Apparent Polar Wander Curve Research Articles

The Apparent Polar Wander Path for South America during the Permian–Triassic

Many of the controversies that arise in global reconstructions for Permian–Triassic time could be resolved by taking into account the large latitudinal and counter-clockwise movement of Gondwana during that interval of time. The proper trace of the apparent polar wander curve should differentiate one position for the Early Permian, another position for the Late Permian and yet another for the Triassic. By doing so and comparing the Apparent Polar Wander Paths (APWP) of South America and Africa it is easy to see that both curves have the same shape, therefore it is possible to arrive at a good fit between them, which previous analyses were unable to achieve. This new proposed Permian–Triassic track of the APWP reveals a hook not hitherto recognized that should be accounted for in global reconstructions.

Motion of Africa and Adria since the Permian: paleomagnetic and paleoclimatic constraints from northern Libya

Paleomagnetic and biostratigraphic data from the Al Azizia Formation of northwestern Libya, consisting of uppermost Middle Triassic/lowermost Upper Triassic limestones, shed new light on the latitudinal drift of Africa and Adria and related climatic changes. A characteristic component of magnetization carried by magnetite delineates paleomagnetic poles which are coincident with coeval poles from the Southern Alps. Data from this study and the literature are integrated, showing that relatively unrotated remnants of the Adria margin like the Southern Alps (e.g., the Dolomites), Istria, Gargano, Apulia and Iblei moved in close conjunction with Africa since at least Permian times. A Permian–Cenozoic apparent polar wander (APW) curve for Africa/Adria is constructed. The paleolatitude trend for northern Libya calculated from this APW superposed to the zonal latitudinal bands of relative aridity and humidity typical of modern-day climate predicts that northern Libya drifted northwards from the equatorial belt to the arid tropic during the Triassic, and crossed the humid subequatorial/arid subtropical boundary zone at Late Triassic times. This inference is fully supported by Permo-Triassic palynological and facies analysis from this study and the literature. We conclude that a zonal climate model coupled with paleomagnetically constrained paleogeographic reconstructions provides a powerful null hypothesis for understanding past climatic conditions.

Palaeomagnetism of the Lower Ordovician Orthoceras Limestone, St. Petersburg, and a revised drift history for Baltica in the early Palaeozoic

Palaeomagnetic investigation of Lower Ordovician limestone in the vicinity of St. Petersburg yields a pole position at latitude 34.7°N, longitude 59.1°E (dp/dm=5.7°/6.4°). A probable primary remanence origin is supported by the presence of a field reversal. The limestone carries one other remanent magnetization component associated with a Mesozoic remagnetization event. An apparent polar wander path is compiled for Baltica including the new result, ranging in age from Vendian to Cretaceous. Ages of the published Lower to mid-Palaeozoic palaeomagnetic pole positions are adjusted in accordance with the timescale of Tucker & McKerrow (1995). The new Arenig result is the oldest of a series of Ordovician and Silurian palaeomagnetic pole positions from limestones in the Baltic region. There are no data to constrain apparent polar wander for the Tremadoc, Cambrian and latest Vendian. If the Fen Complex results, previously taken to be Vendian in age (c. 565 Ma), are reinterpreted as Permian remagnetizations, an Early Ordovician—Cambrian—Vendian cusp in the polar wander path for Baltica is eliminated. The apparent polar wander curve might then traverse directly from poles for Vendian dykes on the Kola peninsula (c. 580 Ma) towards our new Arenig pole (c. 480 Ma). The consequence of this change in terms of the motion of Baltica in Cambrian times is to reduce significantly a rotational component of movement. The new Arenig pole extends knowledge of Ordovician apparent polar wander an increment back in time and confirms the palaeolatitude and orientation of Baltica in some published palaeogeographies. Exclusion of the Fen Complex result places Baltica in mid- to high southerly latitudes at the dawn of the Palaeozoic, consistent with faunal and sedimentological evidence but at variance with some earlier palaeomagnetic reconstructions.

