Infrared Stimulated Luminescence Ages Research Articles

OSL and IRSL dating of raised beach sand deposits along the southeastern coast of Norway

Raised beach sand deposits along the southeastern coast of Norway were dated by optical (OSL) and infrared stimulated luminescence (IRSL) and the quartz and K-feldspar luminescence characteristics were described. Due to the poor quartz luminescence characteristics, only a limited number of samples were suitable for OSL dating. More promising are the K-feldspar extracts, with typical K-feldspar luminescence characteristics and no sign of fading. For equivalent dose (De) determination, sand-size quartz and feldspar extracts were used, applying a single aliquot regenerative (SAR) protocol. Both, OSL and IRSL De estimates show a wide distribution, unexpected for beach deposits. The calculated OSL and IRSL age estimates were generally in good agreement and the correctness of the ages was confirmed by independent age control. Because only a limited number of the quartz samples were suitable for OSL dating, IRSL dating of the K-feldspar represents an alternative to OSL quartz dating.

Luminescence dating of young coastal deposits from New Zealand using feldspar

A new measurement protocol has been tested on K-feldspars from Whanganui Inlet and Parengarenga Harbour, New Zealand. A Single Aliquot Regenerative (SAR) dose protocol, using two successive infrared (IR) stimulations (post-IR IR SAR protocol) is setup for these young (<1000 years) coastal sediments. Significant anomalous fading (g2days=7 %/decade) is observed using the conventional IR signal measured at 50°C. In contrast, the fading rate of the IR signal measured at elevated temperature (150°C) after the IR stimulation at 50°C (a post-IR IR signal) is not significant (g2days≤ 1 %/decade). Surprisingly low residual infrared stimulated luminescence (IRSL) signals were observed for a surface sample, suggesting that accurate ages as young as ∼50 years can be obtained for these recent deposits. IRSL ages ranging between 48±6 years and 1050±50 years are obtained from six samples, indicating that sediment accumulation has occurred at the two sites during the last millennia, despite a falling trend in relative sea-level in Whanganui Inlet and a stable relative sea-level at Parengarenga Harbour.

On the applicability of post-IR IRSL dating to Japanese loess

Recent work on infrared stimulated luminescence (IRSL) dating has focussed on finding and testing signals which show less or negligible fading. IRSL signals measured at elevated temperature following IR stimulation at 50°C (post-IR IRSL) have been shown to be much more stable than the low temperature IRSL signal and seem to have considerable potential for dating. For Early Pleistocene samples of both European and Chinese loess natural post-IR IRSL signals lying in the saturation region of the laboratory dose response curve have been observed; this suggests that there is no significant fading in nature. As a contribution to the further testing of post-IR IRSL dating, we have used 18 samples from two Japanese loess profiles for which quartz OSL and tephra ages up to 600 ka provide age control. After a preheat of 320°C (60 s), the polymineral fine grains (4–11 μm) were bleached with IR at 50°C (200 s) and the IRSL was subsequently measured at 290°C for 200 s. In general, the fading uncorrected post-IR IRSL ages agree with both the quartz OSL and the tephra ages. We conclude that the post-IR IRSL signal from these samples does not fade significantly and allows precise and accurate age determinations on these sediments.

The variegated (VT) tephra: A new regional marker for middle to late marine isotope stage 5 across Yukon and Alaska

The Variegated (VT) tephra, likely sourced from the eastern Aleutian arc, has a geographic distribution that places it amongst the most widespread tephra beds in eastern Beringia. First identified in the Fairbanks area of interior Alaska, it has been identified at eight additional sites ranging from Togiak Bay in southwestern Alaska, to the Klondike area of west-central Yukon. Correlation of these occurrences is established through the equivalence of glass major and trace-element geochemistry, Fe-Ti oxide geochemistry, stratigraphy, and independent age data. In Yukon and Alaska, VT tephra has a minimum bulk tephra volume estimate of ∼32 km 3. Previous age estimates for VT tephra have varied, ranging from a glass fission-track age of 125 ± 30 ka to a weighted mean thermoluminescence (TL) age of 77.8 ± 4.1 ka from bracketing ages on loess. A new infrared stimulated luminescence (IRSL) age of 106 ± 10 ka, paleoenvironmental data, and several TL and IRSL ages from Togiak Bay suggest that the time of deposition is more likely between these previous age estimates: post-marine isotope stage (MIS) 5e but underlying a prominent soil likely associated with MIS 5c, placing it within late MIS 5d.

