滦河冲积扇-三角洲的范围和类型及其演化

从晚更新世晚期(早于距今15 000 年前)至大约距今2 500年前滦河从河北省迁安流出山区,形成以迁安为顶点的老滦河冲积扇-三角洲,大约2500年前滦河改道,在迁安瓜村东北冲出断层破碎带,夺青龙河,形成以滦县为顶点的新滦河冲积扇-三角洲。全新世海侵最大边界为冲积扇和三角洲的分界,该界限以北为老冲积扇和新冲积扇,界限以南为老三角洲(陡河口至溯河口)和新三角洲(溯河口至现代河口北),滦河冲积扇-三角洲的西界在迁安-陡河口,新、老滦河冲积扇-三角洲的界限在滦县-滦南-溯河口,曹妃甸岛是老三角洲废弃后仍然残留的障壁岛。滦河三角洲既具有河控三角洲的特点,也有波控三角洲的特点,但滦河三角洲海岸波能相当低,显现出波控三角洲的特点是因为滦河入海泥沙粒度粗的原因,将它归类于河控-波控三角洲更为合适。

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.