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Chitlang Formation
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Chitlang Fm base reconstruction

Chitlang Fm

Period: 
Silurian

Age Interval: 
early Silurian


Province: 
Nepal Lesser Himalaya

Type Locality and Naming

Katmandu region (Tethyan sequence)


Lithology and Thickness

"The Chitlang Formation is in the core of the Mahabharat Synclinorium is made up mainly of dark gray and purple, soft-weathering slates. In its lower part, there is a conspicuous white quartzite band, whereas towards its upper section, some thin limestone intercalations display wave ripples. The Chitlang Formation is a few hundred meters thick. The Chitlang Formation extends towards the Phulchauki hills, where it is represented by purple slates containing in their lower portion a thick band of white quartzite, followed by a few limestone beds higher in the section. Towards the top part of the slates are intercalated two or three red-purple ferruginous beds, one of which represents the iron ore deposits of Phulchauki (Chap. 21). The iron ores are represented by 10–15 m thick hematitic layers or concretionary bodies. From the ferruginous concretions exposed in the eastern slopes of Phulchauki, The thickness of these Silurian beds of Phulchauki is about 1,000 m.


Lithology Pattern: 
Claystone


Relationships and Distribution

Lower contact

Martin 2017 implies Hirnantian is absent=> Disconformity onto the underlying Chandragiri Limestone Fm.

Upper contact

With the appearance of calcareous slates towards their upper part, the slates of Chitland Fm transitionally pass into the lower part of the Godavari Limestone Fm containing crinoids (Stöcklin and Bhattarai 1977, p. 32).

Regional extent


GeoJSON

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Fossils

Bordet (1961) reported Silurian trilobites as well as other fossils from various locations.


Age 

Martin (2017) suggests a facies correlation to the black marl facies of the lower third of the Dark Band Fm of the Tethyan Himalaya, which is earliest Silurian (anoxic global episode during transgression).

Age Span: 

    Beginning stage: 
Rhuddanian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
443.07

    Ending stage: 
Rhuddanian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
440.49

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.