Although the Gulf of Mexico (GOM) has been the subject of geophysical and geologic studies for several decades, its crustal structures and opening kinematics remain poorly understood largely because of the difficulty in imaging the deeper basinal structure beneath its thick sedimentary and evaporitic layers. We have used gravity and magnetic data combined with seismic reflection and refraction data to better understand the crustal structure and basin opening kinematics. We have focused on the 700-km-long Jurassic continent/ocean transform fault that accommodated counterclockwise rotation of the Yucatan Block along the eastern continental margin of Mexico. We have used recent satellite-derived gravity data to reveal the pattern of spreading ridge-transform segments in the center of the basin. We then derived on a pole of rotation that revealed the kinematics of early opening of the GOM basin and the tectonic control the continent-ocean transform fault, the Western Main Transform fault (WMTF), that defined the continent-ocean boundary (COB) between continental rocks in the eastern Mexico and Jurassic oceanic crust in the western GOM. Regional magnetic anomaly data along with seismic reflection and refraction data were used to further constrain the location of the WMTF. Three 2D gravity models revealed the location of the WMTF approximately 100 km offshore eastern Mexico at its furthest point and extending onshore in southern Mexico. The gravity models found that the contact between continental and oceanic crust is marked by an abrupt increase from 6.5 to 10 km in crustal thickness. To the west of the WMTF, the eastern Mexico margin is underlain by a 60-km-wide zone of stretched continental crust. We also determined a COB for the entire GOM that was consistent with the plate reconstruction, values of crustal thickness based on seismic refraction, and fracture zone azimuths related to the Jurassic spreading system.

Hydrocarbon exploration in the Llanos foreland basin of eastern Colombia has traditionally focused on structural traps. However, in the past decade, the country’s oil demand has generated an increased interest in exploration for stratigraphic traps. We integrated $700{\mathrm{km}}^2$ of 3D seismic data volumes with eight wells in the Central Llanos area to assess the reservoir potential of the fluvial channel deposits of the Late Eocene–Oligocene Carbonera Formation in the Casanare Province. Distinguishing nonproductive, mud-filled channels from productive sand-filled channels is of economic importance for hydrocarbon exploration because both channel types can exhibit a similar seismic character. Our interpretation of the fluvial sandstone and the reservoir identification was based on 3D seismic attributes, including coherence, curvature, and spectral decomposition, and the analysis of fluvial geomorphology. Analysis of stratal slices through coherence, isofrequency amplitude cubes, and curvature cubes revealed (1) a northeast-trending meandering fluvial system with changes in the rivers’ paleoflow direction from southwest to northeast during the period of the Late Eocene to the Early Miocene, (2) development of prospective sandy point bars, scrolls, and sand bar deposits, and (3) channel ridges and bases accentuated by differential compaction dependent on the channel’s filling material. Based on our attribute analysis, we were able to characterize nonprospective mud-filled channels versus prospective sand-filled channels.

The devastating 2010 Haiti earthquake (M_w 7.0) was caused by rupture of the Léogâne, blind, thrust fault located 5 km north of the 1,200‐km‐long, left‐lateral, Enriquillo‐Plantain Garden fault zone (EPGFZ). Unexpectedly, the EPGFZ remained largely quiescent or slightly reactivated during the 2010 earthquake. Nevertheless, the EPGFZ still formed a major, crustal boundary between a coseismically uplifted lowland north of the EPGFZ and a subsided area in the highlands south of the fault. Here we use high‐resolution sonar data from two Haitian Lakes that straddle the EPGFZ to demonstrate the presence of a 10‐ to 15‐km‐wide, 120‐km‐long, late Holocene fold‐thrust belt which deforms clastic, lowland basins along the northern edge of the EPGFZ. In the eastern part of the study area, sonar results from Lake Azuey show that the linear trace of the EPGFZ cutting the Holocene lake bed is more deeply buried and less active than the adjacent, newly discovered, northwest striking, northeast dipping Jimani thrust fault that is part of the adjacent, transpressional belt of en echelon thrusts and folds. This structural relationship between a less active EPGFZ and more recently active, transpression‐related Jimani thrust is remarkably similar to the 2010 epicentral area 70 km to the west between the less active EPGFZ and seismogenic, northeast‐dipping, Léogâne thrust during the 2010 Haiti earthquake. In this complex transpressional zone, we propose that coseismic deformation alternates at recurrence intervals of centuries between oblique, transpression‐related structures (Léogâne, Jimani, and Trois Baies thrusts) and the main strike‐slip, plate boundary fault zone (EPGFZ).

The north–south-trending Tobago-Barbados ridge (TBR) extends 250 km from its southern end at the island of Tobago to its northern end at the island of Barbados. On Tobago, exposed metasedimentary and metaigneous rocks have been identified as fragments of a Mesozoic primitive island arc, whereas on Barbados, exposed sedimentary rocks record Paleogene development of the Barbados accretionary prism (BAP). We integrate gravity data with seismic refraction data, well constraints, and seismic reflection data to improve our understanding of the TBR’s crustal structure, uplift mechanism, along-strike compositional variations in the crust, and tectonic origin. Three 2D gravity models suggest that the TBR is underlain by a “pop-up” crustal block uplifted in the trench between the overriding Caribbean plate and the westwardly subducting South American plate. At approximately 11.75° N, the character of the TBR changes over a distance of 60 km from a symmetrical and more elevated, crystalline, thrust fault-bounded structure to a west-verging thrust belt that is less elevated. The symmetrical pop-up and asymmetrical, west-verging thrust belt accommodate east–west, subduction-related shortening that deforms the westernmost edge of the BAP. We think that the crystalline basement of the southern and central TBR is the buried, northeastern continuation of Mesozoic intraoceanic-arc crust and metamorphic belt of Tobago that accreted along the eastern margin of the Great Arc of the Caribbean during its subduction polarity reversal in the early Cretaceous.

The San Andres rift (SAR), located on the lower Nicaraguan Rise, is a previously poorly studied, active, 015°-trending, bathymetric, and structural rift basin that is 11–27 km (7–17 mi) wide and extends for 346 km (215 mi) across the western flank of the Caribbean plate. In this study, we integrate bathymetric maps, potential field data, and high-resolution, two-dimensional (2-D) seismic lines to understand the crustal structure, tectonic history, and tectonic origin of the SAR, which is one of the active areas within the otherwise stable Caribbean plate. We compiled regional gravity and magnetic data that revealed a negative gravity anomaly and positive magnetic anomaly that we interpret as a result of crustal thinning and an elevated Moho along the main rift axis of the SAR. Forward models of gravity data show four possible interpretations for the origin of the crust underlying and surrounding the SAR. Interpretations of 2-D seismic reflection data show structural features within the upper crust and sedimentary sections typical of other active rift systems including a SAR-parallel, north–south alignment of earthquakes with the larger events showing normal and strike-slip focal mechanisms. Sequential kinematic restorations based on 2-D seismic profiles reveal three major phases of SAR opening: (1) the initial early Eocene rifting stage; (2) middle Eocene extension; and (3) a rapid middle Miocene to early Pliocene extension accompanied by emergence of the San Andres Island as a rift shoulder. We propose slab rollback and intraplate extension as main tectonic mechanisms to explain all rift phases and Neogene volcanism found in the western Caribbean region.