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espanolEn el presente trabajo se estudia la anisotropia de la susceptibilidad magnetica (ASM) en ... more espanolEn el presente trabajo se estudia la anisotropia de la susceptibilidad magnetica (ASM) en varias localidades del margen sudpirenaico. En rocas no deformadas la fabrica magnetica se interpreta como una fabrica sedimentaria que presenta una foliacion paralela a la estratificacion y los ejes kmax agrupados en una direccion preferente que representa la direccion de la paleocorriente. En rocas deformadas el elipsoide asociado a la ASM puede asemejar al elipsoide de deformacion atendiendo al grado de deformacion y a la relacion angular entre fabrica tectonica y fabrica sedimentaria previa. Se evalua tambien la importancia de la contribucion de la fase dia-paramagnetica en la fabrica magnetica en rocas con baja susceptibilidad media. EnglishThe magnetic susceptibility anisotropy of severa! deformed and weakly to non-deformed rocks from the southern Pyrenees has been studied. Shape and orientation of the sUsceptibility anisotropy ellipsoid from nondeformed rocks is related to a sedimentary fabric with magnetic foliation parallel to bedding and magnetic lineation (kmax axes) mostly parallel to the flow direction. This is demonstrated by consistency with standard sedimentological palaeoflow determinations in a detritic unit from the Oliana area. The magnetic fabric from sorne deformed rocks enables the time relationship between the magnetic fabric generation and folding to be determined. In one instance principal directions of the magnitude ellipsoid of susceptibility show orientations consistent with the kinematic fold axes. Another example shows a tectonic fabric which postdates folding. A third case allows the kinematic interpretation of "joint" development to be made. The interference of tectonic and sedimentary fabrics in weakly deformed rocks is evaluated. Moreover, the importance of the paramagnetic phase contribution to the_ magnetic fabric in rocks with low bulk susceptibility (K) is also considered.
Geophysical Journal International, 2005
We report on the magnetic properties and the acquisition of a chemical remanent magnetization (CR... more We report on the magnetic properties and the acquisition of a chemical remanent magnetization (CRM) in a field of 100 µT as a function of temperature and time during the lepidocrocitemaghemite-haematite reaction chain. The development of CRM was monitored at a series of 13 temperatures ranging from 175 to 550 • C; data acquisition was done at the specific formation temperatures for durations of up to 500 hr. Up to acquisition temperatures of 200 • C it takes a considerable time (up to 7 hr) before the CRM is measurable. This time decreases with increasing temperature, reflecting the activation energy of the reaction to form the first maghemite. During the lepidocrocite conversion, formation of two types of maghemite is suggested by two peaks in the CRM versus time curves. Magnetic properties were analysed after various stages in the reaction. They indicate a mixture of superparamagnetic and single-domain maghemite. The first reaction product (obtained after annealing at 200 • C) is a fine-grained yet crystalline maghemite (labelled type A). Before massive maghemite formation occurs, the coercive and remanent coercive forces go through a minimum at intermediate temperatures of 250-300 • C (annealing for 2.5 hr). This minimum lowers to 200-250 • C with increasing annealing time (500 hr). This is probably the result of two processes acting simultaneously-formation of superparamagnetic maghemite particles of a second less crystalline maghemite type (labelled type B) and removal of stacking faults in type A maghemite. The second process is suggested by analogy to the behaviour of natural magnetite/maghemite systems on annealing. Removal of stacking faults is reported to result in a magnetic softening of the grain assemblage. Annealing at 300-350 • C removes most of the lepidocrocite and the second maghemite type, type B, becomes prominent. Haematite formation sets in at slightly higher temperatures, yet the type B maghemite is in part thermally stable up to 600 • C enabling Thellier-Thellier experiments. This stability is also inferred from Arrhenius fitting that shows a comparatively high activation energy for the maghemite to haematite reaction. In Thellier-Thellier experiments the CRM showed a markedly downward convex Arai-Nagata plot while a second thermoremanent magnetization (TRM) showed perfect linear behaviour as expected. This feature may be used to recognize CRM in natural rocks.
Tectonophysics, 1987
A paleomagnetic investigation of the Lower Devonian Llandstadwell Eormation in southwest Wales ha... more A paleomagnetic investigation of the Lower Devonian Llandstadwell Eormation in southwest Wales has yielded a characteristic direction (declination = 196'. inclination =-5') that passes a fold test. Comparison of the corresponding virtual geomagnetic pole (334O E, 39OS) to previously published poles for Great Britain indicates that the magnetization is secondary and likely to be of Carboniferous age. No evidence for post-Herr&an rotation of Pembrokeshire is indicated by our data.
