Miocene to Pleistocene time. In the eastern part of our study area, the Yakataga Formation consists of lenticular sandstone and conglomerate facies associated with fan-delta depositional environments that are overlain by thick-bedded glaciomarine strata. These strata grade to finer-grained sandstone and convoluted mudstone typical of marine shelf environments in the central part of our study area. Along strike in the westernmost part of our study area the Yakataga Formation is interpreted to be laterally equivalent to Neogene strata of the Redwood Formation. These strata include thick-bedded, macrofossil-rich sandstone, well-rounded conglomerate, and thin-bedded mudstone facies that are characteristic of nearshore and shelf depositional environments. These sediments were likely sourced by fluvial systems along the continental margin that served as the backstop for Neogene collision. Preliminary compositional data also suggest that the Redwood Formation was derived from a different source than the Yakataga Formation. Along-strike changes in structural configuration of the Yakataga Formation are also observed. In the easternmost part of our study area adjacent to the Dangerous River zone (DRZ), a possible remnant strike-slip fault system, unconformities between the Yakataga Formation and underlying strata require erosion of 1000s of meters of missing Eocene-Miocene strata. We interpret this part of the mountain range to have undergone the greatest amount of Neogene exhumation. In the

  4. Paleo-ocean chemistry based on records in marine sedimentary opal: implications for effect of Fe and other trace elements on biological productivity

    NASA Astrophysics Data System (ADS)

    Lal, D.; Charles, C. D.; Vacher, L.; Jull, A. J.; McHargue, L.

    2005-05-01

    We report on our discovery that marine opal contains a high fidelity record of dissolved oceanic concentrations of cosmic ray-produced radionuclides, 10Be and 26Al, while also capturing temporal variations in a large number of trace elements such as Ti, Fe, Zn, and Mn. This finding is based on our studies of trace elements (and two cosmogenic nuclides) in biogenic opal, over the last full ice age cycle, in opal derived from the site 1093 and its companion piston core TN057-13 (49o 59'S, 5o 52'E), near the present-day position of the Antarctic Polar Front. The data show potential for determining the controls on global ocean productivity -- in particular, the extent to which marine production can be modulated by external sources of micronutrients. Despite clear evidence for iron limitation in the modern ocean, the sedimentary record of "paleoproductivity" has not as yet offered any clear picture of the possible relationship between the changes in dust flux (known to have occurred over ice age cycles, for example), and regional or global productivity. Thus, with one sedimentary phase and in single sedimentary sections, we now have the potential to compare directly a proxy for aeolian input of micronutrients (e.g. Fe or Ti), with a proxy for production (e.g. 26Al/Al ratios). We expect that studies of the temporal records of trace elements and cosmogenic nuclides in contrasting regions of upwelling and productivity, which exhibit different sensitivities to global climate fluctuations and micronutrient inputs, would lead to a direct and comprehensive test of ideas such as Martin's hypothesis of iron control of atmospheric carbon dioxide Martin (1990), in different oceanic provinces during glacial cycles. Reference: Martin, J.H. Glacial-interglacial CO2 change: the iron hypothesis. Paleoceanography 5, 1-13, 1990.

  5. Macrofossils in Raraku Lake (Easter Island) integrated with sedimentary and geochemical records: towards a palaeoecological synthesis for the last 34,000 years

    NASA Astrophysics Data System (ADS)

    Cañellas-Boltà, N.; Rull, V.; Sáez, A.; Margalef, O.; Giralt, S.; Pueyo, J. J.; Birks, H. H.; Birks, H. J. B.; Pla-Rabes, S.

    2012-02-01

    Macrofossil analysis of a composite 19 m long sediment core from Rano Raraku Lake (Easter Island) was related to litho-sedimentary and geochemical features of the sediment. Strong stratigraphical patterns are shown by indirect gradient analyses of the data. The good correspondence between the stratigraphical patterns derived from macrofossil (Correspondence Analysis) and sedimentary and geochemical data (Principal Component Analysis) shows that macrofossil associations provide sound palaeolimnological information in conjunction with sedimentary data. The main taphonomic factors influencing the macrofossil assemblages are run-off from the catchment, the littoral plant belt, and the depositional environment within the basin. Five main stages during the last 34,000 calibrated years BP (cal yr BP) are characterised from the lithological, geochemical, and macrofossil data. From 34 to 14.6 cal kyr BP (last glacial period) the sediments were largely derived from the catchment, indicating a high energy lake environment with much erosion and run-off bringing abundant plant trichomes, lichens, and mosses into the centre of Raraku Lake. During the early Holocene the infilling of the lake basin and warmer conditions favoured the growth of a littoral plant belt that obstructed terrigenous input. Cladoceran remains and Solanaceae seeds are indicative of reduced run-off and higher values of N and organic C indicate increased aquatic and catchment productivity. From 8.7 to 4.5 cal kyr BP a swamp occupied the entire basin. The increase of Cyperaceae seeds reflects this swamp development and, with oribatid mites and coleopteran remains, indicates a peaty environment and more anoxic conditions in Raraku. At around 4.5 cal kyr BP dry conditions prevented peat growth and there is a sedimentary hiatus. About 800 cal yr BP, peat deposition resumed. Finally, in the last few centuries, a small lake formed within the surrounding swamp. Evidence of human activity is recorded in these

  6. "Sands of Pangea"-analysing the supercontinent formation and the Mesozoic sedimentary record using LA ICP MS U Pb zircon dating on samples from Germany-

    NASA Astrophysics Data System (ADS)

    Hofmann, Mandy; Linnemann, Ulf; Gerdes, Axel; Voigt, Thomas

    2013-04-01

    The Elbe Zone at the northern Bohemian Massif (part of the Central European Variscides, Saxony, Germany) contains important structures and outcrops that help to understand the final pulse of the Variscan Orogeny in Europe leading to the formation of supercontinent Pangea. We will present zircon U-Pb data from that area that allow the timing of the final stage of these movements and of related plutonic, volcano-sedimentary and tectonic processes. In addition, we will show U-Pb detrital zircon ages of sandstones from the Triassic, Jurassic and Cretatceous of Germany to draw conclusions about the sedimentary record and the source areas (provenance analyses) of these "sands of Pangea". We have analysed detrital zircon grains from the Buntsandstein (Lower Triassic) and the Keuper (Upper Triassic) regarding their U-Pb ages. These analyses indicate different zircon ages with a main peak at ca. 250 Ma to ca. 700 Ma. Distinct zircon grains of Meso- and Paleoproterozoic ages were found. In addition to the Triassic samples we analysed detrital zircon grains from the Middle Jurassic (Dogger) and the Cretaceous. The Cretaceous samples show similar ages as the Triassic ones: the main peak of zircon ages lies between ca. 240 Ma and 700 Ma. Also, there are a few isolated zircon grains with Meso- to Paleoproterozoic ages. A real change shows the Jurassic Sandstone, as the zircons of this sample have main ages at ca. 950 Ma to 1900 Ma. The zircon ages show, that the source areas for the Mesozoic sedimentary record changed clearly. We interpret the Paleozoic to Neoproterozoic ages of all samples as the influx of reworked local material, such as the Avalonian/Armorican basement units and the Variscan Basement. In our interpretation, the enormous amounts of Mesoproterozoic to upper Paleoproterozoic zircon ages in the Jurassic sample originated in the oceanic connection between Middle Europe and Baltica, as these specific zircon ages are typical for Baltica. This oceanic connection was

  7. Geomorphological and sedimentary record from Poseidi, N. Greece and relationship with Late Bronze and Iron age settlements

    NASA Astrophysics Data System (ADS)

    Psomiadis, David; Parashou, Theodoros; Albanakis, Konstantinos; Dotsika, Elissavet; Zisi, Nikoleta

    2010-05-01

    Coastal geomorphological features from Poseidi, Chalkidiki, N. Greece have been studied in order to classify the Late Pleistocene and Holocene formations that prevail across the coastal zone of Cape Poseidi. Carbonate cementation in the littoral shelf (beachrocks) indicates phases of coastal instability. The adjacent conglomerate formation and the stratigraphical characteristics of the backshore sedimentary sequence define the geomorphological setting of the human occupation in the area that dates back to 3500 BP. Eretrians settled the area (Pallini peninsula) during the Iron age, while Poseidi was already used for ritual ceremonies of god Neptune. Although ancient Mendi was built on an approximately 100m-high hill, its so-called "Suburb" by Thucydides was reaching the shoreline, and its cemetery was excavated in the beach sediments. Palaeo-shorelines have been reconstructed using bathymetry data and submerged fossil coastlines. The submerged beachrock horizons are spotted northwards at 1m, 1.7m, 2.4m and 3.6m depth as well as the formation occupies the swashzone at two subsequent separated beaches southwards near ancient Mendi. Tectonic movements were also evaluated and reconsidered in relation to coastal archaeological sites for the reconstruction of the geomorphological setting. The dynamic wave regime at Cape Poseidi and the sedimentary characteristics seem to have played a prominent role during stages of relatively stable sea level and influenced the human occupation in the area.

  8. Magnetostratigraphy and palaeoenvironmental records for a Late Cenozoic sedimentary sequence from Lanzhou, Northeastern margin of the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Sun, Donghuai; Zhang, Yuebao; Han, Fei; Zhang, Yan; Yi, Zhiyu; Li, Zaijun; Wang, Fei; Wu, Sheng; Li, Baofeng

    2011-04-01

    Geological studies indicate that several Tertiary fluvial-lacustrine basins existed in northwestern China. Progressive uplift of the Tibetan Plateau forced these Tertiary basins to dry, and eventually became accumulation areas for aeolian sediments. Continuous sedimentary sequences consisting of alluvial-fluvial sediments and aeolian Red Clay occurred in the Lanzhou area. We used palaeomagnetic and palaeoenvironmental techniques to investigate a late Tertiary section that has a Quaternary loess cover. Our results indicate that the area was a low altitude basin with a fluvial-lacustrine environment before ~ 7.2 Ma. Starting from ~ 7.2 Ma, the basin became a dry land and was exposed to aeolian accumulation. The presences of unconformities and sedimentary facies changes suggest that strong tectonic activity occurred during the interval of 3.5-1.8 Ma, which forced the Lanzhou Tertiary Basin to break up and became elevated to its present altitude. Gradual variations in sediment colour, grain-size and magnetic susceptibility imply that the Lanzhou area experienced progressive cooling and drying in the Late Cenozoic due to local tectonic uplift and global cooling.

  9. paleofire: An R package to analyse sedimentary charcoal records from the Global Charcoal Database to reconstruct past biomass burning

    NASA Astrophysics Data System (ADS)

    Blarquez, Olivier; Vannière, Boris; Marlon, Jennifer R.; Daniau, Anne-Laure; Power, Mitchell J.; Brewer, Simon; Bartlein, Patrick J.

    2014-11-01

    We describe a new R package, paleofire, for analysis and synthesis of charcoal time series, such as those contained in the Global Charcoal Database (GCD), that are used to reconstruct paleofire activity (past biomass burning). paleofire is an initiative of the Global Paleofire Working Group core team (www.gpwg.org), whose aim is to encourage the use of sedimentary charcoal series to develop regional-to-global syntheses of paleofire activity, and to enhance access to the GCD data by providing a common research framework. Currently, paleofire features are organized into three different parts related to (i) site selection and charcoal series extraction from the GCD; (ii) charcoal data transformation; and (iii) charcoal series compositing and synthesis. We provide a technical description of paleofire and describe some new implementations such as the circular block bootstrap procedure. We tested the software using GCDv3 data from eastern North America, and provide examples of interpreting results of regional and global syntheses.

  10. The sedimentary record of the 1960 tsunami in two coastal lakes on Isla de Chiloé, south central Chile

    NASA Astrophysics Data System (ADS)

    Kempf, P.; Moernaut, J.; Van Daele, M.; Vermassen, F.; Vandoorne, W.; Pino, M.; Urrutía, R.; Schmidt, S.; Garrett, E.; De Batist, M.

    2015-10-01

    This study describes sediments deposited by the tsunami following the 1960 Great Chilean Earthquake (MW 9.5) in two coastal lakes, Lakes Cucao and Huelde, on the west coast of Isla de Chiloé, south central Chile (42.6°S). Sub-bottom profiles and side scan sonar mosaics illustrate the sedimentary context of transects of gravity cores. The stratigraphy of both lakes features gyttja sedimentation, interrupted by the abrupt emplacement of a sandy layer with mud rip-up clasts and a mud cap. This sandy layer reflects a sudden change in sedimentary environment, most probably caused by a high-energy inundation. Radionuclide analyses (137Cs and 210Pb) date the inundation deposit to shortly before the mid 1960s. The only known event that matches the sedimentological and chronological criteria is the AD 1960 tsunami. Using grain size analysis and comparisons with samples from modern environments, we demonstrate that the proximal (seaward) part of the deposit consists of a mixture of sand derived from subaerial sources and reworked gyttja lake sediment. In the distal (landward) part of Lake Cucao, the sand component is lost and the deposit consists entirely of remobilised lake sediments. The repetition of tsunami deposit sequences in Lake Huelde suggests a minimum of three inundating waves. Sub-bottom profiles and side scan sonar mosaics reveal tsunami inundation over the barrier and more prominently through the outlet river channel. The dominant role of the river channel as a pathway for sediment transport is also described in core samples by tsunami deposits that fine away from the channel mouth. The identification and description of the deposit left by a known tsunami provide important insights into tsunami sedimentation in coastal lakes and have the potential to help in the search for paleotsunami evidence.

  11. Current-controlled Sedimentary Features into Lake Saint-Jean (Québec, Canada): a Record of Wind-driven Processes?

    NASA Astrophysics Data System (ADS)

    Nutz, A.; Schuster, M.; Ghienne, J. F.; Roquin, C.; Hay, M. B.; Retif, F.; Certain, R.; Robin, N.; Raynal, O.; Cousineau, P. A.; Bouchette, F. A.

    2014-12-01

    Lake Saint-Jean is the third largest natural lake in Québec (Canada), however very few studies have focused on the basin-scale limnogeology of this lake. An initial very high-resolution seismic survey of Lake Saint-Jean was conducted in 2011, providing more than 300 km of seismic sections throughout the lake. These seismic profiles permitted the identification of numerous depositional units at a basin-scale (Nutz et al., Boreas 2014). In this contribution, we focus on prominent large-scale, high-energy sedimentary features that are rather atypical in lakes: a sand-prone sedimentary shelf, sediment drifts and extensive erosional surfaces. All of these features may be attributed to wind-driven hydrodynamics affecting the central portion of the lake, at depths well below the wave base. Coupling the seismic profiles with a series of sediment cores and recent dating results, we now can propose a detailed characterization of these sedimentary features including age and context of emplacement, as well as the dominant depositional processes at work. Indeed, a numerical simulation of wind-induced bottom-current distribution based on realistic wind regimes was also applied in order to validate our previous wind-forcing interpretation. This research provides a more thorough understanding of depositional processes at the origin of fine-grained sediment accumulations in lakes. The prevalence of wind-driven processes in some lacustrine depositional systems is also addressed through the presentation of a conceptual depositional model well-suited for high-energy, wind-driven water-bodies. This model is of interest to all geoscientists dealing with present-day lake systems (e.g., reservoir lake management) as well as researchers working with paleo-lacustrine records and strata (e.g., bottom lake anoxia, hiatial surfaces, hydrocarbon exploration).

  12. New Iinsights Iinto Great Plains C4 Grassland Evolution and Paleoenvironmental Change From Paleosol Sedimentary Organic Matter d13C Records Over the Past 5 Myr

    NASA Astrophysics Data System (ADS)

    Chambers, K. L.; Fox-Dobbs, K.; Fox, D. L.; Haveles, A. W.; Snell, K. E.; Uno, K. T.; Polissar, P. J.; Martin, R.

    2015-12-01

    The Meade Basin (MB) of Southwestern Kansas, USA, contains abundant paleosols and mammalian fossil deposits that span the past 5 Myr. Geochemical records derived from paleosols provide insights into paleoenvironmental conditions in MB during the evolution of the Great Plains C4 grassland ecosystem. We measured carbon isotopes in pedogenic carbonates, plant waxes, and bulk sedimentary organic matter (OM) from the same stratigraphic level to directly compare the paleovegetation signal recorded in each proxy; to further understand carbon isotope systematics; and to estimate the relative proportions of C3 plant versus C4 grass biomass. Carbon isotope (δ13C) records were derived from OM preserved in the paleosol matrix and occluded in large carbonate nodules, and used to estimate %C3 plant versus %C4 grass biomass on the landscape. Carbonate δ13C records show a steady increase in C4 grass dominance in MB from <10% C4 biomass in the Miocene to near modern (~80%) levels by the mid Pleistocene. Leaf wax %C4 estimates were more variable, and also generally higher than the carbonate estimates. Our δ13C records of OM occluded in carbonate nodules are highly variable; much more so than the carbonate record generated from the same nodules, and the OM record does not show a clear increase in C4 grass dominance over time. We are able to rule out incomplete removal of carbonate as the source of high variability in OM δ13C values. A potential explanation is that OM occluded in nodules provides a spatial and temporal "snapshot" of aboveground biomass, while nodule carbonate reflects an integrated signal of paleovegetation. When combined, these proxies yield a more comprehensive landscape reconstruction. Specifically, the OM dataset gives insight into changes in paleovegetation heterogeneity over time. Our new understanding of the paleovegetation history in MB is being paired with paleoclimate records such as MAP (from elemental and magnetic proxies) and temperature (from clumped

  13. Sea-ice distribution in the modern Arctic Ocean: Biomarker records from trans-Arctic Ocean surface sediments

    NASA Astrophysics Data System (ADS)

    Xiao, Xiaotong; Fahl, Kirsten; Müller, Juliane; Stein, Ruediger

    2015-04-01

    Records of the spatial and temporal variability of Arctic Ocean sea ice are of significance for understanding the causes of the dramatic decrease in Arctic sea-ice cover of recent years. In this context, the newly developed sea-ice proxy IP25, a mono-unsaturated highly branched isoprenoid alkene with 25 carbon atoms biosynthesized specifically by sea-ice associated diatoms and only found in Arctic and sub-Arctic marine sediments, has been used to reconstruct the recent spatial sea-ice distribution. The phytoplankton biomarkers 24S-brassicasterol and dinosterol were determined alongside IP25 to distinguish ice-free or permanent ice conditions, and to estimate the sea-ice conditions semi-quantitatively by means of the phytoplankton-IP25 index (PIP25). Within our study, for the first time a comprehensive data set of these biomarkers was produced using fresh and deep-frozen surface sediment samples from the Central Arctic Ocean proper (>80°N latitude) characterised by a permanent ice cover today and recently obtained surface sediment samples from the Chukchi Plateau/Basin partly covered by perennial sea ice. In addition, published and new data from other Arctic and sub-Arctic regions were added to generate overview distribution maps of IP25 and phytoplankton biomarkers across major parts of the modern Arctic Ocean. These comprehensive biomarker data indicate perennial sea-ice cover in the Central Arctic, ice-free conditions in the Barents Sea and variable sea-ice situations in other marginal seas. The low but more than zero values of biomarkers in the Central Arctic supported the low in-situ productivity there. The PIP25 index values reflect modern sea-ice conditions better than IP25 alone and show a positive correlation with spring/summer sea ice. When calculating and interpreting PIP25 index as a (semi-quantitative) proxy for reconstructions of present and past Arctic sea-ice conditions from different Arctic/sub-Arctic areas, information of the source of

  14. Lipid biomarkers and pertinent indices from aquatic environment record paleoclimate and paleoenvironment changes

    NASA Astrophysics Data System (ADS)

    Ouyang, Xiaoguang; Guo, Fen; Bu, Hongmei

    2015-09-01

    Lipid biomarkers and their pertinent indices have been used as the most effective proxies for paleoclimate and paleoenvironment conditions. This paper conducts a systematic review on a variety of lipid biomarkers in aquatic sediments and water column that are used as proxies tracing paleoclimate and paleoenvironment information. The sources of those lipid biomarkers are autochthonous and/or allochthonous. General mechanisms of lipid biomarkers used as paleoclimate and paleoenvironment archives include characteristics of carbon chain distribution, temperature adaptation and combined temperature and humidity adaptation. Different lipid indices underpinned by the mechanisms are surrogates for the past precipitation, temperature and humidity as well as plant succession. We propose that the combined use of lipid indices and other biomarkers can expand the outlook of individual index, and provide a better understanding of paleoclimate and paleoenvironment reconstruction.

