These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Magnetostratigraphic dating of the proposed Rhaetian GSSP at Steinbergkogel (Upper Triassic, Austria): Implications for the Late Triassic time scale  

E-print Network

The Late Triassic period is characterized by increasingenvironmental stress that eventually culminatedMagnetostratigraphic dating of the proposed Rhaetian GSSP at Steinbergkogel (Upper Triassic, Austria): Implications for the Late Triassic time scale Silja K. Hüsing , Martijn H.L. Deenen, Jort G

Utrecht, Universiteit

2

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)

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.

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

3

Early Triassic magnetic polarity time scale—integration of magnetostratigraphy, ammonite zonation and sequence stratigraphy from stratotype sections (Canadian Arctic Archipelago)  

NASA Astrophysics Data System (ADS)

Stratotypes defining the stages of the Early Triassic (Griesbachian, Dienerian, Smithian and Spathian) are located on Ellesmere and Axel Heiberg islands in the northern Canadian Arctic. Ammonite-rich horizons are within a clastic outer shelf-to-slope facies of thick progradational wedges of mudstones and siltstones. Three sections were sampled for magnetostratigraphy and interpreted for transgressive and regressive pulses of sedimentation. Using the ammonite zonation as a guide, the transgressive-regressive cycles and magnetostratigraphies have been correlated among the sections and to the published Triassic sequence stratigraphy time scale, thus enabling definition of the magnetic polarity pattern for the upper Griesbachian to Smithian stages in multiple sections. The magnetic polarity and associated sequence stratigraphy pattern for the lower Griesbachian and for the Spathian were derived from single sections. The Griesbachian and Dienerian stages each have two pairs of normal- and reversed-polarity chrons; the Smithian is predominantly of normal polarity, and the Spathian is predominantly of reversed polarity. This magnetic polarity time scale may help to resolve age correlations of North American redbed facies and to define the Permian-Triassic boundary. After correction for variable structural orientations, the mean directions of magnetization from the three sites converge at 296° declination, 57° inclination ( k = 60, ? 95 = 16.5° ; equivalent pole = 41°N, 161°E; paleolatitude = 38°N), which is consistent with the pole derived from nearby Early Permian volcanics and supports a postulated post-Early Triassic, pre-Tertiary counterclockwise rotation of this region with respect to cratonic North America.

Ogg, James G.; Steiner, Maureen B.

1991-10-01

4

A 70 million year astronomical time scale for the deep-sea bedded chert sequence (Inuyama, Japan): Implications for Triassic-Jurassic geochronology  

NASA Astrophysics Data System (ADS)

The astronomical time scale (ATS) has provided high-resolution geochronology. However, the early Mesozoic ATS is still under construction partly due to the lack of continuous pelagic sequences of the early Mesozoic. Here we present ca. ?70 Myr long ATS constructed from the early Mesozoic deep-sea bedded chert sequence exposed in the Inuyama area, central Japan. The sedimentary rhythms of bedded chert display a full range of climatic precession related cycles; ?20-kyr cycle as a chert-shale couplet and ?100-, 405-, 2000- to 4000-, and 10,000-kyr cycles as chert bed thickness variation. The newly established ATS (Inuyama-ATS) is tuned by 405-kyr eccentricity cycle and is anchored at the end-Triassic radiolarian extinction level as 201.4±0.2 Ma. This Inuyama-ATS gives ages consistent with the radiometric ages projected to the Inuyama deep-sea sequence using biostratigraphy and carbon isotope stratigraphy. The Inuyama-ATS provides the age constraints for the Triassic and Jurassic stage boundaries, which support the “Long-Norian” option of Muttoni et al. (2004). Because the deep-sea bedded chert sequence covers a long time interval before the Cretaceous, the ATS for the bedded chert will serve as a template for the astrochronology of Mesozoic and older ages.

Ikeda, Masayuki; Tada, Ryuji

2014-08-01

5

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

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

6

Timing the end-Triassic mass extinction: First on land, then in the sea?  

Microsoft Academic Search

The end-Triassic marks one of the five biggest mass extinctions, but current geologic time scales are inadequate for understanding its dynamics. A tuff layer in marine sedimentary rocks encompassing the Triassic-Jurassic transition yielded a U-Pb zircon age of 199.6 ± 0.3 Ma. The dated level is immediately below a prominent change in radiolarian faunas and the last occurrence of conodonts.

József Pálfy; James K. Mortensen; Elizabeth S. Carter; Paul L. Smith; Richard M. Friedman; Howard W. Tipper

2000-01-01

7

A Mesozoic time scale  

Microsoft Academic Search

We present an integrated geomagnetic polarity and stratigraphic time scale for the Triassic, Jurassic, and Cretaceous periods of the Mesozoic Era, with age estimates and uncertainty limits for stage boundaries. The time scale uses a suite of 324 radiometric dates, including high-resolution Ar-40\\/Ar-39 age estimates. This framework involves the observed ties between (1) radiometric dates, biozones, and stage boundaries, and

Felix M. Gradstein; Frits P. Agterberg; James G. Ogg; Jan Hardenbol; Paul van Veen; Jacques Thierry; Zehui Huang

1994-01-01

8

Testing the fossil record: Sampling proxies and scaling in the British TriassicJurassic  

E-print Network

Testing the fossil record: Sampling proxies and scaling in the British Triassic­Jurassic Alexander March 2014 Available online 30 March 2014 Keywords: Palaeodiversity Fossil record Sampling Proxy Triassic Jurassic The quality of the fossil record varies immensely across taxa, geographic regions

Benton, Michael

9

Residence time indicators in groundwater: the East Midlands Triassic sandstone aquifer  

Microsoft Academic Search

The East Midlands Triassic (Sherwood Sandstone) aquifer which has been the subject of detailed radiometric age studies, is used to investigate both inert and reactive constituents of groundwater as indicators of residence time. Detailed resampling of the aquifer in 1992 has provided a considerable body of new inorganic geochemistry data, though without radiocarbon. Several inert indicators are defined including the

W. M Edmunds; P. L Smedley

2000-01-01

10

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

11

Effects of lithology on geometry and scaling of small faults in Triassic sandstones, East Greenland  

NASA Astrophysics Data System (ADS)

A study of the Lower Triassic sandstones exposed in the Månedalen Fault Zone on Traill Ö, East Greenland, reveals how diagenetic carbonate cement affects the deformational behaviour of sandstones. A siliciclastic sequence of beds ( ?300 m thick) is variably cemented because of the precipitation of carbonate close to stromatolitic interbeds. Displacements or throws of minor faults ( <1.8 m) were sampled along lines through damage zones of major faults (throws >9 m) in three different lithologies: (1) Porous sandstones with little carbonate cement, (2) low-porosity sandstones rich in carbonate cement, and (3) thin beds of carbonate-cemented sandstone in mudstone. The latter shows a strong anisotropy causing fault refraction with syn-kinematic calcite growth in the sandstone beds. Viewed in a microscope, porous sandstones show disaggregated zones with porosity reduced by 40-60%, and cataclastic bands. The development of groups of cataclastic bands was governed by strain-hardening. The low-porous sandstones show cataclastic bands with minor textural change towards the bands. The apparent strength of these sandstones suggests that strain-hardening was much less significant for the development of the faults. Logarithmic plots of N vs D, where N is the cumulative number of faults with throw greater or equal to D, appear to follow linear trends. The least-square regression method gives the following values for the power-law exponent; C=1.01 for 993 faults in the porous sandstones, C=0.70 for 457 faults in carbonate-cemented sandstones, and C=0.38 for 166 faults in the carbonate-cemented sandstones interbedded with mudstones. The estimated confidence intervals for C indicate a true difference in scaling relationships of the samples. The different scaling relationships cannot be linked to strain differences encountered along the traverses. Thus, the lithological heterogeneity arising from local calcite precipitation is thought to be the cause for the differences in deformational style and scaling behaviour.

Steen, Øyvind; Andresen, Arild

1999-10-01

12

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

13

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

NASA Astrophysics Data System (ADS)

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.

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

2012-06-01

14

Coral reef bioerosion in times of crises - the Late Triassic\\/ Early Jurassic example  

Microsoft Academic Search

A study across the major extinction phase of scleractinians during the Late Triassic\\/Early Jurassic was performed. Samples from seven localities in Austria, Morocco and Iran were quantitatively evaluated for macroborings. Each locality represents a turbid or clear-water environment before and after the 5 million years of crisis. Norian reefs suffered almost no bioerosion in clear water but in a turbid

M. Bertling

15

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

NASA Astrophysics Data System (ADS)

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.

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

2001-04-01

16

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

SciTech Connect

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.

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

1985-01-01

17

GSA Geologic Time Scale  

NSDL National Science Digital Library

This Geological Society of America (GSA) site contains a detailed geologic time scale as an educational resource. It may be downloaded to a larger size, and includes all Eras, Eons, Periods, Epochs and ages as well as magnetic polarity information.

1999-01-01

18

Interactive Geological Time Scale  

NSDL National Science Digital Library

This time scale allows students to select multiple time periods from a list and view them on a highlighted display. It shows the relationship between eon, era, period, sub-period, and epoch and also includes the date in mega-annum (Ma) or millions of years before present. The scale reflects the changes in the Cenozoic Era (Tertiary and Quaternary have been eliminated and the Neogene modified) in the most recent International Stratigraphic Charts.

19

The Geologic Time Scale  

NSDL National Science Digital Library

This site contains a large, easy to read, detailed geologic time scale for the Phanerozoic Eon (544 million years ago - Present). This is the period of time, also known as an eon, between the end of the Precambrian and today. The Phanerozoic begins with the start of the Cambrian period, 544 million years ago. It encompasses the period of abundant, complex life on Earth. The chart includes the Era, Period or System, and the Epoch or Series and features a brief description of each.

20

Web Geologic Time Scale  

NSDL National Science Digital Library

The University of California-Berkeley Museum of Paleontology (last mentioned in the June 16, 1995 Scout Report) has recently updated its Web Geologic Time Scale, an online feature that helps users learn about the geologic timeline and explore related museum exhibits. The familiar geologic timeline appears on the main page of the Web site, with hypertext links for each division of time. Every page of the Web Geologic Time Machine site is liberally sprinkled with links to related UCMP Web pages; think of it as a portal to all online information available from the museum. Altogether, this Web site provides a well-organized and comprehensive resource for learning how the planet has changed over time, and would be a great addition to earth or life sciences classroom material for a broad range of grades.

1994-01-01

21

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

Microsoft Academic Search

A comparison of the modern condition with the Permian-Triassic Boundary (PTB) times was made to estimate how severe the modern\\u000a biotic crisis is. About the global changes, the two periods are correlative in carbon dioxide concentration and carbon isotope\\u000a negative excursion, UV strengthening, temperature increase, ocean acidification, and weathering enhancement. The following\\u000a tendencies of biotic crises are also correlative: acceleration

Hongfu Yin; Weihong He; Shucheng Xie

2011-01-01

22

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

SciTech Connect

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.

Elison, M.W.

1993-04-01

23

The Triassic-Jurassic boundary in eastern North America  

NASA Technical Reports Server (NTRS)

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.

Olsen, P. E.; Comet, B.

1988-01-01

24

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

PubMed

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

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

2014-11-27

25

Time scales in LISA  

E-print Network

The LISA mission is a space interferometer aiming at the detection of gravitational waves in the [$10^{-4}$,$10^{-1}$] Hz frequency band. In order to reach the gravitational wave detection level, a Time Delay Interferometry (TDI) method must be applied to get rid of (most of) the laser frequency noise and optical bench noise. This TDI analysis is carried out in terms of the coordinate time corresponding to the Barycentric Coordinate Reference System (BCRS), TCB, whereas the data at each of the three LISA stations is recorded in terms of each station proper time. We provide here the required proper time versus BCRS time transformation. We show that the difference in rate of station proper time versus TCB is of the order of $5 10^{-8}$. The difference between station proper times and TCB exhibits an oscillatory trend with a maximum amplitude of about $10^{-3}$ s.

S. Pireaux

2007-03-23

26

Smithian and Spathian (Early Triassic) ammonoid assemblages from terranes: Paleoceanographic and paleogeographic implications  

Microsoft Academic Search

Early Triassic paleobiogeography is characterised by the stable supercontinental assembly of Pangea. However, at that time, several terranes such as the South Kitakami Massif (SK), South Primorye (SP) and Chulitna (respectively, and presently located in Japan, eastern Russia and Alaska) straddled the vast oceans surrounding Pangea. By means of quantitative biogeographical methods including Cluster Analysis, Non-metric Multidimensional Scaling and Bootstrapped

Arnaud Brayard; Gilles Escarguel; Hugo Bucher; Thomas Brühwiler

2009-01-01

27

Geologic time scale bookmark  

USGS Publications Warehouse

This bookmark, designed for use with U.S. Geological Survey activities at the 2nd USA Science and Engineering Festival (April 26–29, 2012), is adapted from the more detailed Fact Sheet 2010–3059 "Divisions of Geologic Time." The information that it presents is widely sought by educators and students.

U.S. Geological Survey

2012-01-01

28

Early Triassic geologic history of northeastern Nevada  

SciTech Connect

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.

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

1986-08-01

29

Absence of extraterrestrial 3 He in PermianTriassic  

E-print Network

Absence of extraterrestrial 3 He in Permian­Triassic age sedimentary rocks K.A. Farley a,*, P. Ward the Permian­Triassic boundary at Opal Creek, Canada, to determine whether high extraterrestrial helium concentrations are associated with a possible extinction- inducing impact event at this time. No extraterrestrial

Mukhopadhyay, Sujoy

30

Triassic climates — State of the art and perspectives  

Microsoft Academic Search

The climate of the Triassic period was characterized by a non-zonal pattern, dictated by a strong global monsoon system with effects that are most evident in the Tethys realm. This strong monsoonal regime is related to the aggregation of the Pangaean supercontinent, which by Triassic time was already completed. Climate oscillations existed within this framework. The harsh hot-house climatic conditions

Nereo Preto; Evelyn Kustatscher; Paul B. Wignall

2010-01-01

31

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

SciTech Connect

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.

Bebeshev, I.I. [Geological Institute, Moscow (Russian Federation)

1995-03-01

32

THE VERTEBRATE FAUNA OF THE UPPER TRIASSIC CHINLE FORMATION IN NORTHERN ARIZONA  

Microsoft Academic Search

The Upper Triassic Chinle Formation of the southwestern United States preserves one of the most taxonomically diverse records of Late Triassic vertebrates in North America. This record spans at least 25 million years from the Late Carnian to the near end of the Triassic Period (Lucas, 1998). It is a time of faunal turnover, with earlier basal archosaur and temnospondyl

RANDALL B. IRMIS

33

A NEW SHRIMP (DECAPODA, DENDROBRANCHIATA, PENAEOIDEA) FROM THE MIDDLE TRIASSIC OF YUNNAN, SOUTHWEST CHINA  

E-print Network

of the marine ecosystem between Eastern and Western Tethys. INTRODUCTION THE TRIASSIC Period was a pivotal timeA NEW SHRIMP (DECAPODA, DENDROBRANCHIATA, PENAEOIDEA) FROM THE MIDDLE TRIASSIC OF YUNNAN, SOUTHWEST collected from the Middle Triassic Member II of the Guanling Formation in the vicinity of the city of Luxi

Benton, Michael

34

Time scales in cognitive neuroscience  

PubMed Central

Cognitive neuroscience boils down to describing the ways in which cognitive function results from brain activity. In turn, brain activity shows complex fluctuations, with structure at many spatio-temporal scales. Exactly how cognitive function inherits the physical dimensions of neural activity, though, is highly non-trivial, and so are generally the corresponding dimensions of cognitive phenomena. As for any physical phenomenon, when studying cognitive function, the first conceptual step should be that of establishing its dimensions. Here, we provide a systematic presentation of the temporal aspects of task-related brain activity, from the smallest scale of the brain imaging technique's resolution, to the observation time of a given experiment, through the characteristic time scales of the process under study. We first review some standard assumptions on the temporal scales of cognitive function. In spite of their general use, these assumptions hold true to a high degree of approximation for many cognitive (viz. fast perceptual) processes, but have their limitations for other ones (e.g., thinking or reasoning). We define in a rigorous way the temporal quantifiers of cognition at all scales, and illustrate how they qualitatively vary as a function of the properties of the cognitive process under study. We propose that each phenomenon should be approached with its own set of theoretical, methodological and analytical tools. In particular, we show that when treating cognitive processes such as thinking or reasoning, complex properties of ongoing brain activity, which can be drastically simplified when considering fast (e.g., perceptual) processes, start playing a major role, and not only characterize the temporal properties of task-related brain activity, but also determine the conditions for proper observation of the phenomena. Finally, some implications on the design of experiments, data analyses, and the choice of recording parameters are discussed. PMID:23626578

Papo, David

2013-01-01

35

Triassic palaeogeography of Tunisia  

Microsoft Academic Search

A stratigraphic, palaeogeographic and palinspastic synthesis of the Triassic successions in Tunisia is herein documented from a SSE–NNN oriented profile (Saharan Platform, Gulf of Gabes offshore, Tunisian Atlas, Tellian Units) across the northern boundary of the Gondwana Plate and the future South-Tethyan Margin. It is principally based on a reinvestigation of old data and on recent results, particularly related to

F Kamoun; B Peybernès; R Ciszak; S Calzada

2001-01-01

36

Dating the end-Triassic and Early Jurassic mass extinctions, correlative large igneous provinces, and isotopic events  

Microsoft Academic Search

The end-Triassic marks one of the five biggest mass extinctions, and was followed by a well-known second-order extinction event in the Early Jurassic. Previously pub- lished geological time scales were inadequate for correlation of extinctions with other global events and to unravel their dynamics. Here we present a revised time scale based on high-precision U-Pb ages integrated with ammonoid biochronology

Jozsef Palfy; Paul L. Smith; James K. Mortensen

37

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

NASA Astrophysics Data System (ADS)

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.

Gradstein, Felix M.

2010-05-01

38

Advances in time-scale algorithms  

NASA Technical Reports Server (NTRS)

The term clock is usually used to refer to a device that counts a nearly periodic signal. A group of clocks, called an ensemble, is often used for time keeping in mission critical applications that cannot tolerate loss of time due to the failure of a single clock. The time generated by the ensemble of clocks is called a time scale. The question arises how to combine the times of the individual clocks to form the time scale. One might naively be tempted to suggest the expedient of averaging the times of the individual clocks, but a simple thought experiment demonstrates the inadequacy of this approach. Suppose a time scale is composed of two noiseless clocks having equal and opposite frequencies. The mean time scale has zero frequency. However if either clock fails, the time-scale frequency immediately changes to the frequency of the remaining clock. This performance is generally unacceptable and simple mean time scales are not used. First, previous time-scale developments are reviewed and then some new methods that result in enhanced performance are presented. The historical perspective is based upon several time scales: the AT1 and TA time scales of the National Institute of Standards and Technology (NIST), the A.1(MEAN) time scale of the US Naval observatory (USNO), the TAI time scale of the Bureau International des Poids et Measures (BIPM), and the KAS-1 time scale of the Naval Research laboratory (NRL). The new method was incorporated in the KAS-2 time scale recently developed by Timing Solutions Corporation. The goal is to present time-scale concepts in a nonmathematical form with as few equations as possible. Many other papers and texts discuss the details of the optimal estimation techniques that may be used to implement these concepts.

Stein, S. R.

1993-01-01

39

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)

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.

Yin, Hongfu; He, Weihong; Xie, Shucheng

2011-03-01

40

Triassic: the crucial period of post-Palaeozoic crinoid diversification  

Microsoft Academic Search

After their near-extinction around the end of the Permian, crinoids recovered during the Triassic and re-occupied almost all\\u000a ecological niches they had held in Palaeozoic times. Triassic crinoids comprise 33 genera in 12 well-defined families and\\u000a 5 orders of the subclass Articulata; the systematic position of 4 additional families is unknown. The highest diversity was\\u000a before the Mid Carnian Wet

Hans Hagdorn

2011-01-01

41

Modeling orbital changes on tectonic time scales  

NASA Technical Reports Server (NTRS)

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.

Crowley, Thomas J.

1992-01-01

42

Stability of Rasch Scales over Time  

ERIC Educational Resources Information Center

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.…

Taylor, Catherine S.; Lee, Yoonsun

2010-01-01

43

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

Microsoft Academic Search

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

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

2010-01-01

44

A Taxodiaceous Seed Cone from the Triassic of Antarctica  

Microsoft Academic Search

A silicified seed cone is described from the lower Middle Triassic of Antarctica. The cone measures up to 3.4 cm long and 1.4 cm wide, and consists of helically arranged cone scales attached to a eustelic axis. Bract and ovuliferous scale are approximately of equal length and fused at the base. The bract is entire and vascularized by a single

Xuanli Yao; Thomas N. Taylor; Edith L. Taylor

1997-01-01

45

Spondarthritis in the Triassic  

PubMed Central

Background The evidence of several forms of arthritis has been well documented in the fossil record. However, for pre-Cenozoic vertebrates, especially regarding reptiles, this record is rather scarce. In this work we present a case report of spondarthritis found in a vertebral series that belonged to a carnivorous archosaurian reptile from the Lower Triassic (?245 million years old) of the South African Karoo. Methodology/Principal Findings Neutron tomography confirmed macroscopic data, revealing the ossification of the entire intervertebral disc space (both annulus fibrosus and nucleus pulposus), which supports the diagnosis of spondarthritis. Conclusions/Significance The presence of spondarthritis in the new specimen represents by far the earliest evidence of any form of arthritis in the fossil record. The present find is nearly 100 million years older than the previous oldest report of this pathology, based on a Late Jurassic dinosaur. Spondarthritis may have indirectly contributed to the death of the animal under study. PMID:20976231

Cisneros, Juan Carlos; Gomes Cabral, Uiara; de Beer, Frikkie; Damiani, Ross; Costa Fortier, Daniel

2010-01-01

46

Kalman plus weights: a time scale algorithm  

NASA Technical Reports Server (NTRS)

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.

Greenhall, C. A.

2001-01-01

47

Chronology of fluctuating sea levels since the triassic  

SciTech Connect

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.

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

1987-03-06

48

ParaScale: Exploiting Parametric Timing Analysis for Real-Time Schedulers and Dynamic Voltage Scaling  

E-print Network

ParaScale: Exploiting Parametric Timing Analysis for Real-Time Schedulers and Dynamic Voltage for dynamic power conservation by exploiting parametric loop bounds for ParaScale, our intra-task dynamic voltage scaling (DVS) approach. Our results demonstrate that the parametric approach to timing analysis

Mueller, Frank

49

Tephrastratigraphy and Analysis of Tectonic Setting of Triassic Intermediate Volcanic Strata: Nanpanjiang Basin, South China  

Microsoft Academic Search

The Nanpanjiang is a deep-marine basin in the southern margin of the Yangtze microcontinent of South China. The basin contains several shallow-marine carbonate platforms developed in Triassic time. Differential carbonate platform development and subsidence analysis suggests that the Nanpanjiang basin developed into a foreland basin resulting from an arc collision in the southern part of the basin in the Triassic.

T. T. Newkirk

2002-01-01

50

Sedimentology, stratigraphy, and micropalaeontology of the Upper Triassic reefal series in Eastern Sulawesi (Indonesia)  

Microsoft Academic Search

An Upper Triassic (Upper Norian-Rhaetian) carbonate complex, composed of open marine to reefal deposits, has been investigated for the first time in Eastern Sulawesi. The age is based on the occurrence of benthic foraminifera, and also of the Upper Sevatian to Rhaetian conodont Misikella posthernsteini Kozur and Mock. Palynological assemblages contain Upper Triassic-Lower Jurassic palynomorphs. The scleractinian coral Retiophyllia seranica

Rossana Martini; Daniel Vachard; Louisette Zaninetti; Simonetta Cirilli; Jean-Jacques Cornée; Bernard Lathuilière; Michel Villeneuve

1997-01-01

51

Mouse Activity across Time Scales: Fractal Scenarios  

PubMed Central

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

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

52

Earth accretion dynamics and time-scales  

Microsoft Academic Search

The degree to which efficient mixing of new material, losses of volatiles to space and changes in oxidation characterize the impact-driven growth of Earth-like planets in unclear. These processes affect calculated time-scales and can be studied by parallel modeling of data from different radiogenic isotope systems. The W isotope composition of the silicate Earth yields a model time-scale for accretion

A. N. Halliday

2003-01-01

53

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

NASA Astrophysics Data System (ADS)

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.

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

54

The time at the subplanckian scale  

E-print Network

With the theory of special relativity, time has been linked with space into a four-dimensional space-time from which a basic question must be asked: can space be really transformed into time and vice-versa? The response is affirmative if time has the same structural topological structure as space at the subplanckian quantum level in such a way that a discrete structural quantum time constitutes the time part of the space-time internal vacuum of every elementary particle. It has thus been shown that a quantum time, quantized algebraically according to a lattice of time quanta, really exists and is emergent in the sense that time quanta can be transformed into space quanta and vice-versa. Furthermore,this quantum time, only relevant at the subplanckian scale, is proved to be in one-to-one correspondence with the absolute and relative clock times.

Christian Pierre

2007-01-22

55

Time scale synchronization of chaotic oscillators  

E-print Network

This paper presents the result of the investigation of chaotic oscillator synchronization. A new approach for detecting of synchronized behaviour of chaotic oscillators has been proposed. This approach is based on the analysis of different time scales in the time series generated by the coupled chaotic oscillators. This approach has been applied for the coupled Rossler and Lorenz systems.

Alexander Hramov; Alexey Koronovskii

2006-02-25

56

Provenance analysis and tectonic setting of the Triassic clastic deposits in Western Chukotka, Northeast Russia  

NASA Astrophysics Data System (ADS)

The study area is part of the Anyui subterrane of the Chukotka microplate, a key element in the evolution of the Amerasia Basin, located in Western Chukotka, Northeast Russia. The subterrane contains variably deformed, folded and cleaved rhythmic Triassic terrigenous deposits which represent the youngest stage of widespread marine deposition which form three different complexes: Lower-Middle Triassic, Upper Triassic (Carnian) and Upper Triassic (Norian). All of the complexes are represented by rhythmic interbeds of sandstone, siltstone and mudstone. Macrofaunas are not numerous, and in some cases deposits are dated by analogy to, or by their relationship with, other units dated with macrofaunas. The deposits are composed of pelagic sediments, low-density flows, high-density flows, and shelf facies associations suggesting that sedimentation was controlled by deltaic progradation on a continental shelf and subsequent submarine fan sedimentation at the base of the continental slope. Petrographic study of the mineral composition indicates that the sandstones are lithic arenites. Although the Triassic sandstones appear similar in outcrop and by classification, the constituent rock fragments are of diverse lithologies, and change in composition from lower grade metamorphic rocks in the Lower-Middle Triassic to higher grade metamorphic rocks in the Upper Triassic. This change suggests that the Triassic deposits represent an unroofing sequence as the source of the clastic material came from more deeply buried rocks with time.

Tuchkova, M. I.; Sokolov, S.; Kravchenko-Berezhnoy, I. R.

2009-09-01

57

The Time Scale of Evolutionary Innovation  

PubMed Central

A fundamental question in biology is the following: what is the time scale that is needed for evolutionary innovations? There are many results that characterize single steps in terms of the fixation time of new mutants arising in populations of certain size and structure. But here we ask a different question, which is concerned with the much longer time scale of evolutionary trajectories: how long does it take for a population exploring a fitness landscape to find target sequences that encode new biological functions? Our key variable is the length, of the genetic sequence that undergoes adaptation. In computer science there is a crucial distinction between problems that require algorithms which take polynomial or exponential time. The latter are considered to be intractable. Here we develop a theoretical approach that allows us to estimate the time of evolution as function of We show that adaptation on many fitness landscapes takes time that is exponential in even if there are broad selection gradients and many targets uniformly distributed in sequence space. These negative results lead us to search for specific mechanisms that allow evolution to work on polynomial time scales. We study a regeneration process and show that it enables evolution to work in polynomial time. PMID:25211329

Chatterjee, Krishnendu; Pavlogiannis, Andreas; Adlam, Ben; Nowak, Martin A.

2014-01-01

58

The end-triassic mass extinction event  

NASA Technical Reports Server (NTRS)

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.

Hallam, A.

1988-01-01

59

Triassic origin and early radiation of multicellular volvocine algae  

E-print Network

Triassic origin and early radiation of multicellular volvocine algae Matthew D. Herron1 , Jeremiah-studied ETIs is the origin of multicellularity in the green alga Volvox, a model system for the evolution occurred dozens of times independently, for example in the red algae, brown algae, land plants, animals

60

Astrobiology with haloarchaea from Permo-Triassic rock salt  

Microsoft Academic Search

Several viable halophilic archaebacteria were isolated previously from rock salt of Permo-Triassic age in an Austrian salt mine; one of these strains was the first to be recognized as a novel species from subterranean halite and was designated Halococcus salifodinae. The halophilic microorganisms have apparently survived in the salt sediments over extremely long periods of time. Halobacteria could therefore be

H. Stan-Lotter; C. Radax; C. Gruber; A. Legat; M. Pfaffenhuemer; H. Wieland; S. Leuko; G. Weidler; N. Kömle; G. Kargl

2002-01-01

61

Stability of graph communities across time scales  

PubMed Central

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

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

2010-01-01

62

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

NASA Astrophysics Data System (ADS)

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.

Hinnov, L.; Ogg, J. G.

2009-12-01

63

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

USGS Publications Warehouse

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.

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

2002-01-01

64

The plankton turnover at the Permo-Triassic boundary, emphasis on radiolarians  

Microsoft Academic Search

.  The examination of plankton biodiversity through Permian-Triassic period seems to display different patterns of evolution\\u000a depending of the scale of study (taxonomy stratigraphy or biogeography). In this paper we present the state of the art of\\u000a the plankton turnover at the Permo-Triassic and we review more precisely the pattern of extinction and recovery of radiolarians\\u000a during such period, because at

Patrick De Wever; Luis O'Dogherty; ŠPela Gori?an

2006-01-01

65

The plankton turnover at the Permo-Triassic boundary, emphasis on radiolarians  

Microsoft Academic Search

\\u000a The examination of plankton biodiversity through Permian-Triassic period seems to display different patterns of evolution\\u000a depending of the scale of study (taxonomy stratigraphy or biogeography). In this paper we present the state of the art of\\u000a the plankton turnover at the Permo-Triassic and we review more precisely the pattern of extinction and recovery of radiolarians\\u000a during such period, because at

PATRICK DE WEVER; Luis O’Dogherty; Spela Gorican

66

Divergent Time Scale in Axelrod Model Dynamics  

E-print Network

We study the evolution of the Axelrod model for cultural diversity. We consider a simple version of the model in which each individual is characterized by two features, each of which can assume q possibilities. Within a mean-field description, we find a transition at a critical value q_c between an active state of diversity and a frozen state. For q just below q_c, the density of active links between interaction partners is non-monotonic in time and the asymptotic approach to the steady state is controlled by a time scale that diverges as (q-q_c)^{-1/2}.

Vázquez, F

2006-01-01

67

CO2 and the end-Triassic mass extinction.  

PubMed

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

Beerling, David

2002-01-24

68

Early Triassic stromatolites as post-mass extinction disaster forms  

SciTech Connect

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.

Schubert, J.K.; Bottjer, D.J. (Univ. of Southern California, Los Angeles (United States))

1992-10-01

69

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

PubMed

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

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

2004-11-01

70

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

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.

Blodgett, Robert B.; Sralla, Bryan

2008-01-01

71

Time scales in nuclear giant resonances  

E-print Network

We propose a general approach to characterise fluctuations of measured cross sections of nuclear giant resonances. Simulated cross sections are obtained from a particular, yet representative self-energy which contains all information about fragmentations. Using a wavelet analysis, we demonstrate the extraction of time scales of cascading decays into configurations of different complexity of the resonance. We argue that the spreading widths of collective excitations in nuclei are determined by the number of fragmentations as seen in the power spectrum. An analytic treatment of the wavelet analysis using a Fourier expansion of the cross section confirms this principle. A simple rule for the relative life times of states associated with hierarchies of different complexity is given.

WD Heiss; RG Nazmitdinov; FD Smit

2009-12-18

72

Cratering time scales for the Galilean satellites  

NASA Technical Reports Server (NTRS)

An attempt is made to estimate the present cratering rate for each Galilean satellite within the correct order of magnitude and to extend the cratering rates back into the geologic past on the basis of evidence from the earth-moon system. For collisions with long and short period comets, the magnitudes and size distributions of the comet nuclei, the distribution of their perihelion distances, and the completeness of discovery are addressed. The diameters and masses of cometary nuclei are assessed, as are crater diameters and cratering rates. The dynamical relations between long period and short period comets are discussed, and the population of Jupiter-crossing asteroids is assessed. Estimated present cratering rates on the Galilean satellites are compared and variations of cratering rate with time are considered. Finally, the consistency of derived cratering time scales with the cratering record of the icy Galilean satellites is discussed.

Shoemaker, E. M.; Wolfe, R. F.