Physics of the Earth and Planetary Interiors
McClelland-Brown, E., 1982. Discrimination of TRM and CRM by blocking-temperature spectrum analys... more McClelland-Brown, E., 1982. Discrimination of TRM and CRM by blocking-temperature spectrum analysis. Phys. Earth Planet. Inter., 30: 405-4 14. Overlap of blocking-temperature spectra can be caused by three factors: chemical overprinting, the presence of partial thermoremanences (PTRM's) in two coexisting magnetic minerals, and the presence of PTRM's in coexisting multidomain and single-domain states of the same mineral. Multidomain relaxation mechanisms are not well understood and therefore quantitative estimates of overlap due to the coexistence of single-domain and multidomain states of the same mineral cannot be made, although it is evident that such overlap may be large. The maximum overlaps which would be expected at various temperatures due to coexisting single-domain magnetite and hematite are calculated. Where it can be shown that multidomain remanence is negligible, blocking-temperature overlaps which exceed these limits are, therefore, indicative of CRM overprinting.
Physics of the Earth and Planetary Interiors
ABSTRACT
Improving Schools
When language is processed, brain activity occurs not only in the classic ‘language areas’ such a... more When language is processed, brain activity occurs not only in the classic ‘language areas’ such as Broca’s area, but also in areas which control movement. Our systems of understanding, including higher level cognition, are rooted in bodily awareness which needs to be developed as a precursor to intellectual reasoning. Cognition is embodied, and this concept may offer a radical new way of improving school education by improving children’s systems of physical understanding. A new classroom physical intervention, called Move4words, based on embodied cognition, was developed for pupils aged 7–13 years and trialled with 348 typical pupils in 10 mainstream UK schools. Three pilot controlled trials showed significant improvements in academic performance, particularly for struggling pupils performing in the lowest 20 percent. Effect sizes were large for the lowest achievers: Hedges’ g = 0.86 for national examinations at age 11 (KS2 SATs) and g = 1.24 for progress through National Curriculum...
Palaeomagnetism is a powerful tool for identifying rotations about any axis. A palaeomagnetic stu... more Palaeomagnetism is a powerful tool for identifying rotations about any axis. A palaeomagnetic study in basement thrust sheets in the southern Axial Zone, Pyrenees, has demonstrated that 3-D rotations can be identified in basement terrain where no other palaeohorizontal markers exist. Three different movement histories are described within a stack of six thrust sheets. The lowermost unit has experienced doming and tilting about a horizontal axis at a different time Lo clockwise rotation about a vertical axis of 25'. '¡he middle four sheets have rotated clockwise by 35
Primary Teacher Update, 2013
Thrust Tectonics, 1992
ABSTRACT
Thrust Tectonics, 1992
ABSTRACT
The natural remanent magnetism of samples from the sheeted dike complex generated at the Costa Ri... more The natural remanent magnetism of samples from the sheeted dike complex generated at the Costa Rica Rift, drilled in Deep Sea Drilling Project/Ocean Drilling Program Hole 504B, can be resolved into a vertical drilling induced remanent magnetization and a shallow stable remanence by alternating field and thermal demagnetization. We investigate the unblocking temperature and coercivity spectra of these components, and compare these to spectra of thermal, induced, and viscous magnetizations imparted in the laboratory. The drilling-induced remanence is not a simple thermal, induced, or viscous remanence, but probably a piezoremanence acquired in an elevated field. The stable remanence may be a thermal remanence. Comparison of the stable remanence in altered and fresh samples indicates that natural remanent intensity and bulk susceptibility are reduced in more altered samples, but the stability and direction are similar to those in fresh samples. Whereas the stable components of the shee...
Terra Nova, 1996
... These include onland sections on Cyprus where G. margaritae has been found within gypsi-ferou... more ... These include onland sections on Cyprus where G. margaritae has been found within gypsi-ferous clays (Adam, 1976). ... In Late Tortonian time, coarse sediments shed from the evolving mountain belt (Grasso and Pedley, 19881, were ponded in basins in north-central Sicily ...
