TANZANIA ONSHORE PALEOGENE INTEGRATED CORING (TOPIC) (Invited Presentation)

Hemipelagic marine mudstones in outcrops and shallow cores from southern coastal Tanzania contain exquisitely preserved calcareous microfossils and organic biomarkers, allowing studies of biotic, organic and inorganic geochemical proxies. The geology is well understood, with structural blocks bounded by faults gently dipping seaward. Materials obtained in 1998-2009 have been used to document past tropical oceanic and atmospheric conditions, but the records are highly discontinuous. The TOPIC proposal plans to recover 1000-1200 m of upper Paleocene - lower Oligocene sediments. This time interval includes the most recent period of hothouse climate, with atmospheric pCO₂ levels at several times modern levels, and its superimposed, short-term periods of extreme warming (called hyperthermals), characterized by massive emission of carbon compounds in the ocean-atmosphere, ocean acidification, and deoxygenation. It also encompasses the transition into an ice-house world, with establishment of the Antarctic ice sheet. The hemipelagic sediments (paleodepth ~200-500 m) contain open-ocean, bathyal microfossils, and were deposited sufficiently close to land (50-70 km to shoreline) to contain soil bacterial biomarkers, leaf wax, and pollen. The sediments thus record maximum tropical sea surface temperatures during greenhouse conditions, changes in the hydrological and carbon cycles, as well as the marine and terrestrial biotic response to extreme temperatures and global cooling. The cores will enable us to develop a tropical Eocene ‘reference section’ with cyclostratigraphic, magnetostratigraphic, and biostratigraphic tools, and to test whether paleoclimate forcing and response is consistent with the predictions of an ensemble of General Circulation Models (GCMs). Secondary objectives include the nature of microbial ecosystems at depth in uplifted marine sediments in which pore fluid flow has been minimal for tens of millions of years. Significant support has been received from ICDP, and the project team is working to secure the rest of the funding. TOPIC is informally linked to an independent IODP proposal [778-Full2: Tanzania Offshore Paleoclimate (TOP)], which aims to recover offshore records over the Paleocene-Pleistocene, has been graded 'excellent' by IODP and is awaiting scheduling.