Stratigraphic, palaeogeographic and evolutionary significance of late cretaceous and early tertiary normapolles pollen

Abstract

Pollen grains referable to the Normapolles group first appeared during the Cenomanian. They diversified rapidly through the remainder of the Cretaceous and during the early Palaeogene, but by the end of the Eocene they were virtually extinct. They were most numerous in a province which extended from what is now West Siberia across Europe to eastern North America. The Western Interior of North America and West Siberia are considered to delimit the longitudinal boundaries of this province. These areas were submerged during the Late Cretaceous and formed physical barriers to wider dispersal of many Normapolles-producing plants. The Normapolles that have been reported from further afield comprise only minor elements of palynofloras except locally in a few areas where they are apparently relatively abundant. Such records do not invalidate the Siberian and American longitudinal limits but they do require that the concept of the province be altered somewhat to indicate region within which Normapolles are more consistently abundant than elsewhere. Climate must have been as significant an influence on the evolution of the parent plants as it appears to have been in determining the northern and southern boundaries of the province, however vaguely defined these are at present. Palynological analyses of core and cuttings samples from the U.K. continental shelf have helped to refine the northern limit to some extent. Until recently, published maps have included both Svalbard and Greenland in the Normapolles Province. Whilst possibly correct for some of the early Tertiary, Late Cretaceous (Campanian-Maastrichtian) strata in the Northern North Sea and west of the Shetland Islands have yielded Aquilapollenites, Wodehouseia and other taxa typical of the Aquilapollenites Province. The transition between the flora of this boreal region and the European part of the Normapolles Province, which is known to extend as far north as southern Sweden, would thus appear to lie approximately on the latitude of the central North Sea.