Stratigraphy and provenance of forearc sequences in the Lichi Melange, Coastal Range: Geological records of the active Taiwan arc-continent collision
Stratigraphy and provenance of forearc sequences in the Lichi Melange, Coastal Range: Geological records of the active Taiwan arc-continent collision
复制标题
海岸山脉荔枝混杂区弧前序列的地层学和物源：台湾弧-大陆碰撞活动的地质记录
DOI：
10.1002/2017jb014378
复制
发表时间：
2017
影响因子：
3.9
通讯作者：
Yu Mengming
中科院分区：
文献类型：
--
作者：
Chen Wen-Huang;Huang Chi-Yue;Yan Yi;Dilek Yildirim;Chen Duofu;Wang Ming-Huei;Zhang Xinchang;Lan Qing;Yu Mengming
台湾东部海岸山脉的荔枝混杂岩被认为是剪切弧前层序。然而，这些层序的年龄仍然不确定，它们对弧-陆碰撞的意义也被忽视。根据野外调查和微体古生物分析，在荔枝混杂岩中划分出4个独立的生物地层单位，其时间跨度为<8.5 ~ 3.0Ma。这些单元的年龄明显大于东部残留的弧前层序（3.4- 1.2Ma），支持了荔枝混杂岩系起源于弧前盆地下部层序剪切作用的解释。古弧前地层（<8.5- 3.4Ma）在3.4Ma前发生了弧形逆冲作用，形成了与北吕宋海槽西部华栋海岭相似的海深隆起，而东部残留的弧前盆地在3.4- 1.2Ma期间继续沉积。较老的弧前地层具有镜质体反射率值甚至低于残留的弧前序列，这也支持他们被抬升的背逆冲，因此没有经历重大的埋葬。同位素分析表明，<8.5- 6.4Ma弧前沉积物同时来自火山弧和增生棱柱体，表明增生棱柱体的形成时间在<8.5- 6.4Ma。这可能是薄陆壳底侵作用的结果，为弧-陆碰撞的发生提供了良好的时间约束。6.4Ma后弧前沉积物主要来自增生棱柱体，反映了其持续隆升和大规模出露。
The Lichi Mélange in the Coastal Range, eastern Taiwan, is considered as sheared forearc sequences. However, the age of these sequences is still uncertain, and their significance for the arc‐continent collision has been overlooked. Based on field surveys and micropaleontological analysis, four independent biostratigraphic units ranging from <8.5 to 3.0 Ma are discerned in the Lichi Mélange. These units are obviously older than the remnant forearc sequences in the east (3.4–1.2 Ma), supporting the interpretation that the Lichi Mélange arose from the shearing of the lower forearc basin sequences. The stratigraphy also suggests that the older forearc strata (<8.5–3.4 Ma) were deformed and uplifted as a bathymetric high similar to the Huatung Ridge in the western North Luzon Trough by arcward back thrusting before 3.4 Ma, while sedimentation continued in the remnant forearc basin in the east during 3.4–1.2 Ma. The older forearc strata possess vitrinite reflectance values even lower than those of the remnant forearc sequences, which also supports that they were uplifted by back thrusting and therefore did not experience significant burial. Neodymium isotope analysis shows that the <8.5–6.4 Ma forearc sediments were sourced from both the volcanic arc and the accretionary prism, indicating the emergence of the accretionary prism within <8.5–6.4 Ma. It might have resulted from the underplating of thinned continental crust and provides a good time constraint for the onset of arc‐continent collision. The post 6.4 Ma forearc sediments were mainly derived from the accretionary prism, reflecting its constant uplift and large‐scale exposure.