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Sample records for triassic time scale

  1. High-precision U-Pb zircon age from the Triassic of Italy: Implications for the Triassic time scale and the Carnian origin of calcareous nannoplankton and dinosaurs

    NASA Astrophysics Data System (ADS)

    Furin, Stefano; Preto, Nereo; Rigo, Manuel; Roghi, Guido; Gianolla, Piero; Crowley, James L.; Bowring, Samuel A.

    2006-12-01

    The Triassic time scale is poorly constrained due to a paucity of high-precision radiometric ages. We present a 206Pb/238U age of 230.91 0.33 Ma (error includes all known sources) for zircon from an ash bed in the upper Carnian (Upper Triassic) of southern Italy that requires a major revision of the Triassic time scale. For example, the Norian stage is lengthened to more than 20 m.y. The section containing the ash bed is correlated with other Tethyan sections and, indirectly, with the Newark astronomical polarity time scale (APTS). The dating provides also a minimum age for some important climatic and biotic events that occurred during the Carnian. We note a coincidence between these events and the eruption of the large igneous province of Wrangellia, but the possible link between volcanism and climatic and biotic events requires further scrutiny.

  2. Time-scale calibration by U-Pb geochronology: Examples from the Triassic Period

    NASA Astrophysics Data System (ADS)

    Mundil, R.

    2009-05-01

    U-Pb zircon geochronology, pioneered by Tom Krogh, is a cornerstone for the calibration of the time scale. Before Krogh's innovations, U-Pb geochronology was essentially limited by laboratory blank Pb (typically hundreds of nanograms) inherent in the then existing zircon dissolution and purification methods. The introduction of high pressure HF dissolution combined with miniature ion exchange columns (1) reduced the blank by orders of magnitude and allowed mass-spectrometric analyses of minute amounts of material (picograms of Pb and U). Krogh also recognized the need for minimizing the effects of Pb loss, and the introduction of the air-abrasion technique was the method of choice for two decades (2), until the development of the combined annealing and chemical abrasion technique resulted in essentially closed system zircons (3). These are the prerequisite for obtaining precise (permil-level) and accurate radio-isotopic ages of individual zircons contained in primary volcanic ash deposits, which are primary targets for the calibration of the time scale if they occur within fossil bearing sediments. A prime example is the calibration of the Triassic time scale which improved significantly using these techniques. The ages for the base and the top of the Triassic are constrained by U-Pb ages to 252.3 (4) and 201.5 Ma (5), respectively. These dates also constrain the ages of major extinction events at the Permian-Triassic and Triassic-Jurassic boundaries, and are statistically indistinguishable from ages obtained for the Siberian Traps and volcanic products from the Central Atlantic Magmatic Province, respectively, suggesting a causal link. Ages for these continental volcanics, however, are mostly from the K-Ar (40Ar/39Ar) system which requires accounting and correcting for a systematic bias of ca 1 % between U-Pb and 40Ar/39Ar isotopic ages (the 40Ar/39Ar ages being younger) (6). Robust U-Pb age constraints also exist for the Induan- Olenekian boundary (251.2 Ma, (7)) and the Early-Middle Triassic (Olenekian-Anisian) boundary (247.2 Ma, (8, 9)), resulting in a surprisingly short duration of the Early Triassic which has implications for the timing of biotic recovery and major changes in ocean chemistry during this time. Furthermore, the Anisian-Ladinian boundary is constrained to 242.0 Ma by new U-Pb and 40Ar/39Ar ages. Radio-isotopic ages for the Late Triassic are scarce and the only reliable and biostratigraphically controlled age is from an upper Carnian tuff dated to 230.9 Ma (10), yielding a duration of more than 35 Ma for the Late Triassic. The resulting time-scale is at odds with the most recent compilation (11) but arguably more accurate because it is entirely based on U-Pb analyses applied to closed-system zircons with uncertainties at the permil level or better. 1. T. E. Krogh, Geochimica et Cosmochimica Acta 37, 485 (1973); 2. T. E. Krogh, Geochimica et Cosmochimica Acta 46, 637 (1982); 3. J. M. Mattinson, Chemical Geology 220, 47 (2005); 4. R. Mundil, K. R. Ludwig, I. Metcalfe, P. R. Renne, Science 305, 1760 (2004); 5. U. Schaltegger, J. Guex, A. Bartolini, B. Schoene, M. Ovtcharova, Earth and Planetary Science Letters 267, 266 (2008); 6. R. Mundil, P. R. Renne, K. K. Min, K. R. Ludwig, in Eos Trans. AGU, Fall Meet. Suppl. (2006), vol. 87(52), pp. V21A-0543; 7. T. Galfetti et al., Earth and Planetary Science Letters 258, 593 (2007). 8. M. Ovtcharova et al., Earth and Planetary Science Letters 243, 463 (2006). 9. J. Ramezani et al., Earth and Planetary Science Letters 256, 244 (2007). 10. S. Furin et al., Geology 34, 1009 (2006); 11. J. G. Ogg, in A Geologic Time Scale 2004 F. M. Gradstein, J. G. Ogg, A. G. Smith, Eds. (University Press, Cambridge, 2004) pp. 271-306.

  3. High-precision U-Pb zircon geochronological constraints on the End-Triassic Mass Extinction, the late Triassic Astronomical Time Scale and geochemical evolution of CAMP magmatism

    NASA Astrophysics Data System (ADS)

    Blackburn, T. J.; Olsen, P. E.; Bowring, S. A.; McLean, N. M.; Kent, D. V.; Puffer, J. H.; McHone, G.; Rasbury, T.

    2012-12-01

    Mass extinction events that punctuate Earth's history have had a large influence on the evolution, diversity and composition of our planet's biosphere. The approximate temporal coincidence between the five major extinction events over the last 542 million years and the eruption of Large Igneous Provinces (LIPs) has led to the speculation that climate and environmental perturbations generated by the emplacement of a large volume of magma in a short period of time triggered each global biologic crisis. Establishing a causal link between extinction and the onset and tempo of LIP eruption has proved difficult because of the geographic separation between LIP volcanic deposits and stratigraphic sequences preserving evidence of the extinction. In most cases, the uncertainties on available radioisotopic dates used to correlate between geographically separated study areas often exceed the duration of both the extinction interval and LIP volcanism by an order of magnitude. The "end-Triassic extinction" (ETE) is one of the "big five" and is characterized by the disappearance of several terrestrial and marine species and dominance of Dinosaurs for the next 134 million years. Speculation on the cause has centered on massive climate perturbations thought to accompany the eruption of flood basalts related to the Central Atlantic Magmatic Province (CAMP), the most aerially extensive and volumetrically one of the largest LIPs on Earth. Despite an approximate temporal coincidence between extinction and volcanism, there lacks evidence placing the eruption of CAMP prior to or at the initiation of the extinction. Estimates of the timing and/or duration of CAMP volcanism provided by astrochronology and Ar-Ar geochronology differ by an order of magnitude, precluding high-precision tests of the relationship between LIP volcanism and the mass extinction, the causes of which are dependent upon the rate of magma eruption. Here we present high precision zircon U-Pb ID-TIMS geochronologic data for eight CAMP flows and sills from the eastern U.S. and Morocco. These data are used first to independently test the astronomically calibrated time scale and sediment accumulation rates within the Triassic-Jurassic rift basins along the eastern North America. The U-Pb, paleontological, magnetostratigraphic and astronomical data are combined to constrain the onset and duration of the CAMP and clarify the temporal relationship between the CAMP and the ETE. The dataset together allows more precise estimates of eruptive volume per unit time, a requirement for rigorous evaluation of climate-driven models for the extinction.

  4. High resolution U?Pb dating of Middle Triassic volcaniclastics: Time-scale calibration and verification of tuning parameters for carbonate sedimentation

    NASA Astrophysics Data System (ADS)

    Mundil, Roland; Brack, Peter; Meier, Martin; Rieber, Hans; Oberli, Felix

    1996-06-01

    We report high-resolution single-zircon U?Pb age data for Middle Triassic volcaniclastic intercalations in biostratigraphically calibrated pelagic successions of the Southern Alps. The results require a redefinition of the chronometric scale for the Middle Triassic. Moreover, they do not support current models relating cyclic sedimentation in platform carbonates of the Dolomites to orbital tuning. Tight concordant age clusters were obtained for five volcaniclastic layers in three ammonoid biozones of late Anisian to early Ladinian age. Two layers in the (Nevadites) Secedensis Zone yielded identical mean 206Pb /238U ages of 241.2 + 0.8/-0.8 Ma and 241.2 + 0.8/-0.6 Ma (errors given at the 95% confidence level). A layer in the Gredleri Zone is dated at 238.8 + 0.5/-0.2 Ma, and two horizons in the Archelaus Zone yield similar ages of 237.9 + 1.0/-0.7 Ma and 238.0 + 0.4/-0.7 Ma. These results are significantly older than the age values of 233-235 Ma assigned to the Anisian/Ladinian boundary by several current time scales [1-4]. Moreover, our estimate of 240.7-241.3 Ma (depending on biostratigraphic collocation) for the Anisian/Ladinian boundary casts doubts on the reliability of age values of 245-250 Ma proposed by most time scales for the Permian/Triassic boundary. The occurrence of pelagic fossils in basinal sediments as well as in age-equivalent shallow marine Middle Triassic platform carbonates in the Dolomites allows the sedimentary sequences of both environments to be correlated. The 800 m thick Latemar platform (western Dolomites) is characterized by cyclic stacking patterns, which have been interpreted as results of Milankovitch-type high-frequency/low-amplitude sea-level fluctuations. The 12 m.y. interval of platform growth postulated from the assignment of orbital periodicities to the platform carbonate cycles [5,6] is in conflict with a maximum time span of 4.7 m.y. allowed by the present zircon data.

  5. Magnetostratigraphy of the Mayerling section (Austria) and Erenkolu Mezarlik (Turkey) section: Improvement of the Carnian (late Triassic) magnetic polarity time scale

    NASA Astrophysics Data System (ADS)

    Gallet, Yves; Besse, Jean; Krystyn, Leopold; Theveniaut, Herve; Marcoux, Jean

    1994-07-01

    We present a magnetostratigraphic study of two Carnian (late Triassic) pelagic limestone sections from the Northern Calcareous Alps (Mayerling section) and southwestern Turkey (Erenkolu Mezarlik section). Biostratigraphic control is based on conodont zonation for the Mayerling section, and both on conodonts and ammonoids for the Erenkolu Mezarlik section. In both sections, the characteristic magnetization is essentially carried by a mineral of the magnetite family. Eight magnetic intervals are obtained from the Mayerling section and fourteen from Erenkolu Mezarlik. When these results are compared to the Carnian magnetostratigraphic sequence obtained from the Bolucektasi Tepe section, satisfactory correlations are observed and a composite Carnian magnetic polarity time scale containing 24 intervals can be proposed by combining all these results. The lower part of the upper Carnian is however missing (Tuvalian 1 zone and lower part of the Tuvalian 2 zone). No clear correlation is observed between our composite sequence and the other published magnetostratigraphic data of Carnian age. The satisfactory correlation observed between the Mayerling and the Bolucektasi Tepe sections indicates that both sections were deposited in the northern hemisphere, thus providing constraints on the origin of the Antalya nappes.

  6. Patterns of Reef Ecosystem Recovery Indicate That Adverse Early Triassic Ocean Conditions Extended into Middle Triassic Time

    NASA Astrophysics Data System (ADS)

    Kelley, B. M.; Yu, M.; Lehrmann, D. J.; Jost, A. B.; Lau, K. V.; Li, X.; Schaal, E. K.; Payne, J.

    2013-12-01

    The pattern of reef ecosystem recovery from the end-Permian extinction is poorly constrained due to the limited stratigraphic, spatial, and geographic range of reef buildups in Early Triassic and Anisian (early Middle Triassic) strata. In this study, we combined field studies and petrographic analysis to examine the pattern of reef evolution in latest Permian to Late Triassic carbonate platforms in the Nanpanjiang Basin of South China, an area of extensive shallow-water carbonate deposition in the tropical eastern Tethys. We find that early Mesozoic reef recovery in the eastern Tethys was a five-step process: (1) in the immediate aftermath of extinction, calcimicrobial biostromes (P/T boundary microbialites) developed in shallow-water platform settings; (2) in late Induan time, biohermal stromatolites developed in platform interior settings; (3) in latest Spathian time, large-scale Tubiphytes, microbial, and cement reefs lacking skeletal metazoans initiated on the margins and steep upper slopes of carbonate platforms, signaling the return of reefs to platform-margin settings; (4) in the Aegean or Bithynian (early Anisian), diminutive (mm-scale) calcareous sponges and calcareous algae appeared in the Tubiphytes reef, marking the reappearance of skeletal metazoans and calcareous algae to reefs in the eastern Tethys; and (5) in the late Anisian, the appearance of scleractinian corals coincided with increased abundance, size, and diversity of metazoan and algal reef builders. Early Mesozoic reefs of the eastern Tethys were dominated by microbes, Tubiphytes, and early-marine cements until the late Anisian, several million years into the Middle Triassic. The appearance of small metazoan buildups in Early Triassic strata in other parts of the world indicates that potential reef-building organisms were present much earlier. The limited stratigraphic range of those buildups, however, reinforces the interpretation that episodic environmental disturbances such as euxinia, high temperatures, and acidification impacted biotic recovery during Early Triassic time. Our findings of protracted early Mesozoic reef recovery suggest that the causal links between environmental disturbance and biotic recovery extended into Middle Triassic time.

  7. High precision time calibration of the Permian-Triassic boundary mass extinction event in a deep marine context

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    To construct a revised and high resolution calibrated time scale for the Permian-Triassic boundary (PTB) we use (1) high-precision U-Pb zircon age determinations of a unique succession of volcanic ash layers interbedded with deep water fossiliferous sediments in the Nanpanjiang Basin (South China) combined with (2) accurate quantitative biochronology based on ammonoids, conodonts, radiolarians, and foraminifera and (3) tracers of marine bioproductivity (carbon isotopes) across the PTB. The unprecedented precision of the single grain chemical abrasion isotope-dilution thermal ionization mass spectrometry (CA-ID-TIMS) dating technique at sub-per mil level (radio-isotopic calibration of the PTB at the <100 ka level) now allows calibrating magmatic and biological timescales at resolution adequate for both groups of processes. Using these alignments allows (1) positioning the PTB in different depositional setting and (2) solving the age contradictions generated by the misleading use of the first occurrence (FO) of the conodont Hindeodus parvus, whose diachronous first occurrences are arbitrarily used for placing the base of the Triassic. This new age framework provides the basis for a combined calibration of chemostratigraphic records with high-resolution biochronozones of the Late Permian and Early Triassic. Here, we present new single grain U-Pb zircon data of volcanic ash layers from two deep marine sections (Dongpan and Penglaitan) revealing stratigraphic consistent dates over several volcanic ash layers bracketing the PTB. These analyses define weighted mean 206Pb/238U ages of 251.9560.033 Ma (Dongpan) and 252.0620.043 Ma (Penglaitan) for the last Permian ash bed. By calibration with detailed litho- and biostratigraphy new U-Pb ages of 251.9530.038 Ma (Dongpan) and 251.9070.033 Ma (Penglaitan) are established for the onset of the Triassic.

  8. High precision time calibration of the Permo-Triassic boundary mass extinction by U-Pb geochronology

    NASA Astrophysics Data System (ADS)

    Baresel, Bjrn; Bucher, Hugo; Brosse, Morgane; Schaltegger, Urs

    2014-05-01

    U-Pb dating using Chemical Abrasion, Isotope Dilution Thermal Ionization Mass Spectrometry (CA-ID-TIMS) is the analytical method of choice for geochronologists, who are seeking highest temporal resolution and a high degree of accuracy for single grains of zircon. The use of double-isotope tracer solutions, cross-calibrated and assessed in different EARTHTIME labs, coinciding with the reassessment of the uranium decay constants and further improvements in ion counting technology led to unprecedented precision better than 0.1% for single grain, and 0.05% for population ages, respectively. These analytical innovations now allow calibrating magmatic and biological timescales at resolution adequate for both groups of processes. To construct a revised and high resolution calibrated time scale for the Permian-Triassic boundary (PTB) we use (i) high-precision U-Pb zircon age determinations of a unique succession of volcanic ash beds interbedded with shallow to deep water fossiliferous sediments in the Nanpanjiang Basin (South China) combined with (ii) accurate quantitative biochronology based on ammonoids and conodonts and (iii) carbon isotope excursions across the PTB. Using these alignments allows (i) positioning the PTB in different depositional environments and (ii) solving age/stratigraphic contradictions generated by the index, water depth-controlled conodont Hindeodus parvus, whose diachronous first occurrences are arbitrarily used for placing the base of the Triassic. This new age framework provides the basis for a combined calibration of chemostratigraphic records with high-resolution biochronozones of the Late Permian and Early Triassic. Besides the general improvement of the radio-isotopic calibration of the PTB at the 100 ka level, this will also lead to a better understanding of cause and effect relations involved in this mass extinction.

  9. Integrative stratigraphy during extreme environmental changes and biotic recovery time: The Early Triassic in Indian Himalaya

    NASA Astrophysics Data System (ADS)

    Richoz, Sylvain; Krystyn, Leopold; Algeo, Thomas; Bhargava, Om

    2014-05-01

    The understanding of extreme environmental changes as major extinction events, perturbations of global biogeochemical cycles or rapid climate shifts is based on a precise timing of the different events. But especially in such moving environments exact correlations are difficult to establish what underlines the necessity of an integrated stratigraphy by using all tools at disposition. A Lower Triassic section at Mud in the Spiti Valley (Western Himalaya, India) is a candidate section for the GSSP of the Induan-Olenekian Boundary (IOB). The succession was deposited in a deep-shelf setting on the southern margin of the Neotethys Ocean. The section contains abundant fossils allowing a very precise regional biostratigraphy and displays no signs of sedimentary breaks. Analysis of pelagic faunas proves a significant, two-step radiation phase in ammonoids and conodonts close to the Induan-Olenekian boundary. These diversifications are coupled with a short-termed positive ?13Ccarb excursion of global evidence. The Spiti ?13Ccarb excursion displays, however, different amplitude and biostratigraphic position than in other relevant sections for this time interval. In this study, we analyzed ?13Ccarb, ?13Corg, and ?15Norg as well as major, trace, and REE concentrations for a 16-m-thick interval spanning the mid-Griesbachian to early Spathian substages, to better constrains the chain of events. Prior to the first radiation step, high difference gradient between the ?13Ccarb values of tempestite beds with shallow carbonate and carbonate originated in deeper water is interpreted as a sign of a stratified water column. This effect disappears with the onset of better oxygenated conditions at the time of the ammonoid-conodont radiation, which correspond as well to ?13Ccarb, ?13Corg and ?15Norg positive excursions. A decrease in Mo and U concentrations occurring at the same point suggests a shift toward locally less reducing conditions. The second step coincided with the change from terrigenous to almost pure carbonate sedimentation. This new set of data demonstrates from on hand the rapidity of radiation of the pelagic fauna in the aftermath of the Permian-Triassic extinction as soon as environmental conditions were favourable again. On the other hand, it demonstrates that bathymetry, for example, but also other local factors, could have had a significant impact in the timing of these radiations and may hamper solid worldwide correlations.

  10. Occupational Cohort Time Scales

    PubMed Central

    Roth, H. Daniel

    2015-01-01

    Purpose: This study explores how highly correlated time variables (occupational cohort time scales) contribute to confounding and ambiguity of interpretation. Methods: Occupational cohort time scales were identified and organized through simple equations of three time scales (relational triads) and the connections between these triads (time scale web). The behavior of the time scales was examined when constraints were imposed on variable ranges and interrelationships. Results: Constraints on a time scale in a triad create high correlations between the other two time scales. These correlations combine with the connections between relational triads to produce association paths. High correlation between time scales leads to ambiguity of interpretation. Conclusions: Understanding the properties of occupational cohort time scales, their relational triads, and the time scale web is helpful in understanding the origins of otherwise obscure confounding bias and ambiguity of interpretation. PMID:25647318

  11. Teaching about time by understanding Geologic Time Scales: The Geological Society of America Geologic Time Scale and its history

    NASA Astrophysics Data System (ADS)

    Geissman, J. W.; Walker, J. D.

    2012-12-01

    Geologic time scales, of one form or another, are used in most undergraduate geosciences courses, even including introductory physical geology or equivalent. However, satisfactory discussions of how geologic time scales originated, and how they have evolved to modern versions, are far too often conveniently or inconveniently left out of classroom discussions. Yet it is these kinds of discussions that have the potential of solidifying student appreciation of deep time and rates of geologic processes. We use the history and development of the Geological Society of America Geologic Time Scale, which reflects major developments in the fields of stratigraphy, geochronology, magnetic polarity stratigraphy, astrochronology, and chemostratigraphy, as a focus of how specific details of time scales can be used to teach about time. Advances in all of these fields have allowed many parts of the time scale to be calibrated to precisions approaching less than 0.05 %. Notable time intervals for which collaborative, multifaceted efforts have led to dramatic improvements in our understanding of the character and temporal resolution of key evolutionary events, in both marine and terrestrial environments, include the Triassic-Jurassic, Permo-Triassic, and Neoproterozoic-Phanerozoic boundaries (or transitions). Many of the details, but certainly not all, can be incorporated in discussions of how we know about geologic time in the classroom. For example, we presently understand that both the end-Permian ecological crisis and the biostratigraphic Permian-Triassic boundary, as calibrated by conodonts, lie within a ca. 700 ka long normal polarity chron. The reverse to normal polarity transition at the beginning of this chron is ca. 100 ka earlier than the ecological crisis and thus slightly older than the current estimate, based on high precision U-Pb zircon age determinations, of ca. 252.4 Ma for the Permian-Triassic boundary. This polarity transition occurred during the early part of the major negative del 13C isotope excursion that is estimated to have lasted ca. 500 ka beginning in the very latest Permian. Current geologic time scales are vastly improved over the first geologic time scale published by Holmes, nearly a hundred years ago in 1913, that used a total of eight numerical ages to establish the Phanerozoic time scale.

  12. Africa and Madagascar during Permo-Triassic time: The evidence of the vertebrate faunas

    NASA Astrophysics Data System (ADS)

    Battail, Bernard; Beltan, Laurence; Dutuit, Jean-Michel

    Various sediments ranging from the Carboniferous to the Quaternary, including Permo Triassic beds, were deposited on the western margin of Madagascar. These can be compared with the sediments of the African Karoo. Comparative analysis of the vertebrate faunas from Madagascar and Africa, however, shows many differences and gives rise to questions which fall into three categories: phylogenetic relationship, faunal dispersal in Africa and Madagascar, and connection with other parts of Gondwanaland and Laurasia. The Late Permian and Early Triassic ichthyofaunas from Madagascar bear affinities with those of South Africa only at a generic or familial level, but the tetrapod faunas are completely different. The Late Triassic tetrapod fauna of Madagascar is represented only by scarce material; it differs from the South African fauna and can be better compared with that from North Africa. During the Late Permian and Early Triassic, Madagascar was obviously cut from the African continent by a marine barrier. The faunal relationships between Madagascar and North Africa in the Late Triassic can possibly be explained by migrations along the southern shore of the Tethys. Detailed consideration of all the possible connections of Africa and Madagascar with the rest of the world is beyond the scope of this paper. We found it useful, however, to give a few demonstrative examples of such connections in order to place the African and Malagasy faunas in a more global context. The Early Triassic ichthyofaunas from Madagascar are, in part, related to those of South Africa, but they display more affinities with Laurasian faunas from British Columbia, Greenland, and Spitsbergen. In addition, there are, apparently, close relationships between the trematosaurs from Madagascar and from Spitsbergen. The reptilian fauna from the Lystrosaurus zone of South Africa, which has no equivalent in Madagascar, is very closely related to the fauna from the Fremouw Formation of Antarctica. The reptilian fauna from the Cynognathus zone of South Africa can be compared with the fauna of the Puesto Viejo Formation of Argentina. In the Late Triassic there were faunal similarities between Madagascar and the western part of Laurasia, while no obvious connection between South Africa and Laurasia can be detected.

  13. Recognising ocean acidification in deep time: An evaluation of the evidence for acidification across the Triassic-Jurassic boundary

    NASA Astrophysics Data System (ADS)

    Greene, Sarah E.; Martindale, Rowan C.; Ritterbush, Kathleen A.; Bottjer, David J.; Corsetti, Frank A.; Berelson, William M.

    2012-06-01

    While demonstrating ocean acidification in the modern is relatively straightforward (measure increase in atmospheric CO2 and corresponding ocean chemistry change), identifying palaeo-ocean acidification is problematic. The crux of this problem is that the rock record is a constructive archive while ocean acidification is essentially a destructive (and/or inhibitory) phenomenon. This is exacerbated in deep time without the benefit of a deep ocean record. Here, we discuss the feasibility of, and potential criteria for, identifying an acidification event in deep time. Furthermore, we investigate the evidence for ocean acidification during the Triassic-Jurassic (T-J) boundary interval, an excellent test case because 1) it occurs in deep time, beyond the reach of deep sea drilling coverage; 2) a potential trigger for acidification is known; and 3) it is associated with one of the 'Big Five' mass extinctions which disproportionately affected modern-style invertebrates. Three main criteria suggest that acidification may have occurred across the T-J transition. 1) The eruption of the Central Atlantic Magmatic Province (CAMP) and the associated massive and rapid release of CO2 coincident with the end-Triassic mass extinction provide a suitable trigger for an acidification event (full carbonate undersaturation in the surface ocean is possible but improbable). 2) Tentative evidence for a global paucity of carbonate across the end-Triassic mass extinction versus the adjacent stratigraphy is consistent with a predicted sedimentary response to acidification. 3) The end-Triassic mass extinction was particularly selective against acid-sensitive organisms (more so than perhaps any other extinction event) and temporarily eliminated coral reefs. Therefore multiple lines of evidence are consistent with a T-J ocean acidification event within our current resolution to recognise such events in deep time. The conclusion that the end-Triassic extinction was influenced by acidification implies that short-term acidification perturbations may have long-term effects on ecosystems, a repercussion that has previously not been established. Although anthropogenic emissions are more rapid than any event in the geologic record, events such as the T-J can serve as partial analogues for the present anthropogenic carbon release. Since the T-J was such a pronounced crisis for both modern-style marine invertebrates and scleractinian reefs, it is of particular interest in terms of informing projections about the effects of modern ocean acidification.

  14. Position of the Triassic-Jurassic boundary and timing of the end-Triassic extinctions on land: Data from the Moenave Formation on the southern Colorado Plateau, USA

    USGS Publications Warehouse

    Lucas, S.G.; Tanner, L.H.; Donohoo-Hurley, L.; Geissman, J.W.; Kozur, H.W.; Heckert, A.B.; Weems, R.E.

    2011-01-01

    Strata of the Moenave Formation on and adjacent to the southern Colorado Plateau in Utah-Arizona, U.S.A., represent one of the best known and most stratigraphically continuous, complete and fossiliferous terrestrial sections across the Triassic-Jurassic boundary. We present a synthesis of new biostratigraphic and magnetostratigraphic data collected from across the Moenave Formation outcrop belt, which extends from the St. George area in southwestern Utah to the Tuba City area in northern Arizona. These data include palynomorphs, conchostracans and vertebrate fossils (including footprints) and a composite polarity record based on four overlapping magnetostratigraphic sections. Placement of the Triassic-Jurassic boundary in strata of the Moenave Formation has long been imprecise and debatable, but these new data (especially the conchostracans) allow us to place the Triassic-Jurassic boundary relatively precisely in the middle part of the Whitmore Point Member of the Moenave Formation, stratigraphically well above the highest occurrence of crurotarsan body fossils or footprints. Correlation to marine sections based on this placement indicates that major terrestrial vertebrate extinctions preceded marine extinctions across the Triassic-Jurassic boundary and therefore were likely unrelated to the Central Atlantic Magmatic Province (CAMP) volcanism. ?? 2011 Elsevier B.V.

  15. Timing of the Permian-Triassic biotic crisis: implications from new zircon U/Pb age data (and their limitations)

    NASA Astrophysics Data System (ADS)

    Mundil, Roland; Metcalfe, Ian; Ludwig, Kenneth R.; Renne, Paul R.; Oberli, Felix; Nicoll, Robert S.

    2001-04-01

    The most profound biotic crisis in the Earth's history, causing the near extinction of both terrestrial and marine life, occurred at the end of the Permian period about 253 Myr ago and marks the Paleozoic-Mesozoic era boundary. The cause of this event is still a matter of vigorous debate, with both brief and catastrophic as well as gradual mechanisms having been proposed. Similar to a recent landmark study, this study uses the U-Pb method on zircons from the uppermost Permian/lowermost Triassic ash fall deposits at Meishan (Zhejiang Province, SE China) in order to examine time and rate constraints for these events. The results of both this study and previous work show that for these ash layers, the effects of Pb loss are combined with varying amounts and sources of inheritance, resulting in an age scatter which prohibits the extraction of a statistically robust age in many cases. Though the effects of Pb loss on the zircons analyzed in this study were reduced by leaching the grains in hydrofluoric acid (as opposed to commonly applied air abrasion) prior to analysis, the presence within a single ash layer of multiple generations of older xenocrysts (in many cases only slightly older than the depositional age) has made quantitative interpretation even more difficult. When these combined phenomena bias individual zircon ages by less than a percent, they are extremely difficult to deconvolute, and, if multi-grain analyses are used, can become impossible to recognize (because of the resulting age averaging). Monte Carlo simulations using actual measurements of individual zircon crystals show that age excursions due to Pb loss and xenocrystic contamination for the Meishan bentonites are easily homogenized to the point of undetectability when replicate analyses of multi-grain zircon samples are compared. Thus this study uses only high-precision analyses of single crystals, whether from our work or that of previous studies. Three main conclusions have emerged. First, our data require a significant increase in the age of the Permian-Triassic boundary by more than 2 myr compared to the previous study, which shifts the age to a value older than 253 Ma. Second, neither our data nor those from previous work can confirm or negate the possibility of a very abrupt biotic crisis. Third, even large suites of very high-quality, single-zircon U-Pb analyses for these tuffs cannot, in most cases, yield objective, reliable, and robust dates with accuracies at the sub-myr level - though the temptation to perform arbitrary selection of subsets of the analyses for that purpose is almost irresistible. The last conclusion is not an indictment of zircon U/Pb dating in general (other rocks and other zircon populations can - and do - behave very differently), and further technical advances will likely improve our ability to prepare grains or sub-grains of adequately enhanced quality for analysis. Consequently, the results of the present study strongly suggest that for problems requiring time-scale accuracy, inferences from zircon U-Pb dating must be based on sufficiently large suites of single-crystal or crystal domain, high-precision analyses (<1% error) that are realistically interpreted.

  16. Large-scale diabase intrusion in the Durham Triassic Basin of North Carolina: geophysics and geochemistry

    SciTech Connect

    Bolich, R.E.; Bevis, M.G.; Won, I.J.; Fodor, R.V.

    1985-01-01

    Gravity and magnetic data obtained from the Durham Triassic Basin of North Carolina reveal pronounced positive gravity and magnetic anomalies of 10 milligals and 300 gammas, respectively, along the western border of the basin. In the vicinity of these anomalies, diabase outcrops, some with chilled margins and others with flow features, occur sporadically, but have a combined area of about 100 sq. km. Two-dimensional modeling of the gravity data indicates that the diabase body accounts for the gravity anomaly as a semi-continuous subsurface intrusion. The intrusive body is greater than 250 m thick near the western border of the basin, but thins to about 100 m near the center of the basin. Geochemical data for samples recovered from 4 air-drill sites at one diabase outcrop in Butner, North Carolina yield high MgO concentrations, and low FeO, K2O, and TiO2. The geophysical and geochemical data are consistent with an uncontaminated basaltic magma ascending along a major fissure or fissures and into the basin. In the basin, the diabase encountered unlithified sediments, resulting in both intrusive and extrusive forms. Although similar chemical compositions for Mesozoic North American dikes have been reported, this is the first indication of an intrusive body of such a large extent and primitive chemical composition.

  17. Paleomagnetism of the Upper Triassic rocks from south of the Ailaoshan Suture and the timing of the amalgamation between the South China and the Indochina Blocks

    NASA Astrophysics Data System (ADS)

    Huang, Kainian; Opdyke, Neil D.

    2016-04-01

    A high temperature remanence with thermally-discrete unblocking temperature spectra has been isolated from the redbed samples of the Upper Triassic Yiwanshui Formation collected from south of the Ailaoshan Suture in southern Yunnan Province of China. Two groups of directions were observed: the tilt-corrected mean is D/I = 141.4°/31.2° with α95 = 13.0° based on 12 sites for the first group, and D/I = 207.5°/4.9° with α95 = 16.0° based on 5 sites for the second group. The second group of directions was derived from massively bedded rocks with large uncertainties in determination of the paleo-horizontal and is thus deemed inaccurate. The first group of directions passes the foldtest with dual polarity, and is consistent with results previously reported from the same type section, and probably represents primary magnetization of the rock formation. Comparison with the Triassic paleomagnetic poles for the Baoshan Terrane and the South China Block indicates that the Simao and the Baoshan terranes were probably already amalgamated by late Triassic times but the coalescence between them and the South China Block may have not been completed until near the end of the Triassic.

  18. Geologic time scale bookmark

    USGS Publications Warehouse

    U.S. Geological Survey

    2012-01-01

    This bookmark, designed for use with U.S. Geological Survey activities at the 2nd USA Science and Engineering Festival (April 2629, 2012), is adapted from the more detailed Fact Sheet 20103059 "Divisions of Geologic Time." The information that it presents is widely sought by educators and students.

  19. The Triassic-Jurassic boundary in eastern North America

    NASA Technical Reports Server (NTRS)

    Olsen, P. E.; Comet, B.

    1988-01-01

    Rift basins of the Atlantic passive margin in eastern North America are filled with thousands of meters of continental rocks termed the Newark Supergroup which provide an unprecedented opportunity to examine the fine scale structure of the Triassic-Jurassic mass extinction in continental environments. Time control, vital to the understanding of the mechanisms behind mass extinctions, is provided by lake-level cycles apparently controlled by orbitally induced climate change allowing resolution at the less than 21,000 year level. Correlation with other provinces is provided by a developing high resolution magnetostratigraphy and palynologically-based biostratigraphy. A large number of at least local vertebrate and palynomorph extinctions are concentrated around the boundary with survivors constituting the earliest Jurassic assemblages, apparently without the introduction of new taxa. The palynofloral transition is marked by the dramatic elimination of a relatively high diversity Triassic pollen assemblage with the survivors making up a Jurassic assemblage of very low diversity overwhelmingly dominated by Corollina. Based principally on palynological correlations, the hypothesis that these continental taxonomic transitions were synchronous with the massive Triassic-Jurassic marine extinctions is strongly corroborated. An extremely rapid, perhaps catastrophic, taxonomic turnover at the Triassic-Jurassic boundary, synchronous in continental and marine realms is hypothesized and discussed.

  20. Relation of Middle and Late Triassic strata of N-C Nevada to contemporaneous strata of southern Nevada and Utah

    SciTech Connect

    Elison, M.W.

    1993-04-01

    Middle and Late Triassic shelf strata in north-central Nevada comprising dominantly carbonate rocks of the Star Peak Group and overlying siliciclastic and carbonate rocks are overlain tectonically by predominantly siliciclastic basinal strata. Late Triassic slope strata are preserved in the East and Humboldt Ranges. At present, these Triassic rocks are separated from contemporaneous deposits of Utah by roughly 300 km over which time-equivalent ( ) strata are limited to a small, isolated outcrop near Currie, NV. Mesozoic and Cenozoic tectonics and widespread absence of Triassic rocks immediately to the east complicate the relation between the north-central Nevada section and Triassic rocks of southern Nevada and Utah. The gap in Triassic rocks may have resulted from erosion of intervening strata or from tectonic separation of originally contiguous stratal sequences. Some depositional facies of the shelf uniformly cover the preserved outcrop area and do not constrain the scale of the depositional system. Where facies variations are present, they suggest sediment sources to the east and north and deeper water to the west. Facies patterns, however, were influenced by local tectonics and changes in sediment source and supply. Late Triassic strata of N-C Nevada probably are the shallow-marine equivalents of fluvial and lacustrine rocks to the east. Local tectonics and changes in sediment influx require caution regarding interpretation of the original proximity of preserved stratal sequences.

  1. Permian-Triassic Osteichthyes (bony fishes): diversity dynamics and body size evolution.

    PubMed

    Romano, Carlo; Koot, Martha B; Kogan, Ilja; Brayard, Arnaud; Minikh, Alla V; Brinkmann, Winand; Bucher, Hugo; Kriwet, Jrgen

    2016-02-01

    The Permian and Triassic were key time intervals in the history of life on Earth. Both periods are marked by a series of biotic crises including the most catastrophic of such events, the end-Permian mass extinction, which eventually led to a major turnover from typical Palaeozoic faunas and floras to those that are emblematic for the Mesozoic and Cenozoic. Here we review patterns in Permian-Triassic bony fishes, a group whose evolutionary dynamics are understudied. Based on data from primary literature, we analyse changes in their taxonomic diversity and body size (as a proxy for trophic position) and explore their response to Permian-Triassic events. Diversity and body size are investigated separately for different groups of Osteichthyes (Dipnoi, Actinistia, 'Palaeopterygii', 'Subholostei', Holostei, Teleosteomorpha), within the marine and freshwater realms and on a global scale (total diversity) as well as across palaeolatitudinal belts. Diversity is also measured for different palaeogeographical provinces. Our results suggest a general trend from low osteichthyan diversity in the Permian to higher levels in the Triassic. Diversity dynamics in the Permian are marked by a decline in freshwater taxa during the Cisuralian. An extinction event during the end-Guadalupian crisis is not evident from our data, but 'palaeopterygians' experienced a significant body size increase across the Guadalupian-Lopingian boundary and these fishes upheld their position as large, top predators from the Late Permian to the Late Triassic. Elevated turnover rates are documented at the Permian-Triassic boundary, and two distinct diversification events are noted in the wake of this biotic crisis, a first one during the Early Triassic (dipnoans, actinistians, 'palaeopterygians', 'subholosteans') and a second one during the Middle Triassic ('subholosteans', neopterygians). The origination of new, small taxa predominantly among these groups during the Middle Triassic event caused a significant reduction in osteichthyan body size. Neopterygii, the clade that encompasses the vast majority of extant fishes, underwent another diversification phase in the Late Triassic. The Triassic radiation of Osteichthyes, predominantly of Actinopterygii, which only occurred after severe extinctions among Chondrichthyes during the Middle-Late Permian, resulted in a profound change within global fish communities, from chondrichthyan-rich faunas of the Permo-Carboniferous to typical Mesozoic and Cenozoic associations dominated by actinopterygians. This turnover was not sudden but followed a stepwise pattern, with leaps during extinction events. PMID:25431138

  2. Pair plasma relaxation time scales.

    PubMed

    Aksenov, A G; Ruffini, R; Vereshchagin, G V

    2010-04-01

    By numerically solving the relativistic Boltzmann equations, we compute the time scale for relaxation to thermal equilibrium for an optically thick electron-positron plasma with baryon loading. We focus on the time scales of electromagnetic interactions. The collisional integrals are obtained directly from the corresponding QED matrix elements. Thermalization time scales are computed for a wide range of values of both the total-energy density (over 10 orders of magnitude) and of the baryonic loading parameter (over 6 orders of magnitude). This also allows us to study such interesting limiting cases as the almost purely electron-positron plasma or electron-proton plasma as well as intermediate cases. These results appear to be important both for laboratory experiments aimed at generating optically thick pair plasmas as well as for astrophysical models in which electron-positron pair plasmas play a relevant role. PMID:20481841

  3. Early Triassic geologic history of northeastern Nevada

    SciTech Connect

    Paull, R.K.; Paull, R.A.

    1986-08-01

    Conodont biostratigraphic and lithostratigraphic studies of Lower Triassic rocks in northeastern Elko County, Nevada, and adjacent parts of Idaho and Utah provide new information about regional geologic history. A sequential summary of Early Triassic events in this area follows: (1) rapid transgression of the Griesbachian sea to limiting barriers on the south (Oquirrh-Uinta axis) and west (Humboldt highland.). (2) Although the initial Triassic transgression may have persisted farther south and west than present-day evidence indicates, a period of progradation during the Dienerian limited marine sedimentation to northeastern-most Nevada and adjacent states. (3) In Smithian time, a widespread transgression spilled south and west over the earliest Triassic basin margin. (4) The southward flood is characterized by locally spectacular basal conglomerates followed by shallow marine deposits of the Thaynes Formation. (5) The transgression to the west was facilitated by tectonic removal of the restrictive barrier during the Smithian. This resulted in a slope-basin environment that accumulated a thick sequence of shale and calcareous siltstone with interbeds of turbidite conglomerates, olistostromes, and exotic blocks derived from Permian formations in northern Nevada or adjacent Idaho. (6) During a regional progradation in early Spathian time, marine conditions persisted in northeastern Nevada. (7) A final depositional episode is documented by the progressive westward spread of carbonate rocks of the Thaynes Formation. (8) Withdrawal of Triassic seas from northeast Nevada occurred post-latest Early Triassic, since a carbonate sequence of more than 300 m overlies the youngest dated interval.

  4. Timing and Extent of Magmatism Associated With the Permo-Triassic Siberian Large Igneous Province: The Biggest Gets Bigger.

    NASA Astrophysics Data System (ADS)

    Reichow, M. K.; Saunders, A. D.; Pringle, M. S.; Puchkov, V. N.; Safonova, I. Y.; Fedoseev, G. S.; Buslov, M. M.

    2006-12-01

    The generation of large igneous provinces, and whether or not they are responsible for mass extinctions, are hotly debated. The Siberian Traps represent the remnants of the largest Phanerozoic continental flood basalt province, with an estimated original size of 4 x 106 km2 and an original combined volume of at least 2 x 106 km3 (Milanovskiy, 1976). The province may also be responsible for the Permo-Triassic mass extinction at 251 Ma. Despite recent intensive research on the province, the extent and duration of extrusive and related magmatism are still controversial. Although several areas surrounding the Siberian craton have been attributed to the Siberian Traps volcanic activity, the full extent remains conjectural as precise age determinations and chemical correlations between units are missing. Basaltic, gabbroic and rhyolitic rocks occur throughout the West Siberian Basin beneath a thick succession of Mesozoic and Cenozoic sediments. Thicknesses of the lava sequences vary but exceed 2 km in places. Areas with basalt and dolerite rocks supposedly related to the Siberian Traps are also reported further to the north of the Siberian craton, on the Taimyr Peninsula, along the eastern border of the Urals (Chelyabinsk) and in the polar Urals (Vorkuta), and to the south within the Kuznetsk Basin (Kuzbass) and Semeitau (Kazakhstan) areas. We have obtained widespread early Triassic sample material from across Siberia, and present an assessment of published and new geochemical and isotopic age data. Basalts from the West Siberian Basin, and the Chelyabinsk, Kuzbass, Vorkuta regions have chemical characteristics typical of evolved, crustally- contaminated continental flood basalts (e.g., low Mg#, negative Nb anomaly) showing affinities with the Nadezhdinsky suite of the main traps from the Noril'sk area. The Nadezhdinsky suite is known to immediately precede the supposedly main pulse of volcanism that extruded over large areas of the craton. The data indicate that the basalts and associated rhyolites are likely to be a part of the greater Siberian LIP, although it is not yet possible, with the currently available data, to define the duration of activity. We review of the challenges of explaining the generation of the Siberian Large Igneous Province.

  5. Time Scales in Particulate Systems

    NASA Astrophysics Data System (ADS)

    Zhang, Duan

    2013-06-01

    While there are many interests of studying interactions of individual particles, macroscopic collective behavior of particles are our main interest in many practical applications. In this talk, I will give a brief overview of the multiscale methods connecting the physics at individual particles to macroscopic quantities and averaged equations. The emphasis will be on dense dissipative particulate systems, such as powders. Unlike conservative particle systems, such as molecular systems, in a dissipative particle system the concept of thermodynamic equilibrium is not very useful unless in very special cases, because the only true thermodynamically equilibrium state in these systems is the state in which nothing moves. Other than idealized simple systems, mesoscale structures are common and important in many practical systems, especially in dissipative systems. Spatial correlations of these mesoscale structures, such as force chains in dense granular system, particle clusters and streamers in fluidized beds have received some recent attentions, partly because they can be visualized. This talk will emphasize the effects of time correlations related to the mesoscale structures. To consider time correlations and history information of the system, I will introduce the mathematical foundation of the Liouville equation, its applicability and limitations. I will derive the generalized Liouville equations for particulate systems with and without interstitial fluids, and then use them to study averaged transport equations and related closures. Interactions among the time scale of particle interactions, the time scale of the mesocale structures, and the time scale of the physical problem as represented by strain rate will be discussed. The effect of these interactions on the closure relations will be illustrated. I will also discuss possible numerical methods of solving the averaged equations, and multiscale numerical algorithms bridging the particle level calculations to continuum level calculations. This work was sponsored by Stockpile Safety and Surety Program, the Joint DOD/DOE Munitions Technology Development Program, and National Nuclear Security Administrations Science Campaign 2.

  6. Time Scales in Evolutionary Dynamics

    NASA Astrophysics Data System (ADS)

    Roca, Carlos P.; Cuesta, José A.; Sánchez, Angel

    2006-10-01

    Evolutionary game theory has traditionally assumed that all individuals in a population interact with each other between reproduction events. We show that eliminating this restriction by explicitly considering the time scales of interaction and selection leads to dramatic changes in the outcome of evolution. Examples include the selection of the inefficient strategy in the Harmony and Stag-Hunt games, and the disappearance of the coexistence state in the Snowdrift game. Our results hold for any population size and in more general situations with additional factors influencing fitness.

  7. Synchroneity of climatic change and extinctions in the Late Triassic

    NASA Astrophysics Data System (ADS)

    Simms, Michael J.; Ruffell, Alastair H.

    1989-03-01

    Although the Late Triassic was a time of widespread aridity, evidence exists for a significant increase in rainfall during the middle to late Carnian. Upper Triassic playa-lake sediments were interrupted by late Carnian fluviatile sandstones with erosive bases and high kao-linite/illite ratios. There was also an increase in the clastic component of marine sequences during this interval. Middle and upper Carnian marine carbonates show an extreme depletion in ?13C values, consistent with increased fresh-water influx. Large-scale karstic phenomena in limestone areas subaerially exposed during the Late Triassic are a further indication of increased rainfall. Important faunal and floral changes occurred during the Carnian-Norian interval; marine invertebrate turnover was greatest at the lower/middle Carnian boundary, and terrestrial extinctions were concentrated at the Carnian/Norian boundary. The cause of this Carnian pluvial episode may have been related to the rifting of Pangea, through disruption of atmospheric and oceanic circulation patterns, eustatic changes, or the effects of volcanism associated with rifting. A change in surface ocean temperature, salinity or pH, or habitat loss may have caused the decline of many shallow-marine invertebrates at the start of the middle Carnian; a return to arid conditions at the Carnian/Norian boundary would account for the turnover among terrestrial vertebrates and plants.

  8. Characteristic time scale of auroral electrojet data

    SciTech Connect

    Takalo, J.; Timonen, J.

    1994-04-01

    The authors study the different time scales which have been observed in the auroral electrojet (AE) data. Structure function data shows the AE time series experiences a scaling change with a time scale of approximately 2 hours. Autocorrelation measurements also reveal a characteristic time of close to two hours. The authors argue here for a relationship between these two times, and for a relationship between these two times and the time scale of breaks in the power spectrum of the AE data.

  9. The history of the Arabian platform evolution in the Late Permian and Triassic

    SciTech Connect

    Bebeshev, I.I.

    1995-03-01

    On the basis of comprehensive investigations of the Upper Permian and Triassic sequences of the Arabian platform, three stages were recognized, corresponding to distinct time intervals. The first stage corresponds to the Latest Permian-Early Triassic, the second - to the Early-Middle Triassic, the third - to the Late Triassic. Special maps were plotted for the second and third stages, reflecting major paleogeographic and paleotectonic events. An effort was made to test the oil potential of the sequences.

  10. Large-scale progradation, demise and rebirth of a high-relief carbonate platform (Triassic, Lombardy Southern Alps, Italy)

    NASA Astrophysics Data System (ADS)

    Berra, Fabrizio; Jadoul, Flavio; Binda, Marco; Lanfranchi, Alessandro

    2011-07-01

    The Upper Anisian to Early Carnian succession of the Middle Val Brembana-Pegherolo Massif (Central Southern Alps of Italy) records a complete depositional cycle from platform inception to growth, demise and rebirth. The depositional architecture of this system reflects different evolutionary stages: an inception stage which postdates a previous drowning of an Anisian carbonate platform with progradation of the carbonate platform from the nucleation areas, an aggradational stage with increasing water depth in the basins, a progradational stage where steep slopes composed of margin-derived breccias develop and a final crisis corresponding to the subaerial exposure of the platform top, followed by the deposition of shales in the basin before the rebirth of a different type of carbonate factory. The record of this evolution reflects the effects of the change in accommodation space (interplay of subsidence and eustacy), which controls the type and storage sites of the sediments produced by the carbonate factory. The effects of the changes in accommodation space are recorded in the shallow water platform as well as in the intraplatform basins, where the sediments, delivered at different rates from the platform top are stored. As a consequence, the aggradational stage corresponds to reduced sedimentation in the basins (i.e. sediments are stored on the platform top) whereas during progradation resedimented limestones are more common in the basin. Subaerial exposure rapidly halted the carbonate production on the platform top, while a major input of shales (probably reflecting a climate change and/or lowering of the base level) is recorded in the basin, where shales onlap the slope of the previous carbonate system. The rebirth of the carbonate factory after subaerial exposure of the platform top is characterized by a different composition of the carbonate factory, probably reflecting changes of the environmental conditions. The step-by-step recording of the evolution of the carbonate system represents a unique opportunity to record a seismic-scale complete evolutionary cycle of a carbonate system in its different sub-environments, from the platform top to the basin.

  11. Early Triassic seawater sulfate drawdown

    NASA Astrophysics Data System (ADS)

    Song, Huyue; Tong, Jinnan; Algeo, Thomas J.; Song, Haijun; Qiu, Haiou; Zhu, Yuanyuan; Tian, Li; Bates, Steven; Lyons, Timothy W.; Luo, Genming; Kump, Lee R.

    2014-03-01

    The marine sulfur cycle is intimately linked to global carbon fluxes, atmospheric composition, and climate, yet relatively little is known about how it responded to the end-Permian biocrisis, the largest mass extinction of the Phanerozoic. Here, we analyze carbonate-associated-sulfate (CAS) from three Permo-Triassic sections in South China in order to document the behavior of the C-S cycle and its relationship to marine environmental changes during the mass extinction and its aftermath. We find that δ34SCAS varied from +9‰ to +44‰ at rates up to 100‰ Myr-1 during the Griesbachian-Smithian substages of the Early Triassic. We model the marine sulfur cycle to demonstrate that such rapid variation required drawdown of seawater sulfate concentrations to ⩽4 mM and a reduction in its residence time to ⩽200 kyr. This shorter residence time resulted in positive covariation with δ13Ccarb due to strong coupling of the organic carbon and pyrite burial fluxes. Carbon and sulfur isotopic shifts were associated with contemporaneous changes in climate, marine productivity, and microbial sulfate reduction rates, with negative shifts in δ13Ccarb and δ34SCAS linked to warming, decreased productivity, and reduced sulfate reduction. Sustained cooling during the Spathian re-invigorated oceanic overturning circulation, reduced marine anoxia, and limited pyrite burial. As seawater sulfate built to higher concentrations during the Spathian, the coupling of the marine C and S cycles came to an end and a general amelioration of marine environmental conditions set the stage for a recovery of invertebrate faunas. Variation in seawater sulfate during the Early Triassic was probably controlled by climate change, possibly linked to major eruptive phases of the Siberian Traps.

  12. Triassic-Jurassic marine anoxia in response to massive carbon release from CAMP?

    NASA Astrophysics Data System (ADS)

    Ruhl, M.; Bjerrum, C. J.; Canfield, D. E.; Frei, R.

    2012-04-01

    The end-Triassic mass extinction [~201.3 Ma], marked by marine and terrestrial ecosystem collapse and global marine biodiversity loss, coincides with the onset of extensive volcanic activity and emplacement of the Central Atlantic Magmatic Province (CAMP). Massive and rapid greenhouse gas release from surface basalts, subsurface organic rich strata and ocean-floor clathrate-hydrates had a profound impact on the global exogenic carbon cycle and it dramatically increased atmospheric pCO2 values. Although Permian-Triassic [~252 Ma] and early Toarcian [~183 Ma] volcanic carbon release is thought to have initiated global ocean anoxic events, ocean redox changes at the end-Triassic mass extinction are poorly constrained. Marine anoxia is only suggested by organic-rich, finely laminated sediment deposition in marginal marine basins. We studied the biostratigraphically well-constrained Triassic-Jurassic marine sedimentary record from St. Audrie's Bay (UK), which is astronomically calibrated to the continental geomagnetic polarity time-scale (GPTS) of the continental Newark basin. This marine geological archive is marked by precession paced black-shale deposition, similar to Neogene Mediterranean sapropels. We studied redox-sensitive trace element concentrations (e.g. Mo, U, V, Cu, Ni), iron-speciation (FeHR/FeT, FePY/FeHR) and ?34S-pyrite through the end-Triassic mass extinction and subsequent 3 million years of the lower Jurassic. We observe direct stratigraphic correlation between CAMP flood basalt emplacement, strong atmospheric pCO2 increase and development of marine anoxia. This now allows evaluation of mechanistic relations between massive greenhouse gas emissions initiated by CAMP volcanism, subsequent environmental change and upper Triassic and lower Jurassic biotic response.

  13. Time scales of magmatic processes

    NASA Astrophysics Data System (ADS)

    Hawkesworth, Chris; George, Rhiannon; Turner, Simon; Zellmer, Georg

    2004-01-01

    The development of improved analytical techniques has facilitated the application of short-lived isotopes to the study of magmatic processes, and resulted in a renewed interest in a number of other chronometers. Two approaches have been used to determine the time scales of magmatic processes. Isotopic dating provides absolute ages for the growth of mineral phases. This usually involves analyses of mineral separates such that the textural relations of the individual grains are difficult to establish. An exception is zircon, which can be analysed in situ. The second approach is to use relative chronometry based on major, trace element and isotope profiles in crystals that may have been modified by diffusion. These yield information on how long crystals were at a particular temperature, without indicating when this occurred. The ages are obtained on individual crystals, and so age distributions can be determined on different crystals from the same whole rock. The ages of crystals and the liquid, as represented by the groundmass, in an igneous rock can be different, and in a number of cases it has been shown that even the larger, and therefore typically older crystals formed after the fractional crystallisation responsible for the whole rock composition. One implication is that the processes of magma differentiation responsible for whole rock compositions may not necessarily be inferred from the compositional record of the larger crystals. Different approaches are therefore used to investigate the crystallisation history and the differentiation of magmatic suites. Crystallisation rates are 10 -10-10 -11 cm/s, whereas differentiation to high-silica magmas may take up to 210 5 years. The ages of crystals at the time of eruption can range back to 10 5-10 6 years, the older ages tend to be in the more evolved rock types, and it can take 10 5 years for high-silica magmas to be generated at individual volcanic centres. It appears that the generation of such evolved magmas is thermally controlled, for both fractional crystallisation and the generation of crustal melts, and the rates of fractional crystallisation can, for example, be linked to volcanic power outputs. If crystallisation is in response to magma degassing or decompression, it will be fast and there may be too little time for fractional crystallisation to take place.

  14. The Sail-Backed Reptile Ctenosauriscus from the Latest Early Triassic of Germany and the Timing and Biogeography of the Early Archosaur Radiation

    PubMed Central

    Butler, Richard J.; Brusatte, Stephen L.; Reich, Mike; Nesbitt, Sterling J.; Schoch, Rainer R.; Hornung, Jahn J.

    2011-01-01

    Background Archosaurs (birds, crocodilians and their extinct relatives including dinosaurs) dominated Mesozoic continental ecosystems from the Late Triassic onwards, and still form a major component of modern ecosystems (>10,000 species). The earliest diverse archosaur faunal assemblages are known from the Middle Triassic (c. 244 Ma), implying that the archosaur radiation began in the Early Triassic (252.3–247.2 Ma). Understanding of this radiation is currently limited by the poor early fossil record of the group in terms of skeletal remains. Methodology/Principal Findings We redescribe the anatomy and stratigraphic position of the type specimen of Ctenosauriscus koeneni (Huene), a sail-backed reptile from the Early Triassic (late Olenekian) Solling Formation of northern Germany that potentially represents the oldest known archosaur. We critically discuss previous biomechanical work on the ‘sail’ of Ctenosauriscus, which is formed by a series of elongated neural spines. In addition, we describe Ctenosauriscus-like postcranial material from the earliest Middle Triassic (early Anisian) Röt Formation of Waldhaus, southwestern Germany. Finally, we review the spatial and temporal distribution of the earliest archosaur fossils and their implications for understanding the dynamics of the archosaur radiation. Conclusions/Significance Comprehensive numerical phylogenetic analyses demonstrate that both Ctenosauriscus and the Waldhaus taxon are members of a monophyletic grouping of poposauroid archosaurs, Ctenosauriscidae, characterised by greatly elongated neural spines in the posterior cervical to anterior caudal vertebrae. The earliest archosaurs, including Ctenosauriscus, appear in the body fossil record just prior to the Olenekian/Anisian boundary (c. 248 Ma), less than 5 million years after the Permian–Triassic mass extinction. These earliest archosaur assemblages are dominated by ctenosauriscids, which were broadly distributed across northern Pangea and which appear to have been the first global radiation of archosaurs. PMID:22022431

  15. Improving the Geologic Time Scale (Jean Baptiste Lamarck Medal Lecture)

    NASA Astrophysics Data System (ADS)

    Gradstein, Felix M.

    2010-05-01

    The Geologic Time Scale (GTS) provides the framework for the physical, chemical and biological processes on Earth. The time scale is the tool "par excellence" of the geological trade, and insight in its construction, strength, and limitations enhances its function and its utility. Earth scientists should understand how time scales are constructed and its myriad of physical and abstract data are calibrated, rather than merely using ages plucked from a convenient chart or card. Calibration to linear time of the succession of events recorded in the rocks on Earth has three components: (1) the standard stratigraphic divisions and their correlation in the global rock record, (2) the means of measuring linear time or elapsed durations from the rock record, and (3) the methods of effectively joining the two scales, the stratigraphic one and the linear one. Under the auspices of the International Commission on Stratigraphy (ICS), the international stratigraphic divisions and their correlative events are now largely standardized, especially using the GSSP (Global Stratigraphic Section and Point) concept. The means of measuring linear time or elapsed durations from the rock record are objectives in the EARTH TIME and GTS NEXT projects, that also are educating a new generation of GTS dedicated scientists. The U/Pb, Ar/Ar and orbital tuning methods are intercalibrated, and external error analysis improved. Existing Ar/Ar ages become almost 0.5% older, and U/Pb ages stratigraphically more realistic. The new Os/Re method has potential for directly dating more GSSP's and its correlative events. Such may reduce scaling uncertainty between the sedimentary levels of an age date and that of a stage boundary. Since 1981, six successive Phanerozoic GTS have been published, each new one achieving higher resolution and more users. The next GTS is scheduled for 2011/2012, with over 50 specialists taking part. New chapters include an expanded planetary time scale, sequence stratigraphy, Osmium, Carbon and Oxygen stratigraphy, the Cryogenian period, history of the plants, hominid prehistory, and last but not least the Anthropocene. The Cambrian Period is radically improved with 10 standard stages and detailed trilobite biochronology. Ordovician now has a stable international stages and graptolites scale. The integration of a refined 100 and 400 ka sedimentary cycles scale and a truly high-resolution U/Pb ages scale for the Mississippian is a major step towards the global Carboniferous GTS. The Devonian GTS leaves to be desired with lack of firm definitions for its upper boundary, and the long Emsian stage; it also lacks age dates. Its stages scaling is disputed. The Rhaetian and Norian stages in the Triassic and the Berriasian stage in the Cretaceous urgently require lower boundary definitions, and also boundary age dates. The single ~400 ka eccentricity component is very stable and can extend orbital tuning from the Cenozoic well into the Mesozoic portion of the GTS. Jurassic and Cretaceous now have long orbitally tuned segments. A completely astronomical-tuned Geological Time Scale (AGTS) for the Cenozoic is within reach showing unprecedented accuracy, precision and resolution. Burdigalian in the Miocene, and Lutetian, Bartonian and Priabonian stages in the Eocene still require formal definition. The K/T boundary will become about 0.5 ± 0.1 Ma older. After 25 years of research and authorship in the GTS it behoves me to especially thank my colleagues James Ogg, Frits Agterberg, John McArthur and Roger Cooper for longstanding collaboration. As a final note I urge construction of more regional time scales(like developed ‘down under') calibrated to the standard global GTS, to scale regional rock units.

  16. Modeling orbital changes on tectonic time scales

    NASA Technical Reports Server (NTRS)

    Crowley, Thomas J.

    1992-01-01

    Geologic time series indicate significant 100 ka and 400 ka pre-Pleistocene climate fluctuations, prior to the time of such fluctuations in Pleistocene ice sheets. The origin of these fluctuations must therefore depend on phenomena other than the ice sheets. In a previous set of experiments, we tested the sensitivity of an energy balance model to orbital insolation forcing, specifically focusing on the filtering effect of the Earth's geography. We found that in equatorial areas, the twice-yearly passage of the sun across the equator interacts with the precession index to generate 100 ka and 400 ka power in our modeled time series. The effect is proportional to the magnitude of land in equatorial regions. We suggest that such changes may reflect monsoonal variations in the real climate system, and the subsequent wind and weathering changes may transfer some of this signal to the marine record. A comparison with observed fluctuations of Triassic lake levels is quite favorable. A number of problems remain to be studied or clarified: (1) the EBM experiments need to be followed up by a limited number of GCM experiments; (2) the sensitivity to secular changes in orbital forcing needs to be examined; (3) the possible modifying role of sedimentary processes on geologic time series warrants considerably more study; (4) the effect of tectonic changes on Earth's rotation rate needs to be studied; and (5) astronomers need to make explicit which of their predictions are robust and geologists and astronomers have to agree on which of the predictions are most testable in the geologic record.

  17. How severe is the modern biotic crisis?A comparison of global change and biotic crisis between Permian-Triassic transition and modern times

    NASA Astrophysics Data System (ADS)

    Yin, Hongfu; He, Weihong; Xie, Shucheng

    2011-03-01

    A comparison of the modern condition with the Permian-Triassic Boundary (PTB) times was made to estimate how severe the modern biotic crisis is. About the global changes, the two periods are correlative in carbon dioxide concentration and carbon isotope negative excursion, UV strengthening, temperature increase, ocean acidification, and weathering enhancement. The following tendencies of biotic crises are also correlative: acceleration of extinction rates accompanied by parabolic curve of extinction with a turning interval representing the critical crisis; decline of the three main ecosystems: reefs, tropical rain forests and marine phytoplankton. It is also interesting to note that certain leading organism in both periods undergo accelerated evolution during the crisis. The comparison shows that the modern crisis is about at the turning point from decline to decimation. The extinction curve is now parabolic, and the extinction rate has been accelerated, but the decimation is not yet in real. This is also justified by the modern situation of the three main ecosystems. Modern biotic decline may worsen into decimation and mass extinction but may also get better and recover to ordinary evolution. Since human activities are the main cause of the deterioration of environments and organisms, mankind should be responsible and able to strive for the recovery of the crisis. For the future of mankind, Homo sapiens may become extinct, i.e., disappear without leaving descendants, or evolve into a new and more advanced species, i.e., disappear but leave descendants. For a better future, mankind should be conscious of the facing danger and act as a whole to save biodiversity and harmonize with the environments.

  18. Stability of Rasch Scales over Time

    ERIC Educational Resources Information Center

    Taylor, Catherine S.; Lee, Yoonsun

    2010-01-01

    Item response theory (IRT) methods are generally used to create score scales for large-scale tests. Research has shown that IRT scales are stable across groups and over time. Most studies have focused on items that are dichotomously scored. Now Rasch and other IRT models are used to create scales for tests that include polytomously scored items.

  19. Estimates of expansion time scales

    NASA Astrophysics Data System (ADS)

    Jones, E. M.

    Monte Carlo simulations of the expansion of a spacefaring civilization show that descendants of that civilization should be found near virtually every useful star in the Galaxy in a time much less than the current age of the Galaxy. Only extreme assumptions about local population growth rates, emigration rates, or ship ranges can slow or halt an expansion. The apparent absence of extraterrestrials from the solar system suggests that no such civilization has arisen in the Galaxy.

  20. Time scale evolution of avipoxviruses.

    PubMed

    Le Loc'h, Guillaume; Bertagnoli, Stphane; Ducatez, Mariette F

    2015-10-01

    Avipoxviruses are divided into three clades: canarypox-like viruses, fowlpox-like viruses, and psittacinepox-like viruses. Several molecular clock and demographic models available in the BEAST package were compared on three avipoxvirus genes (P4b, cnpv186 and DNA polymerase genes), which enabled to determine that avipoxviruses evolved at a rate of 2-810(-5)substitution/site/year, in the range of poxviruses previously reported evolution rates. In addition, the date of mean time of divergence of avipoxviruses from a common ancestor was extrapolated to be about 10,000-30,000years ago, at the same period as modern poxvirus species. Our findings will facilitate epidemiological investigations on avipoxviruses' spread, origin and circulation. PMID:26231721

  1. Review of time scales. [Universal Time-Ephemeris Time-International Atomic Time

    NASA Technical Reports Server (NTRS)

    Guinot, B.

    1974-01-01

    The basic time scales are presented: International Atomic Time, Universal Time, and Universal Time (Coordinated). These scales must be maintained in order to satisfy specific requirements. It is shown how they are obtained and made available at a very high level of precision.

  2. Out of Sequence Reversed Polarity Zone At The Triassic - Jurassic Boundary

    NASA Astrophysics Data System (ADS)

    Mrton, E.; Halsz, D.

    Standard magnetostratigraphy columns indicate uninterrupted normal polarity across the Triassic - Jurassic boundary. Kent et al. (1995, J. Geophys. Res. 100/B8, 14965- 14998) however, modified the polarity time scale inserting a short reversed polarity zone in the Uppermost Rhtian. The short reversed polarity interval interrupting a long normal polarity zone promised an excellent tool in world-wide definition of the above boundary. The Csvr section in Hungary is one of the few profiles with contin- uous sedimentation during the late Triassic - early Jurassic. Among the fully oriented samples collected from the 44 m. long profile there were several with reversed polarity. They all represent Triassic - Jurassic transition beds. Below and above the transition zone we observed normal polarity. The mean paleomagnetic directions calculated for the normal and reversed polarity groups, respectively, are significantly different. For the first group D=289 I=38 k=16 alpha95=7 are in the geographic, D=300 I=43 k=18 alpha95=7 in the tectonic system. The reversed polarity samples yield D=189 I=-56 k=165 alpha95=5. The Csvr section belongs to an area which rotated in the CCW sense after the Jurassic (Mrton, 1998, Geophys. J. Int. 134, 625-633). The last significant rotation took place around 15 Ma (Mrton and Pcskay, 1998, Acta Geol. Hung. 41/4, 467-476). Clearly the acquisition of the reversed polarity remanence in the Triassic - Jurassic transition beds must be younger than 15 Ma. Consequently the reversed polarity zone identified at the Triassic - Jurassic boundary in the Csvr sec- tion can not be used as a correlation tool.

  3. Kalman plus weights: a time scale algorithm

    NASA Technical Reports Server (NTRS)

    Greenhall, C. A.

    2001-01-01

    KPW is a time scale algorithm that combines Kalman filtering with the basic time scale equation (BTSE). A single Kalman filter that estimates all clocks simultaneously is used to generate the BTSE frequency estimates, while the BTSE weights are inversely proportional to the white FM variances of the clocks. Results from simulated clock ensembles are compared to previous simulation results from other algorithms.

  4. Advances in the Geomagnetic Polarity Time Scale--Developments and Integration with the Geologic Time Scale and Future Directions (Invited)

    NASA Astrophysics Data System (ADS)

    Geissman, J. W.

    2013-12-01

    We celebrate the 50th anniversary of the publication of the Vine-Matthews/Morley-Larochelle hypothesis (Vine and Matthews, Nature, 1963, v. 199, #4897, p. 947-949), which integrated marine magnetic anomaly data with a rapidly evolving terrestrial-based geomagnetic polarity time scale (GPTS). The five decades of research since 1963 have witnessed the expansion and refinement of the GPTS, to the point where ages of magnetochron boundaries, in particular in the Cenozoic, can be estimated with uncertainties better than 0.1%. This has come about by integrating high precision geochronology, cyclostratigraphy at different time scales, and magnetic polarity data of increased quality, allowing extension of the GPTS back into the Paleozoic. The definition of a high resolution GPTS across time intervals of major events in Earth history has been of particular interest, as a specific magnetochron boundary correlated across several localities represents a singular global datum. A prime example is the end Permian, when some 80 percent of genus-level extinctions and a range of 75 to 96 percent species- level extinctions took place in the marine environment, depending upon clade. Much our understanding of the Permian-Triassic boundary (PTB) is based on relatively slowly deposited marine sequences in Europe and Asia, yet a growing body of observations from continental sequences demonstrates a similar extinction event and new polarity data from some of these sequences are critical to refining the GPTS across the PTB and testing synchronicity of marine and terrestrial events. The data show that the end-Permian ecological crisis and the conodont calibrated biostratigraphic PTB both followed a key polarity reversal between a short interval (subchron) of reverse polarity to a considerably longer (chron) of normal polarity. Central European Basin strata (continental Permian and epicontinental Triassic) yield high-quality magnetic polarity stratigraphic records (Szurlies et al., 2003; Szurlies, 2007; and Szurlies, 2013, in press). In combination with cyclostratigraphic records, the normal polarity chron, with both the end-Permian crisis and the biostratigraphic PTB, is estimated to be ~0.7 Ma in duration, with the ecological crisis some 0.2 Ma after the reversal. The author and colleagues are currently refining the magnetic polarity stratigraphy across the PTB contained in strata of the Ochoan/Induan Dewey Lake Formation exposed in west Texas (USA) and in strata of the Beaufort Group of the central Karoo Basin (South Africa). The hematitic siltstones and mudstones of the Dewey Lake Formation yield magnetizations of high quality and are not remagnetized, thus providing an unambiguous polarity record, including what we infer as the R-N transition immediately before the PTB. A continuous core (~150 m) through the entire Dewey Lake Formation from southeast New Mexico will be available for polarity study in early September, 2013. In the Karoo Basin, a nearly continuously exposed 225 +/- m thick section (over 100 distinct sites) near Lootsberg Pass is dominated by non-hematitic siltstone but fine grained sandstone and carbonate concretions in mudstone intervals have been also sampled. At present, it remains unclear whether the Beaufort Group strata in this part of the central Karoo Basin retain a primary magnetization, as the likelihood of remagnetization by ca. 184 +/- Ma mafic sills of the Karoo Large Igneous Province remains a concern.

  5. Astronomical control on climate and vegetation history at the Triassic-Jurassic transition

    NASA Astrophysics Data System (ADS)

    Ruhl, Micha; Bonis, Nina R.; Deenen, Martijn H. L.; Abels, Hemmo A.; Krijgsman, Wout; Kurschner, Wolfram M.

    2010-05-01

    The end-Triassic mass extinction (~201.5 Ma), marked by major terrestrial ecosystem changes and a 50% loss in marine biodiversity, closely coincides with the onset of intensified volcanic activity in the Central Atlantic Magmatic Province (CAMP), the largest igneous province on earth. The end-Triassic environmental crisis is followed by successive recovery in the early Jurassic Hettangian stage. However, accurate timing of events is poorly constrained. Here we present combined chemical and biological proxy records and field observations, covering the uppermost Triassic and lower Jurassic marine successions of St. Audrie's Bay and East Quantoxhead (UK). A floating astronomical time-scale of ~2.5 Myr has been constructed based on the recognition of ~100-kyr eccentricity cycles. Individual black shale occurrences are interpreted to reflect precession-controlled changes in monsoon intensity. Gaseous CO2 release by the increased volcanic activity strongly enhanced greenhouse warming and likely caused a shift from a diverse gymnosperm vegetation to a monotonous Cheirolepidiaceous conifer vegetation. Vegetation distribution at the Triassic-Jurassic transition was likely influenced by the strong temperature and humidity gradient from the oceans to the interior of Pangea. Vegetation cover was mostly situated in coastal regions, with the inlands being more arid. Strong eccentricity-scale paced increases in pollen concentrations suggest the inland expansion of Cheirolepidiaceous vegetation cover, which is likely caused by intensified monsoon activity. Our palynological data further shows precession-scale paced peaks in spore abundance during the mass extinction interval, suggesting astronomical forcing of the hydrological cycle under extreme climatic conditions.

  6. Time-dependent corona models - Scaling laws

    NASA Technical Reports Server (NTRS)

    Korevaar, P.; Martens, P. C. H.

    1989-01-01

    Scaling laws are derived for the one-dimensional time-dependent Euler equations that describe the evolution of a spherically symmetric stellar atmosphere. With these scaling laws the results of the time-dependent calculations by Korevaar (1989) obtained for one star are applicable over the whole Hertzsprung-Russell diagram and even to elliptic galaxies. The scaling is exact for stars with the same M/R-ratio and a good approximation for stars with a different M/R-ratio. The global relaxation oscillation found by Korevaar (1989) is scaled to main sequence stars, a solar coronal hole, cool giants and elliptic galaxies.

  7. Long term stability of atomic time scales

    NASA Astrophysics Data System (ADS)

    Petit, G.; Arias, F.

    2015-03-01

    We review the stability and accuracy achieved by the reference atomic time scales TAI and TT(BIPM). We show that they presently are in the low 10-16 in relative value, based on the performance of primary standards, of the ensemble time scale and of the time transfer techniques. We consider how the 1 10-16 value could be reached or superseded and which are the present limitations to attain this goal.

  8. Putting scales into evolutionary time: the divergence of major scale insect lineages (Hemiptera) predates the radiation of modern angiosperm hosts

    PubMed Central

    Vea, Isabelle M.; Grimaldi, David A.

    2016-01-01

    The radiation of flowering plants in the mid-Cretaceous transformed landscapes and is widely believed to have fuelled the radiations of major groups of phytophagous insects. An excellent group to test this assertion is the scale insects (Coccomorpha: Hemiptera), with some 8,000 described Recent species and probably the most diverse fossil record of any phytophagous insect group preserved in amber. We used here a total-evidence approach (by tip-dating) employing 174 morphological characters of 73 Recent and 43 fossil taxa (48 families) and DNA sequences of three gene regions, to obtain divergence time estimates and compare the chronology of the most diverse lineage of scale insects, the neococcoid families, with the timing of the main angiosperm radiation. An estimated origin of the Coccomorpha occurred at the beginning of the Triassic, about 245 Ma [228–273], and of the neococcoids 60 million years later [210–165 Ma]. A total-evidence approach allows the integration of extinct scale insects into a phylogenetic framework, resulting in slightly younger median estimates than analyses using Recent taxa, calibrated with fossil ages only. From these estimates, we hypothesise that most major lineages of coccoids shifted from gymnosperms onto angiosperms when the latter became diverse and abundant in the mid- to Late Cretaceous. PMID:27000526

  9. Putting scales into evolutionary time: the divergence of major scale insect lineages (Hemiptera) predates the radiation of modern angiosperm hosts.

    PubMed

    Vea, Isabelle M; Grimaldi, David A

    2016-01-01

    The radiation of flowering plants in the mid-Cretaceous transformed landscapes and is widely believed to have fuelled the radiations of major groups of phytophagous insects. An excellent group to test this assertion is the scale insects (Coccomorpha: Hemiptera), with some 8,000 described Recent species and probably the most diverse fossil record of any phytophagous insect group preserved in amber. We used here a total-evidence approach (by tip-dating) employing 174 morphological characters of 73 Recent and 43 fossil taxa (48 families) and DNA sequences of three gene regions, to obtain divergence time estimates and compare the chronology of the most diverse lineage of scale insects, the neococcoid families, with the timing of the main angiosperm radiation. An estimated origin of the Coccomorpha occurred at the beginning of the Triassic, about 245 Ma [228-273], and of the neococcoids 60 million years later [210-165 Ma]. A total-evidence approach allows the integration of extinct scale insects into a phylogenetic framework, resulting in slightly younger median estimates than analyses using Recent taxa, calibrated with fossil ages only. From these estimates, we hypothesise that most major lineages of coccoids shifted from gymnosperms onto angiosperms when the latter became diverse and abundant in the mid- to Late Cretaceous. PMID:27000526

  10. Mouse Activity across Time Scales: Fractal Scenarios

    PubMed Central

    Lima, G. Z. dos Santos; Lobão-Soares, B.; do Nascimento, G. C.; França, Arthur S. C.; Muratori, L.; Ribeiro, S.; Corso, G.

    2014-01-01

    In this work we devise a classification of mouse activity patterns based on accelerometer data using Detrended Fluctuation Analysis. We use two characteristic mouse behavioural states as benchmarks in this study: waking in free activity and slow-wave sleep (SWS). In both situations we find roughly the same pattern: for short time intervals we observe high correlation in activity - a typical 1/f complex pattern - while for large time intervals there is anti-correlation. High correlation of short intervals ( to : waking state and to : SWS) is related to highly coordinated muscle activity. In the waking state we associate high correlation both to muscle activity and to mouse stereotyped movements (grooming, waking, etc.). On the other side, the observed anti-correlation over large time scales ( to : waking state and to : SWS) during SWS appears related to a feedback autonomic response. The transition from correlated regime at short scales to an anti-correlated regime at large scales during SWS is given by the respiratory cycle interval, while during the waking state this transition occurs at the time scale corresponding to the duration of the stereotyped mouse movements. Furthermore, we find that the waking state is characterized by longer time scales than SWS and by a softer transition from correlation to anti-correlation. Moreover, this soft transition in the waking state encompass a behavioural time scale window that gives rise to a multifractal pattern. We believe that the observed multifractality in mouse activity is formed by the integration of several stereotyped movements each one with a characteristic time correlation. Finally, we compare scaling properties of body acceleration fluctuation time series during sleep and wake periods for healthy mice. Interestingly, differences between sleep and wake in the scaling exponents are comparable to previous works regarding human heartbeat. Complementarily, the nature of these sleep-wake dynamics could lead to a better understanding of neuroautonomic regulation mechanisms. PMID:25275515

  11. Decoherence, time scales and pointer states

    NASA Astrophysics Data System (ADS)

    Qureshi, Tabish

    2012-03-01

    Certain issues regarding the time-scales over which environment-induced decoherence occurs, and the nature of emergent pointer states, are discussed. A model system, namely a Stern-Gerlach setup coupled to a quantum mechanical heat-bath is studied. The emergent pointer states for this system are obtained, which are different from those discussed in the literature. It is pointed out that this difference is due to some confusion regarding the decoherence time-scale, which is clarified here.

