424 GEOLOGY OF NORTHWESTERN TEXAS. 



"The Triassic strata underlying the Indian Territory, Northern Texas, New- 

 Mexico, etc., are peculiarly barren of fossils. They are generally reddish 

 sandstones, conglomerates, and shales below, with a series of highly colored 

 indurated marls or fine grained calcareous sandstones above, frequently 

 charged with salt and sometimes including extensive sheets of gypsum, etc." 



This description is an excellent one of the Dockum Beds (Triassic) in Texas, 

 but is not applicable to the Permian beds below. There is not a single bed 

 of conglomerate in the entire strata, as that name is generally used. The 

 conglomerate bed that I have mentioned in the Wichita division is a pecu- 

 liar stratum composed of rounded masses of clay ironstone cemented together 

 by iron. In Texas I have placed the base of the Triassic just where Dr. 

 Newberry has put it in the description above. 



TRIASSIC. 



In the First Annual Report, 1S89, under the head of Dockum Beds, I men- 

 tioned the occurrence of a formation composed of beds of clay, sandstones, 

 and conglomerates situated immediately above the Red Beds of the Permian 

 and below the beds of the Tertiary, which constitute the Plateau of the Llano 

 Escatado at this place. These beds occur probably along the entire base of 

 the plains on the eastern side from Big Springs to the Canadian River. The 

 great amount of petrified wood in the conglomerate is one of its chief charac- 

 teristics. Prof. Jules Marcou, in 1853, found the Triassic along the Cana- 

 dian River, and thus describes it along his route: 



" In this group of Triassic rocks numerous remains of petrified wood, even 

 whole trees, are often met with. On the western declivity of the Sierra 

 Madre, between Zuni and the Rio Colorado Chiquito, there is really a petrified 

 forest of trees thirty and forty feet long, divided in fragments from six to ten 

 feet long, with a diameter of three to four feet, some being still upright, en- 

 closed in the sandstone These beds and remains of petrified wood belong 

 nearly all to the family of the Conifers and some to that of the ferns with 

 arborescent stems and to the Calamodendron."* 



The formation was seen by Dr. Shumard at the head of the North Fork of 

 Red River, in 1852. during Marcy's expedition. Captain Marcy saw it at the 

 head of Prairie Dog Town River, and in his report of the expedition gives a 

 glowing description of it. Although Marcy put it with the marly clays group 

 of the Cretaceous, yet it is easily recognized by his description as the same 

 beds as are seen at Dockum. 



The formation is found on the west side of the plains, and is described by 

 both Marcou and Shumard ; yet it lacks the peculiar feature in that part of 



*Geology of North America, Zurich, 1858. 



