Luo'ao Fm
Type Locality and Naming
It was named by Xu Keqin, Dingyi as the “Luo’ao System” in 1943. The naming section is located in the vicinity of the Luo’ao Village, Yudo County, Jiangxi Province.
Synonym: （罗坳组）
Lithology and Thickness
Lower member represents grey-violet, grey-yellow, purple and dark-grey medium-bedded and massive feldspar-quartz sandstones containing pebbles occasionally, conglomerates, sandy conglomerates, argillaceous siltstones and silty shales, or an alternating layer of tuffaceous sandstones and shales, with occasional occurrence of marls, carbonaceous shales and calcareous concretions, with a thickness of about 222 m. Upper member is composed largely of an alternating layer of purple, grey-violet, grey-yellow and dark-grey thick-bedded feldspar-quartz sandstones, argillaceous siltstones, tuffaceous siltstones and silty shales, intercalated with a small amount of calcareous shales and siltstones, and with occasional occurrence of tuffs, with a thickness of about 596 m, with no top part having been found.
Relationships and Distribution
Lower contact
It is in a conformable or an unconformable contact with the underlying Linshan Fm
Upper contact
In some regions it overlies directly the pre-Mesozoic strata. Regionally, the schematic strat column indicates the next younger unit as Daling Fm
Regional extent
The formation is distributed chiefly in Yudu, Xianxia, Quyang, Ningdu, Huichang, Jishui, Wanan, Linchuan, Qianshan, Anyuan, Xunwu and Yujiang regions. Its lithology in various regions is basically consistent, yet with a greatly changeable thickness from place to place, being of about 3208 m at Quyang, of over 2242 m at Yudu, of over 2866 m at Shijiabian, and at Shigang of Yujiang County being of only 363 m.
GeoJSON
Fossils
It yields bivalves as represented by the Lamprotula（Eol.）-Cuneopsis-Psitunio assemblage, and plant fossils such as Otozamites sp. etc. Besides, there are found in the formation also spore-pollen fossils.
Age
Depositional setting
The formation belongs to fluvial and lacustrine deposits in the intermontane basins.
Additional Information