  15. Detached strata in a Tertiary low-angle normal fault terrane, southeastern California: a sedimentary record of unroofing, breaching, and continued slip

    SciTech Connect

    Miller, J.M.G.; John, B.E.

    1988-07-01

    Miocene sedimentary strata exposed in the eastern Chemehuevi Mountains, southeastern California, record development of an evolving low-angle normal fault system. The sequence includes more than 1 km of conglomerate and sandstone with rare interbedded monolithologic breccia and volcanic flows. Clasts of Peach Springs Tuff in basal units indicate that this succession is younger than 18 Ma. These rocks have been displaced by a regionally extensive low-angle normal fault, the Chemehuevi detachment, and are folded and faulted. Structural reconstructions and the character of associated fault rocks indicate that the Chemeheuvi fault was initiated at a low angle and that the footwall was progressively unloaded through thinning and displacement of its cover during extensional deformation. The syntectonic sedimentary rocks described here provide evidence that movement continued on the gently dipping (< 15/sup 0/) fault even after part of the fault was breached and the footwall eroded. The Conglomerates and sandstones were deposited by stream flow and debris flow on alluvial fans. Synsedimentary faulting is suggested by angular discordance below one monolithologic breccia bed and by local coarsening-upward sequences. Clast types reveal progressive unroofing of hanging-wall rocks to exposer the Chemehuevi fault zone, from which chloritic, brecciated granite clasts were derived. Clasts were then derived from both the hanging wall and the footwall, footwall debris being dominant high in the section. Distinctive clasts show that late displacement on this evolving fault system was on the order of 1 to 5 km.

  16. Denudation history of Eastern Indian peninsula from apatite fission track analysis: Linking possible plume-related uplift and the sedimentary record

    NASA Astrophysics Data System (ADS)

    Sahu, Himansu S.; Raab, Matthias J.; Kohn, Barry P.; Gleadow, Andrew J. W.; Kumar, Devender

    2013-11-01

    The Late Archaean-Early Proterozoic (~ 2.5 Ga) Eastern Dharwar Craton (EDC), eastern India, which underlies much of the drainage basins of the Krishna and Godavari rivers, has undergone an erosionally controlled evolution since the Pan African event (~ 500-550 Ma). This evolution has been responsible for the sedimentation and overall development of the Krishna-Godavari (KG) sedimentary basin. In order to reconstruct the denudation history of the EDC, which forms the hinterland to the petroliferous KG basin, we report apatite fission track (AFT) data from 41 samples. Thermal history modelling suggests that little denudation occurred before Mid-Cretaceous time. However, during the Late Cretaceous, accelerated cooling commenced from a temperature range of 60-75 °C. Assuming a low palaeogeothermal gradient of 10 °C/km, similar to that of the present day, cooling of the EDC translates to ~ 0.5-2 km of denudation during the Late Cretaceous and a total of ~ 4 km since that time. The denudation history is closely related to the sedimentary record in the KG basin. The episode of accelerated cooling in the Late Cretaceous is interpreted as a geomorphic response to uplift of the Indian peninsula possibly resulting from an ascending mantle plume, which produced the voluminous Deccan Traps at the K-T boundary. The denudation history coupled with previous palaeocurrent studies in the KG basin suggest that the Krishna-Godavari drainage system was established in Late Cretaceous time.

  17. Exploring the possibility to detect recent temporal changes in highly disturbed sedimentary records through sampling repetitions and core comparisons of porosity and sand content.

    PubMed

    Giuliani, S; Bellucci, L G; Romano, S; Piazza, R; Turetta, C; Vecchiato, M; Nhon, D H; Frignani, M

    2015-07-01

    Dating of sediment cores in dynamic environments (such as tropical coastal lagoons) is often impossible to achieve, due to the difficulty to recover continuous and undisturbed records. Detailed temporal definition of environmental changes cannot be assured, but there is the possibility that information retained in such sediments can still provide useful insights on local or large-scale sedimentary dynamics, when a specific strategy is adopted. This latter consists in repeated core samplings at the same location and in the comparison of core profiles for basic and easily measurable parameters (porosity and sand content). This approach was tested on sediment cores, collected repeatedly during the period 2005-2010, at the same site of the Thi Nai Lagoon (central Vietnam). The proposed procedure was able to evidence the impact on lagoon sediments of activities linked to the construction of industrial settlements in the area, with dredging removing a consistent sediment layer from 2005 to 2008 and waste dumping providing additional sediment input in the following period. Simple statistic confirmed this scenario, together with core profiles of PCBs, As, Cd, Pb, and Zn. The procedure represents a simple tool to study coastal dynamics in places where the level of accuracy of traditional sediment radiodating cannot be reached. Several ameliorations are suggested in order to help developing the monitoring of sedimentary processes in poorly studied areas. PMID:26130246

  18. Sedimentary record of coseismic subsidence in Hersek coastal lagoon (Izmit Bay, Turkey) and the late Holocene activity of the North Anatolian Fault

    NASA Astrophysics Data System (ADS)

    Bertrand, Sébastien; Doner, Lisa; Akçer Ön, Sena; Sancar, Ummuhan; Schudack, Ulla; Mischke, Steffen; Ćagatay, M. Namik; Leroy, Suzanne A. G.

    2011-06-01

    The late Holocene activity of a restraining bend of the northern strand of the North Anatolian Fault in Izmit Bay was investigated by a sedimentological, geochemical, and paleoecological analysis of sediment cores from Hersek coastal lagoon, NW Turkey. The sediment cores show a succession of sedimentary sequences composed of three units separated by gradual transitions. The first unit is composed of a thin layer of shell debris-rich sediment in abrupt contact with the underlying organic-rich deposits. This unit is overlain by a thick foraminifera-rich mud deposit, and the sequences are capped by an organic-rich mud unit. These sequences are interpreted as silting up, shallowing upward deposits, typical of a lagoon becoming isolated from the sea. We suggest that they represent the sedimentary signature of coseismic subsidence, which was caused by reverse slip at the Hersek bend, and tsunamis in Izmit Bay. Our radiocarbon-dated paleoseismological record indicates (1) the atypical collapse of the hanging wall during the 740 earthquake and (2) subsidence of the footwall during the 987, 1509, and 1719 earthquakes. This study contributes to the understanding of the dynamics of restraining bends, and it highlights the potential of coastal sediments for reconstructing past earthquakes and tsunamis in regions dominated by strike-slip deformations.

  19. Biomarker and molecular isotope approaches to deconvolve the terrestrial carbon isotope record: modern and Eocene calibrations

    NASA Astrophysics Data System (ADS)

    Diefendorf, A. F.; Freeman, K. H.; Wing, S.; Currano, E. D.

    2010-12-01

    Climate, biome, and plant community are important predictors of carbon isotope patterns recorded in leaves and leaf waxes. However, signatures recorded by terrestrial organic carbon and lipids that have mixed floral sources (e.g., n-alkanes) potentially reflect both plant community changes and climate. More taxonomically specific proxies for plants (i.e., di- and tri-terpenoids for conifers and angiosperms, respectively), can help to resolve the relative influences of changing community and climate, provided differences in biomarker production and lipid biosynthetic fractionation among plants can be better constrained. We present biomarker abundance and carbon isotope values for lipids from leaves, branches and bark of 44 tree species, representing 21 families including deciduous and evergreen conifers and angiosperms. n-alkane production differs greatly between conifer and angiosperm leaves. Both deciduous and evergreen angiosperms make significantly more n-alkanes than conifers, with n-alkanes not detected in over half of the conifers in our study. Terpenoid abundances scale strongly with leaf habit: evergreen species have significantly higher abundances. We combine these relative differences in lipid production with published estimates of fluxes for leaf litter from conifer and angiosperm trees to develop a new proxy approach for estimating paleo plant community inputs to ancient soils and sediments. To test our modern calibration results, we have evaluated n-alkanes and terpenoids from laterally extensive (~18 km) carbonaceous shales and mudstones in Eocene sediments (52.6 Ma) at Fifteenmile Creek in the Bighorn Basin (WY, USA). Our terpenoid-based proxy predicts on average a 40% conifer community, which is remarkably close in agreement with a fossil-based estimate of 36%. n-alkane carbon isotope fractionation (leaf-lipid) differs among plant types, with conifer n-alkanes about 2-3‰ 13C enriched relative to those in angiosperms. Since conifer leaves are

  20. Transverse, supraglacially derived crevasse infillings in a Pleistocene ice-sheet margin zone (eastern Poland): Genesis and sedimentary record

    NASA Astrophysics Data System (ADS)

    Godlewska, Anna; Terpiłowski, Sławomir

    2012-08-01

    The so-called 'crevasse infillings' in the marginal zone of the Saalian ice sheet in eastern Poland are atypical relief forms for lowlands glaciated in the Pleistocene. They are located on a high of the Cretaceous/Palaeogene substratum and form isolated ridges arranged in trains parallel to the former ice-sheet margin, i.e., transverse to the movement of the ice sheet. The sedimentary succession of the crevasse infillings consists mainly of undeformed glaciodeltaic deposits. We propose a model of the crevasse infilling development in three phases against the background of ice mass dynamics: 1) ice-sheet advance over a high of the substratum — compressive ice flow that bumped against the high's slope and enrichment of the ice with debris; 2) an overriding of the substratum high by ice masses — a tensional ice-flow regime resulted in significant crevassing; and 3) ice mass stagnation — low energy, supraglacial deltaic sedimentation in isolated ponds between disintegrated ice blocks under frozen bed conditions. Considering this genesis, we suggest classifying these forms as kames instead of crevasse infillings.

  1. What controls past and present organic carbon fluxes in the Arctic Ocean? - New insights from biomarker records

    NASA Astrophysics Data System (ADS)

    Stein, R. H.; Fahl, K.; Xiao, X.; Meheust, M.; Müller, J.

    2012-12-01

    The past and present Arctic Ocean is characterized by distinct changes in sea-ice cover, sea-surface-temperature, river discharge, and oceanic circulation patterns. All these factors also influence the organic carbon (OC) input, preservation and burial in the continental margin and adjacent deep sea areas (cf., Stein and Macdonald, 2004; Stein, 2008). Thus, records of amount and composition of OC in marine surface sediments and sediment cores yield important information on the spatial and temporal variability of Arctic Ocean (paleo-)environments. Especially, biomarker data allow to distinguish between these different processes controlling/influencing OC accumulation in the Arctic Ocean. In this context, we determined concentrations of the sea-ice diatom-derived biomarker IP25 (highly-branched isoprenoid - HBI - with 25 carbon atom; Belt et al., 2007), phytoplankton-derived biomarkers (brassicasterol and dinosterol) and terrigenous biomarkers (e.g., campesterol and long-chain n-alkanes) to estimate recent sea-ice conditions and related surface-water processes in the study area. A combined phytoplankton-IP25 biomarker approach (PIP25 index) is used to reconstruct the modern sea-ice distribution more quantitatively (Müller et al., 2009, 2011; Fahl and Stein, 2012; Stein et al., 2012). Starting from distribution maps of the different biomarker proxies for terrigenous input, sea-ice and primary production and indicative for modern processes controlling OC accumulation, we continue with biomarker data obtained from selected Arctic Ocean sediment cores. The biomarker records from the sediment cores give insights into the variability in river discharge, primary productivity and sea ice as well as OC fluxes from the Last Glacial Maximum to recent times. References Belt, S.T., Massé, G., Rowland, S.J., Poulin, M., Michel, C., LeBlanc, B., 2007. A novel chemical fossil of palaeo sea ice: IP25. Org. Geochem. 38, 16-27. Fahl, K. and Stein, R., 2012. Modern seasonal

  2. Middle Jurassic Topawa group, Baboquivari Mountains, south-central Arizona: Volcanic and sedimentary record of deep basins within the Jurassic magmatic arc

    USGS Publications Warehouse

    Haxel, G.B.; Wright, J.E.; Riggs, N.R.; Tosdal, R.M.; May, D.J.

    2005-01-01

    Among supracrustal sequences of the Jurassic magmatic arc of the southwestern Cordillera, the Middle Jurassic Topawa Group, Baboquivari Mountains, south-central Arizona, is remarkable for its lithologic diversity and substantial stratigraphic thickness, ???8 km. The Topawa Group comprises four units (in order of decreasing age): (1) Ali Molina Formation-largely pyroclastic rhyolite with interlayered eolian and fluvial arenite, and overlying conglomerate and sandstone; (2) Pitoikam Formation-conglomerate, sedimentary breccia, and sandstone overlain by interbedded silt- stone and sandstone; (3) Mulberry Wash Formation-rhyolite lava flows, flow breccias, and mass-flow breccias, with intercalated intraformational conglomerate, sedimentary breccia, and sandstone, plus sparse within-plate alkali basalt and comendite in the upper part; and (4) Tinaja Spring Porphyry-intrusive rhyolite. The Mulberry Wash alkali basalt and comendite are genetically unrelated to the dominant calcalkaline rhyolite. U-Pb isotopic analyses of zircon from volcanic and intrusive rocks indicate the Topawa Group, despite its considerable thickness, represents only several million years of Middle Jurassic time, between approximately 170 and 165 Ma. Sedimentary rocks of the Topawa Group record mixing of detritus from a minimum of three sources: a dominant local source of porphyritic silicic volcanic and subvolcanic rocks, identical or similar to those of the Topawa Group itself; Meso- proterozoic or Cambrian conglomerates in central or southeast Arizona, which contributed well-rounded, highly durable, polycyclic quartzite pebbles; and eolian sand fields, related to Middle Jurassic ergs that lay to the north of the magmatic arc and are now preserved on the Colorado Plateau. As the Topawa Group evidently represents only a relatively short interval of time, it does not record long-term evolution of the Jurassic magmatic arc, but rather represents a Middle Jurassic "stratigraphic snapshot" of the arc

  3. The Imbert Formation of northern Hispaniola: a tectono-sedimentary record of arc-continent collision and ophiolite emplacement in the northern Caribbean subduction-accretionary prism

    NASA Astrophysics Data System (ADS)

    Escuder-Viruete, J.; Suárez-Rodríguez, A.; Gabites, J.; Pérez-Estaún, A.

    2015-06-01

    In northern Hispaniola, the Imbert Formation (Fm) has been interpreted as an orogenic "mélange" originally deposited as trench-fill sediments, an accretionary (subduction) complex formed above a SW-dipping subduction zone, or the sedimentary result of the early oblique collision of the Caribbean plate with the Bahama Platform in the middle Eocene. However, new stratigraphical, structural, geochemical and geochronological data from northern Hispaniola indicate that the Imbert Fm constitutes a coarsening-upward stratigraphic sequence that records the transition of the sedimentation from a pre-collisional forearc to a syn-collisional piggy-back basin. This piggy-back basin was transported on top of the Puerto Plata ophiolitic complex slab and structurally underlying accreted units of the Rio San Juan complex, as it was emplaced onto the North America continental margin units. The Imbert Fm unconformably overlies different structural levels of the Caribbean subduction-accretionary prism, including a supra-subduction zone ophiolite, and consists of three laterally discontinuous units that record the exhumation of the underlying basement. The distal turbiditic lower unit includes the latest volcanic activity of the Caribbean island arc; the more proximal turbiditic intermediate unit is moderately affected by syn-sedimentary faulting; and the upper unit is a (caotic) olistostromic unit, composed of serpentinite-rich polymictic breccias, conglomerates and sandstones, strongly deformed by syn-sedimentary faulting, slumping and sliding processes. The Imbert Fm is followed by subsidence and turbiditic deposition of the overlying El Mamey Group. The 40Ar / 39Ar plagioclase plateau ages obtained in gabbroic rocks from the Puerto Plata ophiolitic complex indicate its exhumation at ∼ 45-40 Ma (lower-to-middle Eocene), contemporaneously to the sedimentation of the overlying Imbert Fm. These cooling ages imply the uplift to the surface and submarine erosion of the complex to

  4. The Imbert Formation of northern Hispaniola: a tectono-sedimentary record of arc-continent collision and ophiolite emplacement in the northern Caribbean subduction-accretionary prism

    NASA Astrophysics Data System (ADS)

    Escuder-Viruete, J.; Suárez-Rodríguez, Á.; Gabites, J.; Pérez-Estaún, A.

    2016-01-01

    In northern Hispaniola, the Imbert Formation (Fm) has been interpreted as an orogenic "mélange" originally deposited as trench-fill sediments, an accretionary (subduction) complex formed above a SW-dipping subduction zone, or the sedimentary result of the early oblique collision of the Caribbean plate with the Bahama Platform in the middle Eocene. However, new stratigraphical, structural, geochemical and geochronological data from northern Hispaniola indicate that the Imbert Fm constitutes a coarsening-upward stratigraphic sequence that records the transition of the sedimentation from a pre-collisional forearc to a syn-collisional basin. This basin was transported on top of the Puerto Plata ophiolitic complex slab and structurally underlying accreted units of the Rio San Juan complex, as it was emplaced onto the North America continental margin units.

