Abstract: This study investigated the extent to which deep-dwelling, infaunal foraminifera bias modern and fossil distributions in the subtropical mangroves of the Everglades (southwest Florida), and which sediment interval should be used as a modern analog for paleoenvironmental studies in this area. Typically, these studies are based on modern analogs from the upper 1 to 2 cm of sediments, as most benthic foraminifera live in the surface 1 cm, but in tropical mangrove environments, deep-dwelling infaunal foraminifera may be more common. The vertical distributions of live assemblages in cores from a mudflat and three mangrove sites were investigated. To examine the preservation potential of dead tests, distributions of wall types and inner test linings were recorded. The living depths of benthic foraminifera showed a landward deepening from 1 to 3 cm in mudflats and low mangroves and from 7 to 10 cm in middle and high mangroves, possibly due to a landward increase in oxygenation of the subsurface sediments. Modern assemblages from the top 2 cm included species common in the deep infauna and contained, on average, 36% of the total standing crop. Additions to total assemblages at greater depths by subsurface production were negligible. Thus, the upper 2 cm of the sediment column would be sufficient as a modern analog for paleoenvironmental studies in the southwestern Everglades. Preservation of dead tests is influenced by a landward increase in the degradation of agglutinated taxa through oxidation/bacterial breakdown of organic cements. Fortuitously, calcareous taxa preserve well in the carbonate-buffered sediments of the Everglades.

Paleobathymetries of consecutively dated stratigraphic sections within the Limón belt, Costa Rica, and Bocas del Toro belt, Panama, are used to calculate rates of emergence for the Caribbean coast of southern Central America over the past 6 m.y. We present estimates of paleoenvironment, paleobathymetry, and rates of emergence for a series of sedimentary units precisely dated as 6.5 to 1.6 Ma. Paleodepths and paleoenvironments are interpreted primarily from preferred habitats of common benthic foraminifera, combined with lithofacies and neotectonics. The Limón and Bocas del Toro belts lie on either side of the northeast-southwest-trending axis of a structural arch that formed from subduction of the Cocos Ridge beneath the Costa Rica-Panama arc complex. Uplift caused by Cocos Ridge subduction began on the southern margin of the arc complex at Burica Peninsula ∼3.6 Ma, and relatively little uplift occurred after ∼1.6 Ma; net rates of emergence from 3.6 to 1.6 Ma were about 1,000 m/m.y. and near 0 m/m.y. thereafter. Effects of Cocos Ridge subduction were not manifest on the northern margin of the arc complex in the Limón and Bocas del Toro basins until after 1.6 Ma. Although sedimentation patterns and coeval, isobathyal benthic foraminiferal faunas were distinctly different in these basins, indicating at least partial isolation, their histories of uplift are similar. Average emergence rates from ∼6 to 3.5 Ma for the Bocas del Toro basin varied from 24 to 90 m/m.y., which could be accounted for by sea-level fall, and from 3.5 to 1.6 Ma there was no measurable emergence in either basin. However, after 1.6 Ma, rates of emergence were as high as 156 m/m.y. on the Caribbean margin, which we attribute to the penetration of the subducting Cocos Ridge. Thus, uplift of the Caribbean margin in the vicinity of the Cocos Ridge northeast extension began 2 m.y. later and was an order of magnitude slower than uplift of the Pacific margin. Timing for the arrival of the Cocos Ridge at the Caribbean margin is supported by its current subduction rate: If the ridge had traveled northeast from the southern Burica Peninsula at 9 cm/yr, in 2 m.y. it would have crossed 180 km, the approximate distance to the Limón basin.