Plenty of braided river delta front deposits and prodelta deposits were discovered in Lower Tertiary Shahejie Formation in Bonan Sag

Shengli Oilfields. They differ greatly from other types of delta deposits. The main body of the delta front consists of subaqueous distributary channel sandbars composed of pebbled sandstone and midium-coarse sandstone. Cross-bedding developed well in the delta

especially lateral accretion cross-bedding formed by lateral displacement and accretion of river channel sandbars.