Science.gov

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. Aminopentol, a possible novel biomarker tracer for methane hydrate stability in sedimentary records

    NASA Astrophysics Data System (ADS)

    Handley, L.; Talbot, H. M.; Cooke, M. P.; Wagner, T.

    2009-04-01

    The Congo Fan is a region of important methane (CH4) storage and seepage: large gas hydrate reservoirs at and just below the sediment surface occur alongside deeply-buried reservoirs of thermogenic methane linked with hydrocarbon source rocks. Methane release from both reservoirs has the potential to drive or respond to changes in local and global climate, thus causing changes in ocean chemical properties and biotic responses. Understanding these mechanisms of methane emission and reconstructing the history of past emissions in the Congo Fan (ODP Site 1075) is the main focus of this study. Bacteriohopanepolyols (BHPs) are lipid membrane constituents of bacteria and occur with a wide range of structural and functional variability. Amino-BHPs are produced by methane-oxidising bacteria and the 35-aminobacteriohopane-30,31,32,33,34-pentol (aminopentol) is a highly specific biomarker for aerobic methane oxidation. Aminopentol abundance varies significantly throughout the studied section with a suspected precession-driven cyclical variability superimposed on longer-term short eccentricity cycles. Compound-specific stable carbon isotope analyses confirm that the amino-BHPs are of methanotrophic origin. A period of sustained greater concentrations and inferred emissions occurs from ca. 500 and 600 ka during which soil organic matter input, as recorded by soil BHP concentrations and the BIT index, is consistently low. Unsaturated 6-bacteriohopanetetrol cyclitol ether, which is interpreted as a biomarker for nitrogen-fixing marine Tricodesmium cyanobacteria, was also found in this interval and is absent from the remainder of the section. This interval could therefore reflect a period of low terrigenous organic matter and associated nutrient input during which nitrogen-fixing bacteria may have flourished in the resultant nutrient-, in particular nitrate, poor water. Ongoing sea surface temperature reconstruction, using the TEX86 proxy, seeks to investigate potential

  3. The Martian sedimentary record

    NASA Technical Reports Server (NTRS)

    Dehon, R. A.

    1987-01-01

    The differences between the surface geology of Mars and earth are discussed. Sedimentary processes and fluvial systems on Mars are examined. Surface mapping reveals the more recent depostional patterns. In future missions, radar sounding, active seismic systems, and on site deep drilling may be required to fully document the depositional history. For the present, identification of sedimentary layers must rest on localities of tectonic or erosional windows, detection of buried surfaces by indirect methods, and deposition or off lap patterns of distribution.

  4. Sedimentary record of erg migration

    SciTech Connect

    Porter, M.L.

    1986-06-01

    The sedimentary record of erg (eolian sand sea) migration consists of an idealized threefold division of sand-sea facies sequences. The basal division, here termed the fore-erg, is composed of a hierarchy of eolian sand bodies contained within sediments of the flanking depositional environment. The fore-erg represents the downwind, leading edge of the erg and records the onset of eolian sedimentation. Basin subsidence coupled with erg migration places the medial division, termed the central erg, over the fore-erg strata. Eolian influence on regional sedimentation patterns is greatest in the central erg, and most of the sand transported and deposited in the erg is contained within this region. Reduction in sand supply and continued erg migration will cover the central-erg deposits with a veneer of back-erg deposits. This upper division of the erg facies sequence resembles closely the fore-erg region. Back-erg deposits may be thin due to limited eolian influence on sedimentation or incomplete erg migration, or they may be completely absent because of great susceptibility to postdepositional erosion. Tectonic, climatic, and eustatic influences on sand-sea deposition will produce distinctive variations or modifications of the idealized erg facies sequence. The resulting variants in the sedimentary record of erg migration are illustrated with ancient examples from western North America, Europe, southern Africa, and South America. 38 references, 2 figures, 2 tables.

  5. 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

  6. 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

  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. 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

  9. Riverine Carbon and the Sedimentary Record on the Continental Shelves

    DTIC Science & Technology

    2004-09-30

    Riverine Carbon and the Sedimentary Record on the Continental Shelves Stefano Miserocchi Istituto Scienze Marine, Sezione Geologia Marina...formerly Istituto di Geologia Marina) Consiglio Nazionale delle Ricerche Via Gobetti, 101 40129 Bologna, Italy phone: +39 (051) 6398880 Fax. +39 (051... Geologia Marina,,(formerly Istituto di Geologia Marina),Consiglio Nazionale delle Ricerche,,Via Gobetti, 101,40129 Bologna, Italy, , 8. PERFORMING

  10. Estimation of sedimentary proxy records together with associated uncertainty

    NASA Astrophysics Data System (ADS)

    Goswami, B.; Heitzig, J.; Rehfeld, K.; Marwan, N.; Ambili, A.; Prasad, S.; Kurths, J.

    2014-06-01

    Sedimentary proxy records constitute a significant portion of the recorded evidence that allow us to investigate paleoclimatic conditions and variability. However, uncertainties in the dating of proxy archives limit our ability to fix the timing of past events and interpret proxy record inter-comparisons. While there are various age-modeling approaches to improve the estimation of the age-depth relations of archives, relatively less focus has been given to the propagation of the age (and radiocarbon calibration) uncertainties into the final proxy record. We present a generic Bayesian framework to estimate proxy records along with their associated uncertainty starting with the radiometric age-depth and proxy-depth measurements, and a radiometric calibration curve if required. We provide analytical expressions for the posterior proxy probability distributions at any given calendar age, from which the expected proxy values and their uncertainty can be estimated. We illustrate our method using two synthetic datasets and then use it to construct the proxy records for groundwater inflow and surface erosion from Lonar lake in central India. Our analysis reveals interrelations between the uncertainty of the proxy record over time and the variance of proxy along the depth of the archive. For the Lonar lake proxies, we show that, rather than the age uncertainties, it is the proxy variance combined with calibration uncertainty that accounts for most of the final uncertainty. We represent the proxy records as probability distributions on a precise, error-free time scale that makes further time series analyses and inter-comparison of proxies relatively simpler and clearer. Our approach provides a coherent understanding of age uncertainties within sedimentary proxy records that involve radiometric dating. It can be potentially used within existing age modeling structures to bring forth a reliable and consistent framework for proxy record estimation.

  11. Estimation of sedimentary proxy records together with associated uncertainty

    NASA Astrophysics Data System (ADS)

    Goswami, B.; Heitzig, J.; Rehfeld, K.; Marwan, N.; Anoop, A.; Prasad, S.; Kurths, J.

    2014-11-01

    Sedimentary proxy records constitute a significant portion of the recorded evidence that allows us to investigate paleoclimatic conditions and variability. However, uncertainties in the dating of proxy archives limit our ability to fix the timing of past events and interpret proxy record intercomparisons. While there are various age-modeling approaches to improve the estimation of the age-depth relations of archives, relatively little focus has been placed on the propagation of the age (and radiocarbon calibration) uncertainties into the final proxy record. We present a generic Bayesian framework to estimate proxy records along with their associated uncertainty, starting with the radiometric age-depth and proxy-depth measurements, and a radiometric calibration curve if required. We provide analytical expressions for the posterior proxy probability distributions at any given calendar age, from which the expected proxy values and their uncertainty can be estimated. We illustrate our method using two synthetic data sets and then use it to construct the proxy records for groundwater inflow and surface erosion from Lonar lake in central India. Our analysis reveals interrelations between the uncertainty of the proxy record over time and the variance of proxies along the depth of the archive. For the Lonar lake proxies, we show that, rather than the age uncertainties, it is the proxy variance combined with calibration uncertainty that accounts for most of the final uncertainty. We represent the proxy records as probability distributions on a precise, error-free timescale that makes further time series analyses and intercomparisons of proxies relatively simple and clear. Our approach provides a coherent understanding of age uncertainties within sedimentary proxy records that involve radiometric dating. It can be potentially used within existing age modeling structures to bring forth a reliable and consistent framework for proxy record estimation.

  12. 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.

  13. Hydraulic jumps within pyroclastic density currents and their sedimentary record

    NASA Astrophysics Data System (ADS)

    Douillet, G.; Mueller, S.; Kueppers, U.; Dingwell, D. B.

    2013-12-01

    This contribution presents a complete and comprehensive formulation of the hydraulic jump phenomenon and reviews sedimentary structures that may be associated with them. Beginning from the general fluid phenomenon, we then focus on examples from pyroclastic density currents in order to infer dynamic parameters on the parent flows. A hydraulic jump is a fluid dynamics phenomenon that corresponds to the sudden increase of the thickness of a flow accompanied by a decrease of its velocity and/or density. A hydraulic jump is the expression of the transition of the flow from two different flow regimes: supercritical to subcritical. This entrains a change in the energy balance between kinetic energy and gravity potential energy. Recently, the terms of 'pneumatic jumps' have been used for similar phenomenon driven within a gas phase, and granular jumps for dense granular flows. It is thought that such strong changes in the flow conditions may leave characteristic structures in the sedimentary record. Indeed, the main variables influencing the sedimentation rate are the flow velocity, particle concentration and turbulence level, all of them strongly affected by a hydraulic jump. Structures deposited by hydraulic/pneumatic jumps have been called cyclic steps and chute and pool structures. Chute and pools represent the record of a single supercritical to subcritical transition, whereas cyclic steps are produced by stable trains of hydraulic jumps and subsequent re-accelerations. Pyroclastic density currents (PDCs) are gas and pyroclasts flows. As such, they can be subjected to granular and pneumatic jumps and their deposit have often been interpreted as containing records of jumps. Steep sided truncations covered by lensoidal layers have been interpreted as the record of internal jumps within density stratified flows. Fines-depleted breccias at breaks in slope are thought to result from the enhanced turbulence at a jump of the entire flow. Sudden increases in thickness of

  14. 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

  15. 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.

  16. 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

  17. Biomarker distributions in different types of sedimentary organic matter isolated from the same sample: Implications for biomarker correlations

    SciTech Connect

    Anderson, K.B.

    1994-06-01

    The observation of qualitatively and quantitatively distinct biomarker distributions in the pyrolysates of Type II and Type III organic matter isolated from the same sample is reported. This demonstrates the clear need for a greater understanding of the relationship between biomarker distributions present in the different components of sedimentary organic matter, and those observed in liquid products generated by maturation. The data imply that it is possible that the biomarker distributions observed in petroleums derived from inhomogeneous source rocks may be disproportionately derived from the various organic components of the sediment. This may result in spurious conclusions concerning oil/source relationships and other geochemical parameters, which suggests that further investigations of these phenomena is well merited.

  18. Origin of orbital periods in the sedimentary relative paleointensity records

    NASA Astrophysics Data System (ADS)

    Xuan, Chuang; Channell, James E. T.

    2008-08-01

    Orbital cycles with 100 kyr and/or 41 kyr periods, detected in some sedimentary normalized remanence (relative paleointensity) records by power spectral analysis or wavelet analysis, have been attributed either to orbital forcing of the geodynamo, or to lithologic contamination. In this study, local wavelet power spectra (LWPS) with significance tests have been calculated for seven relative paleointensity (RPI) records from different regions of the world. The results indicate that orbital periods (100 kyr and/or 41 kyr) are significant in some RPI records during certain time intervals, and are not significant in others. Time intervals where orbital periods are significant are not consistent among the RPI records, implying that orbital periods in these RPI records may not have a common origin such as orbital forcing on the geodynamo. Cross-wavelet power spectra (|XWT|) and squared wavelet coherence (WTC) between RPI records and orbital parameters further indicate that common power exists at orbital periods but is not significantly coherent, and exhibits variable phase relationships, implying that orbital periods in RPI records are not caused directly by orbital forcing. Similar analyses for RPI records and benthic oxygen isotope records from the same sites show significant coherence and constant in-phase relationships during time intervals where orbital periods were significant in the RPI records, indicating that orbital periods in the RPI records are most likely due to climatic 'contamination'. Although common power exists at orbital periods for RPI records and their normalizers with significant coherence during certain time intervals, phase relationships imply that 'contamination' (at orbital periods) is not directly due to the normalizers. Orbital periods are also significant in the NRM intensity records, and 'contamination' in RPI records can be attributed to incomplete normalization of the NRM records. Further tests indicate that 'contamination' is apparently

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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)

  5. 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

  6. Temporal Insights on Biomarker-Based Climate Records (Invited)

    NASA Astrophysics Data System (ADS)

    Drenzek, N.; Stanley, R. H.; Santos, G. M.; Southon, J. R.; Druffel, E. R.; Montlucon, D.; Hughen, K. A.; Eglinton, T. I.

    2010-12-01

    Biomarker reconstructions of climate events usually assume that the incorporation of these molecular fossils into the sedimentary archive is both synchronous with those events and temporally discrete. Studies of marine and terrigenous-sourced lipids have nonetheless uncovered significant lags between initial biosynthesis and ultimate deposition, largely owing to intervening transport processes. Here we quantitatively apportion such residence times for vascular plant leaf waxes, commonly used as proxies for various continental climate parameters, into several components by comparing the radiocarbon profiles of individual long chain fatty acids extracted from sediments to the radiocarbon evolution of atmospheric carbon dioxide using a nonlinear optimization model. We then incorporate these findings into a simplified forward box model in order to reinterpret leaf wax reconstructions of environmental changes at orbital to decadal timescales. Results from case studies in the Caribbean Sea (Cariaco Basin) and coastal British Columbia (Saanich Inlet) indicate that at least two pools of plant wax material can be defined by markedly different residence times in these systems. Fully sixty to ninety percent of long chain fatty acids in study site sediments were sequestered on land for an average of some 3340 and 4860 years, respectively, with the remainder encumbering a much shorter time of nominally ten to fifteen years. The fraction of each homologue passing through these ‘millennial’ and ‘decadal’ reservoirs systematically decreased at shorter chain length, possibly reflecting the influence of varying molecular-level properties such as degradation rate and physiochemical speciation. Viewed through this prism, the record of low frequency (orbital) climate shifts preserved in sediments will appear lagged relative to their actual timing while the magnitude of millennial to higher frequency activity will be muted. These findings indicate that a premium should be placed

  7. 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.

  8. Biomarkers in sedimentary sequences: Indicators to track sediment sources over decadal timescales

    NASA Astrophysics Data System (ADS)

    Chen, F. X.; Fang, N. F.; Wang, Y. X.; Tong, L. S.; Shi, Z. H.

    2017-02-01

    Long-term sedimentary sequence research can reveal how human activities and climate interact to affect catchment vegetation, flooding, soil erosion, and sediment sources. In this study, a biomarker sediment fingerprinting technique based on n-alkanes was used to identify long timescale (decadal) sediment sources in a small agricultural catchment. However, the highly saline carbonate environment and bacterial and algal activities elevated the levels of even-chain n-alkanes in the sediments, leading to an obvious even-over-odd predominance of short and middle components (C15-C26). Therefore, by analyzing three odd, long-chain n-alkanes (C27, C29 and C31) in 27 source samples from cropland, gully, and steep slope areas and one sediment sequence (one cultivated horizon and 47 flood couplets), a composite fingerprinting method and genetic algorithm optimization were applied to find the optimal source contributions to sediments. The biomarker fingerprinting results demonstrated that the primary sediment source is gullies, followed by cropland and steep slope areas. The average median source contributions associated with 47 flood couples collected from sediment core samples ranged from 0 ± 0.1% to 91.9 ± 0.4% with an average of 45.0% for gullies, 0 ± 0.4% to 95.6 ± 1.6% with an average of 38.2% for cropland, and 0 ± 2.1% to 60.7 ± 0.4% with an average of 16.8% for steep slopes. However, because farmers were highly motivated to manage the cropland after the 1980s, over half the sediments were derived from cropland in the 1980s. Biomarkers have significant advantages in the identification of sediments derived from different landscape units (e.g., gully and steep slope areas), and n-alkanes have considerable potential in high-resolution research of environmental change based on soil erosion in the hilly Loess Plateau region.

  9. A Sedimentary Record of the Lower Jaramillo Transition Zone

    NASA Astrophysics Data System (ADS)

    Tait, J. A.; Gurary, G. Z.; Trubikhin, V.; Garbuzenko, A.; Iglesia-Llanos, P.; Ataev, N. M.

    2005-05-01

    Biostratigraphically dated Apsheronian sediments were sampled from two parallel sections near Adjidhere, NW Turkmenistan. Demagnetisation experiments reveal well defined normal and reversed magnetisations carried by magnetite and haematite. The lower/upper parts of the sections correspond to the Matuyama/Jaramillo chrons, and corresponding mean directions coincide with the local dipole field. The central part of the composite section reveals a remarkable and complex record of the transitional field, a significant feature of which is the clustering of VGPs in the S Atlantic, between the S Pole and southern S America. This feature predominates in the earlier phases of the transition and corresponds to the cluster patch previously identified from volcanic records of different transition zones. Another striking feature is the repetition of excursion patterns, with the VGP paths repeatedly moving along preferred paths, before finally reversing in the central part of the profile. Initialy, the field instability is predominantly reversed in character. After the reversal, however, the record shows instability from a predominantly normal condition. These data will be presented and discussed

  10. 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.

  11. 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.

  12. Sedimentary Record of the February 27, 2010, Chile Tsunami

    NASA Astrophysics Data System (ADS)

    Richmond, B. M.; Morton, R. A.; Gelfenbaum, G. R.; Buckley, M. L.

    2010-12-01

    The February 27, 2010 Chilean tsunami altered the coastal landscape along a section of coast characterized by broad sand beaches, fluvial deltas, and occasional rocky headlands. We examined tsunami geologic impacts at five relatively natural sites along a 200 km segment of coast centered on the earthquake epicenter. Data collected included measurements of topography, flow depths, flow directions and flow direction history, inundation distances, vertical erosion, and sediment deposition. The depositional record consisted mostly of sand deposits that were typically less than 25 cm thick. Exceptions were thick tsunami deposits near the mouths of Rio Huenchullami (La Trinchera) and Rio Maule (Constitucion) where sediment supply was abundant. Observations of tsunami geologic impacts included: (1) up to meter-scale changes in coastal-plain elevation as a result of tsunami-induced erosion and deposition; (2) erosion of the land surface was typically greatest near the shoreline and was the result of multiple processes such as tsunami return-flow, inundation scour around the bases of trees and other structures, and a general planation of the land surface near the shoreline; (3) tsunami sand deposits were widespread and extended to near the limit of inundation at most sites; (4) evidence of inundation by multiple waves that arrived at different times from different directions at open coast sites; (5) layers of plane-parallel stratification in some tsunami deposits and the presence of large bedforms at one site indicated that at least some of the sediment was transported as bed load and not as suspended load; (6) where available, coarse clasts such as mud boulders and rock cobbles were transported inland; (7) in forested coastal areas large debris ramparts were constructed near the limit of inundation. A significant finding was that vegetation height and density exerted a strong control on tsunami deposit thickness in the Coliumo Valley. Agricultural and ranching activities

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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

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

    PubMed

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

    2014-02-28

    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.

  19. The Carboniferous carbon isotope record from sedimentary organic matter: can we disentangle the carbon cycle?

    NASA Astrophysics Data System (ADS)

    Davies, S. J.; Bennett, C. E.; Leng, M. J.; Kearsey, T.; Marshall, J. E.; Millward, D.; Reeves, E. J.; Snelling, A.; Sherwin, J. E.

    2014-12-01

    A comprehensive analysis of the δ13C composition of sedimentary organic matter from Euramerican Carboniferous successions indicates there are significant shifts in δ13C through this key time interval. Our studies have revealed that, at an individual location, the source and delivery mechanism of the sediment contribute to the type of organic matter preserved and, in turn this influences the measured δ13C values from bulk sedimentary organic matter of organic matter. In general, where marine-derived organic matter is dominant in these Carboniferous successions then δ13C values are characteristically lower compared to the higher values encountered where terrestrial plant-derived material is most abundant. The implication of these observations is that an apparent carbon isotope excursion identified from the bulk organic matter may reflect a change in transport processes, or depositional environment, rather than a perturbation in the global carbon cycle. In our most recent studies, however, we compare δ13C values from specific wood fragments and bulk sedimentary organic matter from non-marine, marine basinal, and marine shelfal successions from the earliest Mississippian through to the early Pennsylvanian. These data indicate that early Mississippian δ13C of organic matter is far less negative (around -22%0) than material of Late Mississippian age (around -26%0), however by the early Pennsylvanian, δ13C values return to -22%0. There are some δ13C data from brachiopod carbonate from this time interval and similar shifts are indicated. Our data are beginning to address whether we can identify a primary carbon cycle signal from the Carboniferous record using δ13C from a range of sedimentary environments. If we can, there are still questions around what the record is telling us about the global carbon cycle during a period when plant groups, including lycopods and seed ferns, rapidly diversified.

  20. Paleoanthropology. Late Pliocene fossiliferous sedimentary record and the environmental context of early Homo from Afar, Ethiopia.

    PubMed

    DiMaggio, Erin N; Campisano, Christopher J; Rowan, John; Dupont-Nivet, Guillaume; Deino, Alan L; Bibi, Faysal; Lewis, Margaret E; Souron, Antoine; Garello, Dominique; Werdelin, Lars; Reed, Kaye E; Arrowsmith, J Ramón

    2015-03-20

    Sedimentary basins in eastern Africa preserve a record of continental rifting and contain important fossil assemblages for interpreting hominin evolution. However, the record of hominin evolution between 3 and 2.5 million years ago (Ma) is poorly documented in surface outcrops, particularly in Afar, Ethiopia. Here we present the discovery of a 2.84- to 2.58-million-year-old fossil and hominin-bearing sediments in the Ledi-Geraru research area of Afar, Ethiopia, that have produced the earliest record of the genus Homo. Vertebrate fossils record a faunal turnover indicative of more open and probably arid habitats than those reconstructed earlier in this region, which is in broad agreement with hypotheses addressing the role of environmental forcing in hominin evolution at this time. Geological analyses constrain depositional and structural models of Afar and date the LD 350-1 Homo mandible to 2.80 to 2.75 Ma.

  1. A synthesis of sedimentary records of Australian environmental change during the last 2000 years

    NASA Astrophysics Data System (ADS)

    Tyler, J. J.; Karoly, D. J.; Gell, P.; Goodwin, I. D.

    2013-12-01

    Our understanding of Southern Hemispheric climate variability on multidecadal to multicentennial timescales is limited by a scarcity of quantitative, highly resolved climate records, a problem which is particularly manifest in Australia. To date there are no quantitative, annually resolved records from within continental Australia which extend further back in time than the most recent c. 300 years [Neukom and Gergis, 2012; PAGES 2k Consortium, 2013]. By contrast, a number of marine, lake, peat and speleothem sedimentary records exist, some of which span multiple millennia at sub-decadal resolution. Here we report a database of existing sedimentary records of environmental change in Australia [Freeman et al., 2011], of which 25 have sample resolutions < 100 years/sample and which span > 500 years in duration. The majority of these records are located in southeastern Australia, providing an invaluable resource with which to examine regional scale climate and environmental change. Although most of the records can not be quantitatively related to climate variability, Empirical Orthogonal Functions coupled with Monte Carlo iterative age modelling, demonstrate coherent patterns of environmental and ecological change. This coherency, as well as comparisons with a limited number of quantitative records, suggests that regional hydroclimatic changes were responsible for the observed patterns. Here, we discuss the implications of these findings with respect to Southern Hemisphere climate during the last 2000 years. In addition, we review the progress and potential of ongoing research in the region. References: Freeman, R., I. D. Goodwin, and T. Donovan (2011), Paleoclimate data synthesis and data base for the reconstruction of climate variability and impacts in NSW over the past 2000 years., Climate Futures Technical Report, 1/2011, 50 pages. Neukom, R., and J. Gergis (2012), Southern Hemisphere high-resolution palaeoclimate records of the last 2000 years, Holocene, 22

  2. 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

  3. 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

  4. [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.

  5. Tectonic control of the sedimentary record: Constraints from quantitative basin modeling

    SciTech Connect

    Cloetingh, S.A.P.L.; Van Balen, R.T.; Zoetemeijer, B.P. )

    1993-09-01

    The incorporation of finite strength of the lithosphere during rifting in models for extensional basin formation in conjunction with temporal changes in tectonic stress levels leads to the prediction of rapid vertical motions in these basins with a rate and magnitude comparable to second- and third-order changes in relative sea level. We present results of modeling simulations, incorporating the interplay of flank uplift and erosion for rifted basins in the northern Atlantic/North Sea area. The incorporation of the mechanical properties of the lithosphere in forward stratigraphic modeling appears also to be of key importance for an accurate prediction of the record of vertical motions in foreland fold and thrust belts. Models invoking the mechanical coupling between plate flexure and near-surface brittle tectonics are capable of producing onlap/offlap patterns in syntectonic basins sometimes strikingly similar to the basin-fill signatures attributed to third-order glacio-eustatic signals. The full incorporation of structural geological constraints in forward modeling of basin stratigraphy proves to be a powerful instrument in linking different temporal and spatial scales in the sedimentary record. This approach also leads to a quantification of the tectonic control of the sedimentary record in frequency bands hitherto primarily attributed to external forcing functions.

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

    PubMed

    Sluyter, Andrew; Dominguez, Gabriela

    2006-01-24

    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.

  7. 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.

  8. Interpreting carbonate and organic carbon isotope covariance in the sedimentary record.

    PubMed

    Oehlert, Amanda M; Swart, Peter K

    2014-08-19

    Many negative δ(13)C excursions in marine carbonates from the geological record are interpreted to record significant biogeochemical events in early Earth history. The assumption that no post-depositional processes can simultaneously alter carbonate and organic δ(13)C values towards more negative values is the cornerstone of this approach. However, the effects of post-depositional alteration on the relationship between carbonate and organic δ(13)C values have not been directly evaluated. Here we present paired carbonate and organic δ(13)C records that exhibit a coupled negative excursion resulting from multiple periods of meteoric alteration of the carbonate δ(13)C record, and consequent contributions of isotopically negative terrestrial organic matter to the sedimentary record. The possibility that carbonate and organic δ(13)C records can be simultaneously shifted towards lower δ(13)C values during periods of subaerial exposure may necessitate the reappraisal of some of the δ(13)C anomalies associated with noteworthy biogeochemical events throughout Earth history.

  9. 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

  10. 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.

  11. 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.

  12. Lake sedimentary DNA accurately records 20(th) Century introductions of exotic conifers in Scotland.

    PubMed

    Sjögren, Per; Edwards, Mary E; Gielly, Ludovic; Langdon, Catherine T; Croudace, Ian W; Merkel, Marie Kristine Føreid; Fonville, Thierry; Alsos, Inger Greve

    2017-01-01

    Sedimentary DNA (sedDNA) has recently emerged as a new proxy for reconstructing past vegetation, but its taphonomy, source area and representation biases need better assessment. We investigated how sedDNA in recent sediments of two small Scottish lakes reflects a major vegetation change, using well-documented 20(th) Century plantations of exotic conifers as an experimental system. We used next-generation sequencing to barcode sedDNA retrieved from subrecent lake sediments. For comparison, pollen was analysed from the same samples. The sedDNA record contains 73 taxa (mainly genus or species), all but one of which are present in the study area. Pollen and sedDNA shared 35% of taxa, which partly reflects a difference in source area. More aquatic taxa were recorded in sedDNA, whereas taxa assumed to be of regional rather than local origin were recorded only as pollen. The chronology of the sediments and planting records are well aligned, and sedDNA of exotic conifers appears in high quantities with the establishment of plantations around the lakes. SedDNA recorded other changes in local vegetation that accompanied afforestation. There were no signs of DNA leaching in the sediments or DNA originating from pollen.

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

    PubMed

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

    2016-06-07

    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.

  14. 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

  15. 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.

  16. 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.

  17. 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

  18. Sedimentary record of recent climate impacts on an insular coastal lagoon in the Gulf of California

    NASA Astrophysics Data System (ADS)

    Cuellar-Martinez, Tomasa; Ruiz-Fernández, Ana Carolina; Sanchez-Cabeza, Joan-Albert; Alonso-Rodríguez, Rosalba

    2017-03-01

    Sedimentary records are useful to evaluate environmental changes, either from natural or anthropogenic causes, such as global and climate change. The recent changes in accumulation rates and geochemical characteristics (grain size distribution, elemental composition, organic carbon and carbonate concentrations) recorded in a sediment core from San Jose Island Lagoon (SJIL, Gulf of California) were evaluated to determine its relationship with anthropogenic impacts and climatic variability. The 210Pb-derived chronology was corroborated with 239+240Pu and 137Cs stratigraphic markers. The mass accumulation rate increased up to ∼3 times during the past ∼100 years (0.16 ± 0.03 to 0.51 ± 0.06 g cm-2 yr-1). The contents of terrigenous and marine (salinity) indicator elements, as well as fine-grained sediments, also increased considerably, although no anthropization evidences were observed; indeed, the enrichment factor of trace elements indicated that the ecosystem is still a pristine environment. By using multivariate statistical techniques, we inferred that the larger input of fine-grained terrigenous sediments could be related to the enhancement of soil erosion from the catchment, under the influence of higher rainfall rates, especially during the last 20 years. In addition, the higher concentrations of salinity indicator elements most likely resulted from higher evaporation rates in the lagoon, caused by higher minimum atmospheric temperatures. We concluded that recent climate variability has become the main driver for sedimentary geochemical changes in San Jose Island Lagoon. These observations confirmed the usefulness of 210Pb-dated geochemical sediment records to study the impacts of recent climate variability where long-term environmental data is scarce or non-existent.

  19. 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.

  20. 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

  1. A 60-year sedimentary record of natural and anthropogenic impacts on Lake Chenghai, China.

    PubMed

    Zan, Fengyu; Huo, Shouliang; Xi, Beidou; Zhang, Jingtian; Liao, Haiqing; Wang, Yue; Yeager, Kevin M

    2012-01-01

    Recent sediments from Lake Chenghai, China, were investigated at high temporal resolution to trace both natural and anthropogenic effects on the lake using total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), organic phosphorus (Po), inorganic phosphorus (Pi) and organic carbon and nitrogen stable isotopes (delta13Corg and delta15N) in a 137Cs-dated sediment core. The results indicated that the sedimentary record covers the last 60 years, during which the lake had undergone apparent changes in nutrient sources and productivity in response to nutrient loading. Prior to the late 1980s, the nutrient contents in sediments mainly originated from algae and lake productivity was relatively stable. Since the late 1980s, increasing TOC, TN and TP concentrations together with the change of delta13Corg and delta15N suggested anthropogenic perturbations in nutrient loading and lake productivity. Endogenic nutrients derived from algae and anthropogenic inputs were two important sources of sedimentary nutrients. The anthropogenic nutrients mainly originated from the discharge of industrial wastewater and artificial cultivation of Spirulina after the middle 1980s, and domestic wastewater discharged from Yongsheng County since 1993.

  2. 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.

  3. 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.

  4. The geochemical proxies for the eutrophic and hypoxia in the Changjiang estuary: evidence from sedimentary records

    NASA Astrophysics Data System (ADS)

    Xuwen, F.

    2013-12-01

    Three cores were selected in the Changjiang Estuary to study potential hundrend-years eutrophication and hypoxia. The sediment record in the Changjiang Estuary mud area (CEMA) within the region of pronounced hypoxia showed that an increase in TOC (21%), biomarkers (141%) and δ13 Corg (1.6‰PDB ) occurred since 1950s and a marked increase since 1970s. Some redox sensitive elements (RSEs) have been enriched significantly since the late 1960s to 1970s, the rates of Mo/Al, Cd/Al and As/Al increased about 83%, 73% and 50% respectively. And the contents of some biogenic elements also increased since the late 1960s, e.g. Ca(129%), Sr(65%) and P(38%) respectively. For the core sediment in the Cheju Island mud area (SCIMA) outside the hypoxia region, the organic geochemical indicators (TOC, biomarkers and δ13Corg ) increased in difference degrees before 1950s~1970s and then were almost the constant. The RSEs were controlled by 'grain size effects' which indicated no hypoxia occurred. For the core sediment in the Zhejiang coastal mud area (ZCMA) within the region of milder hypoxia, the distribution of biomarkers is highly similar to the CEMA, but the other indictactors such as δ13 Corg et al.were different from the above two cores. Productivity in the SCIMA have been mainly influenced by climate ocean circulation changes over the last 100 years. Productivities in the hypoxia areas were corresponding with the fertilizer consumption and high nutrient inputs from the Changjiang River, which stimulated the algae (e g. brassicasterol, dinosterol) blooming and resulted an enrichment of organic matter. Hypoxia invoked organic matter preserved in the sediment. This study concluded that biomarkers in sediment could be as the eutrophic proxies in the Changjiang Estuary and its adjacent region, and δ13 Corg, RSEs and biogenic elements could be as the proxies to trace or reconstruct history of eutrophication and hypoxia in the CEMA.

  5. 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.

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

    USGS Publications Warehouse

    Draut, Amy; 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

  7. 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.

  8. 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

  9. 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).

  10. 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

  11. 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.

  12. 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)

  13. 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.

  14. Sedimentary records of eutrophication and hypoxia in the Changjiang Estuary over the last 100 years

    NASA Astrophysics Data System (ADS)

    Xuwen, F.; Hongliang, L.; Zhao, M.; Xuefa, S.

    2012-12-01

    We selected two cores in the Changjiang Estuary, one located in the Changjiang Estuary mud area (CEMA) within the region of seasonal hypoxia, the other located in the Cheju Island mud area (SCIMA) and outside the hypoxia region. The grain size, total organic carbon (TOC), stable carbon isotopic ratios (δ13 Corg), biomarkers (the sum of brassicasterol, dinosterol and alkenone) and some redox sensitive elements (RSEs) were determined on the 210Pb-dated sediment cores to study potential hundrend-years eutrophication and hypoxia. The sediment record in CEMA showed that an increase in TOC (21%), biomarkers (141%) and δ13 Corg (1.6‰PDB ) occurred since 1950s and a marked increase since 1970s. These distributions indicated the enhanced productivity and establshed the history of eutrophication in the Changjiang Estuary during the past 100 years. Some RSEs have been enriched significantly since the late 1960s to 1970s, the rates of Mo/Al, Cd/Al and As/Al increased about 83%, 73% and 50% respectively. These data may indicate the onset of hypoxia in the Changjiang Estuary during the last 100 years. The increasing of marine organic matter and RSEs accumulation was corresponding with the fertilizer consumption and high nutrient inputs from the Changjiang River. The riverine runoff of fertilizers and nutrients stimulated the algae (e g. brassicasterol, dinosterol) blooming. Enhanced primary production resulted in an enrichment of organic matter and hypoxia invoked organic matter preserved in the sediment. For the core sediment in SCIMA, the geochemical indicators (TOC, biomarkers and δ13Corg ) increased in difference degrees before 1950s~1970s and then were almost the constant. Productivity in the SCIMA have been mainly influenced by climate ocean circulation changes over the last 100 years. The RSEs were controlled by "grain size effects" which indicated no hypoxia occurred. This study concluded that δ13 Corg, RSEs and biomarkers in sediment could be used to trace or

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. Tephrostratigraphy during 3000 years recorded in the sedimentary sequence of Beppu Bay, central Kyushu, Japan

    NASA Astrophysics Data System (ADS)

    Takemura, K.; Yamada, K.; Kuwae, M.; Yamamoto, M.; Danhara, T.

    2012-12-01

    The tephrostratigraphy around Beppu Bay, central Japan, is investigated using a 9m-long sedimentary core (KT09-3) collected in 2009 with a piston corer. Beppu Bay is located to the east of active volcanic region in Kyushu Island in southwest Japan. Eruptive history of their active volcanoes and widespread tephra records may be preserved in the sedimentary sequence in bay environment. A method to determine the down-hole content of volcanic glass was used in this study. This method consists of four steps: (1) continuous measurement of magnetic susceptibility with lithological observation of sediments, (2) systematic separation of the volcanic glass particles from samples taken at close intervals, and the determination of relative concentration; (3) mineral assemblages counted in the size of 63-125 micro meter fraction; (4) precise measurement of the refractive indices of the separated glass particles. A refractive index measuring system (RIMS) based on the thermal immersion method permitted quick and accurate measurement of the refractive index of a large number of samples. Core (KT09-3) is one of fourteen piston and gravity cores which were retrieved at the center of the basin. Correlation of cores was conducted using sand and silt seams related by events such as turbidite or flood or volcanic ash air fall, and the age-depth model was created by wiggle-matching of forty-two AMS radiocarbon dates from bivalve mollusk shells and excess Pb-210 and Cs-137 concentrations (Kuwae et al., 2012). The sedimentation rates were 230-300 cm/ky. Core is composed of massive diatomaceous clays with 18 event sediments of coarse fractions. Two distinct volcanic ash horizons and several cryptically deposited horizons are found within the sequence. Upper distinct volcanic ash of 509.2 cm depth is composed of many volcanic glasses and heavy minerals of Opx and Cpx with GHb and BHb. Most of volcanic glasses have characteristic high refractive index of about 1.559. This tephra is

  1. 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

  2. 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

  3. Holocene sedimentary record in Lago Fagnano (Tierra del Fuego): Paleoclimate implications

    NASA Astrophysics Data System (ADS)

    Vizcaino, Alexis; Anderson, Lysanna; Wahl, Dave; Dunbar, Rob; Guilderson, Tom; Moy, Chris

    2010-05-01

    Tierra del Fuego is the world's southernmost landmass outside of Antarctica. Together with Patagonia, it represents the only terrestrial region directly influenced by the southern hemisphere westerly winds. The climate of Tierra del Fuego is controlled by the Southern Ocean circumpolar flow and the South Pacific Gyre. This region is also a tectonically active area affected by volcanic and seismic activity related to South American and Scotia-Antarctic plate boundaries. Lago Fagnano is the largest lake in Tierra del Fuego. This E-W trending lake is 100 km long and 5-15 km wide. It lies along the Magallanes-Fagnano fault system that is part of the diffuse left-lateral Scotian Sea - South American plate boundary. Our investigations were carried out on an 8.4 m long piston core obtained at 69 m water depth in Bahía Grande (LF06-PC8), a southwestern lake sub-basin separated from the main lake by a shallow sill. Our studies are based on the integration of sediment, physical properties, pollen, and geochemical analyses. The age model for the core is based on tephrachronology and radiocarbon ages. Additionally, a 800 km long grid of high resolution seismic profiles support the sedimentary analyses and allow the correlation with other cores from within the lake basin. Three distinct intervals are observed in the core. The uppermost interval is characterized by laminated hemipelagic sedimentation with low frequency detrital depositional events. The second interval is affected by mass transport deposits including debris flow and turbidite events. And finally, the oldest interval is characterized by very thin and fine layers associated with high frequency detrital depositional events. Pollen and geochemical analyses (C/N) integrated with the sedimentological interpretation provide reliable proxy records of past variability in the westerly wind field as well as the regional precipitation regime. These records are compared to late glacial ice retreat in the neighboring areas

  4. 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

  5. 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

  6. Basin-Scale nd Isotope Gradients in South Atlantic Marine Sedimentary Records

    NASA Astrophysics Data System (ADS)

    Ran, W.; Abouchami, W.; Zahn, R.; Masque, P.

    2012-12-01

    radiogenic ɛNd values, whereas variable Holocene Pa/Th are combined to less radiogenic ɛNd values. The radiogenic seawater Nd isotope signature is entirely consistent with a predominance at the site during the LGM of a water body different from present-day NADW (ɛNd=-13). Together with existing Nd isotope records [3, 4, 5] this demonstrates the existence of a basin scale North-South Nd isotope gradient consistent with the contention, previously drawn from meridional 231Pa/230Th offsets [1], of a more prominent northward advection of southern component water. The combined 231Pa/230Th - Nd isotope systematics of existing marine sedimentary records has important implication for the significance and interpretation of these proxies as tracers of the dynamics of the Atlantic MOC which will be discussed in view of existing models. [1] Negre et al., Nature, 2010, 468, 84-88. [2] Galer et al., Mineral. Mag., 2011, 75, 883. [3] Rutberg et al., Nature, 2000, 405, 935-938. [4] Piotrowski et al., 2005, Science, 307: 1933-1938. [5] Roberts et al., 2010, Science, 327: 75-77.

  7. 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

  8. 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.

  9. Postglacial sedimentary record of the Southern California continental shelf and slope, Point Conception to Dana Point

    USGS Publications Warehouse

    Sommerfield, C.K.; Lee, H.J.; Normark, W.R.

    2009-01-01

    Sedimentary strata on the Southern California shelf and slope (Point Conception to Dana Point) display patterns and rates of sediment accumulation that convey information on sea-level inundation, sediment supply, and oceanic transport processes following the Last Glacial Maximum. In Santa Monica Bay and San Pedro Bay, postglacial transgression is recorded in shelf deposits by wave-ravinement surfaces dated at 13-11 ka and an upsection transition from coastal to shallow-marine sediment facies. Depositional conditions analogous to the modern environment were established in the bays by 8-9 ka. On the continental slope, transgression is evidenced in places by an increase in sediment grain size and accumulation rate ca. 15-10 ka, a consequence of coastal ravinement and downslope resedimentation, perhaps in conjunction with climatic increases in fluvial sediment delivery. Grain sizes and accumulation rates then decreased after 12-10 ka when the shelf flooded and backfilled under rising sea level. The Santa Barbara coastal cell contains the largest mass of postglacial sediment at 32-42 ?? 109 metric tons, most of which occurs between offshore Santa Barbara and Hueneme Canyon. The San Pedro cell contains the second largest quantity of sediment, 8-11 ?? 109 metric tons, much of which is present on the eastern Palos Verdes and outer San Pedro shelves. By comparison, the mass of sediment sequestered within the Santa Monica cell is smaller at ??6-8 ?? 109 metric tons. The postglacial sediment mass distribution among coastal cells reflects the size of local fluvial sediment sources, whereas intracell accumulation patterns reflect antecedent bathymetric features conducive for sediment bypass or trapping. ?? 2009 The Geological Society of America.

  10. 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

  11. 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

  12. Classification of modern and old Río Tinto sedimentary deposits through the biomolecular record using a life marker biochip: implications for detecting life on Mars.

