Late Neogene chronology and sequence stratigraphy of mixed carbonate-siliciclastic deposits of the Cibao Basin, Dominican Republic

Abstract

A stratigraphic study of late MiocenePliocene mixed carbonate and siliciclastic sediment (upper part of the Yaque Group) was conducted in northern Hispaniola to refi ne the chronostratigraphy of uplifted, nearshore marine sequences in the Cibao Basin. Classic late Neogene sections in these sequences include a spectacularly preserved faunal record for the northern Caribbean. Refi ned ages of the Cercado Formation (6.6-6.0 Ma), the Gurabo Formation (ca. 5.8-4.0 Ma), and the Mao Formation (3.9-3.5 Ma) allow correlation to regional and global sea-level events. Each of the three formations corresponds to one depositional sequence, composed of mixtures, at different proportions, of skeletal debris, mostly coral, and mud-size (silt) siliciclastic sediment. Distinct stratal geometries and lithofacies individualize the three formations, each separated by pebble conglomerates. The Cercado Formation depositional sequence consists of prograding inner-shelf siliciclastic sands and patch reefs. The basal transgressive unit of the Gurabo Formation is made of seaward-prograding low-angle clinothems of bedded and burrowed siliciclastic sand with molluscs and free-living corals. The upper Gurabo unit consists of massive middle-shelf clinothems of silt with bedded reef debris and in situ branching coral thickets. These clinothems grade basinward into massive, deeperwater silt deposits at the shelf edge and basin slopes. The Mao Formation sequence records the transition from lowstand fl uvial-deltaic facies to transgressive and highstand marine clinothems made mostly of coral debris in a silt matrix. In the Mao Formation outcrops, the coral-silt clinothems can be divided into at least 10 high-frequency cycles (40 k.y.?) based on lithofacies. Channelized and slumped coarse siliciclastic sand, gravel, and nonmarine alluvium cap the sequence, likely associated with lowered sea level starting at ca. 3.3 Ma and perhaps the onset of regional uplift. The major lithologic and sequence geometry changes in the Cibao Basin correlate with trends in the oxygen isotope ice-volume proxy and likely refl ect deposition responding to major periods of marine transgression and highstand. An especially prominent feature is the major deepening and margin back step near the Miocene-Pliocene boundary, continuing in the early Pliocene, which resulted in the deposition of the Gurabo Formation. Transgression and sea-level highstand in the late-early Pliocene (3.9-3.5 Ma) produced distinctive margin progradation primarily by coral debris. This progradation event was synchronous with progradation in the nearby western Great Bahama Bank. The different stratal confi gurations of the three sequences can be attributed to a combination of factors, including: (1) shelf morphology and location on the shelf, (2) paleoceanographic conditions such as warm sea-surface temperatures and reduced upwelling, which controlled coral productivity and reef geometry, and (3) the infl ux of siliciclastic mud from the adjacent mountains.

Rise and fall of Pliocene free-living corals in the Caribbean

“…Associated coral and benthic foraminifera samples are presented from 30 localities (Table DR2) of the Cercado and Gurabo Formations and range in age from 6.25 to 4.5 Ma (McNeill et al, 2011).…”

Multi-locus fossil-calibrated phylogeny of Atheriniformes (Teleostei, Ovalentaria)

“…Stratigraphic horizon and locality: Cercado Formation, Dominican Republic. Absolute age estimate: 6 Ma, based on strontium isotope dating (McNeill et al, 2011); 95% soft upper bound of 23 Ma (based on calibration 2, above). Prior setting: Exponential distribution, Mean = 5.67.…”

Strontium Isotope Stratigraphy for Oligocene-Miocene Carbonate Systems in Puerto Rico and the Dominican Republic: Implications for Caribbean Processes Affecting Depositional History

“…The current understanding of ages is mostly based on foraminiferal and nannoplankton assemblages Seiglie 1970, 1975;Vokes 1979;Monroe 1980;Seiglie and Moussa 1984;Saunders et al 1986;Moussa et al 1987;Banerjee et al 2000). More recent studies have refined and further constrained some of the biostratigraphic ages in Puerto Rico and the Dominican Republic using paleomagnetic, strontium isotope, and U/Pb data (Ramírez et al 2006;Maier et al 2007;Dennison et al 2008;McNeill et al 2012;Ruidiaz-Santiago 2013). However, several poorly constrained or conflicting ages still remain in both Puerto Rico and the Dominican Republic.…”

“…Strontium isotope dating especially holds promise for better age constraints because the gradient of the seawater 87 Sr/ 86 Sr curve during the Oligocene-Miocene is mostly steep, which decreases the dating error (McArthur et al 2001). Several studies have successfully used this technique in Oligocene-Miocene shallow-water deposits in the Caribbean from phosphorite (Mallinson et al 1994), bivalve (Robinson 2004;Ramírez et al 2006;Maier et al 2007;McNeill et al 2012;Ruidiaz-Santiago 2013), and chalk (Land 1991) samples.…”