Skip to Main Content
Skip Nav Destination

Lower and Middle Cambrian Shady Dolomite above the St. Clair thrust fault, Tazewell County, Virginia

John F. Windolph
Lower and Middle Cambrian Shady Dolomite above the St. Clair thrust fault, Tazewell County, Virginia (in AAPG Eastern Section meeting; abstracts, Anonymous)
AAPG Bulletin (September 1985) 69 (9): 1451-1452


Previous studies in southwestern Virginia indicate a major decollement at or near the base of the Rome Formation. Recent geologic mapping in the structurally complex southeastern corner of the Amonate quadrangle, southwestern Virginia, identified as much as 800 ft of Shady Dolomite and 600 ft of Rome Formation above the St. Clair thrust fault. The Shady Dolomite, which contains several chert and shale beds up to 1 ft thick, is light gray to white, finely to coarsely crystalline, and thick bedded to massive. The upper part of the unit contains interbeds of grayish-red and reddish-brown shale and siltstone and is in normal stratigraphic sequence with the overlying Rome Formation. "Sunbursts" of barite crystals and pyritized fractures occur approximately 300 ft below the top contact. Above the St. Clair thrust fault, the Shady Dolomite is highly deformed and brecciated, and it contains nappe structures. The dolomite is thrust over Devonian shale, which is overturned and dips 35 degrees to the southeast. The shale is in sequence with strata as young as Late Mississippian. The dolomite dips 55 degrees to the southeast and is truncated by the thrust approximately 1 mi southwest and 0.5 mi northeast of "The Jumps" on State Route 637 at Rourkes Gap, Virginia. This occurrence of Lower and Middle Cambrian strata indicates that the decollement extends locally below the base of the Rome Formation. Fractured zones associated with ramp and splay faults and probable truncated stratigraphic and structural traps may be favorable for the accumulation of hydrocarbons beneath the decollement.

ISSN: 0149-1423
EISSN: 1558-9153
Coden: AABUD2
Serial Title: AAPG Bulletin
Serial Volume: 69
Serial Issue: 9
Title: Lower and Middle Cambrian Shady Dolomite above the St. Clair thrust fault, Tazewell County, Virginia
Title: AAPG Eastern Section meeting; abstracts
Author(s): Windolph, John F., Jr.
Author(s): Anonymous
Affiliation: U. S. Geol. Surv., Reston, VA, United States
Pages: 1451-1452
Published: 198509
Text Language: English
Publisher: American Association of Petroleum Geologists, Tulsa, OK, United States
Meeting name: AAPG Eastern Section Meeting
Meeting location: Williamsburg, VA, USA, United States
Meeting date: 19851110Nov. 10-12, 1985
Summary: Y
Accession Number: 1986-040732
Categories: Structural geology
Document Type: Serial Conference document
Bibliographic Level: Analytic
N33°00'00" - N47°30'00", W87°00'00" - W67°00'00"
N36°55'60" - N37°19'60", W81°54'00" - W81°15'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute.
Update Code: 1986
Program Name: USGSOPNon-USGS publications with USGS authors
Close Modal

or Create an Account

Close Modal
Close Modal