Status of Karur-Kambam-Painavu-Trichur Shear Zone, Southern Granulite Terrain in the Context of Late Mesozoic Dynamic Evolution of Western Ghats:A Geophysical-Geological Perspective

Detailed magnetic and gravity surveys in the Periyar Plateau and adjoining coastal tract (central Kerala) have brought to light a family of four major geophysical lineaments. These include the NNW-SSE trending Idamalayar lineament (LM-1) and the Kerala lineament (LM-2); both housing gabbroic and doleritic dykes dated ~90 Ma and geochemically related to the Marion plume and the NW trending Periyar lineament (LM-3) and Todupuzha lineament (LM-4) housing in part dolerite dykes dated 65 Ma and chemically related to the Reunion plume. The lineaments largely cut across the litho-tectonic framework of the Precambrian basement. Integrating geological evolution of the region, these lineaments seem to have been formed by reactivation of the deep-seated distensional fractures, that facilitated magmatic emplacements during the episodic breakup of Gondwanaland under distinctive mantle thermal regimes of the Late Mesozoic. Possibly, later in the Cenozoic, these lineaments were enlarged to their present dimensions during the uplift of Western Ghats.