Deterministic hydrogeologic modeling of glacial sediments, Washtenaw County, Michigan.

摘要

Glacial deposits in Michigan are a primary reservoir for groundwater and a primary conduit for its transport. The aquifer system was formed by cyclic Pleistocene glaciation, and is composed of intricately interbedded sediments of varying composition and textural character that impose primary control over the transport of groundwater and any associated dissolved contaminants. Local groundwater remediation activity has facilitated compilation of a dataset of well bore lithology data, natural gamma response logs, hydraulic head, and concentration levels of 1,4-dioxane from more than 130 monitoring wells spread over 10km2 (4mi2). Allostratigraphic methods were applied using the available data to interpret internally consistent local hydrostratigraphic architecture.;Data were supplemented by investigation of a relationship between gamma response and mineralogical and textural characteristics of local glacial sediment using the rotosonic core from MW-96. Core sediments were sampled and sieved, optically point-counted, and clay-sized fractions were subject to X-ray diffraction analysis to establish QFL fractions, textural fractions, and clay mineralogy. Linear regression of data indicated correlation between gamma response and texture and mineralogy, suggesting the dependence of total gamma response on a combination of texture with mineralogy. The resulting deterministic model of hydrostratigraphy lays the foundation for future geostatistical analysis of the aquifer system.