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Global climate variability during the late Quaternary is commonly investigated within the framework of the ‘bipolar seesaw’ pattern of asynchronous temperature variations in the northern and southern polar latitudes. The terrestrial hydrological response to this pattern in south-eastern Australia is not fully understood, as continuous, high-resolution, well-dated proxy records for the hydrological cycle in the region are sparse. Here we present a well-dated, highly resolved record of moisture balance spanning 30000–10000 calendar years before present (30–10 ka BP), based on x-ray fluorescence and organic carbon isotope (δ13COM) measurements of a sedimentary sequence from Lake Surprise in south-eastern Australia. The data provide a locally coherent record of the hydrological cycle. Elevated Si (reflecting windblown quartz and clays), and relatively high δ13COM, indicate an extended period of relative aridity between 28 and 18.5 ka BP, interrupted by millennial-scale episodes of decreased Si and δ13COM, suggesting increased moisture balance. This was followed by a rapid deglacial shift to low Si and δ13COM at 18.5 ka BP, indicative of wetter conditions. We find that these changes are coeval with other records from south-eastern Australia and New Zealand, and use a Monte Carlo Empirical Orthogonal Function approach to extract a common trend from three high-resolution records. Our analyses suggest that drivers of the regional hydrological cycle have varied on multi-millennial time scales, in response to major shifts in global atmosphere-ocean dynamics during the last glacial-interglacial transition. Southern Ocean processes were the dominant control on hydroclimate during glacial times, via a strong influence of cold sea surface temperatures on moisture uptake and delivery onshore. Following the last deglaciation (around 18 ka BP), the southward migration of cold Southern Ocean fronts likely resulted in the establishment of conditions more like those of the present day. Millennial-scale variability in records from the region is dominated by a persistent ca. 2300-year periodicity, consistent with other records across the Southern Hemisphere mid-latitudes; however, this pervasive periodicity is not obviously linked to the ‘bipolar seesaw’ and the mechanism remains equivocal.

Late-twentieth century changes in the intensity and migration of Southern Hemisphere westerly winds have been implicated in spatially complex variability in atmospheric and ocean circulation, and ice-sheet dynamics, across the mid- to high-latitudes. A major uncertainty, however, is whether present day hemispheric-wide symmetrical airflow is representative of past behaviour. Here we report a multi-proxy study from Stewart Island and southern Fiordland, New Zealand (46–47°S) reconstructing Holocene changes at the northern limit of westerly airflow. Increased minerogenic input and a pronounced shift in cool-loving vegetation around 5500 years ago is consistent with the establishment of westerly airflow at this latitude in the southwest Pacific. In marked contrast, stronger winds are reported further south over the subantarctic Auckland (50°S) and Campbell (52°S) Islands from 8000 years ago. Intriguingly, reconstructions from the east Pacific suggest a weakening of core westerly airflow after 8500 years ago, but an expansion along the northern limits sometime after 5500 years ago. Our results suggest similar atmospheric circulation changes have been experienced in the Pacific since 5500 years ago, but indicate an expanded network of sites is needed to comprehensively test the driver(s) and impact(s) of Holocene mid-latitude westerly winds across the Southern Hemisphere.

Here we report a ∼2000-year sediment sequence from the Fortescue Marsh (Martuyitha) in the eastern Pilbara region, which we have used to investigate changing hydroclimatic conditions in the arid subtropics of northwest Australia. The Pilbara is located at the intersection of the tropical Indian and Pacific Oceans and its modern rainfall regime is strongly influenced by tropical cyclones, the Intertropical Convergence Zone (ITCZ) and the Indo-Pacific Warm Pool. We identified four distinct periods within the record. The most recent period (P1: CE ∼1990–present) reveals hydroclimatic conditions over recent decades that are the most persistently wet of potentially the last ∼2000 years. During the previous centuries (P2: ∼CE 1600–1990), the Fortescue Marsh was overall drier but likely punctuated by a number of extreme floods, which are defined here as extraordinary, strongly episodic floods in drylands generated by rainfall events of high volume and intensity. The occurrence of extreme floods during this period, which encompasses the Little Ice Age (LIA; CE 1400–1850), is coherent with other southern tropical datasets along the ITCZ over the last 2000 years, suggesting synchronous hydroclimatic changes across the region. This extreme flood period was preceded by several hundred years (P3: ∼CE 700–1600) of less vigorous but more regular flows. The earliest period of the sediment record (P4: ∼CE 100–700) was the most arid, with sedimentary and preservation processes driven by prolonged drought. Our results highlight the importance of developing paleoclimate records from the tropical and sub-tropical arid zone, providing a long-term baseline of hydrological conditions in areas with limited historical observations.