1982-01-01

73

A Triassic Lagerstätte from eastern North America  

Microsoft Academic Search

THE end of the Triassic period is pivotal in the evolution of modern ecosystems1. Despite this, the Triassic remains one of the poorest known periods in the evolutionary history of the terrestrial arthropods. Here we report on fossiliferous shales preserving a nearly complete marginal lacustrine community from the Virginia-North Carolina border that sheds considerable light on this critical interval. Three

Nicholas C. Fraser; David A. Grimaldi; Paul E. Olsen; Brian Axsmith

1996-01-01

74

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

PubMed

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

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

75

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

SciTech Connect

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.

Snow, J.K.; Asmerom, Y. (Harvard Univ., Cambridge, MA (USA)); Lux, D.R. (Univ. of Maine, Orono (USA))

1991-06-01

76

Time Horizon and Social Scale in Communication  

NASA Astrophysics Data System (ADS)

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.

Krantz, D. H.

2010-12-01

77

An optimal modification of a Kalman filter for time scales  

NASA Technical Reports Server (NTRS)

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.

Greenhall, C. A.

2003-01-01

78

An electronic time scale in chemistry  

PubMed Central

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

Remacle, F.; Levine, R. D.

2006-01-01

79

Basin-scale time reversal communications.  

PubMed

During November 1994, broadband acoustic signals were transmitted from a 75-Hz source to a 20-element, 700-m vertical array at approximately 3250 km range in the eastern North Pacific Ocean as part of the acoustic engineering test (AET) of the acoustic thermometry of ocean climate program [Worcester et al., J. Acoust. Soc. Am. 105, 3185-3201 (1999)]. The AET tomography signal can be treated as a binary-phase shift-keying communication signal with an information rate of 37.5 bitss. With the multipath arrivals spanning 5-8 sec, these data represent an extreme case of intersymbol interference. The AET array data are processed using time reversal combined with frequent channel updates to accommodate channel variations over the 20-min long reception, followed by a single channel decision-feedback equalizer. The almost error-free performance using all 20 array elements demonstrates the feasibility of time reversal communications at basin scale. Further, comparable performance of single receive element communications integrating over multiple transmissions indicates that the ocean provided temporal diversity that is as effective as the spatial diversity provided by the array. PMID:19173408

Song, H C; Kuperman, W A; Hodgkiss, W S

2009-01-01

80

Late Permian-early Middle Triassic back-arc basin development in West Qinling, China  

NASA Astrophysics Data System (ADS)

The Late Permian-early Middle Triassic strata of the northern West Qinling area, northeastern Tibetan Plateau, are composed of sediment gravity flow deposits. Detailed sedimentary facies analysis indicates these strata were deposited in three successive deep-marine environments. The Late Permian-early Early Triassic strata of the Maomaolong Formation and the lowest part of the Longwuhe Formation define a NW-SE trending proximal slope environment. Facies of the Early Triassic strata composing the middle and upper Longwuhe Formation are consistent with deposition in a base-of-slope apron environment, whereas facies of the Middle Triassic Anisian age Gulangdi Formation are more closely associated with a base-of-slope fan depositional environment. The lithofacies and the spatial-temporal changes in paleocurrent data from these strata suggest the opening of a continental margin back-arc basin system during Late Permian to early Middle Triassic time in the northern West Qinling. U-Pb zircon ages for geochemically varied igneous rocks with diabasic through granitic compositions intruded into these deep-marine strata range from 250 to 234 Ma. These observations are consistent with extensional back-arc basin development and rifting between the Permian-Triassic Eastern Kunlun arc and North China block during the continent-continent collision and underthrusting of the South China block northward beneath the Qinling terrane of the North China block. Deep-marine sedimentation ended in the northern West Qinling by the Middle Triassic Ladinian age, but started in the southern West Qinling and Songpan-Ganzi to the south. We attribute these observations to southward directed rollback of Paleo-Tethys oceanic lithosphere, continued attenuation of the West Qinling on the upper plate, local post-rift isostatic compensation in the northern West Qinling area, and continued opening of a back-arc basin in the southern West Qinling and Songpan-Ganzi. Rollback and back-arc basin development during Late Permian to early Middle Triassic time in the West Qinling area explains: the truncated map pattern of the Eastern Kunlun arc, the age difference of deep-marine sediment gravity flow deposits between the Late Permian-early Middle Triassic northern West Qinling and the late Middle Triassic-Late Triassic southern West Qinling and Songpan-Ganzi, and the discontinuous trace of ophiolitic rocks associated with the Anyemaqen-Kunlun suture.

Li, Lin; Meng, Qingren; Pullen, Alex; Garzione, Carmala N.; Wu, Guoli; Wang, Yanling; Ma, Shouxian; Duan, Liang

2014-06-01

81

Fullerenes found in the permo-triassic mass extinction period  

Microsoft Academic Search

Fullerenes have been identified by high-performance liquid chromatography with UV-visible spectroscopic analysis of toluene extracts of deep sea claystones from Permo-Triassic (P\\/T) boundary sections in the Inuyama area, central Japan. The analysis reveals the presence of 10-20 parts per trillion of C60 only in the dark-colored rock samples, suggesting the anoxia at the time of the P\\/T boundary 250 million

Takuya Chijiwa; Toshinari Arai; Toshiki Sugai; Hisanori Shinohara; Mineo Kumazawa; Masao Takano; Shin-iti Kawakami

1999-01-01

82

Phreatomagmatic eruption during the buildup of a Triassic carbonate platform (Oman Exotics): eruptive style, associated deformations, and implications on CO2 release by volcanism  

E-print Network

1 Phreatomagmatic eruption during the buildup of a Triassic carbonate platform (Oman Exotics@ujf-grenoble.fr; francois.chauvet@ujf-grenoble.fr Abstract Oman exotics represent remnants of a Triassic carbonate platform in Oman, emphasizing on small- and large-scale deformations of lithified and unlithified s

Paris-Sud XI, Université de

83

Detection of crossover time scales in multifractal detrended fluctuation analysis  

NASA Astrophysics Data System (ADS)

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.

Ge, Erjia; Leung, Yee

2013-04-01

84

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

SciTech Connect

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.

Lucas, S.G. (New Mexico Museum of Natural History, Albuquerque (United States)); Anderson, O.J. (New Mexico Bureau of Mines and Mineral Resources, Socorro (United States))

1992-04-01

85

A late Triassic impact ejecta layer in southwestern Britain.  

PubMed

Despite the 160 or so known terrestrial impact craters of Phanerozoic age, equivalent ejecta deposits within distal sedimentary successions are rare. We report a Triassic deposit in southwestern Britain that contains spherules and shocked quartz, characteristic of an impact ejecta layer. Inter- and intragranular potassium feldspar from the deposit yields an argon-argon age of 214 +/- 2.5 million years old. This is within the age range of several known Triassic impact craters, the two closest of which, both in age and location, are Manicouagan in northeastern Canada and Rochechouart in central France. The ejecta deposit provides an important sedimentary record of an extraterrestrial impact in the Mesozoic that will help to decipher the number and effect of impact events, the source and dynamics of the event that left this distinctive sedimentary marker, and the relation of this ejecta layer to the timing of extinctions in the fossil record. PMID:12434010

Walkden, Gordon; Parker, Julian; Kelley, Simon

2002-12-13

86

Atmospheric methane injection caused end-Triassic mass extinction  

NASA Astrophysics Data System (ADS)

The end-Triassic mass extinction (~201.5 Ma), marked by major terrestrial ecosystem changes and a 50% loss in marine biodiversity, coincides with a distinct negative perturbation in marine C-isotope records. These events have been attributed to the onset of intensified volcanic activity in the Central Atlantic Magmatic Province (CAMP), the largest igneous province on earth. However, global carbon cycle disruption has been questioned due to varying magnitudes of the observed negative excursion between different sedimentary basins. Here, we present compound specific C-isotope data of long-chain n-alkanes derived from waxes of land plants, showing a ~8.5‰ negative excursion coincident with the extinction interval. These data suggest strong 13C depletion of the end-Triassic atmosphere, within 10-20 kyr. The magnitude and rate of C-cycle disruption can only be explained by the injection of ~12x103 Gt of isotopically depleted carbon from the methane-hydrate reservoir. Concurrent vegetation changes reflect strong warming and an enhanced hydrological cycle. Hence the end-Triassic extinction is, for the first time, mechanistically linked to massive carbon release and associated climate change.

Ruhl, Micha; Bonis, Nina R.; Reichart, Gert-Jan; Sinninghe Damsté, Jaap S.; Kürschner, Wolfram M.

2010-05-01

87

A Quaternary Geomagnetic Instability Time Scale  

NASA Astrophysics Data System (ADS)

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.

Singer, B. S.

2013-12-01

88

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

PubMed

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

Ezcurra, Martin D

2010-08-22

89

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

PubMed

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

Kent, Dennis V; Tauxe, Lisa

2005-01-14

90

Climate-carbon cycle simulations of the Permian-Triassic boundary: Implications for the extinction event  

Microsoft Academic Search

The causes for the Permian-Triassic (PT) extinction, the largest mass extinction on record, remain unknown. The period is marked by large scale volcanic eruptions and evidence for widespread ocean anoxia, which have led to suggestions that these events generated, or played a part in, the extinction. Hypercapnia and ocean acidification caused by volcanic emissions of CO2 and CH4 have been

A. Montenegro; P. Spence; K. J. Meissner; M. Eby; M. Melchin; S. T. Johnston

2010-01-01

91

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

Microsoft Academic Search

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

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

2004-01-01

92

Rift-related Triassic Alpine magmatism traced by U-Pb dating and Hafnium isotopes of detrital zircons  

NASA Astrophysics Data System (ADS)

The geodynamic setting and source of syn-sedimentary Triassic igneous activity in the Alpine Tethys is a matter of discussion since long time. There are two contrasting models proposed, either within an extensional environment (e.g. Crisci et al., 1984) or in a subduction-related setting (e.g. Castellarin, 1988); the latter in particular is based on the apparent calc-alkaline geochemical signature. We analyse Triassic and Jurassic sandstones from the southern margin of the Alpine Tethys. Laser-ablation ICP-MS methods are used to date the detrital zircons and to evaluate Hf-isotope ratios in order to characterise the time and type of magmas in which the zircons crystallised. For analyses we have chosen the Early Triassic Fuorn Formation and the Middle Triassic Prosanto and Altein formations (Upper Austroalpine Silvretta nappe), the Middle Jurassic Saluver Formation (Lower Austroalpine Err nappe), the Middle Triassic Buchenstein Formation and the early Late Triassic Val Sabbia Formation (South Alpine domain). The detrital zircon U-Pb ages reveal a main sourcing of the Triassic sandstones in coeval igneous rocks, and alternatively, in Permian igneous and volcaniclastic (Verruccano type) rocks. Triassic re-melting of older continental crust is documented by the presence of post-Variscan, Variscan and older inherited cores in the detrital zircons. A mixed mantle-crust source of the Triassic melts is confirmed by the Hf-isotope ratios. Finally, Triassic rift-related igneous activity developed in a similar crustal setting as the post-Variscan magmatism. We conclude that the Triassic magmas formed through partial melting of the upper mantle, which was deeply modified during the previous Variscan orogeny (Crisci et al. 1984). The rising melts included crustal material, and the apparent calc-alkaline signature was inherited due to recycling of previous subduction-related orogenic cycle products. With regard to the obtained epsilon Hafnium values of the detrital zircons, the post-Variscan (Permian) extension and Triassic Alpine rifting were continuous processes.

Beltran-Triviño, Alejandro; Winkler, Wilfried; Bussien, Denise; von Quadt, Albrecht

2013-04-01

93

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

NASA Astrophysics Data System (ADS)

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.

Oliver, Grahame; Prave, Anthony

2013-10-01

94

Local-time effect on small space-time scale  

E-print Network

The paper presents an investigation of local-time effect - one of the manifestations of macroscopic fluctuations phenomena. Was shown the existence of the named effect for longitudinal distance between locations of measurements up to 500 meters. Also a structure of intervals distribution in neighborhood of local-time peak was studied and splitting of the peak was found out. Obtained results lead to conclusion about sharp anisotropy of space-time.

V. A. Panchelyuga; V. A. Kolombet; M. S. Panchelyuga; S. E. Shnoll

2006-10-18

95

TriassicJurassic boundary events: Problems, progress, possibilities 1. Problems  

E-print Network

As for most geological period boundaries, the Triassic­Jurassic (T­J) transition, 200 million years agoEditorial Triassic­Jurassic boundary events: Problems, progress, possibilities 1. Problems to reconstruct past events, a physical record of their passing is essential. Here again the Triassic

McRoberts, Christopher A.

96

Ion-Beam Sculpting Time Scales Derek Stein,1  

E-print Network

Ion-Beam Sculpting Time Scales Derek Stein,1 Jiali Li,2 and Jene A. Golovchenko1,2 1 Division) A study of ion sculpting dynamics in SiO2 and SiN using periodically pulsed ion beams reveals material nanoscale matter transport can occur over second long time scales after the ion beam has been extinguished

Li, Jiali

97

Estimating ventilation time scales using overturning stream functions  

E-print Network

Estimating ventilation time scales using overturning stream functions Bijoy Thompson & Jonas for estimating ventilation time scales from overturning stream functions is proposed. The stream function may describing an ide- alized semi-enclosed ocean basin ventilated through a narrow strait over a sill

Döös, Kristofer

98

Variability of global lightning activity on the ENSO time scale  

Microsoft Academic Search

Global lightning activity has been studied on the ENSO (El Niño Southern Oscillation) time scale based on recordings of the Earth's Schumann resonances at Nagycenk (NCK), Hungary as well as observations from the OTD (Optical Transient Detector) and the LIS (Lightning Imaging Sensor) satellites in space. Both the intensity and position of lightning activity vary on the ENSO time scale.

G. Sátori; E. Williams; I. Lemperger

2009-01-01

99

LINK BETWEEN COSMIC RAYS AND CLOUDS ON DIFFERENT TIME SCALES  

E-print Network

LINK BETWEEN COSMIC RAYS AND CLOUDS ON DIFFERENT TIME SCALES ILYA G. USOSKIN and GENNADY A is related to a link between the cosmic ray flux and cloudiness. Here we review evidences relating terrestrial climate variability to changes of cosmic ray flux in the Earth's vicinity on different time scales

Usoskin, Ilya G.

100

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

PubMed Central

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 ?13C 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 ?13C 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

Berner, Robert A.

2002-01-01

101

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

PubMed

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

Berner, Robert A

2002-04-01

102

Acceleration time scale in an ultrarelativistic shock  

E-print Network

The acceleration mechanism at ultrarelativistic shocks is investigated using the Monte Carlo simulations. We apply a method of discrete small amplitude particle momentum scattering to reproduce highly anisotropic conditions at the shock and carefully describe the acceleration mechanism. The obtained acceleration times equal $1.0 r_{g}/c$ if the spectral index reach the value of 2.2, independent of physical conditions in the shock. Some other parameters of the acceleration process are also provided.

Janusz Bednarz

2000-05-10

103

Probing Photosynthesis on a Picosecond Time Scale  

PubMed Central

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

Seibert, Michael; Alfano, Robert R.

1974-01-01

104

Acceleration time scale at ultrarelativistic shock waves  

E-print Network

The first-order cosmic ray acceleration at ultrarelativistic shocks is investigated using the Monte Carlo method. We apply a method of discrete particle momentum scattering as a model of particle pitch angle diffusion to reproduce highly anisotropic conditions at the shock wave. Shocks with Lorentz factors $\\gamma$ up to 320 and varying magnetic field inclinations $\\psi$ are considered. Values of diffusion coefficients upstream in the point where energy spectral indices stabilize to the limit 2.2 were calculated. The obtained acceleration time does not depend on shock conditions.

J. Bednarz

1998-08-26

105

Allometric scaling and maximum efficiency in physiological eigen time  

PubMed Central

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 timescale, 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

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

2002-01-01

106

Evidence from ammonoids and conodonts for multiple Early Triassic mass extinctions  

PubMed Central

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

Stanley, Steven M.

2009-01-01

107

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

PubMed

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

Riggs; Lehman; Gehrels; Dickinson

1996-07-01

108

Chron E23r, paleosecular variation, CAMP volcanism and the end-Triassic extinction event (Invited)  

NASA Astrophysics Data System (ADS)

In the early Mesozoic rift basins of eastern North America, CAMP lava flows occur within normal polarity Chron E24n, which according to cycle stratigraphy has a duration of nearly four McLaughlin (405 kyr) cycles, or ~1.6 Ma. In the Newark basin, the level marking the end-Triassic extinction event occurs one Van Houten cycle (20 kyr) before the first CAMP basalt and is preceded within another Van Houten cycle by reverse polarity Chron E23r, one of the shortest (~25 kyr) polarity intervals recognized in the Newark astronomically-tune polarity time scale. This tight chronostratigraphic sequence of events-E23r followed by end-Triassic event and then CAMP lavas within E24n-has been replicated in several sections [1] and a key element (end-Triassic palynofloral turnover preceding the first CAMP lava) is recorded in the Fundy basin of Nova Scotia, where the initial CAMP eruption (North Mountain Basalt) has a rather precise U-Pb (206Pb/238U) zircon date of 201.27± 0.03 Ma [2]. However, two magnetic excursions were found within the Intermediate Basalt (39Ar/40Ar date of 199.9± 0.5 Ma) in the Central High Atlas Mountains of Morocco and correlated to E23r [3, 4], which would imply that the underlying (Lower) basalt unit occurred before and therefore in a possible causal relationship to the end-Triassic extinction event. Paleomagnetic study of the Moroccan basalts also revealed variations in magnetic directions, which were interpreted as a record of secular variation and thus might prove useful for identification of CAMP lavas [4]. We sampled most of the lava flows in the Fundy basin that comprise the ~300 m-thick North Mountain Basalt in outcrop (30 sites) as well as in several industry cores drilled near Margaretsville (GAV-77-3, AV-C-1-4), Freeport (AV-C-1-1), and Westport (AV-C-1-2) in Nova Scotia. We find only two directional groupings for the entire North Mountain Basalt, a finding that basically confirms the results of Carmichael and Palmer [5]. We have yet to find evidence in the Fundy basin for the two excursions that have been reported in the Intermediate basalt (and variously correlated to E23r. However, the progression of VGP clusters corresponding to the directional groups for the North Mountain Basalt resemble those reported by Knight et al. [4] for the Lower and Intermediate lavas from Morocco. We thus speculate that the episodic volcanicity associated with initial phases of CAMP can be correlated over (predrift) distances of ~1000 km on submillennial time-scales of paleosecular variation. 1, Olsen, P.E. et al. 2002, Geol. Soc. Amer. Spec. Paper 356:505-522; 2, Schoene, B. et al., 2006, Geochim. Cosmochim. Acta 70:426-445; 3, Marzoli, A. et al., 2004, Geology 32:973-976; 4, Knight, A.B. et al., 2004, Earth Planet. Sci. Lett. 228:143-160; 5, Carmichael, C.M., Palmer, H. C., 1968, Jour. Geophys. Res. 73:2811-2822.

Kent, D. V.; Wang, H.; Olsen, P. E.

2009-12-01

109

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

USGS Publications Warehouse

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.

Weems, R.E.

1992-01-01

110

Tectonic evolution of the Songpan Garzê and adjacent areas (NE Tibet) from Triassic to Present : a synthesis.  

NASA Astrophysics Data System (ADS)

The 12th May 2008 Wenchuan earthquake in the Longmen Shan occurred on a large thrust fault largely inherited from an Indosinian structure itself probably controlled by an older structural heritage of the South China block continental margin. Within the whole northeast Tibet region, such a structural inheritance has had a major impact on the Tertiary deformation. It appears of primary importance to assess the pre-Tertiary tectonic evolution of the main blocks involved to understand the actual deformation in the eastern edge of Tibet. Over the past decades, the Proterozoic to Cenozoic tectonic, metamorphic and geochronologic history of the Longmen Shan and Songpan Garzê area have been largely studied. We present a synthesis of the tectonic evolution of the Songpan Garzê fold and thrust belt from Triassic to present. The Songpan-Garzê belt was formed during closure of a wide oceanic basin filled with a thick (5 to 15 km) sequence of Triassic flyschoid sediments [10]. Closure of the basin due to Triassic subduction involved strong shortening, intense folding and faulting of the Triassic series. A large-scale décollement, that presently outcrops along the eastern boundary of the belt (Danba area), allowed the growth of a wide and thick accretionary wedge [9]. It develops in the Paleozoic and Triassic series and separates the accretionary prism from an autochthonous crystalline basement [5, 12, 6] which shares many similarities with the basement of the Yangtze Craton (0.7-0.9 Ga). To the north and northwest, below the thickened Triassic series of the belt, the composition (oceanic or continental) of the basement remains unknown. During the Indosinian orogeny the emplacement of orogenic granites (220 - 150 Ma) was associated to crustal thickening [12, 13, 17, 15]. The isotopic composition of granitoids shows that their magma source were predominantly derived from melting of the proterozoic basement with varying degrees of sedimentary material and negligible mantle source contribution. In the Danba area, the décollement outcrops in a large tertiary antiform with a NNW-SSE axis [6, 12, 18]. It has been exhumed too in the hanging wall of the NE-SW faults of the Tertiary Longmen-Shan belt that marks the present day transition from the Tibetan plateau to the Sichuan basin. These faults have episodically absorbed significant shortening since the Late Triassic [3]. The amount and precise timing of post-triassic deformation are difficult to constrain especially because of the difficulty to isolate the tertiary thermochronological signal from the protracted late Triassic - Cretaceous thermal history (e.g. [14]). Nonetheless it is generally accepted that Jurassic - Cretaceous tectonism did not modified the general Triassic architecture of eastern Tibet contrarily to the Tertiary deformation (e.g. [2, 12, 5, 14]). The long-term cooling histories obtained on Mesozoic granites and on the metamorphic series of the Danba dome are very similar showing a very slow and regular cooling during Jurassic and Cretaceous, confirming the absence of major tectonic event between c.a. 150 and 30 Ma [16, 7, 6, 12, 18]. Low temperature thermochronology data indicate that final exhumation and cooling occurred in the Tertiary with an acceleration between 10 and 5 Ma along the major tectonic structures [11, 12, 1, 16, 7,14, 8]. Within the Longmen Shan range, a total denudation of 7 to 10 km is estimated for the late Cenozoic period [1, 7, 4]. Similar amounts of late Tertiary denudation have been estimated along an east-west section across the Xianshuihe fault [16]. 1 : Arne et al., (1997), Tectonophysics 280, 239-256. 2 : Burchfield et al. (1995), International Geology Review 37, 661-735. 3 : Chen and Wilson, (1996), Journal of Structural Geology 18, 413-440. 4 : Clark et al., (2005), Geology 33, 525-528. 5 : Harrowfield and Wilson, (2005), Journal of Structural Geology 27, 101-117. 6 : Huang et al., (2003), Journal of Metamorphic Geology 21(3), 223-240. 7 : Kirby et al., (2002), Tectonics 21(1), 10.1029/2000TC001246. 8 : Lai et al., (2007), Science in Ch

Roger, F.; Jolivet, M.; Malavieille, J.

2009-04-01

111

On time scale invariance of random walks in confined space.  

PubMed

Animal movement is often modelled on an individual level using simulated random walks. In such applications it is preferable that the properties of these random walks remain consistent when the choice of time is changed (time scale invariance). While this property is well understood in unbounded space, it has not been studied in detail for random walks in a confined domain. In this work we undertake an investigation of time scale invariance of the drift and diffusion rates of Brownian random walks subject to one of four simple boundary conditions. We find that time scale invariance is lost when the boundary condition is non-conservative, that is when movement (or individuals) is discarded due to boundary encounters. Where possible analytical results are used to describe the limits of the time scaling process, numerical results are then used to characterise the intermediate behaviour. PMID:25481837

Bearup, Daniel; Petrovskii, Sergei

2015-02-21

112

Time Scaling of Chaotic Systems: Application to Secure Communications  

E-print Network

The paper deals with time-scaling transformations of dynamical systems. Such scaling functions operate a change of coordinates on the time axis of the system trajectories preserving its phase portrait. Exploiting this property, a chaos encryption technique to transmit a binary signal through an analog channel is proposed. The scheme is based on a suitable time-scaling function which plays the role of a private key. The encoded transmitted signal is proved to resist known decryption attacks offering a secure and reliable communication.

Donatello Materassi; Michele Basso

2007-10-23

113

Learning Across Time Scales: Science, Policy, Management, and Communication  

NASA Astrophysics Data System (ADS)

This presentation will draw together common themes raised in the session and discuss lessons learned across time scales and their implications for managers and policy makers concerned with both climate change and variability. Session themes will be examined in the context of the upcoming World Summit on Sustainable Development (WSSD) and considered as opportunities for linking climate change policy discussions with lessons learned from the study of adaptation on seasonal to interannual time scales. The presentation will raise questions about future research directions, discuss recommendations for promoting learning across time scales, and explore options for better communicating the links between climate change and variability.

Stewart, M. M.

2002-05-01

114

Exfoliated pebbles and sheeting in the Triassic  

Microsoft Academic Search

SHATTERED pebbles and sheeted bedrock are common weathering phenomena in most modern deserts1-3 but their existence in ancient desert environments does not seem to have been described. This communication documents their occurrence in South Wales, where they were formed during the Triassic period, some 200 Myr ago.

Maurice E. Tucker

1974-01-01

115

Middle Triassic source rocks in north Lombardy  

SciTech Connect

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.

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

1988-08-01

116

Lystrosaurus zone (triassic) fauna from antarctica.  

PubMed

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

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

1972-02-01

117

Lystrosaurus Zone (Triassic) Fauna from Antarctica  

Microsoft Academic Search

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.

James W. Kitching; James W. Collinson; David H. Elliot; Edwin H. Colbert

1972-01-01

118

Plate tectonic controls on atmospheric CO2 levels since the Triassic  

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

119

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

NASA Astrophysics Data System (ADS)

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.

Brookfield, Michael E.

2008-10-01

120

Asymmetry of Information Flow Between Volatilities Across Time Scales  

E-print Network

Asymmetry of Information Flow Between Volatilities Across Time Scales Ramazan Gen¸cay Faruk Sel horizon is most likely followed by low volatility states at shorter time horizons. On the other hand, a high volatility state at long time horizons does not necessarily imply a high volatility state

Whitcher, Brandon

121

Supraregional seismites in Triassic - Jurassic boundary strata  

NASA Astrophysics Data System (ADS)

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 ?13C 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.

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

122

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)

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.

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

123

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

PubMed

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

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

124

Real-Time Communication for Large Scale Distributed Control Systems  

Microsoft Academic Search

Because of their scale, complexity and requirement of ex- pandability, Large Scale Distributed Control Systems (LSDCS) are usu- ally created in a multistep integration process. To succeed, it has to be governed by well-defined information architecture, appropriate commu- nication infrastructure and the supervisory role of the time notion taken into consideration from the very beginning of the design stage. Mutual

Mariusz Postol

125

Modes and emergent time scales of embayed beach dynamics  

NASA Astrophysics Data System (ADS)

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.

Ratliff, Katherine M.; Murray, A. Brad

2014-10-01

126

Diffusion Time-Scale of Porous Pressure-Sensitive Paint  

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

127

Kibble-Zurek mechanism and finite-time scaling  

NASA Astrophysics Data System (ADS)

The Kibble-Zurek (KZ) mechanism has been applied to a variety of systems ranging from low-temperature Bose-Einstein condensations to grand unification scales in particle physics and cosmology and from classical phase transitions to quantum phase transitions. Here, we show that finite-time scaling (FTS) provides a detailed improved understanding of the mechanism. In particular, the finite time scale, which is introduced by the external driving (or quenching) and results in FTS, is the origin of the division of the adiabatic regimes from the impulse regime in the KZ mechanism. The origin of the KZ scaling for the defect density, generated during the driving through a critical point, is not that the correlation length ceases growing in the nonadiabatic impulse regime, but rather, is that it is taken over by the effective finite length scale corresponding to the finite time scale. We also show that FTS accounts well for and improves the scaling ansatz proposed recently by Liu, Polkovnikov, and Sandvik, [Phys. Rev. B 89, 054307 (2014), 10.1103/PhysRevB.89.054307]. Further, we show that their universal power-law scaling form applies only to some observables in cooling but not to heating. Even in cooling, it is invalid either when an appropriate external field is present. However, this finite-time-finite-size scaling calls for caution in application of FTS. Detailed scaling behaviors of the FTS and finite-size scaling, along with their crossover, are explicitly demonstrated, with the dynamic critical exponent z being estimated for two- and three-dimensional Ising models under the usual Metropolis dynamics. These values of z are found to give rise to better data collapses than the extant values do in most cases but take on different values in heating and cooling in both two- and three-dimensional spaces.

Huang, Yingyi; Yin, Shuai; Feng, Baoquan; Zhong, Fan

2014-10-01

128

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

SciTech Connect

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.

Kushner, Harold J., E-mail: hjk@dam.brown.ed [Brown University, Applied Math (United States)

2010-12-15

129

Mantle plume: The invisible serial killer — Application to the Permian–Triassic boundary mass extinction  

Microsoft Academic Search

The Earth experienced a severe mass extinction at the Permian–Triassic boundary (PTB) about 252 million years ago. This biological catastrophe was accompanied by major changes in geochemical composition of the atmosphere and ocean and the appearance of sedimentary features which had not occurred since the Precambrian time. The eruption of the largest continental flood basalt, the Siberian Traps, overlapped this mass

Ezat Heydari; Nasser Arzani; Jamshid Hassanzadeh

2008-01-01

130

Palaeoclimatology (Communication arising): CO2 and the end-Triassic mass extinction  

Microsoft Academic Search

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

David Beerling

2002-01-01

131

Floral changes across the Triassic\\/Jurassic boundary linked to flood basalt volcanism  

Microsoft Academic Search

One of the five largest mass extinctions of the past 600million years occurred at the boundary of the Triassic and Jurassic periods, 201.6million years ago. The loss of marine biodiversity at the time has been linked to extreme greenhouse warming, triggered by the release of carbon dioxide from flood basalt volcanism in the central Atlantic Ocean. In contrast, the biotic

B. van de Schootbrugge; T. M. Quan; S. Lindström; W. Püttmann; C. Heunisch; J. Pross; J. Fiebig; R. Petschick; H.-G. Röhling; S. Richoz; Y. Rosenthal; P. G. Falkowski

2009-01-01

132

Characteristic Time Scales of Characteristic Magmatic Processes and Systems  

NASA Astrophysics Data System (ADS)

Every specific magmatic process, regardless of spatial scale, has an associated characteristic time scale. Time scales associated with crystals alone are rates of growth, dissolution, settling, aggregation, annealing, and nucleation, among others. At the other extreme are the time scales associated with the dynamics of the entire magmatic system. These can be separated into two groups: those associated with system genetics (e.g., the production and transport of magma, establishment of the magmatic system) and those due to physical characteristics of the established system (e.g., wall rock failure, solidification front propagation and instability, porous flow). The detailed geometry of a specific magmatic system is particularly important to appreciate; although generic systems are useful, care must be taken to make model systems as absolutely realistic as possible. Fuzzy models produce fuzzy science. Knowledge of specific time scales is not necessarily useful or meaningful unless the hierarchical context of the time scales for a realistic magmatic system is appreciated. The age of a specific phenocryst or ensemble of phenocrysts, as determined from isotopic or CSD studies, is not meaningful unless something can be ascertained of the provenance of the crystals. For example, crystal size multiplied by growth rate gives a meaningful crystal age only if it is from a part of the system that has experienced semi-monotonic cooling prior to chilling; crystals entrained from a long-standing cumulate bed that were mechanically sorted in ascending magma may not reveal this history. Ragged old crystals rolling about in the system for untold numbers of flushing times record specious process times, telling more about the noise in the system than the life of typical, first generation crystallization processes. The most helpful process-related time scales are those that are known well and that bound or define the temporal style of the system. Perhaps the most valuable of these times comes from the observed durations and rates of volcanism. There can be little doubt that the temporal styles of volcanism are the same as those of magmatism in general. Volcano repose times, periodicity, eruptive fluxes, acoustic emission structures, lava volumes, longevity, etc. must also be characteristic of pluton-dominated systems. We must therefore give up some classical concepts (e.g., instantaneous injection of crystal-free magma as an initial condition) for any plutonic/chambered system and move towards an integrated concept of magmatism. Among the host of process-related time scales, probably the three most fundamental of any magmatic system are (1) the time scale associated with crystal nucleation (J) and growth (G) (tx}=C{1(G3 J)-{1}/4; Zieg & Marsh, J. Pet. 02') along with the associated scales for mean crystal size (L) and population (N), (2) the time scale associated with conductive cooling controlled by a local length scale (d) (tc}=C{2 d2/K; K is thermal diffusivity), and (3) the time scale associated with intra-crystal diffusion (td}=C{3 L2/D; D is chemical diffusivity). It is the subtle, clever, and insightful application of time scales, dovetailed with realistic system geometry and attention paid to the analogous time scales of volcanism, that promises to reveal the true dynamic integration of magmatic systems.

Marsh, B. D.

2004-05-01

133

Vorticity statistics and the time scales of turbulent strain.  

