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Overall Stratigraphy: major volcanic units of the Yellowstone Plateau volcanic field

The recognition of the three volcanic cycles provides a natural basis for dividing the volcanic rock layers in the Yellowstone area. The major ash-flow tuffs that erupted at the climax of each cycle are the primary rock units of Yellowstone in areas beyond the caldera complex. The table below represents the work of geologists who identified, described, and mapped the different volcanic rock deposits in the Yellowstone area and determined the order in which they erupted during each of the three cycles of activity. The units are shown in stratigraphic sequence (the youngest at the top of the table, oldest at the bottom). Table is from Christiansen (2001).

Stratigraphic units of the Yellowstone Plateau volcanic field

Volcanic Cycle Precaldera Rhyolite Caldera-forming ash-flow tuff Postcaldera rhyolite Contemporaneous plateau-marginal basalts1
Third     Plateau Rhyolite2 Basalts of Snake River Group
Osprey Basalt
Madison River Basalt
Basalt of Geode Creek
Swan Lake Flat Basalt
Basalt of Mariposa Lake

Lava Creek Tuff
(0.64 Ma)

Mount Jackson Rhyolite
Lewis Canyon Rhyolite
    Undine Falls Basalt
Basalt of Warm River
Basalt of Shotgun Valley
Second     Island Park Rhyolite Basalt of the Narrows

Mesa Falls Tuff
(1.3 Ma)

Big Bend Ridge Rhyolite3      
First     Big Bend Ridge Rhyolite 3  

Huckleberry Ridge Tuff
(2.1 Ma)

Rhyolite of Snake River Butte     Junction Butte Basalt
1 Plateau-marginal basaltic volcanism has been intermittently active throughout the history of the Yellowstone area. The basaltic volcanism is not inherently part of the rhyolitic cycles, but for descriptive purposes they are discussed together.
2 The Plateau Rhyolite comprises more than 20 individual flows ranging in age from 70,000 to 160,000 years. Flows of the contemporaneous basalts (Madison River basalt, etc.) range in age from > 110,000 to < 640,000 years ago.
3 Part of the Big Bend Ridge Rhyolite comprises postcaldera flows of the first cycle and part comprises precaldera flows of the second cycle.