Geomagnetic secular variation in the Cretaceous Normal Superchron and in the Jurassic

Biggin, Andrew J.; Hinsbergen, Douwe J.J. van; Langereis, C.G.; Straathof, Gijs; Deenen, M.H.L.

doi:10.1016/j.pepi.2008.07.004

Cited by 159 publications

(286 citation statements)

References 53 publications

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“…The calculated value of VGP scatter (S) utilizing a within site correction (see Biggin et al (2008)) is 10.1. This value is lower than the value of 13.0 recently reported by Veikkolainen & Pesonen (2014), which was based on 27 sites taken from Gose et al (2006) and lower still from the value of 14.2 reported by Smirnov et al (2011) calculated from 15 sites.…”

Section: Paleosecular Variationmentioning

confidence: 99%

A new grand mean palaeomagnetic pole for the 1.11 Ga Umkondo large igneous province with implications for palaeogeography and the geomagnetic field

Swanson‐Hysell¹,

Kilian²,

Hanson

2015

Geophysical Journal International

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corresponds with a normal or reversed geomagnetic field relative to other continents can constrain the relative orientations between cratons with time-equivalent data. This interpretation is particularly important in comparison to Laurentia as it bears on Kalahari's involvement and position in the supercontinent Rodinia. The dominance of south-directed declinations within the Umkondo Province was previously used to suggest that these directions are the same polarity as reversed directions from the early magmatic stage of the Keweenawan Midcontinent Rift of Laurentia. Two Umkondo sills with northerly declinations have U-Pb baddeleyite ages of ca. 1109Ma that are temporally close to dated Midcontinent rift units having reversed directions. Based on this comparison, and paleomagnetic data from younger units in the Kalahari Craton, we favor the option in which the sites with northerly declinations from the Umkondo Province correspond to the reversed polarity directions from the early magmatic stage in the Midcontinent Rift. This interpretation allows for the Namaqua-Natal metamorphic belt of Kalahari to be a conjugate to the Grenville margin of North America and for Kalahari to have become conjoined with Laurentia within the supercontinent Rodinia subsequent to Umkondo LIP magmatic activity. IntroductionPaired paleomagnetic and geochronologic data demonstrate that between ca. 1112 and 1108 Ma there was large-scale magmatism across the Kalahari Craton over an area of ∼2 x 10 6 km 2 ( Fig. 1; Hanson et al., 2004a). Extrusive components of this province are exposed as tholeiitic basalts that occur at the top of the Umkondo Group in Zimbabwe and Mozambique (Swift, 1962;McElhinny, 1966;Moabi et al., 2015) and as rhyolite lavas, pyroclastics and tholeiitic basalts within the Kgwebe Formation of northern Botswana (Modie, 1996;Hanson et al., 2006). However, the majority of exposed remnants of the Umkondo Large Igneous Province (LIP) are shallow-level mafic intrusions de Kock et al., 2014) which are interpreted as feeders to more extensive flood lavas that have largely eroded away (Hanson et al., 2004a).The widespread extent of these intrusions has led to the inference that the lavas covered nearly Swanson-Hysell et al. (2015) (2011) for sources for the geological data. The inset map shows the location of the main map and the broader geological context. The thick translucent gray line on the inset map indicates the interpreted shape of the Kalahari Craton on the interior of the late Mesoproterozoic orogenic belts that is used in the paleogeographic reconstructions (Fig. 4) (Hanson et al., 2004bSöderlund et al., 2010), post-1.83 Ga dolerite sills in the Soutpansberg Group (Brandl, 1981(Brandl, , 1985Geng et al., 2014), and the widespread 0. basement correspond to the Umkondo event is a reasonable one, it is largely untested since there are precise age constraints for only a small fraction of the total exposed intrusions. If high-quality paleomagnetic data can be generated from a given sill, the distinct paleomagnetic poles ...

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Section: Paleosecular Variationmentioning

confidence: 99%

A new grand mean palaeomagnetic pole for the 1.11 Ga Umkondo large igneous province with implications for palaeogeography and the geomagnetic field

Swanson‐Hysell¹,

Kilian²,

Hanson

2015

Geophysical Journal International

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“…Recently, Biggin et al (2008) carefully investigated two key intervals: the Cretaceous Normal Superchron (CNS: 84−125 Ma) when the field was dominantly of a single polarity for 40 Ma and the Jurassic (145−200 Ma), when reversals occurred at an average rate of as much as 4.6 Myr −1 . These are actually periods of time in which the geomagnetic reversal frequency was dramatically different and thus different styles of secular variation are expected.…”

Section: Introductionmentioning

confidence: 99%

Paleomagnetism of early cretaceous arapey formation (Northern Uruguay)

et al. 2010

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We report detailed rock-magnetic and paleomagnetic directional data from 35 lava flows (302 standard paleomagnetic cores) sampled in the Central-Northern region of Uruguay in order to contribute to the study of the paleosecular variation of the Earth's magnetic field during early Cretaceous and to obtain precise Cretaceous paleomagnetic pole positions for stable South America. The average unit direction is rather precisely determined from 29 out of 35 sites. All A 95 confidence angles are less than 8°, which points to small within-site dispersion and high directional stability. Normal polarity magnetizations are revealed for 19 sites and 10 are reversely magnetized. Two other sites yield well defined intermediate polarities. The mean direction, supported by a positive reversal test is in reasonably good agreement with the expected paleodirection for Early Cretaceous stable South America and in disagreement with a 10° clockwise rotation found in the previous studies. On the other hand, paleomagnetic poles are significantly different from the pole position suggested by hotspot reconstructions, which may be due to true polar wander or the hotspot motion. Our data suggest a different style of secular variation during (and just before) the Cretaceous Normal Superchron and the last 5 Ma, supporting a link between paleosecular variation and reversal frequency. K e y wo r d s : paleosecular variation, Cretaceous paleomagnetic poles, Paraná Magmatic Province, Uruguay M.C. Solano et al. 534 Stud. Geophys. Geod., 54 (2010)

