New Concepts in Global Tectonics Journal (www.ncgt.org), v. 1, no. 3, September 2013, pp. 103-117

Discussion

PALAEOMAGNETISM, POLAR WANDER AND GLOBAL

TECTONICS: SOME CONTROVERSIES

David PRATT

This is a response to Karsten Storetvedt’s article ‘Global theories and standards of judgment’ (this

issue, p. 55-101), in so far as it comments on my review paper ‘Palaeomagnetism, plate motion and

polar wander’ (NCGT Journal, v. 1, no. 1, 2013, p. 66-152).

Crustal movements

According to Karsten Storetvedt (p. 57), ‘In his article, David Pratt sets out to question everything that

smacks of lithospheric mobility – basically returning to the late 19th century North American idea of continental-oceanic fixity.’ Given that my article speaks of ‘periodic changes in the distribution of

land and sea’ and refers to abundant evidence showing that large areas of the present oceans were

once dry land, this is a remarkable misunderstanding. In my article I also wrote: The Earth’s crust is in constant motion. The Earth’s relief currently ranges from 8.8 km above sea level to 10.8

km below it. There is ample evidence that mantle heat flow and material transport can cause significant changes

in crustal thickness, composition, and density, resulting in substantial uplifts and subsidences – without the need

for ‘plate collisions’ and ‘subduction’. The scale of vertical movements is indicated by the fact that the thickness

of marine sedimentary layers in mountain belts is commonly over 10 km and can reach 23 km. As far as

horizontal movements are concerned, field evidence indicates that crustal strata can be thrust tens if not

hundreds of kilometres, that crustal extension or shortening of up to hundreds of kilometres has occurred, and that motion of over a hundred kilometres has taken place along some wrench faults. But given the widely

varying thickness of the lithosphere, the existence of deep continental roots, the lack of a continuous

asthenosphere, the absence of some ‘plate’ boundaries, and the correlation between near-surface features and

deep mantle features, the movement of lithospheric slabs as relatively rigid bodies over hundreds or thousands

of kilometres seems utterly impossible. (p. 84)

Storetvedt quotes the first four sentences of this passage (p. 71). At the end of the first sentence about the crust being in constant motion, he adds: ‘[vertically, I suppose]’. He chooses not to quote the

statement about horizontal movements – which contradicts his suggestion that I only recognize

vertical movements.

Space-geodetic data, too, leave no room for doubt about the ongoing horizontal and vertical motions

of the earth’s crust. There is, however, plenty of room for debate about the areal extent and thickness

of the elements of the earth’s crust and lithosphere that are actually moving, how far they have moved, and the forces responsible.

Planetary degassing

According to Karsten Storetvedt, I am a ‘prostrate supporter’ of surge tectonics and look upon Arthur Meyerhoff as a ‘high priest’. In reality, I have never regarded surge tectonics as a definitive global

tectonic model. I do believe that there is strong evidence that vertical and horizontal flows of magma

in the lithosphere have played a significant role in the earth’s geologic history; such concepts originated long before the development of surge tectonics, as Meyerhoff et al. (1996a, p. 20-29) make

clear. The fact that the earth is still degassing is also very pertinent (Williams & Hemley, 2001; Porcelli & Turekian, 2003), and the hypothesis that ascending hydrous fluids can cause crustal

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alteration and motion – which Storetvedt has strongly advocated – is worthy of further investigation.

There has been a lot of discussion in the NCGT group about oceanization/basification (e.g. NCGT Newsletter, no. 12, p. 18-24; and no. 14, p. 18-23), but the last word has not yet been said.

Storetvedt speculates that upstanding sections of the core-mantle boundary (CMB) indicate the main

locations of degassing. He often presents a figure from Morelli & Dziewonski (1987) to support this, claiming that upstanding sections shows ‘close agreement’ with the surface arrangement of oceanic

depressions (his figure 2; included in figure 1 below). However, the agreement is not particularly

impressive, and the figure in question also shows upstanding CMB sections beneath the Scandinavian Shield and most of the Canadian Shield. Storetvedt says that the image he uses is an ‘early version’ of

CMB topography. Examples of more recent versions are given in the figures below, which show that

different tomographic models can lead to very different results.

Fig. 1. (http://yoshida-geophys.jp)

Fig. 2. CMB topography (Soldati et al., 2012, fig. 9).

