Identification of pastoral sites using stable nitrogen and carbon isotopes from bulk sediment samples: a case study in modern and archaeological pastoral settlements in Kenya

2008 ◽  
Vol 35 (4) ◽  
pp. 983-990 ◽  
Author(s):  
Ruth Shahack-Gross ◽  
Allison Simons ◽  
Stanley H. Ambrose
Keyword(s):  
Carbon Isotopes ◽  
Bulk Sediment ◽  
Sediment Samples

scholarly journals Mineralogical and Geochemical Signatures of Metalliferous Sediments in Wocan-1 and Wocan-2 Hydrothermal Sites on the Carlsberg Ridge, Indian Ocean

Minerals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 26 ◽  
Author(s):  
Samuel Olatunde Popoola ◽  
Xiqiu Han ◽  
Yejian Wang ◽  
Zhongyan Qiu ◽  
Ying Ye ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Volcanic Glass ◽  
Mineral Chemistry ◽  
Hydrothermal Systems ◽  
Bulk Sediment ◽  
Sediment Samples ◽  
Metalliferous Sediments ◽  
Metalliferous Sediment ◽  
Carlsberg Ridge ◽  
Hydrothermal Environments

In this paper, we conduct a comparative study on the mineralogy and geochemistry of metalliferous sediment collected near the active hydrothermal site (Wocan-1) and inactive hydrothermal site (Wocan-2) from Wocan Hydrothermal Field, on the Carlsberg Ridge (CR), northwest Indian Ocean. We aim to understand the spatial variations in the primary and post-depositional conditions and the intensity of hydrothermal circulations in the Wocan hydrothermal systems. Sediment samples were collected from six stations which includes TVG-07, TVG-08 (Wocan-1), TVG-05, TVG-10 (Wocan-2), TVG-12 and TVG-13 (ridge flanks). The mineralogical investigations show that sediment samples from Wocan-1 and Wocan-2 are composed of chalcopyrite, pyrite, sphalerite, barite, gypsum, amorphous silica, altered volcanic glass, Fe-oxides, and hydroxides. The ridge flank sediments are dominated by biogenic calcite and foraminifera assemblages. The bulk sediment samples of Wocan-1 have an elevated Fe/Mn ratio (up to ~1545), with lower U contents (<7.4 ppm) and U/Fe ratio (<~1.8 × 10−5). The sulfide separates (chalcopyrite, pyrite, and sphalerite) are enriched in Se, Co, As, Sb, and Pb. The calculated sphalerite precipitation temperature (Sph.PT) yields ~278 °C. The sulfur isotope (δ34S) analysis returned a light value of 3.0–3.6‰. The bulk sediment samples of Wocan-2 have a lower Fe/Mn ratio (<~523), with high U contents (up to 19.6 ppm) and U/Fe ratio (up to ~6.2 × 10−5). The sulfide separates are enriched in Zn, Cu, Tl, and Sn. The calculated Sph.PT is ~233 °C. The δ34S returned significant values of 4.1–4.3‰ and 6.4–8.7‰ in stations TVG-10 and TVG-05, respectively. The geochemical signatures (e.g., Fe/Mn and U/Fe ratio, mineral chemistry of sulfides separates, and S-isotopes and Sph.PT) suggest that sediment samples from Wocan-1 are located near intermediate–high temperature hydrothermal discharge environments. Additionally, relatively low δ34S values exhibit a lower proportion (less than 20%) of seawater-derived components. The geochemical signatures suggest that sediment samples from Wocan-2 has undergone moderate–extensive oxidation and secondary alterations by seawater in a low–intermediate temperature hydrothermal environments. Additionally, the significant δ34S values of station TVG-05 exhibit a higher estimated proportion (up to 41%) of seawater-derived components. Our results showed pervasive hydrothermal contributions into station TVG-08 relative to TVG-07, it further showed the increased process of seafloor weathering at TVG-05 relative to TVG-10.

scholarly journals Development of an improved ramped pyrolysis method for radiocarbon dating and application to Antarctic sediments

