Volcanism, tectonics, and stratigraphic correlations in Puerto Rico

Abstract

Island arc volcanic strata in Puerto Rico, ranging in age from Lower Cretaceous (Aptian) to Eocene and dating from about 120 to 45 Ma, represent one of the longest oceanic arc sequences preserved in the world. Detailed and systematic mapping by the U.S. Geological Survey published between 1959 and 1986 reveal that, although postvolcanic sedimentary platform deposits consisting of limestone and other detrital materials ring the island and cover extensive parts of the arc platform, representative strata of the entire sequence are exposed. The island is subdivided into three volcanic provinces all containing strata without correlative units elsewhere; they are (1) a northeastern volcanic province, separated from the central province by the Cerro Mula Fault, a left-lateral strike-slip fault of mid-Santonian age with displacement of at least 50 km; (2) a central volcanic province, dominated by volcanic debris accumulated during sequential development of five east-west-oriented volcanic belts, and (3) a western volcanic province, with a northwest-southeast-trending boundary of uncertain origin, containing remnants of two sequential island arc volcanic belts of CampanianMaastrichtian and Eocene age.Additionally, in the southwestern corner of the island, the Sierra Bermeja Complex consists of a tectonic melange of partly serpentinized ultramafic rocks representing the lithospheric upper mantle originally composed of spinel-bearing peridotites, including lherzolite, harzburgite, and dunite. The melange incorporates rafts, blocks, and boulder-sized clasts of (1) Lower Jurassic to Upper Cretaceous pelagic sediments (Mariquita Chert), including radiolarian chert of Pacific provenance and later siliceous volcanogenic strata, representing pre-island arc oceanic deposits; and (2) altered mid-ocean ridge basalt (MORB)-like basalts (Cajul Basalt) and amphibolites (Las Palmas amphibolite melange) of probable Lower Jurassic age, representing pre-island arc oceanic crust. Serpentinized peridotite bodies, containing amphibolite, altered MORB-like basalt, and chert, protruded the arc platform in a cold state at several places in the western province. The largest of these, the Monte del Estado Peridotite, was emplaced during the Maastrichtian, through crustal extension associated with left-lateral strike-slip faulting along the Cordillera fault.Volcanic strata preserved in the central province are subdivided into five major volcanic phases on the basis of stratigraphic and geochemical relations. Basalts evolved progressively from early primitive island arc tholeiites in phase I, to calcalkaline basalts in phase II, and finally to incompatible element-enriched shoshonite Jolly, W. T.

Aalenian to Cenomanian Radiolaria of the Bermeja Complex (Puerto Rico) and Pacific origin of radiolarites on the Caribbean Plate

“…The depleted rare earth patterns of these ultramafic rocks are typical of upper mantle peridotite (Jolly et al 1998). …”

Extension in Mona Passage, Northeast Caribbean

“…The Greater Antilles crust in the eastern NCPBZ is likely no thicker than 30 km (Talwani et al, 1959;Jolly et al, 1998;ten Brink, 2005). At shallow depths (b15 km), seismicity is focused in a broad band from southwestern Puerto Rico (predominantly the Lajas Valley) to the eastern Mona Passage, turning north into the Mona Canyon (Fig.…”

Evaluation of ultramafic deposits in the Eastern United States and Puerto Rico as sources of magnesium for carbon dioxide sequestration

“…Jolly et al (1998) imply that these serpentinite bodies are diapirically emplaced through over-lyingCr-etaceoussediments. Regardless of stracture or mechanism, the gravity model implies that the serpentinite is over 2.8-knl thick.…”

“…The highlands of the island consist of an uplifted core of subducted sedimentmy and associated volcanic and plutonic rocks emplaced from 2120 to 45 Ma (Jolly et al 1998). Serpentinized mantle peridotite occurs in three belts restricted to the southwest part of the island (Mattson 1960; Figure 11).…”

“…The serpentinized peridotite (referred to hereafter as serpentinite) is the basal part of one or more disrupted ophiolite sequences. Previous workers claim that most or all Puerto Rican serpentinites were emplaced diapirically through overlying rocks (Jolly et al 1998). Much of the serpentinite occurs as melange, and some occurs as sedimentary deposits draping the edges of the major bodies .…”