Wrench tectonics and polar wander

Karsten Storetvedt thinks that my article ‘sets out to put surge tectonics on the map’, but also

complains that the principal tenets of surge tectonics are not discussed. The main purpose of my

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article, as the title suggests, is to critically review theories connected with palaeomagnetism and polar

wander.

The fundamental assumption that averaged palaeomagnetic poles for specific periods approximately

coincided with past geographic poles is unproved. In addition, fossil magnetism in rocks can be

altered by many factors, remagnetization is common, tectonic movements further complicate the picture, and as a result the palaeomagnetic database is full of inconsistencies. There is great scope for

subjectivity in the selection, processing and interpretation of palaeomagnetic data. According to Lisa

Tauxe (2013): ‘Picking out the meaningful poles from the published data is part of the art of paleomagnetism.’ Richard Kerr (1987) writes: ‘Deciding which are the most reliable paleomagnetic

data has always been a controversial subject, prompting the playful label of “paleomagician” for

practitioners in the field.’

While plate tectonics explains palaeomagnetic data mainly in terms of the motion of entire

lithospheric ‘plates’ together with a relatively small degree of true polar wander, wrench tectonics

explains them mainly in terms of large-scale true polar wander along with ‘modest’ continental/plate rotations and displacements. Storetvedt argues that unevenly distributed degassing from the earth’s

interior would lead to internal mass reorganization and trigger significant polar wander. However, this

would only be the case if the earth possesses a low enough strength and mantle viscosity; my article reviews this controversial issue at length and shows that it is still unresolved. Wrench tectonics claims

that the poles wandered some 35° within 2-3 Myr at the Eocene-Oligocene (E-O) boundary. Tsai &

Stevenson (2007), however, calculated that polar wander was limited to 8° in 10 Myr; they assumed a mantle viscosity of 3 x 1022 Pa S (which may be several orders of magnitude too low) together with

the existence of mantle convection and slab subduction.

Wrench tectonics states that over the past 450 Myr the north pole has moved from about 20°S to its present position, mainly along the 180° meridian, but that there have also been several reversals of

direction. In the Jurassic and lower Cretaceous the poles are said to have been not far from their

present positions, with the equator running across the Central Sahara. At about 100 Ma the equator allegedly shifted to the northern rim of the African continent, but then moved back to the Central

Sahara at 80-60 Ma, before returning to the southern rim of the Mediterranean in the lower Tertiary.

After the alleged rapid burst of polar wander at the E-O boundary (about 35 Ma), when the equator

shifted to around its present position across Central Africa, the equator moved north again in mid-Miocene time, cutting across Central Arabia, before returning to its present location around 5 Ma.

As I said in my article (p. 112), such a scenario, with the poles moving back and forth like a yoyo in more or less the same plane, seriously strains credulity, since internal mass anomalies would have to

arise and decay in a highly contrived and nonrandom fashion. I also pointed to various problems with

interpreting the climate shift at the E-O boundary in terms of polar wander, and highlighted the need to take account of more recent data on post-Eocene climate fluctuations.

Examples of the continental/plate rotations and translations proposed by wrench tectonics are the

following: most of South America rotated ~10º clockwise, while the northern portion rotated anticlockwise, and South America as a whole shifted southward by ~20°. Greater India rotated ~135°

clockwise near the Cretaceous-Tertiary boundary. Antarctica rotated 140° clockwise and Australia 70º

anticlockwise, and the Antarctica-Australia-New Zealand-Melanesia block moved 15° northeastward. As shown in my article, these claims cannot be reconciled with various structural lineaments that run

across oceans and continents. If the proposed continental/plate motions are implausible, something is

seriously wrong with the underlying assumptions of wrench tectonics, whatever its pretensions to be a ‘next-generation global tectonic platform’.

Storetvedt has developed his own method of selecting, handling and interpreting palaeomagnetic data.

The evidence he presents in support of the alleged 35° of polar wander around the E-O boundary provides an insight into his methods. He plots selected palaeomagnetic data for Europe North

America and Africa, ignores actual rock ages on the grounds that remagnetization has probably

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occurred, and simply ‘infers’ that the dates of the palaeopoles progress in a manner consistent with his

theory of a 35° shift of the poles (see figures 6.2 and 6.3 of my article). In his response, Storetvedt says I have not understood that he is talking about remagnetization ages. Perhaps he failed to notice

that I quoted his own remark that ‘magnetization and physical rock ages may easily have been

disconnected by remagnetization’ (p. 113). He does not address my suggestion that it would be better

to present the actual rock ages along with the ‘inferred’ ages and the rationale behind them. After all, if the only constraint on the inferred dates is that they must fit his pet theory, the approach could

hardly be termed ‘scientific’.

