Chronometric Methods Research Articles

Estimating extinction time using radiocarbon dates

The extinction of a species is a key demographic event often signalling major climatic, ecological and/or evolutionary shifts that can be investigated using the fossil record. In that context, radiocarbon (14C) dating has become a popular tool to time and test for scenarios of extinction that can inform on how species respond to past and future ecosystem changes. We develop CRIWM, a method for estimating extinction (and arrival) time from time series of 14C dates while accounting for probability density functions (PDF) deriving from 14C calibration. The sister method GRIWM assumes normal chronometric errors and is inappropriate for 14C chronologies as PDFs are often non-Gaussian and multi-modal. Compared to GRIWM, CRIWM reduces by 4-fold the gap between true and estimated extinction times and the width of the confidence intervals, and is less sensitive to sample size, dating errors and the temporal distribution of specimens in a species’ fossil record. We build the R package Rextinct with three user-friendly functions for computing CRIWM and GRIWM, and the PDF moments, modes and intercepts of 14C calibrations. CRIWM and GRIWM accept time series comprising only 14C dates or observations (fossils, sightings) dated by multiple chronometric methods, and calibration curves for fossils sampled in the Northern and Southern Hemispheres and marine environments. For both methods, we implement two different estimators of extinction time whether they are reliant on a p-value (original conceptualization) or not (novel). CRIWM and Rextinct are robust tools to time extinction and arrival events using 14C chronologies spanning the entire Holocene to 50,000 calendar years Before Present, and can be used to investigate demographic phenomena queried through the fossil record such as migrations, domestications and extirpations.

New Tsallis holographic dark energy with apparent horizon as IR-cutoff in non-flat Universe

In this work, new Tsallis holographic dark energy with apparent horizon as IR-cutoff is constructed in a non-flat Friedmann–Lemaitre–Robertson–Walker Universe. The accelerating expansion phase of the Universe is described by using deceleration parameter, equation of state parameter and density parameter by using different values of new Tsallis holographic dark energy (NTHDE) parameter “[Formula: see text]”. The NTHDE Universe’s transition from a decelerated to an accelerated expanding phase is described by the smooth graph of deceleration parameter. Depending on distinct values of Tsallis parameter “[Formula: see text]”, we have explored the quintessence behavior of the equation of state parameter. We used Hubble data sets obtained using Cosmic Chronometric methods and distance modulus measurement of Type Ia Supernova to fit the NTHDE parameters. Stability of our model by analyzing the squared speed of sound is investigated as well.

Timing, rates and geomorphic controls on holocene loess and aeolian sand deposition using multiple chronometric methods, southeastern Cordillera, Alberta, Canada

Glacier-fed river systems represent potentially significant sediment sources for aeolian processes owing to sediment production, flow seasonality, and winds within mountain settings. We investigate the timing and rates of Holocene loess and aeolian sand deposition in three major river valleys (Bow, North Saskatchewan and Athabasca) of the southeastern Canadian Cordillera through aeolian stratigraphy and dating of sedimentary materials. Source sediments are glacially-derived, seasonally-exposed alluvial deposits. Variation in river morphology promotes source-sediment deposition influenced by bedrock configuration, tributary stream deposition and alluvial fans. Two main settings for aeolian deposition are source-proximal valley-bottom sites and more distal lower-valley sites in sub-alpine and montane forest ecozones. Dating is well-constrained by radiocarbon ages and tephrochronology. Quartz optical dating is complicated, likely owing to minimal recycling of grains and quartz provenance. Mass accumulation rates (MARs) indicate that aeolian deposition was initiated soon after deglaciation and has occurred nearly continuously for at least 10000 years. Loess MARs ranged between 100 and 2500 g·m−2·a−1 during the Holocene. Rates in the last 3000 years are generally two to three times higher than those observed for earlier periods, and are highest in most recent times. We attribute Holocene accumulation at these sites in general to fluvial source sediment availability and the efficacy of forested valleys as sediment traps. The late Holocene increase in MARs is primarily attributed to increased glacial silt and alluvial sediment supply during neoglacial fluctuations including the Little Ice Age.