  12. Microbialites and geochemistry of the Early Triassic enigma?

    NASA Astrophysics Data System (ADS)

    Bour, Ivan; Vennin, Emmanuelle; Thomazo, Christophe; Brayard, Arnaud; Olivier, Nicolas; Escarguel, Gilles; Bylund, Kevin G.; Jenks, Jim; Stephen, Daniel A.

    2013-04-01

    The Permian-Triassic mass extinction, 252 Myr ago, is the most devastating global-scale event ever recorded. Ecological and environmental changes during this interval are commonly assumed to be associated with numerous perturbations (i.e. productivity changes, acidification, redox changes, eustatism) that still remain elusive. The present study focus on the relationships between the redox conditions within the water column, the successive sedimentary deposits and marine community turnovers. Our study is based on new Early Triassic sections from the western USA Basin that preserve diversified reefs and bioaccumulations that contain microbialites and various benthic and pelagic organisms (e.g. serpulids, bivalves, ostracods, gastropods, cephalopods). Such a sedimentary prisitine record provides interesting new prospects to decipher the relationships between lithology, microbial structures and the geochemistry of the water column. Three outcrops were studied: the Mineral Mountains, the Confusion Range and the Pahvant Range, that record a general transgressive trend from proximal to distal deposits during the Smithian substage. Continental to open marine conditions are deduced from sedimentological studies and are related to variations of the microbialite meso- and micro-structures over a short time scale. Hydrodynamics and bathymetry are shown to be the major parameters that influence the morphology and distribution of these microbialites. Additionally to the study of the different microbialites structures and associated depositional environments, the chemiotratigraphic record of both carbon isotopes and major elements indicate a complex and a wide range of variations at short time scale. Carbon isotopes vary from -5 to 2 ‰PDB and FeHR/FeT ratio, after iron speciation, indicate a broad range of variation between 0.1 and 1.5. On the one hand, these analyses suggest potential transient oxygen depletion within the water column. On the other hand, fluctuations of these geochemical proxies seem to be influenced by lithology. We thus suggest that biogeochemical cycles of carbon and iron in the studied sections were influenced by the paleo-bathymetry and the distal to proximal polarity between the three locations. A second order control on the water column geochemistry is also probably the consequence of the microbially-induced carbonate precipitation. This study suggests that the Early Triassic paleoenvironments with the western USA basin were highly variable in terms of sedimentology and geochemistry, but also suggest a low oxygen concentration within the water column during the Smithian substage.

  13. Observing Reality on Different Time Scales

    NASA Astrophysics Data System (ADS)

    Alyushin, Alexey

    2005-10-01

    In the first part of the paper, I examine cases of acceleration of perception and cognition and provide my explanation of the mechanism of the effect. The explanation rests on the conception of neuronal temporal frames, or windows of simultaneity. Frames have different standard durations and yield to stretching and compressing. I suggest it to be the cause of the effect, as well as the ground for differences in perceptive time scales of living beings. In the second part, I apply the conception of temporal frames to model observation in the extended time scales that reach far beyond the temporal perceptive niche of individual living beings. Duration of a frame is taken as the basic parameter setting a particular time scale. By substituting a different frame duration, we set a hypothetical time scale and emulate observing reality in a wider or a narrower angle of embracing events in time. I discuss the status of observer in its relation to objective reality, and examine how reality does change its appearance when observed in different time scales.

  14. A novel proxy links CAMP volcanism with end-Triassic mass extinction and early Jurassic evolution

    NASA Astrophysics Data System (ADS)

    Ruhl, M.; Bjerrum, C. J.; Frei, R.

    2011-12-01

    Global mass extinction events are marked by a major loss of terrestrial and marine biodiversity and the global collapse of ecosystems during times of extensive volcanic activity and the emplacement of large igneous provinces (LIPs). Large-scale greenhouse gas release, initiated by volcanism, had a profound impact on global geochemical cycles (e.g. initiating strong perturbations in ?13C records). Hence, these events may be regarded as natural deep-time analogues for studying mechanistic feedbacks between rapid and large/scale greenhouse gas emissions, environmental change and biotic crises. Such studies require high resolution stratigraphic correlation between volcanic activity, disruption of global geochemical cycles and biotic crises, which at present is poorly constrained. Here we present a novel proxy that records explosive continental volcanic activity in distant marine shale sediments. The proxy builds on the relative abundance of the trace elements Lu, Hf, Y and Nb (monitored as the (Lu/ Hf)/(Y/ Nb)-ratio). We test the method on a marine sedimentary record comprising Central Atlantic Magmatic Province (CAMP) volcanism and the associated end-Triassic global mass extinction, at ~201.38 Ma. We show that the onset of sharp well-defined peaks in the (Lu/ Hf)/(Y/ Nb)-ratio coincides with the end-Triassic biotic crisis. Subsequent subordinate peaks closely correspond to periods of early Jurassic biotic radiation and evolution. Large-scale volcanic activity therefore not only initiated the end-Triassic mass extinction, it possibly also actively punctuated and regulated the pace of early Jurassic evolution. Further, the proxy also records the timing of Siberian Traps volcanism relative to the end-Permian mass extinction, the largest extinction in Earth's history. Hence, this proxy for the first time allows causality studies between increased volcanic activity, disruption of global geochemical cycles and global biodiversity loss, in unprecedented stratigraphic resolution. End-Triassic changes in biodiversity and extinction and evolution of species is most severe in the marine realm. Reactive iron and trace element data (e.g. Mo, U) suggest strong changes in water column redox-conditions and anoxia and euxinia coinciding with CAMP volcanic activity. This suggests that the end-Triassic mass extinction in the marine realm maybe mostly related to marine anoxia, initiated by volcanism driven greenhouse gas release, in at least marginal marine basins.

  15. Time scales of turbulent relative dispersion.

    PubMed

    Bitane, Rehab; Homann, Holger; Bec, Jrmie

    2012-10-01

    Tracers in a turbulent flow separate according to the celebrated t3/2 Richardson-Obukhov law, which is usually explained by a scale-dependent effective diffusivity. Here, supported by state-of-the-art numerics, we revisit this argument. The Lagrangian correlation time of velocity differences increases too quickly for validating this approach, but acceleration differences decorrelate on dissipative time scales. Phenomenological arguments are used to relate the behavior of separations to that of a "local energy dissipation," defined as the average ratio between the cube of the longitudinal velocity difference and the distance between the two tracers. This quantity is shown to stabilize on short time scales and this results in an asymptotic diffusion ?t1/2 of velocity differences. The time of convergence to this regime is shown to be that of deviations from Batchelor's initial ballistic regime, given by a scale-dependent energy dissipation time rather than the usual turnover time. It is finally demonstrated that the fluid flow intermittency should not affect this long-time behavior of the relative motion. PMID:23214642

  16. Time scales of turbulent relative dispersion

    NASA Astrophysics Data System (ADS)

    Bitane, Rehab; Homann, Holger; Bec, Jrmie

    2012-10-01

    Tracers in a turbulent flow separate according to the celebrated t3/2 Richardson-Obukhov law, which is usually explained by a scale-dependent effective diffusivity. Here, supported by state-of-the-art numerics, we revisit this argument. The Lagrangian correlation time of velocity differences increases too quickly for validating this approach, but acceleration differences decorrelate on dissipative time scales. Phenomenological arguments are used to relate the behavior of separations to that of a local energy dissipation, defined as the average ratio between the cube of the longitudinal velocity difference and the distance between the two tracers. This quantity is shown to stabilize on short time scales and this results in an asymptotic diffusion ?t1/2 of velocity differences. The time of convergence to this regime is shown to be that of deviations from Batchelor's initial ballistic regime, given by a scale-dependent energy dissipation time rather than the usual turnover time. It is finally demonstrated that the fluid flow intermittency should not affect this long-time behavior of the relative motion.

  17. Chronology of fluctuating sea levels since the triassic.

    PubMed

    Haq, B U; Hardenbol, J; Vail, P R

    1987-03-01

    Advances in sequence stratigraphy and the development of depositional models have helped explain the origin of genetically related sedimentary packages during sea level cycles. These concepts have provided the basis for the recognition of sea level events in subsurface data and in outcrops of marine sediments around the world. Knowledge of these events has led to a new generation of Mesozoic and Cenozoic global cycle charts that chronicle the history of sea level fluctuations during the past 250 million years in greater detail than was possible from seismic-stratigraphic data alone. An effort has been made to develop a realistic and accurate time scale and widely applicable chronostratigraphy and to integrate depositional sequences documented in public domain outcrop sections from various basins with this chronostratigraphic framework. A description of this approach and an account of the results, illustrated by sea level cycle charts of the Cenozoic, Cretaceous, Jurassic, and Triassic intervals, are presented. PMID:17818978

  18. Chronology of fluctuating sea levels since the triassic

    SciTech Connect

    Haq, B.U.; Hardenbol, J.; Vail, P.R.

    1987-03-06

    Advances in sequence stratigraphy and the development of depositional models have helped explain the origin of genetically related sedimentary packages during sea level cycles. These concepts have provided the basis for the recognition of sea level events in subsurface data and in outcrops of marine sediments around the world. Knowledge of these events has led to a new generation of Mesozoic and Cenozoic global cycle charts that chronicle the history of sea level fluctuations during the past 250 million years in greater detail than was possible from seismic-stratigraphic data alone. An effort has been made to develop a realistic and accurate time scale and widely applicable chronostratigraphy and to integrate depositional sequences documented in public domain outcrop sections from various basins with this chronostratigraphic framework. A description of this approach and an account of the results, illustrated by sea level cycle charts of the Cenozoic, Cretaceous, Jurassic, and Triassic intervals, are presented.

  19. The hippocampus, time, and memory across scales.

    PubMed

    Howard, Marc W; Eichenbaum, Howard

    2013-11-01

    A wealth of experimental studies with animals have offered insights about how neural networks within the hippocampus support the temporal organization of memories. These studies have revealed the existence of "time cells" that encode moments in time, much as the well-known "place cells" map locations in space. Another line of work inspired by human behavioral studies suggests that episodic memories are mediated by a state of temporal context that changes gradually over long time scales, up to at least a few thousand seconds. In this view, the "mental time travel" hypothesized to support the experience of episodic memory corresponds to a "jump back in time" in which a previous state of temporal context is recovered. We suggest that these 2 sets of findings could be different facets of a representation of temporal history that maintains a record at the last few thousand seconds of experience. The ability to represent long time scales comes at the cost of discarding precise information about when a stimulus was experienced--this uncertainty becomes greater for events further in the past. We review recent computational work that describes a mechanism that could construct such a scale-invariant representation. Taken as a whole, this suggests the hippocampus plays its role in multiple aspects of cognition by representing events embedded in a general spatiotemporal context. The representation of internal time can be useful across nonhippocampal memory systems. PMID:23915126

  20. Stability of graph communities across time scales

    PubMed Central

    Delvenne, J.-C.; Yaliraki, S. N.; Barahona, M.

    2010-01-01

    The complexity of biological, social, and engineering networks makes it desirable to find natural partitions into clusters (or communities) that can provide insight into the structure of the overall system and even act as simplified functional descriptions. Although methods for community detection abound, there is a lack of consensus on how to quantify and rank the quality of partitions. We introduce here the stability of a partition, a measure of its quality as a community structure based on the clustered autocovariance of a dynamic Markov process taking place on the network. Because the stability has an intrinsic dependence on time scales of the graph, it allows us to compare and rank partitions at each time and also to establish the time spans over which partitions are optimal. Hence the Markov time acts effectively as an intrinsic resolution parameter that establishes a hierarchy of increasingly coarser communities. Our dynamical definition provides a unifying framework for several standard partitioning measures: modularity and normalized cut size can be interpreted as one-step time measures, whereas Fiedler’s spectral clustering emerges at long times. We apply our method to characterize the relevance of partitions over time for constructive and real networks, including hierarchical graphs and social networks, and use it to obtain reduced descriptions for atomic-level protein structures over different time scales. PMID:20615936

  1. Accuracy metrics for judging time scale algorithms

    NASA Technical Reports Server (NTRS)

    Douglas, R. J.; Boulanger, J.-S.; Jacques, C.

    1994-01-01

    Time scales have been constructed in different ways to meet the many demands placed upon them for time accuracy, frequency accuracy, long-term stability, and robustness. Usually, no single time scale is optimum for all purposes. In the context of the impending availability of high-accuracy intermittently-operated cesium fountains, we reconsider the question of evaluating the accuracy of time scales which use an algorithm to span interruptions of the primary standard. We consider a broad class of calibration algorithms that can be evaluated and compared quantitatively for their accuracy in the presence of frequency drift and a full noise model (a mixture of white PM, flicker PM, white FM, flicker FM, and random walk FM noise). We present the analytic techniques for computing the standard uncertainty for the full noise model and this class of calibration algorithms. The simplest algorithm is evaluated to find the average-frequency uncertainty arising from the noise of the cesium fountain's local oscillator and from the noise of a hydrogen maser transfer-standard. This algorithm and known noise sources are shown to permit interlaboratory frequency transfer with a standard uncertainty of less than 10(exp -15) for periods of 30-100 days.

  2. Triassic temnospondyls of the Pranhita Godavari basin, India

    NASA Astrophysics Data System (ADS)

    Sengupta, Dhurjati Prasad

    2003-03-01

    The Pranhita-Godavari (P-G) basin of central India has yielded Early, Middle and Late Triassic temnospondyl families. Bracyops laticeps, the type for the family Brachyopidae was first described from the Lower Triassic 'Mangli Beds' of the northernmost extension of the P-G basin. In the northern and central parts of the P-G basin itself, the Middle Triassic Yerrapalli Formation has Stanocephalosaurus rajareddyi, a paracyclotosaurid, and the Upper Triassic Maleri Formation has Buettneria maleriensis, a metoposaurid and two other chigutisaurid taxa, Compsocerops cosgriffi and Kuttycephalus triangularis. A critical review of Triassic temnospondyls of the P-G basin indicates that the affinities of S. rajareddyi and K. triangularis are somewhat uncertain and discovery of further material is necessary to establish their relationships among similar temnospondyls of the world. It is also noted that B. maleriensis is displaced by the two chigutisaurid genera and species at the Carnian-Norian boundary. Thus, P-G basin is unique in having Pangaean metoposaurids and exclusively Gondwanan chigutisaurids in successive faunal zones within the same formation. Significantly, the end of Carnian is marked by the demise of metoposaurids in India as well as in Africa and Europe. In North America, their size appears to have diminished during that time.

  3. A comment on the use of flushing time, residence time, and age as transport time scales

    USGS Publications Warehouse

    Monsen, N.E.; Cloern, J.E.; Lucas, L.V.; Monismith, Stephen G.

    2002-01-01

    Applications of transport time scales are pervasive in biological, hydrologic, and geochemical studies yet these times scales are not consistently defined and applied with rigor in the literature. We compare three transport time scales (flushing time, age, and residence time) commonly used to measure the retention of water or scalar quantities transported with water. We identify the underlying assumptions associated with each time scale, describe procedures for computing these time scales in idealized cases, and identify pitfalls when real-world systems deviate from these idealizations. We then apply the time scale definitions to a shallow 378 ha tidal lake to illustrate how deviations between real water bodies and the idealized examples can result from: (1) non-steady flow; (2) spatial variability in bathymetry, circulation, and transport time scales; and (3) tides that introduce complexities not accounted for in the idealized cases. These examples illustrate that no single transport time scale is valid for all time periods, locations, and constituents, and no one time scale describes all transport processes. We encourage aquatic scientists to rigorously define the transport time scale when it is applied, identify the underlying assumptions in the application of that concept, and ask if those assumptions are valid in the application of that approach for computing transport time scales in real systems.

  4. Current relaxation time scales in toroidal plasmas

    SciTech Connect

    Mikkelsen, D.R.

    1987-02-01

    An approximate normal mode analysis of plasma current diffusion in tokamaks is presented. The work is based on numerical solutions of the current diffusion equation in cylindrical geometry. Eigenvalues and eigenfunctions are shown for a broad range of plasma conductivity profile shapes. Three classes of solutions are considered which correspond to three types of tokamak operation. Convenient approximations to the three lowest eigenvalues in each class are presented and simple formulae for the current relaxation time scales are given.

  5. Hemispheric Asymmetries in Substorm Recovery Time Scales

    NASA Technical Reports Server (NTRS)

    Fillingim, M. O.; Chua, D H.; Germany, G. A.; Spann, James F.

    2009-01-01

    Previous statistical observations have shown that the recovery time scales of substorms occurring in the winter and near equinox (when the nighttime auroral zone was in darkness) are roughly twice as long as the recovery time scales for substorms occurring in the summer (when the nighttime auroral region was sunlit). This suggests that auroral substorms in the northern and southern hemispheres develop asymmetrically during solstice conditions with substorms lasting longer in the winter (dark) hemisphere than in the summer (sunlit) hemisphere. Additionally, this implies that more energy is deposited by electron precipitation in the winter hemisphere than in the summer one during substorms. This result, coupled with previous observations that have shown that auroral activity is more common when the ionosphere is in darkness and is suppressed when the ionosphere is in daylight, strongly suggests that the ionospheric conductivity plays an important role governing how magnetospheric energy is transferred to the ionosphere during substorms. Therefore, the ionosphere itself may dictate how much energy it will accept from the magnetosphere during substorms rather than this being an externally imposed quantity. Here, we extend our earlier work by statistically analyzing the recovery time scales for a large number of substorms observed in the conjugate hemispheres simultaneously by two orbiting global auroral imagers: Polar UVI and IMAGE FUV. Our current results are consistent with previous observations. The recovery time scales are observed to be longer in the winter (dark) hemisphere while the auroral activity has a shorter duration in the summer (sunlit) hemisphere. This leads to an asymmetric energy input from the magnetosphere to the ionosphere with more energy being deposited in the winter hemisphere than in the summer hemisphere.

  6. Filling the Triassic Geochronologic Gap: A Continuous Cored Record of Continental Environmental Change in Western North America

    NASA Astrophysics Data System (ADS)

    Olsen, P. E.; Kent, D. V.; Geissman, J. W.; Mundil, R.; Gehrels, G. E.; Irmis, R. B.; Whiteside, J. H.; Schaller, M. F.

    2013-12-01

    The Triassic Period (252.2-201.6 Ma) is bracketed by two mass extinctions, witnessed the evolution of the major groups of modern tetrapods, saw giant bolide impacts, and was typified by generally high atmospheric CO2 and a lack of ice at the poles. Testing hypotheses relevant to these major features of the Triassic, as well as problems related to the Earth system in general, requires temporally well-defined records of environmental and biotic change, especially in terrestrial environments, which until recently were lacking. The NSF and ICDP funded ~500 m long core at Petrified Forest National Park, scheduled to be drilled in Fall, 2013, is part of an interdisciplinary, multi-institutional, Colorado Plateau Coring Project, and is a major step towards providing a network of such records. The core will recover virtually the entire pre-Owl-Rock-Member Late Triassic age Chinle and underlying Early-Middle Triassic age Moenkopi formations. A core is required despite excellent outcrop and a long and distinguished history of study because of ambiguities in local correlation, a lack of constraints on the temporal duration and resolution of biotic events, and an inability to make clear global correlations. Specifically, by integrating a densely sampled paleomagnetic record with high-resolution radioisotopic ages in unquestioned superposition, the new core will allow us to test at least five sets of hypotheses: (1) were marine and continental biotic turnover events in the Late Triassic coupled? (2) was there high faunal provinciality during the existence of the supercontinent of Pangea?; (3) is the time scale of the Newark basin astronomically calibrated GPTS for the Triassic accurate, particularly for the Norian age part that is relevant for mapping the chaotic evolution of the Solar System, as well as global correlations?; (4) is the supposed Carnian-Norian boundary in the Chinle actually a late middle Norian extinction coinciding with the 215.5 Ma Manicouagan impact?; (5) is the stratigraphic record in the Triassic a reflection of changes in local climate due to plate motion through climate belts or changes in global climate driven by other processes, such as CO2 fluctuations? The Petrified Forest core will thus be key to unambiguous testing of these ideas, and observations from it promise to fundamentally change the certainty and specificity of the questions that relate the rich surface record from the Chinle and Moenkopi to Earth system processes.

  7. Liquidity crises on different time scales

    NASA Astrophysics Data System (ADS)

    Corradi, Francesco; Zaccaria, Andrea; Pietronero, Luciano

    2015-12-01

    We present an empirical analysis of the microstructure of financial markets and, in particular, of the static and dynamic properties of liquidity. We find that on relatively large time scales (15 min) large price fluctuations are connected to the failure of the subtle mechanism of compensation between the flows of market and limit orders: in other words, the missed revelation of the latent order book breaks the dynamical equilibrium between the flows, triggering the large price jumps. On smaller time scales (30 s), instead, the static depletion of the limit order book is an indicator of an intrinsic fragility of the system, which is related to a strongly nonlinear enhancement of the response. In order to quantify this phenomenon we introduce a measure of the liquidity imbalance present in the book and we show that it is correlated to both the sign and the magnitude of the next price movement. These findings provide a quantitative definition of the effective liquidity, which proves to be strongly dependent on the considered time scales.

  8. Assessing the record and causes of Late Triassic extinctions

    USGS Publications Warehouse

    Tanner, L.H.; Lucas, S.G.; Chapman, M.G.

    2004-01-01

    Accelerated biotic turnover during the Late Triassic has led to the perception of an end-Triassic mass extinction event, now regarded as one of the "big five" extinctions. Close examination of the fossil record reveals that many groups thought to be affected severely by this event, such as ammonoids, bivalves and conodonts, instead were in decline throughout the Late Triassic, and that other groups were relatively unaffected or subject to only regional effects. Explanations for the biotic turnover have included both gradualistic and catastrophic mechanisms. Regression during the Rhaetian, with consequent habitat loss, is compatible with the disappearance of some marine faunal groups, but may be regional, not global in scale, and cannot explain apparent synchronous decline in the terrestrial realm. Gradual, widespread aridification of the Pangaean supercontinent could explain a decline in terrestrial diversity during the Late Triassic. Although evidence for an impact precisely at the boundary is lacking, the presence of impact structures with Late Triassic ages suggests the possibility of bolide impact-induced environmental degradation prior to the end-Triassic. Widespread eruptions of flood basalts of the Central Atlantic Magmatic Province (CAMP) were synchronous with or slightly postdate the system boundary; emissions of CO2 and SO2 during these eruptions were substantial, but the contradictory evidence for the environmental effects of outgassing of these lavas remains to be resolved. A substantial excursion in the marine carbon-isotope record of both carbonate and organic matter suggests a significant disturbance of the global carbon cycle at the system boundary. Release of methane hydrates from seafloor sediments is a possible cause for this isotope excursion, although the triggering mechanism and climatic effects of such a release remain uncertain. ?? 2003 Elsevier B.V. All rights reserved.

  9. Reccurent Early Triassic marine anoxia, impacts of volcanics?

    NASA Astrophysics Data System (ADS)

    Grasby, Stephen; Beauchamp, Benoit; Sanei, Hamed

    2014-05-01

    NW Pangea records a complex history of recurrent development of anoxia through the Permo-Triassic Biotic Crises. The Early Triassic record from the Smithian strato-type in the Sverdrup Basin, as well as for the more open ocean setting of Svalbard, have organic carbon isotope records that closely correspond to major fluctuations in the inorganic carbon records from the Tethys, demonstrating truly global perturbations of the carbon cycle occurred during this time. Geochemical proxies for anoxia are strongly correlated with carbon isotopes, whereby negative shifts in ?13Corg are associated with shifts to more anoxic to euxinic conditions, and positive shifts are related to return to more oxic conditions. Rather than a delayed or prolonged recovery, the Early Triassic is characterized better by a series of aborted biotic recoveries related to shifts back to ocean anoxia, potentially driven by recurrent volcanism.

  10. Time Ephemeris and Relativistic Scaling of Ephemerides

    NASA Astrophysics Data System (ADS)

    Fukushima, Toshio

    2009-05-01

    Time ephemeris is the location-independent part of the transformation formula relating two time coordinates such as TCB and TCG. It is computed from the corresponding (space) ephemerides providing the relative motion of two spatial coordinate origins associated such as the motion of geocenter relative to the solar system barycenter. The time ephemerides are inevitablly needed in conducting a precise four-dimensional coordinate transformation among various spacetime coodrinate systems such as the GCRS and BCRS. Also, by means of the time average operation, it is useful in determining the information on scale conversion between the pair of coordinate systems, especially scale conversion factors such as LC. In 1995, we presented the first numerically-integrated time ephemeris, TE245, from JPL's planetary ephemeris DE245 (Fukushima 1995, A&Ap, 294, 895-906). Four years later, we updated it to TE405 associated with DE405 (Irwin and Fukushima 1999, A&Ap, 348, 642-652). The former gave an estimate of LC, the scale conversion factor between TCB and TCG, as 1.4808268457(10) x 10-8. Meanwhile the latter renewed it as 1.48082686741(200) x 10-8. Another four years later, by using a precise technique of time avarage, we improved the estimate as 1.4808268559(6) x 10-8 (Harada and Fukushima 2003, AJ, 126, 2557-2561). The main reasons of these uncertainties are the truncation effect in time average and the uncertainty of asteroids' perturbation. The former is a natural limitation caused by the finite length of numerical planetary ephemerides and the latter is due to the uncertainty of masses of some heavy asteroids. In the talk, we review the post-Newtonian formulas to integrate time ephemerides as well as some practical details on their numerical integration. Also, we explain two kinds of techniques of time average. One is a semi-numerical approach as explained in 1991 A&Ap article and the other is purely numerical as given in 2003 AJ paper.

  11. Time Ephemeris and General Relativistic Scale Factor

    NASA Astrophysics Data System (ADS)

    Fukushima, Toshio

    2010-11-01

    Time ephemeris is the location-independent part of the transformation formula relating two time coordinates such as TCB and TCG (Fukushima 2009). It is computed from the corresponding (space) ephemerides providing the relative motion of two spatial coordinate origins such as the motion of geocenter relative to the solar system barycenter. The time ephemerides are inevitably needed in conducting precise four dimensional coordinate transformations among various spacetime coordinate systems such as the GCRS and BCRS (Soffel et al. 2003). Also, by means of the time average operation, they are used in determining the information on scale conversion between the pair of coordinate systems, especially the difference of the general relativistic scale factor from unity such as LC. In 1995, we presented the first numerically-integrated time ephemeris, TE245, from JPL's planetary ephemeris DE245 (Fukushima 1995). It gave an estimate of LC as 1.4808268457(10) 10-8, which was incorrect by around 2 10-16. This was caused by taking the wrong sign of the post-Newtonian contribution in the final summation. Four years later, we updated TE245 to TE405 associated with DE405 (Irwin and Fukushima 1999). This time the renewed vale of LC is 1.48082686741(200) 10-8 Another four years later, by using a precise technique of time average, we improved the estimate of Newtonian part of LC for TE405 as 1.4808268559(6) 10-8 (Harada and Fukushima 2003). This leads to the value of LC as LC = 1.48082686732(110) 10-8. If we combine this with the constant defining the mean rate of TCG-TT, LG = 6.969290134 10-10 (IAU 2001), we estimate the numerical value of another general relativistic scale factor LB = 1.55051976763(110) 10-8, which has the meaning of the mean rate of TCB-TT. The main reasons of the uncertainties are the truncation effect in time average and the uncertainty of asteroids' perturbation. As a compact realization of the time ephemeris, we prepared HF2002, a Fortran routine to compute approximate harmonic series of TE405 with the RMS error of 0.446 ns for the period 1600 to 2200 (Harada and Fukushima 2003). It is included in the IERS Convention 2003 (McCarthy and Petit 2003) and available from the IERS web site; http://tai.bipm.org/iers/conv2003/conv2003_c10.html.

  12. A Triassic aquatic protorosaur with an extremely long neck.

    PubMed

    Li, Chun; Rieppel, Olivier; LaBarbera, Michael C

    2004-09-24

    By Middle Triassic time, a number of reptile lineages had diversified in shallow epicontinental seas and intraplatform basins along the margins of parts of Pangea, including the giraffe-necked protorosaurid reptile Tanystropheus from the Western Tethys (Europe and the Middle East), which grew to approximately 5 to 6 m long. Here we report another long-necked fossil, Dinocephalosaurus, from southwestern China, recently collected in Middle Triassic marine deposits approximately 230 million years old. This taxon represents unambiguous evidence for a fully aquatic protorosaur. Its extremely elongated neck is explained as an adaptation for aquatic life, perhaps for an increase in feeding efficiency. PMID:15448262

  13. Deciphering Time Scale Hierarchy in Reaction Networks.

    PubMed

    Nagahata, Yutaka; Maeda, Satoshi; Teramoto, Hiroshi; Horiyama, Takashi; Taketsugu, Tetsuya; Komatsuzaki, Tamiki

    2016-03-01

    Markovian dynamics on complex reaction networks are one of the most intriguing subjects in a wide range of research fields including chemical reactions, biological physics, and ecology. To represent the global kinetics from one node (corresponding to a basin on an energy landscape) to another requires information on multiple pathways that directly or indirectly connect these two nodes through the entire network. In this paper we present a scheme to extract a hierarchical set of global transition states (TSs) over a discrete-time Markov chain derived from first-order rate equations. The TSs can naturally take into account the multiple pathways connecting any pair of nodes. We also propose a new type of disconnectivity graph (DG) to capture the hierarchical organization of different time scales of reactions that can capture changes in the network due to changes in the time scale of observation. The crux is the introduction of the minimum conductance cut (MCC) in graph clustering, corresponding to the dividing surface across the network having the "smallest" transition probability between two disjoint subnetworks (superbasins on the energy landscape) in the network. We present a new combinatorial search algorithm for finding this MCC. We apply our method to a reaction network of Claisen rearrangement of allyl vinyl ether that consists of 23 nodes and 66 links (saddles on the energy landscape) connecting them. We compare the kinetic properties of our DG to those of the transition matrix of the rate equations and show that our graph can properly reveal the hierarchical organization of time scales in a network. PMID:26641663

  14. The end-triassic mass extinction event

    NASA Technical Reports Server (NTRS)

    Hallam, A.

    1988-01-01

    The end-Triassic is the least studied of the five major episodes of mass extinction recognized in the Phanerozoic, and the Triassic-Jurassic boundary is not precisely defined in most parts of the world, with a paucity of good marine sections and an insufficiency of biostratigraphically valuable fossils. Despite these limitations it is clear that there was a significant episode of mass extinction, affecting many groups, in the Late Norian and the existing facts are consistent with it having taken place at the very end of the period. The best record globally comes from marine strata. There was an almost complete turnover of ammonites across the T-J boundary, with perhaps no more than one genus surviving. About half the bivalve genera and most of the species went extinct, as did many archaeogastropods. Many Paleozoic-dominant brachiopods also disappeared, as did the last of the conodonts. There was a major collapse and disappearance of the Alpine calcareous sponge. Among terrestrial biota, a significant extinction event involving tetrapods was recognized. With regard to possible environmental events that may be postulated to account for the extinctions, there is no evidence of any significant global change of climate at this time. The existence of the large Manicouagan crater in Quebec, dated as about late or end-Triassic, has led to the suggestion that an impact event might be implicated, but so far despite intensive search no unequivocal iridium anomaly or shocked quartz was discovered. On the other hand there is strong evidence for significant marine regression in many parts of the world. It is proposed therefore that the likeliest cause of the marine extinctions is severe reduction in habitat area caused either by regression of epicontinental seas, subsequent widespread anoxia during the succeeding transgression, or a combination of the two.

  15. Scaling laws from geomagnetic time series

    USGS Publications Warehouse

    Voros, Z.; Kovacs, P.; Juhasz, A.; Kormendi, A.; Green, A.W.

    1998-01-01

    The notion of extended self-similarity (ESS) is applied here for the X - component time series of geomagnetic field fluctuations. Plotting nth order structure functions against the fourth order structure function we show that low-frequency geomagnetic fluctuations up to the order n = 10 follow the same scaling laws as MHD fluctuations in solar wind, however, for higher frequencies (f > l/5[h]) a clear departure from the expected universality is observed for n > 6. ESS does not allow to make an unambiguous statement about the non triviality of scaling laws in "geomagnetic" turbulence. However, we suggest to use higher order moments as promising diagnostic tools for mapping the contributions of various remote magnetospheric sources to local observatory data. Copyright 1998 by the American Geophysical Union.

  16. Mesozoic cyclostratigraphy, the 405-kyr orbital eccentricity metronome, and the Astronomical Time Scale (Invited)

    NASA Astrophysics Data System (ADS)

    Hinnov, L.; Ogg, J. G.

    2009-12-01

    Mesozoic cyclostratigraphy from around the world is being assessed to construct a continuous Astronomical Time Scale (ATS) based on Earth’s cyclic orbital parameters. The recognition of a prevalent sedimentary cycling with a ~400-kyr period associated with forcing by the stable 405-kyr orbital eccentricity variation is an important development. Numerous formations spanning 10 to 20 myr (and longer) intervals in the Cretaceous, Jurassic and Triassic clearly express this dominant cycle and provide a robust basis for 405-kyr-scale calibration of the ATS. This 405-kyr metronome will enable extension of the well-defined Cenozoic ATS for scaling of the past quarter-billion years of Earth history. This astronomical calibration has a resolution comparable to the 1% to 0.1% precision for radioisotope dating of Mesozoic ash beds, with the added benefit of providing continuous stratigraphic coverage between dated beds. Extended portions of the Mesozoic ATS have already provided new insights into long-standing geologic problems of seafloor spreading, tectonics, eustasy, and paleoclimate change. Ongoing work is focused on closing gaps in coverage and on collecting duplicate cyclostratigraphic records for the entire Mesozoic Era.

  17. Time sequence and time scale of intermediate mass fragment emission

    NASA Astrophysics Data System (ADS)

    de Filippo, E.; Pagano, A.; Wilczy?ski, J.; Amorini, F.; Anzalone, A.; Auditore, L.; Baran, V.; Berceanu, I.; Blicharska, J.; Brzychczyk, J.; Bonasera, A.; Borderie, B.; Bougault, R.; Bruno, M.; Cardella, G.; Cavallaro, S.; Chatterjee, M. B.; Chbihi, A.; Cibor, J.; Colonna, M.; D'Agostino, M.; Dayras, R.; di Toro, M.; Frankland, J.; Galichet, E.; Gawlikowicz, W.; Geraci, E.; Giustolisi, F.; Grzeszczuk, A.; Guazzoni, P.; Guinet, D.; Iacono-Manno, M.; Kowalski, S.; La Guidara, E.; Lanzan, G.; Lanzalone, G.; Le Neindre, N.; Li, S.; Maiolino, C.; Majka, Z.; Papa, M.; Petrovici, M.; Piasecki, E.; Pirrone, S.; P?aneta, R.; Politi, G.; Pop, A.; Porto, F.; Rivet, M. F.; Rosato, E.; Rizzo, F.; Russo, S.; Russotto, P.; Sassi, M.; Schmidt, K.; Siwek-Wilczy?ska, K.; Skwira, I.; Sperduto, M. L.; ?widerski, ?.; Trifir, A.; Trimarchi, M.; Vannini, G.; Vigilante, M.; Wieleczko, J. P.; Wu, H.; Xiao, Z.; Zetta, L.; Zipper, W.

    2005-04-01

    Semiperipheral collisions in the 124Sn+64Ni reaction at 35 MeV/nucleon were studied using the forward part of the Charged Heavy Ion Mass and Energy Resolving Array. Nearly completely determined ternary events involving projectilelike fragments (PLF), targetlike fragments (TLF), and intermediate mass fragments (IMF) were selected. A new method of studying the reaction mechanism, focusing on the analysis of the correlations between relative velocities in the IMF+PLF and IMF+TLF subsystems, is proposed. The relative velocity correlations provide information on the time sequence and time scale of the neck fragmentation processes leading to production of IMFs. It is shown that the majority of light IMFs are produced within 40 80 fm/c after the system starts to reseparate. Heavy IMFs are formed at times of about 120 fm/c or later and can be viewed as resulting from two-step (sequential) neck rupture processes.

  18. Permo-Triassic boundary and Lower to Middle Triassic in South Tibet

    NASA Astrophysics Data System (ADS)

    Garzanti, E.; Nicora, A.; Rettori, R.

    1998-04-01

    The abundance of conodonts increases sharply across the Permian/Triassic boundary in South Tibet, and as a consequence Griesbachian assemblages are much better defined than Changxingian ones. The " Otoceras latilobatum bed", representing the base of the Triassic at Selong, is a condensed biocalcirudite including abundant macrofossils (crinoids, corals, bryozoans, brachiopods) of Permian aspect associated with a varied conodont assemblage (including Hindeodus parvus) of early Griesbachian age. Condensation and reworking at the P/T boundary is interpreted as related to starvation and subaqueous erosion/redeposition during rapid transgression at the base of the Triassic rather than to subaerial exposure during a first-order sea-level drop. All of the Lower Triassic is strongly condensed, particularly in the west (Gyirong and Selong) where total thickness is 6.5 m at most, to 8.5 m; thickness is more comparable with other Himalayan localities at Tulong, where the Dienerian to Spathian section reaches 20 m. As in central Nepal, carbonate intervals dated as early Griesbachian to Dienerian, early to mid-Smithian and latest Smithian to earliest Aegean are separated by two mudrock intervals (locally reduced to millimetric interbeds) dated as late Dienerian or earliest Smithian and late Smithian. Condensed wackestone/packstone intervals were deposited during transgressive stages on the outermost shelf to continental slope. During highstand stages, mudrock intervals slowly accumulated on the outer shelf, whereas only a thin veneer of mud was deposited close to the shelf-break. Oceanic currents, intruding onto the outermost shelf during peak transgressions, are inferred to be the main causes of winnowing and resuspension of mud during the Spathian, when oxidized packstones in "Ammonitico Rosso" facies were deposited at Tulong. Grey limestones locally with bacterial mats or containing agglutinated foraminifers and intercalated black mudrocks indicate instead dysoxic conditions, which were widespread from Griesbachian to Smithian times. The Middle Triassic is mostly represented by marls and marly wackestones with crinoids, pelagic bivalves and benthic foraminifers. A notable increase in silty to sandy quartzo-feldspathic detritus is recorded at mid-Aegean times, and very fine-grained subarkoses characterize the mid-Anisian section at Tulong. Terrigenous supply was renewed probably in the Early Carnian, but accumulation rates sharply increased only in the latest Carnian and Norian.

  19. Parametric instabilities in picosecond time scales

    SciTech Connect

    Baldis, H.A.; Rozmus, W.; Labaune, C.; Mounaix, Ph.; Pesme, D.; Baton, S.; Tikhonchuk, V.T.

    1993-03-01

    The coupling of intense laser light with plasmas is a rich field of plasma physics, with many applications. Among these are inertial confinement fusion (ICF), x-ray lasers, particle acceleration, and x-ray sources. Parametric instabilities have been studied for many years because of their importance to ICF; with laser pulses with duration of approximately a nanosecond, and laser intensities in the range 10{sup 14}--10{sup 15}W/cm{sup 2} these instabilities are of crucial concern because of a number of detrimental effects. Although the laser pulse duration of interest for these studies are relatively long, it has been evident in the past years that to reach an understanding of these instabilities requires their characterization and analysis in picosecond time scales. At the laser intensities of interest, the growth rate for stimulated Brillouin scattering (SBS) is of the order of picoseconds, and of an order of magnitude shorter for stimulated Raman scattering (SRS). In this paper the authors discuss SBS and SRS in the context of their evolution in picosecond time scales. They describe the fundamental concepts associated with their growth and saturation, and recent work on the nonlinear treatment required for the modeling of these instabilities at high laser intensities.

  20. Triassic deposits of the Chukotka Arctic continental margin (sedimentary implications and detrital zircon data)

    NASA Astrophysics Data System (ADS)

    Tuchkova, Marianna; Sokolov, Sergey; Verzhbitsky, Vladimir

    2013-04-01

    Triassic clastic deposits of Chukotka are represented by rhythmic intercalation of sandstones, siltstones and mudstones. During the Triassic, sedimentation was represented by continental slope progradation. Detrital zircons from Triassic sedimentary rocks were collected for constrain its paleogeographic links to source terranes. Zircons populations from three Chukotka's samples are very similar, and youngest zircon ages show peaks at 236-255 Ma (Miller et al., 2006). Lower Triassic sandstones from the Chaun subterrane do not contain the young population 235-265 Ma that is characteristic of the Upper Triassic rocks from the Anyui subterrane and Wrangel Island. The young zircon population is missing also from the coeval Sadlerochit Group (Alaska) and Blind Fiord Formation of the Sverdrup basin (Miller et al., 2006; Omma et al., 2011). Our data of Triassic sandstones of Wrangel island demonstrate detrital zircons ages dominated by Middle Triassic (227-245 Ma), Carboniferous (309-332 Ma) and Paleoproterozoic (1808-2500 Ma) ages. The new data on Chukotka show that populations of detrital zircons from Chukotka, the Sverdrup basin, and Alaska, the Sadlerochit Mountains included, demonstrate greater similarity than it was previously thought. Consequently, it may be assumed that they originate from a single source situated in the north. The data on zircon age of gabbro-dolerite magmatism in eastern Chukotka (252 Ma. Ledneva et al., 2011) and K-Ar ages obtained for sills and small intrusive bodies (Geodynamics…, 2006) in Lower Triassic deposits allow the local provenance. The presence of products of synchronous magmatism and shallow-water facies in the Lower Triassic sequences confirm this assumption. At the same time, coeval zircons appear only in the Upper Triassic strata. It is conceivable that the young zircon population originates from intrusive, not volcanic rocks, which were subjected to erosion only in the Late Triassic. In our opinion, the assumption of the local source with synchronous magmatism is consistent with the evolution of the petrological-mineralogical and geochemical compositions in the Triassic sandstones of Chukotka. Similar zircon peaks in Triassic rocks of northern Wrangel Island, Sverdrup basin, and Alaska indicate the same provenances for the Triassic periods. It is possible that all obtained data may indirectly support existence of the hypothetical "Hyperborean Platform" or Crockerland-Arctida microcontinent Work was supported by RBRR projects 11-05-00787, 11-05-00074, Scientific school # NSh-5177.2012.5, kontrakts 01/14/20/11; and we are extremely grateful to the TGS company for execution of a joint research project "Geological history of Wrangel Island".

  1. EDITORIAL: Special issue on time scale algorithms

    NASA Astrophysics Data System (ADS)

    Matsakis, Demetrios; Tavella, Patrizia

    2008-12-01

    This special issue of Metrologia presents selected papers from the Fifth International Time Scale Algorithm Symposium (VITSAS), including some of the tutorials presented on the first day. The symposium was attended by 76 persons, from every continent except Antarctica, by students as well as senior scientists, and hosted by the Real Instituto y Observatorio de la Armada (ROA) in San Fernando, Spain, whose staff further enhanced their nation's high reputation for hospitality. Although a timescale can be simply defined as a weighted average of clocks, whose purpose is to measure time better than any individual clock, timescale theory has long been and continues to be a vibrant field of research that has both followed and helped to create advances in the art of timekeeping. There is no perfect timescale algorithm, because every one embodies a compromise involving user needs. Some users wish to generate a constant frequency, perhaps not necessarily one that is well-defined with respect to the definition of a second. Other users might want a clock which is as close to UTC or a particular reference clock as possible, or perhaps wish to minimize the maximum variation from that standard. In contrast to the steered timescales that would be required by those users, other users may need free-running timescales, which are independent of external information. While no algorithm can meet all these needs, every algorithm can benefit from some form of tuning. The optimal tuning, and even the optimal algorithm, can depend on the noise characteristics of the frequency standards, or of their comparison systems, the most precise and accurate of which are currently Two Way Satellite Time and Frequency Transfer (TWSTFT) and GPS carrier phase time transfer. The interest in time scale algorithms and its associated statistical methodology began around 40 years ago when the Allan variance appeared and when the metrological institutions started realizing ensemble atomic time using more than one single atomic clock. An international symposium dedicated to these topics was initiated in 1972 as the first International Symposium on Atomic Time Scale Algorithms and it was the beginning of a series: 1st Symposium: organized at the NIST (NBS at that epoch) in 1972, 2nd Symposium: again at the NIST in 1982, 3rd Symposium: in Italy at the INRIM (IEN at that epoch) in 1988, 4th Symposium: in Paris at the BIPM in 2002 (see Metrologia 40 (3), 2003) 5th Symposium: in San Fernando, Spain at the ROA in 2008. The early symposia were concerned with establishing the basics of how to estimate and characterize the behavior of an atomic frequency standard in an unambiguous and clearly identifiable way, and how to combine the reading of different clocks to form an optimal time scale within a laboratory. Later, as atomic frequency standards began to be used as components in larger systems, interest grew in understanding the impact of a clock in a more complex environment. For example, use of clocks in telecommunication networks in a Synchronous Digital Hierarchy created a need to measure the maximum time error spanned by a clock in a certain interval. Timekeeping metrologists became interested in estimating time deviations and time stability, so they had to find ways to convert their common frequency characteristics to time characteristics. Tests of fundamental physics provided a motivation for launching atomic frequency standards into space in long-lasting missions, whose high-precision measurements might be available for only a few hours a day, yielding a series of clock data with many gaps and outliers for which a suitable statistical analysis was necessary to extract as much information as possible from the data. In the 21st century, the field has been transformed by the advent of atomic-clock-based Global Navigation Satellite Systems (GNSS), the steady increase in precision brought about by rapidly improving clocks and measurement systems, and the growing number of relatively inexpensive small clock ensembles. Although technological transformations have raised the

  2. Paleomagnetic age constrains and magneto-mineralogic implications for the Triassic paleosurface in Europe

    NASA Astrophysics Data System (ADS)

    Franke, Christine; Thiry, Medard; Gomez-Gras, David; Jelenska, Maria; Kadzialko-Hofmokl, Magdalena; Lagroix, France; Parcerisa, David; Spassov, Simo; Szuszkiewicz, Adam; Turniak, Krzysztof

    2010-05-01

    The reconstruction of paleosurfaces represents a unique tool to access the evolution of ancient continents. Paleosurfaces contribute to the study of global changes through paleoweathering features/profiles and record uplift and subsidence of the ancient continents driven by crustal geodynamics and plate tectonics. However, age constraints for basement paleosurfaces are often difficult to obtain since the geological record of ancient land surfaces is usually limited, fragmented by unconformities and scrambled by successive superimposed evolutions, leaving a patchwork of relict landforms and weathering products, discontinuous over time and space. The crystalline basement of European Paleozoic massifs, consisting of igneous and metamorphic rocks, often show Permo-Triassic overprints resulting in underestimated age determinations. These remagnetisations are ubiquitous [e.g. Edel & Schneider, 1995], affecting many emerged Paleozoic rocks in Europe. The rejuvenated age estimations are attributed to an alteration of the primary paleomagnetic signal and carried by secondary hematite [Ricordel et al., 2007; Preeden et al., 2009; Preeden, 2009]. Moreover, published paleomagnetic ages [Ricordel et al., 2007] showed a strong relationship between the remagnetization and the development of pinkish-red crystalline facies associated to the albitized underlying rocks of the Morvan Massif (France). Parcerisa et al. [2009] performed further field and petrographic analyses and proposed that the albitization was linked to the precipitation of secondary haematite. Since hematite forms under oxidising conditions one may deduce that the remagnetization occurring in the Paleozoic crystalline rocks formed during the exposure of these rocks at the Permo-Triassic (paleo)surface. The extent of the altered zone (~200 m in depth) points to a sodium enriched groundwater environment [Thiry et al., 2009]. Demonstrating that the albitized facies are of supergenic origin and bound to the Triassic paleosurface deeply renews the ideas about the evolution of basement areas. The recognition of the Triassic paleosurface on widespread basements in Europe will provide spatio-temporal benchmarks to constrain the ablation of these massifs since the Triassic. This will be a major contribution to the geodynamic modelling of continental evolution of Europe. To deepen our understanding of this paleoalteration phenomenon on a supra-regional scale and to obtain a reasonable distribution of paleomagnetic age determinations, we aim to acquire more tie points for this Permo-Triassic surface, which was preserved in the crystalline basement of Europe throughout the Mesozoic and Cenozoic epochs. We will present results from paleomagnetic investigations as well as magneto-mineralogic analyses of the profiles through albitized granite and porphyry from the Sudetes in SW-Poland and the Catalonian Mountains in NE-Spain, for which preliminary age estimations have been carried out. Further European Paleozoic sample sites are in process. Depending on the depth situation of the sampled facies compared to the weathering profile, the Triassic paleomagnetic ages show dispersion towards rather older ages at the top and younger ages at the bottom of the sequence. This seems to correlate with the results from magneto-mineralogical analyses which show a decreasing hematite concentration with depth. The oldest ages are carried by a single component, identified as single-domain secondary hematite inclusions in the secondary albite crystals. With increasing depth the samples are rather characterized by a two-component signal, still showing (younger) Triassic ages for both components. These were identified as secondary hematite and maghemite. The latter is most probably a product of either low-temperature magnetite oxidation or precipitates during the albitization of the primary rock. These processes are both linked to less oxidising conditions than at the top of the weathering profile. A systematic interpretation of the paleomagnetic ages and the identification of the magnetic carrier assemblage for all European sites will provide valuable insights into (a) the geodynamic evolution of the crystalline complexes, by estimation of erosion/stability rates and (b) an advanced mineralogical understanding of the specific conditions linked to this Triassic paleoweathering event. Edel & Schneider, 1995, Geophys. J. Int., 122, 858-876; Edel et al., 1997, C.R.AS. Paris, Earth Planet. Sci., 325, 479-486. Parcerisa D., Thiry M., Schmitt J.-M., 2009, Albitisation related to the Triassic unconformity in igneous rocks of the Morvan Massif (France)? Int. J. Earth Sci., doi: 10.1007/s00531-008-0405-1. Preeden, U., 2009, Remagnetization in sedimentary rocks of Estonian and shear and fault zone rocks of southern Finland, disertationes geologicae Universatis Tartuensis, Ph.D. thesis, Estonia, 26, 121, ISSN 1406-2658. Preeden U., Mertanen S., Elminen T., Plado J., 2009, Secondary magnetizations in shear and fault zones in southern Finland, Tectonophysics, 49/3-4, 203-213, doi.org/10.1016/j.tecto.2009.08.011. Ricordel C., Parcerisa D., Thiry M., Moreau M.-G., Gomez-Gras D., 2007, Triassic magnetic overprints related to albitization in granites from the Morvan massif (France), Palaeogeogr. Palaeoclimatol. Palaeoecol., 251:268-282. Thiry et al., Parcerisa, D., Ricordel-Prognon, C., Schmitt, J-M., 2009, Sodium storage in deep paleoweathering profiles beneath the Paleozoic-Triassic unconformity, EGU General Assembly 2009, Vienna, Austria.

  3. Time Horizon and Social Scale in Communication

    NASA Astrophysics Data System (ADS)

    Krantz, D. H.

    2010-12-01

    In 2009 our center (CRED) published a first version of The Psychology of Climate Change Communication. In it, we attempted to summarize facts and concepts from psychological research that could help guide communication. While this work focused on climate change, most of the ideas are at least partly applicable for communication about a variety of natural hazards. Of the many examples in this guide, I mention three. Single-action bias is the human tendency to stop considering further actions that might be needed to deal with a given hazard, once a single action has been taken. Another example is the importance of group affiliation in motivating voluntary contributions to joint action. A third concerns the finding that group participation enhances understanding of probabilistic concepts and promotes action in the face of uncertainty. One current research direction, which goes beyond those included in the above publication, focuses on how time horizons arise in the thinking of individuals and groups, and how these time horizons might influence hazard preparedness. On the one hand, individuals sometimes appear impatient, organizations look for immediate results, and officials fail to look beyond the next election cycle. Yet under some laboratory conditions and in some subcultures, a longer time horizon is adopted. We are interested in how time horizon is influenced by group identity and by the very architecture of planning and decision making. Institutional changes, involving long-term contractual relationships among communities, developers, insurers, and governments, could greatly increase resilience in the face of natural hazards. Communication about hazards, in the context of such long-term contractual relationships might look very different from communication that is first initiated by immediate threat. Another new direction concerns the social scale of institutions and of communication about hazards. Traditionally, insurance contracts share risk among a large number of insurees: each contributes a small premium toward a fund that is adequate to cover the large losses that occasionally occur. Participatory processes are needed that extend risk sharing to larger social scales and that reduce adversarial relationships between insurers, insurees, insurance regulators, and governments that intervene or fail to intervene on an ad hoc rather than a contractual basis.

  4. An electronic time scale in chemistry

    PubMed Central

    Remacle, F.; Levine, R. D.

    2006-01-01

    Ultrafast, subfemtosecond charge migration in small peptides is discussed on the basis of computational studies and compared with the selective bond dissociation after ionization as observed by Schlag and Weinkauf. The reported relaxation could be probed in real time if the removal of an electron could be achieved on the attosecond time scale. Then the mean field seen by an electron would be changing rapidly enough to initiate the migration. Tyrosine-terminated tetrapeptides have a particularly fast charge migration where in <1 fs the charge arrives at the other end. A femtosecond pulse can be used to observe the somewhat slower relaxation induced by correlation between electrons of different spins. A slower relaxation also is indicated when removing a deeper-lying valence electron. When a chromophoric amino acid is at one end of the peptide, the charge can migrate all along the peptide backbone up to the N end, but site-selective ionization is probably easier to detect for tryptophan than for tyrosine. PMID:16636279

  5. Early Triassic stromatolites as post-mass extinction disaster forms

    SciTech Connect

    Schubert, J.K.; Bottjer, D.J. )

    1992-10-01

    Aftermaths of mass extinctions have been thought to be characterized by relaxation of ecological constraints accompanied by increased prominence of opportunistic generalists. Such taxa, termed 'disaster forms,' have been shown to increase dramatically in range and abundance after several mass extinction events. The Cambrian-Ordovician stromatolite decline in normal-marine level-bottom environments has been explained as a direct or indirect consequence of increases in ecological constraints, such as greater levels of predation and/or bioturbation of microbial communities, caused by early Paleozoic benthic invertebrate evolution and diversification. Thus, one would predict that in post-Ordovician strata, stromatolites might appear in normal-marine level-bottom environments as disaster forms in the aftermaths of mass extinction particularly devastating to the benthic biota, such as during Early Triassic time. Mounded stromatolites are present in two beds (up to 1.5 m thick) of the Lower Triassic (Spathian) Virgin Limestone Member (Moenkopi Formation) in the southwestern Spring Mountains of Nevada. Stromatolites from level-bottom normal-marine subtidal environments have also been described from other Lower Triassic strata in North America, Europe, and Asia. These stromatolites, unusual in level-bottom normal-marine settings, may have developed locally during the long aftermath (4-5 m.y.) of the Permian-Triassic mass extinction because of partial relaxation of the ecological constraints that typically restricted them from unstressed subtidal, normal-marine, level-bottom environments.

  6. CO2 and the end-Triassic mass extinction.

    PubMed

    Beerling, David

    2002-01-24

    The end of the Triassic period was marked by one of the largest and most enigmatic mass-extinction events in Earth's history and, with few reliable marine geochemical records, terrestrial sediments offer an important means of deciphering environmental changes at this time. Tanner et al. describe an isotopic study of Mesozoic fossil soils which suggests that the atmospheric concentration of carbon dioxide (pCO2) across the Triassic-Jurassic boundary was relatively constant (within 250 p.p.m.v.), but this is inconsistent with high-resolution evidence from the stomatal characters of fossil leaves. Here I show that the temporal resolution of the fossil-soil samples may have been inadequate for detecting a transient rise in pCO2. I also show that the fossil-soil data are consistent with a large increase in pCO2 across the Triassic-Jurassic boundary when variations in the stable carbon isotope (denoted as delta13C) in terrestrial plant leaves are taken into account. These factors suggest that the linkage between pCO2, global warming and the end-Triassic mass extinction remains intact. PMID:11807542

  7. A new chronology for the end-Triassic mass extinction

    NASA Astrophysics Data System (ADS)

    Deenen, M. H. L.; Ruhl, M.; Bonis, N. R.; Krijgsman, W.; Kuerschner, W. M.; Reitsma, M.; van Bergen, M. J.

    2010-03-01

    The transition from the Triassic to Jurassic Period, initiating the 'Age of the dinosaurs', approximately 200 Ma, is marked by a profound mass extinction with more than 50% genus loss in both marine and continental realms. This event closely coincides with a period of extensive volcanism in the Central Atlantic Magmatic Province (CAMP) associated with the initial break-up of Pangaea but a causal relationship is still debated. The Triassic-Jurassic (T-J) boundary is recently proposed in the marine record at the first occurrence datum of Jurassic ammonites, post-dating the extinction interval that concurs with two distinct perturbations in the carbon isotope record. The continental record shows a major palynological turnover together with a prominent change in tetrapod taxa, but a direct link to the marine events is still equivocal. Here we develop an accurate chronostratigraphic framework for the T-J boundary interval and establish detailed trans-Atlantic and marine-continental correlations by integrating astrochronology, paleomagnetism, basalt geochemistry and geobiology. We show that the oldest CAMP basalts are diachronous by 20 kyr across the Atlantic Ocean, and that these two volcanic pulses coincide with the end-Triassic extinction interval in the marine realm. Our results support the hypotheses of Phanerozoic mass extinctions resulting from emplacement of Large Igneous Provinces (LIPs) and provide crucial time constraints for numerical modelling of Triassic-Jurassic climate change and global carbon-cycle perturbations.

  8. An optimal modification of a Kalman filter for time scales

    NASA Technical Reports Server (NTRS)

    Greenhall, C. A.

    2003-01-01

    The Kalman filter in question, which was implemented in the time scale algorithm TA(NIST), produces time scales with poor short-term stability. A simple modification of the error covariance matrix allows the filter to produce time scales with good stability at all averaging times, as verified by simulations of clock ensembles.

  9. Permian-Triassic thermal anomaly of the active margin of South America as a result of plate kinematics reorganization

    NASA Astrophysics Data System (ADS)

    Riel, Nicolas; Jaillard, Etienne; Guillot, Stphane; Martelat, Jean-Emmanuel; Braun, Jean

    2013-04-01

    From Permian to Triassic times, tectonic plate reorganization provoked Pangaea breakup, counterclockwise rotation of Gondwana, closing of the Paleo-Tethys Ocean and opening of the Neo-Tethys oceanic realm. Meanwhile, the switch from arc volcanism to widespread S-type magmatism along the western South American active margin around 275-265 Ma is symptomatic of the onset of a large-scale Permian-Triassic thermal anomaly (PTTA)affecting the whole margin. Here we report metamorphic and U-Pb geochronological results from the El Oro metamorphic complex in the forearc zone of southwestern Ecuador, which recorded the last step, at 230-225 Ma, of the PTTA. The change in the drift direction of Gondwana from north to east at ca. 270 Ma was related to plate reorganization and provoked the verticalization of the subducted Panthalassa slab. As the slab verticalized, strong heat advection produced a high heat flow beneath the active margin inducing the development of a huge thermal anomaly responsible for the PTTA, which lasted 30 Ma. This voluminous magmatic activity culminated at the Permian-Triassic boundary, and may have contributed to the degradation of life conditions on the Earth surface.

  10. Ecosystem remodelling among vertebrates at the Permian-Triassic boundary in Russia.

    PubMed

    Benton, M J; Tverdokhlebov, V P; Surkov, M V

    2004-11-01

    The mass extinction at the Permian-Triassic boundary, 251 million years (Myr) ago, is accepted as the most profound loss of life on record. Global data compilations indicate a loss of 50% of families or more, both in the sea and on land, and these figures scale to a loss of 80-96% of species, based on rarefaction analyses. This level of loss is confirmed by local and regional-scale studies of marine sections, but the terrestrial record has been harder to analyse in such close detail. Here we document the nature of the event in Russia in a comprehensive survey of 675 specimens of amphibians and reptiles from 289 localities spanning 13 successive geological time zones in the South Urals basin. These changes in diversity and turnover cannot be explained simply by sampling effects. There was a profound loss of genera and families, and simplification of ecosystems, with the loss of small fish-eaters and insect-eaters, medium and large herbivores and large carnivores. Faunal dynamics also changed, from high rates of turnover through the Late Permian period to greater stability at low diversity through the Early Triassic period. Even after 15 Myr of ecosystem rebuilding, some guilds were apparently still absent-small fish-eaters, small insect-eaters, large herbivores and top carnivores. PMID:15525988

  11. Astronomical constraints on the duration of the early Jurassic Hettangian stage and recovery rates following the end-Triassic mass extinction (St Audrie's Bay/East Quantoxhead, UK)

    NASA Astrophysics Data System (ADS)

    Ruhl, M.; Deenen, M. H. L.; Abels, H. A.; Bonis, N. R.; Krijgsman, W.; Krschner, W. M.

    2010-06-01

    The end-Triassic environmental crisis with major extinctions in the marine realm is followed by successive recovery in the lower Jurassic Hettangian Stage. Accurate timing of events is however still poorly constrained. In this study, combined field observations and physical and chemical proxy records, covering the uppermost Triassic and lower Jurassic marine successions of St Audrie's Bay and East Quantoxhead (UK), have been used to construct a floating astronomical time-scale of ? 2.5 Myr in length. This time-scale is based on the recognition of meters thick cycles in limestone and (black) shale predominance and concurrent variability in physical and chemical proxy records. Three to five individual black-shale beds occur within these meter-scale sedimentary bundles and are interpreted to reflect precession-controlled changes in monsoon intensity, while the bundles are interpreted as forced by the ? 100-kyr eccentricity cycle. On the basis of these findings, we propose an astronomically constrained duration of the Hettangian stage of 1.8 Myr in the UK and unequal duration of Hettangian ammonite zones (Psilocerasplanorbis zone: ? 250 kyr; Alsatitesliasicus zone: ? 750 kyr; Schlotheimiaangulata zone: ? 800 kyr). Within this astronomical framework, the extinction interval and coinciding negative CIE represent 1 to 2 precession cycles (? 20-40 kyr). The amount of time succeeding the end-Triassic negative carbon isotope excursion (CIE) and preceding the first Jurassic ammonite occurrence (in the UK) is constrained to 6 climatic precession cycles (? 120 kyr). Cyclostratigraphic correlation to the astronomically-tuned sedimentary record of the continental Newark basin (USA) allows to locate the stratigraphic position of the marine defined Triassic-Jurassic and Hettangian-Sinemurian boundary in the continental realm. Continuous low ?13CTOC values throughout the Hettangian and early Sinemurian, succeeding volcanic activity in the Central Atlantic Magmatic Province (CAMP), may suggest a long-term change in Earth's global biogeochemical cycles, which do not fully recover for several million years.

  12. Paleogeographic regionalization of Triassic seas based on conodontophorids

    NASA Astrophysics Data System (ADS)

    Klets, T. V.

    2008-10-01

    Geographic differentiation of conodontophorids between northern and southern latitudes commenced in the Triassic since the early Induan. Cosmopolitan long-lived genera of predominantly smooth morphotypes without sculpturing were characteristic of high-latitude basins of the Panboreal Superrealm. Since the early Olenekian until the Carnian inclusive, this superrealm consisted of the Siberian Realm that extended over Northeast Asia and the Canada-Svalbard Realm that included the Svalbard Archipelago and northern regions of Canada. Throughout the Triassic period, conodontophorids characteristic of the Tethys-Panthalassa Superrealm spanning the Tethys and low-latitude zones of the Pacific were highly endemic, very diverse in taxonomic aspect, having well-developed sculpturing and tempos of morphological transformations. Distinctions between the Early-Middle Triassic conodontophorids from northern and southern zones were not as great as afterward, and their impoverished assemblages from southern Tethyan basins were close in some respects to the Boreal ones. Their habitat basins of that time can be grouped into the Mediterranean-Pacific and India-Pakistan realms. Hence, the extent of geographic differentiation of conodontophorids was not constant and gradually grew, as their taxonomic diversity was reducing in northern basins but relatively increasing in southern ones. The Panboreal e Tethys-Panthalassa superrealms of conodontophorids, which are most clearly recognizable, are close to first-rank paleobiochores (superrealms) established earlier for ammonoids and bivalve mollusks. Main factor that controlled geographic differentiation of Triassic conodontophorids was climatic zoning. Initially lower diversity of southern Tethyan assemblages points probably to relatively cooler water regime in the peri-Gondwanan part of the Tethys. The established patterns in geographic distribution of conodontophorids characterize most likely the real trend of their differentiation and evolution, i.e., the distribution area contraction prior to complete extinction at the end of the Triassic

  13. Reconstructing paleoenvironment in the west-tethyan continental domain at the Late Permian and Early Triassic from sedimentological and palaeobotanical data

    NASA Astrophysics Data System (ADS)

    Bercovici, Antoine; Bourquin, Sylvie; Broutin, Jean; Diez, Jos B.

    2010-05-01

    The final buildup of Pangea at the end of the Palaeozoic led to the formation of massive landmass unrivaled in later times. On a climatic perspective, the end of the Carboniferous ice age opened into a period of progressive warming, creating vast arid regions on land. The lower Triassic is the culmination of this trend, and represents a period where land vegetation is scarce or non-existent. The following work presents the palaeogeographical evolution of the north-western tethyan terrestrial domain (currently most of western Europe), re-evaluated by a sedimentological and palaeobotanical (megafloras and palynofloras) combined approach. Preservation condition required for fossilization is a limit for dating the upper Permian and lower Triassic sedimentary sequences. As the general climate underwent a major warming phase, the use of fossils as biostratigraphical and palaeoenvironmental tools becomes limited. In these conditions, sedimentary proxies linked to climate can be used instead as valuable correlation tools in continental sections. During the Early Permian, continental sedimentation was limited in a series of isolated endoreic basins, in between differences in preservation and floral assemblages can be observed. This partitionning, at the scale of western Europe, is mainly driven by the Variscan topography. However, the general evolution of Permian flora in the western tethyan domain is still linked at the first order to the global warming event. The general aridification of climates on Pangea led to profound modifications of floras long before the Permian/Triassic biotic crisis. In all sedimentary basins of the north-western tethyan domain, with the exception of the Germanic Basin, the Permian/Triassic transition is characterized by a lack of sedimentary deposition of variable time. This period of no record is associated with: (1) an angular uncomformity of increasing angle towards the axis of the Variscan range, (2) important sedimentary flux at the re-initiation of sedimentation during the Triassic, (3) periods of sedimentation stops indicated by palaeosols, (4) a switch in palaeocurrent direction for fluvial systems between the Permian and the Triassic and, (5) by sedimentary transit and bypass during the lower Triassic. All these observations imply the existence of a still active Variscan range, modifying palaeoclimatic conditions and controlling sedimentation in the end-Permian sedimentary basins of western Europe.

  14. Detection of crossover time scales in multifractal detrended fluctuation analysis

    NASA Astrophysics Data System (ADS)

    Ge, Erjia; Leung, Yee

    2013-04-01

    Fractal is employed in this paper as a scale-based method for the identification of the scaling behavior of time series. Many spatial and temporal processes exhibiting complex multi(mono)-scaling behaviors are fractals. One of the important concepts in fractals is crossover time scale(s) that separates distinct regimes having different fractal scaling behaviors. A common method is multifractal detrended fluctuation analysis (MF-DFA). The detection of crossover time scale(s) is, however, relatively subjective since it has been made without rigorous statistical procedures and has generally been determined by eye balling or subjective observation. Crossover time scales such determined may be spurious and problematic. It may not reflect the genuine underlying scaling behavior of a time series. The purpose of this paper is to propose a statistical procedure to model complex fractal scaling behaviors and reliably identify the crossover time scales under MF-DFA. The scaling-identification regression model, grounded on a solid statistical foundation, is first proposed to describe multi-scaling behaviors of fractals. Through the regression analysis and statistical inference, we can (1) identify the crossover time scales that cannot be detected by eye-balling observation, (2) determine the number and locations of the genuine crossover time scales, (3) give confidence intervals for the crossover time scales, and (4) establish the statistically significant regression model depicting the underlying scaling behavior of a time series. To substantive our argument, the regression model is applied to analyze the multi-scaling behaviors of avian-influenza outbreaks, water consumption, daily mean temperature, and rainfall of Hong Kong. Through the proposed model, we can have a deeper understanding of fractals in general and a statistical approach to identify multi-scaling behavior under MF-DFA in particular.

  15. Noether theorem for Birkhoffian systems on time scales

    NASA Astrophysics Data System (ADS)

    Song, Chuan-Jing; Zhang, Yi

    2015-10-01

    Birkhoff equations on time scales and Noether theorem for Birkhoffian system on time scales are studied. First, some necessary knowledge of calculus on time scales are reviewed. Second, Birkhoff equations on time scales are obtained. Third, the conditions for invariance of Pfaff action and conserved quantities are presented under the special infinitesimal transformations and general infinitesimal transformations, respectively. Fourth, some special cases are given. And finally, an example is given to illustrate the method and results.

  16. Upper Triassic stratigraphy and paleobiogeography of Kotel'nyi Island (New Siberian Islands)

    NASA Astrophysics Data System (ADS)

    Bragin, N. Yu.; Konstantinov, A. G.; Sobolev, E. S.

    2012-11-01

    The thorough study of the Upper Triassic reference section located at the Tikhaya River in the central part of Kotel'nyi Island and characterized by uniform clayey lithology and containing diverse cephalopod, molluscan, and radiolarian assemblages made it possible to specify its structure and paleontological characteristic and establish for the first time the upper Anisian Sirenites yakutensis Zone. It is shown that different Late Triassic faunal groups are represented by mixed dominant Boreal and subordinate Tethyan elements. Such proportions are observable through the entire section beginning from the lower Carnian to upper Norian layers. The peculiar taxonomic composition of Late Triassic radiolarian and cephalopod assemblages provides grounds for attributing the region to an autonomous paleobiochore (New Siberian subprovince). The occurrence of both Siberian and Canadian elements in the Late Triassic faunas emphasizes the specific position of this paleobiochore determined by wide connections between basins at that time.

  17. A Major Unconformity Between Permian and Triassic Strata at Cape Kekurnoi, Alaska Peninsula: Old and New Observations on Stratigraphy and Hydrocarbon Potential

    USGS Publications Warehouse

    Blodgett, Robert B.; Sralla, Bryan

    2008-01-01

    A major angular unconformity separates carbonates and shales of the Upper Triassic Kamishak Formation from an underlying unnamed sequence of Permian agglomerate, volcaniclastic rocks (sandstone), and limestone near Puale Bay on the Alaska Peninsula. For the first time, we photographically document the angular unconformity in outcrop, as clearly exposed in a seacliff ~1.3 mi (2.1 km) west of Cape Kekurnoi in the Karluk C?4 and C?5 1:63,360-scale quadrangles. This unconformity is also documented by examination of core chips, ditch cuttings, and (or) open-hole electrical logs in two deep oil-and-gas-exploration wells (Humble Oil & Refining Co.?s Bear Creek No. 1 and Standard Oil Co. of California?s Grammer No. 1) drilled along the Alaska Peninsula southwest of Puale Bay. A third well (Richfield Oil Corp.?s Wide Bay Unit No. 1), south of and structurally on trend with the other two wells, probed deeply into the Paleozoic basement, but Triassic strata are absent, owing to either a major unconformity or a large fault. Here we briefly review current and newly acquired data on Permian and Triassic rocks of the Puale Bay-Becharof Lake-Wide Bay area on the basis of an examination of surface and subsurface materials. The resulting reinterpretation of the Permian and Triassic stratigraphy has important economic ramifications for oil and gas exploration on the Alaska Peninsula and in the Cook Inlet basin. We also present a history of petroleum exploration targeting Upper Triassic reservoirs in the region.

  18. A Quaternary Geomagnetic Instability Time Scale

    NASA Astrophysics Data System (ADS)

    Singer, B. S.

    2013-12-01

    Reversals and excursions of Earth's geomagnetic field create marker horizons that are readily detected in sedimentary and volcanic rocks worldwide. An accurate and precise chronology of these geomagnetic field instabilities is fundamental to understanding several aspects of Quaternary climate, dynamo processes, and surface processes. For example, stratigraphic correlation between marine sediment and polar ice records of climate change across the cryospheres benefits from a highly resolved record of reversals and excursions. The temporal patterns of dynamo behavior may reflect physical interactions between the molten outer core and the solid inner core or lowermost mantle. These interactions may control reversal frequency and shape the weak magnetic fields that arise during successive dynamo instabilities. Moreover, weakening of the axial dipole during reversals and excursions enhances the production of cosmogenic isotopes that are used in sediment and ice core stratigraphy and surface exposure dating. The Geomagnetic Instability Time Scale (GITS) is based on the direct dating of transitional polarity states recorded by lava flows using the 40Ar/39Ar method, in parallel with astrochronologic age models of marine sediments in which O isotope and magnetic records have been obtained. A review of data from Quaternary lava flows and sediments yields a GITS comprising 10 polarity reversals and 27 excursions during the past 2.6 million years. Nine of the ten reversals bounding chrons and subchrons are associated with 40Ar/39Ar ages of transitionally-magnetized lava flows. The tenth, the Guass-Matuyama chron boundary, is tightly bracketed by 40Ar/39Ar dated ash deposits. Of the 27 well-documented excursions, 14 occurred during the Matuyama chron and 13 during the Brunhes chron; 19 have been dated directly using the 40Ar/39Ar method on transitionally-magnetized volcanic rocks and form the backbone of the GITS. Excursions are clearly not the rare phenomena once thought. Rather, during the Quaternary period, they occur nearly three times as often as full polarity reversals. I will address analytical issues, including the size and consistency of system blanks, that have led to the recognition of minor (1%) discrepencies between the 40Ar/39Ar age for a particular reversal or excursion and the best astrochronologic estimates from ODP sediment cores. For example, re-analysis of lava flows from Haleakala volcano, Maui that record in detail the Matuyama-Brunhes polarity reversal have been undertaken with blanks an order of magntitude smaller and more stable than was common a decade ago. Using the modern astrochronologic calibration of 28.201 Ma for the age of the Fish Canyon sanidine standard, results thus far yield an 40Ar/39Ar age of 772 11 ka for the reversal that is identical to the most precise and accurate astrochronologic age of 773 2 ka for this reversal from ODP cores. Similarly, new dating of sanidine in the Cerro Santa Rosa I rhyolite dome, New Mexico reveals an age of 932 5 ka for the excursion it records, in perfect agreement with astrochronologically dated ODP core records. Work underway aims at refining the 40Ar/39Ar ages that underpin the entire GITS by further eliminating the bias between the radioisotopic and astrochronologically determined ages for several reversals and excursions.

  19. Deep-sea record of impact apparently unrelated to mass extinction in the Late Triassic.

    PubMed

    Onoue, Tetsuji; Sato, Honami; Nakamura, Tomoki; Noguchi, Takaaki; Hidaka, Yoshihiro; Shirai, Naoki; Ebihara, Mitsuru; Osawa, Takahito; Hatsukawa, Yuichi; Toh, Yosuke; Koizumi, Mitsuo; Harada, Hideo; Orchard, Michael J; Nedachi, Munetomo

    2012-11-20

    The 34-million-year (My) interval of the Late Triassic is marked by the formation of several large impact structures on Earth. Late Triassic impact events have been considered a factor in biotic extinction events in the Late Triassic (e.g., end-Triassic extinction event), but this scenario remains controversial because of a lack of stratigraphic records of ejecta deposits. Here, we report evidence for an impact event (platinum group elements anomaly with nickel-rich magnetite and microspherules) from the middle Norian (Upper Triassic) deep-sea sediment in Japan. This includes anomalously high abundances of iridium, up to 41.5 parts per billion (ppb), in the ejecta deposit, which suggests that the iridium-enriched ejecta layers of the Late Triassic may be found on a global scale. The ejecta deposit is constrained by microfossils that suggest correlation with the 215.5-Mya, 100-km-wide Manicouagan impact crater in Canada. Our analysis of radiolarians shows no evidence of a mass extinction event across the impact event horizon, and no contemporaneous faunal turnover is seen in other marine planktons. However, such an event has been reported among marine faunas and terrestrial tetrapods and floras in North America. We, therefore, suggest that the Manicouagan impact triggered the extinction of terrestrial and marine organisms near the impact site but not within the pelagic marine realm. PMID:23129649

  20. Deep-sea record of impact apparently unrelated to mass extinction in the Late Triassic

    PubMed Central

    Onoue, Tetsuji; Sato, Honami; Nakamura, Tomoki; Noguchi, Takaaki; Hidaka, Yoshihiro; Shirai, Naoki; Ebihara, Mitsuru; Osawa, Takahito; Hatsukawa, Yuichi; Toh, Yosuke; Koizumi, Mitsuo; Harada, Hideo; Orchard, Michael J.; Nedachi, Munetomo

    2012-01-01

    The 34-million-year (My) interval of the Late Triassic is marked by the formation of several large impact structures on Earth. Late Triassic impact events have been considered a factor in biotic extinction events in the Late Triassic (e.g., end-Triassic extinction event), but this scenario remains controversial because of a lack of stratigraphic records of ejecta deposits. Here, we report evidence for an impact event (platinum group elements anomaly with nickel-rich magnetite and microspherules) from the middle Norian (Upper Triassic) deep-sea sediment in Japan. This includes anomalously high abundances of iridium, up to 41.5 parts per billion (ppb), in the ejecta deposit, which suggests that the iridium-enriched ejecta layers of the Late Triassic may be found on a global scale. The ejecta deposit is constrained by microfossils that suggest correlation with the 215.5-Mya, 100-km-wide Manicouagan impact crater in Canada. Our analysis of radiolarians shows no evidence of a mass extinction event across the impact event horizon, and no contemporaneous faunal turnover is seen in other marine planktons. However, such an event has been reported among marine faunas and terrestrial tetrapods and floras in North America. We, therefore, suggest that the Manicouagan impact triggered the extinction of terrestrial and marine organisms near the impact site but not within the pelagic marine realm. PMID:23129649

  1. Carbon-cycle disturbances and environmental change preceding the end-Triassic mass extinction

    NASA Astrophysics Data System (ADS)

    Ruhl, M.; Ullmann, C. V.; Mette, W.; Korte, C.

