廊固盆地早第三纪浊流沉积的流体性质演化与持续时间

FLUID PROPERTY EVOLUTION AND DURATION OF PALEOGENE TURBIDITY CURRENT DEPOSITS IN LANGGU BASIN

廊固盆地下第三系粒级递变砂岩，系浊流在流动体制下的沉积结果，在其沉积过程中逐渐向牵引流转化。大多数浊流在刚一出现牵引流或出现牵引流之后不久就结束了其沉积史。浊流具有流动速度快、搬运距离短、沉积速度快、持续时间不长的特点。

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.