Storetvedt repeats his stock argument that ‘lithospheric wrenching is latitude-dependent – increasing

in intensity towards the palaeo-equator’ (p. 92). Of the inertial forces he likes to invoke, the

centrifugal force is indeed strongest at the equator, but as I mentioned in my article (p. 56-57), the Coriolis force (which he seems to think can rotate entire continents and the surrounding oceanic

lithosphere) is weakest at the equator, as far as horizontally moving material is concerned.

The Meyerhoff letter Arthur Meyerhoff and Karsten Storetvedt spent a day discussing their respective geotectonic

hypotheses in November 1993. We only have Storetvedt’s account of what was said (including his

interpretation of Meyerhoff’s body language), and some of it reads rather comically. Meyerhoff wrote

a letter on 10 March 1994 (in reply to one from Storetvedt), commenting on their hypotheses. Extracts from this letter were first published in 1999 (NCGT Newsletter, no. 12. p. 25-27), and again in 2010

(no. 55, p. 29). Storetvedt interprets the letter to mean that Meyerhoff had largely embraced wrench

tectonics.

Nowhere in the letter does Arthur Meyerhoff explicitly state that he has abandoned his earlier views

and now fully accepts large-scale polar wander and continental rotations as the only correct explanation of palaeomagnetic, palaeoclimatic and palaeontological data. If he had changed his views

so radically, it seems likely he would have made this known more widely. He remained in contact

with his coauthors until his death on 18 September 1994 but, according to Dong Choi (email, 2013),

he did not give any sign of having significantly revised his views. Nor did he do so in other published correspondence (see, for example, the extracts from a letter he wrote on 20 June 1994 in NCGT

Newsletter no. 6, p. 3-4).

Neither of his two posthumously published works (Meyerhoff et al., 1996a and 1996b) contains the

slightest hint of any ‘conversion’. The biogeography book (accepted for publication in July 1995)

presents palaeoclimatic and palaeontological evidence which is interpreted in the same way as in his

papers in the 1970s. The surge tectonics book (based on material prepared by Meyerhoff, and completed by his coauthors) states that palaeomagnetism is ‘plagued with uncertainties’ (p. 64) and

that polar wander ‘cannot be regarded as anything but speculation’ (p. 8). According to Irfan Taner,

another of his coworkers, Meyerhoff believed that crustal blocks could rotate, but not entire continents (NCGT Newsletter, no. 12, p. 24). This is in line with the evidence for deep continental

roots and the lack of a global asthenosphere, which are highlighted in the surge tectonics book.

Elsewhere in this issue (p. 116-120), Arthur Meyerhoff’s children provide further valuable

information setting the historical record straight.

Palaeoclimate Karsten Storetvedt calls Meyerhoff’s palaeoclimate maps ‘dubious’, and believes that he ‘implicitly

put his palaeo-climatic maps aside’ in his letter. But the maps simply plot the location of

palaeoclimatic indicators on the present globe, based on dozens of sources. It is in the interpretation of

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the data that the controversy lies – and proponents of all tectonic models are seemingly able to cite at

least some such data in support of their theories. The maps in Meyerhoff et al. 1996b are similar to those he published in the 1970s, because the underlying data are largely the same. (For comparison,

see the palaeoclimate maps compiled by Chris Scotese (www.scotese.com), though these have the

disadvantage of being plotted on plate-tectonic continental reconstructions.)

On Storetvedt’s map of Devonian evaporites, red beds and coral limestones (his figure 10), based on

Schwarzbach (1961; see figure 3 below), the evaporite areas show a reasonable match with those on

Meyerhoff et al.’s map (1996b, figure 7), based partly on Boucot & Gray (1983), though Schwarzbach omits some deposits. Storetvedt’s figure 12 (figure 4 below) shows his hypothetical tropical belt for

the mid-Palaeozoic, based on a south palaeopole at 0°E, 20°S; parts of the belt pass through many of

the areas marked in his figure 10.