    2012-04-01

    The end-Triassic mass extinction [~201.3 Ma], marked by marine and terrestrial ecosystem collapse and global marine biodiversity loss, coincides with the onset of extensive volcanic activity and emplacement of the Central Atlantic Magmatic Province (CAMP). Massive and rapid greenhouse gas release from basalts, subsurface organic rich strata and ocean-floor clathrates, had a profound impact on the global exogenic carbon cycle and caused dramatically increased atmospheric pCO2 values. A recent study however suggests global carbon cycle disturbance already (possibly ~100 kyr) before the end-Triassic mass extinction. 13C depleted atmospheric carbon injection at this event may have resulted from Late Triassic dike and sill intrusions possibly releasing thermogenic methane from subsurface organic-rich sediments. We now studied an extended, up to 1 million year long, Late Triassic marine sedimentary record from the western Tethian Eiberg basin (Northern Calcareous Alps, Austria). Sediments were deposited in the deepest part of the Eiberg basin (very close to the base Jurassic Global Stratotype Section and Point at Kuhjoch). High-resolution ?13CTOC, ?13CCARB-Bulk and ?13CCARB-Brachiopods from this record show distinct 1-2 ?13C negative excursions throughout the latest Triassic. This suggests disturbance of the global exogenic carbon cycle already long before the end-Triassic mass extinction. Regular alternations between (laminated) black-shales and carbonate deposition also indicate periodic changes in the palaeo-environment. Variations in the ?18OCARB record, coinciding with ?13C negative excursions, suggest climatic warming. But, distinct negative shifts may also indicate increased fresh-water input along the upper-Triassic western Tethys continental margin. Volcanic activity and palaeo-environmental change occurring already before the end-Triassic mass extinction, may have progressively weakened marine ecosystems, ultimately leading to large-scale marine biodiversity loss.

  2. Atomic time scales for dynamical astronomy

    NASA Astrophysics Data System (ADS)

    Guinot, B.

    1992-06-01

    A series of recommendations on space-time references issued in the framework of the general theory of relativity in 1991 by the International Astronomical Unions (IAU) is presented. The recommendations, their background, the difficulties that were met, and the connection with previous recommendations--with an emphasis on time--are given. For simplicity of theoretical developments in celestial mechanics, several coordinate systems must be defined. The implied definitions of new coordinate times are presented together with their relation between themselves and to other times. International Atomic Time (TAI) is not affected by these recommendations, but appears now as a realization of the ideal terrestrial time having a clear scientific definition.

  3. Permian-Triassic plutonism and tectonics, Death Valley region, California and Nevada

    SciTech Connect

    Snow, J.K.; Asmerom, Y. ); Lux, D.R. )

    1991-06-01

    Significant contractional structures that deform Permian rocks but predate an Early Triassic overlap sequence are recognized within the Cordilleran orogen, western US. Thrusting in the Death Valley region of the orogen, however, has been regarded as Middle Triassic or younger and thus kinematically distinct. The authors present new isotopic age limits on two posttectonic stocks that intrude major structures of the Death Valley thrust belt. The stocks are no younger than Middle Triassic, but are likely Late Permian in age, consistent with stratigraphic and structural data suggesting that thrusting predates the overlap sequence. The authors hypothesize that Permian shortening may have affected more than 700 km of the Cordilleran orogen at the same time arc activity began within cratonic North America but prior to Early Triassic emplacement of the structurally higher Sonomian arc terrane.

  4. Cyclostratigraphy of the Middle Triassic bedded chert sequence in the Chichibu Belt, Southwest Japan

    NASA Astrophysics Data System (ADS)

    Soda, K.; Onoue, T.; Ikeda, M.

    2014-12-01

    Triassic bedded cherts from the Jurassic accretionary complexes in Japan consist of centimeter scale alternations of chert and shale beds. Previous studies have proposed that the rhythmical alternations of Triassic chert and shale beds represent astronomical cycles. Although cyclostratigraphy of the Triassic bedded chert sequence was identified in the Inuyama area of the Mino Belt, central Japan, the validity of its cyclostratigraphy requires detailed cyclostratigraphic correlations to other Triassic bedded chert sequences in Japan. In this study, we performed cyclostratigraphic analysises to the Middle Triassic (Anisian-Ladinian) bedded chert sequence in the Tsukumi area of the Chichibu Belt, southwest Japan. The average duration of a chert-shale couplet in the Middle Triassic bedded chert of the Tsukumi area is ~10 kyr. This duration is inconsistent with the ~20 kyr duration of the precession cycle during the Triassic, which was confirmed by estimated average duration of a chert-shale couplet in the Triassic bedded chert of the Inuyama area. The dominat cycles in a bed number series of thickness variations in the Middle Triassic chert beds show approximately 2-5, 10, 40, 200, 300 and 400 beds cycles. Given that the average duration of one chert-shale couplet is 10 kyr, these cycles correspond to approximately 20-50, 100, 400, 2000, 3000 and 4000 kyr periodicities. The periodicities of the Tsukumi chert are consistent with those of the Inuyama chert (approximately 40-60, 100, 140, 240, 400 and 4000 kyr). Previous paleomagnetic studies have revealed that the Middle Triassic bedded cherts in the Tsukumi area were deposited in the equatorial region (2.1°±5.2°S), whereas the deposition of the Inuyama cherts occur at relatively higher latitude (16.9°±10.2°N). If the interpretation that rhythmical alternations of chert and shale beds are paced by precession and eccentricity cycles is valid, the average duration of a chet-shale couplet from the Tsukumi area might reflect the semi-precession cycle (~10 kyr) in the equator area caused by biannual passage of the Sun. Further cyclostratigraphic analysises will requires to estimate the paleolatitudinally dependent patterns in the cyclicities of the Triassic bedded chert sequences in Japan.

  5. On time scales and time synchronization using LORAN-C as a time reference signal

    NASA Technical Reports Server (NTRS)

    Chi, A. R.

    1974-01-01

    The long term performance of the eight LORAN-C chains is presented in terms of the Coordinated Universal Time (UTC) of the U.S. Naval Observatory (USNO); and the use of the LORAN-C navigation system for maintaining the user's clock to a UTC scale is described. The atomic time scale and the UTC of several national laboratories and observatories relative to the international atomic time are reported. Typical performance of several NASA tracking station clocks, relative to the USNO master clock, is also presented.

  6. Sodium storage in deep paleoweathering profiles beneath the Paleozoic-Triassic unconformity

    NASA Astrophysics Data System (ADS)

    Thiry, M.; Parcerisa, D.; Ricordel-Prognon, C.; Schmitt, J.-M.

    2009-04-01

    A major sodium accumulation has been recognized for long and by numerous authors in the Permo-Triassic salt deposits (Hay et al., 2006). Beside these basinal deposits, important masses of sodium were stored on the continents within deep palaeoweathering profiles in form of albite. Indeed, wide surfaces and huge volumes of granito-gneissic basements of the Hercynian massifs are albitized from North-Africa up to Scandinavia. These albitized rocks have usually been considered as related to tardi-magmatic metasomatic processes (Cathelineau 1986; Petersson and Eliasson 1997). Geometrical arrangement and dating of these alterations point out that these albitizations, or at least a part of them, developed under low temperature subsurface conditions in relation with the Triassic palaeosurface (Ricordel et al., 2007; Parcerisa et al., 2009). Petrology The albitized igneous rocks show a strong alteration with pseudomorphic replacement of the primary plagioclases into albite, replacement of primary biotite by chlorite and minor precipitation of neogenic minerals like albite, chlorite, apatite, haematite, calcite and titanite. Albitized rocks are characterized by their pink coloration due to the presence of minute haematite inclusions in the albite. The development and distribution of the albitization and related alterations above the unaltered basement occurs in three steps that define a vertical profile, up to 100-150 m depth. 1) In the lower part of the profile, albitization occurs within pink-colored patches in the unaltered rock, giving a pink-spotted aspect to the rock. 2) In the middle part of the profile, rocks have an overall pink coloration due to the albitization of the primary Ca-bearing igneous plagioclases. Usually, this facies develops in a pervasive manner, affecting the whole rock, but it may also be restricted to joints, giving a sharp-pink coloration to the fracture wall. 3) Finally, the top of the profile is defined by the same mineral paragenesis as in the pink stage, with an increase in the amount and size of sericite and hematite inclusions. The latter causes the red coloration of the altered rocks. Regional layout Regional distribution of the alterations which affect the Carboniferous igneous and volcanic formations beneath the Jurassic sedimentary cover lead to associate these alterations to the Triassic unconformity. Besides, albitized facies show generally both topographic and regional arrangements, with more altered facies occurring in the mountain highs and in the external parts of the massifs and unaltered facies occurring in the river valleys and in the central parts of the massifs. Moreover, the haematite associated with these albitized basement rocks has been dated from Early Trias by means of paleomagnetism (Ricordel et al, 2007). From this layout and dating, it is deduced that albitization is related to the development of a deep weathering profile (up to 150 m deep) during a long-lasting exposure of the Triassic erosional unconformity (regolith). Geochemistry and paleoenvironmental setting It has to be highlighted that, this alteration may not behave like an "ordinary" weathering profile and occurred under unusual, or at least very specific, geological settings. The scale of the profiles (over 100 m depth) relates this alteration rather to a groundwater environment. The weak mobility of most chemical elements may point to a groundwater with very low outflows and deep water table. This may occur in very subdued landscape and in arid climatic conditions. It has also to be pointed that this alteration may have lasted for several 10's of Ma. Albite formation at low temperature may be envisioned consequently in alkaline, confined waters with sufficient concentrations of sodium and silica. Early attempts of modeling (Schmitt, 1994) have also indicated that a high Na+/K+ ratio is as well probably required. Petrographic data also indicate an import of sodium by the weathering solutions, without any clear enrichment in potassium. The Na+ enrichment is most likely linked with the peculiar geochemical setting of the Triassic environment where for instance halite moulds are very common in transgressive epicontinental deposits. The leaching of such salts, the role of salty marine aerosols, or a periodic/episodic contribution of seawater or evaporative solutions may be equally invoked. Mass balance Taking into account the surpergene origin of albitization and its widespread development on the Paleozoic basement rocks (from Morocco to Scandinavia) means that high amounts of Na+ have been stored in the deep paleoweathering profiles of the Triassic continents. This sodium storage in weathering profiles has to be taken in consideration in addition to the major sodium chloride accumulation in the basins during the Permo-Triassic times. Further investigations are needed to demonstrate the extent of these paleoweathering profiles and then to estimate the amount of this continental sodium storage. References Cathelineau M (1986) The hydrothermal alkali metasomatism effects on granitic rocks: Quartz dissolution and related sub-solidus changes. Jour. Petrol., 27: 945-965. Hay, W.W.; Migdisov, A.; Balukhovsky, A.N.; Wold, C.N.; Flogel, S., Soding, E. (2006) Evaporites and the salinity of the ocean during the Phanerozoic: Implications for climate, ocean circulation and life. Palaeogeography, Palaeoclimatology, Palaeoecology, 240/1-2: 3-46. Parcerisa D., Thiry M., Schmitt J.-M. (2009) Albitisation related to the Triassic unconformity in igneous rocks of the Morvan Massif (France), International Journal of Earth Sciences, DOI: 10.1007/s00531-008-0405-1. Petersson J, Eliasson T (1997) Mineral evolution and element mobility during episyenitization (dequartzification) and albitization in the postkinematic Bohus granite, southwest Sweden. Lithos, 42: 123-146. Ricordel C, Parcerisa D, Thiry M, Moreau M-G, Gómez-Gras D (2007) Triassic magnetic overprints related to albitization in granites from the Morvan massif (France). Palaeogeography Palaeoclimatology Palaeoecology, 251: 268-282. Schmitt JM (1994) Geochemical modelling and origin of the Triassic albitized regolith in southern France. 14th International Sedimentological Congress, Recife, Brazil. Abstracts book S8: 19-21.

  7. Trophic network models explain instability of Early Triassic terrestrial communities.

    PubMed

    Roopnarine, Peter D; Angielczyk, Kenneth D; Wang, Steve C; Hertog, Rachel

    2007-09-01

    Studies of the end-Permian mass extinction have emphasized potential abiotic causes and their direct biotic effects. Less attention has been devoted to secondary extinctions resulting from ecological crises and the effect of community structure on such extinctions. Here we use a trophic network model that combines topological and dynamic approaches to simulate disruptions of primary productivity in palaeocommunities. We apply the model to Permian and Triassic communities of the Karoo Basin, South Africa, and show that while Permian communities bear no evidence of being especially susceptible to extinction, Early Triassic communities appear to have been inherently less stable. Much of the instability results from the faster post-extinction diversification of amphibian guilds relative to amniotes. The resulting communities differed fundamentally in structure from their Permian predecessors. Additionally, our results imply that changing community structures over time may explain long-term trends like declining rates of Phanerozoic background extinction. PMID:17609191

  8. Triassic deformation of Permian Early Triassic arc-related sediments in the Beishan (NW China): Last pulse of the accretionary orogenesis in the southernmost Altaids

    NASA Astrophysics Data System (ADS)

    Tian, Zhonghua; Xiao, Wenjiao; Sun, Jimin; Windley, Brian F.; Glen, Richard; Han, Chunming; Zhang, Zhiyong; Zhang, Ji'en; Wan, Bo; Ao, Songjian; Song, Dongfang

    2015-11-01

    The Beishan orogenic collage (BOC) in the southernmost Altaids provides evidence of the final stage of evolution of the Paleo-Asian Ocean. However, the closure time of the Paleo-Asian Ocean in the BOC is controversial. From field mapping, and structural analysis of mesoscale, superposed folds in Early Triassic sediments in the Hongyanjing Basin in the central BOC, we define at least two phases of deformation, which we can bracket in age as end-Permian to Early-Late Triassic. The sandstones in the basin are poorly sorted with angular clasts, which indicates immaturity characteristic of proximal and rapid deposition. Geochemical data indicate that the Hongyanjing Basin probably developed in an arc-related setting near an active continental margin or mature island arc. Combined with published regional geological data, we interpret the Hongyanjing Basin as a Permian-Early Triassic inter-arc basin between the Carboniferous Mazongshan arc to the north and the Ordovician to Permian Huaniushan-Dundunshan arc to the south. In addition, the age distribution of our sediments shows that the active continental margin or continental arc on which the Hongyanjing arc-related basin sat was somehow independently distributed in the Paleo-Asian Ocean without any major contribution of provenance from the Tarim Craton and Dunhuang Block to the south and Southern Mongolia accretionary system to the north. Deformation of the superposed folds began in the end-Permian, continued in the Early Triassic, and ended before the middle Late Triassic (219 Ma). Therefore the accretionary orogenesis in the Beishan part of the southernmost Altaids was still ongoing in the early to middle Triassic, and it finished in the Late Triassic, which might have been the last pulse of the accretionary orogenesis in the southernmost Altaids. We correlate this terminal event with tectonic developments in the Kunlun and Qinling orogens in the Tethyan domain.

  9. Tethyan magnetostratigrapy from Pizzo Mondello and correlation to the Late Triassic Newark APTS

    NASA Astrophysics Data System (ADS)

    Muttoni, G.; Kent, D. V.; Olsen, P. E.; Bernasconi, S.; Lowrie, W.; Martn Hernndez, F.; di Stefano, P.

    2003-04-01

    We present magnetostratigraphic data and preliminary C13 and O18 stable isotope data from an expanded (?430m-thick) Upper Triassic marine section at Pizzo Mondello from the Sicani Basin of Sicily and review biostratigraphic data from the literature that can be used to define the location of the Carnian/Norian and Norian/Rhaetian boundaries. Pizzo Mondello offers good potentials for magnetostratigraphic correlation of marine biostratigraphic and chemostratigraphic data with the continental Newark astrochronological time scale (APTS) for development of an integrated Late Triassic time scale. The relatively stable average values of 18O centered around 0 are a strong indication that the Cherty Limestone at Pizzo Mondello suffered very little diagenetic overprinting. The Carnian/Norian boundary at Pizzo Mondello seems to be associated with a positive shift of C13 although further work is necessary to evaluate its paleoenvironmental significance. A statistical approach was applied to evaluate various Pizzo Mondello to Newark magnetostratigraphic correlations. Two correlation options, neither unequivocal, have the highest and nearly equivalent correlation coefficients. Option #1 predicts the base of Pizzo Mondello to be correlative with the middle part of the Newark APTS, whereas in Option #2 the base of Mondello starts towards the early part of the Newark APTS. According to sampling density and average sediment accumulation rates of 20-30m/m.y., polarity intervals with durations equal to or less than ?170 k.y. may have been undersampled at Pizzo Mondello. Accordingly, we filtered the high resolution Newark APTS and performed further statistical correlations from which we conclude that Option #2 is preferred. With this option, the Carnian/Norian boundary based on conodonts corresponds to basal Newark magnetozone E7 at about 228 Ma (adopting Newark astrochronology), implying a long Norian with a duration of 20m.y. and a Rhaetian of about 6 m.y. duration. These ages are in fact not inconsistent with the few high quality radiometric dates that are available for Late Triassic time scale calibration. We suggest that Pizzo Mondello is a good candidate for a GSSP for the base of the Norian whereas we find that sections of the "Hallstatt" type , which may be more fossiliferous but have erratic and typically very low average rates of sediment accumulation, are more difficult to correlate with each other and with expanded sections such as Pizzo Mondello and the Newark.

  10. Stratigraphy and correlation of Upper Triassic strata between west Texas and eastern New Mexico

    SciTech Connect

    Lucas, S.G. ); Anderson, O.J. )

    1992-04-01

    Lithostratigraphy and vertebrate biochronology allow precise correlation of Upper Triassic strata between west Texas and eastern New Mexico. Upper Triassic strata are well exposed in west Texas from Oldham to Scurry counties, and are assigned to the Dockum Formation of the Chinle Group. Fossil vertebrates from the Camp Springs and Tecovas Members are of late Carnian age, whereas those from the Copper Member are of early Norian age. Upper Triassic strata in east-central New Mexico, across the Llano Estacado from the west Texas outcrops, correlate as follows: Camper Springs = lower Santa Rose; Tecovas = upper Santa Rosa/Garita Creek; Trujillo = Trujillo ('Cuervo'); Cooper = lower Bull Canyon. Upper Triassic strata in southeastern New Mexico and in Howard and adjacent counties in Texas are the lower Santa Rosa/Camper Springs overlain by mudstones and sandstones that contain late Carnian vertebrates and are informally termed upper member of Dockum Formation. Available data refute several long-held ideas about the Upper Triassic of west Texas. These data demonstrate that: (1) there is a pervasive unconformity at the base of the Dockum Formation that represents much of Triassic time; (2) the Trujillo Member is not correlative with the Santa Rosa of eastern New Mexico: Trujillo is a medial Dockum unit, whereas Santa Rosa is at the base of the Upper Triassic section; (3) very little Dockum mudrock was deposited in lakes; and (4) Dockum rivers flowed almost exclusively to the north, northwest, and west, so there was no closed depositional basin in west Texas during the Late Triassic.

  11. Atmospheric bridge on orbital time scales

    NASA Astrophysics Data System (ADS)

    Lohmann, Gerrit

    2016-01-01

    Large-scale atmospheric patterns are examined on orbital timescales using a climate model which explicitly resolves the atmosphere-ocean-sea ice dynamics. It is shown that, in contrast to boreal summer where the climate mainly follows the local radiative forcing, the boreal winter climate is strongly determined by modulation of circulation modes linked to the Arctic Oscillation/North Atlantic Oscillation (AO/NAO) and the Northern/Southern Annular Modes. We find that during a positive phase of the AO/NAO the convection in the tropical Pacific is below normal. The related atmospheric circulation provides an atmospheric bridge for the precessional forcing inducing a non-uniform temperature anomalies with large amplitudes over the continents. We argue that this is important for mechanisms responsible for multi-millennial climate variability and glacial inception.

  12. Scaling of events spaced in time.

    PubMed

    Fetterman, J G; Stubbs, D A; Dreyfus, L R

    1986-06-01

    Pigeons were trained to peck on a key, which could be lit by red or green light, and produce feeder-light stimuli intermittently. On some trials, food followed the fourth feeder flash providing the key color was red, while on other trials food followed the sixteenth flash providing the color was green. The change in color from red to green was produced by a peck to a second, changeover key. Pigeons typically responded in the presence of red until four or more flashes occured and then, if food had not been delivered, changed the main-key color and responded on the green key. Following training, the variable-interval schedule arranging-feeder light events was changed to longer and shorter values to alter the amount of time (and number of responses) between events. Data from these test days indicate that the change from red to green was influenced by the number of events, but also by the time elapsed and/or responses emitted since the onset of a trial. The results suggest multiple sources of related information and stimulus control when events and behavior occur over time. PMID:24924863

  13. Probing Photosynthesis on a Picosecond Time Scale

    PubMed Central

    Seibert, Michael; Alfano, Robert R.

    1974-01-01

    Fluorescent emission kinetics of isolated spinach chloroplasts have been observed at room temperature with an instrument resolution time of 10 ps using a frequency doubled, mode-locked Nd:glass laser and an optical Kerr gate. At 685 nm two maxima are apparent in the time dependency of the fluorescence; the first occurs at 15 ps and the second at 90 ps after the flash. The intervening minimum occurs at about 50 ps. On the basis of theoretical models, lifetimes of the components associated with the two peaks and spectra (in escarole chloroplasts), the fluorescence associated with the first peak is interpreted as originating from Photosystem I (PSI) (risetime ?10 ps, lifetime ?10 ps) and the second peak from Photosystem II (PSII) (lifetime, 210 ps in spinach chloroplasts and 320 ps in escarole chloroplasts). The fact that there are two fluorescing components with a quantum yield ratio ?0.048 explains the previous discrepancy between the quantum yield of fluorescence measured in chloroplasts directly and that calculated from the lifetime of PSII. The 90 ps delay in the peak of PSII fluorescence is probably explained by energy transfer between accessory pigments such as carotenoids and Chl a. Energy spillover between PSI and PSII is not apparent during the time of observation. The results of this work support the view that the transfer of excitation energy to the trap complex in both photosystems occurs by means of a molecular excitation mechanism of intermediate coupling strength. Although triplet states are not of major importance in energy transfer to PSII traps, the possibility that they are involved in PSI photochemistry has not been eliminated. PMID:4830466

  14. Slow-time acceleration for modeling multiple-time-scale problems

    NASA Astrophysics Data System (ADS)

    Haselbacher, A.; Najjar, F. M.; Massa, L.; Moser, R. D.

    2010-01-01

    The numerical simulation of a system exhibiting a broad range of time scales can be very expensive because the time discretization will in general need to resolve the smallest time scale, and the simulation will have to extend over many times the longest time scale. However, it is common that not all the time scales are of interest for a particular problem. When the long time scales are of primary interest, a number of techniques are available to eliminate the unwanted short time scales from consideration. When the short time scales are of primary interest, a technique for mitigating the consequences of anomalously long time scales is needed. The "slow-time acceleration" technique presented here has been developed to address this problem. In the slow-time acceleration technique, a modified evolution equation is developed in which the longest time scale is much shorter than that of the original system, and which has the same multi-time scale asymptotic structure as the original system. As an example, this approach is applied to the numerical simulation of solid-propellant rockets in which the long time scale is associated with the regression of the burning propellant.

  15. Triassic 40Ar/39Ar ages from the Sakaigawa unit, Kii Peninsula, Japan: implications for possible merger of the Central Asian Orogenic Belt with large-scale tectonic systems of the East Asian margin

    NASA Astrophysics Data System (ADS)

    de Jong, Koen; Kurimoto, Chikao; Ruffet, Gilles

    2009-09-01

    The 218.4 0.4, 228.8 0.9 and 231.9 0.7 Ma 40Ar/39Ar laser probe pseudo-plateau ages (2?; 49-63% 39Ar-release) of very low-grade meta-pelitic whole-rocks from the Sakaigawa unit date high-P/T metamorphism. We argue that this event occurred in a subduction-accretion complex, not along the East Asian continental margin, but on the Pacific side of the proto-Japan superterrane. Proto-Japan was a Permian magmatic arc, presently dispersed in the Japanese islands, which also contained older subduction-accretion complexes. The arc system was fringing but not yet part of the Eurasian continent. The Middle to Late Triassic high-P/T tectono-metamorphic event was partly coeval with proto-Japans collision with proto-Eurasia along the southward extension of the Central Asian Orogenic Belt, causing the main metamorphism in the Hida-Oki terrane. It is possible that this system continued via the Cathaysia block (China) to Indochina. The Late Permian to Middle Triassic Indosinian event might stem from docking of Pacific-derived terranes with Southeast Asias continental margin. The concept of the proto-Japan superterrane implies that the Qinling-Dabie-Sulu suture zone joined the Central Asian Orogenic Belt to the east of the North China craton and did not continue to Japan, as commonly assumed.

  16. Early Triassic marine biotic recovery: the predators' perspective.

    PubMed

    Scheyer, Torsten M; Romano, Carlo; Jenks, Jim; Bucher, Hugo

    2014-01-01

    Examining the geological past of our planet allows us to study periods of severe climatic and biological crises and recoveries, biotic and abiotic ecosystem fluctuations, and faunal and floral turnovers through time. Furthermore, the recovery dynamics of large predators provide a key for evaluation of the pattern and tempo of ecosystem recovery because predators are interpreted to react most sensitively to environmental turbulences. The end-Permian mass extinction was the most severe crisis experienced by life on Earth, and the common paradigm persists that the biotic recovery from the extinction event was unusually slow and occurred in a step-wise manner, lasting up to eight to nine million years well into the early Middle Triassic (Anisian) in the oceans, and even longer in the terrestrial realm. Here we survey the global distribution and size spectra of Early Triassic and Anisian marine predatory vertebrates (fishes, amphibians and reptiles) to elucidate the height of trophic pyramids in the aftermath of the end-Permian event. The survey of body size was done by compiling maximum standard lengths for the bony fishes and some cartilaginous fishes, and total size (estimates) for the tetrapods. The distribution and size spectra of the latter are difficult to assess because of preservation artifacts and are thus mostly discussed qualitatively. The data nevertheless demonstrate that no significant size increase of predators is observable from the Early Triassic to the Anisian, as would be expected from the prolonged and stepwise trophic recovery model. The data further indicate that marine ecosystems characterized by multiple trophic levels existed from the earliest Early Triassic onwards. However, a major change in the taxonomic composition of predatory guilds occurred less than two million years after the end-Permian extinction event, in which a transition from fish/amphibian to fish/reptile-dominated higher trophic levels within ecosystems became apparent. PMID:24647136

  17. Early Triassic Marine Biotic Recovery: The Predators' Perspective

    PubMed Central

    Scheyer, Torsten M.; Romano, Carlo; Jenks, Jim; Bucher, Hugo

    2014-01-01

    Examining the geological past of our planet allows us to study periods of severe climatic and biological crises and recoveries, biotic and abiotic ecosystem fluctuations, and faunal and floral turnovers through time. Furthermore, the recovery dynamics of large predators provide a key for evaluation of the pattern and tempo of ecosystem recovery because predators are interpreted to react most sensitively to environmental turbulences. The end-Permian mass extinction was the most severe crisis experienced by life on Earth, and the common paradigm persists that the biotic recovery from the extinction event was unusually slow and occurred in a step-wise manner, lasting up to eight to nine million years well into the early Middle Triassic (Anisian) in the oceans, and even longer in the terrestrial realm. Here we survey the global distribution and size spectra of Early Triassic and Anisian marine predatory vertebrates (fishes, amphibians and reptiles) to elucidate the height of trophic pyramids in the aftermath of the end-Permian event. The survey of body size was done by compiling maximum standard lengths for the bony fishes and some cartilaginous fishes, and total size (estimates) for the tetrapods. The distribution and size spectra of the latter are difficult to assess because of preservation artifacts and are thus mostly discussed qualitatively. The data nevertheless demonstrate that no significant size increase of predators is observable from the Early Triassic to the Anisian, as would be expected from the prolonged and stepwise trophic recovery model. The data further indicate that marine ecosystems characterized by multiple trophic levels existed from the earliest Early Triassic onwards. However, a major change in the taxonomic composition of predatory guilds occurred less than two million years after the end-Permian extinction event, in which a transition from fish/amphibian to fish/reptile-dominated higher trophic levels within ecosystems became apparent. PMID:24647136

  18. Osmium isotope evidence for a large Late Triassic impact event

    PubMed Central

    Sato, Honami; Onoue, Tetsuji; Nozaki, Tatsuo; Suzuki, Katsuhiko

    2013-01-01

    Anomalously high platinum group element concentrations have previously been reported for Upper Triassic deep-sea sediments, which are interpreted to be derived from an extraterrestrial impact event. Here we report the osmium (Os) isotope fingerprint of an extraterrestrial impact from Upper Triassic chert successions in Japan. Os isotope data exhibit a marked negative excursion from an initial Os isotope ratio (187Os/188Osi) of ∼0.477 to unradiogenic values of ∼0.126 in a platinum group element-enriched claystone layer, indicating the input of meteorite-derived Os into the sediments. The timing of the Os isotope excursion coincides with both elevated Os concentrations and low Re/Os ratios. The magnitude of this negative Os isotope excursion is comparable to those found at Cretaceous–Paleogene boundary sites. These geochemical lines of evidence demonstrate that a large impactor (3.3–7.8 km in diameter) produced a global decrease in seawater 187Os/188Os ratios in the Late Triassic. PMID:24036603

  19. Osmium isotope evidence for a large Late Triassic impact event.

    PubMed

    Sato, Honami; Onoue, Tetsuji; Nozaki, Tatsuo; Suzuki, Katsuhiko

    2013-01-01

    Anomalously high platinum group element concentrations have previously been reported for Upper Triassic deep-sea sediments, which are interpreted to be derived from an extraterrestrial impact event. Here we report the osmium (Os) isotope fingerprint of an extraterrestrial impact from Upper Triassic chert successions in Japan. Os isotope data exhibit a marked negative excursion from an initial Os isotope ratio ((187)Os/(188)Osi) of ~0.477 to unradiogenic values of ~0.126 in a platinum group element-enriched claystone layer, indicating the input of meteorite-derived Os into the sediments. The timing of the Os isotope excursion coincides with both elevated Os concentrations and low Re/Os ratios. The magnitude of this negative Os isotope excursion is comparable to those found at Cretaceous-Paleogene boundary sites. These geochemical lines of evidence demonstrate that a large impactor (3.3-7.8?km in diameter) produced a global decrease in seawater (187)Os/(188)Os ratios in the Late Triassic. PMID:24036603

  20. Singular perturbation and time scale approaches in discrete control systems

    NASA Technical Reports Server (NTRS)

    Naidu, D. S.; Price, D. B.

    1988-01-01

    After considering a singularly perturbed discrete control system, a singular perturbation approach is used to obtain outer and correction subsystems. A time scale approach is then applied via block diagonalization transformations to decouple the system into slow and fast subsystems. To a zeroth-order approximation, the singular perturbation and time-scale approaches are found to yield equivalent results.

  1. Time Scales for Achieving Astronomical Consensus

    NASA Astrophysics Data System (ADS)

    Trimble, Virginia

    The history of science can be recounted in many ways: by addressing the work of one person or school; by starting with the ancients and working chronologically up to the present; by focusing on a particular century; or by tracing a particular important idea as far back and forward as it can be found. The present discussion does none of these. Rather, it adopts the ordering of a standard introductory astronomy textbook, from the solar system via stars and galaxies, to the universe as a whole, and in each regime picks out a few issues that were controversial or wrongly decided for a long time. For each, I attempt to identify a duration of the period of uncertainty or error and some of the causes of the confusion. This is surely not an original idea, though I am not aware of having encountered it elsewhere, and it is not one that is likely to appeal to most 21st century historians of science, for whom the question "Who first got it right?" is not necessarily an important, or even appropriate, one. Some of the stories have been told as historical introductions to conferences and are here summarized and brought up to date. Others I had not previously addressed.

  2. Tetrapod localities from the Triassic of the SE of European Russia

    NASA Astrophysics Data System (ADS)

    Tverdokhlebov, Valentin P.; Tverdokhlebova, Galina I.; Surkov, Mikhail V.; Benton, Michael J.

    2003-01-01

    Fossil tetrapods (amphibians and reptiles) have been discovered at 206 localities in the Lower and Middle Triassic of the southern Urals area of European Russia. The first sites were found in the 1940s, and subsequent surveys, from the 1960s to the present day, have revealed many more. Broad-scale stratigraphic schemes have been published, but full documentation of the rich tetrapod faunas has not been presented before. The area of richest deposits covers some 900,000 km 2 of territory between Samara on the River Volga in the NW, and Orenburg and Sakmara in the SW. Continental sedimentary deposits, consisting of mudstones, siltstones, sandstones, and conglomerates deposited by rivers flowing off the Ural Mountain chain, span much of the Lower and Middle Triassic (Induan, Olenekian, Anisian, Ladinian). The succession is divided into seven successive svitas, or assemblages: Kopanskaya (Induan), Staritskaya, Kzylsaiskaya, Gostevskaya, and Petropavlovskaya (all Olenekian), Donguz (Anisian), and Bukobay (Ladinian). This succession, comprising up to 3.5 km of fluvial and lacustrine sediments, documents major climatic changes. At the beginning of the Early Triassic, arid-zone facies were widely developed, aeolian, piedmont and proluvium. These were replaced by fluvial facies, with some features indicating aridity. At the end of the Middle Triassic, deltaic and lacustrine-marsh formations were dominant, indicating more humid conditions. The succession of Early to Mid Triassic tetrapod faunas documents the recovery of life after the end-Permian mass extinction. The earliest faunas consist only of small, aquatic tetrapods, in low-diversity, low-abundance assemblages. Climbing the succession through the Early Triassic, more terrestrially adapted tetrapods appear, and larger herbivorous and carnivorous reptiles come to dominate in the Mid Triassic as ecosystems were rebuilt.

  3. A reappraisal of the Middle Triassic chirotheriid Chirotherium ibericus Navás, 1906 (Iberian Range NE Spain), with comments on the Triassic tetrapod track biochronology of the Iberian Peninsula

    PubMed Central

    Castanera, Diego; Gasca, José Manuel; Canudo, José Ignacio

    2015-01-01

    Triassic vertebrate tracks are known from the beginning of the 19th century and have a worldwide distribution. Several Triassic track ichnoassemblages and ichnotaxa have a restricted stratigraphic range and are useful in biochronology and biostratigraphy. The record of Triassic tracks in the Iberian Peninsula has gone almost unnoticed although more than 25 localities have been described since 1897. In one of these localities, the naturalist Longinos Navás described the ichnotaxon Chirotherium ibericus in 1906.The vertebrate tracks are in two sandy slabs from the Anisian (Middle Triassic) of the Moncayo massif (Zaragoza, Spain). In a recent revision, new, previously undescribed vertebrate tracks have been identified. The tracks considered to be C. ibericus as well as other tracks with the same morphology from both slabs have been classified as Chirotherium barthii. The rest of the tracks have been assigned to Chirotheriidae indet., Rhynchosauroides isp. and undetermined material. This new identification of C. barthii at the Navás site adds new data to the Iberian record of this ichnotaxon, which is characterized by the small size of the tracks when compared with the main occurrences of this ichnotaxon elsewhere. As at the Navás tracksite, the Anisian C. barthii-Rhynchosauroides ichnoassemblage has been found in other coeval localities in Iberia and worldwide. This ichnoassemblage belongs to the upper Olenekian-lower Anisian interval according to previous biochronological proposals. Analysis of the Triassic Iberian record of tetrapod tracks is uneven in terms of abundance over time. From the earliest Triassic to the latest Lower Triassic the record is very scarce, with Rhynchosauroides being the only known ichnotaxon. Rhynchosauroides covers a wide temporal range and gives poor information for biochronology. The record from the uppermost Lower Triassic to the Middle Triassic is abundant. The highest ichnodiversity has been reported for the Anisian with an assemblage composed of Dicynodontipus, Procolophonichnium, Rhynchosauroides, Rotodactylus, Chirotherium, Isochirotherium, Coelurosaurichnus and Paratrisauropus. The Iberian track record from the Anisian is coherent with the global biochronology proposed for Triassic tetrapod tracks. Nevertheless, the scarcity of track occurrences during the late Olenekian and Ladinian prevents analysis of the corresponding biochrons. Finally, although the Iberian record for the Upper Triassic is not abundant, the presence of Eubrontes, Anchisauripus and probably Brachychirotherium is coherent with the global track biochronology as well. Thus, the Triassic track record in the Iberian Peninsula matches the expected record for this age on the basis of a global biochronological approach, supporting the idea that vertebrate Triassic tracks are a useful tool in biochronology. PMID:26137425

  4. Milankovitch and sub-Milankovitch cycles of the Early Triassic Daye Formation, South China and their geochronological and paleoclimatic implications

    NASA Astrophysics Data System (ADS)

    Wu, H.; Zhang, S.; Feng, Q.; Jiang, G.; Li, H.; Yang, T.

    2011-12-01

    The most profound mass extinction in the Phanerozoic occurred at the end of the Permian, with global loss of nearly 90% of marine invertebrate species and 70% of terrestrial vertebrate genera. Recent studies suggested that volcanisms represented by the Siberian Trap were most likely cause of the end-Permian extinction. The post-extinction periods in the Early Triassic was characterized by low biodiversity, reduced abundance and size of invertebrates, hiatus in coal deposition, anomalously high sediment fluxes, and large perturbations of the carbon cycle, which have been interpreted as the consequence of persistently unfavorable environmental conditions. However, the time framework for the Early Triassic geological, biological and geochemical events is traditionally established by conodont biostratigraphy, but the absolute duration of condont biozones are not well constrained. In this study, a rock magnetic cyclostratigraphy, based on high-resolution analysis (2440 samples) of magnetic susceptibility (MS) and anhysteretic remanent magnetization (ARM) intensity variations, was developed for the 55.1-m-thick, Early Triassic Daye Formation at the Daxiakou section, Hubei province in South China. The Daye Formation shows exceptionally well-preserved lithological cycles with alternations of thin-bedded mudstone, marl and limestone, which are closely tracked by the MS and ARM variations. Power spectral, wavelet and amplitude modulation (AM) analysis of the ARM and MS series reveal strong evidence for the presence of Milankovitch to sub-Milankovitch frequencies dominated by precession index signal and 4-5 ka cycles. Cycles expressed by variations in MS and ARM were likely controlled by the input of fine-grained detrital magnetite, which in turn may be driven by astronomically induced changes in monsoon intensity in the equatorial eastern Tethys during the Early Triassic greenhouse period. On the basis of the 100-ka tuning results, the astronomically constrained duration of the Induan stage is 1.162 Ma, with the Griesbachian and Dienerian substage of 491ka and 671 ka, respectively. The new astronomical time scale also provides time constraints for the conodont and bivalve biozones, the carbonate carbon isotope (δ13C) records and magnetic polarity zones of the Lower Triassic Daye Formation. Time constraints for the conodont biozones include 34 ka for Hindeodus parvus , 24 ka for Isarcicella stachei-I. isarcica, 367 ka for Neogondolella planate-Ng. carinata, 66 ka for Neogondolella discreta, 255 ka for Neospathodus kummeli and 416 ka for Neospathodus dieneri. The Early Smithian negative δ13C shift near the Indun/Olenekian boundary may have happened within 430 ka. Global comparison indicates that Milankovitch and 4-5 ka sub-Milankovitch forcing depositional rhythms may have been common in tropical and sub-tropical carbonate platforms during Early and Middle Triassic time. The ultimate control on the 4-5 ka cycles may have been millennial-scale fluctuations in solar insolation.

  5. Allometric scaling and maximum efficiency in physiological eigen time

    PubMed Central

    Andresen, Bjarne; Shiner, J. S.; Uehlinger, Dominik E.

    2002-01-01

    General optimization results from physics indicate that maximum efficiency of a process, in the sense of minimum overall entropy production, is achieved when the rate of entropy production is constant over time, however not in ordinary clock time but on an, in general varying, eigen time scale, intrinsic to the system. We identify the eigen time of a biological system with physiological time, which generally scales with the 1/4 power of body mass, M1/4, over a vast range of species. Since it is equally well established that metabolic rate scales as M3/4, it follows that organisms produce entropy at the same intrinsic rate, fulfilling a necessary condition for maximum efficiency, and are all, furthermore, equally efficient on the physiological eigen time scale. PMID:11959910

  6. Permo-Triassic vertebrate extinctions: A program

    NASA Technical Reports Server (NTRS)

    Olson, E. C.

    1988-01-01

    Since the time of the Authors' study on this subject, a great deal of new information has become available. Concepts of the nature of extinctions have changed materially. The Authors' conclusion that a catastrophic event was not responsible for the extinction of vertebrates has modified to the extent that hypotheses involving either the impact of a massive extra-terrestrial body or volcanism provide plausible but not currently fully testable hypotheses. Stated changes resulted in a rapid decrease in organic diversity, as the ratio of origins of taxa to extinctions shifted from strongly positive to negative, with momentary equilibrium being reached at about the Permo-Triassic boundary. The proximate causes of the changes in the terrestrial biota appear to lie in two primary factors: (1) strong climatic changes (global mean temperatures, temperature ranges, humidity) and (2) susceptibility of the dominant vertebrates (large dicynodonts) and the glossopteris flora to disruption of the equlibrium of the world ecosystem. The following proximate causes have been proposed: (1) rhythmic fluctuations in solar radiation, (2) tectonic events as Pangea assembled, altering land-ocean relationships, patterns of wind and water circulation and continental physiography, (3) volcanism, and (4) changes subsequent to impacts of one or more massive extra terrestrial objects, bodies or comets. These hypotheses are discussed.

  7. Permo-Triassic tectonism in volcanic arc sequences of the western U.S. Cordillera and implications for the Sonoma orogeny

    NASA Astrophysics Data System (ADS)

    Wyld, Sandra J.

    1991-10-01

    The Permo-Triassic Sonoma orogeny, western U.S. Cordillera, involved tight folding and imbricate thrust faulting of basinal strata of the Golconda allochthon. This event is generally interpreted in terms of accretion of upper Paleozoic volcanic arc rocks of the western U.S. Cordillera ("McCloud arc") to the North American continent, either via back arc basin closure or arc-continent collision. The structural history of the McCloud arc during the Sonoma orogeny is poorly understood, however, as are the implications of this history for tectonic models. This paper presents a synthesis of the Permian to Triassic stratigraphic and structural evolution of the McCloud arc, incorporating new data from the Pine Forest Range, northwest Nevada. The synthesis indicates that, on a regional scale, the arc was affected by widespread uplift but only local tilting, folding and faulting in the Late Permian to Early Triassic. The timing of Permo-Triassic tectonic activity in the McCloud arc is thus similar to the middle Permian to Early Triassic age of deformation in the Golconda allochthon but the structures produced in the two groups of rocks differ markedly. The significance of this contrasting structural response to Sonoma age tectonism can be evaluated by comparison with other better understood examples of arc-continent accretion (back arc basin closure in the southern Andes, "compressional" arc-continent collision in New Guinea and "extensional" arc-continent collision in the Mediterranean). This comparison indicates that the contrasting structural history of the McCloud arc and Golconda allochthon is entirely compatible with an arc-continent accretion model for the Sonoma orogeny and cannot be used as a basis for concluding that the McCloud arc was not involved in the orogenic event. The comparison further indicates that either back arc basin closure or "compressional" arc-continent collision are the most likely settings for the Sonoma orogeny. In contrast, an "extensional" Mediterranean-style arc-continent collision, as has been recently proposed for the earlier (middle Paleozoic) Antler orogeny, is probably not an appropriate analogue for the Sonoma orogeny. The weak structural response of the McCloud arc during Sonoman compression also provides new constraints on the specific processes involved in arc accretion, either via arc-continent collision or back arc basin closure. These constraints suggest that there may be few fundamental differences between the two models during the final stages of arc accretion. Regardless of tectonic setting, Permo-Triassic uplift and associated deformation in the McCloud arc should be considered as much a response to the Sonoma orogeny as is tight folding and imbricate faulting in the Golconda allochthon.

  8. Corrected Late Triassic latitudes for continents adjacent to the North Atlantic.

    PubMed

    Kent, Dennis V; Tauxe, Lisa

    2005-01-14

    We use a method based on a statistical geomagnetic field model to recognize and correct for inclination error in sedimentary rocks from early Mesozoic rift basins in North America, Greenland, and Europe. The congruence of the corrected sedimentary results and independent data from igneous rocks on a regional scale indicates that a geocentric axial dipole field operated in the Late Triassic. The corrected paleolatitudes indicate a faster poleward drift of approximately 0.6 degrees per million years for this part of Pangea and suggest that the equatorial humid belt in the Late Triassic was about as wide as it is today. PMID:15653500

  9. Biogeography of Triassic tetrapods: evidence for provincialism and driven sympatric cladogenesis in the early evolution of modern tetrapod lineages.

    PubMed

    Ezcurra, Martin D

    2010-08-22

    Triassic tetrapods are of key importance in understanding their evolutionary history, because several tetrapod clades, including most of their modern lineages, first appeared or experienced their initial evolutionary radiation during this Period. In order to test previous palaeobiogeographical hypotheses of Triassic tetrapod faunas, tree reconciliation analyses (TRA) were performed with the aim of recovering biogeographical patterns based on phylogenetic signals provided by a composite tree of Middle and Late Triassic tetrapods. The TRA found significant evidence for the presence of different palaeobiogeographical patterns during the analysed time spans. First, a Pangaean distribution is observed during the Middle Triassic, in which several cosmopolitan tetrapod groups are found. During the early Late Triassic a strongly palaeolatitudinally influenced pattern is recovered, with some tetrapod lineages restricted to palaeolatitudinal belts. During the latest Triassic, Gondwanan territories were more closely related to each other than to Laurasian ones, with a distinct tetrapod fauna at low palaeolatitudes. Finally, more than 75 per cent of the cladogenetic events recorded in the tetrapod phylogeny occurred as sympatric splits or within-area vicariance, indicating that evolutionary processes at the regional level were the main drivers in the radiation of Middle and Late Triassic tetrapods and the early evolution of several modern tetrapod lineages. PMID:20392730

  10. Multiple Time Scale Complexity Analysis of Resting State FMRI

    PubMed Central

    Smith, Robert X.; Yan, Lirong; Wang, Danny J.J.

    2014-01-01

    The present study explored multi-scale entropy (MSE) analysis to investigate the entropy of resting state fMRI signals across multiple time scales. MSE analysis was developed to distinguish random noise from complex signals since the entropy of the former decreases with longer time scales while the latter signal maintains its entropy due to a self-resemblance” across time scales. A long resting state BOLD fMRI (rs-fMRI) scan with 1000 data points was performed on five healthy young volunteers to investigate the spatial and temporal characteristics of entropy across multiple time scales. A shorter rs-fMRI scan with 240 data points was performed on a cohort of subjects consisting of healthy young (age 23±2 years, n=8) and aged volunteers (age 66±3 years, n=8) to investigate the effect of healthy aging on the entropy of rs-fMRI. The results showed that MSE of gray matter, rather than white matter, resembles closely that of f−1 noise over multiple time scales. By filtering out high frequency random fluctuations, MSE analysis is able to reveal enhanced contrast in entropy between gray and white matter, as well as between age groups at longer time scales. Our data support the use of MSE analysis as a validation metric for quantifying the complexity of rs-fMRI signals. PMID:24242271

  11. Liquidity Spillover in International Stock Markets through Distinct Time Scales

    PubMed Central

    Righi, Marcelo Brutti; Vieira, Kelmara Mendes

    2014-01-01

    This paper identifies liquidity spillovers through different time scales based on a wavelet multiscaling method. We decompose daily data from U.S., British, Brazilian and Hong Kong stock markets indices in order to calculate the scale correlation between their illiquidities. The sample is divided in order to consider non-crisis, sub-prime crisis and Eurozone crisis. We find that there are changes in correlations of distinct scales and different periods. Association in finest scales is smaller than in coarse scales. There is a rise on associations in periods of crisis. In frequencies, there is predominance for significant distinctions involving the coarsest scale, while for crises periods there is predominance for distinctions on the finest scale. PMID:24465918

  12. Death in Guizhou Late Triassic drowning of the Yangtze carbonate platform

    NASA Astrophysics Data System (ADS)

    Enos, Paul; Wei Jiayong; Lehrmann, Daniel J.

    1998-06-01

    The Yangtze platform in south China formed a stable palaeogeographic element from the Late Proterozoic to the end of the Middle Triassic with deposition of shallow-water carbonates during much of this time. A portion of the Yangtze platform in south-central Guizhou drowned at the transition from Permian to Triassic, as the south-adjacent Nanpanjiang basin encroached about 100 km northward, but a new, stable platform margin was established that persisted through the Early and Middle Triassic. This long history as a stable carbonate platform ended at the transition from the Ladinian to the Carnian. The latest Ladinian rocks, the Yangliujing Formation, are 490 m of shoaling-upward carbonate cycles of grapestone and bioclastic grainstone, fenestral limestone, and stromatolitic dolomudstone, commonly overprinted by extensive subaerial diagenesis. The beginning of the Carnian is marked by a rapid transition to medium-dark-grey, nodular lime mudstones containing ammonoids, conodonts and thin-shelled bivalves, the Zhuganpo Formation. The upper part of this thin pelagic limestone contains many muddy intraclasts, some slightly bored and encrusted, indicating incipient cementation. The overlying Wayao Formation is a condensed black shale with thin interbeds of dark-grey, manganiferous lime mudstone near the base. Ammonoids, conodonts, thin-shelled bivalves, and articulated crinoid stems are abundant. Fine-grained greywacke with sole marks forms prominent bundles within grey, calcareous shale in the overlying Laishike Formation. Ammonoids and thin-shelled bivalves occur sporadically in this 810-m-thick unit. Calcareous shale with thicker-shelled bivalves and packages of cleaner, coarser-grained sandstone characterize the Banan Formation, 460 m thick. The sandstone units generally coarsen and thicken upward, with ripples, medium-scale trough cross-beds, and rare U-tube burrows. Quartzose, coal-bearing siliciclastics 690 m thick form the overlying Huobachong Formation. Thick-bedded, cross-stratified sandstone and conglomerates are amalgamated into thinning- and fining-upward intervals separated by blocky mudstones. This fining-upward motif continues into the overlying Erqiao Formation, but coals are lacking. At the beginning of the Late Triassic (Carnian) the previously stable Yangtze platform, on which peritidal limestones were forming, was drowned and covered by dark lime mud that was cemented into intraclasts and nodular lime mudstone. Black shale and manganiferous pelagic limestone formed a condensed interval, recording maximum submergence. Turbidite sandstone and shale of the Laishike flysch filled the accommodation space of 800 m created during drowning of the Yangtze platform, leading to deposition of shoaling-upward shelf and paralic sandstones and shales, but without significant carbonate production. The succeeding fining-upward siliciclastics are interpreted as braided-stream deposits with coals that mark minor marine incursions. The shallow-shelf and braided-stream deposits form a molasse 1500 m thick. It was apparently derived from the west, in contrast to the underlying flysch where palaeocurrent directions are from the north or northeast. The entire Yangtze platform became emergent during the Late Triassic and was never submerged again. Subtle local differences in the drowning sequences indicate differential subsidence and suggest that tectonics played a role in the death of the Yangtze platform.

  13. Modes and emergent time scales of embayed beach dynamics

    NASA Astrophysics Data System (ADS)

    Ratliff, Katherine M.; Murray, A. Brad

    2014-10-01

    In this study, we use a simple numerical model (the Coastline Evolution Model) to explore alongshore transport-driven shoreline dynamics within generalized embayed beaches (neglecting cross-shore effects). Using principal component analysis (PCA), we identify two primary orthogonal modes of shoreline behavior that describe shoreline variation about its unchanging mean position: the rotation mode, which has been previously identified and describes changes in the mean shoreline orientation, and a newly identified breathing mode, which represents changes in shoreline curvature. Wavelet analysis of the PCA mode time series reveals characteristic time scales of these modes (typically years to decades) that emerge within even a statistically constant white-noise wave climate (without changes in external forcing), suggesting that these time scales can arise from internal system dynamics. The time scales of both modes increase linearly with shoreface depth, suggesting that the embayed beach sediment transport dynamics exhibit a diffusive scaling.

  14. The limit order book on different time scales

    NASA Astrophysics Data System (ADS)

    Eisler, Zoltán; Kertész, János; Lillo, Fabrizio

    2007-06-01

    Financial markets can be described on several time scales. We use data from the limit order book of the London Stock Exchange (LSE) to compare how the fluctuation dominated microstructure crosses over to a more systematic global behavior.

  15. Palaeogeography of Late Triassic red-beds in Singapore and the Indosinian Orogeny

    NASA Astrophysics Data System (ADS)

    Oliver, Grahame; Prave, Anthony

    2013-10-01

    A red-bed facies of the Upper Triassic Jurong Formation has been logged on Sentosa Island, Singapore. An overall coarsening and thickening-upward pattern is well developed. The lower part of the section is dominated by purple-red, massive to finely laminated illite-smectite-kaolin-rich mudstones containing thin, discontinuous lenses of fine sandstone marked by low-angle lamination and small ripples. One dinosaur-like foot print has been discovered in a loose block of red mudstone. It is concluded that this is a lacustrine sequence and it is proposed to name the lake, Lake Sentosa. The upper part of the sequence consists of flat-laminated to trough cross-bedded medium-grained sandstone and granule to cobble conglomerates alternating with purple-red mudstone. The mudstone-sandstone packages are arranged in decametre-scale coarsening-upward cycles. The channelling and decimetre-scale cross-bedding characterising the sandstone and conglomeratic beds is evidence for deposition by flashy fluvial flood processes, possibly feeding into the lake as a fresh water delta. One possible dinosaur trackway in granule size conglomerate has been located. Detrital zircon U-Pb ages vary from 2.7 Ba to 209 Ma with significant populations at 245 Ma and 220 Ma. These ages throw light on the timing of the Indosinian Orogeny. The molasse red-beds of the Jurong Formation were deposited in a half graben formed in the hangingwall of the Bukit Timah Fault when central Peninsular Malaysia went into extension following the climax of the Indosinian Orogeny in the Late Triassic.

  16. Diffusion Time-Scale of Porous Pressure-Sensitive Paint

    NASA Technical Reports Server (NTRS)

    Liu, Tianshu; Teduka, Norikazu; Kameda, Masaharu; Asai, Keisuke

    2001-01-01

    Pressure-sensitive paint (PSP) is an optical pressure sensor that utilizes the oxygen quenching of luminescence. PSP measurements in unsteady aerodynamic flows require fast time response of the paint. There are two characteristic time-scales that are related to the time response of PSP. One is the luminescent lifetime representing an intrinsic physical limit for the achievable temporal resolution of PSP. Another is the time-scale of oxygen diffusion across the PSP layer. When the time-scale of oxygen diffusion is much larger than the luminescent lifetime, the time response of PSP is controlled by oxygen diffusion. In a thin homogenous polymer layer where diffusion is Fickian, the oxygen concentration 1021 can be described by the diffusion equation in one-dimension.

  17. Large Deviations for Two-Time-Scale Diffusions, with Delays

    SciTech Connect

    Kushner, Harold J.

    2010-12-15

    We consider the problem of large deviations for a two-time-scale reflected diffusion process, possibly with delays in the dynamical terms. The Dupuis-Ellis weak convergence approach is used. It is perhaps the most intuitive and simplest for the problems of concern. The results have applications to the problem of approximating optimal controls for two-time-scale systems via use of the averaged equation.

  18. Scale-dependent intrinsic entropies of complex time series.

    PubMed

    Yeh, Jia-Rong; Peng, Chung-Kang; Huang, Norden E

    2016-04-13

    Multi-scale entropy (MSE) was developed as a measure of complexity for complex time series, and it has been applied widely in recent years. The MSE algorithm is based on the assumption that biological systems possess the ability to adapt and function in an ever-changing environment, and these systems need to operate across multiple temporal and spatial scales, such that their complexity is also multi-scale and hierarchical. Here, we present a systematic approach to apply the empirical mode decomposition algorithm, which can detrend time series on various time scales, prior to analysing a signal's complexity by measuring the irregularity of its dynamics on multiple time scales. Simulated time series of fractal Gaussian noise and human heartbeat time series were used to study the performance of this new approach. We show that our method can successfully quantify the fractal properties of the simulated time series and can accurately distinguish modulations in human heartbeat time series in health and disease. PMID:26953181

  19. Two-time-scale inverse problems: formulation and solution

    NASA Astrophysics Data System (ADS)

    Puel, G.; Aubry, D.

    2015-11-01

    The aim here is to study two-time-scale models and their associated parameter identification. When it is possible to consider two well-separated time scales, and when the fast component of the applied loading is periodic, a periodic time homogenization scheme, similar to what exists in space homogenization, can be used to derive a homogenized model. A parameter identification process for this latter is then proposed, consisting in homogenizing with respect to time a classical identification strategy based on the use of adjoint state formulations; it is then applied to an academic example showing the benefits of such a strategy.

  20. Time scales of polymetamorphism from diffusive alteration of garnet growth zoning (Wlz Complex, Eastern Alps)

    NASA Astrophysics Data System (ADS)

    Bestel, M.; Gawronski, T.; Abart, R.

    2009-04-01

    Garnet prophyroblasts in micaschists from the Wlz crystalline complex (Eastern Alps) typically show two distinct growth zones. The first growth zone is of Permian age and forms the garnet cores. The second growth zone is of Cretaceous age and forms the garnet rims. Both growth zones show pronounced compositional zoning. From garnet isopleth geo thermo-barometry garnet growth at temperatures of 550 to 570C and pressures of 400 to 500 MPa is inferred for garnet cores and growth at similar temperatures and pressures of 700 to 800 MPa is inferred for garnet rims. In several samples the primary growth zoning of the garnet cores is modified by late stage diffusive alteration along cracks, around mineral inclusions, and at the interface between the first and second garnet growth zone. Two generations of alteration phenomena are discerned. A first generation of alteration phenomena extends over several 100 m into the pre-existing garnet cores and is ascribed to diffusive exchange with the rock matrix during a long lasting high temperature anneal associated with Permian metamorphism. A second generation of alteration phenomena is restricted to an about 50 m wide zone along the interface between the two garnet growth zones and around mineral inclusion in the second garnet growth zone. These alteration phenomena are ascribed to diffusion controlled exchange between the first and second garnet growth zones and to late stage exchange between garnet and the rock matrix during Eo-Alpine metamorphism in the Cretaceous. Whereas the time scale obtained for the high temperature stage of the Permian event is on the order of 10 Ma, the time scale obtained for the Cretaceous event is only on the order of 0.2 Ma. This reflects the long lived nature of a stage of elevated heat flux and high geothermal gradient associated with an extensional regime in the Austroalpine realm during the Permian and the lower Triassic. The comparatively short duration of the Cretaceous event reflects rapid exhumation of the Austroalpine lower plate subsequent to the intra continental subduction, which was associated with the Eo-Alpine continent-continent collision.

  1. Multi-scale description and prediction of financial time series

    NASA Astrophysics Data System (ADS)

    Nawroth, A. P.; Friedrich, R.; Peinke, J.

    2010-08-01

    A new method is proposed that allows a reconstruction of time series based on higher order multi-scale statistics given by a hierarchical process. This method is able to model financial time series not only on a specific scale but for a range of scales. The method itself is based on the general n-scale joint probability density, which can be extracted directly from given data. It is shown how based on this n-scale statistics, general n-point probabilities can be estimated from which predictions can be achieved. Exemplary results are shown for the German DAX index. The ability to model correctly the behaviour of the original process for different scales simultaneously and in time is demonstrated. As a main result it is shown that this method is able to reproduce the known volatility cluster, although the model contains no explicit time dependence. Thus a new mechanism is shown how, in a stationary multi-scale process, volatility clustering can emerge.

  2. Russian national time scale long-term stability

    NASA Technical Reports Server (NTRS)

    Alshina, A. P.; Gaigerov, B. A.; Koshelyaevsky, N. B.; Pushkin, S. B.

    1994-01-01

    The Institute of Metrology for Time and Space NPO 'VNIIFTRI' generates the National Time Scale (NTS) of Russia -- one of the most stable time scales in the world. Its striking feature is that it is based on a free ensemble of H-masers only. During last two years the estimations of NTS longterm stability based only on H-maser intercomparison data gives a flicker floor of about (2 to 3) x 10(exp -15) for averaging times from 1 day to 1 month. Perhaps the most significant feature for a time laboratory is an extremely low possible frequency drift -- it is too difficult to estimate it reliably. The other estimations, free from possible inside the ensemble correlation phenomena, are available based on the time comparison of NTS relative to the stable enough time scale of outer laboratories. The data on NTS comparison relative to the time scale of secondary time and frequency standards at Golitzino and Irkutsk in Russia and relative to NIST, PTB and USNO using GLONASS and GPS time transfer links gives stability estimations which are close to that based on H-maser intercomparisons.

  3. The Triassic detrital units in the East-Mediterranean realm: back-arcs opening and Cimmerian collision

    NASA Astrophysics Data System (ADS)

    Moix, P.; Stampfli, G. M.

    2009-04-01

    Late Permian and principally Triassic detrital units play an important role in deciphering the geodynamic evolution of the East-Mediterranean area. Some of these units are related to diffuse rifting along the southern margin of Eurasia, whereas others reflect the Cimmerian collision between Gondwana and post-Variscan Eurasia-derived terranes. Several differences within these Triassic detrital units should be noted: they have a different timing of deposition, they are found in autochthonous, para-autochthonous or allochthonous position, and they have different types of substratum and cover series. In addition, the nature of the recycled material is also decisive to make the difference between orogen and rift-related sediments. The investigated sandstones, breccias and conglomerates usually range in age from the Anisian (Scythian?) to the Late Triassic (sometimes Liassic) and are especially well-developed during the Carnian-Norian interval. From the Late Permian to the Late Triassic, the Variscan Cordillera was affected by orogen-scale collapse, leading to widespread rifting, related to slab roll-back of the northward subducting Palaeotethys. This provoked the opening of a series of back-arc basins (i.e. Meliata-Hallstatt, Maliac and Pindos oceans). At the same time, this subduction detached by slab-pull a series of Cimmerian terranes along the northern border of Gondwana and opened the Neotethys to the south of them. The final closure of the Palaeotethys (Cimmerian Event) between the Taurus and the Anatolian terranes produced at places large flysch-molasse deposits often sealed by Jurassic platforms. In southern Europe, the diffuse rifting along the southern margin of Eurasia is recognized in the Carnic Alps. The Carboniferous fore-arc flysch basin (Hochwipfel and Dimon fms) is sealed by a shallow-water sequence of Pennsylvanian-Early Permian age (Pramolo, Rattendorf and Trogkofel groups). The Late Permian rifting is marked by the deposition of the Val Gardena Sandstone and the Bellerophon Fm. This rifting phase is sealed by the Werfen Fm. and the Serla Dolomite. The second phase of rifting is marked by the deposition of the Braies group during the upper Anisian (locally sealed by the latest Anisian-early Carnian Sciliar Dolomite), followed by the deposition of the Buchenstein ("Pietra Verde" pro parte), Wengen (turbiditic sandstones) and San Cassiano Fms until the lower Carnian. This second episode is locally sealed by the Cassian Dolomite and the Val Degano Fm. The third rifting phase is marked by the deposition of the Carnian Dürrenstein Fm, sealed by the late Carnian Raibl Fm. and the Norian Dolomia Principale. On the Turkish transect, the detrital units belonging to the allochthonous series are post-Variscan Anatolian-derived nappes and are often associated with widespread volcanism. They are generally situated at the base of sequences showing shallow marine sedimentation that pass up to pelagic conditions and finish with flysch/wildflysch deposits. The Meliata-Hallstatt "signal" is well-known in the Silická Brezová composite section (Slovakia). The lower to middle Carnian is made of shallow water limestone followed by a rapid subsidence during the lower upper Carnian and the deposition of pelagic limestones, crinoid limestones, calcarenites and micrites themselves followed by Hallstatt Limestones during the entire Norian and lower Rhaetian. The Maliac "signal" is clearly identifiable in the Karaburun Peninsula. The pelagic development made of limestones and radiolarites usually starts during the Spathian above shallow water limestones. The pelagic sedimentation continues during the middle Triassic and the lower Carnian. During the middle Carnian, the sedimentation passes to shallow water limestones and this situation persists during the Upper Triassic and sometimes even higher up. Volcanic events are common in the Spathian and in the Middle Triassic. Late Carnian cherts associated with pillow-lavas of Maliac origin are found on the northern edge of the composite Anatolian-Tauric platform and were assigned to the opening of the Izmir-Ankara Ocean. The Huğlu-Pindos "signal" may be separated into a Pindos "sub-signal" on the Greek transect and a Huğlu "sub-signal" on the Turkish transect. The Pindos "sub-signal" is usually made of shallow water limestone from the Permian up to the Anisian, followed by a rapid deepening during the Middle Carnian, and at places already during the upper Ladinian. Widespread mafic volcanism occurs in the middle to upper Carnian. There are also widespread siliciclastics in the middle Carnian, and in this case the pelagic sediments begin with these siliciclastics or immediately above in the upper Carnian. The sedimentation stays pelagic during the Upper Triassic, persists throughout the Mesozoic and ends with the 2nd Pindos flysch during the Palaeocene/Oligocene. The Huğlu "sub-signal" is similar to the Pindos "sub-signal", but seemingly situated in another position within the Pindos-Huğlu Ocean. This signal is marked by a rapid deepening during the middle Carnian above shallow water limestones. The middle to upper Carnian interval is characterized by the deposition of widespread mafic and intermediate volcanism (Pietra Verde-like green tuffs). The sedimentation stays pelagic during the Upper Triassic (cherty limestones), and passes often to a Liassic Ammonitico Rosso followed by Dogger radiolarian cherts. Then these series were transported southward during a late Cretaceous obduction event. The detrital units belonging to the autochthonous and para-autochthonous series are Gondwana-derived and are often interstratified in platform-type developments ranging locally from the Cambrian to the Miocene. Some of the Triassic units are interpreted to represent the filling of flexural basins (i.e. the Kaşimlar Fm.), and others represent the sedimentation in piggy-back basins (i.e. the Sarpiar Dere Fm.) due to local inversions within the Tauric margin. The Triassic sandstones and conglomerates of the Çayır Fm. are flysch to molasse deposits, but they have been interpreted to be related to flexural uplift and erosion of a rift flank. However, precise analyses and datings of the clasts invalidate clearly this interpretation. Elements from the conglomerates have yielded Upper Carboniferous-Lower Permian pelagic radiolarian cherts, Upper Pennsylvanian Ural-type Fusulinids, Permian pelagic conodonts, Lower, Middle and Upper Permian Fusulinids, Permian and Triassic smaller foraminifers, Lower Triassic pelagic conodonts plus various granites, gneiss, micaschists, quartzites and sandstones. These lithologies are predominantly absent from the Taurus autochthonous, which present a Gondwana-type shallow water development where pelagic strata are never present. Çayır-like sedimentation can be followed over wide areas in Turkey and mark the Eo-Cimmerian unconformity. In addition, conglomerates associated to lower Dogger limestones seal at places Upper Triassic overthrusts, proving de facto a pre-Jurassic tectonic activity due to the Cimmerian collision. These detrital units may be correlated with the Shemshak Formation in the Alborz in Iran where they are clearly associated to the closure of the Palaeotethys and with the base of the Tripolitza Unit known as the Ravdoucha-Tyros beds in Greece. The latter consist of conglomerates, sandstones and violet slates. The elements are polygenic and composed of limestones, sandstones and lydites ranging from Carboniferous to Norian. All these sequences are interpreted as the Eocimmerian flysch-molasse sediments, probably deposited in a foreland basin during a syn- to post-collisional stage between Gondwana and Eurasia-derived terranes.

  4. Resistivity scaling and electron relaxation times in metallic nanowires

    SciTech Connect

    Moors, Kristof; Sorée, Bart; Magnus, Wim; Tőkei, Zsolt

    2014-08-14

    We study the resistivity scaling in nanometer-sized metallic wires due to surface roughness and grain-boundaries, currently the main cause of electron scattering in nanoscaled interconnects. The resistivity has been obtained with the Boltzmann transport equation, adopting the relaxation time approximation of the distribution function and the effective mass approximation for the conducting electrons. The relaxation times are calculated exactly, using Fermi's golden rule, resulting in a correct relaxation time for every sub-band state contributing to the transport. In general, the relaxation time strongly depends on the sub-band state, something that remained unclear with the methods of previous work. The resistivity scaling is obtained for different roughness and grain-boundary properties, showing large differences in scaling behavior and relaxation times. Our model clearly indicates that the resistivity is dominated by grain-boundary scattering, easily surpassing the surface roughness contribution by a factor of 10.

  5. The Inception of the Colorado Plateau Coring Project: Filling the Triassic Geochronologic Gap and Providing a Continuous Record of Continental Environmental Change in Western Equatorial Pangea

    NASA Astrophysics Data System (ADS)

    Geissman, J. W.; Olsen, P. E.; Kent, D. V.; Irmis, R. B.; Gehrels, G. E.; Mundil, R.; Parker, W.; Bachmann, G. H.; Kurschner, W. M.; Sha, J.

    2014-12-01

    The Triassic Period was punctuated by two of the largest Phanerozoic mass-extinctions and witnessed the evolution of elements of the modern biota and the advent of the age of dinosaurs. A rich archive of biotic and environmental changes on land for the early Mesozoic is on the Colorado Plateau, which despite over 100 years of study still remains poorly calibrated in time and poorly registered to other global records. Over 15 years ago, a diverse team of scientists began to develop the concept of a multi-phase, long term Colorado Plateau Coring Project (CPCP). Planning involved two major meetings (DOSECC/NSFICDP supported in Fall, 2007, St. George, UT; and International Continental Drilling Program (ICDP) supported in Spring, 2009, Albuquerque, NM). The National Park Service embraced the concept of Phase One drilling at Petrified Forest National Park (PFNP) in northern Arizona, which exposes one of the most famous and best studied successions of the continental Triassic on Earth, and the Phase One target was decided. Most drilling operation costs were secured from ICDP in Summer, 2010. In late 2013, following more recent NSF support, the research team, utilizing Ruen Drilling Inc., drilled a continuous ~530 m core (60o plunge) through the entire section of Triassic strata (Chinle and Moenkopi fms.) in the north end and a ~240 m core (75o plunge) in lower Chinle and all Moenkopi strata at the south end of the PFNP. Our continuous sampling will place this record in a reliable quantitative and exportable time scale, as a reference section in which magnetostratigraphic, geochronologic, environmental, and paleontologic data are registered to a common thickness scale with unambiguous superposition using pristine samples. The cores are being scanned at the High Resolution X-ray Computed Tomography Facility at UT Austin. They will be transported to the LacCore National Lacustrine Core Facility at U Minnesota, where they will be split, imaged, and scanned for several properties, including XRF data. The core will then be transported to the Rutgers University for sampling. The planning team is contemplating Phase Two options (e.g., the Middle to Lower Triassic marine-influenced section west of the Colorado Plateau (St. George, Utah) area or the Upper Triassic to Lower Jurassic sequence in the Comb Ridge area (Bluff, Utah)).

  6. Triassic actinopterygian fishes: the recovery after the end-Permian crisis.

    PubMed

    Tintori, Andrea; Hitij, Toma; Jiang, Dayong; Lombardo, Cristina; Sun, Zuoyu

    2014-08-01

    In the last 15 years, the discovery of several new actinopterygian fish faunas from the Early and Middle Triassic of the Tethys, cast new light on the timing, speed and range of their recovery after the end-Permian crisis. In addition to several new taxa having been described, the stratigraphical and geographical record of many others have been greatly extended. In fact, most of the new fossiliferous sites are in southern China, thus at the Eastern end of the Tethys, and furthermore a few are somewhat older (Chaohu, Panxian, Luoping) than the major classical Western Tethys sites (Monte San Giorgio). Following these new finds, it is possible to have a better definition of the Triassic recovery stages. Indeed, after a quite short phase till the end of the Smithian (Olenekian, Early Triassic) in which a rather consistent fauna was present all around the Pangea coasts, a major radiation occurred in the Early-Middle Anisian after the new Middle Triassic fish fauna already appeared in the late Early Triassic, thus occuring well before what was previously supposed from the Alps localities. Furthermore, the new assemblages from southern China point to an early broader differentiation among the basal neopterygians rather than in the 'subholosteans', the group that was then dominant in the Western Tethys since the Late Anisian. It stands that during the Norian a new basal neopterygian radiation gave rise to several new branches that dominated the remaining part of the Mesozoic. PMID:24148549

  7. Examination of hypotheses for the Permo-Triassic boundary extinction by carbon cycle modeling.

    PubMed

    Berner, Robert A

    2002-04-01

    The biological extinction that occurred at the Permian-Triassic boundary represents the most extensive loss of species of any known event of the past 550 million years. There have been a wide variety of explanations offered for this extinction. In the present paper, a number of the more popular recent hypotheses are evaluated in terms of predictions that they make, or that they imply, concerning the global carbon cycle. For this purpose, a mass balance model is used that calculates atmospheric CO2 and oceanic delta13C as a function of time. Hypotheses considered include: (i) the release of massive amounts of CO2 from the ocean to the atmosphere resulting in mass poisoning; (ii) the release of large amounts of CO2 from volcanic degassing; (iii) the release of methane stored in methane hydrates; (iv) the decomposition and oxidation of dead organisms to CO2 after sudden mass mortality; and (v) the long-term reorganization of the global carbon cycle. The modeling indicates that measured short-term changes in delta13C at the boundary are best explained by methane release with mass mortality and volcanic degassing contributing in secondary roles. None of the processes result in excessively high levels of atmospheric CO2 if they occurred on time scales of more than about 1,000 years. The idea of poisoning by high levels of atmospheric CO2 depends on the absence of subthermocline calcium carbonate deposition during the latest Permian. The most far-reaching effect was found to be reorganization of the carbon cycle with major sedimentary burial of organic matter shifting from the land to the sea, resulting in less burial overall, decreased atmospheric O2, and higher atmospheric CO2 for the entire Triassic Period. PMID:11917102

  8. Examination of hypotheses for the Permo–Triassic boundary extinction by carbon cycle modeling

    PubMed Central

    Berner, Robert A.

    2002-01-01

    The biological extinction that occurred at the Permian–Triassic boundary represents the most extensive loss of species of any known event of the past 550 million years. There have been a wide variety of explanations offered for this extinction. In the present paper, a number of the more popular recent hypotheses are evaluated in terms of predictions that they make, or that they imply, concerning the global carbon cycle. For this purpose, a mass balance model is used that calculates atmospheric CO2 and oceanic δ13C as a function of time. Hypotheses considered include: (i) the release of massive amounts of CO2 from the ocean to the atmosphere resulting in mass poisoning; (ii) the release of large amounts of CO2 from volcanic degassing; (iii) the release of methane stored in methane hydrates; (iv) the decomposition and oxidation of dead organisms to CO2 after sudden mass mortality; and (v) the long-term reorganization of the global carbon cycle. The modeling indicates that measured short-term changes in δ13C at the boundary are best explained by methane release with mass mortality and volcanic degassing contributing in secondary roles. None of the processes result in excessively high levels of atmospheric CO2 if they occurred on time scales of more than about 1,000 years. The idea of poisoning by high levels of atmospheric CO2 depends on the absence of subthermocline calcium carbonate deposition during the latest Permian. The most far-reaching effect was found to be reorganization of the carbon cycle with major sedimentary burial of organic matter shifting from the land to the sea, resulting in less burial overall, decreased atmospheric O2, and higher atmospheric CO2 for the entire Triassic Period. PMID:11917102

  9. Multiple-time scales analysis of physiological time series under neural control

    NASA Technical Reports Server (NTRS)

    Peng, C. K.; Hausdorff, J. M.; Havlin, S.; Mietus, J. E.; Stanley, H. E.; Goldberger, A. L.

    1998-01-01

    We discuss multiple-time scale properties of neurophysiological control mechanisms, using heart rate and gait regulation as model systems. We find that scaling exponents can be used as prognostic indicators. Furthermore, detection of more subtle degradation of scaling properties may provide a novel early warning system in subjects with a variety of pathologies including those at high risk of sudden death.

  10. Middle Triassic source rocks in north Lombardy

    SciTech Connect

    Gnaccolini, M.; Gaetani, M.; Mattavelli, L.; Leoni, C.; Poliani, G.; Riva, A.

    1988-08-01

    Using molecular geochemistry techniques, we established that the Perledo-Verenna and Meride Formations (Middle Triassic, southern Alps) represent the source rocks of the Gaggiano and Villafortuna deep oil fields discovered 40 km northwest of Milan. To find the geological factors which control the areal extent thickness and organic matter distribution relative to these sequences, a sedimentological and geochemical study was undertaken.

  11. Lystrosaurus zone (triassic) fauna from antarctica.

    PubMed

    Kitching, J W; Collinson, J W; Elliot, D H; Colbert, E H

    1972-02-01

    Tetrapod skeletons recently found in the Fremouw Formation in the Shackleton Glacier area, Transantarctic Mountains, include several forms that closely compare to South African species. Faunal similarities that confirm a close connection between Antarctica and Africa during the Triassic Period lend further support to the concept of Gondwanaland and continental drift. PMID:17755654

  12. Current Status of the Late Triassic and Early Jurassic APTS from Continental Sediments and Correlation with Standard Marine Stages

    NASA Astrophysics Data System (ADS)

    Kent, D. V.; Olsen, P. E.; Muttoni, G.

    2014-12-01

    A reproducible geomagnetic polarity template for the Late Triassic and earliest Jurassic continues to be that determined from ~5,000 meters of cored section in the Newark basin and ~2,500 meters of outcrop section in the Hartford basin, sampled at nominal ~20 kyr intervals according to a well-developed climate cyclicity that characterizes the lacustrine strata present in all but the fluviatile portions of the basins [Kent & Olsen, 1999, 2008 JGR]. The age model is based on the 405 kyr Milankovich climate cycle and pegging the sequence to high precision U-Pb dating of the Central Atlantic Magmatic Province (CAMP) at 201.6 to 200.9 Ma [Blackburn+2013 Science], the initiation of which is practically coincident with the end-Triassic extinction level (formerly set to 202 Ma) and within a climatic precession cycle after magnetochron E23r. The resulting astrochronostratigraphic polarity time scale (APTS) has 66 Poisson-distributed polarity intervals from chrons E8r (~225 Ma) to H27n (~199 Ma) with a constant sediment-accumulation rate extrapolation to chron E1r (~233 Ma). Magnetostratigraphic correlations from the most complete and usually the thickest Tethyan marine sections suggest that the Carnian/Norian boundary occurs within ~E7n [Channell+2003 PPP; Muttoni+2004 GSAB] at an APTS age of 227.5 Ma and for the Norian/Rhaetian boundary anywhere from E16n [Husing+2011 EPSL] at ~210.5 Ma to E20r [Maron+2014 Geology] at ~205.4 Ma depending on choice of conodont taxa, whereas the Hettangian/Sinemurian boundary can be placed at ~199.5 Ma within the marine equivalent of H25r [Husing+2014 EPSL]. These APTS ages are in substantive agreement with available high-precision dates in marine strata for the late Carnian [231 Ma: Furin+2006 Geology], latest Norian [205.5 Ma: Wotslaw+2014 Geology], and the boundaries of the Triassic/Jurassic [201.3 Ma: Guex+2012 PPP] and the Hettangian/Sinemurian [199.5 Ma: Schaltegger+2008 EPSL]. Carnian magnetostratigraphy needs to be improved but attempts to make a composite magnetostratigraphic sequence for the Late Triassic by merging disparate marine and non-marine records have not produced a clearer signal. The Newark-Hartford APTS already provides a framework for long-distance correlation and dating, for example, the timing of dinosaur dispersal across Pangea [Kent+2014 PNAS].

