In Triassic and Lower-Middle Jurassic, there is the acid diagenetic ambient, where inter-pore fluid is from the organic acid released from the coal measures during diagenesis.

• 三迭系至中下侏罗纪煤系为酸性成岩环境，它们在成岩过程中释放的有机酸使隙间流体呈酸性。