Green Desert – Holocene hydrological changes in the Sahara revealed by lipid biomarker analyses of Lake Yoa (Chad)


11,000 years ago, at the beginning of the Holocene, today’s hyper-arid Sahara desert was dotted with large and small lakes, savannah and grassland and in some regions even humid tropical forest. Due to a strengthened African monsoon triggered by strong orbital forcing i.e. summer insolation, more humid conditions compared to today, prevailed in Northern and Central Africa.

Matthias Thienemann

Matthias Thienemann
Project F5

This period is called the “African Humid Period (AHP)”. However, many questions remain unsolved, as the course and the termination of the AHP varies across different archives in Africa, probably due to strong regional vegetational, oceanic and atmospheric feedback mechanisms. Understanding these mechanisms becomes very important, especially since the changes in rainfall happen on a centurial and thus human-relevant time scale. This underlines the need for proxy parameters directly linked to past hydrological and vegetational conditions. Here we present molecular isotopic Data from a 16m long sediment core from Lake Yoa (Tschad), an unique archive from the central Sahara Desert, dating back to the Early Holocene. We use compound specific stable Hydrogen and Carbon isotopes of terrestrial long chained n-alkanes to reconstruct changes in continental rainfall and vegetation type. Our data reveal a rather gradual drying of the central Sahara, following the decline of insolation forcing over the Holocene.

Event Information:

Date, Time: 09/11/2015, 14:45 h – 15:30 h

Location: Room S22, Seminargebäude (Building 106), Universitätsstraße 37 , Cologne

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