鹤岗盆地晚侏罗世石头河子组沉积环境及幕式聚煤作用

鹤岗盆地是一中-新生代内陆盆地，主要含煤地层上侏罗统石头河子组是一套非海相含煤地层，充填于盆地底部，自下而上可划分为三个岩性段，五个亚段和２６个含煤旋回。底部第一亚段沉积期以冲积扇、辫状河环境为主；第二亚段以河流环境为主；第三亚段以河流-三角洲-湖泊环境为主；第四亚段演化为河流环境；第五亚段则以河流、冲积扇环境为主。垂向上五个亚段对应于盆地的填平补齐-扩张-稳定沉降-差异沉降-收缩五个演化阶段。富煤带位于同沉积中心的侧翼，一般含砂率６０%～７０%的区域含煤性最好。含煤旋回受控于盆地周期性地快-慢沉降，聚煤作用发育于每期幕式沉降的缓慢稳定沉降阶段。厚-特厚煤层都与湖泊三角洲冲积平原大面积沼泽化有关。

Depositional Environments of the Shitouhezi Formation and Its Characteristics of the Episodic Coal Accumulation,Upper Jurassic Hegang Basin,Heilongjiang Province

The Shitouhezi Formation is a set of non marine coal bearing strata,filled in the lower part of the Mesozoic-Cenozoic interior basin of Hegang.The strata can be divided into three lithological members including five submembers and 26 small cycles from bottom to the upper part.The first submember was mainly marked by the alluvial fan and braided stream environments;the second submember the fluvial;the third submemeber the fluvial-delta-lacustrine;the 4th the fluvial again;and the 5th the fluvial and alluvial fan.Vertically,the five submembers respond to the five developing bhases which filled the lower areas for horizontal ground of the basin-expanding-subsiding stably-subsiding differently-contracting of the basin.Richer coal-bearing areas are Locatek to the flank of syndepositional anticline bulge.Coal accumulation was controlled mainly by the periodic fast and slow subsiding of the basin.Coal accumulation occurred at each slower and more stable subsiding phase of the episodic subsidence.The exceptionally thick coal beds are related to the largest swamped deltaic plain.