Description: Publication date: Available online 18 June 2018 Source: Quaternary Geochronology Author(s): Meenakshi, Pankaj Kumar, J.P. Shrivastava, Rakesh Chandra, Sundeep Chopra, G.S. Roonwal, Rajveer Sharma High resolution 14 C AMS ages from sequential layers in the late Quaternary Dilpur Formation in Indian Kashmir, reveal glacial and inter-glacial climatic changes archived in this more or less complete aeolian-palaeosol record. The 14 C AMS ages are consistent and fit well within the time window of ∼45–50 ka. Considering the thicknesses (at corresponding stratigraphic heights), the ages obtained for the S1 palaeosol layer provided high resolution ages for the early Holocene period. When compared to the sedimentation rate based time estimates for the successive layers showed direct relationship between absolute ages and the time involved in the deposition. Based on the extrapolation of 14 C AMS ages of the Shankerpora section, the incidences of glaciations occurred at 67–71 ka and 124–127 ka. The glacial and interglacial cycles spanning ∼130 ka encompass a variable number of palaeosols. Temporally, these observations correlate well with the two glaciations earlier reported from the loess palaeosol succession of Xiagaoyuan, Gansu Province, western Chinese Loess Plateau, suggesting perhaps that similar climatic conditions prevailed in this region. Graphical abstract

Description: Publication date: Available online 12 June 2018 Source: Quaternary Geochronology Author(s): Teresa Jordan, Nicolás Blanco, Andrés Quezada, Arturo Jensen, Paulina Vásquez, Fernando Sepúlveda Ritter et al. (2018) analyzed the Quaternary history of a purported paleo-lake in the Atacama Desert of northern Chile. They provide a much more thorough analysis than previous publications of the field relationships where there are landform benches surrounding a bedrock knob, Cerro Soledad. They conclude that the benches formed due to shoreline erosion by a paleo-lake while Cerro Soledad rose in elevation due to tectonic activity. Ritter et al. (2018) also used terrestrial cosmogenic nuclide (Neon, Beryllium, and Aluminum) data to determine a history of the landforms, and thus what they conclude is a history of former lake levels and uplift rate. This Comment examines the distribution of mapped geological units, especially Pliocene lake deposits, relative to the locations sampled and described by Ritter et al. (2018). We find that some of the benches sampled for cosmogenic nuclide dating occur on Miocene and Pliocene lacustrine strata, which opens the possibility that clasts were recycled from Miocene-Pliocene lake deposits into the Pleistocene bench clast population. We reach the alternative interpretation that differential resistance to erosion by hillslope processes created most benched forms on the flanks of Cerro Soledad, rather than generation of the benches by shoreline processes. An alternative exhumation scenario which utilizes the cosmogenic exposure ages better explains many of the landforms. In this scenario, the cosmogenic nuclide exposure dates reveal valley-scale denudation in response to tectonic uplift of Cerro Soledad, reduction of valley floor elevation by dissolution of evaporite units, and capture of the valley by the Loa River, rather than shoreline erosion. Irrespective of the alternative interpretation, the exposure history chronological information provided by Ritter et al. (2018) provides new opportunities to examine environmental fluctuations in the central Atacama Desert.

Description: Publication date: Available online 4 June 2018 Source: Quaternary Geochronology Author(s): Xiao Fu, Tim J. Cohen, Kirstie Fryirs Fluvial terraces in the upper Hunter catchment, southeastern Australia provide a long-term record of river activity in response to climate change in the late Quaternary. Single-grain optically stimulated luminescence (OSL) dating of quartz was applied in this study to investigate the timing of the formation of three fluvial terraces in the upper Hunter catchment. A detailed examination of luminescence properties of individual quartz grains revealed some correlation between their OSL decay rates, intrinsic brightness and dose saturation characteristics. Some quartz grains containing a higher proportion of non-fast components exhibited low brightness in OSL signals and high dose saturation levels. Some grains with slow OSL decays passed the standard rejection criteria, but are likely to yield underestimated equivalent doses (D e s) because of a higher contribution of non-fast components, which were shown to have low thermal stability. Different rejection criteria, including the fast ratio, the dose saturation level and the OSL sensitivity criteria, were tested on the single-grain D e results. The application of a fast ratio rejection criterion was able to successfully identify thermally unstable grains. A new rejection criterion based on dose saturation property was also applied to improve the age of one sample with a large D e . Our dating results identify multiple phases of river valley aggradation in the upper Hunter catchment since late Marine Isotope Stage (MIS) 6; at ∼ 138 ka, ∼90–94 ka, ∼65 ka, ∼26 ka and ∼18 ka. The aggradational episodes of the terraces are correlated with glacial or stadial periods since MIS 6 and these phases of valley-floor aggradation are inferred to be a function of increased sediment supply during the cold periods resulting from strong periglacial activities in the adjacent Australian highlands.

