scholarly journals Late Quaternary climate and environmental reconstruction based on leaf wax analyses in the loess sequence of Möhlin, Switzerland

2017 ◽  
Vol 66 (2) ◽  
pp. 91-100
Author(s):  
Lorenz Wüthrich ◽  
Marcel Bliedtner ◽  
Imke Kathrin Schäfer ◽  
Jana Zech ◽  
Fatemeh Shajari ◽  
...  
Keyword(s):  
Radiocarbon Dating ◽  
Late Quaternary ◽  
Marine Isotope Stage ◽  
Environmental Reconstruction ◽  
Moisture Source ◽  
Leaf Wax ◽  
Mis 3 ◽  
Quaternary Climate ◽  
Leaf Waxes ◽  
Long Chain

Abstract. We present the results of leaf wax analyses (long-chain n-alkanes) from the 6.8 m deep loess sequence of Möhlin, Switzerland, spanning the last  ∼  70 kyr. Leaf waxes are well preserved and occur in sufficient amounts only down to 0.4 m and below 1.8 m depth, so no paleoenvironmental reconstructions can be done for marine isotope stage (MIS) 2. Compound-specific δ2Hwax analyses yielded similar values for late MIS 3 compared to the uppermost samples, indicating that various effects (e.g., more negative values due to lower temperatures, more positive values due to an enriched moisture source) cancel each other out. A pronounced  ∼  30 ‰ shift towards more negative values probably reflects more humid conditions before  ∼  32 ka. Radiocarbon dating of the n-alkanes corroborates the stratigraphic integrity of leaf waxes and their potential for dating loess–paleosol sequences (LPS) back to  ∼  30 ka.

scholarly journals Distinguishing between old and modern permafrost sources in the northeast Siberian land–shelf system with compound-specific <i>δ</i><sup>2</sup>H analysis

2017 ◽  
Vol 11 (4) ◽  
pp. 1879-1895 ◽  
Author(s):  
Jorien E. Vonk ◽  
Tommaso Tesi ◽  
Lisa Bröder ◽  
Henry Holmstrand ◽  
Gustaf Hugelius ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Quantitative Measure ◽  
The Arctic ◽  
Near Surface ◽  
Leaf Wax ◽  
Leaf Waxes ◽  
Shelf Slope ◽  
Siberian Arctic ◽  
Long Chain ◽  
Ice Complex

Abstract. Pleistocene ice complex permafrost deposits contain roughly a quarter of the organic carbon (OC) stored in permafrost (PF) terrain. When permafrost thaws, its OC is remobilized into the (aquatic) environment where it is available for degradation, transport or burial. Aquatic or coastal environments contain sedimentary reservoirs that can serve as archives of past climatic change. As permafrost thaw is increasing throughout the Arctic, these reservoirs are important locations to assess the fate of remobilized permafrost OC.We here present compound-specific deuterium (δ2H) analysis on leaf waxes as a tool to distinguish between OC released from thawing Pleistocene permafrost (ice complex deposits; ICD) and from thawing Holocene permafrost (from near-surface soils). Bulk geochemistry (%OC; δ13C; %total nitrogen, TN) was analyzed as well as the concentrations and δ2H signatures of long-chain n-alkanes (C21 to C33) and mid- to long-chain n-alkanoic acids (C16 to C30) extracted from both ICD-PF samples (n =  9) and modern vegetation and O-horizon (topsoil-PF) samples (n =  9) from across the northeast Siberian Arctic. Results show that these topsoil-PF samples have higher %OC, higher OC ∕ TN values and more depleted δ13C-OC values than ICD-PF samples, suggesting that these former samples trace a fresher soil and/or vegetation source. Whereas the two investigated sources differ on the bulk geochemical level, they are, however, virtually indistinguishable when using leaf wax concentrations and ratios. However, on the molecular isotope level, leaf wax biomarker δ2H values are statistically different between topsoil PF and ICD PF. For example, the mean δ2H value of C29 n-alkane was −246 ± 13 ‰ (mean ± SD) for topsoil PF and −280 ± 12 ‰ for ICD PF. With a dynamic isotopic range (difference between two sources) of 34 to 50 ‰; the isotopic fingerprints of individual, abundant, biomarker molecules from leaf waxes can thus serve as endmembers to distinguish between these two sources. We tested this molecular δ2H tracer along with another source-distinguishing approach, dual-carbon (δ13C–Δ14C) isotope composition of bulk OC, for a surface sediment transect in the Laptev Sea. Results show that general offshore patterns along the shelf-slope transect are similar, but the source apportionment between the approaches vary, which may highlight the advantages of either. This study indicates that the application of δ2H leaf wax values has potential to serve as a complementary quantitative measure of the source and differential fate of OC thawed out from different permafrost compartments.

