DETAILS OF THE SAN LORENZO SECTION. 377 



Arboles mountains, and extending eastward and northward to the con- 

 fluence of El Soro creek and the Rio Grande river, a distance of nearly 

 60 miles. The uplift which formed the Arboles mountains brought up 

 the basal divisions of the Lower Cretaceous series and gave them a strong- 

 tilt to the east and northeast, thus forming a synclinal of Cretaceous rocks 

 in the area between the mountains and the highlands north of Del Rio. 

 Near the river the country is somewhat hilly ; but between these hills 

 and the mountains lies an undulating plain, the highest point of which 

 is formed by the crest of a gentle fold of Washita limestone. On reach- 

 ing the San Dieo:o river the countrv becomes ru2;ged and mountainous, 

 rising rapidl\% and the peak near what is known as the Saddle is o,700 

 feet above sealevel, while the plain is only about 1,500 feet. 



DETAILS OF THE SECTIOX. 



The highest beds, geologically, are found on El Soro creek, and it is at 

 this locality onh' that beds of the Upper Cretaceous (or Black Prairie 

 series of Hill) are found, and even here they have a very limited extent. 

 The entire area may be said to be Lower Cretaceous. 



The general section is as follows : 



Post- Cretaceous. 



Feet. 



Stream gravel and ])ro\vn silt covering part of flat between Las Vacas and 



the San Diego river. Reynosa conglomerate. On hilltops and along 



the San Diego 



Upper Cretaceous. 

 Eagle Ford stage. — Limy clay, shales and flags. Soro creek 40 



Lower Cretaceous. 



Vela stiige. — Heavy l)edded semicrystalline limestone of creamy wliite 



color. Vola roemeri, Hill. El Soro creek 80 



Exogyra arietina stage. Blue, yellow and red clays, with bands of sandy 

 flagstones and concretionary limestones. Exofjijra arieliiui, Koem. ; E. 

 ffrakel* Crag. ; Xodosaria te.rana, Con. ; I'ecten, sp. undet. Hills near Rio 

 (irande 1 l()-ll() 



Washita Limestone stage. — Marly limestone, wliite to blue in color, semi- 

 crystalline in places, arenaceous and l)ituinin(nis at base. O.strea carlnala, 

 Lam. Surface rock of the plain ;>00-4()0 



Capri na stage. — Dark l)lue or gray semicrystallinc! limestone, massive or 

 heavy ])cdded, with much flint, ('aprinti rr'i.^sijihra, Roem. ; (Jri/plnni 

 and sponges. .Mong the San Diego river and in Arboles mountains . . . (iOO- (?) 



♦ Professor Cragin says of the specimens of E. drakei which I submitted to him : "The tendency 

 to freer beak than is usually seen in north Texas .specimens makes it bear a degree of resomblanco 

 to E. arietina, with which, however, it could not be confounded." 



