Prairie wanderings: A land of swamps and seas
By PAUL G. JANTZEN
Contributing writer
This land hasn't always been a tallgrass prairie. How do we know? There are many reasons. I'll mention just a few from my own experience.
The various rocks in Earth's crust are arranged in layers across Kansas. The deeper layers are thought to have been deposited first; those nearest the surface are younger. As we travel westward we go uphill and encounter progressively younger rocks because more of eastern Kansas has eroded away, exposing older layers. In addition, after the Rocky Mountains lifted up about 63 million years ago, sand and silt from their eastern slopes were washed down over western Kansas. Thus much of western Kansas' surface is from only two to 63 million years old, while Marion, Chase, and most other Flint Hills counties' surface is about 260 million years old. This older layer is called the Permian System (because of its prominence in the Russian province of Perm).
Samples collected during the drilling of oil wells in eastern Kansas suggest that prior to the deposit of the Permian System, Kansas was experiencing alternate depressions and elevations of the land and, as a result, advancing and receding of the seas that once covered most of the state. Sometimes marine deposits of limestones and shales settled out; at other times non-marine shales, sandstones, and even coal were left behind as waters receded. Coal was formed from plant remains in swamps later covered by sediments from sea water which compacted them. Much coal has been mined from deeper layers in southeast Kansas.
In the Flint Hills, younger strata have been eroded leaving the Permian System exposed. In Chase County, along K-150, road cuts have exposed a series of strata that were investigated by some of my biology students. They found chert (flint), limestone, shale, and sand layers which had settled out of sea water. They found many fossils of brachiopods (lamp shells), echinoids (sea urchins), and crinoids (sea lillies) lying loosely on the upper surface of Cottonwood limestone. These all were sea animals. The limestone abounded in fossilized fusilinids the size and shape of wheat grains; these also are sea creatures.
In 1991, while working on the history of Clover Cliff Ranch in Chase County, I happened upon the petrified remains of a lamp shell in a creek bed on the ranch. This species now is extinct.
In the summer of 1959, Jack Sensintaffar and I, under the direction of paleobotanist Gilbert Leisman, spent three months studying fossil plants in the shale exposed by an intermittent stream near Americus in Lyon County. Excavations were made in the Eskridge shale a few meters below an outcropping of Cottonwood limestone. The shale was rich with compressed and carbonized leaves which we compared with photos of plants from the same Permian age in other areas. We compared shape, vein patterns, and mode of attachment of leaf units. Many clearly were leaves of trees with names like Pecopteris, a tree fern, and Neuropteris and Alethopteris, both seed ferns and both now extinct. All of these were swampland trees during Permian and earlier times.
We then attacked a more complicated task of identifying the spores and pollen grains from the same shale. This required chemical treatment of tiny quantities of shale to remove the mineral sediments (which interfere with microscopic observation) without altering the spores and pollen grains in the shale. We compared what we saw through the microscope to the enlarged photographs and written descriptions from Europe and Russia of about the same geologic age. I know some German, and a girl working near our laboratory had taken a course in Russian and helped us in the translation.
The spores, pollen grains, and leaves identified from this small area represented many species of tree ferns and seed ferns that once flourished in this vicinity. (The now-extinct seed ferns bore seeds on their leaves rather than in cones or flowers.)
On a summer field trip to the coal fields of southeast Kansas, I collected a coal ball containing a section of the stem of a fossilized, now-extinct, scouring rush or horsetail (Calamites) embedded in limestone. These 40-foot trees grew in the coal swamps in a layer below the Permian System and were extinct by the end of Permian time. With a diamond-bladed saw, I cut out a fist-sized chunk and used the 300-million-year-old stem as a paper weight on my desk.
The traces of coal and the abundance of fossil fern and seed fern leaves, spores, and pollen grains are clear indications that this part of Kansas' surface was at times composed of swamps and marshes. The even more productive coal-bearing strata below our dig site, and further southeast, indicate these swamp conditions were even more widespread in earlier times.
Alternating layers of limestone and shale above and below our dig site, and the fossils of sea animals in nearby corresponding strata suggest that shallow seas advanced and receded numerous times during the Permian period and marshes and swamps existed briefly between these episodes.
Even the creatures that have become extinct served important functions in their world years ago. But many continue their significance as the ancestors of today's creatures with whom we share planet Earth.
