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Hallamulla Formation
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Hallamulla Fm base reconstruction

Hallamulla Fm

Period: 
Ordovician

Age Interval: 
Early Ordovician


Province: 
NW Himalaya Kashmir Basin

Type Locality and Naming

The type location is in Hallamulla village in the Lidder valley. [Original Publication: Srikantia, S.V., Bhargava, O.N. 1983. Geology of the Palaeozoic sequence of the Kashmir Tethys Himalaya in the Lidder Valley. Journal Geological Society of India, 24 (7): 363-377.]

Synonyms: Rishkobal A of Srikantia and Bhargava, 1983; Margan Shale Fm of Shah, 1972.


Lithology and Thickness

Glacial till and Sandstone. 300-400 m thick and commences with purple red, largely matrix-supported diamictites having flattened/stretched pebbles and cobbles of shale and siltstone. A purple conglomerate and sandstone resting above the Cambrian and below the Muth Fm Quartzite, recorded by Wadia (1935) in Gabdori ravines, west of Shams Abari, also belong to the Hallamulla Formation. It is succeeded by gray, purple shale/ slate, cross-bedded quartz arenite and sporadic conglomerate lenses. Towards upper part, the quartz arenite becomes gray brown to rusty brown.


Lithology Pattern: 
Coarse-grained sandstone


Relationships and Distribution

Lower contact

Overlies the Rangmal Fm along an angular unconformity.

Upper contact

Conformably overlain by the Gugaldhar Fm.

Regional extent

Equivalent of the Thango Fm of Spiti.


GeoJSON

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Fossils

Crinoid fragments, Orthis marhaumensis, O. cf. O. calligramma, O. (Nicola) sp. and Leptelloidea (?) sp.


Age 

Though the fauna is not age diagnostic, on the bases of its occurrence above the Cambrian with intervening conglomerate and Silurian fossils in the overlying sequence, the Hallamulla Formation is assigned an Ordovician age, possibly an Early Ordovician.

Age Span: 

    Beginning stage: 
Dapingian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
471.26

    Ending stage: 
Hirnantian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
443.07

Depositional setting

The deposition of the Halamulla Formation commenced along a beach and mainly remained in sandy tidal flat of a rough sea. Towards the terminal part the sedimentation seems to have taken place in inter-tidal environment.


Depositional pattern:  


Additional Information


Compiler:  

O.N. Bhargava & Birendra Singh