Longshan Fm
Type Locality and Naming
Karakorum. It was named by No. 1 Regional Survey Party under the Xinjiang Geological Bureau in 1984. The naming section is located west of Kule Lake of Gannan in the Salijile region northwest of Bayidaban, Xinjiang (E 76°60′, N 34°50′), with its reference section being situated northwest of Karaqigu area on the northern slope of the Karakorum Mts, Xinjiang (E 75°25′, N 37°10′) (Jiang Chunfa, 1993).
Synonym: （龙山组）
Lithology and Thickness
Composed of grey to dark-grey medium-bedded massive limestones and biotic limestones, argillaceous limestones, variegated conglomerates, sandstones and gypsums, with its basal part consisting of a consistent 5-200 m thick stratum of red and grey-green basal conglomerates and feldspar-quartz-sandstones. It is 2670 m in thickness.
Relationships and Distribution
Lower contact
Its basal part is in an unconformable contact with the underlying upper Triassic Series. Regionally, the next older unit is the Bagongbulansha Gr of Early Jurassic.
Upper contact
Regionally, the schematic strat column indicates the next younger unit as Hongqilafu Fm (=gray limestone of Late Jurassic according to [Geological Formation Names of China (1866–2000). Springer], but not in draft Jurassic Lexicon for this current Compiler
Jingeng Sha (coordinator)). Regionally, the next younger unit is also the Kunjirap Fm of late Jurassic).
Regional extent
Karakorum. The formation is distributed essentially in Karaqigu, Hongqilapu and south of Tianshendaban to the east of the latter, Chalukou, Heweitan, Luanshidaban and Bayidaban regions, with a consistent lithology, but a greatly changeable thickness of it, being of 890-3555 m. In most of the above-mentioned regions no top part of the formation has been found, and only in the Hongqilapu area it is in a conformable contact with the overlying Hongqilapu Fm.
GeoJSON
Fossils
The formation yields in the area of Gannan, Salijile region such bivalve fossils as Ceratomya concentrica, Camptonectes (C.) laninata, C. (C.) richei, Myopholas multicostata and Liostrea cf. birmanica; Brachiopods as represented by Burmirhynchia sp., while in the Karaqigu area it yields bivalves as represented by Arcomytilus cf. laitmairensis, Myopholas xinjiangensis, plagiostorma cf. laevisculum, Homonya gibbosa, Pseudotrapezium cardiforme, Radulopecten Karakorumensis, R. giganteus, Plagiostoma wynnei and Modiolus imbricatus, as well as Brachiopod and Gastropod fossils.
Age
Depositional setting
Additional Information
Fraction up in beginning stage: 0.0
Beginning date (Ma):
Ending stage: Callovian
Fraction up in ending stage: 1.0
Ending date (Ma):
Depositional setting:
Depositional-pattern:
Additional Information
Compiler
Jingeng Sha (coordinator)