History of the Salpi Lagoon-sabhka (Manfredonia Gulf, Italy)

Abstract

The Flandrian sea level rise causad the development of sand coasta/ ridges between Gargano Promontory and Murge Highplain. This narrow and long strip delimited a wide coastal lagoon characterized by several connections lo the sea, called the "Salpi lagoon" by the Authors. This is the first attempt fa analyse the geological, geochemical and archaeological evidence in order to reconstruct the evolulion af the Neolithic lagoon-sabhka. Several drillings and agricultural trenches have demonstrated that, during the early and middle Neolithic ages, the lagoon was characterized by typical species of the euryhaline and eurythermal biocoenoses in brackish water (Cerastoderma glaucum, Abra ovata, Hydrobia gr. stagnorum) or of the superficial muddy sands in sheltered areas (Loripes lacteus, Abra ovata and Pirenella conica). These brackish species are replaced towards land with species becoming more sensitive to salinity such as Chara, Planorbis planorbis and Varvata piscinalis. Certainly, the lagoon has existed till 5,470 ± 40 yr BP (AMS date on a shelf of Cerastoderma glaucum). Subsequently. at the beginning of the late Neolithic age the lagoon evolved into a marginaI marine saline pan resembling a sabhka. Gypsum in the form of nodules, isolated crystals, clusters of crystals (rosettes and desert rose) has been found. Mineralogical, geochemical and morphological features of gypsum and the associate evaporite deposits have given a climatological and environmental indication of this period. Gypsum morphologies vary under distinct hydrologieal regimes and they are characteristic of the different subenvironments of the sabhka and therefore they can be used as a sensitive interpretative tool for evaporative palaeoenvironments. In particular the areas corresponding to saline pan, saline mud flat (blocky prisms and blocky hemipyramids morphologies) and sandy seaward side of the saline pan (discoidal hemipyramids morphology: desert roses) of the Salpi sabhka have been recognized. The CF values during the seawater evaporation indicate that solutions were variously diluted wilh inflow waters poor in sodium, rich in calcium and wilh a Mg/K ratio higher than the value found in the present day seawater of the Gulf of Manfredonia. The gypsum deposition suggests an arid or semi-arid climate and, therefore, fhe contribution of fresh water into sabhka was poor. On the other hand, in the Tavoliere p/ain, confined by higher land on three sides, the present climatic conditions tend to be a semiarid continental type, maximized in the central part and coastal zone of the plain (BS according to Köppen Climatic Classilication, 1923, or DdB'd, according to Thorthwaite & Mather, 1957). The proof of this aridification and duration is also given by the analyses of the people and culture of the coastal Tavoliere sites. The late Neolithic records a technological and socioeconomic involution, as pointed out by the skilled permanent farmer who changed into a nomadic shepherd. The settlements were progressively abandoned between the end of fhe 4th millennium BC., through almost all the 3rd millennium BC, uncal. The abandonment of the Tavoliere settlements coincided with the beginning of the Scaloria Cave cutt of the waters. It is reasonable to place the end of the most arid phase when settlements were repopulated and, therefore, starting from the Bronze Age (Coppa Nevigata site, is dated at 3540 ± 60 BP).