New Concepts in Global Tectonics Journal, V. 4, No. 2, June 2016. www.ncgt.org
ESSAYS
A Personal History of the Remagnetization Debate: Accounting for a Mobilistic Earth
Karsten M. Storetvedt
Institute of Geophysics, University of Bergen, Norway karsten.storetvedt@uib.no
“Neither science nor rationality are universal measures of excellence. They are particular traditions, unaware of their historical grounding”. Paul Feyerabend, in: Against Method (1988, p. 231)
“Nearly all scientific research leads nowhere – or, if it does lead somewhere, not in the direction it started”.
Nobel Laureate Peter Medawar, in: Induction and Intuition in Scientific Thought (1969, p. 31)
Preface
Taking a critical look at the progress of knowledge, physicist and science philosopher Paul Feyerabend (1988) argued that science has no special features that render it intrinsically superior to other branches of enquiry; he held that it is impossible – in a rational way – to analyze well-established scientific beliefs because of the intimate involvement of a complex web of human factors. Or as Henry Bauer recently put it:
“So it happens that a theory can win out primarily owing to social and political factors rather than compelling objective evidence” (Bauer, 2016). It is a well-established fact that within any scientific establishment, inter-personal relationships and socio-political pressures have far greater significance than rational judgement and definitive analysis. In this regard, Paul Feyerabend (1988, p. 16-17) spoke his mind when he wrote:
“Just as a well-trained pet will obey his master no matter how great the confusion in which he finds himself, and no matter how urgent the need to adopt new patterns of behaviour, so in the very same way a welltrained rationalist will obey the mental image of his master, he will conform to the standards of argumentation he has learned, he will adhere to these standards no matter how great the confusion in which he finds himself, and he will be quite incapable of realizing that what he regards as the ‘voice of reason’ is but a causal after-effect of the training he had received. He will be quite unable to discover that the appeal to reason to which he succumbs so readily is nothing but a political maneuver”.
Prejudices, for one reason or another, frequently complicate a straight-forward interpretation of data. Besides, observations are always theory-laden – in the sense that they assume, usually without argument or justification, particular background assumptions or a bridging thought constructions. Because a specific set of any kind of observations can potentially always be given a variety of different meanings, neither the observations nor the interpretations form a secure basis for true scientific progress. Thus, the palaeomagnetic record of a specific rock formation may contain several superimposed individual magnetizations of differing origins and intensity – depending on the actual thermal, chemical, and tectonic processes involved; that record can be further complicated by changes of geomagnetic field polarity and/or the dynamical process of true polar wander (the latter corresponding to spatial changes of the Earth’s body).
Therefore, most palaeomagnetic studies may be analytically quite demanding, and a successful interpretative outcome would depend first and foremost on the researcher’s expertise in pattern recognition – a skill which unfortunately is frequently corrupted by a doctrinal and inflexible education. However, where the diverse magnetization components are satisfactorily separated by experimental and analytical techniques, the next step is to put them in a sequential order – using knowledge of the combination of radiometric age patterns, regional-global tectonics, and geological history. Thus, the outcome of a competent and successful palaeomagnetic study is to give important information on the magnetization history of a particular rock sequence – along with its intimate relationships with regional and global tectonophysical events.
Evidence that the high blocking temperature magnetization of rocks may have a dual- or multicomponent configuration, was first demonstrated in volcanic rocks by Wilson (1961) and Wilson and Everitt (1963), and in Palaeozoic sediments by François Chamalaun – a PhD student of Professor K.M. Creer, Newcastle (Chamalaun & Creer, 1963 and 1964). It was obvious that in cases where the natural magnetic moment represented unresolved multicomponent remanences, undesirable artificial scatter would result – thereby blurring the actual palaeomagnetic message and its tectonophysical implications. Hence, it was necessary to ‘clean up’ the science of palaeomagnetism so that its application to global tectonics would be more clear-cut.
François Chamalaun had found that the Devonian magnetization of the Old Red Sandstone sediments of the Anglo-Welsh Cuvette had been strongly overprinted in Permian time by the Kiaman reverse geomagnetic field – apparently instigated by thermochemical processes at the moderate temperatures associated with the regional Hercynian deformation. But questions regarding the overall structure of the natural remanent magnetization (NRM) of these rocks, and the experimental and analytical problems of establishing the magnetization axis of the remaining weak Devonian field component, led to an intensive debate that lasted for nearly 20 years – often referred to as the ‘remagnetization debate’. The ‘new’ palaeomagnetic research philosophy that gradually emerged differed markedly from the original ‘bench physics’ platform (of the 1950s) which had included a number of entrenched assumptions and terminologies: these latter seemed out of step with reality after the experimental work of R.L Wilson and F. Chamalaun. In general, it was probably realized that palaeomagnetism had become a more demanding research field than originally expected. However, replacing the ingrained simplistic ways of thinking with a new and more realistic experimental- analytical approach turned out to be a difficult and long-lasting battle.
As I happened to be a central figure in the remagnetization controversy for more than a decade (from the late 1960s and throughout the 1970s), the present paper gives a personal account of the development of this dispute – describing, in particular, its strong emotional elements as well as its comparatively modest rational component. Katherine Frost Bruner once wrote that “…it is neither good science nor good common sense to put one’s reader to sleep and then expect him to grasp the highlights of an experiment, the significance of which one has assiduously buried” (Bruner 1942, p. 53). When looking behind the curtain of fundamental discussions in science, the strong emotional component inevitably involved can give rise to many entertaining stories. Therefore, I have chosen to present this account in the form of an essay. According to the Norwegian literary critic Jon Rognlien (2016), an essay may ideally be described as a relatively simplistic and limited piece of writing, intelligible to a wide readership, and characterized by a personal and often witty touch. The message of Paul Feyerabend cited above, regarding the lack of a unique cogent procedure for promoting scientific progress, was very clearly demonstrated during the remagnetization debate. As the science of palaeomagnetism is an extension of observatory geomagnetism, it has a much longer history than other geophysical disciplines. Hence, it seems appropriate to begin this essay with a short historical overview.
The Geomagnetic Basis of Palaeomagnetism
The directional property of the Earth’s magnetic field seems to have been known in China as early as the 11th century (cf. Smith and Needham, 1967); subsequently, in the 15th century, its properties of declination and inclination were discovered (cf. Chapman and Bartels, 1940). For navigation purposes, the first map of declination variation in the Atlantic, from 52˚N to 52˚S, was published in 1701 as the General Chart of the Variation of the Compass. In the early 19th century, Alexander von Humboldt, during his voyage to and exploration in South America, intensified studies of the systematic regional variation in the strength of the terrestrial field. Besides his geomagnetic field studies, von Humboldt (1797) also noted that the often strong and disturbing (compass deflecting) effects around exposed mountain summits was likely to be caused by remanent magnetization caused by lightning strokes. Anyway, there was no proper understanding of the global distribution of the geomagnetic field, or of its cause, before the studies of Carl Friedrich Gauss in the late 1830s.
Gauss was the first to give a mathematical description of the dipole component of the field. During the 17th and 18th centuries, the secular (long-term) variations of the terrestrial field had become an established fact, but its rapid diurnal changes were first described by von Humboldt and termed magnetic storms. In his famous paper Allgemeine Theorie der Erdmagnetismus, Gauss (1838) expressed the geomagnetic field potential as a sum of spherical harmonics – concluding that the field was essentially of an internal origin. Since 1838 many more spherical harmonic analyses of the field have been carried out (cf. list in McElhinny, 1973) basically confirming the work of Gauss. However, based on the gradually increasing number of geomagnetic observatories, the series of spherical harmonic studies have shown that, since the time of Gauss, the dipole moment has undergone a relatively steady decrease of a few per cent per century. Subtraction of the estimated best fitting dipole field (the main component) from actual surface observations leads to a residual field which is termed the non-dipole or irregular field.
On the whole, the present geomagnetic field resembles that of a dipole located in the Earth’s centre and inclined at an angle of 11.5˚ to the rotation axis. A comprehensive description of the Earth’s magnetic field and its secular change was given by Vestine et al. (1947), and Nagata (1965), extending the work by Vestine et al., found a westward precessional rotation of the main dipole at a yearly rate of 0.05˚ of longitude. In addition, the non-dipole field forms a number of large-scale circular anomalies which again is drifting westward as well as exhibiting changes in intensity. Bullard et al. (1950) found that, during the first half of the 20th century, the westward drift of the non-dipole field had been at an annual rate of 0.2˚ of longitude. In other words, it appears that both the spatial orientation of the dipole field as well as the individual loci of the irregular field undergo a westward global shift – collectively known as geomagnetic secular variation.
During the 19th century, a number of studies had indicated that recent volcanics contained a fossil (remanent) magnetization acquired roughly parallel to the ambient field during their time of cooling (e.g., Delesse, 1849; Melloni, 1853). Work on the stability of remanent magnetism, issues which had been initiated by Folgerhaiter (1899) by studying archeological material and Italian volcanic rocks, was continued by David (1904), Bruhnes (1906) and Chevallier (1925) who traced the pattern of geomagnetic secular variation during the past 2000 years. Both Folgerhaiter and Bruhnes had found evidence for past reversals of the present field. However, it was, first of all, Matuyama (1929) and then Mercanton (1938), based on oriented samples from Tertiary and Permian volcanics from Japan, Europe and elsewhere, who substantiated the idea that during geological time the Earth’s magnetic field had reversed periodically. In addition, Mercanton argued that, because of the fairly close link between the geomagnetic and rotational axes, it might be possible to test the hypotheses of polar wandering and continental drift (cf. Irving, 1964).
During the first decade after World War II, physicists like W.M. Elsasser (in the US) and P.M.S. Blackett and S.K. Runcorn (in Britain) performed experimental and further theoretical work on the origin of the geomagnetic field. For centuries, it had been known that the surface field undergoes relatively minor but systematic changes in direction; it was now surmised that its mean direction, averaged over a time span of some 10 000 years, could be thought of as originating from a dipole aligned co-axially with the Earth’s rotation axis. According to Runcorn (1954 and 1955), the close coincidence of the average magnetic and rotational axes was likely to be caused by the dominance of the Coriolis Effect acting on the hydrodynamic motions within the assumed fluid outer core. The geophysical implication of this working hypothesis was therefore: 1) the mean geomagnetic declination would be aligned in the palaeo-meridian plane, while 2) the mean magnetic inclination would have a simple geometrical connection with the corresponding palaeolatitude. This geophysical consideration lead to the classical dipole formula: tan I = 2 tan L, where I is average geomagnetic inclination and L the relevant latitude.
