广东全新世海岸线变迁

本文根据海滩岩、滨岸沙坝、贝壳堤、贝丘等7个方面的证据,分4个区段讨论了广东全新世海岸线变迁,并对海岸线变迁的内外动力条件进行分析。

COASTLINE CHANGES OF GUANGDONG IN HOLOCENE

According to the evidences of beach rock, shore bar, shell ridge, shell mound, continental-marine alternating beds, marine abrasion trace and historical records, the authors consider that there are some factors that cause the coastline changes. 1.Structural action influences the coastline. There are 5 neotectonic areas along the coastline of Guangdong, namely, Hanjiang-Rongjiang-Lianjiang down-warping area; eastern Guangdong upwarping area; Zhujiang Delta downwarping area; western Guangdong upwarping area and Leizhou Peninsula downwarping area. Generally speaking, the coastline in the downwarping region moves forward faster than in the upwarping region. In the downwarping region, the coastline can be divided into different periods; In the upwarping region, only two or three sand bars in some bay can be considered as the symbols of coastline. 2. Sea level changes influence the coastline. When the sea level rose quickly in Q41-Q42-1a(12000-6000a B. P.), the coast was a drowned one. When transgre-esion was strong in Q42-1b-Q42-2a(6000-4000 a B. P.),the coastline reached the top of the bay.When the sea level was stable in Q42-2b-Q43, the coastline moved forward fast. 3. Coastal current, sediment, typhoon, sharp flood tide and human action also influence the coastline. For example, sediments that come from the Zhujiang River and Hanjiang River have formed the Zhujiang and Hanjiang Deltas. The coastline in these sections moves forward fast. Also the sediments that come from Zhujiang are transported to the west of Guangdong by coastal current.