Description: Publication date: Available online 9 May 2018 Source: Quaternary Geochronology Author(s): Hao Long, Sumiko Tsukamoto, Jan-Pieter Buylaert, Andrew Sean Murray, Mayank Jain, Manfred Frechen Signal resetting prior to deposition is an important factor for the accuracy of luminescence dating. In this study, resetting of the quartz optically stimulated luminescence (OSL) signal from samples collected from different depositional environments (alluvial, beach, and aeolian sediments) around the Qinghai Lake basin (northeastern Tibetan Plateau) was examined using its inter-comparison with post-IR infrared stimulated luminescence (IRSL) measured at 290 °C (pIRIR 290 ) from K-feldspar. Dose recovery tests were carried out to test the success of the single aliquot regenerative-dose (SAR) protocol for quartz and feldspar. Additionally, stability tests (first IR temperature plateau and g -values) were performed for the pIRIR 290 . We observe that most of the K-feldspar pIRIR 290 and quartz OSL ages are consistent with each other (within 10%), suggesting that the quartz OSL signal was well-bleached prior to the deposition. The ages of loess samples range between ∼13.1 and ∼1.5 ka, the alluvial sediments between ∼35 ka and ∼14 ka, and beach sediments between 60 and 50 ka, corresponding to early Marine Isotope Stage (MIS) 3. These quartz OSL chronologies suggest a lake highstand during very early MIS 3, a lowstand during late MIS 3 and MIS 2, and widespread loess accumulation through the Holocene in the Qinghai Lake basin.

Description: Publication date: Available online 30 April 2018 Source: Quaternary Geochronology Author(s): Xiaomei Nian, Weiguo Zhang, Fengyue Qiu, Jintang Qin, Zhanghua Wang, Qianli Sun, Jing Chen, Zhongyuan Chen, Niankai Liu The optically stimulated luminescence (OSL) sensitivity and OSL signal components of quartz grains were used to investigate provenance changes of Holocene sediments from the Yangtze River delta. The variation of luminescence sensitivity was observed in multiple grain aliquots and single grains of quartz from different sedimentary units of the Yangtze River delta. Laboratory experiments suggest that repeated dosing/bleaching cycles increase the luminescence sensitivity of quartz from the studied sediments. High variable thermal activation curves were observed even for samples from the same sedimentary unit, implying highly diverse sources for the delta deposits of the Yangtze River. Different sedimentary units show quartz with similar OSL component contributions, and repeated dosing/bleaching cycles and heating treatment are unable to affect the relative contributions of the fast and medium components to the bulk OSL signal. The samples from unit 1 (U1, tidal river, 15–11 ka), unit 2 (U2, estuary, 11–9 ka) and unit 6 (U6, delta plain, ca. 1 ka to the present) show relatively higher luminescence sensitivity in comparison to unit 3 (U3, tidal sand ridge, 9–4 ka), unit 4 (U4, prodelta, 4–2.5 ka) and unit 5 (U5, delta front, 2.5–1 ka), implying changing sediment sources over time. Such a temporal variation of sediment source can be explained by the transgressive/regressive history of the Yangtze River delta as well as by Asian monsoon variability since the last deglaciation. It demonstrates that luminescence sensitivity of quartz has great potential for tracing sediment sources in the Yangtze River delta, but more work is needed to characterize specific sources to establish a source-to-sink linkage.

Description: Publication date: Available online 7 May 2018 Source: Quaternary Geochronology Author(s): Mathieu Duval, Rainer Grün, Josep M. Parés, Laura Martín-Francés, Isidoro Campaña, Jordi Rosell, Qingfeng Shao, Juan Luis Arsuaga, Eudald Carbonell, José María Bermúdez de Castro The present study reports the results of the first direct Electron Spin Resonance (ESR) dating study of Homo antecessor , the earliest known hominin species identified in Europe. The analysis of a tooth (ATD6-92) from TD6 unit of Atapuerca Gran Dolina (Spain) following a “semi non-destructive” procedure provides a final age estimate ranging from 624 to 949 ka, which covers all possible uranium uptake scenarios. Last, the additional magnetostratigraphic data collected within TD6 enables to further constrain the initial ESR chronology and to propose an age of between 772 and 949 ka for Homo antecessor , in agreement with previous dating works. Whereas our new results do not refine the existing chronology of stratigraphic unit TD6, they nevertheless support the antiquity of H. antecessor , which pre-dates the estimated divergence age of modern and archaic human lineages based on genetic evidence. This work illustrates the challenges of dating human teeth by means of the ESR method, with the main pitfalls that are sometimes inherent to this specific application (e.g., systematic μCT-scanning of fossil hominin teeth; limited knowledge about the original sedimentary environment for teeth coming from old excavations; heterogeneous spatial distribution or the U-series elements in dental tissues). We identified several sources of uncertainty that may directly impact the accuracy of the age result. In particular, a slight contamination of dentine (〈6%) in the enamel fragment measured by ESR was found to induce a significant age underestimation (33%) if not taken into consideration. It indeed caused not only a D E underestimation (by about 8%), but also produced a massive internal dose rate overestimation (by a factor of about 3.5). In contrast, other sources of uncertainty, such as the heterogeneity of the sedimentary environment, the variability of the water content over time, the previous μCT-scanning of the tooth or the potential preferential creation of unstable NOCORs in the ESR signal, showed here a limited impact on the final age result.

