In order to demonstrate the sedimentary characteristics of gravelly beach-bar in the Lower Cretaceous Tenggeer Formation in the joint area of the Xilinhaolai and Daerqi of the southern gentle slope of the Baiyinchagan sag

Erlian Basin

abundant cores and logging data were utilized to analyze the spatial distribution

texture

sedimentary structure and vertical sedimentary sequences in the context of regional geological setting.The beach-bar conglomerates occur in the debris flow conglomerates and pebble sandstone-mudstone as thin interbeds

featuring in fair roundness but worse sorting

relative abundance of pebbles with barred and flat shape

and Janus configuration of maximum flat plain/major axis.It is in gradational contact with the underlying debris-flow deposits featuring in reverse grading

while it is in abrupt contact with the overlying shallow lake mudstones or debris-flow deposits

featuring

as a whole

in vertical alternation of reverse and normal grading.The sedimentary model in the study area is dominated by elutriation and winnowing of the early debris-flow deposits by the waves in the waterfront and shallow lacustrine.The fine-grained clasts were transported to the shallow lake to form the sandy beach-bar

while the pebbles stayed to form gravelly beach-bar

with troughs possibly occurring between these two deposits system.They were formed under 4 main conditions

namely the powerful water strength

low relief landform

low system tract(LST)and suitable sedimentary sources.