广西涠洲岛全新世上升海滩沉积及其成岩作用

涠洲岛是广西北部湾中的一个火山岛,该岛由第四纪喜山期的喷出岩,主要是玄武岩和火山碎屑岩、凝灰质砂岩等所构成。岛的北部、西部和东部沿岸多处发育有珊瑚岸礁,它们是向海岸地带供应大量各种生物骨壳碎屑的物源区。在海滩地带相应地发育了以生物砂、砾屑为主的海滩沉积。所观察的岛北部和西部的全新世海滩沉积(与海南岛类似的沉积岩层比较,推断可能属全新世)由于海平面下降而处于

HOLOCENE RAISED BEACH SEDIMENTS AND THEIR DIAGENESIS,WEIZHOU ISLAND.GUANGXI

At many places along the coast of Weizhou Island, the coral fringing reefs has developed. Correspondently, the beach sediments consisted of bioclasts developed at the beach. The Holocene beach sediments were rised to the land, and the highest place is about 5m,higher than the present sea level.They are more or less cemented and become an im portant building material for the local residents, In the quarries various deposital structrues can be observed, They are even-stratification with sea- ward dip about 3-10(the major occurrence)，fine-coarse sand-gravel bioclasts in- tercalated beds large scale tabular cross-beddings small cross-bedding， lens of coar- se grain, etc, They represent the products of swash zone, surf zone, beach cusp and storm.