Late Pleistocene and Holocene paleoenvironmental reconstruction of a drowned karst isolation basin (Lošinj Channel, NE Adriatic Sea)

The results of a comprehensive study of submerged paleoenvironments developed along the karstified eastern Adriatic coast during the Late Quaternary are presented in this study. The Lošinj Channel is a drowned karst basin filled with sediments. A multi-proxy analysis of two sediment cores (LK-12 and LK-15) recovered from water depths of 62 and 64 m was conducted. We used magnetic susceptibility, grain size, mineralogy, XRF core scanning, organic and inorganic carbon, total nitrogen, and paleontological data, supplemented with AMS 14C dating results and high-resolution seismic data, to reconstruct the infill history of the Lošinj basin during the Late Pleistocene and Holocene. Our findings include the first detailed description of the presumed Marine Isotope Stage (MIS) 5a marine sediment succession along the eastern Adriatic coast. Deposition in the brackish-to-freshwater lacustrine body (Lošinj paleolake) occurred during MIS 3. Sea level lowstand that followed caused the formation of environmental conditions typical of a karst polje. The post-Last Glacial Maximum (LGM) sea level rise led to the establishment of a brackish marine lake with seawater seepage through the karstified sill at 13.7 cal kyr B.P. The transition to the present-day marine conditions commenced at 10.5 cal kyr B.P. Paleoenvironmental changes in the investigated area can be linked to the presence of a sill at −50 m depth that separates the Lošinj basin from the Kvarnerić Bay. The sill depth determines the isolation or inundation of the investigated basin in response to the changes in sea level. Paleoenvironments reacted sensitively to these changes, and therefore, the study area represents an ideal setting to track regional sea level and climate variabilty. •A paleoenvironmental sedimentary record has been preserved in a silled karst basin in the eastern Adriatic.•Sedimentary successions alternated in the karst basin due to the Late Quaternary sea level fluctuations and sill depth.•The karst basin was occupied by marine and lake environments and karst poljes probably since MIS 5a.•The first sedimentary evidence of an isolated lacustrine MIS 3 environment in the Adriatic Sea is reported.