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Better constrained selection of the Paleozoic West Gondwana (South America) paleomagnetic poles for the APWP determination


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The reliability of an Apparent Polar Wander Path (APWP) obviously depends on the paleomagnetic poles used to determine it. The APWP of Africa and South America are fairly well defined for the 330–260 Ma interval. However, this study pointed out a moderate shift between these two curves, and an incoherency of the South American data, contrary to the African ones, which are homogeneous. A number of South American pole positions were re-evaluated in an effort to better constrain the APWP for the entire continent. Most of discarded poles correspond to sites at the area of the junction of Cordillera with the stable craton. That could have structural implications for the evolution of the western margin of the Gondwana. A new criterion for the evaluation of paleomagnetic poles reliability for APWP is presented. Based on comparison of data from different continents and labeled “coherence” criterion, it is independent from Van der Voo’s ones.
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Stud. Geophys. Geod., 61 (2017), 185198, DOI: 10.1007/s11200-016-1036-9
© 2017 Inst. Geophys. CAS, Prague
Better constrained selection
of the Paleozoic West Gondwana (South America)
paleomagnetic poles for the APWP determination
1 Paléomagnétisme, Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Univ. Paris
Diderot and UMR 7154 CNRS, 4 avenue de Neptune, 94107 Saint-Maur cedex, France
2 CRAAG, B.P. 63, Bouzaréah 16340 Alger, Algeria
Received: May 9, 2016; Revised: September 4, 2016; Accepted: October 3, 2016
The reliability of an Apparent Polar Wander Path (APWP) obviously depends on the
paleomagnetic poles used to determine it. The APWP of Africa and South America are
fairly well defined for the 330
260 Ma interval. However, this study pointed out
a moderate shift between these two curves, and an incoherency of the South American
data, contrary to the African ones, which are homogeneous. A number of South American
pole positions were re-evaluated in an effort to better constrain the APWP for the entire
continent. Most of discarded poles correspond to sites at the area of the junction of
Cordillera with the stable craton. That could have structural implications for the
evolution of the western margin of the Gondwana. A new criterion for the evaluation of
paleomagnetic poles reliability for APWP is presented. Based on comparison of data from
different continents and labeled “coherence” criterion, it is independent from Van der
Voo’s ones.
K e y w o r d s : APWP, paleomagnetic poles, South America, Africa, Late Paleozoic,
Paleoreconstructions, Gondwana
Paleomagnetism is one of the main tools used for paleocontinental reconstructions.
Since the pioneering work of Creer et al. (1954), an Apparent Polar Wander Path (APWP)
has been progressively defined and improved for each main continent. An APWP is a plot
of the sequential positions of paleomagnetic poles from a particular area (tectonic plate,
continent, …), usually shown on the present geographic grid (see Butler, 1992). Well-
defined APWP can be used for innovative methods in paleoreconstruction such as
constraining paleolongitude (Wu and Kravchinsky, 2014). The “excellence” of an APWP
depends mainly on the reliability of the used selection of paleomagnetic poles. APWP
reconstruction methods vary (e.g., Van Alstine and de Boer, 1979; Thompson and Clark,
B. Henry et al.
Stud. Geophys. Geod., 61 (2017)
1981; Harrison and Lindh, 1982; Irving and Irving, 1982; Jupp and Kent, 1987; Le Goff
et al., 1992), but the present paper focuses on pole selection.
Van der Voo (1990) provided an objective method for evaluating paleomagnetic poles.
In the previous studies, a few compilations have applied reliability criteria (e.g., B, A, A*,
A** in Irving and Hastie, 1975; Irving et al., 1976a,b,c), when listing all experimental
data and results. The criteria proposed by Van der Voo (1990) are:
1. Reliable determination of the rock age and a presumption that magnetization is of
the same age. This criterion also implies magnetization polarity not in
contradiction with an expected polarity (particularly for long normal or reversed
2. Sufficient number of samples: N > 24, k (or K) 10 and
) < 16 (precision
parameter and 95% confidence limit, respectively, Fisher, 1953). We suggest that
this criterion could be specified requiring at least 3 independently situated
sampling locations, corresponding to different stratigraphical levels or to distance
between sites of more than 200 m and with at least 4 independent samples per site.
3. Adequate demagnetization that demonstrably includes vector subtraction.
4. Field tests that constrain the age of magnetization.
5. Structural control and tectonic coherence with craton or block involved.
6. The presence of field reversals.
7. No resemblance to paleopoles of younger age (by more than a period).
A paleomagnetic data fulfilling 4 or more of these criteria is considered as “robust”.
Nevertheless, as underlined by Van der Voo (1990), none of these criteria gives a proof
that magnetization is primary (except for the contact test - intrusion magnetization - and
mostly for the conglomerate test, for the criterion 4). Some of them correspond to
necessary but not sufficient conditions (criteria 1, 2, 3 and 5). Other issues related to the
reliability criteria are that the fold test provides key age constraints only when the age of
folding (in a pre-folding magnetization) is close to the age of the rocks. The presence of
reversals (criterion 6) can be found in both primary and secondary magnetizations (Henry
et al., 2004). Poles of different ages (criterion 7) can fall close to younger poles when the
continent has undergone little or no movement (rotational or latitudinal), or if the
continent occupied a similar position at two different time intervals as it was the case for
Africa at 200 and 100 Ma (e.g., Besse and Courtillot, 2002). It is however clear that
criterion like 1 or 5 are sometimes depending on authors interpretation. The main aim of
this paper is to look for another criterion, independent from the Van der Voo’s ones, to
better constrain the selection of paleomagnetic data to establish more reliable APWP.
