Chhaossa Fm
Period:
Neoproterozoic
Age Interval:
Ediacaran, 586 Ma
Province:
N.India Lesser Himalaya
Type Locality and Naming
Simla (Shali Basin), named after Chhaossa village. [Original Publication: Auden, J.B. (1934). The Geology of the Krol Belt. Rec. Geol. Surv. India, 67, 357-454.]
Lithology and Thickness
Shale, siltstone, quartz wacke; -1300m
[Figure: part of Himachal Pradesh geologic map showing relationships among Chhaossa Fm, Sanjauli Fm, InfraKrol Fm, Blaini Fm, Kakara Fm and Subathu Fm (provided by O.N. Bhargava & Birendra Singh)]
Lithology Pattern:
Siltstone
Relationships and Distribution
Lower contact
Conformable with Basantpur Fm
Upper contact
Conformable with Sanjauli Fm
Regional extent
Around Shimla Hills, in the Giri and lower Tons valleys. Correlated with Chandpur Fm.
GeoJSON
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Fossils
None
Age
588 Ma. Age span estimates taken from O.N. Bhargava & Birendra Singh (2021 for Dr. Raju's Lexicon); Singh, Birendra P., 2009. Northwest Himalayan Region. In: D.S.N.Raju and Ravi Misra, Proterozoic and Phanerozoic Integrated Stratigraphy (ONGC Bull. 44, n.2)
Age Span:
Beginning stage:
Ediacaran
Fraction up in beginning stage:
0.5
Beginning date (Ma):
586.90
Ending stage:
Ediacaran
Fraction up in the ending stage:
0.7
Ending date (Ma):
567.66
Depositional setting
A shelf-mud transition zone of a tidal flat complex
Depositional pattern:
Additional Information
It has been variously considered as flysch, subtidal to muddy delta sequence.
Compiler:
O.N. Bhargava & Birendra Singh. Age estimates based on A.J. Martin, 2017. A review of Himalayan stratigraphy, magmatism, and structure. Gondwana Research 49 (2017) 42–80.