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Howard County

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Click on a tile to display information about the associated rock types or formations.
Geologic Map of Howard County (1968)Click for a closer view Click for a closer view Click for a closer view Click for a closer view
Upper Pelitic Schist (Late Precambrian ?)
 Wissahickon Formation Undifferentiated (Late Precambrian ?)
Lower Pelitic Schist (Late Precambrian ?)
 Boulder Gneiss (Late Precambrian ?)
Cockeysville Marble (Late Precambrian ?)
 Setters Formation (Late Precambrian ?)
Ultramafic Rocks (Early Paleozoic- Late Precambrian ?)
 Baltimore Gneiss (Precambrian)
Baltimore Gabbro Complex (Early Paleozoic- Late Precambrian ?)
 Pegmatite Dikes (Paleozoic)
Ijamville Formation / Marburg Schist (Late Precambrian ?)
Diabase Sills and Dikes (Triassic)
Ellicott City Granodiorite (Paleozoic)
Marburg Schist (Late Precambrian ?)
Guilford Quatrz Monzonite (Paleozoic)
Potomac Group (Cretaceous)
Relay Quartz Diorite (Early Paleozoic- Late Precambrian ?)
Lowland Deposits (Quaternary)