Upper Jurassic Platform succession with characteristics of a deeper water intraplatform trough (Mt. Svilaja, Croatia)

Abstract

From the middle part of the Late Jurassic (Kimmeridgian), the hitherto uniform depositional environment of the Adriatic carbonate platform began to show differentiation. In the central part of the platform two intraplatform troughs were formed, one of which stretched from the Karlovac area southward and is known as the Lemeš Trough. The depositional processes that took place within this trough can be observed in the sedimentary succession of Mt. Svilaja. Based on investigated facies characteristics five lithofacies units were distinguished, representing three paleoenvironmental units: (1) shallow subtidal zone below the fair-weather wave-base; (2) intraplatform trough; (3) shallow subtidal zone above the fair-weather wave-base. The environmental changes are related to the tectonically-controlled retrogradation of the shallow subtidal platform, when the deeper-water intraplatform trough area, connected with the open Tethys realm, spread over the sunken part of the platform. Progressive infilling of the trough with bioclastic material led to the re-establishment of the shallow subtidal environment, and the area of the previously existing intraplatform trough was occupied by coral-hydrozoan reefal buildups.