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This correction notice is for an article titled "Origins and evolution of oasis agriculture in the Sahara: Evidence from morphometric analyses of archaeological date palm seeds" published in the journal Holocene. The authors of the article overlooked acknowledging the Libyan Department of Antiquity in their acknowledgments. The authors have requested that the acknowledgement be added to the article, and the journal editor confirms that this correction does not affect the results or conclusions of the paper. [Extracted from the article]

Most recent developments of Schmidt-hammer exposure-age dating (SHD) as a calibrated-age dating tool have been limited by the use of locations at two age control points. This has necessitated: (1) making assumptions about a linear R-value—age relationship; and (2) basing predictions of age errors only on R-value variance at the two age control points. This paper analyses 9900 R-values obtained from multiple-age control points on a sequence of glacio-isostatically raised shorelines with well constrained ages (Skuleskogen High Coast World Heritage Site and environs, Gulf of Bothnia, northern Sweden) ranging from modern to 10.5 ka in age. The sampling design involved 30 measurements on granite beach boulders from 30 sites at 11 age control points. The R-value—age relationship is best described by a linear function (ordinary least squares, OLS) with an R2 of 0.89 (p < 0.0001). Predicted-age errors are calculated using two approaches: (1) OLS regression, which takes account of the uncertainties associated with the regression line and the age control points; and (2) weighted total least squares (WTLS) regression which, in addition, takes account of possible shoreline age errors and the heteroscedasticity of R-value residuals with increasing age. With both approaches, 95% predicted-age errors are relatively modest: ±355—455 years and ±300—515 years, respectively, with larger R-value variance and hence uncertainty for older surfaces, and the possibility of further improvement from a more selective field sampling scheme that differentiates between age-related and non-age-related rock-surface variability. Our results also indicate that for certain lithologies and weathering environments, it is possible to construct reliable calibrated-age curves from relatively few age control points. [ABSTRACT FROM AUTHOR]

This paper describes the potential of correcting the 14C age shift resulting from the contamination of primary aragonites by detrital carbonates using online sequential extraction of CO2. The experiments were carried out on laminated lacustrine aragonites collected from Holocene Dead Sea sediment sections. X-ray diffraction analysis revealed the presence of detrital calcite interpreted to originate from the watershed and transported to the lake with runoff. The contamination could not be separated physically from the sample, potentially contributing decayed 14C (‘dead carbon’) and increasing the age of the aragonite. Sequential extraction of successive fractions of CO2 unveiled the effect of detrital material on the 14C ages, and showed that the first CO2 extract represents the least contaminated 14C fraction that provides the best approximation for the true 14C age (which includes the lake's reservoir age). We calculated the age offset contributed by the contamination range encountered in this study (1–21%) to be about 900 years per 10% contamination. The sequential extraction procedure is recommended for 14C dating of Holocene age lacustrine carbonates suspected to be contaminated with extraneous carbon-bearing materials. [ABSTRACT FROM AUTHOR]

On the basis of glacier and lake-level records, this paper attempts, for the first time, a comparison between high-resolution palaeohydrological and palaeoglaciological data in west-central Europe over the past 3500 years. A data set of tree-ring width, radiocarbon and archaeological data, in addition to historical sources, were used to reconstruct fluctuations of the Great Aletsch, the Gorner and the Lower Grindelwald glaciers in the Swiss Alps. The three ice-streams experienced nearly synchronous advances at c. 1000–600 BC and AD 500–600, 800–900; 1100–1200 and 1300–1860. These glacier fluctuations show strong correspondence with lake-level variations reconstructed in eastern France (Jura mountains and Pre-Alps) and on the Swiss Plateau. This supports the hypothesis of elimatically driven fluctuations. Historical date available for the period since AD 1550 reveal, in detail, various meteorological conditions behind the succesive glacier advances. Howere, in agreement with the general trend shown by the historical data, the synchroneity between glacier advances and periods of higher lake level suggests the impact of general winter cooling and an increase in summer moistur as responsible for reinforced feeding of both glaciers and lakes in west-central Europe ;over the past 3500 years. Finally, comparison between the Great Aletsech glacier and the residual 14C records supports the hypothesis that variations in solar activity were a major forcing factor of climatic oscillations in west-central Europe during the last Holocence. [ABSTRACT FROM AUTHOR]

Multiproxy analysis of two swamps, representative of numerous sites in the Dargaville area, provide a Holocene record of a transition from flooded marine valleys to freshwater swamp-forests. Dendrochronology of subfossil wood from these and other associated sites provide a record of kauri (Agathis) growth and demise over 3600 calendar years. A discrepancy between the abundance of kauri pollen and the timing of maximum kauri forest development, as revealed by dendrochronology, suggests that kauri pollen abundance at our sites is determined by the wetness of the substrate rather than by proximity of source trees. This finding has implications for the palaeoclimatic interpretation of late Quaternary Agathis pollen curves. Kauri has been present in the Dargaville area for more than 7000 14Cyr BP with suitable conditions for the preservation of wood leading to an apparent expansion in Agathis population after ∼3600 cal. yr BP rather than representing a southerly migration of this species. [ABSTRACT FROM AUTHOR]

