Quantitative Biogeography of the Upper Aalenian-Lower Bajocian Ammonites (Western Tethys): Application of the Multivariate Methods

In order to quantify the biogeographic dynamics of ammonites faunas of Upper Aalenian-Lower Bajocian, 9 areas located in Western Tethys were analyzed by the multivariate method (Principal coordinate analysis and calculating similarity index and distance). The results obtained reveal the following facts: -the stability and resemblance during the time of faunas of the Betic Cordillera, Iberian Cordillera, central High Atlas and the Lusitanian basin,-the fluctuation starting from the Laeviuscula zone of Dorset-Somerset, the basin of South-east of France and the folded Middle Atlas. This fluctuation is controlled by several factors: paleotemperature, eustatism, paleogeography, and trophic conditions,-the isolation of faunas of Beni Snassen and Umbria-Marche Apennines.