In connection with the negative outcome of a separate experiment relating planetary magnetic fields to planetary rotation, Professor P.M.S. Blackett (Nobel Laureate for Physics in 1948) had developed a very sensitive astatic magnetometer (see Blackett, 1952) which turned out to be ideal for measuring the commonly weak fossil magnetization in rocks and archaeological material. Meanwhile, studies of the physical and mineralogical basis of rock magnetism and magnetization processes in rocks had had a steady development during the first half of the 20th century, notably by Chevallier (1932), Königsberger (1938) and Néel (1949 and 1955); the extensive studies and compilatory work by Nagata and co-workers in Japan (cf.
Nagata, 1953) summarized the state of the art in the early postwar period. Thus, by the early 1950s, a proper foundation had been laid for more systematic palaeomagnetic studies.
The 1950s: Revolutionary Years in Global Tectonophysics
Assuming the validity of the geocentric dipole field assumption throughout geological time, and providing that secular variation scatter had been smoothed out during the often slow magnetization processes, computation of a palaeomagnetic pole would correspond to the location of the relative geographic pole for any specific geological epoch (cf. Creer et al., 1954). Plotting of palaeomagnetic poles in present coordinates was seen as the best possible way to compare palaeomagnetic directions from different continents. The swiftly increasing palaeomagnetic database in the 1950s showed time-progressive polar curves for individual continents in addition to indicating between-continent discrepancies. Despite an often unsatisfactory scatter of the data, the results were sufficiently regular to be taken seriously. This gave a great boost to the expanding field of palaeomagnetism, and brought the issues of continental drift and polar wandering into the limelight of geoscientific discussion.
The fact that the palaeomagnetic polar curve for Britain was reasonably consistent with the palaeoclimatebased polar shift outlined by Köppen and Wegener (1924) aided the interpretation of accumulated palaeomagnetic data in terms of polar wander and continental drift (cf. Irving 1956; Runcorn, 1956 and 1961). Furthermore, quantitative reasoning by Gold (1955), anticipating that even relatively modest periodic redistribution of planetary mass (on the Earth’s surface or in its interior) could instigate events of polar wander, may have served as additional support for polar wander. From his global survey of palaeomagnetic
data, Irving (1956) concluded that, for individual continents, their ancient latitudes based on
palaeomagnetism were in good agreement with those based on rock evidence for palaeoclimate. However, as the pre-Tertiary pole positions for individual continents did not agree with one another, Irving (1956) suggested that that “prior to Tertiary times the pole has not only shifted its position with respect to certain land-masses, but also that these land-masses have moved relative to one another”.
Around 1954/55, the Runcorn group (first in Cambridge and from 1956 in Newcastle-upon-Tyne) was somewhat reluctant to consider continental drift as the predominant global tectonic mechanism. According to their view, “polar wander was the simpler hypothesis, involving fewer degrees of freedom than continental drift, and the one easier to reconcile with our present model of the Earth” (see Creer et al., 1957). But data from other continents, such as India and North America (e.g., Doell, 1955; Runcorn, 1955, 1956; Clegg et al., 1954, 1956 and 1957), were beginning to pave the way for continental drift. For example, Creer et al. (1957) alluded to the possibility that Europe and North America might have been geographically closer in pre-Jurassic times than they are today. Comparison of palaeomagnetic poles from Britain and India had led Blackett (1956) and Clegg et al. (1956) to conclude that a significant continental displacement must have taken place between the two regions (for further discussion and a robust dismissal of that geophysical hypothesis, see Storetvedt, 2003 and 2010). Using his extended database from North America, Runcorn (1956) finally suggested that a displacement of some 25-30 degrees of longitude was likely to have taken place between the North Atlantic continents. Thus, within the British palaeomagnetic community, continental drift had eventually become at least as important as polar wander.
Satisfactory testing of the dynamo-tectonic hypotheses of polar wander and continental drift demanded accurate palaeomagnetic data which in turn required adequate laboratory tests. However, adequate laboratory techniques were not available in the 1950s. Nevertheless, some palaeomagnetic populations of remanence directions formed well-defined circular-shaped groupings indicating that they most likely represented single-component remanences; in such cases, it was assumed that the measured remanence populations had been implanted at an early stage of rock consolidation. But other studies showed a suspiciously large scatter indicating that any remaining part of an ‘original’ magnetization had been masked by overprinted magnetizations – formed along younger and divergent palaeomagnetic fields. It was obvious that relevant conclusions were critically dependent on the researcher’s analytical skill. Thus, experienced workers might be able to look behind the curtain of secondary magnetic disturbances and thereby gain insight into nature’s actual message, while others – who were stuck in mechanical ways of thinking – couldn’t see the forest for the trees.
In the early stages of palaeomagnetic research, the physicists had introduced the concept of ‘spot’ reading – meaning that the presumed stable magnetization in any locality of sedimentary and volcanic rocks represented the fossil geomagnetic field at around the time the rocks were laid down – acquired either during cooling/solidification of igneous masses or during compaction processes in sediments. But when this laboratory physics assumption was later viewed in conjunction with the slow diagenesis of sedimentary formations and the often slow cooling rate in igneous complexes (see below), the ‘spot’ reading concept became questionable. Even in cases where a single lava flow showed great internal inconsistency of its remanent magnetism, and/or irregular between-lava flow discrepancies, disturbing directional scatter was commonly ‘hidden’ behind statistical averaging-out procedures. In addition, the cooling rate of igneous bodies seemed to be much slower than previously thought; however, in the 1950s and most of the 1960s, the important effect of the combination of time and moderate temperatures was not a central issue in the discussion of palaeomagnetic acquisition processes.
Jaeger (1957) had studied the temperature variation in and around an intrusive sheet as a function of postinjection time. Jaeger’s cooling curves, each corresponding to a particular distance from the contact of a basic dyke with variable thickness, demonstrated that, after a relatively fast rate of initial magma/rock cooling, the curves were levelling off at around 400˚C. Considering, for example, a 100 m thick dyke, it will – according to Jaeger – take about 300 years before the temperature within its central parts would fall to
around 500˚C. During the same time, the cooling of the chilled margin (neglecting the instantaneous cooling at the time of injection) would only have been some 150˚C. Therefore, Jaeger’s calculations would indicate that larger igneous bodies may easily have maintained intermediate temperatures (a few hundred degrees Celsius) for very long time. According to the single domain theory of Néel (1949), it would follow that, at temperatures of around 400˚C, a fossil magnetization of an assembly of iron-oxide grains and with blocking temperatures of around 500˚C would have a lifetime of only one year. Hence, the classical additivity law of partial thermoremanent magnetization (PTRM) seemed inapplicable in most cases.
It had been shown experimentally that the growth of moderate-temperature viscous magnetization is proportional to the logarithm of time (Thellier, 1951; Rimbert, 1959), and an increase in temperature would naturally accelerate such late-stage acquisition processes. But in spite of these theoretical considerations, the palaeomagnetic implications of time and low-temperature chemical processes were seemingly not seriously considered in the 1950s. However, in the early 1960s, new demagnetization studies showed that the remanent magnetization in many rocks was likely to have a far more complex structure than researchers had so far imagined – constituting dual- or multi-component palaeomagnetic records impressed by the combined effect of global dynamo-tectonic events and geomagnetic polarity inversions (see below). The dual-concept of ‘original’ magnetization and ‘spot’ reading of the palaeomagnetic field was consequently in dire straits.
My Entry to Modern Geophysics
My first contact with what was then called modern geophysics was when I, as a graduate student in solid Earth physics in Bergen, I attended a conference on palaeomagnetism and continental drift at Newcastleupon-Tyne in spring of 1961 – organized by the already famous Professor Stanley Keith (Keith) Runcorn. Keith’s Department of Physics had at that time become the undisputed centre of the mobilistic-tectonic research activity in the world, and all the big names in global geoscience made visits to his department. Traditionally, considerations of continental palaeogeography had been based, first of all, on fossils and rock evidence for palaeoclimate, but with the new geophysical discipline of palaeomagnetism, the fields of palaeogeography and global tectonics had acquired a new and promising physico-experimental method. At the meeting in Newcastle, paleomagnetism was considered a science with a great future and, in this pervading mood of confidence I decided to make an academic career within this field. The precursor to my subsequent teaching and research career of more than three decades with palaeomagnetism as its focus was a one-year stay at the Newcastle Physics Department.
At that time, one of Professor Kenneth (Ken) Creer’s PhD students – François Chamalaun – was just finalizing a time-intensive thermal demagnetization study of the Devonian Old Red Sandstone of the AngloWelsh Cuvette, SW England. In many ways, this work became a turning point in experimental
paleomagnetism. François had found that the Anglo-Welsh Cuvette complex had received its bulk NRM in Permian time – some 100 million years after the Old Red sedimentary sequence had been laid down. In other words, extensive Permian magnetic resetting had removed most of the Devonian magnetization. In a geological perspective, this might perhaps not be entirely unsuspected in that the Hercynian fold belt was known to have cut east-west across southernmost Britain. François’ lunch colloquium, in the Physics Penthouse in December 1962, presenting the results of his painstaking thermal demagnetization study, was followed by an intense debate. The new results showed that long-term processes – probably instigated by dynamo-tectonic actions, through a combination of chemical processes and moderate-temperature viscous effects, could lead to sweeping changes of the early palaeomagnetic record (see also below). It was on the cards, that many published palaeomagnetic directions and pole positions – which thus far had not been based on detailed demagnetization analysis, had to be looked into again.
