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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 >~(40)Ar/~(39)Ar dating of latest Pleistocene (41 ka) marine tephra in the Mediterranean Sea: implications for global climate records
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~(40)Ar/~(39)Ar dating of latest Pleistocene (41 ka) marine tephra in the Mediterranean Sea: implications for global climate records

机译：地中海地区最新更新世（41 ka）海洋特非拉的〜（40）Ar /〜（39）Ar年代：对全球气候记录的影响

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Fifty-one ~(40)Ar/~(39)Ar laser heating analyses of sanidine crystals in the C-13 tephra layer, recovered out of a piston core raised from 3000 m depth in the Tyrrhenian Sea, yielded apparent ages between 25 and 112 ka. Twenty-four of these measurements define an age probability maximum and generate an isochron of 41.1 ± 2.1 ka (2σ) with a ~(40)Ar/~(36)Ar intercept of 288 ± 21 that is indistinguishable from the modern atmosphere. However, the entire population is skewed toward older apparent ages with smaller peaks at 48 ka, 55 ka, 67 ka, and 110 ka. The composition of glass shards in the C-13 tephra overlaps that of the SiO_2-rich phase of the 150 km~3 Campanian Ignimbrite which erupted from the Campi Flegrei caldera 130 km northwest of the core site. Although the 41.1 ± 2.1 ka isochron is ～15% older than K-Ar and ~(14)C ages for the Campanian Ignimbrite, it is indistinguishable from recent ~(40)Ar/~(39)Ar age determinations. The Campanian Ignimbrite eruptions were also chemically similar to, and correlated with, the Y-5 ash layer - the most voluminous and widely dispersed the Pleistocene tephra in the Mediterranean region. The age of the Y-5 layer was constrained originally at 38.0 ± 2.5 ka on the basis of astronomical dating of O-isotope stages. The ~(40)Ar/~(39)Ar ages, astronomical dating, plus chemical similarities permit correlation of the C-13 tephra layer with both the Campanian Ignimbrite and the Y-5 tephra layer. The older ages preserved in the C-13 tephra layer may reflect xenocrysts incorporated during the explosive eruption accompanying collapse of the Campi Flegrei caldera 41 ka. The C-13 tephra layer is correlated with a ~(10)Be peak in an adjacent marine core, O-isotope stage 3.12, and immediately preceded a cooling episode corresponding to Heinrich even 4, thus the age of these features is constrained by radioisotope dating. The 41 ka peak in ~(10)Be deposition is a global phenomenon whose age matches that of the Laschamp geomagnetic excursion. Thus, our results provide a new tie point among several polar ice core and marine proxy records of paleoclimate during the past 50 kyr. Precise age information, independent of radiocarbon dating, can be recovered from latest Pleistocene marine tephra using the ~(40)Ar/~(39)Ar laser heating method, despite the presence of multiple components that may have been incorporated during or after its deposition.
机译：从第勒尼安海从3000 m深度升起的活塞芯中回收的C-13特非拉层中的山梨酸晶体的51〜（40）Ar /〜（39）Ar激光加热分析112 ka。其中的二十四个测量值定义了年龄概率最大值，并产生了41.1±2.1 ka（2σ）的等时线，〜（40）Ar /〜（36）Ar截距为288±21，这与现代大气是无法区分的。但是，整个人群偏向年龄较大的表观年龄，在48 ka，55 ka，67 ka和110 ka处出现较小的峰值。 C-13 Tephra中的玻璃碎片组成与150 km〜3坎帕尼亚Ignimbrite富含SiO_2的相重叠，后者是从核心站点西北130 km的Campi Flegrei破火山口喷出的。尽管41.1±2.1 ka等时线比坎帕尼亚火成因岩的K-Ar和〜（14）C年龄大〜15％，但与最近的〜（40）Ar /〜（39）Ar年龄确定没有区别。 Campanian Ignimbrite火山喷发在化学上也与Y-5灰分层相似，并与之相关-Y-5灰分层是地中海地区最广泛，分布最广的更新世特非拉。 Y-5层的年龄最初是根据O同位素阶段的天文年限限制在38.0±2.5 ka。 〜（40）Ar /〜（39）Ar年龄，天文历法以及化学相似性使C-13特菲拉层与Campanian Ignimbrite和Y-5特菲拉层相关。保存在C-13特非拉层中的较老年龄可能反映了伴随着Campi Flegrei破火山口41 ka坍塌而爆发的爆发中的异晶。 C-13特菲拉层与相邻海洋核心的O-同位素阶段3.12中的〜（10）Be峰相关，并且紧接在Heinrich偶数4之前的冷却事件之前，因此这些特征的年龄受到放射性同位素的限制约会。 〜（10）Be沉积中的41 ka峰是一种全球现象，其年龄与Laschamp地磁偏移的年龄相匹配。因此，我们的结果为过去50年间的几个古冰芯和古气候的海洋代理记录提供了新的联系点。可以使用〜（40）Ar /〜（39）Ar激光加热方法从最新的更新世海生前生海藻中获取精确的年龄信息，而与放射性碳年代无关，尽管在沉积过程中或沉积后可能存在多种成分。

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