There is no need to say much of the geological history prior to the Mesozoic as there is probably not a single living organism in N.Z., with fossil ancestors in our Palaeozoic. Palaeozoic marine faunas were fairly similar throughout the world; provinces are recognized, with some endemism, but, in general, the succession here, imperfect as it is, shows changes parallel with those elsewhere, suggesting, that, in general, the Palaeozoic world was almost Wendel Wilkie's dream … one world.

Much the same can be said of the earlier Mesozoic. Our Triassic and Jurassic fauna and flora are quite close to those of, say, New Caledonia, East Indies, the Himalayas, Mediterranean, and the Arctic. We have some endemics, but no typically “Neozelanic” living organisms have ancestors in our Trias and Jurassic, unless the Waikato Heads Jurassic Dicotyledon, Arber's Artocarpidium, is related to a living genus. In the Triassic and Jurassic, a deep, wide, linear trough (“geosyncline”) was present on the position of N.Z., running from the Nuggets, Otago, in a sinuous line across Canterbury and Marlborough, up the North Island to Kawhia and North Auckland. It was a gradually sinking basin, a down-fold, and from what we know of such structures, was almost certainly parallel to a welt, a rising mass of land, which is believed to have been west of the geosyncline. Possibly there were other welts; probably too, the structure was bigger than present N.Z., stretching N.W. and S. to form, perhaps, at times, land connections, or island arcs towards New Guinea … we don't know, but what I have said above makes it unlikely that Trias-Jura paleogeography has much to do with our modern biota; perhaps the tuatara (Sphenodon) could have arrived then. The Trias-Jura period of sedimentation closed with orogeny and uplift of the sediments in the trough, a frequent tendency for what has gone down to go up, like a stationary wave. This is the time (Early Cretaceous) when most bridge builders have tied us up in all directions, and with much excuse. But modern views on the mechanism and pattern of deformed geosynclinal areas would not allow us a “continent” such as many have asked for. N.Z. rocks have never included what are grouped as “continental” deposits; red beds indicating deserts, gypsum and salt deposits; this suggests that we have always had an insular climate of the west-wind belt, and never land of such dimensions as to allow rain-shadow deserts to form in the lee of mountain ranges. Still, we haven't much when it comes to arguing about what was happening out at sea; here in N.Z., uplift of the Trias-Jura geosyncline in the Cretaceous must have amounted to many thousands of feet, slowly of course, with erosion taking it off as it came up, but it doesn't take many thousands of feet to make a mess of the ocean floors. So you could have outside connections then if you wished, but keep them on lines of the known ocean-bottom ridges. What might have come? Sphenodon, as I've mentioned, the ancestors of the moas, kiwi, the N.Z. frogs, Leiopelma, some of the slow-evolving primitive invertebrates (e.g., Peripatus) and the ancestors of the present endemic, or slow evolving, plants. Re the latter we should eventually have some information from pollen, supplemented by leaf and wood studies.

When the geological record recovered from the blow of the post-Jurassic orogeny—which caused a big lacuna in the lower Cretaceous—we find quite a lot of changes, geological and biological. The pattern of the folds, welts and troughs, that later developed, was finer than before; instead of a broad trough some hundreds of miles wide and thousands long, the folds are narrower, short, interfingering, branching. The welts, which would tend to be land, were similarly small, so we are justified in thinking of post-Jurassic New Zealand as being, what it is now, archipelagic in its geography. Changes in the disposition of sea and land were relatively frequent, and were on quite a large scale, the troughs were locally relatively deep, although they became filled with sediment as they sank, the welts rose correspondingly great amounts, locally, but if composed of lately deposited sediment they would erode quickly. A kind of writhing of this part, presumably also other parts, of the Pacific margin, seems to have gone on. I may interpolate that this condition of a changing archipeligo is one that would encourage “speciation,” i.e., the formation of two or more species by successive invasions, re-invasions, or back-invasions of stock from one island to another, and this would account for genera with a multitude of species, and for species in which complete physiological isolation (in the sense of Dobzhansky and others), preventing interbreeding, had not been attained when the two daughter stocks came together again, so that they “hybridised.” It may be convenient to discuss the inferred palaeogeography step by step, before discussing the evidence of fossils.

The Upper Cretaceous sea washed the east coast of the South Island and the coastline, a fluctuating one, ran obliquely through Otago, up through Canterbury, separating areas of intermittent marine deposition to the east (perhaps progressive sea advance from this direction would be better) from an area of land, with intermontane basins, lakes and swamps, separated by mountains, to the west—over Westland and Nelson, and parts of Otago. In the North, sea occupied the strip from East Wellington to East Cape, and much of North Auckland, and we have little to reconstruct the land from, though it must have been on one side or the other of the strip of sea that received sediment. Most people would extend the Westland land, known definitely from its coal-measure record, to the north-west of the Cretaceous sea areas, but this problem of constructing land from our known areas of sea is one that constantly crops up. Certainly no one pattern applied to all the divisions of the Upper Cretaceous. The oldest beds (Taitai), are confined to the eastern strip; the Clarentian is present from Marlborough up to Bay of Plenty, and again in parts of North Auckland; the Piripauan is more extensive, from Otago (south of Dunedin), up to Bay of Plenty, and in many parts of North Auckland, and reaches further inland in Otago-Canterbury. The Teurian and Wangaloan, uppermost Cretaceous stages, are less widely recognised within the same area, and there is a chance that even in the area outlined shoals and islands may have existed, breaking up the area of ea. Our Paleocene and Early Eocene, only lately recognised, have not been fully enough mapped to base conclusions on, but they seem to have followed the Cretaceous basins of the eastern and northern areas. Quartz beds (sands and gravels) and leached light sediments at this time suggest that the land was of low relief, peneplained, and that orogenic movements were slowed down for a while (Macpherson, 1946).

