St. Francois mountains volcanic supergroup

Chiefly alkali rhyolitic ash - flow tuffs, lava flows, and bedded tuffs, with minor trachytes.
State Missouri
Name St. Francois mountains volcanic supergroup
Geologic age Precambrian Y
Lithologic constituents
Igneous > Volcanic > Felsic-volcanic > Rhyolite (Pyroclastic-ash flow)
Igneous > Volcanic > Felsic-volcanic > Trachyte (Pyroclastic-ash flow)
Comments The St. Francois Mountains is a region of formerly extentive volcanic terrane comprising several calderas, cauldron subsidence structures, ring intrusions, and resurgent cauldrons. Three calderas are recognized: the Taum Sauk, the Butler Hill, and the Hawn Peak.
Stratigraphic units Includes Taum Sauk Group and Butler Hill Group.

Howe, W.B. and Koenig, 1961, The Stratigraphic Succession in Missouri: Missouri Geological Survey and Water Resources, Vol XL. 2nd Series.

NGMDB product
Counties Carter - Iron - Madison - Reynolds - Saint Francois - Shannon - Washington - Wayne