The researchers studied where the rocks in the lower first member of Shahejie Formation in the Lixian Slop came from. They looked at water systems, types of minerals, and sandstone thickness to figure out the sources. The rocks mostly came from the north and southwest of the slope, specifically from Taihang Mountain in the west and the Niutuozhen salience in the north. The rocks from the southeast were more important than those from the north, and they all met at Xiliu area.