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The tectonic evolution of SE Anatolia is associated with the collision between the Taurides and the Arabian Platform in the early Cenozoic, after the final closure of the southern branch of the Neotethys ocean during Late Cretaceous to Early Eocene times. The ongoing deformation was characterized by northward movement of Arabia, followed by westward extrusion of Anatolia, having been displaced along the northern and eastern Anatolian transform faults. The neotectonic deformation history between the Anatolian Plate and the Arabian platform since the closure of the southern Neotethyan oceanic basin from Late Cretaceous to present has not been studied in detail paleomagnetically. Therefore we carried out a paleomagnetic study of Mesozoic and Cenozoic rocks at 34 localities along the Bitlis-Zagros suture zone in SE Anatolia located in the boundary region between the Taurides and the Arabian platform and delimited by the Dead Sea Fault. Paleomagnetic results from the area show clockwise rotations of 35.6° ± 14.1° and 26.7° ± 8.0° with respect to the African plate from Upper Jurassic - Lower Cretaceous and Upper Cretaceous limestones, respectively. The paleomagnetic results indicate also an earlier deformation/opening due to the Dead Sea Fault Zone (DSFZ). Farther north on the Tauride Block, counterclockwise rotation of −34.5° ± 12.5° is recorded by Upper Cretaceous limestones. In the SE of the study area on the northern margin of Arabia, however, smaller counterclockwise rotations of -12.3° ± 8.3° and −2.5° ± 10.0° in Late Cretaceous and −12.7° ± 13.6° in middle Eocene rocks show relative tectonic stability. Middle Miocene rocks close to the suture zone show counterclockwise rotation by about −39.4° ± 10.9°, while farther away from the suture zone counterclockwise rotations of −21.9° ± 9.9° and −7.5° ± 5.8° are observed. Paleolatitudinal motion from south to north from the Late Jurassic to the Present is in concordance with the apparent polar wander path of Eurasia and Africa.

The eastern Aegean region has undergone north dipping subduction in the Oligocene, continental collision and then Miocene-Pliocene extension, which is associated with widespread Miocene volcanism. The aim of this study is to assess the possibility of block rotations due to stress variations in the Dikili (İzmir) province, Western Anatolia, based on paleomagnetic data obtained from 35 independent sites in addition to results from 19 sites in earlier studies. The lower Miocene Yuntdağ volcanic rocks were emplaced in three different structural blocks, the Dikili, Zeytindağ and Bergama blocks. Clockwise rotation is found in the Dikili and Zeytindağ blocks that varies from R (± DR) = 12.5° (± 7.4°) in the west to R (± DR) = 35.6°± (13.2°) in the east, respectively. In contrast, a counterclockwise rotation of R (± DR) =-38.1° (± 6.4°) resulted in the Bergama block, in the north of the Dikili and Zeytindağ blocks. A scissor-like basin evolution is suggested during the opening of the Bakırçay graben which led to counterclockwise rotation of the Bergama block and clockwise rotation of the Dikili and Zeytindağ blocks after lower Miocene to present. The rotation pattern derived from results of this study demonstrates that localized small scale deformation due to basin evolution besides regional affects must be considered as part of the deformation matrix in this area., Annals of Geophysics, 64 (6), ISSN:1593-5213

A paleomagnetic study of Cretaceous arc type rocks in the Central-Eastern Pontides and in the Southeastern Taurides investigates the tectonic and paleolatitudinal evolution of three volcanic belts in Anatolia, namely the Northern and Southern Volcanic Belts in the Pontides and the SE Taurides volcanic belt. The paleomagnetic data indicate that magnetizations were acquired prior to folding at most sampling localities/sites, except for those in the Erzincan area in the Eastern Pontides. The Southern Volcanic Belt was magnetized at a paleolatitude between $$23.8_{-3.8}^{+4.2}$$ °N and $$20.2_{-1.2}^{+1.3}$$ °N. Hisarli (J Geodyn 52:114–128, 2011) reported a more northerly paleolatitude ( $$26.6_{-4.6}^{+5.1}$$ °N) for the Northern Volcanic Belt. The comparison of the new paleomagnetic results with previous ones in Anatolia allows to conclude that the Southern Volcanic Belt in the Central-Eastern Pontides was emplaced after the Northern Volcanic Belt as a result of slab-roll back of the Northern Neotethys ocean in the Late Cretaceous. In the Southeast Taurides, Upper Cretaceous arc-related sandstones were at a paleolatitude of $$16.8_{-3.8}^{+4.2}~$$ . The Late Cretaceous paleomagnetic rotations in the Central Pontides exhibit a counterclockwise rotation of $$R\pm \Delta R=-37.1{}^\circ \pm 5.8{}^\circ$$ (Group 1; Cankiri, Yaylacayi Formation) while Maastrichtian arc type rocks in the Yozgat area (Group 2) show clockwise rotations R + ΔR = 33.7° ± 8.4° and R + ΔR = 29.3° ± 6.0°. In the SE Taurides counterclockwise and clockwise rotations of $$R\pm \Delta R=-48.6\text{ }\!\!{}^\circ\!\!\text{ }\pm 5.2\text{ }\!\!{}^\circ\!\!\text{ }$$ and $$R\pm \Delta R=+34.1\text{ }\!\!{}^\circ\!\!\text{ }\pm 15.1\text{ }\!\!{}^\circ\!\!\text{ }$$ are obtained (Group 4; Elazig Magmatic Complex). The Late Cretaceous paleomagnetic rotations in the Pontides follow a general trend in concordance with the shape of the suture zone after the collision between the Pontides and the Kirsehir block. The affect of the westwards excursion of the Anatolian plate and the associated fault bounded block rotations in Miocene are observed in the east of the study area and the SE Taurides.

