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Manas Formation

Manas Fm

Period: 
Cambrian

Age Interval: 
middle Cambrian ?


Province: 
Bhutan

Type Locality and Naming

Lesser Himalaya


Lithology and Thickness

Gray to white, medium- to thick-bedded, medium- to coarse-grained, locally conglomeratic, quartzite exhibiting common trough cross-bedding; interbedded with dark-gray to dark-green, thin-bedded to thinly-laminated phyllite, and medium-gray dolostone (locally divided out) (Bhargava, 1995; Tangri, 1995a; Long et al., 2011A). Intraformational thrust faults indicate structural repetition of multiple, 1.5 to 2.8 km-thick thrust sheets (Long et al., 2011B). Lower greenschist facies (Gansser, 1983).


Lithology Pattern: 
Sandstone


Relationships and Distribution

Lower contact

Major unconformity (ca. 1 billion years!) onto "Sikkim dolomite" (Martin, 2017, diagram) that overlies Pangsari Fm.

Upper contact

Conformably (?) overlain by calcareous claystones of the Phuentsholing Fm.

Regional extent


GeoJSON

null

Fossils


Age 


Age Span: 

    Beginning stage: 
Cambrian Stage 4

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
514.50

    Ending stage: 
Drumian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
500.50

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

Extract from Legend to "Geologic Map of Bhutan" (Long, S., McQuarrie, N., et al., 2011, Journal of Maps). Age spans estimated from correlation diagrams in Martin, A.J. (2017, "A review of Himalayan stratigraphy, magmatism, and structure", Gondwana Research, 49: 42-80; http://dx.doi.org/10.1016/j.gr.2017.04.031), but these are often controversial.