STRATIGRAPHY 



The stratigraphy of the Weno and Pawpaw formations involves the re- 

 gional stratigraphy of the Comanchean area north of the Brazos River, and 

 accordingly, certain lithological and structural features of this region will 

 be described. 



In almost the whole region in question, along the line of outcrop of these 

 two formations between the Brazos and the Red Rivers, the Comanchean 

 sediments are deposited over a large geosyncline whose axis is transverse 

 to the direction of the Comanchean outcrops i. e., roughly northwest- 

 southeast and whose bulk was largely filled in by pre-Comanchean depos- 

 its. However, there is a feeble surface reflection of this buried structure, 

 which influences the thickness and lithologic characters of all Comanchean 

 deposits, including the Weno and Pawpaw formations. The north edge of 

 this deep trough is near the. Red River and the south edge is south of the 

 Brazos ; the north slope is steep and the south slope more gentle. This de- 

 pression, in which the Fort Worth region is located will be called the Fort 

 Worth geosyncline. 



ROCKS UNDERLYING THE WENO AND PAWPAW FORMATIONS 



PRE-COMANCHEAN 



Its extent may be indicated by the meager data available on the under- 

 ground position of the Ellenburger limestone. At Muenster, Cooke County, 

 it was reached at a depth of about 1800 feet, or 1050 feet below sea level. 

 At Myra, Cooke County, the Ellenburger was reached at a depth of 1640 

 feet below the surface or about -900 feet (sea level). 1 In the Polytechnic 

 (Byrens-Burchell No. 1) well near Fort Worth, the Ellenburger if present 

 lies below -3950 feet, at which level the Bend has probably not been reached. 

 The difference in elevations of the last two subsurface points is 3050 feet 

 which represents the minimum change of elevation of the first Ellenburger 

 reached between Myra and Fort Worth, in case the Ellenburger is present 

 at the latter place. Coincidentally the thickness of Pennsylvanian deposits 

 is not more than 600 feet at Myra, but has increased to at least 3600 feet at 

 Fort Worth. Other wells in Tarrant and nearby counties have penetrated 

 similar Pennsylvanian material. 



Farther south there is doubt that the Ellenburger is present. In the 

 Hillsboro well the pre-Cambrian rocks were said to be reached at a depth 



'Matteson, Econ. Geol., XIV, No. 2, p. 1919. 



