318 



R. T. HILL GEOLOGY OF RED RIVER. 



Unconformity 



Pleistocene Gravel 

 AustinChaJl 

 Fish Bed 



has been called the Goodland limestone by the writer. The limestones 

 represent the deepest ocean sedimentation of the Comanche sub-epoch 

 and the culmination of the subsidence during this time. They are 

 overlain by laminated calcareous clays and alternations of stratified 

 limestones, indicating that it was followed by shallowing conditions 

 which continue upward to the top of the Washita division. These 

 shallowing beds (the Kiamitia clays) overlying the Caprina lime- 

 stone constitute the beginning of the Washita division.* 



Extent of the Washita. — The 

 extent of the beds of the 

 Washita division north of Red 

 river is shown upon the map. 

 They commence exactly upon 

 the boundary line of Choctaw 

 nation and Arkansas, where 

 Little river crosses the line. 

 Two or three^miles westward 

 they occur as small spots of 

 prairie in that densely forested 

 region. These prairies of the 

 Washita increase in area to the 

 westward in southern Indian 

 Territory until, north of Deni- 

 son and Gainesville, Texas, 

 they are the prevailing toi:)Og- 

 raphic feature. They then turn 

 southward through Texas and 

 extend to the San Gabriel, near 

 the Colorado, constituting a 

 large part of the prairie regions 

 (the Fort Worth prairie) f of 

 Cook, Denton, Wise Tarrant, 

 Johnson, Bosque and William- 

 son counties. Southwestward, 

 from the San Gabriel to the 

 trans-Pecos mountains, the Washita beds do not constitute extensive 

 areal outcrops owing to the great Balcones fault, which has cut them off 



Attenuation of 

 Lower Members 0*^ 

 Denison6eds. 



Zone of Gryphaea mucronata, Gabb' 

 Indurated layers with fauna. 



mination of E.arceUna. 



}t 



i/<i/iffena wacoensLs bed. 

 6/yphaeaSuiuata, Marcou 



p.pitcheri, with 0^annaca.j 



Ammonites leonensis and 

 Lptaster elejfans. 



10 rt. 



Figure 2.— Structural Detail of the Washita Division 

 at Austin, Texas. 



* In my preliminary annotated check-list of the Cretaceous invertebrate fossils of Texas I in- 

 cluded the upper Oaprotina limestone beds of the Austin section in the Washita division, but am 

 convinced, after fuller study of these beds, that they more properly belong to the Caprina lime- 

 stones and should be placed in the Fredericksburg division. 



t Described in various earlier papers and amplified in my Report on Occurrence of Underground 

 Waters, et cetera. 



