Luminescence Dating Of Sediments Research Articles

Luminescence dating of sediments from central Atacama Desert, northern Chile

Abstract This study examines the feasibility of applying luminescence dating methods to quartz and potassium feldspar (K-feldspar) grains from Quaternary continental deposits of the Mejillones Peninsula and Coastal Cordillera in Central Atacama, northern Chile. Sediment burial ages were calculated using single-aliquot regenerative-dose (SAR) protocols applied to the optically stimulated luminescence (OSL) signal of quartz as well as infrared stimulated luminescence (IRSL) and post-infrared infrared stimulated luminescence (post-IR IRSL) signals of K-feldspar. Considering that the target sedimentary deposits comprise the Late Pleistocene age range, K-feldspar grains were dated using fading-corrected IRSL signals measured at 50 °C (IR50) and post-IR IRSL measured at 225 °C (pIRIR225) to minimize the potential effect of residual doses on calculated ages. The results of the analytical procedures indicate that quartz grains extracted from the studied sediments present a very weak or even no fast OSL component. The combination of a low OSL sensitivity, signal instability and equivalent dose distributions with high overdispersion (>40% for most samples) hinder reliable age estimation using quartz aliquots. Bleaching test results show that the IR50 signal from K-feldspar aliquots is well reset after 20–24 h of light exposure, while the pIRIR225 signal may present residual doses corresponding to between 10 and 15% of the natural signal. IR50 fading rates are ∼6–7%/decade for most studied samples, with exception of one sample which yielded a g-value of 18.77 ± 2.06%/decade. Fading rates for the pIRIR225 signal yielded variable results among sampling sites, with g-values ranging between 0.70 ± 0.24 and 6.77 ± 1.05%/decade. The dating results point out that quartz OSL ages are largely underestimated in relation to K-feldspar fading-corrected IR50 and pIRIR225 ages. Fading-corrected pIRIR225 K-feldspar ages indicate that the alluvial sedimentation in the downthrown block of an active normal fault in Mejillones Peninsula occurred between 163.4 ± 18.4 ka and 87.4 ± 6.6 ka. K-feldspar ages also allow to constrain the age of fault scarp degradation and fault reactivation in two main branches of the Atacama Fault System. In the Naguayan Fault, pIRIR225 ages indicate that faulting occurred after 21.4 ± 3.2 ka while in the Salar del Carmen Fault, faulting is recorded after 14.7 ± 1.0 ka.

The timing and cause of megafauna mass deaths at Lancefield Swamp, south-eastern Australia

Abstract Lancefield Swamp, south-eastern Australia, was one of the earliest sites to provoke interest in Pleistocene faunal extinctions in Sahul (Pleistocene Australia-New Guinea). The systematic investigation of the deposit in the early 1970s identified megafaunal remains dominated by the 100–200 kg kangaroo Macropus giganteus titan. Associated radiocarbon ages indicated that the species was extant until c.30,000 BP, suggesting significant overlap with human settlement of Sahul. This evidence was inconsistent with contemporary models of rapid human-driven extinctions. Instead, researchers inferred ecological tethering of fauna at Lancefield Swamp due to intense drought precipitated localised mass deaths, consistent with Late Pleistocene climatic variability. Later investigations in another part of the swamp, the Mayne Site, remote to the initial investigations, concluded that mass flow disturbed this area, and Electron Spin Resonance (ESR) analyses on megafauna teeth returned wide-ranging ages. To clarify site formation processes and dating of Lancefield Swamp, we excavated new test-pits next to previous trenches in the Classic and Mayne Sites. We compared absolute chronologies for sediments and teeth, sedimentology, palaeo-topography, taphonomy, and macropod age at death across the swamp. Luminescence dating of sediments and ESR analysis of teeth returned ages between c.80,000 and 45,000 years ago. We found no archaeological remains in the bone beds, and evidence of carnivore activity and fluvial action, in the form of reactivated spring flow. The latter disturbed limited parts of the site and substantial areas of the bone beds remained intact. The faunal assemblage is dominated by megafaunal adult Macropus, consistent with mass die-offs due to severe drought. Such droughts appear to have recurred over millennia during the climatic variability of Marine Isotope Stages 4 and 3. These events began tens of millennia before the first appearance of Aboriginal people in Sahul and only the very youngest fossil deposits could be coeval with the earliest human arrivals. Therefore, anthropogenic causes cannot be implicated in most if not all of mass deaths at the site. Climatic and environmental changes were the main factors in site formation and megafauna deaths at Lancefield Swamp.

