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Uzorci lapora s lokaliteta Jakomići (Pazinski bazen) analizirani su s ciljem odredbe starosti naslaga te paleoekološke interpretacije okoliša u kojem su one nastale. Napravljeni su mikroskopski preparati laboratorijskom metodom primjerenom za madstone bogate organskom tvari. Određene su vrste vapenačkog nanoplanktona te je provedena kvantitativna analiza zastupljenosti pojedinih taksona. Na temelju prvih i zadnja pojava vrsta Furcatolithus obtusus te Sphenolithus spiniger određene su podzone MNP16Bc te MNP17A, što odgovara bartonu (gornji dio srednjeg eocena). Kokolitoforidnim zajednicama dominiraju vrste Reticulofenestra bisecta (s 21% udjela u zajednici) koja ukazuje na CIE (Carbon Isotope Excursion) fazu (faza povećane eutrofikacije u okolišu) srednje eocenskog toplinskog optimuma (Middle Eocene Climate Optimum, MECO) i Reticulofenestra producta (25%) koja je karakteristična za post-MECO fazu. Prisutnost kokolita malog morfotipa vrste Coccolithus pelagicus (7 μm) koji su indikatori hladnijih marinskih predjela, a samim time i eutrofikacije u okolišu te toplovodne jedinke Sphenolithus spp. prilagođene oligotrofičnim okolišima upućuju na postojanje nutrikline i termokline u proučavanom području. In order to determine the age of the deposits and paleoecological conditions of the environment, marl samples from Jakomići locality in Pazin basin were analyzed. The samples were laboratory processed by method for organic rich mudstones and prepared for microscopic analysis. Further taxonomic determination of calcareous nannoplankton was done together with quantitative research methods. Based on the first and last occurrences of the species Furcatolithus obtusus and Sphenolithus spiniger, subzones MNP16Bc and MNP17A of Bartonian were determined. Coccolithophorid assemblages are dominated by the species Reticulofenestra bisecta (21%) and Reticulofenestra producta (25%) respectively. Reticulofenestra bisecta indicates the CIE phase (Carbon Isotope Excursion, enhanced eutrophic phase) of the Middle Eocene Climate Optimum (MECO), while Reticulofenestra producta is characteristic of the post-MECO phase. The presence of the small morphotype Coccolithus pelagicus (7 μm), which is a cold water indicator and a warm water indicator of Sphenolithus spp. adapted to oligotrophic environments points to the existence of nutrilicline and thermocline in the water column. |