Description: Publication date: Available online 2 June 2018 Source: Quaternary Geochronology Author(s): Maurycy Żarczyński, Wojciech Tylmann, Tomasz Goslar This study compares different methods to count biogenic varves in Lake Żabińskie in northeastern Poland. To perform this comparison, we used 2000 years-long varved sediment record from this lake because of the well-preserved laminations as well as the independent age controls, i.e. 29 AMS 14 C dates, 137 Cs activity peaks and volcanic glass shards (1875 AD Askja cryptotephra). Microscopic investigations of thin sections allowed us to identify six major varve microfacies along the sediment profile. Using these microfacies, we tested three counting methods and different approaches of counting uncertainty estimation. These methods provided comparable numbers of varves (1943 ± 30, 2034 ± 34, 2028 +34 / -53 ) and similar shapes in the age-depth relations. However, in two methods, we found possible disadvantages in arbitrary assumptions and subjective decisions in the process of chronology building, procedures leading to age underestimation as well as problems with reliable and objective estimations of counting uncertainty. Based on these results, we propose the counting method which include analyses of major varve microfacies and three independent counting without the need for varve-by-varve microscopic investigations. This method provided acceptable results (〈5% uncertainty) and was more objective and less time-consuming. Semi-automatic counting using μXRF Ca record in the sediments was also tested and provided results that can serve as a first approximation of the number of varves. Our study also indicates that different counting strategies may lead to different uncertainty estimations, which may be important in the reliable interpretation of proxy data.

Description: Publication date: Available online 28 May 2018 Source: Quaternary Geochronology Author(s): Junjie Zhang, Sheng-Hua Li Standardised growth curves (SGCs) were established for extracts of potassium feldspar (K-feldspar), plagioclase and polymineral grains from various geological settings (deserts, loess, lake or fluvial deposits) from Northern China. Single-aliquot regenerative-dose (SAR) protocol was used with the measurements of multiple elevated temperature post-IR IRSL (MET-pIRIR) signals from 50 °C to 250 °C with an interval of 50 °C. Regenerative-dose normalisation was applied for the SGC construction. The shapes of the SGCs of K-feldspar vary between IRSL signals measured at different temperatures. For coarse grains (63–180 μm), the SGCs of the K-feldspar, plagioclase and polymineral fractions are close to each other. However, the polymineral fine grains (4–11 μm) have a distinct SGC from the coarse-grain fractions. It may be caused by the difference in alpha irradiation. Two test doses (145 Gy and 72.5 Gy) were applied to construct the SGCs of K-feldspar. The SGC built with the larger test dose has a larger characteristic saturation dose ( D 0 ). Test dose used for equivalent dose ( D e ) measurements need to be the same as the test dose used for SGC construction, otherwise the SGC D e may not be accurately estimated. With the same test dose used, the SGC D e values estimated from the SGCs are identical with the D e values generated from individual dose response curves.

