The initial indication of the Shahejie Formation estuarine environment of the Dongpu Depression was the deposition of seismites and the formation of the marine waterrelated sedimentary structures such as synaeresis. These evidences suggest that the Dongpu Depression has experienced tectonic subsidence and occasional incursion of marine water during the Tertiary.At the beginning of the middle part of the division 4 in the Shahejie Formation, another important event took place; that is, a mass death of fresh water Ostracodes. At the same time, marine trace fossils such as Ophiomorpha and Tigillites started to occur. This substitution suggests that fresh water of the ephemeral lake was replaced by saline water of the estuarine at that time. In the late sedimentary period of the middle part of the division 4 of the Shahejie Formation, coastal high energy environments, such as tidal channels and tidal sand bars, were developed, forming oolitic sandstones, shelly sandstones and trace fossils Arenicloites. Over this period, three environmental units, including distributary channel (terrestrial portion), estuarine point bar (mixed energy portion), tidal channel and tidal bar (marine portion), have been developed in the section and the combination of these environments have recorded periodical sea level changes.There are 10 beds containing fresh water trace fossils, plant traces or paleosols (in Kai well 31), and 12 beds containing marine trace fossils or body fossils as well as marine sediments (Kai well 31, New Hu well 4) in sections of the Shahejie Formation. These facts imply that more than ten periods of sea level changes occurred during deposition of the Shahejie Formation.There are some evidences showing that the fluvial channel might have incised into the banks along palaeovalley between the Lanliao Fault and the Neihuan uplift and have produced an incised valley during sea level fall. During the early period of sea level rise, the accommodation space in the incised valley has been fully or partially filled with sandstones of distributary channel, fluvial point bar and estuarine point bar environments, which constitute the incised valley reservoir type in the Dongpu Depression. During the middle period of sea level rise the tidal channel and tidal bar sandstones have developed in this area, which constitute the shelf onlap reservoir type