  13. Atomic Time Scales for the 21st Century

    NASA Astrophysics Data System (ADS)

    Arias, E. F.

    2014-06-01

    The International Bureau of Weights and Measures, in coordination with international organizations and national institutes, maintains and disseminates Coordinated Universal Time (UTC). Other timescales exist for different purposes. This article describes the state-of-the-art in the elaboration of these time scales.

  14. The Late Triassic bivalve Monotis in accreted terranes of Alaska

    USGS Publications Warehouse

    Silberling, Norman J.; Grant-Mackie, J. A.; Nichols, K.M.

    1997-01-01

    Late Triassic bivalves of the genus Monotis occur in at least 16 of the lithotectonic terranes and subterranes that together comprise nearly all of Alaska, and they also occur in the Upper Yukon region of Alaska where Triassic strata are regarded as representing non-accretionary North America. On the basis of collections made thus far, 14 kinds of Monotis that differ at the species or subspecies level can be recognized from alaska. These are grouped into the subgenera Monotis (Monotis), M. (Pacimonotis), M. (Entomonotis), and M. (Eomonotis). In places, Monotis shells of one kind or another occur in rock-forming abundance. On the basis of superpositional data from Alaska, as well as from elsewhere in North America and Far Eastern Russia, at least four distince biostratigraphic levels can be discriminated utilizing Monotis species. Different species of M. (Eomonotis) characterize two middle Norian levels, both probably within the supper middle Norian Columbianus Ammonite Zone. Two additional levels are recognized in the lower upper Norian Cordilleranus Ammonite Zone utilizing species of M. (Monotis) or M. (Entomonotis), both of which subgenera are restricted to the late Norian. An attached-floating mode of life is commonly attributed to Monotis; thus, these bivalves would have been pseudoplanktonic surface dwellers that were sensitive to surface-water temperature and paleolatitude. Distinctly different kinds of Monotis occur at different paleolatitudes along the Pacific and Arctic margins of the North American craton inboard of the accreted terranes. Comparison between thse craton-bound Monotis faunas and those of the Alaskan terranes in southern Alaska south of the Denali fault were paleoequatorial in latitude during Late Triassic time. Among these terranes, the Alexander terrane was possibly in the southern hemisphere at that time. Terranes of northern Alaska, on the other hand, represent middle, possibly high-middle, northern paleolatitudes.

  15. Scaling properties in time-varying networks with memory

    NASA Astrophysics Data System (ADS)

    Kim, Hyewon; Ha, Meesoon; Jeong, Hawoong

    2015-12-01

    The formation of network structure is mainly influenced by an individual node's activity and its memory, where activity can usually be interpreted as the individual inherent property and memory can be represented by the interaction strength between nodes. In our study, we define the activity through the appearance pattern in the time-aggregated network representation, and quantify the memory through the contact pattern of empirical temporal networks. To address the role of activity and memory in epidemics on time-varying networks, we propose temporal-pattern coarsening of activity-driven growing networks with memory. In particular, we focus on the relation between time-scale coarsening and spreading dynamics in the context of dynamic scaling and finite-size scaling. Finally, we discuss the universality issue of spreading dynamics on time-varying networks for various memory-causality tests.

  16. Constraints on Early Triassic carbon cycle dynamics from paired organic and inorganic carbon isotope records

    NASA Astrophysics Data System (ADS)

    Meyer, K. M.; Yu, M.; Lehrmann, D.; van de Schootbrugge, B.; Payne, J. L.

    2013-01-01

    Large δ13C excursions, anomalous carbonate precipitates, low diversity assemblages of small fossils, and evidence for marine euxinia in uppermost Permian and Lower Triassic strata bear more similarity to Neoproterozoic carbonates than to the remainders of the Permian and Triassic systems. Middle Triassic diversification of marine ecosystems coincided with the waning of anoxia and stabilization of the global carbon cycle, suggesting that environment-ecosystem linkages were important to biological recovery. However, the Earth system behavior responsible for these large δ13C excursions remains poorly constrained. Here we present a continuous Early Triassic δ13Corg record from south China and use it to test the extent to which Early Triassic excursions in δ13Ccarb record changes in the δ13C of marine dissolved inorganic carbon (DIC). Regression analysis demonstrates a significant positive correlation between δ13Corg and δ13Ccarb across multiple sections that span a paleoenvironmental gradient. Such a correlation is incompatible with diagenetic alteration because no likely mechanism will alter both δ13Corg and δ13Ccarb records in parallel and therefore strongly indicates a primary depositional origin. A simple explanation for this correlation is that a substantial portion of the preserved Corg was derived from the contemporaneous DIC pool, implying that the observed excursions reflect variation in the δ13C of the exogenic carbon reservoir (ocean, atmosphere, biomass). These findings support existing evidence that large δ13C excursions are primary and therefore strengthen the case that large-scale changes to the carbon cycle were mechanistically linked to the low diversity and small size of Early Triassic fossils. Associated sedimentary and biogeochemical phenomena further suggest that similar associations in Neoproterozoic and Cambrian strata may reflect the same underlying controls.

  17. Supraregional seismites in Triassic - Jurassic boundary strata

    NASA Astrophysics Data System (ADS)

    Lindström, Sofie; Pedersen, Gunver K.; van de Schootbrugge, Bas; Johansson, Leif; Petersen, Henrik I.; Dybkjær, Karen; Weibel, Rikke; Hansen, Katrine H.; Erlström, Mikael; Alwmark, Carl; Nielsen, Lars Henrik; Oschmann, Wolfgang; Tegner, Christian

    2014-05-01

    The end-Triassic mass extinction event (201.564 Ma) was synchronous with the earliest volcanic phase during the emplacement of the Central Atlantic Magmatic Province (CAMP), a large igneous province (LIP) formed during the initial breakup of Pangea. Volcanic degassing of CO2 and other volatile gases, and/or thermogenic methane, from the CAMP is generally regarded as the main cause of the end-Triassic biotic crisis. However, discrepancies in the durations of the ETE (50 Kyrs) and the CAMP volcanism (600 Kyrs) as well as temporal offsets between carbon cycle perturbations and biotic turnovers suggest a more complex scenario that require further studies of the temporal succession of events in Triassic-Jurassic (TJ) boundary strata. Here, we present and examine multiple episodes of soft-sediment deformation (seismite) within uppermost Rhaetian marine and terrestrial strata of Denmark, Sweden and Germany. These seismites are stratigraphically constrained by palynology and C-isotopes to the latest Rhaetian, and are synchronous to the single seismite layer from the UK, which similarly predates the T/J boundary, and has been explained by an extraterrestrial bolide impact. Instead, we argue that the multiple episodes of soft-sediment deformation, interbedded by undisturbed strata, were formed from repeated intense earthquake activity restricted to an interval within the latest Rhaetian bracketed by two negative excursions in δ13C and also containing palynological evidence for deforestation and fern proliferation. The fact that these biotic changes coincide with repeated seismic activity has implications for the end-Triassic extinction and the CAMP scenario. We discuss the temporal position of the seismites in regards to other end-Triassic events, and argue that their supraregional distribution in pre-TJ-boundary strata of NW Europe may be linked to intensified earthquake activity during CAMP emplacement, rather than an extraterrestrial impact.

  18. Thermodynamics constrains allometric scaling of optimal development time in insects.

    PubMed

    Dillon, Michael E; Frazier, Melanie R

    2013-01-01

    Development time is a critical life-history trait that has profound effects on organism fitness and on population growth rates. For ectotherms, development time is strongly influenced by temperature and is predicted to scale with body mass to the quarter power based on 1) the ontogenetic growth model of the metabolic theory of ecology which describes a bioenergetic balance between tissue maintenance and growth given the scaling relationship between metabolism and body size, and 2) numerous studies, primarily of vertebrate endotherms, that largely support this prediction. However, few studies have investigated the allometry of development time among invertebrates, including insects. Abundant data on development of diverse insects provides an ideal opportunity to better understand the scaling of development time in this ecologically and economically important group. Insects develop more quickly at warmer temperatures until reaching a minimum development time at some optimal temperature, after which development slows. We evaluated the allometry of insect development time by compiling estimates of minimum development time and optimal developmental temperature for 361 insect species from 16 orders with body mass varying over nearly 6 orders of magnitude. Allometric scaling exponents varied with the statistical approach: standardized major axis regression supported the predicted quarter-power scaling relationship, but ordinary and phylogenetic generalized least squares did not. Regardless of the statistical approach, body size alone explained less than 28% of the variation in development time. Models that also included optimal temperature explained over 50% of the variation in development time. Warm-adapted insects developed more quickly, regardless of body size, supporting the "hotter is better" hypothesis that posits that ectotherms have a limited ability to evolutionarily compensate for the depressing effects of low temperatures on rates of biological processes. The remaining unexplained variation in development time likely reflects additional ecological and evolutionary differences among insect species. PMID:24391935

  19. Thermodynamics Constrains Allometric Scaling of Optimal Development Time in Insects

    PubMed Central

    Dillon, Michael E.; Frazier, Melanie R.

    2013-01-01

    Development time is a critical life-history trait that has profound effects on organism fitness and on population growth rates. For ectotherms, development time is strongly influenced by temperature and is predicted to scale with body mass to the quarter power based on 1) the ontogenetic growth model of the metabolic theory of ecology which describes a bioenergetic balance between tissue maintenance and growth given the scaling relationship between metabolism and body size, and 2) numerous studies, primarily of vertebrate endotherms, that largely support this prediction. However, few studies have investigated the allometry of development time among invertebrates, including insects. Abundant data on development of diverse insects provides an ideal opportunity to better understand the scaling of development time in this ecologically and economically important group. Insects develop more quickly at warmer temperatures until reaching a minimum development time at some optimal temperature, after which development slows. We evaluated the allometry of insect development time by compiling estimates of minimum development time and optimal developmental temperature for 361 insect species from 16 orders with body mass varying over nearly 6 orders of magnitude. Allometric scaling exponents varied with the statistical approach: standardized major axis regression supported the predicted quarter-power scaling relationship, but ordinary and phylogenetic generalized least squares did not. Regardless of the statistical approach, body size alone explained less than 28% of the variation in development time. Models that also included optimal temperature explained over 50% of the variation in development time. Warm-adapted insects developed more quickly, regardless of body size, supporting the “hotter is better” hypothesis that posits that ectotherms have a limited ability to evolutionarily compensate for the depressing effects of low temperatures on rates of biological processes. The remaining unexplained variation in development time likely reflects additional ecological and evolutionary differences among insect species. PMID:24391935

  20. Deviations from uniform power law scaling in nonstationary time series

    NASA Technical Reports Server (NTRS)

    Viswanathan, G. M.; Peng, C. K.; Stanley, H. E.; Goldberger, A. L.

    1997-01-01

    A classic problem in physics is the analysis of highly nonstationary time series that typically exhibit long-range correlations. Here we test the hypothesis that the scaling properties of the dynamics of healthy physiological systems are more stable than those of pathological systems by studying beat-to-beat fluctuations in the human heart rate. We develop techniques based on the Fano factor and Allan factor functions, as well as on detrended fluctuation analysis, for quantifying deviations from uniform power-law scaling in nonstationary time series. By analyzing extremely long data sets of up to N = 10(5) beats for 11 healthy subjects, we find that the fluctuations in the heart rate scale approximately uniformly over several temporal orders of magnitude. By contrast, we find that in data sets of comparable length for 14 subjects with heart disease, the fluctuations grow erratically, indicating a loss of scaling stability.

  1. Common scaling patterns in intertrade times of U. S. stocks.

    PubMed

    Ivanov, Plamen Ch; Yuen, Ainslie; Podobnik, Boris; Lee, Youngki

    2004-05-01

    We analyze the sequence of time intervals between consecutive stock trades of thirty companies representing eight sectors of the U.S. economy over a period of 4 yrs. For all companies we find that: (i) the probability density function of intertrade times may be fit by a Weibull distribution, (ii) when appropriately rescaled the probability densities of all companies collapse onto a single curve implying a universal functional form, (iii) the intertrade times exhibit power-law correlated behavior within a trading day and a consistently greater degree of correlation over larger time scales, in agreement with the correlation behavior of the absolute price returns for the corresponding company, and (iv) the magnitude series of intertrade time increments is characterized by long-range power-law correlations suggesting the presence of nonlinear features in the trading dynamics, while the sign series is anticorrelated at small scales. Our results suggest that independent of industry sector, market capitalization and average level of trading activity, the series of intertrade times exhibit possibly universal scaling patterns, which may relate to a common mechanism underlying the trading dynamics of diverse companies. Further, our observation of long-range power-law correlations and a parallel with the crossover in the scaling of absolute price returns for each individual stock, support the hypothesis that the dynamics of transaction times may play a role in the process of price formation. PMID:15244883

  2. Detrital Zircon Link Between Headwaters and Terminus of the Upper Triassic Chinle-Dockum Paleoriver System

    PubMed

    Riggs; Lehman; Gehrels; Dickinson

    1996-07-01

    New detrital-zircon geochronologic data reveal that a through-going paleoriver connected Texas with Nevada in Late Triassic time. Sandstone from the Upper Triassic Santa Rosa Sandstone (Dockum Group) from northwestern Texas contains a detrital zircon suite nearly identical to that found in western Nevada in the Upper Triassic Osobb Formation (Auld Lang Syne Group, correlative with the Chinle Formation). The Santa Rosa Sandstone was derived in large part from the eroded Cambrian core of the Amarillo-Wichita uplift, as evidenced by abundant zircons with ages of 515 to 525 million years. Other zircon grains in the sandstone are Permian, Devonian, Proterozoic, and Archean in age and, with the exception of the Archean grain, are also matched by the population in the Nevada strata. PMID:8688060

  3. Evidence from ammonoids and conodonts for multiple Early Triassic mass extinctions

    PubMed Central

    Stanley, Steven M.

    2009-01-01

    Ammonoids and conodonts, being characterized by exceptionally high background rates of origination and extinction, were vulnerable to global environmental crises, which characteristically intensified background rates of extinction. Thus, it is not surprising that these taxa suffered conspicuous mass extinctions at the times of three negative Early Triassic global carbon isotopic excursions that resembled those associated with the two preceding Permian mass extinctions. In keeping with their high rates of origination, both the ammonoids and conodonts rediversified dramatically between the Early Triassic crises. Other marine taxa, characterized by much lower intrinsic rates of origination, were held at low levels of diversity by the Early Triassic crises; because global mass extinctions affect all marine life, these taxa must have experienced relatively modest expansions and contractions that have yet to be discovered, because they do not stand out in the fossil record and because the stratigraphic ranges of these taxa, being of little value for temporal correlation, have not been thoroughly studied. PMID:19721005

  4. First report of early Triassic A-type granite and syenite intrusions from Taimyr: product of the northern Eurasian superplume?

    NASA Astrophysics Data System (ADS)

    Vernikovsky, Valery A.; Pease, Victoria L.; Vernikovskaya, Antonina E.; Romanov, Andrey P.; Gee, David G.; Travin, Alexey V.

    2003-01-01

    Ion-microprobe U-Th-Pb analyses of zircon from three high-level syenite-granite stocks in the western part of the Taimyr fold-and-thrust belt have yielded early Triassic ages of 249-241 Ma. Those syenite-granite bodies intrude unmetamorphosed late Paleozoic to early Mesozoic terrigenous and volcanic supracrustal rocks, including the early Triassic Siberian traps. 40Ar- 39Ar isotopic ages of 245-233 Ma correlate well with the ion-microprobe data and define the time of closure for the K-Ar isotopic system. Limited geochemical data for the early Triassic syenite-granite plutons show that they have metaluminous compositions, high potassium, high REE and high LIL concentrations, and 87Sr/ 86Sr and ?Nd ratios intermediate between crust and mantle, suggesting a hybrid mantle-crustal origin. We tentatively suggest that they formed in an anorogenic setting as a result of the Permo-Triassic Euroasian superplume.

  5. The first report of the Late Triassic-Early Jurassic passage beds in the Eastern Tethyan Himalaya

    NASA Astrophysics Data System (ADS)

    Yin, Jiarun; Enay, Raymond; Wan, Xiaoqiao

    1999-07-01

    A good exposure of Triassic-Jurassic strata, named the Germig section in the Lanongla area, south Tibet has been investigated recently. Non-marine conditions of the Upper Triassic represented by the Zhamure formation existed in most of south Tibet, but they terminated in the area by the Germig formation which represents a marine transgression from the Late Norian-Rhaetian to the Early and Middle Hettangian. It is reported for the first time that Triassic-Jurassic passage beds with ammonite evidence have been found in Tethyan Himalaya. The earliest Jurassic faunas exhibit affinity with those of Nevada, implying a trans-Pacific dispersal in the early stage of biotic recovery after the end-Triassic mass extinction.

  6. Growing length and time scales in glass-forming liquids

    PubMed Central

    Karmakar, Smarajit; Dasgupta, Chandan; Sastry, Srikanth

    2009-01-01

    The glass transition, whereby liquids transform into amorphous solids at low temperatures, is a subject of intense research despite decades of investigation. Explaining the enormous increase in relaxation times of a liquid upon supercooling is essential for understanding the glass transition. Although many theories, such as the AdamGibbs theory, have sought to relate growing relaxation times to length scales associated with spatial correlations in liquid structure or motion of molecules, the role of length scales in glassy dynamics is not well established. Recent studies of spatially correlated rearrangements of molecules leading to structural relaxation, termed spatially heterogeneous dynamics, provide fresh impetus in this direction. A powerful approach to extract length scales in critical phenomena is finite-size scaling, wherein a system is studied for sizes traversing the length scales of interest. We perform finite-size scaling for a realistic glass-former, using computer simulations, to evaluate the length scale associated with spatially heterogeneous dynamics, which grows as temperature decreases. However, relaxation times that also grow with decreasing temperature do not exhibit standard finite-size scaling with this length. We show that relaxation times are instead determined, for all studied system sizes and temperatures, by configurational entropy, in accordance with the AdamGibbs relation, but in disagreement with theoretical expectations based on spin-glass models that configurational entropy is not relevant at temperatures substantially above the critical temperature of mode-coupling theory. Our results provide new insights into the dynamics of glass-forming liquids and pose serious challenges to existing theoretical descriptions. PMID:19234111

  7. Observation time scale, free-energy landscapes, and molecular symmetry

    PubMed Central

    Wales, David J.; Salamon, Peter

    2014-01-01

    When structures that interconvert on a given time scale are lumped together, the corresponding free-energy surface becomes a function of the observation time. This view is equivalent to grouping structures that are connected by free-energy barriers below a certain threshold. We illustrate this time dependence for some benchmark systems, namely atomic clusters and alanine dipeptide, highlighting the connections to broken ergodicity, local equilibrium, and “feasible” symmetry operations of the molecular Hamiltonian. PMID:24374625

  8. Inferring Synaptic Structure in Presence of Neural Interaction Time Scales

    PubMed Central

    Capone, Cristiano; Filosa, Carla; Gigante, Guido; Ricci-Tersenghi, Federico; Del Giudice, Paolo

    2015-01-01

    Biological networks display a variety of activity patterns reflecting a web of interactions that is complex both in space and time. Yet inference methods have mainly focused on reconstructing, from the networks activity, the spatial structure, by assuming equilibrium conditions or, more recently, a probabilistic dynamics with a single arbitrary time-step. Here we show that, under this latter assumption, the inference procedure fails to reconstruct the synaptic matrix of a network of integrate-and-fire neurons when the chosen time scale of interaction does not closely match the synaptic delay or when no single time scale for the interaction can be identified; such failure, moreover, exposes a distinctive bias of the inference method that can lead to infer as inhibitory the excitatory synapses with interaction time scales longer than the models time-step. We therefore introduce a new two-step method, that first infers through cross-correlation profiles the delay-structure of the network and then reconstructs the synaptic matrix, and successfully test it on networks with different topologies and in different activity regimes. Although step one is able to accurately recover the delay-structure of the network, thus getting rid of any a priori guess about the time scales of the interaction, the inference method introduces nonetheless an arbitrary time scale, the time-bin dt used to binarize the spike trains. We therefore analytically and numerically study how the choice of dt affects the inference in our network model, finding that the relationship between the inferred couplings and the real synaptic efficacies, albeit being quadratic in both cases, depends critically on dt for the excitatory synapses only, whilst being basically independent of it for the inhibitory ones. PMID:25807389

  9. Inferring synaptic structure in presence of neural interaction time scales.

    PubMed

    Capone, Cristiano; Filosa, Carla; Gigante, Guido; Ricci-Tersenghi, Federico; Del Giudice, Paolo

    2015-01-01

    Biological networks display a variety of activity patterns reflecting a web of interactions that is complex both in space and time. Yet inference methods have mainly focused on reconstructing, from the network's activity, the spatial structure, by assuming equilibrium conditions or, more recently, a probabilistic dynamics with a single arbitrary time-step. Here we show that, under this latter assumption, the inference procedure fails to reconstruct the synaptic matrix of a network of integrate-and-fire neurons when the chosen time scale of interaction does not closely match the synaptic delay or when no single time scale for the interaction can be identified; such failure, moreover, exposes a distinctive bias of the inference method that can lead to infer as inhibitory the excitatory synapses with interaction time scales longer than the model's time-step. We therefore introduce a new two-step method, that first infers through cross-correlation profiles the delay-structure of the network and then reconstructs the synaptic matrix, and successfully test it on networks with different topologies and in different activity regimes. Although step one is able to accurately recover the delay-structure of the network, thus getting rid of any a priori guess about the time scales of the interaction, the inference method introduces nonetheless an arbitrary time scale, the time-bin dt used to binarize the spike trains. We therefore analytically and numerically study how the choice of dt affects the inference in our network model, finding that the relationship between the inferred couplings and the real synaptic efficacies, albeit being quadratic in both cases, depends critically on dt for the excitatory synapses only, whilst being basically independent of it for the inhibitory ones. PMID:25807389

  10. Permo-Triassic Boundary Superanoxia and Stratified Superocean: Records from Lost Deep Sea

    PubMed

    Isozaki

    1997-04-11

    Pelagic cherts of Japan and British Columbia, Canada, recorded a long-term and worldwide deep-sea anoxic (oxygen-depleted) event across the Permo-Triassic (or Paleozoic and Mesozoic) boundary (251 ± 2 million years ago). The symmetry in lithostratigraphy and redox condition of the boundary sections suggest that the superocean Panthalassa became totally stratified for nearly 20 million years across the boundary. The timing of onset, climax, and termination of the oceanic stratification correspond to global biotic events including the end-Guadalupian decline, the end-Permian extinction, and mid-Triassic recovery. PMID:9092467

  11. Evolution of a Permo-Triassic sedimentary melange, Grindstone terrane, east-central Oregon

    USGS Publications Warehouse

    Blome, C.D.; Nestell, M.K.

    1991-01-01

    Perceives the Grindstone rocks to be a sedimentary melange composed of Paleozoic limestone slide and slump blocks that became detached from a carbonate shelf fringing a volcanic knoll or edifice in Late Permian to Middle Triassic time and were intermixed with Permian and Triassic slope to basinal clastic and volcaniclastic rocks in a forearc basin setting. Paleogeographic affinities of the Grindstone limestone faunas and volcaniclastic debris in the limestone and clastic rocks all indicate deposition in promixity to an island-arc system near the North American craton. -from Authors

  12. The Late Permian - Early Triassic Evolution of the Western Barents Sea

    NASA Astrophysics Data System (ADS)

    Planke, S.; Svensen, H.; Faleide, J.; Myklebust, R.

    2013-12-01

    The Permian-Triassic boundary was temporarily associated with formation of the Siberian Traps Large Igneous Province. Major Late Permian and Early Triassic subsidence is documented by seismic reflection data in the East Barents Basin. Further west, basin subsidence and an abrupt change from carbonate and evaporite deposition to clastic sedimentation is recorded by industry seismic and well data in the south and onshore Svalbard in the north. The Permian-Triassic boundary is commonly not preserved either due to non-deposition or erosion, but could be locally preserved in depocenters. A major northwestward prograding clastic delta sourced from the Uralian hinterland reached the Norwegian (western) part of the Barents Sea in the earliest Triassic (Induan). We suggest that the large-scale changes in paleoenviroment, vertical motions, and sedimentary processes in the Barents Sea region were strongly influenced by large-scale changes in mantle dynamics and paleoclimate caused by the Siberian Traps igneous event. By analogy with other Large Igneous Provinces, such as the North Atlantic Volcanic Province, regional uplift and subsidence associated with a rising mantle plume may precede the arrival of the plume at the base of the lithosphere with 10's of millions of years. In contrast, the paleoenvironmental changes and the associated extinction were mainly caused by rapid intrusion of magma into sedimentary basins and voluminous igneous eruptions.

  13. A gigantic nothosaur (Reptilia: Sauropterygia) from the Middle Triassic of SW China and its implication for the Triassic biotic recovery.

    PubMed

    Liu, Jun; Hu, Shi-Xue; Rieppel, Olivier; Jiang, Da-Yong; Benton, Michael J; Kelley, Neil P; Aitchison, Jonathan C; Zhou, Chang-Yong; Wen, Wen; Huang, Jin-Yuan; Xie, Tao; Lv, Tao

    2014-01-01

    The presence of gigantic apex predators in the eastern Panthalassic and western Tethyan oceans suggests that complex ecosystems in the sea had become re-established in these regions at least by the early Middle Triassic, after the Permian-Triassic mass extinction (PTME). However, it is not clear whether oceanic ecosystem recovery from the PTME was globally synchronous because of the apparent lack of such predators in the eastern Tethyan/western Panthalassic region prior to the Late Triassic. Here we report a gigantic nothosaur from the lower Middle Triassic of Luoping in southwest China (eastern Tethyan ocean), which possesses the largest known lower jaw among Triassic sauropterygians. Phylogenetic analysis suggests parallel evolution of gigantism in Triassic sauropterygians. Discovery of this gigantic apex predator, together with associated diverse marine reptiles and the complex food web, indicates global recovery of shallow marine ecosystems from PTME by the early Middle Triassic. PMID:25429609

  14. A gigantic nothosaur (Reptilia: Sauropterygia) from the Middle Triassic of SW China and its implication for the Triassic biotic recovery

    PubMed Central

    Liu, Jun; Hu, Shi-xue; Rieppel, Olivier; Jiang, Da-yong; Benton, Michael J.; Kelley, Neil P.; Aitchison, Jonathan C.; Zhou, Chang-yong; Wen, Wen; Huang, Jin-yuan; Xie, Tao; Lv, Tao

    2014-01-01

    The presence of gigantic apex predators in the eastern Panthalassic and western Tethyan oceans suggests that complex ecosystems in the sea had become re-established in these regions at least by the early Middle Triassic, after the Permian-Triassic mass extinction (PTME). However, it is not clear whether oceanic ecosystem recovery from the PTME was globally synchronous because of the apparent lack of such predators in the eastern Tethyan/western Panthalassic region prior to the Late Triassic. Here we report a gigantic nothosaur from the lower Middle Triassic of Luoping in southwest China (eastern Tethyan ocean), which possesses the largest known lower jaw among Triassic sauropterygians. Phylogenetic analysis suggests parallel evolution of gigantism in Triassic sauropterygians. Discovery of this gigantic apex predator, together with associated diverse marine reptiles and the complex food web, indicates global recovery of shallow marine ecosystems from PTME by the early Middle Triassic. PMID:25429609

  15. A gigantic nothosaur (Reptilia: Sauropterygia) from the Middle Triassic of SW China and its implication for the Triassic biotic recovery

    NASA Astrophysics Data System (ADS)

    Liu, Jun; Hu, Shi-Xue; Rieppel, Olivier; Jiang, Da-Yong; Benton, Michael J.; Kelley, Neil P.; Aitchison, Jonathan C.; Zhou, Chang-Yong; Wen, Wen; Huang, Jin-Yuan; Xie, Tao; Lv, Tao

    2014-11-01

    The presence of gigantic apex predators in the eastern Panthalassic and western Tethyan oceans suggests that complex ecosystems in the sea had become re-established in these regions at least by the early Middle Triassic, after the Permian-Triassic mass extinction (PTME). However, it is not clear whether oceanic ecosystem recovery from the PTME was globally synchronous because of the apparent lack of such predators in the eastern Tethyan/western Panthalassic region prior to the Late Triassic. Here we report a gigantic nothosaur from the lower Middle Triassic of Luoping in southwest China (eastern Tethyan ocean), which possesses the largest known lower jaw among Triassic sauropterygians. Phylogenetic analysis suggests parallel evolution of gigantism in Triassic sauropterygians. Discovery of this gigantic apex predator, together with associated diverse marine reptiles and the complex food web, indicates global recovery of shallow marine ecosystems from PTME by the early Middle Triassic.

  16. Trends in Surface Radiation Budgets at Climatic Time Scales

    NASA Astrophysics Data System (ADS)

    Pinker, Rachel T.; Zhang, Banglin; Ma, Yingtao

    2015-04-01

    For assessment of variability and trends in the Earth Radiation Balance, information is needed at climatic time scales. Satellite observations have been instrumental for advancing the understanding of the radiative balance at global scale, however, due to the frequent changes in the observing systems, the length of available satellite records is limited. In this paper we report on an effort to synthesize satellite observations from independent sources to estimates shortwave, longwave and spectral surface radiative fluxes at climatic time scales and use them to learn about their variability and trends. The radiative fluxes were derived in the framework of the MEaSURES and NEWS programs; they are evaluated against ground observations and compared to independent satellite and model estimates. Attention is given to updates on the radiative balance as compared to what is known from shorter time records and from models.

  17. Time Scales for Energy Release in Hall Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Huba, J. D.; Rudakov, L. I.

    2004-05-01

    We present a study of the time scales for energy release in 2D Hall magnetic reconnection. We use the NRL Hall MHD code VooDoo for this study. We consider a 2D reversed field current layer with a magnetic perturbation that initiates the reconnection process. We use boundary conditions that allow inflow and outflow (i.e., not periodic) and let the system reach a steady state. We find that the system goes through three stages: a relatively long current layer thinning process, a fast reconnection phase, and a final steady state phase. We define the time scale for energy release as the fast reconnection period: from onset to steady state. Preliminary results indicate that the time for energy release scales as the initial thickness of the current layer. We apply these results to the magnetotail and magnetopause. Research supported by NASA and ONR.

  18. Evaluation of scaling invariance embedded in short time series.

    PubMed

    Pan, Xue; Hou, Lei; Stephen, Mutua; Yang, Huijie; Zhu, Chenping

    2014-01-01

    Scaling invariance of time series has been making great contributions in diverse research fields. But how to evaluate scaling exponent from a real-world series is still an open problem. Finite length of time series may induce unacceptable fluctuation and bias to statistical quantities and consequent invalidation of currently used standard methods. In this paper a new concept called correlation-dependent balanced estimation of diffusion entropy is developed to evaluate scale-invariance in very short time series with length ~10(2). Calculations with specified Hurst exponent values of 0.2,0.3,...,0.9 show that by using the standard central moving average de-trending procedure this method can evaluate the scaling exponents for short time series with ignorable bias (?0.03) and sharp confidential interval (standard deviation ?0.05). Considering the stride series from ten volunteers along an approximate oval path of a specified length, we observe that though the averages and deviations of scaling exponents are close, their evolutionary behaviors display rich patterns. It has potential use in analyzing physiological signals, detecting early warning signals, and so on. As an emphasis, the our core contribution is that by means of the proposed method one can estimate precisely shannon entropy from limited records. PMID:25549356

  19. Evaluation of Scaling Invariance Embedded in Short Time Series

    PubMed Central

    Pan, Xue; Hou, Lei; Stephen, Mutua; Yang, Huijie; Zhu, Chenping

    2014-01-01

    Scaling invariance of time series has been making great contributions in diverse research fields. But how to evaluate scaling exponent from a real-world series is still an open problem. Finite length of time series may induce unacceptable fluctuation and bias to statistical quantities and consequent invalidation of currently used standard methods. In this paper a new concept called correlation-dependent balanced estimation of diffusion entropy is developed to evaluate scale-invariance in very short time series with length . Calculations with specified Hurst exponent values of show that by using the standard central moving average de-trending procedure this method can evaluate the scaling exponents for short time series with ignorable bias () and sharp confidential interval (standard deviation ). Considering the stride series from ten volunteers along an approximate oval path of a specified length, we observe that though the averages and deviations of scaling exponents are close, their evolutionary behaviors display rich patterns. It has potential use in analyzing physiological signals, detecting early warning signals, and so on. As an emphasis, the our core contribution is that by means of the proposed method one can estimate precisely shannon entropy from limited records. PMID:25549356

  20. Robust Stabilizing Controller Synthesis Based on Discrete-time Noncausal Linear Periodically Time-varying Scaling

    NASA Astrophysics Data System (ADS)

    Hosoe, Yohei; Hagiwara, Tomomichi

    This paper discusses the application of noncausal linear periodically time-varying (LPTV) scaling to the design of discrete-time robust stabilizing controllers. Such a new type of scaling was introduced recently through the lifting technique, and has been shown to be effective for robust stability analysis in terms of reducing conservativeness. This paper thus discusses how and why one could exploit the desirable properties of noncausal LPTV scaling in the context of robust stabilizing controller design, and provides explicit steps for such design, including the suitable selection of the structure of noncausal LPTV scaling and LMI optimization of scaling as well as the controller. Numerical examples are also studied demonstrating that the noncausal LPTV scaling approach leads to less conservative design than the conventional scaling or -synthesis approach.

  1. Plate tectonic controls on atmospheric CO2 levels since the Triassic

    NASA Astrophysics Data System (ADS)

    van der Meer, Douwe; Zeebe, Richard; van Hinsbergen, Douwe; Sluijs, Appy; Spakman, Wim; Torsvik, Trond

    2014-05-01

    Climate trends on time-scales of 10's to 100's of millions of years are controlled by changes in solar luminosity, continent distribution and atmosphere composition. Plate tectonics affect geography, but also atmosphere composition through volcanic degassing of CO2 at subduction zones and mid-ocean ridges. So far, such degassing estimates were based on reconstructions of ocean floor production for the last 150 Million years (Myr) and indirectly, through sea level inversion before 150 Myr. Here we quantitatively estimate CO2 degassing by reconstructing lithosphere subduction evolution, using recent advances in combining global plate reconstructions and present-day structure of the mantle. First, we estimate that since the Triassic (250-200 Myr) until Present, the total paleo-subduction zone length reached up to ~200% of the present-day value. Comparing our subduction zone lengths with previously reconstructed ocean-crust production rates over the past 140 Myr suggests average global subduction rates have been constant, ~6 cm/year: Higher ocean-crust production is associated with longer total subduction length. We compute a Strontium isotope record based on subduction zone length, which agrees well with geological records supporting the validity of our approach: The total subduction zone length is proportional to the summed arc- and ridge volcanic CO2 production and thereby to global volcanic degassing at plate boundaries. We therefore use our degassing curve as input for the GEOCARBSULF model to estimate atmospheric CO2 levels since the Triassic. Our calculated CO2 levels for the mid-Mesozoic differ from previous modeling results and are more consistent with available proxy data.

  2. Memory on multiple time-scales in an Abelian sandpile

    NASA Astrophysics Data System (ADS)

    Sokolov, Andrey; Melatos, Andrew; Kieu, Tien; Webster, Rachel

    2015-06-01

    We report results of a numerical analysis of the memory effects in two-dimensional Abelian sandpiles. It is found that a sandpile forgets its instantaneous configuration in two distinct stages: a fast stage and a slow stage, whose durations roughly scale as N and N2 respectively, where N is the linear size of the sandpile. We confirm the presence of the longer time-scale by an independent diagnostic based on analysing emission probabilities of a hidden Markov model applied to a time-averaged sequence of avalanche sizes. The application of hidden Markov modelling to the output of sandpiles is novel. It discriminates effectively between a sandpile time series and a shuffled control time series with the same time-averaged event statistics and hence deserves further development as a pattern-recognition tool for Abelian sandpiles.

  3. Time scales for molecule formation by ion-molecule reactions

    NASA Technical Reports Server (NTRS)

    Langer, W. D.; Glassgold, A. E.

    1976-01-01

    Analytical solutions are obtained for nonlinear differential equations governing the time-dependence of molecular abundances in interstellar clouds. Three gas-phase reaction schemes are considered separately for the regions where each dominates. The particular case of CO, and closely related members of the Oh and CH families of molecules, is studied for given values of temperature, density, and the radiation field. Nonlinear effects and couplings with particular ions are found to be important. The time scales for CO formation range from 100,000 to a few million years, depending on the chemistry and regime. The time required for essentially complete conversion of C(+) to CO in the region where the H3(+) chemistry dominates is several million years. Because this time is longer than or comparable to dynamical time scales for dense interstellar clouds, steady-state abundances may not be observed in such clouds.

  4. The "terminal Triassic catastrophic extinction event" in perspective: a review of carboniferous through Early Jurassic terrestrial vertebrate extinction patterns

    USGS Publications Warehouse

    Weems, R.E.

    1992-01-01

    A catastrophic terminal Triassic extinction event among terrestrial vertebrates is not supported by available evidence. The current model for such an extinction is based on at least eight weak or untenable assumptions: (1) a terminal Triassic extinction-inducing asteroid impact occurred, (2) a terminal Triassic synchronous mass extinction of terrestrial vertebrates occurred, (3) a concurrent terminal Triassic marine extinction occurred, (4) all terrestrial vertebrate families have similar diversities and ecologies, (5) changes in familial diversity can be gauged accurately from the known fossil record, (6) extinction of families can be compared through time without normalizing for changes in familial diversity through time, (7) extinction rates can be compared without normalizing for differing lengths of geologic stages, and (8) catastrophic mass extinctions do not select for small size. These assumptions have resulted in unsupportable and (or) erroneous conclusions. Carboniferous through Early Jurassic terrestrial vertebrate families mostly have evolution and extinction patterns unlike the vertebrate evolution and extinction patterns during the terminal Cretaceous event. Only the Serpukhovian (mid Carboniferous) extinction event shows strong analogy to the terminal Cretaceous event. Available data suggest no terminal Triassic extinction anomaly, but rather a prolonged and nearly steady decline in the global terrestrial vertebrate extinction rate throughout the Triassic and earliest Jurassic. ?? 1992.

  5. Dynamics symmetries of Hamiltonian system on time scales

    SciTech Connect

    Peng, Keke Luo, Yiping

    2014-04-15

    In this paper, the dynamics symmetries of Hamiltonian system on time scales are studied. We study the symmetries and quantities based on the calculation of variation and Lie transformation group. Particular focus lies in: the Noether symmetry leads to the Noether conserved quantity and the Lie symmetry leads to the Noether conserved quantity if the infinitesimal transformations satisfy the structure equation. As the new application of result, at end of the article, we give a simple example of Noether symmetry and Lie symmetry on time scales.

  6. Relativistic fireballs - Energy conversion and time-scales

    NASA Technical Reports Server (NTRS)

    Rees, M. J.; Meszaros, P.

    1992-01-01

    The expansion energy of a relativistic fireball can be reconverted into radiation when it interacts with an external medium. For expansion with Lorentz factors greater than or approximately equal to 1000 into a typical galactic environment, the corresponding time-scale in the frame of the observer is of the order of seconds. This mechanism would operate in any cosmological scenario of gamma-ray bursts involving initial energies of order a percent of a stellar rest mass, and implies photon energies and time-scales compatible with those observed in gamma-ray bursts.

  7. Time scale analysis of a digital flight control system

    NASA Technical Reports Server (NTRS)

    Naidu, D. S.; Price, D. B.

    1986-01-01

    In this paper, consideration is given to the fifth order discrete model of an aircraft (longitudinal) control system which possesses three slow (velocity, pitch angle and altitude) and two fast (angle of attack and pitch angular velocity) modes and exhibits a two-time scale property. Using the recent results of the time scale analysis of discrete control systems, the high-order discrete model is decoupled into low-order slow and fast subsystems. The results of the decoupled system are found to be in excellent agreement with those of the original system.

  8. Palaeoenvironments and palaeotectonics of the arid to hyperarid intracontinental latest Permian- late Triassic Solway basin (U.K.)

    NASA Astrophysics Data System (ADS)

    Brookfield, Michael E.

    2008-10-01

    The late Permian to late Triassic sediments of the Solway Basin consist of an originally flat-lying, laterally persistent and consistent succession of mature, dominantly fine-grained red clastics laid down in part of a very large intracontinental basin. The complete absence of body or trace fossils or palaeosols indicates a very arid (hyperarid) depositional environment for most of the sediments. At the base of the succession, thin regolith breccias and sandstones rest unconformably on basement and early Permian rift clastics. Overlying gypsiferous red silty mudstones, very fine sandstones and thick gypsum were deposited in either a playa lake or in a hypersaline estuary, and their margins. These pass upwards into thick-bedded, multi-storied, fine- to very fine-grained red quartzo-felspathic and sublithic arenites in which even medium sand is rare despite channels with clay pebbles up to 30 cm in diameter. Above, thick trough cross-bedded and parallel laminated fine-grained aeolian sandstones (deposited in extensive barchanoid dune complexes) pass up into very thick, multicoloured mudstones, and gypsum deposited in marginal marine or lacustrine sabkha environments. The latter pass up into marine Lower Jurassic shales and limestones. Thirteen non-marine clastic lithofacies are arranged into five main lithofacies associations whose facies architecture is reconstructed where possible by analysis of large exposures. The five associations can be compared with the desert pavement, arid ephemeral stream, sabkha, saline lake and aeolian sand dune environments of the arid to hyperarid areas of existing intracontinental basins such as Lake Eyre and Lake Chad. The accommodation space in such basins is controlled by gradual tectonic subsidence moderated by large fluctuations in shallow lake extent (caused by climatic change and local variation) and this promotes a large-scale layer-cake stratigraphy as exemplified in the Solway basin. Here, the dominant fine-grained mature sandstones above the local basal reg breccias suggest water-reworking of wind-transported sediment, as in the northern part of the Lake Chad basin. Growth faulting occurs in places in the Solway basin, caused by underlying evaporite movement, but these faults did not significantly affect pre-late Triassic sedimentation and did not expose pre-Permian units above the basal breccias. There is no evidence of post-early Permian rifting anywhere during deposition of the late Permian to middle Triassic British succession although the succession is often interpreted with a rift-basin model. The arid to hyperarid palaeoclimate changed little during deposition of the Solway basin succession, in contrast to Lakes Eyre and Chad: and this is attributed to tectonic and palaeolatitude stability. Unlike the later Mesozoic- Cenozoic, only limited plate movements took place during the Triassic in western Europe, palaeolatitude changed little, and the Solway Basin remained in the northern latitudinal desert belt from early to mid-Triassic times. However, the influence of the early Triassic impoverished biota on environmental interpretations needs further study.

  9. Time-scale modification of complex acoustic signals in noise

    NASA Astrophysics Data System (ADS)

    Quatieri, Thomas F.; Dunn, Robert B.; McAulay, Robert J.; Hanna, Thomas E.

    1994-02-01

    A new approach is introduced for time-scale modification of short-duration complex acoustic signals to improve their audibility. The method preserves an approximate time-scaled temporal envelope of a signal, thus capitalizing on the perceptual importance of the signal's temporal structure, while also maintaining the character of a noise background. The basis for the approach is a subband signal representation, derived from a filter bank analysis/synthesis, the channel phases of which are controlled to shape the temporal envelope of the time-scaled signal. Channel amplitudes and filter bank inputs are selected to shape the spectrum and correlation of the time-scaled background. The phase, amplitude, and input control are derived from locations of events that occur within filter bank outputs. A frame-based generalization of the method imposes phase consistency and background noise continuity across consecutive synthesis frames. The approach and its derivatives are applied to synthetic and actual complex acoustic signals consisting of closely spaced sequential time components.

  10. Appropriate time scales for nonlinear analyses of deterministic jump systems

    NASA Astrophysics Data System (ADS)

    Suzuki, Tomoya

    2011-06-01

    In the real world, there are many phenomena that are derived from deterministic systems but which fluctuate with nonuniform time intervals. This paper discusses the appropriate time scales that can be applied to such systems to analyze their properties. The financial markets are an example of such systems wherein price movements fluctuate with nonuniform time intervals. However, it is common to apply uniform time scales such as 1-min data and 1-h data to study price movements. This paper examines the validity of such time scales by using surrogate data tests to ascertain whether the deterministic properties of the original system can be identified from uniform sampled data. The results show that uniform time samplings are often inappropriate for nonlinear analyses. However, for other systems such as neural spikes and Internet traffic packets, which produce similar outputs, uniform time samplings are quite effective in extracting the system properties. Nevertheless, uniform samplings often generate overlapping data, which can cause false rejections of surrogate data tests.

  11. How was the Triassic Songpan-Ganzi basin filled? A provenance study

    USGS Publications Warehouse

    Enkelmann, E.; Weislogel, A.; Ratschbacher, L.; Eide, E.; Renno, A.; Wooden, J.

    2007-01-01

    The Triassic Songpan-Ganzi complex comprises >200,000 km2 of 5-15 km thick turbiditic sediments. Although surrounded by several magmatic and orogenic belts, the Triassic high- and ultrahigh-pressure Qinling-Tongbai-Hong'an-Dabie (QTHD) orogen, located several hundred kilometers to the east, was proposed as its major source. Middle to Late Triassic samples from the northern and southern Songpan-Ganzi complex, studied using detrital white mica 40Ar/39Ar ages, Si-in-white mica content, and detrital zircon U/Pb ages, suggest that the northern Songpan-Ganzi deposystem obtained detritus from the north: the north China block, east Kunlun, northern Qaidam, Qilian, and western Qinling; the southern Songpan-Ganzi deposystem was supplied from the northeasterly located Paleozoic QTHD area throughout the Ladinian and received detritus from the Triassic Hong'an-Dabie orogen during the Carnian, indicative of exhumation of the orogen at that time. The QTHD orogen fed the Norian samples in the southeastern southern Songpan-Ganzi deposystem, signifying long drainage channels along the western margin of the south China block. An additional supply from the Emeishan magmatic province and/or the Yidun arc is suggested by the paucity of white mica in the southern Songpan-Ganzi deposystem. Mica ages of Rhaetian sediments from the northwestern Sichuan basin best correlate with those of the Triassic QTHD orogen. Our Si-in-white mica data demonstrate that the high- and ultrahigh-pressure rocks of the Hong'an-Dabie Shan were not exposed in the Middle to Late Triassic. Copyright 2007 by the American Geophysical Union.

  12. Does the Permo-Triassic Geomagnetic Dipole Low Exist?

    NASA Astrophysics Data System (ADS)

    Blanco, D.; Kravchinsky, V. A.; Valet, J. M.

    2010-12-01

    The Siberian trap basalts erupted during a short period of ~1 Myr at the Permo-Triassic boundary. It provides a unique opportunity to study absolute paleointensity during this one of the best-dated periods of Paleozoic era. Previous studies suggest relatively low paleointensity values (Heunemann et al. 2004), result that leads the authors to propose that the Mesozoic Dipole Low could be extended at least to the Permo-Triassic boundary. In this contribution we present new paleointensity results for sills and dykes from the eastern (areas of the kimberlite pipes Sytikanskaya, Yubileinaya and Aikhal) and north-western (intrusions near Norilsk city) parts of the Siberian platform. A total of 341 samples were subject to a modified Thellier-Thellier technique. In order to assure the reliability of the paleointensity estimates partial thermoremanent magnetization checks and multidomain tail check were applied. North-western (Norilsk) samples did not meet reliability criteria and have been rejected from the paleointensity analysis although paleomagnetic analysis demonstrated matching to the expected Permo-Triassic direction of the Siberian traps. Our paleointensity estimates from the eastern trap occurrences show a virtual dipolar moment (VDM) close to the present geomagnetic field value, 5.71±0.92×1022Am2, 5.89±0.37×1022Am2 and 6.21±0.78×1022Am2 for the three study areas, respectively. Our values are about two times higher than reported in Heunemann et al. (2004). There could be a variety of reasons for the discrepancy between our results and previous studies: (1) Magnetostratigraphy studies on the Siberian trap basalts (Gurevitch et al. 2004) have shown that several reversal processes occurred during the time of their formation. As shown by Valet et al. (2005), a period of time is required for the geomagnetic field to recover after a reversal occurrence. During such period it is still possible to have a stable normal or reverse direction and low paleointensity values at the same time (Dormy et al. 2000). We suggest that Heunemann et al. (2004) paleointensity results correspond to a period of stable polarity but relatively low intensity values, while it is possible that our study sills and dykes were intruded during a period were the field had enough time to recovered and stable direction and larger intensity values were acquired. (2) Theoretically, longer cooling rates can lead to overestimates in paleointensity values (Dodson and McClelland 1980; Halgedahl et al. 1980). It could alternatively be a reason for the discrepancy between our intrusive basalts and the previous results obtained from extrusive formations if our study intrusions had long enough time to cool down. Although more study should be done for an accurate reconstruction of the VDM variability at the Permo-Triassic boundary our results suggest that the geomagnetic dipole low cannot perhaps be straightforwardly extended to the Permo-Triassic boundary.

  13. Multiple-Time-Scale Concepts in Turbulent Transport Modeling

    NASA Technical Reports Server (NTRS)

    Hanjalic, K.; Launder, B. E.; Schiestel, R.

    1980-01-01

    Progress in developing a turbulence closure employing two or more independently calculated time scales with which to characterize the rates of progress of different turbulent interactions is reported. The energy containing part of the spectrum is divided into two regions which respond at different rates and in different ways to changes in the environment. The scheme may be regarded as providing an intermediate level of approximation between the relatively simple, but fallible, single-point closures and the vastly more elaborate two-point closures which have so far been applied only to simulating homogeneous flows. The proposed approach requires only slightly more computational effort than single-scale schemes. Computational results are reported for several thin shear flows which show striking improvement in the level of agreement with experiment over that obtained with models employing only one time scale.

  14. Gott Time Machines, BTZ Black Hole Formation, and Choptuik Scaling

    NASA Astrophysics Data System (ADS)

    Birmingham, Danny; Sen, Siddhartha

    2000-02-01

    We study the formation of Baados-Teitelboim-Zanelli black holes by the collision of point particles. It is shown that the Gott time machine, originally constructed for the case of vanishing cosmological constant, provides a precise mechanism for black hole formation. As a result, one obtains an exact analytic understanding of the Choptuik scaling.

  15. Speech Compensation for Time-Scale-Modified Auditory Feedback

    ERIC Educational Resources Information Center

    Ogane, Rintaro; Honda, Masaaki

    2014-01-01

    Purpose: The purpose of this study was to examine speech compensation in response to time-scale-modified auditory feedback during the transition of the semivowel for a target utterance of /ija/. Method: Each utterance session consisted of 10 control trials in the normal feedback condition followed by 20 perturbed trials in the modified auditory

  16. Separation of time scales in the HCA model for sand

    NASA Astrophysics Data System (ADS)

    Niemunis, Andrzej; Wichtmann, Torsten

    2014-10-01

    Separation of time scales is used in a high cycle accumulation (HCA) model for sand. An important difficulty of the model is the limited applicability of the Miner's rule to multiaxial cyclic loadings applied simultaneously or in a combination with monotonic loading. Another problem is the lack of simplified objective HCA formulas for geotechnical settlement problems. Possible solutions of these problems are discussed.

  17. Spectral decomposition of time-scales in hyporheic exchange

    NASA Astrophysics Data System (ADS)

    Wrman, Anders; Riml, Joakim

    2015-04-01

    Hyporheic exchange of heat and solute mass in streams is manifested both in form of different exchange mechanisms and their associated distributions of residence times as well as the range of time-scales characterizing the forcing boundary conditions. A recently developed analytical technique separates the spectrum of time-scales and relates the forcing boundary fluctuations of heat and solute mass through a physical model of the hydrological transport to the response of heat and solute mass. This spectral decomposition can be done both for local (point-scale) observations in the hyporhiec zone itself as well as for transport processes on the watershed scale that can be considered 'well-behaved' in terms of knowledge of the forcing (input) quantities. This paper presents closed-form solutions in spectral form for the point-, reach- and watershed-scale and discusses their applicability to selected data of heat and solute concentration. We quantify the reliability and highlight the benefits of the spectral approach to different scenarios and, peculiarly, the importance for linking the periods in the spectral decomposition of the solute response to the distribution of transport times that arise due to the multitude of exchange mechanisms existing in a watershed. In a point-scale example the power spectra of in-stream temperature is related to the power spectrum of the temperature at a specific sediment depth by means of exact solutions of a physically based formulation of the vertical heat transport. It is shown that any frequency (?) of in-stream temperature fluctuation scales with the effective thermal diffusivity (?e) and the vertical separation distance between the pairs of temperature (?) data as ? ? ?e/(2?2), which implies a decreasing weight to higher frequencies (shorter periods) with depth. Similarly on the watershed-scale one can link the watershed dispersion to the damping of the concentration fluctuations in selected frequency intervals reflecting various environments responsible for the damping. The frequency-dependent parameters indicate that different environments dominate the response at different temporal scales.

  18. Stellar differential rotation and coronal time-scales

    NASA Astrophysics Data System (ADS)

    Gibb, G. P. S.; Jardine, M. M.; Mackay, D. H.

    2014-10-01

    We investigate the time-scales of evolution of stellar coronae in response to surface differential rotation and diffusion. To quantify this, we study both the formation time and lifetime of a magnetic flux rope in a decaying bipolar active region. We apply a magnetic flux transport model to prescribe the evolution of the stellar photospheric field, and use this to drive the evolution of the coronal magnetic field via a magnetofrictional technique. Increasing the differential rotation (i.e. decreasing the equator-pole lap time) decreases the flux rope formation time. We find that the formation time is dependent upon the lap time and the surface diffusion time-scale through the relation ?_Form ? ?{?_Lap?_Diff}. In contrast, the lifetimes of flux ropes are proportional to the lap time (?Life??Lap). With this, flux ropes on stars with a differential rotation of more than eight times the solar value have a lifetime of less than 2 d. As a consequence, we propose that features such as solar-like quiescent prominences may not be easily observable on such stars, as the lifetimes of the flux ropes which host the cool plasma are very short. We conclude that such high differential rotation stars may have very dynamical coronae.

  19. Characterization of a binary karst aquifer using process time scales

    NASA Astrophysics Data System (ADS)

    Birk, Steffen; Wagner, Thomas

    2013-04-01

    Within "a theoretical framework for the interpretation of karst spring signals" (Covington, EGU2012-853-1) process length scales that characterize the travel distances required for damping pulses of physicochemical parameters of spring waters such as electrical conductivity and temperature were derived (Covington et al., J. Geophys. Res., 2012). These length scales can be converted to corresponding process time scales characterizing the travel times needed for damping the pulses. This is particularly convenient if the travel distance is unknown. In this case the time lag between the increase of spring discharge and subsequent physicochemical responses at the spring may provide an estimate of the travel time. In binary karst aquifers with localized recharge from a sinking stream, the recharge pulse can be directly observed and thus travel times are readily obtained from the time delay of the physicochemical spring responses. If the spring response is strongly damped travel times can be inferred from artificial tracer testing. In this work, time scales for carbonate dissolution and heat transport were used for characterizing the binary Lurbach-Tanneben karst aquifer (Austria). This aquifer receives allogenic recharge from the sinking stream Lurbach and is drained by two springs, namely the Hammerbach and the Schmelzbach. The two springs show different thermal responses to two recharge events in December 2008: Whereas the temperature of the Schmelzbach responds within one day after the flood pulse in the Lurbach, the temperature signal is strongly damped at the Hammerbach. The evaluation based on the thermal time scale thus suggests that the Schmelzbach spring is fed by conduits with hydraulic diameters at least in the order of decimetres. In contrast, the damping of the thermal responses at the Hammerbach may be due to lower hydraulic diameters and/or longer residence times. Interestingly, the Hammerbach did show thermal responses in the time before a flood event in August 2005. This suggests that this flood event may have caused a change of the properties of the Hammerbach aquifer such that temperature pulses are more strongly damped than before. As opposed to the thermal responses the electrical conductivity appears to be less affected by this change, which suggests that the hydraulic diameters are still sufficiently large to permit the propagation of chemical signals.

  20. BeiDou Navigation Satellite System and its time scales

    NASA Astrophysics Data System (ADS)

    Han, Chunhao; Yang, Yuanxi; Cai, Zhiwu

    2011-08-01

    The development and current status of BeiDou Navigation Satellite System are briefly introduced. The definition and realization of the system time scales are described in detail. The BeiDou system time (BDT) is an internal and continuous time scale without leap seconds. It is maintained by the time and frequency system of the master station. The frequency accuracy of BDT is superior to 2 × 10-14 and its stability is better than 6 × 10-15/30 days. The satellite synchronization is realized by a two-way time transfer between the uplink stations and the satellite. The measurement uncertainty of satellite clock offsets is less than 2 ns. The BeiDou System has three modes of time services: radio determination satellite service (RDSS) one-way, RDSS two-way and radio navigation satellite service (RNSS) one-way. The uncertainty of the one-way time service is designed to be less than 50 ns, and that of the two-way time service is less than 10 ns. Finally, some coordinate tactics of UTC from the viewpoint of global navigation satellite systems (GNSS) are discussed. It would be helpful to stop the leap second, from our viewpoint, but to keep the UTC name, the continuity and the coordinate function unchanged.

  1. Events during Early Triassic recovery from the end-Permian extinction

    NASA Astrophysics Data System (ADS)

    Tong, Jinnan; Zhang, Suxin; Zuo, Jingxun; Xiong, Xinqi

    2007-01-01

    The Palaeozoic-Mesozoic transition is characterized not only by the biggest Phanerozoic mass extinction, at the end of Permian, but also a prolonged period of recovery of the biota during the succeeding Early Triassic. The delayed recovery is generally attributed to the effects of extreme environmental conditions on the Early Triassic ecosystem. However, there has been very little study of the cause and mechanism of the environmental conditions that prevailed during the period of extinction and subsequent recovery. Research on the Permian-Triassic boundary and Lower Triassic, especially that on environmental events at the beginning of the Triassic in South China, indicates that the slowness of the recovery may be the result of three factors: (1) extreme environmental conditions that persisted through the transitional period and which were maintained by, for example, intermittent contemporary volcanism; (2) a passive evolutionary and ecologic strategy of the biota, in which r-selection taxa were dominant and K-selection forms insignificant; (3) an immature, poorly functioning ecosystem, which had difficulty in responding to and withstanding extreme environmental changes. According to data from South China, environmental changes were frequent during the Late Permian, and especially serious at the Permian-Triassic boundary. The Late Permian ecosystem was well structured and fully functioning as a result of a long period of steady development during the late Palaeozoic, and was capable of resisting general environmental changes. However, increasingly frequent and probably more extreme environmental events in the latest Permian may have led to a general collapse of this ecosystem and to the mass extinction at the end of the Permian. The Early Triassic ecosystem was immature, functioned poorly, and was unable to respond effectively to environmental changes, so that persisting extreme environmental conditions slowed ecosystem reconstruction considerably, and the recovery of the biota therefore took a relatively long time. The environmental events at the Permian-Triassic boundary might not be significantly different from those at other Phanerozoic transitions, but they consisted of a series of events that occurred at intervals during the transitional period.

  2. Time scale controversy: Accurate orbital calibration of the early Paleogene

    NASA Astrophysics Data System (ADS)

    Roehl, U.; Westerhold, T.; Laskar, J.

    2012-12-01

    Timing is crucial to understanding the causes and consequences of events in Earth history. The calibration of geological time relies heavily on the accuracy of radioisotopic and astronomical dating. Uncertainties in the computations of Earth's orbital parameters and in radioisotopic dating have hampered the construction of a reliable astronomically calibrated time scale beyond 40 Ma. Attempts to construct a robust astronomically tuned time scale for the early Paleogene by integrating radioisotopic and astronomical dating are only partially consistent. Here, using the new La2010 and La2011 orbital solutions, we present the first accurate astronomically calibrated time scale for the early Paleogene (47-65 Ma) uniquely based on astronomical tuning and thus independent of the radioisotopic determination of the Fish Canyon standard. Comparison with geological data confirms the stability of the new La2011 solution back to 54 Ma. Subsequent anchoring of floating chronologies to the La2011 solution using the very long eccentricity nodes provides an absolute age of 55.530 0.05 Ma for the onset of the Paleocene/Eocene Thermal Maximum (PETM), 54.850 0.05 Ma for the early Eocene ash -17, and 65.250 0.06 Ma for the K/Pg boundary. The new astrochronology presented here indicates that the intercalibration and synchronization of U/Pb and 40Ar/39Ar radioisotopic geochronology is much more challenging than previously thought.

  3. Conodont paleoecology of Lower Triassic Thaynes Formation

    SciTech Connect

    Carr, T.R.

    1983-03-01

    The Lower Triassic (Smithian) Thaynes Formation represents a broad spectrum of paleoenvironments. Samples arranged along a generalized depth-salinity environmental gradient from tidal flats to a relatively deep, commonly dysaerobic, basin yielded a conodont fauna of 30 form elements. Association and similarity analysis were used to group the conodont elements into eight conodont entities, reflecting both biologic association (multielement apparatuses) and ecologic association (biofacies). Simple chi-square tests and discriminant analyses, using the eight conodont entities, and indicate presence of three distinctive conodont biofacies related to the generalized environmental gradient. The restricted inner shelf biotope was characterized by a conodont fauna dominated by Parachirognathus. The outer shelf biotope was distinguished by a diverse conodont fauna including the distinctive form Furnishius. The biotope farthest offshore consists of a low diversity conodont fauna composed primarily of species of Neogondolella. Some early Triassic conodonts such as Neospathodus and Ellisonia triassica are ubiquitous, and provide the foundation for a inter-basinal conodont zonation. Early Triassic conodont biotopes can be arranged along a generalized environmental gradient that probably reflects changes in hydrographic factors (e.g., salinity, temperature, and energy) which affected the distribution of conodonts.

  4. Characterizing Complex Time Series from the Scaling of Prediction Error.

    NASA Astrophysics Data System (ADS)

    Hinrichs, Brant Eric

    This thesis concerns characterizing complex time series from the scaling of prediction error. We use the global modeling technique of radial basis function approximation to build models from a state-space reconstruction of a time series that otherwise appears complicated or random (i.e. aperiodic, irregular). Prediction error as a function of prediction horizon is obtained from the model using the direct method. The relationship between the underlying dynamics of the time series and the logarithmic scaling of prediction error as a function of prediction horizon is investigated. We use this relationship to characterize the dynamics of both a model chaotic system and physical data from the optic tectum of an attentive pigeon exhibiting the important phenomena of nonstationary neuronal oscillations in response to visual stimuli.

  5. Time-frequency and time-scale analyses for structural health monitoring.

    PubMed

    Staszewski, Wies?aw J; Robertson, Amy N

    2007-02-15

    Signal processing is one of the most important elements of structural health monitoring. This paper documents applications of time-variant analysis for damage detection. Two main approaches, the time-frequency and the time-scale analyses are discussed. The discussion is illustrated by application examples relevant to damage detection. PMID:17255047

  6. The Available Time Scale: Measuring Foster Parents' Available Time to Foster

    ERIC Educational Resources Information Center

    Cherry, Donna J.; Orme, John G.; Rhodes, Kathryn W.

    2009-01-01

    This article presents a new measure of available time specific to fostering, the Available Time Scale (ATS). It was tested with a national sample of 304 foster mothers and is designed to measure the amount of time foster parents are able to devote to fostering activities. The ATS has excellent reliability, and good support exists for its validity.

  7. Constraints on the Heating Time Scale in Active Regions

    NASA Astrophysics Data System (ADS)

    Brooks, D. H.; Warren, H. P.

    2012-08-01

    Understanding the heating time scale is important for constraining models of active region emission. Hinode observations of moss at the bases of high temperature active region core loops are allowing us to study this problem in unprecedented detail. Here we discuss some of our recent results studying the variability of moss properties such as intensity, magnetic flux, Doppler and non-thermal velocity. We find that most of these quantities are relatively constant. One interpretation is that the heating is therefore effectively steady , i.e., heating events occur with a rapid repetition rate. Alternatively, the heating could be low frequency, but only if it occurs on sub-resolution spatial scales.

  8. Triassic/Jurassic faulting patterns of Conecuh Ridge, southwest Alabama

    SciTech Connect

    Hutley, J.K.

    1985-02-01

    Two major fault systems influenced Jurassic structure and deposition on the Conecuh Ridge, southwest Alabama. Identification and dating of these fault systems are based on seismic-stratigraphic interpretation of a 7-township grid in Monroe and Conecuh Counties. Relative time of faulting is determined by fault geometry and by formation isopachs and isochrons. Smackover and Norphlet Formations, both Late Jurassic in age, are mappable seismic reflectors and are thus reliable for seismicstratigraphic dating. The earlier of the 2 fault systems is a series of horsts and grabens that trends northeast-southwest and is Late Triassic to Early Jurassic in age. The system formed in response to tensional stress associated with the opening of the Atlantic Ocean. The resulting topography was a series of northeast-southwest-trending ridges. Upper Triassic Eagle Mills and Jurassic Werner Formations were deposited in the grabens. The later fault system is also a series of horsts and grabens trending perpendicular to the first. This system was caused by tensional stress related to a pulse in the opening of the Gulf of Mexico. Faulting began in Early Jurassic and continued into Late Jurassic, becoming progressively younger basinward. At the basin margin, faulting produced a very irregular shoreline. Submerged horst blocks became centers for shoaling or carbonate buildups. Today, these blocks are exploration targets in southwest Alabama.

  9. Triassic oils and related hydrocarbon kitchens in the Adriatic basin

    SciTech Connect

    Novelli, L.; Demaison, G. )

    1988-08-01

    Without exception, the oils from both the Abruzzi basin and Albanian foredeep are of lower Liassic to Upper Triassic origin. This is demonstrated by biological marker-based correlations between the oils and stratigraphically controlled, carbonate-rich source rocks. The biomarker studies also provided proof to conclude that many of the oils possess low API gravities and high sulfur contents because they are immature rather than biodegraded. Following the geochemical investigations, a computer-aided, basinwise maturation simulation of the hydrocarbon kitchens was carried out, with backstripping in geologic time. The simulations, performed with the Tissot-Espitalie kinetic model, used basin-specific kerogen activation energies obtained by the optimum method. These simulated values were calibrated with observed values in deep wells. Two characteristics diverge from normal petroleum basin situations (e.g., the North Sea basin): sulfur-rich kerogens in the source rocks, featuring relatively low activation energy distributions, and low geothermal gradients in the subsurface. The geographic outlines of simulated Triassic-lower Liassic hydrocarbon kitchens closely coincide with the zones of petroleum occurrence and production in the Adriatic basin. Furthermore, API gravities of the oils are broadly predicted by the mathematical simulations. This methodology has once again shown its ability to rationally high-grade the petroleum-rich sectors of sedimentary basin while identifying those areas where chances of success are extremely low regardless of the presence of structures.

  10. Brownian motion at fast time scales and thermal noise imaging

    NASA Astrophysics Data System (ADS)

    Huang, Rongxin

    This dissertation presents experimental studies on Brownian motion at fast time scales, as well as our recent developments in Thermal Noise Imaging which uses thermal motions of microscopic particles for spatial imaging. As thermal motions become increasingly important in the studies of soft condensed matters, the study of Brownian motion is not only of fundamental scientific interest but also has practical applications. Optical tweezers with a fast position-sensitive detector provide high spatial and temporal resolution to study Brownian motion at fast time scales. A novel high bandwidth detector was developed with a temporal resolution of 30 ns and a spatial resolution of 1 A. With this high bandwidth detector, Brownian motion of a single particle confined in an optical trap was observed at the time scale of the ballistic regime. The hydrodynamic memory effect was fully studied with polystyrene particles of different sizes. We found that the mean square displacements of different sized polystyrene particles collapse into one master curve which is determined by the characteristic time scale of the fluid inertia effect. The particle's inertia effect was shown for particles of the same size but different densities. For the first time the velocity autocorrelation function for a single particle was shown. We found excellent agreement between our experiments and the hydrodynamic theories that take into account the fluid inertia effect. Brownian motion of a colloidal particle can be used to probe three-dimensional nano structures. This so-called thermal noise imaging (TNI) has been very successful in imaging polymer networks with a resolution of 10 nm. However, TNI is not efficient at micrometer scale scanning since a great portion of image acquisition time is wasted on large vacant volume within polymer networks. Therefore, we invented a method to improve the efficiency of large scale scanning by combining traditional point-to-point scanning to explore large vacant space with thermal noise imaging at the proximity of the object. This method increased the efficiency of thermal noise imaging by more than 40 times. This development should promote wider applications of thermal noise imaging in the studies of soft materials and biological systems.

  11. Redescription of Bellerophon asiaticus Wirth (Early Triassic: Gastropoda) from China, and a survey of Triassic Bellerophontacea.

    USGS Publications Warehouse

    Yochelson, E.Y.; Yin, Hongfu

    1985-01-01

    The bilaterally symmetrical gastropod Bellerophon asiaticus Wirth is redescribed from specimens collected in Guizhou Province, PRC. The species is reassigned to Retispira, a common late Paleozoic taxon. Retispira is another example of a Paleozoic gastropod genus that crossed the era boundary. Associated pelecypods that date these Guizhou occurrences as Early Triassic are well known species in PRC and are illustrated. Both Bellerophon and Euphemites probably occur in the Early Triassic, though the quality of illustrations leaves some uncertainty; the existence of Stachella in the Triassic is more problematic. There was no dramatic reduction of the Bellerophontacea from their abundance and diversity in the Permian. It may be a general phenomenon that most late Paleozoic family-level and many generic-level taxa of gastropods were unaffected by the late Permian 'crisis'. from Authors

  12. Feather-like development of Triassic diapsid skin appendages

    NASA Astrophysics Data System (ADS)

    Voigt, Sebastian; Buchwitz, Michael; Fischer, Jan; Krause, Daniel; Georgi, Robert

    2009-01-01

    Of the recent sauropsid skin appendage types, only feathers develop from a cylindrical epidermal invagination, the follicle, and show hierarchical branching. Fossilized integuments of Mesozoic diapsids have been interpreted as follicular and potential feather homologues, an idea particularly controversially discussed for the elongate dorsal skin projections of the small diapsid Longisquama insignis from the Triassic of Kyrgyzstan. Based on new finds and their comparison with the type material, we show that Longisquamas appendages consist of a single-branched internal frame enclosed by a flexible outer membrane. Not supporting a categorization either as feathers or as scales, our analysis demonstrates that the Longisquama appendages formed in a two-stage, feather-like developmental process, representing an unusual early example for the evolutionary plasticity of sauropsid integument.

  13. Probing Fission Time Scales with Neutrons and GDR Gamma Rays

    SciTech Connect

    Schmitt, R. P.; Botting, Tye; Chubarian, G G; Wolf, K; Hurst, B J; Jabs, H; Hamelin, M; Bacak, A; Oganessian, Yuri Ts.; Itkis, M. G.; Kozulin, E M; Kondratiev, N. A.; Salamatin, V S; Pokrovsky, I V; Hanappe, F; de Goes Brennand, E.; Huck, A; Stuttge, L; Liatard, E; Beene, James R; Varner Jr, Robert L; Halbert, Melvyn L; Gan, Ning

    2003-06-01

    The time scales for nuclear fission have been explored using both pre-and postfission neutrons and GDR gamma rays. Four systems were investigated: 133-MeV 16O + 176Yb and 208Pb and 104-MeV 4He + 188Os and 209Bi. Fission fragments were measured in coincidence with PPACs. The neutrons were detected using eight detectors from the DEMON array, while gamma rays were measured using the US BaF2 array. The pre-and postfission gamma rays were determined using moving source fits parallel and perpendicular to the fission fragment emission directions. The time scales for fission for the neutrons were determined using the neutron clock technique. The gamma-ray data were fitted using a statistical model calculation based on the code CASCADE. The results of the fits from both data types were used to extract nuclear friction coefficients, ?, and fission time scales. The ? values ranged from 7 to 20, while the fission times were (31-105) 10?21 s. From Yadernaya Fizika, Vol. 66, No. 6, 2003, pp. 1199-1203.

  14. Sublinear scaling for time-dependent stochastic density functional theory

    SciTech Connect

    Gao, Yi; Neuhauser, Daniel; Baer, Roi; Rabani, Eran

    2015-01-21

    A stochastic approach to time-dependent density functional theory is developed for computing the absorption cross section and the random phase approximation (RPA) correlation energy. The core idea of the approach involves time-propagation of a small set of stochastic orbitals which are first projected on the occupied space and then propagated in time according to the time-dependent Kohn-Sham equations. The evolving electron density is exactly represented when the number of random orbitals is infinite, but even a small number (≈16) of such orbitals is enough to obtain meaningful results for absorption spectrum and the RPA correlation energy per electron. We implement the approach for silicon nanocrystals using real-space grids and find that the overall scaling of the algorithm is sublinear with computational time and memory.

  15. Time scale of diffusion in molecular and cellular biology

    NASA Astrophysics Data System (ADS)

    Holcman, D.; Schuss, Z.

    2014-05-01

    Diffusion is the driver of critical biological processes in cellular and molecular biology. The diverse temporal scales of cellular function are determined by vastly diverse spatial scales in most biophysical processes. The latter are due, among others, to small binding sites inside or on the cell membrane or to narrow passages between large cellular compartments. The great disparity in scales is at the root of the difficulty in quantifying cell function from molecular dynamics and from simulations. The coarse-grained time scale of cellular function is determined from molecular diffusion by the mean first passage time of molecular Brownian motion to a small targets or through narrow passages. The narrow escape theory (NET) concerns this issue. The NET is ubiquitous in molecular and cellular biology and is manifested, among others, in chemical reactions, in the calculation of the effective diffusion coefficient of receptors diffusing on a neuronal cell membrane strewn with obstacles, in the quantification of the early steps of viral trafficking, in the regulation of diffusion between the mother and daughter cells during cell division, and many other cases. Brownian trajectories can represent the motion of a molecule, a protein, an ion in solution, a receptor in a cell or on its membrane, and many other biochemical processes. The small target can represent a binding site or an ionic channel, a hidden active site embedded in a complex protein structure, a receptor for a neurotransmitter on the membrane of a neuron, and so on. The mean time to attach to a receptor or activator determines diffusion fluxes that are key regulators of cell function. This review describes physical models of various subcellular microdomains, in which the NET coarse-grains the molecular scale to a higher cellular-level, thus clarifying the role of cell geometry in determining subcellular function.

  16. Space and time scales in human-landscape systems.

    PubMed

    Kondolf, G Mathias; Podolak, Kristen

    2014-01-01

    Exploring spatial and temporal scales provides a way to understand human alteration of landscape processes and human responses to these processes. We address three topics relevant to human-landscape systems: (1) scales of human impacts on geomorphic processes, (2) spatial and temporal scales in river restoration, and (3) time scales of natural disasters and behavioral and institutional responses. Studies showing dramatic recent change in sediment yields from uplands to the ocean via rivers illustrate the increasingly vast spatial extent and quick rate of human landscape change in the last two millennia, but especially in the second half of the twentieth century. Recent river restoration efforts are typically small in spatial and temporal scale compared to the historical human changes to ecosystem processes, but the cumulative effectiveness of multiple small restoration projects in achieving large ecosystem goals has yet to be demonstrated. The mismatch between infrequent natural disasters and individual risk perception, media coverage, and institutional response to natural disasters results in un-preparedness and unsustainable land use and building practices. PMID:23716006

  17. Integrated Sr isotope variations and global environmental changes through the Late Permian to early Late Triassic

    NASA Astrophysics Data System (ADS)

    Song, Haijun; Wignall, Paul B.; Tong, Jinnan; Song, Huyue; Chen, Jing; Chu, Daoliang; Tian, Li; Luo, Mao; Zong, Keqing; Chen, Yanlong; Lai, Xulong; Zhang, Kexin; Wang, Hongmei

    2015-08-01

    New 87Sr/86Sr data based on 127 well-preserved and well-dated conodont samples from South China were measured using a new technique (LA-MC-ICPMS) based on single conodont albid crown analysis. These reveal a spectacular climb in seawater 87Sr/86Sr ratios during the Early Triassic that was the most rapid of the Phanerozoic. The rapid increase began in Bed 25 of the Meishan section (GSSP of the Permian-Triassic boundary, PTB), and coincided closely with the latest Permian extinction. Modeling results indicate that the accelerated rise of 87Sr/86Sr ratios can be ascribed to a rapid increase (>2.8) of riverine flux of Sr caused by intensified weathering. This phenomenon could in turn be related to an intensification of warming-driven runoff and vegetation die-off. Continued rise of 87Sr/86Sr ratios in the Early Triassic indicates that continental weathering rates were enhanced >1.9 times compared to those of the Late Permian. Continental weathering rates began to decline in the middle-late Spathian, which may have played a role in the decrease of oceanic anoxia and recovery of marine benthos. The 87Sr/86Sr values decline gradually into the Middle Triassic to an equilibrium values around 1.2 times those of the Late Permian level, suggesting that vegetation coverage did not attain pre-extinction levels thereby allowing higher runoff.

  18. Statistical Analysis of Sensor Network Time Series at Multiple Time Scales

    NASA Astrophysics Data System (ADS)

    Granat, R. A.; Donnellan, A.

    2013-12-01

    Modern sensor networks often collect data at multiple time scales in order to observe physical phenomena that occur at different scales. Whether collected by heterogeneous or homogenous sensor networks, measurements at different time scales are usually subject to different dynamics, noise characteristics, and error sources. We explore the impact of these effects on the results of statistical time series analysis methods applied to multi-scale time series data. As a case study, we analyze results from GPS time series position data collected in Japan and the Western United States, which produce raw observations at 1Hz and orbit corrected observations at time resolutions of 5 minutes, 30 minutes, and 24 hours. We utilize the GPS analysis package (GAP) software to perform three types of statistical analysis on these observations: hidden Markov modeling, probabilistic principle components analysis, and covariance distance analysis. We compare the results of these methods at the different time scales and discuss the impact on science understanding of earthquake fault systems generally and recent large seismic events specifically, including the Tohoku-Oki earthquake in Japan and El Mayor-Cucupah earthquake in Mexico.

