Upper Cambrian to Lower Silurian stratigraphic framework of platform-to-basin fades, northeastern British Columbia

2000 ◽  
Vol 48 (2) ◽  
pp. 123-149 ◽  
Author(s):  
L. J. Pyle
Keyword(s):  
British Columbia ◽  
Upper Cambrian ◽  
Lower Silurian ◽  
Stratigraphic Framework

Conodonts from a platform-to-basin transect, lower Ordovician to lower Silurian, northeastern British Columbia, Canada

2003 ◽  
Vol 77 (1) ◽  
pp. 146-171 ◽  
Author(s):  
Leanne J. Pyle ◽  
Christopher R. Barnes
Keyword(s):  
British Columbia ◽  
New Species ◽  
New Genus ◽  
Early Ordovician ◽  
The Road ◽  
Lower Silurian ◽  
Lower Ordovician ◽  
Conodont Fauna

The conodont fauna from nine sections across a platform-to-basin transect in northeastern British Columbia includes species of Early Ordovician (Tremadocian) to Early Silurian (Llandovery) age. A collection of 9,110 conodont elements was recovered from 205 samples taken from nine stratigraphic sections that preserve the platform succession of the Kechika, Skoki, Beaverfoot, McCusker and Nonda Formations and their off-shelf equivalents, the Ospika, Robb, Kenny and Laurier Formations of the Road River Group. The fauna is assigned to 106 species representing 67 genera; the Ordovician species are representative of two faunal realms. One new genus, left in open nomenclature, is described. Five new species include Drepanoistodus latus and four new species left in open nomenclature assigned to the following genera: Walliserodus, Multioistodus?, Pseudooneotodus, and Belodina. The Midcontinent Realm zones recognized include, in ascending order, the Acodus kechikaensis, Oepikodus communis, Jumudontus gananda, Tripodus laevis to Plectodina aculeata zones, Phragmodus undatus and Gamachignathus ensifer? zones. Zonal species of the Atlantic Realm are Microzarkodina flabellum, Eoplacognathus suecicus, Baltoniodus variabilis, Pygodus anserinus, and Amorphognathus tvaerensis. The Silurian fauna, of lower diversity than the Ordovician fauna, is representative of the Distomodus staurognathoides and Pterospathodus amorphognathoides zones.

Form of the trilobite digestive system: alimentary structures in Pterocephalia

1994 ◽  
Vol 68 (2) ◽  
pp. 294-305 ◽  
Author(s):  
Brian D. E. Chatterton ◽  
Zerina Johanson ◽  
George Sutherland
Keyword(s):  
British Columbia ◽  
Digestive System ◽  
Alimentary Tract ◽  
Feeding Habits ◽  
Complex Mixture ◽  
Energy Dispersive ◽  
Sister Taxon ◽  
Energy Dispersive Analysis ◽  
Upper Cambrian ◽  
Order Of Magnitude

Three types of alimentary canals (=midgut) occur in the Annelida and non-trilobite Arthropoda: 1) a sagittal tube with metamerically paired diverticula related to the number of somites; 2) a tube that is constricted slightly between somites; and 3) a simple tubular gut that may taper slightly backwards to the anus. At least two of these three types (1 and 3) occur in the Trilobita. Pterocephalia and Olenoides share the first type with the probable sister taxon to the Trilobita, Naraoia (Nectaspida), and this is probably the plesiomorphic condition for the class. Varying feeding habits may well have made this character homoplastic within each of these groups. The preservation of parts of the alimentary tract in specimens of Upper Cambrian Pterocephalia n. sp. (McKay Group, British Columbia) was probably a function of taphonomic and/or very early diagenetic changes that resulted from the type of food preferred by that trilobite. Other trilobites from the same beds do not have their soft parts preserved. The alimentary structures are preserved in a different fashion from, apparently unattached to, and an order of magnitude larger than genal caeca that occur in this taxon. Thus, genal caeca are regarded as imprints of circulatory rather than alimentary structures.Energy dispersive analysis of a fragment of preserved alimentary tract of Pterocephalia n. sp. showed the presence of Ca, Si, Al, Fe, P, K, Na, and Cl. These alimentary tracts are composed of a complex mixture of minerals that probably includes clays, detrital quartz, carbonates, phosphates, and oxides or hydroxides. The structure of these dark fillings is microcrystalline. The presence of detrital minerals as part of this mixture would suggest that this trilobite was a deposit feeder.

