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… 

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 fast

Very rapid geomagnetic field change recorded by the partial remagnetization of a lava flow

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 faster than

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 rapid

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 unusual

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. A

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 records

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 to

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 unblocking

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 from



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 in

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.

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). Evidence

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 the

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 hundred

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].

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 to

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 a

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. The