| mhorn | Дата: Wednesday, 31.08.2011, 13:06 | Сообщение # 1 |
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| Parent H., Garrido A.C., Schweigert G., Scherzinger A. (2011) The Tithonian ammonite fauna and stratigraphy of Picún Leufú, southern Neuquén Basin, Argentina // Revue de Paléobiologie, Genève. Vol.30. no.1. P.45-104.
Pdf: http://www.ville-ge.ch/mhng/paleo/paleo-pdf/30-1/pal_30_1_04.pdf
A Tithonian section of the Vaca Muerta Formation (362 m in thickness) in Picún Leufú (southern Neuquén Basin, Argentina) was measured and sampled for ammonites. There were recognized seven different lithofacies which represent at least five different episodes of sedimentation. The ammonite fauna is dominated by perisphinctids belonging to three genera of the Ataxioceratidae. The classification proposed for the Andean lower-middle Tithonian Ataxioceratidae includes three genera : two phyletic lineages, Choicensisphinctes Leanza (Lithacoceratinae) and Catutosphinctes Leanza & zeiSS (Torquatisphinctinae), and “Lithacoceras” hyatt represented by apparently two species in the lower Tithonian. Each one of these three genera is rather well characterized by its different ontogeny of sculpture, shell shape and coiling and, moreover, their sexual dimorphism is different, especially by the morphology of the microconchs. Both phyletic lineages include several Andean ammonites described in the literature as unrelated species but showing progressive differentiation with independent evolutionary trends. The ammonite fauna includes accessory elements (in terms of abundance) which belong to the following genera : Physodoceras (macro- and microconchs, Sutneria), Pseudolissoceras, Cieneguiticeras and Pasottia. The Picunleufuense (Standard Chronostratigraphic) Zone for the Andean Tithonian is introduced, including two horizons : the picunleufuense α horizon (standard base of the Picunleufuense Zone) and the picunleufuense β horizon. Upper in the section, within the biozone, or biostratigraphic range, of Pseudolissoceras zitteli, is introduced the perlaevis horizon.
Middle Jurassic - Lower Cretaceous ammonites & aptychi
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