Abstract

Geologic mapping of a portion of the northeastern Front Range, Colorado, has established the relationship between multiple structural events. Planar and linear mesoscopic structural elements indicate three generations of folding (F1 F2, F3) in which three axial-plane foliations (S1 S2, S3) were formed. However, on a macroscopic scale, the superposition of F3 on F2 is unusual in that it does not appear to disturb the areal orientation of F2 folds. An explanation for the apparent lack of refolding is derived from a foliation-trend analysis which indicates that the displacement direction of F3 folding lies parallel with the F2 axial plane. Therefore, when viewed parallel to the S2 axial plane, S2 is folded into a series of sinusoidal folds, but when examined in map view, little folding is apparent. This structural sequence is substantiated in the southwestern portion of the mapped area where a well-developed dome-and-basin pattern emerges. The foliation-trend analysis serves to illuminate a structural geometry that, in turn, resolves an unusual apparent lack of refolding that is characteristic of a large portion of the northeastern Front Range.

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