广东海丰地区下侏罗统长埔组浅海沉积与前陆构造背景

广东省海丰地区是下侏罗统长埔组良好的出露区。长埔组为一套浅海碎屑岩沉积，主要为陆棚泥质沉积背景下的临滨砂坝和浊流沉积。粒度分析显示临滨砂坝沉积的概率累积曲线为两段式，频率直方图为单峰。浊流沉积的概率累积曲线为三段式，频率直方图为双峰。岩相序列为海进-海退过程的岩相组合，砂岩层向上变厚。海进-海退的序列显示出长埔时期海丰地区总体上经历了两次海平面变化。浅海泥质沉积和浊流沉积构成一套复理石序列。马尔科夫链分析显示长埔组具有明显的向上变粗序列。地球化学数据显示长埔组沉积物兼具被动大陆边缘性质和活动大陆边缘性质。砂岩样品成分的Dickinson图解显示，沉积物来源于再旋回造山带，与岩浆弧造山带和俯冲带杂岩体有关，海丰地区靠近逆冲造山带。因此早侏罗世盆地处于挤压下的弧后前陆构造背景，沉积物受再旋回造山带和陆块双物源控制。

Shallow Marine Deposits and the Foreland Tectonic Setting of Changpu Formation of Lower Jurassic in Haifeng,Guangdong

Changpu Formation of lower Jurassic outcropped in Haifeng,Guangdong province is a set of shallow marine clastic deposits,composed of shoreface sandstones and turbidite deposits in the muddy shelf environment.The particle size analysis of sandstones shows that the probability cumulative curve of shoreface sandstone represents two-stage and the frequency histogram is a single peak,and cumulative probability curve of turbidite represents three-stage and the frequency histogram is bimodal.The litho-facies succession of Changpu Formation is a rock association indicating the transgressive-regressive processes with the thickening upward of sandstone layers.The transgressive-regressive succession indicates that two eustatic sea level change occurred during development of Changpu Formation.The shallow muddy and turbidite deposits constitute a flysch succession.Markov chain analysis shows that it is a significant coarsening-upward succession.Geochemical data reveal that sediments of Changpu Formation have features of both passive continental margin and active continental margin.The sediments were from the recycled orogen related to the magmatic arc orogen and subduction complex after analysis of the Dickinson Graphic of sandstone composition.Haifeng region was close to the thrust fault zone.The sedimentary basin developed under a tectonic setting of compressional retro-arc foreland during the early Jurassic,and the basin provenances were both of recycled orogen zone and continental block.