Showing papers on "Absolute dating published in 2021"

Absolute Age and Temperature Constraints on Deformation Along the Basal Décollement of the Jura Fold-and-Thrust Belt From Carbonate U-Pb Dating and Clumped Isotopes

Abstract: During its late-stage evolution, the European Alpine orogen witnessed a northwest-directed propagation of its deformation front along an evaporitic basal decollement into the foreland. This ...

Towards in situ U–Pb dating of dolomite

Abstract: . Recent U–Pb dating by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has demonstrated that reasonable precision (3 %–10 %, 2 σ ) can be achieved for high-resolution dating of texturally distinct calcite phases. Absolute dating of dolomite, for which biostratigraphy and traditional dating techniques are very limited, remains challenging, although it may resolve many fundamental questions related to the timing of mineral-rock formation by syngenetic, diagenesis, hydrothermal, and epigenetic processes. In this study we explore the possibility of dating dolomitic rocks via recent LA-ICP-MS dating techniques developed for calcite. The in situ U–Pb dating was tested on a range of dolomitic rocks of various origins from the Cambrian to Pliocene age – all of which are from well-constrained stratigraphic sections in Israel. We present imaging and chemical characterization techniques that provide useful information on interpreting the resulting U–Pb ages and discuss the complexity of in situ dolomite dating in terms of textural features that may affect the results. Textural examinations indicate zonation and mixing of different phases at the sub-millimeter scale ( 1 µ m), and thus Tera–Wasserburg ages represent mixed dates of early diagenesis and some later epigenetic dolomitization event(s). We conclude that age mixing at the sub-millimeter scale is a major challenge in dolomite dating that needs to be further studied and note the importance of matrix-matched standards for reducing uncertainties of the dated material.

Dating folding beyond folding, from layer-parallel shortening to fold tightening, using mesostructures: lessons from the Apennines, Pyrenees, and Rocky Mountains

Abstract: . Dating syntectonic sedimentary sequences is often seen as the unique way to constrain the initiation, duration, and rate of folding as well as the sequence of deformation in the shallow crust. Beyond fold growth, however, deformation mesostructures accommodate the internal strain of pre-folding strata before, during, and after strata tilting. Absolute dating of syn-folding mesostructures may help constrain the duration of fold growth in the absence of preserved growth strata. Absolute dating of mesostructures related to early-folding layer-parallel shortening and late fold tightening provides an access to the timing and duration of the entire folding event. We compile available ages from the literature and provide new U–Pb ages of calcite cements from veins and faults from four folds (Apennines, Pyrenees, Rocky Mountains). Our results not only better constrain the timing of fold growth but also reveal a contraction preceding and following folding, the duration of which might be a function of the tectonic style and regional sequence of deformation. This study paves the way for a better appraisal of folding lifetime and processes and stress evolution in folded domains.

Direct dating of lithic surface artifacts using luminescence

Abstract: Archaeological surface assemblages composed of lithic scatters comprise a large proportion of the archaeological record. Dating such surface artifacts has remained inherently difficult owing to the dynamic nature of Earth-surface processes affecting these assemblages and because no satisfactory chronometric dating technique exists that can be directly applied to constrain the timing of artifact manufacture, discard, and thus human use of the landscape. Here, we present a dating approach based on optically stimulated luminescence (OSL)—OSL rock-surface burial dating—and apply it to a lithic surface scatter in Tibet. We generate OSL burial ages (age-depth profiles) for each artifact, outline the methodological complexities, and consider the artifact burial ages in the context of local-scale Earth-surface dynamics. The oldest age cluster between 5.2 and 5.5 thousand years is likely related to quarrying activities at the site and thus represents the oldest chronometric age constraints for human presence on the south-central Tibetan plateau.

Radiocarbon Dating of Marine Samples: Methodological Aspects, Applications and Case Studies

Abstract: Radiocarbon dating by AMS (Accelerator Mass Spectrometry) is a well-established absolute dating technique widely used in different areas of research for the analysis of a wide range of organic materials. Precision levels of the order of 0.2–0.3% in the measured age are nowadays achieved while several international intercomparison exercises have shown the high degree of reproducibility of the results. This paper discusses the applications of 14C dating related to the analysis of samples up-taking carbon from marine carbon pools such as the sea and the oceans. For this kind of samples relevant methodological issues have to be properly addressed in order to correctly interpret 14C data and then obtain reliable chronological frameworks. These issues are mainly related to the so-called “marine reservoirs effects” which make radiocarbon ages obtained on marine organisms apparently older than coeval organisms fixing carbon directly from the atmosphere. We present the strategies used to correct for these effects also referring to the last internationally accepted and recently released calibration curve. Applications will be also reviewed discussing case studies such as the analysis of marine biogenic speleothems and for applications in sea level studies.

