A paleomagnetic test for northward tectonic transport of the eastern Selwyn Basin, northern Canadian Cordillera: data from the mid-Cretaceous Ragged Pluton

2008 ◽  
Vol 45 (7) ◽  
pp. 860-869 ◽  
Author(s):  
D. T.A. Symons ◽  
K. Kawasaki ◽  
C. J.R. Hart ◽  
M. J. Harris
Keyword(s):  
North America ◽  
Lower Cambrian ◽  
Remanent Magnetization ◽  
Canadian Cordillera ◽  
Thermal Demagnetization ◽  
Granitic Pluton ◽  
Tectonic Transport ◽  
Paleomagnetic Result ◽  
Stable Characteristic ◽  
Saturation Remanence

Ragged Pluton is a member of the Tungsten Plutonic Suite in the eastern Selwyn Basin. This circular massive 97 Ma granitic pluton is ∼5 km in diameter. It intrudes deformed and metamorphosed clastic strata of the Neoproterozoic to Lower Cambrian Vampire Formation. Thermal and alternating field step demagnetization data for 216 specimens from 21 plutonic sites isolated a stable characteristic remanent magnetization (ChRM) direction at 20 sites of declination D = 325.9°, inclination I = 80.4° (α95 = 2.7°, k = 142). Thermal demagnetization and saturation remanence analysis show that the ChRM is carried by both single-domain pyrrhotite and magnetite. Ragged Pluton’s paleopole at 73.9°N latitude, 191.4°E longitude (dp = 5.0°, dm = 5.2°) is concordant with its co-eval 97 Ma North American reference paleopole, showing at 95% confidence that the pluton has not been significantly rotated or translated relative to North America. This paleomagnetic result favours tectonic models in which the eastern Selwyn Basin is autochthonous, or nearly so, since the mid Cretaceous.

Paleomagnetic dating of magmatic phases at the Cantung tungsten deposit, Northwest Territories, Canada

2014 ◽  
Vol 51 (1) ◽  
pp. 32-42 ◽  
Author(s):  
K. Kawasaki ◽  
D.T.A. Symons
Keyword(s):  
North America ◽  
Lower Cambrian ◽  
Remanent Magnetization ◽  
Open Pit ◽  
Tungsten Deposit ◽  
Metasedimentary Rocks ◽  
Significant Difference ◽  
Paleomagnetic Dating ◽  
Stable Characteristic ◽  
Host Rocks

The Cantung tungsten–copper (W–Cu) skarn orebodies are hosted by Proterozoic and Lower Cambrian metasedimentary rocks next to the Cretaceous “Mine Stock” monzogranite. Paleomagnetic analyses of 283 specimens from the Open Pit scheelite–chalcopyrite orebody (17 sites) and from adjacent host rocks including the aplite dikes (11 sites) isolated a stable characteristic remanent magnetization (ChRM), mostly by alternating field and then thermal step demagnetization. The step demagnetization results along with rock magnetic analyses of the W concentrate show that the main remanence carriers are single- or pseudosingle-domain pyrrhotite, titanomagnetite, and (or) magnetite. There is no statistically significant difference at 95% confidence between the site mean ChRM directions for the W–Cu ore, the host rock, or the aplite dikes populations. This result indicates that the intrusion of the Mine Stock is coeval with the genesis of the scheelite skarn ore and with dike emplacement to give an overall mean ChRM direction of declination 342.9°, inclination 82.0° (N = 22 sites, radius of cone of 95% confidence α95 = 4.2°, precision parameter k = 54.7) that defines a paleopole at 76.2°N latitude, 212.2°E longitude (radius of cone of 95% confidence A95 = 8.1°). This paleopole is concordant with the coeval 98 Ma North American paleopole at 92% confidence, which provides strong evidence that the eastern Selwyn Basin has been an autochthonous part of North America since the mid-Cretaceous.