A revision of Jurassic palaeomagnetic data from Iberia has been carried out in order to investigate the consistency between the palaeomagnetic information and the tectonic models proposed for the western Mediterranean. Due to the presence of a widespread (but partial) remagnetization which affected most Jurassic sediments in Iberia, selection criteria have been designed to avoid completely remagnetized sites. A total of 72 sites have been considered for the palaeomagnetic discussion (35 sites from the Messejana–Plasencia dolerite dyke, 14 sedimentary sites from the Iberian Range and 23 sites from the Betic Cordillera). Three palaeopoles for Iberia have been selected (from the Iberian Massif and from the Iberian Range) for the period around 200 Ma, the Toarcian–Aalenian and the Oxfordian. Data from the Subbetic Zone (Betic Cordillera) are used to constrain the palaeolatitude of the Iberian microplate. Iberian data are in general agreement with the BC02 master curve and the reconstruction parameters used to transfer the Iberian data to Europe, but lower palaeolatitudes than predicted by BC02 master curve are observed in Iberia for the Late Jurassic. Iberia reached a maximum in palaeolatitude during the Toarcian–Aalenian (the reference point of Madrid was at about 37°), and since then, the palaeolatitude decreased (Madrid was at 22° by the Kimmeridgian). Tectonic reference models for the Western Mediterranean (Stampfli and Borel, 2002, 2004) do not fit the Iberian declinations and palaeolatitudes. New palaeogeographic reconstructions are proposed for the Hettangian–Sinemurian, the Toarcian–Aalenian and the Oxfordian.

A new paleomagnetic study was carried out on the Findikli formation in the Amasya region, which is to the north of the Ankara-Erzincan Neotethyan suture zone, in order to better understand the paleogeographic evolution of the Pontides tectonic belt during the Maastrichtian. Samples were collected from volcanoclastic sandstones and lavas at 51 sites. Rock magnetic experiments identified pseudo-single domain (PSD) titanomagnetite as the main magnetic carriers at the majority of sites. Progressive thermal and alternating demagnetization revealed that the characteristic remanent component is removed between 400 and 580 °C or 20–100 mT, respectively. A high temperature component, which indicates the presence of titano-hematite, is found only in some lavas. Declinations show a systematic dispersion across the study area related to tectonic rotations about vertical axes. Inclinations are consistent, however, and yield a mean paleolatitude of 20.0°N ± 2.5° for the Maastrichtian. Comparison of the results from this study with the reference direction of the East Pontides from the Turonian–Campanian is best explained with a model involving slab roll-back and marginal basin formation between 90 and 65 Ma period.

Inactive stalagmites from the Silberen cave system and its surroundings (Muota Valley, Central Switzerland) have been dated by the 230Th/U method (alpha spectrometry and TIMS). Several samples yielded ages of approximately 200 ka (MIS 7) and 320 ka (MIS 9), others were beyond the upper limit of the method (about >350 ka) or might have behaved as open systems with respect to uranium. The following complementary dating methods were applied: 234U/238U, paleomagnetism, palynology and electron spin resonance. Paleomagnetism yielded positive inclination of the natural remanent magnetization of two stalagmite samples, corresponding to the Brunhes-epoch ( The uplift rate of the mountains, the corrosion rate of the karstified surface and the incision of the valley bottom, suggest that karstification started 4 to 3 Ma (Middle to Upper Pliocene). The dated speleothems are therefore substantially younger than the beginning of speleogenesis. Inaktive Stalagmiten aus dem Silberen-Hohlensystem und dessen Umgebung (Zentralschweiz) sind mittels der 230Th/U-Methode (Alpha-Spektrometrie bzw. TIMS) datiert worden. Einige Proben ergaben 230Th/U-Alter zwischen von 320 ka (MIS 9) und 200 ka (MIS 7), andere lagen ausserhalb des Zeitfensters der 230Th/U-Methode (>350 ka), wieder andere konnten offene Uran-Systeme gebildet haben. Erganzend zu den numerischen Datierungen wurden versuchsweise weitere Datierungsmethoden eingesetzt: 234U/238U, Palaomagnetik, Palynologie und Elektronen-Spin-Resonanz. Die Palaomagnetik zeigte bei den zwei untersuchten Tropfsteinen eine positive Inklination der naturlichen remanenten Magnetisierung, was der Brunhes-Epoche ( Aus der bekannten Hebungsrate des Gebirges, dem korrosiven Abtrag der Karstoberflache sowie der Eintiefung des Muotatals wurde abgeleitet, dass die Verkarstung im Untersuchungsgebiet vor 4 bis 3 Ma (Mittleres bis Oberes Pliozan) begonnen hat. Die bislang datierten Karsthohlensedimente sind nach diesem Modell also wesentlich junger als der Anfang der Speleogenese.

