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Marthu Formation
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Marthu Fm base reconstruction

Marthu Fm

Period: 
Ordovician

Age Interval: 
late Ordovician


Province: 
Nepal Lesser Himalaya

Type Locality and Naming

Katmandu region (Tethyan sequence)


Lithology and Thickness

"The Markhu Formation is composed mainly of three rock types: schists, quartzites, and carbonates, occurring in various proportions. About 50% of the total rock volume is represented by marbles. The marble bands range in thickness from a few centimeters to tens of meters. They are medium to coarse crystalline; some of them are pure marbles, displaying white and pink colors, whereas others contain much quartz and mica, including biotite. The marbles consist of amphibole and pyroxene at some localities, especially (but not exclusively) near the granite contacts. The schists and quartzites alternating with the marbles are dark colored, rich in biotite, fine-grained, and also include bands of phyllite and calc-phyllitic rock, where sun cracks and worm tracks are sporadically discerned. The Markhu Formation is about 1,000 m thick at its type locality. At a few places, the Markhu Formation exhibits concentric stromatolitic structures, quite different from those observed in the Dhading Dolomite Fm. A massive lens-shaped body of marble extending for about 18 km in Labang–Khairang could be a reminiscent of a stromatolite reef (Stöcklin and Bhattarai 1977, p. 29)."


Lithology Pattern: 
Clayey limestone


Relationships and Distribution

Lower contact

The underlying Kulikhani Fm passes conformably and transitionally into the Markhu Fm (Stöcklin and Bhattarai 1977, p. 28).

Upper contact

"Through a decrease in the number and thickness of carbonate bands, the Markhu Formation transitionally grades into the overlying Tistung Fm."

Regional extent


GeoJSON

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Fossils


Age 


Age Span: 

    Beginning stage: 
Sandbian

    Fraction up in beginning stage: 
0.7

    Beginning date (Ma): 
454.38

    Ending stage: 
Sandbian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
452.75

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.