Gulangdi Fm
Type Locality and Naming
The Northwest Area Marine Triassic and Jurassic Fault Stratigraphy Conference was named in 1976 and first publicly cited by Xu Xian and others in 1982. The named section is located at the mouth of Gulangdi-Longwu River in Jianzha County, Qinghai.
Synonym:
Lithology and Thickness
It consists of sandy and marl complex marble. Lower part is mainly gray sandstone, rich in feldspar, with a granular sequence layer of medium-grained sandstone-fine sandstone-siltstone and a small rhythm composed of sandstone-slate and tuff, with striated micro-fine laminations, micro-inter-laceration laminations and micro-slope laminations common, with the characteristics of isogenous cumulus. Upper part is gray-green conglomerate, sandstone and mudstone, with a rhythm structure of repeated alternation of conglomerate-coarse sandstone-fine sandstone in the section; and oblique laminations of sandstone, scour surface, wave scar and other sedimentary structures are developed. The total thickness is greater than 3299 m.
Relationships and Distribution
Lower contact
At the bottom, the greenish gray massive conglomerate is in integrated contact with the underlying Jiangligou Gr
Upper contact
At the top, it is in unconformable contact with the overlying Babaoshan Gr
Regional extent
Distributed in a large area in eastern Qinghai, with large variations in lithology and thickness. In the area of Shizhonghe in Jianzha, the lower part is composed of sandstone, slate and tuff; the upper part is composed of sandstone, slate and unstable conglomerate, with a total thickness of 4606 m. In the vast area from south of Amarxiajiang-Jianglong Mountains to north of Xichang Mountains in Henan, the lithology is single, mainly fine clastic rocks, with a thickness of 5000-7000 m. In the area of Tongren Dowa, medium and fine-grained feldspathic sandstone and slate are dominant, with a thickness of more than 7074 m. In the area of Guinan Nanshan, Tongde Beishan and north of Laga Township, the lithology and thickness of this group are very varied. In the south of Guinan Mountain, north of Tongde Mountain, north of Laga Township, and north of Machin County is a set of sandy mud deposits with a total thickness of 14 232 m. In the eastern end of East Kunlun Wen1quan, Heka Mountain, and Daheba, the group contains volcanic rocks and volcanic clastic rocks with a thickness of 615 m.
GeoJSON
Fossils
Lower part produces Arctohungarites involutus, Procladiscites sp., Leiophyllites sp.; the Upper part produces five species of Hollandites, as well as Cuccoceras sp., Sturia sp. Bivalves in the lower part are Posidonia sp. Nuculana sp., Leptochondria sp., L. cf. albertii; in the upper part are Nuculana subperlonga, N. cf. subperlonga, Palaeonucula sp., Palaeoneilo cf. oviformis, Bakevellia sp. etc.
Age
Depositional setting
This group is turbidite sedimentary.
Additional Information