  19. Assestment of correlations and crossover scale in electroseismic time series

    NASA Astrophysics Data System (ADS)

    Guzman-Vargas, L.; Ramrez-Rojas, A.; Angulo-Brown, F.

    2009-04-01

    Evaluating complex fluctuations in electroseismic time series is an important task not only for earthquake prediction but also for understanding complex processes related to earthquake preparation. Previous studies have reported alterations, as the emergence of correlated dynamics in geoelectric potentials prior to an important earthquake (EQ). In this work, we apply the detrended fluctuation analysis and introduce a statistical procedure to characterize the presence of crossovers in scaling exponents, to analyze the fluctuations of geoelectric time series monitored in two sites located in Mexico. We find a complex behavior characterized by the presence of a crossover in the correlation exponents in the vicinity of a M=7.4 EQ occurred on Sept. 14, 1995. Finally, we apply the t-student test to evaluate the level of significance between short and large scaling exponents.

  20. HMC algorithm with multiple time scale integration and mass preconditioning

    NASA Astrophysics Data System (ADS)

    Urbach, C.; Jansen, K.; Shindler, A.; Wenger, U.

    2006-01-01

    We present a variant of the HMC algorithm with mass preconditioning (Hasenbusch acceleration) and multiple time scale integration. We have tested this variant for standard Wilson fermions at ?=5.6 and at pion masses ranging from 380 to 680 MeV. We show that in this situation its performance is comparable to the recently proposed HMC variant with domain decomposition as preconditioner. We give an update of the "Berlin Wall" figure, comparing the performance of our variant of the HMC algorithm to other published performance data. Advantages of the HMC algorithm with mass preconditioning and multiple time scale integration are that it is straightforward to implement and can be used in combination with a wide variety of lattice Dirac operators.

  1. Solar Irradiance Variations on Active Region Time Scales

    NASA Technical Reports Server (NTRS)

    Labonte, B. J. (Editor); Chapman, G. A. (Editor); Hudson, H. S. (Editor); Willson, R. C. (Editor)

    1984-01-01

    The variations of the total solar irradiance is an important tool for studying the Sun, thanks to the development of very precise sensors such as the ACRIM instrument on board the Solar Maximum Mission. The largest variations of the total irradiance occur on time scales of a few days are caused by solar active regions, especially sunspots. Efforts were made to describe the active region effects on total and spectral irradiance.

  2. Time scale interactions and the coevolution of humans and water

    NASA Astrophysics Data System (ADS)

    Sivapalan, Murugesu; Blschl, Gnter

    2015-09-01

    We present a coevolutionary view of hydrologic systems, revolving around feedbacks between environmental and social processes operating across different time scales. This brings to the fore an emphasis on emergent phenomena in changing water systems, such as the levee effect, adaptation to change, system lock-in, and system collapse due to resource depletion. Changing human values play a key role in the emergence of these phenomena and should therefore be considered as internal to the system. Guidance is provided for the framing and modeling of these phenomena to test alternative hypotheses about how they arose. A plurality of coevolutionary models, from stylized to comprehensive system-of-system models, may assist strategic water management for long time scales through facilitating stakeholder participation, exploring the possibility space of alternative futures, and helping to synthesize the observed dynamics in a wide range of case studies. Future research opportunities lie in exploring emergent phenomena arising from time scale interactions through historical, comparative, and process studies of human-water feedbacks.

  3. Scaling Brain Size, Keeping Timing: Evolutionary Preservation of Brain Rhythms

    PubMed Central

    Buzsáki, György; Logothetis, Nikos; Singer, Wolf

    2014-01-01

    Despite the several-thousand-fold increase of brain volume during the course of mammalian evolution, the hierarchy of brain oscillations remains remarkably preserved, allowing for multiple-time-scale communication within and across neuronal networks at approximately the same speed, irrespective of brain size. Deployment of large-diameter axons of long-range neurons could be a key factor in the preserved time management in growing brains. We discuss the consequences of such preserved network constellation in mental disease, drug discovery, and interventional therapies. PMID:24183025

  4. Scaling Laws, Shell Effects, and Transient Times in Fission Probabilities

    SciTech Connect

    Moretto, L.G.; Jing, K.X.; Gatti, R.; Wozniak, G.J.; Schmitt, R.P.

    1995-12-04

    The fission excitation functions for 14 compound nuclei covering a mass range from {ital A}=186 to 213 are shown to scale exactly according to the transition state prediction once shell effects are accounted for. The extracted shell effects correlate closely with those obtained from the ground state masses. No effects of transient times longer than 3{times}10{sup {minus}20} sec are visible. Pairing effects are noticeable at excitation energies at few MeV above the barrier. {copyright} {ital 1995} {ital The} {ital American} {ital Physical} {ital Society}.

  5. Scale dependence of the directional relationships between coupled time series

    NASA Astrophysics Data System (ADS)

    Shirazi, Amir Hossein; Aghamohammadi, Cina; Anvari, Mehrnaz; Bahraminasab, Alireza; Rahimi Tabar, M. Reza; Peinke, Joachim; Sahimi, Muhammad; Marsili, Matteo

    2013-02-01

    Using the cross-correlation of the wavelet transformation, we propose a general method of studying the scale dependence of the direction of coupling for coupled time series. The method is first demonstrated by applying it to coupled van der Pol forced oscillators and coupled nonlinear stochastic equations. We then apply the method to the analysis of the log-return time series of the stock values of the IBM and General Electric (GE) companies. Our analysis indicates that, on average, IBM stocks react earlier to possible common sector price movements than those of GE.

  6. Zircon U-Pb geochronology links the end-Triassic extinction with the Central Atlantic Magmatic Province.

    PubMed

    Blackburn, Terrence J; Olsen, Paul E; Bowring, Samuel A; McLean, Noah M; Kent, Dennis V; Puffer, John; McHone, Greg; Rasbury, E Troy; Et-Touhami, Mohammed

    2013-05-24

    The end-Triassic extinction is characterized by major losses in both terrestrial and marine diversity, setting the stage for dinosaurs to dominate Earth for the next 136 million years. Despite the approximate coincidence between this extinction and flood basalt volcanism, existing geochronologic dates have insufficient resolution to confirm eruptive rates required to induce major climate perturbations. Here, we present new zircon uranium-lead (U-Pb) geochronologic constraints on the age and duration of flood basalt volcanism within the Central Atlantic Magmatic Province. This chronology demonstrates synchroneity between the earliest volcanism and extinction, tests and corroborates the existing astrochronologic time scale, and shows that the release of magma and associated atmospheric flux occurred in four pulses over about 600,000 years, indicating expansive volcanism even as the biologic recovery was under way. PMID:23519213

  7. Scale and time dependence of serial correlations in word-length time series of written texts

    NASA Astrophysics Data System (ADS)

    Rodriguez, E.; Aguilar-Cornejo, M.; Femat, R.; Alvarez-Ramirez, J.

    2014-11-01

    This work considered the quantitative analysis of large written texts. To this end, the text was converted into a time series by taking the sequence of word lengths. The detrended fluctuation analysis (DFA) was used for characterizing long-range serial correlations of the time series. To this end, the DFA was implemented within a rolling window framework for estimating the variations of correlations, quantified in terms of the scaling exponent, strength along the text. Also, a filtering derivative was used to compute the dependence of the scaling exponent relative to the scale. The analysis was applied to three famous English-written literary narrations; namely, Alice in Wonderland (by Lewis Carrol), Dracula (by Bram Stoker) and Sense and Sensibility (by Jane Austen). The results showed that high correlations appear for scales of about 50-200 words, suggesting that at these scales the text contains the stronger coherence. The scaling exponent was not constant along the text, showing important variations with apparent cyclical behavior. An interesting coincidence between the scaling exponent variations and changes in narrative units (e.g., chapters) was found. This suggests that the scaling exponent obtained from the DFA is able to detect changes in narration structure as expressed by the usage of words of different lengths.

  8. Two-time-scale population evolution on a singular landscape

    NASA Astrophysics Data System (ADS)

    Xu, Song; Jiao, Shuyun; Jiang, Pengyao; Ao, Ping

    2014-01-01

    Under the effect of strong genetic drift, it is highly probable to observe gene fixation or gene loss in a population, shown by singular peaks on a potential landscape. The genetic drift-induced noise gives rise to two-time-scale diffusion dynamics on the bipeaked landscape. We find that the logarithmically divergent (singular) peaks do not necessarily imply infinite escape times or biological fixations by iterating the Wright-Fisher model and approximating the average escape time. Our analytical results under weak mutation and weak selection extend Kramers's escape time formula to models with B (Beta) function-like equilibrium distributions and overcome constraints in previous methods. The constructed landscape provides a coherent description for the bistable system, supports the quantitative analysis of bipeaked dynamics, and generates mathematical insights for understanding the boundary behaviors of the diffusion model.

  9. 5nsec Dead time multichannel scaling system for Mssbauer spectrometer

    NASA Astrophysics Data System (ADS)

    Verrastro, C.; Trombetta, G.; Pita, A.; Saragovi, C.; Duhalde, S.

    1991-11-01

    A PC programmable and fast multichannel scaling module has been designed to use a commercial Mssbauer spectrometer. This module is based on a 10 single chip 8 bits microcomputer (MC6805) and on a 35 fast ALU, which allows a high performance and low cost system. The module can operate in a stand-alone mode. Data analysis are performed in real time display, on XT/AT IBM PC or compatibles. The channels are ranged between 256 and 4096, the maximum number of counts is 232-1 per channel, the dwell time is 3 ?sec and the dead time between channels is 5 nsec. A friendly software display the real time spectrum and offers menues with different options at each state.

  10. Time scaling with efficient time-propagation techniques for atoms and molecules in pulsed radiation fields

    SciTech Connect

    Hamido, Aliou; Frapiccini, Ana Laura; Piraux, Bernard; Eiglsperger, Johannes; Madronero, Javier; Mota-Furtado, Francisca; O'Mahony, Patrick

    2011-07-15

    We present an ab initio approach to solving the time-dependent Schroedinger equation to treat electron- and photon-impact multiple ionization of atoms or molecules. It combines the already known time-scaled coordinate method with a high-order time propagator based on a predictor-corrector scheme. In order to exploit in an optimal way the main advantage of the time-scaled coordinate method, namely, that the scaled wave packet stays confined and evolves smoothly toward a stationary state, of which the squared modulus is directly proportional to the electron energy spectra in each ionization channel, we show that the scaled bound states should be subtracted from the total scaled wave packet. In addition, our detailed investigations suggest that multiresolution techniques like, for instance, wavelets are the most appropriate ones to represent the scaled wave packet spatially. The approach is illustrated in the case of the interaction of a one-dimensional model atom as well as atomic hydrogen with a strong oscillating field.

  11. Is there a break in scaling on centennial time scale in Holocene temperature records?

    NASA Astrophysics Data System (ADS)

    Nilsen, Tine; Rypdal, Kristoffer; Fredriksen, Hege-Beate

    2015-04-01

    A variety of paleoclimatic records have been used to study scaling properties of past climate, including ice core paleotemperature records and multi-proxy reconstructions. Records extending further back in time than the Holocene are divided into glacial/interglacial segments before analysis. The methods used to infer the scaling include the power spectral density (Lomb-Scargle periodogram and standard periodogram), detrended fluctuation analysis, wavelet variance analysis and the Haar fluctuation function. All the methods have individual strengths, weaknesses, uncertainties and biases, and for this reason it is useful to compare results from different methods when possible. Proxy-based reconstructions have limited spatial and temporal coverage, and must be used and interpreted with great care due to uncertainties. By elaborating on physical mechanisms for the actual climate fluctuations seen in the paleoclimatic temperature records as well as uncertainties in both data and methods, we demonstrate the possible pitfalls that may lead to the conclusion that the variability in temperature time series can be separated into different scaling regimes. Categorizing the Earth's surface temperature variability into a «macroweather» and "climate" regime has little or no practical meaning since the different components in the climate system are connected and interact on all time scales. Our most important result is that a break between two different scaling regimes at time scales around one century cannot be identified in Holocene climate. We do, however, observe departures from scaling, which can be attributed to variability such as a single internal quasi-periodic oscillation, an externally forced trend, or a combination of factors. If two scaling regimes are claimed to be present in one single time series, both regimes must be persistent. We show that the limited temporal resolution/length of the records significantly lowers the confidence for such persistence. A total of six Holocene ice core paleotemperature records were studied, (GRIP, GISP2 and NGRIP from Greenland, EPICA, Vostok and Taylor Dome from Antarctica). For all time series the estimated scaling exponent β is between 0.1 and 0.3 up to millennial time scales, where a deviation is observed and a seemingly higher value of β is inferred on longer time scales. The Holocene ice core records have by Lovejoy et al. (2012) been claimed to be exceptionally stable, compared to other proxy records such as marine sediment cores. Such a statement should be followed by a discussion about different types of proxy reconstructions and climate conditions. This presentation highlights that care should be taken when comparing the climate of continental land covered by ice, with a marine sediment record representing an oceanographically dynamic area. Different proxies are representative of different environmental variables, and the reconstructions are created to give a general paleoclimatic overview of a certain area, and are in that manner only blurred snapshots of the past climate.

  12. Integrated biochronology for Triassic marine vertebrate faunas of Guizhou Province, South China

    NASA Astrophysics Data System (ADS)

    Sun, Zuoyu; Jiang, Dayong; Ji, Cheng; Hao, Weicheng

    2016-03-01

    The Middle and Upper Triassic marine deposits of Guizhou Province, which yielded exceptionally well-preserved vertebrate faunas, are further investigated. New age-diagnostic conodonts and ammonoids from six measured sections, together with already published data, allow us to construct an integrated biochronology straddling strata from the upper Guanling Formation (Anisian, Middle Triassic) to the basal Xiaowa Formation (Carnian, Upper Triassic). Age constrains for those fossil Lagerstätten are now dated to the substage and zone levels: the Panxian Fauna, within the conodont Nicoraella kockeli Zone and broadly coexisted with the ammonoid 'Schreyerites' binodosus, is suggested as latest Pelsonian (middle Anisian) in age; the Xingyi Fauna is assumed to be not younger than the middle Longobardian (Late Ladinian) because the conodont Paragondolella inclinata with free-blade and the ammonoid Haoceras xingyiensis are recorded from slightly younger strata; the conodont Paragondolella auriformis and the ammonoid Trachyceras multituberculatum and Austrotrachyceras triadicum clearly indicate that the Guanling Fauna is not older than Julian (early Carnian) in age (time interval between Aon Zone or Aonoides Zone). With the new biostratigraphic data, a relative sequence and correlation of the Middle Triassic vertebrate faunas from Guizhou (South China) and Monte San Giorgio (Southern Alps, Switzerland/Italy) is proposed.

  13. The displaced eugeoclinal rocks in the El Paso Mountains and northern Mojave Desert: A Triassic sliver

    SciTech Connect

    Miller, J.S.; Glazner, A.F. . Dept. of Geology); Walker, J.D.; Martin, M.W. . Dept. of Geology)

    1993-04-01

    Many workers have drawn attention to the displaced eugeoclinal rocks in the northern Mojave Desert and El Paso Mountains and their importance in models for the development of an active continental margin in the western Cordillera. Existing models can generally for either strike-slip juxtaposition or thrust emplacement. New field data, U-Pb zircon geochronology, and isotopic data for metasedimentary rocks and plutons in the northern Mojave Desert and El Paso Mountains shed light on the timing and mechanism of emplacement of the eugeoclinal allocthon. The observations and data above indicate that Early Triassic plutons in the northern Mojave Desert came through oceanic lithosphere but later Jurassic plutons intercepted continental lithosphere. The authors suggest a model where eugeoclinal rocks were deposited on oceanic crust which was initially brought southward along a strike-slip fault and later thrust eastward over the cratonal assemblage. Permian thrusting is incompatible with their data and observations. Intrusion of lower Triassic strata by Early Triassic plutons in the Lane Mountain area permits some Early Triassic thrusting but the oceanic affinity of the plutons implies that thrusting did not involve continental lithosphere.

  14. Macropredatory ichthyosaur from the Middle Triassic and the origin of modern trophic networks.

    PubMed

    Frbisch, Nadia B; Frbisch, Jrg; Sander, P Martin; Schmitz, Lars; Rieppel, Olivier

    2013-01-22

    The biotic recovery from Earth's most severe extinction event at the Permian-Triassic boundary largely reestablished the preextinction structure of marine trophic networks, with marine reptiles assuming the predator roles. However, the highest trophic level of today's marine ecosystems, i.e., macropredatory tetrapods that forage on prey of similar size to their own, was thus far lacking in the Paleozoic and early Mesozoic. Here we report a top-tier tetrapod predator, a very large (>8.6 m) ichthyosaur from the early Middle Triassic (244 Ma), of Nevada. This ichthyosaur had a massive skull and large labiolingually flattened teeth with two cutting edges indicative of a macropredatory feeding style. Its presence documents the rapid evolution of modern marine ecosystems in the Triassic where the same level of complexity as observed in today's marine ecosystems is reached within 8 My after the Permian-Triassic mass extinction and within 4 My of the time reptiles first invaded the sea. This find also indicates that the biotic recovery in the marine realm may have occurred faster compared with terrestrial ecosystems, where the first apex predators may not have evolved before the Carnian. PMID:23297200

  15. Integrated Record of Terrestrial Biotic Change from the Upper Triassic Chinle Formation of northern New Mexico

    NASA Astrophysics Data System (ADS)

    Irmis, R. B.; Lindström, S.; Dunlavey, M.; Whiteside, J. H.

    2010-12-01

    The Triassic Period was an interval of major biotic and environmental changes sandwiched between two major mass extinctions. During the Late Triassic (235-201.3 Ma), dinosaurs originated and diversified across Pangaea, and several major extant vertebrate groups also appeared for the first time. Unfortunately, few detailed stratigraphically-precise local-regional paleontological records exist for continental Triassic strata, which hinders any attempt to understand the tempo and mode of biotic change through the Late Triassic. We present a new stratigraphically well-constrained fossil vertebrate and palynomorph record (10-15 Ma in duration) from the upper Chinle Formation of the Chama Basin, northern New Mexico, an area that is famous for preserving one of the best records of early dinosaurs in North America. Our data indicate that vertebrate faunas were generally stable, experiencing only one identifiable species turnover event. Dinosaurs, although relatively diverse, were never abundant components of the fauna. Contemporaneous palynological records indicate that floral composition fluctuated considerably. The drought-tolerant conifer pollen Enzonalasporites and other gymnosperms such as Alisporites and Protodiploxypinus dominate most palynofloral assemblages, but there is a distinct increase in fern spore abundance near the top of the section. In combination with evidence of variability from organic carbon stable isotopes, these data indicate that the vertebrate fauna, including early dinosaurs, remained stable over millions of years despite living within a dynamic ecosystem associated with rapidly changing environmental conditions.

  16. Macropredatory ichthyosaur from the Middle Triassic and the origin of modern trophic networks

    PubMed Central

    Frbisch, Nadia B.; Frbisch, Jrg; Sander, P. Martin; Schmitz, Lars; Rieppel, Olivier

    2013-01-01

    The biotic recovery from Earths most severe extinction event at the Permian-Triassic boundary largely reestablished the preextinction structure of marine trophic networks, with marine reptiles assuming the predator roles. However, the highest trophic level of today's marine ecosystems, i.e., macropredatory tetrapods that forage on prey of similar size to their own, was thus far lacking in the Paleozoic and early Mesozoic. Here we report a top-tier tetrapod predator, a very large (>8.6 m) ichthyosaur from the early Middle Triassic (244 Ma), of Nevada. This ichthyosaur had a massive skull and large labiolingually flattened teeth with two cutting edges indicative of a macropredatory feeding style. Its presence documents the rapid evolution of modern marine ecosystems in the Triassic where the same level of complexity as observed in todays marine ecosystems is reached within 8 My after the Permian-Triassic mass extinction and within 4 My of the time reptiles first invaded the sea. This find also indicates that the biotic recovery in the marine realm may have occurred faster compared with terrestrial ecosystems, where the first apex predators may not have evolved before the Carnian. PMID:23297200

  17. Time Scale Hierarchies in the Functional Organization of Complex Behaviors

    PubMed Central

    Perdikis, Dionysios; Huys, Raoul; Jirsa, Viktor K.

    2011-01-01

    Traditional approaches to cognitive modelling generally portray cognitive events in terms of ‘discrete’ states (point attractor dynamics) rather than in terms of processes, thereby neglecting the time structure of cognition. In contrast, more recent approaches explicitly address this temporal dimension, but typically provide no entry points into cognitive categorization of events and experiences. With the aim to incorporate both these aspects, we propose a framework for functional architectures. Our approach is grounded in the notion that arbitrary complex (human) behaviour is decomposable into functional modes (elementary units), which we conceptualize as low-dimensional dynamical objects (structured flows on manifolds). The ensemble of modes at an agent’s disposal constitutes his/her functional repertoire. The modes may be subjected to additional dynamics (termed operational signals), in particular, instantaneous inputs, and a mechanism that sequentially selects a mode so that it temporarily dominates the functional dynamics. The inputs and selection mechanisms act on faster and slower time scales then that inherent to the modes, respectively. The dynamics across the three time scales are coupled via feedback, rendering the entire architecture autonomous. We illustrate the functional architecture in the context of serial behaviour, namely cursive handwriting. Subsequently, we investigate the possibility of recovering the contributions of functional modes and operational signals from the output, which appears to be possible only when examining the output phase flow (i.e., not from trajectories in phase space or time). PMID:21980278

  18. A microbial carbonate response in synchrony with the end-Triassic mass extinction across the SW UK

    PubMed Central

    Ibarra, Yadira; Corsetti, Frank A.; Greene, Sarah E.; Bottjer, David J.

    2016-01-01

    The eruption of the Central Atlantic Magmatic Province (CAMP)—the largest igneous province known—has been linked to the end-Triassic mass extinction event, however reconciling the response of the biosphere (at local and nonlocal scales) to potential CAMP-induced geochemical excursions has remained challenging. Here we present a combined sedimentary and biological response to an ecosystem collapse in Triassic-Jurassic strata of the southwest United Kingdom (SW UK) expressed as widely distributed carbonate microbialites and associated biogeochemical facies. The microbialites (1) occur at the same stratigraphic level as the mass extinction extinction, (2) host a negative isotope excursion in δ13Corg found in other successions around the world, and (3) co-occur with an acme of prasinophyte algae ‘disaster taxa’ also dominant in Triassic-Jurassic boundary strata of other European sections. Although the duration of microbialite deposition is uncertain, it is likely that they formed rapidly (perhaps fewer than ten thousand years), thus providing a high-resolution glimpse into the initial carbon isotopic perturbation coincident with the end-Triassic mass extinction. These findings indicate microbialites from the SW UK capture a nonlocal biosedimentary response to the cascading effects of massive volcanism and add to the current understanding of paleoecology in the aftermath of the end-Triassic extinction. PMID:26813244

  19. A microbial carbonate response in synchrony with the end-Triassic mass extinction across the SW UK.

    PubMed

    Ibarra, Yadira; Corsetti, Frank A; Greene, Sarah E; Bottjer, David J

    2016-01-01

    The eruption of the Central Atlantic Magmatic Province (CAMP)-the largest igneous province known-has been linked to the end-Triassic mass extinction event, however reconciling the response of the biosphere (at local and nonlocal scales) to potential CAMP-induced geochemical excursions has remained challenging. Here we present a combined sedimentary and biological response to an ecosystem collapse in Triassic-Jurassic strata of the southwest United Kingdom (SW UK) expressed as widely distributed carbonate microbialites and associated biogeochemical facies. The microbialites (1) occur at the same stratigraphic level as the mass extinction extinction, (2) host a negative isotope excursion in δ(13)Corg found in other successions around the world, and (3) co-occur with an acme of prasinophyte algae 'disaster taxa' also dominant in Triassic-Jurassic boundary strata of other European sections. Although the duration of microbialite deposition is uncertain, it is likely that they formed rapidly (perhaps fewer than ten thousand years), thus providing a high-resolution glimpse into the initial carbon isotopic perturbation coincident with the end-Triassic mass extinction. These findings indicate microbialites from the SW UK capture a nonlocal biosedimentary response to the cascading effects of massive volcanism and add to the current understanding of paleoecology in the aftermath of the end-Triassic extinction. PMID:26813244

  20. Terrestrial Waters and Sea Level Variations on Interannual Time Scale

    NASA Technical Reports Server (NTRS)

    Llovel, W.; Becker, M.; Cazenave, A.; Jevrejeva, S.; Alkama, R.; Decharme, B.; Douville, H.; Ablain, M.; Beckley, B.

    2011-01-01

    On decadal to multi-decadal time scales, thermal expansion of sea waters and land ice loss are the main contributors to sea level variations. However, modification of the terrestrial water cycle due to climate variability and direct anthropogenic forcing may also affect sea level. For the past decades, variations in land water storage and corresponding effects on sea level cannot be directly estimated from observations because these are almost non-existent at global continental scale. However, global hydrological models developed for atmospheric and climatic studies can be used for estimating total water storage. For the recent years (since mid-2002), terrestrial water storage change can be directly estimated from observations of the GRACE space gravimetry mission. In this study, we analyse the interannual variability of total land water storage, and investigate its contribution to mean sea level variability at interannual time scale. We consider three different periods that, each, depend on data availability: (1) GRACE era (2003-2009), (2) 1993-2003 and (3) 1955-1995. For the GRACE era (period 1), change in land water storage is estimated using different GRACE products over the 33 largest river basins worldwide. For periods 2 and 3, we use outputs from the ISBA-TRIP (Interactions between Soil, Biosphere, and Atmosphere-Total Runoff Integrating Pathways) global hydrological model. For each time span, we compare change in land water storage (expressed in sea level equivalent) to observed mean sea level, either from satellite altimetry (periods 1 and 2) or tide gauge records (period 3). For each data set and each time span, a trend has been removed as we focus on the interannual variability. We show that whatever the period considered, interannual variability of the mean sea level is essentially explained by interannual fluctuations in land water storage, with the largest contributions arising from tropical river basins.

  1. Prolonged and recurrent global seafloor anoxia in the Early Triassic from uranium isotopic evidence

    NASA Astrophysics Data System (ADS)

    Lau, K. V.; Maher, K.; Kelley, B. M.; Yu, M.; Lehrmann, D. J.; Payne, J.

    2013-12-01

    The end-Permian extinction and prolonged Early Triassic recovery of marine ecosystems have been attributed in part to marine anoxia. However, the spatial and temporal extent of anoxic waters during Early Triassic time remains poorly understood. To better constrain the evolution of seawater conditions, we present a record of ?238/235U and uranium concentrations collected from the Great Bank of Guizhou, a Late Permian to Late Triassic isolated carbonate platform in the Nanpanjiang Basin, South China. The isotopic composition and concentration of uranium are independent constraints on paleoredox conditions and can be used as indicators for the global extent of ocean anoxia. Our ?238/235U results demonstrate that two large negative excursions of up to ~-0.4 occurred in the Induan and in the Spathian, before stabilizing in the Middle Triassic at Late Permian values. Uranium concentrations mirror the isotopic trends, reaching sustained minima of less than 0.2 ppm that correspond to the most negative isotopic values. By placing these observational constraints on a box model of the geological uranium cycle, we calculate that up to half of the continental shelves may have been affected during the two pulses of bottom-water anoxia. The expansion, contraction, and re-expansion of extreme low-oxygen conditions could explain many unresolved aspects of the prolonged recovery of marine ecosystems. The recurrence of widespread anoxia during Spathian time may have interrupted the recovery of marine organisms that began in the more oxic waters of the Smithian. These episodes of significant and prolonged bottom-water anoxia coincide with the most negative ?13C values, suggesting that Early Triassic perturbations to the global carbon cycle were tightly coupled to changes in ocean redox chemistry.

  2. Optimal Control Modification for Time-Scale Separated Systems

    NASA Technical Reports Server (NTRS)

    Nguyen, Nhan T.

    2012-01-01

    Recently a new optimal control modification has been introduced that can achieve robust adaptation with a large adaptive gain without incurring high-frequency oscillations as with the standard model-reference adaptive control. This modification is based on an optimal control formulation to minimize the L2 norm of the tracking error. The optimal control modification adaptive law results in a stable adaptation in the presence of a large adaptive gain. This study examines the optimal control modification adaptive law in the context of a system with a time scale separation resulting from a fast plant with a slow actuator. A singular perturbation analysis is performed to derive a modification to the adaptive law by transforming the original system into a reduced-order system in slow time. A model matching conditions in the transformed time coordinate results in an increase in the actuator command that effectively compensate for the slow actuator dynamics. Simulations demonstrate effectiveness of the method.

  3. Arthropods in amber from the Triassic Period

    PubMed Central

    Schmidt, Alexander R.; Jancke, Saskia; Lindquist, Evert E.; Ragazzi, Eugenio; Roghi, Guido; Nascimbene, Paul C.; Schmidt, Kerstin; Wappler, Torsten; Grimaldi, David A.

    2012-01-01

    The occurrence of arthropods in amber exclusively from the Cretaceous and Cenozoic is widely regarded to be a result of the production and preservation of large amounts of tree resin beginning ca. 130million years (Ma) ago. Abundant 230million-year-old amber from the Late Triassic (Carnian) of northeastern Italy has previously yielded myriad microorganisms, but we report here that it also preserves arthropods some 100Ma older than the earliest prior records in amber. The Triassic specimens are a nematoceran fly (Diptera) and two disparate species of mites, Triasacarus fedelei gen. et sp. nov., and Ampezzoa triassica gen. et sp. nov. These mites are the oldest definitive fossils of a group, the Eriophyoidea, which includes the gall mites and comprises at least 3,500 Recent species, 97% of which feed on angiosperms and represents one of the most specialized lineages of phytophagous arthropods. Antiquity of the gall mites in much their extant form was unexpected, particularly with the Triassic species already having many of their present-day features (such as only two pairs of legs); further, it establishes conifer feeding as an ancestral trait. Feeding by the fossil mites may have contributed to the formation of the amber droplets, but we find that the abundance of amber during the Carnian (ca. 230Ma) is globally anomalous for the pre-Cretaceous and may, alternatively, be related to paleoclimate. Further recovery of arthropods in Carnian-aged amber is promising and will have profound implications for understanding the evolution of terrestrial members of the most diverse phylum of organisms. PMID:22927387

  4. Arthropods in amber from the Triassic Period.

    PubMed

    Schmidt, Alexander R; Jancke, Saskia; Lindquist, Evert E; Ragazzi, Eugenio; Roghi, Guido; Nascimbene, Paul C; Schmidt, Kerstin; Wappler, Torsten; Grimaldi, David A

    2012-09-11

    The occurrence of arthropods in amber exclusively from the Cretaceous and Cenozoic is widely regarded to be a result of the production and preservation of large amounts of tree resin beginning ca. 130 million years (Ma) ago. Abundant 230 million-year-old amber from the Late Triassic (Carnian) of northeastern Italy has previously yielded myriad microorganisms, but we report here that it also preserves arthropods some 100 Ma older than the earliest prior records in amber. The Triassic specimens are a nematoceran fly (Diptera) and two disparate species of mites, Triasacarus fedelei gen. et sp. nov., and Ampezzoa triassica gen. et sp. nov. These mites are the oldest definitive fossils of a group, the Eriophyoidea, which includes the gall mites and comprises at least 3,500 Recent species, 97% of which feed on angiosperms and represents one of the most specialized lineages of phytophagous arthropods. Antiquity of the gall mites in much their extant form was unexpected, particularly with the Triassic species already having many of their present-day features (such as only two pairs of legs); further, it establishes conifer feeding as an ancestral trait. Feeding by the fossil mites may have contributed to the formation of the amber droplets, but we find that the abundance of amber during the Carnian (ca. 230 Ma) is globally anomalous for the pre-Cretaceous and may, alternatively, be related to paleoclimate. Further recovery of arthropods in Carnian-aged amber is promising and will have profound implications for understanding the evolution of terrestrial members of the most diverse phylum of organisms. PMID:22927387

  5. Continental weathering in the Early Triassic in Himalayan Tethys, central Nepal: Implications for abrupt environmental change on the northern margin of Gondwanaland

    NASA Astrophysics Data System (ADS)

    Yoshida, Kohki; Kawamura, Toshio; Suzuki, Shigeyuki; Regmi, Amar Deep; Gyawali, Babu Ram; Shiga, Yuka; Adachi, Yoshiko; Dhital, Megh Raj

    2014-01-01

    The geochemistry of Triassic mudstones in the Himalayan Tethys sequence, central Nepal, was studied with respect to changes in sedimentary facies, grain size, and source rocks. The Triassic sedimentary facies of mudstone and carbonates show deposition in offshore to hemiplegic environments. The rare earth element (REE) pattern of the Permian and Triassic mudstones suggests uniformity correlatable to average shale. The major element geochemistry of the Early Triassic Griesbachian-early Smithian mudstones indicates a sediment supply from strongly weathered sources with the chemical index of alteration (CIA) values of 76-81. However, the mudstones in the late Smithian show weakly weathered sources with CIA values of 68-74. The lower part of the Middle Triassic Anisian mudstones return to Early Triassic paleoweathering levels. There are no significant relationships among lithofacies, the grain size of the sediments, and CIA values. Thus, the abrupt change of the degree of paleoweathering in the Early Triassic, late Smithian time, suggests a dramatic decrease in continental weathering, which is related to a predominantly arid climate in the northern marginal area of Gondwana.

  6. Multiple-Time Scaling and Universal Behavior of the Earthquake Interevent Time Distribution

    SciTech Connect

    Bottiglieri, M.; Godano, C.; Lippiello, E.; Arcangelis, L. de

    2010-04-16

    The interevent time distribution characterizes the temporal occurrence in seismic catalogs. Universal scaling properties of this distribution have been evidenced for entire catalogs and seismic sequences. Recently, these universal features have been questioned and some criticisms have been raised. We investigate the existence of universal scaling properties by analyzing a Californian catalog and by means of numerical simulations of an epidemic-type model. We show that the interevent time distribution exhibits a universal behavior over the entire temporal range if four characteristic times are taken into account. The above analysis allows us to identify the scaling form leading to universal behavior and explains the observed deviations. Furthermore, it provides a tool to identify the dependence on the mainshock magnitude of the c parameter that fixes the onset of the power law decay in the Omori law.

  7. Geometric structure of multiple time-scale nonlinear dynamical systems

    NASA Astrophysics Data System (ADS)

    Bharadwaj, Sanjay

    A new methodology to analyze time-scale structure of smooth finite-dimensional nonlinear dynamical systems is developed. This approach does not assume apriori knowledge of slow and fast variables for special coordinates that simplify the form of the nonlinear dynamics. Conventional approaches to analyze time-scale structure of nonlinear dynamics such as singular perturbation theory proceed from such specialized apriori knowledge which is often not obtainable. Our approach proceeds from spectral analysis of the linear variational dynamics associated with the nonlinear system. The variational dynamics govern the flow on the tangent bundle to the state-space. We decompose the tangent space at each point into spectral subspaces which separate tangent vectors that evolve at different spectral rates. The existence of such measures of spectral rates and corresponding subspaces is established by Sacker and Sell. We have developed a scheme to computationally determine these spectral measures using finite-time Lyapunov exponents and associated direction fields. In the asymptotic limit, the infinite-time Lyapunov direction fields are shown to satisfy useful invariance properties. As a consequence they are shown to uniquely define an invariant spectral filtration, i.e., a collection of nested distributions which are invariant under the nonlinear flow. Using these results, we establish the consistency of these spectral measures with well known results in special cases such as linear time-invariant systems and periodic linear time-varying systems. Differential equations that govern the propagation of Lyapunov directions along orbits of the nonlinear flow are derived using the invariance properties. Methods to apply these spectral analysis tools to construct coordinate transformations that decompose the variational flow are developed. When the Frobenius theorem is applicable, we also show methods to construct a nonlinear transformation of coordinates from the Lyapunov direction fields to decompose the nonlinear dynamics into slow and fast subsystems. In fact, this procedure can be used to transform the two time-scale nonlinear dynamics into a singularly perturbed standard form. Application of these methods for reducing the order of nonlinear dynamics, locating the slow manifold in the state-space and solving boundary value problems arising from hypersensitive optimal control problems is discussed. Several simple examples are used to demonstrate the methods and elucidate the main concepts.

  8. Ti diffusion in quartz inclusions: implications for metamorphic time scales

    NASA Astrophysics Data System (ADS)

    Spear, Frank S.; Ashley, Kyle T.; Webb, Laura E.; Thomas, Jay B.

    2012-12-01

    Quartz inclusions in garnet from samples collected from the staurolite zone in central New England are zoned in cathodoluminescence (CL). The CL intensity is interpreted to be a proxy for Ti concentration and the zoning attributed to Ti diffusion into the quartz grains driven by Ti exchange between quartz and enclosing garnet as a function of changing temperature. The CL zoning has been interpreted using a numerical diffusion model to constrain the time scales over which the diffusion has occurred. Temperature-time histories are sensitive to the presumed peak temperature but not to other model parameters. The total time of the metamorphic heating and cooling cycle from around 450 C to the peak temperature (550-600 C) back to 450 C is surprisingly short and encompasses only 0.2-2 million years for peak temperatures of 600-550 C. The metamorphism was accompanied by large-scale nappe and dome formation, and it is suggested that this occurred as a consequence of in-sequence thrusting resulting in a mid-crustal ductile duplex structure.

  9. Time scale algorithms for an inhomogeneous group of atomic clocks

    NASA Technical Reports Server (NTRS)

    Jacques, C.; Boulanger, J.-S.; Douglas, R. J.; Morris, D.; Cundy, S.; Lam, H. F.

    1993-01-01

    Through the past 17 years, the time scale requirements at the National Research Council (NRC) have been met by the unsteered output of its primary laboratory cesium clocks, supplemented by hydrogen masers when short-term stability better than 2 x 10(exp -12)tau(sup -1/2) has been required. NRC now operates three primary laboratory cesium clocks, three hydrogen masers, and two commercial cesium clocks. NRC has been using ensemble averages for internal purposes for the past several years, and has a realtime algorithm operating on the outputs of its high-resolution (2 x 10(exp -13) s at 1 s) phase comparators. The slow frequency drift of the hydrogen masers has presented difficulties in incorporating their short-term stability into the ensemble average, while retaining the long-term stability of the laboratory cesium frequency standards. We report on this work on algorithms for an inhomogeneous ensemble of atomic clocks, and on our initial work on time scale algorithms that could incorporate frequency calibrations at NRC from the next generation of Zacharias fountain cesium frequency standards having frequency accuracies that might surpass 10(exp -15), or from single-trapped-ion frequency standards (Ba+, Sr+,...) with even higher potential accuracies. The requirements for redundancy in all the elements (including the algorithms) of an inhomogeneous ensemble that would give a robust real-time output of the algorithms are presented and discussed.

  10. Role of Relaxation Time Scale in Noisy Signal Transduction

    PubMed Central

    Maity, Alok Kumar; Chaudhury, Pinaki; Banik, Suman K

    2015-01-01

    Intra-cellular fluctuations, mainly triggered by gene expression, are an inevitable phenomenon observed in living cells. It influences generation of phenotypic diversity in genetically identical cells. Such variation of cellular components is beneficial in some contexts but detrimental in others. To quantify the fluctuations in a gene product, we undertake an analytical scheme for studying few naturally abundant linear as well as branched chain network motifs. We solve the Langevin equations associated with each motif under the purview of linear noise approximation and derive the expressions for Fano factor and mutual information in close analytical form. Both quantifiable expressions exclusively depend on the relaxation time (decay rate constant) and steady state population of the network components. We investigate the effect of relaxation time constraints on Fano factor and mutual information to indentify a time scale domain where a network can recognize the fluctuations associated with the input signal more reliably. We also show how input population affects both quantities. We extend our calculation to long chain linear motif and show that with increasing chain length, the Fano factor value increases but the mutual information processing capability decreases. In this type of motif, the intermediate components act as a noise filter that tune up input fluctuations and maintain optimum fluctuations in the output. For branched chain motifs, both quantities vary within a large scale due to their network architecture and facilitate survival of living system in diverse environmental conditions. PMID:25955500

  11. Fugue: time scales of adaptation in mobile video

    NASA Astrophysics Data System (ADS)

    Corner, Mark D.; Noble, Brian D.; Wasserman, Kimberly M.

    2000-12-01

    Providing interactive video on hand-held, mobile devices is extremely difficult. These devices are subject to processor, memory, and power constraints, and communicate over wireless links of rapidly varying quality. Furthermore, the size of encoded video is difficult to predict, complicating the encoding task. We present Fugue, a system that copes with these challenges through a division along time scales of adaptation. Fugue is structured as three sperate controllers: transmission, video and preference. This decomposition provides adaptation along different time scales: per-packet, per-frame, and per-video. The controllers are provided at modest time and space costs compared to the cost of video encoding. We present simulations confirming the efficacy of our transmission controller, and compare our video controller to several alternatives. We find that, in situations amenable to adaptive compression, our scheme provides video quality equal to or better than the alternatives at a comparable or substantially lower computational cost. We also find that distortion, the metric commonly used to compare mobile video, under-values the contribution smooth motion makes to perceived video quality.

  12. Time scales in the context of general relativity.

    PubMed

    Guinot, Bernard

    2011-10-28

    Towards 1967, the accuracy of caesium frequency standards reached such a level that the relativistic effect could not be ignored anymore. Corrections began to be applied for the gravitational frequency shift and for distant time comparisons. However, these corrections were not applied to an explicit theoretical framework. Only in 1991 did the International Astronomical Union provide metrics (then improved in 2000) for a definition of space-time coordinates in reference systems centred at the barycentre of the Solar System and at the centre of mass of the Earth. In these systems, the temporal coordinates (coordinate times) can be realized on the basis of one of them, the International Atomic Time (TAI), which is itself a realized time scale. The definition and the role of TAI in this context will be recalled. There remain controversies regarding the name to be given to the unit of coordinate times and to other quantities appearing in the theory. However, the idea that astrometry and celestial mechanics should adopt the usual metrological rules is progressing, together with the use of the International System of Units, among astronomers. PMID:21930569

  13. Scaling in a Continuous Time Model for Biological Aging

    NASA Astrophysics Data System (ADS)

    de Almeida, R. M. C.; Thomas, G. L.

    In this paper, we consider a generalization to the asexual version of Penna model for biological aging, where we take a continuous time limit. The genotype associated to each individual is an interval of real numbers over which Dirac δ-functions are defined, representing genetically programmed diseases to be switched on at defined ages of the individual life. We discuss two different continuous limits for the evolution equation and two different mutation protocols, to be implemented during reproduction. Exact stationary solutions are obtained and scaling properties are discussed.

  14. Viscosity and fission time scale of 156Dy

    NASA Astrophysics Data System (ADS)

    van't Hof, G.; Hesselink, W. H. A.; Plompen, A. J. M.; van Schagen, J. P. S.; Harakeh, M. N.; Kalantar-Nayestanaki, N.; Bacelar, J. C. S.; van der Ploeg, H.; Diószegi, I.; Kugler, A.

    1996-10-01

    In the fusion-fission reaction 40Ar+116Cd-->156Dy-->fission, performed at beam energies Eb=216 MeV and 238 MeV, γ rays were measured in coincidence with fission fragments. The γ-ray spectra are interpreted using a modified version of the statistical-model code CASCADE. From a comparison of the experimental and calculated spectra it is deduced that the nuclear viscosity is in the range 0.01<γ<4. The extracted fission time scale is of the order of 10-19 s.

  15. Viscosity, fission time scale and deformation of 156Dy

    NASA Astrophysics Data System (ADS)

    van't Hof, G.; Bacelar, J. C. S.; Diószegi, I.; Harakeh, M. N.; Hesselink, W. H. A.; Kalantar-Nayestanaki, N.; Kugler, A.; van der Ploeg, H.; Plompen, A. J. M.; van Schagen, J. P. S.

    1998-08-01

    In the fusion-fission reaction 40Ar + 116Cd → 156Dy ∗ → fission , at Eb = 216 MeV and 238 MeV, γ-rays were measured in coincidence with fission fragments. The interpretation of the γ-ray spectra is done with the help of a modified version of the statistical-model code CASCADE. The spectra can be reproduced with nuclear viscosities in the range 0.01 < γ < 4. The extracted fission time scale is of the order of 10 -19 s. The CASCADE analysis seems to favor a prolate deformation with β ≈ 0.45.

  16. Time-Dependent Earthquake Forecasts on a Global Scale

    NASA Astrophysics Data System (ADS)

    Rundle, J. B.; Holliday, J. R.; Turcotte, D. L.; Graves, W. R.

    2014-12-01

    We develop and implement a new type of global earthquake forecast. Our forecast is a perturbation on a smoothed seismicity (Relative Intensity) spatial forecast combined with a temporal time-averaged ("Poisson") forecast. A variety of statistical and fault-system models have been discussed for use in computing forecast probabilities. An example is the Working Group on California Earthquake Probabilities, which has been using fault-based models to compute conditional probabilities in California since 1988. An example of a forecast is the Epidemic-Type Aftershock Sequence (ETAS), which is based on the Gutenberg-Richter (GR) magnitude-frequency law, the Omori aftershock law, and Poisson statistics. The method discussed in this talk is based on the observation that GR statistics characterize seismicity for all space and time. Small magnitude event counts (quake counts) are used as "markers" for the approach of large events. More specifically, if the GR b-value = 1, then for every 1000 M>3 earthquakes, one expects 1 M>6 earthquake. So if ~1000 M>3 events have occurred in a spatial region since the last M>6 earthquake, another M>6 earthquake should be expected soon. In physics, event count models have been called natural time models, since counts of small events represent a physical or natural time scale characterizing the system dynamics. In a previous research, we used conditional Weibull statistics to convert event counts into a temporal probability for a given fixed region. In the present paper, we move belyond a fixed region, and develop a method to compute these Natural Time Weibull (NTW) forecasts on a global scale, using an internally consistent method, in regions of arbitrary shape and size. We develop and implement these methods on a modern web-service computing platform, which can be found at www.openhazards.com and www.quakesim.org. We also discuss constraints on the User Interface (UI) that follow from practical considerations of site usability.

  17. A new Lower Triassic ichthyopterygian assemblage from Fossil Hill, Nevada.

    PubMed

    Kelley, Neil P; Motani, Ryosuke; Embree, Patrick; Orchard, Michael J

    2016-01-01

    We report a new ichthyopterygian assemblage from Lower Triassic horizons of the Prida Formation at Fossil Hill in central Nevada. Although fragmentary, the specimens collected so far document a diverse fauna. One partial jaw exhibits isodont dentition with blunt tipped, mesiodistally compressed crowns and striated enamel. These features are shared with the Early Triassic genus Utatsusaurus known from coeval deposits in Japan and British Columbia. An additional specimen exhibits a different dentition characterized by relatively small, rounded posterior teeth resembling other Early Triassic ichthyopterygians, particularly Grippia. This Nevada assemblage marks a southward latitudinal extension for Early Triassic ichthyopterygians along the eastern margin of Panthalassa and indicates repeated trans-hemispheric dispersal events in Early Triassic ichthyopterygians. PMID:26855868

  18. A new Lower Triassic ichthyopterygian assemblage from Fossil Hill, Nevada

    PubMed Central

    Motani, Ryosuke; Embree, Patrick; Orchard, Michael J.

    2016-01-01

    We report a new ichthyopterygian assemblage from Lower Triassic horizons of the Prida Formation at Fossil Hill in central Nevada. Although fragmentary, the specimens collected so far document a diverse fauna. One partial jaw exhibits isodont dentition with blunt tipped, mesiodistally compressed crowns and striated enamel. These features are shared with the Early Triassic genus Utatsusaurus known from coeval deposits in Japan and British Columbia. An additional specimen exhibits a different dentition characterized by relatively small, rounded posterior teeth resembling other Early Triassic ichthyopterygians, particularly Grippia. This Nevada assemblage marks a southward latitudinal extension for Early Triassic ichthyopterygians along the eastern margin of Panthalassa and indicates repeated trans-hemispheric dispersal events in Early Triassic ichthyopterygians. PMID:26855868

  19. The oldest dinosaur? A Middle Triassic dinosauriform from Tanzania

    PubMed Central

    Nesbitt, Sterling J.; Barrett, Paul M.; Werning, Sarah; Sidor, Christian A.; Charig, Alan J.

    2013-01-01

    The rise of dinosaurs was a major event in vertebrate history, but the timing of the origin and early diversification of the group remain poorly constrained. Here, we describe Nyasasaurus parringtoni gen. et sp. nov., which is identified as either the earliest known member of, or the sister–taxon to, Dinosauria. Nyasasaurus possesses a unique combination of dinosaur character states and an elevated growth rate similar to that of definitive early dinosaurs. It demonstrates that the initial dinosaur radiation occurred over a longer timescale than previously thought (possibly 15 Myr earlier), and that dinosaurs and their immediate relatives are better understood as part of a larger Middle Triassic archosauriform radiation. The African provenance of Nyasasaurus supports a southern Pangaean origin for Dinosauria. PMID:23221875

  20. Sequence stratigraphy of the Triassic in the Barentsz Sea

    SciTech Connect

    Skjold, L.JU.; Van Veen, P.M.; Gjelberg, J.; Kristensen, S.E.; Rasmussen, A.; Skott, P.H.; Stoelan, T. )

    1990-05-01

    A regional study of the Triassic in the Barentsz Sea (20-32{degree}E, 71-74{degree}N) revealed sequences that correlate seismically for hundreds of kilometers. Recent offshore drilling results enabled them to establish a biostratigraphic time framework. Comparisons with information from onshore outcrops (such as the Svalbard Archipelago) aided the piecing together of these superregional sequences. Seismic character analysis identified three units with composite progradational patterns (Induan, Olenekian, and Anisian). Fluvial, deltaic, and marine deposits can be distinguished and located relative to the paleocoastlines. Corresponding downlap surfaces suggest the development of condensed intervals, predicted to consist of organic-rich source rocks, as was later confirmed by drilling. Regional predictions based on this sequence-stratigraphic approach have proved valuable when correlating and evaluating well information. The sequences identified also help define third-order sea level curves for the area; these improve published curves thought to have global significance.

  1. Parallel trends in organic and inorganic carbon isotopes across the Permian/Triassic boundary

    SciTech Connect

    Magaritz, M. ); Krishnamurthy, R.V. ); Holser, W.T. Cornell Univ., Ithaca, NY )

    1992-12-01

    Stable carbon isotope ratios in both inorganic and organic reservoirs have been widely applied to model environmental and sedimentological changes on a global scale. Most studies dealing with major extinction events have used the record of inorganic carbon. In this paper the authors report the relation between shifts in carbon-13 content of organic matter and coexisting carbonate fractions at a major extinction event, the Permian/Triassic boundary. They found that both [delta][sup 13]C[sub carb] and [delta][sup 13]C[sub org] of the surface ocean varied dramatically across the boundary, but the fractionation [Delta][sup 13]C between organic matter and carbonate remained constant. This result appreciably restricts the interpretation of changes in the carbon cycle during this critical interval. The new data are best explained by a combination of two mechanisms for variation in [delta][sup 13]C[sub carb]: (1) burial and erosion of organic carbon, with a long time constant; and (2) sequestration of organic carbon into shallow and deep oceanic reservoirs, with a shorter time constant. For application to their case, the first mechanism is limited by possible buildup of marine pCO[sub 2], which would increase the isotopic fractionation factor. The second mechanism is limited in application to short-term transient variations in [delta][sup 13]C. Modeling of the carbon cycle and its variations of [delta][sup 13]C must take both mechanisms into account.

  2. The earth's angular momentum budget on subseasonal time scales

    NASA Technical Reports Server (NTRS)

    Dickey, J. O.; Marcus, S. L.; Steppe, J. A.; Hide, R.

    1992-01-01

    Irregular length of day (LOD) fluctuations on time scales of less than a few years are largely produced by atmospheric torques on the underlying planet. Significant coherence is found between the respective time series of LOD and atmospheric angular momentum (AAM) determinations at periods down to 8 days, with lack of coherence at shorter periods caused by the declining signal-to-measurement noise ratios of both data types. Refinements to the currently accepted model of tidal earth rotation variations are required, incorporating in particular the nonequilibrium effect of the oceans. The remaining discrepancies between LOD and AAM in the 100- to 10-day period range may be due to either a common error in the AAM data sets from different meteorological centers, or another component of the angular momentum budget.

  3. Global coal gap between Permian-Triassic extinction and Middle Triassic recovery of peat-forming plants

    SciTech Connect

    Retallack, G.J.; Veevers, J.J.; Morante, R.

    1996-02-01

    Early Triassic coals are unknown, and Middle Triassic coals are rare and thin. The Early Triassic coal gap began with extinction of peat-forming plants at the end of the Permian (ca. 250 Ma), with no coal known anywhere until Middle Triassic (243 Ma). Permian levels of plant diversity and peat thickness were not recovered until Late Triassic (230 Ma). Tectonic and climatic explanations for the coal gap fail because deposits of fluctuating sea levels and sedimentary facies and paleosols commonly found in coal-bearing sequences are present also in Early Triassic rocks. Nor do we favor explanations involving evolutionary advances in the effectiveness of fungal decomposers, insects or tetrapod herbivores, which became cosmopolitan and much reduced in diversity across the Permian-Triassic boundary. Instead, we favor explanations involving extinction of peat-forming plants at the Permian-Triassic boundary, followed by a hiatus of some 10 m.y. until newly evolved peat-forming plants developed tolerance to the acidic dysaerobic conditions of wetlands. This view is compatible not only with the paleobotanical record of extinction of swamp plants, but also with indications of a terminal Permian productivity crash from {delta}{sup 13}C{sub org} and total organic carbon of both nonmarine and shallow marine shales. 205 refs., 3 figs., 3 tabs.

  4. Surface Radiation Budget Variability at Climatic Time Scales

    NASA Astrophysics Data System (ADS)

    Pinker, R. T.; Ma, Y.; Nussbaumer, E.

    2014-12-01

    Information on Earth Radiation Balance is needed at climatic time scales for enabling assessment of variability and trends in the forcing functions of the climate system. Satellite observations have been instrumental for advancing the understanding of such balance at global scale; yet, the length of available records does not meet climatic needs. Major issues hindering such efforts are related to the frequent changes in satellite observing systems, including the specification of the satellite instruments, and changes in the quality of atmospheric inputs that drive the inference schemes. In this paper we report on an effort to synthesize estimates of shortwave, longwave and spectral surface radiative fluxes by fusing observations from numerous satellite platforms that include MODIS observations. This information was obtained in the framework of the MEaSURES and NEWS programs; it will be evaluated against ground observations and compared to independent satellite and model estimates. Attention will be given to updates on our knowledge on the radiative balance as compared to what is known from shorter time records.

  5. Complex Processes from Dynamical Architectures with Time-Scale Hierarchy

    PubMed Central

    Perdikis, Dionysios; Huys, Raoul; Jirsa, Viktor

    2011-01-01

    The idea that complex motor, perceptual, and cognitive behaviors are composed of smaller units, which are somehow brought into a meaningful relation, permeates the biological and life sciences. However, no principled framework defining the constituent elementary processes has been developed to this date. Consequently, functional configurations (or architectures) relating elementary processes and external influences are mostly piecemeal formulations suitable to particular instances only. Here, we develop a general dynamical framework for distinct functional architectures characterized by the time-scale separation of their constituents and evaluate their efficiency. Thereto, we build on the (phase) flow of a system, which prescribes the temporal evolution of its state variables. The phase flow topology allows for the unambiguous classification of qualitatively distinct processes, which we consider to represent the functional units or modes within the dynamical architecture. Using the example of a composite movement we illustrate how different architectures can be characterized by their degree of time scale separation between the internal elements of the architecture (i.e. the functional modes) and external interventions. We reveal a tradeoff of the interactions between internal and external influences, which offers a theoretical justification for the efficient composition of complex processes out of non-trivial elementary processes or functional modes. PMID:21347363

  6. Reusable Launch Vehicle Control In Multiple Time Scale Sliding Modes

    NASA Technical Reports Server (NTRS)

    Shtessel, Yuri; Hall, Charles; Jackson, Mark

    2000-01-01

    A reusable launch vehicle control problem during ascent is addressed via multiple-time scaled continuous sliding mode control. The proposed sliding mode controller utilizes a two-loop structure and provides robust, de-coupled tracking of both orientation angle command profiles and angular rate command profiles in the presence of bounded external disturbances and plant uncertainties. Sliding mode control causes the angular rate and orientation angle tracking error dynamics to be constrained to linear, de-coupled, homogeneous, and vector valued differential equations with desired eigenvalues placement. Overall stability of a two-loop control system is addressed. An optimal control allocation algorithm is designed that allocates torque commands into end-effector deflection commands, which are executed by the actuators. The dual-time scale sliding mode controller was designed for the X-33 technology demonstration sub-orbital launch vehicle in the launch mode. Simulation results show that the designed controller provides robust, accurate, de-coupled tracking of the orientation angle command profiles in presence of external disturbances and vehicle inertia uncertainties. This is a significant advancement in performance over that achieved with linear, gain scheduled control systems currently being used for launch vehicles.

  7. Reusable Launch Vehicle Control in Multiple Time Scale Sliding Modes

    NASA Technical Reports Server (NTRS)

    Shtessel, Yuri

    1999-01-01

    A reusable launch vehicle control problem during ascent is addressed via multiple-time scaled continuous sliding mode control. The proposed sliding mode controller utilizes a two-loop structure and provides robust, de-coupled tracking of both orientation angle command profiles and angular rate command profiles in the presence of bounded external disturbances and plant uncertainties. Sliding mode control causes the angular rate and orientation angle tracking error dynamics to be constrained to linear, de-coupled, homogeneous, and vector valued differential equations with desired eigenvalues placement. The dual-time scale sliding mode controller was designed for the X-33 technology demonstration sub-orbital launch vehicle in the launch mode. 6DOF simulation results show that the designed controller provides robust, accurate, de-coupled tracking of the orientation angle command profiles in presence of external disturbances and vehicle inertia uncertainties. It creates possibility to operate the X-33 vehicle in an aircraft-like mode with reduced pre-launch adjustment of the control system.

  8. Contributions of different time scales to extreme Paran floods

    NASA Astrophysics Data System (ADS)

    Antico, Andrs; Torres, Mara E.; Diaz, Henry F.

    2015-08-01

    The present study provides the first complete examination of how different time scales contributed to generate the four largest observed floods of the Paran River (1905, 1983, 1992 and 1998). This inspection is based on the results from a previous study where an empirical method was used to decompose a 1904-2010 Paran flow record (monthly means) into several physically meaningful oscillations with distinctive time scales or periods (few months to decades), and a secular increasing trend. We show that all the oscillations largely contributed to the four extreme floods, except an 18-year cycle that did not contribute to the 1992 flood. Sporadic intense constructive interferences between interannual-to-interdecadal (3-85 years) cycles determined (i) the favorable conditions for extreme-flood occurrence, and (ii) notable differences among floods. Indeed, in 1983, the largest flood ever recorded resulted mainly from an exceptionally strong constructive interference between cycles of 3-5, 9, 18 and 31-85 years, which are related to El Nio events, the North Atlantic Oscillation, the South Atlantic Convergence Zone, and the Pacific Ocean, respectively. Contributions of the 31-85-year cycle to the two biggest floods (1983 and 1992) are larger than the contributions of the secular upward trend, suggesting the importance of this slow oscillation in flood formation processes. The implications of our results for understanding and predicting Paran floods are discussed.

  9. Geographic range did not confer resilience to extinction in terrestrial vertebrates at the end-Triassic crisis.

    PubMed

    Dunhill, Alexander M; Wills, Matthew A

    2015-01-01

    Rates of extinction vary greatly through geological time, with losses particularly concentrated in mass extinctions. Species duration at other times varies greatly, but the reasons for this are unclear. Geographical range correlates with lineage duration amongst marine invertebrates, but it is less clear how far this generality extends to other groups in other habitats. It is also unclear whether a wide geographical distribution makes groups more likely to survive mass extinctions. Here we test for extinction selectivity amongst terrestrial vertebrates across the end-Triassic event. We demonstrate that terrestrial vertebrate clades with larger geographical ranges were more resilient to extinction than those with smaller ranges throughout the Triassic and Jurassic. However, this relationship weakened with increasing proximity to the end-Triassic mass extinction, breaking down altogether across the event itself. We demonstrate that these findings are not a function of sampling biases; a perennial issue in studies of this kind. PMID:26261053

  10. Precision optical characterization on nanometer length and femtosecond time scales

    NASA Astrophysics Data System (ADS)

    Bender, Daniel

    This dissertation details progress made in ultrafast optics and time resolved near-field microscopy. First, I will discuss experiments in ultrafast optics. Careful characterization of ultrashort laser pulses is critical for many applications. Because pulse durations are less than a fraction of a picosecond, direct electronic measurement is not possible and optical techniques must be used. I will describe a simple, real-time scheme for visualizing subtle pulse distortion that occurs on the femtosecond time scale. The procedure for generating the modified spectrum autointerferometric correlation (MOSAIC) from the second harmonic generation frequency resolved optical gating (SHG FROG) dataset is shown. The MOSAIC trace provides complimentary visual pulse assessment to SHG FROG. Spectral phase retrieval from the pulse spectrum and MOSAIC is examined. Next, I discuss the concept of laser cooling of solids, i.e. all optical refrigeration in glasses, crystals and semiconductors. Near-field scanning optical microscopy (NSOM) is used in tandem with atomic force microscopy (AFM) to characterize semiconductor heterostructures for potential use in laser cooling. A novel combination of normal force feedback AFM and collection mode NSOM provide unique coincident imagery. Subsurface defects, which adversely affect laser cooling efficiency, are identified and lower nonradiative recombination lifetime by a factor of 10 compared to defect free areas. Time correlated single photon counting (TCSPC) resolves near-field fluorescence lifetimes and simultaneously gives correlation with surface topography. Fluorescence lifetime images (FLIMs) give direct correspondence to and supply supplemental data for AFM.

  11. From Permo-Triassic lithospheric thinning to Jurassic rifting at the Adriatic margin: Petrological and geochronological record in Valtournenche (Western Italian Alps)

    NASA Astrophysics Data System (ADS)

    Manzotti, Paola; Rubatto, Daniela; Darling, James; Zucali, Michele; Cenki-Tok, Bndicte; Engi, Martin

    2012-08-01

    Slices of polycyclic metasediments (marbles and meta-cherts) are tectonically amalgamated with the polydeformed basement of the Dent Blanche tectonic system along a major Alpine shear zone in the Western Alps (Becca di Sal area, Valtournenche Valley). A combination of techniques (structural analysis at various scales, metamorphic petrology, geochronology and trace element geochemistry) was applied to determine the age and composition of accessory phases (titanite, allanite and zircon) and their relation to major minerals. The results are used to reconstruct the polyphase structural and metamorphic histories, comprising both pre-Alpine and Alpine cycles. The pre-Alpine evolution is associated with low-pressure high-temperature metamorphism related to Permo-Triassic lithospheric thinning. In meta-cherts, microtextural relations indicate coeval growth of allanite and garnet during this stage, at ~ 300 Ma. Textures of zircon also indicate crystallisation at HT conditions; ages scatter from 263 to 294 Ma, with a major cluster of data at ~ 276 Ma. In impure marble, U-Pb analyses of titanite domains (with variable Al and F contents) yield apparent 206Pb/238U dates range from Permian to Jurassic. Chemical and isotopic data suggest that titanite formed at Permian times and was then affected by (extension-related?) fluid circulation during the Triassic and Jurassic, which redistributed major elements (Al and F) and partially opened the U-Pb system. The Alpine cycle lead to early blueschist facies assemblages, which were partly overprinted under greenschist facies conditions. The strong Alpine compressional overprint disrupted the pre-Alpine structural imprint and/or reactivated earlier structures. The pre-Alpine metamorphic record, preserved in these slices of metasediments, reflects the onset of the Permo-Triassic lithospheric extension to Jurassic rifting.

  12. Global Precipitation Analyses at Monthly to 3-HR Time Scales

    NASA Technical Reports Server (NTRS)

    Adler, Robert F.; Huffman, George; Curtis, Scott; Bolvin, David; Nelkin, Eric

    2002-01-01

    Global precipitation analysis covering the last few decades and the impact of the new TRMM precipitation observations are discussed. The 20+ year, monthly, globally complete precipitation analysis of the World Climate Research Program's (WCRP/GEWEX) Global Precipitation Climatology Project (GPCP) is used to explore global and regional variations and trends and is compared to the much shorter TRMM(Tropica1 Rainfall Measuring Mission) tropical data set. A trend pattern that is a combination of both El Nino and La Nina precipitation features is evident in the 20-year data set. This pattern is related to an increase with time in the number of combined months of El Nino and La Nina during the 20 year period. Monthly anomalies of precipitation are related to ENSO variations with clear signals extending into middle and high latitudes of both hemispheres. The GPCP daily, 1deg latitude-longitude analysis, which is available from January 1997 to the present is described and the evolution of precipitation patterns on this time scale related to El Nino and La Nina is described. Finally, a TRMM-based 3-hr analysis is described that uses TRMM to calibrate polar-orbit microwave observations from SSM/I and geosynchronous IR observations and merges the various calibrated observations into a final, 3-hr resolution map. This TRMM standard product will soon be available for the entire TRMM period (January 1998- present). A real-time version of this merged product is being produced and is available at 0.25deg latitude-longitude resolution over the latitude range from 50degN-50degS. Images from this data set can be seen at the U.S. TRMM web site (trmm.gsfc.nasa.gov). Examples will be shown, including its use in monitoring flood conditions and relating weather-scale events to climate variations.

  13. Critical time scales for advection-diffusion-reaction processes.

    PubMed

    Ellery, Adam J; Simpson, Matthew J; McCue, Scott W; Baker, Ruth E

    2012-04-01

    The concept of local accumulation time (LAT) was introduced by Berezhkovskii and co-workers to give a finite measure of the time required for the transient solution of a reaction-diffusion equation to approach the steady-state solution [A. M. Berezhkovskii, C. Sample, and S. Y. Shvartsman, Biophys. J. 99, L59 (2010); A. M. Berezhkovskii, C. Sample, and S. Y. Shvartsman, Phys. Rev. E 83, 051906 (2011)]. Such a measure is referred to as a critical time. Here, we show that LAT is, in fact, identical to the concept of mean action time (MAT) that was first introduced by McNabb [A. McNabb and G. C. Wake, IMA J. Appl. Math. 47, 193 (1991)]. Although McNabb's initial argument was motivated by considering the mean particle lifetime (MPLT) for a linear death process, he applied the ideas to study diffusion. We extend the work of these authors by deriving expressions for the MAT for a general one-dimensional linear advection-diffusion-reaction problem. Using a combination of continuum and discrete approaches, we show that MAT and MPLT are equivalent for certain uniform-to-uniform transitions; these results provide a practical interpretation for MAT by directly linking the stochastic microscopic processes to a meaningful macroscopic time scale. We find that for more general transitions, the equivalence between MAT and MPLT does not hold. Unlike other critical time definitions, we show that it is possible to evaluate the MAT without solving the underlying partial differential equation (pde). This makes MAT a simple and attractive quantity for practical situations. Finally, our work explores the accuracy of certain approximations derived using MAT, showing that useful approximations for nonlinear kinetic processes can be obtained, again without treating the governing pde directly. PMID:22680446

  14. Tectonic setting of the Late Triassic volcaniclastic series of the Luang Prabang Basin, Laos, and geodynamic implications from the Triassic to Jurassic in SE Asia

    NASA Astrophysics Data System (ADS)

    Rossignol, Camille; Bourquin, Sylvie; Dabard, Marie-Pierre; Hallot, Erwan; Poujol, Marc; Nalpas, Thierry

    2014-05-01

    The Luang Prabang Basin, located on the eastern margin of the Indochina block, is mainly composed of volcaniclastic continental deposits. The interpretation of U-Pb zircon geochronological dates shows that volcanism is contemporaneous with the sedimentation during the Late Triassic (c.a. 225 to 215 Ma; Blanchard et al., 2013, J. Asian Earth Sci., 70-71; 8-26). At the same time, volcanism is also known along the Eastern margin of the Indochina block (present day Thailand). There are currently two main contrasting interpretations concerning the tectonic setting related to these volcanic events: are they arc-related (e.g. Barr et al., 2006, J. Geol. Soc. London, 163; 1037-1046) or post collisional (e.g. Srichan et al., 2009, Island Arc, 18; 32-51)? We have performed geochemical analysis on both sedimentary and volcanic rocks of the Luang Prabang Basin in order to evaluate the relationships between the volcanic events and to propose a geodynamic interpretation. The geochemical characteristics of the Luang Prabang Late Triassic volcaniclastic and volcanic rocks are compatible with a volcanic arc setting. The confrontation of these results with the stratigraphic evolution of the eastern margin of the Indochina block leads to reconsider the Late Triassic to Jurassic geodynamic evolution of this area. Arc-related volcanism seems to occur during nearly the whole Triassic, implying a subduction of the Paleotethys beneath the Indochina block. As the stratigraphic record of north-eastern Thailand and western Myanmar shows an important stratigraphic gap spanning from the Early to the Middle Jurassic, the collision between the Indochina and the Sibumasu blocks likely occurred at that period.

  15. Continent-scale global change attribution in European birds - combining annual and decadal time scales.

    PubMed

    Jrgensen, Peter Sgaard; Bhning-Gaese, Katrin; Thorup, Kasper; Tttrup, Anders P; Chylarecki, Przemys?aw; Jiguet, Frdric; Lehikoinen, Aleksi; Noble, David G; Reif, Jiri; Schmid, Hans; van Turnhout, Chris; Burfield, Ian J; Foppen, Ruud; Vo?ek, Petr; van Strien, Arco; Gregory, Richard D; Rahbek, Carsten

    2016-02-01

    Species attributes are commonly used to infer impacts of environmental change on multiyear species trends, e.g. decadal changes in population size. However, by themselves attributes are of limited value in global change attribution since they do not measure the changing environment. A broader foundation for attributing species responses to global change may be achieved by complementing an attributes-based approach by one estimating the relationship between repeated measures of organismal and environmental changes over short time scales. To assess the benefit of this multiscale perspective, we investigate the recent impact of multiple environmental changes on European farmland birds, here focusing on climate change and land use change. We analyze more than 800 time series from 18 countries spanning the past two decades. Analysis of long-term population growth rates documents simultaneous responses that can be attributed to both climate change and land-use change, including long-term increases in populations of hot-dwelling species and declines in long-distance migrants and farmland specialists. In contrast, analysis of annual growth rates yield novel insights into the potential mechanisms driving long-term climate induced change. In particular, we find that birds are affected by winter, spring, and summer conditions depending on the distinct breeding phenology that corresponds to their migratory strategy. Birds in general benefit from higher temperatures or higher primary productivity early on or in the peak of the breeding season with the largest effect sizes observed in cooler parts of species' climatic ranges. Our results document the potential of combining time scales and integrating both species attributes and environmental variables for global change attribution. We suggest such an approach will be of general use when high-resolution time series are available in large-scale biodiversity surveys. PMID:26486804

  16. Microbial biodiversity in Alpine Permo-Triassic rock salt

    NASA Astrophysics Data System (ADS)

    Radax, C.; Wieland, H.; Pfaffenhuemer, M.; Leuko, S.; Rittmann, S.; Weidler, G.; Gruber, C.; Stan-Lotter, H.

    2003-04-01

    Alpine Permo-Triassic rock salt (age 200-250 million years) was shown several times to contain living extremely halophilic Archaea. These organisms might stem from ancient populations that became entrapped and persisted in the rock salt since then. For this reason, rock salt is considered a promising model system for the search for bacterial extraterrestrial life. In our studies on biodiversity in Alpine rock salt, we employed both culture-dependent and culture-independent, PCR-based methods. The latter approach indicated the presence of at least 12 distinct sequence types (phylotypes) in our samples, all of which belonged to the extremely halophilic Archaea. None of the recovered sequences was identical to sequences from databases, suggesting the avoidance of contaminants during experimental procedures. Two phylotypes could be assigned to taxonomically described members of this family; the remaining ten phylotypes appeared only remotely related to known genera of the extremely halophilic Archaea. In contrast, attempts to isolate organisms from the same sample on 15 different growth media so far yielded only two groups of isolates that could be differentiated based on their 16S rRNA genes. One group was very similar to Halococcus strains that we frequently isolated from Alpine rock salt; the other group was closely correlated to one of our novel phylotypes. Analyses of whole cell protein patterns allowed to further differentiate the latter group into two different subgroups that could not be distinguished at the molecular level. These results show that both culture-dependent and culture-independent strategies have to be applied in order to obtain a more complete view of microbial biodiversity in Permo-Triassic rock salt: culture-independent methods yield information on the gross microbial diversity in rock salt, whereas subtle differences can currently only be registered between cultivated strains.

  17. Paleomagnetic and magnetostratigraphic investigations of the whitehorse group/quartermaster (Dewey Lake) formation (upper permian-lowermost triassic) in the Palo Duro basin, northwest Texas, USA

    NASA Astrophysics Data System (ADS)

    Collins, Dylan R.

    In northwest Texas, upper Permian to lowermost Triassic hematite-cemented detrital sedimentary rocks, which include a small number of regionally extensive ash beds, were deposited during the time interval of the greatest mass extinction event sequences in Earth history. The magnetic polarity stratigraphy, as well as key rock magnetic properties, of the upper Whitehorse Group (WH) and Quartermaster formations (QM) at selected sections in the Palo Duro Basin, have been determined using thermal, and chemical demagnetization approaches and anisotropy of magnetic susceptibility, acquisition of isothermal remanent magnetization (IRM) and backfield demagnetization, and thermal demagnetization of three component IRM methods. Demagnetization results show that the WH/QM contains a primary/near-primary characteristic remanent magnetization at each level sampled and thus the magnetic polarity stratigraphy for each section can be compared with existing polarity time scales across the Permian-Triassic boundary. Estimated site mean directions yield a paleomagnetic pole for the latest Permian for North America of 57.8N, 130.6E from 38 sampled sites.

  18. The Time Scale of Recombination Rate Evolution in Great Apes.

    PubMed

    Stevison, Laurie S; Woerner, August E; Kidd, Jeffrey M; Kelley, Joanna L; Veeramah, Krishna R; McManus, Kimberly F; Bustamante, Carlos D; Hammer, Michael F; Wall, Jeffrey D

    2016-04-01

    We present three linkage-disequilibrium (LD)-based recombination maps generated using whole-genome sequence data from 10 Nigerian chimpanzees, 13 bonobos, and 15 western gorillas, collected as part of the Great Ape Genome Project (Prado-Martinez J, et al. 2013. Great ape genetic diversity and population history. Nature 499:471-475). We also identified species-specific recombination hotspots in each group using a modified LDhot framework, which greatly improves statistical power to detect hotspots at varying strengths. We show that fewer hotspots are shared among chimpanzee subspecies than within human populations, further narrowing the time scale of complete hotspot turnover. Further, using species-specific PRDM9 sequences to predict potential binding sites (PBS), we show higher predicted PRDM9 binding in recombination hotspots as compared to matched cold spot regions in multiple great ape species, including at least one chimpanzee subspecies. We found that correlations between broad-scale recombination rates decline more rapidly than nucleotide divergence between species. We also compared the skew of recombination rates at centromeres and telomeres between species and show a skew from chromosome means extending as far as 10-15 Mb from chromosome ends. Further, we examined broad-scale recombination rate changes near a translocation in gorillas and found minimal differences as compared to other great ape species perhaps because the coordinates relative to the chromosome ends were unaffected. Finally, on the basis of multiple linear regression analysis, we found that various correlates of recombination rate persist throughout the African great apes including repeats, diversity, and divergence. Our study is the first to analyze within- and between-species genome-wide recombination rate variation in several close relatives. PMID:26671457

  19. Variations in solar Lyman alpha irradiance on short time scales

    NASA Astrophysics Data System (ADS)

    Pap, J. M.

    1992-10-01

    Variations in solar UV irradiance at Lyman alpha are studied on short time scales (from days to months) after removing the long-term changes over the solar cycle. The SME/Lyman alpha irradiance is estimated from various solar indices using linear regression analysis. In order to study the nonlinear effects, Lyman alpha irradiance is modeled with a 5th-degree polynomial as well. It is shown that the full-disk equivalent width of the He line at 1083 nm, which is used as a proxy for the plages and active network, can best reproduce the changes observed in Lyman alpha. Approximately 72 percent of the solar-activity-related changes in Lyman alpha irradiance arise from plages and the network. The network contribution is estimated by the correlation analysis to be about 19 percent. It is shown that significant variability remains in Lyman alpha irradiance, with periods around 300, 27, and 13.5d, which is not explained by the solar activity indices. It is shown that the nonlinear effects cannot account for a significant part of the unexplained variation in Lyman alpha irradiance. Therefore, additional events (e.g., large-scale motions and/or a systematic difference in the area and intensity of the plages and network observed in the lines of Ca-K, He 1083, and Lyman alpha) may explain the discrepancies found between the observed and estimated irradiance values.

  20. Variations in solar Lyman alpha irradiance on short time scales

    NASA Technical Reports Server (NTRS)

    Pap, J. M.

    1992-01-01

    Variations in solar UV irradiance at Lyman alpha are studied on short time scales (from days to months) after removing the long-term changes over the solar cycle. The SME/Lyman alpha irradiance is estimated from various solar indices using linear regression analysis. In order to study the nonlinear effects, Lyman alpha irradiance is modeled with a 5th-degree polynomial as well. It is shown that the full-disk equivalent width of the He line at 1083 nm, which is used as a proxy for the plages and active network, can best reproduce the changes observed in Lyman alpha. Approximately 72 percent of the solar-activity-related changes in Lyman alpha irradiance arise from plages and the network. The network contribution is estimated by the correlation analysis to be about 19 percent. It is shown that significant variability remains in Lyman alpha irradiance, with periods around 300, 27, and 13.5d, which is not explained by the solar activity indices. It is shown that the nonlinear effects cannot account for a significant part of the unexplained variation in Lyman alpha irradiance. Therefore, additional events (e.g., large-scale motions and/or a systematic difference in the area and intensity of the plages and network observed in the lines of Ca-K, He 1083, and Lyman alpha) may explain the discrepancies found between the observed and estimated irradiance values.

  1. Fireballs: Detonation Initiation on the Microsecond Time Scale

    NASA Astrophysics Data System (ADS)

    Kassoy, D. R.; Wojciechowski, K.

