Vitrinite reflectance and carbon chemistry of ODP Leg 122 samples (Table 1)

A summary of shipboard Rock-Eval measurements shows that organic matter in Upper Triassic siltstone from the Wombat Plateau is dominated by Type III kerogen and is thermally immature. Neocomian siltstone from the Exmouth Plateau similarly contain thermally immature Type III organic matter. Overlying Upper Cretaceous to Quaternary carbonates are poor in organic matter at both locations, yet significant amounts of methane-dominated gas are dissolved in the pore waters of the thick carbonate sequence present on the Exmouth Plateau. This dry gas is believed to have migrated from deeper and more mature strata containing Type III kerogen.

Nd and Sr isotope record of ODP Sites 121-756 and 122-762 sediments

We have analyzed the Nd isotopic composition of both ancient seawater and detrital material from long sequences of carbonated oozes of the South Indian Ocean which are ODP Site 756 (Ninety East Ridge (-30°S), 1518 m water depth) and ODP Site 762 (Northwest Australian margin, 1360 m water depth). The measurements indicate that the epsilon-Nd changes in Indian seawater over the last 35 Ma result from changes in the oceanic circulation, large volcanic and continental weathering Nd inputs. This highlights the diverse nature of those controls and their interconnections in a small area of the ocean. These new records combined with those previously obtained at the equatorial ODP Sites 757 and 707 in the Indian Ocean (Gourlan et al., 2008, doi:10.1016/j.epsl.2007.11.054) established that the distribution of intermediate seawater epsilon-Nd was uniform over most of the Indian Ocean from 35 Ma to 10 Ma within a geographical area extending from 40°S to the equator and from -60°E to 120°E. However, the epsilon-Nd value of Indian Ocean seawater which kept an almost constant value (at about -7 to -8) from 35 to 15 Ma rose by 3 epsilon-Nd units from 15 to 10 Ma. This sharp increase has been caused by a radiogenic Nd enrichment of the water mass originating from the Pacific flowing through the Indonesian Passage. Using a two end-members model we calculated that the Nd transported to the Indian Ocean through the Indonesian Pathway was 1.7 times larger at 10 Ma than at 15 Ma. The Nd isotopic composition of ancient seawater and that of the sediment detrital component appear to be strongly correlated for some specific events. A first evidence occurs between 20 and 15 Ma with two positive spikes recorded in both epsilon-Nd signals that are clearly induced by a volcanic crisis of, most likely, the St. Paul hot-spot. A second evidence is the very large epsilon-Nd decrease recorded at ODP Sites 756 and 762 during the past 10 Ma which has never been previously observed. The synchronism between the epsilon-Nd decrease in seawater from 10 to 5 Ma and evidences of desertification in the western part of the nearly Australian continent suggests enhanced weathering inputs in this ocean from this continent as a result of climatic changes.

Distribution of foraminiferal fauna from ODP Hole 122-762C (Table 1)

Planktonic foraminiferal diversity, equitability and biostratigraphic analysis of samples from Ocean Drilling Program (ODP) Leg 122, Hole 762C show that in general, cool water conditions prevailed during the latest Campanian-Maastrichtian in the eastern Indian Ocean. This is indicated by planktonic foraminiferal assemblages characterized by low species diversity and equitability with abundant rugoglobigerinids and heterohelicids. Archaeoglobigerinids, globigerinelloids, hedbergellids, and long-ranging double-keeled globotruncanids are also present in varying abundance but single-keeled forms occur rarely and sporadically. Identification of the stage and zonal boundaries for the studied geologic interval have been achieved through biostratigraphic analyses of closely spaced samples. Three planktonic foraminiferal biozones were identified, namely; in stratigraphic order, the Heterohelix rajagopalani, Contusotruncana contusa and Abathomphalus mayaroensis Zones. In Hole 762C, a Transitional Realm with Austral influences is defined for the latest Campanian to Maastrichtian, as shown by the high relative abundance of fauna characteristic of Transitional and Austral Realms. Austral endemic species such as Archaeoglobigerina australis Huber and Hedbergella sliteri Huber were found in the samples studied but Globigerinelloides impensus Sliter andA rchaeoglobigerina mateola Huber are conspicuously absent. From the latest Campanian to middle Maastrichtian, cooler parts of the Transitional Realm prevailed. A slight warming trend is assumed towards the end of the middle Maastrichtian because the faunas contain more species indicative of warm water conditions. The late Maastrichtian also appears to have been warmer than the latest Campanian-middle Maastrichtian. This conclusion is based on the high diversity and equitability values and recognition of some thermophilic taxa. A Tethyan influence is inferred for the latest Maastrichtian on the basis of an increase of planktonic foraminiferal species diversity and occurrences of several keeled taxa.