Abstract

Recent revisions in placements of Upper Cretaceous stage boundaries in the Western Interior of North America, the development of a corresponding new radiometric time scale, and new palynostratigraphic data from nonmarine sections in the Rocky Mountain region of the United States necessitate revision of the existing palynostratigraphic zonation for the region. A new zone based on nonmarine palynomorphs (Mancicorpus striatus Interval Zone) is defined, the underlying zone that formerly encompassed the new zone is revised, and a change in the name of a previously defined zone is prompted by a revision in palynological nomenclature. Broad-scale palynostratigraphic datums recently established for the Western Interior and data on diachroneity and provincialism of palynofloras provide a frame of reference for the revised nonmarine palynostratigraphic zones and suggest correlations beyond the Rocky Mountain region of the United States.

The definition, composition, age, correlation, and calibration of each of the following palynostratigraphic zones are presented: Plicatella unica Interval Zone (upper Albian through lower Cenomanian); Nyssapollenites albertensis Interval Zone (upper Cenomanian through mid-Coniacian); Proteacidites retusus Interval Zone (mid-Coniacian through upper Santonian); Pseudoplicapollis newmanii Interval Zone (lowermost Campanian); Aquilapollenites senonicus Interval Zone (upper lower through lower middle Campanian); Aquilapollenites quadrilobus Interval Zone, revised (lower middle through upper but not uppermost Campanian); Mancicorpus striatus Interval Zone (uppermost Campanian and lower Maastrichtian); and Wodehouseia spinata Assemblage Zone (upper Maastrichtian). Absolute-age ranges of all zones are recalibrated using the most recent time scale for the region.

The nomenclature of palynological taxa present in the zones is updated. A new species is described: Aquilapollenites collaris (Tschudy & Leopold 1971) Nichols n. sp. (formerly A. delicatus var. collaris).