Rock Topics

Sedimentary Rocks (Part 1)

Sedimentary rocks and sediments are found in four major areas in Virginia: the Coastal Plain, the Mesozoic Basins, the Valley and Ridge, and the Appalachian Plateaus.

Sedimentary Rocks of the Coastal Plain

• The Coastal Plain is underlain mainly by poorly consolidated sediments consisting of mud, sand, and gravel.  Chalk and coquina are common in some areas.  Peat, a form of coal, is found in the Great Dismal Swamp.

GravelsCoastal Plain gravels (Left photograph by Robert Whisonant; right photograph by Stan Johnson)

MapThe Coastal Plain is underlain mainly by unconsolidated sediments.  These photographs show places in the Coastal Plain where sand and gravel are or have been mined.  Left photograph is near Fredericksburg.  Right photograph shows a close-up view of sand and gravel in Henrico County near Richmond. 

Coquina in the Coastal Plain (Photographs by Stan Johnson)

MapCoquina, or fossil hash, is a common sedimentary rock of the Coastal Plain.  The Yorktown Coquina (left) forms Cornwallis Cave (right) near Yorktown.  According to history, British General Cornwallis used this cave to store weapons and ammunition before the Battle of Yorktown in the Revolutionary War.