High-resolution paleosecular variation (PSV) can play an important role in sediment dating and for understanding the temporal characteristics of the geodynamo of the Earth's magnetic field. In this article, based on magnetic susceptibility correlation, a composite sediment profile has been compiled from a ~ 16 m long core (HN-2) and a ~ 8 m deep well (HN-3) in Shuangchiling maar lake, a crater basin located on Hainan Island, Southern China. Fine and homogeneous silty clay corroborates with a stable, continuous and undisturbed deposition. A U-channel-based paleomagnetic study, constrained by AMS14C chronology derived from leaves, plant debris and woods, and supported by rock magnetic data, indicates that the lake sediments document a reliable paleosecular variation (PSV) record since ~ 9000 cal. year BP. Comparison of our PSV features with other records from lakes Biwa (Japan), Erhai (China), Baikal (Russia) as well as archaeomagnetic records demonstrate that the inclination pattern is generally synchronous within chronological uncertainties, suggesting further PSV dating may be valuable for stratigraphic correlation on a regional scale.

Relative paleointensity records from the northern South China Sea, northwest Pacific Ocean were studied in two gravity piston cores. Continuous mineral magnetic and paleomagnetic measurements were made using discrete sediment samples. Detailed rock magnetic parameters, such as thermomagnetic and high-field hysteresis data, indicate that pseudo-single domain magnetite in a narrow range of grain-size and concentration is the main contributor to the remanent magnetization. The uniform magnetic mineralogy meets the commonly accepted criteria for establishing relative paleointensity records. The relative paleointensity (RPI) curves were constructed by normalizing the natural remanent magnetization (NRM) with isothermal remanent magnetization (IRM), both in the 20-60 mT demagnetization state. Dating constraints have been provided by radiocarbon ages in the upper 400 cm of both cores. Furthermore, we have correlated our paleointensity records with NAPIS-75, S.Atlantic-1089, Sint-200 and NOPAPIS-250 to determine the chronological RPI framework for the South China Sea (SCS-PIS). Although some temporal offsets of paleointensity features between the different records have been recognized, their similar shape suggests that relative paleointensity on the 10(3)-10(4) year scale is globally coherent and can provide an age framework for sediments independent of delta(18)O ages. (C) 2009 Elsevier B.V. All rights reserved.

The paper presents results demonstrating the possibility of using data on paleosecular magnetic variations for correlation of young deposits. Using Holocene deposits of the Aral Sea as an example, it is shown that the combination of paleo-and petromagnetic data can be used to reliably correlate sections in presently isolated parts of a basin, as well as to correlate paleohydrologic events and estimate their age with regard for absolute radiocarbon datings. It is established that the most significant drop in the Aral Sea level occurred more than 2000-2500 yr ago and less significant drops that occurred later are dated at about 1500, 750-1050, and 270-500 yr ago. © Pleiades Publishing, Ltd. 2007.

This paper presents the results of the paleomagnetic studies of the Naroch and Svir lake bottom deposits in Belorussia. The objects of study were nine columns of lake-floor sediments, totaling 6.50 m in thickness, collected using a special-type core sampler which did not disturb the structure of the sample material. The absolute dating of the sediments was performed by a radiocarbon method using the macroremains of the organic matter (grass). The columns of the sediments were correlated using their absolute ages, lithologies, and magnetic susceptibility values. All sedimentary rock columns showed a good agreement of the inclination and declination components of the natural remanent magnetization (ChRM) distinguished in all sedimentary rock columns using alternative magnetic field cleaning. The data obtained for all rock columns were summed up to produce the composite curves of ChRM declination and inclination variation for the sediments of these lakes. These data were compared with the archeomagnetic and limnomagnetic data available for Central and East Europe. All records of the paleosecular geomagnetic variations (PSV) showed a good agreement in terms of the morphology of the ChRM declination and inclination. At the same time the sediments of the Belorussian lakes showed a systematically older age and the lower magnitudes of the ChRM declination and inclination variations compared to the other PSV records available. These eects can be explained by the presence of some postdeposition remanent magnetization (PDRM) in the sediments of the Belorussian lakes and by the addition of some "aged" carbon (without 14 C) to the lake from the surrounding carbonate rocks. The basic features of the geomagnetic field variations in Europe are discussed for the last 10-12 thousand years.

