龙门山前缘上三叠统马鞍塘组沉积分布特征及其控制因素

Distribution characteristics and controlling factors of Upper Triassic Ma'antang Formation in the front of Longmen Mountians,Sichuan,China

马鞍塘组在龙门山前缘多次出露和钻遇,由于其岩性的差别较大,对其沉积特征和控制因素一直存有争议。通过四川盆地西北部多个剖面的测量和龙深1井的分析,结合古构造背景和薄片观察,对川西卡尼期的岩相古地理进行了研究,将龙门山前缘马鞍塘期(卡尼期)沉积从北向南主要分为三个区:马鞍塘车站沉积区、汉旺-佛爷洞礁滩沉积区、龙深1井饥饿沉积区。结合当时构造背景,认为马鞍塘期沉积地层主要受到龙门山早期断层带控制。该断层带为正断层性质,但同时也具有走滑特征。由于断层间的互相作用,在龙门山后山带形成"龙门山岛链",在龙门山前缘形成川西北马鞍塘组的三个具不同特征的沉积区。

The Upper Triassic Maantang Formation is discovered in several outcrops and wells in the front of Longmen Mountains.The settings and controlling factors of the Ma＇antang Formation are disputed by many geologists and petro-geologists because the sections are obviously different in petrology and width.Through measuring several sections and analysing Well Longshen 1,the Carnian lithofacies paleogeography of West Sichuan is studied and the Ma＇antang Formation in the research area is divided into three areas： the sedimentary area（symbol： Ma＇antang station）,the sedimentary area of reef-bank（symbol： Hanwang-Foyedong）,and the relatively starved sedimentary area（symbol： Well Longshen 1）.Combined with the tectonic settings,the authors consider that the sedimentary stratium of the Ma＇antang Formation in the front of Longmen Mountains is controlled by several existed faults（for example： the Maowen-Wenchuan fault,the Beichuan-Yingxiu fault etc.）.The ＂Longmen Mountains island chain＂ is believed to be formed by some existed faults by strike slipping.The depositional framework of the Ma＇antang Formation in the research area is controlled by the fault movement.