32 University of Texas Bulletin 



yellow, softer, ferruginous, very arenaceous clay. Their ironstone seams 

 do not exceed 6 inches in thickness and locally are highly indurated. 



SECTION OF THE PAWPAW FORMATION IN ROADSIDE CUTS TWO ANE 



ONE-HALF MILES SOUTHEAST OF GAINESVILLE, TEXAS 



^Section furnished by W. M. Winton 



MAINSTREET: Feet 



White massive limestone with characteristic Mainstreet fossils. Exposed ... 6 



PAWPAW: 



Alternating red ironstone and ferruginous sandy clay layers. About 16 

 compact ironstone layers each 3 to 4 inches thick, alternating with clay 

 layers each about one foot thick. The ironstone layers are similar from 

 bottom to top and the basal 10 feet is more fossiliferous than the upper 

 portion. The ironstone layers contain: Remondia sp., Trigonia sp., 

 Area sp., Engonoceras sp., Nucula sp., Corbula sp., and other nacreous 



and ironstone fossils 21 . 5 



Brown sandstone flag layer 0.5 



Red ironstone layer with Nodosaria texana . 



Brown clay 5 . C 



Red ironstone with Area sp., Ostrea quadriplicata O.B 



Brown clay, sparsely fossiliferous : Area, gastropods 15 . C 



Red calcareous sandstone: Ostrea quadriplicata 2.C 



This is underlain 'by the Quarry Limestone group (see page 36). The 

 thick semi-consolidated sand seen in Grayson County is absent. The Paw- 

 paw outcrop which has turned nearly south at the turning point near Or- 

 lena, makes a narrow north-south strip from Gainesville to the southern 

 border of Tarrant County. The ironstone facies does not persist past 

 the Trinity River, since interstratified clay lenses here largely make up the 

 formation ; as far south as Fort Worth there are large amounts of weath- 

 ered ironstone fragments in the surface debris of the Pawpaw. 1 



Clay Facie* 



This facies of the Pawpaw formation is best developed in the Fort Worth 

 region. From Cooke County southward to the Brazos the Pawpaw is rap- 

 idly thinning, as previously described. At the same time, passing south- 

 ward through Denton and Tarrant Counties the clay facies is encountered, 

 and in the region of the Brazos the marl facies appears. The clay facies 

 grades into each of the other two facies, so that the transitions are gradual. 

 This gradation occurs through the invasion of one facies by seams of the 

 other kind of material. 



'Winton and Adkins: Univ. Texas Bull. 1931, p. 67. 



