| 深海沉积物10Be记录研究 |
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| 引用本文： | 沈承德.深海沉积物10Be记录研究[J].第四纪研究,1997,17(3):203-210. |
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| 作者姓名： | 沈承德 |
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| 作者单位： | 中国科学院广州地球化学研究所!广州，510640 |
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| 摘 要： | DSDP519钻孔10Be测定结果表明，在B／M，M／G两地磁极性倒转期间，10Be产生率均约增加20％。DSDP519孔δ10Be曲线与DSDP502孔δ18O曲线具有明显的正相关关系。CT85－5钻孔10Be曲线在34000±3000aB．P存在明显的峰，峰值比正常值高出2．5倍，9Be，Zn变化曲线中均未观察到此峰，与Vostok冰芯10Be峰在时间上属于同期。这进一步说明了此时期内10Be浓度增加是全球性的，只能归因于10Be产生率的增加。Raisbeck峰讯号可以成为某些储存库精确时标。
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| 关 键 词： | 深海沉积物 10Be |
| 收稿时间： | 1997-05-18 |
| 修稿时间： | 1997-05-28 |
10Be IN DEEP SEA SEDIMENTS |
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| Shen Chengde.10Be IN DEEP SEA SEDIMENTS[J].Quaternary Sciences,1997,17(3):203-210. |
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| Authors: | Shen Chengde |
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| Institution: | Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 |
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| Abstract: | DSDP Site 519 is located in the central South Atlantic, 26°8.20′S, 11°39.97′W with water depth 3 769m. 10Be - CaCO3, correlation of DSDP site 519 shows that 10Be is carried mainly by the non - CaCO3 phases of the sediments, such as clay minerals and feldspars. There is a positive correlation with regressive coefficient 0.85 between 10Be and 9Be in the sediments of DSDP519. The average value of 10Be / 9Be is about 5 × 10-8 within the range of 10Be / 9Be ratio for deep ocean water. 10Be and 9Be come close to a constant equilibrium between the deep ocean water and sinking sediment particles. Relative increases of 20% of 10Be / 9Be ratio are observed in the vicinity of the geomagnetic reversals, B / M and M / G. There is a reasonable good positive cormlation between δ10Be curve of DSDP site 519 and δ18O curve of DSDP site 502.Higher δ10Be (δ10Be maximum) corresponds to more positive δ18O (δ18O maximum).The 10Be / 9Be ratio during glacial, i. e. positive δ18O period, are higher than their average value. Three probable hypotheses can be brought forward to explain the glacial to interglacial differences in the beryllium isotope ratio:（1） The variation of solar activity modulate the intensity of cosmic rays impinging on the earth atmosphere,thus altering the 10Be production rate; （2） Changes in erosional input of 9Be between glacial and interglacial period; （3） The variation in atmospheric cireulation could be responsible for difference in latitudinal 10Be fall out, and changs in oceanic cireulation could result in different distribution of the Be isotopes.Yiou et al. 16] and Raisbeck et al. 17] reported that the 10Be concentration in Vostok ice core, Antanica, displays an increase by a factor of two at 35 000 a B.P.,which is called Raisbeck Peak Event. There is the peak at 35 000 a B.P. only in 10Be curve but not in SO4, δ18O, δD curves. The Raisbeck Peak can only be explained by the increase of 10Be production rate. The Mediterranean sediment core CT85-5 is located in the Tyrrhenian Sea at a water depth of 2 833m. There is a pronounced peak of 2.5 times of the average value for 10Be profile, but not for 9Be and Zn profile at 34 000 ± 3 000 aB.P. The stratigraphic position of 10Be peak is between two tephra layers originated from two volcanic eruptions, Campanian Ignimbrite and Citara,dared by K - Ar, 40Ar - 39Ar and 14C methods. This peak is similar to the increase in the 10Be concentration observed in Vostok ice core at the same age. The present results support the view of a well defined global enhancement of 10Be flux, related to an increase of the production rate, but not to a redistribution of the 10Be fallout between different archives. All cosmogenic radioisotopes with appropriate half - lifes and production rates should show a peak in the same region. All archives recording with a sufficient time resolution should contain this signal in the atmospheric fallout.Therefore this 10Be peak provides a unique relative time marker for the archives.The low mobility of beryllium once it has become attached to mineral surfaces has led to the use of 10Be to stUdy marine sedimentation rates, Mn - nodule growth rates and subduction pathways in are volcanism. Nedules were found to grow at several millimeters per million year by the measurements of 10Be. By measuring the decay of 10Be in deep sea sediments it was determined that pelagic sediments were deposited at the rate of several millimeters per 1 000 years. |
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| Keywords: | deep sea sediments ~(10)Be |
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