Dating Of Quartz Research Articles

OSL-based lateral progradation and aeolian sediment accumulation rates for the Apalachicola Barrier Island Complex, North Gulf of Mexico, Florida

Vertical sediment cores in five separate beach ridge complexes along the north-east Gulf of Mexico Coast were recovered and dated using optically stimulated luminescence (OSL) dating of quartz: these are located on Cape San Blas (CSB), Little St. George Island (LSGI), Richardson's Hammock (RH), St. Joseph Peninsula (SJP) and Saint Vincent Island (SVI). All of these landforms are coastal barrier systems situated along a 100 km stretch of the Florida Panhandle, U.S.A. Two samples were collected for dating from each core. Ridge accumulation rates (RAR) associated with lateral progradation were calculated from the dated samples. We also determined average sediment accumulation rates (ASAR) for two intervals within each sediment core. All OSL ages within the sediment cores were found to be in stratigraphic order or in a few cases statistically indistinguishable. Moreover, all dated ridges were found to be in correct temporal sequence based on their geomorphic positions. Rapidly accreted sequences were found to be backed by St. Joseph Bay in the western region of the study area. More slowly accreted sequences were associated with the more eastern stretches of the study area backed by St. Vincent Sound and Apalachicola Bay. Our ASAR results are in accord with an Australian study of modern dune accumulation. Perhaps our most important finding is that in the barrier island environments of this north-eastern Gulf Coast region, aeolian sedimentation continues well after full vegetative cover develops and stranding of landward ridges takes place. This confirms our similar earlier observation on SVI (López and Rink, 2008). We find that up to approximately one order of magnitude lower sedimentation rates occur after an initial period of more rapid aeolian accumulation for the vertical intervals studied in foredune ridges. Lateral progradation rates of ridge sequences were highly variable within the study area, ranging from 92 to 848 m/100 years, but we did find agreement between some of our slower ridge accumulation rates and those in other areas of Florida and around the world determined using OSL and 14C dating. We conclude that OSL may be used in a regional context to establish variation in progradation rates and aeolian accumulation that varies among systems.

Methodological Aspects on Luminescence Dating of Fluvial Sands from the Moselle Basin, Luxembourg

Methodological Aspects on Luminescence Dating of Fluvial Sands from the Moselle Basin, Luxembourg Optically stimulated luminescence (OSL) dating of quartz and infrared-stimulated luminescence (IRSL) dating of feldspar were applied to fluvial sands from the lower terrace (M1) of the Moselle valley in Luxembourg (western Europe). The dating results indicated that the aggradation period for the sediments from below the M1 alluvial terrace can be correlated to the Weichselian upper Pleniglacial (MIS 2), which is in good agreement with the general chronostratigraphy of the Moselle terrace staircase. The ages were obtained from small aliquots of quartz and feldspars, using the single aliquot regenerative (SAR) protocol. The equivalent dose determination included a series of tests and the selection of the Minimum Age Model as the most appropriate statistical model. This made it possible to provide a reliable methodological background for further luminescence dating of fluvial sediments from the Moselle basin.

A late Pleistocene record of aeolian sedimentation in Blanche Cave, Naracoorte, South Australia

