26 University of Texas Bulletin 



East-West Changes (North Texas and Oklahoma) 



In the whole Red River region these two formations at their outcrops 

 maintain an almost uniform thickness, but they are slightly thicker east- 

 ward as far as Choctaw County, Oklahoma. Their behavior east of this 

 point is unknown to me. 



TABLE OF APPROXIMATE THICKNESS OF WENO AND PAWPAW 



FORMATIONS 



Weno Paw- 

 Locality Lower Upper Total paw 



Denison 45 80 125 60 



Gainesville 40 70 110 44.8 



Blue Mound (Haslet) 27.3 



Fort Worth 12.7 49.6 62.3 24.6 



Riovista '. 10 25 35 5.0 



LITHOLOGICAL CHANGES 



The Weno and Pawpaw formations are marked by striking lithological 

 changes which produce along their outcrops localized lithological regions 

 each with a characteristic fauna. The Pawpaw formation, and to a less 

 extent the Weno, passes from north to south along its outcrop through a 

 "typical" series of lithological fades sand-clay-marl-limestone, which 

 aside from various complicating factors of deposition is usually taken to 

 represent a progressive series of marine facies from near-shore .to off- 

 shore conditions. Likewise the problem of localized faunales is vividly 

 impressed upon one by the situation in the Pawpaw clay (as also in the 

 Weno), where within a few miles one fauna largely disappears and an 

 equally rich and varied, but different one occupies its stratigraphic posi- 

 tion. For example the Gainesville-Denison fauna (Nacreous, Area), the 

 Fort Worth fauna (Turrilites, Engonoceras, Hamites, Scaphites) and the 

 Riovista fauna (Flickia, echinoids) of the Pawpaw formation represent 

 three different marine facies. The narrow ribbon-like outcrop of these 

 formations in North Central Texas and Southern Oklahoma gives only a 

 limited opportunity for the study of these different marine phases, but the 

 following regional differences in the sediments of these formations are ap- 

 parent. 



