engleski

Sedimentology and stratigraphy of Vela Cave - preliminary results (island Korčula, Croatia)

Location and geological setting. Vela Cave (Vela spila in original) is located in the hinterland of Vela Luka town, 130 m a.s.l. This single-chambered cave of Vela Spila today represents only the remnant of once a large system. It has been developed within a fault zone in upper Cretaceous limestones, which are thin to thick bedded and gently dip (20-25°) northwards. Sedimentology. First detailed sediment logging has been conducted in 2002, on two earlier excavated archaeological sections. Section-1 is 5.5m high and 2m wide and Section-2 is 4m high and 6m wide. Samples were taken for grain-size analysis, petrographical and chemical analyses. Deposits are in general very poorly sorted and are represented by alternating clayey sands or gravels and open-work rock debris layers with more or less infiltrated silt or sand. At several levels there are accumulations of cobble-size rock debris. Fossil bone debris occasionally represents over 30% of bulk sample. Several layers are composed only of bones and rock debris and very little infiltrated clayey silt or sand. Carbonate content is very low in fine-grained layers, commonly 5 - 20%, rarely 30-50%, while modal analyses showed domination of amphibole-pyroxene-epidote-quartz mineral association. In Section-1 there is a volcanic ash layer, 2-10 cm thick, composed of 95% alterated volcanic glass shards. Preliminary insight of the Vela Cave sediment sequences indicates on very complex depositional history. Fossil fauna. Preliminary analysis of vertebrate fossil content through sections shows changes in human economy and hunting strategies. Transition between periods are very good defined, providing biostratigraphic zones that correspond with stratigraphy and radiocarbon dating. Stratigraphy. During earlier archaeological investigation of Vela Cave, samples of bones and charcoal have been taken for radiocarbon dating. C14 dating enabled division of four cultural periods Epigravettian, Early Mesolithic, Late Mesolithic and Neolithic which correspond to Late Pleistocene and Holocene. One of the archaeological layers in Section-1 yielded calibrated age of 13.500-11.900 BC (VERA-2346). Immediately above this layer there is the volcanic ash layer. It was defined by the X-ray diffraction analysis of global sample, chemical analyses and microsonde. The quantitative analyses of chemical composition (microsonde) performed on vulcanoclastic particles separated from the global sample showed undoubtable compatibility with pyroclastic products dispersed over Mediterranean by explosive eruption of Napolitan Yellow Tuff (NYT) in Campi Flegrei 14.000 years ago. The NYT layer of Vela Cave was determined in this region for the first time. Thus, it represents an excellent regional chronostratigraphic marker and could probably be traced in other locations.

Vela Cave; island of Korčula; sedimentology; stratigraphy; dating

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