Abstract

The fluviodeltaic Colton Formation (Late Paleocene–Early Eocene) forms a lobate depositional system that prograded from the south into the Laramide Uinta Basin of northeastern Utah (United States) with a preserved sediment volume of ∼3000 km3 and a maximum thickness of ∼1000 m. Joint consideration of detrital zircon ages, paleocurrent trends, and sandstone petrofacies permits an assessment of Colton provenance relations in the context of evolving Cretaceous–Paleogene sedimentation in the Utah foreland. Grains with U-Pb ages younger than 285 Ma derived from the Cordilleran magmatic arc form ∼50% of the detrital zircons in arkosic Colton sand, and were transported ∼750 km to the Uinta Basin from the Mojave segment of the arc by the California paleoriver. Colton sedimentation was the Paleogene culmination of a persistent pattern of Cretaceous sediment transport northward, subparallel to the Sevier thrust front, to supplement east-directed sediment delivery to the retroarc foreland from the Sevier thrust belt. The ratio of longitudinally to transversely derived sediment was enhanced in foreland strata after Laramide deformation produced intraforeland uplifts that screened the foreland belt from Sevier sources. The relative abundance of arc-derived detrital zircons that were contributed to strata of the Utah foreland increased in late Campanian time and remained high into Eocene time. Detrital zircon populations in Paleogene forearc strata of southern California are compatible with coeval derivation of arc-derived detritus in the forearc sands and the Colton backarc sand from a common paleodrainage divide crossing the Mojave region to connect hinterland Nevadaplano and Mexicoplano uplands to the north and south.

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