This is Throwback Thursday #166. In these, we look back into the past at ESCONI specifically and Earth Science in general. If you have any contributions, (science, pictures, stories, etc ...), please sent them to [email protected]. Thanks!
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Bill Kelly collecting fossils in Sylvania, OH in 1959.
Bill Kelly and his wife Wylma were active in ESCONI for many years. Both of them wrote articles for the newsletter. Today, we have an article by Bill entitled "Spring - Illinois". This article appeared in the May 1963 edition of the newsletter, but the content is still very relative today. Bill mentions the 1945 Geologic map of Illinois, which can be found online as part of the Boston Public Library's Norman B. Leventhal Map Center Collection.
SPRING - ILLINOIS
by Bill Kelly
Summer is a coming in, you and I will be walking, swimming, riding, here and there and everywhere around the State of Illinois. I talk to myself, or to whoever will listen, about what is here for me to see and touch, and what was here at some past time and has left a trace for me to see, and perhaps take a little piece home. Illinois can also be studied in depth from books, maps and rocks.
I am not telling you anything new, I may tell you something old. If the old is new to you, well and good, anyway it is Spring, time to look around.
I have before me the Geologic Map of the great State of Illinois 1945, second printing 1953. If you have this map or can get one, hang on to it for the new map of 1961 is not the same. The five wonderful cross sections and their index, also the North-South Meridian have been omitted, and the geologic columns are missing.
Illinois has great mineral wealth. Many industries are based on this wealth, in fact historic man lives on this wealth. This is your home and my home, here are familiar things, rich soils, adequate rainfall, farms, forests, coal mines, quarries, gravel pits, oil wells, streams, rivers, lakes, water wells. Much of this wealth had its origins in the deep past of Geological Time in Illinois.
The first feature we notice, is the generally flat surface or plain, eroded in many places by drainage basins, rivers and stream beds. This is glaciated area. Many of the features and much of the mineral wealth is the replaced material distributed and contributed by the great ice sheets that advanced and retreated repeatedly across the entire state during the Pleistocene's 2 million years. Here is material conveyed by the ice from the territory North including the Northern States and Canada. Here are the sedimentary materials planed from deposits of all the geological periods above the Pennsylvanian Period and deep into the Pennsylvanian Period, covering an estimated 250 million years.
Glacial features are abundant in Illinois. The best known is Lake Michigan. The morains, kames, kettles, eskers, are evident in many places, as are lakes and old lake beds. The location of drainage basins, rivers, streams, including the Mississippi, Ohio, Wabash, Illinois, also the tributaries of these rivers, were determined by the glaciation. The great ice sheets were thousands of feet thick. They were a burden upon the crust of the Earth from which there is still movements of recovery. The last retreat of the ice age was only ten or twelve thousand years ago. We say the last, but we don't know if the Wisconsin Glaciation was the last. We may be in an inter-glacial period now.
There was a long period of great storms and high winds from the West, across the denuded country as the ice sheets retreated. Dust storms contributed great wealth to Illinois in the form of enormous quantities of air-born material and loess, to build our fertile soil. This air-born material added to the glacier-born sand, gravel, rock grindings and clays make Illinois lands productive.
We have glanced across the surface of our inheritance from the glacial periods of the Pleistocene. When we dig deeper we find ourselves in the Calcareous sedimentary deposits in the seas of the Paleozoic Era, for a geologic history of some 250 million years. The first and oldest period of this Era is the Cambrian period, which surfaces along the great Oregon Illinois Plattville fault line running in a Southwesterly direction west of Chicago. The Ordovician Period appears over a large area in the Northwestern part of the state. There are also Ordovician rocks in the disturbed area over a deeply buried ancient volcano in the vicinity of Des Plaines, Illinois. We are right at home in the Silurian Period, for our Dolomite quarries throughout the northeastern part of the state including the Chicago area, were once the coral reefs and atolls of the Silurian Seas. The Devonian stratas are to be found in some areas along the Mississippi Valley.
As we travel southwest and south from Chicago, we are soon aware of Mississippian and Pennsylvanian periods as we approach the coal fields. Here are the strip mines and deep mines, for the recovery of the fossil fuels of the Carboniferous period. These were once great tropical jungles.
These forests of plant life, developed from ancestors that left some small fossil records in earlier periods, as far back as the Silurian period, some 100 million years earlier than the Pennsylvanian. These plants were pioneers in the sense they were adaptable to changing environmental conditions. Though not conscious as we use the term, they were energized by the radiation of the Sun, and the thrust of life to gradually leave their old environment in the sea and migrate toward the estuaries, where streams carried minerals and sediments needed for growth. These plants responded to the increased sunlight for photo- synthesis and the growth of Chlorophyll, to develop rapidly in a burst of evolutionary radiation. They advanced into swamps and finally on to dry land. There pioneers became giants as many grew to over 100-feet in height. Their fossil remains became the Carboniferous Coal measures mined for fuel and chemicals in Illinois. A burst of evolutionary radiation might mean the establishment of a noticeable change in some form, feature, or dimension in the short span of one hundred generations. What is time in the course of natural events.
The Southern tip of Illinois is known as the Illinois Ozarks. There are many hills in this beautiful country and there are also deep faults. The element Fluorine in the form of gas and hydrofluoric acid along with some lead and zinc has intruded as magmic solutions through these deep faults to combine with the sedimentary limestones forming Fluorspar, Calcium Fluoride. This is a valuable and very beautiful mineral, mined in many locations near the Ohio River. Fluorspar crystals are found in a wide range of colors.
In Northwestern Illinois, vicinity of Galena, there are mineralized areas where intrusive magmas have deposited lead and zinc ores in the fissures of the Galena Dolomite. There has been extensive mining in this area.
The Earths crust is never still. Change is continual and never ending. We have the privilege of seeing the processes of change when we view the land we live on in terms of geological time. Happy hunting, fellow rockhounds.
