Radiometric Ages of 

Igneous Rocks From 

Pima, Santa 

Cochise 

Cruz, and 

Counties, 

Southeastern Arizona 

By RICHARD F. MARVIN, T. W. STERN, 

S.C. CREASEY, and HARALD H. MEHNERT 

GEOLOGICAL SURVEY BULLETIN 1379 

A tabulation of K-Ar, Ph-a, and Rb-Sr ages 

for igneous rocks ranging in age from 

Pliocene to Pre cam brian 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1973 
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary 

GEOLOGICAL SURVEY 

V. E. McKelvey, Director 

Library of Congress catalog-card No. 72:600374 

For sale by the Superintendent of Documents, U.S. Govemment Printing Oftlce 

Washington, D.C. 20402-Price: Paper cover-35 cents domestic postpaid or 25 cents GPO Bookstore 

Stock Number 2401-00283 
CONTENTS 

Page 

Abstract ------------------------------------------------------- 1 

Introduction --------------------------------------------------- 1 

Acknowledgments ------------------------------------------- 2 

Radiometric ages ----------------------------------------------- 2 

Discussion ----------------------------------------------------- 4 

References cited ------------------------------------------------ 7 

ILLUSTRATION 

Page 

FIGURE 1. Map of southeastern corner of Arizona showing locations 

of geographic features used in text------------------ 3 

TABLES 

Page 

TABLE 1. Rock type, locality, and calculated age of samples from 

southeastern Arizona ------------------------------ 12 

2. Analytical data for K-Ar ages of mineral samples from 

southeastern Arizona ------------------------------ 23 

3. Analytical data for Pb-a ages of zircon from southeastern 

Arizona ------------------------------------------ 26 

4. Analytical data for Rb-Sr ages of samples from southeastern Arizona ----------------------------------- 26 

5. Major stratigraphic and time divisions ---------------- 27 

III 

RADIOMETRIC AGES OF IGNEOUS ROCKS 

FROM PIMA, SANTA CRUZ, 

AND COCHISE COUNTIES, 

SOUTHEASTERN ARIZONA 

By RICHARD F. MARVINJ T. w. STERNJ 

S. C. CREASEY} and HARALD H. MEHNERT 

ABSTRACT 

The U.S. Geological Survey has determined, by the K-Ar, Rb-Sr, and 

Ph-a methods, 126 radiometric ages of samples from the southeast corner 

of Arizona. All the data pertaining to these determinations, including both 

published and unpublished data, are assembled in tabular form. The radiometric ages of the samples indicate that during the Phanerozoic, from 

Triassic to Pliocene, the region experienced periods of plutonic and volcanic 

activity. Many of the exposed Precambrian rocks have a geologic history 

that extends back approximately 1,300-1,600 m.y. ago. 

INTRODUCTION 

During the last 10 years the U.S. Geological Survey has determined 126 radiometric ages on a total of 100 samples collected in 

Pima, Santa Cruz, and Cochise Counties in the southeast corner 

of Arizona. Many of these ages are unpublished ; the others are 

published, but are scattered through various reports that describe 

regional or local stratigraphy or detailed economic investigations. 

In most reports the analytical data related to the radiometric ages 

are not presented, and in some reports that do contain the analytical data the descriptions of sample localities of the dated rocks 

are missing or they are only generalized. The purpose of the 

present report, therefore, is to assemble the data pertinent to all 

126 ages. 

Many geologists commonly evaluate age determinations only in 

the light of geologic evidence and do not adequately consider the 

importance of the analytical data. Admittedly, an analytically 

valid age may occasionally prove to be geologically spurious because it conflicts with incontrovertible geologic field relations. 

1 
2 RADIOMETRIC AGES OF IGNEOUS ROCKS FROM ARIZONA 

Geologic events or natural physical processes can cause loss or 

gain of radiogenic isotopes after initial crystallization of a mineral, which in turn causes a spurious radiometric age. A geochronologist would require, however, that both the geologic setting 

and the analytical data be evaluated. Full presentation of the analytical data would reveal possible problems arising from the actual 

physical measurements during analysis, and would be useful in 

assessing the reliability of the particular radiometric age. 

The ages and related data presented in this paper can be of aid 

to those familiar with the local geology of southeastern Arizona; 

however, these ages do not constitute a formal geochronological 

study. Examples of such studies made in this region are those of 

the Tucson Mountains by Bikerman and Damon ( 1966) and of the 

Roskruge Mountains by Bikerman ( 1967). 

ACKNOWLEDGMENTS 

We are indebted to many Survey personnel for information and 

courtesies but especially to Harald Drewes, John R. Cooper, Philip 

T. Hayes, FrankS. Simons, and Tom L. Finnell. We also acknowledge the exacting work done by Gerald T. Cebula, John H. Mangum, and George C. Cone in obtaining necessary mineral 

concentrations. 

RADIOMETRIC AGES 

Radiometric ages were determined for a total of 100 rock samples collected from the southeast corner of Arizona. The samples 

are listed in table 1 according to geographic area (for example, 

Sierrita Mountains, Santa Rita Mountains) and within each area, 

according to age, with the youngest first. The relative locations of 

the mountain ranges and hills are shown in figure 1. 

In all, 84 K-Ar, 38 Pb-a, and four Rb-Sr ages were determined. 

The analytical data for these ages are shown in tables 2, 3, and 4, 

respectively. The analytical techniques used are described by 

Evernden and Curtis (1965) for the K-Ar method, Jaffe, Gott.:. 

fried, Waring, and Worthing (1959) for Pb-a, and Peterman, Doe 

and Bartel (1967), for Rb-Sr. Most of the mass spectrometric 

analyses of argon were made with the argon gas under static conditions; all other argon analyses were made under dynamic conditions (Hamilton, 1965, p. 54). Those K-Ar ages of Late Cretaceous or Tertiary age that were determined in the early 1960's 

were reported with only two significant figures, whereas today the 

ages are generally reported with three significant figures. 

Many samples were dated by both the K-Ar and Pb-a methods. 

For other samples, coexistent biotite and hornblende both were 
RADIOMETRIC AGES 

32° 

0 25 50 MILES 

,.-------., 

J I 

~ARIZONA~ L . : -,~ 

FIGURE 1.-Map of southeast corner of Arizona showing locations of 

geographic features mentioned in text. 

3 

analyzed by the K-Ar method. One of the purposes of this procedure, whether using two different age methods or a biotite-hornblende pair, was to check for reduced ages-those caused by a 

thermal event some time after the initial crystallization of the 

rock. Owing to the large degree of uncertainty that is inherent in 

the Pb-a age method, the practice of checking the K-Ar age by the 

Pb-a age is not now usually followed. When possible, a K-Ar mica 

age is now usually checked against an amphibole age from the 

same specimen or against a Rb-Sr whole-rock age. Unfortunately, many rocks can be dated by only one mineral. 

No doubt some reservations will be held concerning these Pb-a 

ages until they are confirmed or disproved by U-Pb isotopic ages. 

However, most Pb-a ages are consistent, within analytical error, 

with the geologic sequence as determined by field evidence within 

a geographic area, such as the Santa Rita Mountains. The large 

number of Pb-a ages determined for different igneous units in this 

region indicates that suitable zircons are available for U-Pb age 

investigations. 

For those who have difficulty in remembering the numerical geologic time scale, truble 5 has been included to help the reader translate the ages listed in table 1 to their corresponding major stratigraphic or time division. It should be noted that many radio-
4 RADIOMETRIC AGES OF IGNEOUS ROCKS FROM ARIZONA 

metric ages are on or near a time division boundary. In these instances, the possible age range, as indicated by the analytical error, may straddle the boundary; for example, the age of a sample 

may be Late Cretaceous or early Paleocene. The geologist, interpreting this radiometric age, may think that geologic field relations indicate a Late Cretaceous age in preference to the early 

Paloocene age. As a result of such decisions, some of the published 

radiometric ages in this tabulation have been interpreted more 

strictly than their analytical error alone would allow. 

DISCUSSION 

The radiometric ages discussed in this report have been of great 

help to geologists in deciphering the geologic history of the many 

intrusions and volcanics in southeastern Arizona. Paleontologic 

control, in many areas, is either nonexistent or of very limited 

help. With the help afforded by these ages, a much clearer understanding of the geologic history has been obtained, both on a local 

basis (see Cooper, 1971; Drewes, 1968, 1970, 197lb, 1972; Hayes 

and others, 1965; and Simons, 1972) and on a regional basis 

(Hayes, 1970a). However, the complete story is not known; some 

ages-discordant ages-indicate tectonic, thermal, or perhaps 

hydrothermal events that complicate or confus·e our understanding of the geologic history. Altered rock or unsuitable material 

prevents determination of ages in crucial areas. Many problems 

remain for geochronologists and geologists. 

For the most part, the Tertiary and Late Cretaceous ages determined for the rocks in this region coincide with the age span of 

igneous episodes determined by detailed geochronologic studies in 

the Tucson, Roskruge, and Chiricahua Mountains of Arizona 

(Bikerman and Damon, 1966; Bikerman, 1967; Marjaniemi, 

1968). These tabulated ages also indicate that igneous activity 

was most intense during the middle Tertiary and during the late 

Late Cretaceous . .and Paleocene. These two periods of intense 

activity agree with the peaks of a histogram of radiometric ages 

drawn by Damon and Mauger (1966) from ages representing the 

entire Basin and Range province. 

