Letter to the Editor: Age of the Rotoehu Ash Comment
Letter to the Editor: Age of the Rotoehu Ash Comment
复制标题
DOI：
10.1080/00288306.1995.9514666
复制
发表时间：
1995-06
影响因子：
2.2
通讯作者：
D. Lowe;A. Hogg
中科院分区：
文献类型：
--
作者：
D. Lowe;A. Hogg
Whitehead & Ditchburn（1994）在他们的记录中考虑了一些与Rotoehu火山灰和Rotoiti火山灰岩的年龄有关的U-Th、ESR和I4 C年龄（Froggatt & Lowe 1990）。Ota等的U-Th不平衡年龄（71±6 ka）与U-Th不平衡年龄（71±6 ka）基本一致。Wilson等人（1989）的K-Ar年龄（64± 4ka）几乎肯定是不正确的，其真实年龄要年轻得多。1992年，他可能太老了。为了支持这一论点，Whitehead & Ditchburn（1994）首先指出了Buhay等人的ESR年龄（45.2± 8.2ka）的问题。（1992），使其年轻5%（42.9± 7.8ka）。其次，他们提出并讨论了四个I4 C年龄，据说它们“令人惊讶地紧密聚集，形成了一个没有异常值的连贯集合”，平均值为35.1+ 2.8 ka*。这四个年龄包括NZ 877和NZ 1126（均已发表），根据目前的IGNS程序修订，分别为37.7±8.3和36.6±5.3 ka;以及NZ 1357和NZ 1366（据称以前未引用），同样修订，分别为31.4±4.4和34.6±7.9 ka。因此，Whitehead & Ditchburn（1994）得出结论，Rotoehu火山灰的年龄可能小于50 ka，并且需要更多的工作来解释为什么这个结果与64±4 ka的K-Ar年龄不同。
In their note, Whitehead & Ditchburn (1994) considered some U-Th, ESR, and I4C dates that relate to the age of the Rotoehu Ash and Rotoiti Ignimbrite members of the Rotoiti Tephra Formation (Froggatt & Lowe 1990). They suggested that the U-Th disequilibrium age (71±6 ka) of Ota et al.(1989) is almost certainly incorrect, the true age being much younger, and hence, by implication, that the K-Ar age (64±4 ka) of Wilson et al.(1992) is likely to be too old. To support this contention, Whitehead & Ditchburn (1994) pointed firstly to problems with the ESR age (45.2±8.2 ka) of Buhay et al.(1992), making it younger by 5%(42.9±7.8 ka). Secondly, they presented and discussed four I4C ages said to be" surprisingly closely clustered and form [ing] a coherent set with no outliers", and with a mean of 35.1+ 2.8 ka*. The four ages comprise NZ877 and NZ1126 (both published previously), revised according to current IGNS procedures to give 37.7±8.3 and 36.6±5.3 ka, respectively; and NZ1357 and NZ1366 (purportedly not cited previously), similarly revised to give 31.4±4.4 and 34.6±7.9 ka, respectively. Whitehead & Ditchburn (1994) thus concluded that the age for Rotoehu Ash is likely to be< 50 ka and that more work is required to explain why this result differs from the K-Ar age of 64±4 ka.