We provide geochemical analyses and grain size data for a clearly layered, 80 cm thick sedimentary deposit close to a roof collapse in Blanche Cave near Naracoorte in SE South Australia. This deposit contains aeolian material deposited between ∼40 ka and 14 ka cal BP and which yields airborne sediments spanning the Last Glacial Maximum, a period of time with little information for the Australian continent. The deposit also contains abundant vertebrate fossil material derived from owl pellets, accumulation and pitfall entrapment. Below the studied profile, large vertebrate remains are found but are not discussed here. No Holocene sedimentation occurred at the site examined in the cave, and the top of the sequence is capped with a layer that has been anthropologically disturbed and contains exotic Pinus pollen. Chronologies of the deposit were obtained using two dating techniques: single stage accelerator mass spectrometer (SSAMS) 14C analysis of 23 charcoal samples and optically stimulated luminescence (OSL) dating of quartz from 6 sediment samples. The 14C chronology is preferred to describe the history of the deposits since the OSL chronology, which consistently overestimates the associated radiocarbon dates, may be inaccurate due to complexities in calculating dose rates, and may in addition represent the timing of sediment deposition through the cave opening rather than sediment transport to the deposit site. Morphological analysis of single quartz grains and grain size analysis indicate different provenance that is confirmed through the geochemical analyses of bulk sediment. Major elements were measured by X-ray Fluorescence (XRF), trace and rare earth elements by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA ICP-MS), and Neodymium isotopic ratios were obtained using a Thermal Ionisation Mass Spectrometer (TIMS). Our results indicate that the aeolian material deposited in Blanche Cave over the 40–14 ka cal BP period originated from different sources across South Australia, although Nd isotopes clearly indicate a close association with sediments of the Kanmantoo Group outcropping along the eastern portion of the Mount Lofty Ranges and the Padthaway Ridge further south, both being located to the NW and NNW of the cave. During the latter part of Marine Isotope Stage 3, conditions were wetter and windblown sediment came from the coastal region just north and south of the Coorong Lagoon, with winds originating from the north-northwest. At that time, woody taxa appear to have vegetated the landscape. During the drier phases, especially the Last Glacial Maximum, sediment came from further inland, thus suggesting a different predominant wind direction, more from the northwest. The deglaciation saw material originating from a more northerly direction.

Testing the applicability of a standardized growth curve (SGC) for quartz OSL dating: Kalahari dunes, South African coastal dunes and Florida dune cordons

Standardized growth curves (SGCs) have recently been developed as a means to reduce measurement times when determining palaeodoses in the standardized luminescence (OSL) dating of quartz, but this approach is not without its critics. We test the performance of SGCs derived from samples from a range of environments in southern Africa and Florida (United States of America). Data presented here suggest that the method performed well when determining low (<50Gy) equivalent dose (De) values from samples with different geological provenances within South Africa. However, the application of an SGC built from South African data performed poorly when used to estimate the palaeodoses of samples from Florida, with seven out of ten samples failing to replicate the single aliquot regenerative (SAR)-derived De value to within ±10%. We thus advocate the use only of regionally based SGCs for full De determination, although SGCs can also be utilized as a way of quickly generating SAR ‘range finders’ irrespective of sample origin. Furthermore, one sample from the Florida site did not show regenerative growth in accordance with any samples from either the South Africa or Florida data, resulting in significant De underestimation when using the SGC. Although the reasons for such behaviour are not yet understood, this re-iterates the recommendation of Burbidge et al. [2006. De determination for young samples using the standardised OSL response of coarse-grain quartz. Radiation Measurements 41(3), 278], to incorporate a single regenerative step in SGC protocols in order to check consistency.

Study on the origin of the Hongshan brecciated copper deposit in Huichang County, Jiangxi Province, China

The Hongshan copper deposit is a typical cryptoexplosive breccia-type deposit, which occurs in a metamorphic rock series of the Mesoproterozoic Taoxiyuan Formation. Orebodies are distributed inside and outside porphyry-cryptoexplosive breccia pipes. The isotope geochemistry of the deposit is consistent with the origin of porphyry breccia: the δ18\(O_{H_2 O} \) values ranging from 1.2‰ to 6.1‰ and the δ34S values varying from 0 to 2.5‰. 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of pyrite, which coexists with ore minerals, indicate it was derived from the orogenic belt. Thermodynamic analysis indicates that the main metals were deposited largely as a result of the decreasing of proton concentrations associated with H2S and CO2 exsolution during explosion and temperature dropping. Based on K-Ar dating of quartz coexisting with ore minerals, the age of mineralization was estimated to be 97.1–98.8 Ma, which suggests that mineralization occurred between the Early and Late Cretaceous. According to the relevant information obtained, a diagenetic and metallogenic pattern in the area has been presented in this paper.

Implications of broad dose distributions obtained with the single-aliquot regenerative-dose method on quartz fine-grains from loess

Six samples were collected from a section of Peoria Loess in Eustis, North America, for optically stimulated luminescence (OSL) dating of quartz, and all except one (LV90) produced narrow dose distributions. A comparative study was conducted on this sample and on a ‘well-behaved’ sample (LV91), involving other dating methods and examination of the quartz OSL. These investigations revealed differences in the quartz OSL growth with dose, OSL response to thermal treatments and the range of components within the OSL signals. An ultra-fast component was found in LV90 that displayed a higher rate of sensitivity change than the fast component and this had a malign influence on the determination of the equivalent dose. The distinctive luminescence characteristics of LV90 imply either a change in wind dynamics and/or the source area for the silt.

