Variaioni climatico-ambientali nell'area mediterranea durante il periodo storico: evidenze geoarcheologiche di cicliche crisi ambientali tipo "effetto serra"

Abstract

An original systematic study on sediments of historical age from various Italian and Egyptian geoarchaeoiogica! sites was carried out Studied sediments were mostly eolian sand, paleosols, alluvium and colluvium deposits and calcareous crusts. The environmental conditions controlling accumulation of each type of sediment have been reconstructed. On the basis of the stratigraphical reconstruction of historical sediments, environmental physical changes and related climatic variations have been identified. Data so far acquired with direct investigations indicates that remarkable climatic-environmentai changes have occurred in the Mediterranean basin between 25° and 45° N lat. since about 2,500 years BP. Geological clues for warm-arid (eolianites, calcareous crusts) and cold-humid (flood deposits, paleosols) periods at different latitudes may be taken as quantitative evidence of the climatic conditions during sedimetation, and testify to cyclic environmental crises of 100 to 150 years duration, each crisis having a return time of about 1000 years. The effect of a climatic phase on environment is different depending on latitude: for instance, during a period of warm-arid environmental crisis in Italy, favourable environmental conditions might occur in Central and North Europe and in the Dead Sea area, as well as during a cold-humid crisis, North Africa might be under favourable environmental conditions.