The youngest igneous rock radiometrically dated by us is a 

basalt flow of late Miocene or early Pliocene age. This basalt flow 

and others that are intercalated with gravels of the Nogales Formation on the west side of the Atascosa Mountains may represent a local outbreak of the same igneous event that produced 

felsic ash flows and basic flows and dikes during the late Miocene 

and ~arly Pliocene (14.4-9.7 m.y.) in the Roskruge Mountains 

(Bikerman, 1967). 
DISCUSSION 5 

No middle Miocene volcanic rocks have been disclosed by our 

ages, although rocks of that age are known elsewhere in southeastern Arizona--dacite near Superior dated by Creasey and 

Kistler (1962) and basaltic andesite in the Tucson Mountains 

dated by Bikerman and Damon (1966). Our radiometric ages do 

indicate widespread igneous activity during the late Oligocene 

and early Miocene (28-23 m.y.). Dikes of this age are known in 

the Sierrita and Santa Rita Mountains (samples 1, 2, 15, table 1), 

in the Roskruge Mountains (Bikerman, 1967), and in the Tucson 

Mountains (Bikerman and Damon, 1966). Tuffs and flows of mappable proportions also formed at this time in the Patagonia 

Mountains (samples 51, 52, table 1), Tucson Mountains (Bikerman and Damon, 1966), Chiricahua Mountains (Marjaniemi, 

1968), Del Bac Hills (Percious, 1968), and Santa Rita Mountains 

-Grosvenor Hills Volcanics (Drewes, 1968). During this same 

period of igneous activity, plutons were emplaced in the Santa 

Rita, Rincon, and Dragoon Mountains (samples 18, 19, 80, 81, 82, 

89, 90, table 1). 

Early and middle Oligocene ages are not common lbut have been 

obtained for plutonic rock in the Rosk,ruge Mountains (Bikerman, 

1967), and for extrusive rock in the Dragoon Mountains (sample 

91, table 1). Similar ages for volcanic rock have also been determined for the Helmet Fanglomerate near the Sierrita Mountains 

(Damon, 1968) and for tuff in the Pantano Formation near the 

Rincon Mountains (Damon and Bikerman, 1964). (The Pantano 

Formation may range in age from late Eocene to early Miocenesee sample 71, taJble 1 this report, and Finnell, 1970, p. A36, who 

assigned an Oligocene to Miocene age.) 

Bikerman and Damon (1966) reported that extrusive activity 

in the Tucson Mountains during late Eocene or early Oligocene 

formed the Rillito Andesite of Brown ( 1939). One or more rhyolitic tuffs in the Pantano ( ?) Formation near the Mustang Mountains are of the same age as the Rillito Andesite. 

A cessation of most igneous activity for about 10 m.y. occurred 

between the middle Tertiary igneous episode and an older igneous 

episode that extended from Late Cretaceous to middle Eocene, 

terminating with the emplacement of the Texas Canyon Quartz 

Monzonite in the Little Dragoon Mountains (sample 88, table 1) 

and (or) with the Eocene igneous activity in the Sierrita Mountains (samples 4, 5, 6, table 1; and Damon and Mauger, 1966). 

This older igneous episode culminated in the late Late Cretaceous 

and Paleocene. 

Intrusive igneous activity during the Paleocene produced stocks 

and plugs in the Sierrita, Santa Rita, and Patagonia Mountains 
6 RADIOMETRIC AGES OF IGNEOUS ROCKS FROM ARIZONA 

(samples 10, 21-25, 53, 54, table 1). Extrusive igneous activity 

also occurred as evidenced by a rhyolite tuff in the Sierrita Mountains (Creasey and Kistler, 1962) and by the Gringo Gulch Volcanics in the Santa Rita Mountains (Drewes, 1968). To the northwest, Paleocene flows and tuffs commonly occur in the Roskruge 

Mountains (Bikerman, 1967) and in the Tucson Mountains 

( Bikerman and Damon, 1966) . 

Dur:ing the Late Cretaceo,us, large stocks were formed in the 

Empire and Whetstone Mountains (samples 74, 75, 76, 79, table 1), 

the Tombstone Hills-the Schieffelin Granodiorite (Creasey and 

Kistler, 1962), and the Santa Rita Mountains-Elephant Head 

Quartz Monzonite, Madera Canyon Granodiorite, and Josephine 

Canyon Diorite (Drewes, 1968). Upper Cretaceous volcanics are 

the Demetrie Volcanics and Red Boy Rhyolite in the Sierrita Mountains (Cooper, 1971), the Salero Formation and the volcanic sections of the Fort Crittenden Formation in the Santa Rita Mountains (Drewes, 1968, 1971b), the volcanics of Dove Canyon in the 

Canelo Hills (Simons, 1972), the trachyandesite of Meadow Valley 

in the Patagonia Mountains (Simons, 1972), Uncle Sam Porphyry 

in Tombstone Hills (Drewes, 1971b, p. C75), and the Sugarloaf 

Quartz Latite in the Dragoon Mountains (Hayes, 1970a, p. B28; 

Drewes, 1971b, p. C75). Similar igneous activity was occurring 

during this time in the Tucson Mountains ( Bikerman and Damon, 

1966) and in the Roskruge Mountains (Bikerman, 1967). 

Volcanic activity during the Early Cretaceous is indicated by 

the volcanic sections of the Temporal and Bathtub Formations 

(Drewes, 1968, 1971b). However, radiometric ages have not confirmed the age designation of these formations (see samples 41, 

46, table 1) . 

Stocks of Jurassic age are the Sierrita Granite of Lacy (1959) 

in the Sierrita Mountains (sample 11, table 1), the Squaw Gulch 

Granite in the Santa Rita Mountains (Drewes, 1968), the granite 

of Comoro Canyon and quartz monzonite of Mount Benedict in the 

Patagonia Mountains (Simons, 1973), the Huachuca Quartz Monzonite in the Huachuca Mountains (Hayes, 1970b), the Gleeson 

Quartz Monzonite in the Dragoon Mountains (Anderson, 1968), 

and the Juniper Flat Granite in the Mule Mountains (Creasey and 

Kistler, 1962). Ages of these plutons range from 178 to 145 m.y. 

and suggest that most of the plutons were emplaced about Middle 

Jurassic. Tuffs and flows of Jurassic age are found in the Canelo 

Hills, Huachuca, Santa Rita, and Patagonia Mountains-Canelo 

Hills Volcanics (Hayes and Raup, 1968; Hayes, 1970a; Drewes, 

1971b; Simons, 1972). The Canelo Hills Volcanics may range in 

age from Trias·sic through Jurassic. 
REFERENCES CITED 7 

A few stocks gave discordant ages-a Jurassic age by the Pb-a 

method and a Late Cretaceous or Paleocene age by the K-Ar method. After considering the geologic possibilities, the geologists 

mapping the stocks decided that the Jurassic age was correct. 

Late Triassic plutons, as indicated by Pb-a ages, are the quartz 

monzonite of Harris Ranch in the Sierrita Mountains ( Coope·r, 

1971, p. D13) and the Piper Gulch Monzonite in the Santa Rita 

Mountains (Drewes, 1968). Triassic flows and tuffs are the Ox 

Frame Volcanics (Cooper, 1971), the Gardner Canyon and Mount 

Wrightson Formations in the Santa Rita Mountains (Drewes, 

1968, 1971b), and the Gardner Canyon Formation in the Empire 

Mountains (sample 77, table 1). 

Those Pb-a ages that suggest a Mississippian, Pennsylvanian, or 

Permian age are probably spurious. The Paleozoic marine sedimentary sequence, ranging in age from Cambrian to Permian, 

indicates that the region was stable and that igneous activity at 

this time was unlikely. 

The presence of Precambrian intrusive rocks in the Sierrita, 

Santa Rita, and Patagonia Mountains is confirmed by Pb-a and 

Rb-Sr ages (samples 14, 48, 49, 61, table 1). In the Santa Rita 

Mountains, it is likely that all K-Ar mica ages for the Precambrian 

Continental Granodiorite (Drewes, 1968) will be reduced ages, 

due to heating caused by Mesozoic and (or) Tertiary igneous 

activity. 

REFERENCES CITED 

Acker, C. J., 1958, Geologic interpretations of a siliceous breccia in the 

Colossal Cave area, Pima County, Arizona: Arizona Geol. Soc. Digest, 

p. 47. -

Anderson, C. A., 1968, Arizona and adjacent New Mexico, in Ore deposits 

of the United States, 1933-1967 (Graton-Sales Volume), v. 2: New 

York, Am. Inst. Mining, Metall. and Petroleum Engineers, p. 1163-1190. 

Berggren, W. A., 1969, Cenozoic chronostratigraphy, planktonic foraminiferal zonation and the radiometric time scale: Nature, v. 224, no. 5224, 

p. 1072-1075. 

Bikerman, Michael, 1967, Isotopic studies in the Roskruge Mountains, Pima 

County, Arizona: Geol. Soc. America Bull., v. 78, no. 8, p. 1029-1036. 

