New contributions for defining the subduction geometries in the converging margin between NW South America and SW Caribbean Basin

Abstract

Hypocentral solutions based on arrival times of first P and S waves recorded by stations of the National Seismological Network of Colombia (NSNC), public datasets of GPS, Gravity and Magnetic, as well as estimations of velocity tomograms, Curie Depth Points and the strain field along NW South America and SW Caribbean Basin, have been used jointly to evaluate the subduction process and interactions of the first order tectonic blocks. A wire model supported by three profiles based on gravity forward modeling, earthquake distribution and b-values, elucidates the sinking behavior of the Caribbean and Nazca under the South America plates, highlighting at least three scenarios of subduction, where in addition to the Caldas Lithospheric Tear, other minor tears are found in the lithospheric system of this region. The wire model shows how the Caribbean Plate accommodates mechanically to transition from flat subduction at the south to steeper subduction at north, lifting differentially the Santa Marta Massif and the Santander Massif along a weakness zone that corresponds with the Santa Marta — Bucaramanga Fault System. The absence of a volcanic arc at present in the Eastern Cordillera and/or the Perij· Range is consequence of the compressional regimen induced by the flat subduction of the Caribbean Plate and its interaction with the Panama tectonic indenter, generating a zone of accumulation of fluids (> 130 km depth) derived from the dehydration process that cannot ascent to surface and impedes the formation of an active magmatism nowadays, though it is possible that during last 9-12 Ma of relevant influence of the Panama Arc against NW South America, other emplacements of magmatic material took place along this orogenic system. Wire model also shows that the low seismic activity inside the Antioquia Batholith is consequence of its rigidity, promoting transfer of strain from west to east derived from the subduction process, generating high seismic activity along its borders, and suggesting that compositional and elastic properties in depth, maintain coherence as a structural body beyond the upper crust. A similar interpretation is indicated for the south of the Eastern Cordillera.

AAPG Datapages/Search and Discovery Article #90330©2018 AAPG Hedberg: Geology of Middle America – the Gulf of Mexico, Yucatan, Caribbean, Grenada and Tobago Basins and Their Margins “Integration of the geology of the area from the southern onshore of North America to the northern onshore of South America”, Siguenza, Guadalajara, Spain, July 2-5, 2018