Science.gov

Sample records for absolute age dating

  1. Towards an absolute chronology for the Aegean iron age: new radiocarbon dates from Lefkandi, Kalapodi and Corinth.

    PubMed

    Toffolo, Michael B; Fantalkin, Alexander; Lemos, Irene S; Felsch, Rainer C S; Niemeier, Wolf-Dietrich; Sanders, Guy D R; Finkelstein, Israel; Boaretto, Elisabetta

    2013-01-01

    The relative chronology of the Aegean Iron Age is robust. It is based on minute stylistic changes in the Submycenaean, Protogeometric and Geometric styles and their sub-phases. Yet, the absolute chronology of the time-span between the final stages of Late Helladic IIIC in the late second millennium BCE and the archaic colonization of Italy and Sicily toward the end of the 8(th) century BCE lacks archaeological contexts that can be directly related to events carrying absolute dates mentioned in Egyptian/Near Eastern historical sources, or to well-dated Egyptian/Near Eastern rulers. The small number of radiocarbon dates available for this time span is not sufficient to establish an absolute chronological sequence. Here we present a new set of short-lived radiocarbon dates from the sites of Lefkandi, Kalapodi and Corinth in Greece. We focus on the crucial transition from the Submycenaean to the Protogeometric periods. This transition is placed in the late 11(th) century BCE according to the Conventional Aegean Chronology and in the late 12(th) century BCE according to the High Aegean Chronology. Our results place it in the second half of the 11(th) century BCE. PMID:24386150

  2. Borehole magnetostratigraphy, absolute age dating, and correlation of sedimentary rocks, with examples from the Paris Basin, France

    SciTech Connect

    Bouisset, P.M. ); Augustin, A.M. )

    1993-04-01

    Total and CEA have conceived and developed two new logging tools which allow continuous, precise, and accurate in-situ magnetic measurements within weakly magnetized sedimentary rocks encountered in uncased industry drilled wells. The combination of these magnetic measurements permits for the first time continuous determination of natural remanent magnetization (NRM) polarities occurring in the logged section. The resulting well magnetostratigraphic sequence (WMS) which may be recognized from well to well (magnetostratigraphic correlations), may also be correlative to a geomagnetic polarity time scale (GPTS) of reference magnetostratigraphic scale (RMS), given adequate dating tie points and lack of noticeable remagnetizations. Application of this method to the Upper Jurrasic formation in four wells of the Paris basin has yielded promising results for both stratigraphic and near absolute age correlations as well as determination of facies diachronisms. The comparison of results obtained from magnetic measurements and from sequence stratigraphy analysis shows that third-order sequence boundaries may be correlative to geomagnetic reversals, but may also be diachronous in wells 80 km or less apart. The potential of borehole magnetic measurements as presented in this paper is still under investigation. However, these encouraging initial results show that this new investigating and dating method could be of great help in the analysis of subsurface stratigraphy by extending the concepts of magnetostratigraphy from the outcrops and laboratory directly into borehole logging. 81 refs., 18 figs.

  3. Plutonium age dating reloaded

    NASA Astrophysics Data System (ADS)

    Sturm, Monika; Richter, Stephan; Aregbe, Yetunde; Wellum, Roger; Mayer, Klaus; Prohaska, Thomas

    2014-05-01

    Although the age determination of plutonium is and has been a pillar of nuclear forensic investigations for many years, additional research in the field of plutonium age dating is still needed and leads to new insights as the present work shows: Plutonium is commonly dated with the help of the 241Pu/241Am chronometer using gamma spectrometry; in fewer cases the 240Pu/236U chronometer has been used. The age dating results of the 239Pu/235U chronometer and the 238Pu/234U chronometer are scarcely applied in addition to the 240Pu/236U chronometer, although their results can be obtained simultaneously from the same mass spectrometric experiments as the age dating result of latter. The reliability of the result can be tested when the results of different chronometers are compared. The 242Pu/238U chronometer is normally not evaluated at all due to its sensitivity to contamination with natural uranium. This apparent 'weakness' that renders the age dating results of the 242Pu/238U chronometer almost useless for nuclear forensic investigations, however turns out to be an advantage looked at from another perspective: the 242Pu/238U chronometer can be utilized as an indicator for uranium contamination of plutonium samples and even help to identify the nature of this contamination. To illustrate this the age dating results of all four Pu/U clocks mentioned above are discussed for one plutonium sample (NBS 946) that shows no signs of uranium contamination and for three additional plutonium samples. In case the 242Pu/238U chronometer results in an older 'age' than the other Pu/U chronometers, contamination with either a small amount of enriched or with natural or depleted uranium is for example possible. If the age dating result of the 239Pu/235U chronometer is also influenced the nature of the contamination can be identified; enriched uranium is in this latter case a likely cause for the missmatch of the age dating results of the Pu/U chronometers.

  4. Urey: to measure the absolute age of Mars

    NASA Technical Reports Server (NTRS)

    Randolph, J. E.; Plescia, J.; Bar-Cohen, Y.; Bartlett, P.; Bickler, D.; Carlson, R.; Carr, G.; Fong, M.; Gronroos, H.; Guske, P. J.; Herring, M.; Javadi, H.; Johnson, D. W.; Larson, T.; Malaviarachchi, K.; Sherrit, S.; Stride, S.; Trebi-Ollennu, A.; Warwick, R.

    2003-01-01

    UREY, a proposed NASA Mars Scout mission will, for the first time, measure the absolute age of an identified igneous rock formation on Mars. By extension to relatively older and younger rock formations dated by remote sensing, these results will enable a new and better understanding of Martian geologic history.

  5. Absolute dating and palaeoenvironmental evolution in Palaeolithic Mani, SW Peloponnesus

    NASA Astrophysics Data System (ADS)

    Christodoulakis, John; Bassiakos, Yannis; Athanassas, Constantin

    2013-04-01

    Data derived from palaeoenvironmental indicators are considered the most reliable in back casting former environmental contexts and also, where possible, in forecasting future trends in the environment. The peninsula of Mani, southern Peloponnesus, southwestern Greece, is a challenging area for studying past environmental changes of the Upper Quaternary, because of its nodal position between three continents, its long and multifarious coastal zone, as well as its active local tectonic regime. A great deal of sea level oscillations and palaeoclimatic and palaeoanthropological evidence have been well-documented in the terrestrial and coastal sedimentery deposits of the peninsula, particularly for the later part of the Quaternary (Kelletat und Gassert, 1975, Imperatori, 1966). That evidence mostly comes from paleoenvironmental indicators such as raised marine notches and marine terraces, as well as from other,indicators, and is frequently associated with sites of paleoanthropological significance An important parameter of those sedimentary deposits is their chronology. To date, the chronological framework of those processes is only loosely constrained. A first effort to produce chronological data for this area was made about twenty years ago by applying electron spin resonance (ESR) dating to speleothems from the local subsurface caverns system and other karst formations. Here, by engaging luminescence dating, we aimed to further control former ESR chronology as well as to extend numeric dating on sedimentary formations previously non-datable through ESR alone (i.e. fluvial/deltaic sediments occurring in the area as well as anthropogenic composite deposits usually including burnt bones and fragments of stone tools). Specifically, optically stimulated luminescence (OSL) dating, combined with the single-aliquot regenerative dose (SAR) protocol, produced a number of ages that are in fair agreement with the previous ESR chronology. Current data allowed us to comprehend

  6. Desert Varnish: Relative and Absolute Dating Using Portable X-Ray Fluorescence

    NASA Astrophysics Data System (ADS)

    Pingitore, N. E.; Lytle, F. W.

    2003-12-01

    Levels of manganese and iron measured in situ with a portable x-ray fluorescence instrument permit relative and absolute dating of desert varnish. This novel technique may have wide potential application to dating Pleistocene and Holocene events and geomorphic surfaces in dry climate settings. Desert varnish is a thin biogenic coating, enriched in Mn and Fe, found on rock surfaces in arid and semi-arid regions. The accumulation of varnish marks the passage of time since a fresh rock surface was created or exposed. Thus the varnish thickness reflects the age of the event that created the fresh surface, whatever the agent was, e.g., a rock fall, a fault movement, or an aboriginal artist. Past attempts to date rock varnish have been marked more by ambiguity or outright failure than by success. Our recent research suggests a practical and rapid method for dating varnish using a portable x-ray fluorescence instrument (PXRF). Varnish thickness encodes two distinct signals, metal and clay. The biogenic Mn and Fe record the passage of time, whereas the accumulation of clay particles is a more time-random process. X-ray fluorescence (XRF) can measure just the "metal thickness" of Mn and Fe in varnish. Earlier tedious microscope techniques focused on physical thickness that includes the noise associated with the clay component. XRF integrates the metal thickness of a broad area of varnish, which is seen to vary significantly in a thin-section traverse. Thus XRF provides a meaningful average thickness over a surface. A portable x-ray fluorescence unit provides rapid, non-destructive, in situ measurements. On outcrop a single analysis takes about 2 minutes and the varnish is not consumed or even disturbed. The hand-held PXRF instrument is simple to operate and relatively inexpensive (\\$ 30,000). PXRF analysis of varnish on independently dated materials yielded a substantive correlation between age and metal (Mn + Fe) thickness. This provided an initial validation of the

  7. Microstructures and Argon age dating

    NASA Astrophysics Data System (ADS)

    Forster, Marnie; Fitz Gerald, John; Lister, Gordon

    2010-05-01

    Microstructures can be dated using 40Ar/39Ar geochronology, but certain conditions apply. In particular the nature of the physical processes that took place during development of need be identified, and the pattern of gas release (and/or retention) during their evolution in nature, and subsequently in the mass spectrometer, during the measurement process. Most researchers cite temperature as the sole variable of importance. There is a belief that there is a single "closure temperature" or a "closure interval" above which the mineral is incapable of retaining radiogenic argon. This is a false conception. Closure is practically relevant only in circumstances that see a rock cooled relatively rapidly from temperatures that were high enough to prevent significant accumulation of radiogenic argon, to temperatures below which there is insignificant loss of radiogenic argon through the remainder of the geological history. These conditions accurately apply only to a limited subset - for example to rocks that cool rapidly from a melt and thereafter remain at or close to the Earth's surface, without subsequent ingress of fluids that would cause alteration and modification of microstructure. Some minerals in metamorphic rocks might display such "cooling ages" but in principle these data are difficult to interpret since they depend on the rate of cooling, the pressures that applied, and the subsequent geological history. Whereas the science of "cooling ages" is relatively well understood, the science of the Argon Partial Retention Zone is in its infancy. In the Argon PRZ it is evident that ages should (and do) show a strong correlation with microstructure. The difficulty is that, since diffusion of Argon is simultaneously multi-path and multi-scale, it is difficult to directly interrogate the distinct reservoirs that store gas populations and thus the age information that can be recorded as to the multiple events during the history of an individual microstructure. Laser

  8. Absolute Dating of Desert Varnish Using Portable X-Ray Fluorescence: Calibration and Testing

    NASA Astrophysics Data System (ADS)

    Pingitore, N. E.; Lytle, F. W.; Rowley, P. D.; Ferris, D. E.

    2004-12-01

    Desert varnish, also called rock varnish, is a thin biogenic layer of Mn-oxides, Fe-oxides, and clays that coats rock surfaces in arid and semi-arid regions. The mass of these metals in the varnish registers cumulative biologic activity over time and presents a possible dating mechanism, subject to appropriate assumptions and restrictions. We have used a portable x-ray fluorescence (PXRF) unit to measure Mn and Fe in numerous desert varnishes, both in the field and laboratory; the anticipated relationship between age and mass emerges from these data. Our attempts to refine the PXRF technique for absolute dating of desert varnish are confounded by the limited number of "dated" varnishes available to calibrate and test the method. Although there is no current method to directly ascertain the age of desert varnish, our search for "dated" varnishes has yielded three suitable types of test materials: (1) The ages of young basalt flows dated by various K/Ar radiometric techniques represent the maximum age of varnish developed on those surfaces. Such rocks are useful in the time range of perhaps 250,000 to 10,000 years; surface spalling with loss of varnish presents an upper time limit and difficulty in dating Holocene basalts presents a lower limit. Basalt flows typically provide horizontal surfaces that are ideal for PXRF measurements because, as a biogenic process, varnish development even at a single site varies with solar orientation. (2) Petroglyphs are the rock art that native peoples produced by pecking away varnish to expose fresh rock. This process restarts varnish development and the pecked surface gradually repatinates over time. At some locales, certain figures, symbols, and stylistic elements can be associated with an archaeological culture of known antiquity and duration, thus providing an age range for such glyphs. In the desert Southwest and Great Basin of the United States, appropriate glyphs are known from the present to at least 7000 years BP. Many of

  9. Teen-Age Dating Violence.

    ERIC Educational Resources Information Center

    Kyle, Karla J.

    It has been estimated that one out of three teenage girls will be involved in an abusive relationship or experience violence in their relationships. Given the fact that studies are showing higher incidence of dating violence reported among teenagers, the importance and usefulness of this topic for anyone who works with adolescents cannot be…

  10. Passive absolute age and temperature history sensor

    SciTech Connect

    Robinson, Alex; Vianco, Paul T.

    2015-11-10

    A passive sensor for historic age and temperature sensing, including a first member formed of a first material, the first material being either a metal or a semiconductor material and a second member formed of a second material, the second material being either a metal or a semiconductor material. A surface of the second member is in contact with a surface of the first member such that, over time, the second material of the second member diffuses into the first material of the first member. The rate of diffusion for the second material to diffuse into the first material depends on a temperature of the passive sensor. One of the electrical conductance, the electrical capacitance, the electrical inductance, the optical transmission, the optical reflectance, or the crystalline structure of the passive sensor depends on the amount of the second material that has diffused into the first member.

  11. Uranium isotopic composition and absolute ages of Allende chondrules

    NASA Astrophysics Data System (ADS)

    Brennecka, G. A.; Budde, G.; Kleine, T.

    2015-11-01

    A handful of events, such as the condensation of refractory inclusions and the formation of chondrules, represent important stages in the formation and evolution of the early solar system and thus are critical to understanding its development. Compared to the refractory inclusions, chondrules appear to have a protracted period of formation that spans millions of years. As such, understanding chondrule formation requires a catalog of reliable ages, free from as many assumptions as possible. The Pb-Pb chronometer has this potential; however, because common individual chondrules have extremely low uranium contents, obtaining U-corrected Pb-Pb ages of individual chondrules is unrealistic in the vast majority of cases at this time. Thus, in order to obtain the most accurate 238U/235U ratio possible for chondrules, we separated and pooled thousands of individual chondrules from the Allende meteorite. In this work, we demonstrate that no discernible differences exist in the 238U/235U compositions between chondrule groups when separated by size and magnetic susceptibility, suggesting that no systematic U-isotope variation exists between groups of chondrules. Consequently, chondrules are likely to have a common 238U/235U ratio for any given meteorite. A weighted average of the six groups of chondrule separates from Allende results in a 238U/235U ratio of 137.786 ± 0.004 (±0.016 including propagated uncertainty on the U standard [Richter et al. 2010]). Although it is still possible that individual chondrules have significant U isotope variation within a given meteorite, this value represents our best estimate of the 238U/235U ratio for Allende chondrules and should be used for absolute dating of these objects, unless such chondrules can be measured individually.

  12. Computational Age Dating of Special Nuclear Materials

    SciTech Connect

    None, None

    2012-06-30

    This slide-show presented an overview of the Constrained Progressive Reversal (CPR) method for computing decays, age dating, and spoof detecting. The CPR method is: Capable of temporal profiling a SNM sample; Precise (compared with known decay code, such a ORIGEN); Easy (for computer implementation and analysis). We have illustrated with real SNM data using CPR for age dating and spoof detection. If SNM is pure, may use CPR to derive its age. If SNM is mixed, CPR will indicate that it is mixed or spoofed.

  13. Absolute ages from crater statistics: Using radiometric ages of Martian samples for determining the Martian cratering chronology

    NASA Technical Reports Server (NTRS)

    Neukum, G.

    1988-01-01

    In the absence of dates derived from rock samples, impact crater frequencies are commonly used to date Martian surface units. All models for absolute dating rely on the lunar cratering chronology and on the validity of its extrapolation to Martian conditions. Starting from somewhat different lunar chronologies, rather different Martian cratering chronologies are found in the literature. Currently favored models are compared. The differences at old ages are significant, the differences at younger ages are considerable and give absolute ages for the same crater frequencies as different as a factor of 3. The total uncertainty could be much higher, though, since the ratio of lunar to Martian cratering rate which is of basic importance in the models is believed to be known no better than within a factor of 2. Thus, it is of crucial importance for understanding the the evolution of Mars and determining the sequence of events to establish an unambiguous Martian cratering chronology from crater statistics in combination with clean radiometric ages of returned Martian samples. For the dating goal, rocks should be as pristine as possible from a geologically simple area with a one-stage emplacement history of the local formation. A minimum of at least one highland site for old ages, two intermediate-aged sites, and one very young site is needed.

  14. Absolute dating of Caribbean cores p6304-8 and p6304-9.

    PubMed

    Rona, E; Emiliani, C

    1969-01-01

    Two deep-sea cores from the central Caribbean have been dated by the thorium-230/ protactinium-231 method. The ages obtained are in agreement with the ages previously obtained from other deep-sea cores from the same area. Because of their greater precision, the new dates provide a more accurate time scale for the past 170,000 years. PMID:17780174

  15. Calibration age and quartet divergence date estimation.

    PubMed

    Brochu, Christopher A

    2004-06-01

    The date of a single divergence point--between living alligators and crocodiles--was estimated with quartet dating using calibrations of widely divergent ages. For five mitochondrial sequence datasets, there is a clear relationship between calibration age and quartet estimate--quartets based on two relatively recent calibrations support younger divergence estimates than do quartets based on two older calibrations. Some of the estimates supported by young quartets are impossibly young and exclude the first appearance of the group in the fossil record as too old. The older estimates--those based on two relatively old calibrations--may be overestimates, and those based on one old and one recent calibration support divergence estimates very close to fossil data. This suggests that quartet dating methods may be most effective when calibrations are applied from different parts of a clade's history. PMID:15266985

  16. Age Dependent Absolute Plate and Plume Motion Modeling

    NASA Astrophysics Data System (ADS)

    Heaton, D. E.; Koppers, A. A. P.

    2015-12-01

    Current absolute plate motion (APM) models from 80 - 0 Ma are constrained by the location of mantle plume related hotspot seamounts, in particular those of the Hawaiian-Emperor and Louisville seamount trails. Originally the 'fixed' hotspot hypothesis was developed to explain past plate motion based on linear age progressive intra-plate volcanism. However, now that 'moving' hotspots are accepted, it is becoming clear that APM models need to be corrected for individual plume motion vectors. For older seamount trails that were active between roughly 50 and 80 Ma the APM models that use 'fixed' hotspots overestimate the measured age progression in those trails, while APM models corrected for 'moving' hotspots underestimate those age progressions. These mismatches are due to both a lack of reliable ages in the older portions of both the Hawaii and Louisville seamount trails and insufficient APM modeling constraints from other seamount trails in the Pacific Basin. Seamounts are difficult to sample and analyze because many are hydrothermally altered and have low potassium concentrations. New 40Ar/39Ar Age results from International Ocean Drilling Project (IODP) Expedition 330 Sites U1372 (n=18), U1375 (n=3), U1376 (n=15) and U1377 (n=7) aid in constraining the oldest end of the Louisville Seamount trail. A significant observation in this study is that the age range recovered in the drill cores match the range of ages that were acquired on dredging cruises at the same seamounts (e.g. Koppers et al., 2011). This is important for determining the inception age of a seamount. The sections recovered from IODP EXP 330 are in-situ volcanoclastic breccia and lava flows. Comparing the seismic interpretations of Louisville guyots (Contreras-Reyes et al., 2010), Holes U1372, U1373 and U1374 penetrated the extrusive and volcanoclastic sections of the seamount. The ages obtained are consistent over stratigraphic intervals >100-450 m thick, providing evidence that these seamounts

  17. An absolute chronology for early Egypt using radiocarbon dating and Bayesian statistical modelling

    PubMed Central

    Dee, Michael; Wengrow, David; Shortland, Andrew; Stevenson, Alice; Brock, Fiona; Girdland Flink, Linus; Bronk Ramsey, Christopher

    2013-01-01

    The Egyptian state was formed prior to the existence of verifiable historical records. Conventional dates for its formation are based on the relative ordering of artefacts. This approach is no longer considered sufficient for cogent historical analysis. Here, we produce an absolute chronology for Early Egypt by combining radiocarbon and archaeological evidence within a Bayesian paradigm. Our data cover the full trajectory of Egyptian state formation and indicate that the process occurred more rapidly than previously thought. We provide a timeline for the First Dynasty of Egypt of generational-scale resolution that concurs with prevailing archaeological analysis and produce a chronometric date for the foundation of Egypt that distinguishes between historical estimates. PMID:24204188

  18. 27 CFR 19.410 - Age and fill date.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2014-04-01 2014-04-01 false Age and fill date. 19.410... Spirits from Customs Custody § 19.410 Age and fill date. For purposes of this part, the age and fill date for spirits imported or brought into the United States will be: (a) The claimed age, as shown on...

  19. 27 CFR 19.410 - Age and fill date.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2013-04-01 2013-04-01 false Age and fill date. 19.410... Spirits from Customs Custody § 19.410 Age and fill date. For purposes of this part, the age and fill date for spirits imported or brought into the United States will be: (a) The claimed age, as shown on...

  20. 27 CFR 19.410 - Age and fill date.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Age and fill date. 19.410... Spirits from Customs Custody § 19.410 Age and fill date. For purposes of this part, the age and fill date for spirits imported or brought into the United States will be: (a) The claimed age, as shown on...

  1. 27 CFR 19.410 - Age and fill date.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Age and fill date. 19.410... Spirits from Customs Custody § 19.410 Age and fill date. For purposes of this part, the age and fill date for spirits imported or brought into the United States will be: (a) The claimed age, as shown on...

  2. Accurate radiocarbon age estimation using "early" measurements: a new approach to reconstructing the Paleolithic absolute chronology

    NASA Astrophysics Data System (ADS)

    Omori, Takayuki; Sano, Katsuhiro; Yoneda, Minoru

    2014-05-01

    This paper presents new correction approaches for "early" radiocarbon ages to reconstruct the Paleolithic absolute chronology. In order to discuss time-space distribution about the replacement of archaic humans, including Neanderthals in Europe, by the modern humans, a massive data, which covers a wide-area, would be needed. Today, some radiocarbon databases focused on the Paleolithic have been published and used for chronological studies. From a viewpoint of current analytical technology, however, the any database have unreliable results that make interpretation of radiocarbon dates difficult. Most of these unreliable ages had been published in the early days of radiocarbon analysis. In recent years, new analytical methods to determine highly-accurate dates have been developed. Ultrafiltration and ABOx-SC methods, as new sample pretreatments for bone and charcoal respectively, have attracted attention because they could remove imperceptible contaminates and derive reliable accurately ages. In order to evaluate the reliability of "early" data, we investigated the differences and variabilities of radiocarbon ages on different pretreatments, and attempted to develop correction functions for the assessment of the reliability. It can be expected that reliability of the corrected age is increased and the age applied to chronological research together with recent ages. Here, we introduce the methodological frameworks and archaeological applications.

  3. Absolute Gravity Datum in the Age of Cold Atom Gravimeters

    NASA Astrophysics Data System (ADS)

    Childers, V. A.; Eckl, M. C.

    2014-12-01

    The international gravity datum is defined today by the International Gravity Standardization Net of 1971 (IGSN-71). The data supporting this network was measured in the 1950s and 60s using pendulum and spring-based gravimeter ties (plus some new ballistic absolute meters) to replace the prior protocol of referencing all gravity values to the earlier Potsdam value. Since this time, gravimeter technology has advanced significantly with the development and refinement of the FG-5 (the current standard of the industry) and again with the soon-to-be-available cold atom interferometric absolute gravimeters. This latest development is anticipated to provide improvement in the range of two orders of magnitude as compared to the measurement accuracy of technology utilized to develop ISGN-71. In this presentation, we will explore how the IGSN-71 might best be "modernized" given today's requirements and available instruments and resources. The National Geodetic Survey (NGS), along with other relevant US Government agencies, is concerned about establishing gravity control to establish and maintain high order geodetic networks as part of the nation's essential infrastructure. The need to modernize the nation's geodetic infrastructure was highlighted in "Precise Geodetic Infrastructure, National Requirements for a Shared Resource" National Academy of Science, 2010. The NGS mission, as dictated by Congress, is to establish and maintain the National Spatial Reference System, which includes gravity measurements. Absolute gravimeters measure the total gravity field directly and do not involve ties to other measurements. Periodic "intercomparisons" of multiple absolute gravimeters at reference gravity sites are used to constrain the behavior of the instruments to ensure that each would yield reasonably similar measurements of the same location (i.e. yield a sufficiently consistent datum when measured in disparate locales). New atomic interferometric gravimeters promise a significant

  4. Age-dating of rockslides: Methods and limitations

    NASA Astrophysics Data System (ADS)

    Ostermann, M.; Sanders, D.; Prager, C.

    2009-04-01

    Age-dating of deposits of catastrophic rockslides is prerequisite to unravel the potential relation between the frequency of mass-wasting events with climatic change or earthquakes. In the Alps, about 250 rockslides exceeding 106 m3 in volume are known, but the age as yet is determined only for a comparatively small number of events. For age determination of rockslide events, different methods are available (e. g. Lang et al., 1999). Radiocarbon Dating In the past few decades, rockslide deposits commonly were proxy-dated by 14C age determination of organic remnants preserved (a) in glacial, fluvio-glacial sediments overridden by the rockslide, (b) within the rockslide mass, or (c) in rockslide-dammed backwater deposits or lakes situated atop the rockslide mass. In each case, the 14C age provides a different constraint on the age of the rockslide event: in case (a), the 14C age represents a maximum age of the event; in case (b), which is quite rare, the 14C age is generally considered as a good proxy of the event age; in case (c) the 14C age represents a minimum age for the rockslide event. Unfortunately, radiocarbon dating often cannot be applied because of absence of suited deposits or exposures thereof, lack of organic remnants or of remnants suited for age-dating, and/or because determined 14C ages are substantially biased. Optically Stimulated Luminescence (OSL) Proxy-dating of rockslide events by OSL can be applied to silt- to sand-sized quartzose sediments present (a) directly below, (b) within, or (c) above/laterally aside a rockslide mass. For each case (a) to (c), the determined ages are subject to the same constraints as outlined for radiocarbon dating. Unfortunately, situations allowing for application of OSL to rockslide event dating are comparatively rare, and the resulting ages tend to have a wide error range. Surface Exposure Dating with cosmogenic radionuclides Surface exposure ages can be determined for rock samples taken from the sliding planes at

  5. Tectonic structures on Mercury: kinematics and age dating

    NASA Astrophysics Data System (ADS)

    Giacomini, Lorenza; Massironi, Matteo; Rothery, David; Di Achille, Gaetano; Marchi, Simone; Galluzzi, Valentina; Ferrari, Sabrina; Fassett, Caleb; Cremonese, Gabriele

    2015-04-01

    At a global scale, Mercury is dominated by contractional features manifested as lobate scarps, wrinkle ridges and high-relief ridges. Here, we show that some of these features are associated with strike-slip kinematic indicators, which we identified using flyby and orbital Mercury Dual Imaging System (MDIS) data and digital terrain models. We recognize oblique-shear kinematics along lobate scarps and high-relief ridges by means of (1) map geometries of fault patterns (frontal thrusts bordered by lateral ramps, strike-slip duplexes, restraining bends); (2) structural morphologies indicating lateral shearing (en echelon folding, pop-ups, pull-aparts); and (3) estimates of offsets based on displaced crater rims and differences in elevation between pop-up structures and pull-apart basins and their surroundings. Transpressional faults, documented across a wide range of latitudes, are found associated with reactivated rims of ancient buried basins and, in most cases, linked to frontal thrusts as lateral ramps hundreds of kilometres long. This latter observation suggests stable directions of tectonic transport over wide regions of Mercury's surface. In contrast, global cooling would imply an overall isotropic contraction with limited processes of lateral shearing induced by pre-existent lithospheric heterogeneities. Mantle convection therefore may have played an important role during the early tectonic evolution of Mercury. Estimating absolute model ages for compressional features and comparing it from what it is envisaged with thermal modeling based on cooling alone can be useful in determining if other processes could have been responsible for lobate scarps nucleation. In particular, ages more ancient that the one predicted by the models would imply other kind of tectonic processes ongoing during the early evolution of Mercury . For this reason, we date an extended thrust system, which we term the Blossom Thrust System, located between 80°E and 100°E, and 30°N and 15

  6. Problems determining relative and absolute ages using the small crater population

    NASA Astrophysics Data System (ADS)

    Xiao, Zhiyong; Strom, Robert G.

    2012-07-01

    The small crater populations (diameter smaller than 1 km) are widely used to date planetary surfaces. The reliability of small crater counts is tested by counting small craters at several young and old lunar surfaces, including Mare Nubium and craters Alphonsus, Tycho and Giordano Bruno. Based on high-resolution images from both the Lunar Reconnaissance Orbiter Camera and Kaguya Terrain Camera, small craters in two different diameter ranges are counted for each counting area. Large discrepancies exist in both the cumulative (absolute model ages) and relative plots for the two different size ranges of the same counting areas. The results indicate that dating planetary surfaces using small crater populations is highly unreliable because the contamination of secondaries may invalidate the results of small crater counts. A comparison of the size-frequency distributions of the small crater populations and impact ejected boulders around fresh lunar craters shows the same upturn as typical martian secondaries, which supports the argument that secondaries dominate the small crater populations on the Moon and Mars. Also, the size-frequency distributions of small rayed lunar and martian craters of probable primary origin are similar to that of the Population 2 craters on the inner Solar System bodies post-dating Late Heavy Bombardment. Dating planetary surfaces using the small crater populations requires the separation of primaries from secondaries which is extremely difficult. The results also show that other factors, such as different target properties and the subjective identification of impact craters by different crater counters, may also affect crater counting results. We suggest that dating planetary surfaces using small crater populations should be with highly cautious.

  7. Contributing to a precise and accurate chronostratigraphic time scale for climatic records: Absolute dating and paleomagnetism in lavas

    NASA Astrophysics Data System (ADS)

    Sasco, Romain; Guillou, Herve; Kissel, Catherine; Wandres, Camille; Carracedo, Juan-Carlos; Perez Torrado, Francisco Jose

    2014-05-01

    Understanding climatic mechanisms requires a robust and precise timescale allowing long-distance and multi-archives correlations. A unique tool to construct such time scales is provided by the Earth magnetic field (EMF), which is independent from climatic variations and the past evolution of which is recorded in most of the geological/climatic archives. Sedimentary sequences provide continuous records of relative intensities of the EMF on stratigraphic time scales, usually based on orbital tuning. They are transferred onto absolute intensity scale and chronological time scale using robust tie points available for the past ~40 ka. However, for older periods this calibration remains poorly constrained. Our study reports on new tie points over the last 200 ka by combining paleomagnetic and geochronological (K/Ar and 40Ar-39Ar dating) studies on lavas. Based on the K-Ar LSCE age database, a set of 18 lava flows corresponding to potential geomagnetic excursions and/or highs and lows in the paleomagnetic intensity as observed from sediments and occurring in the studied time-window were selected in the Canary Islands (Tenerife, La Palma and Gran Canaria). A total of 205 oriented cores were taken from these 18 lava flows. Rock magnetic experiments include thermomagnetic analyses on each core, hysteresis loop and First Order Reversal Curves. Stepwise thermal demagnetizations in zero-field provided reliable mean-site paleomagnetic direction of the EMF for 15 of the flows. Paleointensity values were determined using the original Thellier and Thellier method. Based on previous experiments, 170 samples were analyzed, among which 51% provided reliable paleointensity values (determined using PICRIT-03 criteria). The geochronological study focused on 40Ar-39Ar dating. Based on preliminary paleomagnetic results, 13 flows were analyzed and 11 provided ages consistent at the 2 sigma level with the already available K-Ar ages. This coupled K/Ar - 40Ar-39Ar results strongly constrain

  8. Spectral Age Dating of Volcanic Materials

    NASA Astrophysics Data System (ADS)

    Pearson, N.; Calvin, W. M.

    2015-12-01

    As part of the HyspIRI preparatory airborne campaign, high spectral resolution data of the Mono-Inyo craters had been collected. The Mono-Inyo Craters are a chain of geologically young craters that have been erupted over the past 40,000 years. We show a spectral variation in the 2.21μm absorption band depth (commonly associated with the Si-OH stretch) between craters of different ages. To explain this we propose the devitrification of the surface of the volcanic materials creating a weathering rind that thickens with age. A definite linear correlation between age and band depth is shown for craters less than 5,000 years old and potential logarithmic correlation for older craters. To help test this, hand samples from the craters were collected from several of the volcanic craters and the weathering rind thickness measured using a scanning electron microprobe. This correlation combined with a HyspIRI like dataset could be used to define volcanic hazards in large or remote regions, such as the Aleutian Island Arc or Kamchatka Peninsula.

  9. The Path to an Up-to-date Absolute Gravity Reference System

    NASA Astrophysics Data System (ADS)

    Wilmes, H.; Falk, R.; Wziontek, H.

    2014-12-01

    The determination of precise gravity field parameters is of great importance in a period in which earth sciences are achieving the necessary accuracy to monitor and document global change processes. This is the reason why experts from geodesy and metrology joined in a successful cooperation to make absolute gravity observations traceable to SI quantities, to improve the metrological kilogram definition and to monitor mass movements and smallest height changes for geodetic and geophysical applications. How can we determine such a gravity reference system and secure it over multiple decades? Precise knowledge of the gravity acceleration and definition of standards, models and corrections are an important prerequisite to the definition of the gravity system. Over more than three decades, the absolute gravity community cooperated successfully to obtain the gravity reference in comparisons at intervals of 4 years and to certify metrological equivalence between National Metrology Institutes. With increasing resolution of the absolute gravimeter sensors and new measurement principles it becomes obvious that such comparisons are not sufficient for all applications. Mainly for geodetic purposes it is necessary to sub-divide comparison intervals and maintain a connected network of gravity reference sites where compared absolute gravimeters operate together with superconducting gravimeters to derive a continuous gravity reference function. By means of this distributed monitoring of the gravity reference it will also be possible to relate observations of earlier absolute gravimeters to the present-day and to future instruments. It will be possible to include new sensors like atom interferometers and in future to relate the results of precise optical clocks. With co-located space geodetic sensors like GNSS, SLR and VLBI, these reference sites fulfill the conditions of a geodetic fundamental station as a component of IAG's Global Geodetic Observing System.

  10. Age Dating of Mixed SNM--Preliminary Investigations

    SciTech Connect

    Yuan, D., Guss, P. P., Yfantis, E., Klingensmith, A., Emer, D.

    2011-12-01

    Recently we investigated the nuclear forensics problem of age determination for mixed special nuclear material (SNM). Through limited computational mixing experiments and interactive age analysis, it was observed that age dating results are generally affected by the mixing of samples with different assays or even by small radioactive material contamination. The mixing and contamination can be detected through interactive age analysis, a function provided by the Decay Interaction, Visualization and Analysis (DIVA) software developed by NSTec. It is observed that for mixed SNM with two components, the age estimators typically fall into two distinct clusters on the time axis. This suggests that averaging or other simple statistical methods may not always be suitable for age dating SNM mixtures. Instead, an interactive age analysis would be more suitable for age determination of material components of such SNM mixtures. This work was supported by the National Center for Nuclear Security (NCNS).

  11. Archaeomagnetic Dating of Bronze Age Pottery in Syria: New Intensity Data for 2300 to 1000 BCE

    NASA Astrophysics Data System (ADS)

    Stillinger, M. D.; Feinberg, J. M.; Frahm, E.

    2013-12-01

    In order to construct meaningful site chronologies, Near Eastern archaeologists have traditionally relied on relative dating techniques, such as ceramic seriation and textual/glyptic evidence. The introduction of radiocarbon dating provided archaeologists with an absolute dating tool to address age discrepancies. However, many sites do not contain sufficient or suitable materials for radiocarbon analysis, requiring the need for an alternative absolute dating tool. Archaeomagnetic dating provides such an alternative. Excavations at Tell Mozan (Bronze-Age Urkesh) in northeastern Syria have revealed evidence for nearly 5000 years of occupation in strata containing a variety of diagnostic ceramic artifacts, which form the basis for a well-established relative site chronology. In order to test the agreement between seriation ages and paleomagnetic-derived ages, archaeointensity experiments were conducted on pottery specimens from six well-stratified occupational layers spanning more than a thousand years of the site's primary occupation. Archaeointensity was determined using the IZZI paleointensity protocol of Tauxe and Staudigel (2004), and all estimates were corrected for remanence anisotropy and cooling rate effects, resulting in an 88% success rate (n = 51). The magnetic mineral assemblage of each sample was also characterized using a comprehensive suite of rock magnetic techniques. Final results were compared with previous archaeointensity studies in the region, and 70% of the magnetically-derived ages agree with the archaeologically-derived dates within a 1σ confidence interval, while 76% agreed within 2σ. Artifacts showing disagreement with the seriation chronology are most likely objects in use long after their original firing or the result of contamination of strata from the re-use of previous occupational materials in construction. One specimen appears to confirm the presence of a geomagnetic spike around 1000 BCE previously identified in Syria, Israel

  12. A prospective study to compare serum human placental lactogen and menstrual dates for determining gestational age.

    PubMed

    Whittaker, P G; Lind, T; Lawson, J Y

    1987-01-01

    In a group of 575 healthy pregnant women with certain menstrual dates the estimation of the length of gestation from maternal serum human placental lactogen concentrations has been compared with gestational age calculated from the last menstrual period and ultrasonic measurements of the fetal biparietal diameter. In 412 of these patients labor started spontaneously, and the estimated dates of delivery determined by these three methods were also compared. In the range of 9 to 17 weeks of pregnancy, gestational age can be determined by human placental lactogen measurement to within 7 days (+/- 1 SD) which compares favorably with other methods. Regarding the prediction of the expected date of delivery, 88% were delivered within 2 weeks of the date predicted by last menstrual period, 82% within 2 weeks of the sonar date, and 80% by the date determined by human placental lactogen assessment. Prediction of delivery in a further group of 139 women with uncertain dates gave 73% within 2 weeks by sonar date and 69% within 2 weeks by human placental lactogen determination. We suggest human placental lactogen measurements should become part of routine antenatal care complementing rather than replacing the role of ultrasonic scanning. For those doctors and patients who wish to avoid more exposure to ultrasonic scanning than absolutely necessary, human placental lactogen estimates offer an alternative method for assessing the length of gestation. PMID:3541617

  13. Characterization of Fundamental Luminescence Properties of the Mars Soil Simulant JSC Mars-1 and Their Relevance to Absolute Dating of Martian Eolian Sediments

    NASA Astrophysics Data System (ADS)

    Lepper, Kenneth; McKeever, Stephen W. S.

    2000-04-01

    This report explores the potential for luminescence dating techniques to provide absolute age determinations of eolian sediments on the surface of Mars, including those incorporated in the martian polar ice caps. Fundamental thermally and optically stimulated luminescence properties of bulk samples of JSC Mars-1 soil simulant are reported and their relevance to the development of dating procedures is discussed. The radiation-induced luminescence signals (both thermoluminescence, TL, and optically stimulated luminescence, OSL) from JSC Mars-1 are found to have a wide dynamic dose-response range, with the luminescence increasing linearly to the highest doses used (936 Gy), following irradiation with 90Sr/ 90Y beta particles. The signals are also susceptible to solar resetting, with the OSL signals decreasing to <10% of their original levels within the first 20 min of exposure to sunlight. The TL signal also decays rapidly, being reduced to ˜15% within the first 20 min, but reaches a stable, nonzero level at long bleaching times. Neither the TL nor the OSL signals exhibit fading (i.e., loss of signal after irradiation before TL or OSL readout), nor do they exhibit significant sensitivity changes upon repeated irradiation and readout. These three properties (wide dynamic range, solar bleaching, and signal stability) form a stable base for future investigation of the material for luminescence dating and form a preliminary step toward development of dating protocols for terrestrial analogs of Mars surface materials. We conclude that luminescence dating, properly developed, holds the potential to be a valuable tool for absolute dating of martian eolian sediments

  14. Absolute-dated lake and cave records of the glacial highstand and deglacial regression of Lake Bonneville, Utah, USA

    NASA Astrophysics Data System (ADS)

    McGee, D.; Edwards, R.; Quade, J.; Broecker, W. S.

    2010-12-01

    Lake levels in Utah’s Bonneville Basin declined dramatically during the last deglaciation, likely reflecting changes in the position or intensity of the westerly storm track and increasing summer temperatures over this time period. After a prolonged transgression during the last glacial period, paleolake Bonneville began overflowing its basin at approximately 18 ka and remained hydrologically open until dropping below the overflow threshold (Provo shoreline) sometime between 15.5 and 14 ka. Although previous work has documented the main features of the lake’s history, many questions remain about the precise timing and rate of past lake level changes and their relation to abrupt warm and cold events during the last glacial period and deglaciation. Here we present records from a novel paleohydrological archive: carbonates precipitated within caves flooded by Lake Bonneville. Importantly, the deposits can be precisely dated by U-Th methods with minimal detrital contamination, providing the first high-precision, absolute-dated records of Lake Bonneville’s water balance changes. Additionally, calibrated 14C ages match U-Th ages, showing that Lake Bonneville experienced no measurable reservoir effects and providing an opportunity for improving the 14C calibration between 19 and 26 ka. The deposits appear to reflect periods when a) the lake was above a given cave’s elevation and b) the lake was not overflowing and therefore exceeded calcite/aragonite saturation. The deposits thus record the passage of the lake through each cave’s elevation, the onset and cessation of basin overflow, the isotopic composition of lake water, and changes in lake chemistry between 26 and 13 ka. In Cathedral Cave, the site of the best-studied deposits, carbonate was deposited in four phases, providing precise age constraints on key paleohydrographic events. Phase I (29 ka) is related to a previously unidentified oscillation of lake level above 1352 meters, the cave’s rebound

  15. Radiocarbon dating of marine material: mollusc versus foraminifera ages

    NASA Astrophysics Data System (ADS)

    Callard, L.; Long, A. J.; Plets, R. M.; Cooper, A.; Belknap, D. F.; Edwards, R.; Jackson, D.; Kelley, J. T.; Long, D.; Milne, G. A.; Monteys, X.; Quinn, R.

    2013-12-01

    A key challenge in reconstructing Quaternary environmental change from marine archives is developing a robust chronology. During the last ~50k a-1, radiocarbon dating is the mainstay for many studies. Often investigators are restricted in the material that is available for dating, with studies relying on AMS dating of either mono-specific or mixed assemblages of foraminifera. In some instances, marine molluscs (broken or whole, articulated or disarticulated) may also be present and can provide an alternative or complementary dating target. Previous radiocarbon dating of paired foraminiferal and marine molluscan samples from the Kattegat (Denmark) revealed significant age offsets between these materials, inferred to reflect greater reworking of foraminifera compared to the marine molluscs (Heier-Nielsen et al., 1995). Here we present the results of a comparable study from the Irish Sea Basin, which forms part of a wider investigation into the evidence for the Late Glacial sea-level minima at offshore sites from around Britain and Ireland. We have collected and AMS 14C-dated twelve paired samples of foraminifera and marine shells. The results shows a systematic age offset with the monospecific foraminifera samples consistently giving older ages than their shell counterparts. This offset increases with sample age, reaching a maximum offset of 3000 years in the oldest sample (~ 13 ka cal a BP). These results are consistent with the observations of Heier-Nielsen et al. (1995), and we hypothesize that foraminifera may be more susceptible to reworking from older deposits because of their lower effective density than the shell samples. However, foraminifera size and shape may also be contributing factors. These findings are potentially significant for studies that develop chronologies based on radiocarbon dating of foraminifera alone, since the resulting dates may over-estimate sample age by several thousand years. We conclude by outlining an experimental design that seeks

  16. U-Pb dating of a speleothem of Quaternary age

    NASA Astrophysics Data System (ADS)

    Richards, David A.; Bottrell, Simon H.; Cliff, Robert A.; Ströhle, Klaus; Rowe, Peter J.

    1998-12-01

    We demonstrate that U-Pb dating is a promising method for secondary carbonate materials of Quaternary age and older by obtaining a 206Pb∗/ 238U age for a speleothem with high U (>10 μg g -1) and very low Pb (<10 ng g -1) that is supported by an independent 230Th age. Thermal ionisation mass-spectrometry was used to determine the U and Pb isotopic ratios and concentrations for subsamples of a stalactite from Winnats Head Cave, Peak District, UK. We obtained 206Pb/ 204Pb ratios up to 50, and determined a 206Pb∗/ 238U age of 248 ± 10 ka, which is within error of the 207Pb∗/ 235U age of 333 ± 79 ka and a-spectrometric U-Th age of ˜255 ka. For samples of Tertiary and Quaternary age, the initial state of U-series disequilibrium is an important consideration and, as with most radiometric dating techniques, the mineral must have remained closed to U, Th, Pb, and all intermediate daughters. We show that dense calcite speleothems are ideal in this respect and that no loss of Rn has occurred. Unlike U-series disequilibrium methods, U-Pb dating has no upper limit and, hence, materials of Quaternary age older than 0.6 Ma can be analysed to investigate landscape development, paleoclimate, hominid evolution or hydrogeochemistry in carbonate terrains.

  17. Surface dating of dynamic landforms: young boulders on aging moraines.

    PubMed

    Hallet, B; Putkonen, J

    1994-08-12

    The dating of landforms is crucial to understanding the evolution, history, and stability of landscapes. Cosmogenic isotope analysis has recently been used to determine quantitative exposure ages for previously undatable landform surfaces. A pioneering application of this technique to date moraines illustrated its considerable potential but suggested a chronology partially inconsistent with existing geological data. Consideration of the dynamic nature of landforms and of the ever-present processes of erosion, deposition, and weathering leads to a resolution of this inconsistency and, more generally, offers guidance for realistic interpretation of exposure ages. PMID:17782145

  18. Cation-ratio dating: A new rock varnish age-determination technique

    NASA Astrophysics Data System (ADS)

    Dorn, Ronald I.

    1983-07-01

    Rock varnish coats many surfaces of geomorphic and archaeologic interest in arid lands. All varnish dating techniques are limited by the time lag between the exposure of a surface to subaerial processes and the onset of varnishing. They are valid only where manganese is not remobilized after deposition, for example, in most arid environments. The premise of a new age-determination method, cation-ratio dating, is that the ratio of the more mobile cations (e.g., K and Ca) to titanium in varnish decreases with time. Although there are many inherent assumptions and potential limitations, cation-ratio dating has been verified on relative age-sequences from a Death Valley debris cone, Negev Desert talus flatirons, and prehistoric lake levels at Searles Lake in California. Varnish cation ratios have been calibrated to independently dated surfaces in the Coso volcanic field and vicinity in California. Tentative absolute dates have been assigned to geomorphic surfaces in the Coso area. Cation ratios have been used to distinguish relative ages of archaeologic artifacts in southwestern North America and to demonstrate that varnish at the South Stoddard locality, Mojave Desert, did not form in 25 yr.

  19. Rewriting the Central European Early Bronze Age Chronology: Evidence from Large-Scale Radiocarbon Dating

    PubMed Central

    Knipper, Corina; Friedrich, Ronny; Kromer, Bernd; Lindauer, Susanne; Radosavljević, Jelena; Wittenborn, Fabian; Krause, Johannes

    2015-01-01

    The transition from the Neolithic to the Early Bronze Age in Central Europe has often been considered as a supra-regional uniform process, which led to the growing mastery of the new bronze technology. Since the 1920s, archaeologists have divided the Early Bronze Age into two chronological phases (Bronze A1 and A2), which were also seen as stages of technical progress. On the basis of the early radiocarbon dates from the cemetery of Singen, southern Germany, the beginning of the Early Bronze Age in Central Europe was originally dated around 2300/2200 BC and the transition to more complex casting techniques (i.e., Bronze A2) around 2000 BC. On the basis of 140 newly radiocarbon dated human remains from Final Neolithic, Early and Middle Bronze Age cemeteries south of Augsburg (Bavaria) and a re-dating of ten graves from the cemetery of Singen, we propose a significantly different dating range, which forces us to re-think the traditional relative and absolute chronologies as well as the narrative of technical development. We are now able to date the beginning of the Early Bronze Age to around 2150 BC and its end to around 1700 BC. Moreover, there is no transition between Bronze (Bz) A1 and Bronze (Bz) A2, but a complete overlap between the type objects of the two phases from 1900–1700 BC. We thus present a revised chronology of the assumed diagnostic type objects of the Early Bronze Age and recommend a radiocarbon-based view on the development of the material culture. Finally, we propose that the traditional phases Bz A1 and Bz A2 do not represent a chronological sequence, but regionally different social phenomena connected to the willingness of local actors to appropriate the new bronze technology. PMID:26488413

  20. Rewriting the Central European Early Bronze Age Chronology: Evidence from Large-Scale Radiocarbon Dating.

    PubMed

    Stockhammer, Philipp W; Massy, Ken; Knipper, Corina; Friedrich, Ronny; Kromer, Bernd; Lindauer, Susanne; Radosavljević, Jelena; Wittenborn, Fabian; Krause, Johannes

    2015-01-01

    The transition from the Neolithic to the Early Bronze Age in Central Europe has often been considered as a supra-regional uniform process, which led to the growing mastery of the new bronze technology. Since the 1920s, archaeologists have divided the Early Bronze Age into two chronological phases (Bronze A1 and A2), which were also seen as stages of technical progress. On the basis of the early radiocarbon dates from the cemetery of Singen, southern Germany, the beginning of the Early Bronze Age in Central Europe was originally dated around 2300/2200 BC and the transition to more complex casting techniques (i.e., Bronze A2) around 2000 BC. On the basis of 140 newly radiocarbon dated human remains from Final Neolithic, Early and Middle Bronze Age cemeteries south of Augsburg (Bavaria) and a re-dating of ten graves from the cemetery of Singen, we propose a significantly different dating range, which forces us to re-think the traditional relative and absolute chronologies as well as the narrative of technical development. We are now able to date the beginning of the Early Bronze Age to around 2150 BC and its end to around 1700 BC. Moreover, there is no transition between Bronze (Bz) A1 and Bronze (Bz) A2, but a complete overlap between the type objects of the two phases from 1900-1700 BC. We thus present a revised chronology of the assumed diagnostic type objects of the Early Bronze Age and recommend a radiocarbon-based view on the development of the material culture. Finally, we propose that the traditional phases Bz A1 and Bz A2 do not represent a chronological sequence, but regionally different social phenomena connected to the willingness of local actors to appropriate the new bronze technology. PMID:26488413

  1. Archaeomagnetic Dating of Bronze Age Pottery from Tell Mozan, Syria

    NASA Astrophysics Data System (ADS)

    Stillinger, Michele D.

    The ancient city-state of Urkesh, located at Tell Mozan, Syria, was the political and religious center of the Hurrians, a unique culture that inhabited the northern Syro-Mesopotamian region during the 3rd millennium BCE. The chronology of Urkesh has been divided into seven primary occupational phases, dating from the Early Dynastic II period (2800--2500 BCE) to the Middle Babylonian/ Mitanni Period (1500--1300 BCE). The site has provided an abundance of distinguishing ceramics, seals, seal impressions, and cuneiform tablets, which serve as the foundation for the Urkesh chronology. Working under the assumption that the archaeologically derived chronology at Mozan was reliable, this research tested the accuracy of archaeomagnetic dating using pottery samples from six successive occupational phases. Samples underwent a suite of magnetic mineral characterization tests and archaeointensity measurements using the Thellier-style absolute paleointensity technique of Tauxe and Staudigel (2004). Archaeointensity experiments displayed an 88% success rate and 80% of the samples correlated well with their archaeologically determined dates. A small subset of samples appeared to indicate a possible intensity spike occurring around 2000 BCE. The final results refine the archaeointensity curve for Syria between 2350 and 1200 BCE.

  2. GeMS MCAO observations of the Galactic globular cluster NGC 2808: the absolute age

    NASA Astrophysics Data System (ADS)

    Massari, D.; Fiorentino, G.; McConnachie, A.; Bono, G.; Dall'Ora, M.; Ferraro, I.; Iannicola, G.; Stetson, P. B.; Turri, P.; Tolstoy, E.

    2016-02-01

    Context. Globular clusters are the oldest stellar systems in the Milky Way, and they probe the early epoch of the Galaxy formation. However, the uncertainties on their absolute age are still too large to soundly constrain how the Galactic structures have assembled. Aims: The aim of this work is to obtain an accurate estimate of the absolute age of the globular cluster NGC 2808 using deep IR data obtained with the multi-conjugate adaptive optics system operating at the Gemini South telescope (GeMS). Methods: This exquisite photometry, combined with that obtained in V and I-bands with HST, allowed us to detect the faint Main Sequence Knee feature in NGC 2808 colour magnitude diagram. The difference between this point and the main sequence turn-off is a good age estimator that provides ages with unprecedented accuracy. Results: We find that NGC 2808 has an age of t = 10.9 ± 0.7 (intrinsic) ±0.45 (metallicity term) Gyr. A possible contamination by He-enhanced population could make the cluster up to 0.25 Gyr older. Although this age estimate agrees with the age coming from the classical turn-off method (t = 11.0 Gyr), its uncertainty is a factor ~3 better, since it avoids systematics in reddening, distance assumptions, and photometric zero point determination. The final absolute age indicates that NGC 2808 is slightly younger than other Galactic globular clusters with similar metallicity. Tables of the photometry are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/586/A51

  3. A revised burial dose estimation procedure for optical dating of youngand modern-age sediments

    USGS Publications Warehouse

    Arnold, L.J.; Roberts, R.G.; Galbraith, R.F.; DeLong, S.B.

    2009-01-01

    The presence of genuinely zero-age or near-zero-age grains in modern-age and very young samples poses a problem for many existing burial dose estimation procedures used in optical (optically stimulated luminescence, OSL) dating. This difficulty currently necessitates consideration of relatively simplistic and statistically inferior age models. In this study, we investigate the potential for using modified versions of the statistical age models of Galbraith et??al. [Galbraith, R.F., Roberts, R.G., Laslett, G.M., Yoshida, H., Olley, J.M., 1999. Optical dating of single and multiple grains of quartz from Jinmium rock shelter, northern Australia: Part I, experimental design and statistical models. Archaeometry 41, 339-364.] to provide reliable equivalent dose (De) estimates for young and modern-age samples that display negative, zero or near-zero De estimates. For this purpose, we have revised the original versions of the central and minimum age models, which are based on log-transformed De values, so that they can be applied to un-logged De estimates and their associated absolute standard errors. The suitability of these 'un-logged' age models is tested using a series of known-age fluvial samples deposited within two arroyo systems from the American Southwest. The un-logged age models provide accurate burial doses and final OSL ages for roughly three-quarters of the total number of samples considered in this study. Sensitivity tests reveal that the un-logged versions of the central and minimum age models are capable of producing accurate burial dose estimates for modern-age and very young (<350??yr) fluvial samples that contain (i) more than 20% of well-bleached grains in their De distributions, or (ii) smaller sub-populations of well-bleached grains for which the De values are known with high precision. Our results indicate that the original (log-transformed) versions of the central and minimum age models are still preferable for most routine dating applications

  4. Absolute age of lunar regolith material from the Sea of Fertility

    NASA Technical Reports Server (NTRS)

    Vinogradov, A. P.; Artemov, Y. M.

    1974-01-01

    By averaging the absolute age of lunar regolith materials from the Sea of Fertility for the fine regolith fraction from the core zone V, an age of 4.65 10 to the 9th power + 0.4 10 to the 9th power years was obtained, employing as the primordial Sr-87/Sr-86 ratio 0.69884 (ADOR). Also close to this age value is the age estimate based on the Pb-207/Pb-206 ratio. Using the value 0.69898 (BABI) as a primordial Sr-87/Sr-86 ratio reduces the calculated age of the fine regolith fraction to 4.25 X 10 to the 9th power years. The fine fraction of lunar regolith from the Sea of Fertility is also characterized by a minimum addition of radiogenic Sr-87, a minimum Rb/Sr ratio, and a maximum K/Rb ratio compared with analogous lunar material from other points.

  5. 14C dating of the Early to Late Bronze Age stratigraphic sequence of Aegina Kolonna, Greece

    NASA Astrophysics Data System (ADS)

    Wild, E. M.; Gauß, W.; Forstenpointner, G.; Lindblom, M.; Smetana, R.; Steier, P.; Thanheiser, U.; Weninger, F.

    2010-04-01

    Aegina Kolonna, located in the center of the Saronic Gulf in the Aegean Mediterranean (Greece), is one of the major archaeological sites of the Aegean Bronze Age with a continuous stratigraphic settlement sequence from the Late Neolithic to the Late Bronze Age. Due to its position next to the maritime cross roads between central mainland Greece, the northeast Peloponnese, the Cyclades and Crete, the island played an important role in the trade between these regions. In the course of new excavations, which focused on the exploration of the Early, Middle and Late Bronze Age at Kolonna, several short lived samples from different settlement phases have been 14C-dated with the AMS method at the VERA laboratory. Bayesian sequencing of the 14C data according to the stratigraphic position of the samples in the profile was performed to enable estimates of the transition time between the cultural phases. The Aegina Kolonna 14C sequence is one of the longest existing so far for the Aegean Bronze Age, and therefore of major importance for the absolute Bronze Age chronology in this region. Preliminary results indicate that the Middle Helladic period seems to have started earlier and lasted longer than traditionally assumed. Further, at the present stage of our investigation we can give also a very tentative time frame for the Santorini volcanic eruption which seems to be in agreement with the science derived VDL date.

  6. A self-consistent, absolute isochronal age scale for young moving groups in the solar neighbourhood

    NASA Astrophysics Data System (ADS)

    Bell, Cameron P. M.; Mamajek, Eric E.; Naylor, Tim

    2015-11-01

    We present a self-consistent, absolute isochronal age scale for young ( ≲ 200 Myr), nearby ( ≲ 100 pc) moving groups in the solar neighbourhood based on homogeneous fitting of semi-empirical pre-main-sequence model isochrones using the τ2 maximum-likelihood fitting statistic of Naylor & Jeffries in the MV, V - J colour-magnitude diagram. The final adopted ages for the groups are as follows: 149^{+51}_{-19} {Myr} for the AB Dor moving group, 24 ± 3 Myr for the β Pic moving group (BPMG), 45^{+11}_{-7} {Myr} for the Carina association, 42^{+6}_{-4} {Myr} for the Columba association, 11 ± 3 Myr for the η Cha cluster, 45 ± 4 Myr for the Tucana-Horologium moving group (Tuc-Hor), 10 ± 3 Myr for the TW Hya association and 22^{+4}_{-3} {Myr} for the 32 Ori group. At this stage we are uncomfortable assigning a final, unambiguous age to the Argus association as our membership list for the association appears to suffer from a high level of contamination, and therefore it remains unclear whether these stars represent a single population of coeval stars. Our isochronal ages for both the BPMG and Tuc-Hor are consistent with recent lithium depletion boundary (LDB) ages, which unlike isochronal ages, are relatively insensitive to the choice of low-mass evolutionary models. This consistency between the isochronal and LDB ages instils confidence that our self-consistent, absolute age scale for young, nearby moving groups is robust, and hence we suggest that these ages be adopted for future studies of these groups. Software implementing the methods described in this study is available from http://www.astro.ex.ac.uk/people/timn/tau-squared/.

  7. Genetic ages for Quaternary topographic evolution: A new dating tool

    NASA Astrophysics Data System (ADS)

    Craw, Dave; Burridge, Chris; Norris, Richard; Waters, Jon

    2008-01-01

    All eukaryote populations accumulate mutations in their mitochondrialDNA (mtDNA) over time, so reproductively isolated populationsbecome characterized by distinct mtDNA lineages. In addition,the degree of genetic differentiation among distinct populationscan be used to estimate time elapsed since their isolation.We have identified an informative system for calibrating themtDNA "clock" by genetically comparing freshwater galaxiid fishpopulations isolated in different river drainages. Calibrationusing a range of Quaternary geological events in southern NewZealand shows that the mtDNA divergence rate in galaxiid fishesis between 1% and 2%/100 k.y. up to 250 k.y., with the ratedecreasing with increasing age. The estimated divergence rateslows to around 4%/m.y. for the middle Quaternary, althoughcalibration is poor. A calibration curve has been fitted toall data: divergence (%) = -2.2e-9t + 2.5t + 2.2,where t is isolation age (in m.y.). This molecular clock haspotential as a dating tool for glacially related and activetectonic events that have caused river drainage changes in thelate Quaternary in the Southern Hemisphere, where galaxiidsare widespread. An application of this dating tool to an examplein northern South Island uses three different species of freshwater-limitedfish, and all three data sets imply formation of a drainagedivide at 320 ± 110 ka, at about the time of a majorglacial advance though the divide (oxygen isotope stage 8).

  8. Placing Absolute Timing on Basin Incision Adjacent to the Colorado Front Range: Results from Meteoric and in Situ 10BE Dating

    NASA Astrophysics Data System (ADS)

    Duehnforth, M.; Anderson, R. S.; Ward, D.

    2010-12-01

    A sequence of six levels of gravel-capped surfaces, mapped as Pliocene to Holocene in age, are cut into Cretaceous shale in the northwestern part of the Denver Basin immediately adjacent to the Colorado Front Range (CFR). The existing relative age constraints and terrace correlations suggest that the incision of the Denver Basin occurred at a steady and uniform rate of 0.1 mm yr-1 since the Pliocene. As absolute ages in this landscape are rare, they have the potential to test the reliability of the existing chronology, and to illuminate the detailed history of incision. We explore the timing of basin incision and the variability of geomorphic process rates through time by dating the three highest surfaces at the northwestern edge of the Denver Basin using both in situ and meteoric 10Be concentrations. As the tectonic conditions have not changed since the Pliocene, much of the variability of generation and abandonment of alluvial surfaces likely reflects the influence of glacial-interglacial climate variations. We selected Gunbarrel Hill (mapped as pre-Rocky Flats (Pliocene)), Table Mountain (mapped as Rocky Flats (early Pleistocene)), and the Pioneer surface (mapped as Verdos (Pleistocene, ~640 ka)) as sample locations. We took two amalgamated clast samples on the Gunbarrel Hill surface, and dated depth profiles using meteoric and in situ 10Be on the Table Mountain and Pioneer surfaces. In addition, we measured the in situ 10Be concentrations of 6 boulder samples from the Table Mountain surface. We find that all three surfaces are significantly younger than expected and that in situ and meteoric age measurements largely agree with each other. The samples from the pre-Rocky Flats site (Gunbarrel Hill) show ages of 250 and 310 ka, ignoring post-depositional surface erosion. The ages of the Table Mountain and Pioneer sites fall within the 120 to 150 ka window. These absolute ages overlap with the timing of the penultimate glaciation during marine isotope stage (MIS) 6

  9. Geophysical Age Dating of Seamounts using Dense Core Flexure Model

    NASA Astrophysics Data System (ADS)

    Hwang, Gyuha; Kim, Seung-Sep

    2016-04-01

    Lithospheric flexure of oceanic plate is thermo-mechanical response of an elastic plate to the given volcanic construct (e.g., seamounts and ocean islands). If the shape and mass of such volcanic loads are known, the flexural response is governed by the thickness of elastic plate, Te. As the age of oceanic plate increases, the elastic thickness of oceanic lithosphere becomes thicker. Thus, we can relate Te with the age of plate at the time of loading. To estimate the amount of the driving force due to seamounts on elastic plate, one needs to approximate their density structure. The most common choice is uniform density model, which utilizes constant density value for a seamount. This approach simplifies computational processes for gravity prediction and error estimates. However, the uniform density model tends to overestimate the total mass of the seamount and hence produces more positive gravitational contributions from the load. Minimization of gravity misfits using uniform density, therefore, favors thinner Te in order to increase negative contributions from the lithospheric flexure, which can compensate for the excessive positives from the seamount. An alternative approach is dense core model, which approximate the heterogeneity nature of seamount density as three bodies of infill sediment, edifice, and dense core. In this study, we apply the dense core model to the Louisville Seamount Chain for constraining flexural deformation. We compare Te estimates with the loading time of the examined seamounts to redefine empirical geophysical age dating of seamounts.

  10. Is an absolute level of cortical beta suppression required for proper movement? Magnetoencephalographic evidence from healthy aging.

    PubMed

    Heinrichs-Graham, Elizabeth; Wilson, Tony W

    2016-07-01

    Previous research has connected a specific pattern of beta oscillatory activity to proper motor execution, but no study to date has directly examined how resting beta levels affect motor-related beta oscillatory activity in the motor cortex. Understanding this relationship is imperative to determining the basic mechanisms of motor control, as well as the impact of pathological beta oscillations on movement execution. In the current study, we used magnetoencephalography (MEG) and a complex movement paradigm to quantify resting beta activity and movement-related beta oscillations in the context of healthy aging. We chose healthy aging as a model because preliminary evidence suggests that beta activity is elevated in older adults, and thus by examining older and younger adults we were able to naturally vary resting beta levels. To this end, healthy younger and older participants were recorded during motor performance and at rest. Using beamforming, we imaged the peri-movement beta event-related desynchronization (ERD) and extracted virtual sensors from the peak voxels, which enabled absolute and relative beta power to be assessed. Interestingly, absolute beta power during the pre-movement baseline was much stronger in older relative to younger adults, and older adults also exhibited proportionally large beta desynchronization (ERD) responses during motor planning and execution compared to younger adults. Crucially, we found a significant relationship between spontaneous (resting) beta power and beta ERD magnitude in both primary motor cortices, above and beyond the effects of age. A similar link was found between beta ERD magnitude and movement duration. These findings suggest a direct linkage between beta reduction during movement and spontaneous activity in the motor cortex, such that as spontaneous beta power increases, a greater reduction in beta activity is required to execute movement. We propose that, on an individual level, the primary motor cortices have an

  11. Reduced Haemodynamic Response in the Ageing Visual Cortex Measured by Absolute fNIRS

    PubMed Central

    Ward, Laura McKernan; Aitchison, Ross Thomas; Tawse, Melisa; Simmers, Anita Jane; Shahani, Uma

    2015-01-01

    The effect of healthy ageing on visual cortical activation is still to be fully explored. This study aimed to elucidate whether the haemodynamic response (HDR) of the visual cortex altered as a result of ageing. Visually normal (healthy) participants were presented with a simple visual stimulus (reversing checkerboard). Full optometric screening was implemented to identify two age groups: younger adults (n = 12, mean age 21) and older adults (n = 13, mean age 71). Frequency-domain Multi-distance (FD-MD) functional Near-Infrared Spectroscopy (fNIRS) was used to measure absolute changes in oxygenated [HbO] and deoxygenated [HbR] haemoglobin concentrations in the occipital cortices. Utilising a slow event-related design, subjects viewed a full field reversing checkerboard with contrast and check size manipulations (15 and 30 minutes of arc, 50% and 100% contrast). Both groups showed the characteristic response of increased [HbO] and decreased [HbR] during stimulus presentation. However, older adults produced a more varied HDR and often had comparable levels of [HbO] and [HbR] during both stimulus presentation and baseline resting state. Younger adults had significantly greater concentrations of both [HbO] and [HbR] in every investigation regardless of the type of stimulus displayed (p<0.05). The average variance associated with this age-related effect for [HbO] was 88% and [HbR] 91%. Passive viewing of a visual stimulus, without any cognitive input, showed a marked age-related decline in the cortical HDR. Moreover, regardless of stimulus parameters such as check size, the HDR was characterised by age. In concurrence with present neuroimaging literature, we conclude that the visual HDR decreases as healthy ageing proceeds. PMID:25909849

  12. Revised Age Constraints on Absolute Age Limits for Mercury's Kuiperian and Mansurian Systems

    NASA Astrophysics Data System (ADS)

    Banks, Maria E.; Zhiyong, Xiao; Braden, Sarah E.; Marchi, Simone S.; Barlow, Nadine G.; Chapman, Clark R.; Fassett, Caleb I.

    2015-11-01

    On the basis of morphologically distinct basin and crater deposits, Mercury’s surface units have been subdivided into five time-stratigraphic systems (youngest to oldest): Kuiperian, Mansurian, Calorian, Tolstojan, and pre-Tolstojan. Approximate age limits were initially suggested for these systems on the basis of the lunar-derived impact-flux history. High-resolution and multi-band image data obtained by the MErcury Surface, Space ENviroment, GEochemistry, and Ranging (MESSENGER) spacecraft were used to catalogue fresh impact craters interpreted to have formed during the Mansurian and Kuiperian systems. Mansurian and Kuiperian craters are characterized as morphologically fresh with crisp morphologies, well-preserved rims, few or no superposed craters, continuous ejecta with radial lineaments, and well-defined secondary craters; Kuiperian craters have bright ray systems while Mansurian craters maintain fresh morphologies but no longer have discernable ray systems.The density of fresh craters in these datasets, along with the recent production and chronology function of Marchi et al. [2009], are used to estimate new limits for the boundaries of the two most recent of Mercury’s systems. Given the effects of strength and other parameters (such as density), we estimate a model age for the population of craters that have formed since the onset of the Mansurian of ~1.9 ±0.3 Gyr. Likewise we estimate a model age for the population of craters that have formed since the onset of the Kuiperian of ~300 ±40 Myr. A particularly good fit for the Mansurian crater size frequency distribution (SFD) was found for the NEO-derived crater distribution. The same is true for the Kuiperian SFD, although the fit is not as robust as for the Mansurian SFD.

  13. The absolute age of events in Earth and human history on the basis of radiocarbon dating

    NASA Astrophysics Data System (ADS)

    Pazdur, Anna

    2011-01-01

    Radiocarbon chronometry holds a special place among the many discoveries made in the field of applied nuclear research. Few discoveries in fact, even among those being honored with the Nobel Prize, have had such a powerful and lasting impact on the further development of science. This method, as well as many other complex research methods, which appear to constitute an independent scientific discipline, arose as a result of many years of work by a team of several scientists. However, the actual founder of radiocarbon chronometry was one man, Willard Frank Libby, honored for his contribution with the Nobel Prize in Chemistry in 1960. In Poland, the creative activity in this area was begun in the late 1940s by Włodzimierz Mościcki, who continued it in the last 10 years of his life in the Silesian University of Technology in Gliwice, where he founded the Gliwice Radiocarbon Laboratory.

  14. Adolescents' Age Preferences for Dating Partners: Support for an Evolutionary Model of Life-History Strategies.

    ERIC Educational Resources Information Center

    Kenrick, Douglas T.; And Others

    1996-01-01

    Explored sex differences in adolescent preference for older versus younger mates. Found that teenage males were willing to date females of a wide age range, whereas teenage females prefer dating males from their own age to several years older. Data suggested viewing development of sex differences in dating partner preference from the perspective…

  15. Dating the End of the Greek Bronze Age: A Robust Radiocarbon-Based Chronology from Assiros Toumba

    PubMed Central

    Wardle, Kenneth; Higham, Thomas; Kromer, Bernd

    2014-01-01

    Over 60 recent analyses of animal bones, plant remains, and building timbers from Assiros in northern Greece form an unique series from the 14th to the 10th century BC. With the exception of Thera, the number of 14C determinations from other Late Bronze Age sites in Greece has been small and their contribution to chronologies minimal. The absolute dates determined for Assiros through Bayesian modelling are both consistent and unexpected, since they are systematically earlier than the conventional chronologies of southern Greece by between 70 and 100 years. They have not been skewed by reference to assumed historical dates used as priors. They support high rather than low Iron Age chronologies from Spain to Israel where the merits of each are fiercely debated but remain unresolved. PMID:25222862

  16. Dating the end of the Greek Bronze Age: a robust radiocarbon-based chronology from Assiros Toumba.

    PubMed

    Wardle, Kenneth; Higham, Thomas; Kromer, Bernd

    2014-01-01

    Over 60 recent analyses of animal bones, plant remains, and building timbers from Assiros in northern Greece form an unique series from the 14th to the 10th century BC. With the exception of Thera, the number of 14C determinations from other Late Bronze Age sites in Greece has been small and their contribution to chronologies minimal. The absolute dates determined for Assiros through Bayesian modelling are both consistent and unexpected, since they are systematically earlier than the conventional chronologies of southern Greece by between 70 and 100 years. They have not been skewed by reference to assumed historical dates used as priors. They support high rather than low Iron Age chronologies from Spain to Israel where the merits of each are fiercely debated but remain unresolved. PMID:25222862

  17. Summary of potassium/argon age dating, 1980

    SciTech Connect

    Evans, S.H. Jr.; Brown, F.H.

    1980-11-01

    A significant improvement in efficiency of the K-Ar laboratory was brought about by completion of a second extraction line. Two extractions can now be done routinely each day and the /sup 38/Ar spike ratios of the new table will permit dating of much younger samples than previously. Extensive K-Ar dating of samples from the Mineral Mountains shows intervals of silicic volcanism at 0.5, 0.8 and 7.5 m.y. K-Ar dating of plutonic units does not present a consistent picture, however. Plutonic events 35 to 40 m.y., 29 m.y. and 19 to 21 m.y. ago are suggested but interpretation must be considered preliminary. Joint programs with the US Geological Survey now underway to study the Rb-Sr and U-Pb systematics of the Mineral Mountains pluton should aid in unravelling its history. Dating of basalts from the Cove Creek Domes/Twin Peaks area, Utah, has aided in delineating the timing of basaltic volcanism. This adds to the already extensive data on the chronology of volcanic activity in the area. Dating of samples from the Beowawe Known Geothermal Resources Area, Nevada have confirmed earlier dates indicating major volcanism took place 38 m.y. ago and 17 to 16 m.y. ago.

  18. Age-Sensitive Effect of Adolescent Dating Experience on Delinquency and Substance Use

    ERIC Educational Resources Information Center

    Kim, Ryang Hui

    2013-01-01

    This study uses a developmental perspective and focuses on examining whether the impact of adolescent dating is age-sensitive. Dating at earlier ages is hypothesized to have a stronger effect on adolescent criminal behavior or substance use, but the effect would be weaker as one ages. The data obtained from the National Longitudinal Survey of…

  19. Redefinition of the crater-density and absolute-age boundaries for the chronostratigraphic system of Mars

    USGS Publications Warehouse

    Werner, S.C.; Tanaka, K.L.

    2011-01-01

    For the boundaries of each chronostratigraphic epoch on Mars, we present systematically derived crater-size frequencies based on crater counts of geologic referent surfaces and three proposed " standard" crater size-frequency production distributions as defined by (a) a simple -2 power law, (b) Neukum and Ivanov, (c) Hartmann. In turn, these crater count values are converted to model-absolute ages based on the inferred cratering rate histories. We present a new boundary definition for the Late Hesperian-Early Amazonian transition. Our fitting of crater size-frequency distributions to the chronostratigraphic record of Mars permits the assignment of cumulative counts of craters down to 100. m, 1. km, 2. km, 5. km, and 16. km diameters to martian epochs. Due to differences in the " standard" crater size-frequency production distributions, a generalized crater-density-based definition to the chronostratigraphic system cannot be provided. For the diameter range used for the boundary definitions, the resulting model absolute age fits vary within 1.5% for a given set of production function and chronology model ages. Crater distributions translated to absolute ages utilizing different curve descriptions can result in absolute age differences exceeding 10%. ?? 2011 Elsevier Inc.

  20. Stratigraphy, structure, absolute age, and paleontology of the upper Pleistocene deposits at Sankaty Head, Nantucket Island, Massachusetts

    USGS Publications Warehouse

    Oldale, Robert N.; Valentine, Page C.; Cronin, T. M.; Spiker, E. C.; Blackwelder, B. W.; Belknap, D.F.; Wehmiller, J. F.; Szabo, B. J.

    1982-01-01

    The Sankaty Head cliff exposes drift of at least two glaciations and interglacial marine deposits. Radiocarbon, amino-acid- racemization, and uranium-thorium analyses were used to determine the absolute ages of the beds. The results indicate that 1) the Sankaty Sand correlates with oxygen-isotope stage 5 (Sangamonian), 2) the underlying drift is older than stage 5 (Illinoian or older) , and 3) the overlying drift is Wisconsinan in age. -from Authors

  1. Using peripheral smear review, age and absolute lymphocyte count as predictors of abnormal peripheral blood lymphocytoses diagnosed by flow cytometry.

    PubMed

    Andrews, Jared M; Cruser, Dan L; Myers, Jerome B; Fernelius, Colby A; Holm, Mitchel T; Waldner, Dale L

    2008-09-01

    Absolute lymphocytosis in the elderly raises the possibility of malignancy and generally warrants further investigation. To better correlate clinical variables with the frequency of neoplastic lymphoid processes in this population, we retrospectively reviewed archived flow cytometric analyses from peripheral blood specimens on patients of 50 years of age and older that had been deemed suspicious for a lymphoproliferative process after peripheral smear review. Age, absolute lymphocyte count (ALC), white blood cell count and relative lymphocyte count were correlated with the results of flow cytometry. Of 71 total cases, 42 (59%) had an abnormal immunophenotype. Independent variables that showed significant differences between normal and abnormal immunophenotype were mean age (p = 0.001) and ALC (p = 0.0032). We combined age and absolute lymphocyte count variables to look for the best possible cutoff values to predict the likelihood of an abnormal immunophenotype. ALC cutoff values of >or=4 x 10(9) cells/L for patients over 67 years of age, and >6.7 x 10(9) cells/L for patients between 50 and 67 years of age, had a high sensitivity for detecting an abnormal immunophenotype. PMID:18798107

  2. Terrestrial Ages of Antarctic Meteorites: Up Date 1999

    NASA Technical Reports Server (NTRS)

    Nishiizumi, K.; Caffee, M. W.; Welten, K. C.

