The Huixingshao Formation correlates to the Upper Red Beds in the wider South China region.[1] It is made of purple-red and greyish-green clastic rocks, varying between mudstone and muddy siltstone.[2]
The formation overlies the Xiushan Formation, and underlies the Xiaoxi Formation (Ludlow Red Beds), which was deposited in the Late Silurian following the erosion of the upper Huixingshao Formation.[2] In the Xiushan area, the Xiaoxi Formation was historically considered part of the Huixingshao Formation,[2] but was later reclassified following the discovery of plant fossils and acritarchs.[3]
The Huixingshao Formation preserves a coastal environment supplied with freshwater,[4] on the shelf basin of the Yangtze Sea, a marginal sea of the Qinling Ocean, as it transitioned away from an anoxic environment.[5]Chemical weathering would have led to a nutrient-rich environment, increasing biological productivity during the deposition of the Chongqing Lagerstätte. The environment was warm and humid, following a cooler early Telychian, reflected in an increase in weathering intensity.[6]
