OCCURRENCE OF WATER IN OIL FIELDS. 
21 
Ululate m its deepest portion and remain there, somewhat as the 
surface waters of Great Salt Lake are held in their basin. Where 
the outlet is not entirely closed but is merely restricted, other factors 
enter into the problem, such as the volume and the head of the 
meteoric waters that are tending to drive out the connate water, 
the porosity of the materials through which the waters must pass, 
and such subordinate factors as the dip of the rocks and the distance 
from their outcrop. Even where all the conditions are favorable 
to the retention of the salt water it is evident that some of it near the 
surface will be leached out and that, other things being equal, the 
largest proportion will be retained at the greatest depths. The deeper 
of two deep wells in the same locality would ordinarily be expected 
to yield a more salty water, owing to the smaller volume of circula¬ 
tion in the deeper rocks as compared with those nearer the surface. 
In a region of lenticular beds irregularities are to be expected, for 
the freedom of circulation differs from bed to bed and some sands 
will therefore retain their salt water much longer than others. 
After marine sediments have been elevated to form land and the 
underground circulation thus set up has leached out part or all of the 
connate water the rocks may again subside beneath sea level. In this 
event the fresh water contained in the beds will be partly replaced by 
sea water, and sediments that are laid down over these beds will be 
saturated with sea water. After the second period of elevation has 
occurred and circulation has again been established the process of 
freshening will be repeated. Under these conditions it is evident 
that the older or deeper formations, having undergone longer con¬ 
tinued leaching, may contain less salt water than those nearer the 
surface, where the replacement by fresh water may be incomplete. 
Examples of salt water underlain by fresh water are not uncommon 
on the Atlantic Coastal Plain, 1 and it is possible that similar conditions 
exist in several places along the borders of San Joaquin Valley. 
In the foregoing paragraphs the burial and retention of sea water 
only has been considered, but it is evident that strata laid down in a 
fresh-water lake may contain entrapped fresh water, which is just as 
truly connate as entrapped salt water. In other words, the term con¬ 
nate water as originally employed 2 means simply water occluded in 
the sediments when they were deposited and is not restricted to any 
particular chemical type of water. On the other hand, if used in 
this strict sense, the term should be restricted to water laid down 
with the formation in which it is now found; it therefore should not 
be applied to water that has migrated from one formation to another, 
1 Sanford, Samuel, Saline artesian waters of the Atlantic Coastal Plain: U. S. Geol. Survey Water- Supply 
Paper 258, pp. 75-86,1911. 
Stephenson, L. W., and Palmer, Chase, A deep well at Charleston, S. C.: U. S. Geol. Survey Prof. Paper 
90, pp. 69-94, 1915. 
2 Lane, A. C., Mine waters and their field assay: Geol. Soc. America Bull., vol. 19, p. 501,1909. 
