The Brunhes/Matuyama boundary and magnetic parameters related to climatic changes in Quaternary sediments of Argentina |
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| Affiliation: | 1. CIC-LEMIT, República Argentina, Calle 52 e/121 y 122, 1900 La Plata, Provincia de Buenos Aires, Argentina;2. Department of Earth and Environmental Sciences, LMU, 80333 Munich, Germany;1. Department of Anatomical Sciences and Neurobiology, University of Louisville, Louisville, KY 40202, USA;2. Research Associate, Division of Paleontology, American Museum of Natural History, New York, NY 10024-5192, USA;3. Division of Paleontology, American Museum of Natural History, New York, NY 10024-5192, USA;1. Department of Anthropology, University of Oregon, Eugene, OR 97403-1218, USA;2. Department of Archeology and Heritage Studies, School of Humanities, University of Dar es Salaam, P.O. Box 35050, Tanzania;3. Senckenberg Centre for Human Evolution and Palaeoenvironment at Tübingen, and Institute for Archaeological Sciences, Eberhard Karls Universität Tübingen, 72070 Tübingen, Germany;4. School of Anthropology, University of Arizona, Tucson, AZ 85721, USA;5. Earth and Planetary Sciences, University of California, Santa Cruz, CA 95064, USA;6. Geothe Universität, Seismayerstr, 7060323 Frankfurt am Main, Germany;7. Paleoanthropology, Department of Geosciences, and Senckenberg Centre for Human Evolution and Palaeoenvironment, Eberhard Karls Universität Tübingen, 72070 Tübingen, Germany;1. Key Laboratory of Crustal Dynamics, Institute of Crustal Dynamics, China Earthquake Administration, Beijing, China;2. Institute of Earthquake Engineering for Jiangsu Province, Nanjing, China;1. Research School of Earth Sciences, Australian National University, Building 142 Mills Road, Canberra, ACT 2601, Australia;2. Research School of Physics and Engineering, Australian National University, Building 60, Canberra, ACT 2601, Australia;3. Geosciences, Queensland Museum, 122 Gerler Road, Hendra, Queensland 4011, Australia;4. Subdepartment of Evolution and Development, Uppsala University, Norbyvägen 18A, 752 36 Uppsala, Sweden;5. Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China;6. CAS Center for Excellence in Life and Paleoenvironment, Beijing 100044, China |
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| Abstract: | Rock magnetic properties have been measured in a loess–paleosol sequence in the Gorina Quarry, which previously have been suggested to contain records of the Brunhes and part of the Matuyama polarity chrons. Lowest susceptibility values (below 50 × 10?8 m3/kg) are generally related to intensive weathered horizons, whereas highest values are obtained in loess layers (250 × 10?8 m3/kg) as a result of the greater ferromagnetic content in the parent material. The frequency-dependent part of susceptibility ranges between 0.5% and 6.8%; the higher value was obtained in B horizons of paleosols, which can be attributed to superparamagnetic contributions. Hysteresis loops indicate that the differences in ferrimagnetic and paramagnetic content in the sequence reflect the degree of pedogenesis. The same conclusion can be drawn with isothermal remanent magnetization. This point is relevant for determining past climatic changes because the wind-blown titanomagnetites from Cordillera de Los Andes during glacial periods were altered during interglacial periods. The mode of pedogenesis appears not only to control such alterations but also to produce other magnetic minerals. |
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