Stratigraphy, sedimentology, and geochemistry of the Upper Mississippian Pride Shale in the Appalachian Basin

Abstract

Tide-dominated or tide-influenced coastal marine deposits form some of the most complicated and largest hydrocarbon fields in the world (Wood, 2004 and references cited therein). Good outcrop analogs can provide significant insight to geologists for recognizing tidal influence in core and interpreting petrophysical log data, thus reducing uncertainty and risk when developing depositional models and planning for field development. Despite the observation that 8 of the 12 largest deltas in the modern world are either tide dominated or strongly tidally influenced (Middleton, 1991), many geologists fail to recognize tidal influence in the rock record, perhaps, in part, because of the influence of preexisting paradigms. This seems to be particularly so for many geologists prospecting for hydrocarbons within Pennsylvanian sediments in the Arkoma and Anadarko Basin of the southcentral United States. Although good ancient analogs of tide-dominated deltas exist (see summary table in Feldman et al., 2014), many of these studies inferred tidal influence from the intercalation of sandstone and mudstone, an abundance of fluidized mud deposits, a dominance of structures formed from currents, and the shoreline-perpendicular orientation of elongate sandstone bodies. Few studies have identified sedimentary structures in delta-front and prodelta settings that can be directly related to semidiurnal, semimonthly, and longer-term tidal deposition. This may reflect background interference from storms or variable fluvial discharge that disrupted tidal deposition and thus obscures evidence of fortnightly or longer tidal signals, or it may reflect …