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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Response of beryllium and radiogenic isotope rations in Northern Atlantic Deep Water to the onset of northern hemisphere glaciation
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Response of beryllium and radiogenic isotope rations in Northern Atlantic Deep Water to the onset of northern hemisphere glaciation

机译：北大西洋深水中铍和放射性同位素比值对北半球冰期开始的响应

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摘要

We present time-corrected ratios of cosmogenic ~(10)Be to continent-sourced ~9Be from two Fe-Mn crusts located in the northwest Atlantic in the vicinity of the origins of Northern Atlantic Deep Water (NADW). These initial ~(10)Be/~9Be ratios represent those of the ambient seawater at the time of crust deposition and are constant through the last 7 Ma. Previously published isotope records of radiogenic Nd and Pb isotopes in these crusts show a decrease in #epsilon#_(Nd) and an increase in ~(206)Pb/~(204)Pb over the last 5 Ma. These changes are consistent with a gradual increase in the strength of NADW production, an increase in the Labrador Sea component of NADW, or an increased erosional input into the Labrador Sea. Since the residence time and thus the advective length scales of dissolved Be in deep water lie between those of Nd and P b, records of ~(10)Be/~9Be should, contrary to what has been observed, vary in phase with those of Nd and Pb if these variations are accounted for by changes in paleo-circulation. The observed variations in radiogenic Nd and Pb isotopes are therefore most likely to be explained with an increase in the flux of terrigenous matter in the area of the Labrador Sea, which was possibly associated with ice rafting and selective leaching of Pb isotopes. An increase of the Labrador Sea component that contributes to NADW is also a possibility, but based on the ~(10)Be/~9Be data presented here large-scale changes in the thermohaline circulation can be discounted as cause for the radiogenic tracer variations.
机译：我们提出了经过时间校正的宇宙成因〜（10）Be与源自大陆的〜9Be的比率，该比率来自位于北大西洋深水（NADW）起源附近的西北大西洋的两个Fe-Mn地壳。这些初始〜（10）Be /〜9Be比代表地壳沉积时周围海水的比值，并且在最后7 Ma内都是恒定的。这些地壳中放射性Nd和Pb同位素的先前公布的同位素记录显示，在过去的5 Ma中，＃epsilon #_（Nd）降低，〜（206）Pb /〜（204）Pb升高。这些变化与NADW生产强度的逐步增加，NADW的拉布拉多海部分的增加或对拉布拉多海的侵蚀性输入的增加相一致。由于溶解态Be在深水中的停留时间以及对流长度尺度位于Nd和P b之间，因此〜（10）Be /〜9Be的记录与所观察到的相反，应该与如果这些变化是由古循环的变化引起的，则为Nd和Pb。因此，最有可能用拉布拉多海地区陆源物质通量的增加来解释放射源Nd和Pb同位素的变化，这可能与漂流和Pb同位素的选择性浸出有关。也可能增加导致NADW的拉布拉多海成分，但是根据此处提供的〜（10）Be /〜9Be数据，可以忽略热盐循环中的大规模变化，因为这是放射性示踪剂变化的原因。

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