气候变化领域集成服务门户(CCPortal): Age and origin of leaf wax n-Alkanes in fluvial sediment-paleosol sequences and implications for paleoenvironmental reconstructions

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DOI	10.5194/hess-24-2105-2020
	Age and origin of leaf wax n-Alkanes in fluvial sediment-paleosol sequences and implications for paleoenvironmental reconstructions
	Bliedtner M.; Von Suchodoletz H.; Schäfer I.; Welte C.; Salazar G.; Haas M.; Dubois N.; Zech R.
发表日期	2020
ISSN	1027-5606
起始页码	2105
结束页码	2120
卷号	24 期号:4
英文摘要	Leaf wax n-Alkanes are increasingly used for quantitative paleoenvironmental reconstructions. However, this is complicated in sediment archives with associated hydrological catchments since the stored n-Alkanes can have different ages and origins. 14C dating of the n-Alkanes yields independent age information for these proxies, allowing their correct paleoenvironmental interpretation. This also holds true for fluvial sediment-paleosol sequences (FSPSs) that integrate two different n-Alkane signals: (i) a catchment signal in fluvial sediments and (ii) an on-site signal from local biomass that increasingly dominates (paleo)soils with time. Therefore, the age and origin of n-Alkanes in FSPSs are complex: in fluvial sediment layers they can be pre-Aged and reworked when originating from eroded catchment soils or from organic-rich sediment rocks in the catchment. In (paleo) soils, besides an inherited contribution from the catchment, they were formed on-site by local biomass during pedogenesis. Depending on the different relative contributions from these sources, the n-Alkane signal from an FSPS shows variable age offsets between its formation and final deposition. During this study, we applied compound-class 14C dating to n-Alkanes from an FSPS along the upper Alazani in eastern Georgia. Our results show that preheating the n-Alkanes with 120 C for 8 h before 14C dating effectively removed the shorter chains (C25) that partly originate from n-Alkanes from Jurassic black clay shales in the upper catchment. The remaining petrogenic contributions on the longer chains (C25) were corrected for by using a constant correction factor that was based on the n-Alkane concentrations in a black clay shale sample from the upper catchment. Due to different degrees of pre-Aging and reworking, the corrected leaf wax n-Alkane ages still indicate relatively large age offsets between n-Alkane formation and deposition: while intensively developed (paleo)soils showed no age offsets due to a dominance of leaf wax n-Alkanes produced onsite, less intensively developed paleosols showed much larger age offsets due to larger proportions of inherited leaf wax n-Alkanes from the fluvial parent material. Accordingly, age offsets in nonpedogenic fluvial sediments were largest and strongly increased after 4 ka cal BP. The leaf wax n-Alkane homolog distribution from intensively developed (paleo)soils indicates a local dominance of grasses and herbs throughout the Holocene, which was most likely caused by anthropogenic activity. The leaf wax n-Alkanes from fluvial sediments show a dominance of deciduous trees and shrubs as well as grasses and herbs in different parts of the catchment between 8 and 5:6 ka cal BP. Since no older deciduous tree-or shrub-derived n-Alkanes were dated, this seems to confirm a delayed regional postglacial reforestation of parts of the catchment compared with western and central Europe. © 2020 Copernicus GmbH. All rights reserved.
语种	英语
scopus关键词	Catchments; Deposition; Hydrocarbons; Reforestation; Runoff; Sediments; Shale; Soils; Anthropogenic activity; Constant correction factor; Deciduous trees and shrubs; N-Alkane homologs; Organic-rich sediment; Paleoenvironmental reconstruction; Quantitative paleoenvironmental reconstruction; Relative contribution; Paraffins; alkane; biomass; catchment; fluvial deposit; Jurassic; paleoenvironment; paleosol; parent material; pedogenesis; reconstruction; reforestation; wax; Georgia; United States; Poaceae
来源期刊	Hydrology and Earth System Sciences
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/159426
作者单位	Bliedtner, M., Institute of Geography, Friedrich Schiller University of Jena, Löbdergraben 32, Jena, 07743, Germany, Institute of Geography and Oeschger Centre for Climate Change Research, University of Bern, Bern, 3012, Switzerland; Von Suchodoletz, H., Institute of Geography, University of Technology Dresden, Dresden, 01069, Germany, Institute of Geography, University of Leipzig, Leipzig, 04103, Germany; Schäfer, I., Institute of Geography and Oeschger Centre for Climate Change Research, University of Bern, Bern, 3012, Switzerland; Welte, C., Laboratory of Ion Beam Physics, ETH Zurich, Zurich, 8093, Switzerland; Salazar, G., Department of Chemistry and Biochemistry and Oeschger Centre for Climate Change Research, University of Bern, Bern, 3012, Switzerland; Haas, M., Department of Surface Waters Research and Management, Eawag, Dübendorf, 8600, Switzerland; Dubois, N., Department of Earth Sciences, ETH Zürich, Zurich, 8006, Switzerland; Zech, R., Institute of Geography, Friedrich Schiller University of J...
推荐引用方式 GB/T 7714	Bliedtner M.,Von Suchodoletz H.,Schäfer I.,et al. Age and origin of leaf wax n-Alkanes in fluvial sediment-paleosol sequences and implications for paleoenvironmental reconstructions[J],2020,24(4).
APA	Bliedtner M..,Von Suchodoletz H..,Schäfer I..,Welte C..,Salazar G..,...&Zech R..(2020).Age and origin of leaf wax n-Alkanes in fluvial sediment-paleosol sequences and implications for paleoenvironmental reconstructions.Hydrology and Earth System Sciences,24(4).
MLA	Bliedtner M.,et al."Age and origin of leaf wax n-Alkanes in fluvial sediment-paleosol sequences and implications for paleoenvironmental reconstructions".Hydrology and Earth System Sciences 24.4(2020).