["-. tl') [{) -I

DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY

TRANSCONTINENTAL GEOPHYSICAL SURVEY (35°-39° N) RADIOMETRIC AGE DETERMINATIONS OF ROCKS By Richard F. Marvin

MISCELLANEOUS GEOLOGIC INVESTIGATIONS MAP 1-537

A CONTRIBUTION TO THE UPPER MANTLE PROJECT

["-. tl') lO I PUBLISHED BY THE U.S. GEOLOGICAL SURVEY - 0.. WASHINGTON, D. C. < 1968 ::E DEPARTMENT OF' THE INTERIOR TO ACCOMPANY MAP 1-537 UNITED STATES GEOLOGICAL SURVEY

TRANSCONTINENTAL GEOPHYSICAL SURVEY (35°-39° N)

RADIOMETRIC AGE DETERMINATIONS OF ROCKS

By Richard F. Marvin

A CONTRIBUTION TO THE UPPER MANTLE PROJECT

INTRODUCTION Because all the radiometric ages given by samples occurring Most analyzed materials are from igneous rocks, some are between 35° and 39° N. latitude could not be shown on the from metamorphic rocks, and a few are from sedimentary four maps without undue clutter and crowding, the following rocks. Of the ages tabulated, most indicate the time of crystalli­ tabulation was made as a supplement to the maps to present zation of the analyzed mineral or rock, but many indicate the both plotted and unplotted ages and their localities. Ages ex­ time or effect of some subsequent geologic event, such as re­ cluded from this tabulation are (1) those that might be confusing gional metamorphism or igneous activity, which partly or such as Pb-c~ ages of detrital zircons found in a Paleozoic sedi­ completely reset the radioactive clocks in existing rocks. Such ment but derived from Precambrian rocks; (2) those obtained age distinctions are not made in this tabulation. The data are presented alphabetically by State and, within from minerals that generally "leak" radiogenic argon and thus the State, by age-Cenozoic, Mesozoic, Paleozoic, and ·Pre­ give much younger ages than cogenetic minerals which display cambrian, but are listed systematically under the appropriate good retention of radiogenic argon; and (3) lead-uranium ages time division according to longitude-latitude designation. of uranium minerals that gave ages older than the host rock. All the ages given by a rock specimen or by closely related 207 200 Generally, only the Pb /Pb , age is tabulated although many specimens are listed together. The rock type is reported as an 200 23 207 2 15 208 2 Pb /U s, Pb /U : , and Pb /Thn ages are listed in the aid in evaluating the possible areal extent of the listed age 207 2 reference cited for the Pb jPb 0° age. or ages.

1 RADIOMETRIC AGE DETERMINATIONS Age and material analyzed: m.y., millions of years; ages set in italic are plotted on one of the four maps; material analyzed for radiogenic argon content indicated, in parentheses, by following symbols: B, biotite; C-T, columbite-tantalite; F, potassium feldspar; G, glass; Gl, glauconite; Gm, gummite; H, hornblende; Le, lepidolite; M, muscovite; Mi, mica; Mic., microlite; Min, minerals; Mz, monazite; P, pyroxene; PI, plagioclase; Po, phlogopite; Sa, samarskite; T, tremolite; Th, thorite; U, uraninite; WR, whole rock; Z, zircon

Age Age (m.y.) and Long. W., lat. N. Locality Rock type method material Reference analyzed

ARIZONA Cenozoic ages

110°08'' 35 °35'----- Sec. 12, T. 25 N., R. Trachybasalt, Bidahochi K-Ar 4.1 (WR) ______Evernden and others 21 E. Formation (1964). 113°02', 35°21' ----- Chino ______Hydrothermal alteration K-Ar 63(B) ______Schwartz (1959).

Precambrian ages

112°53'' 35°13'----- S of Seligman ______Chino Creek Granite ___ K-Ar 1330(B) ______Damon and others (1962). 112°03', 36°05' _____ Zoroaster Creek, Grand Zoroaster Granite ______K-Ar 1340(B) ______Aldrich and others Canyon. (1958). Rb-Sr 1350(B) ______Do. 112°07', 36°05'----- Kaibab Trail, Grand Pegmatite in Vishnu Rb-Sr 1530(M) ______Giletti and Damon Canyon. Series. (1961); Damon and Giletti (1961). 1, 550(M) ______Do. Pegmatite in Brahma K-Ar 1410(M) ______Damon and others Schist, Vishnu Series. (1962). Bright Angel TraiL ___ Migmatite zone in Vishnu Rb-Sr 1390(B) ______Giletti and Damon Series. (1961); Damon and Giletti (1961). Brahma Schist, Vishnu K-Ar 1240(B) ______.. Damon and others Series. (1962). 113°40', 35°23' ----- Near V;:tlentine ______Granite ______Rb-Sr 1300(B) ______Giletti and Damon (1961); Damon and Giletti (1961). 113°59', 35°47' Grand Wash Cliffs ____ Quartz monzonite ______Rb-Sr 1510(B) ______Wasserburg and Lanphere (1965). 1517(B) ______Do. 1608(F) ______Do. 1570(F) ______Do. 1500(WR) ______Do. K-Ar 1630(H) ______Do. Pegmatite______Rb-Sr 1667(F) ______Do. 1663(F) ______Do. 1538(Pl) ______Do. 1731(Pl) ______Do. 1663(M) ______Do. 1659(M) ______Do. 1630(F) ______Do. 1520 (Pl) ______Do. 1647(F) ______Do. 1663(F) ______Do. 1616(F) ______Do. Gneiss______Rb-Sr 1593(B) ______Do. K-Ar 1695(H) ______Do. Pegmatite______K-Ar 1610(M) ______Do. Rb-Sr 1635(M) ______Do. 1654(F) ______Do. 114°04', 35°15' _____ 5 milesN of Kingman_ ____ do______Rb-Sr 1515(F) ______Do. 1325 (M) ______Do. 1547(F) ______Do. Inclusion in pegmatite__ Rb-Sr 1345(B) ______Do. 114°08', 35°29' _____ 20 miles N of King- Pegmatite______Rb-Sr 1606(F) ______Do. man. 114 °09', 35 °30' __ _ _ _ 22 miles N of King- Gneiss______Rb-Sr 1360(B) ______Do. man. 114°12', 35°25' ____ _ Chloride______Diana Granite______Rb-Sr 1350(B) ______Giletti and Damon (1961) ; Damon and Giletti (1961). 114°12', 35°26' _____ N of Chloride ______Chloride Granite ______Rb-Sr 1210(B) Do. ------2 RADIOMETRIC AGE DETERMINATIONS-Continued

Age Age (m.y.) and Long. W., lat. N. Locality Rock type method material Reference analyzed

CALIFORNIA Cenozoic ages

116°15', 35°28'(?)-- Avawatz Mountain ___ Tuff in Avawatz Forma- K-Ar 10.7(F) ______Evernden and others tion. (1964). 11.0(F) ______Do. 116°29', 35°09' ----- Sec. 8, T. 12 N, R. 5 Tuff lens in sandstone ___ K-Ar 12.3 (B) ______- _ Do. E. 11.5(Pl) ______Do. 116°21', 36°00' ----- Sec. 20, T. 22 N., R. Quartz monzonite ______K-Ar 18.8±1.2(B) _____ C. W. Chesterman 6 E. (written commun. 1965); California Div. Mines (1965). 116°41', 36°01' _____ Black Mountains ______do ______30 ± 19(Z) ______do ______Pb-a Drewes (1964). 116°42', 36°12' ------Pb-a 4J5±10(Z) ______Do. 116°55', 36°05' ----- Death Valley ______Schist ______K-Ar 30(M) ______Wasserburg and others (1959). 116°56', 36°14' ----- W of sec. 6, T. 20 S., Augen gneiss ______K-Ar 14(B) ______Stern and others R. 47 E. (1966). Felsitic dike ______Pb-a 50±10(Z) ______Do. 116°57', 36°14' ----- W of sec. 19, T. 19 Augen gneiss ______K-Ar 11(B) ______Do. S., R. 47 E. 116°57', 36°16' ----- W of sec. 30, T. 19 Quartz monzonite ______K-Ar 14(F) ______Do. S., R. 47 E. Pb-a 30±10(Z) ______Do. 12(F) ______116°58' 1 36°12' ('?)_- Mouth of Hanaupah Monzonite porphyry ____ K-Ar Do. Canyon. Pb-a 20±10(Z) ______Do. 117°55', 35°25'(?) __ Last Chance Canyon __ Tuff in Ricardo Forma- K-Ar 10.0(B) ______Evernden and others tion. (1964). 1.17°25' 1 36°02' (?)-- Sec. 10, T. 21 S., R. Andesite ______K-Ar 12.6(B) ______Evernden and James 42 E. 13 .O(Pl) ______(1964). Do. 117°52', 36°19' ----- Sec. 6, T. 19 S., R. Pumice chunks in Coso K-Ar 2.2(B) ______Evernden and others 38 E. Formation. (1964). 117°55', 36°11' ----- Sec. 24, T. 20 S., R. Andesite in Coso Forma- K-Ar 2.0(B) __ ,. ______Do. 37}~ E. tion. 117°58'' 37°25'----- Sec. 19, T. 6 S., Basalt of Deep Springs K-Ar 10.8±1.0(WR) ___ Dalrymple (1963). R. 37 E. Valley. 10.9±0.2(?)----- Do. 118°16', 35°06'(?)-- Tehachapi Pass, Tuff breccia in Kinnick K-Ar 17.1 (B) ______Evernden and others Tehachapi Moun- Formation. (1964). tains. 118°18', 36°55'(?)-- Sawmill Canyon _____ ~ Basalt______- ______- K-Ar 0.09±0.09(WR) __ Dalrymple (1964b). 0.06±0.05(WR) __ Do. 118°25', 36°12' _____ Trout Meadows ______do ______K-Ar 3.5 ±0.1(WR) ____ Dalrymple (1963). 118°18' 1 37°03' _-- __ Sec. 30, T. 10 S., R. Rhyolite ______K-Ar 0.99 ± 0.04(G) ____ Cox and others (1963). 34 E. 118°21.', 37°28' _____ Sec. 4, T. 6 S., R. 33 Bishop Tuff ______K-Ar 0.736±0.07(F) ___ Dalrymple and others E. (1965). 0.754±0.08(F) ___ Do. 118°29', 37°18' ----- Sec. 29, T. 7 S., R. 32 Basalt of Coyote Flat_ __ K-A.r 9.6±0.2(WR) ____ Dalrymple (1963). E. 118°34', 37°46' ____ ·_ Sec. 16, T. 2 S., R. 31 Basalt______K-Ar 3.42 avg.(WR) ___ Dalrymple and E. Hirooka (1965). 118°36', 37°33' ----- Sec. 31, T. 4 S., R. 31 Basalt of Owens Gorge __ K-Ar 3.2±0.1(WR) ____ Dalrymple (1963). E. 118°40', ,37°33' ----- Sec. 34, T. 4 S., R. 30 Bishop Tuff ______K-Ar 0.730±0.07(F) ___ Dalrymple and others E. (1965). 0.692±0.06(F) ___ Do. l.18°46', 37°49' ----- Sec. 28, T. 1 S., R. 29 ____ do ______K-Ar 0.639±0.07(F) ___ Do. E. 0.717 ±0.07(F) ___ Do. 118°49'' 37°35'----- Sec. 1H, T. 4 S., R. 29 Basalt of McGee Moun- K-Ar 2.6±0.1(WR) ____ Dalrymple (1963). E. tain. l.18°53', 37°24' _____ Volcanic Knob ______Basalt______- K-Ar 3.6±0.1(WR) ____ Do. 119°42', 35 °23' (?) -- Sec. 22, T. 29 S., R. Glauconitic sandstone K-Ar 23(Gl) ______·Evernden and others 21 E. (drill core). (1961). 119°00'' 37°37'----- Sec. 9, T. 4 S., R. 27 Basak ______K-Ar 3.1±0.1(WR) ____ Dalrymple (1964a). E. 119°02'' 37°20'----- Devils Table ______do ______K-Ar 3.5±0.1(WR) ____ Dalrymple (1963). 119°03', 37°38' ----- Sec. 36, T. 3 N., R. Quartz latite ______K-Ar 0.37 ± 0.04(Pl) Dalrymple (1964a). 26 E. 119°03'' 37°41'----- Sec. 13, T. 3 S., R. 26 Basalt of San Joaquin K-Ar 3.1 ±0.1(WR) ____ Do. E. Mountain.

