Extension across the Indian–Arabian plate boundary:the Murray Ridge
Extension across the Indian–Arabian plate boundary:the Murray Ridge
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DOI：
10.1046/j.1365-246x.2000.00163.x
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发表时间：
2000-08
影响因子：
2.8
通讯作者：
R. Edwards;T. Minshull;R. White
中科院分区：
文献类型：
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作者：
R. Edwards;T. Minshull;R. White
印度洋西北部阿曼湾默里海岭的地震反射剖面显示，在主要走滑的印度-阿拉伯板块边界上有显著的延伸成分。默里岭沿着板块边界的北方部分，在那里它的走向变得更加向东，因此允许一个伸展的分量。达林普尔海槽是一个25公里宽，陡峭的半地堑，边界的大型断层的组件，走滑和正常运动。半地堑东南侧的主断层在海底的落差达1800 m。海槽的西北侧由一系列较小的反向正断层划定。广角地震、重力和磁力模型显示，默里海脊和达林普尔海槽的下面是厚达17公里的结晶地壳，可能是大陆成因。任何由于伸展而导致的地壳减薄都是有限的，没有新的地壳形成。我们倾向于一个板块模型，在这个模型中，印度-阿拉伯板块边界最初位于欧文断裂带以西，可能沿着阿曼大陆边缘，并认为在渐新世-早中新世印度洋板块重组期间，板块边界移动到现在欧文断裂带的位置，进一步向西的运动停止了。在这个时候，变形开始沿着默里岭，与两个隆起的基底高点，并在槽的沉降倾斜最低的沉积单元。Qalhat海山就是在这个时候形成的。随后的沉积物不整合地沉积在倾斜的下部单元上，然后发生断裂，形成现在的基底地形。正断层活动伴随上盘沉降、下盘抬升和剥蚀。平坦的现代沉积物表明，主要的垂直运动已经停止，虽然持续的地震表明，一些断层仍然活跃沿着板块边界。
SUMMARY Seismic reflection profiles from the Murray Ridge in the Gulf of Oman, northwest Indian Ocean, show a significant component of extension across the predominantly strike-slip Indian‐Arabian plate boundary. The Murray Ridge lies along the northern section of the plate boundary, where its trend becomes more easterly and thus allows a component of extension. The Dalrymple Trough is a 25 km wide, steep-sided halfgraben, bounded by large faults with components of both strike-slip and normal motion. The throw at the seabed of the main fault on the southeastern side of the halfgraben reaches 1800 m. The northwest side of the trough is delineated by a series of smaller antithetic normal faults. Wide-angle seismic, gravity and magnetic models show that the Murray Ridge and Dalrymple Trough are underlain by a crystalline crust up to 17 km thick, which may be continental in origin. Any crustal thinning due to extension is limited, and no new crust has been formed. We favour a plate model in which the Indian‐Arabian plate boundary was initially located further west than the Owen Fracture Zone, possibly along the Oman continental margin, and suggest that during the Oligocene‐Early Miocene Indian Ocean plate reorganization, the plate boundary moved to the site of the present Owen Fracture Zone and that motion further west ceased. At this time, deformation began along the Murray Ridge, with both the uplift of basement highs, and subsidence in the troughs tilting the lowest sedimentary unit. Qalhat Seamount was formed at this time. Subsequent sediments were deposited unconformably on the tilted lower unit and then faulted to produce the present basement topography. The normal faulting was accompanied by hanging-wall subsidence, footwall uplift, and erosion. Flat-lying recent sediments show that the major vertical movements have ceased, although continuing earthquakes show that some faulting is still active along the plate boundary.