Abstract

The Cayman Trough exhibits cross-trough lineations, which we interpret as crustal fabric formed parallel to the spreading center at the time of crustal generation. Alignment and variations of the spreading fabric are roughly symmetrically distributed about the mid-Cayman spreading center, as are variations in the cross-trough width of the Cayman Trough. These suggest to us a simple, eight-stage model of stepwise-varying spreading directions and rates. For this model it is assumed that (1) tectonic spreading fabric is perpendicular to spreading direction, (2) cross-trough extension both widens the trough and lengthens the spreading center, and (3) cross-trough compression narrows the trough but does not shorten the spreading center. Combining the spreading-fabric lineation data with these assumptions, we predict a cross-trough width variation that is essentially that of the Cayman. Similar variations in spreading direction should be evidenced elsewhere on the plate boundary if the variations we observe do, in fact, record the history of changes in relative motion between the North American and Caribbean plates.

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