Abstract

Driese et al. (1994) present two independent interpretations that are derived from two different sets of observations for Mississippian rocks in Tennessee and Alabama. First, geochemical data and carbonate petrology are the basis for an interpretation of meteoric diagenesis and subaerial exposure of the top of the Monteagle Limestone; paleosol remnants and local scour surfaces are interpreted to indicate a regional unconformity. Second, the inferred regional unconformity is regarded by Driese et al. (1994) as a sequence boundary that is on-lapped northward by a transgressive systems tract (Hartselle Sandstone), and on that basis, the Hartselle Sandstone is interpreted to represent southward dispersal from a eratonic provenance to a delta system that prograded over the Monteagle Limestone. Driese et al. (1994) link these two interpretations; however, superposition of the Hartselle Sandstone over an exposure surface on the Monteagle Limestone constrains neither the direction of sediment dispersal nor the provenance of the sandstone. Previously published sedimentologic data (Thomas and Mack, 1982) and petrographic data (Mack et al., 1981, 1983) combine to document sediment dispersal from a provenance in the Ouachita orogenic belt on the southwest to a northwest-striking, northeast-facing barrier-island and marine-bar complex (Hartselle Sandstone) that prograded northeastward onto the Monteagle Limestone in northern Alabama (Fig. lDD). This discussion will show that northeastward progradation of a barrier system (Hartselle Sandstone) is entirely compatible with transgression over a subaerial weathering surface on the Monteagle Limestone, and that the interpretation of southward progradation from a cratonic source is not compatible with the sedimentologic and petrographic data for the Hartselle Sandstone. Resolution of the nature and location of the provenance is critical to interpretation of regional tectonic history of the Ouachita and Appalachian orogenic belts and the orogenic foreland.

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