![Research paper thumbnail of Introduction [to Special Section: Magnetotectonics]](https://attachments.academia-assets.com/72077134/thumbnails/1.jpg)
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Journal of the Geological Society, 1999
ABSTRACT
espanolEn el presente trabajo se estudia la anisotropia de la susceptibilidad magnetica (ASM) en ... more espanolEn el presente trabajo se estudia la anisotropia de la susceptibilidad magnetica (ASM) en varias localidades del margen sudpirenaico. En rocas no deformadas la fabrica magnetica se interpreta como una fabrica sedimentaria que presenta una foliacion paralela a la estratificacion y los ejes kmax agrupados en una direccion preferente que representa la direccion de la paleocorriente. En rocas deformadas el elipsoide asociado a la ASM puede asemejar al elipsoide de deformacion atendiendo al grado de deformacion y a la relacion angular entre fabrica tectonica y fabrica sedimentaria previa. Se evalua tambien la importancia de la contribucion de la fase dia-paramagnetica en la fabrica magnetica en rocas con baja susceptibilidad media. EnglishThe magnetic susceptibility anisotropy of severa! deformed and weakly to non-deformed rocks from the southern Pyrenees has been studied. Shape and orientation of the sUsceptibility anisotropy ellipsoid from nondeformed rocks is related to a sedimentary fabric with magnetic foliation parallel to bedding and magnetic lineation (kmax axes) mostly parallel to the flow direction. This is demonstrated by consistency with standard sedimentological palaeoflow determinations in a detritic unit from the Oliana area. The magnetic fabric from sorne deformed rocks enables the time relationship between the magnetic fabric generation and folding to be determined. In one instance principal directions of the magnitude ellipsoid of susceptibility show orientations consistent with the kinematic fold axes. Another example shows a tectonic fabric which postdates folding. A third case allows the kinematic interpretation of "joint" development to be made. The interference of tectonic and sedimentary fabrics in weakly deformed rocks is evaluated. Moreover, the importance of the paramagnetic phase contribution to the_ magnetic fabric in rocks with low bulk susceptibility (K) is also considered.
Geophysical Journal International, 2005
We report on the magnetic properties and the acquisition of a chemical remanent magnetization (CR... more We report on the magnetic properties and the acquisition of a chemical remanent magnetization (CRM) in a field of 100 µT as a function of temperature and time during the lepidocrocitemaghemite-haematite reaction chain. The development of CRM was monitored at a series of 13 temperatures ranging from 175 to 550 • C; data acquisition was done at the specific formation temperatures for durations of up to 500 hr. Up to acquisition temperatures of 200 • C it takes a considerable time (up to 7 hr) before the CRM is measurable. This time decreases with increasing temperature, reflecting the activation energy of the reaction to form the first maghemite. During the lepidocrocite conversion, formation of two types of maghemite is suggested by two peaks in the CRM versus time curves. Magnetic properties were analysed after various stages in the reaction. They indicate a mixture of superparamagnetic and single-domain maghemite. The first reaction product (obtained after annealing at 200 • C) is a fine-grained yet crystalline maghemite (labelled type A). Before massive maghemite formation occurs, the coercive and remanent coercive forces go through a minimum at intermediate temperatures of 250-300 • C (annealing for 2.5 hr). This minimum lowers to 200-250 • C with increasing annealing time (500 hr). This is probably the result of two processes acting simultaneously-formation of superparamagnetic maghemite particles of a second less crystalline maghemite type (labelled type B) and removal of stacking faults in type A maghemite. The second process is suggested by analogy to the behaviour of natural magnetite/maghemite systems on annealing. Removal of stacking faults is reported to result in a magnetic softening of the grain assemblage. Annealing at 300-350 • C removes most of the lepidocrocite and the second maghemite type, type B, becomes prominent. Haematite formation sets in at slightly higher temperatures, yet the type B maghemite is in part thermally stable up to 600 • C enabling Thellier-Thellier experiments. This stability is also inferred from Arrhenius fitting that shows a comparatively high activation energy for the maghemite to haematite reaction. In Thellier-Thellier experiments the CRM showed a markedly downward convex Arai-Nagata plot while a second thermoremanent magnetization (TRM) showed perfect linear behaviour as expected. This feature may be used to recognize CRM in natural rocks.
