The loess-paleosol sequence at Monte Netto: a record of climate change in the Upper Pleistocene of the central Po Plain, northern Italy

Purpose At the northern fringe of the Po Plain (northern Italy), several isolated hills exist, corresponding to the top of Late Quaternary anticlines. These hills were thoroughly surveyed for their soils and surficial geology, furnishing detailed archives of the palaeoenvironmental evolution of the area. A new, thick and complex loess-paleosol sequence, resting upon fluvial/fluvioglacial deposits, exposed in a quarry at the top of the Monte Netto hill was studied in detail to elucidate its significance. Materials and methods Highly deformed fluvial and fluvioglacial deposits, probably of Middle Pleistocene age, are exposed in a clay pit at Monte Netto, underneath a 2- to 4-m-thick loess-paleosol sequence. A geopedological, sedimentological and micropedological investigation of the sequence shows a distinctive difference between the B horizons forming the sequence, while luminescence and radiocarbon age determinations and the occurrence of Palaeolithic lithic assemblages elucidate the chronology of the sequence. Results and discussion The pedosedimentary sequence consists of several loess layers showing different degrees of alteration; loess deposition and weathering occurred, according to optically stimulated luminescence (OSL) and AMS-14C dating as well as archaeological materials, during the Upper Pleistocene. The lower part of the section consists of strongly weathered colluvial sediments overlying fluvial and fluvioglacial sediments. A tentative model of the exposed profiles involves the burial of the anticline, which forms the core of the hill, by loess strata since Marine Isotopic Stage (MIS) 4 and their subsequent weathering (and truncation) during subsequent interstadials. The degree of weathering of buried B horizons increases from the top of the sequence toward the bottom, suggesting a progressive decrease in the intensity of pedogenesis. Finally, the highly rubified paleosol at the top of the hill is regarded as a buried polygenetic soil or a vetusol, developed near the surface since the Middle Pleistocene. Conclusions The palaeopedological, geochronological and geoarchaeological analyses permit to define the phases and steps of development of the Monte Netto pedosedimentary sequence; the lower part of the sequence is dated to the Mid-Pleistocene, whereas loess accumulation occurred between MIS 4 and MIS 2. Moreover, analyses help to clarify the climatic and environmental context of alternating glacial and interstadial phases, during which the sediments where deposited, deformed and weathered

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Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44628/1/10803_2005_Article_BF01537729.pd

Integrated chronological control on an archaeologically significant Pleistocene river terrace sequence: the Thames-Medway, eastern Essex, England

Late Middle Pleistocene Thames-Medway deposits in eastern Essex comprise both large expanses of Palaeolithic artefact-bearing river sands/gravels and deep channels infilled with thick sequences of fossiliferous fine-grained estuarine sediments that yield valuable palaeoenvironmental information. Until recently, chronological control on these deposits was limited to terrace stratigraphy and limited amino-acid racemisation (AAR) determinations. Recent developments in both this and optically stimulated luminescence (OSL) dating make them potentially powerful tools for improving the chronological control on such sequences. This paper reports new AAR analyses and initial OSL dating from the deposits in this region. These results will help with ongoing investigation of patterns of early human settlement. Using AAR, the attribution by previous workers of the interglacial channel deposits to both MIS 11 (Tillingham Clay) and MIS 9 (Rochford and Shoeburyness Clays) is reinforced. Where there are direct stratigraphic relationships between AAR and OSL as with the Cudmore Grove and Rochford Clays and associated gravels, they agree well. Where OSL dating is the only technique available, it seems to replicate well, but must be treated with caution since there are relatively few aliquots. It is suggested on the basis of this initial OSL dating that the gravel deposits date from MIS 8 (Rochford and Cudmore Grove Gravels) and potentially also MIS 6 (Dammer Wick and Barling Gravels). However, the archaeological evidence from the Barling Gravel and the suggested correlations between this sequence and upstream Thames terraces conflict with this latter age estimate and suggest that it may need more investigation

Efeito de lesões produzidas por ácido kaínico no hipocampo de ratos sobre a fosforilação e iminoconteudo da GFAP

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Efeito do lítio sobre a memória e a morfologia de células neuronais de ratos adultos

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Phosphodiesteratic breakdown of endogenous polyphosphoinositides in nerve ending membranes

When a membrane preparation, obtained by freezing and thawing nerve endings labeled by preincubation with 32Pi, is incubated in the presence of millimolar Ca2+, there is a rapid and selective loss of label from the polyphosphoinositides and a concomitant increase in labeled inositol di- and triphosphates recovered. When the membranes are not prelabeled and are exposed to [[gamma]-32P]ATP under similar conditions, phosphatidate labeling is enhanced, indicating increased availability of diacylglycerol. These observations provide evidence for the presence of membrane-bound, Ca2+-stimulated phosphodiesterase activity (phospholipase C) acting on endogenous polyphosphoinositides. The implications of these findings are discussed in respect to the "phosphatidylinositol" cycle.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25217/1/0000657.pd