PrangLmsMbr Fm

The Prang Limestone Member of the Sylhet Fm in its type section it is 144 m thick. [Original Publication: Wilson, G.F., and Metre W.B. 1953: Assam and Arakan, In: Science of Petroleum, vol. 6(1), pp. 119-123]

Synonyms: Earlier Fox (in Heron, 1937) had recognized the Siju Limestone in the Garo hills, which was later shown to be the lateral continuation of the Prang Limestone. (Pandey and Dave, 1998)

Limestone. Type Section Lithology: In the type section along Um Sohryngkew river, the Prang Limestone Member of the Sylhet Fm is represented by grey to greyish white, crystalline and massive limestone. The lower part of the limestone is sandy and a number of calcite veins are seen to traverse it. The distinguishing feature of this limestone is the presence of abundant larger foraminifera. In the Garo hills, it is generally represented by buff to reddish buff, greenish, grey and cream colored, hard, massive cliff forming limestones. At places towards the base, it is arenaceous and contains cherty nodules containing numerous foraminifera. There is not much lithologic variation in the Shillong Plateau, except for the presence of a few shale and sandstone intercalations, (Pandey and Dave, 1998).

Varies between 130 m to 300 m in the Shillong Plateau.

[Figure 1: Paleocene - Lower Eocene sequence of Upper Assam with its subdivisions (after Bharali and Gogoi, 2012)]

The Prang Limestone Member yields a rich fauna. It comprises Discoscyclina dispansa, D. omphalus, Nummulites acutus, N. discorbinus, N. fabiani, Pellatispira, Assilina granulosa and A. spira. The sporaidc yield of planktonic foraminifers include Truncoratoloides rohri, Hantkenina alabamensis, Globorotalia cerroazualensis etc.

Inner to mid shelf environment with fluctuating energy conditions, (Jauhri et al., 2011)