PubMed

Time scales of turbulent strain activity, denoted as the strain persistence times of first and second order, are obtained from time-dependent expectation values and correlation functions of Lagrangian rate-of-strain eigenvalues taken in particularly defined statistical ensembles. Taking into account direct numerical simulation data, our approach relies on heuristic closure hypotheses which allow us to establish a connection between the statistics of vorticity and strain. It turns out that softly divergent prefactors correct the usual "1/s" strain time-scale estimate of standard turbulence phenomenology, in a way which is consistent with the phenomenon of vorticity intermittency. PMID:23944547

Moriconi, L; Pereira, R M

2013-07-01

134

Does the Permo-Triassic Geomagnetic Dipole Low Exist?  

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

135

Universal scaling function in discrete time asymmetric exclusion processes  

NASA Astrophysics Data System (ADS)

In the universality class of the one dimensional Kardar-Parisi-Zhang surface growth, Derrida and Lebowitz conjectured the universality of not only the scaling exponents, but of an entire scaling function. Since Derrida and Lebowitz' original publication this universality has been verified for a variety of continuous time systems in the KPZ universality class. We study the Derrida-Lebowitz scaling function for multi-particle versions of the discrete time Asymmetric Exclusion Process. We find that in this discrete time system the Derrida-Lebowitz scaling function not only properly characterizes the large system size limit, but even accurately describes surprisingly small systems. These results have immediate applications in searching biological sequence databases.

Chia, Nicholas; Bundschuh, Ralf

2005-03-01

136

Sedimentary record of Late Triassic transpressional tectonics of the Longmenshan thrust belt, SW China  

NASA Astrophysics Data System (ADS)

Sedimentary data from field and borehole investigations allow reconstruction of the southwesterly variations of proximal sedimentary processes along the Longmenshan thrust belt during Late Triassic and Early Jurassic times and relating them to the development of a transpression basin. Conglomerates, which are the early indicators of the tectonic activity and orogeny appear for the first time in the second member of the Upper Triassic Xujiahe Formation and crop out only in the northern segment of the Longmenshan thrust belt. They are also present in the central segment in the fourth member of the Xujiahe Formation. In contrast the Early Jurassic Baitianba conglomerates were deposited all along the front of the Longmenshan thrust belt. The contact between the Upper Triassic and Lower Jurassic units is an angular unconformity and or a disconformity in the northern and central segments of the Longmenshan thrust belt, but becomes conformable to the southwest, along the strike. The isopach maps of different stratigraphic units show the along-strike shift of the depocenters with time, the result of southwestward propagating contraction and deformation of the Longmenshan thrust belt. In conjunction with the regional structural analysis and paleocurrent reconstructions, the southwesterly variations of sedimentary processes demonstrate an along-strike kinematic change of tectonic process in the western Sichuan basin from the northeast to the southwest. These data indicates that a transpressional deformation occurred along the Longmenshan thrust belt during the Late Triassic, and was synchronous with the development of the western Sichuan basin, which behaved as a transpressional foreland basin.

Deng, Bin; Liu, Shugen; Jansa, Luba; Cao, Junxing; Cheng, Yang; Li, Zhiwu; Liu, Shun

2012-04-01

137

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

NASA Technical Reports Server (NTRS)

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.

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

1998-01-01

138

The biology of time across different scales Dean V Buonomano  

E-print Network

that span from microseconds to days. In contrast to the technologies devised by humans to keep track of time individuals and society as a whole,the ability to precisely track and tell time is critical across scales positioning systems to the tracking of our yearly trip around the sun. In-between these extremes we track

Buonomano, Dean

139

Estimating ventilation time scales using overturning stream functions  

E-print Network

Estimating ventilation time scales using overturning stream functions Bijoy Thompson & Jonas 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract A simple method for estimating ventilation time-enclosed ocean basin ventilated through a narrow strait over a sill, and the result is compared to age estimates

Döös, Kristofer

140

Atomic Time Scales for the 21st Century  

NASA Astrophysics Data System (ADS)

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.

Arias, E. F.

2014-06-01

141

Parametric Timing Analysis and Its Application to Dynamic Voltage Scaling  

E-print Network

25 Parametric Timing Analysis and Its Application to Dynamic Voltage Scaling SIBIN MOHAN and FRANK (WCETs) to determine if tasks meet deadlines. Static timing analysis derives bounds on WCETs but requires statically known loop bounds. This work removes the constraint on known loop bounds through parametric

Whalley, David

142

Planck Scale Physics, Pregeometry and the Notion of Time  

E-print Network

Recent progress in quantum gravity and string theory has raised interest among scientists to whether or not nature behaves discretely at the Planck scale. There are two attitudes twoards this discretenes i.e. top-down and bottom-up approach. We have followed up the bottom-up approach. Here we have tried to describe how macroscopic space-time or its underlying mesoscopic substratum emerges from a more fundamental concept. The very concept of space-time, causality may not be valid beyond Planck scale. We have introduced the concept of generalised time within the framework of Sheaf Cohomology where the physical time emrges around and above Planck scale. The possible physical amd metaphysical implications are discussed.

S. Roy

2003-11-04

143

Triassic/Jurassic faulting patterns of Conecuh Ridge, southwest Alabama  

SciTech Connect

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.

Hutley, J.K.

1985-02-01

144

Triassic oils and related hydrocarbon kitchens in the Adriatic basin  

SciTech Connect

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.

Novelli, L.; Demaison, G. (AGIP, Milan (Italy))

1988-08-01

145

Thermodynamics Constrains Allometric Scaling of Optimal Development Time in Insects  

PubMed Central

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

Dillon, Michael E.; Frazier, Melanie R.

2013-01-01

146

The drift Hystory of Iran from the Ordovician to the Triassic  

NASA Astrophysics Data System (ADS)

New Late Ordovician, Permian, and Triassic paleomagnetic data from Iran are presented. These data, in conjunction with data from the literature, provide insights on the drift history of Iran as part of Cimmeria during the Ordovician-Triassic. A robust agreement of paleomagnetic poles of Iran and West Gondwana is observed for the Late Ordovician-earliest Carboniferous, indicating that Iran was part of Gondwana during that time. Data for the Late Permian-early Early Triassic indicate that Iran resided on subequatorial palaeolatitudes, clearly disengaged from the parental Gondwanan margin in the southern hemisphere as the result of the opening of the Neotethys Ocean along the eastern margin of Gondwana during the Permian. Since possibly the late Early Triassic, Iran was located in the northern hemisphere close to the Eurasian margin. This northward drift brought Iran to cover much of the Paleotethys in ~35 Myr at an average plate speed of ~7-8 cm/yr. As a novel conclusion, we find that timing, rates, and geometry of Cimmerian tectonics are broadly compatible with the transformation of Pangea from an Irvingian B to a Wegenerian A-type configuration with Neo-Tethyan opening taking place contemporaneously essentially in the Permian.

Muttoni, G.; Mattei, M.; Marco, B.; Zanchi, A.; Gaetani, M.; Berra, F.; Kent, D. V.; Angiolini, L.

2009-05-01

147

Two typical time scales of the piston effect  

NASA Astrophysics Data System (ADS)

The existence of a fourth mode of heat transfer near the critical point, named the piston effect, has been known for more than a decade. The typical time scale of temperature relaxation due to this effect was first predicted by Onuki [Phys. Rev A 41, 2256 (1990)], and this author’s formula has been extensively used since then to predict the thermal behavior of near-critical fluids. Recent studies, however, pointed out that the critical divergence of the bulk viscosity could have a strong influence on piston-effect-related processes. In this paper, we conduct a theoretical analysis of near-critical temperature relaxation showing that the piston effect is not governed by one (as was until now believed) but by two typical time scales. These two time scales exhibit antagonistic asymptotic behaviors as the critical point is approached: while the classical piston-effect time scale (as predicted by Onuki ) goes to zero at the critical point (critical speeding up), the second time scale (related to bulk viscosity) goes to infinity (critical slowing down). Based on this property, an alternative method for measuring near-critical bulk viscosity is proposed.

Carlès, Pierre; Dadzie, Kokou

2005-06-01

148

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

PubMed

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

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

149

Investigating the Geologic Time Scale: Creating posters to Display Trends in Geologic Time  

NSDL National Science Digital Library

This observational inquiry activity involving careful descriptions of rocks and fossil including age will be used to create a scalar accurate geologic time scale. Students will observe and learn that the geologic time scale was created based on changes in fossil, rock, and atmospheric changes.

Atkins, Kim

150

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

PubMed Central

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

Wales, David J.; Salamon, Peter

2014-01-01

151

Conodont paleoecology of Lower Triassic Thaynes Formation  

SciTech Connect

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.

Carr, T.R.

1983-03-01

152

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

USGS Publications Warehouse

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

Yochelson, E.Y.; Yin, Hongfu

1985-01-01

153

Variable Time Scale Rainfall Disaggregation Using Artificial Neural Networks  

NASA Astrophysics Data System (ADS)

Variability of precipitation is the primary factor driving land surface hydrological processes. In order to accurately understand many land surface hydrological processes such as infiltration and Hortonian runoff, an accurate and fine time scale description of precipitation is necessary. In many cases, this is neither time nor cost effective. An alternative to maintaining fine time scale networks of rain gauges is to disaggregate records from gauges with coarser time steps. This research developed disaggregation methods for converting daily rainfall records into hourly records and hourly records into fifteen-minute records using artificial neural networks (ANNs). Artificial neural networks have been successfully utilized in the past in many different areas of natural science including climate change, seismology, and groundwater remediation. More recently, ANNs have been developed to disaggregate hourly rainfall records into fifteen-minute records. This study extends prior research in the use of ANNs by examining their performance when disaggregating into a range of time scales. The performances of the ANNs developed to account for seasonal variability of rainfall in west-central Florida were compared to those of the ANNs that did not account for seasonal variability of rainfall. Network architecture for each feed-forward, backpropagation ANN was developed and optimized. The performances of the final ANNs were compared to determine if the fractal structure of rainfall was conserved across the two time scales studied.

Rokicki, R.; Nachabe, M.

2001-12-01

154

Evaluation of Scaling Invariance Embedded in Short Time Series  

PubMed Central

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

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

2014-01-01

155

Evaluation of scaling invariance embedded in short time series.  

PubMed

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 [Formula: see text]. Calculations with specified Hurst exponent values of [Formula: see text] 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 ([Formula: see text]) and sharp confidential interval (standard deviation [Formula: see text]). 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

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

2014-01-01

156

Time scales for molecule formation by ion-molecule reactions  

NASA Technical Reports Server (NTRS)

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.

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

1976-01-01

157

Relativistic fireballs - Energy conversion and time-scales  

NASA Technical Reports Server (NTRS)

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.

Rees, M. J.; Meszaros, P.

1992-01-01

158

Dynamics symmetries of Hamiltonian system on time scales  

SciTech Connect

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.

Peng, Keke, E-mail: pengkeke88@126.com; Luo, Yiping, E-mail: zjstulyp@126.com [Department of Physics, Zhejiang Sci-Tech University, Hangzhou 310018 (China)] [Department of Physics, Zhejiang Sci-Tech University, Hangzhou 310018 (China)

2014-04-15

159

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

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

160

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

SciTech Connect

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.

Miller, J.S.; Glazner, A.F. (Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Geology); Walker, J.D.; Martin, M.W. (Univ. of Kansas, Lawrence, KS (United States). Dept. of Geology)

1993-04-01

161

TIME DELAY AND MOTION ESTIMATORS BASED ON DIGITAL FAST TIME-SCALING OF RANDOM SIGNALS  

Microsoft Academic Search

The estimation of time-delay and time-scaling is required in many signal processing applications. A parabolic approximation was recently suggested for fine estimation of time delay from sampled signals. The method directly extends to scaling estimation by a parallel multi-rate sampling of the analog received signal. Such rescaling can be implemented by digital techniques and two efficient algorithms are here devised

Gaetano Giunta

162

THEORETICAL REVIEW The Hippocampus, Time, and Memory Across Scales  

PubMed Central

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

Howard, Marc W.; Eichenbaum, Howard

2014-01-01

163

Calcimicrobial cap rocks from the basal Triassic units: western Taurus occurrences (SW Turkey)  

Microsoft Academic Search

A post-extinction calcimicrobial cap rock occurs above the giant Permian skeletal carbonate platform exposed in the western Taurus Mountains (southern Turkey). It was formed during the main step of a very rapid and large-scale platform flooding (Earliest Triassic) and has been found also in other Tethyan localities. This calcimicrobial cap rock, 20 to 40 m thick, consists of thrombolitic and stromatolitic

Aymon Baud; Sylvain Richoz; Jean Marcoux

2005-01-01

164

Comparative responsiveness of Parkinson's disease scales to change over time.  

PubMed

The objective of the study is to examine the comparative responsiveness of outcome measures to assess progression over time in Parkinson's disease (PD). One hundred twenty-eight patients participating in a clinic-based naturalistic study of PD were assessed with the Hoehn and Yahr, UPDRS, MMSE, PDQ-39, PDQL, EQ-5D, and BDI scales at baseline and at 1 year. In addition, 82 patients in a community-based study of patients with PD who had completed self-rated Schwab and England, PDQ-39, EQ-5D, and BDI scales at baseline, were sent the same questionnaires at 1 and 4 years. Responsiveness was assessed using t-tests, standardised effect size, and standardised response mean. In both samples, the Hr-QoL measures were less responsive to change over time than the impairment and disability scales (Hoehn and Yahr, UPDRS, Schwab and England scales). In addition, in the clinic-based sample, Hoehn and Yahr and UPDRS ADL scale ("on") were more responsive to progression over time than UPDRS motor part and ADL part ("off"). Hr-QoL measures are less responsive to change over time than measures of impairment and disability. Although this suggests that these measures are less accurate in detecting subtle changes, it may also indicate that the multifactorial subjective assessment of Hr-QoL adapts to changes over time. Global assessment of overall impairment and disability (which incorporates motor and nonmotor features of PD), however, appeared relatively responsive to change over time in patients in a naturalistic setting. PMID:19199355

Schrag, Anette; Spottke, Annika; Quinn, Niall Patrick; Dodel, Richard

2009-04-30

165

Multi-scale Template Reconstruction of ABL Time Series  

NASA Astrophysics Data System (ADS)

It has been shown previously that a large fraction of instantaneous turbulent time series of 1-D velocity in an atmospheric boundary layer(ABL) can be reconstructed using a set of templates taken from samples of laboratory-scale wall turbulence (Hommema and Adrian [1]). A new analysis is presented in which the 3-D velocity time series from NCAR's HATS (Horizontal Array Turbulence Study) experiment is matched with templates from laboratory-scale flows using wavelet transforms. The template amplitude, temporal scale and temporal location is varied to produce the maximum correlation coefficient. Efficient templates generally take the form of segments through hairpin vortex packets. [1] Hommema S.E., and Adrian R.J.,"Similarity of apparently random structures in the outer region of wall turbulence", Exp. Fluids, 33, 5--12 (2002).

Balakumar, B. J.; Adrian, R. J.

2003-11-01

166

GNSS observations of deep convective time scales in the Amazon  

NASA Astrophysics Data System (ADS)

In the tropics, understanding the shallow-to-deep transition and organization of convection on the mesoscale is made difficult due the paucity of long-term high spatial/temporal resolution data. In this paper, data from the world's first long-term equatorial Global Navigational Satellite System meteorological station in Manaus (Central Amazon) is used to create a new metric, a water vapor convergence time scale, to characterize the temporal evolution of deep convection over a tropical continental region. From 3.5 years of data, 320 convective events were analyzed using a compositing analysis. Results reveal two characteristic time scales of water vapor convergence; an 8 h time scale of weak convergence and 4 h timescale of intense water vapor convergence associated with the shallow-to-deep convection transition. The 4 h shallow-to-deep transition time scale is particularly robust, regardless of convective intensity, seasonality, or nocturnal versus daytime convection. This new result provides a useful metric for both high resolution and global climate models to replicate.

Adams, D. K.; Gutman, Seth I.; Holub, Kirk L.; Pereira, Dulcineide S.

2013-06-01

167

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

E-print Network

We study the formation of BTZ 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.

Danny Birmingham; Siddhartha Sen

1999-08-23

168

Multiple time scale numerical methods for the inverted pendulum problem  

E-print Network

Multiple time scale numerical methods for the inverted pendulum problem Richard Sharp1, Yen (HMM) [1]. We apply the methods to compute the averaged path of the inverted pendulum under a highly and thus compute the average path of the inverted pendulum. 1 Introduction The focus of this paper

Tsai, Yen-Hsi Richard

169

MULTIPLE TIME SCALE NUMERICAL METHODS FOR THE INVERTED PENDULUM PROBLEM  

E-print Network

MULTIPLE TIME SCALE NUMERICAL METHODS FOR THE INVERTED PENDULUM PROBLEM RICHARD SHARP, YEN-HSI TSAI multiscale methods (HMM) [1]. We apply the methods to compute the averaged path of the inverted pendulum approximate the averaged equation and thus compute the average path of the inverted pendulum. 1. INTRODUCTION

Soatto, Stefano

170

Multiple time-scale power system dynamic simulation  

Microsoft Academic Search

A new program, EXSTAB (extended time-scale stability) has been developed for representing a wide variety of power system performance problems, from transient stability through long-term dynamics and voltage instability. The capability of the program includes multiple execution modes and automatic step size selection to address conflicting goals of accuracy and efficiency. The modeling includes a broad range of apparatus to

A. Kurita; H. Okubo; K. Oki; S. Agematsu; D. B. Klapper; N. W. Miller; J. J. Sanchez-Gasca; K. A. Wirgau; T. D. Younkins

1993-01-01

171

Speech Compensation for Time-Scale-Modified Auditory Feedback  

ERIC Educational Resources Information Center

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…

Ogane, Rintaro; Honda, Masaaki

2014-01-01

172

Loss rates and time scales for sodium at Mercury  

NASA Astrophysics Data System (ADS)

The time scales and loss rates for sodium in the exosphere of Mercury are studied here. Sodium comes from release processes occurring at the planetary surface; the amount of surface sodium that is available for release (mostly through thermal- or photon-stimulated desorption) is limited. Loss processes deplete the surface concentration of sodium, which is continuously refilled by diffusion from the interior of regolith grains or by chemical sputtering. Ejected sodium particles may either escape the gravity, also aided by the radiation pressure acceleration, or be photoionized, or fall back onto the surface. Falling particles may either stick to the surface or bounce. A Monte Carlo model, simulating all these processes, is used to obtain the exosphere densities, the global loss rates at different true anomaly angles, and typical time scales for small-term variations, taking into account planet's orbit and rotation speed. Assuming an impulsive event, which causes the enhancement of sodium in the exosphere, the model gives the time scales for the exosphere to recover to a steady-state condition. It is found that time scales go from one or two hour (close to perihelion) to half day (close to aphelion). The escape probability ranges from 20% at perihelion and aphelion up to 40% at true anomaly angles of about 60° and 300°.

Mura, Alessandro

2012-04-01

173

Measuring Change over Time with a Rasch Rating Scale Model.  

ERIC Educational Resources Information Center

When measures are taken on the same individual over time, it is difficult to determine whether observed differences are the result of changes in the person or changes in other facets of the measurement situation (e.g. interpretation of items or use of rating scale). This paper describes a method for disentangling changes in persons from changes in…

Wolfe, Edward W.; Chiu, Chris W. T.

174

Modeling of streamflow processes at different time scales  

Microsoft Academic Search

The analysis and modeling of streamflow processes has attracted the attention of water resources specialists for several decades. A number of models have been suggested in the past for representing seasonal and annual streamflow processes. The topic addressed in this paper centers around the compatibility of stochastic models of streamflow at different time scales. More specifically, given a model for

Paolo Bartolini; Jose D. Salas

1993-01-01

175

The time-scale of escape from star clusters  

Microsoft Academic Search

In this paper a cluster is modelled as a smooth potential (due to the cluster stars) plus the steady tidal field of the Galaxy. In this model there is a minimum energy below which stars cannot escape. Above this energy, however, the time-scale on which a star escapes varies with the orbital parameters of the star (mainly its energy) in

T. Fukushige; D. C. Heggie

2000-01-01

176

Dynamical masses, time-scales, and evolution of star clusters  

E-print Network

This review discusses (i) dynamical methods for determining the masses of Galactic and extragalactic star clusters, (ii) dynamical processes and their time-scales for the evolution of clusters, including evaporation, mass segregation, core collapse, tidal shocks, dynamical friction and merging. These processes lead to significant evolution of globular cluster systems after their formation.

Ortwin Gerhard

2000-07-18

177

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

SciTech Connect

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.

Magaritz, M. (Weizmann Inst., Rehovot (Israel)); Krishnamurthy, R.V. (California Inst. of Technology, Pasadena (United States)); Holser, W.T. (Univ. of Oregon, Eugene (United States) Cornell Univ., Ithaca, NY (United States))

1992-12-01

178

Angular size and emission time scales of relativistic fireballs  

E-print Network

The detection of delayed X-ray, optical and radio emission, ``afterglow,'' associated with gamma-ray bursts (GRBs) is consistent with models, where the bursts are produced by relativistic expanding blast waves, driven by expanding fireballs at cosmological distances. In particular, the time scales over which radiation is observed at different wave bands agree with model predictions. It had recently been claimed that the commonly used relation between observation time t and blast wave radius r, t=r/2\\gamma^{2}c where \\gamma(r) is the fluid Lorentz factor, should be replaced with t=r/16\\gamma^{2}c due to blast wave deceleration. Applying the suggested deceleration modification would make it difficult to reconcile observed time scales with model predictions. It would also imply an apparent source size which is too large to allow attributing observed radio variability to diffractive scintillation. We present a detailed analysis of the implications of the relativistic hydrodynamics of expanding blast waves to the observed afterglow. We find that modifications due to shock deceleration are small, therefore allowing for both the observed afterglow time scales and for diffractive scintillation. We show that at time t the fireball appears on the sky as a narrow ring of radius h=r/\\gamma and width 0.1h, where r and t are related by t=r/2\\gamma^{2}c.

Eli Waxman

1997-09-18

179

The Permo-Triassic Extinction  

NSDL National Science Digital Library

This website covers details about the Permian extinction, which occurred about 250 million years ago. It contains a paleontological overview of the extinction, discussing the life present at that time, evidence for the extinction, and what types of lifeforms disappeared. Other sections discuss various theories about what caused the mass-extinction including volcanism, impacts, climate change, glaciation, Pangea and other proposed theories.

180

Arthropods in amber from the Triassic Period  

PubMed Central

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

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

181

Arthropods in amber from the Triassic Period.  

PubMed

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

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

182

Sequence stratigraphy of the Triassic in the Barentsz Sea  

SciTech Connect

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.

Skjold, L.JU.; Van Veen, P.M.; Gjelberg, J.; Kristensen, S.E.; Rasmussen, A.; Skott, P.H.; Stoelan, T. (Norsk Hydro Research Centre, Bergen (Norway))

1990-05-01

183

The Importance of Rotational Time-scales in Accretion Variability  

NASA Astrophysics Data System (ADS)

For the first few million years, one of the dominant sources of emission from a low mass young stellar object is from accretion. This process regulates the flow of material and angular moments from the surroundings to the central object, and is thought to play an important role in the definition of the long term stellar properties. Variability is a well documented attribute of accretion, and has been observed on time-scales of from days to years. However, where these variations come from is not clear. Th current model for accretion is magnetospheric accretion, where the stellar magnetic field truncates the disc, allowing the matter to flow from the disc onto the surface of the star. This model allows for variations in the accretion rate to come from many different sources, such as the magnetic field, the circumstellar disc and the interaction of the different parts of the system. We have been studying unbiased samples of accretors in order to identify the dominant time-scales and typical magnitudes of variations. In this way different sources of variations can be excluded and any missing physics in these systems identified. Through our previous work with the Long-term Accretion Monitoring Program (LAMP), we found 10 accretors in the ChaI region, whose variability is dominated by short term variations of 2 weeks. This was the shortest time period between spectroscopic observations which spanned 15 months, and rules out large scale processes in the disk as origins of this variability. On the basis of this study we have gone further to study the accretion signature H-alpha, over the time-scales of minutes and days in a set of Herbig Ae and T Tauri stars. Using the same methods as we used in LAMP we found the dominant time-scales of variations to be days. These samples both point towards rotation period of these objects as being an important time-scale for accretion variations. This allows us to indicate which are the most likely sources of these variations.

Costigan, Gráinne; Vink, Joirck; Scholz, Aleks; Testi, Leonardo; Ray, Tom

2013-07-01

184

Probing Fission Time Scales with Neutrons and GDR Gamma Rays  

SciTech Connect

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.

Schmitt, R. P. [Texas A& M University; Botting, Tye [Texas A& M University; Chubarian, G G [Texas A& M University; Wolf, K [Texas A& M University; Hurst, B J [Texas A& M University; Jabs, H [Texas A& M University; Hamelin, M [Texas A& M University; Bacak, A [Texas A& M University; Oganessian, Yuri Ts. [FLNR-JINR, Russia; Itkis, M. G. [FLNR-JINR, Russia; Kozulin, E M [FLNR-JINR, Russia; Kondratiev, N. A. [FLNR-JINR, Russia; Salamatin, V S [FLNR-JINR, Russia; Pokrovsky, I V [FLNR-JINR, Russia; Hanappe, F [Universite Libre de Bruxelles, Brussels, Belgium; de Goes Brennand, E. [Universite Libre de Bruxelles, Brussels, Belgium; Huck, A [CRN, Strasbourg, France; Stuttge, L [CRN, Strasbourg, France; Liatard, E [CRN, Strasbourg, France; Beene, James R [ORNL; Varner Jr, Robert L [ORNL; Halbert, Melvyn L [ORNL; Gan, Ning [ORNL

2003-06-01

185

Reconstructions of solar irradiance on centennial time scales  

NASA Astrophysics Data System (ADS)

Solar irradiance is the main external source of energy to Earth's climate system. The record of direct measurements covering less than 40 years is too short to study solar influence on Earth's climate, which calls for reconstructions of solar irradiance into the past with the help of appropriate models. An obvious requirement to a competitive model is its ability to reproduce observed irradiance changes, and a successful example of such a model is presented by the SATIRE family of models. As most state-of-the-art models, SATIRE assumes that irradiance changes on time scales longer than approximately a day are caused by the evolving distribution of dark and bright magnetic features on the solar surface. The surface coverage by such features as a function of time is derived from solar observations. The choice of these depends on the time scale in question. Most accurate is the version of the model that employs full-disc spatially-resolved solar magnetograms and reproduces over 90% of the measured irradiance variation, including the overall decreasing trend in the total solar irradiance over the last four cycles. Since such magnetograms are only available for about four decades, reconstructions on time scales of centuries have to rely on disc-integrated proxies of solar magnetic activity, such as sunspot areas and numbers. Employing a surface flux transport model and sunspot observations as input, we have being able to produce synthetic magnetograms since 1700. This improves the temporal resolution of the irradiance reconstructions on centennial time scales. The most critical aspect of such reconstructions remains the uncertainty in the magnitude of the secular change.

Krivova, Natalie; Solanki, Sami K.; Dasi Espuig, Maria; Leng Yeo, Kok

186

Sublinear scaling for time-dependent stochastic density functional theory.  

PubMed

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. PMID:25612688

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

2015-01-21

187

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

SciTech Connect

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.

Retallack, G.J. [Univ. of Oregon, Eugene, OR (United States)] [Univ. of Oregon, Eugene, OR (United States); Veevers, J.J.; Morante, R. [Macquarie Univ., New South Wales (Australia)] [Macquarie Univ., New South Wales (Australia)

1996-02-01

188

Time scale of diffusion in molecular and cellular biology  

NASA Astrophysics Data System (ADS)

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.

Holcman, D.; Schuss, Z.

2014-05-01

189

Backpropagation and ordered derivatives in the time scales calculus.  

PubMed

Backpropagation is the most widely used neural network learning technique. It is based on the mathematical notion of an ordered derivative. In this paper, we present a formulation of ordered derivatives and the backpropagation training algorithm using the important emerging area of mathematics known as the time scales calculus. This calculus, with its potential for application to a wide variety of inter-disciplinary problems, is becoming a key area of mathematics. It is capable of unifying continuous and discrete analysis within one coherent theoretical framework. Using this calculus, we present here a generalization of backpropagation which is appropriate for cases beyond the specifically continuous or discrete. We develop a new multivariate chain rule of this calculus, define ordered derivatives on time scales, prove a key theorem about them, and derive the backpropagation weight update equations for a feedforward multilayer neural network architecture. By drawing together the time scales calculus and the area of neural network learning, we present the first connection of two major fields of research. PMID:20615808

Seiffertt, John; Wunsch, Donald C

2010-08-01

190

HIV-1 dynamics at different time scales under antiretroviral therapy.  

PubMed

We exploit a model that considers three compartments: blood plasma (BP), lymphoid tissue-interstitial spaces (LT-IS), and follicular dendritic cells (FDC), for the HIV-1 dynamics under the application of highly active antiretroviral therapy (HAART) which allowed us to unravel distinct viral dynamics occurring in short- (2 days), middle- (21 days), and long-term (183 days) time scales. The different time scales are determined by the viral clearance rate, the ratio of productively infected CD4(+) T cells to chronically infected cells, and the dissociation rate of HIV-1 complexes from FDC. This generates a scenario in which, after an initial transient stage, the viral BP dynamics decouples and becomes governed by the lymphoid tissue (LT) dynamics; in a later stage, a new decoupling occurs in which the LT-IS dynamics is slaved to that of the FDC dynamics. We observed an initial increase in the viremia after HAART in a patient who did not receive protease inhibitors (PI). By means of the above-mentioned model we were able to highlight the relevant parameters which need to be estimated at three different time scales after HAART. PMID:16005903

García, José A; Soto-Ramírez, Luis E; Cocho, Germinal; Govezensky, Tzipe; José, Marco V

2006-01-01

191

Modeling of streamflow processes at different time scales  

NASA Astrophysics Data System (ADS)

The analysis and modeling of streamflow processes has attracted the attention of water resources specialists for several decades. A number of models have been suggested in the past for representing seasonal and annual streamflow processes. The topic addressed in this paper centers around the compatibility of stochastic models of streamflow at different time scales. More specifically, given a model for monthly flows, the models for the processes obtained by aggregation, i.e., models for bimonthly, quarterly, etc., time scales, are derived. Likewise, parameter space and covariance properties of such derived processes as well as the relationship of such properties of different time scales are given. These concepts are applied to modeling streamflow of the Niger River. The developments are restricted to the family of periodic autoregressive moving average (PARMA) processes. For instance, it was found that monthly flows based on the PARMA(2, 1) process leads to PARMA(2, 2) bimonthly flows and stationary ARMA(2, 2) annual flows. Furthermore, applications to modeling the Niger River flows suggest that one can reproduce the seasonal and annual second-order statistics without using disaggregation if PARMA models are used for modeling the seasonal flows.

Bartolini, Paolo; Salas, Jose D.

1993-08-01

192

Scaling brain size, keeping timing: evolutionary preservation of brain rhythms.  

PubMed

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

Buzsáki, György; Logothetis, Nikos; Singer, Wolf

2013-10-30

193

South American Reptiles Found in Virginia: Second Triassic Extinction Constrained in NorthAmerica  

E-print Network

in the Triassic period, with the largest of all extinctions, the Permian-Triassic event (245 Ma), ushering in the period, and an- other great event, the Triassic Jurassic mass ex tinction (201 Ma) closing it (Fig 1South American Reptiles Found in Virginia: Second Triassic Extinction Constrained in North

Olsen, Paul E.

194

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

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

195

A methodological bias toward overestimation of molecular evolutionary time scales.  

PubMed

There is presently a conflict between fossil- and molecular-based evolutionary time scales. Molecular approaches for dating the branches of the tree of life frequently lead to substantially deeper times of divergence than those inferred by paleontologists. The discrepancy between molecular and fossil estimates persists despite the booming growth of sequence data sets, which increasingly feeds the interpretation that molecular estimates are older than stratigraphic dates because of deficiencies in the fossil record. Here we show that molecular time estimates suffer from a methodological handicap, namely that they are asymmetrically bounded random variables, constrained by a nonelastic boundary at the lower end, but not at the higher end of the distribution. This introduces a bias toward an overestimation of time since divergence, which becomes greater as the length of the molecular sequence and the rate of evolution decrease. PMID:12060757

Rodriguez-Trelles, Francisco; Tarrio, Rosa; Ayala, Francisco J

2002-06-11

196

Transposition and Time-Scale Invariant Geometric Music Retrieval  

NASA Astrophysics Data System (ADS)

This paper considers how to adapt geometric algorithms, developed for content-based music retrieval of symbolically encoded music, to be robust against time deformations required by real-world applications. In this setting, music is represented by sets of points in plane. A matching, pertinent to the application, involves two such sets of points and invariances under translations and time scalings. We give an algorithm for finding exact occurrences, under such a setting, of a given query point set, of size m, within a database point set, of size n, with running time O(mn 2logn); partial occurrences are found in O(m 2 n 2logn) time. The algorithms resemble the sweepline algorithm introduced in [1].