    PubMed

    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 0.3-0.5 g 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. Anthropogenic disruptions of the sedimentary record in coastal marshes: Examples from the southern Bay of Biscay (N. Spain)

    NASA Astrophysics Data System (ADS)

    Leorri, Eduardo; Cearreta, Alejandro; Jesús Irabien, María; García-artola, Ane; Corbett, D. Reide; Horsman, Eric; Blake, William H.; Sanchez-Cabeza, Joan-Albert

    2014-09-01

    Understanding sedimentological discontinuities is essential to accurately reconstruct former climatic and sea-level changes from coastal sediments. Four short cores (<50 cm) from two estuaries located in the Bay of Biscay, Northern Spain, have been collected to provide analogues of recent anthropogenic sedimentary disturbance in salt marsh environments. Accurate maps and aerial photography can identify previously reclaimed areas but anthropogenic disruptions are more difficult to detect in regions abandoned before the 1950s and in areas with poor historical records. Our study aimed to provide the tools to identify former land reclamation horizons and apply an established environmental template to interpret a new core record from a previously unsampled estuary. Cores were analyzed using a multidisciplinary approach that includes sedimentology, micropaleontology, geochemistry, and bulk magnetic susceptibility (BMS). Results suggest that areas used for agricultural purposes are characterized in the sediment record by the absence of foraminifera that, after abandonment, are rapidly colonized by salt marsh plants in response to rapid vertical accretion. The initial colonization is marked by the presence of low foraminiferal numbers and a sharp increase in magnetic susceptibility, which proved helpful to improve the timing of the sedimentological boundaries when combined with other proxies. Our results indicate that anthropogenic disruptions to the sedimentary record are common over the recent past (100 years) and likely extend over the historic period in this part of southwestern Europe. These disruptions reflect historic land use changes. In the case of land clearance, proximal sites reflect sudden grain size changes, foraminiferal data and BMS. Distal sites affected by land clearance and the transition from agricultural soils to salt marsh occur in the mud fraction and require a multidisciplinary approach to pin them down. BMS has proven to be very useful when

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    The marine sedimentary record of Miocene to Pleistocene tectonics and glaciation is well preserved along the southern Alaska convergent margin. This margin is well suited for linking proximal to distal sediment transport processes because sediment is being generated by glacial erosion in the highest coastal mountain range on earth and subsequently being transported to the Aleutian subduction zone. We will discuss the sedimentary record from two end members of this system: (1) the proximal marine record now exposed onshore in the high peaks of the coastal ranges, and (2) the offshore distal record preserved in the Surveyor submarine fan system that was cored during the 2013 IODP Expedition 341. Onshore the Miocene non-glacial strata are represented by the Poul Creek Fm. This unit is 2000 m thick and in its upper part consists of mudstone, thin sandstone beds (10-30 cm thick), and thick bedded (1-2 m) highly bioturbated green sandstone beds that contain hummocky stratification. We interpret this unit as being deposited mainly in marine shelf environments. A gradational contact between the Poul Creek and the overlying upper Miocene-Pleistocene Yakataga Formation is marked by a transition to mudstone, thick bedded sandstone and glacial diamictite. This transition to glacial dominated deposition is interpreted to have occurred around 5 Ma based on previous studies. The onshore glacimarine strata are 5 km thick and grade up section from submarine fan to marine shelf strata. In the distal submarine fan record at IODP Site U1417, the upper Miocene strata in the lower part of the Site consist of 340 m of highly bioturbated gray to green mud interbedded with coarse sand and sandy diamict. These coarse-grained units are lithic rich with mainly sedimentary, volcanic, and coal clasts. We interpret these units as being derived from coal-bearing sedimentary strata exposed in the onshore thrust belt. These facies are interbedded with diatom ooze; we interpret this combination of

  19. 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.

  20. 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.

  1. Hydrogen isotope ratios of recent lacustrine sedimentary n-alkanes record modern climate variability

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

    Hydrogen isotope ratios were measured on n-alkanes (n-C 12 to n-C 31) extracted from recent lake surface sediments along a N-S European transect to test if modern climate variability is recorded in these biomarkers. δD values of the n-alkanes are compared to δD values of meteoric water from the IAEA-GNIP database spanning a range from -119‰ in northern Sweden to -41‰ in southern Italy, to lake water δD values, and to mean annual temperatures, varying between -2.0°C in the north and 13.7°C in the south. δD values of the short-chained n-alkanes n-C 12 to n-C 20, excluding algal derived n-C 17 and n-C 19, are higher in the north and lower in the south. The isotopic fractionation ɛ for hydrogen between meteoric water and the short-chained n-alkanes is increasing from N to S by more than 100‰ and is significantly correlated to mean annual temperature for n-C 16 and n-C 18. This suggests that these n-alkanes may originate from a different source in the northern lakes, possibly due to petroleum contamination, or are synthesized using a different biochemical pathway. The n-C 17 and n-C 19 alkanes of algal origin, the n-C 21 and n-C 23 alkanes originating from water plants, and the long-chain n-alkanes n-C 25, n-C 27, n-C 29, and n-C 31 of terrestrial origin, clearly correlate with δD values of meteoric water, lake water, and mean annual temperature, indicating that they excellently record the δD value of meteoric water. The mean hydrogen isotope fractionation ɛ C17/w of -157‰ (SD = 13) between n-C 17 and meteoric water is fairly constant over the wide range of different climates and lake environments, suggesting only minor influence of environmental factors on this biochemical fractionation. This suggests that δD values of n-C 17 are suitable to reconstruct the isotopic composition of source water. The mean fractionation between the long-chain n-alkanes and water is -128‰ (SD = 12). The mean difference of 31‰ between both ɛ values is likely due to

  2. 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.

  3. Thickness detection of sedimentary basin by P-to-S-phases of earthquake recordings at Ibaraki-ken, Japan

    NASA Astrophysics Data System (ADS)

    Hao, K.; Fujiwara, H.

    2007-12-01

    The Kanto sedimentary basin has very complicated geological formations with various sedimentary layers. The thickness of sedimentary basins varies irregularly from zeros to over several thousand meters down to the pre- Neogene bedrock. Therefore, the understanding the thickness is the fundamental in order to study the seismic ground motions. The vertical seismic profile (VSP) method may give a high-resolution seismic image at a borehole in both of P and S wave information. However, VSP is only limited to a few areas since it is too costly to be widely used. A dozen of deep-wells down to 2000 meters with VSP in the Kanto area have been drilled over past 15 years by NIED. In order to extend the high-quality VSP results farthest, we utilize these VSP data to obtain regression functions for sedimentary depth against the travel time difference of direct P and the direct S waves. On the other hands, the travel time difference between the direct P and the converted PS waves may be detected from P-to-S converted phases by means of all-pass function deconvolved from Receiver Functions (APRF) (Izumi et.al., 1990, Satoh, 2005, Hao, et.al., 2005, 2006). Comparing the classic receiver function for detection of interfaces with abrupt velocity changes in the earth crust, this APRF method can identify P-to-S phase in the near- surface interfaces much clearly, even for a high frequency of 10Hz. We use APRF with the VSP regression functions to estimate the thickness of sedimentary basin beneath each ground motion station. The objective area in this paper is whole of Prefecture Ibaraki-ken, which is located at north-east part of Kanto basin. The northern and northwestern of Ibaraki-ken are mountain areas, and Mt. Tsukuba and Lake kasumigaura are located in the center. A total of 112 strong motion stations, in which 84 stations from Sk-net, 19 K-net, and 14 KiK-net, have been targeted to study the underground structure beneath each station. Over 3000x3 records have been visually

  4. 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.

  5. A sedimentary paleomagnetic record of the upper Jaramillo transition from the Lantian Basin in China

    NASA Astrophysics Data System (ADS)

    Wu, Yi; Ouyang, Tingping; Qiu, Shifan; Rao, Zhiguo; Zhu, Zhaoyu

    2015-10-01

    The termination of the Jaramillo (normal to reverse) subchron is a key chronostratigraphic marker for dating global Pleistocene sedimentary sequences. However, the stratigraphic position of the geomagnetic polarity reversal varies greatly across the Chinese Loess Plateau (CLP), from near the bottom of paleosol unit S9 to the middle-upper part of S10. Here, we present paleomagnetic and rock magnetic results from high-resolution sampling of the Yushan loess section of the Lantian Basin located within the southern CLP. Our combined analyses determine that the polarity reversal is located in the middle-lower part of the paleosol unit S10. This stratigraphic position is lower than most of other studies conducted throughout the CLP. We attribute the difference in the location of the reversal to a deeper lock-in depth of remanence acquisition, which may have occurred from postdepositional processes under favorable hydrothermal conditions along the southern margin of CLP. It is important to note that age determinations through magnetic stratigraphy on sedimentary sections, particularly in discontinuous and/or imperfect sequences, should be treated with caution; there are significant differences with respect to the location of the polarity reversal throughout the CLP.

  6. 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.

  7. 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.

  8. Quasi-periodic bedding in the sedimentary rock record of Mars.

    PubMed

    Lewis, Kevin W; Aharonson, Oded; Grotzinger, John P; Kirk, Randolph L; McEwen, Alfred S; Suer, Terry-Ann

    2008-12-05

    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 approximately 10 meters thick, and one site contains hundreds of meters of strata bundled into larger units at a approximately 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.

  9. 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.

  10. 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.

  11. Aquatic environmental changes and anthropogenic activities reflected by the sedimentary records of the Shima River, Southern China.

    PubMed

    Gao, Lei; Wang, Zhuowei; Shan, Jiju; Chen, Jianyao; Tang, Changyuan; Yi, Ming

    2017-03-08

    Reconstructing historical sedimentary records is essential for better understanding the effects of anthropogenic activities on river environments. We used lead-210 to date riverine sediment core from the Shima River in China. We obtained a sedimentary history of 34 years (1982-2015) for core S2, which had a length of 34 cm. The sedimentation rate of 0.304-2.04 cm y(-1) was controlled by both flood events and anthropogenic activities. The conservative element content depth profiles remained relatively constant, suggestive of a relatively stable sediment provenance; therefore, the increase in the sedimentation rate over time was mainly the result of domestic and industrial wastewater effluent and the construction of a rubber dam at the middle and lower reach of the Shima River. From 1982 to 2015, the nutrient and trace metal depth profiles could be divided in three periods based on their trends. From 1982 to 1993, the vertical profiles of nutrients (organic carbon, total phosphorus, and total nitrogen) and three trace metals (nickel, zinc, and manganese) were relatively stable; however, the gradual decrease in copper and cadmium was likely associated with a reduction in agricultural chemical application. From 1993 to 2003, a population explosion and rapid industrialization were responsible for an increase in the input of pollutants into the Shima River, which was partly attenuated by water from the Dong River, leading to a gradual increase in nutrient and trace metal contents. Finally, from 2003 to 2015, the Shima River stopped being used as a source of water due to its deteriorating water quality. The relatively lower velocity of the water flow after the recovery of its flow direction and the reconstruction of the rubber dam in 2009 provided advantageous sedimentary conditions, promoting nutrient accumulation and significant trace metal enrichment.

  12. 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.

  13. A 59-year sedimentary record of metal pollution in the sediment core from the Huaihe River, Huainan, Anhui, China.

    PubMed

    Wang, Jie; Liu, Guijian; Zhang, Jiamei; Liu, Houqi; Lam, Paul K S

    2016-12-01

    An approximately 59-year (1955-2014) sedimentary record of metal elements (Cu, Pb, Zn, Ni, Co, Mn, and Fe) in a sediment core, collected from the Huaihe River, Huainan City, Anhui Province, China, was reconstructed by using (210)Pb geochronology. Copper, Zn, Ni, Co, and Mn evaluated by enrichment factor (EF) indicated minor contamination due to water pollution accidents of the Huaihe River that occurred in 1990s and 2004. Lead presented the most severe pollution among the metals studied, especially during 1957-1974. The use of leaded petrol and atmospheric deposition of coal combustion flue gases could have contributed to Pb contamination. In spite of the general good quality (mean sediment pollution index (SPI) 35.69) of the sediment core evaluated by SPI based on the principal component analysis, worse sediment qualities in the upper section (<6 cm, 2004) were still observed, suggesting intensive human activities causing the increasing concentrations of metals in recent decades.

  14. Sedimentary record of water column trophic conditions and sediment carbon fluxes in a tropical water reservoir (Valle de Bravo, Mexico).

    PubMed

    Carnero-Bravo, Vladislav; Merino-Ibarra, Martín; Ruiz-Fernández, Ana Carolina; Sanchez-Cabeza, Joan Albert; Ghaleb, Bassam

    2015-03-01

    Valle de Bravo (VB) is the main water reservoir of the Cutzamala hydraulic system, which provides 40% of the drinking water consumed in the Mexico City Metropolitan Area and exhibits symptoms of eutrophication. Nutrient (C, N and P) concentrations were determined in two sediment cores to reconstruct the water column trophic evolution of the reservoir and C fluxes since its creation in 1947. Radiometric methods ((210)Pb and (137)Cs) were used to obtain sediment chronologies, using the presence of pre-reservoir soil layers in one of the cores as an independent chronological marker. Mass accumulation rates ranged from 0.12 to 0.56 g cm(-2) year(-1) and total organic carbon (TOC) fluxes from 122 to 380 g m(-2) year(-1). Total N ranged 4.9-48 g m(-2) year(-1), and total P 0.6-4.2 g m(-2) year(-1). The sedimentary record shows that all three (C, N and P) fluxes increased significantly after 1991, in good agreement with the assessed trophic evolution of VB and with historic and recent real-time measurements. In the recent years (1992-2006), the TOC flux to the bottom of VB (average 250 g m(-2) year(-1), peaks 323 g m(-2) year(-1)) is similar to that found in highly eutrophic reservoirs and impoundments. Over 1/3 of the total C burial since dam construction, circa 70,000 t, has occurred in this recent period. These results highlight the usefulness of the reconstruction of carbon and nutrient fluxes from the sedimentary record to assess carbon burial and its temporal evolution in freshwater ecosystems.

  15. 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.

  16. A sedimentary paleomagnetic record of the Matuyama chron from the Western Antarctic margin (ODP Site 1101)

    NASA Astrophysics Data System (ADS)

    Guyodo, Yohan; Acton, Gary D.; Brachfeld, Stefanie; Channell, James E. T.

    2001-08-01

    A high-resolution paleomagnetic record for part of the Matuyama chron (0.7-2.1 Ma) is reported for Ocean Drilling Program Site 1101 (Leg 178), off the Antarctic Peninsula Pacific margin. A rock-magnetic investigation of 62 discrete samples revealed that the natural remanent magnetization (NRM) is carried by pseudo-single domain magnetite. Progressive alternating field demagnetization of 83 m of U-channels provided a polarity stratigraphy down to the Olduvai subchron. Two geomagnetic events preceding the Jaramillo subchron were identified, including the Cobb Mountain polarity interval. The bulk magnetic parameters vary by more than a factor of 20 over the entire time interval, but by less than a factor of 6 over the 0.7-1.1 Ma interval. This latter interval was selected for paleointensity determinations, which were carried out by normalizing the NRM by the anhysteretic remanent magnetization (ARM). Direct comparison of the Site 1101 paleointensity record with other curves available for the same time interval suggests a geomagnetic origin for features present in the record. A more quantitative comparison was achieved by means of a jackknife test performed on nine records of relative paleointensity over the 0.95-1.1 Ma interval. This test yielded no outlier for the period considered, confirming the geomagnetic character of the records. We have constructed a low-resolution stack revealing some of the characteristic paleointensity features of the Jaramillo subchron.

  17. Sedimentary and Volcanic Records of the Laschamp and Mono Lake Excursions from Australia and New Zealand

    NASA Astrophysics Data System (ADS)

    Ingham, E. M.; Roberts, A. P.; Turner, G. M.; Heslop, D.; Ronge, T.; Conway, C.; Leonard, G.; Townsend, D.; Tiedemann, R.; Lamy, F.; Calvert, A. T.

    2014-12-01

    Geomagnetic excursions are short-lived deviations of the geomagnetic field from the normal range of secular variation. Despite significant advances in geomagnetic excursion research over the past 20 years, fundamental questions remain concerning the typical duration and global morphology of excursional geomagnetic fields. To answer such questions, more high-resolution, chronologically well-constrained excursion records are required, particularly from the Southern Hemisphere. We present preliminary paleomagnetic records of the Laschamp (~41 ka) and Mono Lake (~35 ka) excursions from three marine sediment cores from the Bounty Trough, New Zealand margin, and complementary volcanic records of the Laschamp excursion from lavas of Mt Ruapehu, New Zealand. Relatively high sedimentation rates of 12 - 26 cm/kyr in the Bounty Trough during glacial periods allow identification of excursional field behavior at each of the studied core locations. Each core displays one or two excursional events, with rapid directional swings between stable normal polarity and reversed excursional directions, each associated with coincident relative paleointensity minima. These anomalous paleomagnetic directions are interpreted to represent the Laschamp and Mono Lake excursions, based on a combination of tephrochronology, radiocarbon dating, and cyclostratigraphy (defined from core-scanning X-ray fluorescence and magnetic susceptibility records). Beside these records, we present results from fourteen lava flows, on Mt Ruapehu, for which 40Ar-39Ar dating indicates ages of between 39 and 45 ka. The step heating 40Ar-39Ar experiments produced particularly flat age plateaus, with corresponding 2 s.d. errors mostly approaching 1 kyr. The youngest and oldest flows carry normal polarity magnetization, however six flows, dated between 41 and 43 ka, display transitional field characteristics. Three of these flows display a declination swing of around 180o, which coincides with a previously published

  18. 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

  19. Spatial variation, speciation and sedimentary records of mercury in the Guanabara Bay (Rio de Janeiro, Brazil)

    NASA Astrophysics Data System (ADS)

    Covelli, Stefano; Protopsalti, Ioanna; Acquavita, Alessandro; Sperle, Marcelo; Bonardi, Maurizio; Emili, Andrea

    2012-03-01

    As part of the "TAGUBAR" (TAngential GUanabara Bay Aeration Recovery) project, surface and long core sediments of the Guanabara Bay (Rio de Janeiro, Brazil) were investigated for mercury (Hg). The main, but not the only, input of Hg into the Bay's waters is known to be a Chlor-Alkali Plant (CAP) located in the Acarì-São João de Merití River system, on the northwestern side of the Bay. Mercury distribution in surface sediments (<0.1-3.22 mg kg-1, average 0.87±0.80, n=40) seems to be controlled by the organic component, along with sulfur rather than grain-size, where Hg concentrations are less than 1 mg kg-1. Conversely, where the metal contents are higher than 1 mg kg-1, accumulation in surface sediments is mostly related to the presence of nearby contamination sources, such as industrial and urban settlements in the western sector of the Bay. Although total Hg contents in surface sediments exceed the values suggested by the effects-based standard quality guidelines as potentially toxic for the benthic community, results from a sequential extraction procedure showed that the contribution of the more soluble, easily exchangeable and eventually bioavailable Hg phases was found almost negligible (<0.1%). Most of the metal is strongly bound to the mineral lattice of the sedimentary matrix and should therefore be considered almost immobilized. The reduction in Hg accumulation in bottom sediments, expected as a consequence of the adoption of contamination control policies (i.e. Hg-free technologies in the CAP and sewage treating facilities), has not been clearly observed in the core profiles. Current estimates of Hg accumulation rates at the core top range from approximately 1 to 18 mg m-2 yr-1. Pre-industrial bottom core samples indicate that the central and northeastern sectors of the Bay are strongly affected by Hg enrichment: concentrations exceed the estimated baseline concentration by up to 20 factors. A cumulative Hg inventory suggests that the metal content

  20. 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

  1. Demarcation of Typhoon-induced Sedimentary Layers from Lake Records in Southeast China

    NASA Astrophysics Data System (ADS)

    Kandasamy, Selvaraj; Lin, Baozhi; Wang, Huawei; Liu, Qianqian; Lou, Jiann-Yuh; Liu, Zhifei; Chen, Chen-Tung Arthur

    2016-04-01

    Understanding the frequency and cyclicity of extreme events such as tropical storms, heat waves, floods and droughts in monsoon-governed Asia is crucial for the adaptation and mitigation of climate-driven troubles and post-event consequences. Such studies are also critical for the development of future climate-related policies, given that the loss of life and properties during such events in Asia are always many-folds higher than that of the effect of similar disasters in the developed world. Lakes located along the path of typhoons in East Asia may preserve an evidence of storm intensity, because an increased erosion in the confined catchment may increase the clastic sedimentation. Here we investigate ca. 90 cm-long sediment core retrieved from Tian Lake, a coastal island lake located off SE China, for sedimentological, radiometric and geochemical parameters, aiming to reconstruct the effect of past typhoons on the sedimentation history of the lake. We found 4-5 sand-dominated layers in between the regular fine sediments deposition and these sand layers show a close consistency with periods of intense typhoons in the instrumental record. Although the instrumental record suggests an average of 16 typhoons/year in the western North Pacific, the preservation of only 4-5 sand-dominated layers during the last ca. 100 years of accumulation in our core indicates that the sedimentation pattern in Tian Lake may be very sensitive to intense typhoons with category 3 and above. This study will attempt to compare our lacustrine records with the suitable instrumental and other proxy records for understanding mechanisms responsible for intense typhoons and related environmental changes in SE China in the past century.

  2. 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

  3. 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

  4. 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.

  5. The Posidonia oceanica marine sedimentary record: A Holocene archive of heavy metal pollution.

    PubMed

    Serrano, O; Mateo, M A; Dueñas-Bohórquez, A; Renom, P; López-Sáez, J A; Martínez Cortizas, A

    2011-10-15

    The study of a Posidonia oceanica mat (a peat-like marine sediment) core has provided a record of changes in heavy metal abundances (Fe, Mn, Ni, Cr, Cu, Pb, Cd, Zn, As and Al) since the Mid-Holocene (last 4470yr) in Portlligat Bay (NW Mediterranean). Metal contents were determined in P. oceanica. Both, the concentration records and the results of principal components analysis showed that metal pollution in the studied bay started ca. 2800yr BP and steadily increased until present. The increase in Fe, Cu, Pb, Cd, Zn and As concentrations since ca. 2800yr BP and in particular during Greek (ca. 2680-2465cal BP) and Roman (ca. 2150-1740cal BP) times shows an early anthropogenic pollution rise in the bay, which might be associated with large- and short-scale cultural and technological development. In the last ca. 1000yr the concentrations of heavy metals, mainly derived from anthropogenic activities, have significantly increased (e.g. from ~15 to 47μg g(-1) for Pb, ~23 to 95μg g(-1) for Zn and ~8 to 228μg g(-1) for As). Our study demonstrates for the first time the uniqueness of P. oceanica meadows as long-term archives of abundances, patterns, and trends of heavy metals during the Late Holocene in Mediterranean coastal ecosystems.

  6. Sedimentary record of the 1872 earthquake and "Tsunami" at Owens Lake, southeast California

    USGS Publications Warehouse

    Smoot, J.P.; Litwin, R.J.; Bischoff, J.L.; Lund, S.J.

    2000-01-01

    In 1872, a magnitude 7.5-7.7 earthquake vertically offset the Owens Valley fault by more than a meter. An eyewitness reported a large wave on the surface of Owens Lake, presumably initiated by the earthquake. Physical evidence of this event is found in cores and trenches from Owens Lake, including soft-sediment deformation and fault offsets. A graded pebbly sand truncates these features, possibly over most of the lake floor, reflecting the "tsunami" wave. Confirmation of the timing of the event is provided by abnormally high lead concentrations in the sediment immediately above and below these proposed earthquake deposits derived from lead-smelting plants that operated near the eastern lake margin from 1869-1876. The bottom velocity in the deepest part of the lake needed to transport the coarsest grain sizes in the graded pebbly sand provides an estimate of the minimum initial 'tsunami' wave height at 37 cm. This is less than the wave height calculated from long-wave numerical models (about 55 cm) using average fault displacement during the earthquake. Two other graded sand deposits associated with soft-sediment deformation in the Owens Lake record are less than 3000 years old, and are interpreted as evidence of older earthquake and tsunami events. Offsets of the Owens Valley fault elsewhere in the valley indicate that at least two additional large earthquakes occurred during the Holocene, which is consistent with our observations in this lacustrine record.

  7. Regional environmental change and human activity over the past hundred years recorded in the sedimentary record of Lake Qinghai, China.

    PubMed

    Sha, ZhanJiang; Wang, Qiugui; Wang, Jinlong; Du, Jinzhou; Hu, Jufang; Ma, Yujun; Kong, Fancui; Wang, Zhuan

    2017-03-01

    Environmental change and human activity can be recorded in sediment cores in aquatic systems such as lakes. Information from such records may be useful for environmental governance in the future. Six sediment cores were collected from Lake Qinghai, China and its sublakes during 2012 and 2013. Measurements of sediment grain-size fractions indicate that sedimentation in the north and southwest of Lake Qinghai is dominated by river input, whereas that in Lake Gahai and Lake Erhai is dominated by dunes. The sedimentation rates in Lake Qinghai were calculated to be 0.101-0.159 cm/y, similar to the rates in other lakes on the Qinghai-Tibetan Plateau. Using these data and sedimentation rates from the literature, we compiled the spatial distribution of sedimentation rates. Higher values were obtained in the three main areas of Lake Qinghai: two in river estuaries and one close to sand dunes. Lower values were measured in the center and south of the lake. Measurements of total organic carbon (TOC), total nitrogen (TN), phosphorus concentrations, and TOC/TN ratios in three cores (QH01, QH02, and Z04) revealed four horizons corresponding to times of increased human activity. These anthropogenic events were (1) the development of large areas of cropland in the Lake Qinghai watershed in 1960, (2) the beginning of nationwide fertilizer use and increases in cropland area in the lake watershed after 1970, (3) the implementation of the national program "Grain to Green," and (4) the rapid increase in the tourism industry from 2000. Profiles of Rb, Sr concentrations, the Rb/Sr ratio, and grain-size fraction in core Z04 indicate that the climate has become drier over the past 100 years. Therefore, we suggest that lake sediments such as those in Lake Qinghai are useful media for high-resolution studies of regional environmental change and human activity.

  8. 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.

  9. 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

  10. 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

  11. 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

  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. 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.

  15. Sedimentary record of storm deposits from Hurricane Ike, Galveston and San Luis Islands, Texas

    NASA Astrophysics Data System (ADS)

    Hawkes, A. D.; Horton, B. P.

    2012-10-01

    Prehistoric records of land-falling tropical cyclones further our understanding of the spatial and temporal variability of tropical cyclone activity and its relationship with global climatic changes. Here, we describe deposit stratigraphy and sedimentology resulting from overwash during Hurricane Ike, which made landfall on September 13th 2008, to provide a much needed modern analogue for paleo-hurricane deposits and evaluate the hurricane's influence on barrier stability. We compared the volume, grain size distribution, organic content and foraminiferal assemblages of washover deposits at three sites from Galveston and San Luis Islands, Texas that were up to 50 km west of Ike's landfall. Storm surge heights varied between 3.7 and 2.7 m with inland inundation extents of 330 to 113 m. At each of the study sites, Hurricane Ike eroded the shoreline and re-deposited a landward-thinning sand sheet between 0.02 and 0.28 m thick over short-grass prairie/salt-marsh soil. Shoreline erosion estimates suggest that only between 10 and 30% of eroded beach sediment is deposited on land as washover (net gain to barrier elevation), while the remainder is re-deposited subtidally or offshore, a potential net loss to the coastal sediment budget. The washover sediment was readily identifiable by abrupt changes in grain size, organic content, and buried in situ grasses. Foraminiferal assemblages within washover and short-grass prairie/salt-marsh sediments (when present) have similar assemblages, which are dominated by Ammonia spp. and Elphidium spp. These species are common to bay and nearshore environments of the Gulf of Mexico. Foraminiferal species Bolivina subaenariensis, Quinqueloculina seminulum and planktonic species are restricted to the washover deposits, which may suggest sediment provenance from inner shelf environments.

  16. 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.

  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. Typhoon Haiyan's sedimentary record in coastal environments of the Philippines and its palaeotempestological implications

    NASA Astrophysics Data System (ADS)

    Brill, Dominik; May, Simon Matthias; Engel, Max; Reyes, Michelle; Pint, Anna; Opitz, Stephan; Dierick, Manuel; Gonzalo, Lia Anne; Esser, Sascha; Brückner, Helmut

    2016-12-01

    On 8 November 2013, category 5 Supertyphoon Haiyan made landfall on the Philippines. During a post-typhoon survey in February 2014, Haiyan-related sand deposition and morphological changes were documented at four severely affected sites with different exposure to the typhoon track and different geological and geomorphological settings. Onshore sand sheets reaching 100-250 m inland are restricted to coastal areas with significant inundation due to amplification of surge levels in embayments or due to accompanying long-wave phenomena at the most exposed coastlines of Leyte and Samar. However, localized washover fans with a storm-typical laminated stratigraphy occurred even along coasts with limited inundation due to waves overtopping or breaching coastal barriers. On a recent reef platform off Negros in the Visayan Sea, storm waves entrained coral rubble from the reef slope and formed an intertidal coral ridge several hundreds of metres long when breaking at the reef edge. As these sediments and landforms were generated by one of the strongest storms ever recorded, they not only provide a recent reference for typhoon signatures that can be used for palaeotempestological and palaeotsunami studies in the region but might also increase the general spectrum of possible cyclone deposits. Although a rather atypical example for storm deposition due to the influence of infra-gravity waves, it nevertheless provides a valuable reference for an extreme case that should be considered when discriminating between storm and tsunami deposits in general. Even for sites with low topography and high inundation levels during Supertyphoon Haiyan, the landward extent of the documented sand sheets seems significantly smaller than typical sand sheets of large tsunamis. This criterion may potentially be used to distinguish both types of events.

  19. 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

  20. 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

  1. 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

  2. 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.

  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. One century sedimentary record of lead and zinc pollution in Yangzong Lake, a highland lake in southwestern China.

    PubMed

    Zhang, Enlou; Liu, Enfeng; Shen, Ji; Cao, Yanmin; Li, Yanling

    2012-01-01

    Reconstruction of trace metal pollution histories and sources may help us to regulate current pollutant discharge. This is especially important for the highland lakes in southwestern China, which are facing trace metals pollution. We present sedimentary records of 11 metals accumulated in Yangzong Lake since the 1870's, a highland lake in southwestern China. Pollution of lead and zinc (Pb and Zn) was differentiated based on principal component analysis, geochemical normalization, and lead isotope ratios. Nearly all the metals as well as grain size composition show generally constant values before the mid-1980's, denoting stable detrital input in the catchment. Fluctuations in the concentrations of the metals as well as grain size composition since the mid-1980's indicate an increase in soil erosion with strengthened human disturbance in the catchment. After geochemical normalization, Pb and Zn showed constant values before 1990 AD and then a gradual increase in parallel with the variations in 208Pb/206Pb and 207Pb/206Pb ratios, indicating that Pb and Zn pollution occurred. Combining the data of 208pb/206Pb and 207Pb/6Pb ratios in the sediments of Yangzong Lake, leaded gasoline, Pb-Zn ore and coal, and consumption or production historical trends, we deduced that the enhanced Pb and Zn pollution in Yangzong Lake is caused primarily by ore mining and refining.

  5. Sedimentary record of PAHs in the Liangtan River and its relation to socioeconomic development of Chongqing, Southwest China.

    PubMed

    Liu, Ying; Yu, Na; Li, Zhe; Wei, Yanping; Ma, Limin; Zhao, Jianfu

    2012-10-01

    Concentrations of polycyclic aromatic hydrocarbons (PAHs) were detected in sediment cores and surface sediment samples from the Liangtan River of Chongqing, Southwest China. The total concentration of 16 PAHs ranged from 69 to 6251 ng g(-1). The spatial distribution of the PAHs reflects the intensity and scope of human activity in the catchment. A historical record of PAH contamination was reconstructed using a sediment core from a background segment of the river. The characteristic changes of concentrations, fluxes and patterns of 16 PAHs over the past ~90years were captured in detail. An obvious peak of PAH concentration and flux was found in the 1940s, i.e., during war time, and then a sharp increase was observed from the early 1980s to the present. The maximum concentration and flux reached 1260 ng g(-1) and 470 ng cm(-2)year(-1), respectively. The sharp increase was attributed to the contribution of pyrogenic sources of PAHs. The population, length of highways and energy consumption of Chongqing, as indexes of socioeconomic development, were positively correlated with PAH input in the sediment core from the 1950s to the present. The results clearly show that the local socioeconomic development in the last decades remarkably aggravated the environmental load of sedimentary PAHs.

  6. 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.

  7. The Lower Triassic sedimentary and carbon isotope records from Tulong (South Tibet) and their significance for Tethyan palaeoceanography

    NASA Astrophysics Data System (ADS)

    Brühwiler, Thomas; Goudemand, Nicolas; Galfetti, Thomas; Bucher, Hugo; Baud, Aymon; Ware, David; Hermann, Elke; Hochuli, Peter A.; Martini, Rossanna

    2009-12-01

    The Lower Triassic sedimentary and carbonate/organic carbon isotope records from the Tulong area (South Tibet) are documented in their integrality for the first time. New age control is provided by ammonoid and conodont biostratigraphy. The basal Triassic series consists of Griesbachian dolomitic limestones, similar to the Kathwai Member in the Salt Range (Pakistan) and to the Otoceras Beds in Spiti (India). The overlying thin-bedded limestones of Dienerian age strongly resemble the Lower Ceratite Limestone of the Salt Range. They are followed by a thick series of dark green, silty shales of Dienerian-early Smithian age without fauna that strikingly resemble the Ceratite Marls of the Salt Range. This interval is overlain by thin-bedded, light grey fossil-rich limestones of middle to late Smithian age, resembling the Upper Ceratite Limestone of the Salt Range. These are followed by a shale interval of early Spathian age that has no direct counterpart in other Tethyan sections. Carbonate production resumes during the late early and middle Spathian with the deposition of red, bioclastic nodular limestone ("Ammonitico Rosso" type facies). Apart from its colour this facies is similar to the one of the Niti Limestone in Spiti and of the Spathian nodular limestone in Guangxi (South China). As in other Tethyan localities such as Spiti, the early-middle Anisian part of the Tulong section is strongly condensed and is characterized by grey, thin-bedded limestones with phosphatized ammonoids. As for many other Tethyan localities the carbon isotope record from Tulong is characterized by a late Griesbachian-Dienerian positive δ13C carb excursion (2‰), and a very prominent positive excursion (5‰) at the Smithian-Spathian boundary, thus confirming the well-documented perturbations of the global carbon cycle following the Permian-Triassic mass extinction event.

  8. Continuous record of the last 30 ka of Paleosecular Variation in a turbiditic marine sedimentary sequence off the NW Iberian Margin

    NASA Astrophysics Data System (ADS)

    Rey, Daniel; Mohamed, Kais Jacob; Coimbra, Rute

    2014-05-01

    Past variations of the geomagnetic field at decadal to centennial scales are recorded with exceptional quality in lava flows, but these are discontinuous and therefore high temporal resolution analyses of paleosecular variation of the geomagnetic field (PSV) are difficult. For such purposes, marine sediments hold a better potential since they are often regarded as continuous sedimentary archives of a range of environmental processes, in particular PSV. While this assumption is generally valid for the deep abyss, it may not be necessarily true for marginal settings and the vicinity of seamounts, where discontinuous sedimentary flows (e.g. turbidites) occur with a relatively high frequency. In this contribution, we present results from two gravity cores (TG8 and TG10) obtained from the flanks of the Galicia Bank, a structural high in the NW Iberian Margin. These cores are mostly comprised of a turbiditic sequence, with continuous pelagic sedimentation recorded continuously over the last 16 ka. Contrary to what would be expected, Alternating Field demagnetization of the NRM showed a PSV record consistent with the behaviour of the geomagnetic field in this region, which could be correlated with a published record in the adjacent Portuguese Margin (Thouveny et al., 2004). These results show that even in a unstable marine sedimentary setting, affected by discontinuous mass flows and biological activity, the delayed and gradual lock-in of the magnetization allows for a continuous record of the geomagnetic field. References: Thouveny, N., Carcaillet, J., Moreno, E., Leduc, G., Nérini, D., 2004. Geomagnetic moment variation and paleomagnetic excursions since 400 kyr BP: a stacked record from sedimentary sequences of the Portuguese Margin. Earth and Planetary Science Letters 219, 377-396.

  9. 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

  10. Morphology of the Iceland Basin Excursion from a spherical harmonics analysis and an iterative Bayesian inversion procedure of sedimentary records

    NASA Astrophysics Data System (ADS)

    Lanci, Luca; Kissel, Catherine; Leonhardt, Roman; Laj, Carlo

    2008-08-01

    Based on 5 published marine high-resolution sedimentary records of the Iceland Basin Excursion [IBE; Channell, J.E.T., Hodell, D.A., Lehman, B., 1997. Relative geomagnetic paleointensity and ∂ 18O at ODP Site 983/Gardar Drift, North Atlantic since 350 ka. Earth Planet. Sci. Lett. 153, 103-118; Laj, C., Kissel, C., Roberts, A., 2006. Geomagnetic field behavior during the Iceland Basin and Laschamp geomagnetic excursions: a simple transitional field geometry? Geochem. Geophys. Geosystems. 7, Q03004, doi:10.1029/2005GC001122] dated around 186-190 kyr, we present models of the excursional geomagnetic field at the Earth's surface using two different approaches. First a spherical harmonics analysis is performed after synchronization of the records using their paleointensity profiles. Second, we have used an iterative Bayesian inversion procedure, calibrated using the single volcanic data available so far. Both modeling approaches suffer from imperfections of the paleomagnetic signals and mostly from the still poor geographical distribution of detailed records, presently available only from the North Atlantic and the West Pacific. For these reasons, our modeling results should only be regarded as preliminary models of the geomagnetic field during the IBE, susceptible to improvements when including results from future paleomagnetic studies. Nevertheless, both approaches show distinct similarities and are stable against moderate variations of modeling parameters. The general picture is that of a dipole field undergoing a strong reduction, but remaining higher than the non-dipole field all through the excursional process, except for a very short interval of time corresponding to the dipole minimum at the center of the excursion. On the other hand, some differences exist between the results of the two models with each other and with the real data when the virtual geomagnetic pole (VGP) paths are considered. The non-dipole field does not appear to undergo very significant

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

    USGS Publications Warehouse

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

    2014-01-01

    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.

  12. 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

  13. 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.

  14. Sedimentary record of polycyclic aromatic hydrocarbons in a sediment core from the Pearl River Estuary, South China.

    PubMed

    Liu, G Q; Zhang, G; Li, X D; Li, J; Peng, X Z; Qi, S H

    2005-01-01

    Owing to the hydrodynamic and sedimentation conditions, the western shoal of the Pearl River Estuary (PRE) is known to be an important sink of terrestrial substances including particle-associated pollutants from the Pearl River Delta (PRD) region. In this study, we report the sedimentary record of polycyclic aromatic hydrocarbons (PAHs) during the 20(th) century in a sediment core from the western shoal of the PRE. The summation PAH concentration ranged from 59 ng g(-1) to 330 ng g(-1) in the core with two distinct peaks. An initial increase of summation PAH concentration was found around the 1860s. The amounts of PAHs remained relatively constant for roughly 100 years, followed by the first peak in the 1950s. Then, there was a decrease in PAH concentration and flux in the 1960s and 1970s. A sharp increase of PAH concentration was observed in the early 1980s with a maximum concentration in the 1990s. The PAH diagnostic ratios indicated that the PAHs in the sediment core were mainly of pyrolytic origin, and that atmospheric deposition and land runoff may serve as the important pathways for PAHs input to the sediment. The Gross Domestic Product (GDP) was used as an index of socioeconomic development in the PRD region, which was correlated positively with the changes of PAH concentration and flux in the sediment core. The rapid increase in vehicle numbers and energy consumption in the region in the last two decades may have contributed to the rapid PAH increase since the early 1980s. The results clearly elucidated the impact of regional economic development on the estuarine environment.

  15. 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

  16. 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.

  17. Holocene Instabilities of Deep Circulation in the North Atlantic Based on nd and PB Isotope Sedimentary Records

    NASA Astrophysics Data System (ADS)

    Fagel, N.

    2013-12-01

    Many studies revealed the variability of deep ocean circulation over glacial/interglacial cycles. Instabilities in Holocene circulation and deep water production have been documented in marine archives. Unstable deep-water conditions prior to the mid-Holocene optimum were attributed to remnants of ice-sheets. However the millenial variability in Atlantic circulation continued after the melting of the ice-sheets. The correlation between observed NADW disturbances and surface cooling events in Nordic Seas argued for a linkage between surface variability and deep water masses over the Holocene. Nd and Pb isotopic compositions of the clay-size fraction of Holocene sediments were analysed in deep North Atlantic cores to trace the particle provenance. The aims are to identify the origin of the particles driven by deep currents and reconstruct deep circulation changes over the Holocene. Radiogenic signatures can be used as indirect paleoceanographic tracers. In particular Nd and Pb isotopes constitute suitable tracers for the origin of deep sediments in the Labrador Sea. The approach has been demonstrated over different timescales on cores collected at the southern tip of Greenland. Their sediment compositions reflect variable contributions of mantel-derived distal sources from mid-Atlantic Ridge and crustal-derived proximal inputs from Canadian and Greenland margins. As distal inputs are supplied by deep current the sedimentary isotopic composition record the fingerprint of the particles carried by the current. Here we compare the results from the Labrador Sea with three cores retrieved in fracture zones; two of them are located in the Island Basin along the gyre of North Atlantic Deep Water, and the third core is located off the present deep circulation gyre in the Labrador Sea. Whereas sedimentary supplies in the Labrador Sea were derived from proximal sources, the geochemical mixing trends in the Iceland Basin samples indicate pronounced changes in the relative

  18. 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

  19. Late Pliocene/Pleistocene changes in Arctic sea-ice cover: Biomarker and dinoflagellate records from Fram Strait/Yermak Plateau (ODP Sites 911 and 912)

    NASA Astrophysics Data System (ADS)

    Stein, Ruediger; Fahl, Kirsten; Matthiessen, Jens

    2014-05-01

    Sea ice is a critical component in the (global) climate system that contributes to changes in the Earth's albedo (heat reduction) and biological processes (primary productivity), as well as deep-water formation, a driving mechanism for global thermohaline circulation. Thus, understanding the processes controlling Arctic sea ice variability is of overall interest and significance. Recently, a novel and promising biomarker proxy for reconstruction of Arctic sea-ice conditions was developed and is based on the determination of a highly-branched isoprenoid with 25 carbons (IP25; Belt et al., 2007; PIP25 when combined with open-water phytoplankton biomarkers; Müller et al., 2011). Here, we present biomarker data from Ocean Drilling Program (ODP) Sites 911 and 912, recovered from the southern Yermak Plateau and representing information of sea-ice variability, changes in primary productivity and terrigenous input during the last about 3.5 Ma. As Sites 911 and 912 are close to the modern sea-ice edge, their sedimentary records seem to be optimal for studying past variability in sea-ice coverage and testing the applicability of IP25 and PIP25 in older sedimentary sequences. In general, our biomarker records correlate quite well with other climate and sea-ice proxies (e.g., dinoflagellates, IRD, etc.). The main results can be summarized as follows: (1) The novel IP25/PIP25 biomarker approach has potential for semi-quantitative paleo-sea ice studies covering at least the last 3.5 Ma, i.e., the time interval including the onset (intensification) of major Northern Hemisphere Glaciation (NHG). (2) These data indicate that sea ice of variable extent was present in the Fram Strait/southern Yermak Plateau area during most of the time period under investigation. (3) Elevated IP25/PIP25 values indicative for an extended spring sea-ice cover, already occurred between 3.6 and 2.9 Ma, i.e., prior to the onset of major NHG. This may suggest that sea-ice and related albedo effects might

  20. 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.

  1. 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

  2. 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

  3. Orbital pacing of New Zealand hydroclimate during the Early Miocene: Biomarker and compound-specific isotope records from the Foulden Maar diatomite

    NASA Astrophysics Data System (ADS)

    Donatich, S.; D'Andrea, W. J.; Fox, B.; Lee, D. E.

    2012-12-01

    During the Early Miocene, atmospheric CO2 levels were similar to today yet global temperatures were warmer and large, stable polar ice sheets had not yet developed. Examining the climate dynamics of Early Miocene Earth requires quantitative paleoclimate records from terrestrial archives. Foulden Maar (45.5 °S, 170.2 °E) is an annually resolved maar lake deposit on South Island, New Zealand dating from the Oligocene/Miocene boundary. Anoxia in the basin fostered the preservation of a ~100m thick, annually laminated diatomite (the base of which has been dated to 23 ± 0.2 Ma using 40Ar/39Ar dating), and allowed for superb preservation of organic materials, including leaves, flowers, fish skeletons and insects. Here we examine the biomarker record and the hydrogen isotope composition (δD) of leaf waxes (n-alkanoic acids) preserved in Foulden Maar sediments over a ~100,000 year interval of the early Miocene. Leaf wax δD reflects δD of past environmental water and therefore allows hydroclimatic reconstruction at the site. Our record reveals large variations (up to 40 ‰) in leaf wax δD at obliquity and precession timescales and affords quantitative estimates of orbitally forced hydrologic changes during the Early Miocene. Sedimentary terpenoids reflect the composition of paleovegetation at the site and represent an independent proxy to complement pollen analyses throughout the diatomite. Additional biomarker-based analyses (including δ13C of leaf waxes) are currently underway, and up-to-date results will be presented.