The available paleomagnetic data (Derder et al., 2006; McElhinny et al., 2003;
Domeier et al., 2012, Torsvik et al., 2012, Amenna et al., 2014; Table S1 in
Supplementary Data), were used in our Gondwana compilation to build the main APWP.
All APWP described in this paper are shown on the southern hemisphere and in North-
West African coordinates (using the same rotation parameters as in Torsvik et al., 2008,
2012 for the Paleozoic time). The statistical approach that we used to build our APWP
Paleozoic West Gondwana paleomagnetic poles
Stud. Geophys. Geod., 61 (2017)
(Le Goff, 1990; Le Goff et al., 1992) requires that age uncertainty associated with each
pole must fall within a 20 My window around the mean ages on the APWP. We also apply
a secondary weighting based on the number of samples used to define the pole (see Le
Goff et al., 1992).
An incoherency concerning the Gondwana curves was evidenced recently during
a paleomagnetic dating study (age obtained by comparison of a paleomagnetic datum with
the reference APWP for the studied area). This study was carried out in North Africa
(Saharan craton) on the Zarzaïtine formation in the Anai area (Murzuq basin). This
formation is very well-dated at La Reculée section in the Illizi basin, farther north (see
Henry et al., 2014 and Fig. 1 herein), but none paleontological constraints was obtained in
the Murzuq basin. The newly obtained Anai pole for the Zarzaïtine formation was
compared with the Gondwana APWP (Amenna et al., 2014, completed for 240210 Ma
by the APWP of Domeier et al., 2012) and for 200 Ma to present time with the Africa
APWP (Besse and Courtillot, 2002). This comparison surprisingly highlighted relatively
to the Gondwana APWP a weak eastward shift of the Anai pole that does not affect the
significance of the age determination. However, the same moderate eastward shift was
Fig. 1. Apparent polar wander path (APWP, poles with their A
confidence angles) for
Gondwana (for 500250 Ma, after Amenna et al., 2014 and for 240210 Ma, after Domeier et al.,
2012) and for Africa (for 2000 Ma after Besse and Courtillot, 2002) and Late Carboniferous
(Henry et al., 1992; Derder et al., 1994,2001a,b; Amenna et al., 2014) and Early Permian (Derder et
al., 1994) African paleomagnetic poles, from the Illizi and Murzuq basins, in North-West African
coordinates (Anai pole, obtained in a formation of disputable age, was used for paleomagnetic
dating - Henry et al., 2014).
B. Henry et al.
Stud. Geophys. Geod., 61 (2017)
evidenced for all the other African poles for the period 330260 Ma (Fig. 1). The African
APWP for this period is very coherent and well-defined (Fig. 2a; Table S2 in
Supplementary Data) since several new reliable poles were acquired in the Saharan
platform during the last decades (see Table S1 in Supplementary Data). The few poles
from Antarctica and India are relatively scattered and do not yield reliable APWP. On the
contrary, APWP have been obtained from South America and Australia poles (Fig. 2b,c;
Table S2 in Supplementary Data). The main shape of the three curves (Africa, Australia
and South America) is similar in spite of very high uncertainty for the Early Paleozoic
poles from Africa and South America. For the Late Paleozoic, the African and South-
American curves are much better defined than the Australian path. The moderate
difference between the African and Australian APWP could be explained by significant
uncertainties in the reconstruction of the eastern part of the Gondwana (e.g., Schmidt et
al., 1990; Ricou et al., 1990; Li et al., 1993, Powell et al., 1998), as well as by the
relatively large paleomagnetic uncertainties of the Australian curve. This is not the case
for the difference between the South America and Africa paths, the first one being shifted
to the west of the Africa path (Domeier et al., 2011b,2012; Amenna et al., 2014). In fact
both curves are well-defined and the reconstruction Africa - South America in the
Gondwana supercontinent is thought to be highly reliable, even if slightly different
reconstructions were proposed (we used the same rotation parameters as in Torsvik et al.,
2012 for the Paleozoic time; see Nürnberg and Müller, 1991; Torsvik et al., 2008). This
westward shift of the South America APWP could explain, but does not justify, the
difference between the African poles and the Gondwana curve, which depends, at least in
part, on South American data. This difference between the two APWP being not related to
a misfit between Africa and South America, the incoherence arises from the APWP
We therefore reconsidered the selected paleomagnetic poles used to determine the
APWP for Africa and South America for the period 330260 Ma, for which, contrary to
previous periods like the Devonian (Fig. 2), both curves are well-defined. Figure 3 shows
the APWP for Africa (Fig. 3a) and South America (Fig. 3b) and the corresponding
paleomagnetic poles used to build them. The African APWP fits well with most of the
Fig. 2. Apparent polar wander path (APWP, poles with their A
confidence angles) for a) Africa,
b) South America and c) Australia: see pole list in Amenna et al. (2014). All in North-West African
coordinates (rotation parameters from Torsvik et al., 2012).