scholarly journals Distinguishing between old and modern permafrost sources with compound-specific δ<sup>2</sup>H analysis

2017 ◽  
Author(s):  
Jorien E. Vonk ◽  
Tommaso Tesi ◽  
Lisa Bröder ◽  
Henry Holmstrand ◽  
Gustaf Hugelius ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Quantitative Measure ◽  
The Arctic ◽  
Near Surface ◽  
Leaf Wax ◽  
Leaf Waxes ◽  
Shelf Slope ◽  
Alkanoic Acids ◽  
Long Chain ◽  
Ice Complex

Abstract. Pleistocene ice complex permafrost deposits contain roughly a quarter of the organic carbon (OC) stored in permafrost terrain. When permafrost thaws, its OC is remobilized into the (aquatic) environment where it is available for degradation, transport or burial. Aquatic or coastal environments contain sedimentary reservoirs that can serve as archives of past climatic change. As permafrost thaw is increasing throughout the Arctic, these reservoirs are important locations to assess the fate of remobilized permafrost OC. We here present compound-specific deuterium (δ2H) analysis on leaf waxes as a tool to distinguish between OC released from thawing Pleistocene permafrost (Ice Complex Deposits; ICD) and from thawing Holocene permafrost (from near-surface soils). Bulk geochemistry (%OC, δ13C, %total nitrogen; TN) was analyzed as well as the concentrations and δ2H signatures of long-chain n-alkanes (C21 to C33) and mid/long-chain n-alkanoic acids (C16 to C30) extracted from both ICD-PF samples (n = 9) and modern vegetation/O-horizon (Topsoil-PF) samples (n = 9) from across the northeast Siberian Arctic. Results show that these Topsoil-PF samples have higher %OC, higher OC/TN values, and more depleted δ13C-OC values than ICD-PF samples, suggesting that these former samples trace a fresher soil and/or vegetation source. Median concentrations of high-molecular weight n-alkanes (sum of C25-C27-C29-C31) were 210 ± 350 µg/gOC (median ± IQR) for Topsoil-PF and 250 ± 81 µg/gOC for ICD-PF samples. Long-chain n-alkanoic acids (sum of C22-C24-C26-C28) were more abundant than long-chain n-alkanes, both in Topsoil-PF samples (4700 ± 3400 µg/gOC) and in ICD samples (6630 ± 3500 µg/gOC). Whereas the two investigated sources differ on the bulk geochemical level, they are, however, virtually indistinguishable when using leaf wax concentrations and ratios. However, on the molecular-isotope level, leaf wax biomarker δ2H values are statistically different between Topsoil-PF and ICD-PF. The mean δ2H value of C29 n-alkane was −246 ± 13 ‰ (mean ± stdev) for Topsoil-PF and −280 ± 12 ‰ for ICD-PF, whereas the C31 n-alkane was −247 ± 23 ‰ for Topsoil-PF and −297 ± 15 ‰ for ICD-PF. The C28 n-alkanoic acid δ2H value was −220 ± 15 ‰ for Topsoil-PF and −267 ± 16 ‰ for ICD-PF. With a dynamic isotopic range (difference between two sources) of 34 to 50 ‰, the isotopic fingerprints of individual, abundant, biomarker molecules from leaf waxes can thus serve as end-members to distinguish between these two sources. We tested this molecular δ2H tracer along with another source-distinguishing approach, dual-carbon (δ13C-δ14C) isotope composition of bulk OC, for a surface sediment transect in the Laptev Sea. Results show that general offshore patterns along the shelf-slope transect are similar, but the source apportionment between the approaches vary, which may highlight the advantages of either. The δ2H molecular approach has the advantage that it circumvents uncertainties related to a marine end-member, yet the δ13C-δ14C approach has the advantage that it represents the bulk OC fraction thereby avoiding issues related to the molecular-bulk upscaling challenge. This study indicates that the application of δ2H leaf wax values has potential to serve as a complementary quantitative measure of the source and differential fate of OC thawed out from different permafrost compartments.

