Abstract

The lack of a sharp boundary between North and South Atlantic stress fields recorded in the arcs of transform faults and ridge segments suggests a gradual merging of mantle stresses within a broad Central Atlantic plate boundary zone. The nature of descending slabs deep in the mantle beneath North and South America suggests that this intra-American plate boundary zone has existed since the Early Cretaceous, at which time it was located beneath the Gulf of Mexico Basin. Simple Euler sums of North and South America to Africa rotation poles validate the concept of merging stress fields, providing a geologically reasonable trajectory and rotation data for the Yucatan microplate with respect to Africa. The new Yucatan rotation geometry is consistent with initiation of back-arc spreading in the western Gulf of Mexico Basin during the Late Berriasian or Early Valanginian, c. 140 Ma, triggered by a strengthening South Atlantic stress field. Continued spreading and rotation of Yucatan likely persisted through the Late Albian, c. 100 Ma. These findings are supported by Early Cretaceous deposystem architecture, basin margin reef trends and source-rock distribution. Kinematic analysis predicts that most Gulf of Mexico seafloor (c. 60%) was created during the Cretaceous period of stable normal geomagnetic polarity, c. 125–83.5 Ma (the ‘Cretaceous Quiet Zone’). Salt-lubricated detachment faulting in the young Gulf of Mexico likely covered newly formed oceanic crust with large allochthons of Oxfordian–Valanginian strata.

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