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40Ar/39 Ar Geochronology Of The Lowland Creek Volcanic Field And Its Temporal Relations With Other Eocene Volcanic Areas, Vladimir Olegovich Ispolatov
40Ar/39 Ar Geochronology Of The Lowland Creek Volcanic Field And Its Temporal Relations With Other Eocene Volcanic Areas, Vladimir Olegovich Ispolatov
OES Theses and Dissertations
Exposures of the Eocene Lowland Creek Volcanics (LCV) cover an area of 2000 km2 in southwestern Montana, and consist of basal elastic deposits, felsic tuffs, and felsic and intermediate lavas with an aggregate thickness of about 2 km. New 40Ar/39Ar dates show that volcanic activity lasted for at least 4.2 million years (52.7- 48.5 Ma), or even longer (4.5-4.7 million years: from 53.0-53.2 Ma to 48.5 Ma). During evolution of the volcanic field, early explosive volcanism was gradually replaced by extrusive activity. During the transition period (52.7-51.5 Ma), the two volcanic styles coexisted.
The evolution of …