Kurka, M.T., 1997, Mississippian conodonts from southeastern Alaska (Alexander terrane) and Mississippian multi-element apparatus reconstruction: University of Oregon, Eugene, Ph.D. dissertation, 342 p., illust.
A Mississippian conodont fauna is described from the Peratrovich Formation in southeastern Alaska (Alexander terrane), comprising 23 species recovered from shallow-water to outer shelf carbonates. The Peratrovich Formation records a period of relative tectonic quiescence in an island arc setting. Species recovered from the Peratrovich include: Cavusgnathus n. sp. A, C. n. sp. B, C. unicornis, C. altus, C. naviculus, Idioprioniodus healdi, I. claviger, Gnathodus homopunctatus, G. bilineatus, G. girtyi girtyi, G. texanus, G. semiglaber, Hindeodus cristula, H. minutus, Taphrognathus varians, Kladognathus tenuis, Lochreia commutata, Polygnathus communis communis, P. bischoffi, Vogelgnathus campbelli, Hindeodontoides spiculus, Synclydognathus libratus, and Bispathodus utahensis. The species recovered represent most known Mississippian conodont biofacies including the Cavusgnathus-Kladognathus biofacies, the Hindeodus biofacies, and the Gnathodus biofacies. The fauna indicates a Meramecian through late Chesterian (but not latest) age for the Peratrovich Formation. It is a mostly cosmopolitan fauna (two endemic species) and has greatest affinity with coeval faunas described from the western United States. The Alexander terrane, though preserving a long rock record with excellent biostratigraphic control, is controversial with regard to its displacement history and point of origin. Conclusions herein constrain the paleoposition of the Alexander terrane to perhaps 2,000 km west of southern California, and it strongly argues against an eastern Australian provenance, which had a strongly endemic fauna during the Mississippian. The second focus of this study is a review of all Mississippian conodont multi-element apparatuses for which reconstructions are available. Historically, bedding plane assemblages formed the templates upon which dissociated collections were reconstructed, but these are rare, and conodont students have utilized statistical analysis to corroborate and reconstruct those species for which no natural assemblages exist. Problematic are the non-platformed apparatuses (Idioprioniodus and Kladognathus, for example), vicariously shared non-Pa elements, and collections in which many species of a genus co-occur (Siphonodella, e.g.) precluding confident reconstructions of individual species. In spite of these challenges, most Mississippian apparatuses have been reconstructed by a dedicated group over the past 20 years. Illustrations of reconstructed Mississippian conodont apparatuses and a history and discussion of each reconstruction are presented as a synthesis for the first time. Fully realized multi-element reconstructions allow faunal, biostratigraphic, and ecological comparisons between coeval collections intercontinentally.
Theses and Dissertations