In this paper, we first describe the paleointensity furnaces and the procedures specifically designed to minimize oxidation of the samples during Thellier and Thellier paleointensity experiments, routinely used at Gif. We also propose some improvements to the set of criteria commonly used to select the results of ...

Correct determination of absolute paleointensities is essential to investigate past geomagnetic field. There are two types of methods to obtain the paleointensities: the Thellier-type and Shaw-type methods. Many paleomagnetists have so far regarded the former method as reliable. However, there are increasing ...

This paper reports an empirical test of a new nonheating Preisach-based protocol for determining the absolute ancient magnetic field intensity (paleointensity) using a selection of synthetic samples and a large suite of modern lavas and pyroclastic lithic samples. Generally, the Preisach paleointensity estimates compare favorably with ...

Since the 1970s, Thellier and Shaw methods have been most commonly used to determine absolute paleointensity of the geomagnetic field. The principles behind these methods are the same in using thermal remanent magnetization but very different in demagnetization techniques and reliability checks. For ideal samples (e.g. assemblage of ...

For the sake to calibrate the absolute value of the �relative paleointensity variation curve� drawn from sediment cores, Takai et al. (2002) proposed to use pyroclastic flows co-bearing with wide spread tephras. The pyroclastic flows prepare volcanic rocks with TRM, which let us determine absolute ...

Geomagnetic paleointensity estimates are being generated from approximately 45 samples of the Bishop Tuff. Absolute paleointensity data ... ...

Absolute paleointensity estimates from submarine basaltic glass (SBG) typically are of high technical quality and accurately reflect the ambient field when known. SBG contains fine-grained, low-Ti magnetite, in contrast to the high-Ti magnetite in crystalline basalt, which has lead to uncertainty over the origin of the magnetite and its remanence in SBG. ...

Forty-four volcanic units were sampled on the Equatorial Atlantic Island of Fernando de Noronha, Brazil. Twenty-seven sites are from the 1.8-3.3Myr old Quixaba formation, and the others are from the approximately 8-12Myr old Remedios formation. Analyses of paleodirections yielded normal and reverse polarities in both formations with virtual geomagnetic poles (VGPs) and VGP dispersion (Sf) of ...

Tanaka and Kobayashi (2003) reported a paleosecular variation in directions from 21-84 ka volcanic rocks of the Ontake Volcano, Japan. They found two low latitude VGPs from 48 ka (41.9N, 196.2E) and 80 ka (15.9N, 183.3E) lavas, indicating existence of excursions in Japan during the latest Pleistocene. Following this study, we have tried absolute ...

Absolute paleointensity values of the geomagnetic field, measured using microwaves, are obtained from chilled margin samples of proterozoic dykes from the southern superior province of the Canadian Shield. Two age groups of dykes are studied; the 2446-2473 Ma Matachewan swarm, and 2076-2170 Ma dykes from the Biscotasing, Marathon and Fort Frances swarms. ...

The Siberian trap basalts erupted during a short period of ~1 Myr at the Permo-Triassic boundary. It provides a unique opportunity to study absolute paleointensity during this one of the best-dated periods of Paleozoic era. Previous studies suggest relatively low paleointensity values (Heunemann et al. 2004), result that leads the ...

The study of short-term secular variation of geomagnetic field intensity is hampered by the fact that most paleomagnetic recording media do not fulfill the requirements for absolute paleointenisty determinations. Suitable materials are rare and when found may often be hard to date. Copper-slag, an industrial waste of an ancient copper smelting procedure, was recently ...

The sequence of geomagnetic field reversals is widely used to date events younger than 160 Ma, with a resolution of a million years. In oceanic domains, Vine and Matthews (1963) magnetic anomalies have been successfully used for more than 35 years. The major limitation of this chronometer is its low temporal resolution, especially for the recent times: the youngest polarity reversal, between ...

Paleomagnetic and rock magnetic measurements have been made on samples from the 1914 and 1946 Sakurajima andesitic lava flows in order to investigate the suitability of andesite to record both paleodirection and paleointensity. The lava flows were split in to three sites, each of which consists of two or three sub-sites. A range of rock magnetic experiments have been made on ...

Tremendous effort has been put into determination of the intensity behavior of the ancient geomagnetic field yet the details, particularly in the more distant past remain poorly constrained. Submarine basaltic glass has been shown to be nearly ideal material, rock magnetically speaking, for determining absolute paleointensity because it contains single ...

Paleomagnetism of Archean rocks potentially provides information about the early development of the Earth and of the geodynamo. Precambrian layered intrusive rocks are good candidates for paleomagnetic studies: such complexes are commonly relatively unaltered and may contain some single-domain magnetite `armored' by silicate mineral grains. However, layered intrusives often have a strong ...

A precise 40Ar/39Ar age and paleointensity data for the Cretaceous lava flow from Chifeng, southern Inner Mongolia, northeastern China are presented in this study. Detailed rock magnetic investigations including the variation of magnetization with temperature, low temperature susceptibility and hysteresis loops show that pseudo single domain (PSD) grain size high-Ti ...

The Mono Lake geomagnetic excursion was defined from the study of lacustrine sections from Western North America [Denham, 1974; Liddicoat et al., 1979]. The proposed age for this excursion reported in the literature changed in time since the first observation and a debate was even very recently opened about the reliability of the dating at the original section at Wilson Creek. In ice cores, a peak ...

In the last decade, the microwave demagnetization and remagnetization techniques have been successfully incorporated into the Thellier-type method for absolute paleointensity determination. As for the Shaw-type method, similar efforts should be made and thus we have tried to incorporate the microwave techniques into the low temperature ...

In the last decade, the microwave demagnetization and remagnetization techniques (Walton et al., 1992, 1993) have been successfully incorporated into the Thellier-type method for absolute paleointensity determination (e.g. Shaw et al., 1996; Hill and Shaw, 1999). In contrast to the conventional heating by electric ovens for laboratory ...

