CARBONIFEROUS TRANSITION FROM EXTRAREGIONAL TO LOCAL SEDIMENT SOURCES TIED TO INTRACONTINENTAL ANCESTRAL ROCKY MOUNTAINS DEFORMATION

Abstract

This study explores the influence of intracontinental deformation tied to the Ancestral Rocky Mountains (ARM) orogen on sediment dispersal in the Carboniferous through sandstone compositional and detrital zircon provenance analysis. We focus on two areas within proposed transcontinental sediment transport routes in Laurentia: (1) the Hugoton Embayment in southwestern Kansas, where Chesterian and Morrowan sandstones form a stacked incised valley fill complex, one of the few coarse-grained targets for study within carbonate-shale dominated successions and (2) the Arkoma shelf in northwestern Arkansas, where Chesterian through Desmoinesian sandstones capture the transition from a carbonate shelf to a clastic-dominated foreland. A total of 15 core and outcrop samples were collected, resulting in 1544 new detrital zircon U-Pb ages, 582 ages from southwestern Kansas and 962 ages from northwestern Arkansas. Detrital zircon U-Pb age distributions of sandstones from both sites are characterized by major Grenville (1,300-900 Ma) and Taconic-Acadian (500-350 Ma) age clusters and minor components of older age groups, consistent with a dominant source in the Appalachians, tied to Alleghanian orogenesis. However, by the Early Pennsylvanian, the provenance of these two regions diverge. While a dominantly Appalachian signature remains clear in the Arkoma shelf samples, the Hugoton Embayment samples see this signature replaced, in part, by Yavapai-Mazatzal (1800-1600 Ma) and Granite-Rhyolite (1550-1300 Ma) ages, major components of the midcontinent basement likely derived from nearby ARM uplifts. Sandstone composition data also document an increase in feldspar and volcanic lithic grains in these samples, consistent with input from more proximal sources. Comparisons of new data with published data from age-equivalent units across Laurentia indicate a similar shift in provenance, from extraregional to local sediment sources, where ARM deformation was most active. The new data confirm development of a major transcontinental sediment dispersal system in the Late Mississippian tied to the Alleghanian orogeny; however, by the Early Pennsylvanian this system was disrupted by intraplate deformation tied to the ARM orogen.