The middle Eocene (Bortonian) marks a spread of seas over much of the area known or surmised to have been land previously; further inland in Otago, inland Canterbury, much of Westland and Marlborough, but still, apparently, only in eastern and northern North Island. Some believe, with good reason, that this mid-Eocene sea crossed the South Island to link the deposits now known at Broken River (inland Canterbury), and Westland, others, that a central axis persisted. The later Eocene, Kaiatan, and Runangan, saw the formation or growth of deep, somewhat localised troughs in some areas which were filled by fine sediment, carbonaceous in Westland and parts of North Auckland and Nelson, pale, perhaps deeper offshore sediments in Marlborough. The Kaiatan sea spread over coal measures in the Reefton-Murchison area which had apparently escaped the Bortonian transgression. There is no upper Eocene in the east coast, North Island, area, which apparently emerged temporarily.

The Oligocene Whaingaroan Stage saw a widespread transgression of the sea on to areas previously land. It advanced over Southland, persisted in Otago, Westland, Canterbury and Marlborough, Nelson and the Sounds, Wellington Province east coast to Hawke's Bay, if not further north, and advanced over the western North Island (we don't know from what direction), to cover at least the Taumarunui-King Country area, the Waikato basin, and much of North Auckland. In many of these areas coal below the Waingaroan beds testified to the land surfaces (probably upper Eocene) that were covered. You may ask, was any of New Zealand left? Well, the answer is that the Whaingaroan sediment must have come from somewhere, though it may have come from some distance, as it is generally fine in texture, and extensive limestones, lacking much detritus, were among its sedi- mentssediments. We know that there were volcanic islands in the Oamaru district, and there were other areas, in or close to, the limits of New Zealand, that were emergent (central Otago, Ross, parts of Nelson).

In the succeeding Duntroonian and Waitakian stages, marine deposition continued with interruptions locally, temporary emergences, at least to shoals; limestones were deposited locally, and, it is believed, further transgression of the sea occurred in the Otago area, into “Central” Otago.

The upper Oligocene, Otaian to Awamoan stages, saw a recession of the sea from a number of areas. There were quite a few places where extensive Otaian beds were deposited, and Hutchinsonian seas still occupied parts of Westland and Otago, but Awamoan deposits are distinctly limited. The period (the Pareora Epoch) saw the withdrawal of the sea from the whole of the North Island, from Southland, Nelson and many parts of the South Island, even if the withdrawal was only temporary. In North Otago, where sea remained, coarser sediments bespoke increasing relief, inferred to be to the west, and the temporary withdrawals everywhere, or almost everywhere, attest a phase of mid Tertiary mountain-building. In most of Otago and parts of Canterbury, the sea withdrew after the Awamoan, and has not been back since. How large an area was exposed by this post-Awamoan or Awamoan withdrawal of the sea, perhaps better, elevation of the land, we don't know, but in many areas the sediments that would be exposed by such a movement were soft and would be readily washed away. I say this lest it be thought that this fairly widespread elevation, even if, as seems likely, it was of short duration, could have meant a land-bridge. It is certainly a good time to put one if there were evidence for it, and there were notable incomings among the mollusca and foraminifera at this time and a bit later. We know little of the Tertiary history of the New Caledonia ridge, except that that island has apparently been out of the sea since the Oligocene. Possibly, then, this late Oligocene pulsation of the New Zealand part of the Pacific margin could have opened fresh paths for immigration of certain organisms from the north. But not a continuous land bridge, mark you, or we would have a plague of snakes and mammals.

Very soon after the momentary shudder described above, the sea transgressed again over many parts of New Zealand, to deposit rocks of the Southland series. From now on, we feel, there is more justification in trying to draw shorelines; the structures that then determined land and sea are in some way related to the structures that now separate high range from lowland, land from sea, though increasing confidence is, of course, gained as we approach our own time.

