Recenti esplorazioni speleosubacquee nel golfo di Kotor (Montenegro)


Abstract


It
Nel corso del 2005 sono state organizzate tre spedizioni speleosubacquee italo-slovene nel golfo di Kotor (Repubblica Jugoslava del Montenegro). Le immersioni e gli studi eseguiti, nonché i reperti archeologici ritrovati hanno permesso di ricostruire il contesto idrogeologico nel quale si inseriscono le cavità oggetto di esplorazione (Potor, Spilja, Gurdic e Ljuta) e di delineare, nel tempo, l’uso antropico delle stesse.Le cavità sono state oggetto di rilievi accurati e per ciascuna si è cercato di ricostruire il presunto bacino idrogeologico di appartenenza; inoltre con specifiche immersioni nelle zone delle risorgenze a mare si è avuto modo di osservare e documentare le particolari caratteristiche degli ecosistemi subacquei presenti.
En
In 2005 three Italian Slovenian speleological expeditions have been organized in Kotor Gulf (Republic of Montenegro).The studies performed and the cave diving activity allowed to reconstruct the hydrogeological situation of the explored caves (Potor, Spilja, Gurdic and Ljuta). Topographical survey was made in these caves. For each of them the original hydrogeological basin was hypothesized. Moreover, the local ecosystems features were observed and documented in marine resurgence by specific dives. In detail, the Sopot Cave is constituted by a pressure flow tube opening, after a hundred meters, in the sub vertical big chamber: the siphon opens between the blocks. The diving cave system is made by a passage and wells at intervals. Diameter is rarely below 6-8 m, at least in the first part. Rapidly after the entrance, depth settles around -70 m (about -40/50 m in normal conditions water). After a hundred meters a flat-lying passage leads to a narrow between the blocks.The karstic system, which includes Sopot, is relied with an important intermittent submarine spring (sea estavelle), through which one can pass at 30 m depth (in April 2005 – flow 15-20 m3 per second has been estimated) and which is about 300 m from the entrance. During diving exploration of submarines springs, a unique ecosystem has been found, which deserves further study. As a matter of fact, low temperature fresh waters exit, strong mixing of waters, turbidity and poor brightness typical of these sites favours growth in shallow waters (around 15-20 m) of a true "forest" of Gerardia savaglia, with Aplysina aerophoba, Parazoanthus axinellae, Cerianthus membranaceus, Flabellina affinis, and Cratena peregrina. Inside the cavity, in an area of material accumulation, fragments of Venetian ceramics (especially from Venice), datable between the second half of 1500 and the first of 1600, were found. This finding is particularly interesting because it documents of human presence of a cave for water supply at least since XVI century up to recent times. The Spilja spring is located near Risan and represents exsurgence of a karstic complex N-NE of the entrance. The cave is located at the end of a polje, which, in case of flood, is run by an impetuous torrent. The aerial part of the cave is formed by a pressure flow tube with elliptical section two meters high and ten meters large. With the same characteristics, the principal passage continues also in underwater ambiance. In the first trait, sections get lager and go down slowly to -18 m. Gallery then goes up to -3 m and keeps this depth for about 80 m. Then it goes progressively down to -72 m. The Gurdic system is really very complex with an ample front presenting several accesses, starting from Kotor walls. The principal spring (an estavelle in fact) has an easy entrance, facing south, besides the principal road along the fortification walk. The cave (in the part explored in 2005) is exclusively underwater and pours its waters directly into the sea. In summer period, the submarine spring is flood by sea salted waters (sea estavelle). In the initial lake, of great size, fresh and salt waters mix giving the typical halocline effect.

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