Sequence Stratigraphic Signature of a Long Term Greenhouse to Ice-House Transition in Mississippian Ramp Carbonates of Appalachian and Eastern Illinois Basins

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9725308 Read This proposal requests funds to study the large exposures and extensive cores of the Early Mississippian (Osage-Meramecian) carbonate ramp, Appalachian/eastern Illinois Basins, and compare them to Late Mississippian successions, to search for the long term (30 m.y.) stratigraphic response of this tropical carbonate ramp to eustatic and climatic changes associated with Late Paleozoic global greenhouse to icehouse transition. We presently have a large data set on the later Mississippian (Chesterian) units from both the Appalachian and Illinois Basins, which appear to show evidence of deposition under relatively large sea level fluctuations during onset of Late Paleozoic glaciation of Gondwana; these will serve as a basis of comparison with the older units. We propose to log and photo-mosaic the Early and Middle Mississippian ramp facies, which appear to have formed on and above a clinoformal ramp with skeletal ramp margin and downslope banks, a gullied slope and low-stand (?) sand bodies, that built out from an abandoned detaic-marine self. Outcrops and cores will be logged bed-by-bed, to define vertical and lateral extent of component carbonate and siliciclastic facies, presence or absence of regional tidal flat facies, eolianites, types of bounding surfaces and paleosols developed, and any evidence of erosional incision. We will construct detailed regional cross sections to define a high-resolution sequence stratigraphy for the early Mississippian ramp. Additionally, we will extend our later Mississippian (Chesterian) high resolution, sequence stratigraphic outcrop study of the Appalachian Basin, throughout the subsurface Appalachian Basin using core, sample cuttings and wireline logs. We will then use these data sets on the Early to Late Mississippian to evaluate the magnitude of Mississippian sea level fluctuations by computer simulation of our stratigraphic cross-sections. Input parameters will be constrained where possible using the field data. Finally, this data wil l be integrated with the ice-buildup history in Gondwana, to define the stratigraphic response of this tropical ramp to Late Paleozoic global climate change.