Paleomagnetism of Carboniferous strata from the Stellarton Gap

2002 ◽  
Vol 39 (10) ◽  
pp. 1527-1540 ◽  
Author(s):  
W A Morris
Keyword(s):  
Large Scale ◽  
Early Period ◽  
Pole Position ◽  
Subsidence Basin ◽  
Pull Apart Basin ◽  
Paleomagnetic Study ◽  
Acquisition Sequence ◽  
Stratigraphic Position ◽  
Stratigraphic Sequences ◽  
Thermal Subsidence

Deposition of Carboniferous sediments within the Stellarton Graben of Nova Scotia was controlled by displacements on the bounding Hollow and Cobequid fault systems. Periods of both normal and transcurrent faulting have occurred on both faults. As a result, models for the development of the Stellarton Basin have included a pull-apart basin and a thermal subsidence basin. Paleomagnetic study of stratigraphic sequences from within the graben showed evidence for three separate periods of remanence acquisition (ST3 – ST2 – ST1). Ordering the acquisition sequence for these three magnetizations is mainly circumstantial, being based on the distribution of each remanence phase relative to stratigraphic position and deformation of the strata. The oldest magnetization ST3 is grossly divergent from previously reported Carboniferous results suggesting an early period of large-scale clockwise rotation. Magnetization ST2 has a similar pole position to many others from Maritime Carboniferous basins located within the Appalachian orogenic belt. The divergence of these poles from the cratonic poles is interpreted as indicating that these magnetizations were acquired at a time when the reference horizontal was different to the present horizontal. The third magnetization ST3 is identical to a large number of late-stage Carboniferous regional overprint magnetizations. In summary, the paleomagnetic evidence suggests that the Stellarton Basin was formed in an early (Westphalian B to C) pull-apart phase that was followed by a later thermal subsidence phase.

Paleomagnetic study of lower Mesozoic diabase dikes and sills of Connecticut and Maryland

1976 ◽  
Vol 13 (4) ◽  
pp. 597-609 ◽  
Author(s):  
Timothy E. Smith
Keyword(s):  
Middle Jurassic ◽  
Pole Position ◽  
Low Temperature Oxidation ◽  
Temperature Oxidation ◽  
Sea Floor ◽  
Good Convergence ◽  
Faunal Assemblages ◽  
Paleomagnetic Study ◽  
Intrusive Rocks ◽  
Stratigraphic Position

Paleomagnetic results from 61 sites on diabase dikes and sills in Connecticut and Maryland yield a mean pole of position of 100.9 °E. 68.6 °N, α95 = 1.6°. These results combined with those from 7S sites on four diabase sills in the Gettysburg Basin of Pennsylvania produce a mean pole position of 101, 6 °E. 65.4 °N, α95 = 1.3 °from 139 VGPs. These rocks arc probably of Early to early Middle Jurassic age by stratigraphic and inferred stratigraphic position. The paleomagnetic results indicate that the Gettysburg and Hartford Basins did not subside simultaneously.The dispersion of virtual geomagnetic poles about the mean pole of the Connecticut, Pennsylvania, and Maryland intrusive rocks is probably the result of 'homogenization' of magnetic directions during low-temperature oxidation of titanomagnetite to titanomaghemite over a period long enough to erase a considerable amount of dispersion due to secular variation.Rotation of Europe against North America in the prerifting configuration causes good convergence of European Jurassic mean poles and the pole of the Connecticut. Maryland, and Pennsylvania intrusive rocks. This is evidence that separation of the two continents had not begun by Early to early Middle Jurassic time, which is in agreement with earlier findings based on sea-floor magnetic anomalies and faunal assemblages.

scholarly journals Understanding the Processes Causing the Early Intensification of Hurricane Dorian through an Ensemble of the Hurricane Analysis and Forecast System (HAFS)

Atmosphere ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 93
Author(s):  
Andrew Hazelton ◽  
Ghassan J. Alaka ◽  
Levi Cowan ◽  
Michael Fischer ◽  
Sundararaman Gopalakrishnan
Keyword(s):  
Tropical Cyclone ◽  
Large Scale ◽  
Early Stage ◽  
Early Period ◽  
Storm Track ◽  
Key Factors ◽  
Complex Interplay ◽  
Forecast System ◽  
Model Initialization