Paleomagnetic and rock magnetic investigations were undertaken on samples from 14 formations in an attempt to examine the tectonic history of south China and to evaluate competing hypotheses for the amalgamation of the Huanan and Yangtze Blocks. The vast majority of the sampled sites were remagnetized; however, results from the Lower Triassic Xikou Formation appear to have escaped remagnetization. The sites pass a fold test and are in good agreement with other results published by Gilder et al. [Gilder, S., Coe, R.S., Wu, H., Kuang, G., Zhao, X., Wu, Q., 1995. Triassic paleomagnetic data from south China and their bearing on the tectonic evolution of the western circum-Pacific region. Earth Planet. Sci. Lett. 131, 269–287]. From the data, however, it is difficult to constrain the hemisphere of these sites during the Early Triassic and as such, a firm resolution of the competing hypotheses cannot yet be offered.

77 paleomagnetic samples from the Upper Silurian reddish limestone and marlstone of the Shan-Thai-Malay block near Baoshan ( 99.1°E, 24.8°N ), western Yunnan, China, reveal a pre-folding remnant magnetization, with a mean direction of D=49.6°, I= −3.2°, k=9.7, a95=5.5°, corresponding a paleopole at 207.0°E, 36.8°N. These results, unlike the upper Paleozoic data with steeper inclinations published earlier, suggest that the block was located at equatorial latitude during late Silurian time, probably adjacent to the northern margin of Gondwanaland.

A paleomagnetic record of geomagnetic secular variation during the last 3500 yr has been obtained from three lake sediment cores from lake Aslikul in the western Pre-Ural region (Russia). Pollen data provide a time-scale and relative paleotemperatures which can be compared with radiocarbon dated paleotemperature data for this region. Magnetic susceptibility measurements have been used for correlation between cores and reconstruction of composite core data. The paleosecular variations which have been recorded in the lake Aslikul sediments are consistent with results from West-European lakes. Westward shifting inclination features are observed between the more western European and the Pre-Ural regions which have apparent age differences between 200 and 600 years resulting in drift rates which are of the order of 0.1 degrees/year.

Samples were collected for paleomagnetic analysis from 36 sites from six formations west of the Red River Fault in southwestern Yunnan Province, China on the Simao block (23.4°N, 100.8°E) in an attempt to examine the effects of the India-Asia collision on the Asian continent. Paleomagnetic results from rocks ranging from Cretaceous to Miocene in age indicate a large clockwise rotation of these sites with respect to stable Eurasia since the Late Cretaceous. The tectonic-corrected data from Cretaceous samples (mean direction of two formations) are D = 112.6°, I = 34.7°, α95 = 7.5°, k = 9.1, n = 45, for Eocene samples the data are D = 84.7°, I = 38.9°, α95 = 7.6°, k = 12.0, n = 32, and for Miocene samples they are D = 21.1°, I = 35.5°, α95 = 7.1°, k = 15.3, n = 29. The samples from the Paleocene and Pliocene are either remagnetized or too weak to provide stable directions. The Cretaceous sites were sampled from folded beds and these sites pass the fold test. The amount of rotation seen in this study (R = 86.1 ± 9.9° as a mean value for the Cretaceous, R = 76.8 ± 11° for the Eocene, and R = 14.7 ± 10.0° for the Miocene) is significantly larger than that documented in previous studies from the Lower Cretaceous of northwestern and central Yunnan Province and may indicate that differential rotation has taken place in the region. This rotation can be explained by the northward motion and collision of India with Asia in the Paleocene, which caused continuous deformation of southwestern China in the form of strike-slip faulting and clockwise rotation. It is concluded that the rotation and deformation resulting from this collision probably continued from the Paleocene until at least the Miocene.

The stable component of the natural remanent magnetization (NRM) of the Upper Triassic “Calcari con Selce” limestone formation at Marsico Nuovo (Lagonegro Basin, Southern Italy) has an inclination which is about 45° too steep for the expected paleogeographic position. In order to explain this abnormal magnetization direction, several rock magnetic properties such as the dependence of susceptibility on temperature and alternating field frequency, anisotropy of low field susceptibility, anisotropy of anhysteretic remanent magnetization (ARM) and characteristics of acquisition and thermal decay of isothermal remanent magnetization (IRM) have been investigated. Strong inverse fabrics of both susceptibility and ARM have been recognized, which are due to magnetite in the superparamagnetic state on the one hand and in the stable single domain grain size on the other hand. Although internal deformation in the investigated rocks has not been reported in the geological literature, this may be the cause of the observed anisotropies. The anisotropy is probably responsible for the anomalous NRM directions of these limestones.

