Abstract

Early Proterozoic stromatolitic metadolomite bioherms and reefs occur in the Nash Formation, 6,500 feet thick, which is part of a 25,000-ft sequence of metasediments forming the core of the range. The formation is believed to be not less than 1,700 m.y. old. Some 150 bioherms and three reefs were mapped; the former up to 100 feet thick and 10-100 feet long, the latter, 200 feet thick and several thousand feet long. Structural forms and growth patterns are described in geometric terms. Descriptions are based on field observations and 100 large thin sections. Three types of stromatolites recognized are: digitate, undulate, and micro-oncolite. Structural forms include: single and laterally linked domes; spheroidal, ellipsodal, and oblong shaped heads; and combinations. Changes attributable to metamorphism are discussed.

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