12 OIL FIELDS OF TEXAS-LOUISIANA COASTAL PLAIN. [BULL.m 
According to Hilgard, this portion of the coast country is built up 
partly of littoral and esturine deposits and partly of swampy lagoon 
and fluviatile deposits, whose thickness and location are manifestly 
dependent upon the topographic features of the continent at the time 
they were laid down. The land at that time was being slowly 
depressed, as is shown by the nature of the deposits and by the 
numerous superimposed generations of large cypress stumps em- 
bedded in laminated clays, which exhibit the yearly fall of leaves. 
This view was also held by Hopkins in his survey of southwestern 
Louisiana in 1870-71. 
The theories regarding the upbuilding of the Coastal Plain may 
possibly apply to the newest extension in the east, along the Gulf of 
Mexico, which at present is altogether marshy, or to the comparatively 
arid region west of the Nueces River, where at present we find a chain 
of such keys with their accompanying lagoons. The largest of these 
lagoons — Lagima de la Madre — is being rapidly filled up by the drift- 
ing sands from the higher dunes of Padre Island. 
A study of the submerged portion of the Coastal Plain, as shown 
by the Coast Survey charts, shows that the general slope of the sea 
floor as far out at least as the 5-fathom, or 30-foot, line is not more 
than 5 to 7 feet per mile, and that there does not appear to be any 
uniformity in the deposition of the materials forming this floor. 
Lens-shaped deposits of hard blue clay and soft mud occur, irregularly 
interspersed with banks of* fine and coarse gray sand and broken 
shells. The Sabine Bank is reported as being made up of a gray sand, 
with black specks and broken shells, which closely resemble much of 
the gray sand obtained from the different wells in the southeastern 
portion of the oil fields, especially in the neighborhood of Beaumont. 
It is probable that the upbuilding of the Coastal Plain, at least 
throughout about 500 feet of its upper portion, was carried on in the 
same manner as at present. Under the presenl Gulf the sands appear 
to be the heaviest deposits, and the well records show the same con- 
ditions to exist down to a depth of 500 feet. 
The existence of petroleum in this portion of the country has been 
known for many years. In 1860 Wall, ([noting from Taylor's Statis- 
tics of Coal, mentioned the existence within 100 miles of Houston of a 
small lake filled with bitumen or asphaltum, and having in its center 
a spring from which during the summer months an oily liquid (prob- 
ably petroleum) continually boiled up from the bottom/' 
In 1880 S. F. Peckham quotes N. A. Taylor as to the existence of 
maltha in Texas, and gives Sour Lake as one of the localities. On 
the map accompanying his report oil-producing localities are marked 
as follows: At the mouth of the Brazos, near the point where the J. M. 
Guffey Petroleum Company is now drilling; close to Port Arthur, in 
aGeol. of Trinidad, App. G, p. 136; Taylor's Statistics of Coal, p. 223. 
