ACCRETIONARY COMPLEXES OF CUBA, WITH EMPHASIS ON THE ESCAMBRAY COMPLEX (CENTRAL CUBA)

Mesozoic continental margin sedimentary sequences that occupied a portion of the Proto-Caribbean domain (Caribeana) were subducted and metamorphosed below the Caribbean plate during the late Campanian. This event triggered the termination of the Caribbean volcanic arc activity and caused accretion and tectonic emplacement of the subducted complexes. In Cuba these accretionary complexes include Cangre, Pinos, Asunción and Escambray. They show differences in tectonic, metamorphic grade and P-T evolution. Likely, slab flattening in the west of the Caribbean plate and/or opening of the Yucatán basin during the Maastrichtian-Palaeocene favoured exhumation of the Escambray and Pinos complexes below allochtonous volcanic-arc units, whereas Cangre and Asunción were exhumed in a forearc setting.

The Escambray complex forms two structural domes that comprise strongly deformed metasediments, metabasic rocks and metaophiolites. Peak metamorphic conditions range from eclogite-, blueschist- to greenschist-facies. The complex shows an inverted metamorphic pattern with higher-grade on top of lower-grade units. Subducted oceanic material is represented by serpentinite melanges that include blocks of eclogite and blueschists. Geochronological data evidence subduction-exhumation during the late Cretaceous-early Paleogene. The S₁ foliation is only preserved in isoclinal and intrafolial folds. The S₂ main foliation and a S₃ crenulation cleavage are related to NE-directed exhumation. The D₂ phase represents the onset of exhumation of main tectonic units. Parallelism of the S₂ foliation with strongly sheared serpentinite layers/bodies indicates exhumation along major faults of hanging wall mantle or subducted ophiolitic material. The younger structures consist of late-stage domes, semiductile shear zones and brittle structures with development of normal and strike-slip faults that separate deeply subducted crustal rocks of the Escambray in the footwall with less metamorphosed units in the hanging wall (the arc-related Mabujina amphibolite complex) indicating that the nappe stack progressively evolved as a metamorphic core complex.