Geological Research at the IGS
  

Three-dimensional geologic model development of the Huntertown Formation, Allen County, Indiana

Status Start Date End Date Locations
active Aug 1, 2008 Jul 31, 2011 Allen
Director: Sally Letsinger
Other Researchers: Greg Olyphant, Shawn Naylor,
Funding: U.S. Geological Survey (USGS) - Great Lakes Geologic Mapping Coalition
Issue: Our overarching goal is to understand and model in three dimensions the geology of aquifer systems covered by clay-rich deposits derived from ice lobes advancing out of the Great Lakes. This proposal focuses on the Wisconsin Episode Huntertown Aquifer System (HAS) in Allen County, northeastern Indiana, which is important not only because it provides water for a major metropolitan area, Fort Wayne, but also because it is representative of many complex Midwestern glacial aquifers. The HAS consists of the Huntertown Formation which is highly variable but dominated by proglacial sandy deposits that function as an aquifer. The Huntertown Formation is overlain by a clay-rich till, the Lagro Formation, that is widespread over the region and thought to function as an aquitard within the HAS.
Objective: The objective of this project is to develop a three-dimensional geologic model appropriate for representing realistic subsurface conditions in a groundwater flow model of glacial deposits in Huntertown, Indiana (Allen County).
Approach: We generated a 3-D model of Huntertown aquifer system geology as envisioned by Fleming (1994) that features an undifferentiated (homogenous) Lagro Formation. However, our new results suggest that the Lagro Formation depositional model is more complex than previously considered. Accordingly, we will collect and incorporate additional data and interpretations into the model to better represent the complexity of the overlying Lagro Formation. Realistic characterization of the deposits is important for correctly representing groundwater flow dynamics through the geologic materials.
Products: We are producing the following: 1. Industry standard (ESRI) file geodatabase with georeferenced GIS data layers of the major bounding surfaces that comprise the three-dimensional stack of sediments present in the Huntertown Formation. This includes digital elevation models of the bounding surfaces of the formation and the other pertinent surfaces within the study area (currently, 20 layers are represented). 2. Digital format of the three-dimensional geologic model data representing the geomorphic and sedimentary characteristics of the Huntertown Formation discretized into a finite-difference grid appropriate for incorporation into groundwater models (ASCII format). 3. Geostatistical results showing comparisons between borehole lithology data and the three-dimensional geologic model. 4. Representative maps and cross sections showing the relationships of units in the Huntertown Formation.
Benefits: Groundwater is an increasingly critical natural resource that must be managed for sustainable use over time. Groundwater storage and flow in glaciated areas of the central United States is poorly understood, and groundwater pollution is an increasing problem. Simplified, subsurface geologic models of complex glacial deposits do not adequately capture or demonstrate the control that the geology exerts on groundwater occurrence and movement. For example, the Lagro Formation, the unit overlying the Huntertown Formation in the current study area, is regarded as an important aquitard, but its hydrogeologic properties remain poorly known. Emplacement mechanisms and timing, as well as post-depositional changes, such as development of secondary jointing, have likely affected its hydrogeologic properties. A better understanding of the water supply and water-quality issues in such environments can be obtained through realistic characterization of the geology in three dimensions.
Publications:

A GIS-based approach to modeling three-dimensional geology of near-surface glacial morphosequences: Huntertown Formation, northeastern Indiana
Letsinger, S. L., Naylor, S., and Olyphant, G. A., 2009, A GIS-based approach to modeling three-dimensional geology of near-surface glacial morphosequences: Huntertown Formation, northeastern Indiana. Geological Society of America Abstracts with Programs, vol. 41, no. 7, p. 166.

GIS-based potential recharge- and discharge-area mapping from three-dimensional hydrogeologic modeling in glacial terrains of the midwestern United States
Letsinger, S.L., and Olyphant, G.A., 2008, GIS-based potential recharge- and discharge-area mapping from three-dimensional hydrogeologic modeling in glacial terrains of the midwestern United States. Geological Society of America Abstracts with Programs, vol. 40, no. 6, p. 472.


 
 
 
Your session for the Indiana Geological Survey is about to expire in 30 minutes. Please refresh your broswer or click here to restart your session timer.