  4. 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

  5. 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.

  6. Lacustrine lignin biomarker record reveals a severe drought during the late Younger Dryas in southern Taiwan

    NASA Astrophysics Data System (ADS)

    Ding, Xiaodong; Bao, Hongyan; Zheng, Liwei; Li, Dawei; Kao, Shuh-Ji

    2017-03-01

    The Younger Dryas (YD) event, which punctuated the last glacial-Holocene transition period and had a profound impact on global climate, is the most well studied millennial-scale climate event although the triggering mechanism remains debate. Weakened Asian summer monsoon during the YD is recorded in oxygen isotopes of stalagmite from Mainland China. However, lacustrine climate record of the YD event has not been reported from the subtropical land-ocean boundary of the Asian continent near the Pacific warm pool. We provide a lignin biomarker record covering the last deglaciation and early Holocene (17-9 ka BP) from the Dongyuan Lake, southern Taiwan, located at the frontal zone of typhoon invasion. The lignin phenol ratio S/V shows that the vegetation in the catchments had shifted from gymnosperm dominant to angiosperm dominant plants since 12.2 ka BP. Significantly decreased lignin concentrations (TLP and λ8) and elevated lignin degradation parameters ((Ad/Al)v, P/(V + S), DHBA/V) in combination with other organic proxies (TOC, δ13Corg) during the late YD suggest a severe drought had occurred in southern Taiwan during this specific period. Changes in the lignin proxies from the Dongyuan Lake lagged the climate changes registered in stalagmite records by around 500-800 years, suggesting a slow response of vegetation and soil processes to rapid climate changes.

  7. 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

  8. 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.

  9. The Lipid Biomarker Holocene Paleoclimate Record of West China in the Zoige-Hongyuan Peat Deposit

    NASA Astrophysics Data System (ADS)

    Zhou, W.; Zheng, Y.; Meyers, P.; Xie, S.

    2006-12-01

    Paleoclimate reconstructions based on lipid biomarkers from peat bogs are relatively uncommon, although this approach has been widely applied to lake sediments where it yields histories of climate-related changes in types of vegetation and organic matter preservation. We describe stratigraphic patterns in peat lipid biomarker distributions extracted from a well-dated peat core from the Zoige-Hongyuan peat bog. The bog is on the Qinghai-Xizang Plateau of west China on the northeast edge of the Tibetan Plateau and has accumulated a continuous deposit of peat during the latest Pleistocene and the Holocene. A period of warmer climate corresponding to the Holocene Optimum between 9 ka to 5 ka is evident in greater alterations of n-alkanoic acids and n-alkanols and in the appearance of biomarkers diagnostic of greater microbial activity. Changes in local precipitation that modified the water level of the peat bog are indicated by increases in the proportions of C23 and C25 n-alkanes that are mainly derived from submerged/floating plants. Alternations in submergent and emergent plant n-alkane proxies reveal millennial scale rises and falls of the bog water level in the Tibetan Plateau, thereby reflecting variations in Asian monsoon precipitation during the Holocene. Major low water level events occurred around 12.6, 11.3, 10.7, 9.4, 8.3, 6.0, 4.5, 3.1, 2.1, and 1.0 ka. These events correlate well with cold-dry events recorded in same region by other climatic proxies. These results reflect Holocene instability in the Asian monsoon system. Our results indicate that millennial-scale variability in precipitation is more sensitive than temperature in reflecting Asian monsoon climatic dynamics on the Tibetan Plateau.

  10. 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.

  11. 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

  12. 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.

  13. Terrigenous biomarker record off Morocco over the last five glacial cycles

    NASA Astrophysics Data System (ADS)

    Rostek, Frauke; Bard, Edouard; Nave, Silvia

    2013-04-01

    We present a record of terrigenous biomarkers - long chain n-alkanes - supplied to Moroccan coastal sediments over the past 500 kyr representing the last five glacial-interglacial cycles (MD08-3178, 31°17.09'N/11°29.20'W, 2184 m water depth). The eolian n-alkane supply along the eastern margin off the coast of NW Africa originates mainly from the Atlas Mountain region and the Moroccan coastal plain and partly from the northern Sahara. The new geochemical profiles record changes in vegetation cover, wind strength and fluvial transport from the Atlas Mountains. Marine biological productivity proxies and n-alkane concentrations increase during glacial periods suggesting that stronger winds induce upwelling in the ocean and transport hydrocarbons from the continent. Chain-length distribution of n-alkanes points to variations in the relative input of terrestrial C3 and C4 plants. These variations are clearly paced by glacial cycles due to orbital variations as illustrated by their correlation with the alkenone sea surface temperature record measured on the same core (see companion poster by Nave et al.). The relative abundance of C3 plants is seen to be higher during glacial periods whereas the abundance of C4 plants is higher during warmer interglacial periods. Our results suggest that important vegetation changes have occurred in this part of NW Africa during the last 500 kyr. These changes could be due to latitudinal migrations of vegetation belts, with plants adapted to a more humid Mediterranean climate in the north contrasting with arid Saharan vegetation in the south. In addition, the observed changes may also be related to relative changes of source regions of n-alkanes due to wind strength variations.

  14. 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

  15. 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; Stollhofen, Harald; Malatesta, Luca C.; Stanistreet, Ian

    2014-05-01

    Controversy exists over when alluvial fans propagate, when they incise and how this is expressed in the sedimentary record. The Horingbaai Fan-delta at the Skeleton coast provides an end member due to its location in a hyper-arid area and a tectonically quiescent, although continuously uplifting setting. Accordingly, the influence of climate changes on alluvial fan sedimentation is directly assessable. There is pronounced interaction with the marine system during fan evolution, which provides the opportunity to constrain phases of fan progradation based on marine terrace stratigraphy. In this contribution, we will (1) present a detailed stratigraphic framework of the Horingbaai Fan-delta and associated marine terraces, and (2) analyze this framework in order to identify the imprint of past climatic changes on the sedimentary record. The of the Horingbaai Fan-delta sediments have been laid down between 2.6 and 2.4 Ma, based on age constraints from under- and overlying marine terraces. After 2.4 Ma, fan sedimentation was generally reduced and much more irregular due to intervening erosion phases. We propose a new model for late stage sedimentation and erosion phases, using offshore bathymetric and onshore sedimentological data, and conclude that generally decreasing sea-surface temperatures and glacial cycles largely govern the mode of sedimentation since the Early Pleistocene. We compare these findings to other fans at the Skeleton Coast, as well as other systems worldwide. Our study shows that climatic variations may leave distinct imprints in the sedimentological record. Recognizing these in depositional systems worldwide will improve understanding how fan sediments are preserved through time, and whether the reported worldwide increase in sedimentation rates since the Late Cenozoic is real or apparent.

  16. Over 100-year sedimentary record of polycyclic aromatic hydrocarbons (PAHs) and organochlorine compounds (OCs) in the continental shelf of the East China Sea.

    PubMed

    Cai, Yizhi; Wang, Xinhong; Wu, Yuling; Li, Yongyu; Ya, Miaolei

    2016-12-01

    Historical records of polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were analyzed in two dated sediment cores (DH05 and DH11) collected from the continental shelf of the East China Sea (ECS) to investigate the influence of anthropogenic activities on marine sediment over the past century. The concentrations and fluxes of 15 PAHs were in the range of 28.6-96.5 ng g(-1) and 7.6-35.2 ng cm(-2) yr(-1) in DH05 (1920s-2009), 18.8-76.4 ng g(-1) and 13.9-30.9 ng cm(-2) yr(-1) in DH11 (1860s-2009). The sedimentary records of PAHs in the two cores generally reflected the economic development and energy consumption change in China. Identification of sources suggested that PAHs in ECS were predominantly from petrogenic origin and various combustion sources. A change of source from low- and moderate-temperature combustion to high-temperature combustion process was observed. Although a production ban of technical HCH and DDT was imposed in China in 1983, their sedimentary fluxes display increasing trends or strong rebounds from 1980s to 1990s as recorded in the core profiles. High proportions of DDD + DDE and γ-HCH suggested those OCPs mainly derived from early residuals. Temporal trends of PCBs presented relative high levels from 1970s to 1980s and high proportions of PCB congeners with 3-6 chlorines atoms indicated industrial sources.

  17. 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.

  18. 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.

  19. Postglacial climate-change record in biomarker lipid compositions of the Hani peat sequence, Northeastern China

    NASA Astrophysics Data System (ADS)

    Zhou, Weijian; Zheng, Yanhong; Meyers, Philip A.; Jull, A. J. Timothy; Xie, Shucheng

    2010-05-01

    The peat sequence at Hani in northeastern China accumulated over the past 16 cal kyr in a percolation mire in which rain water and ground water seeped through the peat system. The molecular compositions of n-alkanes, n-alkanols, and n-alkanoic acids extracted from the Hani peat sequence reveal different responses to the progressive evolution of climate and changes in the nature of the peat-forming vegetation. Long chain length components that originate from the waxy coatings of subaerial vascular plants dominate the n-alkane distributions throughout the Hani peat sequence. The paleoclimate integrity of these biomarker molecules appears to be well preserved. Most of the n-alkanol distributions are similarly dominated by long chain components that indicate their origins from subaerial plants. In contrast, n-alkanoic acid distributions are dominated by secondary components that record the importance of post-depositional microbial activity in this peat sequence, which evidently can be extensive in a percolation mire. Elevated n-alkane Paq values and C 23/C 29 ratios, which are both molecular proxies for water-loving plants, record an especially moist local climate in the Bølling-Allerød (14.5 to 12.9 ka), Younger Dryas (12.9 to 11.5 ka), and Pre-Boreal (11.5 to 10.5 ka) portions of the Hani peat sequence. Depressed Paq values and C 23/C 29 ratios and larger n-alkane average chain length values indicate that the Holocene Climatic Optimum (10.5 to 6 ka) was a period of warmer climate with lower effective precipitation, which contrasts with evidence of wetter climates in most of East Asia.

  20. An electronic medical record-linked biorepository to identify novel biomarkers for atherosclerotic cardiovascular disease

    PubMed Central

    Ye, Zi; Kalloo, Fara S; Dalenberg, Angela K.; Kullo, Iftikhar J

    2013-01-01

    Background: Atherosclerotic vascular disease (AVD), a leading cause of morbidity and mortality, is increasing in prevalence in the developing world. We describe an approach to establish a biorepository linked to medical records with the eventual goal of facilitating discovery of biomarkers for AVD. Methods: The Vascular Disease Biorepository at Mayo Clinic was established to archive DNA, plasma, and serum from patients with suspected AVD. AVD phenotypes, relevant risk factors and comorbid conditions were ascertained by electronic medical record (EMR)-based electronic algorithms that included diagnosis and procedure codes, laboratory data and text searches to ascertain medication use. Results: Up to December 2012, 8800 patients referred for vascular ultrasound examination and non-invasive lower extremity arterial evaluation were approached, of whom 5268 consented. The mean age of the initial 2182 patients recruited was 70.4 ± 11.2 years, 62.6% were men and 97.6% were whites. The prevalences of AVD phenotypes were: carotid artery stenosis 48%, abdominal aortic aneurysm 21% and peripheral arterial disease 38%. Positive predictive values for electronic phenotyping algorithms were>0.90 for cases (and>0.95 for controls) for each AVD phenotype, using manual review of the EMR as the gold standard. The prevalences of risk factors and comorbidities were as follows: hypertension 78%, diabetes 29%, dyslipidemia 73%, smoking 70%, coronary heart disease 37%, heart failure 12%, cerebrovascular disease 20% and chronic kidney disease 19%. Conclusions: Our study demonstrates the feasibility of establishing a biorepository of plasma, serum and DNA, with relatively rapid annotation of clinical variables using EMR-based algorithms. PMID:24689004

  1. Sedimentary record of PAHs in the Barigui River and its relation to the socioeconomic development of Curitiba, Brazil.

    PubMed

    Machado, Karina S; Figueira, Rubens C L; Côcco, Lilian C; Froehner, Sandro; Fernandes, Cristovão V S; Ferreira, Paulo A L

    2014-06-01

    Concentrations of polycyclic aromatic hydrocarbons (PAHs) were determined in a sediment core collected from the Barigui River, in Curitiba, South Brazil. The USEPA's 16 priority PAH concentrations ranged from 39ng g(-1) to 2350ng g(-1) of dry sediment over a period that corresponds temporally to between ca. 1855 and 2011. The concentrations and patterns of PAH distribution changed over this time period and may be associated with several episodes in the Curitiba's history. Two major PAHs concentration peaks occurred in approximately 1910 and 1970, which might reflect population increases due to immigration programs in the 1890s and the sudden economic development that occurred in Brazil from 1960 to 1980, "The Economic Miracle Period", respectively. Isomeric ratios revealed that the PAHs had predominantly pyrolytic sources. The population, number of highways and electric energy consumption of Curitiba, as indices of socioeconomic development, were positively correlated with PAH deposition in the sediment core from 1855 to 1970, indicating the influence of socioeconomic development on the environmental load of sedimentary PAHs.

  2. 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.

  3. Sedimentary Records of Hyperpycnal Flows and the Influence of River Damming on Sediment Dynamics of Estuaries: Examples from the Nelson, Churchill, Moisie and Sainte-Marguerite Rivers (Canada)

    NASA Astrophysics Data System (ADS)

    St-Onge, G.; Duboc, Q.; Boyer-Villemaire, U.; Lajeunesse, P.; Bernatchez, P.

    2015-12-01

    Sediment cores were sampled in the estuary of the Nelson and Churchill Rivers in western Hudson Bay, as well as in the estuary of the Moisie and Sainte-Marguerite Rivers in Gulf of St. Lawrence in order to evaluate the impact of hydroelectric dams on the sedimentary regime of these estuaries. The gravity cores at the mouth of the Nelson River recorded several cm-thick rapidly deposited layers with a reverse to normal grading sequence, indicating the occurrence of hyperpycnal flows generated by major floods during the last few centuries. These hyperpycnal flows were probably caused by ice-jam formation, which can increase both the flow and the sediment concentration following the breaching of such natural dams. Following the construction of hydroelectric dams since the 1960s, the regulation of river discharge prevented the formation of hyperpycnal flows, and hence the deposition of hyperpycnites in the upper part of the cores. In the core sampled in the estuary of the Churchill River, only one hyperpycnite was recorded. This lower frequency may be due to the enclosed estuary of the Churchill River, its weaker discharge and the more distal location of the coring site.In the Gulf of St. Lawrence, grain size measurements allowed the identification of a major flood around AD 1844±4 years in box cores from both the Sainte-Marguerite and Moisie Rivers, whereas a drastic decrease in variations in the median grain size occurred around AD ~1900 in the estuary of the Sainte-Marguerite River, highlighting the offshore impact of the SM1 dam construction in the early 1900s. Furthermore, sedimentological variations in the box cores from both estuaries have been investigated by wavelet analysis and the sharp disappearance of high frequencies around AD 1900 in the estuary of the dammed river (Sainte-Marguerite River), but not in the estuary of the natural river (Moisie River), also provides evidence of the influence of dams on the sedimentary regime of estuaries.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  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. 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

  7. 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

  8. 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

  9. 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.

  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. Exploring Challenges and Opportunities in Recognizing the Signature of Sea Level, Tectonic Subsidence, and Sediment Supply in the Stratigraphic Record: A Comparison of Field-based and Model-generated Data from Carbonate Sedimentary Records

    NASA Astrophysics Data System (ADS)

    Brady, M. E.; Oliver, D. L.; Bowie, C.

    2014-12-01

    Integrating field and model observations of marine carbonate strata, we investigate how distinct sedimentary basins respond to the same eustatic sea level history, specifically in terms of the preserved record of lithofacies and meter-scale depositional cycles. First, we compare two coeval Devonian sedimentary records characterized by different subsidence regimes (North American 'stable' cratonic interior vs. 'passive' continental margin) and rock accumulation rates (measured over m.y. time scales). Despite the greater potential for subaerial exposure due to minimal accommodation space, stratigraphic and petrographic analyses revealed the apparently significant role of suppressed subtidal sedimentation rates, along with submarine erosion and non-deposition, in limiting both the thickness and number of facies and cycles preserved in the cratonic record compared to the continental margin. To explore insights gained from the field, we use a previously-developed, one-dimensional forward model to generate stratigraphic columns. Knowing the true history underlying each model run, we can test the sensitivity of the resultant stratigraphy to variation in subsidence and sedimentation rates, while maintaining the same eustatic sea level curve. For the model conditions explored, 1) thicker component depositional units reflect higher sedimentation rates; 2) total stratigraphic thickness, numbers of units, and stratigraphic completeness reflect combinations of low enough sedimentation rates and high enough subsidence rates to maintain sufficient accommodation space; and 3) the preserved stratal patterns rarely faithfully record sea level history. The model results lead to new questions that can direct future field studies. Overall, this approach can inform similar investigations in other carbonate, siliciclastic and non-marine records, especially over stratigraphic scales finer than the temporal resolution typically afforded by numerical ages and correlation techniques.

  12. 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

  13. 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

  14. Evolution of the Proterozoic Earth System: Insights from the ∆17O Record of Sedimentary Sulfate Minerals

    NASA Astrophysics Data System (ADS)

    Crockford, P. W.; Hayles, J. A.; Halverson, G. P.; Bekker, A.; Rainbird, R.; Wing, B. A.

    2014-12-01

    Triple oxygen isotope ratios (18O/16O and 17O/16O) are a powerful tool to tease out interconnections within the Surface Earth System, both today and throughout Earth's history. This ability comes from the fact that stratospheric photochemistry imparts a negative ∆17O anomaly (∆17O = δ17O - 0.52×δ18O) to atmospheric oxygen whose magnitude is proportional to pCO2 levels and photosynthetic oxygen production. Atmospheric oxygen readily weathers continental sulfides and, as a result, the secular variations in atmospheric ∆17O values may be recorded in marine sulfate minerals (barite, gypsum and anhydrite). The largest ∆17O anomalies found in the rock record are from peculiar barite layers that immediately post-date the 635 Ma Marinoan Snowball Event. While these anomalies have been interpreted to result from a weak post-glacial photosynthetic O2 flux, the balance of other evidence (e.g., Zn isotope records of near-modern post-glacial productivity) suggests that they instead reflect the elevated CO2 levels thought to be required to exit a snowball state. As this situation illustrates, the ∆17O record by itself does not provide a unique solution between production of the anomaly by stratospheric reactions and its destruction by global biospheric productivity. In the context of additional geological and geochemical constraints, however, a marine sulfate ∆17O record has the potential to provide new insights into paleoatmospheres, paleoclimates, and paleoproductivity. We have produced new data (n ≈ 200) for Proterozoic evaporites that extend the sulfate ∆17O record from the Neoproterozoic to ~2.3 Ga. This data will be interpreted within our current understanding of Proterozoic Earth System Evolution on basinal to global scales and will address key questions that include: Were Paleoproterozoic glacial episodes terminated by elevated pCO2? Was the Great Oxidation Event accompanied by enhanced productivity? Does the lack of C isotope variability throughout

  15. 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

  16. 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

  17. 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.

  18. 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.

  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. Global ice volume during MIS 3 inferred from a sea-level analysis of sedimentary core records in the Yellow River Delta

    NASA Astrophysics Data System (ADS)

    Pico, Tamara; Mitrovica, Jerry X.; Ferrier, Ken L.; Braun, Jean

    2016-11-01

    Estimates of global ice volume during the glacial phase of the most recent ice age cycle are characterized by significant uncertainty, reflecting the relative paucity of geological constraints on sea level relevant to this time interval. For example, during the middle stages of Marine Isotope Stage 3, published estimates of peak global mean sea level (GMSL) relative to the present range from -25 m to -87 m. The large uncertainty in GMSL at MIS 3 has significant implications for estimates of the rate of ice growth in the period leading to the Last Glacial Maximum (∼26 ka). We refine estimates of global ice volume during MIS 3 by employing sediment cores in the Bohai and Yellow Sea that record a migration of the paleoshoreline at ∼50-37 ka through a transition from marine to brackish conditions. In particular, we correct relative sea level at these sites for contamination due to glacial isostatic adjustment using a sea-level calculation that includes a gravitationally self-consistent treatment of sediment redistribution and compaction, and estimate a peak global mean sea level of -38 ± 7 m during the interval 50-37 ka. With suitable sedimentary core records, the approach described herein can be extended to refine existing constraints on global ice volume across the entire glacial period.

  1. 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.

  2. 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.

  3. Holocene climate and glacial history of the northeastern Antarctic Peninsula: the marine sedimentary record from a long SHALDRIL core

    NASA Astrophysics Data System (ADS)

    Michalchuk, Bradley R.; Anderson, John B.; Wellner, Julia S.; Manley, Patricia L.; Majewski, Wojciech; Bohaty, Steve

    2009-12-01

    A high-resolution record of Holocene deglacial and climate history was obtained from a 77 m sediment core from the Firth of Tay, Antarctic Peninsula, as part of the SHALDRIL initiative. This study provides a detailed sedimentological record of Holocene paleoclimate and glacial advance and retreat from the eastern side of the peninsula. A robust chronostratigraphy was derived from thirty-three radiocarbon dates on carbonate material. This chronostratigraphic framework was used to establish the timing of glacial and climate events derived from multiple proxies including: magnetic susceptibility, electric resistivity, porosity, ice-rafted debris content, organic carbon content, nitrogen content, biogenic silica content, and diatom and foraminiferal assemblages. The core bottomed-out in a stiff diamicton interpreted as till. Gravelly and sandy mud above the till is interpreted as proximal glaciomarine sediment that represents decoupling of the glacier from the seafloor circa 9400 cal. yr BP and its subsequent landward retreat. This was approximately 5000 yr later than in the Bransfield Basin and South Shetland Islands, on the western side of the peninsula. The Firth of Tay core site remained in a proximal glaciomarine setting until 8300 cal. yr BP, at which time significant glacial retreat took place. Deposition of diatomaceous glaciomarine sediments after 8300 cal. yr BP indicates that an ice shelf has not existed in the area since this time. The onset of seasonally open marine conditions between 7800 and 6000 cal. yr BP followed the deglacial period and is interpreted as the mid-Holocene Climatic Optimum. Open marine conditions lasted until present, with a minor cooling having occurred between 6000 and 4500 cal. yr BP and a period of minor glacial retreat and/or decreased sea ice coverage between 4500 and 3500 cal. yr BP. Finally, climatic cooling and variable sea ice cover occurred from 3500 cal. yr BP to near present and it is interpreted as being part of the

  4. A 3500-year record of Hg and Pb contamination in a mediterranean sedimentary archive (the Pierre Blanche Lagoon, France).

    PubMed

    Elbaz-Poulichet, F; Dezileau, L; Freydier, R; Cossa, D; Sabatier, P

    2011-10-15

    A sediment core encompassing 3500 years of continuous sedimentation has been collected from a coastal lagoon located on the southwestern French Mediterranean coast. Lead concentrations and stable isotopes show that the sediments have recorded the three major periods of Pb pollution: the Etruscan-Greek-Roman period (650 BC to AD 50), the medieval period (AD 650 to AD 1450), and the modern period (from around AD 1850 to the present). These periods were separated by low pollution periods during the Dark Ages (between AD 50 and 650) and during the 16th century. From the end of the 19th century to the 1960s, Pb pollution increased exponentially. Coal combustion was the major source of Pb in the lagoon in the second half of the 20th century. Both the decrease in coal consumption and the ban on leaded gasoline resulted in a decrease in Pb pollution by a factor of 1.5 between 1973 and 1995. From 1991, sewage treatment plants and incinerators could be the major source of Pb. The average baseline Hg concentration from 1525 BC to AD 900 was 0.017 ± 0.003 μg g⁻¹ (n = 54). The Hg concentrations profile shows three major peaks: in AD 1150, AD 1660, and AD 1969, with the concentrations being respectively 8, 5, and 34 times higher than the baseline levels. The medieval peak (AD 1150) is attributed the medical use of Hg in the town of Montpellier and/or the burning of soil and vegetation. Noticeable Hg pollution was also detected during the 17th century in relation to gold and silver amalgamation in Europe. From the end of the 19th century, Hg concentrations increased exponentially until 1969. This modern pollution is attributed to the burning of coal.

  5. 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.

  6. 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

  7. 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.

  8. What collided with India at ~50 Ma? Constraints from the sedimentary record in the NW Himalaya, Ladakh.

    NASA Astrophysics Data System (ADS)

    Najman, Y.; Jenks, D.; Godin, L.; BouDagher-Fadel, M. K.; Bown, P. R.; Horstwood, M. S.; Garzanti, E.; Bracciali, L.; Millar, I.

    2014-12-01

    with India at 50 Ma and its subsequent collision with Asia at 40 Ma. Such variation should be reflected in the detrital record of material eroded from the arc. We use zircon U-Pb and Hf analyses from Palaeogene sediments deposited in and adjacent to the Indus suture in Ladakh, to further explore the interpretations presented in that research.

  9. 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

  10. Sedimentary records of metal deposition in Japanese alpine lakes for the last 250 years: recent enrichment of airborne Sb and In in East Asia.

    PubMed

    Kuwae, Michinobu; Tsugeki, Narumi K; Agusa, Tetsuro; Toyoda, Kazuhiro; Tani, Yukinori; Ueda, Shingo; Tanabe, Shinsuke; Urabe, Jotaro

    2013-01-01

    Concentrations of 18 elements, including Sb, In, Sn, and Bi, were measured in sediment cores from two pristine alpine lakes on Mount Hachimantai, northern Japan, representing the past 250 years. Vertical variations in concentrations are better explained by atmospheric metal deposition than by diagenetic redistribution of Fe and Mn hydroxide and organic matter. Anthropogenic metal fluxes were estimated from (210)Pb-derived accumulation rates and metal concentrations in excess of the Al-normalized mean background concentration before 1850. Anthropogenic fluxes of Sb and In showed gradual increases starting around 1900 in both lakes, and marked increases after 1980. Comparison of Sb/Pb and Pb stable isotope ratios in sediments with those in aerosols of China or northern Japan and Japanese source materials (recent traffic- and incinerator-derived dust) suggest that the markedly elevated Sb flux after 1980 resulted primarily from enhanced long-range transport in aerosols containing Sb and Pb from coal combustion on the Asian continent. The fluxes of In, Sn, and Bi which are present in Chinese coal showed increasing trends similar to Sb for both study lakes. This suggests that the same source although incinerators in Japan may not be ruled out as sources of In. The sedimentary records for the last 250 years indicate that atmospheric pollution of Sb and In in East Asia have intensified during recent decades.

  11. 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.

  12. 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.

  13. 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

  14. Magnetic susceptibility and cyclostratigraphy of upper Jurassic marly formations (ANDRA, underground research laboratory, Bure, Eastern Paris Basin): Record of Milankovitch cycles, sedimentary gaps, and implications for regional correlation

    NASA Astrophysics Data System (ADS)

    Emilia, H.; Bruno, G.; Pierre-Yves, C.; Slah, B.; Pascal, E.; Linda, H.; Christian, R.

    2006-05-01

    , sedimentary hiatuses of a few hundreds of thousands of years appear to affect the Oxfordian marly formation of the Paris Basin. MS records provide an excellent means for regional stratigraphic correlation, and are especially promising in high resolution cyclostratigraphic studies. Hiatus detection and estimation of their durations can also be considered by such an approach.

  15. 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

  16. 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.

  17. Sedimentary biomarkers along a contamination gradient in a human-impacted sub-estuary in Southern Brazil: a multi-parameter approach based on spatial and seasonal variability.

    PubMed

    de Abreu-Mota, Michelle Alves; de Moura Barboza, Carlos Alberto; Bícego, Márcia C; Martins, César C

    2014-05-01

    The composition and seasonal variations of sedimentary organic matter were investigated along the Cotinga sub-estuary, located in Paranaguá Bay, a large South American estuary where urban activities and the primary Brazilian grain shipping port are sources of pollution. Steroids and hydrocarbons were analyzed in surface sediments collected during the austral winter (2008) and summer (2009) in three distinct sectors, along this sub-estuary in a presumed gradient of fecal contamination. Concentrations ranged from 0.28 to 7.33 μgg (-1) (in dry sample weight thereafter),

  18. 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

  19. 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.

  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. 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.

  2. Sedimentary record of postglacial variability in near-bottom currents, sediment supply and ice rafting on the continental shelf off SW Spitsbergen

    NASA Astrophysics Data System (ADS)

    Sternal, B.; Szczuciński, W.; Forwick, M.; ZajÄ czkowski, M.; Lorenc, S.; Vorren, T. O.

    2012-04-01

    The continental shelf off the west coast of southern Spitsbergen is influenced by the northward-flowing water masses (warmer and more saline Atlantic Water carried by the West Spitsbergen Current and colder, fresher Arctic Water carried by the East Spitsbergen Current), as well as ice rafting. The present study was conducted to identify the influence of these factors on the sedimentary environment and to decipher temporal variations in the intensity of bottom currents, ice rafting off and glacial activity on southwestern Spitsbergen during the past 14,000 years. The study is based on a multiproxy analyses of one gravity core from the outer continental shelf (148 m water depth) in decadal to centennial resolution. Age control was obtained on a basis of ten AMS 14C dates along with 210Pb and 137Cs datings. To infer the style of sedimentation and the sediment supply the core was measured for magnetic susceptibility, X-rayed, analysed for grain-size distribution of bulk sediment and for coarse sand fraction components. The assessment of ice rafting intensity was based on coarse sand fraction counting (IRD), whereas to assume the type of ice rafting, whether by icebergs or sea ice, the analysis of quartz grains roundness was performed. Moreover, relative velocity of bottom currents was estimated by grain-size analysis of sortable silt fraction. We distinguish seven intervals: c. 14,000 - 12,600 cal yr BP - Bølling/Allerød (unit 1); 12,600 - 11,500 cal yr BP - Younger Dryas (unit 2) and 11,500 cal yr BP to present - Holocene (units 3 - 7). The smallest mean sortable silt values, reflecting relatively low bottom current velocity, occurred from the Bølling/Allerød to the early Younger Dryas and after ~0.5 cal ka BP. Increased velocities were inferred for the early Holocene as well as period between 8.8 - 7.8 cal yr BP. The IRD was present throughout the entire record indicating continuous supply of a material delivered from ice rafting, with variable dominance of

  3. A Multi-Decadal 11.5 ka Sedimentary Pigment Record of Aquatic Productivity and Landscape Stability from Torfadalsvatn, North Iceland.

    NASA Astrophysics Data System (ADS)

    Florian, C. R.; Miller, G. H.; Geirsdottir, A.

    2014-12-01

    North Iceland is located in a climatically sensitive region at the interface between the warm Irminger Current and the cold East Greenland Current. Torfadalsvatn (66° 3'41.73"N, 20°23'14.26"W) is a relatively small (0.4 km2) and shallow (z=5.8 m) lake that lies on the Skagi peninsula of northern Iceland approximately 0.5 km from the modern coastline and is ideally situated to compare with regional climate records of nearby marine cores from the North Iceland Shelf. We have employed a multi-proxy approach to reconstruct Holocene terrestrial climate from an 8.4 m sediment core at 15-30 year resolution using sedimentary pigments, organic carbon flux, C:N and their stable isotopes, and biogenic silica measured by Fourier Transform Infrared Spectroscopy. Several proxies show peak values shortly after 8 ka suggesting peak Holocene warmth may have occurred at this time. Elevated canthaxanthin, produced by cyanobacteria, and lutein (green algae and higher plants), along with less negative δ13C and high C:N suggest a productive aquatic environment with abundant aquatic macrophytes. The mid Holocene is characterized by elevated diatom pigment concentration, reduced C:N and lutein concentration suggesting a shift toward a diatom dominated system with continued high aquatic productivity. At ~1.5 ka influx of terrestrial organic matter increases associated with a decrease in aquatic productivity. Terrestrial organic matter continues to increase during the late Holocene, peaking at ~1750 AD potentially associated with minimum local Little Ice Age temperatures. Aquatic productivity, however, continues to decrease until ~1900 AD suggesting that the landscape destabilization signal may have become saturated before minimum temperatures occurred. A comparison of the data from this core with other high-resolution regional climate records will not only increase our understanding of differences in climate histories between north and south Iceland, but will also allow for a better

  4. 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

  5. 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.

  6. 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

  7. Trace metals as biomarkers for eumelanin pigment in the fossil record.

    PubMed

    Wogelius, R A; Manning, P L; Barden, H E; Edwards, N P; Webb, S M; Sellers, W I; Taylor, K G; Larson, P L; Dodson, P; You, H; Da-qing, L; Bergmann, U

    2011-09-16

    Well-preserved fossils of pivotal early bird and nonavian theropod species have provided unequivocal evidence for feathers and/or downlike integuments. Recent studies have reconstructed color on the basis of melanosome structure; however, the chemistry of these proposed melanosomes has remained unknown. We applied synchrotron x-ray techniques to several fossil and extant organisms, including Confuciusornis sanctus, in order to map and characterize possible chemical residues of melanin pigments. Results show that trace metals, such as copper, are present in fossils as organometallic compounds most likely derived from original eumelanin. The distribution of these compounds provides a long-lived biomarker of melanin presence and density within a range of fossilized organisms. Metal zoning patterns may be preserved long after melanosome structures have been destroyed.

  8. 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

  9. Major element compositions of fluid inclusions from hydrothermal vein-type deposits record eroded sedimentary units in the Schwarzwald district, SW Germany

    NASA Astrophysics Data System (ADS)

    Walter, Benjamin F.; Burisch, Mathias; Marks, Michael A. W.; Markl, Gregor

    2017-02-01

    Mixing of sedimentary formation fluids with basement-derived brines is an important mechanism for the formation of hydrothermal veins. We focus on the sources of the sediment-derived fluid component in ore-forming processes and present a comprehensive fluid inclusion study on 84 Jurassic hydrothermal veins from the Schwarzwald mining district (SW Germany). Our data derive from about 2300 fluid inclusions and reveal differences in the average fluid composition between the northern, central, and southern Schwarzwald. Fluids from the northern and southern Schwarzwald are characterised by high salinities (18-26 wt% NaCl+CaCl2), low Ca/(Ca+Na) mole ratios (0.1-0.4), and variable Cl/Br mass ratios (30-1140). In contrast, fluids from the central Schwarzwald show even higher salinities (23-27 wt% NaCl+CaCl2), higher Ca/(Ca+Na) mole ratios (0.2-0.9), and less variable Cl/Br mass ratios (40-130). These fluid compositions correlate with the nature and thickness of the now eroded sedimentary cover rocks. Compared to the northern and the southern Schwarzwald, where halite precipitation occurred during the Middle Triassic, the sedimentary basin in the central Schwarzwald was relatively shallow at this time and no halite was precipitated. Accordingly, Cl/Br ratios of fluids from the central Schwarzwald provide no evidence for the reaction of a sedimentary brine with halite, whereas those from the northern and southern Schwarzwald do. Instead, elevated Ca/(Ca+Na), high SO4 contents, and relatively low Cl/Br imply the presence of a gypsum dissolution brine during vein formation in the central Schwarzwald which agrees with the reconstructed regional Triassic geology. Hence, the information archived in fluid inclusions from hydrothermal veins in the crystalline basement has the potential for reconstructing sedimentary rocks in the former overburden.

  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. 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.

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

    PubMed

    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.

  13. 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.

  14. Evolution of exhumation and erosion in western West Gondwanaland as recorded by detrital zircons of late Neoproterozoic and Cambrian sedimentary rocks of NW and Central Argentina

    NASA Astrophysics Data System (ADS)

    Miller, Hubert; Adams, Christopher; Aceñolaza, Florencio G.; Toselli, Alejandro J.

    2011-04-01

    The evolution of the provenance areas for Late Neoproterozoic, Cambrian and Early Ordovician sedimentary and meta-sedimentary rocks of north central and northwest Argentina is discussed using 123 maximum ages of detrital zircons from 42 samples from this and previously published studies. Most detrital zircon ages fall into two groups: 1,200-900 Ma and 670-545 Ma. These ages are essentially identical for the non- to very low grade metamorphic late Neoproterozoic to Early Cambrian Puncoviscana Formation and the low to high grade metamorphic rocks of Eastern Sierras Pampeanas. Hence, both units are related to similar provenance areas at the same time of sedimentation. The time span from zircon crystallization in the Earth's crust to exhumation and erosion may be very long. This is important when determining maximum ages of sedimentary rocks. Variation of zircon maxima may also be influenced by concurrent sedimentary cover of proposed provenance areas. For the late Mesoproterozoic to early Neoproterozoic zircon age group, an active mountain range of the southwest Brazilian Sunsás orogen is the most probable provenance area. The younger, late Neoproterozoic zircons are related to the continuously developing mountains of the Brasiliano orogen of southwest and south central Brazil. Young zircons, up to 514 Ma, from fossil-bearing Puncoviscana and Suncho Formation outcrops are related to late Early Cambrian volcanism contemporaneous with sedimentation. This situation continues through the Late Cambrian to the Early Ordovician, but the Sunsás orogen provenance diminishes as possible Río de la Plata craton origins become important.

  15. 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‰ (2σ). Equilibrium

  16. 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.

  17. 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.

  18. 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

  19. 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

  20. 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.

  1. Investigating Controls on Sedimentation Through Interpretation of the Syntectonic Cretaceous-Paleogene Sedimentary Record in the San Juan Basin (New Mexico, U.S.A.)

    NASA Astrophysics Data System (ADS)

    Hobbs, K.; Weissmann, G. S.; Fawcett, P. J.

    2015-12-01

    The Cretaceous/Paleogene boundary in the southwestern San Juan Basin is bracketed by the mudstone-dominated Cretaceous Kirtland Formation, the sandstone-dominated Paleocene Ojo Alamo Sandstone, and the mudstone-dominated Paleocene lower Nacimiento Formation. Geochemical trends of fluvial mudstones from these units indicate changing sedimentary source areas through time. While the Kirtland and Nacimiento Formations represent periods of high accommodation within the San Juan Basin, the Ojo Alamo Sandstone represents a period of low accommodation and general reworking and transport by southeast-flowing paleorivers. The Kirtland and Nacimiento Formations thin and fine away from their interpreted source area whereas the Ojo Alamo Sandstone thickens and fines away from the source area. Here we investigate the enigmatic sedimentary architecture of the Ojo Alamo Sandstone, geochemical evidence for a changing source area through this time period, and the complex relationships between sedimentation, source area, accommodation, and basin tectonic evolution. Incorporating new measured sections, petrographic analyses, geochemical trends, and stratigraphic relationships, we propose that the Ojo Alamo Sandstone represents an anomalous short period of low accommodation in the San Juan Basin during the early Laramide Orogeny and explore possible intra- and extra-basinal tectonic, climatic, and sedimentologic explanations as well as implications for understanding the evolution of the basin.

  2. Alkenone temperature records and biomarker flux at the subtropical front on the chatham rise, SW Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Sikes, Elisabeth L.; O'Leary, Teresa; Nodder, Scott D.; Volkman, John K.

    2005-05-01

    Alkenones and a suite of sterol biomarkers were examined in two sediment trap arrays deployed at 300 m depth in subtropical and subantarctic waters to the east of New Zealand from late winter to autumn in 1996-1997. The two traps were located within 200 km of one another and the main difference between the two sites are the differential physical, chemical, and biological characteristics of the different water masses in which they were situated. The alkenone-based reconstructions of water temperatures (U37K') were compared to the COADS monthly averaged satellite and real-time weekly temperatures for the deployment period. The records correlate well with seasonal sea surface temperatures (SST) for the 9 months of the deployment, with temperature reconstructions within 2 °C of regional monthly averages for most of the year. There are a few short periods of poorer agreement where alkenone-based reconstructions deviate by up to 4 °C in both traps. Weekly averages of satellite SST obtained during the time of the deployment indicate that these deviations were not associated with short-term changes in surface temperatures overlying the traps. These instances of poor correlation are not due to lateral advection of particles, but rather seem to reflect differences in environmental controls on alkenone-derived SSTs in the two water masses. Subantarctic traps showed deviations only to warmer than average temperatures. These occurred in early winter and late summer, during times of low lipid fluxes, suggesting that slow growth associated with light limitation may have affected unsaturation levels in the alkenones. The subtropical traps showed deviations only to cooler temperatures, which occurred in the late summer to early autumn. These biases occurred during times of highest lipid fluxes and lowest nutrients in the surface mixed-layer. Alkenone temperatures during maximum flux periods were too cool to be caused by subsurface production alone, suggesting that nutrient

  3. Sedimentary record of seismic events in the Eocene Green River Formation and its implications for regional tectonics on lake evolution (Bridger Basin, Wyoming)

    NASA Astrophysics Data System (ADS)

    Törő, Balázs; Pratt, Brian R.

    2016-10-01

    Outcrops and cores from the top of the lacustrine Tipton Member and the base of the Wilkins Peak Member ( 51.5 Ma) of the Eocene Green River Formation, Bridger Basin in southwestern Wyoming yield a wide variety of sedimentary deformation features many of which are laterally extensive for more than 50 km. They include various types of folds, load structures, pinch-and-swell structures, microfaults, breccias and sedimentary dikes. In most cases deformation is represented by hybrid brittle-ductile structures exhibiting lateral variation in deformation style. These occur in low-energy, profundal organic-rich carbonate mudstones (oil shales), trona beds, tuffs, and profundal to sublittoral silty carbonate deposited in paleolake Gosiute. The deformation is not specific to the depositional environment because sedimentary units stratigraphically higher with similar facies show no deformation. The studied interval lacks any evidence for possible trigger mechanisms intrinsic to the depositional environment, such as strong wave action, rapid sediment loading, evaporite dissolution and collapse, or desiccation, so 'endogenic' causes are ruled out. Thus, the deformation features are interpreted as seismites, and change in deformation style and inferred increase in intensity towards the south suggest that the earthquakes were sourced from the nearby Uinta Fault System. The 22 levels exhibiting seismites recognized in cores indicate earthquakes with minimum magnitudes between 6 and 7, minimum epicentral intensity (MCS) of 9, and varying recurrence intervals in the seismic history of the Uinta Fault System, with a mean apparent recurrence period of 8.1 k.y. using average sedimentation rates and dated tuffs; in detail, however, there are two noticeably active periods followed by relative quiescence. The stratigraphic position of these deformed intervals also marks the transition between two distinct stages in lake evolution, from the balanced-filled Tipton Member to the overlying

  4. Late Miocene sedimentary record of the Danube/Kisalföld Basin: interregional correlation of depositional systems, stratigraphy and structural evolution

    NASA Astrophysics Data System (ADS)

    Sztanó, Orsolya; Kováč, Michal; Magyar, Imre; Šujan, Michal; Fodor, László; Uhrin, András; Rybár, Samuel; Csillag, Gábor; Tőkés, Lilla

    2016-12-01

    The Danube / Kisalföld Basin is the north-western sub-basin of the Pannonian Basin System. The lithostratigraphic subdivision of the several-km-thick Upper Miocene to Pliocene sedimentary succession related to Lake Pannon has been developed independently in Slovakia and Hungary. A study of the sedimentary formations across the entire basin led us to claim that these formations are identical or similar between the two basin parts to such an extent that their correlation is indeed a matter of nomenclature only. Nemčiňany corresponds to the Kálla Formation, representing locally derived coarse clastics along the basin margins (11- 9.5 Ma). The deep lacustrine sediments are collectively designated the Ivanka Formation in Slovakia, while in Hungary they are subdivided into Szák (fine-grained transgressive deposits above basement highs, 10.5 - 8.9 Ma), Endrőd (deep lacustrine marls, 11.6 -10 Ma), Szolnok (turbidites, 10.5 - 9.2 Ma) and Algyő Formations (fine-grained slope deposits, 10 - 9 Ma). The Beladice Formation represents shallow lacustrine deltaic deposits, fully corresponding to Újfalu (10.5 - 8.7 Ma). The overlying fluvial deposits are the Volkovce and Zagyva Formations (10 - 6 Ma). The synoptic description and characterization of these sediments offer a basin-wide insight into the development of the basin during the Late Miocene. The turbidite systems, the slope, the overlying deltaic and fluvial systems are all genetically related and are coeval at any time slice after the regression of Lake Pannon initiated about 10 Ma ago. All these formations get younger towards the S, SE as the progradation of the shelf-slope went on. The basin got filled up to lake level by 8.7 Ma, since then fluvial deposition dominated.