Lower Palaeozoic convergent plate margin volcanism on Bømlo, southwest Norwegian Caledonides: geochemistry and petrogenesis

1986 ◽  
Vol 123 (2) ◽  
pp. 123-142 ◽  
Author(s):  
Harald Furnes ◽  
Harald Brekke ◽  
Jan Nordås ◽  
Jan Hertogen
Keyword(s):  
Trace Element ◽  
Partial Melting ◽  
Spinel Lherzolite ◽  
Continental Flood Basalts ◽  
Element Abundances ◽  
Upper Cambrian ◽  
Lower Silurian ◽  
Range Type ◽  
Lower Palaeozoic ◽  
Norwegian Caledonides

AbstractMajor and trace element analyses of a Lower Palaeozoic metavolcanic sequence of convergent plate type from Bømlo, southwest Norwegian Caledonides, are presented and discussed. This sequence ranges in age from the Upper Cambrian through the Lower Silurian. Petrogenetic models for the lavas in terms of partial melting and crystal fractionation are discussed. Two models are presented for the metabasalts in order to explain their different trace element abundances and ratios:(1) REE modelling, assuming a mantle source with REE abundances twice chondritic, suggests progressively more varied sources with time. Thus the metabasalts from the oldest (Upper Cambrian–Lower Ordovician) Geitung Unit of primitive island arc type, and those of the mid-Ordovician Siggjo Complex of ‘Basin and Range’ type can be modelled in terms of high (around 25%) and moderate (around 5%) degrees of partial melting of spinel lherzolite, respectively. The metabasalts of the post-Ashgillian Vikafjord Group of typical continental flood basalts are compatible with moderate (c. 5–10%) degrees of partial melting of spinel- and garnet-lherzolite sources. The supposed Lower Silurian Langevåg Group of calc-alkaline ‘Andean’ type metabasalts, grading into alkaline to tholeiitic metabasalts of early marginal basin (youngest) character, require low (<5%) to moderate degrees of partial melting of amphibole-, garnet- and spinel-lherzolite sources, respectively.(2) Source heterogeneity, produced by subduction zone-derived enrichment of LIL elements, and contemporaneous stabilization of minor phases which accommodate HFS elements. This process, combined with possible continental contamination, may possibly yield the trace element concentrations and ratios of the different metabasalts by partial melting of modally similar mantle sources.

Cambrian Lagerstätten: their distribution and significance

1985 ◽  
Vol 311 (1148) ◽  
pp. 49-65 ◽  
Keyword(s):  
British Columbia ◽  
Special Reference ◽  
Community Ecology ◽  
Lower Cambrian ◽  
South Australia ◽  
Burgess Shale ◽  
Middle Cambrian ◽  
Upper Cambrian ◽  
Exceptional Preservation ◽  
Biotic Diversity

The geological setting, biotic diversity and taphonomy of Cambrian soft-bodied Lagerstätten are reviewed with special reference to the Lower Cambrian Emu Bay Shale (South Australia) and Kinzers Formation (Pennsylvania), and the Middle Cambrian Stephen Formation (Burgess Shale and adjacent localities, British Columbia). Brief mention is made also of a number of more minor occurrences in the U.S.A., China and Spain. Exceptional preservation in the Upper Cambrian is discussed by K. J. Müller (this symposium). These soft-bodied Lagerstätten afford a series of special insights into the nature of Cambrian life. Emphasis is laid on the information they provide with regards (i) levels of diversity and the proportion of skeletized taxa; (ii) the origin and relative success of bodyplans; (iii) community ecology and evolution.

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