Stafford fault system: Structures documenting Cretaceous and Tertiary deformation along the Fall Line in northeastern Virginia

Four en echelon northeast-trending structures, including southeast-dipping monoclines and northwest-dipping, high-angle reverse faults, have been mapped along the inner edge of the Coastal Plain in northeastern Virginia–an area generally considered to be undeformed. Although displacements are small (15 to 60 m), the structures markedly affect the present distribution and thickness of Coastal Plain sediments.

Structure-contour maps on Cretaceous and Paleocene lithostratigraphic units show that the amount of displacement on the structures increases downward, indicating recurrent movement. The major deformation took place in the Cretaceous and the middle(?) Tertiary, but some latest Tertiary or Quaternary movement is possible.

The structures, herein named the Stafford fault system, extend for at least 56 km parallel to the Fall Line and the northeast-trending reach of the Potomac estuary. This relationship supports the hypothesis that the Fall Line and major river deflections along it have been tectonically influenced.