Palynology and palynostratigraphy of Maastrichtian, Paleocene, and Eocene strata in the Denver Basin, Colorado

Abstract

Palynological analysis provides data for determinations of ages and paleoenvironments of Maastrichtian, Paleocene, and Eocene strata in the Denver Basin. These strata were sampled on the surface at natural and artificial outcrops (construction sites) and in the subsurface via auger, drill core, and well cuttings. Extensive artificial outcrops existed temporarily during construction of the Denver International Airport. The Kiowa core, drilled as part of the Denver Museum of Nature & Science9s Denver Basin Project, is the principal palynostratigraphic reference section for the basin. It is supplemented by data from the Castle Pines core. Palynostratigraphic zonations of the Kiowa and Castle Pines cores are correlated with magnetostratigraphic zonations in the same cores. Regionally known palynostratigraphic biozones are present in the basin, as follows: Aquilapollenites striatus Interval Zone (Maastrichtian) in the Fox Hills and Laramie Formations; Wodehouseia spinata Assemblage Zone (uppermost Maastrichtian) in the lower part of the D1 sequence; Zones P1 through P3 (lower Paleocene) in the upper part of the D1 sequence; Zone P6 (uppermost Paleocene) locally at the base of the D2 sequence; and Zone E (lowermost Eocene) in the D2 sequence, above the basin-wide paleosol unit. The K–T boundary is bracketed by samples from the Kiowa and Castle Pines cores and is located within centimeters at the West Bijou Site. The Paleocene–Eocene boundary is determined to be within the paleosol unit of the Denver Basin, near the base of the D2 sequence. These and other palynological age determinations supplement independent paleobotanical and vertebrate paleontological research in the Denver Basin.