    2000-01-01

    We are continuing our ongoing study of cosmogenic nuclides in Antarctic meteorites. In addition to the studies of exposure histories of meteorites, we study terrestrial ages and pairing of Antarctic meteorites and desert meteorites. Terrestrial ages of Antarctic meteorites provide information on meteorite accumulation mechanisms, mean weathering lifetimes, and influx rates. The determination of Cl-36 (half-life=3.01 x 10(exp 5) y) terrestrial ages is one of our long-term on-going projects, however, in many instances neither Cl-36 or C-14 (5,730 y) yields an accurate terrestrial age. Using Ca-41 (1.04 x 10(exp 5) y) for terrestrial age determinations solves this problem by filling the gap in half-life between C-14 and Cl-36 ages. We are now applying the new Ca-41 - Cl-36 terrestrial age method as well as the Cl-36 - Be-10 method to Antarctic meteorites. Our measurements and C-14 terrestrial age determinations by the University of Arizona group are always complementary.

  3. Dating, Sex, and Substance Use Predict Increases in Adolescents' Subjective Age across Two Years

    ERIC Educational Resources Information Center

    Galambos, Nancy L.; Albrecht, Arne K.; Jansson, S. Mikael

    2009-01-01

    This study examined the nature of the relationship between adolescents' subjective age (how old they feel) and chronological age, and explored whether dating, sex, and substance use predicted increases in adolescents' subjective age across a two-year period. The participants were 570 adolescents who were interviewed when they were first ages 12-19…

  4. Maximum Age Predictions for Optical Dating on Mars Based on Dose/Depth Models and Martian Meteorite Compositions

    NASA Astrophysics Data System (ADS)

    Franklund, R. T.; Lepper, K.

    2004-12-01

    A fundamental need in the Mars exploration portfolio is in-situ absolute dating. Optical dating has been proposed for determining the age of Mars surface features and landforms as well as the rates of martian surface processes. On Earth, the method is employed for Quaternary studies because the technique currently has a terrestrial maximum age limit of approximately 350 ka. This maximum age limit is a function of the saturation dose of the dosimeter material (silicate sediments) and the local ionizing radiation dose rate. The sources of ionizing radiation germane to optical dating are K, Rb, U, Th in the sediment/soil environment and cosmic rays. On Mars the near surface dose rate will be dominated by cosmic rays, however, at depth the decay of radioisotopes will be the principle contributor of ionizing radiation. In this work we present an evaluation of the maximum age limits for OSL dating on Mars as a function of depth. At this time we have considered only static burial. Our calculations are based on published models of and data for: (i) Mars surface cosmic dose rate and its attenuation by martian regolith, (ii) elemental analyses of Mars meteorites, (iii) an experimental evaluation of the saturation dose for the martian soil simulant JSC Mars-1. Our analysis confirms earlier inferences that optical dating should have a greater effective age range on Mars than on Earth. At depths easily accessible by penetrators or moles (1-3 m), maximum optical ages greater than 600 ka are possible. Geochronology on this scale would include at least two stadial/interstadial cycles within Mars' last "Glacial Epoch" (synchronized insolation variations between the poles). A wide range of landforms and surface processes associated with climate variability -- e.g. outwash and lacustrine deposition, large-scale eolian activation -- could potentially be optically dated. At greater depths, that could be reached by mobile drilling rigs or cryobots (10-30m), optical age maximums of 4

  5. Age constraints for Palaeolithic cave art by U-Th dating of thin carbonate crusts

    NASA Astrophysics Data System (ADS)

    Hoffmann, Dirk; Pike, Alistair; Garcia-Diez, Marcos; Pettitt, Paul; Zilhão, João

    2015-04-01

    U-series dating is an important geochronological tool which is widely applied for instance in speleothem based palaeoclimate research. It has also great potential to provide age constraints for Archaeology, especially for sites or artefacts in cave environments. We present our methods to conduct precise U-Th dating of calcite crusts that formed on top of cave paintings. Recent developments in multi-collector (MC) inductively coupled plasma mass spectrometry (ICPMS) U-series dating greatly improved the precision of this method, and sample sizes needed to obtain reliable results were significantly reduced. Based on these developments the U-series technique can be applied for accurate dating of thin calcite crusts covering cave art at many sites, while taking care not to harm the art underneath. The method provides minimum ages for the covered art and, where possible, also maximum ages by dating the flowstone layer the art is painted on. The U-Th method has been used in a number of recent projects to date calcite precipitates above and occasionally below cave paintings in Spain. Initial results from Cantabria have shown that the earliest dated paintings are older than 41.4 ± 0.6 ka, dating at least to the Early Aurignacian period and present a far longer chronology than that based so far on radiocarbon dating. Here we outline our methodology and the steps we take to demonstrate the reliability of U-Th dates, and present some recent results of our ongoing U-Th dating programme.

  6. Absolute model ages of mantled surfaces in Malea Planum and Utopia Planitia, Mars.

    NASA Astrophysics Data System (ADS)

    Willmes, M.; Hiesinger, H.; Reiss, D.; Zanetti, M.

    2009-04-01

    The surface of Mars is partially covered by a latitude-dependent ice-rich smooth mantle in the middle and high latitudes (±30-60°) [1, 2]. These deposits relate to changes in the obliquity of Mars which have led to major shifts in the Martian climate and repeated global episodes of deposition [3]. The deposits vary in thickness and are usually independent of local geology, topography and elevation. In this study we have determined absolute model ages for the mantled surface units in Utopia Planitia (northern hemisphere) and Malea Planum (southern hemisphere) using crater statistics [4]. These regions show a specific type of mantle degradation called scalloped terrain, and modelled crater retention ages of the easily eroded mantle in these regions reveal the time since the last resurfacing. Images from the High Resolution Imaging Science Experiment (HiRISE) (25-50 cm/pixel spatial resolution) on board the Mars Reconnaissance Orbiter (MRO) were analyzed, continuous areas of smooth mantle were mapped, and small, fresh, unmodified craters were counted. Both regions show degradation features of the mantle in varying degrees. The mantle in Utopia Planitia appears heavily modified by polygonal fractures and scalloped depressions [5]. Scalloped depressions are also found in Malea Planum, but the mantle appears much smoother and less modified by periglacial processes [5, 6]. The study areas totalled 722 km² in Utopia Planitia, and 296 km² in Malea Planum. Model ages for these regions were determined using the chronology function of Hartmann and Neukum [4] and the production function Ivanov [7]. The model ages show that the mantle unit for the area mapped in Utopia Planitia is 0.65 (+0.35/-0.41) to 2.9 (+0.69/-0.75) Myr old and Malea Planum is 3.0 (+1.5/-1.7) to 4.5 (+1.3/-1.4) Myr old, and that both regions represent very recent Amazonian terrain. This is also in agreement with the observed young degradation features described by [6, 8]. We acknowledge that the

  7. Insights from fossil coral U-Th age data from the Last Interglacial: Implications for seawater U-isotope composition and interpretation of absolute ages

    NASA Astrophysics Data System (ADS)

    Dutton, A.; Esat, T. M.

    2011-12-01

    For several decades, scientists have exploited the accurate and precise ages provided by mass spectrometric U-series ages of fossil corals that live near the sea surface to develop sea level reconstructions for the Late Quaternary. This technique allows for the calculation of both the age of the coral as well as the U-isotope composition of seawater at the time of growth. Until recently, the seawater [234U/238U] activity ratio was considered invariant over glacial-interglacial cycles that can be dated via U-series given the estimated residence time of U in the oceans of ~400 thousand years. Hence, the calculated initial [234U/238U] ratio of a coral was used as a check for diagenesis and open-system behavior of U and Th isotopes whereby corals that exhibited elevated [234U/238U] ratios were considered altered and their ages considered unreliable. This was a valuable tool as some corals that passed all other diagenetic screening criteria still demonstrated open-system behavior according to this criterion. However, it has since been recognized that the seawater [234U/238U] ratio has varied, even over the past glacial cycle raising questions about the appropriate use of the [234U/238U] diagenetic screening technique as well as regarding the actual history of seawater [234U/238U] variability which remains uncertain. Compilations of coral U-Th age data over the last glacial cycle indicate that the [234U/238U] ratio was significantly lower during the last glacial maximum and similar to that of modern for the last several interglacial periods. Recently, >700 coral U-Th age measurements on Last Interglacial corals were compiled to determine relative sea level reconstructions at globally distributed sites and to assess the eustatic sea level signal given the expected nature of non-eustatic (isostatic and gravitational) effects at each site. Analysis of this compilation demonstrates that the mode in the distribution of initial [234U/238U] values consistently sits

  8. Stellar age dating with thorium, uranium and lead

    NASA Astrophysics Data System (ADS)

    Frebel, Anna; Kratz, Karl-Ludwig

    2009-06-01

    We present HE 1523-0901, a metal-poor star in which the radioactive elements Th and U could be detected. Only three stars have measured U abundances, of which HE 1523-0901 has the most confidently determined value. From comparing the stable Eu, Os, and Ir abundances with measurements of Th and U, stellar ages can be derived. Based on seven such chronometer abundance ratios, the age of HE 1523-0901 was found to be ~13 Gyr. Only an upper limit for Pb could be measured so far. Knowing all three abundances of Th, U, and Pb would provide a self-consistent test for r-process calculations. Pb is the beta- plus alpha-decay end-product of all decay chains in the mass region between Pb and the onset of dominant spontaneous fission above Th and U. Hence, in addition to Th/U also Th, U/Pb should be used to obtain a consistent picture for actinide chronometry. From recent r-process calculations within the classical “waiting-point” model, for a 13 Gyr old star we predict the respective abundance ratios of logγ(Th/U) = 0.84, logγ(Th/Pb) = -1.32 and logγ(U/Pb) = -2.16. We compare these values with the measured abundance ratios in HE 1523-0901 of logγ(Th/U) = 0.86, logγ(Th/Pb) > -1.0 and logγ(U/Pb) > -1.9. With this good level of agreement, HE 1523-0901 is already a vital probe for observational “near-field” cosmology by providing an independent lower limit for the age of the Universe.

  9. A high-resolution, absolute-dated deglacial speleothem record of Indian Ocean climate from Socotra Island, Yemen

    NASA Astrophysics Data System (ADS)

    Shakun, Jeremy D.; Burns, Stephen J.; Fleitmann, Dominik; Kramers, Jan; Matter, Albert; Al-Subary, Abdulkarim

    2007-07-01

    Stalagmite M1-5 from Socotra Island, Yemen in the northwest Indian Ocean provides a robust, high-resolution paleoclimate record from ˜ 27.4-11.1 ka based on 717 stable isotope and 28 230Th measurements. Variations in M1-5 oxygen isotope ratios ( δ18O) are interpreted to be primarily driven by an amount effect related to changes in the mean position and/or intensity of convection of the intertropical convergence zone, the island's only source of precipitation. The M1-5 δ18O time series is strongly correlated to the Greenland ice cores, similar to an older Socotra speleothem deposited from 53-40 ka [S.J. Burns, D. Fleitmann, A. Matter, J. Kramers, A. Al-Subbary, Indian Ocean climate and an absolute chronology over Dansgaard/Oeschger events 9 to 13, Science 301 (2003) 1365-1367], indicating that a North Atlantic-Indian Ocean cold-dry/warm-wet teleconnection persisted through the end of the last glacial period. Peak aridification occurred at ˜ 23 ka and a gradual increase in moisture thereafter was interrupted by an abrupt drying event at ˜ 16.4 ka, perhaps related to Heinrich event 1. Indian Ocean rainfall increased dramatically during the Bølling period and then decreased continuously and gradually through the Allerød and Younger Dryas. The Holocene began abruptly with increased precipitation at 11.4 ka and was followed by a major but short-lived drying during the Preboreal Oscillation at ˜ 11.2 ka. M1-5 is highly correlated to the Dongge Cave record from 15.5-11 ka, suggesting much of the Indian Ocean monsoon region responded similarly to the major climate changes of the last deglaciation. The transitions into the Younger Dryas and to a lesser extent the Bølling are remarkably gradual in M1-5, as they are in all other Asian speleothem records, occurring over several centuries. These gradual transitions are in striking contrast to high-resolution records from around the North Atlantic basin where the transitions are extremely abrupt and generally occur in

  10. Dating, Sex, and Substance Use as Correlates of Adolescents' Subjective Experience of Age

    ERIC Educational Resources Information Center

    Arbeau, Kelly J.; Galambos, Nancy L.; Jansson, S. Mikael

    2007-01-01

    This study examined in a random community-based sample of 664 12-19-year-olds, the relation of subjective experience of age (SEA) with chronological age, dating experience, sexual activity, and substance use. The results revealed a positive linear relation between SEA and chronological age: individuals who were chronologically older felt…

  11. Evaluation of the Re-Os Geochronometer in Organic-rich Mudrocks as a Method for Constraining the Absolute Ages of Neoproterozoic Glaciogenic Deposits

    NASA Astrophysics Data System (ADS)

    Kendall, B. S.; Creaser, R. A.; Ross, G. M.

    2002-12-01

    Absolute-age constraints on the Neoproterozoic glaciations are generally poor due to a paucity of suitable plutonic and volcanic igneous rocks that are temporally and spatially related to Neoproterozoic glaciogenic deposits and are amenable to radiometric dating methods. In this study, the Re-Os isotope systematics of dark gray, sulfidic slates from the Old Fort Point Formation (OFP) of the Windermere Supergroup (near Jasper, Alberta) were examined to test the ability of the Re-Os geochronometer to provide an absolute age constraint for a Neoproterozoic glaciogenic deposit. The OFP has been interpreted as the deep water expression of post-glacial sea level rise and therefore is comparable stratigraphically to cap carbonates that immediately overlie glaciogenic deposits worldwide. Despite the relatively low Re (6-16 ppb) and Os (0.07-0.14 ppb) concentrations and total organic contents (~ 0.5% TOC) of the slates compared to other organic-rich mudrocks used in previous Re-Os isotope studies, precise well-fitted Re-Os isochrons have been obtained with two different dissolution methods. An age of 620.8 +/- 8.1 Ma (MSWD = 0.9; initial 187Os/188Os = 0.68 +/- 0.06) is obtained using conventional aqua regia dissolution. Using a method designed to selectively dissolve organic matter alone, an age of 609.0 +/- 8.3 Ma (MSWD = 1.5; initial 187Os/188Os = 0.62 +/- 0.05) is obtained. These absolute age results are in accord with existing age constraints (e.g., stratigraphically younger Hamill Group with a U-Pb zircon age of 569 Ma). The well-defined Re-Os systematics of the OFP slates demonstrates for the first time that the Re-Os system is not disturbed in organic-rich sediments during lower greenschist (-chlorite) grade metamorphic conditions. The whole-rock analysis of each individual sample yields consistently higher initial 187Os/188Os isotope ratios than the corresponding organic matter analysis and suggests that a significant radiogenic detrital Os component is present

  12. In Situ Geochemical Analysis and Age Dating of Rocks Using Laser Ablation-Miniature Mass Spectrometer

    NASA Technical Reports Server (NTRS)

    Sinha, Mahadeva P.; Hecht, Michael H.; Hurowitz, Joel A.

    2012-01-01

    A miniaturized instrument for performing chemical and isotopic analysis of rocks has been developed. The rock sample is ablated by a laser and the neutral species produced are analyzed using the JPL-invented miniature mass spectrometer. The direct sampling of neutral ablated material and the simultaneous measurement of all the elemental and isotopic species are the novelties of this method. In this laser ablation-miniature mass spectrometer (LA-MMS) method, the ablated neutral atoms are led into the electron impact ionization source of the MMS, where they are ionized by a 70-eV electron beam. This results in a secondary ion pulse typically 10-100 microsecond wide, compared to the original 5-10-nanosecond laser pulse duration. Ions of different masses are then spatially dispersed along the focal plane of the magnetic sector of the miniature mass spectrometer and measured in parallel by a modified CCD (charge-coupled device) array detector capable of detecting ions directly. Compared to conventional scanning techniques, simultaneous measurement of the ion pulse along the focal plane effectively offers a 100% duty cycle over a wide mass range. LAMMS offers a more quantitative assessment of elemental composition than techniques that detect laser-ionized species produced directly in the ablation process because the latter can be strongly influenced by matrix effects that vary with the structure and geometry of the surface, the laser beam, and the ionization energies of the elements. The measurement of high-precision isotopic ratios and elemental composition of different rock minerals by LAMMS method has been demonstrated. The LA-MMS can be applied for the absolute age determination of rocks. There is no such instrument available presently in a miniaturized version that can be used for NASA space missions. Work is in progress in the laboratory for geochronology of rocks using LA-MMS that is based on K-Ar radiogenic dating technique.

  13. Age calibration of weathering fractures in desert clasts: A new approach to dating geomorphic surfaces in arid landscapes

    NASA Astrophysics Data System (ADS)

    D'Arcy, Mitch; Roda Boluda, Duna; Whittaker, Alex

    2014-05-01

    Advances in geomorphological and sedimentological research depend on the availability of reliable exposure age constraints. Establishing robust age models at a high spatial and temporal resolution is crucial for measuring rates of geomorphological change and decoding complex landscapes shaped by time-dependent forces, e.g. climate fluctuations. A number of isotopic and luminescence techniques are now available for dating geomorphic surfaces, however they remain expensive and time-consuming to deploy with detailed coverage over space and time in many study areas. For this reason, quick and accessible methods for correlating and extrapolating these chronologies are needed. In arid landscapes, among others, a variety of weathering-induced changes occur to geomorphic and sedimentary surfaces, and many of these processes occur at predictable rates and can be quantified using objective, field based measurements. One example is the gradual widening of fractures that exist within boulders on desert surfaces, by a combination of processes including salt weathering and freeze-thaw cycles. The recent emergence of very detailed exposure age models in a number of locations means it is now possible to measure the rates of desert weathering processes, and use them as fully calibrated age indicators themselves. With the potential to significantly extend the coverage of existing age constraints, this kind of quantitative age correlation would enable a broad range of geomorphological and sedimentological research that depends on detailed absolute age models. We have measured the mean widths of hundreds of vertical fractures that dissect granitic boulders, on a variety of alluvial surfaces in Owens Valley, California, which have themselves been independently dated in detail using cosmogenic nuclides. Our data demonstrates for the first time that these fractures widen at a predictable, steady rate of approximately 1 mm ka-1 for at least the last 150 ka, in this arid study area in the

  14. Predicting Absolute Risk of Type 2 Diabetes Using Age and Waist Circumference Values in an Aboriginal Australian Community

    PubMed Central

    2015-01-01

    Objectives To predict in an Australian Aboriginal community, the 10-year absolute risk of type 2 diabetes associated with waist circumference and age on baseline examination. Method A sample of 803 diabetes-free adults (82.3% of the age-eligible population) from baseline data of participants collected from 1992 to 1998 were followed-up for up to 20 years till 2012. The Cox-proportional hazard model was used to estimate the effects of waist circumference and other risk factors, including age, smoking and alcohol consumption status, of males and females on prediction of type 2 diabetes, identified through subsequent hospitalisation data during the follow-up period. The Weibull regression model was used to calculate the absolute risk estimates of type 2 diabetes with waist circumference and age as predictors. Results Of 803 participants, 110 were recorded as having developed type 2 diabetes, in subsequent hospitalizations over a follow-up of 12633.4 person-years. Waist circumference was strongly associated with subsequent diagnosis of type 2 diabetes with P<0.0001 for both genders and remained statistically significant after adjusting for confounding factors. Hazard ratios of type 2 diabetes associated with 1 standard deviation increase in waist circumference were 1.7 (95%CI 1.3 to 2.2) for males and 2.1 (95%CI 1.7 to 2.6) for females. At 45 years of age with baseline waist circumference of 100 cm, a male had an absolute diabetic risk of 10.9%, while a female had a 14.3% risk of the disease. Conclusions The constructed model predicts the 10-year absolute diabetes risk in an Aboriginal Australian community. It is simple and easily understood and will help identify individuals at risk of diabetes in relation to waist circumference values. Our findings on the relationship between waist circumference and diabetes on gender will be useful for clinical consultation, public health education and establishing WC cut-off points for Aboriginal Australians. PMID:25876058

  15. Round-robin 230Th–234U age dating of bulk uranium for nuclear forensics

    DOE PAGESBeta

    Gaffney, Amy M.; Hubert, Amélie; Kinman, William S.; Magara, Masaaki; Okubo, Ayako; Pointurier, Fabien; Schorzman, Kerri C.; Steiner, Robert E.; Williams, Ross W.

    2015-07-30

    In an inter-laboratory measurement comparison study, four laboratories determined 230Th–234U model ages of uranium certified reference material NBL U050 using isotope dilution mass spectrometry. The model dates determined by the participating laboratories range from 9 March 1956 to 19 October 1957, and are indistinguishable given the associated measurement uncertainties. As a result, these model ages are concordant with to slightly older than the known production age of NBL U050.

  16. Easy Absolute Values? Absolutely

    ERIC Educational Resources Information Center

    Taylor, Sharon E.; Mittag, Kathleen Cage

    2015-01-01

    The authors teach a problem-solving course for preservice middle-grades education majors that includes concepts dealing with absolute-value computations, equations, and inequalities. Many of these students like mathematics and plan to teach it, so they are adept at symbolic manipulations. Getting them to think differently about a concept that they…

  17. The Relative and Absolute Ages of Old Globular Clusters in the LCDM Framework

    NASA Astrophysics Data System (ADS)

    Trenti, Michele; Padoan, Paolo; Jimenez, Raul

    2015-08-01

    Old globular clusters (GCs) in the Milky Way have ages of about 13 Gyr, placing their formation time in the reionization epoch. We propose a novel scenario for the formation of these systems based on the merger of two or more atomic cooling halos at high redshift (z\\gt 6). First-generation stars are formed as an intense burst in the center of a minihalo that grows above the threshold for hydrogen cooling (halo mass {M}{{h}}∼ {10}8 {M}ȯ ) by undergoing a major merger within its cooling timescale (∼150 Myr). Subsequent minor mergers and sustained gas infall bring a new supply of pristine gas to the halo center, creating conditions that can trigger new episodes of star formation. The dark-matter halo around the GC is then stripped during assembly of the host-galaxy halo. Minihalo merging is efficient only in a short redshift window, set by the {{Λ }}{CDM} parameters, allowing us to make a strong prediction on the age distribution for old GCs. From cosmological simulations, we derive an average merging redshift < z> =9 and a narrow distribution {{Δ }}z=2, implying average GC age < {t}{age}> =13.0+/- 0.2 {Gyr} including ∼0.2 Gyr of star formation delay. Qualitatively, our scenario reproduces other general old GC properties (characteristic masses and number of objects, metallicity versus galactocentric radius anticorrelation, radial distribution), but unlike age, these generally depend on details of baryonic physics. In addition to improved age measurements, direct validation of the model at z∼ 10 may be within reach with ultradeep gravitationally lensed observations with the James Webb Space Telescope.

  18. Luminescence dating and palaeomagnetic age constraint on hominins from Sima de los Huesos, Atapuerca, Spain.

    PubMed

    Arnold, Lee J; Demuro, Martina; Parés, Josep M; Arsuaga, Juan Luis; Aranburu, Arantza; Bermúdez de Castro, José María; Carbonell, Eudald

    2014-02-01

    Establishing a reliable chronology on the extensive hominin remains at Sima de los Huesos is critical for an improved understanding of the complex evolutionary histories and phylogenetic relationships of the European Middle Pleistocene hominin record. In this study, we use a combination of 'extended-range' luminescence dating techniques and palaeomagnetism to provide new age constraint on sedimentary infills that are unambiguously associated with the Sima fossil assemblage. Post-infrared-infrared stimulated luminescence (pIR-IR) dating of K-feldspars and thermally transferred optically stimulated luminescence (TT-OSL) dating of individual quartz grains provide weighted mean ages of 433 ± 15 ka (thousands of years) and 416 ± 19 ka, respectively, for allochthonous sedimentary horizons overlying the hominin-bearing clay breccia. The six replicate luminescence ages obtained for this deposit are reproducible and provide a combined minimum age estimate of 427 ± 12 ka for the underlying hominin fossils. Palaeomagnetic directions for the luminescence dated sediment horizon and underlying fossiliferous clays display exclusively normal polarities. These findings are consistent with the luminescence dating results and confirm that the hominin fossil horizon accumulated during the Brunhes Chron, i.e., within the last 780 ka. The new bracketing age constraint for the Sima hominins is in broad agreement with radiometrically dated Homo heidelbergensis fossil sites, such as Mauer and Arago, and suggests that the split of the H. neanderthalensis and H. sapiens lineages took place during the early Middle Pleistocene. More widespread numerical dating of key Early and Middle Pleistocene fossil sites across Europe is needed to test and refine competing models of hominin evolution. The new luminescence chronologies presented in this study demonstrate the versatility of TT-OSL and pIR-IR techniques and the potential role they could play in helping to refine evolutionary

  19. Dating earthquakes with high-precision thorium-230 ages of very young corals

    NASA Technical Reports Server (NTRS)

    Edwards, R. Lawrence; Wasserburg, G. J.; Taylor, F. W.

    1988-01-01

    Three corals from Vanuatu Islands, whose ages were known from counting annual growth bands, were analyzed by Th-230 age analysis to asses the accuracy of the Th-230 method. The comparison of Th-230 ages with the growth-band ages showed that the Th-230 ages were accurate within an error of + or - 3-5 y. Th-230 dates were then determined for two adjacent emerged heads from Santo Island; the dates were the same, indicating that the heads died at the same time, and consistent with the theory that they were killed by coseismic emergence around 1865 AD. The difference between this data and the data of the only major historically documented earthquake that caused an uplift (1973) suggests a seismic recurrence interval of 108 + or - 4 y for Santo. It is suggested that this approach may be extended back in time and to other localities.

  20. Thermoluminescence dating of sediments: a re-extension of age range for loess

    SciTech Connect

    Johnson, R.J.; Stipp, J.J.; Wintle, A.G.; Tamers, M.A.

    1985-01-01

    Thermoluminescence (TL) dating of wind blown minerals provides a technique whereby non-carbonaceous sediments could be dated to several hundred thousand years. Two recent reports, however, indicate age underestimates on feldspar in some European loesses older than 50 ka, the effect increasing in severity with age. Suggested causes include decay of luminescence centers, or does dependent sensitivity changes. Data presented in this paper do not support these limitations or explanations. TL provides 3 separate techniques of dating sediments, which, when used together, prove to be efficient internal cross checks for mineralogical anomalies or inconsistencies created by any of the individual methods. In the authors studies each sample was dated by all 3 methods whereas the Europeans analyses employed only the Regeneration technique. This work presents results from loess sections in Mississippi, Illinois and Alaska. These show excellent internal consistency, and consistency with both independent dating methods and stratigraphy, with 2 exceptions. Both exceptions were by the Regen technique giving age underestimates up to 30%. The underestimates were found to be caused by a change in mineral sensitivity resulting from the Regen requirements of strong laboratory light-bleaching followed by irradiations. A simple method to test and correct for this condition is presented. TL thus appears to remain a powerful and increasingly flexible method of sediment dating.

  1. Carbon dioxide respiration in the deep vadose zone: Implications for groundwater age dating

    NASA Astrophysics Data System (ADS)

    Bacon, Diana Holford; Keller, C. Kent

    1998-11-01

    In the deep vadose zone at the Dalmeny site, subsurface gas samples were collected and analyzed for CO2 and the 13C and 14C ratios of that CO2. High concentrations of CO2 depleted in 14C near the water table necessitate the use of an open-system model of calcite dissolution to match observed dissolved inorganic carbon 14C ratios just below the water table. Groundwater age-dating models assuming closed-system calcite dissolution predict incorrect groundwater age dates at the Dalmeny site. These results and our field observations suggest that such errors may generally occur where deep-vadose generation of nonmodern CO2 is not accounted for in groundwater age-dating exercises.

  2. Age Dating Fluvial Sediment Storage Reservoirs to Construct Sediment Waiting Time Distributions

    NASA Astrophysics Data System (ADS)

    Skalak, K.; Pizzuto, J. E.; Benthem, A.; Karwan, D. L.; Mahan, S.

    2015-12-01

    Suspended sediment transport is an important geomorphic process that can often control the transport of nutrients and contaminants. The time a particle spends in storage remains a critical knowledge gap in understanding particle trajectories through landscapes. We dated floodplain deposits in South River, VA, using fallout radionuclides (Pb-210, Cs-137), optically stimulated luminescence (OSL), and radiocarbon dating to determine sediment ages and construct sediment waiting time distributions. We have a total of 14 age dates in two eroding banks. We combine these age dates with a well-constrained history of mercury concentrations on suspended sediment in the river from an industrial release. Ages from fallout radionuclides document sedimentation from the early 1900s to the present, and agree with the history of mercury contamination. OSL dates span approximately 200 to 17,000 years old. We performed a standard Weibull analysis of nonexceedance to construct a waiting time distribution of floodplain sediment for the South River. The mean waiting time for floodplain sediment is 2930 years, while the median is approximately 710 years. When the floodplain waiting time distribution is combined with the waiting time distribution for in-channel sediment storage (available from previous studies), the mean waiting time shifts to approximately 680 years, suggesting that quantifying sediment waiting times for both channel and floodplain storage is critical in advancing knowledge of particle trajectories through watersheds.

  3. Reconstruction of the Late Quaternary Glaciation of the Macha Khola valley (Gorkha Himal, Nepal) using relative and absolute ( 14C, 10Be, dendrochronology) dating techniques

    NASA Astrophysics Data System (ADS)

    Zech, W.; Glaser, B.; Abramowski, U.; Dittmar, C.; Kubik, P. W.

    2003-11-01

    Late Quaternary glacier fluctuations in the Macha Khola valley (Gorkha Himal, Nepal) were reconstructed using relative and absolute dating techniques. Our results indicate that younger moraine complexes were left by Late Holocene (<1.7 cal. ka BP), mid-Holocene (ca 3 cal. ka BP), and Lateglacial (ca 13 cal. ka BP) ice advances. Older Late Quaternary glacier advances occurred during Marine Oxygen Isotope Stages (MIS) 2 and 3-4. No relics of Middle or Early Pleistocene glaciations could be found. During MIS 3-4, glaciers advanced down to an altitude of at least 2150 m a.s.l., corresponding to an ELA depression of approximately 1300 m. At about 3500 m a.s.l., the MIS 2 Macha Khola glacier reached almost the thickness of the former MIS 3-4 glacier and retreated some time before 17.9 cal. ka BP. The Lateglacial glacier advanced again several times to altitudes between 2450 and 3400 m a.s.l. The mid-Holocene glaciers extended much farther down-valley than the Late Holocene ones. Dendrochronological data of Abies spectabilis suggested several periods of unfavourable growth conditions especially at the beginning of the 19th (1820) and 20th (1905) centuries.

  4. The Absolute Age of the Globular Cluster M15 Using Near-infrared Adaptive Optics Images from PISCES/LBT.

    NASA Astrophysics Data System (ADS)

    Monelli, M.; Testa, V.; Bono, G.; Ferraro, I.; Iannicola, G.; Fiorentino, G.; Arcidiacono, C.; Massari, D.; Boutsia, K.; Briguglio, R.; Busoni, L.; Carini, R.; Close, L.; Cresci, G.; Esposito, S.; Fini, L.; Fumana, M.; Guerra, J. C.; Hill, J.; Kulesa, C.; Mannucci, F.; McCarthy, D.; Pinna, E.; Puglisi, A.; Quiros-Pacheco, F.; Ragazzoni, R.; Riccardi, A.; Skemer, A.; Xompero, M.

    2015-10-01

    We present deep near-infrared J, {K}{{s}} photometry of the old, metal-poor Galactic globular cluster M15 obtained with images collected with the LUCI1 and PISCES cameras available at the Large Binocular Telescope (LBT). We show how the use of First Light Adaptive Optics (FLAO) system coupled with the PISCES camera allows us to improve the limiting magnitude by ˜2 mag in {K}{{s}}. By analyzing archival Hubble Space Telescope data, we demonstrate that the quality of the LBT/PISCES color-magnitude diagram is fully comparable with analogous space-based data. The smaller field of view is balanced by the shorter exposure time required to reach a similar photometric limit. We investigated the absolute age of M15 by means of two methods: (i) by determining the age from the position of the main-sequence turnoff (MSTO), and (ii) by the magnitude difference between the MSTO and the well-defined knee detected along the faint portion of the MS. We derive consistent values of the absolute age of M15, that is, 12.9 ± 2.6 Gyr and 13.3 ± 1.1 Gyr, respectively. Observations were carried out using the Large Binocular Telescope at Mount Graham, AZ. The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are the University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; the Ohio State University; and the Research Corporation, on behalf of the University of Notre Dame, University of Minnesota, and University of Virginia.

  5. Age-dating of highly enriched Uranium by γ-spectrometry

    NASA Astrophysics Data System (ADS)

    Tam Nguyen, Cong

    2005-02-01

    A non-destructive, γ-spectrometric method for uranium age-dating is reported for the first time. The method relies on measuring the daughter/parent activity ratio 214Bi/ 234U by low-background, high-resolution γ-spectrometry and does not require the use of reference samples of known ages. The initial methodology was derived during a "Round-Robin" exercise, in which the properties of a HEU material relevant to nuclear forensics were assessed by several laboratories. The Uranium-age obtained by this γ-spectrometric method is in agreement with the results reported by other participating laboratories, which used mass-spectrometry for age dating.

  6. THE DYNAMICAL DISTANCE, RR LYRAE ABSOLUTE MAGNITUDE, AND AGE OF THE GLOBULAR CLUSTER NGC 6266

    SciTech Connect

    McNamara, Bernard J.; McKeever, Jean E-mail: jeanm12@nmsu.edu

    2011-11-15

    The internal proper motion dispersion of NGC 6266 was measured using Hubble Space Telescope Wide Field Planetary Camera 2 images with an epoch difference of eight years. The dispersion was found to be 0.041 {+-} 0.001 arcsec century{sup -1}. This value was then equated to the cluster's radial velocity dispersion of 13.7 {+-} 1.1 km s{sup -1} to yield a distance to NGC 6266 of 7054 {+-} 583 pc. Based on this distance we find that the NGC 6266 RR Lyrae stars have M{sub V} = 0.51 {+-} 0.18 mag. This magnitude is in good agreement with that predicted by the M{sub V} versus [Fe/H] relation found by Benedict et al. Using an average [Fe/H] of -1.25 for NGC 6266, their relation predicts M{sub V} = 0.49 {+-} 0.06. Based on the RR Lyrae M{sub V} versus age relation determined by Chaboyer et al., we estimate that NGC 6266 has an age of 11.4 {+-} 2.2 Gyr.

  7. THE IMPACT OF ENHANCED He AND CNONa ABUNDANCES ON GLOBULAR CLUSTER RELATIVE AGE-DATING METHODS

    SciTech Connect

    MarIn-Franch, Antonio; Aparicio, Antonio; Cassisi, Santi; Pietrinferni, Adriano E-mail: antapaj@iac.e E-mail: pietrinferni@oa-teramo.inaf.i

    2010-05-10

    The impact that unrecognized differences in the chemical patterns of Galactic globular clusters (GGCs) have on their relative age determinations is studied. The two most widely used relative age-dating methods, horizontal and vertical, together with the more recent relative MS-fitting method, were carefully analyzed on a purely theoretical basis. The BaSTI library was adopted to perform the present analysis. We find that relative ages derived using the horizontal and vertical methods are largely dependent on the initial He content and heavy element distribution. Unrecognized cluster-to-cluster chemical abundance differences can lead to an error in the derived relative ages as large as {approx}0.5 (or {approx}6 Gyr if an age of 12.8 Gyr is adopted for normalization) and even larger for some extreme cases. It is shown that the relative MS-fitting method is by far the age-dating technique for which undetected cluster-to-cluster differences in the He abundance have less impact. Present results are used in order to pose constraints on the maximum possible spread in the He and CNONa elements abundances on the basis of the estimates-taken from the literature-of the GGCs relative age dispersion obtained with the various relative age-dating techniques. Finally, it is shown that the age-metallicity relation found for young GGCs by the GC Treasury program is a real age sequence and cannot be produced by variations in the He and/or heavy element distribution.

  8. 14C dating of small archaeological samples: neolithic to iron age in the central alpine region

    NASA Astrophysics Data System (ADS)

    Bill, J.; Keller, W. A.; Erne, R.; Bonani, G.; Wölfli, W.

    1984-11-01

    Accelerator mass spectrometry (AMS) radiocarbon 14C dating will widen enormously the range and scope of archaeological investigations. This is due mainly to 100- to 1000-fold sample size reduction over conventional dating. In order to determine the size and the quality of samples that can be accepted for AMS 14C dating, we have selected archaeological samples relating to the Neolithic to Iron Age. The basis of our AMS target preparations is the coking (pyrolysis) of organic matter after elimination of impurities by various physical and chemical treatments. The effect of the morphology as well as of the grain size distribution of the charcoal particles was determined in order to achieve optimal conditions for accelerator dating.

  9. Deep-ocean basalts: inert gas content and uncertainties in age dating.

    PubMed

    Noble, C S; Naughton, J J

    1968-10-11

    The radiogenic argon and helium contents of three basalts erupted into the deep ocean from an active volcano (Kilauea) have been measured. Ages calculated from these measurements increase with sample depth up to 22 million years for lavas deduced to be recent. Caution is urged in applying dates from deep-ocean basalts in studies on ocean-floor spreading. PMID:17779379

  10. ENHANCED RECOVERY METHODS FOR 85KR AGE-DATING GROUNDWATER: ROYAL WATERSHED, MAINE

    EPA Science Inventory

    Potential widespread use of 85Kr, having a constant input function in the northern hemisphere, for groundwater age-dating would advance watershed investigations. The current input function of tritium is not sufficient to estimate young modern recharge waters. While tri...

  11. Age dates of valley network drainage basins and subbasins within Sabae and Arabia Terrae, Mars

    NASA Astrophysics Data System (ADS)

    Bouley, Sylvain; Craddock, Robert A.

    2014-06-01

    The precise timing of valley network drainage basin formation is critical to understanding the history of water and climate on Mars. To determine whether there are any variations in ages within separate drainage basins and subbasins that may reflect local or regional variations in climate or resetting from resurfacing (e.g., impact ejecta or lava flows), we dated 27 basins and subbasins in Sabaea and Arabia Terrae. The age-dating basin technique we employed allowed sufficient precision to give accurate ages and shows that fluvial activity within the basins and subbasins ceased at approximately the same time around the Early Hesperian/Late Hesperian transition. Our results support the hypothesis that valley networks formed during a unique "fluvial optimum" that may have shut off gradually because of a global climate change that affected all areas simultaneously on Mars.

  12. Estimation of submarine mass failure probability from a sequence of deposits with age dates

    USGS Publications Warehouse

    Geist, Eric L.; Chaytor, Jason D.; Parsons, Thomas E.; ten Brink, Uri S.

    2013-01-01

    The empirical probability of submarine mass failure is quantified from a sequence of dated mass-transport deposits. Several different techniques are described to estimate the parameters for a suite of candidate probability models. The techniques, previously developed for analyzing paleoseismic data, include maximum likelihood and Type II (Bayesian) maximum likelihood methods derived from renewal process theory and Monte Carlo methods. The estimated mean return time from these methods, unlike estimates from a simple arithmetic mean of the center age dates and standard likelihood methods, includes the effects of age-dating uncertainty and of open time intervals before the first and after the last event. The likelihood techniques are evaluated using Akaike’s Information Criterion (AIC) and Akaike’s Bayesian Information Criterion (ABIC) to select the optimal model. The techniques are applied to mass transport deposits recorded in two Integrated Ocean Drilling Program (IODP) drill sites located in the Ursa Basin, northern Gulf of Mexico. Dates of the deposits were constrained by regional bio- and magnetostratigraphy from a previous study. Results of the analysis indicate that submarine mass failures in this location occur primarily according to a Poisson process in which failures are independent and return times follow an exponential distribution. However, some of the model results suggest that submarine mass failures may occur quasiperiodically at one of the sites (U1324). The suite of techniques described in this study provides quantitative probability estimates of submarine mass failure occurrence, for any number of deposits and age uncertainty distributions.

  13. What is the true age uncertainty of radiocarbon dated Holocene records?

    NASA Astrophysics Data System (ADS)

    Ho, Sze Ling; Groeneveld, Jeroen; Refeld, Kira; Mollenhauer, Gesine; De Pol-Holz, Ricardo; Nürnberg, Dirk; Laepple, Thomas

    2016-04-01

    Radiocarbon-based age-depth models are the backbone of the chronology of Holocene sediment records. The uncertainty of such age-depth models is often estimated from the uncertainty of the calibrated radiocarbon samples. A necessary assumption hereby is that the age of the samples is representative for the proxies in the same sediment layer they originate from. Here we generate radiocarbon and multiple temperature proxy data in three Holocene sediment cores from the same multi-corer employed in the Southwest Pacific. Surprisingly, whilst radiocarbon ages at the same sediment depth strongly differ between the tubes, multiple independent proxy time-series measured in each of the sediment cores suggest stratified sediments at the site. This is based on the finding that proxy time-series correlate significantly better between sediment cores when analyzed over depth, rather than against core-specific age-depth models based on the radiocarbon dates. If our site is not a pathological special case - an argument which we have no evidence for - our finding has important implications for age-depth modeling and the interpretations of paleoclimate time-series. It suggests that the true age uncertainty of a sediment layer can be much higher than the uncertainty obtained from the radiocarbon dates. An alternative but less likely hypothesis is that the proxy values are modified post-deposition in the sediments, resulting in more consistent stratification than the original climate signal time-series. Our study demonstrates the usefulness of replication of the proxy time series and radiocarbon dates in the quest for chronologic precision and proxy reliability, which are crucial for a more quantitative understanding of Holocene climate evolution.

  14. A multi-centennial time series of well-constrained ΔR values for the Irish Sea derived using absolutely-dated shell samples from the mollusc Arctica islandica

    NASA Astrophysics Data System (ADS)

    Butler, P. G.; Scourse, J. D.; Richardson, C. A.; Wanamaker, A. D., Jr.

    2009-04-01

    Determinations of the local correction (ΔR) to the globally averaged marine radiocarbon reservoir age are often isolated in space and time, derived from heterogeneous sources and constrained by significant uncertainties. Although time series of ΔR at single sites can be obtained from sediment cores, these are subject to multiple uncertainties related to sedimentation rates, bioturbation and interspecific variations in the source of radiocarbon in the analysed samples. Coral records provide better resolution, but these are available only for tropical locations. It is shown here that it is possible to use the shell of the long-lived bivalve mollusc Arctica islandica as a source of high resolution time series of absolutely-dated marine radiocarbon determinations for the shelf seas surrounding the North Atlantic ocean. Annual growth increments in the shell can be crossdated and chronologies can be constructed in a precise analogue with the use of tree-rings. Because the calendar dates of the samples are known, ΔR can be determined with high precision and accuracy and because all the samples are from the same species, the time series of ΔR values possesses a high degree of internal consistency. Presented here is a multi-centennial (AD 1593 - AD 1933) time series of 31 ΔR values for a site in the Irish Sea close to the Isle of Man. The mean value of ΔR (-62 14C yrs) does not change significantly during this period but increased variability is apparent before AD 1750.

  15. Age-Dating Drainage Basins in Sabae and Arabia Terrae, Mars

    NASA Astrophysics Data System (ADS)

    Bouley, S.; Craddock, R. A.

    2013-12-01

    The precise timing of drainage basins is critical to understanding the climate history on Mars. One of the obvious problems with age-dating valley networks is the fact that they are small, linear features that are easily destroyed by large impact craters, thus counting craters on valley networks themselves is difficult at best. We proposed a new global study dating 27 drainage basins and subbasins in Sabaea and Arabia Terrae with the basin age-dating technique. Valley networks are contained within drainage basins, which is defined as the area that contributes water to a particular channel or set of channels . For our study, we used THEMIS (Thermal Emission Imaging System) visible images with a spatial resolution of 100 m/pixel which allow us to count craters with diameter of 1 km and larger. A digital elevation model (DEM) using 1/128 gridded Mars Orbiter Laser Altimeter (MOLA) helped us to extract the 26 basins and sub-basins drainage divides From these measurements, our study shows: (1) that all the drainages basins of a large region seem to cease their main fluvial activity at the same time at the end of the Early Hesperian epoch (~3.54 Gyr); (2) that the basin technique is the most reliable technique to do global age-dating; and (3) that there is a possible correlation between the degradation rate and the elevation. Our conclusions suggest that the main fluvial activity ceased because of a global climate change. We suppose that most of valley networks on Mars we observed today formed during the Early Hesperian and post-dated the early and late Noachian topographic features.

  16. Gamma-spectrometric uranium age-dating using intrinsic efficiency calibration

    NASA Astrophysics Data System (ADS)

    Nguyen, Cong Tam; Zsigrai, József

    2006-01-01

    A non-destructive, gamma-spectrometric method for uranium age-dating is presented which is applicable to material of any physical form and geometrical shape. It relies on measuring the daughter/parent activity ratio 214Bi/234U by low-background, high-resolution gamma-spectrometry using intrinsic efficiency calibration. The method does not require the use of any reference materials nor the use of an efficiency calibrated geometry.

  17. Geoarchaeological dating of Holocene-age, earthquake-induced paleoliquefaction features in southwestern Indiana

    SciTech Connect

    Munson, C.A. ); Munson, P.J.; Garniewicz, R.C. . Dept. of Anthropology)

    1992-01-01

    Although archaeological geology generally involves the application of geological methods to archaeological research questions, recent research on earthquake-induced paleoliquefaction in Indiana provides an example off archeological methods applied to geological questions. Surveys in 1990-1992 have documented numerous paleoliquefaction features in Holocene-age alluvial sediments in the Wabash Valley region of southwestern Indiana that resulted from strong-earthquake shaking. A combination of archaeological and geological dating is critical to the study of prehistoric earthquakes in this region, where evidence of surface faulting is absent. Both direct dating and cross-dating are being used to develop a chronology for stratigraphic sequences within the alluvial facies of the Martinsville Formation. Temporally diagnostic artifacts and archaeological features such as hearths add significantly to the traditional array of datable samples from strata that underlie, overlie, or are penecontemporary with the sand- or gravel-filled dikes and buried sand blows that resulted from liquefaction. Dating of stratigraphic sequences and paleoliquefaction features is essential for estimating the recurrence intervals of prehistoric earthquakes and the geographic extents, epicentral locations, and magnitudes of specific events. Dating of stratigraphic sequences is also relevant to reconstructions of the prehistoric landscapes that were used for human settlement throughout the last 11,000 years.

  18. A practical method of estimating standard error of age in the fission track dating method

    USGS Publications Warehouse

    Johnson, N.M.; McGee, V.E.; Naeser, C.W.

    1979-01-01

    A first-order approximation formula for the propagation of error in the fission track age equation is given by PA = C[P2s+P2i+P2??-2rPsPi] 1 2, where PA, Ps, Pi and P?? are the percentage error of age, of spontaneous track density, of induced track density, and of neutron dose, respectively, and C is a constant. The correlation, r, between spontaneous are induced track densities is a crucial element in the error analysis, acting generally to improve the standard error of age. In addition, the correlation parameter r is instrumental is specifying the level of neutron dose, a controlled variable, which will minimize the standard error of age. The results from the approximation equation agree closely with the results from an independent statistical model for the propagation of errors in the fission-track dating method. ?? 1979.

  19. Theoretical constraints on the precision and age range of rehydroxylation dating

    PubMed Central

    Hare, V. J.

    2015-01-01

    Accurate and precise dating methods are of central importance to archaeology, palaeontology and earth science. This paper investigates the expected precision and age range of rehydroxylation dating, a recently proposed technique for fired clays. An expression for combined measurement uncertainty is presented, which takes into account all significant sources of experimental uncertainty. Numerical simulations are performed for comparison. Combined measurement uncertainties of approximately 5% with respect to the age of the ceramic should be possible given well-designed experiments. In this case, the most significant contribution to combined measurement uncertainty is from effective lifetime temperature. In addition, it is shown that precision should be acceptable for recently fired material (less than 1 year). Mismatch of balance resolution to sample mass results in large variation in combined relative uncertainties, which vary by four orders of magnitude (approx. 1–1160%) across recent experimental studies, rendering some recently reported dates meaningless. It is recommended that this ratio be less than 10−6 for a combined relative uncertainty of less than 1%. The age limits of the technique are set by the value of the rate constant and individual sample mineralogy. This theoretical framework should help future interlaboratory comparison as well as optimizing instrument design. PMID:26064631

  20. Theoretical constraints on the precision and age range of rehydroxylation dating.

    PubMed

    Hare, V J

    2015-04-01

    Accurate and precise dating methods are of central importance to archaeology, palaeontology and earth science. This paper investigates the expected precision and age range of rehydroxylation dating, a recently proposed technique for fired clays. An expression for combined measurement uncertainty is presented, which takes into account all significant sources of experimental uncertainty. Numerical simulations are performed for comparison. Combined measurement uncertainties of approximately 5% with respect to the age of the ceramic should be possible given well-designed experiments. In this case, the most significant contribution to combined measurement uncertainty is from effective lifetime temperature. In addition, it is shown that precision should be acceptable for recently fired material (less than 1 year). Mismatch of balance resolution to sample mass results in large variation in combined relative uncertainties, which vary by four orders of magnitude (approx. 1-1160%) across recent experimental studies, rendering some recently reported dates meaningless. It is recommended that this ratio be less than 10(-6) for a combined relative uncertainty of less than 1%. The age limits of the technique are set by the value of the rate constant and individual sample mineralogy. This theoretical framework should help future interlaboratory comparison as well as optimizing instrument design. PMID:26064631

  1. Uranium-series Comminution Ages for Dating Detrital Sediments: Investigating the Methodological Underpinnings

    NASA Astrophysics Data System (ADS)

    Lee, V. E.; DePaolo, D. J.; Christensen, J. N.; Huber, C.; Henderson, G. M.

    2011-12-01

    The uranium-series comminution age method can be utilized to directly date fine-grained detrital clasts, which are nearly ubiquitous throughout the sediments and soils blanketing the Earth's surface environment. In addition to yielding the comminution age (which is the elapsed time since the detrital particle was reduced below a critical threshold grain size (~50 microns)), sediment transport timescales can also be obtained in settings where the depositional age can be determined using independent dating methods. Therefore, the comminution age method is a powerful approach for investigating the timescales and associated Earth surface processes of a broad range of terrestrial deposits. The basic model for how the comminution age method works is that for grains that have been reduced below the critical threshold size, there is a measurable decrease in the (234U/238U) activity ratio due to time-dependent alpha recoil loss of the 234U daughter following decay of the 238U parent isotope. The magnitude of this decrease yields the comminution age, when information is also taken into account regarding the initial (234U/238U) ratio, as well as the grain surface area over which recoiled 234U daughters are lost (described by a constant termed the recoil loss parameter fα). Although the fundamental concepts underlying the use of the comminution age method as a chronometer are simple and well-established, the complexity of natural samples requires that careful attention be paid to methodological details that can affect the accuracy of the comminution ages obtained from U isotope measurements. Of particular interest for terrestrial samples are potential impacts of both physical and chemical weathering on the U isotope composition of bulk sediments. Weathering processes can potentially obscure and/or alter the U isotopic composition of the detrital fraction by mechanisms such as the production of secondary phases with different U isotope compositions, dissolution-induced removal

  2. Lichenometric Dating of Little Ice Age Moraines in the Cordillera Vilcabamba, Southern Peruvian Andes

    NASA Astrophysics Data System (ADS)

    Taggart, J. R.; Licciardi, J. M.

    2008-12-01

    Lateral and end moraines deposited by two valley glaciers were mapped on the south side of Nevado Tucarhuay (5910 m asl) and on the east side of Nevado Salcantay (6271 m asl) in the Cordillera Vilcabamba in the southern Peruvian Andes (~13°S latitude). The geomorphic expression of outer and inner moraine sequences in these two drainages mimics that of a previously studied pair of moraines in the upper Rio Blanco valley on the south side of Nevado Salcantay. Cosmogenic 10Be surface exposure dating has yielded ages of 9.0 ± 0.3 ka and 195 ± 24 years, respectively, for these outer and inner Rio Blanco moraines. In all three valleys, prominent outer moraines occur ~3-5 km from headwalls and inner moraine ridges are found ~2.5-3 km from headwalls. Recessional moraines found exclusively on the east side of Salcantay indicate multiple early- to late-Holocene glacier pauses, rather than continuous retreat, prior to the latest Holocene glacier readvance. Diameters of the lichen Rhizocarpon subgenus Rhizocarpon were measured on moraine boulders from the inner moraines in all three valleys. Lichen diameters on the two undated inner moraines are consistent with diameters on the inner 10Be-dated Rio Blanco moraine, which signifies similar lichenometric ages and supports synchronous glacier culminations in all three drainages during the Little Ice Age. The new lichen measurements and age estimates provide a critical link between previous lichen studies in the Cordillera Blanca to the north and in the Cordillera Real to the south, thereby increasing spatial coverage of terrestrial paleoclimate information. Moreover, the extensive lichen measurements gathered on the inner 10Be-dated Rio Blanco moraine define a new control point for the Rhizocarpon subgenus Rhizocarpon growth curve in the tropical Peruvian- Bolivian Andes, which will increase the accuracy of lichenometric age estimates in this region. 10Be exposure dating of the inner moraines in adjacent valleys is underway

  3. Age preferences in dating advertisements by homosexuals and heterosexuals: from sociobiological to sociological explanations.

    PubMed

    Burrows, Kathryn

    2013-02-01

    Current sociobiological thought suggests that significant components of mate selection are based on indicators that correlate with the ability to produce and support offspring. Theorists have suggested that men tend to be attracted to and marry younger women, while women tend to be attracted to and marry older men. This behavior is referred to as age hypergamy. I complicate this picture by using gay men as a population in which to explore alternative components of mate selection as reflected in our behavior. Analyses of 120 dating advertisements from gay men and heterosexual men and women indicated that there exists a good measure of hypergamic age preference that is comparable to the heterosexual population and that relates to subjects' gender presentation. Data suggest that the biological-reproductive theory of age hypergamy is incomplete and support a cultural reproduction model of gender role behavior and preference in both heterosexuals and homosexuals. PMID:23179236

  4. 10Be depth profile dating in the Swiss Midlands: deposition ages versus erosion

    NASA Astrophysics Data System (ADS)

    Wüthrich, Lorenz; Zech, Roland; Haghipour, Negar; Terrizzano, Carla; Christl, Marcus; Gnägi, Christian; Veit, Heinz; Ivy-Ochs, Susan

    2015-04-01

    During the Pleistocene, glaciers advanced repeatedly from the Alps into the Swiss Midlands. The exact extents and timing are still under debate, even for the last glacial advances. Decalcification depths, for example, increase from west to east in the western Swiss Midlands and have been interpreted to indicate that the Rhone glacier may have been less extensive during the global Last Glacial Maximum (LGM) at 20 ka than assumed so far [1]. In an attempt to provide more quantitative age control, we applied 10Be depth profile dating [2] on till at five locations in the western part of Switzerland. Two of them lie outside the assumed LGM extent of the Rhone glacier (Niederbuchsiten, St.Urban), two inside the extent of the LGM Rhone glacier (Steinhof, Deisswil) and one profile was taken from the Berne stade (LGM) of the Aare glacier [3]. All surface concentrations are relatively low and indicate massive erosion. Without constrains for age and erosion, depth profile dating yields ages between roughly 15 ka up to more than 1 Ma for the profiles in St. Urban, Niederbuchsiten and Deisswil whereas the profiles in Steinhof and Bern yields only last glacial ages. The wide range of possible exposure ages illustrates, that independent estimates for erosion would be needed to precisely determine the deposition ages of the investigated tills. However, at this point, we interpret the best model fits to our depth profile concentrations as tentative verification of the assumed LGM extent [3]. The spatial patterns of decalcification depths and soil development in the Swiss Midlands deserves further evaluation. [1] Bitterli et al. (2011) Geologischer Atlas der Schweiz, Blatt 1108, Swisstopo [2] Hidy et al. (2010) Geochem. Geophys. Geosyst. 11, doi:10.1029/2010GC003084 . [3] Bini et al. (2009) Switzerland during the Last Glacial Maximum, Swisstopo

  5. Relation of Chlorofluorocarbon Ground-Water Age Dates to Water Quality in Aquifers of West Virginia

    USGS Publications Warehouse

    McCoy; Kurt, J.; Kozar, Mark D.

    2007-01-01

    The average apparent age of ground water in fractured-bedrock aquifers in West Virginia was determined using chlorofluorocarbon (CFC) dating methods. Since the introduction of CFC gases as refrigerants in the late 1930s, atmospheric concentrations have increased until production ceased in the mid-1990s. CFC dating methods are based on production records that date to the early 1940s, and the preservation of atmospheric CFC concentrations in ground water at the time of recharge. As part of the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) and Ambient Ground-Water Monitoring Network (AGN) programs in West Virginia from 1997 to 2005, 80 samples from the Appalachian Plateaus Physiographic Province, 27 samples from the Valley and Ridge Physiographic Province, and 5 samples from the Ohio River alluvial aquifers were collected to estimate ground-water ages in aquifers of West Virginia. Apparent CFC ages of water samples from West Virginia aquifers ranged from 5.8 to 56 years. In the Appalachian Plateaus, topographically driven ground-water flow is evident from apparent ages of water samples from hilltop, hillside, and valley settings (median apparent ages of 12, 14, and 25 years, respectively). Topographic setting was the only factor that was found to be related to apparent ground-water age in the Plateaus at the scale of this study. Similar relations were not found in Valley and Ridge aquifers, indicating that other factors such as bedding or geologic structure may serve larger roles in controlling ground-water flow in that physiographic province. Degradation of CFCs was common in samples collected from methanogenic/anoxic aquifers in the Appalachian Plateaus and suboxic to anoxic aquifers in the Valley and Ridge. CFC contamination was most common in Ohio River alluvial aquifers and carbonate units of the Valley and Ridge, indicating that these highly transmissive surficial aquifers are the most vulnerable to water-quality degradation and may

  6. The evolutionary relationships and age of Homo naledi: An assessment using dated Bayesian phylogenetic methods.

    PubMed

    Dembo, Mana; Radovčić, Davorka; Garvin, Heather M; Laird, Myra F; Schroeder, Lauren; Scott, Jill E; Brophy, Juliet; Ackermann, Rebecca R; Musiba, Chares M; de Ruiter, Darryl J; Mooers, Arne Ø; Collard, Mark

    2016-08-01

    Homo naledi is a recently discovered species of fossil hominin from South Africa. A considerable amount is already known about H. naledi but some important questions remain unanswered. Here we report a study that addressed two of them: "Where does H. naledi fit in the hominin evolutionary tree?" and "How old is it?" We used a large supermatrix of craniodental characters for both early and late hominin species and Bayesian phylogenetic techniques to carry out three analyses. First, we performed a dated Bayesian analysis to generate estimates of the evolutionary relationships of fossil hominins including H. naledi. Then we employed Bayes factor tests to compare the strength of support for hypotheses about the relationships of H. naledi suggested by the best-estimate trees. Lastly, we carried out a resampling analysis to assess the accuracy of the age estimate for H. naledi yielded by the dated Bayesian analysis. The analyses strongly supported the hypothesis that H. naledi forms a clade with the other Homo species and Australopithecus sediba. The analyses were more ambiguous regarding the position of H. naledi within the (Homo, Au. sediba) clade. A number of hypotheses were rejected, but several others were not. Based on the available craniodental data, Homo antecessor, Asian Homo erectus, Homo habilis, Homo floresiensis, Homo sapiens, and Au. sediba could all be the sister taxon of H. naledi. According to the dated Bayesian analysis, the most likely age for H. naledi is 912 ka. This age estimate was supported by the resampling analysis. Our findings have a number of implications. Most notably, they support the assignment of the new specimens to Homo, cast doubt on the claim that H. naledi is simply a variant of H. erectus, and suggest H. naledi is younger than has been previously proposed. PMID:27457542

  7. Allanite age-dating: Non-matrix-matched standardization in quadrupole LA-ICP-MS

    NASA Astrophysics Data System (ADS)

    Burn, M.; Lanari, P.; Pettke, T.; Engi, M.

    2014-12-01

    Allanite Th-U-Pb age-dating has recently been found to be powerful in unraveling the timing of geological processes such as the metamorphic dynamics in subduction zones and crystallization velocity of magmas. However, inconsistencies among analytical techniques have raised doubts about the accuracy of allanite age data. Spot analysis techniques such as LA-ICP-MS are claimed to be crucially dependent on matrix-matched standards, the quality of which is variable. We present a new approach in LA-ICP-MS data reduction that allows non-matrix-matched standardization via well constrained zircon reference materials as primary standards. Our data were obtained using a GeoLas Pro 193 nm ArF excimer laser ablation system coupled to an ELAN DRC-e quadrupole ICP-MS. We use 32 μm and 24 μm spot sizes; laser operating conditions of 9 Hz repetition rate and 2.5 J/cm2 fluence have proven advantageous. Matrix dependent downhole fractionation evolution is empirically determined by analyzing 208Pb/232Th and 206Pb/238U and applied prior to standardization. The new data reduction technique was tested on three magmatic allanite reference materials (SISSb, CAPb, TARA); within error these show the same downhole fractionation evolution for all allanite types and in different analytical sessions, provided measurement conditions remain the same. Although the downhole evolution of allanite and zircon differs significantly, a link between zircon and allanite matrix is established by assuming CAPb and TARA to be fixed at the corresponding reference ages. Our weighted mean 208Pb/232Th ages are 30.06 ± 0.22 (2σ) for SISSb, 275.4 ± 1.3 (2σ) for CAPb, and 409.9 ± 1.8 (2σ) for TARA. Precision of single spot age data varies between 1.5 and 8 % (2σ), dependent on spot size and common lead concentrations. Quadrupole LA-ICP-MS allanite age-dating has thus similar uncertainties as do other spot analysis techniques. The new data reduction technique is much less dependent on quality and homogeneity

  8. Resolving the age of Wilson Creek Formation tephras and the Mono Lake excursion using high-resolution SIMS dating of allanite and zircon rims

    NASA Astrophysics Data System (ADS)

    Vazquez, J. A.; Lidzbarski, M. I.

    2012-12-01

    Sediments of the Wilson Creek Formation surrounding Mono Lake preserve a high-resolution archive of glacial and pluvial responses along the eastern Sierra Nevada due to late Pleistocene climate change. An absolute chronology for the Wilson Creek stratigraphy is critical for correlating the paleoclimate record to other archives in the western U.S. and the North Atlantic region. However, multiple attempts to date the Wilson Creek stratigraphy using carbonates and interbedded rhyolitic tephras yield discordant 14C and 40Ar/39Ar results due to open-system effects, carbon reservoir uncertainties, as well as abundant xenocrysts entrained during eruption. Ion microprobe (SIMS) 238U-230Th dating of the final increments of crystallization recorded by allanite and zircon autocrysts from juvenile pyroclasts yields ages that effectively date eruption of key tephra beds and resolve age uncertainties about the Wilson Creek stratigraphy. To date the final several micrometers of crystal growth, individual allanite and zircon crystals were embedded in soft indium to allow sampling of unpolished rims. Isochron ages derived from rims on coexisting allanite and zircon (± glass) from hand-selected pumiceous pyroclasts delimit the timing of Wilson Creek sedimentation between Ashes 7 and 19 (numbering of Lajoie, 1968) to the interval between ca. 27 to ca. 62 ka. The interiors of individual allanite and zircon crystals sectioned in standard SIMS mounts yield model 238U-230Th ages that are mostly <10 k.y. older than their corresponding rim age, suggesting a relatively brief interval of allanite + zircon crystallization before eruption. A minority of allanite and zircon crystals yield rim and interior model ages of ca. 90-100 ka, and are likely to be antecrysts recycled from relatively early Mono Craters volcanism and/or intrusions. Tephra (Ash 15) erupted during the geomagnetic excursion originally designated the Mono Lake excursion yields a rim isochron age of ca. 41 ka indicating that

  9. Archaeomagnetic dating of a High Middle Age likely iron working site in Corroy-le-Grand (Belgium)

    NASA Astrophysics Data System (ADS)

    Spassov, Simo; Hus, Jozef; Geeraerts, Raoul; Heller, Frédéric

    Archaeological burnt materials and structures provide unique records of direction and intensity of the Earth’s magnetic field in the past, elements that can be absolutely determined applying the archaeomagnetic method. At present, such records within Europe are irregular in both space and time. Presented here is the archaeomagnetic investigation of three kilns that were discovered during a preventive excavation of an archaeological site considered of High Middle Age in Corroy-le-Grand (Belgium) and that are assumed to be related to iron working activities. Archaeological context dating points to kiln operation between the second half of the 10th century until the 12th century AD. As the site is not far from Paris, declination and inclination of the characteristic remanent magnetisation of the kilns were compared with the standard directional secular variation curve for France in order to propose archaeomagnetic dates for the cessation of kiln operation by using probability densities [Lanos, Ph., 2004. Bayesian inference of calibration curves, application to archaeomagnetism. In: Buck, C.E., Millard, A.R. (Eds.), Tools for Constructing Chronologies: Crossing Disciplinary Boundaries. Lecture Notes in Statistics. Springer Verlag, London, pp. 43-82; Lanos, Ph., Le Goff, M., Kovacheva, M., Schnepp, E., 2005. Hierarchical modelling of archaeomagnetic data and curve estimation by moving average technique. Geophysical Journal International 160 (2), 440-476]. This confirms the presumed archaeological age and resulted in more precise time constraints for the last kiln operation. Rock magnetic techniques, proposed by Spassov and Hus [Spassov, S., Hus, J., 2006. Estimating baking temperatures in a Roman pottery kiln by rock magnetic properties: implications of thermochemical alteration for archaeointensity determinations. Geophysical Journal International 167, 592-604], were applied to examine the suitability of the burnt materials from the kilns for archaeointensity

  10. Impacts of age-dependent tree sensitivity and dating approaches on dendrogeomorphic time series of landslides

    NASA Astrophysics Data System (ADS)

    Šilhán, Karel; Stoffel, Markus

    2015-05-01

    Different approaches and thresholds have been utilized in the past to date landslides with growth ring series of disturbed trees. Past work was mostly based on conifer species because of their well-defined ring boundaries and the easy identification of compression wood after stem tilting. More recently, work has been expanded to include broad-leaved trees, which are thought to produce less and less evident reactions after landsliding. This contribution reviews recent progress made in dendrogeomorphic landslide analysis and introduces a new approach in which landslides are dated via ring eccentricity formed after tilting. We compare results of this new and the more conventional approaches. In addition, the paper also addresses tree sensitivity to landslide disturbance as a function of tree age and trunk diameter using 119 common beech (Fagus sylvatica L.) and 39 Crimean pine (Pinus nigra ssp. pallasiana) trees growing on two landslide bodies. The landslide events reconstructed with the classical approach (reaction wood) also appear as events in the eccentricity analysis, but the inclusion of eccentricity clearly allowed for more (162%) landslides to be detected in the tree-ring series. With respect to tree sensitivity, conifers and broad-leaved trees show the strongest reactions to landslides at ages comprised between 40 and 60 years, with a second phase of increased sensitivity in P. nigra at ages of ca. 120-130 years. These phases of highest sensitivities correspond with trunk diameters at breast height of 6-8 and 18-22 cm, respectively (P. nigra). This study thus calls for the inclusion of eccentricity analyses in future landslide reconstructions as well as for the selection of trees belonging to different age and diameter classes to allow for a well-balanced and more complete reconstruction of past events.

  11. First direct dating of a presumed Pleistocene hominid from China: AMS radiocarbon age of a femur from the Ordos Plateau.

    PubMed

    Keates, Susan G; Hodgins, Gregory W L; Kuzmin, Yaroslav V; Orlova, Lyobov A

    2007-07-01

    Human remains from the Xarusgol Valley, Ordos Plateau, northwestern China, have been considered to date to the Late Pleistocene. In order to ascertain their true age, direct AMS (14)C dating of a femur collected in the early 1920s was conducted. The results demonstrate that the femur is very young, with one sample of 'post-bomb' age and the other sample c. 200 years old. This first direct dating of a Chinese fossil hominid underscores the need to apply the same methodology to other Chinese modern human fossils currently believed to be of Pleistocene age. PMID:17490725

  12. Constraints on the age of the Great Sand Dunes, Colorado, from subsurface stratigraphy and OSL dates

    USGS Publications Warehouse

    Madole, Richard F.; Mahan, Shannon; Romig, Joe H.; Havens, Jeremy C.

    2013-01-01

    The age of the Great Sand Dunes has been debated for nearly 150 yr. Seven ages ranging from Miocene to late Holocene have been proposed for them. This paper presents new information—chiefly subsurface stratigraphic data, OSL dates, and geomorphic evidence—that indicates that the Great Sand Dunes began to form in the latter part of the middle Pleistocene. The dunes overlie a thick wedge of piedmont-slope deposits, which in turn overlies sediment of Lake Alamosa, a paleolake that began to drain about 440 ka. The wedge of piedmont-slope deposits extends westward for at least 23 km and is as much as 60 m thick at a distance of 10 km from the Sangre de Cristo Range. Ostracodes from one well indicate that the eastern shoreline of Lake Alamosa extended to within 4.3 km of where the Great Sand Dunes eventually formed. The time represented by the wedge of piedmont-slope deposits is not known exactly, but the wedge post-dates 440 ka and was in place prior to 130 ka because by then the dunes overlying it were sufficiently close and tall enough to obstruct streams draining from the Sangre de Cristo Range.

  13. Age determination of mid-ocean ridge basalts by radiocarbon dating of lithified carbonate crusts

    SciTech Connect

    Kuptsov, V.M.; Bogdanov, Yu.A.; Palkina, A.M.; Lisitsyn, A.P.

    1986-01-01

    The processes that take place in the mid-ocean ridges are the key to their understanding of the evolution of the earth's crust and mantle. Mid-ocean ridge volcanism supplies vast masses of mantle material, forming new oceanic crust. In recent years, comprehensive study has been made of such processes. The problems of geochronology have an important place in these investigations, since only a study of the events in their time sequence will enable them to make a valid estimate of the intensity of these global processes. In 1980, crusts were obtained by the Pikar combined expedition in the Red Sea rift in the 18/sup 0/ study area on the lower tectonic terrace, in the axial zone, and in three deep water basins. Manned deep water submersible, dredges, trawls, bottom samplers, and impact tubes brought up basalts covered with lithified crusts, and also separate lithified crusts, collected from the basalt basement during sampling. The authors have dated the crusts by the radiocarbon method using the benzene technique. Results of the analysis give ages ranging from 2980 to 20,700 years. Results are discussed. The use of lithified carbonate crusts for determining the age of the basalts is effective within the range of the radiocarbon dating method (up to 40,000-45,000 years). This time interval is inaccessible for determinations by other methods of nuclear geochronology, which makes the method especially valuable. 1 reference, 2 figures, 1 table.

  14. Age Dating from Electron Microprobe Analyses of U, Th, and Pb: Geological Advantages and Analytical Difficulties.

    PubMed

    Bowles, John F W

    2015-10-01

    Electron microprobe analysis of U, Th, and Pb in naturally occurring minerals can indicate their age. Where the Pb is entirely due to the radioactive decay of U and Th, the time since mineral formation or equilibration can be calculated. Uraninite (UO2), monazite (REE PO4), zircon (ZrSiO4), and xenotime (YPO4) have been used, the latter containing U and/or Th in minor proportions. Any stable U- or Th-bearing phase can be considered. Careful analysis is required with attention to interferences, background measurement, detection limits, and Pb-free sample preparation. Extended counting times (600 s) at a probe current >200 nA are recommended. Ages can be determined from uraninite older than 2 Ma for a Pb detection limit of 0.02% and up to 700-1,000 Ma, after which Pb can be lost from the structure. The youngest monazite ages permitted by the Pb detection limit are 50-100 Ma and ages greater than 3,000 Ma have been determined. The method does not provide the detail of isotopic methods, but results can be obtained more readily. Examples show dating of cheralite ((Ca,Ce)(Th,Ce)(PO4)2), a rock containing primary and secondary UO2, and a suite of detrital uraninite grains that formed a part of a mineral exploration program. PMID:25936439

  15. Radiocarbon Dating and age Inversions in Lake Chapala Late Holocene Sediments, Western Mexico.

    NASA Astrophysics Data System (ADS)

    Zarate-Del Valle, P.; Israde-Alcantara, I.; Ramírez-Sánchez, H.; Gómez-Salazar, S.; Ríos-Donato, N.

    2006-12-01

    Neotectonic Lake Chapala, the major Mexican freshwater reservoir lies at the north and northeast of the Citala Rift and is linked to history of the active Plio-Quaternary Transmexican Volcanic Belt geological province. Eight radiocarbon 14C dates were obtained on shallow sediment samples from a gravity corer (T46) of 5 cm in diameter and 1.7 m long. The core was collected from the western sector of Lake Chapala (103° 15.43' W, 20° 14.45' N) at water depth of 3.7 m (june 2000). In general, shallow sediments (<2m deep) in Lake Chapala are dark and silty with granulometric median ranging from 10 to 50 μm. Major oxides in sediments are: SiO2 (54.05%), Al2O3 (18.94%), Fe2O3 (6.75%) and CaO (2.57%). The major mineralogical composition of sediments is as follows: plagioclases (25.86%), quartz (20.92%), clays (38.5%), carbonates (2.99%) and TiO2 (1.05%). Radiocarbon ages were measured by accelerator mass spectrometry (AMS) and were obtained through the organic carbon fraction extracted from the bulk sediment samples sliced every 20 cm taken from the whole core. Stratigraphically ordered from highest to lowest, the eight ages reported are: 1) 2,000 ±40 yr on sediments at 30 cm deep; 2) 1,920 ±35 yr on sediments at 50 cm deep; 3) 1,900 ±35 yr on sediments at 70 cm deep; 4) 2,080 ±35 yr on sediments at 90 cm deep; 5) 2,090 ±50 yr on sediments at 110 cm deep; 6) 2,190 ±35 yr on sediments at 130 cm deep; 7) 2,050 ±35 yr on sediments at 150 cm deep and, 8) 1,500 ±35 yr on sediments at 170 cm deep. From the top until 70 cm and from 130 to bottom we observe two age inversions; the interval apparently with no age inversions is from 70cm to 130cm. As it is known the age inversions observed may be due to a) ancient carbon being incorporated into the sediment during deposition; b) unrecognized bioturbation, c) Postdepositional alteration and, d) variations in the apparent geological ages of the different chemical phases comprising the total sediment. Basically, the factors

  16. 187Re - 187Os nuclear geochronometry: age dating with permil precision

    NASA Astrophysics Data System (ADS)

    Roller, Goetz

    2016-04-01

    Recently, 187Re - 187Os nuclear geochronometry, a new dating method combining ideas of nuclear astrophysics with geochronology, has successfully been used to calculate two-point-isochron (TPI) ages for Devonian black gas shales using the isotopic signature of an r-process geochronometer as one data point in a TPI diagram [1]. Based upon a nuclear production ratio 187Re/188Os = 5.873, TPI ages were calculated for 12 SDO-1 (Devonian Ohio Shale, Appalachian Basin) aliquants, for which repeated Re-Os measurements are reported in the literature [2]. TPI ages range from 384.5 ± 2.7 Ma (187Os/188Osi = 0.29413 ± 0.00023) to 387.7 ± 2.1 Ma (187Os/188Osi = 0.29407 ± 0.00019) with a mean of 386.67 ± 1.79 Ma). The result is consistent with the isochronous age from the 12 aliquants alone (386 ± 16 Ma, 187Os/188Osi = 0.31±0.31), which is bracketed by U-Pb ages for the Belpre Ash (381.1 ± 3.3 Ma) and the Tioga Ash bed (390.0 ± 2.5 Ma) [3] from the Appalachian Basin. Hence, SDO-1 can be assigned to the Givetian stage (varcus-zone) of the Middle Devonian, close to the Eifelian/Givetian boundary (using the time-scale of [3] or [4]). If an age is calculated from an isochron diagram for the 12 aliquants including the nuclear geochronometer, a permil precision can be achieved, an interesting feature with respect to any effort towards calibrating the Geologic Timescale. Additionally, a Th/U evolution (or: Th/U-time) diagram can be plotted using U-Pb zircon age data and Th/U ratios from volcanic rocks and ashes reported in the literature [3] for specific Devonian samples from the Appalachian Basin. Since the Re-Os age obtained for SDO-1 can also be connected to its Th/U ratio, it turns out, that Th/U ratios might be helpful age indicators, as demonstrated for the Devonian using the U-Pb and Re-Os datasets. [1] Roller (2015), GSA Abstr. with Programs 47, #248-14. [2] Du Vivier et al. (2014), Earth Planet. Sci. Lett. 389, 23 - 33. [3] Tucker et al. (1998), Earth Planet. Sci. Lett

  17. ON A NEW NEAR-INFRARED METHOD TO ESTIMATE THE ABSOLUTE AGES OF STAR CLUSTERS: NGC 3201 AS A FIRST TEST CASE

    SciTech Connect

    Bono, G.; Di Cecco, A.; Sanna, N.; Buonanno, R.; Stetson, P. B.; VandenBerg, D. A.; Calamida, A.; Amico, P.; Marchetti, E.; D'Odorico, S.; Gilmozzi, R.; Dall'Ora, M.; Iannicola, G.; Caputo, F.; Corsi, C. E.; Ferraro, I.; Monelli, M.; Walker, A. R.; Zoccali, M.; Degl'Innocenti, S.

    2010-01-10

    We present a new method to estimate the absolute ages of stellar systems. This method is based on the difference in magnitude between the main-sequence turnoff (MSTO) and a well-defined knee located along the lower main sequence (MSK). This feature is caused by the collisionally induced absorption of molecular hydrogen, and it can easily be identified in near-infrared (NIR) and in optical-NIR color-magnitude diagrams of stellar systems. We took advantage of deep and accurate NIR images collected with the Multi-Conjugate Adaptive Optics Demonstrator temporarily available on the Very Large Telescope and of optical images collected with the Advanced Camera for Surveys Wide Field Camera on the Hubble Space Telescope and with ground-based telescopes to estimate the absolute age of the globular NGC 3201 using both the MSTO and the {delta}(MSTO-MSK). We have adopted a new set of cluster isochrones, and we found that the absolute ages based on the two methods agree to within 1{sigma}. However, the errors of the ages based on the {delta}(MSTO-MSK) method are potentially more than a factor of 2 smaller, since they are not affected by uncertainties in cluster distance or reddening. Current isochrones appear to predict slightly bluer ({approx}0.05 mag) NIR and optical-NIR colors than observed for magnitudes fainter than the MSK.

