COMPOUND REGRESSIVE AND TRANSGRESSIVE OVERLAP 623 



is an abundant and characteristic fossil of the Comanche Peak and 

 Walnut beds (Fredericksburg) of Texas. A number of other charac- 

 teristic species of this bed do not occur above the Fredericksburg horizon 

 in Texas. On this account Cragin thinks that . . . "the Champion 

 shell-bed should be referred to the Fredericksburg division and perhaps 

 to a horizon not higher than the middle of that division."* 



The Champion shell-bed is underlain by the Cheyenne sandstone, which 

 rests disconformably on the Eed beds. It consists of soft variegated 

 grayish or yellowish cross-bedded sandstones in the lower part, with peb- 

 bles of quartz, clay granite, etc., smoothly water-worn and ranging in 

 size up to a hen's egg. They are often seen in pockets on the Eed beds. 

 Lignite and other carbonaceous matter also occurs here. The upper part 

 consists of alternating vari-colored sandstones, sandy shales, and hard 

 argillaceous shales. The total thickness ranges from 50 to 100 feet. From 

 the upper part of this sandstone dicotyledonous plants of the genera 

 Ehus, Sassafras, Sequoya, etc., are obtained. No animal remains have 

 been recorded from this formation, which is probably entirely of conti- 

 nental origin. 



In the Arbuckle mountains of Indian Territory the Cretacic beds 

 rest on a nearly flat floor of older rocks. The base consists of approxi- 

 mately 240 feet of sands, with local conglomerates at the bottom. They 

 are succeeded by the G-oodland limestone, 20 to 30 feet thick, and a nearly 

 pure limestone formation. Above this lie the Kiamitia clays, Caddo 

 limestone, Bokchito formation, and Bennington limestone, aggregating 

 nearly 840 feet in thickness. The upper beds are slightly eroded and 

 succeeded by the Silo sandstone, which is in part at least of Dakota age.f 



The Goodland limestone is correlated with the entire Fredericksburg — 

 that is, Walnut, Comanche Peak, and Edwards — while the underlying 

 sands are called Trinity. This correlation is no doubt just as erroneous 

 as was the former reference of the Cheyenne sandstone to the Trinity. 

 The fact that a lower Cretacic formation is a basement sand does not 

 make it Trinity in age, since basement sands can be of any age. The 

 combined thickness of the Comanche Peak and Edwards (the Walnut is 

 only a phase of these limestones) on the Eio Grande is in the neighbor- 

 hood of 700 feet, while in Mexico it is still greater. This shows clearly 

 that the Goodland limestone can represent only a part — that is, the upper 

 part, though probably not the highest part — of the Fredericksburg, and 

 that the so-called Trinity sands are really basal sands of Fredericksburg 



* Cragin : Loc. cit, p. 371. 



t Taff : Professional paper no. 31, U. S. Geological Survey, Tishomingo and Atoka 

 folios. 



