Hulan Gr

The Hulan Gr was proposed by the Prospecting Party of Metallurgical Bureau of Jilin Province in 1951 and formally quoted by the Chinese Academy of Geological Sciences (1976). The type section is located in the area of Hulanzhen Township, Panshi County, Jilin Province. The reference section is at Shifeng of Wanyue, Yiyun Township, Dongliao County, Jilin Province.

Synonym: (呼兰群)

The Hulan Gr can be subdivided into three members. Lower member, approximately 2800 m in thickness, is dominated by plagioclase-amphibole-schist, gneiss and tourmaline-bearing two-mica gneiss, with gneiss intercalated with marble at the upper part. Middle member, about 3300 m thick, is mainly composed of biotite gneiss and garnet-schist in its lower part and of white siliceous banded marble and biotite gneiss in the upper part. Upper member, about 4900 m in thickness, is dominated by schist and carbonate rock in its lower part; clastics (slate), volcanic rock (quartzose-schist) and marble in its upper part, and black slate at the top. The lower and middle members belong to deep metamorphosed amphibolite facies, while the upper member is epi-metamorphosed rocks with most protolith textures reserved.

Only corals were found in the upper member: Thamnopora, Cladopora, Spongophyllum, Protathyris, Syringopora, Circophyllum etc. The exact age of this group is uncertain until now.