Dating Very Young Submarine Basalts
From: Rubin, K.H., Macdougall, J.D. and Perfit, M.R. (1994)
210Po-210Pb dating of recent volcanic eruptions on the
sea floor, Nature, 368, 841-844.
This page describes results of the inaugural application of the 210Po-210Pb dating technique to dating mid-ocean ridge eruptions using basalts from 9º50'N on the East Pacific Rise (Rubin et al., Nature 1994). The method itself is described on the 210Po-210Pb dating. page. Basically, one monitors the rate of change of 210Po with time in a lava once it is sampled, to determine the date of eruption, when the Po in the lava was degassed. This dating technique was used to determine the dates of very recent eruptive activity at 9º50'N on the East Pacific Rise (EPR), where it can be argued that the first observations of a deep submarine eruption were made by humans. The dates are depicted on the calendar diagram below. Eruption ages resulted in the following interpretations: | |
Figure 1 (above) Colored bars plotted versus calendar time represent our best-estimate of the time of the eruption for the various EPR basaltsamples we analyzed. The smaller bars show the error in the estimation of the maximum ages for this particular sample set. The inset at the top of the figure gives relevant details of these time bars. The sample data used to calculate these ages is given further below.
Figure 2 (right) 4 year time series of a site on the new lava flow and associated vent fauna (1991-1994). The first year shows baterial floc in the water above the flow, the second year shows a young flow largely devoid of life, and the two subsequent years show increased tube worm colonization/growth. Figure courtesy of Mike Perfit, U. Florida |
|
9°50'N EPR - 210Po Data and Eruption Ages
Sample |
Collection Date |
Location |
Aliquot Number |
Analysis Date |
Total Mass |
Aliquot Mass |
210 Po |
210 Pb |
Eruption Window |
|
|
|
Lat N |
Long W |
|
|
(g) |
(g) |
(dpm/g) |
(dpm/g) |
|
2392-9-G |
5/27/91 |
9°50.6' |
104°17.5' |
1 |
8/15/91 |
8.056 |
2.094 |
0.081 ± 0.008 |
0.117 ± 0.006 |
30 Dec 1990 to 25 Feb 1991 |
|
2 |
11/3/91 |
|
1.609 |
0.092 ± 0.010 |
|
||||
3 |
1/27/92 |
|
1.270 |
0.102 ± 0.013 |
||||||
4 |
5/31/92 |
|
1.268 |
0.107 ± 0.019 |
||||||
5 |
1/15/93 |
|
1.772 |
0.114 ± 0.011 |
||||||
2392-9-WR |
5/27/91 |
9°50.6' |
104°17.5' |
1 |
9/12/91 |
10.238 |
3.409 |
0.107 ± 0.009 |
0.115 ± 0.006 |
--- |
|
2 |
11/7/91 |
|
1.905 |
0.108 ± 0.012 |
|
||||
3 |
5/31/92 |
|
0.993 |
0.111 ± 0.018 |
||||||
4 |
6/21/93 |
|
1.468 |
0.115 ± 0.011 |
||||||
2372-1-G |
4/23/91 |
9°50.6' |
104°17.5' |
1 |
9/23/91 |
4.397 |
1.574 |
0.082 ± 0.008 |
0.119 ± 0.006 |
25 Feb to 23 April 1991 |
|
2 |
11/18/91 |
|
0.765 |
0.088 ± 0.015 |
|
||||
3 |
5/29/92 |
|
0.672 |
0.109 ± 0.025 |
||||||
4 |
1/22/93 |
|
1.473 |
0.115 ± 0.014 |
||||||
2363-7-G |
4/14/91 |
9°50.6' |
104°17.6' |
1 |
1/3/92 |
3.191 |
1.227 |
0.082 ± 0.011 |
0.097 ± 0.005 |
24 Jan to 22 Mar 1991 |
|
2 |
5/29/92 |
|
0.951 |
0.090 ± 0.012 |
|
||||
3 |
2/15/93 |
|
1.008 |
0.095 ± 0.013 |
||||||
2504-1-G |
3/12/92 |
9°50.3' |
104°17.5' |
1 |
6/11/92 |
3.032 |
1.240 |
0.077 ± 0.011 |
0.114 ± 0.005 |
2 Nov to 29 Dec 1991 |
|
2 |
3/12/93 |
|
0.975 |
0.105 ± 0.019 |
|
||||
2497-1b-G |
3/5/92 |
9°53.3' |
104°17.9' |
1 |
6/11/92 |
2.146 |
0.834 |
0.079 ± 0.012 |
0.145 ± 0.007 |
7 Jan to 5 Mar 1992 |
|
2 |
6/21/93 |
|
1.302 |
0.135 ± 0.015 |
|
[
KenChron home page |
Isotope Lab home page |
SOEST home page]