Three-phase tectonic evolution of the northern margin of Puerto Rico as inferred from an integration of seismic reflection, well, and outcrop data

Integration of seismic reflection, well, and outcrop data from the Oligocen e-Pliocene Puerto Rico-Virgin Islands platform (PRVI platform), north of Pu erto Rico, indicates that three major tectonic phases characterize this sei smically-active region within the North America-Caribbean plate boundary zo ne. Tectonic phase I: Cretaceous to Eocene formation and sedimentary infill ing from a southern source area into a forearc basin, formed between down-t o-the-north normal faults near the present-day coast of Puerto Rico and an outer-are ridge near the present-day shelf break. Tectonic phase 1 conclude d the last volcanic are activity in Puerto Rico produced by the subduction of oceanic crust of the North America plate beneath the Caribbean are syste m. Formation of the outer are high defining the northern limit of this elon gate basin may have been related to the accretion of off-scraped sedimentar y rocks beneath the northern margin of Puerto Rico in a manner similar to t hat observed in active arcs, The end of tectonic phase 1 is related to init ial collision between the Caribbean are and the Bahama carbonate platform. Tectonic phase 2. Oligocene to Pliocene formation of a similar to 1600 m th ick, northward-thickening PRVI platform, predominately formed by carbonate rocks. This phase started with a period of non-deposition and erosion, resu lting in an Latest Eocene-Oligocene unconformity. The base of the PRVI plat form is formed by a similar to 400 m thick middle to late Oligocene, basal siliciclastic sequence that prograded northward across the forearc basin. D epositional thicknesses of sedimentary layers deposited during phase 2 are controlled by two large arches: the NNW-trending Guajataca arch appears to have formed as the result of tectonic activity in the Mona Passage area; th e northeast-trending San Juan arch cannot be related to any adjacent struct ure or plate boundary feature. Onlap relations between carbonate rocks of t he platform and both arches suggest that the arches were most active in the period from middle Oligocene to early Miocene. Rocks deposited during Tect onic phase 2 are surprisingly devoid of faults and folds given their centra l position within the North America-Caribbean strike-slip plate boundary zo ne that is known from regional studies to have been active throughout the d eposition of the platform rocks. Tectonic phase 3: Pliocene to Holocene nor thward tilting of the PRVI platform, submerged the northern edge of the pla tform to a depth of 4 km and elevated the southern edge of the platform to several hundred meters above sea level on Puerto Rico. Northward tilting of this area occur-red on the northern limb of a large arch or anticline form ed parallel to the long axis of the island of Puerto Rico and its shelf are as. The arch formed in response to a post-Pliocene convergence between the North America and Caribbean plates. (C) 1999 Elsevier Science B.V. All righ ts reserved.