2021 ◽  
Author(s):  
◽  
Simon Reeve
Keyword(s):  
Last Glacial Maximum ◽  
Radiocarbon Dating ◽  
Glacial Maximum ◽  
Bulk Sediment ◽  
Sediment Samples ◽  
Last Glacial ◽  
Vacuum Line ◽  
Ramped Pyrolysis ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p>Archives of the retreat history of the Antarctic Ice Sheet since the Last Glacial Maximum (~20,000 years ago) are preserved in marine sediment cores from around the margins of Antarctica, but accurate dating methods remain elusive in many areas. Radiocarbon dating of key lithofacies transitions indicative of grounding-line retreat is problematic due to pervasive reworking issues in glacimarine sediments. Bulk sediment material can be radiocarbon dated but yields ages which are not indicative of the time of sedimentation due to the presence of reworked carbon material from pre-Last Glacial Maximum times. Consequently, development of methods to date only the autochthonous carbon component of these sediments are required to date the retreat of the Last Glacial Maximum ice sheet in Antarctica. A new radiocarbon dating capability has been developed at Rafter Radiocarbon Laboratory (RRL), National Isotope Centre, GNS Science, Lower Hutt, in the course of this study. This has entailed designing, building and testing a ramped pyrolysis (RP) system, in which sedimentary material is heated from ambient to ~1000oC in the absence of oxygen (pyrolysed), with the carbon liberated during pyrolysis being combined with oxygen at a temperature of ~800oC to produce CO2. The amount of CO2 produced is measured by a gas analyser and the CO2 is captured in a vacuum line. The method exploits the thermochemical behaviour of degraded organic carbon. Organic carbon which has been least degraded with time breaks down earliest under pyrolysis, so CO2 captured from this fraction most closely approximates the time of deposition of the sediment. CO2 captured at higher temperatures represents more degraded carbon-containing fractions and yields older ages. The RP system includes a gas delivery system to deliver ultra-high purity He (carrier gas) and O2, a furnace system in which to pyrolyse sample material and oxidise the liberated carbon, a CO2 detection system to measure the CO2 produced and a vacuum line system to enable simultaneous collection and processing of CO2. The RRL system was based on the design developed by Dr Brad Rosenheim (University of South Florida (USF)), the originator of the first RP system at the National Ocean Sciences AMS Facility (Woods Hole Oceanographic Institution, Massachusetts, USA), who also provided guidance in this thesis. As part of the study, a visit to USF was undertaken, with sediment samples from Crystal Sound, Antarctic Peninsula being processed in the USF RP system. CO2 collected from RP processing was radiocarbon dated at RRL. The scope of this thesis was to develop and build the RRL RP system, and numerous tests were conducted during this process and are presented in this thesis. As part of this, sediment samples from Crystal Sound were also processed on the RRL RP system, and an interlaboratory comparison was conducted on the same materials processed independently through both the USF and RRL RP systems. In the development and testing of the RRL system, numerous issues were identified and a set of operating protocols developed. Due to time constraints and the scope of this thesis, interlaboratory comparisons were limited in number, but initial results show good reproducibility, and that ramped pyrolysis captured significantly younger carbon populations in both the USF and RRL RP systems than methods using bulk sediment dating alone. Within uncertainties, the ages of the youngest and oldest splits from RP processing of the same material on both systems were indistinguishable.</p>

Using FTIRS as pre-screening method for detection of microplastic in bulk sediment samples

2019 ◽  
Vol 689 ◽  
pp. 341-346 ◽  
Author(s):  
Annette Hahn ◽  
Gunnar Gerdts ◽  
Carolin Völker ◽  
Vincent Niebühr
Keyword(s):  
Screening Method ◽  
Bulk Sediment ◽  
Sediment Samples

scholarly journals A continuous 250,000yr record of oxygen and carbon isotopes in ostracode and bulk-sediment carbonate from Bear Lake, Utah-Idaho

2006 ◽  
Vol 25 (17-18) ◽  
pp. 2258-2270 ◽  
Author(s):  
Jordon Bright ◽  
Darrell S. Kaufman ◽  
Richard M. Forester ◽  
Walter E. Dean
Keyword(s):  
Carbon Isotopes ◽  
Bulk Sediment ◽  
Oxygen And Carbon Isotopes ◽  
Bear Lake

scholarly journals Sediment as a Potential Pool for Lipophilic Marine Phycotoxins with the Case Study of Daya Bay of China