  5. Records of Precambrian Early Palaeozoic volcanic and sedimentary processes in the Central European Variscides: A review of SHRIMP zircon data from the Kaczawa succession (Sudetes, SW Poland)

    NASA Astrophysics Data System (ADS)

    Kryza, Ryszard; Zalasiewicz, Jan

    2008-12-01

    The early, pre-orogenic stages of evolution in the Variscan belt, i.e. rifting processes, opening of sedimentary basins and associated igneous activities, are often obscure because many successions have yielded little or no biostratigraphic data, have a strong metamorphic overprint and are tectonically deformed and dislocated. The increasing application of SHRIMP zircon dating has provided useful constraints on magmatic and metamorphic processes, helped locate probable source areas for detritus within sedimentary successions and facilitated large-scale palaeogeographic correlations. This methodology has recently thrown considerable light on the age and relationships of the previously poorly constrained rock units of the Kaczawa Complex in the Polish West Sudetes. Thus, recent SHRIMP studies in the Kaczawa Mountains have yielded Early Ordovician ages of the initial rift type bimodal volcanic suites at the bottom part of the Kaczawa Succession: c. 503 Ma for metarhyodacites of crustal derivation, and c. 485 Ma for alkaline metatrachytes of mantle signature. These dates provide a firm temporal constraint on the initial rift magmatism interpreted as related to the continental break-up of the northern peripheries of Gondwana. New SHRIMP data from metavolcaniclastic and metasedimentary rocks of the Kaczawa Complex have yielded results that have provided significantly changed interpretations on their age and relationships. For instance, a siliciclastic sequence interpreted as belonging to the lower part of the Kaczawa Complex (the Gackowa Sandstones) and seemingly sourced (using an array of geochemical and mineralogical evidence) from nearby early Ordovician volcanic rocks has, surprisingly, yielded zircon ages not younger than Precambrian and thus this unit has tentatively been reinterpreted as a possible correlative of the Neoproterozoic Lusatian Graywackes. Felsic metavolcaniclastic rocks embedded in the carbonate succession of the Wojcieszów Limestone have yielded

  6. The evolution of the Danube gateway between Central and Eastern Paratethys (SE Europe): Insight from numerical modelling of the causes and effects of connectivity between basins and its expression in the sedimentary record

    NASA Astrophysics Data System (ADS)

    Leever, K. A.; Matenco, L.; Garcia-Castellanos, D.; Cloetingh, S. A. P. L.

    2011-04-01

    The Pannonian and Dacic Basins in SE Europe are presently connected by the Danube River across the South Carpathians, to which they are in a back-arc and foreland position respectively. Part of the Paratethys realm during the Neogene, open water communication between the basins was interrupted by the Late Miocene uplift of the Carpathians. Different mechanisms have been proposed for the formation of the Danube gateway: capture of the upstream lake or an upstream river or incision of an antecedent river. Estimates on its age range from Late Miocene to Quaternary. A related issue is the effect of the large Mediterranean sea level fall related to the Messinian Salinity Crisis on the Paratethys subbasins, specifically the "isolated" Pannonian Basin. In a synthetic numerical modelling study, using a pseudo-3D code integrating tectonics, surface processes and isostasy, we addressed the causes and effects of changes in connectivity between two large sedimentary basins separated by an elevated barrier. Specifically, we aimed to find the expression of connectivity events in the sedimentary record in general and the consequences for the evolution of the Pannonian-Dacic area in particular. We studied a range of parameters including the geometry and uplift rate of the barrier, downstream sea level change and lithosphere rigidity. We found that changes in connectivity are expressed in the sedimentary record through their effect on base level in the upstream basin and supply in the downstream basin. The most important factors controlling the response are the elevation difference between the basins and the upstream accommodation space at the time of reconnection. The most pronounced effect of reconnection through lake capture is predicted for a large elevation difference and limited upstream accommodation space. Downstream increase in sediment supply is dependent on the latter rather than the reconnection event itself. Of the parameters we tested, the rigidity of the lithosphere

  7. Provenance change from the Middle to Late Triassic of the southwestern Sichuan basin, Southwest China: Constraints from the sedimentary record and its tectonic significance

    NASA Astrophysics Data System (ADS)

    Zhu, Min; Chen, Hanlin; Zhou, Jing; Yang, Shufeng

    2017-03-01

    The formation of the Sanjiang and Qinling orogens caused by closure of Paleo-Tethys Ocean along the western and northern margins of the Yangtze block during the early Mesozoic created a unique basin-mountain system. Petrology, geochemistry, geochronology, sedimentary facies and paleocurrent data are integrated in order to investigate the changing provenance of Middle-Late Triassic successions from the southwestern Sichuan region, SW China. The detrital compositions from the Middle Triassic successions indicate low mature sediments of mafic and intermediate rocks origin, which derivation mainly from recycled orogenic and secondarily from the Emeishan Large Igneous Province (ELIP). The detrital zircon U-Pb age distribution pattern of the Middle Triassic sandstone samples exhibits four major age Groups at 257 Ma, 650-500 Ma, 880-710 Ma, and 1000-900 Ma. Combined with the geochemical characteristics, an interior Yangtze block source including the Khamdian uplift and ELIP is suggested. The Late Triassic sedimentary rocks yield seven U-Pb age Groups at 245-210 Ma, 290-260 Ma, 460-410 Ma, 650 Ma, 880-710 Ma, 1900-1600 Ma, and 2600-2400 Ma, which are consistent with the data reported from the Sichuan basin, Songpan Ganzi basin and the southern Yidun terrane, and are partly similar to those of the south Qinling orogen, Jiangnan Xuefeng thrust belt. In contrast to the Middle Triassic successions, the sandstone composition modals and whole-rock geochemistry of the Late Triassic samples denote mature deposits and of intermediate and acid rocks origin. Therefore, during the Late Triassic, the southwestern Sichuan basin received materials from the Songpan Ganzi folded belt and Yidun arc complex dominantly, and from the Qinling orogen and Jiangnan Xuefeng thrust belt subsidiarily. The Sanjiang orogen and the Songpan Ganzi folded belt should have controlled the formation of the southwestern Sichuan basin, while the development of the Qinling orogen and the western Jiangnan

  8. 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.

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

    PubMed

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

    2010-01-01

    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.

  10. 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.

  11. The Eocene-Oligocene sedimentary record in the Chesapeake Bay impact structure: Implications for climate and sea-level changes on the western Atlantic margin

    USGS Publications Warehouse

    Schulte, P.; Wade, B.S.; Kontny, A.; ,

    2009-01-01

    A multidisciplinary investigation of the Eocene-Oligocene transition in the International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) Eyreville core from the Chesapeake Bay impact basin was conducted in order to document environmental changes and sequence stratigraphic setting. Planktonic foraminifera and calcareous nannofossil biostratigraphy indicate that the Eyreville core includes an expanded upper Eocene (Biozones E15 to E16 and NP19/20 to NP21, respectively) and a condensed Oligocene-Miocene (NP24-NN1) sedimentary sequence. The Eocene-Oligocene contact corresponds to a =3-Ma-long hiatus. Eocene- Oligocene sedimentation is dominated by great diversity and varying amounts of detrital and authigenic minerals. Four sedimentary intervals are identified by lithology and mineral content: (1) A 30-m-thick, smectite- and illite-rich interval directly overlies the Exmore Formation, suggesting long-term reworking of impact debris within the Chesapeake Bay impact structure. (2) Subsequently, an increase in kaolinite content suggests erosion from soils developed during late Eocene warm and humid climate in agreement with data derived from other Atlantic sites. However, the kaolinite increase may also be explained by change to a predominant sediment input from outside the Chesapeake Bay impact structure caused by progradation of more proximal facies belts during the highstand systems tract of the late Eocene sequence E10.Spectral analysis based on gamma-ray and magnetic susceptibility logs suggests infl uence of 1.2 Ma low-amplitude oscillation of the obliquity period during the late Eocene. (3) During the latest Eocene (Biozones NP21 and E16), several lithological contacts (clay to clayey silt) occur concomitant with a prominent change in the mineralogical composition with illite as a major component: This lithological change starts close to the Biozone NP19/20-NP21 boundary and may correspond to sequence boundary E10-E11 as observed in

  12. Multi-proxy sedimentary record from Lake Ghirla (N-Italy) reveals hydro-climatic variations and periods of anthropogenic activities during the past 13 kyrs

    NASA Astrophysics Data System (ADS)

    Wirth, Stefanie B.; Gilli, Adrian; Sessions, Alex L.

    2016-04-01

    Lake Ghirla is a small lake that lies in the southern foothills of the Central Alps near the Swiss-Italian border. Climatically, the region is influenced by North Atlantic and Mediterranean weather systems and is frequently affected by severe storm tracks causing heavy precipitation. The catchment with Permian granites and gneisses contains Pb in amounts significant for mining as well as less important concentrations of Cu, As and U. This sensitive setting makes Lake Ghirla a promising site to reconstruct hydro-climatic variations and to track human activity by means of elevated heavy metal concentrations in the lake sediments. The recovered sediment core comprises the entire Younger Dryas-Holocene time period and was analyzed for (i) sedimentological changes to identify flood deposits, for (ii) the hydrogen isotopic composition of terrestrial plant waxes (plant-wax D/H) to constrain hydro-climatic changes, and for (iii) variations of the elemental composition (XRF core scanning, ICP-MS) to understand anthropogenic impacts. During the past 13 kyrs, we observe a high variability of floods with peak periods appearing at ~11, 10.6-8.2, 6-4.9, 2.8-2.7, 2.6-2.4, 1.2-1 and 0.4-0.1 (LIA) cal kyr BP. From a hydro-climatic perspective, the most remarkable result from the plant-wax D/H data is that the Younger Dryas is characterized by no significant change and that the 2.8-2.7 kyr BP and LIA intervals show an increase of plant-wax D/H values. Hence, during these three cool climatic periods temperature effects cannot be solely responsible for plant-wax D/H variation. The southward migration of the westerly storm tracks above the North Atlantic due to climate cooling must have led to a more southern and thus isotopically enriched moisture source for the southern Alps. This moisture-source change likely counter-balanced or even over-rode the temperature-driven isotope effect. Increased sedimentary Cu concentrations at 3.8-3.3 kyr BP are the first evidence for the presence of

  13. Sedimentary record and climatic implications of recurrent deformation in the Tian Shan: Evidence from Mesozoic strata of the north Tarim, south Junggar, and Turpan basins, northwest China

    SciTech Connect

    Hendrix, M.S.; Graham, S.A.; Sobel, E.R.

    1992-01-01

    Detailed stratigraphic, sedimentologic, paleocurrent, and subsidence analyses were conducted on Mesozoic nonmarine sedimentary sections of the south Junggar, north Tarim, and Turpan basins, Xinjang Uygur Autonomous Region, northwest China. These three basins have been foreland basins throughout the Mesozoic and Cenozoic eras, as demonstrated by asymmetrically distributed basinwide sediment accumulations, foreland-style subsidence profiles, and a variety of outcrop and subsurface facies data. Mesozoic paleocurrent indicators measured in the south Junggar and north Tarim basins, as well as Mesozoic sandstone compositions from both basins, indicate that the intervening Tian Shan has existed as a positive physiographic feature partitioning the two basins throughout Mesozoic and Cenozoic time. Paleocurrent, facies, and subsurface isopach data suggest that the Turpan basin was established as a discrete feature by the Early Jurassic period. The timing and style of depositional systems within the north Tarim Mesozoic depocenter, the south Junggar Mesozoic depocenter, and the central Turpan basin are remarkably similar. Upper Triassic strata of each basin consist of alluvial conglomerate and associated braided-fluvial sandstone and siltstone which fine upward into lower through Middle Jurassic, locally organic-rich, meandering-fluvial, and lacustrine strata. Upper Jurassic braided-fluvial red beds in each basin are overlain by a distinct pulse of uppermost Jurassic alluvial conglomerate. Lower Cretaceous exposures consist of fine-grained red beds in north Tarim and Turpan and interbedded red and gray shale with local silty carbonates in south Junggar. Upper Cretaceous strata of the north Tarim and south Junggar basins are composed of alluvial conglomerate with associated braided-fluvial sandstone and siltstone. 94 refs., 17 figs.

  14. Sedimentary record and anthropogenic pollution of a complex, multiple source fed dam reservoirs: An example from the Nové Mlýny reservoir, Czech Republic.

    PubMed

    Sedláček, Jan; Bábek, Ondřej; Nováková, Tereza

    2017-01-01

    While numerous studies of dam reservoirs contamination are reported world-wide, we present a missing link in the study of reservoirs sourced from multiple river catchments. In such reservoirs, different point sources of contaminants and variable composition of their sedimentary matrices add to extremely complex geochemical patterns. We studied a unique, step-wise filled Nové Mlýny dam reservoir, Czech Republic, which consists of three interconnected sub-basins. Their source areas are located in units with contrasting geology and different levels and sources of contamination. The aim of this study is to provide an insight into the provenance of the sediment, including lithogenic elements and anthropogenic pollutants, to investigate the sediment dispersal across the reservoir, and to assess the heavy metal pollution in each basin. The study is based on multi-proxy stratigraphic analysis and geochemistry of sediment cores. There is a considerable gradient in the sediment grain size, brightness, MS and geochemistry, which reflects changing hydrodynamic energy conditions and primary pelagic production of CaCO3. The thickness of sediments generally decreases from proximal to distal parts, but underwater currents can accumulate higher amounts of sediments in distal parts near the thalweg line. Average sedimentation rates vary over a wide range from 0.58cm/yr to 2.33cm/yr. In addition, the petrophysical patterns, concentrations of lithogenic elements and their ratios made it possible to identify two main provenance areas, the Dyje River catchment (upper basin) and the Svratka and Jihlava River catchments (middle and lower basin). Enrichment factors (EF) were used for distinguishing the anthropogenic element contribution from the local background levels. We found moderate Zn and Cu pollution (EF ~2 to 5) in the upper basin and Zn, Cu and Pb (EF ~2 to 4.5) in the middle basin with the peak contamination in the late 1980s, indicating that the two basins have different

  15. Historical flood analysis of the Eistlenbach and Farnigraben torrents in the Hasli Valley (Bernese Alps) inferred from sedimentary records, historical maps and remote sensing

    NASA Astrophysics Data System (ADS)

    Monterrubio, Glòria; Schulte, Lothar

    2016-04-01

    shift to the eastern side of the alluvial fan producing channel incision in the middle stretch of the fan. The Farnigraben torrent has also experienced changes mostly limited to distal area in 1927, 1945 and 1960. These dynamics archived with detail during the last 90 years occurred also in historical times controlling aggradation processes and should be considered when sedimentary and geochemical proxies of the cores are interpreted. On the other hand, important changes of sedimentation rates and facies observed in the cores may provide evidences to estimate the recurrence interval of the tipping points of the oscillating shifts of the Eistlenbach torrent, thus providing millennia-long information regarding hydrological risks in the area of Hofstetten.

  16. 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.

  17. 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

  18. Mass accumulation rate of detrital materials in Lake Suigetsu as a potential proxy for heavy precipitation: a comparison of the observational precipitation and sedimentary record

    NASA Astrophysics Data System (ADS)

    Suzuki, Yoshiaki; Tada, Ryuji; Yamada, Kazuyoshi; Irino, Tomohisa; Nagashima, Kana; Nakagawa, Takeshi; Omori, Takayuki

    2016-02-01

    In the densely populated region of East Asia, it is important to know the mechanism, scale, and frequency of heavy precipitation brought about during the monsoons and typhoons. However, observational data, which cover only several decades, are insufficient to examine the long-term trend of extreme precipitation and its background mechanism. In humid areas, the transport flux of a suspended detrital material through a river system is known to have an empirical power relationship with precipitation. Thus, the sedimentation flux of a fine detrital material could potentially be used as a proxy for reconstructing past heavy precipitation events. To test the idea that the sedimentation flux of detrital materials records past heavy precipitation events (e.g., typhoons), we focused on the detrital flux estimated from the annually laminated sediment of Lake Suigetsu, central Japan, which is capable of accurately correlating the age of detrital flux with the precipitation record. We first established a precise age model (error within ±1 year in average) beginning in 1920 A.D. on the basis of varve counting fine-tuned by correlation between event layers with historical floods. The flux of the detrital material (g/cm2/year) was estimated on the basis of Al2O3 content (wt%), dry bulk density (g/cm3), and sedimentation rate (cm/year) calculated from the age model. The detrital flux of background sedimentation showed a weak positive correlation with annual and monthly (June and September) precipitation excluding heavy precipitation that exceeded 100 mm/day. Furthermore, the thickness of instantaneous event layers, which corresponds to several maxima of detrital flux and is correlated with floods that occurred mainly during typhoons, showed a positive relationship with the total amount of precipitation that caused a flood event. This result suggests that the detrital flux maxima (deposition of event layers) record past extreme precipitation events that were likely associated with

  19. The 8.4 ka lake Agassiz drainage event: its deep-sea sedimentary record and impact on the Atlantic Meridional Overturning

    NASA Astrophysics Data System (ADS)

    Hillaire-Marcel, C.; de Vernal, A.; Piper, D. J.; St-Onge, G.

    2005-12-01

    Many papers have linked the ca. 8.4 ka drainage of the Laurentide Ice Sheet pro-glacial Lake Agassiz (Barber et al, 2002, Nature 400, 344-348) to a significant reduction in the Atlantic Meridional Overturning (AMO) and to climate excursions of variable age and duration in the 8.5-8 ka time frame, with reference to the so-called "8.2 ka event" (see refs. in Rohling and Pelike, 2004, Nature 434, 975-979) based on the Greenland ice core chronology. Unfortunately, none of these papers provide direct marine evidence for a collapse or significant reduction in the AMO, neither for a widespread change in sea-surface conditions over the northern North Atlantic. Moreover, model experiments made with reference to this event lack critical evaluation based on data. Here, we present paleoceanographical records near the source area in the northwest North Atlantic with chronological resolution as high as 15 years per sample in some instances. They provide evidence for two short duration, local sedimentological events (possibly each of one year duration according to Clarke et al., 2003, Science 301, 922-923), but indicate the absence of significant change in sea-surface conditions as well as in the outflow of the deep Western Boundary Under Current, at the resolvable time scale. We conclude that there is no evidence for a significant change in the AMO linked to the drainage event that lasted more than a few tens of years, if at all. Nonetheless, all marine records indicate that the 8.5 to 7.5 ka time interval does correspond to a major large scale re-organisation both of land drainage in NE America and of the North Atlantic climate-ocean system (cf. St-Onge et al., 2003, EPSL 209, 113-130; Keigwin et al., 2005, Paleoceanography, 20, 10.1029/2004PA001074), notably marked by a reduction in the North East North Atlantic Water outflow, an increasing Denmark Strait Overflow and the inception of Labrador Sea Water formation.

  20. Historical levels of heavy metals reconstructed from sedimentary record in the Hejiang River, located in a typical mining region of Southern China.

    PubMed

    Wang, Shaopeng; Wang, Yinghui; Zhang, Ruijie; Wang, Weitao; Xu, Daoquan; Guo, Jing; Li, Pingyang; Yu, Kefu

    2015-11-01

    Historical levels of Pb, Zn, Cd, Cr, Cu, Ni, As, Fe, Al and Mn were found in C1 and C2 sediment cores from the Hejiang River, which is located in a typical mining region of Southern China, the levels date back approximately 57 and 83 years. Temporal variations in the core C1 around the mining peaked in the 1960s, after which they exhibited a decreasing trend, which reflects successful government management. Historical events such as the Pacific War and China's first 5-year economic plan were recorded in core C2, which was collected from the downstream portion of the Hejiang River. Enrichment factors (EF), geo-accumulation (Igeo), and excess flux indicate that severe contamination occurred during the period between 1956 and 1985 due to the release of high amounts of mining waste from human activities around the core C1 region. The highest EF value was displayed by As (67); this was followed by Pb (64), Cd (39), and Zn (35). In contrast, the core C2 sediments exhibited minor pollution because of dilution from tributaries (the Fu River and the Daning River) that do not flow through the mined area and because C2 was farther from the source of the metals. The results of the risk assessment codes (RAC) for both cores indicate that Cd posed a high risk to the local environment. Principal component analysis (PCA) and correlation analysis (CA) revealed that accumulation of heavy metals was mainly due to mining pollution.

  1. A 15,400-year record of climate variation from a subalpine lacustrine sedimentary sequence in the western Nanling Mountains in South China

    NASA Astrophysics Data System (ADS)

    Zhong, Wei; Cao, Jiayuan; Xue, Jibin; Ouyang, Jun

    2015-09-01

    Multi-proxy records of a subalpine lacustrine sequence in Daping Swamp in the western Nanling Mountains provide evidence for exploring climate variability in the past 15,400 yr. Two dry and cool (15,400-14,500 and 13,000-11,000 cal yr BP) and one humid and warm interval (14,500-13,200 cal yr BP), which we correlate to Heinrich Event 1, the Younger Dryas and the Bølling-Allerød event respectively, are revealed. The early Holocene climate (11,000-8000 cal yr BP) was characterized by less humid and warm conditions, suggesting a weaker Asian summer monsoon (ASM) intensity. Our findings indicate that the Holocene optimum occurred between 8000 and 4500 cal yr BP, and the most intensified ASM appears from 8000 to 7000 cal yr BP. After 4500 cal yr BP, climate shifted to relatively cool and dry conditions. We speculate that five short dry and cool events centered at ~ 11,000, 9000, 8400, 6000, and 3500 cal yr BP were linked to the Holocene ice-rafting events detected in the North Atlantic. Migration of the ITCZ, and the oceanic-atmospheric circulations, particularly SST changes in the tropical Pacific may play a pivotal role in climate variation of the study region.

  2. Carbon isotopic fractionation in lipids from methanotrophic bacteria: relevance for interpretation of the geochemical record of biomarkers

    NASA Technical Reports Server (NTRS)

    Summons, R. E.; Jahnke, L. L.; Roksandic, Z.

    1994-01-01

    Experiments with cultured aerobic methane oxidising bacteria confirm that their biomarker lipids will be significantly depleted in 13C compared to the substrate. The methanotrophic bacteria Methylococcus capsulatus and Methylomonas methanica, grown on methane and using the RuMP cycle for carbon assimilation, show maximum 13C fractionation of approximately 30% in the resultant biomass. In M. capsulatus, the maximum fractionation is observed in the earliest part of the exponential growth stage and decreases to approximately 16% as cells approach stationary phase. This change may be associated with a shift from the particulate form to the soluble form of the methane monooxygenase enzyme. Less than maximum fractionation is observed when cells are grown with reduced methane availability. Biomass of M. capsulatus grown on methanol was depleted by 9% compared to the substrate. Additional strong 13C fractionation takes place during polyisoprenoid biosynthesis in methanotrophs. The delta 13C values of individual hopanoid and steroid biomarkers produced by these organisms were as much as l0% more negative than total biomass. In individual cultures, squalene was 13C-enriched by as much as 14% compared to the triterpane skeleton of bacteriohopaneaminopentol. Much of the isotopic dispersion in lipid metabolites could be attributed to shifts in their relative abundances, combined with an overall reduction in fractionation during the growth cycle. In cells grown on methanol, where there was no apparent effect of growth stage on overall fractionation there were still significant isotopic differences between closely related lipids including a 5.3% difference between the hopane and 3 beta-methylhopane skeletons. Hopane and sterane polyisoprenoids were also 13C-depleted compared to fatty acids. These observations have significant implications for the interpretation of specific compound isotopic signatures now being measured for hydrocarbons and other lipids present in sediments and

  3. Climate variability in the past ∼19,000 yr in NE Tibetan Plateau inferred from biomarker and stable isotope records of Lake Donggi Cona

    NASA Astrophysics Data System (ADS)

    Saini, Jeetendra; Günther, Franziska; Aichner, Bernhard; Mischke, Steffen; Herzschuh, Ulrike; Zhang, Chengjun; Mäusbacher, Roland; Gleixner, Gerd

    2017-02-01

    We investigated 4.84-m-long sediment record spanning over the Late Glacial and Holocene from Lake Donggi Cona to be able to reconstruct circulation pattern on the Tibetan Plateau (TP). Presently, Lake Donggi Cona is located at the boundaries of Westerlies and Asian monsoon circulations in the northeastern TP. However, the exact timing and stimulating mechanisms for climatic changes and monsoon shifts in this region are still debated. We used a 19-ka-long stable isotope record of sedimentary n-alkanes to address this discrepancy by providing insights into paleohydrological conditions. The δD of nC23 is influenced by lake water evaporation; the δD values of sedimentary nC29 are mainly controlled by moisture source and temperature changes. Long-chain n-alkanes dominate over the core whereas three mean clusters (i.e. microbial, aquatic and terrestrial) can be inferred. Multi-proxies suggest five major episodes in the history of Lake Donggi Cona. The Lake Donggi Cona record indicates that the Late Glacial (18.4-14.8 cal ka BP) was dominated by low productivity of mainly microbial and aquatic organisms. Relatively low δD values suggest low temperatures and moist conditions eventually caused by stronger Westerlies, winter monsoon and melt-water influence. Likely, the shift (∼17.9 cal ka BP) from microbial to enhanced aquatic input suggests either a change from deep to shallow water lake or a break in local stratification. Between 14.8 and 13.0 cal ka BP, variable climatic conditions prevailed. Although the Westerlies weekend, the increase in temperature enhanced the permafrost and snow melting (displayed by a high sedimentary accumulation rate). Higher δD values indicate increasingly arid conditions with higher temperatures which eventually lead to high evaporative conditions and lowest lake levels. Low vegetation cover and high erosion rates led to high sediment accumulation resulting in stratification followed by anoxia in the terminal lake. From 13.0 to 9.2 cal

  4. Sedimentary Record and Morphological Effects of a Landslide-Generated Tsunami in a Polar Region: The 2000 AD Tsunami in Vaigat Strait, West Greenland

    NASA Astrophysics Data System (ADS)

    Szczucinski, W.; Rosser, N. J.; Strzelecki, M. C.; Long, A. J.; Lawrence, T.; Buchwal, A.; Chague-Goff, C.; Woodroffe, S.

    2012-12-01

    To date, the effects of tsunami erosion and deposition have mainly been reported from tropical and temperate climatic zones yet tsunamis are also frequent in polar zones, particularly in fjord settings where they can be generated by landslides. Here we report the geological effects of a landslide-triggered tsunami that occurred on 21st November 2000 in Vaigat, northern Disko Bugt in west Greenland. To characterise the typical features of this tsunami we completed twelve detailed coastal transects in a range of depositional settings: cliff coasts, narrow to moderate width coastal plains, lagoons and a coastal lake. At each setting we completed a detailed map using a laser scanner and DGPS survey. The tsunami deposits were described from closely spaced trenches and, from the lake, by a series of sediment cores . At each setting we examined the sedimentological properties of the deposits, as well as their bulk geochemistry and diatom content. Selected specimens of arctic willow from inundated and non-inundated areas were collected to assess the impact of the event in their growth ring records. Samples of sediments beneath the AD 2000 deposit were studied for 137Cs to confirm the age of the tsunami and to assess the extent of erosion. Offshore sediment samples, modern beach and soils/sediments underlying the AD 2000 tsunami deposits were sampled to determine tsunami deposit sources. The observed tsunami run-up exceeded 20 m next to the tsunami trigger - a rock avalanche at Paatuut - and up to 10 m on the opposite coast of the fjord. The inland inundation distance ranged from several tens of meters to over 300 m. The wave was recorded as far as 180 km away from the source. The tsunami inundated the coast obliquely to the shoreline in all locations studied. The tsunami frequently caused erosion of existing beach ridges whilst erosional niches were formed inland. The tsunami deposits mainly comprise gravels and very coarse sand. They are over 30 cm thick close to the

  5. Tidal regime of intact planetoid capture model for the Earth-Moon system: Does it relate to the archean sedimentary rock record?

    NASA Technical Reports Server (NTRS)

    Malcuit, Robert J.; Winters, Ronald R.

    1993-01-01

    Regardless of one's favorite model for the origin of the Earth-Moon system (fission, coformation, tidal capture, giant-impact) the early history of lunar orbital evolution would produce significant thermal and earth and ocean tidal effects on the primitive earth. Three of the above lunar origin models (fission, coformation, giant-impact) feature a circular orbit which undergoes a progressive increase in orbital radius from the time of origin to the present time. In contrast, a tidal capture model places the moon in an elliptical orbit undergoing progressive circularization from the time of capture (for model purposes about 3.9 billion years ago) for at least a few 10(exp 8) years following the capture event. Once the orbit is circularized, the subsequent tidal history for a tidal capture scenario is similar to that for other models of lunar origin and features a progressive increase in orbital radius to the current state of the lunar orbit. This elliptical orbit phase, if it occurred, should have left a distinctive signature in the terrestrial and lunar rock records. Depositional events would be associated terrestrial shorelines characterized by abnormally high, but progressively decreasing, ocean tidal amplitudes and ranges associated with such an orbital evolution. Several rock units in the age range 3.6-2.5 billion years before present are reported to have a major tidal component. Examples are the Warrawoona, Fortescue, and Hamersley Groups of Western Australia and the Pangola and Witwatersand Supergroups of South Africa. Detailed study of the features of these tidal sequences may be helpful in deciphering the style of lunar orbital evolution during the Archean Eon.

  6. Influence of hydro-sedimentary factors on mollusc death assemblages in a temperate mixed tide-and-wave dominated coastal environment: Implications for the fossil record

    NASA Astrophysics Data System (ADS)

    Poirier, Clément; Sauriau, Pierre-Guy; Chaumillon, Eric; Bertin, Xavier

    2010-10-01

    Mollusc death assemblages were recovered in 98 subtidal sampling stations on the seafloor of the shallow Pertuis Charentais Sea (Atlantic coast of France). Taxonomic composition and spatial distribution of death assemblages were investigated, as well as their response to sediment grain size (field data), bottom shear stress (coupled tide and wave hydrodynamic modelling), and sediment budget (bathymetric difference map). Results showed that molluscs are likely to be reliable paleoenvironmental indicators since death assemblages were able to acquire ecological changes within years (decadal-scale taphonomic inertia), and live-dead agreement inferred from existing data on living benthic communities was high, except close to river mouths and intertidal mudflats that provide terrestrial and intertidal species to subtidal death assemblages, respectively. Taxonomic composition of these within-habitat death assemblages strongly depended on sediment grain size and bottom shear stress, similarly to living subtidal communities. Post-mortem dispersal of shells, owing to relatively low bottom shear stress in the area, was only of a few 10s to 100s of meters, which shows that death assemblages preserved environmental gradients even at a fine spatial scale. Sediment budget had also a significant influence on death assemblages. Thick-shelled epifaunal species were correlated with erosion areas on one side, and thin-shelled infaunal species with deposition on the other, showing that mollusc fossil assemblages could be used as indicators of paleo-sedimentation rate. This new proxy was successfully tested on a previously published Holocene mollusc fossil record from the same area. It was possible to refine the paleoenvironmental interpretation already proposed, in accordance with existing stratigraphic and sedimentological data.

  7. Reconstruction of past oceanographic variability in Southeast Greenland from marine sedimentary records: The influence from the Atlantic Multi-decadal Oscillation

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    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. The SEDIMICE project ('Linking sediments with ice-sheet response and glacier retreat in Southeast Greenland') investigates past outlet glacier fluctuations in Southeast Greenland. 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. This presentation is based on results from a core retrieved near Sermilik Fjord by Helheim Glacier. The past 6000 years of Irminger water variability on the shelf has been reconstructed by analysing sediments from a side-bassin to the through connecting Sermilik fjord with the Irminger Sea. This reconstruction shows the Late-Holocene climate deterioration and is superimposed by a centennial-scale climate variability, which at times concurs with the climate records obtained for Northwest Europe. A wavelet analysis of the high-resolution K/Ti data (indicating grainsize variability) shows that the AMO (50-70 yr quasi-periodicity) recurrently controls Irminger water variability on the shelf. These results highlight the importance of adequate representation of regional climate modes in prognostic ice-sheet models.

  8. IODP Expedition 334: An Investigation of the Sedimentary Record, Fluid Flow and State of Stress on Top of the Seismogenic Zone of an Erosive Subduction Margin

    NASA Astrophysics Data System (ADS)

    Vannucchi, P.; Ujiie, K.; Stroncik, N.; IODP Exp. 334 Scientific Party, the

    2013-03-01

    The Costa Rica Seismogenesis Project (CRISP) is an experiment to understand the processes that control nucleation and seismic rupture of large earthquakes at erosional subduction zones. Integrated Ocean Drililng Program (IODP) Expedition 334 by R/V JOIDES Resolution is the first step toward deep drilling through the aseismic and seismic plate boundary at the Costa Rica subduction zone offshore the Osa Peninsula where the Cocos Ridge is subducting beneath the Caribbean plate. Drilling operations included logging while drilling (LWD) at two slope sites (Sites U1378 and U1379) and coring at three slope sites (Sites U1378-1380) and at one site on the Cocos plate (Site U1381). For the first time the lithology, stratigraphy, and age of the slope and incoming sediments as well as the petrology of the subducting Cocos Ridge have been characterized at this margin. The slope sites recorded a high sediment accumulation rate of 160-1035m m y-1 possibly caused by on-land uplift triggered by the subduction of the Cocos Ridge. The geochemical data as well as the in situ temperature data obtained at the slope sites suggest that fluids are transported from greater depths. The geochemical profiles at Site U1381 reflect diffusional communication of a fluid with seawater-like chemistry and the igneous basement of the Cocos plate (Solomon et al., 2011; Vannucchi et al., 2012a). The present-day in situ stress orientation determined by borehole breakouts at Site U1378 in the middle slope and Site U1379 in the upper slope shows a marked change in stress state within ~12 km along the CRISP transect; that may correspond to a change from compression (middle slope) to extension (upper slope). doi:10.2204/iodp.sd.15.03.2013

  9. Natural and human-induced environmental change in southern Albania for the last 300 years — Constraints from the Lake Butrint sedimentary record

    NASA Astrophysics Data System (ADS)

    Ariztegui, D.; Anselmetti, F. S.; Robbiani, J.-M.; Bernasconi, S. M.; Brati, E.; Gilli, A.; Lehmann, M. F.

    2010-04-01

    A sediment core from Lake Butrint in southwestern Albania contains an annually-layered sequence covering the last ˜ 300 years. It provides thus an exceptionally well-dated time series to study past climate-driven environmental changes, as well as anthropogenic perturbations along the coast of the Ionian Sea. The varves are composed of organic-rich carbonate couplets and detritus-dominated clay layers. The first are deposited during spring-to-fall, and reflect the chemistry of the lake, which, in turn, is sensitive to 1) the relative importance of marine versus freshwater inputs, 2) relative evaporation rates, and 3) the productivity cycle within the lake. The detrital laminae are deposited during winter, reflecting precipitation and runoff conditions during the wet season. A 2-3‰ stable carbon isotope ratio shift in both bulk organics and authigenic carbonates was attributed to increasing eutrophication towards the end of the 20th century, and validated by historical and instrumental data. An increase in the δ18O of authigenic carbonates by more than 8‰ indicates the progressive salinization of the lake, which can primarily be attributed to man-made perturbations that reduced the freshwater input to the lake and/or enhanced the exchange with seawater from the nearby Ionian Sea. A recent increase in the relative evaporation versus precipitation rates may have additionally contributed to the observed 18O enrichment in the Lake Butrint carbonates. The interdecadal cyclicity in the thickness of the detrital laminae seems to be at least partially controlled by NAO and/or ENSO-like phenomena that modulate precipitation patterns in the eastern Mediterranean. Thus, this study demonstrates the potential of combining microstratigraphic and stable isotopic tools to disentangle anthropogenic and natural environmental changes in Lake Butrint, validated by historical records.

  10. Early Pleistocene to Holocene glacial activity along the southern Alaska continental shelf inferred from the sedimentary record in the northern Gulf of Alaska - preliminary results

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    Preliminary analyses of the lithology at Site U1418 (IODP Expedition 341), located on the proximal Surveyor Fan, provide evidence of continuous presence of tidewater glaciers on the southern Alaska continental shelf for more than c. 1.2 Ma, as well as evidence of prolonged presence of grounded ice at the shelf break and/or the initiation of ice streams. The lowermost lithostratigraphic unit (Unit IV) of the 941 m long record is composed of heavily deformed sediments that are interpreted to be the top of the recently discovered Surveyor mass-transport deposit. Unit III contains mostly laminated mud with thin interbeds of sand, silt and clast-rich muddy diamict with rip-up clasts. A few lonestones of granule and pebble size are present. Massive and laminated mud with scattered lonestones, as well as interbedded intervals of clast-poor diamict (clasts of granule and pebble size) compose Unit II. Unit I contains massive mud with interbedded silt laminae and sand beds. Most silt laminae have the same color as the matrix, but some are lighter. Diatom oozes and graded sand beds occur infrequently and lonestones are present below 3 m. The dominance of mud suggests that sedimentation at Site U1418 was strongly influenced by suspension settling from turbid meltwater plumes emanating into the Gulf of Alaska during the past c. 1.2 Ma. Laminated intervals may reflect temporal variations in meltwater runoff from a single sediment source and/or supply from several sources during the deposition of Units II and III. Lonestones and clasts of granule and pebble size are regarded to be mostly iceberg-rafted debris, indicating that tidewater glaciers have been present on the continental shelf for most of the time since the onset of the deposition of Unit III. Diamicts in Unit II most probably reflect periods of enhanced ice rafting and/or reduced meltwater runoff. Minor silt and sand beds provide evidence of occasional sediment reworking during the deposition of Units II and III. The

  11. Biomarkers from Huronian oil-bearing fluid inclusions: An uncontaminated record of life before the Great Oxidation Event

    NASA Astrophysics Data System (ADS)

    Dutkiewicz, Adriana; Volk, Herbert; George, Simon C.; Ridley, John; Buick, Roger

    2006-06-01

    We report detailed molecular geochemistry of oil-bearing fluid inclusions from a ca. 2.45 Ga fluvial metaconglomerate of the Matinenda Formation at Elliot Lake, Canada. The oil, most likely derived from the conformably overlying McKim Formation, was trapped in quartz and feldspar during diagenesis and early metamorphism of the host rock, probably before ca. 2.2 Ga. The presence of abundant biomarkers for cyanobacteria and eukaryotes derived from and trapped in rocks deposited before the Great Oxidation Event is consistent with an earlier evolution of oxygenic photosynthesis than previously thought and suggests that some aquatic settings had become sufficiently oxygenated for sterol biosynthesis by this time. It also implies that eukaryotes survived several extreme climatic events, including the Paleoproterozoic “snowball Earth” glaciations. The extraction of biomarker molecules from Paleoproterozoic oil-bearing fluid inclusions thus establishes a new method, using low detection limits and system blank levels, to trace evolution of life through Earth's early history that avoids the potential contamination problems affecting shale-hosted hydrocarbons.

  12. Wearable Technology Surveillance Data for the Personal Health Record Using the Omaha System: Noise Exposure, Cardiovascular and Stress Biomarkers.

    PubMed

    Kerr, Madeleine J; Chin, Dal Lae; Monsen, Karen A; Hong, OiSaeng

    2016-01-01

    This poster describes a method to prepare noise and health data from wearable technology for standardized representation in the electronic personal health record thus enabling individuals to identify noise-related health risks. Using a case study approach, the authors demonstrate transformation of data to the Omaha System standardized terminology in order to depict the data graphically in a personal health record.

  13. Sedimentary Rocks and Methane - Southwest Arabia Terra

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  14. High resolution sedimentary record from the Cocos Ridge: evidence of land-ocean linkages in the Eastern Equatorial Pacific over the last 70 ka

    NASA Astrophysics Data System (ADS)

    Murdmaa, I.; Ivanova, E.; Leduc, G.; Beaufort, L.; Peresypkin, V.; Vidal, L.; Ovsepyan, E.; Alekhina, G.; Kravtsov, V.; Vasileva, V.

    2009-04-01

    We analyzed n-alkanes spectra, TOC content, and C/N ratio in the upper 12 m of the giant IMAGES Core MD02-2529 from the Cocos Ridge (08°12.33'N; 84°07.32'W; 1619 m w.d.) to estimate terrestrial organic matter (TOM) and marine organic matter (MOM) contribution to the total organic matter budget in sediments. Multi-proxy studies of nannofossils, benthic and planktic foraminifers reveal productivity variations during the time interval of the last ~ 70 ka recovered by the upper part of the core according to the age model based on AMS-14C dates and benthic oxygen isotope record. According to the shipboard core description, the slightly calcareous hemipelagic mud recovered by Core MD02-2529 contains a considerable admixture of terrestrial plant remains. This is confirmed by optical microscopic and SEM studies which reveal a strong pyritization of the particular terrestrial organic matter. As estimated by the proportion of the mainly terrestrial long-molecular alkanes (C23 - C38) relative to mainly planktic short-molecular ones (C10 - C22), the TOM input largely controls variations in the TOC content throughout the studied core interval, possibly except for the Upper Holocene, where higher TOC values correspond to relatively increased MOM content. TOM strongly dominates over the MOM content in sediments of the beginning of Termination 1, most enriched in total organic matter (up to 3.4% TOC). High content of the TOM is also fixed by n-alkane data over the Younger Dryas and H-events. Mass accumulation rates (MAR) of TOC, as well as terrestrial and marine organic matter, generally support the data on percentages, but show that the MOM flux was considerable even during the maximum TOM input at the beginning of Termination I. We suggest that this abundant TOM flux was related to the glacioeustatic sea level lowstand at the LGM, during which the emerged shelf became a vegetated coastal plain affected by seasonally humid tropical monsoon climate. The terrestrial organic

  15. Gale Sedimentary Rocks

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-439, 1 August 2003

    Gale Crater, located in the Aeolis region near 5.5oS, 222oW, contains a mound of layered sedimentary rock that stands higher than the rim of the crater. This giant mound suggests that the entire crater was not only once filled with sediment, it was also buried beneath sediment. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows some of the eroded remains of the sedimentary rock that once filled Gale Crater. The layers form terraces; wind has eroded the material to form the tapered, pointed yardang ridges seen here. The small circular feature in the lower right quarter of the picture is a mesa that was once a small meteor impact crater that was filled, buried, then exhumed from within the sedimentary rock layers exposed here. This image is illuminated from the left.

  16. Sedimentary Rocks and Dunes

    NASA Technical Reports Server (NTRS)

    2004-01-01

    25 November 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows buttes composed of light-toned, sedimentary rock exposed by erosion within a crater occurring immediately west of Schiaparelli Basin near 4.0oS, 347.9oW. Surrounding these buttes is a field of dark sand dunes and lighter-toned, very large windblown ripples. The sedimentary rocks might indicate that the crater interior was once the site of a lake. The image covers an area about 3 km (1.9 mi) wide. Sunlight illuminates the scene from the lower left.

