22 OIL-FIELD WATERS IN SAN JOAQUIN VALLEY, CAL. 
or to water that has entered the rocks during a second period of 
immersion. 
The general concept of connate water is a valuable one, but the 
practical application of the term in its strict sense is attended by so 
many difficulties that it seems advisable to redefine it in conformity 
to current usage. A sample of salt water may reasonably be called 
connate if it approximates ocean water in chemical composition and if 
it occurs in rocks of marine origin in which the circulation of the water 
is very slight. The water in beds of fresh-water origin may be thought 
to be connate, but as the composition of the body of fresh water in 
which the beds were deposited is unknown, the application of the term 
can not be supported by chemical evidence and must rest wholly on 
geologic considerations of a more or less conjectural nature. In actual 
practice, the term can not be applied to a specific sample of water 
unless chemical evidence can be adduced, that is, unless the composi¬ 
tion of the original body of water is available for comparison, and 
usually this is possible only when the water is of marine origin. Prac¬ 
tically, therefore, the term connate must be restricted to connate 
waters of the marine type, and so far as the writer can learn this 
accords with the common use of the term at the present time. On the 
other hand, it is generally impossible to ascertain how far a water has 
migrated or whether it is actually connate to the rocks in which it 
is now found. (See discussion of analysis 25, p. 61.) If it has 
migrated from one formation to another or if it entered the rocks 
during a later period of immersion, it is not strictly connate, but 
neither is it pluvial or meteoric. If it were ordinarily possible to 
determine these facts it might be advisable to introduce a new term, 
but as it is not the writer believes that the term connate may be 
extended to include such extraneous waters. Although Lane, 1 in 
introducing the term connate, notes that connate water may be either 
salt or fresh, neither he nor any other investigator, so far as the 
writer knows, has ever attempted to apply the term to specific samples 
of fresh water. If, however, this application should become desirable 
a qualifying adjective may be used to distinguish connate fresh water 
from connate marine water. Similarly, if it is desired to use the term 
in its strict etymologic sense—as water that was buried with the bed 
at the time of deposition—a phrase such as “ connate to the bed in 
which it is found” may be used. For practical purposes, therefore, 
connate water may be defined simply as fossil sea water. The term is 
so used in this report, and although it is recognized that connate fresh 
waters are thereby included with the meteoric or pluvial types there 
seems to be no practicable way of distinguishing them. 
The definition here adopted is thus based principally on chemical 
rather than geologic evidence, though as water in contact with rock 
1 Lane, A. C., op. cit. 
