Zircon U–Pb ages from tuff beds of the upper Mesozoic Tetori Group in the Shokawa district, Gifu Prefecture, central Japan †
Zircon U–Pb ages from tuff beds of the upper Mesozoic Tetori Group in the Shokawa district, Gifu Prefecture, central Japan †
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DOI：
10.1111/j.1440-1738.2006.00544.x
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发表时间：
2006-09
期刊：
影响因子：
1.5
通讯作者：
Nao Kusuhashi;Aiko Matsumoto;M. Murakami;T. Tagami;T. Hirata;T. Iizuka;T. Handa;H. Matsuoka
中科院分区：
文献类型：
--
作者：
Nao Kusuhashi;Aiko Matsumoto;M. Murakami;T. Tagami;T. Hirata;T. Iizuka;T. Handa;H. Matsuoka
摘要上中生代Tetori群含有大量的植物、海洋和非海洋动物化石。该研究组有可能提供关键信息，以提高我们对东亚中侏罗世至早白垩世生物群的认识。然而，Tetori群的沉积年龄仍然不确定，如果没有良好的年龄限制，与其他地区的准确对比非常困难。作为获得铁取群地层可靠年龄的第一步，我们使用激光烧蚀电感耦合等离子体质谱法测量了日本中部岐阜县高山市香川区凝灰岩床中锆石的U-Pb年龄。牛丸组、御手洗组和大黑谷组凝灰岩最年轻的可靠U-Pb年龄分别为130.2 ± 1.7、129.8 ± 1.0和117.5 ± 0.7Ma（误差为2SE）。这些结果表明，以前被认为与上侏罗纪至下白垩纪相关的整个昭和地区的铁取群实际上与下白垩纪相关。牛丸组、御手洗组和奥田谷组的最大年龄分别为豪特里安晚期至巴列姆阶、豪特里安晚期至巴列姆阶和巴列姆阶至阿普第阶。
Abstract The upper Mesozoic Tetori Group contains numerous fossils of plants and marine and non‐marine animals. The group has the potential to provide key information to improve our understanding of the Middle Jurassic to Early Cretaceous biota of East Asia. However, the depositional age of the Tetori Group remains uncertain, and without good age constraints, accurate correlation with other areas is very difficult. As a first step in obtaining reliable ages for the formations within the Tetori Group, we used laser ablation‐inductively coupled plasma–mass spectrometry to measure the U–Pb ages of zircons collected from tuff beds in the Shokawa district, Takayama City, Gifu Prefecture, central Japan. The youngest reliable U–Pb ages from the tuff beds of the Ushimaru, Mitarai and Okurodani Formations are 130.2 ± 1.7, 129.8 ± 1.0 and 117.5 ± 0.7 Ma, respectively (errors represent 2 SE). These results indicate that the entire Tetori Group in the Shokawa district, which was previously believed to be correlated to the Upper Jurassic to Lower Cretaceous, is in fact correlated to the Lower Cretaceous. The maximum ages of the Ushimaru, Mitarai and Okurodani Formations are late Hauterivian to Barremian, late Hauterivian to Barremian and Barremian to Aptian, respectively.