<p>The methodology and equipment for palaeomagnetic studies in the 1960s and 1970s was often rather primitive by today's standards. For example, Doell and Cox (1967) imply that the standard procedure for getting a palaeomagnetic direction was simply to measure the natural remanent magnetization, and assume that it represented a reliable primary magnetization direction if it proved sufficiently resistant to one or more of the standard demagnetization techniques. </p>

<p>In contrast, in a modern palaeomagnetic study, I'd expect a far more elaborate methodology: ten or more AF or thermal demagnetization steps per sample (possibly with a pilot study to compare effectiveness of demagnetization methods), measuring remaining remanence at each step; inspection of data in various projections; palaeomagnetic directions obtained by fitting one or more demagnetization components using, for example, PCA (Kirschvink, 1980), Linefind (Kent et al., 1983), or some form of great-circle intersection analysis (e.g. McFadden &amp; McElhinny, 1988); and rock magnetic work (e.g. coercivity spectrum analysis) to provide a better idea of what's carrying the magnetization, and when and how the magnetization components were formed. Stability tests such as the fold test or reversal test might also by employed to check the reliability of the remanence.</p>

<p>In this context, I remember once being told that some large proportion (tens of per cent) of palaeomagnetic directions determined during the early days of the field had subsequently been invalidated when sites and samples were re-analysed using modern methodologies. Occasionally I come across an individual study which explicitly invalidates an earlier one; for example, Turner et al. (1989) revised the findings of Kennett and Watkins (1974), citing  ‘serious errors in the interpretation of the results’.</p>

<p>I've never come across a published study which attempts a quantitative survey of how often such invalidations occur. Does anyone know of any publications which provide such a review of early palaeomagnetic studies and their reproducibility -- or lack thereof?</p>

<hr>

<p>Doell, R. R. and Cox, A. (1967). Analysis of palaeomagnetic data. In Collinson, D. W., Creer, K. M. and Runcorn, S. K., editors, <em>Methods in Palaeomagnetism</em>, number 3 in <em>Developments in Solid Earth Geophysics</em>, pages 340–346. Amsterdam: Elsevier.</p>

<p>Kennett, J. P., &amp; Watkins, N. D. (1974). Late Miocene—Early Pliocene paleomagnetic stratigraphy, paleoclimatology, and biostratigraphy in New Zealand. <em>Geological Society of America Bulletin</em>, 85(9), 1385-1398.</p>

<p>Kent, J. T., Briden, J. C., &amp; Mardia, K. V. (1983). Linear and planar structure in ordered multivariate data as applied to progressive demagnetization of palaeomagnetic remanence. <em>Geophysical Journal International</em>, 75(3), 593-621.</p>

<p>Kirschvink, J. L. (1980). The least-squares line and plane and the analysis of palaeomagnetic data. <em>Geophysical Journal International</em>, 62(3), 699-718.</p>

<p>McFadden, P. L., &amp; McElhinny, M. W. (1988). The combined analysis of remagnetization circles and direct observations in palaeomagnetism. <em>Earth and Planetary Science Letters</em>, 87(1), 161-172.</p>

<p>Turner, G. M., Roberts, A. P., Laj, C., Kissel, C., Mazaud, A., Guitton, S., &amp; Christoffel, D. A. (1989). New paleomagnetic results from Blind River: Revised magnetostratigraphy and tectonic rotation of the Marlborough region, South Island, New Zealand. <em>New Zealand journal of geology and geophysics</em>, 32(2), 191-196.</p>