Marine Drugs ◽  
2019 ◽  
Vol 17 (11) ◽  
pp. 623 ◽  
Author(s):  
Yang Liu ◽  
Peng Zhang ◽  
Sen Du ◽  
Zhuoru Lin ◽  
Yanyan Zhou ◽  
...  
Keyword(s):  
Marine Sediments ◽  
Environmental Pollutants ◽  
Sediment Surface ◽  
Daya Bay ◽  
Toxic Substances ◽  
Sediment Samples ◽  
Tropical Area ◽  
Different Seasons ◽  
Sampling Times

Marine sediments can reserve many environmental pollutants. Lipophilic marine phycotoxins (LMPs) are natural toxic substances widespread in the marine environment; however, evidence of their existence in sediment is scarce. In the present study, in order to explore the occurrence and distribution characteristics of LMPs in sediment, surface sediment samples collected from a tropical area of Daya Bay (DYB) at different seasons, were analyzed using liquid chromatography with tandem mass spectrometry (LC-MS/MS). According to the results, up to six toxin compounds were detected in sediment samples from DYB, OA and DTX1 had the highest levels, followed by PTX2, homo-YTX, AZA2, and GYM. Although AZA2 and GYM were found in most of the sediment, OA, DTX1, homo-YTX, and PTX2 were the predominant toxin compounds, and PTX2 was the most ubiquitous toxin in sediment. The spatial distribution of LMP components in the sediment fluctuated with sampling times, partially according to the physical–chemical parameters of the sediment. There are likely several sources for LMPs existing in surface sediments, but it is difficult to determine contributions of a specific toxin-source in the sediment. Therefore, marine sediments may be a toxin reservoir for LMPs accumulation in benthic organisms via food chains.

scholarly journals Systematic Age Gap of Radiocarbon Dates between Organic Bulk Sediment Samples and Fossil Samples of Animal and Plant in Holocene Core Sediments and Their Causes

2016 ◽  
Vol 125 (2) ◽  
pp. 243-256 ◽  
Author(s):  
Daisuke ISHIMURA ◽  
Takahiro MIYAUCHI ◽  
Ryosuke HAYASE ◽  
Keiichi OHARA ◽  
Tsuyoshi YAMAICHI
Keyword(s):  
Bulk Sediment ◽  
Radiocarbon Dates ◽  
Sediment Samples ◽  
Core Sediments ◽  
Age Gap

scholarly journals 14C AMS Dating of Icelandic Lake Sediments

Radiocarbon ◽  
1997 ◽  
Vol 40 (2) ◽  
pp. 865-872 ◽  
Author(s):  
Árný E. Sveinbjörnsdóttir ◽  
Jan Heinemeier ◽  
Peter Kristensen ◽  
Niels Rud ◽  
Áslaug Geirsdóttir ◽  
...  
Keyword(s):  
Sample Pretreatment ◽  
Bulk Sediment ◽  
Organic Fraction ◽  
Sediment Samples ◽  
Age Diversity ◽  
Plant Remains ◽  
Ams Dating ◽  
Lowermost Part ◽  
Reservoir Age ◽  
Depth Curve

We report an age-depth profile for the sediments of the Lake Hesrvatn, southern Iceland, based on 14C analyses of the organic fraction of bulk sediment samples, molluscs and foraminifera. Our age-depth curve is supported by the occurrence of the well-dated Vedde ash in the lowermost part of the sediments. Comparison of foraminifera dates with the age of the Vedde ash indicates a reservoir age of ca. 400 yr. The results suggest that the sediments at Hestvatn accumulated in a marine environment until ca. 8700 bp and thereafter in freshwater.Owing to the lack of terrestrial macrofossils and the low concentration of molluscs and foraminifera, we were forced to attempt to date most of the core with the organic fraction of the bulk sediment samples. We found, however, that this fraction is not homogeneous in density or 14C age. We believe that during sample pretreatment we managed to isolate a light organic fraction, which closely represents the true age of the sediment, whereas the denser fraction yields ages that are too high. This age diversity may to some extent be explained by the large drainage area of the lake, from which plant remains of different ages may have been washed into the lake.

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