Age of the Missouri River. — Uphaiii. 8i 
Carll in Pennsylvania and since continued and extended by 
Spencer, Foshay, Chamberlin, Leverett, Tight, and others.* 
The upper waters of the Ohio are now known to have flowed 
in preglacial times into the Lake Erie basin ; but apparently the 
drainage thence passed westward, as before noted, being tlius 
tributary to the Cretaceous inland sea, presumably by the way 
of lake Superior, and afterward to the Tertiary river which 
is now the Mississippi, reaching it probably by a route nearly 
coincident with the Illinois river. 
The lower part of the Ohio river basin, with the tributary 
Cumberland and Tennessee basins, may have sent its waters 
directly to the western Cretaceous sea, flowing across the 
country traversed by the Missouri river below Kansas City; 
but with the inauguration of the Mississippi river, during the 
Tertiary era, that trunk stream must have received important 
branches from the lower parts of these two great basins, the 
Ohio and the jNIissouri, nearly as today. Even in the Creta- 
ceous period, too, it is perhaps more probable that the lower 
Ohio and the lower [Missouri from Kansas City eastward, 
with its continuation in the course of the ]^Iississippi, both 
emptied into the Cretaceous ocean near the site of Cairo, Il- 
linois, at the present mouth of the Ohio ; for so far northward 
extended a great embayment of the Atlantic during the Cre- 
taceous and Eocene periods. 
With the epeirogenic uplifting of the Plains from the sea, 
near the end of Cretaceous time, and the contemporaneous 
folding and upheaval of many ranges of the Rocky mountains, 
there ensued very abundant estuarine, lacustrine, and fluvial 
deposition, of partly brackish, but mainly freshwater beds of 
very great extent and depth, often including layers of lignite, 
overlying the marine Cretaceous series. In the Dakotas and 
IMontana and northward, on the country of the upper Missouri 
and the branches of the Saskatchewan, these beds belong al- 
most wholly to the latest Cretaceous stages ; but southward, in 
Wyoming, Nebraska, Colorado, and Kansas, they extend on- 
ward from the late Cretaceous to the Miocene and Pliocene 
periods. Their material has come chiefly from the erosion of 
* The latest and most complete discnssion of the complex history and 
development of the Ohio river system has been given by Frank Lkvkrett in 
Monograph XLI, U. S. Geol. Surrey. "Glacial Formations ami Prainagc 
Features of the Erie and Ohio Basins," 1902, chapter iii, pages 82-l.'19. 