Early Paleozoic Hyolitha from North America: reexamination of Walcott's and Resser's type specimens

1988 ◽  
Vol 62 (2) ◽  
pp. 218-233 ◽  
Author(s):  
John Mark Malinky
Keyword(s):  
North America ◽  
Lower Cambrian ◽  
Type Species ◽  
New Genus ◽  
Early Paleozoic ◽  
Type Specimens ◽  
Middle Cambrian ◽  
Upper Cambrian ◽  
New Family ◽  
The Family

Concepts of the family Hyolithidae Nicholson fide Fisher and the genera Hyolithes Eichwald and Orthotheca Novak have been expanded through time to encompass a variety of morphologically dissimilar shells. The Hyolithidae is here considered to include only those hyolithid species which have a rounded (convex) dorsum; slopes on the dorsum are inflated, and the venter may be flat or slightly inflated. Hyolithes encompasses species which possess a low dorsum and a prominent longitudinal sulcus along each edge of the dorsum; the ligula is short and the apertural rim is flared. The emended concept of Orthotheca includes only those species of orthothecid hyoliths which have a subtriangular transverse outline and longitudinal lirae covering the shell on both dorsum and venter.Eighteen species of Hyolithes and one species of Orthotheca from the Appalachian region and Western Interior were reexamined in light of more modern taxonomic concepts and standards of quality for type material. Reexamination of type specimens of H. similis Walcott from the Lower Cambrian of Newfoundland, H. whitei Resser from the Lower Cambrian of Nevada, H. billingsi Walcott from the Lower Cambrian of Nevada, H. gallatinensis Resser from the Upper Cambrian of Wyoming, and H. partitus Resser from the Middle Cambrian of Alabama indicates that none of these species represents Hyolithes. Hyolithes similis is here included under the new genus Similotheca, in the new family Similothecidae. Hyolithes whitei is designated as the type species of the new genus Nevadotheca, to which H. billingsi may also belong. Hyolithes gallatinensis is referred to Burithes Missarzhevsky with question, and H. partitus may represent Joachimilites Marek. The type or types of H. attenuatus Walcott, H. cecrops Walcott, H. comptus Howell, H. cowanensis Resser, H. curticei Resser, H. idahoensis Resser, H. prolixus Resser, H. resseri Howell, H. shaleri Walcott, H. terranovicus Walcott, and H. wanneri Resser and Howell lack shells and/or other taxonomically important features such as a complete aperture, rendering the diagnoses of these species incomplete. Their names should only be used for the type specimens until better preserved topotypes become available for study. Morphology of the types of H.? corrugatus Walcott and “Orthotheca” sola Resser does not support placement in the Hyolitha; the affinities of these species are uncertain.

Paleomagnetism of the mid-Cretaceous gem-bearing pegmatite dikes of San Diego County, California, USA

2009 ◽  
Vol 46 (9) ◽  
pp. 675-687 ◽  
Author(s):  
D. T.A. Symons ◽  
T. E. Smith ◽  
K. Kawasaki ◽  
M. J. Walawender
Keyword(s):  
Fluid Flow ◽  
Gulf Of California ◽  
Remanent Magnetization ◽  
Sedimentary Rocks ◽  
Economic Importance ◽  
San Diego County ◽  
Magnetization Direction ◽  
Western Zone ◽  
Stable Characteristic ◽  
Tectonic Boundary