CC BY-SA 3.0
2016-04-06T08:27:59.827Z
Again, I don't know if it helps but I just bumped into this article: [Van der Voo (1990)](http://dx.doi.org/10.1016/0040-1951(90)90116-P).
plannapus
CC BY-SA 3.0
2016-04-06T09:27:36.553Z
@plannapus Thanks, this is the closest I've seen to what I was looking for, and a very interesting read! It doesn't actually reanalyse the sites/samples as such, but I'm starting to suspect that this aspect might be misremembered (either by me or by the colleague who told me).
Pont
CC BY-SA 3.0
2015-09-17T07:37:18.410Z
I do not know nearly enough about the specifics of data acquisition in paleomagnetic studies to really judge if it is useful to you but have you looked at ODP's [Handbook for Shipboard Paleomagnetists](http://www-odp.tamu.edu/publications/tnotes/tn18/f_pal.htm)? It contains (in [chapter 6](http://www-odp.tamu.edu/publications/tnotes/tn18/f_pal6.htm)) a review of the various problems they encountered during early DSDP/ODP legs and a small leg-by-leg review of data reliability (in the [appendix 5](http://www-odp.tamu.edu/publications/tnotes/tn18/f_pala.htm#app5)).
plannapus
CC BY-SA 3.0
2015-09-17T07:52:08.763Z
I just noticed they published a [revised version of this handbook](http://www-odp.tamu.edu/publications/tnotes/tn34/TNOTE_34.PDF) a few years ago.
plannapus
CC BY-SA 3.0
2015-09-17T18:30:50.160Z
@plannapus Thanks, I was acquainted with the handbook but only in the newer edition (which lacks that appendix). Unfortunately it's a little tangential to my question, because the comments are about the reliability as evaluated at the time of measurement -- I'm more interested in directions which were considered reliable at the time, but invalidated years later.
Pont
CC BY-SA 3.0
2015-10-16T15:11:42.573Z
@Pont I sampled sediments for paleomagnetism during one of my excursions. I am curious if you could expand on the context of invalidated results - or at least which recent methods you were referring to that you may consider as modern, standard, or better than the original method. Paleomagnetism sampling and analysis may differ depending on the time scale, material to sample, etc. I'd be glad to dig a bit while considering your context in depth.
marsisalie
CC BY-SA 3.0
2015-10-16T17:12:58.583Z
@fre0n Thanks for your interest! I've edited my question to explain what I consider to be typical modern methods, and to give an example of invalidated results.
Pont
CC BY-SA 4.0
2018-10-19T09:25:11.217Z
@Universal_learner I guess I should have done that before because now, since last July, as Elsevier cut off access to Germany (where my institution is), I can't access (legally) that paper anymore (and I forgot to save it at the time).
plannapus
<paleomagnetism><reproducibility><history-of-science>
How reliable were early measurements of palaeomagnetic directions?
Pont
# How reliable were early measurements of palaeomagnetic directions?

(Asked by: username_0 on 2015-03-31)

The methodology and equipment for palaeomagnetic studies in the 1960s and 1970s was often rather primitive by today's standards. For example, Doell and Cox (1967) imply that the standard procedure for getting a palaeomagnetic direction was simply to measure the natural remanent magnetization, and assume that it represented a reliable primary magnetization direction if it proved sufficiently resistant to one or more of the standard demagnetization techniques.

In contrast, in a modern palaeomagnetic study, I'd expect a far more elaborate methodology: ten or more AF or thermal demagnetization steps per sample (possibly with a pilot study to compare effectiveness of demagnetization methods), measuring remaining remanence at each step; inspection of data in various projections; palaeomagnetic directions obtained by fitting one or more demagnetization components using, for example, PCA (Kirschvink, 1980), Linefind (Kent et al., 1983), or some form of great-circle intersection analysis (e.g. McFadden & McElhinny, 1988); and rock magnetic work (e.g. coercivity spectrum analysis) to provide a better idea of what's carrying the magnetization, and when and how the magnetization components were formed. Stability tests such as the fold test or reversal test might also by employed to check the reliability of the remanence.

In this context, I remember once being told that some large proportion (tens of per cent) of palaeomagnetic directions determined during the early days of the field had subsequently been invalidated when sites and samples were re-analysed using modern methodologies. Occasionally I come across an individual study which explicitly invalidates an earlier one; for example, Turner et al. (1989) revised the findings of Kennett and Watkins (1974), citing ‘serious errors in the interpretation of the results’.