  17. Sedimentary Rock Remnants

    NASA Technical Reports Server (NTRS)

    2005-01-01

    29 July 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows knobs of remnant, wind-eroded, layered sedimentary rock that once completely covered the floor of a crater located west of the Sinus Meridiani region of Mars. Sedimentary rock outcrops are common throughout the Sinus Meridiani region and its surrounding cratered terrain.

    Location near: 2.2oN, 7.9oW Image width: width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Autumn

  18. Biomarker evidence for Archean oxygen fluxes (Invited)

    NASA Astrophysics Data System (ADS)

    Hallmann, C.; Waldbauer, J.; Sherman, L. S.; Summons, R. E.

    2010-12-01

    Knowledge of deep-time organismic diversity may be gained from the study of preserved sedimentary lipids with taxonomic specificity, i.e. biomarker hydrocarbons (e.g. Brocks and Summons, 2003; Waldbauer et al., 2009). As a consequence of long residence times and high thermal maturities however, biomarker concentrations are extremely low in most ancient (Precambrian) sediment samples, making them exceptionally prone to contamination during drilling, sampling and laboratory workup (e.g. Brocks et al., 2008). Outcrop samples most always carry a modern overprint and deep-time biogeochemistry thus relies on drilling operations to retrieve ‘clean’ sediment cores. One such effort was initiated by NASA’s Astrobiology Institute (NAI): the Archean biosphere drilling project (ABDP). We here report on the lipids retrieved from sediment samples in drill hole ABDP-9. Strong heterogeneities of extractable organic matter - both on a spatial scale and in free- vs. mineral-occluded bitumen - provide us with an opportunity to distinguish indigenous lipids from contaminants introduced during drilling. Stratigraphic trends in biomarker data for mineral-occluded bitumens are complementary to previously reported data (e.g. S- and N-isotopes, molybdenum enrichments) from ABDP-9 sediments (Anbar et al., 2007; Kaufman et al., 2007; Garvin et al., 2009) and suggest periodic fluxes of oxygen before the great oxidation event. Anbar et al. A whiff of oxygen before the great oxidation event. Science 317 (2007), 1903-1906. Brocks & Summons. Sedimentary hydrocarbons, biomarkers for early life. In: Schlesinger (Ed.) Treatise on Geochemistry, Vol. 8 (2003), 63-115. Brocks et al. Assessing biomarker syngeneity using branched alkanes with quaternary carbon (BAQCs) and other plastic contaminants. Geochimica et Cosmochimica Acta 72 (2008), 871-888. Garvin et al. Isotopic evidence for a aerobic nitrogen cycle in the latest Archean. Science 323 (2009), 1045-1048. Kaufman et al. Late Archean

  19. Pliocene-Pleistocene changes in Arctic sea-ice cover: New biomarker records from Fram Strait/Yermak Plateau (ODP Sites 911 and 912)

    NASA Astrophysics Data System (ADS)

    Stein, Ruediger; Fahl, Kirsten

    2013-04-01

    Recently, a novel and promising biomarker proxy for reconstruction of Arctic sea-ice conditions was developed and is based on the determination of a highly branched isoprenoid with 25 carbons (IP25; Belt et al., 2007). Following this pioneer IP25 study by Belt and colleagues, several IP25 studies of marine surface sediments and sediment cores as well as sediment trap samples from northpolar areas were carried out successfully and allowed detailed reconstruction of modern and late Quaternary sea ice variability in these regions (e.g., Massé et al., 2008; Müller et al., 2009, 2011; Vare et al., 2009; Belt et al., 2010; Fahl and Stein, 2012; for review see Stein et al., 2012). Here, we present new (low-resolution) biomarker records from Ocean Drilling Program (ODP) Sites 911 and 912, representing the Pliocene-Pleistocene time interval (including the interval of major intensification of Northern Hemisphere Glaciation near 2.7 Ma). These data indicate that sea ice of variable extent was present in the Fram Strait/southern Yermak Plateau area during most of the time period under investigation. In general, an increase in sea-ice cover seems to correlate with phases of extended late Pliocene-Pleistocene continental ice-sheets. At ODP Site 912, a significant increase in sea-ice extension occurred near 1.2 Ma (Stein and Fahl, 2012). Furthermore, our data support the idea that a combination of IP25 and open water, phytoplankton biomarker data ("PIP25 index"; Müller et al., 2011) may give more reliable and quantitative estimates of past sea-ice cover (at least for the study area). This study reveals that the novel IP25/PIP25 biomarker approach has potential for semi-quantitative paleo-sea ice studies covering the entire Quaternary and motivate to carry out further detailed high-resolution research on ODP/IODP material using this proxy. 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

  20. Sedimentary Rock Layers

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-348, 2 May 2003

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image acquired in March 2003 shows dozens of repeated layers of sedimentary rock in a western Arabia Terra crater at 8oN, 7oW. Wind has sculpted the layered forms into hills somewhat elongated toward the lower left (southwest). The dark patches at the bottom (south) end of the image are drifts of windblown sand. These sedimentary rocks might indicate that the crater was once the site of a lake--or they may result from deposition by wind in a completely dry, desert environment. Either way, these rocks have something important to say about the geologic history of Mars. The area shown is about 3 km (1.9 mi) wide. Sunlight illuminates the scene from the left.

  1. Schiaparelli's Sedimentary Rocks

    NASA Technical Reports Server (NTRS)

    2004-01-01

    9 October 2004 Schiaparelli Basin is a large, 470 kilometer (292 miles) impact crater located east of Sinus Meridiani. The basin might once have been the site of a large lake--that is, if the sedimentary rocks exposed on its northwestern floor were deposited in water. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a 1.5 meter per pixel (5 ft per pixel) view of some of the light-toned, finely-bedded sedimentary rocks in northwestern Schiaparelli. The image is located near 1.0oS, 346.0oW, and covers an area about 3 km (1.9 mi) wide. Sunlight illuminates the scene from the left.

  2. Tithonium Chasma's Sedimentary Rocks

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-565, 5 December 2003

    Exposures of light-toned, layered, sedimentary rocks are common in the deep troughs of the Valles Marineris system. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an example from western Tithonium Chasma. The banding seen here is an eroded expression of layered rock. Sedimentary rocks can be composed of (1) the detritus of older, eroded and weathered rocks, (2) grains produced by explosive volcanism (tephra, also known as volcanic ash), or (3) minerals that were chemically precipitated out of a body of liquid such as water. These outcrops are located near 4.8oS, 89.7oW. The image covers an area 3 km (1.9 mi) wide and is illuminated from the lower left.

  3. Broken Sedimentary Rocks

    NASA Technical Reports Server (NTRS)

    2005-01-01

    18 May 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows broken-up blocks of sedimentary rock in western Candor Chasma. There are several locations in western Candor that exhibit this pattern of broken rock. The manner in which these landforms were created is unknown; it is possible that there was a landslide or a meteoritic impact that broke up the materials. One attribute that is known: in some of these cases, it seems that the rock was broken and then buried by later sedimentary rocks, before later being exhumed so that they can be seen from orbit today.

    Location near: 6.9oS, 75.5oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Winter

  4. Terby Sedimentary Rocks

    NASA Technical Reports Server (NTRS)

    2004-01-01

    27 December 2003 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows layered sedimentary rock outcrops in Terby Crater, located near 27.7oS, 285.4oW. The layered sediments in Terby are several kilometers thick, attesting to a long history of deposition in this ancient basin. The picture covers an area 3 km (1.9 mi) wide. Sunlight illuminates the scene from the upper left.

  5. Iani Sedimentary Rocks

    NASA Technical Reports Server (NTRS)

    2005-01-01

    23 February 2005 This Mars Global Surveyor (MGS) Orbiter Camera (MOC) image shows light-toned sedimentary rocks exposed by erosion in the Iani Chaos region of Mars.

    Location near: 4.2oS, 18.7oW Image width: 1 km (0.6 mi) Illumination from: upper left Season: Southern Winter

  6. Melas Sedimentary Rocks

    NASA Technical Reports Server (NTRS)

    2004-01-01

    17 July 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows layered, sedimentary rock outcrops in southwestern Melas Chasma, one of the troughs of the vast Valles Marineris system. Sunlight illuminates this scene from the upper left; it is located near 9.8oS, 76.0oW, and covers an area about 3 km (1.9 mi) wide.

  7. Eroded Sedimentary Rock

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-372, 26 May 2003

    This high resolution Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows eroded, layered sedimentary rock exposures in an unnamed western Arabia Terra crater at 8oN, 7oW. The dark material is windblown sand; much of the erosion of these layers may have also been caused by wind. Sunlight illuminates the scene from the left.

  8. Lipid Biomarkers for a Hypersaline Microbial Mat Community

    NASA Technical Reports Server (NTRS)

    Jahnke, Linda L.; Embaye, Tsege; Turk, Kendra A.

    2003-01-01

    The use of lipid biomarkers and their carbon isotopic compositions are valuable tools for establishing links to ancient microbial ecosystems. As witnessed by the stromatolite record, benthic microbial mats grew in shallow water lagoonal environments where microorganisms had virtually no competition apart from the harsh conditions of hypersalinity, desiccation and intense light. Today, the modern counterparts of these microbial ecosystems find appropriate niches in only a few places where extremes eliminate eukaryotic grazers. Answers to many outstanding questions about the evolution of microorganisms and their environments on early Earth are best answered through study of these extant analogs. Lipids associated with various groups of bacteria can be valuable biomarkers for identification of specific groups of microorganisms both in ancient organic-rich sedimentary rocks (geolipids) and contemporary microbial communities (membrane lipids). Use of compound specific isotope analysis adds additional refinement to the identification of biomarker source, so that it is possible to take advantage of the 3C-depletions associated with various functional groups of organisms (i.e. autotrophs, heterotrophs, methanotrophs, methanogens) responsible for the cycling of carbon within a microbial community. Our recent work has focused on a set of hypersaline evaporation ponds at Guerrero Negro, Baja California Sur, Mexico which support the abundant growth of Microcoleus-dominated microbial mats. Specific biomarkers for diatoms, cyanobacteria, archaea, green nonsulfur (GNS), sulfate reducing, and methanotrophic bacteria have been identified. Analyses of the ester-bound fatty acids indicate a highly diverse microbial community, dominated by photosynthetic organisms at the surface.

  9. Melas Sedimentary Rocks

    NASA Technical Reports Server (NTRS)

    2004-01-01

    28 August 2004 Light-toned, layered, sedimentary rock outcrops are common within the vast martian Valles Marineris trough system. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a recent example from southern Melas Chasma at 1.5 m/pixel (5 ft/pixel) resolution. The image is located near 11.3oS, 73.9oW, and covers an area about 1.8 km (1.1 mi) across. Sunlight illuminates the scene from the upper left.

  10. Sedimentary Rocks in Melas

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This Mars Global Surveyor (MGS) Orbiter Camera (MOC) image shows a butte and several other landforms eroded into light-toned, layered, sedimentary rock in southern Melas Chasma. Melas is part of the vast Valles Marineris trough system.

    Location near: 11.8oS, 74.6oW Image width: 3.0 km (1.9 mi) Illumination from: lower left Season: Southern Spring

  11. Sedimentary Rocks in Ganges

    NASA Technical Reports Server (NTRS)

    2004-01-01

    13 November 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows portions of two massifs composed of light-toned, sedimentary rock in Ganges Chasma, part of the Valles Marineris trough system. On the steeper slopes in this vista, dry talus shed from the outcrop has formed a series of dark fans. Surrounded by dark, windblown sand, these landforms are located near 8.6oS, 46.8oW. The image covers an area approximately 3 km (1.9 mi) across and sunlight illuminates the scene from the upper left.

  12. Sedimentary Rock in Candor

    NASA Technical Reports Server (NTRS)

    2005-01-01

    11 February 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dozens of light- and a few dark-toned sedimentary rock layers exposed by faulting and erosion in western Candor Chasma, part of the vast Valles Marineris trough system.

    Location near: 6.5oS, 77.0oW Image width: 3.0 km (1.9 mi) Illumination from: upper left Season: Southern Autumn

  13. South American sedimentary basins

    SciTech Connect

    Urien, C.M.

    1984-04-01

    More than 64 sedimentary basins have been identified on the South American continent. According to their regional structural character and tectonic setting, they are classified in 4 super groups. About 20 interior or intracratonic basins occur on South American cratons (Guayanas, Brazilian, and Patagonian). In most cases, their sedimentary fill is Paleozoic or early Mesozoic. Rift or transverse grabens resulting from incipient sea floor spreading extend towards the continental margin. Seventeen basins are located along the Atlantic stable margin, and consist primarily of half grabens with downfaulted seaward blocks. These rifts (or pull-apart basins) were separated as results of the migration of the African and American continental blocks. Therefore the sedimentation is chiefly Cretaceous and Tertiary. On the western edge of South American cratons, almost 20 basins of downwarped blocks extend from Orinoco down to the Malvinas plateau in a relatively uninterrupted chain of retroarc basins, bordered by the Andean orogen. They lie on a flexured Precambrian and Paleozoic basement, and are highly deformed in the west (Subandean belt) due to the action of compressional forces caused by the tectonic influence of the Mesozoic Andean batholith. Westward, the Pacific margin is bordered by 27 foreland and forearc basins, which alternate from north to south on an unstable or quasistable margin, fringed by a trench and slope complex where the ocean crust is subducted beneath the continental plate.

  14. Faulted Sedimentary Rocks

    NASA Technical Reports Server (NTRS)

    2004-01-01

    27 June 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows some of the layered, sedimentary rock outcrops that occur in a crater located at 8oN, 7oW, in western Arabia Terra. Dark layers and dark sand have enhanced the contrast of this scene. In the upper half of the image, one can see numerous lines that off-set the layers. These lines are faults along which the rocks have broken and moved. The regularity of layer thickness and erosional expression are taken as evidence that the crater in which these rocks occur might once have been a lake. The image covers an area about 1.9 km (1.2 mi) wide. Sunlight illuminates the scene from the lower left.

  15. Meridiani Sedimentary Rocks

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-545, 15 November 2003

    Northern Sinus Meridiani is a region of vast exposures of layered, sedimentary rock. Buried within these layers are many filled impact craters. Erosion has re-exposed several formerly-buried craters in this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image. Arrows 1 and 2 indicate craters that are still emerging from beneath layered material; arrow 3 indicates a crater that has been fully re-exposed. This image is located near 5.1oN, 2.7oW. The area shown is about 3 km (1.9 mi) wide and illuminated from the left/upper left.

  16. Ladon Sedimentary Rocks

    NASA Technical Reports Server (NTRS)

    2005-01-01

    6 June 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows light-toned, layered, sedimentary rocks exposed by the fluids that carved the Ladon Valles system in the Erythraeum region of Mars. These rocks are so ancient that their sediments were deposited, cemented to form rock, and then eroded by the water (or other liquid) that carved Ladon Valles, so far back in Martian history that such liquids could still flow on the planet's surface.

    Location near: 20.8oS, 30.0oW Image width: 3 km (1.9 mi Illumination from: upper left Season: Southern Spring

  17. Sedimentary Rock Outcrops

    NASA Technical Reports Server (NTRS)

    2004-01-01

    16 August 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows eroded layered rock outcrops in a crater north of Meridiani Planum near 2.7oN, 359.1oW. The dozens and dozens of sedimentary rock layers of repeated thickness and similar physical properties at this location suggest that they may have been deposited in a lacustrine (lake) setting. The crater in which these layers occur may once have been completely filled and buried, as is the case for many craters in the Sinus Meridiani region. This image covers an area about 3 km (1.9 mi) across; sunlight illuminates the scene from the left.

  18. Sedimentary Rock Near Coprates

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-420, 13 July 2003

    This mosaic of two Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) narrow angle camera images, one from 2001, the other from 2003, shows light-toned, layered, sedimentary rock outcrops exposed on the floor of a trough that parallels Coprates Chasma in the Valles Marineris system. Layered rocks form the pages from which the history of a place can be read. It may be many years before the story is read, but or now at least we know where one of the books of martian history is found. This picture is located near 15.2oS, 60.1oW. Sunlight illuminates the scene from the left.

  19. Sedimentary condensation and authigenesis

    NASA Astrophysics Data System (ADS)

    Föllmi, Karl

    2016-04-01

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

  20. Variability in aerobic methane oxidation over the past 1.2 Myrs recorded in microbial biomarker signatures from Congo fan sediments

    NASA Astrophysics Data System (ADS)

    Talbot, Helen M.; Handley, Luke; Spencer-Jones, Charlotte L.; Dinga, Bienvenu Jean; Schefuß, Enno; Mann, Paul J.; Poulsen, John R.; Spencer, Robert G. M.; Wabakanghanzi, Jose N.; Wagner, Thomas

    2014-05-01

    Methane (CH4) is a strong greenhouse gas known to have perturbed global climate in the past, especially when released in large quantities over short time periods from continental or marine sources. It is therefore crucial to understand and, if possible, quantify the individual and combined response of these variable methane sources to natural climate variability. However, past changes in the stability of greenhouse gas reservoirs remain uncertain and poorly constrained by geological evidence. Here, we present a record from the Congo fan of a highly specific bacteriohopanepolyol (BHP) biomarker for aerobic methane oxidation (AMO), 35-aminobacteriohopane-30,31,32,33,34-pentol (aminopentol), that identifies discrete periods of increased AMO as far back as 1.2 Ma. Fluctuations in the concentration of aminopentol, and other 35-aminoBHPs, follow a pattern that correlates with late Quaternary glacial-interglacial climate cycles, with highest concentrations during warm periods. We discuss possible sources of aminopentol, and the methane consumed by the precursor methanotrophs, within the context of the Congo River setting, including supply of methane oxidation markers from terrestrial watersheds and/or marine sources (gas hydrate and/or deep subsurface gas reservoir). Compound-specific carbon isotope values of -30‰ to -40‰ for BHPs in ODP 1075 and strong similarities between the BHP signature of the core and surface sediments from the Congo estuary and floodplain wetlands from the interior of the Congo River Basin, support a methanotrophic and likely terrigenous origin of the 35-aminoBHPs found in the fan sediments. This new evidence supports a causal connection between marine sediment BHP records of tropical deep sea fans and wetland settings in the feeding river catchments, and thus tropical continental hydrology. Further research is needed to better constrain the different sources and pathways of methane emission. However, this study identifies the large potential

  1. Correlation of bulk sedimentary and compound-specific δ13C values indicates minimal pre-aging of n-alkanes in a small tropical watershed

    NASA Astrophysics Data System (ADS)

    Lane, Chad S.; Horn, Sally P.; Taylor, Zachary P.; Kerr, Matthew T.

    2016-08-01

    Inherent to sedimentary compound-specific isotopic proxies of paleoecological and paleoclimate change is the assumption that biomarkers are coeval with the surrounding sedimentary matrix. Compound-specific radiocarbon analyses of lake and nearshore marine sediments have indicated a potential offset between the ages of terrestrial biomarkers and their surrounding sediments that could confound efforts to establish strong chronological control for compound-specific isotopic data. We conducted high-resolution compound-specific δ13C analyses of n-alkanes (δ13Calkane) in a well-studied sediment core from Laguna Castilla, Dominican Republic, and compared the results to bulk sedimentary δ13C (δ13Cbulk), fossil pollen, and sediment geochemistry to assess potential 'pre-aging' of alkanes in the terrestrial environment prior to deposition. We found significant positive correlations between δ13Cbulk values and δ13Calkane values, indicating little or no temporal lag in the response of δ13Calkane values to vegetation change and thus little or no offset in the age of terrestrially-derived compounds and the organic fraction of the sedimentary matrix. While this study highlights the need for further research into the variables affecting age offsets between proxy data, we propose the comparison of δ13Cbulk and δ13Calkane values as a method to assess potential age offsets between compound-specific and other proxy datasets, particularly in small watersheds with sediment records containing a high proportion of allochthonous organic matter. This method is more available to researchers than obtaining numerous compound-specific radiocarbon analyses, which are costly and not a routine service offered by radiocarbon facilities.

  2. Detrital zircon record of Paleozoic and Mesozoic meta-sedimentary strata in the eastern part of the Baoshan block: Implications of their provenance and the tectonic evolution of the southeastern margin of the Tibetan plateau

    NASA Astrophysics Data System (ADS)

    Li, Dapeng; Chen, Yuelong; Hou, Kejun; Lu, Zhen; Cui, Di

    2015-06-01

    The Baoshan block is one of the important members in the southeastern margin of the Tibetan Plateau. Cambrian to Jurassic (meta-) sedimentary strata and their metamorphic counterparts were well preserved in the eastern part of the Baoshan block. Zircon U-Pb dating, trace elements, and Hf isotope data for both the Cambrian to Jurassic (meta-) sedimentary sequences and the Lincang granite were used to deduce the provenance of sediments and crustal affinity with eastern Gondwanaland. The Lincang granite outcropped in the Fengqing area is typical S-type, with crystallization age of ~ 230 Ma and narrow range of zircon εHf(t) values from - 15.5 to - 10. Detrital zircons from Paleozoic strata range in age from Archean to early Paleozoic, with age peaks at ~ 2.5, ~ 0.95, and ~ 0.6 Ga. Triassic age peak (~ 230 Ma) was also detected in the Jurassic strata. Detrital zircon εHf(t) values exhibit a wide range from negative to positive for each of the four major age groups, showing the host magma of zircons from these groups have diverse sources. The Baoshan block should be along the Indian margin as the Qiangtang, Tengchong and Simao-Indochina blocks in Early Paleozoic based on the provenance analyses. Sediment inputs eroded from both the Lincang granite and the coeval igneous rocks in the Baoshan and Gongshan blocks were the dominant contributions to the Jurassic strata after the amalgation of the Baoshan and Simao-Indochina blocks. Tectonic processes linking dispersion of the Baoshan-Sibumasu terrane from the Gondwana supercontinent to the collision with the Simao-Indochina block and the deposition of the Cambrian to Jurassic sedimentary sequences were reconstructed.

  3. Use of laboratory simulated pyrolysis in tracing the history of sedimentary organic matter

    NASA Technical Reports Server (NTRS)

    Kaplan, I. R.; Tannenbaum, E.; Huizinga, B. E.

    1986-01-01

    Results from laboratory simulated pyrolyses experiments show that in addition to depth of burial, preservation of kerogen, and hence any morphologic structure in it, is also dependent on the mineral matrix with which it is associated. In the presence of clay minerals, and especially under dry conditions, extractable lipids released during kerogen decomposition are more rapidly destroyed than in the presence of calcite or chert matrices. The result is production of gas, polar bitumen and pyrobitumen and destruction of biomarkers. During such an early reorganization of the kerogen, the biomarker constituents can be destroyed, or unrecognizably altered. The above process of organic residues maturation appears to be inhibited in the presence of water and is significantly reduced where kerogen is hosted in limestones, dolomites or cherts. These minerals have been characteristically found to be the most reliable in yielding morphological fossils and small quantities of extractable bitumen in Archean and Proterozoic rocks. To understand the validity of chemical and morphological fossils, in the early geologic record, it will be necessary to understand the process of kerogen in sedimentary rocks. To test the role of various minerals on the preservation process, kerogen extracted from a variety of rocks has been heated together with montmorillonite, illite and calcite. The kinetics of the process has been monitored and the products quantitatively identified.

  4. Sedimentary Geology Context and Challenges for Cyberinfrastructure Data Management

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  5. Triple oxygen isotope variations in sedimentary rocks

    NASA Astrophysics Data System (ADS)

    Levin, Naomi E.; Raub, Timothy D.; Dauphas, Nicolas; Eiler, John M.

    2014-08-01

    Relatively large (⩾0.2‰) 17O anomalies in the geologic record have been used to recognize atmospheric processes such as photochemical reactions and to trace changes in the partial pressures of O2 and CO2 in Earth’s atmosphere through time. However, recent oxygen isotope measurements of terrestrial rocks, minerals and waters also reveal common, smaller (but statistically significant) deviations from a single mass-dependent fractionation line. These subtle anomalies have been explained through differences in mass-dependent isotopic fractionations for various equilibrium and kinetic mechanisms. Here we present triple oxygen isotope data on sedimentary silica and oxides, including Archean and Phanerozoic cherts, and iron formations. The distribution of data reflects the mass fractionation laws of low-temperature precipitation reactions during growth of authigenic minerals, variation in Δ17O of the waters from which sedimentary minerals precipitate, and equilibrium exchange after initial authigenic formation. We use these results to illustrate the potential for small, mass-dependent variations in Δ17O values of sedimentary rocks to provide constraints on the environmental and climatic conditions in which they formed.

  6. Tracing the Holocene environmental evolution on the island of South Georgia by lipid biomarkers and compound-specific radiocarbon analysis

    NASA Astrophysics Data System (ADS)

    Jivcov, S.; Berg, S.; Kusch, S.; Viehberg, F. A.; Rethemeyer, J.; Melles, M.

    2015-12-01

    We present lipid biomarker data of a sedimentary record that spans the entire Holocene and was recovered from a marine inlet located at the northern coast of South Georgia (Cumberland West Bay) to adress two major objectives, namely: a) the identification of temporal variations in reservoir effects and b) the reconstruction of regional environmental changes during the last deglaciation. For objective a) we compare compound-specific radiocarbon ages of terrigeneous lipid biomarkers (n-alcohols) with 14C ages of bulk sedimentary organic matter to detect potential reservoir effects and changes over time. The study site experienced different environmental conditions following the retreat of the local glaciers in the early Holocene. After an initial freshwater stage when the inlet was separated from the sea, it passed into brackish and finally fully marine conditions. These hydrological changes probably resulted in variable reservoir ages. For objective b) we investigate biomarkers, comprising n-alkanes (C15-C35) and n-alcohols (C14-C28), including high molecular weight compounds typically derived from land plants and low molecular weight compounds like C17 n-alkanes and C16 n-alcohols, mostly originating from aquatic organisms. We noticed an abrupt increase in TOC values and sums of biomarkers after the glacier retreat, culminating in highest concentrations at the transition from freshwater to brackish conditions. Subsequently, the concentrations decline and vary at low levels until the inlet becomes fully marine. The marine stage is characterized by relatively constant TOC values but variable biomarker concentrations. Lowest biomarker levels occur around 1870±134 cal yr BP and between 6204±115 and 9666±161 cal yr BP and correspond to phases of glacier advance as suggested by studies of lake and peat deposits from South Georgia.

  7. The sedimentary structure of linear sand dunes

    PubMed

    Bristow; Bailey; Lancaster

    2000-07-06

    Linear sand dunes--dunes that extend parallel to each other rather than in star-like or crescentic forms--are the most abundant type of desert sand dune. But because their development and their internal structure are poorly understood, they are rarely recognized in the rock record. Models of linear dune development have not been able to take into account the sub-surface structure of existing dunes, but have relied instead either on the extrapolation of short-term measurements of winds and sediment transport or on observations of near-surface internal sedimentary structures. From such studies, it has not been clear if linear dunes can migrate laterally. Here we present images produced by ground penetrating radar showing the three-dimensional sedimentary structure of a linear dune in the Namib sand sea, where some of the world's largest linear dunes are situated. These profiles show clear evidence for lateral migration in a linear dune. Moreover, the migration of a sinuous crest-line along the dune produces divergent sets of cross-stratification, which can become stacked as the dune height increases, and large linear dunes can support superimposed dunes that produce stacked sets of trough cross-stratification. These clear structural signatures of linear dunes should facilitate their recognition in geological records.

  8. Building a Bridge to Deep Time: Sedimentary Systems Across Timescales

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  10. Sedimentary Record of Paleodeformation of the Saint Martin Anticline Reveals the Interaction Between Tectonics, Sedimentation Processes and Relative Sea-level Changes: Ganges-Brahmaputra Delta Burma Arc Collision, SE Bangladesh

    NASA Astrophysics Data System (ADS)

    Bastas-Hernandez, A.; McHugh, C. M.; Mondal, D. R.; Seeber, L.; Steckler, M. S.; Gurung, D.; Mustaque, S.; Marsh, J.; Akhter, S. H.

    2014-12-01

    Along the Ganges-Brahmaputra Delta Burma Arc collision zone, the Indian plate is converging obliquely with the Burma arc with a shortening GPS rate of 14 mm/yr. In this region tectonics, huge sediment supply from the erosion of the Himalayas (>1 GT/yr) and relative sea level changes interact. The extremely thick sediments of the Ganges-Brahmaputra Delta and Fan (~20 km) are being gradually accreted into a very wide thrust-fold belt along this subduction/collision zone. This interaction has led to the formation of a fold-and-thrust belt and wide accretionary prism that is exposed on land and on the shelf of the Burma forearc. Sedimentary sequence and structure document the seismo-tectonic and sedimentary evolution of St Martin's Island, which is an expression of an anticline in the outer part of the accretion forearc. During late Pleistocene sea-level low stands, the anticline and most of the rest of the shelf were exposed. The anticline ridge could then grow, receiving little erosion by local drainages. At some point during sea level rise, the coast advanced over the ridge and bevelled it. Then sea-level continued to rise and new sediment deposited forming an angular unconformity. A low-relief unconformity, in fact, separates the folded strata below from overlying strata of Holocene age. Where now exposed on the island above sea level, the unconformity is ~8000 y old. At that time, sea level was 30 m below the current level and thus rapid tectonic uplift is necessary to account for its current elevation. Dead coral heads of the species Porities that populate the coast were dated with U-Th (Mondal et al., 2013). They document a megathurst rupture and ~ 2m uplift that occurred during the Great Arakan earthquake in 1762 and further earthquakes are likely at ~ 1100 and 800 AD. Studies of the 1762 rupture suggest that the anticline rises during megathrust earthquakes (~2m) and subsides in the interseismic period (a few mm/yr; Steckler and Mondal 2014). Radiocarbon ages

  11. Lipid Biomarkers for a Hypersaline Microbial Mat Community

    NASA Technical Reports Server (NTRS)

    Jahnke, Linda; Orphan, Victoria; Embaye, Tsegereda; Turk, Kendra; Kubo, Mike; Summons, Roger

    2004-01-01

    The use of lipid biomarkers and their carbon isotopic compositions are valuable tools for establishing links to ancient microbial ecosystems. Various lipids associated with specific microbial groups can serve as biomarkers for establishing organism source and function in contemporary microbial ecosystems (membrane lipids), and by analogy, potential relevance to ancient organic-rich sedimentary rocks (geolipids). As witnessed by the stromatolite record, benthic microbial mats grew in shallow water lagoonal environments. Our recent work has focused on lipid biomarker analysis of a potential analogue for such ancient mats growing in a set of hypersaline evaporation ponds at Guerrero Negro, Baja California Sur, Mexico. The aerobic, surface layer of this mat (0 to 1 mm) contained a variety of ester-bound fatty acids (FA) representing a diverse bacterial population including cyanobacteria, sulphate reducers (SRB) and heterotrophs. Biomarkers for microeukaryotes detected in this layer included sterols, C-20 polyunsaturated FA and a highly branched isoprenoid, diagnostic for diatoms. Cyanobacteria were also indicated by the presence of a diagnostic set of mid-chain methylalkanes. C-28, to C-34 wax esters (WXE) present in relatively small amounts in the upper 3 mm of the mat are considered biomarkers for green non-sulphur bacteria. Ether-bound isoprenoids were also identified although in considerably lower abundance than ester-bound FA (approx. 1:l0). These complex ether lipids included archatol, hydroxyarchaeol and a C-40 tetraether, all in small amounts. After ether cleavage with boron tribromide, the major recovered isoprenyl was a C-30:1. This C(sub 30;1) yelded squalane after hydrogenation, a known geobiomarker for hypersaline environments in ancient oils and sediments. In this mat, it represents the dominant Archaeal population. The carbon isotopic composition of biomarker lipids were generally depleted relative to the bulk organic material (delta C-13 TOC -10%). Most

  12. Martian sediments and sedimentary rocks

    NASA Technical Reports Server (NTRS)

    Markun, C. D.

    1988-01-01

    Martian sediments and sedimentary rocks, clastic and nonclastic, should represent a high priority target in any future return-sample mission. The discovery of such materials and their subsequent analysis in terrestrial laboratories, would greatly increase the understanding of the Martian paleoclimate. The formation of Martian clastic sedimentary rocks, under either present, low-pressure, xeric conditions or a postulated, high-pressure, hydric environment, depends upon the existence of a supply of particles, various cementing agents and depositional basins. A very high resolution (mm-cm range) photographic reconnaissance of these areas would produce a quantum jump in the understanding of Martian geological history. Sampling would be confined to more horizontal (recent) surfaces. Exploration techniques are suggested for various hypothetical Martian sedimentary rocks.

  13. Sedimentary petrology. 2nd edition

    SciTech Connect

    Blatt, H.

    1992-01-01

    The second edition of Sedimentary Petrology is extensively revised and updated; much effort has been expended to strengthen the weaknesses of the earlier edition, and much of this effort has been successful. It consists of sixteen chapters. Following two introductory chapters (occurrence of sedimentary rocks; weathering and soils), eleven chapters cover the various sedimentary rock types. Coverage is allocated in proportion to their relative abundance and relative ease of study -- three chapters on conglomerates and sandstones (textures and structures, composition, and diagenesis); one on mud rocks; three on carbonates (limestone textures, structures, and environments; limestone mineralogy and diagenesis; and dolostones); and one each on evaporites, cherts, iron-rich rocks, and phosphorites. A novel and useful chapter on paleogeothermometry rounds out the discussion of rocks, followed by chapters on The Development of a Research Project'' and common laboratory methods.

  14. Sedimentary Rocks of Aram Chaos

    NASA Technical Reports Server (NTRS)

    2004-01-01

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

  15. Evaluating the provenance of Permian-Triassic and Palaeocene-Eocene ash beds by high precision U-Pb and Lu-Hf isotopic analyses of zircons: linking local sedimentary records to global events

    NASA Astrophysics Data System (ADS)

    Eivind Augland, Lars; Jones, Morgan; Planke, Sverre; Svensen, Henrik; Tegner, Christian

    2016-04-01

    Zircons are a powerful tool in geochronology and isotope geochemistry, as their affinity for U and Hf in the crystal structure and the low initial Pb and Lu allow for precise and accurate dating by U-Pb ID-TIMS and precise and accurate determination of initial Hf isotopic composition by solution MC-ICP-MS analysis. The U-Pb analyses provide accurate chronostratigraphic controls on the sedimentary successions and absolute age frames for the biotic evolution across geological boundaries. Moreover, the analyses of Lu-Hf by solution MC-ICP-MS after Hf-purification column chemistry provide a powerful and robust fingerprinting tool to test the provenance of individual ash beds. Here we focus on ash beds from Permian-Triassic and Palaeocene successions in Svalbard and from the Palaeocene-Eocene Thermal Maximum (PETM) in Fur, Denmark. Used in combination with whole rock geochemistry from the ash layers and the available geochemical and isotopic data from potential source volcanoes, these data are used to evaluate the provenance of the Permian-Triassic and Palaeocene ashes preserved in Svalbard and PETM ashes in Denmark. If explosive eruptions from volcanic centres such as the Siberian Traps and the North Atlantic Igneous Province (NAIP) can be traced to distal basins as ash layers, they provide robust tests of hypotheses of global synchronicity of environmental changes and biotic crises. In addition, the potential correlation of ash layers with source volcanoes will aid in constraining the extent of explosive volcanism in the respective volcanic centres. The new integrated data sets will also contribute to establish new reference sections for the study of these boundary events when combined with stable isotope data and biostratigraphy.

  16. Geochemistry of sedimentary ore deposits

    SciTech Connect

    Maynard, J. B.

    1983-01-01

    A text providing a sedimentological treatment of a study on ore deposits, and especially as related to geochemistry. Excellently documented (about 5000 citations). Well indexed with the index of deposits and localities separated. Contents, Iron. Copper and silver. Aluminum and nickel. Manganese. Uranium. Lead and zinc. Volcanic-sedimentary ores. Appendix. Indexes.

  17. Quantitative characterisation of sedimentary grains

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  18. Chemical Composition of the Martian Surface: A Sedimentary Perspective

    NASA Astrophysics Data System (ADS)

    McLennan, Scott M.

    1999-01-01

    The sedimentary rock record is the primary repository of Earth history over the past four billion years. Major and trace element geochemistry and radiogenic isotopes are routinely used to investigate the sources of sediment (provenance) and the various processes that affect sediments throughout their history (e.g., weathering, sedimentary transport and recycling, diagenesis). The most sophisticated analytical methods that are available have been employed in sedimentary geochemistry and in many cases include grain by grain analyses of mineralogy, chemistry and isotopic characteristics. In turn, this information has been used to address many important issues, such as tectonic associations, environments of deposition, paleoclimates, paleohydrology, and crust/mantle evolution. Photographic, spectroscopic and geochemical results, returned from the surface of Mars over many years and many missions, have increasingly pointed towards a wide variety of sedimentary processes playing a dominant role in shaping the Martian surface. Accordingly, there is great potential for applying the knowledge that has been learned from studying terrestrial sedimentary rocks towards evaluating Martian geological history. Chemical and mineralogical analyses from the Martian surface, especially those from the Viking, Pathfinder, and Mars 2001/2003 missions, coupled with greater understanding of basaltic sedimentation on the Earth should provide the sedimentological framework within which to study the chemistry and mineralogy of returned Martian samples.

  19. Sedimentary organic molecules: Origins and information content

    NASA Technical Reports Server (NTRS)

    Hayes, J. M.; Freeman, K. H.

    1991-01-01

    To progress in the study of organic geochemistry, we must dissect the processes controlling the composition of sedimentary organic matter. Structurally, this has proven difficult. Individual biomarkers can often be recognized, but their contribution to total organic materials is small, and their presence does not imply that their biochemical cell mates have survived. We are finding, however, that a combination of structural and isotopic lines of evidence provides new information. A starting point is provided by the isotopic compositions of primary products (degradation products of chlorophylls, alkenones derived from coccoliths). We find strong evidence that the isotopic difference between primary carbonate and algal organic material can be interpreted in terms of the concentration of dissolved CO2. Moreover, the isotopic difference between primary and total organic carbon can be interpreted in terms of characteristic isotopic shifts imposed by secondary processes (responsive, for example, to O2 levels in the depositional environment. In favorable cases, isotopic compositions of a variety of secondary products can be interpreted in terms of flows of carbon, and, therefore, in terms of specific processes and environmental conditions within the depositional environment.

  20. Hydrogen Isotope Biogeochemistry of Plant Biomarkers in Tropical Trees from the Andes to Amazon

    NASA Astrophysics Data System (ADS)

    Feakins, S. J.; Ponton, C.; West, A. J.; Malhi, Y.; Goldsmith, G.; Salinas, N.; Bentley, L. P.

    2014-12-01

    Plant leaf waxes are well known biomarkers for terrestrial vegetation. Generally, their hydrogen isotopic composition (D/H) records the isotopic composition of precipitation, modulated by leaf water processes and a large biosynthetic fractionation. In addition, the D/H of methoxyl groups on tree wood lignin is an emerging technique thought to record the D/H of source waters, without leaf water complications. Using each of these biomarkers as proxies requires understanding D/H fractionations in plant systems, but few studies have directly studied hydrogen isotope biogeochemistry in tropical plants. An approach that has proven helpful is the paired analysis of plant waters and plant biomarkers: in order that fractionations can be directly computed rather than assumed. This presents logistical challenges in remote tropical forest environments. We report on a unique dataset collected by tree-climbers from 6 well-studied vegetation plots across a 4km elevation transect in the Peruvian Andes and Amazonia. We have measured the D/H of stem water and leaf water, and we compare these to precipitation isotopes and stream waters. The goal of the plant water studies is to understand plant water uptake and stem-leaf water isotopic offsets which can vary due to both transpiration and foliar uptake of water in tropical montane forests. We are in the process of measuring the D/H of plant biomarkers (n-alkanoic acids, n-alkanes and lignin methoxyl) in order to assess how these water isotopic signals are encoded in plant biomarkers. We compare the species-specific modern plant insights to the plant leaf wax n-alkanoic acid D/H that we have recently reported from soils and river sediments from the same region, in order to understand how signals of plant biogeochemistry are integrated into geological sedimentary archives. Progress and open questions in tropical isotope biogeochemistry will be discussed at the meeting.

  1. Paleogene biomarker records from the central Arctic Ocean (Integrated Ocean Drilling Program Expedition 302): Organic carbon sources, anoxia, and sea surface temperature

    NASA Astrophysics Data System (ADS)

    Weller, Petra; Stein, Ruediger

    2008-03-01

    During Integrated Ocean Drilling Program Expedition 302 (Arctic Coring Expedition (ACEX)) a more than 200 m thick sequence of Paleogene organic carbon (OC)-rich (black shale type) sediments was drilled. Here we present new biomarker data determined in ACEX sediment samples to decipher processes controlling OC accumulation and their paleoenvironmental significance during periods of Paleogene global warmth and proposed increased freshwater discharge in the early Cenozoic. Specific source-related biomarkers including n-alkanes, fatty acids, isoprenoids, carotenoids, hopanes/hopenes, hopanoic acids, aromatic terpenoids, and long-chain alkenones show a high variability of components, derived from marine and terrestrial origin. The distribution of hopanoic acid isomers is dominated by compounds with the biological 17β(H), 21β(H) configuration indicating a low level of maturity. On the basis of the biomarker data the terrestrial OC supply was significantly enriched during the late Paleocene and part of the earliest Eocene, whereas increased aquatic contributions and euxinic conditions of variable intensity were determined for the Paleocene-Eocene thermal maximum and Eocene thermal maximum 2 events as well as the middle Eocene time interval. Furthermore, samples from the middle Eocene are characterized by the occurrence of long-chain alkenones, high proportions of lycopane, and high ratios (>0.6) of (n-C35 + lycopane)/n-C31. The occurrence of C37-alkenenones, which were first determined toward the end of the Azolla freshwater event, indicates that the OC becomes more marine in origin during the middle Eocene. Preliminary U37K'-based sea surface temperature (SST) values display a long-term temperature decrease of about 15°C during the time interval 49-44.5 Ma (25° to 10°C), coinciding with the global benthic δ18O cooling trend after the early Eocene climatic optimum. At about 46 Ma, parallel with onset of ice-rafted debris, SST (interpreted as summer temperatures

  2. Organic biomarker records spanning the last 34,800 years from the southeastern Brazilian upper slope: links between sea surface temperature, displacement of the Brazil Current, and marine productivity

    NASA Astrophysics Data System (ADS)

    Lourenço, Rafael André; de Mahiques, Michel Michaelovitch; Wainer, Ilana Elazari Klein Coaracy; Rosell-Melé, Antoni; Bícego, Márcia Caruso

    2016-10-01

    Collective assessment of marine and terrigenous organic biomarkers was performed on a sediment core spanning the last 34,800 years on the upper slope southeast of Brazil to verify the signatures of climatic variations in sea surface temperature (SST), marine productivity, and the flux of terrigenous material in this region. This evaluation is based on marine and terrigenous proxies including alkenones, chlorins, aliphatic hydrocarbons, n-alcohols, and fatty acids. This first report of organic biomarker data for this region confirms a correlation between SST, changes in terrigenous organic matter flow into the ocean, and marine productivity over the last 34.8 ka as a response to the displacement of the Brazil Current. Conditions prevailing during marine isotopic stage (MIS) 3 may be considered intermediate between the last glacial maximum (LGM) and the Late Holocene. For MIS 2, a period of low relative sea level, it was verified that the lowest SSTs were associated with the LGM and higher marine productivity. SST increased by up to 4.4 °C between the LGM and the Holocene. This reveals synchronicity between SST on the southeastern Brazilian upper slope and the North Atlantic Ocean SST records reported in earlier studies.

