30 OIL FIELDS OF TEXAS-LOUISIANA COASTAL PLAIN, [bull. 312. 
Sabine, and the low bluffs along Black Lake near Hackberry Island 
in Cameron Parish, La. 
. Between the coastal marshes and the Gulf there is a narrow, newly 
formed strip of sand, with considerable quantities of recent shells. 
This strip appears to form a barrier between the Gulf waters and the 
marsh, and is in most localities elevated a few feet above the marsh. 
DETAILED SECTIONS OF COASTAL PLAIN FORMATIONS. 
The foregoing generalized description of the formations of the Gulf 
Coastal Plain will give most leaders a sufficiently complete idea of 
their character and thickness. For the oil prospector, however, local 
details are important, and these are therefore given in the following 
pages. There is necessarily some repetition of what has gone before, 
since the generalized section is Largely based upon these special sec- 
1 ions. The eastern division of the Gulf Coastal Plain as above 
defined will be described from its western end eastward. 
DETAILED SECTIONS ON THE GUADALUPE. 
The detailed geology of the western end of this eastern division of 
the Gulf Coastal Plain is not well known. South of the outcrops of 
gray sandstones of tin- Fayette beds the country is mostly prairie, and 
the surface, as eastof the Brazos, is made up of clays and sands. Very 
few well records are available, and consequently very little knowledge 
of the underground formations is obtainable. Along the Guadalupe 
River the banks are mostly obscured by deposits of recent material, 
and the few sections seen are referable more to the Fayette sands than 
to the Coastal Plain format ions. 
Throughout this region the ridges forming t he northern boundary 
of the plain may be placed in part with the Fayette sands and in part 
with the succeeding Frio clays, and may be roughly characterized as 
follows : 
General section near the Guadalupe. 
1. Ferruginous gravel containing pebbles of quartz, jasper, carnelian, and chal- 
cedony. 
2. Conglomerate formed from underside of gravel beds. The cementing material 
is calcareous and the conglomerate is only found where the white or gray 
sands prevail. 
8. Brown to red clays and sands, more or less mixed with pebbles, occasionally 
indurated and showing considerable ledges of red or brown sandstone in 
places. 
4. Bluish-gray to gray or dirty white sands, more or less calcareous; and limy 
clays of blue or grayish-blue color. 
5. Thin-bedded, soft, grayish, calcareous sandstones, changing frequently into 
gray calcareous sands. 
6. Red and blue mottled sands. 
No. 4 of this section belongs to the Frio clays, or to that phase of 
those beds peculiar to this section of the country. With but slight 
