Interactions between axial and transverse drainage systems in the late cretaceous cordilleran foreland basin: evidence from detrital zircons in the straight cliffs formation, southern Utah.

摘要

New detrital zircon geochronologic data from the Straight Cliffs Formation of southern Utah provide insight into the controls on stratigraphic architecture of the Western Interior basin during Turonian-Campanian time. Straight Cliffs Formation deposition was influenced by the development of topography in the Sevier fold-thrust belt, but to date, little emphasis has been placed on the tectonic development of the Mogollon highlands of central Arizona. Detrital zircon ages (N=40, n=3650) derived from linked fluvial and shallow marine depositional systems throughout the Kaiparowits Plateau indicate the majority of fluvial sediment was derived from the Mogollon highlands (67%), with subordinate contributions delivered from the Sevier thrust belt (17%) and Cordilleran volcanic sources (16%). The proportion of Sevier detritus increases upsection from 17% in basal fluvial samples to 27% in uppermost strata. Fluvial strata record sediment transport sub-parallel to the Sevier thrust belt, implying the presence of a northeast-flowing axial fluvial system fed by transverse distributive fluvial systems (DFSs) draining the Mogollon highlands and Sevier thrust belt. Shallow marine samples contain Mogollon (44%), volcanic arc (14%), and an increase (relative to contemporaneous fluvial strata) of Sevier thrust belt-derived sediment (42%), which was delivered via longshore currents into southern Utah. Upsection architectural trends in the Straight Cliffs Formation are linked to trends in detrital zircon geochronologic data, indicating that the driving force behind provenance changes also influenced stratigraphic architecture in the Cordilleran foreland basin. The axial fluvial system depositing Straight Cliffs alluvial strata was primarily fed by distributive fluvial systems (DFS) draining the Mogollon highlands during a period of high tectonic activity in the Maria thrust belt and high subsidence rates in the foreland basin (Turonian-Santonian). However, activation of the Paxton duplex in the Sevier thrust belt (early Campanian) uplifted proximal foreland basin strata and enabled DFSs draining the Sevier thrust belt to feed into the axial fluvial system more prominently. This influx of Sevier-derived sediment into the axial fluvial system was recorded by a shift in detrital zircon ages and sandstone modal composition of Straight Cliffs fluvial strata.