The surprise after François’s colloquium had barely subsided before there was another unexpected input to the debate on basic assumptions in palaeomagnetism. In late January 1963, Professor Blackett and his palaeomagnetic research team at Imperial College came to Newcastle to present new and quite surprising results from the approximately 60 million years old lava succession of Mull, Scotland. In addition to measurements of various bulk magnetic parameters, they had also carried out microscopic examination of the magnetic oxides. Blackett’s research group had made the remarkable discovery that there existed a relatively strong correlation between the presumed early Tertiary palaeomagnetic polarity and the degree of deuteric (high-temperature) oxidation of the iron-titanium mineralogy. Moreover, individual lava flows contained anti-parallel magnetizations – i.e., the fossil geomagnetic record of a single flow was represented by magnetization vectors with both normal and reverse polarity, which argued strongly against the general opinion in terms of ‘spot’ readings of the ancient field. Based on numerous laboratory experiments (e.g., Nagata, 1953/61), an individual lava flow should per se be dominated by a well-defined TRM acquired along the direction of the ambient geomagnetic field at the time of cooling. Thus, the Imperial College study indicated that the popular concept of ‘spot’ recordings of the ancient field might be wrong; they suggested that there had been other important mechanisms in action.
The most enigmatic feature of the Imperial College study was that the iron oxide grains in
samples/specimens with reversed magnetization showed a stronger degree of oxidative alteration than those with normal magnetization. However, the Imperial College group was unable to provide a satisfactory explanation for their remarkable results, and they claimed that their microscopic study appeared much more important than measurements of bulk rock magnetic properties – which by then had become standard procedure. In addition, because anti-parallel palaeomagnetic directions were a characteristic feature even in individual Mull lavas, their magnetization history had apparently spanned tens of thousands or perhaps millions of years after solidification of the lava sequence and acquisition of the field polarity at around the time of cooling. Hence, it seemed that slow low temperature secondary alteration of the iron-titanium oxides had led to major changes in the build-up of the remanent magnetization. On the other hand, it was impossible to completely rule out the possibility that some sort of self-reversal mechanism (cf. Nagata 1961) had been at play in the oxide grains.
Palaeomagnetism had acquired unexpected experimental and analytical challenges. Although the surprising results gave the impression of there being ambiguities in the field, my own experience was too modest, and my attachment to the standard terms and thinking of the Runcorn group was too strong to contemplate the idea that the suspicious results could have deeper meaning. But as it happened, it took no more than a few years before I had addressed these unresolved problems; my preoccupation with remagnetization issues made me a ‘rebel’ in the palaeomagnetic community for years to come (see below). In hindsight, after reflection and with distance to the events described, it gradually became clear that my professional ‘conversion’ to the drift-related geophysics, which at that time had become a principal activity in the Newcastle physics department, had been primarily a matter of fitting in socially, i.e., going with the flow.
The reiteration principle – combined with a fascinating international environment – had ensured an effective ‘intellectual’ conversion. Such experiences put the spotlight on researchers’ socio-psychological relationships – the non-intellectual aspects of academic activities which Thomas Kuhn (1962 and1970) and other science analysts claim are crucial for understanding the development of science.
In April 1964, Keith Runcorn and his staff organized a NATO Advanced Study Institute on Methods in Palaeomagnetism. The technical and experimental procedures were thoroughly treated, while analytical questions – the most important part of palaeomagnetic research – were only superficially discussed. In other words, the meeting evaded pre-statistical magnetization intricacies of crucial importance. In 1964, the time was clearly not ripe for the palaeomagnetic community to accept that the field was considerably more demanding than had been originally imagined. However, in the months following the Newcastle conference, two articles were published describing the results from the Anglo-Welsh Cuvette (Chamalaun and Creer, 1964; Chamalaun, 1964) – outlining the experimental work that had aroused such a stir in Newcastle two years earlier. The conventional view that the most stable magnetization always represented the ‘original’ palaeomagnetic field was roundly debunked.
In the fall of 1964, the first textbook on the subject – Paleomagnetism and Its Application to Geological and Geophysical Problems (Irving, 1964) – was published. The book was well written and a welcome contribution to the teaching of the new and promising geophysical science. However, it was based on conventional assumptions that recently had been seriously doubted – namely, that the so-called ‘stable’ magnetization in rocks by definition represented the original palaeomagnetic field. In Bergen, we could eventually make our own palaeomagnetic judgements based on thermal demagnetization studies of Norwegian Old Red Sandstone rocks (e.g., Storetvedt, 1967; Storetvedt and Halvorsen, 1968; Storetvedt et al., 1968). The long and fierce debate on re-magnetization and the Devonian field problem had thus begun. My threshold for secession from the grip of conventional thinking, and the first step towards an independent scientific consciousness, had finally been reached.
Gaining Experience and New Perspectives
Gradually, I had become aware of the strong socio-political factor in science and, during the fall of 1967, I began reading books on the history and sociology of science; in these texts, it was amply demonstrated that the growth of knowledge had always been slow and problematic. With regard to the understanding of paleomagnetism, the published results were clearly of mixed quality: a group of well-defined characteristic magnetizations, presumably representing single component remanences, was intermingled with numerous scattered and obviously unreliable data. I therefore decided to take a critical look at the published results and the polar estimates for the Palaeozoic of Europe. This analysis led to the conclusion that, for a time span of perhaps 300 million years, the relative polar shift had been episodic – not gradual as was commonly believed. Thus, the relative pole of rotation seemed to have been rather firmly trapped between the Ordovician and Upper Carboniferous – defining an overall polar location at around 160˚E, 18˚N (in present grids) and with a corresponding anti-pole in the South Atlantic. Thus, the palaeomagnetic data were consistent with the global palaeoclimate data which had been summarized by the Norwegian zoogeographer Niels Spjeldnæs (Spjeldnæs, 1961) for the Upper Ordovician.
At around Upper Carboniferous time, however, the relative pole had changed by 30˚ of latitude – establishing a new stationary pole at around 165˚E, 45˚N. In other words, the Earth had seemingly undergone a 30˚ angular shift relative to the astronomical axis (Storetvedt, 1968). A sharp Upper Palaeozoic change of palaeolatitude had also been suggested for rock sections in the southern continents (cf. Creer, 1964; Irving, 1966). Therefore, the combined evidence gave further substance to the concept of polar wandering. However, the principal question which preoccupied the palaeomagnetic group in Bergen at that time was the magnetization history of the scattered Old Red Sandstone (ORS) deposits in Norway in comparison with published ORS results for the rest of north-western Europe.
As mentioned above, the Old Red Sandstone sequence of the Anglo-Welsh Cuvette had been subjected to detailed thermal demagnetization studies, and quite unexpected results had been obtained (Chamalaun and Creer, 1963, 1964; Chamalaun, 1964). In addition to the main component – a secondary magnetization of Permo-Carboniferous age (acquired during the long-lasting reverse field – termed the Kiaman period) which apparently had formed during the regional Hercynian tectonic unrest, the authors found that there was a fairly weak high blocking temperature magnetization of suggested pre-folding age. Magnetite was identified as the principal carrier of the overprinted (secondary) magnetization while the high blocking temperature component resided in haematite (Chamalaun, 1964). However, from the published demagnetization results, it was evident that even the high temperature haematite remanence had dual-polarity structure; the general directional trend versus the progressive thermal demagnetization defined an overall northerly shift, but vectorial end-point magnetizations (a must in palaeomagnetic research) had obviously not been reached.
The principal (secondary) magnetization in the Chamalaun/Creer collection, with south-southwesterly declination and predominantly intermediately inclined upward-pointing inclinations, represents the classical Kiaman palaeomagnetic field; however, at higher blocking temperatures, the published results showed that the magnetization vector of individual specimens moved progressively into the NE quadrant – but without reaching final end-points. Nevertheless, from their weak and scattered high temperature magnetizations, the authors proposed a Revised Devonian Pole for Europe (Chamalaun and Creer, 1963 and 1964). That conclusion was obviously a mistake; their weak high temperature remanence population was obviously not cleanly separated. Thence, the published remanence population was unsatisfactorily dispersed, and nor did it satisfy experimental requirements to be accepted as representatives of the Devonian geomagnetic field.
In Bergen, we had studied an ORS succession of the Oslo region – the Ringerike Sandstone (Storetvedt et al., 1968). These uppermost Silurian sediments are fairly undisturbed tectonically, but with a location adjacent to the Oslo Graben which, in Permian time, was dominated by strong igneous activity; it was presumed that these Upper Silurian beds had been subjected to moderate temperature Permian heating and at least partial remagnetization. As it turned out, the magnetization history of the Ringerike Sandstone was quite similar to that of the Anglo-Welsh Cuvette: a generally weak high temperature haematite component was superimposed by an overall much stronger Kiaman (Permian) magnetization. However, the split-apart of the two fossil magnetizations was much easier and more clear-cut in the Ringerike samples than in specimens from the Anglo-Welsh Cuvette. In particular, end-point magnetizations versus progressive thermal demagnetization, which had not been achieved in the Anglo-Welsh collection, were frequently obtained in the Ringerike redbeds.
The problem of estimating the final (high temperature) direction appears basically the same in both Old Red Sandstone formations: Permian re-magnetization processes have affected haematite blocking temperatures close to its Curie (Néel) temperature. Thus, for the Ringerike material, it was shown that substantial changes of the natural remanent magnetization took place a few tens of degrees before the total NRM disappearance. From our study, we concluded that the demagnetization steps at high temperatures had to be much closer than that commonly used at the time. The Ringerike study gave a well-defined average high temperature direction with Declination N31˚E and Inclination 11˚ up (pointing upwards), from which an assumed Siluro-Devonian pole position was estimated at 159˚E, 21˚N (in present coordinates). This shallow-inclined high temperature magnetization suggested a palaeo-equatorial setting of north-western Europe in the Middle Palaeozoic which was consistent with evidence from palaeoclimate (Köppen and Wegener, 1924; Wegener, 1929). Experimentally, the questions regarding the Devonian palaeomagnetic field for Europe seemed reasonably settled. But as it turned out, this was only the beginning of a long and vigorous debate about the Devonian pole, and acceptance of the new views in experimental palaeomagnetism, before the remagnetization debate came to a close in the late 1970s.
