Hans Jørgen Hansen, 1990. "Diachronous extinctions at the K/T boundary; A scenario", Global Catastrophes in Earth History; An Interdisciplinary Conference on Impacts, Volcanism, and Mass Mortality, Virgil L. Sharpton, Peter D. Ward
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Temperatures in Late Cretaceous times were very high (16 to 20°C) at paleolatitude 62°N. It is suggested that these high temperatures were due to high atmospheric concentrations of CO2 caused by volcanism. Associated with the high CO2 production was a production of elementary carbon.
As the volcanism was of the hot-spot type, the dust carried poisonous compounds that reduced the fertility of herbivorous dinosaurs, causing diachronous extinctions. The volcanic activity initiated about 350,000 yr earlier than the marine Cretaceous/Tertiary boundary.
At the peak of volcanic activity the CO2 concentration in the atmosphere passed a threshold value of 5,500 ppm, causing the top of the ocean to become acidic. This resulted in the elimination of calcareous plankton.
Due to volcanic dust veils the temperature of the topmost part of the ocean fluctuated. The fluctuations led to precipitation of carbonate in the upper acidic part of the water column. The result is a chemical sediment deposited on top of the Cretaceous/Tertiary boundary bed.
The Cretaceous/Tertiary extinctions may thus be seen as caused by one long volcanic event with a duration of more than 350,000 yr. It is most likely associated with the extrusion of the Deccan Traps.