10 B. S. Tan' — The Permian of Texas. 



this district. The Carboniferous rocks of central Texas have 

 been divided by the writer* into five divisions, based upon 

 lithological and faunal characteristics, as follows: Richland 

 Sandstone, Milburn Shales, Brown wood Limestone, Waldrip 

 Coal Measures, Coleman Limestone and Clays. The history 

 here indicated is one of gradual submergence until the time of 

 the Brownwood limestone, then an emergence continued 

 through the time of the Coleman strata, which are infra-littoral 

 beds. The Brownwood beds contain the typical marine fossils 

 of the Carboniferous, the Waldrip coal measures combine with 

 these the land flora, and these conditions continue into the 

 Coleman beds. 



The latter are the highest of the Carboniferous strata and 

 near the Permian have less character than lower down. The 

 series consists of alternating beds of limestone and clays and 

 the presence of clay is everywhere evident, even in the purest 

 limestones. Shore lines, proved by ripple-marks, reptile tracks, 

 coal seams and other signs, show that at this time the Carbon- 

 iferous beds were in part subjected to denudation. It is prob- 

 able that the denudation of these rocks was in large measure 

 the source of supply of the clays of the Coleman beds, and the 

 unconsolidated nature of the coastal strip accounts for the 

 general absence of conglomerates and sandstones. 



The shallowness of the water and its muddy character gave 

 rise to or permitted the extension of a new fauna into the seas. 

 That the clear water animals which aided in the formation of 

 the Brownwood limestone still existed in the neighborhood is 

 well proved by their frequent recurrence in certain purer beds 

 of limestone in the Coleman series. They were temporarily 

 forced out by changed conditions and again and again allowed 

 to return. This repeated alternation, both lithologic and fau- 

 nal, is characteristic of the Coleman beds, but the predomi- 

 nant lithologic character is a muddy water deposit and the 

 fauna a mud-loving one, including such species as Myalina, 

 Pinna, Allorisma, Bellerophon, and the like. 



On the western border of the Permian area the same general 

 series of rocks is found in the Carboniferous of the Guadalupe 

 mountains. The lower rocks are here shallow water deposits, 

 followed by deeper water limestones of great thickness, and 

 these in turn by an upper series of alternating beds. Shore 

 lines are absent here, however, proving that this point was not 

 the exact western coast line. Shumard has called these beds 

 Permian, but I have shown in a manuscript report in the 

 hands of the State Geologist of Texas for publication, that 

 they are really Carboniferous, this being proved by palseon- 

 tologic, lithologic, and stratigraphic evidence. 



* First Ann. Rep. State Geol. Survey of Texas, 1890, pp. 201-216. 