MAR comparisons between different chronometric methods for two profiles in the Bodrogkeresztúr area

The deepening and exploration of the loess-palaeosol section at the foot of the Kopasz Hill at Bodrogkeresztúr have been carried out to expand the existing knowledge of the Carpathian foothill palaeoenvironmental factors and their impact. The study deals with particle size analysis, organic matter and carbonate content. For the presentation of age-depth models, the OSL dates of Bodrogkeresztúr (BKT) and the 14C dates of Bodrogkeresztúr, brickyard 1 were used-, and the diagrams of the Accumulation Rates (AR) derived from them. These were compared with Mass Accumulation Rate (MAR) calculations based on OSL and 14C data from BKT and 14C data from Bodrogkeresztúr, brickyard 1. It became evident that there is a significant difference between the two sections, which may be due to the upland position, the overlap, or the wind tunnel effect. Sedimentological studies revealed coarser grain composition, however, the nearly complete absence of coarser sand fraction is also noticeable in the case of BKT. Also, the entire section is characterized by increased carbonate content due to post-sedimentation processes, recarbonization and leaching. The AR and MAR results show the difference between the suitability of different chronometric methods, indicating that the top of both sections may have been redeposited or eroded.

Evaluation of the altitude impact on a point-of-care thromboelastography analyzer measurement: prerequisites for use in airborne medical evacuation courses.

Hemorrhagic shock is the first cause of preventable death in combat. Evacuations of wounded by aircraft are increasingly used and severely injured patients can spend consequent time in the air, mostly during strategic evacuation. In these situations, monitoring of blood coagulation may be pivotal in the management of blood product transfusion. Viscoelastic-guided transfusion is relevant in these situations. However, evaluation of these devices used in aircraft is lacking, especially the impact of decreased atmospheric pressure. The aim of this study is to evaluate the performance of an easy-to-carry viscoelastic system (TEG® 6s, Haemonetics). First, TEG® 6s repeatability, reproducibility, and correlation with chronometric methods and TEG-5000 were assessed on quality controls, healthy volunteers, and patients. Secondly, we tested the influence of vibrations and altitude on TEG® 6s parameters (0ft vs. 8000 ft = 2428m) and on quality control samples (normal and hypocoagulable). TEG® 6s exhibited good correlation with the reference method and TEG® 5000. Repeatability and reproducibility CVs were satisfactory. The tests performed in the hypobaric chamber revealed that performance at 0 ft and 8000 ft (2428m) for 9 out of 13 parameters was not significantly different. However, we showed a significant increasing of CRT.Alpha (p = 0.049), CK.Alpha, CK.MA (p < 0.001 and p < 0.01, respectively) and CFF.MA increased (p < 0.05). Our study provides proof of concept to validate testing in an actual aeromedical situation. Indeed, TEG® 6s appears to ease of use, resistance to high altitude conditions, and reliability on healthy humans. It is necessary to carry out a study on hemorrhagic injured patients in an aircraft.

Unraveling rock art palimpsests through superimpositions: The definition of painting episodes in Los Toldos (southern Patagonia) as a baseline for chronology

This paper aims to link the production of rock paintings in Los Toldos (Argentina) to the human use of the locality in the context of the long term process of the peopling of Patagonia. The study is centered in the construction of a rock art painting sequence from the analysis of superimpositions in Cueva 2 and Cueva 3 sites. Rock art panels were considered as cumulative palimpsests and analyzed through the use of a Harris matrix. Eight painting episodes could be distinguished in Cueva 2, which were related to five painting episodes detected in Cueva 3. The temporal relationships of the different painting episodes respect to a series of natural imprints in the rock supports provided elements for the hypothetical estimation of a coarse grained temporal framework. The first painting episode is underrepresented due to its state of preservation and position in the base of the sequence. Together with the second episode, it is associated to the earliest human occupations of the Pleistocene/Holocene transition. The third, fourth and fifth painting episodes are the most intense and relate to the most intensive human occupations of the middle Holocene. The late Holocene episodes are represented by fewer diverse motifs in Cueva 2. The results of our analysis constitute the baseline from which future compositional analyses need to be performed in order to evaluate the possibility of dating rock art by chronometric methods.

