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BIO- AND SEQUENCE STRATIGRAPHY OF THE LATE CRETACEOUS (MAASTRICHTIAN) QUIRIQUINA FORMATION IN CENTRAL CHILE, INCLUDING PALEOBIOGEOGRAPHICAL ASPECTS OF THE FAUNAL ASSEMBLAGE

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BIO- AND SEQUENCE STRATIGRAPHY OF THE LATE CRETACEOUS (MAASTRICHTIAN) QUIRIQUINA FORMATION IN CENTRAL CHILE, INCLUDING PALEOBIOGEOGRAPHICAL ASPECTS OF THE FAUNAL ASSEMBLAGE
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  BIO- AND SEQUENCE STRATIGRAPHY OF THE LATE CRETACEOUS (MAASTRICHTIAN) QUIRIQUINA FORMATION IN CENTRAL CHILE, INCLUDING PALEOBIOGEOGRAPHICAL ASPECTS OF THE FAUNAL ASSEMBLAGE Christian Salazar  *1  , Wolfgang Stinnesbeck  2  , Luis Arturo Quinzio-Sinn 3  , Ramiro Ulises Bonilla-Parra 3  , Miguel Alvarez 4 and Teresa Torres 5 (1) Museo Nacional de Historia Natural, Parque Quinta Normal s/n, Casilla 787, Santiago, Chile. (2) Institut für Geowissenschaften, Universität Heidelberg, INF 234, 69120 Heidelberg, Germany (3) Departamento Ciencias de la Tierra, Universidad de Concepción, 160 C Concepción, Chile (4) Institut für Nutzpflanzenwissenschaften und Ressourcenschutz (INRES), Universität Bonn,  Nussallee 9, 53115 Bonn. (5) Departamento de Producción Agrícola de la Facultad Ciencias Agronómicas de la Universidad de Chile. * Presenting author:  c.salazar@mnhn.cl  ABSTRACT The Late Cretaceous Quiriquina Formation crops out around Concepción Bay in central Chile and presents a retrogradational pattern in shoreface environments, which may have  been a result of sea level rise (transgression) at the end of Early Maastrichtian. Upsection, low energy offshore facies are developed during the Late Maastrichtian. Thirty ammonite species referred to seventeen genera (Salazar et al.  2010) have been detected and represent one of the most diverse assemblages for the topmost Cretaceous. The presence of    Hypophylloceras (  Neophylloceras )  surya ,  Zelandites varuna , Pachydiscus ( P .)  jacquoti ,   Diplomoceras cylindraceum ,  Baculites anceps, Eubaculites carinatus,    Hoploscaphites constrictus and  Menuites fresvillensis indicates an early Late to Late Maastrichtian age for the unit. The following three biozones are distinguished (from base to top): Zone of  Baculites anceps , Zone of  Eubaculites carinatus  (subdivided into the  Menuites fresvillensis  and Kitchinites darwini  sub-biozones), and Zone without baculitids (subdivided into the  Hoploscaphites constrictus  biozone and a zone without ammonites). Species richness and abundance of ammonoids are high throughout the Quiriquina Formation but gradually decline in the uppermost 10 meters of the section within the unit of green sandstone-siltstone. No ammonoids appear to be present in the last 5 meters of the unit, indicating that  the extinction of ammonites in the region was completed prior to the end of the Maastrichtian. The assemblage shows an Indopacific character, but endemic and cosmopolitan as well as European-Tethyan faunal elements are also present. Acknowledgements We are grateful for financial support to this project was donated bythe Deutsche Forhungdgemeinschaft (STI 128/6) and Proyecto Anillo Antártico ACT 105   Salazar, C. , Stinnesbeck, W. & Quinzio-Sinn, L.A. 2010. Ammonites from the Maastrichtian (Upper Cretaceous) Quiriquina Formation in central Chile.  Neues  Jahrbuch für Geologie und Paläontologie Abhandlungen  257: 181–236.
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