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Maria fold and thrust belt
The Maria fold and thrust belt (MFTB) is a portion of the North American Cordillera orogen in which geological structures accommodate roughly north-south to northwest-southeast vergent Mesozoic age crustal shortening. This lies in contrast to the remainder of the Cordillera, in which shortening is predominantly East-West. Structures associated with the Maria Fold and Thrust Belt are exposed in a series of mountain ranges in southeastern California and western Arizona. Many of the deep structures of the MFTB have been exposed due to east-west to northeast-southwest Cenozoic age extension and unroofing.
In some parts of this fold-and-thrust-belt region, the extension resulted in the emplacement of metamorphic core complexes, the 'type example' of which is defined by the Whipple Mountains in southeastern California.
==Geology==
The Maria fold-and-thrust-belt is defined as the region where the compression that helped create the North American Cordillera – abruptly changed directions. North of the Maria fold-and-thrust-belt, the mountain ranges trend north-south, with east-west compression due to the subduction of the Farallon slab beneath western North America. At the Maria fold-and-thrust-belt, compressional deformation shifts to being generally north-south, with the front of the mountain ranges being defined by a roughly east-west line. This line then shifts gently to the east-southeast, where the Cordilleran deformation diffuses into a broad shear zone in northeastern Mexico.
Another notable feature that differentiates it from the rest of the Cordillera is that the deformation involves the rocks of the North American craton. Deformation in the remainder of the Cordillera only involves rocks that were part of the near-shore and offshore, sedimentary sequences.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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