FEB 6 1. 05 



PROCEEDINGS 



OF THE 



AMERICAN^ PHILOSOPHICAL SOCIETY 



HELD AT PHILADELPHIA 

 FOR PROMOTING USEFUL KNOWLEDGE 



Vol. XLIII. October-December, 1904. No. 178 



AN ATTEMPT TO CORRELATE THE MARINE WITH 



THE NON-MARINE FORMATIONS OF 



THE MIDDLE WEST. 



BY J. B. HATCHER. 



Read April 7, 1904. 



It is the purpose of this paper to call attention to and to direct 

 investigation along certain lines by which, as it appears to the 

 present writer, we may be able eventually to reach a better under- 

 standing regarding the relative age of the various Jurassic and 

 Cretaceous horizons of the Middle West. 



It has doubtless frequently occurred to every geologist and pale- 

 ontologist who has conducted investigations relating to the forma- 

 tions referred to in the title of this paper that marine, terrestrial, 

 fresh and brackish water conditions must have prevailed simulta- 

 neously and continuously over extensive areas in our Middle West 

 throughout that long period in middle and late Mesozoic times 

 during which sea and land alternately held dominion over consid- 

 erable portions of that region. Nevertheless, no serious attempt 

 has been made to correlate the various marine and non-marine 

 deposits with one another. In our geological text-books and in 

 numerous monographs, memoirs and less pretentious papers relat- 

 ing to the geology and paleontology of this region these various 

 formations are described in the text and represented in the accom- 

 panying geological columns as occurring in regular sequence one 

 above the other, and the impression is given that where a marine 

 formation is superimposed by a non-marine or vice veisa the over- 



PROC. AMER PHILOS. SOC. XLIII. 17S. W. PRIXTED DEC. 7, 1904. 



