37-7 Utilizing geology, geophysics, and water chemistry to delineate the hydrostratigraphy of a buried bedrock valley aquifer system in Eastern Iowa, USA

Session: Innovations in Research of Groundwater-Surface Water Interactions over Multiple Spatio-Temporal Scales

Presenting Author:

Joe Honings

Authors:

Honings, Joe¹, Doyle, Thomas², Tassier-Surine, Stephanie A.³, Schilling, Keith⁴, Kerr, Phillip James⁵, Vogelgesang, Jason⁶, Bancroft, Alyssa⁷, St. Clair, Martin⁸

(1) The Iowa Geological Survey, The University of Iowa, Iowa City, IA, USA, (2) The Iowa Geological Survey, The University of Iowa, Iowa City, IA, USA, (3) The Iowa Geological Survey, The University of Iowa, Iowa City, IA, USA, (4) The Iowa Geological Survey, The University of Iowa, Iowa City, IA, USA, (5) The Iowa Geological Survey, The University of Iowa, Iowa City, IA, USA, (6) The Iowa Geological Survey, The University of Iowa, Iowa City, IA, USA, (7) The Iowa Geological Survey, The University of Iowa, Iowa City, IA, USA, (8) The Iowa Geological Survey, The University of Iowa, Iowa City, IA, USA,

Abstract:

Growth of population and industry in eastern Iowa has prompted the need for new groundwater reserves beyond these shallow aquifers to meet the projected future demands. Most drinking water wells in Eastern Iowa are completed in confined sand and gravel aquifers formed by outwash from multiple glacial advances. These coarse-grained sediments are separated by multiple till sheets within a buried bedrock channel. However, information about the underlying bedrock is sparse. The current model of the bedrock topography indicates a complex system of buried bedrock valleys. One of which, known as the Cleona Channel, can be over 100 meters below the ground surface. New knowledge of channel geometry and valley contents would enable delineation of aquifers and provide new insights into Quaternary glaciation and climate dynamics. To this end, the Iowa Geological Survey collected passive seismic measurements from over 400 locations and used the horizontal-vertical spectral ratio (HVSR) technique to estimate the depth to bedrock. Four newly collected rotosonic cores were combined with other high-resolution geologic logs and 2D electrical resistivity surveys to refine channel geometry and locations of sand and gravel bodies. The connectivity of these sand and gravel bodies was investigated using anion, metals, and isotope from 84 samples comprised of wells screened at known subsurface elevations and surface water bodies. The synthesis of these datasets has refined buried channel geometry, as well as delineated and distinguished two regional sand and gravel aquifers separated by a glacio-lacustrine sediment deposited during the penultimate glacial episode.  

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8926

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