TITLES AND ABSTRACTS OV PAPERS 169 



continental in origin, are tlie first above tlie unconformity. Tliese beds prob- 

 ably correspond to the ones mentioned by Mr. Knight that occur about 400 

 feet from tlie bottom of the Red Beds in southern Wyoming. Sandstones 30 to 

 100 feet thick and stron.gly cross-bedded occur about 100 feet above the Popo 

 Agie beds and may be windblown in origin, but all of the rest of the Red Beds 

 in this region seem to be marine. Mr. Knight's observations furnish addi- 

 tional proof of the variety in origin of the Red Beds, but do not prove that 

 they are not largely marine. 



Author's reply to Professor Ha worth : In answer to Professor Haworth, per- 

 mit me to say that if an undoubted marine limestone exhibits cross-bedding 

 similar to the type shown on the screen, then I must modify my ideas as to 

 the significance of cross-bedding. The type of cross-bedding here shown is 

 identical to cross-bedding of the eolian type as described by such authorities 

 as Walther, Huntington, Grabau, etcetera. I question whether the cross-bed- 

 ding in the Pennsylvanian of Kansas belongs to the same genetic type as the 

 cross-bedding under discussion. 



Further remarks were made by Mr. Arthur Keith. 



GENERAL 8TBATIGRAPHIC BREAK BETWEEN PENNSYLVANIAN AND PERMIAN 



IN WESTERN AMERICA 



I5Y WILLIS T. LEE 



( Abstract) 



Criteria usually applied in intercontinental correlation have thus far failed 

 to establish the limits of the Permian in western America to the satisfaction 

 of all geologists. There is lack of agreement as to the significance of different 

 classes of fossils. In some places, as in the Manzano of New Mexico (Lee and 

 Girty, United States Geological Survey Bulletin number 389) , are invertebrates 

 said to be Pennsylvanian and vertebrates (Case, Science, volume 44, page 708, 

 1916) said to be Permian. In other places there seems to be conflict of evi- 

 dence between the invertebrates and the plants, as, for example, in the Elm- 

 dale, Chase, and Wichita formations and their equivalents in Kansas, Okla- 

 homa, and Texas. 



Paleophysiography seems to throw light on the Permian question. Two 

 lines of physical research, structural and lithologic, offer promising results. 

 The upper or red portion of the rocks in New Mexico and elsewhere, assigned 

 with doubt to the Pennsylvanian, is lithologically so different from the lower 

 part, or undoubted Pennsylvanian, that it might properly be given a separate 

 name. These red beds of brackish water and continental origin lie uncon- 

 formably on marine limestone of undoubted Pennsylvanian age and furnish 

 lithologic and structural evidence of orogenic movement and invigorated ero- 

 sion in the Rocky Mountain region preceding their deposition. 



The apparently conflicting lines of evidence are so Involved that in few 

 places do all of them agree on a plane of separation between Pennsylvanian 

 and Permian. Relatively little consideration has thus far been given to physi- 

 cal evidence. However, available data of this kind are sufliciently numerous 

 to indicate that certain unconformities which seem to occui- at different hori- 