Fig. 3. Climatic map of the Devonian (Schwarzbach, 1961, fig. 3). 1 – reef limestones; 2 – Old Red Sandstone

facies; 3 – evaporites; 4 – Iapo Formation and Table Mountain tillite; 5 – upper Devonian tillite; 6 –

palaeomagnetic north and south poles (after Runcorn); 7 – equator and polar circles; B – bauxite.

Fig. 4. Mid-Palaeozoic tropical zone, according to wrench tectonics.

It should be borne in mind, however, that evaporites, red beds and coral limestones are not necessarily tropical indicators. Corals are indicators of overall humid conditions, warm to cold (Boucot, 2009);

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Teichert (1964) cautioned that Palaeozoic corals and stromatoporoids should not be seen as indicators

of any specific water temperature. According to Joachimski et al. (2009), the Devonian palaeotemperature record suggests that microbial reefs dominated during warm to very warm intervals

whereas coral-stromatoporoid reefs flourished during cooler intervals.

Evaporites and red beds are indicators of arid climates. Arid zones can certainly be found in the tropics, but modern evaporites accumulate in desert areas located in two belts situated between about

15° and 45° north and south of the equator (Lugli, 2009). Interestingly, in the late Precambrian/early

Palaeozoic wrench tectonics places the north pole in Pakistan/Iran, in a region with widespread contemporaneous salt deposits (Storetvedt & Bouzari, 2012, fig. 1; Storetvedt & Longhinos, 2012).

The main locations of ancient evaporites are shown in figure 5. From the data plotted on his more detailed maps, Meyerhoff (1970) discovered that 95% of all evaporites from the late Proterozoic to

the present, by volume and by area, lie in regions which today receive less than 100 cm of annual

rainfall, i.e. in today’s dry-wind belts. Neither shifting the continents nor shifting the poles helps to

explain this distribution. Green (1961), too, concluded that ‘the distribution of evaporites through geological time can be explained on the basis of climatic change alone, without necessitating any

changes in relative positions of continental masses, or in positions of the rotational poles of the earth’

(p. 85). Van Houten (1961) showed that although shifting the poles to different palaeoclimatically or palaeomagnetically determined positions would move some Permo-Triassic red-bed deposits closer to

the equator, it would move other deposits very close to the poles.

Fig. 5. Location, approximate size, and age of the world’s major ancient evaporite deposits, together with

modern arid and semiarid areas. (Lugli, 2009, fig. E16)

In his letter to Storetvedt, Meyerhoff says that on some of the palaeoclimate maps the climate zones

do not run parallel to the equator. This is a point he had also emphasized in his earlier papers. Modern climate zones do not run parallel to the equator either, due to the distribution of land and sea,

continental topography and oceanic bathymetry, and related atmospheric and ocean circulation.

Meyerhoff explained the existence of high northern-latitude evaporites in certain geologic periods

partly in terms of the warmer global climate at such times and partly by tracing the history of sill

development across the Arctic and North Atlantic Oceans; the successive appearance of sills finally

diverted the saline waters, in Permian and Triassic times, into central and western Europe and the present Mediterranean. Meyerhoff & Meyerhoff (1976, p. 366) argued that it was no coincidence that

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the only regions with high-latitude evaporites – Proterozoic to Triassic – are the lands which today

border the North Atlantic Ocean and the Eurasian Basin of the Arctic Ocean, this being ‘the one region which is invaded by the only major warm, saline oceanic current to reach latitudes higher than

50°-55°’. Storetvedt dismisses this reasoned argument as ‘ad hoc’. Palaeoclimatologists, however,

regard the opening and closing of ocean gateways as a key factor in understanding past climates.

Palaeozoic glaciations

Storetvedt says that placing the mid-Palaeozoic pole near South Africa is ‘in correspondence with widespread glaciation in Central-South Africa at that time’. To assess this properly, we need to

consider the global distribution of glacial events. The locations of the main glacial deposits during the

three major Palaeozoic glaciations are outlined below.

