Seabed and Surface Sediment Map of the Kvarner Region, Adriatic Sea, Croatia (Lithological Map, 1:500, 000)

Abstract

A lithological map of recent marine sediments and the seabed of the Kvarner region (Adriatic Sea, Croatia) is presented on a scale of 1:500 000. The map was compiled from existing published and unpublished data. This is an area characterised by a number of islands located between the Istrian Peninsula and the Vinodol-Velebit coast. Water depths in channels between the islands reach up to 125 m, compared to depths of 40-50 m in the open waters of the adjacent northern Adriatic. Over most of the Kvarner area, muddy and sandy sediments cover the seafloor. Mud (M) is found on the bottom in Rijeka Bay, the northern part of the Kvarner, in Kvarneric, and in the Vinodol and Velebit channels, whereas over the rest of the Kvarner region seafloor sandy mud (sM) prevails, with subordinate occurence of gravelly mud (gM). Sandy sediments, i.e. muddy sands (mS) dominate in the SW part to the open Adriatic, and west of Rab Island, in the Pag and Velebit Channels. Previous investigations indicate that the fine grained particles that are found in deeper parts of Rijeka Bay, Kvarneric, and Vinodol Channel are of recent origin, and are deposited at water depths below the wave base. Sources of these particles are local permanent and temporary streams and the direct input from weathering processes, along with input by submarine springs (vrulje) near the coast. The large areas of the bottom not covered with sediments, or covered with gravelly and sandy sediments are found above the wave base, i.e. in the erosional wave zone. Coarse-grained material is lithic and/or biogenic. However, due to the very rapid Late glacial-Holocene transgression, when sea-level rose more than a hundred metres, coarse sandy sediments are found below the recent wave base in the SW part towards the open Adriatic, and west of Rab Island, in the Pag and Velebit Channels. Therefore the sediment distribution in the Kvarner region is only partly in dynamic equilibrium with modern hydrodynamic conditions.