We present a compilation of experiments of absolute paleointensity using double heating protocols on very recent lava flows from Hawaii, La R�union, the Canary islands and Santorini. The existence of a sharp distribution of grain sizes carried by a single mineralogical phase always yielded successful determinations of paleointensity ...

A rock-magnetic, paleomagnetic and paleointensity study was carried out on Pliocene volcanic formations from Los Tuxtlas (Trans Mexicain Volcanic Belt) in order to obtain some decisive constraints for the geomagnetic field strength during Pliocene time. Age of the volcanic units lies between 3.1 and 0.8 Ma according to available radiometric data. Thermomagnetic investigations ...

The Unzen Volcano in Japan is a composite volcano consisting of lava domes, lava flows, and pyroclastic deposits with compositions ranging between andesite and dacite. The volcano is subdivided into the Older and Younger Unzen Volcanoes with active periods 150-500 and 0-150 ka, respectively (Hoshizumi et al., 1999). Paleomagnetic cores were collected from 69 sites, and ...

Seven H-group meteorites were studied for paleointensity determination. The method used was the Thellier and Thellier double step heating method. The reiability of the results was estimated from the demagnetization behavior and from the shape of the pTRM/NRM curve. The best values are obtained for Prairie Dog Creek (H3: 1.4 Oe), ...

Paleomagnetic measurements were conducted on Datong volcanic rocks from China, which are thought to have formed in the mid to early Brunhes Chron. Meaningful site-mean paleodirections were obtained from 21 sites which are considered to represent 17 independent cooling units. They give a mean VGP (virtual geomagnetic pole) position of (76.5�N, 7.9�E) with A95=7.7� (N=17), which is ...

Archaeointensity results from 10 pottery fragments from the Kaminaljuyu area (14�37?N, 90�32?W)�Guatemala, whose ages range from 100 to 900 B.C., were determined in order to contribute to the incipient intensity secular variation curve for the preclassic period in Mesoamerica. Magnetic experiments including hysteresis loops, IRM-DIRM and Curie temperature analysis indicate that ...

Fifty years have passed since �mile and Odette Thellier proposed the method of paleointensity determination which bears their names. Although there are precursors in the work of Koenigsberger, credit for the fundamental notion of partial TRMs as building blocks for the construction and reconstruction of thermally produced remanences in nature and the ...

A representative collection of Cretaceous rocks of Mongolia is used for the study of the magnetic properties of the rocks and for determination of the paleodirections and paleointensities H anc of the geomagnetic field. The characteristic NRM component in the samples is recognized in the temperature interval from 200 to 620-660�C. The values of H anc are determined by the ...

During the last 25,000 years there has been low secular variation in the Pacific region. A large directional dataset for this specific time window already exists but will be enlarged by the inclusion of results from our recent analysis of rocks from Hawaii. In addition to the directional data, we have also obtained paleointensity values for a significant number of the samples ...

Recent numerical simulations have yielded the most efficient geodynamo, having the largest dipole intensity when reversal frequency is low. Reliable paleointensity data are limited but heretofore have suggested that reversal frequency and paleointensity are decoupled. We report data from 56 Thellier-Thellier experiments on plagioclase ...

Since a pseudotachylyte is generated through a combination of comminution and frictional melting, it may record an ambient Earth's magnetic field as a thermal remanence during the cooling from friction melt. To test the reliability of determining the paleointensity, the Coe-modified Thellier method was carried out on a small suite of pseudotachylytes in ...

A successive paleointensity variation of the Late Cretaceous (~73.1 Ma) was obtained from the six consecutive lava flows at Jeon-gok Volcanic Complex (JVC) in Korea. A total of 283 samples were collected vertically from the bottom of the flow exposures. For the paleointensity determination, over 200 samples were subjected to the ...

We present Thellier paleointensity data from Vaigat Formation lavas erupted during magnetochron C26r (age ~60 Ma) in west Greenland. The lavas were emplaced in flow fields, as demonstrated by detailed field observations, the finding of consecutive lavas recording the same paleomagnetic field (intensity and direction), and similar composition suggestive of ...

The ability to control magnetic interactions between grains is of fundamental importance in paleointensity studies. We continued to perform experimental simulations to help understand the effect of magnetostatic interaction on Thellier type paleointensity experiments, using artificial synthesized magnetite grains mixed with both ...

We developed an integrated paleointensity measurement scheme to test different analytical protocols and to study the within-site distribution of the resulting sample paleointensity values. We experimented on 24 lava samples from 4 sites from Floreana in the Galapagos Islands, selected on the basis of a paleosecular variation study [D.V. Kent, H. Wang and ...

Data on the long-term evolution of the Earth's magnetic field strength are crucial for understanding mechanisms of geodynamo and constraining models of planetary evolution. Correct interpretation of paleointensity data, however, is ultimately based on our understanding the processes responsible for the formation and preservation of paleointensity signal in ...

The global absolute paleointensity (PINT) database, sponsored by the International Association of Geomagnetism and Aeronomy, recently was updated with new data and published alongside a new queryable interface at http://earth.liv.ac.uk/pint/. Absolute paleointensity determinations are spot readings of the strength ...

The magnetic behavior of synthetic analogs of the carriers of the natural remanent magnetization in stably magnetized lunar samples is studied in order to evaluate standard methods for the determination of paleomagnetization. Synthetic analogs of the iron bearing troilite phases associated with mare basalts that are stable to alternating field demagnetization were prepared by heating mixtures of ...

We have measured the variation in the intensity of the geomagnetic field during the Gauss-Matuyama (N4-R3) polarity reversal by application of the Thelliers' method to specimens of lava flows from Hvalfj�rdur district in Western Iceland (Reynivallahals Mts.). Eleven lava flows all show very similar directions corresponding to an equatorial VGP (Plat=2.9�N, Plong=81.9�E, ...

