The ratio between dibenzothiophen and phenanthrine is less than 1.0,suggesting that the whole Shahejie Formation was formed in weak oxidation environment of fresh water.

• 大民屯凹陷沙河街组的二苯并噻吩与菲的比值都在1.；0以下，表明该凹陷的沙河街组整体上形成于淡水弱氧化环境；