Seismic sedimentology is a newly emerged interdisciplinary subject, which uses seismic data to gain insights into the rocks and their forming processes. It is regarded as an effective tool for mapping high-frequency sequence and depositional systems, and plays an important role in the exploration and production of thin sandstone reservoirs. Because of the scarcity of well data in the deep sag zone, the distribution and the scale of the sandstone reservoir in the deep sag zone are very difficult to determine by using the conventional exploration method. Guided by the third-order sequence-stratigraphic correlations from seismic and wire-line log data, in this study, stratum slices were prepared from a three-dimensional seismic volume to reveal sand-body distribution in the deep sag zone and to map the associated depositional systems distributions in slopes of the depression. With the assistance of the comprehensive analysis of core, lithology and well-logging data, the slump turbidite sandstone reservoirs of different sequences in the deep sag zone were effectively predicted.