The U/Th production ratio from extended independent model

The Meyer and Schramm (M&S) independent model formalism is developed to determine the production ratio of actinide chronometers in the nucleosynthesis era of the Galaxy formation. The production ratio of U/Th is calculated, considering the non-radioactive mass reduction rate of chronometers together with a new production of r-process nuclides over the time interval between the last r-process event and the solidification of meteorites. In the first approach, we considered two extra terms rather than M&S formalism, and the average U/Th production ratio over the duration of nucleosynthesis in stars and supernovas was measured to be $$ 0.5378 \pm_{0.0005}^{0.0006} $$ and $$ 0.5942_{ - 0.0474}^{ + 0.0491} $$. Considering only one extra term rather than M&S original model led to the average production ratio of $$ 0.5603 \pm 0.0007 $$ and $$ 0.5994 \pm_{0.0472}^{0.0487} $$. The calculated results from both approaches are compatible with those of used stellar models and chronometric methods. The advantages of our extended model are in precise determining of actinides production ratios and evaluating a narrow down range for the Galaxy age rather than M&S formalism.

Dynamic Calibration of Automatic Leak-Detection Instruments

Dynamic methods of calibrating automatic leak detectors and manometric monitoring instruments are considered. Attention focuses on chronometric and reduction methods of calibration, which are based on gas emission under pressure through active resistances, employing the frequency principle. High precision is ensured in that the results are independent of the temperature, the humidity, and the gas parameters. Calibration facilitates utilization of the instruments in mass production.

Loess correlations – Between myth and reality

The correlation of loess sequences across global, hemispheric, regional and local scales is one of the most fundamental aspects to loess research. However, despite recent progress in stratigraphic and chronometric methods, the correlation of many loess sequences is often still based on untested assumptions over loess deposition, preservation, soil type and age. As such, the aim of this overview is to provide an adequate framework for evaluation of the accuracy of loess correlations applied on different temporal and spatial scales across Eurasia. This opens up possibilities for detailed temporal and spatial environmental reconstructions across the huge loess provinces of the Eurasia and provides a framework for future extension of this to North America. Additionally, we evaluate the potential development of appropriate sub-millennial scale loess correlations, as well as essentially important chronological approaches for establishing valid correlations between different loess records, such as current improvements in tephrochronology, 14C and luminescence dating techniques.

Nuclear Forensic Science: Analysis of Nuclear Material Out of Regulatory Control

Nuclear forensic science seeks to identify the origin of nuclear materials found outside regulatory control. It is increasingly recognized as an integral part of a robust nuclear security program. This review highlights areas of active, evolving research in nuclear forensics, with a focus on analytical techniques commonly employed in Earth and planetary sciences. Applications of nuclear forensics to uranium ore concentrates (UOCs) are discussed first. UOCs have become an attractive target for nuclear forensic researchers because of the richness in impurities compared to materials produced later in the fuel cycle. The development of chronometric methods for age dating nuclear materials is then discussed, with an emphasis on improvements in accuracy that have been gained from measurements of multiple radioisotopic systems. Finally, papers that report on casework are reviewed, to provide a window into current scientific practice.

Middle Stone Age reduction strategies at the desert's edge: A multi-site comparison across the Gebel Akhdar of northeast Libya

