Morrowan, Atokan, and Desmoinesian (Lower–Middle Pennsylvanian) clastic strata in the Forest City (Iowa, northwest Missouri, eastern Nebraska, and Kansas) and Illinois Basins on the North American midcontinent record the interaction between fluctuations in eustatic sea-level and major tectonic events. One of three major Paleozoic eustatic sea-level lows occurred near the Mississippian/Pennsylvanian boundary and was followed by a eustatic rise that continued into Late Pennsylvanian time. Alleghenian mountain building that is linked to the creation of the Pangean supercontinent also began during latest Mississippian time and continued until latest Pennsylvanian or earliest Permian time. Detrital-zircon geochronology and stratigraphic descriptions allow reconstruction of sediment dispersal patterns associated with these events. Our detrital-zircon signatures from Morrowan–lower Desmoinesian strata in the Illinois Basin are interpreted to reflect a change from regional drainages that reworked underlying Mississippian strata to extensive extrabasinal fluvial systems that supplied detritus shed from southeastern New England. By middle Desmoinesian time, detrital-zircon signatures in the Illinois Basin are more similar to those from coeval units in the central Appalachian Basin, indicating a southward shift in the provenance of the fluvial systems. In the Forest City Basin, Morrowan strata are absent and our detrital-zircon data indicate that Atokan–early Desmoinesian sedimentation was dominated by regional fluvial systems that recycled underlying strata. The introduction of extrabasinal fluvial systems with New England headwaters in the middle Desmoinesian coincided with the overtopping of the Mississippi River Arch and depositional linking of the Forest City and Illinois Basins. The Forest City and Illinois Basins collectively contain an Early–Middle Pennsylvanian sedimentary record in the backbulge depozone of the Alleghenian foreland basin system that reflects overtopping of the forebulge located along the Cincinnati Arch and the effects of eustatic sea-level rise. These results lend credence to the previously proposed transcontinental fluvial systems during late Paleozoic time and help to better constrain their courses.
Lower–Middle Pennsylvanian strata in the North American midcontinent record the interplay between erosional unroofing of the Appalachians and eustatic sea-level rise
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J.K. Kissock, E.S. Finzel, D.H. Malone, J.P. Craddock; Lower–Middle Pennsylvanian strata in the North American midcontinent record the interplay between erosional unroofing of the Appalachians and eustatic sea-level rise. Geosphere doi: https://doi.org/10.1130/GES01512.1
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