Types and vertical structures of Mesozoic unconformity in the compressional abdominal area of Junggar Basin

The recognition of unconformities and their vertical structures is of significance for understanding the tectonic history and petroleum accumulation regularities in the Junggar Basin. According the analysis of tectonic background, outcrops, compound loggings and seismic data, it has a conclusion that there are four types unconformities: onlap/erosion truncation type, concordance/erosion truncation type, onlap/concordance type, concordance/concordance type. Four important unconformity surfaces were identified and analyzed. It's founded that the unconformity has three vertical structures. The upper is glutenite, sandstone layer, the middle is named the decomposed clay layers and the bottom is partial-decomposed rock layers. The unconformities in the compressional abdominal area are not only the important paths for the oil and gas migration, but also are the favourite place for the oil and gas accumulation.