Interpreting and reporting ⁴⁰Ar/³⁹Ar geochronologic data

The ⁴⁰Ar/³⁹Ar dating method is among the most versatile of geochronometers, having the potential to date a broad variety of K-bearing materials spanning from the time of Earth’s formation into the historical realm. Measurements using modern noble-gas mass spectrometers are now producing ⁴⁰Ar/³⁹Ar dates with analytical uncertainties of ∼0.1%, thereby providing precise time constraints for a wide range of geologic and extraterrestrial processes. Analyses of increasingly smaller subsamples have revealed age dispersion in many materials, including some minerals used as neutron fluence monitors. Accordingly, interpretive strategies are evolving to address observed dispersion in dates from a single sample. Moreover, inferring a geologically meaningful “age” from a measured “date” or set of dates is dependent on the geological problem being addressed and the salient assumptions associated with each set of data. We highlight requirements for collateral information that will better constrain the interpretation of ⁴⁰Ar/³⁹Ar data sets, including those associated with single-crystal fusion analyses, incremental heating experiments, and in situ analyses of microsampled domains. To ensure the utility and viability of published results, we emphasize previous recommendations for reporting ⁴⁰Ar/³⁹Ar data and the related essential metadata, with the amendment that data conform to evolving standards of being findable, accessible, interoperable, and reusable (FAIR) by both humans and computers. Our examples provide guidance for the presentation and interpretation of ⁴⁰Ar/³⁹Ar dates to maximize their interdisciplinary usage, reproducibility, and longevity

RNase L Mediated Protection from Virus Induced Demyelination

IFN-α/β plays a critical role in limiting viral spread, restricting viral tropism and protecting mice from neurotropic coronavirus infection. However, the IFN-α/β dependent mechanisms underlying innate anti-viral functions within the CNS are poorly understood. The role of RNase L in viral encephalomyelitis was explored based on its functions in inhibiting translation, inducing apoptosis, and propagating the IFN-α/β pathway through RNA degradation intermediates. Infection of RNase L deficient (RL−/−) mice with a sub-lethal, demyelinating mouse hepatitis virus variant revealed that the majority of mice succumbed to infection by day 12 p.i. However, RNase L deficiency did not affect overall control of infectious virus, or diminish IFN-α/β expression in the CNS. Furthermore, increased morbidity and mortality could not be attributed to altered proinflammatory signals or composition of cells infiltrating the CNS. The unique phenotype of infected RL−/− mice was rather manifested in earlier onset and increased severity of demyelination and axonal damage in brain stem and spinal cord without evidence for enhanced neuronal infection. Increased tissue damage coincided with sustained brain stem infection, foci of microglia infection in grey matter, and increased apoptotic cells. These data demonstrate a novel protective role for RNase L in viral induced CNS encephalomyelitis, which is not reflected in overall viral control or propagation of IFN-α/β mediated signals. Protective function is rather associated with cell type specific and regional restriction of viral replication in grey matter and ameliorated neurodegeneration and demyelination

The Age of the 20 Meter Solo River Terrace, Java, Indonesia and the Survival of Homo erectus in Asia

Homo erectus was the first human lineage to disperse widely throughout the Old World, the only hominin in Asia through much of the Pleistocene, and was likely ancestral to H. sapiens. The demise of this taxon remains obscure because of uncertainties regarding the geological age of its youngest populations. In 1996, some of us co-published electron spin resonance (ESR) and uranium series (U-series) results indicating an age as young as 35–50 ka for the late H. erectus sites of Ngandong and Sambungmacan and the faunal site of Jigar (Indonesia). If correct, these ages favor an African origin for recent humans who would overlap with H. erectus in time and space. Here, we report 40Ar/39Ar incremental heating analyses and new ESR/U-series age estimates from the “20 m terrace" at Ngandong and Jigar. Both data sets are internally consistent and provide no evidence for reworking, yet they are inconsistent with one another. The 40Ar/39Ar analyses give an average age of 546±12 ka (sd±5 se) for both sites, the first reliable radiometric indications of a middle Pleistocene component for the terrace. Given the technical accuracy and consistency of the analyses, the argon ages represent either the actual age or the maximum age for the terrace and are significantly older than previous estimates. Most of the ESR/U-series results are older as well, but the oldest that meets all modeling criteria is 143 ka+20/−17. Most samples indicated leaching of uranium and likely represent either the actual or the minimum age of the terrace. Given known sources of error, the U-series results could be consistent with a middle Pleistocene age. However, the ESR and 40Ar/39Ar ages preclude one another. Regardless, the age of the sites and hominins is at least bracketed between these estimates and is older than currently accepted

The role of inflammation in epilepsy.