Lemström, Kjell

197

Scaling in non-stationary time series. (I)  

NASA Astrophysics Data System (ADS)

Most data processing techniques, applied to biomedical and sociological time series, are only valid for random fluctuations that are stationary in time. Unfortunately, these data are often non-stationary and the use of techniques of analysis resting on the stationary assumption can produce a wrong information on the scaling, and so on the complexity of the process under study. Herein, we test and compare two techniques for removing the non-stationary influences from computer generated time series, consisting of the superposition of a slow signal and a random fluctuation. The former is based on the method of wavelet decomposition, and the latter is a proposal of this paper, denoted by us as step detrending technique. We focus our attention on two cases, when the slow signal is a periodic function mimicking the influence of seasons, and when it is an aperiodic signal mimicking the influence of a population change (increase or decrease). For the purpose of computational simplicity the random fluctuation is taken to be uncorrelated. However, the detrending techniques here illustrated work also in the case when the random component is correlated. This expectation is fully confirmed by the sociological applications made in the companion paper. We also illustrate a new procedure to assess the existence of a genuine scaling, based on the adoption of diffusion entropy, multiscaling analysis and the direct assessment of scaling. Using artificial sequences, we show that the joint use of all these techniques yield the detection of the real scaling, and that this is independent of the technique used to detrend the original signal.

Ignaccolo, M.; Allegrini, P.; Grigolini, P.; Hamilton, P.; West, B. J.

2004-05-01

198

A Hierarchy of Time-Scales and the Brain  

PubMed Central

In this paper, we suggest that cortical anatomy recapitulates the temporal hierarchy that is inherent in the dynamics of environmental states. Many aspects of brain function can be understood in terms of a hierarchy of temporal scales at which representations of the environment evolve. The lowest level of this hierarchy corresponds to fast fluctuations associated with sensory processing, whereas the highest levels encode slow contextual changes in the environment, under which faster representations unfold. First, we describe a mathematical model that exploits the temporal structure of fast sensory input to track the slower trajectories of their underlying causes. This model of sensory encoding or perceptual inference establishes a proof of concept that slowly changing neuronal states can encode the paths or trajectories of faster sensory states. We then review empirical evidence that suggests that a temporal hierarchy is recapitulated in the macroscopic organization of the cortex. This anatomic-temporal hierarchy provides a comprehensive framework for understanding cortical function: the specific time-scale that engages a cortical area can be inferred by its location along a rostro-caudal gradient, which reflects the anatomical distance from primary sensory areas. This is most evident in the prefrontal cortex, where complex functions can be explained as operations on representations of the environment that change slowly. The framework provides predictions about, and principled constraints on, cortical structure–function relationships, which can be tested by manipulating the time-scales of sensory input. PMID:19008936

Kiebel, Stefan J.; Daunizeau, Jean; Friston, Karl J.

2008-01-01

199

Optimal Control Modification for Time-Scale Separated Systems  

NASA Technical Reports Server (NTRS)

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.

Nguyen, Nhan T.

2012-01-01

200

Defining a trend for time series using the intrinsic time-scale decomposition  

NASA Astrophysics Data System (ADS)

We propose criteria that define a trend for time series with inherent multi-scale features. We call this trend the tendency of a time series. The tendency is defined empirically by a set of criteria and captures the large-scale temporal variability of the original signal as well as the most frequent events in its histogram. Among other properties, the tendency has a variance no larger than that of the original signal; the histogram of the difference between the original signal and the tendency is as symmetric as possible; and with reduced complexity, the tendency captures essential features of the signal. To find the tendency we first use the intrinsic time-scale decomposition (ITD) of the signal, introduced in 2007 by Frei and Osorio, to produce a set of candidate tendencies. We then apply the criteria to each of the candidates to single out the one that best agrees with them. While the criteria for the tendency are independent of the signal decomposition scheme, it is found that the ITD is a simple and stable methodology, well suited for multi-scale signals. The ITD is a relatively new decomposition and little is known about its outcomes. In this study we take the first steps towards a probabilistic model of the ITD analysis of random time series. This analysis yields details concerning the universality and scaling properties of the components of the decomposition.

Restrepo, Juan M.; Venkataramani, Shankar; Comeau, Darin; Flaschka, Hermann

2014-08-01

201

Magnetostratigraphy of a Lower-Middle Triassic boundary section from Chios (Greece)  

NASA Astrophysics Data System (ADS)

The Marmarotrapeza Formation at Chios Island (northern Aegean Sea, Greece) is renowned for its Lower-Middle Triassic boundary sections in a marine Tethyan setting. Two sections have been sampled bed by bed to develop a magnetostratigraphic framework for the ammonoid and conodont biostratigraphy. The boundary sections occur within a lower normal (A +)-reverse (B -)-upper normal (C +) polarity sequence. The Lower-Middle Triassic boundary, placed at the first occurrence of the ammonoid genera Aegeiceras ugra Diener, Paracrochordiceras spp., Paradanubites depressus Fantini Sestini and Japonites sp., and close to the first appearance of the conodont species Gondolella timorensis Nogami, occurs in normal polarity zone Chios C +. The overall mean direction of the reversal-bearing characteristic component, whose early acquisition is suggested by a tilt test, is D = 271.2°, I = 33.2° ( ?95 = 11.7°, k = 112.5, N = 3). The inferred paleolatitude of the sampling sites is about 18°N, consistent with either an African or stable European affinity, although the declinations suggest large-scale counter-clockwise rotations with respect to Africa or stable Europe since the Early-Middle Triassic.

Muttoni, G.; Kent, D. V.; Gaetani, M.

1995-12-01

202

Time scales in the context of general relativity.  

PubMed

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

Guinot, Bernard

2011-10-28

203

Ti diffusion in quartz inclusions: implications for metamorphic time scales  

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

204

The role of time scales in extrinsic noise propagation  

NASA Astrophysics Data System (ADS)

Cell-to cell variability in the number of proteins has been studied extensively experimentally. There are many sources of this stochastic variability or noise that can be classified as intrinsic, due to the stochasticity of chemical reactions and extrinsic, due to environmental differences. The different stages in the production of proteins in response to a stimulus, the signaling cascade before transcription, transcription, and translation are characterized by different time scales. We analyze how these time scales determine the effect of the reactions at each stage on different sources of noise. For example, even if intrinsic noise dominates the fluctuations in mRNA number, for typical degradation rates, extrinsic noise can dominate corresponding protein number fluctuations. Such results are important in determining the importance of intrinsic noise at earlier stages of a genetic network on the products of subsequent stages. We examine cases in which the dynamics of the extrinsic noise can lead to differences from cases in which extrinsic noise arises from static (in time) cell-to-cell variations. We will interpret the experiments of Pedraza et al*. in the light of these results. *J. M. Pedraza et al, Science 25 March 2005:Vol. 307. no. 5717, pp. 1965 - 1969.

Iyer-Biswas, Srividya; Pedraza, Juan Manuel; Jayaprakash, C.

2009-03-01

205

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

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

206

Granular impact dynamics: Fluctuations at short time-scales  

NASA Astrophysics Data System (ADS)

Several recent studies on granular impact have used a macroscopic force law which describes the slow (mean) dynamics. However, these force-law models must be modified to capture large fluctuations at short time-scales. Here, we discuss granular impact experiments using photoelastic particles, where high-speed video captures both the intruder dynamics and the local granular force response. We show how to systematically separate the fluctuations from the mean dynamics. We also show that these fluctuations are multiplicative with the mean force, and otherwise decoupled from the dynamics. These observations are instructive in connecting to microscopic processes which generate the fluctuations.

Clark, Abram H.; Kondic, Lou; Behringer, R. P.

2013-06-01

207

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

NASA Astrophysics Data System (ADS)

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.

Dawit, Enkurie L.

2014-11-01

208

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

SciTech Connect

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.

Paull, R.K.; Paull, R.A.; Kraemer, B.R. (Univ. of Wisconsin, Milwaukee (USA))

1989-09-01

209

Multiple scale dynamics in proteins probed at multiple time scales through fluctuations of NMR chemical shifts.  

PubMed

Fluctuations of NMR resonance frequency shifts and their relation with protein exchanging conformations are usually analyzed in terms of simple two-site jump processes. However, this description is unable to account for the presence of multiple time scale dynamics. In this work, we present an alternative model for the interpretation of the stochastic processes underlying these fluctuations of resonance frequencies. Time correlation functions of (15)N amide chemical shifts computed from molecular dynamics simulations (MD) were analyzed in terms of a transiently fractional diffusion process. The analysis of MD trajectories spanning dramatically different time scales (? 200 ns and 1 ms [ Shaw, D. E.; Science 2010, 330, 341 - 346]) allowed us to show that our model could capture the multiple scale structure of chemical shift fluctuations. Moreover, the predicted exchange contribution Rex to the NMR transverse relaxation rate is in qualitative agreement with experimental results. These observations suggest that the proposed fractional diffusion model may provide significative improvement to the analysis of NMR dispersion experiments. PMID:24628040

Calligari, Paolo; Abergel, Daniel

2014-04-10

210

Triassic–Jurassic mass extinction as trigger for the Mesozoic radiation of crocodylomorphs  

PubMed Central

Pseudosuchia, one of the two main clades of Archosauria (Reptilia: Diapsida), suffered a major decline in lineage diversity during the Triassic–Jurassic (TJ) mass extinction (approx. 201 Ma). Crocodylomorpha, including living crocodilians and their extinct relatives, is the only group of pseudosuchians that survived into the Jurassic. We reassess changes in pseudosuchian morphological diversity (disparity) across this time interval, using considerably larger sample sizes than in previous analyses. Our results show that metrics of pseudosuchian disparity did not change significantly across the TJ boundary, contrasting with previous work suggesting low pseudosuchian disparity in the Early Jurassic following the TJ mass extinction. However, a significant shift in morphospace occupation between Late Triassic and Early Jurassic taxa is recognized, suggesting that the TJ extinction of many pseudosuchian lineages was followed by a major and geologically rapid adaptive radiation of crocodylomorphs. This marks the onset of the spectacularly successful evolutionary history of crocodylomorphs in Jurassic and Cretaceous ecosystems. PMID:23536443

Toljagi?, Olja; Butler, Richard J.

2013-01-01

211

Triassic-Jurassic mass extinction as trigger for the Mesozoic radiation of crocodylomorphs.  

PubMed

Pseudosuchia, one of the two main clades of Archosauria (Reptilia: Diapsida), suffered a major decline in lineage diversity during the Triassic-Jurassic (TJ) mass extinction (approx. 201 Ma). Crocodylomorpha, including living crocodilians and their extinct relatives, is the only group of pseudosuchians that survived into the Jurassic. We reassess changes in pseudosuchian morphological diversity (disparity) across this time interval, using considerably larger sample sizes than in previous analyses. Our results show that metrics of pseudosuchian disparity did not change significantly across the TJ boundary, contrasting with previous work suggesting low pseudosuchian disparity in the Early Jurassic following the TJ mass extinction. However, a significant shift in morphospace occupation between Late Triassic and Early Jurassic taxa is recognized, suggesting that the TJ extinction of many pseudosuchian lineages was followed by a major and geologically rapid adaptive radiation of crocodylomorphs. This marks the onset of the spectacularly successful evolutionary history of crocodylomorphs in Jurassic and Cretaceous ecosystems. PMID:23536443

Toljagic, Olja; Butler, Richard J

2013-06-23

212

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

PubMed

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

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

2001-10-01

213

Generalized dynamic scaling for quantum critical relaxation in imaginary time.  

PubMed

We study the imaginary-time relaxation critical dynamics of a quantum system with a vanishing initial correlation length and an arbitrary initial order parameter M0. We find that in quantum critical dynamics, the behavior of M0 under scale transformations deviates from a simple power law, which was proposed for very small M0 previously. A universal characteristic function is then suggested to describe the rescaled initial magnetization, similar to classical critical dynamics. This characteristic function is shown to be able to describe the quantum critical dynamics in both short- and long-time stages of the evolution. The one-dimensional transverse-field Ising model is employed to numerically determine the specific form of the characteristic function. We demonstrate that it is applicable as long as the system is in the vicinity of the quantum critical point. The universality of the characteristic function is confirmed by numerical simulations of models belonging to the same universality class. PMID:25375435

Zhang, Shuyi; Yin, Shuai; Zhong, Fan

2014-10-01

214

Estimating ventilation time scales using overturning stream functions  

NASA Astrophysics Data System (ADS)

A simple method for estimating ventilation time scales from overturning stream functions is proposed. The stream function may be computed using either geometric coordinates or a generalized vertical coordinate, such as potential density (salinity in our study). The method is tested with a three-dimensional circulation model describing an idealized semi-enclosed ocean basin ventilated through a narrow strait over a sill, and the result is compared to age estimates obtained from a passive numerical age tracer. The best result is obtained when using the stream function in salinity coordinates. In this case, the reservoir-averaged advection time obtained from the overturning stream function in salinity coordinates agrees rather well with the mean age of the age tracer, and the corresponding maximum ages agree very well.

Thompson, Bijoy; Nycander, Jonas; Nilsson, Johan; Jakobsson, Martin; Döös, Kristofer

2014-06-01

215

Generalized dynamic scaling for quantum critical relaxation in imaginary time  

NASA Astrophysics Data System (ADS)

We study the imaginary-time relaxation critical dynamics of a quantum system with a vanishing initial correlation length and an arbitrary initial order parameter M0. We find that in quantum critical dynamics, the behavior of M0 under scale transformations deviates from a simple power law, which was proposed for very small M0 previously. A universal characteristic function is then suggested to describe the rescaled initial magnetization, similar to classical critical dynamics. This characteristic function is shown to be able to describe the quantum critical dynamics in both short- and long-time stages of the evolution. The one-dimensional transverse-field Ising model is employed to numerically determine the specific form of the characteristic function. We demonstrate that it is applicable as long as the system is in the vicinity of the quantum critical point. The universality of the characteristic function is confirmed by numerical simulations of models belonging to the same universality class.

Zhang, Shuyi; Yin, Shuai; Zhong, Fan

2014-10-01

216

Polymorphism in ferroic functional elements. Bridging length and time scales  

NASA Astrophysics Data System (ADS)

The present study describes an approach for the scale-bridging modeling of ferroic materials as functional elements in micro- and nanoelectronic devices. Ferroic materials are characterized by temperature-dependent complex ordering phenomena of the internal magnetic, electronic, and structural degrees of freedom with several involved length and time scales. Hence, the modelling of such compounds is not straightforward, but relies on a combination of electronic-structure-based methods like ab-initio and density-functional schemes with classical particle-based approaches given by Monte-Carlo simulations with Ising, lattice-gas, or Heisenberg Hamiltonians, which incorporate material-specific parameters both from theory and experiment. The interplay of those methods is demonstrated for device concepts based on electroceramic materials like ferroelectrics and multiferroics, whose functionality is closely related with their propensity towards structural and magnetic polymorphism. In the present case, such scale-bridging techniques are employed to aid the development of an organic field effect transistor on a ferroelectric substrate generated by the self-assembly of field-sensitive molecules on the surfaces of ferroic oxides. Electronic-structure-based methods yield the microscopic properties of the oxide, the surface, the molecules, and the respective interactions. They are combined with classical particle-based methods on a scale-hopping basis. This combination allows to study the morphology evolution during the self-assembly of larger adsorbate arrays on the (defective) oxide surface and to investigate the interplay of low-temperature magnetic ordering phenomena with the ferroelectric functionality at higher temperatures in multiferroic oxides like the hexagonal manganites. The combination of density-functional data with classical continuum modelling also yielded a model Hamiltonian for the quick determination of the properties of a gate structure based on bio-functionalized carbon nanotubes.

Gemming, S.; Luschtinetz, R.; Chaplygin, I.; Seifert, G.; Loppacher, C.; Eng, L. M.; Kunze, T.; Olbrich, C.

2007-10-01

217

Quantifying catchment-scale mixing and its effect on time-varying travel time distributions  

NASA Astrophysics Data System (ADS)

Travel time distributions are often used to characterize catchment discharge behavior, catchment vulnerability to pollution and pollutant loads from catchments to downstream waters. However, these distributions vary with time because they are a function of rainfall and evapotranspiration. It is important to account for these variations when the time scale of interest is smaller than the typical time-scale over which average travel time distributions can be derived. Recent studies have suggested that subsurface mixing controls how rainfall and evapotranspiration affect the variability in travel time distributions of discharge. To quantify this relation between subsurface mixing and dynamics of travel time distributions, we propose a new transformation of travel time that yields transformed travel time distributions, which we call Storage Outflow Probability (STOP) functions. STOP functions quantify the probability for water parcels in storage to leave a catchment via discharge or evapotranspiration. We show that this is equal to quantifying mixing within a catchment. Compared to the similar Age function introduced by Botter et al. (2011), we show that STOP functions are more constant in time, have a clearer physical meaning and are easier to parameterize. Catchment-scale STOP functions can be approximated by a two-parameter beta distribution. One parameter quantifies the catchment preference for discharging young water; the other parameter quantifies the preference for discharging old water from storage. Because of this simple parameterization, the STOP function is an innovative tool to explore the effects of catchment mixing behavior, seasonality and climate change on travel time distributions and the related catchment vulnerability to pollution spreading.

van der Velde, Y.; Torfs, P. J. J. F.; van der Zee, S. E. A. T. M.; Uijlenhoet, R.

2012-06-01

218

Complex Processes from Dynamical Architectures with Time-Scale Hierarchy  

PubMed Central

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

Perdikis, Dionysios; Huys, Raoul; Jirsa, Viktor

2011-01-01

219

Variability of global lightning activity on the ENSO time scale  

NASA Astrophysics Data System (ADS)

Global lightning activity has been studied on the ENSO (El Niño Southern Oscillation) time scale based on recordings of the Earth's Schumann resonances at Nagycenk (NCK), Hungary as well as observations from the OTD (Optical Transient Detector) and the LIS (Lightning Imaging Sensor) satellites in space. Both the intensity and position of lightning activity vary on the ENSO time scale. The magnitude of the global variation in lightning flash rate is ~10% from La Niña to El Niño. In general, more lightning is observed in the tropical-extratropical land regions during warm, El Niño episodes, especially in Southeast Asia. Although oceanic lightning activity is a minor contributor to global lightning, an opposite behavior is observed in the Pacific and other oceanic regions. More lightning is present during cold, La Niña conditions than during the warm, El Niño episodes. The annual distribution of global lightning is slightly offset from the equator into the Northern Hemisphere due to the north-south asymmetry of the land/ocean area ratio. Schumann resonance intensity variations suggest a southward (equator-ward) shift and satellite observations support this and show in addition an eastward shift in the global position during warm, El Niño episodes. The greatest lightning contrast between warm El Niño and cold La Niña episodes has been identified at the latitudes of descending dry air in the Hadley circulation.

Sátori, G.; Williams, E.; Lemperger, I.

2009-02-01

220

Reusable Launch Vehicle Control In Multiple Time Scale Sliding Modes  

NASA Technical Reports Server (NTRS)

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.

Shtessel, Yuri; Hall, Charles; Jackson, Mark

2000-01-01

221

Nonlinear Dynamics of Extended Hydrologic Systems over long time scales  

NASA Astrophysics Data System (ADS)

We often view our knowledge of hydrology and hence of nature as intransient, at least over the time scales over which we study processes we wish to predict and understand. Over the last few decades, this assumption has come under question, largely because of the vocal expression of a changing climate, but also the recurrent demonstration of significant land use change, both of which significantly affect the boundary conditions for terrestrial hydrology that is our forte. Most recently, the concepts of hydromorphology and social hydrology have entered the discussion, and the notion that climate and hydrology influence human action, which in turn shapes hydrology, is being recognized. Finally, as a field, we seem to be coming to the conclusion that the hydrologic system is an open system, whose boundaries evolve in time, and that the hydrologic system, at many scales, has a profound effect on the systems that drive it -- whether they be the ecological and climatic systems, or the social system. What a mess! Complexity! Unpredictability! At a certain level of abstraction, one can consider the evolution of these coupled systems with nonlinear feedbacks and ask what types of questions are relevant in terms of such a coupled evolution? What are their implications at the planetary scale? What are their implications for a subsistence farmer in an arid landscape who may under external influence achieve a new transient hydro-ecological equilibrium? What are the implications for the economy and power of nations? In this talk, I will try to raise some of these questions and also provide some examples with very simple dynamical systems that suggest ways of thinking about some practical issues of feedback across climate, hydrology and human behavior.

Lall, Upmanu

2014-05-01

222

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

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

223

Northern and eastern margins of the Siberian continent in Triassic  

Microsoft Academic Search

Siliciclastic sedimentation has been predominant on the northern and eastern margins of the Siberian continent since the Triassic period. Seven transgression-regression cycles can be recognized in the Triassic succession: Griesbachien-Dienerian, Smithian-Low Spathian, Upper Spathian, Anissian (with subcycles), Ladian, Carnian, and Norlan (with subcycles). All zonal units were distinguished within transgressive portions of the cycles. Regressive portions of the cycles formed

A. Yu

1993-01-01

224

Modelling Time and Length Scales of Scour Around a Pipeline  

NASA Astrophysics Data System (ADS)

The scour and burial of submarine objects is an area of interest for engineers, oceanographers and military personnel. Given the limited availability of field observations, there exists a need to accurately describe the hydrodynamics and sediment response around an obstacle using numerical models. In this presentation, we will compare observations of submarine pipeline scour with model predictions. The research presented here uses the computational fluid dynamics (CFD) model FLOW-3D. FLOW-3D, developed by Flow Science in Santa Fe, NM, is a 3-dimensional finite-difference model that solves the Navier-Stokes and continuity equations. Using the Volume of Fluid (VOF) technique, FLOW-3D is able to resolve fluid-fluid and fluid-air interfaces. The FAVOR technique allows for complex geometry to be resolved with rectangular grids. FLOW-3D uses a bulk transport method to describe sediment transport and feedback to the hydrodynamic solver is accomplished by morphology evolution and fluid viscosity due to sediment suspension. Previous investigations by the authors have shown FLOW-3D to well-predict the hydrodynamics around five static scoured bed profiles and a stationary pipeline (``Modelling of Flow Around a Cylinder Over a Scoured Bed,'' submit to Journal of Waterway, Port, Coastal, and Ocean Engineering). Following experiments performed by Mao (1986, Dissertation, Technical University of Denmark), we will be performing model-data comparisons of length and time scales for scour around a pipeline. Preliminary investigations with LES and k-? closure schemes have shown that the model predicts shorter time scales in scour hole development than that observed by Mao. Predicted time and length scales of scour hole development are shown to be a function of turbulence closure scheme, grain size, and hydrodynamic forcing. Subsequent investigations consider variable wave-current flow regimes and object burial. This investigation will allow us to identify different regimes for the scour process based on dimensionless parameters such as the Reynolds number, the Keulegan-Carpenter number, and the sediment mobility number. This research is sponsored by the Office of Naval Research - Mine Burial Program.

Smith, H. D.; Foster, D. L.

2002-12-01

225

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

SciTech Connect

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.

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

1986-08-01

226

Nanosecond time scale, high power electrical wire explosion in water  

NASA Astrophysics Data System (ADS)

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 100kA was used. The maximum current rise rate and maximum Joule heating power achieved during wire explosions were dI /dt?500A/ns and 6GW, 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.

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

2006-04-01

227

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

SciTech Connect

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.

Geluk, M.; Van Doorn, D.; Plomp, A.; Duin, E. (Geological Survey of the Netherlands, Haarlem (Netherlands))

1993-09-01

228

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

SciTech Connect

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.

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

1984-04-01

229

Variations in solar Lyman alpha irradiance on short time scales  

NASA Technical Reports Server (NTRS)

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.

Pap, J. M.

1992-01-01

230

Time Scale Dependent SGD due to the Sea Level Change  

NASA Astrophysics Data System (ADS)

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.

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

2009-12-01

231

Real time boronization experiments in CHS and scaling for LHD  

NASA Astrophysics Data System (ADS)

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.

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

232

Bounded diffusive motion on two different time scales in solid  

SciTech Connect

High-energy-resolution quasielastic neutron scattering on three complementary spectrometers has been used to investigate molecular diffusive motion in solid nano- to bulk-sized particles of the alkane n-C32H66. The crystalline-to-plastic and plastic-to-fluid phase transition temperatures are observed to decrease as the particle size decreases. In all samples, localized molecular diffusive motion in the plastic phase occurs on two different time scales: a 'fast' motion corresponding to uniaxial rotation about the long molecular axis; and a 'slow' motion attributed to conformational changes of the molecule. Contrary to the conventional interpretation in bulk alkanes, the fast uniaxial rotation begins in the low-temperature crystalline phase.

Wang, S.-K. [University of Missouri, Columbia; Mamontov, Eugene [ORNL; Bai, M. [University of Missouri, Columbia; Hansen, F.Y. [Technical University of Denmark; Taub, H. [University of Missouri, Columbia; Copley, J.R.D. [National Institute of Standards and Technology (NIST); Garcia Sakai, V [University of Maryland and NIST; Gasparovic, Goran [NCNR and University of Maryland; Jenkins, Timothy [NCNR and University of Maryland; Tyagi, M. [NCNR and University of Maryland; Herwig, Kenneth W [ORNL; Neumann, D. A. [National Institute of Standards and Technology (NIST); Montfrooij, W. [University of Missouri, Columbia; Volkmann, U. G. [Pontifica Universidad Catolica de Chile

2010-01-01

233

Water relations and leaf expansion: importance of time scale.  

PubMed

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

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

2000-09-01

234

Time-scale modelling of the invasive species Robinia pseudoacacia  

NASA Astrophysics Data System (ADS)

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

Tomaž, Podobnikar; Andraž, Ä.?Arni; Imelda, Somodi

2010-05-01

235

Towards a stable numerical time scale for the early Paleogene  

NASA Astrophysics Data System (ADS)

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. Röhl, 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. Günther, 2013. Tracking the evolution of large-volume silicic magma reservoirs from assembly to supereruption. Geology, doi:10.1130/G34366.1

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

2014-05-01

236

Perspective: Time scales in scientific research with an emphasis on microbial cellular and molecular research  

Microsoft Academic Search

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

J. T. Trevors

2010-01-01

237

Dynamic time scale for the Lagrangian subgrid-scale model based on Rice's formula  

NASA Astrophysics Data System (ADS)

The dynamic formulation of Smagorinsky's subgrid-scale model for Large Eddy Simulations (LES) requires averaging to avoid instability due to extreme fluctuations. For complex-geometry flows a Lagrangian approach is often useful [see Meneveau, Lund, and Cabot, JFM 319 (1996)]. However, an ad-hoc choice of the relaxation timescale must be made, often based on resolved strain-rates and stresses at the grid- scale. Recently, Park and Mahesh [Phys. Fluids 21, 065106 (2009)] proposed the attractive notion of using statistics of the error signal itself to determine a timescale dynamically. We extend this approach by using Rice's formula to dynamically estimate the time between mean-crossings of the error signal and set the averaging timescale to be twice this value. The approach requires accumulating Lagrange-averaged square error and its time-derivative squared, which is done using the Eulerian approximation as proposed in the original model. For validation, LES of flow in a channel and through an array of cubes are compared with experimental results. Distributions of the dynamic coefficient, error, and dynamic timescale are shown as a function of distance from the wall. Computational efficiency and memory requirements are also discussed.

Verhulst, Claire; Meneveau, Charles

2011-11-01

238

Fetal development assessed by heart rate patterns--time scales of complex autonomic control.  

PubMed

The increasing functional integrity of the organism during fetal maturation is connected with increasing complex internal coordination. We hypothesize that time scales of complexity and dynamics of heart rate patterns reflect the increasing inter-dependencies within the fetal organism during its prenatal development. We investigated multi-scale complexity, time irreversibility and fractal scaling from 73 fetal magnetocardiographic 30min recordings over the third trimester. We found different scale dependent complexity changes, increasing medium scale time irreversibility, and increasing long scale fractal correlations (all changes p<0.05). The results confirm the importance of time scales to be considered in fetal heart rate based developmental indices. PMID:21621201

Hoyer, Dirk; Nowack, Samuel; Bauer, Stephan; Tetschke, Florian; Ludwig, Stefan; Moraru, Liviu; Rudoph, Anja; Wallwitz, Ulrike; Jaenicke, Franziska; Haueisen, Jens; Schleussner, Ekkehard; Schneider, Uwe

2012-03-01

239

Exact dynamical coarse-graining without time-scale separation.  

PubMed

A family of collective variables is proposed to perform exact dynamical coarse-graining even in systems without time scale separation. More precisely, it is shown that these variables are not slow in general, yet satisfy an overdamped Langevin equation that statistically preserves the sequence in which any regions in collective variable space are visited and permits to calculate exactly the mean first passage times from any such region to another. The role of the free energy and diffusion coefficient in this overdamped Langevin equation is discussed, along with the way they transform under any change of variable in collective variable space. These results apply both to systems with and without inertia, and they can be generalized to using several collective variables simultaneously. The view they offer on what makes collective variables and reaction coordinates optimal breaks from the standard notion that good collective variable must be slow variable, and it suggests new ways to interpret data from molecular dynamics simulations and experiments. PMID:25084883

Lu, Jianfeng; Vanden-Eijnden, Eric

2014-07-28

240

Selective attention to temporal features on nested time scales.  

PubMed

Meaningful auditory stimuli such as speech and music often vary simultaneously along multiple time scales. Thus, listeners must selectively attend to, and selectively ignore, separate but intertwined temporal features. The current study aimed to identify and characterize the neural network specifically involved in this feature-selective attention to time. We used a novel paradigm where listeners judged either the duration or modulation rate of auditory stimuli, and in which the stimulation, working memory demands, response requirements, and task difficulty were held constant. A first analysis identified all brain regions where individual brain activation patterns were correlated with individual behavioral performance patterns, which thus supported temporal judgments generically. A second analysis then isolated those brain regions that specifically regulated selective attention to temporal features: Neural responses in a bilateral fronto-parietal network including insular cortex and basal ganglia decreased with degree of change of the attended temporal feature. Critically, response patterns in these regions were inverted when the task required selectively ignoring this feature. The results demonstrate how the neural analysis of complex acoustic stimuli with multiple temporal features depends on a fronto-parietal network that simultaneously regulates the selective gain for attended and ignored temporal features. PMID:23978652

Henry, Molly J; Herrmann, Björn; Obleser, Jonas

2015-02-01

241

Geologic history of Florida-Bahama platform, Triassic through Paleocene  

SciTech Connect

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.

Winston, G.O.

1988-02-01

242

Early Triassic palaeomagnetic results from the Ryeongnam Block, Korean Peninsula: the eastern extension of the North China Block  

NASA Astrophysics Data System (ADS)

Greenish sandstones in the Early Triassic Nogam Formation of the Ryeongnam Block, Korean Peninsula were collected at 23 sites for palaeomagnetic study. A high-temperature magnetization component with unblocking temperatures of 670-690 degC was isolated from seven sites and yielded a positive fold test at the 95 per cent confidence level. The high-temperature component is interpreted to be of primary origin because the folding age is Middle Triassic. The Early Triassic palaeomagnetic direction for the Ryeongnam Block after tilt correction is D=347.1 deg, I=23.8 deg (?95=5.5 deg). The palaeomagnetic pole (62.5 degN, 336.8 degE, A95=4.7 deg) shows good agreement with the coeval pole for the North China Block, suggesting that the Ryeongnam Block has been part of the North China Block at least since Early Triassic times. A tectonic history of the Korean Peninsula includes obduction of the eastern part of the South China Block onto the central part of the Korean Peninsula in the Permian, with the Ryeongnam Block geographically isolated from the main part of the North China Block. Collision of the North and South China blocks commenced initially at the Korean Peninsula, and suturing of the two blocks progressed westwards.

Uno, Koji

1999-12-01

243

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

ERIC Educational Resources Information Center

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)

Bennington, J. Bret

2000-01-01

244

Evaluating the uncertainty of predicting future climate time series at the hourly time scale  

NASA Astrophysics Data System (ADS)

A stochastic downscaling methodology is developed to generate hourly, point-scale time series for several meteorological variables, such as precipitation, cloud cover, shortwave radiation, air temperature, relative humidity, wind speed, and atmospheric pressure. The methodology uses multi-model General Circulation Model (GCM) realizations and an hourly weather generator, AWE-GEN. Probabilistic descriptions of factors of change (a measure of climate change with respect to historic conditions) are computed for several climate statistics and different aggregation times using a Bayesian approach that weights the individual GCM contributions. The Monte Carlo method is applied to sample the factors of change from their respective distributions thereby permitting the generation of time series in an ensemble fashion, which reflects the uncertainty of climate projections of future as well as the uncertainty of the downscaling procedure. Applications of the methodology and probabilistic expressions of certainty in reproducing future climates for the periods, 2000 - 2009, 2046 - 2065 and 2081 - 2100, using the 1962 - 1992 period as the baseline, are discussed for the location of Firenze (Italy). The climate predictions for the period of 2000 - 2009 are tested against observations permitting to assess the reliability and uncertainties of the methodology in reproducing statistics of meteorological variables at different time scales.

Caporali, E.; Fatichi, S.; Ivanov, V. Y.