Fig. 6. (Meyerhoff et al., 1996b, fig. 5; partly based on Boucot & Gray, 1983)

During the late Ordovician and early Silurian, short but severe glaciations affected parts of North

Africa, the Arabian Peninsula, South Africa, and South America (Ghienne, 2011; Finnegan et al., 2011; Díaz-Martínez et al., 2011; Díaz-Martínez & Grahn, 2007; Le Heron & Howard, 2010; Paris et

al., 1995; Biju-Duval et al., 1981). Glaciomarine deposits with dropstones of Ordovician/Silurian age

have also been found in Canada (Newfoundland/Nova Scotia – located in the wrench-tectonic

equatorial zone) (Schenk & Lane, 1981; Harland, 1981; Kennedy, 1981), and in various parts of Europe – Brittany, Thuringia and the Iberian Peninsula (Doré, 1981; Robardet & Doré, 1988; Steiner

& Falk, 1981; Paris et al., 1995). (See figure 6.) Le Heron & Dowdeswell (2009) rejected the concept

of a gigantic, continuous ice sheet covering a huge area of Gondwana in favour of the idea that small, separate ice sheets developed in different areas.

Most of the Devonian is believed to have been a time of widespread equable climates (Becker et al.,

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2012). Oxygen-isotope data from Australia, Europe and the mid-continent USA indicate that

temperatures were around 30°C in the earliest Devonian, falling to around 23 to 25°C in the mid-Devonian, rising again to around 30°C in the late Devonian, before falling again (Joachimski et al.,

2009). However, the cool-water Malvinokaffric fauna indicates a cooler climate in southern South

America, the southern tip of Africa, and Antarctica in early and middle Devonian times (Boucot &

Gray, 1983). In the Ordovician, Malvinokaffric fauna had extended into North Africa, Arabia, Western Europe, parts of northern South America, and a limited portion of easternmost North

America (see figure 6).

In the late Devonian and earliest Carboniferous, glaciation is believed to have affected northern-

central and southern Africa, and parts of South America, from Peru and Bolivia to the Amazonas and

Parnaíba basins (Caputo & Crowell, 1985; Caputo et al., 2008; Isaacson et al., 2008; Wicander et al., 2011; Streel et al., 2000), though some of the evidence has been called into question (Dickins, 1993).

Contemporaneous tillites and dropstones have also been found in the Appalachian basin of eastern

North America (Brezinski et al., 2008; Cecil et al., 2004), i.e. in the wrench-tectonic equatorial zone.

From the late Carboniferous to the early to middle Permian, a series of glaciations affected parts of

South America, Africa, Arabia, India, Tibet, Australia, and Antarctica (Caputo & Crowell, 1985;

Dickins, 1996; López-Gamundí & Buatois, 2010; Jones & Fielding, 2004). Dropstones, glaciomarine deposits, and diamictites of Pennsylvanian/Permian age have also been reported from Siberia

(Epshteyn, 1981a,b; Chumakov, 1994; Ustritsky, 1973; Raymond & Metz, 2004). (See figures 7 and

9.)

The conventional view is that the late Palaeozoic ice age was a single event lasting tens of millions of

years, but more recent research indicates that it comprised a series of shorter, discrete glacial events

(<1 to ~8 Myr in duration) separated by periods of warmer climate (Fielding et al., 2008a,b; Montañez & Poulsen, 2013). It began with short-lived, localized glacial events in South America around the

Devonian/Carboniferous boundary. In the latest Mississippian and the Pennsylvanian, ice expanded

across South America, southern Africa, Australia, and then Oman and Arabia. In the latter half of the Pennsylvanian, some evidence points toward climatic amelioration, though ice centres continued to

occur. A massive expansion of ice occurred at the Pennsylvanian-Permian boundary, focused on

Antarctica, Australia, southern Africa and South America, and glacial deposits in Siberia indicate that

glaciation was by this time bipolar. Ice sheets reached their maximum extent during the Asselian and early Sakmarian, after which they decayed rapidly. Glaciation may have continued intermittently in

Australia and Siberia throughout the late Early and Middle Permian. While major events appear to

have been synchronized globally, the timing of individual glaciations may have been asynchronous.