Based on my experience with the remanence build-up in Norwegian ORS formations, I wrote (in January 1968) a manuscript entitled On Remagnetization Problems in Palaeomagnetism. The main conclusion was that many of the classical assumptions could no longer be maintained. Detailed demagnetization studies in close temperature steps, instead of the commonly applied ‘blanket cleaning’, indicated that, due to the slow magnetization processes in nature, even a small sample often contained accumulated palaeomagnetic information from perhaps a few million years; this slow magnetization process included both field-reversals as well as polar wandering events. In consequence, the fossil magnetic record might well have a complex structure, so that separation and estimation of the individual remanence components would require more detailed demagnetization studies than usually applied. Up to this juncture (the late 60s), the statistical methods used had largely concealed or misrepresented the real palaeomagnetic information. Time consuming detailed examination of the magnetization structure in small individual specimens then became far more important than superficial standard analysis of a larger sample collection. In 1968, this revelation prompted alarming new thoughts – indeed, rather ‘devastating’ for much of the methodology that had been built up as standardized methods in the field.
My paper on remagnetization (Storetvedt 1968) also included a discussion of palaeomagnetic results from the Lower Tertiary Mull Complex of Scotland (Wilson, 1964) for which Ade-Hall (1964) had given a detailed description of the iron-oxide petrology. According to geological and age descriptions (Richey 1948; Smith 1966), the Mull plateau basalts were affected by later intrusive activity and reheating. In the Wilson’s palaeomagnetic study, all samples had been taken from within the limit of the area affected by pneumatolysis surrounding the great central caldera. The numerous younger dykes cutting through the complex suggested, therefore, a lengthy thermal history including potential remagnetization events. Smith (1966), studying the magnetic polarity in baked contact rocks, had found strong evidence in favour of geomagnetic field reversals during the history of the Scottish Tertiary dyke intrusions. With this background, it seemed likely that moderate temperature reheating of the Tertiary Mull complex had left a composite dual-polarity palaeomagnetic structure in these rocks.
The suggested palaeomagnetic complexity of the Mull lavas was indeed revealed in Wilson’s data; individual lava flows contained an association of normal, reversed and intermediate remanence directions. Regarding the thermal behaviour of individual specimens, Wilson reported that reversed ones retained their directions throughout the whole range of temperatures studied, while samples which initially showed normal polarity behaved anomalously – some changing polarity immediately below the temperature of total NRM disappearance. Specimens with discordant NRM directions either remained discordant or they moved towards the Tertiary palaeomagnetic axis – some attaining normal polarity, others reversing. Statistically, Ade-Hall (1964) had found a distinct petrological difference between normally and reversely magnetized Mull lavas; flows with overall normal polarity were less oxidized than the directionally more stable reversed units. A number of other Tertiary volcanic rocks had been found with a similar correlation between oxidation state and geomagnetic polarity, but self-reversal mechanisms had been ruled out (Wilson, 1966; Watkins and Haggerty, 1965; Wilson and Watkins, 1967).
If remagnetization of the Scottish lavas had occurred in the opposite field direction to that of the original cooling, I reasoned that a variation of magnetic stability might cause the presence of a dual-polarity magnetization. It had become known that the palaeomagnetic field of the Lower Tertiary had basically been reversed, and the overall magnetic stability seemed to increase with the rate of high temperature (deuteric) oxidation (Wilson and Watkins, 1967; Larson et al., 1966) – consisting of the exsolution of ilmenite lamellae and their progressive lower temperature alteration. Thus, the Mull lavas seemed to have acquired their original magnetization in a reversed field, but the remagnetization processes – affecting, in particular, the least oxidized material – might well have persisted into time intervals of normal geomagnetic polarity. Thus, rocks with relatively un-oxidized and therefore ‘soft’ magnetic constituents would be most susceptible to reverse their magnetic moment when the ambient field shifted to normal polarity. This explanation provides a simple solution for the mystery that had surrounded the petrology/polarity correlation for some time.
The change of magnetization polarity versus progressive demagnetization in the Tertiary Mull Complex was indeed very similar to the circumstances observed in the Anglo-Welsh Cuvette and Ringerike ORS sediments. It was evident that remagnetization had become a prevailing problem in palaeomagnetic research – regardless of rock age; in consequence, critical evaluation of demagnetization data was of the utmost importance. Remagnetization was a universal problem, but as it turned out that message would be difficult to convey to the palaeomagnetic community. However, with great enthusiasm, I sent my article on remagnetization to Earth and Planetary Science Letters and shortly afterwards I heard that it had been accepted – as submitted. The reviewer – Professor Edward Bullard, Cambridge – was very positive and particularly pleased that I had found a credible explanation for the enigmatic oxidation/polarity problem in Tertiary lava successions.
The Remagnetization Problems Exposed at an International Conference
The theme at the NATO Advanced Study Institute in Newcastle 1-6 April 1968 was Palaeogeophysics within which topic palaeomagnetic studies had the principal role. It was no longer audible dissent about Wegener’s continental drift; palaeomagnetism had gradually set aside practically all resistance to the idea of lateral continental separation. In addition, the plate tectonic concept was nearing its final breakthrough. For solid Earth geoscientists and a few geologists, the time was characterized by enthusiasm and great expectations. It was therefore no surprise that the 1968 NATO Advanced Study Institute in Newcastle had gathered a relatively large number of participants including the vast majority of the then most influential geoscientists.
The main topic of the first conference day dealt with the latest developments in the study of the Earth’s rotational velocity in the distant and recent past – based on growth rings in fossil shells and corals, as well as astronomical information. The day passed quietly without major disagreements. In contrast, the second day was to be characterized by a significantly higher temperature. The meeting that day had been moved to the University of Durham, and the programme was entirely devoted to palaeomagnetic aspects of the younger geological past, especially to studies of palaeomagnetic secular variation and polarity changes. From the book of abstracts, it was clear that many debatable assertions would be presented – arguments I had refuted in the article that was about to be published in Earth and Planetary Science Letters. I knew that I now would have my baptism of fire in an international scientific setting.
Early in the morning session on the 2nd day, Professor Roderick (Rod) Wilson (now in Liverpool) gave a very elegant lecture on ‘permanent irregular components in the geomagnetic field’. The presentation included a synthesis of Tertiary and younger palaeomagnetic poles for Europe, and his main conclusion was that the estimated polar groups did not match the position of the current geographic poles. Thus, Wilson believed that the Earth’s magnetic field had permanent, and relatively strong, irregular fields and that the mean direction, even for a time span of 30 million years, was not averaged out – as had long been presumed. According to Wilson, the mean palaeomagnetic field direction did not match the field from a hypothesized axial geocentric dipole – one of the basic assumptions in palaeomagnetic research.
If Wilson was right, it would imply that a significant source of error was present in the determination of the apparent polar wander (APW) curve for individual continents, which in turn would create uncertainties for the by then well-accepted model of lateral continental drift. Paleomagnetism had primarily gained its reputation by promoting Wegener’s continental drift. With many scientists from other geosciences present, Wilson’s doubts about the geomagnetic basis of the palaeomagnetic method was something the ‘modern geophysicists’ least of all wanted to hear. In the presence of a broad range of prominent geoscientists, Wilson had in some ways damaged the façade of his own science. The situation was as taken from Erving Goffman’s description of the false play of everyday life (Goffman, 1959): subversive information should not accrue to the uninitiated, because a team must be able to hold onto its ‘confidential matters’. Wilson obviously had ‘sinned’ against these secret decrees. It was not, therefore, surprising that a hefty discussion about the presented claims ensued – a dispute where the speaker initially had complete control.
From my own standpoint, it was obvious that Wilson’s conclusions did not rest on reliable data. The way I understood the palaeomagnetic results from the British Tertiary basalt province, the investigated lavas contained unresolved magnetization problems. Nature (the Earth’s magnetic field) had been blamed for having an irregular behaviour, while in fact the responsibility lay with the researcher himself; he had adhered to an overly simple notion of the acquisition mechanisms of remanent magnetization in his rocks. In the discussion that followed, I was able to underpin my critical arguments with data obtained from Wilson’s own demagnetization studies. In a number of detailed thermal demagnetization experiments, he had presented data revealing that even Tertiary volcanics could have unexpectedly complex palaeomagnetic build-ups (Wilson and Everitt, 1963; Wilson, 1964): in order to split composite magnetizations, which often were responsible for anomalous directional scatter, Wilson’s own studies had demonstrated that it was often necessary to perform detailed thermal demagnetization at high blocking temperatures. It followed that blanket alternating field ‘cleaning’ was of limited value, and if routine statistics were applied on the scattered bulk magnetizations, false and misleading palaeomagnetic conclusions could readily be the result.
During Wilson’s talk, it had seemed as if his earlier experimental clarification had passed into oblivion. This disregard would prove to be fatal to the conclusions of his talk.
Participating at the meeting, there were also a number of MSc students from our Bergen department – including Eirik Fjørtoft. In a geophysical gathering in Bergen in 2001, Eirik told the party what had happened during my discussion with Rod Wilson in 1968; the incident had made such an impression on him that it had always remained very clear in his memory – “as if it happened yesterday”, he said. Rod Wilson, who was a very accomplished lecturer, had begun his presentation by drawing an almost perfect large circle on the board – performed with elegant body control. The audience was very impressed – the start was exemplary, he had the crowd in the palm of his hand. But during the ensuing discussion about the magnetization problems exposed in his data, it was clear to everyone that he was on shaky ground. Suddenly, something had happened which contradicted his conclusions, and in an attempt to wriggle out he initially took on the humorous jacket. But his diversions did not give the expected result; after all, we were in a scholarly setting where only experimental results and scientific arguments were acceptable. According to Eirik Fjørtoft, I had among other things asked about whether specific thermal demagnetization tests had been carried out on his material – to substantiate his claim that at least a significant part of the initial magnetization in his Scottish lavas was intact – which his interpretation took for granted. It took some time before the answer came, and in the wait the assembly was spellbound. By now the audience had understood the seriousness of the situation that had arisen; only a convincing and positive response from the speaker could save his day. But the blunder was a fact when the answer finally came: “No, we did not! We didn’t have the time!”