Pegmatite dikes in the Peninsular Ranges batholith of southwestern California have produced spectacular crystals of semiprecious and precious minerals for over a century. Aside from their economic importance, these dikes straddle a major tectonic boundary and were used to test hypotheses related to the timing and development of this composite batholith. Paleomagnetic analysis of 252 specimens from 20 sites (12 and 8 sites in the western and eastern zones of the batholith, respectively, from 11 mines in five dike districts) isolated a stable characteristic remanent magnetization direction at 19 sites. The site mean directions for the western and eastern zones are statistically indistinguishable at 95% confidence, supporting petrologic and geochemical arguments that the dikes of the two zones are coeval and cogenetic. After correction for the Neogene opening of the Gulf of California, the paleopole for all 19 site mean directions is indistinguishable from the 94 Ma reference paleopole for North America and supports hypotheses that (1) the dikes are genetically related to intrusion of the La Posta-type plutons; (2) the batholith was already assembled beside the northwestern coastline of Mexico at 94 Ma; (3) ENE-side-up tilting of fault blocks in the batholith’s western zone ended by ∼94 Ma; and (4) the far-sided and clockwise-rotated discordant paleopoles found commonly in Late Cretaceous and younger sedimentary rocks of the batholith’s region are mostly the result of inclination-flattening of the remanence and (or) remagnetization by fluid flow, creating a secondary remanence, excluding Neogene tectonic rotations.

Lower Cambrian (Branchian) trilobites and biostratigraphy of the Hanford Brook Formation, southern New Brunswick

2000 ◽  
Vol 74 (5) ◽  
pp. 858-878 ◽  
Author(s):  
Stephen R. Westrop ◽  
Ed Landing
Keyword(s):  
New Species ◽  
Nova Scotia ◽  
North America ◽  
New Brunswick ◽  
Lower Cambrian ◽  
Early Cambrian ◽  
The West ◽  
Middle Cambrian ◽  
Sequence Stratigraphic ◽  
Two New Species

The Hanford Brook Formation, one of the classic Cambrian units of Avalonian North America, contains at least eight species of endemic trilobites, including Berabichia milleri Westrop n. sp., that are assigned to seven genera. The vertical succession of faunas is far more complex than has been recognized previously, with each member containing a lithofacies-specific assemblage. These are, in ascending order: a bradoriid-linguloid Association without trilobites in the nearshore St. Martin's Member, a Protolenus Association in dysaerobic siltstones and sandstones of the Somerset Street Member, and a Kingaspidoides-Berabichia Association in hummocky cross-stratified sandstones of the Long Island Member that overlie a parasequence boundary at Hanford Brook. Due to the breakdown of biogeographic barriers in the late Early Cambrian, two new species-based zones, the Protolenus elegans and Kingaspidoides cf. obliquoculatus zones, share trilobite genera with the Tissafinian Stage of Morocco. This generic similarity has been the basis for correlation of this upper Lower Cambrian interval on the Avalon continent with the West Gondwanan lowest Middle Cambrian. However, the clear facies control on the occurrence of genera in the Hanford Brook Formation and the presence of an abrupt faunal break and unconformity at the base of the Tissafinian in Morocco makes this correlation questionable. The Hanford Brook Formation may represent a late Early Cambrian interval unknown in Gondwana. Sequence-stratigraphic criteria even raise the possibility that the Protolenus Association is the biofacies equivalent of Callavia broeggeri Zone faunas of the Brigus Formation of Newfoundland, Nova Scotia and Massachusetts.

scholarly journals Tracing of traffic-related pollution using magnetic properties of topsoils in Daejeon, Korea

2020 ◽  
Vol 79 (20) ◽  
Author(s):  
Seungwoo Lee ◽  
Seoyeon Kim ◽  
Hyeji Kim ◽  
Youlee Seo ◽  
Yeoncheol Ha ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetic Susceptibility ◽  
Remanent Magnetization ◽  
Coarse Grained ◽  
Morphological Observation ◽  
Exhaust Emission ◽  
Thermal Demagnetization ◽  
Main Street ◽  
Traffic Related Pollution ◽  
The Difference

