BIOTURBATION, INOCERAMID EXTINCTION, AND MID-MAASTRICHTIAN ECOLOGICALCHANGE

Notable among the biological changes of the middle part of the Maastri chtian Age was a major pulse of extinction among inoceramid bivalves. Analysis of the distribution of inoceramid shell fragments suggests th at the population of burrowing organisms increased across the same str atigraphic interval that the bivalve population decreased. A global re organization of ocean circulation that resulted in cooler, better oxyg enated bottom waters is proposed as an explanation for the observed ch anges in the deep sea. Other observations regarding the mid-Maastricht ian are consistent with this hypothesis.