Automated paleomagnetic and rock magnetic data acquisition with an in-line horizontal “2G” system

Mullender, Tom A. T.; Frederichs, Thomas; Hilgenfeldt, Christian; Groot, Loek; Fabian, Karl; Dekkers, Mark J.

doi:10.1002/2016gc006436

Cited by 75 publications

(67 citation statements)

References 35 publications

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“…Demagnetization steps used were 4, 8, 12, 16, 20, 25, 30, 35, 40, 45, 50, 60, and 80 mT for AF treatment and variable temperature increments up to 600 °C for thermal treatment. AF treatment demagnetization was performed on an in‐house developed robotized demagnetization device (Mullender et al, ). We plotted demagnetization diagrams on orthogonal vector diagrams (Zijderveld, ) and determined the magnetic components via principal component analysis (Kirschvink, ).…”

Section: Methodsmentioning

confidence: 99%

The Dynamic History of 220 Million Years of Subduction Below Mexico: A Correlation Between Slab Geometry and Overriding Plate Deformation Based on Geology, Paleomagnetism, and Seismic Tomography

Boschman

Hinsbergen

Kimbrough

et al. 2018

Geochem Geophys Geosyst

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Global tectonic reconstructions of pre‐Cenozoic plate motions rely primarily on paleomagnetic and geological data from the continents, and uncertainties increase significantly with deepening geological time. In attempting to improve such deep‐time plate kinematic reconstructions, restoring lost oceanic plates through the use of geological and seismic tomographical evidence for past subduction is key. The North American Cordillera holds a record of subduction of oceanic plates that composed the northeastern Panthalassa Ocean, the large oceanic realm surrounding Pangea in Mesozoic times. Here we present new paleomagnetic data from subduction‐related rock assemblages of the Vizcaíno Peninsula of Baja California, Mexico, which yield a paleolatitudinal plate motion history equal to that of the North American continent since Late Triassic time. This indicates that the basement rocks of the Vizcaíno Peninsula formed in the forearc of the North American Plate, adjacent to long‐lived eastward dipping subduction at the southern part of the western North American continental margin. Tomographic images confirm long‐lived, uninterrupted eastward subduction. We correlate episodes of overriding plate shortening and extension to flat and steep segments of the imaged slab. By integrating paleomagnetic, geological, and tomographic evidence, we provide a first‐order model that reconciles absolute North American plate motion and the deformation history of Mexico since Late Triassic time with modern slab structure.

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Section: Methodsmentioning

confidence: 99%

The Dynamic History of 220 Million Years of Subduction Below Mexico: A Correlation Between Slab Geometry and Overriding Plate Deformation Based on Geology, Paleomagnetism, and Seismic Tomography

Boschman

Hinsbergen

Kimbrough

et al. 2018

Geochem Geophys Geosyst

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“…Five specimens per site were subjected to AF fields of 2. 5, 5, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 70, 80, 90 and 100 mT, using a robotised 2G DC-SQUID magnetometer in a static 3-axes demagnetisation set-up (Mullender et al, 2016); all demagnetisation data were analysed using RemaSoft (Chadima and Hrouda, 2006). Thermal and AF NRM decay curves were obtained by plotting the NRM intensity as a function of temperature and AF field strength, respectively.…”