Proterozoic palaeomagnetism of the mafic dyke swarms in the high-grade region of southern India

Palaeomagnetic investigations have been carried out on four major dyke swarms (38 sites) in the high-grade metamorphic region of the south Indian shield. A total of 37 sites (243 samples) in four dyke swarms have yielded Precambrian palaeomagnetic vectors after progressive AC and thermal demagnetisation: (1) the Agali-Anaikatti swarm bordering the Nilgiri Massif to the south; (2) the Tiruvannamalai swarm to the interior of the Pondicherry coast; (3) the Dharmapuri swarm towards the west of Tiruvannamalai in the interior of Tamil Nadu; and (4) a few dykes from a swarm in north Kerala on the west coast. Ages of the palaeomagnetic vectors are estimated from available KAr isotope dates on samples from a number of sites from all swarms and RbSr isotope results from the older Agali-Anaikatti dykes. The vectors and their corresponding ages are as follows: D = 13.9°, I = 27°, κ = 94, α 95 = 26, pole = 75.7°N 153.2°E for the ∼2000 Ma Agali-Anaikatti swarm ( N = 2 sites); D = 359.8°, I = 9.2°, κ = 51, α 95 = 10, pole = 79.7°N 101.1°W for the 1800-1750 Ma Dharmapuri swarm ( N = 5 sites); D = 217.2°, I = −50°, κ = 103, α 95 = 24, pole = 51°N 130°E for the 1700-1650 Ma northern Kerala dykes ( N = 2 sites) and D = 106.9°, I = −77.6°, κ = 42, α 95 = 9.4, pole = 18.8°S 125.2°W for the ∼1650 Ma Tiruvannamalai swarm ( N = 7 sites). These results in conjunction with other available good quality data have been used to compile an apparent polar wander curve of India for the Proterozoic Eon. The palaeolatitudes derived from the data show that the Indian Indian landmass was situated at mid-latitudes of the Northern Hemisphere during ∼2000 Ma, at a low latitude near the Equator (∼10°N) during ∼1800-1750 Ma, close to the South Pole region (60°S) by ∼1650 Ma, again near the Equator ∼1000 Ma, near the North Pole (80°N) region at ∼850-800 Ma, and moved to 10–30°N by 750 Ma.

Apparent Polar Wander Path Smoothing with spherical splines

Apparent Polar Wander Curve Smoothing is addressed once again. The association of a suitable mapping from the sphere to the plane and spline smoothing parameterized by ages, known for some years and already used by several authors is the latest of a variety of methods. This study is devoted to its application, complemented with statistical aspects, and extended to parameterization by arclength in order to incorporate poorly dated poles. We also emphasize the connection with other modelling methods. The technique is applied to the European Apparent Polar Wander Path as an example.

Paleomagnetism of mesozoic kimberlites in southern Africa and the cretaceous apparent polar wander curve for Africa

Including those previously published, good paleomagnetic data have been obtained from 48 of 51 sites in 28 separate kimberlites. Radiometric dates (by one or more methods) are available for 17 of these bodies and range from 81 to 145 Ma, with maxima around 90 and 120 Ma. These ages correlate with geochemical contrasts distinguishing what have been designated Group I (younger) and II (older) kimberlites [Smith et al., 1985b]. Stable magnetization appears to be associated with magnetite developed deuterically, after emplacement, but in most bodies, secular variation has not been completely averaged in the remanence acquired. The distribution of “VGPs” calculated is distinctly, but not sequentially, streaked yet correlates broadly with the older and younger petrochemical types. Mean North poles calculated on this basis yield KP1 (N = 14), 81–100 Ma, 64.1°N, 226.1°E, A95 = 5.2 and KP2 (N = 10), 113–145 Ma, 47.6°N, 269.9°E, A95 = 9.7. With the exception of one undated pipe (Meltonwold), which was not included in the averages, and the melilititic Male fissure at Swartruggens (in Group II average), all the kimberlites sampled are normally magnetized. Including these new data, 10 of 17 published African Cretaceous poles meet acceptability criteria specified, and define an apparent polar wander (APW) curve from ∼130 to 75 Ma. The curve appears to consist of two segments, trending latitudinally before ∼100 Ma, and meridionally thereafter. The latter trend is evident even in the distribution of the individual KP1 poles, and may be related to the true polar wander speculated by Gordon and Livermore (1987) to have occurred in that interval.