  18. I-Xe Dating: Comparison of I-Xe and Pb-Pb Ages of Richardton Chondrules and Separated Mineral Phases

    NASA Technical Reports Server (NTRS)

    Pravdivtseva, O. V.; Amelin, Y.; Hohenberg, C. M.; Meshik, A. P.

    2002-01-01

    I-Xe and Pb-Pb ages of individual Richardton chondrules and different mineral phases were compared in order to test the absolute I-Xe age normalization. Additional information is contained in the original extended abstract.

  19. Absolute vs. weight-related maximum oxygen uptake in firefighters: fitness evaluation with and without protective clothing and self-contained breathing apparatus among age group.

    PubMed

    Perroni, Fabrizio; Guidetti, Laura; Cignitti, Lamberto; Baldari, Carlo

    2015-01-01

    During fire emergencies, firefighters wear personal protective devices (PC) and a self-contained breathing apparatus (S.C.B.A.) to be protected from injuries. The purpose of this study was to investigate the differences of aerobic level in 197 firefighters (age: 34±7 yr; BMI: 24.4±2.3 kg.m-2), evaluated by a Queen's College Step field Test (QCST), performed with and without fire protective garments, and to analyze the differences among age groups (<25 yr; 26-30 yr, 31-35 yr, 36-40 yr and >40 yr). Variance analysis was applied to assess differences (p < 0.05) between tests and age groups observed in absolute and weight-related values, while a correlation was examined between QCST with and without PC+S.C.B.A. The results have shown that a 13% of firefighters failed to complete the test with PC+S.C.B.A. and significant differences between QCST performed with and without PC+S.C.B.A. in absolute (F(1,169) = 42.6, p < 0.0001) and weight-related (F(1,169) = 339.9, p < 0.0001) terms. A better correlation has been found in L•min-1 (r=0.67) than in ml•kg-1•min-1 (r=0.54). Moreover, we found significant differences among age groups both in absolute and weight-related values. The assessment of maximum oxygen uptake of firefighters in absolute term can be a useful tool to evaluate the firefighters' cardiovascular strain. PMID:25764201

  20. Using Dissolved Organic Carbon Isotopes for Groundwater Age Dating in Southern Nevada, USA

    NASA Astrophysics Data System (ADS)

    Thomas, James; Hershey, Ronald; Fereday, Wyatt

    2016-04-01

    Dissolved organic carbon (DOC) 14C offers a method to calculate groundwater ages that is more straightforward than dissolved inorganic carbon (DIC) 14C. To obtain corrected DIC 14C groundwater ages requires models that account for chemical and physical processes that affect both 13C and 14C. This is especially true in carbonate-rock aquifers where a fair amount of dissolution and precipitation of carbonate minerals can occur. A first important step in calculating 14C DOC groundwater ages is to determine the initial 14C DOC (A0) values of the groundwater recharge. For this study, recharge area groundwater samples of DOC 14C, collected from 14 different sites, were used to determine the recharge DOC 14C values. These values ranged from 96 to 120 percent modern carbon (pmc), with an average value of 106.2 pmc. These 14C A0 values support the use of a 100 pmc 14C A0 pre-bomb value to calculate DOC 14C groundwater ages for southern Nevada. Several conditions to successfully use DOC 14C to date groundwater need to be met. First, soluble organic carbon content of aquifers needs to be low, so that little DOC is added to the groundwater as it flows from recharge areas down gradient in an aquifer. For this study, volcanic and carbonate aquifer outcrop rocks showed that these rocks contained low soluble organic carbon. Second, it is important that the DOC does not change character down a flow path, which could indicate transformation of DOC along a flow path and/or addition of DOC to the groundwater. Although specific DOC compounds could not be identified for samples collected at four sites, all four groundwater sample spectra show the same general shape over the duration of the HPLC run indicating that the DOC compound composition of groundwater does not significantly change from up-gradient to down-gradient. Third, another factor that could greatly affect DOC 14C groundwater age calculations is matrix diffusion/adsorption of DOC 14C. Laboratory experiments showed that

  1. Dating violence victimization across the teen years: Abuse frequency, number of abusive partners, and age at first occurrence

    PubMed Central

    2012-01-01

    Background Prior longitudinal studies have shown high cumulative dating violence exposure rates among U.S adolescents, with 36 percent of males and 44 percent to 88 percent of females experiencing victimization across adolescence/young adulthood. Despite promising information characterizing adolescents’ dating violence experiences longitudinally, prior studies tended to concentrate on physical and sexual types of violence only, and did not report information on the number of times dating violence was experienced across multiple abusive partners. We used a method similar to the timeline follow-back interview to query adolescents about dating violence victimization from age 13 to 19—including dating violence types (physical, sexual, and psychological), frequency, age at first occurrence, and number of abusive partners. Methods A total of 730 subjects were randomly sampled from university registrar records and invited to complete an online survey, which utilized methods similar to the timeline follow-back interview, to retrospectively assess relationship histories and dating violence victimization from age 13 to 19 (eight questions adapted from widely-used surveys covering physical, sexual, and psychological abuse). Then, for each dating violence type, we asked about the number of occurrences, number of abusive partners, and age at first occurrence. Of 341 subjects who completed the survey, we included 297 (64 percent females; 36 percent males) who had a dating partner from age 13 to 19. Results Fully 64.7 percent of females and 61.7 percent of males reported dating violence victimization between age 13 and 19, with most experiencing multiple occurrences. More than one-third of abused females had two or more abusive partners: controlling behavior (35.6 percent); put downs/name calling (37.0); pressured sex (42.9); insults (44.3); slapped/hit (50.0); and threats (62.5). Males also had two or more abusive partners, as follows: controlling behavior (42.1 percent

  2. Dating of the time of sedimentation using U-Pb ages for paleosol calcite

    SciTech Connect

    Rasbury, E.T.; Hanson, G.N.; Meyers, W.J.

    1997-04-01

    We have sampled paleosol horizons from a continuous core of a rapidly deposited Late Pennsylvanian-Early Permian marine shelf section in Texas. USA. The paleosols occur on the tops of shoaling upward cycles and, based on current time constraints, these cycles average 250 ka and cannot represent longer than 400 ka. As the unconformity which is represented by the paleosol can only be a fraction of the time allowed for deposition of the cycle, the age of minerals that form in the paleosol is effectively the time of sedimentation. The uncertainty on the {sup 238}U-{sup 206}Pb age of brown paleosol calcite from one exposure surface is only 1 Ma. Reported uncertainties on Paleozoic boundaries are greater than 10 Ma. Our early results suggest that the marine sedimentary record may be dated to a precision of 1 Ma with U-Pb analyses of carefully selected paleosol calcite. These results have implications for vastly improving time resolution of the rock record. 21 refs., 3 figs., 1 tab.

  3. Age validation of canary rockfish (Sebastes pinniger) using two independent otolith techniques: lead-radium and bomb radiocarbon dating.

    SciTech Connect

    Andrews, A H; Kerr, L A; Cailliet, G M; Brown, T A; Lundstrom, C C; Stanley, R D

    2007-11-04

    Canary rockfish (Sebastes pinniger) have long been an important part of recreational and commercial rockfish fishing from southeast Alaska to southern California, but localized stock abundances have declined considerably. Based on age estimates from otoliths and other structures, lifespan estimates vary from about 20 years to over 80 years. For the purpose of monitoring stocks, age composition is routinely estimated by counting growth zones in otoliths; however, age estimation procedures and lifespan estimates remain largely unvalidated. Typical age validation techniques have limited application for canary rockfish because they are deep dwelling and may be long lived. In this study, the unaged otolith of the pair from fish aged at the Department of Fisheries and Oceans Canada was used in one of two age validation techniques: (1) lead-radium dating and (2) bomb radiocarbon ({sup 14}C) dating. Age estimate accuracy and the validity of age estimation procedures were validated based on the results from each technique. Lead-radium dating proved successful in determining a minimum estimate of lifespan was 53 years and provided support for age estimation procedures up to about 50-60 years. These findings were further supported by {Delta}{sup 14}C data, which indicated a minimum estimate of lifespan was 44 {+-} 3 years. Both techniques validate, to differing degrees, age estimation procedures and provide support for inferring that canary rockfish can live more than 80 years.

  4. The 238U/235U isotope ratio of the Earth and the solar system: Constrains from a gravimetrically calibrated U double spike and implications for absolute Pb-Pb ages

    NASA Astrophysics Data System (ADS)

    Weyer, Stefan; Noordmann, Janine; Brennecka, Greg; Richter, Stephan

    2010-05-01

    The ratio of 238U and 235U, the two primordial U isotopes, has been assumed to be constant on Earth and in the solar system. The commonly accepted value for the 238U/235U ratio, which has been used in Pb-Pb dating for the last ~ 30 years, was 137.88. Within the last few years, it has been shown that 1) there are considerable U isotope variations (~1.3‰) within terrestrial material produced by isotope fractionation during chemical reactions [1-3] and 2) there are even larger isotope variations (at least 3.5‰) in calcium-aluminum-rich inclusions (CAIs) in meoteorites that define the currently accepted age of the solar system [4]. These findings are dramatic for geochronology, as a known 238U/235U is a requirement for Pb-Pb dating, the most precise dating technique for absolute ages. As 238U/235U variations can greatly affect the reported absolute Pb-Pb age, understanding and accurately measuring variation of the 238U/235U ratio in various materials is critical, With these new findings, the questions also arises of "How well do we know the average U isotope composition of the Earth and the solar system?" and "How accurate can absolute Pb-Pb ages be?" Our results using a gravimetrically calibrated 233U/236U double spike IRMM 3636 [5] indicate that the U standard NBL 950a, which was commonly used to define the excepted "natural" 238U/235U isotope ratio, has a slightly lower 238U/235U of 137.836 ± 0.024. This value is indistinguishable from the U isotope compositions for NBL 960 and NBL112A, which have been determined by several laboratories, also using the newly calibrated U double spike IRMM 3636 [6]. These findings provide new implications about the average U isotope composition of the Earth and the solar system. Basalts display a very tight range of U isotope variations (~0.25-0.32‰ relative to SRM 950a). Their U isotope composition is also very similar to that of chondrites [4], which however appear to show a slightly larger spread. Accepting terrestrial

  5. 230Th-234U Age-Dating Uranium by Mass Spectrometry

    SciTech Connect

    Williams, R W; Gaffney, A M

    2012-04-18

    This is the standard operating procedure used by the Isotope Ratio Mass Spectrometry Group of the Chemical Sciences Division at LLNL for the preparation of a sample of uranium oxide or uranium metal for {sup 230}Th-{sup 234}U age-dating. The method described here includes the dissolution of a sample of uranium oxide or uranium metal, preparation of a secondary dilution, spiking of separate aliquots for uranium and thorium isotope dilution measurements, and purification of uranium and thorium aliquots for mass spectrometry. This SOP may be applied to uranium samples of unknown purity as in a nuclear forensic investigation, and also to well-characterized samples such as, for example, U{sub 3}O{sub 8} and U-metal certified reference materials. The sample of uranium is transferred to a quartz or PFA vial, concentrated nitric acid is added and the sample is heated on a hotplate at approximately 100 C for several hours until it dissolves. The sample solution is diluted with water to make the solution approximately 4 M HNO{sub 3} and hydrofluoric acid is added to make it 0.05 M HF. A secondary dilution of the primary uranium solution is prepared. Separate aliquots for uranium and thorium isotope dilution measurements are taken and spiked with {sup 233}U and {sup 229}Th, respectively. The spiked aliquot for uranium isotope dilution analysis is purified using EiChrom UTEVA resin. The spiked aliquot for thorium isotope dilution analysis is purified by, first, a 1.8 mL AG1x8 resin bed in 9 M HCl on which U adsorbs and Th passes through; second, adsorbing Th on a 1 mL AG1x8 resin bed in 8 M HNO{sub 3} and then eluting it with 9 M HCl followed by 0.1 M HCl + 0.005 M HF; and third, by passing the Th through a final 1.0 mL AG1x8 resin bed in 9 M HCl. The mass spectrometry is performed using the procedure 'Th and U Mass Spectrometry for {sup 230}Th-{sup 234}U Age Dating'.

  6. Age of Barrier Canyon-style rock art constrained by cross-cutting relations and luminescence dating techniques

    NASA Astrophysics Data System (ADS)

    Pederson, Joel L.; Chapot, Melissa S.; Simms, Steven R.; Sohbati, Reza; Rittenour, Tammy M.; Murray, Andrew S.; Cox, Gary

    2014-09-01

    Rock art compels interest from both researchers and a broader public, inspiring many hypotheses about its cultural origin and meaning, but it is notoriously difficult to date numerically. Barrier Canyon-style (BCS) pictographs of the Colorado Plateau are among the most debated examples; hypotheses about its age span the entire Holocene epoch and previous attempts at direct radiocarbon dating have failed. We provide multiple age constraints through the use of cross-cutting relations and new and broadly applicable approaches in optically stimulated luminescence dating at the Great Gallery panel, the type section of BCS art in Canyonlands National Park, southeastern Utah. Alluvial chronostratigraphy constrains the burial and exhumation of the alcove containing the panel, and limits are also set by our related research dating both a rockfall that removed some figures and the rock's exposure duration before that time. Results provide a maximum possible age, a minimum age, and an exposure time window for the creation of the Great Gallery panel, respectively. The only prior hypothesis not disproven is a late Archaic origin for BCS rock art, although our age result of A.D. ∼1-1100 coincides better with the transition to and rise of the subsequent Fremont culture. This chronology is for the type locality only, and variability in the age of other sites is likely. Nevertheless, results suggest that BCS rock art represents an artistic tradition that spanned cultures and the transition from foraging to farming in the region.

  7. Age of Barrier Canyon-style rock art constrained by cross-cutting relations and luminescence dating techniques.

    PubMed

    Pederson, Joel L; Chapot, Melissa S; Simms, Steven R; Sohbati, Reza; Rittenour, Tammy M; Murray, Andrew S; Cox, Gary

    2014-09-01

    Rock art compels interest from both researchers and a broader public, inspiring many hypotheses about its cultural origin and meaning, but it is notoriously difficult to date numerically. Barrier Canyon-style (BCS) pictographs of the Colorado Plateau are among the most debated examples; hypotheses about its age span the entire Holocene epoch and previous attempts at direct radiocarbon dating have failed. We provide multiple age constraints through the use of cross-cutting relations and new and broadly applicable approaches in optically stimulated luminescence dating at the Great Gallery panel, the type section of BCS art in Canyonlands National Park, southeastern Utah. Alluvial chronostratigraphy constrains the burial and exhumation of the alcove containing the panel, and limits are also set by our related research dating both a rockfall that removed some figures and the rock's exposure duration before that time. Results provide a maximum possible age, a minimum age, and an exposure time window for the creation of the Great Gallery panel, respectively. The only prior hypothesis not disproven is a late Archaic origin for BCS rock art, although our age result of A.D. ∼ 1-1100 coincides better with the transition to and rise of the subsequent Fremont culture. This chronology is for the type locality only, and variability in the age of other sites is likely. Nevertheless, results suggest that BCS rock art represents an artistic tradition that spanned cultures and the transition from foraging to farming in the region. PMID:25157162

  8. Age of Barrier Canyon-style rock art constrained by cross-cutting relations and luminescence dating techniques

    PubMed Central

    Pederson, Joel L.; Chapot, Melissa S.; Simms, Steven R.; Sohbati, Reza; Rittenour, Tammy M.; Murray, Andrew S.; Cox, Gary

    2014-01-01

    Rock art compels interest from both researchers and a broader public, inspiring many hypotheses about its cultural origin and meaning, but it is notoriously difficult to date numerically. Barrier Canyon-style (BCS) pictographs of the Colorado Plateau are among the most debated examples; hypotheses about its age span the entire Holocene epoch and previous attempts at direct radiocarbon dating have failed. We provide multiple age constraints through the use of cross-cutting relations and new and broadly applicable approaches in optically stimulated luminescence dating at the Great Gallery panel, the type section of BCS art in Canyonlands National Park, southeastern Utah. Alluvial chronostratigraphy constrains the burial and exhumation of the alcove containing the panel, and limits are also set by our related research dating both a rockfall that removed some figures and the rock’s exposure duration before that time. Results provide a maximum possible age, a minimum age, and an exposure time window for the creation of the Great Gallery panel, respectively. The only prior hypothesis not disproven is a late Archaic origin for BCS rock art, although our age result of A.D. ∼1–1100 coincides better with the transition to and rise of the subsequent Fremont culture. This chronology is for the type locality only, and variability in the age of other sites is likely. Nevertheless, results suggest that BCS rock art represents an artistic tradition that spanned cultures and the transition from foraging to farming in the region. PMID:25157162

  9. Reconstruction of settlement phases at Intermediate Bronze Age structures in the Negev Highlands (Israel) using luminescence dating

    NASA Astrophysics Data System (ADS)

    Junge, Andrea; Lomax, Johanna; Shahack-Gross, Ruth; Dunseth, Zachary C.; Finkelstein, Israel; Fuchs, Markus

    2016-04-01

    OSL dating is usually applied to sediments in paleoenvironmental sciences. However, there is only limited experience with determining the age of archaeological stone structures by OSL using dust deposits associated with these structures. The age of trapped dust deposits may be used to date the onset of settlement (sediment below structures), settlement activity (occupation layer), or the time after settlement (sediment between collapsed walls and roofs). In this study, OSL dating is applied for establishing a chronology of settlement structures situated in the Negev Highlands, Israel. Two archaeological sites are investigated to identify the occupation history, by dating the aeolian dust trapped within the remains of ancient buildings. OSL dating techniques are applied using coarse grain quartz and a standard SAR protocol. First results indicate that the luminescence properties of the trapped sediments are suitable for OSL dating. Therefore, it was possible to date the onset of sedimentation in a later phase of the human occupation or shortly after the settlement was abandoned, which is supported by archaeological evidence gained from pottery finds and the architecture of the buildings.

  10. Radiocarbon Dating

    SciTech Connect

    Buchholz, B A

    2007-12-20

    Radiocarbon dating can be used to determine the age of objects that contain components that were once alive. In the case of human remains, a radiocarbon date can distinguish between a crime scene and an archeological site. Documents, museum artifacts and art objects can be dated to determine if their age is correct for the historical context. A radiocarbon date does not confirm authenticity, but it can help identify a forgery.

  11. Revised age for the Gosses Bluff impact structure, Northern Territory, Australia, based on Ar-40Ar-39 dating

    NASA Astrophysics Data System (ADS)

    Milton, Daniel J.; Sutter, John F.

    1987-09-01

    Ar-40Ar-39 dating of a pumiceous suevite clast from the melt breccia at Gosses Bluff consisting largely of extremely fine-grained sanidine yields a discordant age spectrum, probably reflecting some diffusional loss of argon. High-temperature increments that together yield a near-plateau age of 142.5 Ma are apparently not affected by argon loss and offer the best estimate of the date of the Gosses Bluff event. The event may fall in the latest Jurassic Period, but more likely falls in the earliest Cretaceous, probably in one of the reverse-polarity magnetochrons M16, M17, or M18.

  12. Common-Lead Corrected U-Pb Age Dating of Perovskite by LA-SF-ICP-MS

    NASA Astrophysics Data System (ADS)

    Frei, D.

    2014-12-01

    Perovskite is a very useful mineral for dating the age of emplacement of kimberlites and associated rocks. Conventionally, U-Pb dating of perovskite is achieved using isotope dilution (ID-TIMS) or ion-probe (SHRIMP) techniques, which are time- and cost-intensive. The potential of the rapid and inexpensive laser ablation ICP-MS technique for U-Pb dating of perovskite has been demonstrated recently. We investigated the benefits of single collector magnetic sectorfield ICP-MS (SF-ICP-MS) instruments for U-Pb dating of perovskite by laser ablation. To this end perovskites from two kimberlites from Garnet Lake, W Greenland, and Pyramidefjeld, SW Greenland, have been separated. Multigrain aliquots of both perovskite separates were U-Pb dated by ID-TIMS, yielding emplacement ages of 568 ±11 Ma for the Garnet Lake kimberlite and 151 ±2 Ma for the Pyramidefjeld kimberlite. Subsequently both samples have been dated in-situ by laser ablation employing a ThermoFinnigan Element2 SF-ICP-MS coupled to a NewWave UP 213 laser system. A common lead correction was applied based on the measured 204Pb intensity (after correction for the measured 204(Pb+Hg) gas blank). Perovskite from the Ice River Complex, British Columbia, was used as a secondary standard for quality control purposes. Multiple in-situ measurements of the Ice River perovskite in two different analytical sessions yielded concordia ages of 359 ±3 Ma and 357 ±3 Ma, in excellent agreement with the age of 356 Ma determined by ID-TIMS (Heaman, pers. comm.). Nineteen in-situ analyses of perovskite grains extracted from the Garnet Lake kimberlite yielded a concordia age of 566 ±5 Ma, also in excellent agreement with the age obtained by ID-TIMS. Because of the very low Pb contents in perovskites from the Pyramidefjeld (around 1 ppm) and the associated large uncertainties of the common lead correction, no concordia age could be obtained. However, the in-situ laser ablation analysis yielded a common lead corrected weighted

  13. Radiocarbon Dating, Memories, and Hopes

    DOE R&D Accomplishments Database

    Libby, W. F.

    1972-10-01

    The history of radiocarbon dating from 1939 to the present is reviewed. The basic principles of radiocarbon dating are that cosmic rays make living things radioactive with {sup 14}C to a certain level fixed by the environment and that at death the intake of food stops so no replenishment of the {sup 14}C steadily lost by the immutable decay occurs. Therefore measurement of the degree of decay gives the time lapse since death, i.e., the radiocarbon age. The equipment developed and experiments performed to measure the specific activity of specimens to be dated are described. The results obtained by world-wide experimenters are discussed. These showed that on simultaneity radiocarbon dating is apparently reliable but that absolute dates may be incorrect by as much as 600 to 700 y. The value of radiocarbon dating to archaeologists, geologists, climatologists, and historians is stressed. (LCL)

  14. Characterization of depositional age and structure of sedimentary successions by U-Pb TIMS and LA-ICP-MS dating of volcanic horizons and detrital zircons: an example from the western Trondheim Nappe Complex, Scandinavian Caledonides

    NASA Astrophysics Data System (ADS)

    Gasser, Deta; Grenne, Tor; Corfu, Fernando; Eivind Augland, Lars

    2016-04-01

    Revealing the absolute depositional age of non-fossiliferous sedimentary successions represents a long-lasting challenge in Earth Sciences. Lacking age control hampers the correct interpretation of the temporal evolution of depositional systems, and, if deformed, of the architecture of fold-and-thrust belts. Dating of detrital zircons within clastic sedimentary successions has over the past decades become a popular method to approximate the absolute depositional age and to characterize the source areas of such rocks. If combined with other geochronological information, such as dating of contemporaneous volcanic horizons, a much better resolution of the stratigraphy and structure of non-fossiliferous sedimentary successions can be achieved. The western Trondheim nappe complex in the central Scandinavian Caledonides is a classical area in this respect. On top of Late Cambrian to Early Ordovician ophiolitic fragments, various volcanic, volcano-clastic and clastic successions tell a complex story of island-arc formation, ocean closure and continent collision. Several famous fossil horizons indicate deposition during the Middle to Upper Ordovician (ca. 470-445 Ma), but large areas lack an absolute age control and several contrasting stratigraphic schemes and structural interpretations have been presented in the past. In this contribution we present the results of LA-ICP-MS detrital U-Pb zircon dating of clastic horizons as well as U-Pb TIMS zircon dating of volcanic horizons and magmatic clasts in conglomerates in order to characterize the depositional age and structure of the western Trondheim nappe complex in more detail. Together with field observations, including way up criteria, the zircon data enable significant revisions of existing stratigraphic and structural models. At least four (volcano-)sedimentary successions can be distinguished above the ca. 480-485 Ma greenstones: (1) ca. 470-463 Ma shales, limestones and andesitic porphyrites (Hølonda and Fanabekken

  15. Using a Novel Absolute Ontogenetic Age Determination Technique to Calculate the Timing of Tooth Eruption in the Saber-Toothed Cat, Smilodon fatalis

    PubMed Central

    Wysocki, M. Aleksander; Feranec, Robert S.; Tseng, Zhijie Jack; Bjornsson, Christopher S.

    2015-01-01

    Despite the superb fossil record of the saber-toothed cat, Smilodon fatalis, ontogenetic age determination for this and other ancient species remains a challenge. The present study utilizes a new technique, a combination of data from stable oxygen isotope analyses and micro-computed tomography, to establish the eruption rate for the permanent upper canines in Smilodon fatalis. The results imply an eruption rate of 6.0 millimeters per month, which is similar to a previously published average enamel growth rate of the S. fatalis upper canines (5.8 millimeters per month). Utilizing the upper canine growth rate, the upper canine eruption rate, and a previously published tooth replacement sequence, this study calculates absolute ontogenetic age ranges of tooth development and eruption in S. fatalis. The timing of tooth eruption is compared between S. fatalis and several extant conical-toothed felids, such as the African lion (Panthera leo). Results suggest that the permanent dentition of S. fatalis, except for the upper canines, was fully erupted by 14 to 22 months, and that the upper canines finished erupting at about 34 to 41 months. Based on these developmental age calculations, S. fatalis individuals less than 4 to 7 months of age were not typically preserved at Rancho La Brea. On the whole, S. fatalis appears to have had delayed dental development compared to dental development in similar-sized extant felids. This technique for absolute ontogenetic age determination can be replicated in other ancient species, including non-saber-toothed taxa, as long as the timing of growth initiation and growth rate can be determined for a specific feature, such as a tooth, and that growth period overlaps with the development of the other features under investigation. PMID:26132165

  16. An evaluation of fossil tip-dating versus node-age calibrations in tetraodontiform fishes (Teleostei: Percomorphaceae).

    PubMed

    Arcila, Dahiana; Alexander Pyron, R; Tyler, James C; Ortí, Guillermo; Betancur-R, Ricardo

    2015-01-01

    Time-calibrated phylogenies based on molecular data provide a framework for comparative studies. Calibration methods to combine fossil information with molecular phylogenies are, however, under active development, often generating disagreement about the best way to incorporate paleontological data into these analyses. This study provides an empirical comparison of the most widely used approach based on node-dating priors for relaxed clocks implemented in the programs BEAST and MrBayes, with two recently proposed improvements: one using a new fossilized birth-death process model for node dating (implemented in the program DPPDiv), and the other using a total-evidence or tip-dating method (implemented in MrBayes and BEAST). These methods are applied herein to tetraodontiform fishes, a diverse group of living and extinct taxa that features one of the most extensive fossil records among teleosts. Previous estimates of time-calibrated phylogenies of tetraodontiforms using node-dating methods reported disparate estimates for their age of origin, ranging from the late Jurassic to the early Paleocene (ca. 150-59Ma). We analyzed a comprehensive dataset with 16 loci and 210 morphological characters, including 131 taxa (95 extant and 36 fossil species) representing all families of fossil and extant tetraodontiforms, under different molecular clock calibration approaches. Results from node-dating methods produced consistently younger ages than the tip-dating approaches. The older ages inferred by tip dating imply an unlikely early-late Jurassic (ca. 185-119Ma) origin for this order and the existence of extended ghost lineages in their fossil record. Node-based methods, by contrast, produce time estimates that are more consistent with the stratigraphic record, suggesting a late Cretaceous (ca. 86-96Ma) origin. We show that the precision of clade age estimates using tip dating increases with the number of fossils analyzed and with the proximity of fossil taxa to the node under

  17. Absolute Zero

    NASA Astrophysics Data System (ADS)

    Donnelly, Russell J.; Sheibley, D.; Belloni, M.; Stamper-Kurn, D.; Vinen, W. F.

    2006-12-01

    Absolute Zero is a two hour PBS special attempting to bring to the general public some of the advances made in 400 years of thermodynamics. It is based on the book “Absolute Zero and the Conquest of Cold” by Tom Shachtman. Absolute Zero will call long-overdue attention to the remarkable strides that have been made in low-temperature physics, a field that has produced 27 Nobel Prizes. It will explore the ongoing interplay between science and technology through historical examples including refrigerators, ice machines, frozen foods, liquid oxygen and nitrogen as well as much colder fluids such as liquid hydrogen and liquid helium. A website has been established to promote the series: www.absolutezerocampaign.org. It contains information on the series, aimed primarily at students at the middle school level. There is a wealth of material here and we hope interested teachers will draw their student’s attention to this website and its substantial contents, which have been carefully vetted for accuracy.

  18. Dating a Small Impact Crater: An Age of Kaali Crater (Estonia) Based on Charcoal Emplaced Within Proximal Ejecta

    NASA Astrophysics Data System (ADS)

    Losiak, A.; Wild, E. M.; Geppert, W. D.; Huber, M. S.; Jõeleht, A.; Kriiska, A.; Kulkov, A.; Paavel, K.; Pirkovic, I.; Plado, J.; Steier, P.; Välja, R.; Wilk, J.; Wisniowski, T.; Zanetti, M.

    2015-09-01

    The Kaali crater was formed shortly after (tpq) 1530-1455 BC (3237 ± 10 14C yr BP). This age is based on dating charcoal within the ejecta blanket that makes it directly related to the impact, and not susceptible to potential reservoir effects.

  19. Investigation of origin for seawater intrusion using geophysical well logs and absolute ages of volcanic cores in the eastern part of Jeju Island

    NASA Astrophysics Data System (ADS)

    Hwang, Seho; Shin, Jehyun

    2010-05-01

    Jeju located in the southern extremity of Korea is volcanic island, one of best-known tourist attractions in Korea. Jeju Province operates the monitoring boreholes for the evaluation of groundwater resources in coastal area. Major rock types identified from drill cores are trachybasalt, acicular basalt, scoria, hyalocastite, tuff, unconsolidated U formation, and seoguipo formation and so on. Various conventional geophysical well loggings including radioactive logs (natural gamma log, dual neutron log, and gamma-gamma log), electrical log (or electromagnetic induction log), caliper log, fluid temperature/ conductivity log, and televiewer logs have been conducted to identify basalt sequences and permeable zone, and verify seawater intrusion in monitoring boreholes. The conductivity logs clearly show the fresh water-saline water boundaries, but we find it hard to identify the permeable zones because of the mixed groundwater within the boreholes. Temperature gradient logs are mostly related with lithologic boundaries and permeable zones intersected by boreholes of eastern coasts. The wide range of periodic electrical conductivity logging in the deeper depth of monitoring boreholes indicates the possibility of submarine groundwater discharge. However we did not clearly understand the origin of seawater intrusion in the eastern coast until now. So we analysis the electrical conductivity profiles, record of sea-level change and 40Ar/39Ar absolute ages of volcanic rock cores from twenty boreholes in east coast. From comparing absolute ages of volcanic rock cores and sea-level of their ages, we find that the almost ages of depth showing high salinity groundwater are about 100 Ka, and from 130Ka to about 180Ka. The former is after the interglacial period and the latter is illinoian. These results indicate that the abrupt raising of sea level after illinoian formed the regional coast, and the zone of present seawater intrusion also are above the depth of illinoin period. So

  20. Uranium-series dating of mollusks and corals, and age of Pleistocene deposits, Chesapeake Bay area, Virginia and Maryland

    USGS Publications Warehouse

    Mixon, Robert B.; Szabo, B. J.; Owens, James Patrick

    1982-01-01

    Geologic mapping in conjunction with uranium-series dating of fossil mollusks and corals suggests that the low-lying ( < 17 m in altitude) terrace deposits in the central and southern Chesapeake Bay area include two main depositional sequences, each of which represents a high stand of the sea in late Pleistocene time. The older depositional sequence includes the Accomack and Omar beds of the Delmarva area, the fossiliferous deposits along the lower Rappahannock River, and the Norfolk Formation deposits west of the Suffolk scarp. These beds have yielded a single reliable coral age estimate of 184,000?20,000 years B.P., suggesting an early late Pleistocene age. The younger sequence, including the type beds of the Norfolk Formation and equivalent strata east of the Suffolk scarp, has yielded several coral ages ranging from about 62,000 to 86,000 years B.P. (including ages from our samples and previously reported age estimates); thus, it is clearly late Pleistocene in age. Groupings of ages obtained from our quahog analyses also suggest two transgressive sequences; however, the estimated quahog ages are consistently younger than ages based on coral samples from the same and equivalent stratigraphic units. Stratigraphic, paleoclimatic, and geomorphic data suggest that the estimated uranium-series age of 71,000?7,000 years B.P. for the type beds of the Norfolk, obtained by averaging our coral dates, may be too young by as much as several tens of thousands of years. A postulated equivalency of the type Norfolk beds, upper Pleistocene deposits near Charleston, S.C. (apparent uranium-series age = 95,000?5,000 years), and deposits in the Caribbean area thought to represent the highest sea stand during the last interglacial period (apparent age, 125,000?10,000 years) implies diagenetic modification of coralline material possibly in part because of regional differences in depositional and postdepositional environments.

  1. New uppermost Cambrian U-Pb date from Avalonian Wales and age of the Cambrian-Ordovician boundary

    USGS Publications Warehouse

    Davidek, K.; Landing, E.; Bowring, S.A.; Westrop, S.R.; Rushton, A.W.A.; Fortey, R.A.; Adrain, J.M.

    1998-01-01

    A crystal-rich volcaniclastic sandatone in the lower Peltura scarabaeoides Zone at Ogof-odi near Criccieth, North Wales, yields a U-Pb zircon age of 491 ?? 1 Ma. This late Late Cambrian date indicates a remarkably young age for the Cambrian-Ordovician boundary whose age must be less than 491 Ma. Hence the revised duration of the post-Placentian (trilobite-bearing) Cambrian indicates that local trilobite zonations allow a biostratigraphic resolution comparble to that provided by Ordovician graptolites and Mesozoic ammonites.

  2. Evaluating the reliability of Late Quaternary landform ages: Integrating 10Be cosmogenic surface exposure dating with U-series dating of pedogenic carbonate on alluvial and fluvial deposits, Sonoran desert, California

    NASA Astrophysics Data System (ADS)

    Blisniuk, K.; Sharp, W. D.

    2015-12-01

    To assess the reliability of Quaternary age determinations of alluvial and fluvial deposits across the Sonoran Desert (Coachella Valley and Anza Borrego) in southern California, we applied both 10Be exposure age dating of surface clasts and U-series dating of pedogenic carbonate from subsurface clast-coatings to the same deposits. We consider agreement between dates from the two techniques to indicate reliable age estimates because each technique is subject to distinct assumptions and therefore their systematic uncertainties are largely independent. 10Be exposure dates should yield maximum ages when no correction is made for inheritance and post-depositional erosion is negligible. U-series dating, in contrast, provides minimum dates because pedogenic carbonate forms after deposition. Our results show that: (1) For deposits ca. 70 ka or younger, 10Be and U-series dates were generally concordant. We note, however, that in most cases U-series soil dates exceed 10Be exposure dates that are corrected for inheritance when using 10Be in modern alluvium. This suggests that 10Be concentrations of modern alluvium may exceed the 10Be acquired by late Pleistocene deposits during fluvial transport and hillslope residence (i.e., Pleistocene inherited 10Be). (2) For deposits older than ~70 ka, U-series dates are significantly younger than the 10Be dates. This implies that U-series dates in this region may significantly underestimate the depositional age of older alluvium, probably because of delayed onset of deposition, slow accumulation, or poor preservation of secondary carbonate in response to climatic controls. Thus, whenever possible, multiple dating methods should be applied to obtain reliable ages for late Quaternary deposits.

  3. Modeling Magma Mixing: Evidence from U-series age dating and Numerical Simulations

    NASA Astrophysics Data System (ADS)

    Philipp, R.; Cooper, K. M.; Bergantz, G. W.

    2007-12-01

    -pairs, heterogeneity of particle populations is large. After one overturn event, even the "thin section scale" can contain phenocrysts that derive from the entire magmatic system. We combine these results with time scale information from U-series plagioclase age dating. Apparent crystal residence times from the most evolved and therefore least hybridized rocks for the 1846/47 and 1932 eruptions of Volcan Quizapu are about 5000 and about 3000 yrs, respectively. Based on whole rock chemistry as well as textural and crystal-chemical data, both eruptions tapped the same reservoir and therefore should record similar crystal residence times. Instead, the discordance of these two ages can be explained by magma mixing as modeled above, if some young plagioclase derived from the andesitic recharge magma which triggered the 1846/47 AD eruption got mixed into the dacite remaining in the reservoir after eruption, thus lowering the apparent crystal residence time for magma that was evacuated from the reservoir in 1932.

  4. Confirmation of a late middle Pleistocene age for the Omo Kibish 1 cranium by direct uranium-series dating.

    PubMed

    Aubert, Maxime; Pike, Alistair W G; Stringer, Chris; Bartsiokas, Antonis; Kinsley, Les; Eggins, Stephen; Day, Michael; Grün, Rainer

    2012-11-01

    While it is generally accepted that modern humans evolved in Africa, the specific physical evidence for that origin remains disputed. The modern-looking Omo 1 skeleton, discovered in the Kibish region of Ethiopia in 1967, was controversially dated at ~130 ka (thousands of years ago) by U-series dating on associated Mollusca, and it was not until 2005 that Ar-Ar dating on associated feldspar crystals in pumice clasts provided evidence for an even older age of ~195 ka. However, questions continue to be raised about the age and stratigraphic position of this crucial fossil specimen. Here we present direct U-series determinations on the Omo 1 cranium. In spite of significant methodological complications, which are discussed in detail, the results indicate that the human remains do not belong to a later intrusive burial and are the earliest representative of anatomically modern humans. Given the more archaic morphology shown by the apparently contemporaneous Omo 2 calvaria, we suggest that direct U-series dating is applied to this fossil as well, to confirm its age in relation to Omo 1. PMID:22959819

  5. Absolute Summ

    NASA Astrophysics Data System (ADS)

    Phillips, Alfred, Jr.

    Summ means the entirety of the multiverse. It seems clear, from the inflation theories of A. Guth and others, that the creation of many universes is plausible. We argue that Absolute cosmological ideas, not unlike those of I. Newton, may be consistent with dynamic multiverse creations. As suggested in W. Heisenberg's uncertainty principle, and with the Anthropic Principle defended by S. Hawking, et al., human consciousness, buttressed by findings of neuroscience, may have to be considered in our models. Predictability, as A. Einstein realized with Invariants and General Relativity, may be required for new ideas to be part of physics. We present here a two postulate model geared to an Absolute Summ. The seedbed of this work is part of Akhnaton's philosophy (see S. Freud, Moses and Monotheism). Most important, however, is that the structure of human consciousness, manifest in Kenya's Rift Valley 200,000 years ago as Homo sapiens, who were the culmination of the six million year co-creation process of Hominins and Nature in Africa, allows us to do the physics that we do. .

  6. 235U–231Pa age dating of uranium materials for nuclear forensic investigations

    SciTech Connect

    Eppich, Gary R.; Williams, Ross W.; Gaffney, Amy M.; Schorzman, Kerri C.

    2013-04-03

    Here, age dating of nuclear material can provide insight into source and suspected use in nuclear forensic investigations. We report here a method for the determination of the date of most recent chemical purification for uranium materials using the 235U-231Pa chronometer. Protactinium is separated from uranium and neptunium matrices using anion exchange resin, followed by sorption of Pa to an SiO2 medium. The concentration of 231Pa is measured by isotope dilution mass spectrometry using 233Pa spikes prepared from an aliquot of 237Np and calibrated in-house using the rock standard Table Mountain Latite and the uranium isotopic standard U100. Combined uncertainties of age dates using this method are 1.5 to 3.5 %, an improvement over alpha spectrometry measurement methods. Model ages of five uranium standard reference materials are presented; all standards have concordant 235U-231Pa and 234U-230Th model ages.

  7. Dating the incision of the Yangtze River gorge at the First Bend using three-nuclide burial ages

    NASA Astrophysics Data System (ADS)

    McPhillips, Devin; Hoke, Gregory D.; Liu-Zeng, Jing; Bierman, Paul R.; Rood, Dylan H.; Niedermann, Samuel

    2016-01-01

    Incision of the Yangtze River gorge is widely interpreted as evidence for lower crustal flow beneath the southeast margin of the Tibetan Plateau. Previous work focused on the onset of incision, but the duration of incision remains unknown. Here we present cosmogenic nuclide burial ages of sediments collected from caves on the walls of the gorge that show the gorge was incised ~1 km sometime between 18 and 9 Ma. Thereafter, incision slowed substantially. We resolve middle Miocene burial ages by using three nuclides and accounting for in situ muogenic production. This approach explains the absolute concentrations of 10Be, 26Al, and 21Ne, as well as 26Al/10Be and 21Ne/10Be ratios. A declining incision rate challenges existing geodynamic interpretations by suggesting that either (1) surface uplift has ceased immediately south of the plateau margin or (2) gorge incision is not a useful proxy for the timing of surface uplift.

  8. Age dating of shallow groundwater with chlorofluorocarbons, tritium/helium 3, and flow path analysis, southern New Jersey coastal plain

    USGS Publications Warehouse

    Szabo, Z.; Rice, D.E.; Plummer, L.N.; Busenberg, E.; Drenkard, S.; Schlosser, P.

    1996-01-01

    Groundwater age dating through the combination of transient tracer methods (chlorofluorocarbons (CFCs) and tritium/helium 3 (3H/3He)) and groundwater flow path analysis is useful for investigating groundwater travel times, flow patterns, and recharge rates, as demonstrated by this study of the homogeneous shallow, unconfined Kirkwood-Cohansey aquifer system in the southern New Jersey coastal plain. Water samples for age dating were collected from three sets of nested observation wells (10 wells) with 1.5-m-long screens located near groundwater divides. Three steady state finite difference groundwater flow models were calibrated by adjusting horizontal and vertical hydraulic conductivities to match measured heads and head differences (range, 0.002-0.23 m) among the nested wells, with a uniform recharge rate of 0.46 m per year and porosities of 0.35 (sand) and 0.45 (silt) that were assumed constant for all model simulations and travel time calculations. The simulated groundwater travel times increase with depth in the aquifer, ranging from about 1.5 to 6.5 years for the shallow wells (screen bottoms 3-4 m below the water table), from about 10 to 25 years for the medium-depth wells (screen bottoms 8-19 m below the water table), and from about 30 to more than 40 years for the deep wells (screen bottoms 24-26 m below the water table). Apparent groundwater ages based on CFC- and 3H/3He-dating techniques and model-based travel times could not be statistically differentiated, and all were strongly correlated with depth. Confinement of 3He was high because of the rapid vertical flow velocity (of the order of 1 m/yr), resulting in clear delineation of groundwater travel times based on the 3H/3He-dating technique. The correspondence between the 3H/3He and CFC ages indicates that dispersion has had a minimal effect on the tracer-based ages of water in this aquifer. Differences between the tracer-based apparent ages for seven of the 10 samples were smaller than the error values

  9. Using age of colonizing douglas-fir for the dating of young geomorphic surfaces: a case study

    USGS Publications Warehouse

    Pierson, Thomas C.

    2013-01-01

    Dating of many types of young (<500 year), dynamic, geomorphic landforms (e.g. mass-movement erosional tracks and deposits, alluvial terraces, flood plains, etc.) for purposes of hazard assessment and mitigation commonly requires greater dating precision than is available through radiocarbon dating or other methods. Ages of trees growing on landform surfaces have been used in a number of studies to estimate the time of landform creation or surface clearing, but the time lag between surface formation or disturbance and the reestablishment of trees can vary from 1 to more than 200 years (Desloges and Ryder 1990; Frenzen et al. 1988, 2005; Larsen and Bliss 1998; McCarthy and Luckman 1993; Sigafoos and Hendricks 1969; Winter et al. 2002). Appropriate lag times for selected tree species and for particular climatic and altitudinal ranges must be determined for the method to be useful.

  10. Dating young geomorphic surfaces using age of colonizing Douglas fir in southwestern Washington and northwestern Oregon, USA

    USGS Publications Warehouse

    Pierson, T.C.

    2007-01-01

    Dating of dynamic, young (<500 years) geomorphic landforms, particularly volcanofluvial features, requires higher precision than is possible with radiocarbon dating. Minimum ages of recently created landforms have long been obtained from tree-ring ages of the oldest trees growing on new surfaces. But to estimate the year of landform creation requires that two time corrections be added to tree ages obtained from increment cores: (1) the time interval between stabilization of the new landform surface and germination of the sampled trees (germination lag time or GLT); and (2) the interval between seedling germination and growth to sampling height, if the trees are not cored at ground level. The sum of these two time intervals is the colonization time gap (CTG). Such time corrections have been needed for more precise dating of terraces and floodplains in lowland river valleys in the Cascade Range, where significant eruption-induced lateral shifting and vertical aggradation of channels can occur over years to decades, and where timing of such geomorphic changes can be critical to emergency planning. Earliest colonizing Douglas fir (Pseudotsuga menziesii) were sampled for tree-ring dating at eight sites on lowland (<750 m a.s.l.), recently formed surfaces of known age near three Cascade volcanoes - Mount Rainier, Mount St. Helens and Mount Hood - in southwestern Washington and northwestern Oregon. Increment cores or stem sections were taken at breast height and, where possible, at ground level from the largest, oldest-looking trees at each study site. At least ten trees were sampled at each site unless the total of early colonizers was less. Results indicate that a correction of four years should be used for GLT and 10 years for CTG if the single largest (and presumed oldest) Douglas fir growing on a surface of unknown age is sampled. This approach would have a potential error of up to 20 years. Error can be reduced by sampling the five largest Douglas fir instead of the

  11. Age dating of mineralization and brittle deformation using rhenium-osmium (Re-Os) geochronology in pyrite-bitumen bearing fracture systems

    NASA Astrophysics Data System (ADS)

    Holdsworth, Robert; Dempsey, Eddie; Selby, David; Dichiarante, Anna; Finlay, Alex; Ogilvie, Steven

    2013-04-01

    The relative ages of different fault rocks are generally established using cross-cutting relationships seen in the field and thin section. However, the absolute dating of fault rock formation events remains a problematic issue. In many Phanerozoic basins, hydrocarbon (mainly bitumen)-bearing fault and fracture systems also carry sulphide minerals such as pyrite. The bitumen and pyrite are commonly enriched with rhenium (Re) so that the 187Re-187Os geochronometer can be used to date mineralization and better constrain the timing of brittle deformation. Furthermore, the determined 187Os/188Os composition of the sulphide minerals at the time of formation can yield insights into the origins of the fracture-hosted fluids. We report 3 cases of Re-Os sulphide geochronology from fracture-hosted hydrocarbon-pyrite systems offshore West of Shetland (UK) and in the nearby onshore Orcadian Basin, N Scotland. Hydrocarbon Re-Os data from the Faroe-Shetland Basin (FSB) show that there are four pulses of increased oil generation at 72 ± 5 Ma, 64 ± 4 Ma, 53 ± 14 Ma and 42 ± 6 Ma. These dates remove the need for large scale oil collection within fractured basement and Late Cretaceous reservoirs before re-migration into later Cenozoic reservoirs and agree with more recent models in which oil generation has been retarded by over pressure and that multiple pulses of generation are associated with regional inversion events that occurred during the Late Cretaceous, Paleocene and Oligocene/Miocene. The Clair oil field lies on the SE side of the FSB and a major part of the reservoir lies in Lewisian basement where hosting fractures are infilled with pyrite, calcite and bitumen. The pyrite contains low abundances of Re and Os, with Re-Os isotope compositions that are too similar to yield an isochron, whilst the associated bitumen is enriched in both Re and Os. Regression of the Re-Os data from other parts of the Clair field with the new pyrite Re-Os data obtained here yields a more

  12. Dating and context of three middle stone age sites with bone points in the Upper Semliki Valley, Zaire.

    PubMed

    Brooks, A S; Helgren, D M; Cramer, J S; Franklin, A; Hornyak, W; Keating, J M; Klein, R G; Rink, W J; Schwarcz, H; Smith, J N

    1995-04-28

    The extent to which the earliest anatomically modern humans in Africa exhibited behavioral and cognitive traits typical of Homo sapiens sapiens is controversial. In eastern Zaire, archaeological sites with bone points have yielded dates older than 89(-15)+22 thousand years ago by several techniques. These include electron spin resonance, thermoluminescence, optically stimulated luminescence, uranium series, and amino acid racemization. Faunal and stratigraphic data are consistent with this age. PMID:7725099

  13. Dating the age of admixture via wavelet transform analysis of genome-wide data.

    PubMed

    Pugach, Irina; Matveyev, Rostislav; Wollstein, Andreas; Kayser, Manfred; Stoneking, Mark

    2011-01-01

    We describe a PCA-based genome scan approach to analyze genome-wide admixture structure, and introduce wavelet transform analysis as a method for estimating the time of admixture. We test the wavelet transform method with simulations and apply it to genome-wide SNP data from eight admixed human populations. The wavelet transform method offers better resolution than existing methods for dating admixture, and can be applied to either SNP or sequence data from humans or other species. PMID:21352535

  14. Dating the age of admixture via wavelet transform analysis of genome-wide data

    PubMed Central

    2011-01-01

    We describe a PCA-based genome scan approach to analyze genome-wide admixture structure, and introduce wavelet transform analysis as a method for estimating the time of admixture. We test the wavelet transform method with simulations and apply it to genome-wide SNP data from eight admixed human populations. The wavelet transform method offers better resolution than existing methods for dating admixture, and can be applied to either SNP or sequence data from humans or other species. PMID:21352535

  15. A new Application of Ar-40/Ar-39 Dating: A Provenance Study of Middle Stone Age Obsidian Tools from Ethiopia

    NASA Astrophysics Data System (ADS)

    Nomade, S.; Vogel, N.; Renne, P. R.; Negash, A.

    2004-12-01

    The identification and geographic origin of potential sources for obsidian tools manufactured by MSA (Middle Stone Age) hominid groups is important to reconstruct source utilization and trade routes. Obsidian sourcing is done by geochemical investigation of obsidian artifacts and potential source materials and the identification of possible matches between them [e.g., 1]. Due to uncertainties arising, e.g., from intrasource inhomogeneities [2] additional methods are desirable. As a part of a pilot study, we dated by Ar-40/Ar-39 stepwise heating numerous debitage pieces of obsidian artifacts from an MSA excavation site and several potential source rock samples from a nearby obsidian outcrop in the Gademotta-Kulkuletti area near Ziway lake, Ethiopia. The ages were used, along with chemical data, to trace possible source rocks used to manufacture the artifacts. Most of the debitage samples show ages around 1.29 Ma and exhibit flat, well behaved spectra. Less well behaved spectra are obtained for two debitage samples with ages of about 1.26 Ma, and two with ages of about 0.62 Ma. We point out that despite this significant spread in the ages found, all debitage samples as well as the potential source rocks show homogeneous major and trace elemental compositions generally indicating a positive match in archeological sourcing. The ages of two potential source rocks are about 1.26 and 0.87 Ma. Thus, while there is a match with the two debitage pieces dated at 1.26 Ma, the exact outcrop of the major source for the 1.29 Ma old artifacts has not been identified yet. A second set of samples with further possible source materials for the Kulkuletti artifacts as well as another potential debitage-source material pair from a second excavation site in the Ziway lake area, Porc Epic, are currently being dated and will be presented at the conference. Already this first set of data shows not only the general applicability of Ar-40/Ar-39 dating to archeological obsidian sourcing, but

  16. Effect of age at puberty/conception date on cow longevity.

    PubMed

    Perry, George A; Cushman, Robert

    2013-11-01

    Age at puberty is a critical trait, because pregnancy success during the breeding season is correlated with the percentage of heifers that reach puberty before or early in the breeding season. A negative genetic correlation between age at puberty and heifer pregnancy rate indicate that selection to decrease age at puberty would increase heifer pregnancy rates. Calving late has been reported to increase the chance of calving late or not calving the following year, and heifers need to wean 3 to 5 calves to pay for development costs. Therefore, puberty is important to the sustainability and profitability of beef operations. PMID:24182436

  17. Mississippi Valley-type lead-zinc deposits through geological time: Implications from recent age-dating research

    USGS Publications Warehouse

    Leach, D.L.; Bradley, D.; Lewchuk, Michael T.; Symons, David T. A.; De Marsily, G.; Brannon, J.

    2001-01-01

    Remarkable advances in age dating Mississippi Valley-type (MVT) lead-zinc deposits provide a new opportunity to understand how and where these deposits form in the Earth's crust. These dates are summarized and examined in a framework of global tectonics, paleogeography, fluid migration, and paleoclimate. Nineteen districts have been dated by paleomagnetic and/or radiometric methods. Of the districts that have both paleomagnetic and radiometric dates, only the Pine Point and East Tennessee districts have significant disagreements. This broad agreement between paleomagnetic and radiometric dates provides added confidence in the dating techniques used. The new dates confirm the direct connection between the genesis of MVT lead-zinc ores with global-scale tectonic events. The dates show that MVT deposits formed mainly during large contractional tectonic events at restricted times in the history of the Earth. Only the deposits in the Lennard Shelf of Australia and Nanisivik in Canada have dates that correspond to extensional tectonic events. The most important period for MVT genesis was the Devonian to Permian time, which corresponds to a series of intense tectonic events during the assimilation of Pangea. The second most important period for MVT genesis was Cretaceous to Tertiary time when microplate assimilation affected the western margin of North America and Africa-Eurasia. There is a notable paucity of MVT lead-zinc ore formation following the breakup of Rodinia and Pangea. Of the five MVT deposits hosted in Proterozoic rocks, only the Nanisivik deposit has been dated as Proterozoic. The contrast in abundance between SEDEX and MVT lead-zinc deposits in the Proterozoic questions the frequently suggested notion that the two types of ores share similar genetic paths. The ages of MVT deposits, when viewed with respect to the orogenic cycle in the adjacent orogen suggest that no single hydrologic model can be universally applied to the migration of the ore fluids

  18. Effect of artificial accelerated aging on the optical properties and monomeric conversion of composites used after expiration date.

    PubMed

    Garcia, Lucas da Fonseca Roberti; Mundim, Fabricio Mariano; Pires-de-Souza, Fernanda de Carvalho Panzeri; Puppin Rontani, Regina Maria; Consani, Simonides

    2013-01-01

    This study sought to evaluate how artificial accelerated aging (AAA) affected color stability (ΔE), opacity (ΔOP), and degree of conversion (DOC) for 3 composite materials (Tetric Ceram, Tetric Ceram HB, and Tetric Flow) used both 180 days before and 180 days after their expiration dates. To evaluate the materials' optical properties, 10 specimens of each composite-5 prior to expiration and 5 after the materials' expiration date-were made in a teflon matrix. After polishing, the specimens were submitted to initial color and opacity readings and submitted to AAA for 384 hours; at that point, new readings were taken to determine ΔE and ΔOP. To evaluate monomeric conversion evaluation, 6 specimens from each composite and expiration date-3 prior to AAA and 3 after-were submitted to DOC analysis. Results of the 2-way ANOVA and Bonferroni's tests (P < 0.05) demonstrated that all composites had ΔE values above the clinically acceptable level (ΔE ≥ 3.3). When expiration dates were compared, only Tetric Flow showed a statistically significant difference (P < 0.05). Regardless of the expiration date, ΔOP values for all composites increased after AAA, but not significantly (P > 0.05). The expired Tetric Flow had the highest DOC values (71.42% ± 4.21) before AAA, significantly different than that of the other composites (P > 0.05). It was concluded that both expiration date and AAA affected the properties of the composites tested. PMID:24192739

  19. Using Hα Morphology and Surface Brightness Fluctuations to Age-date Star Clusters in M83

    NASA Astrophysics Data System (ADS)

    Whitmore, Bradley C.; Chandar, Rupali; Kim, Hwihyun; Kaleida, Catherine; Mutchler, Max; Stankiewicz, Matt; Calzetti, Daniela; Saha, Abhijit; O'Connell, Robert; Balick, Bruce; Bond, Howard E.; Carollo, Marcella; Disney, Michael J.; Dopita, Michael A.; Frogel, Jay A.; Hall, Donald N. B.; Holtzman, Jon A.; Kimble, Randy A.; McCarthy, Patrick J.; Paresce, Francesco; Silk, Joseph I.; Trauger, John T.; Walker, Alistair R.; Windhorst, Rogier A.; Young, Erick T.

    2011-03-01

    We use new WFC3 observations of the nearby grand-design spiral galaxy M83 to develop two independent methods for estimating the ages of young star clusters. The first method uses the physical extent and morphology of Hα emission to estimate the ages of clusters younger than τ ≈ 10 Myr. It is based on the simple premise that the gas in very young (τ< a few Myr) clusters is largely coincident with the cluster stars, is in a small, ring-like structure surrounding the stars in slightly older clusters since massive star winds and supernovae have had time to push out the natal gas (e.g., τ ≈ 5 Myr), and is in a larger ring-like bubble for still older clusters (i.e., ≈5-10 Myr). If no Hα is associated with a cluster it is generally older than ≈10 Myr. The second method is based on an observed relation between pixel-to-pixel flux variations within clusters and their ages. This method relies on the fact that the brightest individual stars in a cluster are most prominent at ages around 10 Myr, and fall below the detection limit (i.e., M V < -3.5) for ages older than about 100 Myr. Older clusters therefore have a smoother appearance and smaller pixel-to-pixel variations. The youngest clusters also have lower flux variations, hence the relationship is double valued. This degeneracy in age can be broken using other age indicators such as Hα morphology. These two methods are the basis for a new morphological classification system which can be used to estimate the ages of star clusters based on their appearance. We compare previous age estimates of clusters in M83 determined from fitting UBVIHα measurements using predictions from stellar evolutionary models with our new morphological categories and find good agreement, at the ≈95% level. The scatter within categories is ≈0.1 dex in log τ for young clusters (<10 Myr) and ≈0.5 dex for older (>10 Myr) clusters. A by-product of this study is the identification of 22 "single-star" H II regions in M83, with

  20. Ages, durations and behavioural implications of Middle Stone Age industries in southern Africa: advances in optical dating of individual grains of quartz

    NASA Astrophysics Data System (ADS)

    Jacobs, Z.

    2009-04-01

    Recent developments in OSL dating have focussed on the measurement of individual sand-sized grains of quartz. Single-grain dating allows the identification of contaminant grains in a sample and their exclusion before final age determination, and the ability to directly check the stratigraphic integrity of archaeological sequences and address concerns about post-deposition sediment mixing. These benefits result in single-grain OSL ages being both accurate and precise. Even greater precision can be attained by adopting a systematic approach to the collection and analysis of OSL data. This involves one operator using the same OSL stimulation and detection instrument, laboratory radiation sources, calibration standards, and analytical procedures for all samples. By holding these experimental parameters constant, sources of error common to all samples are removed, enabling far greater resolution of the true age structure. This approach was recently used to determine the timing and duration of two bursts of Middle Stone Age technological and behavioural innovation - the Still Bay (SB) and Howieson's Poort (HP) - in southern Africa. These distinctive artefacts are associated with the first evidence for symbols and personal ornaments, and may have been the catalyst for the expansion of Homo sapiens populations in Africa 80,000-60,000 years ago and for the subsequent migration of modern humans out of Africa. Testing such hypotheses, and the putative role of climate change, has been hampered by poor age constraints for the HP and SB industries. Previous attempts to resolve the start and end dates of these industries had been largely obscured by the chronological' haze' arising from a variety of different materials being dated by different methods using different equipment, calibration standards, measurement procedures and techniques of data analysis. By clearing this haze and placing all ages on a common timescale, we were able to constrain the timing of the SB and HP, and

  1. Dating Red Dwarfs: Determining the Ages of Red Dwarf Stars and their Hosted Planets

    NASA Astrophysics Data System (ADS)

    Guinan, Edward F.; Engle, Scott G.; Kullberg, Evan; Watson, William; Michener, Scott

    2014-06-01

    Red Dwarf (dwarf M=dM) stars comprise over 75% of the stars in the Galaxy. The recent statistical analysis of exoplanet systems from the Kepler Mission indicates that about 15% of red dwarf stars host Earth-size planets orbiting in the liquid water Habitable Zones (HZ) of their host stars. This indicates that within 10 pc 33 Ly) of the Sun (which contains ~240 dM stars), there should be about 35 potentially habitable Earth-size planets. Extrapolating to the entire Galaxy indicates that about 50-100 billion earth-size planets may be orbiting within the HZs of red dwarfs.Determining the ages and radiation/plasma properties of these planet hosting dM stars is crucial in assessing the potential for life on their HZ exoplanets. With these aims in mind we have been carrying out multi-wavelength (X-ray - IR) studies of dM stars as part of our NSF/NASA sponsored “Living with a Red Dwarf” Program. Due to their low masses, nuclear evolution of red dwarfs is very slow and their physical properties (e.g. L/Lo, Teff, R/Ro) do not significantly change over the age of the universe This makes it nearly impossible to determine (nuclear) evolutionary ages as is done with more massive stars. However, their rotation-related magnetic dynamo properties such as- coronal X-ray and chromospheric emissions and star spots coverage dramatically decrease with time as the stars spin down from angular momentum loss via magnetic winds We report on the ongoing calibration of Age-Rotation and (magnetic) Activity relations of dM stars. The ages of the calibrator stars are found from memberships in clusters, & moving groups as well as memberships in wide binaries - ages known from white dwarf & main sequence star components. Kinematical ages are used for old high velocity stars. Using these relations, the ages of a dM stars can be estimated from their measured rotation periods, and/or from coronal & chromospheric emissions. We apply these relations to determine ages of nearby dM stars that host

  2. 40Ar/39Ar dating of Pleistocene tuffs: an accurate age for the Matuyama-Brunhes geomagnetic reversal (MBGR)

    NASA Astrophysics Data System (ADS)

    Mark, D. F.; Renne, P. R.; Morgan, L. E.; Deino, A.; Smith, V. C.; Ellis, B. S.; Pearce, N. J.

    2012-12-01

    Recent recalibrations of the 40Ar/39Ar system [1,2] reveal inconsistencies with some previous ages inferred for the MBGR. An Ar/Ar age [3] for the Bishop Tuff (BT) (which post-dates the MBGR by at least 15.3 ± 2.2 ka [3]) recalculated [2] yields an age of 778.0 ± 3.8 ka (1σ, full systematic uncertainty). The age is c. 10 ka older than the BT zircon ID-TIMS U-Pb age [4] and places the MBGR at c. 793 ka, c. 13 and 20 ka older than astronomical ages for the MBGR of 780 ka [5] and 773 ka [6], respectively. To determine an accurate age for the MBGR, we have made a series of 40Ar/39Ar age determinations for Pleistocene tuffs from both Indonesia and North America that have direct relationships to the MBGR. Blind analyses were conducted at SUERC and BGC. We observed excellent inter-laboratory agreement and no systematic offset in data. Ar/Ar ages are reported relative to [2] (1σ, full systematic uncertainty). Drill cores from ODP Site 758 show the precise location of the MBGR. Below the MBGR are two distal tephra horizons that we have identified as products of two temporally distinct Old Toba Tuff (OTT) eruptions (layer d OTT1 and layer D OTT2). Continuous sedimentation between OTT1 (802.8 ± 0.7 ka, n = 100, MSWD 1.2) and OTT2 (796.2 ± 0.8 ka, n = 62, MSWD 1.3) allows for calculation of an accurate sedimentation rate and for extrapolation of an age from OTT2 to the MBGR. Data define an age for the MBGR of 795.2 ± 0.9 ka. Using tephra above the MBGR boundary, the Middle Toba Tuff (layer C) and Young Toba Tuff (layer A), extrapolation down core supports a MBGR age of c. 795 ka. Recent age data for BT sanidine reported relative to FCs at 28.172 Ma (767.4 ± 1.1 Ma) [7] oddly yielded an Ar/Ar age that was indistinguishable from the BT zircon U-Pb age [4], which is consistent with previous 40Ar/39Ar age measurements made relative to FCs at 28.02 Ma [3]. Thus we made a series of 40Ar/39Ar measurements on the exact same sample as used by Rivera et al. [7] and observed

  3. A new U/Pb date for the basal Meishucun section and implications for the age of the Cambrian explosion

    NASA Astrophysics Data System (ADS)

    Brooks, B. J.; Crowley, J. L.; Bowring, S. A.; Cervato, C.; Jin, Y.

    2006-12-01

    The Early Cambrian of southern China has long been recognized to record the spectacular transition from microscopic small shelly fossils to a fauna characterized by large, diverse higher bilaterians during part of the Early Cambrian evolutionary explosion. Understanding the timing and rate of this evolutionary transition has been aided through the integration of U/Pb geochronology into Cambrian fossil biozones, which has established strong tie-points between platforms. The Meishucun section (Yunnan, China) is one of the units that best preserves what could be considered the prelude to the Cambrian explosion. Several attempts at dating volcanic horizons within this section have resulted in U/Pb zircon dates that range from 538 to 525 Ma, making correlations to sections further afield problematic. This new high-precision U/Pb date of 533 Ma for Meishucun's Bed 5 is in broad agreement but considerably more precise than previous U/Pb ages. This indicates that the low diversity fauna of the Anabarites trisulcatus--Protohertzina anabarica zone persisted for no less than the first 9 m.y. of the Cambrian in China, and sets an additional lower bracket age for the emergence of higher bilaterians (e.g. trilobites, soft-bodied fauna).

  4. Precise Surface Exposure Dating of Early Holocene and Little Ice Age Moraines in the Cordillera Vilcabamba of Southern Peru

    NASA Astrophysics Data System (ADS)

    Licciardi, J. M.; Schaefer, J. M.; Lund, D. C.; Taggart, J. R.

    2008-12-01

    We have established precise ages of two glacial events in the tropical Andean highlands of southern Peru. The field site is located on the flanks of Nevado Salcantay (6271 m asl; 13°20'S latitude), the highest peak in the Cordillera Vilcabamba. A two-fold sequence of nested lateral and end moraines was mapped in a glacial trough emanating from the south face of Salcantay. Well-defined outer and inner moraines were deposited by valley glaciers that terminated 5 km and 3 km, respectively, from their head on the Salcantay massif. Cosmogenic 10Be surface exposure dating of boulders on the outer (n = 7) and inner (n = 7) moraine crests expands upon initial age control for these deposits and improves substantially on the precision of earlier 10Be measurements. The new results yield mean ages of 9.0 ± 0.3 ka for the outer moraine and 195 ± 24 years for the inner moraine, corresponding to glacial events during the early and latest Holocene. These ages are derived using the CRONUS-Earth 10Be exposure age calculator with Lal-Stone production rate scaling and the default height-pressure relationship. The inner moraine age correlates with the timing of the Little Ice Age as defined from northern mid- and high latitude records, and indicates considerable expansion of glaciers heading on Nevado Salcantay during this climatic minimum. Recent geomorphic mapping has identified similar sequences of moraines in adjacent drainages on and near Salcantay, suggesting a broader regional signal of two prominent Holocene glacial events in this segment of the southern Peruvian Andes; 10Be dating of these additional moraines is underway. Our new glacier chronologies complement ice core and lacustrine paleoclimate records in the vicinity, thereby increasing spatial and temporal coverage for identifying patterns of climate change in the tropical Andes during the Holocene. Apart from their paleoclimatic significance, the results also demonstrate a newly- developed capability of 10Be exposure

  5. New ages for Middle and Later Stone Age deposits at Mumba rockshelter, Tanzania: optically stimulated luminescence dating of quartz and feldspar grains.

    PubMed

    Gliganic, Luke A; Jacobs, Zenobia; Roberts, Richard G; Domínguez-Rodrigo, Manuel; Mabulla, Audax Z P

    2012-04-01

    The archaeological deposits at Mumba rockshelter, northern Tanzania, have been excavated for more than 70 years, starting with Margit and Ludwig Köhl-Larsen in the 1930s. The assemblages of Middle Stone Age (MSA) and Later Stone Age (LSA) artefacts collected from this site constitute the type sequences for these cultural phases in East Africa. Despite its archaeological importance, however, the chronology of the site is poorly constrained, despite the application since the 1980s of several dating methods (radiocarbon, uranium-series and amino acid racemisation) to a variety of materials recovered from the deposits. Here, we review these previous chronologies for Mumba and report new ages obtained from optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) measurements on single grains of quartz and multi-grain aliquots of potassium (K) feldspar from the MSA and LSA deposits. Measurements of single grains of quartz allowed the rejection of unrepresentative grains and the application of appropriate statistical models to obtain the most reliable age estimates, while measurements of K-feldspars allowed the chronology to be extended to older deposits. The seven quartz ages and four K-feldspar ages provide improved temporal constraints on the archaeological sequence at Mumba. The deposits associated with the latest Kisele Industry (Bed VI-A) and the earliest Mumba Industry (Bed V) are dated to 63.4 ± 5.7 and 56.9 ± 4.8 ka (thousands of years ago), respectively, thus constraining the time of transition between these two archaeological phases to ~60 ka. An age of 49.1 ± 4.3 ka has been obtained for the latest deposits associated with the Mumba Industry, which show no evidence for post-depositional mixing and contain ostrich eggshell (OES) beads and abundant microlithics. The Nasera Industry deposits (Bed III) contain large quantities of OES beads and date to 36.8 ± 3.4 ka. We compare the luminescence ages with the previous chronologies for

  6. The Couple Who Facebooks Together, Stays Together: Facebook Self-Presentation and Relationship Longevity Among College-Aged Dating Couples.

    PubMed

    Toma, Catalina L; Choi, Mina

    2015-07-01

    Drawing on public commitment theory, this research examined the association between Facebook self-presentations of coupledom and relationship longevity among college-aged dating partners. Using a longitudinal design and a path model analytic approach, this study shows that Facebook self-presentational cues (i.e., being listed as "in a relationship," posting dyadic photographs, writing on the partner's wall) were associated with an increase in relationship commitment for dating couples, which, in turn, increased their likelihood of remaining together after 6 months. Contrary to predictions, the number of mutual Friends and the number of posts written by partners on participants' walls were negatively related to relationship commitment. This study is the first to apply public commitment theory to an online romantic relationship context, and one of the few to examine the effects of Facebook on the state and fate of romantic relationships. PMID:26167834

  7. Isotopic composition analysis and age dating of uranium samples by high resolution gamma ray spectrometry

    NASA Astrophysics Data System (ADS)

    Apostol, A. I.; Pantelica, A.; Sima, O.; Fugaru, V.

    2016-09-01

    Non-destructive methods were applied to determine the isotopic composition and the time elapsed since last chemical purification of nine uranium samples. The applied methods are based on measuring gamma and X radiations of uranium samples by high resolution low energy gamma spectrometric system with planar high purity germanium detector and low background gamma spectrometric system with coaxial high purity germanium detector. The "Multigroup γ-ray Analysis Method for Uranium" (MGAU) code was used for the precise determination of samples' isotopic composition. The age of the samples was determined from the isotopic ratio 214Bi/234U. This ratio was calculated from the analyzed spectra of each uranium sample, using relative detection efficiency. Special attention is paid to the coincidence summing corrections that have to be taken into account when performing this type of analysis. In addition, an alternative approach for the age determination using full energy peak efficiencies obtained by Monte Carlo simulations with the GESPECOR code is described.

  8. In situ radiometric and exposure age dating of the martian surface.

    PubMed

    Farley, K A; Malespin, C; Mahaffy, P; Grotzinger, J P; Vasconcelos, P M; Milliken, R E; Malin, M; Edgett, K S; Pavlov, A A; Hurowitz, J A; Grant, J A; Miller, H B; Arvidson, R; Beegle, L; Calef, F; Conrad, P G; Dietrich, W E; Eigenbrode, J; Gellert, R; Gupta, S; Hamilton, V; Hassler, D M; Lewis, K W; McLennan, S M; Ming, D; Navarro-González, R; Schwenzer, S P; Steele, A; Stolper, E M; Sumner, D Y; Vaniman, D; Vasavada, A; Williford, K; Wimmer-Schweingruber, R F

    2014-01-24

    We determined radiogenic and cosmogenic noble gases in a mudstone on the floor of Gale Crater. A K-Ar age of 4.21 ± 0.35 billion years represents a mixture of detrital and authigenic components and confirms the expected antiquity of rocks comprising the crater rim. Cosmic-ray-produced (3)He, (21)Ne, and (36)Ar yield concordant surface exposure ages of 78 ± 30 million years. Surface exposure occurred mainly in the present geomorphic setting rather than during primary erosion and transport. Our observations are consistent with mudstone deposition shortly after the Gale impact or possibly in a later event of rapid erosion and deposition. The mudstone remained buried until recent exposure by wind-driven scarp retreat. Sedimentary rocks exposed by this mechanism may thus offer the best potential for organic biomarker preservation against destruction by cosmic radiation. PMID:24324273

  9. In Situ Radiometric and Exposure Age Dating of the Martian Surface

    NASA Technical Reports Server (NTRS)

    Farley, K. A.; Malespin, C.; Mahaffy, P.; Grotzinger, J. P.; Vasconcelos, P. M.; Milliken, R. E.; Malin, M.; Edgett, K. S.; Pavlov, A. A.; Hurowitz, J. A.; Grant, J. A.; Miller, H. B.; Arvidson, R.; Beegle, L.; Calef, F.; Conrad, P. G.; Dietrich, W. E.; Eigenbrode, J.; Gellert, R.; Gupta, S.; Hamilton, V.; Hassler, D. M.; Lewis, K. W.; McLennan, S. M.; Ming, D. M.; Navarro-Gonzalez, R.; Schwenzer, S. P.; Steele, A.; Stolper, E. M.; Sumner, D. Y.; Vaniman, D.; Vasavada, A.; Williford, K.; Wimmer-Schweingruber, R. F.

    2014-01-01

    We determined radiogenic and cosmogenic noble gases in a mudstone on the floor of Gale Crater. A K-Ar age of 4.21 +/- 0.35 billion years represents a mixture of detrital and authigenic components and confirms the expected antiquity of rocks comprising the crater rim. Cosmic-ray-produced 3He, 21Ne, and 36Ar yield concordant surface exposure ages of 78 T 30 million years. Surface exposure occurred mainly in the present geomorphic setting rather than during primary erosion and transport. Our observations are consistent with mudstone deposition shortly after the Gale impact or possibly in a later event of rapid erosion and deposition. The mudstone remained buried until recent exposure by wind-driven scarp retreat. Sedimentary rocks exposed by this mechanism may thus offer the best potential for organic biomarker preservation against destruction by cosmic radiation.

  10. A prospective study of young females' sexual subjectivity: associations with age, sexual behavior, and dating.

    PubMed

    Zimmer-Gembeck, Melanie J; Ducat, Wendy H; Boislard-Pepin, Marie-Aude

    2011-10-01

    Sexual self-perceptions are important aspects of sexuality, which can undergo significant change during adolescence and early adulthood. The purpose of this study was to describe these changes among girls (N = 251; ages 16-25) over one year, and to examine associations of sexual self-perceptions (sexual subjectivity) with age, sexual behavior, and romantic status. Sexual body-esteem, perceptions of entitlement to desire and pleasure, sexual efficacy, and sexual self-reflection were investigated as elements of sexual subjectivity. All sexual subjectivity elements were higher among girls who had more sexual experience and/or had steady romantic partners during the study. Perception of entitlement to desire and pleasure increased over time, whereas sexual body-esteem showed the most stability and had minimal associations with sexual or romantic experiences. The greatest increases in sexual subjectivity were found among girls who began the study with the least sociosexual experience and self-reflection also increased for girls who had first coitus after the start of the study. Overall, girls who had sexual intercourse the earliest (before age 16) had the highest sexual subjectivity, but sexual subjectivity increased the most among girls without coital experience or who had more recent first coitus. PMID:21491139

  11. Estimating limiting age for Pleistocene erosional surfaces in central Montana by uranium-series dating of associated travertines.

    USGS Publications Warehouse

    Szabo, B. J.; Lindsey, D.A.

    1986-01-01

    Analysis of three travertine samples from the southeast side of The Park (central Montana) yield an average uranium-thorium age of 73 000 yr. Another sample from the west side of The Park is 320 000 yr old. These results indicate that travertine deposits may have formed at several intervals. The surface beneath The Park travertine is older than about 320 000 yr. Number 2 pediment gravels that contain travertine downslope from the oldest dated sample may be younger than about 320 000 yr. -Authors

  12. The AMS 14C dating of Iron Age rice chaff ceramic temper from Ban Non Wat, Thailand: First results and its interpretation

    NASA Astrophysics Data System (ADS)

    Higham, Charles F. W.; Kuzmin, Yaroslav V.; Burr, G. S.

    2010-04-01

    Pottery tempered with rice chaff from the early Iron Age cemetery of Ban Non Wat site, northeast Thailand, has been subjected to direct AMS 14C dating, using low temperature combustion with oxygen as originally developed by authors. The carbon yield (0.2-0.5%) testifies the suitability of this pottery for dating. However, not all the results are in agreement with expected archaeological ages and other 14C dates from the studied site and neighboring site of Noen U-Loke. This calls for a thorough analysis and interpretation of pottery temper dates from the region.

  13. Desert varnish: potential for age dating via uranium-series isotopes

    SciTech Connect

    Knauss, K.G.; Ku, T.L.

    1980-01-01

    Trace metals and natural radioisotopes are measured in an unusually thick and presumed ancient desert varnish from the Colorado Plateau in Utah. Uranium and thorium concentrations in the sequence: varnish-altered rind-heartrock (Shinarump formation sandstone) indicate that uranium with little accompanying thorium is derived from external sources. The varnish forms a closed system for /sup 230/Th and /sup 231/Pa with equilibrium values for both /sup 230/Th//sup 234/U and /sup 231/Pa//sup 235/U. Selective leaching of the ferromanganese oxides followed by analysis of both the leachate and silicate residue is proposed to allow age determinations.

  14. Desert varnish: potential for age dating via uranium-series isotopes

    SciTech Connect

    Knauss, K.G.; Ku, T.L.

