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Pliensbachian (Lower Jurassic) Ammonites of the Queen Charlotte Islands, British Columbia
Paul L. SmithH. W. Tipper
出版Paleontological Research Institution, 1996
主題Nature / FossilsScience / PaleontologySocial Science / Archaeology
ISBN08771043959780877104391
URLhttp://books.google.com.hk/books?id=YoCMAAAACAAJ&hl=&source=gbs_api
註釋The lower Maude and upper Kunga groups in the central Queen Charlotte Islands provide the most complete and fossiliferous Pliensbachian sequences in North America. Outcrops on Maude Island and at Whiteaves Bay serve as either type or reference sections for the Imlayi, Whiteavesi, Freboldi, Kunae, and Carlottense zones of the standard North American zonation. The Sandilands Formation of the Kunga Group is mostly pre-Pliensbachian in age but exposures on Kunga Island are as young as Whiteavesi Zone. The Sandilands Formation and the succeeding Ghost Creek Formation of the Maude Group were deposited in fairly deep, euxinic water subjected to diminishing pyroclastic and volcaniclastic input, the latter by turbidity currents. Shallowing culminated in the deposition of the coarser sediments of the Fannin Formation which were laid down in higher energy, well oxygenated waters. Most of the Ghost Creek Formation is assignable to the Imlayi Zone with its upper 10 m or so as young as the Whiteavesi Zone; at one level in the Whiteavesi Bay section, it is as young as the Freboldi Zone. The Fannin Formation ranges in age form the Whtieavesi to the Carlottense zones and locally into the Toarcian. This report is the first comprehensive, stratigraphically controlled study of the Pliensbachian ammonoids of the Queen Charlotte Islands. Seven hundred and fourteen localities have yielded at least 1600 specimens assignable to approximately 85 species representing 32 genera of sub-genera and 11 families of ammonoids. Charlotticeras is established as a new subgenus of Fanninoceras and Pacificeras (Repin, 1970) is recognized as a subgenus of Lioceratoides. The following new species are established (in alphabetical order): Acanthopleuroceras thomsoni, Fanninoceras (Charlotticeras) carteri, F. (C.) maudense, Lioceratoides (Leoceratoides) involutum, Oistoceras compressum, Oregonites? dawsoni, Protogrammoceras (Protogrammoceras) skidegatense, and Teynesocoeloceras grahami.