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Abstract:

Deep inside the Frasassi cave complex in the foreland fold and thrust belt of the northeastern Apennines (central Italy), the remains of hundreds of eels (Anguilla anguilla) are found scattered on the shores of phreatic lakes up to 5 m above the water table. These sub-fossil eels, and the speleothemic calcite encrusting some of them, offer the rare opportunity for radiocarbon dating leading to a geochronologic scale for the shorelines, which record the lowering of the water table and the uplifting of the Frasassi area through the Holocene. The lakes' margins are contoured by white microcrystalline calcite rinds, which also record the progressive lowering of the water table. Detailed surveying revealed that these rinds are no longer horizontal, but slightly tilted toward ENE. Thus these rinds record a recent history not only of uplifting, but also of tectonic tilting of this region. The results of our analyses indicate that the Apennine area around Frasassi has been rising, for the past 8000 years, at a mean rate of 0.6 mm/yr, which is consistent with uplifting rates estimated from the step topography arrangement of interglacial fluvial terraces for the whole Quaternary period in this region. This work demonstrates how an interdisciplinary approach to speleologic research can provide a significant contribution to active tectonic studies.