Haua Fteah cave, situated between the Mediterranean coast and the Gebel Akhdar of northeast Libya, preserves rich Middle Stone Age (MSA) and Late Stone Age (LSA) cultural horizons. Excavated in the 1950s and more recently, the richness and time-depth of the cave's archaeological record are unsurpassed by any other site in northern Cyrenaica. As a result, the Haua Fteah sequence has long been used to represent the culture history of the region as a whole. Recent geoarchaeological surveys of the Gebel Akhdar, as well as pre-desert and desert biomes further to the south, have resulted in the discovery of numerous MSA and LSA sites. The vast majority of these sites consist of surface lithics that cannot be dated currently. In contrast, parts of the Haua Fteah sequence have been dated using various chronometric methods. Using data collected through lithic attribute analysis, coupled with various statistical approaches (including Discriminant Function Analysis, or DFA), this paper explores variation in core reduction strategies within Haua Fteah from the early MSA to early LSA. Collections of cores from various sites located throughout the landscape are contrasted against those from Haua Fteah. By comparing undated cores from the landscape with those from different occupation phases at Haua Fteah, DFA classification is tested as a method for imparting an approximate chronology to the former. The results indicate notable variation in reduction strategies within the MSA at Haua Fteah, and notable similarities between early MSA (“Pre-Aurignacian”) and early LSA (“early Dabban”) core morphologies and technologies. Because of the latter in particular, together with several other factors that may be underpinning spatio-temporal variability in core reduction strategies, caution is recommended in loosely assigning approximate chronologies to surface lithic sites.

Thermoluminescent dating of the Late Bronze and Early Iron Age pottery on sites in Kłyżów and Jarosław (SE Poland)

Abstract The absolute chronology of Late Bronze and Early Iron Ages in Polish territories is a result of long-term and complex research. Here, we have investigated the absolute dating of two sites, namely Kłyżów, a cemetery of the Tarnobrzeg Lusatian culture, and Jarosław, a settlement spanning from the late phase of the former to Pomeranian culture, possibly with Jastorf elements. Having been spurred by promising results of thermoluminescence (TL) dating of medieval and Przeworsk materials, we have employed it in those situations, where no other chronometric methods seem to be efficient. TL dating has been combined with typological analysis of the dated pottery and, partially, with radiocarbon method. Albeit the produced TL dates do not represent the level of sought-for fine chronological resolution, they indicate the temporal trends and corroborate the typological research. Our study has shown the potential of TL dating for periods with plateaus on 14C calibration curve. We also have dealt with unexpected TL ages and suggested some solutions of the problem. Finally, we have demonstrated that the condition sine qua non for archaeological interpretation of TL dates is a thorough stylistic-chronological analysis of dated pottery and clear understanding of relations between chronometric dates and the archaeological event to be dated.

Geomagnetic field variations in Western Europe from 1500BC to 200AD. Part I: Directional secular variation curve

To improve the geomagnetic field secular variation curve (SVC) of Western Europe during protohistoric times, archaeomagnetic directions of 39 archaeological kilns or hearths from France were investigated. The dating of each archaeological structure was established with archaeological or chronometric methods. Thirty-seven of these structures are dated from the first millennium BC, one from the end of the second millennium BC and the last one from the fourth millennium BC. Thermomagnetic curves, unblocking temperatures and coercivities suggest that the main carrier of the remanent magnetization is a Ti-poor titanomagnetite. Archaeodirections were obtained by alternating field and thermal demagnetizations on almost 900 specimens. The anisotropy tensor of thermoremanent magnetization was determined for 35 structures and 22 mean archaeodirections were corrected for anisotropy. The new archaeodirections are very consistent with previously published data. A new directional SVC was built using bivariate statistics with selected Western Europe data located within 1000km of Paris. Selection criteria include the number of samples, the dating reliability and the accuracy of the mean archaeodirection. Resulting secular variation between 1500BC and 0AD mainly shows large changes in declination, while inclinations are bracketed between ∼65° and ∼75°. The declinations show a strong maximum with values ∼30–35° around 800–750BC, followed by a sharp decrease to values around 0° at 500BC and close to −7° around 250BC. The main features of the secular variation from 1500BC to 0AD appear to be a dominant westward drift and two major changes around 800 and 250BC. Compared to the global and regional geomagnetic models, the new reference data are better fitted by ARCH3k_cst.1 and SCHA.DIF.3k than by ARCH3k.1 and CALS3k.4 models. The strong variation of the archaeodirection between 1000 and 500BC makes archaeomagnetism very useful for dating purposes.

