| The interaction between gravity flow deposits and contourite deposits has been researched based on the outcrop in Ordovician Pingliang Formation of Pingliang region in Gansu province. It is shown that calcarenite and shale are the mainly lithology of Pingliang Formation, and partly with some calcirudite. It is determined that five typical lithofacies include horizontal bedding shale, massive calcirudite, massive calcarenite, graded bedding calcarenite and lenticular cross bedding calcarenite, which correspond to in situ deep-water deposits, debris flow deposits, turbidites and contourites. The energy of the contour current which moved from east to west paralleling to the slope, might be enhanced in the confined environments of Qinling-Qilian Trough. The scale of gravity flow deposits became weaker from the bottom up in Pingliang Formation, while the scale of contourite deposits became stronger. It is concluded that gravity flow was active and the effect of contour current was weak when the relative sea-level was low, and vice versa. The early gravity flow deposits can be subject to transpotation, reconstruction, redeposition by the contour current and then contourites come into being, on the contrary, it is possible that the early contourites are eroded and destroyed by the gravity flow. |