Bikerman, Michael, and Damon, P. E., 1966, K/ Ar chronology of the Tucson 

Mountains, Pima County, Arizona: Geol. Soc. America Bull., v. 77, 

no. 11, p. 1225-1234. 

Brown, W. H., 1939, Tucson Mountains, an Arizona basin range type: Geol. 

Soc. America Bull., v .. 50, no. 5, p. 697-760. 

Cooper, J. R., 1971, Mesozoic stratigraphy of the Sierrita Mountains, Pima 

County, Arizona: U.S. Geol. Survey Prof. Paper 658-D, 42 p. 

Oooper, J. R., and Silver, L. T., 1964, Geology and ore deposits of the 

Dragoon quadrangle, Cochise County, Arizona: U.S. Geol. Survey Prof. 

Paper 416, 196 p. 
8 RADIOMETRIC AGES OF IGNEOUS ROCKS FROM ARIZONA 

Creasey, S. C., 1967, Geologic map of the Benson quadrangle, Cochise and 

Pima Counties, Arizona: U.S. Geol. Survey Misc. Geol. Inv. Map 1-470. 

Creasey, S. C., and Kistler, R. W., 1962, Age of some copper-bearing porphyries and other igneous rocks in southeastern Arizona, in Short 

papers in geology, hydrology, and topography: U.S. Geol. Survey Prof. 

Paper 450-D, p. D1-D5. 

Damon, P. E., compiler, 1966, Correlation and chronology of ore deposits and 

volcanic rocks-U.S. Atomic Energy Comm. Contract AT(11-1)-689, 

Ann. Prog. Rept. C00-689-100: Tucson, Ariz., Geochronology Labs., 

Univ. Arizona, [153] p. 

--- compiler, 1968, Correlation and chronology of ore deposits and volcanic rocks-U.S. Atomic Energy Comm. Contract AT(ll-1)-689, Ann. 

Prog. Rept. C00-689-100: Tucson, Ariz., Geochronology Labs., Univ. 

Arizona, [261] p. 

Damon, P. E., and Bikerman, Michael, 1964, Potassium-argon dating of 

post-Laramide plutonic and volcanic rocks within the Basin and Range 

province of southeastern Arizona and adjacent areas: Arizona Geol. 

Soc. Digest, v. 7, p. 63-78. 

Damon, P. E., and Mauger, R. L., 1966, Epeirogeny-orogeny viewed from 

the Basin and Range province: Soc. Mining Engineers Trans., v. 235, 

no. 1, p. 99-112. 

Drewes, Harald, 1968, New and revised stratigraphic names in the Santa 

Rita Mountains of southeastern Arizona: U.S. Geol. Survey Bull. 

1274-C, 15 p. 

--- 1970, Structural control of geochemical anomalies in the Greaterville 

mining district, southeast of Tucson, Arizona: U.S. Geol. Survey Bull., 

1312-A, 49 p. 

--- 1971a, Geologic map of the Mount Wrightson quadrangle, southeast 

of Tucson, Santa Cruz and Pima Counties, Arizona: U.S. Geol. Survey 

Misc. Geol. Inv. Map I-614. 

--- 1971b, Mesozoic stratigraphy of the Santa Rita Mountains, southeast 

of Tucson, Arizona: U.S. Geol. Survey Prof. Paper 658-C, 81 p. 

--- 1971c, Geologic map of the Sahuarita quadrangle, southeast of 

Tucson, Pima County, Arizona: U.S. Geol. Survey Misc. Geol. Inv. 

Map I-613. 

--- 1972, Cenozoic rocks of the Santa Rita Mountains, southeast of 

Tucson, Arizona: U.S. Geol. Survey Prof. Paper 746, 66 p. 

Evernden, J. F., and Curtis, G. H., 1965, The potassium-argon dating of 

late Cenozoic rocks in East Africa and Italy: Current Anthropology, 

v. 6, p. 343-385. 

Evernden, J. F, Savage, D. E., Curtis, G. H., and James, G. T., 1964, 

Potass•ium-argon dates and the Cenozoic mammalian chronology of 

North America: Am. Jour. Sci., v. 262, no. 2, p. 145-198. 

Finnell, T. L., 1970, Pantano Formation, in Changes in stratigraphic nomenclature by the U.S. Geological Survey, 1968: U.S. Geol. Survey Bull. 

1294-A, p. A35-A36. 

--- 1971, Preliminary geologic map of the Empire Mountains quadrangle, Pima County, Arizona: U.S. Geol. Survey open-file map. 

Geological Society of London, 1964, The Phanerozoic time-scale-A symposium: Geo.l. Soc. London Quart. Jour., v. 120, Supp., 457 p. 

Gilluly, James, 1956, General geology of central Cochise County, Arizona: 

U.S. Geol. Survey Prof. Paper 281, 169 p. 
REFERENCES CITED 9 

Hamilton, E. 1., 1965, Applied geochronology: London, Academic Press, 

267 p. 

Hayes, P. T., 1970a, Cretaceous paleogeography of southeastern Arizona 

and adjacent areas: U.S. Geol. Surv-ey Prof. Paper 658-B, 42 p. 

--- 1970b, Mesozoic stratigraphy of the Mule and Huachuca Mountains, 

Arizona: U.S. Geol. Survey Prof. Paper 658-A, 28 p. 

Hayes, P. T., and Raup, R. B., 1968, Geologic map of the Huachuca and 

Mustang Mountains, southeastern Arizona: U.S. Geol. Survey Misc. 

Geol. Inv. Map 1-509. 

Hayes, P. T., Simons, F. S., and Raup, R. B., 1965, Lower Mesozoic extrusive rocks in southeastern Arizona-The Canelo Hills Volcanics: U.S. 

Geol. Survey Bull. 1194-M, 9 p. 

Jaffe, H. W., Gottfried, David, Waring, C. L., and Worthing, H. W., 1959, 

Lead-alpha age determinations of accessory minerals of igneous rocks 

(1953-1957): U.S. Geol. Survey Bull. 1097-B, p. 65-148. 

Lacy, W. C., 1959, Structure and ore deposits of the East Sierrita area: 

Arizona Geol. Soc., Guidebook II, p. 186. 

Livingston, D. E., Damon, P. E., Mauger, R. L., Bennett, Richmond, and 

Laughlin, A. W., 1967, Argon 40 in cogenetic feldspar-mica mineral 

assemblages: Jour. Geophys. Research, v. 72, no. 4, p. 1361-1375. 

Lovering, T. G., Cooper, J. R., Drewes, Harald, and Cone, G. C., 1970, Copper 

in biotite from ign·eous rocks in southern Arizona as an ore indicator, 

in Geological Survey research 1970: U.S. Geol. Survey Prof. Paper 

700-B, p. B1-B8. 

Marjaniemi, Darwin, 1968, Tertiary volcanism in the northern Chiricahua 

Mountains, Cochise County, Arizona, in Southern Arizona Guidebook 

3-Geol. Soc. America Cordilleran Sec., 64th ann. mtg., Tucson, 1968: 

Tucson, Ariz., Arizona Geol. Soc., p. 209-214. 

Percious, J. K., 1968, Geology and geochronology of the Del Bac Hills, 

Pima County, Arizona, in Southern Arizona Guidebook 3-Geol. Soc. 

America Cordilleran Sec., 64th ann. mtg., Tucson, 1968: Tucson, Ariz., 

Arizona Geol. Soc., p. 199-207. 

Peterman, Z. E., Doe, B. R., and Bartel, Ardith, 1967, Data on the rock 

GSP-1 (granodiorite) and the isotope-dilution method of analysis for 

Rb and Sr, in Geological Survey research 1967: U.S. Geol. Survey PrQf. 

Paper 575-B, p. B181-B186. 

Simons, F. S., 1972, Mesozoic stratigraphy of the Patagonia Mountains 

and adjoining areas, Santa Cruz County, Arizona: U.S. Geol. Survey 

Prof. Paper 658-E, 23 p. 

--- 1973, Geologic map and sections of the Nogales and Lochiel quadrangles, Santa Cruz County, Arizona: U.S. Geol. Survey Misc. Geol. 

Inv. Map 1-762 (in press). 

TABLES 1-5 
TABLE 1.-Rock tJype, locality, and calculated age of samples from southeastern Arizona 

[~amples are listed, under geographic region, according to age, with the youngest first. Radiometric-age method (K-Ar, Rb-Sr, or Pb-a) and analyzed mineral or material (B for biotite; F. K-feldspar; H. hornblende; M. muscovite; P. plagioclase; s. sanidine; WR. whole rock; and z. zircon) are specified within the parentheses following the calculated age. A;nalyticaJ data are shown on tables 2. 3. and 4] 

Sample 

No. 

Rock type, 

intrusive body. or stratigraphic formation 

1 Andesite ------------------

2 Kersantite ----------------

3 Granodiorite, sheared and 

altered. 

4 Granodiorite porphyry, Ruby 

Star ( ? ) Granodiorite. 

5 Gangue -------------------

6 Altered diorite ------------

Location 

(latitude N .• longitude W.) 

31°56'45" 

111 °04'15" 

31 °59'42·" 

11ro4' 

31 °59'30" 

111 °07' 

31 °58' 

111 °06' 

31 °59'35" 

111 °04' 

31 °52' 

111 °07' 

Calculated age (m.y.) 

