Chronological assessment and palaeoenvironmental implications of the speleothems from the caves at the edge of Fucino Plain (Abruzzo, central Italy)

Abstract

Radiometric and archaeologic data suggest that the speleothems in the natural caves along the carbonate rim of Fucino plain belong to four distinct depositional episodes. The oldest group of features were those from Continenza cave, yielding the U/Th age of 10.5±0.8 Kyr statistically indistinguishable from the 14C reading, measured on charcoal, of 9.7±0.10 Kyr BP (calendar age: 10.9-5-10.6 Kyr BP). In the same cave, within a cultural deposit of Neolithic Age, a further group of speleothems was recognized. The age of these latter, besides the archaeological evidence, has been placed from 6.9 to 6.2 Kyr BP (overall calendar time span: 7.8+6.9 Kyr BP) by several 14C datings run on strictly associated charcoal, thus in fair agreement with the mean age of 8.3±1.0 Kyr provided by U/Th dating of two speleothems. The subsequent phase of speleothems generation, recorded at Ciccio Felice cave, was mainly referred to the Iron Age on the basis of archaeologic data. Finally, a critical evaluation of historical, palaeohydrological and field data strongly support that the speleothems from Cunicoli di Claudio deposited later than the 4th-6th century. By considering the fluctuations of the water level of the former Fucino lake it results that three out of four episodes of speleothems formation took place during significant highstands of the water level. The flowstone dated at some 9.7±0.1 Kyr BP formed during a time span of almost steady lowstand of Fucino lake level. This flowstone could have formed during a humid climatic pulse that did not affect the Fucino lake level because of a coinciding enhanced evaporation due to some rising of the temperature.