Distribution and Origin Model of the Cenozoic Conglomerate Deposits by Electrical Survey in Kuqa Depression of Tarim Basin

Haitao Sun; Haihua Zhu; Dakang Zhong

There was great alluvial fan deposition with thickness up to thousands meters during Cenozoic, the foreland deformation period of Kuqa Depression in Tarim Basin, western China. But this conglomerate filling formed in foreland period became a block to gas exploration in underlying formation. So based on the data of outcrop, well log, seismic and 3D electric survey, we analyzed the conglomerate deposition’s origin and distribution in the Cenozoic foreland basin. Form outcrop, we confirmed the conglomerate’s developmental phase and its size, gradation, sedimentary structure, and composition, by which we classified three deposition types or facies of the conglomerate, and the most dominant was alluvial fan. We measured the thickness and size of several Quaternary alluvial fans in Kuqa Depression by outcrop survey. To study the ancient alluvial fans, we correlated several wells which drilled the Pliocene and Pleistocene alluvial fans, using the well log data, and we also analyzed their distributions by the seismic and electric survey. We found the electric data could be a good response to the conglomerate deposition of alluvial fans. The main conglomerate deposition was formed in Kuqa Formation, Xiyu Formation and Quaternary. There were three distribution models of the alluvial fan in Kuqa Depression, which were mainly controlled by the tectonic activity during the late Cenozoic and the provenance of different river systems at northern boundary of the Kuqa Depression. Both of those two factors together controlled the scale and distribution of conglomerate deposition’s size and the gravel composition. Those alluvial fans were the direct evidence to the foreland deformation of Kuqa Depression, so it could be used to deduce the tectonic deformation history, which have not been confirmed. By analyzing the scale changing processes of alluvial fans, we believed that the foreland tectonic activity started at the Later Kuqa Formation, and the most intense tectonic activity enhanced at Xiyu Formation, which continued until now.

This work was supported by the National Basic Research Program of China (“973” Project, Grant No. 2011CB201104) and the National Natural Science Foundation of China (Grant No.41072104). We also thank to the CNPC for technical and data support.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013