Abstract:

The Qixia Formation,outcroping on the flanks of the Meishan synclinein Changxing,Zhejiang Province,has a total thickness of 236.94meters.It Consists mainly of bioclastic limestone intercalated with two beds of siliceou srocks which were formed by chemical precipitation.This Formation may bedivided into five lithologic members from top to bottom:the Top Limestone Member(18.11m);the Upper Siliceous Rock Member(24.48m);the Chert-bearing Limestone Member(114.11m);the Lower Siliceous Rock Member(24.04m)and the Stink Limestone Member(56.20m).The limestone contains abundant fossils of many species,but is lack ofcarbonate grains,terrigenous debris and sparry calcite cement.No rocks andsedimentary structures of supra-intertidal or evaporite facies are found.These features show a slightly restricted,subtidal,reducing and shallow-seaenvironment with low energy.The biolithite contains plenty of organic matter with more than 3 per-cert of organic carbon.This limestone,especially that of the Stink Limes-tone Member,is a good oil-source rock.Generally,the oil-storing conditionsof the biolithite are poor,but the suite of sparite and granular biolithite inthe upper part of the Chert-bearing Limestone Member in Meishan-Dushanarea can be considered as a favourable reservoir.According to the infrare dspectrum,the oil and gas are in high degree of thermal evolution and oxidization.