Origin of two clay-mineral facies of the Potomac Group (Cretaceous) in the Middle Atlantic States
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Abstract
Sedimentary clay that crops out in the coastal plains of New Jersey, Delaware, the part of Maryland north and east of Washington, B.C., and the northeast half of Washington, D.C., in the nonmarine Cretaceous Potomac Group is predominantly kaolinite and illite. In contrast, in part of southeastern Maryland, the southwest half of Washington, D.C., and most of eastern Virginia, Potomac Group clay is predominantly montmorillonite.
Kaolinite and illite were probably derived by intense acid weathering of metamorphic and granitic rocks to the west during the Cretaceous and were deposited in a well-drained basin. Montmorillonite was most likely produced by deep weathering of a mainly granitic source. Poor drainage and alkaline surface- and ground-water conditions probably accompanied the production, transportation, deposition, and burial of the montmorillonite. Kaolinization of the montmorillonite is taking place now at the surface in northern Virginia.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Origin of two clay-mineral facies of the Potomac Group (Cretaceous) in the Middle Atlantic States |
| Series title | Journal of Research of the U.S. Geological Survey |
| Volume | 6 |
| Issue | 22 |
| Year Published | 1978 |
| Language | English |
| Publisher | U.S. Geological Survey |
| Description | 12 p. |
| First page | 203 |
| Last page | 214 |
| Country | United States |
| State | Delaware, Maryland, New Jersey, Pennsylvania, Virginia |
| Other Geospatial | Potomac Group |
| Google Analytic Metrics | Metrics page |