Pattern of apparent total strain in the bedded anhydrite cap of a folded salt wall

1989 ◽  
Vol 26 (5) ◽  
pp. 983-992 ◽  
Author(s):  
W. M. Schwerdtner ◽  
J. G. Torrance ◽  
J. T. van Berkel
Keyword(s):  
Structural State ◽  
Large Scale ◽  
Canadian Arctic ◽  
Total Strain ◽  
Western Boundary ◽  
Fold Belt ◽  
Clastic Rock ◽  
Nodule Shape ◽  
Straight Segments ◽  
Horizontal Pattern

The dense anhydrite cap of the southern Muskox Ridge salt wall participated in the large-scale buckling of Mesozoic clastic strata at the western boundary of the Tertiary Eureka Sound fold belt on Axel Heiberg Island, Canadian Arctic. This Carboniferous anhydrite is an aggregate of strained diagenetic nodules and contains relict limestone beds that mark the paleohorizontal plane. The well-exposed cap provides an excellent example of fold decollement and redeformation of foliated rocks.The horizontal pattern of the nodule-shape fabric was delineated within folded and straight segments of the cap. Maps for a well-exposed folded segment show systematic variations in the intensity of apparent total strain (r) and the prolateness factor (k). If the nodule fabric pattern of adjacent straight walls represents the prefold structural state of all walls in the area, then the pattern of folding strain can be reconstructed in the southern Muskox Ridge cap. Here, the preflattened anhydrite was deformed by flexural shear in most localities, but was shortened passively near its contact with competent clastic rock.

Structural relationships of the Skeena Fold Belt west of the Bowser Basin, northwest British Columbia

1991 ◽  
Vol 28 (6) ◽  
pp. 973-983 ◽  
Author(s):  
Carol A. Evenchick
Keyword(s):  
Middle Jurassic ◽  
Large Scale ◽  
Volcanic Rocks ◽  
Western Boundary ◽  
Thrust Faults ◽  
Fold Belt ◽  
Clastic Rocks ◽  
Structural Style ◽  
Coast Plutonic Complex ◽  
The Difference

The Skeena Fold Belt is a regional fold and thrust belt that extends across most of the width of the northern Intermontane Belt of the Canadian Cordillera. Structural and stratigraphic relationships at its northeast margin show that it developed between latest Jurassic(?) and early Tertiary time, that it involved strata at least as low as Lower and Middle Jurassic Hazelton Group, and that it is characterized by northeast-verging folds and thrust faults. The structures accommodated at least 44% shortening and appear to root to the west.Most of the fold belt is distinguished by folds in thinly layered Jurassic and Cretaceous clastic rocks of the Bowser and Sustut basins. Its boundary is difficult to establish west of the Bowser Basin in poorly layered Middle Jurassic and older strata. However, map relationships show that Hazelton Group strata are folded with Bowser Lake Group. It is suggested here that the fold belt continues westward to the east margin of the Coast Plutonic Complex, where the increase in metamorphic grade and dominance of plutonic rocks effectively mark the western boundary of the Skeena Fold Belt. The difference in structural style between the Bowser Lake Group and massive volcanic rocks of the Hazelton Group is attributed to their difference in competency. Shortening by thrust faults and large-scale folds in volcanic rocks west of the Bowser Basin may balance with shortening by folds and related detachments in Bowser Lake Group farther east.

The mid-Paleozoic deformation in the Hazen fold belt, Ellesmere Island, Arctic Canada

1990 ◽  
Vol 27 (10) ◽  
pp. 1359-1370 ◽  
Author(s):  
Eva M. Klaper
Keyword(s):  
Large Scale ◽  
Ellesmere Island ◽  
Small Scale ◽  
Northwestern Part ◽  
Fold Belt ◽  
Southeastern Part ◽  
Lower Paleozoic ◽  
Slip Mechanism ◽  
Fold Belts ◽  
Surface Geology

The mid-Paleozoic deformation of lower Paleozoic subgreenschist-facies sediments of the Hazen fold belt in northern Ellesmere Island is represented predominantly by chevron-style folding. Folded multilayers display cleavage fans suggesting synchronous fold and cleavage formation. Bedding-parallel slip indicates a flexural slip mechanism of folding. The geometry of several large-scale anticlinoria has been interpreted as being due to formation of these structures over detachments and thrust ramps.The constant fold geometry, the parallel orientation of faults and large- and small-scale folds, and the axial-plane foliation are related to a single phase of folding with a migrating deformation front in the Hazen fold belt during the mid-Paleozoic orogeny. The minimum amount of shortening in the Hazen and Central Ellesmere fold belts has been estimated from surface geology to increase from 40–50% of the original bed length in the external southeastern part to 50–60% in the more internal northwestern part of the belts.The convergent, thin-skinned nature of the Hazen and Central Ellesmere fold belts indicates that the postulated transpressive plate motions during the accretion of Pearya did not affect the study area.

