Deingjiayao Fm

Lithology and Thickness:

Sandstone, siltstone, and red mudstone are dominated by gray-green and purple-red. Lower part is mainly composed of purple-red, gray-green conglomerate, sandstone, and siltstone with a small amount of red mudstone. Upper part is mainly composed of gray-green, purple-red siltstone and sandstone with red zeolite mudstone. It is 557 m thick.

Lithology-pattern: Sandstone

Relationships and Distribution:

Lower contact:

At the bottom, the variegated conglomerate is in integrated contact with the underlying Xidagou Gr (not yet in Lexicon) or in contact with the fault to the Lugou Fm of early Triassic.

Upper contact:

The top is in integrated contact with the overlying Nanyinger Gr with gray-green and purple-red sandstone.

Regional extent:

Widely distributed in the Wuwei and Jingtai areas in eastern Gansu, most of them are fluvial deposits; in the west of Jiuquan, Zhangye, Minle and northern areas, they are small intermountain or piedmont-fluvial deposits. This group contains zeolite.

GeoJSON:

Fossils:

Plants fossils include: Neocalamites rugosus, Equisetites maximidetatus, Cladophlebis spp., Danaeopsis fecunda, Danaeopsis spp., Todites shensiensis, Todites spp., Glossophyllum shensiense, Pterophyllum sp., Pityophyllum cf. pedunculatum, Annalepis sp. etc. Conchostracan Euestheria yipinglangensis, E. cf. minuta and ancient cod scales.

Age:

In 1989, the "Regional Geology of Gansu Province" officially published the named section and set its age as the Middle Triassic (probably early).

Age span:

Beginning stage: Anisian

Fraction up in beginning stage: 0.0

Beginning date (Ma):

Ending stage: Ladinian

Fraction up in ending stage: 1.0

Ending date (Ma):

Depositional setting:

This group is fluvial-lacustrine deposits. Widely distributed in the Wuwei and Jingtai areas in eastern Gansu, most of them are fluvial deposits; in the west of Jiuquan, Zhangye, Minle and northern areas, they are small intermountain or piedmont-fluvial deposits. This group contains zeolite.

Depositional-pattern:

Additional Information

From 1936 to 1942, Sun Jianchu called the “green sandstone bed” about 1000 m thick above the red sandstone of the Yaogou Gr in the Hexi Corridor and Qilian Mountains as the “Xidagou System” (no specific section). In 1936, it was assigned to Permian-Triassic and then was assigned as the Triassic in 1942. In 1962, Si Xingjian and Zhou Zhiyan classified the lower part of this system in western Gansu into the Permian Yaogou Group. The upper part and the lower part of the overlying Lower Jurassic Longfengshan System were merged into the Xidagou Gr, and the age was determined to be the Triassic. In 1980, the Stratigraphic Table Compilation Group of Gansu Province published the Triassic of the Shezigou section in Sunan County, and separately called the Xidagou Gr for the lower part and the Nanyinger Gr for the upper part. In 1987, Li Peixian and others re-divided the section into 4 parts: the original Middle-Lower System of the Xidagou Gr and the lower part of the overlying original Nanyinger Gr with about 300 m thickness and the Angra flora were assigned to the Upper Permian as Xidagou Gr; The rosy-colored strata of the original Nanyinger Gr with a thickness of about 423 m above the disconformable contact boundary was assigned to the Lower Triassic, named Lugou Fm; the strata above with a thickness of nearly 300 m was assigned to the Middle Triassic Dingjiayao Fm; the remaining part with about 400 m thickness was still called the Nanyinger Gr. In 1989, "Regional Geology of Gansu Province" basically agreed to this division plan. However, only the Lower Series was used as the Xidagou Gr rather than separately Lower Series the Lugou Fm and the Middle Series Dingjiayao Fm. In 1993, Cai Kaidi regarded the Shezigou section as the representative section of the Triassic in the North Qilian-Hexi Corridor but still represented the Xidagou Gr as the middle-lower Triassic. In addition, Cai Kaidi called the Lower Series of Xidagou Gr as the Wufosi Fm and the Middle series of Xidagou Gr as the Dingjiayao Fm. And the Wufosi Fm was originated from the “Wufosi System” and the “Wufosi System” was named by Wang Dexu (1973) for a set of variegated strata with fossil plants. However, according to the lithology and fossil assemblage of this formation, it is the same as the Middle Triassic Dingjiayao Fm rather than the Lower Triassic. So, this book adopts the division scheme of Li Peixian and others.