|mhorn||Дата: Thursday, 03.05.2012, 12:22 | Сообщение # 1|
|Lefort A. (2011) La limite Oxfordien-Kimméridgien (Jurassique supérieur): stratigraphie et paléoenvironnements dans les domaines téthysien (Est et Sud du bassin de Paris, France) et boréal (Ile de Skye, Ecosse). Thèse Université Henri Poincaré - Nancy I. 304 p. |
Pdf : http://tel.archives-ouvertes.fr/docs....ine.pdf
Isotopic (δ18O and δ13C) and elementary geochemical data as well as macro and microfossil associations, show a chemical change in the water of the lagoonal platform in the eastern Paris Basin, during the Late Oxfordian/Early Kimmeridgian interval (Upper Jurassic, ~156 Ma). Gradually, the shallow tropical environments dominated by biomineralization of carbonates became confined, dysoxic and colder. Correlations between depositional environments with similar facies in the Southern and in the Eastern Paris Basin helped to improve the biostratigraphic frameworks. Comparisons between the sequential frames deduced from the palaeoenvironmental evolution of Berry and Lorraine place the maximum regression of a 3rd order cycle at the Planula and Platynota ammonite zones boundary. Recently, the Flodigarry Shale Member, a shaly succession located on the Isle of Skye (Scotland), has been proposed as a possible GSSP (Global Stratotype Section and Point) to define the Oxfordian/Kimmeridgian boundary. The section was studied in order to compare this subboreal series to submediterranean deposits (Paris Basin) by means of other markers such as organic molecular c ontents. It revealed very well preserved biomolecules, among the oldest identified in the world. This thesis provides new palaeontological, geochemical and stratigraphic data in both Jurassic palaeobiogeographic realms. Well documented sections of the Eastern Paris Basin are now available for this interval. Such local observations, integrated in a multidisciplinary approach, should strengthen the correlations across these realms and precise the global factors of the crisis of the carbonate production near the Oxfordian/Kimmeridgian boundary.
Middle Jurassic - Lower Cretaceous ammonites & aptychi