Epilepsy is the third most common chronic brain disorder, and is characterized by an enduring predisposition to generate seizures. Despite progress in pharmacological and surgical treatments of epilepsy, relatively little is known about the processes leading to the generation of individual seizures, and about the mechanisms whereby a healthy brain is rendered epileptic. These gaps in our knowledge hamper the development of better preventive treatments and cures for the approximately 30% of epilepsy cases that prove resistant to current therapies. Here, we focus on the rapidly growing body of evidence that supports the involvement of inflammatory mediators-released by brain cells and peripheral immune cells-in both the origin of individual seizures and the epileptogenic process. We first describe aspects of brain inflammation and immunity, before exploring the evidence from clinical and experimental studies for a relationship between inflammation and epilepsy. Subsequently, we discuss how seizures cause inflammation, and whether such inflammation, in turn, influences the occurrence and severity of seizures, and seizure-related neuronal death. Further insight into the complex role of inflammation in the generation and exacerbation of epilepsy should yield new molecular targets for the design of antiepileptic drugs, which might not only inhibit the symptoms of this disorder, but also prevent or abrogate disease pathogenesis

Syndromics: A Bioinformatics Approach for Neurotrauma Research

Substantial scientific progress has been made in the past 50 years in delineating many of the biological mechanisms involved in the primary and secondary injuries following trauma to the spinal cord and brain. These advances have highlighted numerous potential therapeutic approaches that may help restore function after injury. Despite these advances, bench-to-bedside translation has remained elusive. Translational testing of novel therapies requires standardized measures of function for comparison across different laboratories, paradigms, and species. Although numerous functional assessments have been developed in animal models, it remains unclear how to best integrate this information to describe the complete translational “syndrome” produced by neurotrauma. The present paper describes a multivariate statistical framework for integrating diverse neurotrauma data and reviews the few papers to date that have taken an information-intensive approach for basic neurotrauma research. We argue that these papers can be described as the seminal works of a new field that we call “syndromics”, which aim to apply informatics tools to disease models to characterize the full set of mechanistic inter-relationships from multi-scale data. In the future, centralized databases of raw neurotrauma data will enable better syndromic approaches and aid future translational research, leading to more efficient testing regimens and more clinically relevant findings

Toward a high-resolution 40Ar/39Ar geochronology of the Tatun Volcano Group, Taiwan

Section: Volcanology, Geochemistry, PetrologySession: EARTHTIME Geochronology II Posters: abstract V31A-2306The Tatun Volcano Group [TVG] consists of five volcanic subgroups of which 30 edifices have been identified, all in close proximity to the densely populated Taipei Basin to its south (Song et al., 2000, Journal of the Geological Society of China, in Chinese). Evidence of eruptions is in the form of mostly lava flows, with pyroclastic flows, and ash deposition (Tsai et al., 2010, TAO), consistent with vulcanian and plinian eruptions that are only minimally preserved because of the region’s high weathering rate (Belousov et al., 2010, Journal of Volcanology and Geothermal Research). The TVG is made up of calc...link_to_OA_fulltex

Inter-monitor standard calibration and tests for Ar-Ar biases

Section: Volcanology, Geochemistry, PetrologySession: EARTHTIME Geochronology I: abstract V23C-02A major issue facing the geochronology community is that there are biases between chronometers that have become significant as we interrogate the rock record with ever increasing levels of precision. Despite much progress there are still major issues with building a timescale with multiple chronometers and for testing synchroneity of anomalous events in Earth history. Improvements in methods for determining U-Pb zircon dates has led to their application at precisions of 0.2% or better in rocks even younger than a million years (e.g., Crowley et al., 2007, Geology), and significantly better than 0.1% in some cases (e.g., Bowring et al., 2006, Paleontological Society Papers, Volume 12). Additionally, the inter-calibration experiments for U-Pb using the EARTHTIME tracer have yielded excellent agreement among labs (0.05%) and these values are traceable back to SI units through the EARTHTIME tracer calibration experiment (e.g., Condon et al., in press, Geochimica et Cosmochimica Acta). These advances have greatly extended the need for cross calibrations of the two chronometers and ulti...link_to_OA_fulltex

