The formation encompasses two members. The first member is primarily
calcareous mudstone and
dolomite, indicative of a coastal environment. The second member is a thicker marine sequence of dark
micritic limestone with some dolomite. Two distinct fossil assemblages are found in the second member. The older
Luoping biota preserves abundant
arthropods (including
isopods,
decapods,
mysidaceans and
thylacocephalans) along with fossils from other
invertebrates and
vertebrates, which are rare but well-preserved. The slightly younger
Panxian fauna has a more diverse and common assortment of marine reptiles such as
sauropterygians. A
tuff bed in the Luoping biota has been dated to 244.5 ± 2.2 Ma via
U-Pb SHRIMP dating. The Luoping biota as a whole was deposited over a period of 340 ± 71 kyr. This estimate is justified by
cyclostratigraphic evidence, as indicated by fluctuations of terrestrial
proxy metals. == Fossil content ==