scholarly journals A Late Quaternary climate record based on long chain diol proxies from the Chilean margin

2018 ◽  
Author(s):  
Marijke W. de Bar ◽  
Dave J. Stolwijk ◽  
Jerry F. McManus ◽  
Jaap S. Sinninghe Damste ◽  
Stefan Schouten
Keyword(s):  
Late Quaternary ◽  
Phytoplankton Production ◽  
Last Interglacial ◽  
Quaternary Climate ◽  
Before And After ◽  
Primary Focus ◽  
Multiple Species ◽  
Species Productivity ◽  
Mis 5 ◽  
Long Chain

Abstract. The primary focus of this study is to test the applicability of different paleoenvironmental proxies based on long chain diols, i.e., the LDI as proxy for past SST, the Diol Index as indicator of past upwelling conditions and the NDI as quantitative proxy for nitrate and phosphate concentrations in seawater. The proxies were analyzed in marine sediments recovered at ODP Site 1234, located within the Peru-Chile upwelling system, with a ~ 2 kyr resolution, covering the last 150 kyrs, i.e., encompassing several glacial and interglacial periods. We also generated TEXH86 and UK´37 temperature and planktonic δ18O records, as well as TOC and accumulation rates (ARs) of TOC and lipid biomarkers (i.e., C37 alkenones, GDGTs, dinosterol and loliolide) to reconstruct past phytoplankton production. The LDI-derived SST record co-varies with TEXH86- and UK´37-derived SST records as well as with the planktonic δ18O record, implying that the LDI reflects past SST variations at this site. TOC and phytoplankton AR records indicate increased export production during the Last Interglacial (MIS 5), simultaneous with a peak in the abundance of preserved Chaetoceros diatoms, suggesting intensified upwelling during this period. The Diol Index is relatively low during the upwelling period, but peaks before and after this period, suggesting that Proboscia diatoms were more dominant before and after the period of upwelling. The NDI reveals the same variations as the Diol Index suggesting that the input of nitrate and phosphate was minimal during upwelling, which is unrealistic. We suggest that the Diol Index should perhaps be considered as an indicator for Proboscia (multiple species) productivity instead of upwelling per se, whereas the NDI likely reflects Proboscia alata productivity, and might therefore not be suitable as a more general paleonutrient proxy.

scholarly journals A Late Quaternary climate record based on long-chain diol proxies from the Chilean margin

2018 ◽  
Vol 14 (11) ◽  
pp. 1783-1803 ◽  
Author(s):  
Marijke W. de Bar ◽  
Dave J. Stolwijk ◽  
Jerry F. McManus ◽  
Jaap S. Sinninghe Damsté ◽  
Stefan Schouten
Keyword(s):  
Late Quaternary ◽  
Nutrient Concentrations ◽  
Phytoplankton Production ◽  
Accumulation Rates ◽  
Last Interglacial ◽  
Climate Record ◽  
Quaternary Climate ◽  
Before And After ◽  
Mis 5 ◽  
Long Chain

