Abstract

Detrital zircons with ages of 535 ± 10 Ma in many North American Midcontinent sandstones are commonly attributed to sources in Cambrian synrift igneous rocks along the Southern Oklahoma fault system. New analyses are designed to test the characteristics of proximal detritus from the Wichita and Arbuckle uplifts. Detrital zircons from a sandstone (Lower Permian Post Oak Conglomerate) directly above an unconformable contact with the Wichita Granite Group in the Wichita Mountains have strongly unimodal U-Pb ages of 540–520 Ma and εHft values of +4.7 to +10.1. In contrast, two sandstone samples (Upper Pennsylvanian Vanoss Conglomerate) in the onlapping succession above an angular unconformity on Paleozoic strata on the flank of the Arbuckle anticline have detrital zircons with U-Pb ages that correspond dominantly to the Superior (∼2700 Ma) and secondarily to the Granite-Rhyolite (1480–1320 Ma) and Grenville (1300–970 Ma) provinces of the Laurentian craton. The Vanoss zircons indicate recycling from quartzose sandstones within the Middle Ordovician platform carbonates in the Arbuckle passive-margin cover succession. A stratigraphically higher sandstone (Permian Wellington Formation) above the onlapping conglomerates has a more diverse detrital-zircon population, indicating that sediment dispersal from external sources overwhelmed the proximal detritus in the immediate cover of the Wichita and Arbuckle uplifts. The distinctive εHft values of the proximal detritus from the Cambrian synrift igneous rocks offer potential discrimination from zircons of the same age from Gondwanan accreted terranes, which are represented in the Wellington sample.

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