Geomorphic evidences and chronology of multiple neotectonic events in a cratonic area: Results from the Gavilgarh Fault Zone, central India

The ENE–WSW trending Gavilgarh Fault Zone (GFZ) is an important tectonic lineament within the Central Indian shield. Geomorphological mapping and spatial analyses of rivers were carried out to elucidate the imprints of active tectonics on the fluvial systems of this region. The sinuosity index, width–depth ratio of river valleys, longitudinal profile, S–L index and hypsometric index of the rivers flowing from north to south across the GFZ lineament suggest that the northern side of GFZ was tectonically uplifted. Luminescence dating of sediments from river terraces and calculation of knickpoint migration rates in the rivers indicate occurrence of multiple neotectonic events in GFZ at ca. 65–80ka, ca. 50ka, ca. 30–40ka, and ca. 14ka. Evidences of neotectonic activity, presence of active geothermal springs, and occurrence of recent earthquakes along GFZ suggest that this lineament is tectonically active and there is a need for proper seismic monitoring of this fault zone.

Using Soil Magnetic Properties to Determine the Onset of Pleistocene Human Settlement at Gledswood Shelter 1, Northern Australia

In regions that lack built structures or stratified open archaeological sites, such as precolonial Australia, rockshelters are a major source of detailed information for understanding the nature and timing of human occupation. A key concern is that the proposed ages for the earliest archaeological sites are based on luminescence dating of sediments, rather than directly of cultural materials, leaving the association between the sediments and evidence of human activity questionable. Here, we present evidence of magnetic enhancement associated with cultural horizons within the deposits of a Pleistocene rockshelter in interior northern Queensland. Soil magnetic studies combined with experimental burning show that magnetically enhanced sediments in Gledswood Shelter 1 are the result of anthropogenic burning of hearth fires, which burn hotter and for a longer time than natural wild fires. These techniques appear to work in this setting because of the nature of the local geology and the geological antiquity of the landscape. Susceptibility and frequency dependence of susceptibility signatures provide a critical tool to resolve that human occupation starts at 2.2 m depth within a stratigraphic section. In conjunction with luminescence dating, soil magnetic studies provide an opportunity for archaeologists to resolve the timing of human settlement in Australia and other intracratonic plate settings.

Luminescence dating of sediments from a Palaeolithic site associated with a solution feature on the North Downs of Kent, UK

Optically stimulated luminescence (OSL) dating has been applied to determine the burial age of sediment horizons within a sequence containing Lower Palaeolithic artefacts on an upland site associated with a solution feature (doline) at West Cliffe, located on the North Downs in Kent, UK. The study makes use of a novel extension of the single aliquot OSL measurement procedure to investigate the nature of significant overdispersion in equivalent dose values with very small aliquots of quartz inclusions, enabling single grain resolution to be approached with ∼90 μm diameter quartz extracted from the relatively fine-grained brickearth. A detailed examination of the uniformity of the distribution of radionuclide sources in the sampled volumes was also performed and this included the application of a spatially-resolved technique for beta dose rate measurement. The OSL ages, obtained for the burial of brickearth positioned stratigraphically below and above a clay and flint clast layer containing the artefacts and debitage, place the deposition of the artefacts to between ca 140 and 80 ka ago. This is significantly later than indicated by the artefact typology (>300 ka) and contrary to the expectation of in situ burial indicated by earlier research in this region. If displacement occurred on other upland sites this finding has important implications for establishing the timing of hominin use of the upland areas which, beyond broad attribution to Lower or Middle Palaeolithic origin, is uncertain and similar doubts apply to the interpretation of the environments that prevailed.

Holocene environmental changes in central Inner Mongolia revealed by luminescence dating of sediments from the Sala Us River valley

Luminescence dating of the fluvial and lacustrine sediments from the Sala Us River valley at the south edge of the Mu Us Desert, central Inner Mongolia, is reported. The study region lies in the northwestern marginal zone of the east Asian summer monsoon and is sensitive to climate change. The dating results combined with environmental proxies indicate that the Holocene Climate Optimum period, took place from 8.5 to 5 ka ago and was marked by lake development. After ~5 ka ago, the region became arid, as inferred from lake regression and fluvial activity. Deposition of fluvial sediments lasted from ~5 ka to ~2 ka ago. At about 2 ka ago, incision of the Sala Us River was initiated into the underlying sediments, with a down-cutting rate of ~3–4 cm/yr. Since 2 ka ago, human activities also played an important role in causing environmental change in the region.

