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1·A large amount of burrow fossils are found in pelitic siltstone in the middle Changzhougou Formation of the Mesoproterozoic in the Yanshan area.

在燕山地区中元古代常州沟组中发育有大量的潜穴化石，潜穴产于常州沟组中部的泥质粉砂岩中。

2·Its main rocks is the metamorphic pelitic siltstone, the feldspathic quartz wacke, the fine sandial feldspathic quartz siltstone, the feldspathic wacke and the sericite quartz phyllite etc.

主要岩性有变泥质粉砂岩、长石石英杂砂岩、细砂质长石石英粉砂岩、长石杂砂岩、绢云石英千枚岩等。