Thellier-Thellier paleointensity experiments were carried out on sixty-six basaltic samples coming from three Emperor seamounts (Detroit, Nintoku and Koko) drilled during ODP Leg 197. Twelve samples yield reliable results. One samples from De- troit seamount (81 Ma) gives a VADM of 3.06+/-0.26�1022 Am2. Six samples from Nintoku (56 Ma) give VADMs between ...

A collection of 220 samples from Early Jurassic Newark Supergroup volcanic units (Watchung, Talcott, Holyoke, Hampden and Deerfield basalts) and intrusive units (Manitook and Palisades sills), was studied with the aim of testing the previously suggested occurrence of a low average dipole moment of the Earth's magnetic field some 200 Ma ago. After viscosity tests, alternating field demagnetization ...

We have studied rock magnetic properties of 103 lava flows erupted from Haleakala Volcano on the Island of Maui in Hawai'i. Ages of the flows range between 365�40 years to 52,900�1800 years BP, as determined by 14C dating and comparisons to paleomagnetic directions between flows. Sherrod et al. [JGR, 111, 2006], and Herrero-Bervera and Valet [PEPI, 167, 2007] have previously undertaken ...

Geomagnetic paleointensity determination have been made by the Thellier method using samples from 27 sites in Bulgaria. The samples include bricks, specimens taken from historic kilns, from prehistoric hearths and the sites of ancient fires. The ages of the samples, which range from about 4500 B.C. to the 19th century A.D., have been determined partly by ...

To evaluate the magnetic properties of submarine and subaerial basaltic glass recovered by drilling during ODP Leg 197 at Detroit Seamount (ODP Site 1203) and Koko Seamount (ODP Site 1206) we have conducted a series of rock magnetic measurements and transmission electron microscopy (TEM) analyses. These glass samples have very low natural remanent magnetizations (NRM < 50 nAm2/g) and their ...

Thellier-Thellier paleointensity experiments were carried out on sixty-six basaltic samples coming from three Emperor seamounts (Detroit, Nintoku and Koko) drilled during ODP Leg 197. Seventeen samples yielded reliable results. One sample from Detroit Seamount (81 Ma) gives a VADM of 3.0+/-0.2x1022Am2. Ten samples from Nintoku (56 Ma) give VADMs between ...

Recent archaeomagnetic studies, together with investigations of volcanic and sedimentary units, have greatly improved our record of Earth's magnetic field during the last millennium. Large datasets have allowed field reconstructions of high resolution, but a common deficiency in these models is a large hemispherical bias resulting from a relative lack of reliable intensity and directional data ...

The record of geomagnetic intensity captured in the 2.7 Ga Stillwater Complex (Montana, USA) provides a statistical description of the Archean geodynamo. We present results of modified Thellier paleointensity experiments on 441 core specimens, 114 of which pass strict reliability criteria. The specimens are from 53 sites spanning most of the Banded Series ...

A paleointensity study using the Thellier's method was made on Tertiary basaltic rocks in Inner Mongolia and Hebei Province, northeastern China. K-Ar ages were previously reported for all the rocks, which range around 6-8 Ma and 28-32 Ma. Sample selection was based on total quality of remanence behavior and rock magnetism. High stability to AF and thermal ...

Initial results of paleomagnetic studies of basaltic lava flows from three islands, Isabela, Santa Cruz and Bartra, Galapagos archipielago, focusing on the rock magnetic analyses and preliminary paleointensity determinations, are presented. Remanent magnetizations are well defined and stable to thermal and AF demagnetization. Magnetic susceptibility, remanent magnetization, ...

Here we compare methods of paleointensity analysis as applied to pottery shards. We prefer the Thellier technique because of its foundation in basic rock physics and its associated reliability checks. Nevertheless, we recognize that additional techniques may be useful on problematic samples. We start with multiple specimen techniques. These are attractive ...

A large volume of data on the paleointensity H an obtained by A.S. Bol�shakov and G.M. Solodovnikov is ignored in modern reconstructions because the authors did not indicate whether they used the check-point procedure for the detection of chemical alterations in rocks associated with determination of H an. The paper presents new values of H an determined by the ...

The effect os cooling rate on the intensity of low-field thermoremanent magnetization (TRM) in uniaxial, single-domain magnetite is calculated, using both numerical and analytical techniques. These calculations indicate that when a single-domain assemblage is cooled much more slowly than in a typical laboratory experiment, it can remain magnetically unblocked and in thermal equilibrium with an ...

On the basis of the Thellier palaeointensities reported so far it has been thought that the time-averaged virtual dipole moment (VDM) and virtual axial dipole moment (VADM) for the last few million years are almost the same as the present geomagnetic dipole moment (~8 � 1022 A m2). This estimate has been called into question, however, because recent studies have revealed ...

The San Quint�n volcanic field (SQVF) in Baja California (Mexico) consists of at least 13 volcanic complexes with about 30 lava flows. 40Ar/39Ar step-heating and 3He surface exposure dating experiments suggest eruption ages between 22 and 165 ka. Paleodirections of 14 flows reported here are consistent with normal secular variation. Because of low Curie temperatures and thermal alteration ...

Submarine basaltic glass (SBG) has gained increasing popularity in recent years as a material for use in magnetic paleointensity studies, as it behaves ideally in a Thellier-type paleointensity experiment. Questions have been raised regarding the timing and temperature of (titano-)magnetite formation, in part because the Ti content of ...

Over the past few decades a burgeoning number of relative paleointensity records derived from sediments has contributed greatly to knowledge of geomagnetic paleosecular variation. It is now broadly accepted that there have been repeated large changes in field strength during the Brunhes polarity interval and there are a significant number of geomagnetic excursions ...