[1] A paleomagnetic investigation has been carried out on Middle Eocene volcanic rocks at 23 sites in the eastern Sakarya Zone and the central Pontides of north central Anatolia in order to better understand the regional tectonic evolution of the main zones of northeastern Anatolia in the Middle Eocene. The results constrain the tectonic evolution of the area when evaluated in conjunction with earlier published paleomagnetic directions from 92 localities. Small counterclockwise rotations in the range of R ± ΔR = −1.3 ± 1.4° to R ± ΔR = −17.2 ± 16.8°, with respect to Eurasia, are observed in the central Pontides on the northern side of the North Anatolian Fault (NAF). Clockwise rotations ranging between R ± ΔR = 8.5 ± 15.1° and R ± ΔR = 29.7 ± 12.0° are observed between the NAF and the Sungurlu Fault (SF), in the eastern Sakarya zone. Counterclockwise rotations of R ± ΔR = −18.9 ± 12.4° to R ± ΔR = −42.2 ± 6.9° are observed to the south of the SF. Our findings, combined with previous data, support the indentation model of Kaymakci et al. (2000, 2003a, 2003b), which postulates the collision and northeast directed indentation of the Kirsehir Block into the Sakarya Zone. This model, which was developed to explain the evolution of the Cankiri Basin, can also explain the variable magnitudes of paleomagnetically determined rotations, thrust directions, and the curvature of the North Anatolian ophiolite belt.

Paleomagnetic and rock magnetic experiments on the Triassic Yinkeng Formation and the Permian Changxing Formation sampled from the Permian-Triassic type section, Changxing County, reveal that a high temperature primary direction is isolated in dolomitic samples from the Early Triassic but the Late Permian limestones samples appear to be remagnetized during the Jurassic. A Permian-Triassic pole previously reported for the Changxing Formation from this section (Lin et al., 1985) is not in agreement with results from this study or other poles for that time interval reported for the Yangtze Block and may be remagnetized.

In an effort to contribute to the refinement of the APWP for the Yangtze Block, samples for paleomagnetic analyses were recovered from early Triassic sediments in Hunan Province in southeast China. The samples were taken from opposite limbs of a large syncline in order to apply the fold test and rock magnetic experiments were performed to determine the carriers of remanence. However, instead of refining the APWP, the results present some problems. While the sites pass the fold test, the declinations deviate clockwise with respect to the reference APWP for the block but agree well with other reported results. Due to the paucity of reliable Triassic results from the Yangtze Block and to the small number of sites from this study, it is difficult to determine whether these sites have been rotated or the APWP is incorrect. Both possibilities are explored.

A typical loess stratigraphy in China consists of alternating loess and palaeosol layers, which potentially provide one of the best terrestrial records of palaeoclimate for the past 2.5 Ma particularly as the magnetic susceptibility record of the loess/palaeosol stratigraphy can be strongly correlated with the climatic fluctuations of oxygen isotope ratios from deep sea sediments. Rock magnetic measurements have verified that magnetite, maghaemite and haematite, are the three most important magnetic minerals. The magnetic susceptibility of Chinese loess varies with changes in both magnetite/maghaemite. concentration and grain size. Although the magnetic susceptibility of palaeosols is several times higher than loess, their magnetic fabric has not been enhanced but slightly weakened, which strongly suggests in situ pedogenesis to be the predominant cause of their increased susceptibility.

New preliminary paleomagnetic results from the Lower Triassic limestones in several representative localities of South China support the existence of displaced blocks proposed by Hsu et al. (1988) “Huanan Alps, not South China Platform.” Sci. Sin.(B) , 31 , 109–119. and Hsu et al. (1990) “Tectonics of South China: Key to understanding West Pacific geology.” Tectonophysics 183 , 9–39. Four continental fragments have been recognized based on the geological and paleomagnetic evidence. They are the Yangtze ( D = 232.4°, I = −11.8°, K = 28.2, α 95 = 5.5° ), Xinaggui ( D = 198.0°, I = −32.2°, α 95 = 12.9° ), Cathaysia ( D = 88/0°, I = −13.0°, K = 20.1, α 95 = 9.1° ) and Dongnanya (Late Permian data D = 338.2°, I = −15.9, K = 10.2, α 95 = 14.3° ) blocks. The paleopole positions of the four blocks are scattered and latitudinal discrepancies are apparent. This can be explained by separations and displacements of the blocks instead of by crustal shortening. Differential post-collision rotations, especially clockwise rotations occurred in the blocks, which may be a product of regional and local rotations. The Early Mesozoic tectonics of South China can be interpreted in terms of amalgamation processes of the four continental blocks from the Paleotethys and Gondwanaland towards the Eurasia continent.

