Record of Geology of Texas, 188 7- 18 96. 
245 
94. Tarr, Ralph S. 
The Carboniferous Area of Central Texas. 
Amer. Geologist, Vol. VI, pp. 145-153. Minneapolis, Sept., 
1890. 
Contents: I. General Statement. 1. Position of the formation. 2. 
(Erosion of the Cretaceous. 3. Boundary of the Carboniferous, a. Prob- 
able extent, b. The Silurian area. c. The Lower Carboniferous series. 
II. Description of the Upper Carboniferous series. I. Thickness of the 
series. 2. General stratigraphic relations. 3. Dip of the beds. 4. Divis- 
ion of the series, a. Richland Sandstone, b. Milburn shales, c. Brown- 
wood limestone, d. Waldrip Coal Division, e. Coleman Division. III. 
Summary. 
“The Cretaceous beds in Central Texas have been removed from a por- 
tion of the valley of the Colorado and Brazos rivers so as to reveal the 
underlying Paleozoic nocks. This region, which has been called by Prof. 
R. T. Hill the Central Denuded Area, consists in its southern portion of 
a very much disturbed region of older Silurian and Cambrian rocks with 
granite bosses and possibly Archcean Schists. Uneonformably upon this is 
a belt of lower Carboniferous partly revealed by the erosion of the over- 
lying unconformable upper Carboniferous. Above the latter is Permian. 
“Whether the Cretaceous covered all this central area is a mooted ques- 
tion. There seems to be no evidence to the contrary, and Prof. Hill has 
announced the probability of such former extension. In several places the 
Cretaceous is found resting on the Silurian ; in one place, southwest of 
the Brady, in McCulloch county, at an elevation of 2,000 feet. As the 
Cretaceous at this point is of the lowest division (Trinity of Hill), and 
as Prof. Hill has given evidence that the Cretaceous is in part a deep 
water formation, there seems to be no question that it once covered all 
this region, particularly since the entire area is surrounded by a receding 
Cretaceous bluff. /That the Carboniferous has been uncovered from 
beneath a uniform mantle of Cretaceous strata is evident at first sight. 
Not only is it surrounded by a receding bluff of Cretaceous, but tongues 
of Cretaceous strata extend over, and isolated buttes and very much 
degraded patches remain upon the Carboniferous. The so-called Santa 
Anna mountains of Coleman county consist of two isolated buttes of 
'Cretaceous I’ock, in the center of the Carboniferous, separated from the 
main mass of the Cretaceous on either side by more than fifteen miles.” 
Pp. 145-146. 
“The histoii-y of the Carboniferous system, as briefly outlined in the 
preceding pages, commences with the deposition of a considerable thickness 
of lower Carboniferous limestone on an old shore of Silurian land. An 
interval accompanied by an elevation, a small amount of disturbance, and 
probably some erosion, is followed by the opening of the upper Carbonifer- 
ous. Forty-five hundred feet of sandstone, shales and conglomerate 
included in the Richland division probably represent the Texas equivalent 
of the Millstone grit. Following this quite uniform shallow water deposit, 
was a time of quiet water deposition, during which the Milburn shales 
were laid down with a total thickness of about 160 feet. A submergence, 
at least in the southwest, marks the beginniing of the Brownwood division. 
