Mesozoic Basins Physiography Topics

1. Regional Setting
2. Extent and Boundaries
3. Characteristic Features
• Introduction to Physiography
• Coastal Plain
• Piedmont
• Mesozoic Basins
• Blue Ridge
• Valley and Ridge
• Appalachian Plateaus
• Virginia's Rivers


Mesozoic Basins Physiography: Characteristic Features (Part 1)

• Mesozoic Basins are both physiographic and geologic basins. 

• They are physiographic basins because they form topographic lowlands surrounded by the generally higher Piedmont province.

Mesozoic Basins (formerly called Triassic Basins) like the Richmond Basin, shown here, are gentle lowland depressions within generally higher Piedmont terrain. They are topographic depressions because of the presence of sedimentary rocks in the basins that are softer than surrounding Piedmont crystalline rocks. (Image courtesy of the Virgnia Division of Geology and Mineral Resources)

• They are geologic basins because they are down-dropped fault block depressions that filled with eroded sediments from the Piedmont during the Mesozoic.

245 to 66.4 million years ago

Geologic cross-section showing the fault block nature of the Mesozoic Basins.  Sediment filled valleys as the land subsided along the faults that form the edge of the basin.  Note that igneous rocks (red) are intruded into the sedimentary layers (green).  The present-day East African rift valleys are a good modern example of rift basins. (Image courtesy of the Virginia Division of Geology and Mineral Resources)