    1980-01-01

    Trace metals and natural radioisotopes are measured in an unusually thick and presumed ancient desert varnish from the Colorado Plateau in Utah. Uranium and thorium concentrations in the sequence: varnish--altered rind--heartrock (Shinarump formation sandstone) indicate that uranium with little accompanying thorium is derived from external sources. The varnish forms a closed system for /sup 230/Th and /sup 231/Pa with equilibrium values for both /sup 230/Th//sup 234/U and /sup 231/Pa//sup 235/U. Selective leaching of the ferromanganese oxides followed by analysis of both the leachate and silicate residue is proposed to allow age determinations.

  15. Groundwater contributions and age dating in an alpine basin in the Colorado Rocky Mountains

    NASA Astrophysics Data System (ADS)

    Clow, D. W.; Michel, R.

    2005-12-01

    Groundwater occurrence, age, and its contribution to streamflow were investigated in Loch Vale, an alpine catchment in the Colorado Rocky Mountains. Hydro-geomorphologic mapping, seismic refraction measurements, and porosity estimates indicate that talus slopes are the primary groundwater reservoir, with a storage capacity of 5 to 17 x 106 m3. Ice stored in permafrost is the second largest groundwater reservoir in Loch Vale, accounting for 2 to 4 x 106 m3 of water. The estimated storage capacity of bedrock fractures is comparatively small (0.007 to 0.013 x 106 m3). Although snowmelt provides the majority of annual water flux from the basin, tracer tests and gaging along a stream transect indicate that groundwater flowing from talus can account for ?75% of streamflow at certain times. Talus springs respond quickly to storms, then slowly recede, reflecting rapid transmittal of water through coarse debris at the talus surface and slower release of water from finer-grained sediments at depth. CFC and tritium (3H) data permit setting bounds on mean residence times and on the relative contributions of "new" (< 1year old) and "older" (45 - 50 years old) water under two different simplifying scenarios. The first scenario assumes piston subsurface flow, and the second assumes water is a mixture of "new" and "older" water. CFC samples collected from two springs in Loch Vale during August 2003 had piston-flow model ages of 17 to 22 years, based on CFC-12 and CFC-113 results. Under the old water - new water mixture scenario, 55 to 65% of the water was "new". Monthly samples collected from one of the springs and a nearby creek had 3H concentrations ranging from 9.6 (near current precipitation values) to 17.1 TU. Minimum values occurred during snowmelt and peak values occurred during winter baseflow; this pattern indicates a large new water influence during snowmelt, with a noticeable component of older water during winter. Piston-flow model 3H ages are poorly constrained due to

  16. Dating a small impact crater: An age of Kaali crater (Estonia) based on charcoal emplaced within proximal ejecta

    NASA Astrophysics Data System (ADS)

    Losiak, A.; Wild, E. M.; Geppert, W. D.; Huber, M. S.; Jõeleht, A.; Kriiska, A.; Kulkov, A.; Paavel, K.; Pirkovic, I.; Plado, J.; Steier, P.; VäLja, R.; Wilk, J.; Wisniowski, T.; Zanetti, M.

    2016-04-01

    The estimates of the age of the Kaali impact structure (Saaremaa Island, Estonia) provided by different authors vary by as much as 6000 years, ranging from ~6400 to ~400 before current era (BCE). In this study, a new age is obtained based on 14C dating charred plant material within the proximal ejecta blanket, which makes it directly related to the impact structure, and not susceptible to potential reservoir effects. Our results show that the Kaali crater was most probably formed shortly after 1530-1450 BCE (3237 ± 10 14C yr BP). Saaremaa was already inhabited when the bolide hit the Earth, thus, the crater-forming event was probably witnessed by humans. There is, however, no evidence that this event caused significant change in the material culture (e.g., known archeological artifacts) or patterns of human habitation on Saaremaa.

  17. Application of a New Method for Lunar Crater Age Dating to Copernican Impact Flux

    NASA Astrophysics Data System (ADS)

    Mazrouei, S.; Ghent, R. R.

    2014-12-01

    The Moon's surface, without any substantial atmosphere, weather, or tectonic activity, is a genuine time capsule for events taking place in our region of the Solar System. Previously, geological maps and crater counting methods were used for age determination for terrains and individual features, such as large craters and basins; however, those methods are extremely time consuming, are limited by image quality and availability and the need to identify small craters over datable regions, and are subject to systematic errors derived from uncertainty in the cratering function and small number statistics. We have recently shown that the rockiness of large craters' ejecta, derived from the Lunar Reconnaissance Orbiter's Diviner thermal radiometer data, provides a new method for determining the ages of Copernican craters (younger than roughly one billion years old). This method is not subject to the constraints of traditional crater counting methods using visible images. Here, we apply this new method to search for variations in the impact flux over the Copernican period. We investigate the size-frequency distributions and ejecta rock abundances of rocky craters five kilometers and larger, and compare the results to canonical relationships for Copernican craters. Because the lunar impact cratering rate is directly related to interactions among near-Earth objects and main belt asteroids, our results will provide a new platform for testing various dynamical hypotheses about the evolution of the asteroid belt and interactions within it.

  18. Age and Date for Early Arrival of the Acheulian in Europe (Barranc de la Boella, la Canonja, Spain)

    PubMed Central

    Vallverdú, Josep; Saladié, Palmira; Rosas, Antonio; Huguet, Rosa; Cáceres, Isabel; Mosquera, Marina; Garcia-Tabernero, Antonio; Estalrrich, Almudena; Lozano-Fernández, Iván; Pineda-Alcalá, Antonio; Carrancho, Ángel; Villalaín, Juan José; Bourlès, Didier; Braucher, Régis; Lebatard, Anne; Vilalta, Jaume; Esteban-Nadal, Montserrat; Bennàsar, Maria Lluc; Bastir, Marcus; López-Polín, Lucía; Ollé, Andreu; Vergés, Josep Maria; Ros-Montoya, Sergio; Martínez-Navarro, Bienvenido; García, Ana; Martinell, Jordi; Expósito, Isabel; Burjachs, Francesc; Agustí, Jordi; Carbonell, Eudald

    2014-01-01

    The first arrivals of hominin populations into Eurasia during the Early Pleistocene are currently considered to have occurred as short and poorly dated biological dispersions. Questions as to the tempo and mode of these early prehistoric settlements have given rise to debates concerning the taxonomic significance of the lithic assemblages, as trace fossils, and the geographical distribution of the technological traditions found in the Lower Palaeolithic record. Here, we report on the Barranc de la Boella site which has yielded a lithic assemblage dating to ∼1 million years ago that includes large cutting tools (LCT). We argue that distinct technological traditions coexisted in the Iberian archaeological repertoires of the late Early Pleistocene age in a similar way to the earliest sub-Saharan African artefact assemblages. These differences between stone tool assemblages may be attributed to the different chronologies of hominin dispersal events. The archaeological record of Barranc de la Boella completes the geographical distribution of LCT assemblages across southern Eurasia during the EMPT (Early-Middle Pleistocene Transition, circa 942 to 641 kyr). Up to now, chronology of the earliest European LCT assemblages is based on the abundant Palaeolithic record found in terrace river sequences which have been dated to the end of the EMPT and later. However, the findings at Barranc de la Boella suggest that early LCT lithic assemblages appeared in the SW of Europe during earlier hominin dispersal episodes before the definitive colonization of temperate Eurasia took place. PMID:25076416

  19. Age and date for early arrival of the Acheulian in Europe (Barranc de la Boella, la Canonja, Spain).

    PubMed

    Vallverdú, Josep; Saladié, Palmira; Rosas, Antonio; Huguet, Rosa; Cáceres, Isabel; Mosquera, Marina; Garcia-Tabernero, Antonio; Estalrrich, Almudena; Lozano-Fernández, Iván; Pineda-Alcalá, Antonio; Carrancho, Ángel; Villalaín, Juan José; Bourlès, Didier; Braucher, Régis; Lebatard, Anne; Vilalta, Jaume; Esteban-Nadal, Montserrat; Bennàsar, Maria Lluc; Bastir, Marcus; López-Polín, Lucía; Ollé, Andreu; Vergés, Josep Maria; Ros-Montoya, Sergio; Martínez-Navarro, Bienvenido; García, Ana; Martinell, Jordi; Expósito, Isabel; Burjachs, Francesc; Agustí, Jordi; Carbonell, Eudald

    2014-01-01

    The first arrivals of hominin populations into Eurasia during the Early Pleistocene are currently considered to have occurred as short and poorly dated biological dispersions. Questions as to the tempo and mode of these early prehistoric settlements have given rise to debates concerning the taxonomic significance of the lithic assemblages, as trace fossils, and the geographical distribution of the technological traditions found in the Lower Palaeolithic record. Here, we report on the Barranc de la Boella site which has yielded a lithic assemblage dating to ∼1 million years ago that includes large cutting tools (LCT). We argue that distinct technological traditions coexisted in the Iberian archaeological repertoires of the late Early Pleistocene age in a similar way to the earliest sub-Saharan African artefact assemblages. These differences between stone tool assemblages may be attributed to the different chronologies of hominin dispersal events. The archaeological record of Barranc de la Boella completes the geographical distribution of LCT assemblages across southern Eurasia during the EMPT (Early-Middle Pleistocene Transition, circa 942 to 641 kyr). Up to now, chronology of the earliest European LCT assemblages is based on the abundant Palaeolithic record found in terrace river sequences which have been dated to the end of the EMPT and later. However, the findings at Barranc de la Boella suggest that early LCT lithic assemblages appeared in the SW of Europe during earlier hominin dispersal episodes before the definitive colonization of temperate Eurasia took place. PMID:25076416

  20. Conception rates in farm mink (Neovison vison) in relation to first mating date, age and color variety.

    PubMed

    Felska-Błaszczyk, Lidia; Lasota, Bogdan; Seremak, Beata

    2016-07-01

    The aim of the study was to analyze the effects of the first mating date, age and color variety on the conception rates in farm mink. We analyzed female mink reproductive performance in 492 Sapphire and 463 Standard Black females over 3 or 4 years. The analysis included the number of inefficient matings, the interval between the first inefficient mating and the efficient mating (copulation) and the conception rates. The results show a significant effect of female's age and color variety on the conception rates. The youngest, yearling females of either color needed a higher number of matings per conception, as compared to older, 2- and 3-year-old females. Black females demonstrated a higher number of inefficient matings (1.066), as compared with Sapphires (0.730). Yearling females were most often mated from 1 to 10 March, and older females from 11 to 20 March. Older females achieved better conception rates than the yearlings. Dates between 11 and 25 March proved to be the optimum for the first mating, since the highest conception rates were observed if the females had mated during this period. PMID:26434936

  1. Dating the Stars Next Door: Ages and Coronal X-Ray Activities of Local K-Type Stars

    NASA Astrophysics Data System (ADS)

    Katynski, Marcus; Guinan, Edward F.; Engle, Scott G.

    2016-01-01

    Age is one of the most difficult (but important) basic stellar physical property to determine. One possible means to estimate stellar age is from rotational period; it is known that as cool stars age, they lose angular momentum from magnetic braking and slow-down. Thus, good Rotation-Age relationships exist, which are calibrated with stars possessing reliable ages from: evolutionary tracks and/or memberships in clusters/moving groups or binary star systems. Further, ages of older stars can be estimated from (low) metal abundances and kinematics (high space motions). More recently, age determinations from asteroseismology are also becoming more reliable. Except for the many G, K, M stars in the Kepler/K2 fields, rotational periods are difficult to measure photometrically for older, less active stars since star spots and active regions are smaller & less prominent. Thus measuring the coronal X-ray activity of a star is an appealing alternative. Coronal X-ray emission is generated by the stellar dynamo, and so is directly related to the stars' rotation (and age). Measurement of X-ray fluxes (or upper limits) have been made for most of the nearby stars (within ~20 pc) with data available in the HEASARC archives. During the 1990's the ROSAT X-Ray Satellite carried out an all-sky survey of thousands of X-ray sources, including hundreds of nearby stars, producing a large archival database. Using these and other available X-ray data from XMM-Newton & Chandra, we explore the relation between coronal X-ray activity and stellar age of all stars within 10 pc (32.6 LY), with special emphasis on dK and early dM stars that make up ~85% of the sample. Here we report the progress made in determination the ages these nearby stars. We focused on nearby dK-stars, due to their long lifetimes (>20 Gyr) and habitable zones that lie ~0.5 -1.5 AU from their host stars. They appear to be ideal candidates for hosting potentially habitable planets, making them interesting targets. We present

  2. Summary of Age-Dating Analysis in the Fenner Basin, Eastern Mojave Desert, California

    SciTech Connect

    Davisson, M.L.

    2000-06-01

    Stable isotopes of oxygen (oxygen-18) and hydrogen (deuterium) in water were measured to determine recharge sources for Fenner Basin groundwater. The deuterium and oxygen-18 signatures (reported as {delta}D and {delta}{sup 18}O values) ranged from -11.9 to -9.3 per mil. The more negative values originate from high elevation recharge in the New York Mountains and were also observed in the northern and eastern parts of the groundwater basin. less negative values were observed in the Providence Mountains along the western part of the basin. Groundwater collected in the Fenner Gap (i.e. Project Area) had signatures between -10.6 and -10.9 per mil, suggesting a mixture of recharge from both northern, western, and probably local recharge areas in the basin. The annual contribution of groundwater recharge to Fenner Gap from the Clipper, Marble, and Old Woman mountains is still inconclusive due to lack of isotopic data. Isotopic signatures of mean annual precipitation collected by Friendman and others (1992) at Mitchell Caverns, as well as recently recharged groundwater in the Providence and New York mountains, are similar to the isotopic values in Fenner Gap groundwater. This indicates that this groundwater has a Holocene age (less than 10,000 years old), since groundwater recharged during the Pleistocene had isotopic signatures significantly more negative than today due to past global cooling.

  3. Age Dating Merger Events in Early Type Galaxies via the Detection of AGB Light

    NASA Technical Reports Server (NTRS)

    Bothun, G.

    2005-01-01

    A thorough statistical analysis of the J-H vs. H-K color plane of all detected early type galaxies in the 2MASS catalog with velocities less than 5000 km/s has been performed. This all sky survey is not sensitive to one particular galactic environment and therefore a representative range of early type galaxy environments have been sampled. Virtually all N-body simulation so major mergers produces a central starburst due to rapid collection of gas. This central starburst is of sufficient amplitude to change the stellar population in the central regions of the galaxy. Intermediate age populations are given away by the presence of AGB stars which will drive the central colors redder in H-K relative to the J- H baseline. This color anomaly has a lifetime of 2-5 billion years depending on the amplitude of the initial starburst Employing this technique on the entire 2MASS sample (several hundred galaxies) reveals that the AGB signature occurs less than 1% of the time. This is a straightforward indication that virtually all nearby early type galaxies have not had a major merger occur within the last few billion years.

  4. [Changes in olfaction during ageing and in certain neurodegenerative diseases: up-to-date].

    PubMed

    Bianchi, A-J; Guépet-Sordet, H; Manckoundia, P

    2015-01-01

    Olfaction is a complex sensory system, and increasing interest is being shown in the link between olfaction and cognition, notably in the elderly. In this literature review, we revisit the specific neurophysiological features of the olfactory system and odorants that lead to a durable olfactory memory and an emotional memory, for which the implicit component produces subconscious olfactory conditioning. Olfaction is known to affect cognitive abilities and mood. We also consider the impairment of olfactory function due to ageing and to neurodegenerative diseases, in particular Alzheimer's disease and Parkinson's disease, through anatomopathological changes in the peripheral and central olfactory structures. The high frequency of these olfactory disorders as well as their early occurrence in Alzheimer disease and Parkinson disease are in favour of their clinical detection in subjects suffering from these two neurodegenerative diseases. Finally, we analyse the impact of olfactory stimulation on cognitive performance and attention. Current observational data from studies in elderly patients with Alzheimer-type dementia are limited to multiple sensory stimulation methods, such as the Snoezelen method, and aromatherapy. These therapies have shown benefits for dementia-related mood and behaviour disorders in the short term, with few side effects. Since olfactory chemosensory stimulation may be beneficial, it may be proposed in patients with dementia, especially Alzheimer-type dementia, as a complementary or even alternative therapy to existing medical strategies. PMID:25304170

  5. Comparison of chlorofluorocarbon-age dating with particle-tracking results of a regional ground-water flow model of the Portland Basin, Oregon and Washington

    USGS Publications Warehouse

    Hinkle, Stephen R.; Snyder, Daniel T.

    1997-01-01

    This report describes the results of a study in which chlorofluorocarbon-age dating was used to evaluate the results of a ground-water particle tracker for the Portland Basin in Oregon and Washington.

  6. Inter-comparison exercises on dissolved gases for groundwater dating (GDAT 2012) : analytical uncertainties, apparent ages and other derived parameters.

    NASA Astrophysics Data System (ADS)

    Labasque, Thierry; Aquilina, Luc; Visser, Ate; Vergnaud, Virginie

    2014-05-01

    An inter-laboratory comparison exercise dedicated to environmental tracers used for groundwater dating was organized in 2012 in France. The goal was to compare sampling and analytical protocols through results obtained by the community of groundwater dating laboratories. Sampling and analytical protocols were compared through three different exercises on various supports : (1) on groundwater from a homogeneous aquifer, (2) on groundwater from a fractured heterogeneous aquifer and (3) on an air standard. The two tests allowed 31 Laboratories from 14 countries to compare their protocols for both sampling and analyses. It allows discussing the uncertainties related to sampling protocols issuing from each laboratory methods. The results show a good agreement between laboratories on the aquifers and the air standard. The dispersion of SF6 results in air standard is low (rsd 2%) compared to CFCs (rsd 3 to 7%), even if its concentration is two orders of magnitude lower. Results obtained in recent groundwater (recharge after 1980) show that the uncertainty on groundwater dating with SF6 is between 3 and 4 years. This large uncertainty is mainly due to sampling and/or analytical problems. For CFCs, uncertainties obtained over all the laboratories are less than 2 years for groundwater with recharge between 1965 and 1996. The goal of the inter-laboratory comparison exercise was also to quantify the analytical uncertainty of the 3H and noble gas measurements and to assess whether they meet the requirements for 3H/3He dating and noble gas paleotemperature reconstruction. The reproducibility of the tritium measurements was 13.5%. The reproducibility of the 3He/4He ratio and 4He, Ne, Ar, Kr and Xe concentrations was 1.4%, 1.8%, 1.5%, 2.2%, 2.9%, and 2.4%. The propagated uncertainty of the tritium and noble gas measurements meets the desired precision for typical 3H/3He dating applications. However, the measurement uncertainties for the noble gas concentrations are insufficient to

  7. Mechanism of Inflammation in Age-Related Macular Degeneration: An Up-to-Date on Genetic Landmarks

    PubMed Central

    Parmeggiani, Francesco; Sorrentino, Francesco S.; Romano, Mario R.; Incorvaia, Carlo; D'Angelo, Sergio; Perri, Paolo; De Nadai, Katia; Bonomo Roversi, Elia; Franceschelli, Paola; Sebastiani, Adolfo

    2013-01-01

    Age-related macular degeneration (AMD) is the most common cause of irreversible visual impairment among people over 50 years of age, accounting for up to 50% of all cases of legal blindness in Western countries. Although the aging represents the main determinant of AMD, it must be considered a multifaceted disease caused by interactions among environmental risk factors and genetic backgrounds. Mounting evidence and/or arguments document the crucial role of inflammation and immune-mediated processes in the pathogenesis of AMD. Proinflammatory effects secondary to chronic inflammation (e.g., alternative complement activation) and heterogeneous types of oxidative stress (e.g., impaired cholesterol homeostasis) can result in degenerative damages at the level of crucial macular structures, that is photoreceptors, retinal pigment epithelium, and Bruch's membrane. In the most recent years, the association of AMD with genes, directly or indirectly, involved in immunoinflammatory pathways is increasingly becoming an essential core for AMD knowledge. Starting from the key basic-research notions detectable at the root of AMD pathogenesis, the present up-to-date paper reviews the best-known and/or the most attractive genetic findings linked to the mechanisms of inflammation of this complex disease. PMID:24369445

  8. A simple-rapid method to separate uranium, thorium, and protactinium for U-series age-dating of materials.

    PubMed

    Knight, Andrew W; Eitrheim, Eric S; Nelson, Andrew W; Nelson, Steven; Schultz, Michael K

    2014-08-01

    Uranium-series dating techniques require the isolation of radionuclides in high yields and in fractions free of impurities. Within this context, we describe a novel-rapid method for the separation and purification of U, Th, and Pa. The method takes advantage of differences in the chemistry of U, Th, and Pa, utilizing a commercially-available extraction chromatographic resin (TEVA) and standard reagents. The elution behavior of U, Th, and Pa were optimized using liquid scintillation counting techniques and fractional purity was evaluated by alpha-spectrometry. The overall method was further assessed by isotope dilution alpha-spectrometry for the preliminary age determination of an ancient carbonate sample obtained from the Lake Bonneville site in western Utah (United States). Preliminary evaluations of the method produced elemental purity of greater than 99.99% and radiochemical recoveries exceeding 90% for U and Th and 85% for Pa. Excellent purity and yields (76% for U, 96% for Th and 55% for Pa) were also obtained for the analysis of the carbonate samples and the preliminary Pa and Th ages of about 39,000 years before present are consistent with (14)C-derived age of the material. PMID:24681438

  9. Paleointensity record in zero-age submarine basalt glasses: testing a new dating technique for recent MORBs

    NASA Astrophysics Data System (ADS)

    Carlut, J.; Kent, D. V.

    2000-12-01

    Thellier-Thellier paleointensity experiments were conducted on a collection of glasses from three very recent submarine axial flows. Two were erupted along the Juan de Fuca ridge at around 46°N and one along the East Pacific Rise South at around 18°S. The within-sample dispersion of paleointensity results from the 'Animal Farm' flow (EPR south) is very low and leads to a well-defined mean value of 35.6±1 μT (95% error on the mean) based on 11 glass chips from four independent samples. Today's geomagnetic field intensity in the area is 31.2 μT. Comparing Animal Farm results with published field model reference curves developed for the past 400 yr suggests an eruptive date estimated between 1880 A.D. and 1950 A.D. (taking into account different sources of errors). This is consistent with qualitative evidence for the age of this flow and constitutes the first precise demonstration of using paleointensity as a dating tool for very recent mid-ocean ridge basalts (MORBs). However in the Juan de Fuca area results show a more erratic pattern with samples varying by up to 30% higher and lower from the expected value of about 55 μT. The dispersion is attributed to the large local crustal magnetic anomalies in this area that can lead to inconsistent intensity values over the same unit. Local magnetic anomalies should thus always be checked when doing paleointensity on MORB samples which should also be distributed as widely as possible in a flow unit. When no significant magnetic anomalies are detected the paleointensity dating tool is anticipated to be especially efficient to investigate the volcanic cyclicity along the EPR axis during the last several hundred years.

  10. Tracing and age-dating recycled waste water recharged for potable reuse in a seawater injection barrier, southern California, USA

    SciTech Connect

    Davisson, M L; Esser, B K; Herndon, R L; Hudson, G B

    1998-12-02

    In this report we outline an investigative approach that combines isotopic tracers and tritium-helium-3 (3H-3He) dating to directly measure groundwater mixing and ages. These data can be used to test regulatory compliance in potable water reuse projects (Davisson et al., 1998). We provide an example from a seawater injection barrier located in Orange County, California, which has been injecting advanced- treated waste water into a coastal aquifer for the past 25 years to prevent seawater intrusion. Treatment comprises lime coagulation of secondary waste effluents, followed by re-carbonation, sand filtration, and reverse osmosis. The finished water has a very low TDS (-100 mg/L), which is blended -50% with a low TDS (288 mg/L) native groundwater, making an injection water of -200 mg/L.

  11. Age and evolution of the Grand Canyon revealed by U-Pb dating of water table-type speleothems.

    PubMed

    Polyak, Victor; Hill, Carol; Asmerom, Yemane

    2008-03-01

    The age and evolution of the Grand Canyon have been subjects of great interest and debate since its discovery. We found that cave mammillaries (water table indicator speleothems) from nine sites in the Grand Canyon showed uranium-lead dating evidence for an old western Grand Canyon on the assumption that groundwater table decline rates are equivalent to incision rates. Samples in the western Grand Canyon yielded apparent water table decline rates of 55 to 123 meters per million years over the past 17 million years, in contrast to eastern Grand Canyon samples that yielded much faster rates (166 to 411 meters per million years). Chronology and inferred incision data indicate that the Grand Canyon evolved via headward erosion from west to east, together with late-stage ( approximately 3.7 million years ago) accelerated incision in the eastern block. PMID:18323451

  12. Isotopic age of the Black Forest Bed, Petrified Forest Member, Chinle Formation, Arizona: An example of dating a continental sandstone

    USGS Publications Warehouse

    Riggs, N.R.; Ash, S.R.; Barth, A.P.; Gehrels, G.E.; Wooden, J.L.

    2003-01-01

    Zircons from the Black Forest Bed, Petrified Forest Member, Chinle Formation, in Petrified Forest National Park, yield ages that range from Late Triassic to Late Archean. Grains were analyzed by multigrain TIMS (thermal-ionization mass spectrometry), single-crystal TIMS, and SHRIMP (sensitive, high-resolution ion-microprobe). Multiple-grain analysis yielded a discordia trajectory with a lower intercept of 207 ?? 2 Ma, which because of the nature of multiple-grain sampling of a detrital bed, is not considered conclusive. Analysis of 29 detrital-zircon grains by TIMS yielded U-PB ages of 2706 ?? 6 Ma to 206 ?? 6 Ma. Eleven of these ages lie between 211 and 216 ?? 6.8 Ma. Our statistical analysis of these grains indicates that the mean of the ages, 213 ?? 1.7 Ma, reflects more analytical error than geologic variability in sources of the grains. Grains with ages of ca. 1400 Ma were derived from the widespread plutons of that age exposed throughout the southwestern Cordillera and central United States. Twelve grains analyzed by SHRIMP provide 206Pb*/238U ages from 214 ?? 2 Ma to 200 ?? 4 Ma. We use these data to infer that cores of inherited material were present in many zircons and that single-crystal analysis provides an accurate estimation of the age of the bed. We further propose that, even if some degree of reworking has occurred, the very strong concentration of ages at ca. 213 Ma provides a maximum age for the Black Forest Bed of 213 ?? 1.7 Ma. The actual age of the bed may be closer to 209 Ma. Dating continental successions is very difficult when distinct ash beds are not clearly identified, as is the case in the Chinle Formation. Detrital zircons in the Black Forest Bed, however, are dominated by an acicular morphology with preserved delicate terminations. The shape of these crystals and their inferred environment of deposition in slow-water settings suggest that the crystals were not far removed from their site of deposition in space and likely not far in time

  13. Age of the North Anatolian Fault Segments in the Yalova with U/Th Dating Method by Travertine Data

    NASA Astrophysics Data System (ADS)

    Selim, Haluk; Ömer Taş, K.

    2016-04-01

    Travertine occurrences developed along the segments of the North Anatolian Fault (NAF) in the south of Yalova. Travertines outcrop approximately 1 km2 area. These are middle-thick bedded approximately 20-40 m and back-tilted southward or horizontally. Lithology of travertines deposited such as physolite, stalactites-stalagmites, cave pearls, sharp pebble carbonate nodules, spherical-roller-intricate shapes or laminated banded travertine. Geochemical analyses were performed on the six samples of the travertines. X-ray analysis indicates that all samples are entirely composed of low-Mg calcite. Banded travertines with some tubular structures formed by precipitation from rising hot water are best developed near the toes of the large, hanging-wall-derived alluvial fans, whereas phreatic cement preferentially exists in footwall-derived, alluvial-fan conglomerates. The unit developed clarity which is controlled by normal fault as the structural and morphological, relationship with active tectonics. The travertines are a range-front type. U/Th series age dating results indicate that the travertine deposition extends back to 155 ka and yields ages of 60.000 (± 3, 091) to 153.149 (±13,466) from the range-front type travertines.

  14. Noble Gas Analysis for Mars Robotic Missions: Evaluating K-Ar Age Dating for Mars Rock Analogs and Martian Shergottites

    NASA Technical Reports Server (NTRS)

    Park, J.; Ming, D. W.; Garrison, D. H.; Jones, J. H.; Bogard, D. D.; Nagao, K.

    2009-01-01

    The purpose of this noble gas investigation was to evaluate the possibility of measuring noble gases in martian rocks and air by future robotic missions such as the Mars Science Laboratory (MSL). The MSL mission has, as part of its payload, the Sample Analysis at Mars (SAM) instrument, which consists of a pyrolysis oven integrated with a GCMS. The MSL SAM instrument has the capability to measure noble gas compositions of martian rocks and atmosphere. Here we suggest the possibility of K-Ar age dating based on noble gas release of martian rocks by conducting laboratory simulation experiments on terrestrial basalts and martian meteorites. We provide requirements for the SAM instrument to obtain adequate noble gas abundances and compositions within the current SAM instrumental operating conditions, especially, a power limit that prevents heating the furnace above approx.1100 C. In addition, Martian meteorite analyses from NASA-JSC will be used as ground truth to evaluate the feasibility of robotic experiments to constrain the ages of martian surface rocks.

  15. Teaching Absolute Value Meaningfully

    ERIC Educational Resources Information Center

    Wade, Angela

    2012-01-01

    What is the meaning of absolute value? And why do teachers teach students how to solve absolute value equations? Absolute value is a concept introduced in first-year algebra and then reinforced in later courses. Various authors have suggested instructional methods for teaching absolute value to high school students (Wei 2005; Stallings-Roberts…

  16. Asteroseismology for "à la carte" stellar age-dating and weighing. Age and mass of the CoRoT exoplanet host HD 52265

    NASA Astrophysics Data System (ADS)

    Lebreton, Y.; Goupil, M. J.

    2014-09-01

    Context. In the context of the space missions CoRoT, Kepler, Gaia, TESS, and PLATO, precise and accurate stellar ages, masses, and radii are of paramount importance. For instance, they are crucial for constraining scenarii of planetary formation and evolution. Aims: We aim at quantifying how detailed stellar modelling can improve the accuracy and precision on age and mass of individual stars. To that end, we adopt a multifaceted approach where we carefully examine how the number of observational constraints as well as the uncertainties on observations and on model input physics affect the results of age-dating and weighing. Methods: We modelled in detail the exoplanet host-star HD 52265, a main-sequence, solar-like oscillator that CoRoT observed for four months. We considered different sets of observational constraints (Hertzsprung-Russell data, metallicity, various sets of seismic constraints). For each case, we determined the age, mass, and properties of HD 52265 inferred from stellar models, and we quantified the impact of the model input physics and free parameters. We also compared model ages with ages derived by empirical methods or Hertzsprung-Russell diagram inversion. Results: For our case study HD 52265, our seismic analysis provides an age A = 2.10-2.54 Gyr, a mass M = 1.14-1.32 M⊙, and a radius R = 1.30-1.34 R⊙, which corresponds to age, mass, and radius uncertainties of ~10, ~7, and ~1.5 per cent, respectively. These uncertainties account for observational errors and current state-of-the-art stellar model uncertainties. Our seismic study also provides constraints on surface convection properties through the mixing-length, which we find to be 12-15 per cent lower than the solar value. On the other hand, because of helium-mass degeneracy, the initial helium abundance is determined modulo the mass value. Finally, we evaluate the seismic mass of the exoplanet to be Mpsini = 1.17-1.26 MJupiter, much more precise than what can be derived by Hertzsprung

  17. Round-robin 230Th–234U age dating of bulk uranium for nuclear forensics

    SciTech Connect

    Gaffney, Amy M.; Hubert, Amélie; Kinman, William S.; Magara, Masaaki; Okubo, Ayako; Pointurier, Fabien; Schorzman, Kerri C.; Steiner, Robert E.; Williams, Ross W.

    2015-07-30

    In an inter-laboratory measurement comparison study, four laboratories determined 230Th–234U model ages of uranium certified reference material NBL U050 using isotope dilution mass spectrometry. The model dates determined by the participating laboratories range from 9 March 1956 to 19 October 1957, and are indistinguishable given the associated measurement uncertainties. As a result, these model ages are concordant with to slightly older than the known production age of NBL U050.

  18. Collection, analysis, and age-dating of sediment cores from 56 U.S. lakes and reservoirs sampled by the U.S. Geological Survey, 1992-2001

    USGS Publications Warehouse

    Van Metre, Peter; Wilson, Jennifer T.; Fuller, Christopher C.; Callender, Edward; Mahler, Barbara J.

    2004-01-01

    The U.S. Geological Survey Reconstructed Trends National Synthesis study collected sediment cores from 56 lakes and reservoirs between 1992 and 2001 across the United States. Most of the sampling was conducted as part of the National Water-Quality Assessment (NAWQA) Program. The primary objective of the study was to determine trends in particle-associated contaminants in response to urbanization; 47 of the 56 lakes are in or near one of 20 U.S. cities. Sampling was done with gravity, piston, and box corers from boats and push cores from boats or by wading, depending on the depth of water and thickness of sediment being sampled. Chemical analyses included major and trace elements, organochlorine pesticides, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, cesium-137, and lead-210. Age-dating of the cores was done on the basis of radionuclide analyses and the position of the pre-reservoir land surface in the reservoir and, in a few cases, other chemical or lithologic depth-date markers. Dates were assigned in many cores on the basis of assumed constant mass accumulation between known depth-date markers. Dates assigned were supported using a variety of other date markers including first occurrence and peak concentrations of DDT and polychlorinated biphenyls and peak concentration of lead. A qualitative rating was assigned to each core on the basis of professional judgment to indicate the reliability of age assignments. A total of 122 cores were collected from the 56 lakes and age dates were assigned to 113 of them, representing 54 of the 56 lakes. Seventy-four of the 122 cores (61 percent) received a good rating for the assigned age dates, 28 cores (23 percent) a fair rating, and 11 cores (9 percent) a poor rating; nine cores (7 percent) had no dates assigned. An analysis of the influence of environmental factors on the apparent quality of age-dating of the cores concluded that the most important factor was the mass accumulation rate (MAR) of sediment: the

  19. 40K- 40Ar dating of the Main Deccan large igneous province: Further evidence of KTB age and short duration

    NASA Astrophysics Data System (ADS)

    Chenet, Anne-Lise; Quidelleur, Xavier; Fluteau, Frédéric; Courtillot, Vincent; Bajpai, Sunil

    2007-11-01

    Most mass extinctions coincide in time with outpourings of continental flood basalts (CFB). Some 20 years ago, it was shown [Courtillot, V., Besse, J., Vandamme, D., Montigny, R., Jaeger, J.-J., Cappetta, H., 1986. Deccan flood basalts at the Cretaceous/Tertiary boundary? Earth Planet. Sci. Lett. 80, 361-374; Courtillot, V., Feraud, G., Maluski, H., Vandamme, D., Moreau, M.G., Besse, J., 1988. Deccan flood basalts and the Cretaceous/Tertiary boundary. Nature 333, 843-846; Duncan, R.A., Pyle, D.G., 1988. Rapid eruption of the Deccan flood basalts at the Cretaceous/Tertiary boundary. Nature 333 841-843] that the age of the Deccan traps was close to the Cretaceous-Tertiary (KT) boundary and its duration under 1 Myr. We have undertaken a new geochronological study, using the (unconventional) 40K- 40Ar Cassignol-Gillot technique which is particularly well suited to the potassium-poor Deccan lavas. The mean of 4 determinations from the topmost (Ambenali and Mahabaleshwar) Formations is 64.5 ± 0.6 Ma. They straddle the C29r/C29n reversal boundary for which they provide a new constraint. The mean age of 3 determinations from the oldest (Jawhar) Formation is 64.8 ± 0.6 Ma. The difference in age between top and bottom of a 3500 m composite section, probably comprising 80% of the total Deccan volume, is statistically insignificant, with the overall mean age being 64.7 ± 0.6 Ma ( N = 7). Our results are consistent with the most recent 40Ar/ 39Ar determinations [Knight, K.B., Renne, P.R., Halkett, A., White, N., 2003. 40Ar/ 39Ar dating of the Rajahmundry Traps, eastern India and their relationship to the Deccan traps. Earth Planet. Sci. Lett. 208, 85-99; Knight, K.B., Renne, P.R., Baker, J., Waight, T., White, N., 2005. Reply to '40Ar/39Ar dating of the Rajahmundry Traps, Eastern India and their relationship to the Deccan Traps: Discussion' by A.K. Baksi. Earth Planet. Sci. Lett. 239, 374-382], confirming that there should be no systematic difference between the two methods

  20. Age of the Druksiai-Polotsk deformation zone, Lithuania: a U-Pb dating of metamorphic titanite

    NASA Astrophysics Data System (ADS)

    Vejelyte, Irma; Bogdanova, Svetlana; Salnikova, Ekaterina

    2010-05-01

    The studied Druksiai-Polotsk deformation zone (DPDZ) transects the East Lithuanian Domain (ELD), representing the southern margin of the major Polotsk-Kurzeme zone of faulting in the Baltic-Belarus region. The DPDZ is of 35-40 km wide, E-W trending, and marked well by linear gravity and magnetic anomalies. The crystalline rocks within the DPDZ are granulites, biotite granites, and migmatites, the latter consisting of amphibole-plagioclase paleo- and mesosomes, and plagioclase-quartz-biotite±microcline±amphibole neosomes. Because of ductile shearing gneisses, augen mylonites, mylonites and ultramylonites were produced while tectonic breccias and pseudotachyllite were formed by later brittle deformation. According to geophysical data and the surface morphology of the crystalline basement, a horst-graben structure have recognized along the DPDZ. The graben is filled with Vendian, Cambrian, Ordovician, Silurian and Devonian deposits. A U-Pb dating of titanite from an augen granitoid mylonite in the DPDZ has yielded a concordant age of 1534±9 Ma. This light brown titanite follows the folation in the host rock and was obviously formed during retrogression from amphibolite- to epidote-amphibolite facies and coeval mylonitization. Shear zones of the same age are known in southern and central Sweden and in NE Poland. These E-W trending deformation zones accommodate both mafic and granitoid intrusions and are probably related to an extensional period in the Mesoproterozoic evolution in the western part of the East European Craton. This is a contribution to the project "The Precambrian structure of Baltica as a control of its recent environment and evolution" of the Visby Programme supported by the Swedish Institute and the Lithuanian State Science and Studies Foundation.

  1. Geochemical analyses, age dates, and flow-volume estimates for quaternary volcanic rocks, Southern Cascade Mountains, Washington

    SciTech Connect

    Hammond, P.E.; Korosec, M.A.

    1983-12-01

    Data collected over the last three years as part of a continuing study of the Quaternary volcanic rocks of the southern Cascade Mountains are presented. Whole-rock chemical analyses, selected trace element geochemistry, volume approximations, specific gravity determinations, and locations are provided for most of the 103 samples collected, and 21 radiometric age dates are included. In addition, partial information, including names and flow-volumes, are presented for 98 additional samples, collected for related studies. The study extends from the Columbia River north to the Cowlitz River and Goat Rocks Wilderness area, and from the Klickitat River west to the Puget-Willamette Trough. The volcanic rocks are all younger than 3 million years and consist primarily of tholeiitic and high-alumina basalts and basaltic-andesites erupted from numerous shield volcanoes and cinder cones. A few analyses of more silicic rocks, including hornblende and/or pyroxene andesites and dacites characteristic of the stratovolcanoes of the region, are also presented. However, systematic sampling of the stratovolcanoes in the study area, Mount Adams and Mount St. Helens, was not conducted. A map of the areal extent of Quaternary volcanic units and sample locations is included. It has been based on the 1:125,000 reconnaissance geologic map of the southern Cascade Range by Hammond (1980).

  2. Thermochronology of economic mineral deposits: dating the stages of mineralization at Panasqueira, Portugal, by high-precision 40Ar/ 39Ar age spectrum techniques on muscovite

    USGS Publications Warehouse

    Snee, L.W.; Sutter, J.F.; Kelly, W.C.

    1988-01-01

    This study is an example of a new and powerful application of 40Ar/39Ar age spectrum dating of muscovite. It is now possible to establish time constraints necessary for solving some of the long-standing problems in economic geology. Beyond this, the unique geologic situation of Panasqueira has allowed us to quantify the thermal characteristics of muscovite. Published fluid inclusion data have been used to estimate a muscovite argon closure temperature of ~325??C during rapid cooling or short reheating and a temperature of ~270??C during slow cooling or extended reheating. Argon-loss patterns displayed by all dated muscovites resulted from reheating after original closure; the mechanism for this argon loss appears to have been argon transport by volume diffusion. Thus, 40Ar/39Ar age spectrum dating of muscovite can be used to evaluate thermal conditions controlling argon diffusion as well as age, duration, and number of episodes of mineralization. -from Authors

  3. Eosinophil count - absolute

    MedlinePlus

    Eosinophils; Absolute eosinophil count ... the white blood cell count to give the absolute eosinophil count. ... than 500 cells per microliter (cells/mcL). Normal value ranges may vary slightly among different laboratories. Talk ...

  4. Concordant ages for the Lava Creek Tuff from high-spatial-resolution U-Pb dating of zircon rim faces and single-crystal sanidine 40Ar/39Ar dating

    NASA Astrophysics Data System (ADS)

    Matthews, N. E.; Vazquez, J. A.; Calvert, A. T.

    2013-12-01

    The last great explosive supereruption from the Yellowstone Plateau formed present-day Yellowstone caldera and ejected the >1000 km3 of rhyolite that composes the Lava Creek Tuff (LCT). The LCT eruption blanketed much of the western United States in ash, and consequently is a key chronostratigraphic marker bed for delimiting Quaternary uplift rates, the age of middle Pleistocene glacial and pluvial deposits, and tephra correlation in North America. Previous 40Ar/39Ar dating of the two mineralogically distinct LCT members (A & B) yield ages ranging from ca. 600 ka (Gansecki et al., 1998) to ca. 640 ka (Lanphere et al., 2002). To resolve the timing of eruption and crystallization timescale for the LCT magma, we dated both LCT members using a dual-method approach as follows: (1) ion microprobe (SHRIMP-RG) U-Pb dating and trace-element characterization of the final few micrometers of zircon crystallization by analysis of unpolished rims on indium-mounted crystals, and dating of the onset of zircon crystallization by traditional analysis of sectioned crystal interiors, and (2) laser-fusion 40Ar/39Ar dating of single sanidine crystals from bulk LCT ignimbrite and pumice. The unpolished rims of zircon from LCT members A & B yield indistinguishable ages, with a mean age of 621.8 × 2.5 ka (1σ) after correction for initial 230Th disequilibrium as constrained by ion-probe analyses of LCT melt inclusions. Single sanidine crystals from LCT-B yield a mean age of 624.9 × 2.6 ka (FCT=28.17 Ma) that is indistinguishable from the zircon rim ages for both members. These results indicate that LCT members A & B erupted over a geologically brief interval, which is supported by the direct and gradational contact of their equivalent fallout in distal lacustrine deposits and a lack of field evidence for a significant time-break between the LCT A & B in proximal deposits (Christiansen, 2001), but contrasts with older Yellowstone ignimbrite (e.g., Huckleberry Ridge) that may have erupted

  5. Aging.

    PubMed

    Park, Dong Choon; Yeo, Seung Geun

    2013-09-01

    Aging is initiated based on genetic and environmental factors that operate from the time of birth of organisms. Aging induces physiological phenomena such as reduction of cell counts, deterioration of tissue proteins, tissue atrophy, a decrease of the metabolic rate, reduction of body fluids, and calcium metabolism abnormalities, with final progression onto pathological aging. Despite the efforts from many researchers, the progression and the mechanisms of aging are not clearly understood yet. Therefore, the authors would like to introduce several theories which have gained attentions among the published theories up to date; genetic program theory, wear-and-tear theory, telomere theory, endocrine theory, DNA damage hypothesis, error catastrophe theory, the rate of living theory, mitochondrial theory, and free radical theory. Although there have been many studies that have tried to prevent aging and prolong life, here we introduce a couple of theories which have been proven more or less; food, exercise, and diet restriction. PMID:24653904

  6. Aging

    PubMed Central

    Park, Dong Choon

    2013-01-01

    Aging is initiated based on genetic and environmental factors that operate from the time of birth of organisms. Aging induces physiological phenomena such as reduction of cell counts, deterioration of tissue proteins, tissue atrophy, a decrease of the metabolic rate, reduction of body fluids, and calcium metabolism abnormalities, with final progression onto pathological aging. Despite the efforts from many researchers, the progression and the mechanisms of aging are not clearly understood yet. Therefore, the authors would like to introduce several theories which have gained attentions among the published theories up to date; genetic program theory, wear-and-tear theory, telomere theory, endocrine theory, DNA damage hypothesis, error catastrophe theory, the rate of living theory, mitochondrial theory, and free radical theory. Although there have been many studies that have tried to prevent aging and prolong life, here we introduce a couple of theories which have been proven more or less; food, exercise, and diet restriction. PMID:24653904

  7. An extended magnetic viscous relaxation dating for calibrating an older age: an example of tsunamigenic coral boulders in Ishigaki Island, Japan

    NASA Astrophysics Data System (ADS)

    Sato, T.; Nakamura, N.; Goto, K.; Kumagai, Y.; Minoura, K.; Nagahama, H.

    2015-12-01

    A key to the understanding of past tsunami events is the ability to accurately date them. Analysis of past tsunami sediments is one of the most important tools for past tsunami reconstruction. A typical example of such tsunami sediment is tsunamigenic boulders. In Ishigaki Island, Japan, coral boulders that had been transported by tsunamis were distributed on the beach and land areas. Although the historical occurrences of several huge tsunamis were estimated based on large numbers of radiocarbon dating for coral boulders, radiocarbon dating can not determine a multiple rotational history by multiple tsunamis. A viscous remanet magnetization (VRM) dating method can be used to date any geological event that results in significant movements of a rock. Sato et al. (2014) applied VRM dating for comparing the radiocarbon age of these boulders. If a magnetic-mineral bearing rock is moved or re-oriented, the magnetism of the smaller magnetic grains re-aligns to the direction of the ambient magnetic field with time. This phenomenon is well known as Néel's (1949, 1955) single-domain (SD) relaxation theory. Pullaiah et al. (1975) derived a time-temperature (t-T relation) relation by assuming Néel's (1949, 1955) theory of magnetite. In principle, an experimental combination of short relaxation time and high temperature for removing VRM can determine the unknown relaxation time (tsunami age) at room temperature. We have been applied t-T relation to the coral boulders on Ishigaki Island, but their estimated ages showed older than radiocarbon dating. The longer relaxation time means that the observed magnetic relaxation is slower than the original Néel's theory. Such slow relaxation has been described by a stretched exponential function. The stretched exponential law provided a reasonable fit to the published experimental data. Thus, in this study, we revisit Néel's theory to provide a new t-T relation based on stretched exponential function.

  8. Aging of target lipid parameters in fingermark residue using GC/MS: Effects of influence factors and perspectives for dating purposes.

    PubMed

    Girod, Aline; Spyratou, Alexandra; Holmes, David; Weyermann, Céline

    2016-05-01

    Despite the recurrence of fingermark dating issues and the research conducted on fingermark composition and aging, no dating methodology has yet been developed and validated. In order to further evaluate the possibility of developing dating methodologies based on the fingermark composition, this research proposed an in-depth study of the aging of target lipid parameters found in fingermark residue and exposed to different influence factors. The selected analytical technique was gas chromatography coupled with mass spectrometry (GC/MS). The effects of donor, substrate and enhancement techniques on the selected parameters were firstly evaluated. These factors were called known factors, as their value could be obtained in real caseworks. Using principal component analysis (PCA) and univariate exponential regression, this study highlighted the fact that the effects of these factors were larger than the aging effects, thus preventing the observation of relevant aging patterns. From a fingermark dating perspective, the specific value of these known factors should thus be included in aging models newly built for each case. Then, the effects of deposition moment, pressure, temperature and lighting were also evaluated. These factors were called unknown factors, as their specific value would never be precisely obtained in caseworks. Aging models should thus be particularly robust to their effects and for this reason, different chemometric tools were tested: PCA, univariate exponential regression and partial least square regression (PLSR). While the first two models allowed observing interesting aging patterns regardless of the value of the applied influence factors, PLSR gave poorer results, as large deviations were obtained. Finally, in order to evaluate the potential of such modelling in realistic situations, blind analyses were carried out on eight test fingermarks. The age of five of them was correctly estimated using soft independent modelling of class analogy analysis

  9. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.

    2012-05-15

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  10. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.

    2010-07-13

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  11. 40Ar- 39Ar laser dating of tektites from the Cheb Basin (Czech Republic): Evidence for coevality with moldavites and influence of the dating standard on the age of the Ries impact

    NASA Astrophysics Data System (ADS)

    Di Vincenzo, Gianfranco; Skála, Roman

    2009-01-01

    Moldavites (Central European tektites) are genetically related to the impact event that produced the ˜24-km diameter Ries crater in Germany, representing one of the youngest large impact structures on Earth. Although several geochronological studies have been completed, there is still no agreement among 40Ar- 39Ar ages on both moldavites and glasses from Ries suevites. Even recently published data yielded within-sample mean ages with a nominal spread of more than 0.6 Ma (14.24-14.88 Ma). This age spread, which significantly exceeds current internal errors, must be in part ascribed to geological and/or analytical causes. This study reports the results of a detailed geochronological investigation of moldavites from the Cheb area (Czech Republic), which have never been dated before, and, for comparison, of two samples from type localities, one in southern Bohemia and the other in western Moravia. We used 40Ar- 39Ar laser step-heating and total fusion techniques in conjunction with microscale petrographic and chemical characterization. In addition, with the purpose of ascertaining the influence of the dating standards on the age of the Ries impact and making data from this study and literature consistent with the now widely used Fish Canyon sanidine (FCs) standard, we performed a direct calibration of multi-grain splits of the Fish Canyon biotite (FCT-3) with FCs. The intercalibration factors ( RFCsFCT-3), determined for eight stack positions in one of the three performed irradiations, were indistinguishable within errors and gave an arithmetic mean and a standard deviation of 1.0086 ± 0.0031 (±2 σ), in agreement with previous works suggesting that biotite from the Fish Canyon Tuff is somewhat older (˜0.8%) than the coexisting sanidine. Laser total fusion analysis of milligram to sub-milligram splits of five tektite samples from the Cheb area yielded mostly concordant intrasample 40Ar- 39Ar ages, and within-sample weighted mean ages of 14.66 ± 0.08-14.75 ± 0

  12. Robust date for the Bronze Age Avellino eruption (Somma-Vesuvius): 3945 ± 10 calBP (1995 ± 10 calBC)

    NASA Astrophysics Data System (ADS)

    Sevink, Jan; van Bergen, Manfred J.; van der Plicht, Johannes; Feiken, Hendrik; Anastasia, Carmela; Huizinga, Annika

    2011-05-01

    We found Bronze Age lake sediments from the Agro Pontino graben (Central Italy) to contain a thin (2-3 cm) continuous tephra layer composed of lithics, crystals and minor volcanic glass. Tephrochronological and compositional constraints strongly suggest that this layer represents the Avellino pumice eruption, which has also been identified in Central Italian lake cores. Its provenance is corroborated by electron-microprobe analyses performed on juvenile pumice grains, showing that the tephra layer is probably the distal equivalent of the EU2 event of the Avellino eruption. We used multiple 14C age estimations of two lacustrine sequences with intercalated tephra layer, from the western border zone (Migliara 44.5) and the centre of the former lake (Campo Inferiore), for in tandem dating of this eruption, employing the OxCal code, which yielded a robust age of 3945 ± 10 calBP (1995 ± 10 calBC). To date, this is the only study providing both a terminus post and terminus ante quem of this precision, also demonstrating the advantage of dating distal tephra layers in a clear stratigraphic context over proximal deposits in sequences with major stratigraphic hiatuses. Our new results underscore the importance of the Avellino tephra layer as a precise time marker for studies on the Early Bronze Age of Central Italy.

  13. Accurate and Precise in Situ Zircon U-Pb age Dating With High Sample Throughput by Automated LA-SF-ICP-MS

    NASA Astrophysics Data System (ADS)

    Frei, D.; Gerdes, A.; Schersten, A.; Hollis, J. A.; Martina, F.; Knudsen, C.

    2006-12-01

    Zircon is an ubiquitous mineral in most crystalline rocks as well as clastic sediments. The high resistance to thermal resetting and physical erosion makes zircon an exceptionally useful mineral for precise and accurate dating of thermal geological events. For example, the analysis of the U-Pb ages of detrital zircon grains in clastic sediments is a powerful tool in sedimentary provenance studies. Accurate and precise U-Pb ages of > 100 zircon grains in a sample usually allow to detect all major sedimentary source age components with statistical confidence. U-Pb age dating of detrital zircons is generally the domain of high resolution ion microprobe techniques (high resolution SIMS), where relatively rapid in situ analysis can be achieved. The major limitations of these techniques are sample throughput (about 75 zircon age dates per 24 hours), the very high purchasing and operating costs of the equipment and the need for highly specialised personnel, resulting in high cost. These high costs usually impose uncomfortable restrictions on the number of samples that can be analysed in a provenance study. Here, we present a high sample throughput technique for highly accurate and precise U-Pb dating of zircons by laser ablation magnetic sectorfield inductively coupled plasma mass spectrometry (LA-SF-ICP-MS). This technique takes advantage of recent progress in laser technology and the introduction of magnetic sectorfield ICP-MS instruments. Based on a ThermoFinnigan Element2 magnetic sctorfield ICP-MS and a New Wave UP 213 laser ablation system, this techniques allows U-Pb dating of zircon grains with precision, accuray and spatial resolution comparable to high resolution SIMS. Because an individual analysis is carried out in less than two minutes and all data is acquired automated in pre-set mode with only minimal operator presence, the sample throughput is an order of magnitude higher compared to high resolution SIMS. Furthermore, the purchasing and operating costs of

  14. Comparative 40Ar/39Ar and K-Ar dating of illite-type clay minerals: A tentative explanation for age identities and differences

    NASA Astrophysics Data System (ADS)

    Clauer, Norbert; Zwingmann, Horst; Liewig, Nicole; Wendling, Raymond

    2012-10-01

    The 40K/40Ar (K-Ar) and 40Ar/39Ar dating methods are applied here to the same, very small, micrometric illite-type particles that crystallized under low-temperature (< 175 °C) hydrothermal conditions in deeply buried Rotliegend (Permian) gas-bearing sandstones of NW Germany. Four samples with a total of fifteen size fractions from < 2 to 20-40 μm yield K-Ar ages that range from 166.0 ± 3.4 to 214.0 ± 5.9 Ma. The same size fractions dated by the 40Ar/39Ar method give total-gas ages ranging from 173.3 ± 2.0 to 228.8 ± 1.6 Ma. Nearly all 40Ar/39Ar total-gas ages are slightly older, which cannot be explained by the recoil effect only, the impact of which being amplified by the inhomogeneous shape of the clay minerals and their crystallographic characteristics, with varied crystallinity indices, and a particle width about 10 times large than thickness. The 40Ar/39Ar data outline some advantages, such as the plateaus obtained by incremental step heating of the various size fractions, even if not translatable straight as ages of the illite populations; they allow identification of two generations of authigenic illite that formed at about 200 and 175 Ma, and one detrital generation. However, 40Ar/39Ar dating of clay minerals remains challenging as technical factors, such as the non-standardized encapsulation, may have potential unexpected effects. Both dating methods have their limitations: (1) K-Ar dating requires relatively large samples (ca. 10-20 mg) incurring potential sample homogeneity problems, with two aliquots required for K and Ar analysis for an age determination, also inducing a higher analytical uncertainty; (2) an identified drawback of 40Ar/39Ar dating is Ar recoil and therefore potential loss that occurs during neutronic creation of 39Ar from 39K, mostly in the finer mineral particles. If all the recoiled 39Ar is redistributed into adjacent grains/minerals, the final 40Ar/39Ar age of the analyzed size fraction remains theoretically identical, but it

  15. Redundant 230Th/ 234U/ 238U, 231Pa/ 235U and 14C dating of fossil corals for accurate radiocarbon age calibration

    NASA Astrophysics Data System (ADS)

    Chiu, Tzu-Chien; Fairbanks, Richard G.; Mortlock, Richard A.; Cao, Li; Fairbanks, Todd W.; Bloom, Arthur L.

    2006-09-01

    230Th/ 234U/ 238U dating of fossil corals by mass spectrometry is remarkably precise, but some samples exposed to freshwater over thousands of years may gain and/or lose uranium and/or thorium and consequently yield inaccurate ages. Although a δ 234U initial value equivalent to modern seawater and modern corals has been an effective quality control criterion, for samples exposed to freshwater but having δ 234U initial values indistinguishable from modern seawater and modern corals, there remains a need for additional age validation in the most demanding applications such as the 14C calibration (Fairbanks et al., 2005. Radiocarbon calibration curve spanning 0 to 50,000 years BP based on paired 230Th/ 234U/ 238U and 14C dates on pristine corals. Quaternary Science Reviews 24(16-17), 1781-1796). In this paper we enhance screening criteria for fossil corals older than 30,000 years BP in the Fairbanks0805 radiocarbon calibration data set (Fairbanks et al., 2005) by measuring redundant 230Th/ 234U/ 238U and 231Pa/ 235U dates via multi-collector magnetic sector inductively coupled plasma mass spectrometry (MC-MS-ICPMS) using techniques described in Mortlock et al. (2005. 230Th/ 234U/ 238U and 231Pa/ 235U ages from a single fossil coral fragment by multi-collector magnetic-sector inductively coupled plasma mass spectrometry. Geochimica et Cosmochimica Acta 69(3), 649-657.). In our present study, we regard paired 231Pa/ 235U and 230Th/ 234U/ 238U ages concordant when the 231Pa/ 235U age (±2 σ) overlaps with the associated 230Th/ 234U/ 238U age (±2 σ). Out of a representative set of 11 Fairbanks0805 (Fairbanks et al., 2005) radiocarbon calibration coral samples re-measured in this study, nine passed this rigorous check on the accuracy of their 230Th/ 234U/ 238U ages. The concordancy observed between 230Th/ 234U/ 238U and 231Pa/ 235U dates provides convincing evidence to support closed system behavior of these fossil corals and validation of their 230Th/ 234U/ 238U

  16. Age of the Lava Creek supereruption and magma chamber assembly at Yellowstone based on 40Ar/39Ar and U-Pb dating of sanidine and zircon crystals

    NASA Astrophysics Data System (ADS)

    Matthews, Naomi E.; Vazquez, Jorge A.; Calvert, Andrew T.

    2015-09-01

    The last supereruption from the Yellowstone Plateau formed Yellowstone caldera and ejected the >1000 km3 of rhyolite that composes the Lava Creek Tuff. Tephra from the Lava Creek eruption is a key Quaternary chronostratigraphic marker, in particular for dating the deposition of mid Pleistocene glacial and pluvial deposits in western North America. To resolve the timing of eruption and crystallization history for the Lava Creek magma, we performed (1) 40Ar/39Ar dating of single sanidine crystals to delimit eruption age and (2) ion microprobe U-Pb and trace-element analyses of the crystal faces and interiors of single zircons to date the interval of zircon crystallization and characterize magmatic evolution. Sanidines from the two informal members composing Lava Creek Tuff yield a preferred 40Ar/39Ar isochron date of 631.3 ± 4.3 ka. Crystal faces on zircons from both members yield a weighted mean 206Pb/238U date of 626.5 ± 5.8 ka, and have trace element concentrations that vary with the eruptive stratigraphy. Zircon interiors yield a mean 206Pb/238U date of 659.8 ± 5.5 ka, and reveal reverse and/or oscillatory zoning of trace element concentrations, with many crystals containing high U concentration cores that likely grew from highly evolved melt. The occurrence of distal Lava Creek tephra in stratigraphic sequences marking the Marine Isotope Stage 16-15 transition supports the apparent eruption age of ˜631 ka. The combined results reveal that Lava Creek zircons record episodic heating, renewed crystallization, and an overall up-temperature evolution for Yellowstone's subvolcanic reservoir in the 103-104 year interval before eruption.

  17. Age of the Lava Creek supereruption and magma chamber assembly at Yellowstone based on 40Ar/39Ar and U-Pb dating of sanidine and zircon crystals

    USGS Publications Warehouse

    Matthews, Naomi E.; Vazquez, Jorge A.; Calvert, Andrew T.

    2015-01-01

    The last supereruption from the Yellowstone Plateau formed Yellowstone caldera and ejected the >1000 km3 of rhyolite that composes the Lava Creek Tuff. Tephra from the Lava Creek eruption is a key Quaternary chronostratigraphic marker, in particular for dating the deposition of mid Pleistocene glacial and pluvial deposits in western North America. To resolve the timing of eruption and crystallization history for the Lava Creek magma, we performed (1) 40Ar/39Ar dating of single sanidine crystals to delimit eruption age and (2) ion microprobe U-Pb and trace-element analyses of the crystal faces and interiors of single zircons to date the interval of zircon crystallization and characterize magmatic evolution. Sanidines from the two informal members composing Lava Creek Tuff yield a preferred 40Ar/39Ar isochron date of 631.3 ± 4.3 ka. Crystal faces on zircons from both members yield a weighted mean 206Pb/238U date of 626.5 ± 5.8 ka, and have trace element concentrations that vary with the eruptive stratigraphy. Zircon interiors yield a mean 206Pb/238U date of 659.8 ± 5.5 ka, and reveal reverse and/or oscillatory zoning of trace element concentrations, with many crystals containing high U concentration cores that likely grew from highly evolved melt. The occurrence of distal Lava Creek tephra in stratigraphic sequences marking the Marine Isotope Stage 16–15 transition supports the apparent eruption age of ∼631 ka. The combined results reveal that Lava Creek zircons record episodic heating, renewed crystallization, and an overall up-temperature evolution for Yellowstone's subvolcanic reservoir in the 103−104 year interval before eruption.

  18. Direct Dating of Brittle Faults and Episodic Orogeny, illustrated by Illite Age Analysis of Major Thrusts in the Canadian Rocky Mountains (Invited)

    NASA Astrophysics Data System (ADS)

    van der Pluijm, B.; Pana, D.

    2013-12-01

    Illitization is a common process in shallow fault rocks, which allows direct dating of faulting through a combination of illite polytype quantification from XRD analysis and Ar-Ar encapsulation dating of multiple grain size fractions of clay gouge. The application of Illite Age Analysis (IAA) to fault rocks has the benefit that very small sample volumes can be analyzed, that potassium and argon are measured simultaneously, and that it has high precision. Grain size fraction separation into 3-4 subsamples, typically in the range of <2.0 μm to <0.02 μm, and illite characterization and quantification using modeling of XRD spectra that determines the relative abundance of detrital (2M1) and authigenic (1M/1Md) polytypes, are key to obtaining geologically meaningful results. Both a total gas age, incorporating the recoiled argon fraction after irradiation, and a retention age, omitting the recoiled fraction, are determined for each grain size population. The respective application of these ages is a function of effective illite crystallite thickness, which is determined from XRD patterns and the Scherrer equation. Total gas ages are representative of crystallite sizes on the order of thicknesses obtained from the Ar recoil percentage (<10-15nm), while retention ages are representative of thicker crystallites. Plotting [apparent age] v. [authigenic/detrital illite ratio] for each size fraction and using York data regression produces a lower intercept and error that dates gouge formation (authigenic illite), and an upper intercept and error that reflects phyllosilicate ages in the host rock (detrital illite). Regional application of IAA to 18 fault gouge sites along major thrusts in addition to selected host rocks in the Canadian Rocky Mountains shows that this fold-thrust belt formed through a series of four, eastward-propagating orogenic pulses. In the Main ranges, thrust range from 158-149 Ma, coinciding with Late Jurassic deposition of Kootenay

  19. Potential for timing high-energy marine inundation events in the recent geological past through age-dating of reef boulders in Fiji

    NASA Astrophysics Data System (ADS)

    Terry, James P.; Etienne, Samuel

    2014-12-01

    Transported coastal boulders have increasingly come to represent a valuable element of investigations within the broader framework of multi-proxy approaches applied to coastal hazard studies. Through a case study on Taveuni Island in Fiji, this paper outlines some approaches and hindrances to effective timing of prehistorical high-energy marine inundation events (storms and tsunamis) on tropical coastlines from the evidence of reef-platform carbonate boulders. Various sources of errors are outlined that investigators must consider when attempting to use carbonate boulder ages as a surrogate for timing past events. On Taveuni, uranium : thorium dates with a high level of precision (1-7 years) suggest that major inundation events have a return period of approximately 40-45 years since 1650 AD. Of particular importance, considerably different age dates are provided by coral samples sourced from the top and bottom (i.e. opposite faces) of individual boulders, so highlighting interpretation biases that must be avoided.

  20. An absolutely dated high-resolution stalagmite record from Lianhua Cave in central China: Climate forcing and comparison with Wanxiang Cave and Dongge Cave records over the past 2000 years

    NASA Astrophysics Data System (ADS)

    Li, Hong-Chun; Yin, Jian-Jun; Shen, Chuan-Chou; Mii, Horng-Sheng; Li, Ting-Yong

    2015-04-01

    A 33-cm long aragonite stalagmite (LHD-1) from Lianhua Cave has been dated by MC-ICPMS 230Th/U method on 41 horizons. Very high U contents (1~6ppm) and low Th contents yield excellent 230Th/U dates which provide reliable chronology of the stalagmite on sub-decadal time scale over the past 3350 years. A total of 1716 samples have been measured for δ18O and δ13C, spanning annual resolution over the past 1820 years. The stalagmite δ18O is not only influenced by the 'amount effect', but also affected by the moisture source. Enhanced the tropical monsoon trough under strong EASM brings higher spring quarter rainfall with isotopically light monsoonal moisture in the cave site, resulting in lighter stalagmite δ18O. On decadal or longer time scales, increased solar activity produces warmer condition and stronger summer monsoon which lead to wet climates. On interannual-to-decadal scales, the Walker Circulation under El Niño conditions during cold periods will shift toward the central Pacific and result in weakening of EASM. Under such a circumstance, dry climates will be prevailed in the study area. Based on the δ18O and δ13C records, we have deciphered climatic and vegetation changes of the study area in decadal scales. The highly precise dated LHD-1 record has been compared with previous published Wanxiang Cave and Dongge Cave records. Although some similarities can be found, there are major discrepancies among the three well-dated records, especially during AD 500-700 and AD 1300-1600. In additional, the major weak monsoon periods defined in the Wanxiang Cave record during late Tang Dynasty, late Yuan Dynasty and late Ming Dynasty are not supported by the LHD-1 record. The heaviest δ18O peaks (more than five continuous heavy values) over the past 2000 years appeared around AD 1990-2003, 1657-1662, 1220-1228, 663-669, 363-370, and 1082-1090 (in the order of heavy to light). None of these periods occurred Chinese dynasty collapse.

  1. Age determination of nephrite by in-situ SIMS U-Pb dating syngenetic titanite: A case study of the nephrite deposit from Luanchuan, Henan, China

    NASA Astrophysics Data System (ADS)

    Ling, Xiao-Xiao; Schmädicke, Esther; Li, Qiu-Li; Gose, Jürgen; Wu, Rui-Hua; Wang, Shi-Qi; Liu, Yu; Tang, Guo-Qiang; Li, Xian-Hua

    2015-04-01

    Nephrite is a kind of valuable jade which forms during metamorphism under greenschist facies conditions. Most investigations focus on the genesis of nephrite, however, the formation age of nephrite remains poorly constrained due to the lack of suitable dating methods. In this paper, the petrological, chemical characteristics, and mineral inclusions of nephrite collected from Luanchuan, Henan, China have been studied by optical and electron microscopy and wavelength-dispersive electron microprobe (EMP). The petrological observations show that nephrite consists mainly of tremolite, minor calcite and titanite, occasionally with rutile, quartz, serpentine, chlorite, pyrite, and apatite. The titanite and tremolite which are intergrown with each other share low-energy grain boundaries. It indicates that the two phases are equilibrated and can be considered as cogenetic. The chemical composition of tremolite is high in Si, Mg, Ca, but low in Fe, Cr, and Ni, which indicates that the nephrite from Luanchuan belongs to the dolomite type rather than the serpentinite type. The petrography of different nephrite structures suggests that the grain size of tremolite was determined by the stress intensity undergone during the nephrite formation progress. In-situ Secondary Ion Mass Spectrometer (SIMS) U-Pb dating of titanite from nephrite yielded an age of 361 ± 4 Ma, which is the first estimate for the time of formation of the Luanchuan nephrite deposit. This investigation provides a powerful in-situ dating method to unravel the age of nephrite, which could be served as a tool for future research on other nephrite deposits.

  2. No Relative Age Effect in the Birth Dates of Award-Winning Athletes in Male Professional Team Sports

    ERIC Educational Resources Information Center

    Ford, Paul R.; Williams, A. Mark

    2011-01-01

    Athletes born early within an annual youth age-group selection year are probably more likely to be selected for sports teams and talent development programs than those born later in that year. Overrepresentation of these relatively older athletes in youth and adult sport is known as the relative age effect (RAE). RAEs were found in these popular…

  3. Using an independent geochronology based on palaeomagnetic secular variation (PSV) and atmospheric Pb deposition to date Baltic Sea sediments and infer 14C reservoir age

    NASA Astrophysics Data System (ADS)

    Lougheed, Bryan C.; Snowball, Ian; Moros, Matthias; Kabel, Karoline; Muscheler, Raimund; Virtasalo, Joonas J.; Wacker, Lukas

    2012-05-01

    Dating of sediment cores from the Baltic Sea has proven to be difficult due to uncertainties surrounding the 14C reservoir age and a scarcity of macrofossils suitable for dating. Here we present the results of multiple dating methods carried out on cores in the Gotland Deep area of the Baltic Sea. Particular emphasis is placed on the Littorina stage (8 ka ago to the present) of the Baltic Sea and possible changes in the 14C reservoir age of our dated samples. Three geochronological methods are used. Firstly, palaeomagnetic secular variations (PSV) are reconstructed, whereby ages are transferred to PSV features through comparison with varved lake sediment based PSV records. Secondly, lead (Pb) content and stable isotope analysis are used to identify past peaks in anthropogenic atmospheric Pb pollution. Lastly, 14C determinations were carried out on benthic foraminifera (Elphidium spec.) samples from the brackish Littorina stage of the Baltic Sea. Determinations carried out on smaller samples (as low as 4 μg C) employed an experimental, state-of-the-art method involving the direct measurement of CO2 from samples by a gas ion source without the need for a graphitisation step - the first time this method has been performed on foraminifera in an applied study. The PSV chronology, based on the uppermost Littorina stage sediments, produced ten age constraints between 6.29 and 1.29 cal ka BP, and the Pb depositional analysis produced two age constraints associated with the Medieval pollution peak. Analysis of PSV data shows that adequate directional data can be derived from both the present Littorina saline phase muds and Baltic Ice Lake stage varved glacial sediments. Ferrimagnetic iron sulphides, most likely authigenic greigite (Fe3S4), present in the intermediate Ancylus Lake freshwater stage sediments acquire a gyroremanent magnetisation during static alternating field (AF) demagnetisation, preventing the identification of a primary natural remanent magnetisation for

  4. High Resolution, Absolute Dated Terrestrial Climate Record of Temperature and Precipitation From the Eastern US Covering 0-7ka, 116-127ka, and 145-298 ka

    NASA Astrophysics Data System (ADS)

    Hardt, B. F.; Rowe, H. D.; Springer, G. S.; Cheng, H.; Edwards, R. L.

    2007-12-01

    Analysis of 4 stalagmites from Buckeye Creek Cave (BCC) in West Virginia provides a high resolution record of temperature and precipitation in the eastern US. Periods of coverage include 0-7ka, 116-127ka, and 145-298 ka. Samples were dated using U/Th dating techniques developed for carbonates (Broecker 1963) and adapted for measurement on mass spectrometer (Edwards et al., 1987). The chronology is constrained by 6-14 dates per sample. Replication is the best method to ensure that observed isotopic changes are due to regional climate and not kinetic fractionation or heterogeneous behavior within the cave environment. When replication is available within the BCC record, there is general agreement in the timing, direction, and magnitude of shifts in δ13C and δ18O. Such agreement supports the interpretation of the isotopic composition of speleothem calcite as a climate signal. The δ18O record can reflect either temperature or precipitation. Since the record contains glacial and interglacial intervals and has a range of 2‰ (~5.5 °C at +0.35‰/°C), it is reasonable to conclude that temperature effects determine the isotopic composition of the samples. However, temperature cannot explain the entire record, as Marine Isotope Stages (MIS) 1 and 5e demonstrate more negative values than during full glacial conditions (MIS 6 & 8). Therefore precipitation must be a contributing factor. Such an interpretation is supported by the δ13C record. During arid periods, rock-water interaction time is increased, leading to a positive shift in δ13C (Denniston et al., 2007). Our record is ~4‰ higher during glacial periods than during MIS 1 and 5e. Broadly speaking, our record tracks insolation. However, one remarkable aspect of this record is the behavior of δ18O at insolation peaks. Our record contains four abrupt negative shifts in δ18O during maxima in local summer insolation greater than 520 W/m2. Temperature change does not provide a compelling explanation for this

  5. Advantages of conducting in-situ U-Pb age dating of multiple U-bearing minerals from a single complex: Case in point - the Oka Carbonatite Complex

    NASA Astrophysics Data System (ADS)

    Chen, W.; Simonetti, A.

    2012-12-01

    A detailed radiometric investigation is currently underway focusing on U-bearing accessory minerals apatite, perovskite, and niocalite from the Oka Carbonatite Complex (Canada). One of the main objectives is to obtain a comparative chronology of melt crystallization for the complex. Unlike other commonly adopted U-bearing minerals (e.g., zircon, monazite) for in-situ dating investigations, apatite, perovskite, and niocalite contain relatively high contents of common Pb. Hence, careful assessment of the proportion and composition of the common Pb, and usage of appropriate matrix-matched external standards are imperative. The Madagascar apatite was utilized as the external standard for apatite dating, and the Emerald Lake and Durango apatites were adopted as secondary standards; the latter yield ages of 92.6 ±1.8 and 32.2 ±1.1 Ma, respectively, and these are identical to their accepted ages. Pb/U ages for apatite from Oka were obtained for different rock types, including 8 carbonatites, 4 okaites, 3 ijolites and 3 alnoites, and these define a range of ages between ~105 and ~135 Ma; this result suggests a protracted crystallization history. In total, 266 individual analyses define two peaks at ~115 and ~125Ma. For perovskite dating, the Ice River perovskite standard was utilized as the external standard. The perovskites from one okaite sample yield an age of 112.2 ±1.9 Ma, and is much younger than the previously reported U-Pb perovskite age of 131 ±7 Ma. Hence, the combined U-Pb perovskite ages also suggest a rather prolonged time of melt crystallization. Niocalite is a rare, accessory silicate mineral that occurs within the carbonatites at Oka. The international zircon standard BR266 was selected for use as the external standard and rastering was employed to minimize the Pb-U fractionation. Two niocalite samples give young ages at 110.6 ±1.2 and 115.0 ±1.9 Ma, and are identical to their respective apatite ages (given associated uncertainties) from the same

  6. Preliminary Monazite U-Th-Total Pb Absolute Age Constraints on Crustal Thickening and Siluro-Devonian Dextral Transpression: Central Appalachian Piedmont, SE Pennsylvania

    NASA Astrophysics Data System (ADS)

    Bosbyshell, H.; Srogi, L.; Pyle, J. M.; Blackmer, G. C.

    2007-12-01

    High grade metamorphic rocks in the Central Appalachian piedmont of SE Pa. occur in at least three distinct lithotectonic belts that are bounded by steeply dipping, NE-striking transcurrent or transpressional shear zones. From NW to SE these belts consist of rocks of Laurentian-, uncertain-, and arc-affinity. The central belt is characterized by basement gneiss-cored nappes and associated shallowly to moderately SE dipping S2 foliation. This belt followed a clockwise metamorphic P-T path; maximum temperatures (T ~ 640 °C at P ~ 0.7 GPa) are associated with syn- to post-S2 garnet growth. An increase in pressure of ~ 0.1 GPa is inferred from post- kinematic high-Ca garnet rims. This paper reports preliminary EPMA results on monazite from two samples, WG- 216 and U-154, from the Glenarm Wissahickon, the metasedimentary cover sequence in the central belt. A few monazite grains from WG-216 exhibit small low-Th cores which give latest Cambrian ages (492 +/- 10 Ma, n = 10; n = # of analyses, all precision is reported as 2 s.e.). All grains in WG-216 contain cores with irregular, patchy zoning that yield late Ordovician ages (454 +/- 6 Ma, n = 31). High-Th, low-Y rims, which yield early Devonian ages (410 +/- 11 Ma, n = 12), are present on monazite inclusions in the outer portions of garnet and staurolite, but are absent in monazite inclusions within microlithons characterized by S1 foliation. High-Th, low-Y rims grow along 001 cleavage in S2 foliation-forming micas, so S2 can be no younger than monazite rims. Similar EPMA monazite results were obtained from U-154, also from the Glenarm Wissahickon. At least one Ordovician core is present (455 +/- 4 Ma, n = 8); pre-S2 matrix monazite and one inclusion in staurolite yield late Silurian ages (422 +/- 4 Ma, n = 29); and one inclusion within outermost garnet yields a Devonian age (415 +/- 8 Ma, n = 8). These results constrain the timing of S2 formation and peak metamorphism in the central belt to the early Devonian. The SE

  7. Interactions between hatch dates, growth rates, and mortality of Age-0 native Rainbow Smelt and nonnative Alewife in Lake Champlain

    USGS Publications Warehouse

    Parrish, Donna; Simonin, Paul W.; Rudstam, Lars G.; Pientka, Bernard; Sullivan, Patrick J.