Paleozoic West Gondwana paleomagnetic poles
Stud. Geophys. Geod., 61 (2017)
African poles while the South American one is located between two groups of South
American poles and fitting with neither of these two groups (Fig. 3b). An effect of
inclination shallowing would have affected the data from sedimentary rocks everywhere
and cannot explain this separation into two groups of poles.
It is clear that the South America APWP pole selection is problematic and needs
improvement. Although most poles clearly belong to one of the two groups (NE or SW
groups), it is unclear which group contains some of the Late Paleozoic poles hereafter
called “questionable” poles that are in intermediate position (Fig. 3b). Based on a visual
inspection, we use a NW-SE line as a boundary between the two pole groups on the
present geographic grid (Fig. 3b). We emphasize that the introduction of the NW-SE line
is somewhat arbitrary. In order to check the variability of the obtained poles distribution,
we carried out APWP determination that included the “questionable” poles. The obtained
result for South America APWP was almost the same as without these poles (between
these APWP and only for the most recent mean poles, a very small angular difference,
lower than 2°, was obtained for the corresponding mean poles, defined with 10 My
intervals on the APWP). This introduces the question on which group is representative for
the South American continent. Taking into account the Van der Voo (1990) reliability
criteria, all paleomagnetic data have almost similar weight. To avoid circular reasoning
and obtain unbiased interpretation, the choice of the poles for the South America APWP
needs to be based on data independent from the South America poles. Only one of the
groups of South America poles is in agreement with the poles positions and the associated
well-defined APWP for Africa (Fig. 3b and see poles 19 in Fig. 4). Taking into account
the precise Africa - South America reconstructions within the Gondwana, the north-
eastern group can be considered as the representative of the stable South America APWP,
Fig. 3. Paleomagnetic poles (dots) with the A
confidence angles and corresponding apparent
polar wander paths (APWP) (black thick line) for the period 330260 Ma for: a) poles for Africa
(open circles) and b) South America (retained - north-eastern group: open circles; rejected - south-
western group: crosses; indexes (letters or numbers) correspond to sites locations in Fig. 4). For
comparison, APWP for Africa is indicated. c) Retained poles for the north-eastern group of South
American poles (open circles). All in North-West African coordinates.
B. Henry et al.
Stud. Geophys. Geod., 61 (2017)
close to Tomezzoli (2009) suggestion, but in contradiction with Domeier et al. (2012)
interpretation. In addition using only the data of the north-eastern group, the obtained
APWP correlates very well with the African curve (Fig. 3c). Such approach allows
suggesting a new additional criterion, labeled “coherence” criterion, based on the
research, among data from different and independent sources with homogeneous
characteristics (here from South America and Africa).
On the other hand, the most south-western group data lie to Western South America
(mainly close to the eastern border of the Andes Cordillera), in which the reliability
criterion 5 is not always satisfactorily fulfilled (Fig. 4). This could be related to tectonic
effects suspected in this area. The SW-ward shift of the poles of the south-western group
relative to those of the north-eastern group suggests a clockwise rotation around vertical
axis of the area close to the eastern border of the Andes Cordillera. This rotation could be
Fig. 4. Location of the paleomagnetic sites (from the pole list in Amenna et al., 2014) in South
America: For the South America apparent polar wander path (APWP), retained (north-eastern
group: open squares) and rejected (south-western group; full squares - white squares indicates sites
of the Paganzo basin with data compatible with the north-eastern group) data. Indexes (letters or
numbers) correspond to pole locations in Fig. 3b.
Paleozoic West Gondwana paleomagnetic poles
Stud. Geophys. Geod., 61 (2017)
due to a moderate dextral shearing.along the border of the Cordillera. However, some
poles from this area have positions compatible with the north-eastern group. The
assumption that they were not subjected to disturbances is matter of discussion and
without clear evidence, they cannot be definitely dismissed or accepted. This data
uncoherency within Paganzo basin rather suggests that disturbances were local, but
possibly in a context of moderate deformation along the whole Cordillera border. The use
of criterion 5 in this part of South America seems then not suitable.
Among the rejected data (south-western group, Table 1), two poles were obtained in
stable areas and fully satisfy criterion 5. These poles were obtained from two different
The Independencia group (Rapalini et al., 2006 - site “d” in Figs 3 and 4): The
Late Permian age of the studied levels, based only on a comparison with
a Brazilian formation, is not well defined. The Presence of both magnetic polarities
was used by Rapalini et al. (2006) as an indicator of a post-Kiaman age. However,
the obtained paleomagnetic directions have an orientation close to that of the
“recent” magnetic field (paleomagnetic pole at 80.7S, 7.0E in South American
coordinates) and are likely due to Cenozoic remagnetizations. Such recent
remagnetizations, with positive reversal test, were already obtained in the Algerian
Saharan platform (Henry et al., 2004; Lamali et al., 2014; Amenna, 2015).
The Santa Fé group (Brandt et al., 2009 - site “c” in Figs 3 and 4): The age is
assumed to be “Permo-Carboniferous”, although the upper age limit is not well-
Table 1. Retained South American (Southern hemisphere) paleomagnetic poles in the initial pole
list (Table S1 in Supplementary Data), in NW Africa coordinates for the period 330260 Ma. Age:
the mean age computed from the time scale given in the GPMDB; N: number of sites in each study;
Plat and Plong: pole latitude and longitude, respectively; Q: quality factor (Van der Voo, 1990);
RefNo/ResNo: reference number and result number, respectively, in the Global Paleomagnetic
Database (GPMDB) Ver.4.6 (February 2005) following McElhinny and Lock (1996).