We report a rock magnetic study of the magnetic properties of chondrules from the Allende and Mokoia carbonaceous chondritic meteorites. To characterise the magnetic carriers, we have made detailed magnetic hysteresis analysis including FORC measurements. We have also conducted isothermal acquisition unmixing analysis. We have determined the ancient magnetic field intensities ...

For a better understanding of the ancient magnetic field of the earth, paleointensities are essential. Pristine glass is often dominated by single domain magnetic remanence and alteration can be excluded to the most extent. However a major biasing factor is the magnetic cooling rate dependency. In this study, we validate the method used to correct this effect. A natural ...

Paleomagnetic and paleointensity data from Precambrian rocks are of great importance for understanding the early geodynamo and tectonic evolution of the Earth. We will present results from a rock magnetic and paleomagnetic investigation of basaltic lava flow sequences at Silver Mountain and Sturgeon River Falls in Upper Michigan. While the Silver Mountain and Sturgeon River ...

A combined geochronologic, paleomagnetic and paleointensity investigation has been performed on a lava sequence from the Hannuoba Basalts in northern China. Potassium argon (K Ar) dating indicates that the lava sequence is of late Oligocene to middle Miocene age (�24 15 Ma). Rock magnetic measurements of thermomagnetic curves, hysteresis properties, saturation isothermal ...

ODP leg 203 took place in June-July 2002 and aimed at the drilling of a re-entry hole for the deployment of a future multidisciplinary observatory in the western equatorial Pacific. Eighty-seven meters of basement material were drilled in a 10-12Ma lithosphere. There are very few deep boreholes in "normal" oceanic crust, magnetic measurements on samples collected during this leg can therefore ...

Paleointensity studies have been conducted on six mafic dyke swarms from the Superior Province in Canada with U-Pb ages between 1141 Ma and 2473 Ma (Buchan et al., Tectonophysics 319 (2000) 167-198). The mean direction of the characteristic magnetization for each dyke swarm coincides with results of earlier studies in which the primary origin of the magnetization was ...

We have conducted paleointensity measurements of lavas and pyroclastic flows from Unzen Volcano, Japan. They have been shown in a previous study to contain a record of Brunhes Chron secular variation, with one flow recording a transitional direction (Senbongi geomagnetic excursion; 191 � 17 ka). Various rock magnetic analyses indicate that the main magnetic carriers of ...

We present new paleointensity and paleodirectional data from 100 volcanic sites in the Erebus Volcanic Province (EVP), Antarctica and twenty-one new age determinations by the 40Ar/39Ar incremental heating method. The new EVP data are combined with previously published paleomagnetic and geochronological results, providing a total of 141 sites. 91 sites have been dated and span ...

As part of the effort to establish an archeointensity variation curve for Mesoamerica, 13 archeologically well-identified pottery samples belonging to the Ocozocoautla site (Chiapas) were studied. Analyzed samples consist of 'ofrenda type' pottery fragments found in several caves. Three archeological intervals are involved: 450-100 B.C., 200-550 A.D. and 550-900 A.D. The ...

New Holocene geomagnetic paleointensity records have been constructed from the Western Antarctic Peninsula (WAP), Eastern Antarctic Peninsula (EAP), and from the East Antarctic Margin (EAM). The goal of this work is to develop Antarctic paleointensity reference curves for correlation and dating of Antarctic continental shelf sediments. Sediment sequences ...

We present rock magnetic and palaeointensity data from Holocene Icelandic lava flows, including historical and pre-historical lavas. Susceptibility versus temperature measurements indicate that the magnetic mineralogy is dominated by primary titanomagnetite that have experienced variable degrees of high-temperature oxidisation. The analyses also demonstrate that virtually all studied samples are ...

Statistical analyses of paleomagnetic data from lava flows are used to study geomagnetic field behavior on million year timescales. Previous paleomagnetic studies have lacked high-latitude measurements necessary to investigate the persistence of geomagnetic anomalies observed in the recent and historical field and replicated in some numerical geodynamo simulations. These simulations suggest that ...

Paleomagnetic studies of Faeroe Islands flood basalts (85 lava flows, in average 7 drill cores per flow) agree with the previously suggested C26N-C25R-C25N-C24R magnetostratigraphy. Some parts of the volcanic sequence are characterized by several consecutive flows recording the same paleomagnetic field directions. After grouping such flows into directional groups we obtain 37 independent readings ...

We carried out an integrated paleomagnetic, rock-magnetic and paleointensity study of Miocene volcanic succession from the trans-Mexican volcanic belt (TMVB) north of Guadalajara. A total of 37 consecutive basaltic lava flows (326 oriented standard paleomagnetic cores) were collected at Lazo locality. Continuous susceptibility measurements with temperature and hysteresis ...

The theoretical framework for a new nonheating method of determining absolute ancient magnetic field intensities (paleointensities) is described. The approach is based on a thermally activated Preisach model for interacting, randomly orientated single-domain grains with uniaxial anisotropy. The model includes theoretical features not accommodated by ...

A planetary body's ability to generate a dynamo is dependent on its thermal history and possible energy sources, particularly the convective states of the core and overriding mantle. This dissertation addresses questions regarding the characteristics of magnetic fields for both the Earth and the Moon. The temporal and spatial variations of the Earth's geomagnetic field are investigated using rock ...

A large variation in Phanerozoic geomagnetic reversal rate hints at changes in the core dynamo on time scales of tens of millions of years. Paleosecular variation and paleointensity data from igneous rocks can provide additional information bearing on the energy partitioning of the geodynamo. For example, the non-reversing dynamo of the Cretaceous Normal Superchron (CNS) was ...

Paleointensity of the Cretaceous normal superchron (CNS) has been studied using the middle Cretaceous Iritono granite of the Abukuma massif in northeast Japan. Our previous study [Wakabayashi, K., Tsunakawa, H., Mochizuki, N., Yamamoto, Y., Takigami, Y., 2006. Paleomagnetism of the middle Cretaceous Iritono granite in the Abukuma region, northeast Japan. Tectonophysics 421, ...

