Geology and geochronology of type Chasicoan (late Miocene) mammal-bearing deposits of Buenos Aires (Argentina) |
| |
| Institution: | 1. CONICET-FCEN-UNLPAM, Avenida Uruguay 151, 6300, Santa Rosa, La Pampa, Argentina;2. Department of Geological Sciences, Brown University, Providence, RI 02912-1846, USA;3. CIC-BA, Museo de la Plata, Paseo del Bosque s/n, 1900 La Plata, Argentina;4. Graduate School of Oceanography, University of Rhode Island, RI, USA;5. 210 Petrie Hall, Department of Geology, Auburn University Auburn, AL 36849, USA;1. CONICET, Departamento de Geología Universidad Nacional del Sur, San Juan 670, 8000 Bahía Blanca, Buenos Aires, Argentina;2. Facultad de Ciencias Exactas y Naturales, Universidad Nacional de La Pampa, Avenida Uruguay 151, 6300 Santa Rosa, La Pampa, Argentina;3. CIC, División Paleontología Vertebrados, Museo de La Plata, Paseo del Bosque s/n, 1900 La Plata, Argentina;4. Museo Municipal de Ciencias Naturales “Carlos Darwin”, Urquiza 123, 8109 Punta Alta, Argentina;1. Laboratorio de Paleontología de Vertebrados, Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción (CICYTTP-CONICET- UADER-Provincia de Entre Ríos), Materi y España, E3105BWA, Diamante, Entre Ríos, Argentina;2. Facultad de Ciencias Exactas y Naturales, Universidad Nacional de La Pampa, Uruguay 151, 6300, Santa Rosa, Argentina;3. CONICET, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de La Pampa, Uruguay 151, 6300, Santa Rosa, Argentina;4. Paleontología, IANIGLA, CCT-CONICET Mendoza, Avda. Ruiz Leal s/n, 5500 Mendoza, Argentina;1. Institute of Geochemistry, Mineralogy and Mineral Resources, Charles University, Albertov 6, 128 43, Prague 2, Czechia;2. Czech Geological Survey, Geologická 6, 152 00, Prague 5, Czechia;3. Department of Geology, Faculty of Science, University of Namibia, Private Bag, 13301, Windhoek, Namibia;1. Institut für Erd- & Umweltwissenschaften, Universität Potsdam, 14476 Potsdam, Germany;2. Institut für Geowissenschaften, Goethe Universität Frankfurt, 60438 Frankfurt/Main, Germany;3. Senckenberg Biodiversität & Klima Forschungszentrum (BiK-F), 60325 Frankfurt/Main, Germany;4. Departmento de Geología, Universidad Nacional de Salta, 4400, Salta, Argentina;5. Department of Earth Science and Earth Research Institute, University of California, Santa Barbara, CA 93106, USA;6. Earth & Environmental Systems Institute and Department of Geosciences, Penn State University, University Park, PA 16802, USA;7. Institut für Geowissenschaften, Universität Heidelberg, 69120 Heidelberg, Germany;8. Department of Geological Sciences, University of Texas, Austin, TX 78712, USA |
| |
| Abstract: | The late Miocene Chasicoan mammal-bearing deposits exposed along the lower reach of Arroyo Chasicó are composed of cross-bedded, very fine sandstones interpreted as a channel-bar deposit (lithofacies association 1) grading upward into sandy siltstones (lithofacies association 2), probably accumulated through relatively high-density flows in a marginal channel and/or floodplain environment. The uppermost levels are dominantly composed of mudstones and sandy siltstones (lithofacies association 3) deposited in generally low-energy conditions of sedimentation in a swampy environment. Several paleosols (lithofacies P) are present, indicating that the succession was the result of episodic fluvial sedimentation. The volcaniclastic composition (primary and reworked pyroclastics) suggests that the fluvial system drained the westward region by the Andean foothills. An impact event dated at 9.23 ± 0.09 Ma and recorded by impact glasses (escorias) during deposition of lithofacies Sp enables the fine tuning of the chronology of the deposits through high-resolution magnetostratigraphic profiles, which indicate that the approximately 9.4 m thick succession recorded by lithofacies association 1 and 2 accumulated between 9.43 and 9.07 Ma. The lithofacial arrangement of the succession does not support the current differentiation of the Arroyo Chasicó Formation into the Vivero and Las Barrancas members. Previous biostratigraphic interpretations contain significant inconsistencies in light of the revised stratigraphy proposed here. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
