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U.S. Department of Energy
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Tioga Bentonite in the Appalachian Basin: Final report

Technical Report ·
OSTI ID:6932671
The Tioga Bentonite is an interval up to 258 ft (79 m) thick with several tuff layers. The top of the Tioga middle coarse zone marks the top of the Onesquethaw Stage of the Devonian System throughout 102,000 sq mi (265,000 sq km) in the Appalachian basin. This report lists well and outcrop data for 763 localities where the Tioga Bentonite has been identified in the Appalachian basin. A series of detailed stratigraphic cross sections of the Tioga ash beds shows the internal stratigraphy of the Tioga Bentonite and its relation to overlying and underlying strata. Details of the Tioga internal stratigraphy are portrayed of a series of maps. Grain size data for biotite, quartz, feldspar, zircon, and apatite are also portrayed on maps. All maps in this report are at a scale of 1:1,000,000. In a preliminary phase of this study, the Berea pluton near Fredericksburg, Virginia was considered the best fit for an intrusive equivalent of the volcanic root for the Tioga middle coarse zone, based on thickness and grain-size data of the middle coarse zone and a compatible mineralogy and age of the Berea pluton. It is now believed that the Virginia Blue Ridge and Piedmont were thrust westward many tens of miles by the Alleghany orogeny in Permian time and that the roots of the Tioga volcano may be present only in the subsurface, piercing upward through the true basement and through the Cambrian and Ordovician strata beneath the overthrust crystalline rocks of the Piedmont near Fredericksburg, Virginia. The Tioga volcanic plume of the middle coarse zone was dispersed across the Appalachian, Michigan, and Illinois basins by winds of the Devonian southern trade wind belt, where the Tioga eruptive center was situated before North America drifted to its present location.
Research Organization:
North Carolina Univ., Chapel Hill (USA). Dept. of Geology
DOE Contract Number:
AS05-76ET12139
OSTI ID:
6932671
Report Number(s):
DOE/ET/12139-T2; ON: DE87003866
Country of Publication:
United States
Language:
English