Analysis of Laramide basement-involved deformation, Fra Cristobal Range, New Mexico
In the Fra Cristobal Range near Truth or Consequences, New Mexico, 250 to 500 m(820 to 1640 ft) of relative basement uplift is present. The contact between Precambrian crystalline basement and cover strata (Cambrian and younger) is folded along a north-south deformation front defining the margin of the Laramide uplift. The style of deformation changes along strike from an overturned fold to a central domain of imbricate thrusts of Precambrian granite, overlying a gentle anticline of cover strata, and then back to an overturned fold. These changes in style occur across narrow transition zones characterized by transverse folds and tear faults, suggesting some control from basement structure. West-dipping, high-angle reverse faults and south-plunging S-folds on the overturned eastern limb of the south-plunging, basement-involved anticline suggest eastward vergence with the basement, in part forcing the fold in the cover strata. Closely spaced fractures are present in the granite hinge of the main overturned, basement-cored fold. Abundant microfaults with grains visibly offset are present in thin section. These features indicate a cataclastic flow mechanism to accommodate shortening strain in the core of the fold. The structural styles of the basement-involved Laramide deformation are similar to Berg's fold-thrust model; shortening in the basement is accommodated by imbricate thrusting in the central domain and cataclastic flow on a small scale in the basement-cored folds. Preexisting basement structure may have controlled the location of structural transitions within the belt of crustal shortening and uplift, and movement of basement blocks may have in part forced the observed folding.
- Research Organization:
- Colorado School of Mines, Golden
- OSTI ID:
- 7230203
- Report Number(s):
- CONF-8609129-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 70:8; ISSN AAPGB
- Country of Publication:
- United States
- Language:
- English
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