Paper No. 9
Presentation Time: 10:15 AM
INTERACTIONS BETWEEN AXIAL AND TRANSVERSE DRAINAGE SYSTEMS IN THE CORDILLERAN FORELAND BASIN: EVIDENCE FROM DETRITAL ZIRCONS IN THE STRAIGHT CLIFFS FORMATION (CONIACIAN-SANTONIAN), SOUTHERN UTAH
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 Coniancian – Santonian time. Detrital zircon ages (N = 40, n = 3742) 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 (66%), with subordinate contributions delivered form the Sevier thrust belt (19%) and Cordilleran volcanic arc (15%). The proportion of Sevier detritus increases up-section from 18% in basal fluvial samples to 27% in uppermost strata. Shallow marine samples contain Mogollon (43%), volcanic arc (14%), and a relative increase of Sevier thrust belt-derived sediment (43%), which was delivered via longshore currents into southern Utah. Straight Cliffs Formation deposition was influenced by the development of topography in the Sevier fold and thrust belt, but to date, little emphasis has been placed on the tectonic development of the Mogollon highlands of central Arizona. Provenance data, up-section increases in average grain size, channel amalgamation trends, and a north/northeastward progradation of fluvial facies signal a major influx of sediment from the actively uplifting Mogollon highlands and Maria thrust belt. Fluvial strata record sediment transport parallel to the Sevier foreland basin and perpendicular to the Maria thrust belt, implying the presence of a transverse distributive fluvial system draining the Maria thrust belt. Spatial and temporal trends in alluvial architecture and continuous sediment input from the Mogollon highlands are also consistent with predictions made by DFS models.