遗迹化石在层序地层学研究中的应用

以济阳坳陷古近系沙河街组和塔里木盆地志留系为例,探讨了遗迹化石与层序地层学的关系,表现在3个方面:1)层序界面的识别层序界面位置发育有特征性的受基底控制的遗迹相,且界面上下遗迹组合类型发生变化;2)准层序界面的识别较深水环境中,界面上下生物扰动强度明显差异,界面之下扰动强度较大,扰动指数可达到3,而界面之上几乎没有生物扰动,且在同一准层序内部,由下至上,扰动强度逐渐增大;3)旋回层序的识别:在潮控滨线环境中,单个准层序内部,由下至上,高能环境的Skolithos遗迹组合逐渐变为中低能环境的Planolites-Palaeophycus遗迹组合和低能环境的Cochlichnus-Planolites遗迹组合,由下至上呈现旋回性变化特征。

THE APPLICATIoN oF TRACE FOSSILS TO THE RESEARCH OF SEQUENCE STRATIGRAPHY

Taken the Paleogene Shahejie Formation of the Jiyang Depression and the Silurian of the Central Tarim Basin as examples,the relationships between trace fossils and sequence stratigraphy were investigated. Trace fossils are useful in the study of sequence stratigraphy in several aspects: 1) the recognition of sequence boundaries, diagnostic substrate-controlled ichnofacies tend to occur at sequence boundaries and in addition,ichnofacies tend to change across sequence boundaries; 2) the recognition of parasequence boundaries, bioturbation index tends to increase in a parasequence,up to Index 3 just below parasequence boundaries, above a parasequence boundary, however, bioturbation index is typically low; 3) the recognition and analysis of sequence cyclicity. In tide-controlled foreshore facies,ichno-assemblage exhibits cyclic change within a parasequence,with Skolithos ichno-assemblage representing high energy environments, Planolites-Palaeophycus ichno-assemblage representing middle to low energy environments, and Cochlichnus-Planolites ichno-assemblage occurring predominantly in low energy environments.