Significance of the Bucegi Conglomerate olistoliths in the Albian source-to-sink system from the Carpathian Bend basin in Romania

Abstract

The presence of exotic blocks (or olistoliths) in sedimentary deposits is usually regarded as an indication of a deepwater slope environment. We evaluate olistoliths accumulated in shallow water at the upper edge of a slope setting using outcrop data. The study area is in the Bucegi Mountains in the southeast “bend” of the Carpathian Mountains in Romania. The studied deposits belong to the Bucegi Formation, a dominantly conglomerate succession of Albian age. The Lower Bucegi member has been accumulated as a large conglomerate submarine fan. The Upper Member forms a shelf-to-trench sedimentary system with deposits dominated by sandstones and conglomerates. The olistoliths are embedded in debris flow conglomerates, most of them from the Bucegi Upper Member, and a lower number from the Bucegi Lower Member. The olistoliths are all located in a small ([Formula: see text]) zone, close to the Dambovicioara source area. The olistoliths have been transported into the basin for up to 10 km on relative gentle gradients. The blocks’ deposition is restricted to the shallow-water environment on a narrow low-gradient shelf and in some instances on the upper continental slope. Within the Albian source-to-sink system, the olistoliths occurrence marks the entry zone of the land-derived detrital material into the basin and points to the main sediment transport fairways into deeper parts of the basin.