皖南下奥陶统红花园组的牙形类:生物地层及其宏演化意义

The Ordovician marine life underwent an important biodiversification, called 'Great Ordovician Biodiversification Event (GOBE)', with a more than tripled increase in taxonomic diversity at the family, generic and species level, which is recognized as one of the two significant macroevolutionary events during Paleozoic era. Conodonts attained an important development, its diversity and disparity increased dramatically. Conodont biodiversity pattern during the Ordovician is far from understood. Previously, many conodont workers manily documented conodont biodiversity patterns on the base of published literatures. However, few case studies on conodont biodiversity have been conducted. Thus, the present study aims to investigate Ordovician conodont biodiversification on the base of analyzing conodont faunas of critical strata in the field sections..Hunghuayuan Formation consists of thick grayish white and massive limestone, is a vital strata for analysis of conodont biodiversification, of which age is roughly coeval to Floian. The present project will systematically research the conodont fauna from Hunghuayuan Formation in southern Anhui Province. Based on the study of conodont systematics, conodont biostratigraphy, conodont biodiversity pattern, conodont fauna turnover, biofacies and its relationship with paleoenvironments will be discussed in detail.

奥陶纪生物大辐射是显生宙一次重要的生物宏演化事件，大辐射构建并发展了古生代演化动物群的主体框架。作为奥陶纪的重要海洋生物类群之一，牙形类在本次大辐射过程中获得了重大发展。研究牙形类的辐射演化，实例分析尤为重要。本申请课题将重点着眼于关键剖面、关键层位牙形类的系统古生物学研究，进而分析牙形类的辐射演化型式。拟选定安徽南部下奥陶统红花园组牙形类进行系统研究，揭示红花园组牙形类动物群面貌，建立高精度的生物地层框架，据此，深入探讨早奥陶世弗洛期牙形类的辐射演化型式以及相关重要属种的演化趋势；识别红花园组牙形类群落并讨论其古生态与古地理特征，探索群落演替序列和生物相变化以及它们与环境背景之间的联系。

1）系统研究了皖南红花园组及紫台组牙形刺。识别出5个牙形刺生物带，分别是Serratognathus diversus带、Oepikodus evae带、Periodon sp. A带、Baltoniodus navis带、B. norrlandicus带。其中，在皖南地区扬子台地边缘地区的大坪阶底界以Periodon sp.A的出现为特征。.2）系统研究了皖南石台地区下、中奥陶统红花园组、紫台组牙形刺，运用定量统计方法对牙形刺动物群进行了分析，共识别出Tropodus相、Diaphorodus相、Oepikodus相、Baltoniodus相、Paroistodus相、Periodon相和Protopanderodus相等7个牙形刺生物相，根据牙形刺生物相的演替，可以进一步评估海平面的相对变化。.3）基于皖南的牙形刺化石材料，通过分析牙形类磷灰石氧同位素研究了早奥陶世-中奥陶世初期的古气候变化，结果显示红花园组顶部至紫台组下部，海水水体温度呈逐渐变凉趋势。.4）通过对华北、塔里木板块奥陶纪牙形刺研究资料的分析，研究了该地区奥陶纪牙形刺的辐射演化型式。在华北板块，奥陶纪牙形刺记录了4次多样性峰值，塔里木板块奥陶纪牙形刺则有3次多样性峰值。对比研究显示，各板块间牙形刺辐射演化的差异性可能与各版块的古地理位置及地质动力学背景有关。