Pliocene Atlantic molluscan assemblages from the Mondego Basin (Portugal): Age and palaeoceanographic implications |
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| Authors: | Carlos Marques da Silva Bernard Landau Rosa Domènech Jordi Martinell |
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| Institution: | 1. IDL-FCGUL, Faculdade de Ciências de Lisboa, Ed. C3.3.22, Campo Grande, 1749-016, Portugal;2. CIMA-FCT, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal;3. Departamento de Geología y Geoquímica, Universidad Autónoma de Madrid, 28049-Madrid, Spain;4. Laboratório Nacional de Energia e Geologia (LNEG), Apartado 7586, Alfragide, 2721-866, Portugal;5. Departamento de Geodinámica y Paleontología, Facultad de Ciencias Experimentales, Campus de El Carmen, Avda. Tres de Marzo, 21071-Huelva, Spain;1. Natural History Museum of Denmark, University of Copenhagen, 1350 Copenhagen, Denmark;2. Departamento de Geologia and Instituto Dom Luiz, Universidade de Lisboa, Lisboa, Portugal;3. Departamento de Geologia, Universidade de Trás-os-Montes e Alto Douro, Vila Real, Portugal;4. Centro de Geociências, Universidade de Coimbra, Coimbra, Portugal;5. GeoArch, Unit 6, Block C, Western Industrial Estate, Caerphilly, Wales, United Kingdom;1. Departamento de Biología, Universidad de Las Palmas de Gran Canaria (ULPGC), 35017 Las Palmas de Gran Canaria, Canary Islands, Spain;2. College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331-5503, USA;3. Instituto de Oceanografía y Cambio Global (IOCAG), Universidad de Las Palmas de Gran Canaria (ULPGC), 35017 Las Palmas de Gran Canaria, Canary Islands, Spain;1. Università degli Studi di Milano, Dipartimento di Scienze della Terra ‘A. Desio’, via Mangiagalli 34, Milano, 20133, Italy;2. British Geological Survey, Keyworth, Nottingham, NG12 5GG, UK;3. NERC Isotope Geosciences Facilities, British Geological Survey, Keyworth, Nottingham NG12 5GG, UK;4. Centre for Environmental Geochemistry, School of Geography, University of Nottingham, Nottingham NG7 2RD, UK;5. Università ‘G. D''Annunzio’, Dipartimento di Ingegneria e Geologia, via dei Vestini 31, Chieti Scalo, 66013, Italy;6. Parco Regionale dello Stirone e del Piacenziano, Loc. Scipione Ponte 1, Salsomaggiore Terme, 43039, Italy;1. Department of Geosciences, Williams College, Williamstown, MA 01267, USA;2. Division of Biological Sciences, University of the Philippines in the Visayas, Miagao, Iloilo 5023, Philippines;3. Departamento de Ciencias de la Tierra, Facultad de Ciencias Experimentales, Universidad de Huelva, Campus de El Carmen, Avda. 3 de Marzo, s/n, 21071 Huelva, Spain;4. Faculdade de Ciências da Universidade de Lisboa, Departamento de Geologia e Instituto Dom Luiz de geociências, Campo Grande, 1749-016 Lisboa, Portugal;5. Paleontología, Departamento de Biología, ULPGC, 35017 Las Palmas de Gran Canaria, Spain;1. Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany;2. Department of Biological, Geological and Environmental Sciences, University of Bologna, Piazza Porta San Donato 1, 40126 Bologna, Italy;3. Institute of Geosciences, Johannes Gutenberg University Mainz, J.-J.-Becher-Weg 21, 55128 Mainz, Germany;4. Helmholtz Institute for Functional Marine Biodiversity at the University of Oldenburg, Carl-von-Ossietzky-Str. 9 -11, 26129 Oldenburg, Germany |
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| Abstract: | The Pliocene molluscan assemblage from the Mondego Basin (Portugal, Western Iberia) plays a particularly important role in the understanding of the palaeobiogeography of Neogene–Quaternary molluscs of the Atlantic Frontage of Europe and the western Mediterranean. The importance of these Portuguese molluscan deposits is stressed, as it is the only assemblage representative of the southern portion of the Pliocene French–Iberian biogeographical Province.The Pliocene marine fossiliferous deposits of the Mondego Basin (central-west Portugal) are dated using their nannofossil and molluscan assemblages, as well as Strontium dating. The results suggest a late Zanclean to early Piacenzian age. Chronologically they are equivalent to the Mediterranean Pliocene Molluscan Unit 1 (MPMU1). However, due to the more northern geographical location of the Mondego Basin assemblages, their molluscan content is closer to that of MPMU2 than to that of MPMU1 in the Mediterranean.The presence of a stock of thermophilic taxa in the Mondego assemblage, no longer existent in European waters, enabled us to suggest a palaeoenvironmental reconstruction for mid-Pliocene SSTs in the region. We put forward the hypothesis that the SSTs at the latitude of Mondego, during late Zanclean to early Piacenzian, would be characterized by a yearly SST pattern analogous to that of present-day Cape Blanc (West Africa). Consequently, whilst subtropical conditions existed in the Atlantic Zanclean to mid-Piacenzian at Mondego latitude in the Mediterranean fully tropical conditions prevailed at that time. The Mondego SST estimates correlate with those estimated for MPMU2 in the Mediterranean.The global palaeoenvironmental reconstruction of mid-Pliocene SSTs in the PRISM2 Project suggests, for western Iberia, at Mondego latitude, an August SST of about 23 °C, and a February temperature of about 17 to 18 °C. Our hypothesis suggests similar August SST differing in only half a degree Celsius (23.5 vs. 23 °C) and February SSTs slightly higher (19 vs. 17–18 °C). |
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