The early stages of a tropical cyclone can be a challenge to forecast, as a storm consolidates and begins to grow based on the local and environmental conditions. A high-resolution ensemble of the Hurricane Analysis and Forecast System (HAFS) is used to study the early intensification of Hurricane Dorian, a catastrophic 2019 storm in which the early period proved challenging for forecasters. There was a clear connection in the ensemble between early storm track and intensity: stronger members moved more northeast initially, although this result did not have much impact on the long-term track. The ensemble results show several key factors determining the early evolution of Dorian. Large-scale divergence northeast of the tropical cyclone (TC) appeared to favor intensification, and this structure was present at model initialization. There was also greater moisture northeast of the TC for stronger members at initialization, favoring more intensification and downshear development of the circulation as these members evolved. This study highlights the complex interplay between synoptic and storm scale processes in the development and intensification of early-stage tropical cyclones.

scholarly journals Synchronous combined effects of fishing and climate within a demersal community

2012 ◽  
Vol 70 (2) ◽  
pp. 319-328 ◽  
Author(s):  
Antoni Quetglas ◽  
Francesc Ordines ◽  
Manuel Hidalgo ◽  
Sebastià Monserrat ◽  
Susana Ruiz ◽  
...  
Keyword(s):  
Climate Variability ◽  
Age Structure ◽  
Large Scale ◽  
Southern Oscillation ◽  
Climatic Variability ◽  
Early Period ◽  
Combined Effects ◽  
Population Fluctuations ◽  
Fishing Activity ◽  
The Mediterranean

Abstract Quetglas, A., Ordines, F., Hidalgo, M., Monserrat, S., Ruiz, S., Amores, Á., Moranta, J., and Massutí, E. 2013. Synchronous combined effects of fishing and climate within a demersal community. – ICES Journal of Marine Science, 70: 319–328. Accumulating evidence shows that fishing exploitation and environmental variables can synergistically affect the population dynamics of exploited populations. Here, we document an interaction between fishing impact and climate variability that triggered a synchronic response in the population fluctuations of six exploited species in the Mediterranean from 1965–2008. Throughout this period, the fishing activity experienced a sharp increase in fishing effort, which caused all stocks to shift from an early period of underexploitation to a later period of overexploitation. This change altered the population resilience of the stocks and brought about an increase in the sensitivity of its dynamics to climate variability. Landings increased exponentially when underexploited but displayed an oscillatory behaviour once overexploited. Climatic indices, related to the Mediterranean mesoscale hydrography and large-scale north Atlantic climatic variability, seemed to affect the species with broader age structure and longer lifespan, while the global-scale El Niño Southern Oscillation index (ENSO) positively influenced the population abundances of species with a narrow age structure and short lifespan. The species affected by ENSO preferentially inhabit the continental shelf, suggesting that Mediterranean shelf ecosystems are sensitive to the hydroclimatic variability linked to global climate.

The Paleomagnetism of Kaminak Dikes—No Evidence of Significant Hudsonian Plate Motion

1975 ◽  
Vol 12 (12) ◽  
pp. 2048-2064 ◽  
Author(s):  
K. W. Christie ◽  
A. Davidson ◽  
W. F. Fahrig
Keyword(s):  
Pole Position ◽  
Metamorphic Grade ◽  
Amphibolite Facies ◽  
The Other ◽  
Plate Motion ◽  
Paleomagnetic Study

A paleomagnetic study was done on 28 diabase and 6 lamprophyre dikes from the vicinity of Kaminak Lake in the District of Keewatin. These dikes are Proterozoic and cut across an area of Archean rocks. Their metamorphic grade within this region varies from nil to amphibolite facies. Two stable magnetization directions were obtained from the diabase on AF demagnetization; one from 3 unmetamorphosed diabase dikes of D = 205°, I = 3°, α95 = 24°, with a corresponding pole position at 23.8 °S, 122.3 °W, α95 = 16.5°; the other from the metamorphosed diabase of D = 176°,I = 65°, α95 = 4°, with pole position at 20.4 °N, 92.1 °W, = 6.1°. The first is believed to be thermoremanent and approximately 2300 Ma old, while the second is a metamorphic direction of approximately 1800 Ma. The six lamprophyres give a stable remanence of D = 174°, I = 78°, α9S = 10°, with a pole position at 40.9 °N, 92.8 °W, α95 = 17°, essentially the same as the metamorphosed diabase.A number of samples were also thermally demagnetized. Most of the results obtained were the same as those obtained from the AF treatment. However, one diabase site gave a direction similar to that obtained from the 3 unaltered dikes, and one of the lamprophyres showed a reversal.The pole position of the altered Kaminak diabase relative to that for the unconformably overlying Dubawnt Group suggests that the polar wandering curve for this part of the Aphebian may be more complex than previously thought. It is quite probable that the earlier Aphebian pole positions (Matachewan, Nipissing), as usually plotted, are actually antipodal points in terms of the polar wandering curve.