A scientific presentation with such a brilliant start thus ended up as a huge mistake – because critical magnetization aspects, demonstrated by his previously published results, had been brought up again and not satisfactorily answered. Wilson was clearly captured by one of the epoch’s erroneous assumptions that young lavas per se were unlikely to have acquired new (superimposed) magnetizations after their original solidification and field cooling (TRM). This assumption was obviously so heavily rooted in his mind that contradictory facts, demonstrated in his earlier experimental work (Wilson and Everitt, 1963; Wilson, 1964) had been overlooked. Such situations are found in the development of all sciences; deep seated conventional thinking is one of the main reasons why it always has been difficult to establish transitions from facts to new explanatory theory.
Wilson’s presentation was followed by other reports of palaeomagnetic studies in Tertiary and Quaternary rocks. Virtually all speakers reported cryptic results; puzzling directional elongations and anomalous scatter were especially present in rock sequences containing anti-parallel magnetizations, i.e. in cases where the magnetic field seemed to have changed polarity during the magnetization history of the rocks. The results clearly showed the magnetization history to have a complex build-up; magnetizations obviously consisted of two anti-parallel sub-components that had not been cleanly separated by appropriate demagnetization techniques. This planted new thoughts for palaeomagnetic research – the possibilities and consequences of which the participants seemed not to have thought of before. Therefore, during the discussions, I had the opportunity to introduce new explanations of the submitted data; the results spoke for themselves, and my arguments met no professional opposition.
The striking lack of initiative in the assembly was unexpected. With so many prominent scientists present, it would have been natural to think that I would have got strong opposition. However, it was difficult to know if the audience accepted my propositions or not. After all, I had advocated views that were far from the stereotypical expectations within my research field: therefore, it was natural that the stage would be open for strategic and tactical countermeasures. The image that most of the palaeomagnetists present at the meeting wanted to convey about their field had been damaged – I had obviously stepped on many sore feet and hurt some feelings. Some colleagues seemed confused, but the expression which others communicated through their body language, when they approached me during the breaks, indicated that l had won respect among the audience. ‘The temperature’ in the meeting reached its peak in the late afternoon (2nd conference day), after the Liverpool group had presented the results of a survey in the volcanic dyke swarm intersecting the Mull Complex. None of the previous contributions that day had exposed the magnetization problems as strongly as this talk, presented by Dr Jim Ade-Hall. The Chair, Professor Takesi Nagata (Tokyo) must have felt that there was too much focus on the problems, because when I asked to make another comment, he directed a cautionary finger at me exclaiming: “You again? You’ve said enough”!
After concentrating over a long day, I was very tired, and I have therefore only vague recollections of the subsequent dinner in Durham Castle. My unconventional views had disturbed the palaeomagnetic establishment to the roots, and the many attending experts had been implicitly asked to confront their own beliefs. Before this conference, I regarded science as representing a community of cognitively strong people who knew what they stood for. But now I had gained insight into a completely different professional world. When we, late at night, were back at Northern Counties College, where all the conference participants were staying, I was pleased with the day’s tussle. Without diplomatic doodles, I had gone straight to the point, and my arguments were later described as clean and fair – though obviously not overly diplomatic.
The 3rd day of the conference was devoted the phenomenon of polar wandering. Palaeomagnetic data from several continents were presented. My own lecture on the European geomagnetic field in the Devonian era, a theme which since 1963 had been a controversial issue, was given immediately after lunch though I had frequently put forward critical comments during the morning session. I had never before spoken in front of a large international audience and, as a result of my unusual début the day before I was curious how my lecture would be received. During its course, I had pointed out that unresolved laboratory problems were often clearly exposed in the presented data; because of unreliable palaeomagnetic populations, estimated palaeomagnetic pole positions would naturally also be inaccurate. During the coffee break in the middle of the afternoon session, the atmosphere was very tense. In the foyer, prominent professionals stood in small groups, often along with their students, and discussed in hushed tones strategies to recapture professional control of the field. It was this message their body language signaled – as a young American palaeomagnetist later confirmed. Earlier in the day, towards the end of the morning coffee break Professor G. M. Rutten, a prominent Dutch geologist, came up to me smiling and saying: “I must greet Tomas the Doubting”. We then had an interesting chat on faith and doubts in science.
My own talk was followed immediately by two other talks on the same theme – the Devonian controversy; the first of these contributions dealt with the magnetization of Devonian lavas in the Midland Valley of Scotland, and the second was a general overview of Devonian palaeomagnetism by Professor Ken Creer. The ensuing discussion of the three papers was entirely concerned with the reliability of the results from the last two contributions. Ken Creer’s conclusions were particularly hard hitting as many conventional views in palaeomagnetic research had come under great pressure. When I met Dr David Collinson (Newcastle) during the afternoon coffee break, he was far from happy with my rejection of the conventional stances in palaeomagnetism. His comment was short: “They will hate you for this”! But an American colleague, Professor Bob Hargreaves (Princeton) was far more positive in his judgement: “I agree with everything you say, but you could maybe perform your arguments a bit more diplomatically”! Later in the day, I got in conversation with another Norwegian participant – Professor Niels Spjeldnæs. In response to my direct question as to whether I had been a little too tough during the discussions, he replied: “No, so much they must endure! Truth be told, they have voluntarily gone into this business”!
After the dinner at Northern Counties College at the end of the third day, the participants gathered in the foyer outside the dining room. I stood and talked with a couple of colleagues when one from the Liverpool group came towards us and started a direct verbal assault on me. He claimed that I had overlooked certain important aspects of modern palaeomagnetic research (by the Liverpool group). In fact, as I was quite familiar with their published work, all his accusations were easily refuted. His vociferous attack soon gathered a sizeable crowd of curious people, and as the unfortunate attacker constantly had to backtrack, he became increasingly redder in his face. Finally, he was without a single word. My attacker had made a fool of himself in front of a great number of inquisitive colleagues. He had failed to make me angry, neither had he unsettled me nor diverted me from my contentions.
After this dispute, I retreated to my room and was therefore unable to follow the further discussion behind the scenes. But Eirik Fjørtoft, one of my MSc students, reported that he was sitting with the Liverpool group the entire evening. “They had great need of psychological crisis counselling”, he recalled. According to Eirik, the Liverpool group had admitted that I had only used scientific arguments that no one could contradict. They therefore took the blame upon themselves for the exposure of their own fallacious deductions. The case revolved largely on important facts exposed in their own data. In a sense, they knew about these facts, but, due to the pressure of established habitual thinking, they had not been able to stick to them. Irving Goffman (1959) describes such intricate manoeuvers of self-deception as “self-distantiation”.
In the following years, I had regular contact with Rod Wilson, and he gladly admitted that I had damaged the reputation of his group’s long-standing work on the British Tertiary Basalt Province – notably with regard to their suggestion that there seemed to be a ‘primary connection’ between the degree of oxidation of oxide petrology and the palaeomagnetic field polarity. Although it certainly must have cost him much to concede such a defeat, he was big enough to distinguish between a matter of science and a personal opinion and he showed great generosity towards me – not least during my sabbatical leave in his laboratory in 197273. In science, such magnanimity is a rare trait.
In the 1996 EGS General Assembly in The Hague, I gave two lectures on aspects of global tectonics, including a sketch of my own Wrench Tectonics. During the coffee break after my second lecture, a Romanian seismologist came up to me asking what had led me to a brand new theory of the Earth to which I responded “Oh that is a long and complicated story”. At this point an American colleague, Professor Michael Fuller, suddenly broke into the conversation with the remark: “I know exactly when your scientific independence began! It started when you had trouble in the late 1960s understanding the magnetization of the Old Red Sandstone”! I was impressed with my colleague’s clear understanding of the issues that had triggered my long-standing scientific development. He probably had the intense debate, at the 1968 NATO meeting in Newcastle where his own conclusions had also been subject to strong criticism, fresh in his mind.
Continued Debate and Escalating Unrest
On the journey back to Bergen, after the 1968 meeting in Newcastle, it was time for afterthoughts; many new impressions had to be digested. I had argued that a number of classical methods in palaeomagnetic research did not have a sound basis and stood in contrast to the fairly lengthy magnetization processes in nature. In consequence, I was convinced that the research field needed an entirely new philosophical platform. I had become a young cuckoo in the nest of the establishment, and posed a threat to the leading figures of the discipline that might be at risk losing their authority. But the most important point was that problematic data ought no longer to be ignored or explained away – all data had to be viewed holistically. That new viewpoints needed time for careful consideration and eventual acceptance was perfectly acceptable, but I was not ready for the spectra of strategic and tactical countermeasures that had been revealed in Newcastle – preventing the common ground rules from being systematically reviewed and overthrown. That some groups of colleagues had intimated by their body language disapproval of my arguments had not exactly been an impressive sight. Why was it necessary, in science, to invoke dramatic attitudes as a preventive measure? In any case, it was obvious that camaraderie and doctrinal viewpoints were dangerous to the integrity of science. Let me not forget that my boss in Bergen, Professor Guro Gjellestad, was thrilled with what had happened in Newcastle.
In a public dissertation on 29 November 1969, I defended my doctoral thesis: On Remagnetization and Related Problems in Palaeomagnetism. My principal opponent was Professor Ken Creer, so it was pretty obvious that, after all the brouhaha in Newcastle some 18 months earlier, the discussion would be a professional confrontation between two people who held strongly diverse views – focusing primarily on the magnetization of the Old Red Sandstone, and to which extent the original field cooling magnetization still was the dominant magnetization in the great majority of igneous rocks. The discussion, which lasted one and a half hour, must have been entertaining because the audience frequently broke out in open laughter. Concerning chemical magnetization in igneous rocks, a key question in the debate, I was able to refer to our recently completed investigation of a Permian lava sequence in the northern Oslo Graben (cf. Storetvedt and Petersen, 1970). Discussion surged back and forth – about what was essential and what was ‘immaterial’ experimental data. I had written (Storetvedt, 1968) that there was no such thing as immaterial data (data are data and have to be accounted for). Published results partly constituted single component remanences, but often they were most likely unresolved multicomponent magnetizations. I argued that unless the totality of laboratory results could be given a reasonable overall explanation/ understanding, we would be heading towards a world of juggling art. The audience burst into laughter when the examiner, seemingly a bit perplexed, asked if it was he or the candidate (me) who should be questioned.
