DOI: 10.5194/hess-24-2105-2020
论文题名: Age and origin of leaf wax n-Alkanes in fluvial sediment-paleosol sequences and implications for paleoenvironmental reconstructions
作者: Bliedtner M. ; Von Suchodoletz H. ; Schäfer I. ; Welte C. ; Salazar G. ; Haas M. ; Dubois N. ; Zech R.
刊名: Hydrology and Earth System Sciences
ISSN: 1027-5606
出版年: 2020
卷: 24, 期: 4 起始页码: 2105
结束页码: 2120
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
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. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/162716
Appears in Collections: 气候变化与战略
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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 Jena, Löbdergraben 32, Jena, 07743, Germany
Recommended Citation:
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]. Hydrology and Earth System Sciences,2020-01-01,24(4)