The Circum-Gulf of Mexico and the Caribbean has long been one of the world's most important petroleum provinces, as well as one of the world's most geologically complex regions. These two characteristics have resulted in an extensive amount of ongoing research by both industry and academia. AAPG Memoir 79, The Circum-Gulf of Mexico and the Caribbean, is the first volume in more than a decade to document such a wide range of research on the geology of this vast area. Of the total 44 papers, roughly two-thirds pertain to the Gulf of Mexico, with an emphasis on the Mexican portion of the basin, and to the petroliferous areas of the southern Caribbean, including Colombia, Venezuela, Cuba, and Trinidad and Tobago. The remaining papers relate to the Antilles and Central America, as well as a series of papers that address region-wide topics such as plate tectonic evolution. A significant number of papers were contributed by authors from national oil companies and universities from within the region.
Abstract The compositions of glass clasts in volcaniclastic rocks recovered from drilling at Site 1184 on the eastern salient of the Ontong Java Plateau (OJP) are investigated using microbeam analytical methods for major, minor and trace elements. These data are compared with whole-rock elemental and isotopic data for bulk tuff samples, and with data from basalts on the high plateau of the OJP. Three subunits of Hole 1184A contain blocky glass clasts, thought to represent the juvenile magmatic component of the phreatomagmatic eruptions that generated the volcaniclastic rocks. The glass clasts have unaltered centres, and are all basaltic low-K tholeiites, with flat chondrite-normalized rare earth element (REE) patterns. Their elemental compositions are very similar to the Kwaimbaita-type and Kroenke-type basalts sampled on the high plateau. Each subunit has a distinct glass composition and there is no intermixing of glass compositions between subunits, indicating that each subunit is the result of one eruptive phase, and that the volcaniclastic sequence has not experienced reworking. The relative heterogeneity preserved at Site 1184 contrasts with the uniformity of compositions recovered from individual sites on the high plateau, and suggests that the eastern salient of the OJP had a different type of magma plumbing system. Our data support the hypothesis that the voluminous subaerially erupted volcaniclastic rocks at Site 1184 belong to the same magmatic event as the construction of the main Ontong Java Plateau. Thus, the OJP would have been responsible for volatile fluxes into the atmosphere in addition to chemical fluxes into the oceans, and these factors may have influenced the contemporaneous oceanic anoxic event.
Introduction: The Southern Caribbean margin consists of accreted fragments of the Cretaceous Caribbean oceanic plateau, along with terranes of island arc affinity of a similar age. The relationship between the plateau and the island arc sequences are intriguing, particularly given their close temporal and spatial association. The tectonic origin of these arc related sequences is unclear, and two possible scenarios are being considered: (1) the arcs are unrelated to the plateau, but have been swept up in front of it; and (2) the arcs were built upon the plateau by subduction of normal oceanic crust beneath it. Resolution of this will have important implications for both the origin and the subsequent evolution of the Caribbean plate, and hence the tectonic history of the Caribbean region. This study concentrates on the Dutch Antilles, where both plateauand arcrelated rocks are found, and specifically on the arc sequence exposed on Bonaire. The island of Bonaire consists of two inliers of Cretaceous volcanic and volcaniclastic rocks surrounded by Eocene-Recent cover. Field evidence suggests that the Bonaire volcanics are best interpreted as a distal intraoceanic island arc sequence. Trace element and isotope geochemistry: The volcanic sequence comprises basalts and rhyolites, and shows typical island arc characteristics such as negative Nb and Ti anomalies, and a positive La anomaly, relative to MORB. All of the volcanics appear to be comagmatic, apart from a series of rhyodacite domes, which are geochemically distinct. These domes have higher abundances of most HFSE and REE, in particular Nb and Zr, and chondritenormalised La/Yb ratios of >3 (compared to <2, as for the rest of the sequence). The Bonaire volcanics plot in the MORB field on a Nb/Y vs. Zr/Y plot, indicating that they may not be part of the Caribbean plateau. Trace element data suggest that Sr and Pb isotopes may be susceptible to alteration, so this study concentrates on the Hf-Nd systematics of the Caribbean region. Preliminary Hf-Nd isotope analyses show that samples from the Caribbean plateau, recovered during DSDP Leg 15, form a linear array similar to that shown by hotspot volcanism from the Galapagos islands, extending from the high end of the global OIB field to the field for Pacific N-MORB. The Bonaire volcanics partially overlap the plateau field, but most samples are displaced to slightly higher eHf and lower eNd. These results are consistent with modification of a depleted source (either MORB or a depleted plateau component) by incorporation of a low eHf and eNd sedimentary (or other slab-derived) component. Analysis of additional plateau samples from other areas of the Caribbean (e.g. Aruba) and Gorgona and Colombia [in progress and to be reported] should clarify this.
Basaltic oceanic plateaux are important features in the geological record. Not only do they record ancient mantle plume activity, but they also are believed to be important building blocks in the formation of the continental crust. In this paper we review the salient features of two Cretaceous oceanic plateaux (the Ontong Java and the Caribbean–Colombian): thick sequences of predominantly homogeneous basalt; the occurrence of high-MgO basalt, including komatiites; and an apparent absence of sheeted dyke complexes. In addition, pyroclastic deposits may be scarce. We then explore ways of distinguishing plateaux from basaltic sequences erupted in different tectonomagmatic settings: continental flood basalt provinces; island arcs; back-arc basins; ocean islands and mid-ocean ridges. Using these criteria, potential Archaean and Proterozoic oceanic plateaux are reviewed and identified. Finally, we explore how these remnant oceanic plateaux became incorporated into the continents, by reviewing the proposed accretion mechanisms for the Cretaceous Caribbean–Colombian oceanic plateau, on the basis of evidence from South America and the tonalites of the southern Caribbean island of Aruba.
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