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Is it possible that the geomagnetic field reversal with a weakened geomagnetic field over centuries if not thousands of years (according to the Pittsburgh simulation: https://www.psc.edu/science/glatzmaier.html) and exposure both to cosmic radiation, solar storms and continuous meteor bombardment, multiple "norths and souths" and deregulation of the biospheric clocks e.g. migratory paths of birds and animals using the geomagnetic field for navigation etc., raised volcanic and tectonic activities led to the extinction of Dinosaurs?

Between Matuyama Epoch of 243 million ya to 68 million years ago to Brunhes-Matuyama current epoch

Jacobs, John Arthur. 1994. Reversals of the earth's magnetic field. Cambridge [u.a.]: Cambridge Univ. Press. p 63

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  • $\begingroup$ It may cause adaptative radiation more that an extinction, but it is a non well known topic. $\endgroup$ – Universal_learner May 24 '18 at 5:12
  • $\begingroup$ The fact is I think we realy don't know how much time van allen is perpendicular. Migth be a kind of mutation and genetic pool generator $\endgroup$ – Universal_learner May 27 '18 at 16:32
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Mark's answer is correct, but in my opinion is not clear enough. Let's make it a bit simpler:

Is it possible that the geomagnetic field reversal led to the extinction of Dinosaurs?

NO, DEFINITELY NOT

Here's why:

The cause for the K-Pg extinction event (in which many living species, including dinosaurs, died) is well known: volcanic eruptions (the Deccan Traps) and an impact (Chicxulub). It's still debated which one contributed more to the event, or whether one is the result of the other, but that's not the point. It's not related to magnetism.

In fact, all big five extinction events in Earth's history are well linked to increased volcanic activity (including the Siberian Traps at the time of the largest extinction, the P-T extinction event aka the "great dying").

On the other hand, magnetic reversals happen all the time. Yet, there are no extinctions related to them. Your question also lists several incorrect assumptions:

continuous meteor bombardment

Incorrect: Geomagnetic reversals have no effect on whether we are bombarded by meteors or not.

raised volcanic and tectonic activities

Incorrect: Geomagnetic reversals are not linked to raised volcanic or tectonic activity.

Between Matuyama Epoch of 243 million ya to 68 million years ago to Brunhes-Matuyama current epoch

These are recent magnetic epochs from the Pleistocene, only a few million years ago. Thus unrelated to the K-Pg extinction event (or any event for that matter).

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  • $\begingroup$ [1] The discovery of the reversals of Earth's magnetic field and the description of plate tectonics are two of the main breakthroughs in geophysics in the 20th century. We claim that these two phenomena are correlated and that plate tectonics controls long‐term changes in geomagnetic reversal frequency." agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2011GL048784 $\endgroup$ – Wolves' Shepherd. May 24 '18 at 5:33
  • $\begingroup$ An extremely brief reversal of the geomagnetic field, climate variability and a super volcano phys.org/news/… $\endgroup$ – Wolves' Shepherd. May 24 '18 at 5:39
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    $\begingroup$ The first paper confuses cause and effect. Activity in the core results in the Earth's magnetic field. Heat coming from the core is a contributor to heat in the mantle, driving convection which is the cause of plate tectonics. However, the reversals do not control plate tectonics by themselves and plate tectonics does not control the reversals. $\endgroup$ – Gimelist May 24 '18 at 6:32
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    $\begingroup$ The second link talks about three events happening at the same time. This does not mean they are linked. How many supervolanoes, extreme climate events, and reversals are there that are not temporally linked? Because these events occur regularly, you will find some that occurred at the same time simply by chance. $\endgroup$ – Gimelist May 24 '18 at 6:33
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    $\begingroup$ @Wolves' Shepherd: On the contrary, it was geomagnetic reversals and the pattern they left in the rocks under the Atlantic Ocean that provided the final compelling evidence for plate tectonics: geolsoc.org.uk/Plate-Tectonics/Chap3-Plate-Margins/Divergent/… The reversals occur on average about every 450K years, mass extinctions on a scale of 10-100 million years or so. It's been ~65 million years since the KT extinction: if geomagnetic reversals were the cause, there should have been about 140 similar events since. $\endgroup$ – jamesqf May 24 '18 at 18:31
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It's a commonly-proposed theory that geomagnetic reversals cause extinction events, but there's no evidence for it. There aren't enough mass extinction events for any sort of statistical analysis, and there are a number of geologic processes that can give the illusion of simultaneous reversal and extinction. In particular, an erosion event can erase both the actual extinction event and the actual time of reversal, leaving them apparently both happening at the same time.

Further complicating things is the low resolution of the historic timeline, compared to the short duration of reversal events. As an example, the timing of the extinction of the dinosaurs is known to, at best, a few tens of thousands of years, yet a reversal can take only a few hundred years. Two events that look simultaneous (such as an extinction and a reversal) can actually be separated by thousands of years.

In the specific case of the dinosaurs, there doesn't appear to be evidence of a reversal at the time of extinction.

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