Luminescence dating of K-feldspar from sediments: A protocol without anomalous fading correction

A protocol for optical dating of potassium-rich feldspar (K-feldspar) is proposed. It utilizes the infrared stimulated luminescence (IRSL) signal measured by progressively increasing the stimulation temperature from 50 to 250 °C in step of 50 °C, so-called multi-elevated-temperature post-IR IRSL (MET-pIRIR) measurements. Negligible anomalous fading was observed for the MET-pIRIR signals obtained at 200 and 250 °C. This was supported by equivalent dose (D e) measurements using the IRSL and MET-pIRIR signals. The D e values increase progressively from 50 °C to 200 °C, but similar D e values were obtained for the MET-pIRIR signal at 200 and 250 °C. Measurement of modern samples and bleached samples indicates that the MET-pIRIR signals have small residual doses less than 5 Gy equivalent to about 1–2 ka. We have tested the protocol using various sedimentary samples with different ages from different regions of China. The MET-pIR IRSL ages obtained at 200 and 250 °C are consistent with independent and/or quartz OSL ages.

Lake level variations of Qinghai Lake in northeastern Qinghai-Tibetan Plateau since 3.7 ka based on OSL dating

Qinghai Lake is the largest internally drained lake in China and its unique location makes it sensitive to climate changes. Late glacial climate changes associated with variation in Qinghai Lake levels have been intensively investigated for the past 40 years, with particular attention paid to lake level fluctuation histories between the last interglacial and the Holocene. However, the details of lake level fluctuations during the Holocene are still unclear. Using both optically stimulated luminescence (OSL) dating of quartz (for 22 samples) and infra-red stimulated luminescence (IRSL) of feldspars (only for sample HYW1 whose IRSL age is 37 ± 15 years), a total of 23 samples are dated from paleoshoreline deposits, fluvial sediments and aeolian sands (a total of 13 sections) near the modern lake shore, with ages from 37 ± 15 to 3710 ± 350 years. These ages are used to reconstruct the lake level fluctuation history spanning the last 3700 years. The results indicate that: (1) the youngest IRSL age of 37 ± 15 years is in agreement with the independent age of 39–29 years, suggesting that luminescence dating is able to date decadal samples for sediments from the study area; (2) the lake experienced several oscillations imposed on an overall regressive trend during the past 3700 years; (3) the dated paleoshoreline deposits are generally related to warm and wet periods, suggesting that those shoreline deposits formed during cold and dry periods, if any, may have been modified by later transgressions; (4) lake level fluctuations during the period of 3700–240 years ago are generally consistent with the climate conditions identified in other proxies, with the highest lake level occurring about 1770 years ago; and (5) after 240 years ago the lake level dropped more rapidly, which is inconsistent with the proxy records (showing a warmer and wetter phase).

Luminescence chronology of the loess record from the Tönchesberg section: A comparison of using quartz and feldspar as dosimeter to extend the age range beyond the Eemian

The loess–palaeosol sequences of the Tönchesberg section, located in the East Eifel Volcanic field (Germany) provide an excellent climate archive of the late Middle and the Upper Pleistocene in the Middle Rhine area. Loess deposits from the last Glacial (Weichselian) and the penultimate Glacial (Saalian) are up to 12 m and 15 m thick, respectively, and intercalated by palaeosols. Optically stimulated luminescence (OSL), thermally transferred optically stimulated luminescence (TT-OSL) and infrared stimulated luminescence (IRSL) measurements were carried out on 14 samples from the Tönchesberg section to determine the deposition age and to set up a more reliable chronological framework for the penultimate and last interglacial-glacial cycle. The fine-grained quartz OSL and polymineral IRSL ages are in good agreement with each other and also with the geologically estimated age, but the quartz TT-OSL ages are overestimated. The OSL and IRSL ages range from 16.8 ± 1.2 to 189 ± 16 ka indicating that the youngest loess and the weakly developed soils were deposited during marine isotope stage (MIS) 2 and 3 and that the two marker loess were most likely accumulated in the transition MIS 4/5. Loess and reworked loess postdating the Eemian soil yield ages of 110–115 ka indicating that these deposits very likely correlate to MIS 5d. Loess deposits taken below the Eemian soil are attributed to the transition MIS 6/7. A weakly developed soil above the Tönchesberg scoria yield an age of 189 ± 16 ka indicating an interstadial soil formation during MIS 7. This is in good agreement with preliminary 40Ar/ 39Ar ages for the Tönchesberg scoria and the intercalated tephra layers. Reliable age estimates up to ∼70 ka could be obtained using quartz OSL and up to ∼190 ka using the pulsed post-IR IR signal from feldspar. Hence the infrared stimulated luminescence (IRSL) is considered as the best approach to date the loess from the Middle Rhine area >70 ka.

