SANTA CLARA VALLEY : ELSMERE FIELD. 
101 
been subjected. Indeed, it seems to be an impossibility that such 
can be the history of its development. Moreover, the gravity of the 
oil, between 50° and 60° B., is equally enigmatical. Even if it was 
originally a high-gravity oil, the lighter hydrocarbons would have been 
the first to be given off in the heat, pressure, and fracturing to which 
the rocks have been subjected, and if anything remained it should 
have been the asphaltic or paraffin residue. It may be that the oil is 
of later origin or, in any event, that it was for a time stored in another 
reservoir, perhaps of Vaqueros age, possibly even of Fernando age. It 
is possible that from such a reservoir the light oil, already from some 
cause separated from the heavy oil, may have found its way between 
the two formations and penetrated the crystalline rocks through one 
of their fractured zones. 
Bull. 309—07-8 
