谈女星介(Cypridea)在我国出现的最低层位

DISCUSSION ON THE LOWEST HORIZON OF CYPRIDEA (OSTRACODA) IN CHINA

Cypridea(女星介 )分布在世界许多国家和地区。它的最早出现时代 ,除欧洲为中侏罗世外 ,都见于晚侏罗世。在我国Cypridea分布广泛 ,已在辽、吉、黑、京、冀、晋、蒙、沪、鲁、苏、皖、浙、赣、闽、豫、鄂、湘、粤、桂、琼、滇、川、陕、甘、宁、青、新等 2 7个省、市、自治区以及渤海、黄海海域发现。关于Cypridea在我国出现的最低层位有着不同的意见 ,或上侏罗统或下白垩统。究其原因 ,或是对生物群认识上的分歧 ,或是对含化石地层划分上的异议。通过对四川、湖北、冀北、辽西、甘肃河西走廊、青海、陕甘宁盆地、新疆及东南沿海Cypridea出现最低层位的分析 ,将它们中女星介出现的相同、相似的属种与英国Purbeck层CinderBedsMember上下层位的带化石对比 ,确定了我国晚侏罗世及晚侏罗—早白垩世临界时的生物群 ,从而确认Cypridea在我国出现的最低层位为上侏罗统。

As we are all know,Cypridea(ostracoda) is an important genus,extensively distributed many countries and areas in the world.It plays an important role in the subdivision and correlation of strata,as well as in the palaeogeographic and palaeoclimatic studies ,so it brings to much attention.The earliest age of Cypridea appeared in the Late Jurassic except in Europe ,where it occurs in the Middle Jurassic. In China,Cypridea is extensively distributed ,such as in Liaoning,Heilongjiang,Jilin,Beijing,Hebei,Shanxi,Nei Menggu,Shanghai,Shandong,Jiangsu,Anhui,Zhejiang,Jiangxi,Fujian,Hubei,Hunan, Guangdong,Guangxi ,Hainan,Yunnan,Sichuan,Shanxi,Gansu,Ningxia,Qinghai,Xinjiang and other Provinces,Cities and Autonomous regions.It totals about 492 species. There are different opinions concerning the lower horezon for Cypridea in China,which is recognized as in the Upper Jurassic or Lower Cretaceous.On the basis of previous work,in accordance with analysis of the lowest horizon of Cypridea in Sichuan,Hubei,northern Hebei,western Liaoning,Gansu,Qinghai,Shan Gan Ning Basin,Xinjiang and south eastern coastal areas and etc,as well as comparing with the zone fossils from above and below strata of the Cider Beds Member in Purbeck Beds in England,it is finally considered as the Late Jurassic and from Late Jurassic to Early Cretaceous boundary biological groups.So it can be recognized that the age of the genus Cypridea in China is in the Late Jurassic.