Abstract

A transgressive shallow-marine succession suggested as a reference-section for early Thanetian by the "Early Paleogene working group" (IGCP 286) was studied for its orthophragminid foraminifera from Haymana-Polath Basin in central Anatolia. Orthophragminae, closely associated with Assilina yvettae and Operculina heberti, have been identified in a friable clastic-carbonate sequence which contains Glomalveolina in its different horizons. Basinal sediments with planktonic taxa overlie the shallow-water deposits and preclude the study of orthophragminae higher in the succession. Orthophragminae, studied in oriented sections, were grouped into four categories considering the qualitative and quantitative aspects of megalospheric embryo and morphologic elements of equatorial and lateral chamberlets in equatorial and partly vertical sections. Thus, Discocyclina seunesi, Orbitoclypeus neumannae and Discocyclina sp. 1 have been identified and a new species, Orbitoclypeus haymanaensis, is erected. These assemblages were dated to Thanetian based upon the calcareous nannofossil and planktonic foraminifera identified in the overlying basinal sediments and also the benthonic foraminifera either associated with orthophragminae or present in different horizons of the shallow-marine succession.

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