    2003-11-01

    A mathematical model is developed for detonation initiation following a time and spatially resolved burst of thermal power from an external source into a spherical target of reactive gas. The objective is to produce a detonation in or near the target with the least possible energy input. Source heating occurs on a sub-microsecond time scale, short compared to the acoustic time of the millimeter-sized target. This leads to a period of near inertial confinement, where the pressure rises with temperature, the density change is very small and local Mach number is extremely subsonic. As a result the thermal enegy change is maximized while the induced kinetic energy is minimized. The large temperature increase within the localized high pressure spot initiates a high activation energy, exothermic reaction which spreads hypersonically from the maximum temperature point. The chemical front is co-located with a large localized pressure gradient, responsible for rapid gas acceleration. A detonation appears at the edge of target, in the form of a strong shock with a coupled reaction zone. The evolutionary process differs fundamentally from that in a DDT and that in a traditional model of direct initiation.

  2. Nanosecond time scale, high power electrical wire explosion in water

    SciTech Connect

    Grinenko, A.; Krasik, Ya.E.; Efimov, S.; Fedotov, A.; Gurovich, V.Tz.; Oreshkin, V.I.

    2006-04-15

    Experimental and magnetohydrodynamic simulation results of nanosecond time scale underwater electrical explosions of Al, Cu, and W wires are presented. A water forming line generator with current amplitude up to 100 kA was used. The maximum current rise rate and maximum Joule heating power achieved during wire explosions were dI/dt{<=}500 A/ns and 6 GW, respectively. Extremely high energy deposition of up to 60 times the atomization enthalpy was registered compared to the best reported result of 20 times the atomization enthalpy for energy deposition with a vacuum wire explosion. Discharge channel evolution and surface temperature were analyzed by streak shadow imaging and by a fast photodiode with a set of interference filters, respectively. A 1D magnetohydrodynamic simulation demonstrated good agreement with experimental parameters such as discharge channel current, voltage, radius, and temperature. Material conductivity was calculated to produce the best correlation between the simulated and experimentally obtained voltage. It is shown that material conductivity may significantly vary as a function of energy deposition rate.

  3. Control of Systems With Slow Actuators Using Time Scale Separation

    NASA Technical Reports Server (NTRS)

    Stepanyan, Vehram; Nguyen, Nhan

    2009-01-01

    This paper addresses the problem of controlling a nonlinear plant with a slow actuator using singular perturbation method. For the known plant-actuator cascaded system the proposed scheme achieves tracking of a given reference model with considerably less control demand than would otherwise result when using conventional design techniques. This is the consequence of excluding the small parameter from the actuator dynamics via time scale separation. The resulting tracking error is within the order of this small parameter. For the unknown system the adaptive counterpart is developed based on the prediction model, which is driven towards the reference model by the control design. It is proven that the prediction model tracks the reference model with an error proportional to the small parameter, while the prediction error converges to zero. The resulting closed-loop system with all prediction models and adaptive laws remains stable. The benefits of the approach are demonstrated in simulation studies and compared to conventional control approaches.

  4. Dynamic Leidenfrost Effect: Relevant Time and Length Scales.

    PubMed

    Shirota, Minori; van Limbeek, Michiel A J; Sun, Chao; Prosperetti, Andrea; Lohse, Detlef

    2016-02-12

    When a liquid droplet impacts a hot solid surface, enough vapor may be generated under it to prevent its contact with the solid. The minimum solid temperature for this so-called Leidenfrost effect to occur is termed the Leidenfrost temperature, or the dynamic Leidenfrost temperature when the droplet velocity is non-negligible. We observe the wetting or drying and the levitation dynamics of the droplet impacting on an (isothermal) smooth sapphire surface using high-speed total internal reflection imaging, which enables us to observe the droplet base up to about 100nm above the substrate surface. By this method we are able to reveal the processes responsible for the transitional regime between the fully wetting and the fully levitated droplet as the solid temperature increases, thus shedding light on the characteristic time and length scales setting the dynamic Leidenfrost temperature for droplet impact on an isothermal substrate. PMID:26918994

  5. Plant succession as an integrator of contrasting ecological time scales.

    PubMed

    Walker, Lawrence R; Wardle, David A

    2014-09-01

    Ecologists have studied plant succession for over a hundred years, yet our understanding of the nature of this process is incomplete, particularly in relation to its response to new human perturbations and the need to manipulate it during ecological restoration. We demonstrate how plant succession can be understood better when it is placed in the broadest possible temporal context. We further show how plant succession can be central to the development of a framework that integrates a spectrum of ecological processes, which occur over time scales ranging from seconds to millions of years. This novel framework helps us understand the impacts of human perturbations on successional trajectories, ecosystem recovery, and global environmental change. PMID:25085040

  6. Real time boronization experiments in CHS and scaling for LHD

    NASA Astrophysics Data System (ADS)

    Sagara, A.; Hasegawa, Y.; Tsuzuki, K.; Inoue, N.; Suzuki, H.; Morisaki, T.; Noda, N.; Motojima, O.; Okamura, S.; Matsuoka, K.; Akiyama, R.; Ida, K.; Idei, H.; Iwasaki, K.; Kubo, S.; Minami, T.; Morita, S.; Narihara, K.; Ozaki, T.; Sato, K.; Takahashi, C.; Tanaka, K.; Toi, K.; Yamada, I.

    1997-02-01

    As a promising wall-conditioning technique in LHD under steady-state high magnetic fields with superconducting magnets, real time boronization (RTB) by puffing decaborane B 10H 14 into the main NBI-heated plasma has been first examined in CHS. It is shown that, as compared with the usual glow discharge method, only the 2 orders smaller amount of decaborane is efficient to reduce plasma impurities such as oxygen and metals, resulting in expansion of the operating region of the plasma density and stored energy. The puffing at the inside of the LCFS gives better results on RTB than the outer. Even after RTB on the wall at the room temperature, hydrogen recycling does not increase probably due to the small consumed amount with a high plasma heating power used. The operative RTB parameters expected in LHD are estimated using the first scaling of boronization on the device size.

  7. Time Scale Dependent SGD due to the Sea Level Change

    NASA Astrophysics Data System (ADS)

    Lee, K.; Lee, E.; Hyun, Y.

    2009-12-01

    Submarine groundwater discharge (SGD) is defined as the groundwater outflux across the ocean-land interface. In this study, the variation of amount of SGD due to the sea level change is investigated by means of numerical simulation. Numerical code FEFLOW (Diersh et al., 2005) is used to conduct the simulation and the effect of sea level change on the variation of SGD with different time scales from diurnal cycle to glacial cycle is evaluated. The simulation results indicate that generally, the increase of amplitude of sea level leads to the increase of SGD while the increase of period of sea level change cause more complicated pattern of the variation of SGD. These variations are changed with the aquifer properties, especially, hydraulic conductivity. The simulation results show that the sea level change with different period and amplitude leads to the variation of total SGD and it may explain the unknown source of the unexpectedly high amount of SGD.

  8. X-ray signatures: New time scales and spectral features

    NASA Technical Reports Server (NTRS)

    Boldt, E. A.

    1977-01-01

    The millisecond bursts from Cyg X-1 are investigated and the overall chaotic variability for the bulk of the Cyg X-1 emission is compared to that of Sco X-1, showing that the essential character is remarkably similar (i.e. shot noise) although the fundamental time scales involved differ widely, from a fraction of a second (for Cyg X-1) to a fraction of a day (for Sco X-1). Recent OSO-8 observations of spectra features attributable to iron are reviewed. In particular, line emission is discussed within the context of a model for thermal radiation by a hot evolved gas in systems as different as supernova remnants and clusters of galaxies. Newly observed spectral structure in the emission from the X-ray pulsar Her X-1 is reported.

  9. Nonoscillation for second order sublinear dynamic equations on time scales

    NASA Astrophysics Data System (ADS)

    Erbe, Lynn; Baoguo, Jia; Peterson, Allan

    2009-10-01

    Consider the Emden-Fowler sublinear dynamic equation x[Delta][Delta](t)+p(t)f(x([sigma](t)))=0, where , is a time scale, , where ai>0, 0<[beta]i<1, with [beta]i the quotient of odd positive integers, 1<=i<=m. When m=1, and , (0.1) is the usual sublinear Emden-Fowler equation which has attracted the attention of many researchers. In this paper, we allow the coefficient function p(t) to be negative for arbitrarily large values of t. We extend a nonoscillation result of Wong for the second order sublinear Emden-Fowler equation in the continuous case to the dynamic equation (0.1). As applications, we show that the sublinear difference equation has a nonoscillatory solution, for b>0, c>[alpha], and the sublinear q-difference equation has a nonoscillatory solution, for , q>1, b>0, c>1+[alpha].

  10. Fault rock texture and porosity type in Triassic dolostones

    NASA Astrophysics Data System (ADS)

    Agosta, Fabrizio; Grieco, Donato; Bardi, Alessandro; Prosser, Giacomo

    2015-04-01

    Preliminary results of an ongoing project aimed at deciphering the micromechanics and porosity evolution associated to brittle deformation of Triassic dolostones are presented. Samples collected from high-angle, oblique-slip, 10's to 100's m-throw normal faults crosscutting Mesozoic carbonates of the Neo Tethys (Campanian-Lucanian Platform) are investigated by mean of field geological mapping, optical microscopy, SEM and image analyses. The goal is to characterize in detail composition, texture and porosity of cataclastic rocks in order to assess the structural architecture of dolomitic fault cores. Moreover, the present study addresses the time-space control exerted by several micro-mechanisms such as intragranular extensional fracturing, chipping and shear fracturing, which took place during grain rolling and crushing within the evolving faults, on type, amount, dimensions and distribution of micropores present within the cataclastic fault cores. Study samples are representative of well-exposed dolomitic fault cores of oblique-slip normal faults trending either NW-SE or NE-SW. The high-angle normal faults crosscut the Mesozoic carbonates of the Campanian-Lucanian Platform, which overrode the Lagonegro succession by mean of low-angle thrust faults. Fault throws are measured by considering the displaced thrust faults as key markers after large scale field mapping (1:10,000 scale) of the study areas. In the field, hand samples were selected according to their distance from main slip surfaces and, in some case, along secondary slip surfaces. Microscopy analysis of about 100 oriented fault rock samples shows that, mostly, the study cataclastic rocks are made up of dolomite and sparse, minute survivor silicate grains deriving from the Lagonegro succession. In order to quantitatively assess the main textural classes, a great attention is paid to the grain-matrix ratio, grain sphericity, grain roundness, and grain sorting. By employing an automatic box-counting technique, the fractal dimension of representative samples is also computed. Results of such a work shows that five main textural types are present: 1) fractured and fragmented dolomites; 2) protocataclasites characterized by intense intragranular extensional fracturing; 3) cataclasites due to a chipping-dominated mechanism; 4) cataclasites and ultracataclasites with pronounced shear fracturing; 5) cemented fault rocks, which localize along the main slip surfaces. The first four textural types are therefore indicative to the fault rock maturity within individual cataclastic fault cores. A negative correlation among grain-matrix ratio and grain sphericity, roundness and sorting is computed, which implies that ultracataclasites are made up of more spherical and rounded smaller grains relative to cataclasites and protocataclasites. Each textural type shows distinct D0-values (box-counting dimension). As expected, a good correlation between the D0-value and fault rock maturity is computed. Ongoing analysis of selected images obtained from representative samples of the five textural classes will shed lights on the relative role played by the aforementioned micro-mechanisms on the porosity evolution within the cataclastic fault cores.

  11. Water relations and leaf expansion: importance of time scale.

    PubMed

    Munns, R; Passioura, J B; Guo, J; Chazen, O; Cramer, G R

    2000-09-01

    The role of leaf water relations in controlling cell expansion in leaves of water-stressed maize and barley depends on time scale. Sudden changes in leaf water status, induced by sudden changes in humidity, light and soil salinity, greatly affect leaf elongation rate, but often only transiently. With sufficiently large changes in salinity, leaf elongation rates are persistently reduced. When plants are kept fully turgid throughout such sudden environmental changes, by placing their roots in a pressure chamber and raising the pressure so that the leaf xylem sap is maintained at atmospheric pressure, both the transient and persistent changes in leaf elongation rate disappear. All these responses show that water relations are responsible for the sudden changes in leaf elongation rate resulting from sudden changes in water stress and putative root signals play no part. However, at a time scale of days, pressurization fails to maintain high rates of leaf elongation of plants in either saline or drying soil, indicating that root signals are overriding water relations effects. In both saline and drying soil, pressurization does raise the growth rate during the light period, but a subsequent decrease during the dark results in no net effect on leaf growth over a 24 h period. When transpirational demand is very high, however, growth-promoting effects of pressurization during the light period outweigh any reductions in the dark, resulting in a net increase in growth of pressurized plants over 24 h. Thus leaf water status can limit leaf expansion rates during periods of high transpiration despite the control exercised by hormonal effects on a 24 h basis. PMID:11006301

  12. Time-scale modelling of the invasive species Robinia pseudoacacia

    NASA Astrophysics Data System (ADS)

    Toma, Podobnikar; Andra, .?Arni; Imelda, Somodi

    2010-05-01

    Our contribution is part of the TransEcoNet project (Transnational Ecological Networks in Central Europe) that aims to investigate transboundary ecological networks across Central Europe. An objective of this project is to contribute towards awareness rising on the value and role of ecological networks. This poster presents the activities that are carried out in Pomurje region, Slovenia as our case study area. Pomurje region borders with Austria in the north, to Hungary in the east, and to Croatia in the south. We are investigating the spread of the invasive species Robinia pseudacacia and the underlying causes, and assess landscape scale ecological dynamics (e.g. Mura River floodplains) in ecological networks. The study comprises investigation and mapping of the R. pseudacacia spread with time-series analysis to understand its spatial dynamics. The preliminary studies show that the R. pseudacacia had the most expanded in the region since 1980s. Some of the surfaces were cut and converted back to fields. This reflects the socioeconomic situation in the region. The further study will include statistic, GIS (geographical information systems) and remote sensing techniques. We will apply various character data: satellite imagery, IR-orthophotos, digital elevation models, including LIDAR, contemporary and historical maps, and other spatial/non-spatial data sources. The outputs will include reconstruction of R. pseudacacia-dynamics in the recent decade, modelling the distribution of R. pseudacacia in relation to abiotic environmental factors and land use, and modelling (prediction) the expected distribution of R. pseudacacia in case of climate and land use change. Keywords: invasive species, Robinia pseudacacia, spatial analysis, time-scale analysis, remote sensing, land use change, climate change

  13. Towards a stable numerical time scale for the early Paleogene

    NASA Astrophysics Data System (ADS)

    Hilgen, Frederik; Kuiper, Klaudia; Sierro, Francisco J.; Wotzlaw, Jorn; Schaltegger, Urs; Sahy, Diana; Condon, Daniel

    2014-05-01

    The construction of an astronomical time scale for the early Paleogene is hampered by ambiguities in the number, correlation and tuning of 405-kyr eccentricity related cycles in deep marine records from ODP cores and land-based sections. The two most competing age models result in astronomical ages for the K/Pg boundary that differ by ~750 kyr (~66.0 Ma of Vandenberghe et al. (2012) versus 65.25 Ma of Westerhold et al. (2012); these ages in turn are consistent with proposed ages for the Fish Canyon sanidine (FCs) that differ by ~300 kyr (28.201 Ma of Kuiper et al. (2008) versus 27.89 Ma of Westerhold et al. (2012)); an even older age of 28.294 Ma is proposed based on a statistical optimization model (Renne et al., 2011). The astronomically calibrated FCs age of 28.201 0.046 Ma of Kuiper et al. (2008), which is consistent with the astronomical age of ~66.0 Ma for the K/Pg boundary, is currently adopted in the standard geological time scale (GTS2012). Here we combine new and published data in an attempt to solve the controversy and arrive at a stable nuemrical time scale for the early Paleogene. Supporting their younger age model, Westerhold et al. (2012) argue that the tuning of Miocene sections in the Mediterranean, which underlie the older FCs age of Kuiper et al. (2008) and, hence, the coupled older early Paleogene age model of Vandenberghe et al. (2012), might be too old by three precession cycles. We thoroughly rechecked this tuning; distinctive cycle patterns related to eccentricity and precession-obliquity interference make a younger tuning that would be consistent with the younger astronomical age of 27.89 Ma for the FCs of Westerhold et al. (2012) challenging. Next we compared youngest U/Pb zircon and astronomical ages for a number of ash beds in the tuned Miocene section of Monte dei Corvi. These ages are indistinguishable, indicating that the two independent dating methods yield the same age when the same event is dated. This is consistent with results of single crystal U/Pb zircon dating of the Fish Canyon tuff itself (Wotzlaw et al., 2013), which produced a youngest U/Pb age of 28.196 0.038 Ma that is indistinguishable from the astronomically calibrated age of 28.201 0.046 Ma for the FCs. Finally, youngest U/Pb zircon ages for ash layers that are found directly above the K/Pg boundary in North America are close to 65.9 Ma and thus consistent with the older astronomical age model with an age of ~66.0 Ma for the boundary. Summarizing, the new and published data summarized above unanimously favor the older option of the two alternative astronomical time scales for the early Paleogene. References Kuiper, K.F., A. Deino, F.J. Hilgen, W. Krijgsman, P.R. Renne, and J.R. Wijbrans, 2008. Synchronizing the Rock Clocks of Earth history. Science 320, 500-504. Renne, P.R., G. Balco, K.R. Ludwig, R. Mundil, and K. Min, 2011. Response to the comment by W.H. Schwarz et al. on "Joint determination of 40K decay constants and 40Ar*/40K for the Fish Canyon sanidine standard, and improved accuracy for 40Ar/39Ar geochronology". Geochim. Cosmochim. Acta 75, 5097-5100. Vandenberghe, N., F.J. Hilgen, and R.P. Speijer, 2012. The Paleogene Period. In: The Geological Time Scale 2012, Gradstein, F., et al., eds., Elsevier, pp. 855-921. Westerhold, T., U. Rhl, and J. Laskar, 2012. Time scale controversy: Accurate orbital calibration of the early Paleogene. Geochem. Geophys. Geosyst., 13, Q06015, doi:10.1029/2012GC004096. Wotzlaw, J.-F., U. Schaltegger, D.A. Frick, M.A. Dungan, A. Gerdes, and D. Gnther, 2013. Tracking the evolution of large-volume silicic magma reservoirs from assembly to supereruption. Geology, doi:10.1130/G34366.1

  14. The evidence for ocean acidification across the Triassic-Jurassic boundary

    NASA Astrophysics Data System (ADS)

    Martindale, R. C.; Greene, S. E.; Ritterbush, K. A.; Bottjer, D. J.; Corsetti, F. A.; Berelson, W.

    2012-12-01

    The end-Triassic extinction is one of the "Big Five" mass extinctions of the Phanerozoic and until recently no consensus regarding the cause of this extinction has been established. Over the last decade, a robust temporal correlation between the eruption of the Central Atlantic Magmatic Province (CAMP) and the end-Triassic extinction has been established. This correlation has led to the speculation that the release of CO2 and volatiles from the CAMP flood basalts induced a carbon cycle perturbation that acidified the Triassic oceans. It has also been suggested that an acidification event could have been the key mechanism that caused the end-Triassic marine ecosystem collapse. By combining observations and data from multiple fields such as volcanology, paleoceanography, chemostratigraphy, paleontology, and sedimentology, one can assess whether or not there was an ocean acidification event and to what degree it contributed to the extinction. The eruption of the CAMP flood basalts began at the very end of the Triassic period, albeit before the official Triassic-Jurassic (T-J) boundary, (defined as the first Jurassic ammonite). CAMP is one of the largest continental flood basalts of the Phanerozoic (2-4 million cubic km) and was emplaced extremely rapidly (<1.6-2 Myr) in three to five pulses (possibly hundreds to tens of thousands of years). The massive injection of CAMP CO2 and other volcanic volatiles over such a short period of time would have caused a major change in ocean carbonate chemistry and, if short enough in duration, could have caused significant declines in oceanic carbonate saturation state (an ocean acidification event), possibly even undersaturating parts of the surface ocean with respect to aragonite and calcite. Although the change in saturation state of the ocean is extremely difficult to detect or quantify in the rock record, there is a distinct paucity of primary carbonate sediments in the T-J boundary interval, consistent with an ocean acidification event. Of the seventeen T-J boundary sections only three or four record potentially continuous carbonate deposition across the extinction interval, even so these carbonates are often marls and so may not be truly continuous. Finally, the end-Triassic extinction was particularly selective against pH-sensitive organisms (more so than perhaps any other extinction event). Not only was this extinction event one of the most severe extinctions of the 'Modern Fauna' in the geologic record, it also decimated reef ecosystems built by corals and hypercalcified sponges. End-Triassic extinction rates amongst acid-intolerant organisms and ecosystems are elevated and differ significantly from background extinction so that ocean acidification is a reasonable explanation for the interpreted extinction selectivity during this time interval. Given the volcanic, geochemical, sedimentological, and paleontological changes or events across the T-J interval it is likely that the end-Triassic extinction was heavily influenced by a CAMP-induced ocean acidification event. The dramatic taxonomic and ecosystem turnover at the T-J event implies that short-term acidification events may have long-term effects on ecosystems, a repercussion that has not previously been correlated with acidification events and has implications for future changes in ocean chemistry.

  15. The Colorado Plateau Coring Project (CPCP): A Continuous Cored Record of Triassic Continental Environmental Change in Western North America

    NASA Astrophysics Data System (ADS)

    Olsen, P. E.; Geissman, J. W.; Gehrels, G. E.; Irmis, R. B.; Kent, D. V.; Mundil, R.; Parker, W.; Sha, J.; Molina-Garza, R. S.; Kuerschner, W.; Bachmann, G. H.; Schaller, M. F.; Zakharova, N. V.; Colbert, M.

    2014-12-01

    The Triassic Period (251.9-201.3 Ma) is bound by two of the Earth's largest mass extinctions, suffered several giant bolide impacts and eruption of 3 large igneous provinces, and witnessed evolution of the main components of modern tetrapod communities, and yet has sparse geochronological calibration. To bridge this gap, NSF- and ICDP-funded coring of Phase 1 of the CPCP finished in 12/2013 with the recovery of two major cores (1A, 518m and 2B, 253m; 31km apart) from opposites sides of Petrified Forest National Park spanning nearly the entire Triassic sequence (Chinle & Moenkopi fms) with many U-Pb datable levels (1,2,3) and a recoverable paleomagnetic polarity record (4). The cores will provide a U-Pb and paleomagnetic exportable time scale and sedimentary and geochemical proxies with undoubted superposition testing the motivating hypotheses of: 1) the accuracy of orbitally-paced cyclicity of the Newark APTS (5); 2) apparent climate trends as a function of drift through climate belts (6) and atmospheric CO2 (7); 3) the temporal link between the mid-Late Triassic biotic turnover and the ~100 km Manicouagan impact (1); and 4) the delayed ecological dominance of dinosaurs coupled to climate-driven provinciality (1,8). For orientation, the cores were drilled using a azimuth-tracking device, deviated 30° and 15° from vertical to the SE and S, and CT-scanned. The unprecedented sedimentological and stratigraphic detail visible in the CT-scans, and geophysical logs, plus the ~100% recovery promises successful tests of the motivating hypotheses and provide a superbly detailed reference section for this key episode in Earth system history. 1, Irmis+,2011, EPSL 309:258; 2, Ramazani+, 2011, GSA Bull. 123:2142; 3, Ramazani+, 2014, AJS 314:981; 4, Steiner & Lucas, 2000, JGR B 105:25791; 5, Kent & Olsen, 1999, JGR 104(B6):12831-12841; 6, Kent and Tauxe, 2005, Science 307:240-244; 7, Schaller+, 2012, EPSL 323-324:27-39; 8, Kent +, 2014, PNAS 111:7958-7963.

  16. Magnetostratigraphy and 40Ar/39Ar dating of CAMP lava flows at the Triassic-Jurassic boundary, Morocco

    NASA Astrophysics Data System (ADS)

    Knight, K. B.; Nomade, S.; Renne, P.; Marzoli, A.; Youbi, N.

    2003-04-01

    The Central Atlantic Magmatic Province (CAMP), the largest known flood basalt province in the Phanerozoic, is generally associated with the incipient opening of the Atlantic Ocean at the Triassic-Jurassic boundary ca. 200 Ma. Paleomagnetic sampling targeted packages of CAMP lava flows in central Morocco from condensed sections identified on the basis of field observations and geochemistry. Lava flows in Moroccan CAMP are divided into four basic units, each comprising multiple flows (after Bertrand, 1991): the Formation (Fm.) Inférieure, Fm. Intermédiaire, Fm. Supérieure, and at the top, the Récurrente, separated from the first three by a period of red clay deposition. Oriented cores were demagnetized using both alternating field (AF) and thermal techniques. Cores from the same lava flow processed by AF demagnetization were later crushed for subsequent separation of plagioclase and dated by the 40Ar/39Ar method. Paleomagnetic results reveal wholly normal polarity interrupted by a brief reversal event defined by data from a single flow located at the base of the Fm. Intermédiaire. Preliminary results from a 250 m section of lavas spanning three formations in the Haut Atlas of Morocco confirm the presence of this brief reversal. 40Ar/39Ar analyses of these samples yielded six plateau ages including each formation. These ages are indistinguishable within 2σ error limits, sharing a mean age of 200.9 ± 0.7 Ma (2σ) relative to the Fish Canyon sanidine at 28.02 Ma (Renne et al., 1998). This demonstrates the brevity of these eruptions despite the presence of significant sedimentary horizons between them. These ages are slightly older than the average elsewhere around Pangea, suggesting CAMP volcanism initiated in Morocco and may span the Triassic-Jurassic transition. Correlation of our observed reversal with the E23n, E23r, E24 sequence reported in the Newark basin (Olsen et al., 2003) would further support this. These new data also contribute to the magnetostratigraphic time scale at the Triassic/Jurassic transition and the apparent polar wander path for the African continent ca. 200 Ma.

  17. Length scale of dynamic heterogeneity and its relation to time scales in a glass-forming liquid

    NASA Astrophysics Data System (ADS)

    Dasgupta, Chandan

    2011-03-01

    The role of the length scale of dynamic heterogeneity in the enormous increase in the relaxation times of glass-forming liquids upon supercooling has received much attention recently. Using molecular dynamics simulations and finite-size scaling for a realistic glass-forming liquid, we establish that the growth of dynamic heterogeneity with decreasing temperature is governed by a growing dynamic length scale. We also perform a computational study of a four-point structure factor, defined from spatial correlations of mobility, for the same liquid and show that estimates of the dynamic correlation length and susceptibility obtained from this study are consistent with the results of the finite-size scaling analysis. However, the observed dependence of the simultaneously growing time scale of the long-time ? -relaxation on system size does not exhibit the same scaling behavior as the dynamic heterogeneity: this time scale is instead determined, for all studied system sizes and temperatures, by the configurational entropy, in accordance with the Adam-Gibbs relation. We also investigate the dependence of the time scale of the short-time ? -relaxation on temperature and system size. A finite-size scaling analysis of this dependence reveals the existence of a length scale that grows as the temperature is reduced. Surprisingly, the temperature dependence of this length scale is found to be identical to that of the length scale that governs the growth of dynamic heterogeneity at the ? -relaxation time scale. This result suggests a close connection between short-time dynamics and dynamic heterogeneity at time scales of the order of the ? -relaxation time. This talk is based on work done in collaboration with S. Karmakar, S. Sastry and S. Sengupta.

  18. The Triassic of Timor: Lithostratigraphy, chronostratigraphy and palaeogeography

    NASA Astrophysics Data System (ADS)

    Charlton, T. R.; Barber, A. J.; McGowan, A. J.; Nicoll, R. S.; Roniewicz, E.; Cook, S. E.; Barkham, S. T.; Bird, P. R.

    2009-10-01

    The palaeontologically rich and lithologically diverse Triassic successions of Timor provide a key stratigraphic and palaeontological link between northwestern Australia and other terranes of former eastern Gondwana (present-day Southeast Asia). Timor is now located in the zone of collision between the northern margin of the Australian continent and island arc terranes bordering the Eurasian plate, with the Triassic successions exposed in a fold-and-thrust belt and an extensive mlange complex. Three formal lithostratigraphic units have been defined previously within the main Triassic succession in Timor (Niof, Aitutu and Babulu formations), with a fourth, the Wai Luli Formation, primarily Jurassic in age but extending down into the Triassic. The Niof Formation (Anisian to Ladinian, possibly also Early Triassic) is a fine-grained deepwater succession, succeeded conformably by the Aitutu and Babulu formations (Ladinian to Norian/Rhaetian), which were deposited contemporaneously, with the Aitutu Formation continuing locally into the Lower Jurassic. The Aitutu Formation consists of deep shelf limestones interbedded with shales and marls, while the Babulu Formation is a deltaic to turbiditic siliciclastic succession. The Late Triassic to Jurassic Wai Luli Formation is characterised by marine shales and marls. Informal stratigraphic units include the Cephalopod Limestone Facies, a Rosso Ammonitico-type deposit, which contains an extremely rich fossil fauna (particularly ammonoids) and ranges through the entire Triassic; and the Fatu Limestone and Pualaca Facies which consists of shallow to marginal marine carbonates (mud mounds, oolitic limestones and reefs) restricted to the Late Triassic. Facies diversity was low during the Early Triassic and Anisian, but became more pronounced from the Ladinian and continuing through the Late Triassic, probably as a consequence of renewed tectonic extension. Triassic extension was not associated with major volcanism, unlike a previous phase of extension in the Early Permian. The Cablac Limestone Formation, originally defined as a Miocene stratigraphic element, is now recognised to be at least partly Late Triassic-Early Jurassic in age, with lithologies comparable to parts of the Fatu Limestone. The stratigraphy of these shallow marine carbonate sequences is clearly in need of rigorous revision, but it is not yet possible to suggest appropriate redefined formations.

  19. Use of a Walk Through Time to Facilitate Student Understandings of the Geological Time Scale

    NASA Astrophysics Data System (ADS)

    Shipman, H. L.

    2004-12-01

    Students often have difficulties in appreciating just how old the earth and the universe are. While they can simply memorize a number, they really do not understand just how big that number really is, in comparison with other, more familiar student referents like the length of a human lifetime or how long it takes to eat a pizza. (See, e.g., R.D. Trend 2001, J. Research in Science Teaching 38(2): 191-221) Students, and members of the general public, also display such well-known misconceptions as the "Flintstone chronology" of believing that human beings and dinosaurs walked the earth at the same time. (In the classic American cartoon "The Flintstones," human beings used dinosaurs as draft animals. As scientists we know this is fiction, but not all members of the public understand that.) In an interdisciplinary undergraduate college class that dealt with astronomy, cosmology, and biological evolution, I used a familiar activity to try to improve student understanding of the concept of time's vastness. Students walked through a pre-determined 600-step path which provided a spatial analogy to the geological time scale. They stopped at various points and engaged in some pre-determined discussions and debates. This activity is as old as the hills, but reports of its effectiveness or lack thereof are quite scarce. This paper demonstrates that this activity was effective for a general-audience, college student population in the U.S. The growth of student understandings of the geological time scale was significant as a result of this activity. Students did develop an understanding of time's vastness and were able to articulate this understanding in various ways. This growth was monitored through keeping track of several exam questions and through pre- and post- analysis of student writings. In the pre-writings, students often stated that they had "no idea" about how to illustrate the size of the geological time scale to someone else. While some post-time walk responses simply restated what was done in the walk through time, some students were able to develop their own ways of conceptualizing the vastness of the geological time scale. A variety of findings from student understandings will be presented. This work has been supported in part by the Distinguished Scholars Program of the National Science Foundation (DUE-0308557).

  20. Exceptional vertebrate biotas from the Triassic of China, and the expansion of marine ecosystems after the Permo-Triassic mass extinction

    NASA Astrophysics Data System (ADS)

    Benton, Michael J.; Zhang, Qiyue; Hu, Shixue; Chen, Zhong-Qiang; Wen, Wen; Liu, Jun; Huang, Jinyuan; Zhou, Changyong; Xie, Tao; Tong, Jinnan; Choo, Brian

    2013-10-01

    The Triassic was a time of turmoil, as life recovered from the most devastating of all mass extinctions, the Permo-Triassic event 252 million years ago. The Triassic marine rock succession of southwest China provides unique documentation of the recovery of marine life through a series of well dated, exceptionally preserved fossil assemblages in the Daye, Guanling, Zhuganpo, and Xiaowa formations. New work shows the richness of the faunas of fishes and reptiles, and that recovery of vertebrate faunas was delayed by harsh environmental conditions and then occurred rapidly in the Anisian. The key faunas of fishes and reptiles come from a limited area in eastern Yunnan and western Guizhou provinces, and these may be dated relative to shared stratigraphic units, and their palaeoenvironments reconstructed. The Luoping and Panxian biotas, both from the Guanling Formation, are dated as Anisian (Pelsonian) on the basis of conodonts and radiometric dates, the former being slightly older than the latter. The Xingyi biota is from the Zhuganpo Formation, and is Ladinian or early Carnian, while the Guanling biota is from the overlying Xiaowa Formation, dated as Carnian. The first three biotas include extensive benthos and burrowing in the sediments, and they were located in restricted basins close to shore. Further, even though the Luoping and Panxian biotas are of similar age, their faunas differ significantly, reflecting perhaps palaeogeographically isolated basins. Between the time of the Xingyi and Guanling biotas, there was a major transgression, and the Guanling biota is entirely different in character from the other three, being dominated by pelagic forms such as large floating crinoids attached to logs, very large ichthyosaurs and thalattosaurs, and pseudoplanktonic bivalves, with no benthos and no burrowing. Phylogenetic study of the fishes and marine reptiles shows apparently explosive diversification among 20 actinopterygian lineages very early in the Early Triassic, but a later expansion of marine reptile groups, in the late Olenekian and early Anisian. This offset in diversification patterns is matched by comparisons of feeding guild categories and body size data. New research tools will shed considerable light on the phylogenetic and ecological implications of recovery of mairne vertebrates in the Triassic.

  1. Static substrate deposition: Toward longer time scale deposition simulations

    NASA Astrophysics Data System (ADS)

    Grochola, Gregory; Snook, Ian K.; Russo, Salvy P.

    2011-10-01

    We report on the development of a new method for simulating the deposition of atoms onto surfaces, which allows for longer time scales and/or larger system sizes. The method involves simulating only the deposited material on a purely static substrate and corrects for the missing thermal fluctuations and energy exchange effects that surface atoms experience as a result of a static substrate. This method may be viewed as an intermediate approximation between the discrete kinetic Monte Carlo and the full molecular dynamics (MD) methods, because it retains the full trajectory dynamics for the deposited atoms. The method can achieve speed-up times of approximately two orders of magnitude for submonolayer depositions on large simulation substrates. We first apply the method to an ideal prototypical system involving the deposition of Pt material on Pt substrates with two-dimensional Ag monolayer substrate patterns, where we show that it produces nanostructures and small cluster diffusion behavior almost identical to that observed during full MD simulations. As an ideal second application of the method, we use it to deposit Pt and Au onto a reconstructed Au(111) surface representative of a herringbone reconstruction and comment on the findings. Finally, we comment on the limitations and possible future improvements.

  2. Observing real time motion of nano-scale objects

    NASA Astrophysics Data System (ADS)

    van de Vondel, Joris; Timmermans, Matias; Samuely, Toms; Raes, Bart; Serrier-Garcia, Lise; Moshchalkov, Victor

    2015-03-01

    The dynamics of nanoscale objects is a very interesting field of research with a strong technological impact. Still, the combination of a technique resolving (sub)nanometer particles within a time frame relevant to observe dynamics is a very challenging task. Due to the inherent atomic-scale resolution, scanning tunneling microscopy (STM) is an ideal candidate to achieve this goal. Nevertheless, in most physical systems the dynamic events of the objects under investigation cannot be resolved by conventional STM image acquisition and will only reveal an average trace of the moving object. This is why a strong drive exists to develop new functionalities of STM, which allow studying dynamic events at the nanoscale. We address this issue, for vortex matter in NbSe2, by driving the vortices using an ac magnetic field and probing the induced periodic tunnel current modulations. Our results reveal different dynamical modes of the driven vortex lattice. In addition, by extending a known functionality of STM, (i.e. the `Lazy Fisherman' technique) we can use single pixel information to obtain the overall dynamics of the vortex lattice with submillisecond time resolution and subnanometer spatial resolution. This work is supported by the FWO and the Methusalem funding of the Flemish government.

  3. Halogens: From Annual To a Millennial Time Scale

    NASA Astrophysics Data System (ADS)

    Barbante, C.; Spolaor, A.; Vallelonga, P. T.; Schoenhardt, A.; Gabrieli, J.; Plane, J. M. C.; Curran, M. A.; Bjorkman, M. P.

    2014-12-01

    The role of sea ice in the Earth climate system is poorly defined, although its influence albedo, ocean circulation and atmosphere-ocean heat and gas exchange, in particular there is lack of information about its behaviour in the past. Different approaches have been proposed and used for the past reconstruction of sea ice. Attention has been given to sediment core in which measurement of diatomean assemblage has been discovered to respond to sea ice fluctuations. Recently a class of compounds, the highly branched isoprenoids (in particular the IP25) have been proposed as possible tracers for past sea ice extension. Other strategies have been used to evaluate the sea ice changes, for example multy-proxy approach (Kinnard et al. 2011) but for ice cores the question is still open. Sodium (Na) and Methanesulphonic acid (MSA) are now suggested as possible proxy. Sodium reflects glacial-interglacial sea ice variability but on shorter timescales is strongly influenced by meteorology (Levine et al. 2014). Methanesulphonic Acid, correlates with satellite observations of sea ice extent off the East Antarctic coast, but is reactive and remobilized in ice cores over centennial time scales (Curran, et al. 2003; Rothlisberger et al. 2010). In parallel we propose iodine and bromine, as a possible tracers for past sea ice changes. Bromine is actively involved in destruction chemistry of polar ozone via auto-catalyzed reactions called "Bromine explosions", which occur above seasonal sea ice and causing an excess of bromine in the snow deposition compared to the sea water ratio. Iodine is emitted from algal communities growing under sea ice and then, percolating up to the sea ice surface, it is emitted into the polar atmosphere. We investigate the halogens signal in different sites and with different time coverage; measurements have been carried out in Greenland, Svalbard and Antarctica. We first investigate the conservation of the climate signal in the recent depositions (~3 years coverage) and then we extend the evaluation on a decal, centurial and millennia time scale. The results suggest the connection of Bromine excess with seasonal sea ice extension; Iodine signal shows a different behaviour between the two Poles, hypothetically because of the difference in sea ice physical characteristics, but some questions have to be clarified.

  4. A new Triassic procolophonoid reptile and its implications for procolophonoid survivorship during the Permo-Triassic extinction event.

    PubMed

    Modesto, S; Sues, H D; Damiani, R

    2001-10-01

    A reptile specimen from the Lystrosaurus Assemblage Zone of the Beaufort Group, lowermost Triassic of South Africa, represents a new procolophonoid parareptile. Sauropareion anoplus gen. et sp. nov. is identified as the sister taxon of Procolophonidae in a phylogenetic analysis of procolophonoids. Stratigraphic calibration of the most parsimonious tree reveals that four of the six procolophonoid lineages originating in the Permian Period extended into the succeeding Triassic Period. This relatively high taxic survivorship (67%) across the Permo-Triassic boundary strongly suggests that procolophonoids were little if at all affected by the mass extinction event that punctuated the end of the Palaeozoic Era (ca. 251 million years ago). PMID:11571052

  5. Time-Scales of the Variability of the Atmosphere

    NASA Astrophysics Data System (ADS)

    Barnston, Anthony G.

    1996-05-01

    In this study the time-scales of variability of several weather elements are explored by season and location across the globe, emphasizing the Northern Hemisphere and especially the USA. The resulting description is useful because regions that exhibit low frequency variability (i.e. longer periods than the 2-5 days synoptic-scale) are assumed to be related more directly to changes in boundary conditions (e.g. anomalies of ENSO-related sea-surface temperature [SST], snow cover, etc.). Therefore, this low frequency variability may be predictable at greater ranges than those for which numerical weather prediction is helpful.New as well as established measures of persistence and frequency dependence are used and intercompared. In particular, the standard deviation of the differences between adjacent period means, when compared over a range of period lengths, reflects both autocorrelation and (if applicable) cycle time. Frequency dependence is thereby summarized with minimal computation.The geographical distribution of the amplitude (amount of variability depends largely on latitude and the upstream geographical environment (i.e. higher latitude and continentality of upstream environment tend to increase variability). At most locations, variability is greatest (lowest) during the cold (warm) seasons of the year. The geographical distribution of the dominant frequencies of variability are examined by season for Northern Hemisphere sea-level pressure and 700 hPa geopotential height, and USA surface temperature and precipitation. It is demonstrated that the dominant frequencies tend to vary in parallel across all four fields.In general, weather variables are found to vary at relatively low frequency (long periods) at high latitudes and, to a lesser extent, at subtropical latitudes. At mid-latitude, low frequency variability prevails most over the blocking regions in the eastern and central North Pacific and North Atlantic oceans. High frequency variability occurs in the synoptically active jet exit regions over the western oceans and the eastern and central parts of the Northern Hemisphere continents. Data from the Atmospheric Model Intercomparison Project integration of the National Centers for Environmental Prediction (formerly National Meteorological Center) medium-range-forecast general circulation model, which reproduce the Northern Hemisphere frequency dependence well at 700 hPa, indicate roughly analogous behaviour in the Southern Hemisphere. However, the longitudinal variation of mid-latitude frequency dependence is substantially less in the Southern Hemisphere, possibly because of the comparative absence of large, topographically significant land masses with favourable separation distance.

  6. Wood remains from the Late Triassic (Carnian) of Jordan and their paleoenvironmental implications

    NASA Astrophysics Data System (ADS)

    Abu Hamad, Abdalla M. B.; Jasper, Andr; Uhl, Dieter

    2014-07-01

    During field work in the Triassic of Jordan fossil wood remains have been discovered at five horizons (S-1AR-S-5AR) of the Late Triassic (Carnian) Abu Ruweis Formation in NW Jordan. In most horizons wood remains are too badly preserved to allow for a detailed xylotomic investigation. Only two horizons provided material which exhibited anatomical details: (1) in horizon S-1AR we found rare and rather small fragments of woody charcoal exhibiting cellular details (representing the first macroscopic evidence of paleo-wildfires from the Late Triassic of the Middle East), and (2) in horizon S-5AR surfaces of partly compressed (gagatized) and partly permineralized wood fragments exhibited anatomical details that could be investigated by means of scanning electron microscopy. All wood remains that allow for a detailed investigation show features typical of gymnosperms, but at the moment nothing can be said about a more specific taxonomic affinity of most of the woods, although wood from horizon S-5AR exhibits characteristics of protopinoid wood. Our data provide evidence that gymnospermous woody vegetation cover has existed in the source areas of the sediments deposited in the Abu Ruweis Formation in Jordan and that this woody vegetation occasionally experienced wildfires. This, together with lithological data, provides evidence for a seasonally dry (maybe even arid) climate during deposition of the Abu Ruweis Formation. On a larger scale our findings contribute to the very scarce current knowledge about Late Triassic wildfires on the entire continent Gondwana, from where so far only three records of macro-charcoals, as undisputed evidence of paleo-wildfires, have been published from this period.

  7. Anoxia Precedes the end-Triassic Mass Extinction: Evidence from the Kennecott Point Formation, British Columbia

    NASA Astrophysics Data System (ADS)

    Kasprak, A. H.; Sepúlveda, J.; Price-Waldman, R.; Williford, K. H.; Whiteside, J. H.; Summons, R. E.

    2011-12-01

    The end-Triassic mass extinction (ETE), at 201.4 million years ago, is one of the five largest ecologic disasters of the Phanerozoic eon. Few geologic sections offer the potential to reconstruct environmental and ecological changes at this time in the marine realm with global significance. The Kennecott Point Formation in Haida Gwaii (formerly the Queen Charlotte Islands), British Columbia, preserves a thick sequence of calcareous shales and siltstones deposited on late Triassic basaltic rocks interpreted to be an oceanic plateau resting within the Panthalassic basin, the largest ocean basin at the time of the Triassic-Jurassic transition. This section, which spans the late Norian to the mid-Hettangian, is plausibly the most representative of the global ocean system at this time; however, environmental reconstructions have been mostly based on bulk carbon and sulfur isotope records. Here, we present a record of molecular fossils (biomarkers) and indices indicative of ecological and redox changes (i.e., algal steranes and bacterial hopanes, gammacerane index, homohopane index, 2- and 3- methyl hopane indices) from the Kennecott Point Formation to argue for a period of low oxygen conditions associated with increased stratification, ecological changes, and disrupted nutrient cycling directly preceding the end-Triassic mass extinction. We couple these results with biomarkers indicative of terrestrial input and vegetation disturbance (tricyclic diterpanes and polycyclic aromatic hydrocarbons) to clarify the relationship between ocean biogeochemistry and environmental changes in the terrestrial realm. This record provides new evidence for changing marine conditions preceding and associated with the ETE and allows for a more rigorous investigation into the chronology of events hypothesized to be mechanistically linked to this mass extinction, including abrupt global warming, major alterations to marine primary productivity, and terrestrial vegetation die-off.

  8. Early Triassic conodonts of Jiarong, Nanpanjiang Basin, southern Guizhou Province, South China

    NASA Astrophysics Data System (ADS)

    Chen, Yanlong; Jiang, Haishui; Lai, Xulong; Yan, Chunbo; Richoz, Sylvain; Liu, Xiaodan; Wang, Lina

    2015-06-01

    Jiarong (Huishui County, Guizhou Province, South China) is a key locality for the study of the Early Triassic recovery after the end-Permian mass extinction. The size reduction of conodonts at the Smithian/Spathian transition was first documented in Jiarong, and it is also a locality that contributes to the documentation of the Early Triassic paleo-seawater temperatures. In the Jiarong sections, thirteen conodont zones were identified for the Early Triassic; in ascending order, they are Hindeodus parvus Zone, Hindeodus sosioensis Zone, Clarkina krystyni Zone, Neoclarkina discreta Zone, Neospathodus cristagalli-Eurygnathodus costatus assemblage zone, Novispathodus waageni eowaageni Zone, Novispathodus waageni waageni Zone, Discretella discreta Zone, Pachycladina-Parachirognathus assemblage zone, Novispathodus pingdingshanensis Zone, Icriospathodus collinsoni Zone, Triassospathodus homeri Zone, Triassospathodus triangularis Zone. These conodont zones in the Jiarong sections improve the global correlation of Early Triassic sections and also provide better regional age constraints in an area that is important for studies of recovery from the extinction. Based on the first appearance of Nv. waageni eowaageni, the Induan/Olenekian boundary is recognized at 3.6 m above the base of the Jiarong III Section. The dominance of blade-shaped (segminate) conodonts was replaced by gondola-shaped (segminiplanate) conodonts twice; the first time was in the late Griesbachian, and the second time was in the early Spathian. The dominance of segminiplanate conodonts probably indicates that the deeper seawater environment became more oxygenated during the late Griesbachian and early Spathian for short time intervals, as it is believed that the Griesbachian segminiplanate conodonts favored deeper oxygenated water habitats. A new genus, Spathogondolella gen. nov., and a new species, Spathogondolella jiarongensis sp. nov., have been recognized.

  9. Progress in integrated Late Triassic carbon isotopic stratigraphy of the Northern Calcareous Alps

    NASA Astrophysics Data System (ADS)

    Richoz, Sylvain; Krystyn, Leopold; Lein, Richard

    2015-04-01

    During the Late Triassic, despite new important originations a general decline in biodiversity was marked by a series of steps between the Carnian and the Rhaetian, with the T-J boundary event as final strike. The Reingraben Event and the Julian-Tuvalian boundary are two first massive turnovers; the Carnian-Norian boundary records a major vertebrate turnover, the early to middle Norian boundary comes up with a turnover in both the reefal and pelagic fauna and the most dramatic loss (70%) in biodiversity among Late Triassic molluscs. Around the Norian-Rhaetian boundary, the pelagic fauna of higher trophic level starts declining, whereas the reefs experience a blooming time. A refined stratigraphy and a construction of a well-calibrated carbon isotope reference curve are necessary to decipher between gradual environmental changes and abrupt or even catastrophic events during the Late Triassic. Improvement in the Upper Triassic d13Ccarb curve shows that after a gentle increase until the base of the Carnian, the early Carnian records three negative excursions of 2 to 3‰ amplitude. The two first excursions rebound to previous values, whereas the third negative excursion, at the Julian-Tuvalian boundary, is followed by a positive excursion up to +5‰. The remaining Upper Carnian displays stabile values around 2‰. The Carnian-Norian boundary interval is marked by a minor increase of less than 1‰. The Early to Middle Norian crisis is marked by a turning point from Early Norian slowly increasing carbon isotope values (up to 3.5‰) to gradually decreasing ones until 1.8‰ at the base of the Rhaetian. This Norian decrease display two accelerated steps, one in the middle Norian and the other one just after the Norian-Rhaetian Boundary. This last 1‰ decrease corresponds however to an important change in lithology. The values show then a small increase during the early Rhaetian, with a maximum in the middle Rhaetian (at 2.4‰). The isotopic record remains constant until the top of the Rhaetian with its significant negative shift identified in a number of marine sections in close proximity to the extinction event. The general stability of the curve even through the Norian-Rhaetian boundary crisis event describes a stable oceanic structure prior the mass extinction. From an isotopic point of view, only the two Lower Carnian excursions, the Early Late-Upper Carnian Boundary and the Triassic-Jurassic Boundary can be interpreted as events, whereas other biotic crises of the Late Triassic seem to have occurred during periods of gradual changes in the carbon isotopic composition of seawater.

  10. Permian and Triassic microfloral assemblages from the Blue Nile Basin, central Ethiopia

    NASA Astrophysics Data System (ADS)

    Dawit, Enkurie L.

    2014-11-01

    Palynological investigation was carried out on surface samples from up to 400 m thick continental siliciclastic sediments, here referred to as “Fincha Sandstone”, in the Blue Nile Basin, central Ethiopia. One hundred sixty species were identified from 15 productive samples collected along a continuous road-cut exposure. Six informal palynological assemblage zones have been identified. These assemblage zones, in ascending order, are: “Central Ethiopian Permian Assemblage Zone - CEPAZ I”, earliest Permian (Asselian-Sakmarian); “CEPAZ II”, late Early Permian (Artinskian-Kungurian); CEPAZ III - Late Permian (Kazanian-Tatarian); “CETAZ IV”, Lower Triassic (Olenekian Induan); “CETAZ V”, Middle Triassic (Anisian Ladinian); “CETAZ VI”, Late Triassic (Carnian Norian). Tentative age ranges proposed herein are compared with faunally calibrated palynological zones in Gondwana. The overall composition and vertical distribution of miospores throughout the studied section reveals a wide variation both qualitatively and quantitatively. The high frequency of monosaccate pollen in CEPAZ I may reflect a Glossopterid-dominated upland flora in the earliest Permian. The succeeding zone is dominated by straite/taeniate disaccate pollen and polyplicates, suggesting a notable increase in diversity of glossopterids. The decline in the diversity of taeniate disaccate pollen and the concomitant rise in abundance of non-taeniate disaccates in CEPAZ III may suggest the decline in Glossopteris diversity, though no additional evidence is available to equate this change with End-Permian extinction. More diverse and dominant non-taeniate, disaccate, seed fern pollen assignable to FalcisporitesAlisporites in CETAZ IV may represent an earliest Triassic recovery flora. The introduction of new disaccate forms with thick, rigid sacci, such as Staurosaccites and Cuneatisporites, in CETAZ V and VI may indicate the emergence of new gymnospermous plants that might have favourably adapted to coastal plain wetland environments with the return of humid conditions in the Middle to early Late Triassic. The present data constitute the first paleontologically substantiated record for the existence of Permian strata in the Blue Nile Basin. The new results allow for the first time a reliable biostratigraphic subdivision of the central Ethiopia Karoo and its correlation with coeval strata of adjacent regions in Gondwana. From a phytogeographic point of view, the overall microfloral evidence is in support of the position of central Ethiopia occupying the northern part of the southern Gondwana palynofloral province. In view of palaeoecological and paleoclimatic conditions, the microfloral change from the base to the top of the studied section may indicate a response to shifting climatic belts from warm- and cool-temparate climate in the earliest Permian to progressively drier seasonal conditions at successively higher palaeolatitudes during the Late Permian to Middle Triassic.

  11. Science at the Time-scale of the Electron

    NASA Astrophysics Data System (ADS)

    Murnane, Margaret

    2010-03-01

    Replace this text with your abstract Ever since the invention of the laser 50 years ago and its application in nonlinear optics, scientists have been striving to extend coherent laser beams into the x-ray region of the spectrum. Very recently however, the prospects for tabletop coherent sources, with attosecond pulse durations, at very short wavelengths even in the hard x-ray region of the spectrum at wavelengths < 1nm, have brightened considerably. These advances are possible by taking nonlinear optics techniques to an extreme, and are the direct result of a new ability to manipulate electrons on the fastest, attosecond, time-scales of our natural world. My talk will discuss new experimental data that demonstrates high harmonic generation of laser-like, fully coherent, 10 attosecond duration, soft x-ray beams at photon energies around 0.5keV. Several applications will also be discussed, including making a movie of how electron orbitals in a molecule change shape as a molecule breaks apart, following how fast a magnetic material can flip orientation, understanding how fast heat flows in a nanocircuit, or building a microscope without lenses. [4pt] [1] T. Popmintchev et al., ``Phase matched upconversion of coherent ultrafast laser light into the soft and hard x-ray regions of the spectrum'', PNAS 106, 10516 (2009). [0pt] [2] C. LaOVorakiat et al., ``Ultrafast Soft X-Ray Magneto-Optics at the M-edge Using a Tabletop High-Harmonic Source'', Physical Review Letters 103, 257402 (2009). [0pt] [3] M. Siemens et al. ``Measurement of quasi-ballistic heat transport across nanoscale interfaces using ultrafast coherent soft x-ray beams'', Nature Materials 9, 26 (2010). [0pt] [4] K. Raines et al., ``Three-dimensional structure determination from a single view,'' Nature 463, 214 (2010). [0pt] [5] W. Li et al., ``Time-resolved Probing of Dynamics in Polyatomic Molecules using High Harmonic Generation'', Science 322, 1207 (2008).

  12. Super ENSO and global climate oscillations at millennial time scales.

    PubMed

    Stott, Lowell; Poulsen, Christopher; Lund, Steve; Thunell, Robert

    2002-07-12

    The late Pleistocene history of seawater temperature and salinity variability in the western tropical Pacific warm pool is reconstructed from oxygen isotope (delta18O) and magnesium/calcium composition of planktonic foraminifera. Differentiating the calcite delta18O record into components of temperature and local water delta18O reveals a dominant salinity signal that varied in accord with Dansgaard/Oeschger cycles over Greenland. Salinities were higher at times of high-latitude cooling and were lower during interstadials. The pattern and magnitude of the salinity variations imply shifts in the tropical Pacific ocean/atmosphere system analogous to modern El Nio-Southern Oscillation (ENSO). El Nio conditions correlate with stadials at high latitudes, whereas La Nia conditions correlate with interstadials. Millennial-scale shifts in atmospheric convection away from the western tropical Pacific may explain many paleo-observations, including lower atmospheric CO2, N2O, and CH4 during stadials and patterns of extratropical ocean variability that have tropical source functions that are negatively correlated with El Nio. PMID:12114618

  13. Titan's evaporites structure and their formation time-scale

    NASA Astrophysics Data System (ADS)

    Cordier, D.; Barnes, J.; Le Bahers, T.; Cornet, T.; Ferreira, A.

    2014-04-01

    Hydrocarbons lakes have been discovered in polar regions of Titan (Stofan et al. 2007) [1]. Already, Stofan et al. (2007) noticed features suggesting the occurence of an evaporation process in the recent past. Barnes et al. (2009) [2] performed a detailed study of shoreline features of Ontario Lacus, they interpreted the 5-?m brigth annulus around this lakes as a dry, low-water ice content zone, possibly corresponding to a deposit of organic condensates. Barnes et al. (2011) [3] used a sample of several lakes and lakebeds located in a region south of the Ligeia Mare. They got a strong correlation between RADAR-empty lakes and 5-?m brigth units interpreted as low-water ice content areas. On the theoretical side, Cordier et al. (2013) [4] elaborated a model for the chemical composition of the external layer of these possible organic evaporite deposits. This model was based on a simplified theory of dissolution (ideal solution and regular solution theory) and all computations were performed using a time-scale which did not enable any estimation for the depth of deposits layers.

  14. Detonation initiation on the microsecond time scale: DDTs

    SciTech Connect

    Kuehn, Jeffery A; Kassoy, Dr. David R; Nabity, Mr. Matthew W.; Clarke, Dr. John F.

    2006-01-01

    Spatially resolved, thermal power deposition of limited duration into a finite volume of reactive gas is the initiator for a deflagration-to-detonation transition (DDT) on the microsecond time scale. The reactive Euler equations with one-step Arrhenius kinetics are used to derive novel formulas for velocity and temperature variation that describe the physical phenomena characteristic of DDTs. A nonlinear transformation of the variables is shown to yield a canonical equation system, independent of the activation energy. Numerical solutions of the reactive Euler equations are used to describe the detailed sequence of reactive gas dynamic processes leading to an overdriven planar detonation far from the power deposition location. Results are presented for deposition into a region isolated from the planar boundary of the reactive gas as well as for that adjacent to the boundary. The role of compressions and shocks reflected from the boundary into the partially reacted hot gas is described. The quantitative dependences of DDT evolution on the magnitude of thermal power deposition and activation energy are identified.

  15. Detonation initiation on the microsecond time scale: DDTs

    SciTech Connect

    Kassoy, Dr. David R; Kuehn, Jeffery A; Nabity, Mr. Matthew W.; Clarke, Dr. John F.

    2008-01-01

    Spatially resolved, thermal power deposition of limited duration into a finite volume of reactive gas is the initiator for a deflagration-to-detonation transition (DDT) on the microsecond time scale. The reactive Euler equations with one-step Arrhenius kinetics are used to derive novel formulas for velocity and temperature variation that describe the physical phenomena characteristic of DDTs. A transformation of the variables is shown to yield a canonical equation system, independent of the activation energy. Numerical solutions of the reactive Euler equations are used to describe the detailed sequence of reactive gasdynamic processes leading to an overdriven planar detonation far from the power deposition location. Results are presented for deposition into a region isolated from the planar boundary of the reactive gas as well as for that adjacent to the boundary. The role of compressions and shocks reflected from the boundary into the partially reacted hot gas is described. The quantitative dependences of DDT evolution on the magnitude of thermal power deposition and activation energy are identified.

  16. Depositional and thermal history of Lower Triassic rocks in southwestern Montana and adjacent parts of Wyoming and Idaho

    SciTech Connect

    Paull, R.K.; Paull, R.A.; Kraemer, B.R. )

    1989-09-01

    Forty-two stratigraphic sections in Montana and adjacent parts of Wyoming and Idaho provide the framework for a conodont biostratigraphic and carbonate sedimentologic analysis of Lower Triassic marine rocks. From oldest to youngest, these units are the Dinwoody, Woodside (Red Peak to the east), and Thaynes Formations. The Dinwoody disconformably overlies Upper Permian rocks with little or no physical evidence of a 1 to 6-m.y. hiatus. The initial Triassic transgression was extensive and geologically instantaneous across the study area, and it resulted in deposition of interbedded calcareous mudstone, siltstone, and limestone. The Dinwoody varies in thickness from zero on the northeast to greater than 270 m in the southwest. Maximum thicknesses of Woodside red beds and Thaynes carbonates and siltstones are 244 and 400 m, respectively. Post-Triassic erosion progressively truncated the Thaynes, Woodside, and Dinwoody from north to south across the region. The western margin of the Triassic seaway in the study area is obscured by erosion, structural complexities, igneous activity, and younger sedimentary deposits. The sparse and scattered exposures that remain provide an intriguing mosaic of depositional environments that range from shallow marine to basinal and represent most of Early Triassic time. Lower Triassic rocks produce gas in the Wyoming-Idaho thrust belt, and similar potential may exist in Montana. Conodonts recovered from surface exposures are thermally unaltered except in close proximity to intrusive bodies and within the Medicine Lodge thrust system. This establishes that subsurface units in much of the study area are within the temperature regime for dry gas generation.

  17. Probing Time-Dependent Molecular Dipoles on the Attosecond Time Scale

    NASA Astrophysics Data System (ADS)

    Neidel, Ch.; Klei, J.; Yang, C.-H.; Rouze, A.; Vrakking, M. J. J.; Klnder, K.; Miranda, M.; Arnold, C. L.; Fordell, T.; L'Huillier, A.; Gisselbrecht, M.; Johnsson, P.; Dinh, M. P.; Suraud, E.; Reinhard, P.-G.; Despr, V.; Marques, M. A. L.; Lpine, F.

    2013-07-01

    Photoinduced molecular processes start with the interaction of the instantaneous electric field of the incident light with the electronic degrees of freedom. This early attosecond electronic motion impacts the fate of the photoinduced reactions. We report the first observation of attosecond time scale electron dynamics in a series of small- and medium-sized neutral molecules (N2, CO2, and C2H4), monitoring time-dependent variations of the parent molecular ion yield in the ionization by an attosecond pulse, and thereby probing the time-dependent dipole induced by a moderately strong near-infrared laser field. This approach can be generalized to other molecular species and may be regarded as a first example of molecular attosecond Stark spectroscopy.

  18. A Group Simulation of the Development of the Geologic Time Scale.

    ERIC Educational Resources Information Center

    Bennington, J. Bret

    2000-01-01

    Explains how to demonstrate to students that the relative dating of rock layers is redundant. Uses two column diagrams to simulate stratigraphic sequences from two different geological time scales and asks students to complete the time scale. (YDS)

  19. First occurrence of tetrapod footprints from the continental Triassic of the Sidi Said Maachou area (Western Meseta, Morocco)

    NASA Astrophysics Data System (ADS)

    Hminna, Abdelkbir; Voigt, Sebastian; Klein, Hendrik; Saber, Hafid; Schneider, Jörg W.; Hmich, Driss

    2013-04-01

    The Sidi Said Maachou area in the Moroccan western Meseta preserves a succession, up to 400 m thick, of hitherto poorly studied continental Triassic deposits. Recent detailed geological mapping proposes a lithostratigraphic subdivision of the predominantly red-coloured siliciclastic deposits into three formations. Laminated mudstones and fine-grained sandstones in the upper part of the Oued Oum Er Rbiaa Formation have the most interesting fossil content including plant impressions, rhizoliths, fish scales, and invertebrate and vertebrate traces. These biogenic remains are partially associated with tool marks, microbially induced sedimentary structures, oscillation ripples, desiccation cracks, and halite pseudomorphs, suggesting sedimentation in a playa-like, fluvio-lacustrine system under semiarid conditions. All tetrapod footprints from these beds are assigned to Brachychirotherium parvum and indistinguishable from other occurrences of the ichnogenus in Central Europe and North America. Supposed trackmakers are archosaurs of the crocodile stem-group (Crurotarsi) that were widely spread over Triassic Pangaea. Because Brachychirotherium is only known from Late Triassic (Carnian-Rhaetian) deposits, the same age is attributed to the footprint horizon of the Oued Oum Er Rbiaa Formation. This is the first record of Brachychirotherium on the African continent and the first record of Triassic tetrapod footprints in Morocco outside of the High Atlas.

  20. EON: software for long time simulations of atomic scale systems

    NASA Astrophysics Data System (ADS)

    Chill, Samuel T.; Welborn, Matthew; Terrell, Rye; Zhang, Liang; Berthet, Jean-Claude; Pedersen, Andreas; Jónsson, Hannes; Henkelman, Graeme

    2014-07-01

    The EON software is designed for simulations of the state-to-state evolution of atomic scale systems over timescales greatly exceeding that of direct classical dynamics. States are defined as collections of atomic configurations from which a minimization of the potential energy gives the same inherent structure. The time evolution is assumed to be governed by rare events, where transitions between states are uncorrelated and infrequent compared with the timescale of atomic vibrations. Several methods for calculating the state-to-state evolution have been implemented in EON, including parallel replica dynamics, hyperdynamics and adaptive kinetic Monte Carlo. Global optimization methods, including simulated annealing, basin hopping and minima hopping are also implemented. The software has a client/server architecture where the computationally intensive evaluations of the interatomic interactions are calculated on the client-side and the state-to-state evolution is managed by the server. The client supports optimization for different computer architectures to maximize computational efficiency. The server is written in Python so that developers have access to the high-level functionality without delving into the computationally intensive components. Communication between the server and clients is abstracted so that calculations can be deployed on a single machine, clusters using a queuing system, large parallel computers using a message passing interface, or within a distributed computing environment. A generic interface to the evaluation of the interatomic interactions is defined so that empirical potentials, such as in LAMMPS, and density functional theory as implemented in VASP and GPAW can be used interchangeably. Examples are given to demonstrate the range of systems that can be modeled, including surface diffusion and island ripening of adsorbed atoms on metal surfaces, molecular diffusion on the surface of ice and global structural optimization of nanoparticles.

  1. Using δ18O of Conodont Apatite and Sequence Stratigraphy to Understand Early Triassic (Smithian) Sea-Level Change

    NASA Astrophysics Data System (ADS)

    Yurchyk, S.; Elrick, M.; Atudorei, V.

    2009-12-01

    The Early Triassic climate is conventionally interpreted to have been warm and ice-free. During this time, three globally recognized depositional sequences developed in response to My-scale eustatic sea-level changes. The rates of My-scale sea-level rise and fall are too fast to attribute to changes in mid-ocean ridge activity and too slow to attribute to typical ~20-400 ky orbital cycles that drive glacio-eustasy. Previous studies in the Middle Devonian, Late Cretaceous, and Middle Eocene greenhouse climates have suggested that significant glacio-eustatic sea-level changes were responsible for sequence development. This suggests that these particular greenhouse periods were not uniformly warm and ice-free. We are testing the hypothesis that My- and orbital-scale sea-level changes in the Early Triassic (Smithian) were driven by glacio- and/or thermo-eustasy. To test this hypothesis, Smithian marine successions from two localities in the western United States (Lower Thaynes Formation) were described on a bed-by-bed basis to provide facies and depositional environment interpretations, as well as put the sections into a sequence stratigraphic framework. Samples were collected from both locations for high-resolution (~1-10 m) oxygen isotopic analysis of conodont apatite. Conodont elements are excellent biostratigraphic indicators and the apatite is less susceptible to diagenetic alteration than carbonate minerals, making conodont apatite a reliable proxy for determining changes in ice volume and seawater temperatures in deep time. In northeastern Utah (Weber Canyon), the Smithian sequence (~240 m) is composed of a mixed carbonate-siliciclastic lowstand systems tract (>40 m) and transgressive systems tract (~110 m), a black shale maximum flooding zone (~15 m), and a carbonate-dominated highstand systems tract (~75 m). In western Utah (Confusion Range), the sequence is composed of a coarse-grained, carbonate-dominated transgressive systems tract (>40 m) and a mixed siliciclastic-carbonate highstand systems tract (>60 m). Sequences at both locations display high-frequency (104-105 yr), upward-shallowing, subtidal cycles whose subtle facies changes indicate only minor sea-level changes, which is to be expected given the interpreted warm paleoclimate. The high-frequency, subtidal cycles are not present in the Weber Canyon maximum flooding zone because during that time the platform was too deep to record the effects of high-frequency sea-level changes. If our climatically controlled My- and orbital-scale sea-level hypothesis is correct, then δ18O values should decrease within transgressive and maximum flooding intervals and increase and peak within highstand/lowstand intervals and the conventional interpretation of a uniformly warm Early Triassic climate must be re-evaluated.

  2. Depositional history of Lower Triassic Dinwoody Formation, Bighorn basin, Wyoming and Montana

    SciTech Connect

    Paull, R.A.; Paull, R.K.

    1986-08-01

    The Lower Triassic Dinwoody Formation in the Bighorn basin of Wyoming and Montana records the northeasternmost extent of the widespread and rapid Griesbachian transgression onto the Wyoming shelf. Depositional patterns document a progressive change from sparsely fossiliferous, inner-shelf marine conditions in the southwest and west to restricted, marginal-marine environments to the north and east. Characteristic lithologies include greenish-gray calcareous or dolomitic mudstone and siltstone, very thin to thick beds of gypsum, and thin-bedded, commonly laminated dolomite. A formation thickness of approximately 20 m persists throughout most of the basin but diminishes abruptly near the northern and eastern limits of deposition. The Dinwoody is disconformable on the Ervay Member of the Permian Park City Formation except in the northeasternmost part of the basin, where it locally overlies the Pennsylvanian Tensleep Sandstone. Considering the significant time interval involved, physical evidence at the Permian-Triassic boundary is generally limited to an abrupt lithologic change from light-colored shallow marine or intertidal Permian dolomite to greenish-gray Dinwoody siltstone. The Dinwoody grades vertically as well as laterally to the east and north into red beds of the Lower Triassic Red Peak Formation of the Chugwater Group. The Early Triassic depositional environment in the present-day Bighorn basin was hostile. A sparse molluscan fauna was observed at only one of the 20 sections studied, and no conodonts were recovered from Dinwoody carbonates. Significant amounts of gypsum within the Dinwoody suggest periodic high evaporation from hypersaline waters on a low-energy shallow shelf during intervals of reduced terrigenous sediment supply from the north and east. However, sufficient organic material was present to create reducing conditions, as evidenced by greenish rock color and abundant pyrite.

  3. Tectonic implications of Perm-Triassic paleomagnetic results from north and south China

    NASA Astrophysics Data System (ADS)

    Zhao, Xixi; Coe, Robert S.

    Late Permian and Early Triassic paleomagnetic results of our own and others show that the North China Block (NCB), South China Block (SCB), and Siberia were not in their present positions relative to each other. Paleomagnetic poles for the NCB that derived from our studies of Permian rocks at several localities in Shanxi and Hebei provinces are concordant with poles from other studies of Permian rocks in Shanxi, Gansu, and Inner Mongolia. In addition, our poles for the Permian Emeishan Basalts and those from many other studies of the same formation over a sizeable portion of the SCB are consistent if we reinterpret the polarity of several of them. Early Triassic poles from both blocks are fairly close to the Late Permian ones, and greatly increase the areal extent covered by the data for the SCB. The equatorial paleolatitudes inferred by the data from both blocks are similar, but the mean declination for the SCB is rotated clockwise more than 60 degrees with respect to that for the NCB. To explain these results we propose a simple tectonic model in which initial collision of the blocks occurred in the Early Triassic near the eastern end of their boundary and progressed westward as the SCB rotated clockwise 67 degrees relative to the NCB. Eastward thinning and eventual disappearance of Triassic marine sediments on the northern margin of the SCB support this model. A simple alternative model involves sinistral movement on a transform fault that wraps around the SCB to the north and west, but evidence for the large Mesozoic displacement (2,500 km minimum) is presently lacking. Jurassic and Cretaceous poles for North and South China and for Siberia are overlapping, but no fold or reversal tests are available for the Jurassic data from China. Thus, the major movements between the three blocks were completed at least by the Late Cretaceous, perhaps during Jurassic time.

  4. Development of the Permian-Triassic sequence in the basin Fringe area, southern Netherlands

    SciTech Connect

    Geluk, M.; Van Doorn, D.; Plomp, A.; Duin, E. )

    1993-09-01

    Geological studies in the fringe area of the southern Permian basin led to new insights in the distribution and development of the Permian-Triassic sequence. During the Permian, the fringe area formed a platform, attached to the London-Brabant Massif, while during the Triassic it is characterized by strongly subsiding half grabens. In the southern Netherlands, Rotliegende sandstones and conglomerates have a much wider distribution than previously recognized. The Rotliegende deposits are capped by claystones and carbonates of the Upper Permian Zechstein. In the offshore, an important feeder system of clastics from the London-Brabant Massif was active during deposition of the Rotliegende and the Zechstein. In course of time, the location of major sandstone deposition shifted westward. Deposition of the Triassic Buntsandstein was controlled by the development of a large feeder system, which transported clastics from the Vosges northward, through the Roer Valley Graben and West netherlands Basin into the Off Holland Low. This system was responsible for the deposition of the economically important sheet sandstones of the Volpriehausen, Detfurth, Hardegsen, and Solling formations. A regional unconformity occurs below the Solling Formation. The sandstones are capped by claystones, evaporites, and sandstones of the Rot Formation. During deposition of the Muschelkalk, the differences in subsidence decreased and shallow marine sediments are interbedded with evaporites. Several unconformities occur within the Keuper. In the previous half grabens in the southern Netherlands, the Keuper is incomplete, which may be indicative for a possible reversal of the tectonic movements during this period.

  5. The oldest post-palaeozoic crinoid and permian-triassic origins of the articulata (echinodermata).

    PubMed

    Oji, Tatsuo; Twitchett, Richard J

    2015-04-01

    The Crinoidea are the most primitive class of living echinoderms, and suffered a severe crisis during the Late Permian mass extinction event. All post-Palaeozoic crinoids, including living species, belong to the Articulata, and morphological and recent molecular studies demonstrate that they form a monophyletic clade. The Articulata originated from Palaeozoic cladid crinoids, but the nature and timing of their origination remains obscure. Problems with understanding the origin and early evolution of the Articulata have arisen because the Permian-Triassic crinoid fossil record is particularly poor. We report on a new genus and species from the earliest Triassic, which is the oldest known post-Palaeozoic articulate crinoid and fundamentally alters our understanding of the early evolution of the Articulata. Prior to this study, the most primitive post-Palaeozoic articulate was thought to be Holocrinus of the order Isocrinida. Unexpectedly, the new taxon belongs to the order Encrinida, which reveals a previously hidden diversity of crinoids in the earliest Triassic. Its discovery implies either a dramatic radiation of crinoids in the immediate post-extinction aftermath, when environmental conditions were at their most severe, or a pre-extinction origin of the crown group articulates and survival of multiple lineages. PMID:25826072

  6. Biostratigraphic restudy documents Triassic/Jurassic section in Georges Bank COST G-2 well

    SciTech Connect

    Cousminer, H.L.; Steinkraus, W.E.; Hall, R.E.

    1984-04-01

    In 1977, the COST G-2 well as drilled in Georges Bank, 132 mi (212 km) east of Nantucket Island to a total depth of 21,874 ft (6667 m). Biostratigraphic studies of 363 sidewall and conventional cores and 695 cutting samples resulted in a detailed zonation from the Late Jurassic to the present. Restudy of the original samples, as well as new preparations from previously unstudied core material, resulted in revision of the zonation of the Late Jurassic and older section. On the basis of our study of pollen and spores, dinoflagellates, nannofossils, and foraminifers, we revised the age sequence as follows: 5856 ft (1785 m) Late Jurassic (Thithonian); 6000 ft (1829 m) Kimmeridgian; 6420 ft (1957 m) Oxfordian; 6818 ft (2078 m) Callovian; 8200 ft (2499 m) Bathonian; 9677 ft (2950 m) Bajocian; 14567 ft (4440 m) Norian (Late Triassic). Norian dinoflagellate cysts and Tasmanites sp. indicate that intermittent normal marine sedimentation was taking place on Georges Bank as early as Norian time, although most of the Triassic section (+14,500 ft or 4420 m to T.D.) interpreted as having been deposited under evaporitic sabkha-like conditions. The Norian dinoflagellates (Noricysta, Heibergella, Hebecysta, Suessia, Dapcodinium, and Rhombodella) include species common to both Arctic Canada and the Tethyan region, indicating a possible Late Triassic marine connection.

  7. Mandibular and dental characteristics of Late Triassic mammaliaform Haramiyavia and their ramifications for basal mammal evolution

    PubMed Central

    Luo, Zhe-Xi; Gatesy, Stephen M.; Jenkins, Farish A.; Amaral, William W.; Shubin, Neil H.

    2015-01-01

    As one of the earliest-known mammaliaforms, Haramiyavia clemmenseni from the Rhaetic (Late Triassic) of East Greenland has held an important place in understanding the timing of the earliest radiation of the group. Reanalysis of the type specimen using high-resolution computed tomography (CT) has revealed new details, such as the presence of the dentary condyle of the mammalian jaw hinge and the postdentary trough for mandibular attachment of the middle ear—a transitional condition of the predecessors to crown Mammalia. Our tests of competing phylogenetic hypotheses with these new data show that Late Triassic haramiyids are a separate clade from multituberculate mammals and are excluded from the Mammalia. Consequently, hypotheses of a Late Triassic diversification of the Mammalia that depend on multituberculate affinities of haramiyidans are rejected. Scanning electron microscopy study of tooth-wear facets and kinematic functional simulation of occlusion with virtual 3D models from CT scans confirm that Haramiyavia had a major orthal occlusion with the tallest lingual cusp of the lower molars occluding into the lingual embrasure of the upper molars, followed by a short palinal movement along the cusp rows alternating between upper and lower molars. This movement differs from the minimal orthal but extensive palinal occlusal movement of multituberculate mammals, which previously were regarded as relatives of haramiyidans. The disparity of tooth morphology and the diversity of dental functions of haramiyids and their contemporary mammaliaforms suggest that dietary diversification is a major factor in the earliest mammaliaform evolution. PMID:26630008

  8. Mandibular and dental characteristics of Late Triassic mammaliaform Haramiyavia and their ramifications for basal mammal evolution.

    PubMed

    Luo, Zhe-Xi; Gatesy, Stephen M; Jenkins, Farish A; Amaral, William W; Shubin, Neil H

    2015-12-22

    As one of the earliest-known mammaliaforms, Haramiyavia clemmenseni from the Rhaetic (Late Triassic) of East Greenland has held an important place in understanding the timing of the earliest radiation of the group. Reanalysis of the type specimen using high-resolution computed tomography (CT) has revealed new details, such as the presence of the dentary condyle of the mammalian jaw hinge and the postdentary trough for mandibular attachment of the middle ear-a transitional condition of the predecessors to crown Mammalia. Our tests of competing phylogenetic hypotheses with these new data show that Late Triassic haramiyids are a separate clade from multituberculate mammals and are excluded from the Mammalia. Consequently, hypotheses of a Late Triassic diversification of the Mammalia that depend on multituberculate affinities of haramiyidans are rejected. Scanning electron microscopy study of tooth-wear facets and kinematic functional simulation of occlusion with virtual 3D models from CT scans confirm that Haramiyavia had a major orthal occlusion with the tallest lingual cusp of the lower molars occluding into the lingual embrasure of the upper molars, followed by a short palinal movement along the cusp rows alternating between upper and lower molars. This movement differs from the minimal orthal but extensive palinal occlusal movement of multituberculate mammals, which previously were regarded as relatives of haramiyidans. The disparity of tooth morphology and the diversity of dental functions of haramiyids and their contemporary mammaliaforms suggest that dietary diversification is a major factor in the earliest mammaliaform evolution. PMID:26630008

  9. An aborted Triassic Ocean in west Siberia

    NASA Astrophysics Data System (ADS)

    Aplonov, Sergei

    1988-12-01

    A small buried oceanic basin named the Obsky paleo-ocean has been found in West Siberia. It developed from 235 to 218 m.y. during the Triassic by rift propagation and seafloor spreading inside the west Siberian region of the continent. During the postspreading period the Obsky paleo-ocean did not collapse but instead was covered intact by a layer of sediments with a thickness of up to 15 km. This conclusion is based on detailed interpretation of geophysical and geological data. Striped magnetic anomalies marking the paleo-ocean spreading have been separated from the total magnetic field. They have been dated and interpreted within the framework of the Vine-Matthews concept. Seismic and gravitational data have permitted delineation of the Obsky paleo-ocean depression and contouring of the basement relief within its bounds. Investigation of the Obsky paleo-ocean basalts by means of deep boreholes has indicated that they are chemically similar to oceanic tholeiites and has also confirmed the presence of strong residual magnetism in them. Spreading of the Obsky paleo-ocean was a stage in the initial disintegration of Pangea at the Paleozoic-Mesozoic boundary. The presence of a north trending buried spreading center along the axial zone of West Siberia accounts for many features of the Mesozoic-Cenozoic history of the region and its present-day structure.

