OIL FIELDS OF THE TEXAS-LOUISIANA GULF COASTAL PLAIN. 
By C. W. Hayes. 
INTRODUCTION. 
Shortly after the discovery of oil at Beaumont, in 1901, the system- 
atic study of the stratigraphy and structure of the Gulf Coastal Plain 
was undertaken. Mr. William Kennedy spent nine months in the 
field and the writer about two months collecting data for an economic 
report. A report has been prepared as a Survey bulletin, and is now 
in press, under the above title. The following is a brief summary of 
the conclusions there stated at length : 
Location of the field. — The Gulf Coastal Plain oil field includes a belt 
of country from 50 to 75 miles wide bordering the Gulf of Mexico and 
extending from the vicinity of the Mississippi River in Louisiana 
westward about two-thirds of the distance across Texas. 
TOPOGRAPHY. 
While the whole of this belt is a nearly featureless plain, rising 
gradually from sea level at the Gulf coast toward the north and north- 
west, it may be divided into three subordinate belts, which are some- 
what distinct: (1) Along the margin of the Gulf is a fringe of marsh 
land only slightly above sea level and subject to occasional overflow. 
This fringe is widest in Louisiana and decreases westward to the 
vicinity of Galveston, beyond which it is inconspicuous or absent. 
(2) Inland from the coast marsh is a somewhat broader belt of prairie 
land, its surface rising inland at the rate of about a foot to the mile. 
It has a stiff clay soil and is generally treeless, except for occasional 
bunches of live oak and a fringe along the water courses. (3) The 
third belt has a generally sandy or gravelly soil and is well wooded. 
Its surface rises more rapidly and forms a less perfect plain than the 
other two belts. 
The only topographic features which relieve the monotony of the 
Coastal Plain are occasional low mounds or swells, which rise island- 
like above its even surface. These swells are of exceptional impor- 
tance in the present connection, since they appear to be the external 
indication of conditions which have favored the accumulation of oil 
in commercial quantities. They vary considerably in size and amount 
of relief. At the one extreme are the " salt islands" of Louisiana, and 
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