Brighton Dam Road Quarry (Howard-Montgomery Quarry), Howard Co., Maryland, USA

Age: Proterozoic (541 - 2500 Ma)

Stratigraphic Name: Cockeysville Marble

Description: Metadolomite, calc-schist, and calcite marble are predominant; calc-gneiss and calc-silicate marble widespread but minor; thickness about 750 feet.

Comments: secondary unit description from USGS Geologic Names lexicon (ref MD004): Author has erected a six-fold stratigraphy for the Cockeysville consisting of five unnamed members and one lens to accommodate the variety of rock types. These are the layered marble member (0 to 200 m), the massive metadolostone member (0 to 400 m), the layered metadolostone member (0 to 1.4 km), the massive metalimestone member (0 to 450 m), which includes the calc-gneiss lens (0 to 225 m), and the phlogopitic metalimestone member (0 to 300 m). Each member is described in detail. Thickness of the Cockeysville overall varies from 0 to 1.4 km, the range of the layered metadolostone. The relative ages of these units are uncertain. Unit as a whole is mapped as Cambrian to Ordovician(?). Original map source: In 1995 the Water Resources Division of the U.S. Geological Survey digitized the geologic map of Maryland from the 1968 paper map (Reference MD001). Information about products from the Maryland Geological Survey can be found at http://www.mgs.md.gov/.

Lithology: Major:{marble}, Minor:{calc silicate schist}, Incidental:{calc silicate gneiss}

Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. [133]

Age: Mesoproterozoic (1000 - 1600 Ma)

Lithology: Orthogneiss

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]