34 University of Texas Bulletin 



Marl, containing Nodosaria texana 1.0 



Massive limestone containing Schloenbachia sp. M. (notched tubercles), 

 Nautilus texanus, Epiaster sp., Protocardia sp., Gervilliopsis invaginata 



(one) * 7-4 



CONCEALED BY BED OF STREAM, ESTIMATED 10.0 



Soft whitish marl, no fossils seen 10.0 



Marl Facies 



The transition from clay facies to the marl facies of this formation takes 

 place rather abruptly, within a distance of 2 miles along the outcrop and 

 terminates in central Johnson County, south of which the formation is al- 

 most entirely marly. One mile southeast of Riovista, the Pawpaw is a dis- 

 tinctly marly uniform light yellow, fossiliferous deposit lying between the 

 conspicuous Weno and Mainstreet limestones. It is about 5 feet thick. In 

 the territory covered by this depositional phase the conspicuous pyrite fauna 

 of the Fort Worth region is rare, except a few Turrilites, Area and small 

 gastropods, and other fossils, echinoids and ammonites are abundant. 



SECTION ON WACO-RIOVISTA ROAD, ONE MILE SOUTH OP RIOVISTA, TEXAS 



MAINSTREET: Feet 



Massive white limestone with characteristic Mainstreet fossils: Turrilites 



brazoensis, Kingena, Exogyra, arietina. Exposed 5 



PAWPAW: 



Homogeneous calcareous, straw-yellow marl with a few ironstone and calca- 

 reous fragments, containing Enallaster bravoensis, E. wenoensis, E. 

 riovistae, Holaster sp., Epiaster wenoensis, Plicatula sp., *Flickia boesei, 

 'Schloenbachia, sp., *Turrilites sp., *Arca washitaensis 5.5 



WENO: 



Limestone escarpment in two terraces, poorly exposed at the base, consisting 

 of massive soft limestone with marl interbedding. Contains Enallaster, 

 Epiaster, Holaster, Hemiaster calvini, Pecten subalpinus, Plicatula and 

 many other fossils, Trigonia clavigera. About 40 



DENTON: 



Soft light straw-colored marl containing Gryphea washitaensis, Ostrea cari- 



nata, Pecten subalpinus, Plicatula sp., and Kingena sp. (large) 5 



LIMESTONE FACIES : The equivalents if any of the Pawpaw forma- 

 tion in Central Texas are largely insignificant since they consist of only a 

 minute thickness of very calcareous marl and limestone imbedded in the top 

 of the Georgetown limestone, underneath the Turrilites brazoensis zone 

 which represents the basal Mainstreet formation of North Texas. This sit- 

 uation presumably exists westward to the Trans -Pecos region wherever the 



