scholarly journals Applicability of OSL dating to fine-grained fluvial deposits in the Mekong River floodplain, Cambodia

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Yuji Ishii ◽  
Toru Tamura ◽  
Daniel S. Collins ◽  
Bunnarin Ben
Keyword(s):  
Large River ◽  
Osl Dating ◽  
Mekong River ◽  
Fine Grained ◽  
Transport Distance ◽  
Infrared Stimulated Luminescence ◽  
Single Grain ◽  
Floodplain Deposits ◽  
Osl Age ◽  
Age Estimates

AbstractOptically stimulated luminescence (OSL) dating of fine-grained (4–11 μm) fluvial sediments is rarely attempted but is crucial for constraining the evolution of mud-dominated floodplains. This study investigated the applicability of OSL dating to fine-grained deposits in the Mekong River, Cambodia based on a very young (<600 yr) point-bar to riverbank succession and modern flood deposits. In succession, fine-grained quartz OSL provided the youngest ages, whereas age estimates by multi-grain sand-sized quartz OSL, and feldspar and polymineral infrared-stimulated luminescence are >200 years older than the fine-grained quartz OSL age estimates. Ages of fine-grained quartz OSL are concordant with the minimum ages obtained from the single-grain quartz OSL. These results are supported by the generally small residual doses (<0.1 Gy) measured in modern fine-grained floodplain deposits. This indicates that fine-grained sediments in the Mekong River (Cambodia) are sufficiently bleached at deposition and can yield reliable quartz OSL ages for establishing the chronology of the floodplain. The sufficient bleaching of fine-grained quartz partly results from the long transport distance and may also occur in other large river systems.

scholarly journals Towards an improvement of optically stimulated luminescence (OSL) age uncertainties: modelling OSL ages with systematic errors, stratigraphic constraints and radiocarbon ages using the R package BayLum

Geochronology ◽  
2021 ◽  
Vol 3 (1) ◽  
pp. 229-245
Author(s):  
Guillaume Guérin ◽  
Christelle Lahaye ◽  
Maryam Heydari ◽  
Martin Autzen ◽  
Jan-Pieter Buylaert ◽  
...  
Keyword(s):  
R Package ◽  
Systematic Errors ◽  
Covariance Matrices ◽  
Optically Stimulated Luminescence ◽  
Osl Dating ◽  
Dose Rates ◽  
Determination Procedure ◽  
Single Grain ◽  
Measurement Uncertainties ◽  
Osl Age

Abstract. Statistical analysis has become increasingly important in optically stimulated luminescence (OSL) dating since it has become possible to measure signals at the single-grain scale. The accuracy of large chronological datasets can benefit from the inclusion, in chronological modelling, of stratigraphic constraints and shared systematic errors. Recently, a number of Bayesian models have been developed for OSL age calculation; the R package “BayLum” presented herein allows different models of this type to be implemented, particularly for samples in stratigraphic order which share systematic errors. We first show how to introduce stratigraphic constraints in BayLum; then, we focus on the construction, based on measurement uncertainties, of dose covariance matrices to account for systematic errors specific to OSL dating. The nature (systematic versus random) of errors affecting OSL ages is discussed, based – as an example – on the dose rate determination procedure at the IRAMAT-CRP2A laboratory (Bordeaux). The effects of the stratigraphic constraints and dose covariance matrices are illustrated on example datasets. In particular, the benefit of combining the modelling of systematic errors with independent ages, unaffected by these errors, is demonstrated. Finally, we discuss other common ways of estimating dose rates and how they may be taken into account in the covariance matrix by other potential users and laboratories. Test datasets are provided as a Supplement to the reader, together with an R markdown tutorial allowing the reproduction of all calculations and figures presented in this study.

