SEDIMENTS OF A PITTED LACUSTRINE PLAIN AND THEIR IMPLICATIONS FOR PALEOLAKE LEVEL OF GLACIAL LAKE CHICAGO, CEDAR CREEK TOWNSHIP, MUSKEGON, COUNTY, MICHIGAN

We mapped late Quaternary sediments in Cedar Creek Township, Muskegon County, Michigan to reconstruct sedimentary environments and paleolake levels. These sediments have previously been interpreted as being deposited in Glacial Lake Chicago (GLC) between ~16.8 and 13.7 ka following retreat from the outer Lake Border moraine. The study area lies between the Lake Border and Port Huron moraine systems and contains areas of pitted and non-pitted lake plain with a moraine ridge in the extreme northeast of the township. Sediments were mapped and analyzed using a digital elevation model, soils, water well logs, hand augering, and grain size analyses. Sediments are >80 m thick in the study area and water well logs indicate predominantly sandy sediments with interbedded fines. Wells in the eastern part of the township suggest onlap of GLC sediments onto the Lake Border moraine, which is buried beneath lake sediments in most of the township. Five facies are identified based on mean grain size, sorting, and percent fines and gravel. Facies A is poorly sorted, gravelly, medium to coarse sand containing less than 5% fines, and greater than 2% gravel. Facies B, the most common facies, is moderate to very well sorted, medium sand containing up to 2% gravel. Facies C is moderately well to well sorted fine sand containing less than 10% fines. Facies D is very poorly sorted to poorly sorted, sand with <50% fines. Facies E is fines with less than 25% sand. No systematic variation in texture is seen spatially across the study area. Sediment facies suggest deposition in a glacial lake setting by traction in channels, as underflows in turbidity currents, and rainout of fines. Sediment sources were likely the Muskegon River and the terminus of the Lake Michigan lobe. The elevation of GLC sediment suggests a lake elevation of at least 215 meters above mean sea level. Kettles formed as ice left by the retreating Lake Michigan lobe was buried by GLC sediments, and then melted after lake drainage.