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Evolution of a Dinaric foreland basin fill: flysch and molasse of North Dalmatia

The sedimentary fill of foreland basins stores precious information on the evolution of basin physiography, distribution and changes of depositional settings, as well as relative sea- level fluctuations. In the same time, the sediments record the dynamic interaction of tectonics and sedimentation, so that the evolution of an orogen may be read from foreland basin sediments - the critical source for getting such information. The significance of understanding the sedimentary evolution of foreland basins also derives from the fact that important hydrocarbon reservoirs, including giant fields, have been discovered in foreland basins. Hence, an immense literature has been and is continuously published on foreland basins and manifold aspects of their sedimentary fills. It also includes three special volumes (ALLEN & HOMEWOOD, 1986 ; DOROBEK & ROSS, 1995 ; MASCLE et al., 1998). The North Dalmatian foreland basin fill originated in the context of propagating deformation towards the foreland, so that the deformation and the basin itself were migrating and developing together (e.g. ALLEN & ALLEN, 1990 ; MIALL, 2000). Ideally, the first sign of approaching nappes is the development of a bulge in the foreland area. It is followed by subsidence, which is faster than the sedimentation rate due to the imposed orogenic load. The process leads to the generation of a deep basin, which receive detritus from the orogen. This stage of evolution is called flysch stage (e.g. FLEMINGS & JORDAN, 1989 ; ALLEN et al., 1991 ; CRAMPTON & ALLEN, 1995). When the shortening slows down, the sedimentation rates may outpace the subsidence rates which results in shallow-marine and continental depositional settings. This corresponds to the molasse stage. The foreland basin sediments of N Dalmatia are more than 2.5 km thick, and are known as the Paleogene flysch and molasse of the Dinaric orogen (e.g. CHOROWICZ, 1977 ; HERAK & BAHUN, 1979 ; MARINČIĆ, 1981, among others). These sediments represent an important target of research, crucial for obtaining knowledge on the evolution of the relevant basin and the Dinaric orogen. They include a variety of facies and depositional systems including deep- water, slope, shelf, delta, coast, lacustrine and alluvial. The purpose of this excursion is to observe and discuss selected, main features discovered in this basin, which reflect evolutionary stages of the basin history.

Dinarides, foreland basin, flysch, molasse, North Dalmatia

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