2011-12-01

245

Computing time scales from reaction coordinates by milestoning Tony Faradjian and Ron Elber  

E-print Network

1 Computing time scales from reaction coordinates by milestoning Tony Faradjian and Ron Elber to compute time scales of complex processes following pre- determined milestones along a reaction coordinate not imply a single dominant time scale. The reaction coordinate need not include a single large barrier

Elber, Ron

246

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

USGS Publications Warehouse

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.

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

2007-01-01

247

Return to Coalsack Bluff and the Permian Triassic boundary in Antarctica  

NASA Astrophysics Data System (ADS)

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 ? 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.

Retallack, Gregory J.; Greaver, Tara; Jahren, A. Hope

2007-01-01

248

Science at the Time-scale of the Electron  

NASA Astrophysics Data System (ADS)

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).

Murnane, Margaret

2010-03-01

249

Titan's evaporites structure and their formation time-scale  

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

250

Time Scale Invariance of Cloud Optical Depth Feedbacks in Models  

NASA Astrophysics Data System (ADS)

To have confidence in predictions of future climate, we must understand how important elements of the climate system will respond to warming induced by increasing greenhouse gases. Clouds, and their ability to reflect solar radiation, are an important mechanism for modulating surface temperature. Observational studies of low clouds suggest that cloud albedo increases with increasing cloud-top temperature in the midlatitudes, while albedo decreases in the tropics and subtropics. An important question is whether or not models are able to reproduce this behavior, and to better understand why clouds in different regions my respond differently to temperature. We test the control climate from 7 GCMs with data available in the IPCC CMIP3 archive to determine how the modeled clouds respond to daily, seasonal, and interannual temperature variability. Additionally, we utilize equilibrium climate change runs for the same models to determine if there is time scale invariance with respect to the optical depth feedback, and whether observed variability can assist in projections of long-term climate change. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Gordon, N. D.; Klein, S. A.

2012-12-01

251

Detonation initiation on the microsecond time scale: DDTs  

SciTech Connect

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.

Kassoy, Dr. David R [University of Colorado; Kuehn, Jeffery A [ORNL; Nabity, Mr. Matthew W. [University of Colorado; Clarke, Dr. John F. [Cranfield University

2008-01-01

252

Detonation initiation on the microsecond time scale: DDTs  

SciTech Connect

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.

Kuehn, Jeffery A [ORNL; Kassoy, Dr. David R [University of Colorado; Nabity, Mr. Matthew W. [University of Colorado; Clarke, Dr. John F. [Cranfield University

2006-01-01

253

Climatically driven biogeographic provinces of Late Triassic tropical Pangea  

PubMed Central

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

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

2011-01-01

254

Seismicity in the Triassic Deep River Basin, North Carolina  

NASA Astrophysics Data System (ADS)

The Deep River Basin in central North Carolina is one of a series of Triassic rift basins along the east coast called the Newark Supergroup. Although the east coast lies on a passive plate margin, there is recorded seismicity within all of the coastal states, much of which is attributed to boundary faults of the Newark Supergroup basins. However, this seismicity is conspicuously absent around the Deep River Basin and most of North Carolina east of the Appalachian Mountains. In March 2012 we installed a 12 station broadband seismic network surrounding the Sanford Sub-Basin of the Deep River Basin to measure unrecorded seismicity. Through fifteen months of data collection, we have confidently detected and located more than 160 low magnitude seismic events within the array. However, the event locations cluster in four locations - three of which are near local rock quarries and one is near an unidentified anthropic feature. Further, these events consistently occur between the hours of 9am and 6pm local time, Monday through Friday indicating that they are anthropogenic. The Deep River Basin is one of the most likely places east of the Appalachian Mountains in North Carolina to be seismically active, yet we have measured no natural seismicity. Using receiver functions and known origins of the local seismic events we will be examining the crustal structure beneath the Deep River Basin to explain the conspicuous lack of local seismic activity.

Portner, D. E.; Wagner, L. S.; Fouch, M. J.; James, D. E.; Roman, D. C.; Golden, S.

2013-12-01

255

Triassic synthems of southern South America (southwestern Gondwana) and the Western Caucasus (the northern Neotethys), and global tracing of their boundaries  

NASA Astrophysics Data System (ADS)

Global tracing of the key surfaces of Triassic deposits may contribute significantly to the understanding of the common patterns in their accumulation. We attempt to define synthems - disconformity-bounded sedimentary complexes - in the Triassic successions of southern South America (southwestern Gondwana, Brazil and Argentina) and the Western Caucasus (the northern Neotethys, Russia), and then to trace their boundaries in the adjacent regions and globally. In southern South America, a number of synthems have been recognized - the Cuyo Basin: the Río Mendoza-Cerro de las Cabras Synthem (Olenekian-Ladinian) and the Potrerillos-Cacheuta-Río Blanco Synthem (Carnian-Rhaetian); the Ischigualasto Basin: the Ischichuca-Los Rastros Synthem (Anisian-Ladinian) and the Ischigualasto-Los Colorados Synthem (Carnian-Rhaetian); the Chaco-Paraná Basin: the Sanga do Cabral Synthem (Induan), the Santa Maria 1 Synthem (Ladinian), the Santa Maria 2 Synthem (Carnian), and the Caturrita Synthem (Norian); western Argentina: the Talampaya Synthem (Lower Triassic) and the Tarjados Synthem (Olenekian?). In the Western Caucasus, three common synthems have been distinguished: WC-1 (Induan-Anisian), WC-2 (uppermost Anisian-Carnian), and WC-3 (Norian-lower Rhaetian). The lower boundary of WC-1 corresponds to a hiatus whose duration seems to be shorter than that previously postulated. The synthem boundaries that are common to southwestern Gondwana and the Western Caucasus lie close to the base and top of the Triassic. The Lower Triassic, Ladinian, and Upper Triassic disconformities are traced within the studied basins of southern South America, and the first two are also established in South Africa. The Upper Triassic disconformity is only traced within the entire Caucasus, whereas all synthem boundaries established in the Western Caucasus are traced partly within Europe. In general, the synthem boundaries recognized in southern South America and the Western Caucasus are correlated to the global Triassic sequence boundaries and sea-level falls. Although regional peculiarities are superimposed on the appearance of global events in the Triassic synthem architecture, the successful global tracing suggests that planetary-scale mechanisms of synthem formation existed and that they were active in regions dominated by both marine and non-marine sedimentation.

Ruban, Dmitry A.; Zerfass, Henrique; Pugatchev, Vladimir I.

2009-08-01

256

Probing time-dependent molecular dipoles on the attosecond time scale.  

PubMed

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 (N(2), CO(2), and C(2)H(4)), 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. PMID:23909314

Neidel, Ch; Klei, J; Yang, C-H; Rouzée, A; Vrakking, M J J; Klünder, K; Miranda, M; Arnold, C L; Fordell, T; L'Huillier, A; Gisselbrecht, M; Johnsson, P; Dinh, M P; Suraud, E; Reinhard, P-G; Despré, V; Marques, M A L; Lépine, F

2013-07-19

257

Probing Time-Dependent Molecular Dipoles on the Attosecond Time Scale  

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

258

Representation of Time-Varying Stimuli by a Network Exhibiting Oscillations on a Faster Time Scale  

PubMed Central

Sensory processing is associated with gamma frequency oscillations (30–80 Hz) in sensory cortices. This raises the question whether gamma oscillations can be directly involved in the representation of time-varying stimuli, including stimuli whose time scale is longer than a gamma cycle. We are interested in the ability of the system to reliably distinguish different stimuli while being robust to stimulus variations such as uniform time-warp. We address this issue with a dynamical model of spiking neurons and study the response to an asymmetric sawtooth input current over a range of shape parameters. These parameters describe how fast the input current rises and falls in time. Our network consists of inhibitory and excitatory populations that are sufficient for generating oscillations in the gamma range. The oscillations period is about one-third of the stimulus duration. Embedded in this network is a subpopulation of excitatory cells that respond to the sawtooth stimulus and a subpopulation of cells that respond to an onset cue. The intrinsic gamma oscillations generate a temporally sparse code for the external stimuli. In this code, an excitatory cell may fire a single spike during a gamma cycle, depending on its tuning properties and on the temporal structure of the specific input; the identity of the stimulus is coded by the list of excitatory cells that fire during each cycle. We quantify the properties of this representation in a series of simulations and show that the sparseness of the code makes it robust to uniform warping of the time scale. We find that resetting of the oscillation phase at stimulus onset is important for a reliable representation of the stimulus and that there is a tradeoff between the resolution of the neural representation of the stimulus and robustness to time-warp. PMID:19412531

Shamir, Maoz; Ghitza, Oded; Epstein, Steven; Kopell, Nancy

2009-01-01

259

Detrital zircon provenance of the Late Triassic Songpan-Ganzi complex: Sedimentary record of collision of the North and South China blocks  

USGS Publications Warehouse

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.

Weislogel, A.L.; Graham, S.A.; Chang, E.Z.; Wooden, J.L.; Gehrels, G.E.; Yang, H.

2006-01-01

260

A new chronology for the end-Triassic mass extinction M.H.L. Deenen a,  

E-print Network

from the Triassic to Jurassic Period, initiating the `Age of the dinosaurs', approximately 200 MaA new chronology for the end-Triassic mass extinction M.H.L. Deenen a, , M. Ruhl b , N.R. Bonis b Magmatic Province end-Triassic mass extinction LIP emplacement Argana basin geochronology The transition

Utrecht, Universiteit

261

Climate variations in the Boreal Triassic — Inferred from palynological records from the Barents Sea  

Microsoft Academic Search

This paper presents palynological evidence from the late Early Triassic (late Smithian) to the Late Triassic (Rhaetian) of the Barents Sea area: A continuous palynological succession from an exploration well (7228\\/7-1A) in the Nordkapp Basin (SW Barents Sea) and palynological data from a series of shallow cores drilled at the Svalis Dome (Central Barents Sea) representing selected Triassic intervals. These

Peter A. Hochuli; Jorunn Os Vigran

2010-01-01

262

ELSEVIER Palaeogeography, Palaeoclimatology, Palaeoecology 136 (1997) 79-95 Palaeoenvironmental interpretation of a Triassic-Jurassic  

E-print Network

) 79-95 1. Introduction The close of the Triassic period is marked by one of the five largest mass Palaeoenvironmental interpretation of a Triassic-Jurassic boundary section from Western Austria based the Triassic-Jurassic boundary is described from near the village of Lori3ns in the Vorarlberg region

McRoberts, Christopher A.

263

Evidence for recurrent Early Triassic massive volcanism from quantitative interpretation of carbon isotope fluctuations  

Microsoft Academic Search

Carbon cycle disturbance associated with mass extinction at the end of the Permian Period continued through the Early Triassic, an interval of approximately 5 million years. Coincidence of carbon cycle stabilization with accelerated Middle Triassic biotic recovery suggests a link between carbon cycling and biodiversity, but the cause of Early Triassic carbon isotope excursions remains poorly understood. Previous modeling studies have

Jonathan L. Payne; Lee R. Kump

2007-01-01

264

EON: software for long time simulations of atomic scale systems  

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

265

Redescription of Bellerophon bittneri (Gastropoda: Triassic) from Wyoming.  

USGS Publications Warehouse

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

Yochelson, E.L.; Boyd, D.W.; Wardlaw, B.

1985-01-01

266

Real time density functional simulations of quantum scale conductance  

E-print Network

We study electronic conductance through single molecules by subjecting a molecular junction to a time dependent potential and propagating the electronic state in real time using time-dependent density functional theory ...

Evans, Jeremy Scott

2009-01-01

267

New Paleoenvironmental and Biotic Records from the Triassic-Jurassic Boundary Interval of the Algarve Basin, Portugal  

NASA Astrophysics Data System (ADS)

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 ?13C 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.

Kasprak, A. H.; Whiteside, J. H.; Lopes, F. M.; Brusatte, S. L.; Butler, R. J.; Mateus, O.

2010-12-01

268

Depositional environments of the Permo-Triassic sediments from the Moesian Platform (Romania)  

SciTech Connect

The analysis of lithostratigraphic and geophysics data suggest that during Permian-Lower Triassic and Upper Triassic at least in the northern part of the Moesian Platform has been developed a failed continental rift. This structogenetical evolution of the Moesian Platform has performed a continental environment during of the Permian-Lower Triassic and Upper Triassic as well as predominantly marine one during of the Middle Triassic. The depositional model for the Permian-Lower Triassic and Upper Triassic consists of facies belts of fluviatile, aeolian, evaporite/lacustrine deposits roughly paralleling the main uplifts of the Moesian Platform. The facies belts pass from alluvial fan facies, best developed in proximity to the main uplifts, through fluviatile sands, dune and inter-dune aeolian sands and finally into evaporite/lacustrine facies at the center of the main depressions. The facies associations consist predominantly of the fining-up type sequences. The marine environments for the Middle Triassic consist predominantly of carbonate facies. The best reservoir types consists of conglomerate-, sand- and carbonate-dominated facies associations located at the bottom of Permian-Lower Triassic, Upper Triassic and Middle Triassic respectively. In the north-western part of the Moesian Platform there are twelve oil and gas fields stored into these reservoir types.

Constantin, P. [Bucharest Univ. (Romania)

1995-08-01

269

Time resolved single photon imaging in Nanometer Scale CMOS technology   

E-print Network

Time resolved imaging is concerned with the measurement of photon arrival time. It has a wealth of emerging applications including biomedical uses such as fluorescence lifetime microscopy and positron emission tomography, ...

Richardson, Justin Andrew

2010-06-28

270

Permo-Triassic Events in the Eastern Tethys  

Microsoft Academic Search

Permian and Triassic rocks in the eastern Tethyan region form continuous marine sequences that record the waning phases of the Paleozoic and the early stages of the Mesozoic eras. This book describes and interprets these rocks, summarizing the distribution of major fossil groups in a way that will allow detailed comparison with strata of comparable age in the western Tethys

Walter C. Sweet; Yang Zunyi; J. M. Dickins; Yin Hongfu

2003-01-01

271

PARTITOMORPHITAE, A NEW SUBGROUP OF TRIASSIC AND JURASSIC ACRITARCHS  

Microsoft Academic Search

Three new genera of acritarchs are described: Rugidinium, comprising two new species, R. ornatum and ,R. undulatum, from the Bajocian (Jurassic) of Canada; Thuledinium, represented by a single species, T. groenlandicum , from the Callovian (Jurassic) of Greenland; and Teichertodinium, represented by a single species, T. triassicum, from the Triassic (Anisian) of Pakistan. All three genera share the charac^ teristics

STANLEY A. J. POCOCK; WILLIAM A. S. SARJEANT

272

The Early Triassic ammonoid recovery: Paleoclimatic significance of diversity gradients  

Microsoft Academic Search

Ammonoids recovered much faster than other marine shelly invertebrates after the end-Permian mass extinction. Based on a refined global data set at the basin level, we investigate the paleobiogeographical global latitudinal and longitudinal diversity patterns in terms of climatic changes during the Early Triassic. Such analysis differs from already published qualitative or quantitative studies in that it estimates faunal patterns

Arnaud Brayard; Hugo Bucher; Gilles Escarguel; Frédéric Fluteau; Sylvie Bourquin; Thomas Galfetti

2006-01-01

273

An ancestral turtle from the Late Triassic of southwestern China  

Microsoft Academic Search

The origin of the turtle body plan remains one of the great mysteries of reptile evolution. The anatomy of turtles is highly derived, which renders it difficult to establish the relationships of turtles with other groups of reptiles. The oldest known turtle, Proganochelys from the Late Triassic period of Germany, has a fully formed shell and offers no clue as

Chun Li; Xiao-Chun Wu; Olivier Rieppel; Li-Ting Wang; Li-Jun Zhao

2008-01-01

274

Palaeontology: A polydactylous amniote from the Triassic period  

Microsoft Academic Search

The earliest four-limbed vertebrates, or tetrapods, lived between 370 million and 354 million years ago, during the Late Devonian period, and typically had more than five digits (polydactyly). We have discovered that a preaxial form of polydactyly, in which extra digits are positioned anterior to the first digit, has unexpectedly re-emerged in a marine reptile from the Early Triassic period

Xiao-Chun Wu; Zhan Li; Bao-Chun Zhou; Zhi-Ming Dong

2003-01-01

275

Evidence for a late Triassic multiple impact event on Earth  

Microsoft Academic Search

We present evidence for a multiple impact event that occurred on Earth. Five terrestrial impact structures have been found to possess comparable ages, coincident with the Norian stage of the Triassic period. These craters are Rochechouart (France), Manicouagan and Saint Martin (Canada), Obolon' (Ukraine), and Red Wing (USA). When these impact structures are plotted on a tectonic reconstruction of the

John G. Spray; Simon P. Kelley; David B. Rowley

1998-01-01

276

Tectonic evolution of the Triassic fold belts of Tibet  

Microsoft Academic Search

The Triassic fold belt of North Tibet is mainly composed, from west to east, of the Bayan Har, Songpan–Garzê, and Yidun (or Litang–Batang) terranes. The Indosinian orogeny results from interactions between the South China, North China and Qiangtang (North Tibet) blocks during the closure of the Palaeotethys. A synthesis of the tectonic and geochronological data available on this belt is

Françoise Roger; Marc Jolivet; Jacques Malavieille

2008-01-01

277

A new chronology for the end-Triassic mass extinction  

Microsoft Academic Search

The transition from the Triassic to Jurassic Period, initiating the ‘Age of the dinosaurs’, approximately 200Ma, 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

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

2010-01-01

278

Cathodoluminescence of Late Triassic terebratulid brachiopods: implications for growth patterns  

Microsoft Academic Search

Upper Triassic terebratulid brachiopod Rhaetina shows differential preservation of shell structure under cathodoluminescent (CL) and scanning electron microscope (SEM), indicating intra- and interspecific differences in brachiopod growth patterns.In longitudinal sections, the CL lines appear firstly in inner, ontogenetically older parts of the shell and their outlines are parallel with the internal valve surface in posterior parts of the shell. In

Adam Tomašových; Juraj Farkaš

2005-01-01

279

The Pangea conundrum: Implications of new Paleomagnetic data from Permo-Triassic Araguainha Impact Crater (Central Brazil)  

NASA Astrophysics Data System (ADS)

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; ?95 = 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.

Brandt, D.; Yokoyama, E.; Trindade, R. I.; Tohver, E.

2013-05-01

280

Structure and dating errors in the geologic time scale and periodicity in mass extinctions  

NASA Technical Reports Server (NTRS)

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.

Stothers, Richard B.

1989-01-01

281

Sedimentary evolution of the continental Early-Middle Triassic Cañizar Formation (Central Spain): Implications for life recovery after the Permian-Triassic crisis  

NASA Astrophysics Data System (ADS)

The Permian-Triassic transition (P-T) was marked by important geochemical perturbations and the largest known life crisis. Consequences of this event, as oxygen-depleted conditions and the unusual behavior of the carbon cycle, were prolonged during the Early Triassic interval delaying the recovery of life in both terrestrial and marine ecosystems. Studies on Lower Triassic sediments of continental origin, as in the case of Western Europe, are especially problematic due to the scarcity of fossils and absence of precise dating. The Cañizar Fm. is an Early-Middle Triassic unit of continental origin of the SE Iberian Ranges, E Spain. A detailed sedimentary study of this unit allows a shedding of light on some unresolved problems of the continental deposits of this age. The top of this unit is dated as early Anisian by means of a pollen association, while the age of its base is here estimated as late Smithian or Smithian-Spathian transition. Different facies associations and architectural elements have been defined in this unit. In the western and central parts of the basin, this unit shows sedimentary characteristics of fluvial deposits with locally intercalated aeolian sediments, while in the eastern part there is an alternation of both aeolian and fluvial deposits. Sedimentary structures also indicate changes in the climate conditions, mainly from arid to semiarid. Two marked arid periods when well-preserved aeolian sediments developed during early-middle Spathian and Spathian-Anisian transition. They alternated with two semiarid but more humid periods during the late Spathian and early Anisian. These conditions basically correspond with the general arid and very arid conditions described for central-western European plate during the same period of time. The Ateca-Montalbán High, in the northern border of the study basin, must have represented an important topographic barrier in the western Tethys separating aeolian dominated areas to the N and NE from fluvial dominated areas to the south. The Cañizar Fm. has been subdivided into six members (A-F) separated by seven (1-7) major bounding surfaces (MBS). These surfaces are well recognized laterally over hundred of km and they represent 104-105 My. MBS-5 is considered to be of late Spathian age and it is a clear indication of tectonic activity, represented by a mild unconformity. This event represents a change in the sedimentary characteristics (reactivation) of the unit and from here to the top of the unit are found the first signals of biotic recovery, represented by tetrapod footprints, plants, roots and bioturbation. All of these characteristics and the estimated age represented by the MBS-5 event permit this surface to be related to the coeval Hardegsen unconformity of Central-Western Europe. These first signals of biotic recovery can thus be related to an increased oxygen supply due to the new created paleogeographical corridors in the context of this tectonic activity. These biotic signals occurred 5 My after the Permian-Triassic limit crisis; a similar delay as occurred in other coeval and neighboring basins.

López-Gómez, José; Galán-Abellán, Belén; de la Horra, Raúl; Barrenechea, José F.; Arche, Alfredo; Bourquin, Sylvie; Marzo, Mariano; Durand, Marc

2012-04-01

282

Filling a 30 Million Year Gap: Radioisotopic Age Constraints for the Late Triassic Timescale  

NASA Astrophysics Data System (ADS)

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.

Irmis, R. B.; Mundil, R.

2011-12-01

283

The carbon and sulfur cycles and atmospheric oxygen from middle Permian to middle Triassic  

NASA Astrophysics Data System (ADS)

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.

Berner, Robert A.

2005-07-01

284

Time Scales, Difficulty\\/Skill Duality, and the Dynamics of Motor Learning  

Microsoft Academic Search

\\u000a In this chapter we elaborate on the dynamical basis for the time scales of change in motor learning. It is known that in both\\u000a oscillatory and growth\\/decay processes the exponential characterizes the time scales of change. A few characteristic or even\\u000a multiple time scales can arise from continually evolving landscape dynamics due to bifurcations between attractor organization\\u000a and the transient

Karl M. Newell; Yeou-Teh Liu; Gottfried Mayer-Kress

285

Oil and gas potential of the Triassic in west Siberia  

SciTech Connect

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).

Bochkarev, V.S.; Kulakhmetov, N.KH.; Nesterov, I.I. (ZapSibNIGNI, Tyumen (Russian Federation))

1993-09-01

286

Triassic and Jurassic rocks at Currie, Nevada Preliminary paleontologic evidence  

SciTech Connect

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.

Johnson, E.A.; Dubiel, R.F.; Brouwers, E.M. (Geological Survey, Denver, CO (United States)); Litwin, R.J. (Geological Survey, Reston, VA (United States)); Ash, S.R. (Weber State Coll., Ogden, UT (United States)); Good, S.C. (State Univ. Coll., Cortland, NY (United States))

1993-04-01

287

The Late Triassic and Late Jurassic stress fields and tectonic transmission of North China craton  

NASA Astrophysics Data System (ADS)

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.

Hou, Guiting; Wang, Yanxin; Hari, K. R.

2010-09-01

288

Permian Triassic palynofloral transition in Chintalapudi area, Godavari Graben, Andhra Pradesh, India  

NASA Astrophysics Data System (ADS)

The entire 606 m-thick sedimentary sequence in borecore MCP-7 from Chintalapudi area, Chintalapudi sub-basin has been lithologically designated as Kamthi Formation. However, the palynological investigation revealed five distinct palynoassemblages, which essentially fall under two groups, one group (Palynoassemblage-I, II and III) having dominance of striate disaccates along with presence of some stratigraphically significant taxa, belongs to Late Permian (Raniganj) palynoflora, while the other group (Palynoassemblages IV and V) shows sharp decline in percentage of characteristic taxa of first group, i.e., striate disaccates, and consequent rise or dominance of taeniate and cingulate cavate spores, belongs to Early Triassic (Panchet) palynoflora. Palynoassemblage-I, II and III (Group I) are characterized by dominance of striate disaccates chiefly, Striatopodocarpites spp. and Faunipollenites spp. along with presence of rare but stratigraphically significant taxa, viz., Gondisporites raniganjensis, Falcisporites nuthaliensis, Klausipollenites schaubergeri, Chordasporites sp., Striomonosaccites, ovatus, Crescentipollenites multistriatus, Verticipollenites debiles, Strotersporites crassiletus, Guttulapollenites hannonicus, G. gondwanensis, Hamiapollenites insolitus, Corisaccites alutus, Lunatisporites ovatus, Weylandites spp. and Vitreisporites pallidus. Palynoassemblage-I is distinguished by significant presence of Densipollenites spp. while Palynoassemblage-II shows significant presence of Crescentipollenites spp. and Palynoassemblage-III differs from the above two assemblages in having significant presence of Guttulapollenites hannonicus. Palynoassemblage-IV (Group II) is characterized by high percentage of taeniate disaccates chiefly Lunatisporites spp., while Palynoassemblage-V (Group II) is characterized by cingulate-cavate trilete spores chiefly, Lundbladispora spp. and Densoisporites spp. Striate disaccates show a sharp decline in these two assemblages. In Chintalapudi area Late Permian and Early Triassic palynoflora has been recorded for the first time indicating existence of Raniganj and Panchet sediments as well. The study further supports the earlier studies of Jha and Srivastava (1996) that Kamthi Formation represents Early Triassic (=Panchet Formation) overlying Raniganj equivalent sediments with a gradational contact.

Jha, Neerja; Chary, M. Basava; Aggarwal, Neha

2012-10-01

289

Do the Cotham Member stromatolites of the Late Triassic, SW UK represent extinction "disaster forms"?  

NASA Astrophysics Data System (ADS)

A widespread and well-preserved horizon (~20cm thick) of alternating stromatolite-dendrolite facies occurs at the top of the Cotham Member of the Lilstock Formation in the Upper Triassic (latest Rhaetian) of the SW UK. The close stratigraphic position to the Triassic-Jurassic (T-J) mass extinction interval raises questions about the potential relationship to the mass extinction. Were the Cotham Member stromatolites a result of a decline in taxonomic richness (including decline of bioturbators and grazers) across the Late Triassic extinction episode? Or, were they deposited in a hypersaline lagoon, an environment known to develop microbialites during non-extinction times, and therefore decoupled from the extinction event? Light microscopic observations of thin sections reveal a sparse assemblage of shelly epifauna including molluscs and echinoderm fragments. Carbon and oxygen isotope values of micro-drilled portions of the stromatolites exhibit ?13C values of -0.1% to -1.7% and ?18O values of -0.8% to -2.3%. We also observe 2 thin layers (each about 1mm thick) of gypsum pseudomorphs a few centimeters below the first occurrence of stromatolites. On the one hand, the isotopic evidence and the presence of echinoderm fragments (echinoderms/crinoids generally require open marine conditions) would argue against a restricted lagoonal origin for the stromatolites and dendrolites. On the other hand, the presence of evaporite minerals within cm of the stromatolitic units would argue for at least periodic restriction of the depositional environment. Consequently, more work is needed to unequivocally resolve the depositional environment of the Cotham Member stromatolites and their relevance to the T-J mass extinction.

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

2011-12-01

290

A Middle Triassic thoracopterid from China highlights the evolutionary origin of overwater gliding in early ray-finned fishes.  

PubMed

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

Xu, Guang-Hui; Zhao, Li-Jun; Shen, Chen-Chen

2015-01-01

291

Paleoclimate cycles and tectonic controls on fluvial, lacustrine, and eolian strata in upper Triassic Chinle Formation, San Juan basin  

SciTech Connect

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.

Dubiel, R.F. (Geological Survey, Denver, CO (USA))

1989-09-01

292

Climate during the Permian-Triassic Biosphere Reorganizations. Article 2. Climate of the Late Permian and Early Triassic: General Inferences  

Microsoft Academic Search

The Late Permian-initial Triassic was a period of the Earth climate change, as the glacial climate of the Late Paleozoic was replaced by the non-glacial one of the Mesozoic. The intricate trend of this process is reconstructed and illustrated by schematic paleoclimatic maps. Warming in the second half of the Sakmarian Age resulted in a rapid degradation of huge glacial

N. M. Chumakov; M. A. Zharkov

2003-01-01

293

Metamorphic and volcanic quartz of the siliciclastic Tipuma Formation, West Papua, Indonesia: an insight into Triassic palaeogeography of northern Australia  

NASA Astrophysics Data System (ADS)

The origin and Triassic evolution of the Bird's Head of West Papua has been a subject of active discussion. Many interpretations have been proposed for the Triassic evolution, from active margin to passive margin models. The Bird's Head region is underlain by Australian continental crust and has a relatively complete stratigraphy from Palaeozoic to Recent. The Tipuma Formation is a Mesozoic siliciclastic sequence and a potentially important reservoir. Its sedimentation may record parts of the region's Mesozoic tectonic history, including several phases of rifting. Little is known about the variations in lithologies and their composition, and nothing is known about its provenance. The Tipuma Formation is dominated by red to cream well-bedded mudstone, sandstone and conglomerate. It rests unconformably on the Kemum Formation and is overlain by the Cretaceous Jass Formation. It is difficult to assess the depositional age of the Tipuma Formation due to the absence of fossils. The suggested Triassic age is based solely on its stratigraphic position. The Tipuma Formation was previously thought to be deposited in a stable continental setting. Detrital modes indicate acid plutonic, metamorphic, and recycled sedimentary source rocks for the Tipuma Formation sandstones. Angular volcanic quartz and elongate euhedral zircons suggest a contribution from previously unrecognised contemporaneous acid volcanics. New interpretations suggest that the widespread Permo-Triassic volcanic activity in the Bird's Head was caused by subduction associated with an Andean-type active margin and that the Tipuma Formation was deposited in a fluvial setting close to the volcanic arc. Cathodoluminescence (CL) characteristics of quartz depend on variations in temperature, pressure, and geochemical environment during crystal growth and subsequent events. The CL colour spectra of quartz can be correlated with the formation conditions of the quartz. They can therefore be used as a provenance indicator along with other techniques. Quartz from Tipuma Formation sandstone is dominated by quartz of low-T metamorphic and volcanic origin and only with little plutonic quartz. This strongly suggests an input of detritus derived from contemporaneous acid volcanic rocks and some local low-grade metamorphic rocks. The results confirm assessment based on zircon study of the main contemporaneous volcanic activity, which waned or ceased during deposition of the Middle Member of the Tipuma Formation. Widespread Permo-Triassic volcanic activity in the Bird's Head possibly caused contact metamorphism in the area with uplift and erosion of low-T metamorphic rocks. The Tasman Line continues from Eastern Australia through New Guinea, into the Bird's Head region. At least since the Triassic, the Bird's Head has been part of the Gondwana margin and for the first time, we can provide compelling evidence that volcanic activity has played a major role in this region.

Gunawan, Indra; Hall, Robert; Augustsson, Carita

2013-04-01

294

An analytical framework for quantifying aquifer response time scales associated with transient boundary conditions  

NASA Astrophysics Data System (ADS)

A major challenge in studying coupled groundwater and surface-water interactions arises from the considerable difference in the response time scales of groundwater and surface-water systems affected by external forcings. Although coupled models representing the interaction of groundwater and surface-water systems have been studied for over a century, most have focused on groundwater quantity or quality issues rather than response time. In this study, we present an analytical framework, based on the concept of mean action time (MAT), to estimate the time scale required for groundwater systems to respond to changes in surface-water conditions. MAT can be used to estimate the transient response time scale by analyzing the governing mathematical model. This framework does not require any form of transient solution (either numerical or analytical) to the governing equation, yet it provides a closed form mathematical relationship for the response time as a function of the aquifer geometry, boundary conditions, and flow parameters. Our analysis indicates that aquifer systems have three fundamental time scales: (i) a time scale that depends on the intrinsic properties of the aquifer, (ii) a time scale that depends on the intrinsic properties of the boundary condition, and (iii) a time scale that depends on the properties of the entire system. We discuss two practical scenarios where MAT estimates provide useful insights and we test the MAT predictions using new laboratory-scale experimental data sets.

Jazaei, Farhad; Simpson, Matthew J.; Clement, T. Prabhakar

2014-11-01

295

The lower Triassic microbiolites in Chaohu region, East China and their contribution to the early Triassic recovery  

NASA Astrophysics Data System (ADS)

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

Jia, Zhihai; Zhang, Liwei; Hong, Tianqiu

2010-05-01

296

Rating depression over brief time intervals with the Hamilton Depression Rating Scale: Standard vs. abbreviated scales.  

