Dongshan Fm
Type Locality and Naming
E. Heilongjiang – Wandashan and Sanjiang. The Dongshan Formation was established by Tan Xichou in 1924. Its reference section is in Anmingou 7 km north of the Hegang City, Heilongjiang. Tan Xichou named the volcanic rocks above the Shitouhe bed as the Dongshan bed in the Hegang area, with the age unknown. G. Morita called it the Huashan series in 1993. During the Mesozoic-Cenozoic Stratigraphic Conference of Northeast China held in 1974, the Huashan Gr was named and its lower part was called the Dongshan Formation.
Lithology and Thickness
The Dongshan Formation is built up by gray green and gray brown andesitic volcanic breccia, breccia tuff, volcanic agglomerate, pyroxene andesite with sandstone, siltstone, argillite, sandy conglomerate and gravel-bearing grit. The Dongshan Formation is 698 m thick.
Relationships and Distribution
Lower contact
Its base is marked by yellow sandy conglomerate, which is distinguished from the arkose of the underlying Muling Fm. The two formations show a fault contact.
Upper contact
The top part of the formation is marked by gray green pyroxene andesitic volcanic breccia, which is distinguished from the sandy conglomerate and gravel-bearing tuff and sandstone, showing a conformable contact between the two.
Regional extent
The present formation occurs in Dongshan and Shitoumiaozi of the Hegang City, Longhu of the Boli basin, Tieshan and Meiyaoxishan at the juncture of Jidong and Mishan counties and the Boli County, Huashan of the Mashan Mine and Hengshan of the Chengzihe Mine. It varies considerably both in lithology and thickness. In the Hegang basin, It is mainly represented by gray green pyroxene andesite and pyroclastic rocks with dacite, with a decrease of lava and increase of pyroclastic rocks, and with a decrease of thickness from south to north. It is about 700 m thick and contacts conformably or disconformably with the underlying Muling Formation. In the Boli basin, the formation crops out together with coal measures, which is dominated by andesitic-dacitic tuff, tuffaceous breccia and tuff lava, with tuff sandstone and multiple sedimentary beds. In the Lanfeng area, it is dominated by andesite with tuff and tuff lava and lies conformably on the Muling Formation. It ranges from 900 to 1200 m in thickness.
GeoJSON
Fossils
It bears floras Cladophlebis sp.
Age
Depositional setting
It is mainly of volcanic rock facies with sedimentary rock facies.
Additional Information