Abstract: The Lianglitage formation of Upper Ordovician is rich in reef, which led the domal seismic anomaly bodies in Tazhong area of Tarim basin to be interpreted as reef in recent years. According to the integrated study of seismic and geological analysis, it is indicated that the reef or multiple circled complex reef-banks can not be recognized directly in conventional seismic profiles because the thickness of the reef is less than one eighth of wavelength, the width of it is less than one radius of Fresnel zone. Reefs or complex reef-banks are always invisible and intermixed in the strong reflection (T₇⁴), the top boundary of successive carbonate overlain by interbedded limestone and mud or/and the under 1~2 feeble and discontinuous reflections. Those domal seismic anomaly bodies overlying the strong reflection of T₇⁴, with inner bedding configuration composed of mid-strong reflections, reflect the interbedded configuration of limestone or argillaceous limestone with mudstone, which are the products of sedimentary environment with low-and high-energy transition zones, and the low probability of reef-bank deposits within them. The accurate interpretation shows that such domal bodies are the seismic reflections of nonreef-bank deposits of low angle thrust faults, slope slump accumulative zones and turbidite fans.

Key words: Tazhong area, Ordovician, domal seismic reflection anomaly body, reef, fault structure