STRATIGRAPHY OF THE GATESBURG FORMATION, CENTRAL PENNSYLVANIA: THE NORTHEASTERN MOST EXTENT OF THE GREAT AMERICAN CARBONATE BANK IN THE CENTRAL APPALACHIANS

The Gatesburg Formation includes a suite of carbonate and interbedded siliclastic-carbonate rocks that were deposited in the Appalachian Basin portion of the Great American carbonate bank during the Upper Cambrian. The Gatesburg is composed of five primary members, which are (in descending order): the Mines, Upper Sandy, Ore Hill, Lower Sandy, and Stacy Members. The Mines, Ore Hill, and Stacy Members contain only carbonate lithologies in central Pennsylvania, while the Upper and Lower Sandy Members include variation of interbedded dolostone and sandstone (Laughrey, 2012). The lithologic and stratigraphic investigations in this study are based on a rock core and field research in the Mingoville 7.5-minute quadrangle, Centre County, Pennsylvania.

Field data within the quadrangle were consistent with research done in surrounding areas. Due to the friable nature of certain facies within the formation, outcrops are often highly weathered and scarce. A core was drilled for stratigraphic correlation of the upper members of the Mines, Upper Sandy, and Ore Hill. The core revealed limestone units within the dolostones of the Mines and Upper Sandy Members and dolostones at the stratigraphic position of Ore Hill limestones found in outcrop less than a mile away. Stratigraphic work is therefore complicated by an incomplete understanding of the processes and mechanisms that controlled (and may continue to control) carbonate diagenesis within the Gatesburg Formation. The intention of this research is to create a model of dolomitization that better explains the characteristics of the Gatesburg dolomites as observed in the Mingoville core.

The Mingoville core shows vertical stacking of carbonate facies indicative of cyclical sea-level fluctuations. The low relief of the continental shelf and cyclic nature of these facies suggest that the features observed in this particular core are representative of shelf-wide sedimentation, as opposed to localized sedimentary accumulation. The repetition of algal growth, dolostones, and dolomitic sandstones demonstrates the shifting peritidal and adjacent (shallower) subtidal deposits. This core allowed for a better stratigraphic context to understand shelf-wide paleoenvironmental controls.