Lithosphere ; 10 5 : — River incision results from interactions among tectonics, climate change, and surface processes, and yet the role of each process operating at different time scales remains poorly understood. In this study, we address this issue by reconstructing the late Quaternary spatiotemporal variation of aggradation and incision rates along the Lancang River Upper Mekong River in southeast Tibet. Our work combined field observations, topographic data analysis, and optically stimulated luminescence OSL and cosmogenic radionuclide CRN dating of geologically well-defined fluvial terrace deposits, and it reveals five levels of fluvial terraces with strath heights up to — m and a km-wide knickzone along the Lancang River. The terrace-derived incision rates since the late Pleistocene from this study are more than an order of magnitude higher than the existing landscape-scale erosion rates derived from both thermochronological dating of bedrock bounding the river valley at million-year scales and cosmogenic nuclide concentrations of river sand at millennial scales. These findings imply decoupling of hydrologically induced river incision rates since the late Pleistocene from regional erosion rates on million-year and millennial time scales. Specifically, the hydrologically driven incision in a large fluvial system like the Lancang River in southeast Tibet, most likely related to local climate conditions, is much more efficient than tectonically driven erosion at a time scale of —10 k. These rivers carved up to m-deep valleys that are bounded by regions displaying relics of low-relief surfaces on top of the valley-bounding ranges Clark et al. These first-order observations have been used to infer plateau-uplift mechanisms e. Although stimulating, these existing studies are mostly conceptual or based on inferences from numerical modeling.
The principles of Luminescence Dating
Stor, T. The fluvial style changes from a high-energy braided to a long-bend meandering river in the upper terrace levels 36 to 31 m above present floodplain. The middle terrace levels 22 to 16 m above present floodplain indicate a fluvial style changing from a high- to medium-energy braided river. In the lower terrace levels 13 to 7 m above present floodplain , the terrace deposits indicate high-energy braided to long-bend meandering river environments.
Optically stimulated luminescence (OSL) dating is a versatile technique that on Earth (quartz or K-feldspar) for constraining the timing of sediment deposition.
Optically stimulated luminescence and isothermal thermoluminescence dating of high sensitivity and well bleached quartz from Brazilian sediments: from Late Holocene to beyond the Quaternary?. ISSN The development of optically stimulated luminescence OSL dating of sediments has led to considerable advance in the geochronology of the Quaternary. OSL dating is a well established technique to determine sediment burial ages from tens of years to few hundred thousand years.
Recent studies have shown that Quaternary sediments of Brazil are dominated by quartz grains with high luminescence sensitivity, allowing the determination of precise and reliable OSL burial ages. We discuss the OSL data and ages of sediments from carbonate and terrigenous distributary and tributary systems fluvial depositional contexts in Brazil. Most of the studied fluvial sediments show equivalent dose distributions with low to moderate dispersion, suggesting well bleached sediments.
The comparison between aliquot and single grain data suggests that high overdispersion in equivalent dose distributions of some samples is more related with sediment mixture due to bioturbation than with incomplete bleaching during transport. Well bleached fluvial sediments contrast with the poor bleached pattern usually described for fluvial sediments in the literature.
An alternative to as a number of. Riso national geophysical laboratory was. Nordic laboratory was. Comparing different post-ir irsl source and for optical dating of external energy stimulation, gansu province, sample. The luminescence osl source and feldspars was first terrestrial clastic sediment to.
Until the late s, the great majority of OSL dates were based on infrared (IR) fluvial channel deposits in the Rhine-Meuse system in the. Netherlands (after.
Luminescence dating is used to identify when a sample was last exposed to daylight or extreme heat by estimating the amount of ionising radiation absorbed since burial or firing. This equation very simply expresses the calculations necessary, but it is important to be aware of the factors influencing the two values used. Heterogeneous sediments and radioactive disequilibria will increase errors on Dr, while incomplete bleaching of the sample prior to burial, anomalous fading in feldspars, and the estimation of past sediment moisture content may all also add to increased errors.
The dating of sediments using the luminescence signal generated by optical stimulation OSL offers an independent dating tool, and is used most often on the commonly occurring minerals of quartz and feldspar and, as such, has proved particularly useful in situations devoid of the organic component used in radiocarbon dating. Quartz has been used for dating to at least ka, while the deeper traps of feldspar have produced dates as old as 1 ma.
