ASSESSING SEDIMENT TRANSPORT, PROVENANCE, AND IRON CYCLING DURING THE LATE PALEOZOIC IN THE NORTH AMERICAN SOUTHERN MIDCONTINENT

Abstract

The southern midcontinent archives a relatively complete section recording the tectonic, eustatic, and climatic events spanning the late Paleozoic of North America. Over a century of previous investigations have been conducted on these strata, yet many questions remain to be resolved. This dissertation aims to address targeted aspects of these questions starting in the late Devonian and ending in the middle Pennsylvanian. Chapter I explores the origin and transport mechanism for ubiquitous detrital silt that composes Devono-Mississippian strata in the southern midcontinent. In this study, I integrate paleogeography, sedimentology, geochemistry, and detrital zircon geochronology to test the hypothesis that this silt records eolian transport into epeiric systems. The results from this investigation support the interpretation that eolian dust was deflated off Appalachian clastic wedges and deposited into North American Devono-Mississippian epeiric seas, followed by subaqueous redistribution. Eolian dust may have delivered nutrients essential to primary productivity, such as iron, to Devono-Mississippian epeiric seas, thus promoting organic carbon sequestration. Chapter II builds off chapter 1 to investigate the factors which drove primary productivity and iron cycling within the upper Devonian Woodford Shale. I focus on testing the hypothesis that eolian dust delivered bioavailable iron that enhanced primary productivity and thus organic carbon burial. I integrate inorganic geochemistry (trace metals and iron speciation) with organic geochemistry (total organic carbon and lipid biomarkers) to establish an understanding of the paleoredox environment through time, and discuss potential models for the delivery of highly reactive bioavailable iron. Results fail to show a clear signature of iron dust fertilization, instead supporting the operation of iron shuttling as the dominant mechanism to introduce highly reactive iron. Late Devonian climatic perturbations between greenhouse and icehouse environments likely drove oscillatory redox conditions which in turn controlled the loss or gain of iron in sediments during iron shuttling. In Chapter III, I explore the influences of glacioeustasy, sediment supply and tectonism on sedimentary provenance and continental drainage in the Anadarko Basin during the middle Pennsylvanian. I integrate sedimentology, sequence stratigraphy, petrography and detrital zircon geochronology from cores on the northern and eastern shelves of the Anadarko Basin and within the basin proper. Results indicate that the Anadarko Basin and its shelves received abundant sediment from both northern and eastern sources. The northern source remained connected to the same headwaters and resisted reorganization through successive parts of the eustatic cycles. Building off previous investigations (Smith et al. 2024), the westward migration of the northern source and filling of the Arkoma Basin may have allowed for the encroachment of an easterly sourced drainage system (Kushner et al. 2022) onto the eastern shelf and ultimately into the Anadarko Basin. The occurrence of thick intervals of tidal facies within the Anadarko Basin also suggest that sediment supply kept pace, at least in part, with rapid basin subsidence during the middle Pennsylvanian.