GEOLEX

Summary of Citation: Peach Springs

Publication:
Young, R.A., 1966, Cenozoic geology along the edge of the Colorado
   Plateau in northwestern Arizona: Dissertation Abstracts, sec.
   B, v. 27, no. 6, p. 1994

Usage in Publication:
Peach Springs Tuff

Modifications:	Geologic Province:	Dominant Lithology:
First used	Plateau sedimentary province	Ash Ignimbrite

Summary:
Occurs at edge of Colorado Plateau, northwest AZ. Only widespread formation that can be correlated throughout area is complex tuff herein named Peach Springs Tuff. On Hualapai Plateau composed of ash fall and ignimbrite (welded). West of Lower Grand Wash Cliffs and near Valentine, AZ, uppermost part of this acidic volcanic sequence has aspects of true volcanic flow. Total thickness of tuff decreases to north and northeast which indicates southwesterly source outside plateau. A sample of tuff dated at 18.3 +/-0.6 Ma (Damon, 1964, p.19) was collected from abandoned prevolcanic channel through Milkweed Canyon.

Summary of Citation: Peach Springs

Publication:
Young, R.A., 1970, Geomorphological implications of pre-Colorado
   and Colorado tributary drainage in the western Grand Canyon
   region: Plateau, v. 42, no. 3, p. 107-111

Usage in Publication:
Peach Springs Tuff

Modifications:	Geologic Province:	Dominant Lithology:
Named	Plateau sedimentary province	Ash Ignimbrite

Summary:
Named by Young (1966) in PhD thesis (Dissertation Abstracts). Composed of ash fall and welded ignimbrite; west of Grand Wash Cliffs has aspects of true volcanic flow. Milkweed Canyon diagrammatic cross section shows unit underlies lava flows and Willow Springs Formation (new) and overlies lava flows and Milkweed Member of Buck and Doe Conglomerate. Peach Springs Canyon diagrammatic cross section shows unit overlies Hualapai Volcanics. Sample from tuff collected in Milkweed Canyon was dated as 18.3 +/-0.6 Ma (Damon, 1964, p.19) [thus early Miocene].

Summary of Citation: Peach Springs

Publication:
Young, R.A. and Brennan, W.J., 1974, Peach Springs Tuff; its
   bearing on structural evolution of the Colorado Plateau and
   development of Cenozoic drainage in Mohave County, Arizona:
   Geological Society of America Bulletin, v. 85, no. 1, p.
   83-90

Usage in Publication:
Peach Springs Tuff

Modifications:	Geologic Province:	Dominant Lithology:
Areal limits Isotopic dating Paleomagnetics	Plateau sedimentary province

Summary:
Is single cooling unit, a welded ash-flow tuff of trachytic composition and of normal polarity. Blanketed an area of 2000 sq mi on both sides of the western edge of Colorado Plateau, Mohave Co, AZ, in Plateau sedimentary province. Filled in northeast-trending pre-Colorado River canyons cut in Paleozoic rocks. Had its source west of Cerbat Mountains, in or near Black Mountains. Petrologic descriptions and areal extent map. Easternmost outcrops record deposition of basal, distinctly bedded ash 1 ft thick, locally welded, nonlaminated pinkish tuff 10 ft thick, and upper welded ash flow 30 to 60 ft thick. Western exposures have basal 30 ft ash layer, 137 ft loosely welded tuff containing volcanic pebbles of various lithologies, and upper 84 ft thick welded zone. Erupted at time when declination of geomagnetic field was east of its average value. Dated as 16.9 +/-0.4 and 18.3 +/-0.6 Ma, or middle Miocene by earlier workers.

Summary of Citation: Peach Springs

Publication:
Howard, K.A., Stone, Paul, Pernokas, M.A. and Marvin, R.F.,
   1982, Geologic and geochronologic reconnaissance of the Turtle
   Mountains area, California; west border of the Whipple
   Mountains detachment terrane, IN Frost, E.G., and Martin,
   D.L., eds., Mesozoic-Cenozoic tectonic evolution of the
   Colorado River region, California, Arizona, and Nevada;
   Anderson-Hamilton volume: San Diego, CA, Cordilleran Publishers,
   p. 341-354, Published in conjunction with the Geological
   Society of America symposium and field trip, April, 1982

Usage in Publication:
Peach Springs Tuff

Modifications:	Geologic Province:	Dominant Lithology:
Areal limits Isotopic dating	Mojave basin

Summary:
Tuff resembling Peach Springs Tuff(?) (of Young, 1966) in age and lithology is present east and west of Stepladder Mountains in Sawtooth Range (Chemehuevi Mountains) and in Little Piute Mountains, CA. Consists of welded crystal-rich ash-flow tuff with blue sanidine with ages of 18.1 and 18.3 Ma.

Summary of Citation: Peach Springs

Publication:
Glazner, A.E., Nielson, J.E., Howard, K.A. and Miller, D.M.,
   1986, Correlation of the Peach Springs Tuff, a large-volume
   Miocene ignimbrite sheet in California and Arizona: Geological
   Society of America, Geology, v. 14, no. 10, p. 840-843

Usage in Publication:
Peach Springs Tuff

Modifications:	Geologic Province:	Dominant Lithology:
Areal limits Isotopic dating	Plateau sedimentary province Mojave basin

Summary:
Similarities in stratigraphic position, field appearance, petrography, isotopic ages, paleomagnetic directions and phenocryst composition indicate outcrops of chatoyant sanidine ash-flow tuff in central Mojave Desert may be equivalent to Peach Springs Tuff. If confirmed then Peach Springs Tuff is scattered over area of 35,000 sq km. Mean K-Ar age from sanidine and biotite is 18.3 Ma. Sketch map shows distribution.