Toarcian–Aalenian (Early–Middle Jurassic) radiolarian fauna from the Los Molles Formation,Neuquén Basin,Argentina: Taxonomy and paleobiogeographic affinities |
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| Authors: | Karlos Guilherme Diemer Kochhann Simone Baecker-Fauth Ignacio Pujana Ariane Santos da Silveira Gerson Fauth |
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| Institution: | 1. Institute of Petroleum Geology and Geophysics, Siberian Branch of Russian Academy of Sciences, Ac. Koptyg av. 3 Novosibirsk 90, 630090, Russia;2. Departamento de Geología y CEACT, Universidad de Jaén, Campus Las Lagunillas sn, 23009 Jaén, Spain;1. Univ Lyon, Université Claude Bernard Lyon 1, ENS de Lyon, CNRS, UMR 5276 LGL-TPE, F-69622 Villeurbanne, France;2. Sorbonne Universités, UPMC Université Paris 06, UMR 7193, ISTeP, 75005 Paris, France;3. MARE-Marine and Environmental Sciences Centre, Faculty of Sciences and Technology, Department of Earth Sciences, University of Coimbra, Rua Sílvio Lima, 3030-790 Coimbra, Portugal;4. Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen, Denmark;1. Department für Geo- und Umweltwissenschaften, Paläontologie und Geobiologie, Ludwig-Maximilians-Universität, and Bayerische Staatssammlung für Paläontologie und Geologie, Richard-Wagner-Straße 10, 80333 München, Germany;2. Naturmuseum Südtirol, Bindergasse 1, 39100 Bozen/Bolzano, Italy;3. Laboratory of Palaeobotany and Palynology, Utrecht, The Netherlands;4. National Centre for Biodiversity ‘Naturalis’, P.O.Box 9517, 2300 RA Leiden, The Netherlands;1. Key Laboratory for Evolution of Past Life and Environment in Northeast Asia, Ministry of Education, Changchun 130026, Jilin, and Research Center of Palaeontology and Stratigraphy, Jilin University, Changchun 130026, Jilin, China;2. Department of Ecology and Evolutionary Biology, and Natural History Museum and Biodiversity Research Institute, University of Kansas, Lawrence, KS 66045, USA;3. Department für Geo- und Umweltwissenschaften, Paläontologie und Geobiologie, Ludwig-Maximilians-Universität, and Bayerische Staatssammlung für Paläontologie und Geologie, Richard-Wagner-Straße 10, 80333 Munich, Germany;1. Tomsk Polytechnic University, pr. Lenina 30, Tomsk, 634050, Russia;2. Chinggis Khaan Bank, 15 Chinggis Ave., Ulaanbaatar, Mongolia;1. Department of Geosciences, The University of Tulsa, Tulsa, OK 74104, United States;2. Department of Earth and Planetary Sciences, The University of New Mexico, Albuquerque, NM 87101, United States |
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| Abstract: | This paper reports the occurrence of a Toarcian–Aalenian (Early–Middle Jurassic) radiolarian fauna in the Los Molles Formation, Neuquén Basin, Argentina, as well as comments on its paleobiogeographic affinities. The micropaleontologic analysis was carried out in fine-grained rocks from a turbiditic section of the Los Molles Formation. These samples were first chemically processed using only hydrogen peroxide (H2O2), and afterward treated with acetic (CH3COOH) and hydrofluoric (HF) acids. The first chemical procedure permitted the recovery of only few spongy spumellarians, while the second one enabled to recover more diversified radiolarian assemblages. In general, the studied fauna presents low diversity and abundance, with a strong dominance of spumellarians over nassellarians. The fauna is composed by the genera Paronaella, Homoeoparonaella, Praeconocaryomma, Archaeocenosphaera, Orbiculiformella, Praeparvicingula, and some unidentified spumellarians and nassellarians. According to paleobiogeographic models, the studied Toarcian–Aalenian fauna presents a mid to high latitude affinity. It is possible to infer from those data a bipolar distribution of some taxa, such as Praeparvicingula and probably Praeconocaryomma, between the Northern and Southern hemispheres since the Early Jurassic (Toarcian). |
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