Dahongyu Fm

The base, marked by purple-red shale with sandstone, conformably contact with underlying Tuanshanzi Fm; but a disconformable contact is also seen locally. It even overlapped directly onto the Changzhougou Fm or Archean in the area east of Luanxian County, Eastern Hebei and Jinxi, Xingcheng, Beizhen of Western Liaoning Province.

[Figure: a-The boundary between the Dahongyu Fm and the underlying Tuanshanzi Fm; b,c,d-Volcanic rocks]

The top limit of the member is set at erosional top surface of conophyton-bearing dolomite. Conformable with Tuanshanzi Fm.

NE Hebei-western Liaoning. The Dahonyu Fm is eastern Hebei and western Liaoning provinces, and is characterized by major changes both in thickness and lithological character. In Yanshan mountain area such as in Xinglong-Pinggu-Pingquan, the sandy conglomerate and chert increases (349-220 m thick) and in the area of Jixian-Zunhua-Luanxian Counties the coarse fragment content is increased (408-232 m thick), while in Badaling area it is characterized by interbedding of carbonate and clastic rocks without volcanic rock (81 m thick), but the volcanic rock is developed vastly in Pinggu County (375 m thick): It is dominated by quartz sandstone and feldspar-quartz sandstone in Zhuolu-Xuanhua area (113 m).The Dahongyu Fm showed also changeable character both in lithological character and thickness in western Liaoning Province, i.e. it is up to 996 m thick in Lingyuan, 516 m in Jianping northwest of Lingyuan, 419 m in Chaoyang, 511 m in Jin-xi, 474 m in Yixian, 300 m in Beizhen, i.e. it is greatly thinned in northeast direction. The dolomite bed in upper part of the formation is obviously thickened from west to east, for example it is only 3-5 m in Lingyuan in west, but to east direction it is thickened greatly in Jinxi, Xingcheng and Beizhen, where the formation is even completely composed of dolomite. But it is completely changed to clastic rock in Huludao area, Jinxi.