3 RADIOMETRIC AGE DETERMINATIONS-Continued

Age Age (m.y.) and Long. W., lat. N. Locality Rock type method material Reference analyzed

CALIFORNIA-continued Cenozoic ages-Continued

119°05'' 37°38'----- Near Devils Postpile Basalt ______K-Ar 0.94±0.16(Pl) ___ Dalrymple (1964b). National Monu- nient. 119°06', 37°43' _____ NW of Two Teats Two Teats Quartz Latite_ K-Ar 3.0± 0.1(Pl) _____ Dalrymple (1964a). Mountain. 119°10', 37°31' _____ Sec. 11, T. 5 S., R. 25 Basalt of Pine Flat _____ K-Ar 3.5±0.1(WR) ____ Do. E. 119°12', 37°33' _____ Sec. 36, T. 4 S., R. 25 Snake Meadow Basalt__ K-Ar 3.3±0.1(WR) ____ Do. E. 119°24', 37°07' _____ Sec. 30, T. 9 S., R. 24 Basalt of Sugarloaf K-Ar 9.5 ±0.3(WR) ____ Dalrymple (1963). E. Hill. 119°35'' 37°59'----- Rancheria Mountain __ Latite ______K-Ar 8.9±0.2(B) ______Do. 119°27'' 38°26' (?)-- West Walker River Latite welded tuff ______K-Ar 10. 7(B) ______Evernden and others Canyon. (1961). 119°36', 38°18' _____ Sec. 7, T. 5 N., R. 22 Rhyolite tuff of K-Ar 29.5 ±O.~(F) _____ Dalrymple (1964a). E. Leavitt Creek. 119°47', 38°22' ----- S of Bald Peak ______Basalt______K-Ar 9.3±0.4(WR) ____ Do. 119°47', 38°33'----- Near Silver Peak _____ Nobel Canyon Rhyolite_ K-Ar 4.8±0.1(B)-----~ Do. 4.7 ±0.1(Pl) _____ Do. 119°49', 38°20' ____ - Sec. 29-30, T. 6 N., Basalt______K-Ar 0.15±0.03(WR) __ Dalrymple (1964b). R. 20E. 119°50', 38°19' _____ Sec. 1, T. 5 N., R. 19 Rhyolite of Sonora K-Ar 25.7 ±0.5(B) _____ Dalrymple (1963). E. Pass. Lower Eagle Meadow K-Ar 26.1 ±0.5(B) _____ Dalrymple (1964a). Tuff. 23.3±0.5(F) _____ Do. 119°50', 38°33' _____ Near Upper Kinney Rhyolite tuff ______K-Ar 20.7±0.4(F) _____ Do. Lake. 120°07'' 36°30' (?)-- Sec. 33, T. 16 S., R. Glauconitic sandstone K-Ar 58(G1) ______Evernden and others 17 E. (drill core) . (1961). 120°18', 36°11'(?)-- Sec. 13, T. 20 S., R. ____ do ______K-Ar 59(B) ______Do. 15 E. 120°23'' 36°11' (?)-- Sec. 18, T. 20 S., R. ____ do ______K-Ar 42(Gl) ______- Do. 15 E. 120°02'' 37°55'----- Sec. 19, T. 1 N., R. Latite of Jawbone K-Ar 9.0±0.2(B) ______Dalrymple (1963). 18 E. Ridge. 120°07'' 37°50'----- Sec. 28, T. 1 S., R. Rhyolite ______K-Ar 28.5 ±0.6(F) _____ Dalrymple (1964a). 17 E. 120°18', 38°15'--~-- Sec. 27, T. 5 N., R. Latite ______-· ______K-Ar 9.2±0.2(B) ______Do. 15 E. 120°21', 38°11' ----- Sec. 19, T. 4 N., R. Welded tuff of Rattle- K-Ar 33.2±0.7(Pl) ____ Do. 15 E. snake Hill. 120°22'' 38°11' ----- Sec. 19, T. 4 N., R. Latite of Table K-Ar 9.0±0.2(Pl) _____ Do. 15 E. Mountain. 120°24', 38°07' ----- Sec. 11, T. 3 N., R. Upper tuff, Valley K-Ar 21.1 ± 0.4(F) _____ Do. 14 E. Springs Formation. 120°24', 38°07' _____ Sec. 14, T. 3 N., R. Lower tuff, Valley K-Ar 23.1±0.5(F) _____ Do. 14 E. Springs Formation. 120°25', 38°45' ----- Sec. 3, T. 10 N., R. Rhyolite tuff of Plum K-Ar 23.4± 0.5(F) _____ Do. 14 E. Creek. 120°50', 38°12' ----- Sec. 11, T. 4 N., R. Upper tuff, Valley K-Ar 21.9 ± 0.4(B) _____ Do. 10 E. S'prings Formation. Rhyolite from Valley K-Ar 19.9± 0.4(F) _____ Dalyrmple (1963). Springs Formation. 122°12', 37°53' ___ .__ Berkeley Hills ______Basah ______K-Ar 9.8(WR) ______Evernden and others (1964). 122 °12'' 37°52'----- Sec. 4, T. 1 S., R. Tuff, Siesta Formation __ K-Ar 9.89(Pl) ______Do. 4W. 122°13', 37°53' _____ Berkeley Hills ______Basalt______K-Ar 9.8(WR) ______Do. 122°13', 37°53'(?)-- ____ do ______Volcanics of Grizzly K-Ar 8.9(F) ______-- Do. Peak. 122°13', 37°52'(?)-- ____ do ______Olivine basalt______K-Ar 11.4(WR) ______Do. 122°13'' 37°53' (?)- - ____ do ______Volcanics of Grizzly K-Ar 8.9(F) ______Do. Peak. 122°13', 37°53' ____ - ____ do ______Olivine basalt______K-Ar 7.7(WR) ______Do. 122°19', 38°01' ----- Pinole ______Pinole Tuff, Pinole K-Ar 5.2(F) ______Do. Formation. 122°35'' 38°35' (?)-- Calistoga ______Sonoma Tuff ______K-Ar 3.4(Pl) ______Evernden and James (1964).

4 RADIOMETRIC AGE DETERMINATIONS-Continued

Age Age (m.y.) and Long. W., lat. N. Locality Rock type method material Reference analyzed

CALIFORNIA-continued Mesozoic ages

115°30' 1 35°02' (?) .... Northern Providence Quartz monzonite ______Pb-a .94(Z) ...... ______Jaffe and others (1959) . Mountains. ____ do ______116°08' 1 35°12' (?) .... Soda Mountains ______Pb- .96 (Z) ______Do. 116°22', 35°34' ----- ·Sec. 8 (proj.), T. 17 Diorite ____ .. _____ .. _____ K-Ar 126 ± 7 (B) .. ______C. W. Chesterman N.,R. 6E. (written commun. 1965); California Div. Mines (1965). Pegmatite ______K-Ar 62.9±1.8(B) _____ Do. 117°28' 1 35°12' (?) .... Fremont Peak ______Granite ______Pb-a 85±10(Z) ______USGS unpub. data. .90 ± 10(Mz) ______Do . 117°27' 1 36°14' ...... Thompson Canyon, Quartz monzonite ____ .... K-Ar 178(B) .. _.. ___ .. ___ Hall and MacKevett Argus Range. (1962). Pb-a 180±20(Z) ______Do. 117°29', 36°20'-- --- Darwin Canyon, Argus _____ do ______K-Ar 182(B) ______Do. Range. Pb-a 210±25(Z) ______Do. 117°44', 36°31'(?)-- Hunter Mountain Quartz monzonite_ . _. -- Pb-a 190±20(Z) ______USGS unpub. data. Batholith. 118°34', 35°34'(?)_ - Kern River uranium Isabella Granodiorite __ Pb-a 83(Z) ______Jaffe and others (1959). area. 89(Z) ______Do. 96(Z) ______Do. 100±10(Z) ______USGS unpub. data. 118°00', 36°51.' ----- lnyo Mountains ______Quartz monzonite of K-Ar 154(B) ______Kistler and others Paiute Monument. (1965). 11.8°00', 36°58' _____ P::\poose Flat, lnyo Quartz monzonite ______K-Ar 75(B)------Do. Mountains. 11.8°02', 36°49' ------In yo Mountains ____ . _ Quartz monzonite of K-Ar 1.57(B) .. ______Do. Paiute Monument. 118°08', 36°56' ______do ______.. Tinemaha Granodiorite __ K-Ar 1.23(B) ______Do. 118°20', 36°35' _____ Sierra Nevada ______.. Quartz monzonite __ .. ___ K-Ar 77±15(Pl) ______C.W. Chesterman (written commun. 1965); California Div. Mines (1965). _____ do ______11.8°02', 37°00' _____ Papoose Flat, lnyo K-Ar 81(B)~------Kistler and others Mountain~. (1965). 11.8°17', ::37°04' ----. Sierra Nevada ______Tineniaha Granodiorite __ K-Ar 83(B) ______Do. 118°19', 37°07' ----- ____ do ______do ______K-Ar 91(B) ______Do. 170 (H)_ .... __ ...... __ Do. 11.8°20', 37°08' ----- _____ do ______do ______K-Ar 131(B) ______Do. 183(H) ______Do. 180(H) ______Do. ll8°20', :37°05'----- Sec. 14, T. 10 S., R. :33 Granodiorite ______Pb-a 116(Z) ______Jaffe and others (1959). E. 118°22'' 37°06'----- McMurry Meadows, _____ do ______K-Ar 104(B) ______Kistler and others Sierra Nevada. (1965). 151 (H) ______Do. Sec. !), '1'. 10 S., R 33 Quartz monzonite ______Pb-a 100(Mz) _____ -.- __ Jaffe and others (1959). E. 118°24', 37°14' _____ Sierra Nevada ______Granite ___ .... ______K-Ar 81(B) ______Kistler and others (1965). _____ do ______118°25', 37°1.3' ______do ____ ~------K-Ar 87 (B) .. ______Do. Rb-Sr 87(B) ______Do. 11.8°26', 37°13' _____ Coyote Flat, Sierra Granodiorite ______K-Ar 88(B)------Do. Nevada. l1H 0 27', H7°0(i' __ .. __ Sierra Nevada ______Tinemaha Granodiorite_ K-Ar 78(B) ______Do. 150(H) ______Do. 118°27', :37°07' ______do ______Granite ______.. K-Ar 85(B) ______Do. .l.l8°27'' 37°08' Sec. 26, T. 9 S., R. Quartz monzonite ______Ph-a 105(Z) ______Jaffe and. others 32 E. (1959). J.lH 0 00', ;no07' _____ Sec. 32, T. 9 S., R. Granodiorite ____ .. ___ .. __ Ph-a 112(Z) ______Do. 32 E. Jl8°g.J.', 07°07' ... .. Sierra Nevada ______Inconsolable K-Ar 87(B) ______Kistler and others Granodiorite. (1965). 98(H) ______Do. :1.18°:.!4', :37°10'-_____ Sec. 14, '1'. !) S., R. Granodiorite ______Pb-a 93(Z) ______Jaffe and others 31 E. (1959). 88(Th) ______Do. 11.8°35', 37° lG' _.. ___ Sec. 20, T. 8 S., R. Quartz monzonite ______Pb-a 110(Z) ______Do. 31 E.

5 RADIOMETRIC AGE DETERMINATIONS-Continued

Age Age (m.y.) and Long. W., lat. N. Locality Rock type method material Reference analyzed

