Outline of the Geologic History of the Grand Traverse Region
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Martin, Helen M.
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SubjectGrand Traverse Bay; Kalkaska County; Benzie County; Antrim County; Ellsworth; Cup coral; horn coral; brachiopod; winged shell; petoskey stone; Atrypa; Fossils; Charlevoix; Manistee; Hayes Township
The four counties bordering Grand Traverse Bay with Kalkaska and Benzie counties form a unit sharing the same geologic history. The foundation of the region is a segment of the western rim of the nest of rock bowls that are the bedrock of the Southern Peninsula. The Foundation Through millions of years Michigan was a-building. After the iron formations and the copper bearing lavas were piled on the northern rim of the granitic bowl we call the Michigan Basin, after earth movements had lifted, compressed, folded, metamorphosed or changed, the sediments of the Huronian iron-forming age and had broken and uplifted the copper bearing lava flows of Keweenawan time, then came a time of quiet and of early life known as the Paleozoic, (primitive plants, algae, fungi, bacteria were in existence during the Huronian). During the Paleozoic, six major ocean-encroachments were made over North America, seas entered and retreated from the Michigan Basin. Each major sea ebbed and flowed several times covering the basin in whole or in part. Each time of major encroachment has a name: Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian. Likewise the sediments of each minor sea has been given a name. At least 5^