the fact that their origins lie within three periods of rise and fall covering a total vertical distance of at least 1,600ft. Succession of interglacial and glacial periods, as evidenced by the geological processes of deposition and destruction of deposits, has been demonstrated on South Kaipara Peninsula by the alternating events of terrace formation and erosion of valleys across terraces. The oscillations of sea-level have been complementary, the graph (Fig. 5) showing three maxima which may be correlated with interglacial periods. The various surfaces recorded here, with heights between 11ft, and 550ft., have wide areal distribution throughout North Auckland and a complete succession has been recognized as far north as Doubtless Bay (McDonald, 1951).

Correlation with the relative Pleistocene chronology of Europe seems to be substantiated in two ways. Low curves on the graph, representing regressive sea-levels, indicate glaciations which are identified by working backwards from the Flandrian transgression. Between these recessions the graph shows the positions of high-level terraces formed by return of water to the ocean during warmer interglacial periods. The heights of these terraces, and their particular locations between glaciations, may be correlated directly with the sequence of high sea-levels in Europe and America given by Zeuner (1950, p. 128). To this list have been added glaciations for comparison with data from South Kaipara Peninsula:

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On South Kaipara Peninsula field evidence for the Early Glaciation is not conclusive and the low curve shown on the graph as following the Sicilian high sea-level is inferred from outcrops near Waimauku. West of Waimauku the terrace at 220ft to 240ft. is floored by pumiceous silts and sands of Kaihu Formation at least 154ft. thick which rest on an irregular basement of Manukau Breccia It is not clear whether this sequence represents glacio-eustatic oscillation of the sea or whether it is an inland exposure of the basal contact of the beds described earlier from the western coast.

Terraces situated at higher levels than the Sicilian shoreline (350ft.) and yet part of the same flight, present problems of age and origin which are not readily solved in the present area. It has been recognized in Europe that gradual withdrawal of the ocean from a position approximately 1,200ft. higher than at present began in late Pliocene time and that the glacial period was entered with the Sicilian shoreline at the 100 metre level (Baulig, 1935; Zeuner, 1950, Figs.

46, 50). The lowest late Pliocene surface of Baulig at 180 metres (585ft.) may be correlated with the 550ft. Kaipara plateau, and this would suggest a possible position for the Pliocene-Pleistocene boundary. The age of this Kaipara surface and the underlying unfossiliferous beds is, however, by no means fixed by such a correlation since Movius (1949) has shown that the Villafranchian of Europe should be considered basal Pleistocene rather than Pliocene. Movius does not give details of high-level terraces apart from indicating (Pig 4, p. 386) a surface on the Villafranchian at 250–280 metres, but it seems probable that the age of the terraces discussed by Baulig (1935) will be revised. Nevertheless, Stearns (1945, p. 1074) in describing surfaces at 560ft., 260ft., 215ft., 150ft, 100ft., 45ft., 25ft and 5ft. above modern mean sea-level in the New Hebrides group, pointed out that on paleontological evidence the age of the 560ft. and higher terraces may well be late Pliocene.

In a recent summary of literature Fleming (1953, pp. 77–79) has shown that much of the North Island of New Zealand was in a zone of periglacial climate during the Pleistocene glaciations. From a study of river terraces in Wanganui Subdivision Fleming (p. 80) has adopted a provisional classification of glacial and interglacial phases within which it is possible to recognize correlatives of Zeuner's (1950) Antepenultimate, Penultimate and Last Glaciations. However, the amount of post-Tertiary differential warping that has occurred in the Wanganui area does not allow such correlation any degree of certainty, as emphasized by Fleming (1953, p. 81).

In addition to the striking similarity between the chronology of sea-level movements in the Kaipara district and that in Europe, there are broader features of the Pliocene-Pleistocene history in North Auckland that are matched elsewhere in the world. The abandonment of higher shorelines shows the Pleistocene was a period of discontinuous major retreat of sea-level upon which was superposed the effects of glacial eustasy, with successively lower sea-levels appearing in each interglacial phase. The individual oscillations of sea-level recorded here as due to the alternation of glaciations and interglacials appear small in their range when compared with the total regression of the Pleistocene sea from the 550ft level to the present position Only a part of the water that has “disappeared” can be accounted for by ice-caps now formed at the poles, and some effect other than glacial eustasy is necessary to explain the continued regression throughout the Pleistocene. As a solution to a similar problem in Europe Baulig (1935) expanded the theory of deformational, or diastrophic, eustatism and concluded that there possibly had been simultaneous re-arrangement of large segments of the earth's crust without any evidence in the emergent stable (i.e., non-faulted and non-folded) regions of warped terrace surfaces or tilted sedimentary layers. Some such mechanism of crustal relief is essential in order to allow world correlation of terraces on landmasses that have undergone extensive emergence during the Quaternary.

If any credence is found in the control of landmass emergence by diastrophic eustatism, then an explanation may be given for one problem in the Kaipara district. That is, the 550ft. “late Pliocene transgression” referred to in this text (Fig. 5) may never have occurred as such; it may have been a marine transgression which never reached great heights above present sea-level, but the scale of transgression has been falsely accentuated by diastrophic regression of the ocean during the Pleistocene.