    The Imbert Fm unconformably overlies different structural levels of the Caribbean subduction-accretionary prism, including a supra-subduction zone ophiolite, and consists of three laterally discontinuous units that record the exhumation of the underlying basement. The distal turbiditic lower unit includes the latest volcanic activity of the Caribbean island arc; the more proximal turbiditic intermediate unit is moderately affected by syn-sedimentary faulting; and the upper unit is a (chaotic) olistostromic unit, composed of serpentinite-rich polymictic breccias, conglomerates and sandstones, strongly deformed by syn-sedimentary faulting, slumping and sliding processes. The Imbert Fm is followed by subsidence and turbiditic deposition of the overlying El Mamey Group.

    The 40Ar / 39Ar plagioclase plateau ages obtained in gabbroic rocks from the Puerto Plata ophiolitic complex indicate its exhumation at ˜ 45-40 Ma (lower-to-middle Eocene), contemporaneously to the sedimentation of the overlying Imbert Fm. These cooling ages imply the uplift to the surface and submarine erosion of the complex to

  5. Paleoseismic evidence for pre-historic earthquakes in the sedimentary record of Botnsvatn Lake on the Húsavík-Flatey Fault, North Iceland

    NASA Astrophysics Data System (ADS)

    Avşar, Ulaş; Jónsson, Sigurjón; Geirsdóttir, Áslaug; Miller, Gifford H.

    2014-05-01

    Lacustrine and marine sedimentary records are crucial to evaluate paleoseismicity of offshore faults, since on-fault trenching methods are not applicable on them. Here, we present a case study from the Tjörnes Fracture Zone (TFZ) in North Iceland. The Húsavík-Flatey Fault, which is a part of the TFZ, is a ~100 km-long dextral strike-slip fault, of which almost 80% is offshore. The fault has produced magnitude 6-7 earthquakes in the past and poses a threat to the town of Húsavík, located on the fault, and the surrounding communities. However, information about historical earthquakes in the area is mostly limited to the past 300 years and even for that time period, the size and locations of major earthquakes are uncertain. We collected several piston cores from a small and a shallow lake called Botnsvatn, located on the fault to seek improving the knowledge about past earthquake activity. The longest and most complete core is 4.1 m long and provides a 2500 year-long sedimentary record. The physical and geochemical properties of the sediments along the cores were investigated by means of magnetic susceptibility, gamma-ray density, radiographic images on u-channels and micro-XRF scanning. The chronology of the sediments was constructed from four radiocarbon dates and 67 tephra layers. Five sedimentary events have been detected in the cores. Four of them can be attributed to increased sediment influx, probably due to seismically-triggered landslides in the catchment. The fifth event appears as a stratigraphic horizon of soft sediment deformations and is detected in multiple cores. The youngest event in the sequence temporally coincides with the historical 1872 AD earthquake (M=6.5) in the region. Based on the current preliminary data, we argue that "at least" five large earthquakes took place during the last 2500 years on this section of the fault. However, additional earthquakes may be detected after further sedimentological analyses that are planned in the coming

  6. Black Carbon as a marker for paleofires during the Late Quaternary in sedimentary record of Saci lake (PA) -Brazil

    NASA Astrophysics Data System (ADS)

    Martins, G. S.; Cordeiro, R. C.; Turcq, B.; Sifeddine, A.; Rodrigues, R.; Santos, A. B.; Moreira, L.; Guilles, M. C.; Seoane, J. S.

    2012-12-01

    Controversies still exist about the climate in the South American tropical forest over the Late Quaternary. In the present work, we show a sedimentary profile (SACI-1) of 243 cm in Saci Lake, located in the south of Para state. The paleoclimatic reconstruction was made by several geochemical markers, working as indicators of environmental changes in this lake during the Late Quaternary. Seventeen samples along the SACI-1 core were dated, and an age model was construct used a non-Bayesian, 'classical' age-depth models, showing a basal age of 35,500 cal years BP. The lithological description allows identifying six sedimentary units. Unit VI (35,500-29,900 cal yrs BP) and unit V (29,900-16,400 cal yr BP) are characterized by lowest concentrations of TOC, high values of C/N ratio and δ15N, and low values of chlorophyll derivates. These characteristics suggest a predominance of allochthonous organic matter. Unit V, covers the LGM (Last Maximum Glacial), when was observed the lowest values of TOC and moderate values of both BC concentration and flux (at approximately 162 cm), suggesting a dry period with low water level and wildfires in the region. Unit IV (9,100-8,300 cal years BP), presented a transition from a wetter to a drier climate with decreasing values of TOC and biogeochemical changes associated with a sandy sedimentation, indicating a higher intensity of run-off events. The higher values of C/N ratio and incresing δ13C values in this phase, suggest an increase in C4 vascular plants. The unit III (8,300-5,800 cal years BP) is characterized by a dry climate, with the lowest average values of total organic carbon, suggesting low lake levels. Low values of chlorophyll derivatives indicate a low productivity environment and high levels of clay suggest a low hydrodynamic depositional energy environment. The highest concentration of Black Carbon data indicated an increased occurrence of fires related to this dry climate. This phase was characterized by lower C

  7. Rifting, drifting, convergence and orogenesis: The sedimentary record of the Wernecke Supergroup on the Paleoproterozoic margin of northwestern Columbia

    NASA Astrophysics Data System (ADS)

    Furlanetto, F.; Thorkelson, D. J.; Rainbird, R.; Davis, B.; Gibson, D.; Marshall, D. D.

    2015-12-01

    The Wernecke Supergroup was deposited when the northwestern margin of Laurentia was undergoing major adjustments related to the assembly of the supercontinent Columbia (Nuna) in the late Paleoproterozoic. The succession was deposited between ca. 1663 and ca. 1620 Ma in two clastic to carbonate grand cycles. The detrital zircon population is bimodal, reflecting derivation from cratonic Laurentia. Basin shallowing at the end of the second grand cycle corresponds to a significant younging of detrital zircon populations. Specifically, the late Paleoproterozoic peak of zircon ages shifted from ca. 1900 Ma to ca. 1825 Ma, and the proportion of Archaean and early Paleoproterozoic zircon decreased. These shifts were caused by a change in drainage pattern in northern Laurentia during an early phase of the Forward orogeny, farther inland. The orogeny also led to inversion of the broadly correlative Hornby Bay Group. Zircon younger than 1.75 Ga is present throughout the sedimentary succession and may have originated from small igneous suites in northern Laurentia or larger magmatic arc terranes of the Yavapai and early Mazatzal orogenies in southern Laurentia. Eastern and southern Australia and the intervening Bonnetian arc may have contributed. The Wernecke Supergroup shares similar detrital zircon age and Nd isotope signatures with the Hornby Bay, Muskwa, Athabasca and Thelon successions of Canada; the Tarcoola Formation, Willyama Supergroup, and Isan Supergroup of Australia; and of the Dongchuan-Dahongshan-Hondo successions of South China. These similarities are compelling evidence for a shared depositional system in the late Paleoproterozoic. Western Columbia may have had a dynamic SWEAT-like configuration with Australia, East Antarctica and South China moving in a complex manner near the margin of western Laurentia. All of the continents except for South China underwent post-Wernecke tectonism during the Racklan, Forward, Olarian, Isan, Mazatzal and related orogenies, ca

  8. The Holocene deglaciation of the Byers Peninsula (Livingston Island, Antarctica) based on the dating of lake sedimentary records

    NASA Astrophysics Data System (ADS)

    Oliva, M.; Antoniades, D.; Giralt, S.; Granados, I.; Pla-Rabes, S.; Toro, M.; Liu, E. J.; Sanjurjo, J.; Vieira, G.

    2016-05-01

    The process of deglaciation in the Antarctic Peninsula region has large implications for the geomorphological and ecological dynamics of the ice-free environments. However, uncertainties still remain regarding the age of deglaciation in many coastal environments, as is the case in the South Shetland Islands. This study focuses on the Byers Peninsula, the largest ice-free area in this archipelago and the one with greatest biodiversity in Antarctica. A complete lacustrine sedimentary sequence was collected from five lakes distributed along a transect from the western coast to the Rotch Dome glacier front: Limnopolar, Chester, Escondido, Cerro Negro and Domo lakes. A multiple dating approach based on 14C, thermoluminescence and tephrochronology was applied to the cores in order to infer the Holocene environmental history and identify the deglaciation chronology in the Byers Peninsula. The onset of the deglaciation started during the Early Holocene in the western fringe of the Byers Peninsula according to the basal dating of Limnopolar Lake (ca. 8.3 cal. ky BP). Glacial retreat gradually exposed the highest parts of the Cerro Negro nunatak in the SE corner of Byers, where Cerro Negro Lake is located; this lake was glacier-free since at least 7.5 ky. During the Mid-Holocene the retreat of the Rotch Dome glacier cleared the central part of the Byers plateau of ice, and Escondido and Chester lakes formed at 6 cal. ky BP and 5.9 ky, respectively. The dating of the basal sediments of Domo Lake suggests that the deglaciation of the current ice-free easternmost part of the Byers Peninsula occurred before 1.8 cal. ky BP.

  9. Environment and Climate Changes during the Holocene: Inferred from Sedimentary Record/Proxies of a Paleodelta Region, Southwest Coast of India

    NASA Astrophysics Data System (ADS)

    Allu, N. C.; Prakash, V.; Gautam, P. K.; Bera, S. K.

    2014-12-01

    This work explains the sedimentation history and environment and climate changes during the Holocene along the southwest coast of India. The area is characterized by various landforms such as lagoons, barrier islands, beach ridges, paleostrandlines, alluvial plains, marshy lands and flood plains. Paleodelta, located at the mouth of the modern Periyar River is an important geomorphic marker. A borehole of 40 m depth was drilled in the paleodelta and sediment samples were recovered at different depth intervals. Paleoclimate and paleo-environment were inferred based on geochronology, textural and geotechnical parameters, clay minerals, and pollen analysis results. The bottom of the borehole represents an age of ~ 12 ka BP. Sediments exhibit coarsening texture upwards of the borehole, with fine mud and peat intercalations at the bottom. Six litho facies - muddy sand, sand, sandy mud, silty sand, sandy silt, and mud - were recorded. Geotechnical properties comprising moisture content, organic carbon, plasticity index record high values, whereas low bulk density associated with a low critical shear stress, are recorded. An increase in illite and to a lesser degree smectite with concomitant decrease in kaolinite is observed. Sediment texture represents a major change of depositional environment from marine to fluvial sedimentary facies during the major sea level fall i.e., after 7 ka B.P. The present sea level attained during 4-5 ka B.P; major rise of sea level has taken place from 7-11 ka BP and regression during 7 - 5 ka B.P. These transgression and regression phases introduced the changes in the environment of deposition. The monsoon was dynamic and more intense after the major fall of sea level causing the fluctuations in the fluvial facies. Upward coarsening of grain size in the borehole indicates change in sediment deposition due to increased hydrodynamic conditions and strong fluvial action, which can be linked to marine regression. Geotechnical properties suggest

  10. In search of "Organ III" strata-a sedimentary record of the Medieval Warm Period (ca. AD 900 to 1300)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The period AD 900 to 1300, internationally referred to as the Medieval Warm Period, is a critical time for the archaeological record of the Southwestern USA. During the Medieval Warm Period both alluvial and eolian sedimentation increased, but not to the magnitude of the middle Holocene (the Altithe...

  11. A record of hydrocarbon input to San Francisco Bay as traced by biomarker profiles in surface sediment and sediment cores

    USGS Publications Warehouse

    Hostettler, F.D.; Pereira, W.E.; Kvenvolden, K.A.; VanGeen, A.; Luoma, S.N.; Fuller, C.C.; Anima, R.

    1999-01-01

    San Francisco Bay is one of the world's largest urbanized estuarine systems. Its water and sediment receive organic input from a wide variety of sources; much of this organic material is anthropogenically derived. To document the spatial and historical record of the organic contaminant input, surficial sediment from 17 sites throughout San Francisco Bay and sediment cores from two locations Richardson Bay and San Pablo Bay were analyzed for biomarker constituents. Biomarkers, that is, 'molecular fossils', primarily hopanes, steranes, and n-alkanes, provide information on anthropogenic contamination, especially that related to petrogenic sources, as well as on recent input of biogenic material. The biomarker parameters from the surficial sediment and the upper horizons of the cores show a dominance of anthropogenic input, whereas the biomarker profiles at the lower horizons of the cores indicate primarily biogenic input. In the Richardson Bay core the gradual upcore transition from lower maturity background organics to a dominance of anthropogenic contamination occurred about 70-100 years ago and corresponds to the industrial development of the San Francisco Bay area. In San Pablo Bay, the transition was very abrupt, reflecting the complex depositional history of the area. This sharp transition, perhaps indicating a depositional hiatus or erosional period, dated at pre-1952, is clearly visible. Below, the hiatus the biomarker parameters are immature; above, they are mature and show an anthropogenic overlay. Higher concentrations of terrigenous n-alkanes in the upper horizons in this core are indicative of an increase in terrigenous organic matter input in San Pablo Bay, possibly a result of water diversion projects and changes in the fresh water flow into the Bay from the Delta. Alternatively, it could reflect a dilution of organic material in the lower core sections with hydraulic mining debris.

  12. Ancient Sedimentary Rocks

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-469, 31 August 2003

    The terraced area in this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image is an outcropping of ancient, sedimentary rock. It occurs in a crater in western Arabia Terra near 10.8oN, 4.5oW. Sedimentary rocks provide a record of past environments on Mars. Field work will likely be required to begin to get a good understanding of the nature of the record these rocks contain. Their generally uniform thickness and repeated character suggests that deposition of fine sediment in this crater was episodic, if not cyclic. These rocks might be indicators of an ancient lake, or they might have been deposited from grains settling out of an earlier, thicker, martian atmosphere. This image covers an area 3 km (1.9 mi) across and is illuminated from the lower left.

  13. Hydrological variability in the Northern Levant: a 250 ka multiproxy record from the Yammoûneh (Lebanon) sedimentary sequence

    NASA Astrophysics Data System (ADS)

    Gasse, F.; Vidal, L.; Develle, A.-L.; van Campo, E.

    2011-11-01

    The Levant is a key region in terms of both long-term hydroclimate dynamics and human cultural evolution. Our understanding of the regional response to glacial-interglacial boundary conditions is limited by uncertainties in proxy-data interpretation and the lack of long-term records from different geographical settings. The present paper provides a 250 ka paleoenvironmental reconstruction based on a multi-proxy approach from northern Levant, derived from a 36 m lacustrine-palustrine sequence cored in the small intra-mountainous karstic Yammoûneh basin from northern Lebanon. We combined time series of sediment properties, paleovegetation, and carbonate oxygen isotopes (δc), to yield a comprehensive view of paleohydrologic-paleoclimatic fluctuations in the basin over the two last glacial-interglacial cycles. Integration of all available proxies shows that Interglacial maxima (early-mid MIS 7, MIS 5.5 and early MIS 1) experienced relatively high effective moisture, evidenced by the dominance of forested landscapes (although with different forest types) associated with authigenic carbonate sedimentation in a productive waterbody. Synchronous and steep δc increases can be reconciled with enhanced mean annual moisture when changes in seasonality are taken into account. During Glacials periods (MIS 2 and MIS 6), open vegetation tends to replace the forests, favouring local erosion and detrital sedimentation. However, all proxy data reveal an overall wetting during MIS 6, while a drying trend took place during MIS4-2, leading to extremely harsh LGM conditions possibly linked to water storage as ice in the surrounding highlands. Over the past 250 ka, the Yammoûneh record shows an overall decrease in local effective water, coincident with a weakening of seasonal insolation contrasts linked to the decreasing amplitude of the eccentricity cycle. The Yammoûneh record is roughly consistent with long-term climatic fluctuations in the northeastern Mediterranean region (except

  14. Sources of Contamination in Sedimentary Relative Paleointensity Records: Comparison of Site U1308 (North Atlantic) with Other Matuyama-Brunhes Records

    NASA Astrophysics Data System (ADS)

    Channell, J. E.; Mazaud, A.; Stoner, J. S.

    2006-12-01

    Central Atlantic IODP Site U1308, drilled in 2004, constitutes a re-occupation of DSDP Site 609, drilled in 1983. The site has yielded a polarity magnetic stratigraphy and relative paleointensity record for the last 2 Myr. Brief excursional polarity intervals including the Iceland Basin, Punaruu, Cobb Mt. and Gilsa are clearly recorded in the u-channel record. Comparison of normalized remanence (paleointensity) records for different normalizers (demagnetized ARM, demagnetized IRM, and ARM acquisition) indicate that residuals (differences between the three normalized remanences) coincide with anomalies in magnetic grain-size sensitive parameters. Finer magnetic grain size intervals at this site (as indicated by peaks in karm/k) coincide with higher normalized remanence residuals, and also with interglacial intervals, as denoted by high reflectance (high carbonate). A coincidence of peak interglacials with paleointensity minima that has been noted in other North Atlantic paleointensity records (e.g. ODP Sites 983 and 984) may be attributed to contamination induced by finer magnetite grain populations in these intervals. The question arises as to whether the observed relationship between finer grain sizes and interglacial stages is sufficient to contaminate the normalized remanence record and give rise to the observed orbital power in many paleointensity records. At ODP Site 1089 in the sub-Antarctic South Atlantic, finer magnetic grain sizes are also associated with high carbonate intervals but here the pattern of carbonate variability follows an Indo-Pacific, rather than North Atlantic pattern, with high carbonate intervals coinciding with glacial intervals and terminations (rather than interglacial intervals). Normalized remanence records from Site U1308 (North Atlantic), Site 1089 (South Atlantic) and Pacific, are remarkably similar. The observed contamination associated with high carbonate intervals should be manifest very differently in the North Atlantic and

  15. Thresholds for earthquake-induced hydrological changes in sedimentary aquifers: a record from 9 earthquakes and 107 boreholes in central New Zealand

    NASA Astrophysics Data System (ADS)

    Weaver, Konrad; Cox, Simon; Holden, Caroline; Townend, John

    2016-04-01

    A dense hydrogeological network in central New Zealand has recorded groundwater fluctuations from 12 years of seismic events. Hydrological data over the past 15 years were assessed in 107 boreholes at depths of 4 - 405 m. Nine seismic events (M≥5.9) occurred at near- to far-field distances of 10 - 913 km, shaking the sedimentary aquifers at a wide range of 10‑4 to 103 J/m3 seismic energy densities. The earthquakes produced 258 detectable hydrological responses, exhibiting different polarities (rise or fall), amplitudes (2 to 820 mm, -859 to -2 mm) and timescales (15 min to day [s]). Shaking parameters were calculated from 28 proximal GeoNet broadband seismometers, providing local estimates of peak ground acceleration (PGA) and velocity (PGV), Arias intensity, and spectral amplitudes. ShakeMap model solutions, utilising ground motion prediction equations (GMPEs), were also acquired at borehole sites. Continuous oceanic tidal responses of 38 boreholes were derived using Baytap08, with temporal transmissivity and earthquake-induced changes estimated from tidal properties. The earthquake-induced changes to groundwater level and tidal response are used to infer those events which caused aquifer deformation and changes to the groundwater flow regime. A transient (15 min to 2 hr) / permanent (15 min to day [s]) deformation boundary is observed when shaking reaches ˜1 %g PGA. As well as defining thresholds at which hydrological changes occurred, the central New Zealand dataset provided an opportunity to examine aquifer ability in resistance to the effects induced by earthquakes. Where monitoring is dense and continuous, the absence of responses under certain levels of shaking is equally informative and helps delineate causative processes. On-going work utilises data mining to assess the contribution of seismic, hydrological, and geological parameters to earthquake-induced hydrological changes in sedimentary aquifer systems.