Sierrita Mountains 

24 

26.4±1.0 

36±2 

46±2 

47±2 

47±3 

(K-Ar,B) 

(K-Ar,B) 

(K-Ar,B) 

(K-Ar,B) 

(K-Ar,F) 

(K-Ar,F) 

Comment and (or) reference 

Creasey and Kistler (1962, p. D1, No. 7 

of table 120.1). 

Unpublished age of unmineralized dike 

cutting hypogene copper ore body, 

Mission mine, Pima district; dike is 

related to the same igneous event that 

produced the 24-m.y.-old andesite dikes 

(see sample 1). 

Unpublished age f.or granodiorite; Da- mon and Mauger (1966) obtained 

50.7±1.1 m.y. for muscovite from 

pegmatite cutting this intrusion (J. 

R. Cooper, written commun., 1971). 

Unpublished age; it may have been re- duced by pegmatitic activity dated by 

Damon and Mauger (1966) (see com- ment for sample 3) ; Lovering and 

others ( 1970, p. B5) considered the 

Ruby Star Granodiorite to be Paleo. cene (see sample 10). 

Unpublished age, Mission mine, Pima 

district; probably a reduced age. 

Unpublished age of mineralized rock 

from west end of the Esperanza mine, 

Pima district; probably a reduced age. 

Damon and Mauger ( 1966) obtained 

62.6±2.0 m.y. for altered diorite in 

the same area and 60.6±1.8 m.y. for 

muscovite from quartz veinlets, Esper- anza pit, 31 °52.0'N, 111 °07.7'W. 

~ 

~ 

~ 

> tj 

~ 

0 

a:: 

~ ~ ~ 

Q 

> 

~ 

trJ 

00 

0 

l'!l:j 

~ 

~ 

z 

t%.1 

0 

c::: 

00 

~ Q 

~ 

00 

~ 0 

a:: 

> 

~ ~ 

N 

0 

z 

> 
7 Quartz monzonite porphyry -

8 Rhyolite tuff --------------

9' Coarse biotite veinlets in 

diorite. 

10 Granodiorite, Ruby Star 

Granodiorite. 

11 Alkali granite, Sierrita Granite of Lacy (1959). 

12 Quartz monzonite, quartz 

monzonite of Harris 

Ranch. 

13 Quartz monzonite, quartz 

monzonite of Harris 

Ranch(?). 

14 Gneissic quartz monzonite __ _ 

15 Rhyolite vitrophyre, Box 

Canyon dike swarm. 16 Rhyodacite vitrophyre, Gros- . venor Hills Volcanics. 

17 Latite vitrophyre, Grosvenor 

Hills Volcanics. 

18 Granodiorite, granodiorite of 

the San Cayetano Mountains. 

31 °52'3()" 

111 °07'45" 

31 °57'30" 

111 °04'30" 

31 °53' 

11r09' 

31 °,54'00" 

111 °06'30" 

31 °54' 

111 °11'30" 

31 °52' 

111 °10' 

31 °56' 

111 °16' 

31 °54' 

111 °05' 

31 °45'30" 

110°48'05" 

31 °34'05" 

110°53'10" 

31 °31'15" 

110°50'55" 

31 °32'15" 

110°59'00" 

56 

57 

60±3 

56±3 

60 

150±20 

55±3 

190±20 

210±30 

40±2 

850±100 

(K-Ar,B) 

(K-Ar,B) 

(K-Ar,B) 

(K-Ar,F) 

(K-Ar,B) 

(Pb-ct,Z) 

(K-Ar,B) 

(Pb-ct,Z) 

(Pb-ct,Z) 

(K-Ar,B) 

(Pb-ct,Z) 

Santa Rita Mountains 

25.9±1.3 

26.2±1.9 

26±2 

27±3 

~±W 

2~6±1.3 

(K-Ar,S) 

(K-Ar,P) 

(K-Ar,B) 

(K-Ar,H) 

(Pb-ct,Z) 

(K-Ar,B) 

Creasey and Kistler (1962, p. D1, No. 5 

of table 120.1) . Creasey and Kistler (1962, p. D1, No. 6 

of table 120.1). 

Unpublished ages for diorite from copper prospect 1.6 mi. WNW. of Esper- anza mine; Lovering and others (1970, 

p. B7) mentioned age relations of 

igneous intrusions. 

Creasey and Kistler (1962, p. D1, No. 4 

of table 120.1). 

Ages given by sample T169 (Cooper, 

1971, p. D13); biotite age appears to 

be a reduced age. Damon (1966, p. 23) 

cited a Rb-Sr age of 140±14 m.y. for 

the age of an alkali granite sample 

collected near sample 11. 

Age given by sample T400 (Cooper, 1971, 

p. D13). 

Unpublished ages; biotite age appears to 

be a reduced age. 

Unpublished age for Precambrian granitic complex (J. R. Cooper, written 

commun., 1971). 

Age given by sample 899 (Drewes, 

1971c) . Also see Drewes ( 1972.) 

Age given by sample 710 (Drewes, 

1971a). Drewes (1968, p. C15; 1972.) 

considered the Grosvenor Hills Volcanics to be late(?) Oligocene. 

Ages given by sample 315 (Drewes, 

1971a). See comment for sample 16. 

Age given by sample 687 (Drewes, 

1971a). (Also see Drewes 1972.) 

~ t"'4 

t.:J 

fll 

1-' 

~ 
TABLE 1.-Rock type, locality, and calculated age of samples from southeastern Arizona-Continued 

Sample 

No. 

Rock type, 

intrusive body, or stratigraphic formation 

19 Rhyodacite vitrophyre ------

20 Rhyolite porphyry, Gardner 

Canyon dike swarm. 

21 Granodiorite ___________ .:_ __ _ 

22 Quartz latite porphyry -----

23 _____ do -------------------

24 _____ do -------------------

25 _____ do -------------------

26 Latitic lava, Mount Wrigh~ 

son Formation. 

27 Hornblende dacite porphyry, 

Gringo Gulch Volcanics. 

28 Microgranodiorite, Gringo 

Gulch Volcanics. 

Location 

(latitude N., 

longitude W.) 

Calculated age (m.y.) 

Santa Rita Mountains--Continued 

31 °35'35" 

110°55'35" 

31 °43'13" 

110°46'03" 

31 °50'15" 

110°4S'25" 

31 °52'31" 

110°47'20" 

31 °46'00" 

110°46'45" 

31 °51'15" 

110°45'30" 

31 °51'45" 

110°47'00" 

31 °41'40" 

110°5S'30" 

31 °35'05" 110°46~55" 

31°35'10'' 

110°46'40" 

27.S±2.2 

40±10 

53.5±2.0 

52.2±2.0 

5-3.9±2.0 

55.7±2.2 

55.S±2.1 

56.3±2.1 

60±10 

60.4±4.2 

60±3 

50±10 

(K-Ar,H) 

(Pb-a,Z) 

(K-Ar,B) 

(K-Ar,B) 

(K-Ar,B) 

(K-Ar,B) 

(K-Ar,B) 

(K-Ar,B) 

(Pb-a,Z) 

(K-Ar,H) 

(K-Ar,B) 

(Pb-a,Z) 

Comment and (or) reference 

Age given for sample 5S1 (Drewes, 

1971a). Laccolith intruding Grosvenor 

Hills Volcanics (H. Drewes, written 

commun., 1971). 

Age given by sample 340 (Drewes, 

1971a). Dikes are likely Oligocene (H. 

Drewes, written commun., 1971). 

Age given by sample 1051 (Drewes, 

1971c). Paleocene stock (Lovering and 

others, 1970, p. B4). 

Unpublished age of Paleocene plug men- tioned by Lovering and others ( 1970, 

p. B4). . 

Paleocene plug (Lovering and others, 

1970, p. B4; Drewes, 1970, p. AS). 

Age given by sample 11S5 (Drewes, 

1971c). Paleocene plug (Lovering and 

others, 1970, p. B4; Drewes, 1970, p. 

AS). 

Age given by sample 1245 (Drewes, 

1971c). Paleocene plug (Lovering and 

others, 1970, p. B4). 

Age given by sample 917 (Drewes, 

1971a). Age is spurious as Mount 

Wrightson Formation is Triassic ac- cording to Drewes (196S, p. C6--C7; 

1971b, p. C14). 

Age given by sample 660 (Drewes, 

1971a). (Also see Drewes, 1972.) 

Age given by sample 2S1 (Drewes, 

1971a). (Also see Drewes, 1972.) 

...... 

H:::o. 

~ 

> t:l 

1-4 

0 

~ ~ 1-4 

0 

> 

~ 

l%j 

00 

0 

"%j 

1-4 

C'l 

z 

l%j 

0 

c::: 

00 

~ 

0 

0 

p::: 

00 

"%j 

~ 

0 

a: 

> 

~ 1-4 

~ 

0 

~ 
29 Diorite, Josephine Canyon 

Diorite. 

30 _____ do -------------------

31 Quartz monzonite, Josephine 

Canyon Diorite. 

32 Dacite porphyry -----------

33 Quartz porphyry, Elephant 

Head Quartz Monzonite. 

34 Quartz monzonite, Elephant 

Head Quartz Monzonite. 