The stratigraphic relationships of palaeoecological proxies and use of changepoint analyses to determine the cause and effect relationships between past events has allowed a better understanding of the relative contributions of humans and environmental drivers to Late Quaternary extinctions and of their effects on terrestrial ecosystems. Few studies, however, have validated these approaches at localities where past interactions between vegetation communities and large herbivores are well-documented. Here, we use a peat core from subantarctic Enderby Island to present the first study tracing the spores of dung fungi alongside pollen at a site where the history of mammalian herbivore introductions (and subsequent eradication), and their effects on the vegetation, are precisely known. We find a strong connection between spore influx rates of the dung-fungus Sporormiella and PCA axis 1 of the pollen assemblages, suggesting that past vegetation change caused by herbivore introductions and eradications at the core site can be readily deduced from the palaeoecological record. The response of the vegetation community to the removal of herbivores was so rapid, however, that a difference in timing between changepoints relating to specific pollen taxa, the overall pollen community, and the decline of Sporormiella spores, could not be resolved in our record, despite a sampling resolution of

Accurate estimates of the timing of extinctions (θ) are critical for understanding the causes of major die-off events and for identifying evolutionary or environmental transitions. Yet many studies have demonstrated that sampling biases and underlying statistical assumptions affect the accuracy of model-based estimates of extinction times ( θ ˆ ), and the added uncertainty contributed by inherent (laboratory) dating errors has largely been neglected. Here we provide a general guide (model-selection key) for choosing from among eight alternative ‘frequentist sampling’ (i.e., non-Bayesian) methods, differentiated by their treatment of both the probability of record occurrence and uncertainties in record dates, the most appropriate for a given record. We first provide a methodological framework to characterize time series of dated records as a function of the number of records, the size of the interval between successive records, and laboratory dating errors. Using both simulated data and dated Australian megafauna remains, we then assess how the characteristic of a dataset's time series dictates model performance and the probability of misclassification (false extant vs. false extinct). Among the four classic frequentist methods providing highest model performance, Marshall's (1997) and McCarthy's (1998) methods have the highest model precision. However, high model performance did not prevent misclassification errors, such that the Gaussian-resampled inverse-weighted McInerny (GRIWM) approach is the only method providing both high model accuracy and no misclassification issues, because of its unique down-weighting interval procedure and its ability to account for uncertainties in record dates. Applying the guideline to three time series of extinct Australian species, we recommend using Marshall's, McCarthy's and/or GRIWM methods to infer θ of both Thylacinus sp. and Genyornis sp., because each dataset is characterized by many sightings and a low variance of the interval between records, whereas McInerny's method better suits Diprotodon sp. due to an even lower interval variance.

Fungi which produce their spores on the dung of large herbivores show promise as indicators of the distribution and relative abundance of large herbivores in past environments. Recently, several studies have used counts of spores of such fungi, Sporormiella in particular, to resolve the timing and reveal the ecological consequences of extinction of Pleistocene megafauna. However, there are several problems in the interpretation of the dung-fungus proxy, relating mostly to taphonomic effects on spore accumulation. Here, we describe these problems and show how they can be solved, using new data from the Lynch's Crater site in northeastern Australia. Effects of variation in spore accumulation in relation to position in the sedimentary basin can be controlled by comparing cores from different locations; temporal variation in spore accumulation rates can be attributed to changes in herbivore populations, as distinct from time-varying taphonomic effects, by comparing trends in fungi exclusively associated with herbivore dung to trends for fungi that also sporulate on other substrates; effects of changing vegetation composition can be removed by measuring spore influx rates rather than expressing counts relative to the pollen sum. At Lynch's Crater, these approaches increase our confidence that a decline in dung fungi at ∼40 ka indicates an unprecedented drop in biomass of large herbivores. We also show that before this decline, the biomass of large herbivores at this site was evidently similar to that in North America and western Europe.

This research was carried out while T.P.R. held a UK Natural Environment Research Council studentship (NE/G524328/1) at the University of Exeter. .

