Links Between the Sevier Fold and Thrust Belt, Cordilleran Foreland Basin Architecture and Depositional Process Change: A Transect through the North American Cordilleran Foreland Basin, Utah and Colorado, U.S.A.
Aschoff, J.L. 1, Ron Steel2 (1) Jackson School of Geosciences, University of Texas at Austin, Austin, TX (2) The University of Texas at Austin, Austin, TX
The influence of the Sevier fold-thrust belt on Cordilleran foreland basin stratigraphy is an important element of Rocky Mountain geology; understanding this hinges on how we disentangle the relative importance of drivers such as tectonics, eustasy and climate. A wide array of stratigraphic patterns has been interpreted as “tectonic” or “eustatic” in the Cordillean Foreland Basin (NACFB); yet, it is still unclear how to interpret these patterns because there is no unequivocal link to these drivers. Growth strata offer an unequivocal link between tectonics and sedimentation.
We correlate conglomerate-rich growth-strata successions to distal, genetically-related strata in a ~500 km transect through the NACFB to disentangle the influence of thrust-belt tectonics on foreland basin stratigraphy. We find 4 growth-stratal packages that correlate with distinct stratigraphic patterns in the adjacent foreland basin. Upper and lower growth-strata packages correlate basinwards to high-volume, wave-dominated stratigraphic successions (Blackhawk Fm. and Rollins s.s. Mbr of Mount Garfield Fm.) developed during extensive shoreline progradation with a rising shoreline trajectory. In contrast, the middle two packages correlate with low-volume, tideinfluenced successions (Castlegate and Sego S.S., Bluecastle Tongue, Corcoran and Cozette Mbrs of the Mount Garfield Formation) that reflect flat-to-falling shoreline trajectories. We find that the style and the amount of shoreline progradation correlate with thrust motions recorded by growth strata, and a genetic depositional link between transverse-zone fluvial megafan and extensive marine sand systems.
AAPG Search and Discovery Article #90055©2006 AAPG Rocky Mountain Section Meeting, Billings, Montana