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地球科学(中国地质大学学报) 2015
南海北部陆坡晚白垩世构造逆冲及其成因
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Abstract:
地震资料显示南海北部中生界发育褶皱和逆冲断层等挤压构造,但目前对其成因仍存在争议.通过对南海北部珠江口 盆地东南部陆坡的二维地震剖面进行研究,发现在云荔低隆起-兴荔凸起-兴宁凹陷一带存在2条近NWSE走向并往NE 方向逆冲的逆断层,在东沙隆起南部有2条近南-北走向并具有压扭性质的走滑断层,上述4条断层的平面延伸距离分别约 为130、110、55和58km.综合分析可知,现今位于南海南部的礼乐-巴拉望地块经中侏罗世-早白垩世与华南陆缘发生软碰 撞后,在晚白垩世与华南陆缘在现今荔湾-兴宁凹陷一带进行最后的“焊接缝合”,而上述4条断层可作为该次“焊接缝合”的 间接证据.由于太平洋向华南的俯冲板片在晚白垩世发生了后撤,华南大陆边缘在晚白垩世末开始张裂之前可能整体为区域 均衡抬升、局部陆-陆碰撞缝合的构造格局.
TherearefoldsandthrustfaultsinMesozoicstratainthenortherncontinentalmarginoftheSouthChinaSea,how ever,theirgenesesarestillincontroversy.Inthisstudy,2DseismicprofilesinthesoutheastregionofthePearlRiverMouth basin(PRMB)areinterpreted.TwonortheastwardsthrustingfaultswithapproximatelyNWSEstrikeareidentifiedinthearea ofYunliloweruplift,XingliriseandXingningsag,andtwoapproximatelynorthsouthstrikingcompressionalstrikeslipfaults aredistinguishedinthesouthernareaofDongshauplift.The4faultsmentionedaboveareabout130,110,55and58kmlong, respectively.ItcanbeconcludedthattheLiyue(Reed)BankPalawanblockwhichliesinthesoutherncontinentalmarginofthe SCSunderwentasoftcollisionwithSouthChinacontinentalmarginin MiddleJurassictoEarlyCretaceous,andtheyfinally unitedandsuturedinLateCretaceousapproximatelyalongLiwantoXingningsags.Theaforementioned4faultsmaybethe circumstantialevidencesforthefinalunitingandsuturingbetweentheLiyueBankPalawanblockandtheSouthChinacontinen talmarginintheLateCreta