This paper describes the potential of correcting the 14C age shift resulting from the contamination of primary aragonites by detrital carbonates using online sequential extraction of CO2. The experiments were carried out on laminated lacustrine aragonites collected from Holocene Dead Sea sediment sections. X-ray diffraction analysis revealed the presence of detrital calcite interpreted to originate from the watershed and transported to the lake with runoff. The contamination could not be separated physically from the sample, potentially contributing decayed 14C (‘dead carbon’) and increasing the age of the aragonite. Sequential extraction of successive fractions of CO2 unveiled the effect of detrital material on the 14C ages, and showed that the first CO2 extract represents the least contaminated 14C fraction that provides the best approximation for the true 14C age (which includes the lake's reservoir age). We calculated the age offset contributed by the contamination range encountered in this study (1–21%) to be about 900 years per 10% contamination. The sequential extraction procedure is recommended for 14C dating of Holocene age lacustrine carbonates suspected to be contaminated with extraneous carbon-bearing materials. [ABSTRACT FROM AUTHOR]

A freshwater radiocarbon (14C) reservoir effect (FRE) is a 14C age offset between the atmospheric and freshwater carbon reservoirs. FREs can be on the order of 10 000 14C yr in extreme examples and are a crucial consideration for 14C dating of palaeoenvironmental and archaeological samples. Correction for a FRE may be possible, provided the FRE and the proportion of FRE-affected carbon within a sample can be accurately quantified. However, although such correction is desirable for affected samples, it is essential that such correction is accurate in order to produce useful chronological information. Accuracy of FRE correction can be limited by spatial variation in FRE within a freshwater system, but despite this there is currently a paucity of information to identify and quantify such variability within affected systems. Here we present results of a study that investigates the effects of spatial FRE variation upon dating accuracy within the freshwater system of Lake Mývatn, northern Iceland. A substantial FRE (>10 000 14C yr) has previously been identified in archaeological and modern samples from the region, which shows the potential for considerable spatial variability. The study also assesses the use of δ13C and δ15N in age correction of affected samples. The results show that benthic detritus and organisms at primary trophic levels from locations within the lake are affected by a FRE of at least 3500 14C yr, with clear spatial variation resulting in 14C age differences of up to 7670 14C yr between samples. There is a broad correlation between stable isotope values and FRE within the data set. However, large associated uncertainties currently preclude highly accurate and precise stable isotope-based quantification of the proportion of FRE-affected carbon within archaeological and palaeoenvironmental samples from Mývatn and the surrounding region. [ABSTRACT FROM PUBLISHER]

Optically stimulated luminescence (OSL) dates are reported for silts and very fine sands believed to be loessic sediments from northwest England. At three sites loessic sediments were initially interpreted as primary aeolian deposits, and at two other sites as loess incorporated into the matrix of cemented scree. However, the results of OSL dating indicate a more complex pattern of accumulation than originally hypothesized and have prompted reconsideration of these materials. Whatever the process(es) and underlying cause(s), it is evident that significant amounts of soil erosion occurred on the limestone uplands earlier than previously thought. All but one of the ages fall entirely within the Holocene period and suggest that these deposits contain reworked, rather than primary loess. Four of the five sites are characterized by non-Gaussian dose distributions, and consequently equivalent doses have been estimated using a range of appropriate age models. The implications of differences in the ages derived from the fine silt and fine sand fractions of the samples are considered. Three processes, namely aeolian transport, overland flow and subsoil piping, are invoked to account for the reworking of loess, although their relative contributions cannot be quantified. At one site the inclusion of limestone clasts within the reworked loess strongly suggests that the sediment can be regarded as loess-derived colluvium. Human impacts on the landscape and climate shifts, either separately or in combination, are considered to have been the most likely mechanisms that triggered loess erosion. [ABSTRACT FROM AUTHOR]

The article focuses on the globalization of tephrochronology, the characterization and use of volvanic-ash layers as a unique chronostratigraphic linking and dating tool. According to the author, tephrochronology was practised in many countries due to its practical value in a wide range of subjects including Quaternary stratigraphy, palaeoclimatology, palaeoecology, and physical geography. He cites the new techniques developed in northwestern Europe and Scandinavia in applying to sedimentary sequences on all the continents of the world. He stresses that INTAV, a group of tephrochronologists, is working in non-volcanic countries for scientific advancement.