My examiner, Ken Creer, went on to discuss marine magnetic anomalies which, at that time, were very much in fashion as a means of dating the presumed lateral spreading of the sea-floor. He held that the marine magnetic lineations were prima facie evidence for the existence of cooling magnetization (TRM) in oceanic basalts, an assertion I disputed. In the months prior to the examination of my doctoral dissertation, I had reviewed the existing literature on marine linear magnetic anomalies and evidence from deep sea basalts. I had come to the conclusion that these field anomalies were most likely the product of variable induction by the ambient geomagnetic field – reflecting susceptibility differences and associated variations in metamorphic grades in belts paralleling the mid-ocean ridges. In this explanation, the marine magnetic lineations were products of ridge-parallel tectonic shearing – not a combination of alleged sea-floor spreading and polarity changes of the geomagnetic field which was the popular explanation. It was and is my contention that geomagnetic polarity changes were (and are) a fact, but had no connection with the marine magnetic linear anomalies.
In 1969, however, expressing doubts about the linear, ridge-parallel marine magnetic anomalies, in terms of dating presumed sea-floor spreading, were close to blasphemy in marine geophysical circles. On the other hand, at that time, I was unable to give a reasonable account of the multitude of metamorphic and continental rocks frequently recovered from sites along these ridges. But, contrary to the continental drifters, my boss, Professor Guro Gjellestad, was visibly pleased with the scientific development in her department. A few days after my dissertation she commented: “As I hear, you have become a feared debater in geoscientific forums”!
Based on the ‘revised Devonian pole’ proposed by Chamalaun and Creer (1963 and 1964), Creer had written a number of scientific articles about global palaeomagnetic comparisons which had en passant proposed drastic changes in individual polar wandering paths for the Palaeozoic (Creer, 1964, 1965 and 1967). The cases of complete or partial re-magnetization were also on the agenda in North America. Thus,
Dr Jean Louis Roy (Earth Physics Branch, Ottawa) and colleagues had conducted studies in Old Red Sandstone sequences of the Appalachians and estimated a ‘primary’ magnetization direction that did not match the ‘revised Devonian field’ of Creer and Chamalaun (Roy et al., 1967). Ken Creer responded with a longer rebuttal (Creer, 1969), which the Canadian group in turn found baseless. Their relatively short answer to Creer’s criticism can be summed up by their following statement (Roy et al., 1969, p. 3303): “His
(Creer’s) supporting argument that his interpretation of our data is consistent with his interpretation of the European data (…) carries little weight; there are many European data that are inconsistent with his interpretation of European situations as Storetvedt (1967 and 1968) has repeatedly pointed out”.
Eventually, it began to be accepted that individual sedimentary formations could have a long-lasting magnetization history – including both geomagnetic polarity changes (producing superimposed normal and reversed magnetizations) as well as shift(s) of the palaeomagnetic dipole axis (caused by polar wandering). Hence, composite magnetizations with two or more sub-components could easily occur in nature. Focus was then put on researchers’ analytical skills, especially their ability to see general features within an overall complex observational structure (pattern recognition), and then be able to estimate individual directions of magnetization. Palaeomagnetic research had become a much more demanding science than before – both experimentally and analytically, and many routine operations and assumptions, established in the 1950s and early 1960s, had lost their primary importance. Most workers in the field still hoped that volcanic rocks were more reliable for palaeomagnetic purposes than sediments, and that the classical fieldcooling magnetization (TRM) would not be particularly affected by the challenging problems revealed in sediments. But that would prove to be wishful thinking.
Partial Remagnetization in Volcanics
Rod Wilson (Wilson, 1964) had demonstrated that even a single Tertiary lava flow could have magnetizations with anti-parallel field components, and our study in the northern part of the Oslo Graben (Storetvedt and Petersen, 1970) had corroborated that fact. In addition to a relatively weak ‘original’ (Permian) magnetization, with its well-established reverse polarity, these volcanics had been strongly affected by Lower Mesozoic remagnetization – defined by a slightly steeper axis of magnetization. Thus, from the uppermost flow of the succession both normal and reverse magnetizations were found – forming a well-defined post-Permian field axis. Furthermore, the original ilmenite and exsolved titanomagnetite grains were subjected to a nearly complete low temperature oxidative transformation – forming an irregular and extremely fine intergrowth of haematite and rutile. From rock magnetic and mineralogic studies, we concluded that the present magnetization of the investigated lavas must be of chemical origin and probably formed over a time span of more than 50 million years after their emplacement. In other words, the lengthy magnetization history involved both field reversals and an event of relative polar wandering (spatial resetting of the globe).
During the first half of 1970s, the remagnetization issue had become a universal problem that threatened the professional stability of the palaeomagnetic community. Despite the discomfort caused by the fluid situation, there was great curiosity within palaeomagnetic circles. This was probably an important reason why my scientific papers did not meet appreciable resistance in the early 1970s – at least, not officially. In September 1970, a meeting was arranged at the Geophysical Institute, University of Munich, to discuss important issues in palaeomagnetic research: oxidation problems in volcanic rocks were among the main themes. In my own lecture, I discussed a number of unresolved examples from the literature (Storetvedt, 1971). By now, it was widely accepted that palaeomagnetism was beset with analytical problems, though there was a conspicuous silence around the issue. Authors frequently made superficial comments about remagnetization, but published results demonstrated that there was a great deal of confusion about how the problems should be handled.
It was my curiosity about the obvious disparities between published data and corresponding conclusions which led me to Portugal in 1970 – to embark on a palaeomagnetic examination of the 65 million years old Lisbon volcanics. It was not unexpected that my study (Storetvedt, 1973) yielded results that confirmed the latent problems exposed in earlier published work (Watkins and Richardson, 1968; Van der Voo and Zijderveld, 1971). Instead of the expected single palaeomagnetic group formed by the original fieldcooling, I found two markedly different remanence populations, both with normal (northerly) declination. One of these groups had relatively steep inclinations (~ 60° down) – corresponding to the present axial dipole field in Portugal and agreeing with what the majority of workers in the field thought would be the expected result, while the dominant and unsuspected group was almost horizontal. Based on the new laboratory data, I concluded that the original titanomagnetite was likely to have been nearly completely oxidized to cation-deficient phases (titanomaghaemite) and that the original TRM therefore had been replaced by slowly acquired low-temperature chemical remanences.
My results from the Lisbon area, in particular the near-horizontal magnetization, triggered a degree of dismay in the western palaeomagnetic community and some untoward reactions. A few European and North American colleagues informed me about gossips saying that the reason for my divergent results was imperfections in the palaeomagnetic instruments in Bergen. Other rumours claimed that my results had been ‘constructed’; while a third ‘explanation’ said that I had deliberately chose divergent directions in order to disagree with others. Sometimes I was confronted by rhetorical questions like: Why do you always disagree with us? But the professional controversy went much deeper than the implications of the rumours factory. However, in the 1970s, the geophysical implication of my sub-horizontal magnetization of the Lisbon volcanics was not understood – not even by me.
The common perception at the time was that, over the past 60 million years or so, the Earth had held its present spatial orientation and this would accordingly result in the average geomagnetic model field (an axial geocentric dipole) having a steep magnetization axis (in Portugal) with inclinations of about 60 degrees – of normal (down) and/or reverse (up) polarity. The flat magnetization was therefore enigmatic. However, I saw no reason to doubt my results, and I argued that if colleagues from other European and American laboratories had taken a more critical look at their own observational data they would have reached the same conclusion. The conflict was primarily a question of how laboratory measurements were treated. In fact, it was a conflict between the (old) traditional procedures – including statistical smoothing of divergent (but important) data, and a more critical evaluation of directional pattern during progressive demagnetization.
Eventually, other laboratories found magnetizations with shallow inclinations in Tertiary rocks – in locations along the Mediterranean region and the Alpine part of the Middle East and Central Asia (e.g., Beck and Schermer, 1994; Beck et al., 2001; Gilder et al., 2001; Si and Van der Voo, 2001). For example, in 1992, I received letter from Professor Michel Westphal (Strasbourg) informing me that he himself had found shallow magnetizations similar to those I had reported from Portugal twenty years earlier and later corroborated by further palaeomagnetic and radiometric age studies (Storetvedt et al. 1987; Storetvedt et al., 1990). Michel Westphal enclosed a manuscript on which he invited my comments (cf. Westphal, 1973). According to my evaluation of existing palaeomagnetic data, the Lower Tertiary (65-35 million years ago) palaeoequator passed east-west along the southern borders of the Mediterranean (Storetvedt, 1990). Thus, two decades after my first presentation of the shallow magnetization of the Lisbon volcanic, the results were no longer disputed. In fact, by the end of the 19th century, palaeo-climatological data had indicated Lower Tertiary tropical conditions for the Mediterranean, while Northern Europe experienced warm temperate climate at that time (cf. reviews by Köppen and Wegener, 1924; Wegener, 1929); see also Pomerol (1982) for a detailed palaeoclimate description of the sub-tropical conditions in southern Europe during the Lower Tertiary.
During a visit to a British university in early 1973, I stopped by the computer room of the institute where a colleague was studying the printouts from one of his ongoing investigations. We began to talk about the graphs and stereo-plots unfolded on the table, and I commented on some of the results displayed which I thought revealed a clear case of a two-component palaeomagnetic structure. Suddenly, he got up from his chair and, without a word, quickly gathered up all his material and rushed out of the room. Slightly puzzled by the overeager exodus of my colleague, I quickly perceived what had happened. My comments had disturbed the expected outcome of his study, and he was therefore not receptive to alternative suggestions.
