Study of the Early Cretaceous (Albian) Faunas of the Cottonwood District

点击翻译按钮获取中文摘要

The project will establish a modern taxonomic base for studies of biostratigraphy, biogeography, and evolution of the middle Cretaceous (Albian) faunas (predominantly ammonites) of the Pacific rim of North America and will refine the biostratigraphic standard of reference for this interval in the Cottonwood District of northern California. A detailed standard of reference is prerequisite to an understanding of paleobiological problems of biofacies, biogeography and patterns of evolution, and for chronostratigraphy. It is also needed for stratigraphic and structural problems requiring a high degree of biostratigraphic resolution. Such a study would: 1) elucidate the microstructural, morphologic, and ontogenetic characteristics of many unstudied ammonite taxa; 2) would enable some evolutionary sequences to be recognized and their patterns to be examined; 3) permit examination of hypotheses of ammonite evolution proposed by German, Russian, and French writers; 4) enable a refined correlation of the Lower Cretaceous strata around the Pacific rim with the classical sections in Europe and with sequences originating in the Tethyan seaway, e.g. Caucasus, Indian; 5) enable paleobiogeographic and biofacial interpretations some of which are now masked by antiquated taxonomy; 6) permit a better understanding of the history of the region and its faunas; 7) permit a more balanced view of the Cretaceous history of North America; 8) permit assessment of proposed mid-Cretaceous extinction events.