High-resolution analysis of ombrogenous peats often reveals pollen frequencies that change markedly from one sample to the next, indicating limited postdepositional mixing. This raises the question whether - with sufficiently thin samples - seasonal differences in pollen deposition can be observed. Seasonal resolution in peat would provide a dating technique with an accuracy similar to that of other, annually banded archives. To study the limits of temporal resolution, contiguous 0.5 mm thick slices of slightly humified Sphagnum section Cuspidata peat were palynologically analysed. No seasonal patterns in the pollen stratigraphy could be observed. This is ascribed to the mixing of pollen grains as a result of small-scaled vertical water movements and to the horizontal mode of shoot layering in the Sphagnum species. The latter process may also be the cause of a smoothed annual signal. Because of the absence of seasonal differentiation, the palynological distinction of annual peat layers is not feasible. [ABSTRACT FROM AUTHOR]

Andesite tephras have not been used in tephrostratigraphic studies to the same extent as rhyolitic units because they are seen as being chemically more complex than the latter. They are particularly difficult to ‘fingerprint’ owing to apparent heterogeneity in glass analyses from single andesitic layers. Using case study tephras from two andesite volcanoes in New Zealand, Mts Taranaki and Ruapehu, glass chemical heterogeneity is shown to be due predominantly to (1) differing particle types generated during closed- and open-vent phases of single eruption sequences, resulting in a broad range of glass compositions, and (2) contaminated glass microprobe analyses by various proportions of microlite phase(s). A simple evaluation procedure using least-squares mixing calculations is presented to classify glass data sets for hybrid analyses and to estimate the proportions of the main contaminant microlite phase. By employing particle morphology studies as well as the glass-analysis evaluation procedure, variations in andesitic glass compositions can be significantly reduced. Hence this approach shows promise for enabling the use of some andesitic tephras for tephrostratigraphic correlation. This may facilitate the addition of a new degree of resolution in tephrostratigraphic records. [ABSTRACT FROM AUTHOR]

Tree-ring based mass balance reconstructions developed for Peyto Glacier, Alberta, Canada are compared with measured conditions in the Pacific Ocean over the last century and, using reconstructions of Pacific climate indices, over the past ∼ 300 years, at interannual and decadal–interdecadal timescales. Tree-ring reconstructed winter balance totals at Peyto Glacier in La Niña, negative Pacific Decadal Oscillation (PDO) and La Niña/negative PDO years significantly exceed those in El Niño, positive PDO and El Niño/positive PDO years, respectively. The same phase pairings of reconstructed summer mass balance do not differ significantly. These findings confirm those seen in the measured mass balance records and shorter (100 years) tree-ring and instrumental climate record-based reconstructions, suggesting similar relationships have existed over the past ∼ 300 years. Maps showing the regression of Pacific sea surface temperatures (SSTs) on the seasonal mass balance series indicates that both winter and, albeit more weakly, summer mass balance series are related to ENSO-like patterns of SST variability in the Pacific Ocean at both interannual and interdecadal timescales. [ABSTRACT FROM AUTHOR]

A continuous ∼ 5280 calendar (cal.) yr long cryptotephrostratigraphic record of a peat core from northern New Zealand demonstrates that cryptotephra studies can enhance conventional tephra records by extending the known distribution of ash fall and enabling re-assessment of volcanic hazards. A systematic sampling strategy was used to locate peaks in glass-shard concentrations and to determine loci of individual geochemical populations, and a palynological method involving spiking samples with Lycopodium spores was adapted to facilitate accurate counting of glass-shard concentrations. Using glass-shard major element compositions, and a core chronology based on eight AMS 14C ages and two visible macroscopic tephra layers, Taupo Tephra (Unit Y) (1688–1748 cal. BP) and Tuhua Tephra (6800–7230 cal. BP) (2σ-age ranges), four cryptotephras were correlated with known eruptions: Whakaipo (Unit V) (2743–2782 cal. BP), Stent (Unit Q) (4240–4510 cal. BP), and Unit K (4970–5290 cal. BP), erupted from Taupo Volcanic Centre, and Whakatane Tephra (5470–5600 cal. BP) erupted from Okataina Volcanic Centre. Mixed glass populations were found in the core, most likely an artefact of post-depositional remobilization of shards vertically (both up and down) in the peat or on its surface by wind, or a result of closely spaced eruption events, or a combination of these. A secondary glass population identified within the macroscopic Taupo Tephra was tentatively attributed to either an earlier phase within that eruption or to mixing with a slightly older Taupo-derived eruptive or (less likely) a currently unknown Okataina-derived eruptive. These results indicate that, in the absence of continuous cryptotephrostratigraphic analysis, a peak in shard concentrations may not in itself be indicative of the 'true' stratigraphic (ie, isochronous) level of a tephra layer. For cryptotephra studies of peat cores, we recommend (1) using a detailed sampling strategy for the analysis of distal tephra-derived glass to detect and account for any mixed populations and possible vertical spread of glass shards through the peat, and (2) analysing more shards from larger samples to help 'capture' sparsely represented cryptic andesitic tephra deposits. [ABSTRACT FROM AUTHOR]