Pleistocene terracing phases in the metropolitan area of Bari - AAR dating and deduced uplift rates of the Apulian Foreland

Abstract: We performed detailed geological and geomorphological analyses on a series of marine terraces located around the city of Bari (southern Italy). Absolute dating was obtained by applying amino acid racemisation (AAR) to ostracod valves taken from deposits lying on marine terraces. The combination of literature data, field geological surveys, digital terrain model analysis, and absolute dating allowed us to recognise and map: i) four terrace surfaces bordered by four inner edges which date to MIS 7.5, 7.3, 7.1, and 5.5; and ii) three terraced deposits, which date to MIS 7.5, 7.1, and 5.5. These new data represent the first dated terraced deposits (older than MIS 5) of the coastal stretch of the Apulian foreland between Trani and Taranto. Using inner edges of the terraces as palaeo sea level markers, we calculate the mean uplift rates that characterised this portion of the Apulian foreland from MIS 7.5, 7.3, 7.1, 5.5 to the present day; these rates are 0.28, 0.255, 0.15 and 0.01 mm/y, respectively. These new dated Pleistocene terraced deposits allow to refine the knowledge on the chronology, the spatial extension and rate of the uplift and, in general, on the Pleistocene geodynamics of the Apulian foreland.

Radiocarbon dating of pre-columbian peruvian funerary bundles of the chancay culture

Abstract: The article presents the results of the absolute dating of 31 pre-Columbian funerary bundles excavated on the Cerro Colorado site located in the northern part of the Peruvian Central Coast, where the Chancay culture developed in the last centuries before the Spanish invasion. The typical custom in this region was to wrap the dead with textiles and a vegetal material, by which the bundle was created. The funerary bundles of the Cerro Colorado differed in terms of the complexity, quantity and quality of the materials used (especially textiles and metal ornament). Before our project, there was not a single radiocarbon (14C) date for an undisturbed Chancay tomb, which made it impossible to understand the temporal dependency between the elaborated, standard, and modest bundles. Our results finally shed light on their proper chronological position, also demonstrating that the most elaborate bundles were created between the 13th and 15th centuries.

Paleoceanology of the Sea of Azov in the Holocene (Based on Geological Survey Data and Investigation of Malacofauna on the Dolgaya Spit)

Abstract: The article presents the results of investigations conducted by members of SSC RAS on the Dolgaya Spit in 2019–2020. The following types of data are analyzed: satellite imagery, coastal current measurements, borehole drilling, malacofauna research, and absolute age determinations of coastal sediments. In accordance with the extension of ancient longshore bars and the sequence of their connection to each other, six geomorphological generations are distinguished, reflecting the course of the Nymphaean and, partly, earlier transgressions. The radiocarbon dating data on mollusk shells suggests that the main part of the accumulative body of the spit was formed over 1 ka, in the interval of 2.5–1.5 ka ago. Based on field observations, it was concluded that the current velocities at the western coast of the spit are two to three times higher than at the eastern coast. A list of about 20 species and supraspecific taxa of shellfish from the coastal sediments of the Dolgaya Spit is presented. It is noted that the bulk (more than 90%) of shell sediments making up the longshore bars are valves of Cerastoderma glaucum shells.

Combination of a Green and a Traditional Method for Estimating Relative and Absolute Ink Age: A Case Study of Ballpoint Pen Ink Dating in Vietnam.

Abstract: The dating of ink in questioned documents remains a significant challenge in forensic investigations in Vietnam and other countries. Many forensic examination methods have been usually applied to ensure the highest accuracy of the assessment results while maintaining high environment awareness. In this study, paper characteristics were physically tested to confirm source similarity, and the relative ink dating was established by high-performance thin-layer chromatography (HPTLC). Absolute ink dating by solvent and dye identification was performed by Raman spectrometry—a green technique, using a time-dependent degradation model for crystal violet and the comparison between 2-phenoxyethanol peak intensities. We found that the relative dating of the questioned document was 14 ± 3 months lesser than that of the reference samples, i.e., the absolute age of the questioned samples was estimated to be 24 ± 3 months. The combination of the conventional HPTLC method with the dynamic crystal violet degradation Raman model provides promising results for relative and absolute ink dating of ballpoint pens, which can be applied for documents written 1–15 years prior to the time of examination. The combination of the abovementioned methods demonstrated an acceptable error margin, affording highly practical applications in modern forensic science.

New dates of a Northern Italian loess deposit (Monte Orfano, Southern pre-Alps, Brescia)

Abstract: Loess in Northern Italy has been usually considered deposited during the MIS 4-2 period, which corresponds to the last Pleistocene glacial cycle. In particular, no absolute dating evidenced loess depositions older than ca. 89 ka. We investigated two strongly rubified soil profiles in the southern margin of the Alpine range in Lombardy to prove their aeolian origin and age of formation. We analysed the granulometry of all genetic horizons of these strongly rubified soils, and a total of 8 samples were collected for luminescence dating purpose. Most of the analysed soil horizons were dominated by silt and were characterized by the s-shaped granulometric curve, typical of loess materials. A particularly high clay content evidenced a strong weathering degree. A deep horizon was particularly clay rich, and it was interpreted as a typical Terra-Rossa horizon. Luminescence dates increased with depth, reaching 122 ka for the deepest loess layer and 453 ka (minimum age) for the Terra-Rossa horizon. The deepest observed loess layer represents the oldest quantitatively dated aeolian deposition in Northern Italy up to now.