A multi-proxy Lateglacial environmental record is described from Sluggan Bog in County Antrim, Northern Ireland. Pollen, plant macrofossil, charcoal, sediment chemistry, stable isotope and sedimentological data provide a multi-faceted picture of local and regional environmental changes during the transition from the Last Cold Stage to the beginning of the present interglacial, and enable a series of distinctive palaeoenvironmental ‘events’ to be identified. A combination of radiometric and AMS radiocarbon dates on both humic and humin sediment fractions, and on charcoal fragments and plant macrofossils, provides one of the most closely-constrained radiocarbon timescales for any Lateglacial site in the British Isles. The evidence suggests that an initial period of warm conditions, beginning in the Sluggan record around 14.2 ka b2k (before AD 2000), and when open Salix-Betula woodland was locally present, was succeeded first by a heathland phase, then by a re-establishment of wood and scrub, before this was replaced during the later part of the Lateglacial (Woodgrange) Interstadial by species-rich grassland. In terms of timing, this sequence corresponds very closely to the GI-1e, GI-1d, GI-1c series of events in the Greenland NGRIP ice core. A short-lived Betula phase towards the end of the interstadial in the Sluggan sequence may reflect the short-lived climatic warming of GI-1a, although the radiocarbon age model suggests that it occurred prior to that event. There is a similar age discrepancy between the two sequences at the end of the interstadial with the onset of the Nahanagan (Younger Dryas) Stadial in Sluggan appearing to predate that in NGRIP by up to 200 yrs. By contrast, there is a very close correspondence between the date on the onset of the Holocene inferred from the pollen record in Sluggan (11.69 ka b2k) and the age of the Pleistocene–Holocene boundary (11.7 ka b2k) in NGRIP. While uncertainties remain over the climatic signals in the later interstadial, the evidence suggests that during the early and mid-interstadial and at the onset of the Holocene, Northern Ireland and Greenland appear to have been broadly phase-locked in their response to hemispherical climate change.

The INTIMATE protocol for the correlation of marine ice core and terrestrial records is here updated, reflecting recent developments in palaeoclimate research. Originally focussed on Last Glacial to Interglacial Transition (LGIT: 22,000–11,500 years B.P.), the INTIMATE group has now extended its study period back to 60,000 years. As a first step, the INTIMATE event stratigraphy has now been extended to include 8000–48,000 b2k based on a combined NGRIP and GRIP isotope profile against a GICC05 chronology and key tephra horizons from Iceland and continental European volcanic sources. In this lead article of this INTIMATE special issue we introduce some of the recent achievements of the INTIMATE community and discuss the challenges associated with extending the INTIMATE approach back in time, focussing in particular on the chronological problems inherent in comparing different proxy records. The INTIMATE approach has thus far been limited predominantly to the North Atlantic and Australasian regions and we also discuss the potential to extend the INTIMATE protocol beyond these regions.

The rate at which a once-abundant population declines in density prior to local or global extinction can strongly influence the precision of statistical estimates of extinction time. Here we report the development of a new, robust method of inference which accounts for these potential biases and uncertainties, and test it against known simulated data and dated Pleistocene fossil remains (mammoths, horses and Neanderthals). Our method is a Gaussian-resampled, inverse-weighted McInerny et al. (GRIWM) approach which weights observations inversely according to their temporal distance from the last observation of a species' confirmed occurrence, and for dates with associated radiometric errors, is able to sample individual dates from an underlying fossilization probability distribution. We show that this leads to less biased estimates of the ‘true’ extinction date. In general, our method provides a flexible tool for hypothesis testing, including inferring the probability that the extinctions of pairs or groups of species overlap, and for more robustly evaluating the relative likelihood of different extinction drivers such as climate perturbation and human exploitation.

The latter part of the Last Glacial Interval (LGI; 60,000 to 11,700 years ago) experienced a range of climatic and environment extremes. To elucidate the mechanisms of these changes requires records of past variability that are precisely dated and correlated on the same absolute timescale. However, despite decades of research, it is still not possible to align most marine and terrestrial records of past change with ice-core records, largely because of ongoing uncertainties over the conversion of pre-Holocene 14C ages on to a calendar timescale and uncertainties with in ice-core chronologies. As a result, it is equivocal whether climate changes in both hemispheres during the LGI led, lagged or were synchronous with one another. A decadally-resolved radiocarbon calibration is urgently required to test these models of the Earth system. Here we report radiocarbon measurements obtained from subfossil New Zealand kauri (Agathis australis) spanning a collective 3500 years dated between 25,000 and 45,000 years ago. The results are compared to the recently published international calibration curve IntCal09 and to the marine Cariaco Basin datasets. We show that kauri have considerable potential for development of a Southern Hemisphere component of a unified global calibration curve suite, and that tree-ring sequences can be superposed on other radiocarbon records to constrain atmospheric–marine offsets and precisely test the synchronicity of abrupt climate change.

