Charles William Collinson

“ SUGGESTIONS FOR COLLECTING PENNSYLVANIAN PLANTS Where to Look for Plant Fossils
Pennsylvanian plants are most commonly found in shales directly overlying coal beds. The shales are believed to be of nonmarine origin like the coals and may contain fossils either in ironstone concretions or on the bedding planes. The shale layers as well as the concretions should be examined. Where the bed directly overlying the coal consists of black slaty shale or limestone containing marine fossils, plant remains are rarely abundant or well preserved. ”

“ Fossils were discovered in outcrops along Mazon Creek more than a century ago and collections later were made from scores of conical spoil heaps at underground mines. After coal stripping began in the 1920’s, great numbers of specimens were collected.
In the stripping operations, the concretion-bearing beds are commonly the last to be placed on the spoil heap. Weathering softens and removes the shales and leaves the nodules concentrated on the surface. Each season brings a new crop of concretions to the surface. ”

“ Almost anywhere in the large coal producing areas of southern Illinois plant fossils can be found either in spoil heaps or in outcrops along stream, road, and railroad cuts. The thick Pennsylvanian sandstones that crop out in a belt extending through Gallatin, Saline, Williamson, and Jackson Counties generally contain compressions or replacements of trunks or other woody plant parts. ”

“ Insects 10 more than four inches long were common and some are known to have been more than a foot long with a wingspread proportionately broad. Ancestors of the modern spiders, scorpions, centipedes (one fossil found in Illinois was twelve inches long) , cockroaches, and dragonflies are represented by several hundred species.
The fossilized plants of Pennsylvanian time belonged to only a few main categories: scale and seal trees, ancient scouring rushes (horsetails) , herbaceous Sphenophyllum, ferns, seed ferns, and cordaitean trees. ”

“ The remarkable fossils represent plants that lived during the geologic period called the Pennsylvanian or Coal Age and are the result of special geologic conditions that occurred repeatedly during the period. ”

“ A notable number and variety of well preserved plant fossils have been produced from a locality along Court Creek in East Galesburg. The Rock Island (No. 1) Coal is mined in the area and the fossils appear to have come from the shale overlying it.
Fossil plants also have been found in shales above the Colchester (No. 2) Coal in the vicinity of DeLong and with the Herrin (No. 6) Coal in mines southeast of Victoria. ”

“ In the vicinity of Morris on the northwest edge of the Mazon Creek area, fossil ferns have been found along the north side of the Illinois River and in the banks of the Illinois-Michigan Canal. About a mile north in an area of strip mining, fossil-bearing concretions have been found in shale and irregular sandstone layers. ”

“ True ferns do not produce cones or seeds, but spores, which develop in cases called sporangia. The sporangia frond showing are attached in clusters (sori) to the lower side or margins of the leaves. In modern ferns the sporangia may also occur on fertile spikes. ”

“ Such a cycle of deposition was repeated again and again during Pennsylvanian time, and after burial each layer of plant material gradually lost most of its liquids and gases and was slowly converted into one of the numerous coal beds presently found in Illinois.
Reconstruction of Pennsylvanian Coal-forming Swamp
In some places in the state conditions existed that were especially favorable for preservation of plants, and there delicately preserved fossils are found in great numbers. ”

“ Only about one nodule in ten contains plant remains.
Approximately 25 to 30 species have been found in this region. The productivity of the area was shown by George Langford, Sr., a well known midwestern fossil collector. He and his son split about 250 thousand concretions during a 140-day period and obtained some 25 thousand plant specimens. Fine specimens still can be collected in a few hours.
The plant collecting localities in Will and Grundy Counties along Mazon Creek, four to six miles southeast of the town of Morris, were the first to be well known. Ferns are especially abundant. ”

“ Not all Pennsylvanian trees were large, however. Small forms are known, including the important undergrowth genera Lycopodites and Selaginellites. In woody types the trunk consisted of an inner region of conducting and supporting tissues, surrounding concentric cortical layers, and an outer layer of corklike bark. Although the fossil impressions of the various bark layers have been given separate generic names, these are not commonly used. ”

“ Coal and the Murphysboro Coal. Nearly all have come from shaft mines that are not easily accessible to the collector.
One currently good outcrop locality for collecting plant fossils from the shale above the Murphysboro Coal is just southeast of Murphysboro.
Other Southern Illinois Localities
Other collecting localities have been recorded west of McLeansboro in Hamilton County, northwest of Mt. 30 Vernon in Jefferson County, near Grayville in White County, and in the Friendsville area of Wabash County. There is no doubt that careful search will turn up many more. ”

“ Notes about the locality should be put in the same bag as fossils from that locality so that there is no possibility of confusion.
Some fossils are so fragile or porous that they should be covered with a hardening protective coat of crude gum arabic solution. ”

“ These fossil cones frequently are found in Illinois.
Sphenophyllum first appeared during the Devonian Period, some 300 million years ago, but did not become abundant until Pennsylvanian time. The genus continued through the Permian but died out in Triassic time.
14 FERNS
(Plates 1 and 3)
True ferns, like those living in today’s woodlands, were common in the Pennsylvanian forests. Some species attained heights of 30 to 40 feet. Their fronds (compound leaves divided into segments or leaflets) commonly were five to six feet long. ”