RECORDS. 305 



SECTION OF GEOLOGY AND MINERALOGY. 

 January i8, 1904. 



Section met at 8:15 P. M., Professor James F. Kemp 

 presiding. 



The minutes of the last meeting of the Section were read and 

 approved. 



In the absence of the Secretary, Dr. A. A. JuHen was ap- 

 pointed Secretary pro tcin. 



The following program was then offered : 



J. D. Irving, Microscopic Structure and Origin of Cer- 

 tain Stylolitic Structures in Limestone. 



J. Howard Wilson, Recent Journeys Among Localities 

 Noted for the Discovery of Remains of Prehistoric 

 Man. 



Summary of Papers. 



From an extended examination of stylolitic Hmestones col- 

 lected in Indiana and Wyoming, mainly by Mr. M. L. Fuller 

 and himself. Dr. Irving has drawn the following conclusions 

 regarding the origin of the peculiar structures : 



1. They were initiated along a thin clay layer in limestone and 

 have been produced by the interpenetration of the limestone 

 material on either side of this clay seam. 



2. They are entirely independent of the presence of fossils 

 existing in the rock, for they occur equally in those portions of 

 the rock where fossils are absent and where they are present. 



3. They were not formed by metamorphic agencies, or by the 

 weight of overlying strata, or by other causes which would tend 

 to distort and crush the rock material. 



4. They were produced by a cause which operated on the 

 material of the rock while it was yet unconsolidated, and in a 

 condition approximating that which obtained at the time of 

 deposition. 



5. They originated under great pressure, the rock material 

 being sufficiently soft to allow the bending of individual stylo- 

 lites, and yet potentially rigid so that organisms were sharply 

 sheared off while held in the soft matrix. 



