engleski

Biotic resilience of foraminifera on environmental conditions around the Middle Eocene Climate Optimum (MECO): Dinaric Foreland Basin

During the Eocene, the transient carbonate ramp system developed in the Central Neo-Tethys region in front of the evolving Dinaric foreland basin (Ćosović et al., 2018). Shallow-water carbonates and deep-water carbonate-clastic successions crop out in the southeastern part of the Outer Dinarides (Pelješac Peninsula, Hvar Island). The investigation of benthic and planktonic foraminifera coupled with geochemical and sedimentological data provided evidence for accurate age attribution of the deposits (early Bartonian, SBZ 17, E11), recognition of two ramp facies belts (middle to outer), the rate of terrigenous input in basin deposits and changes in the composition of foraminifera around the MECO. The ramp deposits were characterized by scattered and reworked Larger benthic foraminiferal (LBF) tests, and according to the alternation of periods of low (intense bioturbation) and higher energy the various types of LBF accumulations originated. Tests of large Nummulites and orthophragminids (Discocyclina sp., in particular) are predominant, whereas sphaerogypsinids, miliolids, asterigerinids and opeculinids are less abundant. Towards the younger deposits, Solenomeris and annelids became more numerous, while representatives of genus Nummulites and associated fauna became less diversified. The adjacent basins were dominate by the eutrophic deep-dwelling large subbotinids, whose abundances increased slightly towards the younger part, in contrast to the large oligotrophic acarininids, whose abundances decreased in the younger part. The assemblages of smaller benthic foraminifera are poorly preserved, show low diversity, and are rarely found compared to the planktonic foraminifera, scarce in specimens. The detailed reconstruction suggests that eutrophication occurred during sedimentation and the oxygen content on the seafloor may have decreased.

Dinaric foreland basin ; Bartonian ; Benthic foraminifera ; Planktonic foraminifera

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