Evidence for the Preservation of Technogenic Tritiated Organic Compounds in an Estuarine Sedimentary Environment

The macrotidal Severn Estuary (southwestern UK) has received a broad range of industrial discharges since the beginning of the Industrial Revolution. A more recent anthropogenic input to the estuary has been technogenic tritium (specifically organically bound tritium, OBT). This was derived from a specialized industrial laboratory producing custom radiolabeled compounds for life science research and diagnostic testing from 1980 until 2008. While it was generally acknowledged that the radiological impact of the tritium discharges into the Estuary was small, public concern motivated the company and regulatory agencies to commission several research studies from 1998 to 2005 to better understand their environmental impact. This study examined OBT interaction with estuarine sediment by acquiring a broad range of geochemical and sedimentological data from a suite of sediment cores collected from the northern side of the Estuary. Two important observations are that the OBT compounds are strongly bound to the clay/silt fraction of sediment and that the down-core OBT profiles in intertidal and subtidal sediments are broadly similar to the discharge record. Geochemical and chronometric methods (Cu, Pb and Zn elemental profiles, (210)Pb, (137)Cs) provide important corroboration of the OBT record. A key additional piece of evidence that firmly authenticated the established chronology was the discovery of a previously unreported sedimentary marker layer that was generated by a major storm surge that occurred on December 13, 1981. Although this study has provided clear evidence of systematic accumulation of OBT in sedimentary sinks of the region, an estimation of its depositional inventory shows it represents only a small fraction of the total discharge. This modest retention in the principal sedimentary sinks of the Severn Estuary system reflects the particular dynamics of this highly macrotidal sediment starved estuary.

Chronology of the Obi-Rakhmat Grotto (Uzbekistan): First Results on the Dating and Problems of the Paleolithic Key Site in Central Asia

The Obi-Rakhmat Grotto is one of the key Paleolithic sites in Central Asia. Archaeological excavations have revealed 22 strata containing archaeological materials. Lithic assemblages from all cultural layers display features similar to both late Middle Paleolithic blade industries and early Upper Paleolithic complexes in Southwest Asia and the Siberian Altai Mountains; this suggests a gradual Middle-to-Upper Paleolithic transition occurred in western Central Asia. Hominid remains found at Obi-Rakhmat (layer 16) show a mixture of archaic and modern traits. Different chronometric methods (radiocarbon, optically stimulated luminescence [OSL], U-series, and electron spin resonance [ESR]) were applied to the site's deposits. It appears that 14C dates are more reliable in terms of correspondence to the general framework of the Paleolithic of Central Asia and neighboring regions, and after critical analysis and the deletion of outliers, the upper part of the site's cultural sequence can be dated between 36,000–41,400 BP (layer 7) and ∼48,800 BP (layer 14.1). The U-series dating results are less secure due to the high uranium content and the presence of detritus, which contaminates dated sediments (travertine). The OSL dating gave uniform ages for all cultural succession (∼8 m of deposits), and confirms a very rapid sedimentation rate. Results of ESR dating depend greatly on the choice of uptake model. Dates calculated for the early uptake to some extent correspond to 14C data. The linear uptake chosen by Skinner et al. (2007) makes sediments very old (about 55,000–90,000 yr ago), which contradicts 14C dates and does not correspond well to the regional archaeological context.

Pointing to numbers and grasping magnitudes

The cognitive representation of numbers has been studied with chronometric methods but these cannot resolve the current debate about the metrical structure of the "mental number line". We recorded spatial behaviour as blindfolded adults described the locations of numbers (e.g., "where is 3?") by pointing and the lengths of magnitudes (e.g., "how much is 56?") by gesturing. Their unconstrained spatial behaviour revealed idiosyncratic spatial associations for numbers and largely supports a linear representation of magnitudes.

