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Abstract

Numerous conceptual models (interpretations) exist for the origin and early development of the Gulf of Mexico Basin. Geophysical data (aeromagnetic, gravity, and seismic data), new concepts, and geologic datasets (paleontologic and paleobathymetric) are rarely fully incorporated into these models, and the result is often incomplete or inaccurate models. The size of the basin, a lack of lithologic control on deep stratigraphy (outcrops and well penetrations), and poor seismic imaging at depth because of the thickness of the post-rift sedimentary cover sequence contribute to the diversity of concepts and models.

Constraints can be placed on the timing, architectural development, and control of the sedimentary fill, thereby resulting in a more concise and integrated basin model. For example, it must be recognized that the Gulf of Mexico Basin is part of the Central Atlantic Magmatic Province (CAMP). Therefore, the importance of seaward-dipping reflectors (SDRs) in the Gulf of Mexico Basin suggests a subaerial origin for extruded “proto-oceanic” crust, thereby implying that revisions to some of the published models are necessary because of the style of breakup represented by seaward-dipping reflectors. Understanding that the edges of salt in the northern Gulf of Mexico and the Campeche (Sigsbee) salt basins do not lend themselves to a “jigsaw” restoration for a variety of reasons, significantly affects the interpretation and timing of continental breakup. In addition, interpreting the presence of what may be two “breakup” events, each separating syn-rift from post-rift strata (inferred from seismic interpretations) in the deep-water, northern Gulf of Mexico, suggests a polyphase basin evolution prior to deposition of the thick sequence of late Mesozoic and Cenozoic post-rift sediments. Correct identification of the Mid-Cretaceous Sequence Boundary on seismic datasets (aka the Mid-Cretaceous Unconformity), rather than the previously misinterpreted seismic event (recently established by paleontologic data to represent the Cretaceous-Tertiary Boundary), is critical to constraining the architecture and timing of structural and stratigraphic events. Incorporating the existence of Cretaceous through Eocene “Oceanic Red Beds” in the deep-water Gulf of Mexico constrains the paleobathymetric evolution of the basin during this time, resulting in a more coherent model. Publicly released paleontologic data from key, deep-water wells penetrating older strata in the area of the U.S. offshore Gulf of Mexico, using benthonic foraminifera as paleobathymetric indicators, show that generally, this area deepens over time, such that the basin in the area represented by these wells is deeper than, or as deep today as, it has ever been. The polyphase evolution of the Gulf of Mexico Basin, the effects of the loading of the Mexican Cordilleran complex, and the occurrence of igneous dikes, sills, and flows in the northern Gulf of Mexico, often in association with salt structures, should be considered. The change in provenance direction estimated to occur between the Paleocene and the Oligocene from northwest to south has implications for many models of the basin.

This paper points out a few constraints and issues to address in evaluating models of the Gulf of Mexico Basin and is not intended as still another model for basin evolution. Integrating these constraints into interpretations of the origin and development of the early Gulf of Mexico is extremely important since, paraphrasing Dr. Raymond Price, a model that incorporates all the data and observations may not be right, but one that does not is always wrong.

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