32 OIL FIELDS OF TEXAS-LOUISIANA COASTAL PLAIN, [bull. 212. 
a bowlder-like form. From these beds the country slopes very gently 
until it merges into the great Coastal Plain proper. Very few sections 
are obtainable within the limits of the plain, but from the shallow cut- 
tings seen in this section the underlying beds appear to be blue limy 
clays. About 3 miles south of Port Lavaca, in Calhoun County, on 
Chocolate Bayou, a cutting along the bank is as follows: 
Section on Chocolate Bayou, ■>' miles south of Port Lavaca. 
Feet. 
1. Black soil 2to3 
2. Gray calcareous clay, in places blue with limy nodules 3 to 5 
3. Chocolate-colored clay 2 
These gray calcareous clays, or their blue phase, outcrop in a belt 
stretching across the country as far east as the Sabine River and 
probably much farther. The clays with their calcareous concretions 
have been recognized in Wharton and Brazoria counties, in the neigh- 
borhood of Houston and Beaumont, and near Orange, in Orange 
County. They also appear in Louisiana. 
DETAILED SECTIONS ON THE COLORADO AND BRAZOS. 
Eastward through the counties of Jackson, Matagorda, Wharton, 
Brazoria, Fort Bend, Colorado, and Austin the country presents the 
general appearance characteristic of the Coastal Plain. In Colorado 
and Austin counties the Fayette sands with their overlying Frio clays 
are fairly well developed. In the middle and southern portions of 
Austin County tin- Fayette beds, in the form of coarse calcareous 
sandstones, are found underlying the Frio clays, which in this locality 
are bluish-gray limy clays, with the limy concretions broken and pow- 
dery where exposed. Gray calcareous sandstones appear in the 
banks of the Brazos at Cochran's ferry, near Buckhorn post-office, in 
Austin County, underlying the grayish-blue calcareous Frio clays. 
Throughout the same area many of the higher grounds are occupied 
by ferruginous and gray gravels. At Seely, in Austin Count} 7 , the 
Frio clays are comparatively thin, being only 35 to -40 feet in thick- 
ness, and overlie the upper sandstones of the Fayette 
In the neighborhood of Richmond and Rosenberg, in Fort Bend 
County, the coastal deposits comprise a series of dark-brown to black 
calcareous clays, more or less intermixed witli deposits of sand. No 
surface sections are visible, and in the vicinity of the Brazos River 
the recent alluvium is so heavy that no reliable sections are to be 
found. Occasional low bluffs showing interstratified blue clays and 
sands occur, but these give no distinctive indications as to their age. 
The dip of these beds is apparently to the east of south, but the 
exposures are in such condition that no great reliance can be placed 
upon them. 
The only wells drilled to any depth in this portion of the country 
