Challenging assumptions of sediment routing in retroarc foreland basins: Detrital zircon evidence for axial versus transverse drainages in the Late Cretaceous of southern Utah, USA

Abstract

AbstractDepositional models for retroarc foreland basin systems commonly imply a direct link between thrust belt dynamics and sediment supply, despite documented complexity between orogen‐transverse and orogen‐parallel (axial) sediment routing systems. Previous detrital zircon provenance studies from the Straight Cliffs Formation in the Kaiparowits Plateau of southern Utah indicate primary axial source areas to the south (Mogollon Highlands), and southwest (Cordilleran magmatic arc), with relatively minor transverse input from the Sevier fold‐thrust belt to the west. Complementary data from 32 new samples are presented to investigate whether these trends persist in correlated strata from sections most proximal to the active fold‐thrust belt, as well as strata proximal to the Mogollon Highlands. This study aims to improve statistical robustness through higher‐n datasets (>300 analyses/sample) and addresses the possibility of recycling of zircon grains from strata in the exhumed Sevier fold‐thrust belt. Based on this provenance dataset, we infer that orogen‐transverse deposition was mainly limited to the most proximal sections (within ca. 75 km of the fold‐thrust belt), but included episodic distribution across the foredeep that was associated with distinct intervals of widespread amalgamated sand and gravel sheet deposits. In contrast, more distal parts of the foredeep record long‐distance fluvial transport (>400 km) of zircons from the active Cordilleran magmatic arc as well as Yavapai‐Mazatzal basement rocks in central Arizona (the Mogollon Highlands). Palaeogeographic reconstructions suggest the apex of a large basin‐axial fluvial system may have been located at the structural syntaxis between the Sevier fold‐thrust belt and western margin of the Mogollon Highlands. This interpretation is supported by detrital zircon data presented here, thus extending the possibility that the Palaeogene ‘California River’ may have existed by at least Late Cretaceous time. Ultimately, these data point to extrabasinal controls on sediment supply, which was largely decoupled from flexural accommodation controls in this archetype retroarc foreland basin.