Skeleton Lake, Ontariwvidence for a Paleozoic impact crater'
Skeleton Lake, Ontario (lat. 4SCI5'N, long. ?8"27'\2'), contains an approximately circular depression, 3.6 krn in diameter and 65 m maximurn depth, which appears to truncate the regional geological and physiographic trends of the local Precambiian gneisses and rnign~atites. Outcrops of breccia are present on the northern lake shore, and erratics of Ordovician limestone, evidently scoured from the lake bottom by glaciation, occur along the south shore. Aerornagnetic data indicate a field of low uniform magnetic intensity across the lake, in contrast to the variable regional magnetic pattern. A detailed gravity survey has revealed u circular gravity anomaly of -3 .3 -+ 0.7 mGal (-33 9? pm. s ?) over the depression. The anomaly has been modelled by bowl-shaped distributions of low density brecciated rocks. These observations suggest that the Skeleton Lake deprehsion is the eroded remnant of an impact crater of I'aleozoic age which has been preserved by a covering of Ordovician sediments until recently exhumed.