35 Rhyodacite welded tuff, Salero Formation. 

36 Quartz diorite -------------

37 Quartz monzonite ----------

38 Granite, Squaw Gulch Granite. 

39 _____ do -------------------

40 Porphyritic granodiorite, 

Continental Granodiorite. 

31 °33'55" 

110°50'40" 

31 °34'55" 

110°51'10" 

31 °32'50" 

110°49'40" 

31 °37'25" 

110°47'30" 

31 °42'35" 

110°56'00" 

31 °43'35" 

110°53'50" 

31 °35'45" 

110°55'35" 

31 °55'20" 

110°42'30" 

31 °55'50" 

110°43'36" 

31 °36'30" 

110°56'20" 

31 °34'15" 

110°49'05" 

31 °37'03" 

110°55'45" 

60±10 

67±3 

60±10 

60±20 

67±3 

60±10 

68.2±3.0 

170±20 

69.0±2.9 

190±30 

72.5±3.3 

73.6±2.8 

73.8±2.6 

145±6 

160±20 

160±20 

159±7 

(Pb-a,Z) 

(K-Ar,B) 

(Pb-a,Z) 

(Pb-a,Z) 

(K-Ar,H) 

(Pb-a,Z) 

(K-Ar,B) 

(Pb-a,Z) 

(K-Ar,B) 

(Pb-a,Z) 

(K-Ar,B) 

(K-Ar,B) 

(K-Ar,B) 

(K-Ar,B) 

(Pb-a,Z) 

(Pb-a,Z) 

(K-Ar,B) 

Age given by sample 292 (Drewes, 

1971a). Josephine Canyon Diorite is 

Late Cretaceous according to Drewes 

1968, p. G12). 

Ages given by sample 316 (Drewes, 

1971a). See comment for sample 29. 

Age of fine-grained quartz monzonite 

phase of the Josephine Canyon Diorite, 

sampl·e 507 (Drewes, 1971a). See com- ment for sample 29. 

Ages given by sample 379 from Paleo- cene dike (Drewes, 1971a). 

Ages given by sample 754 (Drewes, 

1971a). An age of Late Cretaceous 

for the Elephant Head Quartz Monzonite has been designated, but a J urasSiic age is not geologically impossible (Drewes, 1968, p. C13-C14). 

Ages given by sample 876 (Drewes, 

1971a). See comment for sample 33. 

Age given by sample 580 (Drewes, 

1971a). Drewes (19•68, p. Cll-C12; 

1971b, p. C74-G75) stated that the 

Salero Formation is Late Cretaceous. 

Simons ( 1972, p. E21). 

Unpublished age of quartz diorite stock 

mapped by Finnell (1971). 

Unpublished age of quartz monzonite 

stock mapped by Finnell (1971). 

Ages given by sample 605 (Drewes, 

1971a) . Squaw Gulch Granite described by Drewes (1968, p. C8). 

Age given by sample 282 (Drewes, 

1971a). See comment for sample 38. 

Unpublished age given by sample of 

recrystallized Precambrian granodiorite (H. Drewes, written commun., 

1971). 

tot 

~ t::-:J 

Ul 

...... 

Q1 
TABLE 1.-Rock type, locality, and calculated age of samples from southeastern Arizona--Continued 

Sample 

No. 

Rock type. 

intrusive body. or stratigraphic formation 

41 Rhyolitic welded tuff, Temporal Formation. 

42 Monzonite, Piper Gulch Monzonite. 

43 Quartz monzonite, Piper 

Gulch Monzonite. 

44 Dacite flow, upper member 

of Gardner Canyon Formation. 

45 Latitic lava, middle member 

of Mount Wrightson Formation. 

46 Dacite volcanic breccia, middle member of Bathtub 

Formation. 

47 Rhyolite tuff, tuff member of 

Fort Crittenden Formation. 

Location 

(latitude N., 

longitude W.) 

Calculated age (m.y.) 

Santa Rita Mountains--Continued 

31°34'40" 

110°47'50" 

31 °37'40" 

110°49'35" 

31°45'30" 

110°46' 

31 °43'15" 

110°46'05" 

31°42'00" 

110°51'00" 

31 °37'25" 

110°47'30" 

31°40'25" 

110°57'00" 

180±20 

180±20 

180±30 

190±20 

220±30 

250±45 

260±30 

(Pb-e~,Z) 

(Pb-e~,Z) 

(Pb-e~,Z) 

(Pb-e~,Z) 

(Pb-e~,Z), 

(Pb-e~,Z) 

(Pb-e~,Z) 

Comment and (or) reference 

Age given by sample 905 (Drewes, 

1971a). Drewes (1968, p. C8-C9; 1971b~ p. C33-C34) wrote that the 

Temporal Formation is probably 

Early Cretaceous and that the dated 

zircons may be xenocrystic, coming 

from the underlying Squaw Gulch 

Granite regolith. 

Age given by sample 280 (Drewes, 

1971a). Drewes ( 1968, p. C8-C9) described the Piper Gulch Monzonite as Triassic. 

Unpublished age. See comment for sam- ple 42. 

Age given by sample 339 (Drewes, 

1971a). Gardner Canyon Formation 

is Triassic according to Drewes ( 1968, 

p. C7; 1971b, p. C24). Simons (1972, 

p. E2). 

Age given by sample 918 (Drewes, 

1971a). Mount Wrightson Formation 

described by Drewes ( 1968, p. C6-C7). 

Age given by sample 1113 (Drewes, 

1971a). The Bathtub Formation is 

Early Cretaceous according to Drewes 

(1968, p. C9-C10; 1971b, p. C43). Zir- con age is too old. 

Age given by sanmple 1046 (Drewes, 

1971a). The Fort Crittenden Formation is Late Cretaceous according to 

Drewes (1968, p. C10-Cll; 1971b, p. 

C63) . Zircon age is too old. , 

....... 

0) 

~ 

> t:::l 

1-4 

0 

~ ~ 1-4 

0 

> Cj) 

1::'=.1 

00 

0 

l'%j 

1-4 

Cj) 

z 

t:-:2 

0 

c::: 

00 

~ 

0 

n 

~ 

00 

;a 

0 

~ 

> 

~ 1-4 

t."' 

0 

z 

> 
48 Porphyroblastic granodiorite, 

Continental Granodiorite. 

49 _____ do -------------------

50 Olivine basalt, Nogales Formation. 

51 Rhyolite tuff ---------------

52 -----do -------------------

53 Granodiorite ---------------

54 Quartz monzonite ----------

55 Alkali syenite, granite of Co- moro Canyon. 

31 °47'55" 

110°48'30" 

31°47'55" 

110°46'50" 

31 °27' 

111 °03'30" 

31°27'40" 

110°40' 

31 °29'15" 

110°48'15" 

31 °23'15" 

110°43' 

31 °20'30" 

110°44'45" 

31°28' 

110°46'30" 

1360±200 

55.5±2.4 

1450±160 

800±80 

(Pb-«Z,Z) 

(K-Ar,B) 

(Pb-«Z,Z) 

(Rb-Sr,WR) 

Atascosa Mountains 

12.6±0.8 (K-Ar,WR) 

Patagonia Mountains 

23±2 (K-Ar,B) 

27±3 (K-Ar,H) 

26±2 (K-Ar,B) 

58±3 (K-Ar,B) 

58±5 (K-Ar,H) 

58±3 (K-Ar,B) 

150±20 (Pb-«Z,Z) 

Ages given by sample 1046 (Drewes, 

1971c). Drewes (1968, p. C5) described the Continental Granodiorite as Precambrian. K-Ar age is a re- duced age. Biotite shows recrystallization fabric (H. Drewes, written 

commun., 1971). 

Ages given by sample 914 (Drewes, 

1971c). Rb-Sr age is a reduced age. 

See comment for sample 48. 

Unpublished age of basalt flow intercalated in gravels of the Nogales 

Formation (H. Drewes, written com- mun., 1971). 

Unpublished ages. 

Unpublished age. Damon and Bikerman 

(1964) obtained 25.3±5.1 m.y. for 

biotite from same locality (F. S. 

Simons, written commun., 1971). Unpubli~hed ageg for probable Paleo- cene pluton. Damon and Mauger 

(1966) determined a K-Ar age of 

63.9±2.0 m.y. for sample of quartz 

diorite collected at 31°23.2'N, 

l10°43.1'W. 

Unpublished age for quartz monzonite 

facies of granodiorite pluton dated 

by sample 53 (F. S. Simons, written 

commun., 1971). See comment for 

sample 53. 

Unpublished age. Granite of Comoro 

Canyon is Jurassic according to Si- mons (1972, p. E10). Pluton mapped 

by Simons (1973). 

s 

~ fll 

~ "'""' 
TABLE 1.-Rock type, locality, and calculated age of samples from southeastern Arizona-Continued 

Sample 

No. 

Rock type, 

intrusive body, or stratigraphic formation 

56 Tuff, Nogales Formation ----

57 Quartz monzonite, quartz 

monzonite of Mount Benedict. 

58 Granite, granite of Comoro 

Canyon. 

59 Quartz monzonite ----------

60 Granite, granite of Comoro 

Canyon. 

61 Quartz monzonite ----------

62 Quartz monzonite, Huachuca 

Quartz Monzonite. 

