A High-Resolution Sequence Stratigraphic Analysis of High-Frequency Sequences: Cozzette Sandstone, Mount Garfield Formation, Book Cliffs, Colorado

Andrew S. Madof and Diane L. Kamola
University of Kansas, Lawrence, KS

High resolution sequence stratigraphy was used to analyze and predict the stratigraphic architecture of nearshore systems of the Cozzette Sandstone Member of the Upper Cretaceous Mount Garfield Formation. High resolution sequence stratigraphy provides a better understanding of the stratigraphic architecture of the high frequency depositional sequences which characterize this member, as well as allowing important changes occurring along depositional dip to be deciphered.

Eight sections within the Cozzette Sandstone, averaging 65-70 m in thickness and spanning a distance of over 40 km, were measured oblique to depositional dip in the eastern Book Cliffs of western Colorado. Through the correlation of these measured sections, the Cozzette Sandstone was found to be comprised of strata contained within four high frequency depositional sequences, which consisted of parasequences with marine and nonmarine-to-marginal marine facies. These sequences are “abbreviated” when compared to sequences in older Cretaceous strata within the Book Cliffs. Parasequences with marine facies are comprised of genetically-related upward-coarsening progradational stratal packages, while parasequences with nonmarine-to-marginal marine facies are more complex. These parasequences consist of genetically-related upward-coarsening and upward-fining aggradational stratal packages.

The highstand systems tracts are comprised dominantly of progradationally stacked, wave-dominated shoreface successions, with paleoshorelines trending N-S to NNW-SSE. Conversely, the transgressive systems tracts are comprised of parasequences with nonmarine to marginal marine facies, interpreted as part of estuarine successions. Such successions are interpreted to form in response to aggradation during a relative transgression in sealevel. These estuarine successions have been partitioned into genetically-unrelated high- and low-energy end-members.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005