SESS 2_16022011_TPR3.pub Il Quaternario Italian Journal of Quaternary Sciences 24, (Abstract AIQUA, Roma 02/2011), Congresso AIQUA Il Quaternario Italiano: conoscenze e prospettive Roma 24 e 25 febbraio 2011 LOESS IN NORTHERN ITALY. NEW INSIGHTS ON DATING, ENVIRONMENT, AND ARCHAEOLOGY Mauro Cremaschi1, Helena Rodnight2, Andrea Zerboni1 & Christoph Spötl2 1Dipartimento di Scienze della Terra “A. Desio”, Università degli Studi di Milano 2Institut für Geologie und Paläontologie, Leopold-Franzens-Universität, Innsbruck Corresponding author: M. Cremaschi ABSTRACT: Cremaschi M. et al., Loess in Northern Italy. New insights on dating, environment, and archaeology. (IT ISSN 0349-3356, 2011) Age, sedimentation, soil forming processes, and geoarchaeological implication of the loess in Northern Italy are discussed on the basis of new OSL dating obtained at several key-sequences in the Apennine margin of the Po Plain and on the base of recent literature. The comparison of field data, soil properties, and luminescence ages offers a new perspective in studying the loess of the Po Plain during the MIS 4 to MIS 2. RIASSUNTO: Cremaschi M. et al., Loess in Italia settentrionale. Nuove informazioni sull’età, l’ambiente e l’archeologia. (IT ISSN 0349-3356, 2011) In questo contributo si discutono l’età, i processi sedimentari, di alterazione e le implicazioni geoarcheologiche del loess in Italia settentrionale, principalmente sulla base di nuove datazioni OSL su alcune sequenze chiave posizionate lungo il margine Appenninico della pianura del Po e di dati editi. Dal confronto tra evidenze di terreno, proprietà dei suoli e datazioni radiometriche emerge una nuova prospettiva di studio per i loess del bacino padano tra il MIS 4 e il MIS 2. Key words: loess, Northern Italy, OSL dating, glacial phase, Mousterian culture. Parole chiave: loess, Italia settentrionale, datazioni OSL, fase glaciale, cultura Mousteriana.  Loess deposits in Northern Italy are widespread, as in most of the circum-Mediterranean regions; they are typical of the Glacial Pleistocene ages (COUDÉ-GAUSSEN, 1990 CREMASCHI, 1990) and are related to poorly vegetated soil surfaces and dry climate (CREMASCHI, 1990). In Northern Italy loess occurs as thin sheets at the top of polygenetic paleosols, with the exception of few stratigraphic sequences (BUSACCA & CREMASCHI, 1998; RELLINI et al., 2009). Furthermore, loess deposits are systematically associated with Middle Palaeolithic archaeological evidence, indicating that the loess belt surrounding the Po plain was densely occupied at that time, representing an ecosystem suitable for human life. Recently, an effort has been made to explore different sources for radiometric dating (CREMASCHI et al., 1987, 1990; FERRARO et al., 2004; MARTINI et al., 2001), which appears essential to face the wide range of questions involved in loess research (sedimentation, weathering, climate change, human behaviour). Radiocarbon dating (Fig. 1) was applied on chernozem-type horizons buried in loess (Val Sorda and Gajum) and in the anthropogenic fill of caves with a windblown silt component (Riparo Tagliente and Grotta di Fumane). Moreover, TL ages were obtained on fire -damaged flint artefacts buried into loess sequences (Ghiardo and Bagaggera sites). All the available ages indicate that the loess sedimentation in Northern Italy begun during the MIS 4 and continued until the late MIS 2. Recent research in the Val Sorda sequence (Fig. 2) proved the suitability of loess for OSL and IRSL dating and provided results consistent with other chronometric indicators (FERRARO, 2009).  