Reports
Stratigraphy of the Frederick Valley and its relationship to karst development
2004, Brezinski, D.K.
Report of Investigations 75
Abstract
The Frederick Valley of Maryland is a tightly folded overturned syncline that exposes easily soluble carbonate rocks that range in age from Early Cambrian to Early Ordovician. The valley is bordered on the west by Early Triassic alluvial deposits and on the east by metamorphosed rocks of the Westminster terrane. The Cambrian Frederick Formation was mapped utilizing a four-member subdivision that includes the Monocacy (new name), Rocky Springs Station, Adamstown, and Lime Kiln members. The Ordovician Grove Formation is herein subdivided into the Ceresville (new name), Fountain Rock (new name), and Woodsboro (new name) members, in ascending stratigraphic order. The older units in this study were formed in deep water at oceanic depths. As the rocks of the Frederick Formation accumulated, they steadily aggraded upward towards sea level so that the top of the formation was deposited in shallow water at the edge of the North American continent. The Grove Formation was deposited in sand shoals and algal reefs that were ultimately drowned during an Early Ordovician submergence. The Triassic Leesburg Formation was deposited in large alluvial fans at the margin of fault basins during extension and rifting that formed the Atlantic Ocean.
From these data, a relative scale of karst susceptibility was developed to assist land-use planners, developers, and the public in recognizing areas of high karst susceptibility. The Ceresville, Woodsboro, and Fountain Rock members of the Grove Formation and the Lime Kiln Member of the Frederick Formation have very high karst susceptibility. When unlined drainage, storm-water management areas, drainage diversions, or quarries are placed in proximity to these units, soil-cover collapses are likely to occur. A slightly lesser karst susceptibility is recognized for the Rocky Springs Station Member of the Frederick Formation. The Triassic Leesburg Formation, and the Monocacy and Adamstown members of the Frederic Formation have comparatively low karst susceptibility.