Label Age
[Ma] N Plat
[°E] Rock Unit Q RefNo/ResNo
Mid to Late Permian (240270)255 Ma
8 255 8 47.9 59.0 Choique Mahuida Fm., Argentina 4 689
7 263 35 46.2 65.9 Sierra Chica, la Pampa, Argentina 6 Torsvik et al. (2012)
Early Permian (270290)280 Ma
6 275 20 32.8 65.1 Tunas Fm., Argentina 6 8459
Late Carboniferous 2 (290310)300 Ma
4 300 10 34.6 49.1 Pilar and Cas Fms, Chile 6 598
3 310 10 21.5 46.8 La Tabla Fm., Chile 4 597
2 310 12 24.8 39.2
Itarare Subgroup, Tubarao Group,
Brazil 3 2369
1 310 15 24.2 44.3 Piaui Formation, Brazil 3 3134
5 310 10 26.1 54.5 Pular and Cas Fms, Chile 6 Torsvik et al. (2012)
B. Henry et al.
Stud. Geophys. Geod., 61 (2017)
established (the Santa Fé formation is overlain by a Cretaceous group). This
suggests that this age could be not well constrained. In addition, the Santa Fé
virtual geomagnetic poles (VGP) are relatively scattered, with an elongated
distribution likely indicating a possible composite magnetization or more simply
a geological formation corresponding to a very large age window, possibly up to
Triassic (Ernesto et al., 2015) but not up to Lower Cretaceous (e.g., Geuna and
Vizán, 1998; Solano et al., 2010).
Table 1. Continuation: Not-retained South American (Southern hemisphere) paleomagnetic poles.
Label Age
[Ma] N Plat
[°E] Rock Unit Q RefNo/ResNo
Mid to Late Permian (240270)255 Ma
g 240 1 50.3 42.1
Amana Fm., Pagonzo, Goupr,
Argentina 5 Torsvik et al. (2012)
r 240 14 49.1 54.6
Puesto Viejo Fm. volcanis,
Mendoza 6 Torsvik et al. (2012)
a 248 6 50.4 25.5 Mitu Group red beds, Peru Torsvik et al. (2012)
d 260 10 46.3 49.8 Independencia Group, Paraguay Torsvik et al. (2012)
q 263 4 53.1 49.0 Porphyritic Series, Argentin 1205
f 265 1 53.3 49.2
La Colina Fm., Los Colorados,
Argentina 2721
Early Permian (270290)280 Ma
h 270 23 54.5 48.1
Middle Paganzo II, Upper Beds,
Argentina 3 3035
o 270 16 54.4 57.7 Tambillos Fm., Argentina 4 6376
m 278 9 35.3 55.8
Middle Paganzo II, Huaco,
Argentina 3 3038
k 278 26 31.8 55.1
Middle Paganzo II, Lower Beds,
Argentina 4 3036
p 278 16 51.8 60.5
Tambillos, Uspallate Basin,
Argentina 4 Torsvik et al. (2012)
b 280 9 43.5 26.1 Copacabana Group Sediments, Peru 4 Torsvik et al. (2012)
i 283 1 54.1 35.8 La Colina Fm., Paganzo 4 Torsvik et al. (2012)
e 290 19 53.9 50.2
Rio del Penon Fm. sediments and
del Agua Fm. Volcanics, Argentina
4 Torsvik et al. (2012)
Late Carboniferous 2 (290310)300 Ma
l 300 4 34.4 55.4 La Colina Basalt, Argentina 4 2490
c 300 60 34.0 33.5 Santa Fé Group, Brazil 4 Torsvik et al. (2012)
j 310 57 25.3 29.3 La Colina Fm., Argentina 5 7
Late Carboniferous 1 (310330)320 Ma
n 320 18 15.7 47.4 Hoyade Verde Synfold, Argentina 4 6378
Paleozoic West Gondwana paleomagnetic poles
Stud. Geophys. Geod., 61 (2017)
Other poles obtained from sites located near the Cordillera are also rejected due to the
limited reliability of criterion 5 as discussed below; precisely:
The poles (labels “a” and “b” in Figs 3 and 4) from the Copacabana group
(Rakotosolofo et al., 2006) and the Mitu group (Creer, 1970) were obtained in
areas affected by strong tectonics, probably including rotations, as shown by
Gilder et al. (2003).
The remaining poles (labels “e” to “s” in Figs 3 and 4) were obtained in the
Paganzo basin (Thompson, 1972; Valencio et al., 1977; Sinito et al., 1979; Geuna
et al., 2004,2010). According to Geuna et al. (2010), all the area was subjected to
a counter clockwise and southwards movement of the region with respect to the
rest of Gondwana. As shown in Fig 4, some Paganzo poles have positions
compatible with those of the north-eastern group (e.g., Embleton, 1970; Rapalini
and Vilas, 1971). These poles are presently not retained because of the proximity
of the studied sites with other sites showing disturbed data. As underlined above,
APWP determinations integrating or not these poles, provide almost the same final
result for the South America path.
