New evidence for extraordinarily rapid change of the geomagnetic field during a reversal

  title={New evidence for extraordinarily rapid change of the geomagnetic field during a reversal},
  author={Robert S. Coe and Michel Pr{\'e}v{\^o}t and Pierre Camps},
Palaeomagnetic results from lava flows recording a geomagnetic polarity reversal at Steens Mountain, Oregon suggest the occurrence of brief episodes of astonishingly rapid field change of six degrees per day. The evidence is large, systematic variations in the direction of remanent magnetization as a function of the temperature of thermal demagnetization and of vertical position within a single flow, which are most simply explained by the hypothesis that the field was changing direction as the… Expand
Very rapid geomagnetic field change recorded by the partial remagnetization of a lava flow
[1] A new paleomagnetic result from a lava flow with a distinctive, two-part remanence reinforces the controversial hypothesis that geomagnetic change during a polarity reversal can be much fasterExpand
Revisiting the initial sites of geomagnetic field impulses during the Steens Mountain polarity reversal
SUMMARY We present a new palaeomagnetic investigation of the two sites from the Steens Mountain (Oregon) volcanic record of a Miocene polarity reversal which were supposed to record very fastExpand
Remagnetization of lava flows spanning the last geomagnetic reversal
Large directional changes of remanent magnetization within lava flows that cooled during geomagnetic reversals have been reported in several studies. A geomagnetic scenario implies extremely rapidExpand
Transitional geomagnetic impulse hypothesis: Geomagnetic fact or rock-magnetic artifact?
A striking feature of the Steens Mountain (Oregon) geomagnetic polarity reversal is the two (maybe three) extremely rapid field directional changes (6 degrees per day) proposed to account for unusualExpand
Geomagnetic fluctuations during a polarity transition
The extensive Roza Member of the Columbia River Basalt Group (Washington State) has intermediate paleomagnetic directions, bracketed by underlying normal and overlying reverse polarity flows. AExpand
The complexity of reversals
Geomagnetic reversals could be far more complex than even the best, most detailed paleomagnetic record in hand. Sequences of lava flows can give accurate spot readings of the field but yield recordsExpand
New evidence on an episode of geomagnetic instability, recorded in middle Miocene lava flows in Northwest Iceland
Information on the character of paleomagnetic polarity transitions and major excursions is important to understanding of the generation of the geomagnetic field. The main aim of this study was toExpand
On the possibility of recovering palaeo-diurnal magnetic variations in transitional lava flows: 2. An experimental case study
Abstract Geomagnetic field variations of external origin may be enhanced during periods of transitional field behaviour, particularly when the dipole moment is low, in which case they are likely toExpand
Remagnetization in lava flows recording pretransitional directions
Basaltic lava flows associated with the last reversal in three distinct volcanic sequences of the island of La Palma are characterized by overlapping components with very high unblockingExpand
Evidence from lava flows for complex polarity transitions: the new composite Steens Mountain reversal record
SUMMARY Geomagnetic polarity transitions may be significantly more complex than are currently depicted in many sedimentary and lava-flow records. By splicing together paleomagnetic results fromExpand


Evidence suggesting extremely rapid field variation during a geomagnetic reversal
Abstract Large, systematic variations in direction of high-temperature remanence as a function of vertical position occur in a basalt flow from the Miocene volcanic sequence at Steens Mountain,Expand
How the geomagnetic field vector reverses polarity
A highly detailed record of both the direction and intensity of the Earth's magnetic field as it reverses has been obtained from a Miocene volcanic sequence. The transitional field is low inExpand
The Steens Mountain (Oregon) geomagnetic polarity transition: 1. Directional history, duration of episodes, and rock magnetism
The thick sequence of Miocene lava flows exposed on Steens Mountain in southeastern Oregon is well known for containing a detailed record of a reversed-to-normal geomagnetic polarity transition.Expand
The Character of the Field During Geomagnetic Reversals
It is well established that the geomagnetic field, which is predominantly dipolar at the earth's surface, has alternated between normal and reverse polarity through geologic time (Figure 1). EvidenceExpand
Non-Dipole Behaviour During an Upper Miocene Geomagnetic Polarity Transition in Oregon
Summary The palaeomagnetism of a section of 71 successive lavas from southeastern Oregon is presented. A geomagnetic polarity change from reversed to normal polarity which took place during theExpand
The Steens Mountain (Oregon) geomagnetic polarity transition: 2. Field intensity variations and discussion of reversal models
We carried out an extensive paleointensity study of the 15.5±0.3 m.y. Miocene reversed-to-normal polarity transition recorded in lava flows from Steens Mountain (south central Oregon). One hundredExpand
A geomagnetic polarity time scale for the period 0–17 Ma, based on 40Ar/39Ar plateau ages for selected field reversals
Utilizing 40Ar/39Ar plateau ages for selected field reversals at ∼ 1, 2, 10, 16 and 34 Ma, a geomagnetic polarity time scale (GPTS) is constructed, following the technique of Cande and Kent [1992].Expand
Some statistical properties of palaeomagnetic directions in Icelandic lava flows
Summary. This paper extends the efforts of Kristjansson & McDougall to obtain a semi-quantitative description of various long-term (0.1–10 Myr) properties of the geomagnetic field in Iceland. Due toExpand
Conductivity discontinuities in the upper mantle beneath a stable craton
We present evidence for approximate collocation of seismic and electrical transitions in the upper mantle. More than two years of very long period magnetotelluric (MT) data were recorded at aExpand
The Magnetic and Opaque Petrological Response of Basalts to Regional Hydrothermal Alteration
Summary The alteration state of basalt lavas is shown to be largely the result of the combined action of two alteration processes, deuteric oxidation and regional hydrothermal alteration. TheExpand