Lure Fm
Type Locality and Naming
The type section is located at Dangduogou, 24 km northwest of Têwo County, Gansu Province. It was named by Xi’an Institute of Geology and Mineral Resources and Gansu No 1 Team of Regional Geological Survey in 1973. Qin Fong and Gan Yiyan formally quoted it in 1976.
Lithology and Thickness
Limestone. The formation is composed of gray to dark-gray medium- to thick-bedded fine-grained bioclastic limestone, thin- to medium-bedded calcarenite and dolomitized bioclastic limestone intercalated with limestone, sandy shale and calcareous siltstone. In the middle and upper parts, it is intercalated with multiple layers of reefal facies. It is 238.6 m thick.
Relationships and Distribution
Lower contact
It conformably overlies the iron-bearing clastic rock of the Dangduo Fm.
Upper contact
It conformably underlies the Xiawuna Fm.
Regional extent
The lithology and thickness of this formation are stable in the west. It is 170-210 m thick from Luqu to Xiawuna and gets slightly thicker to 239 m at Dangduogou. Eastwards at the Yiwagou section, the clastic content of epicontinental origin gradually increases, therefore the thickness can reach up to 812.4 m.
GeoJSON
Fossils
There are abundant brachiopods and corals, and a few bivalve, gastropod, ostracoda, trilobites and conodonts etc. The Brachiopods can be divided into the Unicinulus subcordiformis-Spissophyllum massivum assemblage zone in the lower part, the Indospirifer-Syringopora eifeliensis assemblage zone in the middle part and the Productella morsovensis-Redstonea kuznetskiensis assemblage zone in the upper part.
Age
Depositional setting
The depositional facies sequence from bottom to top is suggested as: open platform, to platform basin, to a semi-restricted platform, then a platform-marginal reef facies.
Additional Information