峡东地区上兰多维列统的几丁虫

UPPER LIANDOVERY CHITINOZOA FROM EASTERN YANGTZE GORGES

本文介绍了峡东地区上兰多维列统几丁虫的地质分布特征,系统建立了几丁虫生物组合,阐述了这些组合的地层意义,并与国内外同期地层中的几丁虫进行了对比.结合几丁虫共生的腕足类及笔石的生态特征,探讨了峡东地区上兰多维列统几丁虫的生态特征.此外,还描述了两个几丁虫新种.

Based on the investigation of Upeer Llandovery chitinozoan collected from the Upper Longmaxi to Shamao Formation (Upper Llandovery) at Wangjiawan section of Yichang, Jianyangping section of Xinshan, Tizikou section of Yidu and Luoyanshan section of Changyang in the eastern Yangtze Gorges, the four chitinozoan assemblage zones can be recognized in this particular area as follows:1. Conochitina edjelensis elongata Assemblage ZoneThis assemblage is present in the upper part of Longmaxi to Upper Member of Luore-ping Formations, and characterized by the occurence of Conochitine edjelensis elongata. The upper limit is defined by the first appearance of Conochitina emmastensis. This assemblage zone is likely equivalent to the middle-upper M. Sedgiwickii Zone in age due to coexistance of it with graptolites of M. Sedgiwickii Zone in the Upper longmaxi Formation and Pen-tamerus the Upper Member of Luoreping formation. Other chitinozoans of this zone are Conochitina edjelensis,Desmochitina sp. etc..2. Conochitina emmastensis-Conochitina iklaensis Assemblage zoneThis assamblage zone, occuring in lower part of Shamao Formation, is marked by the appearance of Conochitina emmastensis at the base and the disappearance of C. iklaensis at the top respectively. Other chitinozoans in this zone include Conochitina edjelensis, C. brevis. C. gordonensis etc.. Considering that C. iklaensis and C. edjelensis.usually could not rnag up over the M. Sedgiwickii Zone in horizon it is suggested that this assemblage zone is probably corresponding to the Upper M. Sedgiwickii Zone.3. Cyathochifina shamaoensis sp. nov. Assemblage ZoneThis assemblage zone characterized by the presence of this new species in the Second Member of Shamao Formation of Wangjiawan section. It need further study whether this zone is just correlated with the internal of 5. tarrisculus Zone in age.4. Angochifina longicollis Assemblage ZoneA. longicollis found in the upper part oP'Shamao Group' at the Tizikou section of Yidu is thought to be corresponding to a part of the M. crispus Zone in age.Based on the analyses of benthic assemblage of brachiopod (BA) or depth zonation of graptolite(GA). Some suggestions concerning chitinozoan ecology are present in this paper as following.1. The chitinozoan occurred in BA2 is characterized by relative abundance of Angochitina species or other chitinozoan, which with lower diversity but higher frequence.2. Conochitina may be occurred in the sea-bottoms of BA2 to BA4,but there are highest diversity and frequence in BA3 and it may be concerned with that Conochitina itself is benthic type.