PENNSYLVANIAN. 427 



fossils. In the western part of Alta Verapaz these dolomites are, it is true, not entirely wanting, 

 but limestones, hmestone conglomerate, and breccia greatly predominate. The Umestones rest 

 conformably upon the Santa Rosa terrane. 



Complete lists of the Carboniferous fossils identified for Sapper by StoUey are 

 given in an earlier paper by Sapper. ^"^ 



H 14. CENTRAL TEXAS. 



The following notes are selected from the forthcoming Llano-Bm"net folio 

 and from a bulletin ''^^ on the mineral resources of the region, both by Paige: 



The Carboniferous of the Llano-Burnet district is represented by hmestone and shale 

 formations of lower Pennsylvanian age. The limestone forms the lower portion of the system 

 and has been mapped as the Marble Falls hmestone. The shale, in which are included sandstone 

 lentUs, overlies the hmestone and is mapped as the Smithwick shale. 



The Marble Falls limestone is separated from the underlying EUenburger limestone (Cam- 

 brian and Ordovician), by a thin limestone conglomerate, though in one place a very coarse 

 angular conglomerate or breccia was observed. There are some locahties, however, where httle 

 •or no discordance could be noted, as, for example, in the small basin 5 miles northeast of Blufton. 

 The boundary at the top of the formation is sharp, and the Smithwick shale succeeds with 

 perfect accordance in dip. 



The Marble FaUs limestone is believed to be not more than 450 feet in thickness. It is 

 composed of alternating beds of dark and light gray, dove-colored, and dark blue to black lime- 

 stone. Many beds carry an abundance of cherty nodules, largely of a decidedly dark or black 

 color. The color of this chert is diagnostic in distinguishing this formation from the underlying 

 EUenburger hmestone, in which the chert is of a decidedly lighter color. The formation usually 

 may also be distinguished by the petroliferous odor wliich it emits on being struck a sharp blow 

 with a hammer. The Marble Falls limestone is confined largely to the southeast quarter of 

 the Burnet quadrangle, but a small patch occurs northeast of Blufton and there are consider- 

 able areas in Riley Mountain. 



The two following sections wiU iUustrate the lithology of the formation: 



Section of Marble Falls limestone in Riley Mountain, in stream 7|- miles north of south edge and 



If. miles west of east edge of Llano quadrangle. 



Very hard, compact, neai'ly black limestone ; some chert; nonfossiliferous. Feet. 



Thin, dai'k, very hard limestone; conchoidal fractm-e; weathers buff; platy and considerable 



black chert 10 



Rather massive gray limestone; some black chert 10 



Thin-bedded, very fine grained black slaty limestone 20 



Rather massive dove-colored limestone 20 



Thin-bedded slates or slaty limestone, black or dark graj-; weathers yellow; apparently no 



fossils 35 



Massive, coarse brown limestone 5 



Thin-bedded limestone with cherts, gray-browns; marly in some places; weathers light yellow- 

 ish; few fossils noted in talus slopes 50 



Crystalline grayish-brown limestone; some fossil fragments 12 



Massive brown limestone with large amount of chert 7 



Coarse-grained brown limestone containing considerable light chert; weathers into a slope of 



talus - 9 



Irregular limestone, gray to brown, fine grained, nonfossiliferous 32 



Thin-bedded, very dark fine-grained limestones with a large quantity of black chert; a few 



fossils. 

 Irregular-ly bedded fine-grained brown and gray limestone; A-ery fossiliferous at base; bitumi- 

 nous odor strong; some parts of base are mostly Productus remains 22 



Mostly thin-bedded fine to coai-se grained brown and dark-gray limestone, highly fossiliferous. . 8 



Thin-bedded hackly limestone, brownish, sugary; bituminous odor 6J 



Conglomeratic limestone containing pebbles of white chert and fine-grained light limestone 2 



EUenburger limestone (Cambrian and Ordovician). 



" 248 



