Age and Petrogenesis of the Lower Cretaceous North Coast Schist of Tobago, a Fragment of the Proto-Greater Antilles Inter-American Arc System

The North Coast Schist of Tobago is part of the leading edge of the Caribbean Plate, which has been in oblique collision with northern South America for much of the Cenozoic. The North Coast Schist is dominated by two volcanic “formations” metamorphosed under greenschist-facies conditions during later deformation. The Parlatuvier Formation mostly consists of mafic to intermediate tuffs and tuff breccias with a U-Pb zircon ID-TIMS age of Ma. Trace element data and radiogenic isotopes reveal that the Parlatuvier Formation is derived from a heterogeneous subduction-modified, locally incompatible trace element–enriched, mantle source with some rocks containing the highest 176Hf/177Hf ratios found in the offshore Caribbean. The Mount Dillon Formation comprises silicified tuffs and tuff breccias that are derived from a more isotopically enriched mantle source with a significant slab fluid-related component. A thin belt of amphibolite-facies dynamothermally metamorphosed metavolcanic rocks lies in contact with a younger island arc pluton. Some of these amphibolites have an isotopically similar source to the Parlatuvier Formation but lack a clear subduction-related component. The age, geochemical heterogeneity, and proximal nature of eruption confirm that the North Coast Schist lay within an east-dipping proto–Greater Antilles arc. We propose that the arc system at the time of North Coast Schist magmatism was actively rifting, possibly during development of a back-arc basin. This arc system shut down during the Cretaceous, making way for southwest-dipping Greater Antilles subduction and relative eastward motion of the Caribbean Plate

Hydrocarbon Accumulation Analysis by Reconstructing the Canyon-Fill Sequence using Seismic Stratigraphic Interpretation in the Central Gulf Coastal Plain of Texas

The Texas Gulf region has been extensively studied and explored due to its high volume of oil and gas accumulation. One of the most highly productive sequences in the region is the lower Wilcox Group, which was deposited during a gradually sea level rising. The high rate of Tertiary sedimentary source influx and repeatedly transgression and regression resulted in numerous reservoirs and ideal traps. Regression caused the development of incised canyon systems, and later the canyon was filled with marine shales during the transgression. The complex canyon-fill sequence makes petroleum accumulation possible. Both stratigraphic and structural trapping mechanisms are found in the study area. The stratigraphy of the Wilcox Group is divided based on the lithological data and electric logs. In order to investigate the lateral variations of erosional sequences and the distributions of thin-bed sand bodies, we correlate the well logging across the survey. The seismic sequences and related sandstones are identified on the seismic sections after the well-to-seismic tie. Finally, the complex canyon-fill system is rebuilt and the hydrocarbon accumulation pattern is analyzed by conducting seismic stratigraphic interpretation in the study area