Deformation mode in the frontal edge of an arc–arc collision zone: subsurface geology, active faults and paleomagnetism in southern central Hokkaido, Japan
Deformation mode in the frontal edge of an arc–arc collision zone: subsurface geology, active faults and paleomagnetism in southern central Hokkaido, Japan
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DOI：
10.1016/j.tecto.2004.09.003
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发表时间：
2005-01
期刊：
影响因子：
2.9
通讯作者：
Y. Itoh;T. Ishiyama;Y. Nagasaki
中科院分区：
文献类型：
--
作者：
Y. Itoh;T. Ishiyama;Y. Nagasaki
根据地下地质描述了北海道中南部新生代弧-弧碰撞带的前缘。反射地震和钻探勘测描绘了南北向褶皱逆冲带的地质结构。北海道中部西向断块绵延200公里，逆冲活动自新近纪晚期以来一直向西传播。从岩心获得的白垩纪古地磁数据和基底岩性的亲和力表明碰撞前缘底板冲断层的下沉块体与古东北日本弧之间存在联系。属于上升块体的岩心样本的剩余磁化强度表明渐新世后逆时针旋转。它与同一块体的地表旋转运动相反，因此需要对断层结构和块体旋转进行更详细的研究，以了解褶皱逆冲带的变形模式。钻孔中有机质的成熟度表明第四纪开始被逆冲掩埋。因此，弧-弧碰撞的变形前沿正处于地壳收缩的活跃、新生阶段。
Frontal edge of a Cenozoic arc–arc collision zone in southern central Hokkaido is described based on subsurface geology. Reflection seismic and drilling surveys delineate geologic structure of the N–S fold-and-thrust belt. West-verging faulted blocks extend as long as 200 km in central Hokkaido, and the activity of thrust has been propagating westward since the late Neogene. The Cretaceous paleomagnetic data obtained from cores and the affinity in basement lithology implies a connection between the downthrown block of a floor thrust of the collision front and paleo-northeast Japan arc. Remanent magnetization of core samples belonging to the upthrown block indicates post-Oligocene counterclockwise rotation. It is opposite to surface rotational motions of the same block, then more detail study on fault architecture and block rotation is required to understand the mode of deformation of the fold-and-thrust belt. Maturity level of organic matters in a borehole suggests that burial by the thrusting initiated in the Quaternary. Thus, the deformation front of the arc–arc collision is in an active, nascent stage of crustal contraction.