Présence d'une association micropaléontologique de la biozone à Praeorbitolina cormyi (Aptien inférieur) dans l'Urgonien de Tanzanie méridionale. Implications paléogéographiques au niveau de la marge indienne de l'Afrique

Abstract

Outer shelf calcarenites from Urgonian limestones (Kiturika beds) outcropping in the southern coastal basin of Tanzania yield in the localities of Lisongele Hill and Mavudyi Gorges a micropaleontological assemblage from Early Bedoulian (upper part) -Late Bedoulian (lower part) with, particularly, Praeorbitolina cormyi Schroeder, Palorbitolina lenticularis (Blum.), ? Choffatella decipiens Schlumb., Archaeolithothamnium rude Lem. and Marinella lugeoni Pfender. These limestones overlie green silts containing Late Bedoulian Ammonites as Valdedorsella akuschaense Anth. and Cheloniceras cf. cornuelianum d'Orb. The above-mentioned microfauna shows a certain originality within its East-African and Arabian paleobiogeographic context : different from all known the assemblages of Aptian carbonate from Somalia, Ethiopia, Oman and Saudi Arabia where Praeorbitolines never have been observed, it shows South-Iranian affinities. Its migration southward to such meridional latidudes might have traversed marginal parts of the later Indian microplate, still bound to Africa at this time.

Orbitolina episodes in carbonate platform evolution: the early Aptian model from SE Spain

“…In the late Barremian-early Aptian the cardinal form of this group was Palorbitolina lenticularis (Blumenbach), a species known from Mexico (Meza, 1980), the Central Atlantic (Gupta and Grant, 1971), the Mediterranean, Middle East and African regions (Pelissie et aI., 1982;Peybernes, 1982;Peybernes and Forster, 1987;Simmons and Hart, 1987), Borneo (Hofker, 1963) and the Philippines (Wolcke and Scholz, 1988).…”