Discovery and Significance of Seismites in Late Tertiary Yanchang Formation of Ordos Basin

Key words: 
• seismites /
• Ordos Basin /
• Yanchang Formation /
• vertical succession of seismites

Abstract: Seismites is a kind of catastrophic event rock. By the observation of drilling cores, there are many special structures which were generated by ancient widespread earthquake recorded in the seismites of the Triassic Yangchang Formation in Ordos Basin, such as liquefaction sandstone vein, faultgraded, vibrational liquefaction deformation structure, pillow structure, ball structure, tearing mudstone fragment and slumps. The vertical sequence of seismites in Triassic Yangchang Formation, from bottom to top, included 7 units: underlying unshocked layer, shattered layer, laddershaped faulted layer, vibrational liquefaction deformation structure bed，liquefied sandstone vein bed，pillow structure and partner structure layer，homogenized bed and overlying unshocked layer. The first discovery of seismites could be used to analyze the intensively active period of basincontrolling boundary, and the seismites themselves were a kind of potential reservoir.