Structural evolution of the Roanoke area, Virginia

Approximately 70 square miles of Roanoke, Botetourt, and Bedford counties and northern Roanoke were mapped in detail in an attempt to reconstruct the structural evolution of this critical area situated at the arcuate junction of the Southern and Central Appalachians. The area includes approximately 15,000 feet of Paleozoic sedimentary rocks which range in age from Early Cambrian to Early Mississippian. Most strata are allochthonous and comprise four imbricated thrust blocks delimited from northwest to southeast by the Pulaski, Salem, Max Meadows, and Blue. Ridge faults. Indigenous rocks comprise the Read-Coyner Mountain and Bonsack anticlinal fensters and a probable fenster in Roanoke. The Read-Coyner Mountain fenster effectively separates the Catawba syncline and related Pulaski block structures to the northwest from the Salem block to the southeast, whereas the Bonsack fenster intervenes between the Salem and Max Meadows blocks. The eastern part of the area contains salients of the Blue Ridge, Max Meadows, and Salem blocks and a cross-structure delineated by northwesterly trending allochthonous and indigenous structural elements. Reconstruction of pre-thrusting basin geometry from structural and stratigraphic evidence reveals the following arrangement of structural elements from southeast to northwest: (1) Blue Ridge anticlinorium, (2) ancestral Catawba syncline and related portions of the Pulaski block, (3) Read Mountain anticlinorium, now partially exposed in fensters, and (4) Blacksburg synclinorium. Stratigraphic evidence indicates that each of these structures evolved, at least in part, contemporaneously with deposition. Thrusting was probably initiated in Mississippian time with inception of the proto-Pulaski fault in the basement beneath the Blue Ridge anticlinorium. Subsequent thrusting apparently originated from within the proto-Pulaski and Pulaski blocks in a progressive sequence from northwest to southeast. The proto-Pulaski fault propagated from the basement to near the base of the Rome beneath the rooted Catawba syncline and then was deflected surfaceward along the southeastern flank of the Read Mountain anticlinorium. After initial movement by plunger-like stresses, the incompetent, structurally low Rome became detached from the sole of this thrust block and was left behind, while overlying beds continued to advance along the newly defined Pulaski fault. The Pulaski block was then forcibly shoved over the Read Mountain anticlinorium and into the Blacksburg synclinorium until it encountered the structural front to the northwest. Continued application of tangential stress through the impounded Blue Ridge anticlinorium and yoked Catawba syncline induced Salem thrusting within the Pulaski block over the southeastern flank of the Read Mountain anticline. The Max Meadows fault probably originated by resurrection of the original Rome-soled proto-Pulaski block over the Bonsack anticline. The final stages of thrusting probably involved movement of both the Max Meadows block and the dismembered anticlinal Blue Ridge block. After thrusting, both allochthonous and indigenous blocks were folded and locally faulted, and nearly 10,000 feet of structural relief was imparted on the Pulaski thrust and overlying Catawba syncline. The Tinker Mountain-Coyner Mountain cross-structure probably originated contemporaneously with deposition but developed largely after thrusting by vice-like lateral compression and contemporaneous downwarp generated in the structural, possibly primary embayment of the Roanoke area.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Geology

Department dc:contributor.department

Geology

Grantor dc:publisher

Virginia Polytechnic Institute

Year dc:date.issued

1968

Author dc:creator

• Hazlett, William Henry

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10919/118900

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/118900