西秦岭地区志留/泥盆系过渡带中的鱼类微体化石及其组合序列

西秦岭是开展华南板块志留/泥盆系界线层序研究的一个重要地区.该区普通沟剖面中的志留/泥盆系过渡带包括羊路沟组上部和下普通沟组下部,产丰富的鱼类微体化石,包括花鳞鱼类、棘鱼类、软骨鱼类及盾皮鱼类.这些化石构成两个完全不同的鱼类微体化石组合:羊路沟组合和下普通沟组合.通过与波罗的海等地区鱼类微体化石带的对比,羊路沟和下普通沟组合的地质时代分别为志留纪普里道利世晚期和早泥盆世洛霍考夫期早期.西秦岭地区志留/泥盆系过渡带中的鱼类微体化石及其组合序列的研究,为该区志留/泥盆系界线的精确确定提供了重要的古鱼类学证据.

THE MICROVERTEBRATE REMAINS AND ASSEMBLAGE SEQUENCES ACROSS THE SILURIAN/DEVONIAN TRANSITION IN WEST QINLING,CHINA

West Qinling is an important area for the study of the Silurian/Devonian Boundary(SDB) in the South China Block.The SDB sequence in the Putonggou Section includes the upper part of the Yanglugou Formation and the lower part of the Xiaputonggou Formation,in which microvertebrate remains(thelodonts,placoderms,acanthodians and chondrichthyans) in association with conodonts and brachiopods have been collected.Two microvertebrate assemblages are recognized in the Putonggou Section:the Yanglugou Assemblage from the upper part of the Yanglugou Formation,and the Xiaputonggou Assemblage from the lower part of the Xiaputonggou Formation in association with the conodont Icriodus woschmidti woschmidti.The Yanglugou Assemblage yields the acanthodians Gomphonchus sandelensis and Ischnacanthidae gen.indet.,and the Xiaputonggou Assemblage includes the thelodonts(Parathelodus scitulus,P.asiaticus and P.cornuformis),the acanthodians(Nostolepis gracilis,N.striata,N.tewonensis,Gansuichthys liui,Poracanthodes zoigenensis,Poracanthodes cf.P.porosus,Ischnacanthys sp.),the chondrichthyan(Arauzia ? sp.),and the placoderm(a pectoral fin fragment of Chuchinolepis ? sp.).Based on the correlation with the microvertebrate biozones in East Baltic,the Yanglugou and Xiaputonggou assemblages are referred to the Late Pridoli and the early Lochkovian respectively,thus providing paleoichthyological evidence for the location of the SDB in West Qinling.