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Upper Nawakot Gr
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Upper Nawakot Gr base reconstruction

Upper Nawakot Gr

Period: 
Calymmian

Age Interval: 
early Calymmian


Province: 
Nepal Lesser Himalaya

Type Locality and Naming

Katmandu region (Lesser Himalayan succession). It generally occurs below the Mahabharat Thrust (Main Central Thrust) and hence has undergone intense deformation. Inverted metamorphism too has significantly affected its upper end.


Lithology and Thickness

The Upper Nawakot Group represents a broad unit of slates, limestones, phyllites, quartzites, and amphibolites. " Dark bluish-gray to black, soft-weathering, and highly cleaved slates and phyllites represent the lower Benighat Slates Fm. … The Malekhu Limestone Fm is one of the conspicuous units and is constituted of thin-bedded, platy dolomitic and siliceous limestones of pale yellow color. … The Robang Fm phyllites comprise primarily green-gray sericite– chlorite phyllites and some darker slates."


Lithology Pattern: 
Continental marl


Relationships and Distribution

Lower contact

Erosional disconformity onto Dhading Dolomite Fm (upper unit of the Lower Nawakot Gr).

Upper contact

The Mahabharat Thrust or Main Central Thrust brings the Kathmandu Complex (of which the Raduwa Fm is the lowest formation of the Bhimphedi Gr) over the Upper Nawakot Gr (Robang Fm is the uppermost preserved unit). However, on some rare occasions, the thrust approaches the Siwaliks, concealing the whole Lesser Himalayan sequence. The Main Central Thrust is commonly associated with a sheared and mylonitized zone.

Regional extent


GeoJSON

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Fossils


Age 


Age Span: 

    Beginning stage: 
Calymmian

    Fraction up in beginning stage: 
0.2

    Beginning date (Ma): 
1,560.00

    Ending stage: 
Calymmian

    Fraction up in the ending stage: 
0.35

    Ending date (Ma):  
1,530.00

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

Descriptions from Megh Raj Dhital (2015, Geology of Nepal: Regional Perspective of the Classic Collided Orogen, Springer Publ., 499 pp.). 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.