This study analyzed the sedimentary characteristics of shallow water deltic sand bodies grown with frequent changes of lake level

summarized their vertical superimposition relationship and areal distribution

and finally established their superimposition pattern

based on the theory of high resolution sequence stratigraphy

combined with a dataset consisting of seismic

logging

core and experiment data.Through analysis

we found that: ① distributary channels (CHs) and mouth bar-beach bar complexes are the main sand body types of the shallow water deltas in the Penglaizhen Formation.In the plan view

the distributary channels are mainly branch-shaped

distributing along the source direction

and MBCs are strip-shaped

parallel to the bank line;while vertically

sand bodies of different genetic types are superimposed into various types of composite sand bodies. ② As relief reduces gradually from the tectonically active margin to the basin

the stream energy decreases linearly with the gradient descent of the river system.Accordingly

the width and depth of the distributary channels of the shallow water delta decrease downwards.The low frequency lake level fluctuation controls the progradation and retrogradation of shallow water delta

whereas the change of high frequency lake levels determines the distribution and superimposition patterns of sand bodies of different genetic types. ③ The sedimentation evolution model of the Late Jurassic shallow water deltas in the foreland basin of Western Sichuan Depression was established

and four types of superimposition patterns for sand bodies there were classified

including superimposed low-accommodation channels

rivers over bar

superimposed high-accommodation channels and superimposed mouth bars.