A new textbook on palaeomagnetism was published in 1973 – Palaeomagnetism and Plate Tectonics (McElhinny, 1973). Beforehand, there were great expectations for this publication. Almost ten years had elapsed since Ted Irving’s book was published – Palaeomagnetism and its Applications to Geological and Geophysical Problems (Irving, 1964), and in the meantime there had been significant technical and analytical developments in the field. The plate tectonic climate of opinion – which from 1967 onwards had gradually taken on primacy in the geosciences community, permeated McElhinny’s book. But in many ways, as a textbook ion palaeomagnetism, it was superficial compared to Irving’s book. Instead of giving technical and other relevant information, the book was a classical ‘take-over’ document in traditional palaeomagnetism – admitting of no reservations as to the way the then current data were interpreted. All significant issues in the field were treated as being beyond reasonable doubt, and the remaining issues explained away. The problem of re-magnetization, which for several years had caused concern and doubt in the palaeomagnetic community, was only marginally mentioned. The tenor of the book is best characterized by a short paragraph about this issue which ends with the following bombastic and dismissive conclusion (McElhinny, 1973, p. 271):
“There has been far too liberal a use of the general hypothesis that the ‘magnetic’ age of rock formations is likely to be significantly younger than its (sic) stratigraphic age. The hypothesis has far too many degrees of freedom to be scientifically attractive.”
This was written just three years before the re-magnetization problems were widely accepted (see below), and which for years came to usher in a new mindset for palaeomagnetic research. McElhinny’s firm rejection was in effect just verbiage. In reality, the book is a good example of Thomas Kuhn’s description of the scientific establishment’s consistent suppression of crucial innovations. Because new creative inputs necessarily undermine the contemporary basic scientific practice and obligations, Kuhn (1970, p.136-137) argues that the typical scientific texts often omit the details that later researchers would consider to be sources of important clarifications.
Memories from IUGG General Assemblies: 1971 and 1975
During IUGG’s General Assembly in Moscow, August 1971, I met for the first time Professor Ernst (Ernie) Deutsch, Memorial University of Newfoundland, St John’s, Newfoundland. “Oh my God, thanks that I finally got to meet you!” – He exclaimed. He told me that remagnetization was “hotly debated” in North America. He admitted the palaeomagnetic community had fervently hoped that the complications that had been exposed at the NATO conference in Newcastle in 1968 would prove to be greatly exaggerated, and that the uncertainties would therefore gradually fade away. Instead, the doubts had continued in that complex palaeomagnetic ‘case stories’ had appeared constantly in the literature. Ernie evidently regarded Jean Louis Roy (Ottawa) and me as the worst professional ‘troublemakers’. The doubts that had been thrown on the standard interpretational and analytical results had caused a feeling of discomfort that cast shadows over the research community’s idealized picture of the new geophysical science. I had to understand, Ernie explained, that the outside world ought not to become aware of contradictions in the image that had been drawn of paleomagnetism as a ground- breaking modern science. In that way, Jean Louis Roy and I were considered professional traitors.
In consequence of this conflict of professional views, the palaeomagnetic research community faced a crisis, and the associated stress sometimes led to ‘pressure valves’ becoming involuntarily wide open. Such a situation occurred during the Moscow Assembly – when, during conversation with a German colleague, he exclaimed in despair: “Please, do not talk more about the unsettled problems in palaeomagnetism; I am simply getting sick of it”! In order to understand such emotional outbursts, it is important to understand that in order to preserve the inspiration as well as the team spirit in a research community, it is not sufficient just to repress thoughts and/or observations that might menace the status quo, but also to seek ways of overcoming the researchers’ own nagging doubt.
Despite occasional vociferous reactions, the remagnetization debate continued tirelessly. To judge by the ever harsher tone in reports on my submitted manuscripts, after 1974, it was obvious that the professional conflict was about to escalate. Moreover, we were by then approaching a new geophysical congress – the IUGG 1975 General Assembly in Grenoble. It was somehow in the air that, during this meeting, some kind of clarification in the long-standing controversy had to emerge. As expected, the scientific contradictions quickly came to the surface, and there was hardly a single palaeomagnetic session without alternative explanations of the conventional interpretations being put forward. Again, it was the Jean Louis Roy and myself who led the attacks on what we regarded as obsolete methods and untenable arguments. The verbal feuds could at times reach great intensity. Much power, professional prestige and self-respect was at stake which clearly showed in the body language of the protagonists.
Sitting in the front row was Professor Norman Watkins (Rhode Island) who, famed as a critical, hard, yet constructive debater, participated very actively in the debate. On our way to lunch after one of the morning sessions, he came up with many witty comments about the many revealing body signals we had witnessed. In the months before the Grenoble meeting, I had, with former graduate students, submitted an article to an international journal. It soon emerged that another research group had been working in the same volcanic region. It was not totally unexpected, therefore, that the editor had chosen two people from the other group as our referees. The two reviewers represented the conventional views that I had long since abandoned. It was only to be expected that the assessments of the two reviewers would hardly be neutral. Their article had been published in late spring, at about the time our own manuscript was submitted. It was just before my departure for Grenoble that I received their reviews which made much of our alleged omission of their ‘detailed work’. We were accused of being both selective and of having ignored other researchers’ important work. These two scientific colleagues had condemned our manuscript and judged it as being unworthy of publication.
Just after dinner early on during the Grenoble meeting, one of the critical reviewers (an Australian) turned on me and began a personal attack. The major tenet of the accusatory broadside which he launched was as to why “I had ignored their most recent extensive work”. That we had not seen it before submitting our manuscript made no impact on him however much I assured that I had been unaware of their work until immediately before my departure for Grenoble. He simply refused to believe me, and his suspicion and irascible temperament triggered a series of condescending remarks about our work. After these initial accusations, riddled with prejudice, he evidently ran out of ammunition and the conversation eventually became a little more sober-minded. Even so, he did not discard his haughty tone. He had not participated in the vituperative discussions during the palaeomagnetic sessions, but now it seemed he was ready to ‘take the bull by the horns’. As I did not react to his aggressive rumblings, he raised his voice by a few more notches, but without changing my own views one iota.
My colleague was caught in the ‘statistical’ way of palaeomagnetic thinking. He wrongly thought that the most important aspect of a palaeomagnetic study was the mean direction of magnetization, representing that of the actual dipole field, which was revealed if the number of rock samples and directional measurements were sufficiently large. According to standard practice, it had been customary to argue that anomalous and scattered directions of magnetization were products of relatively short-lived irregular field changes (secular variation) which could be eliminated by statistical averaging-out procedures – providing the data base was large enough. This Australian colleague asserted that the number of measurements, associated with ‘blanket laboratory cleaning’ was therefore the alpha and omega in palaeomagnetic research. For my part, I argued that the traditional methods often distorted the actual palaeomagnetic information and that such uncritical analyses concealed essential aspects of the palaeomagnetic record. For example, I suggested that what he referred to as ‘irregular secular variation’ in Tertiary volcanics was more likely to be unresolved dualpolarity magnetization – being without geomagnetic and palaeomagnetic significance. I insisted that the way forward in palaeomagnetic research was detailed studies of individual samples; owing to the slow magnetization processes in nature, it was not unlikely that even a relatively modest rock collection might unfold a dual- or multi-component palaeomagnetic build-up – including both geomagnetic polarity changes and relative polar wander. In the eyes of my Australian colleague, such arguments sounded preposterous. What is more, he insinuated that he felt sorry for my students who received such a daunting and erroneous perception of reality. To such accusations, I replied that he would do well to think about what his attitudes conveyed to his own students. With examples from the literature, it was easy to dismiss his mixture of erroneous scientific arguments and emotional accusations. Gradually he was unable to respond to my counter-arguments, and his facial features revealed that he felt uncomfortable with the situation. He had started convinced of his own invincibility sure to win in any scientific exchange with me, but rather than emerging victorious from an unseemly brawl, he had gradually entangled himself in contradictions of his own making and thus been outmaneuvered. After our nearly two-hour long debate, the blunder was a fact – for my colleague. Mumbling, he turned away suddenly, and with bowed head and curved back he disappeared. I didn’t see him again for the rest of the Grenoble conference.
When I left Grenoble, after the two weeks long meeting, it was with strange feelings. The palaeomagnetic discussions had never been tougher. Shortly after returning home, I began to receive manuscripts from journals that were to publish special palaeomagnetic issues based on the presentations in Grenoble. It seemed as though attitudes had suddenly become more open and self-critical; the former resistance was about to abate. The Chair of the Programme Committee for the EGS General Assembly, Amsterdam 1976 rang me to ask if I would accept the responsibility for a symposium on Reliability of Palaeomagnetic Results: Criteria, Methods and Error Estimation at the next EGS meeting (1976). I accepted without hesitation.
A Scientific Turning Point: An Elusive Revolution
With the more positive attitudes that now prevailed after the Grenoble meeting, it was quite straightforward to assemble a broad programme for the EGS Symposium in Amsterdam in September 1976. In the friendlier and more courageous atmosphere that had arisen, a few colleagues even revealed what alarming effect my two early papers on re-magnetization (Storetvedt 1968, 1970) had had on the their work. In these more level-headed times, even ‘secret’ confessions about problems of interpretation were divulged. Dr Jean Louis Roy (Ottawa), who recently had published the results of a detailed study on the magnetization of Canadian Devonian sediments (Roy & Park 1974), was invited as key note speaker and allocated a full hour for his presentation. The influx of contributions became so great that the Dutch organizers had to allocate extra time to the symposium. In addition, Professor Heinrich Soffel (Munich) was recruited as co-convener.
All the brouhaha around remagnetization, which had been so prominent the previous year (in Grenoble), had now been superseded by curiosity, and almost all the key people in the field was present. The symposium which spanned one and a half days – with a total of 12 hours of lectures and discussions – was in every way a successful event. For the first time, the larger palaeomagnetic research community could, step by step, be made familiar with the thinking that was likely to be the new core philosophy in the subject. Opposition had finally been laid to rest.
After the end of the symposium, the vast majority of participants were standing in the foyer outside the auditorium. It seemed as though everyone thought it had been a rewarding experience. Two PhD students, from England and the Netherlands respectively, said that the symposium had opened their eyes. But a Danish colleague, Dr Niels Abrahamsen (Aarhus) came up with an even clearer admission: “Now I have finally understood what you’ve talked about all these years”! The remagnetization aspect had finally become a realistic and advantageous viewpoint in palaeomagnetic research.
