Sedimentological infill of the Middle Triassic half-graben below Mt. Vernar in Julian Alps, Slovenia

Abstract

Early beginnings of the Middle Triassic extension in the areas surrounding the western embayment of the Neotethys are evidenced in formation of small half-graben basins, local emergences of the underlying platform, and/or deposition of coarse-grained breccia. The succession related to the creation and infilling of one of these half-grabens is exposed on the slopes of the base of Mt. Vernar in eastern Julian Alps, Slovenia. The lowermost exposed unit within the half-graben is the Uggowitz Breccia, which attains thickness of up to 150 m. It is followed by a few tens of meters of red nodular limestone (the informal 'Vernar member'), followed by the second, thinner Uggowitz Breccia unit, succeeded by sandstone and sandy limestone (the informal “Krma member”), rich in shallow marine foraminifers and plant material. The basin-filling succession is followed by indistinctly bedded and then massive limestone of the Schlern Formation. Late Anisian (Ilyrian) age is assumed for the sediments of the half-graben based on the clast composition and comparison with regional sequence stratigraphic schemes. Breccias likely deposited in shallow marine or marginal marine setting. Individual beds are interpreted as subaqueous debris-flow deposits.