GujaratAlluvium Fm
Type Locality and Naming
SUBSURFACE and OUTCROP: Gujarat Alluvium is exposed all over the Cambay Basin and in Well Broach-6 (depth interval: surface to 184 m.), 184 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.]. The nomenclature of Chandra and Chowdhary (1969) has been adopted in the subsequent works. Reference well: Well Cambay-40 (depth interval: Surface to 285 m), 285 m thickness.
Lithology and Thickness
Sand. In holostratotype section, it comprises of coarse to pebbly sands, gravel and kankars. In hypostratotype section, it consists mainly of coarse-grained sands, gravels, yellow to grey clay and claystone.
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 2: Generalized stratigraphy of the Cambay Basin. (from Jaiswal and Bhattacharya, 2018, J.EarthSyst.Sci., 127:65)]
Relationships and Distribution
Lower contact
In the basinal area south of Narmada, it lies unconformably over the Jhagadia Fm, and in the north up to Mahisagar river in South Cambay Basin it has gradational contact with underlying Jambusar Fm.
Upper contact
The distinction of the formation with underlying Jhagadia Fm is not clear in Mehsana subblock and Sanchor-Patan block in the north. In Dhanduka well No. 1, along the western margin, Gujarat Alluvium Fm directly lies unconformably over the Deccan Traps Fm.
Regional extent
The alluvium completely conceals the subsurface geology of the Cambay Basin.
GeoJSON
Fossils
The formation is devoid of microfauna.
Age
Depositional setting
Additional Information