- Usage in publication:
-
- Buck Mountain Shut-ins Formation
- Modifications:
-
- Named
- Dominant lithology:
-
- Lava
- Tuff
- AAPG geologic province:
-
- Midcontinent region
Summary:
Buck Mountain Shut-ins Formation. Unit is part of sequence of Precambrian volcanic rocks associated with Taum Sauk caldera in western part of St. Francois Mountains, southeast Missouri (Midcontinent region). Notable exposures on Pond Ridge, and High Top, Lindsey, North Bell, and Russell Mountains, Iron and Reynolds Counties, Missouri. Consists of a sequence of black, andesitic lava flows containing white plagioclase phenocrysts; interbedded with bedded air-fall tuffs and at least one rhyolitic ash-flow tuff. Thickness 80 to 1000 m. Overlies Pond Ridge Rhyolite (new); underlies Ironton Rhyolite (new). Age is Precambrian. Report includes geologic map. Unit named and described on stratigraphic column (table 1).
Buck Mountain Shut-ins Formation replaces: Middlebrook Group (north flank of Russell Mountain), Stouts Creek Rhyolite (Buck Mountain Shut-ins, Pond Ridge, and north flank of Russell Mountain), and Van East Group (High Top, Lindsey, and North Bell Mountains) as mapped by Tolman and Robertson (1969, Missouri Geol. Survey Rpt. Inv., no. 44); tuff of Mill Creek, tuff and lava flows of Lake Springs, and base of Unit A of tuff of Stouts Creek of Anderson (1970, Missouri Geol. Survey Rpt. Inv., no. 46); and Unit 720 of Berry and Bickford (1972, Bull. Volcanology, v. 36, p. 303-318).
Type section: in SE/4 sec. 33, T. 34 N., R. 3 E., Ironton quadrangle, MO. Named from exposure in Buck Mountain Shut-ins [presumably near Buck Mountain, Iron Co., MO].
Source: Modified from GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
-
- Buck Mountain Shut-ins Formation
- Modifications:
-
- Revised
- AAPG geologic province:
-
- Midcontinent region
Summary:
Buck Mountain Shut-ins Formation, 4th formation from base (of 12) of /Taum Sauk Group (new) of /St. Francois Mountains Volcanic Supergroup (revised). Study area is St. Francois Mountains, southeast Missouri (Midcontinent region). Overlies Pond Ridge Rhyolite (revised) of Taum Sauk; underlies Ironton Rhyolite (revised) of Taum Sauk. Age is Precambrian Y. Nomenclature listed in table 1.
[Conflicts with nomenclature guidelines (ACSN, 1970; NACSN, 1983, 2005, 2021): name Taum Sauk used for both group and formation within it (Taum Sauk Rhyolite has priority); name St. Francois Mountains applied concurrently to two different units in same area; a [supergroup] name combines a geographic name with the term ["supergroup,"] and no lithic designation is included.]
Source: Modified from GNU records (USGS DDS-6; Denver GNULEX).
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
Asterisk (*) indicates published by U.S. Geological Survey authors.
"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).
Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).