HR: 1340h
AN: GP13A-0022    [Abstracts]
TI: Tracking Pleistocene Environmental Changes in Continental Archives: the Magnetic Record of the Pianico-Sellere Lacustrine Sequence (Northern Italy)
AU: * Rousse, S
EM: Sonia.Rousse@NGU.NO
AF: ETH, Institute of Geophysics, ETH-Honggerberg, Zurich, 8093 Switzerland
AU: * Rousse, S
EM: Sonia.Rousse@NGU.NO
AF: Center for Geodynamics, NGU, Leiv Eirikssons vei 39, Trondheim, 7491 Norway
AU: Keller, L
EM: kellerli@student.ethz.ch
AF: ETH, Institute of Geophysics, ETH-Honggerberg, Zurich, 8093 Switzerland
AU: Hirt, A M
EM: hirt@mag.ig.erdw.ethz.ch
AF: ETH, Institute of Geophysics, ETH-Honggerberg, Zurich, 8093 Switzerland
AU: Ravazzi, C
EM: cesare.ravazzi@idpa.cnr.it
AF: C.N.R., Instituto per la Dinamica dei Processi Ambientali, Sezione di Milano, Unit… di Dalmine, Via Pasubio 3/5, Dalmine, 24044 Italy
AB: Climatic and environmental changes, which occurred during the last two millions years in the complex Alpine settings in Northern Italy, led to the formation of several intra-valley basins, where sediments accumulated. Continuous lacustrine sedimentary successions often developed within these basins, therefore providing high-resolution records of climatic variability. A magneto-mineralogical investigation of the Pleistocene lacustrine succession from Pianico-Sellere in Northern Italy revealed a general relationship between the magnetic parameters and the pollen and sediment records, covering an interglacial-glacial interval. A combination of magnetic parameters was used to interpret environmental conditions at the time of deposition of the lacustrine sediments. The high concentration of diamagnetic minerals combined with a weak signal made the interpretation particularly complex. The diamagnetic phases consist mainly of calcite, dolomite, quartz and clay minerals. The larger ferromagnetic particles (> 30 nm) were found to be mainly consisting of low-coercive minerals (i.e. magnetite, maghemite or greigite), whereas high-coercivity phases (i.e. goethite or hematite) often had grain sizes in the superparamagnetic range. The low-coercive phases displayed a uniform grain size distribution. The magnetic parameters were shown to reflect large-scale variations as well as short scale events. Variations could be correlated with changes in climate, detrital supply, sedimentary regimes or other short-term events. One change in sedimentary regime and its corresponding transition to colder climate may be linked to volcanic activity. The mass susceptibility from periods with a colder climate was controlled by the concentration in ferromagnetic minerals.
DE: 1512 Environmental magnetism
DE: 1540 Rock and mineral magnetism
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 9335 Europe
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005