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Submerged landscapes of the eastern Adriatic Sea

Submerged paleolandscapes of the Eastern Adriatic Sea host a large diversity of landscapes containing records of long-term paleoenvironmental change, climate, and sea level. The Croatian coastal region (Fig 1.) is a part of Maritime Dinaric Alps (termed also as the Dalmatian coast) which and coincides with the Mesozoic Adriatic Carbonate Platform (AdCP). To date, there is a very limited knowledge concerning the submerged karst paleolandscapes of the eastern Adriatic coast and the Late Quaternary sedimentary sequences along the eastern part of the Mid Adriatic Deep (MAD). Multidisciplinary research by application of the high-resolution geophysical surveys (multibeam, side-scan sonar and subbottom profiler), in combination with sedimentological, petrophysical, geochemical (trace elements and isotopes), micropaleontological allowed an unique insight to the geomorphology and processes that shaped the Eastern Adriatic seafloor. The submerged Late Pleistocene and Holocene environments that occur include isolation basins (karst poljes, dolines, lakes), lagoons, deltas, estuaries, submarine channels and shelf slopes. In the central part of the Adriatic these different environments compose an integrated system ; thus, they can’t be analysed separately. The existing gaps in understanding of the climatic and environmental changes, including sea-level related landscape changes and their interplay during the last Late Quaternary eustatic cycle. 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 (Brunović et al., 2020), Kvarnerić, Novigradsko more and Karinsko more (Hasan et al.2020), Veliko jezero on Mljet Island (Razum et al., 2020), Telašćica bay, Pirovački zaljev bay and Koločepski kanal. The LGM lakes of Lošinjski kanal and Valun bay were flooded at onset of the Holocene (Brunović et al., 2020), 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 (Razum et al., 2020). Flooding of the Kornati channel basin began 10, 2 ky cal. BP. Based on detailed high resolution geophysical surveys it was possible to determine the thickness of Holocene sediments and the timing of drowning of the Krka river channel from its early Holocene mouth at Zlarin Island and the formation of the estuary 7500 years ago. The Pleistocene landscape of the Jadro river consists of an incised valley in Eocene flysch beds in Kaštela bay and a wide Pleistocene floodplain in the channel between the islands of Čiovo, Šolta and Brač, draining into the southern part of the MAD. Due to the low sediment yield from the Dinaric karst (Milliman et al., 2016) the sediment influx in basins during the Holocene the thickness of these deposits is in the range of less than < 3m. High-resolution seismic data were interpreted to reveal the structure of the late Pleistocene to Holocene deposits and determine the location of the paleoshorelines. Offshore Žirje Island it was possible to identify submerged high sea cliffs and marine abrasion platforms formed during standstills indicating paleoshorlines along the eastern slopes of the MAD, with relative sea level of: − 25m, − 55, -70m to-75, − 95, − 120 and − 135 m for MIS 5d, MIS 5b, MIS 3, MIS 4, and MIS 2 respectively. The geophysical and core data, as well as paleoecological reconstructions suggest that the route along the eastern Adriatic Sea was a land surface and habitable by at least about 11, 000 years ago. The research was funded by the Croatian Science Foundation through projects LoLADRIA (HRZZ-IP- 2013-11-9419) and project QMAD (HRZZ-IP-2019-04- 8505).

submerged landscapes, marine sediments, lake sediments, Late Quaternary, sea-level rise

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