|Geologic age||Late Devonian|
Sedimentary > Clastic > Sandstone (Bed)
Sedimentary > Clastic > Siltstone (Bed)
|Comments||Secondary unit description from USGS Geologic Names lexicon (ref. MI016): Bedford Shale and Berea Sandstone are not exposed in MI. They record, in the subsurface, a southwestward growth of a deltaic system into the Antrim sea during Kinderhookian time. The Berea attains a thickness of 79 m in Huron Co. but thins northwestward, westward, and southwestward away from the thumb area and is absent in the eastern half of the Michigan basin. Unit is generally 15 to 30 m throughout its extent. Consists predominantly of light gray sandstone that is fine grained in the lower and upper parts of the formation but medium to coarse grained in the middle. It is silty and pyritic in its lower part.|
Milstein, Randall L. (compiler), 1987, Bedrock geology of southern Michigan: Geological Survey Division, Michigan Dept. of Natural Resources, scale 1:500,000.
USGS Geologic Names lexicon found at: http://ngmdb.usgs.gov/Geolex/
|Counties||Lenawee - Livingston - Macomb - Oakland - Saint Clair - Sanilac - Washtenaw - Wayne|