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“…Делались также предсказания, что амп-литуда вековых вариаций (кучность может быть использована как один из параметров для оценки этой амплитуды) должна заметно отличаться для суперхронов одной поляр-ности и эпох с частой сменой полярности [McFadden et al, 1988], что в целом подтверж-далось имевшимися тогда данными. Спра-ведливости ради надо заметить, что повтор-ная проверка, проведенная недавно для гораздо большего массива более надежных данных, вроде бы подтвердила предсказание, но, по сравнению с предыдущим анализом [McFadden et al, 1988], выявила гораздо меньшие различия, близкие к данным со ста-тистическими погрешностями [Biggin et al, 2008b]. Среди приведенных на рис.…”

Section: интерпретация и обсуждение результатовunclassified

“…А что же со вторым предположением? Допускалось, что амплитуда вариаций может зависеть от частоты инверсий [Tarduno et al, 2002;Biggin et al, 2008b], о чем уже гово-рилось выше. Есть работы, в которых утверждается, что в архее уровень вариаций был ниже [Biggin et al, 2008a;Smirnov et al, 2011].…”

Section: интерпретация и обсуждение результатовunclassified

Late Paleozoic Geomagnetic-Field Estimates From Paleomagnetic Studies of Permian Lavas in Northeastern Kazakhstan

2014

GiG

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Одним из наиболее надежных способов получить информацию о характеристиках древнего гео-магнитного поля является палеомагнитное изучение мощных лавовых толщ. Однако на сегодня данные такого типа чаще всего имеют возраст менее 5 млн лет, их гораздо меньше для остальной части кайнозоя и всего мезозоя, есть два полноценных результата по докембрийским породам, но их совершенно нет для палеозоя. С целью получить первые оценки характеристик геомагнитного поля в эту эру было про-ведено исследование толщи позднепермских базальтов и риолитов Северо-Восточного Казахстана. В данной статье представлены предварительные результаты по части коллекции (66 потоков (сайтов)) из разреза мощностью около 1600 м. С помощью ступенчатой чистки во всех сайтах с небольшой погреш-ностью была выделена характеристическая компонента обратной полярности. Эта компонента имеет доскладчатый возраст и, вероятнее всего, первична. Во всей совокупности данных не найдено ни одного аномального направления намагниченности, а средние направления характеристической компоненты по сайтам хорошо сгруппированы (склонение D = 243.3°, наклонение I = -57.0°, кучность k = 79.1, ра-диус круга доверия α 95 = 2.0°, 65 сайтов). Сравнение с опубликованными данными по мощным лавовым сериям кайнозоя и мезозоя показывает, что вековые вариации в поздней перми были намного слабее, чем в мезозое и кайнозое, а само геомагнитное поле было менее возмущенным. Еще большее различие обнаружено по отношению к моделям вековых вариаций, построенным на основе позднекайнозойских данных. Геомагнетизм, палеомагнетизм, палеозой, мощные лавовые толщи, характеристики геомаг-нитного поля. LATE PALEOZOIC GEOMAGNETIC-FIELD ESTIMATES FROM PALEOMAGNETIC STUDIES OF PERMIAN LAVAS IN NORTHEASTERN KAZAKHSTANM.L. Bazhenov, R. Van der Voo, J.J. Meert, N.M. Levashova, and I.S. Ipat'eva Paleomagnetic studies of thick lava series are one of the most reliable sources of data on the ancient geomagnetic fi eld. However, most of such data are younger than 5 Ma, with much fewer results on the rest of the Cenozoic and the Mesozoic. Two wholesome results are available for the Precambrian but none for the Paleozoic. Late Permian basalts and rhyolites from northeastern Kazakhstan were studied to obtain fi rst estimates of the geomagnetic-fi eld characteristics during that period. We present preliminary results on part of the collection (66 fl ows (sites)) from a section ~1600 m thick. The characteristic component of reversed polarity was isolated by stepwise demagnetization at all the sites with a slight error. This component is of prefolding age and, most likely, primary. No abnormal magnetization direction is observed in the data, and the average directions of the characteristic component at the sites are tightly clustered (D = 243.3º; I = -57.0º, k = 79.1; α 95 = 2.0º; 65 sites). As compared with the published data on Cenozoic and Mesozoic thick lava series, secular variation was much weaker in the Late Permian than in the Mesozoic or Cenozoic, and the geomagnetic fi eld was less disturbed. Secular-variation m...

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Geomagnetic secular variation in the Cretaceous Normal Superchron and in the Jurassic

Cited by 159 publications

References 53 publications

A new grand mean palaeomagnetic pole for the 1.11 Ga Umkondo large igneous province with implications for palaeogeography and the geomagnetic field

A new grand mean palaeomagnetic pole for the 1.11 Ga Umkondo large igneous province with implications for palaeogeography and the geomagnetic field

Paleomagnetism of early cretaceous arapey formation (Northern Uruguay)

Late Paleozoic Geomagnetic-Field Estimates From Paleomagnetic Studies of Permian Lavas in Northeastern Kazakhstan

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