Permian division and correlation and distribution of volcanic rocks of Tarim basin
塔里木盆地二叠系划分对比与火山岩分布

Based on the basin-wide analysis of well, outcrops and tracing of seismic data, the underground Permian petrologic stratigraphy is re-divided and correlated throughout the Tarim Basin. Permian System upward consists of one aggradation interval and three retrogradation intervals of natural gamma ray logs. The aggradation interval belongs to Nanzha Formation, and the other three intervals belong to respectively Kupkuciman Formation, Kaipeleicike Formation and Shajingzi Formation. Nanzha Formation is dominated by rocks of brown gray shales interbedded with thin limestones that represent littoral to neritic deposits during the last transgression in Tarim basin. Kupkuciman and Kaipeleicike Formations are two cycles from basic to acidic volcanic rocks or from basic volcanic to terrestrial clastic rocks. Shajingzi Formation is an allocycle from alluvial fan to branded channel to meandering fluvial deposition resulted from a tectonic movement. The Permian volcanic rocks are thicker over the areas from Hetian River to Tazhong to Shuntuoguole. The volcanic rocks are atypically 0~60m in Kupkuciman Formation, and 0~200m or locally over 400m in Kaipeleicike Formation. The volcanic rocks of Kaipeleicike Formation are accumulated further northeast compared to that of Kupkuciman Formation. Over the middle to west region of Tarim basin, part of Kupkuciman volcanic rocks might have formed underwater. Volcanic passage and craters seen on seismic sections are distributed extensively on the anticlines or fault nose structures in uplifted region and rarely seen in depression area. Volcanic rocks can serve as cap or shelter rocks of a pool, or be reworked to be one kind of reservoir rocks, but mostly the volcanic activity might have affected or to some extent destroyed the earlier formed oil-gas pools.