浙江临安板桥奥陶系胡乐组笔石新材料及其意义

报道在浙江临安板桥奥陶系剖面的胡乐组中发现的较丰富的笔石动物群,包括Pterograptus elegans,Expansograptus sp.1,Tylograptus sp.,Cryptograptus?sp.,Archicli macograptus angulatus,A.caelatus,Procli-macograptus angustatus等主要属种,应属达瑞威尔阶Pterograptus elegans笔石带。这一发现表明,临安板桥一带的胡乐组时代跨度非常局限,底界比浙赣交界"三山地区"的胡乐组之底高2个笔石带,顶界对比则低2个笔石带。其下伏牯牛潭组的顶界与宜昌三峡地区相比,也低了2个笔石带,具明显的穿时现象。

NEW MATERIAL OF GRAPTOLITE FROM THE ORDOVICIAN HULO FORMATION IN BANQIAO SECTION,LIN’AN,ZHEJIANG AND ITS SIGNIFICANCE

New material of graptolites is found from the Hulo Formation of the Banqiao section, Lin’an, Zhejiang Province. The assemblage contains Pterograptus elegans, Expansograptus sp. 1,Tylograptus sp.,Cryptograptus? sp.,Archiclimacograptus angulatus, A. caelatus and Proclimacograptus angustatus, and indicates an age of the Pterograptus elegans Biozone (Darriwilian, Middle Ordovician) for the Hulo Formation. A comparison of the Hulo Formation in the Banqiao section with the same formation in the JCY (Jiangshan-Changshan-Yushan) area bordering the Jiangxi and Zhejiang provinces shows that the Hulo Formation in Banqiao, Lin’an is much more constrained, with its base being two graptolite biozones higher and its top being two biozones lower than in the JCY area. The Hulo Formation overlies conformably the Kuniutan Formation, the top boundary of the Kuniutan Formation is thus two biozones lower than that in its type area (Yangtze Gorges Area), and is apparently diachronous.