Abstract The present study was designed to explore the possibility of roadside pollution screening using magnetic properties of topsoil samples in Daejeon, South Korea. Low-field magnetic susceptibility, frequency dependence of magnetic susceptibility, susceptibility of anhysteretic remanent magnetization, isothermal remanent magnetization (IRM) acquisition and demagnetization, back-field IRM treatment, and thermal demagnetization of composite IRM were determined for roadside topsoil samples. Magnetic susceptibility measured on 238 samples from the upper 5 cm of the topsoils ranged from 8.6 to 82.5 × 10–5 SI with a mean of 28.3 ± 10.8 × 10–5 SI. The proximal zone, 55 m wide area situated on either side of the main street, exhibited an enhancement of magnetic susceptibility. In areas distant from the main street, low magnetic susceptibility (< 50 × 10–5 SI) was observed. The topsoil samples exhibited significant susceptibility contrasts, suggesting that two dimensional magnetic mapping was effective in identifying traffic-related pollution. A few magnetic hotspots with intensities of magnetic susceptibility near or over 50 × 10–5 SI might reflect the difference in topographic elevation and surface morphology. Among various IRM-related parameters, remanence of coercivity was most significant statistically. In most samples, IRM component analysis provided dual coercivity components. Thermal demagnetization of composite IRM and morphological observation of magnetic separates suggest angular magnetite produced by vehicle non-exhaust emissions spherical magnetite derived from exhaust emission to be the dominant contributors to the magnetic signal. It is likely that lower- and higher-coercivity components represent the presence of coarse-grained angular magnetite and fine-grained spherical magnetite, respectively.

New occurrences of Leukadiella and Paroniceras (Ammonoidea) from the Toarcian (Lower Jurassic) of the Canadian Cordillera

1995 ◽  
Vol 69 (1) ◽  
pp. 89-98 ◽  
Author(s):  
G. K. Jakobs
Keyword(s):  
North America ◽  
Mediterranean Region ◽  
Lower Jurassic ◽  
Canadian Cordillera ◽  
Rare Occurrence ◽  
Western Tethys ◽  
North American Cordillera ◽  
Queen Charlotte Islands ◽  
The North ◽  
New Occurrences

Previous studies of the Toarcian of the North American Cordillera have mentioned the rare occurrence of Paroniceras in the Queen Charlotte Islands. Recent work has identified the presence of Leukadiella in the Middle Toarcian of the Queen Charlotte Islands, the Spatsizi area, and the Hazelton area. They occur with Rarenodia planulata, Peronoceras pacificum, Peronoceras verticosum, and Phymatoceras cf. P. pseudoerbaense. The Leukadiella specimens are well preserved and generally larger than those found in the Mediterranean region. Taxa present in North America include Paroniceras sternale, Leukadiella ionica, Leukadiella amuratica, Leukadiella aff. L. helenae, and Leukadiella aff. L. ionica. Morphologically Leukadiella is closely related to such genera as Hildaites and Hildoceras and is more suitably placed within the subfamily Hildoceratinae rather than the Bouleiceratinae. The distribution of Leukadiella and Paroniceras indicates the influence of the Hispanic Corridor linking western Tethys and the eastern Pacific during the Middle Toarcian.

Palaeoscolecids from the Balang Fauna of the Qiandongian (Cambrian Series 2), Guizhou, China

2015 ◽  
Vol 153 (3) ◽  
pp. 438-448 ◽  
Author(s):  
JIN PENG ◽  
DIYING HUANG ◽  
YUANLONG ZHAO ◽  
HAIJING SUN
Keyword(s):  
New Species ◽  
North America ◽  
Siberian Platform ◽  
Lower Cambrian ◽  
Burgess Shale ◽  
A New Species

AbstractWronascolex is a taxon of palaeoscolecids. It is commonly represented by isolated button-like microfossils or compressed individuals, which are found worldwide in strata ranging from the Cambrian Series 2 to Series 3. The earliest representative of Wronascolex is known from the Sinsk Formation of the lower Cambrian of the Siberian Platform. Other species occur in Burgess Shale-type biotas of Cambrian age from Australia, Spain and North America. New palaeoscolecid material from the Balang Fauna of the Cambrian Series 2 of eastern Guizhou represents a new species of Wronascolex, W. geyiensis sp. nov., and extends the geographic and stratigraphic distribution of Wronascolex, as well as providing additional evidence for understanding its morphology based upon correlation of body configuration and cuticular ornaments.

