Occurrence of Inoceramus Remains in Late Mesozoic Pelagic and Hemipelagic Sediments

Abstract

Remains of the bivalve genus Inoceramus have long been known to occur in Cretaceous neritic marine sediments from many regions of the globe. In recent years, Inoceramus fragments and prisms have also been found in fine-grained hemipelagic and pelagic Mesozoic sediments sampled by the Deep Sea Drilling Project. A common characteristic of these occurrences is that they have been found most frequently in drill sites close to continental margins, though occurrences from open ocean paleoenvironments have also been reported. Since the Inoceramus fossils have been observed in sediments presently under several hundred to several thousand meters water depth, a re-evaluation of the paleoecology of this fossil group seems timely, especially with respect to paleodepth of deposition. It can be shown that Inoceramus was confined to the upper bathyal and neritic environments (continental and island slopes and shelves) where they lived as epibenthos on the substratum. In several regions these sediments indicate reducing conditions below the sediment/water interface.