HAYES ANI 
KENNEDY. 
'] GEOLOGY OF EASTERN DIVISION. 27 
been considered as the upper member of the preceding sands and 
clays, and is therefore placed with the Lafayette. These gravels 
have evidently been derived from the Lafayette, by a process of 
assorting and rearranging, at a time when the sand beds of this age 
overspread the greater portion of this region. They are made up 
chiefly of chert, quartz, agate, jasper, and some crystalline rocks, of 
which only the quartz and crystalline pebbles bear evidence of having 
traveled very far. The chert is peculiar in its angular and suban- 
gular condition. These gravel beds are more extensive toward the 
Mississippi Valley region than to the west in Texas, where they appear 
to gradually thin out. 
These gravels have been here considered as forming the basal mem- 
ber of the gray sands, clays, and gravels which, with their overlying 
heavy beds of yellow, blue, brown, and black calcareous clays and 
brown and gray sands, form what McGee calls the Columbia and the 
deposits of clays and sands long ago denominated, by Hilgard the 
Port Hudson clays. This brings them within the Pleistocene. They 
appear in many of the wells to have a thickness of from 50 to 250 
feet, or even more. 
BEAUMONT CLAYS. 
Overlying the Columbia as above defined is a series of yellow, gray, 
blue, brown, and black clays with brown sands. These beds are 
sometimes thinly stratified or laminated, but frequently massive. 
The laminated beds are usually interstratified with thin beds of blue 
and gray or grayish- white sand. The clays carry considerable quan- 
tities of calcareous nodules irregularly distributed, in many places 
shells of Pleistocene or Recent age, and great quantities of decaying 
wood in the form of tree trunks, bark, and leaves. Among these 
the cypress appears as the most prominent, and among the inverte- 
brate fauna found the Rangia cuneata (Gray) and an undetermined 
oyster are the prevailing forms. 
In Texas the prevailing colors of these clays are blue, yellow, and 
brown ; in Louisiana are occasional deposits of red clay. In many fea- 
tures the blue clays of these Beaumont beds strongly resemble the 
blue Frio clays, and, from the generally low dip of the beds through- 
out the regions occupied by both and the known existence of small 
flexures or shallow undulations, might be erroneously correlated with 
these underlying Frio beds. The chief differences between them, 
apart from their geologic position, appear to be the presence of wood 
in the Beaumont beds and the condition of the calcareous nodules. 
In the Frio clays these nodules appear to have a definite horizon and 
to lie in a more or less stratified condition, to have regular lines, and 
to be continuous with the blue clay. Although in several regions 
replaced by gypsum crystals, they continue in the regular lineal 
arrangement. In the Beaumont beds these nodules do not appear to 