Topographic Rossby Waves in the Abyssal South China Sea

2021 ◽  
Author(s):  
QI QUAN ◽  
ZHONGYA CAI ◽  
GUANGZHEN JIN ◽  
ZHIQIANG LIU
Keyword(s):  
South China Sea ◽  
Group Velocity ◽  
South China ◽  
Large Scale ◽  
Rossby Waves ◽  
Western Boundary ◽  
Horizontal Shear ◽  
Boundary Current ◽  
China Sea ◽  
Topographic Rossby Waves

AbstractTopographic Rossby waves (TRWs) in the abyssal South China Sea (SCS) are investigated using observations and high-resolution numerical simulations. These energetic waves can account for over 40% of the kinetic energy (KE) variability in the deep western boundary current and seamount region in the central SCS. This proportion can even reach 70% over slopes in the northern and southern SCS. The TRW-induced currents exhibit columnar (i.e., in-phase) structure in which the speed increases downward. Wave properties such as the period (5–60 days), wavelength (100–500 km), and vertical trapping scale (102–103 m) vary significantly depending on environmental parameters of the SCS. The TRW energy propagates along steep topography with phase propagation offshore. TRWs with high frequencies exhibit a stronger climbing effect than low-frequency ones and hence can move further upslope. For TRWs with a certain frequency, the wavelength and trapping scale are dominated by the topographic beta, whereas the group velocity is more sensitive to the internal Rossby deformation radius. Background circulation with horizontal shear can change the wavelength and direction of TRWs if the flow velocity is comparable to the group velocity, particularly in the central, southern, and eastern SCS. A case study suggests two possible energy sources for TRWs: mesoscale perturbation in the upper layer and large-scale background circulation in the deep layer. The former provides KE by pressure work, whereas the latter transfers the available potential energy (APE) through baroclinic instability.

scholarly journals Storm Track Response to Oceanic Eddies in Idealized Atmospheric Simulations

2018 ◽  
Vol 32 (2) ◽  
pp. 445-463 ◽  
Author(s):  
A. Foussard ◽  
G. Lapeyre ◽  
R. Plougonven
Keyword(s):  
Large Scale ◽  
Heat Budget ◽  
Storm Track ◽  
Convective Heating ◽  
Western Boundary ◽  
Boundary Currents ◽  
Oceanic Fronts ◽  
Budget Analysis ◽  
Poleward Shift ◽  
Oceanic Eddies

ABSTRACT Large-scale oceanic fronts, such as in western boundary currents, have been shown to play an important role in the dynamics of atmospheric storm tracks. Little is known about the influence of mesoscale oceanic eddies on the free troposphere, although their imprint on the atmospheric boundary layer is well documented. The present study investigates the response of the tropospheric storm track to the presence of sea surface temperature (SST) anomalies associated with an eddying ocean. Idealized experiments are carried out in a configuration of a zonally reentrant channel representing the midlatitudes. The SST field is composed of a large-scale zonally symmetric front to which are added mesoscale eddies localized close to the front. Numerical simulations show a robust signal of a poleward shift of the storm track and of the tropospheric eddy-driven jet when oceanic eddies are taken into account. This is accompanied by more intense air–sea fluxes and convective heating above oceanic eddies. Also, a mean heating of the troposphere occurs poleward of the oceanic eddying region, within the storm track. A heat budget analysis shows that it is caused by a stronger diabatic heating within storms associated with more water advected poleward. This additional heating affects the baroclinicity of the flow, which pushes the jet and the storm track poleward.

scholarly journals Dynamical effect of the total strain induced by the coherent motion on local isotropy in a wake

2013 ◽  
Vol 720 ◽  
pp. 393-423 ◽  
Author(s):  
F. Thiesset ◽  
L. Danaila ◽  
R. A. Antonia
Keyword(s):  
Circular Cylinder ◽  
Large Scale ◽  
Bluff Body ◽  
Initial Conditions ◽  
Scale Up ◽  
Wake Flow ◽  
Total Strain ◽  
Coherent Motion ◽  
Square Cylinder ◽  
Local Isotropy

