| 1. |
- Bate, Stephen, et al.
(författare)
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Pottery versus sediment : Optically stimulated luminescence dating of the Neolithic Vinca culture, Serbia
- 2017
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Ingår i: Quaternary International. - : Elsevier BV. - 1040-6182 .- 1873-4553. ; 429, s. 45-53
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Tidskriftsartikel (refereegranskat)abstract
- Optically stimulated luminescence (OSL) dating was applied to the Neolithic Vinca culture's type-site, Vinca Belo-Brdo, to establish best protocols for routine luminescence dating of similar Holocene sites, critical in understanding Neolithic to Chalcolithic cultural development. Equivalent dose (De) values were investigated for sediment samples using 63-90 mm grains on large and small aliquots, and single-grain laser luminescence (SGLL), and for pottery samples using large aliquots of 4-11 mm grains. The effects of changing water content and the different techniques available to establish radionuclide concentration were explored for their impacts on dose rate (Dr) estimates. Ages for two pottery samples of 6.74 +/- 0.37 ka and 7.04 +/- 0.47 ka are in line with the existing AMS radiocarbon chronology for the site and are regarded as the best dates available. Sediment samples at Vinca show poor signal strength, and the uncertainty over past water content, in addition to the possibility of mixing and/or partial bleaching of the quartz, means that we do not recommend the use of sediment-derived ages at complex archaeological sites such as Vinca. OSL dating of fired pottery however, presents a powerful tool for generating independent chronologies at archaeological sites as well as providing additional constraints for Bayesian age models.
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| 2. |
- Blomdin, Robin, et al.
(författare)
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Timing of the deglaciation in Southern Patagonia : testing the applicability of k feldspar irsl
- 2012
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Ingår i: Quaternary Geochronology. - : Elsevier BV. - 1871-1014 .- 1878-0350. ; 10, s. 264-272
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Tidskriftsartikel (refereegranskat)abstract
- The timing of the ice margin retreat of the Late Glacial Patagonian Ice Sheet (PIS) in southern Patagonia has been the object of discussion for many years. In order to resolve questions about the complex response of the PIS to past climate change, any geological interpretation and data modelling need evaluation against an absolute chronology. The aim of this project is to investigate the applicability of OSL dating to sediments from southern Patagonia; in particular, we examine the dating potential of K-feldspar IRSL signals. Samples were collected from landforms interpreted as being deposited during deglaciation of the PIS, with an expected age range of 17 and 22 ka, and from recently deposited sediment. We measure small aliquots and single grain distributions using an IR50 SAR protocol with IRSL stimulation at 50 degrees C following a preheat at 250 degrees C (held for 60 s). Uncertainties are assigned to our individual dose estimates based on the over-dispersion (OD) observed in laboratory gamma dose recovery experiments (22% for small aliquots and 18% for single grains). Then the possible effects of incomplete bleaching and differential fading are examined. For our natural samples we observe environmental ODs between 30 and 130% and mean residual doses between similar to 30 and 80 Gy. Minimum age models are used to identify the part of the dose population that is most likely to have been well-bleached and results from these models are compared. The models give ages that are consistent with each other; this may imply that they successfully identified the fully-bleached grains in the distributions, although there are some discrepancies between our small aliquot and single grain data. We observe large fading rates (on average 7.9 +/- 0.6%/decade for large aliquots) but nevertheless a comparison of our fading corrected ages with the expected age range shows that 2 out of 3 ages are consistent with geological interpretation and an established radiocarbon and cosmogenic nuclide chronology. We conclude that these investigations suggest that fading corrections can be based on laboratory average small aliquot/single grain fading rates. The third age is supported by an alternative geological interpretation, and the two ages consistent with the existing chronology imply that in the Strait of the Magellan the hills of the Brunswick peninsula (>70 m.a.s.l) were deglaciated at around 22 ka.
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| 3. |
- Buylaert, Jan-Pieter, et al.
(författare)
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A detailed post-IR IRSL chronology for the last interglacial soil at the Jingbian loess site (northern China)
- 2015
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Ingår i: Quaternary Geochronology. - : Elsevier BV. - 1871-1014 .- 1878-0350. ; 30, s. 194-199
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Tidskriftsartikel (refereegranskat)abstract
- The chronology of dust deposition and climate during the last interglacial is poorly known on the Chinese Loess Plateau. Here, 51 samples were taken from the similar to 5 m S1 palaeosol (MIS5) at the desert marginal Jingbian site to develop what is currently the most detailed S1 chronology on the Plateau using instrumental dating techniques. We use the post-IR IRSL signal from sand-sized grains of K-rich feldspar. Signal resetting in the agricultural layer shows that it is possible to almost completely zero this signal in nature. First IR stimulation plateau measurements show that there is no clear dependence of D-e on first IR stimulation temperature between 50 and 260 degrees C suggesting negligible signal fading. Resultant ages are consistent with a last interglacial age (similar to 130 to similar to 75 ka) and are also consistent within errors with continuous linear sedimentation rates. The average mass accumulation rate for S1 is similar to 150 g m(-2) a(-1), considerably higher than at many other sites but within the overall range of Loess Plateau estimates. The remarkably stable sediment accumulation at the site contrasts with a more complex record of environmental and monsoonal change recorded in grain-size and magnetic susceptibility.
