An integrated biostratigraphic approach to the Albian/Cenomanian boundary in eastern Greenland

Combined collection of Cretaceous macrofauna and microbiota in eastern Greenland has enabled the precision of dating the dinocyst zonation to be refined. Initial dating of sediments based only on dinocyst evidence of Nøhr Hansen (1993, GGU Bull. 166) placed the Albian-Cenomanian boundary above the Epilopidosphaeridia spinosa Subzone in the upper part or top of the Subtilisphaera kaIaalliti Zone. However, in the present study, the Albian-Cenomanian boundary was discovered to be located much lower in the dinocyst succession. In this revised scheme the boundary is placed within the Wigginsiella grandstandica Subzone in the early part of the kalaalliti Zone. The reason for the modification is the co-occurrence of reliable Cenomanian macrofauna, such as the ammonite Schloenbachia varians and bivalves of the Inoceramus crippsi group in association with dinocysts of the Wigginsiella grandstandica, Odontichitina ancala and Ovoidinium? sp. 1 zones. A revised integrated macro- and microbiostratigraphical zonal scheme is proposed for parts of the Albanian and Cenomanian stages in eastern Greenland. It is based on ammonites, mainly hoplitids, gastroplitinids, schloenbachiids and mortoniceratids, inoceramid bivalves, belemnites, dinoflagellate cysts and foraminiferans. The kalaalliti Zone ranges from Upper Albian, through the Cenomanian and possibly into the Turdnian stages. It is expected that this revised scheme of zones will be of significance for offshore biostratigraphic studies in the North Atlantic region and in the Arctic.