A palaeomagnetic investigation of a Permian redbed sequence from a mining drill core

Summary Samples spanning 66 m of Permian redbeds were collected from a vertical, but azimuthally unoriented, drill core obtained during a uranium exploration programme in the Lodeve Basin of southern France. Inclinations are well grouped (?= - 6.5°, k= 121.5) and consistent with the known Permian palaeolatitude of Europe. Declinations have been estimated by using a sedimentological model involving tectonically-rotated cross-bed laminations. The results are very encouraging and suggest a pole at 151°E, 53°N (δp= 1°, δm = 2°, N= 43), which agrees well with the Eurasian apparent polar wander curve. The small polar discrepancy could well be due to secular variation, which is consistent with the small variance and presumed short time spanned by the sequence. Fully oriented surface samples confirm these findings, and support the validity of the orientation model. Temporal variations revealed by the stratigraphic ordering can be interpreted as slow dipole wobble, on a time-scale of 105 yr or more, on which is superimposed a more rapid nondipole secular variation. It appears that the core stores of the world could become - at least under favourable circumstances - an important source of palaeomagnetic information.

A refined apparent polar wander curve for the transdanubian central mountains and its bearing on the mediterranean tectonic history

Recently obtained palaeomagnetic data have given a fairly detailed apparent polar wander (A.P.W.) curve for the Mesozoic of the Transdanubian Central Mountains which has been compared with other A.P.W. curves from the Mediterranean area. The similarity of the A.P.W. curves enabled a unified A.P.W. curve to be constructed for the Central Mediterranean region. It has been shown that the new Mediterranean A.P.W. curve is in full agreement, even in details, with the updated A.P.W. curve for Africa. This confirms the existence during the entire Mesozoic of a single Central Mediterranean megatectonic unit rigidly attached to Africa. Its positions with respect to the pole can now be traced back in more detail than before.

Paleomagnetism and magnetic fabric of the Gallen massive sulfide deposit, Rouyn-Noranda, Canada

Twenty oriented drill cores were collected from the outcrop of the Gallen massive sulfide deposit in the Rouyn-Noranda area in order to investigate remanent magnetization and anisotropy of magnetic susceptibility in the deposit. The purpose was to obtain inforrnation on the emplacement of the deposit. Electrical resistivity is high enough to allow 60-Hz alternating fields (AF) to be used for stability testing of the remanent magnetization. For thermal demagnetization, the heating chamber was first evacuated and then filled with argon. Alternating field demagnetization in a peak field of 30 mT yielded well-grouped stable directions carried by relatively high coercivity magnetite. The mean direction and pole position are: 137, +50, and 43 degrees W, 2 degrees S, dm=9 degrees , dp=6 degrees , respectively. The pole position falls on the 1,750- to 1,700-m.y. part of the apparent polar wander curve for North America, suggesting that the magnetization was acquired after the probable Archean formation of the deposit. The anisotropy of susceptibility (generally

Late Palaeozoic palaeomagnetic data for Wrangellia: resolution of the polarity ambiguity

Wrangellia and the Alaska Peninsula terrane are two of the many allocthonous terranes making up southern Alaska today. Palaeomagnetic data from these areas clearly indicate low palaeolatitudes in the early Mesozoic. Because of local and regional rotations, the mean declination of the palaeomagnetic vectors is uncertain. This, in addition to incomplete temporal coverage, has led to an ambiguity in the polarity of the vector, and hence an ambiguity in whether the palaeolatitudes determined are in the Northern or Southern Hemisphere. The data considered here have resolved the ambiguity for Wrangellia, and by implication for the Alaska Pennisula terrane, and also allow the construction of a highly speculative apparent polar wander curve.

