Latitude:                         40° 30' 50"N

Longitude:                      79° 57' 05"W

Quadrangle:                    Glenshaw 7 1/2'

Age:                                Pennsylvanian

Formation(s):                  Conemaugh Group, Glenshaw Formation, Bakerstown shale and overlying Saltsburg sandstone.

Purpose:                         This site offers some interesting sedimentological and structural features in the shales and the sandstone.

Park adjacent to Target truck and auto dealership. Parking available for motor coach with permission. Recommended for all age groups with caution.

(Make sure you get an up-to-date PAT Transit schedule:

No PAT Transit Service.

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 6.2 miles. Make a right into car dealer. Outcrop is behind car dealership in old quarry pit.

See map and figures.

This is an old sandstone quarry that exhibits some very interesting sedimentary structures, particularly on the large blocks that are at the base of the outcrop. Look for three-dimensional examples of cross bedding and soft-sediment deformation. Also, look for the iron staining adjacent to joint surfaces and the calcite mineralization on the joint surfaces. These two features attest to the movement of mineral saturated groundwaters through the rocks before they were exposed by erosion and human activity.

Geologic History: Environment of Deposition:

The Saltsburg sandstone represents a local regression as a distributary channel prograded out into the shallow sea. The underlying Bakerstown shale is marine, most likely prodelta clays and delta front sediments that were deposited in front of the advancing channel.

Distributary Environment  (from Horne and others, 1978).

Click on the thumbnails below for pictures of the outcrops:

A view of the lower portion of the outcrop. Bakerstown shales with overlying Saltsburg sandstone.

A view of the upper section of the outcrop. The Saltsburg sandstone.

Calcite mineralization along joints in the sandstone. This calcite was precipitated from shallow groundwater that passed through these rocks when there was significantly more overburden.

Highly weathered multiple joints in the shales.

Leisengang banding adjacent to a joint surface in the sandstone. This is the result of iron-rich groundwaters passing through the joints and infiltrating the sandstone. Found on several blocks of sandstone in the rubble.

Interesting faults displacing cross-beds in the sandstone. Found on several blocks of sandstone in the rubble. These are not tectonic faults, but instead are probably due to soft-sediment deformation due to loading.

Clay rip-up clasts in the sandstone. Found in several blocks of sandstone in the rubble.

The silty shales contain rare to uncommon plant fragment fossils.

Busch, R. M., and Brezinski, D. K., 1984, Stratigraphic analysis of Carboniferous rocks in southwestern Pennsylvania using a hierarchy of transgressive-regressive units: Field Trip Guidebook for the Eastern Section Meeting of the American Association of Petroleum Geologists. 104 p.

Brezinski, D. K., 1983, Developmental Model for the Appalachian Basin marine Incursion: Northeastern Geology, v. 5, p. 92-99.

Donahue, J., and Rollins, H. B., 1974, Conemaugh (Glenshaw) Marine Events: Field Guidebook for the third Annual Meeting of the American Association of Petroleum Geologists. 104 p.

Donahue, J., and Rollins, H. B., 1979, Coal Geology of the Northern Appalachians: Field Trip Guidebook for the Ninth International Congress of Carboniferous Stratigraphy and Geology. 45 p.

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.

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.

Hoskins, D. M., 1973 third printing, Fossil Collecting in Pennsylvania: Pennsylvania Geological Survey Bulletin G 40, 126 pages.

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.

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)