Insight into the sediment dynamics of a high-impact low-frequency mass movement event using single-grain feldspar luminescence in the Pokhara valley, Nepal

2021 ◽  
Author(s):  
Anna-Maartje de Boer ◽  
Wolfgang Schwanghart ◽  
Jürgen Mey ◽  
Jakob Wallinga ◽  
Basanta Raj Adhikari ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Mass Movement ◽  
Low Frequency ◽  
High Impact ◽  
Osl Dating ◽  
Transport Dynamics ◽  
Infrared Stimulated Luminescence ◽  
Single Grain ◽  
Pokhara Valley ◽  
Insight Into

&lt;p&gt;Mass movements play an important role in landscape evolution of high mountain areas such as the Himalayas. Yet, establishing numerical age control and reconstructing transport dynamics of past events is challenging. To fill this research gap, we investigated the potential of Optically Stimulated Luminescence (OSL) dating and tracing methods. OSL dating analyses of Himalayan sediments is extremely challenging due to two main reasons: i) the OSL sensitivity of quartz, typically the mineral of choice for dating sediments younger than 100 ka, is poor, and ii) highly turbid conditions during mass movement transport hamper sufficient OSL signal resetting prior to deposition which eventually results in age overestimation. In this study, we aim to bring OSL dating to the test in an extremely challenging environment. First, we assess the applicability of single-grain feldspar dating of mass movement deposits in the Pokhara valley, Nepal. Second, we exploit the poor bleaching mechanisms to get insight into the sediment dynamics of this paleo-mass movement through bleaching proxies. The Pokhara valley is a unique setting for our case-study, considering the availability of an extensive independent radiocarbon dataset (Schwanghart et al., 2016) as a geochronological benchmark.&lt;/p&gt;&lt;p&gt;Single-grain infrared stimulated luminescence signals were measured at 50&amp;#176;C (IRSL50) and post-infrared infrared stimulated luminescence signals at 150&amp;#176;C (pIRIR-150). As expected, results show that the IRSL50 signal is better bleached than the pIRIR150 signal. A bootstrapped Minimum Age Model (bMAM) is applied to retrieve the youngest subpopulation to estimate the palaeodose. However, burial ages calculated based on this palaeodose overestimate the radiocarbon ages by an average factor of ~8 (IRSL50) and ~35 (pIRIR150). This shows that dating of the Pokhara Formation with our single-grain approach was not successful. Large inheritances in combination with the scatter in the single-grain dose distributions show that the sediments have been transported prior to deposition under extreme limited light exposure which corresponds well with the highly turbid nature of the sediment laden flood and debris flows that emplaced the Pokhara Formation.&lt;/p&gt;&lt;p&gt;To investigate the sediment transport dynamics in more detail we studied three bleaching proxies: the percentage of grains in saturation (2D0 criteria), percentage of well-bleached grains (2&amp;#963; range of bMAM-De) and the overdispersion (OD). Neither of the three bleaching proxies indicate a spatial relationship with run-out distances of the mass movement deposits. We interpret this as virtual absence of bleaching during transport, which reflects the catastrophic nature of the event. While single-grain feldspar dating did not provide reliable burial ages of the Pokhara mass movement deposits, our approach has great potential to provide insight in sediment transport dynamics of high-impact low-frequency mass movement events in mountainous region.&lt;/p&gt;&lt;p&gt;&lt;em&gt;References&lt;/em&gt;&lt;/p&gt;&lt;p&gt;Schwanghart, W., Bernhardt, A., Stolle, A., Hoelzmann, P., Adhikari, B. R., Andermann, C., ... &amp; Korup, O. (2016). Repeated catastrophic valley infill following medieval earthquakes in the Nepal Himalaya.&amp;#160;Science,&amp;#160;351(6269), 147-150.&lt;/p&gt;

scholarly journals Towards an improvement of OSL age uncertainties: modelling OSL ages with systematic errors, stratigraphic constraints and radiocarbon ages using the R package BayLum

2020 ◽  
Author(s):  
Guillaume Guérin ◽  
Christelle Lahaye ◽  
Maryam Heydari ◽  
Martin Autzen ◽  
Jan-Pieter Buylaert ◽  
...  
Keyword(s):  
R Package ◽  
Systematic Errors ◽  
Covariance Matrices ◽  
Osl Dating ◽  
Dose Rates ◽  
Determination Procedure ◽  
Supplementary Material ◽  
Single Grain ◽  
Measurement Uncertainties ◽  
Osl Age

