HAYES AND 
KENNEDY 
D ] ACCUMULATION OF OIL. 145 
of northern Louisiana. a lie has shown that these saline springs are 
associated with dome-shaped uplifts and that they fall naturally into 
a linear arrangement, the axes being parallel with those of the Gulf 
Coastal Plain and probably continuations of the same. 
The lines shown on the map may be considered as coinciding with 
the main structural axes of the region, which are actual or potential 
lines of dislocation, either by folding or by fracture. The date of 
initial movement on these axes can not be fixed exactly, but it must 
be as far back as the Miocene, since the thickness of Miocene forma- 
tions is affected by the doming which has taken place at various 
points. The movement has been continued through the late Tertiary 
and into the present, since it affects the most recent deposits of the 
region, excepting perhaps the present river alluvium. The initial 
movement may even date back to Cretaceous time, and some evidence 
in the northern Louisiana salines points to such a conclusion. 
The character of the movement can not be determined with cer- 
tainty, and it doubtless includes both flexing and faulting. Its most 
striking characteristic appears to be the concentration of differential 
effect at certain points which form the mounds of uplift, of which 
Spindletop may be regarded as the type. It may be, however, that 
these local uplifts are purely secondary and are not due to the same 
cause which produced the axial movements; in other words, that the 
lines of weakness which give rise to the main structural axes merely 
afford the necessary favorable conditions for the development of these 
secondary structures. 
It will be noted from the descriptions given on previous pages that 
the various domes differ widely in amount of elevation. This is 
shown by a comparison of Sour Lake and Spindletop with High Island 
and Damon Mound. The former elevations are much less conspicu- 
ous than the latter, which have passed beyond the point where they 
are adapted to form oil reservoirs. It is quite possible, therefore, 
that there are other elevations even less conspicuous' than Spindletop, 
or perhaps not at all apparent at the surface, which may be equally 
well adapted for oil reservoirs. Such structures might easily escape 
notice if no elevation had taken place upon them since the deposition 
of the recent clays. 
If such inconspicuous or entirely obscured structures do exist, as 
seems probable, they will almost certainly occur along the lines indi- 
cated on the accompanying map, and along these lines, therefore, 
are the best places for conducting systematic prospecting in the Gulf 
Coastal Plain. It should be fully understood in advance that the 
chances of finding oil by drilling at any particular point along these 
lines are small, but they are much larger than the chances of finding 
it by drilling at random anywhere on the Coastal Plain. 
a The salines of north Louisiana, by A. C. Veateh: Geological Survey of Louisiana, Report 
for 1902. 
Bull. 212—03 10 