CALIFORNIA-continued Mesozoic ages-Continued

118°36'' 37°14'----- Sierra Nevada ______Tungsten Hills Quartz Rb-Sr 75(B) ______Kistler and others Monzonite. (1965). K-Ar 76(B) ______Do. 118°37'' 37°13'----- ____ do ______Lamarck Granodiorite __ K-Ar 77(B) ______Do. 84(H) ______Do. 118°37'' 37°25' ----- ____ do ______Wheeler Crest Quartz K-Ar 69(B) ______Do. Monzonite. 96 (H) ______Do. 118°37', 37°26' ______do ______do ______K-Ar 79(B) _-·- ______Do. 99 (H) ______Do. 118°38'' 37°24'----- ____ do ______do ______K-Ar 81(B) ______Do. 118°41'' 37°22'----- ____ do ______Tungsten Hills Quartz K-Ar 7.HB)------Do. Monzonite. 118°43'' 37°21'----- ____ do ______do ______K-Ar 75(B) ______Do. 118°43'' 37°22'----- W of Pine Creek Quartz monzonite ______Pb-a 116(Z) ______Jaffe and others mine. (1959). 118°43'' 37°28'----- Sierra Nevada ______Round Valley Peak K-Ar 87(B) ______Kistler and others Granodiorite. (1965). 84(H) ______Do. 118°44'' 37°28'----- Near Bishop ______Granodiorite ______Pb-a 88(Z)~------Jaffe and others (1959). 118°49'' 37°13'----- Goddard pendant, Sheared granodiorite ____ K-Ar 86(B) ______Kistler and others Sierra Nevada. (1965). 118°56'' 37°14'----- Sierra Nevada ______Mount Givens K-Ar 85(B) ______Do. Granodiorite. 87(H) ______Do. 118°58', 37°05' ______do ______Granodiorite ______K-Ar 85(B) ______Do. Mount Givens K-Ar 87(B) ______Do. Granodiorite. 86(H) ______Do. 118°59', 37°00' ______do ______Granodiorite ______K-Ar 83(B) ______Do. 9~(H) ______Do. 119°03'' 36°20'----- Sec. 20, T. 18 S., R. ____ do ______K-Ar 109±4(B) ______Putman and Alfors 27 E. (1965). 119°05'' 36°17'----- S~c. 7, T. 19 S., R. Aplite ______K-Ar 136 ± 5 (B) ______Do. 27 E. 119°06'' 36°17' ----- Sec. 7, T. 19 S., R. Granodiorite ______K-Ar 128 ± 5(B) ______Do. 27 E. 119°14', 36°57' _____ Sec. 27, T. 11 S., R. Schist ______K-Ar 105 ± 6(H) ______C. W. Chesterman 25 E. (written commun. 1965) ; California Div. Mines (1965). 119°15', 36°58' _____ Sec. 16, T. 11 S., R. Granodiorite ______K-Ar 101 ±5(B) ______Do. 25 E. 119°29', 36°58' ----- Sierra Nevada ______do ______K-Ar 97(B) ______Kistler and others (1965). 115(H) ______Do. 1 ____ do ______113(B) ______119°31', 36°54 ----- Pyroxene-quartz diorite_ K-Ar Do. 1~1 (H) ______Do. 119°03', 37°19' ______do ______Mount Givens Granodio- K-Ar 82(B) ______Do. rite. 119°05', 37°09' ----- ____ do ______Porphyritic biotite gran- Rb-Sr 82(B) ______Do. ite. K-Ar 83(B) ______Do. 119°08', 37°16' ----- ____ do ______Granodiorite ______K-Ar 88(B) ______Do. 119°09', 37°14' ----- ____ do ______Porphyritic biotite K-Ar 82(B) ______Do. granite. Granodiorite ______K-Ar 83(B) ______Do. 88 (H) ______Do. 119°17', 37°09' ______do ______do ______K-Ar 9~(B) ______Do. 91 (H) ______Do. 119°19'' 37°06'----- ____ do ______do ______~---- K-Ar 90(B) ______Do. 119°22', 37°55' _____ Near Yosemite Na- Cathedral Peak Granite_ K-Ar 83.7(B) ______Curtis and others tiona] Park. (1958). 119°23', 37°03' ----- Sierra Nevada ______Granodiorite ______K-Ar 89(B) ______Kistler and others (1965). 109(H) ______Do. 119°24', 37°01' ______do ______do ______K-Ar 89(B) ______Do. 119°24', 37°55'(?)-- Near Yosemite N a- Johnson Granite Por- K-Ar 82.4(B) ______Curtis and others tional Park. phyry. (1958). 119°28'' 37°49'----- Sec. 28, T. 1 S., R. 23 Half Dome Quartz Pb-a 88(Th) ______Jaffe and others (1959). E. Monzonite. 117(Z) ______Do.

6 RADIOMETRIC AGE DETERMINATIONS-Continued

Age Age (m.y.) and Long. W., lat. N. Locality Rock t~pe method material Reference ·I I 1 •, I • I ~ '!I ·~\ ; II analyzed

CALIFORNIA -continued Mesozoic ages-Continued

119°30'' 37°50'----- Near Yosemite Na- Pegmatite in Hoffman K-Ar 76.9(B) ______Curtis and others tional Park. Quartz Monzonite. (1958). 119°30', 37°51'----- ____ do ______Pe&matite in Sentinel K-Ar 86.4(B) ______Do. ranodiorite. 119°32', 37°44'(?)-- Yosemite National Half Dome Quartz Mon- K-Ar 84.1(B) ______Do. Park. zonite. 119°35', 37°44' ______do ______Sentinel Granodiorite __ K-Ar 88.4(B) ______Do. 119°43', 37°44' _____ Sec. 25, 1.'. 2 S., R. El Capitan Granite ____ Pb-a 94(Z) ______Jaffe and others (1959). 20 E. 119°44'' 37°41'----- Sec. 14, T. 3 S., R. 20 Granodiorite ______Pb-a 103(Z) ______Do. E. 119°44', 37°44' _____ Near Yosemite Na- El Capitan granite ______K-Ar 92.2(B) ______Curtis and others tional Park. (1958). 119°45'' 37°43' (?)-- ____ do ______Gateway Granodiorite __ K-Ar 92.9(B) ______Do. Arch Rock Granite _____ K-Ar 95.3(B) ______Do. 119°52', 38°22' ______Sonora Pass area _____ Granodiorite __ K-Ar 87.0(B) ______Gromme and Merrill (1965). 90.1 (H) ______Do. 119°55'' 38°20'----- ____ do ______Quartz monzonite ______K-Ar 83.0(B) ______Do. 83.6(B) ______Do. 84.2(H) ______Do. 120°34'' 35°25' (?) - .. Sec. 10, T. 29 S., R. Santa Margarita K-Ar 84.1 (B) ______Curtis and others 13 E. Granodiorite. (1958). 120°03', ~7°24' _____ Sec. 24, T. 6 S., R. 17 Quartz monzonite ______K-Ar 142.9(B) ______Do. E.; Guadalupe Mountain. 121°14', 36°26' _____ Sec. 29, 1.'. 17 S., R. 7 Gabilan Mesa Quartz K-Ar 83.8(B) ______Do. E. Diorite. 121°40', 36°33' _____ Sec. 17, T. 16 S., R. Quartz diorite ______K-Ar 66.0± 1.8(B) _____ C. W. Chesterman 3E. (written commun. 1965); California Div. Mines (1965). 121°56', 36°31'----- Carmel Cove, Carmel Santa Lucia Grano- K-Ar 81.6(B) ______Curtis and others Bay. diorite. (1958). 121 °56'' 36°37'--- - Monterey quadrangle_ Granitic rock ______K-Ar 75.9± 1.9(B) _____ C. W. Chesterman (written commun. 1965) ; California Div. Mines (1965). 121 °07', 38°49'----. Sec. 18, 1.'. 11 N., R. Quartz diorite ______K-Ar 136 (B) ______Evernden and others 8 E. (1961). 121°14', 38°47' _____ Sec. 19, T. 11 N., R. Rocklin Granodiorite ___ K-Ar 130.6(B) ______Curtis and others 7E. (1958). 131.5(B) ______Do. 122°03', 37°01'----- Felton quadrangle ____ Granitic rock _____ ~ ____ K-Ar 71.0±0.9(B) _____ C. W. Chesterman (written commun. 1965); California Div. Mines (1965). 122°25', 37°33'---- . Pi larci tas Dam Site ___ Montara Quartz Diorite_ K-Ar 91.6(B) ______Curtis and others (1958). 122°30', 37°31' _____ Montara Mountain Granitic rock ______K-Ar 86.2± 3.4(B) _____ C. W. Chesterman quadrangle. (written commun. 1965); California Div. Mines (1965). 123°02', 37°45'(?)-- Farallon Islands ______Farallon Quartz Diorite_ K-Ar 89.5(B) ______Curtis and others (1958). 123°00', 38°00'(?)-- Point Reyes(?) ______Point Reyes K-Ar 83.9(B) ______Do. Granodiorite. 123°04', 38°10' _____ Bodega Head Pluton __ Quartz diorite ______K-Ar 92±3(H) ______USGS unpub. data. 123°06', 38°32' _____ Sec. 17, T. 8 N., R. Metabasalt in glau- K-Ar 135(M) ______Lee and others (1964). 11 w. cophane schist. 123°07', 38°32' ----- Sec. 18, 'r. 8 N., R. ____ do ______K-Ar 150(M) ______Do. 11 w. Rb-Sr 150(M) ______Do. Metashale in glau- K-Ar 135 (M) ______Do. cophane schist. 130(M) ______Do. 123°09', 38°43' ----- Sec. 11, T. 10 N., R. Metabasalt in glau- K-Ar 140 (M) ______Do. 12 w. · cophane schist.

7 RADIOMETRIC AGE DETERMINATIONS-Continued

Age Age .(m.y.) and Long. W., lat. N. Locality Rock type method material Reference analyzed·

CALIFORNIA-continued Paleozoic age

119°05', 36°14' _____ Sec. 31, T. 19 S., R. Metachert in K-Ar 307 ± 30(T) ______Putman and Alfors 27 E. serpentinite. (1965).

Precambrian ages

115°28', 35°28' _____ Mountain Pass Gneiss ______K-Ar 1580±40(B) _____ Lanphere (1964). district. Rb-Sr 1530±55(B) _____ Do. 115°31', 35°30' ----- ____ do ______do ______K-Ar 1560 ±40(B) _____ Do. Rb-Sr 1460±50(B) ____ ·_ Do. Pegmatite ______K-Ar 1660±40(B) _____ Do. Rb-Sr 1640±60(B) _____ Do. 1600±60(F) _____ Do. 115°32', 35°29' _____ Near Birthday Shaft, Shonkinite ______K-Ar 1440±35(B)----- Do. Mountain Pass 1385 ±35(B) _____ Do. district. Rb-Sr 1380±50(B) _____ Do. 1415 ±80(B) _____ Do. Mountain Pass Barite carbonate Ph-a 1020(Mz) ______Jaffe and others (1959). district. rock. 911(Mz) ______Do. Shonkinite ______Ph-a 932(Z) ______Do. 846(Z) ______Do. 811(Z) ______Do. 877(Z) ______Do. Barite carbonate rock ___ Ph-a lOOO(Mz) ______Do. Pb20BfTh232 925(Mz) ______Jaffe (1955). 115°42'' 35°42'----- Winters Pass Hills ____ Pegmatite ______Rb-Sr 1700 ± 65 (F) _____ Lanphere (1964). 116°08', 35°50' _____ Death Valley ______Granite gneiss ______K-Ar 990(B) ______Wasserburg and others (1959). Rb-Sr 1410(B) ______Do. 116°55', 35°59' ______do ______Schist______K-Ar 1500(Mi) ______Do. Rb-Sr 1480(Mi) ______Do. Pegmatites ______K-Ar 1600(M) ______Do. 1730(M) ______Do. Rb-Sr 1700(M) ______Do. 1660(M) ______Do. 1570(F) ______Do. 116°55'' 35°57'----- Warm Spring Canyon, "Pahrump diabase" K-Ar 231 (H) ______W asserburg and others Panamint Range. sill. (1964). 840(P) ______Do. Rb-Sr 1090(WR) ______Do. 116°56', 36°14' _____ W of Sec. 6, T. 20 S., Augen gneiss ______Pbzo1 /Ph zoo 1800(Z) ______Stern and others R. 47 E. (1966). 116°57', 36°14' _____ W of Sec. 30, T. 19 S., ____ do ______Pb2o1 /Phzoo 1555(Z) ______Do. R. 47 E. 117°05', 36°04'(?)_- Panamint Range _____ Mafic flow in Kingston Rb-Sr 1330(WR) ______Wasserburg and others Peak Formation, (1964). Pahrump Series. 117°06'' 36°02' ('?)-- Pleasant Canyon, Augen gneiss ______Rb-Sr 1600(WR) ______Lanphere and others Panamint Range. (1964). 1580(WR) ______Do. ,1410(WR) ______Do. 1470(WR)------Do. 1290(WR) ______Do. 1380(WR) ______Do. Cobble in conglomerate, Rb-Sr 850(WR) ______Wasserburg and others Pahrump Series. (1964). 117°06', 36°05'('?)_- Near Sentinel Peak, Dike in Pahrump Rb-8r 1610(WR) ______Do. Panamint Range. Series.

COLORADO Cenozoic ages

106°32', 37°48'('?) __ . Baughman Creek, San Quartz latite porphyry __ Ph-a 17(Z) ______Jaffe and others (1959). Juan Mountains. 21(Z) ______Do. 106°35'' 37°22'----- Klondike Mountain, Quartz latite ______Pb-a 12(Z) ______Do. San Juan Mountains. 106°46', 37°15'. ____ E of Square Top Quartz latite porphyry __ Ph-a 10(Z) ______Do. Mountain, San 11(Z) ______Do. Juan Mountains. 8 RADIOMETRIC AGE DETERM INATIONS-Conti nued

Age Age (m.y.) and Long. W., lat. N. Locality Rock type method material Reference analyzed

COLORADo-continued Cenozoic ages-Continued

Square Top Mountain, Granite ______K-Ar 27.0(B) ____ ., __ _ _ Faul and others (1959). San J min Moun­ 21.4{B) ______Do. tains. 106°49'' 37°28' (?)_- San Juan Mountains __ Treasure Mountain Pb-a 22(Z) ______Jaffe and others (1959). Rhyolite. 106°57', 37°51' ----- Near Sunnyside, San Quartz latite______Pb-a 22(Z) ______Do. Juan Mountains. 106°58'' 37°21'----- Jackson Mountain, San Quartz latite porphyry __ Ph-a 14(Z) ______Do. Juan Mountains. 106°04', 38°39' ----- Near Salida______Quartz latite welded- K-Ar 34±3(B)______USGS unpub. data. tuff. 34±3(G)______Do. 39±3(F)______Do. 107°01' 1 38°03' (?)-- Spring Creek, San Rhyolite, Hinsdale For- Pb-a 15(Z) ______Jaffe and others (1959). Juan Mountains. mation. 107°16', 38°27' ____ _ Sapinero Mesa ______Welded-tuff______K-Ar 27 ±3(B) ______USGS unpub.· data. 107°22' 1 38°00' (?) _- Alpine Gulch, San Granite~______Pb-a 23(Z) ______Jaffe and others (1959). Juan Mountains. 107°33', ·38°29'- ---- Black Canyon of the Ashftow in West Elk · K-Ar 23 ± 2(B) ______USGS unpub. data. Gunnison. Breccia. 25±2(B) Do.

