Geophysical data acquisition in oceanic domains is challenging, implying measurements with low and/or nonhomogeneous spatial resolution. The evolution of satellite gravimetry and altimetry techniques allows testing 3‐D density models of the lithosphere, taking advantage of the high spatial resolution and homogeneous coverage of satellites. However, it is not trivial to discretise the source of the gravity field at different depths. Here, we propose a new method for inferring tectonic boundaries at the crustal level. As a novelty, instead of modeling the gravity anomalies and assuming a flat Earth approximation, we model the vertical gravity gradients (VGG) in spherical coordinates, which are especially sensitive to density contrasts in the upper layers of the Earth. To validate the methodology, the complex oceanic domain of the Caribbean region is studied, which includes different crustal domains with a tectonic history since Late Jurassic time. After defining a lithospheric starting model constrained by up‐to‐date geophysical data sets, we tested several a‐priory density distributions and selected the model with the minimum misfits with respect to the VGG calculated from the EIGEN‐6C4 data set. Additionally, the density of the crystalline crust was inferred by inverting the VGG field. Our methodology enabled us not only to refine, confirm, and/or propose tectonic boundaries in the study area but also to identify a new anomalous buoyant body, located in the South Lesser Antilles subduction zone, and high‐density bodies along the Greater, Lesser, and Leeward Antilles forearcs.
Summary The complex Moho topography beneath the northwestern Andes is the result of multiple geodynamic processes during the Cenozoic. To contribute to our understanding of the Moho depth distribution beneath this region, we inverted gravity data from two widely used satellite-derived datasets (EGM2008, EIGEN-6C4) and one regional airborne Bouguer gravity anomaly map (ANH2010). Their inversion allowed choosing the ANH2010, based on lower residual gravity and a higher agreement with seismic estimations, as the most suitable dataset to gain insights into the Moho depth beneath the northwestern Andes and its relationship with previously identified tectonic features. The inverted Moho argues for a 40 to 50 km depth beneath the Central and Eastern cordilleras, reaching depths beyond 50 km below the Eastern Cordillera, and shallower depths between 30-40 km mainly along the foreland region to the east, the Western Cordillera, and the coastal plains. Three main thickened crust features of regional extent were identified: (1) a deep Moho expression with a crustal thickness greater than 40 km in the northwesternmost foreland region, which we consider a direct consequence of the adjacent thickened Eastern Cordillera involving the fold and thrust deformation migration from the range towards the foreland, and the flexural deformation proposed for the eastern foothills; (2) a regional deep Moho expression (50-60 km) along the axis of the Eastern Cordillera, related to its shortening history including multiple phases of Cenozoic thick-skinned deformation and magmatic underplating; and (3) a Moho deeper than 60 km in a southern latitude (1°S-1°N) beneath the modern magmatic arc, whose interpretation is more complex, likely a combined result of mafic addition to the base of the crust, foundering tectonics, and lateral displacement of the lower crust prompted by the subducting Carnegie ridge.
Abstract. Remnants of the Caribbean Large Igneous Plateau (C-LIP) are found as thicker than normal oceanic crust in the Caribbean Sea that formed during rapid pulses of magmatic activity at ∼91–88 and ∼76 Ma. Strong geochemical evidence supports the hypothesis that the C-LIP formed due to melting of the plume head of the Galápagos hotspot, which interacted with the Farallon (Proto-Caribbean) plate in the eastern Pacific. Considering plate tectonics theory, it is expected that the lithospheric portion of the plume-related material migrated within the Proto-Caribbean plate in a north–north-eastward direction, developing the present-day Caribbean plate. In this research, we used 3D lithospheric-scale, data-integrative models of the current Caribbean plate setting to reveal, for the first time, the presence of positive density anomalies in the uppermost lithospheric mantle. These models are based on the integration of up-to-date geophysical datasets from the Earth's surface down to 200 km depth, which are validated using high-resolution free-air gravity measurements. Based on the gravity residuals (modelled minus observed gravity), we derive density heterogeneities both in the crystalline crust and the uppermost oceanic mantle (<50 km). Our results reveal the presence of two positive mantle density anomalies beneath the Colombian and the Venezuelan basins, interpreted as the preserved fossil plume conduits associated with the C-LIP formation. Such mantle bodies have never been identified before, but a positive density trend is also indicated by S-wave tomography, at least down to 75 km depth. The interpreted plume conduits spatially correlate with the thinner crustal regions present in both basins; therefore, we propose a modification to the commonly accepted tectonic model of the Caribbean, suggesting that the thinner domains correspond to the centres of uplift due to the inflow of the hot, buoyant plume head. Finally, using six different kinematic models, we test the hypothesis that the C-LIP originated above the Galápagos hotspot; however, misfits of up to ∼3000 km are found between the present-day hotspot location and the mantle anomalies, reconstructed back to 90 Ma. Therefore, we shed light on possible sources of error responsible for this offset and discuss two possible interpretations: (1) the Galápagos hotspot migrated (∼1200–3000 km) westward while the Caribbean plate moved to the north, or (2) the C-LIP was formed by a different plume, which – if considered fixed – would be nowadays located below the South American continent.
Abstract. Remnants of the Caribbean Large Igneous Plateau (CLIP) are found as thicker than normal oceanic crust in the Caribbean Sea, that formed during rapid pulses of magmatic activity at ~ 91–88 Ma and ~ 76 Ma. Strong geochemical evidence supports the hypothesis that the CLIP formed due to melting of the plume head of the Galápagos hotspot, which interacted with the Farallon (Proto-Caribbean) plate in the east Pacific. Considering the plate tectonics theory, it is expected that the lithospheric portion of the plume-related material migrated within the Proto-Caribbean plate, in a north–north-eastward direction, developing the present-day Caribbean plate. In this research, we used 3D lithospheric-scale, data-integrative models of the current Caribbean plate setting to reveal, for the first time, the presence of positive density anomalies in the uppermost lithospheric mantle. These models are based on the integration of up-to-date geophysical datasets, from the Earth’s surface down to 200 km depth, which are validated using high-resolution free-air gravity measurements. Based on the gravity residuals (modelled minus observed gravity), we derive density heterogeneities both in the crystalline crust and the uppermost oceanic mantle (
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