    2016-01-01

    Timing of hatch in fish populations can be critical for first-year survival and, therefore, year-class strength and subsequent species interactions. We compared hatch timing, growth rates, and subsequent mortality of age-0 Rainbow Smelt Osmerus mordax and Alewife Alosa pseudoharengus, two common open-water fish species of northern North America. In our study site, Lake Champlain, Rainbow Smelt hatched (beginning May 26) almost a month earlier than Alewives (June 20). Abundance in the sampling area was highest in July for age-0 Rainbow Smelt and August for age-0 Alewives. Late-hatching individuals of both species grew faster than those hatching earlier (0.6 mm/d versus 0.4 for Rainbow Smelt; 0.7 mm/d versus 0.6 for Alewives). Mean mortality rate during the first 45 d of life was 3.4%/d for age-0 Rainbow Smelt and was 5.5%/d for age-0 Alewives. Alewife mortality rates did not differ with hatch timing but daily mortality rates of Rainbow Smelt were highest for early-hatching fish. Cannibalism is probably the primary mortality source for age-0 Rainbow Smelt in this lake. Therefore, hatching earlier may not be advantageous because the overlap of adult and age-0 Rainbow Smelt is highest earlier in the season. However, Alewives, first documented in Lake Champlain in 2003, may increase the mortality of age-0 Rainbow Smelt in the summer, which should favor selection for earlier hatching.

  8. Dating of Modern Human Evolution

    NASA Astrophysics Data System (ADS)

    Grun, R.

    Dating studies on palaoeanthropological sites is usually carried out on material associ- ated with the human remains, such as the sediment, charcoal or other fauna rather than the human specimen itself. The reason lies in the fact that most dating techniques are destructive and because the hominid remains are too rare to be sacrificed for dating. This indirect dating approach is in many cases not satisfactory, because: (i) the human remains are often buried into the sediments and the association with other materials is uncertain (e.g. Skhul, Qafzeh, etc.); (ii) faunal remains or minerals from the sediment are re-worked from older deposits (see e.g. present discussion of the age of the Homo erectus remains in Indonesia; (iii) the hominid fossils were discovered at a time when no careful excavations were carried out and it is impossible to correlate the specimen with other datable material (which applies tonearly 90% of all palaeoanthropological specimens). For example, the hominid burial site of Qafzeh in Israel has been dated by several independent dating laboratories with a multitude of methods. However, the data are still not accepted by some because the dating has not been carried out on the hominid specimen. Until recently, hominid fossils could only be dated by radiocarbon. This method reaches back to about 40,000 years. As a consequence, all the older fossils could not be analysed and many important questions in our understanding of human evolution could not be addressed. Human remains are scarce and extremely valuable, therefore any sort of destruction has to be kept to an absolute minimum. This is of particular importance in Australia where any human fossils are sacred. Thus, for the analysis of hominid material it was necessary to develop a more or less non-destructive techniques. This has been ac- complished in recent years by the application of ESR dating of tooth enamel and a combination of gamma spectrometric and TIMS U-series dating of bones. The exam

  9. Radiometric Dating Does Work!

    ERIC Educational Resources Information Center

    Dalrymple, G. Brent

    2000-01-01

    Discusses the accuracy of dating methods and creationist arguments that radiometric dating does not work. Explains the Manson meteorite impact and the Pierre shale, the ages of meteorites, the K-T tektites, and dating the Mount Vesuvius eruption. (Author/YDS)

  10. Using H-Alpha Morphology and Surface Brightness Fluctuations to Age-Date Star Clusters in M83

    NASA Astrophysics Data System (ADS)

    Whitmore, Bradley C.; Chandar, R.; Kim, H.; Kaleida, C.; Stankiewicz, M.; O'Connell, R.; SOC, WFC3

    2011-01-01

    We use WFC3 observations of the nearby grand design spiral galaxy M83 to develop two independent methods for estimating the ages of young star clusters. The first method uses the physical extent and morphology of H-alpha emission to estimate the ages of clusters younger than 10 Myr. It is based on the simple premise that the gas in very young (< few Myr) clusters is largely coincident with the cluster stars, is in a small, ring-like structure surrounding the stars in slightly older clusters (i.e., 5 Myr), and is in larger ring-like bubbles for older clusters (i.e., 5 - 10 Myr). The second method is based on an observed relation between pixel-to-pixel flux variations within clusters and their ages. This method relies on the fact that the brightest individual stars in a cluster are most prominent at ages around 3 - 10 Myr, and fall below the detection limit (i.e., Mv < -3.5) for ages older than 100 Myr old. The older clusters therefore have a smoother appearance and smaller pixel-to-pixel variations. We compare age estimates of clusters in M83 derived from these two techniques with estimates determined from fitting UBVIHalpha observations with model predictions, and find good agreement at the 90 % level, with an scatter of 0.2 dex in log age for young clusters (< 10 Myr) and 0.5 dex for older (> 10 Myr) clusters. This project is based on Early Release Science observations made by the WFC3 Scientific Oversight Committee. We are grateful to the Director of the Space Telescope Science Institute for awarding Director's Discretionary time for this program. Support for program #11360 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  11. Absolute biological needs.

    PubMed

    McLeod, Stephen

    2014-07-01

    Absolute needs (as against instrumental needs) are independent of the ends, goals and purposes of personal agents. Against the view that the only needs are instrumental needs, David Wiggins and Garrett Thomson have defended absolute needs on the grounds that the verb 'need' has instrumental and absolute senses. While remaining neutral about it, this article does not adopt that approach. Instead, it suggests that there are absolute biological needs. The absolute nature of these needs is defended by appeal to: their objectivity (as against mind-dependence); the universality of the phenomenon of needing across the plant and animal kingdoms; the impossibility that biological needs depend wholly upon the exercise of the abilities characteristic of personal agency; the contention that the possession of biological needs is prior to the possession of the abilities characteristic of personal agency. Finally, three philosophical usages of 'normative' are distinguished. On two of these, to describe a phenomenon or claim as 'normative' is to describe it as value-dependent. A description of a phenomenon or claim as 'normative' in the third sense does not entail such value-dependency, though it leaves open the possibility that value depends upon the phenomenon or upon the truth of the claim. It is argued that while survival needs (or claims about them) may well be normative in this third sense, they are normative in neither of the first two. Thus, the idea of absolute need is not inherently normative in either of the first two senses. PMID:23586876

  12. Age of the Lava Creek supereruption and magma chamber assembly at Yellowstone based on 40Ar/39Ar and U-Pb dating of sanidine and zircon crystals

    NASA Astrophysics Data System (ADS)

    Vazquez, J. A.; Matthews, N. E.; Calvert, A. T.

    2015-12-01

    The last supereruption from the Yellowstone Plateau formed Yellowstone caldera and ejected the >1000 km3 of rhyolite that composes the Lava Creek Tuff (LCT). Tephra from the eruption blanketed much of the western United States, and is a key Quaternary chronostratigraphic marker, in particular for dating deposition of mid-Pleistocene glacial and pluvial deposits in western North America. We performed 40Ar/39Ar dating of single sanidines to delimit eruption age, and ion microprobe U-Pb and trace-element analyses of crystal faces on single zircons to characterize magmatic evolution and date near-eruption crystallization, as well as analyses of crystal interiors to date the interval of zircon crystallization. Sanidines from the two LCT members A and B yield an 40Ar/39Ar isochron date of 631 ± 4 ka (2σ). Crystal faces on zircons from both members yield a weighted mean 206Pb/238U date of 627 ± 6 ka (2σ) and have trace element concentrations that vary with eruptive stratigraphy. Zircon interiors yield a weighted mean 206Pb/238U date of 660 ± 6 ka, and reveal reverse and/or oscillatory zoning of trace element concentrations, with many crystals containing high-U concentrations and dark cathodoluminescence (CL) cores. These crystals with high-U cores are possibly sourced from 'defrosting' of melt-impregnated margins of the growing subvolcanic reservoir. LCT sanidines mirror the variation of zircon composition within the eruptive stratigraphy, with crystals from upper LCT-A and basal LCT-B having bright-CL rims with high Ba concentrations, suggesting late crystallization after addition of less evolved silicic magma. The occurrence of distal LCT in stratigraphic sequences marking the Marine Isotope Stage 16-15 transition supports the apparent eruption age of ca. 631 ka. These results reveal that Lava Creek zircons record episodic heating, renewed crystallization, and an overall up-temperature evolution for Yellowstone's subvolcanic reservoir in the 103-104 year interval

  13. Memory for time: how people date events.

    PubMed

    Janssen, Steve M J; Chessa, Antonio G; Murre, Jaap M J

    2006-01-01

    The effect of different formats on the accuracy of dating news and the distribution of personal events was examined in four conditions. In the first, participants had to date events in the absolute time format (e.g., "July 2004"), and in the second, they had to date events in the relative time format (e.g., "3 weeks ago"). In the other conditions, they were asked to choose between the two formats. We found a small backward telescoping effect for recent news events and a large forward telescoping effect for remote events. Events dated in the absolute time format were more accurate than those dated in the relative time format. Furthermore, participants preferred to date news events with the relative time format and personal events with the absolute time format, as well as preferring to date remote events in the relative time format and recent events in the absolute time format. PMID:16686113

  14. High precision dating of mass extinction events: a combined zircon geochronology, apatite tephrochronology, and Bayesian age modelling approach of the Permian-Triassic boundary extinction

    NASA Astrophysics Data System (ADS)

    Baresel, Björn; Bucher, Hugo; Brosse, Morgane; Bagherpour, Borhan; Schaltegger, Urs

    2016-04-01

    Chemical abrasion isotope dilution thermal ionization mass spectrometry (CA-ID-TIMS) U-Pb dating of single-zircon crystals is preferably applied to tephra beds intercalated in sedimentary sequences. By assuming that the zircon crystallization age closely approximate that of the volcanic eruption and ash deposition, U-Pb zircon geochronology is the preferred approach for dating mass extinction events (such as the Permian-Triassic boundary mass extinction) in the sedimentary record. As tephra from large volcanic eruptions is often transported over long distances, it additionally provide an invaluable tool for stratigraphic correlation across distant geologic sections. Therefore, the combination of high-precision zircon geochronology with apatite chemistry of the same tephra bed (so called apatite tephrochronology) provides a robust fingerprint of one particular volcanic eruption. In addition we provide coherent Bayesian model ages for the Permian-Triassic boundary (PTB) mass extinction, then compare it with PTB model ages at Meishan after Burgess et al. (2014). We will present new high-precision U-Pb zircon dates for a series of volcanic ash beds in deep- and shallow-marine Permian-Triassic sections in the Nanpanjiang Basin, South China. In addition, apatite crystals out of the same ash beds were analysed focusing on their halogen (F, Cl) and trace-element (e.g. Fe, Mg, REE) chemistry. We also show that Bayesian age models produce reproducible results from different geologic sections. On the basis of these data, including litho- and biostratigraphic correlations, we can precisely and accurately constrain the Permian-Triassic boundary in an equatorial marine setting, and correlate tephra beds over different sections and facies in the Nanpanjiang Basin independently from litho-, bio- or chemostratigraphic criteria. The results evidence that data produced in laboratories associated to the global EARTHTIME consortium can provide age information at the 0.05% level of 206

  15. ABSOLUTE PROPERTIES OF THE ECLIPSING BINARY STAR V335 SERPENTIS

    SciTech Connect

    Lacy, Claud H. Sandberg; Fekel, Francis C.; Claret, Antonio E-mail: fekel@evans.tsuniv.edu

    2012-08-15

    V335 Ser is now known to be an eccentric double-lined A1+A3 binary star with fairly deep (0.5 mag) partial eclipses. Previous studies of the system are improved with 7456 differential photometric observations from the URSA WebScope and 5666 from the NFO WebScope, and 67 high-resolution spectroscopic observations from the Tennessee State University 2 m automatic spectroscopic telescope. From dates of minima, the apsidal period is about 880 years. Accurate (better than 2%) masses and radii are determined from analysis of the two new light curves and the radial velocity curve. Theoretical models match the absolute properties of the stars at an age of about 380 Myr, though the age agreement for the two components is poor. Tidal theory correctly confirms that the orbit should still be eccentric, but we find that standard tidal theory is unable to match the observed asynchronous rotation rates of the components' surface layers.

  16. Paleomagnetism of Upper Jurassic to Lower Cretaceous volcanic and sedimentary rocks from the western Tarim Basin and implications for inclination shallowing and absolute dating of the M-0 (ISEA?) chron

    NASA Astrophysics Data System (ADS)

    Gilder, Stuart; Chen, Yan; Cogné, Jean-Pascal; Tan, Xiaodong; Courtillot, Vincent; Sun, Dongjiang; Li, Yongan

    2003-02-01

    Stepwise demagnetization isolates a stable magnetic component in 13 sites of basalt flows and baked sediments dated at 113.3±1.6 Ma from the Tuoyun section, western Xinjiang Province, China. Except for one flow from the base of the ˜300 m thick section, the rest have exclusively reversed polarity. The sequence correlates with chron M-0 in some geomagnetic polarity time scales, which potentially places the section just before the start of the Cretaceous Long Normal polarity superchron. Five of 11 sites of Early Cretaceous red beds that underlie the basalts possess coherent directions that pass both fold and reversals tests. Six sites of Upper Jurassic red beds have a magnetic component that was likely acquired after folding in the Tertiary. The mean paleolatitude of the Lower Cretaceous red beds is 11° lower than that of the Lower Cretaceous basalts suggesting the red beds underestimate the true field inclination. We further test this result by calculating the paleolatitudes to a common point of the available Early Cretaceous to Present paleomagnetic poles from red beds and volcanic rocks from central Asian localities north of the Tibetan Plateau. We find that paleolatitudes of volcanic rocks roughly equal the paleolatitudes calculated from the reference Eurasian apparent polar wander path (APWP) and that paleolatitudes of red beds are generally 10-20° lower than the paleolatitudes of volcanic rocks and those predicted from the reference curve. Our study suggests that central Asian red beds poorly record the Earth's field inclination, which leads to lower than expected paleolatitudes. Good agreement in paleolatitudes from volcanic rocks and the Eurasian APWP argues against proposed canted and non-dipole field models.

  17. Luminescence- and Infrared-Radiofluorescence dating of the Acheulean- to Middle Stone Age sedimentary sequence at Montagu Cave, Western Cape Provence, South Africa

    NASA Astrophysics Data System (ADS)

    Lauer, Tobias; Archer, Will; Sumner, Alexandra

    2016-04-01

    Montagu Cave is an archaeological site located on the edge of the Langeberg mountain range, about 160 km NE of Cape Town, in South Africa. The archaeological and sedimentary units at Montagu Cave comprise two Acheulean sequences which are separated from one another by a substantial archaeological hiatus. There is an additional Middle Stone Age sequence which overlies the Acheulean horizons, and contains layers attributed to the Howiesons Poort, as well as multiple other Middle Stone Age sub-stages. Hence, Montagu Cave provides a unique opportunity to investigate quite complex population level questions concerning the behavioral differences between modern and pre-modern populations in southern Africa. However, thus far, the chronological context of the sediment-layers at the site remains unclear. It is therefore critical to provide a resilient chronological framework for the timing of human activity at the site. This study concerns the potential of luminescence dating for the sedimentary sequence preserved at Montagu cave. The collected samples are tested on their quartz- and feldspar luminescence signal properties. Various optical dating techniques (quartz OSL; pIRIR290) will be applied, and the results of each compared in order to obtain information on the suitability of the material for luminescence dating, and to establish a chronological framework for this important archaeological site. Furthermore, the infrared-radiofluorescence (IR-RF) signal behavior will be tested on potassium feldspars, as IR-RF is a method being able to date back up to > 600 ka. IR-RF therefore has the potential to cover the expected time-frame of the sediments at Montagu-cave.

  18. Age depth model construction of the upper section of ICDP Dead Sea Deep Drilling Project based on the high-resolution 14C dating

    NASA Astrophysics Data System (ADS)

    Kitagawa, H.; Nakamura, T.; Neugebauer, I.; Schwab, M. J.; Brauer, A.; Goldstein, S. L.; Stein, M.

    2014-12-01

    To reconstruct environmental, climatic and tectonic histories of the Levant, a deep drilling has been accomplished in the northern basin of the Dead Sea during the fall winter of 2010-2011 by the Dead Sea Deep Drilling Project (DSDDP) in the framework of the ICDP program. The sediment cores from site 5017-1 (water depth of ~300 m) recorded the paleoenvironmental and paleohydrological changes in the Dead Sea and the Levant during the last two glacial-interglacial cycles (Neugebauer et al., QSR in press). To provide precise timing of sedimentological - limnological events in the lake and its watershed, and more critically the relative timing of these events, radiocarbon dating of >70 well-preserved terrestrial plants and some carbonate deposits from the upper 150 m long section of the sediment core were performed. Based on the high-resolution radiocarbon dating, a statistical age-depth model was constructed with assumptions on the deposition condition and the radiocarbon age offset of carbonate samples. We discuss the practicality and the limitation of the age-depth model toward interpreting the high-resolution records of environmental, climatic and tectonic events recorded in the long sediment cores from site 5017-1.

  19. On the age of the Onverwacht Group, Swaziland sequence, South Africa. [radioactive dating of stratified igneous rocks

    NASA Technical Reports Server (NTRS)

    Jahn, B.-M.; Shih, C.-Y.

    1974-01-01

    Some rocks of the Onverwacht Group, South Africa, have been analyzed for Rb and Sr concentrations and Sr isotopic composition. These rocks include volcanic rocks, layered ultramafic differentiates and cherty sediments. Whole rock data indicate that the Rb-Sr isotopic systems in many samples were open and yield no reasonable isochron relationships. However, the data of mineral separates from a basaltic komatiite define a good isochron of 3.50 (plus or minus .2) b.y. with an initial Sr-87/Sr-86 ratio of 0.70048 plus or minus 5. The orthodox interpretation of this age is the time of the low grade metamorphism. It is reasonable to assume that the age of 3.50 b.y. might also represent the time of initial Onverwacht volcanism and deposition. The initial Sr-87/Sr-86 ratio obtained above is important to an understanding of the Sr isotopic composition of the Archean upper mantle.

  20. Dating Melt Rock 63545 By Rb-Sr and Sm-Nd: Age of Imbrium; Spa Dress Rehearsal

    NASA Technical Reports Server (NTRS)

    Nyquist, L. E.; Shih, C. Y.; Reese, Y. D.

    2011-01-01

    Apollo 16 sample 63545 was initially described as one of a group of 19 generally rounded, fine-grained, crystalline rocks that were collected as rake samples [1]. This 16 g "rocklet" was collected at Station 13 on the ejecta blanket of North Ray Crater at the foot of Smoky Mountain [2]. Originally classified as a Very High Alumina (VHA) basalt on geochemical grounds [3], it was later argued to be an impact melt rock [4]. Here we report a Rb-Sr and Sm-Nd isotopic study that shows that some portions of the rock failed to reach isotopic equilibrium on last melting in agreement with the impact melt rock interpretation. Nevertheless, by omitting mineral fractions that are discordant with the majority of the data, we arrive at the time of last melting as 3.88 plus or minus 0.05 Ga ago. This age is in agreement with the Ar-39/Ar-40 plateau age of 3839 plus or minus 23 Ma [5], if the latter is adjusted for the 1.4-1.8% revision in the age of the hornblende monitor [6]. This investigation was undertaken in part as proof-of-concept for SPA-basin sample return.

  1. Direct dating of hydrothermal W mineralization: U-Pb age for hübnerite (MnWO 4), Sweet Home Mine, Colorado

    NASA Astrophysics Data System (ADS)

    Romer, Rolf L.; Lüders, Volker

    2006-09-01

    We have investigated the potential of hübnerite for U-Pb dating. Hübnerite forms typically at medium to low-temperatures in a wide range of pneumatolytic-hydrothermal mineral deposits, particularly porphyry molybdenum and Sn-specialized granites. Hübnerite from the Sweet Home Mine (Alma, Colorado) formed in a Pb-rich, U-poor environment, but still developed relatively radiogenic Pb isotopic compositions. The low Pb common contents in hübnerite (0.075 to 0.155 ppm) demonstrate that Pb is efficiently excluded from the crystal lattice. In contrast, U may substitute for Mn. The U-Pb data of hübnerite scatter. Most of the scatter originates from samples with 206Pb/ 204Pb values below 50, where Pb blank contributes up to 30% to Pb total. Using the least radiogenic galena Pb, samples with 206Pb/ 204Pb values above 70 have overlapping 206Pb∗/ 238U and 207Pb∗/ 235U values and yield a 206Pb/ 238U age of 25.7 ± 0.3 Ma (2σ). Late stage apatite from the Sweet Home Mine yields a 206Pb/ 204Pb- 238U/ 204Pb isochron corresponding to an age of 24.8 ± 0.5 Ma (2σ). A comparison of the U-Pb hübnerite ages with literature 40Ar/ 39Ar ages on earlier sericite and the U-Pb age on later apatite suggests that (i) hübnerite yields accurate U-Pb ages and (ii) the evolution of the Sweet Home mineralization from greisen-type mineralization to medium-temperature hydrothermal vein mineralization took place in a few hundred thousand years at most. Aqueous low-N 2-bearing and aqueous inclusions in the dated hübnerite have homogenization temperatures between 325 and 356 °C and moderate salinity (up to 6.7 wt% NaCl equiv.). Thus, hübnerite represents one of the rare examples of a mineral that can be dated accurately and carries petrological information.

  2. Zircon U-Pb dating from the mafic enclaves in the Tanzawa Tonalitic Pluton, Japan: Implications for arc history and formation age of the lower-crust

    NASA Astrophysics Data System (ADS)

    Suzuki, Kazue; Yamamoto, Shinji; Sawaki, Yusuke; Aoki, Kazumasa; Omori, Soichi; Kon, Yoshiaki; Hirata, Takafumi; Li, Yibing; Takaya, Yutaro; Fujinaga, Koichiro; Kato, Yasuhiro; Maruyama, Shigenori

    2014-05-01

    The petro-chemical characteristics of the arc lower-crust, important for understanding continental growth, have been rarely obtained because of their scarcity at the surface of the Earth. To constrain the formation age of the arc lower-crust, U-Pb zircon dating was applied to mafic enclaves in tonalites of the Tanzawa Tonalitic Pluton (TTP), which is regarded as the exposed middle crust of the former Izu-Bonin-Mariana arc, using a laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS).

  3. Refined depositional history and dating of the Tongaporutuan reference section, north Taranaki, New Zealand: new volcanic ash U-Pb zircon ages, biostratigraphy and sedimentation rates

    USGS Publications Warehouse

    Maier, K.L.; Crundwell, Martin P.; Coble, Matthew A.; Kingsley-Smith, Peter R.; Graham, Stephan A.

    2016-01-01

    This study presents new radiometric ages from volcanic ash beds within a c. 1900 m thick, progradational, deep-water clastic slope succession of late Miocene age exposed along the north Taranaki coast of the North Island, New Zealand. The ash beds yield U–Pb zircon ages ranging from 10.63 ± 0.65 Ma to 8.97 ± 0.22 Ma. The new ages are compatible with and provide corroboration of New Zealand Tongaporutuan Stage planktic foraminiferal and bolboformid biostratigraphic events identified in the same section. The close accord between these two age datasets provides a stratigraphically consistent and coherent basis for examining margin evolution. The arrival of a prograding clastic wedge and ensuing upward shoaling is recorded by sedimentation rates c. 2000 m/Ma–1 that are an order of magnitude higher than sedimentation rates on the precursor deep basin floor. This outcrop study provides new constraints for interpreting analogous subsurface deposits in Taranaki Basin and complements the regional late Miocene biostratigraphic dating framework.

  4. The absolute path command

    2012-05-11

    The ap command traveres all symlinks in a given file, directory, or executable name to identify the final absolute path. It can print just the final path, each intermediate link along with the symlink chan, and the permissions and ownership of each directory component in the final path. It has functionality similar to "which", except that it shows the final path instead of the first path. It is also similar to "pwd", but it canmore » provide the absolute path to a relative directory from the current working directory.« less

  5. The absolute path command

    SciTech Connect

    Moody, A.

    2012-05-11

    The ap command traveres all symlinks in a given file, directory, or executable name to identify the final absolute path. It can print just the final path, each intermediate link along with the symlink chan, and the permissions and ownership of each directory component in the final path. It has functionality similar to "which", except that it shows the final path instead of the first path. It is also similar to "pwd", but it can provide the absolute path to a relative directory from the current working directory.

  6. Developing 226Ra and 227Ac age-dating techniques for nuclear forensics to gain insight from concordant and non-concordant radiochronometers

    DOE PAGESBeta

    Kayzar, Theresa M.; Williams, Ross W.

    2015-09-26

    The model age or ‘date of purification’ of a nuclear material is an important nuclear forensic signature. In this study, chemical separation and MC-ICP-MS measurement techniques were developed for 226 Ra and 227Ac: grand-daughter nuclides in the 238U and 235U decay chains respectively. The 230Th-234U, 226Ra-238U, 231Pa-235U, and 227Ac-235U radiochronometers were used to calculate model ages for CRM-U100 standard reference material and two highly-enriched pieces of uranium metal from the International Technical Working Group Round Robin 3 Exercise. In conclusion, the results demonstrate the accuracy of the 226Ra-238U and 227Ac-235U chronometers and provide information about nuclide migration during uranium processing.

  7. Anomalous radiocarbon ages from a Holocene detrital organic lens in Alaska and their implications for radiocarbon dating and paleoenvironmental reconstructions in the arctic

    USGS Publications Warehouse

    Nelson, R.E.; Carter, L.D.; Robinson, S.W.

    1988-01-01

    Eleven radiocarbon age determinations clearly show that a lens of Holocene fluvial organic debris on the Alaskan Arctic Coastal Plain contains mostly pre-Holocene organic material. Radio-carbon ages of identified plant macrofossils indicate the material was deposited about 9000 to 9500 yr B.P. Radiocarbon analyses of bulk samples from this deposit, however, range from 13,300 to 30,300 yr B.P. Most of the old organic matter seems to be in the smaller size fractions in the deposit, particularly in the fraction between 0.25 and 0.5 mm, but all size fractions are contaminated. Particular caution must be exercised in submitting bulk samples for radiocarbon dating from areas where conditions favor redeposition of isotopically "dead" carbon. ?? 1988.

  8. The effects of acid leaching on 40Ar/39Ar age dating results using samples from the Walvis Ridge hotspot trail

    NASA Astrophysics Data System (ADS)

    Klath, J. F.; Koppers, A. A.; Heaton, D. E.; Schnur, S.

    2013-12-01

    In this study we systematically explore how acid leaching can be used to reduce the negative effects of seawater alteration on the 40Ar/39Ar age dating of submarine basalts. Koppers et al (2000) showed that acid leaching of groundmass samples generated more consistent ages as well as ages more concordant with phenocrystic mineral phases, compared to samples that were left untreated. By studying the effects of progressively increasing the strength and length of acid treatment, we will show how acid leaching of groundmass separates reduces alteration while leaving the initial eruption signature intact. Samples were chosen from the Walvis ridge hotspot trail in the southeast Atlantic. Three samples were selected based on degree and style of alteration. Two samples (basalt and basaltic andesite) appear highly altered in thin section. The basalt contains diffuse iddingsite alteration that is pervasive throughout the groundmass. The basaltic andesite displays focused secondary mineral phases within and around abundant vesicles. The third sample, a trachyte, shows relatively minor degrees of alteration in thin section. These groundmass separates were divided into four splits and treated with a progressively stronger acid and for longer duration. One split from each rock was left untreated to act as a baseline. Of the other three splits from each sample, one was treated with a mild leach (1N HCl and 1N HNO3), one a strong leach (1N HCl, 1N HNO3, 6N HCl, and 3N HNO3), and lastly the strong leach performed twice. The samples were then handpicked to remove any remaining visible alteration. The untreated samples were picked as well, removing the most distinctly altered grains. All splits were analyzed by electron microprobe, x-ray fluorescence (XRF) and the incremental heating 40Ar/39Ar dating method. We will report on the results of an image analysis of microprobe backscatter images and elemental maps taken of individual groundmass grains. This analysis will show the location

  9. Origins of the Iberomaurusian in NW Africa: new AMS radiocarbon dating of the Middle and Later Stone Age deposits at Taforalt Cave, Morocco.

    PubMed

    Barton, R N E; Bouzouggar, A; Hogue, J T; Lee, S; Collcutt, S N; Ditchfield, P

    2013-09-01

    Recent genetic studies based on the distribution of mtDNA of haplogroup U6 have led to subtly different theories regarding the arrival of modern human populations in North Africa. One proposes that groups of the proto-U6 lineage spread from the Near East to North Africa around 40-45 ka (thousands of years ago), followed by some degree of regional continuity. Another envisages a westward human migration from the Near East, followed by further demographic expansion at ∼22 ka centred on the Maghreb and associated with a microlithic bladelet culture known as the Iberomaurusian. In evaluating these theories, we report on the results of new work on the Middle (MSA) and Later Stone (LSA) Age deposits at Taforalt Cave in Morocco. We present 54 AMS radiocarbon dates on bone and charcoals from a sequence of late MSA and LSA occupation levels of the cave. Using Bayesian modelling we show that an MSA non-Levallois flake industry was present until ∼24.5 ka Cal BP (calibrated years before present), followed by a gap in occupation and the subsequent appearance of an LSA Iberomaurusian industry from at least 21,160 Cal BP. The new dating offers fresh light on theories of continuity versus replacement of populations as presented by the genetic evidence. We examine the implications of these data for interpreting the first appearance of the LSA in the Maghreb and providing comparisons with other dated early blade and bladelet industries in North Africa. PMID:23891007

  10. A new Late Triassic age for the Puesto Viejo Group (San Rafael depocenter, Argentina): SHRIMP U-Pb zircon dating and biostratigraphic correlations across southern Gondwana

    NASA Astrophysics Data System (ADS)

    Ottone, Eduardo G.; Monti, Mariana; Marsicano, Claudia A.; de la Fuente, Marcelo S.; Naipauer, Maximiliano; Armstrong, Richard; Mancuso, Adriana C.

    2014-12-01

    The Puesto Viejo Group crops out in the San Rafael Block, southwest Mendoza, at approximately 35° S and 68°20‧ W. It consists of the basal mainly grayish Quebrada de los Fósiles Formation (QF) overlying by the reddish Río Seco de la Quebrada Formation (RSQ). The basal unit includes both plant remains (pleuromeians and sphenopsids) and vertebrates (scattered fish scales, dicynodont synapsids and remains of an archosauriform). In contrast, the RSQ beds have yielded only tetrapods, although a more diverse fauna. The latter includes cynodonts as Cynognathus, Pascualognathus and Diademodon, and also dicynodonts (Vinceria and Kannemeyeria). Based on the assemblage of tetrapod taxa the bearing levels were correlated to the Cynognathus AZ of South Africa and thus referred to the Middle Triassic (Anisian). We obtained a SHRIMP 238U/206Pb age of 235.8 ± 2.0 Ma from a rhyolitic ignimbrite interdigitated between the QF and RSQ formations at the Quebrada de los Fósiles section. This new radiometric date for the Puesto Viejo Group suggests that the tetrapod fauna in the RSQ beds existed, instead, during the Late Triassic (early Carnian) some 10 Ma later than the currently accepted age. Two scenarios might explain our results: first, the Cynognathus AZ of South Africa is wrongly assigned to the lower Middle Triassic (Anisan) and should be considered younger in age, Late Triassic (Carnian); second, the relative age of the Cynognathus AZ of South Africa is correct but the inferred range of Cynognathus and Diademodon is incorrect as they were present during the Late Triassic (Carnian) at least in South America. In any case, this new date pose serious doubts about the validity of biostratigraphic correlations based solely on tetrapod taxa, a common practice for Triassic continental successions across Gondwana.

  11. The SEEDS High-Contrast Imaging Survey: Exoplanet and Brown Dwarf Survey for Nearby Young Stars Dated with Gyrochronology and Activity Age Indicators

    NASA Astrophysics Data System (ADS)

    Kuzuhara, Masayuki; Tamura, Motohide; Helminiak, Kris; Mede, Kyle; Brandt, Timothy; Janson, Markus; Kandori, Ryo; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Hashimoto, Jun

    2015-12-01

    The SEEDS campaign has successfully discovered and characterized exoplanets, brown dwarfs, and circumstellar disks since it began in 2009, via the direct imaging technique. The survey has targeted nearby young stars, as well as stars associated to star-forming regions, the Pleiades open cluster, moving groups, and debris disks. We selected the nearby young stars that have been dated with age indicators based on stellar rotation periods (i.e., gyrochronology) and chromoshperic/coronal activities. Of these, nearly 40 were observed, with ages mainly between 100 and 1000 Myr and distances less than 40 pc. Our observations typically attain the contrast of ~6 x 10-6 at 1'' and better than ~1 x 10-6 beyond 2'', enabling us to detect a planetary-mass companion even around such old stars. Indeed, the SEEDS team reported the discovery that the nearby Sun-like star GJ 504 hosts a Jovian companion GJ 504b, which has a mass of 3-8.5 Jupiter masses that is inferred according to the hot-start cooling models and our estimated system age of 100-510 Myr. The remaining observations out of the selected ~40 stars have resulted in no detection of additional planets or brown dwarf companions. Meanwhile, we have newly imaged a low-mass stellar companion orbiting the G-type star HIP 10321, for which the presence of companion was previously announced via radial velocity technique. The astrometry and radial velocity measurements are simultaneously analyzed to determine the orbit, providing constraints on the dynamical mass of both objects and stellar evolution models. Here we summarize our direct imaging observations for the nearby young stars dated with gyrochrolorogy and activity age indicators. Furthermore, we report the analysis for the HIP 10321 system with the imaged low-mass companion.

  12. A glacial chronology for post Little Ice Age glacier changes based on proglacial geomorphology, tree rings, OSL- and 14C-dating at Mt. Pulongu, southeastern Tibet

    NASA Astrophysics Data System (ADS)

    Loibl, David; Hochreuther, Philipp; Hülle, Daniela; Zhu, Haifeng; Lehmkuhl, Frank

    2014-05-01

    The remote eastern Nyainqêntanglha Range contains numerous temperate monsoonal glaciers which are highly sensitive to climate change. However, there is still a great lack of information on late Holocene glacier fluctuations and the factors driving these changes. We conducted field work at two large debris covered glaciers on the northern and southern slopes of Mt. Pulongu (~6,300 m a.s.l.). Detailed geomorphological mapping of the proglacial settings revealed similar patterns of two major and three minor/recessional glacial advances. At the northern glacier, tree ring dating for the moraines of the two major advances resulted in minimum ages of ~1670 AD and ~1745 AD, respectively. These Little Ice Age (LIA) ages are supported by geochemical measurements on glacial and glacio-fluvial sediments from these settings showing almost no signs of chemical weathering. Further evidence, including 14C-age and depositional characteristics of a buried tree, and moraine topography, suggest that the second advance was stronger but was hampered by a dead ice relict of the previous advance. At the northern glacier, this obstacle led to an ice tailback and subsequently to lateral moraine oversteepening and breaching, resulting in a large lateral glacier lobe. At the southern glacier, the valley is narrower and hence did not allow the formation of a lateral glacier lobe. However, the proglacial setting, i.e. pronounced push moraines, suggests a similar sequence of events. Furthermore, both settings contain two moraine-dammed lakes in similar positions. A combination of OSL-dating, tree ring based reconstruction of the local climate, and constraints from the proglacial geomorphological setting enabled the inclusion of the 3 minor moraine stages into the glacial chronology. This multiproxy-approach resulted in a well-established morphochronology with multiple direct and indirect dates that allow the reconstruction of the glacial fluctuations at Mt. Pulongu since the LIA. A regional

  13. MASS-TO-LIGHT RATIOS FOR M31 GLOBULAR CLUSTERS: AGE DATING AND A SURPRISING METALLICITY TREND

    SciTech Connect

    Strader, Jay; Huchra, John P.; Smith, Graeme H.; Brodie, Jean P.

    2009-08-15

    We have obtained velocity dispersions from Keck high-resolution integrated spectroscopy of 10 M31 globular clusters (GCs), including three candidate intermediate-age GCs. We show that these candidates have the same V-band mass-to-light (M/L{sub V} ) ratios as the other GCs, implying that they are likely to be old. We also find a trend of derived velocity dispersion with wavelength, but cannot distinguish between a systematic error and a physical effect. Our new measurements are combined with photometric and spectroscopic data from the literature in a re-analysis of all M31 GC M/L{sub V} values. In a combined sample of 27 GCs, we show that the metal-rich GCs have lower M/L{sub V} than the metal-poor GCs, in conflict with predictions from stellar population models. Fragmentary data for other galaxies support this observation. The M31 GC fundamental plane is extremely tight, and we follow up an earlier suggestion by Djorgovski to show that the fundamental plane can be used to estimate accurate distances (potentially 10% or better)

  14. Calibration of cosmogenic noble gas production based on 36Cl-36Ar ages. Part 2. The 81Kr-Kr dating technique

    NASA Astrophysics Data System (ADS)

    Leya, I.; Dalcher, N.; Vogel, N.; Wieler, R.; Caffee, M. W.; Welten, K. C.; Nishiizumi, K.

    2015-11-01

    We calibrated the 81Kr-Kr dating system for ordinary chondrites of different sizes using independent shielding-corrected 36Cl-36Ar ages. Krypton concentrations and isotopic compositions were measured in bulk samples from 14 ordinary chondrites of high petrologic type and the cosmogenic Kr component was obtained by subtracting trapped Kr from phase Q. The thus-determined average cosmogenic 78Kr/83Kr, 80Kr/83Kr, 82Kr/83Kr, and 84Kr/83Kr ratiC(Lavielle and Marti 1988; Wieler 2002). The cosmogenic 78Kr/83Kr ratio is correlated with the cosmogenic 22Ne/21Ne ratio, confirming that 78Kr/83Kr is a reliable shielding indicator. Previously, 81Kr-Kr ages have been determined by assuming the cosmogenic production rate of 81Kr, P(81Kr)c, to be 0.95 times the average of the cosmogenic production rates of 80Kr and 82Kr; the factor Y = 0.95 therefore accounts for the unequal production of the various Kr isotopes (Marti 1967a). However, Y should be regarded as an empirical adjustment. For samples whose 80Kr and 82Kr concentrations may be affected by neutron-capture reactions, the shielding-dependent cosmogenic (78Kr/83Kr)c ratio has been used instead to calculate P(81Kr)/P(83Kr), as for some lunar samples, this ratio has been shown to linearly increase with (78Kr/83Kr)c (Marti and Lugmair 1971). However, the 81Kr-Kr ages of our samples calculated with these methods are on average ~30% higher than their 36Cl-36Ar ages, indicating that most if not all the 81Kr-Kr ages determined so far are significantly too high. We therefore re-evaluated both methods to determine P(81Kr)c/P(83Kr)c. Our new Y value of 0.70 ± 0.04 is more than 25% lower than the value of 0.95 used so far. Furthermore, together with literature data, our data indicate that for chondrites, P(81Kr)c/P(83Kr)c is rather constant at 0.43 ± 0.02, at least for the shielding range covered by our samples ([78Kr/83Kr]c = 0.119-0.185; [22Ne/21Ne]c = 1.083-1.144), in contrast to the observations on lunar samples. As expected

  15. Using chemical, hydrologic, and age dating analysis to delineate redox processes and flow paths in the riparian zone of a glacial outwash aquifer-stream system

    USGS Publications Warehouse

    Puckett, L.J.; Cowdery, T.K.; McMahon, P.B.; Tornes, L.H.; Stoner, J.D.

    2002-01-01

    A combination of chemical and dissolved gas analyses, chlorofluorocarbon age dating, and hydrologic measurements were used to determine the degree to which biogeochemical processes in a riparian wetland were responsible for removing NO3- from groundwaters discharging to the Otter Tail River in west central Minnesota. An analysis of river chemistry and flow data revealed that NO3- concentrations in the river increased in the lower half of the 8.3 km study reach as the result of groundwater discharge to the river. Groundwater head measurements along a study transect through the riparian wetland revealed a zone of groundwater discharge extending out under the river. On the basis of combined chemical, dissolved gas, age date, and hydrologic results, it was determined that water chemistry under the riparian wetland was controlled largely by upgradient groundwaters that followed flow paths up to 16 m deep and discharged under the wetland, creating a pattern of progressively older, more chemically reduced, low NO3- water the farther one progressed from the edge of the wetland toward the river. These findings pose challenges for researchers investigating biogeochemical processes in riparian buffer zones because the progressively older groundwaters entered the aquifer in earlier years when less NO3- fertilizer was being used. NO3- concentrations originally present in the groundwater had also decreased in the upgradient aquifer as a result of denitrification and progressively stronger reducing conditions there. The resulting pattern of decreasing NO3- concentrations across the riparian zone may be incorrectly interpreted as evidence of denitrification losses there instead of in the upgradient aquifer. Consequently, it is important to understand the hydrogeologic setting and age structure of the groundwaters being sampled in order to avgid misinterpreting biogeochemical processes in riparian zones.

  16. Optical Dating of Martian Eolian Sediments by Robotic Spacecraft

    NASA Astrophysics Data System (ADS)

    Sears, Derek W. G.; Lepper, Kenneth; McKeever, W. S.

    2000-07-01

    The Martian polar ice caps record a wealth of information about the past history and climate of Mars, but as pointed out by Clifford et al. in the summary of the First International Conference on Mars Polar Science and Exploration, 'The single greatest obstacle to unlocking and interpreting the geologic and climatic record preserved at the [martian] poles is the need for absolute dating.' Stratification in the polar caps arises, at least in part, from the incorporation of eolian material into the ice, and dune fields near the poles indicate eolian transport is an important surfical process in this region of Mars. Eolian materials are ideally suited for sediment dating using luminescence methods. Luminescence dating techniques have been used successfully to make absolute age determinations for numerous terrestrial Quaternary eolian deposits. Clifford et al. also concluded that cost, simplicity, and potential for minaturization make luminescence dating more feasible than isotopic methods for in situ dating by robotic landers. In fact, the water detection equipment of the Deep Space 2 microprobes and the MECA on the Mars Polar Lander contain components similar to those required for luminescence dating.

  17. Mobility and age of black carbon in two temperate grassland soils revealed by differential scanning calorimetry and radiocarbon dating

    NASA Astrophysics Data System (ADS)

    Leifeld, Jens; Feng, Xiaojuan; Eglinton, Timothy; Wacker, Lukas

    2015-04-01

    Black carbon (BC) is a natural component of soil organic matter (SOM) and abundant in many ecosystems. Its stability, due to its relative resistance to microbial decomposition, means it plays an important role in soil C sequestration. A recent review suggests that BC may be mobile in soil; hence, its contribution to a stable SOM pool may change over time due to its lateral or vertical reallocation (Rumpel et al. 2014). However, direct evidence of the mobility of BC, particularly with reference to its vertical mobility, is scarce. We studied the amount of BC in two temperate grassland fields (eutric clayey Camibsol,) that were established in 2001 on former cropland. Volumetric soil samples (0-50 cm, 5 cm increments) were taken at 10 spots in each field in 2001, 2006 and 2011. One of the fields was ploughed in 2007 and the sward was re-sown. BC content was measured by differential scanning calorimetry for a total number of c. 500 samples. The mean BC/OC ratio was 0.10 (±0.05) and reached 0.25 in some samples. Radiocarbon measurements from 24 bulk soil samples revealed relatively small 14C contents in 2001 (92±2.7 pMC) which increased over time (2006: 99.0±1.1 pMC; 2011: 99.1±1.1 pMC). Thermal fractionation of BC by DSC revealed calibrated BC ages of 400 to 1000 years (pMC 87-94), suggesting that BC originates from medieval and post-medieval fire clearings. The change in soil signature may have been caused by a preferential transport of old BC down the soil profile, leading to a selective enrichment of younger soil C over time. In line with this interpretation the DSC measurements suggest that in both fields, BC concentrations significantly decreased for most layers between 2001 and 2006. However, between 2006 and 2011, no further vertical reallocation was observed in the continuous grassland, whereas BC contents of the field ploughed in 2007 significantly increased in the top layers. Together, these data suggest that ploughing in 2001 triggered subsequent

  18. Fine-tuning of age integrating magnetostratigraphy, radiocarbon dating, and carbonate cyclicity: Example of lacustrine sediments from Heqing basin (Yunnan, China) covering the past 1 Myr

    NASA Astrophysics Data System (ADS)

    Hu, Shouyun; Goddu, Srinivasa Rao; Appel, Erwin; Verosub, Ken

    2007-05-01

    High-resolution magnetostratigraphy, wavelength spectra of carbonate cyclicities, and AMS radiocarbon dating are integrated to establish an optimum age model for a 168 m long drill core of lacustrine sediments from Heqing basin, Yunnan Province, southwestern China. A 14C age of 51.62 +2.42/-1.85 kyr BP is obtained at a depth of 7.3 m. Remanent magnetization is carried by maghemite and partly in addition by magnetite, both showing the same direction. The polarity sequence clearly reveals the Brunhes/Matuyama (B/M) boundary at 141.5 m. Blake Event is found between 16.3 and 17.5 m, and the upper boundary of Jaramillo is indicated at 167.0 m. Carbonate content and magnetic susceptibility were used for spectral analysis. Fourier analysis was done on the depth section for sliding windows with different window lengths. The spectra within the range of window centers (30-140 m) show a dominant long wavelength, which changes from about 18.5 m in the lower part (>65 m depth) to about 14.5 m in the upper part (<65 m depth) of the core. It is assumed that the long wavelength peak represents the 95-kyr Milankovitch eccentricity cycle. The B/M boundary and Blake Event match very well with this model, but the age of Jaramillo is strongly underestimated. Fourier spectra of sliding windows slightly indicate a drop of the sedimentation rate at the lowermost part of the core. An optimum age model is calculated by cubic spline interpolation using tie points from 14C dating, magnetostratigraphy ('true' ages of Blake Event, B/M boundary, and Jaramillo), and wavelengths of carbonate (change in sedimentation rate at 65 m). Alternative depth-to-age transfer functions were tested, i.e. a wavelength age model (using sedimentation rates with 14C as a tie point), a cyclostratigraphic model (using bandpass-filtered carbonate data corresponding to 95 kyr eccentricity cycles) and correlation of carbonate variations to the marine oxygen isotope curve. However, none of the approaches lead to a

  19. Age and tectonic setting of Late Archean greenstone-gneiss terrain in Henan Province, China, as revealed by single-grain zircon dating

    SciTech Connect

    Kroener, A.; Compston, W.; Guo-wei, Z.; An-lin, G.; Todt, W.

    1988-03-01

    The authors report precise U-Pb zircon ages for single grains of a metarhyodacite from the Late Archean Dengfeng greenstone belt in Henan Province, China, near the southern margin of the North China craton. Most grains belong to an igneous population whose U-Pb isotopic systematics define a straight line intersecting concordia at 2512 +/- 12 Ma, and this is interpreted as the time of crystallization of the original greenstone volcanics. Several grains are distinctly older, between 2576 +/- 9 and 2945 +/- 44 Ma, and the authors interpret the older grains as xenocrysts of pre-greenstone continental crust that provide evidence for crustal derivation or crustal contamination of the original rhyodacitic lava. The xenocrysts suggest evolution of the Dengfeng greenstone belt in a continental environment that may be represented by the Taihua high-grade gneisses bordering the Dengfeng greenstones and for which the authors obtained ages of 2806 +/- 7 and 2841 +/- 6 Ma. The data add evidence to the now widely held concept that most Archean greenstones developed on or near older continental crust and were therefore prone to crustal contamination. In such cases, conventional zircon dating may not always record the precise age of rock formation.

  20. 10Be dating of the Narsarsuaq moraine in southernmost Greenland: evidence for a late-Holocene ice advance exceeding the Little Ice Age maximum

    NASA Astrophysics Data System (ADS)

    Winsor, K.; Carlson, A. E.; Rood, D. H.

    2014-08-01

    In southernmost Greenland near Narsarsuaq, the terminal Narsarsuaq moraine was deposited well outside of a historical Little Ice Age (LIA) moraine adjacent to the modern ice margin. Using 10Be surface exposure dating, we determine Narsarsuaq moraine abandonment at 1.51 ± 0.11 ka. A second set of 10Be ages from a more ice-proximal position shows that ice has been within or at its historical (i.e., LIA) extent since 1.34 ± 0.15 ka. Notably, Narsarsuaq moraine abandonment was coincident with climate amelioration in southern Greenland. Southern Greenland warming at ˜1.5 ka was also concurrent with the end of the Roman Warm Period as climate along the northern North Atlantic sector of Europe cooled into the Dark Ages. The warming of southern Greenland and retreat of ice from the Narsarsuaq moraine is consistent with studies suggesting possible anti-phase centennial-scale climate variability between northwestern Europe and southern Greenland. Other southernmost Greenland ice-margin records do not preclude a pre-LIA ice-margin maximum, potentially concurrent with a Narsarsuaq advance prior to ˜1.51 ka, but also lack sufficient ice-margin control to confirm such a correlation. We conclude that there is a clear need to further determine whether a late-Holocene pre-LIA maximum was a local phenomenon or a regional southern Greenland ice maximum, and if this advance and retreat reflects a regional fluctuation in climate.

  1. Late Pleistocene ages for the most recent volcanism and glacial-pluvial deposits at Big Pine volcanic field, California, USA, from cosmogenic 36Cl dating

    NASA Astrophysics Data System (ADS)

    Vazquez, J. A.; Woolford, J. M.

    2015-09-01

    The Big Pine volcanic field is one of several Quaternary volcanic fields that poses a potential volcanic hazard along the tectonically active Owens Valley of east-central California, and whose lavas are interbedded with deposits from Pleistocene glaciations in the Sierra Nevada Range. Previous geochronology indicates an ˜1.2 Ma history of volcanism, but the eruption ages and distribution of volcanic products associated with the most-recent eruptions have been poorly resolved. To delimit the timing and products of the youngest volcanism, we combine field mapping and cosmogenic 36Cl dating of basaltic lava flows in the area where lavas with youthful morphology and well-preserved flow structures are concentrated. Field mapping and petrology reveal approximately 15 vents and 6 principal flow units with variable geochemical composition and mineralogy. Cosmogenic 36Cl exposure ages for lava flow units from the top, middle, and bottom of the volcanic stratigraphy indicate eruptions at ˜17, 27, and 40 ka, revealing several different and previously unrecognized episodes of late Pleistocene volcanism. Olivine to plagioclase-pyroxene phyric basalt erupted from several vents during the most recent episode of volcanism at ˜17 ka, and produced a lava flow field covering ˜35 km2. The late Pleistocene 36Cl exposure ages indicate that moraine and pluvial shoreline deposits that overlie or modify the youngest Big Pine lavas reflect Tioga stage glaciation in the Sierra Nevada and the shore of paleo-Owens Lake during the last glacial cycle.

  2. Late Pleistocene ages for the most recent volcanism and glacial-pluvial deposits at Big Pine volcanic field, California, USA, from cosmogenic 36Cl dating

    USGS Publications Warehouse

    Vazquez, Jorge A.; Woolford, Jeff M

    2015-01-01

    The Big Pine volcanic field is one of several Quaternary volcanic fields that poses a potential volcanic hazard along the tectonically active Owens Valley of east-central California, and whose lavas are interbedded with deposits from Pleistocene glaciations in the Sierra Nevada Range. Previous geochronology indicates an ∼1.2 Ma history of volcanism, but the eruption ages and distribution of volcanic products associated with the most-recent eruptions have been poorly resolved. To delimit the timing and products of the youngest volcanism, we combine field mapping and cosmogenic 36Cl dating of basaltic lava flows in the area where lavas with youthful morphology and well-preserved flow structures are concentrated. Field mapping and petrology reveal approximately 15 vents and 6 principal flow units with variable geochemical composition and mineralogy. Cosmogenic 36Cl exposure ages for lava flow units from the top, middle, and bottom of the volcanic stratigraphy indicate eruptions at ∼17, 27, and 40 ka, revealing several different and previously unrecognized episodes of late Pleistocene volcanism. Olivine to plagioclase-pyroxene phyric basalt erupted from several vents during the most recent episode of volcanism at ∼17 ka, and produced a lava flow field covering ∼35 km2. The late Pleistocene 36Cl exposure ages indicate that moraine and pluvial shoreline deposits that overlie or modify the youngest Big Pine lavas reflect Tioga stage glaciation in the Sierra Nevada and the shore of paleo-Owens Lake during the last glacial cycle.

  3. Dating Violence

    MedlinePlus

    ... Parents of Teens Crime, Teens, and Trauma Assault Bullying and Harassment Child Sexual Abuse Dating Violence Sexual ... Parents of Teens Crime, Teens, and Trauma Assault Bullying and Harassment Child Sexual Abuse Dating Violence Sexual ...

  4. Dating the Vinland Map

    ScienceCinema

    None

    2013-07-17

    Scientists from Brookhaven National Laboratory, the University of Arizona, and the Smithsonian Institution used carbon-dating technology to determine the age of a controversial parchment that might be the first-ever map of North America.

  5. Dating the Vinland Map

    SciTech Connect

    2013-01-04

    Scientists from Brookhaven National Laboratory, the University of Arizona, and the Smithsonian Institution used carbon-dating technology to determine the age of a controversial parchment that might be the first-ever map of North America.

  6. Improving the knowledge of pesticide and nitrate transfer processes using age-dating tools (CFC, SF6, 3H) in a volcanic island (Martinique, French West Indies).

    PubMed

    Gourcy, Laurence; Baran, Nicole; Vittecoq, Benoit

    2009-09-01

    Numerous successful examples of CFC and SF(6) groundwater dating applications were recently published. However the proposed CFC/SF(6) method needs various hydrodynamic parameters that are not always available. In order to predict groundwater-quality trends in areas where the hydrogeological context is poorly known, a dating method using tritium, CFC and SF(6) was successfully implemented in Martinique. Hydrogeological understanding is limited in this volcanic island where groundwater contamination by pesticides and nitrate has been recently proven in various areas. A negative correlation was observed between nitrate concentrations and groundwater ages while pesticide contamination showed a more complex schema. Consequently the presence of old groundwater clearly explained the absence or low pesticide and nitrate concentrations in some areas. However a possible degradation of the water quality is to be feared in the future. In view of the relatively long transfer times and the complexity of the remobilization processes of solutes, the expected effects of any modifications in the use of fertilizers, or of changes in pesticide-use legislation, would take a long time to become apparent. PMID:19631404

  7. Improving the knowledge of pesticide and nitrate transfer processes using age-dating tools (CFC, SF 6, 3H) in a volcanic island (Martinique, French West Indies)

    NASA Astrophysics Data System (ADS)

    Gourcy, Laurence; Baran, Nicole; Vittecoq, Benoit

    2009-09-01

    Numerous successful examples of CFC and SF 6 groundwater dating applications were recently published. However the proposed CFC/SF 6 method needs various hydrodynamic parameters that are not always available. In order to predict groundwater-quality trends in areas where the hydrogeological context is poorly known, a dating method using tritium, CFC and SF 6 was successfully implemented in Martinique. Hydrogeological understanding is limited in this volcanic island where groundwater contamination by pesticides and nitrate has been recently proven in various areas. A negative correlation was observed between nitrate concentrations and groundwater ages while pesticide contamination showed a more complex schema. Consequently the presence of old groundwater clearly explained the absence or low pesticide and nitrate concentrations in some areas. However a possible degradation of the water quality is to be feared in the future. In view of the relatively long transfer times and the complexity of the remobilization processes of solutes, the expected effects of any modifications in the use of fertilizers, or of changes in pesticide-use legislation, would take a long time to become apparent.

  8. ALPHA SPECTROMETRIC EVALUATION OF SRM-995 AS A POTENTIAL URANIUM/THORIUM DOUBLE TRACER SYSTEM FOR AGE-DATING URANIUM MATERIALS

    SciTech Connect

    Beals, D.

    2011-12-06

    Uranium-233 (t{sub 1/2} {approx} 1.59E5 years) is an artificial, fissile isotope of uranium that has significant importance in nuclear forensics. The isotope provides a unique signature in determining the origin and provenance of uranium-bearing materials and is valuable as a mass spectrometric tracer. Alpha spectrometry was employed in the critical evaluation of a {sup 233}U standard reference material (SRM-995) as a dual tracer system based on the in-growth of {sup 229}Th (t{sub 1/2} {approx} 7.34E3 years) for {approx}35 years following radiochemical purification. Preliminary investigations focused on the isotopic analysis of standards and unmodified fractions of SRM-995; all samples were separated and purified using a multi-column anion-exchange scheme. The {sup 229}Th/{sup 233}U atom ratio for SRM-995 was found to be 1.598E-4 ({+-} 4.50%) using recovery-corrected radiochemical methods. Using the Bateman equations and relevant half-lives, this ratio reflects a material that was purified {approx} 36.8 years prior to this analysis. The calculated age is discussed in contrast with both the date of certification and the recorded date of last purification.

  9. Schmidt-hammer exposure-age dating (SHD) of Lateglacial rock glacier systems near the eastern margin of the European Alps

    NASA Astrophysics Data System (ADS)

    Kellerer-Pirklbauer, Andreas

    2016-04-01

    Rock glaciers are widespread permafrost landforms in Austria. Various rock glacier inventories list more than 4500 rock glaciers in the country; some 30-40% of them are intact. Relict (permafrost free) and pseudo-relict rock glaciers (sporadic and isolated permafrost particularly near the root zone) prevail in number. Rock glaciers are commonly formed over a period of several ka. Dating such landforms helps to understand palaeoclimatic conditions. In this study three rock glaciers consisting of gneiss were dated applying the Schmidt-hammer exposure-age dating (SHD) method. The rock glaciers are located at three neighbouring cirques in the Seckauer Tauern Range named Reichart Rock Glacier (RRG, area 1.26 km², length 1800 m, elevation range 1520-1940 m a.s.l.), Schöneben Rock Glacier (SRG, 0.11 km², 750 m, 1715-1905 m a.s.l.), and Dürrtal Rock Glacier (DRG, 0.08 km², 850 m, 1750-1980 m a.s.l.). RRG is one of the largest rock glaciers in Austria. All three landforms are influenced by lenses of permafrost at present (as indicated by ERT). During the LGM the Seckauer Tauern were covered by valley glaciers and deglaciation occurred presumably already early in the Alpine Lateglacial period. An analogue N-type Schmidt-hammer (proceq) was used for measuring the surface strength of stable blocks at the rock glacier surface by recording a rebound value (R-value) of a spring-loaded bolt. The R-value gives a relative measure of the surface hardness and hence time since exposure to weathering. Eight (RRG) or six (SRG, DRG) Schmidt-hammer measurement sites (with 50-100 individual readings) aligned along longitudinal transects (=former central flow line) between a talus slope (with relatively fresh boulders) in the root zone and the frontal ridge were measured. Mean R-value differences of 30.5 at RRG, 25.1 at SRG, and 20.7 at DRG were revealed along the three transects. The differences between the lowest and the highest R-value at the rock glaciers itself were 19.0 at RRG, 15

  10. Dating Violence

    ERIC Educational Resources Information Center

    Stader, David L.

    2011-01-01

    Dating violence is a form of student-on-student victimization and is a serious school safety issue. Research indicates that at a minimum, 10 percent of high school students are victims of dating violence in one form or another. Among female high school students that date, some data indicate that as many as 30 percent may be victims of dating…

  11. DATE PALM

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This book chapter reviews date palm biology and cultivation. Date palm (Phoenix dactylifera L.) is one of the oldest fruit crops grown in the arid regions of the Arabian Peninsula, North Africa, and the Middle East. The exact origin of the date palm is unknown but most probably the area of origin w...

  12. Electronic Absolute Cartesian Autocollimator

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.

    2006-01-01

    An electronic absolute Cartesian autocollimator performs the same basic optical function as does a conventional all-optical or a conventional electronic autocollimator but differs in the nature of its optical target and the manner in which the position of the image of the target is measured. The term absolute in the name of this apparatus reflects the nature of the position measurement, which, unlike in a conventional electronic autocollimator, is based absolutely on the position of the image rather than on an assumed proportionality between the position and the levels of processed analog electronic signals. The term Cartesian in the name of this apparatus reflects the nature of its optical target. Figure 1 depicts the electronic functional blocks of an electronic absolute Cartesian autocollimator along with its basic optical layout, which is the same as that of a conventional autocollimator. Referring first to the optical layout and functions only, this or any autocollimator is used to measure the compound angular deviation of a flat datum mirror with respect to the optical axis of the autocollimator itself. The optical components include an illuminated target, a beam splitter, an objective or collimating lens, and a viewer or detector (described in more detail below) at a viewing plane. The target and the viewing planes are focal planes of the lens. Target light reflected by the datum mirror is imaged on the viewing plane at unit magnification by the collimating lens. If the normal to the datum mirror is parallel to the optical axis of the autocollimator, then the target image is centered on the viewing plane. Any angular deviation of the normal from the optical axis manifests itself as a lateral displacement of the target image from the center. The magnitude of the displacement is proportional to the focal length and to the magnitude (assumed to be small) of the angular deviation. The direction of the displacement is perpendicular to the axis about which the

  13. Paleo-Environment and C-14 Dating: The Key to the Depositional Age of the Tha Chang and Related Sand Pits, Northeastern Thailand

    NASA Technical Reports Server (NTRS)

    Putthapiban, P.; Zolensky, M.; Jull, T.; Demartino, M.; Salyapongse, S.

    2012-01-01

    Tha Chang sand pits, Nakhon Ratchasima Province and many other sand pits in the area adjacent to the Mun River are characterized by their fluviatile environment in association with mass wasting deposits, along the paleo-river channel and the flood plain of the Mun River. Sediments of these deposits are characterized by clasts of various rock types especially the resistant ones with frequent big tree trunks, logs and wood fragments in different sizes and various stages of transformation from moldering stage to lignification and petrification. Widespread pyritization of the lower horizon suggests strongly reducing environment during burial. The Tha Chang deposits have been received much attention from geoscientists especially paleontologist communities, as they contain fragments of some distinct vertebrate species such as Stegadon sp., hominoid primate, rhinoceros Aceratherium and others. Based on the associated mammal fauna and hominoid fossils, the late Miocene ( 9 - 6 Ma) was given for the time of deposition of this sand and gravel unit. Some other reports believed that sediments and materials of these sand and gravel quarries (pits) were deposited by high-energy flood pulses contemporaneous with the tektites forming event during mid-Pleistocene at c. 0.8 Ma. Interpretation from Palynostratigraphical study suggested that the lower horizon of Tha Chang sand pit was deposited during Pliocene/Pleistocene period and the upper horizons are Pleistoncene/Holocene. It is crystal clear that all the fluviatile sediments including tektites and almost all fossil fragments being deposited in these sand pits were, likely a multiple times reworked materials. Only some old bamboo trees, some old crowling trees and fossils grasses observed on the old river bank are considered in situ. C-14 dating of 5 old wood specimens from Tha Chang Sand Pits, 15 old wood specimens from Chumpuang Sand Pits and one sample of old pottery from a Chumpuang Sand Pit were carried out in the NSF

  14. ABSOLUTE POLARIMETRY AT RHIC.

    SciTech Connect

    OKADA; BRAVAR, A.; BUNCE, G.; GILL, R.; HUANG, H.; MAKDISI, Y.; NASS, A.; WOOD, J.; ZELENSKI, Z.; ET AL.

    2007-09-10

    Precise and absolute beam polarization measurements are critical for the RHIC spin physics program. Because all experimental spin-dependent results are normalized by beam polarization, the normalization uncertainty contributes directly to final physics uncertainties. We aimed to perform the beam polarization measurement to an accuracy Of {Delta}P{sub beam}/P{sub beam} < 5%. The absolute polarimeter consists of Polarized Atomic Hydrogen Gas Jet Target and left-right pairs of silicon strip detectors and was installed in the RHIC-ring in 2004. This system features proton-proton elastic scattering in the Coulomb nuclear interference (CNI) region. Precise measurements of the analyzing power A{sub N} of this process has allowed us to achieve {Delta}P{sub beam}/P{sub beam} = 4.2% in 2005 for the first long spin-physics run. In this report, we describe the entire set up and performance of the system. The procedure of beam polarization measurement and analysis results from 2004-2005 are described. Physics topics of AN in the CNI region (four-momentum transfer squared 0.001 < -t < 0.032 (GeV/c){sup 2}) are also discussed. We point out the current issues and expected optimum accuracy in 2006 and the future.

  15. Spatial and temporal variation of the last ice age mega-floods in the Pacific Northwest: Sediment provenance using single-aliquot K/Ar dating

    NASA Astrophysics Data System (ADS)

    Gombiner, J.; Hendy, I. L.; Hemming, S. R.; Fleisher, M. Q.; Pierce, E.; Mesko, G.; Dale, C. L.; Ages-Argon GeochronologyThe Earth Sciences

    2010-12-01

    Glacial outburst floods (jokulhaups) are important, but poorly understood, drivers of climate change during large-scale deglaciations. Meltwater fluxes are one of the climate forcings with the most uncertain histories included in climate modeling of the last 21 kyr. Outburst flood events are not included in modeled meltwater fluxes due to their small volume, though they are one of the fastest delivery mechanisms for freshwater to the ocean. The most significant outburst floods known to have occurred during the last deglaciation came from glacial Lake Missoula between 18 and 15 kyr BP. Although the volume of meltwater delivered to the North Pacific Ocean was small, the speed of delivery and sediment content of these floods was large. Here we present data that constrain the location and timing of outburst flooding to the N Pacific. Single aliquot bulk K/Ar dates of fine silts and clays from a deep sea core collected off Vancouver Island, British Columbia [MD-02-2496 (48°58’47”N: 127°02’14”W; 2043m water depth)] provide a geochemical fingerprint of the provenance of glacial marine sediments. K/Ar ages, combined with mapped continental geology, allow for the identification of potential source regions for individual flood layers in the core. K/Ar ages in this study represent an integrated age of the entire sediment package delivered to the core site. This includes the Proterozoic Belt-Purcell metasediments (which glacial Lake Missoula covered), the Miocene/Pliocene Columbia Plateau Basalts (which were heavily eroded by the Missoula Floods), and the largely Cenozoic rocks of the coastal and Cascade mountain ranges. Initial results indicate a significant variation in K/Ar ages between background sedimentation and flood deposition events. Missoula Flood outburst sediments appear to have K/Ar ages of around 300 million years while background sediments appear to have K/Ar ages of less than 100 million years. Timing of outburst flood deposits has been determined by

  16. Rare-element granitic pegmatite of Miocene age emplaced in UHP rocks from Visole, Pohorje Mountains (Eastern Alps, Slovenia): accessory minerals, monazite and uraninite chemical dating

    NASA Astrophysics Data System (ADS)

    Uher, Pavel; Janák, Marian; Konečný, Patrik; Vrabec, Mirijam

    2014-04-01

    The granitic pegmatite dike intruded the Cretaceous UHP rocks at Visole, near Slovenska Bistrica, in the Pohorje Mountains (Slovenia). The rock consists mainly of K-feldspar, albite and quartz, subordinate muscovite and biotite, while the accessory minerals include spessartine-almandine, zircon, ferrocolumbite, fluorapatite, monazite- (Ce), uraninite, and magnetite. Compositions of garnet (Sps48-49Alm45-46Grs + And3-4 Prp1.5-2), metamict zircon with 3.5 to 7.8 wt. % HfO2 [atom. 100Hf/(Hf + Zr) = 3.3-7.7] and ferrocolumbite [atom. Mn/(Mn + Fe) = 0.27-0.43, Ta/(Ta + Nb) = 0.03-0.46] indicate a relatively low to medium degree of magmatic fractionation, characteristic of the muscovite - rare-element class or beryl-columbite subtype of the rare-element class pegmatites. Monazite-(Ce) reveals elevated Th and U contents (≤11 wt. % ThO2, ≤5 wt. % UO2). The monazite-garnet geothermometer shows a possible precipitation temperature of ~495 ± 30 °C at P~4 to 5 kbar. Chemical U-Th-Pb dating of the monazite yielded a Miocene age (17.2 ± 1.8 Ma), whereas uraninite gave a younger (~14 Ma) age. These ages are comtemporaneous with the main crystallization and emplacement of the Pohorje pluton and adjacent volcanic rocks (20 to 15 Ma), providing the first documented evidence of Neogene granitic pegmatites in the Eastern Alps. Consequently, the Visole pegmatite belongs to the youngest rare-element granitic pegmatite populations in Europe, together with the Paleogene pegmatite occurrences along the Periadriatic (Insubric) Fault System in the Alps and in the Rhodope Massif, as well as the Late Miocene to Pliocene pegmatites in the Tuscany magmatic province (mainly on the Island of Elba).

  17. Radiocarbon Dating.

    PubMed

    Van Strydonck, Mark

    2016-04-01

    Although most historians and art historians consider the radiocarbon dating technique not to be very precise by their criteria, the method has gained much importance over the last decades. Radiocarbon dating is increasingly used in the field of textile research and old polychrome statues, but also objects made of ivory, stucco, paper, and parchment are dated with the technique. Especially after the introduction of the AMS technique, a boom of this type of research has been noticed. PMID:27573138

  18. Use of National and International Growth Charts for Studying Height in European Children: Development of Up-To-Date European Height-For-Age Charts

    PubMed Central

    Bonthuis, Marjolein; van Stralen, Karlijn J.; Verrina, Enrico; Edefonti, Alberto; Molchanova, Elena A.; Hokken-Koelega, Anita C. S.; Schaefer, Franz; Jager, Kitty J.

    2012-01-01

    Background Growth charts based on data collected in different populations and time periods are key tools to assess children’s linear growth. We analyzed the impact of geographic factors and the secular trend on height-for-age charts currently used in European populations, developed up-to-date European growth charts, and studied the effect of using different charts in a sample of growth retarded children. Methods and Findings In an international survey we obtained 18 unique national height-for-age charts from 28 European countries and compared them with charts from the World Health Organization (WHO), Euro-Growth reference, and Centers of Disease Control and Prevention (CDC). As an example, we obtained height data from 3,534 children with end-stage renal disease (ESRD) from 13 countries via the ESPN/ERA-EDTA registry, a patient group generally suffering from growth retardation. National growth charts showed a clear secular trend in height (mean height increased on average 0.6 cm/decade) and a North-South height gradient in Europe. For countries without a recent (>1990) national growth chart novel European growth charts were constructed from Northern and Southern European reference populations, reflecting geographic height differences in mean final height of 3.9 cm in boys and 3.8 cm in girls. Mean height SDS of 2- to 17-year-old ESRD patients calculated from recent national or derived European growth charts (−1.91, 95% CI: −1.97 to −1.85) was significantly lower than when using CDC or WHO growth charts (−1.55, 95% CI: −1.61 to −1.49) (P<0.0001). Conclusion Differences between height-for-age charts may reflect true population differences, but are also strongly affected by the secular trend in height. The choice of reference charts substantially affects the clinical decision whether a child is considered short-for-age. Therefore, we advocate using recent national or European height-for-age charts derived from recent national data when monitoring growth

  19. Implants as absolute anchorage.

    PubMed

    Rungcharassaeng, Kitichai; Kan, Joseph Y K; Caruso, Joseph M

    2005-11-01

    Anchorage control is essential for successful orthodontic treatment. Each tooth has its own anchorage potential as well as propensity to move when force is applied. When teeth are used as anchorage, the untoward movements of the anchoring units may result in the prolonged treatment time, and unpredictable or less-than-ideal outcome. To maximize tooth-related anchorage, techniques such as differential torque, placing roots into the cortex of the bone, the use of various intraoral devices and/or extraoral appliances have been implemented. Implants, as they are in direct contact with bone, do not possess a periodontal ligament. As a result, they do not move when orthodontic/orthopedic force is applied, and therefore can be used as "absolute anchorage." This article describes different types of implants that have been used as orthodontic anchorage. Their clinical applications and limitations are also discussed. PMID:16463910

  20. Absolute Equilibrium Entropy

    NASA Technical Reports Server (NTRS)

    Shebalin, John V.

    1997-01-01

    The entropy associated with absolute equilibrium ensemble theories of ideal, homogeneous, fluid and magneto-fluid turbulence is discussed and the three-dimensional fluid case is examined in detail. A sigma-function is defined, whose minimum value with respect to global parameters is the entropy. A comparison is made between the use of global functions sigma and phase functions H (associated with the development of various H-theorems of ideal turbulence). It is shown that the two approaches are complimentary though conceptually different: H-theorems show that an isolated system tends to equilibrium while sigma-functions allow the demonstration that entropy never decreases when two previously isolated systems are combined. This provides a more complete picture of entropy in the statistical mechanics of ideal fluids.

  1. The absolute chronology and thermal processing of solids in the solar protoplanetary disk.

    PubMed

    Connelly, James N; Bizzarro, Martin; Krot, Alexander N; Nordlund, Åke; Wielandt, Daniel; Ivanova, Marina A

    2012-11-01

    Transient heating events that formed calcium-aluminum-rich inclusions (CAIs) and chondrules are fundamental processes in the evolution of the solar protoplanetary disk, but their chronology is not understood. Using U-corrected Pb-Pb dating, we determined absolute ages of individual CAIs and chondrules from primitive meteorites. CAIs define a brief formation interval corresponding to an age of 4567.30 ± 0.16 million years (My), whereas chondrule ages range from 4567.32 ± 0.42 to 4564.71 ± 0.30 My. These data refute the long-held view of an age gap between CAIs and chondrules and, instead, indicate that chondrule formation started contemporaneously with CAIs and lasted ~3 My. This time scale is similar to disk lifetimes inferred from astronomical observations, suggesting that the formation of CAIs and chondrules reflects a process intrinsically linked to the secular evolution of accretionary disks. PMID:23118187

  2. Dating Violence

    MedlinePlus

    ... Dating violence can cause serious harm to your body and your emotions. If you are in an abusive relationship, get help. Leaving an abusive dating relationship See a doctor or nurse to take care of any physical problems. And reach out for support for your emotional ...

  3. Ground water/surface water interactions in Lake Naivasha, Kenya, using delta 18O, delta D, and 3H/3He age-dating.

    PubMed

    Ojiambo, B S; Poreda, R J; Lyons, W B

    2001-01-01

    We have analyzed a series of ground water samples from the Lake Naivasha region, Kenya, for their helium isotopic composition. Lake Naivasha is unique among the East Africa Rift Valley lakes in that it is fresh. It has long been thought that the low salinity of this lake is due, in part, to rapid water loss from the lake into the local ground water system. Our results show that the Olkaria geothermal waters, south of the lake, are devoid of tritium and, thus, are more than 50 years old. An important implication of these results is that even if Olkaria geothermal reservoir water originated from Lake Naivasha, it has been underground for a long time, (> 50 years) and is not derived from present-day Lake Naivasha water. This flow time is of the same order of magnitude as conservative major solutes, such as chloride, as determined through residence time calculations. On the north side of Lake Naivasha, deep wells (91 m) have water approximately 20 years old. Water from these wells has stable isotopic values resembling those of nearby rivers, and high-elevation eastern Rift water. This indicates that this water recharges from rains from high eastern Rift Valley escarpments. Many of the shallow wells on the south side of the lake have 3H/3He ages between four and 17 years. The young ages and the delta 18 O-enriched signature of the water from these wells indicate that they are recharged by a mixture of water from the lake, Rift flanks, and water from deep pumping wells that is recharged during irrigation. Water mixing ratio calculations using delta 18O and delta D isotopes show that about 50% to 70% of the southern ground water system is derived from the lake, while the Olkaria geothermal reservoir water shows that 40% to 50% of this water is originally lake water. Calculated mean recharge rates range from 0.10 to 1.59 m/yr with a mean of 0.52 +/- 0.40 m/yr. Estimated horizontal velocity from 3H/3He age dating between Lake Naivasha and a well about 3 km to the south is

  4. Absolute neutrino mass measurements

    NASA Astrophysics Data System (ADS)

    Wolf, Joachim

    2011-10-01

    The neutrino mass plays an important role in particle physics, astrophysics and cosmology. In recent years the detection of neutrino flavour oscillations proved that neutrinos carry mass. However, oscillation experiments are only sensitive to the mass-squared difference of the mass eigenvalues. In contrast to cosmological observations and neutrino-less double beta decay (0v2β) searches, single β-decay experiments provide a direct, model-independent way to determine the absolute neutrino mass by measuring the energy spectrum of decay electrons at the endpoint region with high accuracy. Currently the best kinematic upper limits on the neutrino mass of 2.2eV have been set by two experiments in Mainz and Troitsk, using tritium as beta emitter. The next generation tritium β-experiment KATRIN is currently under construction in Karlsruhe/Germany by an international collaboration. KATRIN intends to improve the sensitivity by one order of magnitude to 0.2eV. The investigation of a second isotope (137Rh) is being pursued by the international MARE collaboration using micro-calorimeters to measure the beta spectrum. The technology needed to reach 0.2eV sensitivity is still in the R&D phase. This paper reviews the present status of neutrino-mass measurements with cosmological data, 0v2β decay and single β-decay.

  5. Absolute neutrino mass measurements

    SciTech Connect

    Wolf, Joachim

    2011-10-06

    The neutrino mass plays an important role in particle physics, astrophysics and cosmology. In recent years the detection of neutrino flavour oscillations proved that neutrinos carry mass. However, oscillation experiments are only sensitive to the mass-squared difference of the mass eigenvalues. In contrast to cosmological observations and neutrino-less double beta decay (0v2{beta}) searches, single {beta}-decay experiments provide a direct, model-independent way to determine the absolute neutrino mass by measuring the energy spectrum of decay electrons at the endpoint region with high accuracy.Currently the best kinematic upper limits on the neutrino mass of 2.2eV have been set by two experiments in Mainz and Troitsk, using tritium as beta emitter. The next generation tritium {beta}-experiment KATRIN is currently under construction in Karlsruhe/Germany by an international collaboration. KATRIN intends to improve the sensitivity by one order of magnitude to 0.2eV. The investigation of a second isotope ({sup 137}Rh) is being pursued by the international MARE collaboration using micro-calorimeters to measure the beta spectrum. The technology needed to reach 0.2eV sensitivity is still in the R and D phase. This paper reviews the present status of neutrino-mass measurements with cosmological data, 0v2{beta} decay and single {beta}-decay.

  6. Geochemistry and Age Dating of Ancient and Modern CO2 -rich Hydrothermal Systems as Natural Analogues for CO2 storage: Examples from Australia and Eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Uysal, I.; Golding, S.; Esterle, J.; Feng, Y.; Zhao, J.

