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Last glacial environments in S Italy as recorded in a sediment-paleosol sequence, lacustrine and marine sediments

Daniela Sauer1, Achim Brauer2, Riyad Al-Sharif3, Sandra Heibili4, Helmut Brückner5, Fabio Scarciglia6, Alexandra Hilgers5, Thomas Scholten4, Karl Stahr3
1 Institute of Geography, Dresden University of Technology, Helmholtzstr. 10, D-01069 Dresden, Germany
2 Section Climate Dynamics and Landscape Evolution, Deutsches GeoForschungsZentrum GFZ, Helmholtz Center Potsdam, Telegrafenberg, D-14473 Potsdam, Germany
3 Institute of Soil Science and Land Evaluation, Hohenheim University, Emil-Wolff-Str. 27, D-70599 Stuttgart, Germany
4 Institute of Geography, University of Tübingen, Rümelinstraße 19-23, D-72070 Tübingen, Germany
5 Institute of Geography, University of Cologne, Albertus-Magnus-Platz, D-50923 Cologne, Germany
6 Earth Sciences Department, University of Calabria, Via Pietro Bucci – Cubo 15B, I-87036 Arcavacata di Rende (CS), Italy

Invited Talk 7.3 in Freie Themen

19.09.2012, 09:10-09:30, H8

During fieldwork on soil development on marine terraces in Calabria (South Italy) we discovered an alluvial fan overlying a marine terrace near Lazzaro. The terrace consists of a several meters thick gravel body and is generally attributed to MIS 5.5 (e.g. Dumas and Raffy, 2006). ESR dating of a well-preserved colony of Mytilus sp., embedded in the terrace body at 7 m depth, resulted in an age of 109.6 ± 10.8 ka. Due to the strong tectonic uplift of the area (1.3 m ka-1) the alluvial fan has been dissected by a creek so that its internal structure has been exposed, exhibiting the alternation of several sedimentation and soil formation phases. The paleosols are mainly characterized by accumulation of organic matter, bioturbation features and secondary carbonates. They represent Chernozem- and Phaeozem-like soils that very likely formed in steppe to forest steppe environments under continental climatic conditions.  

The same environmental conditions that are reflected in the Lazzaro paleosols have been reconstructed based on pollen records from lake sediment cores. Italy has a number of lakes with high-resolution Late-Pleistocene to Holocene paleo-climate and paleo-vegetation archives. A high-resolution Late Pleistocene lacustrine record close to the Lazzaro area is from Lago Grande di Monticchio. Its pollen record indicates temperate deciduous forest from 87.98 to 82.73 ka; vegetation fluctuation from 82.73 to 59.00 ka, then Artemisia steppe; alternation between steppe (stadials) and wooded steppe (interstadials) from 59.00 to 25.90 ka; and again open steppe from 25.90 to 14.30 ka (Last Glacial Maximum) (Watts et al., 1996; Allen et al., 2000; Brauer et al., 2007).

Organic matter of the two uppermost Lazzaro paleosols has been 14C-dated. Their humus is 26.7-28.7 and 28.8-30.3 cal ka old. Thus, the formation of these soils falls into the period for which the lacustrine record indicates an alternation between steppe and wooded steppe (Fig. 1). It is still an open question whether the sedimentation that interrupted the ecologically stable times of soil formation was activated by fluctuations in climate and vegetation cover or by tectonics. The fact that pedogenesis falls into a period of frequent environmental oscillations suggests that the phases of sedimentation are to a certain degree driven by changes in climate and vegetation cover. More data on additional soil-sediment profiles are required to check if paleopedological, lacustrine and marine records can be correlated to obtain an integral reconstruction of paleo-climate, -vegetation,
-geomorphodynamics and -pedogenesis in the region.

The soils were analyzed for texture, soil organic carbon (SOC), carbonates, Fed, total elemental composition (XFA on fused discs) and micromorphology. Fed values reflect pedogenetic cycles in the alluvial fan more clearly than SOC contents, which are not as high in the paleosols as might be expected according to their dark color. Strong carbonate accumulation occurs in the lowermost part of the profile, between 513 and 693 cm. Its thickness and in parts very massive character suggest that enrichment through slope water has contributed to the carbonate accumulation.

Another valuable paleo-record for South Italy is the core GNS84-C106 obtained from the Gulf of Salerno. Di Donato et al. (2008) reconstructed the following climatic conditions, based on foraminifera and pollen, for the period of formation of the Lazzaro paleosols:

- relative maximum in MAT (12-13 °C) and MAP (600 mm) around 30 ka BP;

- slight decrease of MAT (11-12 °C) and MAP (580-590 mm) until ~27.5 ka BP;

- relative maximum in MAT (14-15 °C) and MAP (~820 mm) at ~25 ka BP.

We conclude that Chernozem- and Phaeozem-like soils developed during the last glacial period in South Italy in steppe and forest steppe environments. These soils have been preserved only where they had been buried before the climate shifted again to Mediterranean type. Otherwise, organic matter was rapidly decomposed and the soils turned into reddish-brown Mediterranean soils.

Financial support by the German Research Foundation (DFG) is gratefully acknowledged (research grant SA 1033/2-1).

Fig. 1: Left: Upper section of the Monticchio pollen record (from Brauer et al., 2007, PNAS 104 (2): 450-455; overall record goes back to MIS 6); right: The two uppermost Lazzaro paleosols. Dates are calibrated 14C ages of soil organic matter, using CALIB Version 6.1.0 radiocarbon calibration program (Stuiver & Reimer, 2011).
Fig. 1: Left: Upper section of the Monticchio pollen record (from Brauer et al., 2007, PNAS 104 (2): 450-455; overall record goes back to MIS 6); right: The two uppermost Lazzaro paleosols. Dates are calibrated 14C ages of soil organic matter, using CALIB Version 6.1.0 radiocarbon calibration program (Stuiver & Reimer, 2011).



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Letzte Änderung 25.07.2012