Lithospheric and Slab Configurations From Receiver Function Imaging in Northwestern South America, Colombia

Abstract

The northwestern corner of South America presents a highly complex geodynamical setting including the convergence between South America, Nazca, and Caribbean plates; which also entails heterogeneity and complexity in the lithospheric structure. Here, we present depth‐migrated common‐conversion point (CCP) teleseismic receiver function profiles carried out using seismological data between 2011 and 2020 from the Colombian Geological Service, combined with some stations of observatories and international networks. These profiles provide better constraints on the lateral interpretation of the main lithospheric discontinuities in this region. We provide an updated crustal thickness map displaying some differences from previous studies, especially in the northernmost part of the cordilleran system. Our results also show some intracrustal features such as the regional detachment surface beneath the Eastern Cordillera and the presence of deep melt reservoirs under the Central Cordillera and the Paipa‐Iza complex in the Eastern Cordillera. We also discuss the lithospheric thickness and the potential existence of a highly hydrated and serpentinized mantle wedge under the forearc over the slab segment south of the Caldas tear. Furthermore, the CCP profiles further support the subduction system segmentation under northwestern South America, with at least five slab segments, two of them overlapping between ∼5.5 and ∼8°N, three belonging to the Nazca plate, and two having a Caribbean origin. The Bucaramanga nest appears to be linked to the interaction between the two northmost slab segments, while the Cauca cluster might be related to a slab dehydration process of a highly fractured zone.

Lithosphere Removal in the Sierra Nevada de Santa Marta, Colombia

“…between the absence of cool and dense mantle lithosphere underneath (mass deficit), the high-density shallow rocks in the SNSM (100 km•m −3 denser), and a locally thin crust (Moho depth of ∼38 km as shown in Figure 9e) with residual eclogitized material that is directly underlain by a shallow sublithospheric mantle (excess of mass near the Moho as shown in Figure 8a). Although there are uncertainties in the crustal thickness in the SNSM, the modeled value is similar to the estimates between 35 and 40 km from Sanchez-Rojas and Palma (2014), Poveda et al (2018), andMojica-Boada et al (2022). The observed Bouguer gravity anomaly and topography along A -A′ and B -B′ are from the EIGEN-GL04C Global gravity field model (Förste et al, 2008) and the ASTER Global Digital Elevation model V003 (NASA/ METI/AIST/Japan Spacesystems & U.S./Japan ASTER Science Team, 2019), respectively.…”

“…The present‐day plots show the current Bouguer gravity anomaly ( g B ), and the gray arrow indicates the location of the Caribbean‐South America plate boundary. In the present‐day plots, the position of the Caribbean slab and continental Moho from receiver functions (Mojica‐Boada et al., 2022) are shown with orange and yellow lines, respectively; other geometry is inferred. Diagonal lines in the Caribbean slab at other times indicate that its position and geometry is not constrained.…”

Lithospheric Delamination as the Driving Mechanism of Intermediate-depth Seismicity in the Bucaramanga Nest, Colombia

“…2, we can observe a belt of slab-related seismicity composed of several small clusters, but forming a nearly linear structure. Note that this seismicity lineament is observed in both sides of the BN, which indicates that the BN is located in the middle part of the subducting plate, and not at the edge, as proposed by some authors 3,17,19,21 .…”

“…We can also observe that the Benioff seismicity at the depth of 130 km forms a continuous lineament of earthquakes on both sides of the BN. This may indicate that the BN seismicity occurs in the middle part of the slab and is not associated with the interaction of different plates, as suggested by some authors 3,17,19,21 . The intensity of the BN seismic process is by more than an order of magnitude stronger than the background slab seismicity.…”

“…Based on seismic velocity tomography, Chiarabba et al 16 suggested that the BN develops at the Nazca plate, which extends further north, to the limits between the Panama arc and the Caribbean plate. Syracuse et al 17 The latest models, created with the use of nite-frequency teleseismic tomography 9,18 and teleseismic receiver function 19 , revealed more complex con gurations with several slab segments, some of which are overlapped. In particular, Cornthwaite et al 18 identi ed three distinct segments of the Caribbean Plate.…”