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Paleoclimate records from the Atacama Desert are rare and mostly discontinuous, mainly recording runoff from the Precordillera to the east, rather than local precipitation. Until now, paleoclimate records have not been reported from the hyperarid core of the Atacama Desert (<2 mm/yr). Here we report the results from multi-disciplinary investigation of a 6.2 m drill core retrieved from an endorheic basin within the Coastal Cordillera. The record spans the last 215 ka and indicates that the long-term hyperarid climate in the Central Atacama witnessed small but significant changes in precipitation since the penultimate interglacial. Somewhat ‘wetter’ climate with enhanced erosion and transport of material into the investigated basin, commenced during interglacial times (MIS 7, MIS 5), whereas during glacial times (MIS 6, MIS 4–1) sediment transport into the catchment was reduced or even absent. Pelagic diatom assemblages even suggest the existence of ephemeral lakes in the basin. The reconstructed wetter phases are asynchronous with wet phases in the Altiplano but synchronous with increased sea-surface temperatures off the coasts of Chile and Peru, i.e. resembling modern El Niño-like conditions.

A systematic investigation of amorphous and crystalline vapor deposited ice layers with thickness ranging from less than 100 nm to more than 5 μm has been performed using Fourier transform (FT) reflection−absorption infrared spectroscopy (RAIRS). Al and Au surfaces were used for the vapor deposition and very similar results were obtained on both. The spectra were recorded both with polarized and nonpolarized radiation and simulated with a simple Fresnel reflection model and empirical optical indices from the literature. Optical effects peculiar to this technique like surface suppression or enhancement of vibrational modes, saturation of intense absorptions, and IR interferences, are found to distort the spectra to a greater or lesser extent over the whole thickness range investigated. The diverse spectral band shapes and intensities are globally well reproduced with the mentioned Fresnel model. Some noteworthy discrepancies are, however, observed in the most intense peaks of the polarized spectra, which are affected by larger distortions. Whenever possible, the present measurements have been compared with published spectra recorded under similar conditions and a good accordance has been found. This comparison and the spectral simulations can reconcile seeming discrepancies in the previous literature data.

This contribution documents the process of assessing the quality of data within a compilation of legacy geochronological data relating to the last British-Irish Ice Sheet, a task undertaken as part of a larger community-based project (BRITICE-CHRONO) that aims to improve understanding of the ice sheet's deglacial evolution. As accurate reconstructions depend on the quality of the available data, some form of assessment is needed of the reliability and suitability of each given age(s) in our dataset. We outline the background considerations that informed the quality assurance procedures devised given our specific research question. We describe criteria that have been used to make an objective assessment of the likelihood that an age is influenced by the technique specific sources of geological uncertainty. When these criteria were applied to an exisiting database of all geochronological data relating to the last British-Irish Ice Sheet they resulted in a significant reduction in data considered suitable for synthesis. The assessed data set was used to test a Bayesian approach to age modelling ice stream retreat and we outline our procedure that allows us to minimise the influence of potentially erroneous data and maximise the accuracy of the resultant age models.publishersversionPeer reviewe

The southernmost terrestrial extent of the Irish Sea Ice Stream (ISIS), which drained a large proportion of the last British-Irish Ice Sheet, impinged on to the Isles of Scilly during Marine Isotope Stage 2. However, the age of this ice limit has been contested and the interpretation that this occurred during the Last Glacial Maximum (LGM) remains controversial. This study reports new ages using optically stimulated luminescence (OSL) dating of outwash sediments at Battery, Tresco (25.5 AE 1.5 ka), and terrestrial cosmogenic nuclide exposure dating of boulders overlying till on Scilly Rock (25.9 AE 1.6 ka), which confirm that the ISIS reached the Isles of Scilly during the LGM. The ages demonstrate this ice advance on to the northern Isles of Scilly occurred at $26 ka around the time of increased ice-rafted debris in the adjacent marine record from the continental margin, which coincided with Heinrich Event 2 at $24 ka. OSL dating (19.6 AE 1.5 ka) of the post-glacial Hell Bay Gravel at Battery suggests there was then an $5-ka delay between primary deposition and aeolian reworking of the glacigenic sediment, during a time when the ISIS ice front was oscillating on and around the Llŷn Peninsula, $390 km to the north.