40Ar/39Ar dating of the Thanet gabbro, Ontario: looking through the Grenvillian metamorphic veil and implications for paleomagnetism

In this first dating study of the Thanet gabbro complex from the Hastings Basin area we have obtained K–Ar evidence to support the geological contention that this pluton (and, by inference, others nearby) has escaped the severity of the Grenvillian metamorphic overprint. Specifically, a reliable date of 1200 Ma for a hornblende demonstrates that this body was emplaced at least 100 Ma earlier than the peak of metamorphism in the adjacent Haliburton Highlands.From considerations of possible cooling histories and a proposed Grenville apparent polar wander (APW) curve we deduce that only the Thanet magnetization component with the lowest laboratory blocking temperatures (Th3) was likely acquired as a thermoremanent magnetization, whereas the other two components were probably acquired as low-temperature chemical remanent magnetizations. Furthermore, the Th3 component was likely set before 1.0 Ga, consistent with our earlier proposed Grenville Loop.

Paleomagnetic data and pelagic sediment facies and the motion of the Pacific Plate relative to the spin axis since the Late Cretaceous

In order to study the motion of the Pacific plate with respect to the spin axis during the Cenozoic and Upper Cretaceous we combined an analysis of the distribution of pelagic sediments on the sea floor with paleomagnetic data collected on the Pacific plate. The facies distribution of sediments is used to determine the time when an equatorial crossing took place at as many sites as possible. By combining these two independent data sets, bounds can be placed on the relative motion of the ‘hot spots’ with respect to the spin axis. The data strongly suggest that the Hawaiian hot spot has remained close to its present latitude for the last 70 m.y. with an uncertainty in the rate of latitudinal motion of about 1 cm/yr. A set of continental paleomagnetic data was selected on the basis of the number of samples used, the degree of secondary demagnetization, the uncertainty of the mean direction of magnetization, and the tectonic stability of the region. These data are used to obtain independently the apparent polar wander curve of the Pacific plate. If the plates were rigid and the finite rotations were not grossly in error, reliable continental paleomagnetic poles rotated relative to the Pacific plate would yield a pole path consistent with the sediment facies data and with Pacific paleomagnetic data. Whereas the data from the Pacific plate indicate a latitudinal motion of almost 30° during the last 70 m.y., the rotated paleomagnetic poles from the continents cluster around the present‐day north pole and require essentially no latitudinal displacement of the plate during this same period of time. Several hypotheses are considered to explain this large discrepancy: a nondipolar behavior of the paleomagnetic field, insufficient quality of the existing Cenozoic paleomagnetic catalogue, or a large amount of internal deformation in the Antarctic or Pacific plate from the Upper Cretaceous to the Lower Oligocene.

Reinterpretation of the North American apparent polar wander curve for the interval 800–1500 Ma

We have reviewed the geochronology of rocks having paleopoles in the interval 800–1500 Ma from North America, Greenland, and the Baltic Shield. The present uncertainties in the acquisition times of the remanent magnitizations allow the construction of a simplified apparent polar wander curve for North America that incorporates Sveconorwegian paleopoles in a Grenville Loop, and that places poles from the El Paso, Stoer Group, and Aillik Bay rocks on the Logan Loop. Furthermore, the sense of motion through poles older than ~ 1.3 Ga is reversed to permit the shortest connection to poles older than 1.6 Ga. As well, the timing and shape of the Hadrynian Track are modified so that it begins in the Atlantic hemisphere at ~ 800 Ma and terminates in the Pacific at ~ 650 Ma, representing a minimum average continental drift rate of ~ 10 cm/year for this interval.

Paleomagnetic results from some southern African kimberlites, and their tectonic significance

Paleomagnetic data are reported from kimberlite occurrences of three distinct age groups: (1) National (one pipe), D = 221°, I = −51°, k = 41, α95 = 7.2°, age ∼1140 m.y., (2) Swartruggens (three fissures), mean D = 293°, I = −46°, k = 22, α95 = 26,9°, age = ∼150 m.y., and (3) six bodies in and adjacent to Lesotho, D = 350°, I = −69°, K = 66, α95 = 8.3° with age spread of ∼90 + 5 m.y. Analysis of these and previously published data suggests that most individual kimberlite bodies give acceptable paleomagnetic (as distinct from virtual geomagnetic) poles. This leads to a revised apparent polar wander curve for Africa in upper Mesozoic time and suggests that the time of kimberlite emplacement does coincide with intervals of rapid plate motion, although this cannot be the primary cause of their intrusion.

