Subsurface Maps and Illustrations 



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attempt should be made to contour the widely scattered points so that the 

 features shown bear out the regional trends or tendencies. Often the 

 subsurface geologist is called upon to construct structure maps where 

 little is known about the regional trends. However, there are usually 

 some clues in the datum elevations themselves. A common but often 

 erroneous assumption is that most of the higher wells are on the highest 

 parts of local structures, and most of the lower ones are on the lowest 

 points of the structures. When starting to contour the subsurface map, 

 it is better not to be too strictly constrained by the few scattered eleva- 



FiGURE 479. Examples of simple and interpretative contouring of the same data. 



