The scientists studied different types of sediment in the Middle Ordovician Pingliang Stage in the southern part of the Ordos Basin. They identified various sedimentary facies, including those found in open marine platforms, shallow platform edges with reefs, and deep water trench facies. By analyzing the distribution of these facies, they were able to create a map showing where each type of sediment is located. This information helps us understand how the sediments were deposited over time and can guide future gas exploration efforts.