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Archaeocyatha from the Colville and Salmo area of Washington and British Columbia

University of British Columbia

Archaeocyathids are an extinct group of animals that lived and thrived in the warm, clear marine waters of the Lower Cambrian. In general shape, they resemble rugose corals, but in skeletal details, numerous differences between these groups exist, i.e. inner and outer walls, central cavities, parieties, etc. are unique to Archaeocyathids. The Archaeocyathids which are the subject of this thesis were collected by Dr. H. Little from the South Fork of the Salmo River, and from north of Colville, Washington. In the Salmo area, they occur in a narrow band of limestone at the base of the Laib group. The Colville collection is from an outcrop of Old Dominion limestone. The identification and description of the species present in these collections are the main considerations of the thesis. Two new species are described, Ethmophyllum lineatus and Syringocnema colvillensis. The former species occurs in the Lower Cambrian limestone of the Laib group, Salmo area; the latter is reported from the Old Dominion limestone of the Colville area. Archaeocyathids may be useful in the correlation of Lower Cambrian formations, providing further accurately located (stratigraphically) collections are made. At present, insufficient stratigraphic data are available to erect Archaeocyathid zones. However, some attempt to correlate the known Archaeocyathid occurrences is made. In correlating the ten known Archaeocyathid occurrences from Washington to the Yukon Territory, it is suggested that the most southerly, Colville, Washington, is stratigraphically lower than the Salmo occurrence, and that the latter is, in turn, stratigraphically lower than the northern localities. These northern occurrences are considered to be late Lower Cambrian. The age assigned to the northern localities is, in general, based on stratigraphic and paleontological evidence other than that afforded by Archaeocyathids. The occurrences of Archaeocyathids in the northern part of the Cordillera are given below with their related lithologic unit where possible: 1) Colville, Washington - Old Dominion limestone 2) Salmo, B.C. - lower part of the Laib group 3) Dogtooth Range, B.C. - Donald formation 4) Quesnel Lake, B.C. - Cariboo series 5) Sinclair Mills, B.C. - 6) Pine Pass, B.C. - Misinchinka schists 7) Aiken Lake, B.C. - upper Wolverine complex 8) McDame Creek, B.C. - Atan group 9) Wolf Lake, Yukon Territory - Lord's group B and c units 10) Quiet Lake, Yukon Territory – It is believed that these occurrences outline the western edge of the geosyncline present in this region in Lower Cambrian time.

Text

2012-02-24

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http://hdl.handle.net/2429/40879

Geological Sciences

University of British Columbia

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