Single-domain (SD) particle ensembles are the best studied systems in rock magnetism. Yet, even for this simple system, a complete theoretical treatment of the acquisition of thermochemical remanent magnetization (TCRM) is missing. Based on the SD theory of chemical-remanent magnetization (CRM), it is generally taken for granted that TCRM acquisition is less efficient than acquisition of a ...

Single-domain (SD) particle ensembles are the best studied systems in rock magnetism. Yet even for this simple system, a complete theoretical treatment of the acquisition of thermochemical remanent magnetization (TCRM) is missing. On the basis of the SD theory of chemical remanent magnetization, it is generally taken for granted that TCRM acquisition must be less efficient than acquisition of a ...

Rock magnetometers based on superconducting quantum interference devices (SQUIDs) are currently the tool of choice for most paleomagnetic studies. Here we discuss the development of a new ultra-sensitive spin-exchange relaxation free (SERF) atomic magnetometer (Kominis, Kornack, Allred, Romalis, Nature, 422, 596-599, 2003) for paleomagnetic applications. The magnetometer utilizes the optical ...

New archeointensity values have been determined from seven Spanish kilns sampled at the same archeological site and dated by archeological constraints as between 1100 and 1200 A.D. The directions of the characteristic remanent magnetization and paleointensities have been obtained from classical Thellier experiments conducted on 69 samples collected from ...

Absolute palaeointensity determination is a long-winded and complicated procedure. The Thellier-Thellier technique, in particular, requires multiple heating and cooling steps. Magnetic minerals are often chemically unstable, and multiple heatings may cause oxidation, hence aiding the subsequent neo-formation of remanence carriers during the procedure. ...

We report a paleomagnetic study of the magnetic remanence recorded by a piece of the Allende carbonaceous chondritic meteorites. We have cut the sample up into sub-millimetre pieces to access the uniformity of the natural remanent magnetisation recorded through the meteorite. We have measured the anisotropy of anhysteretic remanent magnetization in the samples, to assess the degree to which ...

The famous Brunhes article establishing the reality of geomagnetic reversals was pub- lished in 1906. Brunhes' first researches in the field, however, date back to 1901-1902. It seems, therefore, appropriate to celebrate this 100th anniversary jointly with the 25th anniversary of the GSA publication of the classic Gubbio magnetostratigraphic study by our friend and colleague William Lowrie. We ...

Determining the strength of ancient planetary magnetic field is pivotal to understanding the evolution of planets and asteroids in the solar system. While the Thellier-type double heating technique provides the most faithful field strength information for rocks carrying a thermoremanent magnetization (TRM), many extraterrestrial rock samples respond unfavorably to heat ...

Variations of the Earth magnetic field during the first millennium B.C. in Western Europe remain not very well constrained, especially archeointensity. Three salt-kilns (MOA, MOB and MOC) sampled in Moyenvic (Lorraine, Eastern France) have been studied to provide new reference data. Each kiln has been dated by radiocarbon in the First Iron Age or Hallstatt period (between VIII and Vth Century BC). ...

Determining the absolute intensity of Earth's magnetic field from rocks has proven to be fraught with pitfalls that paleomagnetists have sought to overcome with carefully crafted but often tediously time-consuming measurement protocols. Without at least some form of protocol, little confidence is given to a paleointensity determination, and even with ...

Earth's dynamic history can be investigated by looking at the mark left in the paleomagnetic record. Core processes drive the continuously changing geomagnetic field, which has been recorded on Earth's surface by newly forming igneous rocks and sediments. We construct a continuous time varying model of Paleomagnetic Axial Dipole Moment (PADM) variations over the past two million years using ...

We have determined the paleointensity of eight lavas flows that recorded the last 10kyrs of geomagnetic field behavior from the youngest and largest of the two edifices of the island of Maui (i.e. Hana Volcanics, East Maui) with the multispecimen parallel differential pTRM method (Dekkers and Bohnel, EPSL, 248, 508-517, 2006). The flows are characterized by irreversible Curie ...

Chondritic meteorites are rare, yet incredibly valuable windows into the geophysical and geochemical environment of the early solar system. Dusty olivine grains containing exsolved nanometer-scale iron-nickel alloy inclusions are present in many chondritic meteorites and their remanent magnetization may give insight into the strength of the solar dynamo at the time of chondrule formation. ...

Paleointensities were determined by the Thellier method for six dated lava flows from the Cha�ne des Puys (France), with ages from 7 to 12 ka (ka=kiloannum before present). The three younger flow overlap the archaeomagnetic period for Europe, and the older flows extend the record to more ancient times. Our results support the quasi-sinusoidal variation ...

We present the results of analyzing a representative collection of the middle Miocene 12.4-10.0 Ma basalts that compose the volcanic cover of the Shufan and Sovgavan plateaus, namely the Nikolo-L'vovsk (NL) and Sovetskaya Gavan (SG) volcanic fields. Preliminary data are obtained about the relicts of some volcanic edifices within the West and East Sikhote-Alin volcanic belts, namely the ...

We have determined the paleointensity of nine lavas flows that recorded the last 10 kyrs of geomagnetic field behavior from the youngest and largest of the two edifices of the island of Maui (i.e. Hana Volcanics, East Maui) with the multispecimen parallel differential pTRM method [Dekkers and B�hnel, EPSL, 248, 508-517, 2006]. The flows are characterized by irreversible ...

We present new rock-magnetic and archaeointensity results of some pre-Columbian potteries found at archaeological caves in Chiapas, Southeast Mexico. The ceramics studied consist mostly of tiles of different archaeological artifacts. Their archeological ages cover mainly two ranges: from 550-250 BC and from 100-500 AD. `Rock-magnetic' experiments which included susceptibility vs. temperature and ...

