Previous studies have suggested a variety of causes for the end-Permian extinction event including a bolide impact, flood basalt volcanism, methane clathrate dissociation, or some combination of catastrophic processes. One common feature of these hypotheses is the prediction of an enhanced earliest Triassic greenhouse. New high-resolution geochemical results from Graphite Peak, Antarctica suppo...

The end of the Palaeozoic is marked by two mass-extinction events during the Middle Permian (Capitanian) and the Late Permian (Changhsingian). Given similarities between the two events in geochemical signatures, such as large magnitude negative dC anomalies, sedimentological signatures such as claystone breccias, and the approximate contemporaneous emplacement of large igneous provinces, many a...

The effects of mineralogy and geological setting on trace metal concentration and distribution within six weathered profiles developed sandstone and mudstone was assessed. Primary minerals occurring in the weathered profiles are quartz, plagioclase, and K-feldspar. Kaolinite is the most dominant secondary mineral followed by mixed layers of smectite-illite, illite, hematite, siderite, and occas...

24 25 Chemical weathering and mechanical erosion are first order processes of long-term 26 tropical morphogenesis, which is still poorly deciphered for lack of time constraints. We 27 address this issue by laser-probe 39 Ar40 Ar dating of generations of cryptomelane [K128 2Mn8O16, nH2O] from the manganese ore deposit of Tambao in northern Burkina Faso. This 29 Mn deposit results from the superg...

The carbon-cycle significance of soil carbonate fluxes is subject to large uncertainties because it is not clear precisely how much calcium is derived from atmospheric sources compared with that from the chemical weathering of silicate minerals. In the petrocalcic horizon (calcrete) of a Pleistocene soil from the USDA–SCS Desert Project area near Las Cruces, NM, approximately 1.5 g Ca=cm3 has b...