利用碳氧同位素识别碳酸盐岩层序界面

Using Carbon and Oxygen Isotopes to Identify Carbonate Strata Sequence Interface

为更好地识别碳酸盐岩的层序界面,以周口店地区的马家沟组与本溪组、铁岭组与下马岭组两个不整合界面为例,综合采用野外露头及岩性特征描述。采集不整合面附近岩样进行稳定碳氧同位素检测,得出马家沟组稳定同位素测定值δ13C(PDB)‰为-6.19‰～-0.69‰,δ18O(PDB)‰为-10.57‰～-9.08‰,属浅海相沉积;铁岭组δ13C(PDB)‰为-2.44‰～-0.67‰,δ18O(PDB)‰为-8.39‰～-4.47‰,属潮间带沉积。将检测数据进行曲线拟合,证明与该地区沉积环境完全吻合,借此可以识别其不整合面。故提出结合不整合剖面及其岩性组合变化,利用稳定碳氧同位素检测可作为识别碳酸盐岩层序界面的另一种有效方法。

To better identify carbonate sequence interface, In Zhoukoudian area with Majiagou group, Benxi group, Tieling group and Xiamaling group of two unconformity interface as an example, the comprehensive field outcrop observation and lithologic variation characteristics description, gathering near the unconformity surface sam- ple test stable carbon and oxygen isotopes,acquisition unconformity surface rock near by detecting δ13C（PDB） %o and δ18O （PDB） %o numerical change quasi synthetic corresponding curve are analysed to identify unconformity surface. Majiagou group of stable isotope measured value 813C （PDB） ‰ for -6. 19 ‰ -0. 69 ‰,δ18O （PDB） ‰ for -10. 57 ‰ - -9.08 ‰, belongs to the neritic facies sedimentation. Tieling groupδ13C （PDB） ‰ for -2. 44 ‰ - -0. 67 ‰, δ18O（PDB） ‰ for -8.39 ‰ - -4. 47 ‰, belongs to the intertidal zone de- posit, prove that accord with the depositional environment in the region, it can identify the unconformity surface. So combining unconformity profile characteristics and lithologic combination changes, the use of stable carbon oxy- gen isotope detection can be used as identification of carbonate rock sequence interface in addition a kind of effective method.