Open Geosciences 2(4), 514-523 (2010). doi:10.2478/v10085-010-0023-6, Published by De Gruyter Open, Warsaw

Based on palaeomagnetic measurements a three-stage model for the formation of lateritic duricrusts that postulates a para-autochthonous origin of the duricrusts, is proposed. The directions of the natural remanent magnetization (NRM) which reside in lithogenic magnetite contained in the duricrust matrix, have no preferential orientation. The NRM directions of in situ formed hematite contained in the micronodules of the duricrusts, are randomly distributed. The random distribution of the hematite magnetization directions suggests a para-autochthonous origin of the ferriferous micronodules which is explained by erosion and reworking prior to consolidation of the duricrusts. These processes lead to a mechanical iron accumulation at the top of the lateritic profiles.

Nearly all paleomagnetic studies in south China have encountered problems with remagnetization. The region underwent widespread tectonic deformation during the Mesozoic and the warm, humid climate causes rapid weathering of surficial sediments. Paleomagnetic results from three Carboniferous formations from three provinces in southeast China reveal two possible overprinting ages: one is probably a post-folding Cretaceous remagnetization and the other appears to be a Jurassic overprint which may be associated with the collision and suturing of the Yangtze and the Huanan or North China Blocks. The Jurassic overprint is found in sediments with both magnetite and hematite as primary magnetic remanence carriers. The remagnetization pre-dates deformation in at least one of the formations, further constraining the overprint to the Jurassic or late Triassic.

A Late Permian to Early Triassic magnetostratigraphic reference section is presented. The Lower Triassic part is based on results from marine limestone sections in South China published earlier [1,2]. Reliable new Permian data are added here which have been collected in the Nammal gorge (Salt Range, Northwest Pakistan) where marine sediments have been deposited quasi-continuously with occasional minor hiatuses during the late Palaeozoic to early Mesozoic. About 50% of the Permian samples from the Nammal section contain, hidden beneath a strong recent or Tertiary overprint, a characteristic remanent magnetization (ChRM) which is very likely of Permian age. This component, which was imprinted on the southern hemisphere, has normal as well as reversed polarity with a normal mean direction (Decl. = 289.3°, Incl. = −50.3°,α95 = 4.3°,N = 113) which is in close agreement with the palaeofield direction expected for a site belonging to the Indian plate as part of Gondwanaland during the Permian. In the lower Upper Permian several normal polarity zones are recognized. This contradicts the current assumption that rocks of this age belong to the long, reversely polarized Kiaman hyperzone. The Kiaman interval must end and the Illawarra hyperzone of mixed polarity must begin in or prior to the lowermost Upper Permian. The Permian/Triassic boundary at Nammal as well as in the Chinese sections is situated very close to a transition from a reversed to a normal polarity zone. The Upper Permian at Nammal together with the Lower Triassic South China sections is estimated to cover about 20 Ma. Nearly 30 polarity changes are observed which result in an average reversal frequency very similar to that observed during the early Tertiary. The reversal rate after the end of the long-lasting reversed Kiaman hyperchron apparently increases in a manner similar to that after the end of the Cretaceous Long Normal Superchron. Only a few polarity zones are found in the lower Upper Permian, while progressively more frequent reversals follow in the Lower Triassic.

Goethite and hematite in ferriferous oolitic beds of Callovian age from the Jura mountains (Switzerland, France) carry either pre- and/or post-tectonic magnetization. The frequent pre-tectonic origin of goethite magnetization indicates a temperature range during formation of the arcuate Jura mountain belt below the goethite Neel temperature of about 100°C. The scatter of the pre-tectonic paleomagnetic directions (D = 11.5°E, I = 55.5°; α95 = 4.7) which reside both in goethite and hematite, provides strong evidence that the arcuate mountain belt was shaped without significant rotation. The paleomagnetic results support tectonic thin-skinned models for the formation of the Jura mountain belt.

Paleomagnetic and structural analyses have been conducted on three well-exposed sections through a 6–8 km thick pile of molassic red beds (Murree formation) in the lowermost tectonic unit of the Hazara-Kashmir Syntaxis. Micropaleontological age determinations of the lowermost Murree sediments indicate Late Paleocene deposition (55 m.y.). From south to north, the sections are situated in the Jhelum, Neelum (both in Azad Kashmir), and Kaghan (northeastern Pakistan) valleys. Thermal demagnetization experiments suggest that haematite with high unblocking temperatures carries stable characteristic remanence directions. The relationship between finite strain and magnetic fabric was established by mapping deformed reduction spot strain markers and by measuring the anisotropy of magnetic susceptibility (AMS). For the Jhelum valley the weakly tectonized Murree beds are characterized by flattened AMS ellipsoids resulting from diagenetic compaction. Inclination values suggest that the Murree foreland basin started to develop at about 8°N during the early suturing of India and the development of island arcs to the north. India has moved northward by at least 2600 km since collision with Eurasia in the Paleocene. Declination values suggest 45° of clockwise rotation of the block supporting the Murree formation relative to the Indian craton. For the Neelum and Kaghan valleys, quantitative strain mapping shows a progressive increase of deformation northward. NRM directions rotate passively toward the cleavage plane which parallels the foliation of the AMS ellipsoids. NRM directions and AMS ellipsoids are deformed because of superposition of tectonic strain on a primary compactional strain. The AMS pattern is interpreted in light of this superposition, and a regional deformation path from south to north is suggested. A tectonic rotation model is proposed which is consistent with the transport directions around the Hazara-Kashmir Syntaxis and the rotation of thrust sheets indicated by the NRM data. This model relates the convergent transport directions with the mean indentation direction of India into Asia.