The wandering palaeopoles proposed by wrench tectonics shift some Palaeozoic glacial centres into

higher latitudes, but move other glacial deposits into lower latitudes, as far as the equator (see

Storetvedt’s figure 13 for his palaeoequators1). The same latitudinal spread of Palaeozoic glacial

deposits occurs if the poles are kept in their present positions. Even today ‘there are small glaciers

near or at the equator on all transequatorial continents, and, during the peak of Pleistocene glaciation,

some glaciers were widespread and at fairly low elevations’ (Meyerhoff & Teichert, 1971, p. 303-

304). In plate-tectonic reconstructions, Palaeozoic glaciations extended at their peak from the south pole to 20-30°S (Montañez & Poulsen, 2013); palaeomagnetic uncertainties allow the positions of

continents to be adjusted to keep glacial centres away from the equator.

1 Wrench tectonics places the north pole at 180°E, 20°N in the upper Ordovician (~450 Ma) and also in the Devonian (Storetvedt, 1997, figures 1.3, 3.4, 3.6). According to the ‘global’ polar wander path (1997, fig. 9.5), based on selected data from Africa and Europe, the pole was still in virtually the same place (about 21°N) in the lower Carboniferous (~350 Ma). By the upper Carboniferous-Permian (~300 Ma) it had moved to about 41°N. All wrench-tectonic palaeoequators for the past 450 Myr pass through two points on the present equator, at 90°E and 90°W.

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Fig. 7. (Meyerhoff et al., 1996b, fig. 8)

Needless to say, glaciations are not just polar phenomena, but can also occur at lower latitudes if the

elevation or other local factors produce suitable climatic conditions. The onset of glaciation is related to temperature, the presence of highlands, and the availability of moisture (Meyerhoff & Teichert,

1971). Mountain and valley glaciation played a major role in many of the Palaeozoic glacial events

(Dickins, 1985a; Meyerhoff & Teichert, 1971; Meyerhoff & Meyerhoff, 1974; Jones & Fielding,

2004; Fielding et al., 2008a; Montañez & Poulsen, 2013). Plate tectonicists initially assumed the existence in the late Palaeozoic of a massive icecap centred on the migrating palaeo-south pole in

Gondwana, but most now recognize the existence of small to moderate-size ice sheets emanating from

multiple ice centres during successive, short-lived glacial events, separated by warmer, sometimes ice-free conditions (Montañez & Poulsen, 2013). The size of Palaeozoic continental ice sheets (mainly

Asselian) is still a matter of contention; Dickins (1985a, 1992, 1993, 1996) presents a very critical

assessment of the evidence.

A fundamental feature of the earth’s evolving climate over geologic time is the succession of globally

warm and cool periods, resulting in significant changes in the width of climate zones. It is an

inescapable fact that regions can undergo dramatic changes of climate without any change in latitude. For instance, a lowermost Permian cold-water sequence (including tillites) is found in Arabia,

Pakistan, Peninsular and Himalayan India, and Tibet, containing Gondwanan fauna of low taxic

diversity. Above it lies a carbonate-bearing unit deposited in shallow, warm-water, tropical-subtropical seas, with rich, diversified, Tethyan fauna. In fact, early Permian cold-water Gondwanan

faunas are succeeded abruptly by Tethyan warm-water faunas from the Indian subcontinent to New

Guinea and Western Australia, and from the subcontinent to the Andes (Meyerhoff et al., 1996b;

Dickins, 1985b).

After reviewing climatic data for different continents during the Permian, Dickins (1985b) concluded:

If climate is to be taken as an indication of latitude during the Permian and other possible factors are put aside, it

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would be expected on the basis of this information that India would be closest to the equator, cratonic South

America and southern Africa further away, Australia further away again and Antarctica farthest. [T]his

information does not readily fit the currently proposed continental reconstructions for this time. (p. 87)

Moving the poles may help to explain selected evidence for particular periods but, as shown in my

literature review, when a broad range of climatic, faunal and floral data are considered, the evidence is

found to be readily compatible with the present location of the poles. The bipolar distribution of many

biotas since at least Devonian time strongly supports this (Meyerhoff et al., 1996b). A major unknown is the precise location and size of now sunken landmasses in different geologic periods, and how they

affected ocean and atmospheric circulation and faunal and floral migration.

On the basis of the inferred direction of ice movement, plate tectonicists believe that during the early

Permian, glaciers advanced into the Paraná basin of central-eastern South America from Africa, into

South Africa, eastern India and southern Australia from Antarctica, and into the sea basins of the Himalayas and Tibet from Australia (Chumakov & Zharkov, 2002). If the inferred ice movements are

correct, the glaciers could have originated on now sunken landmasses (Dickins et al., 1992; Vasiliev

& Yano, 2007). In the late Ordovician/early Silurian, the sedimentary record of glaciation in the Peru-

Bolivia basin indicates that glacial centres and sediment sources were located on a landmass to the west, including the Arequipa massif (Caputo et al. 2008; Díaz-Martínez et al., 2011). This, too, is an

area where various lines of evidence point to a former Palaeozoic landmass (Dickins, 1994).

