摘要： 二连盆地吉尔嘎朗图凹陷是一个陆相断陷聚煤盆地,下白垩统赛汉塔拉组是其主要含煤地层,作者利用岩心、钻孔资料对其岩相类型、沉积相、层序地层及聚煤作用特征进行研究。(1)赛汉塔拉组主要由砂砾岩、砂岩、粉砂岩、泥岩、碳质泥岩及厚层褐煤组成,发育扇三角洲平原相、扇三角洲前缘相、辫状河三角洲平原相、辫状河三角洲前缘相、滨浅湖相,分别属于扇三角洲沉积体系、辫状河三角洲沉积体系和湖泊沉积体系。(2)识别出2种层序界面:不整合面和下切谷冲刷面,将赛汉塔拉组划分为2个三级层序。从层序Ⅰ到层序Ⅱ,煤层厚度逐渐增大,聚煤作用逐渐增强。(3)在滨浅湖环境下厚煤层主要形成于湖侵体系域早期,在扇/辫状河三角洲环境下厚煤层主要形成于湖侵体系域晚期,煤层厚度在凹陷中部最大,向西北和东南方向均变小。聚煤作用明显受基底沉降作用影响,可容空间增加速率与泥炭堆积速率相平衡,从而形成了区内巨厚煤层。
关键词:
吉尔嘎朗图凹陷,
断陷盆地,
赛汉塔拉组,
湖侵体系域,
聚煤作用
Abstract: The Jiergalangtu Sag of Erlian Basin is a continental faulting coal basin and the Early Cretaceous Saihantala Formation is its main coal-bearing strata. In this paper,we studied lithofacies types,sedimentary facies,sequence stratigraphy and coal accumulation characteristics by means of core and drilling data. (1) The Saihantala Formation is mainly composed of sandy conglomerate,sandstone,siltstone,mudstone,carbonaceous mudstone and thick-bedded lignite. Three depositional systems were classified,including fan delta,braided fluvial delta and lake. The fan delta system consists of fan deltaic plain and fan deltaic front facies;the braided fluvial delta system is composed of braided fluvial deltaic plain and braided fluvial deltaic front facies;and the lacustrine system includes littoral lake and shallow lake. (2) Key stratigraphic surfaces, i.e., the unconformity and the erosional base of incised valley filling sandstones,are recognized,and the target coal measures are subdivided into two third-order sequences. Seam thickness and coal accumulation increase from sequence Ⅰ to sequence Ⅱ. (3) The thick coal seams,which were developed from the coastal and shallow lacustrine environments,were mainly formed in the early transgressive systems tract,and the thick coal seams,which were developed from the fan delta or the braided delta environments,were mainly formed at the end of the transgressive systems tract. The thickest coal bed was distributed in the central zone of the sag,which thins out towards northwest and southeast of the basin. Coal accumulation was significantly controlled by basin subsidence,and the increasing rate of accommodation space was well balanced with the rate of peat accumulation,thus forming a regionally very thick coal seam.
Key words:
Jiergalangtu Sag,
faulting basin,
Saihantala Formation,
transgressive systems tract,
coal accumulation
中图分类号:
王帅,邵龙义,闫志明,孙钦平,王东东,鲁静,孙斌. 二连盆地吉尔嘎朗图凹陷下白垩统赛汉塔拉组层序地层及聚煤特征[J]. 古地理学报, 2015, 17(3): 393-404.
Wang Shuai, Shao Longyi, Yan Zhiming, Sun Qinping, Wang Dongdong, Lu Jing, Sun Bin. Sequence stratigraphy and coal accumulation of the Lower Cretaceous Saihantala Formation in Jiergalangtu Sag of Erlian Basin[J]. JOPC, 2015, 17(3): 393-404.