habitat rupestre.pdf - Società Friulana di Archeologia

FLORA IN THE RAVINE AREAM. MasiPuglia, ItaliaRavines in the Ionian Murge are very common. These areerosive formations in the Apulian carbonate basement, whichwere formed since a million years, when more rains occurred.The rock substratum of the Murgia is constituted of carbonaterocks, which were originated through the sedimentationof calcium carbonate in a sea environment. The most ancientrock is the “Limestone of Altamura”, constituted of microscopicand compact sediments from the Late Cretaceous:this is testified by the presence of fossil Rudists, which livedin flat and scarcely deep seabed and in tropical conditions.In the Cenozoic Era, the sea transgressions, the uplift of thecarbonate basement and the climatic variations dried up theMediterranean Sea and created geographic corridors, as theBalkans.From the Pliocene (about two millions years ago) to one millionyears ago, the Murgia partially sunk (subsidence), and afurther sedimentation occurred. In this sea environment, fewmeters deep and in mild climatic conditions, the rests of organismsliving on the seabed and the fragments of limestonefrom the erosion of emerging areas accumulated.The sedimentary pile is carbonate as the “limestone of Altamura”,but the sediments are coarse, and the diagenesiscreated a porous and friable rock, the so called “ravine limestone”.This rock allowed the formation of natural prehistor-ic shelters, which were successively enlarged to create newspaces, niches and openings (windows, chimneys, cisternsconducts).Since the Quaternary (Pleistocene) the climate cooled down,with at least four cold periods and oscillations of the sealevel. During the last glaciation, the sea regression restoredthe bridges of emerging lands which linked Apulia to theBalkans for thousands years.Since one million years, the sea regression has caused theemersion of the present Murgia, with its superficial layer of“ravine limestone”: constituted of a more recent, soft andfriable rock, it rests on the deeper layers of “limestone ofAltamura”.The rain waters eroded the different layers of limestone sedimentsalong the steeper lines; the deep and wide erosionshave determined the characteristic geomorphologic structureof the land. As time passed by, watercourses have eroded thesuperficial limestone and the deeper limestone of Altamura.The whole palaeogeographic and palaeoclimatic events gaveorigin to the geomorphologic structure of a ravine environment,which conditioned the actual phytogeographical structure;the vegetation of the typical Mediterranean shrublandand the Garrigue of the Murgian tableland was forged andbroadened.Fig. 1 Panoramic view of Gravina di Riggio, Grottaglie (TA).183volumeRicerca_OK_2012-11-15.indd 183 16/11/2012 15:03:10