Paleozoic ages

105°18', 38°17'(?) _ _ Wet Mountains______Albite syenite______Pb-a 580(Z) ______Jaffe and others (1959). 601(Z) ______Do. 590(Z) ______Do. 644(Z) ______Do. 605(Z) ______Do. 655(Z) ______Do. 105°22', 38°15'(?) ______do______Syenite______K-Ar 485±24(WR) ___ _ USGS unpub. data. 107°02', 38°15'----- Iron HilL ______do ______Pb-a ____ _ 525(Z) ______Jaffe and others (1959). 583(Z) ______Do.

Precambrian ages

102°59', 37°11' ----- Sec. 12, T. 33 S., R. Granite (drill cuttings) __ Rb:-Sr 1280±100(WR) __ Muehlberger and others 50W. (in press). 104°11', 37°56' ----- Sec. 25, T. 24 S., R. Granite gneiss (drill Rb-Sr 1600±90(WR)__ _ Do. 61 w. core). 104°53', 38°21' _____ Sec. 4, T. 20 S., R. ____ do ______Rb-'-Sr 1300±60(M) ____ Do. 67W. 104°56', 38°45' ----- Gold Camp Road _____ Mount Rosa Granite ____ K-Ar _____ 1020(B) ______Giffin and Kulp (1960) . 104°57', 38°45' ----- Mount Rosa area ______do ______Pb-a 1110± 125(Z) ____ USGS unpub. data. 104°57', 38°53' ____ - Ute Pass ______Pikes Peak Granite ______K-Ar 1030(B) ______Giffin and Kulp (1960) _____ do ______do ______980(B) ______104 °57' 1 38°53' ('?)-- K-Ar Aldrich and others (1958). Rb-Sr 1020(B) ______Do. 105°02', 37°58'('?) -- Wet Mountains ______San Isabel Granite ______Pb-a 1430±200(Z) _____ Boyer (1962). 105°53' 1 37°38' -- __ - Sec; 16, T. 39 N., R. Granitic gneiss (drill K-Ar 1260(B) ______Muehlberger and oth- 10 E. core). ers (in press). 105°02'' 38°51' ----- Top of Pikes Peak ____ Pikes Peak Granite _____ K-Ar 1060(B) ______Aldrich and others (1958). Rb-Sr 1080(B) ______Do. Pb2o1 /Pb2oo _ 980(Z) ______Do. Windy Point Granite ____ K-Ar 980(B) Giffin and Kulp (1960). 105°02', 38°51'(?)-- Pikes Peak ______Pikes Peak Granite _____ Pb-a 1050± 115(Z) ____ USGS unpub. data. 995± 110(Z) Do. 1055± 115(Z) _____ Do. 105°04',, 38°53' (?) __ Pikes Peak Toll Road______do ______K-Ar 1010(B) ______~ Giffin and Kulp (1960). 1030(B) ______Do. 105°16', 38°09' ----- Wet Mountains ______Granite ______Pb-a 1380±155(Z) ____ USGS unpub. data. 105°16', 38°26'----- Arkansas River Biotite gneiss ______K-Ar 1470(B) ______Giffin and Kulp (1960). Canyon. 10.5°17', 38°13' _____ Wet Mountains ______Alaskitic granite ______~ Pb-a 1360± 150(Z) ____ USGS unpub. data. Alaskitic facies of gneiss_ Pb- 1615± 180(Z) ____ Do. 1600± 180(Z) ____ Do.

9 RADIOMETRIC AGE DETERMINATIONS-Continued

Age Age (m.y.) and Long. W., lat. N. Locality Rock type method material Reference analyzed

COLORADo-continued Precambrian ages-Continued

105°20'' 38°28'---- ~ Royal Gorge ______Granite ______K-Ar 1540(B) ______Giffin and Kulp (1960). 105°20', 38°12'(?) -- Wet Mountains ______do ______Ph-a 755(Z) ______Jaffe and others (1959). Granite gneiss ______Pb- 1220(Z) ______Do. 1130(Z) ______Do. 1080(Z) Do. 105°22'' 38°13'----- _____ do ______Metasediment ______Ph- 1295± 145(Mz) ___ USGS unpub. data. 105°22'' 38°11' ----- _____ do ______Gneiss ______Pb- 1405 ± 155(Z) ____ Do. 105°33', 38°26'(?) -- Arkansas River Biotite gneiss ______K-Ar 1290(B):. ______Giffin and Kulp (1960). rr Canyon. 1300(B) ______Do. 105°49',38°54' _____ Trout Creek Pass _____ Granite ______K-Ar 1430(B) ______Do. 106°20',38°29' _____ Monarch Pass ______Biotite gneiss ______K-Ar 1330(B) Do. 106°37'' 38°35'----- Sec. 22, T. 50, N., R. Pegmatites ______Rb-Sr 1465(B) ______Wetherill and Bickford 3 E. (1965). 1434(B) ______Do. 1444(B) ______Do. 1433(F) ______Do. 106°38', 38°28' _____ Near Brown Derby Granite ______Rb-Sr 1275±30(WR+ Do. Mine. Min) (isochron). 106°38'' 38°28' ----- Near Doyleville ______do ______K-Ar 1280(B) ______Aldrich and others (1958). Rb-Sr 1310(B) ______Do. pb2o1 /Pb2o6 1540 ± 140(Z) ____ Do. 106°38'' 38°32' ----- Brown Derby mine; Pegmatite ______K-Ar 1330 avg.(Le) ____ Do. Sec. 3, T. 49 N., Rb-Sr 1420 avg.(Le) ____ Do. R. 3 E. Pb2o1 /Pb2o6 1350(Mic) ______Do. 1390(C-T) ______Do. 1170(Mz) ______Do. 106°38', 38°50' _____ NE of Almont______Granite ______Rb-Sr 1397±35(WR+ Wetherill and Bickford Min) (iso- (1965). chron). 106°39', 38°32' ___ -- Sec. 4, T. 50 N(?)., ____ do ______Rb-8r 1384±20 (WR+ Do. R. 3 E. Min) (iso- chron). 106°40'' 38°32' ----- Sec. 32, T. 50 N., R. Pegmatite ______Rb-8r 1250(M) ______Do. 3 E. 1395(WR) ______Do. 1366(B) ______Do. 1437(F) ______Do. 106°40', 38°35' _____ Sec. 20, T. 50 N., R. ____ do ______Rb-8r 1031(B) ______Do. 3 E. 1129(B) ______Do. 1384(M) ______Do. 1390(F) ______Do. 106°42', 38°16' _____ SW of Doyleville _____ Granite ______Rb-Sr 1365±25(WR+ Do. Min) (iso- chron). 107°26', 37°32' _____ Hinsdale County _____ Eolus Granite ______K-Ar 1390±40(B) _____ USGS unpub. data. 1460±70(H) ____ ~ Do. 107°24'' 38°27' ----- Curecanti Creek ______Curecanti Quartz Rb-Sr 1130±50(M) ____ Do. Monzonite. 107°26', 38°26' _____ Between Cinnarron Biotite gneiss ______K-Ar 1130(B) ______Giffin and Kulp and Sapinero. (1960). 107°41', 38°33' _____ Black Canyon of the ____ do ______K-Ar 980(B) ______Do. Gunnison. 107°43', 38°34' _____ Vernal Mesa ______·__ Quartz monzonite from Rb-Sr 1130±50(B) _____ USGS unpub. data. Vernal Mesa Granite. 108°57', 37°02' _____ Sec. 7, T. 32 N., R. Leucogranite (drill core)_ Rb-Sr 1810(F) ______Fitzsimmons (1963). 19 w. 108°35', 38°50'('?) ___ Unaweep Canyon _____ Granite of Uncompahgre K-Ar 1300(B) ______Aldrich and others Formation. (1955); (1958). Rb-8r 1370(B) ______Do. pb2o1 /Pb2o6 1810± 160(Z?) ___ Do. I ILLINOIS Paleozoic ages

88°20', 37°25'(?)--- Downeys Bluff, Rosi- Diabase ______K--Ar 269 ± 13 (B) ______R. E. Zartman (writ- clare. Rb-8r 260±30(B) ______ten commun., 1965). 88°22', 37°33'(?)--- Hicks Dome ______Explosion breccia ______K-Ar 281±14(H)______Do. 258 ± 13 (B) ______Do.

10 RADIOMETRIC AGE DETERMINATIONS-Continued

Age Age (m.y.) and Long. W., lat. N. Locality Rock type method material Reference analyzed

KANSAS Mesozoic age

95°47',37°45' ______Woodson County _____ Micaperiodotite ______K-Ar 91±5(B) ______Do.

Precambrian ages

95°42', 37°47'----··- Sec. 13, '1'. 26 S., R. Granite porphyry bould- Rb-Sr 1220 ± 80 (F) ____ _ Muehlberger and others 15 E. ers. (in press). 96°58', 37°48'-·--- - Sec. 11, '1'. 26 S., R. Granite (drill cuttings) __ Rb-Sr 1240±210(F) ___ _ Do. 4 E. 1190±70(B) ______Do. 96°22', 38°40' _____ - Sec. 30, '1'. 17 S., R. Gneissic granite (drill Rb-Sr 1420±lOO(F) ___ _ Do. 7 E. cuttings). 96°36', 38°21' ______Sec. 1, '1'. 20 S., R. Granite gneiss (drill Rb-Sr 1450 ± 120 (F) ___ _ Do. 7 E. cuttings). 96°41', 38°32' ______Sec. 14, '1'. 16 S., R. Micaceous quartzite Rb-Sr 1400 ± 110 (WR) __ Do. 9 E. (drill core). K-Ar 1260(WR) Do. Quartz-sericite schist K-Ar 1290 ______Cole and Merriam (drill core). (1962). 96°50', 38°03' ____ -- Sec. 13, '1'. 23 S., R. Granite gneiss (drill Rb-Sr 1400 ± 120 (F) ___ _ Muehlberger and others 5 E. cuttings). (in press). 97°11', 37°15' ______Sec. 23, T. 32 S., R. Granite (drill cuttings) __ Rb-Sr 1340±120(F) Do. 2 E. 98°28', 37°39' .. _____ Sec. 30, '1'. 27 S., R. Chloritized granite (drill K-Ar 1100 ______Cole and others (1964). 10 w. core). Rb-Sr 1350 ______Do. 98°28', 38°51' ______Sec. 8, '1'. 14 S., R. Gneissic biotite granite Rb-Sr 1420±140(WR) __ Muehlberger and others lOW. (drill core). (in press). K-Ar 1200(B) ______Do. 98°47', 38°40' ______Sec. 18, T. 16 S., R. Biotite quartzite (drill Rb-Sr 1350±190(WR)__ Do. 13 w. core). 99°00', 38°25' ____ -- Sec. 5, '1'. 19 S., R. Quartz-sericite schist K-Ar 1460 ______Cole and Merriam (drill core). 15 w. ____ do ______(1962). 99°05', 38°28' ------Sec. 21, '1'. 18 S., R. K-Ar 1200 ______Do. 16W. 99°08', 38°31' ______Sec. 5, '1'. 18 S., R. Gneissic granite (drill K-Ar 1260 ______Do. 16 w. core). 99°30', 38°31' ______Sec. 36, '1'. 17 S., R. Altered chyastolite(?) K-Ar 1165--- _·_------Do. 11 w. schist (drill core). 99°30', 38°45' ______Sec. 12, '1'. 15 S., R. Altered granite gneiss K-Ar 900(B) ______Cole and others 20W. (drill core). (1964). 1.00°56', 38°45' _____ Sec. 13, '1'. 1.5 S., R. Biotite granite (drill Rb-Sr 1410±150(F) ___ _ Muehlberger and 33 w. cuttings). others (in press). lOl 0 18', 37°06' _____ Sec. 13, '1'. 34 S., R. Granite (drill core) _____ Rb-Sr 1260±60(WR) __ _ Do. 37W. 101. 0 35', 38°50' _____ Sec. 18, '1'. 14 S., R. Gneissic biotite granite Rb-Sr 1510±120(F) ___ _ Do. 38 w. (drill cuttings).

KENTUCKY Paleozoic ages

88°11', 37°21'(?) ___ Adams Drill Hole ____ Diabase (drill core) _____ K-Ar 252 ± 13(B) ______R. E. Zartman (written commun., 1965). Rb-Sr 295±35(B)______Do.

MARYLAND Paleozoic age

77°15', 38°59' (?) _ _ _ Bear Island, Potomac Granite______Ph-a 568(Z) ______Jaffe and others River. (1959).