CALCULATION OF THE MAGNETIZATION OF UPLIFTS FROM COMBINING TOPOGRAPHIC AND MAGNETIC SURVEYS

Geophysics ◽  
1967 ◽  
Vol 32 (4) ◽  
pp. 678-707 ◽  
Author(s):  
M. L. Richards ◽  
V. Vacquier ◽  
G. D. Van Voorhis
Keyword(s):  
Pacific Ocean ◽  
Horizontal Plane ◽  
Large Scale ◽  
Geomagnetic Latitude ◽  
Pole Position ◽  
Present Position ◽  
Paleomagnetic Pole ◽  
The Pacific ◽  
Geomagnetic Pole ◽  
The Pacific Ocean

The direction and magnitude of the magnetization of a uniformly magnetized structure can be computed by combining topographic and magnetic surveys. The previously reported method has been extended to include more than one structure, each possessing its particular magnetization. Also, the bottom of the structure need not be a horizontal plane but can be an arbitrary surface. The method was applied to 21 seamounts, one laccolith and two Aleutian volcanoes. Four of the seamounts were found to be reversely magnetized. The virtual paleomagnetic pole positions for 16 Pacific Ocean seamounts, representing three widely separated locations, are significantly different from the present geomagnetic pole position but near Mesozoic virtual pole positions from Australia. For two locations, radiometric age determinations give an average date for their formation in the Cretaceous. The apparent 30 degree shift in geomagnetic latitude of the seamounts is interpreted as the result of large scale movements of the Pacific Ocean floor or, alternatively, as the result of the paleomagnetic equator being north of its present position in the Pacific during the growth of the seamounts.

Extent of Grenvillian remanence components in rocks of the Southern Province

1982 ◽  
Vol 19 (4) ◽  
pp. 698-708 ◽  
Author(s):  
M. Stupavsky ◽  
D. T. A. Symons
Keyword(s):  
Magnetic Field ◽  
North America ◽  
Thin Section ◽  
Sedimentary Rocks ◽  
Pole Position ◽  
River Valley ◽  
Field Reversal ◽  
Paleomagnetic Study ◽  
Northern Portion ◽  
Sediment Matrix

Early Aphebian Gowganda sedimentary rocks and intruding Nipissing diabase sills were sampled for paleomagnetic study at 88 sites (~500 cores, ~1000 specimens) along two ~42 km long profiles extending north from the Grenville Front into the Cobalt Plate of the Southern Structural Province in the River Valley – Lake Temagami area of Ontario. After AF demagnetization a postfolding pre-Nipissing ~2200 Ma remanence was found in eight of the 37 Gowganda sediment sites that were > 2 km north of the front, giving a pole at 109°W, 63°N (dp = 10°, dm = 19°). The Nippissing diabase from > 2 km north of the front retains a stable antiparallel prefolding N1 remanence direction in 22 of 40 sites, giving a pole position of 85°W, 17°S (dp = 6°, dm = 10°). These "south and down" remanence directions found in the southern portion of the plate contrast with the antiparallel "north and up" directions found in the northern portion, thereby indicating the occurrence of either two nearly cogenetic Nipissing intrusive events or the sequential emplacement of the Nipissing during an Earth's magnetic field reversal across the plate. At two sites a Nipissing remagnetized remanence was found in Gowganda sediments with a pole of 115°W, 18°S. Also three "Nipissing" sites give a pole at 164°W, 3°N, which is close to the known pole for the later ~1.25 Ga Sudbury olivine diabase dikes. One site is adjacent to a large dike and two were found on thin-section examination to be olivine diabase. The eight sites in Gowganda sediment matrix and conglomerate clasts and in Nipissing diabase from within < 2 km from the front were found to have a postfolding metamorphic remanence with a Grenville orogenic pole at 45°W, 51°N (dp = 19°, dm = 21°). Finally, the results lead to a suggested revision in the APW path for the ~2300–~1650 Ma interval for North America.

