Neyveli Formation

The lignite seam of the Nyeveli-Jayamkondacholapuram area is a sub horizontal lensoid body occurring in between an upper zone of poorly consolidated sandstone, white clay and mottled clyed sandstone and a lower zone of poorly indurate thick sandstone(aquifer zone) with minor intercalations of thin ash grey to grey shale, calcareous siltstone, sandy limestones etc

            The lignite field extends over a distance of 40Km in a north-south direction and is about 10Km wide in an east-west direction. The lignite seam, varying in thickness from 8 to 22 m, is underlain by sand with artesian aquifers which exert an upward pressure. The lignite seam is overlain by grey to white argillaceous sandstones, clay and sands. The Cuddalore Formation for the most part is covered by Quaternary sediments and recent alluvium. The overburden above the lignite seam is up to 55m in thickness. The lignite seam does not extend as a single unit throughout the area, but is split up. Occurrence of clay beds both above and below the lignite seam is recorded in the mine sections.

            Palynological and microfossil studies of the lignite seams and the associated sediments of the Neyveli Formation, led to the inference that the age of the Neyveli Formation is of Eocence age, while the Cuddalore Formation separated from the underlying Neyveli Formation by an unconformity, is of Mio-Pliocence age. Mio-Pliocence palynoflora profusely occur in the clay and carbonaceous shales of the Cuddalore Formation.