Stratigraphy

Stratigraphy of the Western Ghats

The Western Ghats range represents the type section of Deccan Traps as 2.8 km of lava is exposed here. The Western Ghats lavas have been mapped and studied by numerous workers (e.g. Najafi et al., 1981; Mahoney et al., 1982; Cox and Hawkesworth, 1985; Beane et al., 1986; Lightfoot and Hawkesworth, 1988; Peng et al., 1994; Melluso et al., 2004). The flows are predominantly tholeiitic basalts. Picritic flows (MgO content ≥10%) are rare in the Western Ghats, but common in the Northwestern Deccan (Krishnamurthy and Cox, 1977; Krishnamurthy et al., 2000; Melluso et al., 2006), as are alkali basalts lamprophyres, nephelinites and carbonatites (Viladkar, 1981; Basu et al., 1993; Gwalani et al., 1993; Simonetti et al., 1995; Simonetti et al., 1998). 

The Western Ghats lava pile has been divided into three subgroups 

Wai (YOUNGEST)

Lonavala, and

Kalsubai (OLDEST)

(Cox and Hawkesworth, 1985; Beane et al., 1986; Beane, 1988; Peng et al., 1994).

Each subgroup has in turn been subdivided into formations; and an individual formation consists of numerous flows grouped as members or chemical types

The Deccan Traps of the type area have been divided into eleven formations based on geochemistry, among which the most definitive are the Ambenali, Poladpur, and Bushe formations.

Bushe lavas show the strongest signatures of contamination

by the continental crust. The Ambenali is the thickest formation and is the least contaminated. The Poladpur may be laterally the most extensive among all formations