scholarly journals Capturing the Trajectory of Psychological Status and Analyzing Online Public Reactions During the Coronavirus Disease 2019 Pandemic Through Weibo Posts in China

2021 ◽  
Vol 12 ◽  
Author(s):  
Yi-Chen Chiang ◽  
Meijie Chu ◽  
Shengnan Lin ◽  
Xinlan Cai ◽  
Qing Chen ◽  
...  
Keyword(s):  
Social Media ◽  
Public Opinion ◽  
Language Processing ◽  
High Frequency ◽  
Large Scale ◽  
Early Period ◽  
Psychological Status ◽  
Internet Users ◽  
External Stimuli ◽  
High Frequency Words

When a major, sudden infectious disease occurs, people tend to react emotionally and display reactions such as tension, anxiety, fear, depression, and somatization symptoms. Social media played a substantial awareness role in developing countries during the outbreak of coronavirus disease 2019 (COVID-19). This study aimed to analyze public opinion regarding COVID-19 and to explore the trajectory of psychological status and online public reactions to the COVID-19 pandemic by examining online content from Weibo in China. This study consisted of three steps: first, Weibo posts created during the pandemic were collected and preprocessed on a large scale; second, public sentiment orientation was classified as “optimistic/pessimistic/neutral” orientation via natural language processing and manual determination procedures; and third, qualitative and quantitative analyses were conducted to reveal the trajectory of public psychological status and online public reactions during the COVID-19 pandemic. Public psychological status differed in different periods of the pandemic (from December 2019 to May 2020). The newly confirmed cases had an almost 1-month lagged effect on public psychological status. Among the 15 events with high impact indexes or related to government decisions, there were 10 optimism orientation &gt; pessimism orientation (OP) events (2/3) and 5 pessimism orientation &gt; optimism orientation (PO) events (1/3). Among the top two OP events, the high-frequency words were “race against time” and “support,” while in the top two PO events, the high-frequency words were “irrationally purchase” and “pass away.” We proposed a hypothesis that people developed negative self-perception when they received PO events, but their cognition was developed by how these external stimuli were processed and evaluated. These results offer implications for public health policymakers on understanding public psychological status from social media. This study demonstrates the benefits of promoting psychological healthcare and hygiene activity in the early period and improving risk perception for the public based on public opinion and the coping abilities of people. Health managers should focus on disseminating socially oriented strategies to improve the policy literacy of Internet users, thereby facilitating the disease prevention work for the COVID-19 pandemic and other major public events.

Terrestrial and extraterrestrial chemical components of early Archean impact spherule layers from Fairview Gold Mine, northern Barberton greenstone belt, South Africa

2021 ◽  
Author(s):  
Grace Juliana Gonçalves de Oliveira ◽  
Wolf Uwe Reimold ◽  
Álvaro Penteado Crósta ◽  
Natalia Hauser ◽  
Christian Koeberl ◽  
...  
Keyword(s):  
South Africa ◽  
Greenstone Belt ◽  
Large Scale ◽  
Chemical Components ◽  
Gold Mine ◽  
Barberton Greenstone Belt ◽  
Stratigraphic Position ◽  
Exploration Drilling ◽  
The Impact ◽  
Drill Cores

