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| Titel |
Sedimentary profile from oxbow lake as an archive for past productivity and vegetation changes: a case study from Ganges basin, West Bengal, India |
| VerfasserIn |
Subhadeep Rakshit, Sambit Ghosh, Prasanta Sanyal, Anoop Ambili |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250104245
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| Publikation (Nr.) |
 EGU/EGU2015-3666.pdf |
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| Zusammenfassung |
| Isotope (δ13CSOM) and biomarker (lipid n-alkane) investigations has been carried out on
three sedimentary profiles (ca. 1.8 m depth) collected from Mohanpur, West Bengal, India
with the aim of reconstructing paleovegetational and paleoproductivity changes. Satellite
images reveal that the investigated sediments has been deposited in an oxbow lake setting of
the river Ganges. The correlation of the three sedimentary profiles has been achieved using
lithological and isotopic (δ13CSOM) marker layers. The total organic carbon (TOC)
content of the profile ranges from 0.9% to 0.1%. The isotopic analysis (δ13CSOM)
shows values mostly fluctuating between -19.2‰ to -22‰ with a rapid excursions
(~5) showing enriched δ13CSOMvalue (-14.2) observed at ca. 1.5 m depth. The
biomarker studies of the profile reveals dominant preferences in short carbon chain
(C14, C16, C18, C20) with a little preferences for higher chain (C29, C31, C33).
Interestingly, n-alkanes at 1.5 m depth shows very high concentration in short chain
n-alkanes. Since the lower chain n-alkane represents aquatic vegetation/productivity and
higher chain indicates the terrestrial contribution, the data from the investigated
sedimentary profile shows contribution mostly from aquatic vegetation with a little
contribution from terrestrial plants. This inference has been further corroborated by
δ13CSOMvalues (-19.2‰ to -22) of the sedimentary profile typical of mixed aquatic and
terrestrial vegetation. Additionally, the enriched δ13CSOMvalue (-14.2) coupled with
very high concentration of short chain n-alkanes at 1.5 m depth reveals intense
lake eutrophication. The development of rigorous chronology and high resolution
data set of additional analytical parameters (e.g., C/N, δ15N) will provide crucial
paleoclimate data set from this unexplored setting of Indian summer monsoon domain. |
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