Abstract. We present three-dimensional (3-D) models that describe the present-day thermal and rheological state of the lithosphere of the greater Kenya rift region aiming at a better understanding of the rift evolution, with a particular focus on plume–lithosphere interactions. The key methodology applied is the 3-D integration of diverse geological and geophysical observations using gravity modelling. Accordingly, the resulting lithospheric-scale 3-D density model is consistent with (i) reviewed descriptions of lithological variations in the sedimentary and volcanic cover, (ii) known trends in crust and mantle seismic velocities as revealed by seismic and seismological data and (iii) the observed gravity field. This data-based model is the first to image a 3-D density configuration of the crystalline crust for the entire region of Kenya and northern Tanzania. An upper and a basal crustal layer are differentiated, each composed of several domains of different average densities. We interpret these domains to trace back to the Precambrian terrane amalgamation associated with the East African Orogeny and to magmatic processes during Mesozoic and Cenozoic rifting phases. In combination with seismic velocities, the densities of these crustal domains indicate compositional differences. The derived lithological trends have been used to parameterise steady-state thermal and rheological models. These models indicate that crustal and mantle temperatures decrease from the Kenya rift in the west to eastern Kenya, while the integrated strength of the lithosphere increases. Thereby, the detailed strength configuration appears strongly controlled by the complex inherited crustal structure, which may have been decisive for the onset, localisation and propagation of rifting.

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The density structure of the oceanic lithosphere north of Iceland is key for understanding the effects of the Iceland plume on the greater Jan Mayen‐East Greenland Region. We obtain the 3‐D density structure of the sediments and the crust from regional reflection and refraction seismic lines. The temperature and related density structures of the mantle between 50 and 250 km are derived from a shear wave velocity (Vs) tomography model. To assess the density between the Moho and 50‐km depth, we combine forward and inverse 3‐D gravity modeling. Beneath the Middle Kolbeinsey Ridge (MKR) region, a deep, broad negative mantle density anomaly occurs under the Kolbeinsey Ridge. It is overlain by a narrower uppermost mantle NE‐SW elongated negative density anomaly, which is increasingly displaced eastward of the spreading axis northward. It crosses the West Jan Mayen Fracture Zone and becomes weaker approaching the Mohn's spreading ridge. The effect of this anomaly is consistent with significantly shallower basement on the eastern side of the MKR. We interpret this as the result of thermal erosion of the lithosphere by hot asthenospheric flow out from the Iceland plume, possibly the main driver for several eastward jumps of the MKR during the last 5.5 Ma. The cause for the deviation of the flow may be that the West Jan Mayen Fracture Zone is easier to cross in a region where the difference in lithospheric thickness is small. That implies that the bottom lithospheric topography exerts a regional but not local influence on upper asthenospheric flow.

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.