Abstract. Statistical analysis has become increasingly important in the field of OSL dating since it has become possible to measure signals at the single grain scale. The accuracy of large chronological datasets can benefit from the inclusion, in chronological modelling, of stratigraphic constraints and shared systematic errors. Recently, a number of Bayesian models have been developed for OSL age calculation; the R package BayLum allows implementing different such models, in particular for samples in stratigraphic order which share systematic errors. We first show how to introduce stratigraphic constraints in BayLum; then, we focus on the construction, based on measurement uncertainties, of dose covariance matrices to account for systematic errors specific to OSL dating. The nature (systematic versus random) of errors affecting OSL ages is discussed, based – as an example – on the dose rate determination procedure at the IRAMAT-CRP2A laboratory (Bordeaux). The effects of the stratigraphic constraints and dose covariance matrices are illustrated on example datasets. In particular, the interest of combining the modelling of systematic errors with independent ages, unaffected by these errors, is demonstrated. Finally, we discuss other common ways of estimating dose rates and how they may be taken into account in the covariance matrix by other potential users and laboratories. Test datasets are provided as supplementary material to the reader, together with an R Markdown tutorial allowing to reproduce all calculations and figures presented in this study.

scholarly journals Distributed model of hydrological and sediment transport processes in large river basins in Southeast Asia

2015 ◽  
Vol 12 (7) ◽  
pp. 6755-6797 ◽  
Author(s):  
S. Zuliziana ◽  
K. Tanuma ◽  
C. Yoshimura ◽  
O. C. Saavedra
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
River Basin ◽  
River Basins ◽  
Large River ◽  
Mekong River ◽  
Distributed Model ◽  
Mekong River Basin ◽  
Chao Phraya River ◽  
Large River Basins

Abstract. Soil erosion and sediment transport have been modeled at several spatial and temporal scales, yet few models have been reported for large river basins (e.g., drainage areas > 100 000 km2). In this study, we propose a process-based distributed model for assessment of sediment transport at a large basin scale. A distributed hydrological model was coupled with a process-based distributed sediment transport model describing soil erosion and sedimentary processes at hillslope units and channels. The model was tested on two large river basins: the Chao Phraya River Basin (drainage area: 160 000 km2) and the Mekong River Basin (795 000 km2). The simulation over 10 years showed good agreement with the observed suspended sediment load in both basins. The average Nash–Sutcliffe efficiency (NSE) and average correlation coefficient (r) between the simulated and observed suspended sediment loads were 0.62 and 0.61, respectively, in the Chao Phraya River Basin except the lowland section. In the Mekong River Basin, the overall average NSE and r were 0.60 and 0.78, respectively. Sensitivity analysis indicated that suspended sediment load is sensitive to detachability by raindrop (k) in the Chao Phraya River Basin and to soil detachability over land (Kf) in the Mekong River Basin. Overall, the results suggest that the present model can be used to understand and simulate erosion and sediment transport in large river basins.

scholarly journals New Insights Into the Genesis of the “Poznań Clays” – Upper Neogene of Poland

2020 ◽  
Vol 30 (1) ◽  
pp. 18-32 ◽  
Author(s):  
Piotr Maciaszek ◽  
Lilianna Chomiak ◽  
Paweł Urbański ◽  
Marek Widera
Keyword(s):  
Facies Analysis ◽  
Cross Sectional ◽  
Fine Grained ◽  
Late Neogene ◽  
Floodplain Deposits ◽  
Uppermost Portion

AbstractThe present study focuses on the upper Neogene deposits, called the “Poznań Clays”, that cover more than 75,000 km2 of Poland. They are situated between the first mid- Polish lignite seam and the glaciogenic deposits of the Pleistocene age. Lithostratigraphically, the “Poznań Clays” belong to the uppermost portion of the lignite-bearing Grey Clays Member and the whole Wielkopolska Member (Poznań Formation). The examined fine-grained sediments include mud-rich floodplain deposits with palaeosol remnants and large sandy-muddy or muddy palaeochannel bodies. Therefore, taking into account facies analysis, cross-sectional geometry, and the planform of the palaeochannels, it can be stated that the “Poznań Clays” formed in the environment of a late Neogene anastomosing river.