AbstractWe assess the extent to which local isotropy (LI) holds in a wake flow for different initial conditions, which may be geometrical (the shape of the bluff body which creates the wake) and hydrodynamical (the Reynolds number), as a function of the dynamical effects of the large-scale forcing (the mean strain, $ \overline{S} $, combined with the strain induced by the coherent motion, $\tilde {S} $). LI is appraised through either classical kinematic tests or phenomenological approaches. In this respect, we reanalyse existing LI criteria and formulate a new isotropy criterion based on the ratio between the turbulence strain intensity and the total strain ($ \overline{S} + \tilde {S} $). These criteria involve either time-averaged or phase-averaged quantities, thus providing a deeper insight into the dynamical aspect of these flows. They are tested using hot wire data in the intermediate wake of five types of obstacles (a circular cylinder, a square cylinder, a screen cylinder, a normal plate and a screen strip). We show that in the presence of an organized motion, isotropy is not an adequate assumption for the large scales but may be satisfied over a range of scales extending from the smallest dissipative scale up to a scale which depends on the total strain rate that characterizes the flow. The local value of this scale depends on the particular nature of the wake and the phase of the coherent motion. The square cylinder wake is the closest to isotropy whereas the least locally isotropic flow is the screen strip wake. For locations away from the axis, the study is restricted to the circular cylinder only and reveals that LI holds at scales smaller than those that apply at the wake centreline. Arguments based on self-similarity show that in the far wake, the strength of the coherent motion decays at the same rate as that of the turbulent motion. This implies the persistence of the same degree of anisotropy far downstream, independently of the scale at which anisotropy is tested.

scholarly journals Characterizing ERA-Interim and ERA5 surface wind biases using ASCAT

Ocean Science ◽  
2019 ◽  
Vol 15 (3) ◽  
pp. 831-852 ◽  
Author(s):  
Maria Belmonte Rivas ◽  
Ad Stoffelen
Keyword(s):  
Large Scale ◽  
Surface Wind ◽  
Atmospheric Stability ◽  
Ocean Current ◽  
Western Boundary ◽  
Boundary Current ◽  
Wind Stress Curl ◽  
Meridional Winds ◽  
Mesoscale Convective ◽  
Transient Wind

Abstract. This paper analyzes the differences between ERA-Interim and ERA5 surface winds fields relative to Advanced Scatterometer (ASCAT) ocean vector wind observations, after adjustment for the effects of atmospheric stability and density, using stress-equivalent winds (U10S) and air–sea relative motion using ocean current velocities. In terms of instantaneous root mean square (rms) wind speed agreement, ERA5 winds show a 20 % improvement relative to ERA-Interim and a performance similar to that of currently operational ECMWF forecasts. ERA5 also performs better than ERA-Interim in terms of mean and transient wind errors, wind divergence and wind stress curl biases. Yet, both ERA products show systematic errors in the partition of the wind kinetic energy into zonal and meridional, mean and transient components. ERA winds are characterized by excessive mean zonal winds (westerlies) with too-weak mean poleward flows in the midlatitudes and too-weak mean meridional winds (trades) in the tropics. ERA stress curl is too cyclonic in midlatitudes and high latitudes, with implications for Ekman upwelling estimates, and lacks detail in the representation of sea surface temperature (SST) gradient effects (along the equatorial cold tongues and Western Boundary Current (WBC) jets) and mesoscale convective airflows (along the Intertropical Convergence Zone and the warm flanks for the WBC jets). It is conjectured that large-scale mean wind biases in ERA are related to their lack of high-frequency (transient wind) variability, which should be promoting residual meridional circulations in the Ferrel and Hadley cells.

scholarly journals Origin of the Shangfang Tungsten Deposit in the Fujian Province of Southeast China: Evidence from Scheelite Sm–Nd Geochronology, H–O Isotopes and Fluid Inclusions Studies

Minerals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 713 ◽  
Author(s):  
Lü-Yun Zhu ◽  
Shao-Yong Jiang ◽  
Run-Sheng Chen ◽  
Ying Ma
Keyword(s):  
Fluid Inclusions ◽  
Large Scale ◽  
Tectonic Setting ◽  
Critical Role ◽  
Isotope Analysis ◽  
Western Boundary ◽  
Ionization Mass ◽  
Tungsten Deposit ◽  
Nanling Range ◽  
Metallogenic Belt

