Notes on the ephemeral lake of Le Piane, near Isernia (Molise, Central Italy)

Abstract

Some trenches observed in the Le Piane area, NE of Isernia, at an height of approximately 456 m, have allowed to find the presence of lacustrine sediments deposited on the bed of an ephemeral lake. This lake has been present at least in two periods, previous to 4020±80 years BP the first one, more recent than 1560+70 years BP, the second. The lacustrine and alluvial sediments and the soils, has allowed to recognize the climatic and environmental evolution of the area. In particular, the formation of the ephemeral lake seems caused by the damming of its outlet by means of the sediments of an alluvial fan; its desappearance can be attributed to the erosion of the sill, caused by the same outlet, when the alluvial sedimentation on the Tremoricci fan ceased or reduced drastically. We recognized two phases of strong sediment load, more recent than 4020+80 years BP and 1560±70 years BP, produced by seasonal streams flowing to the Le Piane area, during two periods of morphological instability. The environmental variations correspond, also for their chronology, with those found in others places of the Central Apennines, in particular in the Abruzzi Apennines.