Jambusar Fm

SUBSURFACE: Well Jambusar-1 (depth interval 100-408 m), It is of 308 m thickness. [Original Publication: Chandra, P.K. and Chowdhary, L.R. (1969) Stratigraphy of the Cambay Basin, ONGC Bull., vol. 6 (2), pp. 37-50.]. Reference well: i) Broach-6 (depth interval 184 – 800 m); ii) Cambay-40 (depth interval 285 – 487 m); iii) Nawagam-22 (depth interval 137 – 255 m). In Broach-6, the thickness is 616 m while in Cambay-40 and Nawagam-22 the thickness is 190 m and 118 m, respectively. (after Pandey and Dave, 1998)

Sandy clay. In holostratotype, it consists of yellow and grey clays, coarse sand and kankar. In Broach-6 it is composed mainly of coarse sands, kankar and clay. In Cambay-40, it is composed of grey to dark grey claystone, coarse-grained sandstone, gravelly sands with minor shale. In Nawagam-22, the dominant lithology is yellow and grey clays, coarse sand, gravels and kankars.

NOTE: " Kankar or kunkur is a sedimentological term derived from Hindi, occasionally applied to detrital or residual rolled, often nodular calcium carbonate formed in soils of semi-arid regions. It forms sheets across alluvial plains and can occur as discontinuous lines of nodular kankar or as indurated layers in stratigraphic profiles more commonly referred to as calcrete, hardpan or duricrust." (from Wikipedia)

[Figure 1: Rock units and their reference sections in Cambay Basin (after Pandey et al., 1993)]

[Figure 2: Generalized stratigraphy of the Cambay Basin. (from Jaiswal and Bhattacharya, 2018, J.EarthSyst.Sci., 127:65)]

The formation contains species of Sphaeroidinella, Cibicides, Elphidium, Globigerina, Nodosaria, Nonion, Spiroloculina, Toralia, Eponides, Quinqueloculina etc.