The pedostratigraphic record of a middle Pleistocene continental succession exposed in the Sessano intramountain depression (Italy) is studied in this work. The basin infilling consists of fluvio-lacustrine deposits interlayered with buried soils and volcaniclastic ash layers, that include trachytic/phonolitic pumices identified by SEM-EDS, presumably sourced from Roccamonfina volcano. The basal tephra dates to 438 ka BP (Ar/Ar). The buried soils are characterized by gley (Bg) horizons at the stratigraphic base, intermediate calcic (Bk) horizons and Bss horizons with vertic features, argillic (Bt) horizons at the top. Argillic horizons and ash layers (CBt) show abundant laminated clay coatings (in places alternated with clayey-silt coatings), variably degenerated as observed in thin sections under the optical microscope between crossed polars. Micromorphological observations revealed also the occurrence of Fe-Mn segregations, alternating bleached and illuviated zones, calcite concretions. Clay mineralogy consists of illite, halloysite, smectite, vermiculite and kaolinite. The phyllosilicates suggest seasonally-contrasted moisture regimes rather than prolonged water availability, that conversely favours short-range order clays, probably absent as indicated by low Alo%+0.5 Feo% values. The studied succession records an overall moist environment. Higher water availability is recorded at the base, where hydromorphic features and moderate clay illuviation suggest interstadial conditions (milder phases during a glacial, probably OIS 12). A shift to a drier and cooler environment is testified by CaCO3 concretions and dominance of herbaceous pollen taxa in the intermediate stratigraphic portion, pointing to full glacial conditions of OIS 12. A moisture (and possibly temperature) increase towards likely interglacial climate of subsequent OIS 11 is indicated by abundant clay illuviation and Fe-Mn staining, coupled with very rare/oxidized pollen grains in the upper succession.
Middle Pleistocene paleoenvironmental changes recorded in a pedostratigraphic succession of Sessano (Molise, Italy): a multidisciplinary approach
SCARCIGLIA, Fabio;
2011-01-01
Abstract
The pedostratigraphic record of a middle Pleistocene continental succession exposed in the Sessano intramountain depression (Italy) is studied in this work. The basin infilling consists of fluvio-lacustrine deposits interlayered with buried soils and volcaniclastic ash layers, that include trachytic/phonolitic pumices identified by SEM-EDS, presumably sourced from Roccamonfina volcano. The basal tephra dates to 438 ka BP (Ar/Ar). The buried soils are characterized by gley (Bg) horizons at the stratigraphic base, intermediate calcic (Bk) horizons and Bss horizons with vertic features, argillic (Bt) horizons at the top. Argillic horizons and ash layers (CBt) show abundant laminated clay coatings (in places alternated with clayey-silt coatings), variably degenerated as observed in thin sections under the optical microscope between crossed polars. Micromorphological observations revealed also the occurrence of Fe-Mn segregations, alternating bleached and illuviated zones, calcite concretions. Clay mineralogy consists of illite, halloysite, smectite, vermiculite and kaolinite. The phyllosilicates suggest seasonally-contrasted moisture regimes rather than prolonged water availability, that conversely favours short-range order clays, probably absent as indicated by low Alo%+0.5 Feo% values. The studied succession records an overall moist environment. Higher water availability is recorded at the base, where hydromorphic features and moderate clay illuviation suggest interstadial conditions (milder phases during a glacial, probably OIS 12). A shift to a drier and cooler environment is testified by CaCO3 concretions and dominance of herbaceous pollen taxa in the intermediate stratigraphic portion, pointing to full glacial conditions of OIS 12. A moisture (and possibly temperature) increase towards likely interglacial climate of subsequent OIS 11 is indicated by abundant clay illuviation and Fe-Mn staining, coupled with very rare/oxidized pollen grains in the upper succession.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