PubMed

Although antidepressant trials typically use weekly ratings to examine changes in symptoms over six to 12 weeks, antidepressant treatments may improve symptoms more quickly. Thus, rating scales must be adapted to capture changes over shorter intervals. We examined the use of the 17-item Hamilton Depression Rating Scale (HDRS) to evaluate more rapid changes. Data were examined from 58 patients with major depressive disorder or bipolar disorder enrolled in double-blind, placebo-controlled, crossover studies who received a single infusion of ketamine (0.5 mg/kg) or placebo over 40 min then crossed over to the other condition. HDRS subscales, a single HDRS Depressed mood item, and a visual analogue scale were used at baseline, after a brief interval (230 min), and one week post-infusion. Effect sizes for the ketamine-placebo difference were moderate (d > 0.50), but one and two-item HDRS subscales had the smallest effects. Response rates on active drug were lowest for the complete HDRS (43%); the remaining scales had higher response rates to active drug, but the shortest subscales had higher response rates to placebo. Correlations between the changes from baseline to 230 min post-ketamine across scores were similar for most subscales (r = 0.82-0.97), but correlations using the single items were lower (r < 0.74). Overall, effect sizes for drug-placebo differences and correlations between changes were lower for one- and two-item measures. Response rates were lower with the full HDRS scale. The data suggest that, to best identify rapid antidepressant effects, a scale should have more than two items, but fewer items than a full scale. PMID:25592045

Luckenbaugh, David A; Ameli, Rezvan; Brutsche, Nancy E; Zarate, Carlos A

2015-02-01

297

The Theory of Scale Relativity: Non-Differentiable Geometry and Fractal Space-Time1  

E-print Network

The Theory of Scale Relativity: Non-Differentiable Geometry and Fractal Space-Time1 Laurent NOTTALE of scale relativity is to derive the physical behavior of a non-differentiable and fractal space of the relativity of scales. We mainly study in this contribution the effects induced by internal fractal structures

Nottale, Laurent

298

Nanometer-scale recording with transition time at nanosecond D.X. Shia,b,*  

E-print Network

Nanometer-scale recording with transition time at nanosecond D.X. Shia,b,* , D.C. Baa , S.J. Panga 2001; accepted 23 July 2001 Abstract Recording at a nanometer-scale on 3-phenyl-1-ureidonitrile (CPU Nanometer-scale data storage has stimulated much attention during the few past years because of its great

Gao, Hongjun

299

Compile-Time Dynamic Voltage Scaling Settings: Opportunities and Limits  

NSDL National Science Digital Library

The Parapet research group at Princeton University focuses on power-related issues in computer hardware and software design. Citing the importance of power efficiency both in mobile applications as well as in the general goal of shrinking technology sizes on chips, the authors of this paper discuss the role of dynamic voltage scaling (DVS) in managing power during runtime. This interesting technique enables control of "the power consumption by varying a processor's supply voltage...and clock frequency." The paper identifies specific factors that contribute to the effectiveness of DVS and considers the extent to which it can save power.

Malik, Sharad

300

Motor skill acquisition across short and long time scales: a meta-analysis of neuroimaging data.  

PubMed

In this systematic review and meta-analysis, we explore how the time scale of practice affects patterns of brain activity associated with motor skill acquisition. Fifty-eight studies that involved skill learning with healthy participants (117 contrasts) met inclusion criteria. Two meta-contrasts were coded: decreases: peak coordinates that showed decreases in brain activity over time; increases: peak coordinates that showed increases in activity over time. Studies were grouped by practice time scale: short (?1 h; 25 studies), medium (>1 and ?24 h; 18 studies), and long (>24h to 5 weeks; 17 studies). Coordinates were analyzed using Activation Likelihood Estimation to show brain areas that were consistently activated for each contrast. Across time scales, consistent decreases in activity were shown in prefrontal and premotor cortex, the inferior parietal lobules, and the cerebellar cortex. Across the short and medium time scales there were consistent increases in supplementary and primary motor cortex and dentate nucleus. At the long time scale, increases were seen in posterior cingulate gyrus, primary motor cortex, putamen, and globus pallidus. Comparisons between time scales showed that increased activity in M1 at medium time scales was more spatially consistent across studies than increased activity in M1 at long time scales. Further, activity in the striatum (viz. putamen and globus pallidus) was consistently more rostral in the medium time scale and consistently more caudal in the long time scale. These data support neurophysiological models that posit that both a cortico-cerebellar system and a cortico-striatal system are active, but at different time points, during motor learning, and suggest there are associative/premotor and sensorimotor networks active within each system. PMID:24831923

Lohse, K R; Wadden, K; Boyd, L A; Hodges, N J

2014-07-01

301

Emergence of cooperation through coevolving time scale in spatial prisoner's dilemma  

NASA Astrophysics Data System (ADS)

We study evolutionary prisoner’s 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.

Rong, Zhihai; Wu, Zhi-Xi; Wang, Wen-Xu

2010-08-01

302

Late Triassic bimodal igneous rocks in eastern Heilongjiang Province, NE China: Implications for the initiation of subduction of the Paleo-Pacific Plate beneath Eurasia  

NASA Astrophysics Data System (ADS)

This paper reports new zircon LA-ICP-MS and SIMS U-Pb ages and Hf isotope data, and whole-rock major and trace element data for Late Triassic igneous rocks of eastern Heilongjiang Province, NE China. These data provide new insights into the timing of the initiation of subduction of the Paleo-Pacific Plate beneath the Eurasian continent. The zircon U-Pb age data indicate that a suite of Late Triassic (228-202 Ma) igneous rocks is present within the Songnen-Zhangguangcai Range Massif and within the western margin of the Khanka Massif. The Late Triassic igneous rocks within the Songnen-Zhangguangcai Range Massif consist of basalts, basaltic andesites, gabbro-diabases, and rhyolites, whereas coeval igneous rocks in the western margin of the Khanka Massif consist of hornblende gabbros and syenogranitic porphyries. These Late Triassic rocks constitute a geochemically bimodal igneous rock association that contains mafic rocks enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE), and depleted in heavy rare earth elements (HREE) and high field strength elements (HFSE) such as Nb, Ta, Zr, Hf, and Ti. Zircons from these mafic rocks have ?Hf (t) values and TDM1 ages of +2.8 to +9.8 and 477-733 Ma, respectively, suggesting that they formed from a primary magma generated by the partial melting of depleted lithospheric mantle material that had been previously modified by subduction-related fluids. The coeval felsic rocks are characterized by enrichments in LREEs and LILEs, and depletions in HREEs and HFSEs (including Nb, Ta, and Ti), and their zircons have ?Hf (t) values and TDM2 ages of +0.6 to +7.9 and 766 to 1461 Ma, respectively, implying that these rocks were generated during the partial melting of juvenile crustal material. The Late Triassic bimodal igneous rocks in eastern Heilongjiang Province, combined with the regional geologic information, therefore record a post-orogenic extensional environment related to the final late Permian-Early Triassic closure of the Paleo-Asian Ocean. In addition, the presence of Late Triassic bimodal igneous rocks within the eastern margin of the Eurasian continent suggests that the subduction of the Paleo-Pacific Plate beneath the Eurasian continent began after the Late Triassic.

Wang, Feng; Xu, Wen-Liang; Xu, Yi-Gang; Gao, Fu-hong; Ge, Wen-chun

2015-01-01

303

Time scales of variability associated with Nordeste precipitation  

SciTech Connect

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.

Sperber, K.R. (Lawrence Livermore National Lab., CA (USA)); Hameed, S. (State Univ. of New York, Stony Brook, NY (USA). Inst. for Terrestrial and Planetary Atmospheres)

1991-06-01

304

Uranium comminution ages: Sediment transport and deposition time scales  

NASA Astrophysics Data System (ADS)

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.

DePaolo, Donald J.; Lee, Victoria E.; Christensen, John N.; Maher, Kate

2012-11-01

305

Time and length scales within a fire and implications for numerical simulation  

SciTech Connect

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.

TIESZEN,SHELDON R.

2000-02-02

306

STRUCTURAL CHANGE ON MULTIPLE TIME SCALES AS A CORRELATE OF MUSICAL COMPLEXITY  

E-print Network

STRUCTURAL CHANGE ON MULTIPLE TIME SCALES AS A CORRELATE OF MUSICAL COMPLEXITY Matthias Mauch Mark of recorded music, and argue that it is related to a particular notion of musical complex- ity. Structural at a different time scale. We describe an efficient implementation of the feature and dis- cuss its properties

Mauch, Matthias

307

A dual-time-scale finite element model for simulating cyclic deformation of polycrystalline alloys  

Microsoft Academic Search

A dual-time scale finite element model is developed in this pa per for simulating cyclic defor- mation in polycrystalline alloys. The material is characte rized by crystal plasticity constitutive relations. The finite element formulation of the initial-bo undary value problems with cyclic load- ing involves decoupling the governing equations into two sets of problems corresponding to two different time scales.

Mitsuteru Asai; Somnath Ghosh

2007-01-01

308

Time Scales in the JPL and CfA Ephemerides  

NASA Technical Reports Server (NTRS)

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.

Standish, E. M.

1998-01-01

309

Time scales in the JPL and CfA ephemerides  

Microsoft Academic Search

Over the past decades, the IAU has repeatedly at- tempted to correct its definition of the basic fundamental argu- ment used in the ephemerides. Finally, they have defined a time system which is physically possible, according to the accepted standard theory of gravitation: TCB (\\

E. M. Standish

310

Optimum merger time-scales and binary evolution  

Microsoft Academic Search

A study of galaxy mergers, on the basis of the collisional theory, using galaxy models without halos and considering the evolution of the proginator galaxies only from a time when the gravitational interaction between them is physically significant, indicates that most of the mergers are affected in 2 to 3 orbital periods for progenitors of comparable mass: shorter and longer

Tapan K. Chatterjee

1993-01-01

311

Cooling down quantum bits on ultrashort time scales  

NASA Astrophysics Data System (ADS)

Quantum two-state systems, known as quantum bits (qubits), are unavoidably in contact with their uncontrolled thermal environment, also known as a macroscopic 'bath'. The higher the temperature of the qubits, the more impure their quantum state and the less useful they are for coherent control or quantum logic operations, hence the desirability of cooling down the qubits as much and as fast as possible, so as to purify their state prior to the desired operation. Yet, the limit on the speed of existing cooling schemes, which are all based on Markovian principles, is either the duration of the qubit equilibration with its bath or the decay time of an auxiliary state to one of the qubit states. Here we pose the conceptual question: can one bypass this existing Markovian limit? We show that highly frequent phase shifts or measurements of the state of thermalized qubits can lead to their ultrafast cooling, within the non-Markov time domain, well before they re-equilibrate with the bath and without resorting to auxiliary states. Alternatively, such operations may lead to the cooling down of the qubit to arbitrarily low temperatures at longer times. These anomalous non-Markov cooling processes stem from the hitherto unfamiliar coherent quantum dynamics of the qubit-bath interaction well within the bath memory time.

Gordon, Goren; Bensky, Guy; Gelbwaser-Klimovsky, David; Bhaktavatsala Rao, D. D.; Erez, Noam; Kurizki, Gershon

2009-12-01

312

Scale relativity and fractal space-time: theory and applications  

E-print Network

belt objects, value of solar and solar-like star cycles), to sciences of life (log-periodic law-time. This theory leads (i) to a generalization of possible physically relevant fractal laws, written as partial for species punctuated evolution, human development and society evolution), to Earth sciences (log-periodic

Nottale, Laurent

313

Scaling the -relaxation time of supercooled fragile organic liquids  

Microsoft Academic Search

It was shown recently [1] that the structural $\\\\alpha $ -relaxation time $\\\\tau $ of supercooled o-terphenyl depends on a single control parameter $\\\\Gamma $ , which is the product of a function of density $E(\\\\rho )$ , by the inverse temperature T -1. We extend this finding to other fragile glassforming liquids using light scattering data. Available experimental results

C. Dreyfus; A. Le Grand; J. Gapinski; W. Steffen; A. Patkowski

2004-01-01

314

Scaling the alpha -relaxation time of supercooled fragile organic liquids  

Microsoft Academic Search

It was shown recently [1] that the structural alpha -relaxation time tau of supercooled o-terphenyl depends on a single control parameter Gamma , which is the product of a function of density E(rho ), by the inverse temperature T -1. We extend this finding to other fragile glassforming liquids using light scattering data. Available experimental results do not allow to

C. Dreyfus; A. Le Grand; J. Gapinski; W. Steffen; A. Patkowski

2004-01-01

315

Space-time scales of internal waves: A progress report  

Microsoft Academic Search

We present a revised model for the distribution of internal wave energy in wave number frequency space. The model is empirical, guided by the following measurements: moored spectra and moored coherences for horizontal and vertical separations (MS, MHC, MVC as functions of frequency), towed spectra and towed vertical and time-lagged coherences (TS, TVC, TLC as functions of horizontal wave number),

Christopher Garrett; Walter Munk

1975-01-01

316

Brain connectivity at different time-scales measured with EEG  

PubMed Central

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

Koenig, T; Studer, D; Hubl, D; Melie, L; Strik, W.K

2005-01-01

317

Frequency Scaled Time Domain Equalization for OFDM in Wireless Communication  

Microsoft Academic Search

In this paper, the use of Orthogonal Frequency Division Multiplexing (OFDM), combined with a Time Domain Equalizer (TEQ), is investigated for broadband fixed wireless access systems. OFDM systems use a Cyclic Prefix (CP) that is inserted at the beginning of each sym- bol to convert the linear convolution of data and channel into a circular one. If the CP is

V. S. Abhayawardhana; I. J. Wassell

2002-01-01

318

Scaling properties of induction times in heterogeneous nucleation  

NASA Technical Reports Server (NTRS)

The heterogeneous-to-homogeneous induction time ratio is obtained as a function of the contact angle in the asymptotic limit of a high nucleation barrier. Model-dependent corrections to t(ind) are investigated, particularly in cases of the Turnbull-Fisher model used in numerical simulations by Greer et al. (1990).

Shneidman, Vitaly A.; Weinberg, Michael C.

1991-01-01

319

Does expressive timing in music performance scale proportionally with tempo?  

Microsoft Academic Search

Evidence is presented that expressive timing in music is not relationally invariant with global tempo. Our results stem from an analysis of repeated performances of Beethoven's variations on a Paisiello theme. Recordings were made of two pianists playing the pieces at three tempi. In contrast with the relational-invariance hypothesis (see Repp, 1994), between-tempo correlations were in general lower than within-tempo

Peter Desainl; Henkjan Honing

1994-01-01

320

Length scale and time scale effects on the plastic flow of fcc metals  

Microsoft Academic Search

We examine size scale and strain rate effects on single-crystal face-centered cubic (fcc) metals. To study yield and work hardening, we perform simple shear molecular dynamics simulations using the embedded atom method (EAM) on single-crystal nickel ranging from 100 atoms to 100 million atoms and at strain rates ranging from 107 to 1012 s?1. We compare our atomistic simulation results

M. F. Horstemeyer; M. I. Baskes; S. J. Plimpton

2001-01-01

321

Ichthyosaurs from the French Rhaetian indicate a severe turnover across the Triassic-Jurassic boundary.  

PubMed

Mesozoic marine reptiles went through a severe turnover near the end of the Triassic. Notably, an important extinction event affected ichthyosaurs, sweeping a large part of the group. This crisis is, however, obscured by an extremely poor fossil record and is regarded as protracted over the entire Norian-earliest Jurassic interval, for the lack of a more precise scenario. The iconic whale-sized shastasaurid ichthyosaurs are regarded as early victims of this turnover, disappearing by the middle Norian. Here we evaluate the pattern of this turnover among ichthyosaurs by analysing the faunal record of two Rhaetian localities. One locality is Autun, eastern France; we rediscovered in this material the holotypes or partial 'type' series of Rachitrema pellati, Actiosaurus gaudryi, Ichthyosaurus rheticus, Ichthyosaurus carinatus and Plesiosaurus bibractensis; a revised taxonomic scheme is proposed. The second assemblage comes from a new locality: Cuers, southeastern France. Both these assemblages provide several lines of evidence for the presence of shastasaurid-like ichthyosaurs in the Rhaetian of Europe. These occurrences suggest that both the demise of shastasaurids and the sudden radiation of neoichthyosaurians occurred within a short time window; this turnover appears not only more abrupt but also more complex than previously postulated and adds a new facet of the end-Triassic mass extinction. PMID:25256640

Fischer, Valentin; Cappetta, Henri; Vincent, Peggy; Garcia, Géraldine; Goolaerts, Stijn; Martin, Jeremy E; Roggero, Daniel; Valentin, Xavier

2014-12-01

322

Chemostratigraphic reconstruction of biofacies: Molecular evidence linking cyst-forming dinoflagellates with pre-Triassic ancestors  

NASA Astrophysics Data System (ADS)

New data from numerous detailed mass-spectrometric studies have detected triaromatic dinosteroids in Precambrian to Cenozoic rock samples. Triaromatic dinosteroids are organic geochemicals derived from dinosterols, compounds known in modern organisms to be the nearly exclusive widely occurring products of dinoflagellates. We observed the ubiquitous occurrence of these dinosteroids in 49 Late Triassic through Cretaceous marine source rocks and the absence of them in 13 Permian-Carboniferous source rocks synergistic with the dinoflagellate cyst record. However, finding dinosteroids in lower Paleozoic and Precambrian strata presents challenging results for molecular paleontologists, evolutionary biologists, palynologists, and especially for those concerned with the food web at various times of biological crisis. Other than the few species known as parasites and symbionts, many other dinoflagellate species are important as primary producers. The presence of Precambrian to Devonian triaromatic dinosteroids gives chemostratigraphic evidence of dinoflagellates (or other organisms with similar chemosynthetic capabilities) in rocks significantly older than the oldest undisputed dinoflagellate fossils (dinoflagellate cysts from the Middle Triassic, ˜ 240 Ma), and older than the putative Silurian ˜ 420 Ma) dinocyst,Arpylorus antiquus (Calandra) Sargent, from Tunisia. This systematic chemostratigraphic approach can shed light not only on lineages of dinoflagellates and their precursors, but potentially on many other lineages, especially bacteria, algae, plants, and possibly some metazoans.

Moldowan, J. Michael; Dahl, Jeremy; Jacobson, Stephen R.; Huizinga, Bradley J.; Fago, Frederick J.; Shetty, Rupa; Watt, David S.; Peters, Kenneth E.

1996-02-01

323

Body Size Evolution in Conodonts from the Cambrian through the Triassic  

NASA Astrophysics Data System (ADS)

The size of an organism exercises tremendous control over its physiology, life history, and ecology, yet the factors that influence body size evolution remain poorly understood. One major limitation is the lack of appropriate datasets spanning long intervals of evolutionary time. Here, we document size trends in conodonts (tooth-like microfossils from marine chordates) because they evolved rapidly and are known to change size during intervals of environmental change. By measuring photographs from the Catalogue of Conodonts (Ziegler 1982), we compiled a database of conodont P1 element measurements for 575 species and subspecies from the Cambrian through Triassic periods. Because tooth size correlates with body size in conodont animals and their extant relatives, conodont element length can serve as a proxy for the size of the conodont animal. We find that mean and maximum size across species increased during the early Paleozoic, peaked during the Devonian-Mississippian, and then generally decreased until conodonts went extinct at the end of the Triassic. We used regression analyses to compare conodont mean size trends to potential environmental predictors, such as changing atmospheric pO2, atmospheric pCO2, and sea level. Conodont size exhibited poor correlation with these environmental factors, suggesting that conodont evolution may have been more strongly influenced by other environmental covariates or ecological variables such as predation and competition.

Schaal, E. K.; Morgan, D. J.; Payne, J.

2013-12-01

324

Ichthyosaurs from the French Rhaetian indicate a severe turnover across the Triassic-Jurassic boundary  

NASA Astrophysics Data System (ADS)

Mesozoic marine reptiles went through a severe turnover near the end of the Triassic. Notably, an important extinction event affected ichthyosaurs, sweeping a large part of the group. This crisis is, however, obscured by an extremely poor fossil record and is regarded as protracted over the entire Norian-earliest Jurassic interval, for the lack of a more precise scenario. The iconic whale-sized shastasaurid ichthyosaurs are regarded as early victims of this turnover, disappearing by the middle Norian. Here we evaluate the pattern of this turnover among ichthyosaurs by analysing the faunal record of two Rhaetian localities. One locality is Autun, eastern France; we rediscovered in this material the holotypes or partial `type' series of Rachitrema pellati, Actiosaurus gaudryi, Ichthyosaurus rheticus, Ichthyosaurus carinatus and Plesiosaurus bibractensis; a revised taxonomic scheme is proposed. The second assemblage comes from a new locality: Cuers, southeastern France. Both these assemblages provide several lines of evidence for the presence of shastasaurid-like ichthyosaurs in the Rhaetian of Europe. These occurrences suggest that both the demise of shastasaurids and the sudden radiation of neoichthyosaurians occurred within a short time window; this turnover appears not only more abrupt but also more complex than previously postulated and adds a new facet of the end-Triassic mass extinction.

Fischer, Valentin; Cappetta, Henri; Vincent, Peggy; Garcia, Géraldine; Goolaerts, Stijn; Martin, Jeremy E.; Roggero, Daniel; Valentin, Xavier

2014-12-01

325

Restudy of conodont biostratigraphy of the Permian-Triassic boundary section in Zhongzhai, southwestern Guizhou Province, South China  

NASA Astrophysics Data System (ADS)

New conodont samples have been systematically collected at high stratigraphic resolution from the upper part of the Longtan Formation through to the lower part of the Yelang Formation at the Zhongzhai section, southwestern Guizhou Province, South China, in an effort to verify the first local occurrence of Hindeodus parvus in relation to the Permian-Triassic boundary at this section. The resampled conodont fauna from the Permian-Triassic boundary interval comprises five identified species and two undetermined species in Hindeodus and Clarkina. Most importantly, the first local occurrence of Hindeodus parvus is found for the first time from the bottom of Bed 28a, 18 cm lower than the previously reported first local occurrence of this species at this section. Considering the previously accepted PTB at the Zhongzhai section, well calibrated by conodont biostratigraphy, geochronology and carbon isotope chemostratigraphy, this lower (earlier) occurrence of H. parvus suggests that this critical species could occur below the Permian-Triassic boundary. As such, this paper provides evidence that (1) the first local occurrences of H. parvus are diachronous in different sections with respect to the PTB defined by the First Appearance Datum (FAD) of this species at its GSSP section in Meishan, China and that (2) the lower stratigraphic range of H. parvus should now be extended to latest Permian.

Zhang, Yang; Zhang, Ke-Xin; Shi, G. R.; He, Wei-Hong; Yuan, Dong-Xun; Yue, Ming-Liang; Yang, Ting-Lu

2014-02-01

326

Behavior of carbonate shelf communities in the Upper Triassic of Nevada: Evidence of impact mediated faunal turnover  

SciTech Connect

The carbonate shelf sediments of the Luning and Gabbs Formations of Nevada span the last several million years of the Triassic. This richly fossiliferous sequence provides a relatively continuous record of benthic community behavior during a long interval of global biotic turnover. Upper Carnian-Lower Norian and Upper Norian sea floors in this region were inhabited by a variety of invertebrate communities, all of them mollusc-dominated. Across a range of offshore shelf to basinal environments and throughout repeated community replacements, the most abundant and diverse taxa were infaunal and epifaunal bivalves and ammonites. The sequence of Upper Triassic molluscan communities was interrupted by a Lower or Middle Norian interval of brachiopod-dominated faunas. Although preserved in similar offshore carbonate shelf sediments, these communities are nearly devoid of the infaunal bivalves and ammonites that characterize both older and younger assemblages in the section. This pattern, of a temporary replacement of molluscan communities by brachiopod faunas, mimics that reported for some shelf assemblages across the Cretaceous-Tertiary boundary. That brief resurgence of brachiopods is linked to a sharp drop in marine primary productivity, which suggests that a disruption of planktonic food chains may also have occurred early in the Norian. The timing and pattern of Carnian-Norian faunal and physical events and their resemblance to K/T sequences are consistent with the proposal that an asteroid impact played a role in the Upper Triassic faunal transition.

Hogler, J.A. (Univ. of California, Berkeley, CA (United States). Museum of Paleontology)

1993-04-01

327

Rock-inhabiting fungi originated during periods of dry climate in the late Devonian and middle Triassic.  

PubMed

Non-lichenized rock-inhabiting fungi (RIF) are slow-growing melanized ascomycetes colonizing rock surfaces in arid environments. They possess adaptations, which allow them to tolerate extreme abiotic conditions, such as high UV radiations and extreme temperatures. They belong to two separate lineages, one consisting in the sister classes Dothideomycetes and Arthoniomycetes (Dothideomyceta), and the other consisting in the order Chaetothyriales (Eurotiomycetes). Because RIF often form early diverging groups in Chaetothyriales and Dothideomyceta, the ancestors of these two lineages were suggested to most likely be rock-inhabitants. The lineage of RIF related to the Chaetothyriales shows a much narrower phylogenetic spectrum than the lineage of RIF related to Dothideomyceta, suggesting a much more ancient origin for the latter. Our study aims at investigating the times of origin of RIF using a relaxed clock model and several fossil and secondary calibrations. Our results show that the RIF in Dothideomyceta evolved in the late Devonian, much earlier than the RIF in Chaetothyriales, which originated in the middle Triassic. The origin of the chaetothyrialean RIF correlates well with a period of recovery after the Permian-Triassic mass extinction and an expansion of arid landmasses. The period preceding the diversification of the RIF related to Dothideomyceta (Silurian--Devonian) is also characterized by large arid landmasses, but temperatures were much cooler than during the Triassic. The paleoclimate record provides a good explanation for the diversification of fungi subjected to abiotic stresses and adapted to life on rock surfaces in nutrient-poor habitats. PMID:21944211

Gueidan, Cécile; Ruibal, Constantino; de Hoog, G S; Schneider, Harald

2011-10-01

328

Ophiuroids discovered in the middle triassic hypersaline environment.  

PubMed

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

Salamon, Mariusz A; Nied?wiedzki, Robert; Lach, Rafa?; Brachaniec, Tomasz; Gorzelak, Przemys?aw

2012-01-01

329

Proportional hazards regression in epidemiologic follow-up studies: an intuitive consideration of primary time scale.  

PubMed

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

Cologne, John; Hsu, Wan-Ling; Abbott, Robert D; Ohishi, Waka; Grant, Eric J; Fujiwara, Saeko; Cullings, Harry M

2012-07-01

330

Temperature Responses to Spectral Solar Variability on Decadal Time Scales  

NASA Technical Reports Server (NTRS)

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.

Cahalan, Robert F.; Wen, Guoyong; Harder, Jerald W.; Pilewskie, Peter

2010-01-01

331

A review of selected triassic to Early Cretaceous ferns  

Microsoft Academic Search

After becoming nearly extinct during the Permian, the ferns began a slow recovery during the Triassic as the climate of the\\u000a earth moderated. As a result, a considerable number and variety were present and widely distributed during the Jurassic and\\u000a Early Cretaceous. However, with the rapid expansion of the angiosperms during the Late Cretaceous, the ferns once again became\\u000a reduced

William D. Tidwell; Sidney R. Ash

1994-01-01

332

Paleomagnetism of Upper Triassic Diabase from Southeastern Pennsylvania: Further Results  

Microsoft Academic Search

Seventy-eight reliable sites in Upper Triassic diabase from southeastern Pennsylvania yield a pleomagnetic pole at 62.0øN, 104.5øE, about 0.5 ø from an earlier pole calculation based on a preliminary study of 20 sites. Site poles have a Fisherian distribution, with an angular standard deviation of 7.4 ø , considerably less than the dispersion predicted by models based on the present

1972-01-01

333

The Paleomagnetism of a Triassic Diabase Dike in Nova Scotia  

Microsoft Academic Search

The paleomagnetism of a 110-km-long diabase dike in the southern part of Nova Scotia has been studied. A potassium-argon whole-rock age determination has confirmed the Triassic age assignment to the dike rocks. The magnetic stability and other magnetic properties of the rocks were examined, and the presence of a stable component was established. An analysis of the palcomagnetic data establishes

A. Larochelle; R. K. Wanless

1966-01-01

334

The Triassic section north of Currie, Elko County, Nevada  

SciTech Connect

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.

Lucas, S.G.; Goodspeed, T.H. (New Mexico Museum of Natural History, Albuquerque, NM (United States))

1993-04-01

335

Paleogeographic regionalization of Triassic seas based on conodontophorids  

Microsoft Academic Search

Geographic differentiation of conodontophorids between northern and southern latitudes commenced in the Triassic since the\\u000a early Induan. Cosmopolitan long-lived genera of predominantly smooth morphotypes without sculpturing were characteristic of\\u000a high-latitude basins of the Panboreal Superrealm. Since the early Olenekian until the Carnian inclusive, this superrealm consisted\\u000a of the Siberian Realm that extended over Northeast Asia and the Canada-Svalbard Realm that

T. V. Klets

2008-01-01

336

Paleomagnetic and Geological Implications of Magnetic Properties of the Triassic Diabase of Southeastern Pennsylvania  

Microsoft Academic Search

Preliminary measurements of magnetic properties of Triassic diabase in south- eastern Pennsylvania imply a Triassic geomagnetic pole in central Siberia, at 62øN, 105øE. This pole is virtually identical to that obtained from paleomagnetic studies of rocks of similar age in New Jersey and Arizona. A North American Triassic pole, the mean of six independent determinations, is located at 62øN, 101øE.

M. E. Beck

1965-01-01

337

Skillful North Atlantic predictability extends beyond decadal time scale  

NASA Astrophysics Data System (ADS)

The recently emerged field of near-term climate prediction aims at skillfully predicting the regional climate variations for a time horizon of up to 30 years. However, all dynamical decadal prediction systems employed to date focus on a much shorter forecast horizon, even if there are indications that skilful predictions may be achieved for lead times beyond a decade. In this study we try to push the current decadal prediction boundary by extending the forecast window from the classical length (standard CMIP5 decadal prediction setup) of 10 years to 20 years. For this purpose we employ the MPI-ESM-LR CMIP5 decadal prediction system that makes use of an oceanic initialization from a MPI-OM NCEP/NCAR forced ocean simulation over the period 1948-2012. Estimates of 3-D temperature and salinity anomalies from this simulation are used to initialize a 6-member ensemble of 20-yr-long hindcasts starting on every 1st Jan between 1960 and 2012. The skill of the initialized decadal hindcast experiments is assessed against the benchmark prediction skill of the non-initialized hindcast simulations and statistical forecasts. We focus in the presentation on the North Atlantic, a region robustly identified as exhibiting the highest predictive skill beyond the global warming trend and an important driver of climate variability over Europe and North America. Our results show that indeed, in accordance to several potential predictability studies, the predictive skill and the added-value from the ocean initialization remains statistically significant during the whole 20yr of the forecast time over the North Atlantic Subpolar Gyre, eastern subtropical North Atlantic and Western Mediterranean basin. The skilful extended range predictability is achieved not only for surface quantities such as sea surface temperature and sea level height, but also for upper ocean heat and salt content variations. Therefore, our results support recent observational analyses suggesting that the integrated effect of the North Atlantic Oscillation onto the ocean leads to useful predictions of the AMV 15-to-20 years later. In addition, the recent NAO weakening might also explain the consistent cooling tendency of the North Atlantic Subpolar Gyre SSTs of our forecast ensemble over the next 5 years.

Matei, Daniela; Jungclaus, Johann; Marotzke, Jochem

2014-05-01

338

An Algorithm for Real-Time Visualization of Large-Scale Terrain  

Microsoft Academic Search

Large-scale terrain real-time visualization has been widely used in GIS, virtual reality, games, simulation, etc. Based on existing terrain simplification algorithm, this paper proposes an algorithm for real-time visualization of terrain with data block partition, dynamic dispatching and view-dependant. This algorithm can implement the real-time fast walkthrough for large-scale terrain. With view frustum culling, triangle strip optimizing, cracks elimination and

Jin Hailiang; Liu Huijie

2009-01-01

339

Detection of Sequential Polyubiquitylation on a Millisecond Time-Scale  

PubMed Central

The pathway by which ubiquitin chains are generated on substrate via a cascade of enzymes consisting of an E1, E2 and E3 remains unclear. Multiple distinct models involving chain assembly on E2 or substrate have been proposed. However, the speed and complexity of the reaction have precluded direct experimental tests to distinguish between potential pathways. Here we introduce new theoretical and experimental methodologies to address both limitations. A quantitative framework based on product distribution predicts that the really interesting new gene (RING) E3s SCFCdc4 and SCF?-TrCP work with the E2 Cdc34 to build polyubiquitin chains on substrates by sequential transfers of single ubiquitins. Measurements with millisecond time resolution directly demonstrate that substrate polyubiquitylation proceeds sequentially. Our results present an unprecedented glimpse into the mechanism of RING ubiquitin ligases and illuminate the quantitative parameters that underlie the rate and pattern of ubiquitin chain assembly. PMID:19956254

Pierce, Nathan W.; Kleiger, Gary; Shan, Shu-ou; Deshaies, Raymond J.

2009-01-01

340

A potential biomarker for the Permian Triassic ecological crisis  

NASA Astrophysics Data System (ADS)

A unique biomarker, a C 33n-alkylcyclohexane ( n-heptacosylcyclohexane), which strongly increases in abundance within the extinction interval of the end-Permian ecological crisis, is here reported from the key Permian-Triassic (P-Tr) marine section in Greenland. Prior to this study, this compound had been known from Early Triassic organic-rich marine rocks and oils from the northern Perth Basin, Western Australia for two decades. We have identified the compound in high relative abundance in 29 samples from P-Tr marine sections from two separate paleogeographic localities, from Laurasia and Gondwana. Relative concentrations of the C 33n-alkylcyclohexane show similar changes to the relative abundances of extinct spinose acritarchs ( Veryhachium and Micrhystridium) indicating that the source organism of the C 33n-alkylcyclohexane is associated with the depositional environments/facies in which the acritarchs are identified. These organisms probably formed the cornerstone of the unique marine ecosystem that thrived in the extinction aftermath in the Early Triassic Ocean.

