engleski

Late Quaternary evolution of lakes and submerged paleo-karst on the Eastern Adriatic

The Croatian coastal region is a part of Maritime Dinaric Alps which and coincides with the Adriatic Carbonate Platform (AdCP). The some of the coastal karst depressions developed into larger lakes, although not numerous (<10) these Holocene lakes are quite evenly distributed along the coast from Istria (Ćepić polje) in the north to the Baćina lakes and the Neretva river delta in the southern part of the Croatian Adriatic coast. Due to the permeable nature of karst some of the coastal lakes never developed as freshwater bodies (Veliko jezero, Mljet Isalnd). Sediment core records show a tight correlation between sea level rise and lake formation during early Holocene. Terrestrial sequences in the Croatian coastal karst regions are often incomplete due to erosion or nondeposition. Therefore, accumulation of lake and marine sediments offer complete and well-dated archives spanning most of the Holocene. Since a part of the karstified AdCP is drowned and its palaeo- dolines, depressions of variable size, as indicated by seismic data, contain up to 900 m of well stratified sediments (Kvarnerić bay, N. Adriatic) allowing insight to earlier periods of the Quarternary. Generally the larger karst depressions lie between the islands at present day water depths of - 40 m to -90 m. These geomorphological and sedimentological landscapes contain archives of climate and have experienced repeated relative sea-level cycles during the Quaternary. The submerged landscapes sediments that have experienced repeated relative sea-level cycles. Between the last interglacial (MIS 5.5, 125 kyr BP) and Holocene (10 kyr cal BP) periods the present submerged depressions of Kvarnerić bay (-80 to -90 m below present day sea level), Valun bay and Lošinjski kanal due to submerged sills at various sea depths and the amounts of fresh water feeding the basins during the glacial low-stand favored development shallow glacial freshwater lakes. The ongoing LoLADRIA (Lost Lake Landscapes of the Eastern Adriatic Shelf) project is using 5-10 m long sediment cores collected from 17 sites (7 lacustrine and 12 marine) along eastern Adriatic coast. These sediments allowed multyproxy reconstructions of the Holocene millennial- and centennial-scale environmental change. A landscape reconstruction of selected sites, based on high resolution geophysical methods, allowed insight to the preserved changes of marine sediments, submerged landscapes and the morphology of paleo-lakes in Lošinjski kanal, Kvarnerić, Novigradsko more and Karinsko more, Pirovački zaljev and Koločepski kanal. The thickness of paleo-lake sediments varies from up to 2 m in Karinsko more to more 10 m in Lošinjski kanal. Details of environmental change are extracted for the integrating mineralogy, lithostratigraphy, biostratigraphy (pollen, foraminifers, ostracodes, tephrostraigraphy and chemical stratigraphy, with well-defined 14C AMS radiocarbon chronologies. Most of the present day lakes along eastern Adriatic coast formed during the early Holocene (Bokanjačko blato, Vransko jezero near Biograd, Veliko jezero- Mljet). Vransko jezero on the Island of Cres survived from the Pleistocene as probably did lake Crniševo (Baćina lakes). The LGM lakes of Lošinjski kanal and Valun bay were flooded at onset of the Holocene, while the Pleistocene lake in Pirovac bay was flooded by the sea 8 ky cal. BP and Veliko jezero on Mljet Island at 3 ky cal. BP. The Holocene lakes of Čepić polje, Bokanjačko blato, Nadinsko blato, Vrgoračko polje and most of the lakes of the Neretva river delta ceased to exist during the early 20th century due to human intervention to gain agricultural lands. This work is supported by Croatian Science Fund Project LoLADRIA (Project no. 9419) and the EMODnet Geology II project funded by EC DG Mare.

Late Pleistocene ; Holocene ; submerged coast ; lake sediments ; sea level rise

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