Kinematic parameters and crustal building blocks for the greater Gulf of Mexico

Many rotation poles have been proposed for the Gulf of Mexico. Previous to 2014, these poles were based on various geologic criterion of fit, loosely constrained by the physiography of the sea floor and potential fields anomalies. Since 2014, a number of improvements in satellite-altimetry based gravity have made oceanic fracture zones and spreading centers readily observable. Here we provide a pole of rotation describing sea floor spreading in the Gulf of Mexico, using classic tectonic applications of spherical geometry to a quasi-automatically extracted fracture zone set from a recent satellite based gravity anomaly grid. Given this pole, which lies just south of Cuba (21.624, -82.167), we also compute a magnetic spreading model in the NE GOM, nested into a margin spanning potential fields 2D model, constrained by recent published refraction and reflection data. The 2D profile indicates Gulf of Mexico (GOM) magnetic anomalies can be explained using published Jurassic polarity chrons and average properties of oceanic magnetization as far north as an en-echelon set of pronounced magnetic anomalies, which require a substantial contribution from remnant and induced magnetization to fit the observed data. The properties used in our model support the interpretation that these anomalies are caused by exhumed mantle. Our transect also indicates an exhumed lower crustal body coinciding with a pronounced magnetic low, inboard of the exhumed mantle, and out board of the limit of upper continental crust. The synthesis of observations we present broadly supports the hypothesis of mantle exhumation along an outer marginal detachment as described by some authors, and is inconsistent with the interpretation of volcanic SDRs at the limit of oceanic crust as argued by others. The timing of chrons used in our forward model were determined by nesting the rotations derived here into a global plate circuit, and allowing the motion of South America to determine the end of sea floor spreading in the GOM ( 152 Ma). In our proposed model, rifting initiates ca. 203 Ma. Mantle exhumation initiates ca. 169 Ma, when breakup begins to propagate between South America and the Yucatan, resulting in preferential stress on the southern extent of the peninsula, yielding a torque that causes the peninsula to "spin" out of the GOM, rather than "translate" with the South American continent. Sea floor spreading occurs in the NE GOM around 164 Ma after continental lower crust and mantle are exhumed. When breakup along the South American-Yucatan margin is complete, sea floor spreading ceases around 152 Ma. We suggest the kinematics of mantle exhumation were governed by the same rotation pole as sea floor spreading, but that the rest of the "rift" phase was governed by the poles describing the relative motion of North and South America.