44 OIL FIELDS OF TEXAS-LOUISIANA COASTAL PLAIN, [hull. 212. 
rations or soft sandstone. The sands are often cross bedded and con- 
tain nodules or concretions of pinkish clay varying in size from a few 
inches to a foot in diameter; the clays are blue and red, laminated or 
tlii nly stratified, and bine and red mottled. These beds toward the 
western end of the district, or in the Brazos River section, appear 
chiefly in their brown cross-bedded sandy condition, and small expo- 
sures of them may be seen in the river banks north and west of Hemp- 
stead and also in the shallow cuttings on the Houston and Texas 
Central Railroad between Hempstead and Hockly, in Waller County, 
where they appear to merge into the general level of the Coastal 
Plain proper. So small a difference in elevation occurs that these 
brown sands may be said to be the lowest member of the coastal 
deposits in this region. At Conroe, in Montgomery County, these 
beds still maintain their brown sandy character, although they have 
risen more than 80 feet above their level at Hempstead. Northward 
from Conroe these beds occur as laminated blue and red claj^s, and 
eastward along the Trinity they appear as bright-red, pink, and brown 
heavy-bedded clays, rising to considerable elevations above the river 
valley. At Dodge, in Walker County, they are between 20 and 30 
feet in depth and overlie the blue joint clay of the Frio beds, and at 
Point Blank, 14 miles farther east, brown sands of this series are seen 
overlying the blue calcareous Frio clays. The red sands forming the 
capping of the Sun Mounds in Waller County may possibly belong to 
these beds, although the present conditions would presuppose a large 
amount of erosion or a considerable uplift after these sands were laid 
down. Occasional deposits of gravel appear in connection with these 
sands. 
These brown sands and clays appear to mark the beginning of a 
new epoch. They are unconformable with the underlying Frio clays, 
and in many places have so overlapped them as to obscure them alto- 
gether. At other places much erosion has taken place before the 
deposition of the brown sands and clays. In many places the sands 
are cross bedded and show an otherwise irregular deposition. The 
total thickness of the sands and clays of this division has been esti- 
mated at 350 feet. 
These beds are referred to the Lafayette and are correlated with 
the Oakville beds in the western end of the plain and the Loup Fork 
beds by Dumble and regarded as of late Miocene or early Pliocene 
age. 
Southward from these brown sands and clays is a series of gray- 
white, bluish-gray mottled, and yellow sands with occasional thin 
lens-like deposits of blue, gray, and yellow clays containing irregular 
gravel deposits and many concretions and beds of indurated sands 
forming a soft sandstone. These practically occupy the whole country 
from the upper margin of the underlying brown clays to the latitude 
of Houston. Owing to the generally level surface of the country 
occupied by these beds, reliable sections are rarely seen. These 
