KrolD Fm

Simla (Shali Basin), Himachal Pradesh-Uttarakhand, the name Krol Series was first given by Medlicott (1864) to a series of limestone, red and green shales and sandstones seen in the Krol Mountain near Solan in Simla area. [Original Publication: Auden, J.B.,1934. The geology of the Krol Belt. Rec. Geol. Surv. Indi. 67, 357-454.]

[Figure: Krol Gr lithology table (provided by O.N. Bhargava & Birendra Singh)]

Dolomitic limestone. It comprises an alternation of dolomitic limestone, microbial cherty limestone and dolostone shale with shale in excess of limestone. The limestone is sulphurous and of cherty type particularly in its upper part. In the Nigali Dhar syncline of the Inner Krol Belt, in addition to cherty limestone, calcilutite of cement grade is also found. Its upper part is dolomitic. The chert is pale and occurs as thin wisps and in continuous band. The associated shales are of black, red, green and orange colours. Rare conglomerates with clasts of vein quartz and chert are also preserved.

Ediacaran fossils in Krol D (E1) from Shanker et al. (1997); Beltanella, Beltanelliformis, Conomedusites, Cyclomedusa, Tirasiana. Fossil data from (Jiang et al., 2002).

Deposition is in an inner intertidal zone and partly in supratidal zone within an extensive algal mat complex in a condition of increased salinity. Increased pH value and salinity conditions are indicated by-magnesite. Stromatolite algal mat facies represents deposition under normal salinity conditions. Detailed sequence stratigraphic studies identified several disconformable surfaces (Jiang et al. 2002) indicating interruptions in largely tidal to intertidal (Singh 1980) sedimentation in a shallow NW-sloping marine Krol Basin, with minor phases of deep-water environment (Jiang et al. 2003).

Srikantia and Bhargava, 2021; Jain et al., 2020 and Jiang et al., 2002.