Lunar samples record an impact 4.2 billion years ago that may have formed the Serenitatis Basin

Abstract: Impact cratering on the Moon and the derived size-frequency distribution functions of lunar impact craters are used to determine the ages of unsampled planetary surfaces across the Solar System. Radiometric dating of lunar samples provides an absolute age baseline, however, crater-chronology functions for the Moon remain poorly constrained for ages beyond 3.9 billion years. Here we present U–Pb geochronology of phosphate minerals within shocked lunar norites of a boulder from the Apollo 17 Station 8. These minerals record an older impact event around 4.2 billion years ago, and a younger disturbance at around 0.5 billion years ago. Based on nanoscale observations using atom probe tomography, lunar cratering records, and impact simulations, we ascribe the older event to the formation of the large Serenitatis Basin and the younger possibly to that of the Dawes crater. This suggests the Serenitatis Basin formed unrelated to or in the early stages of a protracted Late Heavy Bombardment. Shocked apatite and merrillite in lunar norites from the Apollo 17 Station 8 record impact events around 4.2 and 0.5 billion years ago, the former of which could represent the formation age of the Serenitatis Basin, according to U-Pb and Pb-Pb dating.

Some problems of the application of the U–Th series and radiocarbon absolute dating techniques to Quaternary fluviolacustrine deposits in the Morsott commune of Algeria

Abstract: Two radioisotopic dating methods are applied to Quaternary fluviolacustrine detritus deposits in the commune of Morsott in northeastern Algeria. The studied profile shows an open and contaminated environment. In the case of the shells of molluscs, the choice of identical samples for both the dating methods is wise. Obtained results are different; thus, positioning the chronology of the Quaternary sequence is difficult. The uranium–thorium (U–Th) series technique gives a younger age than that provided by radiocarbon (14C) in Holocene. For carbonates at the base of the study sequence, the age difference is 278,154 ka BP. In the lowermost level of limestone crusts in the last Pleistocene, 14C gives a younger age than that provided by the U–Th series technique, rendering the chronological order of the levels inconsistent. Despite the corrections of the U–Th series technique and the age calibrations of 14C, this method is recommended for open systems (environments). Contamination related to either post depositional parameters or sample preparation techniques is certain in this type of open environments. In open environment applications, the reliability of the U–Th series or 14C technique changes from the upper to the bottom of the studied series as the function of various external parameters. For this reason, including other techniques is necessary to confirm and understand the chronology of Quaternary.

Radiocarbon dating of a late antique necropolis from felanitx (mallorca, balearic islands)

Abstract: The excavation of a building in the village of Felanitx in the eastern part of the island of Mallorca (Balearic Islands) has revealed the existence of a small necropolis. The inhumations did not provide grave goods except for a bronze belt buckle for which the typological study suggests a Late Antique chronology. The stratigraphical sequence however seems to suggest a possible evolution of the space across time since some graves are cut by others. In order to obtain an absolute date for the necropolis and to verify if there are chronological differences between the graves, a total of 6 human bones samples have been 14C dated by AMS. The results of the radiocarbon dating confirm a Late Antique chronology (4th to 7th century AD) for the graves but do not suggest a chronological evolution. Despite the fact that the knowledge of the necropolis is still fragmentary, the results are extremely important because they provide an absolute date for a Late Antique necropolis in the Mallorcan rural area.

Information theory based Electron Paramagnetic Resonance dating

Abstract: Chronometric dating is becoming increasingly important in areas such as the Origin and evolution of Life on Earth and other planets, Origin and evolution of the Earth and the Solar System... Electron Spin Resonance (ESR) dating is based on exploiting effects of contamination by chemicals or ionizing radiation, on ancient matter through its absorption spectrum and lineshape. Interpreting absorption spectra as probability density functions (pdf), we use the notion of Information Theory (IT) distance allowing us to position the measured lineshape with respect to standard limiting pdf's (Lorentzian and Gaussian). This paves the way to perform dating when several interaction patterns between unpaired spins are present in geologic, planetary, meteorite or asteroid matter namely classical-dipolar (for ancient times) and quantum-exchange-coupled (for recent times). In addition, accurate bounds to age are provided by IT from the evaluation of distances with respect to the Lorentz and Gauss distributions. Dating arbitrary periods of times~\cite{Anderson} and exploiting IT to introduce rigorous and accurate date values might have interesting far reaching implications not only in Geophysics, Geochronology~\cite{Bahain}, Planetary Science but also in Mineralogy, Archaeology, Biology, Anthropology~\cite{Aitken}, Paleoanthropology~\cite{Taylor,Richter}...