occur. The associated rocks are all sandstones and shales, which sometimes attain a thickness of 10,000 feet The ironstone shale stage is so called on account of the lenses of clay ironstone which, as in the Rānīganj coalfield, sometimes occur in sufficient abundance to supply a valuable iron-ore. All these stages are in general conformity with one another, though the upper may be found to overlap the lower.
Pānchet series.There is generally, however, a slight unconformity between the uppermost stage of the Dāmuda series and the next, which is distinguished as the Pānchet series. The Pānchets are characterized by the absence of coal-seams, being composed of micaceous sandstones, often of a greenish colour, with bands of red clay. The series is well-known on account of the reptilian and amphibian fossil bones it has yielded, besides a few fossil plants which show more pronounced affinities with those of the Dāmudas than with the higher beds.
The whole of the foregoing series–Tālcher, Dāmuda, and Pānchet–make up the lower division of the Gondwāna system, being cut off from the Upper Gondwānas by a marked stratigraphical break, accompanied by a contrast in fossil contents. The plants of the Lower Gondwāna beds include many equisetaceous forms, while those of the Upper Gondwānas show a prevalence of cycads and conifers ; the species of common genera of ferns, as well as other orders, are quite distinct in the two divisions.
Upper Gondwānas.The Upper Gondwānas have a lower series, distinguished as the Rājmahāl series in Bengal and as the Mahādevas in the central parts of the Peninsula. The Mahādevas attain a thickness of 10,000 feet in the Sātpurā area, most of the rocks being sandstones and unfossiliferous. The Rājmahāls, on the other hand, have yielded a number of fossil plants, and are interesting, too, on account of the great sheets of basaltic lava interstratified with the shaly and sandy sediments, attaining thickness of over 2,000 feet. Rājmahāl and Mahādeva series.The Rājmahāl lava-flows are often amygdaloidal like those of the Deccan trap series, the cavities yielding agates and zeolites of considerable variety and beauty.
Marine beds of Upper Gondwāna age.Rocks of Upper Gondwana age occur at various places along the east coast of the Peninsula. In some cases marine fossils have been found associated with the plant-bearing beds, and these have helped to fix the position of the Upper Gondwānas in the standard scale of marine strata. More pronounced evidence as to the age of the upper limit of the Gondwānas is afforded by the occurrence of plant-bearing
