..., previously mapped as undivided welded tuff, includes the tuff of Cove mine (34.4 Ma) and unit B of the Bates Mountain Tuff (30.6 Ma). These tuffs dip 30° to 50° east, suggesting that their west-dipping contacts with underlying Paleozoic rocks (previously mapped as depositional) are normal faults. Tertiary...

... used to determine the fission track ages. The Bates Mountain Tuff was dated at 24.0 m.y. (F.T.) and 24.0 m.y. (K-Ar). The Fish Creek Mountains Tuff has a fission-track age of 24.4 m.y., and a K-Ar age of 23.9 m.y. The average fission-track age for the Caetano Tuff is 34.9 m.y., and it has an average K...

... is a unique characteristic of each cooling unit. Ash-flow sheets investigated include the Stone Cabin Formation, the tuff of Pancake Summit, the Windous Butte Formation, the Needles Range Formation, the Bates Mountain Tuff, and the tuff of Clipper Gap, of Oliogcene to early Miocene age. The original areas...

...). In the western part of the study area, the Bates Mountain Tuff is interbedded with undated andestic and/or dacitic lava flows (Tad) mapped by Stewart and McKee (1977) and Moore et al. (2005) . These flows are present both above and beneath the Bates Mountain Tuff, whereas similar lavas (the dacite of Wood...

... by gravitational sliding of steeply tilted and uplifted tuff over the intrusion. The B and C units of the Bates Mountain Tuff show the normal, moderate, east dip resulting from middle Miocene extension ( Colgan et al., 2008 . ...

...Figure 7. Equal-area projections of site and group mean directions (triangles as projected on the upper hemisphere, reverse polarity) and their 95% confidence cones from paleomagnetic sites of the tuff of Campbell Creek and C unit of the Bates Mountain Tuff. Tilt corrections were applied where...

...TABLE 3. WHOLE-ROCK GEOCHEMISTRY OF PUMICEOUS RHYOLITE TUFF COMPARED TO NINE HILL AND BATES MOUNTAIN TUFFS ...

.... Calderas not erupting during the time intervals covered by this figure are in light red. Blue lines and arrowheads are paleovalleys as in Figure 1 . B—Bates Mountain; C—Carson Range; CA—Clan Alpine Mountains; CH—Candelaria Hills; D—Desatoya Mountains; E—Excelsior Mountains; F—Fish Creek Mountains; G...

..., and the acid tuffs of the Fydlyn Group are indistinguishable in the field from acid intrusions in the Ordovician around Mynachdy (302921). It may also be significant that the outcrops of the Fydlyn Group occur in a correspond- ing structural position to the Caradocian volcanics of Parys Mountain in eastern...

...: G, Gariboldi (Macdonald & Bailey 1973); F, Fantale (Gibson 1970); Western USA: GF, Gold Flat Tuff, TR, Trail Ridge Tuff, both Black Mountain centre, Nevada (Noble & Parker 1974); GC, Grouse Canyon Tuff, Silent Canyon centre, Nevada (Noble & Parker 1974); SM, Soldier Meadow Tuff, Nevada (Noble...

...; Tertiary rocks occur as local dolerite dikes. The geology of northeastern Anglesey, based on mapping by Greenly (1919) , Bates (1964), and Cominco (1974–1981 ), is shown in Figure 2 . In the Parys Mountain area, the main lithologies are rhyolites and shales. The field terms that we informally follow...

... (Reedman et al. 1984; Gibbons 1985; cf. Nutt & Smith 1981; Neuman 1984). Intense post-Ordovician deformation (Bates 1974) has obscured evidence of earlier tectonism at Parys Mountain, but the petrochemistry and submarine ensialic volcanism, and the earlier history, point to the persistence of Ordovician...