下扬子区奥陶纪牙形刺多样性演变初探

ORDOVICIAN CONODONT DIVERSIFICATION OF THE LOWER YANGTZE VALLEY

根据前人和作者现有资料,对下扬子地区,特别是宁镇地区奥陶纪已经报道的牙形刺属种进行厘定,并按牙形刺带逐带进行多样性统计分析,初步编制出该地区奥陶纪牙形刺属种的地层延限表。研究表明:下扬子区牙形刺在奥陶纪的宏演化经历了3次较明显的辐射事件,分别发生在特马豆克期晚期-弗洛期早期(Serratognathusdiversus带)、大坪期早期(Baltoniodus triangularis带)、达瑞威尔期晚期(Eoplacognathus suecicus带);此外,还经历了2次快速增长期,分别发生在达瑞威尔期早期(Lenodus antivariabilis带)、桑比期晚期至凯迪期早期(Hamaro-dus europaeus带),后者可能与局部环境变化有关。研究表明:华南海平面升降对下扬子区牙形刺宏演化趋势有重要影响。

After restudy on the Ordovician conodont taxonomy and ranges of the conodont species published before and our new materials, the conodont stratigraphical ranges in each zone of the Lower Yangtze Valley （especially that of the Nanjing Hills area） are summarized. Five bio-events can be recognized during the Ordovician. The conodont radiation in the studied area reached its acme at the Tremadocian-Floian boundary （Serratognathus diversus Zone）, early Dapingian （Baltoniodus triangularis Zone）, and Middle-Late Darriwilian （Eoplacognathus suecicus Zone）. Besides, the conodont species has experienced a rapid increase during the early Darriwilian （Lenodus antivariabilis Zone） and early Katian （Hamarodus europaeus Zone）. The research suggests that the conodont radiation may be related to the local sea-level change.