Sedimentary evolution of an inner foreland basin margin: Palaeogene Promina beds of the type area, Mt. Promina (Dinarides, Croatia)

Abstract

Mt. Promina became famous for its coal mines, vertebrate remains and fossil flora, and for the use of its name in denoting sediments covering a wide area of the Dinaric coastal range. The Promina Beds of the type area, Mt. Promina, are up to 1 km thick and evolved in the context of propagating Dinaric deformation towards the foreland. They consist of eight sedimentary units differing in facies, i.e. depositional environments and systems, which include alluvial, lacustrine, deltaic, lagoonal and shelf deposits. The sedimentary units constitute three depositional cycles. Cycle I is represented by a late lowstand alluvium, while Cycles II and III consist of transgressive and highstand (regressive) systems tracts. Cycle III also includes a coastal onlap of limestones and an alluvial onlap. Transgressive tracts are specific in being represented by lacustrine deposits and having non-erosive bases. Falling-stage sediments have not been identified. The Promina Beds of Mt. Promina represent an example of sedimentary and sequence evolution at a foreland basin margin. The evolution of this margin is characterised by structural and stratigraphic complexities including syndepositional folding, growth strata, angular unconformities, intraformational faulting, alluvial and marine onlaps onto deformed basement, and tectonically induced, proximal-distal variations in facies and sediment thickness. The origin of lacustrine transgressive tracts may have been related to backtilting in the proximal part of the basin. High sediment supply and subsidence pulses are proposed to have been the two main factors which shaped the depositional styles, sequence development and distribution of sediments. The dominant role of tectonism in the sedimentary evolution was related to the position of the area within deforming; marginal parts of the foreland basin, situated in close vicinity to the main, active Dinaric thrust units.