Description: Publication date: Available online 25 May 2018 Source: Quaternary Geochronology Author(s): A. Galli, M. Caccia, M. Martini, L. Panzeri, F. Maspero, S. Fiorentino, M. Vandini, E. Sibilia This paper deals with a Thermoluminescence (TL) study of ancient mosaic tesserae from the qasr (winter residence) of Khirbat al-Mafjar, amazing palace of the Islamic caliphs located in the plain of Jericho. In literature, works dealing with the dating of mosaic tesserae usually rely on the dosimetric properties of the microcrystalline inclusions in the silica matrix rather than on the matrix itself. On the other hand, in the last decades, commercial glasses have been demonstrated to be suitable for retrospective accidental dosimetry. In this work, we applied a protocol widely used for the mobile phones’ glasses, the so-called “pre-bleached with blue LEDs” protocol, to evaluate the archeological dose absorbed by some Khirbat al-Mafjar tesserae in order to confirm their dating based on archaeological evidence. As for commercial glasses, the TL signal from ancient tesserae presents anomalous fading and it is light sensitive. The experimental protocol circumvents these problems isolating the thermally more stable TL signal with an optical pretreatment and allowing the determination of a fading curve for each analyzed sample. Using an integrative approach, we estimated the fading correction for these tesserae and we retrieved their ages. The results are partially in agreement with those hypothesized on historical ground and show good potentialities for the dating of amorphous archaeological glassy materials.

Description: Publication date: Available online 25 May 2018 Source: Quaternary Geochronology Author(s): M. Fuchs, J. Lomax Stone pavements are typical landforms in arid environments, composed of a monolayer of clasts at the surface, associated with an underlying unit of eolian fines. They represent important paleoenvironmental sediment archives, for which reliable chronostratigraphic age constraints are needed. In a first study on stone pavements from the Mojave Desert/USA and Badia Desert/Jordan it could be demonstrated that optically stimulated luminescence dating (OSL) on quartz represents a promising dating method for the eolian fines, but quartz OSL results remained challenging, because the D e distributions were unexpectedly broad and OSL fine- and coarse-grain ages were significantly different (Fuchs et al., 2015). The reason for this age difference was unclear and methodological as well as geomorphological arguments were proposed. Here we present new quartz OSL results from additional study sites and various environmental settings, to better understand possible methodological or geomorphological reasons for the previously detected age characteristics. Stone pavements from the Negev Desert/Israel, from Fuerteventura/Spain and from the Black Rock Desert/USA are investigated in this new study, and their OSL results derived from different grain sizes are compared and discussed.

Description: Publication date: Available online 30 April 2018 Source: Quaternary Geochronology Author(s): X. Rui, B. Li, Y.J. Guo, J.F. Zhang, B.Y. Yuan, F. Xie A large range of equivalent dose ( D e ) values was observed by applying the single-aliquot regenerative-dose (SAR) procedure to the optically stimulated luminescence (OSL) signal of single grains of quartz extracted from sediments at the Yujiagou site in the Nihewan Basin, north China. Many quartz grains yielded D e values close to zero, which results in severe age underestimation when compared with the results of potassium-rich feldspar grains measured using post-infrared infrared stimulated luminescence (pIRIR) procedure. Dose recovery tests suggest that the SAR protocol is suitable for D e determination. However, a large grain-to-grain variation in thermal stability was identified based on single-grain pulse-annealing measurements. We found that most of the zero-dose or low-dose grains are associated with thermally unstable OSL signals, which explains the large dispersion of the quartz OSL D e distribution. This is further confirmed by the short lifetime of the unstable OSL signals obtained using single-aliquot pulse-annealing test.

