Microfacies analysis and palaeoenvironmental interpretation of Lower Oligocene, shallow-water carbonates (Gornji Grad beds, Slovenia)

The microfacies and palaeoenvironment of Lower Oligocene carbonates of the Gornji Grad beds from Slovenia are investigated. These beds form part of a transgressive succession overlying both terrigenous sediments (sandstones a nd conglomerates) and marine carbonates of Eocene age as well as transgress ing directly over Triassic limestones. They are followed by foraminiferal r ich marls. The carbonates were investigated using multivariate statistical techniques on point counts of thin sections. They are dominated by poorly s orted biogenic rudstones with pack-/wackestone matrix; pack- and grainstone s are subordinate. The biogenic components of the carbonates are dominated by coralline red algae (9 genera with 11 species), corals, small benthic, l arge benthic, and encrusting foraminifera as well as bivalves. Gastropods, bryozoans, brachiopods, echinoderms, serpulids, and green algae are subordi nate. The well preserved components allow details pertaining to taxonomy, g rowth-forms and taphonomic features to be observed. The following carbonate facies are distinguished: 1) nummulitic, 2) bivalve, 3) foraminiferal - co ralline algal, 4) grainstone, 5) coralline algal, 6) coralline algal - cora l, and 7) coral facies. All the carbonate facies represent fully marine con ditions within the photic zone. They are interpreted with respect to substr ate composition and stability, water turbulence, terrigenous input and ligh t.