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Reef and nonreef aquifers - A comparison of hydrogeology and geochemistry, northwestern Indiana

Ground Water

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Abstract

The principal bedrock aquifer system across much of Indiana consists of carbonate rocks of Silurian and Devonian age. The Silurian-Devonian aquifer system is used extensively for irrigation in northwestern Indiana and is approximately 170 m thick. Reef and nonreef carbonate aquifers in northwestern Indiana were assessed using hydrogeology (lithology, geophysical logs, aquifer tests) and geochemistry (major ions and stable isotopes). The study showed differences in water quantity and quality between the reef and nonreef aquifers. The reef aquifer had few shales, abundant fossiliferous material (up to 100 m thick), and high porosities (10 to 15%). The nonreef aquifer had abundant shales, less fossiliferous material (a few meters thick), and low porosities. Total transmissivities at the reef sites were 697 m2/d, (meters squared per day) and 4831 m2/d, compared to 46 m2/d at the nonreef site. Flowpaths in the nonreef aquifer were associated with fractures and poorly connected moldic porosity with larger fractures and better connected vuggy porosity in the reef aquifer. Water chemistry data for the nonreef aquifer showed mean concentrations of sodium (235 mg/L [milligrams per liter]), sulfate (160 mg/L), sulfide (13 mg/L), fluoride (2.7 mg/L), and dissolved solids (635 mg/L) approximately two to five times larger when compared to mean concentrations in the reef aquifer. Ground water at the nonreef site was classified as a sodium-bicarbonate type while that at the reef sites was calcium-magnesium bicarbonate. The oxygen/deuterium isotope data indicates recharge from modern precipitation and not Pleistocene-age recharge.The principal bedrock aquifer system across much of Indiana consists of carbonate rocks of Silurian and Devonian age. The Silurian-Devonian aquifer system is used extensively for irrigation in northwestern Indiana and is approximately 170 m thick. Reef and nonreef carbonate aquifers in northwestern Indiana were assessed using hydrogeology (lithology, geophysical logs, aquifer tests) and geochemistry (major ions and stable isotopes). The study showed differences in water quantity and quality between the reef and nonreef aquifers. The reef aquifer had few shales, abundant fossiliferous material (up to 100 m thick), and high porosities (10 to 15%). The nonreef aquifer had abundant shales, less fossiliferous material (a few meters thick), and low porosities. Total transmissivities at the reef sites were 697 m2/d, (meters squared per day) and 4831 m2/d, compared to 46 m2/d at the nonreef site. Flowpaths in the nonreef aquifer were associated with fractures and poorly connected moldic porosity with larger fractures and better connected vuggy porosity in the reef aquifer. Water chemistry data for the nonreef aquifer showed mean concentrations of sodium (235 mg/L [milligrams per liter]), sulfate (160 mg/L), sulfide (13 mg/L), fluoride (2.7 mg/L), and dissolved solids (635 mg/L) approximately two to five times larger when compared to mean concentrations in the reef aquifer. Ground water at the nonreef site was classified as a sodium-bicarbonate type while that at the reef sites was calcium-magnesium bicarbonate. The oxygen/deuterium isotope data indicates recharge from modern precipitation and not Pleistocene-age recharge.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Reef and nonreef aquifers - A comparison of hydrogeology and geochemistry, northwestern Indiana
Series title:
Ground Water
Volume
37
Issue:
2
Year Published:
1999
Language:
English
Publisher:
Natl Ground Water Assoc
Publisher location:
Westerville, OH, United States
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Ground Water
First page:
194
Last page:
203
Number of Pages:
10