Ignoring the reliability criterion 5, the “rejected” poles (south-western group, Table 1)
and the “retained” ones (north-eastern group, Table 1) have a similar Q factor (mostly
Q ~ 4). The final selection for the South American APWP was therefore based on
a complementary criterion related to the coherence of these poles with the precisely-
defined APWP for another continent, (the African one). Combined with other reliable
Gondwana data (Table S1 in Supplementary Data except rejected poles in the Table 1),
the retained South America poles yield an improved Gondwana APWP and a proposal for
Pangea reconstruction (Table S3 in Supplementary Data).
It is well-known for a long time that the western margin of South America was
affected by strong tectonics, particularly rotations (e.g., Butler et al., 1995; Macedo-
Sanchez et al., 1992; McFadden et al., 1995; Beck, 1998; Prezzi and Vilas, 1998; Somoza
and Tomlinson, 2002; Arriagada et al., 2006). Contrarily to this western area, the eastern
side of South America is a stable cratonic area. The “interference” zone between these
two areas is not everywhere clearly defined. Detailed analyzes of this zone (e.g., Carrapa
et al., 2014; Daxberger and Ritler, 2015) are key elements to better understand the
structural evolution of the South America. Paleomagnetism could provide one of the most
efficient approaches to this aim.
The present work shows that the problem is quite complex. The fact that the rejected
poles c and d, acquired in stable cratonic area, have disputable age of magnetization
acquisition shows that remagnetizations could also have had a significant effect. The
differences between paleomagnetic result within the Paganzo basin highlights the
importance of the reconsideration of these previous data (Tomezzoli, 2009; Domeier et al.,
2012; Tomezzoli et al., 2013).
B. Henry et al.
Stud. Geophys. Geod., 61 (2017)
The use of the new “coherence” criterion proposed by this study, yields to better
constrain the South America apparent polar wander path (APWP). It highlights a zone,
close to the eastern border of the Andes Cordillera, were paleomagnetic data are
disturbed. One of the important implications of the present work is to point out the major
interest of new paleomagnetic studies, not limited to Paleozoic formations, in this
“junction” zone. Though often difficult to publish in the present editorial context, these
studies represent in fact a key element for a better reconstruction of South America,
particularly at the limit between the deformed western and the stable eastern parts. In this
context, paleomagnetism appears as the single tool to point out possible rotations and
displacements in such areas. For the Paganzo basin, previous results have to be
reconsidered and new studies have to be developed in order to obtain a detailed picture of
its structural evolution. Similar areas along the eastern border of the Cordillera could also
be studied in order to have a more realistic understanding of the tectonic evolution in this
key part of South America, and therefore of the margin of the Western Gondwana.
Acknowledgements: We are very grateful to Jean Besse, Renata Tomezzoli and Augusto
Rapalini for constructive remarks that efficiently improved the paper, and to Diana and Neli
Jordanova, Karim Meziane and Joseph Meert for help with the manuscript.
Thanks also to Juan Jose
Vilalain and an anonymous reviewer for detailed and constructive comments.
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... centers have also been proposed, sourcing glacial-related facies to basins located around them. Again, the paleolatitudes of several of these hypothetic centers are too low (Scotese et al., 1999;Torsvik and Cocks, 2013;Henry et al., 2016) to expect the inception of glacial centers there. Most plausibly is that these areas behaved as low relief, non-subsiding regions, by-passed by the ice advance toward lower latitudes. ...
... When this information is plotted in Gondwana reconstructions, a clear radiating pattern comes out, evidencing a dispersing ice flow from polar regions (located in Antarctica) to areas located at lower latitudes within the supercontinent (Fig. 9). Although these indicators clearly have not the same age, during the involved time span (325-295 M.a.) the Apparent Polar Wander Path (APWP) of the southern pole stayed within Antarctica (Scotese et al., 1999;Torsvik and Cocks, 2013;Henry et al., 2016). The apparent polar displacement during this time was about of 1000 km, so assuming a "fixed" pole for the analyzed period seems to be an acceptable approximation for the discussion purposes. ...
... 6. Proposed LPIA ice sheet extension. 7. Apparent Polar Wander Path (APWP) for Gondwana(Henry et al., 2016) for the analyzed period. Af: Africa; An: Antarctica, In; India; Mg: Madagascar; SA: South America; Eq: Equator; S.P.: South Pole. ...
Two granitic boulders from the Pennsylvanian Tarija Formation were sampled in order to perform laboratory analyses to define their possible provenance. This formation, deposited during the Late Paleozoic ice age (LPIA), represents the climax of glacial-related sedimentation in the Tarija Basin. The boulders were collected from massive diamictite levels in the Cerro Piedras locality, in Eastern Cordillera. Zircons concentrated from these boulders yield Precambrian U-Pb ages. One of the obtained dates has a Concordia Age of 2068.97 ± 6.06 Ma, indicating a crystallization in Paleoproterozoic times. The obtained ages restrict the candidate source areas to remote regions, located along the cratonic, eastern side of South America. The Rio de la Plata craton is considered the most likely source area. Several granitoids in the Uruguayan portion of the craton (especially in the Piedra Alta Terrane) have radiometric ages between 2.1 and 2.0 G.a., providing a suitable source for the Tarija Formation boulders. The direction and sense of glacial movement indicators described both in the Tarija Basin and in Uruguay support this remote (at least 1500 km) provenance. The remote provenance of the analyzed boulders implies a sedimentary transport by glacial ice from Uruguayan sources to the northern end of Argentina, proving the occurrence of a continental scale ice sheet. Although the single, continental ice sheet theory has been questioned in the last decades, and alternative models were proposed, direct evidence presented here supports the single ice sheet model.
