On the basis of the vertical variation regularities of sedimentary structures

grain size parameters

Saph discrimination numbers and sedimentary factes

the variation of fluid property of Paleogene turbidity current in the Langgu basin is quantitatively analyzed; the deposition rate function of the turbidity currents is established combined with bouma hydraulic analysis and laboratory results; the time of single turbidity current deposition is calculated by means of this function. Researches above show that the monograde bedding sandstones in this basin were deposited under torrent regime; turbidity currents gradually became tractive currents during deposition. Most of the turbidity currents ended their deposition as soon as tractive current emerges of not long after that. The turbidity currents had the characteristics of fast flow

short transportation

fast deposition and short duration.