EXTENTS, TYPE AND EVOLUTION OF LUANHE RIVER FAN-DELTA SYSTEM, CHINA

The Luanhe River ran off the mountain area at Qian'an, Hebei Province before about 2500 years ago and then formed the old Luanhe Rive fan-delta with its apex at Qian'an (7000-about 2500 cal. aBP). About 2500 years ago the Luanhe River changed its channel and formed the young Luanhe River fan-delta with its apex at Luanxian (2500 cal aBP). The western boundary of the Luanhe Rive fan-delta is located at Qian'an-the Douhe River mouth. The boundary between the old and young fan-deltas is at Luanxian-Luannan-the Suhe River mouth. The Luanhe River has high sediment discharge and concentration when it enters the sea, and its channel shifted for several times on the alluvial fan, forming many deltaic lobes in lobate shape. The deltaic coast is an low wave energy environment. Because barrier islands form off the mouth, the delta looks like a wave-dominated delta, which is closely related with coarser sediments-sand. The Luanhe River delta, in fact, is a river-wave dominated delta.