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Shorter Contributions
to General Geology
1958
GEOLOGICAL SURVEY PROFESSIONAL PAPER 334
This Professional Paper was published
as separate chapters A H
UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1962
UNITED STATES DEPARTMENT OF THE INTERIOR
STEW ART L. UDALL, Secretary
GEOLOGICAL SURVEY
Thomas B. Nolan, Director
For sale by the Superintendent of Documents, U.S. Government Printing OfficeWashington 25, D.C.
CONTENTS
[The letters in parentheses are those used to designate the separate chapters]Page
(A) Tables for the calculation of lead isotope ages, by L. R. Stieff, T. W. Stern, Seiki Oshiro, and F. E. Senftle_________ 1(B) Fossils of the Littleton formation (Lower Devonian) of New Hampshire, by A. J. Boucot and Robert Arndt_________. 41(C) Trilobites of the Upper Cambrian Dunderberg shale, Eureka district, Nevada, by Allison R. Palmer_ _-____-___-__-__ 53(D) Late Paleozoic Gastropoda from northern Alaska, by Ellis Y. Yochelson and J. Thomas Dutro, Jr___________________ 111(E) Upper Cretaceous Pelecypods of the genus Inoceramus from northern Alaska, by David L. Jones and George Gryc_____ 149(F) Ammonites of Early Cretaceous age (Valanginian and Hauterivian) from the Pacific Coast States, by Ralph W. Imlay_ 167 (G) Dispersion characteristics of montmorillonite,kaolinite, and illite clays in waters of varying quality, and their control
with phosphate dispersants, by B. N. Rolfe, R. F. Miller, and I. S. McQueen___________________________________ 229(H) Geology of southeastern Ventura basin, Los Angeles County, California, by E. L. Winterer and D. L. Durham________ 275
ni
U.S. GOVERNMENT PRINTING OFFICE : 1962 O -581734
Tables for the Calculation
of Lead Isotope AgesBy L. R. STIEFF, T. W. STERN, SEIKI OSHIRO, and F. E. SENFTLE
SHORTER CONTRIBUTIONS TO GENERAL GEOLOG
GEOLOGICAL SURVEY PROFESSIONAL PAPER 334-A
Tables for the calculation of geologic age using the. .' r r>l206/TT238 DU207/TT23S D U 207 I r> U 206atomic ratios oj rb /U , rb /U , rb /rb ,
and Pb208 /Th 32. This report concerns work done on
behalf of the U. S. Atomic Energy Commission and
is published with the permission of the Commission
UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1959
UNITED STATES DEPARTMENT OF THE INTERIOR
FRED A. SEATON, Secretary
GEOLOGICAL SURVEY
Thomas B. Nolan, Director
The U. S. Geological Survey Library has cataloged this publication as follows:
Stieff, Lorin Roll ins, 1920-Tables for the calculation of lead isotope ages, by L. K.
Stieff f and others] Washington, U. S. Govt. Print. Off., 1959.
iv, 40 p. diagrs., tables. 30 cm. (U. S. Geological Survey. Pro fessional paper 334-A. Shorter contributions to general geology)
"Tables for the calculation of geologic age using the atomic ratios of Pb206/U238, Pb207/U235, Pb207/Pb206, and Pb208/Th232."
Bibliography: p. 7.1. Lead Isotopes. 2. Isotopes Tables, etc. 3. Geological time
i. Title. (Series: U. S. Geological Survey. Professional paper 334-A. Series: U. S. Geological Survey. Shorter contributions to general geology)
550.1
For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C. - Price 35 cents (paper copy)
CONTENTS
Abstract-- _ __________________________Introduction ___________-_-_---_____-_Methods of computation--_____-_______
The Nd/Np relation.______________The Nw/Nm relation___.,._____.__
Sample age calculation________________Correction for original common lead.
Page 1 1 33456
Sample age calculation ContinuedPb2oe/U2»8 age method___.__________._.Pb207/U23B age method__________.__.__.Pb207/Pb206 age method..._______________Pbzos/Th232 age method_______-_____._.
Literature cited.________..-______--__-__-_Tables for the calculation of lead isotope ages.
ILLUSTRATIONS
Page
677779
FIGURE 1. Atomic ratio Nd/N p plotted against the age, t, showing the plus and minus tolerance curves.-. 2. Atomic ratio Nw,/Nm plotted against the age, t, showing the plus and minus tolerance curves.
TABLES
TABLE 1. Physical constants used in calculation of tables-__.______-_-___---__-_---__-__-2. Errors in t produced by uncertainties in the physical constants used in calculation.3. Range and interval of <_________.__.________-_______..______________________.4. Decay constants X,- (y-1).-_-_____._.___-_____-_-______-__-________-_-______-
m
LETTER SYMBOLS
X decay constantt age, in millions of yearsT half lifeN number of atomsNd number of atoms of daughter productsNp number of atoms of parentk present-day atomic ratio of U238 to U235V yearR atomic ratio
SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY
TABLES FOR THE CALCULATION OF LEAD ISOTOPE AGES
By L. R. STIEFF, T. W. STERN, SEIKI OSHIRO, and F. E. SENFTLE
ABSTRACT
Tables are presented for calculating geologic age by using theatomic ratios of Pb2°«/U238 , Pb2°YU235, Pb207/Pb206, and Pb2"8/Th232 .
Tables of values of Nd/Np and t are given for the age equation
where A is the decay constant,t is age, in millions of years,Nd is the number of atoms of daughter products,
and Np is the number of atoms of parent.Values for Ntm/Nm and t are also given in tabular form for
the age equation
A/2 1)
where N^m and A/2oe are the number of atoms of radiogenic Pb207 and Pb206, respectively, and where k, the present-day atomic ratio of U238 to U235, is taken as 137.7. The half lives (T) of U238, U235, and Th232 used in the calculations are: r238 =4.51X 109 years, 71235=7.13X108 years, Tm=lA2X 1010 years.
The tables cover selected values of t from 1 to 6,000 million years (6X 109 years) at intervals of t ranging from 1 to 15 million years. Only the calculated errors in t resulting from experi mental uncertainties in the determinations of the decay con stants and relative abundance of U238 and U235 have been in cluded. An example is given for a hypothetical geologic age calculation by use of these tables.
INTRODUCTION
Although lead isotope age calculations are in general not difficult to make, both graphs and nomographs are available in the literature to simplify these computa tions. Holmes (1931, p. 208) published in "The Age of the Earth" a graphical solution of the age equation involving total lead, uranium, and thorium. Eight years later Wickman (1939, p. 6) published several nomographs that gave ages in millions of years equiva lent to the weight ratios of Pb206/U238, Pb^/Pb206 , and Pb 208/Th232. More recently, Kulp and others (1954, p. 345) have prepared nomographs of the three age ratios mentioned above as well as the ratios of Pb207/U235 in terms of numbers of atoms rather than in weight percent.
During the course of geochronological studies mr-de by the U. S. Geological Survey it was found desirable to have age equivalents for the various lead isotope ratios at smaller intervals and over a greater range of time than could be obtained from the references men tioned above. Initially, these tables were calculated for the atomic ratios of Pb206/U238, Pb 207/U235, Pb^/Pb206 ,
and Pb 208/Th232 at intervals of t of 1 million years from 1 million years to 6,000 million years. The tables in this paper are an abridgment of the original tables. The calculations were carried to 6,000 million years, an age greater than the probable age of the earth, so tH.t speculative calculations could be made. They are being published because it has been found that for certain types of analysis of isotopic age data these tables are more satisfactory than the published nomo graphs. For example, the tables offer greater accuracy and ease of manipulation than the nomographs in making repeated solutions of the age equations. Siich repeated calculations are particularly useful in evaluat ing different geologic processes which have produced discordant ages.
The general form of the age equations used to com pute the tables was developed by Kovarik (1931, p. 73), Keevil (1939, p. 195), and others. Solutions were obtained for equations of the form
The equation
N_d N,
'207
=expX£
& (expX238<
was solved by iteration. It is important to note that the ratios otNJN, and Nm/Nm in the present tables are given as ratios of number of atoms of daughter (Nd) to number of atoms of parent (Nf), and number of atoms of Pb207 (Nwi) to Pb206 (Moe) and not in terms of weight percent.
The authors wish to express their appreciation to F. W. Reilly and D. B. Rock of the Computer Branch for their aid in the operation of the computer, and also
1
SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY
to Raynor L. Duncomb, Julena S. Duncomb and G. M. Clemence, of the U. S. Naval Observatory, for their cooperation and help in preparing the tables for printing. This work is part of a program being con ducted by the U. S. Geological Survey on behalf of the Division of Research of the U. S. Atomic Energy Commission.
The half lives, decay constants, and ratio of U238/U235 used in the calculations are shown in table 1, along with those used by Wickman and by-Kulp and others. The values used in this paper were chosen for the following reasons. Fleming and others (1952, p. 642) discuss in some detail the earlier work on the determination of the half life of U235 . The weighted average of all
previous measurements is numerically tl ?- same as their value with a slightly larger probable error. The half- life data of Fleming and others was therefore chosen for these calculations. These authors have also dis cussed the past determinations of the I alf life of U238 . From their "best values" a half life of (4.51 ± 0.007) X 109 years has been calculated. More recently Kovarik and Adams (1955, p. 46) have redetermined three of their original specimens. Their newest value, (4.507± 0.009) X109 years, lies within the limits of error of the "best value" calculation of Fleming and others. In view of the small differences in half lives, as well as the differences in probable error, a value of (4.51 ± 0.01) X 109 years was therefore chosen.
TABLE 1. Physical constants used in calculation of tables
Nuclide
U238 .
U235 _ __ _ - .
Xh232
Atomic ratio IT238/!!235 _____________ _
This paper
i T= (4.51 ± 0.01) X109yX=1.5369 X10-1°y-1
i T=(7.13±0.16)X108yX = 9.72|,X10-1V1
2 T=(1.42±0.07)Xl010yX=4.88, 3 X10-»y-1
3 137.7±0.32
Kulp and others, 1954
T= (4.49 ± 0.0 l)X109yX=1.541X10-10y-1 T=(7.13±0.16)X108yX = 9.722XlO-10y- 1 T=(1.39±0.02)X1010yX= 4.987 XW-ny~ l
137.7 ±0.5
Vickman, 1939
!T=4.56X109yX=1.52X10-i°y-1 T=7.14X108yX=9.72X10-10zr1 T=1.39X10«>yX=4.99X10-"y-1
139.0±1.0
1 Fleming and others, 1952, p. 642.2 Senftle, Parley, and Lazar, 1956, p. 1629.3 Senftle, Stleff, Cuttitta, and Kuroda, 1957, p. 189.
Kovarik and Adams (1938, p. 413) have also deter mined the half life of Th232 as (1.39±.03)X1010 years. In their very thorough and excellent paper they deter mined in addition the branching ratio of Bi212 . Recently this branching ratio and the half life of thorium have been redetermined by Senftle, Farley, and Lazar (1956). Using a pulse-counting technique they obtained a branching ratio 7.4 percent higher than that obtained by Kovarik and Adams. Although the half life as determined by Kovarik and Adams does not directly depend on the branching ratio of Bi212 , the half life was determined from the basic alpha-count data. In spite of the careful alpha-counting techniques used by Kovarik and Adams, the differences in the branching ratio of Bi212 raise some questions on the earlier Th232 half-life determinations. Also, their calculations de pended on the existence of radioactive equilibrium between Th232 and Th228 based on the age of the thorite and the assumption that the daughter products were undisturbed by processes of alteration and weathering. Senftle, Farley, and Lazar, however, have shown that even for a specimen of fresh thorite chosen because it showed no signs of alteration, the Ra224 was 9.5 percent less than the equilibrium amounts; this implies a loss of its parents Th228 and Ra228 . The tendency of radio genic daughter products to migrate has been pointed
out in detail by Rosholt (1958). Hence, the value of the half life (1.42±0.07)X1010 years as determined by Senftle and others was used, even though the quoted percent of error is somewhat larger than that of Kovarik and Adams.
The determination of the atomic ratio N238/N235 has been discussed by Fleming and others (1952, p. 642). They observe that a mean value of 137.7 "falls within the limits of error of all values reported." Kulp and others (1954, p. 345) used a value of 137.7±0.5. More recently Senftle, Stieff, Cuttitta, and Kuroda (1957, p. 190) have shown an average value of 137.7 ± 0.32 for 13 uranium specimens. Thi? value with its somewhat smaller probable error has been used for these calculations.
In general, the ratios in the tables r,re given to four significant places, a value somewhat better than can be justified by present physical measurements and analytical methods. The remaining two numbers in smaller type have been included because of their usefulness in certain theoretical calculations. Corre sponding to each ratio a value of t plus or minus the error may be read from the tables or may be directly interpolated as a first approximation if the exact value of the ratio desired is not found. Tl e limits of error for t shown in the tables have been calculated by using only the limits of experimental error reported for
TABLES FOR THE CALCULATION OF LEAD ISOTOPE AGES
the determinations of the decay constants and the are treated more fully in the section "Methods of abundance ratios, and the error term has been rounded computation." to the nearest 0.1 million years. The error calculations
TABLE 2. Errors in t produced by uncertainties in the physical constants used in calculation
Age method
pb206/U238
pb207/U235 ____________________________________
Pb207/Pb206 ___ ___-_-_-_--____-_-_. _ _ _
Pb208/Th232__ ____________________________________
Errors In calculation of various ages, both in millions of years
100
±0. 22±2. 24
±57. 18 ±4. 93
500
±1. 11
±11. 22 ±63.95 ±24. 65
1,600
±3. 33 ±33. 66 ± 82. 21 ±73. 94
2,500
±5.54 ±56. 10
± 102. 38 ± 123. 24
4,500
±9. 98 ± 100. 98 ± 146. 50 ± 221. 83
6,000
± 13. 30 ± 134. 69 ± 181. 65 ± 295. 77
Table 2 lists for several different t's the limits of error in the age calculations resulting from the uncertainties in the physical constants used. This table shows that the limits of error in calculated age for the Pb206/!!238 method are less than the limits of error for the other three methods. The selection of intervals of t (table 3) was determined in part by the limits of error for the
TABLE 3. Range and interval of t
Range (years)
!X10«to 500 X106 500X106 to 1,500X10* 1,500X10* to 2,500X10* 2,500X10* to 4,500X10* 4,509X10* to 6,000X10*
Interval (years)
1X10* 2X10« 5X10*
10X10* 15X10*
might be obtained for the same value of t. Admittedly, the intervals chosen for the abridged tables are smaller that the uncertainties in the calculated ages introduced by the most precise analytical techniques currently available. However, improvements in the quantitative determination of lead, uranium, thorium, and hotopic abundance may ultimately permit the measurersent of small differences in age (1 to 2 million years) of radio active minerals from rocks of Cambrian age or younger.
METHODS OF COMPUTATION
THE Nd/Np RELATION
For the purpose of programing this work for the digital computer, the general form of the age ec uation was used,
** &_ T>___\ j 1"Tr"
J.\1i(1)
method. In spite of the larger errors inherent in the other methods, the same interval of t has been used for all four tables in order that equivalent ratios
where i=l, 2, 3 and .7=1, 2, 3.
The values of the decay constants with their limits, X, , used for these calculations are shown in tab11 ^ 4.
TABLE 4. Decay constants \i.(y~')
X
U238Ai 1 = i.5369 xiO-10 U28«X2, = 9.7216 X10-10 Th232X3. = 4.8813 X10-"
X plus error
Xi2 =1.5335 X10-10 H = 9.5082 X10-10 *32 = 4.6520 X 10-"
X minus error
*i3 =1.54o3 X10-»° X23 = 9.9447X10-'°*33 =5. 1344X10-" ^
In computing expX^f 1 the exponential series was expanded
to the uncertainties in the decay constants was simpli fied in the following graphical treatment shown in figure 1. By virtue of the geometry in figure 1,
and the recursion -. --. -= . was used to evaluate (n l)\n n\
the series. No round off was used in the evaluation and the maximum error in expX^Z can be shown to be less than 5X10"5 .
The problem of calculating the errors in the ages due
where t2 is the age for a plus error in X and £3 is the age for a minus error in X. Therefore,
and(3b)
SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY
t
FIOTJRE 1. Atomic ratio Nd/Np plotted against the age, t, showing the plus and minus tolerance curves.
Simplifying and taking logarithms,
and
(4a)
(4b)
Also it is evident from figure 1 that MN=ti t3 and NO=t2 ti. Thus, by the substitution the error in the age, MN and NO, can be simply evaluated in a con venient form,
and
N0=t ll?-
(5a)
(5b)
If new, more nearly accurate, values of the decay constants become available, it is a simple matter to obtain the corrected age from the tables. For example, suppose the half life of the Th232 is changed from 1.42± 0.07X1010 years to 1.45±0.02X1010 years. Calcu lated in this way using T instead of X, the new value of the age, </ say, will be
. , 1.45 t.1.42
Similarly, t2 ' and t3 ' will be
1.47
and
1.42
1.43 t '' 1.42
Then, if one assumes an experimental ratio of A^os/A^a of (O.OSOOaa), the corresponding value of ti (A^os/A^ table) is 1,OOOX106 years. The new half-life value would yield </, tj', and t$ ages of 1,021 X106 years, 1,035X106 years, and 1,007X106 years, respec tively. Thus, the tables can still be used even if new values of the half lives are redetermined at a later date.
RELATION
(6)
THE
The general equation,
Nm_v_ expV- 1
'206 *l( ji 1)
was used for computing the Pb207/Pb206 table. The value, ki, used for the U238/!!238 atomic ratio was 137.7 ±0.32 where fc2 and fe3 designate the aburdance ratios with the plus and minus tolerances, respectively.
TABLES FOR THE CALCULATION OF LEAD ISOTOPE AGES
As in the Nd/Np relation previously described, the calculation of limits of error in the age due to uncertain ties in the decay constants has been simplified for programing on the digital computer. By use of a similar graphical argument as shown in figure 2, it can be seen that
i 1 _ expX22 £ 2
and
R=
1) k2 (expXl2 « 2 1)
1 _ expX23 £ 3 1:-!) k3 (expXl3 * 3 -l)
(7a)
(7b)
However, unlike the previous solution, the equations (7a, b) have no direct solution for t2 and t3 and an iterative-approximation method had to be used. The left-hand sides of the equations can be evaluated. The right-hand sides are quotients of infinite series in t2 and t3 . An initial guess was made for t2 or £3, as the case may be, and a test for equality was made. Succes sive approximations were made to the t values until equality was obtained.
For the particular case where tl = t2 =t3 Q, the ratio R is indeterminate. However, by using L'Hospital's ule an approximate but quite accurate value of R can
be obtained. Hence, the limits of the ratios as- t\, t2) and <3->0, are #:=0.045936 , #2 =0.0449, ard R3 =0.0470. Thus, radiogenic lead being formed at the present time should and does have a NWI/NSM ratio between 0.045 and 0.047, a value very close to the experimentally observed value.
From the age tables it can be seen that below an age of 56X106 years, the Pb^/Pb206 method has errors that are larger than the calculated value of t. As has been mentioned, this error is due only to the uncertain ties in the physical constants used in the calculations. It is shown in figure 2 for an age t, (which is lesn than 56X106 years) that the horizontal line (a-6) between the ages representing the plus and minus tolerances does not intersect the upper curve on the positive side of the coordinates because of the flatness of the curves in this region. Also, this "flatness" and the round-off error cause oscillation of approximately 0.1 to 1.0 million years in the quoted error in t for ages lesr? than 400 million years, and small irregularities in tl ^ 5th and 6th places of the A^/A^oe ratio for the range from 0 to 50 million years.
SAMPLE AGE CALCULATION
A hypothetical uraninite gave the following chemical data: U=43.646 percent, Pb=7.532 percent, Th=5.20!
N207N,206
/?, = 0.0470
/?, = 0.0459
/?2 = 0.0449
485342 O 5£FIGURE 2. Atomic ratio Nsm/Nim plotted against the age, t, showing the plus and minus tolerance curves.
6 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY
percent. For an exact age solution in terms of numbers of atoms it is not necessary to convert these data from the chemical to physical scale of atomic weights by multiplying these values by the conversion factor 1.0002783 given by Nier (1950). This conversion factor cancels out in the lead-uranium ratio age calculations.
However, for an exact age solution, it is necessary to use the calculated physical atomic weight of the lead based on the isotopic composition of the sample being dated rather than the physical atomic weight of average common lead, 207.282. The physical atomic weight of this hypothetical radiogenic lead is obtained by multi plying the four lead atom percent abundances by the respective physical atomic weights for the individual lead isotopes. Using the isotopic atomic masses given by Sullivan (1957), 204.0368, 206.039, 207.041, and 208.041, the calculated atomic weight of the radiogenic lead in the uraninite is 206.32. The weight percent of lead corrected for this small factor is :
Failure to correct for differences in atomic weight will result in errors of approximately 0.2 to 0.5 percent in the calculated lead-uranium and lead-thorium ages depending on the atomic weight of the lead in the radioactive mineral and the physical constants used in the calculation.
Isotopic analyses, in atom percent, of lead in uraninite and asso ciated hypothetical galena
Pb204
Pb208pK207
pVj208
Lead In
Uranlnlte
0. 1957 81. 178
8. 642 9.984
Associated hypothetical
galena
1.43, 23. 30, 23. 277 51. 98!
The presence of lead originally deposited (common lead) with the uraninite and not produced by the radio active decay of the uranium or thorium in the mineral is indicated by 0.1957 percent Pb204 in the isotopic analysis of the lead extracted from the uraninite. Pb204 is the only isotope of lead not known to be pro duced by radioactive decay. The isotopic analysis of the hypothetical galena associated with the uraninite is assumed to approximate closely the isotopic com position of the nonradiogenic lead originally deposited with the uraninite. As this galena also contains Pb206 ,
Pb207, and Pb208 , it is necessary to correct the uraninite lead before the age calculations can be made.
CORRECTION FOB ORIGINAL COMMON LEAD
The correction for the original common lead may be made in the following way:
1. Using Pb204 as the "index" of the amount of original lead present, a factor proportional to the amount of Pb204 present in the uraninite (0.1957) com pared to the Pb204 in the galena (1.438) is obtained.
0.1957 1.43B
=0.13628
2. This factor, when multiplied by the percent abundances of the lead isotopes in the associated galena, will give the proportional amounts of Pb204 , Pb206 , Pb207 , and Pb208 originally present in the uraninite.
Pb204 =1.436 X0.13628 =0.1957
Pb206 =23.306 X0.13628 =3.176
Pb207=23.277 X0.13628 =3.172
Pb208 =51.981 X0.13628 =7.084
3. The isotopic analysis of the lead, in atom percent, from the uraninite is then corrected for the original lead present.
Isotopic analysis of uran-
Isotopic analysis of origi nal lead present __ ___
Radiogenic lead pro duced by U+Th _ ...
Pbiw
0. 1957
-. 1957
0.000
Pb«»
81. 178
-3. 17,
7&002
Fb«"
F. 642
-?. 172
f . 470
Pb*»
9. 984
-7.084
2. 90o
AQB METHOD
The Pb206/U238 age is obtained by first multiplying the weight percent (chemical scale) of totrl lead by the corrected percent of radiogenic Pb206 produced by the uranium and dividing by the weight perc3nt (chemical scale) of total uranium multiplied by the atom percent abundance of U238, that is 7.567 X78.00; divided by 43.6 46 X99.27s. It is then necessary to convert this weight ratio into an atomic ratio by dividing the physical atomic weight of the uranium, 2?8.103, by the physical atomic weight of the lead, 206.32; that is,
238.103206.32
= 1.154o-
As Avagadro's number would appear in both the denominator and numerator, it can be canceled out
TABLES FOR THE CALCULATION OF LEAD ISOTOPE AGES
without altering the numerical value of the ratio Nd/Np . The age calculation thus becomes
7.567X78.002 \,-i -leA _ rk I K7Q=43646><99>273 X1.154o-0.15720.
From the tables read 950 ±2.1 million years.
Pb2o7/xj2sj AGE METHOD
Similarly, the Pb207/!!236 age is obtained by multi plying the chemical weight percent of total lead by the corrected atom percent abundance of radiogenic Pb207 and dividing by the chemical weight percent of total uranium multiplied by the atom percent abundance of U235 . The conversion factor of weight to atom percent, 1.1 540, is used to change the lead-uranium ratio to an atomic ratio. The Pb207/!!235 age thus becomes
The Pb^/Th232 age thus becomes
From the tables read 950 ±2 1. 3 million years.
Pb2°VPb2M AGE METHOD
The age calculated from the Pb^/Pb206 ratio may be obtained directly from the isotopic composition of the remaining radiogenic Pb206 and Pb207 . The Pb207/Pb206 age thus becomes
NmlNtot -,
From the tables read 950 ±71.9 million years.
Pb«»/Th232 AGE METHOD
The Pb208/Th232 age is obtained by multiplying the total chemical weight percent of lead by the atom per cent abundance of remaining radiogenic Pb208 and divid ing by the total chemical weight percent of thorium times 100. This ratio is converted to an atomic ratio by using the following factor:
232.111 206.32 ~ L1250°'
From the tables read 950 ±46. 8 million years.Physical isotopic masses were calculated from data
given by Huizenga (1955) and by Sullivan (1957).
LITERATURE CITED
Fleming, E. H., Jr., Ghiorso, A., and Cunningham, B. B., 1952,The specific alpha-activities and half -lives of U284 , U23 ", andU236 : Phys. Rev., v. 88, p. 642-652.
Holmes, Arthur, 1931, Radioactivity and geological time, pt. 4of The age of the earth: Natl. Research Council Bull. 80,p. 124-459.
Huizenga, J. R., 1955, Isotopic masses A>201: Physica, v. 21,p. 410-424.
Keevil, N. B., 1939, The calculation of geological age: Am. Jour.Sci., v. 237, p. 195-214.
Kovarik, A. F., 1931, Calculating the age of minerals from radioactivity data and principles, pt. 3 of The age of the earth:Natl. Research Council Bull. 80, p. 73-123.
Kovarik, A. F. and Adams, N. I., Jr., 1938, The disintegrationconstant of thorium and the branching ratio of thorium C:Phys. Rev., v. 54, p. 413-421.
1955, Redetermination of the disintegration constant ofU238 : Phys. Rev., v. 98, p. 46.
Kulp, J. L., Bate, G. L., and Broecker, W. S., 1954, Presentstatus of the lead method of age determination: Am. Jour.Sci., v. 252, p. 345 365.
Nier, A. O., 1950, A redetermination of the relative abundancesof the isotopes of carbon, nitrogen, oxygen, argon, andpotassium: Phys. Rev., v. 77, p. 789.
Rosholt, J. N., 1958, Radioactive disequilibrium studies as anaid in understanding the natural migration of uranium andits decay products: United Nations Internat. Conf. Peaceful Uses of Atomic Energy, 2d, Geneva, 1958, Proc. v. 2,Survey of raw material resources, p. 230-236.
Senftle, F. E., Farley, T. A., and Lazar, N., 1956, Half-life ofTh282 and the branching ratio of Bi2U : Phys. Rev., v. 104,p. 1629.
Senftle, F. E., Stieff, L. R., Cuttitta, Frank, and Kuroda, P. K., 1957, Comparison of the isotopic abundance of U236 and U238
and the radium activity ratios in Colorado Plateau uraniumores: Geochim. et Cosmochim. Acta, v. 11, p. 189-193.
Sullivan, W. H., 1957, Trilinear chart of nuclides: U. S. Government Printing Office, Washington 25, D. C.
Wickman, F. E., 1939, Some graphs on the calculation o* geological age: Sveriges Geol. Undersokning Arsbok, v. 33,no. 7, p. 1-8.
TABLES FOR THE CALCULATION OF LEAD ISOTOPE AGES[Numbers above tables are the ages, in millions of years, that are given on each page]
TABLES FOR THE CALCULATION OF LEAD ISOTOPE AGES
1-50
11
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0.0001530.0003070.0004610.0006i40.0007680.0009220,0010750.0012290.0013830.0015370.0016910.0018450.0019980.0021530% 0023o70.0024620.0026150.0027690.0029240.0030770.0032320.0033860.0035400.0036940.0038490.00400 20.0041570.0043120.0044660,0046200.0047750.0049300.0050830,0052380.0053930.0055470.0057020.0058570.0060io0.0061650.0063200.0064750.0066290.0067840.0069390.0070930.0072490.0074o40.0075580.007713
AgeNumber
of years
123456789
101112131415161718192021222324252627282930
3132333435363738394041424344454647484950
Error+
0.00,00,00.00.00,00.00,00.00.00,00.00,00,00,00.00.00.00,00.00,0o.o0.10.10.10,10.10.10.10.1
0.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10,10.1
N 207/N 235
Ratio
0.0009720.0019450.0029200.0038950.0048710.0058490.0068280.0078070.0087870.0097680.0107500.0117330.0127170.0137020.0146880.0156740.0166&20.0176510.0186420.0196330.0206240.0216160.0226090.0236050.0246oo0.0255970.0265950.0275930.0285920.0295930.0305940.0315970.0326oo0.0336050.0346o90.0356i60.0366220.0376320.0386410.0396510.0406620.0416740.0426870.0437020.0447160.0457320.0467490.0477670.0487870.0498o7
AgeNumber
of years
123456789
101112131415161718192021222324252627282930
3132333435363738394041424344454647484950
Error ±
0.00.00.10.10.10.10.20.20.20.20.20.30.30.30.30.40.40.40.40,40.50.50.50,50.60.60.60.60.70.70.70.70.70.80.8
0.80,80.90.90.90.90.91.01.01,01,01.11.1XIXI
"2077*206
Ratio
0.0459550.0459740.0459930.0460i20,0460300.0460490.0460680.0460870.0461060.046124
0.0461430.0461620.0461810.0462oo0.0462i90.0462370.0462560.0462750.0462940.0463130.0463370.0463610.0463800.0463990.0464i70.0464360.0464550.0464740.0464930.0465i30.0465320.0465510.0465700.0465890.0466070.0466260.0466450.0466640.0466820.0467oi0.0467200.0467390.0467580.0467770.0467960.0468i50.0468340.0468530.0468720.046891
AgeNumber
of years
123456789
101112131415161718192021222324252627282930
3132333435363738394041424344454647484950
Error +
55855.255.255.255.155.155.155.155.155.156.656,757,756.756.655.656.556.655.856.9
56.356.356.456.656,156.956.456.056.356.556.256.056.656.456.156.456,256.156.856.556.456.356,656.556.356.656.256,156,556.5
N2 08/^2 3 2
Ratio
0.0000480.0000970.0001460.0001950.0002440.0002920.0003410.000390010004390.0004880,0005360,0005850.0006340.0006830.0007320.0007810.0008290,0008780.0009270.0009760.0010250.0010730.0011220.0011710,0012200.0012690.0013170.0013660.0014160.0014650.0015140.0015630.00l6ii0.0016600.0017090.0017580.001807O.OOlSss0.0019040.0019530.0020o30.00205 20.0021oo0.0021490.0021980.0022470.0022960.0023450.0023930.002442
AgeNumber
of years
123456789
101112131415161718192021222324252627282930
3132333435363738394041424344454647484950
Error +
o.o0,10.10.20,2
0.30.30.40.40.50.50.60.60.70.70.80.80.90.9xoxoXIXIX2X2X31,3X4X4X5X5X6X6X7X7X8X8X9X92.02.02.12,12.22.22.32,32.42,42.5
12 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY
51-100
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0.0078680.0080220.0081780.0083330.0084880.0086430.0087980.0089530.0091o80.0092630.0094180.0095730,0097280.0098840,010038
0.0101940.0103500.0105050.0106600.0108150.0109710.0111260.0112810.0114370.011592
0.0117480.0119040.0120580.0l22i40.0123700.0125260.0126810.0128370.0129930.013148
0.0133040.0134600.0136150.0137710.0139270.0140820.0142380.0143950.0145510.0147060.0148620,0l50i90.0151740.0153300.015487
AgeNumber
of years
51525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899
100
Error ±
0.10.10.10.10.10.10.10.10.10.1
0.10.10.10.10.10.10.10.20,20,20.20.20.20.20.20.20.20.20.20.20.20,20.20.20,20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.2
^207/^235
Ratio
0.0508290,0518500.0528730.0538970.0549220.0559470.0569760.0580o30.0590320.0600630.0610930.0621250.0631590.0641930.0652280.0662640.0673oi0.0683390.0693780.0704180.0714590.0725oi0.0735450.0745890.0756340.0766810.0777270.0787750.0798250.0808750.0819260.0829790.0840320.0850860.0861420.0871980.0882550.0893i50.0903740.0914340.0924960.0935580.0946210.0956870.0967530.0978190.0988870.0999560.1010250,102096
AgeNumber
of years
51525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899
100
Error+
1112121212
13131313131.41414141515151515161616161717171.71818181818191919192,02.02.02.02.02.12.12.12.12.22.22.22.22.2
N 207/N206
Ratio
0.0469io0,0469290,0469480.0469670,0469860.0470050.0470240.0470430.0470620.0470810.0471oo0,0471i90,0471380.0471570.0471760,0471960.0472160.0472430.0472640,0472840.0473oi0.0473220.0473440.0473610.0473830.0474oi0.0474180.0474430,0474620,0474790.0474980.0475200.0475380.0475570.0475790.0475980.0476160.0476400,0476580,0476770.0477oo0.0477190.0477350,0477550.0477780.0477980.0478150.0478380.0478570,047874
AgeNumber
of years
51525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899
100
Error
±
56.656,756.456.456.556.456.556.556.556.656.656,756,856.756,956.856.656.756.856.956.756.856.956.956.956.956.857.057.056.956.957.057.056.957.157.056.957,157.057,157.257.257.157.157.357.357.257.357.357.2
^208/^232
Ratio
0.0024920.0025410.0025900.0026380.0026870.0027360.0027850.0028350.0028830,0029320,0029ai0.0030300.0030790.0031280.0031770.0032260.0032750,0033240.0033730.0034210.0034710.0035200.0035690.0036180.0036670.0037150.0037650.0038i40.0038630.0039i20.0039600.0040io0.0040590.0041oa0.0041570.0042050.0042550.0043o40.0043530.0044o20.0044510, 0045oo0,0045490.0045980.0046470.0046960.0047450.0047940.0048430.004892
AgeNurrber
of years
51525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899
100
Error +
2.52.62.62.72.72,82.82.92.93.03.03.13.13.23,23.33,33,43.43.53.53,53.63.63,73.73.83.83.93.94.04.04.14,14.24.24,34,34.44,44.54.54,64.64.74.74.84.84.94,9
TABLES FOR THE CALCULATION OF LEAD ISOTOPE AGES
101-150
13
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0,0156420,0157980,0159550.0161io0.0162670.0164230,0165800.0167350,0168920.0170480.0172o40.0173610.0175i70.0176730.0178300.0179860.0181420.0182990.0184570.0186i40.0187&90.0189260.0190830.0192390.0193960.0195530.0197090.0198&60.0200230.0201790.0203360.0204930.0206500.0208o70.0209640.0211210.0212770.0214340,0215920.0217480.0219o50.0220630.0222i90.0223760.0225340.0226910.0228480.0230ns0.0231630.023320
AgeNumber
of years
101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150
Error +
0.20.20.20,20.20,20.20.20,20.20.20,20.30.30.30,30.30.30,30.30.30,30,30.30.30.30.30,30.30.30,30,30,30.30.30.30.30,30,30.30,30.30.30.30,30,30.30.30.30.3
"207/^235
Ratio
0.1031680.1042420.1053160.1063910.1074&60.1085430,1096220.1107010,1117820.1128620.1139450.1150280.1161i30.1171990.1182850.1193720.1204&10.1215510.1226430.1237340.1248270.1259220.1270i601281ii0.1292io0.1303090.1314070.1325080.1336090.1347ii0.1358150.1369210.1380260.1391330,1402410.1413sn0.1424&00.1435720.1446840,1457970.1469ii0.1480270.1491430.1502&10.1513800.1524990.1536210.1547420.1558&50.156989
AgeNumber
of years
101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150
Error +
2.32,32,32.32.42.42.42.42.42.52.52.52.52.62.62,62.62.62.72,72.72.72.82.82.82.82.82.92.92.92.93.03.03.03.03.13.13.13.13.13.23.23.23.23.33.33,33.33.33.4
^207/^206
Ratio
0.0478980.0479i80.0479360.0479590.0479760.0479970, 0480is0.0480380.0480570,0480770.0480980.0481160.0481370.0481590.0481770.0481980,0482200.0482380.0482550.0482740.0482980.0483170,0483360.0483580.0483780.0483970.0484i90.0484390.0484580.0484800.0485oo0,0485210.0485400.0485&00.0485810.0486oi0,0486230.0486440.0486&20.0486850.0487050,0487230.0487460.0487&70.0487860.0488060.0488270.0488480.0488&70.048888
AgeNumber
of years
101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150
Error +
57.457.557.357.557.357.457.357.557.457,457.557.457.557.757.657.657.757.657.457.457.657.557.557.657.657.657.757.757.657.757.857.857.757.857.857.857.957,957.858.057,957.858.058,158.058.058.058.158.158.0
N208/
Ratio
0,0049420,0049900.0050,390,0050880.0051380.0051870.0052360.0052840,0053340,0053830,0054320,0054810.0055300.0055790.0056280.0056780.0057270.0057750,0058240.0058740.0059230.0059720.00602200060700.0061i90,0061680.0062i80.0062&70,0063i50.0063650.0064i40.0064&30.0065i30.0065610.0066io0.0066&00.0067090.0067580.0068080.0068560,0069o50.0069550.0070040.0070530.0071020.0071510.0072oo0.0072500.0072990.007348
//V232
AgeNumber
of years
101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150
Error +
5.05,05.15,15,25.25.35,35.45,45.5$55,65.65.75.75.85.85.95,96,06.06.16,16.26.26.36,36.46.46.56.56.66.66,76.76.86.Q6,96.97.07.07.07.17.17,27.27.37.37,4
485342 O 59-
14 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY
151-200
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0.0234780.0236350,0237920.0239500, 0241070,0242640.0244220.0245790.0247360.024894
0.0250520.0252090.0253660,0255240.0256820.0258390.0259970.0261550.0263i20.026470
0.0266290.0267860.0269440.0271020.0272600.0274i70.0275760.0277340.0278910.028049
0.0282070.0283650.0285230.0286810.028839
0.0289970.0291550.0293150.0294720.029631
0.0297890.0299470.0301Q50.0302640.0304220.0305800.0307390.0308960.0310550.0312i4
AgeNumber
of years
151152153154155
156157158159160
161162163164165
166167168169170
171172173174175176177178179180
181182183184185
186187188189190
191192193194195
196197198199200
Error ±
0.30.30.30.30.3
0.30.30.40.40.4
0,40.40.40.40.40.40.40.40.40.4
0.40.40.40.40.40.40.40.40.40.4
0.40.40.40.40.4
0.40.40,40.40.4
0.40.40.40.40.40.40.40.40.40.4
*207/"235
Ratio
0,1581160.1592410.1603690,1614970162627
0.1637580.1648900.1660230.1671,570.1682930.1694290.1705660.1717060.1728440.173985
0.1751270.1762&90.1774i40.1785600.1797070.1808530.1820o20.1831510.1843020.1854530.1866070.1877620.1889i70.1900730.191231
0.1923870.1935490.1947io0.1958710.197034
0.1981990.1993640.2005310.2016980.202867
0.2040360.2052070.2063790.2075540.2087290.2099040.2110810.2122590.2134380.2146i7
AeeNumber
of years
151152153154155
156157158159160
161162163164165
166167168169170
171172173174175176177178179180
181182183184185
186187188189190
191192193194195196197198199200
Error ±
3.43.43.43.53.5
3.53.53.53.63.6
3.63.63.73.73.7
3.73.73.83.83.8
3.83.93.93.93.93.94.04.04.04.0
4.14.14.14.14.2
4.24.24.24.24.3
4.34,34.34.44.44.44.44.44.54.5
N 207/
Ratio
0.0489080.0489280.0489500.0489690.0489900.0490i20.0490310.0490530.0490750.049095
0.0491i40,0491360.0491580.0491780.0491980.0492200.0492400.0492600.0492820.049303
0.0493210.0493440.0493640.0493840,0494050.0494280.0494470,0494680,0494900.0495H
0.0495310.0495530.0495740.0495950.0496160.0496380.0496590.0496770.0497oo0.049720
0.0497410.0497620.0497840.0498040.0498260.0498480,0498680.0498910.0499i20.049932
'*206
AgeNumber
of years
151152153154155
156157158159160
161162163164165
166167168169170
171172173174175
176177178179180181182183184185186187188189190
191192193194195
196197198199200
Error
±
58.058.058.158,058.1
58.258.158.258.358.2
58.258.358.458.358.3
58.458.358.358.458.5
58.358.458.458.458.458,558.458.458.658.658.5sa658.653,658.658.758.758.658.758.7
58.758.758.858.758.858.858.858,958.958.8
^208/^232
Ratio
0.0073970.0074460.0074950.0075450.007594
0.0076420,0076920.0077410.0077910.007840
0.0078880.0079380.0079870.0080370.008086
0.0081350.0081840.0082330.0082830.0083320.0083810.0084300,0084790.0085290.0085780.0086270.0086760.0087250.0087750.008824
0.0088740.0089230.0089710.0090210,0090700.0091200.-0091690.0092i80.0092670.0093i7
0.0093660.0094i50,0094640,0095i30,0095630.0096i20.0096620.0097ii0.0097600, 009809
AgeNumber
of years
15115?15315415515<>157153159160
16116?163164165166167168169170
1711721731741751761771781791PO
in1P21831P41P5
1M1P71PB1P9190
191192193194195
196197198199200
Error +
7.47.57,57.67,67,77.77.87.87.97.98.08.08.18.1
8.28.28.38.38.4
8.48.58.58.68.6a78.78.88.88.9
8.99.09.09.19.19.29.29.39.39,4
9.49.59.59.69.69.79.79.89.89.9
TABLES FOR THE CALCULATION OF LEAD ISOTOPE AGES
201-250
15
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0.0313730.0315300,0316900.0318490.0320o70.0321660.0323250.0324820.0326410,0328oo0.0329580.0331i70.0332760.0334350.0335940.0337540.0339i30.0340710.0342300,0343890.0345470.0347o70.0348&60.0350240.0351830.0353430.0355030.0356&10,0358210.0359800.0361390.0362980.0364580.0366i60.0367760.0369350.0370950.0372540.0374i40.0375740.0377320.0378920.03805 20.0382ii0.0383700.0385300.0386900.0388500.0390io0.039169
AgeNumber
of years
201202203204205206207208209210
211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250
Error ±
0.40.40.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50,50.50.50,50.50.50.50.50,50.50.60.6
^207/^235
Ratio
0.2158oo0.2169820.2181&60.2193500.2205360.2217220.2229i30.2241oi0.2252910.2264840.2276760.2288700.2300660.2312&30,2324600.2336&00.2348580.2360600.2372&20.2384&60.2396&90.2408750.2420830.2432910.2445oo0.2457H0.2469220.2481340.2493480.2505640.2517790.2529980.2542i60.2554360.2566580.2578790.2591030.2603280.2615540.2627800.2640o80.2652380.2664&90.2677oi0.2689340.2701680.2714030.2726390.2738780.275116
AeeNumber
of years
201202203204205206207208209210
211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250
Error +
4.54.54.64.64.64,64.64.74.74.74.74,84.84.84.84.84,94.94.94.95.05.05.05.05,05.15.15.15.15.25.25,25.25.35.35.35.35.35.45.45.45,45,55.55.55.55.55,65,65.6
"207/^206
Ratio
0.0499520.0499760.0499950.0500i50.050038O.OSOOss0.0500790.0501030.0501240.0501450.0501670.0501880.0502090.0502300.0502510.0502710.0502920.0503150.0503370,0503580.0503810.0504oi0.0504220.0504450.0504670.0504870.0505080.0505310.0505510.0505730.0505950.0506170.0506370.0506610.0506820.0507040.0507250.0507470.0507680.0507890.0508120.0508330.0508550.0508770.0509oo0,0509210.0509420.0509630.050985O.OSlOos
AgeNumber
of years
201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250
Error +
58.859,058.9sas59,058.958.959,159.159.059,159,159.159.159.159.059.059.259.259.259,359.259,259.359.359.259.359.459,359.359,459,459.459.559.559,559.559,559.559.559,659.559.659.659,759.759,659,659,659.7
N208/
Ratio
0.0098590.0099080.0099580.0100060.010056
0.0101050.0101550,0102040.0102530,0103020.0103520.0104010.0104510.0105oo0.0105490,0105980.0106480,0106970,0107470.0107950,0108450.0108940.0109440.0109930.011043
0.0110910.0111410.0111900.0112400.0112900.0113380.0113880.0114370,0114870.011536
0.0115850.0116340.0116840.0117340.011783
0.0118330.0118810.0119310,0119800.0120300.0120800.0121280.0121780.0122270.012277
^232
AgeNumber
of years
201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250
Error +
9.910.010.010,110.110.210.210,310,310.410.410,510,510.510.610.610.710.710.810.810.910.911,01101111L111.211211.311311.411411.511511611611711711811.811911912.012.012.112112.212.212312.3
SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY
251-300
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
"206/^238
Ratio
0.0393290.0394890.0396480.0398070.0399680.0401290.0402880,0404480.0406080.0407670^0409270,0410870.0412460.0414080.0415&80.0417280.0418870.0420480.0422080.0423&70,0425290.0426890.0428490.0430090.0431700.0433290.0434900.0436500.0438i20.0439710.0441320.0442930.0444520.0446i30.0447750.0449350.0450950.0452560.0454i60.0455770.0457380.0459oo0.0460590.0462200.0463810.0465410.0467020.0468&30.0470240.047185
AgeNumber
of years
251252253254255256257258259260
261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300
Error±
0.60.60.60.60.60,60.60.60.60.60.60.60.60.60.60.60,60.60.60.60.60.60.60.60.60.60.60.60.60.60.60.60.60.60.60.60.60.60.60,60.60.60.60.70.70.70.70.70.70.7
N 207/N235
Ratio
0.2763570.2775990.2788410.2800840.2813300.2825750.2838250.2850720.2863220.2875740.2888250.2900780.2913350,2925900.293847
0,29510602963650.2976250.2988890.300152
0.3014i60.3026810.3039480.3052160.3064860,3077570.3090300.3103020.3115770.3128520.3141280.3154070.3166870.3179680,3192490.3205320.3218i70.3231020.3243900.3256780.3269&70.3282580.3295490.3308440.3321380.3334330.3347290.33602703373270.338627
AgeNumber
of years
251252253254255256257258259260
261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290
291292293294295296297298299300
Error ±
5.65.75.75.75.75.75.85.85.85.85.95.95.95.95.96.06,06.06,06.16.16.16.16.16.26,26.26.26.36.36.36.36.46.46.46.46,4656,56,56.56.66.66.66.66.66.76.76.76.7
"207/N206
Ratio
0.0510290.0510510.0510740,0510960.0511i70.0511370.0511610.0511820.0512040.0512270.0512490.0512710.0512950.0513i40.0513360.0513580.0513820.0514030.0514250.0514490.0514690.0514910.0515i30.0515360.0515570.0515810.0516030.0516250.0516460,0516700.0516910.0517i30,0517370.0517590.0517790.0518o20,0518250.0518470.0518710.0518920.0519i40.0519360.0519600.0519820.052 Oo 40.0520280.05205 o0.0520720.0520950.0521i7
AgeNumber
of years
251252253254255256257258259260
261262263264265
266267268269270
271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300
Error+
59.759,759.859,859.759.759.859.859.859.859.959.960.059.959.959,960.060.060.060,160.060,060.060.160% 060.160,260.260.160.260,160.260.360.360.260.260.360.360.460.3
60.360.360,460.460.4
60.560.560.560.560,5
^208/^232
Ratio
0.0123270.0123750.0124250,0124740.0125240.0125740.0126230.0126720.0127210.0127710.0128210.0128700,0129i90.0129&90.0130i8
0.0130&80.0131170.0131660.0132i60.0132&50.0133150.0133650.0134i40.0134630.0135130.0135620.0136120.0136620.0137io0.0137&00.0138io0.0138590.0139090.0139580.0140070,0140570,0141070.0141560.0142060.0142550,0143040,0143540.0144040.0144530,014502
0.0145520,0146o20.0146510, Ol47oi0.014751
AgeNuml °r
of years
251252253254255256257258259260261262263264265
266267268269270
2712722732742752762772782792802£12£<l2£32£42£52£62872£82 £02<50
2912922S32<542952<562972982co3CO
Error +
12.412.412.512.512.612,612.712,712.812.812.912.913.013.013.1
13.113.213,213.313,313.413.413.513.513.613.613-713,713.813.813.913,914.014.014.0
14.114.114.214.214.314.314.414.414.514.5
14.614,614-714.714.8
TABLES FOR THE CALCULATION OF LEAD ISOTOPE AGES
301-350
17
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
N 206/N 238
Ratio
0.0473470.0475070.0476680.0478290.047990
0.0481510.0483i30.0484740.0486340.048796
0.0489580.0491i80.0492800.0494410.0496oi
0.0497640.0499250.0500860.0502470.0504o9
0.0505700.0507320.0508940.0510550.0512i6
0.0513780.0515400.0517oi0.0518630.052025
0.0521850.0523480.0525io0.0526720.052833
0.0529950.0531580.0533190.0534810.053643
0.0538040.0539670.0541290.0542900.054452
0.0546i50.0547780.0549390.0551oi0.0552&3
AgeNumber
of years
301302303304305
306307308309310
311312313314315
316317318319320
321322323324325
326327328329330
331332333334335
336337338339340
341342343344345
346347348349350
Error +
0.70.70.70,70.7
0.70.70.70.70,7
0.70.70.70.70.7
0.70.70.70.70.7
0.70.70,70.70.7
0.70.70.70.70.7
0.70.70.70.70.7
0.70.70.70.80.8
0.80.80.80.80.8
0.80.80.80.80.8
"2077*235
Ratio
0.3399300.3412340.3425370.3438430.345151
0.3464590.3477690.3490800.3503930.351705
0.3530220.3543360.3556540.3569730.358293
0.3596i30.3609350.3622590.3635840.3649ii
0.3662380.3675680.3688980.3702280.371561
0.3728960.3742310.3755670.3769050.378244
0.3795840.3809280.3822700.3836150.384959
0.3863060.3876540,3890040.3903560.391708
0.3930&20.3944i60.3957730,3971310.398489
0.3998490.4012ii0.4025740.4039390.405303
AgeNumber
of years
301302303304305
306307308309310
311312313314315
316317318319320
321322323324325
326327328329330
331332333334335
336337338339340
341342343344345
346347348349350
Error +
6.86.86.86.86.86.96.96.96.97,0
7.07.07.07.07.1
7.17,17.17.27,2
7.27.27.27.37.3
7.37.37.47.47.4
7.47.57.57.57.5
7.57.67.67.67.6
7.77.77.77.77.7
7.87.87.87.87.9
N 207/
Ratio
0.0521390.0521620.0521850.0522070.052230
0.0522530.0522740.0522970.0523210.052343
0.0523&50.0523890.0524H0.0524340.052458
0.0524790.0525020.0525250.0525480.052570
0.0525940.0526i60.0526380.0526610.052685
0.0527080.0527300.0527530.0527760.052799
0.0528230.0528450.0528680.0528910.0529i4
0.0529370.0529590.0529830.0530o60.053029
0.0530530.0530750.0530980.0531220.053145
0.0531670.0531900.0532i40.0532380.053261
/N206
AgeNumber
of years
301302303304305
306307308309310
311312313314315
316317318319320
321322323324325
326327328329330
331332333334335
336337338339340
341342343344345
346347348349350
Error +
60.560.560.660.660.6
60.660,660.660.760.7
60.760.760.760,860.8
60.860.860.860.860.8
60.960.960.960.96X0
61.061.061.061.061.0
61.161.161.161,161.1
61.161161261.2612
61.261.261.261.261.3
61.36X261.36X36X3
N208/
Ratio
0.0147990.0148490.0148990.0149490.014998
0.0150470.0150970.0151470.0151960.015246
0.0152950.0153440.0153940,0154440.015494
0.0155430.0155920.0156420.0156920.015741
0.0157910.0158400.0158900.0159400.015989
0.0160390.0160880.0161380.0161870.016237
0.0162870.0163370.0163860.0164350.016485
0.0165350.0165850.0166340.0166830.016733
0.0167830.0168330.0168820.0169310.016981
0.0170310.0170810.0171310.0171800.017229
^232
A^eNumber ~
, Error of +
years
301 14.8302 14.9303 14.9304 15.0305 15.0
306 15.1307 15.1308 15.2309 15.2310 15.3
311 15.3312 15.4313 15.4314 15.5315 15.5
316 15.6317 15.6318 15.7319 15.7320 15.8
321 15.8322 15.9323 15.9324 16,0325 16.0
326 16.1327 16.1328 16.2329 16.2330 16.3
331 16.3332 16.4333 16.4334 16.5335 16.5
336 16.6337 16.6338 16.7339 16.7340 16.8
341 16.8342 16.9343 16.9344 17.0345 17.0
346 17.1347 17.1348 17.2349 17.2350 17.3
18 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY
351-400
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
N 206/N 238
Ratio
0.0554260.0555880.0557500.0559i20.0560750.0562370.0563990.0565610.0567240.0568870.0570490.0572ii0.0573740.0575360.0576990.0578620.0580230.0581870.0583500.0585110.0586740.0588380.0590oi0.0591620.0593250.0594890.0596510.0598140,0599770,0601400.0603030.0604660.0606280.0607920,0609550.0611180,0612810.0614440.0616080.0617700.0619340,0620970.0622600,0624230.0625870.0627500.0629130.0630770.0632410.063403
AgeNumber
of years
351352353354355356357358359360361362363364365366367368369370371372373374375376377378379380381382383384385386387388389390391392393394395396397398399400
Error±
0.80.80.80.80.80.80.80.80.80.80.80.80.80,80.80.80.80.80.80.80.80.80.80.80.80.80.80,80.80.80.80,80.80,90.90.90.90.90.90.90.90.90.90.90.90.90.90.90.90.9
"207
Ratio
0.4066710.4080400.4094080.4107800.4121510.4135240.4149oo0.4162760.4176550.4190320.4204i30.4217940.4231780.4245620.4259470.4273330.4287220.4301io0.4315010.4328950.4342890.4356830.4370800.4384770.4398760.4412770.4426800.4440820,4454860,4468920.4483010.4497080.4511i90.4525300.4539430.4553560.4567710.4581900.4596090.4610280.4624490.4638700.4652940.4667180.4681470.4695750.4710040.4724350.4738660.4753oo
/"235
AeNumber
of years
351352353354355356357358359360361362363364365366367368369370371372373374375376377378379380381382383384385386387388389390391392393394395396397398399400
e
Error±
7.97.97.97.98.08.08.08.08.18.18.18.18.18.28,28.28.28,38,38.38,38.38.48.48.48,48.58.5as8.58.58.68.68.68.68.78.78.78,78.88.88.88.88.88.98.98.9a99.09.0
N 2Q7/N 206
Ratio
0.0532830.0533070.0533300.0533540.0533760.0534oo0.0534240.0534470.0534700.0534930.0535170.0535410.0535640.0535870.0536io0.0536330.0536580.0536800.0537040.0537290,0537520.0537740.0537980.0538230,0538460.0538690.0538930.0539i70.0539400.0539640.0539870.0540ii0.0540360.0540580.0540820.0541060.0541300.0541540.0541770.0542o20.0542250.0542480.0542730.0542970.0543200.0543440.0543680.0543920.0544150.054440
AgeNumber
of years
351352353354355356357358359360361362363364365366367368369370371372373374375376377378379380381382383384385386387388389390391392393394395396397398399400
Error +
6X46X46X46X46X46X461,56X56X56X56X66X661.66X66X66X66X76X66X66X76X76X66X76X86X86X86X86X96X86X86X96X96X96X96X962.062.062.062.062,062.062.062.162.162.162.162.262.262.262.2
N208/N2 3 2
Ratio
0,0172790.0173290.0173790,0174280.0174780.0175270.0175770.0176270.0176770.0177260.0177760.0178260.0178750.0179250.0179740.0180240.0180740,0181240.0181740.0182230.0182720.0183220.0183730.0184230,0184730.0185220.0185720.0186220.0186720.0187220.0187700.0188200.0188700,0189200.0189700.0190i90.0190690.0191190.0191690.0192190.0192690.0193180,0193670.0194170.0194670.0195170.0195660.0196160.0196&60,019716
AgeNumber
of years
35135?35335435535635735835936036136?3633643653663673683693703713723733743753763773783793PO3P13P?3P33P4385386387388389390391392393394395396397398399400
Error +
17.317.417.417.517.517.517.617,617.717.717.817.817.917,918.018.018.118.118.218,218,318,318,418.418,518.518.618,618,7181718,8ias18,918.919.019.019,119.119,219,219,319.319,419,419.519,519.619.619,719.7
TABLES FOR THE CALCULATION OF LEAD ISOTOPE AGES
401-450
19
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0.0635680.0637310.0638940.0640570,064222
0.0643840.0645480.0647i30.0648750.065039
0.0652040.0653&70.0655300.0656940.065859
0.0660210.0661850.0663500.0665i30.066677
0.0668420.0670o50.0671&90.0673340,067498
0.0676&10.0678260.0679900.0681530.068318
0,0684820.0686460.0688ii0.0689750.069138
0.0693040.0694&80.0696320.0697970.0699&1
0.0701250.0702900.0704540.0706i90.070783
0.0709480.0711i30.0712770.0714410.071607
Age
Number of
years
401402403404405
406407408409410
411412413414415
416417418419420
421422423424425
426427428429430
431432433434435
436437438439440
441442443444445
446447448449450
Error +
0.90.90.90.90.9
0.90.90.90.90.9
0.90.90.90,90.9
0.90.90.90.90.9
0.90.90.90.90.9
0.90.90.9101.0
1010101.010
101.01.01.01,0
1.0101.01.01.0
1.0101,01.0XO
^207/^235
Ratio
0,4767370.4781710.4796080.4810490.482489
0.4839300.4853740.4868200.4882650.489712
0.4911600.4926io0.4940&30.4955160.496971
0.4984270.4998850.5013440,5028040.5042&7
0.5057290.5071920.5086530.5101260.511595
0.5130650.5145370,5160o90,5174850.518960
0,5204370.5219i70.5233980,5248780.5263&1
0.5278450.5293330.5308210.5323090.5338oo
0.5352910.53678405382780.5397740.541275
0.5427730.5442730.5457740.5472770.548782
Age
Number of
years
401402403404405
406407408409410
411412413414415
416417418419420
421422423424425
426427428429430
431432433434435
436437438439440
441442443444445
446447448449450
Error+
9.09.09.09.19.1
9.19.19.29.29.2
9.29.29.39.39.3
9.39.49.49.49.4
9.49.59.59.59,5
9.69.69.69.69.6
9.79.79.79.79.8
9.89.89.89.99.9
9.99.99.9
10.010.0
10010.010.110.110.1
W 207/
Ratio
0.0544630.0544870.0545120.0545360,054559
0.0545840.0546080.0546310,0546560.054680
0.0547030.0547280.0547530.0547760.0548oo
0.0548250.0548490.0548730,0548980.054922
0.0549450.0549700.0549940.0550i80.055042
0.0550&80.0550910.0551160.0551410.0551&5
0.0551890.0552i40.0552380.0552&20.055288
0.0553110.0553360.0553610.0553850.0554io
0.0554340.0554590.0554830.0555080.055533
0,0555570.0555810.0556070.0556320.055655
'W 206
Age
Number of
years
401402403404405
406407408409410
411412413414415
416417418419420
421422423424425
426427428429430
431432433434435
436437438439440
441442443444445
446447448449450
Error +
62.262.262.362.362.3
62.362.462.362.462.4
62.362.462.562.462.5
62.562.562.562.662.6
62.562.662.662.662.6
62.762.762.762.762.7
62.762,862.862,862,9
62.862.862.962.962.9
62.962,962.963.063.0
63.063.063.163.163.0
N208/N232
Ratio
0,0197660,0198150.0198&50.0l99i50.0199&5
0, 0200i50.0200650.0201i40.0201&40,0202i4
0,0202640.0203140.0203&30.0204i30.0204&3
0.0205130.0205&30, 0206120.0206&20.0207i2
0.0207&20.0208i20.0208&20.0209110.020961
0.0210ii0.0210&10.0211110.0211600.0212io
0.0212&00,0213io0.0213&00, 0214io0.021459
0,0215o90,0215590.0216090.0216590.021708
0.0217580.0218080.0218580, 0219o80.021957
0.0220070.0220580, 0221080.0221580.0222o8
Ag-
Number of
years
401402403404405
406407408409410
411412413414415
416417418419420
421422423424425
426427428429430
431432433434435
436437438439440
441442443444445
446447448449450
Error +
19.819.819.919.920.0
20.020,120,120,220.2
20L320.320.420.420.5
20,520.620.620,720.7
20,820.820.920.921.0
21.021.021,121.121.2
21.221.321.321.421.4
21.521.521.621.62X7
21.721,82X821.92X9
22.022.022,122.122.2
20 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY
451-500
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0.0717710.0719350.0721oi0.0722660.072430
0.0725950.0727&10.0729260,0730910.073256
0.0734200.0735850.0737510,0739i50,0740800.0742460.0744H0.0745760.0747410.0749060.0750720,0752370.0754030.0755&70.0757320.0758980.0760&30.0762290.0763940.076560
0,0767250,0768900.0770570.0772210.077388
0.0775530.0777180.0778840.0780500.078215
0.0783810.0785470.0787130.0788780.0790440.0792io0,0793760.0795420.0797080.079873
AgeNumber
of years
451452453454455
456457458459460
461462463464465466467468469470
471472473474475
476477478479480
481482483484485
486487488489490
491492493494495496497498499500
Error±
1.01.01.01.01.0
1.01.01.01.01.0
1.01.01.01.01.0
1.01.01.01.01.01.01.01.01.1u1.11.11.1u1.11.11.11.11.11.11.11.1u1.1uu1.11.1u1.11.1u1.11.11.1
^207/^235
Ratio
0.5502890.5517970.5533070.5548i80.5563300.5578430.5593&00.5608750.5623920.5639i3
0.5654330.5669570.5684810.5700070.5715330.5730600.5745920.5761230.5776560.5791910.5807270.5822640.5838030.5853430.586885
0.5884290.5899740.5915200.5930&90,5946i70.5961680.5977220.5992760.6008320.602389
0.6039470.6055070.6070690.6086320.610197
0.6117610.6133300.6148980.6164&90.618043
0.6196i70.6211910.6227670.6243460.625927
AeeNumber
of years
451452453454455
456457458459460
461462463464465
466467468469470
471472473474475
476477478479480
481482483484485
486487488489490
491492493494495496497498499500
Error±
10.110.110.210.210.2
10.210.310.310.310,3
10.310,410.410.410.4
10.510.510.510.510,510.610.610.610.610.710.710.710J10.710.8
10.810.810.810.910.9
10.910.911.011.011.0HO11.011.1HI11.111.111.211.21X2U2
W 207/W206
Ratio
0.0556810.0557060.0557300.0557540.055780
0,0558040.0558280.0558530.0558780.055902
0.0559280.0559530.0559770.0560030.056028
0.0560520.0560770.0561020.0561270.0561520.0561770.0562020.0562260.0562520.056278
0.0563020.0563280.0563520.0563780.056402
0.0564280.0564540.0564780.0565040.056528
0.0565540.0565800.0566050.0566300.056656
0.0566800.0567060.0567310.0567570.0567820.0568070.0568330.0568580.0568830.0569io
AgeNumber
of years
451452453454455
456457458459460
461462463464465
466467468469470
471472473474475476477478479480
481482483484485
486487488489490
491492493494495496497498499500
Error +
63.163.163.163.163.2
63.263.163,263.263.2
63.263.363.263.363.3
63.363.363.363.463.4
63.463.463.463.463.563.563.563.563.563.5
63.663.663.663.663.663.763.763.763.763.8
63.763.863.863.863.863.863.963.963.963.9
N208/N232
Ratio
0.0222570.0223070.0223570.0224070.022457
0,0225060.0225560.0226060.0226560.022707
0,0227560.0228060.0228560.0229060.0229560.0230060.02305 50.0231050.0231.560.023*07
0.0232570.0233060.0233560.0234060.0234560.0235060.0235560.0236060.0236560.023706
0.0237560.0238060.0238550.0239o60,023956
0.0240o60.0240560.0241050.0241550.024206
0.0242560.0243o60.0243550.0244o50.0244550.0245060.0245560.0246060.0246550.024705
AgeNumber
of years
451452453454455
456457458459460
4614*2463464465
4664674*8469470
471472473474475
476477478479480481432433434435
436437488439490
491492493494495496497498499500
Error +
22,222.322.322.422.4
22.522.522.622,622.722.722,822.822,922.923.023.023.123.123.223.223.323.323.423.423.523.523.623.623.7
23.723.823.823.923.924,024.024.124.124.2
24.224.324.324,424.4
24.524.524.524.624.6
TABLES FOR THE CALCULATION OF LEAD ISOTOPE AGES
502-600
21
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
"2067*238
Ratio
0.0802060.0805380.0808700.0812020.081534
0.0818680.0822oo0.0825320.0828660,083198
0,0835320.0838640.08419?0.0845310.0848&4
0.0851980.0855310.0858650.0861990.086532
0.0868660.0872020.0875350.0878700.088204
0.0885380.0888730.0892080.0895440.089878
0.0902i30.0905480.0908830.0912i80.091555
0.0918900.0922260.0925610.0928960.093234
0.0935&90.0939060.0942410.0945770.0949i5
0.0952510.0955870.0959250.0962610.096598
Age
Number of
years
502504506508510
512514516518520
522524526528530
532534536538540
542544546548550
552554556558560
562564566568570
572574576578580
582584586588590
593594596598600
Error ±
1.11.11.1XI1.11.11.1XIXI1.2X21.2X2X2X2
X2X2X21.2X2
1.21.21.21.2X2
X21.21.2X2X2
1.21,3X3X3X3
X3X3X3X3X3
X3X3X31.3X3
X3X3X3X3X3
N 207/N235
Ratio
0.6290900.6322&20.6354360.6386210.641809
0.6450050.6482070.6514150.6546270.657850
0.6610750.6643060.6675470.6707920.674043
0.6773030.6805680.6838370.6871160.690399
0.6936880.6969840.7002880.7035950.7069ii
0.7102330.7135610.7168950.7202400.723585
0.7269390.7303010.7336690.7370420.740425
0.7438io0.7472030.7506050.7540i20.757425
0.7608470.7642720.7677060.7711470,774595
0.7780490.7815090.7849760.7884500.791929
Age
Number of
years
502504506508510
512514516518520
522524526528530
532534536538540
542544546548550
552554556558560
562564566568570
572574576578580
582584586588590
592594596598600
Error +
1X31X31X41X41X4
1X51X51X61X61X7
1X71X811.81X81X9
1X912.012.012.112.1
12.212.212.312.312.3
12.412.412.512.512.6
12.612.712.712.712.8
12.812.912.913.013.0
13.113.113.213.213.2
13.313.313.413.413.5
^207/^206
Ratio
0.0569&00.0570ii0.0570620.0571130.057165
0.0572i50.0572670.0573190.0573690.057422
0.0574730.0575250.0575770.0576280.057680
0.0577320.0577840.0578360.0578880.057941
0.0579930.0580440.0580970.0581490.058202
0.0582550.0583070.0583600.0584i20.058465
0.0585180.0585710.0586250.0586780.058730
0.0587840.0588370.0588910.0589450.058997
0.0590510.0591040.0591590.0592i30.059266
0.0593200.0593740.0594270.0594820.059536
Age
Number of
years
502504506508510
512514516518520
522524526528530
532534536538540
542544546548550
552554556558560
562564566568570
572574576578580
582584586588590
592594596598600
Error +
63.964.064.064.064.1
64.164.264.264.264.2
64.364.364.464.364.4
64.464.564.564.664,6
64.764.664.764.764.8
64.864.864.964.964.9
65.065.065.165.165.1
65.165,265.265.365.3
6"5.365.365.465.565.5
65.565.565,665,665,6
N20B/N2 3 2
Ratio
0.0248060.0249050.0250060.0251060.025205
0.0253060.0254060.0255060.0256060.025706
0.0258060.0259070.0260o60.0261070.026207
0.0263070.0264070.0265070.0266080.026709
0.0268080.0269090.0270io0.0271090.0272io
0.0273090.0274io0.0275ii0.0276io0.0277ii
0.0278i20.0279ii0.0280i20.0281120.0282i3
0.0283130.0284i30.0285140.0286150.0287i4
0.0288150.0289i60.0290i60.0291160.029216
0.0293i80.0294i90.0295190.0296 2 o0.029720
Age
Number of
years
502504506508510
512514516518520
522524526528530
532534536538540
542544546548550
552554556558560
562564566568570
572574576578580
582584586588590
592594596598600
Error +
24.724.824.925.025.1
25.225.325.425.525.6
25.725.825.926.026,1
26.226,326.426.526.6
26.726,826.927.027,1
27.227.327.427.527.6
27.727.827.928.028.1
28.228.328.428.528.6
28.728.828.929.029.1
29.229,329.429.529.6
22 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY
602-700
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0.0969360.0972730.0976ii0.0979470.0982850.0986230.0989610.0992990.0996360.0999740.1003130.1006500.1009900.1013270.101666
0.1020050.1023440.1026820.1030220.103360O.l037oo0.1040390.1043790.1047190.1050580.1053980.1057380.1060770.1064180.1067570.1070970.1074390.1077780.1081200.1084590.1088oo0.1091420.1094820.1098240.110165
0.1105060.1108480.1111890.1115310.111872
0.1122i40.1125570.1128980.1132400.113583
AgeNumber
of years
602604606608610612614616618620622624626628630632634636638640642644646648650652654656658660662664666668670672674676678680682684686688690692694696698700
Error ±
1.313131.314
14141,41414
1414141414
1414141414
1414141414
1415151515
1515151515
1515151515
1515151515
1515151516
"207/^235
Ratio
0,7954i70.7989ii0.8024i30.8059210,8094360.8129570.8164860.8200200.8235620.8271130.8306670.8342310.8378oi0.8413770.8449610.8485520.8521500.8557540.8593650.8629850.8666110.8702420.8738840,8775290.8811830.8848460.8885130.8921890.8958720.8995610.9032570.9069630.9106730.9143920.9181170.9218500.9255910.9293390.9330940.9368550.9406270.9444030.9481860.9519790,9557780.9595850.9633970.9672200.9710470.974883
AgeNumber
of years
602604606608610612614616618620622624626628630632634636638640642644646648650652654656658660662664666668670672674676678680682684686688690692694696698700
Error +
13,513.613.613.613.7
13.713.813.813.913.9
14.014.014.014.114.1
14,214.214.314.314.4
14.414.514.514.514.6
14.614.714.714.814.8
14.914.914.915,015.0
15.115.115.215.215.3
15.315.315.415,415.5
15.515.615.615.715.7
N 207/N 206
Ratio
0.0595900.0596440.0596980.0597540.0598080.0598620.0599i70.0599710.0600260.0600810.0601360.0601910.0602460.0603oi0.0603560.0604ii0.0604670.0605230.0605770.0606340.0606890.0607440.0608oo0.0608550.0609i20.0609670.0610230.0610800.0611350.061192
0.0612490.0613040.0613610.0614170.0614740.0615310.0615870.0616440.0617oi0.0617580.0618150.0618720.0619290.0619860.0620440.0621oi0.0621580.0622i60.0622730.062331
AgeNumber
of years
602604606608610612614616618620622624626628630632634636638640642644646648650652654656658660662664666668670672674676678680682684686688690692694696698700
Error +
65.765.765.765.865.865.865.965.966,066.066,066,166.166.166.166.266,266.366.366.466,466,466,466,466.566,566.666,666,666.766.766,766.866,866.966,966.967.067.067.067.167.167.167.267,267.367.367.367.367.4
N208/N232
Ratio
0.0298200.0299210.0300210.0301220.0302230.0303230.0304240.0305250.0306240.0307250.0308250.0309260.0310270.0311270.0312280.0313290.0314290.0315300.0316310.0317320,0318340.0319340.0320350.0321360.0322360.0323370.0324370.0325380.0326390.0327390.0328410,0329420.0330420.0331430.0332430.0333440.0334460.0335460,0336480.0337490.0338500.0339510.0340510.0341520.0342540.0343540.0344550.0345570.0346570.034758
AgeNumber
of years
602604606608610612614616618620622624626628630632634636638640
6426446466486506526546566586*>Q
6^)26*46%6^)86706726746766786BO6B26Q46B6688690692694696698700
Error +
29.729.829.930.030.130.230.330,430,530.630.730.830.931031131231331431531,531631731.831932.032,132,232.332.432.532.632,732.832.933.033.133.233.333.433.533.633.733.833.934.034.134.234.334.434.5
TABLES FOR THE CALCULATION OF LEAD ISOTOPE AGES
702-800
23
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
N 206//V 238
Ratio
0.1139250.1142680.1146090.1149520.1152950.1156380.1159810.1163250.1166670.1170n
0.1173540.1176970.1180420.1183850.1187290.11907 30.1194i60.1197^10.1201050.1204490.1207950.1211390.1214840.1218290.1221730.1225180.1228630.1232080.1235530.1238980.1242440.1245890.1249340.1252830,1256280.1259740.1263200.1266&50.1270i20.1273590.1277050.12805 20.1283980.1287460.1290930.1294400.1297870.1301350.1304830.130829
AgeNumber
of years
702704706708710
712714716718720
722724726728730732734736738740
742744746748750752754756758760
762764766768770772774776778780782784786788790792794796798800
Error ±
1.616161616
161616161616161616161616161616161617171717171717171717171717171717171717171717181818181818
^207/^235
Ratio
0.9787290.9825780.9864370.9903040.994176
0.9980571001947100584210097441013659101757710215021025439102937910333281037288104125110452241.0492031053191105718910611911065203106922310732491077288108132810853771089439109350410975781101661110575211098491113957
1118071112219011263221.13045911346071.13876311429231.1470941.15127011554591159653116385711680 7011722871176515
AgeNumber
of years
702704706708710
712714716718720
722724726728730732734736738740
742744746748750752754756758760
762764766768770
772774776778780
782784786788790792794796798800
Error ±
15.815.815.815.915.916016.016.116.116.216216.216.316.316.416.416.516.516.616.616.716.716.716.816.816.916.917017.017.117117.117.217.217.3
17.317.417.417.517.517.517.617.617.717.717,817.817.917.918.0
^207/^206
Ratio
0.0623890.0624460.0625050.0625630.062620
0.0626780.0627370.0627940.0628530,0629ii
0.0629700.0630280.0630860.0631450.0632040.0632630,0633220.0633810.0634400.0634990.0635570.0636170.0636760.0637350,0637950.0638550.0639i 40.0639740.0640340.0640940.0641540.0642i40.0642750,0643330.0643940.0644540.0645140.0645760,0646360.0646960.0647570.0648180.0648790.0649390.0650oo0.0650610.0651230.0651830.0652440.065306
AgeNumber
of years
702704706708710
712714716718720
722724726728730732734736738740742744746748750752754756758760
762764766768770
772774776778780
782784786788790792794796798800
Error
±
67.467.467.567.667,667.667.667.667.767.767.867.867.867.967.968.068.068.068.168.168.168.16a268.268.368.368.368.468.468.468.568.568,668.668.6
68.768.768.868.868.868.968.968.968.969.069.069.169.169.169.2
^208/^232
Ratio
0.0348590,0349600.0350610.0351620.0352630.0353640.0354660,0355670,0356690,0357690,0358710,0359710.03607 20,0361740,0362740.0363760.0364770,0365780,0366790,0367800,0368810.0369830,0370840.0371860.0372880,0373880,0374900,0375900.0376920,0377940,0378940,0379960,0380980,0381980,0383oo
0,0384oi0,0385o20,0386o50,0387060,0388o70.0389090, 0390io0,0391i20,03 92 120.0393140,0394i60.0395i70.0396i80,0397200.039821
AgeNumber
of years
702704706708710
712714716718720
722724726728730732734736738740
742744746748750752754756758760
762764766768770
772774776778780782784786788790792794796798800
Error ±
34.634.734.834.935.0
35.135.235.335.435.535.635.735.835.936.0
36.136.236.336.436.536.636.736.836.937.0
37.137.237.337.437.537,637.737.837.938.0
38.138.238.338.438.5
38.538.638.738.838.939.039.139.239.339.4
24 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY
802-900
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0.1311770.1315250.1318720,1322200.1325680.1329170.1332660.1336140.1339&20.1343H0.1346600.1350090.1353570.1357060.1360560.1364050.1367530.1371040.1374530.1378030.1381530.1385010.1388520.1392oi0.139554
0.1399040.1402530.1406050.1409550.1413040.1416560.1420070.1423590.1427io0.143061
0.1434130.1437630.1441160.1444670.1448190.1451720.1455230.1458750.1462280.1465800.1469330.1472850.1476370.1479920.148344
AgeNumber
of years
802804806808810
812814816818820822824826828830
832834836838840
842844846848850
852854856858860862864866868870872874876878880882884886888890892894896898900
Error±
1.81.81.81.8X81.8X81,8X81.81.81.81,81.81.8X8X8X9191.91.919X91.91.9
X91.9191.91.91.9X91.91.91.91.91.9X91.92.02.02.02,02,02.02.02.02.02.02.0
"207/^235
Ratio
1.1807521.1849961.1892481.1935io1,1977771.2020551.2063411,21063612149371.2192491.2235691.227894X2322331,2365761.240929X2452901.2496591.2540373,2584231,262819X2672231,2716351.2760581,2804861.28492512893731293826X2982911,30276613072461.311735X3162371.3207451.3252601,3297881.3343213,3388641.3434161.3479761,352546U57126X361713X3663081.3709i21.3755281.3801521.3847831,3894261,3940751,398732
AeeNumber
of years
802804806808810812814816818820822824826828830832834836838840842844846848850852854856858860862864866868870872874876878880882884886888890892894896898900
Error +
18.018.018.118.118.218.218.318.318.418.418.418.518.518.618.618.718.718.818.818.818.918.919.019,019.119.119.219.219.319.3
19.319.419.419.519.519.619.619.719.719.719,819.819,919.920.020.020.120.120.220.2
N 207/N2Q6
Ratio
0.0653680,0654290.0654910.0655530.0656150.0656760.0657380.0658oo0.0658&20.0659240.0659860.0660480.0661ii0.0661740,0662360.0662980.0663&20,0664240.0664870.0665500.0666120.0666760.0667390.0668030.0668&50.0669290.0669930, 0670550.0671200.0671840.0672470.0673H0.0673750.0674390.0675030.0675&70.0676320.0676960.0677600.0678250.0678890.0679 5 40,0680i90.0680 8 40.0681490.0682i40.0682790,0683440.0684090.068474
AgeNumber
of years
802804806808810
812814816818820822824826828830
832834836838840
842844846848850852854856858860862864866868870872874876878880882884886888890892894896898900
Error +
69.269.269,369.369.469.469.469.569,569,569.569.669.669.769.769,769,869.869.969.969.970.070.070.170,170.170.170.170.270.370.370.370.470.470.470.570.570.570.670.670.670.770.770.870,870.870.970.970.971.0
N208/
Ratio
0.0399230,0400250.0401260,0402280.0403290.0404310,0405330.0406340,0407360.0408370,0409380,0410400.0411410,0412430.0413460.0414470.0415490.0416500.0417520.0418540.0419550.0420570.0421590,0422600,0423620.0424&30.0425660.0426680.0427700.0428720.0429740.0430750,0431770,0432790.0433800.0434820.0435840.0436870.0437890.0438900.0439920.0440950.0441960.0442980.044399
0.0445oi0.0446040,0447050.0448080.0449H
^232
AgeNurrber
of years
802804806808810812814816818820822824826828830832834836838£40842£44£46£48£50£52£54£56essf<SO
f^2FMf*>6f68f70
T72P74P76P78PRO
F82P84P86P88P90
P92P94P96P98900
Error ±
39.539.639.739.839.940.040.140.240.340.440.540.640.740.840,941.041141241.341.441.541.64X741.843,942.042.142.242,342.442,542.642.742,842.943,043.143.243.343,443.543.643,743.843.944.044.144.244.344.4
TABLES FOR THE CALCULATION OF LEAD ISOTOPE AGES
902-1000
25
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0,1486950.1490490.1494020.1497560.150109
0.1504630.1508170.1511700.1515260.151879
0.1522320.1525870.1529420.1532950.153650
0.1540040.1543600.1547150.1550690.155425
0.1557800.1561350.1564910.1568460.157202
0.1575570.1579i30.1582700.1586250.158982
0.1593370.1596950.1600520.1604070.1607&5
0.1611210.1614780.1618360.1621920.162549
0.1629070.1632640.1636220.1639800.164338
0.1646960.1650540.1654120.1657710.166129
Age
Number of
years
902904906908910
912914916918920
922924926928930
932934936938940
942944946948950
952954956958960
962964966968970
972974976978980
982984986988990
992994996998
1000
Error ±
2.02.02.02.02.0
2.02.02.02,02.0
2.02.02.12.12.1
2.12.12,12.12.1
2.12,12.12.12.1
2.12.12.12.12,1
2.12.12.12.12.2
2.22.22.22.22.2
2.22.22.22.22.2
2.22.22.22.22.2
^207/^235
Ratio
1,4034041,4080791,4127671,417465X4221&9
1,4268811,4316071,4363393,4410781,445831
1,4505911.45535814601421.4649271,469722
1.4745331,4793481,4841 7 21.4890o61,493850
1.4987061.5035661.50844115133201.518213
15231161,5280231.5329441.5378/41,542813
1,5477631.5527201.5576891.5626651,567654
1,5726511,5776561,5826771,5877021,592736
1,5977851.6028401,6079051,6129801,618067
1,6231611.6282631,6333841.6385071,643640
Age
Number of
years
902904906908910
912914916918920
922924926928930
932934936938940
942944946948950
952954956958960
962964966968970
972974976978980
982984986988990
992994996998
1000
Error +
20.220.320.320.420.4
20.520.520.620.620.6
20.720.720.820,820.9
20.921,021,021,021,1
21,121.221,221.321.3
21,421.42X521,521.5
2X62],621,72X72X8
2X821.92X92X922.0
22.022.122.122.222.2
22.322.322.422.422.4
N 207/N206
Ratio
0.0685410.0686060.0686720.0687370.068803
0.0688690.0689340.0690oi0.0690660.069133
0.0691990.0692&50.0693320.0693990.069465
0.0695320.0695980.0696650.0697320.069799
0.0698660.0699330, 0700oi0.0700680.070135
0.0702030.0702710.0703380.0704060.070474
0.0705420, 0706io0.0706780,0707470.070814
0.0708830.0709520.0710200.0710890.071158
0.0712270,0712960.0713640.0714330.071503
0.0715720.0716410,0717n0,0717800.071850
Age
Number of
years
902904906908910
912914916918920
922924926928930
932934936938940
942944946948950
952954956958960
962964966968970
972974976978980
982984986988990
992994996998
1000
Error +
7X07X17X17X17X2
7X271.27X37X37X3
7X47X47X47X57X5
7X67X67X67X67X7
7X77X77X87X87X9
7X972.072.072.072.1
72.172.172.272.272.2
72.372.372.372.472.4
72,572.572.572.672.6
72.672.772.772.772,8
N208/
Ratio
0.0450i20.0451140.0452150.0453180.045420
0.0455210.0456240.0457260.0458270.045931
0.0460320.0461350.0462370.0463380,046441
0.0465430.0466450.0467470.0468490.046952
0.0470550.0471560.0472590.0473610.0474&3
0.0475650.0476670.0477690.0478750.047974
0.0480 7 70,0481800,0482810.0483840.048485
0.0485880.0486910.0487930.0488960.048999
0.0491oo0.0492030.0493050.0494070.0495io
0.0496120.0497160.0498180.0499200.050023
^232
Age
Number of
years
902904906908910
912914916918920
922924926928930
932934936938940
942944946948950
952954956958960
962964966968970
972974976978980
982984986988990
992994996998
1000
Error
±
44.544.644.744.844.9
45.045.145.245.345.4
45.545.545.645.745.8
45.946,046.146,246,3
46.446.546,646.746.8
46.947.047,147,247.3
47.447,547.647.747.8
47.948.04ai48.248.3
48.448.54a648.748.8
48.949.049.149.249.3
26 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY
1002-1100
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0.1664870.1668460.1672030.1675630,1679220.1682820.1686400.1689990.1693590.1697190.1700780.1704380.1707970.1711580.1715180.1718770.1722380.1725980.1729590.1733200.1736800.1740410.1744020.1747640.1751250.1754850.1758470.1762080.1765700.1769320.1772930.1776550.1780i60.1783800.1787420.1791040.1794660.1798300.1801920.1805560.1809i80.1812810.1816450.1820080.1823720.1827350.1830990.1834630.1838250.184190
AgeNumber
of years
10021004100610081010101210141016101810201022102410261028103010321034103610381040104210441046104810501052105410561058106010621064106610681070107210741076107810801082108410861088109010921094109610981100
Error ±
2.22.22.22.22.22.22.22.32.32.32.32.32.32.32.32.32.32.32.32.32.32.32.32.32.32.32.32.32.32.42.42.42.42.42.42.42.42.42.42.42.42.42.42.42.42,42.42.42.42,4
N 207/N235
Ratio
1,6487891.6539411,659107X6642841,6694691,6746621,6798721,6850841,6903091,6955481.7007911,7060491,7113151,7165921,7218781.7271781,7324831.7378oi1,7431291,7484711,7538191.7591771,7645481.7699291,7753201,7807211.7861321,7915531,7969881,8024311,8078851,8133511,8188251.8243io1,8298081,8353151.8408311,8463631,8519021,857451I,8630i21,8685871,8741681,8797601,8853681,8909801,896606X9022481,9078941913552
AgeNumber
of years
10021004100610081010101210141016101810201022102410261028103010321034103610381040104210441046104810501052105410561058106010621064106610681070107210741076107810801082108410861088109010921094109610981100
Error +
22.522.522.622.622.722.722.822.822.822.922.923.023.023.123.123.223.223.223.323.323.423.423.523.523.623.623.723.723.723.823.823.923.924.024.024.124.124.124,224.224.324.324.424.424.524.524.524.624.624.7
N 207/N206
Ratio
0.0719200.0719890.0720600,0721290.0721990.0722690.0723400.0724io0.0724800.0725510.0726220.0726920.0727630.0728340.0729050.0729760.0730470.0731190.0731900.0732610.0733330.0734040.0734760.0735470.0736i90.0736920.0737640.0738360.0739080.0739800,0740530.0741250.0741980.0742700.0743430.0744i60.0744890.0745620.0746360.0747080.0747820.0748560.0749290.0750o20.07507 60.0751500.0752240.0752980,0753720.075446
AgeNumber
of years
10021004100610081010101210141016101810201022102410261028103010321034103610381040104210441046104810501052105410561058106010621064106610681070107210741076107810801082108410861088109010921094109610981100
Error +
72.872.872.972.973.073.073.173,173.173.273.273.273.373.373.473.473.473.573.573.573.673.673.673.773.773.873.873.873.973.973.974.074.074.074.174.174.274.274.274.274.374.474.474.474.474.574.574.674.674.6
^208/^232
Ratio
0.0501260.0502270.0503300,0504320.0505350.0506390.0507400.0508430.0509460.0510480.0511510.0512530.0513560.0514600.0515610.0516640.0517670.0518690.0519720.0520740.0521770.0522810.0523830,0524860.0525890.0526910.0527940.0528960.0529990.0531030.0532050.0533080.0534H0.0535130.0536160.0537190.0538230.0539260.0540280.0541310.0542340.0543360.0544400.0545420.0546460,0547490.0548510.0549550.0550580.055160
AgeNumber
of years
10021004100610081010101210141016101810201022102410261028103010321034103610381040104210441046104810501052105410561058106010621064106610681070107210741076107810801082108410861088109010921094109610981100
Error +
49.449.549.649.749.849.950.050.150.250.350,450.550.650.750.850.951.051.15X25X35X45X55X65X75X85X952.052.152.252.352.452.552.552.652.752.852.953.053,153.253.353.453.553.653.753.853.954.054.154.2
TABLES FOR THE CALCULATION OF LEAD ISOTOPE AGES
1102-1200
27
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0.1845540.1849i80.1852830.1856480.1860ii
0.1863760.1867400.1871060.1874710.187836
0.1882oi0.1885670.1889310.1892970.1896610.1900290,1903940.1907590.1911260.191492
0.1918590.1922240.1925910.1929590.193325
0.1936900.19405 90.1944250.1947930,195161
0.1955280.1958960.1962630.1966320.1969990.1973660.1977360.1981030.1984710.1988400.1992080.1995770.1999450.2003i40.200683
0.20105 20.2014220.2017910.2021600,202531
AgeNumber
of years
11021104110611081110
11121114111611181120
11221124112611281130
11321134113611381140
11421144114611481150
11521154115611581160
11621164116611681170
11721174117611781180
11821184118611881190
11921194119611981200
Error ±
2.42.42.52.52.5
2,52.52.52.52.5
2.52.52.52,52.5
2.52.52.52.52.52.52.52.52.52.5
2.62.62.62.62.6
2.62.62.62.62.6
2.62.62.62.62.62.62.62.62.62.62.62.62.72.72.7
Ratio
1.9192251.9249051.9305981.9363021.9420i6
1.9477411.9534801.9592271.9649851.970758
1.9765371.9823331,9881381.9939531.9997772.0056152.0114662.0173252.0231972.029084
2.0349782.0408842.0468032.0527322.058672
2.0646292,0705912.0765672.0825542.088556
2.0945642.1005902,1066242.1126672,118727
2.1247972,1308782.1369742.1430772.149193
2.1553232.1614642.1676162.1737802.179961
2.1861462.1923462.1985622.2047862.211023
^v235.Age
Number of
years
11021104110611081110
11121114111611181120
11221124112611281130
11321134113611381140
11421144114611481150
11521154115611581160
11621164116611681170
11721174117611781180
11821184118611881190
11921194119611981200
Error ±
24.724.824,824.924.925.025.025.025.125.1
25.225.225.325.325.4
25.425.425.525.525.625.625.725.725.825.8
25.925.925.926.026.0
26,126.126.226.226,3
26.326.326.426.426.526.526.626.626.726.726.726.826.826.926.9
^207/^206
Ratio
0.0755210.0755950.0756690.0757440.075819
0.0758930.0759690.0760430.0761180.076193
0,0762690.0763440.0764200,0764950.076571
0.0766460.0767220.0767990.0768740.076951
0.0770270.0771030.0771800.0772560.077333
0.0774io0.0774860.0775630.0776400.0777i7
0,0777940.0778720.0779490.0780260.078104
0,0781820.0782590.0783380.0784i60.0784940.0785720.0786500.0787290.0788080.078886
0.0789650.0790430.0791230.0792020.079280
AgeNumber
of years
11021104110611081110
11121114111611181120
11221124112611281130
11321134113611381140
11421144114611481150
11521154115611581160
11621164116611681170
11721174117611781180
11821184118611881190
11921194119611981200
Error
±
74.774.774.774.874.8
74.874.974.974.975.075,075.175,175.275.2
75.275.275.375.375.475,475.475.575.575.6
75.675.675.775.775.7
75.875.875975.975.976.076.076,176,176.176,276,276,276.376,3
76,476,476.476,576,5
N208/N232
Ratio
0.0552630.0553670.0554700.0555730.0556750,0557790.0558820,0559840.0560890.056191
0.0562940,0563980,0565oo0.0566030.056707
0.0568io0.0569140.0570160,0571190.057223
0.0573250.0574300,0575330.0576360.057739
0.0578430.0579450.0580490,0581520,058256
0,0583590.0584620.0585650.0586690.058772
0,0588760,0589780.0590820.0591860.059288
0.0593930.0594970.0595990.0597030.059806
0.0599090.0600i30,0601i70,0602200.060324
AgeNumber
of yearr
1102110411061108me1112111411161118112 C
1122112411261128113C
1132113411361138114C
1142114411461148use1152.115411561158116C
1162116411661168117C
1172117411761178118C
1182118411861188119C
119211941196119812 oe
Error
54,354,454.554.654.7
54.854.955.055.155.2
55.355.455.555,655.7
55.855.956,056,156.2
56.356.456,556.656,7
56,856.957.057.157.2
57.357.457.557.657.7
57.857.958.058.158.2
58.358,458,558,658,758,858.959.059,159,2
28 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY
1202-1300
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0.2028990.2032680.2036400,2040o90.2043790.2047510.2051200,2054900.2058620.2062310.2066030.2069740.2073450.2077160.2080880.2084600.2088300.2092030.2095750.2099450.2103190.2106900.2110620.2114350.2118060.2121810.2125530,2129240.2132980.2136710.2140450.2144i70.2147900.2151650.2155380.2159H0.2162860.2166580.2170330.2174070.2177800.2181560.2185300.2189050.2192790.2196530.2200300.2204050.2207790.221155
yv Q.QNumber
of years
12021204120612081210
121212141216121812201222122412261228123012321234123612381240124212441246124812501252125412561258126012621264126612681270127212741276127812801282128412861288129012921294129612981300
Error ±
2.72.72.72.72.72.72.72,72.72.72.72,72.72.72.72.72.72.72.72.7
2.82.82,82.82.82.82.82.82.82.82,82.82.82,82.82,82.82.82,82.82.82,82.92.92.92.92.92,92.92.9
"207/^35
Ratio
2.2172752.2235342.2298092.2360952.2423922.2487012.2550272.2613612.2677052.274067
2.2804392.2868242.2932212.2996302.3060512.3124822.3189342.3253922.3318&02.3383472.3448442.3513552.3578782.3644122.3709592.3775232.3840922,3906782.3972792.4038922.4105162.4171562.4238042.4304692.4371452.4438332.4505342.4572542.4639802.4707202.4774732.4842442.4910262.4978172.5046272.5114482.5182812.5251292.5319882.538864
AgeNumber
of years
1202120412061208121012121214121612181220
12221224122612281230
12321234123612381240
124212441246124812501252125412561258126012621264126612681270127212741276127812801282128412861288129012921294129612981300
Error ±
27,027.027.127,127.227.227.227.327,327.427.427.527,527.627.627,627.727.727.827.827.927.928.028.028.128.128.128.228.228.328.328.428,428.528.528.528,628.628.728.728.828.828.928.928.929.029,029.129.129.2
N 207/
Ratio
0.0793600.0794400.0795180.0795980.0796780.0797570.0798380.0799i80.0799970.080078O.OSOIss0.0802380.0803190.0803990.0804790.0805600.0806420.0807220.0808030.0808850.0809&50.0810470.0811290.0812io0,0812920.0813730.0814550.0815380.0816200.0817020.0817840.0818670,0819500,0820320.0821i50.0821980,0822800.0823640.0824470.0825300.0826140.0826970.0827810.0828640.0829490,0830330.0831i60,0832oo0,0832850.083369
/N
AgeNumber
of years
12021204120612081210121212141216121812201222122412261228123012321234123612381240124212441246124812501252125412561258126012621264126612681270127212741276127812801282128412861288129012921294129612981300
Error
76.576,676,676.776.776.776.876,876.876.976.976,977.077.077.0
77.177.177.277.277,377.377.377.477,477.477.577.577.577.677.677.777.777.877.877.877.977.977.978,078.078.078.178.178,178.278.378.378.378.478.4
N208/
Ratio
0.0604270.0605310.0606330.0607380.060842
0.0609450.0610 4 80.0611520.0612560.061360
0,0614630.0615660.0616700.0617730.0618780.0619820.0620850.0621890,0622910.0623950.0625oo0.0626030.0627070.0628H0, 0629i40.0630! 90.0631220.0632260,0633300.0634330.0635370.0636420.0637450.0638490.0639520.0640560.0641610,0642640.0643680.0644720.0645760.0646810,0647850.0648880,0649920.0650950.0651990,0653050.0654080.065512
//v232Age
Number of
years
120212 0412 OS120°1210
12121214121612181220
12221224122612281230
123212341236123B1240
124212441246124812501252125412561258126012621264126612681270
127212741276127812801282128412S612SB12901292129412*3^12 co13CO
Error
59,359.459.559.559.659.759.859.960.060.160,260.360.460.560.660,760,860,96X06X16X26X36X46X56X66X76X86X962,062.162.262,362,462.562.662.762,862.963,063.163.263.363.463.563,663,763.863.964.064.1
TABLES FOR THE CALCULATION OF LEAD ISOTOPE AGES
1302-1400
29
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0.2215300.2219060.2222810.2226560.223034
0.2234080.2237860.2241610.2245380.2249i4
0.2252900.2256670.2260440.2264210,226798
0.2271750,2275520.2279310.2283080.2286860.2290640.2294400,2298200.2301960,230575
0.2309540.2313320.2317H0.23209 n0.232467
0,2328470.2332260.2336040,2339840.2343630.2347440.2351220,2355020.2358820,236262
0.2366430,2370220,2374oi0,2377830.2381630,2385430,2389240,2393060,2396870.240068
AgeNumber
of years
13021304130613081310
13121314131613181320
13221324132613281330
13321334133613381340
13421344134613481350
13521354135613581360
13621364136613681370
13721374137613781380
13821384138613881390
13921394139613981400
Error
2.92,92.92.92.9
2,92.92.92.92.9
2.92.92.92.92.9
3.03.03.03.03.03.03.03.03.03.0
3,03.03.03.03,0
3.03.03.03.03.0
3.03.03,13.13.1
3.13.13.13.13.13.13.13.13.13.1
N 207/N23 5
Ratio
2.5457522,5526532.5595642.5664952.573437
2.5803882,5873602.5943382.6013352.608345
2.6153672.6224032.6294552.6365i62.643593
2.6506842.6577922.6649062.6720412.6791882.6863492,6935222,7007i42.7079i52,7151292.7223622.7296072.7368632.7441362.751424
2.7587242.7660412.7733702.7807H2.7880722.7954452.8028312.8102322.8176492.825076
2.8325212.8399812.8474542.8549392,8624452,8699602,8774912.8850392.8926oo2.900174
AgeNumber
of years
13021304130613081310
13121314131613181320
13221324132613281330
13321334133613381340
13421344134613481350
13521354135613581360
13621364136613681370
13721374137613781380
13821384138613881390
13921394139613981400
Error ±
29,229.329.329.429.4
29.429,529.529.629,6
29.729.729.829,829,8
29,929.930.030.030.130.130.230.230,230.3
30.330.430.430.530.5
30.630.630.730.730.7
30.830.830.930.93X0
31.03X13X13X13X23X23X33X33X43X4
N 207/N206
Ratio
0,0834540,0835380,0836230,0837080.083793
0.0838780,0839630,0840490.0841340,0842i9
0, 0843050.0843910.0844770.0845620.084648
0,0847350.0848210.0849070.0849930.085080
0.0851670,0852540,0853400.0854280, 0855150.0856020.0856900.0857770,0858640.0859530.0860400,0861280.0862i70.0863040.086393
0.0864810.0865700.0866580,0867470.086836
0.0869250.0870i40.0871040.0871930.0872820.0873720.0874620.0875510.0876410.087731
AgeNumber
of years
13021304130613081310
13121314131613181320
13221324132613281330
13321334133613381340
13421344134613481350
13521354135613581360
13621364136613681370
13721374137613781380
13821384138613881390
13921394139613981400
Error
78.478.578,578.578.6
78.678.678.778.778,8
78,878.978,978.978,979,079,079.179,179,1
79.279.279.379.379.3
79.479.479,479,579.579.679,679.679.779.7
79.779.879.879,979.9
79.980,080,080,180,1
80,180,280,280,280.3
N208/
Ratio
0,0656160.0657190.0658250.0659280.066032
0.0661360.0662390.0663450.0664490,066552
0,0666570.0667600.0668650.0669700,067073
0.0671770.0672830,0673860.0674900,0675940.0676980.0678040,0679070.0680ii0.0681160,0682190.0683250.0684280,0685330,068637
0.0687400.0688460,0689510.0690540.069159
0.0692630,0693680.0694720.0695760,069680
0.0697860.0698890.0699940.0700980.0702030.0703080.0704120.0705160.0706210,070726
/N232
AgeNumber
of years
13021304130613081310
13121314131613181320
13221324132613281330
13321334133613381340
13421344134613481350
13521354135613581360
13621364136613681370
13721374137613781380
13821384138613881390
13921394139613981400
Error
64,264.364.464.564.6
64.764.864.965.065,1
65.265.365.465.565.6
65.765,865,966.066.166.266.366,466.566.566.666.766,866.967.0
67.167.267.367.467.5
67.667.767.867,968.0
68,168.268.368.468,5
68.668.768.868.969.0
30 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY
1402-1500
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0.2404480.2408310.2412H0.2415940.2419750,2423570.2427380.2431210.2435030.2438860.2442&80.2446520.2450340.2454i50.2458oo0.2461810.2465660.2469480.2473320.2477150.2480990.2484820.2488660.2492500.2496340.2500i90.2504oi0.2507870.2511720.2515570.2519410.2523250.2527H0,2530950.2534800,2538660.2542510.2546380.2550220.2554090,2557960,2561810,256569
AgeNumber
of years
140214041406140814101412141414161418142014221424142614281430
14321434143614381440
14421444144614481450
145214541456145814601462146414661468147014721474147614781480148214841486
0,256954 14880.257340 14900.257728 14920.2581130.2585oo
14941496
0.258887 14980.259274 1500
Error ±
3.13.13.13,13.13.13.13.13.13.13.23.23.23.23.23.23.23.23.23.23.23.23.23.23.2
3.23.23.23.23.23.23.23,33.33.33.33.33.33,33.33.33.33.33,33.33.33.33.33.33.3
^207/^235
Ratio
2.9077672.9153722.9229912.9306302.9382782.9459412.9536242,9613i52,9690242.9767502.9844892.9922443.0000i53.0078oo3.0155973.0234U3.0312453.0390903.0469493.0548293.0627193.0706253.0785523.0864863.094438
3.1024io3.1103933.1183893.1264io3.1344403,1424843.1505483.1586263.1667183.1748303.1829543.1910943.1992483.2074233.2156H3.2238143.2320373.2402733.2485233.2567953.2650793,2733793.2816983.2900293.298375
AgeNumber
of years
140214041406140814101412141414161418142014221424142614281430
14321434143614381440
14421444144614481450
14521454145614581460
14621464146614681470
147214741476147814801482148414861488149014921494149614981500
Error
3X53X53X63X63X63X731.731.83X83X93X932.032.032.032.132.132.232.232.332.332,432.432.432.532.5
32.632.632.732.732.832.832.932.932.933.033.033.133.133.233.233.333.333.333.433.433.533.533.633.633.7
N 207/N 206
Ratio
0.0878220,0879ii0.0880o20.0880920.0881830.0882740.0883650.0884560.0885470.0886380.0887290.0888200.0889i20.0890o40.0890950.0891880.0892790.0893720.0894640.0895570.0896490.0897420.0898350.0899280.090021
0.0901x30.0902080.0903oo0.0903940.0904870.09058X0.0906750.0907690.0908640.0909580.0910 5 20.0911470.0912410.0913360.0914300.0915250.0916210.0917150.0918H0.0919o70.0920o20.0920980.0921940.092290
AgeNumber
of years
14021404140614081410
141214141416141814201422142414261428143014321434143614381440
14421444144614481450
145214541456145814601462146414661468147014721474147614781480148214841486148814901492149414961498
0.092386 1500
Error
80.380.480.480.480.580,580.680.680.680.780.780.780.880.880.880.980.98X08X08X18X18X18X28X28X2
8X381.38X38X48X48X58X58X68X68X68X78X78X78X88X88X88X98X982.082.082.082.182.182.282.2
N208/
Ratio
0.0708300.0709340.0710390.0711440.071248
0.0713530.0714580.0715620.0716670.0717710.0718760.0719800.0720850.0721900.0722950.0723990.0725040.0726090.0727140.0728190.0729240.0730290.0731340.0732370.0733430.0734480.0735520.0736570.0737620.0738670,0739720.0740760.0741820.0742870.0743910.0744960.0746oi0.0747060.0748H0,0749i50.0750210.0751260.0752300.0753350.0754400.0755460.0756510.0757550.0758610.075966
/N232
AgeNumber
of yearr
1402140/1140614 OP1410
141214141416141P1420
1422142/11426142P1430
143214311436143P1440
1442144/1144614481450
1452145^1456145P1460
14621461146614681470147214741476147P148014821484148614881490149214911496149P1500
Error
69.169.269,369.469.569.669,769.869.970.070.170,270,370.470.570.670,770.870.97X0
7X17X271.37X47X5
7X67X77X87X972.0
72.172.272.372.472,572.672.772,872.973.0
73.173.273.373.473.573.573.673.773.873.9
TABLES FOR THE CALCULATION OF LEAD ISOTOPE AGES
1505-1750
31
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0.2602430.2612110.2621800.2631510,2641200.2650940.2660670.2670390.2680i30.2689890.2699640.2709410.2719170.2728950.2738720.2748520.2758330.2768140.2777960.2787770.2797610.2807450.2817290.2827140.2837020.2846880.2856760.2866630.2876530.2886420.2896320.2906240.2916160.2926io0.2936020.2945980.2955920.2965890.2975840.2985840,2995810,3005800,3015810.3025800.3035810.3045840,3055880.3065910.3075950.308599
AgeNumber
of years
1505151015151520152515301535154015451550
1555156015651570157515801585159015951600
1605161016151620162516301635164016451650
1655166016651670167516801685169016951700
1705171017151720172517301735174017451750
Error ±
3.33,33,43.43.4
3.43,43.43.43.43.43.53.53.53.53.53,53.53.53.5
3.63.63.63.63.63.63.63.63.63.73.73.73.73.73.73.73,73.73.83.83.83.83.83.83.83.83.83.93.93.9
"207/^235
Ratio
3.3193223.3403693.3615203.3827723.4041253.4255853.4471493.4688213.4905993.5124733.5344633.5565573.5787613.6010733.6234893.6460i93.6686563.6914063.7142693.7372353.7603203.7835i63.8068233.8302463.8537783.8774303.9011983.9250823.9490793.9731903.9974244.0217754.0462444.0708344.095538
4.1203704.1453184.1703924.1955874.2208984.2463424.2719054.2975934.3234074.3493424.3754084.4016024.4279224.4543744.480945
AgeNumber
of years
1505151015151520152515301535154015451550
1555156015651570157515801585159015951600
160516101615162016251630163516401645165016551660166516701675168016851690169517001705171017151720172517301735174017451750
Error i
33.833.934.034.134.234.334,434.634.734.834.935.035.135,235.335,535.635,735.835,9
36.036.136,236.436.536.636.736.836.937.037.137,337,437.537.637.737.837,938.038,138.338,438.538.638.738.838.939.039.239.3
N 207/
Ratio
0.0926260.0928680.0931110.0933540.0935980.0938420.0940880.0943350.0945820.0948290.0950780.0953280.0955780.0958300.0960820.0963350.0965880.0968430.0970980.0973550.0976120.0978700.0981280.0983880.0986480.0989io0.0991720.0994350.0996990.0999640.1002300.1004960.1007640.1010320.1013010.1015710.1018430.1021i40.1023880.1026600.1029350.1032110.1034870.1037650.1040430,1043220.1046020.1048830,1051650,105448
'"206
AgeNumber
of years
1505151015151520152515301535154015451550
1555156015651570157515801585159015951600
1605161016151620162516301635164016451650
16551660166516701675168016851690169517001705171017151720172517301735174017451750
Error +
82.382,482.582.682.782.882,983,083,183.2
83.383.483.583,683.783.883.984.084.184,2
84.384.384.484,584.684.784.884.985.085.185.285.385.485.585.685.785.885,986.0B6.186.286.386.486.586.686.786.886.987.087.1
^208/^232
Ratio
0,0762290,0764910,0767540.0770i70.0772790.0775420,0778060.0780680.0783310.0785950.0788570.0791210,0793840.0796490.0799120.0801760,0804390.0807020.0809660,0812300.0814940.0817580.0820220.0822860,0825500,0828i40.0830780.0833430.0836080.0838730.0841370,0844oi0,0846660,0849310.0851960.0854600.0857250.0859900.0862550.0865210.0867860.0870510,0873170.0875830.0878490.0881i40.0883800.0886450.0889io0.089176
AgeNumber
of years
1505151015151520152515301535154015451550
1555156015651570157515801585159015951600
1605161016151620162516301635164016451650
16551660166516701675168016851690169517001705171017151720172517301735174017451750
Error ±
74.274.474,774.975.275,475.775.976.276,476.776.977.177.477.677.978.178.478.678.979.179.479.679.980.180.480,680.881181381.683,882,182.382.682.883.183.383,683.884.084.384.584.885,0
85.385,585,886.086.3
32 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY
1755-2000
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0,3096o60,3106i40.3116210.3126300,313637
0.3146480.3156580.3166710.3176820.3186960.3197080.3207230.3217390.3227560.3237710.3247890,3258070.3268270.3278480.3288&7
0.3298900.3309ii0.3319350.3329590,3339840.3350o90.3360350.3370620,33808 90.3391i90.3401470.3411790.3422090.3432410.344274
0.3453080,3463410.3473770.3484ii0.349450
0.3504880.3515250.3525&40.3536040.354645
0,3556850,3567280.3577710.3588i60.359859
AgeNumber
of years
17551760176517701775
17801785179017951800
1805181018151820182518301835184018451850
18551860186518701875188018851890189519001905191019151920192519301935194019451950
1955196019651970197519801985199019952000
Error ±
3.93.93.93.93.9
3.94.04.04.04.0
4.04.04.04.04.0
4.14.14.14.14.1
4.14.14.14.14.24.24.24.24,24.2
4.24.24.24.34.34.34.34.34,34.3
4,34.34.44.44.4
4.44.44.44.44.4
^207/^235
Ratio
4.5076534.5344934.5614&24.5885544.615787
4,6431534.6706504.6982824.7260434.753945
4.7819844,8101564.8384684.8669i34.895498
4.9242304.9530974.9821065.0112505.040542
5.0699765.0995545.1292755.1591365,189152
5,2193075.2496135.2800685.3106&45.3414i4
5.3723155,4033655.4345685,4659i55.497425
5.5290845.5608985.5928725.6249875.657274
5.6897io5.7223io5.7550&65.7879765.821053
5.8542915.8876915.9212525.9549705,988862
AgeNumber
of years
1755176017651770177517801785179017951800
18051810181518201825
18301835184018451850
1855186018651870187518801885189018951900
19051910191519201925
19301935194019451950
1955196019651970197519801985199019952000
