Pennsylvania’s forests looked different in the Carboniferous and Early Permian

Deborah Painter (USA)

A singer named Perry Como caused this article to be written. Perhaps it would be more correct to credit his statue. My friend Richard and I took a road trip in June 2018 to a conference in Cranberry Township, Pennsylvania, USA for a three-day weekend. On Sunday afternoon, we were facing a seven hour drive south back to our homes. Fortunately, the weather was sunny and mild, a good way to conclude a trip that had been plagued with thunderstorms earlier. We were both tired, but Richard allowed me to stop off Interstate 79 to Canonsburg, Pennsylvania to see a statue in honour of Perry Como, an American celebrity of the mid-twentieth century.

I admit I didn’t know why I wanted to see it, since I am not especially a fan of the recording artist and television star, and neither is Richard. However, I was curious about it because I had read that it continuously plays music. I also thought Canonsburg (Fig. 1), a quick turn off the Interstate highway in Washington County, might be a good stopping place for us to find a restaurant before proceeding on the long journey back.

Perry Como’s mellow style of jazz and big band made him a recipient of a Kennedy Center Award for outstanding achievement in the performing arts. His style and choice of music was not unlike those of the even more popular singer and television and film star, Dean Martin. Interestingly, Martin was born in Steubenville, Ohio, only 59 or 60 kilometres northwest. In a reference to Como’s very relaxing songs, Martin once joked that he “used to go over to Perry’s to borrow a cup of sleep”. The two were not the only ‘crooners’ from that general area.

Another Canonsburg native who was a popular ballad style recording artist during the same three-decade time period is Bobby Vinton. The town approached him about a statue in 2004. His opinion was that there are many more crucial needs in the world for money than a statue just to honour him. I know not why so many major twentieth century singers were born in the vicinity. The marvels I usually hunt for in Pennsylvania are of the geological variety. In fact, Western Pennsylvania is coal country. Its Carboniferous period rocks are known around the world.

Leaving the Como statue (Fig. 2), we drove through the small Pittsburgh suburb on a northbound road looking for a place to eat. I saw a gray cliff in a ‘swale’ in a tiny wooded area near a kitchen and bathroom remodelling company, and asked Richard if we could inquire about stopping to ask permission to look for fossils. I said I would pay for a hotel for the night if we were able to do any fossil hunting. The poor fellow did agree. When we located the company’s owner, who also happened to be the manager, he also agreed. “Just don’t use any tools or shovels or climb on the rocks,” he said.

I promised we would not. I asked if I could take photographs and he agreed, as long as we did not tell others of the actual location. I asked the thin, moustachioed gentleman if people often asked to look for fossils there. He replied no and seemed a bit rushed, so I thanked him for his time and gave him our contact information. At the bottom of a landscaped hillside (Fig. 3) was the low cliff and swale that had caught my attention from the road. Without the aid of my geologist’s hammer, and carrying only my camera and a plastic bag, I walked up and down the base of the thickly bedded shale cliff picking up small loose slabs of shale.

The cliff was approximately four meters in height above the swale (Fig. 4). Within a few minutes, I found something. It was a broken piece with a portion of a large plant stem approximately 17cm in length, and the foliage of that ancient plant (Fig. 5).

The foliage presented as whorls of thin leaflets surrounding it where they had become separated from the stem prior to fossilisation. The fossils lay as thin carbon layers on the same plane as the surface of the split and broken rock slab. The opposite face of the slab had no plain fossils (Fig. 6). If it had been reposing on the ground with this side facing upright, I would not have noticed any plant fossils. That taught me a lesson: turn loose slabs and pieces over and examine all sides.

We looked for another hour and this was the only fossil. It was getting late now and we were ready to call it a day.

Later, at the tidy little bed and breakfast nearby where we secured for the night, we relaxed and I looked up the site on Pennsylvania’s Department of Conservation and Natural Resources, a GIS referenced geologic mapping service, paGEODE Pennsylvania GEOlogic Data Exploration (https://www.gis.dcnr.state.pa.us/pageode/).