... On one hand, it is well known that the paleomagnetism is also a powerful tool to determine drift of the main tectonic plates and to provide paleocontinental reconstructions (e.g., Van der Voo 1993;McElhinny et al. 2003;Derder et al. 2006;Torsvik et al. 2012;Henry et al. 2017). Thus, it could give a global vision of the Paleozoic drift patterns of whole Gondwana and of the African plate after the opening of the Atlantic Ocean. ...
... Table 1). Reliability criteria (Van der Voo 1990; Henry et al. 2017) and paleomagnetic tests yielded separation of Table 1) and secondary (Table 2) magnetizations. Used tests (see Table 1) were fold test (Aifa et al. 1990;Derder et al. 2001aDerder et al. , c, 2009Merabet et al. 2005;Smith et al. 2006;Amenna et al. 2014) (Fig. 6), reversal test (Derder et al. 2001a) (Fig. 7) and contact test (Derder et al. 2016) (Fig. 8). ...
... The dip of the Paleozoic formations during intrusion has been determined by a small circles approach (see Henry et al. 2004a and references herein). It was interesting to notice that this dip had in some sites higher values than Fig. 11 Comparison of the Zarzaitine Illizi (Kies et al. 1995;Derder et al. 2001d), Anaï , Arrikine (Derder et al. 2016), Aïr (Hargraves et al. 1987) and Tin Serririne ) paleomagnetic poles with the Gondwana and Africa APWP (500-250 Ma- Henry et al. 2017;240-210 Ma-Domeier et al. 2012 and200-0 Ma-Besse andCourtillot 2002). K/Ar age of the Tin Serririne dolerites . ...
Numerous paleomagnetic studies were performed in the western Saharan basins, particularly during the last decades. Primary magnetization of the sedimentary formations older than Bashkirian appeared as totally overprinted. By contrast, 23 new coherent paleomagnetic poles, mainly from Bashkirian to Autunian age and from Middle Triassic to Lias age, were determined. These new data greatly improved the Apparent Polar Wander Path (APWP) for Africa, and consequently for the whole Gondwana, especially for the Upper Carboniferous. The corresponding paleoreconstruction strongly argued for an A2 Pangea during this last period. By its comparison with paleomagnetic data from undated geological units, this new APWP provided dating of these units. Paleomagnetic data highlighted also the existence of a post-Liassic regional tectonic event having affected the Paleozoic cover in the Sahara platform. Finally, several magnetic overprints, pointed out in these studies, are of chemical origin, with likely a significant role of ground-fluids. Indeed, fluids migration phenomena often favored chemical changes and remagnetization process. Upper Carboniferous, Permian and Upper Cretaceous–Cenozoic overprinting ages were thus probably linked to regional geochemical events that occurred in the Saharan Platform.
... The aim of this work was thus to highlight the main features of the WAC and its evolution during the Proterozoic through palaeomagnetism and the existing literature (Besse and Courtillot 2002;Domeier et al. 2012;Amenna et al. 2014;Merabet et al. 2014Merabet et al. , 2016Henry et al. 2017;Derder et al. 2019), since this part of the world is lacking palaeomagnetic data in general. ...
... A comparison with the APWP of RPC (Halls et al. 2001;Rapalini et al. 2015;Franceschinis et al. 2019) provides a few interesting poles that help to locate the Eglab-Yetti terranes at different periods of time (Fig. 13). The APWP of the present study closely follows the tentative APWP proposed by several authors for ages older than 200 Ma (Domeier et al. 2012;Amenna et al. 2014;Merabet et al. 2014Merabet et al. , 2016Henry et al. 2017;Derder et al. 2019). Very old data could not be considered since the development of new tools and analytical techniques allowed separation of magnetization components and identification of their possible carriers, but can, nevertheless, in some cases be used for discussion. ...
New palaeopoles have been calculated for the West African Craton (WAC) using palaeomagnetic data obtained on 178 cores of the Yetti–Eglab intrusions and stromatolite-bearing formation. One, two or three components of magnetization on 172 (14 sites) and 37 (6 sites) oriented specimens or cores were isolated mainly on doleritic dykes. High and low unblocking temperature components were evidenced in the dykes but also at four sites of the well-dated Hank stromatolite-bearing formation (875–890 Ma). Rock magnetic analyses show stable remanent magnetizations mainly carried by magnetite (or titanomagnetite) but may also reveal the presence of hematite, pyrrhotite and goethite. Regarding the recently constructed apparent polar wander path of the WAC until 500 Ma, these newly computed remanent components seem to be mainly older, some of which could be remagnetizations at different periods. However, according to geological dating and literature, the Yetti and Eglab terranes belonging to the WAC were amalgamated around 1.9 Ga and involved in the formation of the Columbia Supercontinent. The palaeopole computed for the stromatolite-bearing formation corresponds with the location of Rodinia Supercontinent at its early stages of amalgamation. The geodynamic evolution of the WAC with respect to both supercontinents suggests that the Eglab and Yetti could be separated by oceanic crust before 1.9 Ga. A volcanic arc developed during the subduction of this ocean followed by crustal thickening that generated an intrusive suite (Aftout granites) when it was at low northern latitudes. Baltica and Rio de la Plata cratons were close to the WAC after 1.7 Ga, following a nearly similar path between 1.7 and 0.9 Ga. In Africa, the collapse of the Birimian orogen was probably contemporaneous with the fragmentation of Columbia. At 0.9 Ga, Baltica was probably not attached to the WAC since the latter was not affected by the later Grenvillian orogen.