scholarly journals Luminescence Dating of Fluvial Deposits from the Weser Valley, Germany

2015 ◽  
Vol 42 (1) ◽  
Author(s):  
Julia Roskosch ◽  
Sumiko Tsukamoto ◽  
Manfred Frechen
Keyword(s):  
Late Pleistocene ◽  
Luminescence Dating ◽  
Marine Isotope Stage ◽  
Coarse Grained ◽  
Performance Tests ◽  
Luminescence Signal ◽  
Fluvial Deposits ◽  
Fine Grained ◽  
Infrared Stimulated Luminescence ◽  
Off Time

Abstract Luminescence dating was applied on coarse-grained monomineralic potassium-rich feld-spar and polymineralic fine-grained minerals of five samples derived from fluvial deposits of the Riv-er Weser in northwestern Germany. We used a pulsed infrared stimulated luminescence (IRSL) single aliquot regenerative (SAR) dose protocol with an IR stimulation at 50°C for 400 s (50 μs on-time and 200 μs off-time). In order to obtain a stable luminescence signal, only off-time IRSL signal was rec-orded. Performance tests gave solid results. Anomalous fading was intended to be reduced by using the pulsed IRSL signal measured at 50°C (IR50), but fading correction was in most cases necessary due to moderate fading rates. Fading uncorrected and corrected pulsed IR50 ages revealed two major fluvial aggradation phases during the Late Pleistocene, namely during marine isotope stage (MIS) 5d (100 ± 5 ka) and from late MIS 5b to MIS 4 (77 ± 6 ka to 68 ± 5 ka). The obtained luminescence ages are consistent with previous 230Th/U dating results from underlying interglacial deposits of the same pit, which are correlated with MIS 7c to early MIS 6.

Fluvial transport dynamics in the Rangitikei River (New Zealand) unravelled through single-grain feldspar luminescence

2020 ◽  
Author(s):  
Anne Guyez ◽  
Stephane Bonnet ◽  
Tony Reimann ◽  
Jakob Wallinga
Keyword(s):  
New Zealand ◽  
Light Exposure ◽  
River Sediments ◽  
High Ratio ◽  
Sediment Flux ◽  
Fluvial Terraces ◽  
The Past ◽  
Transport Distance ◽  
Fluvial Transport ◽  
Single Grain

&lt;p&gt;Over the past decades, luminescence has been widely used for dating sedimentary deposits. Several recent publications suggest luminescence signals can also be used to investigate fluvial transport. Here we explore what information luminescence signals yield in past and present sediment dynamics in the Rangitikei River (RR), New Zealand (Bonnet et al., 2019).&lt;/p&gt;&lt;p&gt;We present a dataset of 30 samples from fluvial terraces and modern river sediments of the RR. For each of the samples, we measured pIRIR luminescence signals of 300 individual sand-sized grains of feldspar (Reimann et al., 2012). We interpret results to evaluate differences between past and modern transport conditions, and to infer information on lateral input of bedrock particles in different river sections.&lt;/p&gt;&lt;p&gt;The information obtained from the single-grain analysis is incredibly rich, and requires new metrics for interpretation. To quantify the percentage of grains that were eroded from bedrock (or very old deposits) and re-deposited with minimal light-exposure, we identified grains for which the pIRIR signal is above 85% of full saturation (Wintle, 2006). For grains below this saturation threshold, we used the bootstrapped minimum age model (Galbraith et al.,1999; Cunningham and Wallinga, 2012) to determine the palaeodose, the best estimate of the natural radiation dose received by grains since their last deposition and burial event. For the modern deposits, we interpret the palaeodose to indicate the light-exposure of the best-bleached grains. Thereby, it provides a proxy of fluvial transport distance of the sediment grains.&lt;/p&gt;&lt;p&gt;For the modern river sediments we obtain palaeodoses between 2 and 6 Gy. A decreasing trend in palaeodose downstream suggests that part of the grains are transported through the entire system and are gradually bleached through light exposure during this process. The downstream trend in palaeodose of the RR is influenced by the connection of a major tributary, the Kawhatau River (KR), characterized by higher palaeodoses. Based on the observed trends, we estimate that the KR contributes three times more to modern sediment flux down the confluence than the upstream RR. Moreover, we observe that downstream of the confluence the percentage of saturated grains increase, which implies significant local input of bedrock particles from valley sides.&lt;/p&gt;&lt;p&gt;Data from recent (Holocene) autogenic fluvial terraces were acquired downstream the RR/KR confluence. They show a high to very high ratio of saturated grains (30-70%). We also document a downstream increasing trend of the percentage of saturated grains in these fluvial terraces, much stronger than for modern deposits. The maximum is observed for terraces at elevation of +28/+34 m, with an input of saturated grains that doubles over a distance of 100 km. As a consequence, saturated grains represent up to 70 % of the grain population in the most downstream sample. This implies a stronger lateral input of bedrock particles in the past, during recent incision of the river and a significant contribution of valley walls to the sediment flux of the RR, probably through landslides and/or lateral fluvial erosion.&lt;/p&gt;

