The Chicxulub asteroid impact (Mexico) and the eruption of the massive Deccan volcanic province (India) are two proposed causes of the end-Cretaceous mass extinction, which includes the demise of nonavian dinosaurs. Despite widespread acceptance of the impact hypothesis, the lack of a high-resolution eruption timeline for the Deccan basalts has prevented full assessment of their relationship to the mass extinction. Here we apply uranium-lead (U-Pb) zircon geochronology to Deccan rocks and show that the main phase of eruptions initiated ~250,000 years before the Cretaceous-Paleogene boundary and that >1.1 million cubic kilometers of basalt erupted in ~750,000 years. Our results are consistent with the hypothesis that the Deccan Traps contributed to the latest Cretaceous environmental change and biologic turnover that culminated in the marine and terrestrial mass extinctions.

No abstract

No abstract

Environmental and depositional changes across the Late Cenomanian oceanic anoxic event (OAE2) in the Sinai, Egypt, are examined based on biostratigraphy, mineralogy, d13 C values and phosphorus analyses. Comparison with the Pueblo, Colorado, stratotype section reveals the Whadi El Ghaib section as stratigraphically complete across the late Cenomanian-early Turonian. Foraminifera are dominated by high-stress planktic and benthic assemblages characterized by low diversity, lowoxygen and low-salinity tolerant species, which mark shallow-water oceanic dysoxic conditions during OAE2. Oyster biostromes suggest deposition occurred in less than 50 m depths in low-oxygen, brackish, and nutrient-rich waters. Their demise prior to the peak d 13 C excursion is likely due to a rising sea-level. Characteristic OAE2 anoxic conditions reached this coastal region only at the end of the d 13 C plateau in deeper waters near the end of the Cenomanian. Increased phosphorus accumulations before and after the d 13 C excursion suggest higher oxic conditions and increased detrital input. Bulk-rock and clay mineralogy indicate humid climate conditions, increased continental runoff and a rising sea up to the first d 13 C peak. Above this interval, a dryer and seasonally well-contrasted climate with intermittently dry conditions prevailed. These results reveal the globally synchronous d 13 C shift, but delayed effects of OAE2 dependent on water depth.

The Maltese archipelago and south-eastern Sicily include an Uppermost Oligocene to Upper Miocene hemipelagic sedimentary succession representing the Malta-Hyblean plateau, which limits the eastern Mediterranean to the west. This succession hosts a unique and well-exposed series of condensed and allochthonous phosphate-rich beds, which were formed in a sedimentary regime of erosion, sediment reworking and frequent gravity-flow deposition. The combination of nannofossil biostratigraphy and 87 Sr/ 86 Sr isotope stratigraphy allows for the precise attribution of ages to the phosphate deposits and for the distinction of three periods of major phosphogenesis. The first phase occurred between 24AE5 and 21 Ma and 25 and 18AE9 Ma (clustering of ages between 25 and 22AE5 Ma) on Malta and Sicily, respectively. The second and third phases of phosphogenesis are documented from the Maltese Islands and are dated as 17AE2 to 13AE1 Ma and 10AE9 to 9AE8 Ma, respectively. The phosphate-rich beds are associated with hiatuses and phases of important condensation which, for the oldest phosphogenic period, envelop the time period of 23AE2 to 22 Ma for the Fomm Ir Rhi Bay section (Malta) and from 19AE1 to 16AE3 Ma for the sections of Sampieri and Modica (Sicily). For the second phase of phosphogenesis on the Maltese Islands, a consistent hiatus was found which embraces the time period of approximately 17 to 15 Ma. Also the third phase of phosphogenesis appears to be associated with a major hiatus, which probably envelops the time period between 12AE5 and 10AE9 Ma, but a better age control is needed here. The correspondence in timing of the Maltese-Sicilian phases of phosphogenesis with major phases of phosphogenesis outside the Mediterranean realm, to maxima in oceanic phosphorus-burial rates and maxima in the d 13 C benthic foraminiferal record suggests that the palaeoceanographic evolution of the eastern Mediterranean was well in phase with that of other ocean basins until at least the early Late Miocene, despite its increasing isolation due to the gradual closure of the Eurasian-Arabian Strait and progressive sea-level fall.