Grice, Kliti; Twitchett, Richard J.; Alexander, Robert; Foster, C. B.; Looy, Cindy

2005-07-01

341

Studying the time scale dependence of environmental variables predictability using fractal analysis.  

PubMed

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

Yuval; Broday, David M

2010-06-15

342

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)

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.

Lovejoy, Shaun; Elias, Lydia

2014-05-01

343

On the time scale associated with Monte Carlo simulations.  

PubMed

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. PMID:25429930

Bal, Kristof M; Neyts, Erik C

2014-11-28

344

Updating the planetary time scale: focus on Mars  

USGS Publications Warehouse

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.

Tanaka, Kenneth L.; Quantin-Nataf, Cathy

2013-01-01

345

On the time scale associated with Monte Carlo simulations  

NASA Astrophysics Data System (ADS)

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.

Bal, Kristof M.; Neyts, Erik C.

2014-11-01

346

Implications from Paleomagnetic Age Constrains and Petrology Analyses on the Reconstruction of the Triassic Paleosurface in Europe - Examples from Catalonia and the Polish Sudetes (Invited)  

NASA Astrophysics Data System (ADS)

The crystalline basement rocks (such as granites and rhyolithes) of European Variscan massifs often show Permo-Triassic paleomagnetic remagnetizations resulting in underestimated age determinations. These rejuvenated ages are attributed to an alteration of the primary paleomagnetic signal recently carried by the neo-formation of secondary hematite. Hematite forms under oxic conditions. Thus, one may deduce that the remagnetization of the Paleozoic crystalline rocks occurs once the basement rocks are exposed at the Permo-Triassic (paleo)surface. Permo-Triassic remagnetizations are ubiquitous, affecting many emerged Paleozoic rocks in Europe (and beyond) and suggesting a major weathering event under oxic conditions. The extent of the altered zone (> 100 m in depth) points to a sodium enriched groundwater environment. The Na+ enrichment is likely related to the Triassic environment characterized by widespread salt deposits, such as leaching of salt, marine aerosols, periodic/episodic contribution of seawater or evaporative solutions. Under these uncommon shallow conditions the basement rocks containing feldspars (mainly granites and gneisses) suffered an ubiquitous process of alteration consisting in the albitization of feldspars (fsp). The most visible feature of this alteration at outcrop scale is the pervasive red staining of the rock due to the presence of associated Fe-oxide inclusions, which are responsible for the penetrative red colour of the rock. Examination by petrographical microscopy shows that the fsp replacement by albite is pseudomorphic and the shape and optical properties of the parent fsp are preserved in the daughter grain. The composition of the albitized fsp is very constant and close to the albite end-member, displaying values of Ab96-97 in all studied massifs. In cathodoluminescence microscopy, the albitized fsp display a noticeable lack of luminescence, whereas the primary fsp usually show luminescence. The SEM images revealed that secondary albite contains widespread ?m and nm pores. Observations under SEM and HRSEM show that this microporosity is hoisting Fe-oxides inclusions responsible for the red colour. Most of the Fe-oxides tends to concentrate in the larger pores and in the majority of the imaged pores these Fe-oxides appears to be arranged in aggregates of nm size botryoids attached to the pore walls. Demonstrating that the albitized facies are of supergenic origin and that they are 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 these areas.

Parcerisa, D.; Franke, C.; Fabrega, C.; Yao, K.; Thiry, M.

2013-12-01

347

Modelling soil carbon movement by erosion over large scales and long time periods  

NASA Astrophysics Data System (ADS)

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.

Quinton, John; Davies, Jessica; Tipping, Ed

2014-05-01

348

Time-scale and state dependence of the carbon-cycle feedback to climate  

NASA Astrophysics Data System (ADS)

Climate and atmospheric CO2 concentration are intimately coupled in the Earth system: CO2 influences climate through the greenhouse effect, but climate also affects CO2 through its impact on the amount of carbon stored on land and in the ocean. The change in atmospheric CO2 as a response to a change in temperature () is a useful measure to quantify the feedback between the carbon cycle and climate. Using an ensemble of experiments with an Earth system model of intermediate complexity we show a pronounced time-scale dependence of . A maximum is found on centennial scales with values for the model ensemble in the range 5-12 ppm °C-1, while lower values are found on shorter and longer time scales. These results are consistent with estimates derived from past observations. Up to centennial scales, the land carbon response to climate dominates the CO2 signal in the atmosphere, while on longer time scales the ocean becomes important and eventually dominates on multi-millennial scales. In addition to the time-scale dependence, modeled show a distinct dependence on the initial state of the system. In particular, on centennial time-scales, high values are correlated with high initial land carbon content. A similar relation holds also for the CMIP5 models, although for computed from a very different experimental setup. The emergence of common patterns like this could prove to usefully constrain the climate-carbon cycle feedback.

Willeit, Matteo; Ganopolski, Andrey; Dalmonech, Daniela; Foley, Aideen M.; Feulner, Georg

2014-04-01

349

Computational Modeling of Semiconductor Dynamics at Femtosecond Time Scales  

NASA Technical Reports Server (NTRS)

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.

Agrawal, Govind P.; Goorjian, Peter M.

1998-01-01

350

Computational Modeling of Semiconductor Dynamics at Femtosecond Time Scales  

NASA Technical Reports Server (NTRS)

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.

Agrawal, Govind P.; Goorjian, Peter M.

1998-01-01

351

Scaling Behavior of the First Arrival Time of a Random-Walking Magnetic Domain  

SciTech Connect

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.

Im, M.-Y.; Lee, S.-H.; Kim, D.-H.; Fischer, P.; Shin, S.-C.

2008-02-04

352

Using Focused Regression for Accurate Time-Constrained Scaling of Scientific Applications  

SciTech Connect

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%.

Barnes, B; Garren, J; Lowenthal, D; Reeves, J; de Supinski, B; Schulz, M; Rountree, B

2010-01-28

353

Permo-Triassic reconstruction of western Pangea and the evolution of the Gulf of Mexico&solCaribbean region  

NASA Astrophysics Data System (ADS)

A Permo-Triassic reconstruction of western Pangea (North America, South America, Africa) is proposed that is characterized by (1) definition of the North Atlantic fit by matching of marginal offsets (fracture zones) along the opposing margins, (2) a South Atlantic fit that is tighter than the BuIlard fit and that is achieved by treating Africa as two plates astride the Benue Trough and related structures during the Cretaceous, (3) complete closure of the Proto-Atlantic Ocean between North and South America, accomplished by placing the Yucatan block between the Ouachita Mountains and Venezuela, (4) a proposed Hercynian suture zone that separates zones of foreland thrusting from zones of arc-related magmatic activity; to the northwest of this suture lie the Chortis block and Mexico and most of North America, and to the southeast lie South America, the Yucatan Block, Florida and Africa, and (5) satisfaction of paleomagmatic data from North America, South America, and Africa. Beginning with the proposed reconstruction, the relative motion history of South America with respect of North America is defined by using the finite difference method. Within the framework provided by the proposed relative motion history, an evolutionary model for the development of the Gulf of Mexico and Caribbean region is outlined in a series of 13 plate boundary reconstructions at time intervals from the Jurassic to the present. The model includes (1) formation of the Gulf of Mexico by 140 Ma, (2) Pacific provenance of the Caribbean plate through the North America-South America gap during Cretaceous time, (3) Paleocene-Early Eocene back arc spreading origin for the Yucatan Basin, whereby Cuba is the frontal arc and the Nicaragua Rise-Jamaica-Southern Hispaniola is the remnant arc, and (4) 1200 km of post-Eocene cumulative offset along both the Northern and Southern Caribbean Plate Boundary Zones, allowing large-scale eastward migration of the Caribbean plate with respect to the North and South American Plates.

Pindell, James; Dewey, John F.

1982-04-01

354

Time operators in stroboscopic wavepacket basis and the time scales in tunneling  

E-print Network

We demonstrate that the time operator that measures the time of arrival of a quantum particle into chosen state can be defined as a self-adjoint quantum-mechanical operator using periodic boundary conditions on applied to wavefuncions in energy representation. The time becomes quantized into discreet eigenvalues and the eigenstates of the time operator, the stroboscopic wavepackets introduced recently [Phys. Rev. Lett. 101, 046402 (2008).] form orthogonal system of states. The formalism provides simple physical interpretation of the time-measurement process and direct construction of normalized, positive definite probability distribution for the quantized values of the arrival time. The average value of the time is equal to the phase time but in general depends on the choise of zero time eigenstate, whereas the uncertainity of the average is related to the traversal time and is independent of this choise. The general fromalism is applied to a particle tunneling through resonant tunneling barrier in 1D.

Bokes, P

2010-01-01

355

Time operators in stroboscopic wavepacket basis and the time scales in tunneling  

E-print Network

We demonstrate that the time operator that measures the time of arrival of a quantum particle into chosen state can be defined as a self-adjoint quantum-mechanical operator using periodic boundary conditions on applied to wavefuncions in energy representation. The time becomes quantized into discreet eigenvalues and the eigenstates of the time operator, the stroboscopic wavepackets introduced recently [Phys. Rev. Lett. 101, 046402 (2008).] form orthogonal system of states. The formalism provides simple physical interpretation of the time-measurement process and direct construction of normalized, positive definite probability distribution for the quantized values of the arrival time. The average value of the time is equal to the phase time but in general depends on the choise of zero time eigenstate, whereas the uncertainity of the average is related to the traversal time and is independent of this choise. The general fromalism is applied to a particle tunneling through resonant tunneling barrier in 1D.

P. Bokes

2010-12-05

356

Reconstructing the growth of a fracture set using fluid inclusion microthermometry, El Alamar Formation (Triassic), NE Mexico  

NASA Astrophysics Data System (ADS)

Aperture-frequency data collected by scanline surveys of natural fractures in tight-gas sandstones and their outcrop analogs commonly follow a power-law aperture size scaling distribution that spans the aperture range from the microscale (apertures <0.1 mm) to the macroscale. The coefficient of the power-law equation represents the fracture intensity whereas the exponent reflects the relative abundance of large to small fractures. Comparing data sets collected in rock units from different tectonic regimes and burial settings, and from different structural positions within mesoscopic structures in the same rock unit, we find that the coefficient increases with increasing fracture strain but the exponent stays relatively constant. This suggests that microscopic fractures (microfractures) grow along with macroscopically visible fractures (macrofractures) throughout the evolution of the fracture set. To test this interpretation, we modeled the development of a power-law set of fractures consistent with the observation of incremental fracture opening through the crack-seal mechanism of repeated cycles of fracture opening and cementation. The simulation is an Excel routine that randomly distributes fracture opening increments among a set of active fractures. We compared the modeled sequence of cement increments and the resulting aperture size distribution against fracture scaling and cement timing data collected from the Triassic El Alamar Formation in NE Mexico. Cement timing was inferred through crosscutting relationships and comparison with fluid inclusion microthermometric data from other fracture sets that indicate that the fracture set used for this field validation formed during uplift and ambient cooling. Thus, opening temperature for this fracture set, serves as a proxy for fracture timing. The field scaling and fluid inclusion data are broadly consistent with the numerical simulation. New microfractures appear to have formed throughout the period of active fracture growth. Some microfractures grew to large sizes; some that formed early never reactivated. New microfractures formed amid dense arrays of pre-existing, actively growing fractures. The simulation does not account for fracture spatial arrangement, but the natural data show some correlation between fracture location and timing, suggesting that clusters of fractures may grow concurrently.

Hooker, J. N.; Eichhubl, P.; Laubach, S.

2012-12-01

357

Costs and cost scaling in time-domain integral-equation analysis of electromagnetic scattering  

Microsoft Academic Search

Computation of scattering from multi-wavelength bodies is expensive, and costs scale with up to the sixth power of the incident frequency. Conventional integral-equation time-domain methods have costs scaling with the fifth power. Here are described modifications to the IETD approach that offer the prospect of a reduction in cost scaling, to possibly the third power of frequency, and an associated

S. J. Dodson; S. P. Walker; M. J. Bluck

1998-01-01

358

Tectonically controlled magnetic fabrics in the Iberian Triassic basin  

NASA Astrophysics Data System (ADS)

A relationship between the orientation of the magnetic susceptibility ellipsoid and the strain ellipsoid has been demonstrated by using the anisotropy of magnetic susceptibility (AMS) in sedimentary rocks. Studies also interpret an early development of the magnetic fabric, which registers the stress pattern acting during deposition. But this primary fabric can be overwritten by successive deformation phases, and these changes have been registered even in weakly deformed sediments. This work studies the AMS registered in an inverted basin where no penetrative compression-related structures have been recognized. Although inversion took place, strata remain weakly deformed, with shallow dips in most part of the area. Triassic sedimentary rocks from the Castilian Branch of the Iberian Range (NE Spain) are studied. The Castilian Branch started to develop as a rift basin during the Late Permian-Early Triassic with NW-SE and NE-SW faults affecting Upper Permian materials. Buntsandstein red beds accumulated in asymmetric half-grabens with strong thickness variations related to their position within the troughs and highs. After the Mid-Triassic, a marine and transitional sedimentation spanned throughout the Iberian Range (Keuper and Muschelkalk). Jurassic to Upper Cretaceous deposits unconformably covered the Triassic sediments with thickness of a few hundreds of meters. During the Paleogene, tectonic inversion took place, developing gentle folds and steeply-dipping reverse faults, resulting from the reactivation of extensional Triassic faults. The particular lithology of the Buntsandstein red beds also allows determining the influence of ferromagnetic phases in the AMS. We analyzed 815 standard specimens from 55 sites in a KLY-3S Kappabridge (AGICO) susceptometer to obtain the bulk susceptibility and the orientation of the three main eigenvectors of the magnetic ellipsoid. In order to determine the magnetic carriers of the bulk susceptibility, 22 temperature dependent susceptibility curves (from 40 to 700°C) were carried out, combining the susceptometer with a CS-3 furnace. Sites are representative of all the red beds sectors from the Castilian Branch, limited by different extensional structures acting during Triassic rifting. The magnetic susceptibility ranges between 80 and 350 x 10-6 SI. Most of the thermomagnetic curves indicate the presence of a high fraction of hematite as ferromagnetic mineral. In other cases, hematite and phyllosilicates are present in the same proportion, usually coinciding with samples from sites with the lowest susceptibility values. In some cases neoformation of magnetite takes place during heating. Results show kmin always subperpendicular to the bedding plane, according to a sedimentary fabric. kmax indicates four main directions for the magnetic lineation: NW-SE, NNE-SSW and, less represented N-S and E-W. These variations in lineation directions are directly related to several tectonic events, and can be interpreted according to i) the direction of the major extensional structures nearest to each site (suggesting an extensional-influenced origin for the lineation), ii) the geographic position of the basin sectors, depending on their proximity to the inverted faults (that would suggest a partial tectonically-influenced secondary magnetic fabric), iii) the age of the studied rocks, suggesting a stronger influence of extensional features in Early Triassic rocks, progressively diminishing upwards within the sedimentary sequence.

García-Lasanta, C.; Oliva-Urcia, B.; Román-Berdiel, T.; Casas-Sainz, A.; Gil-Peña, I.; Sánchez-Moya, Y.; Sopeña, A.

2012-04-01

359

Parametric scaling studies of the energy confinement time for neutral beam heated Heliotron E plasmas  

Microsoft Academic Search

A kinetic analysis of the global energy confinement time for neutral beam heated Heliotron E plasmas has been performed with a 1-D, time independent transport analysis code, PROCTR-Mod. From a regression analysis of a representative sample selection of the presented data sets, the global energy confinement time, , is found to scale as , where ? = 0.53 0.10, ?

F. Sano; Y. Takeiri; K. Hanatani; H. Zushi; M. Sato; S. Sudo; T. Mutoh; K. Kondo; H. Kaneko; T. Mizuuchi; H. Okada; S. Morimoto; K. Itoh; S. Besshou; M. Nakasuga; Y. Nakamura; N. Noda; K. Akaishi; O. Motojima; M. Wakatani; T. Obiki; A. Iiyoshi; M. Murakami; H. C. Howe

1990-01-01

360

Space-time cascades and the scaling of ECMWF1 reanalyses: fluxes and fields2  

E-print Network

4/20/11 1 Space-time cascades and the scaling of ECMWF1 reanalyses: fluxes and fields2 S. Lovejoy1 scale networks32 are invariably sparse [Lovejoy et al., 1986] and aircraft data are not only limited fractal and34 sloping [Lovejoy et al., 2004], [Lovejoy et al., 2009c]. Although satellite data are nearly

Lovejoy, Shaun

361

Factor Structure and Scale Reliabilities of the Adjective Check List Across Time  

ERIC Educational Resources Information Center

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…

Miller, Stephen H.; And Others

1978-01-01

362

Mastering Uncertainty and Risk at Multiple Time Scales in the Future Electrical Grid  

SciTech Connect

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.

Chertkov, Michael [Los Alamos National Laboratory; Bent, Russell W. [Los Alamos National Laboratory; Backhaus, Scott N. [Los Alamos National Laboratory

2012-07-10

363

Nitrogen isotope chemostratigraphy across the Permian-Triassic boundary at Chaotian, Sichuan, South China  

NASA Astrophysics Data System (ADS)

Nitrogen isotopic compositions of upper Permian to lowermost Triassic rocks were analyzed at Chaotian in northern Sichuan, South China, in order to clarify changes in the oceanic nitrogen cycle around the Permian-Triassic boundary (P-TB) including the entire Changhsingian (Late Late Permian) prior to the extinction. The analyzed ca. 40 m thick interval across the P-TB at Chaotian consists of three stratigraphic units: the upper Wujiaping Formation, the Dalong Formation, and the lowermost Feixianguan Formation, in ascending order. The upper Wujiaping Formation, ca. 10 m thick, is mainly composed of dark gray limestone with diverse shallow-marine fossils such as calcareous algae and brachiopods, deposited on the shallow shelf. In contrast, the overlying Dalong Formation, ca. 25 m thick, is mainly composed of thinly bedded black mudstone and siliceous mudstone containing abundant radiolarians, deposited on the relatively deep slope/basin. Absence of bioturbation, substantially high total organic carbon contents (up to 15%), and abundant occurrence of pyrite framboids in the main part of the Dalong Formation indicate deposition under anoxic condition. The lowermost Feixianguan Formation, ca. 5 m thick, is composed of thinly bedded gray marl and micritic limestone with minor fossils such as ammonoids and conodonts, deposited on the relatively shallow slope. ?15NTN values are in positive values around +1 to +2‰ in the upper Wujiaping Formation implying denitrification and/or anammox in the ocean. ?15NTN values gradually decrease to -1‰ in the lower Dalong Formation and are consistently low (around 0‰) in the middle Dalong to lowermost Feixianguan Formation. No clear ?15NTN shift is recognized across the extinction horizon. The consistently low ?15NTN values suggest the enhanced nitrogen fixation in the ocean during the Changhsingian at Chaotian. Composite profiles based on previous and the present studies demonstrate the substantial ?15N variation on a global scale in the late Permian to earliest Triassic; a systematic ?15N difference by low and high latitudes is particularly clarified. Although the enhanced nitrogen fixation throughout the Changhsingian at Chaotian was likely a regional event in northwestern South China, the composite ?15N profiles imply that the sea area in which fixed nitrogen is depleted has gradually developed worldwide in the Changhsingian, possibly acting as a prolonged stress to shallow-marine biota.

Saitoh, Masafumi; Ueno, Yuichiro; Nishizawa, Manabu; Isozaki, Yukio; Takai, Ken; Yao, Jianxin; Ji, Zhansheng

2014-10-01

364

Approximate solution of the probability density function of bedload transport rate over multiple time scales  

NASA Astrophysics Data System (ADS)

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

Fu, X.; Ma, H.; Heyman, J.; Mettra, F.; Ancey, C.

2013-12-01

365

Mechanistic scaling of ecosystem function and dynamics in space and time: Ecosystem Demography model version 2  

E-print Network

Mechanistic scaling of ecosystem function and dynamics in space and time: Ecosystem Demography] Insights into how terrestrial ecosystems affect the Earth's response to changes in climate and rising contain detailed mechanistic representations of biological processes affecting terrestrial ecosystems

Moorcroft, Paul R.

366

Predictability of North Atlantic Tropical Cyclone Activity on Intraseasonal Time Scales  

E-print Network

Predictability of North Atlantic Tropical Cyclone Activity on Intraseasonal Time Scales JAMES I Recent work suggests that there may exist skill in forecasting tropical cyclones (TC) using dynamically initialization. 1. Introduction Developing skillful tropical cyclone (TC) forecasts using statistical (e

Webster, Peter J.

367

Bi-Hamiltonian structures for integrable systems on regular time scales  

NASA Astrophysics Data System (ADS)

A construction of the bi-Hamiltonian structures for integrable systems on regular time scales is presented. The trace functional on an algebra of ?-pseudodifferential operators, valid on an arbitrary regular time scale, is introduced. The linear Poisson tensors and the related Hamiltonians are derived. The quadratic Poisson tensors are given by the use of the recursion operators of the Lax hierarchies. The theory is illustrated by ?-differential counterparts of Ablowitz-Kaup-Newell-Segur and Kaup-Broer hierarchies.

Szablikowski, B?a?ej M.; B?aszak, Maciej; Silindir, Burcu

2009-07-01

368

New time-scale criteria for model simplification of bio-reaction systems  

PubMed Central

Background Quasi-steady state approximation (QSSA) based on time-scale analysis is known to be an effective method for simplifying metabolic reaction system, but the conventional analysis becomes time-consuming and tedious when the system is large. Although there are automatic methods, they are based on eigenvalue calculations of the Jacobian matrix and on linear transformations, which have a high computation cost. A more efficient estimation approach is necessary for complex systems. Results This work derived new time-scale factor by focusing on the problem structure. By mathematically reasoning the balancing behavior of fast species, new time-scale criteria were derived with a simple expression that uses the Jacobian matrix directly. The algorithm requires no linear transformation or decomposition of the Jacobian matrix, which has been an essential part for previous automatic time-scaling methods. Furthermore, the proposed scale factor is estimated locally. Therefore, an iterative procedure was also developed to find the possible multiple boundary layers and to derive an appropriate reduced model. Conclusion By successive calculation of the newly derived time-scale criteria, it was possible to detect multiple boundary layers of full ordinary differential equation (ODE) models. Besides, the iterative procedure could derive the appropriate reduced differential algebraic equation (DAE) model with consistent initial values, which was tested with simple examples and a practical example. PMID:18694523

Choi, Junwon; Yang, Kyung-won; Lee, Tai-yong; Lee, Sang Yup

2008-01-01

369

Recovery from the most profound mass extinction of all time  

PubMed Central

The end-Permian mass extinction, 251 million years (Myr) ago, was the most devastating ecological event of all time, and it was exacerbated by two earlier events at the beginning and end of the Guadalupian, 270 and 260?Myr ago. Ecosystems were destroyed worldwide, communities were restructured and organisms were left struggling to recover. Disaster taxa, such as Lystrosaurus, insinuated themselves into almost every corner of the sparsely populated landscape in the earliest Triassic, and a quick taxonomic recovery apparently occurred on a global scale. However, close study of ecosystem evolution shows that true ecological recovery was slower. After the end-Guadalupian event, faunas began rebuilding complex trophic structures and refilling guilds, but were hit again by the end-Permian event. Taxonomic diversity at the alpha (community) level did not recover to pre-extinction levels; it reached only a low plateau after each pulse and continued low into the Late Triassic. Our data showed that though there was an initial rise in cosmopolitanism after the extinction pulses, large drops subsequently occurred and, counter-intuitively, a surprisingly low level of cosmopolitanism was sustained through the Early and Middle Triassic. PMID:18198148

Sahney, Sarda; Benton, Michael J

2008-01-01

370

Towards a verifiable real-time, autonomic, fault mitigation framework for large scale real-time systems  

Microsoft Academic Search

Designing autonomic fault responses is difficult, particularly in large-scale systems, as there is no single ‘perfect’ fault\\u000a mitigation response to a given failure. The design of appropriate mitigation actions depend upon the goals and state of the\\u000a application and environment. Strict time deadlines in real-time systems further exacerbate this problem. Any autonomic behavior\\u000a in such systems must not only be

Abhishek Dubey; Steven Nordstrom; Turker Keskinpala; Sandeep Neema; Ted Bapty; Gabor Karsai

2007-01-01

371

C 1-Almost Periodic Solutions of BAM Neural Networks with Time-Varying Delays on Time Scales  

PubMed Central

On a new type of almost periodic time scales, a class of BAM neural networks is considered. By employing a fixed point theorem and differential inequality techniques, some sufficient conditions ensuring the existence and global exponential stability of C 1-almost periodic solutions for this class of networks with time-varying delays are established. Two examples are given to show the effectiveness of the proposed method and results.

Li, Yongkun; Zhao, Lili; Yang, Li

2015-01-01

372

A hybrid procedure for MSW generation forecasting at multiple time scales in Xiamen City, China  

SciTech Connect

Highlights: ? We propose a hybrid model that combines seasonal SARIMA model and grey system theory. ? The model is robust at multiple time scales with the anticipated accuracy. ? At month-scale, the SARIMA model shows good representation for monthly MSW generation. ? At medium-term time scale, grey relational analysis could yield the MSW generation. ? At long-term time scale, GM (1, 1) provides a basic scenario of MSW generation. - Abstract: Accurate forecasting of municipal solid waste (MSW) generation is crucial and fundamental for the planning, operation and optimization of any MSW management system. Comprehensive information on waste generation for month-scale, medium-term and long-term time scales is especially needed, considering the necessity of MSW management upgrade facing many developing countries. Several existing models are available but of little use in forecasting MSW generation at multiple time scales. The goal of this study is to propose a hybrid model that combines the seasonal autoregressive integrated moving average (SARIMA) model and grey system theory to forecast MSW generation at multiple time scales without needing to consider other variables such as demographics and socioeconomic factors. To demonstrate its applicability, a case study of Xiamen City, China was performed. Results show that the model is robust enough to fit and forecast seasonal and annual dynamics of MSW generation at month-scale, medium- and long-term time scales with the desired accuracy. In the month-scale, MSW generation in Xiamen City will peak at 132.2 thousand tonnes in July 2015 – 1.5 times the volume in July 2010. In the medium term, annual MSW generation will increase to 1518.1 thousand tonnes by 2015 at an average growth rate of 10%. In the long term, a large volume of MSW will be output annually and will increase to 2486.3 thousand tonnes by 2020 – 2.5 times the value for 2010. The hybrid model proposed in this paper can enable decision makers to develop integrated policies and measures for waste management over the long term.

Xu, Lilai, E-mail: llxu@iue.ac.cn [Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, 1799 Jimei Road, Xiamen 361021 (China); Xiamen Key Lab of Urban Metabolism, Xiamen 361021 (China); Gao, Peiqing, E-mail: peiqing15@yahoo.com.cn [Xiamen City Appearance and Environmental Sanitation Management Office, 51 Hexiangxi Road, Xiamen 361004 (China); Cui, Shenghui, E-mail: shcui@iue.ac.cn [Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, 1799 Jimei Road, Xiamen 361021 (China); Xiamen Key Lab of Urban Metabolism, Xiamen 361021 (China); Liu, Chun, E-mail: xmhwlc@yahoo.com.cn [Xiamen City Appearance and Environmental Sanitation Management Office, 51 Hexiangxi Road, Xiamen 361004 (China)

2013-06-15

373

Feasibility of measuring the Shapiro time delay over meter-scale distances  

E-print Network

The time delay of light as it passes by a massive object, first calculated by Shapiro in 1964, is a hallmark of the curvature of space-time. To date, all measurements of the Shapiro time delay have been made over solar-system distance scales. We show that the new generation of kilometer-scale laser interferometers being constructed as gravitational wave detectors, in particular Advanced LIGO, will in principle be sensitive enough to measure variations in the Shapiro time delay produced by a suitably designed rotating object placed near the laser beam. We show that such an apparatus is feasible (though not easy) to construct, present an example design, and calculate the signal that would be detectable by Advanced LIGO. This offers the first opportunity to measure space-time curvature effects on a laboratory distance scale.

S. Ballmer; S. Márka; P. Shawhan

2009-05-05

374

Evolution of the elastic moduli of seismogenic Triassic Evaporites subjected to cyclic stressing  

NASA Astrophysics Data System (ADS)

Seismic cycles lead to variations in rock physical properties. Quantifying these changes is of key importance in building reliable crustal deformation models. Here we report laboratory measurements of the uniaxial compressive strength (UCS), Young's modulus and Poisson's ratio, both static (Es, ?s) and dynamic (Ed, ?d) of the seismogenic Triassic Evaporites of the Northern Apennines. Triassic Evaporites are composed of dolostones, anhydrites and gypsum. Gypsum was the weakest lithology, with UCS values ranging from 10 to 26 MPa; anhydrite exhibited intermediate values from 52 to 144 MPa; and dolostones were the strongest with a maximum UCS of 228 MPa. During uniaxial cyclic stressing experiments, we observed complex variations in Es and? ?s with: large increases are observed in the early cycles (stage 1), followed by essentially constant values (stage 2), before Es decreases and ?s increases approaching failure (stage 3). Complementary microseismicity (acoustic emission, AE) data show no significant AE during stage 1, then the stress needed to induce AE remained essentially constant (stages 2 and 3). Integration of mechanical data with microstructural observations suggests a first stage dominated by compaction and strengthening, a second stage characterised by quasi-elastic behaviour associated with the development of randomly oriented microfractures, and a third stage of weakening due to the growth of macrofractures parallel to the direction of the load. Laboratory dynamic elastic moduli are, on average, in agreement with dynamic elastic moduli used in crustal modelling. However static values of Young's modulus are about 50% lower than dynamic ones, and static values of Poisson's ratio are about 40% higher with respect to dynamic values. These observations suggest that the frequency effect on the difference between laboratory and crustal scale dynamic moduli values is rather small and that static values of modulus are more appropriate for crustal deformation modelling than seismically derived values.

Trippetta, F.; Collettini, C.; Meredith, P. G.; Vinciguerra, S.

2013-04-01

375

Early Triassic stromatolites in a siliciclastic nearshore setting in northern Perth Basin, Western Australia: Geobiologic features and implications for post-extinction microbial proliferation  

NASA Astrophysics Data System (ADS)

An Early Triassic stromatolite deposit in Gondwana is documented from the Smithian succession of the Lower Triassic Kockatea Shale Formation in the Northampton area, northern Geraldton, Western Australia. Abundant tube-like sheaths of filaments and tiny circular microspherule balls are well preserved in laminae of the Northampton stromatolites, which are characterized by finely laminated domes and digitate high-relief columns. These filament sheaths are superficially analogous to their counterparts of modern stromatolites, and thus are interpreted as putative fossilized filamentous cyanobacteria. Elemental mapping of EDS analysis shows very high contents of both Fe and Si elements as well as common presence of both S and Al elements along the laminae of the stromatolites, suggesting that the stromatolites may have been ferritized or silicified. Both ferritization and silicification may have played a crucial role in the exceptional preservation of the micro-structures in the Northampton stromatolites. The high content of Al along the laminae indicates that the stromatolites may have been influenced by terrigenous fine-grained clastics during their growth. The Northampton stromatolites show several growth modes, initiating on either pebbles/conglomerates or sandy seafloor and building laminar domes and digitate, high-relief columns during an initial transgression period. Steady increase in sea level facilitated the growth of stromatolites. The Early Triassic stromatolites ceased growth due to either rapid rise in sea level or increased clay influx probably sourced from increased weathering on land at that time, or both. The occurrence of the Northampton stromatolites in the siliciclastic succession, in comparison with published records of Early Triassic microbialites, reveals that post-extinction microbialites were widespread in the Smithian. Stromatolites show a broad geographic distribution from low-latitude to southern high-latitude regions of Gondwana and inhabited not only carbonate settings, but also siliciclastic nearshore settings. All features of these Early Triassic stromatolites indicate a microbial bloom in the aftermath of the P-Tr mass extinction.