Single- and Multigrain Luminescence Dating of Sediments Related to the Greenville Fault, Eastern San Francisco Bay Area, California

Near urban areas and extending ∼60 km along the eastern margin of the Livermore Valley, the Greenville fault is the easternmost right-lateral strike-slip fault of the San Andreas system in the greater San Francisco Bay area. Notwithstanding the 1980 Livermore earthquake sequence (mainshock M L 5.9) on the Greenville fault, there is no record of recency or of Holocene rates of activity on the Greenville fault, yet this fault exhibits clear geomorphic evidence of late Quaternary faulting. In trenches parallel and normal to the fault through alluvial fan deposits at the Laughlin Road site only pedogenic carbonate was available for ![Graphic][1] dating. Therefore, we applied several photon-stimulated luminescence (PSL) sediment-dating procedures to the silt and sand fractions of six samples. The polymineral-fine-silt multi-aliquot age estimates are generally inaccurate, but the single-grain quartz (SGQ) and multigrain quartz single-aliquot regenerative-dose (SAR) ages from sand grains are in stratigraphic sequence. In trench 3A these SAR ages range from 125±11 yrs (before 2007) within the topmost unit L to 13.45±0.79 ka in the base of the lowermost channel-fill unit G. The SAR PSL results demonstrate the importance of the use of SGQ dating for such sediments and provide the first numerical ages used to constrain the slip rate on the Greenville fault. Trench exposures reveal that unit G is an alluvial sequence infilling a paleochannel offset in a right-lateral sense along the northern Greenville fault. Age estimates from upper and middle unit G bracket deposition of subunit Gb are between 11.12±0.55 ka and 10.64±0.85 ka and those from middle and lower unit G bracket deposition of subunit Go are between 11.12±0.55 ka and 13.45±0.79 ka. These SAR PSL age estimates and measurements of the lateral offset constrain a preliminary slip-rate estimate to about 2 mm/yr or higher for the northern Greenville fault zone. [1]: /embed/inline-graphic-1.gif

Extending the maximum age achievable in the luminescence dating of sediments using large quartz grains: A feasibility study

The feasibility of extending the upper dating limit in the luminescence chronometry of sediments using centimeter size quartz grains has been investigated. In general for such large sized quartz grains, the total dose is from radioelements external to the grain and this dose gets progressively attenuated towards the grain centre. Thus, for a centimeter size grain, a finite portion of the inner volume largely receives only the gamma dose. Such a reduced dose implies a delayed onset of saturation and hence offers the prospects of a higher age limit. Monte-Carlo simulations were used to compute beta dose depth distribution inside such grains when irradiated by beta particles from 40K, 212Bi ( 232Th-series) and 234mPa and 214Bi ( 238U-series). These computations suggest that quartz grains of up to 6–10 mm diameter would have an inner core of ∼2–6 mm that receives minimal beta dose. Given that gamma dose is only a third to a fourth of the total dose, this approach offers the prospect of a three to four fold increase in the age limit obtainable by luminescence methods. This contribution discusses the conceptual formalism, computational aspects and outlines some of the practical difficulties and remedial measures for routine applications.

Effects of inhomogeneity and contamination in k0-INAA of low (K, Th, U)-content sand for the annual radiation dose determination in luminescence dating

Abstract It was demonstrated that for the determination of the annual radiation dose for use in luminescence dating of sediments, one should be aware of possible material inhomogeneities when applying analysis methods (such as k 0-INAA) with sample intakes of the order of the gram (to be compared with Ge gamma-ray spectrometry in cylindrical or Marinelli geometry, the latter involving ∼1.5 kg material). Moreover, when trying to remove the inhomogeneity, care should be taken to avoid contamination of the elements investigated, especially in the case of low (K, Th, U)-content sand with a considerable abrasive action (such as the Ossendrecht coversand dealt with in the present work). Whereas contamination was indeed shown to happen when grinding the material in a porcelain mortar, a satisfactory technique proved to be agate-ball milling.