Infrared stimulated luminescence dating of an Eemian (MIS 5e) site in Denmark using K-feldspar

Buylaert, J.-P., Huot, S., Murray, A.S. & Van den haute, P.: Infrared stimulated luminescence dating of an Eemian (MIS 5e) site in Denmark using K-feldspar. Boreas, 10.1111/j.1502-3885.2010.00156.x. ISSN 0300-9483. Infrared stimulated luminescence (IRSL) dating of K-feldspars may be an alternative to quartz optically stimulated luminescence (OSL) dating when the quartz OSL signal is too close to saturation or when the quartz luminescence characteristics are unsuitable. In this paper, Eemian (MIS 5e) coastal marine sands exposed in a cliff section on the coast of southern Jutland (Denmark) are used to test the accuracy and precision of IRSL dating using K-feldspars. This material has been used previously to test quartz OSL dating (Murray & Funder 2003): a small systematic underestimation of <10% compared to the expected age of ∼130 ka was reported. In our study, a single-aliquot regenerative-dose (SAR) IRSL protocol is used to determine values of equivalent dose (De) and the corresponding fading rates (g values). A significant age underestimation (of up to ∼35%) is observed; this is attributed to anomalous fading. Using a single site-average fading rate of 3.66 ± 0.09%/decade to correct the IRSL ages for all samples provides good agreement between the average fading-corrected K-feldspar age (119 ± 6 ka) and the independent age control (132–125 ka). This is despite the reservations of Huntley & Lamothe (2001) that their fading correction method is not expected to work on samples older than ∼20–50 ka. This fading-corrected feldspar result is not significantly different from the overall revised quartz age (114 ± 7 ka) also presented here. We conclude that fading-corrected IRSL ages measured using K-feldspar may be both precise and accurate over a greater age range than might be otherwise expected.

Luminescence dating of Upper Pleistocene loess from the Island of Susak in Croatia

The loess-paleosol sequence on the island of Susak is a detailed Late Pleistocene archive of climate change in the North Adriatic Sea of Croatia. Quaternary deposits on Susak are up to 90 m thick and consist of loess, loess derivatives and sand, intercalated by numerous paleosols and at least three tephra layers. Infrared stimulated luminescence (IRSL) dating was carried out on polymineral fine-grained material. Thirteen samples were collected from two sections on Susak to study the timing of loess accumulation and soil formation. The single aliquot regenerative (SAR) protocol, as well as the multiple aliquot additive-dose (MAAD) protocol, were applied for equivalent dose ( D e) determination. The IRSL ages were fading corrected. Independent age control is provided by radiocarbon dating of charcoal remains. The results show that loess and loess derivatives from the investigated sections represent a very detailed record correlating to the Marine Isotope Stage (MIS) 3, with short periods of stronger sand deposition and occasional volcanic activity. The extraordinary thickness of the deposits is very likely related to the vicinity of the River Po plain which extended to the southeast due to marine regressions of the Adriatic Sea during the cold periods of the Pleistocene.

Last Interglacial Age for aeolian and marine deposits and the Nahoon fossil human footprints, Southeast Coast of South Africa

Three hominid footprints preserved as casts were found in 1964 in Pleistocene aeolianites of the Nahoon Formation near East London, South Africa. Dating of the footprint-bearing aeolianite proved a lengthy and problematic task. Previous age estimates included a radiocarbon age of 29,090 − 390 + 410 years BP [Deacon, H.J., 1966. The dating of the Nahoon footprints. South African Journal of Science 62, 111–113], an infrared stimulated luminescence (IRSL) age of 144 ± 4 ka, a thermoluminescence age of 236 ± 8 ka (TL) and a luminescence subtraction age based on the IRSL and TL estimates of 75 ± 9 ka [Vogel, J.C., Wintle, A.G., Woodborne, S.M., 1999. Luminescence dating of coastal sands: overcoming changes in environmental dose rate. Journal of Archaeological Science 26, 729–733]. Thus there was no consistency among the ages derived using different dating methods. Here we describe optically stimulated luminescence (OSL) dating of quartz grains from a new set of samples collected from the footprint-bearing aeolianite and from associated geological formations. We also re-assessed the dose rate parameters for the sample for which TL and IRSL ages were reported and analysed the OSL signal from this sample. The new OSL dating yielded a coherent series of ages consistent with the stratigraphy as well as global and local sea level history. The indicated footprint age of 124 ± 4 ka thus relates to an important period of modern human evolution.