The natural remanent magnetization of andesitic pumice erupted from the Nevado del Ruiz volcano (Colombia) in 1985 is reversed with respect to the present geomagnetic field because of self-reversal. Laboratory thermoremanent magnetization acquired in fields of

The presence of at least one Block (Pallatanga Block) derived from the Caribbean–Colombian Oceanic Plateau has been proposed in the Western Cordillera of Ecuador. New 40Ar/39Ar dating of the basement of the coastal blocks (90–87 Ma) and fossil ages in the overlying Calentura Fm. (89–84 Ma) argue for late Turonian–Coniacian extrusion of the basement of the Pinon block. Paleomagnetic inclinations indicate that the mafic basement of the Pinon and San Lorenzo blocks extruded at equatorial, low southern latitudes. No subsequent significant latitudinal drift can be observed during the Cretaceous. Rapid changes in paleomagnetic declination between 73 and 70 Ma in both the Pinon and the San Lorenzo blocks indicate that the large igneous province, which originally hosted the coastal blocks experienced a major tectonic event during Late Campanian times. Similar Late Turonian–Coniacian basement ages and Late Campanian tectonic events are reported in the Pallatanga Block of the Western Cordillera. We propose that the Pinon, San Lorenzo and Pallatanga blocks all derive from a common large igneous province, the Caribbean–Colombian Oceanic Plateau, and were incorporated into the South American margin by collision during the Late Campanian (73–70 Ma).

Stratigraphic studies on loess deposits in the intramontane basin of Valle de Tafi (27°S, 66°W) revealed up to 31 intercalated paleosols. In order to clarify the chronostratigraphic position of the sediments, we performed paleomagnetic investigations in the 50-m-thick Las Carreras section. The characteristic remanent magnetization (ChRM) obtained after alternating field (AF) demagnetization gives clear evidence of the Matuyama-Brunhes boundary (MBB) at a profile depth of 26.7 m , and of the Jaramillo subchron at depths from 38.7 to 44.9 m . We assign a minimum age of 1.15 Ma to the onset of loess sedimentation, which calls for a complete reassessment of the antiquity of loess in the region. Thus, the Las Carreras sequence, which is probably continuous and complete, represents one of the longest Quaternary terrestrial paleoclimatic records reported from the southern hemisphere. The magnetic susceptibility signal follows the behavior known for Argentinian eolian sediments — though with certain restrictions and an overall weak correlation with pedostratigraphy. This behavior is opposite to the pattern reported from the Chinese Loess Plateau (CLP) and seems to be influenced strongly by changing source materials contributing to the susceptibility signal in Valle de Tafi.

Paleomagnetic and paleontologic data from the Valle della Contessa (Umbrian Apennines, Italy) span a 14 m.y. gap in previous magnetostratigraphic sections and reveal several intervals of reversed characteristic remanent magnetization (ChRM) in limestones and marls of the Albian Marne a Fucoidi. Rock magnetic data indicate that the reversed ChRM is carried by hematite having high unblocking temperatures (∼ 625–690° C). Hematite with these unblocking temperatures also carries a normal polarity ChRM in other intervals. A potential bias towards the identification of normal polarity is present since at every horizon measured a normal polarity component, carried by magnetite and hematite, is isolated at lower unblocking temperatures (∼300–600°C). Bulk magnetic properties vary throughout the measured section. In the portion containing most of the reversed ChRM intervals, hematite is the dominant carrier of natural remanent magnetization, while magnetite is the dominant carrier stratigraphically above and below. These changes correspond approximately with lithology. The zone of dominant hematite magnetization is marked by reddish bands (pigmentary hematite) which can be correlated throughout Umbria and are thought to record changes in the oxidation state of the seafloor during deposition. Two models may account for the observed magnetization directions. The reversed magnetizations may record a remagnetization which occurred at least 18 m.y. after deposition, while the beds were still flat-lying, in reversed polarity chron 33R (83–79 Ma) or later. If the reversed ChRM represents a remagnetization, the process is potentially of great importance since it can produce magnetization patterns which resemble polarity intervals. Alternatively, the reversed magnetizations may have been acquired during intense seafloor oxidation episodes during the mid-Albian (107–104 Ma) and may record unrecognized intervals of reversed geomagnetic field polarity. Milankovitch-like bedding cyclicity can be used to tune the sedimentation rate and obtain estimates of the duration of the potential reversed intervals. Using these estimates, two of the potential reversed polarity intervals are of sufficient duration (> 100 kyr) to be recognizable in both detailed stratigraphic sections and marine magnetic anomaly surveys. A primary magnetization model predicts that several intervals of reversed magnetization should be found near the boundary of the Biticinella breggiensis and Ticinella primula foraminiferal zones and within the Prediscosphaera cretacea nannofossil zone on a worldwide basis.