Description: Publication date: Available online 18 May 2018 Source: Quaternary Geochronology Author(s): Jesús Alcalá-Reygosa, David Palacios, Irene Schimmelpfennig, Lorenzo Vázquez-Selem, Leopoldo García-Sancho, Osvaldo Franco-Ramos, José Villanueva, José Juan Zamorano The knowledge of the eruptive history of volcanic centers allows for improving the evaluation of the related risks and hazards in populated areas, but substantially depends on the ability of dating the lava flows. However, traditional methods such as U-Th/He, 40 Ar- 39 Ar, 40 K- 40 Ar and radiocarbon dating are not always suitable. Therefore, an alternative approach based on the combination of in situ -produced 36 Cl based cosmic ray exposure dating, lichenometry and dendrochronology was tested on two lava flows (called Lava flow “A” and “B”) from Pico de Orizaba (Mexico), previously attributed to 16th and 17th century eruptions, respectively. The presented results show that both lava flows are significantly older than their assumed 16th and 17th century ages. Regarding lava flow “A”, the measured in situ -produced 36 Cl concentrations lead to a mean age of 3.03 ± 0.70 ka, while dendrochronology and lichenometry yield minimum ages of 834 and 1130 years, respectively. Regarding lava flow “B”, the measured in situ -produced 36 Cl concentrations lead to a mean age of 1.45 ± 0.35 ka, whereas lichenometry gives a minimum age of ∼1000 years. Overall, this demonstrates that the combination of in situ -produced 36 Cl based cosmic ray exposure dating, lichenometry and dendrochronology has a considerable potential for dating purposes on young deposits and landforms, in particular on lava flows at high elevation sites.

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 10 May 2018 Source: Quaternary Geochronology Author(s): Zhong He, Hao Long, Linhai Yang, Jie Zhou Palaeoflood reconstruction is of great importance to extend the flooding records and improve the understanding of their relationships with climatic change and geomorphologic evolution. As a large active rift basin in central China, Weihe Basin subsided and infilled in response to the uplift of the Tibetan Plateau and Asian monsoon variations. Many rivers drain out the erodible Chinese Loess Plateau with tremendous detritus and then build up considerable fluvial sequences. Scarcity of organic material and potential poor bleaching make the fluvial deposits difficult to date with radiocarbon and optically stimulated luminescence (OSL) technique, and as a result hinder the palaeoflood reconstruction. This study attempts to compare OSL ages resulted from different grain size fractions of quartz, and then cross-checks with independent radiocarbon ages, aiming to choose proper method to reconstruct the chronology of a fluvial sequence from the valley bank of Shichuan River, a tributary of Weihe River. The results show that the coarse quartz grains experienced better bleaching than fine quartz grains, and the comparison with AMS 14 C ages further confirms the efficient bleaching of the coarse quartz grains before burial. The sufficient bleaching of the coarse fraction could be attributed to sediment source from the upstream mountainous areas and long-distance transportation. Finally, five palaeoflood events were identified at the times of approximately 2.3–2.6 ka, 3.7–3.9 ka, 4.1–4.7 ka, 6.2–6.8 ka, and 8.9–9.2 ka, corresponding to the periods with intensified rainstorm and vegetation degradation associated with climatic deterioration. This study provides a regional evidence to improve our understanding of the response of river system evolution to climate change.

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 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.

Description: Publication date: June 2018 Source: Quaternary Geochronology, Volume 46

Description: Publication date: Available online 14 May 2018 Source: Quaternary Geochronology Author(s): Robin Blomdin, Arjen P. Stroeven, Jonathan M. Harbor, Natacha Gribenski, Marc W. Caffee, Jakob Heyman, Irina Rogozhina, Mikhail N. Ivanov, Dmitry A. Petrakov, Michael Walther, Alexei N. Rudoy, Wei Zhang, Alexander Orkhonselenge, Clas Hättestrand, Nathaniel A. Lifton, Krister N. Jansson Spanning the northern sector of High Asia, the Altai region contains a rich landform record of glaciation. We report the extent, chronologies, and dynamics of two paleoglaciers on opposite flanks of the Ikh Turgen mountains (In Russian: Chikhacheva Range), straddling the border between Russia and Mongolia, using a combination of remote sensing-based glacial geomorphological mapping, 10 Be surface exposure dating, and geomorphometric analysis. On the eastern side (Mongolia), the Turgen-Asgat paleoglacier, with its potential for developing a large accumulation area (∼257 km 2 ), expanded 40 km down valley, and mean ages from a latero-frontal moraine indicate deglaciation during marine oxygen isotope stage (MIS) 3 (45.1 ± 1.8 ka, n = 4) and MIS 2 (22.8 ± 3.3 ka, n = 5). These minimum age constraints are consistent with other 10 Be glacial chronologies and paleoclimate records from the region, which indicates glacier culmination during cold and wet conditions coinciding with MIS 3 (piedmont-style glaciation; inferred for a few sites across the region) and glacier culmination during cold and dry conditions coinciding with MIS 2 (mainly valley-style glaciation; inferred from several sites across the region). On the western side (Russia), the Boguty paleoglacier had a smaller accumulation area (∼222 km 2 ), and advanced 30 km down valley across a low gradient forefield. Surface exposure ages from two moraine complexes on this side of the mountains exhibit wide scatter (∼14–53 ka, n = 8), making paleoclimate inferences and comparison to other proxies difficult. Ice surface profile reconstructions imply that the two paleoglaciers likely shared an ice divide.