Palynology of Middle Cretaceous Black Clay Facies from Deep Sea Drilling Project Sites 417 and 418 of the Western North Atlantic

Abstract

A palynological study of 23 samples of black and green claystones of middle Cretaceous age recovered from DSDP Sites 417 and 418 documents the position of a subtropical flora interference belt in a climatically differentiated North Atlantic realm. A relatively large dinoflagellate/pollen ratio and lack of significant wood cuticle suggest moderately long-distance transportation of land- derived components by surface currents. These components tend to de- crease numerically upsection, but show a uniform composition. These sediments fit into the pollen-zones I, II, and III ranging from the early Aptian to early Cenomanian (Doyle and Robbins, 1977). Several new angiosperm forms are identified, including the oldest known occurrence of a monoporate form. Dinoflagellates, acritarchs, and microforaminifers dominate the palynomorpn spectrum. Their occurrence is closely linked with complex lithologies interbedded on a decimeter scale. The palynomorphs are equally well preserved, but vary in abundance in the black and green claystones and are rare in nannofossil chalks, radiolarian sands, or red-brown clays to marls. The overall sedimentation rate appears to have been slow, but individual thin, carbonaceous black clay beds are commonly dominated by a single dinoflagellate species which may be evidence of high productivity following circulation events in a closed basin.