  16. A 200 year sedimentary record of progressive eutrophication in Lake Greifen (Switzerland): Implications for the origin of organic-carbon-rich sediments

    SciTech Connect

    Hollander, D.J. ); McKenzie, J.A. ); Haven, H.L. ten )

    1992-09-01

    Over the past 200 years Lake Greifen, a small lake in northeastern Switzerland, has undergone dramatic changes in primary productivity and eutrophication due to increased nutrient supply from agricultural activity and industrialization. A 40 year historical record of the water-column chemistry indicates that productivity and eutrophication reached a maximum in 1974, after which stricter regulations on the input of nutrients resulted in a progressive decrease. Collected cores show the sedimentary expression of this anthropogenically induced eutrophication by a well-developed annual sedimentation and by enhanced values of total organic carbon, organic-carbon accumulation rates, and hydrogen indices (HI) of the kerogens. Analyses of the carbon isotopic composition of sedimentary carbonates and organic matter reveal that the fractionation between these two phases varies with the HI of kerogens. This observation is explicable in terms of changing productivity and preservation of the organic matter, and the CO[sub 2 (aq)] budget of the water body. The authors propose that if high primary productivity were primarily responsible for the preservation and accumulation of organic matter, then a negative correlation will occur between [Delta][delta][sup 13]C[sub calcite-organic matter]([Delta][delta][sup 13]C[sub cal-om]) and HI values. In an environment with relatively low to moderate productivity but with bottom-water anoxia, a positive correlation will exist between [Delta][delta][sup 13]C[sub cal-om] and HI values. This study of Lake Greifen has implications for understanding paleoenvironmental controls on ancient organic-carbon-rich sediments.

  17. A Geochemical and Sedimentary Record of High Southern Latitude Holocene Climate Evolution from Lago Fagnano, Tierra del Fuego

    SciTech Connect

    Moy, C M; Dunbar, R B; Guilderson, T P; Waldmann, N; Mucciarone, D A; Recasens, C; Austin, J A; Anselmetti, F S

    2010-11-19

    Situated at the southern margin of the hemispheric westerly wind belt and immediately north of the Antarctic Polar Frontal zone, Tierra del Fuego is well-positioned to monitor coupled changes in the ocean-atmosphere system of the high southern latitudes. Here we describe a Holocene paleoclimate record from sediment cores obtained from Lago Fagnano, a large lake in southern Tierra del Fuego at 55{sup o}S, to investigate past changes in climate related to these two important features of the global climate system. We use an AMS radiocarbon chronology for the last 8,000 years based on pollen concentrates, thereby avoiding contamination from bedrock-derived lignite. Our chronology is consistent with a tephrochronologic age date for deposits from the middle Holocene Volcan Hudson eruption. Combining bulk organic isotopic ({delta}{sup 13}C and {delta}{sup 15}N) and elemental (C and N) parameters with physical sediment properties allow us to better understand sediment provenance and transport mechanisms and to interpret Holocene climate and tectonic change during the last 8,000 years. Co-variability and long-term trends in C/N ratio, carbon accumulation rate, and magnetic susceptibility reflect an overall Holocene increase in the delivery of terrestrial organic and lithogenic material to the deep eastern basin. We attribute this variability to westerly wind-derived precipitation. Increased wind strength and precipitation in the late Holocene drives the Nothofagus forest eastward and enhances run-off and terrigenous inputs to the lake. Superimposed on the long-term trend are a series of abrupt 9 negative departures in C/N ratio, which constrain the presence of seismically-driven mass flow events in the record. We identify an increase in bulk {delta}{sup 13}C between 7,000 and 5,000 cal yr BP that we attribute to enhanced aquatic productivity driven by warmer summer temperatures. The Lago Fagnano {delta}{sup 13}C record shows similarities with Holocene records of sea surface

  18. A geochemical and sedimentary record of high southern latitude Holocene climate evolution from Lago Fagnano, Tierra del Fuego

    NASA Astrophysics Data System (ADS)

    Moy, Christopher M.; Dunbar, Robert B.; Guilderson, Thomas P.; Waldmann, Nicolas; Mucciarone, David A.; Recasens, Cristina; Ariztegui, Daniel; Austin, James A.; Anselmetti, Flavio S.

    2011-02-01

    Situated at the southern margin of the hemispheric westerly wind belt and immediately north of the Antarctic Polar Frontal zone, Tierra del Fuego is well-positioned to monitor coupled changes in the ocean-atmosphere system of the high southern latitudes. Here we describe a Holocene paleoclimate record from sediment cores obtained from Lago Fagnano, a large lake in southern Tierra del Fuego at 55°S, to investigate past changes in climate related to these two important features of the global climate system. We use an AMS radiocarbon chronology for the last 8000 yr based on pollen concentrates, thereby avoiding contamination from bedrock-derived lignite. Our chronology is consistent with a tephrochronologic age date for deposits from the middle Holocene Volcán Hudson eruption. Combining bulk organic isotopic (δ13C and δ15N) and elemental (C and N) parameters with physical sediment properties allows us to better understand sediment provenance and transport mechanisms and to interpret Holocene climate and tectonic change during the last 8000 yr. Co-variability and long-term trends in C/N ratio, carbon accumulation rate, and magnetic susceptibility reflect an overall Holocene increase in the delivery of terrestrial organic and lithogenic material to the deep eastern basin. We attribute this variability to westerly wind-derived precipitation. Increased wind strength and precipitation in the late Holocene drives the Nothofagus forest eastward and enhances run-off and terrigenous inputs to the lake. Superimposed on the long-term trend are a series of abrupt 9 negative departures in C/N ratio, which constrain the presence of seismically-driven mass flow events in the record. We identify an increase in bulk δ13C between 7000 and 5000 cal yr BP that we attribute to enhanced aquatic productivity driven by warmer summer temperatures. The Lago Fagnano δ13C record shows similarities with Holocene records of sea surface temperature from the mid-latitude Chilean continental

  19. Integrated stratigraphy of the Smirra Coring: a new reference sedimentary record for the early Paleogene from the Umbria-Marche Basin (Northern Apennines, Italy)

    NASA Astrophysics Data System (ADS)

    Turtù, Antonio; Lauretano, Vittoria; Catanzariti, Rita; Galeotti, Simone; Lanci, Luca; Moretti, Matteo; Lourens, Lucas J.

    2016-04-01

    The early Paleogene represents a critical time interval in Earth's history characterized by prolonged greenhouse conditions, culminating in a series of extreme global warming events (i.e. hyperthermals), as well as large uncertainties in the Geological Time Scale. Therefore new, high-resolution, geological records are crucial in providing novel constraints on these topics. The Paleogene Umbria-Marche sections of the Northern Apennines (Italy) have shown to be suitable for integrated stratigraphy allowing regional-to-global correlations and environmental reconstructions across this time interval. Among several well-known sections, a new sedimentary record is provided by the Smirra Coring, which recovered an undisturbed sequence of rocks (~120 m from 4 overlapping holes) spanning the upper Scaglia Fms. (early Paleocene - middle Eocene) of the Umbria-Marche pelagic succession. Here we present a new, high-resolution, integrated stratigraphic framework (magnetostratigraphy, calcareous nannofossil biostratigraphy, physical properties, calibrated XRF core scanning and cyclostratigraphy) of the ~93 m composite section drilled in Smirra Holes 1 and 2. The succession extends almost continuously, with modest tectonic disturbance affecting its lowermost part with minor faulting. The resulting magnetic stratigraphy defines a succession of normal and reversed polarity magnetozones. The correlation of the paleomagnetic polarity sequence with the latest Geomagnetic Polarity Timescales (GPTSs; e.g. CK95, GTS 2004 and 2012), also constrained through nannofossil biostratigraphy, shows that the section spans the late Paleocene - middle Eocene from chrons C21n (~46 Ma) to C26r (~60 Ma). The overall sedimentation rates computed at Smirra are fully comparable with those from coeval sections from the Umbria-Marche Basin, ranging from ~10 m/Ma, between chrons C21n and C22n, to ~6 m/Ma, between chrons C22r and the base of the section. However, the sedimentation rates vary considerably

  20. Sedimentary Rocks

    NASA Technical Reports Server (NTRS)

    2005-01-01

    6 November 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows outcrops of sedimentary rocks in a crater located just north of the Sinus Meridiani region. Perhaps the crater was once the site of a martian lake.

    Location near: 2.9oN, 359.0oW Image width: width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Autumn

  1. The Owen Ridge uplift in the Arabian Sea: Implications for the sedimentary record of Indian monsoon in Late Miocene

    NASA Astrophysics Data System (ADS)

    Rodriguez, Mathieu; Chamot-Rooke, Nicolas; Huchon, Philippe; Fournier, Marc; Delescluse, Matthias

    2014-05-01

    The pelagic cover of the Owen Ridge in the Arabian Sea recorded the evolution of the Indian monsoon since the Middle Miocene. The uplift of the Owen Ridge resulted from tectonic processes along the previously unidentified Miocene India-Arabia plate boundary. Based on seismic reflection data tied with deep-sea drilling to track the Miocene India-Arabia plate boundary, we propose a new timing for the uplift of the Owen Ridge and highlight its impact on the record of climate changes in pelagic sediments. The new dataset reveals a fracture zone east of the Owen Ridge corresponding to the fossil plate boundary, and documents that the main uplift of the Owen Ridge occurred close to ˜8.5 Ma, and is coeval with a major uplift of the east Oman margin. Late Miocene deformation at the India-Arabia plate boundary is also coeval with the onset of intra-plate deformation in the Central Indian Ocean, suggesting a kinematic change of India and surrounding plates in the Late Miocene. The uplift of the Owen Ridge above the lysocline at ˜8.5 Ma accounts for a better preservation of Globigerina bulloides in the pelagic cover, previously misinterpreted as the result of a monsoon intensification event.

  2. Solar vs. Tidal Forcing of Centennial to Decadal Scale Variability in Marine Sedimentary Records from the Western Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Kirkwood, G.; Domack, E.; Brachfeld, S.

    2004-12-01

    Prior studies on Holocene marine sediments from the Antarctic Peninsula, including ODP Site 1098 and USAP N. B. Palmer jumbo piston cores have revealed pronounced multi-century scale variations within a number of paleoenvironmental proxies. In order to fully understand the exact timing of this signal an ultra-high resolution jumbo piston core from the Schollaert Drift was correlated with the well-known Palmer Deep record. A precise and accurate radiocarbon chronology is now available from the former site that utilizes in-situ mollusks, rather than bulk organic matter. The resulting time series spans the last 5000 years over the 20 m length of core NBP99-03 JPC28 and the surface stratigraphy of kasten core NBP01-07 KC8. The corrected and calibrated ages (with an applied reservoir correction of 1170 years) of 10 mollusks dated by the National Ocean Sciences Accelerator Mass Spectrometry Facility and the University of Arizona TAMS facility were used to construct an age-depth profile for JPC28 and KC8. A linear trend (R2 value of 0.993) of the age-depth profile was used to extrapolate the constant time interval between magnetic susceptibility measurements, which were analyzed every 1 cm. Dominant periods in the upper 10 m of the time series were identified using the Arand Spectral Analysis Package (Howell, 2001). This analysis revealed a single pronounced maxima at 160 years, which is inconsistent with the dominant periods found in time series of climate proxies from other sites on the western side of the Antarctic Peninsula. In particular, periods of 200 and 400 years, which are dominant in the Palmer Deep site (Warner and Domack, 2002), are not present in the Schollaert Drift. The spectral peaks derived from the two records are significantly different at the 95% confidence level. The cycles in the Palmer Deep record have been associated with solar variability, where as the 160 year cycle in the Schollaert Drift is close to a 180 year cycle in tidal forces (Keeling

  3. Sedimentary record of relay zone evolution, Central Corinth Rift (Greece): Role of fault propagation and structural inheritance.

    NASA Astrophysics Data System (ADS)

    Hemelsdaël, Romain; Ford, Mary; Meyer, Nicolas

    2013-04-01

    Relay zones along rift border fault systems form topographic lows that are considered to allow the transfer of sediment from the footwall into hanging wall depocentres. Present knowledge focuses on the modifications of drainage patterns and sediment pathways across relay zones, however their vertical motion during growth and interaction of faults segments is not well documented. 3D models of fault growth and linkage are also under debate. The Corinth rift (Greece) is an ideal natural laboratory for the study of fault system evolution. Fault activity and rift depocentres migrated northward during Pliocene to Recent N-S extension. We report on the evolution of a relay zone in the currently active southern rift margin fault system from Pleistocene to present-day. The relay zone lies between the E-W East Helike (EHF) and Derveni faults (DF) that lie just offshore and around the town of Akrata. During its evolution the relay zone captured the antecedent Krathis river which continued to deposit Gilbert-type deltas across the relay zone during fault interaction, breaching and post linkage phases. Moreover our work underlines the role that pre-existing structure in the location of the transfer zone. Offshore fault geometry and kinematics, and sediment distribution were defined by interpretation and depth conversion of high resolution seismic profiles (from Maurice Ewing 2001 geophysical survey). Early lateral propagation of the EHF is recorded by synsedimentary fault propagation folds while the DF records tilted block geometries since initiation. Within the relay zone beds are gradually tilted toward the basin before breaching. These different styles of deformation highlight mechanical contrasts and upper crustal partition associated with the development of the Akrata relay zone. Onshore detailed lithostratigraphy, structure and geomorphological features record sedimentation across the subsiding relay ramp and subsequent footwall uplift after breaching. The area is

  4. The U-Pb age and Hf isotope record of detrital zircons from Paleozoic sedimentary rocks of the proto-Andean accretionary orogen

    NASA Astrophysics Data System (ADS)

    Bahlburg, Heinrich

    2010-05-01

    -Pb detrital zircon ages (n= c. 5900) from Paleozoic sedimentary rocks representing the proto-Andes from Ecuador to Patagonia shows that age peaks coincide very well with the timing of assembly and dispersal of supercontinents. The coincidence with the respective record including collisional orogenic belts indicates that the preservational bias is not necessarily as pronounced a factor in shaping this record as previously thought. A similar compilation of Hf isotope data from proto-Andean detrital zircons (n= c. 620) shows a major divergence from the global patterns presented by Hawkesworth et al. (2009). The global data indicate peaks of juvenile crust production at the Archean-Paleoproterozoic transition and between 1.9 and 1.6 Ga. Subsequent orogenic cycles are not strongly reflected by juvenile data. This dichotomy is interpreted as due to the preferential preservation of evolved late stage orogenic crust in the rock record. In contrast, the detrital zircon Hf data from Paleozoic proto-Andean sedimentary rocks located in the the Andes from northern Peru to Patagonia reveal two important patterns, (i) production of juvenile crust occurred in the SW Amazonia Orogenic System and the proto-Andes throughout the Late Archean and Proterozoic; and (ii) a maximum seems to have been attained in the Rondonia-San Ignacio and Sunsas orogenic cycles between 1.55 and 0.9 Ga. The production of juvenile crust appears to have become a minor factor in this region at the Precambrian-Phanerozoic boundary. References Campbell, I.H. & Allen, C.M., 2008, Nature Geoscience 1, 554-558. Evans, D.A.D., 2009, Geological Society, London, Special Publication 327, 371-404. Hawkesworth, C. et al., 2009. Science 323, 49-50.

  5. Sedimentary record on the Indian Summer Monsoon since the Last Glacial Maximum: Evidence from the southeastern Andaman Sea

    NASA Astrophysics Data System (ADS)

    Shi, Xuefa; Liu, Shengfa; Cao, Peng; Khokiattiwong, Somkiat; Kornkanitnan, Narumol

    2016-04-01

    The Indian Summer Monsoon (ISM) generated by across-equatorial pressure gradient between the Asian continent and the southern Indian Ocean is a major component of the Asian monsoon system and establishes interactions among the ocean, land and atmosphere. Provenance and paleoclimate changes in the Andaman Sea during the last 26 ka were reconstructed from high-resolution records of grain-size, major elements and Sr-Nd isotopes in core ADM-9. The values of ɛNd(0) and 87Sr/86Sr were in good agreement with those of Irrawaddy River sediments, indicating a common source of origin. Two sensitive grain-size intervals (3.4-7.5 and 16.8-21.2 μm) were identified; the former was controlled primarily by sea-level change, whereas the latter was related to Irrawaddy River discharge and South-west Current transport driven by the ISM. Proxies of chemical weathering (K/Al) and terrigenous input (Ti/Ca) coupled with sensitive grain-size interval (16.8-21.2 μm population) revealed that the ISM was weak during ~15-26 ka BP and then strengthened gradually to a maximum during ~7-9 ka BP; subsequently, the ISM exhibited a generally declining trend to ~2 ka BP. The variation of the ISM recorded in this work is consistent with ISM variations observed in an open area in the northern Indian Ocean and in adjacent continents, implying the evolution of the Asia summer monsoon since 26 ka.

  6. Sedimentary Rock Layers

    NASA Technical Reports Server (NTRS)

    2004-01-01

    27 January 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows layers of sedimentary rock in a crater in western Arabia Terra. Layered rock records the history of a place, but an orbiter image alone cannot tell the entire story. These materials record some past episodes of deposition of fine-grained material in an impact crater that is much larger than the image shown here. The picture is located near 3.4oN, 358.7oW, and covers an area 3 km (1.9 mi.) wide. Sunlight illuminates the scene from the lower left.

