Stouts Creek rhyolite (new) of Van East group (new). Briefly summarized in reports by: F.G. Snyder and R.E. Wagner, p. 13, 14, 15, W.C. Hayes and J.A. Martin, p. 28, 29, W.C. Hayes, P.D. Procter, and J.A. Martin, p. 39, this volume (noted in road logs); and W.C. Hayes, p. 83 (table 1), this volume. New names are credited to Tolman and Robertson (in prep.) [1969, Missouri Div. Geol. Survey Water Res. Rpt. Inv., no. 44 (Contrib. to Precambrian Geol., no. 1)]. A purple rhyolite. In contact with Silvermine granite, Magee granite, Knoblick granite, and Butler Hill granite. Intrudes Carver Creek granite porphyry. Age is Precambrian.
Occurs in St. Francois Mountain area. Specimens collected from southwest corner of W/2 lot 3 W., T. 33 N., R. 4 E. Stouts Creek is in Iron Co., southeastern MO.

Source: Modified from US geologic names lexicon (USGS Bull. 1350, p. 727-728).

Whole rock Rb-Sr age determined to be 1315 +/-35 m.y. Study area in St. Francois Mountains, southeast MO, Midcontinent region. Older than Munger granite porphyry and Magee granite (1260 +/-30 m.y.); younger than Hogan Mountain and Royal Gorge rhyolites, rhyolite of Johnson Shut-ins, and Pilot Knob felsite (1420 +/-30 m.y.); and Silvermine and Butler Hill granites (1400 to 1450 m.y.).

Source: GNU records (USGS DDS-6; Denver GNULEX).

Stouts Creek rhyolite of Van East group. Present in St. Francois Mountains, southeastern Missouri. Is the most extensive unit in study area. Rock has dense subvitreous aphanitic groundmass with clear quartz and light red feldspar phenocrysts. May represent a single flow. In Ironton area, subdivided into three informal units (ascending): (1) lower unit, a brownish-purple to gray-chocolate-brown, characteristically coarse aphanite with small feldspar and quartz phenocrysts, about 100 feet thick; (2) middle unit (most conspicuous and widespread), a dense purple rhyolite with quartz and salmon red feldspar phenocrysts, about 400 feet thick; (3) upper unit, a flow breccia, 100 to 200 feet thick. Age is Precambrian.
Type locality: at Stouts Creek shut-ins, in sec. 2, T. 33 N., R. 4 E., Iron Co., MO.
Notable exposures on Grassy Mountain, north of Lake Killarney, in northeastern part of T. 33 N., R. 4 E., Iron Co., and southeast of Van East Mountain in Madison Co.
[GNU remark (Feb. 16, 1990, USGS DDS-6; Denver GNULEX): Thickness not discussed; stratigraphic relationships of units of Van East not discussed in text; geologic map (plate 1) missing from library copy of report.]

Source: Modified from GNU records (USGS DDS-6; Denver GNULEX).

Rb-Sr age of 1354 +/-20 m.y. determined on whole rock/mineral separates; U-Pb age not determined. Rb-Sr ages on some rocks are consistently lower than U-Pb ages probably due to removal of Sr from rock. Age of most rocks studied is about 1500 m.y., but a real event as recorded by Rb-Sr occurred about 1300 m.y. ago. Samples are taken from St. Francois Mountains, southeast MO, Midcontinent region.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Rb-Sr data on whole rock samples yields an age of 1327 +/-27 m.y. Rb-Sr data probably underestimates actual age; low age probably due to Sr loss. Samples taken in T32N, R4E, Iron Co; T33N, R4, 5E, Iron and Madison Cos; and T34N, R4E, St. Francois and Iron Cos., MO, Midcontinent region (specific localities listed in appendix 3). Analytical data in appendix 4.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Stouts Creek Rhyolite. Nomenclature of Tolman and Robertson (1969) revised because of better understanding of regional structure and recognition of individual units consisting of ash-flow tuffs, air-fall tuffs, lava flows, and mixtures of these. Stouts Creek is restricted to type locality, Stouts Creek Shut-ins, Iron County, western St. Francois Mountains, southeast Missouri (Midcontinent region). Elsewhere, replaced with newly named formations (alphabetical): Bell Mountain Rhyolite (Crane, Russell, and Taum Sauk Mountains); Buck Mountain Shut-ins Formation (Buck Mountain Shut-ins, Pond Ridge, and Russell Mountain); Cedar Bluff Rhyolite (Pond Ridge and Shepherd Mountain); Ironton Rhyolite (Buck and Russell Mountains, and Pond Ridge); Lindsey Mountain Rhyolite (Russell, Taum Sauk, Vail, and Wildcat Mountains); Pond Ridge Rhyolite (Buck Mountain, Pond Ridge, and Shepherd Mountain Lake); Royal Gorge Rhyolite (Royal Gorge area, and College Hill); Russell Mountain Rhyolite (Russell, Taum Sauk, Vail, and Wildcat Mountains); and Shepherd Mountain Rhyolite (Pond Ridge).

Source: Modified from GNU records (USGS DDS-6; Denver GNULEX).

Whole rock Rb-Sr age of 1327 +/-27 m.y. on Stouts Creek in St. Francois Mountains, MO, Midcontinent region.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Not used in Lake Killarney quad, Iron and Madison Cos, MO, Midcontinent region. Stouts Creek as mapped by Tolman and Robertson (1969) is replaced by newly named informal Lake Killarney unit and Grassy Mountain ignimbrite.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Not used in Ketcherside Mountain area, located within St. Francois Mountains, southeast MO, Midcontinent region. Replaced by informal Ketcherside Mountain ignimbrite and by Grassy Mountain Ignimbrite. Table 1 shows comparison of nomenclature with previous workers.

Source: GNU records (USGS DDS-6; Denver GNULEX).