Thango Fm
Type Locality and Naming
Type section is in Thango meadow in the Parahio Valley (Spiti) (Srikantia, 1981). [Original Publication: Srikantia, S. V., Ganesan, T. M., Sinha, P. K. and Tirkey, B. 1976. Geology of Part of Zanskar Mountains, Ladakh Himalaya with special reference to late Caledonian “Kurgiakh Orogeny”. “Geology, Mineral Resources and Natural Resources of Power Development of Himalayas with particular Reference to Kashmir”. Geological Survey of India, Abstracts, 1–3. Srikantia, S.V., 1981. The lithostratigraphy, sedimentation and structure of Proterozoic–Phanerozoic formations of Spiti basin in the higher Himalaya of Himachal Pradesh, India. In: Sinha, A.K. (Ed.), Contemporary Geoscientific Researches in India (a commemorative volume in honor of S.P. Nautiyal). Bishen Singh Mahendra Pal Singh, Dehra Dun, pp. 31–48; Nanda, M.M. and Singh, M.P. (1977) Stratigraphy and sedimentation of the Zanskar area, Ladakh and adjoining parts of the Lahaul region of Himachal Pradesh. Him. Geol., v.6, pp.365-388].
Synonyms: Thaple Formation (Nanda and Singh, 1977)
[Figure: Zanskar-Spiti-Kumaun region location (provided by Om Bhargava)]
Lithology and Thickness
Sandstone. Mainly comprises purple quartzite, shale, siltstone with bands of pink polymictic conglomerate and grit containing intra formational clasts. 700 m (thinning towards NW direction (in the Zanskar region it pinches out near Tangze village, Kurgiakh Valley).
[Figure 1: Field photograph showing the purple quartzite of the Thango Formation in middle and upper part in the Pin Valley, Spiti.]
[Figure 2: Lower part of the Thango Formation showing polymictic conglomerate at Shian Section, Pin Valley, Spiti.]
[Figure 3: Field photograph of the Thango Formation in the Parahio Valley, Spiti]
Relationships and Distribution
Lower contact
Angular unconformity with the underlying Kunzam La Fm.
Upper contact
Conformably (?) overlain by the Takche Fm; but age estimates for both would imply absence of middle Ordovician.
Regional extent
Zanskar-Spiti and Himachal Pradesh to Kumaun-Garhwal region of Northwest Tethyan Himalaya: Purni-Kurgiakh valley in Zanskar to the Garhwal region.
[Figure: Paleozoic successions of Himalayas West-to-East (after Bhargava, 2008)]
GeoJSON
Fossils
In Spiti-Kinnaur region it contains brachiopods: Leptena trachealis; Orthis testudinaria; Orthis thakli; Orthis porcata; Refinesquina muthensis, pentamerids; Coral: Streptelasma sp. Gastropods: Bellerophon sp. Trace fossils are (Bhargava et al., 1984) Phycodes circinatum; Raphistoma sp. Trochonema sp.; Skolithos sp and Planolites.
Age
Depositional setting
Shallow marine to marginally subaerial depositional environment.
Additional Information