Dipl.-Geol. Rony Küchler

• Organic and Isotope Geochemistry
  - lipid biomarkers and their isotopic signatures for environmental interpretations
  - transport and preservation of organic compounds
• Paleoclimatology and Paleoceanography
  - changes in hydrology, vegetation and dust transport
  - link between ocean-continent interactions and climate variability

Northwest African biomes and climate variability during the Pliocene
(Pliocene ABC)

Funding: German Research Foundation (DFG), within the scope of the special interest programme IODP/ODP (Supervisors: Prof. Dr. Gerold Wefer, Dr. Enno Schefuß)


In general, this project aims to specify the climate and vegetation history of NW Africa in terms of variability and its causes during the Pliocene. In order to gain a better understanding of the paleo-hydrology of NW Africa, a biomarker study on well-dated continuous marine archives from the subtropical northeast Atlantic is already in progress. Compound-specific hydrogen isotope measurements on plant lipids will serve as a proxy for past precipitation intensities. In the low-latitudes, especially in monsoonal regions, rainfall isotopic compositions are strongly coupled to the amount of precipitation leading to lower δD values in areas of high precipitation and vice versa. The stable carbon isotope composition of the same compounds provides insights into the relative contribution of C3 (shrubs and trees) and C4 (grasses) plants to the vegetation cover. As C4 grasses are adapted to aridity, accompanied by an offset in δ13C of their plant waxes compared to C3 plants, these variations can be used to draw interferences between the development of the modern savannah ecosystem, consisting of C4 grasses, and climate variability in NW Africa. These results will be compared with pollen data and sea surface temperature estimates from the same sediments.

Two main hypotheses are crucial for the accomplishment of this work:
1. The closure of the Central American Seaway (CAS) has introduced the Mid-Pliocene Warm Period (MPWP) by redirecting warm waters from low- to high-latitudes, leading to elevated humidity and extensions of woodland and forest biomes in NW Africa.
2. NW African climate and vegetation changes are mainly driven by variations in the Atlantic Meridional Overturning Circulation (AMOC).

To evaluate these hypotheses, we intend to compare the NW African vegetation development and hydrologic cycle during the MPWP and accordingly the final closure of the CAS with the preceding time interval featuring a still intact CAS. During these times, northern hemisphere glaciations were minor. To figure out differences between the Pliocene reconstructions and modern conditions, the results will be compared with the same type of data covering the last glacial cycle (last 130 ka).