This paper demonstrates the use of tephrochronology in dating the earliest archaeological evidence for the settlement of Iceland. This island was one of the last places on Earth settled by people and there are conflicting ideas about the pace and scale of initial colonisation. Three tephra layers, the Landnám ('land-taking') tephra layer (A.D. 877 ± 1), the Eldgjá tephra (A.D. 939) and the recently dated V-Sv tephra (A.D. 938 ± 6) can be found at 58% of 253 securely-dated early settlement sites across the country. The presence of the tephras permits both a countrywide comparison, and a classification of these settlement sites into pre-Landnám, Landnám and post-Landnám. The data summarised here for the first time indicate that it will be possible to reconstruct the tempo and development of the colonisation process in decadal resolution by more systematically utilising the dating potential of tephrochronology.

precise and accurate radiocarbon chronologies are essential to achieve tight chronological control for the ~ 750-years since Polynesian settlement of New Zealand. This goal has, however, been elusive. While radiocarbon datasets in the region are typically dominated by marine and estuarine shell dates, such chronological information has been ignored by those interpreting the timing of key events because a detailed regional calibration methodology for marine shell, comparable to the highly precise Southern Hemisphere calibration curve, is lacking. In this paper, we present the first temporal 14 C marine offset (ΔR) model for new Zealand based on paired estuarine/marine and terrestrial radiocarbon dates from 52 archaeological contexts. Our dataset displays significant offsets between the measured new Zealand data and the modelled global marine radiocarbon curve. these shifts are associated with oceanographic fluctuation at the onset of the Little Ice Age ~ AD 1350-1450 (650-500 Bp). the application of a regional and temporal correction to archaeological shell dates provides complimentary information to terrestrial radiocarbon production and has the potential to add structure to the blurred chronology that has plagued archaeological theories about the colonization of New Zealand, and other Pacific islands, for decades. The short prehistory of human occupation of New Zealand (NZ) has been vigorously debated for many decades. Recent research suggests that colonization started in the mid to late thirteenth century AD 1,2 , but that sustained, widespread settlement was later 3,4. Walter et al. 5 have argued that an apparent strong archaeological (i.e. radiocarbon [ 14 C]) signal in the early fourteenth century is evidence of a mass migration event 5 , but this is not universally accepted 6. By the mid-fifteenth century, moa (large flightless birds) had become extinct in the North Island with the last remnant populations soon dying out in the South Island 4,7. During this time, settlement had expanded from sheltered coastal locations into inland regions and the extent and intensity of gardening increased 8,9. By the end of the fifteenth century, fortified settlements (pā) began to be built across the landscape for reasons that are not yet clear 10. These events most likely occurred at different rates in different places across NZ. Artefacts that document adaptation to new tasks, environments and materials often display regional variation, before eventually transforming into traditional Māori styles 11,12. Despite thousands of published 14 C dates, the middle, or transitional phase of Māori archaeology (~ AD 1450 to AD 1650), has been described by Anderson (p.7) 9 as a "shadowland between highlights of Polynesian colonisation and classic Māori culture". A lack of 14 C precision over a "particularly wiggly portion of the radiocarbon calibration curve" is commonly cited as the limiting factor 5. Marine shell remains an important material for 14 C dating in the Pacific because it is common in archaeological sites and is easy ...

Archaeological chronologies use many radiocarbon ( 14 C) dates, some of which may be misleading. Strict 'chronometric hygiene protocols', which aim to enhance the overall accuracy and precision of 14 C datasets by removing all potentially problematic samples, mean that so few dates remain in some locations that accurate chronologies cannot be established. 14 C dates on charcoal can be affected by an 'old-wood' effect, and so they are often removed from analyses, despite > 40,000 being available worldwide, representing > $25 million. We show that when a Bayesian chronological model is used, which incorporates an Outlier Model specific to wood charcoal, the 14 C dataset of

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Accurately dating when people first colonized new areas is vital for understanding the pace of past cultural and environmental changes, including questions of mobility, human impacts and human responses to climate change. Establishing effective chronologies of these events requires the synthesis of multiple radiocarbon (14C) dates. Various “chronometric hygiene” protocols have been used to refine 14C dating of island colonization, but they can discard up to 95% of available 14C dates leaving very small datasets for further analysis. Despite their foundation in sound theory, without independent tests we cannot know if these protocols are apt, too strict or too lax. In Iceland, an ice core-dated tephrochronology of the archaeology of first settlement enables us to evaluate the accuracy of 14C chronologies. This approach demonstrated that the inclusion of a wider range of 14C samples in Bayesian models improves the precision, but does not affect the model outcome. Therefore, based on our assessments, we advocate a new protocol that works with a much wider range of samples and where outlying 14C dates are systematically disqualified using Bayesian Outlier Models. We show that this approach can produce robust termini ante quos for colonization events and may be usefully applied elsewhere.