Page:Transactions NZ Institute Volume 9.djvu/618

Rh Island, Napier, where it occurs at the sea level, and is there overlaid by the Napier limestones, which have a thickness of about 300 feet.

A little further to the north at Tangoio it is somewhat less, and is divided by strata of dark grey clays and softer yellowish limestone. Further inland it again increases in thickness, being probably 300 feet deep along the bluffs of Purotangihia range. These limestones and associated beds form to the north of Napier a high broken plateau, rising at Purohutangihia to 2,046 feet, and thence sloping gradually to the sea near Tangoio, where the cliffs are 250 feet high, but rising again towards the north at Matangimoe, where the cliffs are 1,200 feet in height above the sea. The limestone generally has steep escarpments bounding it, often quite inaccessible. It is full of fossils, generally rolled and worn, principally Pecten and Ostrea. In some places, however, the shells are perfect, as in a branch of the Mangapikopiko stream, where the bottom of the valley is strewn with large oyster shells in incredible quantities.

This limestone (if we except the much later formed deposits of shingle, pumice, and river terraces) is the youngest of the rocks in the district of which this paper treats. It has a very considerable extension to the south of Napier, reaching as far as the upper end of the Wairarapa Valley, and is probably of the same age as the limestones found on the southern flanks of the Kaimanawa Ranges on the other side of the Ruahine Mountains. That it has suffered very great denudation I have not the slightest doubt, as it gradually rose from the sea by the action of running streams, and I may add by the wind, which as a denuding agent is by no means to be despised, at all events in this part of the country. An inspection of the map (Pl. XXII.) will show that several out-lying patches are scattered over the district, extending inland to Maungaharuru, and northwards to Whakapunake and the Mahia Peninsula. All these isolated portions dip regularly towards the centre line of the Hawke Bay basin, and with one exception the fossils are the same, as far as my imperfect knowledge of the subject goes. This exception is the mass of limestone capping the hills to the east of the Wairoa River, and extending to Whakapunake. Here the rock is composed almost entirely of Waldheimia shells, giving it in places a peculiar botryoidal appearance. Whether the other fossils common to the rock in other places are present also, I am unable to say, but I saw none in the few places I was able to examine. The dip of the underlying strata is also hidden in this part, excepting on the bluffs of Whakapunake, where the limestone appears to rest on the Maungaharuru sandstones, but a little to the north of Te Hiwera, the Papa is seen dipping south-south-west, whilst the Waldheiniia beds dip nearly west. At Moumoukai, on the Nuhaka River, is