FACIES FACTOR IN Moore (1949) defines a sedimentary facies 



CORRELATION as an "areally segregated part of differing 



nature belonging to any genetically related 

 body of sedimentary deposits"; stated somewhat differently — any areally segre- 

 gated part of a stratigraphic unit (lithogenetic, time-stratigraphic, time) . The 

 relationships of these parts must be analyzed lithologically and paleontologically 

 in four dimensions before correlations are of value. Twenhofel (1953) 

 emphasizes this point by saying . . . "when two deposits of the geologic column 

 have been found to hold pretty much the same organisms, it has been assumed 

 that the two deposits have synchronous relations. It is equally, if not more 

 valid, to assume that the two deposits were laid down under similar environ- 

 ments and may actually be somewhat different in age . . .". 



The facies principle is not always recognized nor practiced by many 

 geologists. As a result, serious errors have been made in correlating stratigraphic 



Figure 23-5. Facies correlation. This cross section shows a limestone grading down dip 

 into a subsurface shale. The interval involving this lateral change is bounded by two 

 blanket sandstones. Four wells have been drilled, and their penetrated sections are 

 shown by the stratigraphic columns. As indicated by these columns, it would be 

 difficult to establish the true lateral lithic relationship on the basis of only well data. 

 To prove or disprove this relationship would require the drilling of several more wells 

 in the interfingered part of the section; for example, the limestone in Well 2 does 

 not represent the same time interval as that in Well 3; it is equivalent to only the 

 middle part of that penetrated in Well 3. The absence of the limestone in Well 1 

 could be accounted for by faulting or unconformity if the lateral lithologic relationship 

 were not known. 



443 