Description: Publication date: Available online 22 April 2018 Source: Quaternary Geochronology Author(s): Lauren J. Davies, Peter Appleby, Britta J.L. Jensen, Gabriel Magnan, Gillian Mullan-Boudreau, Tommy Noernberg, Bob Shannon, William Shotyk, Simon van Bellen, Claudio Zaccone, Duane G. Froese High-resolution studies of peat profiles are frequently undertaken to investigate natural and anthropogenic disturbances over time. However, overlapping profiles of the most commonly applied age-dating techniques, including 14 C and 210 Pb, often show significant offsets (>decadal) and biases that can be difficult to resolve. Here we investigate variations in the chronometers and individual site histories from six ombrotrophic peat bogs in central and northern Alberta. Dates produced using pre- and post-bomb 14 C, 210 Pb (corroborated with 137 Cs and 241 Am), and cryptotephra peaks, are compared and then integrated using OxCal's P_Sequence function to produce a single Bayesian age model. Environmental histories for each site obtained using physical and chemical characteristics of the peat cores, e.g. macrofossils, humification, ash content, and dry density, provide important constraints for the models by highlighting periods with significant changes in accumulation rate, e.g. fire events, permafrost development, and prolonged surficial drying. Despite variable environmental histories, it is possible to produce high-resolution age-depth models for each core sequence. Consistent offsets between 14 C and 210 Pb dates pre-1960s are seen at five of the six sites, but tephra-corrected 210 Pb data can be used to produce more coherent models at three of these sites. Processes such as permafrost development and thaw, surficial drying and local fires can disrupt the normal processes by which chronological markers and environmental records are incorporated in the peat record. In consequence, applying standard dating methodologies to these records will result in even greater uncertainties and discrepancies between the different dating tools. These results show that using any single method to accurately date peat profiles where accumulation has not been uniform over time may be unreliable, but a comprehensive multi-method investigation paired with the application of Bayesian statistics can produce more robust chronologies. New cryptotephra data for the Alberta region are also reported here, including the historical Novarupta-Katmai 1912 eruption, White River Ash (East), and glass from Mt. St. Helens, Mt. Churchill, and probable Aleutian sources.

Description: Publication date: Available online 19 April 2018 Source: Quaternary Geochronology Author(s): Tabito Matsu'ura, Junko Komatsubara, Naokazu Ahagon We investigated the deep-sea sedimentary sequences of Holes ODP1150A and ODP1151C and refined the Late and Middle Pleistocene tephrostratigraphy and cryptotephrostratigraphy in the NW Pacific Ocean. Further, we correlated tephras in these sequences with marine isotope stage (MIS)-correlated tephras of Hole Chikyu C9001C and created robust age models for the ODP holes. We first counted glass shards and heavy mineral grains in marine sediment samples from the ODP holes and analyzed the major-element chemistry of glass shards and of cummingtonite grains associated with shard spikes. Then, using these major-element compositions, we correlated some glass shard spikes of Hole ODP1150A with known dated tephras for the first time: G5 with Towada-Ofudo (late MIS 3); G8 with Numazawa-Kanayama (MIS 3–4); G12.3 with Naruko-Nisaka (MIS 5b–c); G12.4 with Dokusawa (MIS 5b–c); G12.5 with C9001C G3.1 (MIS 5b–c); G13.1 with Sambe-Kisuki (MIS 5c); G13.2 with Toya (MIS 5d); G16 with C9001C G7 and G8 (MIS 7a–b); either G16.2 or G17 with C9001C G10 (MIS 7b–c); G19.5 with Shiobara-Otawara (mid MIS 8); and G21.1 with Naruohama-IV (MIS 10d). We also confirmed previously reported tephra correlations: G1 with Towada-Hachinohe (MIS 1/2 boundary); G6 with Shikotsu-1 (MIS 3); and G12 with Aso-4 (MIS 5b). Similarly, we correlated some spikes of Hole ODP1151C with known dated tephras for the first time: G0.2 with C9001C G10 (MIS 7c); G1 with ODP1150A G18; G2 with ODP1150A G19.3; G3 with Shiobara-Otawara (mid MIS 8); G3.4 with ODP1150A G20; G4.4 with C9001C G19.3 (MIS 13 or 13/14 boundary); G9 with Kaisho-Kamitakara (MIS 15–16); and G10.8 with C9001C G25.2, 25.3, 25.4, or 25.6 (MIS 18). The tephrostratigraphy results indicate that sediments corresponding to 400–770 ka (from slightly older than the Naruohama-IV tephra to the base of the Brunhes chron) are not preserved in the sediments of Hole ODP1150A. We suggest that our tephra-based age models for Holes ODP1150A and ODP1151C are more reliable than the previously reported Middle Pleistocene biohorizon-based model, which was constructed on the basis of a poorly preserved fossil record.