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Aqide Formation

Aqide Fm

Period: 
Permian

Age Interval: 
P2, (10), Kungurian Stage (mid-Cisuralian Epoch; mid-Early Permian)


Province: 
Inner Mongolia

Type Locality and Naming

The type section of the Lower member is located on the southern side of the Maihanhada area, Sunbur Village, Left Banner of Alashan, Inner Mongolia; and the type section of the Upper member is on the northern side of the Haierhan in the Aqide area.


Lithology and Thickness

Volcaniclastics. Lower member is grey calcareous greywacke and tuff, intercalated with limestone lenses, being abundant in fossils, with a thickness of 1084 m. Upper member is grey-green and dark-grey andesite, dacite and tuffaceous sandstone, with intermediate-acidity volcanic lava and volcaniclastic rocks being predominant, and with a thickness of 773 m. Total thickness of the formation is 1857 m.


Lithology Pattern: 
Volcanics


Relationships and Distribution

Lower contact

Conformable contact -- the basal fine-grained volcaniclastic rocks are continuous deposits in relation to the underlying dolomitic limestone of Maihanhada Fm.

Upper contact

Unconformable contact to the overlying Harsuhai Gr.

Regional extent

The formation is distributed in the Wuhaxibi, Maihanhadar, Wulanbaixing, Hangwula areas of the Ertina Banner, as well as on the southern margin of the Badanjilin Desert.


GeoJSON

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Fossils

Lower member yields ammonoids and brachiopods fossils as represented by the Uraloceras-Waagenoconcha-Uncinunellina assemblage. Upper member is represented by the Uraloceras-Linoproductus-Stenoscisma assemblage.


Age 

Both members yield the ammonoids Uraloceras involutum and U. belgushkense, belonging to the Qixia’an Stage, which is equivalent to the international Kungurian Stage (late-Cisuralian Epoch; late-Early Permian).

Age Span: 

    Beginning stage: 
Kungurian

    Fraction up in beginning stage: 
0.5

    Beginning date (Ma): 
278.84

    Ending stage: 
Wordian

    Fraction up in the ending stage: 
0.6

    Ending date (Ma):  
266.29

Depositional setting


Depositional pattern:  


Additional Information

Paleomagnetic specimens were collected from the upper part of the Aqide Fm (102.6°E, 41.7°N). (Zhu Hong et al., 1987) The direction of the average remanent magnetization has a magnetic declination (D) of 195.6° and a magnetic inclination (I) of 36.5°, with the semi-apex angle (α95) of the circular cone of confidence of 9.5° and the clustering parameter (K) of 9.3. The corresponding virtual geomagnetic pole is at 86.2°E, 26.8°S, with the uncertainty of δρ= 6.3°, δm=10.9°. This indicates that the Permian strata had received a Reversed-polarity magnetization at a paleolatitude of 19.7°N, and that the site has rotated 16° clockwise since the middle Permian.


Compiler:  

Li Li