Radon loss from encapsulated sediments in Ge gamma-ray spectrometry for the annual radiation dose determination in luminescence dating

In Ge gamma-ray spectrometry for the annual radiation dose determination in the luminescence dating of sediments, the picture of 226Ra enrichment or depletion (in the 238U decay series) obtained via measurement of its 214Pb and 214Bi daughters may be disturbed by the 222Rn-content of the sample being decreased due to manipulations such as drying and pulverizing. Therefore, it is common practice to start the measurement only about 1 month after encapsulating the material, after which the 226Ra(1600 a)-222Rn(3.82 d) mother-daughter equilibrium is re-established. Evidently, this only holds on condition that no significant escape of Rn occurs out of the sediment after making it up for counting. In order to experimentally investigate this effect, in the present work measurements were carried out with various types of dried and pulverized sediments that were either encapsulated in screw-cap polystyrene vials or in sealed glass containers, or that were mixed with molten wax followed by solidification in a cylindrical geometry. From the results obtained, it could be concluded that preparation and counting of the sediment-wax mixture is the method of choice.

Dating the Quaternary: progress in luminescence dating of sediments

Luminescence dating comprises a collection of numerical-age techniques that are among the most significant chronological tools currently used in Quaternary research. This paper briefly reviews the key historical developments in luminescence dating, from its roots in thermoluminescence dating of heated minerals to the development of optical dating methods for sunlight-exposed sediments. We describe the principles and practicalities of the various techniques commonly used in luminescence dating, including multiple-aliquot, single-aliquot and single-grain procedures, and we discuss some of the latest approaches to recognising and minimising potential errors in age estimation (e.g., by means of component analysis and dose distribution methods in optical dating). The overview also introduces the other papers in this special issue of Quaternary Science Reviews, which address a selection of important issues in basic research, technique development and application of luminescence dating to critical questions in the geological and archaeological sciences, illustrated with examples from around the world and the last million years of Earth history.

Optimum aluminum absorber thickness of a small X-ray irradiator for equivalent dose determination

A small X-ray irradiator (Varian VF-50J X-ray tube) has some advantages over the conventional radioactive sources for equivalent dose determination, as required for example in the process of luminescence dating of sediments and sherds. One advantage of the X-ray irradiator is that the photon energies below a few keV, which may cause an error in the equivalent dose value, can be eliminated by an aluminum absorber. Data is presented to establish the optimum thickness of the aluminum absorber, found to be about 50 μm.

Luminescence chronology of Late Pleistocene glacial deposits in North Westland, New Zealand

The chronology of the Late Pleistocene glacial history of North Westland, South Island of New Zealand, is refined by luminescence dating of sediments. It is demonstrated by two case studies that ages determined by different luminescence techniques agree well with the results of radiocarbon dating. Luminescence ages determined for sediments from two key sites of the Loopline Formation confirm the previous correlation of this unit with marine isotope stage (MIS) 4. This indicates that Late Pleistocene glaciers reached their last maximum extent in North Westland during the early part of the Otira (Last) Glaciation. Furthermore, initial dating evidence on coarse alluvial deposits in the lowlands indicates their formation during MIS 5b and MIS 5d. It is probable that these coarse gravel deposits are outwash related to glacial advances. If so, both advances were probably much less extensive than the glaciations during MIS 4 and MIS 2.

A performance comparison of k0-based ENAA and NAA in the (K, Th, U) radiation dose rate assessment for the luminescence dating of sediments

Recently, in our laboratory an intercomparison was made of methods for the annual radiation dose determination (assessed from direct radiation counting and/or from the measurement of the K, Th and U contents) applied to luminescence dating of loess and sand sediment, whereby the emphasis was put on their precision and accuracy. Although these properties are important, the duration of the measurement is also a practically relevant aspect. Indeed, direct alpha, beta and gamma-counting can last a week or more, and the determination of K, Th and U via NAA can take up to three weeks to enable proper gamma-ray spectrometry of the long-lived 233 Th/233Pa. Therefore, in the present work the performance of k0-based epiCd-NAA (ENAA, with irradiation under a cadmium cover) when applied to sediments is compared to k0-NAA. As concluded, with the use of k0-ENAA the analysis turnaround time could be considerably reduced from ~3 weeks to ~ 2.5days, while maintaining satisfactory accuracy, precision and determination sensitivity.