The early Miocene Altonian sea lapped parts of Otago, but did not go far from the present coast; it flooded the Waiau depression of Southland; it was widespread in North Canterbury and Marlborough, in Westland, and in Nelson and the Murchison area. Possibly the main axis, the mass of Otago and the line of the Alps were by now delineated, as a pretty low, not highly mountainous, land. In the North, much of the East coast was flooded, certainly in an area east of a line projected through Masterton and Takapau; Altonian seas covered many parts, if not the whole, of the area west of Taumarunui north across North Auckland Peninsula, where the sediments are believed to be derived from a land to the west of the present coast. A western land, of gneissic and granite rocks, west of the North Island, has been inferred from the nature of sediments at various times between the Triassic and the Pliocene. In North Auckland, volcanoes broke out at the end of the Altonian, forming extensive deposits in the Waitakerei Range, at Whangarei, Great Barrier, and Coramandel, possibly also to the south; and it is almost certain that much of North Auckland, and further south perhaps to the latitude of about Raglan, emerged from the sea at this time, and was not again submerged for a long while, if at all. North Auckland thus has a fairly long history as land, but much of Otago is a bit older.

The Clifdenian sea followed the Altonian in parts of Southland (Waiau Valley), Westland, and elsewhere, and in the eastern part of the North Island and the central western part (Mokau River to King Country). The Lilburnian, however, is less extensively developed than the Altonian. The Waiauan sea advanced again locally, even on the margin of Otago, in the Waiau, in Canterbury (Oxford district) Marlborough, Westland and persisted through from the Altonian in the Eastern North Island. The Waiauan sea persisted in North Taranaki, inland to about Taumarunui at least, north to Mangapehi (south of Te Kuiti) and Taupo. It may have extended in from the Gisborne area to the Urewera … there is a blank in our knowledge there, but I think some Tertiary of about this age has been recorded from east of Waikaremoana. But nothing is known of any transgression to the north.

The Tongaporutuan stage saw a southward retreat of the north coast of the big King Country to North Taranaki “bight” which had had a long history as sea; the coast must have been out at sea north of about Raglan, and have swung in to the King Country, thence south inland of the headwaters of the Wanganui River, perhaps then obliquely south to the Wanganui, then S.W. to Cook Strait. On the east, the sea occupied much of the East Cape to Palliser Bay area. But there were probably at times small islets in both the eastern and western seas. Land between these seas is inferred to have crossed Cook Strait, and to have occupied much of the central axis. In the south, Tongaporutuan seas were persent in Marlborough and N. Canterbury but are not known elsewhere in Canterbury, nor in Otago. In Southland, the sea still occupied the Waiau depression, and, what is more, flooded eastern Fiordland, i.e., the area between Lake Hauroko and Port Craig (western Southland), which had previously been emergent to some extent. On the west, Tongaporutuan seas continued to occupy parts of the foothill-lowland area of Westland, and flowed well in to the Murchison basin, which had a rather violent period of geosynclinal sinking, as an inland basin in which thick estuarine beds, including coal, were deposited.

All this Miocene time, there were oscillations caused by orogenic movements everywhere; upfolds would emerge as island arcs, with fluctuating shorelines moving back and forth, straits and embayments would be formed and shortly be closed again, and we are far from being able to draw exact shorelines. Volcanoes are known to have been active in the Altonian of N. Auckland; in the Tongaporutuan of the Mokau area, probably from centres now out to sea; and at the same period, roughly, other volcanoes affected the east coast area near Hawke's Bay: these also may have been outside N.Z.'s present boundaries, or may have been early eruptions from the Taupo area.

The Kapitean (latest Miocene), was a period when the sea occupied much the same area as previously. There may have been further retreat in North Taranaki, but the main interest in Kapitean palaeogeography, however, is the transgression over the middle parts of New Zealand which introduced the great Pliocene depressions. Thus there is Kapitean over the East Cape peninsula as far as about Te Kaha in the Bay of Plenty; the sea came from the west right up to the shores of Taupo, perhaps further, and the sediments preserved show no sign of vulcanism so that all the volcanic rocks of that area are Pliocene or younger. Possibly a strait or straits formed across the Ruahine-Tararua axis at this time, or a little later. Certainly in the Opoitian there was further transgression over the North Island axis and for the first time since the Altonian, the sea bit into the Auckland Peninsula near Waikato Heads. The same areas were still flooded in the South Island, but there is evidence, from the estuarine nature of deposits in the Waiau, and in North Canterbury, and from coarser deposits locally, that the land areas were rising.

In the Waitotaran, I would say that North Auckland began to take its present shape. The sea flooded the Manukau lowlands, perhaps formed a strait through the peninsula, and possibly many other “lowlands,” such as the Kaipara, the Thames Graben, and Waikato Basins had been formed. By now, the Western Bight of Taranaki had dwindled, but the coast still went from about New Plymouth across to Raetahi, then flowed through a strait between islands into Hawke's Bay, and extended over the whole of that province, reaching up to Waikaremoana. The South boundary of this ancestral Cook Strait is hard to define; the Ruahines stood up as an island; so did the Tararuas which were probably linked to Marlborough. Possibly the coast was somewhere north of Nelson-Marlborough, swinging up to the Manawatu Strait, and then south through a maze of islands and shoals to Masterton and Palliser Bay. In Marlborough-North Canterbury the seas were becoming restricted between growing islands, and the Kai-