Paleogeographic and paleotectonic setting of Laramide sedimentary basins in the central Rocky Mountain region

摘要: In the Rocky Mountain region between central Montana and New Mexico, sedimentologically isolated nonmarine basins were produced by basement deformation during Laramide orogeny within area formerly occupied a broad Late Cretaceous foreland basin in which laterally continuous marine facies had accumulated previously. structures of varying trend scale reflect heterogeneity crustal strain caused shear continental lithosphere an underlying subhorizontal slab subducted oceanic lithosphere. include perimeter along cratonic periphery arcuate province, axial north-south intramontane trend, ponded located farther west closer to overthrust belt. Twelve specific stratigraphic sedimentologic criteria for onset, duration, termination allow chronology development be inferred independently each basin. Maastrichtian initiation was approximately synchronous throughout but systematically diachronous from north south early late Eocene time. Widespread erosion surfaces truncate syntectonic sequences are overlain largely volcanic volcaniclastic post-Laramide strata age Oligocene south. Fluvial depositional systems draining toward Great Plains dominant basins, at times large lakes that served as regional sediment traps. Paleocene drainages also led eastward interior, partly interconnected developed several mid-Eocene time either closed hydrologically, or else they drained westward into "Tyee" paleoriver Pacific Northwest.