A comparison of biomarker records of northeast African vegetation from lacustrine and marine sediments (ca. 3.40 Ma)

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doi: 10.1016/j.orggeochem.2007.06.008
Author(s): Feakins, Sarah J.; Eglinton, Timothy I.; deMenocal, Peter B.
Author Affiliation(s): Primary:
Lamont-Doherty Earth Observatory, Palisades, NY, United States
Woods Hole Oceanographic Institution, United States
Volume Title: Organic Geochemistry
Source: Organic Geochemistry, 38(10), p.1607-1624. Publisher: Elsevier, International. ISSN: 0146-6380
Note: In English. Based on Publisher-supplied data
Summary: Integrated terrestrial and marine records of northeast African vegetation are needed to provide long high resolution records of environmental variability with established links to specific terrestrial environments. In this study, we compare records of terrestrial vegetation preserved in marine sediments in the Gulf of Aden [Deep Sea Drilling Project (DSDP) Site 231] and an outcrop of lacustrine sediments in the Turkana Basin, Kenya, part of the East African Rift System. We analyzed higher plant biomarkers in sediments from both deposits of known equivalent age, corresponding to a ca. 50-100 ka humid interval prior to the β-Tulu Bor eruption ca. 3.40 Ma, when the Lokochot Lake occupied part of the Turkana Basin. Molecular abundance distributions indicate that long chain n-alkanoic acids in marine sediments are the most reliable proxy for terrestrial vegetation (Carbon Preference Index, CPI=4.5), with more cautious interpretation needed for n-alkanes and lacustrine archives. Marine sediments record carbon isotopic variability in terrestrial biomarkers of 2-3 ppm, roughly equivalent to 20% variability in the C3/C4 vegetation contribution. The proportion of C4 vegetation apparently increased at times of low terrigenous dust input. Terrestrial sediments reveal much larger (2-10 ppm) shifts in n-alkanoic acid δ13C values. However, molecular abundance and isotopic composition suggest that microbial sources may also contribute fatty acids, contaminating the lacustrine sedimentary record of terrestrial vegetation. Abstract Copyright (2007) Elsevier, B.V.
Year of Publication: 2007
Research Program: DSDP Deep Sea Drilling Project
Key Words: 02 Geochemistry; 06 Petrology, Sedimentary; Africa; Aliphatic hydrocarbons; Alkanes; Arabian Sea; Biomarkers; C-13/C-12; Carbon; DSDP Site 231; Deep Sea Drilling Project; East Africa; East African Rift; Geochemistry; Gulf of Aden; Hydrocarbons; Indian Ocean; Isotope ratios; Isotopes; Kenya; Lacustrine environment; Lacustrine sedimentation; Lake sediments; Leg 24; Marine sediments; N-alkanes; Organic compounds; Sedimentation; Sediments; Stable isotopes; Turkana Basin; Vegetation
Coordinates: N115304 N115305 E0481443 E0481442
Record ID: 2009043211
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands