The Geological
Timescale Versus Radiometric Dating
By
Paul Nethercott
November 2014
The Cryptic Period
4,567 To 4,600 Million Years Ago
1. Pb-Pb Dating Constraints,
Geochimica et Cosmochimica Acta, 2007, Volume 71, Pages 1583 - 1604
|
Pb206/Pb207 |
Pb206/Pb207 |
Pb206/Pb207 |
|
5,379 |
5,100 |
4,971 |
|
5,359 |
5,082 |
4,969 |
|
5,344 |
5,082 |
4,955 |
|
5,336 |
5,077 |
4,937 |
|
5,334 |
5,073 |
4,935 |
|
5,333 |
5,056 |
4,934 |
|
5,325 |
5,043 |
4,933 |
|
5,321 |
5,035 |
4,930 |
|
5,296 |
5,035 |
4,923 |
|
5,267 |
5,030 |
4,919 |
|
5,259 |
5,029 |
4,917 |
|
5,258 |
5,029 |
4,915 |
|
5,250 |
5,023 |
4,898 |
|
5,245 |
5,022 |
4,882 |
|
5,244 |
5,020 |
4,877 |
|
5,244 |
5,019 |
4,875 |
|
5,238 |
5,018 |
4,856 |
|
5,235 |
5,016 |
4,828 |
|
5,215 |
5,015 |
4,800 |
|
5,210 |
5,008 |
4,800 |
|
5,193 |
5,000 |
4,793 |
|
5,185 |
4,997 |
4,783 |
|
5,166 |
4,991 |
4,774 |
|
5,133 |
4,981 |
4,769 |
|
5,129 |
4,977 |
4,755 |
|
5,128 |
4,976 |
4,746 |
|
5,120 |
4,974 |
4,740 |
|
5,106 |
4,972 |
4,731 |
|
5,102 |
4,971 |
4,716 |
|
5,101 |
4,971 |
4,713 |
2. Resolution Reveals New Problems,
Geochemica Et Cosmochemica Acta, 2009, Volume 73, Pages 5212 - 5223
|
Potential Problem |
Level of Awareness and Suggested Actions |
|
1 |
The most important. |
|
Presence of non-radiogenic Pb of |
Recognized by most of the community. |
|
unknown isotopic composition |
Better methods for removal of non-radiogenic Pb are required. |
|
|
|
|
2 |
Important and common |
|
Deviations from closed system evolution |
Requires monitoring U–Pb concordance and |
|
(loss of Pb, gain or loss of U). |
studying distribution of U and radiogenic Pb. |
|
|
|
|
3 |
Important and common |
|
Misidentification of the processes that |
Requires studying distribution of U and radiogenic Pb. |
|
start or reset the isotopic clocks. |
Improving experimental reference data set for element migration caused |
|
|
by diffusion, alteration and shock, and linking isotopic dating |
|
|
to the studies in mineralogy and petrology of meteorites. |
|
|
|
|
4 |
Important |
|
Analytical problems such as fractionation, |
Problems are widely recognized. |
|
instrument-specific, and blank subtraction. |
Ongoing analytical developments help to reduce them. |
|
|
|
|
5 |
Potentially important |
|
Fractionation of radiogenic Pb isotopes |
Recognized by some ‘‘terrestrial” geochronologists. |
|
induced by leaching of alpha recoil tracks. |
Less known to meteoriticists. |
|
|
Detailed experimental studies are required |
|
|
to understand the nature and extent of fractionation. |
|
|
|
|
6 |
Unlikely but not impossible |
|
Variations in the 235U/238U ratio. |
Variations in terrestrial rocks are recently discovered, |
|
|
not observed in meteorites so far. |
|
|
Monitoring 235U/238U ratio is desirable. |
|
|
|
|
7 |
Insignificant for most studies |
|
Uncertainties in the half lives of 238U and 235U. |
New precise determinations of half lives are desirable but not crucial. |
|
|
|
|
8 |
Insignificant for most studies |
|
Deviations of the 234U/238U ratio |
Further improvement in the models of r-process. |
|
from secular equilibrium. |
Experimental simulation of asteroidal alteration with subsequent |
|
|
U-series analysis are desirable but not crucial |
3. Group IVB Iron Meteorites,
Geochimica et Cosmochimica Acta, Volume 72 (2008) Pages 2198–2216
|
187Os/188Os |
187Os/188Os |
|
695 |
-14 |
|
690 |
-132 |
|
688 |
-148 |
|
688 |
-152 |
|
682 |
-170 |
|
680 |
-170 |
|
678 |
-228 |
|
537 |
-228 |
|
537 |
-271 |
|
76 |
-302 |
4. Speculations About The Age Of The Earth,
Earth and Planetary Science Letters, Volume 47 (1980) Pages 370-382
|
207Pb/206Pb |
207Pb/206Pb |
207Pb/206Pb |
|
5,204 |
5,179 |
5,057 |
|
5,300 |
5,173 |
5,056 |
|
5,272 |
5,170 |
5,056 |
|
5,270 |
5,166 |
5,054 |
|
5,254 |
5,164 |
5,053 |
|
5,254 |
5,164 |
5,052 |
|
5,251 |
5,157 |
5,051 |
|
5,245 |
5,148 |
5,044 |
|
5,243 |
5,145 |
5,022 |
|
5,233 |
5,137 |
5,021 |
|
5,221 |
5,128 |
5,018 |
|
5,219 |
5,102 |
4,982 |
|
5,214 |
5,101 |
4,982 |
|
5,203 |
5,076 |
4,976 |
|
5,200 |
5,074 |
4,962 |
|
5,197 |
5,071 |
4,962 |
|
5,197 |
5,070 |
4,919 |
|
5,181 |
5,070 |
4,828 |
|
5,180 |
5,063 |
4,374 |
5. Ages Of Basaltic Achondrites,
Geochimica et Cosmochimica Acta, Volume 61, No. 8, pp. 1713-1731, 1997
|
Pb207/Pb206 |
Pb207/Pb206 |
Pb207/Pb206 |
|
5,135 |
4,961 |
4,665 |
|
5,096 |
4,960 |
4,619 |
|
5,094 |
4,950 |
4,613 |
|
5,081 |
4,929 |
4,595 |
|
5,064 |
4,929 |
4,586 |
|
5,057 |
4,927 |
4,574 |
|
5,043 |
4,921 |
4,558 |
|
5,029 |
4,907 |
4,557 |
|
5,021 |
4,887 |
4,553 |
|
5,018 |
4,855 |
4,551 |
|
4,999 |
4,849 |
4,530 |
|
4,997 |
4,801 |
4,525 |
|
4,995 |
4,757 |
4,515 |
|
4,985 |
4,751 |
4,505 |
|
4,983 |
4,744 |
4,499 |
|
4,978 |
4,733 |
4,485 |
|
4,976 |
4,716 |
4,479 |
|
4,972 |
4,716 |
4,458 |
|
4,970 |
4,686 |
4,371 |
|
4,964 |
4,670 |
|
6. History Of The Pasamonte Achondrite,
Earth and Planetary Science Letters, Volume 37, 1977, Pages 1-12
|
206Pb/238U |
207Pb/235U |
207Pb/206Pb |
208Pb/232Th |
87Rb/86Sr |
|
5,694 |
5,032 |
4,573 |
14,800 |
6,674 |
|
5,597 |
4,806 |
4,963 |
8,627 |
6,169 |
|
5,336 |
4,784 |
4,912 |
4,922 |
6,102 |
|
4,907 |
4,663 |
4,709 |
4,678 |
5,771 |
|
4,903 |
4,646 |
4,664 |
4,160 |
4,984 |
|
4,874 |
4,645 |
4,572 |
3,597 |
4,671 |
|
4,814 |
4,645 |
4,555 |
3,549 |
4,451 |
|
4,522 |
4,536 |
4,542 |
570 |
4,437 |
|
4,500 |
4,523 |
4,535 |
295 |
3,903 |
|
3,390 |
4,421 |
4,534 |
-9,600 |
3,903 |
|
3,380 |
4,136 |
4,534 |
-10,700 |
3,738 |
|
3,290 |
4,061 |
4,534 |
3,738 |
|
|
3,215 |
4,014 |
4,520 |
3,307 |
|
|
2,953 |
3,955 |
4,519 |
2,869 |
|
|
1,851 |
3,419 |
4,515 |
2,412 |
|
|
1,798 |
3,396 |
4,510 |
||
|
1,477 |
3,161 |
4,484 |
||
|
377 |
1,786 |
4,468 |
||
|
376 |
1,784 |
4,457 |
||
|
296 |
1,724 |
4,454 |
||
|
277 |
1,644 |
4,454 |
||
|
103 |
865 |
4,440 |
7. Single grain (U-Th)/He Ages, Acapulco Meteorite,
Earth and Planetary Science Letters, 2003, Volume 209, Pages 323 - 336
|
U/Th |
|
4,909 |
|
4,839 |
|
4,839 |
|
4,786 |
|
4,779 |
|
4,775 |
|
4,631 |
|
4,003 |
|
3,704 |
|
3,253 |
|
3,128 |
|
1,452 |
References
1. Pb-Pb Dating Constraints, Geochimica et Cosmochimica Acta, 2007, Volume 71, Pages 1583 - 1604
2. Resolution Reveals New Problems, Geochemica Et Cosmochemica Acta, 2009, Volume 73, Pages 5212 - 5223
3. Group IVB iron meteorites, Geochimica et Cosmochimica Acta, Volume 72 (2008) Pages 2198–2216
4. Speculations About The Age Of The Earth, Earth and Planetary Science Letters, Volume 47 (1980) Pages 370-382
5. Ages Of Basaltic Achondrites, Geochimica et Cosmochimica Acta, Volume 61, No. 8, pp. 1713-1731, 1997
6. History Of The Pasamonte Achondrite, Earth and Planetary Science Letters, Volume 37, 1977, Pages 1-12
7. Single grain (U-Th)/He ages, Acapulco meteorite, Earth and Planetary Science Letters, 2003, Volume 209,
Pages 323 - 336