rOWA ACADEMY OF SCIENCES. 



59 



The fault has been traced northwestwardly for a distance of 

 fully fifty miles and doubtless extends four to five times that 

 distance further. For a considerable distance on either side of 

 it an extensive vertical section is shown. In Pike and Lincoln 

 counties, Missouri, the detailed succession and areal extent of 

 the various formations have been recently made out with a 

 degree of exactness that has not yet been attained in any other 

 locality in the whole interior basin. For this reason particular 

 attention is directed at this time to this region. The complete 

 section represented is as follows : 



GENERAL GEOLOGI0A.L SECTION NEA.R 0A.P A.U GRE3. 



In the nomenclature of the geological formations a number of 

 new names appear. This has been rendered necessary on account 

 of the fact that the various beds thus christened cannot be com- 

 pared directly with the formations of similar age in other parts 

 of the Mississippi valley. The disturbance which the strata 

 have undergone has brought up to the surface in a very limited 

 area the rocks of the earliest half of the Paleozoic in the 

 very midst of those of the latter part of the same era. Thus 

 older strata rise in a long monocline, and are abruptly cut off 

 on the south by the great Cap-au-Gres fault. The layers, of 



