THE MORRISON FORMATION 659 



southern Kansas (Kiowa, Comanche, Barber, and Clark Counties), 

 where the Dakota sandstone is separated from the Red Beds by 

 100 to 150 feet of Comanche shales and sandstones, representing 

 not the whole series but probably only its upper, or Washita, group. 

 The attenuated margin of late Comanche deposits has been recog- 

 nized by means of marine invertebrates as far north as Salina, Kansas, 

 where it rests directly on the Permian and beneath the Dakota. 

 Its occurrence at several points in Oklahoma, and eastern New 

 Mexico, especially at Mesa Tucumcari, has long been known, but 

 until recently there was no evidence that Comanche sediments with 

 their marine fauna approached the dinosaur-bearing Morrison for- 

 mation more closely than several hundred miles. 



In 1 901 Lee announced the discovery of the Morrison formation 1 

 in southeastern Colorado on the Purgatoire River, and its probable 

 occurrence as far south as the Cimarron in New Mexico. It had 

 previously not been known east of the Rocky Mountain foothills. 

 The following year Lee continued 2 his explorations south and east 

 and found the Morrison on Canadian River 3 in New Mexico, as well 

 as on the Cimarron. He also suggested its correlation with the 

 Comanche series in the following words: 



In Mr. Hill's folio of the Texas region he gives a section showing the geology 

 of the Texas region. This region embraces the exposures which I studied along 

 the Canadian, and extends to within a few miles of the Rio Cimarron. According 

 to Mr. Hill's section the Lower Cretaceous, consisting of the Trinity, Fredericks- 

 burg, and Washita, lies between the Red Beds and the Dakota. If Mr. Hill's 

 section represents correctly the age of the formations in the Canadian valley, 

 then the shales and possibly the Exeter sandstone, must be of Lower Cretaceous 

 age. But the shales, as I have already shown, are probably the same as the 

 dinosaur-bearing shales of the Purgatory. There is some probability, therefore, 

 that the Morrison formation may be identical with some part of the Lower Cre- 

 taceous of the Texan region. 



This suggestion and the argument supporting it would have force 

 if Hill's generalized Texas section were applicable to the Canadian 

 valley, and if sedimentation had been continuous from the Red 

 Beds to the Dakota inclusive. Several years earlier Hill suggested 

 the possible equivalence of the Atlantosaurus beds with the basal 

 or Trinity group of the Comanche series. 



1 Journal of Geology, Vol. IX, pp. 343-52. 



2 Journal of Geology, Vol. X, pp. 36-58. 3 Pp. 56, 57. 