Formula omitted] determination for young samples using the standardised OSL response of coarse-grain quartz

It has recently been shown that it is possible to construct standardised curves of the sensitivity corrected growth in optically stimulated luminescence (OSL) with exposure to ionising radiation, and that they may be used in the dating of quartz and polymineral samples. Standardised growth curves are particularly advantageous where measurement time is limited, as once they have been defined, only the natural signal and the response to a subsequent test dose are required in order to determine the equivalent dose of a sub-sample. The present study is concerned with the application of the standardised growth curve approach to OSL dating of Holocene age samples. Systematic changes in the shape of the standardised growth curve of coarse-grain quartz are identified as the size of the test dose is varied, because of non-proportionality between the test dose and the luminescence test response. The effect is characterised by fitting the change in gradient of the standardised growth curve as test dose is varied. An equation is defined to describe standardised growth as a function of regenerative dose and test dose. Regenerative dose responses of other samples in this study are treated as unknowns and recovered through different growth curves to compare precision and accuracy of various methods of D e determination. The standardised growth curve is found to yield similar precision to conventional fits of single aliquot regenerative data, but slightly poorer accuracy. The standardised growth curve approach was refined by incorporating the measurement of one regenerative response for each aliquot as well as its natural signal. Measurements of this additional data point for aliquots of 22 samples were used to adjust the standardised growth equation, improving its accuracy. The incorporation of this additional data point also indicated a systematic uncertainty of 2.4% in the estimates of D e .

Single grains dating of volcanic quartz from pyroclastic flows using Red TL

The potential benefit of red thermoluminescence (RTL) dating of quartz is related to the signal's stability over time scales of 100 ka to 1 Ma. RTL dating has been tested on volcanic quartz grains in a late Pleistocene pyroclastic flow which erupted from the Toya caldera in Hokkaido, Japan. New TL equipment installed with a small X-ray irradiator facilitated using the regenerative dose method for single grain (or aliquot) for RTL dating. A suitable combination of filters and photomultiplier gave effective RTL readouts while eliminating the black body emission of the heating device. Preliminary examination of the output showed that the new equipment provided RTL signals even from single quartz grains. The RTL signal did not show any sensitivity changes after 10 cycles of reproducibility, making it suitable for a construction of a regenerative dose curve for each grain and aliquot, with no correction for sensitivity changes. The ages resulting from the regenerative dose method are in good agreement with that of a multiple aliquot slide method and approximately concordant with ages estimates based on previous geological evidence.

40Ar−39Ar dating of quartz from ore in the baiyangping Cu−Co polymetallic ore-concentrated area, Lanping Basin, Yunnan

40Ar-39Ar fast neutron activation age spectrum of quartz in ore collected from the Baiyangping Cu-Co polymetallic ore-concentrated area, Lanping Basin, is saddle-shaped. The plateau age, minimum appearance age and isochron age shown on the spectra are 56.53±0.43 Ma, 55.52±1.78 Ma and 55.90±0.29 Ma respectively. The age data are consistent with each other within 1σ uncertainties. Because the given initial 40Ar/36Ar value of 294.7±1.14 is very close to Nier's value (295.5±5), both plateau and isochron ages may be considered as the forming time of quartz. So the age of 55.90-56.53 Ma represents the forming age of ore deposits. It is obvious that the ore deposits were formed during the Early Himalayan period.

A single-aliquot regenerative-dose method based on IR [formula omitted] bleaching of the fast OSL component in quartz