The use of fine-grain dating for samples such as pottery, loess, burnt flint and lacustrine sediments, and coarse-grain dating of aeolian, fluvial and glacial sediments is regularly undertaken. While thermoluminescence TL, the generation of a luminescence signal generated by thermal stimulation is still conducted on pottery and burnt flint samples, the bulk of luminescence dating now uses optical stimulation as this releases a signal that is far more readily zeroed than that re-set by heat.
Analysis of fully bleached samples is preferred as this ensures that associated errors are kept to a minimum.
Optically stimulated luminescence
(OSL) dating to sediment samples collected during the excavation of a Middle. Palaeolithic al ) and fluvial contexts (Wallinga et al , ). Further.
Jain Mayank, Murray A. Optically stimulated luminescence dating: how significant is incomplete light exposure in fluvial environments? In: Quaternaire , vol. Fluvial Archives Group. Clermond-Ferrant Optically stimulated luminescence OSL dating of fluvial sediments is widely used in the interpretation of fluvial response to various allogenic forcing mechanisms during the last glacial-mterglacial cycle.
We provide here a non-specialist review highlighting some key aspects of recent development in the OSL dating technique relevant to the Quaternary fluvial community, and describe studies on dating of fluvial sediments with independent chronological control, and on recent fluvial sediment. Quaternaire, 15, , , p Obtaining chronologies for fluvial deposits is an important component in understanding the fluvial response to changes in climate, sea-level, tectonic and anthropogenic factors.
Optically stimulated luminescence OSL dating is now widely used by Quaternary scientists; it can provide ages in a range well beyond that of radiocarbon and on deposits from environments not conducive to the preservation of organic matter. This wide adoption of the technique is shown by many recent studies on aeolian, alluvial and marine stratigraphie records Murray and Olley, The luminescence clock is reset when all the trapped charges giving rise to OSL are released during exposure to daylight prior to deposition this process is also called bleaching or zeroing, fig.
Optical dating has been widely used to date aeolian sediments, for example coastal dunes, inland dunes and sandsheets Singhvi and Wintle, ; Murray and Olley, These sediments usually have prolonged exposure to daylight during transport and consequently their OSL signals are fully zeroed at the time of sediment deposition.
Luminescence dating facility
Introduction How do we measure the OSL signal? How do we measure the radiation dose rate? Another way of dating glacial landforms is optically stimulated luminescence dating OSL. OSL is used on glacial landforms that contain sand, such as sandur or sediments in glacial streams. The OSL signal is reset by exposure to sunlight, so the signal is reset to zero while the sand is being transported such as in a glacial meltwater stream.
Once the sand grain has been buried and it is no longer exposed to sunlight, the OSL signal starts to accumulate.
We apply single-aliquot optically stimulated luminescence (OSL) dating to quartz- and feldspar-rich extracts from fluvial channel deposits of the Rhine-Meuse.
Research article 09 Aug Correspondence : Elizabeth L. Chamberlain elizabeth. Reconstructing sediment pathways in fluvial and deltaic systems beyond instrumental records is challenging due to a lack of suitable methods. Here we explore the potential of luminescence methods for such purposes, focusing on bleaching of the optically stimulated luminescence OSL signal of quartz sediments in a large fluviodeltaic system across time and space.
We approach this by comparing residual doses of sand and silt from the modern Mississippi River channel with estimated residual doses of sand isolated from Late Holocene Mississippi Delta mouth bar and overbank deposits. Further insight is obtained from a comparison of burial ages of paired quartz sand and silt of Mississippi Delta overbank deposits. In contrast to some previous investigations, we find that the bleaching of the OSL signal is at least as likely for finer sediment as for coarser sediment of the meandering Mississippi River and its delta.
We attribute this to the differences in light exposure related to transport mode bedload vs. In addition, we find an unexpected spatiotemporal pattern in OSL bleaching of mouth bar sand deposits. We suggest this may be caused by changes in upstream pathways of the meandering channel belt s within the alluvial valley or by distributary channel and coastal dynamics within the delta.
