PROBLEMATIC KARST FILLINGS OF LATE LOWER PLEISTOCENE AGE IN A CAVE OF THE LESSINI MOUNTAINS (VENETIAN FORE ALPS, VERONA)

Abstract

The excavation of a small cave in the Lessini Mountains, north of Verona, allowed a study of an archaeological complex attributable to the Copper Age. A fossiliferous breccia, rich in bones of small mammals and birds has been found below the archaeological levels. During 2005 and 2006, the results of paleontological excavations supervised by Benedetto Sala provided a faunal assemblage correlated to the late Biharian. These excavations stimulated a preliminary study of the geological, geomorphological and morphodynamic context of the cave and its surroundings, in order to understand its genetic context. Particular attention was paid to the breccia, containing numerous small exotic pebbles, mostly 5-12 mm in diameter. We consider three different hypotheses for the provenience of the exotic pebbles: I) they have been transported and displaced in the area by morphodynamic agents, such as ancient glaciers, and/or watercourses II) they derive from a completely eroded geological formation, that has been reworked and deposited in this karst trap, III) they are the result of "ecofacts" caused by birds. All these possible explanations, have some open issues. The “ecofacts” is the most intriguing hypothesis and perhaps the most likely: pebbles could have been transported by birds which use to swallow them to help digestion, then to expel them in boluses or in the excrements. According to this hypothesis, birds could have chosen the cave, or others connected cavities, as nests or as perches. In fact, in the breccia there are bones of large birds of prey, not jet studied. In time, probably, different species of birds have colonized these natural niches, as: vultures, eagles, owls, ravens, etc. So it is very difficult to state what kind of birds could have brought here their preys (the small mammals of which we find the bones), and what kind of birds could have transported the small pebbles. Only further excavations and studies will perhaps allow a full clarification of the processes of site formation.