Braided stream depostion and provenance of the Upper Cretaceous-Paleocene(?) Canaan Peak Foramtion, Sevier foreland basin, southwestern Utah

Schmitt, James; Geological Society of America; Jones, David; Goldstrand, Patrick

Canaan Peak formation detritus was derived from erosion of highlands created by Cretaceous Sevier-style thrust-fault development to the west in southeastern Nevada and western Utah and destributed across an extensive gravel-dominated braidplain complex. However, it is not possible to determine whether Canaan Peak deposition records active uplift or is postorogenic. Sediment was transported eastward a minimum distance of 45 to 60 km and was subject to continuous high-energy reworking within the Canaan Peak fluvial system, resulting in destruction of all but the most stable clast lithologies. The purpose of this investigation is to determine the depositional environments and provenance of the Upper Cretaceous to Paleocene(?) Canaan Peak Formation of southwestern Utah in order to evaluate the paleogeographic and paleotectonic significance of this coarse-grained unit. Specific goals of this study include determination of the following parameters: 1) lithofacies present and their lateral and vertical relations, 2) depositional environments, 3) composition of Canaan Peak conglomerates and associated sandstones, 4) paleocurrents, and 5) provenance.... The Upper Cretaceous to Paleocene(?) Canaan Peak Formation of southwestern Utah consists of approximately 100 m of cobble conglomerate and subordinate sandstone. Coarse-grained lithofacies include massive to very crudely stratified pebble to cobble conglomerate (Gm) and trough cross-stratified conglomerate (Gt). Minor associated lithofacies include trough (St) and planar (Sp) cross-stratified sandstone and scour-fill sandstone (Ss). Gravel deposition occurred during high-discharge periods within a Scott/Donjek-type perennial braided Ouvial system on longitudinal bars (Gm) and sinuous-crested transverse bars (Gt), and as a product of longitudinal bar-top and interbar channel scour filling (Gt). Sand accumulated under lower How-velocity conditions through migration of interbar channel dunes and transverse bars (St/Sp) and development of scour and fill deposits (Ss). Clast imbrication and trough-axis orientation measurements indicate east to northeast paleoflow directions. Gravel-sized clasts are predominantly resistant lithologies including Upper Precambrian-Cambrian quartzite, fossiliferous Paleozoic chert, and some silicified middle Jurassic volcanic rocks; less resistant Paleozoic limestone clasts are only locally abundant. Canaan Peak Formation detritus was derived from erosion of highlands created by Cretaceous Sevier-style thrust-fault development to the west in southeastern Nevada and western Utah and distributed across an extensive gravel-dominated braid plain complex. However, it is not possible to determine whether Canaan Peak deposition records active uplift or is postorogenic. Sediment was transported eastward a minimum distance of 45 to 60 km and was subject to continuous high-energy reworking within the Canaan Peak fluvial system, resulting in destruction of all but the most stable clast lithologies.

Braided stream depostion and provenance of the Upper Cretaceous-Paleocene(?) Canaan Peak Foramtion, Sevier foreland basin, southwestern Utah

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