Geomorphological aspects, lithology and pollen analysis of Holocene sediments of Agordo lake (eastern Dolomiti)

Abstract

: A geomorphological outline of Agordo valley pointed out many terraces produced by subsequent phases of erosion. The highest of this terraces is probably ascribabfe to stage 22 of the oxigen isotope curve (850 ka BP). The Agordo lake was formed by damming the Cordevole stream, 5800 years BP The following evolution and the filling up of the lake (lasted in all 500 years) are due to the development of Missiaga-Bordtna conoid and to the strong contribution of the main river and of all tributaries. The successive reduction of the width of Cordevole plain, subsequent of the lowering of the lake bed, originated three orders of terraces. The granulomere analysis of some samples allowed the classification of lacustrine sediments as sandy silts, silts and clayey silts, while the diffrattometric analysis singled out the mineralogical composition of the sediments. The vegetation of the surroundings of the lake was reconstructed by means of fossil pollen analysis and consisted of a well developed and dense coniferous forest, dominated by Picea for all the time stretch recorded by the pollen diagram. Pollen analysis of present time moss polsters gives a useful tool for comparison with the past vegetation recorded in the sediments of the lake.