Luminescence chronology of cave sediments at the Atapuerca paleoanthropological site, Spain

Ascertaining the timing of the peopling of Europe, after the first out-of-Africa demographic expansion at the end of the Pliocene, is of great interest to paleoanthropologists. One of the earliest direct evidences for fossil hominins in western Europe comes from an infilled karstic cave site called Gran Dolina at Atapuerca, in a stratum ∼1.5 m below the Brunhes–Matuyama (B–M) geomagnetic boundary (780 ka) within lithostratigraphic unit TD6. However, most of the meters of fossil- and tool-bearing strata at Gran Dolina have been difficult to date. Therefore, we applied both thermoluminescence (TL) and infrared-stimulated-luminescence (IRSL) multi-aliquot dating methods to fine-silt fractions from sediment samples within Gran Dolina and the nearby Galería cave site. We also applied these methods to samples from the present-day surface soils on the surrounding limestone hill slopes to test the luminescence-clock-zeroing-by-daylight assumption. Within the uppermost 4 m of the cave deposits at Gran Dolina, TL and paired TL and IRSL ages range stratigraphically from 198 ± 19 ka to 244 ± 26 ka. Throughout Gran Dolina, all luminescence results are stratigraphically self-consistent and, excepting results from two stratigraphic units, are consistent with prior ESR-U-series ages from progressively deeper strata. Thermoluminescence ages culminate at 960 ± 120 ka approximately 1 m below the 780 ka B–M boundary. At Galería, with one exception, TL and IRSL ages range stratigraphically downward from 185 ± 26 ka to 503 ± 95 ka at the base of the lowermost surface-inwash facies. These results indicate that TL and (sometimes) IRSL are useful dating tools for karstic inwash sediments older than ca. 100 ka, and that a more accurate chronostratigraphic correlation is now possible among the main Atapuerca sites (Gran Dolina, Galería, Sima de los Huesos). Furthermore, the oldest TL age of ca. 960 ka from Gran Dolina, consistent with biostratigraphic and paleomagnetic evidence, implies a probable numeric age of 900–950 ka for the oldest hominin remains (∼0.8 m below the TL sample). This age window suggests a correspondence to Marine Isotope Stage (MIS) 25, a relatively warm and humid interglaciation.

Luminescence dating of a gigantic palaeolandslide in the Gobi-Altay mountains, Mongolia

In an attempt to date a palaeolandslide that took place along the Baga Bogd Massif, in Mongolia, the infrared stimulated luminescence (IRSL) method has been applied to lacustrine silty sediments directly overlying the landslide mass. The IRSL age estimates obtained on alkali feldspar grains (>40 μm) and polymineral fine grains (4–11 μm) provide a minimum age for the landslide event. The IRSL ages on alkali feldspars corrected for long-term fading using the protocol of Mejdahl (1988, 1989) suggest that the palaeolandslide occurred at the beginning of the Last Interglacial. These are in good agreement with the 10Be cosmogenic dates obtained on faulted and abandoned alluvial fans in the Gobi-Altay mountains. This study demonstrates for the first time that the IRSL dating method can successfully be applied for establishing landslide chronologies.

Luminescence investigation of loess and tephra from Halfway House section, Central Alaska

Infrared stimulated luminescence (IRSL) properties of the Old Crow tephra and bracketing loess from the Halfway House site in Central Alaska are investigated in order to test newly developed techniques, including SAR and recently proposed fading corrections. Loess samples investigated show a standard growth of luminescence with regenerative dose while the tephra sample is less sensitive by an order of magnitude and saturates at lower dose. The growth curves obtained using multiple-aliquots regeneration (MAR) saturate at a higher value than those with the single-aliquot regeneration (SAR) protocol. Fading rate determinations for these samples are shown to be imprecise and no noticeable difference was observed between loess and tephra materials. Anomalous fading corrections using an average g value of 5% are applied to the natural test dose signal intensity using the dose rate correction (DRC) method. IRSL ages obtained for loess are in agreement with the expected age while the tephra age is lower than expected, suggesting the measured fading rate is underestimated for this material.

