Shaliyan Fm

Himachal Pradesh-Uttarakhand, Tal Gr, Medlicott (1864) first recognised certain rocks in the Tal Valley immediately east of the Ganga which were consequently referred as the “Tal Beds”. A broad classification of the Tal Gr is proposed in the Nigalidhar syncline (Bhargava et al.,1998) and in Mussoorie syncline by (Shaker, 1975). Since Tal Gr is complete and best exposed in the Nigalidhar syncline, the terminology adopted from this syncline. [Original Publication: Medlicott, H.B. (1864). On the Geological Structure and relations of the southern portion of the Himalayan ranges between the rivers Ganges and Ravee. Mem. Geol. Surv. India, 3(2)., 1-212.] [Bhargava, O.N., Singh, I., Hans, S.K., Bassi, U.K. (1998). Early Cambrian trace and trilobite fossils in the Nigali Dhar Syncline (Sirmaur district, Himachal Pradesh), lithostratigraphic correlation and fossil contents of the Tal Gr. Himalayan Geology, v. 19, pp. 89–108].

Siltstone. It comprises a sequence of earthy siltstone, chert and carbonaceous shale, minor limestone and phosphorite members in the ascending order.

Earthy Siltstone Member: It is dominantly made of grey to earthy siltstone, shale with subordinate limestone in basal part and chert and sporadic phosphatic nodules in upper part, the siltstone is thick bedded to massive and it constitutes 75% of the total association of the member. Pyrite is also found in this member. This Member contains Ediacaran fossil Shaanxilithes ningqiangensis (Tarhan et al., 2013), at several levels in the calcareous sand/siltstone and argillaceous limestone. It is extensively developed in the Nigali Dhar Syncline and is almost totally absent in the Korgai Syncline. The chert beds that occur in its upper part have proved barren of any fossil.

Chert Member: The chert bed in general is black though dark grey green, white (novaculite) and brown types are also encountered. Green chert is exposed on the saddle NW of Burech while novaculite is developed on the Baga ridge. Grey limestone and nodules are associated with chert. Grey, black, carbonaceous and brown shale is associated with the chert Member in the upper part of the sequence. The brown shale is poorly phosphatic yielding from trace to 10%, Pyrite is sparsely seen. Important and diagnostic acritarchs Micrhystridium lanceolatum and Paracymatiospaera irregularis of Cambrian age have been recorded in the Chert Member of the Korgai Syncline (Tiwari, 1996, 1999). Excellently preserved small shelly fauna of Meishucunian Stage (Brasier and Singh, 1987) in the Mussoorie Syncline is known from this stratigraphic level (in Mussoorie Syncline, the Chert and Carbonaceous members have not been separated).

Carbonaceous Member: It comprises black, cherty, phosphatic shale, silty shale, siltstone, minor limestone, granular phosphorite, nodules and cherty beds in the basal part. The interstratified fine-grained sills of basic rocks occur within the aforecited sequence at Skandon and Burech.

Precambrian fossil Shaanxilithes ningqiangensis found in the Earthy Siltstone Member (Tarhan et al., 2014); Chert Member yielded Small Shelly Fauna (SSFs) of the Meishucunian age (early Cambrian) in Mussoorie syncline includes Protohertzina- Anabarites assemblage. Diagnostic acritarchs Micrhystridium lanceolatum, Paracymatiospaera irregularis (early Cambrian age) occurs in Chert Member in Korgai syncline.

Not available

See Srikantia and Bhargava, 2021; and the correlation chart (fig.6) from (H. Xu, J.G. Meert and M.K. Pandit, Geoscience Frontiers 13 (2022).