The Shangfang deposit is a recently discovered large-scale tungsten deposit (66,500 t at 0.23% WO3), which is located near the western boundary of the Southeastern Coastal Metallogenic Belt (i.e., Zhenghe–Dafu fault), and adjacent to the northeast of the Nanling Range Metallogenic Belt. Unlike many other W–Sn deposits in this region that occur within or near the granites, the orebodies in the Sangfang deposit all occur within the amphibolite of Palaeoproterozoic Dajinshan Formation and have no direct contact to the granite. In this study, we carry out a thermal ionization mass spectrometer (TIMS) Sm-Nd isotope analysis for the scheelites from the orebody, which yields a Sm–Nd isochron age of 157.9 ± 6.7 Ma (MSWD = 0.96). This age is in good agreement with the previously published zircon U–Pb age (158.8 ± 1.6 Ma) for the granite and the molybdenite Re–Os age (158.1 ± 5.4 Ma) in the deposit. Previous studies demonstrated that the W–Sn deposits occurring between Southeastern Nanling Range and Coastal Metallogenic Belt mainly formed in the two periods of 160–150 Ma and 140–135 Ma, respectively. The microthermometry results of fluid inclusions in scheelite and quartz are suggestive of a near-isothermal (possibly poly-baric) mixing between two fluids of differing salinities. The H–O isotope results illustrate that the ore-forming fluids are derived from magma and might be equilibrated with metamorphic rocks at high temperature. The Jurassic granite pluton should play a critical role for the large hydrothermal system producing the Shangfang W deposit. Furthermore, the negative εNd(t) of −14.6 obtained in the Shanfang scheelite suggests for the involvement of the deep crustal materials. In general, subduction of the paleo-Pacific plate caused an extensional tectonic setting with formation of the Shangfang granites and related W mineralization, the geological background of which is similar to other W deposits in the Nanling Range Metallogenic Belt.

A Comparison of Southern Ocean Air–Sea Buoyancy Flux from an Ocean State Estimate with Five Other Products

2011 ◽  
Vol 24 (24) ◽  
pp. 6283-6306 ◽  
Author(s):  
Ivana Cerovečki ◽  
Lynne D. Talley ◽  
Matthew R. Mazloff
Keyword(s):  
Heat Flux ◽  
Southern Ocean ◽  
Heat Loss ◽  
Large Scale ◽  
Heat Fluxes ◽  
Buoyancy Flux ◽  
Western Boundary ◽  
Turbulent Heat ◽  
Radiative Fluxes ◽  
State Estimate

Abstract The authors have intercompared the following six surface buoyancy flux estimates, averaged over the years 2005–07: two reanalyses [the recent ECMWF reanalysis (ERA-Interim; hereafter ERA), and the National Centers for Environmental Prediction (NCEP)–NCAR reanalysis 1 (hereafter NCEP1)], two recent flux products developed as an improvement of NCEP1 [the flux product by Large and Yeager and the Southern Ocean State Estimate (SOSE)], and two ad hoc air–sea flux estimates that are obtained by combining the NCEP1 or ERA net radiative fluxes with turbulent flux estimates using the Coupled Ocean–Atmosphere Response Experiment (COARE) 3.0 bulk formulas with NCEP1 or ERA input variables. The accuracy of SOSE adjustments of NCEP1 atmospheric fields (which SOSE uses as an initial guess and a constraint) was assessed by verification that SOSE reduces the biases in the NCEP1 fluxes as diagnosed by the Working Group on Air–Sea Fluxes (Taylor), suggesting that oceanic observations may be a valuable constraint to improve atmospheric variables. Compared with NCEP1, both SOSE and Large and Yeager increase the net ocean heat loss in high latitudes, decrease ocean heat loss in the subtropical Indian Ocean, decrease net evaporation in the subtropics, and decrease net precipitation in polar latitudes. The large-scale pattern of SOSE and Large and Yeager turbulent heat flux adjustment is similar, but the magnitude of SOSE adjustments is significantly larger. Their radiative heat flux adjustments patterns differ. Turbulent heat fluxes determined by combining COARE bulk formulas with NCEP1 or ERA should not be combined with unmodified NCEP1 or ERA radiative fluxes as the net ocean heat gain poleward of 25°S becomes unrealistically large. The other surface flux products (i.e., NCEP1, ERA, Large and Yeager, and SOSE) balance more closely. Overall, the statistical estimates of the differences between the various air–sea heat flux products tend to be largest in regions with strong ocean mesoscale activity such as the Antarctic Circumpolar Current and the western boundary currents.

Whole-Rock Rb/Sr Ages of Metamorphic Rocks from Northern Ellesmere Island, Canadian Arctic Archipelago. I. The Gneiss Terrain between Ayles Fiord and Yelverton Inlet

1975 ◽  
Vol 12 (1) ◽  
pp. 90-94 ◽  
Author(s):  
A. K. Sinha ◽  
Thomas Frisch
Keyword(s):  
Regional Metamorphism ◽  
Canadian Arctic ◽  
Ellesmere Island ◽  
Metamorphic Rocks ◽  
Canadian Arctic Archipelago ◽  
Fold Belt ◽  
Late Precambrian

The first Precambrian ages from the Northern Ellesmere Fold Belt are reported. Six rocks from the largest gneiss terrain in northern Ellesmere Island yield a Late Precambrian age (minimum 742 ± 12 m.y.) of regional metamorphism. Relatively high initial 87Sr/86Sr suggests that the rocks were derived from crustal materials.

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