Shidao

an islet of Xisha Islands

is a tableland composed of upper Pleisto-cene bioclastic limestone.Its formation was clearly affected both by sea level fluctuation and crustal movement

suffered a environment of low level and arid climate of postglacial age.Shidao now exhibits a geomorphological envi-ronment of offshore sand bar and lagoon.Therefore

its strata present steeper slope and shows antiform sedimentary structure.According to the joints and calcite developed within spaces of lamellations

it has been subjected to influ-ence of crustal movement.The uncomformity between the upper Pleistocene sediments and recent sedi-ments and the C

14

age dating demonstrates that there had been fluctuation of sea level.This means that a high sea level stage might occur.As for the age reversal of the bioclastic limestones

it is considered to be the result of particular condition of the islet

i.e.the conventional stratigra-phical law does not work in the present islet.Lithofacies of bioclastic limestones

its property

thickness and the pattern of arrangement

has exerted significant influence on the landform of erosion and accumulation of this islet.