726 INDEX TO THE STKATIGEAPHY OF NOKTH AMEKICA. 



the State that they haTe sometimes been described as a separate formation, to which the name 

 Queen City has been applied by Kennedy." 



"The lower beds of the Wilcox in northeastern Texas, which are seen to underlie the beds 

 above described, are similar in all respects to the deposits occurriag on the Brazos." 



West of the Colorado River the Wilcox or its representatives have not been definitely 

 •traced, but the studies of Penrose, Vaughan, and Dumble have proved that it is extensively 

 developed along the Rio Grande. Vaughan ^^^^ has shown that on the Rio Grande 3^ mUes 

 above the mouth of San Ambrosia Creek, Maverick County, sandstones and thinly bedded 

 lignitic sands carrying Midway fossils underlie coarser sands outcropping in the vicinity of the 

 Chupadero ranch and extending thence northeastward through Carrizo Springs and Batesville. 

 These sands are the Carrizo sands of Owen ^'^ and are probably the lower portion of the Wilcox. 

 They are at least 150 feet thick. They are overlain by about 300 feet of fine-grained micaceous 

 sandstones, which are succeeded by alternating beds of clay, shales, and sandstones, at least 

 400 feet thick, and these in turn by clays, sandstones, and lignite beds 190 feet thick, ^^^d 

 Dumble '^''^ reports: "About 35 feet above the San Pedro seam [Santo Tomas] there is a band 

 of shell breccia which contains a great number of fossils. Among there were Ostrea divaricata 

 Lea, Anomia epJiippoides Gabb, Corbula texana Gabb, and many others." These fossils belong 

 to the Claiborne group and occur between the two coal seams in this mine, or the last division 

 of the section described above belongs to the Claiborne. The Wilcox along the Rio Grande is 

 probably at least 850 feet thick. 



Claiborne group. — In central Lo.uisiana the Claiborne group is divisible into a lower fossilif- 

 erous formation, the St. Maurice, and an upper formation, the Cockfield, which contains no 

 marine fossils. The St. Maurice formation is much more calcareous, glauconitic, and clayey 

 than the underlying Wilcox formation and where typically developed contains no lignitic nor 

 lignitiferous matter, though to the north it changes to lignitiferous sands and clays and 

 merges into the undifferentiated Eocene. 



The thickness of the St. Maurice formation is 250 to 300 feet in the region about Monroe, 

 but increases to over 500 feet at Winiifield. On Sabine River the thickness, calculated from 

 dip observations, is 550 feet.^^" In a weU recently put down near Robinsons Ferry, Tex., at a 

 depth of 1,250 feet fossils were obtained that W. H. DaU regards as Claiborne, indicating that 

 the thickness is as much as 700 feet. 



Harris *'"° says: "The Claiborne group borders the Sabine^uplift. It is represented only by- 

 patches in Gregg, Marion, and Cass counties, Tex, and Caddo and Bossier parishes. La., where 

 it has been for the most part carried away by long-continued erosion. It spreads out exten- 

 sively in Rusk and Nacogdoches counties, Tex.,, and Bienville and Winn parishes. La., where 

 the dip is slight, but it narrows down in Sabiae Parish, where a steep dip carries it beneath the 

 later Tertiary deposits." 



The northwestern area of the St. Maurice formation referred to in the following note of 

 Harris ^"''^ probably represents the Mount Selman formation of Texas. 



"In the Caddo field, as already defined, marine Claiborne fossils have been found in but 

 one locality, by the roadside about one-fourth of a mile east or east-southeast of the railway 

 station at Vivian. Here, as at Roberta, Bolinger, and Plaindealing, in Bossier Parish, and in 

 Ouachita County, Ark., the fossils are in the form of casts in very ferrugiuous indurated layers. 

 From their appearance, which is very different from that of the fossil species so abundant and 

 characteristic of the Claiborne from Bienville Parish to Nacogdoches County on the south, it 

 is inferred that either these northern forms existed under considerably different conditions 

 from their southern relatives or they represent a somewhat older type of life. It is possible 

 that the Sabine uplift was more or less manifest in early Eocene or perhaps even late Cretaceous 

 time. Desoto Parish, La., as well as Shelby, Panola, and Harrison counties, Tex., may have 

 constituted an island in Claiborne time. The ferruginous, more or less brackish waters to the 

 north of the island would naturally contain a very different fauna from that flourishing in the 

 pure sea water to the south." 



" Kennedy, William, Proc. Acad. Nat. Sci. Philadelphia, 1895, pp. 135, 136. 



