Changes in oceanic circulation, sea level changes, and onset and fluctuations of the Indian monsoon characterize the Neogene. Located in the Indian Ocean, the Maldives carbonate edifice bears a record of these paleoclimatic changes. The archipelago, which rests on a volcanic basement ridge, is characterized by a double row of atolls encompassing a basin connected to the open ocean through passages. This basin, since the partial drowning of parts of the carbonate platform during the middle Miocene, serves as a depositional center of current-controlled deposits (drifts). This sedimentary system of drowned platform parts and drifts is the target of IODP Expedition 359, which aims to reconstruct its paleoceanographic evolution over the past 23 My.

Expedition 359 is designed to recover a series of neritic and hemipelagic deposits for the reconstruction of changes affecting the shallow-water carbonate factory of the edifice but also of the fluctuations in the ocean currents, which probably triggered this evolution. This reconstruction will be achieved by drilling 7 holes aligned into 2 transects covering shallow to deep-water deposits. The expedition builds on a series of seismic data sets that image the different steps of carbonate platform evolution and of previously drilled Ocean Drilling Program (ODP) Site 716.

More than 1200 km north of the Maldives sites (Figure F1), proposed Site KK-03B will be drilled on the western continental margin of India. Similar to the Maldives, the oceanographic conditions are dominated by the monsoon but with enhanced precipitation and continental freshwater influx due to orographic rain along the Western Ghats range that borders the western coast of India. Drilling is expected to recover a continuous sedimentary sequence containing a combined record of paleoclimate in peninsular India and an oceanic record of sea surface and intermediate water masses into the Eocene and possibly Paleocene.