ABSTRACT Early Archean spherule layers, widely accepted to represent distal ejecta deposits from large-scale impact events onto the early Earth, have been described from several stratigraphic levels of the Barberton greenstone belt in South Africa. Recently, exploration drilling at the Fairview Gold Mine (25°43′53″S, 31°5′59″E) in the northern domain of the belt resulted in the discovery of a new set of spherule layer intersections. The Fairview spherule layers in drill cores BH5901, BH5907, BH5911, and BH5949 were intersected just a few meters apart, at about the same stratigraphic position within the transition from the Onverwacht Group to the Fig Tree Group. The Fairview spherule layers have petrographic and chemical similarities to at least three other well-known Barberton spherule layers (S2–S4), and multiple spherule layer bed intersections in drill cores BARB5 and CT3, all from about the same stratigraphic position. They are not uniform in composition, in particular with respect to abundances of highly siderophile elements. The highest concentrations of moderately (Cr, Co, Ni) and highly siderophile (Ir) elements are within the range of concentrations for chondrites and, thus, reinforce the impact hypothesis for the generation of the Fairview spherule layers. Iridium peak concentrations and Cr/Ir interelement ratios for spherule layer samples from drill cores BH5907, BH5911, and BH5949 suggest admixtures of 50%–60% chondritic material, whereas for the BH5901 spherule layer, only an admixture of 1% chondritic material is indicated. We discuss whether these four Fairview spherule layers represent the same impact event, and whether they can be correlated to any of the S2–S4, CT3, and BARB5 intersections.

The Second Repeat in Beethoven's Sonata-Form Movements: Tonal, Formal and Motivic Strategies

2021 ◽  
Vol 8 (1) ◽  
pp. 1-41
Author(s):  
James S. MacKay
Keyword(s):  
Paradigm Shift ◽  
Large Scale ◽  
Early Period ◽  
Classical Period ◽  
Sonata Form ◽  
Scale Design ◽  
Pro Forma ◽  
Late Works

Around the middle of the Classical period, there was a paradigm shift concerning sectional repeats in sonata-form movements. Whereas previously the repeat of both halves (exposition and development/recapitulation) was virtually pro forma, by the late 1700s composers typically only indicated the first repeat. When composers began to indicate the second repeat infrequently, this decision took on greater musical significance.<br/> Whereas Haydn and Mozart indicated the second repeat frequently, even in their late works, Beethoven indicated this repeat rarely (nineteen times in works with opus numbers). This infrequency is noteworthy and prompts the question: Are there issues of formal balance or tonal/motivic connections that would be lost if performers omitted this repeat? I will examine these works in depth, noting similarities in formal balance, motivic content, tonal procedures, and large-scale design. Although many of these movements date from Beethoven's early period, he also indicated the second repeat six times after 1800, including the finale of his last quartet, Op. 135. We can conclude that repeating a sonata-form movement's second half remained an option for Beethoven late in life, even after he had ostensibly broken definitively with the formal conventions of his Classical predecessors.

scholarly journals Binary Interaction between Typhoons Fengshen (2002) and Fungwong (2002) Based on the Potential Vorticity Diagnosis

2008 ◽  
Vol 136 (12) ◽  
pp. 4593-4611 ◽  
Author(s):  
Chung-Chuan Yang ◽  
Chun-Chieh Wu ◽  
Kun-Hsuan Chou ◽  
Chia-Ying Lee
Keyword(s):  
Potential Vorticity ◽  
Large Scale ◽  
Early Period ◽  
Subtropical High ◽  
Binary Interaction ◽  
Monsoon Circulation ◽  
Good Representation ◽  
Steering Flow ◽  
Large Scale Flow ◽  
Storm Characteristics

Abstract A cyclonic loop was observed in the track of Typhoon Fungwong (2002) when it was about 765 n mi from Supertyphoon Fengshen (2002). It is shown that Fungwong’s special path is associated with the circulation of Fengshen, and such an association is regarded as an indication of binary interaction. In this paper, the binary interaction between Fengshen and Fungwong is studied based on the potential vorticity diagnosis. The impacts of large-scale flow fields on their motions are also investigated. Furthermore, the sensitivity of the storm characteristics to the binary interaction is demonstrated by the mesoscale numerical model simulations with different sizes and intensities for the initial bogused storms. Results of the study show that before Fungwong and Fengshen interacted with each other, their motions were governed by the large-scale environmental flow, that is, mainly associated with the subtropical high. During this binary interaction, Fungwong’s looping is partly attributed to Fengshen’s steering flow. This pattern shows up first as a case of one-way interaction in the early period, and then develops into a mutual interaction during the later stages. The numerical experiments show the sensitivity of the storm size and intensity to the binary interaction, implicating that a good representation of the initial storm vortex is important for the prediction of binary storms. Further analyses also indicate the influence of the monsoon trough and subtropical high systems on the binary interaction. These results provide some new insights into the motions of nearby typhoons embedded in the monsoon circulation.

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