  10. Petrogenesis and geodynamic implications of the Mid-Triassic lavas from East Kunlun, northern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Li, Xiaowei; Huang, Xiongfei; Luo, Mingfei; Dong, Guochen; Mo, Xuanxue

    2015-06-01

    Lying in the northern margin of the Tibetan Plateau, the East Kunlun Orogenic Belt (EKOB) is characterized by widespread of the late Permian to Late Triassic magmatic rocks. In order to better understand magma genesis and evolution during the waning stage of the Paleo-Tethyan oceanic subduction and subsequent collision, we present zircon U-Pb dating and Lu-Hf isotopes, whole-rock major and trace elements, and Sr-Nd isotope data for the Triassic volcanic lavas in the Haishigou area of the EKOB, northern Tibet. Lithologically, the Haishigou volcanic lavas are mainly composed of dacites and rhyolites. The LA-ICP-MS zircon U-Pb analyses for rhyolites have shown that the Haishigou volcanic rocks formed during the Middle Triassic with ages of ca. 244-245 Ma. The Haishigou volcanic lavas actually belong to part of the Middle Triassic Naocangjiangou Formation, rather than the Late Triassic Elashan Formation. Geochemically, Haishigou volcanic lavas have SiO2 = 60.31-76.19 wt% and K2O = 2.60-4.18 wt%, placing them in high-K calc-alkaline series. These lavas are characterized by enrichment in some large-ion lithophile elements (e.g., Rb, K and Pb) and light rare earth elements and depletion in some high field strength elements (e.g., Nb, Ta, and Ti), with geochemical affinities to those rocks forming in a continental or an oceanic arc setting. All the volcanic rocks exhibit high initial 87Sr/86Sr ratios (0.70614-0.70841) and moderately negative εNd(t) values (-5.9 to -4.3) that imply a continental rather than oceanic type magma source. The rhyolites in the Haishigou volcanics exhibit moderately negative to slightly positive εHf(t) values (-4.2 to 1.4). Combined with their zircon Hf two-stage model ages of 1187-1538 Ma and whole-rock Nd two-stage model ages of 1.37-1.38 Ga, it can be inferred that the crustal growth of East Kunlun occurred during the Mesoproterozoic, making them similar in age to the lower crust metamorphic basement beneath the EKOB (i.e., the Xiaomiao Group). We suggest that the Haishigou dacites were generated by partial melting of the mafic lower crust beneath the EKOB with addition of a mantle-derived mafic component and that the rhyolites were produced by fractional crystallization from a dacitic parent. Taking into account the Late Permian to Triassic geological record from the EKOB and surrounding regions, we argue that the Middle Triassic volcanic rocks in the Haishigou area erupted during the northward subduction of the Paleo-Tethyan oceanic plate. Consequently, the timing of closure of the Paleo-Tethyan Ocean just south of the EKOB is no earlier than the Middle Triassic.

  11. Life crises on land across the Permian-Triassic boundary in South China

    NASA Astrophysics Data System (ADS)

    Peng, Yuanqiao; Shi, G. R.

    2009-02-01

    The western Guizhou and eastern Yunnan area of southwest China commands a unique and significant position globally in the study of Permian-Triassic boundary (PTB) events as it contains well and continuously exposed PTB sections of marine, non-marine and marginal-marine origin in the same area. By using a range of high-resolution stratigraphic methods including biostratigraphy, eventostratigraphy, chronostratigraphy and chemostratigraphy, not only are the non-marine PTB sections correlated with their marine counterparts in the study area with high-resolution, the non-marine PTB sections of the study area can also be aligned with the PTB Global Stratotype Section and Point (GSSP) at Meishan in eastern China. Plant megafossils ("megaplants") in the study area indicate a major loss in abundance and diversity across the PTB, and no coal beds and/or seams have been found in the non-marine Lower Triassic although they are very common in the non-marine Upper Permian. The megaplants, however, did not disappear consistently across the whole area, with some elements of the Late Permian Cathaysian Gigantopteris flora surviving the PTB mass extinction and locally even extending up to the Lower Triassic. Palynomorphs exhibit a similar temporal pattern characterized by a protracted stepwise decrease from fern-dominated spores in the Late Permian to pteridosperm and gymnosperm-dominated pollen in the Early Triassic, which was however punctuated by an accelerated loss in both abundance and diversity across the PTB. Contemporaneous with the PTB crisis in the study area was the peculiar prevalence and dominance of some fungi and/or algae species. The temporal patterns of megaplants and palynomorphs across the PTB in the study area are consistent with the regional trends of plant changes in South China, which also show a long-term decrease in species diversity from the Late Permian Wuchiapingian through the Changhsingian to the earliest Triassic, with about 48% and 77% losses of species occurring respectively in the end-Wuchiapingian and end-Changhsingian. Such consistent patterns, at both local and regional scales, contradict the hypothesis of a regional isochronous extinction of vegetation across the PTB, and hence call into question the notion that the end-Permian mass extinction was a one-hit disaster. Instead, the data from the study area and South China appears more consistent with a scenario that invokes climate change as the main driver for the observed land vegetation changes across the PTB in South China.

  12. Geologic history of Florida-Bahama platform, Triassic through Paleocene

    SciTech Connect

    Winston, G.O.

    1988-01-01

    This study is based on top-to-bottom examination of samples from 146 wells from the Florida-Bahama platform. Following Triassic graben formation, three different structural configurations develop through time. In the Late Jurassic-Coahuilan, a northwestern and southeastern sedimentary province were separated by the Sarasota arch, located on the west Florida shelf. Modern basin configurations, which began to appear in the Comanchean, were modified by tectonics in Cuba in the early Gulfian. From the Late Jurassic through the Comanchean, the continental margin was occupied by a carbonate complex that restricted marine circulation in some areas In the southeast, this barrier caused the deposition of lagoonal carbonates and anhydrites; in the north, clastics were deposited. Carbonate-evaporite deposition in the south ended at the close of the Comanchean and was followed by the deposition of chalk and chalky limestone in the Gulfian. During this epoch, the rapid subsidence of the Blake Plateau basin to bathal depths and the collapse of the Florida straits were associated with tectonic activity in northern Cuba. By the middle Gulfian, the Rebecca Shoal barrier reef had appeared on the upthrown northern side of the straits. This barrier reef expanded to encircle the florida peninsula completely, at which time the Cedar Keys (Paleocene) lagoonal dolomite-anhydrite deposition was initiated.

  13. Geologic history of Florida-Bahama platform, Triassic through Paleocene

    SciTech Connect

    Winston, G.O.

    1988-02-01

    This study is based on top-to-bottom examination of samples from 146 wells from the Florida-Bahama platform. Following Triassic graben formation, three different structural configurations develop through time. In the Late Jurassic-Coahuilan, a northwestern and southeastern sedimentary province were separated by the Sarasota arch, located on the west Florida shelf. Modern basin configurations, which began to appear in the Comanchean, were modified by tectonics in Cuba in the early Gulfian. From the Late Jurassic through the Comanchean, the continental margin was occupied by a carbonate complex that restricted marine circulation in some areas. In the southeast, this barrier caused the deposition of lagoonal carbonates and anhydrites; in the north, clastics were deposited. Carbonate-evaporite deposition in the south ended at the close of the Comanchean and was followed by the deposition of chalk and chalky limestone in the Gulfian. During this epoch, the rapid subsidence of the Blake Plateau basin to bathal depths and the collapse of the Florida straits were associated with tectonic activity in northern Cuba. By the middle Gulfian, the Rebecca Shoal barrier reef had appeared on the upthrown northern side of the straits. This barrier reef expanded to encircle the Florida peninsula completely, at which time the Cedar Keys (Paleocene) lagoonal dolomite-anhydrite deposition was initiated.

  14. The inverted Triassic rift of the Marrakech High Atlas: A reappraisal of basin geometries and faulting histories

    NASA Astrophysics Data System (ADS)

    Domènech, Mireia; Teixell, Antonio; Babault, Julien; Arboleya, Maria-Luisa

    2015-11-01

    The High Atlas of Morocco is an aborted rift developed during the Triassic-Jurassic and moderately inverted during the Cenozoic. The Marrakech High Atlas, with large exposures of basement and Triassic early syn-rift deposits, is ideal to investigate the geometries of the deepest parts of a rift, constituting a good analogue for pre-salt domains. It allows unraveling geometries and kinematics of the extensional and compressional structures and the influence that they exert over one another. A detailed structural study of the main Triassic basins and basin-margin faults of the Marrakech High Atlas shows that only a few rift faults were reactivated during the Cenozoic compressional stage in contrast to previous interpretations, and emphasizes that fault reactivation cannot be taken for granted in inverted rift systems. Preserved extensional features demonstrate a dominant dip-slip opening kinematics with strike-slip playing a minor role, at variance to models proposing a major strike-slip component along the main basin-bounding faults, including faults belonging to the Tizi n'Test fault zone. A new Middle Triassic paleogeographic reconstruction shows that the Marrakech High Atlas was a narrow and segmented orthogonal rift (sub-perpendicular to the main regional extension direction which was ~ NW-SE), in contrast to the central and eastern segments of the Atlas rift which developed obliquely. This difference in orientation is attributed to the indented Ouzellarh Precambrian salient, part of the West African Craton, which deflected the general rift trend in the area evidencing the major role of inherited lithospheric anisotropies in rift direction and evolution. As for the Cenozoic inversion, total orogenic shortening is moderate (~ 16%) and appears accommodated by basement-involved large-scale folding, and by newly formed shortcut and by-pass thrusting, with rare left-lateral strike-slip indicators. Triassic faults commonly acted as buttresses.

  15. A mathematical model for time perception with experimentally obtained subjective time scales for humans and rats.

    PubMed

    Eisler, H; Eisler, A D

    1991-01-01

    The concept of sensation measurement with the entailing subjective scales is explained. It is shown that linearity between, e.g. sensation halving values and standard values implies that subjective sensation (output) grows as a power function of the physical measure of the stimulus (input). This outcome can be used in the scaling of subjective duration, based on reproduction experiments, i.e., experiments in which the participants are required to reproduce given time intervals, e.g., indicated by noise. It will be shown that what is reproduction for the participant is halving for the experimenter, making it possible to determine the parameters of the power function. The model is confirmed experimentally for humans and rats, the rats having a lower exponent than adults. In a recent experiment it was shown that the reproduced durations differ between female and male observers as well as for different sound intensities. These differences could be attributed to differences in parameter values. An interesting observation is that almost all power functions exhibit a discontinuity, possibly indicating a switch between different neural loops as the durations become longer. PMID:1760963

  16. Climatically driven biogeographic provinces of Late Triassic tropical Pangea

    PubMed Central

    Whiteside, Jessica H.; Grogan, Danielle S.; Olsen, Paul E.; Kent, Dennis V.

    2011-01-01

    Although continents were coalesced into the single landmass Pangea, Late Triassic terrestrial tetrapod assemblages are surprisingly provincial. In eastern North America, we show that assemblages dominated by traversodont cynodonts are restricted to a humid 6 equatorial swath that persisted for over 20 million years characterized by semiprecessional (approximately 10,000-y) climatic fluctuations reflected in stable carbon isotopes and sedimentary facies in lacustrine strata. More arid regions from 520N preserve procolophonid-dominated faunal assemblages associated with a much stronger expression of approximately 20,000-y climatic cycles. In the absence of geographic barriers, we hypothesize that these variations in the climatic expression of astronomical forcing produced latitudinal climatic zones that sorted terrestrial vertebrate taxa, perhaps by excretory physiology, into distinct biogeographic provinces tracking latitude, not geographic position, as the proto-North American plate translated northward. Although the early Mesozoic is usually assumed to be characterized by globally distributed land animal communities due to of a lack of geographic barriers, strong provinciality was actually the norm, and nearly global communities were present only after times of massive ecological disruptions. PMID:21571639

  17. Climatically driven biogeographic provinces of Late Triassic tropical Pangea.

    PubMed

    Whiteside, Jessica H; Grogan, Danielle S; Olsen, Paul E; Kent, Dennis V

    2011-05-31

    Although continents were coalesced into the single landmass Pangea, Late Triassic terrestrial tetrapod assemblages are surprisingly provincial. In eastern North America, we show that assemblages dominated by traversodont cynodonts are restricted to a humid 6 equatorial swath that persisted for over 20 million years characterized by "semiprecessional" (approximately 10,000-y) climatic fluctuations reflected in stable carbon isotopes and sedimentary facies in lacustrine strata. More arid regions from 5-20 N preserve procolophonid-dominated faunal assemblages associated with a much stronger expression of approximately 20,000-y climatic cycles. In the absence of geographic barriers, we hypothesize that these variations in the climatic expression of astronomical forcing produced latitudinal climatic zones that sorted terrestrial vertebrate taxa, perhaps by excretory physiology, into distinct biogeographic provinces tracking latitude, not geographic position, as the proto-North American plate translated northward. Although the early Mesozoic is usually assumed to be characterized by globally distributed land animal communities due to of a lack of geographic barriers, strong provinciality was actually the norm, and nearly global communities were present only after times of massive ecological disruptions. PMID:21571639

  18. The Luoping biota: exceptional preservation, and new evidence on the Triassic recovery from end-Permian mass extinction

    PubMed Central

    Hu, Shi-xue; Zhang, Qi-yue; Chen, Zhong-Qiang; Zhou, Chang-yong; L, Tao; Xie, Tao; Wen, Wen; Huang, Jin-yuan; Benton, Michael J.

    2011-01-01

    The timing and nature of biotic recovery from the devastating end-Permian mass extinction (252 Ma) are much debated. New studies in South China suggest that complex marine ecosystems did not become re-established until the middlelate Anisian (Middle Triassic), much later than had been proposed by some. The recently discovered exceptionally preserved Luoping biota from the Anisian Stage of the Middle Triassic, Yunnan Province and southwest China shows this final stage of community assembly on the continental shelf. The fossil assemblage is a mixture of marine animals, including abundant lightly sclerotized arthropods, associated with fishes, marine reptiles, bivalves, gastropods, belemnoids, ammonoids, echinoderms, brachiopods, conodonts and foraminifers, as well as plants and rare arthropods from nearby land. In some ways, the Luoping biota rebuilt the framework of the pre-extinction latest Permian marine ecosystem, but it differed too in profound ways. New trophic levels were introduced, most notably among top predators in the form of the diverse marine reptiles that had no evident analogues in the Late Permian. The Luoping biota is one of the most diverse Triassic marine fossil Lagersttten in the world, providing a new and early window on recovery and radiation of Triassic marine ecosystems some 10 Myr after the end-Permian mass extinction. PMID:21183583

  19. Global terrestrial biogeochemistry: Perturbations, interactions, and time scales

    SciTech Connect

    Braswell, B.H. Jr.

    1996-12-01

    Global biogeochemical processes are being perturbed by human activity, principally that which is associated with industrial activity and expansion of urban and agricultural complexes. Perturbations have manifested themselves at least since the beginning of the 19th Century, and include emissions of CO{sub 2} and other pollutants from fossil fuel combustion, agricultural emissions of reactive nitrogen, and direct disruption of ecosystem function through land conversion. These perturbations yield local impacts, but there are also global consequences that are the sum of local-scale influences. Several approaches to understanding the global-scale implications of chemical perturbations to the Earth system are discussed. The lifetime of anthropogenic CO{sub 2} in the atmosphere is an important concept for understanding the current and future commitment to an altered atmospheric heat budget. The importance of the terrestrial biogeochemistry relative to the lifetime of excess CO{sub 2} is demonstrated using dynamic, aggregated models of the global carbon cycle.

  20. Carbonate "Clumped" Isotope Determination of Seawater Temperature During the End-Triassic Extinction Event

    NASA Astrophysics Data System (ADS)

    Gammariello, R. T., Jr.; Petryshyn, V. A.; Ibarra, Y.; Greene, S. E.; Corsetti, F. A.; Bottjer, D. J.; Tripati, A.

    2014-12-01

    Stromatolites are laminated sedimentary structures that are commonly thought to be created by cyanobacteria, either through the trapping and binding of sediment, or through metabolically-induced precipitation. However, stromatolite formation is poorly understood. In general, stromatolite abundance was higher in the Proterozoic than the Phanerozoic, but notable increases in stromatolite abundance occur in association with Phanerozoic mass extinction events. Here, we focus on stromatolites from the latest Triassic Cotham Marble (United Kingdom) that are associated with the extinction interval. The end-Triassic mass extinction is coincident with large-scale volcanism in the Central Atlantic Magmatic Province (CAMP) and the associated breakup of Pangea. Some hypothesize that CAMP-associated increases in atmospheric CO2 led to a rise in global temperatures and ocean acidification that caused or enhanced the extinction. In order to quantify the role of climate change with respect to the end-Triassic mass extinction, we applied the carbonate "clumped" isotope paleothermometer to the well-preserved Cotham Marble stromatolites. The stromatolites were deposited in the shallow Tethys Sea, and today occur in several localities across the southwestern UK. The stromatolites alternate on the cm scale between laminated and dendrolitic microstructures and each was microdrilled for clumped isotope analysis. The two microstructures display different temperatures of formation, where the dendrolitic portions apparently grew under cooler conditions than laminated layers, and younger layers grew in cooler conditions than older layers. Our results suggest that temperature fluctuated and potentially trended towards amelioration of the warm temperatures during the deposition of the Cotham Marble.

  1. Paleoenvironmental significance of carbonate microbialites from the uppermost Rhaetian (latest Triassic) southwestern United Kingdom

    NASA Astrophysics Data System (ADS)

    Ibarra, Y.; Corsetti, F. A.; Greene, S. E.; Bottjer, D. J.

    2013-12-01

    Several upper Triassic sections of the southwestern United Kingdom contain a laterally extensive (2,000 km2), thin (~20 cm) unit of carbonate microbialites known regionally as the Cotham Marble. The microbialites occur as discrete mounds that range from about 0.5 to 2 meters in diameter and are internally composed of alternating dendritic and laminated mesofabrics. The dendritic portions are composed of microspar/micrite, contain abundant putative pyrite coated filamentous microfossils, and have elevated total organic carbon (TOC) relative to the interstitial fill. Here, we highlight two very striking features of the Cotham Marble microbialites which offer clues to local paleoenvironmental conditions across the end-Triassic mass extinction interval: (1) the microbialites contain extensive laterally continuous fabrics with mm-scale laminae that are represented in samples separated by at least 10 km and (2) the microbialites preserve fine, sub-mm scale details of microbial mat branching patterns. The proliferation and preservation of largely undisturbed, laterally continuous fabrics and delicate microbial mat textures indicate the microbialites were lithified very quickly likely from growth in waters with an anomalously high saturation state with respect to calcium carbonate. High saturation state possibly resulted from accelerated weathering conditions due to the emplacement of the Central Atlantic Magmatic Providence (CAMP). The fine-grained, dominantly micritic nature of the microbialites bears a strong textural resemblance to their Precambrian counterparts in contrast to the coarse-grained fabrics of modern marine microbialites. Such fine-grained textures are rare in Phanerozoic marine microbialites but are known to occur during other mass extinction episodes. Therefore, the Cotham Marble microbialites could indicate a brief return to microbial carbonate deposition as a consequence of the end-Triassic mass extinction.

  2. Time-delay quasars: Scales and orders of magnitudes

    NASA Astrophysics Data System (ADS)

    Saha, P.

    2004-02-01

    We can think of a lensed quasar as taking the Hubble time, shrinking it by 10-11, and then presenting the result to us as a time delay; the shrinking factor is of the order of fractional sky-area that the lens occupies. This cute fact is a straightforward consequence of lensing theory, and enables a simple rescaling of time delays. Observed time delays have a 40-fold range, but after rescaling the range reduces to 5-fold. The latter range depends on details of the lens and lensing configuration - for example, quads have systematically shorter rescaled time delays than doubles - and is as expected from a simple model. The hypothesis that observed time-delay lenses all come from a generalized-isothermal family can be ruled out. But there is no indication of drastically different populations either.

  3. Evidence for prosauropod dinosaur gastroliths in the Bull Run Formation (Upper Triassic, Norian) of Virginia

    USGS Publications Warehouse

    Weems, R.E.; Culp, M.J.; Wings, O.

    2007-01-01

    Definitive criteria for distinguishing gastroliths from sedimentary clasts are lacking for many depositional settings, and many reported occurrences of gastroliths either cannot be verified or have been refuted. We discuss four occurrences of gastrolith-like stones (category 6 exoliths) not found within skeletal remains from the Upper Triassic Bull Run Formation of northern Virginia, USA. Despite their lack of obvious skeletal association, the most parsimonious explanation for several characteristics of these stones is their prolonged residence in the gastric mills of large animals. These characteristics include 1) typical gastrolith microscopic surface texture, 2) evidence of pervasive surface wear on many of these stones that has secondarily removed variable amounts of thick weathering rinds typically found on these stones, and 3) a width/length-ratio modal peak for these stones that is more strongly developed than in any population of fluvial or fanglomerate stones of any age found in this region. When taken together, these properties of the stones can be explained most parsimoniously by animal ingestion and gastric-mill abrasion. The size of these stones indicates the animals that swallowed them were large, and the best candidate is a prosauropod dinosaur, possibly an ancestor of the Early Jurassic gastrolith-producing prosauropod Massospondylus or Ammosaurus. Skeletal evidence for Upper Triassic prosauropods is lacking in the Newark Supergroup basins; footprints (Agrestipus hottoni and Eubrontes isp.) from the Bull Run Formation in the Culpeper basin previously ascribed to prosauropods are now known to be underprints (Brachychirotherium parvum) of an aetosaur and underprints (Kayentapus minor) of a ceratosaur. The absence of prosauropod skeletal remains or footprints in all but the uppermost (upper Rhaetian) Triassic rocks of the Newark Supergroup is puzzling because prosauropod remains are abundant elsewhere in the world in Upper Triassic (Carnian, Norian, and lower Rhaetian) continental strata. The apparent scarcity of prosauropods in Upper Triassic strata of the Newark Supergroup is interpreted as an artifact of ecological partitioning, created by the habitat range and dietary preferences of phytosaurs and by the preservational biases at that time within the lithofacies of the Newark Supergroup basins.

  4. Return to Coalsack Bluff and the Permian Triassic boundary in Antarctica

    NASA Astrophysics Data System (ADS)

    Retallack, Gregory J.; Greaver, Tara; Jahren, A. Hope

    2007-01-01

    Coalsack Bluff was the first discovery site in Antarctica for the latest Permian to earliest Triassic reptile Lystrosaurus. This together with discovery of Permian Glossopteris leaves during the heroic age of Antarctic exploration, indicated not only that Antarctica was part of Gondwanaland, but also that Antarctic rocks recorded faunas from the greatest of all mass extinctions at the Permian-Triassic boundary. Pinpointing the exact stratigraphic level of this life crisis has recently become possible using δ 13C values in terrestrial organic matter. Multiple, short-lived events of 13C depletion may reflect carbon cycle crises, with the isotopic change a measure of terrestrial and atmospheric disequilibrium. Additional evidence for ecosystem reorganization came from changes in paleosol types and their root traces. Such studies previously completed at the Antarctic localities of Graphite Peak, Mount Crean, Portal Mountain, Shapeless Mountain and Allan Hills, are here extended to Coalsack Bluff. Carbon isotopic values in Permian rocks at Coalsack Bluff average - 23.08 ± 0.25‰, but begin to decline within the last coal with leaves ( Glossopteris), roots ( Vertebraria) and permineralized stumps ( Araucarioxylon) of glossopterids. The low point in ä 13C values is - 27.19‰ at 5.6 m above the last coal, which is capped by unusually abundant pyrite, and a claystone breccia with common clasts of redeposited clayey soils. Above this are massive quartz-rich sandstones of braided streams, considered a geomorphic response to deforestation and soil erosion following the mass extinction. Distinctive berthierine-bearing paleosols (Dolores pedotype) within these sandstones have unoxidized iron taken as evidence of severe groundwater hypoxia. Other paleosols at this stratigraphic level are like those in other Early Triassic rocks of Antarctica, which indicate unusually warm and humid conditions for such high paleolatitude lowlands. Waterlogging is also indicated by newly discovered kinds of paleosol (Ernest pedotype) with groundwater calcretes. The lack of peat accumulation in such waterlogged lowlands, berthierine in paleosols and large negative carbon isotopic shift at Coalsack Bluff support the idea of atmospheric pollution with methane from submarine and permafrost clathrates as a cause for the Permian-Triassic mass extinction. Hypoxic soils would have killed lowland plants by preventing root respiration and hypoxic air would have challenged vertebrates with pulmonary edema. Causes for catastrophic methane release remain unclear. Flood basalt eruptions, dolerite intrusions into coal measures, submarine landslides, tectonic faulting, and bolide impact suggested for episodes of methane release at other times are also plausible for the Permian-Triassic boundary.

  5. Long-term oceanic changes prior the end-Triassic mass extinction

    NASA Astrophysics Data System (ADS)

    Clémence, Marie-Emilie; Mette, Wolfgang; Thibault, Nicolas; Korte, Christoph

    2014-05-01

    A number of potential causes and kill mechanisms have been proposed for the end-Triassic mass extinction such as palaeoclimatic and sea-level variations, massive volcanism and ocean acidification. Recent analysis of the stomatal index and density of fossil leaves and geochemical research on pedogenic carbonate nodules are suggestive of rising atmospheric CO2 concentration and fluctuating climate in the Rhaetian. It seems therefore probable that the end-Triassic event was preceded by large climatic fluctuations and environmental perturbations in the Rhaetian which might have partly affected the composition and diversity of the terrestrial and marine biota prior to the end-Triassic interval. The Northern Calcareous Alps (NCA) has long been favored for the study of the Rhaetian, since the GSSP of the Triassic/Jurassic (T/J) boundary and other important T/J sections are situated in this region. However, the most famous Rhaetian sections in the NCA are composed of carbonates from the Koessen Formation and were situated in a large isolated intraplatform Basin (the Eiberg Basin), bordered to the south-east by a well-developed coral reef in the NW of the Tethys border. Several Rhaetian sections composed of marls and shales of the Zlambach Formation were deposited at the same time on the other side of this reef, in the oceanic Halstatt Basin, which was in direct connection to the Tethys. Here, we present new results on sedimentology, stable isotope and trace element analysis of both intraplatform and oceanic basin deposits in the NCA. Intraplatform Rhaetian sections from the Koessen Formation bear a few minor intervals of shales with enrichments in organic matter, some of which are associated to carbon isotopic excursions. Oceanic sections from the Hallstatt Basin are characterized at the base by very cyclic marl-limestone alternations. Higher up in the section, sediments progressively turn into pure shale deposits and the top of the Formation is characterized by organic-rich, laminated black shales. This interval of black shales is associated with a 2 per mil negative carbon isotopic excursion and a strong warming as suggested by fluctuations in oxygen isotopes. Forthcoming geochemical and paleontological analysis on these two Formations should help us : (1) better constrain the stratigraphy of the Rhaetian in the NCA by correlating geochemical and climatic events that took place both in the intraplaform (Eiberg) and oceanic (Hallstatt) Basin, (2) decipher localized vs large Tethyan anoxic events and associated carbon-cycle perturbations and (3) constrain the possible influence of Rhaetian climatic perturbations on the biota before the end-Triassic mass extinction.

  6. Exploring large scale time-series data using nested timelines

    NASA Astrophysics Data System (ADS)

    Xie, Zaixian; Ward, Matthew O.; Rundensteiner, Elke A.

    2013-01-01

    When data analysts study time-series data, an important task is to discover how data patterns change over time. If the dataset is very large, this task becomes challenging. Researchers have developed many visualization techniques to help address this problem. However, little work has been done regarding the changes of multivariate patterns, such as linear trends and clusters, on time-series data. In this paper, we describe a set of history views to fill this gap. This technique works under two modes: merge and non-merge. For the merge mode, merge algorithms were applied to selected time windows to generate a change-based hierarchy. Contiguous time windows having similar patterns are merged first. Users can choose different levels of merging with the tradeoff between more details in the data and less visual clutter in the visualizations. In the non-merge mode, the framework can use natural hierarchical time units or one defined by domain experts to represent timelines. This can help users navigate across long time periods. Gridbased views were designed to provide a compact overview for the history data. In addition, MDS pattern starfields and distance maps were developed to enable users to quickly investigate the degree of pattern similarity among different time periods. The usability evaluation demonstrated that most participants could understand the concepts of the history views correctly and finished assigned tasks with a high accuracy and relatively fast response time.

  7. Associated skeletons of a new middle Triassic "Rauisuchia" from Brazil.

    PubMed

    Frana, Marco Aurlio G; Ferigolo, Jorge; Langer, Max C

    2011-05-01

    For more than 30 million years, in early Mesozoic Pangea, "rauisuchian" archosaurs were the apex predators in most terrestrial ecosystems, but their biology and evolutionary history remain poorly understood. We describe a new "rauisuchian" based on ten individuals found in a single locality from the Middle Triassic (Ladinian) Santa Maria Formation of southern Brazil. Nine articulated and associated skeletons were discovered, three of which have nearly complete skulls. Along with sedimentological and taphonomic data, this suggests that those highly successful predators exhibited some kind of intraspecific interaction. Other monotaxic assemblages of Triassic archosaurs are Late Triassic (Norian-Rhaetian) in age, approximately 10 million years younger than the material described here. Indeed, the studied assemblage may represent the earliest evidence of gregariousness among archosaurs, adding to our knowledge on the origin of a behavior pattern typical of extant taxa. PMID:21445632

  8. A Dynamically Computed Convective Time Scale for the KainFritsch Convective Parameterization Scheme

    EPA Science Inventory

    Many convective parameterization schemes define a convective adjustment time scale ? as the time allowed for dissipation of convective available potential energy (CAPE). The KainFritsch scheme defines ? based on an estimate of the advective time period for deep con...

  9. Kinematic restoration of the Mediterranean region since the Triassic

    NASA Astrophysics Data System (ADS)

    van Hinsbergen, Douwe; Torsvik, Trond; Matenco, Liviu; Schmid, Stefan; Maffione, Marco; Spakman, Wim

    2014-05-01

    The Mediterranean region is one of the most complexly deformed areas in the world and its tectonic evolution has been instrumental in the development of numerous fundamental geological principles and geodynamic concepts. Reconstructions of the Mediterranean region invariably demonstrated that the area had a complex paleogeography with ribbon continents or micro-plates and narrow, elongated ocean basins systems in Mesozoic time. A western and northern ocean basin system was genetically related to the Atlantic Ocean, opened in Jurassic time and is known as the Alpine Tethys Ocean. A southern and eastern basin system was genetically related to the Neotethys domain located between Gondwana and Eurasia and - in the Mediterranean realm - opened in Triassic to Jurassic times. Continental domains of variable size within and between these ocean systems rifted away from Eurasia or Africa. This mosaic of pieces of continental and oceanic lithosphere became consumed by a complex configuration of subduction zones that accommodated convergence between the African and Eurasian plates since middle Jurassic times. Since Oligocene time, the overriding plate above subduction zones throughout the Mediterranean region became extended, locally leading to formation of new ocean floor, as a result of roll-back of subducted slab segments, culminating in todays complex and strongly curved configuration of subduction zones and slab segments. An area such as the tectonically complex Mediterranean invites attempt to kinematic restoration, and various reconstructions are already available. However, by now such reconstructions are no more merely a translation of - frequently qualitative - geological data into a quantitative description of surface evolution: with the advent of 3-dimensional numerical modeling tools that can be kinematically driven by plate reconstructions, they become critical input for attempts to integrate surface evolution into mantle dynamics. An increasingly widely used platform for kinematic reconstructions is the freely available GPlates plate kinematic reconstruction software (http://www.gplates.org). We provide the first fully quantitatively described GPlates-based kinematic reconstruction of the Mediterranean region back to Triassic time. Classic plate reconstructions assume plate rigidity, and motion concentrated along discrete plate boundaries. Convergence between Africa-Europe plate boundary in the Mediterranean region is, however, associated with regionally distributed deformation. In this reconstruction, we attempt to restore this distributed deformation, which in practice means that we allow for polygons to change shape and area over time. This reconstruction may (i) be used as input for numerical models that aim to constrain the geodynamic evolution of (parts of) the Mediterranean history, (ii) allow comparing relative tectonic motions of the Mediterranean region to the mantle using mantle reference frames, and (iii) provide regional kinematic context for future geological studies. Upon final publication, all shape and rotation files of this reconstruction will be made publically available, which may serve as a platform for further improvement when new constraints demand so, or when the reader wishes to test different tectonic scenarios.

  10. Multiple dolomitization events in Triassic latemar buildup, the dolomites, northern Italy

    SciTech Connect

    Wilson, E.N.

    1988-02-01

    Partially dolomitized grainstones of the Middle Triassic Latemar buildup (Dolomites, northern Italy) exhibit a range of texturally distinct dolomite types. Petrographic and field observations of spatial associations and cross-cutting relationships among dolomites allow unravelling of the paragenesis of dolomitization events. Three generations of dolomite are preserved in the Latemar. Microdolomite, the earliest generation, occurs as replacement of allochems and as cement in thin (5-15 cm) exposure caps of meter-scale subtidal cycles. These dolomite crusts are texturally and chemically analogous to the Holocene supratidal crusts of Florida and the Bahamas. Saddle dolomite cements, the second generation, fill or line pores and fractures through the platform. The final generation is massive replacement of limestone by coarse, crystalline dolomite, which occupies a 2-3 km/sup 3/ mushroom-shaped zone in the center of the buildup and includes a wide array of fabrics. Here, subtidal limestones are altered to porous sucrosic dolomite, while microdolomite caps are altered to dense dolomite mosaics. Saddle dolomite cements remain as relics surrounded by replacement rhombs. Two important conclusions are (1) early dolomite is preserved as poorly ordered microdolomite (unless overprinted by a later dolomitization event) and accounts for an insignificant volume of the Latemar dolomite, and (2) saddle dolomite cements, often regarded as late-stage burial, occur before massive replacement. Standard textural classification of Latemar dolomites hindered the resolution of the timing of dolomitization events. Instead, paragenetic relationships provided a powerful tool for grouping dolomites into generations representing specific diagenetic events in specific dolomitizing environments.

  11. Lethally Hot Temperatures During the Early Triassic Greenhouse

    NASA Astrophysics Data System (ADS)

    Sun, Yadong; Joachimski, Michael M.; Wignall, Paul B.; Yan, Chunbo; Chen, Yanlong; Jiang, Haishui; Wang, Lina; Lai, Xulong

    2012-10-01

    Global warming is widely regarded to have played a contributing role in numerous past biotic crises. Here, we show that the end-Permian mass extinction coincided with a rapid temperature rise to exceptionally high values in the Early Triassic that were inimical to life in equatorial latitudes and suppressed ecosystem recovery. This was manifested in the loss of calcareous algae, the near-absence of fish in equatorial Tethys, and the dominance of small taxa of invertebrates during the thermal maxima. High temperatures drove most Early Triassic plants and animals out of equatorial terrestrial ecosystems and probably were a major cause of the end-Smithian crisis.

  12. Redescription of Bellerophon bittneri (Gastropoda: Triassic) from Wyoming.

    USGS Publications Warehouse

    Yochelson, E.L.; Boyd, D.W.; Wardlaw, B.

    1985-01-01

    Bellerophon bittneri Newell and Kummel is an Early Triassic bellerophontacean from the Dinwoody Formation in the Wind River Mountains. The available type material consists of one fair, but incomplete, external mold, which resembles a Bellerophon but is actually a Retispira. After repeated search, additional specimens were found at one locality in the southern Wind River Range of Wyoming; Retispira bittneri is redescribed from this new material. Like other Triassic bellerophontaceans, there is nothing unusual about the species apart from occurrence in the Mesozoic; it is clearly congeneric with Permian Retispira from underlying rocks. -Authors

  13. Lethally hot temperatures during the Early Triassic greenhouse.

    PubMed

    Sun, Yadong; Joachimski, Michael M; Wignall, Paul B; Yan, Chunbo; Chen, Yanlong; Jiang, Haishui; Wang, Lina; Lai, Xulong

    2012-10-19

    Global warming is widely regarded to have played a contributing role in numerous past biotic crises. Here, we show that the end-Permian mass extinction coincided with a rapid temperature rise to exceptionally high values in the Early Triassic that were inimical to life in equatorial latitudes and suppressed ecosystem recovery. This was manifested in the loss of calcareous algae, the near-absence of fish in equatorial Tethys, and the dominance of small taxa of invertebrates during the thermal maxima. High temperatures drove most Early Triassic plants and animals out of equatorial terrestrial ecosystems and probably were a major cause of the end-Smithian crisis. PMID:23087244

  14. Modelling financial markets with agents competing on different time scales and with different amount of information

    NASA Astrophysics Data System (ADS)

    Wohlmuth, Johannes; Andersen, Jrgen Vitting

    2006-05-01

    We use agent-based models to study the competition among investors who use trading strategies with different amount of information and with different time scales. We find that mixing agents that trade on the same time scale but with different amount of information has a stabilizing impact on the large and extreme fluctuations of the market. Traders with the most information are found to be more likely to arbitrage traders who use less information in the decision making. On the other hand, introducing investors who act on two different time scales has a destabilizing effect on the large and extreme price movements, increasing the volatility of the market. Closeness in time scale used in the decision making is found to facilitate the creation of local trends. The larger the overlap in commonly shared information the more the traders in a mixed system with different time scales are found to profit from the presence of traders acting at another time scale than themselves.

  15. Structure and dating errors in the geologic time scale and periodicity in mass extinctions

    NASA Technical Reports Server (NTRS)

    Stothers, Richard B.

    1989-01-01

    Structure in the geologic time scale reflects a partly paleontological origin. As a result, ages of Cenozoic and Mesozoic stage boundaries exhibit a weak 28-Myr periodicity that is similar to the strong 26-Myr periodicity detected in mass extinctions of marine life by Raup and Sepkoski. Radiometric dating errors in the geologic time scale, to which the mass extinctions are stratigraphically tied, do not necessarily lessen the likelihood of a significant periodicity in mass extinctions, but do spread the acceptable values of the period over the range 25-27 Myr for the Harland et al. time scale or 25-30 Myr for the DNAG time scale. If the Odin time scale is adopted, acceptable periods fall between 24 and 33 Myr, but are not robust against dating errors. Some indirect evidence from independently-dated flood-basalt volcanic horizons tends to favor the Odin time scale.

  16. Time scales of variability associated with Nordeste precipitation

    SciTech Connect

    Sperber, K.R. ); Hameed, S. . Inst. for Terrestrial and Planetary Atmospheres)

    1991-06-01

    The Northeast section of Brazil, called the Nordeste, experiences flood and drought regimes as the norm rather than the exception. This region receives its principal dose of precipitation during March--April, subsequent to regions to the west and north due to its proximity to the southern Atlantic subtropical high. A weakening of this anticyclone and strengthening of its counterpart in the northern Atlantic during this season results in the farthest southward penetration of the ITCZ and the Nordeste rainy season. Fluctuations in the large-scale circulation of the atmosphere, such as ENSO, modulate the track of the ITCZ causing the interannual drought or flood conditions that plague this region. Empirical studies have shown that Nordeste rainfall is related to the sea-surface temperature (SST) in the tropical Atlantic Ocean. 16 refs., 4 figs.

  17. Scaling expectations for the time to establishment of complex adaptations.

    PubMed

    Lynch, Michael

    2010-09-21

    Although the vast majority of research in evolutionary biology is focused on adaption, a general theory for the population-genetic mechanisms by which complex adaptations are acquired remains to be developed. The issue explored here is the procurement of novel traits that specifically require multiple mutations to achieve a fitness advantage. By highlighting the roles played by the forces of mutation, recombination, and random genetic drift, and drawing from observations on the joint constraints on these factors, the ways in which rates of acquisition of specific types of adaptations scale with population size are explored. These general results provide insight into a number of ongoing controversies regarding the molecular basis of adaptation, including the adaptive utility of recombination and the role of drift in the passage through adaptive valleys. PMID:20823237

  18. Microsecond-Scale Timing Precision in Rodent Trigeminal Primary Afferents

    PubMed Central

    Bale, Michael R.; Campagner, Dario; Erskine, Andrew

    2015-01-01

    Communication in the nervous system occurs by spikes: the timing precision with which spikes are fired is a fundamental limit on neural information processing. In sensory systems, spike-timing precision is constrained by first-order neurons. We found that spike-timing precision of trigeminal primary afferents in rats and mice is limited both by stimulus speed and by electrophysiological sampling rate. High-speed video of behaving mice revealed whisker velocities of at least 17,000°/s, so we delivered an ultrafast “ping” (>50,000°/s) to single whiskers and sampled primary afferent activity at 500 kHz. Median spike jitter was 17.4 μs; 29% of neurons had spike jitter < 10 μs. These results indicate that the input stage of the trigeminal pathway has extraordinary spike-timing precision and very high potential information capacity. This timing precision ranks among the highest in biology. PMID:25878266

  19. Nonlinear acoustic time reversal imaging using the scaling subtraction method

    NASA Astrophysics Data System (ADS)

    Scalerandi, M.; Gliozzi, A. S.; Bruno, C. L. E.; Van Den Abeele, K.

    2008-11-01

    Lab experiments have shown that the imaging of nonlinear scatterers using time reversal acoustics can be a very promising tool for early stage damage detection. The potential applications are however limited by the need for an extremely accurate acquisition system. In order to let nonlinear features emerge from the background noise it is necessary to enhance the signal-to-noise ratio as much as possible. A comprehensive analysis to determine the nonlinear components in a recorded time signal, an alternative to those usually adopted (e.g. fast Fourier), is proposed here. The method is based on the nonlinear physical properties of the solution of the wave equation and takes advantage of the deficient system response scalability with the excitation amplitude. In this contribution, we outline the adopted procedure and apply it to a nonlinear time reversal imaging simulation to highlight the advantages with respect to traditional imaging based on a fast Fourier analysis of the recorded signals.

  20. Uranium comminution ages: Sediment transport and deposition time scales

    NASA Astrophysics Data System (ADS)

    DePaolo, Donald J.; Lee, Victoria E.; Christensen, John N.; Maher, Kate

    2012-11-01

    The uranium isotope comminution age is determined from the 234U/238U ratio and reflects the timescale associated with the transformation of bedrock to sediment. The comminution age is applicable to Late Pleistocene sediments and measures the amount of time elapsed since sediment generation by mechanical weathering and erosion. The age significance of the 234U/238U ratios is based on physical disruption of the 238U-decay series by recoil loss of 234Th that occurs in mineral grains smaller than 50 ?m. Results from study of fine-grained deep sea sediments in the North Atlantic Ocean, alluvial sediments in California and Australia, and modern glacial outwash are encouraging, but critical aspects of the method require further investigation. Particular issues are the effects of laboratory chemical leaching treatment on sediment samples and estimation of 234U loss rates as a function of grain size. In the North Atlantic marine environment the U isotope variations are inferred to reflect differences in the transport time of the sediment-the time elapsed between the generation of the small sediment particles by glacial action in Iceland and Fennoscandian source areas, and the time of deposition on the seafloor in the North Atlantic Ocean at a drift site south of Iceland. Calculated transport times vary from less than 10 kyr to about 400 kyr, and correlate with provenance and glacial cycles. Application to alluvial sediments in California and Australia suggests that where sediments are glacially-derived and transported short distances, the U comminution age may approximate the sedimentation age, but in larger basins that are not glaciated the sediments retain information about residence/transport times that can extend to ca. 400 kyr. To verify that initial 234U/238U ratios for glacial sediments are close to the secular equilibrium ratio, outwash from several major glaciers around the world was measured and found to be within 1% of the accepted equilibrium 234U/238U value.

  1. Singular perturbations and time scales (SPaTS) in discrete control systems-An overview

    NASA Technical Reports Server (NTRS)

    Naidu, D. S.; Hibey, J. L.; Price, D. B.

    1987-01-01

    Recent developments in the theory of singular perturbations and time scales (SPaTS) in discrete control systems are reviewed. Sources of discrete models and the effect of the discretizing interval on the model are examined. The analysis of two-time scale systems is presented to bring out typical characteristic features of SPaTS. In the control of the two-time scale systems, the important issue of multirate sampling is addressed.

  2. Probing single-photon ionization on the attosecond time scale.

    PubMed

    Klünder, K; Dahlström, J M; Gisselbrecht, M; Fordell, T; Swoboda, M; Guénot, D; Johnsson, P; Caillat, J; Mauritsson, J; Maquet, A; Taïeb, R; L'Huillier, A

    2011-04-01

    We study photoionization of argon atoms excited by attosecond pulses using an interferometric measurement technique. We measure the difference in time delays between electrons emitted from the 3s(2) and from the 3p(6) shell, at different excitation energies ranging from 32 to 42 eV. The determination of photoemission time delays requires taking into account the measurement process, involving the interaction with a probing infrared field. This contribution can be estimated using a universal formula and is found to account for a substantial fraction of the measured delay. PMID:21561188

  3. Probing Single-Photon Ionization on the Attosecond Time Scale

    SciTech Connect

    Kluender, K.; Dahlstroem, J. M.; Gisselbrecht, M.; Fordell, T.; Swoboda, M.; Guenot, D.; Johnsson, P.; Mauritsson, J.; L'Huillier, A.; Caillat, J.; Maquet, A.; Taieeb, R.

    2011-04-08

    We study photoionization of argon atoms excited by attosecond pulses using an interferometric measurement technique. We measure the difference in time delays between electrons emitted from the 3s{sup 2} and from the 3p{sup 6} shell, at different excitation energies ranging from 32 to 42 eV. The determination of photoemission time delays requires taking into account the measurement process, involving the interaction with a probing infrared field. This contribution can be estimated using a universal formula and is found to account for a substantial fraction of the measured delay.

  4. Probing Single-Photon Ionization on the Attosecond Time Scale

    NASA Astrophysics Data System (ADS)

    Klünder, K.; Dahlström, J. M.; Gisselbrecht, M.; Fordell, T.; Swoboda, M.; Guénot, D.; Johnsson, P.; Caillat, J.; Mauritsson, J.; Maquet, A.; Taïeb, R.; L'Huillier, A.

    2011-04-01

    We study photoionization of argon atoms excited by attosecond pulses using an interferometric measurement technique. We measure the difference in time delays between electrons emitted from the 3s2 and from the 3p6 shell, at different excitation energies ranging from 32 to 42 eV. The determination of photoemission time delays requires taking into account the measurement process, involving the interaction with a probing infrared field. This contribution can be estimated using a universal formula and is found to account for a substantial fraction of the measured delay.

  5. Computer Response Time Measurements of Mood, Fatigue and Symptom Scale Items: Implications for Scale Response Time Uses.

    ERIC Educational Resources Information Center

    Ryman, David H.; And Others

    1988-01-01

    Describes study conducted with U.S. Marine Corps enlisted personnel to measure response time to computer-administered questionnaire items, and to evaluate how measurement of response time might be useful in various research areas. Topics addressed include mood states; the occurrence of straight lining; and experimental effects of sleep loss and

  6. Multi-time scale perspective in analyzing cardiovascular data.

    PubMed

    Lackner, H K; Batzel, J J; Rssler, A; Hinghofer-Szalkay, H; Papousek, I

    2014-01-01

    Cardiovascular dynamic and variability data are commonly used in experimental protocols involving cognitive challenge. Usually, the analysis is based on a sometimes more and sometimes less well motivated single specific time resolution ranging from a few seconds to several minutes. The present paper aimed at investigating in detail the impact of different time resolutions of the cardiovascular data on the interpretation of effects. We compared three template tasks involving varying types of challenge, in order to provide a case study of specific effects and combinations of effects over different time frames and using different time resolutions. Averaged values of hemodynamic variables across an entire protocol confirmed typical findings regarding the effects of mental challenge and social observation. However, the hemodynamic response also incorporates transient variations in variables reflecting important features of the control system response. The fine-grained analysis of the transient behavior of hemodynamic variables demonstrates that information that is important for interpreting effects may be lost when only average values over the entire protocol are used as a representative of the system response. The study provides useful indications of how cardiovascular measures may be fruitfully used in experiments involving cognitive demands, allowing inferences on the physiological processes underlying the responses. PMID:24702493

  7. Brain connectivity at different time-scales measured with EEG

    PubMed Central

    Koenig, T; Studer, D; Hubl, D; Melie, L; Strik, W.K

    2005-01-01

    We present an overview of different methods for decomposing a multichannel spontaneous electroencephalogram (EEG) into sets of temporal patterns and topographic distributions. All of the methods presented here consider the scalp electric field as the basic analysis entity in space. In time, the resolution of the methods is between milliseconds (time-domain analysis), subseconds (time- and frequency-domain analysis) and seconds (frequency-domain analysis). For any of these methods, we show that large parts of the data can be explained by a small number of topographic distributions. Physically, this implies that the brain regions that generated one of those topographies must have been active with a common phase. If several brain regions are producing EEG signals at the same time and frequency, they have a strong tendency to do this in a synchronized mode. This view is illustrated by several examples (including combined EEG and functional magnetic resonance imaging (fMRI)) and a selective review of the literature. The findings are discussed in terms of short-lasting binding between different brain regions through synchronized oscillations, which could constitute a mechanism to form transient, functional neurocognitive networks. PMID:16087445

  8. Time Scales in the JPL and CfA Ephemerides

    NASA Technical Reports Server (NTRS)

    Standish, E. M.

    1998-01-01

    Over the past decades, the IAU has repeatedly attempted to correct its definition of the basic fundamental argument used in the emphemerides. Finally, they have defined a time system which is physically possible, according to the accepted standard theory of gravitation.

  9. Detrital zircon provenance of the Late Triassic Songpan-Ganzi complex: Sedimentary record of collision of the North and South China blocks

    USGS Publications Warehouse

    Weislogel, A.L.; Graham, S.A.; Chang, E.Z.; Wooden, J.L.; Gehrels, G.E.; Yang, H.

    2006-01-01

    Using detrital zircon geochronology, turbidite deposystems fed from distinct sediment sources can be distinguished within the Songpan-Ganzi complex, a collapsed Middle to Late Triassic turbidite basin of central China. A southern Songpan-Ganzi deposystem initially was sourced solely by erosion of the Qinling-Dabie orogen during early Late Triassic time, then by Qinling-Dabie orogen, North China block, and South China block sources during middle to late Late Triassic time. A northern Songpan-Ganzi system was sourced by erosion of the Qinling-Dabie orogen and the North China block throughout its deposition. These separate deposystems were later tectonically amalgamated to form one complex and then uplifted as the eastern Tibet Plateau. ?? 2006 Geological Society of America.

  10. A Novel Multiple-Time Scale Integrator for the Hybrid Monte Carlo Algorithm

    SciTech Connect

    Kamleh, Waseem

    2011-05-24

    Hybrid Monte Carlo simulations that implement the fermion action using multiple terms are commonly used. By the nature of their formulation they involve multiple integration time scales in the evolution of the system through simulation time. These different scales are usually dealt with by the Sexton-Weingarten nested leapfrog integrator. In this scheme the choice of time scales is somewhat restricted as each time step must be an exact multiple of the next smallest scale in the sequence. A novel generalisation of the nested leapfrog integrator is introduced which allows for far greater flexibility in the choice of time scales, as each scale now must only be an exact multiple of the smallest step size.

  11. Bi-Plasma Interactions on Femtosecond Time-Scales

    SciTech Connect

    Not Available

    2011-06-22

    Ultrafast THz radiation has important applications in materials science studies, such as characterizing transport properties, studying the vibrational response of materials, and in recent years, controlling materials and elucidating their response in intense electromagnetic fields. THz fields can be generated in a lab setting using various plasma-based techniques. This study seeks to examine the interaction of two plasmas in order to better understand the fundamental physics associated with femtosecond filamentation processes and to achieve more efficient THz generation in a lab setting. The intensity of fluorescence in the region of overlap was measured as a function of polarization, power, and relative time delay of the two plasma-generating laser beams. Results of time dependent intensity studies indicate strikingly similar behaviors across polarizations and power levels; a sudden intensity spike was observed at time-zero, followed by a secondary maxima and subsequent decay to the initial plasma intensity. Dependence of the intensity on the power through either beam arm was also observed. Spectral studies of the enhanced emission were also carried out. Although this physical phenomenon is still not fully understood, future studies, including further spectral analysis of the fluorescence overlap, could yield new insight into the ultrafast processes occurring at the intersection of femtosecond filaments, and would provide a better understanding of the mechanisms for enhanced THz production.

  12. Massive Red-Staining and Albitization of Feldspars in Paleozoic Basement Rocks of Western Europe and Their Association with the Triassic Palaeogeography

    NASA Astrophysics Data System (ADS)

    Fabrega, C.; Parcerisa, D.; Franke, C.; Thiry, M.; Yao, K.; Gómez-Gras, D.

    2013-12-01

    Albitization of feldspars is a widespread mineral replacement process of the upper crust. An ubiquitous and pervasive red-staining albitization of feldspars has been observed in the feldspathic rocks of the Variscan basement in the Sudetes, Armorican, Morvan, Roc de Frausa and Montseny-Guilleries Massifs (Western Europe). These crystalline massifs were strongly eroded during Permian and Triassic times and suffered a long-lasting exposition in the Permian-Triassic palaeosurface. The albitized rocks contain minute Fe-oxides hoisted within the microporosity of the secondary albite. The intimate textural relationship between the Fe-oxides and the albite strongly suggest that they are coetaneous with albitization. The microscope, cathodoluminescence, SEM and EMPA analyses reveal that almost all plagioclases and some K-feldspars are albitized in those areas close to the Permian-Triassic palaeosurface. Moving downwards the palaeosurface the albitization of Variscan rocks progressively disappears. Field mapping of the albitized areas points to estimated thickness about 100-200m. In the uppermost parts of the profile almost all plagioclases are totally albitized and the rock shows a strong and pervasive reddening, whereas in the lowermost parts the mineral replacement is restricted to fractures and neighbouring walls and the rock in tinted with a soft pink colour. These observations suggest that albitization is linked to that palaeosurface and constitutes a paleoalteration profile beneath the Permian-Triassic palaeosurface. All these observations suggest that the mineral replacement could have been driven by descending Na+ rich brines related with or coming from the Permian-Triassic palaeosurface. Ricodel et al. (2007) determined a Triassic age for the paleomagnetic signature of the Fe-oxides hoisted within the microporosity of albite in the Morvan Massif. The narrow textural relationship between the Fe-oxides and the albite support the idea that this is the age of albitization in this massif. The similarities in the petrographycal and geometrical aspects between the five studied massifs strongly suggest that they could record a common albitization event that affected the basement rocks of the Permian-Triassic palaeosurface during Triassic times. Although albitization usually is a deep process which occurs at depths greater then 900 m, during the end of the Permian and the beginning of the Triassic geochemical conditions of the atmosphere and the hydrosphere were radically distinctive and without equal in the earth. This exclusive geochemical conditions should had a role in de development of unusual shallow chemical reactions. In this contexts albitization developed close to the surface. The shallow Triassic albitization of the Variscan basement of Western Europe, and maybe around the Triassic continental long-lasting world, can be a useful tool in the reconstruction of the continental areas around the Triassic basins. [1] Ricordel, C., Parcerisa, D., Thiry, M., Moreau, M. G., & Gómez-Gras, D. (2007). Triassic magnetic overprints related to albitization in granites from the Morvan Massif (France). Palaeogeography, Palaeoclimatology, Palaeoecology, 251, 268-282.

  13. Quantifying the uncertainty of the annular mode time scale and the role of the stratosphere

    NASA Astrophysics Data System (ADS)

    Kim, Junsu; Reichler, Thomas

    2015-10-01

    The proper simulation of the annular mode time scale may be regarded as an important benchmark for climate models. Previous research demonstrated that this time scale is systematically overestimated by climate models. As suggested by the fluctuation-dissipation theorem, this may imply that climate models are overly sensitive to external forcings. Previous research also made it clear that calculating the AM time scale is a slowly converging process, necessitating relatively long time series and casting doubts on the usefulness of the historical reanalysis record to constrain climate models in terms of the annular mode time scale. Here, we use long control simulations with the coupled and uncoupled version of the GFDL climate model, CM2.1 and AM2.1, respectively, to study the effects of internal atmospheric variability and forcing from the lower boundary on the stability of the annular mode time scale. In particular, we ask whether a model's annular mode time scale and dynamical sensitivity can be constrained from the 50-year-long reanalysis record. We find that internal variability attaches large uncertainty to the annular mode time scale when diagnosed from decadal records. Even under the fixed forcing conditions of our long control run at least 100 years of data are required in order to keep the uncertainty in the annular mode time scale of the Northern Hemisphere to 10 %; over the Southern Hemisphere, the required length increases to 200 years. If nature's annular mode time scale over the Northern Hemisphere is similarly variable, there is no guarantee that the historical reanalysis record is a fully representative target for model evaluation. Over the Southern Hemisphere, however, the discrepancies between model and reanalysis are sufficiently large to conclude that the model is unable to reproduce the observed time scale structure correctly. The effects of ocean coupling lead to a considerable increase in time scale and uncertainty in time scale, effects which are noticeable in both troposphere and stratosphere. We further use the model simulation to investigate the dynamical coupling between the stratosphere and the troposphere from the perspective of the annular mode time scale. Over the Northern Hemisphere, we find only weak indication for influences from stratosphere-troposphere coupling on the annular mode time scale. The situation is very different over the Southern Hemisphere, where we find robust connections between the annular mode time scale in the stratosphere and that in the troposphere, confirming and extending earlier results of influences of stratospheric variability on the troposphere.

  14. Temperature Responses to Spectral Solar Variability on Decadal Time Scales

    NASA Technical Reports Server (NTRS)

    Cahalan, Robert F.; Wen, Guoyong; Harder, Jerald W.; Pilewskie, Peter

    2010-01-01

    Two scenarios of spectral solar forcing, namely Spectral Irradiance Monitor (SIM)-based out-of-phase variations and conventional in-phase variations, are input to a time-dependent radiative-convective model (RCM), and to the GISS modelE. Both scenarios and models give maximum temperature responses in the upper stratosphere, decreasing to the surface. Upper stratospheric peak-to-peak responses to out-of-phase forcing are approx.0.6 K and approx.0.9 K in RCM and modelE, approx.5 times larger than responses to in-phase forcing. Stratospheric responses are in-phase with TSI and UV variations, and resemble HALOE observed 11-year temperature variations. For in-phase forcing, ocean mixed layer response lags surface air response by approx.2 years, and is approx.0.06 K compared to approx.0.14 K for atmosphere. For out-of-phase forcing, lags are similar, but surface responses are significantly smaller. For both scenarios, modelE surface responses are less than 0.1 K in the tropics, and display similar patterns over oceanic regions, but complex responses over land.

  15. Emergence of cooperation through coevolving time scale in spatial prisoner's dilemma

    NASA Astrophysics Data System (ADS)

    Rong, Zhihai; Wu, Zhi-Xi; Wang, Wen-Xu

    2010-08-01

    We study evolutionary prisoners dilemma game by considering adaptive strategy-selection time scale among individuals according to a win-slower, lose-faster rule: if an individual successfully resists the invasion of an opponent, she is prone to hold her strategy for longer time through decreasing her strategy-selection time scale; otherwise, she increases the time scale because of losing. We find that the greater the losers increase their strategy-selection time scales, the better for cooperation. Interestingly, optimal cooperation can be induced by proper adaptive rate in the strategy-selection time scale. Our results may have potential implications in the design of consensus protocol in multiagent systems.

  16. Perspective: time scales in scientific research with an emphasis on microbial cellular and molecular research.

    PubMed

    Trevors, J T

    2010-07-01

    Scientists use time to describe and research the universe in which humans live. Geologists and evolutionary biologists often use time scales in the millions to billions of years while biochemists and molecular biologists use time scales in the milliseconds or less. The atom smashers use time scales that are almost the speed of light. However, in some areas of research such as molecular-based activities in cells, it is very challenging to obtain data sets in molecular time scales. This has been a challenge to obtaining accurate and precise measurements at the cell and molecular levels of organization in living organisms. Measurements of specific cellular and molecular activities are often made over time scales longer than the actual molecular events. The data sets obtained become estimates over seconds, minutes and hours and not measurements over milli- and nanoseconds. The question can then be posed - how representative and accurate are our data sets when the time scales are not synchronized with the actual living events? In this article, the role of time scales in scientific research and our understanding of living microorganisms are examined with an emphasis on cell and molecular time scales. PMID:20350572

  17. Invited review article: The statistical modeling of atomic clocks and the design of time scales.

    PubMed

    Levine, Judah; Ibarra-Manzano, O

    2012-02-01

    I will show how the statistical models that are used to describe the performance of atomic clocks are derived from their internal design. These statistical models form the basis for time scales, which are used to define international time scales such as International Atomic Time and Coordinated Universal Time. These international time scales are realized by ensembles of clocks at national laboratories such as the National Institute of Standards and Technology, and I will describe how ensembles of atomic clocks are characterized and managed. PMID:22380071

  18. Invited Review Article: The statistical modeling of atomic clocks and the design of time scales

    SciTech Connect

    Levine, Judah

    2012-02-15

    I will show how the statistical models that are used to describe the performance of atomic clocks are derived from their internal design. These statistical models form the basis for time scales, which are used to define international time scales such as International Atomic Time and Coordinated Universal Time. These international time scales are realized by ensembles of clocks at national laboratories such as the National Institute of Standards and Technology, and I will describe how ensembles of atomic clocks are characterized and managed.

  19. Time scale of magma differentiation in arcs from protactinium-radium isotopic data

    NASA Astrophysics Data System (ADS)

    Asmerom, Yemane; Dufrane, S. Andrew; Mukasa, Samuel B.; Cheng, Hai; Edwards, R. Lawrence

    2005-08-01

    Absolute chronology of magma differentiation processes has been a long-desired goal, given its importance in understanding magma chamber dynamics and its connection to a fundamental understanding of the style and frequency of volcanic eruptions. Broad estimates of the duration of magma differentiation and overall crustal residence times have been made based on a variety of indirect approaches, such as physical models of magma chamber cooling, rates of crystal growth and settling, and long-lived radiogenic isotopes. In contrast, combined 231Pa-235U data may provide a robust measure of the time scale of magma differentiation. Based on 231Pa-235U, 230Th-238U and 226Ra-230Th data from Taal volcano, Luzon Arc, Philippine Archipelago, we show that 231Pa-235U data may provide a robust direct measure of the time scale of magma differentiation. A closed-system magma fractionation model gives a 231Pa-235U differentiation time scale in the range of 30 k.y., while the 226Ra-230Th time scale is considerably younger. The time scales are reconciled if we consider either fluid-mixing or magma-mixing models. The fluid-mixing model gives a time scale of differentiation similar to the 231Pa-235U closed-system time scale and is supported by the 230Th-238U data. The magma-mixing model gives a considerably longer time, in the range of 55 k.y. The combined observations support the robustness of the 231Pa-235U chronology, indicating a differentiation time scale in the range of 30 k.y., although this time scale for other volcanoes may vary depending on size and thermal state of the magma chamber. The 226Ra-230Th closed-system model ages, which yield much younger estimates for magma differentiation, are not likely to reflect time scales of magma differentiation.

  20. Age and provenance of Triassic to Cenozoic sediments of West and Central Sarawak, Malaysia

    NASA Astrophysics Data System (ADS)

    Breitfeld, H. Tim; Galin, Thomson; Hall, Robert

    2015-04-01

    Sarawak is located on the northern edge of Sundaland in NW Borneo. West and Central Sarawak include parts of the Kuching and Sibu Zones. These contain remnants of several sedimentary basins with ages from Triassic to Cenozoic. New light mineral, heavy mineral and U-Pb detrital zircon ages show differences in provenance reflecting the tectonic evolution of the region. The oldest clastic sediments are Triassic (Sadong Formation and its deep marine equivalent Kuching Formation). They were sourced by a Triassic (Carnian to Norian) volcanic arc and reworked Paleoproterozoic detritus derived from Cathaysialand. The Upper Jurassic to Cretaceous Pedawan Formation is interpreted as forearc basin fill with distinctive zircon populations indicating subduction beneath present-day West Sarawak which initiated in the Late Jurassic. Subsequent subduction until the early Late Cretaceous formed the Schwaner Mountains magmatic arc. After collision of SW Borneo and other microcontinental fragments with Sundaland in the early Late Cretaceous, deep marine sedimentation (Pedawan Formation) ceased, and there was uplift forming the regional Pedawan-Kayan unconformity. Two episodes of extension followed and were responsible for basin development on land in West Sarawak from the latest Cretaceous onwards, probably in a pull-apart setting. The first episode is associated with sediments of the Kayan Group, deposited in the Latest Cretaceous (Maastrichtian) to Eocene, and the second episode with Upper Eocene sediments of the Ketungau Basin. Zircon ages indicate volcanic activity throughout the Early Cenozoic in NW Borneo, and inherited zircon ages indicate reworking of Triassic and Cretaceous rocks. A large deep marine basin, the Rajang Basin, was north of the Lupar Line Fault in Central Sarawak (Sibu Zone) from the Late Cretaceous to the Late Eocene. Zircons from sediments of the Rajang Basin indicate they have similar ages and provenance to contemporaneous terrestrial sediments of the Kayan Group and Ketungau Basin to the south, suggesting a narrow steep continental Sundaland margin at the position of the Lupar Line, and a large-scale sedimentary connection between the terrestrial and deep marine basins in the Late Cretaceous to Late Eocene. A recent reconstruction for the proto-South China Sea proposed an isolated so-called Semitau terrane colliding with SW Borneo and Sundaland in the Late Eocene. Our data show that the area of the Kuching and Sibu Zones were connected with SW Borneo and Sundaland from the Cretaceous onwards. The Cretaceous and Cenozoic sedimentary basins were sourced by alternations of Schwaner Mountains and Malay Tin Belt rocks. Our new age and provenance data cannot be explained by an isolated Semitau terrane and a Late Eocene collision.

  1. 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.

  2. Time and length scales within a fire and implications for numerical simulation

    SciTech Connect

    TIESZEN,SHELDON R.

    2000-02-02

    A partial non-dimensionalization of the Navier-Stokes equations is used to obtain order of magnitude estimates of the rate-controlling transport processes in the reacting portion of a fire plume as a function of length scale. Over continuum length scales, buoyant times scales vary as the square root of the length scale; advection time scales vary as the length scale, and diffusion time scales vary as the square of the length scale. Due to the variation with length scale, each process is dominant over a given range. The relationship of buoyancy and baroclinc vorticity generation is highlighted. For numerical simulation, first principles solution for fire problems is not possible with foreseeable computational hardware in the near future. Filtered transport equations with subgrid modeling will be required as two to three decades of length scale are captured by solution of discretized conservation equations. By whatever filtering process one employs, one must have humble expectations for the accuracy obtainable by numerical simulation for practical fire problems that contain important multi-physics/multi-length-scale coupling with up to 10 orders of magnitude in length scale.

  3. New Paleoenvironmental and Biotic Records from the Triassic-Jurassic Boundary Interval of the Algarve Basin, Portugal

    NASA Astrophysics Data System (ADS)

    Kasprak, A. H.; Whiteside, J. H.; Lopes, F. M.; Brusatte, S. L.; Butler, R. J.; Mateus, O.

    2010-12-01

    Studies of carbonate, bulk organic, and compound-specific stable isotopes of carbon have shown that the Triassic-Jurassic boundary interval (including the end-Triassic mass extinction) displays major, global perturbations to the carbon cycle. These records are instrumental not only in reconstructing environmental change, as they are thought to reflect ecosystem instability and changing atmospheric gas inventories, but, due to their global nature, can be useful tools for stratigraphic correlation. The Algarve Basin, a deformed, extensional basin in the south of Portugal, has potential for yielding insight into the dramatic paleoenvironmental and faunal changes that occurred during the latest Triassic through earliest Jurassic. During this time interval, the basin records an evolution from continental to marginal marine sediments that are interbedded with radioisotopically dated Central Atlantic Magmatic Province (CAMP) basalts, thought to be a major causative agent in the end-Triassic mass extinction. Recent field excavations in the Algarve Basin have documented terrestrial vertebrate remains at multiple horizons, including a rich bone bed densely packed with well-preserved remains of large stereospondyl temnospondyls (skull length up to ~1 meter) positioned close to the Triassic-Jurassic boundary. These stereospondyls may represent some of the latest surviving members of their groups in Europe, and occur in a time interval in which stereospondyl material is scarce and represented primarily by isolated and fragmentary material. Unfortunately, the paleoenvironmental and chronologic framework of the Algarve Basin is not well constrained, despite its importance as a critical record of this time in Earth history. We present a preliminary bulk organic carbon isotope record of early Mesozoic rift-basin sediments from the Algarve Basin. This record exhibits significant variability, but appears to record a trend towards more negative values at the top of the section, though this needs better constraint with further sampling. Although the potential for changes in the source of organic material can be expected to have an effect on the overall signal, the presence of depleted δ13C values in proximity to CAMP basalts relative to stratigraphically lower sections points to the potential for identifying key negative excursions associated with Triassic-Jurassic boundary events in the Algarve Basin.

  4. Modeling geomagnetic storms on prompt and diffusive time scales

    NASA Astrophysics Data System (ADS)

    Li, Zhao

    The discovery of the Van Allen radiation belts in the 1958 was the first major discovery of the Space Age. There are two belts of energetic particles. The inner belt is very stable, but the outer belt is extremely variable, especially during geomagnetic storms. As the energetic particles are hazardous to spacecraft, understanding the source of these particles and their dynamic behavior driven by solar activity has great practical importance. In this thesis, the effects of magnetic storms on the evolution of the electron radiation belts, in particular the outer zone, is studied using two types of numerical simulation: radial diffusion and magnetohydrodynamics (MHD) test-particle simulation. A radial diffusion code has been developed at Dartmouth, applying satellite measurements to model flux as an outer boundary condition, exploring several options for the diffusion coefficient and electron loss time. Electron phase space density is analyzed for July 2004 coronal mass ejection (CME) driven storms and March-April 2008 co-rotating interaction region (CIR) driven storms, and compared with Global Positioning System (GPS) satellite measurements within 5 degrees of the magnetic equator at L=4.16. A case study of a month-long interval in the Van Allen Probes satellite era, March 2013, confirms that electron phase space density is well described by radial diffusion for the whole month at low first invariant <400~MeV/G, but peaks in phase space density observed by the ECT instrument suite at higher first invariant are not reproduced by radial transport from a source at higher L. A 3D guiding center code with plasmasheet injection is used to simulate particle motion in time-dependent MHD fields calculated from the Lyon-Fedder-Mobarry global MHD code, as an extension of the Hudson et al. (2012) study of the Whole Heliosphere Interval of CIR-driven storms in March-April 2008. Direct comparison with measured fluxes at GOES show improved comparison with observations relative to the 2D guiding center test particle simulations and enhancement of flux at >0.6 MeV by an order of magnitude over 24 hours as observed.

  5. Triassic and Jurassic rocks at Currie, Nevada Preliminary paleontologic evidence

    SciTech Connect

    Johnson, E.A.; Dubiel, R.F.; Brouwers, E.M. ); Litwin, R.J. ); Ash, S.R. ); Good, S.C. )

    1993-04-01

    A sequence of continental rocks overlies the Lower Triassic Thaynes Formation in a poorly exposed syncline near Currie in northeastern NV. The authors recognize four lithostratigraphic units above the Thaynes near Currie and provide new paleontologic data. In ascending order, unit 1 (120 ft) consists of reddish-brown, very fine grained sandstone. Unit 2 (50 ft) consists of light-gray, trough cross-stratified, coarse-grained, conglomeratic sandstone. Unit 3 (at least 500 ft) consists of green, red, and brown sandstone and mudstone. Unit 4 occurs as isolated outcrops of reddish-orange, fine- to medium-grained sandstone. New fossil evidence, while not definitive, constrain the age of this sequence. Plant megafossils in unit 1 include (1) a specimen with narrow ovate leaves, possibly from an early Mesozoic conifer and (2) abundant fragments of probable Neocalamites. The presence of these fossils and the absence of any angiosperm leaves or wood fragments suggest an early Mesozoic age. Ostracodes in unit 3 are exclusively Darwinula sp., and their association with conchostracans in the absence of younger ostracodes suggests a Triassic age. Finally, two small outcrops, previously mapped as Triassic/Jurassic, contain the gastropods Pilidae indet. and Lymnaea sp., which resemble Late Cretaceous to Paleocene faunas. The sequence is similar to the nearest Lower Mesozoic section on the Colorado Plateau at Cove Fort, Utah, 165 miles to the southeast. The authors' new evidence supports the longstanding correlation of units 1--4 with the Lower Triassic Moenkopi Formation (part), the Shinarump and Petrified Forest Members of the Upper Triassic Chinle Formation, and the Lower Jurassic Navajo Sandstone of the Plateau. These rocks at Currie demonstrate that the Early Mesozoic depositional systems of the Colorado Plateau extended at least this far west and provide constraints on Early Mesozoic tectonism in the eastern Great Basin.

  6. Oil and gas potential of the Triassic in west Siberia

    SciTech Connect

    Bochkarev, V.S.; Kulakhmetov, N.KH.; Nesterov, I.I. )

    1993-09-01

    Permian-Triassic rocks are widely spread within the West Siberian basin, and they include volcanics, volcanoclastics, and clastics. Their thickness varies from tens of meters of 3000 m. Recently, three commercial oil pools have been discovered in Triassic effusive-sedimentary rocks. These discoveries, together with other geological and geochemical data, identify the Triassic complex as a major play. Oil-bearing intervals have been found in three different types of sequences; a fourth also may be prospective. The first type is represented by lacustrine-terrigenous sediments, which comprise oil-saturated sandstones interbedded with basalts (the Turin series). Oil influxes were obtained in the Yakhlinskaya and Triyurtin-skaya structures in the Shaim region. The second type is distinguished from the first by the presence of coal-bearing intervals in the upper part. Oil was produced in the Yerofeyev area of the Chelyabinsk garben. The third type differs from the other two by the presence of potassic rhyolites and dacites. Their age is not precisely dated, and supposedly they are of Permian age. The largest oil influxes have been obtained from fractured and eroded rocks of this type in the Rogozhnikovskaya and other places in the Krasnoleninsk region. Rhyodacites often underlie Turin basalts, but locally they occur in the upper part of the series. Triassic and Permian-Trissic rocks of the three types are overlain by Jurassic and Cretaceous rocks with a large break. The fourth type of section is completely terrigenous (Tampei series). It is developed in the northern part of west Siberia. Here Triassic sediments are overlain by the Jurassic complex without a break. According to well-log data, productive horizons occur at Urengoy and Beregovaya (in the Urengoy region).

  7. Scale (in)variance in a unified diffusion model of decision making and timing.

    PubMed

    Simen, Patrick; Vlasov, Ksenia; Papadakis, Samantha

    2016-03-01

    Weber's law is the canonical scale-invariance law in psychology: when the intensities of 2 stimuli are scaled by any value k, the just-noticeable-difference between them also scales by k. A diffusion model that approximates a spike-counting process accounts for Weber's law (Link, 1992), but there exist surprising corollaries of this account that have not yet been described or tested. We show that (a) this spike-counting diffusion model predicts time-scale invariant decision time distributions in perceptual decision making, and time-scale invariant response time (RT) distributions in interval timing; (b) for 2-choice perceptual decisions, the model predicts equal accuracy but faster responding for stimulus pairs with equally scaled-up intensities; (c) the coefficient of variation (CV) of decision times should remain constant across average intensity scales, but should otherwise decrease as a specific function of stimulus discriminability and speed-accuracy trade-off; and (d) for timing tasks, RT CVs should be constant for all durations, and RT skewness should always equal 3 times the CV. We tested these predictions using visual, auditory and vibrotactile decision tasks and visual interval timing tasks in humans. The data conformed closely to the predictions in all modalities. These results support a unified theory of decision making and timing in terms of a common, underlying spike-counting process, compactly represented as a diffusion process. (PsycINFO Database Record PMID:26461957

  8. Updating the planetary time scale: focus on Mars

    USGS Publications Warehouse

    Tanaka, Kenneth L.; Quantin-Nataf, Cathy

    2013-01-01

    Formal stratigraphic systems have been developed for the surface materials of the Moon, Mars, Mercury, and the Galilean satellite Ganymede. These systems are based on geologic mapping, which establishes relative ages of surfaces delineated by superposition, morphology, impact crater densities, and other relations and features. Referent units selected from the mapping determine time-stratigraphic bases and/or representative materials characteristic of events and periods for definition of chronologic units. Absolute ages of these units in some cases can be estimated using crater size-frequency data. For the Moon, the chronologic units and cratering record are calibrated by radiometric ages measured from samples collected from the lunar surface. Model ages for other cratered planetary surfaces are constructed primarily by estimating cratering rates relative to that of the Moon. Other cratered bodies with estimated surface ages include Venus and the Galilean satellites of Jupiter. New global geologic mapping and crater dating studies of Mars are resulting in more accurate and detailed reconstructions of its geologic history.

  9. On the time scale associated with Monte Carlo simulations

    SciTech Connect

    Bal, Kristof M. Neyts, Erik C.

