Bruce McFadgen

<p>The arrival of the great Maori waka and the settlement of New Zealand some seven or eight hundred years ago are described in oral history, but details of exactly when and how colonisation occurred are undocumented. Radiocarbon dating of early archaeological sites is particularly problematic, due to the inbuilt age of datable materials, and non-linearity and ambiguity in the calibration of measurements to calendar dates. Hangi stones, used as heat retainers in traditional Maori earth ovens, hold thermoremanent records of Earth’s magnetic field at the time of their last cooling. Matching the directions of these magnetizations to established reference curves provides alternative, archaeomagnetic, estimates of age. Our results cover the past 700 years, with a cluster of dates between 1500 and 1600 AD, from both North and South Islands, but none earlier than 1300 AD, thus supporting a model of rapid coordinated migration around that time. Archaeointensity data have been obtained from sixteen distinct archaeological features, including twelve hangi from eight sites, and from them the first archaeointensity record for New Zealand has been constructed. To this has been added other archaeointensity and palaeointensity data from the SW Pacific region and virtual axial dipole moments (VADMs) have been plotted. This plot outlines steady VADM values of about 8 x10<sup>22</sup> Am<sup>2</sup> from 1000-1300 AD, and 9.5 x10<sup>22</sup> Am<sup>2</sup> from 1500 AD to the present, with an intervening sharp peak in the early 15<sup>th</sup> century when the VADM reached about 13 x10<sup>22</sup> Am<sup>2</sup>. This peak bears many similarities to archaeomagnetic “jerks” and “spikes” in northern hemisphere records from the first millennia BC and AD. However, it is the first such feature to be found in the southern hemisphere at this date, suggesting, in accordance with recent modelling, that it may be a feature of the non-dipole field, associated with rapid growth and decay of an intense flux patch on the core-mantle boundary.</p>

Hangi stones, used to retain heat in traditional Maori earth ovens (hangi), may carry records of Earth's magnetic field when they were last used. Sixteen archaeological features, including 12 hangi, from eight sites were sampled and their palaeomagnetic data used to construct the first archaeointensity record for New Zealand, covering the past 700 years. A combination of radiocarbon dating of associated charcoal and archaeomagnetic dating of palaeomagnetic directions was used to obtain a ‘preferred’ date of each palaeointensity. A plot of virtual axial dipole moment (VADM) for the SW Pacific region outlines steady VADM values of about 8 × 1022 A m2 from 1000 to 1300 AD and 9.5 × 1022 A m2 from 1500 AD to the present, with a sharp peak in the early fifteenth century when the VADM reached about 13 × 1022 A m2. This peak bears many similarities to archaeomagnetic ‘jerks’ and ‘spikes’ in Northern Hemisphere records from the first millennia BC and AD. However, it is the first such fe...

ABSTRACT Smoothed curves are least-squares fitted to three sets of decadal radiocarbon calibration data from New Zealand and British Isles (AD 1725-1935) and western North America (AD 1145-1945). The curves are compared with each other and with a curve previously calculated from New Zealand data (AD 1335-1745). The smoothing procedure results in reduced standard deviations of the curves, but at the expense of time resolution. The comparison shows a variable 14C offset between the northern and southern hemispheres of 0-70 years (Southern Hemisphere older), and a Northern Hemisphere longitudinal variation of -20 to +60 years (British Isles generally older than western North America).

... Titre du document / Document title. Radiocarbon calibration curve variations and their implications for the interpretation of New Zealand prehistory. Auteur(s) / Author(s). MCFADGEN BG (1) ; KNOX FB ; COLE TRL ; ... Method. ; Dating. ; Chemical analysis. ; Radiocarbon. ; Population ...

ABSTRACT We Fourier transformed and filtered calibration curve data to compensate for the averaging effect of radiocar-bon-dating sets of adjacent tree rings. A Wiener Filter was also applied to minimize the effects of the counting errors of the dates on the resulting calibration curve and to produce a least-squares curve through the data. The method is illustrated using a short 14C-dated tree-ring sequence from New Zealand to produce a calibration curve at yearly intervals for New Zealand matai (Prumnopitys taxi folia). The resulting curve has a nominal standard error of 10±3 yr, which is ca. half the average stan-dard error of the original raw data.

... Figure 2 Detrended calibration curves from the west coast of North America (Douglas fir), British Isles (European oak), and New Zealand (cedar) compared with the Wolf, Sporer, Maunder, and Dalton periods of climatic cooling in the North Atlantic (Masarik and Beer 1999 ...

