Department of Earth Science |Northeastern Illinois University
Aqueous Geochemistry
Earth Science 406
Fall 2002

Conference Presentation Abstract

Journal Article: “Reef and Nonreef Aquifers – A Comparison of Hydrology and Geochemistry, Northwestern Indiana”
by Douglas J. Schnoebelen and Noel C. Krothe (Ground Water Vol. 37, No. 2, 1999)

Abstract written by Amjad Asaf

The objective of this research study was to find out the differences in the hydrogeology and geochemistry of the reef and nonreef aquifers of Silurian and Devonian age.  This study was done in the Northwestern part of Indiana where the most
of the Silurian and Devonian rocks were Corel Reefs and some other rocks were argillaceous carbonates and these rocks underlied unconsolidated glacial deposits.  The thickness of these rocks was about 170 meters.  During the research different methods were used, like, lithology, geophysical, geochemical and aquifer tests.  Three sites were selected for the study.  At site #1, the aquifer rock contained shale with less fossiliferous material and had low porosity and transmissivity.  At sites #2 and #3, the rocks were mainly reefs with few shale and had high porosity and transmissivity.  The site #2 was close to the Kankakee River.  The regional flow in the aquifers was towards the River.  Both aquifers had different ground water flow and geochemical characteristics.

Three well of 6 inch diameter were installed along a line perpendicular to Kankakee River and total depth of each well was about 198 meters in to the aquifers.  Lithologic as well as geophysical logs were made at the sites. Total 12 samples were
collected from three well site at different depth zones, 2 from site #1 and five each from sites #2 and #3. At sites, samples’s temperatures was recorded with their alkalinity and dissolved Sulfide. These samples were analyzed for chemical constituents, stable isotopes of Oxygen and Hydrogen, specific conductance, pH and Eh in labs. WATEQF computer program was used to find the possible chemical reactions and saturation indexes for present minerals. The ground water at site #1 was classified as Sodium-Bicarbonate type and at sites #2 and #3 Calcium-Magnesium-Bicarbonate type. At each site there were minor changes with depth. The stable isotopes were used to identify that ground water at different depths in aquifers was from modern recharge and not from Pleistocene era.

Last updated December 2, 2002