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Re: NS reversals



On 06 May 1998 18:19:36 Brian Whatcott <inet@intellisys.net> wrote:

My (not extensive) reading suggests that geomagnetic field reversal is
an 'instant' event as judged by the geological record. ... These
techniques can hardly distinguish a thousand year difference in general,
so that is how long a 'geological' instant may be.

It is true that geochronolical estimates are not very accurate as far as
absolute timing. But relative timing (for a sequence of events) can be
very accurate, sometimes within one year. I read about this recently but
do not have a specific illustration. So let me invent one. Suppose you
find a tree under a glacial strata. The C14 method tells you that the age
of this tree is 30,000 years plus, or minus 2000. You are studying climatic
fluctuations by examining rings. You may be able to discover a repetitive
pattern of very dry years, perhaps every 11 years, by looking for very
thin rings in your sample.

The realistic situation (I will try to find the reference) is indeed
related to the speed of a magnetic reversal. Something very recent and
very contraversial among geologists. Can somebody be more specific?

Ludwik Kowalski