  3. Polygon/Cracked Sedimentary Rock

    NASA Technical Reports Server (NTRS)

    2004-01-01

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

  4. Sedimentary Rocks of Aram Chaos

    NASA Technical Reports Server (NTRS)

    2004-01-01

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

  5. Biomarkers in pediatrics: children as biomarker orphans.

    PubMed

    Savage, William J; Everett, Allen D

    2010-12-01

    Biomarkers have enormous potential to improve patient care by establishing tests of diagnosis, prognosis, and treatment effects. Successfully translating a biomarker from discovery to clinical application demands high-quality discovery research and high-quality clinical studies for biomarker validation; however, there are additional challenges that face biomarker research in pediatrics. There are also additional characteristics of pediatric medicine that make biomarker research especially needed. This review focuses on the fundamentals of biomarkers, the additional considerations needed for applying biomarker research to children, and recommendations for advancing pediatric biomarker research.

  6. Sources for sedimentary bacteriohopanepolyols as revealed by 16S rDNA stratigraphy.

    PubMed

    Coolen, Marco J L; Talbot, Helen M; Abbas, Ben A; Ward, Christopher; Schouten, Stefan; Volkman, John K; Damsté, Jaap S Sinninghe

    2008-07-01

    Bacteriohopanoids are widespread lipid biomarkers in the sedimentary record. Many aerobic and anaerobic bacteria are potential sources of these lipids which sometimes complicates the use of these biomarkers as proxies for ecological and environmental changes. Therefore, we applied preserved 16S ribosomal RNA genes to identify likely Holocene biological sources of bacteriohopanepolyols (BHPs) in the sulfidic sediments of the permanently stratified postglacial Ace Lake, Antarctica. A suite of intact BHPs were identified, which revealed a variety of structural forms whose composition differed through the sediment core reflecting changes in bacterial populations induced by large changes in lake salinity. Stable isotopic compositions of the hopanols formed from periodic acid-cleaved BHPs, showed that some were substantially depleted in (13)C, indicative of their methanotrophic origin. Using sensitive molecular tools, we found that Type I and II methanotrophic bacteria (respectively Methylomonas and Methylocystis) were unique to the oldest lacustrine sediments (> 9400 years BP), but quantification of fossil DNA revealed that the Type I methanotrophs, including methanotrophs related to methanotrophic gill symbionts of deep-sea cold-seep mussels, were the main precursors of the 35-amino BHPs (i.e. aminopentol, -tetrol and -triols). After isolation of the lake approximately 3000 years ago, one Type I methanotroph of the 'methanotrophic gill symbionts cluster' remained the most obvious source of aminotetrol and -triol. We, furthermore, identified a Synechococcus phylotype related to pelagic freshwater strains in the oldest lacustrine sediments as a putative source of 2-methylbacteriohopanetetrol (2-Me BHT). This combined application of advanced geochemical and paleogenomical tools further refined our knowledge about Holocene biogeochemical processes in Ace Lake.

  7. Imaging Biomarkers or Biomarker Imaging?

    PubMed Central

    Mitterhauser, Markus; Wadsak, Wolfgang

    2014-01-01

    Since biomarker imaging is traditionally understood as imaging of molecular probes, we highly recommend to avoid any confusion with the previously defined term “imaging biomarkers” and, therefore, only use “molecular probe imaging (MPI)” in that context. Molecular probes (MPs) comprise all kinds of molecules administered to an organism which inherently carry a signalling moiety. This review highlights the basic concepts and differences of molecular probe imaging using specific biomarkers. In particular, PET radiopharmaceuticals are discussed in more detail. Specific radiochemical and radiopharmacological aspects as well as some legal issues are presented. PMID:24967536

  8. Origin and palaeoenvironmental significance of C25 and C27n-alk-1-enes in a 25,000-year lake-sedimentary record from equatorial East Africa

    NASA Astrophysics Data System (ADS)

    van Bree, L. G. J.; Rijpstra, W. I. C.; Cocquyt, C.; Al-Dhabi, N. A.; Verschuren, D.; Sinninghe Damsté, J. S.; de Leeuw, J. W.

    2014-11-01

    We studied the distribution of long-chain alkenes (n-C23 to n-C31) in well-dated sediments from Lake Challa, a deep crater lake near Mt. Kilimanjaro in equatorial East Africa, to reveal signatures of palaeo-environmental and palaeo-climatic changes affecting the production of these compounds during the last 25 kyr. The apolar fractions of organic sediment extracts dated to the last 16 kyr showed an unusual dominance of δ13C-depleted n-C25:1 and n-C27:1 alk-1-enes. These alkenes were not detected in soil and litter from near the shoreline and from the inner rim of the crater, pointing to an autochthonous, aquatic source. Analysis of suspended particulate matter indicated that the n-alk-1-enes are produced in the well-oxygenated upper 30 m of the water column, indicating a phytoplanktonic origin. Sedimenting particles collected monthly from December 2006 to November 2007 showed increased fluxes of n-alk-1-enes following the locally prominent short rain season in November-December. Green algae and/or cyanobacteria were identified as candidate sources of these alkenes. Production of the n-C25:1 and n-C27:1 alkenes in Lake Challa was much reduced during the Last Glacial Maximum and early late-glacial period, suggesting a temperature or CO2 effect on habitat suitability. We explored the potential of n-alk-1-ene accumulation rates, and of a derived Alkene Index [n-C27:1]/([n-C25:1] + [n-C27:1]), to record longer-term climatic changes. The Alkene Index record of Lake Challa over the past 25 kyr shows clear periodicity with a dominant frequency of ∼2.3 kyr, potentially indicative of monsoon variability directly or indirectly forced by variation in solar radiation.

  9. Variability of river discharge and Atlantic-water inflow at the Laptev Sea continental margin during the past 15,000 years: implications from maceral and biomarker records

    NASA Astrophysics Data System (ADS)

    Boucsein, B.; Fahl, K.; Stein, R.

    2000-08-01

    In order to reconstruct the depositional environment from the Laptev Sea continental slope and shelf during the past 15,000 years BP maceral analysis was carried out on two sediment cores (PS2458-4, PS2725-5) and compared with organic-geochemical parameters. During the transition from the Last Glacial to the Holocene the environment of the Laptev Sea shelf was controlled by the post-glacial sea level rise, variations in river discharge, surface-water productivity, and Atlantic-water inflow along the Eurasian continental margin. Based on our results, we identify the following significant changes of the environment: (a) at approximately 13,500 years BP the first step of deglaciation (Termination 1a) is documented by the deposition of marine and fresh-water organic matter; (b) at approximately 10,400 years BP the first post-glacial influence of Atlantic-water inflow along the Eastern Laptev Sea continental margin is indicated by an increase in marine organic matter; (c) at the beginning of the Holocene an increased fluvial supply is documented by an increase in fresh-water alginite; and (d) since 9500-8000 years BP modern marine conditions are established at the Laptev Sea continental margin as documented in increased amounts of marine macerals, biomarkers (dinosterol, brassicasterol, short-chain fatty acids), and dinoflagellate cysts.

  10. Sedimentary Rocks in Ladon Vallis

    NASA Technical Reports Server (NTRS)

    2004-01-01

    25 January 2004 This is a Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture of an outcrop of light-toned, layered, sedimentary rock exposed by erosion in Ladon Vallis. These rocks preserve clues to the martian past. However, like books in a library, one needs to go there and check them out if one wishes to read what the layers have to say. This November 2003 picture is located near 21.1oS, 29.8oW, and covers an area 3km (1.9 mi.) wide. Sunlight illuminates the scene from the left.

  11. Sedimentary rocks of early Mars.

    PubMed

    Malin, M C; Edgett, K S

    2000-12-08

    Layered and massive outcrops on Mars, some as thick as 4 kilometers, display the geomorphic attributes and stratigraphic relations of sedimentary rock. Repeated beds in some locations imply a dynamic depositional environment during early martian history. Subaerial (such as eolian, impact, and volcaniclastic) and subaqueous processes may have contributed to the formation of the layers. Affinity for impact craters suggests dominance of lacustrine deposition; alternatively, the materials were deposited in a dry, subaerial setting in which atmospheric density, and variations thereof mimic a subaqueous depositional environment. The source regions and transport paths for the materials are not preserved.

  12. Evidence for only minor contributions from bacteria to sedimentary organic carbon

    NASA Technical Reports Server (NTRS)

    Hartgers, W. A.; Sinninghe Damste, J. S.; Requejo, A. G.; Allan, J.; Hayes, J. M.; de Leeuw, J. W.

    1994-01-01

    Because their molecular signatures are often prominent in extracts of sediments, bacteria are thought to be important contributors to petroleum source beds. It has been shown recently, however, that abundances of biomarkers do not always reflect relative contributions to sedimentary organic carbon (Corg). The contribution of photosynthetic green sulphur bacteria to sediments can be assessed effectively because the diagenetic products of distinctive carotenoids from these organisms occur widely and their biomass is isotopically labelled, being enriched in 13C. We show here that, although sediments and oils from the Western Canada and Williston basins contain prominent biomarkers of photosynthetic bacteria, the absence of 13C enrichment in the total Corg requires that the bacterial contribution is in fact minimal. Although the importance of bacterial reworking of sedimentary debris cannot be doubted, we argue that our findings, when considered in conjunction with those from other settings, suggest that bacterial biomass may commonly represent only a minor component of total Corg in carbonaceous rocks.

  13. Multisensor classification of sedimentary rocks

    NASA Technical Reports Server (NTRS)

    Evans, Diane

    1988-01-01

    A comparison is made between linear discriminant analysis and supervised classification results based on signatures from the Landsat TM, the Thermal Infrared Multispectral Scanner (TIMS), and airborne SAR, alone and combined into extended spectral signatures for seven sedimentary rock units exposed on the margin of the Wind River Basin, Wyoming. Results from a linear discriminant analysis showed that training-area classification accuracies based on the multisensor data were improved an average of 15 percent over TM alone, 24 percent over TIMS alone, and 46 percent over SAR alone, with similar improvement resulting when supervised multisensor classification maps were compared to supervised, individual sensor classification maps. When training area signatures were used to map spectrally similar materials in an adjacent area, the average classification accuracy improved 19 percent using the multisensor data over TM alone, 2 percent over TIMS alone, and 11 percent over SAR alone. It is concluded that certain sedimentary lithologies may be accurately mapped using a single sensor, but classification of a variety of rock types can be improved using multisensor data sets that are sensitive to different characteristics such as mineralogy and surface roughness.

  14. Inversion of Extensional Sedimentary Basins

    NASA Astrophysics Data System (ADS)

    Buiter, Susanne J. H.; Pfiffner, O. Adrian

    The evolution of extensional sedimentary basins is governed by the surrounding stress field and can, therefore, be expected to be highly sensitive to variations in these stresses. Important changes in basin geometry are to be expected in the case of an even short-lived reversal from extension to compression. We investigate the evolu- tion of fold and thrust structures which form in compression after extension, when basin forming processes have come to a complete stop. To this purpose, we use a two- dimensional, viscoplastic model and start our experiments from a pre-existing exten- sional geometry. We illustrate the sensitivity of the evolving structures to inherited extensional geometry, sedimentary and erosional processes, and material properties. One series of our model experiments involves the upper- to middle crust only in order to achieve a high detail in the basin area. We find that our results agree with examples from nature and analogue studies in, among others, the uplift and rotation of syn-rift sediments, the propagation of shear zones into the post-rift sediments and, in specific cases, the development of back-thrusts or basement short-cut faults. We test the out- come of these models by performing a second series of model simulations in which basins on a continental margin are inverted through their progressive approach of a subduction zone. These latter models are on the scale of the whole upper mantle.

  15. Finding The Baseline--Putting Recent Eutrophication Of Two South Texas Coastal Water Bodies Into Perspective By Using Sedimentary Records To Examine The Long-Term, Natural Variability Of The Systems

    NASA Astrophysics Data System (ADS)

    Besonen, M. R.; Zimba, P.; Hill, E.; Tissot, P.; Mckay, M.; Silliman, J.

    2013-12-01

    reservoirs along the Nueces River, the primary inflow for the system. The lack of long-term environmental monitoring records makes it difficult to disentangle the complex interrelationships between the natural and anthropogenic factors that have contributed to eutrophication. To address this issue, we are examining proxy evidence from sediment cores to look back in time, and understand the true baseline conditions and natural variability of these systems long before they were affected by anthropogenic impacts. We are using a suite of geological, chemical, and biological indicators including color spectral reflectance (for total chlorophyll content), organic carbon content via loss-on-ignition, Terrigenous/Aquatic Ratio (TARHC), TOC, C/N ratio analysis, pigment analysis via HPLC, and microfossil assemblage analysis. Age control for the stratigraphy will be provided by radiometric age analyses using 137Cs, 210Pb, and 14C. Initial results from spectral reflectance scanning of sediment cores from the Nueces Estuary appear to indicate an increased chlorophyll content up core, which probably reflects a long-term increase of primary productivity in the system.

  16. Sedimentary 12-n-Propylcholestanes, Molecular Fossils Diagnostic of Marine Algae.

    PubMed

    Moldowan, J M; Fago, F J; Lee, C Y; Jacobson, S R; Watt, D S; Slougui, N E; Jeganathan, A; Young, D C

    1990-01-19

    Certain C(30)-steranes have been used for identifying sedimentary rocks and crude oils derived from organic matter deposited in marine environments. Analysis of a C(30)-sterane from Prudhoe Bay oil indicates that these C(30)-steranes are 24-n-propylcholestanes that apparently are derived from precursor sterols 24-n-propylidene-cholesterols and 24-n-propylcholesterol. These widely occurring sterols are biochemically synthesized in modern oceans by members of an order (Sarcinochrysidales) of chrysophyte algae. These data thus imply that C(30)-sterane biomarkers in sedimentary rocks and crude oils have a marine origin. Screening of a few organic-rich sedimentary rocks and oils from throughout the Phanerozoic suggests that these C(30)-steranes first appeared and, therefore, their source algae evolved between Early Ordovician and Devonian.

  17. Age of Terrestrial Biomarkers in Fluvial Transit Across the Andes-Amazon Reveal Timescales of Carbon Storage and Turnover

    NASA Astrophysics Data System (ADS)

    Ponton, C.; Feakins, S. J.; West, A. J.; Galy, V.

    2014-12-01

    Environmental signatures carried by fluvially-exported terrestrial organic matter are shaped by storage, remineralization and replacement at various spatial and temporal scales. Uncertainties in the timescales of these processes are key caveats in the accurate interpretation of sedimentary records. As part of a multi-isotope leaf wax biomarker project, we report the age of biomarkers transported by rivers from mountain to floodplain across the Andes-Amazon transition in southern Peru. We tracked the age of organic carbon using the radiocarbon (14ΔC) composition of plant leaf waxes extracted from particulate organic carbon (POC) in river suspended sediments. Leaf waxes from POC are younger in mountain headwaters (<500 yrs old) and increase in age across the floodplain (>1000 yrs). Downstream aging is associated with the greater storage potential and residence times in lowland mineral soils and sedimentary sequences that include Pleistocene age eroding river terraces. Given three key observations that 1) carbon loading in suspended sediment does not substantively change from Andes to Amazon, 2) ~80% of sediment is sourced in the Andes, and 3) age increases downstream (this study); we find proof of the decoupling of organic carbon from sediment, which we attribute to loss of Andean carbon and replacement during transport.

  18. Fossil Fuel Biomarkers in Sewage Sludges: Environmental Significance

    NASA Astrophysics Data System (ADS)

    Payet, C.; Bryselbout, C.; Morel, J.-L.; Lichtfouse, E.

    Fossil fuel biomarkers, or "molecular fossils," are specific organic substances found in coals, petroleums, and sedimentary rocks. They are formed during millions of years of sedimentary burial by geochemical alteration of biological molecules, such as cholesterol, under the effect of biodegradation, temperature, pressure, and mineral catalysis, to produce geochemically mature molecules, for example, aromatic steroids (Fig. 1). Since fossil fuel biomarkers have a very specific molecular structure betraying fossil fuel sources, such markers should be useful in assessing the fossil fuel contamination of various modern media such as soils, plants, waters, and modern sediments. Here the identification of fossil fuel biomarkers of high geothermal maturity in sewage sludges provides evidence of the contamination of sludges by petroleum products. The most likely sources of contamination are contaminated vegetal food, road dust, and soil particles carried by rain water.

  19. Sedimentary record of environmental evolution off the Yangtze River estuary, East China Sea, during the last ˜13,000 years, with special reference to the influence of the Yellow River on the Yangtze River delta during the last 600 years

    NASA Astrophysics Data System (ADS)

    Liu, Jian; Saito, Yoshiki; Kong, Xianghuai; Wang, Hong; Xiang, Lihui; Wen, Chun; Nakashima, Rei

    2010-08-01

    A 35.60-m-long core (ECS-0702) recovered from a water depth of 22 m in the muddy area off the Yangtze River estuary was analyzed for sedimentary characteristics, clay and detrital mineral components, and element geochemistry as well as by AMS 14C dating to document sediment provenance changes and environmental evolution during the postglacial period in the study area. On the basis of the lithology, the benthic foraminiferal and ostracod assemblages, and the AMS 14C ages, we divided the core into four depositional units (DU1-DU4 in descending order) representing the postglacial sedimentary sequence during the last ˜13,000 years. DU 4 was deposited in a littoral to tidal-flat environment during ˜13,000-11,500 cal yr BP; DU 3 in a nearshore, subtidal environment upwards to the nearshore shelf with tidal influence in response to the postglacial sea-level rise during ˜11 500-7400 cal yr BP; DU 2 in a tide-affected, nearshore shallow-sea environment during ˜7400-540 cal yr BP, on the delta-front of the Yangtze River when the delta was actively prograding; and DU 1 in a nearshore shallow-sea environment during the last ˜540 years, on the delta-front under modern marine conditions. In DU 1, the depositional rate was much higher than in the underlying units, and the sediment composition reflects more influence from the Yellow River; this unit can therefore be logically linked to the period when the Yellow River last discharged into the South Yellow Sea, from AD 1128 to 1855. According to historical records, this period can be divided into an early stage (AD 1128-1494), when the shoreline near the Yellow River mouth was advancing slowly eastward, and a late stage (1495-1855), when the shoreline was advancing rapidly. The initiation of DU 1 deposition corresponds to the latter part of the early stage, suggesting that since that time, a relatively large amount of sediment from the Old Yellow River mouth area has been transported to the offshore area of the Yangtze River

  20. Compound Specific D/H Records of Marine and Terrestrial Biomarkers From Core MD972151 in the Southern South China Sea During the Last Glacial-Interglacial Cycle

    NASA Astrophysics Data System (ADS)

    Izawa, Y.; Yamamoto, M.; Seki, O.; Kawamura, K.; Chen, M.

    2006-12-01

    Hydrological changes in the Western Pacific Warm Pool are a recent central issue of the paleoclimate study for the tropical Pacific. Here we present 150-kyr records of deuterium/hydrogen ratios of short- and long-chain n-fatty acids, which derived from aquatic organisms and terrestrial higher plants, respectively, in the IMAGES MD972151 core. The delta D of short-chain fatty acids (C16 and C18) ranged from ~-220 to ~-150 permil vs SMOW. A strong negative shift of delta D occurred at ~17 ka, which is attributed to the decrease of salinity in the southern South China Sea, suggesting an enhanced riverine discharge. The delta D of long-chain fatty acids (C24 to C28) ranged from ~-160 to ~-120 permil. The delta D showed a minimum at ~17 ka. This phenomenon is attributed to changes in either moisture or precipitation D/H ratio. These findings suggest a drastic change of hydrological dynamics in the Western Pacific Warm Pool in the early stage of the last deglaciation.

  1. Riverine Carbon and the Sedimentary Record on the Continental Shelves

    DTIC Science & Technology

    2005-09-30

    Geologia Marina (formerly Istituto di Geologia Marina) Consiglio Nazionale delle Ricerche Via Gobetti, 101 40129 Bologna, Italy phone: +39 (051...Marine, Sezione Geologia Marina,(formerly Istituto di Geologia Marina),Consiglio Nazionale delle Ricerche,Via Gobetti, 101,40129 Bologna, Italy, , 8

  2. Riverine Carbon and the Sedimentary Record on the Continental Shelves

    DTIC Science & Technology

    2003-09-30

    Geologia Marina (formerly Istituto di Geologia Marina) Consiglio Nazionale delle Ricerche Via Gobetti, 101 40129 Bologna, Italy phone: +39 (051...ORGANIZATION NAME(S) AND ADDRESS(ES) Istituto Scienze Marine, Sezione Geologia Marina,(formerly Istituto di Geologia Marina),Consiglio Nazionale delle

  3. Biomarkers from varved lake sediments: evidence for the 8.2 ka climate event in Sweden

    NASA Astrophysics Data System (ADS)

    Das, S. K.; Bendle, J. A.; Snowball, I.; Seki, O.; Zillin Snowball, L.; Stanton, T.

    2009-12-01

    In order to quantify the variability of Holocene climate fluctuations in northern Europe a multi-proxy biomarker (inter alia: n-alkanes, n-alkanoic acids, n-alkanols) analyses were carried out on a continuous varved sediment sequence from Lake Kälksjön in west-central Sweden. The most extreme Holocene climate anomaly in northern hemisphere is considered as a cold event that took place at c. 8200 cal. yr BP (Grootes et al. 1993; Alley et al. 1997). Interestingly, winter snow accumulation is reportedly enhanced in Sweden in between 8100 and 7750 cal. yr BP (Zillén and Snowball, 2009). This study investigates the sedimentary record of this rapid climate change event as recorded by the biomarkers incorporated into one a long, continuous Holocene varve sequence. Our data reveal enhanced catchment erosion between 8100 and 8000 cal. yr BP peaking at c. 8050 cal. yr BP. This is evident from the higher input of land plant derived biomarkers, which is the major source of organic matter in the lake sediment. The enhanced erosion is interpreted as the catchment response to the colder winters and increased accumulation of snow that led to more intense spring discharge from melting snowpack. This finding is consistent with similar finding in other Swedish lakes (Zillén and Snowball, 2009) and most likely represent the geomorphic response to a multi-centennial scale climatic cooling that occurred between 8500 and 7500 cal. yr BP (Zillén and Snowball, 2009). In addition, we present new analyses of bacterial branched glycerol dialkyl glycerol tetraethers (br-GDGTs), and the compound specific hydrogen (δD) isotopic composition of lake macrophyte biomarkers. Br-GDGTs record changes in the temperature and pH of catchment and lake sediments. The δD in plant lipids includes a strong signal incorporated from environmental water during growth, thus such data can record histories of changing lake water δD, which itself is a function of changes in lake temperature and moisture

  4. Investigating Coccolithophorid Biology in the Sedimentary Laboratory

    NASA Astrophysics Data System (ADS)

    McClelland, H. L. O.; Barbarin, N.; Beaufort, L.; Hermoso, M.; Rickaby, R. E. M.

    2014-12-01

    Coccolithophores are the ocean's dominant calcifying phytoplankton; they play an important, but poorly understood, role in long-term biogeochemical climatic feedbacks. Calcite producing marine organisms are likely to calcify less in a future world where higher carbon dioxide concentrations will lead to ocean acidification (OA), but coccolithophores may be the exception. In coccolithophores calcification occurs in an intracellular vesicle, where the site of calcite precipitation is buffered from the external environment and is subject to a uniquely high degree of biological control. Culture manipulation experiments mimicking the effects of OA in the laboratory have yielded empirical evidence for phenotypic plasticity, competition and evolutionary adaptation in asexual populations. However, the extent to which these results are representative of natural populations, and of the response over timescales of greater than a few hundred generations, is unclear. Here we describe a new sediment-based proxy for the PIC:POC (particulate inorganic to particulate organic carbon ratio) of coccolithophore biomass, which is equivalent to the fractional energy contribution to calcification at constant pH, and a biologically meaningful measure of the organism's tendency to calcify. Employing the geological record as a laboratory, we apply this proxy to sedimentary material from the southern Pacific Ocean to investigate the integrated response of real ancient coccolithophore populations to environmental change over many thousands of years. Our results provide a new perspective on phenotypic change in real populations of coccolithophorid algae over long timescales.

  5. Elastic Properties of Sedimentary Rocks

    NASA Astrophysics Data System (ADS)

    Melendez Martinez, Jaime

    Sedimentary rocks are an important research topic since such rocks are associated to sources of ground water as well as oil, gas, and mineral reservoirs. In this work, elastic and physical properties of a variety of sedimentary samples that include glacial sediments, carbonates, shales, one evaporite, and one argillite from a variety of locations are investigated. Assuming vertical transverse isotropy, ultrasonic compressional- and shear-waves (at 1 MHz central frequency) were measured as a function of confining pressure on all samples with the exception of glacial samples which were tested assuming isotropy. Tensile strength tests (Brazilian test) were also carried out on selected glacial samples and, in addition, static-train measurements were conducted on shales and argillite samples. Lithological and textural features of samples were obtained through thin section techniques, scanning electron microscopy images and micro-tomography images. X-ray diffraction and X-Ray fluorescence provided the mineralogical oxides content information. Porosity, density, and pore structure were studied by using a mercury intrusion porosimeter and a helium pycnometer. The wide range of porosities of the studied samples (ranging from a minimum of 1% for shales to a maximum 45% for some glacial sediments) influence the measured velocities since high porosity sample shows an noticeable velocity increment as confining pressure increases as a consequence of closure of microcracks and pores, unlike low porosity samples where increment is quasi-lineal. Implementation of Gassmann's relation to ultrasonic velocities obtained from glacial samples has negligible impact on them when assuming water saturated samples, which suggests that state of saturation it is no so important in defining such velocities and instead they are mainly frame-controlled. On the other hand, velocities measured on carbonate and evaporite samples show that samples are at best weak anisotropic, thus the intrinsic

  6. Evidence from carbon isotope measurements for diverse origins of sedimentary hydrocarbons

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  7. Lipid Biomarker Preservation in Silica-Depositing Hydrothermal Analogs

    NASA Astrophysics Data System (ADS)

    Jahnke, L. L.; Parenteau, M. N.; Farmer, J. D.

    2010-12-01

    The discovery of extensive silica-rich deposits at Home Plate in the Columbia Hills indicates that hydrothermal conditions once existed on Mars (Squyres et al. 2008). Two types of environments could have been responsible for forming these materials: fumaroles or hydrothermal springs. Examples of both types of these thermal features are found throughout Yellowstone National Park (YNP). The discovery of bona fide microfossils in ancient cherts indicates that silica deposition was an excellent mechanism for organic preservation on the early Earth. Given the importance that organic biomarkers have played in identifying some of the earliest microbial life on Earth and the potential for a similar habitable period on Mars, examination of the preservation of organic biomarkers within various hydrothermal, silica-rich modern analogs is essential for future interpretation of Martian organics. Cyanobacterial mats and biofilms are common inhabitants of hydrothermal spring systems worldwide, at temperatures below 73°C and over a broad range of pH, from acidic to alkaline. Bacteriohopanepolyols (BHPs) are the biological precursors for the abundant fossil hopanes recovered from sedimentary rock (Brocks et al. 1999; Summons et al. 1999). The 2-methyl homologs are generally considered a biomarker for cyanobacterial-dominated paleoecosystems. Some evidence exists that the complex molecular structure of BHP is retained upon entombment in hydrothermal silica and that rapid incorporation into the silica matrix may enhance preservation (Gibson et al. 2008). Here we report on the preservation of microbial lipids in several alkaline and acidic, silica-depositing hotsprings in YNP with particular emphasis on the potential for BHP preservation. Brocks JJ et al (1999) Archaean molecular fossils and the early rise of the eukaryotes. Science 185: 1033-1036 Gibson RA et al (2008) Bacteriohopanepolyol signatures of cyanobacterial and methanotrophic bacterial populations recorded in a geothermal

  8. Dependence between Ventilation and Climate as recorded with Biomarkers over the last 420,000 years in the Guianas Region (North-western Amazon Basin)

    NASA Astrophysics Data System (ADS)

    Rama, O.; Lopez-Otalvaro, G.; Martrat, B.; Flores, J.; Sierro, F. J.; Grimalt, J. O.

    2009-12-01

    was recorded over Marine Isotope Stage (MIS) 8. Additionally, warmer periods occurred during the early Holocene (SST=28.1C) or the last interglacial (MIS 5e, 29C). Temperatures similar to present were observed during MIS 11c (28C). Autochthonous marine productivity traced dependence between vertical stratification of the surface water, trade wind strength and precession motion between northern hemisphere spring and perihelion, consistent with previous results [Lopez-Otalvaro et al., 2009]. Recurring surface and deep water destabilizations have been identified. Fluvial continental contributions, reached maximal values during cold events, when the Amazon River plume extended to the core location. Ventilation variability at the core site was modulated by the eccentricity of the Earth’s orbit. Rapid oxygenation changes were more pronounced during deglaciations and interglacials, but tending to decrease, gradually or abruptly, while glacials progressed.

  9. The records of terrestrial and marine biomarkers in South China Sea EXP349 Sites U1432C and U1433A, B: Implications for East Asian monsoon variability and paleoceanographic variations.

    NASA Astrophysics Data System (ADS)

    hyun, Sangmin; kim, Songyi

    2016-04-01

    Marine and terrestrial biomarkers, alkenones and n-alkanes compound, were investigated in sediment taken from the South China Sea (SCS) IODP Sites Exp. U1432C, U1433A and U1433B to evaluate Asian monsoon variability and paleoceanographic variations. Alkenone-based sea surface temperature (SSTalk) from the northern Site (U1432C) ranges from approximately 18.2oC to 28.3oC with an average of 24.4oC (n=65). Estimated SSTalk were slightly higher in the southern Site U1433A than at U1432C. SSTalk in Site U1433A ranges from 24.3oC to 27.4oC with an average 26.1oC (n=32), showing as much as 1.7oC higher SSTs than at U1432C. High concentrations of n-alkanes (nC21-35) are present throughout the Site SC1432C with strong fluctuations in the upper part (average = 496ug/g, n=140). The much higher records at U1433A and U1433B show long-range variations, but the concentration of n-alkanes remains constant below 244mbsf in Site 1433B (less than 200ug/g), suggesting an important change occurred at this horizon, dividing two different environmental domains. These differences in SSTalk and n-alkane concentration between two Sites might not only link with latitudinal location but also the influx of terrestrial biomarker due to the Asian monsoon variability and local oceanographic variations since the last approximately 1.5 Ma. Several indices of Average Chain Length (ACL) and Carbon Preferences Index (ICP) showed large shifts and fluctuations in both Sites. In particular, one of the paleo-plant proxy, Paq, also shows time-dependent large fluctuations in both Sites suggesting long time-scale variations in the flux of terrestrial organic compound as well as paleoclimatic changes in the East Asian area.

  10. A MIS 15-MIS 12 record of environmental changes and Lower Palaeolithic occupation from Valle Giumentina, central Italy

    NASA Astrophysics Data System (ADS)

    Villa, Valentina; Pereira, Alison; Chaussé, Christine; Nomade, Sébastien; Giaccio, Biagio; Limondin-Lozouet, Nicole; Fusco, Fabio; Regattieri, Eleonora; Degeai, Jean-Philippe; Robert, Vincent; Kuzucuoglu, Catherine; Boschian, Giovanni; Agostini, Silvano; Aureli, Daniele; Pagli, Marina; Bahain, Jean Jacques; Nicoud, Elisa

    2016-11-01

    An integrated geological study, including sedimentology, stable isotope analysis (δ18O, δ13C), geochemistry, micromorphology, biomarker analysis, 40Ar/39Ar geochronology and tephrochronology, was undertaken on the Quaternary infill of the Valle Giumentina basin in Central Italy, which also includes an outstanding archaeological succession, composed of nine human occupation levels ascribed to the Lower and Middle Palaeolithic. 40Ar/39Ar dating, and other palaeoenvironmental and tephrochronological data, constrain the sedimentary history of the whole succession to the MIS 15-MIS 12 interval, between 618 ± 13 ka and 456 ± 2 ka. Palaeoenvironmental proxies suggest that over this time interval of about 150 ka, sedimentary and pedogenic processes were mainly influenced by climatic changes, in particular by the pulsing of local mountain glaciers of the Majella massif. Specifically, the Valle Giumentina succession records glacio-fluvial and lacustrine sedimentation during the colder glacial periods and pedogenesis and/or alluvial sedimentation during the warmer interglacial and/or interstadial periods. During this interval, tectonics played a negligible role as a driving factor of local morphogenesis and sedimentation, whereas the general regional uplift experienced in the Middle Pleistocene led to capture of the basin and its definitive extinction after MIS 12. These data substantially improve previous knowledge of the chronology and sedimentary evolution of the succession, providing for the first time, a well constrained chronological and palaeoenvironmental framework for the archaeological and human palaeoecological record of Valle Giumentina.

  11. Assessing the distribution of sedimentary C40 carotenoids through time.

    PubMed

    French, K L; Rocher, D; Zumberge, J E; Summons, R E

    2015-03-01

    A comprehensive marine biomarker record of green and purple sulfur bacteria (GSB and PSB, respectively) is required to test whether anoxygenic photosynthesis represented a greater fraction of marine primary productivity during the Precambrian than the Phanerozoic, as current models of ocean redox evolution suggest. For this purpose, we analyzed marine rock extracts and oils from the Proterozoic to the Paleogene for C40 diagenetic products of carotenoid pigments using new analytical methods. Gas chromatography coupled with tandem mass spectrometry provides a new perspective on the temporal distributions of carotenoid biomarkers for phototrophic sulfur bacteria, specifically okenane, chlorobactane, and paleorenieratane. According to conventional paleoredox interpretations, this revised stratigraphic distribution of the GSB and PSB biomarkers implies that the shallow sunlit surface ocean (<24 m) became sulfidic more frequently in the geologic past than was previously thought. We reexamine whether there is evidence supporting a planktonic source of GSB and PSB pigments in marine systems or whether additional factors are required to explain the marine phototrophic sulfur bacteria record. To date, planktonic GSB and PSB and their pigments have been identified in restricted basins and lakes, but they have yet to be detected in the unrestricted, transiently sulfidic, marine systems. Based on modern observations, additional environmental factors, including basin restriction, microbial mats, or sediment transport, may be required to fully explain GSB and PSB carotenoids in the geologic record.

  12. The Sedimentary Signature of Recent Tsunamis

    NASA Astrophysics Data System (ADS)

    Jaffe, B. E.; Peters, R. B.; Richmond, B. M.

    2011-12-01

    The 2011 Tohoku-Oki tsunami, which killed approximately 21,000 and at most locations in northeastern Japan inundated farther inland than historic tsunamis, underscores the need to use the geologic record for an accurate assessment of tsunami hazard. The ability to identify tsunami deposits, the primary geologic record of tsunamis, has greatly improved as teams of scientists have collected data on deposit and flow characteristics as soon as possible after recent tsunamis. Although sand and boulder transport and deposition were reported for the 1946 tsunami in Hawaii, detailed post-tsunami sedimentological surveys were not conducted until the early 1990s. Since then, documenting sedimentary deposits has been part of the scientific response to nearly all major tsunamis. In total, there have been detailed geologic surveys of more than a dozen tsunamis; these surveys have increased in scope and sophistication. Sandy tsunami deposits on coastal plains have common characteristics (Peters and Jaffe, 2010). They are typically deposited in sheets that drape pre-existing topography. Deposits are absent near the shoreline in a zone of bypass or erosion that increases in width with tsunami size and can extend more than 100 m inland. Deposits generally thin landward, typically are less than 30 cm thick near the shoreline, but in rare cases may be more than a meter thick locally in depressions and bends in rivers. Conversely deposits are thinner on local topographic highs, such as ridges. Deposits are comprised of layers that are interpreted as forming during half-wave cycles. Typically there are 1 to 4 layers, each with a sharp lower contact. Each layer's lower portion is often either massive or inversely graded and its top suspension graded, a form of normal grading created when sediment in suspension settles out of the water column as the flow speed decreases. In muddy environments, deposits commonly contain mud and soil rip-up clasts and mud often caps the deposits or

  13. Fossil steroids record the appearance of Demospongiae during the Cryogenian period.

    PubMed

    Love, Gordon D; Grosjean, Emmanuelle; Stalvies, Charlotte; Fike, David A; Grotzinger, John P; Bradley, Alexander S; Kelly, Amy E; Bhatia, Maya; Meredith, William; Snape, Colin E; Bowring, Samuel A; Condon, Daniel J; Summons, Roger E

    2009-02-05

    The Neoproterozoic era (1,000-542 Myr ago) was an era of climatic extremes and biological evolutionary developments culminating in the emergence of animals (Metazoa) and new ecosystems. Here we show that abundant sedimentary 24-isopropylcholestanes, the hydrocarbon remains of C(30) sterols produced by marine demosponges, record the presence of Metazoa in the geological record before the end of the Marinoan glaciation ( approximately 635 Myr ago). These sterane biomarkers are abundant in all formations of the Huqf Supergroup, South Oman Salt Basin, and, based on a new high-precision geochronology, constitute a continuous 100-Myr-long chemical fossil record of demosponges through the terminal Neoproterozoic and into the Early Cambrian epoch. The demosponge steranes occur in strata that underlie the Marinoan cap carbonate (>635 Myr ago). They currently represent the oldest evidence for animals in the fossil record, and are evidence for animals pre-dating the termination of the Marinoan glaciation. This suggests that shallow shelf waters in some late Cryogenian ocean basins (>635 Myr ago) contained dissolved oxygen in concentrations sufficient to support basal metazoan life at least 100 Myr before the rapid diversification of bilaterians during the Cambrian explosion. Biomarker analysis has yet to reveal any convincing evidence for ancient sponges pre-dating the first globally extensive Neoproterozoic glacial episode (the Sturtian, approximately 713 Myr ago in Oman).

  14. Growth-dependent hydrogen isotopic fractionation of algal lipid biomarkers in hypersaline Isabel Lake (México)

    NASA Astrophysics Data System (ADS)

    Romero-Viana, Lidia; Kienel, Ulrike; Wilkes, Heinz; Sachse, Dirk

    2013-04-01

    In this study, we evaluated the potential of the hydrogen isotopic composition of algal lipid biomarkers as a proxy for past hydroclimatic variability in hypersaline Isabel Lake, Mexico (Eastern Pacific). We compared rainfall variability recorded in the region over the last 65 years with changes in δD values of the most abundant compounds preserved in the uppermost 16 cm of lake sediment. Changes in δD values of the 1,15-C32 diol (δDdiol), a specific biomarker of algal populations, were related to rainfall variability; specifically, n-alkyl diols were more deuterium-enriched (depleted) during wetter (drier) periods. Strikingly, neither the magnitude of lipid biomarker isotopic changes over interannual timescales (of up to 70-80‰) nor the direction of that variability can be explained by changes in δD values of the water source or salinity fluctuations (approximately 30 on the practical salinity scale) controlled by seasonal rainfall. However, changes in sedimentary biomarker composition, higher total organic carbon content and less negative δ13C values of the 1,15-C32 diol indicate enhanced algal growth during wetter periods. We find that these conditions result in less negative δD values of n-alkyl diols. We hypothesize that due to higher lipid demand during enhanced algal growth, an increasing proportion of hydrogen for lipid synthesis is derived from the cytosol via oxidation of polysaccharides, which may cause a deuterium enrichment of the acetogenic compounds. This study has significant implications for paleohydrological reconstructions using algal lipid δD values, particularly in highly seasonal environments such as Isabel Lake. In such environments, δD values of specific algal lipid biomarkers may not record the full seasonal cycle in source water δD but appear to be mainly controlled by the physiological state of algal populations. Our data provide the first evidence that changes in D/H fractionation due to algal growth conditions can be recorded

  15. Historical records of coastal eutrophication-induced hypoxia

    NASA Astrophysics Data System (ADS)

    Gooday, A. J.; Jorissen, F.; Levin, L. A.; Middelburg, J. J.; Naqvi, S. W. A.; Rabalais, N. N.; Scranton, M.; Zhang, J.

    2009-02-01

    Under certain conditions, sediment cores from coastal settings subject to hypoxia can yield records of environmental changes over time scales ranging from decades to millennia, sometimes with a resolution of as little as a few years. A variety of biological and geochemical proxies derived from such cores have been used to reconstruct the development of eutrophication and hypoxic conditions over time. Proxies based on 1) the preserved remains of benthic organisms (mainly foraminiferans and ostracods), 2) sedimentary features (e.g. laminations) and 3) sediment chemistry and mineralogy (e.g. presence of sulphides and redox-sensitive trace elements) reflect conditions at or close to the seafloor. Those based on 4) the preserved remains of planktonic organisms (mainly diatoms and dinoflagellates), 5) pigments and lipid biomarkers derived from prokaryotes and eukaryotes and 6) organic C, N and their isotope values reflect conditions in the water column. However, the interpretation of these proxies is not straightforward. A central difficulty concerns the fact that hypoxia is strongly correlated with, and often induced by, organic enrichment (eutrophication), making it difficult to separate the effects of these phenomena in sediment records. The problem is compounded by the enhanced preservation in anoxic and hypoxic sediments of organic microfossils and biomarkers indicating eutrophication. The use of hypoxia-specific indicators, such as the trace metals molybdenum and rhenium and the bacterial biomarker isorenieratene, which have not been used often in historical studies, may provide a way forward. All proxies of bottom-water hypoxia are basically qualitative; their quantification presents a major challenge to which there is currently no satisfactory solution. Finally, it is important to separate the effects of natural ecosystem variability from anthropogenic effects. Despite these problems, in the absence of historical data for dissolved oxygen concentrations, the

  16. Historical records of coastal eutrophication-induced hypoxia

    NASA Astrophysics Data System (ADS)

    Gooday, A. J.; Jorissen, F.; Levin, L. A.; Middelburg, J. J.; Naqvi, S. W. A.; Rabalais, N. N.; Scranton, M.; Zhang, J.

    2009-08-01

    Under certain conditions, sediment cores from coastal settings subject to hypoxia can yield records of environmental changes over time scales ranging from decades to millennia, sometimes with a resolution of as little as a few years. A variety of biological and geochemical indicators (proxies) derived from such cores have been used to reconstruct the development of eutrophication and hypoxic conditions over time. Those based on (1) the preserved remains of benthic organisms (mainly foraminiferans and ostracods), (2) sedimentary features (e.g. laminations) and (3) sediment chemistry and mineralogy (e.g. presence of sulphides and redox-sensitive trace elements) reflect conditions at or close to the seafloor. Those based on (4) the preserved remains of planktonic organisms (mainly diatoms and dinoflagellates), (5) pigments and lipid biomarkers derived from prokaryotes and eukaryotes and (6) organic C, N and their stable isotope ratios reflect conditions in the water column. However, the interpretation of these indicators is not straightforward. A central difficulty concerns the fact that hypoxia is strongly correlated with, and often induced by, organic enrichment caused by eutrophication, making it difficult to separate the effects of these phenomena in sediment records. The problem is compounded by the enhanced preservation in anoxic and hypoxic sediments of organic microfossils and biomarkers indicating eutrophication. The use of hypoxia-specific proxies, such as the trace metals molybdenum and rhenium and the bacterial biomarker isorenieratene, together with multi-proxy approaches, may provide a way forward. All proxies of bottom-water hypoxia are basically qualitative; their quantification presents a major challenge to which there is currently no satisfactory solution. Finally, it is important to separate the effects of natural ecosystem variability from anthropogenic effects. Despite these problems, in the absence of historical data for dissolved oxygen

  17. The provenance of vegetation and environmental signatures encoded in vascular plant biomarkers carried by the Ganges-Brahmaputra rivers

    NASA Astrophysics Data System (ADS)

    Galy, Valier; Eglinton, Timothy; France-Lanord, Christian; Sylva, Sean

    2011-04-01

    Organic matter carried by rivers and deposited in continental and marine sediments contains valuable information on past environmental conditions and their impact on the terrestrial biosphere. In order to use sedimentary records to reconstruct past environmental conditions on the continents, such as vegetation cover and type, or precipitation intensity, we need to understand the provenance of the organic signatures and how they are transferred, and potentially modified, by fluvial transport to the sedimentary reservoir. In particular, we need to understand how environmental conditions are imprinted in the composition of riverine particulate organic carbon. Here we investigate the stable carbon and hydrogen isotopic signatures of vascular plant leaf wax biomarkers in the modern-day Ganges and Brahmaputra river complex, one of the largest fluvial systems on Earth. The distribution of n-alkanes and n-alkanoic acids in Ganges-Brahmaputra river sediments suggests that vascular plant inputs are consistently a significant component of the organic carbon pool. Molecular δ 13C measurements reveal that C 3 vegetation inputs delivered by the Himalayan rivers are partly degraded and replaced by mixed C 3/C 4 vegetation input in the floodplain. The hydrogen isotopic composition of long-chain (C 24+) n-alkanoic acids, in combination with their stable C isotopic composition, provides constraints on the isotopic composition of the environmental water used by higher plants within the drainage basin. Calculated compositions compare well with the depleted δD isotopic ratios of the river water during the summer monsoon, suggesting that H-isotopic compositions of long-chain alkanoic acids are a valuable proxy for the composition of summer monsoon moisture in the Ganges-Brahmaputra basin. Detailed studies of the "isotopic anatomy" of modern river systems are critical for informed interpretation of marine sedimentary records in river-influenced continental margins.