Tectonophysics, 1987
A paleomagnetic investigation of the Lower Devonian Llandstadwell Eormation in southwest Wales ha... more A paleomagnetic investigation of the Lower Devonian Llandstadwell Eormation in southwest Wales has yielded a characteristic direction (declination = 196'. inclination =-5') that passes a fold test. Comparison of the corresponding virtual geomagnetic pole (334O E, 39OS) to previously published poles for Great Britain indicates that the magnetization is secondary and likely to be of Carboniferous age. No evidence for post-Herr&an rotation of Pembrokeshire is indicated by our data.
Physics of the Earth and Planetary Interiors
McClelland-Brown, E., 1982. Discrimination of TRM and CRM by blocking-temperature spectrum analys... more McClelland-Brown, E., 1982. Discrimination of TRM and CRM by blocking-temperature spectrum analysis. Phys. Earth Planet. Inter., 30: 405-4 14. Overlap of blocking-temperature spectra can be caused by three factors: chemical overprinting, the presence of partial thermoremanences (PTRM's) in two coexisting magnetic minerals, and the presence of PTRM's in coexisting multidomain and single-domain states of the same mineral. Multidomain relaxation mechanisms are not well understood and therefore quantitative estimates of overlap due to the coexistence of single-domain and multidomain states of the same mineral cannot be made, although it is evident that such overlap may be large. The maximum overlaps which would be expected at various temperatures due to coexisting single-domain magnetite and hematite are calculated. Where it can be shown that multidomain remanence is negligible, blocking-temperature overlaps which exceed these limits are, therefore, indicative of CRM overprinting.
Physics of the Earth and Planetary Interiors
ABSTRACT
Improving Schools
When language is processed, brain activity occurs not only in the classic ‘language areas’ such a... more When language is processed, brain activity occurs not only in the classic ‘language areas’ such as Broca’s area, but also in areas which control movement. Our systems of understanding, including higher level cognition, are rooted in bodily awareness which needs to be developed as a precursor to intellectual reasoning. Cognition is embodied, and this concept may offer a radical new way of improving school education by improving children’s systems of physical understanding. A new classroom physical intervention, called Move4words, based on embodied cognition, was developed for pupils aged 7–13 years and trialled with 348 typical pupils in 10 mainstream UK schools. Three pilot controlled trials showed significant improvements in academic performance, particularly for struggling pupils performing in the lowest 20 percent. Effect sizes were large for the lowest achievers: Hedges’ g = 0.86 for national examinations at age 11 (KS2 SATs) and g = 1.24 for progress through National Curriculum...
Palaeomagnetism is a powerful tool for identifying rotations about any axis. A palaeomagnetic stu... more Palaeomagnetism is a powerful tool for identifying rotations about any axis. A palaeomagnetic study in basement thrust sheets in the southern Axial Zone, Pyrenees, has demonstrated that 3-D rotations can be identified in basement terrain where no other palaeohorizontal markers exist. Three different movement histories are described within a stack of six thrust sheets. The lowermost unit has experienced doming and tilting about a horizontal axis at a different time Lo clockwise rotation about a vertical axis of 25'. '¡he middle four sheets have rotated clockwise by 35
Primary Teacher Update, 2013
Thrust Tectonics, 1992
ABSTRACT
Thrust Tectonics, 1992
ABSTRACT
The natural remanent magnetism of samples from the sheeted dike complex generated at the Costa Ri... more The natural remanent magnetism of samples from the sheeted dike complex generated at the Costa Rica Rift, drilled in Deep Sea Drilling Project/Ocean Drilling Program Hole 504B, can be resolved into a vertical drilling induced remanent magnetization and a shallow stable remanence by alternating field and thermal demagnetization. We investigate the unblocking temperature and coercivity spectra of these components, and compare these to spectra of thermal, induced, and viscous magnetizations imparted in the laboratory. The drilling-induced remanence is not a simple thermal, induced, or viscous remanence, but probably a piezoremanence acquired in an elevated field. The stable remanence may be a thermal remanence. Comparison of the stable remanence in altered and fresh samples indicates that natural remanent intensity and bulk susceptibility are reduced in more altered samples, but the stability and direction are similar to those in fresh samples. Whereas the stable components of the shee...
Terra Nova, 1996
... These include onland sections on Cyprus where G. margaritae has been found within gypsi-ferou... more ... These include onland sections on Cyprus where G. margaritae has been found within gypsi-ferous clays (Adam, 1976). ... In Late Tortonian time, coarse sediments shed from the evolving mountain belt (Grasso and Pedley, 19881, were ponded in basins in north-central Sicily ...
Journal of the Geological Society, 1999
ABSTRACT