Huangjian Fm
Type Locality and Naming
Western Zhejiang. The Huangjian Formation was designated by Zou Xinhu and Che Qishi in 1962. The section for the designation is at Huangjianshan of the southwest Jiande County, Zhejiang. Lower-Middle formation in Jiangde Gr.
Lithology and Thickness
The Huangjian Formation is mainly represented by gray green, gray purple and gray white acidic lava, acidic pyroclastic rocks, occasionally with intermediate lava and with volcanic rock beds made up of sedimentary rocks. It contacts conformably with both the overlying and underlying strata. It is 943 m thick.
Relationships and Distribution
Lower contact
Its base marked by gray-gray brown massive rhyolite porphyry and rhyolitic tuff lava is distinguished from the underlying Laocun Fm consisting of purple red clayey siltstone with fine sandstone. The formation lies conformably on the underlying Laocun Fm and somewhere overlaps or lies unconformably on the older strata.
Upper contact
Its top is bounded by blue gray tuffaceous conglomerate with tuffaceous grit of the overlying Shouchang Fm.
Regional extent
The formation is distributed in the Shouchang-Linpu and Chunan-Linan areas of northwest Zhejiang. Its lithology and thickness are different from place to place. In the Shouchang-Linpu area, rhyolite porphyry is predominant while acid tuff, ignimbrite, sediment tuff and sedimentary rocks are of secondary importance in Shouchang and Pujiang. In Pujiang, Bajiaojian-Shoufengshan and Dayanshan of Jiande, the formation is represented by from below upward moderately basic-moderately acidic-acidic volcanic eruptive rhythms; in Zhuji, Xiaoshan and Linpu it is dominated by moderately acid-acid pyroclastic rocks with small amounts of intermediate and acidic lava, sandstone and siltstone; and in Hengcunfu and Xindeng of Tonghu, it is represented by monomorphic dacitic crystal ignimbrite, varying from 175 to 943 m in thickness from southwest to northeast, up to 1551 m in Dashan of Wangjia of Jiantang of Shaoxing. In the Chunan-Linan area, greatly thick-bedded volcanic accumulation is developed around Tianmushan, with a cumulative thickness of more than 4389.5 m.
GeoJSON
Fossils
It yields insects Mesolygeus sp., and floras Ruffordia geopperti and Onychopsis elongata near Guangxiangsi of Shaoxing; Cladophlebis cf. parva and Desmiophyllum sp. in Dajiaoling of Pujiang; Coniopteris bureiensis and Podozamites sp. in Chenjiawu of Linan; sporopollen grains dominated by Classopollis sp. collected from the sedimentary partings near Yanghuitou of Kangshan of Huzhou.
Age
Depositional setting
Additional Information