Section: Demagnetisation Of the Natural Remanent Magnetisationmentioning

confidence: 99%

Full-vector geomagnetic field records from the East Eifel, Germany

Monster

Langemeijer

Wiarda

et al. 2018

Physics of the Earth and Planetary Interiors

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A B S T R A C TTo create meaningful models of the geomagnetic field, high-quality directional and intensity input data are needed. However, while it is fairly straightforward to obtain directional data, intensity data are much scarcer, especially for periods before the Holocene. Here, we present data from twelve flows (age range ∼ 200 to ∼ 470 ka) in the East Eifel volcanic field (Germany). These sites had been previously studied and are resampled to further test the recently proposed multi-method palaeointensity approach. Samples are first subjected to classic palaeomagnetic and rock magnetic analyses to optimise the subsequent palaeointensity experiments. Four different palaeointensity methods -IZZI-Thellier, the multispecimen method, calibrated pseudo-Thellier, and microwave-Thellier -are being used in the present study. The latter should be considered as supportive because only one or two specimens per site could be processed. Palaeointensities obtained for ten sites pass our selection criteria: two sites are successful with a single approach, four sites with two approaches, three more sites work with three approaches, and one site with all four approaches. Site-averaged intensity values typically range between 30 and 35 μT. No typically low palaeointensity values are found, in line with paleodirectional results which are compatible with regular palaeosecular variation of the Earth's magnetic field. Results from different methods are remarkably consistent and generally agree well with the values previously reported. They appear to be below the average for the Brunhes chron; there are no indications for relatively higher palaeointensities for units younger than 300 ka. However, our young sites could be close in age, and therefore may not represent the average intensity of the paleofield. Three of our sites are even considered coeval; encouragingly, these do yield the same palaeointensity within uncertainty bounds.

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“…Samples were thermally demagnetized in a magnetically shielded furnace (residual field <10 nT) with steps of 20 to 30°C up to a maximum of 450°C. Alternating field demagnetization was applied in a magnetically shielded room with an in-house built robot with steps of 3 to 10 mT to a maximum of 100 mT (Mullender et al, 2016). For both methods, the remanent magnetization was measured after each demagnetization step with a 2G Enterprises DC SQUID magnetometer (2G Enterprises, Sand City, CA, USA) with an instrumental noise level of ca 2*10 À12 Am 2 ; typical NRM intensities were at least two orders of magnitude higher.…”

Section: Palaeomagnetismmentioning

confidence: 99%

Conceptual models for short‐eccentricity‐scale climate control on peat formation in a lower Palaeocene fluvial system, north‐eastern Montana (USA)

et al. 2017

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Fluvial systems in which peat formation occurs are typified by autogenic processes such as river meandering, crevasse splaying and channel avulsion. Nevertheless, autogenic processes cannot satisfactorily explain the repetitive nature and lateral continuity of many coal seams (compacted peats). The fluvial lower Palaeocene Tullock Member of the Fort Union Formation (Western Interior Williston Basin; Montana, USA) contains lignite rank coal seams that are traceable over distances of several kilometres. This sequence is used to test the hypothesis that peat formation in the fluvial system was controlled by orbitally forced climate change interacting with autogenic processes. Major successions are documented with an average thickness of 6Á8 m consisting of ca 6 m thick intervals of channel and overbank deposits overlain by ca 1 m thick coal seam units. These major coal seams locally split and merge. Time-stratigraphic correlation, using a Cretaceous-Palaeogene boundary event horizon, several distinctive volcanic ash-fall layers, and the C29r/C29n magnetic polarity reversal, shows consistent lateral recurrence of seven successive major successions along a 10 km wide fence panel perpendicular to east/south-east palaeo-flow. The stratigraphic pattern, complemented by stratigraphic age control and cyclostratigraphic tests, suggests that the major peat-forming phases, resulting in major coal seams, were driven by 100 kyr eccentricity-related climate cycles. Two distinct conceptual models were developed, both based on the hypothesis that the major peatforming phases ended when enhanced seasonal contrast, at times of minimum precession during increasing eccentricity, intensified mire degradation and flooding. In model 1, orbitally forced climate change controls the timing of peat compaction, leading to enhancement of autogenic channel avulsions. In model 2, orbitally forced climate change controls upstream sediment supply and clastic influx determining the persistence of peat-forming conditions. At the scale of the major successions, model 2 is supported because interfingering channel sandstones do not interrupt lateral continuity of major coal seams.1

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Automated paleomagnetic and rock magnetic data acquisition with an in-line horizontal “2G” system

Cited by 75 publications

References 35 publications

The Dynamic History of 220 Million Years of Subduction Below Mexico: A Correlation Between Slab Geometry and Overriding Plate Deformation Based on Geology, Paleomagnetism, and Seismic Tomography

The Dynamic History of 220 Million Years of Subduction Below Mexico: A Correlation Between Slab Geometry and Overriding Plate Deformation Based on Geology, Paleomagnetism, and Seismic Tomography

Full-vector geomagnetic field records from the East Eifel, Germany

Conceptual models for short‐eccentricity‐scale climate control on peat formation in a lower Palaeocene fluvial system, north‐eastern Montana (USA)

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