CHARACTERIZATION OF SEDIMENTARY FACIES AND FLOW PROPERTIES FROM CONVENTIONAL CORE IN THE PENNSYLVANIAN SAGINAW AQUIFER, CENTRAL LOWER MICHIGAN; USE IN ENHANCED GROUNDWATER MODELS

High resolution groundwater models aid in better management of groundwater resources through more accurate characterization and quantification of aquifer systems. Detailed assessment of flow properties in the context of sedimentary facies provide high quality data input for more accurate groundwater models. Pennsylvanian bedrock in the Central Lower Michigan, Ingham-Eaton-Clinton, Tri-Counties region comprises the Saginaw Aquifer, the Grand River and Saginaw formations. Data for this study was obtained from core collected at a site of surface-derived chlorinated hydrocarbons in Mason, Ingham County, Michigan. The Saginaw Aquifer consists of a predominantly sandstone and shale succession organized in sand-dominated channel fill and inter-channel facies. The aquifer also contains distinct soil horizons, minor coal, and tidally influenced, estuarine facies all deposited in a fluvial-deltaic depositional system. Sandstone channel-fill facies, to 40m thick, contributes most of the water used in the Tri-Counties area. Data obtained from conventional core inspection, porosity-permeability plugs, mini-permeameter measurements, and petrographic image analysis were used to estimate flow properties, including pore geometry and correlate these properties to sedimentary facies. Fine- to medium-grained, quartzose, channel-fill sandstone facies have matrix porosity and permeability from 20 to 27% and 403 to 3290 millidarcies, respectively. Channel-margin facies consisting of interbedded medium- to coarse-grained sandstone and interbedded silty shale and fine-grained sandstone have porosity and permeability of 20-24% and 593 to 2230 millidarcies. Visual inspection of core indicates a lack of significant mega-fractures consistent with matrix control on Saginaw Aquifer flow properties. Dissolution of early calcite cement is the likely origin of high matrix porosity and permeability.