    2008-12-01

    We investigated physico-chemical conditions during mineral authigenesis in CO2-rich ancient and recent hydrothermal environments in Eastern Australia (Gunnedah and Bowen Basins) and Turkey, respectively. We performed Rb-Sr and U-series dating of clay-carbonate associations and travertine veins respectively to evaluate the degassing and storage history of CO2. Intense carbonate veining and coal seam cleat mineralisation in the Gunnedah Basin took place as a result of heat and CO2 release associated with magmatism during the breakup of Gondwana in the Late Cretaceous. Widespread carbonate veining and cementation in the Bowen Basin occurred as products of basin-wide CO2 rich meteoric hydrothermal fluids during the Late Triassic extension. CO2 has largely been used for carbonate precipitation (calcite, siderite, ankerite and dawsonite) in eastern Australian basins; however, some high proportion of CO2 has been stored in coal seams as adsorbed molecules on coal. Significant CO2 degassing is common in geothermal fields in Turkey, as manifested by recent deposition of travertine pools and terraces as well as travertine vein networks in damage zones of active major fault systems. Trace element geochemistry indicates that transient ascent of CO2-bearing fluids during seismic strain cycles without significant interaction with basement and host rocks resulted in rapid precipitation of the vein travertine near the surface. Such veins and associated breccias formed by hydraulic fracturing in response to overpressure of CO2-rich fluids. Correlation of high-precision U-series ages with global/regional climate events indicates that late Quaternary climate variability may have controlled the geothermal water circulation that regulates CO2 accumulation and the generation of CO2 over-pressurised reservoirs and their behaviour during seismic events.

  7. Absolute Identification by Relative Judgment

    ERIC Educational Resources Information Center

    Stewart, Neil; Brown, Gordon D. A.; Chater, Nick

    2005-01-01

    In unidimensional absolute identification tasks, participants identify stimuli that vary along a single dimension. Performance is surprisingly poor compared with discrimination of the same stimuli. Existing models assume that identification is achieved using long-term representations of absolute magnitudes. The authors propose an alternative…

  8. Be Resolute about Absolute Value

    ERIC Educational Resources Information Center

    Kidd, Margaret L.

    2007-01-01

    This article explores how conceptualization of absolute value can start long before it is introduced. The manner in which absolute value is introduced to students in middle school has far-reaching consequences for their future mathematical understanding. It begins to lay the foundation for students' understanding of algebra, which can change…

  9. Topics in Chemical Instrumentation: Cl. Thermoluminescence. Part III. Application to Archeological Dating.

    ERIC Educational Resources Information Center

    Manche, Emanuel P.; Ewing, Galen W., Ed.

    1979-01-01

    Thermoluminescence and its application to archeological dating are considered in this article. Descriptions are given of the method, the required doses, absolute and relative dating, complications, and the relation of this type of dating to other methods. (SA)

  10. [Geriatrics: an absolute necessity].

    PubMed

    Oostvogel, F J

    1982-02-01

    The medical care for elderly people could be greatly improved. If no specific attention is paid immediately, namely through the various training courses and by way of further and part-time schooling, then this medical care will remain unsatisfactory. This situation worsens continually due to the growing number of elderly people and, within this group, a much higher rate of very aged people. Increasing the care in institutions is altogether unsatisfactory. The problem should be dealt with structurally and the emphasis placed upon prevention and early-diagnosis. There is an urgent need for an integrated method, keeping in mind the limits of the elderly person, from the physical, psychological and social aspects. This demands teamwork in a multidisciplinary system inside as well as outside the institutions. It demands a thorough knowledge of geriatrics based upon gerontology. Geriatricians are urgently needed in this development together with doctors in nursing homes, general practitioners and specialists, so that the necessary care may be established as quickly as possible. PMID:7101393

  11. Dating slate belts using 40Ar/39Ar geochronology and zircon ages from crosscutting plutons: A case study from east-central Maine, USA

    NASA Astrophysics Data System (ADS)

    Ghanem, Hind; Kunk, Michael; Ludman, Allan; Bish, David; Wintsch, Robert

    2016-04-01

    Determining the tectonic significance of slate belts is a persistent problem in many orogenic belts because of the lack of time constraints on the age of deposition and the age(s) of cleavages. We have solved this problem in east-central Maine where the ages of the regional Acadian cleavage (S1) and local ductile fault zone cleavage (S2) were both constrained using 40Ar/39Ar geochronology and the ages of crosscutting plutons. Applying 40Ar/39Ar geochronology to rocks with multiple generations of muscovite was possible because each cleavage-forming muscovite records a crystallization age rather than a cooling age due to the low grade of regional metamorphism. Evidence for metamorphic crystallization in rocks dominated by regional Acadian cleavage (S1) comes from the truncations of detrital and authigenic muscovite and chlorite grains by new muscovite and chlorite grains that define the S1 foliation. In rocks that display two foliations, the evidence comes from the truncations of chlorite and muscovite grains defining all earlier fabrics by new muscovite grains in the younger folia (S2). Step-heating experiments using the 40Ar/39Ar technique on twelve samples all yielded sigmoidal age spectra. The low-temperature steps produced a hump in the age spectra, indicating 39Ar recoil into adjacent interlayered chlorite grains, the latter interlayering confirmed by back-scattered electron imaging. Continuing steps climbed steadily from those with minimum apparent ages as young as ~381 Ma to steps with maximum ages as old as 466 Ma. The samples with the lowest minimum apparent age steps are those in which the S2 cleavage-forming mica population dominates. In contrast, the oldest apparent age steps are from samples that have the highest modal abundance of detrital micas. The Middle Ordovician age of the maximum age steps is interpreted to be the minimum cooling age of the detrital micas. The minimum 40Ar/39Ar age steps of muscovite in the samples that display only S1 cleavage

  12. AMS 14C and OSL/IRSL dating of the Dunaszekcső loess sequence (Hungary): chronology for 20 to 150 ka and implications for establishing reliable age-depth models for the last 40 ka

    NASA Astrophysics Data System (ADS)

    Újvári, Gábor; Molnár, Mihály; Novothny, Ágnes; Páll-Gergely, Barna; Kovács, János; Várhegyi, András

    2014-12-01

    As revealed by 18 AMS radiocarbon and 24 OSL/IRSL ages the Dunaszekcső loess-paleosol sequence is an excellent terrestrial record of paleoenvironmental change in the Carpathian Basin for the last 130 ka, with significant soil forming episodes during the Eemian interglacial (130-115 ka, MIS 5e) and in some subsequent MIS 5 stages, and distinct periods of loess accumulations during the MIS 4 and MIS 2. Charcoals from the sequence made it possible to test the accuracy of 14C ages from mollusc shells. This approach revealed that 14C ages from some gastropods having small shells (<10 mm) (Succinella oblonga, Vitrea crystallina) are statistically indistinguishable from the ages of charcoals, while others (Clausiliidae sp., Chondrula tridens) show age anomalies up to 600-800 years. OSL and pIRIR@290 ages are found to be consistently older, while post-IR OSL ages are younger than the 14C ages from charcoals and molluscs by some thousands of years, except for pIRIR@225 ages that match the radiocarbon ages quite well. OSL and IRSL ages have scatters up to 7-10 thousand years within 40 ka, while charcoals and small molluscs yield consistent ages with relatively low variability. Beyond the observation that some small molluscs seem to yield reliable 14C ages, calibrated 2σ age ranges of the radiocarbon data (ca 500-800 years for 20 to 30 ka) are an order of magnitude narrower than those of the OSL/IRSL methods (1800-4000 years for 25 to 35 ka). Thus, for establishing chronologies within 40 ka, which are both accurate and precise enough to address issues like synchroneity of millennial-scale paleoenvironmental events across regions (e.g. North Atlantic and Europe), AMS radiocarbon dating of shells of specific loess molluscs and charcoals may probably be a powerful chronological tool. However, additional work is definitely required involving 14C and OSL/IRSL dates from other loess sequences to further test the performance of these two supposedly robust chronometers.

  13. Crystallization ages of the A-type magmatism of the Graciosa Province (Southern Brazil): Constraints from zircon U-Pb (ID-TIMS) dating of coeval K-rich gabbro-dioritic rocks

    NASA Astrophysics Data System (ADS)

    Vlach, Silvio R. F.; Siga, Oswaldo; Harara, Ossama M. M.; Gualda, Guilherme A. R.; Basei, Miguel A. S.; Vilalva, Frederico C. J.

    2011-12-01

    Zircon U-Pb (ID-TIMS) ages for gabbro-dioritic rocks and for a monzogranite from the Graciosa Province of A-type granites and syenites, southern Brazil, are presented. Two gabbro-dioritic samples gave concordant ages (580 ± 2, 583 ± 3 Ma), while less precise upper intercept ages were obtained for another one (584 ± 8 Ma) and the monzogranite (585 ± 12 Ma). The best results indicate crystallization ages of the basic-intermediate magmas around 580-583 Ma. Micro-structural evidences and structural relationships between the mafic-intermediate rocks and the much more abundant granites and syenites demonstrate that magmas mingled and partially mixed with one another during emplacement and crystallization. Therefore, the results are representative of the overall magmatism. The extensional A-type magmatism occurred ca. 10-30 Ma after (1) emplacement and crystallization of the high-K calc-alkaline syn- to late-collisional batholiths, (2) peak regional metamorphism, and (3) final amalgamation of the Luis Alves, Curitiba, and Paranaguá terrains. It is suggested that the whole magmatism occurred in a short time interval and there is no evidence of spatial or temporal migration of the magmatic foci. ID-TIMS zircon dating of coeval basic-intermediate rocks may yield better emplacement and crystallization ages than direct dating of granitic and syenitic rocks, which are more susceptible to inheritance and/or late- to post-magmatic disturbances.

  14. Blood pressure targets and absolute cardiovascular risk.

    PubMed

    Odutayo, Ayodele; Rahimi, Kazem; Hsiao, Allan J; Emdin, Connor A

    2015-08-01

    In the Eighth Joint National Committee guideline on hypertension, the threshold for the initiation of blood pressure-lowering treatment for elderly adults (≥60 years) without chronic kidney disease or diabetes mellitus was raised from 140/90 mm Hg to 150/90 mm Hg. However, the committee was not unanimous in this decision, particularly because a large proportion of adults ≥60 years may be at high cardiovascular risk. On the basis of Eighth Joint National Committee guideline, we sought to determine the absolute 10-year risk of cardiovascular disease among these adults through analyzing the National Health and Nutrition Examination Survey (2005-2012). The primary outcome measure was the proportion of adults who were at ≥20% predicted absolute cardiovascular risk and above goals for the Seventh Joint National Committee guideline but reclassified as at target under the Eighth Joint National Committee guideline (reclassified). The Framingham General Cardiovascular Disease Risk Score was used. From 2005 to 2012, the surveys included 12 963 adults aged 30 to 74 years with blood pressure measurements, of which 914 were reclassified based on the guideline. Among individuals reclassified as not in need of additional treatment, the proportion of adults 60 to 74 years without chronic kidney disease or diabetes mellitus at ≥20% absolute risk was 44.8%. This corresponds to 0.8 million adults. The proportion at high cardiovascular risk remained sizable among adults who were not receiving blood pressure-lowering treatment. Taken together, a sizable proportion of reclassified adults 60 to 74 years without chronic kidney disease or diabetes mellitus was at ≥20% absolute cardiovascular risk. PMID:26056340

  15. Absolute paleointensity from Hawaiian lavas younger than 35 ka

    USGS Publications Warehouse

    Valet, J.-P.; Tric, E.; Herrero-Bervera, E.; Meynadier, L.; Lockwood, J.P.

    1998-01-01

    Paleointensity studies have been conducted in air and in argon atmosphere on nine lava flows with radiocarbon ages distributed between 3.3 and 28.2 ka from the Mauna Loa volcano in the big island of Hawaii. Determinations of paleointensity obtained at eight sites depict the same overall pattern as the previous results for the same period in Hawaii, although the overall average field intensity appears to be lower. Since the present results were determined at higher temperatures than in the previous studies, this discrepancy raises questions regarding the selection of low versus high-temperature segments that are usually made for absolute paleointensity. The virtual dipole moments are similar to those displayed by the worldwide data set obtained from dated lava flows. When averaged within finite time intervals, the worldwide values match nicely the variations of the Sint-200 synthetic record of relative paleointensity and confirm the overall decrease of the dipole field intensity during most of this period. The convergence between the existing records at Hawaii and the rest of the world does not favour the presence of persistent strong non-dipole components beneath Hawaii for this period.

  16. Estimating divergence dates and substitution rates in the Drosophila phylogeny.

    PubMed

    Obbard, Darren J; Maclennan, John; Kim, Kang-Wook; Rambaut, Andrew; O'Grady, Patrick M; Jiggins, Francis M

    2012-11-01

    An absolute timescale for evolution is essential if we are to associate evolutionary phenomena, such as adaptation or speciation, with potential causes, such as geological activity or climatic change. Timescales in most phylogenetic studies use geologically dated fossils or phylogeographic events as calibration points, but more recently, it has also become possible to use experimentally derived estimates of the mutation rate as a proxy for substitution rates. The large radiation of drosophilid taxa endemic to the Hawaiian islands has provided multiple calibration points for the Drosophila phylogeny, thanks to the "conveyor belt" process by which this archipelago forms and is colonized by species. However, published date estimates for key nodes in the Drosophila phylogeny vary widely, and many are based on simplistic models of colonization and coalescence or on estimates of island age that are not current. In this study, we use new sequence data from seven species of Hawaiian Drosophila to examine a range of explicit coalescent models and estimate substitution rates. We use these rates, along with a published experimentally determined mutation rate, to date key events in drosophilid evolution. Surprisingly, our estimate for the date for the most recent common ancestor of the genus Drosophila based on mutation rate (25-40 Ma) is closer to being compatible with independent fossil-derived dates (20-50 Ma) than are most of the Hawaiian-calibration models and also has smaller uncertainty. We find that Hawaiian-calibrated dates are extremely sensitive to model choice and give rise to point estimates that range between 26 and 192 Ma, depending on the details of the model. Potential problems with the Hawaiian calibration may arise from systematic variation in the molecular clock due to the long generation time of Hawaiian Drosophila compared with other Drosophila and/or uncertainty in linking island formation dates with colonization dates. As either source of error will

  17. Estimating Divergence Dates and Substitution Rates in the Drosophila Phylogeny

    PubMed Central

    Obbard, Darren J.; Maclennan, John; Kim, Kang-Wook; Rambaut, Andrew; O’Grady, Patrick M.; Jiggins, Francis M.

    2012-01-01

    An absolute timescale for evolution is essential if we are to associate evolutionary phenomena, such as adaptation or speciation, with potential causes, such as geological activity or climatic change. Timescales in most phylogenetic studies use geologically dated fossils or phylogeographic events as calibration points, but more recently, it has also become possible to use experimentally derived estimates of the mutation rate as a proxy for substitution rates. The large radiation of drosophilid taxa endemic to the Hawaiian islands has provided multiple calibration points for the Drosophila phylogeny, thanks to the "conveyor belt" process by which this archipelago forms and is colonized by species. However, published date estimates for key nodes in the Drosophila phylogeny vary widely, and many are based on simplistic models of colonization and coalescence or on estimates of island age that are not current. In this study, we use new sequence data from seven species of Hawaiian Drosophila to examine a range of explicit coalescent models and estimate substitution rates. We use these rates, along with a published experimentally determined mutation rate, to date key events in drosophilid evolution. Surprisingly, our estimate for the date for the most recent common ancestor of the genus Drosophila based on mutation rate (25–40 Ma) is closer to being compatible with independent fossil-derived dates (20–50 Ma) than are most of the Hawaiian-calibration models and also has smaller uncertainty. We find that Hawaiian-calibrated dates are extremely sensitive to model choice and give rise to point estimates that range between 26 and 192 Ma, depending on the details of the model. Potential problems with the Hawaiian calibration may arise from systematic variation in the molecular clock due to the long generation time of Hawaiian Drosophila compared with other Drosophila and/or uncertainty in linking island formation dates with colonization dates. As either source of error will

  18. Age dating and flow path evaluation of groundwater by SF6 and microbe in the foot of Mt. Fuji, central Japan

    NASA Astrophysics Data System (ADS)

    Yamamoto, Chisato; Tsujimura, Maki; Kato, Kenji; Nagaosa, Kazuyo; Sakakibara, Koichi; Umei, Yohei; Ohara, Kazuma

    2016-04-01

    A variety of industries are developed at the foot of volcanic mountains in Japan and the groundwater is major source for industrial activity in those regions. The age of groundwater has been estimated to be from 10 to 30 years in Mt. Fuji regions by using 36Cl and 3H. However, the age has not been evaluated using SF6 with higher time resolution in these regions. Also, the total number of prokaryotes shows a specific value in each spring water, suggesting different path and age of the groundwater. Therefore, we aim to estimate residence time and the groundwater flow in three dimensions using the multi-tracers approach; CFCs, SF6, the total number of prokaryotes, the stable isotopes of oxygen-18, deuterium. We collected totally 25 spring water samples in Mt. Fuji and analyzed concentration of inorganic ions, the stable isotopes of oxygen-18, deuterium, CFCs, SF6. The apparent age of the spring water was estimated to be ranging from 4 to 19 years at the foot of Mt. Fuji. These results are reasonable as considering the existed age data by36Cl (Tosaki, 2008) in this region. The spring water with younger age tends to show higher total number of prokaryotes, suggesting that the groundwater flows dominantly through the shallow and young lava with the higher total number of prokaryotes, leads to younger age. Focusing on a specific spring water, the seasonal change of SF6 and total number of prokaryotes were monitored. The spring water showed a younger age and higher total number of prokaryotes during the high water flow season, whereas it showed an older age and lower total number of prokaryotes. Therefore, the total number of prokaryotes shows a good negative correlation with the residence time of the spring/ groundwater in space and time. This shows a possibility that the total number of prokaryotes could be a useful tracer of groundwater for time and space in the three dimensions information.

  19. Global absolut gravity reference system as replacement of IGSN 71

    NASA Astrophysics Data System (ADS)

    Wilmes, Herbert; Wziontek, Hartmut; Falk, Reinhard

    2015-04-01

    The determination of precise gravity field parameters is of great importance in a period in which earth sciences are achieving the necessary accuracy to monitor and document global change processes. This is the reason why experts from geodesy and metrology joined in a successful cooperation to make absolute gravity observations traceable to SI quantities, to improve the metrological kilogram definition and to monitor mass movements and smallest height changes for geodetic and geophysical applications. The international gravity datum is still defined by the International Gravity Standardization Net adopted in 1971 (IGSN 71). The network is based upon pendulum and spring gravimeter observations taken in the 1950s and 60s supported by the early free fall absolute gravimeters. Its gravity values agreed in every case to better than 0.1 mGal. Today, more than 100 absolute gravimeters are in use worldwide. The series of repeated international comparisons confirms the traceability of absolute gravity measurements to SI quantities and confirm the degree of equivalence of the gravimeters in the order of a few µGal. For applications in geosciences where e.g. gravity changes over time need to be analyzed, the temporal stability of an absolute gravimeter is most important. Therefore, the proposition is made to replace the IGSN 71 by an up-to-date gravity reference system which is based upon repeated absolute gravimeter comparisons and a global network of well controlled gravity reference stations.

  20. Optical and thermoluminescence dating of Middle Stone Age and Kintampo bearing sediments at Birimi, a multi-component archaeological site in Ghana

    NASA Astrophysics Data System (ADS)

    Quickert, Nicole A.; Godfrey-Smith, Dorothy I.; Casey, Joanna L.

    2003-05-01

    We report the first luminescence ages for the archeological and geological sediments forming the substrate of the Birimi archaeological site in the Northern Region of Ghana. The site's significance rests on the fact that it contains a rich collection of artifact assemblages representative of three distinct cultures, and that, on the basis of artifact typology, the earliest assemblage is diagnostic of the Middle Stone Age (MSA) . In situ occurrences of MSA artifacts are found at over 1 m below today's surface. They are overlain by a ceramic-rich complex of a sedentary or semi-sendentary Later Stone Age culture known as the Kintampo. The western half of the site is dominated by the industrial remains of Iron Age smelting activity. Elemental, mineralogical, and sedimentological analysis of the cultural and sub-cultural sedimentary horizons at the site revealed at least three distinct lithostratigraphic units. The quartz sediments are derived from the sandstone of the Gambaga escarpment, mass wasted and accreted fluvially at a rate of 3.2 cm/ka, forming a wide terrace at Birimi. Silts and finer fractions derive from windblown dust, likely from White Volta River and granitic sources to the north. Soil forming processes and wide fluctuations in moisture have progressively reduced the sediments at depth to the resistant quartz and kaolinite, with rich iron oxide coatings, and created two ironstone horizons composed of goethite-cemented quartz nodules. Multiple aliquot green-light stimulated optical ages for 125-150 μm quartz grains yielded ages of 23.6±2.9 and 40.8±11.8 ka for the MSA-bearing sediments, and 58.4±15.3 ka for the base of the terrace. Radiocarbon ages on charcoal from Kintampo-bearing units are 3.36-3.83 ka cal BP, and are supported by thermoluminescence (TL) ages on pottery sherds and burnt house daub fragments of this cultural complex. A 0.4 ka age on sediment from the site's surface confirms that the quartz zeroes well when exposed to natural light

  1. A 13 ± 3 ka age determination of a tholeiite, Pinacate volcanic field, Mexico, and improved methods for 40Ar/ 39Ar dating of young basaltic rocks

    NASA Astrophysics Data System (ADS)

    Turrin, Brent D.; Gutmann, James T.; Swisher, Carl C., III

    2008-11-01

    Among the youngest lava flows of the Pinacate volcanic field, Sonora, Mexico, is a large outpouring of tholeiite, the Ives flow. This tube-fed pahoehoe flow contrasts sharply with other Pinacate lavas in its great volume, alkali-poor composition and morphologic features, which include novel small structures named "spatter tubes." Despite its K-poor character, young age, and the presence of excess 40Ar, we determined a 40Ar/ 39Ar age on samples of this flow at 13 ± 3 ka. Such an age determination is made possible via careful monitoring of the mass discrimination of the mass spectrometer and by stacking results from multiple incremental-heating experiments into a single, composite isochron. This age is among the youngest ever to be determined with such precision by the 40Ar/ 39Ar method on a K-poor tholeiite.

  2. The age of the Keystone thrust: laser-fusion 40Ar/39Ar dating of foreland basin deposits, southern Spring Mountains, Nevada

    USGS Publications Warehouse

    Fleck, R.J.; Carr, M.D.

    1990-01-01

    Nonmarine sedimentary and volcaniclastic foreland-basin deposits in the Spring Mountains are cut by the Contact and Keystone thrusts. These synorogenic deposits, informally designated the Lavinia Wash sequence by Carr (1980), previously were assigned a Late Jurassic to Early Cretaceous(?) age. New 40Ar.39Ar laser-fusion and incremental-heating studies of a tuff bed in the Lavinia Wash sequence support a best estimate age of 99.0 ?? 0.4 Ma, indicating that the Lavinia Wash sequence is actually late Early Cretaceous in age and establishing a maximum age for final emplacement of the Contact and Keystone thrust plates consistent with the remainder of the Mesozoic foreland thrust belt. -from Authors

  3. A comparison of U/Th and rapid-screen 14C dates from Line Island fossil corals

    NASA Astrophysics Data System (ADS)

    Grothe, Pamela R.; Cobb, Kim M.; Bush, Shari L.; Cheng, Hai; Santos, Guaciara M.; Southon, John R.; Lawrence Edwards, R.; Deocampo, Daniel M.; Sayani, Hussein R.

    2016-03-01

    Time-consuming and expensive radiometric dating techniques limit the number of dates available to construct absolute chronologies for high-resolution paleoclimate reconstructions. A recently developed rapid-screen 14C dating technique reduces sample preparation time and per sample costs by 90%, but its accuracy has not yet been tested on shallow-water corals. In this study, we test the rapid-screen 14C dating technique on shallow-water corals by comparing 44 rapid-screen 14C dates to both high-precision 14C dates and U/Th dates from mid- to late-Holocene fossil corals collected from the central tropical Pacific (2-4°N, 157-160°W). Our results show that 42 rapid-screen 14C and U/Th dates agree within uncertainties, confirming closed-system behavior and ensuring chronological accuracy. However, two samples that grew ˜6500 years ago have calibrated 14C ages ˜1000 years younger than the corresponding U/Th ages, consistent with diagenetic alteration as indicated by the presence of 15-23% calcite. Mass balance calculations confirm that the observed dating discrepancies are consistent with 14C addition and U removal, both of which occur during diagenetic calcite recrystallization. Under the assumption that aragonite-to-calcite replacement is linear through time, we estimate the samples' true ages using the measured 14C and U/Th dates and percent calcite values. Results illustrate that the rapid-screen 14C dates of Holocene-aged fossil corals are accurate for samples with less than 2% calcite. Application of this rapid-screen 14C method to the fossil coral rubble fields from Kiritimati Island reveal significant chronological clustering of fossil coral across the landscape, with older ages farther from the water's edge.

  4. Absolute transition probabilities of phosphorus.

    NASA Technical Reports Server (NTRS)

    Miller, M. H.; Roig, R. A.; Bengtson, R. D.

    1971-01-01

    Use of a gas-driven shock tube to measure the absolute strengths of 21 P I lines and 126 P II lines (from 3300 to 6900 A). Accuracy for prominent, isolated neutral and ionic lines is estimated to be 28 to 40% and 18 to 30%, respectively. The data and the corresponding theoretical predictions are examined for conformity with the sum rules.-

  5. Preliminary Ar-40/Ar-39 age spectrum and laser probe dating of the M1 core of the Manson Impact Structure, Iowa: A K-T boundary crater candidate

    NASA Astrophysics Data System (ADS)

    Kunk, M. J.; Snee, L. W.; French, B. M.; Harlan, S. S.; McGee, J. J.

    1993-03-01

    Preliminary Ar-40/Ar-39 age spectrum and laser probe dating results from new drill core from the 35-km-diameter Manson Impact Structure (MIS), Iowa indicates a reasonable possibility that the MIS is a Cretaceous-Tertiary (K-T) boundary impact event. Several different types of samples from a melt-matrix breccia, a unit of apparent crater fill intersected by the M1 core, were analyzed. Ar-40/Ar-39 results from these samples indicate a maximum age for the MIS of about 65.4 plus or minus 0.4(2 sigma) Ma. Petrographic analyses of the samples indicate a high probability that all the dated samples from the melt-matrix breccia contain relict grains that were not entirely melted or degassed at the time of impact, suggesting that the actual age of the MIS could be somewhat younger than our preliminary results indicate. The results are consistent with a previously published age estimate of shocked microcline from the MIS central uplift of 65.7 plus or minus 1.0 Ma.

  6. Preliminary Ar-40/Ar-39 age spectrum and laser probe dating of the M1 core of the Manson Impact Structure, Iowa: A K-T boundary crater candidate

    NASA Technical Reports Server (NTRS)

    Kunk, M. J.; Snee, L. W.; French, B. M.; Harlan, S. S.; Mcgee, J. J.

    1993-01-01

    Preliminary Ar-40/Ar-39 age spectrum and laser probe dating results from new drill core from the 35-km-diameter Manson Impact Structure (MIS), Iowa indicates a reasonable possibility that the MIS is a Cretaceous-Tertiary (K-T) boundary impact event. Several different types of samples from a melt-matrix breccia, a unit of apparent crater fill intersected by the M1 core, were analyzed. Ar-40/Ar-39 results from these samples indicate a maximum age for the MIS of about 65.4 plus or minus 0.4(2 sigma) Ma. Petrographic analyses of the samples indicate a high probability that all the dated samples from the melt-matrix breccia contain relict grains that were not entirely melted or degassed at the time of impact, suggesting that the actual age of the MIS could be somewhat younger than our preliminary results indicate. The results are consistent with a previously published age estimate of shocked microcline from the MIS central uplift of 65.7 plus or minus 1.0 Ma.

  7. Radiometric 81Kr dating identifies 120,000-year-old ice at Taylor Glacier, Antarctica.

    PubMed

    Buizert, Christo; Baggenstos, Daniel; Jiang, Wei; Purtschert, Roland; Petrenko, Vasilii V; Lu, Zheng-Tian; Müller, Peter; Kuhl, Tanner; Lee, James; Severinghaus, Jeffrey P; Brook, Edward J

    2014-05-13

    We present successful (81)Kr-Kr radiometric dating of ancient polar ice. Krypton was extracted from the air bubbles in four ∼350-kg polar ice samples from Taylor Glacier in the McMurdo Dry Valleys, Antarctica, and dated using Atom Trap Trace Analysis (ATTA). The (81)Kr radiometric ages agree with independent age estimates obtained from stratigraphic dating techniques with a mean absolute age offset of 6 ± 2.5 ka. Our experimental methods and sampling strategy are validated by (i) (85)Kr and (39)Ar analyses that show the samples to be free of modern air contamination and (ii) air content measurements that show the ice did not experience gas loss. We estimate the error in the (81)Kr ages due to past geomagnetic variability to be below 3 ka. We show that ice from the previous interglacial period (Marine Isotope Stage 5e, 130-115 ka before present) can be found in abundance near the surface of Taylor Glacier. Our study paves the way for reliable radiometric dating of ancient ice in blue ice areas and margin sites where large samples are available, greatly enhancing their scientific value as archives of old ice and meteorites. At present, ATTA (81)Kr analysis requires a 40-80-kg ice sample; as sample requirements continue to decrease, (81)Kr dating of ice cores is a future possibility. PMID:24753606

  8. Radiometric 81Kr dating identifies 120,000-year-old ice at Taylor Glacier, Antarctica

    PubMed Central

    Buizert, Christo; Baggenstos, Daniel; Jiang, Wei; Purtschert, Roland; Petrenko, Vasilii V.; Lu, Zheng-Tian; Müller, Peter; Kuhl, Tanner; Lee, James; Severinghaus, Jeffrey P.; Brook, Edward J.

    2014-01-01

    We present successful 81Kr-Kr radiometric dating of ancient polar ice. Krypton was extracted from the air bubbles in four ∼350-kg polar ice samples from Taylor Glacier in the McMurdo Dry Valleys, Antarctica, and dated using Atom Trap Trace Analysis (ATTA). The 81Kr radiometric ages agree with independent age estimates obtained from stratigraphic dating techniques with a mean absolute age offset of 6 ± 2.5 ka. Our experimental methods and sampling strategy are validated by (i) 85Kr and 39Ar analyses that show the samples to be free of modern air contamination and (ii) air content measurements that show the ice did not experience gas loss. We estimate the error in the 81Kr ages due to past geomagnetic variability to be below 3 ka. We show that ice from the previous interglacial period (Marine Isotope Stage 5e, 130–115 ka before present) can be found in abundance near the surface of Taylor Glacier. Our study paves the way for reliable radiometric dating of ancient ice in blue ice areas and margin sites where large samples are available, greatly enhancing their scientific value as archives of old ice and meteorites. At present, ATTA 81Kr analysis requires a 40–80-kg ice sample; as sample requirements continue to decrease, 81Kr dating of ice cores is a future possibility. PMID:24753606

  9. New Sakmarian ages for the Rio Bonito formation (Paraná Basin, southern Brazil) based on LA-ICP-MS U-Pb radiometric dating of zircons crystals

    NASA Astrophysics Data System (ADS)

    Cagliari, Joice; Lavina, Ernesto Luiz Correa; Philipp, Ruy Paulo; Tognoli, Francisco Manoel Wohnrath; Basei, Miguel Angelo Stipp; Faccini, Ubiratan Ferrucio

    2014-12-01

    Two ash fall beds (tonstein) sampled from the post-glacial Permian deposits of the Paraná Basin have provided new U-Pb radiometric age constraints for this stratigraphic interval. The zircon grains were recovered from tonstein layers interbedded with fine-grained and carbonaceous lithologies in the middle portion of the Rio Bonito Formation. In both samples, the dominant population is interpreted as generated by explosive volcanism, as having formed immediately before the eruption. Based on 238U/206Pb, the selected zircon grains from the dominant population have weighted mean ages of 290.6 ± 2.8 Ma and 281.7 ± 3.2 Ma, corresponding to the Sakmarian and Kungurian ages in the Cisuralian epoch, respectively. These ages constrain the time of the deposition of the tonstein horizons and have important stratigraphic implications for the Late Paleozoic evolution of both the Paraná Basin and the southwestern region of Gondwana. The results presented here and the radiometric data already published suggest that deposition of the post-glacial coal-bearing deposits of the Rio Bonito Formation was probably initiated before the Early Permian. Thus, we infer that the climate had already ameliorated by this period in order to allow for the formation and accumulation of peat in this region of Gondwana.

  10. Integrated J- and H-band spectra of globular clusters in the LMC: implications for stellar population models and galaxy age dating

    NASA Astrophysics Data System (ADS)

    Lyubenova, M.; Kuntschner, H.; Rejkuba, M.; Silva, D. R.; Kissler-Patig, M.; Tacconi-Garman, L. E.

    2012-07-01

    Context. The rest-frame near-IR spectra of intermediate age (1-2 Gyr) stellar populations are dominated by carbon based absorption features offering a wealth of information. Yet, spectral libraries that include the near-IR wavelength range do not sample a sufficiently broad range of ages and metallicities to allow for accurate calibration of stellar population models and thus the interpretation of the observations. Aims: In this paper we investigate the integrated J- and H-band spectra of six intermediate age and old globular clusters in the Large Magellanic Cloud (LMC). Methods: The observations for six clusters were obtained with the SINFONI integral field spectrograph at the ESO VLT Yepun telescope, covering the J (1.09-1.41 μm) and H-band (1.43-1.86 μm) spectral range. The spectral resolution is 6.7 Å in J and 6.6 Å in H-band (FWHM). The observations were made in natural seeing, covering the central 24″ × 24″ of each cluster and in addition sampling the brightest eight red giant branch and asymptotic giant branch (AGB) star candidates within the clusters' tidal radii. Targeted clusters cover the ages of ~1.3 Gyr (NGC 1806, NGC 2162), 2 Gyr (NGC 2173) and ~13 Gyr (NGC 1754, NGC 2005, NGC 2019). Results.H-band C2 and K-band 12CO (2-0) feature strengths for the LMC globular clusters are compared to the models of Maraston (2005). C2 is reasonably well reproduced by the models at all ages, while 12CO (2-0) shows good agreement for older (age ≥ 2 Gyr) populations, but the younger (1.3 Gyr) globular clusters do not follow the models. We argue that this is due to the fact that the empirical calibration of the models relies on only a few Milky Way carbon star spectra, which show different 12CO (2-0) index strengths than the LMC stars. The C2 absorption feature strength correlates strongly with age. It is present essentially only in populations that have 1-2 Gyr old stars, while its value is consistent with zero for older populations. The distinct spectral

  11. 29 CFR 4022.10 - Earliest PBGC Retirement Date.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... after the date the participant reaches age 55, the Earliest PBGC Retirement Date for the participant is... reaches age 55, the Earliest PBGC Retirement Date for the participant is the date the participant reaches... participant reaches age 55, the PBGC will make a determination, under the facts and circumstances, as...

  12. Optomechanics for absolute rotation detection

    NASA Astrophysics Data System (ADS)

    Davuluri, Sankar

    2016-07-01

    In this article, we present an application of optomechanical cavity for the absolute rotation detection. The optomechanical cavity is arranged in a Michelson interferometer in such a way that the classical centrifugal force due to rotation changes the length of the optomechanical cavity. The change in the cavity length induces a shift in the frequency of the cavity mode. The phase shift corresponding to the frequency shift in the cavity mode is measured at the interferometer output to estimate the angular velocity of absolute rotation. We derived an analytic expression to estimate the minimum detectable rotation rate in our scheme for a given optomechanical cavity. Temperature dependence of the rotation detection sensitivity is studied.

  13. The Absolute Spectrum Polarimeter (ASP)

    NASA Technical Reports Server (NTRS)

    Kogut, A. J.

    2010-01-01

    The Absolute Spectrum Polarimeter (ASP) is an Explorer-class mission to map the absolute intensity and linear polarization of the cosmic microwave background and diffuse astrophysical foregrounds over the full sky from 30 GHz to 5 THz. The principal science goal is the detection and characterization of linear polarization from an inflationary epoch in the early universe, with tensor-to-scalar ratio r much greater than 1O(raised to the power of { -3}) and Compton distortion y < 10 (raised to the power of{-6}). We describe the ASP instrument and mission architecture needed to detect the signature of an inflationary epoch in the early universe using only 4 semiconductor bolometers.

  14. Absolute calibration of optical flats

    DOEpatents

    Sommargren, Gary E.

    2005-04-05

    The invention uses the phase shifting diffraction interferometer (PSDI) to provide a true point-by-point measurement of absolute flatness over the surface of optical flats. Beams exiting the fiber optics in a PSDI have perfect spherical wavefronts. The measurement beam is reflected from the optical flat and passed through an auxiliary optic to then be combined with the reference beam on a CCD. The combined beams include phase errors due to both the optic under test and the auxiliary optic. Standard phase extraction algorithms are used to calculate this combined phase error. The optical flat is then removed from the system and the measurement fiber is moved to recombine the two beams. The newly combined beams include only the phase errors due to the auxiliary optic. When the second phase measurement is subtracted from the first phase measurement, the absolute phase error of the optical flat is obtained.

  15. The impact of minimum legal drinking age laws on alcohol consumption, smoking, and marijuana use: evidence from a regression discontinuity design using exact date of birth.

    PubMed

    Yörük, Barış K; Yörük, Ceren Ertan

    2011-07-01

    This paper uses a regression discontinuity design to estimate the impact of the minimum legal drinking age laws on alcohol consumption, smoking, and marijuana use among young adults. Using data from the National Longitudinal Survey of Youth (1997 Cohort), we find that granting legal access to alcohol at age 21 leads to an increase in several measures of alcohol consumption, including an up to a 13 percentage point increase in the probability of drinking. Furthermore, this effect is robust under several different parametric and non-parametric models. We also find some evidence that the discrete jump in alcohol consumption at age 21 has negative spillover effects on marijuana use but does not affect the smoking habits of young adults. Our results indicate that although the change in alcohol consumption habits of young adults following their 21st birthday is less severe than previously known, policies that are designed to reduce drinking among young adults may have desirable impacts and can create public health benefits. PMID:21719131

  16. Consideration of geomorphological uncertainties with terrestrial cosmogenic nuclide dating (TCND): combining Schmidt-hammer and 10Be dating, Southern Alps, New Zealand

    NASA Astrophysics Data System (ADS)

    Winkler, Stefan

    2010-05-01

    "by vision". Especially in regions like the Southern Alps affected of considerable neo-tectonic activity and paraglacial erosion, post-depositional movement of any boulders on moraine ridges cannot be excluded a priori. On base on these considerations, an attempt to combine TCND with Schmidt-hammer measurements for the dating of Holocene moraines and the reconstruction of a regional glacier chronology has been developed (Winkler 2009). Cosmogenic 10Be dating delivers ‘absolute' ages for the exposure of boulder surfaces, i.e. the same surface tested with the Schmidt-hammer relative-age dating technique. Therefore, Schmidt-hammer measurements can successfully endorse the selection of representative boulders for TCND and effectively avoid sampling boulders that have been exposed to post-depositional movement (e.g. rotation). Additionally, the number of boulders sampled for TCND can be reduced, positive in the light of economic and conservational considerations. Results from the application of this combined ‘multi-proxy-approach' at a number of individual glaciers in Westland/Tai Poutini and Mt Cook/Aoraki National Parks of the Southern Alps proof its potential. At least three ‘Little Ice Age'-type events culminating around 2,300, 1,600, and 1,000 years ago and predating the "Little Ice Age" have been confirmed. The construction of a dating curve based on both Schmidt-hammer and cosmogenic (10Be) dating results shows high significance and demonstrates the high potential of this attempt. References: Schaefer, J.M., Denton, G.H., Kaplan, M., Putnam, A., Finkel, R.C., Barrell, D.J.A., Andersen, B.G., Schwartz, R., McIntosh, A., Chinn, T. & Schlüchter, C. (2009): High-frequency Holocene glacier fluctuations in New Zealand differ from the northern signature. Science 324, 622 - 625. Winkler, S. (2009): First attempt to combine terrestrial cosmogenic nuclide (10Be) and Schmidt hammer relative-age dating: Strauchon Glacier, Southern Alps, New Zealand. Central European

  17. Development of a precise and accurate age-depth model based on 40Ar/39Ar dating of volcanic material in the ANDRILL (1B) drill core, Southern McMurdo Sound, Antarctica

    NASA Astrophysics Data System (ADS)

    Ross, J. I.; McIntosh, W. C.; Dunbar, N. W.

    2012-10-01

    High precision 40Ar/39Ar dates on a variety of volcanic materials from the AND-1B drill core provide pinning points for defining the chronostratigraphy for the core. The volcanic materials dated include 1) felsic and basaltic tephra, 2) interior of a ~ 3 m thick intermediate submarine lava flow, and 3) felsic and basaltic volcanic clasts. In the upper 600 m of the core, two felsic tephra, two basaltic tephra and the intermediate laval flow yield precise and depositional ages, with further maximum age constraints from volcanic clasts. Below 600 m in the core, tephric intervals are significantly altered and maximum age constraints only are available from volcanic clasts. The ages for eight stratigraphic intervals are 1) 17.17-17.18 mbsf, basaltic clast (maximum depositional age 0.310 ± 0.039 Ma, all errors quoted at 2σ), 2) 52.80-52.82 mbsf, three basaltic clasts (maximum depositional age 0.726 ± 0.052 Ma), 3) 85.27-85.87 mbsf felsic tephra (1.014 ± 0.008 Ma), 4) ~ 112-145 mbsf sequence of basaltic tephra (1.633 ± 0.057 to 1.683 ± 0.055 Ma), 5) 480.97-481.96 mbsf pumice-rich mudstone (4.800 ± 0.076 Ma), 6) 646.30-649.34 mbsf intermediate lava flow (6.48 ± 0.13 Ma), 7) 822.78 mbsf kaersutite phenocrysts from volcanic clasts (maximum depositional age 8.53 ± 0.53 Ma) and 8) ~ 1280 mbsf, three volcanic clasts (maximum depositional age 13.57 ± 0.13 Ma). Minimum average sediment accumulation rates or 102 and 87 m/Ma for the upper and lower 650 m of core, respectively were calculated using the 40Ar/39Ar analyses. The volcanic material recovered from AND-1B also reveals a general northward progression of volcanism in Southern McMurdo Sound.

  18. Micro Radiocarbon Dating - Applications and challenges in Alpine glaciology

    NASA Astrophysics Data System (ADS)

    Hoffmann, Helene; Bohleber, Pascal; Wagenbach, Dietmar

    2015-04-01

    The interpretation of proxy records from ice cores obtained at cold small scale Alpine glaciers is hampered first and foremost because of challenges in obtaining a reliable age scale, especially for highly thinned basal ice. Where conventional stratigraphic dating methods fail, either due to complex flow dynamics or missing layering, radiocarbon measurements of organic impurities are up to now the only option to retrieve absolute age markers. Supplementing stratigraphic records, age of basal ice itself can provide valuable information on paleoclimatic conditions, e.g. related to the onset of formation of the respective ice body. In this respect, potential targets are basal sections of Alpine ice cores and small isolated ice patches or ice caves. Organic material in ice can be separated mainly by size into DOC (Dissolved Organic Carbon) and POC (Particulate Organic Carbon). Here we focus on radiocarbon dating of the POC fraction, because the DOC fraction is known to be biased by in situ production at high Alpine sites. Concentrations of POC in high Alpine ice can be very low, ranging from about 10 µgC per kg ice to 50 µgC per kg ice. This becomes an immediate challenge when sampling ice cores, where available masses for dating are typically in the order of a few hundred grams of ice. After developing an unique sample preparation system we managed to reduce the process blank reproducibly below one microgram carbon, independent of other sample characteristics. Utilizing a gas ion source at the Accelerator Mass Spectrometer MICADAS at the Klaus-Tschira-Lab in Mannheim (Germany) we are now able to reliably date samples with concentrations as low as 10 µg carbon. Accordingly, this approach becomes applicable for high Alpine ice samples. Here we present first results from POC radiocarbon dating of Alpine ice cores along with selected basal ice samples from smaller ice caps and cave ice in order to obtain a broader picture regarding age ranges of Alpine ice bodies. For

  19. Copper-bearing encrustations: a tool for age dating and constraining the physical-chemical regime during the late Quaternary in the Wadi Araba, southern Jordan

    NASA Astrophysics Data System (ADS)

    Dill, H. G.; Techmer, A.; Botz, R.

    2013-07-01

    The alluvial-fluvial drainage system in the Wadi Araba, southern Jordan, incised into Cambrian clastic sedimentary and felsic igneous rocks giving rise to a disseminated Cu-(Mn) mineralization of diagenetic and epigenetic origin along the southern branch of the Dead Sea Transform Fault (=DSTF). During the Late Pleistocene and Holocene, the primary Cu sulfides were replaced by secondary minerals giving rise to hypogene to supergene encrustations, bearing Cu silicates, Cu carbonates, Cu oxychlorides and cupriferous vanadates. They occur in fissures, coat walls and developed even-rim/meniscus and blocky cements in the arenites near the surface. The first generation cement has been interpreted in terms of freshwater vadose hydraulic conditions, while the second-generation blocky cement of chrysocolla and malachite evolved as late cement. The Cu-Si-C fluid system within the Wadi Araba drainage system is the on-shore or subaerial facies of a regressive lacustrine regime called the "Lake Lisan Stage", a precursor of the present-day Dead Sea. Radiocarbon dating (younger than 27,740 ± 1,570 years), oxygen-isotope-based temperature determination (hot brine-related mineralization at 60-80 °C, climate-driven mineralization at 25-30 °C) and thermodynamical calculations let to the subdivision of this secondary Cu mineralization into four stages, whose chemical and mineralogical composition was controlled by the variation of the anion complexes of silica and carbonate and the chlorine contents. The acidity of the pore water positively correlates with the degree of oxidation. The highest aridity and most intensive evaporation deduced from the thermodynamical calculations were achieved during stage 3, which is coeval with late Lake Lisan. Geogene processes causing Cu-enriched encrustations overlap with man-made manganiferous slags. The smelter feed has been derived mainly from Cu ore which developed during Late Pleistocene in the region.

  20. Radioactive dating of the elements

    NASA Technical Reports Server (NTRS)

    Cowan, John J.; Thielemann, Friedrich-Karl; Truran, James W.

    1991-01-01

    The extent to which an accurate determination of the age of the Galaxy, and thus a lower bound on the age of the universe, can be obtained from radioactive dating is discussed. Emphasis is given to the use of the long-lived radioactive nuclei Re-187, Th-232, U-238, and U-235. The nature of the production sites of these and other potential Galactic chronometers is examined along with their production ratios. Age determinations from models of nucleocosmochronology are reviewed and compared with age determination from stellar sources and age constraints form cosmological considerations.

  1. Uranium Series Accessory Crystal Dating of Magmatic Processes

    NASA Astrophysics Data System (ADS)

    Schmitt, Axel K.

    2011-05-01

    Complex and protracted crystallization histories over geologic timescales are recorded in accessory minerals (e.g., zircon, allanite). Although magmatic crystallization was traditionally assumed to occur essentially instantaneously for the purposes of interpreting mineral geochronometers with low absolute time resolution for ancient samples, it emerged relatively recently that magmatic crystallization can occur over extended durations. This discovery arose from applying high-spatial-resolution accessory mineral dating techniques for uranium series isotopes to young volcanic and cognate plutonic rocks. The emerging pattern from these studies is that individual crystals and crystal populations record crystallization episodes lasting from <1,000 to many hundreds of thousands of years. Accessory mineral dating of volcanic rocks and cognate plutonic xenoliths opens new research avenues for crystal age fingerprinting that correlates pyroclastic deposits, lavas, and plutonic rocks by using characteristic age distributions. It also provides direct observations on magmatic accumulation and residence times, and the preeruptive configuration of subterraneous magma bodies and intrusive complexes with implications for the forecasting of volcanic eruptions. Awareness of potentially protracted crystallization in igneous rocks should guide the interpretation of accessory mineral ages.

  2. The AFGL absolute gravity program

    NASA Technical Reports Server (NTRS)

    Hammond, J. A.; Iliff, R. L.

    1978-01-01

    A brief discussion of the AFGL's (Air Force Geophysics Laboratory) program in absolute gravity is presented. Support of outside work and in-house studies relating to gravity instrumentation are discussed. A description of the current transportable system is included and the latest results are presented. These results show good agreement with measurements at the AFGL site by an Italian system. The accuracy obtained by the transportable apparatus is better than 0.1 microns sq sec 10 microgal and agreement with previous measurements is within the combined uncertainties of the measurements.

  3. Identifying sources of dissolved organic carbon in agriculturally dominated rivers using radiocarbon age dating: Sacramento-San Joaquin River Basin, California

    USGS Publications Warehouse

    Sickman, James O.; DiGiorgio, Carol L.; Davisson, M. Lee; Lucero, Delores M.; Bergamaschi, Brian A.

    2010-01-01

    We used radiocarbon measurements of dissolved organic carbon (DOC) to resolve sources of riverine carbon within agriculturally dominated landscapes in California. During 2003 and 2004, average Δ14C for DOC was -254‰ in agricultural drains in the Sacramento-San Joaquin Delta, -218‰ in the San Joaquin River, -175‰ in the California State Water Project and -152‰ in the Sacramento River. The age of bulk DOC transiting the rivers of California's Central Valley is the oldest reported for large rivers and suggests wide-spread loss of soil organic matter caused by agriculture and urbanization. Using DAX 8 adsorbent, we isolated and measured 14C concentrations in hydrophobic acid fractions (HPOA); river samples showed evidence of bomb-pulse carbon with average Δ14C of 91 and 76‰ for the San Joaquin and Sacramento Rivers, respectively, with older HPOA, -204‰, observed in agricultural drains. An operationally defined non-HPOA fraction of DOC was observed in the San Joaquin River with seasonally computed Δ14C values of between -275 and -687‰; the source of this aged material was hypothesized to be physically protected organic-matter in high clay-content soils and agrochemicals (i.e., radiocarbon-dead material) applied to farmlands. Mixing models suggest that the Sacramento River contributes about 50% of the DOC load in the California State Water Project, and agricultural drains contribute approximately one-third of the load. In contrast to studies showing stabilization of soil carbon pools within one or two decades following land conversion, sustained loss of soil organic matter, occurring many decades after the initial agricultural-land conversion, was observed in California's Central Valley.

  4. Radiocarbon dating of terrestrial carbonates

    USGS Publications Warehouse

    Pigati, Jeffrey S.

    2014-01-01

    Terrestrial carbonates encompass a wide range of materials that potentially could be used for radiocarbon (14C) dating. Biogenic carbonates, including shells and tests of terrestrial and aquatic gastropods, bivalves, ostracodes, and foraminifera, are preserved in a variety of late Quaternary deposits and may be suitable for 14C dating. Primary calcareous deposits (marls, tufa, speleothems) and secondary carbonates (rhizoliths, fracture fill, soil carbonate) may also be targeted for dating when conditions are favorable. This chapter discusses issues that are commonly encountered in 14C dating of terrestrial carbonates, including isotopic disequilibrium and open-system behavior, as well as methods used to determine the reliability of ages derived from these materials. Recent methodological advancements that may improve the accuracy and precision of 14C ages of terrestrial carbonates are also highlighted.

  5. Dating sediments using luminescence signals

    SciTech Connect

    Wintle, A. )

    1993-05-01

    Before siting a nuclear power station or a nuclear waste repository, it is necessary to establish that the area has been free of earthquake activity for a sufficient period of time. Evidence of past earthquake activity is often provided by faults in surface sediments. Age limits for fault formation can be set by obtaining the depositional ages of the sediment unit in which the fault was formed and the overlying sediment. A useful technique would be one that dating could be applied to the mineral grains that make up the sediments and that would give the time that has passed since the grains were blown or washed into position. Luminescence dating techniques, of which the most well known is thermo-luminescence (TL), provide such information. This approach has been successful in dating movement on the Wasatch Fault in Utah. A combination of TL and radiocarbon dates indicated that three faulting events had occurred within the past 5000 years. 2 refs., 1 fig.

  6. Antiquity of man in America indicated by radiometric dates on the Yuha burial site

    USGS Publications Warehouse

    Bischoff, J.L.; Merriam, R.; Childers, W.M.; Protsch, R.

    1976-01-01

    MUCH evidence suggests that man was present in the Western Hemisphere before 12,000 yr ago, but the case has remained less than conclusive 1. In some situations, the geological age of the site is reasonably well established but the association or nature of the artefacts is questionable2,3. In other cases, museum specimens of human bones dated by radiocarbon analysis of collagen lack desirable information concerning site location, geology, and stratigraphy even though the accuracy of their absolute ages seems valid4-6. We report here the results of radiometric dates of the Yuha burial site from Imperial County, California, for which the geology and stratigraphy have been documented and reported in detail7. ?? 1976 Nature Publishing Group.

  7. ESR dating of pseudotachylite

    NASA Astrophysics Data System (ADS)

    Shimada, A.; Toyoda, S.; Takagi, H.; Arita, K.

    2002-12-01

    ESR (electron spin resonance) dating method has been used to determine the ages of quaternary events. When a mineral receives natural radiation, a part of paired electrons in quartz are ionized, and are trapped by lattice defects and impurties as unpaired electrons. The amount of unpaired electrons increases with time. The ESR age is obtained by dividing the total dose of natural radiation by the natural dose rate. Gamma ray doses are given to the sample to obtain the total dose by extrapolating the dose response of the signal intensity to the zero ordinate. The natural dose rate is calculated from U, Th, and K concentrations, and so on. Quartz is one of the promising minerals useful for ESR dating. In the present paper, we attempted to obtain ages of a land slide event. We collected pseudotachylite from Lantan, Himalaya. A land of about 4 km in diameter has found to have slid several kilometers resulting in pseudotachylite at the base. The samples were gently crushed sieved and soaked in 6N HCl for 1 night and then in 20% HF for two hours, but quartz grains were too small to be extracted. However, ESR signals of characteristic quartz were observed. As long as the sample is uniform, it is not crucial to extract pure quartz grains. With the usual procedure of ESR dating, gamma ray irradiation and ESR measurements, we obtained accumulated natural doses of 290 to 450 Gy. The concentrations of radioactive elements, K, U, Th, which give most of the natural dose to quartz grains, were measured by the low background gamma ray spectrometry. We obtained 7.62 ppm of uranium, 21.1 ppm of thorium, and 3.72% of K2O. Assuming the cosmic dose rate of 0.1mGy/y, we obtained 6.08 mGy/y as the natural dose rate. The ESR ages are obtained by dividing the accumulated doses by the natural dose rate to be 49ka from Al center signal (an electronic hole trapped at Al impurity in quartz) and 74ka from Ti center signal (an electron trapped at Ti impurity in quartz) for a sample, and 56ka and

  8. Lifetime of an ocean island volcano feeder zone: constraints from U-Pb dating on coexisting zircon and baddeleyite, and 40/39Ar age determinations, Fuerteventura, Canary Islands

    USGS Publications Warehouse

    Allibon, James; Ovtcharova, Maria; Bussy, Francois; Cosca, Michael; Schaltegger, Urs; Bussien, Denise; Lewin, Eric

    2011-01-01

    High-precision isotope dilution - thermal ionization mass spectrometry (ID-TIMS) U-Pb zircon and baddeleyite ages from the PX1 vertically layered mafic intrusion Fuerteventura, Canary Islands, indicate initiation of magma crystallization at 22.10 ± 0.07 Ma. The magmatic activity lasted a minimum of 0.52 Ma. 40Ar/39Ar amphibole dating yielded ages from 21.9 ± 0.6 to 21.8 ± 0.3, identical within errors to the U-Pb ages, despite the expected 1% theoretical bias between 40Ar/39Ar and U-Pb dates. This overlap could result from (i) rapid cooling of the intrusion (i.e., less than the 0.3 to 0.6 Ma 40Ar/39Ar age uncertainties) from closure temperatures (Tc) of zircon (699-988 °C) to amphibole (500-600 °C); (ii) lead loss affecting the youngest zircons; or (iii) excess argon shifting the plateau ages towards older values. The combination of the 40Ar/39Ar and U/Pb datasets implies that the maximum amount of time PX1 intrusion took to cool below amphibole Tc is 0.8 Ma, suggesting PX1 lifetime of 520,000 to 800,000 Ma. Age disparities among coexisting baddeleyite and zircon (22.10 ± 0.07/0.08/0.15 Ma and 21.58 ± 0.15/0.16/0.31 Ma) in a gabbro sample from the pluton margin suggest complex genetic relationships between phases. Baddeleyite is found preserved in plagioclase cores and crystallized early from low silica activity magma. Zircon crystallized later in a higher silica activity environment and is found in secondary scapolite and is found close to calcite veins, in secondary scapolite that recrystallised from plagioclase. close to calcite veins. Oxygen isotope δ18O values of altered plagioclase are high (+7.7), indicating interaction with fluids derived from host-rock carbonatites. The coexistence of baddeleyite and zircon is ascribed to interaction of the PX1 gabbro with CO2-rich carbonatite-derived fluids released during contact metamorphism.

  9. Reinvestigation of age model for relative paleointensity stack and application to Lake Baikal record

    NASA Astrophysics Data System (ADS)

    Oda, H.

    2014-12-01

    The age model for relative paleointensity stack PISO-1500 (Channell et al., 2009) is based on IODP U1308 from North Atlantic. Channell et al. (2008) developed the age model for U1308 by correlating the benthic oxygen isotope curve with LR04 oxygen isotope stack (Lisiecki&Raymo, 2005). LR04 stack is known as oxygen isotope stack for benthic foraminifarra, whose age model is dependent on ice volume model with a certain time lag. On the other hand, Caballero-Gill et al. (2012) developed an absolute age model based on U-Th dating for stalagmites from China and correlated the oxygen isotope curve with that on planctonic foraminiferra for a deep-sea core from South China Sea. The age model based on absolute dating for stalagmite was then transfered to oxygen isotope curve of benthic forraminiferra for the same core. This enables to provide absolute age model on PISO-1500 for the past 350 kyrs. The resulting modified PISO-1500 was applied on paleomagnetic records from Lake Baikal to provide an age model based on relative paleointensity. Finally, this age model was compared with alternative age model based on correlation of biogenic silica record with insolation at the site (Prokopenko et al., 2006) and the reason for the discrepancy will be discussed.

  10. 210Pb dating

    USGS Publications Warehouse

    Swarzenski, Peter W.

    2014-01-01

    Roughly fifty years ago, a small group of scientists from Belgium and the United States, trying to better constrain ice sheet accumulation rates, attempted to apply what was then know about environmental lead as a potential geochronometer. Thus Goldberg (1963) developed the first principles of the 210Pb dating method, which was soon followed by a paper by Crozaz et al. (1964), who examined accumulation history of Antarctic snow using 210Pb. Shortly thereafter, Koide et al. (1972, 1973) adapted this technique to unravel sediment deposition and accumulation records in deep-sea environments. Serendipitously, they chose to work in a deep basin off California, where an independent and robust age model had already been developed. Krishanswami et al. (1971) extended the use of this technique to lacustrine deposits to reconstruct depositional histories of lake sediment, and maybe more importantly, contaminant inputs and burial. Thus, the powerful tool for dating recent (up to about one century old) sediment deposits was established and soon widely adopted. Today almost all oceanographic or limnologic studies that address recent depositional reconstructions employ 210Pb as one of several possible geochronometers (Andrews et al., 2009; Gale, 2009; Baskaran, 2011; Persson and Helms, 2011). This paper presents a short overview of the principles of 210Pb dating and provides a few examples that illustrate the utility of this tracer in contrasting depositional systems. Potential caveats and uncertainties (Appleby et al., 1986; Binford, 1990; Binford et al., 1993; Smith, 2001; Hancock et al., 2002) inherent to the use and interpretation of 210Pb-derived age-models are also introduced. Recommendations as to best practices for most reliable uses and reporting are presented in the summary.

  11. Radiocarbon dates of late quaternary mammals in the Archangelsk Region and their contribution to reconstructions of the last glaciation in Eastern Europe

    NASA Astrophysics Data System (ADS)

    Ponomarev, D. V.; Markova, A. K.; van Kolfschoten, T.; van der Plicht, J.

    2012-06-01

    Twelve new AMS (Accelerator Mass Spectrometry) dates of large Quaternary mammal remains were reported: mammoth ( Mammuthus primigenius, bison ( Bison priscus), and musk ox ( Ovibos pallantis) found in the Archangelsk Region. The absolute age of the identified samples varies from 46 000 to 22 000 calibrated years ago. These data suggest that a substantial part of the Archangelsk Region was not covered by ice during the indicated time interval.

  12. Planets Around Low-mass Stars (PALMS). V. Age-dating Low-mass Companions to Members and Interlopers of Young Moving Groups

    NASA Astrophysics Data System (ADS)

    Bowler, Brendan P.; Shkolnik, Evgenya L.; Liu, Michael C.; Schlieder, Joshua E.; Mann, Andrew W.; Dupuy, Trent J.; Hinkley, Sasha; Crepp, Justin R.; Johnson, John Asher; Howard, Andrew W.; Flagg, Laura; Weinberger, Alycia J.; Aller, Kimberly M.; Allers, Katelyn N.; Best, William M. J.; Kotson, Michael C.; Montet, Benjamin T.; Herczeg, Gregory J.; Baranec, Christoph; Riddle, Reed; Law, Nicholas M.; Nielsen, Eric L.; Wahhaj, Zahed; Biller, Beth A.; Hayward, Thomas L.

    2015-06-01

    We present optical and near-infrared adaptive optics (AO) imaging and spectroscopy of 13 ultracool (>M6) companions to late-type stars (K7-M4.5), most of which have recently been identified as candidate members of nearby young moving groups (YMGs; 8-120 Myr) in the literature. Three of these are new companions identified in our AO imaging survey, and two others are confirmed to be comoving with their host stars for the first time. The inferred masses of the companions (˜10-100 MJup) are highly sensitive to the ages of the primary stars; therefore we critically examine the kinematic and spectroscopic properties of each system to distinguish bona fide YMG members from old field interlopers. The new M7 substellar companion 2MASS J02155892-0929121 C (40-60 MJup) shows clear spectroscopic signs of low gravity and, hence, youth. The primary, possibly a member of the ˜40 Myr Tuc-Hor moving group, is visually resolved into three components, making it a young low-mass quadruple system in a compact (≲100 AU) configuration. In addition, Li i λ6708 absorption in the intermediate-gravity M7.5 companion 2MASS J15594729+4403595 B provides unambiguous evidence that it is young (≲200 Myr) and resides below the hydrogen-burning limit. Three new close-separation (<1″) companions (2MASS J06475229-2523304 B, PYC J11519+0731 B, and GJ 4378 Ab) orbit stars previously reported as candidate YMG members, but instead are likely old (≳1 Gyr) tidally locked spectroscopic binaries without convincing kinematic associations with any known moving group. The high rate of false positives in the form of old active stars with YMG-like kinematics underscores the importance of radial velocity and parallax measurements to validate candidate young stars identified via proper motion and activity selection alone. Finally, we spectroscopically confirm the cool temperature and substellar nature of HD 23514 B, a recently discovered M8 benchmark brown dwarf orbiting the dustiest-known member of the

  13. Dating volcanic ash by use of thermoluminescence

    SciTech Connect

    Berger, G.W. )

    1992-01-01

    The fine-silt-sized (4-11 {mu}m) grains of glass separated from four samples of independently dated, 8 to 400 ka, tephra beds provide accurate thermoluminescence (TL) ages. This demonstration of reliable TL dating of volcanic glass provides a new tephrochronometer for deposits spanning the Holocene to middle Pleistocene age range.

  14. Cosmology with negative absolute temperatures

    NASA Astrophysics Data System (ADS)

    Vieira, J. P. P.; Byrnes, Christian T.; Lewis, Antony

    2016-08-01

    Negative absolute temperatures (NAT) are an exotic thermodynamical consequence of quantum physics which has been known since the 1950's (having been achieved in the lab on a number of occasions). Recently, the work of Braun et al. [1] has rekindled interest in negative temperatures and hinted at a possibility of using NAT systems in the lab as dark energy analogues. This paper goes one step further, looking into the cosmological consequences of the existence of a NAT component in the Universe. NAT-dominated expanding Universes experience a borderline phantom expansion (w < ‑1) with no Big Rip, and their contracting counterparts are forced to bounce after the energy density becomes sufficiently large. Both scenarios might be used to solve horizon and flatness problems analogously to standard inflation and bouncing cosmologies. We discuss the difficulties in obtaining and ending a NAT-dominated epoch, and possible ways of obtaining density perturbations with an acceptable spectrum.

  15. Formation ages and thermal histories of fracture-filling hematite and Mn-oxide in Precambrian basement from (U-Th)/He dating and 4He/3He diffusion experiments

    NASA Astrophysics Data System (ADS)

    Reiners, P. W.; Shuster, D. L.; Evenson, N.

    2015-12-01

    Secondary Fe- and Mn-oxides in bedrock form from fluid flow associated with events that may not be preserved in stratigraphic records. (U-Th)/He chronometry is well suited for dating these phases but potential diffusive loss of 4He can complicate interpretations. Here we show that measuring He diffusion kinetics of dated samples can resolve whether ages record formation or cooling. Proterozoic (1.6 Ga) volcanics in Aravaipa Canyon, southern Arizona, contain 1.4-1.6-Ga quartz-vein-hosted hematite, as well as 1.0-1.1-Ga hematite precipitated on fractures and overlain by 20-30-Ma Mn-oxide. Hematite 4He/3He age spectra and multi-domain (MD) diffusion models are consistent with a small proportion (4-10%) of domains between 1-500 nm, larger proportions (5-15%) of 1-10 μm domains, and a majority (60-75%) of domains of 80-150 μm. Although the smallest domains would have extremely low He retentivity, models predict bulk "closure temperatures" of 180-200 °C. The 1.4-1.6-Ga quartz-vein hematite likely formed soon after eruption of its host rock, and has not been hotter than ~250 °C for Ma durations. The 1.0-1.1 Ga age of the fracture-fill hematite likely also records the timing of precipitation, but from fluids associated with nearby diabase of the same age. In contrast, the 4He/3He MD model of the 20-30-Ma Mn-oxide requires ~80% of 1-100 nm domains and 20% between 1-10 μm. Although the Mn-oxide likely formed at the same time as the hematite it coats, its age records transient heating from overlying 28-Ma volcanics. In all cases, approximate crystal sizes observed in SEM images are consistent with the predictions of MD modeling, and support the assumed kinetics of He diffusion (~147-157 kJ/mol and ~2.2×10-4 cm2/s for hematite, and ~134 kJ/mol and ~4×10-3 cm2/s for Mn-oxide).These results suggest that specular hematite can have bulk He closure temperatures at least as high as 200 °C and in some cases record precipitation; this is supported by our results on specularite

  16. New developments with Schmidt-hammer exposure-age dating (SHD): Comparison of mechanical and electronic Schmidt-hammers - towards a conversion factor for Q- and R-values

    NASA Astrophysics Data System (ADS)

    Winkler, Stefan; Matthews, John; Corbett, David

    2014-05-01

    Developed as an instrument for in situ destruction-free testing of concrete hardness in construction works, the Schmidt-hammer has subsequently been introduced and applied in various fields of geomorphology and geology. In the context of investigating Late Glacial and Holocene glacier chronologies, the Schmidt-hammer has been widely used as a relative-age dating technique. Such applications have for example successfully separated moraines formed during different glacier advance periods ('Little Ice Age'-type events). Pilot studies combined Schmidt-hammer measurements with available radiocarbon ages in order to achieve age constraints. Schmidt-hammer exposure-age dating (SHD) combining Schmidt-hammer and terrestrial cosmogenic nuclide dating (TCND) has recently been successfully applied in Norway and New Zealand. Schmidt-hammer tests have also been used to ensure the representativeness of boulders selected for TCND sampling. Especially in mountain regions with a high "geomorphological uncertainty" with the dating of Holocene moraines the inherited multi-proxy approach of SHD owns a considerable potential for reliable investigations of Late Glacial/Holocene glacier chronologies and their palaeoclimatic interpretation. An electronic Schmidt-hammer (named SilverSchmidt) was introduced by the manufacturer of the original mechanical Schmidt-hammer (Proceq SA) a few years ago. It offers especially facilities for much easier data processing and constitutes, therefore, a major improvement and potential replacement for the mechanical Schmidt-hammer. However, its different approach to the measurement of surface hardness - based on Q-(velocity) values instead of R-(rebound) values - means that measurements from the two instruments are not easily interconvertible. Prior to any considerations of using the instruments interchangeably or replacing the mechanical Schmidt-hammer in future studies with the SilverSchmidt, comparative tests under field conditions need to be undertaken

  17. First krypton-81 dating of glacial ice at Taylor Glacier, Antarctica

    NASA Astrophysics Data System (ADS)

    Severinghaus, J. P.

    2015-12-01

    A long-held dream of glaciologists has been the direct radiometric dating of ancient glacial ice. Carbon-14 is unfortunately complicated by in-situ cosmogenic production of this isotope from cosmic ray spallation on oxygen nuclei in the ice. Krypton-81 is an ideal tracer in several ways: it has no anthropogenic sources, is made in the atmosphere by cosmic ray spallation on stable krypton nuclei, and it has a half-life of 229 kyr, which is a useful age range for ancient glacial ice samples. However, the abundance of krypton-81 is dauntingly low. Recent analytical advances by a team of physicists at Argonne National Labs has now made it possible to measure practical quantities of ice (50 kg) by Atom Trap Trace Analysis (ATTA), a technique using lasers to cool krypton-81 atoms to absolute zero and trap them, enabling accurate counting of single atoms. The precision attained by this technique approaches 0.5%, implying an age accuracy of about 1000 yr for samples from the last interglacial period. Here we show that krypton-81 dating has been successfully applied for the first time, to an outcrop of ancient ice dating from the last interglacial period (125 kyr BP) at Taylor Glacier, Antarctica, which is independently dated using methane and d18O of atmospheric oxygen for stratigraphic matching to well-dated Chinese speleothem records.

  18. Bushveld-aged fluid flow, peak metamorphism, and gold mobilization in the Witwatersrand basin, South Africa: Constraints from in situ SHRIMP U-Pb dating of monazite and xenotime

    NASA Astrophysics Data System (ADS)

    Rasmussen, Birger; Fletcher, Ian R.; Muhling, Janet R.; Mueller, Andreas G.; Hall, Greg C.

    2007-10-01

    In situ U-Pb dating of monazite and xenotime in gold reefs and unmineralized greenschist facies sedimentary rocks from the Witwatersrand basin, South Africa, reveals two episodes of tectonothermal activity. A major event between 2.06 and 2.03 Ga is recorded in the Wit-watersrand and Transvaal Supergroups in the northwestern and central basin, and broadly coincides with the ca. 2.06 Ga Bushveld event. In the central and southern basin, a previously unrecognized event has been dated between 2.14 and 2.12 Ga. The widespread geographic and stratigraphic occurrence of Bushveld-aged monazite and xenotime, including both auriferous reefs and unmineralized strata, indicates that metamorphism and fluid flow associated with magmatism was pervasive, affecting most of the succession (>10 km thick) in the central and northern parts of the basin. The metamorphic phosphate dates, which are younger away from the complex, indicate a lag of 20-30 m.y. between emplacement and phosphate growth in the central basin (˜100 km south), suggesting that heat related to magmatism was transferred southward at an average rate of 3-5 mm yr-1. The absence of 2.06-2.03 Ga phosphates in the Welkom goldfield at the southern end of the basin implies that Bushveld-related heating and fluid flow did not affect this part of the basin. The intergrowth of ca. 2.045 Ga monazite with gold in quartz-pebble conglomerate from the West Rand goldfield indicates that fluid flow related to the Bushveld event caused mobilization of gold in the Witwatersrand basin.

  19. Potential improvement of Schmidt-hammer exposure-age dating (SHD) of moraines in the Southern Alps, New Zealand, by application of the new electronic Schmidt-hammer (SilverSchmidt)

    NASA Astrophysics Data System (ADS)

    Winkler, Stefan; Corbett, David

    2014-05-01

    The Southern Alps of New Zealand are among the few key study sites for investigating Holocene glacier chronologies in the mid-latitudinal Southern Hemisphere. Their characteristic highly dynamic geomorphological process systems prove, however, to be a considerable challenge for all attempts to date and palaeoclimatologically interpret the existing Holocene moraines record. As a multi-proxy approach combining 10Be terrestrial cosmogenic nuclide dating (TCND) with Schmidt-hammer testing, the recently developed Schmidt-hammer exposure-age dating (SHD) has already shown its potential in this study area (cf. Winkler 2005, 2009, 2013). An electronic Schmidt-hammer (named SilverSchmidt) was introduced by the manufacturer of the original mechanical Schmidt-hammer (Proceq SA) a few years ago. It offers, in particular, facilities for much easier data processing and constitutes a major improvement and potential replacement for the mechanical Schmidt-hammer. However, its different approach to the measurement of surface hardness - based on Q-(velocity) values instead of R-(rebound) values - is a potential drawback. This difference effectively means that measurements from the two instruments are not easily interconvertible and, hence, that the instruments cannot be used interchangeably without previous comparative tests of both instruments under field conditions. Both instruments used in this comparative study were N-type models with identical impact energy of 2.207 Nm for the plunger. To compare both instruments and explore interconvertibility, parallel measurements were performed on a selected number of boulders (10 boulders per site with 5 impacts each, at least 2 sites per moraine) on moraines of homogeneous lithology but different established ages covering the entire Holocene and the Late Glacial. All moraines are located east of the Main Divide of the Southern Alps at Mueller Glacier, Tasman Glacier, and in the outer Tasman River Valley. All paired samples (n = 50) were

  20. Geochemical, zircon U-Pb dating and Sr-Nd-Hf isotopic constraints on the age and petrogenesis of an Early Cretaceous volcanic-intrusive complex at Xiangshan, Southeast China

    NASA Astrophysics Data System (ADS)

    Yang, Shui-Yuan; Jiang, Shao-Yong; Jiang, Yao-Hui; Zhao, Kui-Dong; Fan, Hong-Hai

    2011-01-01

    The Late Mesozoic geology of Southeast China is characterized by extensive Jurassic to Cretaceous magmatism consisting predominantly of granites and rhyolites and subordinate mafic rocks, forming a belt of volcanic-intrusive complexes. The Xiangshan volcanic-intrusive complex is located in the NW region of the belt and mainly contains the following lithologies: rhyodacite and rhyodacitic porphyry, porphyritic lava, granite porphyry with mafic microgranular enclaves, quartz monzonitic porphyry, and lamprophyre dyke. Major and trace-element compositions, zircon U-Pb dating, and Sr-Nd-Hf isotopic compositions have been investigated for these rocks. The precise SHRIMP and LA-ICP-MS zircon U-Pb dating shows that the emplacement of various magmatic units at Xiangshan took place within a short time period of less than 2 Myrs. The stratigraphically oldest rhyodacite yielded a zircon U-Pb age of 135 ± 1 Ma and the overlying rhyodacitic porphyry has an age of 135 ± 1 Ma. Three porphyritic lava samples yielded zircon U-Pb ages of 136 ± 1 Ma, 132 ± 1 Ma, and 135 ± 1 Ma, respectively. Two subvolcanic rocks (granite porphyry) yielded zircon U-Pb ages of 137 ± 1 Ma and 137 ± 1 Ma. A quartz monzonitic porphyry dyke, which represented the final stage of magmatism at Xiangshan, also yielded a zircon U-Pb age of 136 ± 1 Ma. All these newly obtained precise U-Pb ages demonstrate that the entire magmatic activity at Xiangshan was rapid and possibly took place at the peak of extensional tectonics in SE China. The geochemical data indicate that all these samples from the volcanic-intrusive complex have an A-type affinity. Sr-Nd-Hf isotopic data suggest that the Xiangshan volcanic-intrusive complex derived mainly from remelting of Paleo-Mesoproterozoic crust without significant additions of mantle-derived magma. However, the quartz monzonitic porphyry, which has zircon Hf model ages older than the whole-rock Nd model ages, and which has ɛNd(T) value higher than the other rocks

  1. Teen Dating Violence

    MedlinePlus

    ... dating violence prevention initiative seeks to reduce dating violence and increase healthy relationships in high-risk urban communities through comprehensive, multisector prevention. Division of Adolescent ...

  2. Post-glacial landforms dating by lichenometry in Iceland - the accuracy of relative results and conversely

    NASA Astrophysics Data System (ADS)

    Decaulne, Armelle

    2014-05-01

    Lichenometry studies are carried out in Iceland since 1970 all over the country, using various techniques to solve a range of geomorphologic issues, from moraine dating and glacial advances, outwash timing, proglacial river incision, soil erosion, rock-glacier development, climate variations, to debris-flow occurrence and extreme snow-avalanche frequency. Most users have sought to date proglacial landforms in two main areas, around the southern ice-caps of Vatnajökull and Myrdalsjökull; and in Tröllaskagi in northern Iceland. Based on the results of over thirty five published studies, lichenometry is deemed to be successful dating tool in Iceland, and seems to approach an absolute dating technique at least over the last hundred years, under well constrained environmental conditions at local scale. With an increasing awareness of the methodological limitations of the technique, together with more sophisticated data treatments, predicted lichenometric 'ages' are supposedly gaining in robustness and in precision. However, comparisons between regions, and even between studies in the same area, are hindered by the use of different measurement techniques and data processing. These issues are exacerbated in Iceland by rapid environmental changes across short distances and, more generally, by the common problems surrounding lichen species mis-identification in the field; not mentioning the age discrepancy offered by other dating tools, such as tephrochronology. Some authors claim lichenometry can help to a precise reconstruction of landforms and geomorphic processes in Iceland, proposing yearly dating, others includes margin errors in their reconstructions, while some limit its use to generation identifications, refusing to overpass the nature of the gathered data and further interpretation. Finally, can lichenometry be a relatively accurate dating technique or rather an accurate relative dating tool in Iceland?

