CHARACTERISTICS OF DOUBLE-CIRCULAR SLOPE BREAK AND THE CONTROL ON SEDIMENTARY PROCESS IN THE SONGLIAO BASIN, NE CHINA

The characteristics of slope break during depression stage in the Songliao basin of NE China are analyzed and indicate that double flexure slope breaks extend in a circle across the basin. One is nominated inner slope break, and the other is external slope break. Under different regional stress fields, the control of slope break on sedimentary process is different. Under the extensional stress field, the sedimentary system of meandering river is found in the inner slope break and the braided river sedimentary system is in the external one. The sandbody of channel is favorable reservoirs. The typical example comes from the Quantou Formation (K1q). Under the compressive stress field, there are local alluvial fans and the braided river sedimentary system at the edge of external slope break. The delta plain is found between the inner and external slope breaks. In the inner slope break, there are the former delta sediments and lots of the mouth bars of delta front, and the fluxoturbidite is also found there. The sandbody of delta front and the turbidite in lake are favorable reservoirs. The typical example comes from the Yaojia Formation (K2y).