THE SALT DEPOSITS 213 
salt sometimes pass from the dome into the adjacent beds. 
More than sixty of these salt domes have been found during 
the development of the Louisiana oilfield, some by the use 
of the torsion balance and the earthwaves due to explosions. 
The salt dome at Spindletop gave the clue to the oilfields of 
Mexico. 
Salt domes have been explained by igneous action; 
but they are secondary formations due to ascending water. 
The salt dome area is underlain by Kainozoic and Cretaceous 
rocks, and doubtless by salt-bearing beds belonging to the 
Trias or Permian. Most of the Louisiana salt domes are 
regularly arranged, as at the angles of a network; they 
probably occur where intersecting faults afforded a channel 
up which water charged with salt escaped from the under- 
Fic. 55.—SaLT DOME AT 
THE Baicor OILFIELD, 
RuMANIA. 
sands and gravels with 
land and fresh-water 
shells; D, Dacic—oil 
beds with lignite, P, 
Pontic—marine marls; 
M, Meotic — Pliocene 
fresh-water sands. S, 
salt intrusion. (After 
Slomnicki and Meyer, 
1925.) 
0 
lying red sandstones. As the water approached the surface 
it was cooled and deposited its salt in the channel. Further 
salt was added to the base of the block and the crystalli- 
zation of this salt pushed the mass like a spear-head through 
the soft wet clays (cf. Fig. 637). 
The Egeln dome in Germany (Fig. 56) contains a vertical 
thickness of 4000 feet of continuous salt. This thickness is 
due in part to the salt being uptilted and repeated by over- 
thrust faults ; but the salt has been partly squeezed into this 
pillar and enlarged by solution and redeposition during the 
faulting. The faults are of Kainozoic age and were due 
to disturbances connected with the uplifting of the Alps, 
A salt dome at Aschersleben occurs beside the great faults 
along the compressed fold of the northern Harz Mountains. 
A similar salt intrusion occurs at Baicoi in the Rumanian 
silfields (Fig. 55).