Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/168



On the skirts of that elevated district in the county of Antrim and in the eastern division of Londonderry, which is occupied by the more recent flœtz rocks (namely lias, green sand and chalk, surmounted by a vast cap of basalt) extensive deposits of sandstone occur, forming the basis on which this lofty platform appears to repose.

These deposits of sandstone appear therefore to be in every instance of greater antiquity than the lias which they support, they seem also to be partly coeval with and partly more recent than the formations already described, as they are seen either alternating with or overlying the members of those formations where they can be traced in connexion with them.

They may be considered as identified partly with the coal sandstones of England, and partly with the formation here known by the name of red rock marle, the lower beds of these deposits being referable to the former class of rocks and the higher which contain gypsum to the latter; to ascertain however the precise demarcation of these subdivisions is a task for which materials are as yet wanting.

A further difficulty occurs in two instances, namely, at Cushendall bay and at Murloch bay, where these deposits are brought apparently into contact with the old red sandstone, without the intervention of the coal measures or their associated limestone, so that it is hardly possible to assign the points at which the old sandstone terminates, and is succeeded by these younger members of the same family.

The sandstones intended to be described in the following article, occupy the following localities.