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Precambrian stromatolites replaced with epidote in a prebatholithic sequence of Reynolds County, Missouri.

Small structures, considered to be stromatolites, similar to the laminar and small domal stromatolite Ozarkcollenia, occur in ferruginous Mesoproterozoic bedded tufts of the Cope Hollow Formation near Johnson's Shut-ins, Reynolds County, Mo. Arranged as clusters on bedding surfaces of fine grained volcanic tuff, these structures are believed to have been originally composed of calcite. Regional metamorphism of the rocks in the Johnson's Shutins area converted the calcite of these small domal stromatolites to epidote. Reaction halos of iron-deficient tuff surround the stromatolite layers where iron was locally assimilated by them during epidote formation. These Mesoproterozoic structures and the similar ones composed of calcite from Iron County are the oldest known evidence of biogenic activity in Missouri and this part of North America.

* Stinchcomb, B.L. Geology Department, St. Louis Community College-Florissant Valley.
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Title Annotation:Geology and Geophysics, Senior Division
Publication:Transactions of the Missouri Academy of Science
Article Type:Abstract
Geographic Code:1U4MO
Date:Jan 1, 2005
Words:132
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