Luminescence Dating Of Fluvial Deposits Research Articles

Luminescence dating of delta sediments: Novel approaches explored for the Ganges-Brahmaputra-Meghna Delta

Deltas where luminescence dating is most essential due to organic-poor geologic records are also those where it is often most challenging due to unsuitable luminescence properties of quartz grains, associated with rapid production of young clastic sediment. One example is the Ganges-Brahmaputra-Meghna Delta (GBMD), where Himalaya uplift drives erosion, production, and delivery to the delta plain of poorly sensitized quartz sand. Luminescence dating of fluvial deposits may be further complicated by partial bleaching prior to deposition. Here, we use GBMD quartz and polymineral sediment, including sand and silt fractions, with constrained depositional ages between a few years and a few centuries to test novel approaches to luminescence dating of fluvial deposits in an otherwise challenging setting. This produces the first delta-wide assessment of GBMD sediment luminescence dateability. We use a new multiple-signal SAR (MS-SAR) bleaching index (BI) to explore zeroing of the luminescence signals of sediment prior to deposition and to quantify the IR, pIRIR, and TL residual doses of GBMD polymineral silt with well-reset BSL signals. This test establishes BI values that can be used to identify sufficient bleaching of Holocene sediment with unknown depositional ages, thereby improving confidence in quartz silt dating. We find that GBMD quartz sand is unsuitable for luminescence dating in most localities. By contrast, GBMD silt is sufficiently bleached and has universally suitable luminescence characteristics, enabling dating of GBMD deposits up to the Last Glacial Maximum. Our findings in the GBMD establish methodology for obtaining and validating luminescence ages for fluvial deposits in challenging settings with unsuitable quartz sand.

Luminescence Dating of Fluvial Deposits from the Weser Valley, Germany

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 (IR<sub>50</sub>), 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 <sup>230</sup>Th/U dating results from underlying interglacial deposits of the same pit, which are correlated with MIS 7c to early MIS 6.

Luminescence Dating of Fluvial Deposits in the Rock Shelter of Cueva Antón, Spain

The fluvial sediments at Cueva Antón, a Middle Palaeolithic rock shelter located in the valley of the River Mula (Southeast Spain), produced abundant lithic assemblages of Mousterian affinities. Radiocarbon dates are available for the upper part of the archaeological succession, while for the middle to lower parts chronometric data have been missing. Here we present luminescence dating results for these parts of the succession. Quartz OSL on small aliquots and single grain measurements yield ages ranging from 69 ± 7 ka to 82 ± 8 ka with a weighted mean of 72 ± 4 ka for sub-complexes AS2 to AS5. Equivalent dose estimates from large aliquots were highest and inconsistent with those from single grains and small multiple grain aliquots. This is probably caused by the presence of over-saturating grains, which have been quantified by single grain measurements. Additional post-IR IRSL measurements on coarse grained feldspar give strong support to a well-bleached quartz OSL signal. While independent chronometric control is missing, the results are within the expected age range and support the notion of a rapid accumulation of the fluvial deposits.

Luminescence dating of fluvial deposits in Vojvodina, N Serbia: First results

This paper reports on the first investigations into the potential of luminescence dating to establish a chronological framework for fluvial processes in the Tisa River Valley in Vojvodina, N Serbia. A total of 18 samples were collected from a terrace exposure near Mužlja, which comprised non-fluvial deposits at the top and fluvial deposits at the base. The luminescence characteristics of sand-sized quartz and potassium feldspar grains were investigated using a single-aliquot regenerative dose (SAR) protocol. The quartz separates exhibit a complex behaviour, making this dosimeter less suited for optical dating. Investigations into the behaviour of infrared stimulated luminescence (IRSL) measured at 50 °C (IR50) from K-rich feldspar extracts showed that preheating in excess of 60 s at 225 °C leads to significant sensitivity changes. The effect of IR stimulation on the thermoluminescence (TL) signal and that of preheating on IRSL intensity were examined; the results are inconclusive with respect to thermal stability, but are not inconsistent with the idea that the data do not reflect depletion of an electron trap. The IR50-signal measured after a preheat of 60 s at 115 °C behaves well in the SAR protocol, although it suffers from anomalous fading. Assuming that the signal is thermally stable, the fading-corrected ages suggest that deposition occurred during the end of the Late Pleniglacial and the early Late Glacial, which is consistent with geological expectations. Our observations demonstrate that IRSL dating of feldspar holds potential for establishing a chronology of fluvial dynamics of the Tisa River in N Serbia. Further methodological investigations are desirable; however, as issues relating to the stability and resetting of the IRSL signal remain to be resolved.

Luminescence dating of fluvial deposits: applications to geomorphic, palaeoseismic and archaeological research

Fluvial deposits and landforms are important archives of river response to climate, tectonics and base level change and are commonly associated with archaeological sites. Unlike radiocarbon dating, the target material for optically stimulated luminescence (OSL) dating (sands and silts) is nearly ubiquitous in fluvial deposits and the age range for OSL spans the last glacial–interglacial cycle, a time period of interest to many Quaternary scientists. Recent advances in OSL techniques and the development of single‐grain dating capabilities have now allowed fluvial deposits, and other deposits commonly afflicted with incomplete zeroing of the luminescence signal, to be dated. The application of OSL dating to fluvial deposits is discussed with respect to its potential to provide important contributions to research in the fields of geomorphology, palaeoseismology and archaeology. Examples are given from each research field.

Optically stimulated luminescence dating of fluvial deposits: a review

Optically Stimulated Luminescence (OSL) dating allows age determination of sediments deposited during the last glacial‐interglacial cycle. This relatively new technique therefore enables chronological frameworks to be established for fluvial deposits that often cannot be dated by other means. The OSL signal of quartz and feldspar minerals is reset by light exposure during fluvial transport, and builds up as a result of ionizing radiation after burial of the minerals. Incomplete resetting of the OSL signal because of inadequate light exposure in the fluvial environment can result in age overestimations, especially for relatively young samples. Methods used for the detection of incomplete resetting, or poor bleaching, are reviewed. It is argued that technique s measuring the OSL signal from small subsamples (aliquots) are most promising for detecting poor bleaching and for obtaining the true age for a sample in which not all grains had their OSL signal completely removed at deposition. Quartz should be the mineral of choice, because it has been shown to yield the most reliable results and because its OSL signal is more rapidly reset than that of feldspar. Aliquot size should be small, with aliquots ideally consisting of a single grain of quartz for samples in which the majority of grains are poorly bleached. Using single‐aliquot dating of coarse‐grain quartz, age offsets between zero and a few thousand years have been found for modern fluvial deposits. The validity of single‐aliquot quartz OSL dating has been demonstrated by application to known‐age samples, but for the older age range (>˜13 ka) further proof of the accuracy of the method is essential. The application of quartz OSL dating to investigations of fluvial deposits opens a new realm of possibilities to be explored, as is highlighted by some examples of geological applications.

Optically stimulated luminescence dating of fluvial deposits: a review

Optically stimulated luminescence dating of fluvial deposits: a review