  3. Improving HST Pointing & Absolute Astrometry

    NASA Astrophysics Data System (ADS)

    Lallo, Matthew; Nelan, E.; Kimmer, E.; Cox, C.; Casertano, S.

    2007-05-01

    Accurate absolute astrometry is becoming increasingly important in an era of multi-mission archives and virtual observatories. Hubble Space Telescope's (HST's) Guidestar Catalog II (GSC2) has reduced coordinate error to around 0.25 arcsecond, a factor 2 or more compared with GSC1. With this reduced catalog error, special attention must be given to calibrate and maintain the Fine Guidance Sensors (FGSs) and Science Instruments (SIs) alignments in HST to a level well below this in order to ensure that the accuracy of science product's astrometry keywords and target positioning are limited only by the catalog errors. After HST Servicing Mission 4, such calibrations' improvement in "blind" pointing accuracy will allow for more efficient COS acquisitions. Multiple SIs and FGSs each have their own footprints in the spatially shared HST focal plane. It is the small changes over time in primarily the whole-body positions & orientations of these instruments & guiders relative to one another that is addressed by this work. We describe the HST Cycle 15 program CAL/OTA 11021 which, along with future variants of it, determines and maintains positions and orientations of the SIs and FGSs to better than 50 milli- arcseconds and 0.04 to 0.004 degrees of roll, putting errors associated with the alignment sufficiently below GSC2 errors. We present recent alignment results and assess their errors, illustrate trends, and describe where and how the observer sees benefit from these calibrations when using HST.

  4. Absolute oral bioavailability of ciprofloxacin.

    PubMed

    Drusano, G L; Standiford, H C; Plaisance, K; Forrest, A; Leslie, J; Caldwell, J

    1986-09-01

    We evaluated the absolute bioavailability of ciprofloxacin, a new quinoline carboxylic acid, in 12 healthy male volunteers. Doses of 200 mg were given to each of the volunteers in a randomized, crossover manner 1 week apart orally and as a 10-min intravenous infusion. Half-lives (mean +/- standard deviation) for the intravenous and oral administration arms were 4.2 +/- 0.77 and 4.11 +/- 0.74 h, respectively. The serum clearance rate averaged 28.5 +/- 4.7 liters/h per 1.73 m2 for the intravenous administration arm. The renal clearance rate accounted for approximately 60% of the corresponding serum clearance rate and was 16.9 +/- 3.0 liters/h per 1.73 m2 for the intravenous arm and 17.0 +/- 2.86 liters/h per 1.73 m2 for the oral administration arm. Absorption was rapid, with peak concentrations in serum occurring at 0.71 +/- 0.15 h. Bioavailability, defined as the ratio of the area under the curve from 0 h to infinity for the oral to the intravenous dose, was 69 +/- 7%. We conclude that ciprofloxacin is rapidly absorbed and reliably bioavailable in these healthy volunteers. Further studies with ciprofloxacin should be undertaken in target patient populations under actual clinical circumstances. PMID:3777908

  5. Laboratory for Radiokrypton Dating

    NASA Astrophysics Data System (ADS)

    Zappala, J. C.; Jiang, W.; Bailey, K. G.; Lu, Z. T.; Mueller, P.; O'Connor, T. P.

    2015-12-01

    Due to its simple production and transport in the terrestrial environment, 81Kr (half-life = 230,000 yr) is the ideal tracer for old water and ice with mean residence times in the range of 105-106 years, a range beyond the reach of 14C. 81Kr-dating is now available to the earth science community at large thanks to the development of an efficient and selective atom counter based on the Atom Trap Trace Analysis (ATTA) method. ATTA is a laser-based atom counting method where individual neutral atoms of the desired isotope are selectively captured by laser beams, and their fluorescence detected via a CCD camera. ATTA is unique among trace analysis techniques in that it is free of interferences from any other isotopes, isobars, atomic or molecular species. The ATTA instrument at Argonne's Laboratory for Radiokrypton Dating is capable of measuring both 81Kr/Kr and 85Kr/Kr ratios of environmental samples in the range of 10-14-10-10. For 81Kr-dating in the age range of 150 kyr - 1500 kyr, the required sample size is 5 micro-L STP of krypton gas, which can be extracted from approximately 100 kg of water or 40 kg of ice. For 85Kr/Kr analysis, the sample size can be smaller by an order of magnitude. We are continually developing the method towards higher counting efficiency, smaller sample sizes requirements, and higher sample throughput rates. In the past four years, we have performed radiokrypton analysis of over 150 groundwater and ice samples extracted by collaborators from all seven continents. Sample collection and purification was performed by groups including the University of Chicago, the University of Illinois at Chicago, the University of Bern, and the International Atomic Energy Agency. This work is supported by the U.S. DOE, Office of Nuclear Physics, under contract DE-AC02-06CH11357.

  6. Absolute Instability in Coupled-Cavity TWTs

    NASA Astrophysics Data System (ADS)

    Hung, D. M. H.; Rittersdorf, I. M.; Zhang, Peng; Lau, Y. Y.; Simon, D. H.; Gilgenbach, R. M.; Chernin, D.; Antonsen, T. M., Jr.

    2014-10-01

    This paper will present results of our analysis of absolute instability in a coupled-cavity traveling wave tube (TWT). The structure mode at the lower and upper band edges are respectively approximated by a hyperbola in the (omega, k) plane. When the Briggs-Bers criterion is applied, a threshold current for onset of absolute instability is observed at the upper band edge, but not the lower band edge. The nonexistence of absolute instability at the lower band edge is mathematically similar to the nonexistence of absolute instability that we recently demonstrated for a dielectric TWT. The existence of absolute instability at the upper band edge is mathematically similar to the existence of absolute instability in a gyroton traveling wave amplifier. These interesting observations will be discussed, and the practical implications will be explored. This work was supported by AFOSR, ONR, and L-3 Communications Electron Devices.

  7. Developing 226Ra and 227Ac age-dating techniques for nuclear forensics to gain insight from concordant and non-concordant radiochronometers

    SciTech Connect

    Kayzar, Theresa M.; Williams, Ross W.

    2015-09-26

    The model age or ‘date of purification’ of a nuclear material is an important nuclear forensic signature. In this study, chemical separation and MC-ICP-MS measurement techniques were developed for 226 Ra and 227Ac: grand-daughter nuclides in the 238U and 235U decay chains respectively. The 230Th-234U, 226Ra-238U, 231Pa-235U, and 227Ac-235U radiochronometers were used to calculate model ages for CRM-U100 standard reference material and two highly-enriched pieces of uranium metal from the International Technical Working Group Round Robin 3 Exercise. In conclusion, the results demonstrate the accuracy of the 226Ra-238U and 227Ac-235U chronometers and provide information about nuclide migration during uranium processing.

  8. Absolute negative mobility of interacting Brownian particles

    NASA Astrophysics Data System (ADS)

    Ou, Ya-li; Hu, Cai-tian; Wu, Jian-chun; Ai, Bao-quan

    2015-12-01

    Transport of interacting Brownian particles in a periodic potential is investigated in the presence of an ac force and a dc force. From Brownian dynamic simulations, we find that both the interaction between particles and the thermal fluctuations play key roles in the absolute negative mobility (the particle noisily moves backwards against a small constant bias). When no the interaction acts, there is only one region where the absolute negative mobility occurs. In the presence of the interaction, the absolute negative mobility may appear in multiple regions. The weak interaction can be helpful for the absolute negative mobility, while the strong interaction has a destructive impact on it.

  9. Cosmogenic nuclide dating of Sahelanthropus tchadensis and Australopithecus bahrelghazali: Mio-Pliocene hominids from Chad

    PubMed Central

    Lebatard, Anne-Elisabeth; Bourlès, Didier L.; Duringer, Philippe; Jolivet, Marc; Braucher, Régis; Carcaillet, Julien; Schuster, Mathieu; Arnaud, Nicolas; Monié, Patrick; Lihoreau, Fabrice; Likius, Andossa; Mackaye, Hassan Taisso; Vignaud, Patrick; Brunet, Michel

    2008-01-01

    Ages were determined at two hominid localities from the Chad Basin in the Djurab Desert (Northern Chad). In the Koro Toro fossiliferous area, KT 12 locality (16°00′N, 18°53′E) was the site of discovery of Australopithecus bahrelghazali (Abel) and in the Toros-Menalla fossiliferous area, TM 266 locality (16°15′N, 17°29′E) was the site of discovery of Sahelanthropus tchadensis (Toumaï). At both localities, the evolutive degree of the associated fossil mammal assemblages allowed a biochronological estimation of the hominid remains: early Pliocene (3–3.5 Ma) at KT 12 and late Miocene (≈7 Ma) at TM 266. Atmospheric 10Be, a cosmogenic nuclide, was used to quasicontinuously date these sedimentary units. The authigenic 10Be/9Be dating of a pelite relic within the sedimentary level containing Abel yields an age of 3.58 ± 0.27 Ma that points to the contemporaneity of Australopithecus bahrelghazali (Abel) with Australopithecus afarensis (Lucy). The 28 10Be/9Be ages obtained within the anthracotheriid unit containing Toumaï bracket, by absolute dating, the age of Sahelanthropus tchadensis to lie between 6.8 and 7.2 Ma. This chronological constraint is an important cornerstone both for establishing the earliest stages of hominid evolution and for new calibrations of the molecular clock. PMID:18305174

  10. Cosmogenic nuclide dating of Sahelanthropus tchadensis and Australopithecus bahrelghazali: Mio-Pliocene hominids from Chad.

    PubMed

    Lebatard, Anne-Elisabeth; Bourlès, Didier L; Duringer, Philippe; Jolivet, Marc; Braucher, Régis; Carcaillet, Julien; Schuster, Mathieu; Arnaud, Nicolas; Monié, Patrick; Lihoreau, Fabrice; Likius, Andossa; Mackaye, Hassan Taisso; Vignaud, Patrick; Brunet, Michel

    2008-03-01

    Ages were determined at two hominid localities from the Chad Basin in the Djurab Desert (Northern Chad). In the Koro Toro fossiliferous area, KT 12 locality (16 degrees 00'N, 18 degrees 53'E) was the site of discovery of Australopithecus bahrelghazali (Abel) and in the Toros-Menalla fossiliferous area, TM 266 locality (16 degrees 15'N, 17 degrees 29'E) was the site of discovery of Sahelanthropus tchadensis (Toumaï). At both localities, the evolutive degree of the associated fossil mammal assemblages allowed a biochronological estimation of the hominid remains: early Pliocene (3-3.5 Ma) at KT 12 and late Miocene ( approximately 7 Ma) at TM 266. Atmospheric (10)Be, a cosmogenic nuclide, was used to quasicontinuously date these sedimentary units. The authigenic (10)Be/(9)Be dating of a pelite relic within the sedimentary level containing Abel yields an age of 3.58 +/- 0.27 Ma that points to the contemporaneity of Australopithecus bahrelghazali (Abel) with Australopithecus afarensis (Lucy). The 28 (10)Be/(9)Be ages obtained within the anthracotheriid unit containing Toumaï bracket, by absolute dating, the age of Sahelanthropus tchadensis to lie between 6.8 and 7.2 Ma. This chronological constraint is an important cornerstone both for establishing the earliest stages of hominid evolution and for new calibrations of the molecular clock. PMID:18305174

  11. U/Th-dating living and young fossil corals from the central tropical Pacific

    NASA Astrophysics Data System (ADS)

    Cobb, Kim M.; Charles, Christopher D.; Cheng, Hai; Kastner, Miriam; Edwards, R. Lawrence

    2003-05-01

    This study evaluates the accuracy of U/Th dates for young (< a few thousand years old) reef corals, both living and fossil, and explores strategies for refining those dates. The high precision of the U/Th method (±1-2%) for dating young corals is well-established. Earlier studies have demonstrated the method's accuracy for select samples of known age. However, these studies have focused on typical samples that have extremely low 232Th concentrations (tens of pg/g). Here we study the dating systematics of young corals that have low but significant amounts of 232Th (up to 1000 pg/g), indicating the presence of small fractions of non-radiogenic 230Th (i.e. 230Th not generated by in situ U decay). We report U/Th ages for living and subaerially exposed fossil corals from Palmyra Island, located in the central tropical Pacific, that range from 50 to 700 yr old. The Palmyra corals contain varying amounts of 232Th and small fractions of associated non-radiogenic 230Th. Uncertainty associated with the correction for non-radiogenic 230Th can lead to significant errors in U/Th dates. We have characterized non-radiogenic 230Th/ 232Th values, ( 230Th/ 232Th) nr, as a means of minimizing this source of error. We calculate ( 230Th/ 232Th) nr values ranging from 0 to 2×10 -5 for the Palmyra living corals by comparing measured U/Th dates to absolute dates for the living coral, whose chronology is well-established. For the fossil corals, we employ three different approaches to arrive at ( 230Th/ 232Th) nr estimates. First, we compare measured U/Th dates to absolute dates in samples from a young fossil coral that overlaps the living coral. Next, we use the firm relative dating constraints imposed by five overlapping fossil corals from the 14th-15th centuries to calculate ( 230Th/ 232Th) nr values. Finally, we attempt to anchor the 14th-15th century floating coral chronology to an absolute chronology by correlating the climate signals in the coral records to those in absolutely

  12. Dating and Marriage

    MedlinePlus

    ... Family : Dating & Marriage Subscribe Translate Text Size Print Dating and Marriage Dating and Marriage If you are living with HIV, ... Living! Having HIV does not prevent you from dating or marrying—it just may require a little ...

  13. Age Estimation in Forensic Sciences

    PubMed Central

    Alkass, Kanar; Buchholz, Bruce A.; Ohtani, Susumu; Yamamoto, Toshiharu; Druid, Henrik; Spalding, Kirsty L.

    2010-01-01

    Age determination of unknown human bodies is important in the setting of a crime investigation or a mass disaster because the age at death, birth date, and year of death as well as gender can guide investigators to the correct identity among a large number of possible matches. Traditional morphological methods used by anthropologists to determine age are often imprecise, whereas chemical analysis of tooth dentin, such as aspartic acid racemization, has shown reproducible and more precise results. In this study, we analyzed teeth from Swedish individuals using both aspartic acid racemization and radiocarbon methodologies. The rationale behind using radiocarbon analysis is that aboveground testing of nuclear weapons during the cold war (1955–1963) caused an extreme increase in global levels of carbon-14 (14C), which has been carefully recorded over time. Forty-four teeth from 41 individuals were analyzed using aspartic acid racemization analysis of tooth crown dentin or radiocarbon analysis of enamel, and 10 of these were split and subjected to both radiocarbon and racemization analysis. Combined analysis showed that the two methods correlated well (R2 = 0.66, p < 0.05). Radiocarbon analysis showed an excellent precision with an overall absolute error of 1.0 ± 0.6 years. Aspartic acid racemization also showed a good precision with an overall absolute error of 5.4 ± 4.2 years. Whereas radiocarbon analysis gives an estimated year of birth, racemization analysis indicates the chronological age of the individual at the time of death. We show how these methods in combination can also assist in the estimation of date of death of an unidentified victim. This strategy can be of significant assistance in forensic casework involving dead victim identification. PMID:19965905

  14. Electron-microprobe Th-U-Pb monazite dating in Early-Palaeozoic high-grade gneisses as a completion of U-Pb isotopic ages (Wilson Terrane, Antarctica)

    NASA Astrophysics Data System (ADS)

    Schulz, B.; Schüssler, U.

    2013-08-01

    The electron microprobe (EMP) Th-U-Pb monazite bulk chemical dating method was applied to granulite-facies rocks of the Wilson Terrane in Antarctica. A combination of this method to isotopic U-Pb-SHRIMP ages for the evaluation of metamorphic processes required the analysis of reference monazites. These can be subdivided into three groups: a) Monazite with variable total Pb at constant Th (e.g. VK-1) is unsuitable for EMP data evaluation; b) Monazite with highly variable total Pb and Th, but with at least some Th/Pb approximating an apparent isochrone (e.g. MPN) is partly useful; and c) Monazite with constant Th/Pb at high Th (e.g. Madmon monazite) is best suitable for the combined approach and can be additionally used to improve the Th calibration for EMP. Study of monazite in grain mounts and in thin sections led to partly different but complementary results: Older monazites with EMP ages up to 680 Ma occur mainly in a grain mount from diatexite and metatexite and are interpreted as detrital relics. Some of these monazites show structures and mineral-chemical zonation trends resembling metasomatism by alkali-bearing fluids. A marked mobility of Th, P, Ce, Si and U is observed. The age of the metasomatic event can be bracketed between 510 and 450 Ma. Furthermore, in the grain mount and in numerous petrographic thin sections of migmatites and gneisses, the EMP Th-U-Pb and SHRIMP U-Pb monazite data uniformly signal a major metamorphic event with a medium-pressure granulite facies peak between 512 and 496 Ma. Subsequent isothermal uplift and then amphibolite-facies conditions between 488 and 466 Ma led to crystallisation of pristine monazite. The high-grade metamorphic event, related to the Ross Orogeny, can be uniformly traced more than 600 km along strike in the Wilson Terrane.

  15. Peer involvement in adolescent dating violence.

    PubMed

    Stephenson, Pam S; Martsolf, Donna; Draucker, Claire Burke

    2013-06-01

    This study investigated the ways in which peers are involved in adolescent dating violence. Eighty-eight young adults aged 18-21 were interviewed and asked to reflect on aggressive dating relationships they experienced as teens. The researchers used grounded theory to analyze the data. Findings showed that male and female peers were involved in adolescent dating violence in unique ways. Male peers were involved in dating violence by participating in the aggression, agitating the aggression, being the competition, trivializing the aggression, and keeping tabs on the recipient. Female peers were involved in dating violence by deserting the recipient, cheating with the boyfriend, being the audience, needling the male dating partner, and helping the recipient. Male and female peers were involved similarly in adolescent dating violence by confronting the partner. School nurses working with adolescents are uniquely positioned to approach adolescents about dating violence. Interventions aimed at promoting discussions with adolescents are discussed. PMID:23239788

  16. Thai female adolescents' perceptions of dating violence.

    PubMed

    Thongpriwan, Vipavee; McElmurry, Beverly J

    2009-10-01

    We explored how Thai female adolescents describe the meaning and context of dating violence. Twenty-four students, aged 15-17, were purposively recruited from a secondary school in Bangkok for individually audio-taped interviews. The interviews lasted 45- 70 minutes. ATLAS ti 5.2 was selected for content analysis. Five themes emerged, including characteristics of adolescent romantic relationships, influences on adolescent romantic relationships, perceptions of dating violence, cycle of dating-violence experiences, and influences on adolescents' perceptions of dating violence. The findings indicate a foundation for developing culturally sensitive programs for dating-violence prevention among Thai adolescents. PMID:19742362

  17. Optically stimulated luminescence dating of late Holocene raised strandplain sequences adjacent to Lakes Michigan and Superior, Upper Peninsula, Michigan, USA

    USGS Publications Warehouse

    Argyilan, Erin P.; Forman, Steven L.; Johnston, John W.; Wilcox, Douglas A.

    2005-01-01

    This study evaluates the accuracy of optically stimulated luminescence to date well-preserved strandline sequences at Manistique/Thompson bay (Lake Michigan), and Tahquamenon and Grand Traverse Bays (Lake Superior) that span the past ∼4500 yr. The single aliquot regeneration (SAR) method is applied to produce absolute ages for littoral and eolian sediments. SAR ages are compared against AMS and conventional 14C ages on swale organics. Modern littoral and eolian sediments yield SAR ages 14C ages on swale organics. Significant variability in 14C ages >2000 cal yr B.P. complicates comparison to SAR ages at all sites. However, a SAR age of 4280 ± 390 yr (UIC913) on ridge77 at Tahquamenon Bay is consistent with regional regression from the high lake level of the Nipissing II phase ca. 4500 cal yr B.P. SAR ages indicate a decrease in ridge formation rate after ∼1500 yr ago, likely reflecting separation of Lake Superior from lakes Huron and Michigan. This study shows that SAR is a credible alternative to 14C methods for dating littoral and eolian landforms in Great Lakes and other coastal strandplains where 14C methods prove problematic.

  18. Derivation of Absolute Model Ages for Lunar Lobate Scarps

    NASA Astrophysics Data System (ADS)

    van der Bogert, C. H.; Hiesinger, H.; Banks, M. E.; Watters, T. R.; Robinson, M. S.

    2012-03-01

    Crater size-frequency distribution measurements indicate that the Mandel'shtam and Lee-Lincoln scarps were active as recently as ~91 Ma and ~75 Ma, respectively. These results confirm that lobate scarps are some of the youngest features on the Moon.

  19. Direct comparisons between absolute and relative geomagnetic paleointensities: Absolute calibration of a relative paleointensity stack

    NASA Astrophysics Data System (ADS)

    Mochizuki, N.; Yamamoto, Y.; Hatakeyama, T.; Shibuya, H.

    2013-12-01

    Absolute geomagnetic paleointensities (APIs) have been estimated from igneous rocks, while relative paleomagnetic intensities (RPIs) have been reported from sediment cores. These two datasets have been treated separately, as correlations between APIs and RPIs are difficult on account of age uncertainties. High-resolution RPI stacks have been constructed from globally distributed sediment cores with high sedimentation rates. Previous studies often assumed that the RPI stacks have a linear relationship with geomagnetic axial dipole moments, and calibrated the RPI values to API values. However, the assumption of a linear relationship between APIs and RPIs has not been evaluated. Also, a quantitative calibration method for the RPI is lacking. We present a procedure for directly comparing API and RPI stacks, thus allowing reliable calibrations of RPIs. Direct comparisons between APIs and RPIs were conducted with virtually no associated age errors using both tephrochronologic correlations and RPI minima. Using the stratigraphic positions of tephra layers in oxygen isotope stratigraphic records, we directly compared the RPIs and APIs reported from welded tuffs contemporaneously extruded with the tephra layers. In addition, RPI minima during geomagnetic reversals and excursions were compared with APIs corresponding to the reversals and excursions. The comparison of APIs and RPIs at these exact points allowed a reliable calibration of the RPI values. We applied this direct comparison procedure to the global RPI stack PISO-1500. For six independent calibration points, virtual axial dipole moments (VADMs) from the corresponding APIs and RPIs of the PISO-1500 stack showed a near-linear relationship. On the basis of the linear relationship, RPIs of the stack were successfully calibrated to the VADMs. The direct comparison procedure provides an absolute calibration method that will contribute to the recovery of temporal variations and distributions of geomagnetic axial dipole

  20. Inequalities, Absolute Value, and Logical Connectives.

    ERIC Educational Resources Information Center

    Parish, Charles R.

    1992-01-01

    Presents an approach to the concept of absolute value that alleviates students' problems with the traditional definition and the use of logical connectives in solving related problems. Uses a model that maps numbers from a horizontal number line to a vertical ray originating from the origin. Provides examples solving absolute value equations and…

  1. Absolute optical metrology : nanometers to kilometers

    NASA Technical Reports Server (NTRS)

    Dubovitsky, Serge; Lay, O. P.; Peters, R. D.; Liebe, C. C.

    2005-01-01

    We provide and overview of the developments in the field of high-accuracy absolute optical metrology with emphasis on space-based applications. Specific work on the Modulation Sideband Technology for Absolute Ranging (MSTAR) sensor is described along with novel applications of the sensor.

  2. Monolithically integrated absolute frequency comb laser system

    DOEpatents

    Wanke, Michael C.

    2016-07-12

    Rather than down-convert optical frequencies, a QCL laser system directly generates a THz frequency comb in a compact monolithically integrated chip that can be locked to an absolute frequency without the need of a frequency-comb synthesizer. The monolithic, absolute frequency comb can provide a THz frequency reference and tool for high-resolution broad band spectroscopy.

  3. Introducing the Mean Absolute Deviation "Effect" Size

    ERIC Educational Resources Information Center

    Gorard, Stephen

    2015-01-01

    This paper revisits the use of effect sizes in the analysis of experimental and similar results, and reminds readers of the relative advantages of the mean absolute deviation as a measure of variation, as opposed to the more complex standard deviation. The mean absolute deviation is easier to use and understand, and more tolerant of extreme…

  4. Investigating Absolute Value: A Real World Application

    ERIC Educational Resources Information Center

    Kidd, Margaret; Pagni, David

    2009-01-01

    Making connections between various representations is important in mathematics. In this article, the authors discuss the numeric, algebraic, and graphical representations of sums of absolute values of linear functions. The initial explanations are accessible to all students who have experience graphing and who understand that absolute value simply…

  5. Absolute Income, Relative Income, and Happiness

    ERIC Educational Resources Information Center

    Ball, Richard; Chernova, Kateryna

    2008-01-01

    This paper uses data from the World Values Survey to investigate how an individual's self-reported happiness is related to (i) the level of her income in absolute terms, and (ii) the level of her income relative to other people in her country. The main findings are that (i) both absolute and relative income are positively and significantly…

  6. The ID-KArD technique: In-situ dating on Mars

    NASA Astrophysics Data System (ADS)

    Cartwright, J. A.; Farley, K. A.; Hurowitz, J.; Asimow, P. D.; Jacobson, N. S.

    2013-12-01

    The ability to measure absolute ages on the Martian surface is crucial for understanding the planet's evolution. A detailed geological history of the Moon has been determined through analysis of returned samples from specific units, and relative ages calculated by crater counting techniques. However, without returned samples or in-situ dating analyses, we lack absolute age markers for Mars and thus cannot accurately or precisely date its well-documented surface. Instead, we have relied on an estimated Mars/Moon cratering ratio and relative crater counting techniques in an attempt to calculate surface ages and classify geological units. The use of such relative parameters diminishes the precision and accuracy for surface age calculations, and thus highlights the need for independent age determinations from returned samples or in-situ dating. In this research, we describe our technique - ID-KArD (Isotope Dilution K-Ar Dating) - intended for in-situ age dating of geological units on the Martian surface. ID-KArD resolves two challenges that have previously obstructed in-situ age dating on Mars: 1) High fusion temperatures are avoided with the use of a lithium-borate flux; 2) Sample mass measurement is not required, due to the addition of an isotope dilution doubly-spiked glass. The glass has a known 39Ar/41K ratio, which removes the need for concentration measurements. Thus, only isotope ratios are required for a K-Ar age determination. ID-KArD has the potential to address Mars chronology inaccuracies, and would be a suitable technique for consideration on future missions. In the first phase of ID-KArD proof of concept, we selected a Viluy trap basalt (K2O ~ 0.7 wt%), with concordant K-Ar and Ar-Ar ages of 354.3 × 3.5 and 357.7 × 1.4 Ma respectively (Courtillot et al., 2010). An aliquot was combined into a crucible with the flux and the spike glass for separate Ar (MAP 215:50, Caltech), followed by K (KEMS, GRC) isotopic analysis. Combining our results, we obtained

  7. Absolute instability of the Gaussian wake profile

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.; Aggarwal, Arun K.

    1987-01-01

    Linear parallel-flow stability theory has been used to investigate the effect of viscosity on the local absolute instability of a family of wake profiles with a Gaussian velocity distribution. The type of local instability, i.e., convective or absolute, is determined by the location of a branch-point singularity with zero group velocity of the complex dispersion relation for the instability waves. The effects of viscosity were found to be weak for values of the wake Reynolds number, based on the center-line velocity defect and the wake half-width, larger than about 400. Absolute instability occurs only for sufficiently large values of the center-line wake defect. The critical value of this parameter increases with decreasing wake Reynolds number, thereby indicating a shrinking region of absolute instability with decreasing wake Reynolds number. If backflow is not allowed, absolute instability does not occur for wake Reynolds numbers smaller than about 38.

  8. Laboratory for Radiokrypton Dating

    NASA Astrophysics Data System (ADS)

    Lu, Z.; Bailey, K.; Jiang, W.; Müller, P.; O'Connor, T. P.; Zappala, J. C.

    2013-12-01

    Due to its simple production and transport processes in the terrestrial environment, the long-lived noble-gas isotope 81Kr (half-life = 230 kyr) is the ideal tracer for studying old water and ice in the age range of 10^5-10^6 years, a range beyond the reach of 14C. 81Kr dating, a concept pursued in the past four decades by numerous laboratories employing a variety of techniques, is now available for the first time to the earth science community at large. This is made possible by the development of ATTA-3 (Jiang et al., GCA 91, 1-6; 2012), an efficient and selective atom counter based on the Atom Trap Trace Analysis method (Chen et al., Science 286, 1139-1141; 1999). The instrument is capable of measuring both 81Kr/Kr and 85Kr/Kr ratios of environmental samples in the range of 10^-14-10^-10. For 81Kr-dating in the age range of 150 - 1,500 kyr, the required sample size is 5 - 10 micro-L STP of krypton gas, which can be extracted from approximately 100 - 200 kg of water or 40 - 80 kg of ice. For 85Kr/Kr analysis, the required sample size is generally smaller by an order of magnitude because of the isotope's higher initial abundance in the atmosphere. The Laboratory for Radiokrypton Dating is currently equipped to analyze up to 120 samples per year. With future equipment upgrades, this limit can be increased as demand grows. In the period since November 2011, the Laboratory has measured both 81Kr/Kr and 85Kr/Kr ratios in over 50 samples that had been extracted by collaborators from six different continents. The samples were from groundwater wells in the Great Artesian Basin (Australia), Guarani Aquifer (Brazil), and Locust Grove (Maryland); from brine wells of the Waste Isolation Pilot Plant (New Mexico); from geothermal steam vents in Yellowstone National Park; from near-surface ice at Taylor Glacier, Antarctica; and from deep mines in South Africa. Sample collection and purification was performed by groups including the University of Illinois at Chicago, University

  9. The Hamburg/ESO R-process enhanced star survey (HERES). IV. Detailed abundance analysis and age dating of the strongly r-process enhanced stars CS 29491-069 and HE 1219-0312

    NASA Astrophysics Data System (ADS)

    Hayek, W.; Wiesendahl, U.; Christlieb, N.; Eriksson, K.; Korn, A. J.; Barklem, P. S.; Hill, V.; Beers, T. C.; Farouqi, K.; Pfeiffer, B.; Kratz, K.-L.

    2009-09-01

    We report on a detailed abundance analysis of two strongly r-process enhanced, very metal-poor stars newly discovered in the HERES project, CS 29491-069 ([Fe/H]=-2.51, [r/Fe]=+1.1) and HE 1219-0312 ([Fe/H]=-2.96, [r/Fe]=+1.5). The analysis is based on high-quality VLT/UVES spectra and MARCS model atmospheres. We detect lines of 15 heavy elements in the spectrum of CS 29491-069, and 18 in HE 1219-0312; in both cases including the Th II 4019 Å line. The heavy-element abundance patterns of these two stars are mostly well-matched to scaled solar residual abundances not formed by the s-process. We also compare the observed pattern with recent high-entropy wind (HEW) calculations, which assume core-collapse supernovae of massive stars as the astrophysical environment for the r-process, and find good agreement for most lanthanides. The abundance ratios of the lighter elements strontium, yttrium, and zirconium, which are presumably not formed by the main r-process, are reproduced well by the model. Radioactive dating for CS 29491-069 with the observed thorium and rare-earth element abundance pairs results in an average age of 9.5 Gyr, when based on solar r-process residuals, and 17.6 Gyr, when using HEW model predictions. Chronometry seems to fail in the case of HE 1219-0312, resulting in a negative age due to its high thorium abundance. HE 1219-0312 could therefore exhibit an overabundance of the heaviest elements, which is sometimes called an “actinide boost”. Based on observations collected at the European Southern Observatory, Paranal, Chile (Proposal Number 170.D-0010). Table 8 is only available in electronic form at http://www.aanda.org

  10. The Antarctica component of postglacial rebound model ICE-6G_C (VM5a) based on GPS positioning, exposure age dating of ice thicknesses, and relative sea level histories

    NASA Astrophysics Data System (ADS)

    Argus, Donald F.; Peltier, W. R.; Drummond, R.; Moore, Angelyn W.

    2014-07-01

    A new model of the deglaciation history of Antarctica over the past 25 kyr has been developed, which we refer to herein as ICE-6G_C (VM5a). This revision of its predecessor ICE-5G (VM2) has been constrained to fit all available geological and geodetic observations, consisting of: (1) the present day uplift rates at 42 sites estimated from GPS measurements, (2) ice thickness change at 62 locations estimated from exposure-age dating, (3) Holocene relative sea level histories from 12 locations estimated on the basis of radiocarbon dating and (4) age of the onset of marine sedimentation at nine locations along the Antarctic shelf also estimated on the basis of 14C dating. Our new model fits the totality of these data well. An additional nine GPS-determined site velocities are also estimated for locations known to be influenced by modern ice loss from the Pine Island Bay and Northern Antarctic Peninsula regions. At the 42 locations not influenced by modern ice loss, the quality of the fit of postglacial rebound model ICE-6G_C (VM5A) is characterized by a weighted root mean square residual of 0.9 mm yr-1. The Southern Antarctic Peninsula is inferred to be rising at 2 mm yr-1, requiring there to be less Holocene ice loss there than in the prior model ICE-5G (VM2). The East Antarctica coast is rising at approximately 1 mm yr-1, requiring ice loss from this region to have been small since Last Glacial Maximum. The Ellsworth Mountains, at the base of the Antarctic Peninsula, are inferred to be rising at 5-8 mm yr-1, indicating large ice loss from this area during deglaciation that is poorly sampled by geological data. Horizontal deformation of the Antarctic Plate is minor with two exceptions. First, O'Higgins, at the tip of the Antarctic Peninsula, is moving southeast at a significant 2 mm yr-1 relative to the Antarctic Plate. Secondly, the margins of the Ronne and Ross Ice Shelves are moving horizontally away from the shelf centres at an approximate rate of 0.8 mm yr-1, in

  11. Food Product Dating

    MedlinePlus

    ... Formula What do can codes mean? Dates on Egg Cartons UPC or Bar Codes Storage Times Refrigerator ... primarily on perishable foods such as meat, poultry, eggs and dairy products. "Closed" or "coded" dating might ...

  12. Isotope age of the rare metal pegmatite formation in the Kolmozero-Voron'ya greenstone belt (Kola region of the Fennoscandian shield): U-Pb (TIMS) microlite and tourmaline dating

    NASA Astrophysics Data System (ADS)

    Kudryashov, Nikolay; Lyalina, Ludmila; Mokrushin, Artem; Zozulya, Dmitry; Groshev, Nikolay; Steshenko, Ekaterina; Kunakkuzin, Evgeniy

    2016-04-01

    surface contamination being placed the ultrasonic bath with the 7N HNO3 solution. The discordia constructed for seven measured microlite weights is characterized by upper intercepts with concordia at 2454±8 Ma, which probably reflects the time of rare metal pegmatite crystallization, coeval with the age of tourmaline granites. Taking into consideration the obtained U--Pb age of microlite, it may be assumed that the tourmaline granites dated back to 2520±70 Ma served as the most probable parental rocks for rare metal pegmatites of the Vasin-Myl'k deposit. The work is supported by RFBR No 16-05-00367, No 16-05-00427 and project No 0231-2015-0005

  13. Peer Involvement in Adolescent Dating Violence

    ERIC Educational Resources Information Center

    Stephenson, Pam S.; Martsolf, Donna; Draucker, Claire Burke

    2013-01-01

    This study investigated the ways in which peers are involved in adolescent dating violence. Eighty-eight young adults aged 18-21 were interviewed and asked to reflect on aggressive dating relationships they experienced as teens. The researchers used grounded theory to analyze the data. Findings showed that male and female peers were involved in…

  14. Radiocarbon dating of the Shroud of Turin

    NASA Astrophysics Data System (ADS)

    Damon, P. E.; Donahue, D. J.; Gore, B. H.; Hatheway, A. L.; Jull, A. J. T.; Linick, T. W.; Sercel, P. J.; Toolin, L. J.; Bronk, C. R.; Hall, E. T.; Hedges, R. E. M.; Housley, R.; Law, I. A.; Perry, C.; Bonani, G.; Trumbore, S.; Woelfli, W.; Ambers, J. C.; Bowman, S. G. E.; Leese, M. N.; Tite, M. S.

    1989-02-01

    Very small samples from the Shroud of Turin have been dated by accelerator mass spectrometry in laboratories at Arizona, Oxford and Zurich. As controls, three samples whose ages had been determined independently were also dated. The results provide conclusive evidence that the linen of the Shroud of Turin is mediaeval.

  15. Absolute optical instruments without spherical symmetry

    NASA Astrophysics Data System (ADS)

    Tyc, Tomáš; Dao, H. L.; Danner, Aaron J.

    2015-11-01

    Until now, the known set of absolute optical instruments has been limited to those containing high levels of symmetry. Here, we demonstrate a method of mathematically constructing refractive index profiles that result in asymmetric absolute optical instruments. The method is based on the analogy between geometrical optics and classical mechanics and employs Lagrangians that separate in Cartesian coordinates. In addition, our method can be used to construct the index profiles of most previously known absolute optical instruments, as well as infinitely many different ones.

  16. A Date with Violence.

    ERIC Educational Resources Information Center

    Lowe, Robert; And Others

    1997-01-01

    Teen dating violence is common but preventable. A survey of Texas high schoolers showed that half of respondents had been victims of dating violence. A majority of both sexes believed that certain behaviors justified being hit by their dating partners. It is important to raise the awareness of school personnel, parents, and students. Peer…

  17. A Proof of Concept for In-Situ Lunar Dating

    NASA Astrophysics Data System (ADS)

    Anderson, F. S.; Whitaker, T.; Levine, J.; Draper, D. S.; Harris, W.; Olansen, J.; Devolites, J.

    2015-12-01

    We have obtained improved 87Rb-87Sr isochrons for the Duluth Gabbro, an analog for lunar KREEP rocks, using a prototype spaceflight laser ablation resonance ionization mass spectrometer (LARIMS). The near-side of the Moon comprises previously un-sampled, KREEP rich, young-lunar basalts critical for calibrating the <3.5 Ga history of the Moon, and hence the solar system, since 3.5 Ga. Measurement of the Duluth Gabbro is a proof of concept of lunar in-situ dating to constrain lunar history. Using a novel normalization approach, and by correcting for matrix-dependent isotope effects, we have been able to obtain a date of 1100 ± 200 Ma (Figure 1), compared to the previously established thermal ionization mass spectrometry measurement of 1096 ± 14 Ma. The precision of LARIMS is sufficient to constrain the current 1 Ga uncertainty of the lunar flux curve, allowing us to reassess the timing of peak lunar volcanism, and constrain lunar thermal evolution. Furthermore, an updated lunar flux curve has implications throughout the solar system. For example, Mars could have undergone a longer epoch of voluminous, shield-forming volcanism and associated mantle evolution, as well as a longer era of abundant volatiles and hence potential habitability. These alternative chronologies could even affect our understanding of the evolution of life on Earth: under the classic chronology, life is thought to have originated after the dwindling of bombardment, but under the alternative chronology, it might have appeared during heavy bombardment. In order to resolve the science questions regarding the history of the Moon, and in light of the Duluth Gabbro results, we recently proposed a Discovery mission called MARE: The Moon Age and Regolith Explorer. MARE would accomplish these goals by landing on a young, nearside lunar basalt flow southwest of Aristarchus that has a crater density corresponding to a highly uncertain absolute age, collecting >10 rock samples, and assessing their

  18. Dating of ballpoint pen ink.

    PubMed

    Hofer, R

    2004-11-01

    In this paper we describe a case in which a cash book, dated of the year 2000, was sent to the Forensic Science Division, Document Laboratory, Zurich Canton Police in March 2003. The questioned document was a list of 29 pages containing a consecutive handwritten numbering and dated entries (payments) made of blue ballpoint pen ink. By definition, a cash book has to be written by hand and the entries have to be made daily. The questioned document was suspected to have been written within a short period (e.g., a few hours) and backdated. The document lab was asked to determine the date of the entries of the questioned list. On one hand, we were asked, if the cash book had been kept on account consecutively during the period of one year, and on the other hand, the judges were interested in knowing, if the document could have been written in 2003 and back dated to 2000. To answer these questions, the document was examined for latent elements by electrostatic detection device (ESDA). The relative dating of the entries was performed by the quantification of the ballpoint pen ink dyes and their degradation products using HPLC. Results show that it is possible to determine the relative age of entries written by ballpoint pen within a relatively short time scale, if storage and supporting material of the different samples are the same or at least similar. PMID:15568713

  19. Datation U_Pb : âge de mise en place du magmatisme bimodal des Jebilet centrales (chaîne Varisque, Maroc). Implications géodynamiquesU_Pb dating: emplacement age of the bimodal magmatism of central Jebilet (Variscan Belt, Morocco). Geodynamic implications

    NASA Astrophysics Data System (ADS)

    Essaifi, Abderrahim; Potrel, Alain; Capdevila, Ramon; Lagarde, Jean-Louis

    2003-01-01

    The bimodal magmatism of central Jebilet is dated to 330.5 +0.68-0.83 Ma by UPb dating on zircons. This age, similar to that of the syntectonic Jebilet cordierite-bearing granitoids, corresponds to the age of the local major tectonometamorphic event. The syntectonic plutonism of the Jebilet massif, composed of tholeiitic, alkaline, and peraluminous calc-alkaline series, is variegated. Magmas emplacement was favoured by the local extension induced by the motion along the western boundary of the Carboniferous basins of the Moroccan Meseta. The Jebilet massif exemplifies the activation of various magmas sources during an episode of continental convergence and crustal wrenching.

  20. Orion Absolute Navigation System Progress and Challenge

    NASA Technical Reports Server (NTRS)

    Holt, Greg N.; D'Souza, Christopher

    2012-01-01

    The absolute navigation design of NASA's Orion vehicle is described. It has undergone several iterations and modifications since its inception, and continues as a work-in-progress. This paper seeks to benchmark the current state of the design and some of the rationale and analysis behind it. There are specific challenges to address when preparing a timely and effective design for the Exploration Flight Test (EFT-1), while still looking ahead and providing software extensibility for future exploration missions. The primary onboard measurements in a Near-Earth or Mid-Earth environment consist of GPS pseudo-range and delta-range, but for future explorations missions the use of star-tracker and optical navigation sources need to be considered. Discussions are presented for state size and composition, processing techniques, and consider states. A presentation is given for the processing technique using the computationally stable and robust UDU formulation with an Agee-Turner Rank-One update. This allows for computational savings when dealing with many parameters which are modeled as slowly varying Gauss-Markov processes. Preliminary analysis shows up to a 50% reduction in computation versus a more traditional formulation. Several state elements are discussed and evaluated, including position, velocity, attitude, clock bias/drift, and GPS measurement biases in addition to bias, scale factor, misalignment, and non-orthogonalities of the accelerometers and gyroscopes. Another consideration is the initialization of the EKF in various scenarios. Scenarios such as single-event upset, ground command, and cold start are discussed as are strategies for whole and partial state updates as well as covariance considerations. Strategies are given for dealing with latent measurements and high-rate propagation using multi-rate architecture. The details of the rate groups and the data ow between the elements is discussed and evaluated.

  1. Bullying Predicts Reported Dating Violence and Observed Qualities in Adolescent Dating Relationships.

    PubMed

    Ellis, Wendy E; Wolfe, David A

    2015-10-01

    The relationship between reported bullying, reported dating violence, and dating relationship quality measured through couple observations was examined. Given past research demonstrating similarity between peer and dating contexts, we expected that bullying would predict negative dating experiences. Participants with dating experience (n = 585; 238 males, M(age) = 15.06) completed self-report assessments of bullying and dating violence perpetration and victimization. One month later, 44 opposite-sex dyads (M(age) = 15.19) participated in behavioral observations. In 10-min sessions, couples were asked to rank and discuss areas of relationship conflict while being video-recorded. Qualities of the relationship were later coded by trained observers. Regression analysis revealed that bullying positively predicted dating violence perpetration and victimization. Self-reported bullying also predicted observations of lower relationship support and higher withdrawal. Age and gender interactions further qualified these findings. The bullying of boys, but not girls, was significantly related to dating violence perpetration. Age interactions showed that bullying was positively predictive of dating violence perpetration and victimization for older, but not younger adolescents. Positive affect was also negatively predicted by bullying, but only for girls. These findings add to the growing body of evidence that adolescents carry forward strategies learned in the peer context to their dating relationships. PMID:25355858

  2. Absolute magnitudes of trans-neptunian objects

    NASA Astrophysics Data System (ADS)

    Duffard, R.; Alvarez-candal, A.; Pinilla-Alonso, N.; Ortiz, J. L.; Morales, N.; Santos-Sanz, P.; Thirouin, A.

    2015-10-01

    Accurate measurements of diameters of trans- Neptunian objects are extremely complicated to obtain. Radiomatric techniques applied to thermal measurements can provide good results, but precise absolute magnitudes are needed to constrain diameters and albedos. Our objective is to measure accurate absolute magnitudes for a sample of trans- Neptunian objects, many of which have been observed, and modelled, by the "TNOs are cool" team, one of Herschel Space Observatory key projects grantes with ~ 400 hours of observing time. We observed 56 objects in filters V and R, if possible. These data, along with data available in the literature, was used to obtain phase curves and to measure absolute magnitudes by assuming a linear trend of the phase curves and considering magnitude variability due to rotational light-curve. In total we obtained 234 new magnitudes for the 56 objects, 6 of them with no reported previous measurements. Including the data from the literature we report a total of 109 absolute magnitudes.

  3. A New Gimmick for Assigning Absolute Configuration.

    ERIC Educational Resources Information Center

    Ayorinde, F. O.

    1983-01-01

    A five-step procedure is provided to help students in making the assignment absolute configuration less bothersome. Examples for both single (2-butanol) and multi-chiral carbon (3-chloro-2-butanol) molecules are included. (JN)

  4. U-series Dating of Stalagmites from Borneo

    NASA Astrophysics Data System (ADS)

    Adkins, J. F.; Partin, J.; Cobb, K.; Clark, B.

    2006-12-01

    In a series of field campaigns dating back to the fall of 2003 we have collected over 60 stalagmites from the Gunung Buda cave system in Sarawak, Malaysia (4°N, 115°E). At least twenty of these samples have excellent calcite preservation and span an age range from modern to over 500,000 years old. The bulk of the collection is of early glacial to Holocene age and can provide multiple overlapping records of climate variability from the Western Pacific Warm Pool. However, generating absolute U-series ages from this collection is challenging. The host rock is a Miocene aged limestone that is covered by rainforest with virtually no topsoil development. This setting leaves the typical stalagmite sample with a low uranium concentration (100s of ppb), a low initial δ234U (-650‰ to -100‰), and a relatively high detrital Th concentration (10s to 100s of pmol/g). We have generated age models in these difficult circumstances by making over 150 MC-ICP-MS measurements of the 238U-234U-230Th-232Th disequilibrium system. Ages are limited by our correction for initial 230Th. This is a common problem in U-series dating of stalagmites that we have addressed by generating a "histogram" of initial 230/232 values. With 14 isochrons from four separate stalagmites spanning the glacial maximum through the Holocene we can conservatively constrain the initial 230/232 atom ratio to be 60±10x10-6. There are small differences in the weighted mean of this value between stalagmites, but no systematic differences with time within a stalagmite. The very low δ234U values are intriguing and must represent the effects of recent weathering of the host limestone. These low and variable δ234U ratios also make it imperative to calculate the initial 230/232 ratios with full three-dimensional isochrons, extrapolating to zero U-238 on a "Rosholt Diagram" does not produce a consistent answer between the samples. Overall we can produce 2 sigma age errors that are better than 1% for the combined

  5. Thermoluminescence dating of Australian palaeo-earthquakes

    USGS Publications Warehouse

    Hutton, J.T.; Prescott, J.R.; Bowman, J.R.; Dunham, M.N.E.; Crone, A.J.; Machette, M.N.; Twidale, C.R.

    1994-01-01

    Thermoluminescence (TL) dating is a useful tool for determining the age of prehistoric earthquakes by dating deposits that are stratigraphically related to fault scarps that formed during the earthquakes. TL dating of aeolian sand in the area of the 1988 Tennant Creek, Northern Territory, earthquakes provides evidence that similar earthquakes have not ruptured the causative faults for at least 50 ka. Pilot TL measurements of deposits associated with the Roopena and Ash Ridge fault scarps near Whyalla on Eyre Peninsula, South Australia, suggest an age of 140 ka for the Quaternary deposits associated with the formation of the scarps. ?? 1994.

  6. The Sea Peoples, from Cuneiform Tablets to Carbon Dating

    PubMed Central

    Kaniewski, David; Van Campo, Elise; Van Lerberghe, Karel; Boiy, Tom; Vansteenhuyse, Klaas; Jans, Greta; Nys, Karin; Weiss, Harvey; Morhange, Christophe; Otto, Thierry; Bretschneider, Joachim

    2011-01-01

    The 13th century BC witnessed the zenith of the Aegean and Eastern Mediterranean civilizations which declined at the end of the Bronze Age, ∼3200 years ago. Weakening of this ancient flourishing Mediterranean world shifted the political and economic centres of gravity away from the Levant towards Classical Greece and Rome, and led, in the long term, to the emergence of the modern western civilizations. Textual evidence from cuneiform tablets and Egyptian reliefs from the New Kingdom relate that seafaring tribes, the Sea Peoples, were the final catalyst that put the fall of cities and states in motion. However, the lack of a stratified radiocarbon-based archaeology for the Sea People event has led to a floating historical chronology derived from a variety of sources spanning dispersed areas. Here, we report a stratified radiocarbon-based archaeology with anchor points in ancient epigraphic-literary sources, Hittite-Levantine-Egyptian kings and astronomical observations to precisely date the Sea People event. By confronting historical and science-based archaeology, we establish an absolute age range of 1192–1190 BC for terminal destructions and cultural collapse in the northern Levant. This radiocarbon-based archaeology has far-reaching implications for the wider Mediterranean, where an elaborate network of international relations and commercial activities are intertwined with the history of civilizations. PMID:21687714

  7. The Sea Peoples, from cuneiform tablets to carbon dating.

    PubMed

    Kaniewski, David; Van Campo, Elise; Van Lerberghe, Karel; Boiy, Tom; Vansteenhuyse, Klaas; Jans, Greta; Nys, Karin; Weiss, Harvey; Morhange, Christophe; Otto, Thierry; Bretschneider, Joachim

    2011-01-01

    The 13(th) century BC witnessed the zenith of the Aegean and Eastern Mediterranean civilizations which declined at the end of the Bronze Age, ∼3200 years ago. Weakening of this ancient flourishing Mediterranean world shifted the political and economic centres of gravity away from the Levant towards Classical Greece and Rome, and led, in the long term, to the emergence of the modern western civilizations. Textual evidence from cuneiform tablets and Egyptian reliefs from the New Kingdom relate that seafaring tribes, the Sea Peoples, were the final catalyst that put the fall of cities and states in motion. However, the lack of a stratified radiocarbon-based archaeology for the Sea People event has led to a floating historical chronology derived from a variety of sources spanning dispersed areas. Here, we report a stratified radiocarbon-based archaeology with anchor points in ancient epigraphic-literary sources, Hittite-Levantine-Egyptian kings and astronomical observations to precisely date the Sea People event. By confronting historical and science-based archaeology, we establish an absolute age range of 1192-1190 BC for terminal destructions and cultural collapse in the northern Levant. This radiocarbon-based archaeology has far-reaching implications for the wider Mediterranean, where an elaborate network of international relations and commercial activities are intertwined with the history of civilizations. PMID:21687714

  8. Jasminum flexile flower absolute from India--a detailed comparison with three other jasmine absolutes.

    PubMed

    Braun, Norbert A; Kohlenberg, Birgit; Sim, Sherina; Meier, Manfred; Hammerschmidt, Franz-Josef

    2009-09-01

    Jasminum flexile flower absolute from the south of India and the corresponding vacuum headspace (VHS) sample of the absolute were analyzed using GC and GC-MS. Three other commercially available Indian jasmine absolutes from the species: J. sambac, J. officinale subsp. grandiflorum, and J. auriculatum and the respective VHS samples were used for comparison purposes. One hundred and twenty-one compounds were characterized in J. flexile flower absolute, with methyl linolate, benzyl salicylate, benzyl benzoate, (2E,6E)-farnesol, and benzyl acetate as the main constituents. A detailed olfactory evaluation was also performed. PMID:19831037

  9. Identification and dating of the Mono Lake excursion in lava flows from the Canary islands.

    NASA Astrophysics Data System (ADS)

    Guillou, Hervé; Laj, Carlo; Carracedo, Juan-Carlos; Kissel, Catherine; Nomade, Sebastien; Perez-Torrado, Francisco; Wandres, Camille

    2010-05-01

    age is, within the uncertainties, consistent with 33.5 to 34.5 ka distribution of the 10Be peak (centered at 34 ka) in NGRIP core. The directional deviation observed at these sites coupled with a first absolute dating of this excursion indicates that it can constitute an accurate chronostratigraphic tie point for many geological and climatic studies, similarly to the Laschamp excursion. In addition, the different directions and intensities obtained from the four sites with statistically similar ages imply a short duration for this excursion (shorter than the age uncertainty).

  10. Universal Cosmic Absolute and Modern Science

    NASA Astrophysics Data System (ADS)

    Kostro, Ludwik

    The official Sciences, especially all natural sciences, respect in their researches the principle of methodic naturalism i.e. they consider all phenomena as entirely natural and therefore in their scientific explanations they do never adduce or cite supernatural entities and forces. The purpose of this paper is to show that Modern Science has its own self-existent, self-acting, and self-sufficient Natural All-in Being or Omni-Being i.e. the entire Nature as a Whole that justifies the scientific methodic naturalism. Since this Natural All-in Being is one and only It should be considered as the own scientifically justified Natural Absolute of Science and should be called, in my opinion, the Universal Cosmic Absolute of Modern Science. It will be also shown that the Universal Cosmic Absolute is ontologically enormously stratified and is in its ultimate i.e. in its most fundamental stratum trans-reistic and trans-personal. It means that in its basic stratum. It is neither a Thing or a Person although It contains in Itself all things and persons with all other sentient and conscious individuals as well, On the turn of the 20th century the Science has begun to look for a theory of everything, for a final theory, for a master theory. In my opinion the natural Universal Cosmic Absolute will constitute in such a theory the radical all penetrating Ultimate Basic Reality and will substitute step by step the traditional supernatural personal Absolute.

  11. Chemical Principles Revisited: Archaeological Dating.

    ERIC Educational Resources Information Center

    Rowe, M. W.

    1986-01-01

    Discusses methods used to date archaeological artifacts and other remains. They include: (1) nuclear dating techniques (radiocarbon dating, accelerator radiocarbon dating, thermoluminescence, and others); (2) chemical dating techniques (amino acid racemization, obsidian hydration dating, elemental content changes, and thermal analysis dating); and…

  12. Date Palm Germplasm

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This book chapter reviews date palm genetic resources and their conservation. Date palm (Phoenix dactylifera) is an important food crop in the Middle East and North Africa. Its center of origin and diversity most probably is the area near Iraq/Iran. From there, it spread throughout its present range...

  13. Radiometric Dating in Geology.

    ERIC Educational Resources Information Center

    Pankhurst, R. J.

    1980-01-01

    Described are several aspects and methods of quantitatively measuring geologic time using a constant-rate natural process of radioactive decay. Topics include half lives and decay constants, radiogenic growth, potassium-argon dating, rubidium-strontium dating, and the role of geochronology in support of geological exploration. (DS)

  14. Dating Violence in Russia

    ERIC Educational Resources Information Center

    Lysova, A. V.

    2007-01-01

    The phenomenon of violence in interpersonal relationships has been little studied in Russia, and the phenomenon of violence between dating partners has not been the object of scientific interest at all. The study on which the present article is based was designed to obtain information about the violence in dating among students enrolled in…

  15. Choosing a Calving Date

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Calving date affects cost and timing of production events. Due to the polyestrous nature of beef females, producers can choose a calving date that fits their production system and geographic region. Any time an entire production system is considered, decision making becomes complex. Any calving syst...

  16. Absolute isotopic abundances of TI in meteorites

    NASA Astrophysics Data System (ADS)

    Niederer, F. R.; Papanastassiou, D. A.; Wasserburg, G. J.

    1985-03-01

    The absolute isotope abundance of Ti has been determined in Ca-Al-rich inclusions from the Allende and Leoville meteorites and in samples of whole meteorites. The absolute Ti isotope abundances differ by a significant mass dependent isotope fractionation transformation from the previously reported abundances, which were normalized for fractionation using 46Ti/48Ti. Therefore, the absolute compositions define distinct nucleosynthetic components from those previously identified or reflect the existence of significant mass dependent isotope fractionation in nature. The authors provide a general formalism for determining the possible isotope compositions of the exotic Ti from the measured composition, for different values of isotope fractionation in nature and for different mixing ratios of the exotic and normal components.

  17. Molecular iodine absolute frequencies. Final report

    SciTech Connect

    Sansonetti, C.J.

    1990-06-25

    Fifty specified lines of {sup 127}I{sub 2} were studied by Doppler-free frequency modulation spectroscopy. For each line the classification of the molecular transition was determined, hyperfine components were identified, and one well-resolved component was selected for precise determination of its absolute frequency. In 3 cases, a nearby alternate line was selected for measurement because no well-resolved component was found for the specified line. Absolute frequency determinations were made with an estimated uncertainty of 1.1 MHz by locking a dye laser to the selected hyperfine component and measuring its wave number with a high-precision Fabry-Perot wavemeter. For each line results of the absolute measurement, the line classification, and a Doppler-free spectrum are given.

  18. Stimulus probability effects in absolute identification.

    PubMed

    Kent, Christopher; Lamberts, Koen

    2016-05-01

    This study investigated the effect of stimulus presentation probability on accuracy and response times in an absolute identification task. Three schedules of presentation were used to investigate the interaction between presentation probability and stimulus position within the set. Data from individual participants indicated strong effects of presentation probability on both proportion correct and response times. The effects were moderated by the ubiquitous stimulus position effect. The accuracy and response time data were predicted by an exemplar-based model of perceptual cognition (Kent & Lamberts, 2005). The bow in discriminability was also attenuated when presentation probability for middle items was relatively high, an effect that will constrain future model development. The study provides evidence for item-specific learning in absolute identification. Implications for other theories of absolute identification are discussed. (PsycINFO Database Record PMID:26478959

  19. Absolute calibration in vivo measurement systems

    SciTech Connect

    Kruchten, D.A.; Hickman, D.P.

    1991-02-01

    Lawrence Livermore National Laboratory (LLNL) is currently investigating a new method for obtaining absolute calibration factors for radiation measurement systems used to measure internally deposited radionuclides in vivo. Absolute calibration of in vivo measurement systems will eliminate the need to generate a series of human surrogate structures (i.e., phantoms) for calibrating in vivo measurement systems. The absolute calibration of in vivo measurement systems utilizes magnetic resonance imaging (MRI) to define physiological structure, size, and composition. The MRI image provides a digitized representation of the physiological structure, which allows for any mathematical distribution of radionuclides within the body. Using Monte Carlo transport codes, the emission spectrum from the body is predicted. The in vivo measurement equipment is calibrated using the Monte Carlo code and adjusting for the intrinsic properties of the detection system. The calibration factors are verified using measurements of existing phantoms and previously obtained measurements of human volunteers. 8 refs.

  20. Precise Measurement of the Absolute Fluorescence Yield

    NASA Astrophysics Data System (ADS)

    Ave, M.; Bohacova, M.; Daumiller, K.; Di Carlo, P.; di Giulio, C.; San Luis, P. Facal; Gonzales, D.; Hojvat, C.; Hörandel, J. R.; Hrabovsky, M.; Iarlori, M.; Keilhauer, B.; Klages, H.; Kleifges, M.; Kuehn, F.; Monasor, M.; Nozka, L.; Palatka, M.; Petrera, S.; Privitera, P.; Ridky, J.; Rizi, V.; D'Orfeuil, B. Rouille; Salamida, F.; Schovanek, P.; Smida, R.; Spinka, H.; Ulrich, A.; Verzi, V.; Williams, C.

    2011-09-01

    We present preliminary results of the absolute yield of fluorescence emission in atmospheric gases. Measurements were performed at the Fermilab Test Beam Facility with a variety of beam particles and gases. Absolute calibration of the fluorescence yield to 5% level was achieved by comparison with two known light sources--the Cherenkov light emitted by the beam particles, and a calibrated nitrogen laser. The uncertainty of the energy scale of current Ultra-High Energy Cosmic Rays experiments will be significantly improved by the AIRFLY measurement.

  1. Absolutely relative or relatively absolute: violations of value invariance in human decision making.

    PubMed

    Teodorescu, Andrei R; Moran, Rani; Usher, Marius

    2016-02-01

    Making decisions based on relative rather than absolute information processing is tied to choice optimality via the accumulation of evidence differences and to canonical neural processing via accumulation of evidence ratios. These theoretical frameworks predict invariance of decision latencies to absolute intensities that maintain differences and ratios, respectively. While information about the absolute values of the choice alternatives is not necessary for choosing the best alternative, it may nevertheless hold valuable information about the context of the decision. To test the sensitivity of human decision making to absolute values, we manipulated the intensities of brightness stimuli pairs while preserving either their differences or their ratios. Although asked to choose the brighter alternative relative to the other, participants responded faster to higher absolute values. Thus, our results provide empirical evidence for human sensitivity to task irrelevant absolute values indicating a hard-wired mechanism that precedes executive control. Computational investigations of several modelling architectures reveal two alternative accounts for this phenomenon, which combine absolute and relative processing. One account involves accumulation of differences with activation dependent processing noise and the other emerges from accumulation of absolute values subject to the temporal dynamics of lateral inhibition. The potential adaptive role of such choice mechanisms is discussed. PMID:26022836

  2. Landsat-5 TM reflective-band absolute radiometric calibration

    USGS Publications Warehouse

    Chander, G.; Helder, D.L.; Markham, B.L.; Dewald, J.D.; Kaita, E.; Thome, K.J.; Micijevic, E.; Ruggles, T.A.

    2004-01-01

    The Landsat-5 Thematic Mapper (TM) sensor provides the longest running continuous dataset of moderate spatial resolution remote sensing imagery, dating back to its launch in March 1984. Historically, the radiometric calibration procedure for this imagery used the instrument's response to the Internal Calibrator (IC) on a scene-by-scene basis to determine the gain and offset of each detector. Due to observed degradations in the IC, a new procedure was implemented for U.S.-processed data in May 2003. This new calibration procedure is based on a lifetime radiometric calibration model for the instrument's reflective bands (1-5 and 7) and is derived, in part, from the IC response without the related degradation effects and is tied to the cross calibration with the Landsat-7 Enhanced Thematic Mapper Plus. Reflective-band absolute radiometric accuracy of the instrument tends to be on the order of 7% to 10%, based on a variety of calibration methods.

  3. The absolute frequency of the 87Sr optical clock transition

    NASA Astrophysics Data System (ADS)

    Campbell, Gretchen K.; Ludlow, Andrew D.; Blatt, Sebastian; Thomsen, Jan W.; Martin, Michael J.; de Miranda, Marcio H. G.; Zelevinsky, Tanya; Boyd, Martin M.; Ye, Jun; Diddams, Scott A.; Heavner, Thomas P.; Parker, Thomas E.; Jefferts, Steven R.

    2008-10-01

    The absolute frequency of the 1S0-3P0 clock transition of 87Sr has been measured to be 429 228 004 229 873.65 (37) Hz using lattice-confined atoms, where the fractional uncertainty of 8.6 × 10-16 represents one of the most accurate measurements of an atomic transition frequency to date. After a detailed study of systematic effects, which reduced the total systematic uncertainty of the Sr lattice clock to 1.5 × 10-16, the clock frequency is measured against a hydrogen maser which is simultaneously calibrated to the US primary frequency standard, the NIST Cs fountain clock, NIST-F1. The comparison is made possible using a femtosecond laser based optical frequency comb to phase coherently connect the optical and microwave spectral regions and by a 3.5 km fibre transfer scheme to compare the remotely located clock signals.

  4. Relative and absolute stability in perceived parenting behaviour: a longitudinal study with children and adolescents.

    PubMed

    Carrasco, M A; Rodríguez, M A; Del Barrio, M V; Holgado, F P

    2011-02-01

    Patterns of relative and absolute stability in parental behaviour with children and adolescents are reported. The sample comprised 523 youth (58.7% girls). Data were collected at three time periods: T1 (M age = 11.1 yr.), T2 (M age = 12.2 yr.), and T3 (M age = 13.2 yr.), each separated by one year. According to children's reports, relative consistency was moderate in both mothers and fathers, particularly as regards communication and strict control. In contrast, as children got older, parental rearing practices related to strict control and hostility decreased. There was a similarity between fathers and mothers in terms of relative and absolute stability. Relative stability was affected by the child's sex, the parenting variable, and the time period; however, the patterns of absolute stability reveal no differences by sex. PMID:21526601

  5. 238U-230Th dating of chevkinite in high-silica rhyolites from La Primavera and Yellowstone calderas

    USGS Publications Warehouse

    Vazquez, Jorge A.; Velasco, Noel O.; Schmitt, Axel K.; Bleick, Heather A.; Stelten, Mark E.

    2014-01-01

    Application of 238U-230Th disequilibrium dating of accessory minerals with contrasting stabilities and compositions can provide a unique perspective on magmatic evolution by placing the thermochemical evolution of magma within the framework of absolute time. Chevkinite, a Th-rich accessory mineral that occurs in peralkaline and metaluminous rhyolites, may be particularly useful as a chronometer of crystallization and differentiation because its composition may reflect the chemical changes of its host melt. Ion microprobe 128U-230Th dating of single chevkinite microphenocrysts from pre- and post-caldera La Primavera, Mexico, rhyolites yields model crystallization ages that are within 10's of k.y. of their corresponding K-Ar ages of ca. 125 ka to 85 ka, while chevkinite microphenocrysts from a post-caldera Yellowstone, USA, rhyolite yield a range of ages from ca. 110 ka to 250 ka, which is indistinguishable from the age distribution of coexisting zircon. Internal chevkinite-zircon isochrons from La Primavera yield Pleistocene ages with ~5% precision due to the nearly two order difference in Th/U between both minerals. Coupling chevkinite 238U-230Th ages and compositional analyses reveals a secular trend of Th/U and rare earth elements recorded in Yellowstone rhyolite, likely reflecting progressive compositional evolution of host magma. The relatively short timescale between chevkinite-zircon crystallization and eruption suggests that crystal-poor rhyolites at La Primavera were erupted shortly after differentiation and/or reheating. These results indicate that 238U-230Th dating of chevkinite via ion microprobe analysis may be used to date crystallization and chemical evolution of silicic magmas.

  6. Comparison of amino acid racemization geochronometry with lithostratigraphy, biostratigraphy, uranium-series coral dating, and magnetostratigraphy in the Atlantic Coastal Plain of the southeastern United States

    NASA Astrophysics Data System (ADS)

    McCartan, L.; Owens, J. P.; Blackwelder, B. W.; Szabo, B. J.; Belknap, D. F.; Kriausakul, N.; Mitterer, R. M.; Wehmiller, J. F.

    1982-11-01

    The results of an integrated study comprising litho- and biostratigraphic investigations, uranium-series coral dating, amino acid racemization in molluscs, and paleomagnetic measurements are compared to ascertain relative and absolute ages of Pleistocene deposits of the Atlantic Coastal Plain in North and South Carolina. Four depositional events are inferred for South Carolina and two for North Carolina by all methods. The data suggest that there are four Pleistocene units containing corals that have been dated at about 100,000 yr, 200,000 yr, 450,000 yr, and over 1,000,000 yr. Some conflicts exist between the different methods regarding the correlation of the younger of these depositional events between Charleston and Myrtle Beach. Lack of good uranium-series dates for the younger material at Myrtle Beach makes the correlation with the deposits at Charleston more difficult.

  7. Comparison of amino acid racemization geochronometry with lithostratigraphy, biostratigraphy, uranium-series coral dating, and magnetostratigraphy in the Atlantic Coastal Plain of the southeastern United States

    USGS Publications Warehouse

    McCartan, L.; Owens, J.P.; Blackwelder, B. W.; Szabo, B. J.; Belknap, D.F.; Kriausakul, N.; Mitterer, R.M.; Wehmiller, J. F.

    1982-01-01

    The results of an integrated study comprising litho- and biostratigraphic investigations, uranium-series coral dating, amino acid racemization in molluscs, and paleomagnetic measurements are compared to ascertain relative and absolute ages of Pleistocene deposits of the Atlantic Coastal Plain in North and South Carolina. Four depositional events are inferred for South Carolina and two for North Carolina by all methods. The data suggest that there are four Pleistocene units containing corals that have been dated at about 100,000 yr, 200,000 yr, 450,000 yr, and over 1,000,000 yr. Some conflicts exist between the different methods regarding the correlation of the younger of these depositional events between Charleston and Myrtle Beach. Lack of good uranium-series dates for the younger material at Myrtle Beach makes the correlation with the deposits at Charleston more difficult. ?? 1982.

  8. U-Pb Dating of Carbonates: A Complement to Clumped Isotope Analyses

    NASA Astrophysics Data System (ADS)

    Rasbury, T.; Suarez, M. B.

    2014-12-01

    Carbonates are ubiquitous in nature, forming in a variety of settings at the surface and through burial. The field and petrographic relationships of carbonate phases can often be linked to the depositional setting and burial path(s) that the sedimentary pile has experienced. Clumped isotopes are taking on an important role of testing the temperature of formation of the carbonates, and combined with other approaches such as fluid inclusion analyses offers tremendous potential for testing basin evolution models. However, while the relative ages of carbonates are often fairly easily elucidated, the absolute ages of the events recorded in carbonates are not. U-Pb dating of carbonates offers the best potential for constraining the ages. However, not all fluids have favorable U/Ca ratios. U-Pb dated groundwater carbonates from the Late Triassic New Haven Arkose give an age of 211 +/- 2 Ma, consistent with the known age of deposition. Late bright luminescent calcite from the same formation gives an age of 81+/-11 Ma, constraining the age (both primary and secondary) of carbonate formation. Clumped isotope analyses of primary carbonate phases show somewhat elevated temperatures between 50-60o C, some 30 degrees hotter than other estimates for this Triassic equatorial setting, and are more likely the result of re-ordering of 13C-18O bonds at depth. Apparently the primary calcite, appears to have preserved its depositional U-Pb systematics, however bond re-ordering or recrystallization of these carbonates appear to reflect values closer to thermal equilibrium with the last phase of carbonate formation (bright luminescent calcite, 81 ± 11 Ma). Further work on these samples will target these younger calcites to determine if this later calcite phase records similar temperatures.

  9. Helium-uranium dating of corals.

    NASA Technical Reports Server (NTRS)

    Bender, M. L.

    1973-01-01

    Fanale and Schaeffer (1965) determined He/U ages of corals and other aragonitic fossils, and found that the results generally agreed with independent age estimates. As a more extensive and rigorous test of the reliability of He/U ages of fossil corals, I have determined He/U ages of forty-five independently dated Cenozoic corals. Uranium and thorium isotope compositions and Rn-222 retentivities were also determined as consistency checks. The results indicate that reliable ages are obtained when certain consistency tests are met and specified corrections are made.

  10. Absolute partial photoionization cross sections of ozone.

    SciTech Connect

    Berkowitz, J.; Chemistry

    2008-04-01

    Despite the current concerns about ozone, absolute partial photoionization cross sections for this molecule in the vacuum ultraviolet (valence) region have been unavailable. By eclectic re-evaluation of old/new data and plausible assumptions, such cross sections have been assembled to fill this void.

  11. Solving Absolute Value Equations Algebraically and Geometrically

    ERIC Educational Resources Information Center

    Shiyuan, Wei

    2005-01-01

    The way in which students can improve their comprehension by understanding the geometrical meaning of algebraic equations or solving algebraic equation geometrically is described. Students can experiment with the conditions of the absolute value equation presented, for an interesting way to form an overall understanding of the concept.

  12. Teaching Absolute Value Inequalities to Mature Students

    ERIC Educational Resources Information Center

    Sierpinska, Anna; Bobos, Georgeana; Pruncut, Andreea

    2011-01-01

    This paper gives an account of a teaching experiment on absolute value inequalities, whose aim was to identify characteristics of an approach that would realize the potential of the topic to develop theoretical thinking in students enrolled in prerequisite mathematics courses at a large, urban North American university. The potential is…

  13. Increasing Capacity: Practice Effects in Absolute Identification

    ERIC Educational Resources Information Center

    Dodds, Pennie; Donkin, Christopher; Brown, Scott D.; Heathcote, Andrew

    2011-01-01

    In most of the long history of the study of absolute identification--since Miller's (1956) seminal article--a severe limit on performance has been observed, and this limit has resisted improvement even by extensive practice. In a startling result, Rouder, Morey, Cowan, and Pfaltz (2004) found substantially improved performance with practice in the…

  14. On Relative and Absolute Conviction in Mathematics

    ERIC Educational Resources Information Center

    Weber, Keith; Mejia-Ramos, Juan Pablo

    2015-01-01

    Conviction is a central construct in mathematics education research on justification and proof. In this paper, we claim that it is important to distinguish between absolute conviction and relative conviction. We argue that researchers in mathematics education frequently have not done so and this has lead to researchers making unwarranted claims…

  15. Absolute Points for Multiple Assignment Problems

    ERIC Educational Resources Information Center

    Adlakha, V.; Kowalski, K.

    2006-01-01

    An algorithm is presented to solve multiple assignment problems in which a cost is incurred only when an assignment is made at a given cell. The proposed method recursively searches for single/group absolute points to identify cells that must be loaded in any optimal solution. Unlike other methods, the first solution is the optimal solution. The…

  16. Nonequilibrium equalities in absolutely irreversible processes

    NASA Astrophysics Data System (ADS)

    Murashita, Yuto; Funo, Ken; Ueda, Masahito

    2015-03-01

    Nonequilibrium equalities have attracted considerable attention in the context of statistical mechanics and information thermodynamics. Integral nonequilibrium equalities reveal an ensemble property of the entropy production σ as = 1 . Although nonequilibrium equalities apply to rather general nonequilibrium situations, they break down in absolutely irreversible processes, where the forward-path probability vanishes and the entropy production diverges. We identify the mathematical origins of this inapplicability as the singularity of probability measure. As a result, we generalize conventional integral nonequilibrium equalities to absolutely irreversible processes as = 1 -λS , where λS is the probability of the singular part defined based on Lebesgue's decomposition theorem. The acquired equality contains two physical quantities related to irreversibility: σ characterizing ordinary irreversibility and λS describing absolute irreversibility. An inequality derived from the obtained equality demonstrates the absolute irreversibility leads to the fundamental lower bound on the entropy production. We demonstrate the validity of the obtained equality for a simple model.

  17. Stimulus Probability Effects in Absolute Identification

    ERIC Educational Resources Information Center

    Kent, Christopher; Lamberts, Koen

    2016-01-01

    This study investigated the effect of stimulus presentation probability on accuracy and response times in an absolute identification task. Three schedules of presentation were used to investigate the interaction between presentation probability and stimulus position within the set. Data from individual participants indicated strong effects of…

  18. Precision absolute positional measurement of laser beams.

    PubMed

    Fitzsimons, Ewan D; Bogenstahl, Johanna; Hough, James; Killow, Christian J; Perreur-Lloyd, Michael; Robertson, David I; Ward, Henry

    2013-04-20

    We describe an instrument which, coupled with a suitable coordinate measuring machine, facilitates the absolute measurement within the machine frame of the propagation direction of a millimeter-scale laser beam to an accuracy of around ±4 μm in position and ±20 μrad in angle. PMID:23669658

  19. Dating tectonic structures on Mercury

    NASA Astrophysics Data System (ADS)

    Giacomini, L.; Massironi, M.; Marchi, S.; Cremonese, G.

    2012-09-01

    Mercury surface appears to be interested by several tectonic structures, the most interesting ones being numerous lobate scarps formed mainly thanks to planet cooling and contraction. The Messenger cameras (MDIS WAC and NAC) allowed us to map several structures not previously detected. Among these a 250 km-long thrust has been detected crossing a peak ring basin. The region encircled within the inner ring of the basin is covered by a smooth plain with evidence of a sin-deformational emplacement. Dating this smooth plain with crater counting technique allowed us to give an age constrain of the tectonic structure.

  20. Ice Core Dating Software for Interactive Dating of Ice Cores

    NASA Astrophysics Data System (ADS)

    Kurbatov, A. V.; Mayewski, P. A.; Abdul Jawad, B. S.

    2005-12-01

    Scientists involved in ice core dating are well familiar with the problem of identification and recording the depth of annual signals using stable isotopes, glaciochemistry, ECM (electrical conductivity), DEP (dielectric properties) and particle counter data. Traditionally all parameters used for ice core dating were plotted as a function of depth, printed and after years were marked on the paper, converted to depth vs. age time scale. To expedite this tedious and manual process we developed interactive computer software, Ice core Dating (ICD) program. ICD is written in Java programming language, and uses GPL and GPL site licensed graphic libraries. The same 3.5 Mb in size pre-compiled single jar file, that includes all libraries and application code, was successfully tested on WinOS, Mac OSX, Linux, and Solaris operating systems running Java VM version 1.4. We have followed the modular design philosophy in our source code so potential integration with other software modules, data bases and server side distributed computer environments can be easily implemented. We expect to continue development of new suites of tools for easy integration of ice core data with other available time proxies. ICD is thoroughly documented and comes with a technical reference and cookbook that explains the purpose of the software and its many features, and provides examples to help new users quickly become familiar with the operation and philosophy of the software. ICD is available as a free download from the Climate Change Institute web site ( under the terms of GNU GPL public license.

  1. Meteorite bombardment and dating of planetary surfaces. Thesis - Feb. 1983

    NASA Technical Reports Server (NTRS)

    Neukum, G.

    1984-01-01

    Dating by measurement of impact crater frequencies developed in the past years primarily on the basis of the data from the missions to the Moon and Mars. The method allows a good relative dating to be obtained and the moons of Jupiter and Saturn through photographic analyses. A cratering chronology was obtained for the period between the oldest Moon crust (4.3 to 4.4 billion years) to the present time which gives a good absolute dating of any areas of the Moon's surface.

