PALEOGEOGRAPHIC EVOLUTION OF THE LATE CRETACEOUS NORTH AMERICAN CORDILLERAN FORELAND BASIN: AN EXEMPLAR OF THE COMBINED INFLUENCE OF TECTONICS, SEA LEVEL, AND SEDIMENT SUPPLY THROUGH TIME

The stratigraphic record from the North American Cordilleran foreland basin (CFB) serves as a critical archive of how tectonics, sea-level and sediment supply interacted throughout the geologic past, providing valuable insights into the formation and filling of foreland basins. By integrating a range of stratigraphic, sedimentologic, and geochronological datasets from previous stratigraphic research and new data, the roles of various geological processes within the CFB are better constrained, especially more enigmatic subcrustal processes probably related to large-scale mantle flows. This study summarizes the complex paleogeographic evolution of the central part of the CFB in 25 temporally constrained paleogeographic maps illustrating high-resolution shoreline history (location and migration trend) and distribution of gross depositional environments through the Late Cretaceous.

Detailed stratigraphic synthesis and paleogeographic maps of the CFB indicate that sediment fill of the CFB was subject to complex interactions of tectonics (both local and regional scale and both crustal and subcrustal processes), eustasy, and sediment supply. Although crustal processes such as flexural subsidence caused by loading of the Sevier fold-thrust belt and local Laramide structures has long been considered as the overriding subsidence mechanism for the development of the CFB, the effect of mantle-induced dynamic topography (uplift and subsidence) is evident in newly developed paleogeographic maps here. Subcrustal processes such as mantle flow, possibly associated with enhanced coupling by subduction of an oceanic plateau (i.e., the conjugate Shatsky rise) attached to the Farallon plate, were documented as an important mechanism influencing the subsidence/uplift and sediment dispersal patterns in the CFB since at least ~ 85 Ma. High-resolution reconstruction of the geohistory of the CFB through holistic approaches will greatly advance our understanding of the roles of different allogenic factors in sediment filling of the CFB and enable us to better use the stratigraphic record of foreland basins as important archives of paleoenvironmental evolutions and the interaction between surficial and deep Earth processes through geological time.