Preliminary report on the radiolarian age of the Upper Cretaceous Matoya Group (Shimanto belt) in the Toba District, Mie Prefecture, Southwest Japan
Preliminary report on the radiolarian age of the Upper Cretaceous Matoya Group (Shimanto belt) in the Toba District, Mie Prefecture, Southwest Japan
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DOI：
10.9795/bullgsj.68.57
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发表时间：
2017-04
期刊：
影响因子：
--
通讯作者：
S. Nakae;T. Kurihara
中科院分区：
文献类型：
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作者：
S. Nakae;T. Kurihara
志摩半岛（纪伊半岛东端）多巴区的详细野外测绘和放射虫年代测定揭示了上白垩统Matoya群的Coniacian-Campanian泥岩。该群属于沿着库拉板块俯冲到古亚洲大陆之下的板块边界形成的四万十带（北方亚带）。在51个不同泥岩露头的放射虫样品中，有7个样品的放射虫组合保存较好，主要集中在3个年龄组：（i）早科尼亚世，（ii）早康潘世或中Santonian-Middle Campanian，（iii）中晚康潘世。这一证据有可能在年代学和地层学上将Matoya群划分为几个单元。
A detailed field mapping and radiolarian dating in the Toba District, the Shima Peninsula (eastern tip of the Kii Peninsula) have revealed Coniacian–Campanian mudstones of the Upper Cretaceous Matoya Group. This group belongs to the Shimanto belt (northern subbelt) that formed along the plate boundary where the Kula plate has been subducting beneath the paleo-Asian continent. Seven out of 51 radiolarian-bearing samples from different outcrops of mudstone yield relatively well-preserved radiolarian assemblages, which are concentrated in three age-groups: (i) Early Coniacian, (ii) Early Campanian or Middle Santonian–Middle Campanian, and (iii) Middle–Late Campanian. This evidence has a potential to chronologically and stratigraphically divide the Matoya Group into several units.