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Dark Band Formation
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Dark Band Fm base reconstruction

Dark Band Fm

Period: 
Silurian

Age Interval: 
early Silurian


Province: 
Nepal Tethyan Himalaya

Type Locality and Naming

Dark Band Fm (Bodenhausen et al., 1964; Fuchs et al., 1988)


Lithology and Thickness

Dark pelitic marker


Lithology Pattern: 
Claystone


Relationships and Distribution

Lower contact

Overlies the North Face Quartzite

Upper contact

Disconformably (?) overlain by an unnamed unit of dark limestone and marl ["Higher up in the sequence, which is invariably quite disturbed tectonically, dark limestones and marls yielded Early Devonian (Pragian) monograptids and tentaculitids (Bordet et al., 1967, 1971).", then the Muth Fm quartzite.

Regional extent

"Widespread transgression at Early Silurian times is recorded by euxinic graptolite-bearing mudrocks in the central Himalaya, passing westward to better oxygenated, multicoloured shaly to silty limestones in western Dolpo (Fuchs, 1977) to Kumaon ("Variegated Silurian'' of Heim and Gansser, 1939) and finally to arenaceous ramp to reef carbonates in Kinnaur (Bassi, 1989) and Spiti (e.g. Goel and

Nair, 1977; Bhargava and Bassi, 1986); two oolitic ironstone horizons are recognized in Spiti, where sub- arkosic terrigenous detritus becomes dominant towards the west."


GeoJSON

{"type":"Feature","geometry":{"type":"MultiPolygon","coordinates":[[[[80.9,29.9],[81.03,29.45],[82.61,28.65],[84.89,27.99],[85.62,27.89],[86.24,27.65],[87.74,27.11],[87.96,26.99],[87.9,27.71],[87.23,27.61],[86.24,27.74],[85.64,28.03],[84.46,28.38],[82.74,29.23],[80.9,29.9]]]]}}

Fossils

"contains an early Silurian (Llandovery) graptolite fauna (Strachan et al., 1964; Bordet et al., 1967)."


Age 

Early Silurian

Age Span: 

    Beginning stage: 
Rhuddanian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
443.07

    Ending stage: 
Telychian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
432.93

Depositional setting


Depositional pattern:  


Additional Information

A major transgressive episode (globally) during earliest Silurian.


Compiler:  

Extracted from Garzanti (1999, "Stratigraphy and sedimentary history of the Nepal Tethys Himalaya passive margin", Jour. Asian Earth Sci., 17: 805-827]