Mukta Fm

Well B – 57 – 11, (depth interval 1940 – 1987 m). [Original Publication: Zutshi, P.L., Sood, A., Mahapatra, P., Ramani, K.K.V., Dwivedi, A.K. and Stivastava, H.C. 1993. Lithostratigraphy of Indian Petroliferous Basins, document V, Bombay Offshore Basin, KDMIPE, ONGC Publication, pp. 1-383.], [Mathur et al., 1983. Age and paleoecology of the Basal Clastics in Bombay High, Heera-Panna and Ratnagiri Area: An unpublished ONGC report.]. The name derived from the Mukta field, where its stratotype has been described. Reference wells: Well R – 12 – 3 (depth interval 1620 -1729 m); Well D – 12 – 1 (depth interval 2552 – 2715 m); Well D – 4 – 1 (depth interval 3620 – 3700 m). 109 m thickness in Well R-12-3, 163 m thickness in Well D-12-1 and 80 m thickness in Well D-4-1

[Figure: Lithostratigraphy in Mumbai Offshore blocks (from NDRDGH.gov.in; after Jitendra Misra, 2009)]

Synonyms: This formation was initially recognized as a member of the Bassein Fm by Mathur et al. (1983). The Bassein Fm has two remarkable units of wider mappability; the lower ‘B Zone’ and upper ‘A Zone’ below the H3 marker in the Mukta-Bassein-Heera field area. The upper ‘A Zone’ has been designated as the Mukta Fm by Zushti et al. (1993).

Limestone and marl. In the type area, the formation consists of a massive limestone unit underlain by a 15-20 m thick zone of radioactive shales and marlstone. The limestone is fossiliferous. The shale is fossiliferous and carbonaceous. In well SS-1, it shales out. 47m thickness in the type section.

[Figure 1: Formations and their reference sections in Mumbai Offshore Basin (after Pandey and Dave, 1998)]

Foraminiferal assemblage including Nummulites fitchteli.