CHAPTER IV. 



DESCRIPTION OF THE PERMO-CARBONIFEROUS BEDS IN EASTERN 



NORTH AMERICA. 



IOWA. 



East of the beds in Texas, Oklahoma, and Kansas, no vertebrate fossils 

 of Permo-Carboniferous age have been found closer than Illinois, but certain 

 deposits in Webster County, Iowa, have been doubtfully referred to the 

 Permian, and more or less directly coiTelated with the western deposits. 

 Wilder'' describes the deposits around Fort Dodge as red shales and sand- 

 stones, with considerable gypsum lying unconformably upon the St. Louis 

 limestone. 



The narrow sea in which was deposited the Wreford and overlying lime- 

 stone in Kansas and southern Nebraska probably did not extend much 

 farther east than Ozarkia, though its easternmost deposits have been removed 

 by erosion. To the north it may have extended into southwestern Iowa (see 

 Schuchert's Paleogeographic map of the Late Permian), and even into north- 

 western Missoiui. 



The author has recently examined the beds in the vicinity of Fort Dodge, 

 Iowa, and found nothing either in the character of the material or the mode 

 of deposition which would warrant the assumption that they were in any 

 way connected with the Red Beds deposits farther west. The red and parti- 

 colored clays and shales have in many places the appearance of residual clays 

 formed by the decomposition of a limestone. There can be little doubt that 

 they were formed in the last part of the Paleozoic and so may, perhaps, be 

 reckoned as Permo-Carboniferous, possibly formed at the same time as the 

 Red Beds, but under radically different conditions, either as the result of 

 mature decomposition of the land surface east of the Permo-Carboniferous 

 sea or in some inland body of swampy water. 



East of Iowa no deposits referable to the Permo-Carboniferous are found 

 nearer than eastern Illinois. This is easily understood when we reflect how 

 long the region had been exposed to erosion, and how slight and thin must 

 have been the deposits, which were essentially terrestrial or fluviatile, or 

 perhaps occasionally lacustrine. 



ILLINOIS. 



The nature and exact age of the limited deposits near Danville, Vermil- 

 ion County, lUinois, is still doubtful. The suggestion by Baur and Case, 

 following Cope, that they are accumulations from a Permian river which 

 excavated its channel in the Pennsylvanian limestone has been questioned by 



•Wilder, 12th Annual Report, Geological Survey o£ Iowa, p. 631. Norton and others. Underground 

 Water Resources of Iowa, U. S. Geological Survey, Water Supply Paper No. 293, p. 86. 



6 77 