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| 4. |
- Giosan, Liviu, et al.
(författare)
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On the Holocene evolution of the Ayeyawady megadelta
- 2018
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Ingår i: Earth Surface Dynamics. - : Copernicus GmbH. - 2196-6311 .- 2196-632X. ; 6:2, s. 451-466
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Tidskriftsartikel (refereegranskat)abstract
- The Ayeyawady delta is the last Asian megadelta whose evolution has remained essentially unexplored so far. Unlike most other deltas across the world, the Ayeyawady has not yet been affected by dam construction, providing a unique view on largely natural deltaic processes benefiting from abundant sediment loads affected by tectonics and monsoon hydroclimate. To alleviate the information gap and provide a baseline for future work, here we provide a first model for the Holocene development of this megadelta based on drill core sediments collected in 2016 and 2017, dated with radiocarbon and optically stimulated luminescence, together with a reevaluation of published maps, charts and scientific literature. Altogether, these data indicate that Ayeyawady is a mud-dominated delta with tidal and wave influences. The sediment-rich Ayeyawady River built meander belt alluvial ridges with avulsive characters. A more advanced coast in the western half of the delta (i.e., the Pathein lobe) was probably favored by the more western location of the early course of the river. Radiogenic isotopic fingerprinting of the sediment suggests that the Pathein lobe coast does not receive significant sediment from neighboring rivers. However, the eastern region of the delta (i.e., Yangon lobe) is offset inland and extends east into the mudflats of the Sittaung estuary. Wave-built beach ridge construction during the late Holocene, similar to several other deltas across the Indian monsoon domain, suggests a common climatic control on monsoonal delta morphodynamics through variability in discharge, changes in wave climate or both. Correlation of the delta morphological and stratigraphic architecture information on land with the shelf bathymetry, as well as its tectonic, sedimentary and hydrodynamic characteristics, provides insight on the peculiar growth style of the Ayeyawady delta. The offset between the western Pathein lobe and the eastern deltaic coast appears to be driven by tectonic-hydrodynamic feedbacks as the extensionally lowered shelf block of the Gulf of Mottama amplifies tidal currents relative to the western part of the shelf. This situation probably activates a perennial shear front between the two regions that acts as a leaky energy fence. Just as importantly, the strong currents in the Gulf of Mottama act as an offshore-directed tidal pump that helps build the deep mid-shelf Mottama clinoform with mixed sediments from the Ayeyawady, Sittaung and Thanlwin rivers. The highly energetic tidal, wind and wave regime of the northern Andaman Sea thus exports most sediment offshore despite the large load of the Ayeyawady River.
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| 5. |
- Guo, Benhong, et al.
(författare)
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Dominant precessional forcing of the East Asian summer monsoon since 260 ka
- 2022
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Ingår i: Geology. - : Geological Society of America. - 0091-7613 .- 1943-2682. ; 50:12, s. 1372-1376
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Tidskriftsartikel (refereegranskat)abstract
- One of the most perplexing problems in paleoclimate research is how orbital cyclicities force East Asian summer monsoon (EASM) precipitation variation over the middle to late Quaternary. Chinese loess records suggest that EASM precipitation was dominated by 100 k.y. cycles controlled by Northern Hemisphere ice sheet forcing. In contrast, speleothem records suggest that EASM precipitation was dominated by 23 k.y. cycles caused by Northern Hemisphere summer insolation forcing. In order to resolve this inconsistency, we present high-resolution paleoclimate records from Xijin drill cores on the western Chinese Loess Plateau for the past 260 k.y., the rough upper limit of luminescence dating. Magnetic susceptibility (χ) shows clear 23 k.y. precessional cycles over interglacials but has constant low values over glacials. This is interpreted as indicating a lack of pedogenesis, such that χ cannot record EASM precipitation variations, rather than an absence of EASM variation itself. To circumvent this issue, we use inversed sand content as an alternative proxy for EASM precipitation over glacials and splice this with the interglacial logarithmic χ from Xijin drill cores. This new record reveals dominant 23 k.y. cycles over both interglacials and glacials, consistent with speleothem δ18O data and dominant insolation forcing. These findings allow a consistent understanding of EASM variability and forcing mechanisms from both loess and speleothem archives, resolving one of the largest debates in past monsoon research. These results challenge suggestions of high-latitude ice sheet forcing of the EASM based on slowly accumulated loess records from the central Loess Plateau.
