8th International Nannoplankton Association Conference


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Osman Varol:
Didemnid Ascidian Spicules and nannofossils from the Middle East

A detailed quantitative study, carried out on the didemnid ascidian spicules from the carbonate-rich sediments of Late Jurassic age in the Middle East, is described. The assemblages are dominated by variations of Ascidites dubius Bonet & Benveniste-Velasquez (1971) which constitute over 90% of the assemblages. Several subspecies in Didemnum minutum Bonet & Benveniste-Velasquez (1971) are described based on the arrangement and the number of rays in the spicule. Didemnoides rosetta Bonet & Benveniste-Velasquez (1971) is rare and restricted to early Kimmeridgian sediments in the study areas.

Ascidian spicules are associated with rare and low-diversity nannofossil assemblages only in certain parts of the sections, indicating a relatively deeper palaeoenvironmental setting. The assemblages comprise species of Watznaueria, Cyclagelosphaera and Ellipsagelosphaera. In the study area, the last occurrence of Cyclagelosphaera deflandrei (>13µm) was found in the Early Kimmeridgian, whereas the last occurrence of Watznaueria manivitiae (>13µm) was found in the Oxfordian.


Bonet , F. & Benveniste-Velasquez, N. 1971. Espiculas, de ascidites fosiles y actulaes. Revista del Instituto Mexicano del Petroleo, 3: 8-35.


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