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bash. The silico magnesian beds of Logansport, he says, "part with the 

 greater portion of the calcareous matter at Peru, becoming argillaceous, 

 while in Wabash this bed is characteristically argillaceous, and. in appeai'- 

 ance very similar to the hydraulic stone at Louisville." In his general 

 section of Wabash County he places (1) porous limei'ock at the top, and 

 gives its thickness at from to 40 feet; (2) paving stone, 8 feet; (3) thick- 

 bedded argillaceous limestone, 10 to 20 feet; (4) hydraulic limestone, 10 to 

 50 feet, and referred the whole series to the Niagara group. The sub- 

 divisions adopted by Elrod and Benedict in their report on the Geology 

 of Wabash County, 1891, do not differ greatly from those of Prof. Gollett. 

 They placed the quarry stone, the equivalent of his paving stone and 

 thick-bedded ai-gillaeeous limestone, at the top of the series. Between the 

 quarry stone and his hydraulic limestone they recognized a local stratum 

 of laminated shale, closely related to the quarry stone, and all below the 

 laminated shale was called cement shale or cement rock. The porous 

 limei'ock was not given a separate place in the section, because it was 

 the opinion of the writers that it did not form a distinct geologic horizon; 

 but was composed of the changed materials derived from the quarry stone 

 and the underlying formations, but came mainly from the quarry stone 

 layers. The materials were recemented by infiltration, and, as a conse- 

 quence, the beds have no ti'ue stratification planes. For it they adopted 

 the name picket rock, a local term then in common use at Wabash. 



These correlations are deemed necessary that the reader may under- 

 stand the stratigraphic position of the Wabash County unconformities, 

 and the probable relations of the others of the Wabash Valley. 



A very remarkable and plain example of unconformity between the 

 quan-y stone layers and the blue cement rock may be seen on the east 

 bank of Lagro Creek, one-half mile north of Lagro. Hei'e 30 feet of 

 horizontal quarrj' stone abuts against a nearly perpendicular wall of 

 cement rock. Below the unconformity, in the creek channel, the cement 

 rock is found to be continuous and connected with the south wall of the 

 unconformity and to pass under the more recent quarry stone. Dip is 

 scarcely appreciable in any of the layers. Other unconfoi-mities of gi'eat 

 interest are those at the Martin Willis quarry, south of Lagro, on the 

 township line pike, and at Leonard Hyman's quarry, on the Mississinewa 

 River. At these quarries the quarry stone rests on the laminated shale 

 in a valley. On one side of the Martin Willis quarry the shale rises 10 

 feet above the lowest exposed horizontal layers of quarry stone. 