A test case for anomalous fading correction in IRSL dating

Infrared-stimulated luminescence (IRSL) dating of feldspars has the potential to date deposits beyond the age range of quartz optical (OSL) dating. Successful application of feldspar IRSL dating is, however, often precluded due to anomalous-fading, the tunnelling of electrons from one defect site to another. In this paper we test procedures proposed for anomalous-fading correction by comparing feldspar IRSL and quartz OSL dating results on a suite of samples from continental deposits from the southeastern Netherlands. We find that even after anomalous-fading correction IRSL ages underestimate the burial age of the deposits and argue that this may be a consequence of a dependency of anomalous fading rate on the dose rate and on the absorbed dose.

The potential of optically stimulated luminescence for medieval building; A case study at Termez, Uzbekistan

Luminescence techniques thermoluminescence (TL) and optically stimulated luminescence (OSL) are generally used to assess the chronology of the last firing of ceramics. In the field of building archaeology, fired bricks can be dated by these techniques. Nevertheless, these luminescence ages are not exactly related to the construction of the building itself, but to the production of the building materials. In some cases, re-use is possible and this raises problems with the interpretation of the dating results. This led us to employ optically stimulated luminescence in a less conventional way. Before bricks were sealed in masonry by mortar, they would have been exposed to day light, and, as a result, the optical traps of the crystals on the material surface should have been bleached (zeroed by light). Dating the end of the bleaching period is possible by OSL using blue light for stimulation and by IRSL (infrared stimulated luminescence) using IR stimulation. Thus the OSL or IRSL age for these crystals is directly related to the construction of the architectural structure. Experiments were carried out to determine the suitability of this approach and to solve practical problems of sampling. The results show that the bleaching light penetrates between 0.5 to 1 mm into the bricks, according to their transparency. This depth is sufficient to collect enough quartz and feldspar inclusions that have been affected by light in the past, and thus date the construction of the masonry directly. Attempts at surface dating of bricks collected at the medieval citadel of Termez, Uzbekistan, already dated by TL, were the starting point of this research.

TL and IRSL dating of Jiahu relics and sediments: clue of 7th millennium BC civilization in central China

Thermoluminescence (TL) dating of pottery and infrared stimulated luminescence (IRSL) dating of sediments from early Neolithic layers at the Jiahu site, Henan Province, east-central China, have been achieved. The pottery TL ages range from 6800 (±450) to 8900 (±640) years and the sediment IRSL ages from 6750 (±760) to 8860 (±870) years confirming former 14C data. Both TL and IRSL ages agree well with each other. They reinforce the very early existence of a fully developed Neolithic civilization in central China, starting already in the first half of the 7th millennium BC and lasting about 2100 years. From these layers finds of bone flutes and Chinese characters have already been reported [X. Li, G. Harbottle, J. Zhang, C. Wang, The earliest writing? Sign use in the seventh millennium BC at Jiahu, Henan Province, China, Antiquity 77 (2003) 31–44; J. Zhang, G. Harbottle, C. Wang, Z. Kong, Oldest playable musical instruments found at Jiahu early Neolithic site in China, Nature 401 (1999) 366–368.] The Jiahu pottery of the 7th millennium BC belongs to the earliest in China and elsewhere.

Late Quaternary hillslope evolution recorded in eastern South African colluvial badlands

Infrared stimulated luminescence (IRSL) ages have been obtained from a sequence of sandy colluvial deposits in northern KwaZulu–Natal. Comparison of the IRSL ages on sand-sized, potassium-rich feldspars, with radiocarbon dates on A-horizon organic matter from buried palaeosols within the colluvial succession shows good agreement between the dating techniques. When compared with palaeoenvironmental records, the data suggest that the colluvium accumulated during arid stages of the Late Quaternary, whilst pedogenesis repeatedly occurred at intervals of hillslope stability which may reflect periods of greater humidity. Temperature does not seem to have been a forcing factor in the landscape development. Extensive colluviation took place during the arid Last Glacial Maximum, but the occurrence of several palaeosols indicates that it was a time of fluctuating climatic conditions.

Late Holocene dune accretion and episodes of persistent drought in the Great Plains of Northeastern Colorado

The Great Plains of the Mid West USA contain dunefields which display stratigraphic evidence of episodic sand drift throughout the Holocene and, in some cases, the Late Pleistocene. Widespread aeolian activity has been linked to persistent megadroughts caused by a weakening of the tropical moisture-laden circulation from the Gulf of Mexico and equatorial Pacific. Infrared stimulated luminescence (IRSL) dating has been applied to two exposures in the Fort Morgan dunefield of northeastern Colorado where radiocarbon-dated buried soils provide ages for land surface stability. IRSL ages show that sand drift occurred episodically during the Late Holocene at 4.85, 2.37, 1.06, 0.80, 0.6–0.53 and 0.37 ka.

