Abstract: Stratigraphic and Ecologic Analyses of the Tropic Shale, Escalante Core, Southern Utah (WISK Continental Drilling Program)

Erle G. Kauffman, Elana L. Leithold, Walter Dean

Continuous cores through basinal facies offer a unique opportunity for high-resolution (centimeter-scale), integrated sedimentologic, geochemical, and paleobiologic studies of marine environments. The WISK Continental Drilling Program obtained a 300-m core through the Cenomanian-Turonian Tropic Shale and upper Dakota Sandstone near Escalante, Utah, within the foredeep of the Western Interior Cretaceous foreland basin. Detailed sequence stratigraphic, cyclostratigraphic, sedimentologic, geochemical, paleobiological, and event chronostratigraphic analyses of this core are in progress; preliminary results are (1) lithostratigraphic equivalents to the

Graneros, Greenhorn, and Carlile formations and component members are recognized in the Tropic Shale; (2) regionally correlative second- and third-order depositional sequences, systems tracts, and surfaces can be defined in shale-dominated strata using new sequence stratigraphic models for fine-grained facies; these models are dependent upon integrated sedimentologic, geochemical, and biological profiles, and recognition of thin condensation/omission surfaces; (3) parasequence-scale units, many representing Milankovitch climate cycle deposits, can be recognized in late TST through HST facies; (4) changing benthic community structure and taphonomic patterns within this core reflect gradients in depth, substrate characteristics, oxygen, and current activity during deposition of the Gree horn cyclothem; (5) a highly refined system of chronology, using molluscan biostratigraphy, event chronostratigraphy using bentonites, lag and condensation deposits, storm and sediment gravity flow deposits, geochemical spikes, and ecostratigraphic changes provide a means of regionally correlating the depositional history of the Escalante core, through graphic correlation, with sections throughout the Western Interior Cretaceous basin. Results are illustrated.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994