uIntroduction

uFigure captions

uPlate tectonics

uReconstructions

uIntroduction

uFigure captions

uPlate tectonics

uReconstructions

uIntroduction

uFigure captions

uPlate tectonics

uReconstructions

uIntroduction

uFigure captions

uPlate tectonics

uReconstructions

Figure and Table Captions

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Mesozoic Plate Tectonics 

While there is a considerable volume of published seismic and biostratigraphic data that provides credible evidence of Triassic - Jurassic rifting around virtually the entire Gulf margin, compelling evidence of significant pre-Berriasian (Jurassic) plate movements related to seafloor spreading and ocean crust formation is lacking. Although several seismic stratigraphic studies that transect the northeastern and western margins of the deep Gulf Basin suggest a Jurassic age for the oldest basin-filling sediments, interpreting Callovian (late Middle Jurassic) Louann Salt as autochthonous. It is equally plausible that the salt is allochthonous, having been included in the base of large superficial detachments containing post-synrift - pre-drift strata of Late Jurassic and earliest Cretaceous age deposited originally on attenuated continental crust of Gulf Rim. The Sea of Cortez (Gulf of California) provides a well documented analog for this type of margin failure during early opening. Observations of Jurassic strata overlying undated oceanic crust therefore do not directly imply a Jurassic crustal age.  

Outcropping and drilled Mesozoic strata of the Gulf rim, the presence of buried plume-related alkalic basaltic volcanoes of middle and Late Cretaceous age, and the geometric requirement that the Yucatan Platform be rotated into a position along the Texas - Louisiana margin to allow the reassembly of Pangea are the principal constraints on the origin of the Gulf of Mexico. There is general agreement among researchers that the opening of the western basin of the Gulf of Mexico reflects the counterclockwise rotation of a Yucatan microplate. Following recently published paleomagnetic evidence the Chiapas portion of the Maya Block is treated as a separate microplate in this study. It is recognized that the rotation of a Yucatan microplate about the relatively well-known Euler rotation poles that opened the North Atlantic Ocean cannot account for the most probable trajectory of Yucatan. Published opening solutions designed to provide an ideal Yucatan trajectory are purely kinematic, not addressing the implications of a unique Gulf of Mexico stress field on planetary-scale mantle processes that drive plate motions. Departing from a purely kinematic solution for Yucatan microplate motion, this study focuses on a rotation geometry linked to the stresses that moved the major North and South American plates. Details of the predicted timing and direction of Yucatan microplate rotation thus depend on the changing relative positions of the well known North Atlantic and South Atlantic Euler (rotation) poles. Comparison of North and South Atlantic rotation poles and the history of Berriasian to Barremian (Neocomian) rifting between South America and Africa, which heralded development of a South Atlantic stress field, directly imply a post-late Berriasian (Cretaceous) opening of the western Gulf of Mexico. Application of the South Atlantic opening pole positions and angular velocities to the opening of the western Gulf of Mexico further predicts that Yucatan microplate rotation was mostly completed by early Aptian time (~109 Ma BP).  

The new Gulf of Mexico microplate kinematics proposed here predicts that most Gulf of Mexico seafloor (~60 %) was created during the Early Cretaceous period of stable geomagnetic polarity (120.4 - 83.5 Ma BP). The absence of obvious magnetic lineations in the deep western basin is therefore a predictable element of Gulf evolution. A further consequence of post-Berriasian opening of the western Gulf of Mexico is that the thick succession of Norphlet to Cotton Valley sediments that built-up on thick Louann Salt (Callovian) in Oxfordian to early Berriasian time were likely to have destabilized as Yucatan moved away from the Texas-Louisiana margin. The movement of large superficial detachments into the nascent Gulf Basin would have covered virtually all of the oldest (Berriasian to earliest Aptian) oceanic crust located nearest the basin margin. Magnetic spreading anomalies M10N to M0 would thus have been strongly diminished or completely destroyed. In applying a Gulf of California model, the superficial detachment phase in the western Gulf of Mexico Basin began with the first plate movements initiated by mantle stresses and therefore very likely coincided with the development of the deeper crustal detachments that are characteristic of the early stages of asymmetric continental fragmentation.  

Analysis of dated oceanic plateau basalt accumulations and the inferred tracks of related mantle plumes indicate that two hotspots transited the central Gulf of Mexico basin during the Late Mesozoic. By holding mantle plumes fixed relative to Africa, a procedure considered valid for Atlantic hotspots, tracks are predicted that pass through the Gulf of Mexico at critical times in its evolution. One hotspot, recorded in conjugate oceanic plateau basalts of the Ceara and Sierra Leone Rises in the Central Atlantic, is traced to a Triassic position within the Central Atlantic Magmatic Province underlying the Bahamas and central Cuban microplates. The Ceara-Sierra Leone Rise hotspot exited the Gulf through South Florida in the Jurassic as North America began moving away from Africa. The second important Gulf of Mexico hotspot is recorded in accumulations of oceanic plateau basalts that comprise the Beata and Aves Ridges in the Eastern Caribbean. The Beata-Aves Ridge hotspot entered the Gulf region through West Texas, passing beneath the Rio Grande Rift in the Barremian. It was centered in the western Gulf basin in the middle Cenomanian and exited the basin beneath Yucatan in the early Campanian. The Bermuda hotspot is also important for explaining regional geology. It transited north of the Gulf basin proper, passing beneath the Mississippi Embayment in Turonian through Campanian time. Alkalic basalts of the northern Gulf Rim, which date between 110 and 60 Ma BP, probably record the combined effects of the Beata-Aves Ridge and Bermuda hotspots. The northern end of the modern Caribbean Arc may be pinned at the present location of the Beata-Aves Ridge hotspot.

Plate Reconstructions 

Examples of Gulf Basin evolution constrained by this new planetary view of microplate motion are provided in a series of plate reconstructions that begin with the development of a rift valley system that breaks the Yucatan Platform off the North American Plate (Figure 1) and ends with a fully opened Gulf of Mexico Basin (Figure 2). Implications for the petroleum systems of the Gulf Basin are outlined in Table 1.  

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