Publications

2015

Monster, M. W. L., L. V. de Groot, and M. J. Dekkers (2015), MSP-Tool: a VBA-based software tool for the analysis of multispecimen paleointensity data, Frontiers in Earth Science, 3:86. doi: 10.3389/feart.2015.00086 (Open Access)

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MSP Tool is a VBA-based software tool that evaluates paleointensity data acquired using the multispecimen protocol. It calculates the three ratios according to the commonly adopted protocols, as well as a number of other parameters proposed by Fabian and Leonhardt (2010). Data are analyzed using bootstrap statistics. A progressive alteration criterion and the location where the multispecimen linear regression intersects the y axis serve as reliability checks. Furthermore, overprints and misalignment are detected by isolating the NRM remaining and pTRM gained and comparing their declinations and inclinations. The NRM remaining and pTRM gained are used to calculate ‘alignment-corrected’ multispecimen plots. The program was tested on lava samples that had been given a full TRM and that had acquired their pTRMs at angles of 0, 15, 30 and 90° with respect to their NRMs. MSP-Tool adequately detected and largely corrected these artificial alignment errors.

Monster, M. W. L., L. V. de Groot, A. J. Biggin, and M. J. Dekkers (2015), The performance of various palaeointensity techniques as a function of rock magnetic behaviour – A case study for La Palma, Physics of the Earth and Planetary Interiors, 242, 36–49, doi:10.1016/j.pepi.2015.03.004. (ScienceDirect)

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Three different palaeointensity methods were applied to six historical and three carbon-dated flows from the island of La Palma (Spain); in total fifteen sites were processed. The two 20th-century flows were sampled at multiple locations as their obtained directions and intensities can be compared directly to those from the International Geomagnetic Reference Field (IGRF). After determination of the declinations and inclinations of the natural remanent magnetisation (NRM) by thermal and alternating-field demagnetisation, the samples were subjected to standard rock magnetic analyses to determine their Curie and alteration temperatures. Based on these characteristics, the sites were allocated to one of four rock magnetic groups labelled L*, L, C, and H, a division primarily based on the temperature-dependent behaviour of the low-field susceptibility that has been used in studies of other volcanic edifices. Scanning elec- tron microscope (SEM) observations revealed little oxidation and exsolution (oxidation classes I to III). Palaeointensities were determined using the classic Thellier–Thellier method (Aitken and IZZI protocols), the microwave method and the domain-state-corrected multispecimen method. Thellier–Thellier and microwave results were analysed using the ThellierTool A and B sets of selection criteria as modified by Paterson et al. (2014). Their combined success rate was around 40%. Of the eight IGRF sites, two yielded average intensities within 10% of the IGRF value. For the microwave method, three sites repro- duced the IGRF intensity within 10%. In the domain-state-corrected multispecimen protocol, just one site (site 9, 1971) passed the ‘ARM-test’ (applied in retrospect) and showed less than 3% progressive alteration. Its multispecimen result reproduced the palaeofield within error. The other IGRF sites over- or underestimated the palaeofield by up to 50%. The seven older sites produced plausible palaeointensities, generally within a few lT of model data, and if multiple methods were successful, the results were within error of each other. For all three PI methods, it seems that sites with low Curie temperatures (<150 °C; group L⁄), are more likely to pass all selection criteria while substantially over- or underestimating the palaeofield. It is hypothesised that time-dependent processes after cooling of the lava would be a prime reason for this discrepancy: PI experiments with a laboratory thermoremanent magnetisation (TRM), imparted at a temperature above the site’s dominant Curie temperature but below its alteration temperature, yielded the correct intensity of the laboratory-imparted TRM. When two or three methods agree to within a few lT, the obtained palaeointensity is close to the palaeofield. Multi-method consistency provides an additional palaeointensity reliability check.

2010 (BSc project)

Semrau, S., M. W. L. Monster, M. van der Knaap, B. I. Florea, T. Schmidt, and M. Overhand (2010), Membrane lysis by gramicidin S visualized in red blood cells and giant vesicles, BBA – Biomembranes, 1798(11), 2033–2039, doi:10.1016/j.bbamem.2010.07.001. (ScienceDirect)

Theses

MSc thesis (Utrecht University, Geophysics, 2011): Comparison of the domain-state-corrected multispecimen method with the microwave and Thellier-Thellier methods using historical lavas from La Palma, Spain. (PDF)

BA thesis (Leiden University, History, 2010): Homoioi en hypomeiones. De syssitia en de afname van het aantal Spartanen. (About the Spartan syssitia.)

BSc thesis (Leiden University, Physics, 2009): The influence of the antimicrobial peptide gramicidin S on red blood cells and giant vesicles. (PDF)