Biomarker Methods in Paleoclimatology: Applications to the Southeast African Margin and Mediterranean Region

<p>In southeastern Africa (Chapter 2), the distribution of isoprenoidal glycerol dialkyl glycerol tetraethers (GDGTs) and the hydrogen isotopic composition of plant waxes (δD_wax) from International Ocean Discovery Project Site U1478 are used to document Indian Ocean sea surface temperatures and rainfall during the Plio-Pleistocene. As this period (~4–2 Ma) encompasses the switch in Indonesian Throughflow source waters, the mid-Pliocene warm period, and the onset of intensified Northern Hemisphere glaciation during early hominid evolution in Africa, these data add to our understanding of global and regional climate dynamics and archaeology. Ultimately, Chapter 2 addresses a critical spatiotemporal gap in geologic records of African climate and helps establish regional rainfall controls related to the Indian Ocean and high-latitude glaciation that may inform forecasts of future climate.</p><p>In northeastern Greece (Chapter 3), high-resolution δD_wax data are produced to establish seasonal atmospheric patterns associated with glacial-interglacial (Marine Isotope Stages (MIS) 1–5) environmental change in the northern Mediterranean over the last ~140 kyr. The δD_wax record provides clear evidence for enhanced precipitation seasonality associated with an improved winter storm track during the interglacials of MIS 1 and 5. Although glacial conditions and overall reductions in rainfall are apparent for MIS 2–4, δD_wax and molecular distributions indicate more humid summers that may have supported the migration of early humans across Europe. The δD_wax record produced for Chapter 3 represents the only one of its kind for the region, resolving seasonal rainfall dynamics and providing continuous, sub-millennial hydroclimatic context for early human dispersal out of Africa.</p><p>In western Greece at Etoliko Lagoon (Chapter 4), a suite of biomarkers is used to evaluate aquatic productivity and community composition over the last ~200 years. Algal-derived molecules illustrate aquatic ecosystem change associated with the Little Ice Age, North Atlantic Oscillation (NAO), and human activities that altered lagoon hydrography and nutrient inputs. As environmental monitoring of the Etoliko ecosystem has only recently begun, Chapter 4 provides valuable insight into the natural variability of the lagoon and allows for a refined interpretation of climatic vs. human impacts on aquatic ecosystem structure in a unique and locally important setting.</p>