A reliable and detailed record of the variation of the Earth's virtual dipole moment (VDM) provides important constraints for the understanding of geodynamo processes. However, the dataset available is very scarce. This holds true especially for the Mesozoic. An excellent opportunity to study the behaviour of the Earth's magnetic field with high temporal resolution are the Siberian Trap basalts, ...

Paleointensity data from Precambrian rocks are of great importance for understanding the evolution of early geodynamo. However the Precambrian paleointensity database remains very limited. Here we report new results of our rock magnetic and paleointensity investigations carried out on samples collected from a sequence of lava flows (11 ...

Absolute paleomagnetic field intensity data derived from thermally magnetized lavas and archeological objects provide information about past geomagnetic field behavior, but the average field strength, its variability, and the expected statistical distribution of these observations remain uncertain despite growing data sets. We investigate these issues for the 0 1 Ma field ...

Seventy Mid Miocene lava flows from flood basalt piles near Neskaupstadur (East Iceland) were sampled, which provide a quasi-continuous record of geomagnetic field variations. Samples were collected along the profile B of Watkins and Walker [Watkins, N., Walker, G.P.L., 1977. Magnetostratigraphy of eastern Iceland. Am. J. Sci. 277, 513-584], which was extended about 250 m farther down in a ...

Silicate minerals can contain minute magnetic inclusions that are well suited as recorders of the ancient magnetic field. In a magnetic hysteresis survey of natural minerals in 1997-1998, workers in the University of Rochester lab found that natural olivine and pyroxene separated from mafic lavas tended to contain multi- domain magnetic inclusions, whereas plagioclase feldspars hosted smaller ...

The paleomagnetism of superposed lava flows on Kauai, Hawaii shows that the ancient geomagnetic field was unusually strong following a reverse-to-normal polarity transition that occurred about 4 million years ago. Paleointensities were determined by a standard experimental procedure (Thelliers' method) that recreates the process of remanence ...

We present new results from basaltic lavas erupted in 1951 and 1995 on the island of Fogo, Cape Verde, to help link the success rate of palaeointensity experiments to specific rock magnetic properties. Variations on Thellier, Shaw, microwave and multi-specimen parallel differential pTRM methods, as well as the Wilson method were used to estimate historical palaeointensity, ...

A high-resolution Holocene paleomagnetic secular variation (PSV) and relative paleointensity (RPI) stack was constructed using u-channel paleomagnetic data from six radiocarbon-constrained marine sedimentary sequences raised along the main axis of the Laurentian Channel (eastern Canada), from its head to its mouth. Centennial- to millennial-scale declination and inclination ...

Thellier Thellier experiments were carried out on 216 lava samples collected by the USGS on the Big Island. 35 individual flows from the Kilauea, Mauna Loa and Hualalai volcanoes are represented and independent radiocarbon dating of the flows yields absolute ages ranging from 290 to 20,240 yrs old. The palaeomagnetic analysis was ...

There is a clear need of new archeomagnetic data from the southern hemisphere to better constrain the global geomagnetic field models over the past few millennia. In particular, less than 5% of all available absolute archeointensity data have been obtained from this hemisphere. We will present the first archeointensity data obtained for Brazil from the analysis of several ...

We have studied the paleomagnetism of the middle Cretaceous Iritono granite of the Abukuma massif in northeast Japan. Paleomagnetic samples were collected from ten sites of the Iritono garnite (102 Ma 40Ar- 39Ar age) and two sites of its associated gabbroic dikes. The samples were carefully subjected to alternating field and thermal demagnetizations and to rock magnetic analyses. Most of natural ...

Absolute paleomagnetic field intensity data derived from thermally magnetized lavas and archeological objects provide information about past geomagnetic field behavior, but the average field strength, its variability, and the expected distribution of these observations remain uncertain despite growing data sets. We investigate these issues for the 0-1 Ma field using data from ...

Current millennial-scale time-varying global geomagnetic field models suffer from a lack of intensity data compared to directional data, because only thermoremanently magnetized material can provide absolute information about the past field strength. The number of archeomagnetic artifacts that can provide such data diminishes rapidly prior to 3000 B.C. Sediment cores provide ...

Large numbers of Relative Paleomagnetic field Intensity (RPI) and Absolute Paleointensity (API) data have been used to study variations in Earth's magnetic field strength on million year timescales. We examine the behavior of the geomagnetic field and its time derivative in the PADM2M global model of Paleomagnetic Axial Dipole Moment variations for the ...

Modern geomagnetic field modeling and statistical simulations both indicate that paleointensity (as well as directional) data are necessary to provide an unbiased view of paleosecular variation and the time-averaged geomagnetic field. It has also been speculated that very long term paleointensity variations might provide clues about the evolution of the ...

values, consistent with previous paleointensity data from norite. Craddock and Magloughlin study a series

Until recently, we thought we knew where ancestral Native Americans came from (central Siberia, then across Beringia), and when they arrived (about 13 000 cal BP, after a trek between the recently separated Canadian ice sheets after Fiedel, 2006). Recent theories of American origins postulate multiple pre-Clovis migrations including Transpacific or coastal voyages by Australians, Melanesians, or ...

Over millennial time scales, the atmospheric production of the cosmonuclid 10Be (half-life 1.387 � 0.012 Ma [Shmeleff et al., 2009; Korschinek et al., 2009]) is modulated by the geomagnetic field strength, following a negative power law (e.g. Lal, 1988; Masarik and Beer, 2009). With respect to paleomagnetic reconstructions, 10Be-derived paleointensity records can therefore ...

The Hawaiian volcanoes, in principle, offer the opportunity of observing the geomagnetic field behavior from present back to 5.72 Ma (from the Big Island of Hawaii to the island of Kauai). Thus, new paleomagnetic measurements coupled with radioisotopic dating are revolutionizing our understanding of the geodynamo by providing terrestrial lava records of the short-term behavior of the paleomagnetic ...

