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Geology of the Provinces of Canterbury and Westland, New Zealand : a report comprising the results of official explorations

Geological Survey of Mount Pleasant, Banks Peninsula, 1860

Geological Survey of Mount Pleasant, Banks Peninsula, 1860.

My examinations of Mount Pleasant, the mountain in question, began on December the 1st, of that year, and occupied me for about a fortnight. On December the 19th I presented my Report,* together with 34 geological specimens, in illustration, to his Honor the Superintendent, with which that gentleman proceeded to Melbourne to obtain if possible a new contractor for that important work. Mr Moorhouse made a preliminary arrangement with Messrs. Holmes and Co. of that city, and after these gentlemen had satisfied themselves from a personal inspection of the ground that the deposits to be pierced by the tunnel were not of such difficult nature as the former contractors had imagined, and that the main results of my survey might be relied upon, the new contract for the continuation of the work was finally settled. This important undertaking to which Canterbury owes a great deal of its remarkable progress was brought to a successful termination on May 25, 1866, when both adits met near the centre, the tunnel being open for railway traffic on December 9, 1867. A careful geological examination of the range between Lyttelton and the Canterbury plains, which has an average altitude of 1300 feet, and a more general survey of the mountains forming Lyttelton Harbour showed that Banks Peninsula consists of page 3several extinct craters, mostly submarine, that the ridge or caldron wall to be pierced by the railway tunnel was built up by a great number of basaltic lava streams, beds of tufas and agglomerates of varying thickness, dipping at an average angle of nine degrees to the north, and that the deposits were traversed by vertical dykes of trachyte, filling fissures passing through them, and having been injected from below. As this was the first instance of an ancient crater wall of large dimensions being passed through by a tunnel, from which valuable geological data could be obtained, I followed the work as it proceeded, with a considerable degree of interest, and in the geological description of Banks Peninsula I shall be able to give some details of no mean scientific interest, which these important engineering works disclosed.

During my stay in Canterbury the Provincial Grovernmeut did me the honour to offer me the appointment of Provincial Geologist, which I accepted; and, after going back to Nelson for a few weeks, I returned to Canterbury towards the middle of February to begin my labours.

* Report of a Geological Survey of Mount Pleasant, presented to his Honor the Superintendent, and laid before the Provincial Council, Dec. 20, 1860.

† The tunnel was laid out and its execution solely superintended by Mr Edward Dobson, C.E., Provincial Engineer.