Frasnian-Famennian boundary near Jasper, Alberta, Canada
The extinction event at the Frasnian-Famennian boundary cannot be associated with a first-order event, whether impact, volcanic or other. However, data from Alberta and western Australia suggest a sudden flooding of cratonic areas by anoxic water as the immediate or second-order cause. In the Rocky Mountains near Jasper, Alberta abrupt sedimentological, geochemical and faunal changes occur between bioturbated dolomitic siltstones below and thinly laminated, very pyritic, argillaceous lime mudstones above. The siltstones which overlie thick subtidal sediments that infilled Middle Frasnian reef topography, were deposited in shallow, well oxygenated water and contain a Frasnian gigas Zone conodont fauna. In contrast, the overlying lime mudstones which pass upward into beds with Famennian triangularis Zone conodonts, represent deposition under strongly anoxic conditions; the contained pyrite has anomalously high delta/sup 34/S values suggesting prolonged bacterial reduction of sulfate to sulfide. The abrupt change to anoxic conditions could have been triggered by an ocean turn-over event as a result of which cratonic areas were flooded with anoxic water. This in turn would have caused a sharp reduction of the biomass and large-scale faunal extinctions.
- Research Organization:
- Geological Survey of Canada, Calgary
- OSTI ID:
- 6596187
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALBERTA
SEDIMENTARY ROCKS
GEOCHEMISTRY
PALEONTOLOGY
AGE ESTIMATION
BIOLOGICAL EXTINCTION
CRETACEOUS PERIOD
FOSSILS
ISOTOPE RATIO
REDOX REACTIONS
REDUCTION
STRATIGRAPHY
TERTIARY PERIOD
CANADA
CENOZOIC ERA
CHEMICAL REACTIONS
CHEMISTRY
GEOLOGIC AGES
GEOLOGY
MESOZOIC ERA
NORTH AMERICA
ROCKS
580400* - Geochemistry- (-1989)
580100 - Geology & Hydrology- (-1989)