Palaeoecological effects of back-arc spreading on Miocene benthic communities, SW Japan Arc
Palaeoecological effects of back-arc spreading on Miocene benthic communities, SW Japan Arc
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弧后扩张对日本西南弧中新世底栖群落的古生态影响
DOI：
10.1016/j.palaeo.2016.03.027
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
K.
中科院分区：
文献类型：
--
作者：
Nara;M.;Aikou;K.
中新世早期至中期，亚洲大陆东北缘弧后盆地（现称日本海）迅速发育。然后整个日本西南弧（弧）顺时针旋转得非常快。这一事件与位于弧南侧的另一个弧后盆地的打开有关。就在这个开口之后，非常年轻的热洋板块开始俯冲到弧下。这种俯冲引起了迅速的隆升，并在中新世晚期加强了弧的剥蚀。中新统下—中第三系Misaki群为厚3000 m的前弧盆地充填体，由波浪为主的浅海沉积和上覆辫状平原沉积组成。其主要特征是低技术多样性和技术结构的缺乏。例如，尽管其他“正常”的近海沉积物通常是高度生物扰动的，但在测量的近海沉积物中，高达96%的总厚度是非或非常轻微的生物扰动。虽然生物扰动较少的沉积物以前被认为是缺氧沉积物，但缺氧水不太可能在高度开放的波浪主导的浅海环境中发育。与两个弧后盆地的扩张相关的高度活跃的构造和强迫俯冲很可能导致了腹地的大量沉积，同时期隈研群的沉积学特征和整个Misaki盆地的过度沉积（高频率和快速沉积）证明了这一点。这种过度沉积得到了一系列证据的支持，例如整个组中普遍存在的软沉积物变形，估计的净沉积率（超过136至230厘米/年）等，很可能导致了整个盆地中退化动物的定居，并稀释了它们的技术结构。中新世早期至中期，极为活跃的构造-沉积作用对全盆地异常底栖生态系统和底栖结构的发育起了重要作用。
During the early to middle Miocene, rapid development of backarc basins, now known as the Sea of Japan, occurred in the NE margin of the Asian Continent. Then the entire SW Japan Arc (the arc) was rotated clockwise very rapidly. Such an event was associated with the opening of another backarc basin located to the south of the arc. Immediately after this opening, the very young, hot oceanic plate began to subduct underneath the arc. This subduction caused rapid uplifting and enhanced the denudation of the arc, in the post-early Miocene.The lower to middle Miocene Misaki Group is a 3,000 m-thick siliciclastic forearc basin fill, consisting of wave-dominated shallow-marine and overlying braid-plain deposits. Its defining features are the low ichnodiversity and paucity of ichnofabrics. For instance, up to 96% of the total thickness of the measured offshore deposits are non- or very slightly-bioturbated, despite the other “normal” offshore deposits are generally highly bioturbated. Although the less bioturbated sediments were previously considered as anoxic deposits, anoxic water was unlikely to develop within the highly open wave-dominated shallow-marine settings.The highly active tectonics associated with the spreading of the two backarc basins and the forced subduction most likely caused sediment mass-production in the hinterland, as evidenced by the sedimentological features of the coeval Kuma Group, and over-sedimentation (highly frequent and rapid sedimentation) that was taken place across the entire Misaki Basin. This over-sedimentation, supported by a series of evidence, such as the pervasive soft-sediment deformation across the group, estimated rate of net aggradation (more than 136 to 230 cm/kyr), etc., most likely induced the colonisation of depauperated fauna, and diluted their ichnofabrics, across the entire basin. The extremely active tectono-sedimentation played an important role in the development of the basin-wide anomalous benthic ecosystems and ichnofabrics during the early to middle Miocene.