11 RADIOMETRIC AGE DETERMINATIONS-Continued

Age Age (m.y.) and Long. W., lat. N. Locality Rock type method material Reference analyzed

MISSOURI Paleozoic ages

90°15', 37°45'(?)--- SE of Avon, Cash Kimberlite ____ ·______K-Ar 377 ± 19(B) ______R. E. Zartman Farm. (written commun., 1965). Rb-Sr 420 ± 25 (B) ______Do. Saline Creek, .SE of Mica peridotite ______~ K-Ar 388±19(B) ______Do. Avon. Rb-Sr 365 ±30(B) ______Do.

Precambrian ages

90°28'' 37°34'------Near Fredericktown __ Pegmatite(?) ______K-Ar 1405(M) ______Tilton and others (1962). Rb-Sr 1430(M) ______Do. Pb2o1;Pb2oo 1425(Z) ______Do. 90°39', 37°40' ------Near Graniteville _____ Granite _____ .. ______K-Ar 1280(B) ______Do. Rb-Sr 1320(B) ______Do. 90°42'' 37°38' ------Quarry, Sec. 22, T. Pegmatite ______K-Ar 1250(M) ______Muehlberger and 34 N., R. 3 E. others (in press). Rb-Sr 1210(M) ______Do. 90°43', 37°18' ------Sec. 4, T. 30 N., R. Annapolis Rhyolite _____ Rb-Sr 1330±80(WR) ___ Do. 3E. 90°48'' 37°44'------Sec. 14, T. 35 N., R. Granitic rock ______Rb-Sr 1120(B) ______Do. 2 E. K-Ar 1230(B) ______Do. 90°48'; 37°40' ------Sec. 11, T. 34 N., R. Porphyritic Graniteville Rb-Sr 1190±60(WR) __ _ Do. 2E. Granite (drill core). 90°50', 37°31' ______Sec. 21, T. 33 N., R. Munger Granite Por- Rb-Sr 1220±70(WR) __ _ Do. 2 E. phyry. 90°17', 38°51'(?) ____ Sec. 7, T. 47 N., R. Granite (drill core) _____ Rb-Sr 1330±70(F) _____ Do. 7 E. 90°45', 38°38' ------Sec. 25, T. 45 N., R. Rhyolite porphyry (drill Rb-Sr 1260 ± 60 (WR) ___ Do. 2 E. core). 90°54', 38°52' ______Sec. 34, T. 48 N., R. Biotite diorite (drill K-Ar 1400(B) ______Do. 1 E. core). 9P04', 38°07'(?) ___ Sec. 8, T. 39 N., R. Rhyolite porphyry ______Rb-Sr 1290±60(WR) __ _ Do. 1 w. Sec. 8, T. 39 N., R. Aplite ______Rb-Sr 1310±70(F) _____ Do. 1 w. 92°06'' 37°00'------Sec. 24, T. 27 N., R. Biotite diorite (drill K-Ar 1270(B) ______Do. 15 w. core). 92°42'' 37°54'------Near Decatursville ___ Pegmatite ______K-Ar 1350(M) ______Do. ____ do ______SW of Decatursville __ ------1290CM) ______Tilton and others (1962). Rb-Sr 1445(M) ______Do. 92°48', 38°11' ______Sec. 34, T. 40 N., R. Granite (drill core) _____ Rb-Sr 1520±90(WR) __ _ Muehlbergu and 17W. others (in press). 94°09', 37°45' ______Sec. 6, T. 34 N., R. Biotite adamellite (drill Rb-Sr 1370±80(WR) __ _ Do. 29W. core). K-Ar 1330(B) ______Do.

NEVADA Cenozoic ages

114°47', 35°40' ----- Sec. 24, Sec. 25, T. 26 Granite ______Pb-a 38(Z) ______Jaffe and others (1959). S., R. 64 E. 114 °50'' 35°40'----- Sec. 28, T. 26 S., R. ____ do ______: _____ K-Ar 26~HB) _ ------Armstrong (1963). 64 E. 114°50', 35°44' _____ . Sec. 27, T. 25 S., R. Andesite ______K-Ar ,15 ±2(B) ______Do. 64 E. 114°50', 35°59' _____ Sec. 4, T. 23 S., R. Granodiorite porphyry __ K-Ar 16±2(B) ______Do. 64 E. 114°31', 36°38' ----- Sec. 17, T. 15 S., R. Tuff in Horse Spring K-Ar 23(B) ______Schilling (1965). 67 E. Formation. 114 °32', 36°38' ----- Sec. 8, T. 15 S., R. ____ do ______K-Ar 23±3(B) ______Armstrong (1963). 67 E. 114 °50'' 36°00'----- Sec. 4, T. 23 S., R. Monzonite ______Pb-a 53 (Z) ____ .______Jaffe and others 64 E. (1959).

12 RADIOMETRIC AGE DETERMINATIONS-Continued

Age Age (m.y.) and Long. W.1 lat. N. Locality Rock type method material Reference analyzed

NEVADA -continued Cenozoic ages-Continued

114°51'1 36°01' _____ Sec. 201 T. 22 N.1 R. Andesite porphyry ______K-Ar 13±2(B) ______Armstrong (1963). 64 E. 114 °22' 1 37°50'----- Sec. 271 T. 1 S. 1 R. Ignimbrite in Needles K-Ar 262:~(B) ______Do. 68 E. Range Formation. 114°10'1 38°58' ----- Snake Range ______Xenolith in quartz Pb-a 40±10(Z) ______USGS unpub. data. monzonite(?). 114 °12' 1 38°58'----- ____ do ______~_ Aplite ______K-Ar 31±3(M) ______Do. 114°15'1 38°56' ______do ______Xenolith in quartz Pb-a 20±10(Z) ______Do. monzonite(?). 114°18', 38°45'(?)-- ____ do ______Welded tuff ______K-Ar 31 ±3(B) ______Do. Pb-a 50±15(Z) ______Do. 114°56', 38°46' _____ Sec. 32, T. 11 N., R. Tuff ______K-Ar 32.0(B) ______Evernden and others 63 E. (1964). 115°58', 36°54' _____ Massachusetts Ammonia Tanks K-Ar 12.1 ±0.45(B) ____ R. W. Kistler (written Mountain. Member, Timber commun., 1966). Mountain Tuff. 115°52', 36°59' ----- Nye Canyon ______Vitric tuff ______.. __ K-Ar 11 ± 1 (F) ______USGS unpub. data. 115°04', 37°22' _____ Sec. 6, T. 7 S., R. Ignimbrite ______K-Ar 242:~(B) ______Armstrong (1963). 62 E. 115°59' 1 37°38'----- NE of Belted Peak ___ Tuffs of Antelope K-Ar 25.3 ± 0.68(B) ___ . R. W. Kistler (written Springs. commun., 1966). 115°10', 38°57' _____ Sec. 31, T. 13 N., R. Welded tuffs ______.. _____ K-Ar 32.8(B) ______Evernden and others 61 E. (1964). 115°21', 38°36' _____ Sec. 4, T. 8 N., R. Ignimbrite in Needles K-Ar 262:~ (B) ______Armstrong (1963). 59 E. Range Formation. 115°27', 38°42' _____ Sec. 34, T. 10 N., R. Dacite(?) porphyry _____ K-Ar 302:~(B) ______Do. 58 E. 362:~(B) ______Do. 115°28', 38°50' _____ Sec. 5, T. 1l N., R. Adamellite ______.... ____ K-Ar 272:~(B) ___ .. _____ Do. 58 E. 312:~(B) ______Do. 115°30', 38°52' ----- Sec. 36, T. 12 N., R. ____ do ______K-Ar 362:~(B) ______Do. 57 E. ____ do ______115°35', 38°21' ----- Sec. 29, T. 6 N., R. K-Ar 232:~(B) ______Do. 57 E. 115°50'1 38°09' _____ Sec. 7, T. 3 N., R. Rhyodacitic welded ash K-Ar 22.6±0.7(B) _____ USGS unpub. data. 55 E.; Quinn Can- flow. yon Range. 115°57', 38°25' _____ Sec. 6, T. 6 N., R. 54 ____ do ______K-Ar 25.4±0.8(B) _____ Do. E.; Pancake Range. 116°14'1 36°59' ----- Piapi Canyon ______Tiva Canyon Member, K-Ar 12.4±0.46(B) ____ R. W. Kistler (written Paintbrush Tuff. commun., 1966). 116°16', 36°56' ----- Nye County ______Fraction Tuff ______K-Ar 15.0 ± 0.55(B) ____ Do. 116°17', 36°54' ______do ______Topopah Spring Mem- K-Ar 13.2 ± 0.42(B) ____ Do. ber, Paintbrush Tuff. 116°53', 36°54' _____ SE of Topopah Spring_ Tiva Canyon Member, K-Ar 12.4±0.40(B) ____ Do. Paintbrush Tuff. 116°06', 37°34' _____ Belted Peak ______Tuff ______K-Ar 26.1 ±0.71(B) ____ Do. 116°20' 1 37°37'--- __ Trailer Pass, Kawich Fraction Tuff ______K-Ar 17.8±0.48(B) __ __ Do. Range. 116°21', 37°04' ----- Nye County ______Tuff ______K-Ar 9.4± 1.98(B) _____ Do. 9.6±0.26(F) _____ Do. 116°25', 37°56' ----- SE of Kawich Peak ______do ______K-Ar 21.5 ± 0.48(B) ____ Do. 116°26' 1 37°03'--- __ Nye County ______Timber Mountain Tuff __ K-Ar 11.7±0.43(B)~--- Do. 116°26', 37°08' _____ NW of Scrugham Spearhead Member, K-Ar 7.5 ±0.20(F) _____ Do. Peak. Thirsty Canyon Tuff. 116°28', 37°12' ______do ______Ammonia Tanks Mem- K-Ar 11.4 ± 0.50(B) ____ Do. ber, Timber Mountain Tuff.

13 RADIOMETRIC AGE DETERMINATIONS-Continued

Age Age (m.y.) and Long. W., lat. N. Locality Rock type method material Reference analyzed

NEVADA -continued Cenozoic ages-Continued

116°30', 37°04' ____ _ Nye County ______Timber Mountain Tuff__ K-Ar 11.1 ± 0.30(F) __ _ _ R. W. Kistler (written commun., 1966). 116°32'' 37°03'----- Buttonhook Wash .. ______do______K-Ar 10.5±0.28(F)____ Do. 116°35', 37°18' ----- NW of Black Moun- Labyrinth Canyon Mem- K-Ar 6.2± 0.17(F) __ __ _ Do. tain. her, Thirsty Canyon Tuff. Piapi Canyon ______Ammonia Tanks Mem- K-Ar 10.9±0.35(B)____ Do. her, Timber Mountain 10.8±0.40(F)_ _ _ _ Do. Tuff. 11.2±0.49(B)____ Do. 116°36', 37°12' ----- ____ do ______Rainier Mesa Member, K-Ar 10.4±0.27(F)____ Do. Timber Mountain Tuff. 116°57'' 38°44'----- Sec. 8, T. 10 N., R. 45 Welded ash flow______K-Ar 26.1 ±0.8(B)__ _ __ USGS unpub. data. E.; Toquinea Range. Goldfield Hills ______Dacite vitrophyre______K-Ar 21.1 ± 0.57 (B) ___ _ R. W. Kistler (written commun., 1966). 117°30',37°59' ___ - Near Silver Peak_ .. __ .. Granitic intrusive______K-Ar 19.5±0.6(B) ____ _ USGS unpub. data. 117°41', 37°45' ____ _ do __ .. _ .. ______Pegmatite______K-Ar 50.6 ± 1.5(M) ___ _ Do. Granitic complex ___ -·-__ K-Ar 42.1± 1.3(B) ____ _ Do. 117°52', 37°58' ____ _ Darmes Coal mine near Tuff in Esmeralda For- K-Ar 12.7(B) ______Evernden and James Coaldale Junction. mation. (1964). Cedar l'v[ountain area______do______K-Ar 11.5(F) ______Evernden and others (1964). 10.7(B) ______Do. 117°48'·, 38°30' ______Cedar Mountain; T. 8 Quartz monzonite______Pb-a 40 ± 10(Z) ______Ross (1961). N.,R.37E. 118°05', 37°56' _____ T. 1 N., R. 35 E. ____ Tuff m Esmeralda For- K-Ar 11.1(B) ______Evernden and others mation. (1964). 11.4(B) ______Do. 118°55',38°31' _____ Sec.6,T.7N.,R.28E. RhyolitetuffinAldrich K-Ar 11.2(B) ______Do. Station Formation. 11.0(B) ______Do. 10.6(G) ______Do. 10.5(B) ______Do. 11.2(B) ______Do. Tuff in Coal Valley For- K -Ar 10.8(B) ______Do. mation. 119°19', 38°38' ___ __ Smith Valley______Dacite tuff in Morga.n K-Ar 9.3(B) ______Do. Ranch Formation.

