HIGH-RESOLUTION CORRELATION OF THE UPPER CRETACEOUS STRATIGRAPHY BETWEEN THE BOOK CLIFFS AND THE WESTERN HENRY MOUNTAINS SYNCLINE, UTAH, U.S.A.

摘要

This study presents high-resolution correlations of the Upper Cretaceous stratigraphy between the Book Cliffs and the western Henry Mountains Syncline in Utah. The objective of this study is to understand changes in patterns of regional sediment dispersal during the Late Cretaceous on the western margin of the Cretaceous Western Interior Seaway. The intensely studied Book Cliffs consist of formations deposited in terrestrial, marginal-marine, and open-marine environments. A composite section was logged at Coal Canyon near Green River, UT. The western Henry Mountains Syncline is located in south-central Utah ~135 km S-SW of Coal Canyon. A composite section was logged at Blind Trail. High-resolution correlation between the Book Cliffs and Henry Mountains is not straightforward because the correlative interval in the Henry Mountains succession is highly condensed (~1015m) relative to the Book Cliffs succession (\u3e1750m). This is in part due to their proximal vs. distal locations from the Sevier thrust front and unequal rates of accommodation creation caused by spatially variable subsidence and uplift patterns. Correlating at high-resolution from Coal Canyon to the Henry Mountains section poses similar challenges as correlating from the eastern Book Cliffs to the Wasatch Plateau because key stratigraphic surfaces in shallow-marine successions cannot necessarily be carried into coeval coastal plain strata up-depositional dip. Radiogenic isotope ages and biostratigraphic data provide age constraints on correlations between the Coal Canyon and Blind Trail sections. Correlations are based on vertical facies and depositional environmental stacking patterns, and changes in sediment dispersal directions at discrete stratigraphic horizons derived from 745 paleocurrent measurements. Recognition of these patterns suggest that the Muley Canyon Sst., Muley Canyon Coal Zone at the base of the Masuk Fm., and the Masuk Fm. correlate to the Star Point Fm., basal Blackhawk transgressive coal zones, and the Blackhawk Fm., respectively, in the Wasatch Plateau. These interpretations provide the means to then correlate the Henry Mountains and Book Cliffs sections as well as allowing pinning points that constrain correlations both up- and down-stratigraphic section.Adviser: Christopher R. Fielding