Shortly after the EGS meeting in Amsterdam, I went to Canada for a sabbatical leave at the University of Western Ontario. This stay made it possible for me to follow the development of the re-magnetization debate from the other side of the Atlantic. Selected contributions at the Amsterdam symposium were to be published in a special issue of the journal Physics of the Earth and Planetary Interiors and, as editor of this issue, I chose reviewers among the leading scientists in the field. I also received review requests from a couple of American journals with which I had previously no contact. This gave me a unique opportunity to follow the ongoing transformation in palaeomagnetism from the inside – watching the transition away from what until then had been the conventional assumptions and methods in the field, to the new concepts that were likely to take over as future basic treatment and argumentation. Submitted manuscripts written in this period of restructuring gave great insight into the disorientation within a science during a conceptual revolution. Just as the dual concept of continental drift and polar wander had permeated the
palaeomagnetic research community in the 1960s and later, it was now the concepts of remagnetization and multi-component palaeomagnetism which served as the popular concepts and represented the necessary renovation and updating of the field. But how well founded actually was the new conceptual framework?
New professional views and understandings had become ‘legalized’ and were well on the way of becoming key elements in the scientific vocabulary. However, the vast majority of workers were obviously perplexed about how to deal with the new, palaeomagnetic platform, vis-à-vis their own data. The modern mindset had left its mark on the researchers’ terminological and procedural attire, but the content of the incoming conceptual framework was barely able to fit within the outer shell. Although the vast majority of palaeomagnetists in reality still lived in ‘the old days’, they all liked to appear as if they always had belonged to the modern camp. The members of the palaeomagnetic mainstream were in the process of changing their allegiance and manner of expression without having real insight into how, in practice, they should relate to the change. After all, the development was going in the right direction, and the academic transformation would inevitably take time.
To facilitate investigations of palaeomagnetism in the real world in the light of the new understanding of the subject, new analytical techniques were introduced during the 1970s (e.g., Roy & Park 1974; Halls 1976, 1978). Remagnetization and multicomponent palaeomagnetism had suddenly become important topics at scientific gatherings. At the 1978 meeting of the Canadian Geophysical Union, held at the University of Western Ontario, these issues were prominent in the palaeomagnetic sessions. The old terminology had largely been abandoned; it was as if the once popular, but now outdated, way of thinking had never existed. At one of the sessions, Professor Charles Carmichael (UWO) reminded the audience of the long and painful history of the remagnetization debate. However, it was particularly striking how newcomers in the debate pretended as if they had been born and raised with the new argumentation pattern though it may well have cost the ‘old timers’ considerable intellectual effort to jettison their flawed modes of thinking and investigating.
The same tendency to repress evidence of the principles and procedures that were common place before the
1976-revolution continued at the IUGG General Assembly in Canberra (1979), where Professor Henry Halls (Toronto) and I were responsible for a symposium on multicomponent palaeomagnetism. For young researchers and students who attended the Canberra Assembly, it must have been practically impossible to discover that palaeomagnetic research, a few years earlier, had undergone an idea-wise system change. The vast majority of senior workers in the field concealed the fact that the traditional academic stance had only recently been undermined. But those who had inside knowledge of what had happened a few years earlier would be able to recognize the truth of Thomas Kuhn’s description of the invisibility of scientific revolutions. Kuhn wrote:
“I suggest that there are excellent reasons why revolutions have proved to be nearly invisible. Both scientists and laymen take much of their image of creative scientific activity from an authoritative source [textbook] that systematically disguises – partly for important functional reasons – the existence and significance of scientific revolutions” (Kuhn, 1970, p. 136).
Textbooks are primarily intended to convey the contemporary vocabulary and conceptual basis for a particular science. For such books to gain acceptance among the leaders in a specific scientific discipline, and thus achieve the greatest possible authority and influence, it is of course necessary to present the subject in a light that is likely to be the most acceptable. Therefore, frequent references to contemporary scientists are an important prerequisite. The majority of the more senior generation of scholars have to accept that a veil of forgetfulness is being thrown over their work. The traditional development is portrayed as a linear learning processes with contemporary numerous fellow players. The fact that real progress in the sciences has always happened in jerks or wobbles, through more or less conspicuous scientific revolutions, is often overlooked. The contemporary reigning science administration dynasty (which often excludes the relatively small creative elite) will naturally ensure that tradition, as far as possible, is maintained. Since the academic leadership attains its authority primarily through its defence of traditional views, textbook descriptions of revolutionary innovations will naturally be delayed – if not suppressed.
The tendency of conservation of the stereotypical perceptions by the medium of the textbook was well demonstrated in the case of paleomagnetism. The first edition of McElhinny’s book (1973) had virtually written off the importance of remagnetization, while it failed to discuss seriously the often enigmatic large spreads in specific palaeomagnetic populations. These problems were more or less consciously concealed through the use of statistical methods, thereby giving specific palaeomagnetic populations a touch of false precision. Thus, the possibility that anomalously scattered individual palaeomagnetic populations might represent superimposed magnetizations from widely different geological eras was not acknowledged. In consequence, the experimental processing of the fossil magnetization was given a rather superficial treatment.
McElhinny’s book came in a new edition in 1979, but in spite of the fact that the professional platform of palaeomagnetism had undergone a comprehensive realignment in 1976-1977, and that a number of new analytical methods had been published during the 1970s, the 1979 textbook contained no visible changes or additions. Students and young researchers were therefore given the impression that there was nothing new to convey. The next textbook – Palaeomagnetism: principles and applications in geology, geophysics and archaeology (Tarling, 1983), mentioned remagnetization en passant, but not until the early 1990s do textbooks include a limited number of dual-component examples in most simplistic varieties (Butler, 1992; Van der Voo, 1993). Conclusions from a multiplicity of contemporary palaeomagnetic investigations can be rather obscure; the few examples which are displayed in current palaeomagnetic articles, and claimed to represent alleged characteristic features, often contradict the final conclusion. In the absence of relevant scholarly texts on how to handle multi-component cases in a proper way, it seems that, overall, the analytical insight is surprisingly modest (if not downright misleading).
When compared with geological and isotopic data, careful analysis of the fossil magnetic record of a particular rock formation, can give essential information of the region’s tectonic and thermochemical history. A good example has been uncovered in the Lower Devonian Cheviot Complex of NE England (Storetvedt et al., 1992; Mitchell et al., 1993). From these studies, a Devonian-Lower Carboniferous axis of magnetization was well established, showing good agreement with the corresponding early magnetizations of the Foyers Old Red Sandstone, N. Scotland (Storetvedt et al., 1990) and the Lower Carboniferous lavas of the southern Midland Valley (Rother and Storetvedt, 1991). In addition to giving important information on the Devonian-Lower Carboniferous palaeomagnetic field for NW Europe, the moderate magnetic overprinting gave new information as to the significance of the regional Hercynian tectono-thermochemical processes and mineral alteration.
Today there is full acceptance that the fossil magnetism in rocks generally consists of two or more superimposed palaeo-field components, but the number of authoritative palaeomagnetic studies is very limited. The problem is not the lack of experimental and analytical methods, but rather a notable lack of skill of the investigators to see the solutions inherent in their data base. The ability to perceive the actual physical pattern (pattern recognition), which in part is hidden behind the curtain of observational complexity is, however, uncommon. According to physicist and science philosopher John Ziman (1978), it is rather a rare ability. Improper treatment of raw data can, of course, easily lead to more or less distorted results and artificial palaeomagnetic scatter.
In addition, if scientists are being misled by unrealistic expectations – closely linked to some non-functional bridging theory, such as plate tectonics – everything is set for the production and publication of a significant amount of scientific junk. These built-in problems not only apply to paleomagnetism, but are a built-in complication in all other experimental sciences – such as seismology and its associated studies of the Earth’s interior. Over the years I have had many confidential conversations with colleagues, within various branches of geophysics, about interpretation problems. Many of them have admitted that they just do not understand the overall structure of their data. Yet, in the literature and in academic forums, such problems are rarely or never touched upon
During the EGS Assembly in Nice in the spring of 1998, during one of the coffee breaks, I was standing in a larger group of colleagues – in energetic conversation about results that had just been presented at one of the palaeomagnetic sessions. During our conversation, Dr Ann Hirt (ETH, Zurich) turned to me smiling with the following remark: “That’s right – you were one of the protagonists in the debate on
remagnetization more than 20 years ago!” To which remark I replied in the same cheerful manner “Oh, you mean when the palaeomagnetic community uncritically embraced new concepts, without really understanding what they had accepted? The reaction to my overt utterance resulted in a few seconds of absolute silence, before the group’s liberating laughter resounded through the corridor. A tacit knowledge had suddenly acquired a comic tint. At this discussion, it was not mentioned, however, that plate tectonics, in its present super-mobilistic everything-goes- anywhere state (which has allowed continents to drift around like corks on the ocean), in many ways has corrupted the overall healthy state of palaeomagnetic research which had been slowly acquired during the 1960s and 1970s.
Science is unfortunately not the logical, rational and honest enterprise we often pretend it to be. It is appropriate, therefore, to end this essay with some honest and revealing words by Nobel laureate Peter Medawar (1969, p. 11): – Ask a scientist what the scientific method is and he will adopt an expression that is at once solemn and shifty-eyed: solemn because he feels he ought to declare an opinion; shifty-eyed because he is wondering how to conceal the fact that he has no opinion to declare.
Acknowledgements: Writing a natural science article with a strong historical-sociological component, in a language other than one’s own, is in no way an easy matter. Thus, in order to prevent the use of incorrect words and to avoid, as much as possible, clumsiness of expressions, I have, during the last 15 years, benefitted greatly from editorial help from my old friend Christopher Argent, London; his many corrections have saved me from some egregious mistakes in English-language syntax besides numerous other improvements of my texts – including the present essay. I owe him my sincere thanks – indeed more than I can express – for his never failing enthusiasm and help during many years.
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