Error +
39.439,539.639.739.8
39.940.140.240.340.4
40.540.640.740.841.0
41.141.241.341.441.5
41.641.743,942.042.1
42.242.342.442.542.6
42.742.943.043.143.243.343.443.543.643.843.944.044,144.244.3
44.444.544.744.844.9
N 207/N2Q6
Ratio
0.1057320.1060i60.1063020.1065880,106877
0.1071650.1074540.1077440.1080360.108328
0.1086220.1089i60.1092110.1095070.109805
0.1101030,1104030.1107030.1110040.111307
0.1116090.1119i40.1122i90.1125250.112833
0,1131410.1134510,1137610.1140730.1143850.1146990,1150i30,1153290,1156450,115963
0.1162820.1166020.1169220,1172450.117567
0.1178910.1182i70,1185430.1188700.119199
0.1195290.1198590.1201910.1205240.120858
AgeNumber
of years
17551760176517701775
17801785179017951800
1805181018151820182518301835184018451850
18551860186518701875188018851890189519001905191019151920192519301935194019451950
1955196019651970197519801985199019952000
Error
±
87.287.387,487.587.6
87.787.887.988.088.1
88.288.388.488.588,6
88.788.888.989.089.1
89.289.389.489.589.689.789.889.990.090.1
90.290.390,490.590.6
90.790.890.991.091.1
91.291,391.491.591.6
93,791,89X992.092.1
^208/^232
Ratio
0,0894420,0897080.0899740.0902400,0905060.0907720,0910380.0913050.0915720,091839
0.0921040.0923710,0926370,0929040.093170
0.0934370.0937040.0939710.0942380,094505
0.0947720.0950390.0953060.0955750.095842
0.0961090.0963770.0966440.0969i30.0971800,0974480.0977170,0979840.0982520.098520
0,0987880,0990560.0993240.0995930.0998&2
0.1001300.1003980.1006&80.1009360.1012050.1014730.101742O.l020io0,1022790,102549
AgeNuirber
of years
1755176017651770177517801785179017951£00
18051£10IE 1518201£251£301£35U401£45If50
If551£60lf<>5If701£75IfBO1PB5If901P951°00
19051910191519201°25
1°301935194019451950
1955196019651970197519801985199019952000
Error ±
86,586.887.087.387.587.7sao88,288.588.789.089.289.589.790.0
90.290.590.791093,291.491.791.992.292.4
92.792.993.293.493.793.994.294.494,694.9
95.195.495.695.996.1
96.496.696.997.197.497,697.998.198.398.6
TABLES FOR THE CALCULATION OF LEAD ISOTOPE AGES
2005-2250
33
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0.3609050.3619510.3629980.36404?0.365094
0.3661440.3671940.3682450.3692960.370349
0.3714030.3724580.3735ii0.3745690,375624
0,3766820.3777420.3787990.3798590.380921
0.3819820,3830430.3841o90.3851720.386236
0.3873030.3883680.3894360.3905040.3915 73
0.3926430.3937i40.3947830.3958570.3969 3 o
0.3980o50.3990780,4001540.4012310.402307
0.4033870.4044640.4055460.4066250.407706
0.4087880.4098730.4109560.4120410,413125
AgeNumber
of years
20052010201520202025
20302035204020452050
20552060206520702075
20802085209020952100
21052110211521202125
21302135214021452150
2155216021652170217521802185219021952200
2205221022152220222522302235224022452250
Error +
4.44.54.54.54.5
4.54.54.54.54.5
4.64,64.64.64.6
4.64.64.64.64.7
4.74.74.74.74.7
4.74.74.74.84.8
4.84.84.84.84.8
4.84.84.94.94.9
4.94.94.94.94.9
4.95.05.05.05.0
L N 207/N 235
Ratio
6, 0229i86.0571406.0915266.1260766.160799
6.1956956.2307586.2659926.3013916.336972
6.3727206.4086486.4447496.4810i96.517473
6,5541o46.5909i26.6279046,6650646.7024i4
6.7399466.7776626.8155616.8536386.891908
6.9303646.9690057.0078397.0468527.086061
7.1254657,1650587.2048447.2448i97.284996
7.3253657.3659 3 37.4066987.4476557.4888i9
7.5301857.5717517,6135187.6554857.697660
7.7400417.7826287.8254267.8684227.911637
AgeNumber
ofyears
20052010201520202025
20302035204020452050
20552060206520702075
20802085209020952100
21052110211521202125
21302135214021452150
21552160216521702175
21802185219021952200
22052210221522202225
22302235224022452250
Error±
45.045.145.245.345.4
45.645.745.845.946.0
46.146.246.346.546.6
46.746.846.947.047.1
47.247.347.547.647.7
47.847.948.048.148.2
48.448,548.648.748.8
48.949.049.149.349.4
49,549.649.749.849.9
50.050.250.350.450.5
N 207/N206
Ratio
0.1211930.1215300,1218670.1222050.122545
0.1228860.1232280.1235710.1239i60.124261
0.1246070.1249550.1253050.1256540.1260o6
0.1263580.1267H0.1270670.1274230.127779
0.1281380.1284980,1288580,1292200.129584
0.1299480.1303140.1306810.1310490.131419
0.1317890,1321610.1325350.1329090.133285
0,1336610.1340400.1344i90.1348oo0.135182
0.1355650.1359510.1363360.1367230,137112
0,1375020.1378930.1382860,1386790.139075
AgeNumber
of years
20052010201520202025
20302035204020452050
20552060206520702075
20802085209020952100
21052110211521202125
21302135214021452150
21552160216521702175
21802185219021952200
22052210221522202225
22302235224022452250
Error +
92.292.392.492.592.6
92.792.892.993.093.1
93.293.393.493.593.6
93.793.893.994.094.1
94.294.394.494.594.6
94,794.894.995.095.1
95.295.395.595.695.7
95,895.996,096.196,2
96.396.496.596.696.7
96.896.997.097,197.2
N208/N 232
Ratio
0.1028180,1030870.1033560.1036260,103895
0.1041660,1044350.1047040.1049740.105243
0.1055i40.1057830.1060530.1063220.106593
0,1068630.1071330,1074020.1076740.107944
0.1082140.1084860,1087560.1090260.109296
0.1095680.1098380.1101080,1103800.110652
0,1109220.1111940,1114650,1117380.112008
0,1122790.1125510,1128220.1130950.113366
0.1136370,1139o90.1141810,1144530,114724
0.1149960.1152690,1155400.1158140.116087
AgeNumber
ofyears
20052010201520202025
20302035204020452050
20552060206520702075
20802085209020952100
21052110211521202125
21302135214021452150
21552160216521702175
21802185219021952200
22052210221522202225
22302235224022452250
Error +
98,899,199,399.699.8
100,1100.310061008101,1
101.3101.5101,8102.0102.3
102.5102.8103.0103.3103.5
103.8104.0104.3104.5104.8
105.0105.2105.5105.7106.0
106.2106.5106.7107.0107.2
107.5107.7108,0108.2108.5
108.7108,9109.2109.4109.7
:.09.9110,2110.4110.7110.9
34 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY
2255-2500
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
"206/^238
Ratio
0.4142ii0.4153oo0,4163860.4174770.4185&50.4196580.4207470.4218400.4229320.4240260.4251210.4262i70.4273i30.4284090.4295o90.4306080,4317070.4328070.4339io0, 4350i20,4361i60,4372i90,4383250.4394300.440537
0.4416430.4427520.4438&20.4449710.4460820.4471930.4483070.4494i90.4505350.4516480.4527650.4538820.4549980,4561i70,4572360.4583570.4594790,4606o20.4617230,4628490.4639720.4650970.4662240.4673520,468478
AgeNumber
of years
22552260226522702275228022852290229523002305231023152320232523302335234023452350
235523602365237023752380238523902395240024052410241524202425243024352440244524502455246024652470247524802485249024952500
Error +
5.05.05.05.05.05.15.15.15.15.15.15.15.15.15,25.25.25.25.25.25,25.25.25.3
. 5,35.35.35.35.35.35.35.35.45.45.45.45.45.45.45.45.45.55.55.55.55.55.55.55.55.5
. N 207
Ratio
7.955067.998708.042548.086608,13088
8.175378.220o88.265oi8.310i48.355518.401io8.446918,492948.539i98.585678.632388.679328.726498.773878.821508.869368.917458.965779.014339.063i29.112i69.161439.210959.260709.310&99.360939.411429.462i69.513i39.564369.615849.667569.719559.771779.824269.877oo9.930oo9.98327
10.0367710,0905510.1446010.1989010.2534710.3083010.36340
7^235
AgeNumber
of years
225522602265227022752280228522902295230023052310231523202325233023352340234523502355236023652370237523802385239023952400240524102415242024252430243524402445245024552460.24652470247524802485249024952500
Error +
50.650.750,850,95X15X25X35X45X551.65X75X85X952.152.252.352,452.552.652.752.853,053.153.253.353.453.553.653.753.954.054.154.254.354.454.554.654,854.955.055.155.255.355.455.555.755.855.956.056.1
N 207/
Ratio
0.1394720.1398690.1402&90,1406690.1410710.1414740.1418790.1422850.1426930,1431o20.1435i20,1439230.1443370.1447510.1451670.1455840.1460030.1464230.1468440.1472&70.1476910.1481i80.1485440.1489730.1494030.1498350,1502680.1507030.1511390.1515770,1520i60.1524560,1528990.1533410.1537870.1542340.1546820,1551320.1555830,1560360.1564900.1569450.1574030.1578&20.1583220.1587840.1592480.1597i30,1601800,160649
^206
AgeNumber
of years
22552260226522702275228022852290229523002305231023152320232523302335234023452350
235523602365237023752380238523902395240024052410241524202425243024352440244524502455246024652470247524802485249024952500
Error
±
97.397.497.597.697.797.897.998.098.198.298,398.498.598.698.798.898,999,099,199.399,399,599.699.799.899.9
100,0100.1100.2100.3100.4100.5100.6100.7100.8100.910X0101,110X210X310X410X510X610X810X9102,0102.1102.2102.3102.4
N208/W 232
Ratio
0.1163600.1166320.1169040.1171760.1174500.1177220.1179950.1182&70,1185400.1188130.1190860.1193590.1196320.1199070.1201800.1204530.1207270.12lOoi0,1212740.1215480,1218220.1220950.1223690,1226430, 1229160.1231910.1234640.1237390.1240i40.1242880.1245620,1248370.1251130.1253870.1256610.1259360.1262io0.1264850.1267&00.127036
0.1273io0.1275850.1278&00.1281370,1284ii0.1286870.1289&30.1292*90.1295150.129790
AgeNumber
of years
22552260226522702275228022852290229523002305231023152320232523302335234023452350
23552360236523702375238023852390239524002405241024152420242524302435244024452450
2455246024652470247524802485249024952500
Error +
111.211X411X711X9112,1112.4112.6112.9113.1113,4113.6113.9114.1114.4114,6114.9115.1115.4115.6115.8nea116.3116.6116.8117.1117.3117.6117.8118.1118.3118.6118.8119.0119.3119.5119.8120.0120.3120.5120.812X012X312X512X8122.0122.3122.5122.7123.0123.2
TABLES FOR THE CALCULATION OF LEAD ISOTOPE AGES
2510-3000
35
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0.4707370.4729990.4752660.4775350,4798o60.4820830.4843630.4866440.4889330.4912220.4935i50.4958i30.4981i30.5004i80.5027260.5050370.5073520.5096710.5119920.5143i80.5166470.5189810.5213i60.5236560.5260oo0.5283490.5306980.5330520.5354io0.5377710.5401370.5425060.5448780.5472540.5496340.5520i70.5544060.5567960.5591900.5615880.5639930.5663970,5688050.5712160.5736350.5760550.5784790.5809070.5833390.585775
AgeNumber
of years
25102520253025402550256025702580259026002610262026302640265026602670268026902700271027202730274027502760277027802790280028102820283028402850286028702880289029002910292029302940295029602970298029903000
Error ±
5.65.65.65.65.75.75.75.75.75^85.85^85.85.95.95.95.95.96,06.06.06.06.16.16.16.16.16.26,26.26,26.36.36.36.36.36.46,46.46,46.56,56.56,56.56,66.66.66.66.7
^207
Ratio
10.4744210.5865010.6997010.8139910.9294011.0459411.1636111.282441X4024311,5235811.6459311.769471X8942112.020i912.1473712,2758112.4055012.5364612.6687012.8022212.9370613.0732113.2106913.3495313.4897013.6312513.7741713.9185114.0642614.2114114.360o214.510o614.6615914.8145914.9690815.1250815.2826015.4416715.6022915.7644715.9282616.0936116.2606116.4292316.5994916.7714316.9450217.1203417.2973717.476io
/^235
AgeNumber
of years
25102520253025402550256025702580259026002610262026302640265026602670268026902700271027202730274027502760277027802790280028102820283028402850286028702880289029002910292029302940295029602970298029903000
Error ±
56,356.556.857.057.257.457.757.958.158.358.658.859.059.259.559.759.960.160.460.660.86X06X36X56X76X962.262.462.662.863.163.363.563.764.064.264.464.664.965,165.365.565.866.066.266.466.666.967.167,3
N 207/N 206
Ratio
0.1615910.1625390.1634930.1644550.1654230.1663970.1673780.1683670.1693610.1703630.1713720.1723870.1734090.1744390.1754750.1765i90.1775700.1786280.1796940.1807670.1818470.1829350.1840300.1851330.1862440.1873610.1884880.1896220.1907640.1919130.1930710.1942360.1954io0.1965920.1977820.1989800.2001860.2014020.2026260.2038580.2050970.2063470.2076050.2088730.210148
0.2114320.2127260,2140280,2153400,216660
AgeNumber
of years
25102520253025402550256025702580259026002610262026302640265026602670268026902700271027202730274027502760277027802790280028102820283028402850286028702880289029002910292029302940295029602970298029903000
Error
±
102,6102.8103.0103.2103.4103.6103.8104.1104.3104.5104.7104,9105,1105.3105.5105.7106,0106.2106.4106.6106.8107.0107.2107.4107.7107.9108.1108.3108.5108.7108.9109,1109,4109.6109.8110.0110.2110,4110.6110.911X111X311X511X711X9112.1112.4112.6112.8113.0
N208/N 232
Ratio
0.1303410.1308930.1314440.1319970.1325500.1331040.1336570.1342io0.1347630.1353170.1358710.1364280.1369820,1375370,1380920.1386470.1392030.1397600.1403160.1408740.1414300.1419880.1425460.1431030,1436610.1442190.1447780.1453380.1458960.1464560.1470i60.1475750,1481360,1486950.1492570.1498i80.1503810.1509420.1515030.1520650.1526270.1531920.1537540.1543170.1548800.1554450.1560080.1565720.1571380.157704
AgeNumber
of years
251C252C253C254C255C256C257C258C259C26002610262026302640265026602670268026902700271027202730274027502760277027802790280028102820283028402850286028702880289029002910292029302940295029602970298029903000
Error +
123,7124.2124.7125.2125.7126,2126,7127,2127.7128.2128.7129.2129.6130.1130,613X113X6132.1132,6133.1133.6134.1134.6135.1135.6136.1136.5137.0137,5138.0138.5139.0139.5140.0140.514X014X5142.0142.5143,0143.5143.9144.4144.9145.4145.9146,4146.9147.4147,9
36 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY
3010-3500
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0.5882i30.5906560.5931030.5955530.5980o60.6004&40.6029280.6053930.6078&20.6103350.6128ii0.6152920.6177770.6202&60.6227570.6252550.6277520.6302560.6327&50.6352750,6377910.6403io0.6428330.6453600.6478910.6504250.6529&50.6555060.6580520.6606oo
0.6631550.6657140.6682760.6708430.6734120.6759850.6785640.6811480.6837330.6863230.6889i60.6915130.6941i40.6967210.6993300.7019440.7045610.7071830.7098080.712439
AgeNumber
of years
3010302030303040305030603070308030903100
31103120313031403150316031703180319032003210322032303240325032603270328032903300
3310332033303340335033603370338033903400
3410342034303440345034603470348034903500
Error ±
6,76.76.76,76.86.86.86.86.96.9
6.96.96.97.07.07,07.07.17.17.17.17.17.27.27,27.27.37.37.37.3
7.37.47.47.47.47.57.57.57.57.57.67.67.67.67,67.77.77.77.77.8
N 207/N 235
Ratio
17.6566117.8388518.02289182087418.39637
18.5858618.7771818,970 4 o19.1655019.3624819.5614119.7622719.965io20.1699220.3767120.5855520.7964121.0093521.224372X441462X660702X882o622.1056122.3313322.5592422.7894023.0217923.2564623.4934423.7327023.9743224.2182924.4646524.7134224.964&0
25.2182625.4743825.733oi25.994i826.2578726.5241626.7930327.0645527.3387327.6155527.895H28.1773728.4624128.7502429.04086
AgeNumber
of years
30103020303030403050306030703080309031003110312031303140315031603170318031903200321032203230324032503260327032803290330033103320333033403350336033703380339034003410342034303440345034603470348034903500
Error ±
67.567.868.068.268.468.768.969.169,369.669.870.070.270.570.770.97X171.47X67X872.072.372.572.772.973.273.473.673.874.174.374.574.775,075.275.475.675.876.176.376.576.777.077.277.477.677,978.178.378.5
^2077
Ratio
0.2179910.2193300.2206780.2220 3 70.2234040.2247820.2261&80.2275640.2289710.2303870.2318i40.2332490.2346960.2361520.2376190.2390950.2405830.2420810.2435890.2451080.2466380.2481780.2497290.2512920.2528650.2544490.2560440.2576510.2592700.2609oo0.2625410.2641930.2658570.2675330.269221
0,2709210,2726330,2743560.2760930.2778410.2796020.2813760.2831620,2849610.2867720.2885960.2904340.2922840.2941480,296024
//V206
AgeNumber
of years
301030203030304030503060307030803090310031103120313031403150316031703180319032003210322032303240325032603270328032903300
33103320333033403350
33603370338033903400
3410342034303440345034603470348034903500
Error
±
113.2113,4113.7113.9114.1
114.3114.5114.7115.0115.2115.4115.6115.8116.0116.3116.5116.7116.9117.1117,3117.6117,8118.0118.21184118,7118.9119.1119.3119,5119.8120,0120.2120.4120.6120.9121.112X312X512X712X9122.2122.4122.6122.8123.1123.3123.5123,7123.9
N208/N 232
Ratio
0.1582680,1588330.1593990.1599&60.1605310.1610980.1616&50.1622330.1628oo0.1633680.1639360.1645040.16507 20.1656420.1662ii0,1667800.1673490.1679200.1684900.1690600.1696310.1702030.1707740.1713460,1719i70.1724890.1730620.1736350.1742080.1747820.1753540.1759280.1765020.1770770.1776510.1782260.1788020.1793770.1799550.180530
0.1811060.1816830.1822600.1828390.1834150.1839920.1845710.1851480,1857270.186307
AgeNumber
ofyear?
