Naslov
The Holocene paleolimnology of Lake Vrana (Biograd) and implications to its formation

Autori
Ilijanić, NIkolina ; Miko, Slobodan ; Hasan, Ozren ; Bakrač Koraljka ; Hajek-Tadesse, Valentina ; Banak, Adriano

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

Izvornik
Knjiga sažetaka 3. znanstveni skup Geologija kvartara u Hrvatskoj s međunarodnim sudjelovanjem / - Zagreb : Hrvatska akademija znanosti i umjetnosti (HAZU), 2013, 26-26

Skup
3. znanstveni skup Geologija kvartara u H rvatskoj s međunarodnim sudjelovanjem

Mjesto i datum
Zagreb, Hrvatska, 21.03.2013. - 23.03.2013

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
Paleolimnology; lake formation; paleoclimate reconstruction

Sažetak
Paleolimnology uses the physical, chemical and biological informations contained in lake sediments to assess past environmental characteristics. Based on multiproxy investigations of an 1100 cm long sediment core from Lake Vrana and a 765 cm core from the Pirovac bay marine lagoon, a reconstruction of palaeoenvironmental dynamics in the lake catchment and the influence of sea level rise during the Holocene, is proposed. Evidences from mineralogy, geochemistry, nutrients (C and N), palynology, macrofossils and ostracods fauna show that Lake Vrana experienced changes during the Holocene. Lake Vrana is the largest natural lake in Croatia and is situated near the Adriatic Sea (1 km). It is characterized by very shallow water, sometimes intruded by sea with chloride contents reaching 4500 mg/l, with an average depth of 2, 4 m. It is mostly supplied by the rainfall, freshwater stream input and also by the groundwater springs in its catchment. It is connected to the sea through the channel Prosika, excavated in the late 19th century to drain the water from the adjacent Vransko polje, used for agriculture and vineyards. This channel today presents danger to the lake fauna as sea water enters the lake through it during low lake levels and high tides. Lake salinity also increases due to decrease in rainfall, which allows the intrusion of the salt water through permeable limestone rocks. The bottom of Lake Vrana lies about 3 m bellow the present sea level, while Pirovac bay has its maximum depth about 25 m in the middle, while on the edges it is surrounded by the sea ridges with the max depth of 6, 5 m. Pirovac bay was a lake that coexisted with Vrana lake during the early Holocene and was flooded by the rising sea. Ostracod freshwater fauna is introduced by Heterocypris salina and Ilyocypris bradyi in the deeper sediments in Pirovac bay, followed by abrupt domination of marine fauna and ostracod species Pterygocythereis jonesii on 264-265 cm, dated on cal 6590 +/-40 BP. In Lake Vrana sequence from freshwater to brackish ostracods can be tracked. Such ostracod assamblage, together with macrofossils, dominated by Bithynia tentaculata and Lymnea peregra, constrain the paleohydrology of the lake. According to pollen analysis (mixed conifer-deciduous forests dominated by Pinus, and open areas with herbaceous xerophytic communities and grasses), the oldest sediments (885-1100 cm) could belong to Preboreal and Boreal period. The middle part belongs to Atlantic period while vegetation was dominated by Mediterranean oak. Younger sediments could reveal population from Roman period until present times. These multiproxy analyses combined with chronologies based on AMS 14C dates and suggest that the intrusion of the sea could have occurred around 7 kyr BP. During this period the lake evolved from an open freshwater lake to a more saline lake. Mineralogy of the lake sediments was compared to the rocks in the catchment area to find a possible source. Catchment area consists of carbonate rocks, flysch deposits, loess like deposits and a thin soil cover of terra rossa and cambisols. There are strong erosion processes within the catchment, followed by the strong winds (eolian erosion), which contribute material to the lake. Dominant terrigenous input is characterized by detrital quartz, feldspars and clay minerals. Calcite and aragonite are dominant endogenic minerals within lake sediments. These multiproxy studies provide an important new environmental and paleoclimate reconstruction for the Holocene of the middle Eastern Adriatic coastal area.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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