Plio–Pleistocene palaeogeography of the Llanura Costera del Caribe in eastern Hispaniola (Dominican Republic): Interplay of geomorphic evolution and sedimentation

Abstract : This paper aims to reconstruct the palaeogeographic evolution of the Llanura Costera del Caribe (LCC) in eastern Hispaniola (Dominican Republic) during the Pleistocene, adding new insights to published information on Pliocene–Early Pleistocene deposits. The LCC is a generally flat region comprising the unfolded sedimentary cover of the Cordilleras Central and Oriental. Within this cover, the Pliocene–Early Pleistocene Yanigua Formation,mainly consisting of marl, changes seawards to the mainly limestone Los Haitises Formation. Both units formed in a shallow-water platform rimmed by a reef barrier at least in the latest depositional stages. The overlying Pleistocene La Isabela Formation consists of two major offlapping reef terraces, in which a reef core enclosed a lagoon, and prograded over forereef bioclastic debris. Two belts in LCC's morphostructure directly reflect its sedimentary evolution. The Inner Belt extends over the marly substrate of the Yanigua Formation and the Coastal Belt comprises three major surfaces corresponding to the depositional top of the Los Haitises Formation (Upper Surface), and to the Upper and Lower terraces of the La Isabela Formation (Intermediate and Lower Surfaces, respectively). The MIS 5e age of the 10–20 m high Lower Terrace implies a low uplift rate of 0.033–0.068 mm/yr for the Lower Surface. The Pliocene–Early Pleistocene platform was emergent in the Early–Middle Pleistocene. The Early Pleistocene reef barrier separated endorheic watersheds extending over the former shelf lagoon from the open ocean. Reefs built the Upper Terrace of the La Isabela Formation during one or several Middle Pleistocene highstands and the Lower Terrace during MIS 5e and previous highstands. Siliciclastic deposits in this terrace record the opening to the Caribbean Sea of watersheds in the eastern LCC. The Lower Terrace emersion and opening of the large drainage systems of the western and central LCC took place after MIS 5e. Relative sea level fall and emersion of a large area did not imply increased terrigenous sedimentation in the adjacent marine basin. Development of endorheic watersheds over most of the emergent surface delayed the diachronic arrival of siliciclastics into the marine basin for hundreds of thousands of years.