Magnetism of Quaternary sediments was the topic of a well-attended symposium held during the 13th INQUA (International Union of Quaternary Research) congress in Beijing, China, August 2–9. More than 40 papers were delivered by scientists from Belgium, England, France, Germany, Japan, New Zealand, Sweden, Switzerland, Taiwan, the United States, the Soviet Union, Yugoslavia, and other countries. The host country contributed to a productive session that was part of the first large scientific meeting to take place in Beijing after the June 4, 1989, upheaval. Nearly half of the studies focused on paleomagnetic and rock magnetic properties of loess in Alaska, Central Asia, China, and New Zealand. Magnetostratigraphic polarity dating was done at some sections in the western (Shaw et al.) and central Chinese loess plateau (Bai and Hus; Wang and Evans; Yue). The interpretation of the polarity pattern found in the western loess plateau still is not unambiguous. In the central part, certain polarity boundaries, such as the Brunhes/Matuyama (B/M) boundary, are found in slightly different stratigraphic positions (Hus et al.; Yue). In deep-sea sediments the lock-in depth of natural remanent magnetization (NRM) at the B/M boundary seems to be a linear function of sedimentation rate (de Menocal et al.). Although the magnetization process in the Chinese loess is not well understood, detailed records of polarity transitions have been reported for the B/M and the Jaramillo R→N transition (Ma et al.; Rolph).

Goethite and hematite are the main magnetic phases contained in two ferriferous middle Jurassic beds which are exposed within the Mandach structure, the major tectonic structure of the eastern tabular Jura of northern Switzerland. The iron oxidic phases in a reddish brown sparry limestone known as Spatkalk were formed diagenetically, whereas these phases are weathering products in a stratigraphically slightly younger oolitic bed. The hematite in the oolitic bed was magnetized after the Jura main tectonic event in the Miocene whereas the hematite in the Spatkalk was magnetized before the Miocene. The goethites in the oolitic bed carry a pretectonic and in the Spatkalk a syntectonic magnetization. Physical and chemical data show that the goethite which was resistant to remagnetization contains an Al-substitution of 3.4 mol% resulting in a Neel temperature of 90°C. The remagnetized goethite has an Al-content of 10.7 mol% and a Neel temperature of 70°C. The different goethite properties indicate that the tectonic formation of the Mandach structure occurred under low-temperature conditions below 90°C.

The palaeomagnetism of sediments and volcanics of Middle Devonian to Early Carboniferous age has been studied in the Hercynian realm of the Vosges, Harz and Franconian Forest (France and Germany). After appropriate cleaning, characteristic directions of natural remanent magnetization (NRM) have been determined, which are considered to be of pretectonic origin according to rock magnetic and structural geological evidence. A mean palaeopole for the Devonian rocks in the areas investigated was determined at — 29.7°N and 9.0°E. The site latitude derived from the Devonian rocks agrees very well with that observed in Great Britain and Britanny. The significant difference in longitude between our Devonian poles and the other European data may be due to an anticlockwise rotation of central Europe with respect to the northern Hercynian Foreland. The Carboniferous rocks yield a mean palaeopole at —41.7°N and 340.4°E, matching the Carboniferous part of the European polar wander path. A fold test within Carboniferous greywackes from the Harz mountains proves a pre-folding origin of the NRM of these rocks. However, this stable magnetization direction indicates local or regional tectonic displacement. Our results do not support any major latitudinal motions of continental segments in central Europe during the Hercynian orogeny. The Palaeozoic palaeomagnetic data from the Vosges, Franconian Forest, Harz, Britanny and Central Massif can be used to interpret the Hercynides in terms of a large scale shear belt.

One of the fundamental principles of palaeomagnetism and rock magnetism states that the direction of natural remanent magnetization (NRM) is acquired parallel to the applied field. However, ferromagnetic mineral phases with complex microstructures may violate this rule1,2 and produce a magnetization vector which is antiparallel to the direction of the external field. Andesitic pumice, which was hurled several kilometres during the disastrous 1985 eruption of the Nevado del Ruiz volcano (Colombia), carries a stable but reversed NRM with southerly declination and negative inclination. Heating experiments show that this magnetization is due to a self-reversal mechanism which also induces a reversed thermoremanent magnetization (TRM) in the laboratory field. Thus we have used the Nevado del Ruiz 1985 pumice, which was magnetized in the present well-known geomagnetic field, to demonstrate for the first time that self reversal has actually controlled the process of NRM acquisition.