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A Planetary View of Mesozoic Plate Tectonics in the Gulf of Mexico*
By
Richard H. Fillon1
Search and Discovery Article #30032 (2005)
Posted April 24, 2005
*Adapted from extended abstract prepared for presentation at AAPG International Conference & Exhibition, Cancun, Mexico, October 24-27, 2004.
1Earth Studies Group, New Orleans, LA 70131 ([email protected])
Introduction
In many respects the geology of the Gulf of Mexico is better understood than other comparable marginal seas due primarily to its long history of drilling and reflection seismic acquisition by the petroleum industry. However, the petroleum accumulations and thick Tertiary section that attract industry also restrict scientific ocean drilling. To date only the carbonate margin of the southern Gulf and Quaternary fans in the deep eastern basin have been targeted. Discovering new details of the nature and timing of the opening of the Gulf basin, therefore, presents a considerable challenge. The goal of this ongoing study is to determine whether the opening of the Gulf of Mexico is a predictable manifestation of the planetary-scale superswell-related mantle stresses that drive the movements of major plates and to evaluate implications for Gulf of Mexico petroleum systems.
Predicting microplate kinematics within the poorly defined boundary zone that separates North Atlantic and South Atlantic spreading is pivotal in this analysis. It is postulated that the movements of continental microplates in the Gulf of Mexico are driven by mantle stresses that moved first North America and then South America away from Africa.
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While there is a considerable volume of published seismic and
Outcropping and drilled Mesozoic strata of the Gulf rim, the presence of
buried plume-related alkalic basaltic volcanoes of middle and Late
Cretaceous 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 ReconstructionsExamples 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. |