EFFECT OF VARYING CIRCUMSTANCES ON PRINCIPLES AND CRITERIA OF CORRELATION
The practice of stratigraphic correlation—that is, the determination of the time relations of marine and continental deposits in widely separated areas by other means than continuous tracing of beds—is rarely a simple process. Often, indeed, the problems to be solved prove exceedingly intricate. With the progress of the science many rules and criteria for establishing contemporaneity in geologic events have been suggested and applied with varying success in the practical work of the geologist. At first most of these rules and criteria seemed sound in principle and widely, if not universally, applicable; but as our stock of facts increased, the correlations indicated by them became more and more uncertain.
At present there are no formally recognized rules that, taken either singly or in combinations, will insure uniformly reliable results under all circumstances. Criteria whose worth has been proved for . . .