摘要
海南岛西北岸有晚更新世以来二期火山活动,共5次喷发,沿海岸密集的火山喷发孔、岩流堆积,构成了独特的海蚀型火山港湾岸。火山活动改变了沿岸地形、河流流向与沉积环境,使海岸沉积相数次变化。据岩石学研究,该区系洋岛型橄榄玄武岩及大洋中脊型拉斑玄武岩,反映了海南岛—北部湾海底有扩张的迹象。
There have been two periods of volcanism with 5 eruptions in the area of northwestern Hainan Island. The first one occurred in late Pleistocene, dating back to 5.2X104 a B. P.. It formed a lava field which covered a sandy deposit. This was later baked and altered. Another eruption took place 2.5X104 a B. P. The lava which emitted at that time consists of olivine basalt and tholeiite basalt; the flow ripples of elastics of them are still well-preserved Later eruptions occurred in the Holocene, which many small breached craters appearing on the coasts and islands around and in the Beibu Bay. The last of these eruptions raised the former shingle beaches 15 m high and the former tidal flat to form terrace 20 m above sea level.
This volcanic belt runs along the seashore which trends in northeast direction. It might be the result of a crustal extension in the Beibu Bay and Yingge Sea, Since the earth crust here is only 30 km thick. At present barrier coral reefs are well-developed along this volcanic coast. Most probably, they have basalt thus emitted as their basement, since the geothermal gradient here is favorable for their growth.
出处
《地理学报》
EI
CSSCI
CSCD
北大核心
1990年第3期321-330,T002,共11页
Acta Geographica Sinica
关键词
海岸
火山
海南
研究
西北部
Hainan Island
Volcanic toast
Sea bed spreading in Beibu Bay