We propose a model for the seismic driving of environmental changes and illustrate it using a case study from New Zealand dated to the 15th Century AD. A "seismic staircase" shows a chronological progression of environmental outcomes that includes tsunami, rock avalanches, vegetation disturbance, rapid coastal dune building, river aggradation, and abandonment of prehistoric coastal settlements. The 15th Century event appears to be unique in the past Millenium and is most notable for its period of rapid coastal dune building. The coincidence of a catastrophic El Niño episode in the mid 15th Century AD may have served to move sediments rapidly through the terrestrial system thus delimiting clearly separate geomorphological after-effects. We contend that seismic driving is a major factor in determining paleoenvironmental change in tectonically active areas during the Holocene and provides the palaeoenvironmental context within which smaller scale events operate.

ABSTRACT Four stranded beach ridge deposits are recognised at Avoca Point, Kaikoura and are considered to have been uplifted by earthquakes. An uplift rate of 1.5 mm/year is derived from beach ridge heights and radiocarbon dates. Earthquake uplifts are dated at 1900 years ago (amount unknown), 1400 years ago (1.1 m), 400 years ago (0.8 m), and 200 years ago (1.1 m).Intermittent human occupation, probably for fishing, fowling and scavenging, was located on the actively-growing Beach Ridge C, between the sea and a lagoon. Cultural remains have very probably been mixed with the beach ridge deposits, with naturally stranded shells, and with bones from carcasses stranded by wave action.

Abstract Gauging the effect of14C-depleted marine foods on radiocarbon ages requires an accurate assessment of the likely proportion of marine foods in the diet. Several factors must be considered, including region-specific δ13C, δ15N and δ34S data values (regional stable ...

ABSTRACT Archaeological excavation of a Maori occupation site at Lake Poukawa shows the site was probably occupied between 150 and 300 years ago and has been badly disturbed by European farming. There is no evidence for human occupation before the Taupo Pumice eruption.

ABSTRACT Four depositional episodes based on sand deposits and the soils on them are proposed for Holocene coastal sand dunes on Chatham Island: Te Onean Depositional Episode (c. 5,000 to 2,200 years BP), Okawan Depositional Episode (c. 2,200 to 450 years BP), Kekerionean Depositional Episode (c. 450 to 150 years BP) and Waitangian Depositional Episode (c. 150 years BP to present day). Each depositional episode has two phases: an unstable phase with a high rate of deposition and no soil formation, followed by a stable phase with a low rate of deposition and soil formation. The Okawan, Kekerionean, and Waitangian episodes closely match late Holocene depositional episodes on the New Zealand mainland. The earliest human occupation remains (Moriori) are in Kekerionean sands and the inferred date for Moriori settlement of Chatham Island is between 400 and 450 years BP. Bones of Hooker's sea lion are found in Te Onean and Okawan deposits. The most recent bones are in Kekerionean middens and it is inferred that Hooker's sea lion was driven from the Chatham Islands by human predation. The depositional episodes appear to be unrelated to sea level changes, tectonic activity, or cultural influence. It is suggested that they may be related to coastal erosion initiated by storms.

ABSTRACT “Mystic Fires of Tamaatea” is the title given to a section of a book entitled “Tsunami: The underrated hazard” written by Edward Bryant and published by Cambridge University Press in 2001. In it the author links New Zealand evidence for widespread forest destruction and Maori place‐names and legends with the 15th century timing of an apparent Tunguska‐type meteor impact in the South Island of New Zealand, Chinese, and Japanese meteor sightings, comets, and “mega"‐tsunamis in Australia. This paper critically reviews the lines of evidence used, and finds no evidence, either Maori or geological, for a 15th century meteor impact in New Zealand. In the book, all Maori place‐names have been incorrectly translated, the radiocarbon chronology is incorrect, and there is no consideration of the numerous potential tsunami sources that were active in New Zealand in the 15th century.

ABSTRACT Four stranded beach ridge deposits are recognised at Avoca Point, Kaikoura and are considered to have been uplifted by earthquakes. An uplift rate of 1.5 mm/year is derived from beach ridge heights and radiocarbon dates. Earthquake uplifts are dated at 1900 years ago (amount unknown), 1400 years ago (1.1 m), 400 years ago (0.8 m), and 200 years ago (1.1 m).Intermittent human occupation, probably for fishing, fowling and scavenging, was located on the actively-growing Beach Ridge C, between the sea and a lagoon. Cultural remains have very probably been mixed with the beach ridge deposits, with naturally stranded shells, and with bones from carcasses stranded by wave action.

This thesis deals mainly with central New Zealand. The writer's archaeological excavations are described in Appendices. Lists are prepared giving all archaeological radiocarbon dates on wood, charcoal, moa bones, human bones and marine shells, for New Zealand up to 1974. The dates are sorted according to material, and the dates and their standard errors corrected. A stratigraphic system based on soils and Loisels pumice and tied to the corrected radio carbon dates is set up for central New Zealand. Radiocarbon and stratigraphy provide dates for vegetation changes' Moahunter sites, cultivation sites, and for the artifact assemblages that are independently grouped as either Early or Late. Change from Early to Late is explained by cultural breakdown and an initial movement of culture from south to north, The sequence of events postulated is summarised in a Table at the end of the text.