A Record of Tropical Vegetation Change from Terrestrial Biomarkers Preserved in Cariaco Basin Sediments
Abstract
A record of tropical vegetation change since the last glacial maximum was established using terrestrial biomarkers preserved in Cariaco Basin sediments. Vascular plant biomarkers derived from proximal terrestrial sources preserved in these anoxic sediments can be compared to previously established records of North Atlantic climate change from the same location. The terrestrial biomarkers used consisted of C24-C32 n-alkanoic acids, which are derived from plant leaf waxes. Average carbon chain length and δ 13C of n-alkanoic acids were used to construct the vegetation record. For C30 and C32 n-alkanoic acids, δ 13C variations of more than 3‰ between the last glacial maximum and the present interglacial period suggest changes in the character of terrestrial biota that parallel changes in climate, as inferred from North Atlantic sediment and Greenland ice core records. Terrestrial biomarker δ 13C data indicates that C3 plants predominated in this area of the tropics during warm periods, such as the B\o{}lling-Aller\o{}d and the Holocene, and C4 plants proliferated during cold periods, such as the last glacial maximum and the Younger Dryas. The tradeoff between C3 and C4 plants represents a switch from arid grasslands to more humid forest vegetation as the climate warmed. Average carbon chain length data also show variations synchronous with climate changes during the last deglaciation. The biomarker record agrees with pollen data previously developed from Cariaco Basin sediments, confirming that leaf wax compounds preserved in marine sediments can accurately record terrestrial vegetation changes. This study shows that terrestrial biomarkers are a useful paleoclimate proxy and could be used to compare marine and terrestrial climate changes in the same marine sediment core. With the aid of automated analytical techniques, these compounds can be analyzed much more quickly than pollen, and can therefore be used for construction of long, high-resolution records.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2001
- Bibcode:
- 2001AGUSM..OS41A05M
- Keywords:
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- 1055 Organic geochemistry;
- 4267 Paleoceanography