Abstract The Late Cretaceous is a significant geologic period in the South China Sea area, as it marks the tectonic transition from the early Paleo-Pacific Plate subduction to the subsequent Cenozoic rifting related to the opening of the SCS. However, the Late Cretaceous tectonic evolution of the South China Sea area is yet to be clearly defined, and it is at present largely debated in the literature. In this paper, mainly on the basis of ~240,000 km2 newly acquired 3D seismic reflection data, 94 industrial wells and existing U Pb ages of basement granitoids, we carried out an integrated interpretation, mapping and analysis of the pre-Cenozoic (> 66 Ma) structures within the basement of the Cenozoic rift basin in the northern South China Sea area, that can be crucial for a broad understanding of the Late Cretaceous tectonic evolution of this region. Results of this analysis suggest that three Late Cretaceous fault systems can be identified in the northern South China Sea margin: 1) the WNW-striking thrust system, 2) ENE-striking extensional fault system, and 3) ENE-striking thrust system. These three fault systems are considered to have developed in the Late Cretaceous since they are superimposed on the well dated Late Jurassic to Early Cretaceous (161.6–101.7 Ma) arc-related granitoids that define most of the basement of the Cenozoic rift basin within the study area. This new structural evidence, combined with a review of previous studies, led us to propose a renewed multi-phase geodynamic evolutionary model of the South China Sea area during the Late Cretaceous. The first tectonic event that can be recognized generated the WNW-striking thrust system and is, in this paper, interpreted to have formed as a result of a sinistral transpressional event that took place in the South China Sea area and adjacent areas around 100 Ma at the Early-Late Cretaceous boundary. This transpressional event was likely related to intense oblique convergence between the Paleo-Pacific Ocean Plate and the Eurasia Plate. The second tectonic phase that was identified in this paper (~100 Ma to ~72 Ma) is defined by an extensional event that generated the largely ENE-striking extensional fault systems and associated basins, which is interpreted to be related to the back-arc extension that took place in this period in response to the slab roll back and high-angle subduction of the Paleo-Pacific Plate. This extensional phase eventually led to the opening of the Proto-South China Sea on the SE margin of the proto-South China Block, and it should be distinguished from the Cenozoic rifting phases that are related to the opening of the South China Sea. The third and last tectonic phase that was recognized in this paper is a compressional event that took place in the late stage of the Late Cretaceous (~72 Ma to ~66 Ma) and was responsible for the development of the ENE-striking thrust system. We suggest that this post-subduction (post-Yanshanian) compressional event can be interpreted to have developed in response to process of ridge push related to the sea floor spreading of the Proto-South China Sea.

中文翻译：

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南海地区晚白垩世构造演化：3D地震反射资料的概述及新视角

摘要 晚白垩世是南海地区一个重要的地质时期，它标志着从早期古太平洋板块俯冲到随后与南海开放相关的新生代裂谷的构造转变。然而，南海地区晚白垩世构造演化尚未明确界定，目前在文献中存在较大争议。本文主要根据新获得的~240,000 km2 3D地震反射资料、94口工业井和基底花岗岩类现有U Pb年龄，对前新生代（> 66 Ma ) 南海北部新生代裂谷盆地基底内的构造，这对于广泛了解该地区晚白垩世构造演化至关重要。分析结果表明，在南海北部边缘可以识别出三个晚白垩世断层系统：1）WNW 走向的逆冲断层系统，2）ENE 走向的伸展断层系统，以及 3）ENE 走向的逆冲断层系统。这三个断层系统被认为是在晚白垩世发育，因为它们叠加在晚侏罗世至早白垩世（161.6-101.7 Ma）与弧相关的花岗岩上，这些花岗岩定义了研究中新生代裂谷盆地的大部分基底区域。这一新的构造证据，结合对以往研究的回顾，促使我们提出了晚白垩世南海地区的多阶段地球动力学演化模型。可以识别的第一个构造事件产生了西西西向冲断系统，在本文中被解释为由发生在 100 Ma 左右的南海地区和邻近地区的左旋挤压事件的结果。早-晚白垩世边界。这种挤压事件很可能与古太平洋板块和欧亚板块之间的强烈倾斜辐合有关。本文确定的第二个构造阶段（~100 Ma 到~72 Ma）是由一个伸展事件定义的，该事件产生了以 ENE 为主的伸展断层系统和相关盆地，这被解释为与弧后相关这一时期发生的伸展是为了响应古太平洋板块的板块回滚和大角度俯冲。这一拉张期最终导致了原华南地块东南缘的原南海张开，应区别于与南海张开有关的新生代裂谷期。本文中识别的第三个也是最后一个构造阶段是发生在晚白垩世晚期（~72 Ma 至~66 Ma）的挤压事件，并且负责 ENE 冲断逆冲系统的发展。我们认为，这次俯冲后（燕山期后）挤压事件可以解释为响应与原南海海底扩张相关的海脊推动过程。应区别于与南海开放有关的新生代裂谷期。本文所识别的第三个也是最后一个构造阶段是发生在晚白垩世晚期（~72 Ma 至~66 Ma）的挤压事件，并负责 ENE 冲断逆冲系统的发展。我们认为，这次俯冲后（燕山期后）挤压事件可以解释为响应与原南海海底扩张相关的海脊推动过程。应区别于与南海开放有关的新生代裂谷期。本文中识别的第三个也是最后一个构造阶段是发生在晚白垩世晚期（~72 Ma 至~66 Ma）的挤压事件，并且负责 ENE 冲断逆冲系统的发展。我们认为，这次俯冲后（燕山期后）挤压事件可以解释为响应与原南海海底扩张相关的海脊推动过程。本文中识别的第三个也是最后一个构造阶段是发生在晚白垩世晚期（~72 Ma 至~66 Ma）的挤压事件，并且负责 ENE 冲断逆冲系统的发展。我们认为，这次俯冲后（燕山期后）的挤压事件可以解释为响应与原始南海海底扩张相关的海脊推动过程。本文中识别的第三个也是最后一个构造阶段是发生在晚白垩世晚期（~72 Ma 至~66 Ma）的挤压事件，并且负责 ENE 冲断逆冲系统的发展。我们认为，这次俯冲后（燕山期后）挤压事件可以解释为响应与原南海海底扩张相关的海脊推动过程。