    2014-11-28

    Uniform-acceptance force-bias Monte Carlo (fbMC) methods have been shown to be a powerful technique to access longer timescales in atomistic simulations allowing, for example, phase transitions and growth. Recently, a new fbMC method, the time-stamped force-bias Monte Carlo (tfMC) method, was derived with inclusion of an estimated effective timescale; this timescale, however, does not seem able to explain some of the successes the method. In this contribution, we therefore explicitly quantify the effective timescale tfMC is able to access for a variety of systems, namely a simple single-particle, one-dimensional model system, the Lennard-Jones liquid, an adatom on the Cu(100) surface, a silicon crystal with point defects and a highly defected graphene sheet, in order to gain new insights into the mechanisms by which tfMC operates. It is found that considerable boosts, up to three orders of magnitude compared to molecular dynamics, can be achieved for solid state systems by lowering of the apparent activation barrier of occurring processes, while not requiring any system-specific input or modifications of the method. We furthermore address the pitfalls of using the method as a replacement or complement of molecular dynamics simulations, its ability to explicitly describe correct dynamics and reaction mechanisms, and the association of timescales to MC simulations in general.

  10. Record of the end-Triassic crisis in south-western Sicily: palaeoenvironmental changes reflected by the carbonate facies architecture.

    NASA Astrophysics Data System (ADS)

    Cacciatore, M. S.; di Stefano, P.

    2009-04-01

    The Sciacca-Monti Sicani area, in south-western Sicily, offers a regional example of the facies architecture in an Upper Triassic/Lower Jurassic carbonate shelf margin to slope zone. It allows us to evaluate the interplay of different controlling factors on the sedimentary dynamics of a South Tethyan basin margin across the Triassic/Jurassic boundary. In this segment of the Maghrebian thrust and fold belt, the Triassic/Jurassic facies associations and their spatial relationships were restored by the correlation of selected sections from several structural units. The Triassic carbonate shelf consists of thick successions of peritidal-lagoonal cycles (Sciacca Fm.). Our studies reveal that a NW-SE trending Dachstein-type reef edged the shelf of the platform towards east. This implies the contiguity of the carbonate shelf with a high-energy, open-marine environment, providing the optimum oligotrophic life conditions for sponge-coral-algae communities. A terminal complex, consisting of chaetetid-dominated boundstones, characterizes the Rhaetian topmost zone of the reef, probably because of the end-Triassic biotic crisis. A sharp discontinuity surface on top of the uppermost Triassic platform strata (Triasina facies) is overprinted in places by karstic dissolution. It is interpreted as a result of a Late Rhaetian sea-level fall. A lowering of the sea-level is also supported by the presence of fine skeletal grainstones in the slope-basinal successions. This implies a downslope forced shedding of reef-derived biodetritus, favoured probably by the shifting of the active bioconstruction to the outer shelf margin/upper slope. Around the Rhaetian-Hettangian boundary, a widespread clastic carbonate wedge was formed downslope by the cannibalization of the Upper Triassic reef. The selective source of clastics (Upper Triassic reef extraclasts) suggests, as trigger mechanisms, margin collapses coupled to an intense wave erosion of the reef limestones during the lowstand stage. Transtensional tectonics activity along the shelf edge, inducing margin retreats, is documented by local angular unconformities, so we cannot exclude the contribution of brittle deformations to the the production of clastic materials. The aggradation of Thaumatoporella-mollusc bearing peritidal cycles in the shelf and of oolitic-bioclastic sands along the shelf-edge indicate the recovery of the carbonate productivity during Early Jurassic times coupled to a sea-level rise during Hettangian times. Moreover an intense shedding of carbonate sands in the adjacent slope and peribasinal areas is recorded in all the studied deep-water successions. In the distal slope zone the observed switching of the intrabasinal carbonate supply from scarce biodetritus containing reef-derived foraminifers (e.g. Galeanella, Siculocosta and others) to abundant oolitic and skeletal sands, bearing Aeolisaccus sp. and Siphovalvulina gibraltarensis, can be used as a proxy of the Triassic/Jurassic boundary.

  11. Salinization of aquifers at the regional scale by marine transgression: Time scales and processes

    NASA Astrophysics Data System (ADS)

    Armandine Les Landes, A.; Davy, P.; Aquilina, L.

    2014-12-01

    Saline fluids with moderate concentrations have been sampled and reported in the Armorican basement at the regional scale (northwestern France). The horizontal and vertical distributions of high chloride concentrations (60-1400mg/L) at the regional scale support the marine origin and provide constraints on the age of these saline fluids. The current distribution of fresh and "saline" groundwater at depth is the result mostly of processes occurring at geological timescales - seawater intrusion processes followed by fresh groundwater flushing -, and only slightly of recent anthropogenic activities. In this study, we focus on seawater intrusion mechanisms in continental aquifers. We argue that one of the most efficient processes in macrotidal environments is the gravity-driven downconing instability below coastal salinized rivers. 2-D numerical experiments have been used to quantify this process according to four main parameter types: (1) the groundwater system permeability, (2) the salinity degree of the river, (3) the river width and slope, and (4) the tidal amplitude. A general expression of the salinity inflow rates have been derived, which has been used to estimate groundwater salinization rates in Brittany, given the geomorphological and environmental characteristics (drainage basin area, river widths and slopes, tidal range, aquifer permeability). We found that downconing below coastal rivers entail very high saline rates, indicating that this process play a major role in the salinization of regional aquifers. This is also likely to be an issue in the context of climate change, where sea-level rise is expected.

  12. Variability Trends in QSOs Over Monthly Time Scales

    NASA Astrophysics Data System (ADS)

    Fleming, B. T.; Kennefick, J.

    2005-12-01

    Variation in quasar magnitude from night to night can reveal long term variability trends as well as have a greater chance of detecting sudden luminosity changes than a typical long-term variability survey. In this study, five quasars with a range of properties were observed approximately every other night over 40 days using the 24" NFO webscope in Silver City, NM. Three 200 second exposure images were taken in both the R and V color filters each observation. Two passbands were used so that the data could be correlated to support findings. The images were stacked and processed using IRAF and SExtractor. Differential photometry using field stars was utilized. The five quasars were selected so that as large a range of redshift and absolute magnitude observable by the NFO webscope was represented. They are: (1) MRK 0877 with z=0.1124, (2) 3C-334 a RQQ with z=0.5551, (3) HS 1603+3820 a very luminous, very distant QSO with z=2.51, and two quasars from the QUEST survey (J1507-0202 and J1507-0207) which were selected because they both showed evidence of magnitude variations during the QUEST1 survey. Two of the observed quasars showed no significant variability. 3C-334 displayed a sudden apparent magnitude jump in both passbands, with Δ mR = 0.5602 ± 0.0474, corresponding to an increase of 6.62E+11 solar luminosities on June 21st. The magnitude returned to previous levels by the next observation. QUEST 1507-0202 and MRK 0877 suggested evidence of small long term variability over the 40 day study. Future observations revealing significant changes in magnitude corresponding to these trends may lead to the conclusion that these slow long-term variations can be detected over a 40 day time period with frequent observations. Funding was provided through an Arkansas Space Center grant.

  13. Computational Modeling of Semiconductor Dynamics at Femtosecond Time Scales

    NASA Technical Reports Server (NTRS)

    Agrawal, Govind P.; Goorjian, Peter M.

    1998-01-01

    The main objective of the Joint-Research Interchange NCC2-5149 was to develop computer codes for accurate simulation of femtosecond pulse propagation in semiconductor lasers and semiconductor amplifiers [I]. The code should take into account all relevant processes such as the interband and intraband carrier relaxation mechanisms and the many-body effects arising from the Coulomb interaction among charge carriers [2]. This objective was fully accomplished. We made use of a previously developed algorithm developed at NASA Ames [3]-[5]. The new algorithm was tested on several problems of practical importance. One such problem was related to the amplification of femtosecond optical pulses in semiconductors. These results were presented in several international conferences over a period of three years. With the help of a postdoctoral fellow, we also investigated the origin of instabilities that can lead to the formation of femtosecond pulses in different kinds of lasers. We analyzed the occurrence of absolute instabilities in lasers that contain a dispersive host material with third-order nonlinearities. Starting from the Maxwell-Bloch equations, we derived general multimode equations to distinguish between convective and absolute instabilities. We find that both self-phase modulation and intensity-dependent absorption can dramatically affect the absolute stability of such lasers. In particular, the self-pulsing threshold (the so-called second laser threshold) can occur at few times the first laser threshold even in good-cavity lasers for which no self-pulsing occurs in the absence of intensity-dependent absorption. These results were presented in an international conference and published in the form of two papers.

  14. Computational Modeling of Semiconductor Dynamics at Femtosecond Time Scales

    NASA Technical Reports Server (NTRS)

    Agrawal, Govind P.; Goorjian, Peter M.

    1998-01-01

    The Interchange No. NCC2-5149 deals with the emerging technology of photonic (or optoelectronic) integrated circuits (PICs or OEICs). In PICs, optical and electronic components are grown together on the same chip. To build such devices and subsystems, one needs to model the entire chip. PICs are useful for building components for integrated optical transmitters, integrated optical receivers, optical data storage systems, optical interconnects, and optical computers. For example, the current commercial rate for optical data transmission is 2.5 gigabits per second, whereas the use of shorter pulses to improve optical transmission rates would yield an increase of 400 to 1000 times. The improved optical data transmitters would be used in telecommunications networks and computer local-area networks. Also, these components can be applied to activities in space, such as satellite to satellite communications, when the data transmissions are made at optical frequencies. The research project consisted of developing accurate computer modeling of electromagnetic wave propagation in semiconductors. Such modeling is necessary for the successful development of PICs. More specifically, these computer codes would enable the modeling of such devices, including their subsystems, such as semiconductor lasers and semiconductor amplifiers in which there is femtosecond pulse propagation. Presently, there are no computer codes that could provide this modeling. Current codes do not solve the full vector, nonlinear, Maxwell's equations, which are required for these short pulses and also current codes do not solve the semiconductor Bloch equations, which are required to accurately describe the material's interaction with femtosecond pulses. The research performed under NCC2-5149 solves the combined Maxwell's and Bloch's equations.

  15. Empirical study on structural properties in temporal networks under different time scales

    NASA Astrophysics Data System (ADS)

    Chen, Duanbing

    2015-12-01

    Many network analyzing methods are usually based on static networks. However, temporal networks should be considered so as to investigate real complex systems deeply since some dynamics on these systems cannot be described by static networks accurately. In this paper, four structural properties in temporal networks are empirically studied, including degree, clustering coefficient, adjacent correlation, and connected component. Three real temporal networks with different time scales are analyzed in this paper, including short message, telephone, and router networks. Moreover, structural properties of these temporal networks are compared with that of corresponding static aggregation networks in the whole time window. Some essential differences of structural properties between temporal and static networks are achieved through empirical analysis. Finally, the effect of structural properties on spreading dynamics under different time scales is investigated. Some interesting results such as turning point of structure evolving time scale corresponding to certain spreading dynamics time scale from the point of view of infected scale are achieved.

  16. The Triassic dicynodont Kombuisia (Synapsida, Anomodontia) from Antarctica, a refuge from the terrestrial Permian-Triassic mass extinction.

    PubMed

    Frbisch, Jrg; Angielczyk, Kenneth D; Sidor, Christian A

    2010-02-01

    Fossils from the central Transantarctic Mountains in Antarctica are referred to a new species of the Triassic genus Kombuisia, one of four dicynodont lineages known to survive the end-Permian mass extinction. The specimens show a unique combination of characters only present in this genus, but the new species can be distinguished from the type species of the genus, Kombuisia frerensis, by the presence of a reduced but slit-like pineal foramen and the lack of contact between the postorbitals. Although incomplete, the Antarctic specimens are significant because Kombuisia was previously known only from the South African Karoo Basin and the new specimens extend the taxon's biogeographic range to a wider portion of southern Pangaea. In addition, the new finds extend the known stratigraphic range of Kombuisia from the Middle Triassic subzone B of the Cynognathus Assemblage Zone into rocks that are equivalent in age to the Lower Triassic Lystrosaurus Assemblage Zone, shortening the proposed ghost lineage of this taxon. Most importantly, the occurrence of Kombuisia and Lystrosaurus mccaigi in the Lower Triassic of Antarctica suggests that this area served as a refuge from some of the effects of the end-Permian extinction. The composition of the lower Fremouw Formation fauna implies a community structure similar to that of the ecologically anomalous Lystrosaurus Assemblage Zone of South Africa, providing additional evidence for widespread ecological disturbance in the extinction's aftermath. PMID:19956920

  17. The Triassic dicynodont Kombuisia (Synapsida, Anomodontia) from Antarctica, a refuge from the terrestrial Permian-Triassic mass extinction

    NASA Astrophysics Data System (ADS)

    Frbisch, Jrg; Angielczyk, Kenneth D.; Sidor, Christian A.

    2010-02-01

    Fossils from the central Transantarctic Mountains in Antarctica are referred to a new species of the Triassic genus Kombuisia, one of four dicynodont lineages known to survive the end-Permian mass extinction. The specimens show a unique combination of characters only present in this genus, but the new species can be distinguished from the type species of the genus, Kombuisia frerensis, by the presence of a reduced but slit-like pineal foramen and the lack of contact between the postorbitals. Although incomplete, the Antarctic specimens are significant because Kombuisia was previously known only from the South African Karoo Basin and the new specimens extend the taxons biogeographic range to a wider portion of southern Pangaea. In addition, the new finds extend the known stratigraphic range of Kombuisia from the Middle Triassic subzone B of the Cynognathus Assemblage Zone into rocks that are equivalent in age to the Lower Triassic Lystrosaurus Assemblage Zone, shortening the proposed ghost lineage of this taxon. Most importantly, the occurrence of Kombuisia and Lystrosaurus mccaigi in the Lower Triassic of Antarctica suggests that this area served as a refuge from some of the effects of the end-Permian extinction. The composition of the lower Fremouw Formation fauna implies a community structure similar to that of the ecologically anomalous Lystrosaurus Assemblage Zone of South Africa, providing additional evidence for widespread ecological disturbance in the extinctions aftermath.

  18. Mars Polar Motion at Short Time-Scale.

    NASA Astrophysics Data System (ADS)

    Dehant, V. M.; de Viron, O.; Karatekin, O.; van Hoolst, T.

    2005-12-01

    The rotation of Mars is not constant in time and presents irregularities that are mostly associated with the seasonal CO2 mass exchange between Mars' atmosphere and polar caps. This large mass redistribution (about a third of the total atmospheric mass is considered to be exchanged) induces variations in Mars' rotation speed as well as in polar motion. The effects of the atmosphere on the rotation can be estimated by using the angular momentum approach: because of conservation of angular momentum of Mars (solid body and atmosphere), considered as isolated, any change in the angular momentum of the atmosphere is associated with an opposite change in the angular momentum of the solid body of the planet. Mars' polar motion is computed for Mars models with three homogeneous layers (solid inner core, fluid outer core, and mantle) for different excitation causes (atmosphere, ice caps, and quakes). We estimate the amplitude of the polar motion resulting from atmospheric excitation, for a reasonable interval of damping factor values, for the two polar motion normal modes, i.e. the Chandler wobble and the Inner Core wobble. We show how the amplitude of the CW excited by the atmospheric noise can be interpreted in terms of anelasticity of the Martian mantle, through the CW damping factor. The damping is estimated from the observation of the mode itself under hypotheses on the type of forcing noise. We show that the signature of the inner core in the polar motion is very small, and is unlikely to be detected with the present observational precision. We further investigate the possibility to excite these normal modes through Marsquakes, and show that the predicted quake moments are not large enough to excite polar motion to an observable level. The analysis of polar motion, and in particular the determination of its normal mode components, is promising because normal mode periods and amplitudes are directly related to the properties of the deep interior. The precision needed to get useful information is very demanding, and requires improvement of the Martian rotation measurements. A first step could be the deployment of a long-lived network of landers at the Martian surface.

  19. Carbon cycle dynamics following the end-Triassic mass extinction: Constraints from paired ?13Ccarb and ?13Corg records

    NASA Astrophysics Data System (ADS)

    Bachan, Aviv; van de Schootbrugge, Bas; Fiebig, Jens; McRoberts, Christopher A.; Ciarapica, Gloria; Payne, Jonathan L.

    2012-09-01

    Constraining the carbon isotopic changes associated with the end-Triassic mass extinction is key to understanding the causes of the extinction and dynamics of recovery from it. Yet the pattern and timing of ?13C variation surrounding the extinction remain poorly constrained. Here we present close to 1000 new ?13C measurements from six newly sampled sections in Italy. We observe a sharp negative excursion in ?13Ccarb coincident with the disappearance of the Triassic fauna, and two positive excursions above it. The negative ?13Ccarb excursion in these sections does not occur in ?13Corg suggesting a possible diagenetic origin. In contrast, the interval of elevated ?13C occurs in both carbonate and organic carbon, suggesting that it is likely to be a primary feature. The positive excursions in the Lombardy Basin (southern Alps) and Mt. Cefalo (southern Apennines) appear to be time correlative on the basis of their position above the disappearance of characteristically Triassic biota. However, it is less certain that they are time correlative with positive excursions in other sections worldwide, as few options exist that honor both bio- and chemostratigraphy. Nonetheless, similarity to other events that are interpreted as global, as well as carbon cycle considerations, suggest that the isotopic enrichment is best interpreted to reflect a shift in the isotope composition of the global surface carbon reservoir. Our data indicate that perturbation of the global carbon cycle was not confined to the immediate vicinity of the extinction interval, but rather persisted for substantial length of geologic time afterwards.

  20. The lower Triassic microbiolites in Chaohu region, East China and their contribution to the early Triassic recovery

    NASA Astrophysics Data System (ADS)

    Jia, Zhihai; Zhang, Liwei; Hong, Tianqiu

    2010-05-01

    The lower Triassic is well preserved in Chaohu Region, Anhui Province, East China. It can be divided into Yinkeng Formation (80 meters thick, was formed during the Indian and early Smitian), Helongshan Formation (21 meters thick, was formed during the end Smithian) and Nanlinghu Formation (more than 157 meters thick, was formed during the Spathian) from bottom to top. It is mainly composed of carbonatites such as micrite limestones and nodular limestones, as well as shales and calcareous marls. The lower Triassic in this area has been well researched for more than a decade, and many fossils such as ammonites, bivalves, fishes, ichthyosaurus, conodonts, and ichnofossils have been found, but the microbiolites have been neglected. Microbiolites were mainly outcropped in the Helongshan Formaiton and the lower Nanlinghu Formation. In the lower Helongshan Formaiton, tens microbial mat layers and thin bedded calcareous marl layers formed cyclothems which have been named as nodular limstones. The thin-section observation of the microbial mats indicate that many films and thin-shell bivalve fragments deposited almost horizontally. In the upper Helongshan Formaiton, six microstromatolite bioherm layers were outcropped in the thin bedded calcareous marl layers. The diameter of the stromatolite column is about 2 millimeters, the bioherms are lenticular and no more than 3 centimeters thick in the central, their diameters change from 5 centimeters to 30 centimeters, calcareous marls were deposited around the bioherms, and many ammonoids, bivalves and burrows were found in such layers. The microfacies differentiation of the stromatolites such as the basement, reef core and the capping beds can be recognised clearly in thin sections. Several microstromatolite layers were outcropped in the micritic limestones with a stable thickness of 15 millimeters in the lower Nanlinghu Formation and the stromatolite column look like the ones in the Helongshan Formation. Few microbiolites have been found in the middle and upper Nanlinghu Formation. The macro fossil association of the lower Triassic in Chaohu region is quite different in different Formations. Ammonoids and bivalves can be found in the whole lower Triassic strata, and they are especially dominant in the Yinkeng Formation and lower Helongshan Formaiton, worms and borrowing animals can be found in the middle Helongshan Formation, fishes can be found in the uppermost Helongshan Formation and the lower Nanlinghu Formation, and the oldest ichthyosaurus in the world can be found in the upper Nanlinghu Formation. According to the changing characters of the fossil association in this area, it is indicated that the high-level ecosystem had been formed in this area in the late early Triassic, and the appearance of the microbiolites in the Helongshan Formation might be the milestone for the early Triassic recovery. Though the global recovery process after the Permian-Triassic mass extinction might be postponed to the end of the early Triassic, regional recovery process in Chaohu region might start at the end Smithian and actualized at the middle Spathian. The microbioilites might be the original impetus for the early Triassic recovery. Key words: microbiolites, early Triassic, regional recovery, Chaohu region Acknowledgments This work is supported by the grants from National Natural Science Fundation of China (No. 40902096 and No.J0830522) and the IGCP 572 program. * Corresponding author: zhihai.jia@gmail.com

  1. The Pangea conundrum: Implications of new Paleomagnetic data from Permo-Triassic Araguainha Impact Crater (Central Brazil)

    NASA Astrophysics Data System (ADS)

    Brandt, D.; Yokoyama, E.; Trindade, R. I.; Tohver, E.

    2013-05-01

    This paper presents a new Permo-Triassic paleomagnetic pole for South America based on impact-related material from the Araguainha Dome. The relative position of southern and northern continents in Pangea between the Carboniferous and the Triassic has been a topic of intense debate for almost half a century, since when T. Irving has shown dramatic inconsistencies between the original A. Wegener's Pangea and the then-available paleomagnetic data. Recent compilations of paleomagnetic poles for both hemispheres of Pangea (Laurussia and Gondwana) seem to concur that part of those inconsistencies are related to the quality of the Carboniferous to Triassic paleomagnetic record and emphasize the urgent need for high-quality data for this time period. Permo-Triassic paleomagnetic data for South America were obtained mainly from sedimentary rocks, which are inherently affected by several recording problems such as inclination shallowing or remagnetization, also presenting large uncertainties in their ages. Thus, it is necessary to improve the database with paleomagnetic poles derived from igneous rocks carrying stable thermoremanent magnetization that can be easily dated. However, volcanic rocks are scarce for this time period at the central part of the continent. In this way, we targeted the well-dated melt impact material from the Araguainha dome. The Araguainha Dome is the biggest and oldest complex impact structure yet recognized in South America. It is 40 km wide and has excavated about 2500 meters of the sedimentary rocks of the Paraná basin, reaching the basement crystalline rocks. A multi-method dating of the impact melts provided a precise age for the impact at 254.7 ± 2.5 Ma overlapping the Permo-Triassic limit. The same impact-related melt sheets and dykes were sampled for paleomagnetic studies in 23 sites (138 specimens). Alternating field and thermal demagnetization indicate stable, usually univectorial magnetizations carried by magnetite and hematite. All sites but one show coherent directions along the same normal polarity with a resulting mean at Dec = 356.4°; Inc = -38.7°; N = 22; k = 95.6; α95 = 3.2°, and a paleomagnetic pole at Lat= -83.7; Lon=340.2; K=87.6; A95=3.3°; SB=8.1°. The pole matches the apparent polar wander path built from a selection of high-quality poles from the West Gondwana (Domeier et al., 2012, Tectonophysics, doi:10.1016/j.tecto.2011.10.021). Our result provides a strong constraint on the position of Gondwana at the Permo-Triassic boundary and favors the Pangea A reconstruction.

  2. Filling a 30 Million Year Gap: Radioisotopic Age Constraints for the Late Triassic Timescale

    NASA Astrophysics Data System (ADS)

    Irmis, R. B.; Mundil, R.

    2011-12-01

    The Triassic Period records a critical interval of Phanerozoic Earth history, including major paleoenvironmental changes in a greenhouse world, recovery from one mass extinction and the onset of another, and the origin of modern terrestrial ecosystems. Recent efforts have been instrumental in calibrating the timing of these events by producing numerous high resolution radioisotopic ages from Early and Middle Triassic marine strata that facilitate building of a robust 20 Ma chronostratigraphic framework. This contrasts starkly with the Late Triassic (Carnian, Norian, and Rhaetian stages), where ~30 Ma of the timescale is virtually uncalibrated by high-resolution radioisotopic data. This is the only interval of such long duration in the Mesozoic or Cenozoic that remains so poorly constrained by reliable absolute ages, despite the occurrence of major events such as the origin and early diversification of dinosaurs, major reef building episodes in marine ecosystems, key paleoenvironmental changes (e.g., Carnian Pluvial Event), and large extraterrestrial bolide impacts (e.g., Manicouagan). An additional challenge is that the biostratigraphically-defined marine timescale cannot be applied globally, so that other areas (e.g., New Zealand) have independent timescales that cannot be confidently correlated to classic Laurasian sections. All of these problems preclude formulating robust first-order hypotheses about the Late Triassic world. We present new CA-TIMS U-Pb zircon data from volcaniclastic units within both marine and terrestrial strata that aim at calibrating the timescale itself and as a result constrain the timing of some of these major events in Earth history. Several preliminary ages support the hypothesis that the Norian Stage was very long, ~20 Ma. Our new data from marine sequences in New Zealand demonstrate that the timescale divisions there do not correlate directly with biostratigraphic boundaries in the Tethys; specifically, the Ladinian-Carnian boundary is somewhere within the Kaihikuan biozone, and the lower Otamitan biozone is correlative with the mid-Norian. Our new data from the terrestrial Chinle Formation in the southwestern US demonstrate that all of this formation is Norian in age or later, younger than South American sequences it had previously been correlated with. This supports the hypothesis that the rise of dinosaurs was diachronous, occurring later in North America than in Argentina and Brazil. These new ages also constrain a major faunal turnover event in the middle Chinle Fm to the mid-Norian, close in age to the Manicouagan impact event. Correlation and calibration of these major events will be further strengthened by the unambiguous superposition provided by core samples, such as the forthcoming Colorado Plateau Coring Project.

  3. The carbon and sulfur cycles and atmospheric oxygen from middle Permian to middle Triassic

    NASA Astrophysics Data System (ADS)

    Berner, Robert A.

    2005-07-01

    The results of a theoretical isotope mass balance model are presented for the time dependence of burial and weathering-plus-degassing fluxes within the combined long-term carbon and sulfur cycles. Averaged data for oceanic ? 13C and ? 34S were entered for every million years from 270 to 240 Ma (middle Permian to middle Triassic) to study general trends across the Permian-Triassic boundary. Results show a drop in the rate of global organic matter burial during the late Permian and a predominance of low values during the early-to-middle Triassic. This overall decrease with time is ascribed mainly to epochs of conversion of high biomass forests to low biomass herbaceous vegetation resulting in a decrease in the production of terrestrially derived organic debris. Additional contributions to lessened terrestrial carbon burial were increased aridity and a drop in sea level during the late Permian which led to smaller areas of low-lying coastal wetlands suitable for coal and peat deposition. Mirroring the drop in organic matter deposition was an increase in the burial of sedimentary pyrite, and a dramatic increase in the calculated global mean ratio of pyrite-S to organic-C. High S/C values resulted from an increase of deposition in marine euxinic basins combined with a decrease in the burial of low-pyrite associated terrestrial organic matter. The prediction of increased oceanic anoxia during the late Permian and early Triassic agrees with independent studies of the composition of sedimentary rocks. Weathering plus burial fluxes for organic carbon and pyrite sulfur were used to calculate changes in atmospheric oxygen. The striking result is a continuous drop in O 2 concentration from 30% to 13% over a twenty million year period. This drop was brought about mainly by a decrease in the burial of terrestrially derived organic matter. but with a possible contribution from the weathering of older organic matter on land. It must have exerted a considerable influence on animal evolution because of the role of O 2 in respiration. Some examples are the extinction of many vertebrates, loss of giant insects and amphibians, and the restriction of animals to low elevations. It is concluded that the extinction of plants may have contributed to the extinction of animals.

  4. The Late Triassic and Late Jurassic stress fields and tectonic transmission of North China craton

    NASA Astrophysics Data System (ADS)

    Hou, Guiting; Wang, Yanxin; Hari, K. R.

    2010-09-01

    The transmission of the tectonic regime from the Paleo-Asian Ocean to the Pacific Ocean during Mesozoic era was reconstructed using the modeling of Late Triassic (T 3) and Late Jurassic (J 3) stress fields employing two dimensional linear finite element models (2-D FEM). The model at T 3 proposes that Qinling-Dabie-Sulu orogens coevally collided and the model J 3 proposes that Subei block continued to collide with the North China block along the Sulu orogen while the collision of the Qinling-Dabie orogen was terminated. The stress fields at T 3 and J 3 during the two episodes were calculated based on mechanical conditions under different deviatoric stresses acting along the boundaries of the North China craton by elastic finite modeling. The transmission between two episodes of stress fields resulted from Qinling-Dabie-Sulu collision between North China and South China in the Late Triassic period, and from continued collision between the Subei block and North China by the NW-trending movement of Izanagi plate during Late Jurassic. The results from modeling of the Mesozoic stress fields of the North China suggest that late Jurassic was the key transmission period of the tectonic regime of the North China block when large scale thrusting triggered the subsequent destruction of the North China craton.

  5. Longitudinal fluvial drainage patterns within a foreland basin-fill: Permo-Triassic Sydney Basin, Australia

    NASA Astrophysics Data System (ADS)

    Cowan, E. Jun

    1993-05-01

    The north-south trending Permo-Triassic Sydney Basin (southern sector of the Sydney-Bowen Basin) is unique compared to many documented retro-arc foreland basins, in that considerable basin-fill was derived from a cratonic source as well as a coeval fold belt source. Quantitative analysis of up-sequence changes in sandstone petrography and palaeoflow directions, together with time-rock stratigraphy of the fluvial basin-fill, indicate two spatially and temporally separated depositional episodes of longitudinal fluvial dispersal systems. A longitudinal drainage-net similar in geometry to the modern Ganga River system (reduced to 60% original size) explains many of the palaeoflow patterns and cross-basinal petrofacies variation recorded in the basin-fill. The Late Permian to Early Triassic rocks reveal a basin-wide southerly directed fluvial drainage system, contemporaneous with east-west shortening recorded in the New England Fold Belt. In contrast, the Middle Triassic strata reveal a change to an easterly directed fluvial system, correlated to a shift in orogenic load to a NW-SE orientation in the fold belt northeast of the basin. The detailed petrofacies variation in the deposits of the second longitudinal fluvial dispersal system reveals vertical jumps in petrofacies compositions, with uniform compositions between jumps. The petrological jumps are interpreted as the result of minor fault adjustments in the fold belt, resulting in changing rates of sediment supply to the foreland basin. Uninterrupted erosion of the same terrain most likely caused the compositional uniformity between jumps. The identification of similar longitudinal fluvial systems, with transverse variation in detrital composition, is likely to help resolve the tectonic history of foreland fold belts elsewhere.

  6. Cyclo-, magneto-, and bio-stratigraphic constraints on the duration of the CAMP event and its relationship to the Triassic-Jurassic boundary

    NASA Astrophysics Data System (ADS)

    Olsen, Paul E.; Kent, Dennis V.; Et-Touhami, Mohammed; Puffer, John

    Early Mesozoic tholeiitic flood basalts of the Central Atlantic Magmatic Province (CAMP) are interbedded throughout much of their extent with cyclical lacustrine strata, allowing Milankovitch calibration of the duration of the extrusive episode. This cyclostratigraphy extends from the Newark basin of the northeastern US, where it was first worked out, to Nova Scotia and Morocco and constrains the outcropping extrusive event to less than 600 ky in duration, beginning roughly 20 ky after the Triassic-Jurassic boundary, and to within one pollen and spore zone and one vertebrate biochron. Based principally on the well-known Newark astronomically calibrated magnetic polarity time scale with new additions from the Hartford basin, the rather large scatter in recent radiometric dates from across CAMP (>10 m.y. ), centering on about ˜200 m.y., is not likely to be real. Rather, the existing paleomagnetic data from both intrusive and extrusive rocks suggest emplacement of nearly all the CAMP within less than 3 m.y. of nearly entirely normal polarity. The very few examples of reversed magnetizations suggest that some CAMP activity probably occurred just prior to the Triassic-Jurassic boundary. Published paleomagnetic and 40Ar/39Ar data from the Clubhouse Crossroads Basalt are reviewed and with new paleomagnetic data suggest that alteration and possible core misorientation could be responsible for the apparent differences with the CAMP. The Clubhouse Crossroads Basalt at the base of the Coastal Plain of South Carolina and Georgia provides a link to the volumetrically massive volcanic wedge of seaward dipping reflectors present in the subsurface off the southeastern US that may be part of the same igneous event, suggesting that the CAMP marks the formation of the oldest Atlantic oceanic crust.

  7. Proportional hazards regression in epidemiologic follow-up studies: an intuitive consideration of primary time scale.

    PubMed

    Cologne, John; Hsu, Wan-Ling; Abbott, Robert D; Ohishi, Waka; Grant, Eric J; Fujiwara, Saeko; Cullings, Harry M

    2012-07-01

    In epidemiologic cohort studies of chronic diseases, such as heart disease or cancer, confounding by age can bias the estimated effects of risk factors under study. With Cox proportional-hazards regression modeling in such studies, it would generally be recommended that chronological age be handled nonparametrically as the primary time scale. However, studies involving baseline measurements of biomarkers or other factors frequently use follow-up time since measurement as the primary time scale, with no explicit justification. The effects of age are adjusted for by modeling age at entry as a parametric covariate. Parametric adjustment raises the question of model adequacy, in that it assumes a known functional relationship between age and disease, whereas using age as the primary time scale does not. We illustrate this graphically and show intuitively why the parametric approach to age adjustment using follow-up time as the primary time scale provides a poor approximation to age-specific incidence. Adequate parametric adjustment for age could require extensive modeling, which is wasteful, given the simplicity of using age as the primary time scale. Furthermore, the underlying hazard with follow-up time based on arbitrary timing of study initiation may have no inherent meaning in terms of risk. Given the potential for biased risk estimates, age should be considered as the preferred time scale for proportional-hazards regression with epidemiologic follow-up data when confounding by age is a concern. PMID:22517300

  8. Tethyan and German Triassic stratigraphy, correlation and numerical ages

    NASA Astrophysics Data System (ADS)

    Kozur, Heinz W.; Bachmann, Gerhard H.

    2010-05-01

    The correlation of the Germanic Triassic with the Tethyan Triassic is well constrained biostratigraphically. However, radiometric data are lacking and have to be imported for numerical calibration of litho- and chronostratigraphic units. These imported data can be extended to intervals without primary numerical data by astronomical calibration with Milankovitch cycles that are well recognisable in continental lake deposits of the Germanic Triassic, and correlated back to the marine realm. Such cross-correlation is a powerful method for improving numerical stage ages in the marine realm. The calculations of numerical ages for the Germanic Lower and Middle Triassic by astronomical calibration are remarkably close to the subsequently published most recent radiometric data of different authors. For the Lower Triassic, up to the base of the Anisian, the 252.5 ± 0.3 Ma for the basal I. isarcica Zone at Meishan (Mundil et al., 2001) was taken as a reference value. On this base, Kozur (2003) calculated a numerical age of 252.6 Ma for the Permian-Triassic boundary, which age was later confirmed with new radiometric data by Mundil et al. (2004). Bachmann & Kozur (2004) correlated the base of the Stammen Beds (= base Thuringian Chirotherium Sandstone) with the Anisian base and calculated for this boundary 247 Ma. Lehrmann et al. (2006) used high-precision single zircon data for determination of the Anisian base at 247.2 Ma. In the mainly marine Germanic Middle Triassic the radiometric data from the Tethyan Middle Triassic can be used after marine biostratigraphic correlation. Both the older (late Illyrian and Ladinian) and newer radiometric data (early and middle Anisian) fit well with the ages calculated by astronomical calibration. The greatest problems are in the Upper Triassic, where very few radiometric data are known. At present there are mutually exclusive ages that have been proposed for the Carnian-Norian boundary, each based on radiometric dates. These conflicting data have produced a "short Norian model" and a "long Norian model." In the SW USA, there are several new radiometric data from which approximately 218 Ma can be calculated for the Norian base (Irmis & Mundil, 2008, and J. Ramezani, CPCP Meeting Albuquerque, May 2009). This value is close to the 216.5 Ma of the Norian base by Gradstein et al. (2004) and Ogg et al. (2008). From these data a duration of the Norian of 10.5-12 myrs results (short Norian model). Such contradicts, however, the 230.91 ± 0.33 Ma for the late early Tuvalian (Furin et al., 2006) and a corrected age of 231.4 Ma for the Tuvalian Adamanian LVF of Ishigualasto, Argentina (Irmis & Mundil, 2008) which would require a minimum duration of the Tuvalian of 14-15.5 myrs. The Tuvalian substage would then be longer than the entire Norian, which seems very improbable. The long Norian model of Gallet et al. (2003) placed the Norian base at ~227 Ma in the lower Stockton Formation of the Newark Basin and estimated the duration of the Norian as ~25 myrs. According to biostratigraphic data this Norian base lies within the middle Tuvalian, and the duration of the Norian is too long. Bachmann & Kozur (2004) and Kozur & Weems (2007) placed the Norian base between 223 to 226 Ma and assumed a Norian duration of 17-20 myrs. These data fit well with the Tuvalian radiometric ages (Lagonegro Basin, Furin et al., 2006; Ishigualasto, Irmis & Mundil, 2008), and with the basal Norian age of 225 ± 3 Ma from Alaska (Gehrels et al., 1987).

  9. A Middle Triassic thoracopterid from China highlights the evolutionary origin of overwater gliding in early ray-finned fishes.

    PubMed

    Xu, Guang-Hui; Zhao, Li-Jun; Shen, Chen-Chen

    2015-01-01

    Gliding adaptations in thoracopterid flying fishes represent a remarkable case of convergent evolution of overwater gliding strategy with modern exocoetid flying fishes, but the evolutionary origin of this strategy was poorly known in the thoracopterids because of lack of transitional forms. Until recently, all thoracopterids, from the Late Triassic of Austria and Italy and the Middle Triassic of South China, were highly specialized 'four-winged' gliders in having wing-like paired fins and an asymmetrical caudal fin with the lower caudal lobe notably larger than the upper lobe. Here, we show that the new genus Wushaichthys and the previously alleged 'peltopleurid' Peripeltopleurus, from the Middle Triassic (Ladinian, 235-242 Ma) of South China and near the Ladinian/Anisian boundary of southern Switzerland and northern Italy, respectively, represent the most primitive and oldest known thoracopterids. Wushaichthys, the most basal thoracopterid, shows certain derived features of this group in the skull. Peripeltopleurus shows a condition intermediate between Wushaichthys and Thoracopterus in having a slightly asymmetrical caudal fin but still lacking wing-like paired fins. Phylogenetic studies suggest that the evolution of overwater gliding of thoracopterids was gradual in nature; a four-stage adaption following the 'cranial specialization-asymmetrical caudal fin-enlarged paired fins-scale reduction' sequence has been recognized in thoracopterid evolution. Moreover, Wushaichthys and Peripeltopleurus bear hooklets on the anal fin of supposed males, resembling those of modern viviparious teleosts. Early thoracopterids probably had evolved a live-bearing reproductive strategy. PMID:25568155

  10. Paleoclimate cycles and tectonic controls on fluvial, lacustrine, and eolian strata in upper Triassic Chinle Formation, San Juan basin

    SciTech Connect

    Dubiel, R.F. )

    1989-09-01

    Sedimentologic study of the Upper Triassic Chinle Formation in the San Juan basin (SJB) indicates that Late Triassic paleoclimate and tectonic movements influenced the distribution of continental lithofacies. The Shinarump, Monitor Butte, and Petrified Forest Members in the lower part of the Chinle consist of complexly interfingered fluvial, floodplain, marsh, and lacustrine rocks; the Owl Rock and Rock Point Members in the upper part consists of lacustrine-basin and eolian sandsheet strata. Facies analysis, vertebrate and invertebrate paleontology, and paleoclimate models demonstrate that the Late Triassic was dominated by tropical monsoonal circulation, which provided abundant precipitation interspersed with seasonally dry periods. Owl Rock lacustrine strata comprise laminated limestones that reflect seasonal monsoonal precipitation and larger scale, interbedded carbonates and fine-grained clastics that represent longer term, alternating wet and dry climatic cycles. Overlying Rock Point eolian sand-sheet and dune deposits indicate persistent alternating but drier climatic cyclicity. Within the Chinle, upward succession of lacustrine, alternating lacustrine/eolian sand-sheet, and eolian sand-sheet/dune deposits reflects an overall decrease in precipitation due to the northward migration of Pangaea out of low latitudes dominated by monsoonal circulation.

  11. A Middle Triassic thoracopterid from China highlights the evolutionary origin of overwater gliding in early ray-finned fishes

    PubMed Central

    Xu, Guang-Hui; Zhao, Li-Jun; Shen, Chen-Chen

    2015-01-01

    Gliding adaptations in thoracopterid flying fishes represent a remarkable case of convergent evolution of overwater gliding strategy with modern exocoetid flying fishes, but the evolutionary origin of this strategy was poorly known in the thoracopterids because of lack of transitional forms. Until recently, all thoracopterids, from the Late Triassic of Austria and Italy and the Middle Triassic of South China, were highly specialized four-winged gliders in having wing-like paired fins and an asymmetrical caudal fin with the lower caudal lobe notably larger than the upper lobe. Here, we show that the new genus Wushaichthys and the previously alleged peltopleurid Peripeltopleurus, from the Middle Triassic (Ladinian, 235242 Ma) of South China and near the Ladinian/Anisian boundary of southern Switzerland and northern Italy, respectively, represent the most primitive and oldest known thoracopterids. Wushaichthys, the most basal thoracopterid, shows certain derived features of this group in the skull. Peripeltopleurus shows a condition intermediate between Wushaichthys and Thoracopterus in having a slightly asymmetrical caudal fin but still lacking wing-like paired fins. Phylogenetic studies suggest that the evolution of overwater gliding of thoracopterids was gradual in nature; a four-stage adaption following the cranial specializationasymmetrical caudal finenlarged paired finsscale reduction sequence has been recognized in thoracopterid evolution. Moreover, Wushaichthys and Peripeltopleurus bear hooklets on the anal fin of supposed males, resembling those of modern viviparious teleosts. Early thoracopterids probably had evolved a live-bearing reproductive strategy. PMID:25568155

  12. A Lagrangian subgrid-scale model with dynamic estimation of Lagrangian time scale for large eddy simulation of complex flows

    NASA Astrophysics Data System (ADS)

    Verma, Aman; Mahesh, Krishnan

    2012-08-01

    The dynamic Lagrangian averaging approach for the dynamic Smagorinsky model for large eddy simulation is extended to an unstructured grid framework and applied to complex flows. The Lagrangian time scale is dynamically computed from the solution and does not need any adjustable parameter. The time scale used in the standard Lagrangian model contains an adjustable parameter θ. The dynamic time scale is computed based on a "surrogate-correlation" of the Germano-identity error (GIE). Also, a simple material derivative relation is used to approximate GIE at different events along a pathline instead of Lagrangian tracking or multi-linear interpolation. Previously, the time scale for homogeneous flows was computed by averaging along directions of homogeneity. The present work proposes modifications for inhomogeneous flows. This development allows the Lagrangian averaged dynamic model to be applied to inhomogeneous flows without any adjustable parameter. The proposed model is applied to LES of turbulent channel flow on unstructured zonal grids at various Reynolds numbers. Improvement is observed when compared to other averaging procedures for the dynamic Smagorinsky model, especially at coarse resolutions. The model is also applied to flow over a cylinder at two Reynolds numbers and good agreement with previous computations and experiments is obtained. Noticeable improvement is obtained using the proposed model over the standard Lagrangian model. The improvement is attributed to a physically consistent Lagrangian time scale. The model also shows good performance when applied to flow past a marine propeller in an off-design condition; it regularizes the eddy viscosity and adjusts locally to the dominant flow features.

  13. The space-time variability and scaling of climate data, climate models and their converge as functions of space-time scale

    NASA Astrophysics Data System (ADS)

    Lovejoy, Shaun; Elias, Lydia

    2014-05-01

    Climate models are evaluated by comparing them with other models and (when possible), with climate data: one attempts to match the data and numerics as closely as possible pixel by pixel, time step by time step- i.e. deterministically. As a consequence very little attention has been paid to understanding the space-time statistical properties of the models and data. There is little understanding of the convergence of the model and data to their 'climates' and to each other. In the time domain, there is no objective definition of the distinction between weather and climate in the spatial domain, there is corresponding lack of understanding of climate regions. In order to overcome this, we systematically study the statistics of fluctuations (primarily of temperature but also precipitation and pressure) as function of space and time. For both data and models, we find that in space, that fluctuations increase up to about 5000 km before starting to decrease; this quantitatively defines the typical size of regional climates. In time, we find that fluctuations decrease out to about 10-30 years in the industrial epoch, out to 50 -100 years in the pre-industrial epoch and then starts to increase; this defines the difference between 'macroweather' and the climate. Applying fluctuation analysis to longer time scales, we examine last millennium simulations from four GCMs, we show that control runs only reproduce macroweather. When various (reconstructed) climate forcings are included, in the recent (industrial) period they show global fluctuations strongly increasing at scales >_10-30 yr, which is quite close to the observations. However, in the preindustrial period we find that the multicentennial variabilities are too weak and by analysing the scale dependence of solar and volcanic forcings, we argue that these forcings are unlikely to be sufficiently strong to account for the multicentennial and longer-scale temperature variability. A likely explanation is that the models lack important slow 'climate' processes such as land ice or various biogeochemical processes. This technique can be used to show that the error in estimating the global temperature is about 0.03K, and this - surprisingly - at any time scale out to over 100 years. Similarly, in space the different surface temperature only start to converge (i.e. to agree with each other) at scales larger than ? 2000 km. The same fluctuation analysis technique can be used to quantify the convergence of the models to the model climates and to the real climate. By comparing different realizations of the NASA GISS model historical simulations (from 1850), we show that in time, they converge to each other (i.e. to the model climate) at the slow rate ?t-0.3; however in space, they diverge up to about 5000km (? ?t0.4) only converging to their climate at larger scales, this 'continental scale' is thus the smallest scale that can be attained by climate models and this likely imposes a fundamental limit on regional skill. By comparing the model to the data (20C reanalysis), we find that the two differ by between 1 and 2K at all space and time scales - beyond about 8 months, temporal averaging does not improve agreement, nor does spatial averaging help much. However, if the long tem averages are know and removed - so that one considers anomalies - space-time statistics of the model and the data are remarkably similar. This indicates that the model produces space-time fields of similar type to the data, but that the model and real climates are significantly different.

  14. Duration and Eruptive Chronology of CAMP: Implications for Central Atlantic Rifting and the Triassic-Jurassic Boundary

    NASA Astrophysics Data System (ADS)

    Nomade, S.; Knight, K. B.; Beutel, E.; Renne, P. R.; Verati, C.; Feraud, G.; Marzoli, A.

    2005-12-01

    The Central Atlantic Magmatic Province (CAMP) is among the largest igneous provinces on Earth, emplaced synchronously with or just prior to the Triassic-Jurassic boundary ca. 200 Ma. In great part due to the controversial connection between the occurrence of CAMP and the events of the Triassic-Jurassic boundary, the demand for better constraints on the duration and eruptive chronology of this province has increased. A careful review and selection of available ages, as well as 16 new ages from the Carolinas, Newark basin (US), French Guyana and Morocco are presented. Judicious selection yields a total of 59 dates for CAMP, ranging from 202 to 190 Ma covering every part of the CAMP. Extrusive activity commenced abruptly around 200 Ma, reaching peak volume and intensity around 199 Ma on the African margin. The main period of CAMP magmatism is confirmed as brief, but is suggested to consist of at least two phases over 1.5 Ma, during which time data suggest a southward migration of the magmatism from the Africa-North American margins towards South America. Two volumetrically minor, but distinctive magmatic peaks at 195 and 192 Ma are mirrored in data from all three continents, highlighted by our statistical approach. Despite significant advances in our understanding of the chronology of CAMP, we emphasize that the lack of a well-defined Triassic-Jurassic boundary age, as well as an absence of relevant comparison between U/Pb and Ar/Ar data for this time period remain limiting factors to unambiguously linking CAMP in time with the events of the Triassic-Jurassic boundary.

  15. Modelling soil carbon movement by erosion over large scales and long time periods

    NASA Astrophysics Data System (ADS)

    Quinton, John; Davies, Jessica; Tipping, Ed

    2014-05-01

    Agricultural intensification accelerates physical erosion rates and the transport of carbon within the landscape. In order to improve understanding of how past, present and future anthropogenic land-use change has and will influence carbon and nutrient cycling, it is necessary to develop quantitative tools that can predict soil erosion and carbon movement at large temporal and spatial scales, that are consistent with the time constants of biogeochemical processes and the spatial scales of land-use change and natural resources. However, representing erosion and its impact on the carbon cycle over large spatial scales and long time periods is challenging. Erosion and sediment transport processes operate at multiple spatial and temporal scales with splash erosion dominating at the sub-plot scale and occurring within seconds, up to gully formation operating at field-catchment scales over days to months. In addition, most erosion production observations are made at the experimental plot scale, where fine time scales and detailed processes dominate. This is coupled with complexities associated with carbon detachment, decomposition and uncertainties surrounding carbon burial rates and stability - all of which occur over widely different temporal and spatial scales. As such, these data cannot be simply scaled to inform erosion and carbon representation at the regional scale, where topography, vegetation cover and landscape organisation become more important controls on sediment fluxes. We have developed a simple energy-based regional scale method of soil erosion modelling, which is integration into a hydro-biogeochemical model that will simulate carbon, nitrogen and phosphorus pools and fluxes across the UK from the industrial revolution to the present day. The model is driven by overland flow, dynamic vegetation cover, soil properties, and topographic distributions and produces sediment production and yield at the 5km grid scale. In this paper we will introduce the modelling approach and examine some of the challenges facing attempts to erosion and carbon transport processes at larger spatial and temporal scales.

  16. Studying the time scale dependence of environmental variables predictability using fractal analysis.

    PubMed

    Yuval; Broday, David M

    2010-06-15

    Prediction of meteorological and air quality variables motivates a lot of research in the atmospheric sciences and exposure assessment communities. An interesting related issue regards the relative predictive power that can be expected at different time scales, and whether it vanishes altogether at certain ranges. An improved understanding of our predictive powers enables better environmental management and more efficient decision making processes. Fractal analysis is commonly used to characterize the self-affinity of time series. This work introduces the Continuous Wavelet Transform (CWT) fractal analysis method as a tool for assessing environmental time series predictability. The high temporal scale resolution of the CWT enables detailed information about the Hurst parameter, a common temporal fractality measure, and thus about time scale variations in predictability. We analyzed a few years records of half-hourly air pollution and meteorological time series from which the trivial seasonal and daily cycles were removed. We encountered a general trend of decreasing Hurst values from about 1.4 (good autocorrelation and predictability), in the sub-daily time scale to 0.5 (which implies complete randomness) in the monthly to seasonal scales. The air pollutants predictability follows that of the meteorological variables in the short time scales but is better at longer scales. PMID:20465249

  17. Time scale of dynamic heterogeneity in model ionic liquids and its relation to static length scale and charge distribution.

    PubMed

    Park, Sang-Won; Kim, Soree; Jung, YounJoon

    2015-11-21

    We study how dynamic heterogeneity in ionic liquids is affected by the length scale of structural relaxation and the ionic charge distribution by the molecular dynamics simulations performed on two differently charged models of ionic liquid and their uncharged counterpart. In one model of ionic liquid, the charge distribution in the cation is asymmetric, and in the other it is symmetric, while their neutral counterpart has no charge with the ions. It is found that all the models display heterogeneous dynamics, exhibiting subdiffusive dynamics and a nonexponential decay of structural relaxation. We investigate the lifetime of dynamic heterogeneity, ?(dh), in these systems by calculating the three-time correlation functions to find that ?(dh) has in general a power-law behavior with respect to the structural relaxation time, ?(?), i.e., ?(dh) ? ?(?)(?(dh)). Although the dynamics of the asymmetric-charge model is seemingly more heterogeneous than that of the symmetric-charge model, the exponent is found to be similar, ?(dh) ? 1.2, for all the models studied in this work. The same scaling relation is found regardless of interactions, i.e., with or without Coulomb interaction, and it holds even when the length scale of structural relaxation is long enough to become the Fickian diffusion. This fact indicates that ?(dh) is a distinctive time scale from ?(?), and the dynamic heterogeneity is mainly affected by the short-range interaction and the molecular structure. PMID:26467181

  18. Integration of molecules and new fossils supports a Triassic origin for Lepidosauria (lizards, snakes, and tuatara)

    PubMed Central

    2013-01-01

    Background Lepidosauria (lizards, snakes, tuatara) is a globally distributed and ecologically important group of over 9,000 reptile species. The earliest fossil records are currently restricted to the Late Triassic and often dated to 227 million years ago (Mya). As these early records include taxa that are relatively derived in their morphology (e.g. Brachyrhinodon), an earlier unknown history of Lepidosauria is implied. However, molecular age estimates for Lepidosauria have been problematic; dates for the most recent common ancestor of all lepidosaurs range between approximately 226 and 289 Mya whereas estimates for crown-group Squamata (lizards and snakes) vary more dramatically: 179 to 294 Mya. This uncertainty restricts inferences regarding the patterns of diversification and evolution of Lepidosauria as a whole. Results Here we report on a rhynchocephalian fossil from the Middle Triassic of Germany (Vellberg) that represents the oldest known record of a lepidosaur from anywhere in the world. Reliably dated to 238–240 Mya, this material is about 12 million years older than previously known lepidosaur records and is older than some but not all molecular clock estimates for the origin of lepidosaurs. Using RAG1 sequence data from 76 extant taxa and the new fossil specimens two of several calibrations, we estimate that the most recent common ancestor of Lepidosauria lived at least 242 Mya (238–249.5), and crown-group Squamata originated around 193 Mya (176–213). Conclusion A Early/Middle Triassic date for the origin of Lepidosauria disagrees with previous estimates deep within the Permian and suggests the group evolved as part of the faunal recovery after the end-Permain mass extinction as the climate became more humid. Our origin time for crown-group Squamata coincides with shifts towards warmer climates and dramatic changes in fauna and flora. Most major subclades within Squamata originated in the Cretaceous postdating major continental fragmentation. The Vellberg fossil locality is expected to become an important resource for providing a more balanced picture of the Triassic and for bridging gaps in the fossil record of several other major vertebrate groups. PMID:24063680

  19. A multiscale mass scaling approach for explicit time integration using proper orthogonal decomposition

    SciTech Connect

    G. J. de Frias; W. Aquino; K. H. Pierson; M. W. Heinstein; B. W. Spencer

    2014-03-01

    One of the main computational issues with explicit dynamics simulations is the significant reduction of the critical time step as the spatial resolution of the finite element mesh increases. In this work, a selective mass scaling approach is presented that can significantly reduce the computational cost in explicit dynamic simulations, while maintaining accuracy. The proposed method is based on a multiscale decomposition approach that separates the dynamics of the system into low (coarse scales) and high frequencies (fine scales). Here, the critical time step is increased by selectively applying mass scaling on the fine scale component only. In problems where the response is dominated by the coarse (low frequency) scales, significant increases in the stable time step can be realized. In this work, we use the proper orthogonal decomposition (POD) method to build the coarse scale space. The main idea behind POD is to obtain an optimal low-dimensional orthogonal basis for representing an ensemble of high-dimensional data. In our proposed method, the POD space is generated with snapshots of the solution obtained from early times of the full-scale simulation. The example problems addressed in this work show significant improvements in computational time, without heavily compromising the accuracy of the results.

  20. Volcanism as the cause for the Triassic-Jurassic mass-extinction? Progress of the CoBi workgroup

    NASA Astrophysics Data System (ADS)

    Deenen, M. H.; Bonis, N. R.; Ruhl, M.; Krschner, W. M.; Krijgsman, W.; Reitsma, M.; van Bergen, M. J.; Chellai, E.

    2008-12-01

    The Triassic-Jurassic mass-extinction (200 Ma), one of the most severe of the Phanerozoic with 50% marine genera loss, coincides with a period of extensive volcanism related to the initial break-up of Pangaea. A causal relationship, however, is still debated since the North American basalt units are always found above a major palynological turnover. In addition there is no conclusive correlation with marine sections where the mass extinction coincides with two distinct negative carbon-isotope shifts preceding the first Jurassic ammonites. Here we develop an accurate time-frame for the Triassic-Jurassic boundary events by integrating astrochronology and geobiology and we show that the onset of volcanism is most likely responsible for the major turnover in palynology, a modest anomaly in Iridium, a major perturbation in the carbon-isotopes values and the extinction events recorded in conodonts and terrestrial vertebrates

  1. Scaling Behavior of the First Arrival Time of a Random-Walking Magnetic Domain

    SciTech Connect

    Im, M.-Y.; Lee, S.-H.; Kim, D.-H.; Fischer, P.; Shin, S.-C.

    2008-02-04

    We report a universal scaling behavior of the first arrival time of a traveling magnetic domain wall into a finite space-time observation window of a magneto-optical microscope enabling direct visualization of a Barkhausen avalanche in real time. The first arrival time of the traveling magnetic domain wall exhibits a nontrivial fluctuation and its statistical distribution is described by universal power-law scaling with scaling exponents of 1.34 {+-} 0.07 for CoCr and CoCrPt films, despite their quite different domain evolution patterns. Numerical simulation of the first arrival time with an assumption that the magnetic domain wall traveled as a random walker well matches our experimentally observed scaling behavior, providing an experimental support for the random-walking model of traveling magnetic domain walls.

  2. Using Focused Regression for Accurate Time-Constrained Scaling of Scientific Applications

    SciTech Connect

    Barnes, B; Garren, J; Lowenthal, D; Reeves, J; de Supinski, B; Schulz, M; Rountree, B

    2010-01-28

    Many large-scale clusters now have hundreds of thousands of processors, and processor counts will be over one million within a few years. Computational scientists must scale their applications to exploit these new clusters. Time-constrained scaling, which is often used, tries to hold total execution time constant while increasing the problem size along with the processor count. However, complex interactions between parameters, the processor count, and execution time complicate determining the input parameters that achieve this goal. In this paper we develop a novel gray-box, focused median prediction errors are less than 13%. regression-based approach that assists the computational scientist with maintaining constant run time on increasing processor counts. Combining application-level information from a small set of training runs, our approach allows prediction of the input parameters that result in similar per-processor execution time at larger scales. Our experimental validation across seven applications showed that median prediction errors are less than 13%.

  3. Scaling behavior of the first arrival time of a random-walking magnetic domain.

    PubMed

    Im, M-Y; Lee, S-H; Kim, D-H; Fischer, P; Shin, S-C

    2008-04-25

    We report a universal scaling behavior of the first arrival time of a traveling magnetic domain wall into a finite space-time observation window of a magneto-optical microscope enabling direct visualization of a Barkhausen avalanche in real time. The first arrival time of the traveling magnetic domain wall exhibits a nontrivial fluctuation and its statistical distribution is described by universal power-law scaling with scaling exponents of 1.34+/-0.07 for CoCr and CoCrPt films, despite their quite different domain evolution patterns. Numerical simulation of the first arrival time with an assumption that the magnetic domain wall traveled as a random walker well matches our experimentally observed scaling behavior, providing an experimental support for the random-walking model of traveling magnetic domain walls. PMID:18518241

  4. A wavelet based approach to measure and manage contagion at different time scales

    NASA Astrophysics Data System (ADS)

    Berger, Theo

    2015-10-01

    We decompose financial return series of US stocks into different time scales with respect to different market regimes. First, we examine dependence structure of decomposed financial return series and analyze the impact of the current financial crisis on contagion and changing interdependencies as well as upper and lower tail dependence for different time scales. Second, we demonstrate to which extent the information of different time scales can be used in the context of portfolio management. As a result, minimizing the variance of short-run noise outperforms a portfolio that minimizes the variance of the return series.

  5. Geomorphological stability of Permo-Triassic albitized profiles - case study of the Montseny-Guilleries High (NE Iberia)

    NASA Astrophysics Data System (ADS)

    Parcerisa, D.; Casas, L.; Franke, C.; Gomez-Gras, D.; Lacasa, G.; Nunez, J. A.; Thiry, M.

    2010-05-01

    Massif paleoalteration profiles (≥ 200 m) occur in the upper parts of the Montseny-Guilleries High (NE Catalan Coastal Ranges). The profiles consist of hard albitized-chloritized-hematized facies in the lower part and softer kaolinized-hematized facies in the upper part of the section. Preliminary paleomagnetic data show Triassic ages for both, the albitized and the kaolinized parts, and point to a surficial formation altered under oxidising conditions. Similar paleoalteration profiles have already been described and dated to Triassic ages elsewhere in Europe [Schmitt, 1992; Ricordel et al., 2007; Parcerisa et al., 2009]. These Permian-Triassic alterations are following a succession of different mineral transformations from the top to the base of the profile: 1) Red facies are defined by an increase in the amount and size of haematite crystals leading to the red colour of the rocks. The increase on haematite content is pervasively affecting the whole rock and is accompanied by the kaolinitization of the feldspars. 2) Pink facies: here, the granite shows an uniform pink colouration, which is mainly due to the albitization of the primary Ca-bearing plagioclases, accompanied by a precipitation of minute haematite, sericite, and calcite crystals inside the albite. Additionally primary biotite is fully chloritized. The pink granites are much more resistant to the present-day weathering than the "unaltered" facies at the base of the profile. 3) Spotted facies is characterized by a partial alteration of the rock, which caused a pink-screened aspect to the rock. The alteration developed along the fractures and is less well developed or absent in the non-fractured zones. In the pink-screened facies, the plagioclases are partially albitized and contain numerous hematite inclusions. Biotites are usually almost entirely chloritized. 4) Unaltered facies: These granites are coloured white to greyish, containing plagioclase and K-feldspar that do not show any trace of albitization. Biotites are not or weakly chloritized. However, these "unaltered" (or primary) granites are strongly weathered into granite boulders embedded in grus by the present-day climatic conditions. The maturest paleoprofiles occur at the northern part of the Catalan Coastal Ranges (i.e. the Montseny-Guilleries High) where the Variscan basement remained exposed during Triassic times. Towards the South the profiles progressively disappear and Triassic sediments acquire their maximum thickness here. The alteration profiles are related with the Permo-Triassic paleosurface still outcroping on wide areas [Gómez-Gras and Ferrer, 1999]. They are partially covered by Triassic fluvial sandstones (Buntsandstein facies) in the South [Gómez-Gras, 1993] and by Palaeocene alluvial conglomerates in the West [Anadón et al., 1979]. The Triassic paleosurface shows a remarkable stability successively outcropping during Mesozoic and Tertiary times, the pre-Tertiary exhumation and even the present day weathering affected very little these albitized profiles. The hardness and thus preservation of the Triassic paleosurface is mainly related to the albitization. The albitized granites are entirely lacking anorthitic plagioclase, which is much more sensitive to chemo-mechanical weathering. Development of albite and additional chloritization of the primary biotite crystals render the rocks much more resistant to weathering and erosion. This stability is particularly well expressed in case of the Montseny-Guilleries High, which is limited by a high fault scarp at the south-eastern margin. The albitized top of the scarp shows remarkably hard fresh rocks, whereas the base of the scarp (formed of primary, non-albitized facies) is deeply weathered into gruss. This is causing much smother landscape reliefs in the valleys and thalwegs. Since a long time the remarkable persistence of the Triassic paleosurface expressed in the Paleozoic massifs has been highlighted by geomorphologists. Only recently we could draw the link of the paleosurface preservation to its albitisation [Battiau-Queney, 1996; Widdowson, 1997]. Anadón, P., Colombo, F., Esteban, M., Marzo, M., Robles, S., Santanach, P., Solé-Sugrañes, L.., 1979. Evolución tectonostratigráfica de los Catalánides. Acta Geológica Hispánica, 14: 242-270. Battiau-Queney Y., 1996, A tentative classification of paleoweathering formations based on geomorphological criteria. Geomorphology, 16, p. 87-102. Gómez-Gras, D., 1993. El Permotrias de la Cordillera Costero Catalana: facies y petrologia sedimentaria (Parte I). Boletin Geologico y Minero, 104(2): 115-161. Gómez-Gras, D., Ferrer, C., 1999. Caracterización petrológica de perfiles de meteorización antiguos desarrollados en granitos tardihercínicos de la Cordillera Costero Catalana. Revista de la Sociedad Geológica de España, 12(2): 281-299. Parcerisa, D., Thiry, M., Schmitt, J.M., 2009. Albitisation related to the Triassic unconformity in igneous rocks of the Morvan Massif (France). International Journal of Earth Sciences (Geol Rundsch). DOI 10.1007/s00531-008-0405-1 Ricordel, C., Parcerisa, D., Thiry, M., Moreau, M.G., Gómez-Gras, D., 2007. Triassic magnetic overprints related to albitization in granites from the Morvan massif (France). Palaeogeography, Palaeoclimatology, Palaeoecology, 251: 268-282. Schmitt J.M., 1992, Triassic albitization in southern France : an unusual mineralogical record from a major continental paleosurface. in : Mineralogical and geochemical records of paleoweathering, IGCP 317, Schmitt J.M., Gall Q., (eds), E.N.S.M.P. Mém. Sc. de la Terre, 18, p. 115-132. Widdowson M., 1997, The geomorphological and geological importance of palaeosurfaces. in: Widdowson M. (ed.), Palaeosurfaces: recognition, reconstruction and palaeoenvironmental interpretation. Geol. Soc. Special Publ., 120, p. 1-12.

  6. Correlation transfer in stochastically driven neural oscillators over long and short time scales.

    PubMed

    Abouzeid, Aushra; Ermentrout, Bard

    2011-12-01

    In the absence of synaptic coupling, two or more neural oscillators may become synchronized by virtue of the statistical correlations in their noisy input streams. Recent work has shown that the degree of correlation transfer from input currents to output spikes depends not only on intrinsic oscillator dynamics, but also on the length of the observation window over which the correlation is calculated. In this paper we use stochastic phase reduction and regular perturbations to derive the correlation of the total phase elapsed over long time scales, a quantity that provides a convenient proxy for the spike count correlation. Over short time scales, we derive the spike count correlation directly using straightforward probabilistic reasoning applied to the density of the phase difference. Our approximations show that output correlation scales with the autocorrelation of the phase resetting curve over long time scales. We also find a concise expression for the influence of the shape of the phase resetting curve on the initial slope of the output correlation over short time scales. These analytic results together with numerical simulations provide new intuitions for the recent counterintuitive finding that type I oscillators transfer correlations more faithfully than do type II over long time scales, while the reverse holds true for the better understood case of short time scales. PMID:22304123

  7. Time scale defined by the fractal structure of the price fluctuations in foreign exchange markets

    NASA Astrophysics Data System (ADS)

    Kumagai, Yoshiaki

    2010-04-01

    In this contribution, a new time scale named C-fluctuation time is defined by price fluctuations observed at a given resolution. The intraday fractal structures and the relations of the three time scales: real time (physical time), tick time and C-fluctuation time, in foreign exchange markets are analyzed. The data set used is trading prices of foreign exchange rates; US dollar (USD)/Japanese yen (JPY), USD/Euro (EUR), and EUR/JPY. The accuracy of the data is one minute and data within a minute are recorded in order of transaction. The series of instantaneous velocity of C-fluctuation time flowing are exponentially distributed for small C when they are measured by real time and for tiny C when they are measured by tick time. When the market is volatile, for larger C, the series of instantaneous velocity are exponentially distributed.

  8. Mastering Uncertainty and Risk at Multiple Time Scales in the Future Electrical Grid

    SciTech Connect

    Chertkov, Michael; Bent, Russell W.; Backhaus, Scott N.

    2012-07-10

    Today's electrical grids enjoy a relatively clean separation of spatio-temporal scales yielding a compartmentalization of grid design, optimization, control and risk assessment allowing for the use of conventional mathematical tools within each area. In contrast, the future grid will incorporate time-intermittent renewable generation, operate via faster electrical markets, and tap the latent control capability at finer grid modeling scales; creating a fundamentally new set of couplings across spatiotemporal scales and requiring revolutionary advances in mathematics techniques to bridge these scales. One example is found in decade-scale grid expansion planning in which today's algorithms assume accurate load forecasts and well-controlled generation. Incorporating intermittent renewable generation creates fluctuating network flows at the hourly time scale, inherently linking the ability of a transmission line to deliver electrical power to hourly operational decisions. New operations-based planning algorithms are required, creating new mathematical challenges. Spatio-temporal scales are also crossed when the future grid's minute-scale fluctuations in network flows (due to intermittent generation) create a disordered state upon which second-scale transient grid dynamics propagate effectively invalidating today's on-line dynamic stability analyses. Addressing this challenge requires new on-line algorithms that use large data streams from new grid sensing technologies to physically aggregate across many spatial scales to create responsive, data-driven dynamic models. Here, we sketch the mathematical foundations of these problems and potential solutions.

  9. Ophiuroids Discovered in the Middle Triassic Hypersaline Environment

    PubMed Central

    Salamon, Mariusz A.; Nied?wiedzki, Robert; Lach, Rafa?; Brachaniec, Tomasz; Gorzelak, Przemys?aw

    2012-01-01

    Echinoderms have long been considered to be one of the animal phyla that is strictly marine. However, there is growing evidence that some recent species may live in either brackish or hypersaline environments. Surprisingly, discoveries of fossil echinoderms in non-(open)marine paleoenvironments are lacking. In Wojkowice Quarry (Southern Poland), sediments of lowermost part of the Middle Triassic are exposed. In limestone layer with cellular structures and pseudomorphs after gypsum, two dense accumulations of articulated ophiuroids (Aspiduriella similis (Eck)) were documented. The sediments with ophiuroids were formed in environment of increased salinity waters as suggested by paleontological, sedimentological, petrographical and geochemical data. Discovery of Triassic hypersaline ophiuroids invalidates the paleontological assumption that fossil echinoderms are indicators of fully marine conditions. Thus caution needs to be taken when using fossil echinoderms in paleoenvironmental reconstructions. PMID:23185442

  10. Factor Structure and Scale Reliabilities of the Adjective Check List Across Time

    ERIC Educational Resources Information Center

    Miller, Stephen H.; And Others

    1978-01-01

    Investigated factor structure and scale reliabilities of Gough's Adjective Check List (ACL) and their stability over time. Employees in a community mental health center completed the ACL twice, separated by a one-year interval. After each administration, separate factor analyses were computed. All scales had highly significant test-retest…

  11. Factor Structure and Scale Reliabilities of the Adjective Check List Across Time

    ERIC Educational Resources Information Center

    Miller, Stephen H.; And Others

    1978-01-01

    Investigated factor structure and scale reliabilities of Gough's Adjective Check List (ACL) and their stability over time. Employees in a community mental health center completed the ACL twice, separated by a one-year interval. After each administration, separate factor analyses were computed. All scales had highly significant test-retest

  12. Time scales of porphyry Cu deposit formation: insights from titanium diffusion in quartz

    USGS Publications Warehouse

    Mercer, Celestine N.; Reed, Mark H.; Mercer, Cameron M.

    2015-01-01

    Porphyry dikes and hydrothermal veins from the porphyry Cu-Mo deposit at Butte, Montana, contain multiple generations of quartz that are distinct in scanning electron microscope-cathodoluminescence (SEM-CL) images and in Ti concentrations. A comparison of microprobe trace element profiles and maps to SEM-CL images shows that the concentration of Ti in quartz correlates positively with CL brightness but Al, K, and Fe do not. After calibrating CL brightness in relation to Ti concentration, we use the brightness gradient between different quartz generations as a proxy for Ti gradients that we model to determine time scales of quartz formation and cooling. Model results indicate that time scales of porphyry magma residence are ~1,000s of years and time scales from porphyry quartz phenocryst rim formation to porphyry dike injection and cooling are ~10s of years. Time scales for the formation and cooling of various generations of hydrothermal vein quartz range from 10s to 10,000s of years. These time scales are considerably shorter than the ~0.6 m.y. overall time frame for each porphyry-style mineralization pulse determined from isotopic studies at Butte, Montana. Simple heat conduction models provide a temporal reference point to compare chemical diffusion time scales, and we find that they support short dike and vein formation time scales. We interpret these relatively short time scales to indicate that the Butte porphyry deposit formed by short-lived episodes of hydrofracturing, dike injection, and vein formation, each with discrete thermal pulses, which repeated over the ~3 m.y. generation of the deposit.

  13. A Dynamically Computed Convective Time Scale for the Kain–Fritsch Convective Parameterization Scheme

    EPA Science Inventory

    Many convective parameterization schemes define a convective adjustment time scale τ as the time allowed for dissipation of convective available potential energy (CAPE). The Kain–Fritsch scheme defines τ based on an estimate of the advective time period for deep con...

  14. Metamorphism of Triassic sediments from the Dunbarton Basin, South Carolina

    SciTech Connect

    Snipes, D.S.; Warner, R.D. . Earth Sciences Dept.); Price, V. Jr. ); Thayer, P. . Geology Dept.)

    1993-03-01

    Modal analyses and microprobe studies were performed on eight core samples obtained from the US Geological Survey Well A1 324. The well is situated in the southern part of the buried Triassic Dunbarton Basin, about 1 km south of the US Department of Energy's Westinghouse Savannah River Company Site. The samples came from an interval of 407.0--413.4 m beneath the land surface. At the well site, Triassic red beds are overlain by Late Cretaceous and Tertiary sediments which have an aggregate thickness of 408 m. The sample from a depth of 407 m is a weathered, poorly sorted, clayey sandstone from the basal portion of the Late Cretaceous Cape Fear Formation. This specimen is not metamorphosed; whereas, the Triassic specimens taken from an interval of 411.6--413.4 m exhibit evidence of thermal metamorphism as well as hydrothermal alteration. In hand specimen, three of the samples (412.8--413.4 m) resemble hornfelses. These samples exhibit decussate texture. Results of modal analyses of the two deepest specimens follow: plagioclase (43-52%), quartz (9-23%), chlorite (22-29%), epidote (1-6%), hematite (3-4%), and magnetite (2-3%). Relict detrital quartz grains, especially the finer ones, are mostly angular-to-subangular and the grain boundaries show little evidence of rounding. The authors feel that hydrothermal alteration was the principal metamorphic process. This belief is supported by the fact that most of the plagioclase has undergone extensive sericitization. In addition, the presence of abundant chlorite together with a minor amount of epidote supports this interpretation. The alteration halo extends upward for 1.8 m. This interpretation is based on the observation that two Triassic arkose sandstone specimens (411.6 m, 412.2 m) contain clouded, slightly sericitized K-feldspar and plagioclase grains in a matrix of red-colored smectite.

  15. The Triassic section north of Currie, Elko County, Nevada

    SciTech Connect

    Lucas, S.G.; Goodspeed, T.H. )

    1993-04-01

    More than 600 m of Triassic strata are exposed just N of Currie, Nevada in secs. 8--9 T29N, R64E. The Thaynes Formation is 468 m of limestone, calcareous shale and siltstone that rest disconformably on the Permian Gerster Formation. A 7.7-m-thick interval of ammonite packstones is 8.8 m above the base of the Thaynes in the NW1/4NW1/SW1/4 sec. 8. Ammonites from these packstones indicate the Tardus Zone of late Smithian age. The Shinarump Formation of the Chinle Group (Upper Triassic) disconformably overlies the Thaynes Formation and is 19.4 m of trough-crossbedded, silica-pebble conglomerate and quartzarenite with silicified wood in the SW1/4SW1/4SW1/4 sec. 9. Shinarump crossbeds dip to the N. Chinle Group strata above the Shinarump are 169.2 m thick and consist of reddish brown siltstone, fine sandstone and minor micritic limestone. Ripple laminations and horizontal bedding are the dominant bedforms. These strata are assigned to the Rock Point Formation, the top of which is cut by a fault N of Currie. Upper Triassic nonmarine strata north of Currie are the northwesternmost outcrops of the Chinle Group. Rock Point strata here are tidal flat facies that indicate proximity of the Late Triassic shoreline in northeastern Nevada. However, it is likely that the Chinle Group strata N of Currie are allochthonous, having been originally deposited to the E in what is now Utah.

  16. NEA Scout Solar Sail: Half-scale Fold Time Lapse - Duration: 37 seconds.

    NASA Video Gallery

    In this time lapse, the Near-Earth Asteroid Scout (NEA Scout) CubeSat team rolls a half-scale prototype of the small satellite's solar sail in preparation for a deployment test. During its mission,...

  17. Sensitivity of Southern Ocean overturning to wind stress changes: Role of surface restoring time scales

    NASA Astrophysics Data System (ADS)

    Zhai, Xiaoming; Munday, David R.

    2014-12-01

    The influence of different surface restoring time scales on the response of the Southern Ocean overturning circulation to wind stress changes is investigated using an idealised channel model. Regardless of the restoring time scales chosen, the eddy-induced meridional overturning circulation (MOC) is found to compensate for changes of the direct wind-driven Eulerian-mean MOC, rendering the residual MOC less sensitive to wind stress changes. However, the extent of this compensation depends strongly on the restoring time scale: residual MOC sensitivity increases with decreasing restoring time scale. Strong surface restoring is shown to limit the ability of the eddy-induced MOC to change in response to wind stress changes and as such suppresses the eddy compensation effect. These model results are consistent with qualitative arguments derived from residual-mean theory and may have important implications for interpreting past and future observations.

  18. Approximate solution of the probability density function of bedload transport rate over multiple time scales

    NASA Astrophysics Data System (ADS)

    Fu, X.; Ma, H.; Heyman, J.; Mettra, F.; Ancey, C.

    2013-12-01

    Bedload transport rate in mountain rivers is highly fluctuating and has strong stochastic behavior even under steady flow conditions. Its stochastic description thus offers deeper insights into its dynamics than the deterministic one. As a random quantity, it is sampled from experimental devices at a given time resolution i.e. the sampling time scale. Previous studies showed that bedload transport behaves as a scale-dependent process. (Singh et al., 2009). In this study, we report bedload transport rate characteristics over different sampling time scales from an experimental study. Then, starting from Ancey's Markov model (Ancey et al., 2008), we propose a theoretical expression for bedload transport rate that is valid across multiple sampling time scales. Although the complete probability density function(PDF) cannot be analytically obtained, all

  19. Palaeo-equatorial temperatures and carbon-cycle evolution at the Triassic- Jurassic boundary: A stable isotope perspective from shallow-water carbonates from the UAE

    NASA Astrophysics Data System (ADS)

    Honig, M. R.; John, C. M.

    2013-12-01

    The Triassic-Jurassic boundary was marked by global changes including carbon-cycle perturbations and the opening of the Atlantic Ocean. These changes were accompanied by one of the major extinction events of the Phanerozoic. The carbon-cycle perturbations have been recorded in carbon isotope curves from bulk carbonates, organic carbon and fossil wood in several Tethyan locations and have been used for chemostratigraphic purposes. Here we present data from shallow-marine carbonates deposited on a homoclinal Middle Eastern carbonate ramp (United Arab Emirates). Our site was located at the equator throughout the Late Triassic and the Early Jurassic, and this study provides the first constraints of environmental changes at the low-latitudes for the Triassic-Jurassic boundary. Shallow-marine carbonate depositional systems are extremely sensitive to palaeoenvironmental changes and their usefulness for chemostratigraphy is being debated. However, the palaeogeographic location of the studied c