63 _____ do -------------------

64 Granodiorite, Huachuca 

Quartz Monzonite. 

65 Welded tuff, Canelo Hills 

Volcanics. 

Location 

(latitude N., 

longitude W.) 

Calculated age (m.y.) 

Patagonia Mountains--Continued 

31 °23'30" 

110°56' 

31 °24'30" 

110°55"30" 

31 °26'30" 

110°47' 

31 °27' 110°49~ 

31 °29'45" 

110°46'00" 

31 °25'35" 

110°42'10" 

31 °22' 

110°17' 

31 °21'15" 

110°15'15" 

31 °21' 

110°15' 

31 °23'20" 

110°23'. 

153±10 

160±7 

164±19 

160±20 

240±30 

520±60 

1280±150 

(K-Ar,H) 

(K-Ar,B) 

(K-Ar,H) 

(Pb-a.,Z) 

(Pb-a.,Z) 

(Pb-a.,Z) 

(Pb-a.,Z) 

Huachuca Mountains 

90±30 

164±6 

210±30 

144±6 

144±11 

(Pb-a.,Z) 

(K-Ar,B) 

(Pb-a.,Z) 

(K-:Ar,B) 

(Rb-Sr,WR) 

Comment and (or) reference 

This age is spurious as tuff is part of 

upper Tertiary Nogales Formation 

(F. S. Simons, written commun., 

1971). 

Unpublished ages. Pluton mapped by 

Simons (1973). 

Age given by sample 14 (Simons, 1972, 

p. Ell, table 1). See comment for 

sample 55. 

Age is anomalous; pluton is Precambrian ( ?) (F. S. Simons, written commun~. 1971). 

Age is spurious (F. S. Simons, written 

commun., 1971). See comment for 

sample 55. 

Unpublished age. Pluton mapped by 

Simons ( 1973) . 

Unpublished age which appears to be 

too young for this Jurassic pluton. 

See comment for sample 63. 

Hayes ( 1970b, p. A10) considered this 

pluton to be Jurassic; mapped by 

Hayes and Raup (1968). 

Unpublished age which appears to be 

too old for this Jurassic pluton. See 

comment for sample 63. 

Hayes (1970b, p. AS); Simons (1972, 

p. E2) . Rb-Sr age has not been published previously. 

1-4 

00 

~ 

> t::J 

,..... 

0 

~ 

~ ,..... 

~ 

(j 

> 

~ 

t:z:J 

00 

0 

l'%j 

,..... 

~ 

z 

t.:z:J 

0 

q 

00 

~ 

0 

(j 

~ 

00 

~ 

~ 

0 

~ 

> 

~ ,..... 

IS 

0 

~ 
66 Andesite, andesite unit in 

Glance Conglomerate. 

67 Latitic welded tuff, trachyandesite of Meadow Valley. 

68 Partly welded latitic tuff, volcanics of Dove Canyon. 

69 Welded tuff, Ganelo Hills Volcanics. 

70 Rhyolitic tuff, Canelo Hills 

Volcanics. 

71 Rhyolitic tuff, Pantano(?) 

Formation. 

72 Latitic welded tuff ---------

73 Dacite, Pantano Formation __ 

74 Quartz monzonite ----------

75 _____ do ---------------~---

76 _____ do -------------------

31 °27'45" 

110°23'10" 

31 °28'45" 

110°36' 

31 °24'45" 

110° 30' 45" 

3P24' 

110°23' 

31 °29 .. 30" 

110°32' 

31 °37' 

110°25' 

3P39' 

110°28' 

31 °52'48" 

110°39'51" 

31 °54' 

110°38' 

31°54'30" 

110°39·'20" 

31 °53'15" 

110° 37' 40" 

220±35 

Canelo Hills 

72.1±3.0 

72±4 

165±6 

173± 8 

(Pb-11,Z) 

(K-Ar,B) 

(K-Ar,B) 

(K-Ar,B) 

(K-Ar,B) 

Mustang Mountains 

38.9±1.5 (K-Ar,B) 

310±40 (Pb-11,Z) 

Empire Mountains 

28.0±1.1 

70.3±2.5 

8()±15 

110±20 

(K-Ar,B) 

(K-Ar,B) 

(Pb-11,Z) 

(Pb-11,Z) 

Unpublished age which is too old for 

this unit or field assignment by Hayes 

and Raup (1968) is in error (P. T. 

Hayes, written commun., 1971). 

Simons ( 1972, - p. E21). Formation 

mapped by Simons (1973). 

Simons (1972, p. E18). Formation 

mapped by Simons (1973). 

Hayes ( 1970a, p. B20). Tuff placed in 

Ganelo Hills Volcanics by P. T. Hayes 

(written commun., 1971) . Hayes and others (1965, p. M7); Drewes 

( 1971b, p. C'25) ; Simons ( 1972, p. 

E2, and p. Ell, sample 12 of table 1). 

Unpublished age of Pantano ( ?) Formation (H. Drewes, written commun., 

1971) which was mapped as "Tertiary 

gravels, deformed" by Hayes and 

Raup (1968). Finnell (1970, p. A36) 

has described the Pantano Formation as Oligocene to Miocene near the Empire Mountains. 

Unpublished age that is spurious; tuff is 

Triassic-Jurassic according to map- ping by Hayes and Raup (1968). 

Finnell (1970, p. A36). 

Unpublished age for pluton mapped by 

Finnell (1971). 

Do. 

Do. 

~ 

~ l%J 

til 

1-l 

= 
TABLE 1.-Rock type, locality, and calculated age of samples from southeastern Arizona--Continued 

Sample 

No. 

Rock type. 

intrusive body. or stratigraphic formation 

77 Rhyolite(?) tuff, Gardner 

Canyon Formation. 

78 Rhyolitic welded tuff, Gard- ner Canyon ( ?) Formation. 

79 Granodiorite ---------------

80 Quartz monzonite ----------

81 Granodiorite ---------------

82 -----do -------------------

83 Pegmatite -----------------

84 Mica schist, Pinal Schist----

85 _____ do -------------------

86 Quartz monzonite, Rincon 

Location 

(latitude N •• longitude W.) Calculated age (m.y.) 

Empire Mountains--Continued 

31 °55'50" 

110°36'40" 

31 °51'07" 

110°44'58" 

31 °46'18" 

110°25'21" 

32°07' 

110°28' 

32°07' 

110°25' 

32°12' 

110°27' 

32°12' 

110°27' 

32°12' 

110°27' 

32°13'30" 

110°25'30" 

32°06' 

170±35 (Pb-u,Z) 

210±30 (Pb-u,Z) 

Whetstone Mountains 

74±4 

74±4 

(K-Ar,B) 

(K-Ar,H) 

Rinc:on Mountains 

23.5±0.9 (K-Ar,B) 

24.8±0.9 (K-Ar,M) 

26.3±0.9 (K-Ar,B) 

27.3±1.1 (K-Ar,B) 

36.8±1.6 (K-Ar,M) 

28.4±1.1 (K-Ar,B) 

33.8±1.2 (K-Ar,B) 

29.0±0.9 (K-Ar,M) 

28.9±1.0 (K-Ar,M) 

1540±60 (K-Ar,B) 

Comment and (or) reference 

Unpublished age for formation mapped 

by Finnell (1971). Drewes (1971b, p. 

C24) provisionally stated that this 

formation is Triassic. 

Do. 

Ages determined for pluton mapped by 

Creasey (1967). 

Unpublished ages for pluton. 

Unpublished ages for pluton. 

Unpublished age for granodiorite stock. 

Unpublished age for pegmatite within 

the granodiorite stock_ listed for sam- ple 82 (H. Drewes, written commun., 

1970). 

Unpublished age given by recrystallized 

Precambrian Pinal Schist (H. Drewes, 

written commun., 1970). 

Do. 

Unpublished age for Rincon Valley 

tl:) 

0 

~ 

> t1 

-

0 

~ t-3 

~ 

-

0 

> c;1 

t:t:J 

til 

0 

~ 

-

c;1 

z 

t:t:J 

0 

c:: 

til 

~ 

0 

0 

~ 

00 

;a 

0 

ts: 

> 

~ 

-

N 

0 

z 

> 
Valley Granite of Acker 

(1958). 

87 ----'-do -------------------

88 Quartz monzonite, Texas 

Canyon Quartz Monzonite. 

89 Quartz monzonite, Stronghold 

Granite. 

90 _____ do -------------------

91 Andesite, andesite member of 

Sugarloaf Quartz Latite. 

92 Quartz latite tuff, S 0 Volcanics. 

93 Welded tuff, Sugarloaf 

Quartz Latite. 

94 Quartz monzonite, Gleeson 

Quartz Monzonite. 

110°26' 

32°05' 

110°37' 

32°06' 

110°05' 

31 °56' 

109°59'30" 

31 °56' 

110°00' 

31 °48' 

109°47' 

31 °44' 

109°53' 

31 °43' 

109°47' 

31 °44' 

109°52'30" 

1450±50 

1560±100 

(K-Ar,B) 

(K-Ar,H) 

Uttle Dragoon Mountains 

50±3 

52±3 

(K-Ar,B) 

(K-Ar,B) 

Dragoon Mountains 

25.9±2 

26±2 

33.3±2.6 

47±2 

72.8±2.8 

178±5 

(K-Ar,B) 

(K-Ar,B) 

(K-Ar,H) 

(K-Ar,B) 

(K-Ar,B) 

(K-Ar,M) 

Granite which was thought by Acker 

(1958) to be Laramide but it is Precambrian on the basis of radiometric 

dating. 

