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

Key words: 
• Shitouhezi formation /
• depositional environments /
• coal accumulation /
• episodic subsidence

Abstract: The Shitouhezi Formation is a set of non-marine coal-bearing strata, filled in the lower part of theMesozoic- Cenozoic interior basin of Hegang. The strata can be divided into three lithological membersincluding five submembers and 26 small cycles from bottom to the upper part. The first submember wasmainly 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 andalluvial fan. Vertically, the five submembers respond to the five developing bhases which filled the lowerareas for horizontal ground of the basin- expanding- subsiding stably- subsiding differently- contract-ing 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 accu-mulation occurred at each slower and more stable subsiding phase of the episodic subsidence. The excep-tionally thick coal beds are related to the largest swamped deltaic plain.