科研之友
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摘要
The deep lacustrine turbidite sandstone widely develops in Chang-1 interval of Triassic Yanchang Formation, and well exposes in Zichang area of the central Ordos Basin. Based on outcrop observation, the deep lacustrine turbidite sandstone was finely analyzed to study the sedimentary architectural elements of the lacustrine turbidite sandstone. 7 different types of lithofacies, including massive sandstone facies(Sm), massive sandstone facies with teared intraclasts(Smt), parallel bedding sandstone facies(Sh), ripple cross bedding siltstone facies(Fr), contemporaneous deformed structural siltstone facies(Fd), horizontal lamination siltstone facies(Fl)and mudstone facies(Fm), were summarized in Chang-1 interval of Zichang area; and 3 kinds of architectural elements, including channel(CH), levee(LV)and lobe(LB), were recognized. The channel architectural elements can be further divided into 4 types according to their vertical association of lithofacies and spatial distribution characteristics, which correspond to different parts of turbidite fan. In the upper fan area, channel Ⅰ(Smt-Fm-Sm)is developed, and the lateral extensibility of sand body is limited. The middle fan area is mainly composed of channel II (Sm-Sh-Fr-Fl-Fm)and channel Ⅲ(Sm-Fr-Fl-Fm); the two types of sandbodies have very large extensibility and are the main components of deep-water sandbodies of Chang-1 interval in Zichang area. In the lower fan area, channel IV(Sm-Fl-Fm)with poor lateral extensibility is developed. According to the distinction of different types of channels, the depositional model for deep water sandstones of Chang-1 interval in Zichang area was preliminarily proposed.
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