Do. 

Unpublished ages for stock described 

by Cooper and Silver (1964) as probably early Tertiary. These ages are in good agreement with K-Ar ages determined by Livingston and others 

( 1967) for this intrusion. 

Unpublished age for pluton mapped by 

Gilluly (1956) and designated as Tertiary. Damon and Bikerman (1964) 

obtained an age of 22±3 m.y. for a sample of Stronghold Granite collected 

at 3r55'24"N, 109°58'00"W. 

Do. 

Unpublished age for formation mapped by Gilluly (1956) and designated by 

him as Cretaceous or Tertiary. 

Unpublished age for formation mapped 

by Gilluly (1956) and designated as Tertiary. Sample collected from lower 

tuff member (H. Drewes, written 

commun., 1970). 

Hayes (1970a, p. B28); Drewes (1971b, 

p. C75. 

Anderson (1968, p. 1167). 

s 

~ fll 

~ 

..... 
TABLE 1.-Rock type, locality, and calculated age of samples from southeastern Arizona--Continued 

Rock type, Location 

Sample intrusive body, or (latitude N., 

No. stratigraphic formation longi·tude W.) 

95. Rhyolite ------------------ 31 °39'12" 

110°02'42" 

96 Rhyodacite, U nC'le Sam Por- 31 °41~15" 

phyry. 110°14'45" 

97 Granodiorite, Schieffelin 31 °43"48" 

Granodiorite. 110°06'09" 

98 Granite, Juniper Flat Gran- 31 °30'10" 

ite. 110°00'09" 

99 Granodiorite --------------- 32°06' 

109°24' 

100 Quartz monzonite, quartz 31°5~ 

monzonite of Jhus Canyon. 109°14' 

Calculated age (m.y.) 

Tombstone Hills 

63 (K-Ar,B) 

71.9±2.7 (K-Ar,B) 

72 (K-Ar,B) 

Mule Mountains 

163 (K-Ar,B) 

186 (Rb-Sr,B) 

188 (Rb-Sr,B) 

Chiricahua Mountains 

30.7±1.1 (K-Ar,B) 

30.9±1.2 (K-Ar,B) 

Comment and (or) reference 

Creasey and Kistler (1962, p. Dl, No. 

2 of table 120.1). 

Late Cretaceous age according to Drewes 

(1971b, p. C75). This intrusive breccia was accorded a Tertiary age by Gilluly (1956). 

Creasey and Kistler (1962, p. D1, No. 

3 of table 120.1). 

Creasey and Kistler (1962, p. Dl, No. 

1 of table 120.1). Rb-Sr ages have 

been recalculated with X = 1.39 X 

10-u /yr for Rb~~'~'. 

Small stock cutting thrust-faulted Paleozoic rocks (H. Drewes, written com- mun., 1971) . H. Drewes and F. E. Williams (unpub. 

data). 

~ 

~ 

~ 

> t:l 

1-4 

0 

is: 

~ ~ 1-4 

(") 

> 

~ 

t.zJ 

00 

0 

l'%j 

1-4 

~ t.zJ 

0 

c::: 

00 

;a. 

0 

(") 

~ 

00 

~ 

~ 

> 

~ 1-4 

N 

0 

z 

> 
TABLES 23 

TABLE 2.-Analytical data for K-Ar ages of mineral samples from 

southeastern Arizona 

Decay constant: K40 >-e = 0.585 X 10-10 /yr. X/3 = 4. 72 X 1o-1o /yr. 

Atomic abundance: K40 /K = 1.19XlO-' 

[Analysts: Argon analyzed by H. H. Mehnert, S. C. Creasey, H. H. Thomas, and R. F. 

Marvin, except as noted. Potassium values determined (by flame photometry using a lithium internal standard) by Violet Merr1tt, except as noted. Sample description and 

locality shown on table !] _____________________ _ 

Sample 

No. 

Analyzed 

mineral 

1

1

-----Biotite ---------- 2 ----------do --------

3 __________ do -------- 4 __________ do---------

5 -----K-feldspar ------ 6 __________ do --------

'? _____ Biotite ----------

81----------do --------- 9 -----Biotite --------- K-feldspar _____ _ 

l01 _____ Biotite --------- 11 __________ do ---------

13 ----------do ---------

15 -----Sanidine --------

16 _____ Plagioclase ------

17 _____ Biotite --------- Hornblende --~-- 18 _____ Biotite ---------

19 _____ Hornblende -----

21 _____ Biotite ---------

22 ----------do ---------

23 _____ Biotite ---------

24 __________ do ---------

25 ----------do ---------

27 _____ Hornblende -----

28 _____ Biotite --------- 30 __________ do --------- 32 _____ Hornblende ----- 33 _____ Biotite ---------

34 __________ do ---------

35 __________ do ---------

36 ----------do ---------

37 __________ do ---------

38 __________ do ---------

See footnotes at end of table. 

K20 

(percent) 

* Ar40 X 10-10 * Ar40 Calculated age 

(moles/gram) (percent) (m.y.) 

Sierrita Mountains 

4.66 

8.25 

8.29 

2 7.26 

2 6.58 8 16.04 

3 14.92 

5.98 

7.16 

3 8.62 

3.45 

7.28 

2 6.37 

2 8.24 

1.69 

3.240 

3.87 

4.49 

11.38 

10.63 

6.15 

7.47 

7.782 

2.902 

8.10 

5.22 

4.94 

Santa Rita Mountains 

5.92 

6.13 

6.18 

6.17 

'.82 

2 6.45 

.751 15 8.19 

8.37 

15 .69 

.69 

7.09 

7.12 

8.67 

8.97 

7.17 

7.39 

7.87 

7.93 

8.43 

8.38 

11 .69 

.69 2 6.13 

2 7.46 

2 .693 5 8.41 

8.40 

8.14 

8.35 

15 4.94 

4.88 

6.88 

6.86 

8.89 

8.88 

5 5.52 

5.31 

2.345 

0.3185 

2.49 

0.305 

3.400 

.28 

5.682 

5.545 

7.119 

6.071 

6.603 

7.080 

.62 

5.54 

7.52 

.702 

8.598 

8.548 

5.36 

7.608 

9.862 

12.11 

71 

86 

73 

42 

74 

58 

89 

92 

91 

51 

88 

79 

81 

60 

56 

71 

44 

84 

59 

90 

88 

95 

89 

94 

87 

71 

80 

78 

57 

94 

88 

86 

95 

94 

94 

24±1 

26.4±1.0 

36±2 

46±2 

47±2 

47±3 

56±2 

57±2 

60±3 

56±3 

60±2 

55±3 

40±2 

25.9±1.3 

26.2±1.9 

26±2 

27±3 

27.6±1.3 

27.8±2.2 

53.5±2.0 

52.2±2.0 

53.9±2.0 

55.7±2.2 

55.8±2.1 

56.3±2.1 

60.4±4.2 

60±3 

67±3 

67±3 

68.2±3.0 

69.0±2.9 

72.5±3.3 

73.6±2.8 

73.8±2.6 

145±6 
24 RADIOMETRIC AGES OF IGNEOUS ROCKS FROM ARIZONA 

TABLE 2.-Analytical data for K-Ar ages of mineral samples from 

southeastern Arizona-Continued 

Sample Analyzed Kl!O *Ar'O X lo-10 *Ar'O Calculated age 

No. minerl!l (percent) (moles/gram) (percent) (m.y.) 

Santa Rita Mountains--Continued 

40 __________ do --------- 11 7.40 18.15 96 159±7 

7.43 

48 __________ do --------- 8.83 7.323 92 55.5±2.4 

8.79 

Ataseosa Mountains 

50-----Whole rock------ 1.18 .2218 69 12.6±0.8 

1.19 

Patagonia Mountains 

51 _____ Biotite --------- 2 8.58 2.02 20 23±2 

Hornblende ----- .514 .212 42 27±3 

52 -----Biotite --------- 2 6.73 2.59 20 26±2 

53 -----Biotite --------- 2 6.32 5.52 80 58±3 

Hornblende ----- .355 .311 39 58±5 54 _____ Biotite --------- 8.49 7.40 85 58±3 

56 _____ Hornblende ----- .78 1.829 90 153±10 

.77 

57 -----Biotite --------- 6.50 15.89 96 160±7 

6.41 

Hornblende 164±19 ----- .55 1.395 59 

.55 

Huachuca Mountains 

63 _____ Biotite --------- 7.47 18.76 96 164±6 

7.41 

65 ----------do --------- ll7.73 17.06 93 144±6 

Canelo Hills 

67 -----Biotite --------- 8.20 8.824 96 72.1±3.0 

8.06 

68 ----------do --------- 2 6.61 7.13 73 72±4 

69 __________ do --------- 8.48 21.53 98 165±6 

8.45 

70 __________ do --------- 2 6.69 17.88 81 173±8 

Mustang Mountains 

71 -----Biotite --------- 8.45 4.870 87 38.9±1.5 

8.37 

Empire Mou~tains 

73 _____ Biotite --------- 8.17 3.403 84 28.0±1.1 

8.17 

74 __________ do --------- 8.92 9.421 96 70.3±2.5 

8.93 

Whetstone Mountains 

79 _____ Biotite --------- 11 7.03 7.811 86 74±4 

Hornblende .609 .6824 63 74±4 

Rincon Mountains 

80 _____ Biotite --------- 8.94 3.124 79 23.5±0.9 

8.97 

Muscovite ------- 9.79 3.611 79 24.8±0.9 

9.84 
TABLES 25 

TABLE 2.-Analytical data for K-Ar ages of mineral samples from 

soutkeastern Arizona-Continued · 

Sample Analyzed K20 *A1-M~ X l0-10 *A.J:MJ 

No. mineral (percent) (moles/gram) (percent) 

