Abstract

The 3.13 m long bathyal piston core En20-2 from the northern Leeward Islands (17°49.9′N, 63°02.4′W, water depth 680 m) was sampled every 20 cm. The Pleistocene-Holocene boundary occurred at 107 cm, and the base of the core lay above the Atlantic extinction of Pulleniatina obliquiloculata (34 ka BP). The core yielded throughout both (a) a deep-water association (DWA) of middle bathyal benthonic foraminifera and (b) a shallow-water association (SWA; up to 56% of total recovery) comprising back-reef, epiphytal species. The environmental trends suggested by the two groups are compared.

Although sea-levels during the Late Pleistocene and Early Holocene rose abruptly, there was no abrupt change in the DWA at the Pleistocene-Holocene boundary, but a gradual change from a higher-productivity fauna (Bulimina spp., Uvigerina spp.) at the base of the core to a lower-productivity fauna (Cassidulina spp., Globocassidulina spp.) at the top. Microhabitat preference changed from shallow-infaunal at the core base to primarily epifaunal at the top. Diversity and species dominance did not differ significantly between the Late Pleistocene and the Holocene.

Percentage abundances of species were calculated separately for the DWA and SWA. Seventy significant correlations were found between the percentage abundances of individual DWA and SWA species, the two strongest correlations - both positive - being between (a) Neoconorbina terquemi and Uvigerina laevis, and (b) Amphistegina gibbosa and Cassidulina curvata. The percentage abundance of U. laevis decreased up-section, whereas the percentage abundance of A. gibbosa increased up-section, reflecting a change in the nutrient flux over time that impacted on both the DWA and the SWA. Positive correlations between the DWA low-productivity indicator Globocassidulina subglobosa and the SWA species Asterigerina carinata, Elphidium discoidale, Peneroplis bradyi and P. proteus suggests that these four SWA species comprise a guild.

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