Single-domain theory for the reversible effect of small uniaxial stress upon the remanent magnetization of rock

1977 ◽  
Vol 14 (9) ◽  
pp. 2047-2061 ◽  
Author(s):  
J. P. Hodych
Keyword(s):  
Remanent Magnetization ◽  
Thermal Activation ◽  
Magnetocrystalline Anisotropy ◽  
Uniaxial Stress ◽  
Titanium Content ◽  
Single Domain ◽  
Stress Axis ◽  
Compression Axis ◽  
Saturation Remanence ◽  
Approximate Expressions

This paper on small uniaxial stress changing the remanent magnetization of rock is a companion to my previous paper on stress changing susceptibility, both phenomena being of current interest in attempts at earthquake forecasting.Theoretical expressions are derived (using rigorous energy-minimization but ignoring thermal activation) for reversible change in remanence parallel to the stress axis for samples containing single-domain grains of a ferromagnet with cubic magnetocrystalline anisotropy (K1 positive or negative) and anisotropic magnetostriction. The grains are assumed to be non-interacting and randomly oriented spheres or ellipsoids of revolution elongated along [Formula: see text], [Formula: see text], or [Formula: see text]. Also, approximate expressions are given for samples containing multidomain grains with very strongly pinned walls. Thermal (or chemical), anhysteretic, and saturation remanence are discussed.For remanence change perpendicular to the stress axis, one expects −1/2 the above expressions for change parallel to the stress axis, which is easily proven for thermal remanence.The expressions predict that for magnetite-bearing rock the decrease in thermal remanence along a 100 bar (1 × 104 kPa) compression axis should be 0.76% for spherical single-domain grains, 0.27% for 1.4 to 1 elongation along [Formula: see text], and 0.09% for great elongation along [Formula: see text]. The decrease for equidimensional multidomain grains with strongly-pinned walls should be ~0.38%. These are all much smaller than the corresponding estimates for susceptibility, but both remanence and susceptibility decreases should become larger and more comparable as titanium content increases.

Upper Precambrian–Lower Cambrian biota from the northwest of Argentina

1986 ◽  
Vol 123 (4) ◽  
pp. 367-375 ◽  
Author(s):  
Florencio Gilberto Aceñolaza ◽  
Felipe Ramón Durand
Keyword(s):  
North America ◽  
Lower Cambrian ◽  
Trace Fossils

AbstractThe principal characters of the biota from Upper Precambrian–Lower Cambrian rocks in the northwest of Argentina are described. It is possible to observe two groups: the trace fossils and the medusoid impressions. At the same time, a regional palaeogeographical analysis is attempted as well as a comparison with outcrops of similar age from the Gondwanaland area and from North America.

Paleomagnetism of the 1180 Ma Grenvillian Umfraville gabbro, Ontario

1978 ◽  
Vol 15 (6) ◽  
pp. 956-962 ◽  
Author(s):  
D. T. A. Symons
Keyword(s):  
Remanent Magnetization ◽  
Pole Position ◽  
Paleomagnetic Data ◽  
Grenville Province ◽  
Thermal Demagnetization ◽  
Before And After ◽  
Primary Origin

The 1180 ± 20 Ma Umfraville gabbro is a slightly metamorphosed stock in the Grenville Province. It was sampled at 17 sites (183 specimens). After alternating field and thermal demagnetization the gabbro retains the same very stable remanent magnetization of primary origin both before and after screening. The screened AF direction from 10 sites (96 specimens) gives a pole position of 166°E, 11°S (δp = 7°, δm = 10°). This position is ≈ 13° southeast of that originally reported for the gabbro by Hood. This pole position either does not fit or necessitates modifications to the four hypotheses that have been invoked to explain Grenville paleomagnetic data.

Sign in / Sign up

Export Citation Format

Share Document