DISCOVERY AND PRELIMINARY INVESTIGATIONS OF THE REMAINS OF AN EARLY HOLOCENE FOREST ON THE FLOOR OF SOUTHERN LAKE-MICHIGAN

Tree stumps in growth position were discovered in 1989 in southern Lake Michigan in 24 to 26 m of water (152 to 150 m above MSL) about 25 km east-southeast of Chicago Harbor. At least 50 stumps occur in an area of about 8,500 m2. The stumps generally range from 15 to 30 cm in diameter and stand as much as 1.2 m above the lake bottom. The lake bottom in the vicinity of the stumps is sand and gravelly sand forming either a veneer or low relief (0.5 m) ridges atop a nearly flat surface of soft, silty clay. Three stumps have been recovered for species identification and radiocarbon dating. An oak was dated at 8,120 +/- 100 BP and 8,380 +/- 100 BP. One sample each from an ash and an oak gave identical dates of 8,320 +/- 70 BP. The find is interpreted as the remains of a forest established during the post-glacial, extreme-low lake phase (Chippewa low) and drowned during lake-level rise (Nipissing transgression.)