Testing direct dating of Alpine faults by luminescence and ESR

2020 ◽  
Author(s):  
Sumiko Tsukamoto ◽  
David Tanner ◽  
Christian Brandes ◽  
Christoph von Hagke
Keyword(s):  
Esr Spectra ◽  
Fault Gouge ◽  
Esr Dating ◽  
Fine Grained ◽  
Infrared Stimulated Luminescence ◽  
Minimum Age ◽  
History Of ◽  
Recent Earthquakes ◽  
Age Range ◽  
Saturation Dose

&lt;p&gt;For a better understanding of the recent exhumation history of the Alps and the distribution of palaeo- and recent earthquakes within the orogen, it is important to elucidate the Quaternary activity of major faults. In this study, we test the applicability of luminescence and electron spin resonance (ESR) dating, which have ultralow closure temperatures, to directly date fault gouge of the Simplon Fault. A dark grey to black, fine-grained fault gouge was sampled near Visp, Switzerland, from an outcrop that exposes rocks that formed at ductile/brittle conditions. Quartz and feldspar grains were extracted from the sample; quartz grains were used for ESR dating, whereas feldspar grains were used for infrared stimulated luminescence (IRSL) dating.&lt;/p&gt;&lt;p&gt;The IRSL measurements reveal that the natural post-IR IRSL signal, stimulated at 225&amp;#176;C (pIRIR&lt;sub&gt;225&lt;/sub&gt;) was in saturation. The pIRIR&lt;sub&gt;225&lt;/sub&gt; signal had an extremely low saturation dose, with a characteristic saturation dose (D&lt;sub&gt;0&lt;/sub&gt;) of ~90 Gy. The natural IRSL signal at 50&amp;#176;C (IR&lt;sub&gt;50&lt;/sub&gt;) is about 80 % of the laboratory saturation, so that this signal is presumably in the field saturation. The IR&lt;sub&gt;50 &lt;/sub&gt;also showed a small D&lt;sub&gt;0&lt;/sub&gt; of ~250 Gy. Although these D&lt;sub&gt;0&lt;/sub&gt; values are unexpectedly small, the IRSL signals can be used to calculate the minimum age of the last seismic movement of the fault.&lt;/p&gt;&lt;p&gt;Both natural and laboratory-irradiated ESR spectra did not contain detectable Ti centre. Therefore, only the Al centre was used for ESR dating. The natural Al centre from the fault was not in saturation, with a preliminary equivalent dose value of ~1500 Gy. Since the last seismogenic movement most likely only partially reset the Al centre, the ESR age can be regarded as the maximum age of the last event.&amp;#160; We show that by combining luminescence and ESR dating, it is possible to narrow down the age range of the last seismic activity on the fault.&lt;/p&gt;

scholarly journals Recuperated OSL dating of fine-grained quartz in Chinese loess

2006 ◽  
Vol 1 (2) ◽  
pp. 89-100 ◽  
Author(s):  
X.L. Wang ◽  
Y.C. Lu ◽  
A.G. Wintle
Keyword(s):  
Osl Dating ◽  
Chinese Loess ◽  
Fine Grained
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