Gigantic Ordovician volcanic ash fall in North America and Europe: Biological, tectonomagmatic, and event-stratigraphic significance
- Univ. of Cincinnati, OH (United States)
- Ohio State Univ., Columbus (United States)
- Illinois State Geological Survey, Champaign (United States)
Biostratigraphical, geochemical, isotopic, and paleogeographic data suggest that the Millbrig K-bentonite, one of the thickest and most widespread Ordovician volcanic ash beds in eastern North America, is the same as the so-called 'Big Bentonite' in Baltoscandia. This is the first time that the same K-bentonite has been identified in both North America and Europe, and it serves as a unique event-stratigraphic marker over a large portion of the Northern Hemisphere. This eruption produced at least 340 km[sup 3] of dense-rock-equivalent ash that was deposited in a layer up to 1-2 m thick over several million square kilometers. As much as 800 km[sup 3] of additional ash may have fallen into the Iapetus Ocean, for a total of 1,140 km[sup 3]. Trace element geochemistry shows that the ash was derived from a felsic calc-alkalic magmatic source characteristic of volcanism in a continental crust-based, destructive plate-margin setting. This is one of the largest, if not the largest, ash falls recorded in Earth's Phanerozoic stratigraphic record, but its recognizable effect on faunas and floras was minimal, and it did not result in a global extinction event. The Millbrig-Big Bentonite bed provides accurate time control for sedimentologic, paleoecologic, and paleogeographic reconstructions across plates positioned in tropical (Laurentia) and temperate (Baltica) latitudes during Middle Ordovician time.
- OSTI ID:
- 6991783
- Journal Information:
- Geology; (United States), Journal Name: Geology; (United States) Vol. 20:10; ISSN 0091-7613; ISSN GLGYBA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580000* -- Geosciences
AGE ESTIMATION
ASHES
BENTONITE
CHEMISTRY
CLAYS
COMBUSTION PRODUCTS
CORRELATIONS
DEPOSITION
EUROPE
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC HISTORY
GEOLOGIC MODELS
GEOLOGIC STRATA
GEOLOGIC STRUCTURES
GEOLOGY
IGNEOUS ROCKS
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MATERIALS
NORTH AMERICA
ORDOVICIAN PERIOD
PALEONTOLOGY
PALEOZOIC ERA
PLATE TECTONICS
RESIDUES
ROCKS
STRATIGRAPHY
TECTONICS
VOLCANIC ROCKS
VOLCANOES