... The Tadrart pole can be compared with the APWP for Africa (Besse and Courtillot 2002;Domeier et al. 2012, modified from Le Goff et al. 1992Amenna et al. 2014;Henry et al. 2017) for a period with a sufficiently welldefined APWP (i.e., since 330 Ma). To have a reliable comparison, the variation, as a function of age, of the angular difference between the Tadrart chert pole and the APWP (including angular uncertainties A 95 from this pole and from each mean pole of the APWP) was analyzed (Fig. 10). ...
To improve the poor Gondwana paleomagnetic database for Devonian times, detailed paleomagnetic analyses were performed on red chert-like rocks and partly silicified paleosols within the Lower Devonian Ikniouen level (fine-grained sandstones including red ironstone) in conformity within the sub-horizontal Tadrart coarse white formations of the Murzuq basin. Silicification, limited to this level that is only a few meters thick, was probably due to tropical warm climatic conditions during and shortly after the rock deposition. In two sections 40 km away each other, paleomagnetic data point out a high-temperature Characteristic Remanent Magnetization (ChRM) with very well-defined mean direction, positive reversal test and relatively high (5) Q and R scores. Rock magnetic data indicate minerals of the hematite family, but the presence of a minor amount of other mineral phases remains possible. At least part of the ChRMs are Chemical Remanent Magnetizations, likely acquired during or shortly after deposition. The corresponding paleomagnetic results (paleomagnetic pole at 28.6° E and 71.1° S, with K = 1004, A95 = 1.5°) could have major geodynamical implications for the Gondwana supercontinent. In fact, ChRM acquired in this level during or shortly after deposition should imply a much-unexpected fast latitudinal continental drift of the Gondwana during the Lower Devonian or a significant and fast true polar wander. Though much more difficult to match with the ChRM and geological characteristics, the only possible alternative interpretation for the Ikniouen data should be a chemical remagnetization acquired during the Late Cretaceous–Early Paleocene times.
... They use paleomagnetic and rock-magnetic evidence to support a primary origin of the magnetization and in turn use this to question the validity of the TK03 paleosecular variation (PSV) model (Tauxe & Kent, 2004), when applied to the Paleozoic. However, the evidence presented for primary magnetizations is scant, and the study neglects a growing body of evidence that testifies to widespread secondary magnetizations affecting Paleozoic to early Mesozoic rocks in South America (e.g., Bilardello et al., 2018;Font et al., 2011Font et al., , 2012Henry et al., 2017). The failure to properly consider the extent and consequences of remagnetization in these rocks undercuts the authors' conclusions about paleofield behavior and validity of PSV models for the Paleozoic. ...
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The late Pennsylvanian glacial rhythmites of the Mafra Formation (Itararé Group) from the Paraná Basin of Southern Brazil, have a complex rock‐magnetic signature. Rock‐magnetic tests imply that both hematite and magnetite in varying grain sizes are responsible for the magnetic remanence. Thermal and alternating field (AF) demagnetization of the natural remanence reveal different behaviors that are attributed to a mixture of remanence‐carrying magnetic minerals and grain sizes, implying a series of magnetic overprints. A great circle analysis of the distribution characteristic directions reported suggests that these rocks may not be entirely immune from magnetic overprints acquired during the Jurassic‐Cretaceous in the context of widespread remagnetizations in South America. The nature of the magnetization recorded by these rocks warrants caution in their use for the evaluation of paleosecular variation models.
... presence of SD grains is taken to demonstrate that the remanence is stable regardless of whether it is specifically attributed to those grains; positive fold tests are often taken as proof of primary magnetizations instead of the mere indication that the remanence was likely acquired prior to the deformation event. Similar assertions can be made regarding other stability tests like the conglomerate or reversal tests, for example, even though their validities have been questioned (Henry, Merabet, et al. 2004, Henry et al. 2017, Heslop & Roberts 2018a. ...
... Some poles from the Andean Cordillera [e.g., Jesinkey et al., 1987;Gilder et al., 2003;Rakotosolofo et al., 2006] were included in recent compilations even though they have undergone a complex kinematic evolution, including vertical axis rotations [Somoza and Tomlinson, 2002;Geuna and Escosteguy, 2004;Arriagada et al., 2008;Henry et al., 2016]. For this reason, poles from the Andean Cordillera were not included in this contribution. ...
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The paleogeography of pre break-up Pangea at the beginning of the Atlantic Spreading has been a subject of debate for the past 50 years. Reconciling this debate involves theoretical corrections that cast doubt on available data and paleomagnetism as an effective tool for performing paleoreconstructions. This 50-year-old debate focuses specifically on magnetic remanence and its ability to correctly record the inclination of the paleomagnetic field. In this paper, a selection of paleopoles was made to find the great circles containing the paleomagnetic pole and the respective sampling site. The true dipole pole (TDP) was then calculated by intersecting these great circles, effectively avoiding non-dipolar contributions and inclination shallowing, in an innovative method. The great circle distance between each of these TDPs and the paleomagnetic means show the accuracy of paleomagnetic determinations in the context of a dominantly geocentric, axial and dipolar geomagnetic field. The TDPs calculated allowed a bootstrap analysis to be performed to further consider the flattening factor that should be applied to the sedimentary derived paleopoles. It is argued that the application of a single theoretical correction factor for clastic sedimentary-derived records could lead to a bias in the paleolatitude calculation and therefore to incorrect paleogeographic reconstructions. The unbiased APWP makes it necessary to slide Laurentia to the West in relation to Gondwana in a B-type Pangea during the Upper Carboniferous, later evolving, during the Early Permian, to reach the final A-type Pangea configuration of the Upper Permian. This article is protected by copyright. All rights reserved.
