lU) Trenton Limestone of Minneapolis and St. Paul — Hall. 



with the calcite and occasionally either mineral appears massive 

 in the rock itself, but never in large quantities. While many 

 cavities are scattered throughout the compact bands which go to 

 make up the mass of this layer, by far the larger part are arranged 

 in horizontal layers from a fraction of an inch to an inch and a 

 half in thickness. Tlie fossils are so numerous along these harder 

 bands that the composition of the rock must be almost clear cal- 

 cium carbonate. 



As the glacial drift was removed, in stripping the quarry, a 

 very prominent glacial striation was disclosed. The striae had a 

 direction nearly north and south. The evenness and continuity 

 of these markings and the plane surface on which they lie are 

 another evidence that the river gorge has been formed since glacial 

 times. 



The layers of this quarry, as just enumerated, are in other 

 places capped by a layer of green shale. This is the case at Finn's 

 Olen, in Ramsey county, at South Saint Paul, near the linseed oil 

 works and at several other known places . At our quarry this soft, 

 shaly layer could not withstand the severe ploughing of the glacial 

 period, and became mingled with the sand and gravel from more 

 northern localities. It is still here in the city in places, as a well 

 recently dug by M. D. Rhame, just south of the University grounds, 

 abundantly shows. This green shale abounds in fossils, — brach- 

 iopods, lamellibranchs, gasteropods, cephalopods and bryozoans are 

 all intermingled in great profusion. This layer is doubtless the 

 representative of what occurs at other places in the state as 

 Middle Trenton, in N. H. Winchell's Greology of Hennepin 

 county as "the (xreen shales,"* and in Wisconsin where it is called 

 by T. C . Chamberlin the Lower Blue Limestone.f 



The drift material itself is of the common coarse gravel with 

 bowlders scattered through it. These bowlders often reach the 

 weight of several tons. 



*5th An. Rep., Geol. and Nat. Hist. Sur. Minn., p. 147. 

 tGeology of Wisconsin. Vol. I, p. 162. 



