(A) Raised Beaches.

Before proceeding to treat of the Great Glacier Period of New Zealand, I consider it convenient to speak first of two other formations, partly deposited before this important era in the geological history of this Island began. The first of these formations consists of a deposit of marine shells, raised about 100 feet above the sea level, near the mouth of the Motanau river, situated in the northern portion of the East Coast. This bed, which I was not able to trace to the south, contains, according to Professor Hutton's researches, only recent shells, with the sole exception of Mactra rudis. It is thus of post pliocene (or quarternary) age, but I am unable to say if the deposit in question is of pre-glacier age, no morainic or alluvial deposits, formed during the Great Glacier period being found in its proximity. One fact, however, is certain, namely, that the land in post pliocene times in the northern portion of the province along the east coast stood at a lower level than at the central and southern portions. Thus, whilst the raised beach near Motanau rises about 100 feet above the sea level, gradually getting lower and disappearing near the mouth of the Waipara altogether, in all the more southern portions of the coast, where the country has not been subjected to fluviatile action, only beds of loess or silt are met with near the sea level. They either cover the hill sides for several hundred feet or form downs of large extent.

page 367

If such beaches had been formed on the lower slopes of Banks' Peninsula we should certainly have ample evidence as to their existence; however, beyond a small oscillation averaging at most 15 to 20 feet in vertical height, no rising of the ground has there taken place. Everywhere on the lower slopes, where the volcanic rocks are not exposed, thick beds of loess invariably cover them. And even where shells occur as high as six to eight feet above high water mark, it is very possible that they might have been placed there by the agency of an exceptionally high tide. The same may be said of the Timaru plateau, consisting in its upper portion of beds of loess, which can be followed about ten miles inland. Either volcanic rocks or loess beds form bold cliffs along the seashore, where splendid sections are open to our examination, but nowhere is there any sign of raised beaches or littoral deposits, any marine shells found at the foot of the cliffs having been brought there by the tides. Still more to the south, there is ample evidence that the cliffs of loess now situated several miles inland were at one time washed by the sea. Deposits of boulders and sand travelling northwards with the sea currents, and enclosing sometimes to the west of them lagoons and marshes, gradually shut these cliffs off from the ocean. The most careful examination has never revealed the least sign of any raised beaches amongst them.

The following shells have been collected in the bed in question occurring near Motanau:—Fusus corticatus, Fusus dilatatus, Fusus plebæus, Buccinum costatum, Struthiolaria nodulosa, Galyptræa maculata, Crypta contorta, Imperator imperialis, Rotella zealandica, Polydonta tiarata, Gibbula nitida, Siphonaria denticulata, Ampullacera avellana, Dentalium pacificum, Mulinia notata, Tellina deltoidalis, Mactra rudis, Mesodesma cuneata, Mytilus magellanicus, Modiola albicosta, Pecten latieostatus, Pecten zealandia, Terebratella rubicunda, and Rhynchonella nigricans.