The marine radiocarbon reservoir effect is an offset in 14C age between contemporaneous organisms from the terrestrial environment and organisms that derive their carbon from the marine environment. Quantification of this effect is of crucial importance for correct calibration of the 14C ages of marine-influenced samples to the calendrical timescale. This is fundamental to the construction of archaeological and palaeoenvironmental chronologies when such samples are employed in 14C analysis. Quantitative measurements of temporal variations in regional marine reservoir ages also have the potential to be used as a measure of process changes within Earth surface systems, due to their link with climatic and oceanic changes. The various approaches to quantification of the marine radiocarbon reservoir effect are assessed, focusing particularly on the North Atlantic Ocean. Currently, the global average marine reservoir age of surface waters, R(t), is c. 400 radiocarbon years; however, regional values deviate from this as a function of climate and oceanic circulation systems. These local deviations from R(t) are expressed as ΔR values. Hence, polar waters exhibit greater reservoir ages (ΔR = c. +400 to +800 14C y) than equatorial waters (ΔR = c. 0 14C y). Observed temporal variations in ΔR appear to reflect climatic and oceanographic changes. We assess three approaches to quantification of marine reservoir effects using known age samples (from museum collections), tephra isochrones (present onshore/offshore) and paired marine/terrestrial samples (from the same context in, for example, archaeological sites). The strengths and limitations of these approaches are evaluated using examples from the North Atlantic region. It is proposed that, with a suitable protocol, accelerator mass spectrometry (AMS) measurements on paired, short-lived, single entity marine and terrestrial samples from archaeological deposits is the most promising approach to constraining changes over at least the last 5 ky BP. [ABSTRACT FROM AUTHOR]

Problems are often encountered in accurately establishing the rates of processes associated with river channel change. In this study, optical dating was used to obtain the lateral migration rate of an abandoned meander bend on the Klip River, eastern Free State, South Africa. Five samples were collected by augering along a transect across an approximately 200-m-wide scroll-bar sequence on the inner meander bend, and an additional sample was collected from the channel fill of the related oxbow lake. Optically stimulated luminescence (OSL) ages were derived for each sample using the single-aliquot regenerative-dose protocol on small aliquots of quartz. Incomplete bleaching was evident in some of the samples and thus the appropriate statistical analysis was performed using the 'finite mixture model' for the scroll-bar samples and the 'minimum age model' for the channel-fill sample. The ages calculated were in the correct chronological order for the depositional sequence, which was formed over the last ∼ 1000 years. The average rate of lateral migration across the scroll-bar sequence was found to be ∼ 0.16 m/yr but with an apparent increase in the rate occurring during the early sixteenth century. Where quartz-rich alluvium exists, the methods used in this study can potentially be applied to other river systems, enabling rates of channel change processes to be determined. [ABSTRACT FROM AUTHOR]

The potential oftropical speleothems as a climate proxy has been investigated. Amplitudes of δ18O and δ13C variations are found to be large and are likely to be primarily controlled by past rainfall. Contribution from past temperature variations seems to be relatively small. The 'amount effect' in rainfall has been observed and quantified by analysing rainwater samples collected during a monsoon season. A tentative chronology to these speleothems is asssigned by the 14C radiometric dating method. Assuming that the variations in the δ18O of cave carbonates are solely due to the past variations in rainfall, a history ofthe latter has been reconstructed. A high-resolution rainfall reconstruction up to the last ~3400 years is now available from Gupteswar cave, Orissa, subject to validation of dates by the U-Th method. It is observed that in a tropical speleothem δ13C is dominantly controlled by rainfall. The study has shown that tropical Indian speleothems faithfully record the annual (≈ monsoon) rainfall in the cave site. [ABSTRACT FROM AUTHOR]

A tongue of very coarse rockslide debris that extends 1.25km downvalley below Beinn Alligin in NW Scotland has been variously interpreted as a glacier-cored rock glacier, landslide debris redistributed by glacier ice or an excess-runout landslide. Exposure dating with cosmogenic 10Be demonstrates that the the debris mass was emplaced at 3950 ± 320yr BP, and therefore was not associated with glacier ice. Calculations based on frictional considerations imply that the feature is an excess-runout rock avalanche (sturzstrom) deposit. The morphological characteristics of the deposit appear consistent with movement by grainflow or fragmental flow. Failure is inferred to reflect time-dependent paraglacial stress release and consequent propagation of an internal joint network, but may have been triggered by seismic activity. The late-Holocene age of failure implies persistence of the effects of paraglacial stress release over a timescale of several millennia. [ABSTRACT FROM AUTHOR]