Chen, Zhong-Qiang; Wang, Yongbiao; Kershaw, Stephen; Luo, Mao; Yang, Hao; Zhao, Laishi; Feng, Yuheng; Chen, Jianbo; Yang, Li; Zhang, Lei

2014-10-01

376

Permian to Late Triassic evolution of the Longmen Shan Foreland Basin (Western Sichuan): Model results from both the lithospheric extension and flexure  

NASA Astrophysics Data System (ADS)

The lithosphere was extended during the Permian-Middle Triassic in the Yangtze Craton where the Sichuan Basin located, and then bent due to thrusting of the Longmen Shan orogen, leading to formation of the Longmen Shan Foreland Basin (Western Sichuan) during the Late Triassic Indosinian orogeny. The lateral variation of the lithospheric strength resulted by former differential extension would inevitably influence the subsequent evolution of the foreland basin. In order to investigate this, both extensional and flexural models were applied in modeling Permian-Late Triassic basin evolution. A 2D kinematic extensional model was initially developed along a profile crossing the Yangtze Craton to simulate the lithospheric thermal evolution during the Permian-Middle Triassic. Based on the thermal results, the thermal-rheological structure, as well as the effective elastic thickness of the lithosphere (Te), was then determined. Extension model show that the stretching factors decrease gradually from Songpan-Ganzi to the Sichuan Basin, leading to variable thermal-rheological structure and increased Te from west to east. Taking into account of the Te variation, a flexural model was finally constructed to investigate the evolution of the Longmen Shan Foreland Basin during the Late Triassic spanning the time period c. 227-206 Ma. Three episodes were divided according to the corresponding tectonostratigraphic units. By matching the stratigraphic observations, three phase advance distances eastward of the Longmen Shan along the Qingchuan-Maowen Fault turned out to be 18, 22, and 18 km. It implied a slow and similar thrust advance rate of 3.6 (c.227-222 Ma), 2.2 (c.222-212 Ma), and 3 mm/yr (c.212-206 Ma), respectively.

He, Lijuan

2014-10-01

377

Return to Coalsack Bluff and the Permian Triassic boundary in Antarctica  

Microsoft Academic Search

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

Gregory J. Retallack; Tara Greaver; A. Hope Jahren

2007-01-01

378

Events during Early Triassic recovery from the end-Permian extinction  

Microsoft Academic Search

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

Jinnan Tong; Suxin Zhang; Jingxun Zuo; Xinqi Xiong

2007-01-01

379

A petrologic comparison of Triassic plutonism in the San Gabriel and Mule Mountains, southern California  

SciTech Connect

Triassic magmatism in the southwest US Cordillera forms a semicontinuous magmatic arc extending from northwestern Nevada to southeastern California. Quartz monzodioritic and quartz monzonitic rocks and associated diorites and granites are widespread in southeastern California, and the authors suggest that these rocks represent exposure of a structurally deeper part of the Triassic arc, where it was emplaced into comparatively thick Proterozoic crust. Elemental and isotopic data suggest that Triassic quartz monzodiorites and quartz monzonites in the Mule and San Gabriel Mountains were derived from a relatively undepleted, nonradiogenic mafic lithospheric source, with virtually no upper crustal interaction. Very limited data for associated Triassic ( ) diorites indicate a wide range in composition and a surprisingly radiogenic isotopic signature. Younger Triassic( ) granites record a strong geochemical signature of interaction with continental crust, including inherited zircon and high initial Sr ratios but comparatively less radiogenic Pb isotopic compositions. The major and trace element geochemistry of Late Triassic plutonic rocks in southeastern California is similar in many respects to akalic components of the Triassic arc in the Mojave Desert. However, contemporaneous rocks farther north have a calc-alkalic signature, perhaps reflecting the variation in age and composition of lithosphere across which the Triassic arc was constructed.

Barth, A.P. (Indiana Univ.-Purdue Univ., Indianapolis (USA)); Tosdal, R.M.; Wooden, J.L. (Geological Survey, Menlo Park, CA (USA))

1990-11-10

380

Events during Early Triassic recovery from the end-Permian extinction  

E-print Network

Events during Early Triassic recovery from the end-Permian extinction Jinnan Tong a,, Suxin Zhang 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

Tong, Jinnan

381

Quantification of sediment supply : a method and an example from Triassic of Western European basins  

Microsoft Academic Search

Triassic is a key period of Earth history, with tectonic, climatic and eustatic events. It corresponds to (i) the initial fragmentation of the Pangea, (ii) a transition from Paleozoic ice house to Mesozoic green house, (iii) a sea-level rise from Upper Triassic, followed by an eustatic fall during Lias. This special geological setting has led to the formation of large

S. Peron; S. Bourquin; M. Duran; F. Fluteau; F. Guillocheau

2003-01-01

382

Reef expansion during the Triassic: Spread of photosymbiosis balancing climatic cooling  

Microsoft Academic Search

The PaleoReefs Database indicates that reef abundance increased profoundly during the Triassic period, from a pronounced low in the Early Triassic to a major peak in the Norian. This expansion is also evident when standardizing for sampling. Corresponding to the reef expansion is a relative increase of scleractinian corals as reef builders, whereas the contribution of hypercalcifying sponges and microbes

Wolfgang Kiessling

2010-01-01

383

Correlation of upper Triassic strata between southern Colorado Plateau and southern High Plains, New Mexico  

SciTech Connect

Almost 600 m of Upper Triassic strata are exposed in the Hagan basin. They pertain to the basal Agua Zarca member of the Chinle Formation (as much as 80 m), overlain by about 500 m of mud-rock-dominated red beds of the Petrified Forest Member of the Chinle Formation. The top of the Triassic section here is the 5.5-24 m-thick Correo Sandstone Bed of Chinle Formation, which is disconformably overlain by the medial silty member of the Middle Jurassic Entrada Sandstone. At Lamy, approximately 370 m of Upper Triassic strata represent the westernmost outcrops of the Triassic section typical of the Tucumcari basin. This Triassic section consists of about 140 m of Santa Rosa Formation (divisible into three members) overlain by a mud-rock-dominated section (Chinle Formation) split by a medial sandy interval, the Cuervo member (Trujillo Formation of the Palo Duro basin). The youngest Triassic strata near Lamy are rhythmically bedded sediments of the Redonda Member. Based on lithologic similarity, stratigraphic position, and limited paleontological data, the central New Mexico Upper Triassic strata support for the following correlations (from west to east): (1) Shinarump = Agua Zarca = Santa Rosa; (2) lower Petrified Forest = lower shale member of the Chinle = Tecovas; (3) Sonsela = Poleo = Cuervo = Trujillo; (4) upper Petrified Forest = upper shale member of the Chinle; and (5) Owl Rock = Redonda = Correo. These correlations reflect homotaxis of sedimentary cycles across a broad region of the southern Western Interior during the Late Triassic.

Lucas, S.G. (New Mexico Museum of Natural History, Albuquerque (USA))

1989-09-01

384

MAGNETOSTRATIGRAPHY OF THE MIDDLE AND UPPER TRIASSIC: MERCIA MUDSTONE GROUP, SOUTH DEVON, UK  

E-print Network

MAGNETOSTRATIGRAPHY OF THE MIDDLE AND UPPER TRIASSIC: MERCIA MUDSTONE GROUP, SOUTH DEVON, UK , UK to other European upper Triassic VGP's. The dual polarity palaeomagnetic signal is carried by haematite probability experienced an extended period of haematite authigenesis, evident by specimens which occur near

385

Laboratory Investigations An Examination of Triassic Cynodont Tooth Enamel Chemistry Using Fourier Transform Infrared Spectroscopy  

Microsoft Academic Search

The Cynodontia are considered to be partic- ularly significant as their remains document the reptile- to-mammal transition during the Permian and Triassic periods. Studies examining cynodont morphology and anatomy have shown that these animals acquired increasingly mammal-like characteristics during their evolution. In this study, we use Fourier Transform Infrared spectroscopy to assess the enamel structure of several Triassic cynodonts. Extant

J. Botha; J. Lee-Thorp; M. Sponheimer

2004-01-01

386

A critical re?evaluation of the Late Triassic dinosaur taxa of North America  

Microsoft Academic Search

The North American Triassic dinosaur record has been repeatedly cited as one of the most complete early dinosaur assemblages. The discovery of Silesaurus from Poland and the recognition that Herrerasaurus and Eoraptor may not be theropods have forced a re?evaluation of saurischian and theropod synapomorphies. Here, we re?evaluate each purported Triassic dinosaur from North America on a specimen by specimen

Sterling J. Nesbitt; Randall B. Irmis; William G. Parker

2007-01-01

387

Archosaur remains from the Otter Sandstone Formation (Middle Triassic, late Anisian) of Devon, southern UK  

E-print Network

Archosaur remains from the Otter Sandstone Formation (Middle Triassic, late Anisian) of Devon. Introduction The Middle Triassic Otter Sandstone Formation of the south coast of Devon has been a source and incomplete in the Otter Sandstone Formation, and hitherto have been largely undiagnostic. Benton and Gower

Benton, Michael

388

Increasing temperature forcing reduces the Greenland Ice Sheet's response time scale  

NASA Astrophysics Data System (ADS)

Damages from sea level rise, as well as strategies to manage the associated risk, hinge critically on the time scale and eventual magnitude of sea level rise. Satellite observations and paleo-data suggest that the Greenland Ice Sheet (GIS) loses mass in response to increased temperatures, and may thus contribute substantially to sea level rise as anthropogenic climate change progresses. The time scale of GIS mass loss and sea level rise are deeply uncertain, and are often assumed to be constant. However, previous ice sheet modeling studies have shown that the time scale of GIS response likely decreases strongly with increasing temperature anomaly. Here, we map the relationship between temperature anomaly and the time scale of GIS response, by perturbing a calibrated, three-dimensional model of GIS behavior. Additional simulations with a profile, higher-order, ice sheet model yield time scales that are broadly consistent with those obtained using the three-dimensional model, and shed light on the feedbacks in the ice sheet system that cause the time scale shortening. Semi-empirical modeling studies that assume a constant time scale of sea level adjustment, and are calibrated to small preanthropogenic temperature and sea level changes, may underestimate future sea level rise. Our analysis suggests that the benefits of reducing greenhouse gas emissions, in terms of avoided sea level rise from the GIS, may be greatest if emissions reductions begin before large temperature increases have been realized. Reducing anthropogenic climate change may also allow more time for design and deployment of risk management strategies by slowing sea level contributions from the GIS.

Applegate, Patrick J.; Parizek, Byron R.; Nicholas, Robert E.; Alley, Richard B.; Keller, Klaus

2014-12-01

389

Validating a rapid-update satellite precipitation analysis across telescoping space and time scales  

NASA Astrophysics Data System (ADS)

In order to properly utilize remotely sensed precipitation estimates in hydrometeorological applications, knowledge of the accuracy of the estimates are needed. However, relatively few ground validation networks operate with the necessary spatial density and time-resolution required for validation of high-resolution precipitation products (HRPP) generated at fine space and time scales (e.g., hourly accumulations produced on a 0.25° spatial scale). In this article, we examine over-land validation statistics for an operationally designed, meteorological satellite-based global rainfall analysis that blends intermittent passive microwave-derived rainfall estimates aboard a variety of low Earth-orbiting satellite platforms with sub-hourly time sampling capabilities of visible and infrared imagers aboard operational geostationary platforms. The validation dataset is comprised of raingauge data collected from the dense, nearly homogeneous, 1-min reporting Automated Weather Station (network of the Korean Meteorological Administration during the June to August 2000 summer monsoon season. The space-time RMS error, mean bias, and correlation matrices were computed using various time windows for the gauge averaging, centered about the satellite observation time. For ±10 min time window, a correlation of 0.6 was achieved at 0.1° spatial scale by averaging more than 3 days; coarsening the spatial scale to 1.8° produced the same correlation by averaging over 1 h. Finer than approximately 24-h and 1° time and space scales, respectively, a rapid decay of the error statistics was obtained by trading-off either spatial or time resolution. Beyond a daily time scale, the blended estimates were nearly unbiased and with an RMS error of no worse than 1 mm day-1.

Turk, Francis Joseph; Sohn, Byung-Ju; Oh, Hyun-Jong; Ebert, Elizabeth E.; Levizzani, Vincenzo; Smith, Eric A.

2009-09-01

390

First Triassic palaeomagnetic constraints from Junggar (NW China) and their implications for the Mesozoic tectonics in Central Asia  

E-print Network

of the Mesozoic Tibetan and the Cenozoic Himalayan collisions. Triassic is a crucial period to understandFirst Triassic palaeomagnetic constraints from Junggar (NW China) and their implications Transcurrent tectonics Triassic Reactivation a b s t r a c t Northwestern China belts result from

Cogne, Jean-Pascal

391

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

E-print Network

Triassic greenhouse period. On the basis of the 100-ka tuning results, the astronomically constrainedMilankovitch and sub-Milankovitch cycles of the early Triassic Daye Formation, South China 2011 Handling Editor: J.G. Meert Keywords: Early Triassic Milankovitch cycles Sub-Milankovitch cycles

Jiang, Ganqing

392

Anomalies in global carbon cycling and extinction at the Triassic/Jurassic boundary: evidence from a marine  

E-print Network

. Introduction The Late Triassic was a period of intense biological change involving both marine and nonAnomalies in global carbon cycling and extinction at the Triassic/Jurassic boundary: evidence from This study investigates whether the end-Triassic biotic crisis was coupled with a perturbation of the marine

Gilli, Adrian

393

PUBLISHED ONLINE: 13 JULY 2009 | DOI: 10.1038/NGEO577 Floral changes across the Triassic/Jurassic  

E-print Network

occurred at the boundary of the Triassic and Jurassic periods, 201.6 million years ago. The loss of marineARTICLES PUBLISHED ONLINE: 13 JULY 2009 | DOI: 10.1038/NGEO577 Floral changes across the Triassic volcanism. Here we present pollen, spore and geochemical analyses across the Triassic/Jurassic boundary from

394

Triassic arc-derived detritus in the Triassic Karakaya accretionary complex was not derived from either the S Eurasian margin (Istanbul terrane) or the N Gondwana margin (Taurides)  

NASA Astrophysics Data System (ADS)

We present new U-Pb zircon source age data for Upper Triassic sandstones of the Istanbul Terrane (S Eurasian margin) and also for Triassic sandstones of the Taurides (N Gondwana margin). The main aim is to detect and quantify the contribution of Triassic magmatism as detritus to either of these crustal blocks. This follows the recent discovery of a Triassic magmatic arc source for the Triassic sandstones of the Palaeotethyan Karakaya subduction-accretion complex (Ustaömer et al. 2013; this meeting). Carboniferous (Variscan) zircon grains also form a significant detrital population, plus several more minor populations. Six sandstone samples were studied, two from the ?stanbul Terrane (Bak?rl?k?ran Formation of the Kocaeli Triassic Basin) and four from the Tauride Autochthon (latest Triassic Üzümdere Formation and Mid-Triassic Kas?mlar Formations; Bey?ehir region). Detrital zircon grains were dated by the laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS) U-Pb method at Goethe University, Frankfurt. Our results do not reveal Triassic detritus in the Üzümdere Formation. The U-Pb age of the analysed zircon grains ranges from 267 Ma to 3.2 Ga. A small fraction of Palaeozoic zircons are Permian (267 to 296 Ma), whereas the remainder are Early Palaeozoic. Ordovician grains (4%) form two age clusters, one at ca. 450 Ma and the other at ca. 474 Ma. Cambrian-aged grains dominate the zircon population, while the second largest population is Ediacaran (576 to 642 Ma). Smaller populations occur at 909-997 Ma, 827-839 Ma, 1.8-2.0 Ga and 2.4-2.6 Ga. The sandstones of the Kas?mlar Formation have similar zircon age cluster to those of the somewhat younger Üzümdere Formation, ranging from 239 Ma to 2.9 Ga. A few grains gave Anisian ages. Cambrian zircon grains are less pronounced than in the Kas?mlar Formation compared to the Üzümdere Formation. The detrital zircon record of Tauride sandstones, therefore, not indicates significant contribution of Triassic or Carboniferous (Variscan) arc sources, in marked contrast to those of the Triassic Karakaya subduction complex. In comparison, the ages of the analysed zircons in the Upper Triassic sandstones of the Istanbul Terrane range from 294 Ma to 3.1 Ga. Triassic zircons are again absent, while Variscan-aged zircons (294 to 339 Ma) dominate the zircon population. Additional zircon populations are dated at 554 to 655 Ma, 0.9 to 1.2 Ga, 1.5 Ga, 1.65 Ga, 2.0 to 2.15 and 2.5 to 2.8 Ga. The Precambrian zircon age spectra are compatible with derivation from an Avalonian/Amazonian/Baltic crustal provenance. In summary, there is no evidence in either the Triassic sandstones of the ?stanbul Terrane or of the Taurides of the Triassic magmatic arc source that dominates the Triassic Karakaya subduction-accretion complex. Where then was the source of the Karakaya arc detritus? A likely option is that the Karakaya subduction-accretion complex is an exotic terrane that was detached from a source magmatic arc and displaced to its present location, probably prior the initial deposition of the Early Jurassic cover sediments. This study was supported by TUBITAK, Project No: 111R015

Ustaömer, Timur; Ayda Ustaömer, Petek; Robertson, Alastair H. F.; Gerdes, Axel; Zulauf, Gernold

2014-05-01

395

Time scale for cyclostome evolution inferred with a phylogenetic diagnosis of hagfish and lamprey cDNA sequences.  

PubMed

The Cyclostomata consists of the two orders Myxiniformes (hagfishes) and Petromyzoniformes (lampreys), and its monophyly has been unequivocally supported by recent molecular phylogenetic studies. Under this updated vertebrate phylogeny, we performed in silico evolutionary analyses using currently available cDNA sequences of cyclostomes. We first calculated the GC-content at four-fold degenerate sites (GC(4)), which revealed that an extremely high GC-content is shared by all the lamprey species we surveyed, whereas no striking pattern in GC-content was observed in any of the hagfish species surveyed. We then estimated the timing of diversification in cyclostome evolution using nucleotide and amino acid sequences. We obtained divergence times of 470-390 million years ago (Mya) in the Ordovician-Silurian-Devonian Periods for the interordinal split between Myxiniformes and Petromyzoniformes; 90-60 Mya in the Cretaceous-Tertiary Periods for the split between the two hagfish subfamilies, Myxininae and Eptatretinae; 280-220 Mya in the Permian-Triassic Periods for the split between the two lamprey subfamilies, Geotriinae and Petromyzoninae; and 30-10 Mya in the Tertiary Period for the split between the two lamprey genera, Petromyzon and Lethenteron. This evolutionary configuration indicates that Myxiniformes and Petromyzoniformes diverged shortly after the common ancestor of cyclostomes split from the future gnathostome lineage. Our results also suggest that intra-subfamilial diversification in hagfish and lamprey lineages (especially those distributed in the northern hemisphere) occurred in the Cretaceous or Tertiary Periods. PMID:17261918

Kuraku, Shigehiro; Kuratani, Shigeru

2006-12-01

396

Northern and eastern margins of the Siberian continent in Triassic  

SciTech Connect

Siliciclastic sedimentation has been predominant on the northern and eastern margins of the Siberian continent since the Triassic period. Seven transgression-regression cycles can be recognized in the Triassic succession: Griesbachien-Dienerian, Smithian-Low Spathian, Upper Spathian, Anissian (with subcycles), Ladian, Carnian, and Norlan (with subcycles). All zonal units were distinguished within transgressive portions of the cycles. Regressive portions of the cycles formed practically instantaneously. Very high sedimentation rate (300-3000 mm/1000 yr), specific structures of sedimentary rocks, and distribution of unconformities led to the conclusion that active avalanche sedimentation at the basin margins was of major significance. six facies regions are recognized in the sedimentation area: Taimyr, Kotuy-Anabar, Leno-Anabar, Bur-Olenek, Verkhoyansk, and Novosibirsk (New Siberian Islands). The main source areas were located at the Patoma Mountains for the eastern margin and at the Anabar anticline and Olenek uplift for the northern margin. Most sediments were transported to the eastern margin by a large river with a huge delta which was similar in size to the modern Lena's delta. Sediments were further distributed by contour streams. Local synsedimentary structures controlled the paleogeography of the entire area. The paleogeographical evolution of the eastern margin is the history of this delta development. The rifting activities with the trappean magmatism were the main events at the northern margin, especially in the Talmyr area. The pelagic sedimentation has been predominant in the New Siberian Islands area and most of the Laptev Sea aquatoria. The organic-rich sediments have been distinguished in Low Olenekian (Smithian), Low Anissian, Low Ladinian, and Low Carnian substages. Most of them could be hydrocarbon source rocks. Triassic oil and gas seeps have been discovered at the northern portion of the Vilyui syncline, near the Lena's delta and the Nordvic Bay.

Egorov, A.Yu. (Aerogeologiya, Moscow (Russian Federation))

1993-09-01

397

Stromatolite beds from lower Triassic Virgin Formation, Spring Mountains, Nevada  

SciTech Connect

Extensive beds of marine stromatolites are a typical feature of the Precambrian and lower Paleozoic stratigraphic record. Because stromatolites of younger age are generally thought to have been deposited in refugia of nonmarine salinity, two beds of large marine stromatolites found in the lower Triassic (Scythian) Virgin Formation (Spring Mountains, Nevada) are unusual in their occurrence. Stromatolite mounds averaging about 1 m in height merge laterally to form the largest and stratigraphically lowest of the two stromatolite beds (about 1 m thick), and mounds in a higher bed (averaging about 75 cm thick) may be separated by several meters and are 50 cm to 1 m high. Spaces between mounds are filled with accumulations of the overlying sediment, and, in the lower stromatolite bed, thin beds of crinoidal debris. Mounds in both beds consist of broad stromatolite domes, which range from 5 to 25 cm high and 10 to 55 cm wide, and drape slightly over one another, exhibiting a hummocky upper surface in outcrop. Where weathered in cross section, the domes appear to consist of roughly hemispherical laminae defined by alternating lighter and darker gray layers, or may consist of several smaller columns, which appear to have grown together. The occurrence of these two large stromatolite beds in marine post-Paleozoic rocks may be related to the unique conditions following the Permian-Triassic mass extinction event. Lower diversity and abundance of those grazing organisms thought to have caused the Phanerozoic retreat of stromatolites to refugia may have permitted the growth of these relatively large stromatolites in the Early Triassic.

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

1989-04-01

398

Sedimentology of a muddy alluvial deposit: Triassic Denwa Formation, India  

NASA Astrophysics Data System (ADS)

Triassic Upper Denwa Formation (˜ 380 m) in the Satpura Gondwana basin, central India is a mudstone-dominated fluvial succession that comprises isolated ribbon-shaped (2-5-m-thick) channel-fill bodies encased within fine-grained extra-channel deposits. Eight architectural elements are recognized, of which five belong to channel-fill deposits and the remaining three to extra-channel deposits. Majority of channel-fill deposits are characterized by sandy or muddy inclined heterolithic strata (IHS) that record limited lateral accretion of point bars or benches (constrained by cohesive banks) in mixed- to suspended-load sinuous channels. A few ribbon bodies are mud rich and attest to nearly stagnant conditions in partly abandoned channels. A few single- or multistorey ribbon bodies that are dominantly sandy and lack inclined strata represent deposits of straight, laterally stable channel. The smallest ribbon bodies (˜ 1 m thick) of calcirudite/calcarenite possibly represent deposits of secondary channels in the interfluves. Coexistence of channel-fill bodies of different dimension, lithology and internal organization in restricted stratigraphic intervals suggests an anabranching system having channels with different fill histories. The extra-channel deposits mainly comprise red mudstone (1-5 m thick) that indicates pervasive oxidation of overbank sediments in well-aerated and well-drained setting. Sporadically developed calcic vertisols suggest a hot, semi-arid climate during the Upper Denwa period. Sandy to heterolithic sheets (70 cm to 2 m thick) with sharp, planar basal surfaces are replete with features suggestive of unconfined sheet flow. Also at places there are indications of subaqueous emplacement of sands. These bodies with paleocurrent oblique to that of the channel-fills are interpreted as crevasse splay deposits. Tabular heterolithic bodies (3-5 m thick) are characterized by undulating basal surface, complex organization of sandstone lenses interwoven with heteroliths and red mudstone (in decimeter-scale) with desiccation cracks. Such tabular bodies are attributed to repetitive, sheet-like and poorly channelized splaying. Very thick (10 to 20 m) mudstones intervals are inexplicable in terms of overbank flooding only. Poorly developed pedogenic features in sandy to muddy heterolithic sheets and certain mudstone intervals and well-developed cumulative paleosols in surrounding mudstone highlights the contrast between rapidly emplaced splay deposits and slowly accumulated floodplain deposits. The Denwa channels are comparable with modern, low-gradient and low-energy anabranching river system in which the sediment load is dominantly fine-grained. The semi-arid climate possibly facilitated enhanced supply of fines to the Upper Denwa system. However, sediment partitioning and distribution in a particular channel was controlled by flow diversion to and from other channels in that anabranching system. Low flow strength with periodic flood events, high bank strength and a rate of sediment supply that slightly exceeded that of onward transport probably were important factors for the development of the Upper Denwa anabranching system.

Ghosh, Parthasarathi; Sarkar, Soumen; Maulik, Pradip

2006-09-01

399

Paleomagnetism and Magnetostratigraphy of the Upper Triassic Chinle Group in North- Central, Western and Eastern New Mexico  

NASA Astrophysics Data System (ADS)

The Upper Triassic Chinle Group spans most of the Late Triassic and was deposited by a large scale fluvial system. Chinle Group strata are composed of predominantly red to purple mudstones with lesser orange siltstones and buff to red sandstones. In the Chama Basin, north-central New Mexico, both lower and upper Chinle strata are well-exposed and sections at several localities have been sampled to develop a more complete magnetic reversal chronology for the Late Triassic of the American Southwest. Localities in eastern and west- central New Mexico were also sampled for comparative purposes. Sampling at all sections concentrated on hematitic mudrocks and these materials typically carry a well-defined, well-grouped, dual polarity magnetization dominated by pigmentary hematite with laboratory unblocking temperatures about 660C we interpret as a primary, Late Triassic remanence (e.g., Painted Desert Mbr., corrected grand mean: D = 182.9°, I = 4.4°, ?95 = 2.9°, k = 61.7, N/No = 40/45 sites (14 levels of N polarity, 26 levels of R polarity). The Shinarump Formation (lowest unit of the Chinle Group) failed to yield interpretable magnetizations. The Salitral, Poleo, Petrified Forest and Rock Point formations all yielded magnetizations with either south or north-seeking declinations and shallow inclinations, comparable to those of the Painted Desert Member(e.g.: Poleo Formation grand mean: D = 183.1°, I = 0.3deg, ?95 = 5.7°, k = 33.9, N/No = 20/30). Although the Chinle Group of New Mexico was sampled at a relatively coarse sampling interval, the composite, yet incomplete,magnetic reversal chronology derived from these sections compares, at a gross scale, to similar age strata from Arizona, eastern North America and the Tethyan region of southern Europe. Chinle Group strata of Carnian age (based on palynostratigraphy) are of mixed polarity. Lower Norian strata are dominantly of reverse polarity and upper Norian strata are of mixed polarity. Paleopoles calculated from averaged VGPs show very little motion along the apparent polar wander path throughout the Carnian (Salitral Fm. Pole: 56.9°N, 62.0°E, A95 = 4.8°) and early Norian (Petrified Forest Fm., Painted Desert Member: 55.3°N, 67.3°E, A95 = 3.2°), followed by a shift in the pole position in the Late Norian (Rock Point Fm.: 58.5°N, 42.4°E, A95 = 14.8deg).

Zeigler, K. E.; Geissman, J. W.

2007-12-01

400

Change ?S of the entropy in natural time under time reversal: Complexity measures upon change of scale  

NASA Astrophysics Data System (ADS)

The entropy S in natural time as well as the entropy in natural time under time reversal S- have already found useful applications in the physics of complex systems, e.g., in the analysis of electrocardiograms (ECGs). Here, we focus on the complexity measures ?l which result upon considering how the statistics of the time series ? S?ft[\\equiv S- S-\\right] changes upon varying the scale l. These scale-specific measures are ratios of the standard deviations ?(? S_l) and hence independent of the mean value and the standard deviation of the data. They focus on the different dynamics that appear on different scales. For this reason, they can be considered complementary to other standard measures of heart rate variability in ECG, like SDNN, as well as other complexity measures already defined in natural time. An application to the analysis of ECG —when solely using NN intervals— is presented: We show how ?l can be used to separate ECG of healthy individuals from those suffering from congestive heart failure and sudden cardiac death.

Sarlis, N. V.; Christopoulos, S.-R. G.; Bemplidaki, M. M.

2015-01-01

401

Real-time probe of reaction centers in solid combustions on the subsecond time scale  

SciTech Connect

A quick-scanning extended x-ray-absorption fine-structure (QEXAFS) technique has been devised to follow the local atomic coordination changes about selected reactants in a class of highly exothermic solid-combustion reactions. Real-time EXAFS measurements during the combustion were made in the time frame of a few seconds. By tuning the monochromator to a specific energy, at which maximum changes occur in an EXAFS feature of an element transforming from the reactant to the product phase, a time resolution of 20 ms was achieved. The Ni+Al[r arrow]NiAl reaction has been investigated in some detail in light of a possible intermediate phase in the so-called after-burn'' region. The present QEXAFS findings together with the recent time-resolved diffraction data on the same system lends experimental insights into the structural macrokinetics of this class of combustion systems.

Frahm, R. (Hamburger Synchrotronstrahlungslabor HASYLAB at DESY, Notkestrasse 85, D-2000 Hamburg 52 (Germany)); Wong, J. (Hamburger Synchrotronstrahlungslabor HASYLAB at DESY, Notkestrasse 85, D-2000 Hamburg 52 (Germany) Lawrence Livermore National Laboratory, University of California, P.O. Box 808, Livermore, California 94551 (United States)); Holt, J.B.; Larson, E.M.; Rupp, B.; Waide, P.A. (Lawrence Livermore National Laboratory, University of California, P.O. Box 808, Livermore, California 94551 (United States))

1992-10-01

402

Fast Similarity Search in the Presence of Noise, Scaling, and Translation in Time-Series Databases  

Microsoft Academic Search

We introduce a new model of similarity of time se- quences that captures the intuitive notion that two sequences should be considered similar if they have enough non-overlapping time-ordered pairs of subse- quences thar are similar. The model allows the am- plitude of one of the two sequences to be scaled by any suitable amount and its offset adjusted appropriately.

Rakesh Agrawal; King-ip Lin; Harpreet S. Sawhney; Kyuseok Shim

1995-01-01

403

Disk File Management in a Medium-Scale Time-Sharing System.  

ERIC Educational Resources Information Center

The paper descibes a compact and highly efficient disk file management system responsible for the management and allocation of space on moving head disk drives in a medium-scale time-sharing system. The disk file management system is a major component of the Experimental Time-Sharing System (ETSS) developed at the Learning Research and Development…

Fitzhugh, Robert J.; Pethia, Richard D.

404

The Late Triassic Central Patagonian Batholith: Magma hybridization, 40Ar/39Ar ages and thermobarometry  

NASA Astrophysics Data System (ADS)

The Late Triassic Central Patagonian Batholith is a key element in paleogeographic models of West Gondwana just before to the break-up of the supercontinent. The preexisting classification of units of this batholith was mainly based on isotopic and geochemical data. Here we report the results of field mapping and petrography, backed up by three new 40Ar/39Ar biotite ages, which reveal previously unnoticed relationships of the rocks in the batholith. Based on the new information we present a reorganization of units where the batholith is primarily formed by the Gastre and the Lipetrén superunits. The Gastre Superunit is the oldest magmatic suite and is composed of I-type granites which display evidence of felsic and mafic magma interaction. It is formed by 4 second-order units: 1) equigranular hornblende-biotite granodiorites, 2) porphyritic biotite-hornblende monzogranites, 3) equigranular biotitic monzogranites and 4) hornblende quartz-diorites. Emplacement depth of the Gastre Superunit is bracketed between 6 and 11 km (1.8-3 kbar), and the maximum recorded temperatures of emplacement are comprised between 660 and 800 °C. The recalculated Rb/Sr age is 222 ± 3 Ma and the porphyritic biotite-hornblende monzogranites yielded a 40Ar/39Ar age in biotite of 213 ± 5 Ma. On the other hand, the Lipetrén Superunit is made up by fine-grained biotitic monzo- and syenogranites that postdate magma hybridization processes and intrude all the other units. The recalculated Rb/Sr age for this suite is identical to a 40Ar/39Ar age in biotite extracted from one of its monzogranites (206.4 ± 5.3 and 206 ± 4 Ma, respectively). This and the observed textural features suggest very fast cooling related to a subvolcanic emplacement. An independent unit, the “Horqueta Granodiorite”, which has previously been considered as the record of a Jurassic intrusive stage in the Central Patagonian Batholith, gave a 40Ar/39Ar age in biotite of 214 ± 2 Ma. This and the reexamination of available isotopic data allow propose that this granodiorite unit is part of the Late Paleozoic intrusives in the region. The Late Triassic Central Patagonian Batholith is overlain by 190-185 Ma volcano-sedimentary rocks, suggesting that it was exposed sometime between the latest Triassic and earliest Jurassic times, roughly coeval with a major accretionary episode in the southwestern margin of Gondwana.

Zaffarana, Claudia B.; Somoza, Rubén; López de Luchi, Mónica

2014-11-01

405

Evolutionary and Ecological Sequelae of Mass Extinctions: Examples From the Continental Triassic-Jurassic Boundary  

NASA Astrophysics Data System (ADS)

The Triassic-Jurassic boundary at ˜200 Ma marks one of the five major mass-extinctions of the Phanerozoic and, depending on the metrics used, was similar in magnitude to the K-T mass extinction. In continental environments about 50% of all tetrapod families are eliminated and although floral diversity change is difficult to gauge, a similar proportion of palynomorph taxa disappear at the boundary. The extinction event appears to