  7. Fifty-year sedimentary record of heavy metal pollution (Cd, Zn, Cu, Pb) in the Lot River reservoirs (France).

    PubMed

    Audry, Stéphane; Schäfer, Jörg; Blanc, Gérard; Jouanneau, Jean-Marie

    2004-12-01

    The Lot-Garonne fluvial system is known for its historic heavy metal pollution resulting from mining and smelting activities since the late 19th century. Here, we report 137Cs activities and heavy metal (Cd, Zn, Cu, Pb and V) concentration-depth profiles from sediment cores retrieved in 2001 from three reservoirs in the Lot River. High mean sedimentation rates of 2.4-2.8 cm a(-1) are indicated by 137Cs dating. The reservoir sediments have recorded the heavy metal deposition and thus allow establishing a connection between the temporal evolution of the heavy metal pollution and historical changes in smelting and waste-treatment proceedings. Based on heavy metal concentrations in sediments upstream of the anthropogenic inputs and bottom-sediments of the furthest downstream core (interpreted as old soil or riverbed), concentrations of approximately 17, approximately 82, approximately 0.33 and approximately 28 mg kg(-1) for Cu, Zn, Cd and Pb, respectively, are proposed as natural background values for the Lot fluvial system. The geoaccumulation index (Igeo [Müller, G., 1979. Schwermetalle in den Sedimenten des Rheins-Veränderungen seit. Umschav 79, 133-149.]) revealed that the Lot River sediments must be considered as "severely polluted" in Cd and Zn. Moreover, despite remediation efforts undertaken in the former smelting site, the Lot River is still "severely" (Igeo approximately 4) and "moderately to severely" (Igeo>2) impacted by Cd and Zn inputs, respectively. PMID:15325457

  8. Composite sedimentary record of falling stages of Pleistocene glacio-eustatic cycles in a shelf setting (Crotone basin, south Italy)

    NASA Astrophysics Data System (ADS)

    Massari, F.; Sgavetti, M.; Rio, D.; D'Alessandro, A.; Prosser, G.

    1999-08-01

    A thick Pleistocene shelf and nearshore cyclical succession was deposited in the S. Mauro sub-basin of the Crotone basin (southern Italy). The regressive units of the cycles are mostly represented by coastal siliciclastic and bioclastic prograding wedges showing a clinoform geometry. These are separated by blanket-like deposits of high lateral persistence recording major transgressive episodes. The aim of this paper is (1) to describe facies patterns and depositional setting of two prograding wedges, particularly focussing on their polycyclic internal architecture, (2) to analyze these units within a sequence-stratigraphic framework, and (3) to speculate on the possible origin of the small-scale cyclicity. The two wedges analyzed in this paper consist of a number of shingles. Individual shingles consist of two physically connected units: (1) a relatively thin package of sigmoid clinoforms, grading into (2) a volumetrically dominant package of oblique-tangential clinoforms with toplap terminations. The shingles are bounded by seaward-dipping surfaces with sigmoid clinoform geometry, which are ravinement surfaces updip, passing into conformable flooding surfaces downdip. The wedges are thus organized into high-frequency, small-scale sequences, each comprising transgressive, highstand and falling-stage systems tracts. As a whole, individual prograding wedges are interpreted as forced-regressive units, as the shoreline was subject to an overall shift basinwards and downwards along a low-angle trajectory, in spite of the repeated minor relative sea-level rises. Tectonic subsidence, and particularly the syndepositional growth of gentle synclines, are thought to have been the key factors allowing the preservation of these forced-regressive units. Progradation of the wedges took place in a high-energy wave climate characterized by high frequency of storms and very efficient alongshore redistribution of sediments. Recurrent, storm-driven, offshore currents led to intense

  9. Geological Impacts and Sedimentary Record of the February 27, 2010, Chile Tsunami-La Trinchera to Concepcion

    USGS Publications Warehouse

    Morton, Robert A.; Buckley, Mark L.; Gelfenbaum, Guy; Richmond, Bruce M.; Cecioni, Adriano; Artal, Osvaldo; Hoffmann, Constanza; Perez, Felipe

    2010-01-01

    The February 27, 2010, Chilean tsunami substantially altered the coastal landscape and left a permanent depositional record that may be preserved at many locales along the central coast of Chile. From April 24 to May 2, 2010, a team of U.S. Geological Survey (USGS) and Chilean scientists examined the geological impacts of the tsunami at five sites along a 200-km segment of coast centered on the earthquake epicenter. Significant observations include: (1) substantial tsunami-induced erosion and deposition (+/- 1 m) on the coastal plain; (2) erosion from return flow, inundation scour around the bases of trees, and widespread planation of the land surface; (3) tsunami sand deposits at all sites that extended to near the limit of inundation except at one site; (4) evidence of multiple strong onshore waves that arrived at different times and from different directions; (5) vegetation height and density controlled the thickness of tsunami deposits at one site, (6) the abundance of layers of plane-parallel stratification in some deposits and the presence of large bedforms at one site indicated at least some of the sediment was transported as bed load and not as suspended load; (7) shoreward transport of mud boulders and rock cobbles where they were available; and (8) the maximum tsunami inundation distance (2.35 km) was up an alluvial valley. Most of the tsunami deposits were less than 25 cm thick, which is consistent with tsunami-deposit thicknesses found elsewhere (for example, Papua New Guinea, Peru, Sumatra, Sri Lanka). Exceptions were the thick tsunami deposits near the mouths of Rio Huenchullami (La Trinchera) and Rio Maule (Constitucion), where the sediment supply was abundant. The substantial vertical erosion of the coastal plain at Constitucion

  10. Fifty-year sedimentary record of heavy metal pollution in the lagoon of Oualidia (Moroccan Atlantic coast)

    NASA Astrophysics Data System (ADS)

    Zourarah, B.; Maanan, M.; Carruesco, C.; Aajjane, A.; Mehdi, K.; Conceição Freitas, M.

    2007-03-01

    The Oualidia lagoon is known for its heavy metal pollution resulting from mining and smelting activities since the late 19th century. Here, we report 137Cs and 210Pb activities and heavy metal concentration depth profiles from sediment cores retrieved in 1997. High mean sedimentation rates of 0.6-1 cm/y are indicated by 210Pb and 137Cs dating. The lagoon sediments have recorded heavy metal deposition and thus allow establishment of a connection between the temporal evolution of the heavy metal pollution and historical changes in smelting and waste-treatment proceedings. Through a study of the evolution of heavy metal contents, we can distinguish between two categories of metals: Al, Fe and Cr contents have varied around a mean value over the last seven decades and could have natural origins. Pb, Zn, Cu and Hg have relatively more elevated contents than those of the natural geochemical background, especially in the station in front of illegal sewerage discharges. These metals are enriched at depths between 20 and 30 cm; this corresponds to the period between 1960 and 1975, which was characterized by the setting up of the main suburbs and the first aquaculture farms that surround the lagoon. The pollution intensity of the lagoon is determined by enrichment factors and the geo-accumulation index, which show that the lagoon of Oualidia is unpolluted to moderately polluted on the Geo-I scale of Müler (1979. Schwermetalle in den Sedimenten, des Rheins-Veränderungen seit 1971. Umschau 79 (24), 778-783.).

  11. Revisiting "You are what you eat, +1‰": Bacterial Trophic Structure and the Sedimentary Record

    NASA Astrophysics Data System (ADS)

    Pearson, A.; Tang, T.; Mohr, W.; Sattin, S.

    2015-12-01

    "You are what you eat, +1‰" is a central principle of carbon stable isotope (δ13C) distributions and is widely applied to understand the structure and ordering of macrobiotic ecosystems. Although based on observations from multicellular organisms that are able to ingest "food", this idea also has been applied to Precambrian ecosystems dominated by unicellular, microbial life, with the suggestion that such systems could sustain ordered trophic structures observable in their isotopes. However, using a new approach to community profiling known as protein stable isotope fingerprinting (P-SIF), we find that the carbon isotope ratios of whole proteins separated from environmental samples show differences only between metabolically-distinct autotrophs; heterotrophs are not 13C-enriched. In parallel, a survey of the relative distribution of 13C between biochemical classes - specifically acetogenic lipids, isoprenoid lipids, amino acids, and nucleic acids/sugars - across a variety of bacterial species appears to be a function of the main carbon metabolite, not an indicator of heterotrophy vs. autotrophy. Indeed, autotrophy, heterotrophy, and mixotrophy all are indistinguishable when the primary food source is fresh photosynthate, i.e., sugar. Significant assimilation of acetate is diagnosed by acetogenic lipids that are relatively 13C-enriched vs. isoprenoid lipids. Mixed-substrate heterotrophy, in contrast, satisfies the classic "…+1‰" rule for bulk biomass, yet simultaneously it collapses the biochemical patterns of 13C almost completely. Together these observations point to a paradigm shift for understanding the preservation of bulk organic and lipid δ13C signatures in the rock record, suggesting that patterns of δ13Corg must primarily reflect changing carbon inputs, not the extent or intensity of heterotrophy.

  12. An Assessment of the Influence of Orbital Forcing on Late Pliocene Global Sea-Level Using a Shallow-Marine Sedimentary Record from the Wanganui Basin, New Zealand.

    NASA Astrophysics Data System (ADS)

    Sefton, J.; Naish, T.; Mckay, R. M.; Turner, G. M.; Morgans, H. E. G.; Seward, D.; Alloway, B.

    2015-12-01

    Classical Milankovitch Theory suggests variance in the orbital cycles of precession (21 kyr) and obliquity (41 kyr) should have a profound influence on insolation and ice volume. However, the globally-integrated ice volume proxy record (benthic δ18O) during the Late Pliocene (3.0-2.6 Ma) is dominated by obliquity-paced cycles, and lacks a significant precession component. A number of hypotheses have been proposed to explain this phenomenon, but paleoclimate records independent of the benthic δ18O record are required to test these. The Wanganui Basin, New Zealand, contains a shallow-marine Neogene sedimentary succession that is widely recognised as an important site for examining sea-level/ice volume changes at orbital frequencies. Here, we present a record of paleobathymetric changes at an orbital resolution from the Late Pliocene Mangaweka Mudstone outcrop succession. Modern analogue-calibrated water-depth proxies of grainsize and benthic foraminifera census data were used to evaluate paleobathymetric changes. An integrated magneto-, bio- and tephrostratigraphy was developed that constrains the outcrop succession to between ~3.0 Ma and 2.58 Ma. Nine distinct cycles spanning ~400,000 years are identified in the grainsize and benthic foraminifera assemblages. Within the uncertainty of the age model, the Mangaweka Mudstone grainsize cycles can be matched one-for-one to the δ18O cycles, as they display a similar pattern of frequency and amplitude. The frequency of these cycles (and the corresponding interval in the δ18O record) are dominated by the 41 kyr year obliquity cycle, but with a subordinate eccentricity component. Therefore, the fluctuations in the grainsize and benthic foraminifera proxies likely represent an indirect response to global sea-level fluctuations via their effect on continental shelf sediment transport mechanisms. The implications for the orbital theory of the ice ages are that during the Late Pliocene, global ice volume changes responded

  13. Gale Sedimentary Rocks

    NASA Technical Reports Server (NTRS)

    2005-01-01

    15 April 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows outcroppings of layered, sedimentary rock in eastern Gale Crater. North-central Gale Crater is the site of a mound that is more than several kilometers thick and largely composed of sedimentary rocks that record a complex history of deposition and erosion. At one time, Gale Crater might have been completely filled and buried beneath the martian surface.

    Location near: 4.9oS, 221.6oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Winter

  14. Sedimentary records of mangrove evolution during the past one hundred years based on stable carbon isotope and pollen evidences in Maowei, SW China

    NASA Astrophysics Data System (ADS)

    Xia, Peng; Meng, Xianwei; Li, Zhen; Feng, Aiping

    2016-06-01

    Mangroves accumulate sedimentary sequences, where cores can provide historical records of mangrove evolution with past climate change and human activity. The study traced the history of mangrove evolution during the past one hundred years in a mangrove swamp of Maowei Sea, SW China. The sedimentation rates (0.38-0.95 cm yr-1) were calculated on the basis of ln (210Pbxs/Al) and mass depth in the core sediments. Chemical tracers, such as δ13Corg and C:N values, were utilized to trace the contribution of mangrove-derived organic matter using a ternary mixing model. Because of potential diagenetic alteration and / or overlap in the isotopic signatures of different components, simultaneous use of mangrove pollen diagrams can help to supplement some of these limitations. Combined with mangrove pollen, mangrove evolution was reconstructed and could be divided into three stages: flourishment (1886-1905 AD), slight degradation (1905-1949 AD) and rapid degradation period (1949-2007 AD), which was consistent with previous reports. The reclamation of mangrove swamps to shrimp ponds was the major reason for rapid degradation of mangrove ecosystems in recent years, rather than climate change in the region.

  15. Traces of microbial activity in the deep sediment of the Dead Sea: How is life influencing the sedimentary record of this hypersaline lake ?

    NASA Astrophysics Data System (ADS)

    Thomas, Camille; Ebert, Yael; Kiro, Yael; Stein, Mordechai; Ariztegui, Daniel

    2016-04-01

    As part of the ICDP-sponsored Dead Sea Deep Drilling Project (DSDDP), a multi-disciplinary study has been carried out to understand the influence that microbial communities can have on the Dead Sea sedimentary record. Organic matter (lipids) and DNA extraction have been performed along the main core retrieved from the center of the modern Dead Sea. They revealed different associations of microbial communities, influenced by changing climatic and limnological regimes during sedimentation. Moreover, imaging and chemical characterization of authigenic iron-sulfur minerals have revealed the unexpected presence of an active sulfur cycle in the sediment. In particular, their morphology and Fe/S ratios are coherent with incomplete sulfate reduction, limited by sulfur reduction, and often resulting in the preservation of greigite. In glacial period intervals, pyritization may be complete, indicating full sulfate reduction probably allowed by significant accumulation of organic matter in the alternating aragonite and detritus (aad) facies. The DSDDP core provides a unique opportunity to investigate deep diagenetic processes and to assess the role of microbial activity in the Dead Sea hypersaline sediment. Our study shows that this microbial activity influences the carbon and sulfur phases, as well as magnetic fractions, potentially affecting proxies used for paleoenvironmental and paleoclimatic reconstructions.

  16. The evolution of the North Atlantic Oscillation for the last 700 years inferred from D/H isotopes in the sedimentary record of Lake Azul (Azores archipelago, Portugal).

    NASA Astrophysics Data System (ADS)

    Rubio de Ingles, Maria Jesus; Shanahan, Timothy M.; Sáez, Alberto; José Pueyo, Juan; Raposeiro, Pedro M.; Gonçalves, Vitor M.; Hernández, Armand; Trigo, Ricardo; Sánchez López, Guiomar; Francus, Pierre; Giralt, Santiago

    2015-04-01

    The δD plant leaf wax variations provide insights on precipitation and evaporation evolution through time. This proxy has been used to reconstruct the temporal evolution of the North Atlantic Oscillation (NAO) climate mode since this mode rules most of the climate variability in the central North Atlantic area. A total lipid extraction preparation and the correspondent analyses in the IRMS have been done for 100 samples from the uppermost 1.5 m of the sedimentary infill of Lake Azul (Azores archipelago, Portugal). According to the chronological model, established by 210Pb profile and 4 AMS 14C dates, this record contains the environmental history of the last 730 years. The reconstructed precipitation variations obtained from D/H isotope values, suggest that this area has suffered significant changes in its distribution and intensity rainfall patterns through time. The end of the Medieval Climate Anomaly (MCA, 1100- 1300 AD) is characterized by a progressive enrichmentof D/H isotope values which meant decreasing arid conditions. These rainfalls' increase might be interpreted by a shift from positive to negative dominance of the NAO. The Little Ice Age (LIA, 1300 - 1850 AD) was characterized by two humid periods (1300- 1550 AD and 1650 - 1850 AD) separated by a relatively dry period. These precipitation oscillations are clearly visible by marked changes in the D/H isotope values. The LIA was followed by the persistence of the positive NAO mode, exhibited by the depletion of the D/H isotope signal, which indicated an overall decrease of the precipitation in the central North Atlantic area. Surprisingly, the D/H of the last 100 years, characterized by the present global warming and a persistent positive NAO mode, display large fluctuations most possibly linked to an enhancement of the storminess which is in concordance with the data fluctuations observed in the instrumental record for the last 80 years in the archipelago. This climatic evolution is in accordance with

  17. Distribution of tetraether lipids in the 25-ka sedimentary record of Lake Challa: extracting reliable TEX86 and MBT/CBT palaeotemperatures from an equatorial African lake

    NASA Astrophysics Data System (ADS)

    Sinninghe Damsté, Jaap S.; Ossebaar, Jort; Schouten, Stefan; Verschuren, Dirk

    2012-09-01

    The distribution of isoprenoid and branched glycerol dialkyl glycerol tetraether (GDGT) lipids was studied in the sedimentary record of Lake Challa, a permanently stratified, partly anoxic crater lake on the southeastern slope of Mt. Kilimanjaro (Kenya/Tanzania), to examine if the GDGTs could be used to reconstruct past variation in regional temperature. The study material comprised 230 samples from a continuous sediment sequence spanning the last 25 ka with excellent age control based on high-resolution AMS 14C dating. The distribution of GDGTs showed large variation through time. In some time intervals (i.e., from 20.4 to 15.9 ka BP and during the Younger Dryas, 12.9-11.7 ka BP) crenarchaeol was the most abundant GDGT, whereas at other times (i.e., during the Early Holocene) branched GDGTs and GDGT-0 were the major GDGT constituents. In some intervals of the sequence the relative abundance of GDGT-0 and GDGT-2 was too high to be derived exclusively from lacustrine Thaumarchaeota, suggesting a sizable contribution from methanogens and other archaea. This severely complicated application of TEX86 palaeothermometry in this lake, and limited reliable reconstruction of lake water temperature to the time interval 25-13 ka BP, i.e. the Last Glacial Maximum and the period of post-glacial warming. The TEX86-inferred timing of this warming is similar to that recorded previously in two of the large African rift lakes, while its magnitude is slightly or much higher than that recorded at these other sites, depending on which lake-based TEX86 calibration is used. Application of calibration models based on distributions of branched GDGTs developed for lakes inferred temperatures of 15-18 °C for the Last Glacial Maximum and 19-22 °C for the Holocene. However, the MBT/CBT palaeothermometer reconstructs temperatures as low as 12 °C for a Lateglacial period centred on 15 ka BP. Variation in down-core values of the BIT index are mainly determined by the varying production rate of

  18. Demise of the northern Tethyan Urgonian carbonate platform and subsequent transition towards pelagic conditions: The sedimentary record of the Col de la Plaine Morte area, central Switzerland

    NASA Astrophysics Data System (ADS)