I've never come across a published study which attempts a quantitative survey of how often such invalidations occur. Does anyone know of any publications which provide such a review of early palaeomagnetic studies and their reproducibility -- or lack thereof?

---

Doell, R. R. and Cox, A. (1967). Analysis of palaeomagnetic data. In Collinson, D. W., Creer, K. M. and Runcorn, S. K., editors, *Methods in Palaeomagnetism*, number 3 in *Developments in Solid Earth Geophysics*, pages 340–346. Amsterdam: Elsevier.

Kennett, J. P., & Watkins, N. D. (1974). Late Miocene—Early Pliocene paleomagnetic stratigraphy, paleoclimatology, and biostratigraphy in New Zealand. *Geological Society of America Bulletin*, 85(9), 1385-1398.

Kent, J. T., Briden, J. C., & Mardia, K. V. (1983). Linear and planar structure in ordered multivariate data as applied to progressive demagnetization of palaeomagnetic remanence. *Geophysical Journal International*, 75(3), 593-621.

Kirschvink, J. L. (1980). The least-squares line and plane and the analysis of palaeomagnetic data. *Geophysical Journal International*, 62(3), 699-718.

McFadden, P. L., & McElhinny, M. W. (1988). The combined analysis of remagnetization circles and direct observations in palaeomagnetism. *Earth and Planetary Science Letters*, 87(1), 161-172.

Turner, G. M., Roberts, A. P., Laj, C., Kissel, C., Mazaud, A., Guitton, S., & Christoffel, D. A. (1989). New paleomagnetic results from Blind River: Revised magnetostratigraphy and tectonic rotation of the Marlborough region, South Island, New Zealand. *New Zealand journal of geology and geophysics*, 32(2), 191-196.

**Tags:** paleomagnetism, reproducibility, history-of-science

> **Comments:**
> **username_1**: I do not know nearly enough about the specifics of data acquisition in paleomagnetic studies to really judge if it is useful to you but have you looked at ODP's [Handbook for Shipboard Paleomagnetists](http://www-odp.tamu.edu/publications/tnotes/tn18/f_pal.htm)? It contains (in [chapter 6](http://www-odp.tamu.edu/publications/tnotes/tn18/f_pal6.htm)) a review of the various problems they encountered during early DSDP/ODP legs and a small leg-by-leg review of data reliability (in the [appendix 5](http://www-odp.tamu.edu/publications/tnotes/tn18/f_pala.htm#app5)).  
> **username_1**: I just noticed they published a [revised version of this handbook](http://www-odp.tamu.edu/publications/tnotes/tn34/TNOTE_34.PDF) a few years ago.  
> **username_0**: @username_1 Thanks, I was acquainted with the handbook but only in the newer edition (which lacks that appendix). Unfortunately it's a little tangential to my question, because the comments are about the reliability as evaluated at the time of measurement -- I'm more interested in directions which were considered reliable at the time, but invalidated years later.  
> **username_2**: @username_0 I sampled sediments for paleomagnetism during one of my excursions. I am curious if you could expand on the context of invalidated results - or at least which recent methods you were referring to that you may consider as modern, standard, or better than the original method. Paleomagnetism sampling and analysis may differ depending on the time scale, material to sample, etc. I'd be glad to dig a bit while considering your context in depth.  
> **username_0**: @fre0n Thanks for your interest! I've edited my question to explain what I consider to be typical modern methods, and to give an example of invalidated results.  
> **username_1**: Again, I don't know if it helps but I just bumped into this article: [Van der Voo (1990)](http://dx.doi.org/10.1016/0040-1951(90)90116-P).  
> **username_0**: @username_1 Thanks, this is the closest I've seen to what I was looking for, and a very interesting read! It doesn't actually reanalyse the sites/samples as such, but I'm starting to suspect that this aspect might be misremembered (either by me or by the colleague who told me).  
> **username_1**: @Universal_learner I guess I should have done that before because now, since last July, as Elsevier cut off access to Germany (where my institution is), I can't access (legally) that paper anymore (and I forgot to save it at the time).  

---

## 0 answers

