Diachroniczne wymieranie na granicy kreda-trzeciorzęd: scenariusz

Hans Jorgen Hansen



It is argued that the temperatures in late Cretaceous were very high (16-20°C) at paleolatitude 62N. It is suggested that this is related to very high atmospheric concentration of CO2 caused by volcanism. Associated with the high levels of CO2 is a production of elementary carbon. As the volcanism was of the hot spot type, the dust carried poisonous compounds lowering the fertility of herbivorous dinosaurs causing diachronous extinctions. This initiated about 350000 y. earlier than the marine K/T boundary. At the peak of volcanic activity the CO2 concentration in the atmosphere passed a treshold value of 5500 ppm causing the top of the ocean to become acidic. This killed the calcareous plankton and epiplanktonic larvae. Associated with pulsed supply of elementary carbon and other volcanic dust veils the surface temperature of the topmost part of the ocean fluctuated slightly. This led to precipitation of carbonate in the topmost acidic part of the ocean leading to deposition of a chemical sediment. The K/T extinction may thus be seen as one long volcanic event with a. duration of more than 350000 y. most likely associated with the extrusion of the Deccan Traps basalts.

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