    Föllmi, Karl B.; Gainon, François

    2008-04-01

    The sedimentary succession of the Col de la Plaine Morte area (Helvetic Alps, central Switzerland) documents the disappearance of the northern Tethyan Urgonian platform in unprecedented detail and suggests stepwise platform demise, with each drowning phase documented by erosion and phosphogenesis. The first identified drowning phase terminated Urgonian carbonate production in a predominantly photozoan mode. Using a correlation of the whole-rock δ13C record with the well-dated record from SE France, its age is inferred to as Middle Early Aptian (near the boundary between the weissi and deshayesi zones). A subsequent drowning phase is dated by ammonites and by a correlation of the whole-rock δ13C record as Late Early Aptian (late deshayesi to early furcata zone). A third drowning phase provides an ammonite-based age of Early Late Aptian ( subnodosocostatum and melchioris zones) and is part of a widely recognized phase of sediment condensation and phosphogenesis, which is dated as latest Early to Middle Late Aptian (late furcata zone to near the boundary of the melchioris and nolani zones). The fourth and final drowning phase started in the latest Aptian ( jacobi zone) as is also indicated by ammonite findings at the Col de la Plaine Morte. The phases of renewed platform-carbonate production intervening between the drowning phases were all in a heterozoan mode. During the ultimate drowning phase, phosphogenesis continued until the Early Middle Albian, whereas condensation processes lasted until the Middle Turonian. Coverage of the external margin of the drowned Urgonian platform by a drape of pelagic carbonates started only in the Late Turonian. During the Santonian, the external part of the drowned platform underwent normal faulting and saw the re-exposure of already lithified Urgonian carbonates at the seafloor. Based on the here-inferred ages, the first drowning phase just precedes oceanic anoxic episode 1a (OAE 1a or "selli event") in time, and the second

  19. Terrestrial biomarker records in Seomjin Estuary in the South Sea of Korea: Implication for terrestrial flux and environmental changes

    NASA Astrophysics Data System (ADS)

    kim, Songyi; hyun, Sangmin; Kim, Wonnyon; Hyeong, Kiseong

    2016-04-01

    High-resolution records of terrestrial biomarkers, n-alkane compounds, were investigated in two gravity cores (SJP-2 and SJP-4) to evaluate variations in terrestrial organic matter influx. Based on 14C dating, sediments in both cores were deposited during the mid-Holocene; the ages of the bottom sediments of SJP-2 and SJP-4 reached 5,500 Cal yr BP and 5,000 Cal yr BP, respectively. High concentrations of total n-alkanes (nC25-35) in the two cores showed an increasing tendency from 4,500 yr to ca. 2,000 yr. The composition changed at the boundary of 2,500 yr in both cores, suggesting a variation in terrestrial biomarker influx at this time. Several indices including average chain length (ACL), carbon preference index (ICP), and paleo-vegetation index (Paq) showed coincident variations in both cores; ACL exhibited a narrow range of variations with a slight shift at 2,500 yr, CPI showed a decreasing tendency from 4,000 yr to 2,500 yr, and Paq increased during these intervals. Furthermore, the ratios of C23/C31 and C25/C31, indicate a relative abundance of epicuticular wax from vascular plants with coincident variations in both cores, and this also marched well with Paq. CPI excursions suggested that the total n-alkane proxy of the two cores might not only be linked to local climatic variability but also to local oceanographic conditions due to the different sedimentation rates. Variations in paleovegetation and paleoclimate around the study area might be strongly associated with the influx of terrestrial organic compounds derived from vascular plants. Additional 14C dating and isotope study of individual n-alkane biomarkers will provide detailed information on paleoclimatic and paleovegetation changes.

  20. Sedimentary record of regional deformation and dynamics of the thick-skinned southern Puna Plateau, central Andes (26-27°S)

    NASA Astrophysics Data System (ADS)

    Zhou, Renjie; Schoenbohm, Lindsay M.; Sobel, Edward R.; Carrapa, Barbara; Davis, Donald W.

    2016-01-01

    The Puna Plateau, adjacent Eastern Cordillera and the Sierras Pampeanas of the central Andes are largely characterized by thick-skinned, basement-involved deformation. The Puna Plateau hosts ∼N-S trending bedrock ranges bounded by deep-seated reverse faults and sedimentary basins. We contribute to the understanding of thick-skinned dynamics in the Puna Plateau by constraining regional kinematics of the poorly understood southern Puna Plateau through a multidisciplinary approach. On the southeastern plateau, sandstone modal composition and detrital zircon U-Pb and apatite fission-track data from Cenozoic strata indicate basin accumulation during the late Eocene to early Oligocene (∼38-28 Ma). Provenance analysis reveals the existence of a regional-scale basin covering the southern Puna Plateau during late Eocene to early Oligocene time (∼38-28 Ma) that was sourced from both the western plateau and the eastern plateau margin and had a depocenter located to the west. Petrographic and detrital zircon U-Pb data reveal erosion of proximal western and eastern sources after ∼12 Ma, in mid-late Miocene time. This indicates that the regional basin was compartmentalized into small-scale depocenters by the growth of basement-cored ranges continuing into the late Miocene (∼12-8 Ma). We suggest that the Cenozoic history of the southern Puna Plateau records the formation of a regional basin that was possibly driven by lithospheric flexure during the late Eocene to early Oligocene, before the growth of distributed basement-cored ranges starting as early as the late Oligocene.

  1. 2700 years of Mediterranean environmental change in central Italy: a synthesis of sedimentary and cultural records to interpret past impacts of climate on society

    NASA Astrophysics Data System (ADS)

    Mensing, Scott A.; Tunno, Irene; Sagnotti, Leonardo; Florindo, Fabio; Noble, Paula; Archer, Claire; Zimmerman, Susan; Pavón-Carrasco, Francisco Javier; Cifani, Gabriele; Passigli, Susanna; Piovesan, Gianluca

    2015-05-01

    Abrupt climate change in the past is thought to have disrupted societies by accelerating environmental degradation, potentially leading to cultural collapse. Linking climate change directly to societal disruption is challenging because socioeconomic factors also play a large role, with climate being secondary or sometimes inconsequential. Combining paleolimnologic, historical, and archaeological methods provides for a more secure basis for interpreting the past impacts of climate on society. We present pollen, non-pollen palynomorph, geochemical, paleomagnetic and sedimentary data from a high-resolution 2700 yr lake sediment core from central Italy and compare these data with local historical documents and archeological surveys to reconstruct a record of environmental change in relation to socioeconomic history and climatic fluctuations. Here we document cases in which environmental change is strongly linked to changes in local land management practices in the absence of clear climatic change, as well as examples when climate change appears to have been a strong catalyst that resulted in significant environmental change that impacted local communities. During the Imperial Roman period, despite a long period of stable, mild climate, and a large urban population in nearby Rome, our site shows only limited evidence for environmental degradation. Warm and mild climate during the Medieval Warm period, on the other hand, led to widespread deforestation and erosion. The ability of the Romans to utilize imported resources through an extensive trade network may have allowed for preservation of the environment near the Roman capital, whereas during medieval time, the need to rely on local resources led to environmental degradation. Cool wet climate during the Little Ice Age led to a breakdown in local land use practices, widespread land abandonment and rapid reforestation. Our results present a high-resolution regional case study that explores the effect of climate change on

  2. Constraining aggradation and degradation phases of alluvial fans in the sedimentary record: a case study from the Namib Desert, NW Namibia

    NASA Astrophysics Data System (ADS)

    von Hagke, Christoph; Malatesta, Luca C.; Ayoub, Francois; Stollhofen, Harald

    2015-04-01

    Along the Southern African margin it remains unclear whether the topography is the result of one or more Neogene uplift phases possibly related to mantle-driven dynamic topography, or a remnant of uplift due to pre-South Atlantic rifting and breakup during the Mesozoic. Whereas offshore seismic profiles and raised marine terraces onshore suggest phases of accelerated Neogene uplift, cosmogenic nuclide dating of river sediments and thermochronological data indicate constant uplift since post-Gondwana breakup. In this contribution we report present day erosion rate estimates from a fan-delta outboard the rift shoulder of the passive margin (i.e. the Great Escarpment), located in an area where erosion rate estimates on different timescales exist. Additionally, this fan-delta preserves elevated marine terraces on its surface, providing a unique time stratigraphic framework. It thus allows for direct comparison of erosion and uplift rate data as well as offshore-onshore correlation of sedimentary records. We constrain present day erosion rates of the system using quantitative sedimentology, and compare these results with published estimates of millennial and million year timescales. At present, erosion rates are 1.33E -06 mm/a, which is more than one order of magnitude lower than rates derived from cosmogenic nuclides, and several magnitudes lower than rates derived from thermochronological data. This shows that erosion rates constantly declined since the uplift pulse related to passive margin break-up. Subsequent erosional phases have not been effective enough to perturb this overall long-term trend. This is not in conflict with uplift rates inferred from raised beaches along the passive margin, if corrected for timescale dependent bias. With this study we are able to reconcile the confounding results from different data sets.

  3. A record of Appalachian denudation in postrift Mesozoic and Cenozoic sedimentary deposits of the U.S. Middle Atlantic continental margin

    USGS Publications Warehouse

    Poag, C.W.; Sevon, W.D.

    1989-01-01

    The complex interplay between source-terrain uplift, basin subsidence, paleoclimatic shifts, and sea-level change, left an extensive sedimentary record in the contiguous offshore basins of the U.S. middle Atlantic margin (Salisbury Embayment, Baltimore Canyon Trough, and Hatteras Basin). Isopach maps of 23 postrift (Lower Jurassic to Quaternary) a allostratigraphic units, coupled with a revised stratigraphic framework, reveal that tectonism, by regulating sediment supply (accumulation rate), dominated the interplay of forcing mechanisms. Tectonic pulses are evidenced by abruptly accelerated sediment accumulation, marked latitudinal shifts in the location of depocenters, and regional changes in lithofacies. Relatively rapid tectonic subsidence during the Early and Middle Jurassic history of the basins may have enhanced sediment accumulation rates. Beginning in the Late Jurassic, however, subsidence rates decreased significantly, though occasional short pulses of subsidence may have effected relative sea-level rises. Sea-level change heavily influenced the distribution and redistribution of sediments one they reached the basins, and paleoclimate regulated the relative abundance of carbonates and evaporites in the basins. We conclude that source terrains of the central Appalachian Highlands were tectonically uplifted, intensely weathered, and rapidly eroded three times since the Late Triassic: (1) Early to Middle Jurassic (Aalenian to Callovian); (2) mid-Early Cretaceous (Barremian); and (3) Late Cenozoic (Middle Miocene). Intervals of tectonic quiescence following these three tectonic pulses provided conditions suitable for the formation of regional erosion surfaces, geomorphic features commonly reported to characterize the central Appalachian Highlands. This series of three, irregularly spaced, tectonic/quiescent cycles does not, however, match the traditional four-cycle concept of post-Triassic Appalachian "peneplanation". ?? 1989.

  4. Sedimentary records of trace elements from large European lakes (Switzerland) document historic to recent freshwater pollution and climate-induced runoff variations

    NASA Astrophysics Data System (ADS)

    Thevenon, F.; Wirth, S. B.; Fujak, M.; Poté, J.; Thierry, A.; Chiaradia, M.; Girardclos, S.

    2011-12-01

    Continuous sedimentary records of anthropogenic and natural trace elements determined by ICPMS, from 5 large and deep perialpine lakes from Central Europe (Switzerland), evidence the environmental impacts of industrial fossil fuel pollution. In fact, the greatest increase in heavy metal pollution was registered at all the studied sites following the European industrial revolution of ca. AD 1800; with the highest values during the middle part of the 20th century. On a regional scale, anthropogenic heavy metal input subsequently stopped increasing thanks to remediation strategies such as the implementation of wastewater treatment plants (WWTPs). On the other hand, the discharge of industrial treated wastewaters into Vidy Bay of Lake Geneva during the second part of the 20th century involved the sedimentation of highly contaminated sediments in the area surrounding the WWTP outlet pipe discharge; less than 4 km from the main supply of drinking water of Lausanne (127'000 hab.). Microbial analyses furthermore reveal i) high increase in bacterial densities following the lake eutrophication in the 1970s, and that ii) the related sediments can be considered as a reservoir of antibiotic resistant bacteria/genes (of human origin). We finally compare instrumental hydrological data over the last century with variations of lithogenic trace elements (e.g., titanium) as registered in three large lakes (Brienz, Thun and Bienne) connected by the River Aar. This task allows to better constraining the runoff variations on a regional scale over the last decades for the the River Aar, and its possible increase under warming climate conditions in the European Alps.

  5. Lipid Biomarker Records Across the Permian-Triassic Boundary from Kap Stosch, Greenland

    NASA Astrophysics Data System (ADS)

    Hays, L. E.; Love, G. D.; Foster, C. B.; Grice, K.; Summons, R. E.

    2006-12-01

    The end-Permian extinction was the most severe in the past 500 million years of the Earth's history and evidence that an oceanic anoxic event (OAE) occurred contemporaneously has been presented previously [1,2]. OAEs have, therefore, been proposed as responsible for the mass mortality, and if the anoxic ocean was also euxinic, the release of hydrogen sulfide during upwelling and/or transgression provides an extinction agent in the ocean as well as on land. Chlorobiaceae, as indicators of photic zone euxinia (PZE), utilize hydrogen sulfide as an electron donor for anoxygenic photosynthesis. The detection of isorenieratane and a series of short-chain monoaromatic aryl isoprenoids, biomarkers for Chlorobiaceae, in sediments indicates the presence of hydrogen sulfide in the photic zone of the water column during sediment deposition. The Kap Stosch area in Eastern Greenland was identified as a Permian-Triassic boundary (PTB) outcrop of homogeneous shale, silty shale, and siltstone facies [3]. Another late Permian section in Eastern Greenland, the Ravnefjeld Formation, has framboidal pyrites indicative of sulfidic deep water [4]. A sample suite from the Kap Stosch region was studied using standard organic geochemistry methods including stable isotopic analyses of organic carbon, Rock-Eval pyrolysis, and biomarker hydrocarbon analysis. Aryl isoprenoids, including isorenieratane, were present in all samples studied and the concentrations were observed to fluctuate in tandem with TOC, similar to other Mesozoic OAEs. The molecular ratios of pristane/phytane and hopanes/steranes as well as the 2-methyl-hopane index (2-MHI) fluctuated dramatically through this section as they do at the type section at Meishan and in the Perth Basin [5]. The 2-MHI shows an inverse pattern to the total aryl isoprenoids, perhaps indicative of instability in the form of primary productivity in the water column during euxinic episodes. This can result in nitrogen limitation and a competitive

  6. Fluvial system response to abrupt climate change: sedimentary record example of the Paleocene-Eocene Thermal Maximum (PETM) in the South-Pyrenean foreland basin, Spain

    NASA Astrophysics Data System (ADS)

    Chen, Chen; Castelltort, Sebastien; Foreman, Brady; Hassenruck-Gudipati, Hima J.

    2015-04-01

    understand river response to the PETM climate change and try to assess the possible precipitation perturbations at the PETM in the study area and how these are transferred into the sedimentary record.

  7. Mid Holocene Evidence of High Energy Events in the Geological Record: Sedimentary Deposits from Cauvery Delta Coast, SE Coast of India.

    NASA Astrophysics Data System (ADS)

    Karthikeyan, A.; Seshachalam, S.; Jonathan, M. P.; Roy, P. D.

    2014-12-01

    The Cauvery Basin is one of the important sedimentary basins of southern India and provides information on geological processes since the Cretaceous. Most of the studies in the basin have been carried out on the sediments representing Cretaceous with less emphasis on the Quaternary period with marine high energy event. In the present study, we present the sedimentological and micro fauna assemblages in the 150 cm long trench from the Kameshwaram village, Nagapattinam District, South East Coast of India, in order to reconstruct the past event. OSL and Carbon dating of sand layer sediments from the Cauvery Basin provide the first proxy-record of marine event from the region over the Mid Holocene. A multi proxy approach using trench sediments from Cauvery Delta Coast, East coast of Tamil Nadu provides a high resolution record of high energy event. The dating of the event layer indicates 6 and 8 kyrs also below the layer shell layer was preserved, the radio carbon date of the shell layer was 6545 BC. A combination of sedimentological parameters of grain size, sorting, geochemical analysis (XRF) of Fe, Mn, Ti, Cr, Cu, Ni, Sr, Zr and foraminifera species like Ammonia beccarri, Ammonia dentate and Asterorotalia trispinosa were identified. The sediment layers have thinning-up sequences and it starts from 130 cm to the bottom of the layer 150 cm which included shell debris, and rip-up clasts. In addition, characteristic variations in elemental content at the bottom units of Zr, Ti, Ca is showing higher concentration, which is an indicator of high-energy depositional event often associated with an increase in Ti (2.08 % to 16.016 %) and Sr (116 ppm to 275 ppm). Ca on the other hand suggests a marine influence and Fe, Mn, Cr, Ni values are showing lower concentration indicating that the high marine energy event had inundated the Nagapattinam district in SE coast of India. Based on the multiproxy evidences, we conclude that this could be a major marine event during the Mid

  8. Terrestrial Plant Biomarkers Preserved in Cariaco Basin Sediments: Records of Abrupt Tropical Vegetation Response to Rapid Climate Changes

    NASA Astrophysics Data System (ADS)

    Hughen, K. A.; Eglinton, T. I.; Makou, M.; Xu, L.; Sylva, S.

    2004-12-01

    Organic-rich sediments from the anoxic Cariaco Basin, Venezuela, preserve high concentrations of biomarkers for reconstruction of terrestrial environmental conditions. Molecular-level investigations of organic compounds provide a valuable tool for extracting terrestrial signals from these annually laminated marine sediments. Differences in hydrogen isotopic fractionation between C16-18 and C24-30 n-alkanoic acids suggest a marine source for the shorter chain lengths and a terrestrial source for the longer chains. Records of carbon and hydrogen isotopes, as well as average carbon chain length (ACL), from long-chain n-alkanoic acids parallel millennial-scale changes in vegetation and climate between the late Glacial and Preboreal periods, 15,000 to 10,000 years ago. Data from all terrestrial chain lengths were combined to produce single δ D and δ 13C indices through deglaciation, exhibiting enrichment during the late Glacial and Younger Dryas and depletion during the Bolling-Allerod and Preboreal periods. δ D reflects the hydrogen isotopic composition of environmental water used for plant growth, combined with evaporative enrichment within leaf spaces, and as such may act as a proxy for local aridity. Leaf wax δ 13C, which is a proxy for C3 versus C4 metabolic pathways, indicates that C3 plants predominated in the Cariaco watershed during warm/wet Bolling-Allerod and Holocene periods, and C4 plant biomass proliferated during cool/dry Glacial and Younger Dryas intervals. Coupled carbon and hydrogen isotopic measurements together clearly distinguish deglacial climatic periods as wetter with C3 vegetation versus drier with C4 vegetation. High resolution biomarker records reveal the rapidity of vegetation changes in northern South America during the last deglaciation. The leaf wax data reveal that local vegetation biomass, although not necessarily entire assemblages, shifted between arid grassland and wetter forest taxa on timescales of decades. Comparison of ACL

  9. Combined terrestrial and marine biomarker records from an Icelandic fjord: insights into Holocene climate drivers and marine/ terrestrial responses

    NASA Astrophysics Data System (ADS)

    Moossen, H. M.; Seki, O.; Quillmann, U.; Andrews, J. T.; Bendle, J. A.