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| 6. |
- Kalinska-Nartisa, Edyta, et al.
(författare)
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Age and sedimentary record of inland eolian sediments in Lithuania, NE European Sand Belt
- 2015
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Ingår i: Quaternary Research. - : Cambridge University Press (CUP). - 0033-5894 .- 1096-0287. ; 84:1, s. 82-95
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Tidskriftsartikel (refereegranskat)abstract
- We present a study based on four inland eolian locations in Eastern, Central and Southeastern Lithuania belonging to the northeastern part of the 'European Sand Belt' (ESB). Although there have been several previous studies of the ESB, this north-eastern extension has not been investigated before in any detail. The sedimentary structural-textural features are investigated and a chronology was derived using optically stimulated luminescence on both quartz and feldspar. The sedimentary structures and the rounding and surface characteristics of the quartz grains argue for a predominance of eolian transport. Additionally, some structural alternations and a significant contribution of non-eolian grains are interpreted as inherited local glacial/glaciofluvial-bearing lithologies. Three main (glaciolacustrine-) eolian phases are distinguished based on the position in the landscape and the luminescence ages: (1) An older eolian series around 15 to 16 ka, possibly correlated with the cold GS-2a event according to the GRIP stratigraphy, and (2) a younger eolian series around 14.0 ka, possibly representing the GI-Id and 1c events. The older eolian series is underlain by (3) a glaciolacustrine-eolian series for which the period of deposition remains uncertain due to the significant discrepancy between the ages based on quartz and feldspar. (C) 2015 University of Washington. Published by Elsevier Inc. All rights reserved.
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| 7. |
- Kalinska-Nartisa, Edyta, et al.
(författare)
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The north-eastern aeolian 'European Sand Belt' as potential record of environmental changes : A case study from Eastern Latvia and Southern Estonia
- 2016
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Ingår i: Aeolian Research. - : Elsevier BV. - 1875-9637. ; 22, s. 59-72
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Tidskriftsartikel (refereegranskat)abstract
- The Latvian and Estonian inland dunes belong to the north-eastern part of the 'European Sand Belt' (ESB). These dunes are widely distributed over broad glaciolacustrine plains and Late Glacial alluvial deltas, considered to be potential sources for the aeolian material. Little is known about these aeolian sediments and their substratum; here we present a detailed sedimentary structural and textural characterisation together with a luminescence-based chronology. Through a comparison between grain-size, rounding of quartz grains and surface characteristics in medium/coarse (0.5-0.8 mm) sand, and the light mineral content, we found an alternation of aeolian and periglacial components. Further, short-lasting aeolian abrasion and/or transportation periods, and a significant contribution of a nearby sediment source are suggested. Luminescence dating points to aeolian sand accumulation and dune formation between ~16 ka and ~9 ka. However, we also observed some presumably watertable controlled environmental conditions at ~13 ka; this corresponds with the occurrence of an ice-dammed/proglacial lake.
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| 8. |
- Li, Guoqiang, et al.
(författare)
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A comprehensive dataset of luminescence chronologies and environmental proxy indices of loess-paleosol deposits across Asia
- 2024
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Ingår i: npj Climate and Atmospheric Science. - : Springer Nature. - 2397-3722. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- Loess-paleosol sequences have been used in Asia to study climate and environmental changes during the Quaternary. The scarcity of age control datasets and proxy indices analysis data for Asian loess has limited our understanding of loess depositional processes and the reconstruction of paleoclimatic changes from loess-paleosol records. In this study, we present a dataset that includes 1785 quartz optically stimulated luminescence ages and 1038 K-feldspar post-infrared infrared stimulated luminescence ages from 128 loess-paleosol sequences located in different regions of Asia. We generate 38 high-resolution age-depth models of loess records based on the provided datasets. We provide data on 12,365 grain size records, 14,964 magnetic susceptibility records, 2204 CaCO3 content records, and 3326 color reflection records. This dataset contains the most detailed and accurate chronologies and proxy index data for loess records in Asia yet published. It provides fundamental data for understanding the spatial-temporal variations in loess depositional processes and climatic changes across the continent during the mid-late Quaternary.
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| 9. |
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| 10. |
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