南阳凹陷西大岗露头区核桃园组裂离不整合的发现及其地质意义

Discovery and significance of the breakup unconformity in the Hetaoyuan Formation, Nanyang depression

摘要: 本文重点解剖南阳凹陷唐河低凸起西大岗露头区核桃园组二段中亚段(E₂ h₂²)与上亚段(E₂ h₂¹)的接触界。通过实测剖面,结合室内岩石薄片鉴定、粒度分析、X衍射和地球化学分析,确认该接触界面实为裂离不整合,不同于前人认识的"古暴露面",系由北东向控盆断裂——曲洼断裂强烈的伸展作用所造成,代表了南阳凹陷以南部控盆断裂为主向以东部控盆断裂为主的转变。

Abstract: The present paper focuses on the boundary and the sedimentary strata between the middle submember (E₂ h₂²) and upper submember (E₂ h₂¹) of the second member of the Hetaoyuan Formation in the Xidagang outcrop areas, Nanyang depression. The authors contend on the basis of thin section examination, granulometric analysis, X-ray diffraction patterns and geochemical signatures that the boundary should be a breakup unconformity rather than the formerly "palaeoexposure surface". This breakup unconformity resulted from the highly extension of the Quwa fault, a NE-trending fault, and represents the transition from the southern faults to the eastern faults in the Nanyang depression.