    2012-12-01

    Holocene climate change has affected human cultures throughout at least the last 4000 years (D'Andrea et al., 2011). Today, studying Holocene climate variability is important, both to constrain the influence of climate change on ancient cultures and to place contemporary climate change in a historic context. Organic geochemical biomarkers are an ideal tool to study how climatic changes have affected terrestrial and marine ecosystems, as a host of different biomarker based climate proxies have emerged over recent years. Applying the available biomarker proxies on sediment cores from fjordic environments facilitates the study of how climate has affected terrestrial and marine ecosystems, and how these ecosystems have interacted. Ìsafjardardjúp fjord in Northwest Iceland is an ideal location to study North Atlantic Holocene climate change because the area is very sensitive to changes in the oceanic and atmospheric current systems (Hurrell, 1995; Quillmann et al., 2010). In this study we present high resolution (1 sample/30 calibrated years) terrestrial and marine biomarker records from a 38 m sediment core from Ìsafjardardjúp fjord covering the Holocene. We reconstruct sea surface temperature variations using the alkenone derived UK'37 proxy. Air temperature changes are reconstructed using the GDGT derived MBT/CBT palaeothermometer. We use the average chain length (ACL) variability of n-alkanes derived from terrestrial higher plant leaf waxes to reconstruct changing precipitation regimes. The relationship between ACL and precipitation is confirmed by comparing it with the δD signature of the C29 n-alkane and soil pH changes inferred by the CBT proxy. The combined sea surface and air temperature and precipitation records indicate that different climate changing drivers were dominant at different stages of the Holocene. Sea surface temperatures were strongly influenced by the melting of the remaining glaciers from the last glacial maximum throughout the early

  10. Methane turnover and environmental change from Holocene biomarker records in a thermokarst lake in Arctic Alaska

    USGS Publications Warehouse

    Elvert, Marcus; Pohlman, John; Becker, Kevin W.; Gaglioti, Benjamin V.; Hinrichs, Kai-Uwe; Wooller, Matthew J.

    2016-01-01

    Arctic lakes and wetlands contribute a substantial amount of methane to the contemporary atmosphere, yet profound knowledge gaps remain regarding the intensity and climatic control of past methane emissions from this source. In this study, we reconstruct methane turnover and environmental conditions, including estimates of mean annual and summer temperature, from a thermokarst lake (Lake Qalluuraq) on the Arctic Coastal Plain of northern Alaska for the Holocene by using source-specific lipid biomarkers preserved in a radiocarbon-dated sediment core. Our results document a more prominent role for methane in the carbon cycle when the lake basin was an emergent fen habitat between ~12,300 and ~10,000 cal yr BP, a time period closely coinciding with the Holocene Thermal Maximum (HTM) in North Alaska. Enhanced methane turnover was stimulated by relatively warm temperatures, increased moisture, nutrient supply, and primary productivity. After ~10,000 cal yr BP, a thermokarst lake with abundant submerged mosses evolved, and through the mid-Holocene temperatures were approximately 3°C cooler. Under these conditions, organic matter decomposition was attenuated, which facilitated the accumulation of submerged mosses within a shallower Lake Qalluuraq. Reduced methane assimilation into biomass during the mid-Holocene suggests that thermokarst lakes are carbon sinks during cold periods. In the late-Holocene from ~2700 cal yr BP to the most recent time, however, temperatures and carbon deposition rose and methane oxidation intensified, indicating that more rapid organic matter decomposition and enhanced methane production could amplify climate feedback via potential methane emissions in the future.

  11. Biomarker and stable carbon isotopic signatures for 100-200 year sediment record in the Chaihe catchment in southwest China.

    PubMed

    Wang, Yanhua; Yang, Hao; Zhang, Jixiang; Xu, Meina; Wu, Changbin

    2015-01-01

    Natural inputs and anthropogenic influences on lakes and their catchments are reflected in the sediment record. In the present study, the extractable organic compounds from sediments in the Chaihe catchment of the Dianchi watershed were analyzed to characterize source inputs. Results show that the sediments are dominated by odd numbered n-alkanes (n-C16-n-C33), maximizing at n-C17, n-C29 and n-C31. Aliphatic hydrocarbon may be composed of terrestrial plants and bacteria. The values of δ(13)C27, δ(13)C29 and δ(13)C31 of n-alkanes exhibit a range from -33.27‰ to -25.46‰, from -35.76‰ to -28.47‰ and from -33.67‰ to -27.42‰, respectively and three records strongly covary with depth, falling within the range of C3 plants in the study area. An isotopic model revealed C3 plant contribution to sedimentary organic matter (OM) ranging from 40.75% to 97.22%. The values of ACL27-33, CPI27-33, OEP, Paq, Pr/Ph, (C27+C29)/2C31, (C21+C23+C25)/3C17 and nC26(-)/nC27(+) are consistent with the C3 plant predominance. A constant CRS model gave the accumulation rates ranging from 2.69 to 8.46mma(-1) spanning 1885-2010. It was concluded that OM transport in the Chaihe catchment was influenced strongly by human activities resulting in enhanced eutrophication. PMID:25261816

  12. Tetraether biomarker records from a loess-paleosol sequence in the western Chinese Loess Plateau

    PubMed Central

    Jia, Guodong; Rao, Zhiguo; Zhang, Jie; Li, Zhiyang; Chen, Fahu

    2013-01-01

    The ubiquitous occurrence of glycerol dialkyl glycerol tetraethers (GDGTs) in soils and their ability to record temperature and environmental changes offer the prospect of independently reconstructing continental paleotemperature and paleoenvironment from the loess-paleosol sequences (LPS) from the Chinese Loess Plateau (CLP). In this study we present records of GDGT-derived proxies for the last 70 kyr from the Yuanbao LPS, western CLP. Temperature record reconstructed from the cyclization and methylation index of branched tetraethers (MBT-CBT) displays that the onset of deglacial warming at ~20 kyr before present (BP) precedes the strengthening of summer monsoon at ~15 kyr BP, which is in agreement in timing with previous MBT-CBT temperature records from the southeastern CLP. The maximal deglacial warming of ~10°C is slightly higher than those in the southeastern CLP, perhaps due to the higher latitude and farther inland of the study site. The Branched and Isoprenoid Tetraether (BIT) index shows higher values (0.87–0.96 range, 0.93 average) in the glacial loess and lower values (0.76–0.91 range, 0.83 average) in the Holocene paleosols, with a steady decreasing trend since the early Holocene. The decreasing trend could suggest enhanced Thaumarchaeota relative to GDGT producing bacteria activity since the early Holocene, but other possibilities, such as preferential degradation of isoprenoid GDGTs or upward increase in living archaea relative to bacteria in the paleosol profile, cannot be fully excluded. Our results thus demonstrate the need of future study on microbial community structure in soil column and differential degradation of GDGT molecules. PMID:23898324

  13. Evolution of Sedimentary Rocks

    NASA Astrophysics Data System (ADS)

    Veizer, J.; MacKenzie, F. T.

    2003-12-01

    For almost a century, it has been recognized that the present-day thickness and areal extent of Phanerozoic sedimentary strata increase progressively with decreasing geologic age. This pattern has been interpreted either as reflecting an increase in the rate of sedimentation toward the present (Barrell, 1917; Schuchert, 1931; Ronov, 1976) or as resulting from better preservation of the younger part of the geologic record ( Gilluly, 1949; Gregor, 1968; Garrels and Mackenzie, 1971a; Veizer and Jansen, 1979, 1985).Study of the rocks themselves led to similarly opposing conclusions. The observed secular (=age) variations in relative proportions of lithological types and in chemistry of sedimentary rocks (Daly, 1909; Vinogradov et al., 1952; Nanz, 1953; Engel, 1963; Strakhov, 1964, 1969; Ronov, 1964, 1982) were mostly given an evolutionary interpretation. An opposing, uniformitarian, approach was proposed by Garrels and Mackenzie (1971a). For most isotopes, the consensus favors deviations from the present-day steady state as the likely cause of secular trends.This chapter attempts to show that recycling and evolution are not opposing, but complementary, concepts. It will concentrate on the lithological and chemical attributes of sediments, but not deal with the evolution of sedimentary mineral deposits (Veizer et al., 1989) and of life ( Sepkoski, 1989), both well amenable to the outlined conceptual treatment. The chapter relies heavily on Veizer (1988a) for the sections dealing with general recycling concepts, on Veizer (2003) for the discussion of isotopic evolution of seawater, and on Morse and Mackenzie (1990) and Mackenzie and Morse (1992) for discussion of carbonate rock recycling and environmental attributes.

  14. Oligo-Miocene syn-rift and Miocene post-rift sedimentary records: the tectono-stratigraphic development of the northern proximal margin of the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Robinet, J.; Razin, P.; Serra Kiel, J.; Gallardo Garcia, A.; Grelaud, C.; Roger, J.; Leroy, S.; Malaval, M.

    2012-04-01

    The northern margin of the Gulf of Aden results from the Oligo-Miocene rifting (34Ma) leading to continental break-up and the oceanic spreading since the Burdigalian (17.6 Ma). We, here, investigate in detail the tectono-stratigraphy development of the Ashawq Graben belonging to the proximal part of northern margin (southern Oman, Dhofar). This graben exhibits sedimentary records of syn-rift and post-rift sequences, so-called Dhofar (Rupelian-Burdigalian) and Fars (middle Miocene-Pliocene) Groups respectively. Analyzing the deposit conditions and sequences geometries provide fundamental inputs for the whole margin understanding. An accurate sedimentological and biostratigraphical analysis evidences two second-order sea level cycles corresponding to the syn-rift and the post-rift units separated by an erosive surface with paleo-karst cavities. The first stage of the rifting expresses as a regional uplift which led to set up of an early Oligocene mix platform system (Ashawq Fm., Shizar Mb.) overlying the proximal platform (Aydim Fm.) and continental (Zalumah Fm.) system deposit of the late Eocene to earliest Oligocene time. Then, the rift extension process during early Oligocene leads to verticals movements along normal faults and increase of the accommodation rate in the Ashawq graben. Such increase of accommodation is fully compensated by an important carbonate production leading to the aggradation of a thick reefal carbonate platform (Ashawq Fm., Nakhlit Mb.). An acceleration of the extension processes during late Oligocene time reaches an increase of the tectonic subsidence associated to the partial drowning and collapsing of the platform and to the set up of carbonate gravity-flow deposits in a deep basin (Mughsayl Fm.). In the most proximal realm, the sedimentation rate attempts to compensate the accommodation rate resulting in a differential aggradation of the reefal carbonate platform, sometimes in the form of patch reef. At the early Miocene time, the

  15. 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.

  16. Reconciling late Quaternary transgressions in the Bohai Sea, China to the global sea level changes, and new linkage of sedimentary records to three astronomical rhythms

    NASA Astrophysics Data System (ADS)

    Yi, Liang

    2013-04-01

    Terminations. Science 326, 248-252. Ding, Z.L., Yu, Z.W., Rutter, N.W., Liu, T.S., 1994. Towards an orbital time scale for chinese loess deposits. Quaternary Science Reviews 13, 39-70. IOCAS (Institute of Oceanology, Chinese Academy of Sciences), 1985. Bohai Sea Geology. Science Press, Beijing, China. Liu, T., 2009. Loess and Arid Environment. Anhui Science & Techonology Press, Hefei, China. Wang, Y., Cheng, H., Edwards, R.L., An, Z., Wu, J., Chen, C.-C., Dorale, J.A., 2001. A High-Resolution Absolute-Dated Late Pleistocene Monsoon Record from Hulu Cave, China. Science 294, 2345-2348. Wang, Y., Cheng, H., Edwards, R.L., Kong, X., Shao, X., Chen, S., Wu, J., Jiang, X., Wang, X., An, Z., 2008. Millennial- and orbital-scale changes in the East Asian monsoon over the past 224,000 years. Nature 451, 1090-1093. Yi, L., Yu, H., Ortiz, J.D., Xu, X., Chen, S., Ge, J., Hao, Q., Yao, J., Shi, X., Peng, S., 2012a. Late Quaternary linkage of sedimentary records to three astronomical rhythms and the Asian monsoon, inferred from a coastal borehole in the south Bohai Sea, China. Palaeogeography, Palaeoclimatology, Palaeoecology 329-310, 101-117. Yi, L., Lai, Z.P., Yu, H.J., Xu, X.Y., Su, Q., Yao, J., Wang, X.L., Shi, X., 2012b. Chronologies of sedimentary changes in the south Bohai Sea, China: Constraints from luminescence and radiocarbon dating. Boreas, doi: 10.1111/j.1502-3885.2012.00271.x. Yi, L., Yu, H.J., Ortiz, J.D., Xu, X.Y., Qiang, X.K., Huang, H.J., Shi, X., Deng, C.L., 2012c. A reconstruction of late Pleistocene relative sea level in the south Bohai Sea, China, based on sediment grain-size analysis. Sedimentary Geology 281, 88-100. Zhao, S., Yang, G., Cang, S., Zhang, H., Huang, Q., Xia, D., Wang, Y., Liu, F., Liu, C., 1978. Transgression's stratas and shoreline changes in the south coast of Bohai Bay, China. Oceanologia et Limnologia Sinica 9, 15-25.

  17. Abiologic silicon isotope fractionation between aqueous Si and Fe(III)-Si gel in simulated Archean seawater: Implications for Si isotope records in Precambrian sedimentary rocks

    NASA Astrophysics Data System (ADS)

    Zheng, Xin-Yuan; Beard, Brian L.; Reddy, Thiruchelvi R.; Roden, Eric E.; Johnson, Clark M.

    2016-08-01

    Precambrian Si-rich sedimentary rocks, including cherts and banded iron formations (BIFs), record a >7‰ spread in 30Si/28Si ratios (δ30Si values), yet interpretation of this large variability has been hindered by the paucity of data on Si isotope exchange kinetics and equilibrium fractionation factors in systems that are pertinent to Precambrian marine conditions. Using the three-isotope method and an enriched 29Si tracer, a series of experiments were conducted to constrain Si isotope exchange kinetics and fractionation factors between amorphous Fe(III)-Si gel, a likely precursor to Precambrian jaspers and BIFs, and aqueous Si in artificial Archean seawater under anoxic conditions. Experiments were conducted at room temperature, and in the presence and absence of aqueous Fe(II) (Fe(II)aq). Results of this study demonstrate that Si solubility is significantly lower for Fe-Si gel than that of amorphous Si, indicating that seawater Si concentrations in the Precambrian may have been lower than previous estimates. The experiments reached ∼70-90% Si isotope exchange after a period of 53-126 days, and the highest extents of exchange were obtained where Fe(II)aq was present, suggesting that Fe(II)-Fe(III) electron-transfer and atom-exchange reactions catalyze Si isotope exchange through breakage of Fe-Si bonds. All experiments except one showed little change in the instantaneous solid-aqueous Si isotope fractionation factor with time, allowing extraction of equilibrium Si isotope fractionation factors through extrapolation to 100% isotope exchange. The equilibrium 30Si/28Si fractionation between Fe(III)-Si gel and aqueous Si (Δ30Sigel-aqueous) is -2.30 ± 0.25‰ (2σ) in the absence of Fe(II)aq. In the case where Fe(II)aq was present, which resulted in addition of ∼10% Fe(II) in the final solid, creating a mixed Fe(II)-Fe(III) Si gel, the equilibrium fractionation between Fe(II)-Fe(III)-Si gel and aqueous Si (Δ30Sigel-aqueous) is -3.23 ± 0.37‰ (2

  18. Late Miocene biomarker and pollen records in Southeast Atlantic Ocean sediments indicate environmental changes

    NASA Astrophysics Data System (ADS)

    Rommerskirchen, Florian; Dupont, Lydie; Condon, Tegan; Mollenhauer, Gesine; Schefuß, Enno

    2010-05-01

    , probably driven by the formation of the West Antarctic ice sheet [1,2]. The transport way for terrestrial organic matter, pollen and spores changed from riverine to predominantly airborne contribution potentially accompanied by a change of the source area. However, pollen records and molecular stable carbon and hydrogen isotopic measurements of plant leaf wax n-alkanes exhibit spreading grassy vegetation due to a stepwise growing aridity in South Africa. After 8 Myrs BP terrestrial floral assemblages got more affinity to those of the Pleistocene and mark the beginning of the floral change towards C4-dominance. We infer that by the end of the Miocene C4 grasslands became important in Southwest Africa. References [1] Zachos, J. et al. (2001) Science 292, 686-693. [2] Diester-Haass, L.D., et al. (1990) Paleoceanogr. 5, 685-707. [3] Tipple, B.J., Pagani, M. (2007) Annu. Rev. Earth Planet. Sci. 35, 435-461.

  19. Sedimentary response to sea ice and atmospheric variability over the instrumental period off Adélie Land, East Antarctica

    NASA Astrophysics Data System (ADS)

    Campagne, Philippine; Crosta, Xavier; Schmidt, Sabine; Noëlle Houssais, Marie; Ther, Olivier; Massé, Guillaume

    2016-07-01

    Diatoms account for a large proportion of primary productivity in Antarctic coastal and continental shelf zones. Diatoms, which have been used for a long time to infer past sea surface conditions in the Southern Ocean, have recently been associated with diatom-specific biomarkers (highly branched isoprenoids, HBI). Our study is one of the few sedimentary research projects on diatom ecology and associated biomarkers in the Antarctic seasonal sea ice zone. To date, the Adélie Land region has received little attention, despite evidence for the presence of high accumulation of laminated sediment, allowing for finer climate reconstructions and sedimentary process studies. Here we provide a sequence of seasonally to annually laminated diatomaceous sediment from a 72.5 cm interface core retrieved on the continental shelf off Adélie Land, covering the 1970-2010 CE period. Investigations through statistical analyses of diatom communities, diatom-specific biomarkers and major element abundances document the relationships between these proxies at an unprecedented resolution. Additionally, comparison of sedimentary records to meteorological data monitored by automatic weather station and satellite derived sea ice concentrations help to refine the relationships between our proxies and environmental conditions over the last decades. Our results suggest a coupled interaction of the atmospheric and sea surface variability on sea ice seasonality, which acts as the proximal forcing of siliceous productivity at that scale.