Meso zoic ages

114 °34'' 36°25'----- Sec. 36, T. 17 S., R. 66 Tuff in Willow Tank For- K-Ar 90.4±2.7(B)_____ Schilling (1965). E. mation. 114 °12'' 38°52'----- T.11 N., R. 69 E.; Lex­ Quartz monzonite______Ph-a 225 ± 25(Z) ______Adair and Stringham ington Creek. (1960). Snake Range ______do______K-Ar 83±4(M) ______USGS unpub. data. ____ do ______do______K-Ar 79±4(M) ______Do. 73±4(B) ______Do. Ph-a 170±20(Z) ______Do. 114°15', 38°55' ____ _ T. 12 N., R. 69 E.; ____ do______Ph-a 145 ± 20(Z) ______Adair and Stringham Snake Creek. (1960). 114°15', 38°56' ____ _ Snake Range ______Xenolith in quartz Ph-a 220 ± 30 (Z) ______USGS unpub. data. monzonite(?). 114°17', 38°56' ______do ______Quartz monzonite ______K-Ar 124±6(B) ______Do. Ph-a 190±20(Z) ______Do. 114°21', 38°58' ____ _ Sec. 28, T. 13 N., R. Leuco-adamellite ______K-Ar 89":.~3 (B) ______Armstrong (1963). 68 E. 100":.~5 (B) -~- ____ _ Do. Snake Range______Aplite______K-Ar 130 ± 6 (M) ______USGS unpub. data. Ph-a 190±20(Z) ______Do. 114 °22', 38°58' ----- ____ do ______Quartz monzonite ______K-Ar 94 ± 5 (B) ______Do. Ph-a 220 ± 25 (Z) ______Do. 116°04'' 37°14' (?)-- Climax Composite ____ do______K-Ar 93±5 avg.(B) ___ _ Houser and Poole Stock; T. 8 S., R. (1961), and USGS 53 E. unpub. data. Ph-a 330±35(Z) ______Do. 230±25(Z) ______Do. 116°12', 37°14' ----- Gold Meadows stock__ Porphyritic quartz Pb-a 140±20(Z) ______USGS unpub. data. monzonite. 130±20(Z) __ _-=- __ Do. 116°13'' 37°14'----- ____ do______Granite______Ph-a 80 ± 15 (Z) ______Do. 14 RADIOMETRIC AGE DETERM INA liONS-Continued 1

Age Age (m.y.) and Long. W., lat. N. Locality Rock type method material Reference analyzed

NEVADA -continued Mesozoic ages-Continued

117°41', 37°22'(?)-- Southern Sylvania Quartz monzonite ______K-Ar 155±8(B) ______Schilling (1965). Mountains. ____ do ______153± 117°45' 1 37°43'----- Sec. 34, T. 5 S., R. K-Ar 5(B) ______Do. 38 E. 118°02', 38°20'(?)-- Sec. 23(?), T. 6 N., R. ____ do ______K-Ar 68.7±1.8(B) _____ Do. 35 E.

Precambrian ages

---~~ 114°04', 36°39' _____ Sec. 9, T. 15 S., R. Pegmatite ______K-Ar U/70± 140(M) ___ Do. 71 E. 114°09', 36°17'(?) __ North Virgin Gneiss ______K-Ar 1390(B) ______Wasserburg and Mountains. Lanphere (1965). Rb-Sr 1620(WR) ______Do. 1597(F) ______Do. Amphibolite ______K-Ar 1650(H) ______Do. Pegmatite ______Rb-Sr 1360(F) ______Do. 1455(F) ______Do. ____ do ______114 °10', 36°17' ----- Snowflake mine; T. K-Ar 910(F) ______Do. 18 S., R. 70 E. 1385 (M) ______Do. 1390(B) ______Do. Rb-Sr 1707(F) ______Do. 1610(M) ______Do. 1353(B) ______Do. 114°10', 36°15' _____ Gold Butte area ______Pegmatite in rapakivi Rb-Sr 1061(F) ______Do. granite. 114°11', 36°17' ______do ______Rapakivi granite ______Rb-Sr 1031(F) ______Do. 1032(F) ______Do. 822(B) ______Do. 114 °13' 1 36°11'--- __ Nevada Mica mine, Pegmatite ______K-Ar 1185(M) ______Do. Gold Butte area. 785(F) ______Do. Rb-Sr 1335 (M) ______Do. 1682(F) ______Do. Granite ______.927(Z) ______115°13' 1 35°29'----- Crescent Peak; T. 28 Pb-a Jaffe and others S., R. 61 E. (1959). ____ do ______0 115°00' 1 36°12'----- Sec. 24, T. 20 S., R. K-Ar 1450-:~~ (B) ______Armstrong (1963). 62 E. 1300-:~~(B) ______Do. 117°41' 1 37°48'-- _- _ 5 miles NW of Silver Pegmatite ______Rb-Sr 620-700(Le) _____ Schilling (1965). Peale

NEW MEXICO Cenozoic ages

106°00', 35°52' _____ Sec. 17, T. 19 N., R. Dacitic(?) vitric ash ____ Pb-a 18(Z) ______Jaffe and others 9 E. (1959). 32(Z) ______106°02' 1 35°28'---- .. Cerrillos Hills ______Monzonite_ .. ______Pb-a · Do. 35(Z) ______Do. 46(Z) ______Do. 46(Z) ______Do. 23(Z) ______106°28' 1 35°45' ('?)-- Valles Mountains _____ Granodiorite ______Pb-a Do. 16(Z) ______Do. 107°44' 1 35°15' ----- Lobo Canyon .. ______Obsidian boulder __ . _.. __ K-Ar 2.3 (F) ______Bassett and others (1963a). 2.8(F) _____ "' _____ Do. 1.8(G) ____ ·______Do. 1.1(G) ______Do. 107°48' 1 35°12'--- __ Grants Ridge ______Volcanic rocks ______K-Ar 3.3 avg. ______Do.

Precambrian ages

103°51' 1 36°47'----- Sec. 4, T. 29 N., R. Granite (drill cuttings) __ Rb-Sr 1270±60(B) _____ Muehlberger and 29 E. others (in press). 104°40', 3~ 0 54' _____ Sec. 12, T. 19 N., R. Granite (drill core) _____ Rb-Sr 1350± 120(F) ____ Do. 21 E. K-Ar 1320(M) ______Do. 104°43' 1 35°10' -- ___ Sec. 22, T. 11 N., R. Gneissic granite (drill Rb-8r 1610± 140(WR) __ Do. 21 E. core). 1350(B) ______Do. 15 RADIOMETRIC AGE DETERMINATIONS-Continued

Age Age (m.y.) and Long. W., lat. N. Locality Rock type method material Reference analyzed

NEW MEXICO-continued Precambrian ages-Continued

105°14', 35°35'(?)__ Las Vegas______(?) ______Pb207 /Pb206 1340(Mz) ______Nier and others (1941) . 105°35', 35°50'(?) _ _ Pidlite mine______Pegmatite(?)______K-Ar 1280(Le) ______Aldrich and others (1958). Rb-Sr 1490(Le) ______Do. 105°55', 35°35' _____ SE of Santa Fe ______Aplitic granite ______Ph-a 718(Z) ______Jaffe and others (1959). 105°48', 36°11' _____ Harding.mine, near Pegmatite ______Rb-Sr 1320(M) ______Aldrich and others Dixon. (1958). 1290(M) ______Do. K-Ar 1250(M) ______Do. Rb-Sr 1350(M) ______Do. K-Ar 1260(M) ______Do. Rb-Sr 1260(M) ______Do. Pb2o1 /Pb2o6 1180(Mic) ______Do. 940(Mic) ______Do. 105°48', 36°11'(?) _ _ Near Dixon______Conglomerate of Vadito Ph-a 1550± 175(Z) ___ _ USGS unpub. data. Formation of Montgomery (1953). 106°27', 35 °12' __ _ _ _ Sandia Excarpment_ __ Granite______Pb207 /Pb206 1475(Z) ______Tilton and others (1962). K-Ar 1300(B) ______Do. Rb-Sr 1340(B) ______Do. 106°01', 36°31'(?) _ _ Petaca______Pegmatite______Pb207 /Pb206 875±30(Sa) ____ _ Eckelmann and Kulp (1957).

NORTH CAROLINA Paleozoic ages

Nella Teer quarry ____ Granite ______K-Ar 238(B) ______., __ Kulp and Eckelmann (1961). 78°26', 36°20' ______Graystone quarry, Migmatite______K-Ar 259(B) ______Do. Henderson. 79°56', 35°58' ______Near High Point_____ Granite______K-Ar 352± 13(B) ______Long and others (1959). 80°00'' 35°15'------Montgomery County_ Tuff ______~ ______Pb-a 440±60(Z) ______White and others (1!?-63). 470±60(Z) ______Do. Isenhour quarry, Syenite______Ph-a 450±50(Z) ______Overstreet and others Concord. (1961). Granite______Pb-a 445±50(Z) ______Do. 360±40(Z) ______Do. 430 ± 50(Z) ______Do. 300±35(Z) ______Do. Gneissic granodiorite____ Pb-a 505±55(Z) ____ -" Do. 495±55(Z) ______Do. 380± 100(Z) ____ _ Do. 470±55(Z) ______Do. 80°36', 35°22' ______Near Concord ______Saprolite from Ph-a 410±80(Z) ______USGS unpub. data. syenite. 80°38', 35°22' ___ --- S of Concord ______Augite syenite ______Ph-a 305±200(Z) ____ _ Overstreet and others (1961). 540±200(Z) ____ _ Do. 80°00'' 36°30' ('?)--- Knight mine ______Pegmatite ______Rb-Sr 321 ± 17 (M) ____ _ Deuser and Herzog (1962). 80°15'' 36°30' (?)--- Spencer mine ____ ~ ______do ______Rb-Sr 276 ± 15(M) ____ _ Do. 80°38'' 36°31'------Near M t. Airy ______Granite ______K-Ar 356±13(B) ______Long and others (1959). 81 °05', 35°19' ------Near Bessemer City __ Bessemer Granite ______Ph-a 491(Z) ______Jaffe and others (1959). 81°16', 35°25' ______Near Lincolnton ______Carolina Gneiss ______K-Ar 315± ll(M) ______Long and others (1959). 81 °26', 35°15' ------6 miles E of Shelby ___ Cherryville Quartz Ph-a 260(Mz) ______Jaffe and others (1959). Monzonite. 81°31', 35°32' ______Toluca ______Toluca Quartz Mon- Pb207 /Pb20G 480±50(Z)______Davis and others (1962). zonite. Rb-Sr 250(B) ______Do. 81 °32'' 35°32'------Acre rock quarry, ____ do ______Ph-a 442(Z) ______Jaffe and others (1959). Toluca. Pegmatite ______Ph-a 427 (Z) ______Do. 435(Z) ______Do. 380(Mz) ______Do. 377(Mz) ______Do. 456(Z) ______Do. 81 °32', 35°33' ______NW of Toluca______Saprolite of gneissic Ph-a 319(Mz) ______Do. granite. 16 RADIOMETRIC AGE DETERMINATIONS-Continued

Age Age (m.y.) and Long. W., lat. N. Locality Rock type method material Reference analyzed