Palaeomagnetic ages of late cretaceous and tertiary weathered profiles in the Eromanga Basin, Queensland

Two iron-enriched weathered profiles, both widely distributed in the Eromanga and Surat Basins of Queensland, have been investigated palaeomanetically. Normal and reversed polarities have been obtained from each profile, indicating that the weathering events spanned at least one reversal of the geomagnetic field. The minimum duration of weathering for the older of the two profiles is estimated as 10,000 years. The palaeomagnetic directions when compared with the Late Cretaceous and Cainozoic apparent polar wander curve for Australia give a Maastrichtian to Early Eocene age for one profile and an approximately Late Oligocene age for the other. These ages are consistent with times of high palaeotemperature indicated by oxygen isotope analysis of marine fossils of the Southeast Indian Ocean. The pole position for the younger profile is not significantly different from pole positions obtained in previous palaeomagnetic investigations of weathered rocks in Western Australia, South Australia and the Northern Territory, supporting the long-held view of a mid-Tertiary continent-wide weathering event in Australia.

Palaeomagnetism and K-Ar dating of the Carboniferous Andacollo Series (Argentina) and the age of its hydrothermal overprinting

Palaeomagnetic data from 15 hand samples collected in a sequence of tuffs of Carboniferous age (Andacollo Series) exposed in western Argentina (37°10′S, 70°38′W) are given. These samples show hydrothermal alteration. After AF and thermal cleaning the majority of samples show reversed polarity and yield a palaeomagnetic pole at 73.6°S, 64.7°E ( d ψ = 6°,d χ = 9° ). By comparing the position of this pole with the apparent polar wander curve recognized for the Late Palaeozoic and Mesozoic of South America, quantitative support for a Cretaceous age for the cleaned remanence of these samples is given. K-Ar dating of the Andacollo rocks indicates a mean age of 69 ± 4m.y.; this suggests that the isotopic system of these rocks became closed in Late Cretaceous time. Palaeomagnetic and radiometric data agree indicating a Cretaceous age for the hydrothermal alteration of the Andacollo rocks.

The palaeomagnetism of 2400 m.y. old rocks from the Australian Pilbara craton and its relation to Archaean-Proterozoic tectonics

Palaeomagnetic results are described from 16 sites distributed in two traverses across the Black Range dyke. The dyke, a quartz gabbro dated radiogenically at 2329 ± 89 m.y., is one of the principal members of the NNE trending Black Range Suite which intruded the Archaean assemblage of granite plutons and greenstone belts of the Pilbara craton at around the time of the Archaean-Lower Proterozoic boundary. Results are also presented from 9 sites in the Cajuput dyke. The field evidence is consistent with this dyke having acted as a feeder for the overlying Mount Roe Basalt, the basal member of the Lower Proterozoic Fortescue Group. The Cajuput dyke also trends NNE and is thought to belong to the Black Range Suite. Samples of metamorphosed granite collected in the baked contact zone of the Black Range dyke exhibit various degrees of remagnetization. Directions of magnetization in material from the remelted granite margins are close to the mean direction of magnetization for the dyke. Beyond about 30 m from the contact, the effects of remagnetization are absent. The pole positions computed from site-mean virtual geomagnetic poles for the Black Range dyke and the Cajuput dyke lie at lat. 32°S, long. 154°E (A95 = 9°) and lat. 46°S, long. 146°E (A95 = 22°), respectively. They fall on the Australian apparent polar wander curve drawn for the period pre-2000 m.y. which until now was based primarily on data from the Yilgarn craton. These data suggest that it is improbable that the younger, intervening mobile belt between the Yilgarn and Pilbara cratons was generated through the process of a plate tectonic, continent/continent-type convergence.