Late Pleistocene luminescence chronology of loess deposition in the Missouri and Mississippi river valleys, United States

The loess stratigraphy of the mid-continental U.S. is an important proxy record for the advance of the North American ice sheet into the catchment of the Mississippi, Missouri and Ohio rivers. One of the most outstanding problems is deciphering the age of the loess deposits in this area during the Late Pleistocene. We used multiple-aliquot additive dose procedures under infrared stimulated luminescence (IRSL) and single aliquot regeneration (SAR) protocols to resolve ages of loess at the Loveland Silt type locality, Iowa, the Pleasant Grove School section, Illinois, and the Bonfils Quarry section, Missouri. Radiocarbon dated levels in the Peoria Loess and Roxana Silt were used to test the accuracy of the IRSL and SAR methods. SAR on polymineral and quartz extracts yielded underestimates in age by 20–55%, whereas IRSL gave concordant ages to the 14C control and was used to date the loess sequences. The oldest loess, the Bonfils Silt, gave IRSL ages between 159 and 264 ka and are considered non-finite estimates because the luminescence response was near saturation with additive β dose. The Loveland Silt at the type locality exhibited considerable luminescence in growth with additive β dose and yielded the mean age of 159±14 ka (n=4). The Teneriffe Silt gave a mean IRSL age of 93±5 ka (n=4) which, overlaps at two σ with a previous TL age and indicates deposition sometime between 100 and 80 ka. The Roxana Silt yielded stratigraphically consistent IRSL ages between ca. 60 and 30 ka. Luminescence and radiocarbon dating indicate that there were four distinct periods of loess deposition in the Mississippi and Missouri river basins at ca. 180–140 ka, 100–80 ka, 60–30 ka, and 25–12 ka which are concordant with periods of meltwater input to the Gulf of Mexico, another proxy of glaciation in mid-continental North America.

The Last Interglacial to Glacial Transition, Togiak Bay, Southwestern Alaska

An 18-m-high coastal bluff at Togiak Bay (northwestern Bristol Bay, southwestern Alaska) exposes marine, lacustrine, fluvial, glacial, volcanic, and organic deposits that record the ∼50,000-year-long transition from the peak of the last interglaciation to the early Wisconsin glaciation. The base of the section is dominated by stratified sand and silt extending up to 4.3 m above sea level; marine diatoms are present, and pollen assemblages are characterized by relatively high percentages of Picea, Alnus, and Betula and low percentages of Poaceae and Cyperaceae. The marine sediment was probably deposited during the peak of marine oxygen-isotope stage (OIS) 5e. An infrared stimulated luminescence (IRSL) age of 151,000±13,000 yr from near the base of the exposure is permissive of this correlation. The marine sand and silt are overlain by 0.8 m of peaty silt with diatoms that record a transition from marine to lacustrine conditions. During this interval, Poaceae and Cyperaceae dominate the pollen assemblages, and Picea and shrubs are nearly absent, suggesting that herb tundra occupied the landscape. This interval probably encompasses OIS 5d on the basis of the herb tundra and an IRSL age of 119,000±10,000 yr from 60 cm below the marine/lacustrine transition. The organic mud is overlain by 3.1 m of stratified sand and organic silt that apparently record shallowing of the lake; reappearance of spruce and shrubs (=OIS 5c?); and subsequent deepening of the lake (=OIS 5b?); followed by aggradation of a floodplain (=OIS 5a?), which was dry at the time basaltic lava buried the site. Thermoluminescence analyses on lava-baked sediment indicate that the eruption occurred 70,000±10,000 yr ago. Sometime thereafter, but prior to 53,600 14C yr B.P. an outlet of the Ahklun Mountains ice cap advanced over the site and deposited ∼7 m of bouldery ice-contact drift. The sedimentary sequence contains at least four tephra beds. Major- and trace-element chemistry provide a basis for correlating two of the tephras with tephra beds at nearby sites. The tephras, luminescence ages, and correlations with marine isotope stages provide the geochronological control to place the Togiak Bay section into a global context. The site serves as an important new reference section for late Pleistocene paleoenvironmental change in eastern Beringia.