Impact production of CO_2 by the Cretaceous/Tertiary extinction bolide and the resultant heating of the Earth

Abstract

Evidence at the Cretaceous/Tertiary boundary suggests that the proposed 'extinction' bolide struck a continental or shallow marine terrane. This evidence includes: shocked quartz and feldspar grains found in the boundary layer inherited from a range of rock types; a high ^(87)Sr/^(86)Sr ratio in some planktonic fossils which could reflect continental-derived Sr(ref.5); and evidence that the platinum-group-element-rich clay layer is underlain (at some localities) by a deposit of possible tsunamic origin. These observations and data demonstrate that sea level at the end of the Cretaceous was ~150-200 m higher than at present, suggesting the possibility that the extinction bolide struck a shallow marine carbonate-rich sedimentary section. Here we show that the impact of such a bolide (~5km in radius) onto a carbonate-rich terrane would increase the CO_2 content of the atmosphere by a factor of two to ten. Additional dissolution of CO_2 from the ocean's photic zone could release much larger quantities of CO_2. The impact induced release of CO_2, by itself, would enhance atmospheric greenhouse heating and give rise to a worldwide increase in temperature from 2 K to 10 K for periods of 10^4 to 10^5 years.

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