REPLACED DEPOSITION OF GRAVITY FLOWS ALONG MOVING A DEEP WATER DUSTPAN THALWEG

In the early stage of the deposition of the 3rd Member of Tertiary,Shahejie Section,a dustpan thalweg developed between Qingzuji and Changheng faults due to differential faultings in western Dongpu Depression and the strike line of the thalweg paralled with the axial line of the depression.Since the gravity flows entered the dustpan thalweg from the opposite directions of south aud north,it had to be turned in direction and moved along the extensional trend of the thalweg.Therefore,the replaced deposition of the gravity flow developed,for which the recognized configuration is band or ellipsoid.1,Laterally,the sand sequences are quite thick at central part and thin out toward both sides with obvious changes in grain size.2,Vertically,the upper the sequence,the finer the grain size.The depositional facies includes channel and outflow subfacies with four microfacies of channel axis,point bar (bam),outflow near channel and outflow far from channel in which the channel microfacies are the most active depositional unit with moving feature.However,the replaced deposition of gravity flows is a frontier for oil/gas exploration.