关键词: 等深流沉积, 水道-天然堤体系, 中奥陶统, 鄂尔多斯盆地

Abstract: Contourite is an important sedimentary type of traction current deposits in a deep-water environment. Although there has
been a lot of research on contourites, most studies focus on contour concurrent deposition in modern oceans by bathymetric
investigation and deep-sea drilling (DSDP, ODP and IODP). Following the implementation of the IODP (Integrated Ocean Drilling
Program) Expedition 339 (The Mediterranean outflow), the study of contourites has reached a new stage for analyzing the vertical and
lateral succession of contour drifts. However, there is still a great restriction on further study of contourites, especially on the
depositional model for contour currents because of the big gap between modern sea floor and stratigraphic records. This article is
focused on the ancient contour current deposits developed in the northwestern margin of the Ordos Basin, in Darriwilian Stage, Middle
Ordovician. Sedimentology analysis based on the detailed field work in shixiagu section, Hainan area in Wuhai city of Inner Mongolia
allows us to differentiate three vertical successions, i.e., the medium-to thin-bedded amalgamated limestone, the alternation of
limestone-mudstone unit and mudstone, and the striation mudstone is the notable characteristics in the lower, middle, and upper part of
the Kelimoli Formation, respectively. These three successions are proposed to represent the deposits of channel, levee, and basin in
deep-water environments where contour currents dominate. Thus, a conceptual model of deep-water channel-levee system for the
deposition of contour currents is developed from the geological records in the western Ordos Basin

Key words: contour current deposition, channel-levee system, Middle Ordovician, Ordos Basin