POST-PALEOZOIC UPLIFTS. 317 



same terrane upon the opposite side of the latest uplift. Upon the northeast 

 the Trinity-Silurian contact is about three hundred feet lower than the base of 

 the Cretaceous at a Silurian contact on the southwestern border.* The Capitol 

 granite in the southeast is in part overlaid by the Cretaceous unconformably, 

 the altitude of the contact being variable, and the basal Cretaceous strata dif- 

 fering accordingly. More than this, upon the north, east, and west there is a 

 thickness of some 300 feet of Trinity sands, which are absent from much of the 

 southern border. Practically over the district between longitude 98 degrees 

 20 minutes, and from latitude 30 degrees 30 minutes to latitude 31 degrees 

 1 minutes, there is not a scrap of Cretaceous, excepting minute prongs, which 

 may cross these boundaries from the main outlying area. This uncovered tract 

 of 2300 square miles does not represent the whole of the region now bare of 

 Cretaceous, nor all of the region which has not been covered, for there is a 

 long tongue or promontory, running eastward in the central part, the inner 

 end of which has here been taken as the western boundary, whereas large tracts 

 north and south of this extend farther west. The topography, the geologic 

 structure, the dip of the Cretaceous beds, the absence of the lower beds upon 

 the southeast, the littoral character of the sediments, and the relations of the 

 Cretaceous strata to the earlier rocks, each and all indicate that this area was 

 above the sea during Cretaceous times. There is much variety in the basal 

 members of the Trinity Series, and in almost every case the material is locally 

 derived from the subjacent strata. The conglomerates which lie beneath are 

 in contact with almosi every bed, in different places, from the earliest granites 

 to the Carboniferous, respectively, and the lithologic character is nearly as 

 changeable. The structure is that of beach deposits of near-by origin, and 

 the old shore line can be approximately traced in many places. 



There is, however, a peculiarity which, at first sight, may seem to conflict 

 with the views here expressed. This is the precipitous character of the Cre- 

 taceous escarpment in many places, and the present great elevation of the 

 Cretaceous summit along the borders of the interior area at many points. A 

 cursory examination of the Cretaceous alone might readily result in the con- 

 viction that this system had once crossed the lower lying territory, although 

 I can not conceive of such a condition in the case in question without the re- 

 tention of any remnant whatever over so wide an area; for the erosion and 

 faulting have been such as to give opportunity for the preservation of relics 

 of any beds which once covered the tract. But it is wrong to assume that 

 the general level of the Cretaceous is higher than the earlier rocks in the un- 

 covered region. There are plenty of exposures of granites and other rocks of 

 Pre-Cretaceous age which now stand above the average level of the Cretace- 



* This Cretaceous base is certainly made up of much higher strata than the lowest Trinity 

 beds. 



