Abstract

Three generations of geopetal fills occur in boundstone cavities in the allochthonous blocks. Generation 1 geopetals of lime mud on algal frame formed while reefs were in place. Generation 2 geopetals of lime mud on marine cement formed after displacement of reef masses into foreslope-slope settings. Generation 3 geopetals of dolomite silt, which rests on earlier calcite cement and is postdated by saddle dolomite, formed during deep burial and deformation of the sequence. Reefal blocks are composed of Epiphyton and Girvanella boundstone, thrombolites, and stromatolitic carbonates. The sequence of Epiphyton to Girvanella boundstone to thrombolite to stromatolite probably reflects increasing restriction and shallowing of the shelf edge periodically. Synsedimentary marine cements are abundant, and are mainly isopachous, banded neospar with local radial fibrous habit. The blocks of algal and cryptalgal limestone in the Shady Dolomite exhibit a greater variety of fabrics than have been recorded from shelf edges of equivalent Cambrian age. Furthermore, the association of cryptalgal deposits along with calcified-algal reefs in a shelf edge setting is significant.--Modified journal abstract.

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