Monday, 6 October 2008
George R. Brown Convention Center, Exhibit Hall E
The sediments of the southern coastal Tanzania contain exceptionally well preserved microfossils and have been targeted in recent years by the “Tanzania Drilling Project” (TDP), an informal collaboration of researchers studying Cretaceous-Neogene paleoclimate. Drilling in 2007 was near Lindi, where previous TDP works had cored ~35 m of upper Campanian-lower Maastrichtian claystones and mapped upper Campanian to lower Oligocene sediments based on scarce surface exposures. During 2007, a total of 380 m of core was recovered. Three holes collectively spanned the uppermost Albian to upper Cenomanian (Planomalina buxtorfi sub-Zone to Rotalipora cushmani Zone) and include organic carbon isotopic evidence suggesting recovery of at least the base of OAE2; two holes recovered a thick sequence of the lower to middle Turonian (Whiteinella archaeocretacea to Helvetoglobotruncana helvetica Zones) with the Coniacian marker Dicarinella concavata in the highest samples; and one hole recovered the lower to upper Campanian (Globotruncanita elevata to Radotruncana calcarata Zones). Stratigraphic gaps exist in the lower Cenomanian, upper Turonian and Santonian, and the Cenomanian-Turonian boundary is not demonstrably conformable. Lithologies include thin intervals of light, coarse sandstones and sandy siltstones with occasional woody debris separating thicker intervals of dark claystone containing rare bivalves and ammonites and thin interbeds of silt to fine sandstone. Organic-rich, finely laminated claystones were also recovered at parts of the Turonian sequence. Beyond the refinements to knowledge of the local stratigraphy and subsurface geology, these results coupled with ongoing geochemical and biostratigraphic studies are being used to examine Late Cretaceous greenhouse climates. Of particular interest is the temperature history in the region, whether sedimentological and geochemical data together support Late Cretaceous glacial episodes, and how the tropical-subtropical East African shelf environment behaved during OAE2 and other Late Cretaceous events.