MAPPING AND CHARACTERIZING A RELICT LACUSTRINE DELTA IN CENTRAL LOWER MICHIGAN USING SOIL AND WATER WELL DATA IN A GIS

This research identifies and characterizes a sandy, relict delta of Glacial Lake Saginaw in the central Lower Peninsula of Michigan. The delta formed at the mouth of the Chippewa River during the late-Wisconsinan, when proglacial lake waters inundated the lowlands west of present day Saginaw Bay. The delta was first identified in a GIS, using digital soil data. Sandy textures of the delta stand in contrast to the background soils of the lake plain, which are typically loamy, having formed in fine-grained lacustrine sediment and waterlain loamy tills of the Saginaw lobe. A total of 151 samples of sandy textured C horizon material from the delta, coupled with 20 samples of loamy-textured till from the adjacent highland, were sampled and their textural properties measured using laser diffractometry. The data were joined in a GIS, interpolated using ordinary kriging, and analyzed to identify textural trends across the surface of the delta. Data gleaned from 3276 groundwater well logs across the delta were examined similarly, and used to estimate sand thickness and to further refine the delta boundary. The delta, roughly 18 km wide and 28 km long, is thickest (~5-6 m) at its center, and thins away from the river. This study represents the first use of these methods to identify, characterize and map a relict Quaternary delta in the Midwest US. The results of this study will help refine our understanding of late-Wisconsinan sedimentation and how it influences soil patterns in the Saginaw basin.