Paleopedological studies of littoral deposits provide potentially useful tools for understanding the response of the sedimentary systems to tectonics (i.e. uplift and subsidence) versus climate and sea- level changes occurred along the Mediterranean coasts, during the late Quaternary. An example is reported from the Baratti Gulf cliff section formed during the last interglacial cycle. The upper Pleistocene-Holocene succession of the Baratti Gulf exhibits significant vertical changes from marine to continental deposits, marked by several erosional discontinuities. Four stacked transgressive units capped by buried weathering profiles have been recognized (Cortemiglia et a!., 1983). These transgressions, recorded by foreshore to upper shoreface deposits (Sarti eta!., 2005), should correspond to four sea-level high-stands correlated with MIS 5c, MIS Sa, MIS 3 and the transition of MIS 2-1, respectively (Mauz, 1999). A continental deposit of aeolian origin with an oligotypical mollusc assemblage separates the younger two transgressive units from the older two. Tentatively this layer has been correlated with MIS 4 (Sarti et a!., 2005). A detailed geopedological survey (mainly micromorphological) was conducted on selected vertical profiles, in order to improve the stratigraphic and depositional history of the Baratti Gulf deposits. Fieldbased profile descriptions of paleosols evidenced that they are incomplete (absence of topsoil horizons), and deeply truncated by erosion. Moreover, the paleosols show a different degree of pedogenic expression, progressively more intense from younger to older paleosols. Their major pedogenic features and formative processes occurred polycyclically, attesting distinct and relict pedogenetic phases not in equilibrium with the present- day environmental condition. Each paleosols developed in a moist, warm and forest environment, and at the end of each pedogenetic cycle a decline of the vegetation cover associated to a climatic deterioration caused a general retrogradation of the soil properties (polygenetic soil evolution). The effect of "glacial phases" is mostly reflected in erosion and soil truncation processes recorded by the bounding surfaces at the top of the transgressive cycles. Following the previous considerations, the transgressive events probably took place at the onset of the warm-humid interglacial periods while the subsequent subaerial exposure and pedogenesis of the marine-coastal deposits represent the closing events of the interglacial cycles. The paleosols of the Baratti Gulf cliff section record regional and global climatic events providing information into the tectono-sedimentary and climate evolution of the area during the late Pleistocene. This study may support the knowledge of the variability of the most important climatic events during last interglacial soil evolution on the Mediterranean area.
Paleoclimatic significance of the last interglacial paleosols of the Baratti Gulf cliff section (southern Tuscany, Italy)
SARTI, GIOVANNI;ZANCHETTA, GIOVANNI;
2010-01-01
Abstract
Paleopedological studies of littoral deposits provide potentially useful tools for understanding the response of the sedimentary systems to tectonics (i.e. uplift and subsidence) versus climate and sea- level changes occurred along the Mediterranean coasts, during the late Quaternary. An example is reported from the Baratti Gulf cliff section formed during the last interglacial cycle. The upper Pleistocene-Holocene succession of the Baratti Gulf exhibits significant vertical changes from marine to continental deposits, marked by several erosional discontinuities. Four stacked transgressive units capped by buried weathering profiles have been recognized (Cortemiglia et a!., 1983). These transgressions, recorded by foreshore to upper shoreface deposits (Sarti eta!., 2005), should correspond to four sea-level high-stands correlated with MIS 5c, MIS Sa, MIS 3 and the transition of MIS 2-1, respectively (Mauz, 1999). A continental deposit of aeolian origin with an oligotypical mollusc assemblage separates the younger two transgressive units from the older two. Tentatively this layer has been correlated with MIS 4 (Sarti et a!., 2005). A detailed geopedological survey (mainly micromorphological) was conducted on selected vertical profiles, in order to improve the stratigraphic and depositional history of the Baratti Gulf deposits. Fieldbased profile descriptions of paleosols evidenced that they are incomplete (absence of topsoil horizons), and deeply truncated by erosion. Moreover, the paleosols show a different degree of pedogenic expression, progressively more intense from younger to older paleosols. Their major pedogenic features and formative processes occurred polycyclically, attesting distinct and relict pedogenetic phases not in equilibrium with the present- day environmental condition. Each paleosols developed in a moist, warm and forest environment, and at the end of each pedogenetic cycle a decline of the vegetation cover associated to a climatic deterioration caused a general retrogradation of the soil properties (polygenetic soil evolution). The effect of "glacial phases" is mostly reflected in erosion and soil truncation processes recorded by the bounding surfaces at the top of the transgressive cycles. Following the previous considerations, the transgressive events probably took place at the onset of the warm-humid interglacial periods while the subsequent subaerial exposure and pedogenesis of the marine-coastal deposits represent the closing events of the interglacial cycles. The paleosols of the Baratti Gulf cliff section record regional and global climatic events providing information into the tectono-sedimentary and climate evolution of the area during the late Pleistocene. This study may support the knowledge of the variability of the most important climatic events during last interglacial soil evolution on the Mediterranean area.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
