Aptian Thrusting Event in the Hispaniola Island Arc

Pacific derived models of the Caribbean seem to require that a reversal in subduction polarity occurs in the mid Cretaceous. The best place to demonstrate that such a dramatic tectonic event took place is in the island of Hispaniola. The Amina-Maimon belt and Loma Caribe serpentinite belt in Hispaniola lies between the remains of the Lower Cretaceous arc tholeite (Los Ranchos Fm.) and the upper Cretaceous calc-alkalic arc (Tireo Fm.) terranes. The Amina-Maimon rocks are meta-tuffs and lavas geochemically similar to the Lower Cretaceous Los Ranchos formation. Structurally the Amina-Maimon are mylonitic and phyllonitic schists that show strongly lineated fabrics, sheath folds and doubly vergent isoclinal folds typical of intense simple shear. Penetrative deformation is greatest in the structurally highest part of the body and deceases structurally downward even into the Los Ranchos Formation. Kinematic data from the Maimon segment of the belt indicates a top-to-the-north or northwest motion; in the Amina segment the structural transport was top-to-the-west-northwest. The structures in the Amina-Maimon are interpreted as due to the thrusting of the Loma Caribe mass onto the Lower Cretaceous arc. The thrusting was obliquely right-lateral in the present reference frame, but may have been rotated in later Oligocene left lateral deformation. The timing of this event is constrained by the overlying and undeformed Hatillo Limestone whose base is uppermost lower Albian. Thus, the deformation was likely in the Aptian. Recent age dates from the closely related suprasubduction zone metamafites of the Rio Verde Complex are in the 110-118 Ma range. Age dates from the subduction zone rocks in northern Hispaniola might indicate that NE facing subduction began in the Aptian. Thus, it appears that the deformation in central Hispaniola is related to the tectonic event that initiated SW dipping subduction.