Bhander Fm

Highest Formation (Group) in Upper Vindhyan Gr. Correlation of individual facies-members between the EAST and the WEST sub-basins is controversial.

Synonym: Bhandar Gr (used as Group by Basu- and Chakrabarti, 2020; but as Formation by Sarkar and Banerjee, 2020, which is used here).

In WEST: Upward succession of Ganurgarh Shale, Lakheri Limestone, Samria Shale, Bundi Hill Sandstone, Sirbu Shale, Maiher Sandstone, Balwan Limestone, and Dholpura Shale. Ganurgarh Shale is " dark red to reddish-brown, grayish-green and purple shale. It is arenaceous in places and calcareous at the top." (Kumar, 2012). Lakheri Limestone has a possible diamictite at base, and consists of reddish-brown to gray limestone (no stromatolites) and shales. Samria Shale "is greenish, reddish, brown, purple and pale and grey colored shale with dolomitic limestone bands. The dolomitic limestone shows algal mats and poorly developed stromatolites." (Komar, 2012). Bundi Hill Sandstone is pinkish-red to reddish-brown, white to light grey sandstone attaining a thickness of c. 250 m. Sirbu Shale (which may not be same as Sirbu Shale in the EAST) is greenish or pale grey, purple red and brown shale with siltstone intercalations. Maiher Sandstone (called Shikaoda Sandstone in Basu and Chakrabarti, 2020) is reddish-brown, purple, pink and pale grey medium- to fine-grained sandstone with a maximum thickness of 150 m. Balwan Limestone (up to 120 ) is grey to grayish-black, greenish-blue and pink limestone, with stromatolites in the upper part. Dholpura Shale is pinkish-purple, reddish-brown or gray shale with intercalations of siltstone and fine-grained sandstone.

In EAST: Upward succession of Ganurgarh Shale, Bhander Limestone, Lower Bhander Sandstone, Sirbu Shale, Upper Bhander Sandstone. "The Ganurgarh Shale, the lowermost member of the Bhander Formation, appears reddish grey in outcrop and is composed of alternation between fine sandstone and mudstone layers with plenty of ripples on the bed surface. .. gradational transition into the shoreface carbonate of the Bhander limestone indicate marginal marine paleogeography" (Sarkar and Banerjee, 2020). Bhander Limestone has several transitions between offshore and nearshore domains, and includes different stromatolite morphologies. Interpreted as an open carbonate ramp setting; and presence of oolitic and intraclastic horizons with mega-ripples suggest high-energy conditions. Lower Bhandar Sandstone (ca. 42 m thick) primarily consists of red mudstone and fine-grained sandstone on a prograding shelf. The Sirbu Shale contains stromatolitic and oolitic patches alternating with grey shale at the lower part. This part has been interpreted as a lagoonal deposit followed by entirely siliciclastic shelf deposits. An organic-rich, sand-free shale, devoid of emergence features overlies the lagoonal shale, intervened by a cm-thick conglomerate and sandstone beds"(Sarkar and Banerjee, 2020). The Upper Bhandar Sandstone is well sorted quartz arenite, predominantly reddish brown in color. It has differing interpretations – nearshore littoral, to fluvial and deltaic.

In the upper part of the Ballwan Limestone, there is a δ13C anomaly that has been interpreted as the Bitter Springs δ13C anomaly (George et al., 2018). If valid, then this would imply a Late Tonian, not Middle Tonian, age for the upper part of the Bhandar Gr in the EAST. For the Lakheri Limestone member, it has been suggested from very negative carbon-isotope values that these carbonates strongly resemble the base-Ediacaran cap carbonates. "Also, presence of a tilloid horizon underlying Lakheri Limestone might strengthen this claim." However, that would imply that the reported anomaly from the higher Balwan Limestone Fm that is interpreted as the Bitter Springs excursion would be mid-Ediacaran. Interesting question.