Rincon Mountains--Continued 

81 -----Biotite --------- 9.26 3.617 68 

9.26 

82 ----------do --------- 8.93 3.627 85 

8.93 

83 -----Muscovite ------ 8.69 4.776 58 

8.74 

84 -----Biotite --------- 9.59 4.039 95 

9.54 

85 ----------do --------- 9.47 4.766 97 

9.50 

Muscovite ------ 10.54 4.513 69 

10.44 

10.52 4.507 69 

10.46 86 _____ Biotite --------- 5.90 207.6 99 

5.89 

87 __________ do --------- 7.09 227.7 99 

7.08 

Hornblende ----- .61 22.12 99 

.63 

Little Dragoon Mountains 

88 _____ Biotite --------- 11 9.19 6.859 90 

-----dO --------- 8.68 6.758 86 

Dragoon Mountains 

89 _____ Biotite --------- 2 7.92 2.767 65 

90 __________ do --------- 11 9.00 3.473 74 

91 _____ Hornblende ----- .80 .3938 66 

.80 92 _____ Biotite --------- 11 9.77 5.705 75 

93 __________ do --------- 8.73 9.550 90 

8.71 

94 -----Muscovite 11.94 27.42 99 

Tombstone Hills 

9~ -----Biotite --------- 8.96 8.70 

96 __________ do --------- 5.65 6.102 90 

5.64 

9~ ----------do --------- 4.01 4.46 

Mule Mountains 

981 _____ Biotite --------- 6.61 17.1 

Chiricahua Mountains 

99 _____ Biotite --------- 9.00 4.122 79 

9.05 

100 __________ do --------- 8.32 3.821 91 

8.29 

*Radiogenic argon. 1 Analytical data adapted from Creasey and Kistler (1962, p. D1, table 120.1). 

Data not exactly as shown by them. a Analysts: H. Collins Whitehead and Lois Schlocker. a Analysts: P. L. D. Elmore and H. Smith. 

'Average of 10 determinations. 6 Analyst: Wayne Mountjoy. 

Calculated age 

(m.y.) 

26.3±0.9 

2.7.3±1.1 

36.8±1.6 

28.4±1.1 

33.8±1.2 

29.0±0.9 

28.9±1.0 

1540±60 

1450±50 

1560±100 

50±3 

52±3 

25.9±2 

26±2 

33.3±2.6 

47±2 

72.8±2.8 

178±5 

63±3 

71.9±2.7 

72±3 

163±7 

30.7±1.1 

30.9±1.2 
26 RADIOMETRIC AGES OF IGNEOUS ROCKS FROM ARIZONA 

TABLE 3.-Analytical data for Pb-a. ages of zircon from southeastern Arizona 

[Radioactivity of the zircons was measured by an alpha counter by T. W. Stern. All lead 

determinations were made by Harold Westley, except Nos. 38, 45, 58, and 76 which were made by Norma Rait. All lead concentrations were determined by spectrographic methods. 

Superscript "s" in the lead column indicates a single determination. All other values are average of duplicate determinations. Samples with less than 10 ppm lead are difficult to analyze and therefore less confidence is placed in their age. Ages were calculated by 

the following equations: 

CPb t (age) = --(for age range of o-200 m.y.). a. where "C" is the constant, 2485, which is based on an assumed Th/U ratio of 1.0. a is the 

alpha counts per milligram per hour. 

T (age) = t - '-h kt• (for age range 20o-1,700 m.y.), 

where "k" is the decay constant, 1.56 X I0-4., which is based on the above assumed Th/U 

ratio. Sample descriptions and locality shown on table 1] 

Sample Pb Calculated age Sample Pb Calculated age 

No. almglhr (ppm) (m.y.) No. afmg/hr (ppm) (m.y.) 

Sierrita Mountains Santa Rita Mountains--Continued 

11 

12 

13 

14 

17 

20 

26 

28 

29 

30 

31 

32 

33 

34 

38 

39 

41 

42 

43 

44 

45 

796 

246 

590 

270 

46.5 

18.5 

49.5 

99 

Santa Rita Mountains 

268 

1338 

154 

250 

356 

247 

402 

285 

775 

633 

113 

435 

134 

568 

229 

149 

375 

3.9 

23 

3.6 

4.8 

9.1 

6.2 

9.9" 

7.08 

54.2 

48 

7.3 

28.1 

9.9 

42 

16.3 

11.5 

33.7 

150±20 

190±20 

210±30 

850±100 

40±10 

40±10 

60±10 

50±10 

60±10 

60±10 

60±20 

60±20 

170±20 

190±30 

160±20 

160±20 

180±20 

180±20 

180±30 

190±20 

220±30 

46 

47 

48 

49 

55 

58 

59 

60 

61 

62 

64 

65 

72 

75 

76 

77 

78 

107 

220 

127 

125 

11.1 

23.2 

79 

83.5 

Patagonia Mountains 

79 4.7 

168 11.0 

251 24.59 

273 60.0 

207 120 

Huachuca Mountains 

333 129 

365 31 

108 9.8 

Mustang Mountains 

134 17.2 

Empire Mountains 

326 10.9 

215 9.5 

154 10.3 

179 15.5 

250±45 

260±30 

1360±200 

1450±160 

150±20 

160±20 

240±30 

520±60 

1280±150 

90±30 

210±30 

220±35 

310±40 

80±15 

110±20 

170±35 

210±30 

TABLE 4.-Analytical data for Rb-Sr ages of samples from southeastern 

Arizona 

Decay constants for Rb87 : A/:1 = 1.39 X lfrlllyr. 

Isotope abundance: Rb87 /Rb = 0.283 gig. [Analysts: for samples 49 and 65, Z. E. Peterman, R. A. Hildreth, and W. T. Henderson; 

for sample 96, analytical data from Creasey and Kistler (1962, p. Dl, table 120.1). Sample 

descriptions and locality shown on table 1] 

Sample Analyzed Rb 87 Total Sr Sr87* SrB'i* Calculated age 

No. material (ppm) (ppm) (ppm) (percent) m.y.) 

Santa Rita Mountains 

49 Whole rock 81.9 230 

Huachuca Mountains 

65 Whole rock 115.7 64.7 

Mule Mountains 

96 Biotite ------------- 384 _____ do ------------ 388 

* Radiogenic strontium. 1 Assumed initial Sr8'1 I SrB6 of 0. 703. 2 Assumed initial SrB7 I srsa of o. 7065. 3 Recalculated using RbB'l : >. = 1.39 X 10-n y-1• 

22.2 

21.3 

0.964 

0.245 

0.994 

1.017 

5.8 

5.2 

1 800±80 

2 144±11 

3 186±7 

188±8 
TABLES 27 

TABLE 5.-Major stratigraphic and time divisions 

Subdivisions in use by the U.S. Geological Survey Age esti- mates com- monly used 

Era or for boundEra them System or Period Series or Epoch aries (in 

million 

years)l 

Quaternary Holocene 

Cenozoic Pleistocene 1.5-2 Tertiary Pliocene ca. 7 Miocene 

26 Oligocene 87-38 Eocene 58-54 Paleocene 65 

Cretaceous Upper (Late) 

Lower (Early) 186 Upper (Lat~) 

Jurassic Middle (Middle) 

Mesozoic Lower (Early) 190-195 Upper (Late) 

Triassic Middle (Middle) 

Lower (Early) 225 

Permian Upper (Late) 

Lower (Early) 280 

fll 

::s Upper (Late) frn Q>a Pennsylvanian Middle (Middle) 

~~ Lower (Early) ~fll 821 

0>. Mississippian Upper (Late) 'foo Lower (Early) ~ 

0 

I;taleozoic Upper (Late) 845 

Devonian Middle (Middle) 

Lower (Early) 

Upper (Late) 

895 

Silurian Middle (Middle) 

Lower (Early) 480-4.W 

Ordovician 

Upper (Late) 

Middle (Middle) 

Lower (Early) ca. 500 

Upper (Late) 

Cambrian Middle (Middle) 

Lower (Early) 570 

Precambrian 

1 From Geological Society of London (1964, p. 26o-262). 

·NoTE.-Estimates for ages of time boundaries are under continuous study and subject to refinement and controversy. Examples of other EStimates for the Cenozoic part of the 

scale are given by Berggren ( 1969) and Evernden, Savage, Curtis, and James ( 1964). 

U.S. GOVERNMENT PRINTING OFFICE : 1973 o-~5