Geology & Mineral Resources, Water Supply & Quality

Geology and Mineral Resources

About five hundred million years ago the mid-continent was covered by a Silurian Sea where some of the first life forms appeared – corals, primitive fish, cephalopods and sea lilies.  As these organisms died, they floated to the bottom of the sea, creating a layer of thick sludge which later turned into limestone, the oldest layer in a series of strata that underlays Fulton County.  The pillars of the “old” courthouse in Lewistown are said to be made of Spoon River limestone.

Fulton County is located on the western edge of the geologic structure known as the Illinois Basin.  The formation of the Illinois Basin began approximately 300 million years ago, brought about by a series of contortions which left a giant depression in Central and Southern Illinois, as an extensive system of valleys became deeply entrenched into the bedrock surface.  Many of the features within the basin, such as the Illinois and the Spoon Rivers, have been determined largely by these early activities.

Vast swamps containing giant ferns and forests covered the area.  As the flora died, they settled to the bottom of the basin and after many millennia, decomposed into peat and eventually coal.  Swampy periods alternating with periods in which the land was covered with water, resulted in the development of numerous coal beds separated by beds of shale, sandstone and limestone.  Over time these strata filled the basin with a layered series of valuable resources.

These Pennsylvanian age resources, including several important mine-able coals, underlie the Lewistown-Spoon River area. Mining of the Rock Island Coal Member (Tradewater Formation) and younger coals of the Carbondale Formation, especially the Colchester, Springfield, and Herrin Coal Members, made Fulton County an important coal-producing area for many years.

About 750,000 years ago Illinois was covered by glaciers and Fulton County was partly covered with ice during three separate glacial periods.  During a fourth and most recent glacial period, the Wisconsin, the ice sheet was within approximately ten miles of Fulton County and left wind and water deposits, namely loess and silt, in the Illinois Valley and its tributaries.  Both the withdrawal of the ice and the great flood known as the Kankakee Torrent produced the landforms as we see them today. Glaciers left extensive deposits of sand and gravel that have been quarried for many years.

Fulton County’s soils developed in a variety of materials, loess being the majority, with glacial drift, alluvium, eolian deposits, bedrock residuum, overburden from surface mining, or a combination of these.  Different soil types determine use and management for crops, pasture, forestland, building sites, sanitary facilities, highways and other transportation systems, parks and other recreational facilities, and wildlife.

Water Supply and Quality

Fulton County is blessed with abundant surface water resources.  The Illinois River forms some 30.5 miles of the eastern boundary, and Spoon River flows for 52 miles through its center.  These two rivers plus their major tributaries such as Cedar Creek, Coal Creek, Putt Creek, Otter Creek, Copperas Creek, and others total 186 miles and 3, 751 acres of flowing major streams.  Natural lakes along the Illinois River such as Anderson Lake, Rice Lake, and Emiquon add approximately 8,000 more acres of water.