Paleonvironmental interpretation of Quaternary Coccolith assemblages from the Gulf of Aqaba (Elat), Red Sea

• Amos Winter ^[1]
  1. [1] Hebrew University of Jerusalem

     Hebrew University of Jerusalem

     Israel

     
• Localización: Revista española de micropaleontología, ISSN 0556-655X, Vol. 14, Nº. 1-3, 1982, págs. 291-314
• Idioma: inglés
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• Resumen

  • The distribution of 41 coccolith species in five deep sea cores from the Gulf of Aqaba and the northernmost Red Sea is described. Late Pleistocene climatic fluctuations spanning the last 150,000 yrs. BP in the Red Sea and Gulf of Aqaba, are reflected in the distribution pattern of 7 ecologically significant species which delineate 4 major and 13 minor stratigraphic zones. Detailed, multiple stratigraphic framework is provided by combining coccolithophorids with other calcareous planktonic groups studied in the same cores. Stratigraphic correlation and age determination beyond the radiocarbon range are possible by comparing the stable oxygen isotope values obtained from the cores with the generalized open ocean curve.

    Throughout the latest Quaternary the Gulf of Aqaba coccoliths are well preserved, highly diverse and characteristic of tropical-subtropical assemblages. The interplay of E. huxleyi and G. oceanica is the most conspicuous feature of the core record except during isotope stage 5 and the glacial maximum of stage 6 when G. ericsoni dominates the assemblage.

    Temperature variation seems to have played a minor role in determining characteristics of core assemblages except in the case of G. ericsoni during isotope stages 5 and upper 6 and of G. caribbeanica during transitional intervals. Rise of salinity to more than 50 % during the last Glacial maximum prevented the presence of all coccolithophores. G. oceanica seems to have the greatest tolerance for high salinities. Nutrient content seems to be an important ecological parameter affecting coccolithophores and to be the cause for increased abundances of G. oceanica during glacial times. Stratification of the water column seems to inhibit the development of G. oceanica and may explain the good agreement between the ratio of E. huxleyi and the A5180 curve of benthic-planktonic foraminifera. The higher abundance of G. oceanica and C. leptoporus in one core may be attributed to its location in the proximity of a major Wadi which occasionally brings fresh water and nutrients from the land into the Gulf.

    Evolutionary or ecological factors may account for G. ericsoni's exceedingly high abundance during the last Interglacial. G. cf. ornata and Crenalithus spp. are closely related and may be morphotypic variations of G. ericsoni. E. huxleyi is found in high abundances in the Aqaba cores earlier (about 25 K years) than reported elsewhere. This indicates that the Gulf may have been the evolutionary center for this species.