Site: GLENS 8-3:
Lower Brush Creek Shale north of Glenshaw Glass Company, Rt. 8, Wittmer, PA
Latitude: 40° 31' 25"N
Longitude: 79° 56' 52"W
Quadrangle: Glenshaw 7 1/2'
Age: Pennsylvanian
Formation(s): Conemaugh Group, Lower Brush Creek shale and underlying Mahoning sandstone interval.
Purpose:
This site shows a rather monotonous section of the freshwater shale and siltstone.Access and Parking:
Park along access road to car repair shop. Outcrop is south of road along path leading to old quarry pit. Parking available for motor coach at car repair shop with permission. Recommended for all age groups.
Mass Transit Directions:
(Make sure you get an up-to-date PAT Transit schedule:
No PAT Transit service.
Driving Directions:
From the Cathedral of Learning, Drive 0.7 mi. west on Fifth Avenue. Make a Left on Craft Av. Go 0.1 mi., then make a right onto Blvd. of Allies, go 1.6 mi. then bear right onto I-579. Stay on I-579 across the Allegheny River then get onto Rt. 28 East. Go approximately 6.6 miles and take the exit for Rt. 8 North (Etna). From the end of the exit ramp, stay on Rt. 8 (Butler Street) for approximately 2.5miles. Make a left to car repair service. Outcrop is on left in old quarry pit.
See map and figures.
What you will see:
This is a relatively thick monotonous section of gray-green shale and siltstone layers that become reddish toeard the top of the exposed section. The shales contain rare fossils of plant fragments. The lowermost siltstones of the Mahoning sandstone interval locally exhibit good examples of cross-bedding and mudcracks in a clacareous claystone layer. There are also good examples of tectonic joints with three dominant orientations 300°-310°, 80°-90°, and 335°-340° (see Evans, 1994). This site is near Locality Nine of Cain (1977).
Geologic History: Environment of Deposition:
The Lower Brush Creek shales at this location may represent interdistributary bay sediments. These rocks eventually grade into the Brush Creek marine limestone.
Distributary Environment (from Horne and others, 1978).
Click on the thumbnails below for pictures of the outcrops:
| A view of the outcrop. |
 |
| A close-up view of the shale section. |
 |
| Another view of the shale section to the north of the above photo. |
 |
Fossils:
The silty shales contain rare to uncommon plant fragment fossils.
References:
Berryhill, H. L., Jr., Schweinfurth, S. P., and Kent, B. H., 1971, Coal-bearing Upper Pennsylvanian and Lower Permian Rocks, Washington area, Pennsylvania: U. S. Geological Survey Professional Paper 621, 47p.
Cain, B. A., 1977, Carboniferous paleomagnetics of the Appalachian Basin: Stratigraphy, depositional environments, and some paleomagnetic relationships of Pennsylvanian strata in western Pennsylvania: M.S Thesis, University of Pittsburgh, Pittsburgh, Pennsylvania, 107p.
Edmunds, W. E., Skema, V. W., Flint, N. K., 1999, Pennsylvanian, in Shultz, C. H., ed, The Geology of Pennsylvania, Pennsylvania Geological Survey Special Publication 1, p. 149-169.
Evans, M. A., 1994, Joints and decollement zones in the Middle Devonian shales: Evidence for multiple deformation events in the central Appalachian Plateau: Geological Society of America Bulletin, v. 106, p.447-460.
Harper, J. A., 1990, Fossil Collecting in the Pittsburgh Area, Pittsburgh Geological Society Guidebook. 50 pages.
Horne, J. C., Ferm, J. C., Caruccio, F. T., and Baganz, B. P., 1978, Depositional models in coal exploration and mine planning in Appalachian region: American Association of Petroleum Geologists Bulletin, v. 62, p. 2379-2411.
Johnson, M. E., 1928, Geology and Mineral Resources of the Pittsburgh Quadrangle, Pennsylvania: Pennsylvania Geological Survey Bulletin A 27, 236 p.
Leighton, H. 1945, The Geology of Pittsburgh and its Environs: A Popular Account of the General Geological Features of the Region: Carnegie Institute Press, 2nd edition, Pittsburgh, PA , 80p.
Shaw, E. W., and Munn, M. J., 1911, Geologic Atlas of the United States: Burgettstown-Carnegie Folio, United States Geological Survey Folio 177 Field Edition, 123p.
Wagner, W. R., and others, 1970, Geology of the Pittsburgh Area: Pennsylvania Geological Survey General Geology Report G 59, 145p.
Click here for an image of the County Geologic Map (1880)