新疆准噶尔盆地西北缘晚泥盆世法门期地层之划分

Subdivision of Famennian(Late Devonian)strata in the northwest border of the Junggar Basin,Xinjiang,Northwestern China

新疆准噶尔沙尔布尔提山及其附近地区是中国准噶尔—兴安地层区上泥盆统及下石炭统发育的代表地区,其中和布克河中游东岸(萨尔巴根德山地区)是过去受到广泛关注的和布克河组建组典型地区,但因构造改造强烈,导致和布克河组原剖面的描述出现多种问题,其层序及与洪古勒楞组的关系长期以来有着不同的意见。经过多年的野外工作,文中建立了萨尔巴根德山地区法门阶的层序,鉴于该地区的层序与布龙果尔剖面基本相似,认为取消和布克河组的名称,而代之统一使用洪古勒楞组是合理的。萨尔巴根德山地区的法门阶地层由洪古勒楞组及黑山头组(下部)组成,其中洪古勒楞组含弓石燕类等腕足动物及"Cyrtoclymenia"、Platyclymenia等菊石,自下而上可划分为5段(均为新名称):(1)萨尔巴段以大套灰岩为特征;(2)龙口段以大套灰绿色砂岩、砾岩、粉砂岩为特征;(3)杜古尔段以泥质灰岩及泥灰岩为特征;(4)乌兰段以紫红色疙瘩状砂质灰岩、紫红色及灰绿色硅质粉砂岩、硅质泥岩为特征;(5)查斯段以灰色钙质砂岩-钙质粉砂岩至砂质灰岩为特征。上覆黑山头组(下部)以深灰色硅质粉砂岩、硅质泥岩、硅质岩、细砂岩、紫红色粉砂质、硅质泥页岩为特征,含腕足类Syringothyris-Spirifer腕足动物群及Cymaclymenia等菊石,属泥盆系顶部层位。

The Xar Burd Mountain and adjacent places are a representative area for the Devonian and Lower Carboniferous in the Junggar-Hinggan Stratigraphic Regions.The eastern side of the Hebukehe River at its middle reaches（the Saerbagende Mountain area）is the typical locality of the Hebukehe Formation,which has been widely known to the Chinese Devonian workers.However,due to its severe tectonic deformation/modification,many problems were not resolved in the description of the original type section of the Hebukehe Formation.There have been different opinions about its lithological sequence and relation with the Hongguleleng Formation.Based on field investigation in the past few years,Famennian lithological sequence in the Saerbagende Mountain（Saerba in short）area has been established.Owing to the overall similarity of stratigraphic sequence between the Saerbagende Mountain area and the Bulongguoer section,it is naturally reasonable that the name of＂Hebukehe Formation＂should be abandoned and that the name of Hongguleleng Formation should be used instead.The Famennian in the Saerba area consists of the Hongguleleng Formation and the lower part of the Heishantou Formation.The Hongguleleng Formation contains cyrtospiriferid brachiopods and＂Cyrtoclymenia＂and Platyclymeniaammonoids and can be subdivided into five members（all new names）,in ascending order：（1）Saerba Member,characterized by a suite of（shelly）limestones;（2）Longkou Member,characterized by a suite of grayish green sandstone,conglomerate,and siltstone;（3）Duguer Member,characterized by a suite of marly and argillaceous limestones;（4）Wulan Member,characterized by a suite of purplish red＂nodular＂sandy limestone,purplish red and grayish green siliceous siltstone and siliceous mudstone;（5）Chasi Member,characterized by a suite of gray（weathered yellowish）calcareous sandstone/calcareous siltstone and sandy limestone.The overlying Heishantou Formation（lower part only）is the topmost Devonian strata,characterized by a suite of dark gray siliceous siltstone,siliceous mudstone,cherts,fine sandstone and purplish red silty,siliceous mudstone-shale,bearing the brachiopod Syringothyris-Spirifer fauna and the ammonoid Cymaclymenia.