  20. Biomarker Record From the Tisdale Group (2707 - 2705 Ma) and Porcupine Group (2685 - 2673 Ma) of the Abitibi Subprovidence, Timmins, Ontario, Canada

    NASA Astrophysics Data System (ADS)

    Ventura, G. T.; Kenig, F.

    2004-12-01

    Saturated/unsaturated and aromatic hydrocarbon fractions extracted from greenshist facies metasedimentary greywackes, siltstones, and shales of the Tisdale (2707-2705 Ma) and Porcupine Group (2685-2673 Ma) of the Abitibi Subprovince, Ontario Canada were analyzed for biomarkers. Core and hand samples were obtained from three mines run by Porcupine Joint Ventures and the core library at the Ministry of Northern Development and Mines, Timmins, Ontario. Tisdale Group sedimentary facies were previously interpreted as laminated massive sulfide and/or interflow sediments interstratified by subaqueous komatitic-tholeiitic flows. Porcupine Group turbidite facies were interstratified by massive, brecciated alkaline lava flows and reworked volcaniclastic facies. All Porcupine Group samples contained primary depositional fabric. Biomarker maturity calculations indicate the sediments are mature and either reached or surpassed oil generation. All samples contained hopanes C27 22,29,30-trisnorhopane-II (Ts & Tm), C29 α β -30-norhopane, C29 18α -30-norneohopane, C{30 } α β hopane, C30 β α - hopane, and C31-C35 (22S & R) homohopanes. Most samples contained C27-C29 (20S & R) β α diacholestane, C27-C29 α β β cholestane (20S & R), C27-C29 α α α cholestane (20S & R), and 4-methyl steroids. Tricyclic terpanes ranging from C19-C29, but were not present in all samples. Biomarkers from the Tisdale Group samples are similar to those found in modern hydrothermal systems and include unresolved complex mixtures, abundant branched alkanes with quaternary carbon atoms, alkyl-cyclohexanes (C16-C29 with strong odd over even dominance), alkyl-cyclopentanes (C16-C29) containing only even carbon number homologs), and C37-C40 acyclic and cyclic archeal isoprenoids. Biomarkers from the Porcupine Group samples include C16-C35, branched alkanes, C16-C29 alkyl-cyclohexanes and alkyl-cyclopentanes (with no carbon number preference). Aromatic fraction for this group were generally low and

  1. 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

  2. Soft-sediment deformation structures in Cambrian Series 2 tidal deposits (NW Estonia): implications for identifying endogenic triggering mechanisms in ancient sedimentary record

    NASA Astrophysics Data System (ADS)

    Põldsaar, Kairi

    2015-04-01

    Soft-sediment deformation structures (SSDS) are documented in several horizons within silt- and sandstones of the Cambrian Series 2 (Dominopolian Stage) Tiskre Formation, and some in the below-deposited argillaceous deposits of the Lükati Formation (northern part of the Baltoscandian Palaeobasin, NW Estonia). The aim of this study was to map, describe, and analyze these deformation features, discuss their deformation mechanism and possible triggers. Load structures (simple load casts, pillows, flame structures, convoluted lamination) with varying shapes and sizes occur in the Tiskre Fm in sedimentary interfaces within medium-bedded peritidal rhythmites (siltstone-argillaceous material) as well as within up to 3 m thick slightly seaward inclined stacked sandstone sequences. Homogenized beds, dish-and-pillar structures, and severely deformed bedding are also found within these stacked units and within a large tidal runoff channel infill. Autoclastic breccias and water-escape channels are rare and occur only in small-scale -- always related to thin, horizontal tidal laminae. Profound sedimentary dykes, sand volcanoes, and thrust faults, which are often related to earthquake triggered soft sediment deformation, were not observed within the studied intervals. Deformation horizon or horizons with large flat-topped pillows often with elongated morphologies occur at or near the boundary between the Tiskre and Lükati formations. Deformation mechanisms identified in this study for the various deformation types are gravitationally unstable reversed density gradient (especially in case of load features that are related to profound sedimentary interfaces) and lateral shear stress due to sediment current drag (in case of deformation structures that not related to loading at any apparent sedimentary interface). Synsedimentary liquefaction was identified as the primary driving force in most of the observed deformation horizons. Clay thixotropy may have contributed in the

  3. Sedimentary dynamic processes of a contourite drift formation in the South China Sea: from long-term in situ observations to geological records

    NASA Astrophysics Data System (ADS)

    Liu, Z.; Zhao, Y.; Zhang, Y.; Li, J.; Wen, K.; Li, X.; Tuo, S.; Zhong, G.

    2015-12-01

    Contourites are sediments deposited or substantially reworked by thermohaline-induced deepwater bottom currents. The study of contourites with growing interests is widely conducted in seismic stratigraphy, paleoceanography, paleoclimatology, and hydrocarbon exploration. However, the sedimentary dynamic process producing contourites in the deepwater environment is still poorly understood. This research presents an interdisciplinary approach from long-term in situ mooring and tripod observations, multi-beam seabed morphology, seismic stratigraphy, to IMAGES (Marion Dufresne) piston coring and ODP (JOIDES Resolution) drilling studies on the formation of a contourite drift on the lower slope of the northern South China Sea. The contourite drift with ~520 m thick is distributed in water depths ranging from 1650 m to 2500 m and has been accumulated since 1.5 Ma in early Pleistocene. The nowadays contour currents in the northern South China Sea were observed with velocities generally ranging in 0-2 cm/s with a dominant flow direction of ~250º (southwestward/along-slope). However, the relatively stable contour currents were disturbed by several bursts of increased velocities up to 8-11 cm/s, each lasting 2-3 weeks and followed by a direction reversal, which were caused by passing-through of deep-reaching mesoscale eddies. The along-slope sediment transport is induced by both mesoscale eddy and contour currents, and these suspended sediments are mainly derived from Taiwan according to provenance analysis of sediments traps equipped on moorings. Seismic stratigraphy and core sample analysis (oxygen isotope stratigraphy, clay mineralogy, and grain size) reveal a long sedimentary history with strong influence of deepwater currents that have carried the majority of Taiwan-sourced sediments moving westward since early Pleistocene. The glacial-cyclic terrigenous input from various surrounding drainage systems and their transport processes from fluvial source to deep-sea sink are

  4. Detrital zircon record of the early Paleozoic meta-sedimentary rocks in Russian Altai: Implications on their provenance and the tectonic nature of the Altai-Mongolian terrane

    NASA Astrophysics Data System (ADS)

    Chen, Ming; Sun, Min; Cai, Keda; Buslov, Mikhail M.; Zhao, Guochun; Rubanova, Elena S.; Voytishek, Elena E.

    2015-09-01

    An integrated U-Pb and Hf-isotope study on detrital zircons from the early Paleozoic meta-sedimentary rocks along the Charysh-Terekta-Ulagan-Sayan suture zone in Russian Altai was conducted in order to trace their provenance and tectonic setting. Most of the zircons possess oscillatory zoning and high Th/U ratios (> 0.1), indicating their magmatic origin. The investigated samples yield similar zircon populations, i.e., dominant groups with late Neoproterozoic to early Paleozoic ages, followed by those from Mesoproterozoic to late Neoproterozoic and minor ones from Archean to middle Mesoproterozoic, indicating multiple tectono-thermal events in the source area. Comparison with surrounding tectonic units shows that the Tuva-Mongolian terrane and its adjacent island arcs possibly provided substantial materials to the sedimentary basin. These rocks show detrital zircon age patterns and Hf-isotope compositions similar to their counterparts in the Chinese Altai and Tseel terrane in western Mongolia, but different from those in the Gorny Altai terrane. Therefore, the investigated meta-sedimentary units possibly represented the northernmost segment of the Altai-Mongolian terrane. With combination of previous studies in the Chinese Altai and Tseel terrane, our data suggest that the Altai-Mongolian terrane possibly represents a coherent continental arc-accretionary prism system built upon the active margin of the western Mongolia during the Cambrian to Ordovician and thus does not support the micro-continent model with a passive margin. A compilation of U-Pb and Hf-isotope data of detrital zircons from the whole Altai-Mongolian terrane shows that the source area (i.e., the western Mongolia) underwent two most extensive magmatic activities at ca. 1.02-0.67 Ga and 0.67-0.43 Ga. These zircons possess both positive and negative εHf(t) values, suggesting significant crustal growth and reworking during the magmatic activities. Our study underlines a crucial role of Precambrian

  5. Morphology and Structure of the Algiers Deep-Sea Fan and Possible Sedimentary Record of the 2003 Boumerdès Earthquake (Maradja Project)

    NASA Astrophysics Data System (ADS)

    Babonneau, N.; Cattaneo, A.; Harster, M.; Deverchere, J.; Yelles, K.; Savoye, B.; Domzig, A.

    2007-12-01

    The Algerian margin is a Cenozoic passive margin along the plate boundary between Eurasia and Africa, presently reactivated in compression. The deformation is expressed by ESE-WNW-aligned inverse faults associated with moderate to large earthquakes. Earthquakes can generate sediment instabilities on the continental slope; for instance, strong turbidity currents are likely responsible of submarine cable breaks observed at the foot of the continental slope, after the Boumerdes earthquake in may 2003. In the Boumerdes-Algiers area, the Algiers canyon is the main sediment pathway from the shelf to the deep sea environment. Since Maradja surveys in 2003 and 2005, high-resolution bathymetric and backscatter images are available over an area of 1200 km along the margin. The morpho-bathymetric interpretation supported by seismic reflection data allowed to identify the Quaternary Algiers deep-sea fan and its main morphological features: the canyon, the main valley, the sedimentary ridge, and the distal deposits confined in mini-basins. The Algiers canyon is characterised by two tributary paths in the upper slope. The maximum incision is about 600 m deep. The canyon fed a 30 km long turbidity valley, spreading westward along the foot of the slope and bordered by the sedimentary ridge on the right side. The sedimentary ridge is covered by large sediment wave features, probably generated by turbidity overflow currents. The Algiers deep-sea fan has a complex structure resulting from the interaction between turbidity sedimentation, compressive tectonic structures and salt tectonic. In the upper part, the morphology of the Algiers canyon and fan is strongly controlled by inverse faults creating morphological highs and scarps. In the distal part, the sea floor morphology is highly deformed by salt diaprism, which control the paths of active sediment transport and the location of deposition area (mini-basins). Sediment gravity cores collected on the deep-sea fan show recent

  6. Carbon isotopes of plant biomarkers record past changes in the carbon cycle, but separating signal from noise is key to reducing uncertainties

    NASA Astrophysics Data System (ADS)

    Diefendorf, A. F.; Freeman, K. H.; Wing, S. L.; Currano, E. D.

    2014-12-01

    The carbon isotopic composition of plant biomarkers (δ13C) can provide unique insights into the past carbon cycle perturbations and associated climate change, however local records are influenced by ecological processes, local climate, as well as changes in the carbon isotope composition of the atmosphere. To examine the sources and amounts of geographic variation, we focused on long-term changes in the carbon cycle. We combined modern calibrations, δ13C of biomarkers in sediment, and Monte Carlo analyses to measure and predict the fractionation of carbon isotopes by plants (Δleaf) and to estimate error. We used data from multiple sites of different ages, in the western U.S. For each age and location, Δleaf was calculated from the δ13C of plant biomarkers and atmospheric δ13C values inferred from marine carbonates. Δleaf values calculated from n-alkanes and triterpenoids (angiosperm biomarkers) were found to be the same at each site. Δleaf calculated from diterpenoids (conifer biomarkers) was 2‰ lower. This is consistent with differences in Δleaf between living angiosperms and conifers. Predicted Δleaf values, from modern calibrations and paleoclimate data, were consistently offset (0.7‰) from measured values indicating that modern calibrations are useful for reconciling past changes in plant fractionation and that vegetation and precipitation, like modern plants, were the key controls on Δleaf in ancient vegetation. However, uncertainties in the measured and predicted Δleaf values were very large (>2‰, 1σ). A one-at-a-time sensitivity analysis indicates that 'biological noise' in modern calibrations explains most of this uncertainty. If the full extent of this biological noise were transferred to sediments, then extracting signal from noise would be challenging. However, we speculate that the process of deposition homogenizes variability at the leaf and tree level thereby reducing 'biological noise' observed in modern calibrations.

  7. Where's the glass? Biomarkers, molecular clocks, and microRNAs suggest a 200-Myr missing Precambrian fossil record of siliceous sponge spicules

    NASA Astrophysics Data System (ADS)

    Sperling, E. A.; Robinson, J.; Pisani, D.; Peterson, K.

    2010-12-01

    The earliest evidence for animal life comes from the fossil record of 24-isopropylcholestane, a sterane found in Cryogenian deposits, and whose precursors are found in modern demosponges, but not choanoflagellates, calcareans, hexactinellids, or eumetazoans. However, many modern demosponges are also characterized by the presence of siliceous spicules, and there are no convincing demosponge spicules in strata older than the Cambrian. This temporal disparity highlights a problem with our understanding of the Precambrian fossil record - either these supposed demosponge-specific biomarkers were derived from the sterols of some other organism and are simply retained in modern demosponges, or spicules do not primitively characterize crown-group demosponges. Resolving this issue requires resolving the phylogenetic placement of another group of sponges, the hexactinellids, which not only make a spicule thought to be homologous to the spicules of demosponges, but also make their first appearance near the Precambrian/Cambrian boundary. Using two independent analytical approaches and data sets - traditional molecular phylogenetic analyses and the presence or absence of specific microRNA genes - we show that demosponges are monophyletic, and that hexactinellids are their sister group (together forming the Silicea). Thus, spicules must have evolved before the last common ancestor of all living siliceans, suggesting the presence of a significant gap in the silicean spicule fossil record. Molecular divergence estimates date the origin of this last common ancestor well within the Cryogenian, consistent with the biomarker record, and strongly suggests that siliceous spicules were present during the Precambrian but were not preserved.

  8. Preservation of terrestrial plant biomarkers from Nachukui Formation sediments and their viability for stable isotope analysis

    NASA Astrophysics Data System (ADS)

    Kahle, E.; Uno, K. T.; Polissar, P. J.; Lepre, C. J.; deMenocal, P. B.

    2013-12-01

    Plio-Pleistocene sedimentary records from the Turkana Basin in eastern Africa provide a unique opportunity to compare a high-resolution record of climate and terrestrial vegetation with important changes in the record of human evolution. Molecular biomarkers from terrestrial vegetation can yield stable isotope ratios of hydrogen and carbon that reflect ancient climate and vegetation. However, the preservation of long-chain plant wax biomarkers in these paleosol, fluvial, and lacustrine sediments is not known, and this preservation must be studied to establish their utility for molecular stable isotope studies. We investigated leaf wax biomarkers in Nachukui Formation sediments deposited between 2.3 and 1.7 Ma to assess biomarker preservation. We analyzed n alkane and n alkanoic acid concentrations and, where suitable, molecular carbon and hydrogen isotope ratios. Molecular abundance distributions show a great deal of variance in biomarker preservation and plant-type source as indicated by the carbon preference index and average chain length. This variation suggests that some samples are suitable for isotopic analysis, while other samples lack primary terrestrial plant biomarker signatures. The biomarker signal in many samples contains significant additional material from unidentified sources. For example, the n-alkane distributions contain an unresolved complex mixture underlying the short and mid-chain n-alkanes. Samples from lacustrine intervals include long-chain diacids, hydroxy acids and (ω-1) ketoacids that suggest degradation of the original acids. Degradation of poorly preserved samples and the addition of non-terrestrial plant biomarkers may originate from a number of processes including forest fire or microbial alteration. Isotopic analysis of well-preserved terrestrial plant biomarkers will be presented along with examples where the original biomarker distribution has been altered.

  9. Ganges Sedimentary Rocks

    NASA Technical Reports Server (NTRS)

    2004-01-01

    24 May 2004 Mariner 9 images acquired in 1972 first revealed a large, light-toned, layered mound in Ganges Chasma, part of the vast Valles Marineris trough system. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a higher-resolution view of these rocks than was achieved by Mariner 9 or Viking, and higher than can be obtained by Mars Odyssey or Mars Express. The image, with a resolution of about 3.7 meters (12 feet) per pixel, shows eroded layered rock outcrops in Ganges Chasma. These rocks record a history of events that occurred either in Ganges Chasma, or in the rocks brought to the surface by the opening of Ganges Chasma. Either way, the story they might tell could be as fascinating and unprecedented as the story told by sedimentary rocks investigated this year in Meridiani Planum by the Opportunity Mars Exploration Rover ... no one knows. The image is located near 7.3oS, 48.8oW, and covers an area about 3 km (1.9 mi) across. The picture is illuminated by sunlight from the upper left.

  10. A 150-year record of ancient DNA, lipid biomarkers and hydrogen isotopes, tracing the microbial-planktonic community succession controlled by (hydro)climatic variability in a tropical lake

    NASA Astrophysics Data System (ADS)

    Smittenberg, Rienk; Yamoah, Kweku; Callac, Nolwenn; Fru, Ernest Chi; Chabangborn, Akkaneewut; Rattray, Jayne; Wohlfarth, Barbara

    2016-04-01

    We investigated the decadal variations in phytoplankton communities, and their response to environmental and climatic conditions, from a ˜150 year long sedimentary archive of Lake Nong Thale Prong (NTP), southern Thailand. We applied a combination of analyses: lipid biomarkers, compound-specific hydrogen isotopes, bulk carbon and nitrogen concentrations and isotopes, environmental SEM, and fossil DNA using qPCR targeted to specific taxa. Past hydrological conditions were reconstructed using the hydrogen isotopic composition of leaf wax n-alkanes. Temperatures were reconstructed using the tetraether-based MBT/CBT index, measured using a new and efficient reverse-phase HPLC-MS method. The climatological data compared well with meteorological data from the last decades. Reconstructed drier and warmer conditions from ˜1857-1916 Common Era (CE) coincided with oligotrophic lake water conditions and dominance of the green algae Botryococcus braunii - evidenced by a combination of both fossil DNA and the occurrence of characteristic botryococcene lipids. A change to higher silica (Si) input ˜1916 CE was related to increased rainfall and lower temperatures concurring with an abrupt takeover by diatom blooms lasting for 50 years - as evidenced by ancient DNA, characteristic highly branched isoprenoid lipids, and SEM. From the 1970s onwards, more eutrophic conditions prevailed, and these were likely caused by increased levels of anthropogenic phosphate (P), aided by stronger lake stratification caused by dryer and warmer conditions. The eutrophic conditions led to increased primary productivity in the lake, consisting again of a Botryococcus sp., although this time not producing botryococcene lipids. Moreover, Cyanobacteria became dominant - again evidenced by ancient DNA and the characteristic C19 alkane. Throughout the record, stratification and primary production could be linked to the intensity of methane cycling, by targeting and quantifying the mcrA gene that is used