Optimization of laboratory illumination in optical dating

Sohbati, Reza; Murray, Andrew; Lindvold, Lars René; Buylaert, Jan‐Pieter; Jain, Mayank

doi:10.1016/j.quageo.2017.02.010

Cited by 34 publications

(15 citation statements)

References 24 publications

(20 reference statements)

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“…Samples were processed at the Nordic Laboratory for Luminescence Dating, Roskilde, Denmark, under subdued orange light (Sohbati et al. 2017). For luminescence measurements, 9–18 cores (as many as possible depending on the size of each cobble) of ~10 mm in diameter and ~10–30 mm long were drilled from each cobble using a diamond‐tipped, water‐cooled coring drill, and then cut at intervals of ~1.5 mm using a low‐speed, water‐cooled wafering saw, equipped with a 0.3‐mm‐thick diamond‐tipped blade.…”

Section: Methodsmentioning

confidence: 99%

Optical dating of cobble surfaces determines the chronology of Holocene beach ridges in Greenland

Souza

Sohbati

Murray

et al. 2021

Boreas

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We constrain the age of a cobble beach ridge system in Greenland using Optically Stimulated Luminescence (OSL) dating of buried cobble surfaces. Luminescence signals from six cobbles are measured using infrared (IR) stimulation at 50 °C (IR50) and 180 °C (pIRIR180); these cobbles represent four progressively younger beach ridges lying between ~35 and ~6 m above present sea level. Luminescence–depth profiles show that the IR50 signals in all the samples and pIRIR180 signals in four out of six samples are well bleached to depths >1.2 mm into the cobble surfaces. Equivalent doses in well‐bleached cobble surface slices (i.e. <1.2 mm) are measured and divided by the effective environmental dose rate to the cobble surfaces in order to derive burial ages. Both IR signals are corrected for anomalous fading using the sample‐specific ratio of the field to the laboratory saturation levels. Our results are consistent with a depositional model predicting that the investigated portion of the beach ridge system built out continuously during relative sea level fall between ~5.3 and ~1.9 ka ago. The optical ages suggest that the rate of construction varied considerably, with the highest rates ~3.4 ka ago. Additionally, the lowest‐elevation beach ridge investigated here provides the first evidence for a higher‐than‐present relative sea level, between 1.5 and 2 ka ago, in the Disko coastal region.

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Section: Methodsmentioning

confidence: 99%

Optical dating of cobble surfaces determines the chronology of Holocene beach ridges in Greenland

Souza

Sohbati

Murray

et al. 2021

Boreas

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“…One block was further cut into ~3 × 5 × 1 cm slabs (Fig. 5), perpendicular to its original surface (by aligning the flat glacially polished exposed surface at 90° with the cutting blade), using a large water-cooled diamond saw under subdued orange light 66 . One of these slabs was used directly (without polishing) for the HR-IRPL measurements reported here.…”

Section: Methodsmentioning

confidence: 99%

Optical bleaching front in bedrock revealed by spatially-resolved infrared photoluminescence

Sellwood

Guralnik

Kook

et al. 2019

Sci Rep

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Optically stimulated luminescence (OSL) dating of sediment, based on the accumulation of trapped charge in natural crystals since their last exposure to daylight, has revolutionised our understanding of the late Quaternary period. Recently, a complementary technique called luminescence rock surface dating (RSD), which uses differential spatial eviction of trapped charges in rocks exposed to daylight, has been developed to derive exposure and burial ages, and hard-rock erosion rates. In its current form, the RSD technique suffers from labour intensive sample preparation, uncertainties in the depth and dose rate estimates, and poor resolution of the luminescence-depth profile. Here, we develop a novel, 2D luminescence imaging technique for RSD of large rock slabs (3 × 5 cm) to overcome these challenges. We utilize the recently discovered infrared photoluminescence (IRPL) signal for direct, non-destructive imaging of the luminescence-depth profile in a sub-aerially exposed granitic rock, with an unprecedented spatial resolution of ~140 µm. We further establish a correlation between luminescence and geochemistry using micro X-ray fluorescence (µXRF) spectroscopy. Our study promises a substantial advancement in luminescence imaging and paves the path towards novel applications using 2D dating, micro-dosimetry in mixed composition samples, and portable instrumentation for in-situ luminescence measurements.

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“…Preliminary sample preparation took place in Moscow under orange LED lights (Sohbati et al . 2017). After disaggregating and wet‐sieving, the resulting fine and medium sand fractions (90–250 μm) were treated with 10% HCl, then 10% H 2 O 2 , and finally 10% HF, before the samples were transferred to the Nordic Laboratory for Luminescence Dating at Risø, Denmark.…”

Section: Sampling Laboratory Sample Preparation and Instrumental Facmentioning

confidence: 99%

First reliable chronology for the Early Khvalynian Caspian Sea transgression in the Lower Volga River valley

Kurbanov

Murray

Thompson

et al. 2020

Boreas

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During the late Quaternary, dramatic changes in relative sea level (~170 m) are known to have occurred in the Caspian Sea. However, all previous attempts at resolving the uncertainty associated with the timing of these transgressive/regressive events, primarily using radiocarbon, have produced inconclusive or controversial results. Here we present the first reliable chronology for the largest known transgression (Early Khvalynian). This was derived using optically stimulated luminescence (OSL) analysis of sand‐sized quartz, with support from infrared stimulated luminescence (IRSL) from K‐rich feldspar grains, all extracted from 16 sediment samples collected along the Lower Volga River. These samples were taken from loessic sediments, marine clays (known as Chocolate Clays) and the overlying modern soils exposed at three sections (Srednyaya Akhtuba, Raygorod, Leninsk) ~200 km upstream of the present‐day estuary. The differential bleaching rates of the quartz OSL and feldspar IRSL signals were used to evaluate the degree of resetting of quartz (and feldspar) signals; it was possible to conclude that all signals, and particularly quartz OSL, were sufficiently reset at deposition to allow accurate age estimation. Our results show unambiguously that the Early Khvalynian marine Chocolate Clays present at all three sections were deposited post‐LGM, between ~17 and ~13.1 ka ago. These age estimates are further constrained by those from the overlying Kastanozem soils (9.6–0.7 ka) and underlying loess‐soil series (32–19 ka), confirming a young (17–13 ka) age of the transgressive stage of the Early Khvalynian. Relative sea level during this period must have been well above the sampling altitudes of 11.7 m a.s.l. (Srednyaya Akhtuba), 11.3 m a.s.l. (Raygorod) and 4.7 m a.s.l. (Leninsk) to explain the absence of significant alluvial sand and to allow the deposition of the fine Chocolate Clays marker horizon.

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Optimization of laboratory illumination in optical dating

Cited by 34 publications

References 24 publications

Optical dating of cobble surfaces determines the chronology of Holocene beach ridges in Greenland

Optical dating of cobble surfaces determines the chronology of Holocene beach ridges in Greenland

Optical bleaching front in bedrock revealed by spatially-resolved infrared photoluminescence

First reliable chronology for the Early Khvalynian Caspian Sea transgression in the Lower Volga River valley

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