MISSISSIPPI PERIOD 547 



Mississippic Period (new emendation) 166 



(Lower Mississippian or Kinderhook and Osage of geologists) 



See plates 78-80, and pages 494, 495 



The extensive inundation of the Middle Devonic was maintained to the 

 early Upper Devonic, and was followed by an emergence of seemingly 

 small extent. The retreat of this water was most marked in the region 

 along the eastern side and the northern part of the Cordilleran sea, where 

 it may have represented as much as 10 per cent of the previous inunda- 

 tion, but in the United States it does not appear to have been greater than 

 from 5 to 9 per cent. In other words, the Devonic was not closed by a 

 very decided emergence, as was the case in most of the previous periods. 

 For this reason the faunal changes in the Cordilleran sea are thought to 

 have appeared slowly, and were not of a marked character. In the area 

 of the eastern United States, however, the physical changes were far more 

 decided, owing to the filling up of the northeastern marine basins toward 

 the close of the Devonic and the local emergence in progress in that region. 



Toward the close of the Keokuk the period terminated by considerable 

 emergence in all the seas, but more especially in the Cordilleran sea, 

 which appears to have been completely blotted out toward the end of the 

 Mississippic. At a few localities in Montana faunas of supposed Saint 

 Louis or Meramec time have been reported, but according to Ulrich some 

 of the fossils are clearly of the Pottsville. These faunas can now be 

 duplicated in Arkansas from horizons of early Pottsville age. 



Mississippian sea. — In the southern part of the Mississippian sea of 

 late Devonic time the Chemung emergence was continued into the Kin- 

 derhookian epoch. The new or Fern Glen transgression from the Gulf of 

 Mexico began to appear as early as the Bradfordian, depositing the Chat- 

 tanooga black shale with almost no organic remains. This invasion 

 spread north along the Mississippi valley east of Missouria and west of 

 the Cincinnati axis, as far as southern Indiana. This is the southern 

 Kinderhookian of Weller. Finally, late in the Kinderhookian (Fern 



ice The more useful references to the literature on the Kinderhook faunas and forma- 

 tions are the following : 



Weller : Transactions of the Academy of Sciences, Saint Louis, 1899, 1900, 1901, 1905, 

 and 1906. Journal of Geology, 1898, 1901, 1905, and 1909. Iowa Geological Survey, 

 vol. x, 1900. 



Bassler : Smithsonian Miscellaneous Collections, Quarterly, no. 1814, 1908. 



Prosser : Journal of Geology, 1901 and 1902. American Geologist, 1904. 



Girty : Monograph XXXII, part ii, IT. S. Geological Survey, 1899. Professional Paper 

 no. 16, U. S. Geological Survey, 1903. Proceedings of the Washington Academy of Sci- 

 ences, 1905. 



Rowley : Missouri Bureau of Geology and Mines, vol. viii, 1908. 



Stevenson : Bull. Geological Society of America, vol. 14, 1903. 



