Page:Journal of the Asiatic Society of Bengal Vol 29.djvu/384

354 The rocks of the Rániganj field and their approximate thickness in feet, are, in descending order, Of these beds the Damúda group alone contains coal. This enormous thickness of beds is cut off on the south by a fault, the downthrow of which cannot be less than 10,000 to 11,000 feet.

The lowest or Talchir group, first separated in 1856 from observations in Orissa, consists of a series of fine sandstones and mudstones, frequently of a peculiar greenish colour, and becoming coarser towards the top, while towards the base they are commonly composed of the finest silt, in which there occur, in patches, gneiss boulders of enormous size, some having been measured as much as 15 feet in diameter. It is most difficult to account for so anomalous an occurrence as that of these huge blocks in the finest mud, for any current which could roll or even move the former would necessarily sweep away the latter, and although such a phenomenon appears absurd in India, judging from the climate of the present day, the action of ice, probably of the form known as ground ice, appears to be the only geological agent which can account for all the circumstances, by explaining the transport of the boulders.

The Talchir group had not undergone a very great amount of denudation, prior to the deposition of the Damúda rocks. It is, however, completely overlapped in the eastern portion of the Rániganj field, although well developed in the west. Very few fossils have as yet been obtained from these beds, those found are entirely plants, and shew distinctions from Damúda forms.

Beds belonging to the Talchir group have now been discovered in Orissa, in Central India, in Beerbhoom, where they occur in numerous scattered patches, and in one or two places on the west side of the