中德维宪阶-谢尔普霍夫阶界线层的菊石和牙形刺生物地层对比研究

Significant eustatic fluctuations in late Visean and early Serpukhovian were caused by the effect of the prominent late Palaeozoic global cooling. This led to frequent sedimentary discontinuities and enhanced the biotic provincialism, and in turn brought many difficulties in biostratigraphic correlations and the selection of a global stratotype section and point (GSSP) for the Visean-Serpukhovian (V/S) boundary. Although the conodont Lochriea ziegleri from deep-water facies is widely accepted as the most potential index species for the boundary, its correlation with ammonoids is still unclear because the evolutionary relationships among some ammonoid taxa are under debate for their provincial reasons...The features of ammonoid and conodont faunas and their evolutionary lineages during the V/S transition in different basins will be investigated in this study. The global biostratigraphic correlation within the V/S interval will be discussed based on the updated high-resolution ammonoid and conodont stratigraphic framework in different regions including South China, Northwest China and the Rhenish Mountains, Germany. Meanwhile, the relation between the evolutionary diversities of ammonoids and conodonts and their environmental backgrounds will be analyzed. A better understanding on their palaeoecology and palaeobiogeography will be obtained based on the quantitative or semi-quantitative analysis of diversities of ammonoid and conodont taxa and the analysis of their sedimentary facies.

地质时期生物多样性与重大环境事件研究以及高分辨率综合年代地层学研究是目前地球科学研究的热点。石炭纪维宪期与谢尔普霍夫期之交，冰室效应显著。受频繁的海平面变化影响，很多地区的地层沉积并不连续，生物分区性特征得到加强，给地层划分对比及全球层型研究带来了困难。目前，牙形刺是维宪阶与谢尔普霍夫阶界线标志的首选门类，但其与菊石之间的对比仍存在一些问题。本项目将重点聚焦我国华南、西北以及德国莱茵山等地的界线层剖面，通过菊石与牙形刺的系统古生物学和全球对比研究，恢复这一时期各地区菊石与牙形刺动物群的基本面貌，识别出各自的演化谱系，进而建立起界线层高精度的菊石与牙形刺生物地层对比框架。同时，结合物种多样性的定量或半定量统计以及沉积环境分析等，探讨菊石和牙形刺的演化多样性与环境背景之间的关系，并在古生态学与古生物地理学方面提出新认识。

石炭纪维宪期与谢尔普霍夫期冰室效应显著，致使地层对比存在一定困难。目前，全球谢尔普霍夫阶底界标志尚未确立，牙形刺虽然是首选标志门类，但与菊石以及有孔虫的对比仍存在一定问题。根据项目设计，本研究对维宪阶-谢尔普霍夫阶界线附近的牙形刺与菊石等其它生物标志的对比进行了完善。在本研究中，对华南深水相的纳饶、罗悃、牛桥等剖面牙形刺生物地层学的研究，在界线层识别出牙形刺30余种以及Lochriea属的演化谱系。据此可划分为二至三个牙形刺带，并以Lochriea ziegleri的演化首现位置作为谢尔普霍夫阶底界标志。目前，在纳饶剖面验证了该分子与界线有孔虫标志的对应关系；对华南浅水相的雅水剖面牙形刺生物地层学的研究，首次在华南报道了两类较为少见的牙形刺分子，并结合有孔虫生物地层提出了维宪中晚期浅水牙形刺Cavusgnathus属可能存在的演化谱系。该演化谱系的识别可提高这一时期浅水牙形刺生物地层的对比精度；对新疆卡拉吉拉菊石以及牙形刺生物地层的研究，可建立当地菊石以及牙形刺生物地层的对比关系，但目前获得的牙形刺非华南常见类型，因而跨地区的对比仍存在一定问题，有待后续进一步验证。