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Mljet Island ; Palaeolimnological reconstruction of the Veliko Jezero Lake

Our findings and conclusions regarding lake development, based mostly on the geochemical and mineralogical data, are similar to those of Wunsam et al. (1999). The sediment sequence starts with a palaeosol sediment interlayered with thick Neapolitan Yellow Tuff tephra (14.6 ka BP). Based on heavy mineral analyses, parent material for paleosoil is derived from aeolian sands deposited on the SE part of the Island mixed with minor influence from recent soils (Fig. 8). During the Holocene sea level rise, a salt marsh was formed which existed for approximately 2 ka after which the lake started to form. In the first stage the lake was shallow, slightly brackish with a limited marine influence, represented in the core by the interval from 345 to 305 cm. In the second stage, the lake became more influenced by marine waters, probably due to the rising sea level which led to an increased connection between sea and lake through highly permeable karst, which also led to the deepening of the lake. In this stage aragonite precipitates and some diatom species (N. oblonga), together with the increase in some redox sensitive elements, indicates possible anoxic conditions (interval from 300-275 cm). In the third stage, a massive fresh water intrusion occurred. After the deposition of the Mercato tephra (tephra at 250 cm), during stage four, an increase in salinity was observed over a short interval (from 250-222 cm). Conversely, in stage five a decrease in salinity occurred as a result of freshwater inflow (interval from 222-185cm). In the last stage 6, the marine influence is increasing as a result of sea water intrusion through the Soline channel, initially only during high tides (the interval from 185-123 cm). Finally, a marine intrusion occurred through the Soline channel at a core depth of 123 cm (3.3 ka BP) and the lake ceased to exist. At first, after the sea water intrusion oxic sediment conditions are met, but soon, due to the isolation of the basin, sediment conditions started to be suboxic to anoxic.

Mljet, Veliko jezero, sediments, tephra, Holocene

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