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Paleogene conical agglutinated walls foraminifera in the Tethys realm – Biostratigraphy, palaeoecology

Due to specific, restricted shallow-water environments that inhabited and relatively low abundances, the Paleogene conical foraminifera with agglutinated shells among larger benthic foraminifera are relatively unknown. They can be considered as a powerful tool in recognition of transgressions or shallowing upward sequences within regression. The assemblage passed through dramatic changes in composition and reduction in diversity when co-occurred with larger, complex miliolids. Up to now, 11 genera and 18 species are described from sediments deposited in Tethyan bioprovinces, in area stretching from Atlantic to Indo Pacific region. The appearance of diversified association of conical foraminifera coincides with the Late Paleocene (Thanetian, SBZ 3 and 4). In northern Tethyan bioprovince (W Pyreneans and Paleogene Adriatic Carbonate Platform) 7 species are found, while in Corfu 4, 1 in E Turkey and 8 in Iran. On the southern margin, these foraminifera are found in Oman and Somalia. Contrary to the Ilerdian (Ypresian, SBZ 5 -9), when conical foraminifera were rare, in the Cuisian (Late Ypresian, SBZ 10, 11-12), for the second time, they became abundant and their association was highly diversified. Species were found in the Middle - Late Cuisian and Early Lutetian sediments deposited on Apulia platform (Trentinara Fm), Adriatic Carbonate Platform (Coskinolina liburnica Stache was known from 1875), in Afghanistan (4 species) and Pakistan (3 species), while their findings in Balucistan is considered very important for paleobiogeographic interpretation. Interestingly, being absent from the southern margin of Tethys till the Late Lutetian, they populated shallow-water settings of Tunisia, Egypt, Somalia and Iran (Jahrum Fm, with 7 taxa still not well defined) from the Late Lutetian to the Bartonian. The distinguished internal architecture of shell was recorded in the Paleocene specimens as variable (embryonic trochospiral coiling, marginal trough with radial exoskeletal partitions or undivided marginal chamber lumen) and stable elements (overall simple conical morphology, adult uniserial chamber arrangement, pillars in itraseptal space, septum as apertural face and agglutinated walls without internal structures). The decreasing in test size and number of structural elements are evolutionary trends of these foraminifera. According to published data (not recently updated), in Caribbean region conical foraminifera are known from upper part of the Early Eocene, and continued to live up to the Late Eocene. 6 genera (2 known from Tethys) and 9 species were found.

Paleogene; conical foraminifera; agglutinated wall; Tethys; biostratigraphy; palaeoecology

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