Radiocarbon Dating of Architectural Mortar: A Case Study in the Maya Region, Quintana Roo, Mexico

The use of radiocarbon dating to analyze mortar and charcoal inclusions within mortar or plaster is a useful way to date the construction of architecture, particularly when options for other chronometric methods are limited. In the Yalahau region of northern Quintana Roo, Mexico, members of the Yalahau Regional Human Ecology Project have faced challenges in dating buildings made of large blocks of stone in the Megalithic architectural style. The Megalithic style poses serious problems for any analysis, as excavating into structures with stones weighing several tons can be dangerous, expensive, and time consuming. Additionally, there are no associated sculptures, texts with dates, or other traditionally accessible chronological markers. These factors have resulted in a reliance on a ceramic chronology despite the uncertainty of the dating of many ceramic types in this region, as well as the questionable contextual associations between recovered ceramics and architectural construction phases. Megalithic-style structures at the ancient Maya site of El Naranjal have residual mortar with charcoal inclusions left behind during the mortar-making processes that can be extracted and dated with AMS 14C methods. Several samples of mortar and charcoal were obtained from structures 1 and 10 from exposed exterior walls and an interior vault. The resulting dates confirm the date for the construction based on ceramics excavated from the same site.

Stratigraphic relations of australites in the Port Campbell Embayment, Victoria

Abstract— In the Port Campbell Embayment of Victoria, australites have been found in situ in channel deposits of the Hanson Plain Sand of Pliocene and Pleistocene age. The large majority of the australites, however, occur as a lag deposit at the basal contact of the Sturgess Sand of late Pleistocene and Holocene age and are spatially correlated with ferruginous sandstone clasts that are derived from the Hanson Plain Sand. Some of the tektites are imbedded in or bonded to the ferruginous sandstone clasts, but most are found as individual tektite fragments. A few percent of the tektites have nearly perfectly preserved, complete aerodynamically shaped forms. The sandstone clasts and associated tektites have been reworked from the much older underlying Hanson Plain and have been locally concentrated in the lag deposit. Some tektites also occur at higher levels in the Sturgess Sand, almost invariably in association with stone flakes, exotic stones transported by the aborigines and, locally, with middens of mollusc shells. Circumstantial evidence indicates that the aborigines transported the tektites found in the upper part of the Sturgess, particularly at Stanhope Bay. As Port Campbell australites unequivocally occur in strata much older than the late Pleistocene and Holocene Sturgess, there is no longer any conflict between the apparent stratigraphic age of the tektites and the middle Pleistocene ages obtained by various chronometric methods.

Interview with Michael I. Posner

Michael Posner has been professor of psychology at the University of Oregon since 1965. His work has generally been in the area of selective attention. During the 1960s and 1970s, Posner's work relied primarily on chronometric methods and is best described in his Paul Fitts lectures published as Chronometric Explorations of Mind. From 1979 to 1985 Posner directed a laboratory at Good Samaritan Hospital and worked on the role of the parietal lobe and other structures involved in visual orienting. From 1985 to 1988 Posner directed a neuropsychology laboratory in St. Louis where he worked with Marc Raichle and Steve Petersen in developing PET methods appropriate to cognitive studies (see Images of Mind with M. Raichle). Since 1988, Posner has been working on combined spatial and temporal studies exploring the plasticity of human attention and skill acquisition. Posner's work has been recognized by membership in the U.S. National Academy of Sciences, APAs Distinguished Scientific Contribution Award and William James book award (with M. Raichle), and by the Vollum award for outstanding contribution to science and technology in the pacific northwest.

NEW PERSPECTIVES ON COLLUVIAL BOULDER DEPOSITS IN THE SOUTHWESTERN GREAT BASIN, USA

Colluvial boulder fields are ubiquitous on desert hillslopes in the Basin and Range Province. Five chronometric methods indicate that colluvial boulder fields in this region have been active in the late Pleistocene and Holocene: visual appearance, radiocarbon dating of wood, macrofossil analysis, varnish radiocarbon dating, and varnish cation ratio dating. A new method is presented to constrain the ages of colluvial boulder fields, using the presence of stable rock varnish and 36Cl; this method indicates that colluvial deposits at Buckhorn Mesa, southern Nevada, must be ≤ 310 ka. Rather than interpreting colluvial deposits from the traditional desert geomorphology framework of “relict” or “active,” we suggest that these features be studied from the perspective of ongoing processes using an independently established chronometic sequence.