NORTH CAROLINA-continued Paleozoic ages-Continued

81 °34'' 35°16'------Shelby ______Cherryville Quartz Mon- Rb-Sr 375(B) ______Davis and others (1962). zonite. 350. (M) ______Do. 81 °34'' 35°16' (?)--- Shelby area ______Carolina Gneiss ______Pb-a 356(Z) ______Jaffe and others (1959). 400(Mz) ______Do. Schist of the Carolina Pb-a 420(Z) ______Do. gneiss. 389(Mz) ______Do. 393(Z) ______Do. 395(Mz) ______Do. 413(Mz) ______Do. 81 °35', 35°50' (?) --·· McGee mine ______Pegmatite ______Rb-Sr 317±15(M) _____ Deuser and Herzog (1962). 81 °44', 35°26' ------Hollis ______Toluca Quartz Mon- Pb-a 377(Mz) ______Jaffe and others (1959). zonite. 81°46', 35°58' ______Mortimer ______Gneiss ______Rb-Sr 350(B) ______Davis and others (1962). 81 °50'' 35°25' ('?)--- Rutherford County_ .. _ Henderson Granite _____ Pb-a 357(Z) ______Jaffe and others (1959). 81 °25'' 36°15' ('?)--- Haw mine ______Pegmatite ______~ Rb-Sr 334± 17(M) _____ Deuser and Herzog (1962). 81 °30'' 36°26' ('?)- -- Knob Hill mine ______Gneiss ______K-Ar 335(B) ______Kinkel and others (1965). 345(B) ______Do. Rb-Sr 310(B) ______Do. 320(B) ______Do. 81 °30', 36°26'(?)-- _____ do ______Ore zone gangue ______K-Ar 435(B) ______Do. 465(B) ______Do. Rb-Sr 320(B) ______Do. 320(B) ______Do. 81°48', 36°13' ______Near Valle Crucis _____ Cranberry Gneiss ______K-Ar 378(WR) ______Carr and Kulp (1957, listed for Virginia). 81 °55'' 36 °05' (?)- -- C. Ridge mine ______Pegmatite ______Rb-Sr 348±17(M) Deuser and Herzog (1962). 82°04', 35°57'(?)--- Spruce Pine district_ __ Saprolite of Cranberry Pb-a 503(Z) ______Jaffe and others (1959). Gneiss. 471(Z) ______Do. Pegmatite ______K-Ar 332(Mi) ______Carr and Kulp (1957). 329(Mi) ______Do. 346(Mi) ______Do. Spruce Pine area _____ Carolina Gneiss ______K-Ar 341 ±13(M+B) __ Long and others (1959). Pegmatite ______K-Ar 334 ± 15 (M) _____ Do. 334±15(M) _____ Do. 348±15(M) ______Do. 341±15(M) ______Do. 82°06', 35°58' ------6 miles NNW of Spruce _____ do ______K-Ar 335 (M) ______- Aldrich and others Pine. (1958). Rb-Sr 375(M) ______Do. 385(F) ______Do. Pb207 /Pb20G 400 ± 50(U) ______Davis and others (1962). 420±50(U) ______Do. Spruce Pine area ______do_l ______K-Ar 330 (M) ______Goldich and others (1961). 82°10'' 35 °55' (?)- -- Abernathy mine ______do ______~------Rb-Sr 340±20(M) _____ Deuser and Herzog (1962). 311 ± 16(B) ______Do. 82°17', 35°14' ______Jones mine ______Syenite pegmatite ______Pb-a 280±30(Z) ______Overstreet and others (1961). 300±45(Z) ______Do. 82°25', 35°50'(?) ___ Mudhole mine ______Pegmatite ______Rb-Sr 328 ± 18(M) _____ Deuser and Herzog (1962). 82°33', 35°46' ______Near Stocksville ______Carolina Gneiss ______K-Ar 357 ± 13 (B) ______Long and others (1959). Rb-Sr 330 ± 13 (B) ______Do. 82°58', 35°30' ______Near Waynesville ______do ______K-Ar 344(M) ______Kulp and Eckelmann . (1961). 82°02'' 36 °02' (?)- -- Wiseman mine, Spruce Pegmatite ______Pb~07 /Pb20G 380±80(Sa) _____ Eckelmann and Kulp Pine area. (1957). McKinney mine, _____ do ______Pb207 /Pb20G 300 ±40(Sa) _____ Do. Spruce Pine area. 342±20(Sa) ______do ______Do. Flat Rock mine, Pb~o1 /Pb2oo 372± 15(U) ______Do. Spruce Pine area. 355±20(Gm) ____ Do. 82°02'' 36°02' (?)--- Mars Hill, Spruce Pine . ____ do ______Pb207 /Pb20G 235± 70(Mz) _____ Do . area. 17 RADIOMETRIC AGE DETERMINATIONS-Continued

Age Age (m.y.) and Long. W., lat. N. Locality Rock type method material Reference analyzed

NORTH CAROLINA -continued Paleozoic ages-Continued

82°05'' 36°03' ('?)--- Mitchell County _____ Pegmatite(?) ______Pb2o1 /Pb2or, 405 ± 60(Sa) _____ Eckelmann and Kulp (1957). 82°11', 36°01' ______Near Red Hill______Metadiabase dikes ______K-Ar 433±15(B) ______Long and others (1959). 457±21(B) ______Do. 82°15'' 36°01'------Deyton Bend ______Banded gneiss ______K-Ar 320(B) ______Davis and others (1962). Rb-Sr 355(B)_~------Do. 83°03', 35°33'('?) ___ Haywood County ____ Granitoid band in augen Pb-a 531(Z) ______Jaffe and others (1959). gneiss. 529(Z) ______Do. 83°08', 35°06'-----·· Near Cashier ______Whiteside Granite ______Ph-a 358(Mz) ______Do. 83°14', 35°03' ______Highlands ______do ______Pb-a 368(Mz) ______Do. 83°17', 35°28' ______4 miles W of Soco Carolina Gneiss ______K-Ar 359(B) ______Kulp and Eckelmann Gap. (1961). 83°20'' 35°03'------5 miles W of High- Whiteside Granite ______Pb-a 413(Mz) ______Jaffe and others (1959). lands. 437(Mz) ______Do. 83°23'' 35°12'------Near Franklin ______Carolina Gneiss ______K-Ar 307(B) ______Kulp and Eckelmann (1961). 83°23'' 35°16'------Gay ______Pegmatite ______.. ___ K-Ar 348± 13(M) _____ Long and others (1959). Carolina Gneiss ______K-Ar 438± 14(B) ______Do. Rb-Sr 333 ± 15(B) ______Do. 83°25'' 35°10' ('?)-- - Iotla mine ______.. ____ Pegmatite ______. Rb-Sr 512±28(M) _____ Deuser and Herzog (1962). 293 ± 15(B) ______Do. 83°25'' 35°34'------SE of Newfound Gap_ Ocoee Series (Late K-Ar 382(B) ______Kulp and Eckelmann Precambrian). (1961). 83°27', 35°26' ______Bryson City ______Pegmatite ______K-Ar 535(Mi) ______Carr and Kulp (1957). 555(Mi) ______Do. 340 ± 13 (M) _____ Long and others (1959). ____ do ______83°30'' 35°10' ('?)--- Grindstaff mine ______Rb-Sr 508 ± 27 (M) _____ Deuser and Herzog (1962). 256 ± 14 (B) ______Do. 83°30'' 35°12'------6.3 miles E of Carolina Gneiss ______Pb-a 587(Z) ______Jaffe and others (1959). Franklin. 83°49', 35°13' ______Near Andrews ______Valleytown Formation __ K-Ar 373(B) ______Kulp and Eckelmann (1961).

Precambrian ages

81 °46', 35°58' ------Mortimer ______Gneiss ______Pb2o1 /Pb2o6 1020(Z) ______Davis and others (1962). 81°30', 36°26'(?) ___ Knob Ore mine ______Ore zone gangue ______K-Ar 1120(H) ______Kinkel and others (1965). 81 °41', 36°01' ------Blowing Rock ______Augen gneiss ______Pb2o1 /Pb2o6 1055(Z) ______Davis and others (1962). Blowing Rock Gneiss ___ Pb2o1 /Pb2o6 1060(Z) ______Tilton and others (1960). Pb-a 1020 ± 115(Z) ____ USGS unpub. data. 81 °56', 36°02' ------Near Crossnore ______Granite gneiss ______Pb2o7 /Pb2o6 800 ± 50(Z) ______Davis and others (1962). K-Ar 840(H) ______Do. 81 °56', 36°14' ------Dark Ridge ______Gneiss ______K-Ar 660(B) ______Do. Rb-Sr 810(B) ______Do. 82°42', 35°48' ______Near White Rock ____ Cranberry Gneiss ______K-Ar 695 ±23(B) ______Long and others (1959). 82°57', 35°49' ______Max Patch Mountain_ Max Patch Granite ____ Pb-a 912(Z) ______Jaffe and others (1959) (listed under Tenn.). 82°15', 36°01' ______Deyton Bend ______Banded gneiss ______Pb2o7 /Pb2oo 1270(Z) ______Davis and others (1962). Cranberry Gneiss ______Pb-a 1040(Z) ______Stern and Rose (1961). 83°20', 35°03' ______5 miles W of Highlands_ Whiteside Granite ______Ph-a 708(Z) ______Jaffe and others (1959). 83°30', 35°12' ______6.3 miles E of Carolina Gneiss ______Pb-:-a 622(Z) ______Do. Franklin.

18 RADIOMETRIC AGE DETERMINATIONS-Continued

Age Age (m.y.) and Long. W., lat. N. Locality Rock type method material Reference analyzed

OKLAHOMA Paleozoic ages

99°25', 35°01'----···· Sec. 9, T. 6 N., R. Headquarters granite___ Rb-Sr 520 ± 30 (F)______Tilton and others 21 w. (1962). . !)9°59', 35°11.'. -· -···· Sec. 7, T. 8 N., R. Diorite (drill cuttings)__ K -Ar 500(B) ______Muehlberger and others 26 w. (in press).

Precambrian ages

94°34', 35°24' ---··. Sec. 20, T. 11 N., R. Rhyolite porphyry (drill Rb-Sr 1230± l80(WR) __ Do. 26 E. core). !)4°53', 35°09' ---· _ Sec. 28, T. 8 N., R. Hornblende granite Rb-Sr 1200±90(F) ---- Do. 23 E. (drill core). 95°03', 36°23'--··--- Sec. 15, T. 22 N., R. Spavinaw Granite ______Rb-Sr 1280± 100(F) ____ Do. 21 E. 95°33', 36°15'.. . _ Sec. 36, T. 21 N., R. Micrographic granite Rb-Sr 1230± 140(F) ____ Do. 16 E. porphyry (drill cut- tings). 96°09', 36°34'-----· Sec. 8, T. 24 N., R. Rhyolite porphyry (drill Rb-Sr 1190±70(WR) ___ Do. 11 E. cuttings). 96°14', 35°58' ___ . _ Sec. 10, T. 17 N., R. Micrographic granite Rb-Sr 1160 ± 50 (WR) ___ Do. 10 E. porphyry (drill cut- tings). 96°18', 36°22'---·· _ Sec. 24, T. 22 N., R. Microgranite prophyry Rb-Sr 1240± 140(F) ____ Do. 9E. (drill cuttings). 06°27', 36°17' ______Sec. 20, T. 21 N., R. Rhyolite porphyry (drill . Rb-Sr 1180±70(WR)___ Do. 8E. core). !)6°28', 36°37' ______Sec. 29, T. 25 N., R. Microgranite porphyry Rb-Sr 1150±80(WR) ___ Do. 8 E. (drill core). 96°59', 36°26'-----· Sec. 33, T. 23 N., R. Rhyolite porphyry (drill Rb-Sr 1270± 100(WR) __ Do. 3 E. core). 97°27', 35°25'------Sec. 19, T. 11 N., R. Granite gneiss (drill Rb-Sr 1150 ± 200 (F) ____ Do. 2W. cuttings). 97°13', 36°54' ______Sec.17, T. 28 N., R. Adamellite (drill core) ___ Rb-Sr 1220 ± 90(F) _____ Do. 1 E. 1210± 120(WR) __ Do. 102°51', 36°56' ____ Sec. 33, T. 6 N., R. Micrographic granite Rb-Sr 1290±60(WR)_ __ Do. 2 E. (drill core).

SOUTH CAROLINA Paleozoic ages

81°1.7', 35°05' ______Near Henry Knob, Yorkville Quartz Mon- Pb-a 262(Z) ______Jaffe and others (1959) York County. zonite. (listed under North Carolina). 81°40', 35°03' ______Near Gaffney ______Gaffney Marble ______K-Ar 309 ± 11 (Po) _____ Long and others (1959). Near Tigerville ______255 30 82°15'' 35°04'---- 0 - Pegmatite syenite('?) ____ Pb-a ± (Z) ______Overstreet and others (1961). 270±30(Z) ______Do. 260 ± 30(Z) ______Do.

TENNESSEE Paleozoic ages

82°04'' 36°12'------Roan Mountain ___ .. __ Beech Granite ______K-Ar 380(B) ______Davis and others (1962): Rb-Sr 420(B)----~----- Do. 570(F) ______Do. Cranberry Gneiss ______K-Ar 357 ± 13(B) ______Long and others (1959). 82°06'' 36°17' ------Near Hopson ______Beech Granite _____ .. ___ K-Ar 418± 16(B) ______Do. Rb-Sr 439±17(B) ______Do. 572±29(F) ______Do. 83°57', 35°38' ______Murray Gap ______Glauconitic sandstone, K-Ar 439(Gl) ______. Hurley and other:; Murray Shale, Chil- (1960). howee Group (Lower Cambrian). Rb-Sr 552±30(Gl) _____ Do.

19 RADIOMETRIC AGE DETERMINATIONS-Continued

Age Age (m.y.) and Long. W., lat. N. Locality Rock type method material Reference analyzed

TENNESSEE-continued Paleozoic ages-Continued

84°16', 35°35' ______Vonore ______Bays Formation ______uz3s/Pb2oo 453± 10(WR) ____ Adams and others (1960). 84°22', 35°03' ______Eureka mine, Duck- Hornblendite ______K-Ar 478(H) ______Kinkel and others town. (1965). Boyd mine, Duck- Ore zone gangue ______. _ K-Ar 387 (H) ______Do. town. Ducktown ______Ocoee Series ______K-Ar 327 (M) ______Kulp and Eckelmann (1961). Ore zone gangue ______K-Ar 374(B) ______Do. 366(B) ______7 __ Do. 84°29', 35°06' ------4.5 miles W of Duck- Ocoee Series (Late K-Ar 434±15(B) ______Long and others town. Precam brian). (1959). Rb-Sr 329 ± 13 (B) ______Do. 85°43', 35°57' ------Slego Bridge, E of Bentonite in Chat- K-Ar 340±7(B) ______Faul (1960). Smithville. tanooga Shale. 85°44'' 35°55'------Youngs Bend area, Chattanooga Shale ______uz3s/Pbzoa 350 avg.(WR) ____ Cobb and Kulp (1960). Smithville. 85°56'' 36°01'--- ~-- Dowelltown ______Carters Limestone, u23s;pbzoa 446±10(WR) ____ Adams and others Stones River Group. (1960). 86°02'' 36°05'------Alexandria ______do ______u23s;pbzoa 452± 10(WR) ____ Do. 86°46'' 36°10' (?)--- Nashville ______do ______uz3s;pbzoa 438± 10(WR) ____ Do.

