Table 1 Lithofacies of the upper Guantao Formation in the Zhanhua Sag, Bohai Bay Basin.

Gm

At the bottom of the complete fining upward cycle; above the erosional surface, about 5–20 cm thick

Channel lag deposition²⁷

St

Trough cross bedded medium- to fine-grained sandstone; siltstone trough lamina can be observed, the angles vary from 10 to 30°

The migration of 3D dunes²

Sp

Medium- to fine-grained sandstone; planar cross bedded fine-grained sandstone; high angles vary from 20 to 35° and low angle vary from 10 to 15°

The migration of the dunes or bars²⁸

Sh

Horizontally bedded fine-grained sandstone; above lithofacies Sp

A stable directional flow¹⁷

STrc

Ripple cross-laminated siltstone; usually alternates with Sh, Fr, Fd facies

The sediment supply is under a low condition oscillating environment³

Fd

Siltstone to mudstone; Deformation bedding shape; usually alternates with Fr, Fl, Fm facies

The sediment supply is under a low condition oscillating environment²⁹

M

Massive mudstone; gray, purple and mottled claystone or mudstone; with root traces, bioturbation, mottling

Floodplain deposits¹