HAYES AM) 
KENNEDY. 
PKEVIOUS KNOWLEDGE OF THE REGION. 11 
reports of the Texas State Geological Survey have been cursory and 
of a very general character. The most important is as follows : 
Immediately bordering the Gulf shore and forming the underlying slope we 
find a series of beds of clays, sandy clays, blue, yellow, red, and often mottled, 
which frequently appear black upon the surface from the combination of vege- 
table matter with the lime of the calcareous nodules which are found scattered 
through them. These clays are heavy, massive, containing small crystals of gyp- 
sum in places, and so compact that bluffs from 15 to 20 feet in height are often 
found along the streams and bay shores even in such a moist climate as that of 
Texas. 
The various strata which form these beds dip so slightly to the southeast as to 
appear nearly horizontal, and form the basis of the level coast prairies which 
stretch inland from the Gulf for distances varying from 50 to 1 00 miles. 
While the underlying beds of clay are seemingly identical for the entire Gulf 
coast, the overlying soil is somewhat different, being more sandy on the eastern 
and western borders and more clayey between the Brazos and Nueces rivers. « 
McGee regarded these deposits as belonging in part to his Lafayette 
formation and in part to his Columbia. He considers the region to 
have been built up for the most part from long wave-built keys sepa- 
rated from the mainland by sounds, although he says that " east of 
Galveston the keys and sounds appear to fail; yet the wave-built 
barriers are continuous as in southern Texas and eastern Mexico, 
though submerged beneath the Gulf waters to form Sabine Bank, 
Trinity Shoals, and Ship Shoal, and their connecting scries of bars 
parallel with the coast." 6 
R. T. Hill describes these plains as a belt of prairie land not over 
100 miles wide bordering the Gulf of Mexico in Louisiana and Texas. 
He regards it as a grass-covered constructional plain newly reclaimed 
from the Gulf of Mexico. The interior margin of this plain rises 
scarcely 100 feet above the sea, and it is characterized by an exceed- 
ingly level surface hardly broken except by a few low drainage 
grooves, which become fewer and more faintly developed toward the 
Rio Grande. Upon this plain a youthful drainage system is being 
established, while the seaward extensions of the through-flowing 
streams cross it. These rivers have wide and deepty indented valleys 
with gently terraced slopes filled witli old alluvium. 
The floor of the sea border of Texas is a submerged gently sloping sandy plain, 
or shelf, extending 50 miles seaward. By action of tide, wave current, and wind 
this sand is piled into long island strips which fringe the coast and stand almost 
at sea level. These are separated from the land by shallow lagoons, in which 
most of the sediments of the river are deposited. The building up of the sand 
bars by wind and w r ave and the filling up of the lagoons between them by river 
sediments, in connection with gradual uplift, may possibly explain the origin of 
much of the adjacent coast prairie. c 
Sufficient work has not been done in southwestern Louisiana to 
give us any clue to the structure of that portion of the Coastal Plain. 
a First Ann. Rept. Geol. Survey Texas, 1889, p. xxxii. 
*> Twelfth Ann. Rept. U. S. Geol. Survey, 1892, p. 316. 
cPhys. Geography of Texas: Topographic Atlas, U. S. Geol. Survey, folio 3. 
