K/Ar Chronology of the Tucson Mountains, Pima County, Arizona

Bikerman, Michael; Damon, Paul E.

doi:10.1130/0016-7606(1966)77[1225:acottm]2.0.co;2

Cited by 12 publications

(18 citation statements)

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“…The large zoned Amole pluton exposed in the northern Tucson Mountains (Figure 2) is a resurgent ring intrusion which cuts and arches the steeply dipping caldera fill upward to the east and north [Lipman, 1989]. K-Ar biotite ages of about 73 Ma for this intrusion [Bikerman and Damon, 1966] indicate that it was emplaced soon after eruption of the Cat Mountain Tuff, within analytical uncertainties of the isotopic ages. The volume of slide breccia is greater than the volume of ash flow tuff within the northern parts of the caldera fill, implying catastrophic subsidence in this sector.…”

Section: Introductionmentioning

confidence: 86%

Late Cretaceous paleomagnetism of the Tucson Mountains: Implications for vertical axis rotations in south central Arizona

Hagstrum¹,

Lipman²

1991

J. Geophys. Res.

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The Tucson Mountains of southern Arizona are the site of an Upper Cretaceous caldera from which the rhyolitic Cat Mountain Tuff was erupted at about 72 Ma. Two magnetic units within the Cat Mountain Tuff are distinguished by paleomagnetic data in both the northern and southern Tucson Mountains. The resurgent Amole pluton (≃72 Ma) in the northern Tucson Mountains was emplaced soon after eruption of the Cat Mountain Tuff but cooled and was magnetized after northeastward tilting (50°–85°) of the adjacent caldera‐fill sequence. Petrologic and paleomagnetic data indicate that the lower magnetic unit of the Cat Mountain Tuff caps the Silver Bell Mountains to the northwest. A previous paleomagnetic investigation (N = 34) indicates that the Silver Bell Mountains have been rotated clockwise 30°±16° (95% confidence level) about a vertical axis relative to cratonic North America. A similar paleomagnetic study of Upper Cretaceous volcanic, volcaniclastic, and intrusive units in the Tucson Mountains (N = 26) indicates that these rocks have been rotated 7°±14° clockwise relative to stable North America. A direct comparison of paleomagnetic directions for the lower unit of the Cat Mountain Tuff shows a 17°±10° clockwise rotation between the Silver Bell Mountains and the Tucson Mountains which supports the relative accuracy of the absolute rotations determined for these two mountain ranges. Preliminary paleomagnetic directions for middle Tertiary units from the Silver Bell and Tucson Mountains are consistent with clockwise rotation having occurred prior to deposition of these rocks. Clockwise rotation of crustal blocks in southern Arizona likely was associated with strike‐slip movement on major northwest trending faults in the region, and this movement may have been related to oblique subduction of oceanic plates along the western continental margin in Late Cretaceous and early Tertiary time. The available paleomagnetic data indicate that rocks in southern Arizona have not remained unrotated with respect to North America since Late Cretaceous time and that vertical axis rotations may have played an important role in the region during Laramide deformation.

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Section: Introductionmentioning

confidence: 86%

Late Cretaceous paleomagnetism of the Tucson Mountains: Implications for vertical axis rotations in south central Arizona

Hagstrum¹,

Lipman²

1991

J. Geophys. Res.

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“…to the upper andesite (Brown, 1939) at the top (about 28 m.y.) (Damon and Bikerman, 1964;Bikerman and Damon, 1966;Percious, 1968), perhaps including the thin conglomerate (Brown, 1939, p. 735-736 and pi. 1) that underlies the Rillito andesite.…”

Section: Pantano Formationmentioning

confidence: 99%

“…to about 19 m.y. in age (Damon and Bikerman, 1964;Bikerman and Damon, 1966;Percious, 1968). The flows are considered to be correlative with the lower Tinaja beds.…”

