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首页> 外文期刊>Journal of Asian earth sciences >Is spreading prolonged, episodic or incipient in the Andaman Sea? Evidence from deepwater sedimentation
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Is spreading prolonged, episodic or incipient in the Andaman Sea? Evidence from deepwater sedimentation

机译：在安达曼海中传播的时间是延长的，偶发的还是初期的？深水沉积的证据

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摘要

The Central Andaman Basin (CAB) is generally accepted to be a site of continuous sea floor spreading since the Early Pliocene (～4.0 Ma). The adjacent Alcock and Sewell Rises, and part of the East Andaman basin have been interpreted as probable Miocene oceanic crust. Published seismic lines across the eastern half of the spreading centre show that 100's m thickness of sediment are present right up to the central trough. The central trough margins are faulted, uplifted and tilted away from the central trough. The youngest sediment is ponded and onlaps the tilted central trough margin, while older faulted sediment lies within the trough. Such a configuration is incompatible with continuous spreading. Instead, either spreading in the central basin was episodic, probably comprising a Late Miocene-Early Pliocene phase of spreading, followed by extension accommodated in the Alcock and Sewell rise area (by faulting and dike intrusion), and then a recent (Quaternary) return to spreading in the central trough; or the central trough marks an incipient spreading centre in hyper-thinned continental (or possibly island arc) crust. To resolve these possibilities regional satellite gravity data was inverted to determine crustal type and thickness. The results indicate the CAB is oceanic crust, however the adjacent regions of the Alcock and Sewell Rises and the East Andaman Basin are extended continental crust. These regions were able to undergo extension before seafloor spreading, and when seafloor spreading ceased. Unpublished seismic reflection data across the East Andaman Basin supports the presence of continental crust under the basin that thins drastically westwards towards the spreading centre. Episodic seafloor spreading fits with GPS data onshore that indicate the differential motion of India with respect to SE Asia is accommodated on widely distributed structures that lie between the trench and the Sagaing Fault.
机译：自上新世（〜4.0 Ma）以来，安达曼中部盆地（CAB）通常被认为是海底连续扩散的地点。邻近的阿尔科克和塞维尔上升，以及东安达曼盆地的一部分被认为是可能的中新世洋壳。已发布的横跨扩散中心东半部的地震线显示，直到中心槽处都存在100微米厚的沉积物。中央槽缘断裂，隆起并倾斜远离中央槽。最年轻的沉积物被堆积在倾斜的中央槽边缘上，而较早的断层沉积物位于该槽中。这样的配置与连续扩展不兼容。取而代之的是，在中部盆地的任何一次扩张都是偶发性的，可能包括中新世晚期至上新世晚期的扩张，然后在阿尔科克和塞韦尔隆起区进行扩张（通过断层和堤防侵入），然后又是最近一次（第四纪）回归在中央槽中扩散；或中央低谷标志着超薄的大陆（或可能是岛弧）地壳的初期扩散中心。为了解决这些可能性，对区域卫星重力数据进行了反演以确定地壳类型和厚度。结果表明，CAB为洋壳，而Alcock和Sewell Rises和东安达曼盆地的相邻区域为扩展的大陆壳。这些区域能够在海底扩散之前和海底扩散停止时进行扩展。整个安达曼东部盆地尚未公布的地震反射数据支持了该盆地下方大陆壳的存在，该大陆壳向西向稀薄地向着扩散中心倾斜。间歇性海底扩散与陆上GPS数据吻合，表明印度相对于东南亚的差异运动被容纳在位于海沟和实皆断层之间的分布广泛的结构上。

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