Naslov
SUBMERGED KARST RIVER CHANNELS OF ZRMANJA, CETINA, NERETVA AND KOLOČEP RIVERS IN THE EASTERN ADRIATIC COAST (CROATIA)

Autori
Hasan, Ozren ; Miko, Slobodan ; Brunović, Dea ; Ilijanić, Nikolina ; Papatheodorou, George ; Geraga, Maria ; Christodoulou, Dimitris ; Čurić, Matej ; Meštrović, Ivor ; Šolaja, Dragana ; Bakašun, Marko

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Book of abstracts / Novak, Matevž ; Rman, Nina - Ljubljana : Geološki zavod Slovenije, 2018, 45-45

ISBN
978-961-6498-60-9

Skup
5. slovenski geološki kongres

Mjesto i datum
Velenje, Slovenija, 03.10.2018. - 05.10.2018

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
submerged landscapes, river valleys, eastern Adriatic coast, Holocene

Sažetak
Vast areas of the Adriatic shelf were exposed during the postglacial low relative sea level (RSL), enabling formation of lakes and river channels. After Last Glacial Maximum (LGM) those areas were consecutively submerged during Holocene transgression (Correggiari et al., 1996). Here we present research of karst rivers Zrmanja, Cetina, Neretva and Koločep located along the Eastern Adriatic Coast. Well preserved submerged river channels and their floodplains are detected using high resolution acoustic geophysical methods coupled with bathymetric data and compared to RSL curve for the Adriatic region (Lambeck et al., 2011, Correggiari et al., 1996). Seismic data for Zrmanja River shows river channels incised into Pleistocene clastic rocks exposed during the early Holocene. Larger channel flowing from Karin Sea into Novigrad Sea joined Zrmanja and continued into Velebit Channel. Numerous river channels visible in profiles point to the existence of braided river system. As the RSL rose, marine sediments overlie fluvial and terrestrial sediments after 11440 BP (Hasan, 2017). Marine sediments are acoustically homogenous and 9 - 16 m thick. RSL rise caused a formation of 27 m thick alluvial fan in the present Zrmanja River mouth. Present floodplain of Neretva River extends over 10 km. According to geophysical data, similar floodplain formed some 60 km to the W, between islands Hvar, Šćedro and Korčula. Islands consist of Cretaceous limestones that create acoustic basement of the sedimentary basin. Basement is overlain by fluvial sediments with parallel to subparallel stratified reflectors onlapping on the basin edges. According to RSL curve (Lambeck et al., 2011), fluvial sedimentation began approximately 14000 BP at 85 m b.s.l. After the basin was filled up to 70 m b.s.l., Neretva floodplain widened to Korčula Island, creating a 10 km wide floodplain. Major erosional surface is visible, as Neretva River eroded older fluvial sediments. Two meters of marine sediments overlie fluvial sediments. Present Cetina river mouth is located at the exit from the canyon in the town of Omiš. Seismic data reveals that river did not flow in NW direction as a continuation of today’s flow but created a channel along the coast in SSE direction. During the postglacial period, river eroded flysch sequences creating over 10 m deep and 350 m wide channel. Due to a Holocene RSL rise, river channel was infilled with fluvial sediments. As sediments were deposited in the channel, Cetina created a 3 km wide floodplain. Fluvial sediments are overlain by 3-5 m thick marine sediment sequence. Koločep Channel geophysical data reveals nine acoustic units (marine, lake or fluvial). During the LGM intensive erosion occurred in the central part of the basin. Sediments were transported by torrents, whose springs still exist today as vruljas at depths of 45-50 m b.s.l. Torrents formed a river flowing through Veliki vratnik passage in SW direction towards Mljet Island, and continued along it’s coastline towards the west. Eastern bank of the “Koločep” River was bounded by eolian sand bar. River ceased to exist as RSL rose to approximately 50 m b.s.l. Part of the submerged channel between Pelješac and Mljet Islands is well defined on bathymetry data.

Izvorni jezik
Engleski

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