Cosmogenic 10 Be and 26 Al in marine sediments

Amin, Basri; Kharkar, D.P.; Lai, Derrick Y.F.

doi:10.1016/0011-7471(76)90906-2

Cited by 13 publications

(8 citation statements)

References 17 publications

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“…The number of atoms of '0Be in a volume v cm3 of ocean sediments is therefore no = 1.5 x 10-2 -e-t/2.2x106 = 1.6 x 1O10 v (sols) e -t12.2x 106 where s is the sedimentation rate, t is the age of the sediment in years, and SO = 3 x 10-5 cm/year (a typical deepsea value for s). The number of decays per minute from a sample ofrock is dno = 0.014v(sols)et22xl0l dt Despite such extremely low decay rates, 1"Be has been used in studies of both seafloor spreading (12) and manganese nodule formation (13). Its usefulness derives partially from the extreme rarity of ordinary beryllium in sediment, approximately 3 x 10-6 by weight (14); by chemically extracting the beryllium from the sediment, the activity per gram of material is increased by a factor of 3 x 105.…”

Section: Beryllium-10 Detectionmentioning

confidence: 99%

Radioisotope Dating with a Cyclotron

Muller

1977

Science

318

119

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By considering radioisotope dating as a problem in trace element detection, and by using the cyclotron as a high-energy mass spectrometer for this purpose, we have shown that one can greatly increase the maximum age that can be determined while simultaneously reducing the size of the sample required. The cyclotron can be used to detect atoms or simple molecules that are present at the 10(-16) level or greater. For (14)C dating one should be able to go back 40,000 to 100,000 years with 1- to 100-mg carbon samples; for (10)Be dating, 10 to 30 million years with 1-mm(3) to 10-cm(3) rock samples; for tritium dating, 160 years with a 1-liter water sample. The feasibility of the technique has been demonstrated experimentally by measuring the tritium/deuterium ratio in a sample 24 years old. For samples many half-lives old, the fractional error in the age is small even if rates of production or deposition of the isotopes. Although cyclotrons are expensive to build, their operating costs are relatively low. If several samples are dated per hour the cost per date may not be substantially higher than it is today for decay dating. There are already more than 50 cyclotrons in operation which have the potential to do radioisotope dating, and their application to important problems of dating and trace element analysis should prove very fruitful.

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Section: Beryllium-10 Detectionmentioning

confidence: 99%

Radioisotope Dating with a Cyclotron

Muller

1977

Science

318

119

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“…At X -3 x 10 -2 pc, the +20% fluctuations in wH give a measure of the time averaged variations and are consistent with cosmic-ray produced activities in meteorites (14) . Shorter term variations on the other hand would be larger and could be detectable in the Be 10 activities in deep-sea sediments (15,16) 2. E.N.…”

Section: Statistical Discrete-source Model Of Local Cosmic Raysmentioning

confidence: 99%

Statistical Discrete-Source Model of Local Cosmic Rays

1970

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“…21 The chronology is again, of course, directly dependent on the 10 Be half-life, as well as the assumed nitrogen production cross section mentioned earlier (the neutron-induced reaction probably being the dominant process in this case also).…”

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confidence: 85%

Half-Life ofBe10

Yiou

Raisbeck

1972

Phys. Rev. Lett.

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analysis of (6b) shows that for a 4-0, a continuous displacive transition will occur at some X c (a) with X c (a) an increasing function of a. An interesting feature of this instability-driven transition is that the transition becomes increasingly sharp as a -0. Thus, if this were used to model a real physical system, a case could occur in which it would be impossible experimentally to determine that the transition was not first order. The results for (6b) are as shown in Table I. In conclusion, a clearer picture of the transition found in Ref. 4 is now available. In the absence of a symmetry-breaking term there should be no transition. In the presence of one (which could be implicitly introduced through the MFA), there should be a second-order transition. These results are for an idealized model. In a real, physical system, there should be at least a weak symmetry-breaking term. Then, since the transition is of the instability-driven type (with the instability of the Coulomb lattice providing an effective "hump" for the TO mode) there would be a sharp second-order transition with almost a first-order character. If this were accompanied by, for example, a lattice distortion, the transition could be a real, first-order transition.Cosmogenic radionuclides having very long half-lives can be useful dating tools in a number of astrophysical, geophysical, and cosmochemical problems. One of the most prominent of such species is the nuclide 10 Be, which has significant applications in studying the history of cosmic rays, 1 meteorites, 2 lunar samples, 3 marine sediments, 4 and polar deposits. 5 The generally accepted 6 half-life of 10 Be is (2.7 ±0.4)xi0 6 yr, a value based on two separate experiments carried out more than 20 years ago. 7, 8 We have become interested in the question of the accuracy of this number because of its importance in trying to "date" cosmic-ray ages. 1 Although we had no reason to suspect a large error Thus, the first-order character of either the MFA or SPA treatment of the instability-driven transition should not be considered spurious, but rather a strong indication of the inherent instability of the system.We are especially appreciative of a critical examination of our results by W. J. Camp.Any quartic Hamiltonian with a single degree of freedom can be scaled to the form (6). This is also the region where k B T is of the order of the depth of one of the minima of the effective doublewell potential associated with the long-wave length optic mode.in the accepted value, we felt its widespread use warranted an attempt to reduce the error limits. While we have not yet succeeded in that goal, we have found a value which is in strong disagreement with the older number, and which should have important implications in a number of fields of study.The two essential quantities in the determination of any half-life which is too long to be followed directly are the decay rate and the number of atoms of the decaying species, Usually the former can be measured directly, while the latter is obtained by a ma...

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Cosmogenic 10 Be and 26 Al in marine sediments

Cited by 13 publications

References 17 publications

Radioisotope Dating with a Cyclotron

Radioisotope Dating with a Cyclotron

Statistical Discrete-Source Model of Local Cosmic Rays

Half-Life ofBe10

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