Page:Transactions NZ Institute Volume 9.djvu/616

Rh denuded off, are seen dipping at a considerable angle, forming hills which are quite characteristic and different in shape to the Papa hills of the overlying formation. I have termed these beds the "Middle Papa," to distinguish them from those of the same lithological characters both above and below them. They are composed of the same bluish marly clays, with intercalated seams of harder, more sandy Papa. Their general dip is about 10°, varying in direction from south-east, near Maungaharuru, to south and south-west as their northern termination is reached. Fossils are plentiful, but, as is usually the case when embedded in Papa, are of so fragile a nature that it is very difficult to preserve them. I obtained eighteen different species of Testacea from these beds in different parts. In this formation we first see signs of local disturbance, which is not continued, as far as I am aware, into the overlying one. We must therefore suppose that the movement took place before the deposition of the later ones, and was confined to a small area; this being very near the axis of the synclinal basin. As a general rule, the uniformity in amount and direction of the dip in each formation, over large areas, is very remarkable, and shows, I imagine, that the last elevation which brought the beds into their present position must have been on a large scale, and extending over a protracted period. It is probable that this Middle Papa thins out considerably towards the south, as is shown on the map. It is, however, I think, present at Pohue, a point on the Taupo road, although I did not actually see the rock itself, but a large Dentalium, which is a characteristic fossil of the beds, was brought to me there, and described to me as having been found in blue clay at the foot of the Titiokura Pass.

Lying conformably on the Middle Papa is found a considerable thickness of brown soft sandstone, overlaid by beds of conglomerate formed of slaty pebbles cemented together by ferruginous matter. The best section of them is seen along the Taupo road from Rangimaipapa Hill to Te Pohue Lake. Both beds thin out and gradually disappear to the north. The conglomerate itself is very easily traced across country by the steep escarpments it presents, especially towards the west or uptilted side. I saw no fossils in either of these beds.

We next come to the Upper Papa, which there is every reason to believe is not conformable to the conglomerate underneath. Of this, however, I cannot be certain, as I had not time to search in positions which would show their line of junction. This Papa is wonderfully full of fossils, of which I brought away 21 different species, many other larger ones being much too fragile to get out of their matrix. The nature of this rock is