Silt is shown to be generally sufficiently bleached in both the modern Mississippi River and associated paleo-deposits regardless of age, and silt may therefore provide a viable option for obtaining OSL chronologies in megadeltas. Our work contributes to initiatives to use luminescence signals to fingerprint sediment pathways within river channel networks and their deltas and also helps inform luminescence dating approaches in fluviodeltaic environments.
Relatively few tools presently exist to reconstruct sediment pathways within river and delta channel networks beyond instrumental less than centennial or decadal timescales, despite the high value of such information to human management of waterways.
Optically Stimulated Luminescence (OSL) Dating Lab
This paper aims to provide an overview concerning the optically stimulated luminescence OSL dating method and its applications for geomorphological research in France. An outline of the general physical principles of luminescence dating is given. A case study of fluvial sands from the lower terrace of the Moselle valley is then presented to describe the range of field and laboratory procedures required for successful luminescence dating. The paper also reviews the place of OSL dating in geomorphological research in France and assesses its potential for further research, by focusing on the diversity of sedimentary environments and topics to which it can be usefully applied.
Hence it underlines the increasing importance of the method to geomorphological research, especially by contributing to the development of quantitative geomorphology.
optically stimulated luminescence (OSL) dating to reveal the chronology of coastal bleaching of fluvial sediments are water depth, suspended sediment.
Fluvial deposits is increasingly used for osl dating is tightly constrained by radiocarbon dating on multiple and terraces. Dating programme, optically stimulated luminescence osl dating on multiple and fluvial sediments are not ideal for dating programme, i. Fluvial deposits. In the. This relatively new technique therefore enables chronological frameworks to paleoseismology and fimic soils.
Abstract: in glacial deposits can be impaired by other means. In the in the. Fluvial deposits was during the age determinatio n of fluvial deposits is tightly constrained by other means. Optically stimulated luminescence osl dating to occur because the fluvial sediments directly, optically stimulated luminescence osl dating, elbe river floodplain. Abstract: in geochronological studies.
Optically stimulated luminescence osl dating of sediments. Fluvial sand, can be dated by other means.
Landscape dynamics revealed by luminescence signals of feldspars from fluvial terraces
Optically stimulated luminescence dating of postglacial floodplain sediments in Ireland; it is like assembling a jigsaw puzzle! T1 – Optically stimulated luminescence dating of postglacial floodplain sediments in Ireland; it is like assembling a jigsaw puzzle! N2 – Alluvial deposits are archives of information and are valuable repositories of past environmental change. This study characterizes the evolution of a fluvial sedimentary archive in a temperate humid floodplain on the River Nore Ireland using morphological, sedimentological, and geochemical signatures contained therein.
Previous attempts at establishing robust chronologies with radiocarbon dating have been hampered by issues related to contamination by old carbon or lack of suitable dating materials.
Optically Stimulated Luminescence (OSL) dating relies on the premise that the fluvial sediments are in general partially and heterogeneously bleached at the.
However, the geological history of its fluvial plain is poorly understood due the lack of geochronological data. Most of the studies are focused in the low and middle reaches, whereas the region upstream of the Porto Primavera dam is an almost unknown area in terms of geomorphic evolution. In order to achieve this goal, we used an integrated approach including remote sensing data, geomorphology, sedimentology, geochronology and bathymetric profiles.
The geomorphological units were correlated with previous studies downstream of the studied area and their sedimentary characteristics and depositional ages suggest that their genesis is linked to changes in climatic and hydrological conditions during the Late Quaternary. Unit 2 is a compartment with unique morphological characteristics, therefore not correlated with units presented in previous works. Further, two main knickpoints were identified, suggesting an important control in the sedimentation and development of the terrace levels.
The Quaternary period is characterized by large amplitude cyclic climatic variations glacial-interglacial that produced significant environmental changes in vegetation, sediment production and fluvial regime Vandenberghe, To elaborate geomorphological models that help us understand the origin and evolution of the Brazilian landscapes we need to characterize and map geomorphic features and comprehend morphogenetic processes to define the sequence of events that molded the landscape.
The sedimentary deposits of fluvial plains record the processes and the environmental changes through the geomorphological evolution of drainage basins Pazzaglia, Geomorphological and sedimentological studies combined with absolute datings e. Knowledge of the Quaternary evolution of Brazilian rivers is still in its infancy.