陕西镇巴早寒武世海绵骨针化石  

EARLY CAMBRIAN SPONGE SPICULE FOSSILS FROM ZHENBA COUNTY,SOUTHERN SHAANXI PROVINCE

作　　者：赵鑫[1] 李国祥[1] 

机构地区：[1]现代古生物学和地层学国家重点实验室

出　　处：《微体古生物学报》2006年第3期281-294,共14页Acta Micropalaeontologica Sinica

基　　金：国家自然科学基金项目(Nos.40572006;40372020);中国科学院创新项目资助

摘　　要：作者对采自陕西省镇巴县下寒武统西蒿坪段和水井沱组下部碳酸盐岩地层的海绵骨针化石进行了研究。三叶虫及小壳化石的生物地层学资料表明西蒿坪段和水井沱组下段属于筇竹寺阶。化石经室内醋酸浸泡处理后获得,骨针化石保存较好、类型多样,其中属于六射海绵纲的骨针3类,普通海绵纲的骨针6类,分类未定的骨针1类(Nabaviellasp.);并详细地对各类骨针化石进行了描述。虽然普通海绵骨针类型多样,但六射海绵的骨针丰度远高于普通海绵。简要地探讨了海绵骨针的保存方式,对比和分析了西蒿坪段和水井沱组海绵骨针化石组成的差异。结合同时代产自皖南荷塘组和云南澄江动物群中特异保存的海绵软躯体化石资料,认为虽然海绵动物起源于新元古代末期,但躯体海绵化石和骨针化石都显示海绵动物的大辐射事件发生在早寒武世筇竹寺期。The abrupt diversification of animals at the Ediacaran-Cambrian transition is one of the most important events in the history of life, and this event has been called the Cambrian Explosion （or Radiation） in literature. Besides bilaterian animals, nonbilaterians, such as cnidarians and sponges, are also part of the diversification event （Xiao et al. , 2005）. During past years, many progresses on the study of Early Cambrian sponges have been made along with discovery of diverse sponge fossils of exceptional preservations, e.g. the Chengjlang Biota, Niutitang Biota, Hetang Biota. All these researches show that the sponge radiation event occurred in the Qiongzhusian Age. Unlike body fossils, the work on disartlculated sponge spicules is relatively limited, although sponge spicules could be very abundant and diverse through acid maceration of Early Cambrian carbonate samples in laboratory. The purpose of this paper is to describe the sponge spicules collected from the Lower Cambrian of southern Shaanxi, to document the preservation mechanism of these sponge spicules, and to discuss the implication for the early Cambrian sponge radiation. Sponge spicules studied herein were collected from dolomites of the Lower Cambrian Xihaoping Member and from nodular limestones of the lower Shuijingtuo Formation at the Xiaoyang and Yudu sections, Zhenba County, Shaanxi Province （Text-figs. 1, 2）. Both sections are situated on the present-day northern margin of the Yangtze Platform. Biostratigraphic data of both trilobites and bradoriids indicate that these sponge spicules are of the Early Cambrian Qiongzhusian age （Li et al., 2004）. The spicules were extracted from dolo- mites and limestones with 5%--7% acetic acid, and examined under SEM after being coated with gold. The preservation of spicules is variable. The original composition of the spicules is opal （SiO2. nH2O）, which is unstable mineral. Subsequently, opal alteration during diagenesis usually results in the formation of quartz spicules, which were for

关 键 词：海绵骨针 西蒿坪段 水井沱组 早寒武世 陕西 

分 类 号：Q915[天文地球—古生物学与地层学]