40 Ar/ 39 Ar ages of tephras intercalated in astronomically tuned Neogene sedimentary sequences in the eastern Mediterranean
40 Ar/ 39 Ar ages of tephras intercalated in astronomically tuned Neogene sedimentary sequences in the eastern Mediterranean
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地中海东部天文学调整的新近纪沉积层序中插有火山灰的 40 Ar/ 39 Ar 年龄
DOI：
10.1016/j.epsl.2004.03.005
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发表时间：
2004
影响因子：
5.3
通讯作者：
J. Wijbrans
中科院分区：
文献类型：
--
作者：
K. Kuiper;F. Hilgen;J. Steenbrink;J. Wijbrans
本文提出了新的40ar /39Ar数据，这些数据来源于地中海上新世和晚中新世天文定年序列中的火山灰层，旨在解决两种独立绝对定年方法之间相互校准的不一致性。40Ar/39Ar碱基年龄比相同火山灰层的天文年龄系统地年轻0.7-2.3%。如果采用改进的全误差传播法计算40ar /39Ar年龄的绝对误差，则除了托勒密上部灰烬的差异最大外，其他差异的显著性都消失了。总方差主要由40k到40ar的衰变活度（~ 70%）和初级标准GA1550黑云母中放射性成因40arin的量（~ 15%）决定。如果40ar /39Ar的年龄是相对于天文年代标准计算的，这些参数的影响就会大大减少，从而得到更可靠的年龄，并大大减少40ar /39Ar定年的误差。Taylor Creek Rhyolite （TCR）和Fish Canyon Tuff (FCT) sanidine的天文校正年龄分别为28.53±0.02 Ma和28.21±0.04 Ma（±1 S.E.），如果我们从更可靠的Cretan A1灰层开始计算的话。对于较年轻的托勒密火山灰层（相当于28.61 Ma的FCT）发现的巨大差异，最可能的解释是这部分序列调整的错误。
We present new40Ar/39Ar data for sanidine and biotite derived from volcanic ash layers that are intercalated in Pliocene and late Miocene astronomically dated sequences in the Mediterranean with the aim to solve existing inconsistencies in the intercalibration between the two independent absolute dating methods.40Ar/39Ar sanidine ages are systematically younger by 0.7–2.3% than the astronomical ages for the same ash layers. The significance of the discrepancy disappears except for the upper Ptolemais ashes, which reveal the largest difference, if an improved full error propagation method is applied to calculate the absolute error in the40Ar/39Ar ages. The total variance is dominated by that of the activity of the decay of40K to40Ar (∼70%) and that the amount of radiogenic40Arpin the primary standard GA1550 biotite (∼15%). If the40Ar/39Ar ages are calculated relative to an astronomically dated standard, the influence of these parameters is greatly reduced, resulting in a more reliable age and in a significant reduction of the error in40Ar/39Ar dating. Astronomically calibrated ages for Taylor Creek Rhyolite (TCR) and Fish Canyon Tuff (FCT) sanidine are 28.53±0.02 and 28.21±0.04 Ma (±1 S.E.), respectively, if we start from the more reliable results of the Cretan A1 ash layer. The most likely explanation for the large discrepancy found for the younger Ptolemais ash layers (equivalent to FCT of 28.61 Ma) is an error in the tuning of this part of the sequence.