Comparison of the TRM of the Yellowstone Group and the DRM of some Pearlette ash beds
Air fall ash beds (Pearlette) originating from rhyolitic eruptions in the Yellowstone‐Island Park region of Wyoming and Idaho are discontinuous but widespread throughout the western United States. Accumulation and deposition of ashes occurred in low‐energy fluvial and lacustrine environments. These ash beds have been correlated, according to their chemistry and remanent magnetism, with specific eruptions of tuffs of the Pleistocene Yellowstone Group. Type O Pearlette ash beds are normally magnetized and correlate with the Lava Creek Tuff (0.60 m.y.), whereas type S Pearlette ash beds are reversely magnetized and correlate with the Mesa Falls Tuff (1.22 m.y.). The mean direction of detrital remanent magnetization (DRM) of 11 type O Pearlette ash beds is identical to the mean direction of thermal remanent magnetization (TRM) of the Lava Creek Tuff after correcting for differences in site latitude and longitude. Considered separately, only 2 of the 13 Pearlette ash beds studied possess mean inclinations significantly shallower than, and only 4 have mean declinations significantly different from, those of their correlative tuffs. Identical directions of magnetization measured from evenly laminated and highly contorted type O ash suggest that a readjustment of magnetic grains in water‐saturated ash shortly after deposition may account for the close agreement of TRM and DRM.
Citation Information
Publication Year | 1979 |
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Title | Comparison of the TRM of the Yellowstone Group and the DRM of some Pearlette ash beds |
DOI | 10.1029/JB084iB09p04525 |
Authors | Richard L. Reynolds |
Publication Type | Article |
Publication Subtype | Journal Article |
Series Title | Journal of Geophysical Research B: Solid Earth |
Index ID | 70209701 |
Record Source | USGS Publications Warehouse |
USGS Organization | Geosciences and Environmental Change Science Center |