Cenozoic Stratigraphy of Southwestern High Plateaus of Utah

Isotopic ages and stratigraphy of Cenozoic rocks of the Marysvale volcanic field and adjacent areas, west-central Utah

“…The tuff units are widespread southwest of the Marysvale field in southwestem Utah and southeastern Nevada (Mackin, 1960;Anderson and Rowley, 1975;Siders and Shubat, 1986;Best, Christiansen, and others, 1989;Best and others, 1993;Rowley, Nealey, and others, in press;Scott and others, in press). Many are intertongued with Marysvale rocks only in the southwestern part of the Marysvale field (in the southern Black Mountains and Markagunt Plateau); an exception is the Wah Wah Springs Formation, which is distributed over most of the Marysvale field (Row ley, Anderson, and others, 1978;Best, Christiansen, and Blank, 1989).…”

“…A series of ash-flow tuff units belonging to the Quichapa Group (Williams, 1967;Anderson and Rowley, 1975) are exposed along the southwestern margin of the Marysvale field. The oldest of these is the Leach Canyon Formation, a tan, poorly welded, crystal-poor, rhyolite ashflow tuff whose source is not known but which, on the basis of isopach data (Williams, 1967), may be near the north side of the Caliente caldera complex of Nevada-Utah, about 180 km southwest of Marysvale.…”

“…These relatively highly evolved rocks were derived from shallow source cupolas of an underlying batholith; numerous intrusions are currently exposed, emplaced into Bullion Canyon and other volcanic units. Using terminology adapted from Parsons (1965Parsons ( , 1969 and Smedes and Prostka (1973), Anderson and Rowley (1975) applied "vent facies" to rocks deposited in and near sources made up of clustered stratovolcanoes and ''alluvial facies" for more distal flank asemblages. Vent-facies rocks consist mainly of lava flows, autoclastic flow breccia, and volcanic mudflow breccia that were deposited on the slope of a volcanic edifice (stratovolcano), whereas alluvial facies rocks consist of volcanic mudflow breccia, conglomerate, and sandstone deposited farther away on the edifice and in valleys draining the edifice.…”

“…Mehnert and C.W. Naeser established the chronology of the detailed stratigraphy, and many of the ages obtained are given in earlier reports (such as Cunningham and Steven, 1979a;Rowley, Steven, and others, 1979; Anderson and Rowley (1975, fig. 1) and Steven and others (1979, fig.…”

“…Two of these students, J.J. Anderson and P.D. Rowley, applied Mackin's concepts to the northern Markagunt Plateau and southern Sevier Plateau beginning in 1963, and developed the first modem stratigraphic framework of the southern part of the Marysvale volcanic field (for example, Anderson and Rowley, 1975); K-Ar ages of numerous units in the same area were determined by Fleck and others (1975). Williams and Hackman (1971) described the basic stratigraphy of the eastern Marysvale field.…”