--> ABSTRACT: Early Mesozoic Rifting West of Gulf of Mexico as it Opened From Fully Closed Condition, by Dewitt C. Van Siclen; #91026 (2010)

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Early Mesozoic Rifting West of Gulf of Mexico as it Opened From Fully Closed Condition

Dewitt C. Van Siclen

A fully closed Gulf of Mexico (GOM) placed Yucatan southeast of the Marathon thrusts, at the northwest corner of Paleozoic South America (SA), where it spearheaded the thrusting. SA was then rigidly joined to Africa in the Gondwana megacontinent, which remained stationary relative to the mantle plumes as North America (NA) moved generally northwestward to open simultaneously the GOM and central North Atlantic (CNAO). In the CNAO, a self-sustaining spreading center became established only after spreading had ceased on three transient centers as each migrated too far from the mothering mantle plumes alongside Africa and a successor developed back over them.

Corresponding resumptions of spreading in the plumeless, passively opening GOM occurred within Gondwana, thereby transferring blocks of it to the NA plate near their present relative positions. Thus, after initial rifting opened the interior basins, the first such jump transferred them and their southern rim to NA. The Callovian salt in the deep GOM was deposited during lowered sea level of the second spreading cessation. Renewed spreading then formed the GOM's salt-free strip, which separated Yucatan from southern Mexico (SM), thereby transferring SM to NA. The third jump left Yucatan with NA and inaugurated continuous spreading in the Caribbean Sea.

Upper Triassic red beds from southerly sources are almost continuous from western Texas into southeastern Nevada, demonstrating substantial uplift along this sector of the international border. Southward, straddling the Arizona-California line, the rifted edge of the NA craton crops out alongside the narrow west-northwest-trending McCoy basin. It and its likely continuation as the Bisbee basin of southeasternmost Arizona are reminiscent of the interior rifts beneath the northern Gulf coastal plain. Cratonic sediments similar to those of the McCoy basin were deposited farther south in marine environments during the Middle Jurassic. These and the extensive Callovian salt of northeastern Mexico formed contemporaneously with the deep GOM salt in a second wider rift complex across northern Mexico. This rifting is required by SM's position beside Yucatan, ag inst which it was driven, across the GOM's salt-free third rift, by interaction of NA with the eastern Pacific plates. The western Cordilleran rocks have been relocated relatively northward, intensely deformed and altered by these interactions, masking rift-stage relationships.

AAPG Search and Discovery Article #91026©1989 AAPG Southwest Section, March 19-21, 1989, San Angelo, Texas.