286 B. T. Hill — North American Cretaceous History. 



as shown by the phenomenal outcrops in the salines of Louisi- 

 ana and on the island of Jamaica.* 



The Comanche epoch of subsidence was closed by the great 

 elevation of an extensive land area of which little is as yet 

 known, except that it must have endured a length of time 

 sufficient for the complete modification of species, for not one 

 of those of the Comanche series has thus far been found to 

 pass upward into the later beds of America, although one or 

 two are found in Europe. The records of this elevation are 

 two-fold. First, an unmistakable and omnipresent unconformity 

 between its beds and those of the succeeding Upper Cretace- 

 ous — the Meek and Hayden section of the northwest and its 

 Atlantic coast equivalents. Second, the littoral conditions indi- 

 cated by the land flora of the Dakota sandstone which must 

 have been deposited along its shore line, marking the next 

 great epoch to be described. This unconformity is seen not 

 only in the absolute lack of parallelism in beds and the com- 

 plete lithologic and faunal changes, but also in the fact that 

 the same basal horizons of the Upper Cretaceous rest at differ- 

 ent places, owing to unequal erosion, upon different horizons 

 of the eroded surface of the lower Comanche series. The 

 elevation at the close of the Comanche epoch is also illustrated 

 by the disturbances recorded in the strata of southwestern 

 Texas as shown in the following trans-section of the Austin- 

 ]S"ew Braunfels unconformity at Austin, the Upper Cretace- 

 ous series resting unconformably upon the greatly disturbed 

 strata of the lower. The Comanche series are here greatly 

 faulted along the fold of what could be appropriately termed 

 the most eastward of the series of American monoclines and 

 which marks the first plateau, the eastern margin of which con- 

 tinues westward to the Rio Grande. This elevation evidently 

 took place before the beginning of the Upper Cretaceous. 



* The peculiar occurrence of Cretaceous limestone in certain salines of Louisi- 

 ana, some two huudred miles coastward from the main area of the Cretaceous 

 exposures, was noted by Dr. Eugene W. Hilgard in various publications, but 

 before the presence of any marine beds, except the Upper of the Cretaceous 

 system, had been admitted in this country. Some two years ago. Judge Law- 

 rence C. Johnson of the TJ. S. Geological Survey showed the writer some speci- 

 mens of the material recently collected from these '• Cretaceous Islands." They 

 were found to be both lithologically and paleontologically identical with the 

 marine Cretaceous of the Comanche series of the west Central Texas. The 

 nearest outcrop of the main area of the formation is at Cerro Gordo, Arkansas, 

 on the Choctaw line, and all the area intervening is covered by Quaternary de- 

 posits. Why these islands should occur along this Cretaceous " backbone " of 

 Louisiana as Hilgard has termed it, can only be explained upon the hypoth- 

 esis that there exists in that vicinity some ancient and as yel undescribed disturb- 

 ance. Another datum which adds interest to this inquiry is the fact that upon 

 the island of Jamaica, as personal observers and the reports of the Geological 

 Survey of Great Britain have led me to believe, there are also Cretaceous rocks 

 of the same horizon, directly in the strike of the Louisiana outcrops. In view 

 of these facts, the investigation of Cuba is awaited with much interest, for it is 

 probable that these outcrops were once continuous. 



