Interpretation

Thick sand sediments in the facies association I are interpreted as fluvial or distributary channel deposits (Figure 4N), while fine-grained plant remnants in flood plain and mire provide the source for the formation of ORC, all developing in the Shanxi Formation. The ORCs in sandstone are chiefly the products of either: (1) scouring of the bottom underlying semi-consolidated peat by the high energy turbulent flow; (2) lateral erosion or slumping of bank sediments triggered by the water flow (high-density turbidity or quasi-stable flow). The ORC from di fferent parts in sandstone underwent di fferent sedimentation. Only a small amount of produced ORCs is similarly in-situ deposited in the vicinity of the erosion surface or after short-distance rolling transport. However, most of the produced ORCs are carried away and reworked by the water flow and water-transported debris [68]. The scattered floating ORC is the result of hindered setting in a high-density turbulent flow. After intense modification and long-distance transport, the ORC breaks up into small pieces of high maturity and deposits as the energy of the water flow diminishes. The loaded ORC, in the form of weakly continuous cross-lamination, is formed under the condition of transitional to high flow regime. In the low flow regime, the fragmented ORC is shaped into the continuous lamellar aggregate.

#### *4.2. Facies Association II*
