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Raduwa Formation
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Raduwa Fm base reconstruction

Raduwa Fm

Period: 
Ediacaran

Age Interval: 
early Ediacaran


Province: 
Nepal Lesser Himalaya

Type Locality and Naming

Katmandu region (Tethyan sequence)


Lithology and Thickness

The Bhimphedi Gr begins with the Raduwa Formation, represented dominantly by dark green-gray mica schists of coarse crystalline aspect. Biotite is the predominating mineral; but sericite, muscovite, chlorite, and garnet are also commonly present. Red garnets sometimes reach up to 1 cm in diameter. Amphibole and pyroxene are also locally present, whereas staurolite, kyanite, and sillimanite are observed in the Mahesh Khola, north of Kathmandu, and around Sankhu. The schists usually contain lenses and veins of quartz, which impart a gneissic appearance to the rock. The Raduwa Formation also contains some subordinate bands of gray micaceous quartzite and its pale green or white, purer varieties. The prominent bands of such rocks exposed in a tributary of the Jhiku Khola in its upper reach, are designated as the Chak Quartzite Beds. These quartzites grade locally into coarse-grained gneisses, composed primarily of feldspar and quartz with minor thin alternations of garnetiferous or sericite–chlorite schist (Stöcklin and Bhattarai 1977, p. 24). The Raduwa Formation has a maximum thickness of 2,000 m, but it seldom attains that value.


Lithology Pattern: 
Sandy claystone


Relationships and Distribution

Lower 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.

Upper contact

Martin (2017) implies that the contact to the overlying Bhainsedobdan Marble Fm is a minor discontinuity; but alternatively " he upper contact of the Raduwa Fm with the Bhainsedobhan Marble Fm is perfectly transitional, and marked by an approximately 20–30 m thick sequence of schist and marble." (Dhital, 2015).

Regional extent


GeoJSON

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Fossils


Age 


Age Span: 

    Beginning stage: 
Ediacaran

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
635.00

    Ending stage: 
Ediacaran

    Fraction up in the ending stage: 
0.5

    Ending date (Ma):  
586.90

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.