Triassic Pelagic Limestones in Pillow Lavas in the Oresje Quarry near Gornja Bistra, Medvednica Mt. (Northwest Croatia)

Abstract

Investigated outcrops in the Oresje quarry near Gornja Bistra on Medvednica Mt. contain pillow lavas and massive metabasalts with fragments of carbonate rocks between them. The effusive rocks were determined as high-Ti tholeiitic metabasalts, corresponding to those which originated in the MOR area, which today represent obducted, allochthonous parts of Triassic oceanic crust. Carbonate rock fragments are characterised by micrite, biomicrosparite, fossiliferous microsparite, biosparite and sparite types, all of which are more or less recrystallised. From their appearance between pillows, together with hyaloclasts they were determined as peperites. Micropalaeontological analysis of conodonts from the limestone samples indicated a Middle Triassic age, which is also the age of the effusive rocks discovered in the quarry.