Section: Tinaja Bedsmentioning

confidence: 99%

Geohydrology and water resources of the Tucson basin, Arizona

Davidson¹

1970

Open-File Report

117

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The major source of water in the Tucson basin is the vast volume of ground water in storage in the aquifer underlying the basin. Ground water is pumped for irrigation, public supply, and industrial uses and is partially replenished by the infiltration of streamflow along the major streams and the basin perimeter. The basin is in southeastern Arizona and is a broad northwest-trending valley arcuately bounded by mountain ranges on the eastern and western sides. The 1,000-square-mile basin is about 50 miles long and is 15 to 20 miles wide in the southern and central parts and 4 miles wide at the northwest outlet. The surface of the basin slopes northwestward from an altitude of about 3,500 feet at the southern edge to an altitude of about 2,000 feet at the northwestern edge. The mountains on the west side of the basin range from 3,000 to 6,000 feet in altitude, and those on the east side range from 6,000 to 8,000 feet in altitude. The mean annual precipitation is only about 12 inches on the basin surface and 25 inches or slightly more in the mountains. Because most of the precipitation is evaporated or transpired, the mean annual streamflow past gaging stations on the major streams is only about 10,000 to 20,000 acre-feet. The major streams generally are dry during more than 300 days each year, and the flows generally last 3 days or less. Because of the erratic occurrence and quantity of flow, streamflow is not used directly as a water supply. The mean annual streamflow out of the basin is slightly more than 17,000 acrefeet. The aquifer that underlies the basin surface consists of the Pantano Formation and Tinaja beds of Tertiary age and the Fort Lowell Formation and surficial deposits of Quaternary age. These units are more than 2,000 feet thick and are composed mainly of loosely consolidated to moderately cemented silty sand to silty gravel. In the south-central part of the basin and in a small area in the northern part, a thick section of clayey silt to mudstone fills a structural depression caused by downfaulting of the Pantano Formation and the older units. The chemical quality of the ground water in most of the basin is suitable for public supply. Most of the water in the upper part of the aquifer contains less than 500 mg/1 (milligrams per liter) dissolved solids, and in most of the area the range in dissolved-solids content is from 250 to 1,500 mg/1; in El E2 WATER RESOURCES OF THE TUCSON BASIN a few isolated places concentrations as great as 3,000 mg/1 occur. The dissolved solids are mainly calcium, sodium, and bicarbonate. Ground water in the northern and northeastern parts of the basin generally contains less than 300 mg/1 dissolved solids and is moderately hard; elsewhere the dissolved-solids content generally ranges from 300 to 500 mg/1, and the water is hard. In the deep part of the aquifer the water generally contains less than 500 mg/1 dissolved solids, mainly sodium and bicarbonate, and is soft; but where the aquifer grades into clayey silt or mudstone, the water may contain more than 2,000 mg/1 dis...

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“…The large zoned granodioritic-granitic Amole pluton exposed along the northwest flank of the Tucson Mountains appears to be a resurgent ring intrusion that arches the caldera fill, including postcaldera lavas, upward to the east and north. The ages of the caldera-related volcanic rocks are constrained as Late Cretaceous (70-75 Ma) by published conventional K-Ar ages (Bikerman and Damon, 1966), and new 40Af_39 Ar determinations (L.W. Snee and P.W.…”

Section: The Tucson Mountains Caldera: Anatomy Of An Asymmetric Trap-mentioning

confidence: 99%

USGS research on mineral resources, 1994: Part B, Guide book for field trips

Lane¹

1994

Circular

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K/Ar Chronology of the Tucson Mountains, Pima County, Arizona

Cited by 12 publications

References 0 publications

Late Cretaceous paleomagnetism of the Tucson Mountains: Implications for vertical axis rotations in south central Arizona

Late Cretaceous paleomagnetism of the Tucson Mountains: Implications for vertical axis rotations in south central Arizona

Geohydrology and water resources of the Tucson basin, Arizona

USGS research on mineral resources, 1994: Part B, Guide book for field trips

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