Tiaojishan Fm

Beijing, Liaoning

Jingeng Sha (coordinator) Group for the Regional Stratigraphic Chart of Beijing City, 1977).

Synonym: （髫髻山组）; The Lanqi Fm (named by Zhao Zhongfu, Zhao Baolin in 1959) in western Liaoning and the “Shuiquangou Fm” in the Niuyingzi Basin of the Guojiadianzi Village of Lingyuan County can be regarded as a synonym of thihs formation.

Lithology and Thickness:

The formation represents a set of strata consisting largely of intermediate volcanic rocks and volcaniclastics occurring in between the Jiulongshan Fm and the Tuchengzi Fm. The main rock types are represented by dark-violet, violet-brown and grey-green andesite, andesitic basalt, amphibole-andesite, pyroxene-andesite, andesitic lava-breccia andesitic breccia and andesitic agglomerate, intercalated with purple, grey-brown and grey-green sandstone, conglomerate, siltstone and mudstone. Its thickness is 291-3731 m.

Lithology-pattern: Lava

Relationships and Distribution:

Lower contact:

It disconformably overlies the Jiulongshan Fm (in the area of the Tiaoji Mts), or overlies unconformably the Paleozoic Erathem and still older strata (in the area of the Baihua Mts).

Upper contact:

Its top part is disconformably overlain by the Tuchengzi Fm

Regional extent:

The formation is distributed mainly at West Hills of Beijing City, in the areas of Xinglong-Kuancheng, Fengning-Luanping, Chengde-Pingquan, and Xuanhua-Weixian County of northern Hebei. In western Liaoning it is distributed in the areas of Beipiao, Chaoyang, Jinxi, Jianchang and Lingyuan. Both the lithology and thickness of the formation are changeable from region to region. The development of the formation is characterized by its being composed essentially of intermediate volcanic clastics and volcanic lava, intercalated with a small amount of sedimentary rocks with a great thickness, being of 2772 m in the area of Tiaoji Mts; of 3731 m in the area of Miaofeng Mts; of over 2079 m in the area of Baihua Mts; and of 919-1208 m in the Miyun-Xinglong area east of Beijing City. In the Xuanhua-Xiahuayuan area the formation is composed mainly of andesite and andesitic breccia, intercalated with tuff and sandy shale, with a thickness of 1478 m. In the Qinglong-Kuancheng region it is composed of intermediate volcanic clastics, lava and sedimentary rocks, with a thickness of about 2624 m. At Beishui Spring of Weixiao County it is composed largely of andesitic lava-breccia, andesitic breccia and agglomerate, intercalated with a small amount of andesite, basalt, siltstone, tuffaceous sandstone and sandy conglomerate, with a thickness of only 299 m. In the areas of Changheyingzi and Dashui Spring-Wubaoshi Gully of Changgao Township, Beipiao County it is composed largely of grey-violet andesite, breccia and agglomerate, intercalated with three and more interlayers of sedimentary rocks, yielding abundant plant fossils, with a thickness of over 2000 m. In the Lama Gully area of Xia’ershijiazi village, Liantugou Township, Chaoyang County it is composed of grey-white tuffaceous breccia, grey-black porphyritic andesite and basaltic andesite, intercalated with grey-green tuffaceous sandstone, and is exposed incompletely due to its being dissected by fault. In the area of Dizangsi Township of Yixian County to Batuyingzi Township of Beipiao County it is about 600-1600 m in thickness, containing silicified woods. The middle part of the Xidashan volcanic rock series in the Linglongtar Township of Jianchang County is composed of grey-white sandy shale and paper oil shale, yielding plant, bivalve, Eosestheria, insect and fish fossils.

GeoJSON:

Fossils:

In the area of Xiajia Gully, Xuanhua County it yields plant fossils such as Coniopteris hymenophylloides, Cladophlebis whitbyensis, Eboracia lobifolia, Hausmannia cf. leeiana and Pseudocycas manchurensis. In western Liaoning the plant fossils contained belong to a late-stage assemblage of the Coniopteris-Phoenicopsis flora.

Age:

Schematic strat column in the previous "red Chinese Lexicon" had implied that the Tiaojishan Fm was Bathonian. Diying Huang (2019; Jurassic integrative stratigraphy and timescale of China. Science China: Earth Sciences, v. 62) re-assigns this Tiaojishan Fm as mid-Oxfordian through Kimmeridgian followed by a Tithonian-Berriasian Tuchengzi Fm. However, some dates from Tuchengzi Fm seem to imply it extends down into Kimmeridgian (see that entry); therefore, span of Tiaojishan Fm (Lanqi Fm) for graphic purposes and consistency put here as mid-Oxf through mid-Kimm.

Age span:

Beginning stage: Oxfordian

Fraction up in beginning stage: 0.5

Beginning date (Ma):

Ending stage: Kimmeridgian

Fraction up in ending stage: 0.5

Ending date (Ma):

Depositional setting:

It is interpreted as a lacustrine environment.

Depositional-pattern:

Additional Information

Compiler

Jingeng Sha (coordinator)