Palaeomagnetism of 4 dolerite dikes around Listed, Bornholm (Denmark)

Four dolerite dikes from the island of Bomholm have been investigated with the purpose of determining the palaeomagnetic pole positions and the magnetic ages, and to contribute to the general knowledge of the geological development of Bomholm. A total of 137 specimens were cored from 67 oriented hand samples from the dikes. After a.f. demagnetizations up to 1800 oe, three significantly different stable mean directions were isolated. The poles and Fisher statistics are for the Vaseaa dike l6°S, 128°E, N = 11, cns = 9°; for the Listed dike 14°N, 250°E, N= 32, "'" = 4°; and for the Vigehavn dike 15°N, 159°E, N = 7, "'" = 6°, while the Bolshavn dike gives two directions, a remagnetized direction A with a pole position of 13° N, 153° E, N = 9, aos = 9°, and a 'ghost' (supposed original) direction B with pole 21°N, 224°E. A comparison with known palaeomagnetic poles from Northwestern Europe and North America suggests that the palaeomagnetic data may be interpreted as follows: After cooling of the Svaneke granite the Vaseaa dike was probably injected around 1200 Myr. Some 200 Myr later the fault system was reactivated and injection of the Listed and Bolshavn dikes took place. Finally, the same fault system was reactivated once again in lower to mid-Palaeozoic time and the Vigehavn dike was intruded; at the same time the Bolshavn dike was partially remagnetized leaving only weak traces of the original direc­tion of magnetization. During all the time covered, Bomholm was at fairly low latitudes, between 7° and 26°. By a reconstruction of the apparent polar wander curve it is argued that the polarity should be reversed for poles older than 1200 Myr to give a better fit of known data.

The drift of the Indian subcontinent; an interpretation of recent palaeomagnetic data

The Precambrian and Phanerozoic drift of the Indian subcontinent is discussed on the hand of available palaeomagnetic data. Hard secondary magnetization components of Early Tertiary Deccan Trap origin were found in a number of red beds studied. Incompatabilities in some previously published red beds data of mainly Early Gondwana age are presumably due to incompletely cleaned results. A modified apparent polar wander curve is proposed after rejecting certain data on the grounds, that they reflect a later Deccan Trap remagnetization. The spatial and temporal relations between the Early Cretaceous Rajmahal Trap- and the Early Tertiary Deccan Trap effusions does not accord with a mantle fixed hot spot model. The Indian palaeomagnetic data when compared with data from the other Gondwanaland continents favour the hypothesis of an early fragmentational movement of Gondwanaland before Penno-Triassic times. Implications of available palaeomagnetic data on the convergence of India and Asia are discussed in relation to some recent plate tectonic models.

A Discussion on global tectonics in Proterozoic times - Palaeomagnetic evidence for a Proterozoic super-continent

The Precambrian apparent polar wander (a.p.w.) curve for Africa is now defined in a general way from ca . 2700 million years (Ma) to Palaeozoic times, and is compared here with palaeomagnetic results from other Precambrian regions. Loops present in the African and North American a.p.w. curves between 2000 and 1000 Ma can be matched in size and shape, and when superimposed show that the AfroArabian and North American regions were in continuity at this time. Data from other Gondwanaland continents are reviewed and seem to be consistent with the SmithHallam reconstruction to ca . 2100 Ma for South America, to ca . 1800 Ma for India, and possibly for Australia back to ca . 2100 Ma. The a.p.w. curve from the Baltic and Ukrainian Shields can be matched with that from Africa and North America such that there was crustal continuity prior to 1000 Ma with the Gothide and Grenville mobile belts in great-circle alignment. The limited palaeomagnetic data from the Siberian Shield do not allow it to be placed uniquely with respect to the other land masses but are consistent with a position in juxtaposition with the Baltic-Ukrainian Shields such that massive anorthosites and ca . 1000 Ma mobile belts are in alignment with those from elsewhere. The palaeomagnetic evidence is consistent with a model in which the bulk of the Precambrian shields were aggregated together as a single super-continent during much of Proterozoic times, the most prominent feature of which is a great circle alignment of massive anorthosites (2250-1000 Ma) along a belt which also became a concentrated zone of igneous intrusion by rapakivi granites and alkaline intrusions, and culminated in generation of long linear mobile belts at 1150 ± 200 Ma and thick graben sedimentation. The predominance of this feature during much of the Proterozoic suggests that a simple mantle convection system pertained during this time. The proposed super-continent is not greatly different in form from the later shortlived super-continent Pangaea, formation of which may have involved relatively minor redistribution of the sialic regions in late Precambrian (probably post-800 Ma) and Palaeozoic times.