A detailed rock magnetic study of eight historical dacitic lava flows from Santorini, covering the time interval between 46 AD and 1950 AD, is presented along with palaeointensity determinations encompassing different experimental approaches such as: the classical Thellier-Thellier method (Thellier and Thellier 1959), Coe's version of ...

Volcanic glasses are often claimed to be one of the best materials for the paleointensity studies. However, it is usually difficult to find the correct paleointensity values to compare. In Kyusyu Island, Japan, there are a series of pyroclastic flows containing volcanic glasses. From those welded tuffs of the pyroclastic flows, we can carry out ...

that there may be a magnetostatic interaction effect operating near 300 �C in lunar Thellier�Thellier studies remanent magnetization (SIRM) (Sugiura and Strangway, 1980). The thermal demagnetizing effects of the lunar with special reference to effects of meteorite impact. Proc. Lunar Sci. Conf. 5th, 2827�2839. N�el, L., 1949

The failure of lunar samples to satisfy minimal criteria for classical paleointensity determinations has led to skepticism of the case for an ancient lunar dynamo. There are however practical and fundamental reasons why such experiments are doomed to failure in most lunar samples. In such methods, NRMs in successive blocking temperatures ranges are thermally demagnetized and ...

We carried out a detailed and continuous paleomagnetic re-sampling of the reversed-to-normal Eocene -36 Ma- geomagnetic transition recorded in the Liverpool (NSW, Australia) volcanic range [Hoffman, 1986]. Our main objective was to obtain a precise description of the variation in the paleofield vector (direction and absolute intensity) as the geomagnetic field reverses. With ...

Three kilns and a collection of baked bricks from Italian archaeological sites have been studied for archaeointensity determination using the Thellier method as modified by Coe. All sites are dated based on archaeological information and their ages range from 500 to 800 AD and 1500 to 1700 AD. Rock magnetic studies identify magnetite, Ti- magnetite and hematite as the main ...

Fragmentary knowledge on geomagnetic field intensity in Barremian-Cenomanian stage obtained from sediment rocks is summarized. Three types of periodical variations are revealed in the paleointensity behavior. The types differ by the amplitude and duration (tens of millennia, hundreds of millennia and more than million years). It is found that in all the magnetopolar intervals ...

Normalized remanence (relative geomagnetic paleointensity) records for the last 500 kyr can be matched between two Iceland Basin Ocean Drilling Program (ODP) sites (984 and 983) and correlated with other high-resolution records. Directional secular variation is, however, not easily correlated between sites due to inadequate recording, at these mean sedimentation rates (12-15 ...

The relative paleointensity of the earth's magnetic field from ODP Site 851 has been characterized by progressive decay towards polarity reversals, followed by sharp recovery of pre-reversal values [1]. We resampled the Gilbert-Gau� reversal boundary of this deep-sea core, and show that during demagnetization this `saw-toothed' pattern disappears. Further, the recently ...

We present new archeointensity results obtained from 127 potsherds and baked brick fragments dated from the last four millennia BC which were collected from different Syrian archeological excavations. High temperature magnetization measurements were carried out using a laboratory-built triaxial vibrating sample magnetometer (Triaxe), and ancient field intensity determinations were derived from the ...

of Earth Sciences was presented. Among 14 specific sessions devoted to Geomagnetism and Paleomagnetism, one in the fields of rock-magnetism, paleointensity and paleomagnetism. The idea to publish the present special and Space 21 contributions dealing with paleomagnetic, rock-magnetic and paleointensity studies can be found

to obtain a relative paleointensity record in the Matuyama chron from this region. The core reached to about as KR0310-PC1 and covers the Brunhes chron (Yamazaki, 1999), was incorporated because the upper part in the late Matuyama chron is not lower than that during the Brunhes chron, which does not support

Determining the strength of the ancient geomagnetic field (paleointensity) can be time consuming and can result in high data rejection rates. The current paleointensity database is therefore dominated by studies that contain only a small number of paleomagnetic samples (n). It is desirable to estimate how many samples are required to obtain a reliable ...

Layered intrusions are a source for reliable measurements of the ancient geomagnetic field. Their magnetic properties are also an indirect record of crystal accumulation and postcumulus processes. This dissertation examines these two separate but related issues. Chapters 1, 2, and 3 focus on changes in geomagnetic field intensity over long time scales appropriate to changes in core-mantle boundary ...

The 8 ka B.P. (6050 BCE) pantelleritic obsidian flow on Mayor Island, Bay of Plenty, New Zealand, has been investigated using 30 samples from two sites. Due to a very high paramagnetic/ferromagnetic ratio it was not possible to determine the remanence carriers. This is despite the fact that the samples were studied intensively at low, room and high temperatures. We infer that a stable remanence ...

Comparison of the global and author's data on of the ancient geomagnetic field intensity with the reversal frequency and activity of the some endogenic processes (large basalt effusions, riftogenesis cyclic) was carried out. It was found that changes of the mean values of the paleointensity for a geological century and reversal frequency in an interval 0 - 160 million years ...

In the seven years since its development, the FORC method has evolved into a powerful new technique for probing the microscopic mechanisms of magnetic behavior. The original motivation for development of the method was to obtain more detailed information about the magnetic mineralogy and magnetic grain-size distribution of natural geologic samples consisting of magnetite, maghemite and/or ...

We report a survey carried out on basalt flows from Amsterdam Island (Southeastern Indian Ocean) in order to check the presence of intermediate directions interpreted as belonging to a geomagnetic field excursion within the Brunhes epoch, completing this palaeomagnetic record with palaeointensity determinations and radiometric dating. Because the palaeomagnetic sampling was done over a few hours ...

Amongst the multiple scientific activities of Prof. J.J. Hus one cannot deny major centres of interest in archaeology and our cultural heritage: in the footsteps of Prof. E. Thellier in France he applied to archaeology the principles of palaeomagnetism. His main objective was to establish reference curves for the secular variation of inclination and declination of the ...

