Twenty-five million years of subduction-accretion-exhumation during the Late Cretaceous-Tertiary in the northwestern Caribbean: The Trinidad Dome, Escambray Complex, Central Cuba

Abstract

The Trinidad dome, Escambray complex, Central Cuba, forms part of an accretionary wedge built-up during intra-oceanic subduction in the Caribbean from the Late Cretaceous (∼75 Ma) to Tertiary. Fieldwork, microscopic studies, P-T estimates and new ⁴⁰Ar/³⁹Ar isotopic data indicate a tectono-metamorphic evolution involving five deformation phases. Three main stages (D₁, D₂ and D₃) were responsible for the subduction-exhumation of the units during metamorphic development. ⁴⁰Ar/³⁹Ar isotopic data allow for the first time, an evaluation of the complete time interval from subduction/collision to final exhumation. D₁ deformation took place at 60.5 ± 0.6 Ma during subduction and was characterized by a prograde path with HP peak metamorphic conditions in eclogite facies in the Monforte nappe (the highest structural nappe) and greenschist metamorphism in the La Sierrita, Yaguanabo and Rio Chiquito nappes (at lower structural levels). D₂ deformation (56.32 ± 0.40 Ma) included a short-lived heating event in the lower nappes that caused incipient recrystallization at lower amphibolite facies, but was generally linked to decompression and retrograde metamorphism to greenschist conditions during folding and NNE thrusting of all nappes. Parallelism of the main S₂ foliation and serpentinite lenses indicates D₂ was the main phase of exhumation. During D₃, exhumation and NNE thrusting continued as the units were progressively incorporated into the growing accretionary wedge until about 50 Ma. Structures related to D₄ are post-metamorphic and reflect the domal structure. D₅ strike-slip and normal faults cut the tectonic pile, and low angle normal faults are more abundant towards the dome rim indicating exhumation of the Escambray. Field observations, structures, and the inverted distribution of the P-T conditions in the wedge suggest exhumation mechanisms by underthrusting/underplating and erosion combined with extension at the surface. Subduction/accretion/exhumation in the Trinidad dome thus occurred from 75 to 50 Ma, indicating a period of 25 million years of deformation history in the northern Caribbean realm.