UPPER CRETACEOUS OF TENNESSEE 383 



in this part of Dickson County, Tennessee. A cut on the railroad 

 about two miles east of McEwen shows, resting on chert of the 

 St. Louis formation, about thirty feet of very compact, hard, white 

 chert gravel which is very typical of the Tuscaloosa belt across the 

 state. No paleontological evidence has been obtained from the 

 gravels about McEwen to determine the age of these deposits, 

 but after a study of the lithology as well as the geographic and 

 topographic relations, the Tuscaloosa age of the McEwen gravels 

 can hardly be doubted. These gravels are made up of well-rounded 

 water-worn pebbles, most of which are one inch or less in diameter, 

 although many are larger, often ranging up to cobbles six inches 

 in diameter. Many individuals approach a sphere in outline, and 

 in this respect they differ from the river gravels which are common 

 in terraces along the western Tennessee Valley. In the river 

 gravels of this region the individuals are often flat, elongated, and 

 subangular. Small discoidal quartzite pebbles are often con- 

 spicuous in the terrace conglomerates. The Tuscaloosa con- 

 glomerates consist for the most part of pebbles and bowlders 

 derived from the Lower Carboniferous cherts which are common 

 in this part of the Mississippi basin. Water-worn sandstone and 

 iron-oxide pebbles have not been observed in the Tuscaloosa. This 

 is another feature which serves to distinguish the Upper Cretaceous 

 gravels from the more recent terrace gravels in this part of the 

 embayment region, even though the latter may rest directly on 

 the former, as is frequently the case in the western Tennessee 

 Valley. 



South of McEwen, as stated above, the isolated Tuscaloosa 

 gravel areas may be traced along the highland rim across Lewis 

 County into Wayne and Hardin counties and farther into Missis- 

 sippi and Alabama, where they are overlain by marine Eutaw 

 deposits, and consequently paleontologic evidence may be obtained. 



The Tuscaloosa extends also north of McEwen. About three 

 miles west of Canton in Trigg County, Kentucky, at a point just 

 east of where the Fulton and Nashville Highway crosses the divide 

 between the Tennessee and Cumberland rivers, is an exposure of 

 Upper Cretaceous which has already been reported. This expo- 

 sure occurs in the top of the divide, which is probably more than 



