Latitude:                             40° 10' 52"N

Longitude:                         80° 13' 24"W

Quadrangle:                       Washington East 7 1/2'

Age:                                     Permian

Formation(s):                     Dunkard Group, Upper Limestone member of Washington Formation to Lowermost Greene Formation.

Purpose:                            This is the uppermost part of the Dunkard Washington Formation. Good collecting of plant fossils from the gray shales and microfauna fossils from the limestones.

                                                    Section approximately 60 feet stratigraphically above WASHE 6-1.

Park in Hotel (Fairfield Inn) parking lot down hill from site and walk up to site. Parking available for motor coach with permission from Hotel. Alternatively, park in Wal Mart parking lot and walk up. Recommended for all age groups with caution. Road is very busy, stay on grass.

The above map does not include new roadways and development in the area.

(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 0.3 mi. then bear right onto entrance ramp to I-376. Stay on this highway through the Fort Pitt tunnels. Go a total of 8.0 mi. and exit onto I-79 south. Go 20.5 miles then exit onto I-70 east. Once on I-70 east, go 1.2 miles and exit on Beau Street. At end of exit ramp, make a right and go 800 feet. Turn left and follow road to parking as described above.

See map and figures.

There are several important features to look for in this outcrop. First, the interbedded freshwater limestones and dark gray shales are typical of the part of the Dunkard Group sequence. As noted below, the shales contain abundant microfauna fossils and fish teeth.  Second, the sandstone channel cuts into the shale-limestone sequence, and has a sharp erosional base and is typical of shifting distributary channels.  Finally, the shales just below the sandstone contain some of the best plant fossils found in the Dunkard Group in this area, particularly large imprints of Lepidodentron and occasional cones. The plant fossils are found on the hillside on the north end of the outcrop.

Geologic History: Environment of Deposition:

During the early Permian, western Pennsylvania was located approximately 5 to 10 degrees south of the equator and had a tropical to subtropical environment. Some geologists suggest that the area was in a similar setting to that of modern-day New Guinea. Western Pennsylvania was the site of a deltaic system that bordered a large shallow sea coving much of the central North America. Sediments were fed into the delta region by large river systems originating in the growing Alleghanian mountains to the east. The mountains were growing because of the continuing convergent and collision of North America and the African portion of the Gondwana supercontinent.

Locally, large fresh to brackish water lakes would develop in the inter-distributary parts of the delta. According to Harper (1990), deposition in these large lakes involved carbonate precipitation by algae or other organisms. The conspicuous laminations (layering) that can be seen in many limestone layers is attributed to algal growth that occurred in extensive mats. Also found in these limestones are common breccia-conglomerates that may have formed by periodic drying of the lakebed and the formation of desiccation cracks. Long periods of exposure to weathering processes broke apart the lime beds forming breccias. These breccias were then covered with additional lake sediments as the lakes refilled (Berryhill and others, 1971)

The influx of silt and clay that did occur resulted in alteration of thicker carbonate and thinner non-carbonate muds that lithified into the limestones and shales that can be seen in this outcrop. A modern day analogue for these large lakes might be Lake Ponchartrain in the Mississippia delta region.

Below is a satellite image of the Lake Pontrarchain area.

The sandstone channel represents one of many in the Lower Waynesburg formation which represents the upper delta plain environment that extends into a regional basin that is being filled from the rising Appalachian mountains to the southeast (today's direction) and from highlands to the north (today's direction).

Here are the facies relationships in the Upper Pennsylvanian Uniontown Formation and the Permian Waynesburg Formation in southern Pennsylvanian and Northern West Virginia.  This is from an untitled late 1970's guidebook by A. C. Donaldson (West Virginia University, retired).

The above two figures show the modern Ganges Delta. Compare with the paleogeographic map above.

Click on the thumbnails below for pictures of the outcrops:

A view of a portion of the outcrop nearest Beau Street. Note the sandstone channel cutting down into the freshwater limestone sequence.

A close-up of the limestone sequence. Several of the more shaley darker layers contain ostracode hashes with common very small fish teeth.

One of the lepidodendron specimens found in the shale interval directly below the sandstone channel.

A Lepidodentron? cone fossil.

Very common plant fossils in the shales immediately below the sandstone channel. Occasional ostracodes, fish scale and teeth may be found in the limestones. In the dark shales between the limestones layers there are fossil hash layers that contain abundant ostracodes as well as fish teeth.

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.

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.

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)