Palaeomagnetic fantasies and discrepancies Figure 8 shows the plate-tectonic reconstruction for the mid-Devonian. A striking feature is the extent

to which Asia in particular has been chopped up into numerous separate units. Boucot & Gray (1983),

although staunch supporters of plate tectonics, severely criticized the modern palaeomagnetically-

inspired tendency to ‘slice and dice’ continents and shuffle the pieces around. They argued, for example, that a fragmented Asia was contradicted by the presence of lithofacies belts extending across

vast areas of the region, and that lithostratigraphic and biostratigraphic data also ruled out major

displacement between Europe, Africa and the Middle East. They presented an alternative reconstruction for the Devonian which they claimed was in accordance with geologic and climatic

evidence – but given that it is based on seafloor spreading, it violates a mass of data on the

‘anomalous’ age and composition of the seafloor.

Fig. 8. Plate-tectonic palaeogeographic reconstruction for the mid-Devonian (Becker et al., 2012).

KO = Kolyma-Omolon (northeast Russia); J = Japan; N.CH = North China; S.CH = South China;

KAZ. = Kazachstania (part of central Asia); TM = Tarim (western China); TB = Tibet; B.MA = Burma-Malaya;

IC = Indochina; NZ = New Zealand.

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The very different palaeogeographies to which different interpretations of (sometimes different) palaeomagnetic data can give rise can be seen by comparing figure 8 with the wrench-tectonic

reconstruction in figure 4. Numerous palaeolatitude discrepancies can be found, and they sometimes

become worse if corrections are made for the post-Palaeozoic continental movements postulated by

wrench tectonics. Karsten Storetvedt has not yet given his solution to the palaeomagnetically-based fragmentation of Eurasia, so it is not yet known how much the various blocks/terranes will have to be

rotated or displaced, and how much data selectivity or other ‘palaeomagic’ will be required to fit them

into the overall wrench-tectonic scheme.

According to Powell & Li (1994), the south pole was located off the coast of southern Chile at 400

Ma, reached eastern Brazil at 360 Ma, was in Central Africa at 340 Ma, moved across Antarctica from about 330 to 260 Ma, and then entered Australia, and was off the coast of West Antarctica at 175 Ma

(see figure 9).2 According to wrench tectonics, on the other hand, the south pole was never in any of

these precise locations in the middle to late Palaeozoic (the discrepancy ranges from ~10° to ~90°),

and Antarctica only became polar after about 35 Ma.

Fig. 9. The legendary Gondwana supercontinent, showing late Palaeozoic basins with glacial evidence in their stratigraphic record. Glacial episode I = late Devonian-earliest Carboniferous; Glacial episode II = early Late

Carboniferous; Glacial episode III = late Carboniferous-early Permian. (Circled numbers refer to chapters of the

GSA publication in question.) (López-Gamundí & Buatois, 2010, fig. 1)

To illustrate the variation in plate-tectonic reconstructions, five more apparent polar wander paths are shown in figure 10. Palaeomagnetists are free to fight out their differences among themselves.

2 In plate-tectonic literature, it is normal to give the 95% confidence circle radius for palaeomagnetic poles – often around 10° for the Palaeozoic (Robardet & Doré, 1988; Torsvik et al., 2012). This does not seem to be standard practice in wrench-tectonic literature.

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Fig. 10. Left: Four apparent polar wander paths (Torsvik & Van der Voo, 2002, fig. 4). The one by Scotese &

Barrett is said to give palaeoclimatic indicators precedence over palaeomagnetic data. Right: APW path by

Torsvik & Van der Voo (2002, fig. 5). Numbers are in millions of years.

Conclusion To repeat my previous article’s conclusion: ‘Geological, geophysical, palaeontological and

palaeoclimatic data do not require large-scale plate motion or polar wander; they point to nondrifting

continents and stable poles, with vertical tectonic movements causing periodic changes in the distribution of land and sea.’

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