The site was mapped within the Waynesburg Formation, Permian and Pennsylvanian periods (the latter known as the Upper Carboniferous in Europe). The upper member consists of gray to black, locally calcareous shale containing siderite nodules, and medium-and light-gray sandstone. It ranges in thickness from about 1.5m to 15m. The Little Washington coal occurs at the base. The middle member is medium-gray shale, sandstone and light-gray siltstone. The lower member is medium-gray shale, sandstone and siltstone, and ranges in thickness from about 15m to 30m. The Waynesburg coal is at its base. The Waynesburg sandstone, which overlies the Waynesburg coal, is light gray, massive and cross-bedded, and locally grades laterally and vertically to siltstone and shale.

My fossil was the horsetail-like plant called Annularia. This genus was abundant during the upper Carboniferous and lower Permian, approximately 307 to 251 million years ago and comprise a common fossil of western Pennsylvania. Ten species have been described from fossils of the Canadian Maritime Provinces strata alone. The Annularia were large plants belonging to the phylum Sphenophyta. Whorls of narrow leaflets were arranged about a thin stem. In earlier times of paleontological discovery, the nomenclature Calamites was given to the stem. Like modern horsetails, the Carboniferous and Permian plants favoured moist or wet freshwater habitats.

Many species grew to prodigious heights of twenty meters or taller and formed the Earth’s first forests. Such plants flourished as dominant terrestrial vegetation from the late Devonian into the early Permian, but a gradual change to a drier climate favoured the evolution of the gymnosperms, which bear their seeds in cones. Gymnosperms (for example, monkey puzzle trees, pines and the like) were widespread during the Permian, growing alongside the sphenophytes.

Today, the sphenophytes are represented by a single genus, Equisetum (that is, the horsetail), and are found on several continents. Most are small; the largest reach a height of less than one metre. They are not flowering plants or conifers. They produce spores rather than seeds in a cones or fruit. There is an alternation of generation between the tiny, gamete producing ‘gametophytes’ and the tall, spore producing sporophytes. The latter have a cone like structure atop their stems. The cone might be attached to the green stem or grow independently of the photosynthetic stem on a separate stem. Nineteen fronds in a whorl gave us a hint of the possible species of the plant preserved as carbon film.

A comprehensive paper authored by Alvarez and Wagner on North American Annularia and Asterophyllites species was very helpful, but did not enable us to make a positive identification of my carbon film fossils based on the photographs and descriptions of similar fossils in the paper on Carboniferous species of the Maritime Provinces. None of the species precisely matched my own. The specimen was an upper Carboniferous-lower Permian species or possibly two species side by side.

The Permian is represented from fewer localities in Pennsylvania than is the Carboniferous. The Permian is known for the Alleghanian Orogeny, a time of mountain building resulting from continental margin collisions. As the land rose in elevation along the continental margins of what we now call North Africa with what we now call North America, the enormous coal producing swamp forests diminished.

The crust was shortened along the eastern edge of North America by hundreds of miles in the areas we now call North Carolina and Tennessee through thrust faults placing rock belts atop one another. As a consequence, many rocks of Permian and Carboniferous age are missing from the surficial bedrock along the Eastern Seaboard of the United States. More still were eroded away over the millions of years. They are now sand along some beach or clay at the bottom of some wetland. Thankfully, plenty of Carboniferous and Permian fossiliferous strata are exposed at the surface in the twenty-first century.

Perry Como once recorded a song titled “Funny How Time Slips Away”.

References

Alvarez, Vasquez, and Robert H. Wagner. 2017. A revision of Annularia and Asterophyllites species from the lower Westphalian (Middle Pennsylvanian) of the Maritime Provinces of Canada. Atlantic Geology 53, 17-62.

Hagerup, Olaf, and Vagn Petersson. 1960. Botanical Atlas – Mosses, ferns, conifers, horsetails, lycopods, phylogeny. Volume 2. Ejnar Munksgaard Publishers. 299 pages.

Pennsylvania Department of Conservation and Natural Resources GIS referenced geologic mapping service. paGEODE Pennsylvania GEOlogic Data Exploration: https://www.gis.dcnr.state.pa.us/pageode/

The Permian in Pennsylvania, US: The Paleontology Portal: http://paleoportal.org/index.php?globalnav=time_space&sectionnav=state&state_id=9&period_id=11

UPI.com December 28, 2004. “Bobby Vinton vetoes statue on his honor”: https://www.upi.com/Entertainment_News/2004/12/28/Bobby-Vinton-vetoes-statue-on-his-honor/68701104296034/d