  2. Teen Dating Violence.

    ERIC Educational Resources Information Center

    O'Keeffe, Nona K.; And Others

    1986-01-01

    Surveyed high school students (N=256) in Sacramento, California. Found that 35.1 percent had experienced some form of abuse in their dating relationships. Explored the severity of the violence and its intergenerational component. (Author/ABB)

  3. Primate molecular divergence dates.

    PubMed

    Steiper, Michael E; Young, Nathan M

    2006-11-01

    With genomic data, alignments can be assembled that greatly increase the number of informative sites for analysis of molecular divergence dates. Here, we present an estimate of the molecular divergence dates for all of the major primate groups. These date estimates are based on a Bayesian analysis of approximately 59.8 kbp of genomic data from 13 primates and 6 mammalian outgroups, using a range of paleontologically supported calibration estimates. Results support a Cretaceous last common ancestor of extant primates (approximately 77 mya), an Eocene divergence between platyrrhine and catarrhine primates (approximately 43 mya), an Oligocene origin of apes and Old World monkeys (approximately 31 mya), and an early Miocene (approximately 18 mya) divergence of Asian and African great apes. These dates are examined in the context of other molecular clock studies. PMID:16815047

  4. Petroleum fingerprinting: Dating a gasoline release

    SciTech Connect

    Johnson, M.D.; Morrison, R.D.

    1996-09-01

    Dating a gasoline releases is particularly important in situations involving a contaminated gasoline service station. Often the station begins under the control of a major oil company, and as it ages and deteriorates it may be operated by a series of smaller operators. When facing a claim for contamination, often operators blame former operators. Fingerprinting is one of several successful methods used to date petroleum releases on contaminated sites. The topics covered in this article are inventory reconciliation; reverse groundwater modeling; hydrocarbon fingerprinting.

  5. Combined Use of Absolute and Differential Seismic Arrival Time Data to Improve Absolute Event Location

    NASA Astrophysics Data System (ADS)

    Myers, S.; Johannesson, G.

    2012-12-01

    Arrival time measurements based on waveform cross correlation are becoming more common as advanced signal processing methods are applied to seismic data archives and real-time data streams. Waveform correlation can precisely measure the time difference between the arrival of two phases, and differential time data can be used to constrain relative location of events. Absolute locations are needed for many applications, which generally requires the use of absolute time data. Current methods for measuring absolute time data are approximately two orders of magnitude less precise than differential time measurements. To exploit the strengths of both absolute and differential time data, we extend our multiple-event location method Bayesloc, which previously used absolute time data only, to include the use of differential time measurements that are based on waveform cross correlation. Fundamentally, Bayesloc is a formulation of the joint probability over all parameters comprising the multiple event location system. The Markov-Chain Monte Carlo method is used to sample from the joint probability distribution given arrival data sets. The differential time component of Bayesloc includes scaling a stochastic estimate of differential time measurement precision based the waveform correlation coefficient for each datum. For a regional-distance synthetic data set with absolute and differential time measurement error of 0.25 seconds and 0.01 second, respectively, epicenter location accuracy is improved from and average of 1.05 km when solely absolute time data are used to 0.28 km when absolute and differential time data are used jointly (73% improvement). The improvement in absolute location accuracy is the result of conditionally limiting absolute location probability regions based on the precise relative position with respect to neighboring events. Bayesloc estimates of data precision are found to be accurate for the synthetic test, with absolute and differential time measurement

  6. Viscous linear stability of axisymmetric low-density jets: Parameters influencing absolute instability

    NASA Astrophysics Data System (ADS)

    Srinivasan, V.; Hallberg, M. P.; Strykowski, P. J.

    2010-02-01

    Viscous linear stability calculations are presented for model low-density axisymmetric jet flows. Absolute growth transitions for the jet column mode are mapped out in a parametric space including velocity ratio, density ratio, Reynolds number, momentum thickness, and subtle differences between velocity and density profiles. Strictly speaking, the profiles used in most jet stability studies to date are only applicable to unity Prandtl numbers and zero pressure gradient flows—the present work relaxes this requirement. Results reveal how subtle differences between the velocity and density profiles generally used in jet stability theory can dramatically alter the absolute growth rate of the jet column mode in these low-density flows. The results suggest heating/cooling or mass diffusion at the outer nozzle surface can suppress absolute instability and potentially global instability in low-density jets.

  7. Dating the Homo erectus bearing travertine from Kocabaş (Denizli, Turkey) at at least 1.1 Ma

    NASA Astrophysics Data System (ADS)

    Lebatard, Anne-Elisabeth; Alçiçek, M. Cihat; Rochette, Pierre; Khatib, Samir; Vialet, Amélie; Boulbes, Nicolas; Bourlès, Didier L.; Demory, François; Guipert, Gaspard; Mayda, Serdar; Titov, Vadim V.; Vidal, Laurence; de Lumley, Henry

    2014-03-01

    Since its discovery within a travertine quarry, the fragmentary cranium of the only known Turkish Homo erectus, the Kocabaş hominid, has led to conflicting biochronological estimations. First estimated to be ˜500 ka old, the partial skull presents a combination of archaic and evolved features that puts it as an intermediate specimen between the Dmanisi fossils (Homo georgicus) and the Chinese Zhoukoudian skulls (Homo erectus) respectively dated to 1.8 to ˜0.8 Ma. Here we present a multidisciplinary study combining sedimentological, paleontological and paleoanthropological observations together with cosmogenic nuclide concentration and paleomagnetic measurements to provide an absolute chronological framework for the Upper fossiliferous Travertine unit where the Kocabaş hominid and fauna were discovered. The 26Al/10Be burial ages determined on pebbles from conglomeratic levels framing the Upper fossiliferous Travertine unit, which exhibits an inverse polarity, constrains its deposition to before the Cobb Mountain sub-chron, that is between 1.22 and ˜1.5 Ma. The alternative match of the normal polarity recorded above the travertine with the Jaramillo subchron (lower limit 1.07 Ma) may also be marginally compatible with cosmogenic nuclides interpretation, thus the proposed minimum age of 1.1 Ma for the end of massive travertine deposition. The actual age of the fossils is likely to be in the 1.1-1.3 Ma range. This absolute date is in close agreement with the paleoanthropological conclusions based on morphometric comparisons implying that Kocabaş hominid belongs to the Homo erectus s.l. group that includes Chinese and African fossils, and is different from Middle and Upper Pleistocene specimens. Furthermore, this date is confirmed by the large mammal assemblage, typical of the late Villafranchian. Because it attests to the antiquity of human occupation of the Anatolian Peninsula and one of the waves of settlements out of Africa, this work challenges the current

  8. Exploring new dating approaches for parasites: the worldwide Apodanthaceae (Cucurbitales) as an example.

    PubMed

    Bellot, Sidonie; Renner, Susanne S

    2014-11-01

    Gene trees of holoparasitic plants usually show distinctly longer branch lengths than seen in photosynthetic closest relatives. Such substitution rate jumps have made it difficult to infer the absolute divergence times of parasites. An additional problem is that parasite clades often lack a fossil record. Using nuclear and mitochondrial DNA sequences of Apodanthaceae, a worldwide family of endoparasites living inside Fabaceae and Salicaceae, we compared several dating approaches: (i) an uncorrelated lognormal (UCLN) model calibrated with outgroup fossils, (ii) ages of host lineages as a maximal age in an UCLN model, (iii) user-assigned local clocks, and (iv) outgroup-fossil-calibrated random local clocks (RLC) with varying prior probabilities on the number of permitted rate changes (RLCu and RLCp models), a variable that has never been explored. The resulting dated phylogenies include all 10 species of the family, three in Australia, one in Iran, one in Africa, and the remainder in the Americas. All clock models infer a drastic rate jump between nonparasitic outgroups and Apodanthaceae, but since they distribute the rate heterogeneity differently, they result in much-different age estimates. Bayes factors using path and stepping-stone sampling indicated that the RLCp model fit poorly, while for matR, topologically unconstrained RLCu and UCLN models did not differ significantly and for 18S, the UCLN model was preferred. Under the equally well fitting models, the Apodanthaceae appear to be a relatively old clade, with a stem age falling between 65 and 81my, the divergence of Apodanthes from Pilostyles between 36 and 57my ago, and the crown age of the Australian clade 8-18my ago. In our study system, host-age calibrations did not yield well-constrained results, but they may work better in other parasite clades. For small data sets where statistical convergence can be reached even with complex models, random local clocks should be explored as an alternative to the

  9. Hunting for eruption ages in accessory minerals

    NASA Astrophysics Data System (ADS)

    Vazquez, J. A.

    2012-12-01

    A primary goal in geochronology is to provide precise and accurate ages for tephras that serve as chronostratigraphic markers for constraining the timing and rates of volcanism, sedimentation, climate change, and catastrophic events in Earth history. Zircon remains the most versatile accessory mineral for dating silicic tephras due to its common preservation in distal pyroclastic deposits, as well as the robustness of its U-Pb and U-series systems even after host materials have been hydrothermally altered or weathered. Countless studies document that zircon may be complexly zoned in age due to inheritance, contamination, recycling of antecrysts, protracted crystallization in long-lived magma reservoirs, or any combination of these. Other accessory minerals such as allanite or chevkinite can retain similar records of protracted crystallization. If the goal is to date the durations of magmatic crystallization, differentiation, and/or magma residence, then these protracted chronologies within and between accessory minerals are a blessing. However, if the goal is to date the timing of eruption with high precision, i.e., absolute ages with millennial-scale uncertainties, then this age zoning is a curse. Observations from ion microprobe 238U-230Th dating of Pleistocene zircon and allanite provide insight into the record of near-eruption crystallization in accessory minerals and serve as a guide for high-precision whole-crystal dating. Although imprecise relative to conventional techniques, ion probe analysis allows high-spatial resolution 238U-230Th dating that can document multi-millennial age distributions at the crystal scale. Analysis of unpolished rims and continuous depth profiling of zircon from small and large volume eruptions (e.g., Coso, Mono Craters, Yellowstone) reveals that the final several micrometers of crystallization often yield ages that are indistinguishable from associated eruption ages from the 40Ar/39Ar or (U-Th)/He methods. Using this approach, we

  10. Radiocarbon dating: Jewish inspiration of Christian catacombs

    NASA Astrophysics Data System (ADS)

    Rutgers, Leonard V.; van der Borg, Klaas; de Jong, Arie F. M.; Poole, Imogen

    2005-07-01

    The famous catacombs of ancient Rome are huge underground cemeteries, of which two Jewish catacomb complexes of uncertain age and 60 early-Christian catacombs have survived. Here we use radiocarbon dating to determine the age of wood originating from one of the Jewish catacombs and find that it pre-dates its Christian counterparts by at least 100 years. These results indicate that burial in Roman catacombs may not have begun as a strictly Christian practice, as is commonly believed, but rather that its origin may lie in Jewish funerary customs.

  11. The Mono Lake Excursion Recorded in Phonolitic Lavas From Tenerife (Canary Islands): Paleomagnetic Analyses and Coupled K/Ar and Ar/Ar Dating.

    NASA Astrophysics Data System (ADS)

    Kissel, C.; Guillou, H.; Laj, C. E.; Carracedo, J. C.; Nomade, S.; Perez-Torrado, F.; Wandres, C.

    2011-12-01

    Studies of geomagnetic excursions is important for the knowledge of the geodynamo, and also because they may be used as precise time markers in various geological records (sediments, lavas and ice via their impact on the production of cosmogenic isotopes). In volcanic rocks, the identification of excursions is very challenging given the sporadic nature of the volcanic eruptions. However, it is a critical step because it allows absolute paleointensity determinations to be obtained, coupled with absolute dating methods. We present here a coupled paleomagnetic/dating investigation conducted on three different lava flows from the island of Tenerife (Canary Islands; Spain) erupted during the Mono Lake excursion (MLE). Paleomagnetic analyses consist in zero field demagnetizations (AF and/or thermal) and of Thellier and Thellier experiments using the PICRIT-03 set of criteria to select reliable intensity determinations. For dating, the unspiked K-Ar and the 40Ar/39Ar methods were coupled at LSCE for two of the flows and the third flow, with lower content in radiogenic 40Ar (40Ar*) was dated only using the unspiked K-Ar method. One of the flows is characterized by a direction largely deviated from the one expected from an axial geocentric dipole (GAD) field. Its paleointensity value is very low (7.8 μT). The two other sites are characterized by inclinations slightly shallower than the GAD value and by low intensity values (about 12 and 21 μT; present value: 38μT). The three K/Ar ages combined with two 40Ar/39Ar ages range from 32.0 to 33.2 ka and they are not statistically distinguishable from one another. It therefore appears that these lavas have recorded the MLE (the only excursion in this time interval) confirming its brief duration (shorter than the minimum age uncertainties available). The mean age is younger but, within the uncertainties and depending on the age of the standard we use, consistent with the age of the 10Be peak and of the marine intensity low when

  12. Absolute and relative dosimetry for ELIMED

    SciTech Connect

    Cirrone, G. A. P.; Schillaci, F.; Scuderi, V.; Cuttone, G.; Candiano, G.; Musumarra, A.; Pisciotta, P.; Romano, F.; Carpinelli, M.; Presti, D. Lo; Raffaele, L.; Tramontana, A.; Cirio, R.; Sacchi, R.; Monaco, V.; Marchetto, F.; Giordanengo, S.

    2013-07-26

    The definition of detectors, methods and procedures for the absolute and relative dosimetry of laser-driven proton beams is a crucial step toward the clinical use of this new kind of beams. Hence, one of the ELIMED task, will be the definition of procedures aiming to obtain an absolute dose measure at the end of the transport beamline with an accuracy as close as possible to the one required for clinical applications (i.e. of the order of 5% or less). Relative dosimetry procedures must be established, as well: they are necessary in order to determine and verify the beam dose distributions and to monitor the beam fluence and the energetic spectra during irradiations. Radiochromic films, CR39, Faraday Cup, Secondary Emission Monitor (SEM) and transmission ionization chamber will be considered, designed and studied in order to perform a fully dosimetric characterization of the ELIMED proton beam.

  13. Probing absolute spin polarization at the nanoscale.

    PubMed

    Eltschka, Matthias; Jäck, Berthold; Assig, Maximilian; Kondrashov, Oleg V; Skvortsov, Mikhail A; Etzkorn, Markus; Ast, Christian R; Kern, Klaus

    2014-12-10

    Probing absolute values of spin polarization at the nanoscale offers insight into the fundamental mechanisms of spin-dependent transport. Employing the Zeeman splitting in superconducting tips (Meservey-Tedrow-Fulde effect), we introduce a novel spin-polarized scanning tunneling microscopy that combines the probing capability of the absolute values of spin polarization with precise control at the atomic scale. We utilize our novel approach to measure the locally resolved spin polarization of magnetic Co nanoislands on Cu(111). We find that the spin polarization is enhanced by 65% when increasing the width of the tunnel barrier by only 2.3 Å due to the different decay of the electron orbitals into vacuum. PMID:25423049

  14. Absolute-magnitude distributions of supernovae

    SciTech Connect

    Richardson, Dean; Wright, John; Jenkins III, Robert L.; Maddox, Larry

    2014-05-01

    The absolute-magnitude distributions of seven supernova (SN) types are presented. The data used here were primarily taken from the Asiago Supernova Catalogue, but were supplemented with additional data. We accounted for both foreground and host-galaxy extinction. A bootstrap method is used to correct the samples for Malmquist bias. Separately, we generate volume-limited samples, restricted to events within 100 Mpc. We find that the superluminous events (M{sub B} < –21) make up only about 0.1% of all SNe in the bias-corrected sample. The subluminous events (M{sub B} > –15) make up about 3%. The normal Ia distribution was the brightest with a mean absolute blue magnitude of –19.25. The IIP distribution was the dimmest at –16.75.

  15. Absolute radiometry and the solar constant

    NASA Technical Reports Server (NTRS)

    Willson, R. C.

    1974-01-01

    A series of active cavity radiometers (ACRs) are described which have been developed as standard detectors for the accurate measurement of irradiance in absolute units. It is noted that the ACR is an electrical substitution calorimeter, is designed for automatic remote operation in any environment, and can make irradiance measurements in the range from low-level IR fluxes up to 30 solar constants with small absolute uncertainty. The instrument operates in a differential mode by chopping the radiant flux to be measured at a slow rate, and irradiance is determined from two electrical power measurements together with the instrumental constant. Results are reported for measurements of the solar constant with two types of ACRs. The more accurate measurement yielded a value of 136.6 plus or minus 0.7 mW/sq cm (1.958 plus or minus 0.010 cal/sq cm per min).

  16. Asteroid absolute magnitudes and slope parameters

    NASA Technical Reports Server (NTRS)

    Tedesco, Edward F.

    1991-01-01

    A new listing of absolute magnitudes (H) and slope parameters (G) has been created and published in the Minor Planet Circulars; this same listing will appear in the 1992 Ephemerides of Minor Planets. Unlike previous listings, the values of the current list were derived from fits of data at the V band. All observations were reduced in the same fashion using, where appropriate, a single basis default value of 0.15 for the slope parameter. Distances and phase angles were computed for each observation. The data for 113 asteroids was of sufficiently high quality to permit derivation of their H and G. These improved absolute magnitudes and slope parameters will be used to deduce the most reliable bias-corrected asteroid size-frequency distribution yet made.

  17. Absolute calibration of TFTR helium proportional counters

    SciTech Connect

    Strachan, J.D.; Diesso, M.; Jassby, D.; Johnson, L.; McCauley, S.; Munsat, T.; Roquemore, A.L.; Barnes, C.W. |; Loughlin, M. |

    1995-06-01

    The TFTR helium proportional counters are located in the central five (5) channels of the TFTR multichannel neutron collimator. These detectors were absolutely calibrated using a 14 MeV neutron generator positioned at the horizontal midplane of the TFTR vacuum vessel. The neutron generator position was scanned in centimeter steps to determine the collimator aperture width to 14 MeV neutrons and the absolute sensitivity of each channel. Neutron profiles were measured for TFTR plasmas with time resolution between 5 msec and 50 msec depending upon count rates. The He detectors were used to measure the burnup of 1 MeV tritons in deuterium plasmas, the transport of tritium in trace tritium experiments, and the residual tritium levels in plasmas following 50:50 DT experiments.

  18. Absolute enantioselective separation: optical activity ex machina.

    PubMed

    Bielski, Roman; Tencer, Michal

    2005-11-01

    The paper describes methodology of using three independent macroscopic factors affecting molecular orientation to accomplish separation of a racemic mixture without the presence of any other chiral compounds, i. e., absolute enantioselective separation (AES) which is an extension of a concept of applying these factors to absolute asymmetric synthesis. The three factors may be applied simultaneously or, if their effects can be retained, consecutively. The resulting three mutually orthogonal or near orthogonal directors constitute a true chiral influence and their scalar triple product is the measure of the chirality of the system. AES can be executed in a chromatography-like microfluidic process in the presence of an electric field. It may be carried out on a chemically modified flat surface, a monolithic polymer column made of a mesoporous material, each having imparted directional properties. Separation parameters were estimated for these media and possible implications for the natural homochirality are discussed. PMID:16342798

  19. An absolute measure for a key currency

    NASA Astrophysics Data System (ADS)

    Oya, Shunsuke; Aihara, Kazuyuki; Hirata, Yoshito

    It is generally considered that the US dollar and the euro are the key currencies in the world and in Europe, respectively. However, there is no absolute general measure for a key currency. Here, we investigate the 24-hour periodicity of foreign exchange markets using a recurrence plot, and define an absolute measure for a key currency based on the strength of the periodicity. Moreover, we analyze the time evolution of this measure. The results show that the credibility of the US dollar has not decreased significantly since the Lehman shock, when the Lehman Brothers bankrupted and influenced the economic markets, and has increased even relatively better than that of the euro and that of the Japanese yen.

  20. From Hubble's NGSL to Absolute Fluxes

    NASA Technical Reports Server (NTRS)

    Heap, Sara R.; Lindler, Don

    2012-01-01

    Hubble's Next Generation Spectral Library (NGSL) consists of R-l000 spectra of 374 stars of assorted temperature, gravity, and metallicity. Each spectrum covers the wavelength range, 0.18-1.00 microns. The library can be viewed and/or downloaded from the website, http://archive.stsci.edu/prepds/stisngsll. Stars in the NGSL are now being used as absolute flux standards at ground-based observatories. However, the uncertainty in the absolute flux is about 2%, which does not meet the requirements of dark-energy surveys. We are therefore developing an observing procedure that should yield fluxes with uncertainties less than 1 % and will take part in an HST proposal to observe up to 15 stars using this new procedure.

  1. Metallic Magnetic Calorimeters for Absolute Activity Measurement

    NASA Astrophysics Data System (ADS)

    Loidl, M.; Leblanc, E.; Rodrigues, M.; Bouchard, J.; Censier, B.; Branger, T.; Lacour, D.

    2008-05-01

    We present a prototype of metallic magnetic calorimeters that we are developing for absolute activity measurements of low energy emitting radionuclides. We give a detailed description of the realization of the prototype, containing an 55Fe source inside the detector absorber. We present the analysis of first data taken with this detector and compare the result of activity measurement with liquid scintillation counting. We also propose some ways for reducing the uncertainty on the activity determination with this new technique.

  2. Absolute photoionization cross sections of atomic oxygen

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Pareek, P. N.

    1985-01-01

    The absolute values of photoionization cross sections of atomic oxygen were measured from the ionization threshold to 120 A. An auto-ionizing resonance belonging to the 2S2P4(4P)3P(3Do, 3So) transition was observed at 479.43 A and another line at 389.97 A. The experimental data is in excellent agreement with rigorous close-coupling calculations that include electron correlations in both the initial and final states.

  3. Absolute photoionization cross sections of atomic oxygen

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Pareek, P. N.

    1982-01-01

    The absolute values of photoionization cross sections of atomic oxygen were measured from the ionization threshold to 120 A. An auto-ionizing resonance belonging to the 2S2P4(4P)3P(3Do, 3So) transition was observed at 479.43 A and another line at 389.97 A. The experimental data is in excellent agreement with rigorous close-coupling calculations that include electron correlations in both the initial and final states.

  4. Silicon Absolute X-Ray Detectors

    SciTech Connect

    Seely, John F.; Korde, Raj; Sprunck, Jacob; Medjoubi, Kadda; Hustache, Stephanie

    2010-06-23

    The responsivity of silicon photodiodes having no loss in the entrance window, measured using synchrotron radiation in the 1.75 to 60 keV range, was compared to the responsivity calculated using the silicon thickness measured using near-infrared light. The measured and calculated responsivities agree with an average difference of 1.3%. This enables their use as absolute x-ray detectors.

  5. Relative errors can cue absolute visuomotor mappings.

    PubMed

    van Dam, Loes C J; Ernst, Marc O

    2015-12-01

    When repeatedly switching between two visuomotor mappings, e.g. in a reaching or pointing task, adaptation tends to speed up over time. That is, when the error in the feedback corresponds to a mapping switch, fast adaptation occurs. Yet, what is learned, the relative error or the absolute mappings? When switching between mappings, errors with a size corresponding to the relative difference between the mappings will occur more often than other large errors. Thus, we could learn to correct more for errors with this familiar size (Error Learning). On the other hand, it has been shown that the human visuomotor system can store several absolute visuomotor mappings (Mapping Learning) and can use associated contextual cues to retrieve them. Thus, when contextual information is present, no error feedback is needed to switch between mappings. Using a rapid pointing task, we investigated how these two types of learning may each contribute when repeatedly switching between mappings in the absence of task-irrelevant contextual cues. After training, we examined how participants changed their behaviour when a single error probe indicated either the often-experienced error (Error Learning) or one of the previously experienced absolute mappings (Mapping Learning). Results were consistent with Mapping Learning despite the relative nature of the error information in the feedback. This shows that errors in the feedback can have a double role in visuomotor behaviour: they drive the general adaptation process by making corrections possible on subsequent movements, as well as serve as contextual cues that can signal a learned absolute mapping. PMID:26280315

  6. Absolute distance measurements by variable wavelength interferometry

    NASA Astrophysics Data System (ADS)

    Bien, F.; Camac, M.; Caulfield, H. J.; Ezekiel, S.

    1981-02-01

    This paper describes a laser interferometer which provides absolute distance measurements using tunable lasers. An active feedback loop system, in which the laser frequency is locked to the optical path length difference of the interferometer, is used to tune the laser wavelengths. If the two wavelengths are very close, electronic frequency counters can be used to measure the beat frequency between the two laser frequencies and thus to determine the optical path difference between the two legs of the interferometer.

  7. Radioactive fallouts as temporal makers for glacier ice cores dating

    NASA Astrophysics Data System (ADS)

    Clemenza, M.; Cucciati, G.; Maggi, V.; Pattavina, L.; Previtali, E.

    2012-06-01

    In this paper, we intend to show how analytical methods used in nuclear physics, as gamma spectroscopy, are powerful tools for the dating of environmental archives. Specifically, we will show how events related to the release in the environment of great amount of radioactive isotopes ( e.g., atmospheric nuclear test explosions) can be used as temporal markers in alpine glaciers. The radio-isotope selected for the dating of ice carrots is 137Cs , because of its chemical and nuclear properties. The radioactive measurements have been conducted using a low-background high-purity germanium detector. The sensitivity for the prepared samples is 10mBq/kg. We will illustrate how dating curves (date versus depth of the sample) can be considered as an absolute calibrator for all the other chemical dating methods used on glacier samples analyses.

  8. Dating Modern Deltas: Progress, Problems, and Prognostics

    NASA Astrophysics Data System (ADS)

    Stanley, Jean-Daniel

    Radiocarbon dating is the method most frequently used to date Holocene deltaic sequences, but less than one quarter of 14C dates are within +/-500 years of predicted age. Such dates tend to be unreliable, in other words, often too old and commonly inverted upsection, and core sample dates obtained near deltaic plain surfaces may be as old as mid- to late Holocene. Stratigraphic irregularities result primarily from downslope reworking of upland alluvial sediment, with displacement of "old carbon" in the sediment that accumulates in lower valleys and deltaic plains. Use of dates that are too old results in inaccurately calculated rates (most often too low) of relative sea-level rise and/or land subsidence. More reliable timing of deltaic sediment requires a multiple-method dating approach, including, where possible, identification of associated archaeological material. Developing an accurate dating strategy is a critical step for implementing reliable coastal protection measures needed for the rapidly increasing human populations in these low-lying, vulnerable nearshore settings.

  9. Developing a Relationship Between LIBS Ablation and Pit Volume for In Situ Dating of Geologic Samples

    NASA Technical Reports Server (NTRS)

    Devismes, D.; Cohen, B. A.; Gillot, P.-Y.

    2015-01-01

    In planetary exploration, in situ absolute geochronology is an important measurement. Thus far, on Mars, the age of the surface has largely been determined by crater density counting, which gives relative ages. These ages can have significant uncertainty as they depend on many poorly constrained parameters. More than that, the curves must be tied to absolute ages to relate geologic timescales on Mars to the rest of the solar system. Thus far, only the lost lander Beagle 2 was designed to conduct absolute geochronology measurements, though some recent attempts using MSL Curiosity show that this investigation is feasible (Reference Farley here) and should be strongly encouraged for future flight.

  10. Absolute dosimetry for extreme-ultraviolet lithography

    NASA Astrophysics Data System (ADS)

    Berger, Kurt W.; Campiotti, Richard H.

    2000-06-01

    The accurate measurement of an exposure dose reaching the wafer on an extreme ultraviolet (EUV) lithographic system has been a technical challenge directly applicable to the evaluation of candidate EUV resist materials and calculating lithography system throughputs. We have developed a dose monitoring sensor system that can directly measure EUV intensities at the wafer plane of a prototype EUV lithographic system. This sensor system, located on the wafer stage adjacent to the electrostatic chuck used to grip wafers, operates by translating the sensor into the aerial image, typically illuminating an 'open' (unpatterned) area on the reticle. The absolute signal strength can be related to energy density at the wafer, and thus used to determine resist sensitivity, and the signal as a function of position can be used to determine illumination uniformity at the wafer plane. Spectral filtering to enhance the detection of 13.4 nm radiation was incorporated into the sensor. Other critical design parameters include the packaging and amplification technologies required to place this device into the space and vacuum constraints of a EUV lithography environment. We describe two approaches used to determine the absolute calibration of this sensor. The first conventional approach requires separate characterization of each element of the sensor. A second novel approach uses x-ray emission from a mildly radioactive iron source to calibrate the absolute response of the entire sensor system (detector and electronics) in a single measurement.

  11. Absolute versus relative ascertainment of pedophilia in men.

    PubMed

    Blanchard, Ray; Kuban, Michael E; Blak, Thomas; Cantor, James M; Klassen, Philip E; Dickey, Robert

    2009-12-01

    There are at least two different criteria for assessing pedophilia in men: absolute ascertainment (their sexual interest in children is intense) and relative ascertainment (their sexual interest in children is greater than their interest in adults). The American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, 3rd edition (DSM-III) used relative ascertainment in its diagnostic criteria for pedophilia; this was abandoned and replaced by absolute ascertainment in the DSM-III-R and all subsequent editions. The present study was conducted to demonstrate the continuing need for relative ascertainment, particularly in the laboratory assessment of pedophilia. A total of 402 heterosexual men were selected from a database of patients referred to a specialty clinic. These had undergone phallometric testing, a psychophysiological procedure in which their penile blood volume was monitored while they were presented with a standardized set of laboratory stimuli depicting male and female children, pubescents, and adults.The 130 men selected for the Teleiophilic Profile group responded substantially to prepubescent girls but even more to adult women; the 272 men selected for the Pedophilic Profile group responded weakly to prepubescent girls but even less to adult women. In terms of absolute magnitude, every patient in the Pedophilic Profile group had a lesser penile response to prepubescent girls than every patient in the Teleiophilic Profile group. Nevertheless, the Pedophilic Profile group had a significantly greater number of known sexual offenses against prepubescent girls, indicating that they contained a higher proportion of true pedophiles. These results dramatically demonstrate the utility-or perhaps necessity-of relative ascertainment in the laboratory assessment of erotic age-preference. PMID:19901237

  12. Radiocarbon Dating the Anthropocene

    NASA Astrophysics Data System (ADS)

    Chaput, M. A.; Gajewski, K. J.

    2015-12-01

    The Anthropocene has no agreed start date since current suggestions for its beginning range from Pre-Industrial times to the Industrial Revolution, and from the mid-twentieth century to the future. To set the boundary of the Anthropocene in geological time, we must first understand when, how and to what extent humans began altering the Earth system. One aspect of this involves reconstructing the effects of prehistoric human activity on the physical landscape. However, for global reconstructions of land use and land cover change to be more accurately interpreted in the context of human interaction with the landscape, large-scale spatio-temporal demographic changes in prehistoric populations must be known. Estimates of the relative number of prehistoric humans in different regions of the world and at different moments in time are needed. To this end, we analyze a dataset of radiocarbon dates from the Canadian Archaeological Radiocarbon Database (CARD), the Palaeolithic Database of Europe and the AustArch Database of Australia, as well as published dates from South America. This is the first time such a large quantity of dates (approximately 60,000) has been mapped and studied at a global scale. Initial results from the analysis of temporal frequency distributions of calibrated radiocarbon dates, assumed to be proportional to population density, will be discussed. The utility of radiocarbon dates in studies of the Anthropocene will be evaluated and potential links between population density and changes in atmospheric greenhouse gas concentrations, climate, migration patterning and fire frequency coincidence will be considered.

  13. Première datation des lydiennes paléozoïques dans les Hellénides internes (mont Parnis, Grèce); implications géologiquesFirst age dating of the Lydian stones in the Inner Hellenides (Mount Parnis, Greece); geological significances.

    NASA Astrophysics Data System (ADS)

    Caridroit, Martial; Ferrière, Jacky; Dégardin, Jean-Marie; Vachard, Daniel; Clément, Bernard

    2000-09-01

    Using radiolarian and conodont remains, a Tournaisian age has been obtained from the Lydian rocks (or lydites) of the Parnis Mount (Greece); this result is the first direct age dating of the Lydian rocks of continental Greece. In the same area, some limestone strata, interbedded in sandstones, yield Carboniferous and Permian foraminifers; the established stratigraphy is not consistent and so, the Lydian rocks have to be considered as blocks in an olistostrome unconformably overlain or thrusted by Triassic limestones. Otherwise, the Lydian rocks are interpreted as biogenic siliceous deposits due to the absence of carbonate sedimentation (not as a high siliceous production).

  14. Thermoluminescence dating of Hawaiian basalt

    USGS Publications Warehouse

    May, Rodd James

    1979-01-01

    The thermoluminescence (TL) properties of plagioclase separates from 11 independently dated alkalic basalts 4,500 years to 3.3 million years old and 17 tholeiitic basalts 16 years to 450,000 years old from the Hawaiian Islands were investigated for the purpose of developing a TL dating method for young volcanic rocks. Ratios of natural to artificial TL intensity, when normalized for natural radiation dose rates, were used to quantify the thermoluminescence response of individual samples for age-determination purposes. The TL ratios for the alkalic basalt plagioclase were found to increase with age at a predictable exponential rate that permits the use of the equation for the best-fit line through a plot of the TL ratios relative to known age as a TL age equation. The equation is applicable to rocks ranging in composition from basaltic andesite to trachyte over the age range from about 2,000 to at least 250,000 years before present (B.P.). The TL ages for samples older than 50,000 years have a calculated precision of less than :t 10 percent and a potential estimated accuracy relative to potassium-argon ages of approximately :t 10 percent. An attempt to develop a similar dating curve for the tholeiitic basalts was not as successful, primarily because the dose rates are on the average lower than those for the alkalic basalts by a factor of 6, resulting in lower TL intensities in the tholeiitic basalts for samples of equivalent age, and also because the age distribution of dated material is inadequate. The basic TL properties of the plagioclase from the two rock types are similar, however, and TL dating of tholeiitic basalts should eventually be feasible over the age range 10,000 to at least 200,000 years B.P. The average composition of the plagioclase separates from the alkalic basalts ranges from oligoclase to andesine; compositional variations within this range have no apparent effect on the TL ratios. The average composition of the plagioclase from the tholeiitic

  15. Should precise numerical dating overrule glacial geomorphology?

    NASA Astrophysics Data System (ADS)

    Winkler, Stefan

    2016-04-01

    Numerical age dating techniques, namely different types of terrestrial cosmogenic nuclide dating (TCND), have achieved an impressive progress in both laboratory precision and regional calibration models during the past few decades. It is now possible to apply precise TCND even to young landforms like Late Holocene moraines, a task seemed hardly achievable just about 15 years ago. An increasing number of studies provide very precise TCND ages for boulders from Late Holocene moraines enabling related reconstruction of glacier chronologies and the interpretation of these glacial landforms in a palaeoclimatological context. These studies may also solve previous controversies about different ages assigned to moraines obtained by different dating techniques, for example relative-age dating techniques or techniques combining relative-age dating with few fixed points derived from numerical age dating. There are a few cases, for example Mueller Glacier and nearby long debris-covered valley glacier in Aoraki/Mt.Cook National Park (Southern Alps, New Zealand), where the apparent "supremacy" of TCND-ages seem to overrule glacial geomorphological principles. Enabled by a comparatively high number of individual boulders precisely dated by TCND, moraine ridges on those glacier forelands have been primarily clustered on basis of these boulder ages rather than on their corresponding morphological position. To the extreme, segments of a particular moraine complex morphologically and sedimentologically proven to be formed during one event have become split and classified as two separate "moraines" on different parts of the glacier foreland. One ledge of another moraine complex contains 2 TCND-sampled boulders apparently representing two separate "moraines"-clusters of an age difference in the order of 1,500 years. Although recently criticism has been raised regarding the non-contested application of the arithmetic mean for calculation of TCND-ages for individual moraines, this

  16. The Realities of Date Rape.

    ERIC Educational Resources Information Center

    Presley, Cara; Watson, Jennifer; Williams, Audrey R.

    This poster presentation addresses the issue of date rape, specifically in the college environment. Highlighted are date rape statistics, demographics, and date rape drugs. Also discussed are date rape warnings and prevention strategies. It is concluded that college and university administrators must place the issue of date rape and acquaintance…

  17. The Dating Game.

    ERIC Educational Resources Information Center

    Zerger, Monte J.

    1998-01-01

    Presents activities to cultivate the tendency to see special qualities in numbers that can be played on certain calendar days. Includes games on the constant of the day, Fibonacci and golden ratio dates, primes, powers, December 25, and the day of the year. (ASK)

  18. Biodiversity of date palm

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The date palm (Phoenix dactylifera) is the dominant component upon which the sustainable biophysical and socio-economic structures of the oasis ecosystem are based; a fruit tree with unique nutritional, biochemical and biophysical characteristics, a rich source of aesthetic and cultural values, and ...

  19. Development of a luminescence planetary surface dating instrument

    NASA Astrophysics Data System (ADS)

    Jain, M.; Lapp, T.; Andersen, M. T.; Hannemann, S.; Murray, A. S.; Duller, G. A. T.; Merrrisen, J.

    2012-04-01

    Luminescence dating (LD) is uniquely positioned for absolute, in-situ, dating of recent (< 1Ma) events on Mars such as the formation of sedimentary landforms, volcanic rocks and salt precipitates. These data can in turn help understand and predict the impact of climate-driven changes on Mars, for example, atmosphere-land interactions, global sand and dust movements and redistribution of volatiles (H2O and CO2). This understanding is critical for any manned mission to Mars and for our understanding of the planetary surface evolution. Despite this potential, the technology transfer from terrestrial to in-situ Martian dating is not trivial. Here we first provide a brief overview of the scientific issues involved in luminescence dating on Mars (e.g. dosimetric characteristics of Martian materials and modelling of cosmic-ray dose rate) and then the technical constraints on an instrument design appropriate for remotely-programmable mobile use on the Martian surface. The challenge is to develop a miniaturised portable luminescence reader that is as sensitive as a laboratory-based instrument and at the same time has sufficient flexibility for fully automated performance. Such an instrument could provide stratigraphic ages if deployed on a rover with a sub-surface drilling capability, or provide a survey of surface chronologies over extensive areas. To this end we have designed and manufactured an 'elegant breadboard' Planetary Surface Dating Instrument (PSDI) in a project supported by ESA. The PSDI is light weight and compact (~1 kg, ~1.4 litres) and has 3 different reloadable sample positions which can be rotated to sit under 3 different optical subunits or an x-ray irradiator. The optical subunits consists of three different detection channels (one red and two UV/blue) each based on a miniature photomultiplier tube, and three types of laser light stimulation sources (two 915 nm, one 530 nm and one 405 nm) that can be operated in continuous-wave or pulsed mode. The

  20. COnstructing Proxy-Record Age models (COPRA)

    NASA Astrophysics Data System (ADS)

    Marwan, Norbert; Rehfeld, Kira; Goswami, Bedartha; Breitenbach, Sebastian F. M.; Kurths, Jürgen

    2013-04-01

    Reliable age models are fundamental for any palaeoclimate reconstruction. The increasing availability of high-resolution palaeoclimate time series, e.g., based on speleothem archives, has attracted some new activity in the development of alternative and novel approaches for reconstructing chronologies. Challenges in this effort are (semi-)automatic outlier, reversal, and hiatus detection and treatment, as well as the inclusion of information on age uncertainties and independent layer counting to improve the overall precision of the chronology. However, different dating strategies, different kinds of palaeoarchive formation, dating uncertainties, and different chronology construction methods cause a limited comparability of the different palaeoclimate records. We present a recently developed framework which addresses these challenges and which allows the incorporation of layer counting data to improve the reconstructed chronology of a given time series. Moreover, we introduce the concept of an "absolute" time scale, a common time axis which works as an invariant reference allowing the comparison of different palaeoclimate records. This concept translates the age uncertainties into uncertainties in the proxy values. This framework is implemented as an open source software (COPRA) for Octave and Matlab.

  1. Absolute plate motion of Africa around Hawaii-Emperor bend time

    NASA Astrophysics Data System (ADS)

    Maher, S. M.; Wessel, P.; Müller, R. D.; Williams, S. E.; Harada, Y.

    2015-06-01

    Numerous regional plate reorganizations and the coeval ages of the Hawaiian Emperor bend (HEB) and Louisville bend of 50-47 Ma have been interpreted as a possible global tectonic plate reorganization at ˜chron 21 (47.9 Ma). Yet for a truly global event we would expect a contemporaneous change in Africa absolute plate motion (APM) reflected by physical evidence distributed on the Africa Plate. This evidence has been postulated to take the form of the Réunion-Mascarene bend which exhibits many HEB-like features, such as a large angular change close to ˜chron 21. However, the Réunion hotspot trail has recently been interpreted as a sequence of continental fragments with incidental hotspot volcanism. Here we show that the alternative Réunion-Mascarene Plateau trail can also satisfy the age progressions and geometry of other hotspot trails on the Africa Plate. The implied motion, suggesting a pivoting of Africa from 67 to 50 Ma, could explain the apparent bifurcation of the Tristan hotspot chain, the age reversals seen along the Walvis Ridge, the sharp curve of the Canary trail, and the diffuse nature of the St. Helena chain. To test this hypothesis further we made a new Africa APM model that extends back to ˜80 Ma using a modified version of the Hybrid Polygonal Finite Rotation Method. This method uses seamount chains and their associated hotspots as geometric constraints for the model, and seamount age dates to determine APM through time. While this model successfully explains many of the volcanic features, it implies an unrealistically fast global lithospheric net rotation, as well as improbable APM trajectories for many other plates, including the Americas, Eurasia and Australia. We contrast this speculative model with a more conventional model in which the Mascarene Plateau is excluded in favour of the Chagos-Laccadive Ridge rotated into the Africa reference frame. This second model implies more realistic net lithospheric rotation and far-field APMs, but

  2. Neighborhood Factors and Dating Violence Among Youth

    PubMed Central

    Johnson, Renee M.; Parker, Elizabeth M.; Rinehart, Jenny; Nail, Jennifer; Rothman, Emily F.

    2015-01-01

    Context The purpose of this review is to summarize the empirical research on neighborhood-level factors and dating violence among adolescents and emerging adults to guide future research and practice. Evidence acquisition In 2015, 20 articles were identified through a search of the literature using PubMed. Eligible articles included those that: (1) had been published in a peer-reviewed journal since 2005; (2) reported a measure of association between at least one neighborhood-level factor and dating violence; and (3) had a study population of youth aged <26 years. We abstracted information about the studies, including measurement of dating violence and neighborhood factors, and measures of effect. Evidence synthesis Results were summarized into three categories based on the aspect of neighborhood which was the focus of the work: demographic and structural characteristics (n=11), neighborhood disorder (n=12), and social disorganization (n=8). There was some evidence to suggest that neighborhood disadvantage is associated with dating violence, but very little evidence to suggest that residence characteristics (e.g., racial heterogeneity) are associated with dating violence. Results do suggest that perceived neighborhood disorder is associated with physical dating violence perpetration, but do not suggest that it is associated with physical dating violence victimization. Social control and community connectedness are both associated with dating violence, but findings on collective efficacy are mixed. Conclusions Existing research suggests that neighborhood factors may be associated with dating violence. However, there is a limited body of research on the neighborhood context of dating violence and more rigorous research is needed. PMID:26296444

  3. 10Be dating of Neogene halite

    NASA Astrophysics Data System (ADS)

    Belmaker, Reuven; Lazar, Boaz; Beer, Jürg; Christl, Marcus; Tepelyakov, Natalya; Stein, Mordechai

    2013-12-01

    Direct radioactive dating of ancient halite formations is difficult because this mineral typically lacks conventionally datable material. We describe an attempt to date Neogene halite using the cosmogenic isotope 10Be (T1/2 = 1.39 Ma). We dated marine-derived salt deposits from the Sedom and Amora (The Hebrew forms of Sodom and Gomorrah) Formations, Dead Sea basin, Israel. To verify whether Be is incorporated into marine halite we measured the stable isotope 9Be, 7Be (the short lived “cosmogenic brother” of 10Be having T1/2 = 53.3 d), and 10Be in evaporation pans of sea-salt production plants. The data suggest that seawater beryllium is incorporated into the halite with a halite-brine distribution coefficient, (KD) of about unity. A 10Be/9Be decay curve constructed for Sedom Formation halite yielded an age that lies in the range of ∼2-6 Ma. The 10Be decay curve constructed for Sedom Formation halite yielded an age that lies in the range of 3-5 Ma. This age is consistent with previous estimates of the Sedom Formation age. Furthermore, this age lies in the same range of 10Be in situ ages obtained on the lacustrine Erq El Ahmer Formation located in the northern Jordan Valley. This may imply that during the Mid Pliocene the Sedom Lagoon, the water-body that deposited the Sedom Formation, might have been already disconnected from the open sea.

  4. Landsat-7 ETM+ radiometric stability and absolute calibration

    USGS Publications Warehouse

    Markham, B.L.; Barker, J.L.; Barsi, J.A.; Kaita, E.; Thome, K.J.; Helder, D.L.; Palluconi, Frank Don; Schott, J.R.; Scaramuzza, P.

    2002-01-01

    Launched in April 1999, the Landsat-7 ETM+ instrument is in its fourth year of operation. The quality of the acquired calibrated imagery continues to be high, especially with respect to its three most important radiometric performance parameters: reflective band instrument stability to better than ??1%, reflective band absolute calibration to better than ??5%, and thermal band absolute calibration to better than ??0.6 K. The ETM+ instrument has been the most stable of any of the Landsat instruments, in both the reflective and thermal channels. To date, the best on-board calibration source for the reflective bands has been the Full Aperture Solar Calibrator, which has indicated changes of at most -1.8% to -2.0% (95% C.I.) change per year in the ETM+ gain (band 4). However, this change is believed to be caused by changes in the solar diffuser panel, as opposed to a change in the instrument's gain. This belief is based partially on ground observations, which bound the changes in gain in band 4 at -0.7% to +1.5%. Also, ETM+ stability is indicated by the monitoring of desert targets. These image-based results for four Saharan and Arabian sites, for a collection of 35 scenes over the three years since launch, bound the gain change at -0.7% to +0.5% in band 4. Thermal calibration from ground observations revealed an offset error of +0.31 W/m 2 sr um soon after launch. This offset was corrected within the U. S. ground processing system at EROS Data Center on 21-Dec-00, and since then, the band 6 on-board calibration has indicated changes of at most +0.02% to +0.04% (95% C.I.) per year. The latest ground observations have detected no remaining offset error with an RMS error of ??0.6 K. The stability and absolute calibration of the Landsat-7 ETM+ sensor make it an ideal candidate to be used as a reference source for radiometric cross-calibrating to other land remote sensing satellite systems.

  5. Clock time is absolute and universal

    NASA Astrophysics Data System (ADS)

    Shen, Xinhang

    2015-09-01

    A critical error is found in the Special Theory of Relativity (STR): mixing up the concepts of the STR abstract time of a reference frame and the displayed time of a physical clock, which leads to use the properties of the abstract time to predict time dilation on physical clocks and all other physical processes. Actually, a clock can never directly measure the abstract time, but can only record the result of a physical process during a period of the abstract time such as the number of cycles of oscillation which is the multiplication of the abstract time and the frequency of oscillation. After Lorentz Transformation, the abstract time of a reference frame expands by a factor gamma, but the frequency of a clock decreases by the same factor gamma, and the resulting multiplication i.e. the displayed time of a moving clock remains unchanged. That is, the displayed time of any physical clock is an invariant of Lorentz Transformation. The Lorentz invariance of the displayed times of clocks can further prove within the framework of STR our earth based standard physical time is absolute, universal and independent of inertial reference frames as confirmed by both the physical fact of the universal synchronization of clocks on the GPS satellites and clocks on the earth, and the theoretical existence of the absolute and universal Galilean time in STR which has proved that time dilation and space contraction are pure illusions of STR. The existence of the absolute and universal time in STR has directly denied that the reference frame dependent abstract time of STR is the physical time, and therefore, STR is wrong and all its predictions can never happen in the physical world.

  6. Achieving Climate Change Absolute Accuracy in Orbit

    NASA Technical Reports Server (NTRS)

    Wielicki, Bruce A.; Young, D. F.; Mlynczak, M. G.; Thome, K. J; Leroy, S.; Corliss, J.; Anderson, J. G.; Ao, C. O.; Bantges, R.; Best, F.; Bowman, K.; Brindley, H.; Butler, J. J.; Collins, W.; Dykema, J. A.; Doelling, D. R.; Feldman, D. R.; Fox, N.; Huang, X.; Holz, R.; Huang, Y.; Jennings, D.; Jin, Z.; Johnson, D. G.; Jucks, K.; Kato, S.; Kratz, D. P.; Liu, X.; Lukashin, C.; Mannucci, A. J.; Phojanamongkolkij, N.; Roithmayr, C. M.; Sandford, S.; Taylor, P. C.; Xiong, X.

    2013-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission will provide a calibration laboratory in orbit for the purpose of accurately measuring and attributing climate change. CLARREO measurements establish new climate change benchmarks with high absolute radiometric accuracy and high statistical confidence across a wide range of essential climate variables. CLARREO's inherently high absolute accuracy will be verified and traceable on orbit to Système Internationale (SI) units. The benchmarks established by CLARREO will be critical for assessing changes in the Earth system and climate model predictive capabilities for decades into the future as society works to meet the challenge of optimizing strategies for mitigating and adapting to climate change. The CLARREO benchmarks are derived from measurements of the Earth's thermal infrared spectrum (5-50 micron), the spectrum of solar radiation reflected by the Earth and its atmosphere (320-2300 nm), and radio occultation refractivity from which accurate temperature profiles are derived. The mission has the ability to provide new spectral fingerprints of climate change, as well as to provide the first orbiting radiometer with accuracy sufficient to serve as the reference transfer standard for other space sensors, in essence serving as a "NIST [National Institute of Standards and Technology] in orbit." CLARREO will greatly improve the accuracy and relevance of a wide range of space-borne instruments for decadal climate change. Finally, CLARREO has developed new metrics and methods for determining the accuracy requirements of climate observations for a wide range of climate variables and uncertainty sources. These methods should be useful for improving our understanding of observing requirements for most climate change observations.

  7. Absolute properties of the triple star HP Aurigae

    SciTech Connect

    Lacy, Claud H. Sandberg; Burks, Charles L.; Torres, Guillermo; Wolf, Marek E-mail: clburks@email.uark.edu E-mail: wolf@cesnet.cz

    2014-01-01

    New photometric, spectroscopic, and eclipse timing observations of the eclipsing binary star HP Aur allow for very accurate orbital determinations, even in the presence of a third body and transient starspot activity. The eclipsing binary masses are determined to an accuracy of ±0.4% and the radii to ±0.6%. The masses are 0.9543 ± 0.0041 and 0.8094 ± 0.0036 solar masses, and the radii are 1.0278 ± 0.0042 and 0.7758 ± 0.0034 solar radii, respectively. The orbital period in the outer orbit is accurately determined for the first time: 4.332 ± 0.011 yr. A comparison with current theories of stellar evolution shows that the components' absolute properties can be well-matched by the current models at an age of about 7 billion years.

  8. The neurocognitive components of pitch processing: insights from absolute pitch.

    PubMed

    Wilson, Sarah J; Lusher, Dean; Wan, Catherine Y; Dudgeon, Paul; Reutens, David C

    2009-03-01

    The natural variability of pitch naming ability in the population (known as absolute pitch or AP) provides an ideal method for investigating individual differences in pitch processing and auditory knowledge formation and representation. We have demonstrated the involvement of different cognitive processes in AP ability that reflects varying skill expertise in the presence of similar early age of onset of music tuition. These processes were related to different regions of brain activity, including those involved in pitch working memory (right prefrontal cortex) and the long-term representation of pitch (superior temporal gyrus). They reflected expertise through the use of context dependent pitch cues and the level of automaticity of pitch naming. They impart functional significance to structural asymmetry differences in the planum temporale of musicians and establish a neurobiological basis for an AP template. More generally, they indicate variability of knowledge representation in the presence of environmental fostering of early cognitive development that translates to differences in cognitive ability. PMID:18663250

  9. First derivative versus absolute spectral reflectance of citrus varieties

    NASA Astrophysics Data System (ADS)

    Blazquez, Carlos H.; Nigg, H. N.; Hedley, Lou E.; Ramos, L. E.; Sorrell, R. W.; Simpson, S. E.

    1996-06-01

    Spectral reflectance measurements from 400 to 800 nm were taken from immature and mature leaves of grapefruit ('McCarty' and 'Rio Red'), 'Minneola' tangelo, 'Satsuma' mandarin, 'Dancy' tangerine, 'Nagami' oval kumquat, and 'Valencia' sweet orange, at the Florida Citrus Arboretum, Division of Plant Industry, Winter Haven, Florida. Immature and mature leaves of 'Minneola' tangelo had greater percent reflectance in the 400 to 800 nm range than the other varieties and leaf ages measured. The slope of the citrus spectral curves in the 800 nm range was not as sharp as conventional spectrometers, but had a much higher reflectance value than those obtained with a DK-2 spectrometer. Statistical analyses of absolute spectral data yielded significant differences between mature and immature leaves and between varieties. First derivative data analyses did not yield significant differences between varieties.

  10. The Neurocognitive Components of Pitch Processing: Insights from Absolute Pitch

    PubMed Central

    Lusher, Dean; Wan, Catherine Y.; Dudgeon, Paul; Reutens, David C.

    2009-01-01

    The natural variability of pitch naming ability in the population (known as absolute pitch or AP) provides an ideal method for investigating individual differences in pitch processing and auditory knowledge formation and representation. We have demonstrated the involvement of different cognitive processes in AP ability that reflects varying skill expertise in the presence of similar early age of onset of music tuition. These processes were related to different regions of brain activity, including those involved in pitch working memory (right prefrontal cortex) and the long-term representation of pitch (superior temporal gyrus). They reflected expertise through the use of context dependent pitch cues and the level of automaticity of pitch naming. They impart functional significance to structural asymmetry differences in the planum temporale of musicians and establish a neurobiological basis for an AP template. More generally, they indicate variability of knowledge representation in the presence of environmental fostering of early cognitive development that translates to differences in cognitive ability. PMID:18663250

  11. ABSOLUTE PROPERTIES OF THE ECLIPSING BINARY STAR HY VIRGINIS

    SciTech Connect

    Sandberg Lacy, Claud H.; Fekel, Francis C. E-mail: fekel@evans.tsuniv.edu

    2011-12-15

    HY Vir is found to be a double-lined F0m+F5 binary star with relatively shallow (0.3 mag) partial eclipses. Previous studies of the system are improved with 7509 differential photometric observations from the URSA WebScope and 8862 from the NFO WebScope, and 68 high-resolution spectroscopic observations from the Tennessee State University 2 m automatic spectroscopic telescope, and the 1 m coude-feed spectrometer at Kitt Peak National Observatory. Very accurate (better than 0.5%) masses and radii are determined from analysis of the new light curves and radial velocity curves. Theoretical models match the absolute properties of the stars at an age of about 1.35 Gy.

  12. ABSOLUTE PROPERTIES OF THE TRIPLE STAR CF TAURI

    SciTech Connect

    Lacy, Claud H. Sandberg; Torres, Guillermo; Claret, Antonio E-mail: gtorres@cfa.harvard.edu

    2012-12-01

    CF Tau is now known to be an eclipsing triple star with relatively deep total and annular eclipses. New light and radial velocity curves as well as new times of minima were obtained and used for further modeling of the system. Very accurate (better than 0.9%) masses and radii of the eclipsing pair are determined from analysis of the two new light curves, the radial velocity curve, and the times of minimum light. The mass and luminosity of the distant third component is accurately determined as well. Theoretical models of the detached, evolved eclipsing pair match the observed absolute properties of the stars at an age of about 4.3 Gyr and [Fe/H] = -0.14.

  13. The National Geodetic Survey absolute gravity program

    NASA Astrophysics Data System (ADS)

    Peter, George; Moose, Robert E.; Wessells, Claude W.

    1989-03-01

    The National Geodetic Survey absolute gravity program will utilize the high precision afforded by the JILAG-4 instrument to support geodetic and geophysical research, which involves studies of vertical motions, identification and modeling of other temporal variations, and establishment of reference values. The scientific rationale of these objectives is given, the procedures used to collect gravity and environmental data in the field are defined, and the steps necessary to correct and remove unwanted environmental effects are stated. In addition, site selection criteria, methods of concomitant environmental data collection and relative gravity observations, and schedule and logistics are discussed.

  14. An absolute radius scale for Saturn's rings

    NASA Technical Reports Server (NTRS)

    Nicholson, Philip D.; Cooke, Maren L.; Pelton, Emily

    1990-01-01

    Radio and stellar occultation observations of Saturn's rings made by the Voyager spacecraft are discussed. The data reveal systematic discrepancies of almost 10 km in some parts of the rings, limiting some of the investigations. A revised solution for Saturn's rotation pole has been proposed which removes the discrepancies between the stellar and radio occultation profiles. Corrections to previously published radii vary from -2 to -10 km for the radio occultation, and +5 to -6 km for the stellar occultation. An examination of spiral density waves in the outer A Ring supports that the revised absolute radii are in error by no more than 2 km.

  15. Characterization of the DARA solar absolute radiometer

    NASA Astrophysics Data System (ADS)

    Finsterle, W.; Suter, M.; Fehlmann, A.; Kopp, G.

    2011-12-01

    The Davos Absolute Radiometer (DARA) prototype is an Electrical Substitution Radiometer (ESR) which has been developed as a successor of the PMO6 type on future space missions and ground based TSI measurements. The DARA implements an improved thermal design of the cavity detector and heat sink assembly to minimize air-vacuum differences and to maximize thermal symmetry of measuring and compensating cavity. The DARA also employs an inverted viewing geometry to reduce internal stray light. We will report on the characterization and calibration experiments which were carried out at PMOD/WRC and LASP (TRF).

  16. Absolute calibration of the Auger fluorescence detectors

    SciTech Connect

    Bauleo, P.; Brack, J.; Garrard, L.; Harton, J.; Knapik, R.; Meyhandan, R.; Rovero, A.C.; Tamashiro, A.; Warner, D.

    2005-07-01

    Absolute calibration of the Pierre Auger Observatory fluorescence detectors uses a light source at the telescope aperture. The technique accounts for the combined effects of all detector components in a single measurement. The calibrated 2.5 m diameter light source fills the aperture, providing uniform illumination to each pixel. The known flux from the light source and the response of the acquisition system give the required calibration for each pixel. In the lab, light source uniformity is studied using CCD images and the intensity is measured relative to NIST-calibrated photodiodes. Overall uncertainties are presently 12%, and are dominated by systematics.

  17. Absolute angular positioning in ultrahigh vacuum

    SciTech Connect

    Schief, H.; Marsico, V.; Kern, K.

    1996-05-01

    Commercially available angular resolvers, which are routinely used in machine tools and robotics, are modified and adapted to be used under ultrahigh-vacuum (UHV) conditions. They provide straightforward and reliable measurements of angular positions for any kind of UHV sample manipulators. The corresponding absolute reproducibility is on the order of 0.005{degree}, whereas the relative resolution is better than 0.001{degree}, as demonstrated by high-resolution helium-reflectivity measurements. The mechanical setup and possible applications are discussed. {copyright} {ital 1996 American Institute of Physics.}

  18. Absolute method of measuring magnetic susceptibility

    USGS Publications Warehouse

    Thorpe, A.; Senftle, F.E.

    1959-01-01

    An absolute method of standardization and measurement of the magnetic susceptibility of small samples is presented which can be applied to most techniques based on the Faraday method. The fact that the susceptibility is a function of the area under the curve of sample displacement versus distance of the magnet from the sample, offers a simple method of measuring the susceptibility without recourse to a standard sample. Typical results on a few substances are compared with reported values, and an error of less than 2% can be achieved. ?? 1959 The American Institute of Physics.

  19. Absolute Priority for a Vehicle in VANET

    NASA Astrophysics Data System (ADS)

    Shirani, Rostam; Hendessi, Faramarz; Montazeri, Mohammad Ali; Sheikh Zefreh, Mohammad

    In today's world, traffic jams waste hundreds of hours of our life. This causes many researchers try to resolve the problem with the idea of Intelligent Transportation System. For some applications like a travelling ambulance, it is important to reduce delay even for a second. In this paper, we propose a completely infrastructure-less approach for finding shortest path and controlling traffic light to provide absolute priority for an emergency vehicle. We use the idea of vehicular ad-hoc networking to reduce the imposed travelling time. Then, we simulate our proposed protocol and compare it with a centrally controlled traffic light system.

  20. Uranium-series dating and growth characteristics of the deep-sea scleractinian coral: Enallopsammia rostrata from the Equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Houlbrèque, Fanny; McCulloch, Malcolm; Roark, Brendan; Guilderson, Tom; Meibom, Anders; Kimball, Justine; Mortimer, Graham; Cuif, Jean-Pierre; Dunbar, Robert

    2010-04-01

    The deep-sea coral, Enallopsammia rostrata, a member of the Dendrophylliidae family, is a major structure-forming species that creates massive dendroid colonies, up to 1 m wide and 0.5 m tall. Living colonies of E. rostrata have been collected using the PISCES submersibles from three locations from 480 to 788 m water depth in the Line Islands (˜160°W) in the Equatorial Pacific. We have applied to these colonies a high sensitivity, low blank technique to determine U-series ages in small quantities (70 ± 15 mg) of modern and near modern calcareous skeletons using MC-ICP-MS (Multi-collector Inductively Coupled Plasma Mass Spectrometer). The application of this method to living slow-growing colonies from a range of sites as well as the observations of axial growth patterns in thin sections of their skeletons offer the first expanded and well constrained data on longevity, growth pattern and mean growth rates in E. rostrata. Absolute dated specimens indicate life spans of colonies ranging from 209 ± 8 yrs to 605 ± 7 yrs with radial growth rates from 0.012 to 0.072 mm yr -1 and vertical extension rates from 0.6 to 1.9 mm yr -1. The linear growth rates reported here are lower than those reported for other deep-sea scleractinian corals ( Lophelia pertusa and Madrepora oculata). The U-series dating indicates that the growth ring patterns of E. rostrata are not consistent with annual periodicity emphasizing the importance of absolute radiometric dating methods to constrain growth rates. Slow accretion and extreme longevity make this species and its habitat especially vulnerable to disturbances and impacts from human activities. This dating method combined with observation of growth patterns opens up new perspectives in the field of deep-sea corals since it can provide quantitative estimates of growth rates and longevity of deep-sea corals in general.

  1. Determination of the absolute contours of optical flats

    NASA Technical Reports Server (NTRS)

    Primak, W.

    1969-01-01

    Emersons procedure is used to determine true absolute contours of optical flats. Absolute contours of standard flats are determined and a comparison is then made between standard and unknown flats. Contour differences are determined by deviation of Fizeau fringe.

  2. Retrospective Birth Dating of Cells

    SciTech Connect

    L.Spalding, K; Bhardwaj, R D; Buchholz, B A; Druid, H; Frisen, J

    2005-04-19

    The generation of cells in the human body has been difficult to study and our understanding of cell turnover is limited. Extensive testing of nuclear weapons resulted in a dramatic global increase in the levels of the isotope {sup 14}C in the atmosphere, followed by an exponential decrease after the test ban treaty in 1963. We show that the level of {sup 14}C in genomic DNA closely parallels atmospheric levels, and can be used to establish the time point when the DNA was synthesized and cells were born. We use this strategy to determine the age of cells in the cortex of the adult human brain, and show that whereas non-neuronal cells are exchanged, occipital neurons are as old as the individual, supporting the view that postnatal neurogenesis does not take place in this region. Retrospective birth dating is a generally applicable strategy that can be used to measure cell turnover in man under physiological and pathological conditions.

  3. Optical dating of tufa via in situ aeolian sand grains: A case example from the Southern High Plains, USA

    USGS Publications Warehouse

    Rich, J.; Stokes, S.; Wood, W.; Bailey, R.

    2003-01-01

    Precipitated carbonates (commonly termed tufas or travertines) maybe of considerable utility for palaeoenvironmental reconstruction. Their potential, however, for such reconstruction is commonly limited by difficulties associated with their absolute age control. Attempts to date such deposits via uranium series techniques have been complicated by their chemically open behaviour. Here we describe an alternative approach to date tufa deposits associated with ephemeral saline lake basins from the Southern High Plains, USA. We have optically dated sand grains of a mixed aeolian/fluvial (spring fed) origin as the integrating dosimeter. We assume that the grains are fully resetting prior to their incorporation into the tufa deposits and employ a time-dependent disequilibrium dosimetric model to account for the build-up of uranium series daughter products. The approach was applied to a set of four samples with known stratigraphic association. We obtained stratigraphically sensible optical ages ranging from 78??8 to 56??4ka. These data are consistent with existing palaeoenvironmental models of regional recharge. ?? 2003 Elsevier Science Ltd. All rights reserved.

  4. A simple method for in-situ zircon U-Th-He dating

    NASA Astrophysics Data System (ADS)

    Vermeesch, P.; Carter, A.

    2012-04-01

    In situ U-Th-He dating of zircon by laser ablation offers significant advantages over the current practice of whole grain degassing and dissolution: It dramatically increases sample throughput. Measuring the U and Th content of zircon by isotope dilution requires dissolution in hydrofluoric acid at high temperature and pressure using a Parr bomb for up to 48 hours. In contrast, measuring the U and Th content by LA-ICP MS, SIMS, or EMPA can be done in a matter of minutes. The process of in-situ measurements of U and Th content of grains yields U-Th-Pb ages as a by-product. Thus, in-situ dated zircon crystals are double-dated by default, opening up exciting new research opportunities in detrital geochronology. We here propose a simple four step procedure to measure in-situ U-Th-He ages without the need to know any absolute U, Th, or He concentrations: Polish and mount two sets of grains in indium: a standard of known U-Th-He age, and the sample of interest, whose age is unknown. Ablate the grains and measure the raw helium signal (in A, V, or Hz) of the sample along with helium measurements of the age standard. Measure the U and Th signals of the standard and the sample by LA-ICP-MS (in Hz). Obtain the U-Th-He age of the sample by scaling its U, Th, and He signals to those of the standard. In practice, the standard and the unknown are combined on a pairwise basis. This is done by calculating the normalised U, Th, and He concentrations of the standard from its known age and measured Th/U ratio, and then using this normalised composition as a benchmark against which to compare the U, Th, and He signals of the unknown. The Th/U ratio of the standard can be determined from its measured 208Pb/206Pb ratio, removing the need to use NIST glass as a reference material: 232 208 λ238t 23T8h-= 206Pb(eλ-t-1) U Pb(e 232 - 1) (1) It is important to note that the Th/U ratio only needs to be determined for the standard. In other words, the use of Equation 1 does not require U

  5. Standardization of the cumulative absolute velocity

    SciTech Connect

    O'Hara, T.F.; Jacobson, J.P. )

    1991-12-01

    EPRI NP-5930, A Criterion for Determining Exceedance of the Operating Basis Earthquake,'' was published in July 1988. As defined in that report, the Operating Basis Earthquake (OBE) is exceeded when both a response spectrum parameter and a second damage parameter, referred to as the Cumulative Absolute Velocity (CAV), are exceeded. In the review process of the above report, it was noted that the calculation of CAV could be confounded by time history records of long duration containing low (nondamaging) acceleration. Therefore, it is necessary to standardize the method of calculating CAV to account for record length. This standardized methodology allows consistent comparisons between future CAV calculations and the adjusted CAV threshold value based upon applying the standardized methodology to the data set presented in EPRI NP-5930. The recommended method to standardize the CAV calculation is to window its calculation on a second-by-second basis for a given time history. If the absolute acceleration exceeds 0.025g at any time during each one second interval, the earthquake records used in EPRI NP-5930 have been reanalyzed and the adjusted threshold of damage for CAV was found to be 0.16g-set.

  6. Absolute rates of hole transfer in DNA.

    PubMed

    Senthilkumar, Kittusamy; Grozema, Ferdinand C; Guerra, Célia Fonseca; Bickelhaupt, F Matthias; Lewis, Frederick D; Berlin, Yuri A; Ratner, Mark A; Siebbeles, Laurens D A

    2005-10-26

    Absolute rates of hole transfer between guanine nucleobases separated by one or two A:T base pairs in stilbenedicarboxamide-linked DNA hairpins were obtained by improved kinetic analysis of experimental data. The charge-transfer rates in four different DNA sequences were calculated using a density-functional-based tight-binding model and a semiclassical superexchange model. Site energies and charge-transfer integrals were calculated directly as the diagonal and off-diagonal matrix elements of the Kohn-Sham Hamiltonian, respectively, for all possible combinations of nucleobases. Taking into account the Coulomb interaction between the negative charge on the stilbenedicarboxamide linker and the hole on the DNA strand as well as effects of base pair twisting, the relative order of the experimental rates for hole transfer in different hairpins could be reproduced by tight-binding calculations. To reproduce quantitatively the absolute values of the measured rate constants, the effect of the reorganization energy was taken into account within the semiclassical superexchange model for charge transfer. The experimental rates could be reproduced with reorganization energies near 1 eV. The quantum chemical data obtained were used to discuss charge carrier mobility and hole-transport equilibria in DNA. PMID:16231945

  7. Transient absolute robustness in stochastic biochemical networks.

    PubMed

    Enciso, German A

    2016-08-01

    Absolute robustness allows biochemical networks to sustain a consistent steady-state output in the face of protein concentration variability from cell to cell. This property is structural and can be determined from the topology of the network alone regardless of rate parameters. An important question regarding these systems is the effect of discrete biochemical noise in the dynamical behaviour. In this paper, a variable freezing technique is developed to show that under mild hypotheses the corresponding stochastic system has a transiently robust behaviour. Specifically, after finite time the distribution of the output approximates a Poisson distribution, centred around the deterministic mean. The approximation becomes increasingly accurate, and it holds for increasingly long finite times, as the total protein concentrations grow to infinity. In particular, the stochastic system retains a transient, absolutely robust behaviour corresponding to the deterministic case. This result contrasts with the long-term dynamics of the stochastic system, which eventually must undergo an extinction event that eliminates robustness and is completely different from the deterministic dynamics. The transiently robust behaviour may be sufficient to carry out many forms of robust signal transduction and cellular decision-making in cellular organisms. PMID:27581485

  8. Absolute Electron Extraction Efficiency of Liquid Xenon

    NASA Astrophysics Data System (ADS)

    Kamdin, Katayun; Mizrachi, Eli; Morad, James; Sorensen, Peter

    2016-03-01

    Dual phase liquid/gas xenon time projection chambers (TPCs) currently set the world's most sensitive limits on weakly interacting massive particles (WIMPs), a favored dark matter candidate. These detectors rely on extracting electrons from liquid xenon into gaseous xenon, where they produce proportional scintillation. The proportional scintillation from the extracted electrons serves to internally amplify the WIMP signal; even a single extracted electron is detectable. Credible dark matter searches can proceed with electron extraction efficiency (EEE) lower than 100%. However, electrons systematically left at the liquid/gas boundary are a concern. Possible effects include spontaneous single or multi-electron proportional scintillation signals in the gas, or charging of the liquid/gas interface or detector materials. Understanding EEE is consequently a serious concern for this class of rare event search detectors. Previous EEE measurements have mostly been relative, not absolute, assuming efficiency plateaus at 100%. I will present an absolute EEE measurement with a small liquid/gas xenon TPC test bed located at Lawrence Berkeley National Laboratory.

  9. Sentinel-2/MSI absolute calibration: first results

    NASA Astrophysics Data System (ADS)

    Lonjou, V.; Lachérade, S.; Fougnie, B.; Gamet, P.; Marcq, S.; Raynaud, J.-L.; Tremas, T.

    2015-10-01

    Sentinel-2 is an optical imaging mission devoted to the operational monitoring of land and coastal areas. It is developed in partnership between the European Commission and the European Space Agency. The Sentinel-2 mission is based on a satellites constellation deployed in polar sun-synchronous orbit. It will offer a unique combination of global coverage with a wide field of view (290km), a high revisit (5 days with two satellites), a high resolution (10m, 20m and 60m) and multi-spectral imagery (13 spectral bands in visible and shortwave infra-red domains). CNES is involved in the instrument commissioning in collaboration with ESA. This paper reviews all the techniques that will be used to insure an absolute calibration of the 13 spectral bands better than 5% (target 3%), and will present the first results if available. First, the nominal calibration technique, based on an on-board sun diffuser, is detailed. Then, we show how vicarious calibration methods based on acquisitions over natural targets (oceans, deserts, and Antarctica during winter) will be used to check and improve the accuracy of the absolute calibration coefficients. Finally, the verification scheme, exploiting photometer in-situ measurements over Lacrau plain, is described. A synthesis, including spectral coherence, inter-methods agreement and temporal evolution, will conclude the paper.

  10. Absolute Spectrophotometry of 237 Open Cluster Stars

    NASA Astrophysics Data System (ADS)

    Clampitt, L.; Burstein, D.

    1994-12-01

    We present absolute spectrophotometry of 237 stars in 7 nearby open clusters: Hyades, Pleiades, Alpha Persei, Praesepe, Coma Berenices, IC 4665, and M 39. The observations were taken using the Wampler single-channel scanner (Wampler 1966) on the Crossley 0.9m telescope at Lick Observatory from July 1973 through December 1974. 21 bandpasses spanning the spectral range 3500 Angstroms to 7780 Angstroms were observed for each star, with bandwiths ranging from 32Angstroms to 64 Angstroms. Data are standardized to the Hayes--Latham (1975) system. Our measurements are compared to filter colors on the Johnson BV, Stromgren ubvy, and Geneva U V B_1 B_2 V_1 G systems, as well as to spectrophotometry of a few stars published by Gunn, Stryker & Tinsley and in the Spectrophotometric Standards Catalog (Adelman; as distributed by the NSSDC). Both internal and external comparisons to the filter systems indicate a formal statistical accuracy per bandpass of 0.01 to 0.02 mag, with apparent larger ( ~ 0.03 mag) differences in absolute calibration between this data set and existing spectrophotometry. These data will comprise part of the spectrophotometry that will be used to calibrate the Beijing-Arizona-Taipei-Connecticut Color Survey of the Sky (see separate paper by Burstein et al. at this meeting).

  11. A Conceptual Approach to Absolute Value Equations and Inequalities

    ERIC Educational Resources Information Center

    Ellis, Mark W.; Bryson, Janet L.

    2011-01-01

    The absolute value learning objective in high school mathematics requires students to solve far more complex absolute value equations and inequalities. When absolute value problems become more complex, students often do not have sufficient conceptual understanding to make any sense of what is happening mathematically. The authors suggest that the…

  12. Using, Seeing, Feeling, and Doing Absolute Value for Deeper Understanding

    ERIC Educational Resources Information Center

    Ponce, Gregorio A.

    2008-01-01

    Using sticky notes and number lines, a hands-on activity is shared that anchors initial student thinking about absolute value. The initial point of reference should help students successfully evaluate numeric problems involving absolute value. They should also be able to solve absolute value equations and inequalities that are typically found in…

  13. 20 CFR 404.1205 - Absolute coverage groups.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 20 Employees' Benefits 2 2010-04-01 2010-04-01 false Absolute coverage groups. 404.1205 Section... INSURANCE (1950- ) Coverage of Employees of State and Local Governments What Groups of Employees May Be Covered § 404.1205 Absolute coverage groups. (a) General. An absolute coverage group is a...

  14. Dating Violence among College Students

    ERIC Educational Resources Information Center

    Iconis, Rosemary

    2013-01-01

    Dating violence is a significant problem on college campuses. More than one-fifth of the undergraduate dating population are physically abused by their dating partners and an even greater percentage are psychologically abused. Researchers have identified risk factors for college student dating violence. Preventive interventions are strongly…

  15. Luminescence dating of ancient Darhad basin, Mongolia

    NASA Astrophysics Data System (ADS)

    Cheul Kim, Jin; Yi, Sangheon; Lim, Jaesoo; Kim, Ju-Yong

    2016-04-01

    Darhad basin is located in the northern Mongolia, in the western end of the Baikal Rift Zone. In contrast to the neighboring Lake Hovsgol, Mongolia's largest and deepest lake, the Darhad is a drained lake basin. It is ~100 km long (north-south), 20-40 km wide and covered by sediments which locally exceed 500 m thickness (Zorin et al., 1989). Darhad basin is characterized by alternating episodes of expansion and desiccation that are closely related with the Pleistocene damming events. Previous studies of the Darhad Basin suggest that the last paleolake was dammed by a large glacier or the sediments (Selivanov, 1967, 1968; Krivonogov et al., 2005; Gillespie et al., 2008). Especially, recent expansion of the paleolake might be caused by the two glacial maxima during MIS 4 and 2. However, glacier-dammed lakes might be short-lived, dried up and permafrost occurred in the drained basin during the Holocene period. The uppermost paleolake sediments (13.2 m depth) are exposed following the curvature of the meandering river (called "Hodon outcrop"). It is considered the most likely site for the youngest paleolake sediments because it is distributed in the northern middle part of the paleolake. Krivonogov et al. 2012 described the Hodon outcrop with the sedimentological and chronological data. Age dating of 16 samples (11 mollusk shells, 5 wood fragments) indicated that Hodon outcrop sediments were deposited between 10.1±7 and 4.9±5 ka. However, the ages obtained on shells much older dates than the matched wood samples because of ingestion of old carbon by mollusks. The age difference between shells and wood fragments is a minimum of 1.73 ka and a maximum of 3.41 ka (average 2.5 ka). In this case, 14C ages from shells should be corrected with appropriate correction factor. However, the old carbon effects could vary temperally and spatially in the Darhad paleolake. The limited number of the 14C ages from wood fragments result in a simple linear trend in the depth-age curve

  16. Music Technology in the Preschool? Absolutely!

    ERIC Educational Resources Information Center

    Nardo, Rachel

    2008-01-01

    Most music educators are unaware that one of the earliest known electronic music keyboards for children dates back to 1952. It was unsophisticated in appearance, but much like the inventions of today, the mid-century electronic musical toy piqued the interest of children, and they begged their parents to buy it for them. The invention was name