  18. Exploring the provenance of vegetation and environmental signatures encoded in vascular plant biomarkers carried by the Ganges-Brahmaputra rivers

    NASA Astrophysics Data System (ADS)

    Galy, V.; Eglinton, T. I.; France-Lanord, C.; Sylva, S.

    2010-12-01

    Organic matter carried by rivers and deposited in continental and marine sediments contains valuable information on past environmental conditions and their impact on the terrestrial biosphere. In order to use sedimentary records to reconstruct past environmental conditions on the continents, such as vegetation cover and type, or precipitation intensity, we need to understand the provenance of the organic signatures and how they are transferred, and potentially modified, by fluvial transport to the sedimentary reservoir. In particular, we need to understand how environmental conditions are imprinted in the composition of riverine particulate organic carbon. Here we investigate the stable carbon and hydrogen isotopic signatures of vascular plant leaf wax biomarkers in the modern-day Ganges and Brahmaputra river complex, one of the largest fluvial system on Earth. Molecular stable C isotope ratio measurements reveal that C3 vegetation inputs delivered by the Himalayan rivers are partly degraded and replaced by mixed C3/C4 vegetation input in the floodplain. The hydrogen isotopic composition of long-chain n-alkanoic acids, in combination with their stable C isotopic composition, provides constraints on the isotopic composition of the meteoric water used by the plants. Calculated compositions compare well with the depleted D/H isotopic ratios of the heavy rains of the summer monsoon. Notably, in the Ganges basin, the isotopic compositions calculated at the base of the range and in the floodplain are identical, suggesting that H-isotopic compositions of long-chain n-alkanoic acids are a valuable proxy for the composition of summer monsoon precipitation in the Ganges-Brahmaputra basin. Using sedimentary records near the terminus of this river system, such measurements could provide insights into summer monsoon rainfall intensity in the past.

  19. Chlorine isotope behavior during prograde metamorphism of sedimentary rocks

    NASA Astrophysics Data System (ADS)

    Selverstone, Jane; Sharp, Zachary D.

    2015-05-01

    Chlorine stable isotope compositions of two sedimentary sequences and their metamorphic equivalents were measured in order to study fractionation effects during prograde metamorphism and devolatilization. Protoliths (n = 25) were collected from a 50 m section of Triassic fluvial and playa-lake strata and Jurassic (Liassic) marine black shales in a well-characterized quarry. Low greenschist to middle amphibolite facies equivalents (n > 80) were collected from the Glarus Alps, Urseren Zone, and Lucomagno region. Bulk δ37Cl values are constant within individual sedimentary layers, but vary from -2.0 to + 2.4 ‰ in Triassic rocks and from -3.0 to 0‰ in the black shales. Dolomitic and gypsiferous samples have positive δ37Cl values, but marls and shales are isotopically negative. Bulk Cl contents show only small declines during the earliest stages of metamorphism. Metamorphic equivalents of the Triassic and Liassic protoliths record the same overall ranges in δ37Cl as their protoliths. Samples with highly correlated bulk compositions but different metamorphic grade show no statistically significant difference in δ37Cl. These data lead to the following conclusions: (1) Terrestrial and marine sedimentary rocks display large primary heterogeneities in chlorine isotope composition. As a result, an unambiguous "sedimentary signature" does not exist in the chlorine stable isotope system. (2) No isotopic fractionation is discernable during metamorphic devolatilization, even at low temperatures. Alpine-style metamorphism thus has little to no effect on bulk chlorine isotopic compositions, despite significant devolatilization. (3) Cl is largely retained in the rocks during devolatilization, contrary to the normally assumed hydrophilic behavior of chlorine. Continuous release of mixed-volatile C-O-H fluids likely affected Cl partitioning between fluid and minerals and allowed chlorine to remain in the rocks. (4) There is no evidence for fluid communication across (meta)sedimentary

  20. The White Nile sedimentary system

    NASA Astrophysics Data System (ADS)

    Garzanti, Eduardo; Andò, Sergio; Padoan, Marta; Resentini, Alberto; Vezzoli, Giovanni; Villa, Igor

    2014-05-01

    The Nile River flows for ~6700 km from south of the Equator to finally reach the Mediterranean Sea at northern subtropical latitudes (Woodward et al. 2007). This is the longest sedimentological laboratory on Earth, a unique setting in which we are investigating changes in sediment composition associated with diverse chemical and physical processes, including weathering and hydraulic sorting. The present study focuses on the southern branch of the Nile across 20° of latitude, from hyperhumid Burundi and Rwanda highlands in central Africa to Khartoum, the capital city of Sudan at the southern edge of the Sahara. Our study of the Kagera basin emphasizes the importance of weathering in soils at the source rather than during stepwise transport, and shows that the transformation of parent rocks into quartzose sand may be completed in one sedimentary cycle (Garzanti et al. 2013a). Micas and heavy minerals, less effectively diluted by recycling than main framework components, offer the best key to identify the original source-rock imprint. The different behaviour of chemical indices such as the CIA (a truer indicator of weathering) and the WIP (markedly affected by quartz dilution) helps us to distinguish strongly weathered first-cycle versus polycyclic quartz sands (Garzanti et al. 2013b). Because sediment is efficiently trapped in East African Rift lakes, the composition of Nile sediments changes repeatedly northwards across Uganda. Downstream of both Lake Kyoga and Lake Albert, quartzose sands are progressively enriched in metamorphiclastic detritus supplied from tributaries draining amphibolite-facies basements. The evolution of White Nile sediments across South Sudan, a scarcely accessible region that suffered decades of civil war, was inferred from the available information (Shukri 1950), integrated by original petrographic, heavy-mineral and geochemical data (Padoan et al. 2011). Mineralogical and isotopic signatures of Bahr-el-Jebel and Sobat sediments, derived

  1. Defining Pesticide Biomarkers

    EPA Pesticide Factsheets

    Biomarkers are measurable substances or characteristics in the human body that can be used to monitor the presence of a chemical in the body, biological responses or harm to health. This Web page describes categories of biomarkers and provides examples.

  2. BIOMARKERS OF REPRODUCTIVE TOXICITY

    EPA Science Inventory

    Identification and verification of anatomical, endocrine, cellular and molecular biomarkers is crucial for successful clinical diagnosis and treatment of toxicity and disease, as well as basic toxicological, epidemiological and other research. Various in situ biomarkers of repro...

  3. Biomarkers in Computational Toxicology

    EPA Science Inventory

    Biomarkers are a means to evaluate chemical exposure and/or the subsequent impacts on toxicity pathways that lead to adverse health outcomes. Computational toxicology can integrate biomarker data with knowledge of exposure, chemistry, biology, pharmacokinetics, toxicology, and e...

  4. Biomarkers in Veterinary Medicine.

    PubMed

    Myers, Michael J; Smith, Emily R; Turfle, Phillip G

    2017-02-08

    This article summarizes the relevant definitions related to biomarkers; reviews the general processes related to biomarker discovery and ultimate acceptance and use; and finally summarizes and reviews, to the extent possible, examples of the types of biomarkers used in animal species within veterinary clinical practice and human and veterinary drug development. We highlight opportunities for collaboration and coordination of research within the veterinary community and leveraging of resources from human medicine to support biomarker discovery and validation efforts for veterinary medicine.

  5. Origin of sedimentary organic matter at the Northern Cascadia Margin

    NASA Astrophysics Data System (ADS)

    Kaneko, M.; Naraoka, H.

    2007-12-01

    Gas hydrate in marine sediments may have important roles on global carbon cycle and climatic change. We examined origins of sedimentary organic matter and bacterial activity in deep and hydrate-bearing sediment cored in Site U1327 and U1328 at northern Cascadia Margin by IODP Exp311, using σ13C of total organic carbon (TOC), σ15N of total nitrogen (TN), σ34S of total sulfur (TS), and σ13C of biomarkers in hydrocarbon fraction. In both sites, TOC/TN ratios and σ13C of TOC values ranged from 5.5 to 18.0 and -25.7 to -21.5 ‰, respectively, suggesting that sedimentary organic matter is a mixture of terrestrial and marine sources. Long chain (n)-alkanes (C27, C29, and C30), known as biomarkers of terrestrial higher plant were most abundant components (up to ~50 μg/gCorg) through down to 300 mbsf, and their σ13C values (-34.3 to -28.7 ‰) reveal their C3 plant origin. In addition, very long-chain alkene (C37) occurred in some sediments, which suggests the blooming by coccolithophore in the past. σ34S of TS values at both sites show large variation between -30 to +20 ‰. Most of σ34S of TS values were less than present σ34S value of seawater sulfate (+20.3 ‰). This is attributable to isotope fractionation during microbial sulfate reduction. Crocetenes including one double bond occurred in deep sediments with higher σ13C values (-23 ‰) than the reported σ13C values (< ~ -100 ‰, Elvert et al, 2000), providing possibility of heterotrophic archaea using marine organic matter as a carbon source. Pentamethylicosane (PMI) was detected in relatively high concentrations at 249 mbsf at Site U1328 and its σ13C value was -46.4 ‰. This PMI could be chemoautotrophic archaea in origin such as methanogen. Diploptene was also detected in most sediments with the σ13C value of -37 to -35 ‰, probably being characteristic of chemoautotrophic bacteria.

  6. Strong motion from surface waves in deep sedimentary basins

    USGS Publications Warehouse

    Joyner, W.B.

    2000-01-01

    It is widely recognized that long-period surface waves generated by conversion of body waves at the boundaries of deep sedimentary basins make an important contribution to strong ground motion. The factors controlling the amplitude of such motion, however, are not widely understood. A study of pseudovelocity response spectra of strong-motion records from the Los Angeles Basin shows that late-arriving surface waves with group velocities of about 1 km/sec dominate the ground motion for periods of 3 sec and longer. The rate of amplitude decay for these waves is less than for the body waves and depends significantly on period, with smaller decay for longer periods. The amplitude can be modeled by the equation log y = f(M, RE) + c + bRB where y is the pseudovelocity response, f(M, RE) is an attenuation relation based on a general strong-motion data set, M is moment magnitude, RE is the distance from the source to the edge of the basin, RB is the distance from the edge of the basin to the recording site, and b and c are parameters fit to the data. The equation gives values larger by as much as a factor of 3 than given by the attenuation relationships based on general strong-motion data sets for the same source-site distance. It is clear that surface waves need to be taken into account in the design of long-period structures in deep sedimentary basins. The ground-motion levels specified by the earthquake provisions of current building codes, in California at least, accommodate the long-period ground motions from basin-edge-generated surface waves for periods of 5 sec and less and earthquakes with moment magnitudes of 7.5 or less located more than 20 km outside the basin. There may be problems at longer periods and for earthquakes located closer to the basin edge. The results of this study suggest that anelastic attenuation may need to be included in attempts to model long-period motion in deep sedimentary basins. To obtain better data on surface waves in the future

  7. Displacement propagators of brine flowing within different types of sedimentary rock.

    PubMed

    Verganelakis, Dimitris A; Crawshaw, John; Johns, Michael L; Mantle, Michael D; Scheven, Ulrich; Sederman, Andrew J; Gladden, Lynn F

    2005-02-01

    This paper explores the correlation between different microstructural characteristics of porous sedimentary rocks and the flow properties of a Newtonian infiltrating fluid. Preliminary results of displacement propagator measurements of brine solution flowing through two types of sedimentary rock cores are reported. The two types of rocks, Bentheimer and Portland, are characterized by different porosities, pore-size distributions and permeabilities. Propagators have been measured for brine flow rates of 1 and 5 ml/min. Significant differences are seen between the propagators recorded for the two rocks, and these are related to the spatial distribution of porosity within these porous media.

  8. Hydrogeologic framework of sedimentary deposits in six structural basins, Yakima River basin, Washington

    USGS Publications Warehouse

    Jones, M.A.; Vaccaro, J.J.; Watkins, A.M.

    2006-01-01

    The hydrogeologic framework was delineated for the ground-water flow system of the sedimentary deposits in six structural basins in the Yakima River Basin, Washington. The six basins delineated, from north to south are: Roslyn, Kittitas, Selah, Yakima, Toppenish, and Benton. Extent and thicknesses of the hydrogeologic units and total basin sediment thickness were mapped for each basin. Interpretations were based on information from about 4,700 well records using geochemical, geophysical, geologist's or driller's logs, and from the surficial geology and previously constructed maps and well interpretations. The sedimentary deposits were thickest in the Kittitas Basin reaching a depth of greater than 2,000 ft, followed by successively thinner sedimentary deposits in the Selah basin with about 1,900 ft, Yakima Basin with about 1,800 ft, Toppenish Basin with about 1,200 ft, Benton basin with about 870 ft and Roslyn Basin with about 700 ft.

  9. Layer formation in sedimentary fingering convection

    NASA Astrophysics Data System (ADS)

    Reali, J. F.; Garaud, P.; Alsinan, A.; Meiburg, E.

    2017-04-01

    When particles settle through a stable temperature or salinity gradient they can drive an instability known as sedimentary fingering convection. This phenomenon is thought to occur beneath sediment-rich river plumes in lakes and oceans, in the context of marine snow where decaying organic materials serve as the suspended particles, or in the atmosphere in the presence of aerosols or volcanic ash. Laboratory experiments of Houk and Green (1973) and Green (1987) have shown sedimentary fingering convection to be similar to the more commonly known thermohaline fingering convection in many ways. Here, we study the phenomenon using 3D direct numerical simulations. We find evidence for layer formation in sedimentary fingering convection in regions of parameter space where it does not occur for non-sedimentary systems. This is due to two complementary effects. Sedimentation affects the turbulent fluxes and broadens the region of parameter space unstable to the $\\gamma$-instability (Radko 2003) to include systems at larger density ratios. It also gives rise to a new layering instability that exists in $\\gamma-$stable regimes. The former is likely quite ubiquitous in geophysical systems for sufficiently large settling velocities, while the latter probably grows too slowly to be relevant, at least in the context of sediments in water.

  10. Use of Molecular Fossils for the Interpretation of Paleoenvironments on Early Earth: The Synthesis of Lipid Biomarkers by Methane-Oxidizing Bacteria

    NASA Technical Reports Server (NTRS)

    Jahnke, Linda L.; Summons, Roger E.; Chang, Sherwood (Technical Monitor)

    1994-01-01

    Over the course of Earth's history, the most important biological influence has come from the evolution of oxygenic photosynthesis and the development of an oxygen-rich biosphere. Although the availability of free oxygen had profound effects on subsequent biological and planetary evolution, clear paleobiological evidence of the timing of this transition is lacking. Recent technical advances in the microanalysis of organic matter has made it possible to detect residual molecules (biomarkers) in proterozoic (2.5 to 0.6 billion years) sedimentary rock characteristic of specific groups of microorganisms. When coupled with the carbon isotopic fractionations characteristic of biological systems and the new field of compound specific isotope analysis, biomarkers could prove to be a powerful tool for decoding ancient biochemistry from the geological record. We have been studying the carbon isotope fractionations associated with the synthesis of organic biomarker molecules in several types of methane-oxidizing bacteria that should have been key to carbon cycling in paleoenvironments after the evolution of oxygenic photosynthesis.

  11. Biomarkers in clinical medicine.

    PubMed

    Chen, Xiao-He; Huang, Shuwen; Kerr, David

    2011-01-01

    Biomarkers have been used in clinical medicine for decades. With the rise of genomics and other advances in molecular biology, biomarker studies have entered a whole new era and hold promise for early diagnosis and effective treatment of many diseases. A biomarker is a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes or pharmacologic responses to a therapeutic intervention (1). They can be classified into five categories based on their application in different disease stages: 1) antecedent biomarkers to identify the risk of developing an illness, 2) screening biomarkers to screen for subclinical disease, 3) diagnostic biomarkers to recognize overt disease, 4) staging biomarkers to categorise disease severity, and 5) prognostic biomarkers to predict future disease course, including recurrence, response to therapy, and monitoring efficacy of therapy (1). Biomarkers can indicate a variety of health or disease characteristics, including the level or type of exposure to an environmental factor, genetic susceptibility, genetic responses to environmental exposures, markers of subclinical or clinical disease, or indicators of response to therapy. This chapter will focus on how these biomarkers have been used in preventive medicine, diagnostics, therapeutics and prognostics, as well as public health and their current status in clinical practice.

  12. Sedimentary complexes of the cover of the Dzabkhan continental block: Different sedimentary basins and source areas

    NASA Astrophysics Data System (ADS)

    Letnikova, E. F.; Vishnevskaya, I. A.; Letnikov, F. A.; Vetrova, N. I.; Shkolnik, S. I.; Kostitsyn, Yu. A.; Karakovskii, E. A.; Reznitskii, L. Z.; Kanygina, N. A.

    2016-10-01

    The geochemical and Sm-Nd isotope characteristics of Late Precambrian and Early Cambrian sandstones previously related to the sedimentary cover of the Dzabkhan continental block are reported. It is established that the Riphean and Vendian sedimentary rocks of the Ul'zitgol'skaya and Tsaganolomskaya Formations were accumulated within the Dzabkhan continental block as a result of recycling of the terrigenous deposits formed at the expense of destruction of basement rocks and younger granite. The formation of terrigenous rocks of the Bayangol'skaya Formation after a gap in sedimentation occurred in the sedimentary basin, where only the Late Riphean formations of the juvenile crust, probably of the Dzabkhan-Mandal block were the sources, without the contribution of the ancient crustal material. The Tsaganolomskaya and Bayangol'skaya Formations were formed in different sedimentary basins and cannot be related to the same complex.

  13. Circulating glioma biomarkers

    PubMed Central

    Kros, Johan M.; Mustafa, Dana M.; Dekker, Lennard J.M.; Sillevis Smitt, Peter A.E.; Luider, Theo M.; Zheng, Ping-Pin

    2015-01-01

    Validated biomarkers for patients suffering from gliomas are urgently needed for standardizing measurements of the effects of treatment in daily clinical practice and trials. Circulating body fluids offer easily accessible sources for such markers. This review highlights various categories of tumor-associated circulating biomarkers identified in blood and cerebrospinal fluid of glioma patients, including circulating tumor cells, exosomes, nucleic acids, proteins, and oncometabolites. The validation and potential clinical utility of these biomarkers is briefly discussed. Although many candidate circulating protein biomarkers were reported, none of these have reached the required validation to be introduced for clinical practice. Recent developments in tracing circulating tumor cells and their derivatives as exosomes and circulating nuclear acids may become more successful in providing useful biomarkers. It is to be expected that current technical developments will contribute to the finding and validation of circulating biomarkers. PMID:25253418

  14. Geochemistry of Fine-grained Sediments and Sedimentary Rocks

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

    , 1981; Berner et al., 1983; Kump et al., 2000), with a shifting emphasis toward sophisticated characterization of the linkages among solid Earth, oceans, biosphere, cryosphere, atmosphere, and climate, mediated by short- and long-term biogeochemical cycles. As a result, one of the primary objectives of current geological inquiry is improved understanding of the interconnectedness and associated feedback among the cycles of carbon, nitrogen, phosphorous, oxygen, and sulfur, and their relationship to the history of Earth's climate. This "Earth System" approach involves uniformitarian extrapolations of knowledge gained from modern environments to proxy-based interpretations of environmental change recorded in ancient strata. The strength of modern data lies with direct observations of pathways and products of physical, chemical, and biological processes, but available time-series are short relative to the response times of many of the biogeochemical systems under study. By contrast, stratigraphically constrained geological data offer time-series that encompass a much fuller range of system response. But with the enhanced breadth of temporal resolution and signal amplitude provided by ancient sedimentary records comes a caveat - we must account for the blurring of primary paleo-environmental signals by preservational artifacts and understand that proxy calibrations are extended from the modern world into a nonsubstantively uniformitarian geological past.Fortunately, detrital sedimentary rocks preserve records of multiple proxies (dependent and independent) that illuminate the processes and conditions of sediment formation, transport, deposition, and burial. An integrated multiproxy approach offers an effective tool for deconvolving the history of biogeochemical cycling of, among other things, carbon and sulfur, and for understanding the range of associated paleo-environmental conditions (e.g., levels of atmospheric oxygen and carbon dioxide, oceanic paleoredox, and

  15. Biomarkers for Parkinson's disease.

    PubMed

    Sherer, Todd B

    2011-04-20

    Biomarkers for detecting the early stages of Parkinson's disease (PD) could accelerate development of new treatments. Such biomarkers could be used to identify individuals at risk for developing PD, to improve early diagnosis, to track disease progression with precision, and to test the efficacy of new treatments. Although some progress has been made, there are many challenges associated with developing biomarkers for detecting PD in its earliest stages.

  16. The Biomarker Guide

    NASA Astrophysics Data System (ADS)

    Peters, K. E.; Walters, C. C.; Moldowan, J. M.

    2005-01-01

    Biomarkers are compounds found in crude oil with structures inherited from once-living organisms. They persist in oil spills, refinery products and archaeological artifacts, and can be used to identify the origin, geological age and environmental conditions prevalent during their formation and alteration. These two volumes will be an invaluable resource for geologists, petroleum geochemists, biogeochemists, environmental and forensic scientists, natural product chemists and archaeologists. The first of two volumes of The Biomarker Guide discusses the origins of biomarkers and introduces basic chemical principles relevant to their study. It goes on to discuss analytical techniques, and the applications of biomarkers in environmental and archaeological problems.

  17. Petroleum potential of the Libyan sedimentary basins

    SciTech Connect

    Hammuda, O.S.; Sbeta, A.M.

    1988-08-01

    Contrary to prevailing opinion, all Libyan sedimentary basins and the Al-Jabal Al-Akhdar platform contain prolific petroleum accumulations with very high prospectivity. A systematic review of the types of traps and pays in this central part of the southern Mediterranean province reveals great variability in reservoir and source rock characteristics. The reservoir rocks are of almost all geologic ages. The thick source rock sequences also vary in nature and organic content. The organic-rich facies have accumulated in intracratonic and passive margin basins or in marginal seas. Most of the oil discovered thus far in these basins is found in large structural traps. Future discoveries of stratigraphic traps or small structural traps will require intensified efforts and detailed studies using up-to-date multidisciplinary techniques in sedimentary tectonics, biostratigraphic facies analysis, and geochemical prospecting in order to develop a better understanding of these basins, thus improving their prospectivity.

  18. Tide-influenced sedimentary environments and facies

    SciTech Connect

    De Boer, P.L.; Van Gelder, A.; Nio, S.D.

    1988-01-01

    This volume contains examples of recent as well as fossil tide-influenced sedimentary facies. Studies of recent tidal processes and sediments provide an insight into the way in which tidal facies and sequences develop, and into the processes which are active. The studies performed on fossil rocks give information on one-to-one scale model experiments that have been executed by nature both relatively recently and in the distant past. In this work, the parallel presentation of papers on recent and fossil examples of tide-influenced sedimentary facies and environments follows the philosophy of comparative sedimentology, aiming at an understanding of both the past and the present, with the aim also, of forecasting future developments.

  19. About the Relation Between Geodynamics of the Sedimentary Basin and the Properties of Crude Oil

    NASA Astrophysics Data System (ADS)

    Muslimov, R.; Plotnikova, I.

    2012-04-01

    Earlier, we wrote and reported about the modern geodynamic activity of the territory of South-Tatar arch, where the Romashkino oil field. We identified a periodic change in flow rates of oil and oil density at Romashkino and other oil fields of the South Tatar arch. Now we have studied the composition of oils and bitumoids from uneven (in terms of age) deposites of the sedimentary cover and basement rocks in the zones of possible hydrocarbon seepage in the central squares of Romashkinskoye field. The results of the comparative studies allowed us to come to the conclusion that the formation of oil-bearing deposits of Romashkinskoye field owes to the income and mixing of hydrocarbons (HC) fluids from different sources. The analysis of geological and production data (GPD) that was held during the many years of exploitation of the development wells of Romashkinskoye field by TatNIPIneft under the direction of I.F. Glumov suggests contemporary inflow of hydrocarbons in the industrial oil reservoir of the Pashi horizon of Romashkinskoye field and the existence of localized areas of inflow of new portions of HC. A number of criteria was worked out in the analysis of the GPD; that allowed us to identify among the total number of wells those, in which the process of hydrocarbon seepage was recorded with the greatest probability. Such wells were called anomalous. One of the directions of this research was to study the geochemical characteristics of oil from anomalous wells and to determine the degree of similarity and difference between this oil and the oil from both normal wells (in which the signs of deep seepage is not recorded), and bituminoid from the crystalline basement and sedimentary cover. If the hypothesis of a recurrent (also in modern times) influx of deep hydrocarbon is correct, then the oil from the anomalous wells should have specific features in comparison with the wells located outside the areas of the expected inflow. The results of geochemical studies of

  20. Experimental model to study sedimentary kidney stones.

    PubMed

    Grases, F; Llobera, A

    1998-01-01

    An experimental model to reproduce, to some extent, the conditions prevailing during the formation of the so-called sedimentary urinary stones, was developed. The results obtained demonstrated that in the absence of organic matter no calcium phosphate crystals were deposited in cavities with scarce liquid renovation. Nevertheless, in such case a regular hydroxyapatite layer was developed on the walls around the cavity. The presence of crystallization inhibitors cannot stop indefinitely the crystal development. Therefore, phytate manifested important inhibitory effects in concentrations normally found in urine (0.77-1.54 x 10(-6) mol/l), whereas citrate only manifested important inhibitory effects when found at high urinary concentrations (2.64 x 10(-3) mol/l). When mucin (a glycoprotein) was present in the urine, a clear deposit of calcified organic material was formed. The organic matter appeared mixed with the spherulites of hydroxyapatite, this demonstrating the capacity of the glycoprotein agglomerates to act as heterogeneous nucleants of calcium salts and their important role in the formation of sedimentary stones. The structural features of the obtained in vitro deposits were compared with the fine structure of human sedimentary phosphate calculi. Scanning electron microscopy images demonstrated a good correspondence between in vitro experiments and in vivo observations.

  1. A Robust Biomarker

    NASA Technical Reports Server (NTRS)

    Westall, F.; Steele, A.; Toporski, J.; Walsh, M. M.; Allen, C. C.; Guidry, S.; McKay, D. S.; Gibson, E. K.; Chafetz, H. S.

    2000-01-01

    Polymers of bacterial origin, either through cell secretion or the degraded product of cell lysis, form isolated mucoidal strands as well as well-developed biofilms on interfaces. Biofilms are structurally and compositionally complex and are readily distinguishable from abiogenic films. These structures range in size from micrometers to decimeters, the latter occurring as the well-known, mineralised biofilms called stromatolites. Compositionally bacterial polymers are greater than 90 % water, with while the majority of the macromolecules forming the framework of the polymers consisting of polysaccharides (with and some nucteic acids and proteins). These macromolecules contain a vaste amount of functional groups, such as carboxyls, hydroxyls, and phosphoryls which are implicated in cation-binding. It is the elevated metal- binding capacity which provides the bacterial polymer with structural support and also helps to preserves it for up to 3.5 b.y. in the terrestrial rock record. The macromolecules, thus, can become rapidly mineralised and trapped in a mineral matrix. Through early and late diagenesis (bacterial degradation, burial, heat, pressure and time) they break down, losing the functional groups and, gradually, their hydrogen atoms. The degraded product is known as "kerogen". With further diagenesis and metamorphism, all the hydrogen atoms are lost and the carbonaceous matter becomes graphite. until the remnant carbonaceous material become graphitised. This last sentence reads a bit as if ALL these macromolecules break down and end up as graphite., but since we find 441 this is not true for all of the macromolecules. We have traced fossilised polymer and biofilms in rocks from throughout Earth's history, to rocks as old as the oldest being 3.5 b.y.-old. Furthermore, Time of Flight Secondary Ion Mass Spectrometry has been able to identify individual macromolecules of bacterial origin, the identities of which are still being investigated, in all the samples

  2. Hydrogen isotope ratios of lacustrine sedimentary n-alkanes as proxies of tropical African hydrology: Insights from a calibration transect across Cameroon

    NASA Astrophysics Data System (ADS)

    Garcin, Yannick; Schwab, Valérie F.; Gleixner, Gerd; Kahmen, Ansgar; Todou, Gilbert; Séné, Olivier; Onana, Jean-Michel; Achoundong, Gaston; Sachse, Dirk

    2012-02-01

    Hydrogen isotope values (δD) of sedimentary aquatic and terrestrial lipid biomarkers, originating from algae, bacteria, and leaf wax, have been used to record isotopic properties of ancient source water (i.e., precipitation and/or lake water) in several mid- and high-latitude lacustrine environments. In the tropics, however, where both processes associated with isotope fractionation in the hydrologic system and vegetation strongly differ from those at higher latitudes, calibration studies for this proxy are not yet available. To close this gap of knowledge, we sampled surface sediments from 11 lakes in Cameroon to identify those hydro-climatological processes and physiological factors that determine the hydrogen isotopic composition of aquatic and terrestrial lipid biomarkers. Here we present a robust framework for the application of compound-specific hydrogen isotopes in tropical Africa. Our results show that the δD values of the aquatic lipid biomarker n-C17 alkane were not correlated with the δD values of lake water. Carbon isotope measurements indicate that the n-C17 alkane was derived from multiple source organisms that used different hydrogen pools for biosynthesis. We demonstrate that the δD values of the n-C29 alkane were correlated with the δD values of surface water (i.e., river water and groundwater), which, on large spatial scales, reflect the isotopic composition of mean annual precipitation. Such a relationship has been observed at higher latitudes, supporting the robustness of the leaf-wax lipid δD proxy on a hemispheric spatial scale. In contrast, the δD values of the n-C31 alkane did not show such a relationship but instead were correlated with the evaporative lake water δD values. This result suggests distinct water sources for both leaf-wax lipids, most likely originating from two different groups of plants. These new findings have important implications for the interpretation of long-chain n-alkane δD records from ancient lake sediments

  3. Biomarkers present in asphaltenes

    SciTech Connect

    Philp, R.P.

    1985-01-01

    The significance and distribution of biomarkers in sediments, source rocks and crude oils are well documented in the literature. Little attention has been directed towards the biomarkers that are present in the asphaltene fractions of crude oils and source rock extracts. Asphaltene fractions by definition are insoluble in certain solvents and consist of high molecular components which makes them difficult to analyze by techniques commonly used to characterize the soluble extracts. Asphaltenes are ideally suited for analysis by microscale pyrolysis techniques (py) combined with gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Utilization of the multiple ion detection technique in conjunction with the py-GC-MS analyses permits the distribution of the steranes, triterpanes and other biomarker produced by pyrolysis of the asphaltenes to be easily determined. It is proposed in this paper to discuss the pyrolysis of asphaltene from a variety of source rocks and analysis of the biomarkers, released by the pyrolysis. These biomarkers distributions can be used to obtain information on source and maturity of the organic matter in a similar manner to using the soluble biomarkers. It is proposed to discuss the asphaltene biomarker distributions and also to speculate as to why certain biomarkers are present only in the extracts and asphaltenes and not produced by pyrolysis of the kerogens.

  4. Respiratory Toxicity Biomarkers

    EPA Science Inventory

    The advancement in high throughput genomic, proteomic and metabolomic techniques have accelerated pace of lung biomarker discovery. A recent growth in the discovery of new lung toxicity/disease biomarkers have led to significant advances in our understanding of pathological proce...

  5. Biomarkers in Parkinson's disease.

    PubMed

    Morgan, John C; Mehta, Shyamal H; Sethi, Kapil D

    2010-11-01

    Biomarkers are objectively measured characteristics that are indicators of normal biological processes, pathogenic processes, or responses to therapeutic interventions. To date, clinical assessment remains the gold standard in the diagnosis of Parkinson's disease (PD) and clinical rating scales are well established as the gold standard for tracking progression of PD. Researchers have identified numerous potential biomarkers that may aid in the differential diagnosis of PD and/or tracking disease progression. Clinical, genetic, blood and cerebrospinal fluid (proteomics, transcriptomics, metabolomics), and neuroimaging biomarkers may provide useful tools in the diagnosis of PD and in measuring disease progression and response to therapies. Some potential biomarkers are inexpensive and do not require much technical expertise, whereas others are expensive or require specialized equipment and technical skills. Many potential biomarkers in PD show great promise; however, they need to be assessed for their sensitivity and specificity over time in large and varied samples of patients with and without PD.

  6. Biomarkers of Reflux Disease.

    PubMed

    Kia, Leila; Pandolfino, John E; Kahrilas, Peter J

    2016-06-01

    Gastroesophageal reflux disease (GERD) encompasses an array of disorders unified by the reflux of gastric contents. Because there are many potential disease manifestations, esophageal and extraesophageal, there is no single biomarker of the entire disease spectrum; a set of GERD biomarkers that each quantifies specific aspects of GERD-related pathology might be needed. We review recent reports of biomarkers of GERD, specifically in relation to endoscopically negative esophageal disease and excluding conventional pH-impedance monitoring. We consider histopathologic biomarkers, baseline impedance, and serologic assays to determine that most markers are based on manifestations of impaired esophageal mucosal integrity, which is based on increased ionic and molecular permeability, and/or destruction of tight junctions. Impaired mucosal integrity quantified by baseline mucosal impedance, proteolytic fragments of junctional proteins, or histopathologic features has emerged as a promising GERD biomarker.

  7. Rare earth elements and neodymium isotopes in sedimentary organic matter

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  8. Long-term sedimentary recycling of rare sulphur isotope anomalies.

    PubMed

    Reinhard, Christopher T; Planavsky, Noah J; Lyons, Timothy W

    2013-05-02

    The accumulation of substantial quantities of O2 in the atmosphere has come to control the chemistry and ecological structure of Earth's surface. Non-mass-dependent (NMD) sulphur isotope anomalies in the rock record are the central tool used to reconstruct the redox history of the early atmosphere. The generation and initial delivery of these anomalies to marine sediments requires low partial pressures of atmospheric O2 (p(O2); refs 2, 3), and the disappearance of NMD anomalies from the rock record 2.32 billion years ago is thought to have signalled a departure from persistently low atmospheric oxygen levels (less than about 10(-5) times the present atmospheric level) during approximately the first two billion years of Earth's history. Here we present a model study designed to describe the long-term surface recycling of crustal NMD anomalies, and show that the record of this geochemical signal is likely to display a 'crustal memory effect' following increases in atmospheric p(O2) above this threshold. Once NMD anomalies have been buried in the upper crust they are extremely resistant to removal, and can be erased only through successive cycles of weathering, dilution and burial on an oxygenated Earth surface. This recycling results in the residual incorporation of NMD anomalies into the sedimentary record long after synchronous atmospheric generation of the isotopic signal has ceased, with dynamic and measurable signals probably surviving for as long as 10-100 million years subsequent to an increase in atmospheric p(O2) to more than 10(-5) times the present atmospheric level. Our results can reconcile geochemical evidence for oxygen production and transient accumulation with the maintenance of NMD anomalies on the early Earth, and suggest that future work should investigate the notion that temporally continuous generation of new NMD sulphur isotope anomalies in the atmosphere was likely to have ceased long before their ultimate disappearance from the rock record.

  9. Late Holocene sedimentary environments of south San Francisco Bay, California, illustrated in gravity cores

    USGS Publications Warehouse

    Woodrow, Donald L.; Fregoso, Theresa A.; Wong, Florence L.; Jaffe, Bruce E.

    2014-01-01

    Data are reported here from 51 gravity cores collected from the southern part of San Francisco Bay by the U.S. Geological Survey in 1990. The sedimentary record in the cores demonstrates a stable geographic distribution of facies and spans a few thousand years. Carbon-14 dating of the sediments suggests that sedimentation rates average about 1 mm/yr. The geometry of the bay floor and the character of the sediment deposited have remained about the same in the time spanned by the cores. However, the sedimentary record over periods of centuries or decades is likely to be much more variable. Sediments containing a few bivalve shells and bivalve or oyster coquinas are most often found west of the main channel and near the San Mateo Bridge. Elsewhere in the south bay, shells are rare except in the southernmost reaches where scattered gastropod shells are found.

  10. [Biomarkers in Alzheimer's disease].

    PubMed

    García-Ribas, G; López-Sendón Moreno, J L; García-Caldentey, J

    2014-04-01

    The new diagnostic criteria for Alzheimer's disease (AD) include brain imaging and cerebrospinal fluid (CSF) biomarkers, with the aim of increasing the certainty of whether a patient has an ongoing AD neuropathologic process or not. Three CSF biomarkers, Aß42, total tau, and phosphorylated tau, reflect the core pathological features of AD. It is already known that these pathological processes of AD starts decades before the first symptoms, so these biomarkers may provide means of early disease detection. At least three stages of AD could be identified: preclinical AD, mild cognitive impairment due to AD, and dementia due to AD. In this review, we aim to summarize the CSF biomarker data available for each of these stages. We also review the actual research on blood-based biomarkers. Recent studies on healthy elderly subjects and on carriers of dominantly inherited AD mutations have also found biomarker changes that allow separate groups in these preclinical stages. These studies may aid for segregate populations in clinical trials and objectively evaluate if there are changes over the pathological processes of AD. Limits to widespread use of CSF biomarkers, apart from the invasive nature of the process itself, is the higher coefficient of variation for the analyses between centres. It requires strict pre-analytical and analytical procedures that may make feasible multi-centre studies and global cut-off points for the different stages of AD.

  11. Biomarkers as tracers for life on early earth and Mars

    NASA Technical Reports Server (NTRS)

    Simoneit, B. R.; Summons, R. E.; Jahnke, L. L.

    1998-01-01

    Biomarkers in geological samples are products derived from biochemical (natural product) precursors by reductive and oxidative processes (e.g., cholestanes from cholesterol). Generally, lipids, pigments and biomembranes are preserved best over longer geological times and labile compounds such as amino acids, sugars, etc. are useful biomarkers for recent times. Thus, the detailed characterization of biomarker compositions permits the assessment of the major contributing species of extinct and/or extant life. In the case of the early Earth, work has progressed to elucidate molecular structure and carbon isotropic signals preserved in ancient sedimentary rocks. In addition, the combination of bacterial biochemistry with the organic geochemistry of contemporary and ancient hydrothermal ecosystems permits the modeling of the nature, behavior and preservation potential of primitive microbial communities. This approach uses combined molecular and isotopic analyses to characterize lipids produced by cultured bacteria (representative of ancient strains) and to test a variety of culture conditions which affect their biosynthesis. On considering Mars, the biomarkers from lipids and biopolymers would be expected to be preserved best if life flourished there during its early history (3.5-4 x 10(9) yr ago). Both oxidized and reduced products would be expected. This is based on the inferred occurrence of hydrothermal activity during that time with the concomitant preservation of biochemically-derived organic matter. Both known biomarkers (i.e., as elucidated for early terrestrial samples and for primitive terrestrial microbiota) and novel, potentially unknown compounds should be characterized.

  12. Development of source specific diatom lipids biomarkers as Antarctic Sea Ice proxies

    NASA Astrophysics Data System (ADS)

    Smik, Lukas; Belt, Simon T.; Brown, Thomas A.; Lieser, Jan L.; Armand, Leanne K.; Leventer, Amy; Allen, Claire S.

    2016-04-01

    triene III, in particular. This may have important implications for the use of these biomarkers for paleo sea ice reconstructions. Sedimentary distribution showed significant variation in abundances of diene II and triene III between different regions of Antarctica, but also on a more local scale, potentially reflecting a high degree of sensitivity towards individual sea ice dynamics that favour the individual species responsible for their biosynthesis. However, highest concentrations of diene II were generally observed in near coastal locations, consistent with the identification of elevated abundances of this HBI in first year or land fast ice in these settings. The identification of the sea ice diatom source of diene II will likely be significant in interpretations of the occurrence of this biomarker in paleo sea ice records.

  13. Phanerozoic growth of the epicontinental sedimentary reservoir: implications for long-term sea level change

    NASA Astrophysics Data System (ADS)

    Husson, J. M.; Peters, S. E.

    2015-12-01

    Earth's sedimentary carapace contains the largest surface-accessible reservoir of biogeochemically sensitive elements and contains several times more water than all of the present-day ice caps and glaciers combined. It is, therefore, widely recognized that on timescales of ~1 Myr, one of the most important factors governing the evolution of many Earth systems is the exchange of materials into and out of the sedimentary shell. Although it is rarely assumed that these rates of exchange are invariant, it is generally presumed that the sedimentary reservoir as a whole behaves as a single large, slowly cycling system in which erosion and sediment storage are balanced; hence the expectation that there is no net change in sediment volume. Here, using the Macrostrat database, which consists of surface and subsurface data for 1,474 locations as well as more than 700K geologic map-based polygons, we show that the sedimentary reservoir is best conceived of as multiple reservoirs with different intrinsic cycling rates determined by tectonic and environmental contexts of deposition. We also show that the volume of sediment stored on presently subaerially exposed North America has increased markedly during the Phanerozoic. Initiation of growth in the size of this epicontinental sedimentary reservoir is well recorded by the Great Unconformity, which separates predominately Precambrian-aged, low porosity crystalline and metamorphic basement rocks from overlying, more porous Cambrian and younger sedimentary deposits. Geologic map-based data from Eurasia and Australia suggest similar overall patterns globally. Thus, after burial of the subaerially exposed Great Unconformity surface by Cambrian-Ordovician sediments, the groundwater storage capacity of the continents increased by more than 15 million cubic km (~1% of present ocean volume). Subsequent burial by younger sedimentary deposits further increased epicontinental groundwater storage capacity to the ~130 million cubic km it

  14. Commentary: statistics for biomarkers.

    PubMed

    Lovell, David P

    2012-05-01

    This short commentary discusses Biomarkers' requirements for the reporting of statistical analyses in submitted papers. It is expected that submitters will follow the general instructions of the journal, the more detailed guidance given by the International Committee of Medical Journal Editors, the specific guidelines developed by the EQUATOR network, and those of various specialist groups. Biomarkers expects that the study design and subsequent statistical analyses are clearly reported and that the data reported can be made available for independent assessment. The journal recognizes that there is continuing debate about different approaches to statistical science. Biomarkers appreciates that the field continues to develop rapidly and encourages the use of new methodologies.

