Biogeography and ecostratigraphy of Late Quaternary planktonic foraminiferal taphocoenoses in the Leeward Islands, Lesser Antilles, NE Caribbean Sea

The Leeward Islands lie within an oceanographically complex area influenced by North Atlantic Gyre flow and the Orinoco plume. Late Quaternary planktonic foraminiferal assemblages are reported from three middle bathyal piston cores (from NW to SE: En20-2, En20-10, En20-16) in the Leeward Islands. En20-2 was obtained closest to the 200 m bathymetric contour, En20-10 farthest offshore. The bathyal benthonic foraminifera from En20-2 are indicative of high surface productivity. The planktonic foraminiferal assemblages differ between the cores. The “Globigerinoides ruber group” (= white and pink G. ruber + G. cyclostomus) typically increases shoreward, but in this study it was most abundant in En20-10. West of the study area (i.e., around Puerto Rico), white-walled specimens form ~ 66% of the “G. ruber group”, but in the Leeward Islands the percentages are higher (mean 81.7% of total “G. ruber group”). Globigerinita glutinata and Globoturborotalia rubescens (pink) were at their most abundant in the SE core En20-16, while G. rubescens (white) was at its most abundant in the NW core En20-2. Comparison with benthonic foraminiferal distributions suggests that the following planktonic species have potential as indicators of surface productivity, Globigerinella aequilateralis, G. glutinata and Globorotalia inflata being indicative of enhanced surface productivity and Globigerinoides immaturus, G. trilobus var. and Globorotalia tumida of low surface productivity. Bottom-up SHE Analysis for Biozone Identification (SHEBI) indicates that each core contains several abundance biozones (ABs), but these do not correlate between the cores. Alpha diversities were SE = 8.3–14.3 effective species, while beta diversities ranged from 0.65 to 1.54, but only two were statistically significant. Complementarities (64.7–87.6%) indicate that the AB boundaries reflect changes in the relative abundances of species, not overall diversity.

► Bathyal benthonic foraminifera in the Leeward Islands reflect fluctuations in surface productivity.
► Planktonic foraminifera show similar small-scale (< 150 km) changes in assemblages.
► Assemblages changed independently at the three sites examined.
► There was no change in diversity at the Pleistocene\Holocene boundary.
► Globigerinoides ruber is most abundant offshore, close to the Anegada Passage.