We have performed a palaeointensity study of the Oshima 1986 lava in order to examine the reliability of the Thellier and LTD-DHT Shaw methods with special reference to high-temperature oxidation states of magnetic grains. Coe's version of the Thellier method was applied to fifteen specimens from five block samples. The palaeointensities determined by this ...

It has been suggested that volcanic glass is a perfect material for paleomagnetic research, especially for paleointensity studies, as it is often pristine and contains a magnetic fraction in the SD range. Furthermore, all biasing effects which are usually hard or impossible to detect in other recording media, are either absent or can be corrected for by using mineralogical and ...

The Columbia River basalts (CMB) are the smallest and youngest (17-5 Ma) large igneous province in the world, characterized by large individual flow volumes with both normal and reversed polarities. We have collected basaltic samples at sites distributed in large areas of the Columbia River Basalt province and applied our new paleointensity method on these samples for ...

Reversals in the polarity of Earth's magnetic field have long been used to provide age constraints on oceanic crust and other geologic materials. More recently, it has been recognized that shorter period variations in field intensity hold the potential for placing tighter age constraints on a variety of processes and materials. Archeological artifacts, sedimentary sections, and young volcanic ...

The double heating technique of the Shaw method with low-temperature demagnetisation (LTD-DHT Shaw method) for determination of geomagnetic palaeointensity is applied to samples exhibiting high-temperature oxidation states from the Kilauea 1970 lava, Hawaii Island. Results are obtained for 11 of the 12 specimens prepared from five block samples, yielding an average palaeointensity of 38.2 � 2.8 ...

In the pseudo-Thellier method for relative palaeointensity determinations (Tauxe et al. 1995) the slope of the NRM intensity left after AF demagnetization versus ARM intensity gained at the same peak field is used as a palaeointensity measure. We tested this method on a marine core from the Azores, spanning the last 276 kyr. We compared the pseudo-Thellier ...

Analysis of old paleomagnetic data and new mineral magnetic data from a sediment core from the central equatorial Pacific Ocean indicates that this core can be used for determination of relative geomagnetic paleointensity. These data indicate that during the Jaramillo subchron, there was a gradual decrease in paleointensity from the onset of the subchron ...

A detailed record of variations in the direction and intensity of the geomagnetic field over the past 1.2 Myrs has been obtained from an ~120-m-thick sedimentary section cored at ODP Site 980 on the Feni Drift (North Atlantic). The record has high resolution due to high mean sedimentation rates (11.3 cm/kyr for the Brunhes Chron and 5.5 cm/kyr for the Matuyama Chron), paleomagnetic measurements ...

A sedimentary record collected from beneath the former Larsen-A Ice Shelf reveals the Holocene history of the Larsen-A region. The record begins with the transition from grounded ice to a floating ice shelf, completed by 10.7 � 0.5 ka, and ends with the modern recession. The record contains several late Holocene diatomaceous ooze layers that suggest proximity to productive open-water events. ...

A technique has been developed for the encapsulation of rock samples in order to prevent the chemical alterations which commonly accompany paleointensity measurements at elevated temperatures. The technique involves vacuum pumping at about 100 C of the sample as placed in a silica tube. The tube containing the sample and a Ti 'getter' are sealed under vacuum. Measurements can ...

This dissertation addresses the resolution and reliability of paleomagnetic records obtained from oceanic and marine sediments, with a particular focus on records of relative geomagnetic paleointensity. It shows the methods used to recover such signals by constructing a high-resolution paleomagnetic record from the Ocean Drilling Program (ODP) Site 1101, which covers the ...

Time domain correlations of common features among relative paleointensity records from sedimentary cores are invaluable to paleomagnetism and paleoclimatology. Sediments with high accumulation rates might now provide millennial scale correlations of temporal variations in the geomagnetic dipole moment. Errors in the ages of paleomagnetic data samples, however, can make such ...

We have studied the short-term evolution of the geomagnetic field recorded by long volcanic sequences in Iceland and Hawaii. The eastern Icelandic sequences correspond to 45 and 49 individual lava flows sampled and range in age from 12.9 to 10.21 Ma as reported by Watkins and Walker [Watkins and Walker, 1977. Am J. Sci. 277, 513-584] and are labeled as profiles C and D. Also sampled were long ...

During IODP Expeditions 320 and 321, basement basalts with estimated ages of about 53, 50, 46, 38, 26, 24 and 18 Ma were recovered from eastern equatorial Pacific. We took cylindrical mini cores with 2.5 cm diameter from split core-catcher samples or working halves. From Site U1337 (estimated crust age of 24 Ma), four and two mini cores were taken from azimuthally un-oriented core segments with ...

In areas far away from active plate boundaries and previously glaciated regions, ecologically sensitive coral reefs provide an ideal laboratory for studying the timing and extent of deglaciation events as well as climatic change/variability at sub-millennial timescales. We have studied the Post Last-Glacial-Maximum (Post-LGM) coral reef terrace sediments recovered from the island of Tahiti on IODP ...

... Title : Hoeren unter Wasser: Absolute Reizschwellen und Richtungswahr nehnumg (Underwater Hearing: Absolute Thresholds and Sound ...

... Title : Absolute Gravity Measurements with Reversible Pendulums at Potsdam, 1968-1969 (Absolute Schwaremessungen mit Reversionpendein in ...

Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission. ARCADE Launching 2001 ARCADE logo. The Absolute Radiometer for Cosmology, ...

Conventional Thellier and microwave (MW) palaeointensity experiments, accompanied by rock magnetic tests, were conducted on samples from an early Tertiary (ca. 49 Ma) basaltic intrusion [the Peats Ridge (PR) basalt] from the Sydney Basin. Thermomagnetic and low-temperature susceptibility measurements suggest that the dominant magnetic mineral is Ti-enriched titanomagnetite ...