Lynch's Crater provides the main reference section for late Quaternary environmental change in northeast Australia. We have identified a cryptotephra horizon within late Marine Isotope Stage-5 (MIS-5) lake sediments obtained from the site. The major element geochemistry of this tephra has been compared with data from southwest Pacific sources, and our results indicate that the cryptotephra is most likely to be of Papuan origin. This is the first discovery of an aerially derived tephra in Australia that originated from outside the mainland. The Lynch's Crater tephra is potentially an important marker horizon which could be used to connect disparate palaeoarchives at a time of significant climatic and environmental change.

Dating climatic and environmental records with accuracy and precision is critical if we are to robustly test hypotheses of synchronous change between the hemispheres. In the southern hemisphere, the advance of the New Zealand Franz Josef Glacier to the Waiho Loop terminal moraine has been used as evidence of synchronous global change during the Younger Dryas Chronozone. However, radiocarbon ages for wood incorporated into the sediments associated with the advance span an interval of ∼900 years. Here we demonstrate that weathered ‘old’ wood was incorporated into the deposit prior to, or during, the advance, and that this material is highly susceptible to contamination by young carbon, resulting in the wide range of age estimates reported previously. We have identified material with little evidence of reworking (well-preserved wood with bark attached) that provides a statistically robust mean radiocarbon age of 11,062±30 BP (∼13.1 ka) for the advance of the Franz Josef Glacier. The timing of this event falls within the later part of the Antarctic Cold Reversal. Comparison with local, regional and global records suggests that cold conditions in the Southern Ocean were probably experienced in New Zealand at this time, driving the glacial advance.

The collapse of the Laurentide Ice Sheet and release of freshwater 8740–8160 years ago abruptly raised global sea levels by up to 1.4 m. The effect on human populations is largely unknown. Here we constrain the time of the main sea level rise and investigate its effect on the onset of the Neolithic across Europe. An analysis of radiocarbon ages and palaeoshoreline reconstruction supports the hypothesis that flooding of coastal areas led to the sudden loss of land favoured by early farmers and initiated an abrupt expansion of activity across Europe, driven by migrating Neolithic peoples.

Tephrochronology, a key tool in the correlation of Quaternary sequences, relies on the extraction of tephra shards from sediments for visual identification and high-precision geochemical comparison. A prerequisite for the reliable correlation of tephra layers is that the geochemical composition of glass shards remains unaltered by natural processes (e.g. chemical exchange in the sedimentary environment) and/or by laboratory analytical procedures. However, natural glasses, particularly when in the form of small shards with a high surface to volume ratio, are prone to chemical alteration in both acidic and basic environments. Current techniques for the extraction of distal tephra from sediments involve the ‘cleaning’ of samples in precisely such environments and at elevated temperatures. The acid phase of the ‘cleaning’ process risks alteration of the geochemical signature of the shards, while the basic phase leads to considerable sample loss through dissolution of the silica network. Here, we illustrate the degree of alteration and loss to which distal tephras may be prone, and introduce a less destructive procedure for their extraction. This method is based on stepped heavy liquid flotation and which results in samples of sufficient quality for analysis while preserving their geochemical integrity. In trials, this method out-performed chemical extraction procedures in terms of the number of shards recovered and has resulted in the detection of new tephra layers with low shard concentrations. The implications of this study are highly significant because (i) the current database of distal tephra records and their corresponding geochemical signatures may require refinement and (ii) the record of distal tephras may be incomplete due to sample loss induced by corrosive laboratory procedures. It is therefore vital that less corrosive laboratory procedures are developed to make the detection and classification of distal glass tephra more secure.

A technique for determining the radiocarbon age of both organic-carbon and carbonate-carbon in the eggshell of the large flightless birds Genyornis newtoni (now extinct) and Dromaius novaehollandiae (extant emu) is presented here. Stepped combustion (for organic-carbon) and stepped acidification (for carbonate-carbon) were used to obtain multiple age determinations for each sample, from which an assessment of the reliability of the ages is possible. Analysis of a Genyornis newtoni eggshell fragment known to have an age considerably beyond the limit of radiocarbon dating has indicated that the backgrounds obtainable using this approach are 0.122±0.033 pMC for the organic-carbon fraction and 0.070±0.025 pMC for the carbonate-carbon fraction. These backgrounds suggest that finite ages up to 50,000–55,000 BP are readily achievable on eggshell using stepped combustion/acidification. Analysis of a single fragment of Genyornis eggshell from Williams Point, central South Australia, suggests that significant contamination of the organic-carbon fraction of the eggshell is possible, while ages for the carbonate fraction appear more reliable and indicate that the eggshell has an age of at least 49,000±2000 BP. A total of six analyses of single Genyornis newtoni and Dromaius novaehollandiae eggshell fragments from the Wood Point deposit in southern South Australia suggest ages for the samples of 41,000±800 and 37,900±700 BP, respectively, while an optically stimulated luminescence (OSL) sample from a location very close to the Genyornis sample has an age of 55±5 ka (1σ). The OSL and calibrated radiocarbon ages for the Genyornis sample and the sand matrix overlap at two standard deviations, suggesting the most likely age for the eggshell and the sand matrix is ∼45 cal ka BP or earlier.

