GEOSCAN, résultats de la recherche


TitreNammal Nala (Salt Range, Pakistan): a potential GSSP candidate for the Induan/ Olenekian boundary (Early Triassic)
AuteurWare, D; Goudemand, N; Bucher, H; Orchard, M J; Schneebeli-Hermann, E; Hochuli, P A; Brühwiler, T; Krystyn, L; Roohi, G
Source34th International Geological Congress, abstracts; 2012 p. 1
Séries alt.Secteur des sciences de la Terre, Contribution externe 20120102
Réunion34th International Geological Congress; Brisbane; AU; août 5-10, 2012
SujetsTrias inférieur; stratigraphie paléontologique; extinctions biotiques; biostratigraphie; paléontologie; Mésozoïque; Trias
Programmebassins sédimentaires du Yukon, GEM : La géocartographie de l'énergie et des minéraux
Résumé(disponible en anglais seulement)
A reliable high resolution biochronological framework of the Early Triassic time interval is pivotal to the understanding of the biotic recovery in the aftermath of the Permian/Triassic mass extinction. Definition of the Induan/Olenekian boundary (IOB) is an important step in providing this framework. Here we present high resolution biostratigraphic results based on new data on ammonoids and conodonts from Nammal Nala (Salt Range, Pakistan) and show that the first occurrence of both the Flemingitidae, a typical Smithian ammonoid family, and the conodont genus Novispathodus would provide a suitable datum for a GSSP. These bioevents coincide with a positive shift of d13Corg of ca. 6permil, with a sequence boundary, and with a palynofacies change (Hermann et al., 2011). In Nammal the IOB would fall within the stratigraphically expanded Ceratite Marls without any significant facies change, thus representing an ideal configuration for the definition of this boundary.
We recognize the same sequence of faunal associations in two other GSSP candidates for this boundary. The first one, located at Mud, India, (Krystyn et al., 2007) contains ammonoids and conodonts. At Mud, the faunal turnover occurs 1 m below the previously proposed IOB. It is associated with a facies change, in a comparatively condensed section. No palynological record is available. The second candidate section, at Chaohu, South China (Chinese Triassic Working Group, 2007) is condensed and lacks adequate ammonoid and palynological records. Hence, the Nammal section provides by far the most complete and best suited profile for the definition of the IOB.