Isotopic and Molecular Proxies for climate and vegetation shifts along the Portuguese and NW African margins since the last glacial period: the CHEETA Cruise Transect

In July, 2007 a sediment coring and water sampling cruise aboard R/V Oceanus was conducted off the Portuguese and NW African margins as part of the CHEETA (Changing Holocene Environments of the Eastern Tropical Atlantic) program. Gravity core and multicore pairs were recovered at 28 stations along a transect from 40°N-15°N paralleling the continental slope. One of the major goals of the CHEETA program is to utilize multiple organic proxies including elemental data and the abundance and isotopic composition of bulk organic matter and higher plant leaf wax alkanes to constrain regional variations in continental climate and terrigenous supply. The meridional array of gravity cores cover different climate and vegetation zones in the SW Mediterranean and NW Africa, that transmit terrigenous signals to the adjacent continental margin, providing a rare opportunity to assess the sensitivity of these different proxies to continental supply, climate, and vegetation during past glacial-interglacial climate conditions. The elemental, isotopic and molecular analyses are used for reconstruction of past continental climate and hydrological conditions in subtropical and tropical eastern Africa. We present new high resolution isotopic and molecular records that demonstrate significantly different trends in climate, upwelling and continental supply along the core transect. Carbon isotope profiles clearly trace the extent and history of the subtropical savannah vegetation belt.