  15. Metabolic products as biomarkers

    USGS Publications Warehouse

    Melancon, M.J.; Alscher, R.; Benson, W.; Kruzynski, G.; Lee, R.F.; Sikka, H.C.; Spies, R.B.; Huggett, Robert J.; Kimerle, Richard A.; Mehrle, Paul M.=; Bergman, Harold L.

    1992-01-01

    Ideally, endogenous biomarkers would indicate both exposure and environmental effects of toxic chemicals; however, such comprehensive biochemical and physiological indices are currently being developed and, at the present time, are unavailable for use in environmental monitoring programs. Continued work is required to validate the use of biochemical and physiological stress indices as useful components of monitoring programs. Of the compounds discussed only phytochelatins and porphyrins are currently in biomarkers in a useful state; however, glutathione,metallothioneins, stress ethylene, and polyamines are promising as biomarkers in environmental monitoring.

  16. Organic geochemical characterization of the Lower-Middle Triassic sedimentary rocks from south China

    NASA Astrophysics Data System (ADS)

    Saito, R.

    2015-12-01

    The most devastated environments and depleted biodiversity on Earth occurred during the Early Triassic epoch following the latest Permian mass extinction. Complete biotic recovery, characterized by a return to pre-extinction diversity levels, took an extraordinarily long time (ca. 5 x 106 yr), probably because harsh conditions developed repeatedly during the Early Triassic. Newly obtained organic geochemistry data from south China area, indicated a variety of biotic (eukaryotic algae, cyanobacteria, bacteria, and archaea) and environmental fluctuations (redox) during the Early Triassic. Remarkably, some sedimentary rocks from Lower Triassic strata contain rare biomarkers such as biphytanes and okenane, whch are biomarkers for archaea and purple sulfur bacteria, respectively. This is the first study to describe in detail primary producers, microbes, and redox conditions in the Early-Early Middle Triassic, on the basis of biomarkers such as steranes, 2-methyl hopanes, hopanes, biphytanes, regular isoprenoids, n-alkanes, okenane, chlorobactane, β-carotane, and γ-carotane. The results greatly not only increase our understanding of the recovery processes that occurred following the Permian mass extinction, but also emphasize an effectiveness of organic geochemistry against the Early Triassic.

  17. Areal distribution of sedimentary facies determined from seismic facies analysis and models of modern depositional systems

    SciTech Connect

    Seramur, K.C.; Powell, R.D.; Carpenter, P.J.

    1988-02-01

    Seismic facies analysis was applied to 3.5-kHz single-channel analog reflection profiles of the sediment fill within Muir Inlet, Glacier Bay, southeast Alaska. Nine sedimentary facies have been interpreted from seven seismic facies identified on the profiles. The interpretations are based on reflection characteristics and structural features of the seismic facies. The following reflection characteristics and structural features are used: reflector spacing, amplitude and continuity of reflections, internal reflection configurations, attitude of reflection terminations at a facies boundary, body geometry of a facies, and the architectural associations of seismic facies within each basin. The depositional systems are reconstructed by determining the paleotopography, bedding patterns, sedimentary facies, and modes of deposition within the basin. Muir Inlet is a recently deglaciated fjord for which successive glacier terminus positions and consequent rates of glacial retreat are known. In this environment the depositional processes and sediment characteristics vary with distance from a glacier terminus, such that during a retreat a record of these variations is preserved in the aggrading sediment fill. Sedimentary facies within the basins of lower Muir Inlet are correlated with observed depositional processes near the present glacier terminus in the upper inlet. The areal distribution of sedimentary facies within the basins is interpreted using the seismic facies architecture and inferences from known sediment characteristics proximal to present glacier termini.

  18. The potassic sedimentary rocks in Gale Crater, Mars, as seen by ChemCam Onboard Curiosity

    USGS Publications Warehouse

    Le Deit, Laetitia; Mangold, Nicolas; Forni, Olivier; Cousin, Agnes; Lasue, Jeremie; Schröder, Susanne; Wiens, Roger C.; Sumner, Dawn Y.; Fabre, Cecile; Stack, Katherine M.; Anderson, Ryan; Blaney, Diana L.; Clegg, Samuel M.; Dromart, Gilles; Fisk, Martin; Gasnault, Olivier; Grotzinger, John P.; Gupta, Sanjeev; Lanza, Nina; Le Mouélic, Stephane; Maurice, Sylvestre; McLennan, Scott M.; Meslin, Pierre-Yves; Nachon, Marion; Newsom, Horton E.; Payre, Valerie; Rapin, William; Rice, Melissa; Sautter, Violaine; Treiman, Alan H.

    2016-01-01

    The Mars Science Laboratory rover Curiosity encountered potassium-rich clastic sedimentary rocks at two sites in Gale Crater, the waypoints Cooperstown and Kimberley. These rocks include several distinct meters thick sedimentary outcrops ranging from fine sandstone to conglomerate, interpreted to record an ancient fluvial or fluvio-deltaic depositional system. From ChemCam Laser-Induced Breakdown Spectroscopy (LIBS) chemical analyses, this suite of sedimentary rocks has an overall mean K2O abundance that is more than 5 times higher than that of the average Martian crust. The combined analysis of ChemCam data with stratigraphic and geographic locations reveals that the mean K2O abundance increases upward through the stratigraphic section. Chemical analyses across each unit can be represented as mixtures of several distinct chemical components, i.e., mineral phases, including K-bearing minerals, mafic silicates, Fe-oxides, and Fe-hydroxide/oxyhydroxides. Possible K-bearing minerals include alkali feldspar (including anorthoclase and sanidine) and K-bearing phyllosilicate such as illite. Mixtures of different source rocks, including a potassium-rich rock located on the rim and walls of Gale Crater, are the likely origin of observed chemical variations within each unit. Physical sorting may have also played a role in the enrichment in K in the Kimberley formation. The occurrence of these potassic sedimentary rocks provides additional evidence for the chemical diversity of the crust exposed at Gale Crater.

  19. Biomarker time out.

    PubMed

    Petzold, Axel; Bowser, Robert; Calabresi, Paolo; Zetterberg, Henrik; Uitdehaag, Bernard M J

    2014-10-01

    The advancement of knowledge relies on scientific investigations. The timing between asking a question and data collection defines if a study is prospective or retrospective. Prospective studies look forward from a point in time, are less prone to bias and are considered superior to retrospective studies. This conceptual framework conflicts with the nature of biomarker research. New candidate biomarkers are discovered in a retrospective manner. There are neither resources nor time for prospective testing in all cases. Relevant sources for bias are not covered. Ethical questions arise through the time penalty of an overly dogmatic concept. The timing of sample collection can be separated from testing biomarkers. Therefore the moment of formulating a hypothesis may be after sample collection was completed. A conceptual framework permissive to asking research questions without the obligation to bow to the human concept of calendar time would simplify biomarker research, but will require new safeguards against bias.

  20. Phanerozoic cycles of sedimentary carbon and sulfur.

    PubMed

    Garrels, R M; Lerman, A

    1981-08-01

    A reservoir model of a Recent steady-state sedimentary system in which the reduced sulfur and oxidized sulfur reservoirs were coupled with the oxidized carbon and reduced carbon reservoirs was constructed. The time curve of the sulfur isotope ratios of the sedimentary sulfate reservoir was used to drive the model back to the beginning of Cambrian time (600 million years ago), producing the reservoir sizes and isotope values and material fluxes of the carbon-sulfur system. The predicted values of carbon isotope ratios of the carbonate reservoir agree well with observed values, showing that the model is basically sound. Some general conclusions from this success are (i) material flux rates in the carbon-oxygen-sulfur system of the geologic past (averaged over tens of millions of years) lie within about a factor of 2 of Recent rates. (ii) The oxidation-reduction balances of Phanerozoic time were dominated by reciprocal relationships between carbon and sulfur compounds. (iii) The rate of production of atmospheric oxygen by storage in sediments of organic carbon of photosynthetic origin increased from the Cambrian Period to the Permian Period and declined somewhat from the Permian Period to the Present. (iv) The storage of oxygen in oxidized sulfur compounds kept pace (within the limits of the data) with oxygen production. (v) Transfer of oxygen from CO(2) to SO(4) from the Cambrian to the Permian Period was several times the Recent free oxygen content of the atmosphere.

  1. African sedimentary basins - Tectonic controls on prospectivity

    SciTech Connect

    Bunter, M.A.G.; Crossley, R.; Hammill, M.; Jones, P.W.; Morgan, R.K.; Needham, D.T.; Spaargaren, F.A. )

    1991-03-01

    An important prerequisite for the evaluation of any sedimentary basin is the understanding of its regional tectonic setting. This is especially so in the underexplored regions of Africa. The majority of African sedimentary basins developed in an extensional setting although some have undergone subsequent compressional or transpressional deformation. The geometry and evolution of these basins is often influenced by basement structure. The extensional phase of basin development controls not only the distribution of syn-rift sediments but also the magnitude of post-rift regional subsidence and the preservation or removal of pre-rift sediments. This has important consequences for exploration models of syn-rift and pre-rift source rocks and reservoirs. Post-rift basin inversion and uplift provide crucial controls on the preservation of mature source rocks and quality of reservoirs. The distribution, nature, timing, and possible mechanisms of this uplift in Africa will be addressed. The hydrocarbon prospectivity of African basis appears to be highly variable although the limited exploration of some regions makes the exact extent of this variability unclear. Basins considered potentially prospective range from late Precambrian to Tertiary in age. The various tectonic controls outlined above, and criteria for the evaluation of underexplored areas, will be demonstrated by reference to basins studied by The Robertson Group. Examples described include basins from Bagon, Angola, Namibia, East Africa, Tertiary Rift and Karoo Rifts, and North Africa (Sudan, Egypt, Algeria, and Morocco).

  2. Geothermal resources of California sedimentary basins

    USGS Publications Warehouse

    Williams, C.F.; Grubb, F.V.; Galanis, S.P.

    2004-01-01

    The 2004 Department of Energy (DOE) Strategic Plan for geothermal energy calls for expanding the geothermal resource base of the United States to 40,000 MW of electric power generating potential. This will require advances in technologies for exploiting unconventional geothermal resources, including Enhanced Geothermal Systems (EGS) and geopressured geothermal. An investigation of thermal conditions in California sedimentary basins through new temperature and heat flow measurements reveals significant geothermal potential in some areas. In many of the basins, the combined cooling effects of recent tectonic and sedimentary processes result in relatively low (<60 mW/m2) heat flow and geothermal gradients. For example, temperatures in the upper 3 km of San Joaquin, Sacramento and Ventura basins are typically less than 125??C and do not reach 200??c by 5 km. By contrast, in the Cuyama, Santa Maria and western Los Angeles basins, heat flow exceeds 80 mW/m2 and temperatures near or above 200??C occur at 4 to 5 km depth, which represents thermal conditions equivalent to or hotter than those encountered at the Soultz EGS geothermal site in Europe. Although the extractable geothermal energy contained in these basins is not large relative to the major California producing geothermal fields at The Geysers or Salton Sea, the collocation in the Los Angeles basin of a substantial petroleum extraction infrastructure and a major metropolitan area may make it attractive for eventual geothermal development as EGS technology matures.

  3. Biomarkers in ALH84001???

    NASA Technical Reports Server (NTRS)

    Treiman, Allen H.

    1999-01-01

    D. McKay and colleagues suggested that four sets of features in ALH84001 were biomarkers, signs of an ancient martian biota that once inhabited the meteorite. Subsequent work has not validated their hypothesis; each suggested biomarker has been found to be ambiguous or immaterial. Nor has their hypothesis been disproved. Rather, it is now one of many hypotheses about the alteration of ALH84001. Additional information is contained in the original extended abstract.

  4. UAS-based quantification of sedimentary body changes at Langgriesgraben, Styria, Austria

    NASA Astrophysics Data System (ADS)

    Schöttl, Stefan; Seier, Gernot; Rascher, Eric; Sulzer, Wolfgang; Sass, Oliver

    2016-04-01

    The creek's sedimentary body at Langgriesgraben is characterized by inconstant but recurring earth surface changes. Mass transport and deposition occur partly spontaneously and endanger primary infrastructure, in particular a main road. It is often mentioned in literature that the use of small and lightweight UAS is promising. To contribute to that, this study focuses on the documentation and quantification of carried sedimentary material by using a hexacopter in a high alpine environment. The images which were captured on two different dates, allow generating orthophotos and DEMs. The comparison of these derivatives enables a deeper understanding of the sedimentary body and its conditions. Our specific study area is a part of a bigger research area of another research project (Sedyn-X). One of the main goals of that project is to create a conceptual model of the sedimentary cascade for the entire Johnsbachtal catchment and to quantify geomorphic processes (e.g. erosion, transport and rearrangement of sediments). Therefore Terrestrial Laser Scanning recordings are performed as well. Through the generated surface models from different eras, changes in surface and volume can be quantified. The photogrammetric surface models can be compared with almost simultaneous ALS and TLS recordings. Apart from that, the outcomes will provide hard facts for decision-makers. The UAS related processing steps and methods (e.g. DGPS, SfM) are more or less established and well-known, but the applicability of UAS for recording feasible data, has to be proved constantly. We assume that our results will answer concrete questions and thus reduce expected damage and costs.

  5. Quantitative compositional analysis of sedimentary materials using thermal emission spectroscopy: 1. Application to sedimentary rocks

    NASA Astrophysics Data System (ADS)

    Thorpe, Michael T.; Rogers, A. Deanne; Bristow, Thomas F.; Pan, Cong

    2015-11-01

    Thermal emission spectroscopy is used to determine the mineralogy of sandstone and mudstone rocks as part of an investigation of linear spectral mixing between sedimentary constituent phases. With widespread occurrences of sedimentary rocks on the surface of Mars, critical examination of the accuracy associated with quantitative models of mineral abundances derived from thermal emission spectra of sedimentary materials is necessary. Although thermal emission spectroscopy has been previously proven to be a viable technique to obtain quantitative mineralogy from igneous and metamorphic materials, sedimentary rocks, with natural variation of composition, compaction, and grain size, have yet to be examined. In this work, we present an analysis of the thermal emission spectral (~270-1650 cm-1) characteristics of a suite of 13 sandstones and 14 mudstones. X-ray diffraction and traditional point counting procedures were all evaluated in comparison with thermal emission spectroscopy. Results from this work are consistent with previous thermal emission spectroscopy studies and indicate that bulk rock mineral abundances can be estimated within 11.2% for detrital grains (i.e., quartz and feldspars) and 14.8% for all other mineral phases present in both sandstones and mudstones, in comparison to common in situ techniques used for determining bulk rock composition. Clay-sized to fine silt-sized grained phase identification is less accurate, with differences from the known ranging from ~5 to 24% on average. Nevertheless, linear least squares modeling of thermal emission spectra is an advantageous technique for determining abundances of detrital grains and sedimentary matrix and for providing a rapid classification of clastic rocks.

  6. Biomarkers for neuromyelitis optica.

    PubMed

    Chang, Kuo-Hsuan; Ro, Long-Sun; Lyu, Rong-Kuo; Chen, Chiung-Mei

    2015-02-02

    Neuromyelitis optica (NMO) is an acquired, heterogeneous inflammatory disorder, which is characterized by recurrent optic neuritis and longitudinally extensive spinal cord lesions. The discovery of the serum autoantibody marker, anti-aquaporin 4 (anti-AQP4) antibody, revolutionizes our understanding of pathogenesis of NMO. In addition to anti-AQP4 antibody, other biomarkers for NMO are also reported. These candidate biomarkers are particularly involved in T helper (Th)17 and astrocytic damages, which play a critical role in the development of NMO lesions. Among them, IL-6 in the peripheral blood is associated with anti-AQP4 antibody production. Glial fibrillary acidic protein (GFAP) in CSF demonstrates good correlations with clinical severity of NMO relapses. Detecting these useful biomarkers may be useful in the diagnosis and evaluation of disease activity of NMO. Development of compounds targeting these biomarkers may provide novel therapeutic strategies for NMO. This article will review the related biomarker studies in NMO and discuss the potential therapeutics targeting these biomarkers.

  7. Combined heavy mineral and biomarker analysis in silt: a novel approach for provenance studies (Indus Fan, IODP Expedition 355)

    NASA Astrophysics Data System (ADS)

    Andò, Sergio; Bratenkov, Sophia; Hahn, Annette; George, Simon; Clift, Peter D.; Garzanti, Eduardo

    2016-04-01

    versus Indian Peninsular sources of detritus. Considered together, the organic and inorganic compositional fingerprints of sediments opens up a new frontier for future studies of the largely unexplored deep-marine sedimentary record. Cited references S. Andò, P. Vignola, E. Garzanti, 2011. Raman counting: a new method to determine provenance of silt. Rend. Fis. Acc. Lincei, 22: 327-347. S. Andò, E. Garzanti, 2014. Raman spectroscopy in heavy-mineral studies. Geological Society, London, Special Publications, 386 (1), 395-412.

  8. Implication of biomarkers signatures of the Ulleung Basin, East Sea, during the Pleistocene

    NASA Astrophysics Data System (ADS)

    Choi, Jiyoung; Lee, Kyung Eun; Kim, Ji-Hoon; Bahk, Jang-Jun; Yoo, Dong-Geun

    2014-05-01

    In this study, the molecular distribution of the n-alkanes, alkenone and C/N ratio and δ13C of bulk sediment were used to assess changes in organic matter (OM) source and transport which could be related with paleoclimate change. The proxy records corresponding to the Pleistocene have been obtained from the well-studied the Ulleung Basin Gas Hydrate Expedition 2 (UBGH2) site 11 in the Ulleung Basin, East Sea. The distribution of carbon preference index (CPI) of n-alkane encountered in this study confirmed the importance of terrestrial OM in the marine sediment. Alkenone has been widely applied for sea surface temperature (SST) reconstruction. The data results show that CPI values generally increase with decreasing paleo-SST. Plot of C/N ratio versus δ13C shows a predominance of marine algae origin in the study area. It may indicate that the minimum CPI in warm period is related with the contribution of probably enhanced biodegradation, while the maximum CPI value in cold period result from restrain of OM input associated with sea level lowering. It is likely that the vertical variations of the biomarkers signature reflect the shifts in sedimentary environment and transportation related with change of ocean currents and sea level during the Pleistocene period.

  9. Lipid biomarkers for bacterial ecosystems: studies of cultured organisms, hydrothermal environments and ancient sediments

    NASA Technical Reports Server (NTRS)

    Summons, R. E.; Jahnke, L. L.; Simoneit, B. R.

    1996-01-01

    This paper forms part of our long-term goal of using molecular structure and carbon isotopic signals preserved as hydrocarbons in ancient sediments to improve understanding of the early evolution of Earth's surface environment. We are particularly concerned with biomarkers which are informative about aerobiosis. Here, we combine bacterial biochemistry with the organic geochemistry of contemporary and ancient hydrothermal ecosystems to construct models for the nature, behaviour and preservation potential of primitive microbial communities. We use a combined molecular and isotopic approach to characterize lipids produced by cultured bacteria and test a variety of culture conditions which affect their biosynthesis. This information is then compared with lipid mixtures isolated from contemporary hot springs and evaluated for the kinds of chemical change that would accompany burial and incorporation into the sedimentary record. In this study we have shown that growth temperature does not appear to alter isotopic fractionation within the lipid classes produced by a methanotropic bacterium. We also found that cultured cyanobacteria biosynthesize diagnostic methylalkanes and dimethylalkanes with the latter only made when growing under low pCO2. In an examination of a microbial mat sample from Octopus Spring, Yellowstone National Park (USA), we could readily identify chemical structures with 13C contents which were diagnostic for the phototrophic organisms such as cyanobacteria and Chloroflexus. We could not, however, find molecular evidence for operation of a methane cycle in the particular mat samples we studied.

  10. Biomarker pigment signatures in Cochin back water system - A tropical estuary south west coast of India

    NASA Astrophysics Data System (ADS)

    Aneeshkumar, N.; Sujatha, C. H.

    2012-03-01

    Sedimentary biomarker pigments around Cochin estuary situated in the southwest coast of India were determined by HPLC. Fucoxanthin, an indicator of diatom was observed to be the most abundant carotenoid pigment in the estuary. Dinoflagellate derived carotenoid pigment peridinin was confined in the southern part of estuary and zeaxanthin pigment indicative of cyanobacteria were more found in sites influenced by anthropogenic activities. One compound having close similarity to fucoxanthin was also detected. Alloxanthin (cryptophyceae), chl b (green algae), canthaxanthin, neoxanthin, lutein and peridinin isomer were also detected by spectra and corresponding algal class were identified. The highest concentration of chl a (11.01 μg g-1) found near to the anthropogenic affected area while the lowest chl a (0.65 μg g-1) was recorded in industrial area. Degradation products of chl a, such as pheophorbide and pheophytin were observed and principal mode of mechanism of degradation were derived. Higher pheopigments content than chl a, reflects a density trapping of dead cells and early degradation of phytopigments from grazing activities.

  11. Modern sedimentary environments in a large tidal estuary, Delaware Bay

    USGS Publications Warehouse

    Knebel, H. J.

    1989-01-01

    Data from an extensive grid of sidescan-sonar records reveal the distribution of sedimentary environments in the large, tidally dominated Delaware Bay estuary. Bathymetric features of the estuary include large tidal channels under the relatively deep (> 10 m water depth) central part of the bay, linear sand shoals (2-8 m relief) that parallel the sides of the tidal channels, and broad, low-relief plains that form the shallow bay margins. The two sedimentary environments that were identified are characterized by either (1) bedload transport and/or erosion or (2) sediment reworking and/or deposition. Sand waves and sand ribbons, composed of medium to coarse sands, define sites of active bedload transport within the tidal channels and in gaps between the linear shoals. The sand waves have spacings that vary from 1 to 70 m, amplitudes of 2 m or less, and crestlines that are usually straight. The orientations of the sand waves and ribbons indicate that bottom sediment movement may be toward either the northwest or southeast along the trends of the tidal channels, although sand-wave asymmetry indicates that the net bottom transport is directed northwestward toward the head of the bay. Gravelly, coarse-grained sediments, which appear as strongly reflective patterns on the sonographs, are also present along the axes and flanks of the tidal channels. These coarse sediments are lag deposits that have developed primarily where older strata were eroded at the bay floor. Conversely, fine sands that compose the linear shoals and muddy sands that cover the shallow bay margins appear mainly on the sonographs either as smooth featureless beds that have uniform light to moderate shading or as mosaics of light and dark patches produced by variations in grain size. These acoustic and textural characteristics are the result of sediment deposition and reworking. Data from this study (1) support the hypothesis that bed configurations under deep tidal flows are functions of current

  12. Copper Deposits in Sedimentary and Volcanogenic Rocks

    USGS Publications Warehouse

    Tourtelot, Elizabeth B.; Vine, James David

    1976-01-01

    Copper deposits occur in sedimentary and volcanogenic rocks within a wide variety of geologic environments where there may be little or no evidence of hydrothermal alteration. Some deposits may be hypogene and have a deep-seated source for the ore fluids, but because of rapid cooling and dilution during syngenetic deposition on the ocean floor, the resulting deposits are not associated with hydrothermal alteration. Many of these deposits are formed at or near major tectonic features on the Earth's crust, including plate boundaries, rift valleys, and island arcs. The resulting ore bodies may be stratabound and either massive or disseminated. Other deposits form in rocks deposited in shallow-marine, deltaic, and nonmarine environments by the movement and reaction of interstratal brines whose metal content is derived from buried sedimentary and volcanic rocks. Some of the world's largest copper deposits were probably formed in this manner. This process we regard as diagenetic, but some would regard it as syngenetic, if the ore metals are derived from disseminated metal in the host-rock sequence, and others would regard the process as epigenetic, if there is demonstrable evidence of ore cutting across bedding. Because the oxidation associated with diagenetic red beds releases copper to ground-water solutions, red rocks and copper deposits are commonly associated. However, the ultimate size, shape, and mineral zoning of a deposit result from local conditions at the site of deposition - a logjam in fluvial channel sandstone may result in an irregular tabular body of limited size; a petroleum-water interface in an oil pool may result in a copper deposit limited by the size and shape of the petroleum reservoir; a persistent thin bed of black shale may result in a copper deposit the size and shape of that single bed. The process of supergene enrichment has been largely overlooked in descriptions of copper deposits in sedimentary rocks. However, supergene processes may be

  13. Modern sedimentary facies of the open Pacific coast and Pleistocene analogs from Montery Bay, California

    USGS Publications Warehouse

    Dupre, W.R.; Clifton, H.E.; Hunter, R.E.; Field, Michael E.; Field, Michael E.; ,

    1980-01-01

    Depositional processes and sedimentary structures of wave-dominated Pacific coastal environments vary systematically with water depth. The depth-limited open-coast facies identifiable by their sedimentary structures are the inner shelf, barred or nonbarred nearshore, beach, and coastal dune facies. These facies are most commonly preserved in shallowing-upward progradational sequences. The vertical sequence of sedimentary structures preserved in marine terrace deposits in the northern Monterey Bay region is very similar to that predicted on the basis of the modern facies. Few marine sediments deposited during the marine transgression that accompanied rising sea level were preserved. Most of the the marine and eolian sediments form a progradational sequence deposited mainly during intervals of falling sea level. In contrast, the sediments that form the adjacent fluvial terraces were deposited mainly during periods of rising sea level and became entrenched during the subsequent lowering of sea level. In combination, these fluvial, marine, and eolian deposits provide a record of a complete eustatic cycle. The recognition of the role of changing sea level in controlling patterns of coastal sedimentation and landform development during the Quaternary allows the development of a generalized model for Quaternary sedimentation along a wave-dominated coastline. The application of this model has aided in the interpretation of older Pleistocene sediments in the region (e.g. the Aromas Sand). It also has resulted in the recognition of at least eleven glacio-eustatic cycles preserved in the stratigraphic record of the Monterey Bay area during the Quaternary.

  14. Biomarkers for antipsychotic therapies.

    PubMed

    Pich, Emilio Merlo; Vargas, Gabriel; Domenici, Enrico

    2012-01-01

    Molecular biomarkers for antipsychotic treatments have been conceptually linked to the measurements of dopamine functions, mostly D(2) receptor occupancy, either by imaging using selective PET/SPECT radioactive tracers or by assessing plasma prolactin levels. A quest for novel biomarkers was recently proposed by various academic, health service, and industrial institutions driven by the need for better treatments of psychoses. In this review we conceptualize biomarkers within the Translational Medicine paradigm whose goal was to provide support to critical decision-making in drug discovery. At first we focused on biomarkers as outcome measure of clinical studies by searching into the database clinicaltrial.gov. The results were somewhat disappointing, showing that out of 1,659 antipsychotic trials only 18 used a biomarker as an outcome measure. Several of these trials targeted plasma lipids as sentinel marker for metabolic adverse effects associated with the use of atypical antipsychotics, while only few studies were aimed to new disease specific biological markers. As an example of a mechanistic biomarker, we described the work done to progress the novel class of glycine transporter inhibitors as putative treatment for negative symptoms of schizophrenia. We also review how large-scale multiplex biological assays were applied to samples from tissues of psychiatric patients, so to learn from changes of numerous analytes (metabolic products, lipids, proteins, RNA transcripts) about the substrates involved in the disease. We concluded that a stringent implementation of these techniques could contribute to the endophenotypic characterization of patients, helping in the identification of key biomarkers to drive personalized medicine and new treatment development.

  15. Kidney biomarkers in cirrhosis.

    PubMed

    Francoz, Claire; Nadim, Mitra K; Durand, François

    2016-10-01

    Impaired renal function due to acute kidney injury (AKI) and/or chronic kidney diseases (CKD) is frequent in cirrhosis. Recurrent episodes of AKI may occur in end-stage cirrhosis. Differential diagnosis between functional (prerenal and hepatorenal syndrome) and acute tubular necrosis (ATN) is crucial. The concept that AKI and CKD represent a continuum rather than distinct entities, is now emerging. Not all patients with AKI have a potential for full recovery. Precise evaluation of kidney function and identification of kidney changes in patients with cirrhosis is central in predicting reversibility. This review examines current biomarkers for assessing renal function and identifying the cause and mechanisms of impaired renal function. When CKD is suspected, clearance of exogenous markers is the reference to assess glomerular filtration rate, as creatinine is inaccurate and cystatin C needs further evaluation. Recent biomarkers may help differentiate ATN from hepatorenal syndrome. Neutrophil gelatinase-associated lipocalin has been the most extensively studied biomarker yet, however, there are no clear-cut values that differentiate each of these conditions. Studies comparing ATN and hepatorenal syndrome in cirrhosis, do not include a gold standard. Combinations of innovative biomarkers are attractive to identify patients justifying simultaneous liver and kidney transplantation. Accurate biomarkers of underlying CKD are lacking and kidney biopsy is often contraindicated in this population. Urinary microRNAs are attractive although not definitely validated. Efforts should be made to develop biomarkers of kidney fibrosis, a common and irreversible feature of CKD, whatever the cause. Biomarkers of maladaptative repair leading to irreversible changes and CKD after AKI are also promising.

  16. Lung Cancer Biomarkers.

    PubMed

    I, Hoseok; Cho, Je-Yoel

    2015-01-01

    Lung cancer is the most frequently occurring cancer in the world and continually leads in mortality among cancers. The overall 5-year survival rate for lung cancer has risen only 4% (from 12% to 16%) over the past 4 decades, and late diagnosis is a major obstacle in improving lung cancer prognosis. Survival of patients undergoing lung resection is greater than 80%, suggesting that early detection and diagnosis of cancers before they become inoperable and lethal will greatly improve mortality. Lung cancer biomarkers can be used for screening, detection, diagnosis, prognosis, prediction, stratification, therapy response monitoring, and so on. This review focuses on noninvasive diagnostic and prognostic biomarkers. For that purpose, our discussion in this review will focus on biological fluid-based biomarkers. The body fluids include blood (serum or plasma), sputum, saliva, BAL, pleural effusion, and VOC. Since it is rich in different cellular and molecular elements and is one of the most convenient and routine clinical procedures, serum or plasma is the main source for the development and validation of many noninvasive biomarkers. In terms of molecular aspects, the most widely validated ones are proteins, some of which are used in the clinical sector, though in limited accessory purposes. We will also discuss the lung cancer (protein) biomarkers in clinical trials and currently in the validation phase with hundreds of samples. After proteins, we will discuss microRNAs, methylated DNA, and circulating tumor cells, which are being vigorously developed and validated as potential lung cancer biomarkers. The main aim of this review is to provide researchers and clinicians with an understanding of the potential noninvasive lung cancer biomarkers in biological fluids that have recently been discovered.

  17. Remote sensing of some sedimentary rocks.

    NASA Technical Reports Server (NTRS)

    Brennan, P. A.; Lintz, J., Jr.

    1971-01-01

    Sedimentary rocks including varying sized clastics and carbonates were overflown by aircraft between 1966 and 1971 producing data in the ultraviolet to microwave regions of the electromagnetic spectrum. This paper reports that multispectral analysis increases the ease and rapidity of discrimination of rock types having subtle differences in physical characteristics, but fails to enhance and may degrade distinctions where physical characteristics are significantly different. Brief resumes of color and color IR photographic data are presented. Thermal infrared is found to be useful in the mapping of rock units, but limitations such as moisture variation, soil cover, and vegetation may exceed in one formation the distinction between differing lithologies. A brief review of previously published SLAR data is included for completeness. Remote sensing techniques should reduce field geological effort by as much as 50%.

  18. Sedimentary processes and crustal cycling on Venus

    NASA Technical Reports Server (NTRS)

    Warner, J. L.

    1983-01-01

    Sediment exists on the Venus surface. It is observed in Venera images between outcrops and boulders of sedimentary rocks. Sediment is produced by pyroclastic volcanism and chemical weathering. Chemical weathering is driven by an enhanced activity of water and an elevated surface temperature. Sediment is transported by wind action and lithified by cementration and diagenesis. Cementation may be by carbonate or silica cement; diagenesis may be products of chemical weathering acting as cement, or by compaction and recrystallization of sediment into a texture with interlocking grains. Sediment may be transported from the top of sialic continents (such as Ishtar) to the modal plains where it is deposited, lithified, and integrated into thy local crust. As new layers are added, the bottom of the crust melts and is, in part, returned to the mantle. A steady-state chemical exchange might exist by this mechanism of crustal cycling that links atmosphere, continents, modal plains, and mantle.

  19. Search for the Evolution of Steroid Biosynthesis in the Geological Record

    NASA Astrophysics Data System (ADS)

    Brocks, J. J.

    2004-12-01

    To study the evolution of the structure of organisms we can directly examine fossilized shells, skeletons and petrified cells. In contrast, for the tentative reconstruction of the phylogeny of biosynthetic pathways, such as steroid anabolism, we rely entirely on the comparative molecular biology of living organisms. Thus, without fossil evidence, the times in geological history when successive steps of a metabolic pathway evolved remain particularly elusive. Molecular clocks of genes coding for the enzymes involved in a biosynthetic pathway might provide a rough guess when a natural product first appeared in geological time, but they are intrinsically unreliable without calibration points in the distant past. However, it might be possible to trace the evolutionary history of some biosynthetic pathways directly in the geological record by searching for hydrocarbon biomarkers of anabolic intermediates. Biomarkers are molecular fossils of natural products. They often retain the diagnostic carbon skeleton of their biological precursor and remain stable over hundreds of millions of years enclosed in organic-rich sedimentary rocks. Sterane hydrocarbons are particularly abundant biomarkers and potentially suitable for the search of biosynthetic intermediates. Steranes are the fossil equivalents of functionalized steroids found in eukaryotes and certain bacteria. The biosynthesis of typical eukaryotic steroids such as cholesterol (C27), ergosterol (C28) and sitosterol (C29) from the acyclic precursor squalene (C30) involves more than 20 enzymatic steps. The most crucial steps include modification of the carbon skeleton by removal of several methyl groups from the ring system and addition of alkyl groups to the steroid side chain. The evolution of this complex pathway must have occurred over geologically significant periods of time and likely involved several preadaptive intermediates that represented structurally less derived but fully functional lipids. Thus, if a

  20. Permanganate diffusion and reaction in sedimentary rocks.

    PubMed

    Huang, Qiuyuan; Dong, Hailiang; Towne, Rachael M; Fischer, Timothy B; Schaefer, Charles E

    2014-04-01

    In situ chemical oxidation using permanganate has frequently been used to treat chlorinated solvents in fractured bedrock aquifers. However, in systems where matrix back-diffusion is an important process, the ability of the oxidant to migrate and treat target contaminants within the rock matrix will likely determine the overall effectiveness of this remedial approach. In this study, a series of diffusion experiments were performed to measure the permanganate diffusion and reaction in four different types of sedimentary rocks (dark gray mudstone, light gray mudstone, red sandstone, and tan sandstone). Results showed that, within the experimental time frame (~2 months), oxidant migration into the rock was limited to distances less than 500 μm. The observed diffusivities for permanganate into the rock matrices ranged from 5.3 × 10(-13) to 1.3 × 10(-11) cm(2)/s. These values were reasonably predicted by accounting for both the rock oxidant demand and the effective diffusivity of the rock. Various Mn minerals formed as surface coatings from reduction of permanganate coupled with oxidation of total organic carbon (TOC), and the nature of the formed Mn minerals was dependent upon the rock type. Post-treatment tracer testing showed that these Mn mineral coatings had a negligible impact on diffusion through the rock. Overall, our results showed that the extent of permanganate diffusion and reaction depended on rock properties, including porosity, mineralogy, and organic carbon. These results have important implications for our understanding of long-term organic contaminant remediation in sedimentary rocks using permanganate.

  1. Thermal evolution of sedimentary basins in Alaska

    USGS Publications Warehouse

    Johnsson, Mark J.; Howell, D.G.

    1996-01-01

    The complex tectonic collage of Alaska is reflected in the conjunction of rocks of widely varying thermal maturity. Indicators of the level of thermal maturity of rocks exposed at the surface, such as vitrinite reflectance and conodont color alteration index, can help constrain the tectonic evolution of such complex regions and, when combined with petrographic, modern heat flow, thermogeochronologic, and isotopic data, allow for the detailed evaluation of a region?s burial and uplift history. We have collected and assembled nearly 10,000 vitrinite-reflectance and conodont-color-alteration index values from the literature, previous U.S. Geological Survey investigations, and our own studies in Alaska. This database allows for the first synthesis of thermal maturity on a broadly regional scale. Post-accretionary sedimentary basins in Alaska show wide variability in terms of thermal maturity. The Tertiary interior basins, as well as some of the forearc and backarc basins associated with the Aleutian Arc, are presently at their greatest depth of burial, with immature rocks exposed at the surface. Other basins, such as some backarc basins on the Alaska Peninsula, show higher thermal maturities, indicating modest uplift, perhaps in conjunction with higher geothermal gradients related to the arc itself. Cretaceous ?flysch? basins, such as the Yukon-Koyukuk basin, are at much higher thermal maturity, reflecting great amounts of uplift perhaps associated with compressional regimes generated through terrane accretion. Many sedimentary basins in Alaska, such as the Yukon-Koyukuk and Colville basins, show higher thermal maturity at basin margins, perhaps reflecting greater uplift of the margins in response to isostatic unloading, owing to erosion of the hinterland adjacent to the basin or to compressional stresses adjacent to basin margins.

  2. Analysis and Discrimination of Sedimentary, Metamorphic, and Igneous Rocks Using Laser-Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Rai, Ab. Kr.; Maurya, G. S.; Kumar, R.; Pathak, A. K.; Pati, J. K.; Rai, Aw. K.

    2017-01-01

    This study deals with the analysis of rocks using laser-induced breakdown spectroscopy (LIBS) coupled with principal component analysis. The spectra of sedimentary, metamorphic, and igneous rock samples were recorded in the 200-900 nm spectral range. The atomic lines of elements such as Si, Ca, Mg, Fe, Na, and K along with lighter elements, namely C, H, N, and O, were observed in these spectra. Multivariate analysis in combination with LIBS was used to classify the samples. For principal component analysis, a 12 × 5849 data matrix was formed using the results of LIBS. The plot of the analysis revealed similarities between the sedimentary and metamorphic rock samples compared with the igneous rock sample. Thus, the present study demonstrates that LIBS coupled with principal component analysis can become an important tool for rapid classification and in-situ discrimination of rock samples.

  3. Biomarkers of sepsis.

    PubMed

    Faix, James D

    2013-01-01

    Sepsis is an unusual systemic reaction to what is sometimes an otherwise ordinary infection, and it probably represents a pattern of response by the immune system to injury. A hyper-inflammatory response is followed by an immunosuppressive phase during which multiple organ dysfunction is present and the patient is susceptible to nosocomial infection. Biomarkers to diagnose sepsis may allow early intervention which, although primarily supportive, can reduce the risk of death. Although lactate is currently the most commonly used biomarker to identify sepsis, other biomarkers may help to enhance lactate's effectiveness; these include markers of the hyper-inflammatory phase of sepsis, such as pro-inflammatory cytokines and chemokines; proteins such as C-reactive protein and procalcitonin which are synthesized in response to infection and inflammation; and markers of neutrophil and monocyte activation. Recently, markers of the immunosuppressive phase of sepsis, such as anti-inflammatory cytokines, and alterations of the cell surface markers of monocytes and lymphocytes have been examined. Combinations of pro- and anti-inflammatory biomarkers in a multi-marker panel may help identify patients who are developing severe sepsis before organ dysfunction has advanced too far. Combined with innovative approaches to treatment that target the immunosuppressive phase, these biomarkers may help to reduce the mortality rate associated with severe sepsis which, despite advances in supportive measures, remains high.

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

    NASA Technical Reports Server (NTRS)

    Ojakangas, R. W.

    1983-01-01

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

  5. Biomarkers intersect with the exposome.

    PubMed

    Rappaport, Stephen M

    2012-09-01

    The exposome concept promotes use of omic tools for discovering biomarkers of exposure and biomarkers of disease in studies of diseased and healthy populations. A two-stage scheme is presented for profiling omic features in serum to discover molecular biomarkers and then for applying these biomarkers in follow-up studies. The initial component, referred to as an exposome-wide-association study (EWAS), employs metabolomics and proteomics to interrogate the serum exposome and, ultimately, to identify, validate and differentiate biomarkers of exposure and biomarkers of disease. Follow-up studies employ knowledge-driven designs to explore disease causality, prevention, diagnosis, prognosis and treatment.

  6. Benthic foraminiferal response to sedimentary disturbance in the Capbreton canyon (Bay of Biscay, NE Atlantic)

    NASA Astrophysics Data System (ADS)

    Duros, P.; Silva Jacinto, R.; Dennielou, B.; Schmidt, S.; Martinez Lamas, R.; Gautier, E.; Roubi, A.; Gayet, N.

    2017-02-01

    Living (Rose Bengal stained) and dead benthic foraminifera were investigated at 6 deep-sea sites sampled in the Capbreton canyon area (Bay of Biscay, France). Three sites were located along the canyon axis at 301 m, 983 m and 1478 m and 3 stations were positioned on adjacent terraces at 251 m, 894 m and 1454 m. Sedimentary features indicate that frequent sedimentary disturbances of different magnitudes occur along the Capbreton canyon axis and adjacent terraces. Such environmental conditions cause the presence of very particular benthic environments. Along the 6 studied sites, different foraminiferal responses to various sedimentary patterns are observed revealing the complexity of this canyon environment. Some sites (Gitan 3 (canyon axis), Gitan 5 (canyon axis) and Gitan 6 (terrace)) are characterized by moderate to low standing stocks and low diversity and are mainly dominated by pioneer taxa such as Fursenkoina brady, Reophax dentaliniformis and Technitella melo suggesting a recent response to turbidite deposits recorded at these sites. Others sites (Gitan 1 and Gitan 2) show extremely high standing stocks and are mainly dominated by the opportunistic Bolivina subaenariensis and Bulimina marginata. Such faunal characteristics belonging to a more advanced stage of ecosystem colonization indicates strongly food-enriched sediment but extremely unstable conditions. Moderate standing stocks and diverse assemblage composed of species such as Uvigerina mediterranea and U. peregrina has only been observed at the terrace site Gitan 4. More stable sedimentary conditions recorded at this terrace seem to be suitable to the development of a dense and diverse foraminiferal community. Numerous neritic allochtonous species were observed in the dead foraminiferal fauna. These allochthonous species mainly originate from shelf areas (<60 m).

  7. Long Term Trends in Subantarctic Nutrient Consumption: Evidence from Sedimentary and Diatom-Bound Nitrogen Isotopes

    NASA Astrophysics Data System (ADS)

    Bedsole, P.

    2014-12-01

    It has been proposed that the long term increase in Subantarctic opal export during glacial periods, centered around 1 Ma, is related to enhanced iron deposition and, potentially, carbon dioxide drawdown. New bulk sedimentary and diatom-bound nitrogen isotope records are used in combination with opal accumulation data from ODP Site 1090 to investigate controls on export production over the last 3 Ma. Sedimentary nitrogen content tracks opal during periods of high iron accumulation, especially after ~1 Ma. Bulk sedimentary nitrogen isotope trends are negatively correlated with sedimentary N-content and opal accumulation. This may be signal weaker nutrient consumption during times of high production, perhaps as a result of enhanced vertical nutrient supply. Alternatively, this variation in bulk, where high values occur in organic poor intervals, is consistent with other evidence for nitrogen isotopic alteration during periods of low export to the seafloor. The diatom-bound nitrogen isotope record does not have a clear relationship with opal or iron accumulation. A long term shift in the diatom-bound N isotope values is apparent, where the average diatom-bound δ15N from 0.5-1 Ma is 4.4 ‰, and from