engleski

Late Quaternary geomorphological evolution of the Prokljan Lake on the Eastern Adriatic coast (Dalmatia)

Freshwater carbonates (tufa deposits) form during interglacial warm periods and can be used as a paleoclimatic and paleoenvironmental indicators. Tufa deposits are typical features of the Dinaric karst of Croatia. In the Prokljan Lake, which is a part of the Krka River estuary located on the eastern Adriatic coast, several submerged tufa barriers were recognized. With the Holocene transgression, the Prokljan Lake drowned and the Krka River estuary was formed. We used detailed multibeam survey (MBES bathymetry and MBES backscatter), side scan sonar and subbottom acoustics to characterize the submerged paleolandscapes of the Prokljan Lake and the upper part of the estuary. The bathymetry and side scan data indicate that the submerged paleolandscape consist of partly burried tufa barriers, small lakes and carbonate mounds. Tufa barriers and carbonate mounds are distinguished on the backscatter data as strong reflectors. Ground truth data was provided in the form of 36 grab samples and seafloor images. Geomorphological and geological classification of the seabed were produced. Sediment samples were analyzed for grain size, magnetic susceptibility, mineral composition (XRD), bulk density and carbon and nitrogen concentrations. Five sediment cores were taken in the lake area and together with the high- resolution seismic profiles, enabled the identification of three sedimentary units: fluvial, brackish and marine. Tufa barriers were probably formed during the transition from the Pleistocene into the Holocene and had a predominant influence on the Holocene flooding of the Krka River canyon. Based on their geomorphology and depth in the Prokljan Lake, the flooding of the Krka River canyon started at approx. 9300 y BP. This multiproxy study allowed a reconstruction of the seabed geomorphology and paleoenvironmental evolution of the Prokljan Lake. The obtained data is also valuable for predicting the estuary response to the future sea level rise.

Krka estaury ; geomorphology ; acoustic geophysic methods ; tufa barriers ; Holocene

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