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Paleocene-Eocene boundary and larger benthic foraminiifera on the Paleogene Adriatic carbonate platform (Sopada section, SW Slovenia)

The larger benthic foraminifera (LBF) from the Paleocene-Eocene boundary on the Paleogene Adriatic carbonate platform document foraminiferal turnover and complex environmental conditions. In studied shallow-water carbonate ramp sediments, the transition from Thanetian SBZ 4 to Early Ypresian (Ilerdian) SBZ 5 is marked by an abrupt appearance of LBF, dominance of complex miliolids, first onset of true spherical alveolinids, and large assilinids. The Thanetian SBZ 4 LBF characterized the diversification of Assilina azilensis, Ass. yvettae, rare occurrences of Glomalveolina levis, G. dachelensi, Nummulites catari, Hottingerina lukasi, Thomasella labyrinthica, complex miliolids (Lacazina blumenthali) and rotaliids. Close to the termination of the late Paleocene small sized foraminiferal specimens occur. The LBF assemblage is interpreted as the first stage of the Global Community Maturation (GCM) During the lowest Eocene (Ypresian, earlier part of the SBZ 5) generic and species level increased, small and less preserved alveolina, A. globula, A. dolioliformis, A. avellana, and large shell assilinid’s A. tectosaga appeared. Remarkable is abundance of “Lazarus spp.” as L. blumenthali, Th. labyrinthica, Pseudolacazina donatae and rotaliids. The high diversification of spherical alveolinids at most A. aramaea than A. dolioliformis, A. varians, A. globula, A. avellana, along with rare L. blumenthali, large Assilina ex gr. ammonea and Nummulites spp. characterize the following Ypresian sub-zone. The differences in species composition and test morphologies allow us to divide SBZ 5 into two subzone (SBZ 5A and SBZ 5B). In Ypresian SBZ 6 intraspecific variability of spherical and ovoidal large form of alveolinids (A. daniensis, A. solida, A. pasticillata and A. ellipsoidalis) continued to develop.

Palaeocene–Eocene boundary; Larger benthic foraminifera; SBZs 4–6; Paleogene Adriatic carbonate platform

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