EOLIAN DUST SOURCED DEVONO-MISSISSIPPIAN MUDROCKS OF THE GREATER NORTH AMERICAN MIDCONTINENT

Siliciclastic mudstone, calcareous siltstone, and chert characterize several intervals of the Devono-Mississippian of the Laurentian epeiric sea. While these units have been long studied and exploited for their hydrocarbon resource potential, the origin and transport processes of the siliciclastic fraction to the marine environment remains enigmatic and largely unresolved as they do not connect to any proximal fluvio-deltaic feeder systems. To test the hypothesis of an eolian origin for the siliciclastic fines of these stratal units, we integrate refined paleogeographic maps, continental-scale stratigraphic correlations, surface wind circulation models and data from these units throughout Oklahoma on particle-size distributions, whole-rock-geochemistry and detrital zircon geochronology. Grain size of the silicate mineral fraction from the Upper Devonian Woodford Shale ranges from 4-12 µm whereas various Kinderhookian to early Chestarian units yield modes between 5-83 µm. Geochemical data from the Woodford Shale and Sycamore Limestone units show an enrichment in SiO₂ and depletion in Al₂O₃. Detrital zircon geochronology from the Sycamore Limestone and Caney Shale show primary detrital contributions from Appalachian sources. An Appalachian source is consistent with paleogeographic reconstructions which show the primary locus for clastic deposition on Laurentia to be large deltaic complexes emanating off the Acadian/Neoacadian orogen (Catskill, Price-Pocono, and Mauch Chunk deltas). Climate models show easterlies across the craton during arid austral winter months. These analyses suggest that dust was seasonally deflated from subaerially desiccated flood plains off Appalachian clastic wedges and transported northwest-westward across Laurentia. Following deposition within the marine environment, siliciclastic fines underwent subaqueous reworking and re-sedimentation prior to final deposition. The delivery of dust likely fertilized Laurentian epeiric seas which may have stimulated organic productivity, aiding in the generation of many of these organic-rich units.