Precambrian ages

82°03', 36°16' ------Laurel Gap ______Rare earth vein ______Pb2o1 !Pb2oa _ 820(Z) ______Davis and others (1962). 82°04', 36°12' ______Roan Mountain ______Beech Granite ______Pb2o1 /Pbzoa 700(Z) ______Do. 82°11', 36°14' ______Near Hampton ______Cranberry Gneiss ______K-Ar 640 ± 22(B) ______Lorig and others (1959). Rb-Sr 719±25(B) ______Do. 82°11', 36°17' ______Pardee Point ______Banded gneiss ______Pb2o1 /Pbzoo 1230(Z) ______Davis and others (1962). Rb-Sr 880(B) ______Do. Granite gneiss ______Pb2o1 /Pb2oo 940(Z) ______Do. K-Ar 770(B) ______Do. Rb-Sr 890(B) ______Do. Cranberry Gneiss ______K-Ar 770(B) ______Tilton and others (1960). Rb-Sr 890(B) ______Do. K-Ar 800 ± 27 (B) ______Long and others (1959). Rb-Sr 892±30(B) ______Do. 82°11', 36°16' ______SE of Hampton ______do ______K-Ar 67 4 ± 22 (B) ______Do. ____ do ______do ______K-Ar 648 ± 22 (B) ______Do. 82°11'' 36°15' ------_ ___ do ______82°11', 36°11' ______SSE of Hampton ___ - K-Ar 527 ± 18(B) ______Do. 84°22', 35°03' ______Calloway mine, Ore zone gangue ______K-Ar 1045(H) ______Kinkel and others Ducktown. (1965). 992(H) ______Do. Ducktown ______do ______K-Ar !200(B) ______Do. 87°08', 35°20' ------Near Campbellsville __ Granite (drill core) _____ Rb-Sr 1120 ± 30 (F) _____ Wasserburg and other~ (1962).

TEXAS Precambrian ages

101 °05', 35°26'(?)-- Carson County ______Granite (drill core) _____ Rb-Sr 1140 ± 120 (F) ____ Muehlberger and others (in press). 101 °27', 35°35' (?)-- ~---do ______Amphibolite gneiss K-Ar 1230(H) ______Do. (drill core). 101°50', 35°26' _____ Potter County ______Granite (drill core) _____ Rb-Sr 1260±40(F) _____ Wasserburg and others (1962). 1190±70(WR) __ _ Do. 102°15', 35°57'(?)-- Hartley County ______Rhyolite porphyry Rb-Sr 1180 ± 130(F) ____ Muehlberger and (drill core). others (in press). 102°35', 35°25'(?)-- Oldham County ______Micrographic granite Rb-Sr 1130±100(WR) __ Do. porphyry (drill core).

20 RADIOMETRIC AGE DETERMINATIONS-Continued

Age Age (m.y.) and Long. W., lat. N. Locality Rock type method material Reference analyzed

UTAH Cenozoic ages

Sec. 14, T. 26 S., R. Soda syenite porphyry_ .. K-Ar 25.5 ± 2.5(P) ___ . Stern and others 24 E.; La Sal (1965). Mountains. Pb~oa;un~ 32.2(Z) ______Do. Sec. 15, T. 26 S., R. Monzonite porphyry ___ _ K-Ar 22.5 ±3.3(P) ____ _ Do. 24 E.; La Sal Pb20GfU2~S 32.2(Z) ______Do. Mountains. Sec. 5, T. 26 S., R. Diorite porphyry (relict K-Ar 54.8± 1.5(H) ____ _ Do. 24 E.; La Sal hornblende?). Mountains. 109°17', 38°33'(?) .. Mineral Mountain; Syenite porphyry ___ . Pb-a 25(Z) _ .. . _ Jaffe and others (1959). La Sal Mountains. 25(Z) ______Do. 109°16', 38°33'(?)-- North Mountain; La Monzonite porphyry_ .. __ 55(Z) __ Do. Sal Mountains. 51(Z) ______Do. Newly Weds mine, Pyroxene andesite of K-Ar 2.9.5 (F) ______Bassett and others Marysville area. Bullion Canyon (1963b). Volcanics. Mineral Hills mine, Quartz monzonite ______K-Ar 26.0(B) ___ _ Do. Marysville area. VCA mine, Marysville .. ___ do _____ ...... ___ . __ K-Ar 24.3(B) ____ . Do. area. ____ do ______Prospector mine, K-Ar 23.6(13)---- Do. Marysville area. 112°1.5', 38°28'----.- N of Marysville ______Mount Belknap Vol­ K-Ar 17.8(G) ______Do. canics. Beaver Creek, Marys­ ____ do ______K-Ar 20.0(G) ______. Do. ville area. 19.5(G) ______. _ Do. 112°15', 38°29' ----- N of Marysville ______do ______K-Ar 15.6(G) __ _ Do. 112015', 38°31' ----- Antelope Canyon, ____ do ______K-Ar 13.7(G) ______Do. Marysville area. 112°16', 38°23' ____ _ Deer Trail mine, Hydrothermal altera­ K-Ar 13.5(M) ______. _ Do. Tushar Range. tion. Pb/U 13(U) ______Do. 112°16', 38°30' ____ _ Deer Creek Canyon, Moun~Belknap Vol- K-Ar 19.0(G) __ _ ----- Do. Marysville area. eames.· Iron Springs district_ _ Granodiorite porphyry .. K-Ar . 24~~(B) _ _ _ Armstrong (1963). 113°12', 37°45' ----­ ___ do ______ll3 °12'' 37°46' (?)-- Volcanic rock .. ______. _ Pb-a 19(Z) __ Jaffe and others (195!-)). Three Peaks Intrusive __ . Pb-a 22(Z) ______Do. Tuff ______.. _. . ____ _ Pb-cx 28(Z) ______Do. 1.f3°05', 38°27' ----- Rocky Range ___ .. ___ _ Quartz monzonite .. ___ .. _ K-Ar 20.8±0.6(B) ____ _ USGS unpub. data. 27.0±0.8(H) ____ _ Do. 113007', 38°29' ----­ OK Stock ______.. ___ _ Granodiorite .. ____ .. _____ K-Ar 28.4 ± 0.9(H) ____ _ Do. ll3 °07'' 38°24' ----- San Francisco dis- Porphyritic quartz mon- K-Ar 20.9±0.6(B) ____ _ Do. trict. zonite. 113°14', 38°27' ____ _ Near San Francisco Biotite tuft' ______K-Ar 22.4±0.7(B) ____ _ USGS unpub. data. district. ll3°16', 38°17' __ --- ____ do ______Tuff in the Needles K-Ar 29.0±0.9(B) __ . _. Do. Range· Formation. 29.2±0.9(H) ___ _. Do. 113°16', 38°27' ______do ______Red ignimbrite______K-Ar 21.9± 0.7(F)- ~--- Do. 113°19', 38°29' ___ .... Cactus Stock ______Granodiorite______K-Ar 28.0 ±0.8(B) ____ . Do. ll3°50', 38°37' ___ __ Condor Canyon, Ignimbrite______K-Ar 26~~(B) ______Armstrong (1963). Needles Range. 24~~(B) ______Do.

Mesozoic ages ll0°02', 38°46' _____ Sec. 3, T. 24 S., R. Bentonite in the Carmel K-Ar 154(13) ______Marvin and others 17 E. Formation. (1965). Rb-Sr 163±10(B) ______Do. 110°07', 38°44' _____ Sec. 11, T. 24 S., R. ____ do ______K-Ar 140(B) ______Do. 16 E. Rb-Sr 147±15(B) ______Do. 112°40', 37°13' __ .:_ __ Sec. 30, T. 41 S., R. ____ do______K-Ar 162(B) ______Do. 7W. 151(B) ______~ Do. Rb-Sr 163±10(B) ______Do. 163±15(B) ______Do. 148± 15(B) ______Do. 113°48', 37°12'_____ Sec. 32, T. 40 S., R. ____ do _____ .. ______K-Ar 165(B) ______Do. 17 w. 112°43 ', 38 °23' (?) _ _ Mineral Range ______Granite ______.. __ .. _ Pb-a 241(Z) ______Armstrong (1963).

21 RADIOMETRIC AGE DETERMINATIONS-Continued

Age Age (m.y.) and Long. W., lat. N. Locality Rock type method material Reference analyzed

UTAH-continued Precambrian ages

113°52', 37°05' _____ Beaver Dam Amphibole______K-Ar 1660(H) ______Wasserburg and Mountains. Lanphere (1965). Pegmatite______Rb-Sr 1500(F) ______~ Do. Granodiorite______Rb-Sr 1379(B) ______Do.

VIRGINIA Meso zoic ages

Wenger Farm, Teschenite, alkalic K-Ar 152±5(B) ______Johnson and Milton Augusta County. dike complex. (in press). 151 ± 10(H) ______Do.

Paleozoic ages

77°55', 37°21' .. _ Morefield mine, Pegmatite___ __. Rb-Sr 261 ± 13 (M) ____ _ Deuser and Herzog Amelia County. (1962). 77°58', 37°22' ____ .. . Champion mine, _____ do______Rb-Sr 270± 13(M) ____ _ Do. Amelia County. 77°59', 37°21' ___ . . Rutherford #2 mine, _____ do______Rb-Sr 289± 14(M) ____ _ Do. Amelia County. 77°50', 38°05'. _.. . _ Sulphur mine __ _ Ore zone gangue______K-Ar 365 (B + M) ______Kinkel and others

(1965) 0 330(H) ______Do. 77°54', 38°02' __ _ _ _ Armin ius mine ______. _____ do ______K-Ar 305(B) ______Do. 78°11', 37°45' _____ . Columbia ______Granodiorite gneiss ____ _ K-Ar 301 ± 15(B) ______Smith and others (1964). Rb-Sr 400± 125(B) ____ _ Do. Pb-a 400±50(Z) ______Do. Near Ore Bank______Biotitic slate in Arvonia K-Ar 324 ± 12 (B) ______Do. Formation. North of Big Island, Schist______K-Ar 287±18(B+M) __ Do. James River. 78°30'' 37°30' (?)-- .. London-Virginia mine_ Ore zone gangue______K-Ar 300(B) ______Kinkel and others (1965). 78°16'' 38°39'--- .. - .. 1.7 miles W of Sperry- Granodiorite gneiss_____ Pb-a 508(Z) ______Jaffe and others (1359). ville. 510(Z) ______Do. 1.6 miles W of Sperry- _____ do______Pb-a 470(Z) ______Do. ville. 449(Z) ______Do. 468(Mz) ______Do. Skyline Drive, Shen­ . Hypersthene granodio­ Pb-a 567(Z) ______Do. andoah N a tiona! rite gneiss. 586(Z) ______Do. Park. White Oak Canyon, Old Rag Granite-______Pb-a 417(Z) ______Do. Shenandoah N a­ 428(Z) ______Do. tiona! Park. Near Strasburg ______Bentonite in Martins­ Pb-a 410 ± 50(Z) ______USGS unpub. data. burg Shale (Ordovi­ 400±45(Z)______Do. cian). 79°24'' .37°22'-- . Near Good______Lynchburg Gneiss ____ _ K-Ar 370 ± 13(B) _.. _ __ Long and others (1959). 79°38'' 38°27'--- -. 2}f miles NE of High- Granite felsophyre dike __ Pb-a 316(Z)______Jaffe and others (1959). town. Gossan-Lead or Mona- Ore zone gangue ______.. _ K-Ar 430(M) ______Kinkel and others rat mine. (1965). Rb-Sr 310(M) ______Do. 81°11',36°37'----·-·· Near Independence ___ Cranberry Gneiss ______K-Ar 402(WR) ______Carr and Kulp (1957).

Precambrian ages

Marys Rock Tunnel, Granodiorite gneiss_____ K-Ar 800(B) ______Tilton and others Shenandoah N a­ (1960). tiona! Park. Rb-Sr 880(B) ______Do. Pb207 /Pb20G 1150(Z) ______Tilton and others (1958). Rb-Sr 980 ± 90(F) ______Doe and others (1965). Hogback Ridge, Shen- _____ do ______Rb-Sr 980 ± 90(F) ______Do. andoah N a tiona! Park.

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