SURFICIAL GEOLOGY OF THE 7.5 TOPOGRAPHIC WARREN QUADRANGLE, JO DAVIESS AND STEPHENSON COUNTIES, ILLINOIS

The Warren Quadrangle is part of the 7.5 minute series. Located between Longitude of 90°00’ and 89°52’30” and Latitude of 42°30’ and 42°2’30”, the Warren Quadrangle is positioned in Jo Daviess and Stephenson Counties in Northwestern Illinois. This mapping project is a part of a statewide program attempting to modernize the surficial topographic maps using the 7.5 minute series and the 1:24,000 scale. A preliminary surficial geological map was constructed in GIS with the aid of the Soil Survey of Jo Daviess and Stephenson Counties provided by the United States Department of Agriculture to identify the parent materials. Initial mapping and reviewing of well log records indicate that the dominant stratigraphic units are Peoria Silt (Qps) from the Wisconsin Episode, carbonates from the Galena and Platteville Groups (Ogp), which are from the Ordovician Period, and silty alluvium from the Hudson Episode, Cahokia Formation (c). The quadrangle includes the boundary between the glaciated and Driftless areas. In the absence of glacial till, Peoria Silt, usually light yellow, is the most dominant surficial geological formation. The second most abundant stratigraphic units are the Galena and Platteville Group, composed of yellow limestone, shale, and chert. Initial fieldwork seems to indicate that only the Galena Group is present at the surface within the Warren Quadrangle. The Cahokia Formation is present in recent creeks and in the flood plains of those creeks. Evidence of glacial material from the Wisconsin Episode, Ogle Member of Glasford Formation (og), was found in the Southeast portion of the Quadrangle.

A water quality study is also being completed with the goal of attaining a better understanding of how field and laboratory parameters change over the course of a year. Laboratory parameters being monitored are major ions and biological oxygen demand. Field parameters being monitored include: alkalinity, carbon dioxide, dissolved oxygen, pH, specific conductance, temperature, and turbidity. The data from the water quality study will be used to construct piper diagrams which will then be used to see if it is possible to distinguish the different parent materials for each of the sample collection locations.