A multi-proxy environmental record for the Devensian (Weichselian) Lateglacial and early Holocene periods, which includes pollen, plant macrofossil, coleopteran, geochemical and stable-isotope data, is described from a site at Llanilid, South Wales, UK. The geochronology of the sequence is derived from two age–depth models which show a broad measure of agreement over much of the profile. This data set provides the basis for a detailed reconstruction of changing environmental conditions in western Britain during the transition from the Last Cold Stage to the present (Holocene) interglacial (ca 15,000–10,000 cal yr BP). Two marked cooling episodes are recorded during the course of the Lateglacial Interstadial (Greenland Interstadial 1), with mean July temperatures falling by more than 5°C from a maximum of around 20°C during the early Interstadial, and by a further 4–5°C around 13,100 cal yr BP. The initial drop in temperature led to a reduction in Juniperus scrub, while the second, and more abrupt temperature decline resulted in a significant contraction in areas of Betula woodland. A relatively slight and short-lived warming during the later Interstadial enabled tree birch to expand once again. Mean July temperatures of 10–11°C characterised the Loch Lomond/Younger Dryas Stadial (Greenland Stadial 1) between ca 12,600 and 11,400 cal yr BP, during which time a scrub tundra with Betula , Salix and a range of open-habitat taxa became established locally. The onset of the Holocene Interglacial at ca 11,400 cal yr BP is marked by an abrupt temperature rise of the order of 9°C, and by the rapid expansion of Betula woodland. The Llanilid palaeoclimate record is similar to that from the Gransmoor site in northeast England, and also to the climatic sequence inferred from the GRIP ice core, particularly during the later part of the Lateglacial Interstadial (ca 14,000–12,600 cal yr BP), during the Loch Lomond/Younger Dryas Stadial and in the early Holocene. The Llanilid chronology is less secure during the early part of the Lateglacial Interstadial (pre-14,000 cal yr BP), but it is possible that warming may have begun earlier in this part of western Britain than in Greenland.

This study presents the results of an extensive radiocarbon dating program at the Nauwalabila I site in northern Australia. The results show that the radiocarbon chronology at Nauwalabila is reliable to ∼130 cm depth, but below this depth coarse charcoal has been variably altered during a period in the early Holocene when an ephemeral groundwater table reached close to the ground surface of the time. Below ∼150 cm none of the radiocarbon ages can be considered to indicate reliably the age of deposition of the sediments. Luminescence dates near the surface and at 110 cm are concordant with the radiocarbon chronology in the upper part of the sequence, and hence the aberrant radiocarbon results below ∼150 cm do not constitute a reason to doubt the accuracy of the luminescence chronology deeper in the stratigraphy. A conservative estimate of the age of the sequence, based on extrapolation of results from that portion of the sequence where the radiocarbon chronology is considered to be reliable, is consistent with the chronology proposed previously from luminescence dating. Both chronologies therefore suggest occupation of the site before 50,000 years. Based on sediment characteristics and the distribution of quartz, chert, quartzite and ‘quartz crystal’ artefacts, there is no evidence that there has been significant vertical displacement of artefacts relative to the surrounding sand matrix. Both chemical alteration and physical translocation of charcoal contributed to the aberrant ages at depth in the deposit. The results point to the need for careful assessment of the suitability of charcoal for radiocarbon dating prior to analysis and to the dangers of relying on a small number of radiocarbon dates in the development robust site chronologies. Strategies for screening samples for suitability include (i) microscopic examination, (ii) not analysing samples unless they survive the full ABOX pretreatment, (iii) not analysing samples unless the material is significantly larger than the sediment matrix, (iv) using CHN analysis on both untreated and pretreated material to check for organic contamination and (v) using stepped combustion to check for concordancy in the ages of carbon released at successively higher temperatures.