This paper presents some recent OSL dates performed on three soil profiles (Fig. 2) developed on loess and placed along the pede-Apennine, at Ghiardo Cave and Cavriago (RE) and at Borgetto (PR). Sampling sites are c. 40 km apart, although they belong to the same geomorphological position, represented by Pleistocene terraces. All profiles show the same sedimentological, pedological and geoarchaeological characteristics: a shallow layer of loess, up to 1 m thick which lies upon fluvial clay. In the loess a Sol Lessive a pseudogley (Haplic Udalf) is developed, displaying the horizons sequum: Ap, E, 2Bt, 2Bc. The underlying fluvial clay (3Bw, 3Ck horizons) has outstanding vertic proprieties and a mukkara-type microrelief. Mousterian artifacts (of Levallois technique) were found at the investigated sites, mostly buried in the 3 Bw and 2Bc horizons; the latter represents the buried topographic surface and the lithological discontinuity where later pedological processes precipitated Fe and Mn hydroxides as nodules and concretions. Eight preliminary OSL dates were obtained, ranging from 47000 to 18000 years and covering 95 - 97 96 Fig. 1, Published radiocarbon, TL, and OSL dating results from several loess sequences located in Northern Italy (references in the text). Datazioni al radiocarbonio, TL e OSL note in letteratura e ottenute in alcune sequenze di loess distribuite in Italia settentrionale (referenze bibliografiche riportate nel testo).  Fig. 2, (a) Stratigraphic section of Val Sorda site, indicating radiocarbon and luminescence dating results (modified, FERRARO, 2009). (b) Stratigraphic section at Cavriago, indicating the sampling points for OSL analyses. (a) La sezione stratigrafica esposta presso la Val Sorda; i risultati di datazioni al radiocarbonio, OSL e IRSL sono indicati (modificata da FERRARO, 2009). (b) La sezione stratigrafica esposta presso Cavriago, con indicati i punti di campionamento per le datazioni OSL. M. Cremaschi et al. 97 Ms. received: Testo ricevuto il the whole chronologic interval between MIS 4 and MIS 2. These results have several consequences: i) they confirm an Upper Pleistocene age for the loess sheets covering the pede-Apennine terraces of the Po valley and allowing a correlation with the loess spread at the southern margin of the Alps (isolated terraces in the northern Po Plain, pede- Alpine terraces, sequences of the Garda moraine system, loess in the Lessini caves); ii) each profile shows a regular, progressive decrease in loess age toward its surface. This is indicative of a persistent accumulation of dust (decanting from the atmosphere). Evidence of syndepositional loess weathering – the development of a slow-rate aggrading cumulic soil – was detected in thin sections by microcharcoals and bioturbation and indicates a steppe environment affected by recurrent fire episodes. The syndepositional pedological features are obscured and partly erased by subsequent Holocene soil forming processes (clay illuviation, shrinking and swelling, hydromorphism; CREMASCHI, 1987, 2008). iii) The chronological difference between the burned flint tools (around 70000-60000 years) and on loess sediments (47000-18000 years) may indicate that Mousterian hunters settled the margin of the Apennine at the beginning of the MIS 4 in suitable environmental conditions, and later left the region, when a severe dry climate prevailed, leading to a stronger loess sedimentation . REFERENCES BUSACCA A. & CREMASCHI M. (1998) - The role of time versus climate in the formation of deep soils of the Apennine fringe of the Po Valley, Italy. 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(2001) - Thermoluminescence (TL) dating of burnt flints: problems, perspectives and some examples of application. Journal of Cultural Heritage, 2, 179-190. RELLINI I., TROMBINO L., FIRPO M. & ROSSI P.M. (2009) - Extending westward the loess basin between the Alps and the Mediterranean region: micromorphological and mineralogical evidences from the northern scope of the Ligurian Alps, Northern Italy. Geografia Fisica e Dinamica Quaternaria, 32, 103-116. January 20, 2011 20 gennaio 2011 Loess in Northern Italy. New insights on dating ...