A 19 to 17 Ma amagmatic extension event at the Mid-Atlantic Ridge: Ultramafic mylonites from the Vema Lithospheric Section

A >300 km long lithospheric section (Vema Lithospheric Section or VLS) is exposed south of the Vema transform at 11 degrees N in the Atlantic. It is oriented along a seafloor spreading flow line and represents similar to 26 Ma of accretion at a single 80 km long segment (EMAR) of the Mid-Atlantic Ridge. The basal part of the VLS exposes a mantle unit made mostly of relatively undeformed coarse-grained/porphyroclastic peridotites that were sampled at close intervals. Strongly deformed mylonitic peridotites were found at 14 contiguous sites within a similar to 80 km stretch (similar to 4.7 Ma interval); they are dominant in a time interval of 1.4 Ma, from crustal ages of 16.8 to 18.2 Ma (mylonitic stretch). Some of the mylonites are "dry," showing anhydrous high-T deformation, but most contain amphibole. The mylonitic peridotites tend to be less depleted than the porphyroclastic peridotites on the basis of mineral major and trace elements composition, suggesting that the mylonites parent was a subridge mantle that underwent a relatively low degree of melting. The Sr, Nd, and O isotopic composition of the amphiboles is MORB-like and suggests either that seawater did not contribute to their isotopic signature or that their isotopic ratios re-equilibrated during fluid circulation in the upper mantle. Four (40)Ar/(39)Ar ages, on three amphiboles separated from the peridotites, are close to crustal ages predicted from magnetic anomalies, confirming that the amphiboles formed close to ridge axis. We propose that crustal accretion at the EMAR segment has been mostly symmetrical for the 26 Ma of its recorded history, except for the similar to 1.4 Ma interval of prevalent ultramafic mylonites (mylonitic stretch) that may record a period of quasi-amagmatic asymmetric accretion of oceanic lithosphere close to the ridge-Vema transform intersection, possibly with development of detachment faults. This interval may correspond to a thermal minimum of the subridge upwelling mantle, marking the transition from a period of decreasing to one of increasing mantle melting below the EMAR segment

Terminal Pleistocene to early Holocene volcanic eruptions at Zuni Salt Lake, west-central New Mexico, USA

Zuni Salt Lake (ZSL) is a large maar in the Red Hill-Quemado volcanic field located in west-central New Mexico in the southwestern USA. Stratigraphic analysis of sections in and around the maar, coupled with optically stimulated luminescence (OSL) and accelerator mass spectrometry (AMS) C-14 dating, indicate that ZSL volcanic activity occurred between similar to 13.4 and 9.9 ka and was most likely confined to a <= 500-year interval sometime between similar to 12.3 and 11.0 ka. The basal volcanic unit consists of locally widespread basaltic ash fallout interpreted to represent a violent or wind-aided strombolian eruption tentatively attributed to Cerro Pomo, a scoria cone similar to 10 km south of ZSL. Subsequent eruptions emanated from vents near or within the present-day ZSL maar crater. Strombolian eruptions of multiple spatter and scoria cones produced basaltic lava and scoria lapilli fallout. Next, a phreatomagmatic eruption created the maar crater and surrounding tephra rim and apron. ZSL eruptions ended with strombolian eruptions that formed three scoria cones on the crater floor. The revised age range of ZSL is younger and more precise than the 190-24 ka 2-sigma age range derived from previous argon dating. This implies that other morphologically youthful, argon-dated volcanoes on the southern margin of the Colorado Plateau might be substantially younger than previously reported.National Science Foundation IGERT Fellowship in Archaeological Science from the University of Arizona; Geological Society of America Graduate Student Research Grant [10716-14]; P.E.O. Scholar Award; Department of Geosciences, University of Arizona12 month embargo; First Online: 04 January 2017This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]