lunedì 27 febbraio 2012

MIDDLE AND LATE PLEISTOCENE GLACIATIONS IN THE CAMPO FELICE BASIN


The Quaternary Research journal homepage: www.elsevier.com/locate/ygres
Research made by Carlo Giraudi, Giulia Bodrato, Marianna Ricci Lucchi, Nicola Cipriani. Igor M. Villa, Biagio Giazzio, Giovanni M. Zuppi.
Campo Felice view - foto by Fabrizio Soldati
The present article refers to research conducted in the tectonic-kars depression of Campo Felice in the central Apennines (Italy), in which glacial, alluvional and lacustrine sediments have been preserved. Stratigraphic interpretations of sediments underlying in Campo Felice Plain are based on evidence obtained from nine continous-core boreholes.
The boreholes reach a dept of 120 m and provide evidence of five sedimentation cycles separated by erosion surfaces. Each cycle is interpreted as an initial response to mainly warm stage, characterized by low-energy alluvial and colluvial deposition, pedogenesis, and limited episodes of marsh formation. In turn, a mainly cold stage follows during which a lake formed, and glaciers developed and expanded, leading to deposition of glacial and fluvioglacial deposits. The chronological framework is established by eleven accelerator mass spectrometer C ages and three Ar-Ar ages on leucites from interbedded tephra layers. These age determination indicate five glacial advantages that respectively occurred during marine oxygen isotope stages.
The Apennine chain, which forms the backbone of the Italian peninsula, extends in a NNW-SSE direction between latitudes 44°40'N and 37°57'N is surrounded on three sides by the Mediterranean Sea. The northeast slope of the higher peak (Gran Sasso, 2912 m) supports the Calderone Glacier. This glacier currently is experiencing major ablation (Giraudi, 2005).
The mountain chains of the central and western Mediterranean basins have been studied relatively little from the viewpoint of glacial traces prior to the last glacial maximum (LGM).
The Campo Felice Plain is a small plain located in a closed tectonic-karst basin surrounded by Meso-Cenozoic limestone ridges (Bosi and Manfredini, 1967; Accordi et al. 1986). The plain occurs at altitudes between about 1520 and 1600m. Thick lake sediments bordered by deposits of glacial, fluvioglacial, alluvial, detrital and aeolian origin occur in the lowest portions of Campo Felice. Some small ponors act as water outflows (Giraudi, 1998, 2001).
The tectonic-karst depression of Campo Felice is surrounded by mountains consisting completely of carbonate rocks. The depression contains a sedimentological record of past glaciations which are hard to date by means of surficial expressions. Stratigraphic examination of the sediments underlying the Campo Felice Plain was undertaken from information provided by nine continuous-core boreholes. These boreholes contain evidence representing five sedimentation cycles.
Each cycle involves an initial sedimentaion of low energy fluvial, colluvial and marsh deposits, separated by modest erosion surfaces. The sediments are pedogenically altered and are something very rich in organic matter. The sediments also include reworked volcanic minerals. The sedimentation of non-calcareous deposits took place in periods characterized by phases of arboreal exphansion. The geomorphic and sedimentation processes that occurred durigng the Holocene indicate a similar environmental evolution of this type. The non-calcareous sediments in each of the cycles are overlain by mainly silty-clayey lacustrine deposits of high carbonate composition and extremely low organic matter content. In the marginal area of the plain, the lacustrine deposits of the last four cycles are interfingered with the sandy gravel sediments. Each cycle has thus been interpreted as a succession of a prevalently warm stage, characterized by the absence of any widespread lake development although limited episodes of small lakes or marsh formation may have occurred. In turn, a prevalenthly cold stage followed, during which a lake formed in conjunction with the development and expansion of the glaciers. The composite chronology of the Campo Felice sediments supports the recognition of five glacial advantages.
This work has been carried out as part of the CNR's Special Project "Lacustrine Sedimentation-Palaeoenvironment-Palaeoclimate".
Campo Felice general view
We thank Elsevier from which we draw some parts of this article. Our aim is to promote knowledge of our territory even turning to foreign countries whose tourists could enjoy the unspoilt beauty of Campo Felice.

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