Geomorphologic changes of the Velebit Channel during Late Pleistocene and Holocene (NE Adriatic)

Abstract

The Velebit Channel and its marginal basins in the northeastern Adriatic Sea were analyzed in order to reconstruct the geomorphological evolution of this area during the Late Pleistocene and Holocene (130 ka, MIS 5 to MIS 1) using detailed seabed maps, new data on sea-level changes, and submarine investigation. Submerged parts of the canyon, paleodeltas, traces of ancient lakes, and a large polje were discovered by analyzing these maps. Significant climate fluctuation during the Late Pleistocene and Holocene caused large variations in the Adriatic sea-level. On the very indented karst relief, the paleogeographic changes were quite impressive. The paleoflow of the Zrmanja River incised a canyon in the present Velebit Channel. A reconstruction of the paleoflow of the Zrmanja River shows that it could be traced at least 140 km from the current mouth during the Last Glacial Maximum. The transition from the marine to terestric/ freshwater/lacustrine environment in the southeastern part of the Velebit Channel and in the marginal basins took place when the sea level dropped and oscillated between -20 m and -50 m (110-70 ka B.P.) after reaching a maximum of +5 m in 125 ka B.P. (MIS 5e). The basin in the northwest remained connected to the Kvarnerić marine basin at sea-level between -50 m and -80 m (70-30 ka B.P.). The sea completely receded from the Velebit Channel and Kvarnerić basin became polje during the Last glacial maximum (30-20 ka B.P.) when the sea level fluctuated between -100 and -120 m, whereas lakes probably remained in the deep depressions. During rapid sea-level rise between 19 and 7 ka B.P. the sea flooded a large part of the Zrmanja paleoriver valey and canyon (all of the Velebit Channel) and the sea penetrated into marginal basins. At the beginning of the stagnation of the Adriatic Sea level 7 ka B.P. a fine example of drowned fluviokarst relief was formed and the dynamics of water in the karst underground became similar to the present.