REPORT OF THE STATE GEOLOGIST. lxv 



The western border of the sea was certainly not beyond the Franklin 

 Mountains. For the present synclinal, which includes by far the greater 

 part of these formations, is limited on the west by the Guadalupe 

 Mountains, and, although the elevation of this range was in Post- 

 Paleozoic times, they may have formed the western shore. Other rem- 

 nants of the same rock series exist between these mountains and the 

 Franklins. This synclinal valley has an average width of over 300 

 miles, and the eastern edge of the basin has an elevation of less than 

 800 feet, while the same strata on the west are fully 4000 feet higher. 

 This gradual rise, which averages only 12 feet to the mile if the entire 

 distance be considered, is in fact much more rapid toward the west. 



The deposits in the early Carboniferous Sea show a condition of com- 

 paratively deep waters at its beginning and the deposition in them of 

 limestones of considerable thickness, followed by shallower water and 

 shaly beds with a great number of characteristic fossils. In places these 

 lowest limestones and shales seem to show an unconformity of deposi- 

 tion with the overhing sandstone; and for this reason, and the finding 

 of a species of fossil shell which is considered characteristic of the Sub- 

 Carboniferous, it was supposed that these beds might belong to that pe- 

 riod. A careful examination of the fossils seems to point to a prepon- 

 derance of coal measure forms, however, some of which are as charac- 

 teristic of that period as the first named was of the Sub-Carboniferous. 

 The final determination must therefore await more careful stratigraphic 

 and paleontologic work than has yet been done. The beds contain one 

 or more thin seams of coal, but neither of them are likely to prove of 

 any commercial value ; but its beds of carbonaceous shale may prove 

 to be a reservoir of gas or oil at some point north of its outcrop along 

 the San Saba River. As this formation is well exposed at McAnnelly's 

 Bend, in San Saba County, it will be known as the Bend Series. 



THE RICHLAND-GORDON SANDSTONES. 



The rocks of the undoubted Carboniferous begin on the eastern bor- 

 der by a series of sandstones of such character as imply the existence 

 of littoral conditions at no great distance. In the Colorado coal field 

 these sandstones, with the underlying clays and sands, are given the 

 name of Richland Sandstones, and in the Brazos coal fields sandstones 

 of similar position and composition have been named the Gordon Sand- 

 stones. 



These sandstone beds are practically barren of coal, and merely mark 