G. (2014). Reliability of equivalent-dose determination and age-models in the OSL dating of historical and modern palaeoflood sediments. Quaternary Geochronology, 22, 11-24. DOI: 10.1016/j.quageo.2014 Elsevier Editorial System(tm) for Quaternary Geochronology Manuscript DraftManuscript Number: QUAGEO-D-12-00096R1Title: Reliability of equivalent-dose determination and age-models in the OSL dating of historical and modern palaeoflood sediments Abstract: The challenge of accurately estimating the deposition age of incompletely-bleached samples in luminescence dating has motivated developments in the analysis of single grain dose distributions, and a number of statistical approaches have been proposed over the last few years. In this study, we compare the behaviour of the arithmetic average, the so-called 'robust statistics', the Central Age Model (CAM), the Minimum Age Model (MAM) and the Internal-External Consistency Criterion (IEU), when applied to single-grain and small multi-grain (~30 grains per aliquot) dose distributions from a sequence of eight recent (40-1000 years old) flash-flood deposits. These sediments are expected to be incompletely bleached, but all have age control from historical records. Modifications were made to allow the use of the standard CAM and MAM models with dose distributions containing near zero and negative dose values. An assessment of minimum uncertainty on individual dose estimates is based on the over-dispersion (OD) determined in dose recovery tests making use of gamma-irradiated samples. We then present a detailed analysis of the impact of appropriate uncertainty assignment on minimum (MAM and IEU) burial dose estimates. The results of the various models are discussed in terms of the accuracy of the resulting age, and we conclude that, overall, the IEU approach generates the most accurate ages. We also demonstrate that accurate IEU ages can be obtained from multi-grain measurements if an age off-set of ~40 years can be considered to be unimportant for the samples in question. From our study we conclude that these and similar young slack-water flood deposits can be accurately dated using quartz OSL, opening up the possibility of establishing time series of flood discharge in catchments for which no instrumental or historical record exists. 1Reliability of equivalent-dose determination and age-models in the OSL dating of 1 historical and modern palaeoflood sediments 2 3 Medialdea 1,3 , A., Thomsen 2 , K.J., Murray 3 , A.S., Benito 1 , G. 41. Museo Nacional de Ciencias Naturales, CSIC, Serrano 115bis, 28006 Madrid, 5Spain. amedialdea@mncn.csic.es 6 2. Center for Nuclear Technologies, Technical University of Denmark, DTU Risø 7Campus, Frederiksborgvej 399, 4000 Roskilde, Denmark. The challenge of accurately estimating the deposition age of incompletely-bleached 13 samples in luminescence dating has motivated developments in the analysis of 14 single grain dose distributions, and a number of statistical approaches have been 15proposed over the last few years. In this study, we comp...

The eastern England terrestrial glacial sequences are critical to the spatial and temporal reconstruction of the last British−Irish Ice sheet (BIIS). Understanding glacial behaviour in the area of the Humber Gap is key as its blockage by ice created extensive proglacial lakes. This paper maps the glacial geomorphology of the Humber Gap region to establish for the first time the extent and thickness of the North Sea Lobe (NSL) of the BIIS. Findings establish the westerly maximal limit of the NSL. Ten new luminescence ages from across the region show the initial Skipsea Till advance to the maximal limits occurred regionally at c. 21.6 ka (Stage 1) and retreated off‐shore c. 18 ka (Stage 2). Punctuated retreat is evident in the south of the region whilst to the immediate north retreat was initially rapid before a series of near synchronous ice advances (including the Withernsea Till advance) occurred at c. 16.8 ka (Stage 3). Full withdrawal of BIIS ice occurred prior to c. 15 ka (Stage 4). Geomorphic mapping and stratigraphy confirms the existence of a proto Lake Humber prior to Stage 1, which persisted to Stage 3 expanding eastward as the NSL ice retreated. It appears that proglacial lakes formed wherever the NSL encountered low topography and reverse gradients during both phases of both advance and retreat. These lakes may in part help explain the dynamism of parts of the NSL, as they initiated ice draw down and associated streaming/surging. The above record of ice‐dammed lakes provides an analogue for now off‐shore parts of the BIIS where it advanced as a number of asynchronous lowland lobes.

We report the first chronology, using four new optically stimulated luminescence dates, on the sedimentary record of Glacial Lake Pickering, dammed by the North Sea Lobe of the British-Irish Ice Sheet during the Dimlington Stadial (24-11 ka cal BP). Dates range from 17.6 AE 1.0 to 15.8AE 0.9 ka for the sedimentation of the Sherburn Sands at East Heslerton, which were formed by multiple coalescing alluvial fans prograding into the falling water levels of the lake and fed by progressively larger volumes of debris from the Wolds. Fan formation ceased $15.8 ka, at a time when permafrost was degrading and nival-fed streams were no longer capable of supplying sediment to the fans. A further age of 10.1 AE 0.7 ka dates the reworking of coversand into the early part of the Holocene, immediately post-dating Younger Dryas periglacial structures. A 45-m lake level dates to $17.6 ka, when the North Sea Lobe was already in retreat, having moved eastward of the Wykeham Moraine; it stood further east at the Flamborough Moraine by $17.3 ka. The highest (70 m) lake level and the occupation of the Wykeham Moraine date to an earlier phase of the North Sea Lobe occupation of the Vale of Pickering. #