PROVENANCE PATTERNS OF UPPER PALEOZOIC AND MESOZOIC SANDSTONES OF THE COLORADO PLATEAU (Invited Presentation)

As part of a forthcoming monograph “Tectonosedimentary Relations of Mesozoic Strata on the Colorado Plateau,” Bill Dickinson compiled all available detrital-zircon data from upper Paleozoic and Mesozoic strata of the region and integrated this information with stratigraphic, paleomagnetic, paleoclimatic, eustatic, and paleogeographic constraints. Following are several main conclusions:

Eolian sandstones of Pennsylvanian-Permian age were sourced in large part from the Appalachian orogen, with transport by westward-flowing transcontinental rivers north of the Ancestral Rockies and by eolian processes in western Pangea that moved sediment toward the southwest. This transcontinental dispersal system was enabled by emergence of the southern-central Appalachian orogen combined with destruction of the transcontinental arch due to Ancestral Rocky Mountains tectonism. Lower to Middle Triassic strata (Moenkopi) consist of sediments shed from the eastern Mexico magmatic arc and also reworked from upper Paleozoic eolianites, whereas Upper Triassic fluvial strata (Chinle) were sourced largely from the Ouachita orogen and the Late Triassic Cordilleran magmatic arc. As the Colorado Plateau migrated northward out of tropical paleolatitudes, Lower to Middle Jurassic eolianites (Wingate, Navajo, Entrada) record a second phase of derivation from the Appalachian orogen, with westward transport by transcontinental rivers and southward-directed deflation of riverine and marine sand by eolian processes. Intervening fluvial strata (Kayenta-Moenave) record reworking of eolianite detritus plus incorporation of <285 Ma grains derived from the eastern Mexico and Cordilleran magmatic arcs. Upper Jurassic (Morrison) and Lower Cretaceous (Cedar Mountain-Burro Canyon) strata consist in large part of sediment reworked from the underlying eolianites, with minor contributions from the Cordlleran magmatic arc. In summary, sandstones of the Colorado Plateau record a rich history of derivation from many different source regions, complemented by significant recycling through progressively younger units, with patterns controlled by interactions between convergent-margin and collisional tectonics, paleogeography, eustatic variations in sea level, and changes in paleoclimate due to latitudinal change.