**6. Conclusions**

(1) It is proposed to use the descriptive vocabulary organic-rich clasts (ORC) to collectively represent carbonaceous fragments, carbonaceous mudstone clasts, shale clasts, dark mudstone clasts and plant fragments developed in coal-bearing sandstones.

(2) A total of five sedimentary environments of ORC were identified, including fluvial channels, crevasse fans, tidal channels, sand flats, and subaqueous debris flow deposits.

(3) The occurrence of ORCs in coal-bearing sandstones is not only controlled by the changes of the water flow during transportation, but also related to the decomposition resistance of their components. After a series of processes during water flow transport, ORCs shows the characteristic of obvious mechanical di fferentiation in the vertical direction. Based on this, we propose that ORCs can be classified into four types: diamictic organic-rich clasts, floating organic-rich clasts, loaded lamellar organic-rich clasts, and thin interlayer organic-rich clasts.

(4) The changes in water flow energy during transportation play a controlling role in the formation of ORCs. We have summarized two formation mechanisms of ORCs in coal-bearing sandstones, including the long-term altering of continuous water flow and the short-term water flow acting triggered by sudden events.

**Author Contributions:** Conceptualization, G.Y.; methodology, G.Y.; software, G.Y.; validation, G.Y., W.H., J.Z. and N.S.; formal analysis, G.Y.; investigation, N.S.; resources, G.Y.; data curation, G.Y.; writing—original draft preparation, G.Y.; writing—review and editing, W.H. and J.Z.; visualization, G.Y.; supervision, W.H.; project administration, W.H.; funding acquisition, W.H. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was financially supported by the National Major Science and Technology Projects of China (No.2016ZX05066001-003) and National Natural Science Foundation of China (No. U1910205).

**Acknowledgments:** Special thanks are given to China United Coalbed Methane Corporation for providing the studied samples and data.

**Conflicts of Interest:** The authors declare no conflicts of interest.