Abstract. In this study we have applied different indices based on long-chain diols, i.e., the long-chain diol index (LDI) as a proxy for past SST, the diol index as an indicator of past upwelling conditions, and the nutrient diol index (NDI) as a proxy for nitrate and phosphate concentrations in seawater. The proxies were analyzed in marine sediments recovered at ODP Site 1234, located within the Peru–Chile upwelling system, with a ∼2 kyr resolution covering the last 150 kyr. We also generated TEX86H and U37K′ temperature and planktonic δ18O records, as well as total organic carbon (TOC) and accumulation rates (ARs) of TOC and lipid biomarkers (i.e., C37 alkenones, GDGTs, dinosterol, and loliolide) to reconstruct past phytoplankton production. The LDI-derived SST record covaries with TEX86H- and U37K′-derived SST records as well as with the planktonic δ18O record, implying that the LDI reflects past SST variations at this site. TOC and phytoplankton AR records indicate increased export production during the last interglacial (MIS 5), simultaneous with a peak in the abundance of preserved Chaetoceros diatoms, suggesting intensified upwelling during this period. The diol index is relatively low during the upwelling period, but peaks before and after this period, suggesting that Proboscia diatoms were more abundant before and after the period of upwelling. The NDI reveals the same trends as the diol index, suggesting that the input of nitrate and phosphate was minimal during upwelling, which is unrealistic. We suggest that the diol index and NDI should perhaps be considered as indicators for Proboscia productivity instead of upwelling conditions or nutrient concentrations.

scholarly journals Radiocarbon Dating of Leaf Waxes in the Loess-Paleosol Sequence Kurtak, Central Siberia

Radiocarbon ◽  
2017 ◽  
Vol 59 (1) ◽  
pp. 165-176 ◽  
Author(s):  
Mischa Haas ◽  
Marcel Bliedtner ◽  
Igor Borodynkin ◽  
Gary Salazar ◽  
Sönke Szidat ◽  
...  
Keyword(s):  
Environmental Changes ◽  
Gas Chromatograph ◽  
Central Siberia ◽  
Mis 3 ◽  
Fraction Collector ◽  
Quaternary Climate ◽  
Leaf Waxes ◽  
Infrared Stimulated Luminescence ◽  
Good Agreement ◽  
The Last Glacial

AbstractLoess-paleosol sequences (LPS) are valuable archives for Quaternary climate and environmental changes. So far, LPS are generally dated using luminescence, with ~10% uncertainties, or radiocarbon (14C) analyses in the rare cases that charcoal or macrofossils are available. For this study, we determined 14C ages of leaf waxes (long-chain n-alkanes) extracted from the LPS Kurtak in central Siberia. 14C ages range from 16.7 to 22.9 ka cal BP for the last glacial loess and from 24.5 to 35.3 ka cal BP for the paleosol correlated with marine isotope stage (MIS) 3. Overall, this is in good agreement with independent age control based on stratigraphy, infrared stimulated luminescence (IRSL) dating, and 14C dating on charcoal and macrofossils. However, strong cryoturbation and solifluction seem to have affected the MIS 3 paleosol early during MIS 2. Our results corroborate the stratigraphic integrity of leaf waxes, and highlight their potential for dating LPS back to ~35–40 ka BP. Compared to compound-specific 14C analyses, which are very time-consuming and require specialized instrumentation (gas chromatograph with fraction collector), 14C dating of leaf waxes as a whole compound class is relatively quick and straightforward and warrants further investigation as a chronological tool.

Compositions and isotopic differences of iso- and anteiso-alkanes in black mangroves (Avicennia germinans) across a salinity gradient in a subtropical estuary

2016 ◽  
Vol 13 (4) ◽  
pp. 623 ◽  
Author(s):  
Ding He ◽  
Bernd R. T. Simoneit ◽  
Blanca Jara ◽  
Rudolf Jaffé
Keyword(s):  
Environmental Stress ◽  
Salinity Gradient ◽  
Carbon Number ◽  
Dry Weight ◽  
Avicennia Germinans ◽  
Stress Factors ◽  
Chemical Tracers ◽  
Leaf Wax ◽  
Leaf Waxes ◽  
Long Chain

