Nearshore Deposits in the Middle Eocene Clastic Succession in Northern Dalmatia (Dinarides, Croatia)

摘要

The Middle Eocene clastic succession in the Radovin Syncline is approximately 900 m thick and consists of hemipelagic and flysch-type deposits in its lower part, and shallow-marine sediments in its upper portion. The upper portion embraces a unit of sandstones and conglomerates, which is represented by several facies. Flat- and low-angle laminated, and hummocky cross-stratified sandstones (S1) originated by storm-related processes in the shoreface. Cross-bedded sandstones (S2) reflect longshore, offshore, and onshore flows also in shoreface settings. Flat-laminated sandstones with planar truncations (S3) reflect swash processes. Some sandstones possibly originated in the offshore transition zone. Conglomerate-sandstone couplets (CS) originated by storm-induced flows in the shoreface. Main conglomerates (CM) mostly reflect various processes and modifications performed in upper shoreface and beachface settings of a reflective coast. Most Cross-bedded conglomerates (CX) reflect longshore flows and dissipative conditions. There are also conglomerates which have possibly been deposited by gravity flows related to river floods. The shoreline was oriented NW-SE. The architecture of the sandstone-conglomerate unit is thought to result from the interfingering of deltas and nearshore sandy systems. Deltas were of the shelf-type, and were predominantly “wave-dominated”. The sediments studied reflect molasse-type deposition, which was induced by early post-flysch changes in basin evolution and the palaeogeography of the Palaeogene clastic basin in the coastal Dinarides.