Trenton Limestone of Minneapolis and St. raid — Hall. \ V 



FIG.1. 



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'^ 0^^_£^^ ■e^^^^'^S/ ' S^ 



A^y'-'^y"- ::-^''- ■'■^y-i: -l::^:^'--.-^^ 





^'^■'W^^^^ 



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Fig. 2. Section oi the Lower Silurian at the quari-y, foot ol Sixth Ave. S. K , Minne- 

 apolis. Numbpred in ascending :;rder. 



No. 1. The underlying Saint Peter Sandstone. Texture, (?olor and composition 

 very uniform. Thickness 104 feet. Only a portion of this thickness is repr«»seiited in 

 the figure. 



No. 2. The layer of green shaly sandstone two feet in thickness. 



No. 3. "The building stone layer." Thickness about 15 feet. Bottom portion 

 quite argillaceous with an irregular contact zone with the carbonate above. Through- 

 out the whole thickness oi this layer there is an irregular alternation of calcareous 

 and argillaceous bands, and the calcareous bands become thinner towards the top. 



No. 4. A layer which is highly aluminous and siliciius. It exhibits but slight 

 banding due to sedimentation. It crumbles easily on exposure to the air. Thickness. 

 6 feet 9 inches. 



No. o. The upper fossiliferous layer strongly marked by alternating abundance and 

 paucity of fossil forms. These fossils are largely the Htrophomena minnesotenais 

 Winchell called in Owens' report on the Geological Survey of Wisconsin, lona and Min- 

 nesota, the Leptcena deltoidea Hall, with which are S.alternata Conrad, Streptorhynchus 

 filitextum Hall, Orthis tricenaria Conrad, and several lamellibranchs and gasteropods. 

 The layer is 5 feet 4 inches thick. It carries glacial stria; on its surface. 



No. 6. The glacial drift covering the rocks to a depth of six feet. The "Green shales" 

 are not ])resent at this quarry. 



