Nonrandom geomagnetic reversal times and geodynamo evolution

作者：Olson Peter^*; Hinnov Linda A; Driscoll Peter E

来源：Earth and Planetary Science Letters, 2014, 388: 9-17.

DOI：10.1016/j.epsl.2013.11.038

• geodynamo
• polarity reversals
• Geomagnetic Polarity Time Scale
• superchrons
• Sherman's test

Sherman's omega-test applied to the Geomagnetic Polarity Time Scale (GPTS) reveals that geomagnetic reversals in the Phanerozoic deviate substantially from random times. For 954 Phanerozoic reversals, omega exceeds the value expected for uniformly distributed random times by many standard deviations, due to three constant polarity superchrons and clustering of reversals in the Cenozoic C-sequence. Reversals are nearly periodic in several portions of the Mesozoic M-sequence, and during these times omega falls below random by several standard deviations, according to some chronologies. Polarity reversals in a convection-driven numerical dynamo with fixed control parameters have an overall omega-value that is slightly lower than uniformly random due to weak periodicity, whereas in a numerical dynamo with time-variable control parameters the combination of superchrons and reversal clusters dominates, yielding a large omega-value that is comparable to the GPTS. Sherman's test applied to shorter Phanerozoic reversal sequences reveals two geodynamo time scales: hundreds of millions of years represented by superchrons and reversal clusters that we attribute to time-dependent core-mantle thermal interaction, plus unexplained variations lasting tens of millions of years characterized by alternation between random and nearly periodic reversals.

• 出版日期2014-2-15