东江三角洲地貌特征

GEOMORPHOLOGICAL CHARACTERISTICS AND DEVELOPMENT IN EAST RIVER DELTA

本文应用地貌学、年代学、沉积学、历史地理学等方法,讨论了东江三角洲的范围,分析了周边地貌和三角洲地貌的特征,研究了构造、气候、河流、海洋诸因素对地貌发育的影响,提出了地貌发育过程的5个阶段的新看法。

Based on geomorphology, chronology, sedimentology and historic geography, the range of East River delta was studied and the top of the delta was believed to be at the mouth of Chilinxia gorge which stretches upstream about 23 km. The circumjacent and delta geomorphic characteristics were studied, the former is characterized by a mountain circumference, multitudinous streams which converge into the delta and an irregular circumference, the latter is characterized by a low and smooth plain, a crisscross network of streams and prosperous deposition. Some factors which influence the geomorphological development of East River delta were also studied. 1. the fault block basin controls, the geomrphological development. 2. big amount of water and silt with the south subtropic monsoon climate is the sources of delta sedimentation; 3. the stream flows are the main external forces in the process of geomorphological development in this area. 4, transgression, tidal current and saltwater encroachment are the main marine forces to mould the present delta.According to the drill holes and their analyses of chronology, sedimentology, paleontology, the process of geomorphological development of East River delta can be divided into 5 periods. (1) Q.23-1 period of alluvial deposition.(2) Q23-2 period of old delta in which the top of delta was near Zhongtan.(3) Q33 period of weathering and alluvial fans. (4) Q14-Q24 period of new delta in which the top of delta reached near the mouth of Chilinxia gorge.(5) Q34 period of deposition and stretching of the present delta plain.