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I'ndiana University Studies 



continuing parallei^ > ; t ! \ again converge into a single seam. 

 In such cases, the c ombined thickness of the clay residue of 

 the branching seams is equal to the thickness of that of the 

 larger, single seam (see Fig. 36). At the places of branch- 

 ing, these subordinate seams cut across the lamination at a 

 small angle. Such phenomena result from solution along a 

 branching crevice. How could such a stratigraphic distribu- 

 tion of clay be explained by the pressure theory? The ex- 

 planation of ''double caps" (see p. 85) would also be very 

 difficult by other theories than that of solution. 



Occurrence of Stylolites along Disconformities. The 

 occurrence of stylolites along the disconformable contact of 

 two different geologic formations furnishes unusual evidence 

 that the phenomena originated by the actual removal of hard- 

 ened rock, rather than by the differential compression of 

 plastic sediments. The writer has in mind, especially, the 

 presence of stylolites along the undulating contact of the 

 Monroe (Silurian) with the Columbus (Devonian) limestones 

 of central Ohio-, and along the disconformity between the 

 Louisville (Silurian) and Geneva (Devonian) limestones of 

 southern Indiana. The latter observation was made by the 

 writer in the vicinity of North Vernon, Ind. Here, the un- 

 conformity represents a ''lost interval" of several geologic 

 ages, the Louisville limestone being Niagaran (Lockport) in 

 age, while the Geneva limestone is correlated with the Onon- 

 daga. It is an absurdity, of course, to conceive the two forma- 

 tions as having existed as soft plastic rock at the same time, 

 as would be necessary under the pressure theory. 



4. Other Evidence which Supports the Solution Theory 



Deposits of Mineral Matter. Since there is an excess 

 amount of solution of mineral matter at the ends of stylolites, 

 because of the increase in pressure there, the solvent might 

 become supersaturated, in which case a precipitation of the 

 excess mineral matter would take place in the cavities and 

 crevices where the pressure is less or absent (see pp. 50 and 

 66). Abundant evidence of this is found in field investiga- 

 tions. The presence of mineral matter on the side-surfaces 

 of the columns (where pressure is at a minimum) has long 



Observations at this hoi'izon have been made by Professor J. Ernest Carman, in 

 his studies of the Monroe formation of Ohio. 



