Latitude:                         40° 31' 30"N north outcrop, 40° 31' 25"N south outcrop

Longitude:                      80° 00' 33"W north outcrop, 80° 00' 27"N south outcrop

Quadrangle:                    Emsworth 7 1/2'

Age:                                Pennsylvanian

Formation(s):                  Conemaugh Group, Casselman Formation Pittsburgh redbeds through Ames coal, Ames limestone, and Grafton sandstone.

Purpose:                          This is a combined site offering a complete section through a non-marine - marine - non-marine sequence. Good fossil collecting.

Actually two separate outcrops. The more northerly outcrop is behind Shop n' Save. The southerly outcrop is behind Best Buy. Parking available for motor coach at both sites. Outcrops are at and above parking lot level. Much talus allows for good access for collecting. Recommended for all age groups with caution.

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

From Oakland, take any bus to downtown Pittsburgh. Then 11A, 12A, or 13A north North Hills Shopping Center. Outcrops are behind the center as described above. Return.

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 I-279 North. Exit McNight Road (Truck 19 North). Go 2.3 miles then make a left into the Shopping Center Area.

See map and figures.

In the northern outcrop area, the Ames limestone sits atop a cliff that is accessible by a steep climb along the slope to the west. The

Geologic History: Environment of Deposition:

The environmental history represented at this site starts with the Pittsburgh redbeds that are exposed below the Ames limestone. These red shales have been interpreted as a paleosol horizon (ancient soil zone) on the Pennsylvanian delta by Donahue and Rollins (1974). They suggest that the red color and the claystone texture is similar to a laterite soil weathering profile. Lying above the redbeds is occasionally a thin (< 30 cm) coal referred to as the Harlem coal. This coal is very spotty in its distribution and does not occur here in Frick park. Instead, here we find the redbeds overlain by a very thin black carbonaceous shale which is in turn overlain by the Lower Ames shale, the first evidence that the delta is being flooded with seawater in a transgression. The shale is calcareous and commonly contains microfauna of gastropods, bivalves and brachiopods. The Ames limestone is one of several marine units within the Upper Pennsylvanian Conemaugh Group. The unit represents complete flooding of the delta during the maximum transgression (most extensive sea) of the Pennsylvanian period here in western Pennsylvania. The rocks were deposited in a shallow sea approximately 100 km northwest of the shoreline. The environment was relatively quiet subtidal with very little clastic (silt or clay) input from the land far to the east. The water depth was probably no more than 20 m. The limestone is divided into three parts: the Lower Ames limestone which is a micritic (fine-grained) fossiliferous limestone), the Middle Ames Shale which represents a brief regression, possibly associated with an influx of sediment from the delta plain to the east; and finally, the Upper Ames Limestone which is a micritic fossiliferous limestone indicating a return to quiet, clear water, marine conditions. Above the limestone is a little of the Upper Ames shale preserved. This shale marks the beginning of the retreat of the Ames sea and the influx of fine-grained sediments from the deltas to the east.

Paleogeographic map showing the region during the during Ames limestone.

Click on the thumbnails below for pictures of the outcrops:

A view of the south outcrop showing the Pittsburgh redbeds at the base, The resistant Ames limestone (tan) and the Grafton sandstone at the top.

A close-up of the Ames coal - Ames limestone interval exposed at the top of the northern outcrop. Hammer head is on base of coal.

Some of the fossils found in the Ames Limestone interval.

Interesting Leisengang banding in a block of sandstone. Gray part was apparently unaffected by infiltrating iron-rich waters.

A good example of iron staining due to groundwater infiltration of a sandstone by a joint surface.

The Ames is a very fossil-rich unit. All of the fossils are marine, and include brachiopods (crurithyris and neochonetes are most common), crinoids, horn corals, pelecepods, and gastropods. In addition fish teeth can be found in the Ames. The fossils are generally very small, but abundant. For a list of brachiopod and mollusc fossils, see Brezinski (1983). For pictures of the fossils see Hoskins (1973) or go to the fossils page.

Al-Qayim, B. A., 1983, Facies analysis and depositional environments of the Ames marine member (Virgilian) of the Conemaugh Group (Pennsylvanian) in the Appalachian Basin [Ph.D. dissertation]: Pittsburgh, Pennsylvania, University of Pittsburgh, 306 p.

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.

Busch, R. M., and Rollins, H. B., 1984, Correlation of Carboniferous strata using a hierarchy of transgressive-regressive units: Geology, v. 12, p. 471-474.

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, Paleoecolgical anatomy of a Conemaugh (Pennsylvanian) marine events: in Briggs, G., ed., Carboniferous of the Southeastern United States, Geological Society of America Special Paper 148, p. 153-170.

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.

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.

Saltsman, A. L., 1986, Paleoenvironment of the Upper Pennsylvanian Ames Limestone and associated rocks near Pittsburgh, Pennsylvania: Geological Society of America Bulletin, v. 97, p. 222-231.

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)