In the optically stimulated luminescence (OSL) dating of quartz, the presence of significant medium and slow components in the initial-OSL signal (first 0.8 s or so) can give rise to erroneous dose estimates. Thus it is desirable to develop a dose estimation method that is based on the OSL from the fast component alone. In this paper, the reduction of fast component OSL by high temperature infrared (IR) stimulation is investigated. It is shown that, in the temperature range from 120– 190 ∘ C , it is possible to deplete the fast component preferentially using IR stimulation. The thermal assistance energy required for IR stimulation ( 1.49 eV ; 830 nm ) of the fast component is calculated to be 0.41 ± 0.02 eV . However, the elevated temperature IRSL of quartz has a poor signal-to-noise ratio; hence a single-aliquot regenerative-dose (SAR) protocol based on a differential-OSL signal (the difference between the two short OSL signals separated by an elevated temperature IR stimulation) is proposed. The measurement conditions are optimised following examination of both the photoionisation cross-sections of the fast component for different stimulation temperatures, and possible thermally induced sensitivity changes arising from holding the samples at high temperatures for long periods ( ∼ 1500 s ). The resulting equivalent dose values, and those from a conventional SAR protocol based on the initial-OSL signal, are compared with the expected doses for several samples. We observe that for samples with relatively strong medium and slow components, the SAR protocol based on isolation of the fast component (derived by IR depletion of the OSL) gives significantly more accurate estimates than the SAR protocol using net initial OSL signals. On the other hand, accurate dose estimates are obtained from samples dominated by the fast component using both protocols. Finally, the implications are discussed for dosimetry using quartz.

Magmatic Gold Mineralization in the Western Qinling Orogenic Belt: Geology and Metallogenesis of the Baguamiao, Liba and Xiaogouli Gold Deposits

Abstract The superlarge Baguamiao, large Liba and Xiaogouli gold deposits represent three typical gold deposits different from the Carlin type in the western Qinling Orogenic Belt. Based on Ar‐Ar dating of quartz from ores, U‐Pb dating of single zircon from granite, tracing of H and O isotopes and studies on the mineralogy and texture of spots and bleached alteration developed in wall rocks, this paper focuses the relations between gold deposits and granite to clarify the origin of gold deposits and the metallogenesis in the tectonic evolution of the Qinling Orogenic Belt. The comprehensive studies show that the age of the granite (148.1–244 Ma) is identical with that of the gold deposits (131.91–232.56 Ma). It is suggested that the granite has close temporal, spatial and genetic relationship with the gold deposits. The granite provides a heat source, water source and considerable amount of ore‐forming material. Finally, it is concluded that the orogeny by collision, emplacement of the granite and positioning of the gold deposits represent a successive process. Both the granite and gold deposits resulted from the syn‐orogeny and post‐orogeny tectonic evolution.

Choice of the Most Appropriate Thermal Treatment in Optical Dating of Quartz

A method of identifying the most appropriate thermal annealing or preheating treatment for optical dating of quartz is proposed. The procedures can also be used in equivalent dose determination using single and multiple aliquot techniques. It is found that optically stimulated luminescence (OSL) from quartz can be either increased or decreased after preheating. An increase in OSL signal is attributed to thermal charge transfer from non-OSL traps into OSL traps or change in OSL sensitivity. This enhancement is dependent on preheating time and temperature. The decay of the OSL signal by heating is mainly from a single type of OSL trap. Implications for quartz optical dating are discussed.

Photoluminescence dating of quartz and feldspars from loess

Photoluminescence dating of quartz and feldspars from loess

Optical dating of quartz with single aliquots: Problems and improvements

Optical dating of quartz with single aliquots: Problems and improvements

Electron spin resonance (ESR) dating

ESR dating has been systematically applied in earth sciences and archaeology since 1975 when Ikeya dated a stalactite from the Akiyoshi cave in Japan. In the meantime this new technique has been successfully applied to the dating of materials such as speleothems, spring deposited travertines, mollusc shells, corals, and tooth enamel. The present research focuses on the dating of quartz which allows the age assessment of heated ceramics, volcanic rocks, intrafault material, or windblown sediments. ESR dating is based on the measurement of the number of paramagnetic centers in a mineral. These centers are generated by alpha-, beta-, and gamma-radiation of the matural radioelements such as U, Th, and K, and have accumulated over time. Two parameters have to be determined: the accumulated dose (AD) and the dose rate ( D) to which the sample was exposed. This review comprises three major parts: (a) introduction into ESR dating; (b) application of the method; and (c) appendices giving detailed description of dose rate calculation, physical basis of electron spin resonance, the ESR spectrometer and ESR lines. The major emphasis lies on the outline of the application of ESR dating. This includes the discussion of the ESR-signals of the various materials, sampling, sample preparation, and measurement techniques.