南沙海域中生代构造挤压及其成因

MESOZOIC TECTONIC COMPRESSION AND ITS GENESIS IN THE SEA AREA OF NANSHA

为研究南海南部南沙海域中生界挤压构造变形特征及其成因,对研究区内多道地震剖面资料进行了解释,结果表明研究区内中生代地层曾遭受过不同程度的挤压变形,并在中生代末期遭受过强烈的剥蚀作用。为了进一步研究中生代地层的挤压构造特征,通过平衡剖面计算的方法去除了研究区新生代构造的影响并对中生代地层构造挤压率进行了计算。结果表明研究区的中生代地层曾遭受过两组相反方向应力的挤压,两组不同应力方向的挤压变形均表现为北强南弱和西强东弱的特征。这种挤压应力方向和强度的变化可能与古南海的扩张以及南沙地块不同部位向北漂移的速率有关。

The Mesozoic of the Nansha block of the southern South China Sea has suffered various degrees of compression in addition to a strong denudation by the end of Mesozoic.Multi-channel seismic data are interpreted to reveal the characteristics and genesis of the Mesozoic tectonic deformation.Tectonic restoration was conducted to remove the Cenozoic deformation and at the same time the Mesozoic tectonic compression ratios were calculated.Through them we found that there were two compressive stresses coming from opposite directions,one from S（S）E and another from N（N）W.The strength of the stresses decreased from the west to the east and from the north to the south.The variations in compression ratios may be related to the opening of the proto-South China Sea and the change in drifting rate of the Nansha block northward.