The effect of different sample-calibrant composition in gamma-ray spectrometry for the assessment of the radiation dose rate in the luminescence dating of sediments

One of the basic steps in luminescence dating is the determination of the annual radiation dose. Among the suitable determination methods in the case of sediment dating is HPGe gamma-ray spectrometry, primarily yielding the concentrations of K, Th and U via measurement of gamma-rays emitted by 40K and by 232Th and 235,238U and their decay products. These determinations involve both large-volume samples (with cylindrical or Marinelli geometry) and low-energy gamma-rays (down to the 210Pb 46.5 keV line). In view of this, calculations have been made in the present work in order to investigate possible inaccuracies related to gamma-ray attenuation, which may be different in samples and calibrants which have considerably different composition (elemental concentration and packing density). The calculations are based on the introduction of correction factors containing “effective solid angles” (proportional to the peak detection efficiencies), which are believed to give “correct” concentration results. It was found that, in some cases, significant errors could be committed when not performing proper corrections. Therefore, it is concluded that in practice this possible source of inaccuracy should be kept in mind, thus making it necessary to have a fair knowledge of the properties of the materials (samples and calibrants) under investigation.

Luminescence Dating of Sediments from the Luthern Valley, Central Switzerland, and Implications for the Chronology of the Last Glacial Cycle

The advancing glaciers of the last glacial maximum either eroded or deeply buried older sediments in the Swiss Alpine Foreland. However, part of the Swiss Plateau was not covered by ice and is therefore an excellent area for investigating climate and environmental change during the Upper Pleistocene. Repeated fluvial sequences can be studied in several pits along the Luthern Valley. The chronological framework is based on lithostratigraphy, pollen analysis, U/Th dating, and, recently, heavy mineral analysis and luminescence dating. The oldest unit, the Untere Zeller Schotter braided river deposit, represents cold climate conditions and presumably a glaciation prior to the Eemian Interglaciation. The last interglacial period and the very beginning of the last glacial cycle is represented by the Mittlere Zeller Schotter, sediments of a meandering fluvial system. Younger braided river sediments, the Obere Zeller Schotter, seem to correlate with the cold climate of oxygen isotope stage (OIS) 4. Weathering of the top of the Obere Zeller Schotter is likely to represent the OIS 3. The advancing Reuss glacier caused erosion of the recent Luthern Valley, cutting into older sediments, with local loess accumulation during the last glacial maximum as indicated by cover sediments on top of the fluvial sequence.

Luminescence dating of Middle Stone Age Deposits at Die Kelders

Luminescence dating of sediments has not been used extensively for dating Middle Stone Age deposits in South Africa, despite its potential for contributing to a poorly dated record. Such deposits at Die Kelders cave, on the southern South African coast, consist of narrow bands of occupation debris separated by thicker layers of aeolian sands containing much less evidence of occupation. Homogeneous, aeolian sediments are usually considered ideal for luminescence dating. Here we report luminescence analyses of five samples from these sands that demonstrate sufficient bleaching prior to burial to validate dating and that yield ages of about 60–70ka, in agreement with other evidence from sedimentology, archaeology and electron spin resonance. Lack of significant differences in the ages suggests the deposits accumulated fairly rapidly during the early part of the Last Glaciation.

Luminescence Dating of Sediments

Luminescence Dating of Sediments

Multidating studies of Batadomba Cave, Sri Lanka

In order to explore the reliability of dating techniques and to determine which materials are most useful for the establishment of precise chronologies, 14C, ESR, TL and OSL analyses were carried out on charcoal, bones. shells and sediments from the archaeological site of Batadomba Cave, Sri Lanka. The dating techniques were complemented by Fourier transform infra-red (FTIR) spectrometry, X-ray diffraction analysis as well as scanning electron microscopy (SEM). Compared with the new and existing charcoal 14C chronology, radiocarbon dating of shells, luminescence dating of sediments as well as ESR dating of shells provided reasonable agreement. Outliers could be explained by diagenetic alteration of the samples. ESR dating of bones seems to he fraught with many complications, but also provided some reasonable age estimates.

Luminescence dating of sediments from Buctouche Spit, New Brunswick

In this paper we describe our efforts to determine the formation chronology of a sequence of dunes on Buctouche Spit, a Holocene deposit on the northeast coast of New Brunswick. Optical dating, using infrared stimulation of K-feldspar grains, yielded ages ranging from 5 ± 30 a for an embryo dune to 765 ± 45 a for the oldest dune. Thermoluminescence ages, although less precise, support the recent formation of the dunes. The ages exhibit the expected sedation from youngest to oldest and are consistent with historical evidence coupled with an assumed constant sediment aggradation rate. The age resolution obtained was very good and we conclude that the optical dating method used here shows great promise.