Geomagnetic Polarity Zones for Icelandic Lavas

Dagley, P.; Wilson, R. L.; Ade-Hall, J. M.; Walker, G. P. L.; Haggerty, Stephen E.; Sigurgeirsson, T.; Watkins, N. D.; Smith, Peter J.; Edwards, J. G.; Grasty, R L

doi:10.1038/216025a0

Cited by 124 publications

(61 citation statements)

References 22 publications

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“…Duncan & Helgason (1998) reported an 40 Ar/ 39 Ar plateau age on plagioclase from a tuff layer in the Hólmatindur horizon at 10.72 + 0.14 Ma (recalculated relative to the revised age of the FCs monitor standard of 28.201 + 0.046 Ma from Kuiper et al (2008)). Correlation between the magneto-stratigraphic profiles of Dagley et al (1967) and Watkins & Walker (1977) and the present geomagnetic polarity time scale of Ogg (2012) suggests that the Á lftafjörður central volcano was emplaced in 9.5 -10 Ma-old host rocks.…”

Section: The á Lftafjörður Central Volcano and Its Associated Dyke Swarmmentioning

confidence: 85%

Magma flow and palaeo-stress deduced from magnetic fabric analysis of the Álftafjörður dyke swarm: implications for shallow crustal magma transport in Icelandic volcanic systems

Eriksson

Riishuus

Elming

2014

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Neogene regional mafic dykes extending north of the Á lftafjörður central volcano in east Iceland are studied to test models of dyke swarm emplacement at spreading ridges. This is accomplished by using anisotropy of magnetic susceptibility to define fossilized magma flow regimes. The imbrication of the foliation plane, defined by the minor susceptibility axis, is used as an indicator of the flow direction. Contemporaneous shear resolved on the dyke walls may modify a pure flow-induced fabric and such shear regimes are therefore retracted. The magma flow and palaeo-stress resolved on the dykes are determined in 13 of 24 dykes. The magma flow is interpreted as subhorizontal and northwards directed away from the central volcano for nine dykes, and found to be vertical in three cases. The preferentially subhorizontal magma flow in the Á lftafjörður swarm suggests that dyke propagation in this type of Icelandic volcanic system originates in shallow crustal magma chambers. The regional tectonic palaeo-stress field is deduced to cause oblique spreading across the Á lftafjörður dyke swarm and govern a subhorizontal dextral shear component on the dyke planes during propagation. This interpretation is not in conflict with the left-stepping en echelon trend distribution of individual dykes relative to the trend of the swarm.

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Section: The á Lftafjörður Central Volcano and Its Associated Dyke Swarmmentioning

confidence: 85%

Magma flow and palaeo-stress deduced from magnetic fabric analysis of the Álftafjörður dyke swarm: implications for shallow crustal magma transport in Icelandic volcanic systems

Eriksson

Riishuus

Elming

2014

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“…The work of Dagley et al (1967) on polarities in the Eastern Iceland lava pile indicated (along with later K-Ar dates) that geomagnetic reversals had occurred on average at least 6 times per Myear in the period from 2 to 13 Ma ago. Kristjansson and McDougall (1982) analyzed patterns of reversals in dated sequences from elsewhere in the country, deducing a reversal rate of at least 8/Myear.…”

Section: Average Lengths Of Geomagnetic Chrons and Transitionsmentioning

confidence: 96%

Paleomagnetism and magnetic anomalies in Iceland

Kristjánsson

Jónsson

2007

Journal of Geodynamics

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“…Any thermal alteration resulting from the laboratory heating used to give the J, Shaw, P. Dagley Dagley et al (1967), from whose collection samples were taken for both the dating (Mussett, Ross & Gibson 1980;Ross & Mussett 1976) and for the field magnitude analysis. The dotted line indicates the sequential link between sections P and Q. thermal alteration in the low coercive force region (marked R for rejected).…”

Section: Field Magnitude Measurementsmentioning

confidence: 99%