The present work wants to investigate geomorphological evolution and soil erosion rate in two clayey small catchments, whose main element of correlation is represented by the contemporary starting of the last phase of deepening of the hydrographic network, attributed at the end of Late Pleistocene. The former sample area (area 1, about 60 km2) is that of the Formone river, left tributary of the Orcia river (Tuscany-Italy), where detailed geomorphological analyses concerned only its final sector. More in particular, the study area is represented by a 5 km-long sector of valley (up to the confluence with the Orcia), about 12 km2 wide and elevation ranging between 300 and 600 m a.s.l., characterized by the presence of several orders of alluvial and erosion terraces, covering a mainly Pliocene clayey bedrock. The structural setting is characterized by mainly sub-horizontal strata, thinny stratified and slightly fractured. Small catchments of few square kilometers of extension (both from the right and the left side) flow directly to the main valley. The latter area (area 2) is constituted by a portion of the Imera settentrionale river basin (Sicily), about 42 km2 wide and characterized by a mainly clayey Miocene bedrock, locally overlaid by Late Miocene sandy-conglomeratic units. Radiometric dating have been carried out on charcoal material coming from three samples of soils, two from area 1 and one from area 2. In the area 1, two samples placed roughly at the top of a recent fluvial terrace (about 15 meters above the thalweg) and on the watershed of a tributary small catchment, gave an age of 2780±40 yrs B.P. and 14050±70 yrs B.P. respectively. On the other hand, the dating of the sample collected in the Imera settentrionale river basin, placed on the watershed of a tributary small catchment, is still in progress. Although the chronological datum is not available, basing on geomorphological correlations between surfaces considered coevals, it seems realistic to hypothesize a temporal evolution of the hydrographic network analogous to that of the area 1. These chronological constraints allowed to reconstruct, by means of topographic reconstructions and GIS analyses, the geomorphological evolution of the two sample areas and to estimate the soil erosion rate for the time interval considered (last 15,000 years). The results obtained are consistent with the data available in literature both for the Tyrrhenian side of central Italy and for the inland Italy and, more in particular, confirmed that very intense erosion processes occurred as a consequence the Holocene climatic improvement. Moreover, the results are perfectly comparable with those observed by the same authors in the peri-Adriatic belt of central Italy.

Geomorphological evolution and soil erosion rate in two clayey small catchments of central and island Italy during the last 15,000 years.

ARINGOLI, Domenico;MATERAZZI, Marco;PAMBIANCHI, Gilberto
2010-01-01

Abstract

The present work wants to investigate geomorphological evolution and soil erosion rate in two clayey small catchments, whose main element of correlation is represented by the contemporary starting of the last phase of deepening of the hydrographic network, attributed at the end of Late Pleistocene. The former sample area (area 1, about 60 km2) is that of the Formone river, left tributary of the Orcia river (Tuscany-Italy), where detailed geomorphological analyses concerned only its final sector. More in particular, the study area is represented by a 5 km-long sector of valley (up to the confluence with the Orcia), about 12 km2 wide and elevation ranging between 300 and 600 m a.s.l., characterized by the presence of several orders of alluvial and erosion terraces, covering a mainly Pliocene clayey bedrock. The structural setting is characterized by mainly sub-horizontal strata, thinny stratified and slightly fractured. Small catchments of few square kilometers of extension (both from the right and the left side) flow directly to the main valley. The latter area (area 2) is constituted by a portion of the Imera settentrionale river basin (Sicily), about 42 km2 wide and characterized by a mainly clayey Miocene bedrock, locally overlaid by Late Miocene sandy-conglomeratic units. Radiometric dating have been carried out on charcoal material coming from three samples of soils, two from area 1 and one from area 2. In the area 1, two samples placed roughly at the top of a recent fluvial terrace (about 15 meters above the thalweg) and on the watershed of a tributary small catchment, gave an age of 2780±40 yrs B.P. and 14050±70 yrs B.P. respectively. On the other hand, the dating of the sample collected in the Imera settentrionale river basin, placed on the watershed of a tributary small catchment, is still in progress. Although the chronological datum is not available, basing on geomorphological correlations between surfaces considered coevals, it seems realistic to hypothesize a temporal evolution of the hydrographic network analogous to that of the area 1. These chronological constraints allowed to reconstruct, by means of topographic reconstructions and GIS analyses, the geomorphological evolution of the two sample areas and to estimate the soil erosion rate for the time interval considered (last 15,000 years). The results obtained are consistent with the data available in literature both for the Tyrrhenian side of central Italy and for the inland Italy and, more in particular, confirmed that very intense erosion processes occurred as a consequence the Holocene climatic improvement. Moreover, the results are perfectly comparable with those observed by the same authors in the peri-Adriatic belt of central Italy.
2010
9785895751619
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11581/213919
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