Gettysburg Formation
The Gettysburg Formation is a mapped bedrock unit consisting primarily of sandstones, conglomerates, and shales. The Gettysburg Formation was first described in the Gettysburg area of Adams County, Pennsylvania in 1929, and over the following decade was mapped in adjacent York County, Pennsylvania and Frederick County, Maryland. It was then typically called the "Gettysburg shale," and was described as "thick red shales and soft red sandstones." The majority of this early mapping was done by G. W. Stose, A. I. Jonas, and Florence Bascom. Later workers described it as "Red, medium- to fine-grained sandstone and shale." The rock unit was formalized into a Formation in 1963 by J. D. Glaeser. Glaeser re-mapped some areas previously mapped as the Gettysburg Formation to the Hammer Creek Formation. A major groundwater resources study of the Gettysburg Formation and other formations of the Newark Supergroup in Pennsylvania was published by Charles R. Wood in 1980. Depositional Environment The Gettysburg Formation and other formations of the Newark Supergroup were deposited in the Gettysburg Basin, just one of many Triassic rift basins existing on the east coast of North and South America, which formed as plate tectonics pulled apart Pangaea into the continents we see today.