ENVIRONMENTAL CHANGES IN THE BOIANO INTRAMONTANE BASIN (MOLISE, ITALY) SINCE THE TIMES OF ANCIENT BOVIANUM (IVTH CENTURY BC)

Abstract

The ancient Samnitic and Roman towns of Bovianum, located at the base of the northern slope of the Matese Mountains and partially extending within one of the most depressed sectors of the Boiano intramontane basin, were strongly influenced by historical palaeoenvironmental changes mainly due to climatic and man-induced variations and subordinately to the effects of historical seismicity. These changes influenced the evolution in time of the urban settlement layout extensions, which shifted alternatively towards the Matese slope and its piedmont area and the plain. In particular the Samnitic-Roman Municipium (IV century B.C.-I century A.C.) was located mainly within the piedmont area and only partially within the plain, while other smaller settlements were founded at the top of the palaeosurfaces of Mt. Crocella and Civita. From the I to the IV century A.C., the Roman Colonia expanded both towards the plain and the slope, thanks to the reclamation of the most depressed sectors of the plain, as well as to slope terracing and buildings, respectively. After the IV century A.C. and up until the XIX-XX century AD, the plain sector was gradually abandoned, while the urban areas were mainly concentrated at the top of the Civita paleosurface and within the piedmont area. Within the last two centuries the plain was newly occupied, conversely the Civita settlement was gradually abandoned. With the intent of investigating the main palaeoenvironmental changes and their causes, an integrated multidisciplinary analysis of the morpho-stratigraphical and historical-archaeological data was carried out. Facies analyses of two core successions, retrieved from the central area of the modern village of Boiano, and a critical review of archaeostratigraphical records of older archaeological excavations, allowed for the identification of 10 archaeostratigraphical units. The sedimentary succession intercepted by the core located at the base of the piedmont area base of the Matese slope was made up of alternating layers of paleosols, debris cone deposits and man-induced fills, the succession coming from the core located in the plain sector, instead, by alternating layers of paleosols and fluvial marshy-deposits. The tephro-stratigraphic data allowed to chronologically constrain the uppermost 7 to 9 m thick portion of the Boiano filling (named Boiano upper fill) to the Later Upper Pleistocene-Holocene. Archaeological data from older excavations and the archaeological remains included in the core successions then allowed to date most of the aggradation and waterlogging phases recognized in the piedmont area and plain sector, respectively. At least three debris cone deposition phases could be recognized which are chronologically constrained prior to the IV century A.C., between the IV century A.C. and the Middle Age and between the XVI and XIX centuries AD, respectively, and can be most likely correlated with the well documented periods of climatic deterioration known as the Iron Age, the Dark Age (IV-IX centuries AD) and the Little Ice Age (XVI-XIX centuries AD), respectively. Likewise debris deposition, as well as waterlogging affected the plain mainly during the above mentioned periods and can be certainly -at least partially -attributed to the mentioned periods of climate deterioration characterized by increased rainfalls and consequent rising of the ground water level. Waterlogging events, however but could have been favored also by tectonic subsidence, caused by the earthquakes which affected the Boiano area during the III-II century B.C. and in 853, 1456 and 1805 AD.