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Following the work of Wolbach et al., who studied reduced carbon across the 65 Ma-old Cretaceous-Tertiary extinction boundary, a study was conducted to analyze reduced carbon across the 92 Ma-old Cenomanian-Turonian (C-T) extinction horizon, in the hope that evidence could be gathered which might support a particular mechanism for these extinction events. Currently two sample sites are being analyzed for reduced carbon content at the C-T boundary: Red Wash, New Mexico and Chispa Summit, Texas. Both sample sites are from the Western Interior Basin of North America. During the time of the extinctions 92 million years ago, the basin was an inland sea. Preliminary data suggest a decrease in the amount of carbonaceous residue found at the boundary at both sample sites. This would indicate that the extinction event was not rapid, as lower amounts of reduced carbon are generally more characteristic of extinctions caused by slow changes in climate vs sudden changes caused by catastrophic events. Slow climate changes would allow microorganisms time to digest (oxidize) the carbon in dead plankton before sedimentation, thus decreasing the amount of reduced carbon preserved in the rock. A mechanism for the C-T extinctions consistent with previous data as well as preliminary results obtained in this study is the opening of deep sea fissures at the ocean floor, increasing certain metal concentrations in seawater, and, more importantly, increasing water temperatures. Plankton unable to adapt to these new conditions would become extinct.



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