The Nugrus Shear Zone (NSZ) of southern central Egypt is a major ductile shear structure with controversial origins. It lies east of the Hafafit Gneissic Complex (HGC) and separates the Central and South Eastern Desert terranes of Egypt. The NSZ has been correlated with the Najd Fault system in Saudi Arabia, and shares orientation and kinematic characteristics with the Najd fault. Previous microstructural studies of the NSZ and HGC have concluded a polydeformation history for the Nugrus area, involving early NW-ward thrusting, followed by NW-SE transcurrent shearing. This contribution reports a combined rock magnetic and palaeomagnetic study of the shear zone and wallrocks that gives a conclusive evidence for the previously mentioned tectonic scenario. Furthermore, the palaeopoles obtained correlate well with the available geochronologically dated poles from Northern Africa, leading to inferred ages for the deformation and thermal events of the area. These ages confirm the previous proposed tectonic models. Three components of Natural Remanant Magnetization (NRM) direction (CA, CB and CD) are identified. Component CA represents the Characteristic Remanent Magnetization (ChRM). Components CB and CD are considered to be secondary magnetization. CA is consistent with arc-related deformation and magmatism at ∼ 700–680 Ma. CB and CD represent the protracted Najd-related shear deformation and transpression at ∼ 650–550 Ma.
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In Ordovician and Silurian sedimentary formations of the Murzuq basin (Saharan platform, Algeria), different remagnetization processes have been highlighted. These magnetic overprints totally replaced the primary magnetization. They are mainly due to chemical phenomena. Even in a site affected by contact metamorphism during Devonian, chemical changes, associated to the acquisition of the thermo-remanent overprint, were important, affecting the characteristics of the magnetite grains. In the remaining sites, remagnetizations of Cenozoic age have also a chemical origin and are carried by magnetite as well as by hematite. Contrary to what is generally deemed, these remagnetizations processes appeared limited to very short duration of acquisition, and to very local geographical extension.
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A paleomagnetic studystudywork was carried out on the Alto Paraguay Province (APP), a belt of alkaline complexes that parallel the Paraguay river for more than 40 km at the border of Brazil and Paraguay. The province is well dated by 40Ar/39Ar method giving ages in the range 240–250 Ma with a preferred age of 241 Ma. Intrusive rocks are predominant but the stocks may be topped by lava flows and ignimbrites. Paleomagnetic work on stocks, dikes and flows of the APP identified normal and reversed magnetic components which are carried mainly by titanomagnetites. The calculated paleomagnetic pole located at 319ºE 78ºS (α
The magnetic properties of the Carboniferous-Permian red beds of the Patquía Formation at Punta del Viento, Sierra de Umango and some previously reported localities, all in the Paganzo Basin (Argentina) have been studied. Whereas all sites are characterized by hematite as the main magnetic carrier and a reversed-polarity magnetic remanence, we found a pattern of variation in magnetic properties along the integrated column for Patquía Formation. The Lower Member (Late Carboniferous) showed higher intensity of natural and saturation isothermal remanent magnetisation (NRM and SIRM, respectively) than the Permian Upper Member. The fall in NRM intensity from the Lower to Upper Member of the Patquía Formation may be related to a change in quantity and/ or grain-size of the hematite pigment, which may reflect the change in environmental and/or depositional setting. As for directional values of NRM, paleomagnetic poles reported for both sections are clearly different. The lower section provided a pole position coincident with Late Carboniferous poles for Gondwana, while the upper section poles are departed from the Early Permian position. We cannot decide whether the Upper Member pole is due to a primary magnetisation at 290 Ma or to a remagnetisation at ~260-270 Ma; even so, the obtained paleomagnetic pole is robust and indicates a rapid apparent polar wander in a ~30° counter clockwise rotation of the region, after deposition of the Late Carboniferous lower section, and in coincidence with the San Rafael Orogenic Phase.
The remanent magnetizations of samples of sediments and lavas from Great Britain, representative of widely different geological epochs, have been studied. Evidence for the stability of these magnetizations from times soon after the formation of the rocks has been found. These results seem most easily interpreted in terms of a dipole field, the polarity of which frequently reverses. In Pre-Tertiary times the axis of this dipole field diverges considerably from the present geographical axis and this is tentatively interpreted as a slow change in the axis of rotation of the earth with respect to its surface.
Currently presented reconstructions of Gondwana derive from Du Toit and fits India with Antarctica. However, present geological knowledge necessitates an India-Antarctica fit but this did not lead to a complete solution which could avoid a questionable oceanic gap within the megacontinent. We propose a solution which is based upon the geological and paleomagnetic data, is consistent with the recent oceanic data and accounts for the major fault zone which splits Antarctica into two parts. There is an abridged English version. -English summary