The quantitative distribution of planktonic foraminifera, pteropods, and coccolithophorids, as well as oxygen-isotope variations were analyzed in four deep-sea cores from the Gulf of Aqaba (Elat) and the northernmost Red Sea. The core record covers about 150,000 yr. Detailed stratigraphic subdivision is facilitated by combining all calcareous plankton groups. Time-stratigraphic correlation and dating beyond the radiocarbon range are possible by comparison of the oxygen-isotope curves. During the glacial maximum salinity rose to more than 50‰, while winter temperature of the upper waters fell by at least 4°C compared to the present. The rise in salinity can be accounted for by sea-strait dynamics and lowering of sea level. The Gulf of Aqaba and the Red Sea were continuously connected through the Straits of Tiran, and there is no indication of desiccation during the glacial maximum.
Scanning electron microscopy of the architecture of Rotalina inermis Terquem, 1882, the type-species of the genus Pararotalia Le Calvez, 1949, and of Rotalia mexicana Nuttall, 1928, the type-species of the genus Neorotalia Bermudez, 1952, reveals that both taxa have in common: 1) an umbilical bowl closed by either a single or a compound umbilical plug; 2) an interiomarginal extraumbilical aperture, restricted by a toothplate that protrudes with a free edge into the aperture and forms an umbilical spiral canal; and 3) a septal flap and intraseptal interlocular spaces. Rotalia mexicana, however, also possesses an enveloping canal-system, similar to that found in the Calcarinidae. For this reason Neorotalia must be regarded as a valid distinct genus, not synonymous with Pararotalia, as proposed by some authors. Calcarina calcar d'Orbigny, 1839, variously placed by authors in Rotalia Lamarck, 1804, in Pararotalia Le Calvez, 1949, and lately again in Calcarina d'Orbigny, 1826, is shown to possess the same basic architecture as Neorotalia and is placed, consequently, into this latter genus. Irregular supplementary apertures occurring in N. calcar are not considered of generic value and neither are they regarded as indicating a relationship with Nautilus spengleri Gmelin, 1788, the type-species of Calcarina. The latter, although characterized by a complex enveloping canal-system, possesses primary multiple interioareal main apertures, surrounded by thick rims, as well as a small umbilical plate, but lacks a toothplate with a free edge. For comparison, Pararotalia spinigera (Le Calvez, 1949) and Neorotalia viennoti (Greig, 1935) were also studied. The subfamily Pararotaliinae Reiss, 1963, is emended to include the canal-system as a characteristic feature. A glossary of selected terms is appended.
Abstract. Planktonic and benthonic foraminifera live in the desert‐enclosed, hypersaline and oligotrophic Gulf of Aqaba and northernmost Red Sea near the edge of their ecological tolerance. Marked changes in foraminiferal abundance patterns in the past, resulting from hydrological shifts related to global climatic fluctuations, facilitate a high‐resolution ecostratigraphic subdivision of deep‐sea records covering the last 150,000 years. Of particular significance are the foraminiferal plankton/benthos ratios, the presence/absence pattern of such species as Globigerinoides sacculifer, as well as the frequency variation of Globigerina bulloules‐falconensis, Buliminacea, Miiiolacea and various “rotaliform” species. Paleoceanographic interpretation of the shifts in assemblage composition and of stable oxygen isotope data obtained on planktonic foraminifera and pteropods indicates that during glacial intervals ‐ because of global cooling, lowered sea‐level and reduced water exchange at the straits of Bab‐el‐Mandeb ‐ the temperature of the upper waters fell by about 4–6 oC (to 15–17 oC), salinity rose by about 10%o to more than 50%0 while residence time of the water became longer and the input/output ratio of nutrients became higher. As a consequence, fertility of the photic zone was higher, the organic content of the sediments increased and oxygen levels in the deep basin became reduced. Thus, sea level‐oscillations and strait‐dynamics played a major role in the foraminiferal paleoecology of the Red Sea.
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