301C302C303G304C305C306C307C308C309C310C
311C312 C313C314C315C316C317C318C319C320C321032203230324032503260327032803290330033103320333033403350336033703380339034003410342034303440345034603470348034903500
Error ±
148.4148.9149.4149.9150.4150.8151.315X8152.3152.8153.3153.8154.3154.8155.3155.8156.3156,8157.3157.7158.2158.7159,2159.7160.2160.7161.216X7162.2162.7163.2163.7164.2164.6165.1165.6166.1166.6167.1167.6168.1168.6169.1169,6170.1170.6171,117X5172.0172,5
TABLES FOR THE CALCULATION OF LEAD ISOTOPE AGES
3510-4000
37
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Ratio
0.7150730.7177120,7203530.7229970.725648
0.7283040.7309610.7336230.7362920.7389&1
0.7416370.7443160.7469980.7496860.752377
0.7550700.7577700.7604740,7631820.765894
0.7686io0.7713290,7740560.7767840.779517
0.7822540.7849960.7877400.7904890.793244
0.7960oi0.7987640.8015300.8043010.807077
0.8098570.8126410.8154300,8182220.8210i8
0.8238170.8266230.8294320.8322470.835065
0.8378870.8407150.8435460.8463820.849221
AgeNumber
of years
35103520353035403550
35603570358035903600
36103620363036403650
36603670368036903700
37103720373037403750
37603770378037903800
38103820383038403850
38603870388038903900
39103920393039403950
39603970398039904000
Error ±
7.87.87.87.87.9
7.97.97.98.08.0
8.08.08.08.18.1
8.18.18.28.28,2
8.28.28.38.38.3
8,38.48.48.48.4
8.48.58.58.58.5
8.68,68,68.68.6
8.78.78,78.78.8
8.88.88.88.88,9
N 207/N 235
Ratio
29.3343429.630&529.9299030.2320330.53715
30.8452631.1563331.4704831.7876632,10798
32.4314332.758oo33.0877933.4207833.75705
34.0966034.4394534.7856735.1352335.48826
35.8447336,2046436.568ii36,9350937.30569
37.6799238.0577638.4393338.8245939.21365
39.6065240.0031840.4037540.8082041,21664
41.6290742.0454942.4660242.890&243.3194 o
43.7523844.1895344.631oi45.0767545.52689
45,9814446.4403746.9038347.371 7 847.84434
AgeNumber
of years
35103520353035403550
35603570358035903600
36103620363036403650
36603670368036903700
37103720373037403750
37603770378037903800
38103820383038403850
38603870388038903900
39103920393039403950
396039703Q8039904000
Error ±
78,879.079.279.479.7
79.980.180,380.680.8
8X081.281.58X781.9
82.182.482.6 82.883.0
83.383.583.783.984.2
84.484.684.885.085.3
85.585.785.986.286.4
86.686.887.187.387.5
87.788.088.288,488.6
88.989.189.389.589.8
N 207/N206
Ratio
0.2979i40.2998170.3017350.3036660.3056io
0.3075680.3095400.3115270.3135260.315542
0.3175700.3196140,3216720.3237450.325833
0.3279360.3300530.3321860.3343340.336497
0.3386760.3408?!0.3430800.3453060.347548
0.3498060.3520800.3543710.3566780.3590oi
0,3613420.3636980.3660730.3684630.370871
0.3732960.3757390.3781990.3806770.383173
0.3856880.3882200.3907700.3933380.395925
0,3985320.4011550,4037990.4064610.409143
AgeNumber
of years
35103520353035403550
35603570358035903600
36103620363036403650
36603670368036903700
37103720373037403750
37603770378037903800
38103820383038403850
38603870388038903900
3910392039303940
Error +
124.2124.4124.6124.8125.0
125.3125.5125.7125,9126,2
126.4126.6126.8127,0127,3
127.5127,7127.9128.2128.4
128.6128.8129.0129.3129.5
129.7129.9130.2130.4130,6
130.813X113X313X5131.7
132.0132.2132.4132.6132.9
133,1133.3133.5133,8
3950 134.0
3960 134.23970 134.43980 134,73990 134.94000 135.1
N208/N232
Ratio
0.1868850.1874660.1880450.1886250.189206
0.1897850.1903660.1909470.1915300.192112
0.1926940.1932760,1938590.1944410.195023
- 0.1956070.1961920,1967770.1973590.197944
0.1985290.1991i40.1996990.2002870.200872
0.2014590.2020440.2026310.2032180.203806
0.2043930.2049820.2055710.2061590.206748
0.2073360.2079270.2085170.2091080.209697
0.2102880.2108790.2114700.2120610,212653
0,2132450.2138380.2144310.2150230.215616
AgeNumber
of years
35103520353035403550
35603570358035903600
36103620363036403650
36603670368036903700
37103720373037403750
37603770378037903800
38103820383038403850
38603870388038903900
3910
Error ±
173,0173.5174.0174.5175.0
175.5176.0176.5177.0177.5
178.0178.5178.9179,4179.9
180.4180.9181.418X9182.4
182.9183.4183.9184,4184.9
185,4185.8186.3186,8187.3
187.8188,3188.8189.3189.8
190.3190.819X3191.8192.3
192.73920 193.23930 193.73940 194.23950 194,7
3960 195,23970 195.73980 196,23990 196.74000 197.2
38 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY
4010-4500
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
N 206/N 238
Age
Ratio Numfber Errorof +
years
0.85206? 4010 8.9 0.8549i5 4020 8.9 0.857765 4030 8,9 0.860626 4040 9.0 0.863486 4050 9.00.866352 4060 9.0 0.869224 4070 9.0 0.872099 4080 9.0 0.874978 4090 9.1 0.877861 4100 9.10.880750 4110 9.1 0.883644 4120 9.1 0.886540 4130 9.2 0.889443 4140 9.2 0.892347 4150 9.20.895257 4160 9.2 0.898172 4170 9.2 0.901092 4180 9.3 0.9040i7 4190 9.3 0.906946 4200 9.30.909879 4210 9.3 0.9128i7 4220 9.4 0.915759 4230 9.4 0.918705 4240 9.4 0.921655 4250 9.40.9246i3 4260 9.4 0.927571 4270 9.5 0.930537 4280 9.5 0,933506 4290 9.5 0.936480 4300 9.50,939459 4310 9.6 0.942441 4320 9.6 0.945430 4330 9.6 0.948422 4340 9.6 0.951420 4350 9.60.9544i9 4360 9.7 0.957428 4370 9.7 0.960438 4380 9.7 0.963453 4390 9.7 0.966472 4400 9.80.969496 4410 9.8 0.972527 4420 9.8 0.9755&2 4430 9.8 0.978598 4440 9.8 0.981642 4450 9.90.984690 4460 9.9 0.987743 4470 9.9 0.9908oo 4480 9.9 0.993862 4490 10.0 0.996930 4500 10.0
^207/^35
AgeD,, Number Ratio Error
of +years
48.32153 4010 90.0 48.80331 4020 90.2 49.28987 4030 90.4 49.781i2 4040 90.7 50.27722 4050 90.950.778i7 4060 9U 5X28396 4070 9X3 51.79474 4080 9X6 52.31046 4090 9X8 52.83127 4100 92.053.357i7 4110 92.2 53,888i6 4120 92.5 54.42438 4130 92.7 54.96579 4140 92.9 55.51254 4150 93,156.06464 4160 93.4 56.62207 4170 93.6 57.185oi 4180 93.8 57.75338 4190 94.0 58.32736 4200 94.258,90696 4210 94.5 59.492i5 4220 94.7 60,083i2 4230 94.9 60.67980 4240 95.1 6X28238 4250 95.461.89085 4260 95.6 62.505i9 4270 95.8 63.12560 4280 96.0 63.752oi 4290 96.3 64.38459 4300 96,565.02336 4310 96.7 65.66830 4320 96.9 66.319&2 4330 97.2 66.97722 4340 97.4 67.64132 4350 97.668.31191 4360 97.8 68.98897 4370 98.1 69.67272 4380 98.3 70.36308 4390 98.5 7X06025 4400 98.77X76425 4410 99.0 72.47503 4420 99.2 73.19284 4430 99,4 73.91758 4440 99.6 74.64949 4450 99.975.38854 4460 100.1 76.13473 4470 100.3 76.88829 4480 100.5 77.649i4 4490 100.8 78.41750 4500 10X0
N 207/N206
AgeD . Number ~ Ratio . . Error
°f + years ~*
0,411844 4010 135> 0.414564 4020 135.6 0.417306 4030 135.8 0.420064 4040 136.0 0.422845 4050 136.20.425646 4060 136,5 0.428465 4070 136,7 0,431306 4080 136.9 0,434167 4090 137.2 0.437050 4100 137.40.439952 4110 137.6 0.442875 4120 137.8 0.445821 4130 138.1 0.448787 4140 138.3 0.451776 4150 138.5
0.454786 4160 138.7 0.457817 4170 139.0 0.460870 4180 139.2 0.463945 4190 139.4 0.467043 4200 139.60.470163 4210 139.9 0.473306 4220 140.1 0.476472 4230 140.3 0.479660 4240 140.6 0.482873 4250 140.80.486107 4260 14X0 0.489367 4270 14X2 0.492649 4280 141.5 0.495955 4290 14X7 0.499286 4300 14X90.502640 4310 142.2 0.506020 4320 142,4 0.509423 4330 142.6 0.512851 4340 142.8 0.516304 4350 143.10.519784 4360 143.3 0.523286 4370 143,5 0.5268i6 4380 143.8 0.530371 4390 144.0 0.533953 4400 144.20.537561 4410 144.4 0.541193 4420 144.7 0.544853 4430 144.9 0.548541 4440 145.1 0.552255 4450 14^40.555996 4460 145.6 0.559763 4470 145.8 0.563560 4480 146.0 0.567383 4490 146.3 0.571234 4500 146.5
N2 08/N2 3 2
AgeD Number Ratio Error
of +yearr
0,2162io 4010 197.7 0.216803 4020 198.2 0.217397 4030 198.7 0.217994 4040 199.2 0.218587 4050 199.60.219183 4060 200.1 0.219776 4070 200.6 0.220372 4080 20X1 0.220969 4090 201.6 0.221563 4100 202.1
0.222160 4110 202.6 0.222758 4120 203.1 0.223355 4130 203.6 0.223952 4140 204.1 0.224550 4150 204.60.225147 4160 205.1 0,225745 4170 205^6 0.226343 4180 206,1 0.226942 4190 206,5 0.227542 4200 207.00.228142 4210 207.5 0.228741 4220 208.0 0.229341 4230 208.5 0.229941 4240 209.0 0,230542 4250 209.50.231142 4260 210.0 0,231745 4270 210.5 0.232345 4280 211.0 0.232948 4290 21X5 0.233549 4300 212,00.234150 4310 212.5 0,234753 4320 213.0 0.235356 4330 213.5 0.235960 4340 213.9 0.236563 4350 214.40.2371&7 4360 214.9 0.237771 4370 215,4 0.238375 4380 215.9 0.238980 4390 216.4 0.239584 4400 216.90,240190 4410 217.4 0.240796 4420 217.9 0.241402 4430 218,4 0,2420o7 4440 218.9 0.2426i4 4450 219.40.243221 4460 219.9 0.243828 4470 220.4 0.244435 4480 220.8 0.245044 4490 22X3 0.245651 4500 22X8
TABLES FOR THE CALCULATION OF LEAD ISOTOPE AGES
4515-5250
39
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
N 206/N 238
Age
Ratio Nufer Errorof +
years
1.001538 4515 10,0 1006158 4530 10.0 1.010789 4545 10.1 1.015429 4560 10.1 1020080 4575 10.11024745 4590 10.2 1029416 4605 10.2 I0341oo 4620 10.2 1038795 4635 10.3 1043499 4650 10.31048218 4665 10.3 1052944 4680 10.4 1057683 4695 10.4 1062431 4710 10.4 1067192 4725 10.51.071963 4740 10.5 1,076746 4755 10.5 1081538 4770 10,6 1086344 4785 10.6 1091157 4800 10.61095986 4815 10.7 1100823 4830 10.7 1105671 4845 10.7 1110532 4860 10.8 1115402 4875 10.81120283 4890 10.8 1125177 4905 10.9 1130084 4920 10.9 l,1350oi 4935 10.9 1139928 4950 1101.144866 4965 HO 1149817 4980 11.0 1154777 4995 HI 1159751 5010 111 1164737 5025 11.11169733 5040 11.2 1174743 5055 112 1179759 5070 11.2 1184791 5085 113 1189836 5100 1131.194887 5115 11,3 1199953 5130 114 1.205033 5145 114 1210122 5160 114 1215222 5175 1151.220333 5190 115 1225459 5205 H5 1230598 5220 116 1.235744 5235 116 1240905 5250 11.6
^207/^35
AeeD Number Ratio Error
° f ± years
79.5840 4515 1013 80.7678 4530 1017 819688 4545 102.0 83.1876 4560 102.3 84,4243 4575 102.785.6790 4590 103.0 86.9524 4605 103.3 88.2443 4620 103.7 89.5553 4635 104.0 90.8854 4650 104.392.2351 4665 104.7 93.6047 4680 105.0 94.9943 4695 105.4 96.40 4 5 4710 105.7 97.8352 4725 106.099,2870 4740 106.4
100.7602 4755 106.7 102,2550 4770 107.0 I03.77i8 4785 107.4 105,3107 4800 107.7106.8723 4815 108.1 108.4569 4830 108.4 110.0647 4845 108.7 1116963 4860 109.1 113.35i6 4875 109.4115.03i4 4890 109.7 116.7358 4905 110.1 118.4652 4920 110.4 120.22o2 4935 110.7 122.0007 4950 1111123.80 7 5 4965 1114 125.6409 4980 1118 127.50ii 4995 112.1 129.3888 5010 112.4 13130 4 o 5025 112.8133.2474 5040 113,1 135.2195 5055 113.4 137,22o4 5070 113.8 139.2508 5085 114,1 14131io 5100 114.4143.40i3 5115 114.8 145.5226 5130 115.1 147.6748 5145 115.5 149.8588 5160 115.8 152.0748 5175 116.1154.3233 5190 116.5 156.6049 5205 116.8 158.92oo 5220 117.1 1612692 5235 117.5 163.6527 5250 117,8
W 207/W 206
Agen . Number ^ Ratio . Error
°f + years ~
0.577064 4515 146.9 0.582959 4530 147,2 0.5889i7 4545 147,5 0.594943 4560 147.9 0.601034 4575 148,20.607190 4590 148.6 0.6134i8 4605 148,9 0.619712 4620 149.3 0.626076 4635 149.6 0,6325ii 4650 150,00.6390i4 4665 150.3 0,645592 4680 150.7 0,652241 4695 1510 0.6589&5 4710 1513 0.6657&2 4725 15170,672634 4740 152.0 0.679582 4755 152.4 0.686608 4770 152.7 0.6937io 4785 153,1 0.700892 4800 153.40.708152 4815 153.8 0.715494 4830 154.1 0,7229i7 4845 154.5 0.730422 4860 154.8 0.7380io 4875 155.20,745683 4890 155.5 0,753441 4905 155.9 0.761283 4920 156,2 0.7692i4 4935 156.6 0.777233 4950 156,90.785341 4965 157.3 0.793539 4980 157.6 0.801829 4995 158.0 0,8l02io 5010 158.3 0,818684 5025 158.70.827252 5040 159.0 0.8359i5 5055 159.4 0.844678 5070 159.7 0,853536 5085 160.1 0.862491 5100 160,40,871550 5115 160,8 0,880708 5130 1611 0.889966 5145 1615 0,899330 5160 1618 0.908798 5175 162.20.918373 5190 162.5 0.928053 5205 162.9 0.937839 5220 163.2 0.947739 5235 163.6 0.957747 5250 163.9
N208/N232
AgeD Number ^ Ratio Error
of +years
0,246564 4515 222.6 0,247475 4530 223.3 0,248389 4545 224.0 0,249304 4560 224.8 0.250220 4575 225.50.251134 4590 226,3 0.252051 4605 227.0 0.2529&7 4620 227.7 0,253887 4635 228.5 0,254805 4650 229.20,255723 4665 230,0 0,256643 4680 230.7 0.257564 4695 2314 0.258486 4710 232.2 0,259407 4725 232.90.260330 4740 233.7 0,261252 4755 234,4 0,262175 4770 235.1 0.2631oo 4785 235.9 0.264026 4800 236,60.264951 4815 237.4 0.265879 4830 238,1 0.266806 4845 238.8 0.267734 4860 239.6 0.268662 4875 240.30.269592 4890 2411 0,270521 4905 2418 0.271451 4920 242.5 0.272383 4935 243.3 0.273316 4950 244.00.274247 4965 244.8 0,275182 4980 245.5 0.276115 4995 246.2 0.277050 5010 247.0 0,277985 5025 247.70,278921 5040 248.5 0.279858 5055 249.2 0,280795 5070 249.9 0,281734 5085 250.7 0,282673 5100 25140.283613 5115 252.1 0.284553 5130 252.9 0.285493 5145 253.6 0.286436 5160 254.4 0.287377 5175 255.10.288319 5190 255.8 0.289263 5205 256^6 0,2902 07 5220 257.3 0.291154 5235 258.1 0.2921oo 5250 258.8
40 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY
5265-6000
Geologic age, in millions of years, calculated from the atomic ratios of indicated isotopes
^206/^238
Age
Ratio Error of +
years
3,246076 5265 11,71.2512s 9 5280 11.71,2564s? 5295 1171.261664 5310 11.83,266883 5325 1X8X2721i6 5340 1X8X277361 5355 1X9X282616 5370 1X91.287885 5385 1X91.293166 5400 12.0X298458 5415 12.03,303764 5430 12.0X309080 5445 12.1X3144ii 5460 12.11,319752 5475 12.1X325105 5490 12.21.330471 5505 12,2X335850 5520 12.21.3412 4 3 5535 12.31.346645 5550 12.3
X352062 5565 12.31.357491 5580 12.4X362931 5595 12.41.368385 5610 12,43,373851 5625 12.51.379330 5640 12.5X384823 5655 12.51,390327 5670 12.6X395843 5685 1261.401373 5700 12.6X4069i5 5715 12.7X412469 5730 12,7X418041 5745 12,7X423620 5760 12.81,429214 5775 12.81,434819 5790 12.8X440439 5805 12.91.446073 5820 12.91.451718 5835 12.9X457377 5850 13.01.463050 5865 13.01.468733 5880 13,01.474434 5895 13,11.480143 5910 13.11.485867 5925 13.1X491604 5940 13.2X497355 5955 13.2X503120 5970 13.2X508897 5985 13.3X514686 6000 13.3
"2077*235
AgeD Number Ratio Error
of 4.years
166.0713 5265 118,1168.5255 5280 118.517X0157 5295 118.8173,5424 5310 119.2176.1064 5325 119.5178.7079 5340 119.8181.3477 5355 120.2184.0262 5370 120,5186.7440 5385 120,8189.5020 5400 12X2192.30o2 5415 12X5195.1398 5430 12X9198.02o8 5445 122.2200.9442 5460 122.5203.9108 5475 122.9206.9207 5490 123.2209.9750 5505 123,5213.0740 5520 123.9216.2185 5535 124,2219.40 94 5550 124.5222.6469 5565 124.9225.9323 5580 125.2229.2657 5595 125,6232.6480 5610 125.9236.0802 5625 126,2239.5627 5640 126.6243.09&5 5655 126.9246.6820 5670 127.2250.32o2 5685 127,6254.0120 5700 127.9257.7578 5715 128.226X5590 5730 128.6265.4157 5745 128.9269.3290 5760 129.3273.30oi 5775 129.6277.3292 5790 129.9281.4179 5805 130.3285.5662 5820 130.6289.7756 5835 130.9294.0470 5850 13X3298.3809 5865 13X6302.7788 5880 13X9307,24o9 5895 132.331X7686 5910 132.6316.3631 5925 133.0321.0249 5940 133.3325.7554 5955 133.6330.5550 5970 134.0335.4252 5985 134,3340.3672 6000 134.6
N 207/N 206
Age Number ,-, Ratio . Error
of +years
0,967868 5265 164.30.978103 5280 164,60,988449 5295 165.00,9989i3 5310 165.3X009496 5325 165.71.020194 5340 166.0X0310i4 5355 166.4X041955 5370 166.7I,0530i8 5385 167.1X064205 5400 167.41.075518 5415 167.8X086958 5430 168.1X098527 5445 168.51.110223 5460 168.93,122054 5475 169.2X1340i7 5490 169.63,1463.15 5505 169.91.158347 5520 170.3X170715 5535 170.6X183227 5550 17X0
X195876 5565 17X31.208669 5580 17X7X221606 5595 172.01.234687 5610 172.4X2479i8 5625 172.7X261296 5640 173,1X274825 5655 173.5X288506 5670 173.8X302343 5685 174.2X316335 5700 174,5X330485 5715 174.9X344797 5730 175^2X359264 5745 175.6X3739oo 5760 175.9X3887oo 5775 176,3X403668 5790 176.7X418805 5805 177.0X4341ii 5820 177.41.449591 5835 177,7X465247 5850 178.1X481078 5865 178.4X497092 5880 178.8X513282 5895 179.1X529659 5910 179.51.546222 5925 179.9X562972 5940 180.2X5799i2 5955 180.6X5970 4 i 5970 180.9X614366 5985 18X3X631891 6000 18X6
N208/N232
AgeD . Number _ Ratio Error
of +years
0.293046 5265 259.50,293992 5280 260.30,294939 5295 26X00.295890 5310 261,80.296838 5325 262,50.297788 5340 263.20.298738 5355 264.00.299689 5370 264.70.300642 5385 265.50.301595 5400 266.2
0.302547 5^15 266.90.303501 5^30 267,70.304456 5445 268.40.305413 5460 269.20.306369 5475 269.90.307324 5490 270.60.308282 5505 271,40.309240 5520 272.10.310201 5535 272.90.311160 5550 273,6
0.312119 5565 274.30.313080 5580 275.10.314042 5595 275.80.315005 5*10 276.50.315968 5*25 277.30.316932 5*40 278.00.317896 5*55 278.80.318862 5*70 279,50.319829 5685 280.20.320794 5700 28X00.321763 5715 28X70.322730 5730 282.50.323699 5745 283.20.324669 5760 283.90.325639 5775 284,70.326609 5790 285.40.327581 5805 286.20.328554 5820 286,90,329528 5835 287.60.3305oo 5850 288.4
0.331474 5865 289.10.332450 5880 289.90.333427 5895 290.60.334404 5910 29X30.335381 5925 292.10.336359 5940 292,80.337338 5955 293,60.338317 5970 294.30.339298 5985 295.00.340279 6000 295,8
U. S. GOVERNMENT PRINTING OFFICE: 1959 O 485342