Environmental contextMangroves dominate at the interface between land and sea, especially along tropical and subtropical coasts. To gain a better understanding of how mangroves respond to various environmental stress factors, we investigated the use of monomethylalkanes as potential chemical tracers for black mangroves. The application of these chemical tracers could elucidate how black mangroves respond to environmental stress such as sea level rise in mixed mangrove environments. AbstractA series of iso- and anteiso-monomethylalkanes (MMAs) with carbon numbers from C23 to C35 and C14 to C34 respectively were detected in Avicennia germinans. These compounds were present in varying amounts up to 54.1, 1.0 and 3.4µg g–1 dry weight in the leaves, bark and the crustose lichens attached to the bark of A. germinans respectively. These MMAs were not detected in the leaf waxes of Rhizophora mangle and Laguncularia racemosa, but were detected in significantly lower abundances (2–6% of that in A. germinans leaf wax) in the bark and lichen of R. mangle. Significant odd-carbon number distributions and even-carbon number distributions were observed for long chain (C ≥ 25) iso- (maximising at C31) and anteiso-MMAs (maximising at C32) respectively in A. germinans leaf wax. However, no obvious carbon number preferences were detected for bark and lichen. The long chain (LC) iso- and anteiso-MMAs in A. germinans leaf waxes were found to be enriched in 13C by 0.3–4.3 and 0.7–4.2 per mille (‰) compared to the n-alkanes with the same carbon numbers respectively across the salinity gradient of 19.7–32.0 practical salinity units (psu). In comparison, the LC iso- and anteiso-MMAs were found to be more depleted in D by 6.1–55.1 and 7.3–57.0 ‰ compared to the n-alkanes with same carbon numbers respectively. The results imply that A. germinans could be another important source of iso- and anteiso-alkanes in sediments and soils, and that these compounds could potentially be used as biomarkers for this species in mixed mangrove environments.

scholarly journals Leaf wax <i>n</i>-alkanes in modern plants and topsoils from eastern Georgia (Caucasus) – implications for reconstructing regional paleovegetation

2018 ◽  
Vol 15 (12) ◽  
pp. 3927-3936 ◽  
Author(s):  
Marcel Bliedtner ◽  
Imke K. Schäfer ◽  
Roland Zech ◽  
Hans von Suchodoletz
Keyword(s):  
Regional Scale ◽  
Chemical Degradation ◽  
Terrestrial Plants ◽  
Tropical Regions ◽  
Caucasus Region ◽  
Leaf Wax ◽  
Leaf Waxes ◽  
Southern Caucasus ◽  
Physical And Chemical ◽  
Long Chain

Abstract. Long-chain n-alkanes originate from leaf waxes of higher terrestrial plants, they are relatively resistant against physical and chemical degradation and are preserved in sediment archives for at least millennial timescales. Since their homologue patterns discriminate between vegetation forms, they were increasingly used for paleovegetation reconstructions during the last years. However, before any robust interpretation of the long-chain n-alkane patterns in sediment archives, reference samples from modern vegetation and topsoil material should be investigated at a regional scale. Apart from some temperate and tropical regions, such systematic regional studies on modern plant and topsoil material are still largely lacking.To test the potential of leaf wax-derived n-alkane patterns for paleoenvironmental studies in the semi-humid to semi-arid central southern Caucasus region, we investigated the influence of different vegetation forms on the leaf wax n-alkane signal in modern plants and topsoil material (0–5 cm) from eastern Georgia. We sampled (i) sites with grassland/herbs that included steppe, cultivated grassland and meadows, and (ii) sites that are dominated by deciduous hornbeam forests.The results show that long-chain n-alkanes originate from leaf waxes of higher terrestrial plants and that their homologue pattern allow to discriminate between different vegetation forms: n-Alkanes derived from sites with grassland/herbs are mainly dominated by C31, while n-alkanes derived from sites with deciduous trees/shrubs show high abundances of C29. Thus, long-chain n-alkanes have a great potential when used for regional paleovegetation reconstructions. Moreover, the n-alkane distributions of the topsoils do not show correlations with mean annual temperatures and precipitation along the investigated transect. As degradation of organic matter can affect the leaf wax n-alkane distribution, we further present an updated end-member model that includes our results, accounts for degradation effects and enables semi-quantitative reconstructions of past vegetation changes in the central southern Caucasus region.

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