LINKS BETWEEN THRUST-BELT KINEMATICS, FORELAND BASIN ARCHITECTURE AND DEPOSITIONAL PROCESS CHANGE: A 500 KM TRANSECT THROUGH THE NORTH AMERICAN CORDILLERAN FORELAND BASIN, UTAH AND COLORADO, USA

Understanding the precise relationship between fold-thrust belts and foreland basin stratigraphy hinges on how we disentangle the relative importance of drivers such as tectonics, eustasy and climate. An array of stratigraphic patterns has been interpreted as “tectonic” or “eustatic” in the North American Cordillean Foreland Basin (NACFB); yet, it is still unclear how to interpret these patterns because there are few unequivocal links to the external controls. Physical and numerical modeling has provided insight on how stratigraphic patterns can reflect allogenic drivers; however, these models are still contentious because they do not take account of stratigraphic detail and are limited in temporal/spatial scale. Testing and modifying models against outcrop data is vital because the rock record does contain the signals of tectonics, eustasy and climate. Growth strata provide an unequivocal “tectonic” link between fold-thrust belt kinematics and stratigraphic patterns in the NACFB. We use a slightly different approach to delineate this link by correlating conglomerate-rich growth-strata successions (e.g., Horton et al., 2004) to distal, genetically-related strata in a ~500 km transect through the NACFB. 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, tide-influenced successions (Castlegate and Sego S.S., Bluecastle Tongue, Corcoran and Cozette Mbrs of the Mount Garfield Formation) that reflect flat-to-falling shoreline trajectories. The style and the magnitude of shoreline progradation correlate with frontal thrust motions in the NACFB, and there is a genetic link between transverse-zone fluvial megafan depositional systems and extensive marine sandstone tongues.