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Earth and Planetary Science Letters 414 (2015) 156–163
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Earth and Planetary Science Letters
www.elsevier.com/locate/epsl
The Cretaceous opening of the South Atlantic Ocean
Roi Granot a,∗ , Jérôme Dyment b
a
b
Department of Geological and Environmental Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
Institut de Physique du Globe de Paris, CNRS UMR 7154, Sorbonne Paris Cité, Université Paris Diderot, 75005 Paris, France
a r t i c l e
i n f o
Article history:
Received 2 October 2014
Received in revised form 8 January 2015
Accepted 13 January 2015
Available online xxxx
Editor: P. Shearer
Keywords:
plate motions
South Atlantic
magnetic anomalies
quiet zone
a b s t r a c t
The separation of South America from Africa during the Cretaceous is poorly understood due to the
long period of stable polarity of the geomagnetic field, the Cretaceous Normal Superchron (CNS, lasted
between ∼121 and 83.6 Myr ago). We present a new identification of magnetic anomalies located
within the southern South Atlantic magnetic quiet zones that have arisen due to past variations in the
strength of the dipolar geomagnetic field. Using these anomalies, together with fracture zone locations,
we calculate the first set of magnetic anomalies-based finite rotation parameters for South America and
Africa during that period. The kinematic solutions are generally consistent with fracture zone traces
and magnetic anomalies outside the area used to construct them. The rotations indicate that seafloor
spreading rates increased steadily throughout most of the Cretaceous and decreased sharply at around
80 Myr ago. A change in plate motion took place in the middle of the superchron, roughly 100 Myr ago,
around the time of the final breakup (i.e., separation of continental–oceanic boundary in the Equatorial
Atlantic). Prominent misfit between the calculated synthetic flowlines (older than Anomaly Q1) and the
fracture zones straddling the African Plate in the central South Atlantic could only be explained by a
combination of seafloor asymmetry and internal dextral motion (<100 km) within South America, west
of the Rio Grande fracture zone. This process has lasted until ∼92 Myr ago after which both Africa and
South America (south of the equator) behaved rigidly. The clearing of the continental–oceanic boundaries
within the Equatorial Atlantic Gateway was probably completed by ∼95 Myr ago. The clearing was
followed by a progressive widening and deepening of the passageway, leading to the emergence of north–
south flow of intermediate and deep-water which might have triggered the global cooling of bottom
water and the end for the Cretaceous greenhouse period.
© 2015 Elsevier B.V. All rights reserved.
1. Introduction
Seafloor spreading between South America and Africa began
around Anomaly M13 (134 Myr ago, Channell et al., 1995) in the
southernmost part of the South Atlantic Ocean and then propagated northward toward the Equatorial Atlantic Ocean. The initial breakup probably resulted from the inception of the Tristan
hotspot that formed the Paraná–Etendeka large igneous province
(Renne et al., 1992). Despite their geodynamic and paleooceanographic importance, the relative motions between the two plates
during most of the breakup period are still poorly resolved due to
the lack of reversal-related magnetic anomalies on crust of age 121
(Anomaly M0y) to 83.6 (Anomaly C34y) Myr old (Malinverno et al.,
2012; Ogg, 2012). This crust, formed during the Cretaceous Normal
Superchron (CNS), is termed the magnetic “quiet zone” and is the
focus of the present study.
*
Corresponding author. Tel.: +972 8 6477509.
E-mail address: [email protected] (R. Granot).
http://dx.doi.org/10.1016/j.epsl.2015.01.015
0012-821X/© 2015 Elsevier B.V. All rights reserved.
The available kinematic models for the opening of the South
Atlantic during the CNS (Eagles, 2007; Heine et al., 2013; Jones
et al., 1995; Moulin et al., 2010; Nürnberg and Müller, 1991)
are based on interpolation between the rotation parameters of
M0y and C34y, predicting an opening age of ∼110–104 Myr ago
(clearing of continental–oceanic boundaries, COBs) for the Equatorial Atlantic Gateway, even though equatorial sedimentary facies and subsidence rates (Pletsch et al., 2001) and global compilation of benthic foraminifera stable isotopes (Friedrich et al.,
2012) indicate that the establishment of deep-water circulation
between the South and Central Atlantic Basins started roughly
10–15 Myr later. Recent studies have tried to overcome this contradiction by using either the seaward-edge of the salt basins
(Torsvik et al., 2009) or gravity scars located within the South
Atlantic quiet zones (Pérez-Díaz and Eagles, 2014) to constrain
the rotation parameters during the superchron. These works had
to assume that these markers were stable since their formation
(i.e., isochrones-like features) and assign ages, which are poorly
constrained.
R. Granot, J. Dyment / Earth and Planetary Science Letters 414 (2015) 156–163
157
Fig. 1. Tectonic map of the South and Equatorial Atlantic Oceans superimposed on a satellite-derived free-air gravity field (Sandwell et al., 2014). Magnetic picks and FZs
crossings are shown with empty symbols for the six anomalies used (rounded ages are shown in Myr). Filled symbols show the rotated picks (rotation parameters from
Table 1). The gray flowlines are calculated on the basis of the rotation parameters of Cande et al. (1988), covering the last 79 Myr (Anomaly C33o to present), and the red
lines are flowlines calculated on the basis of the new stage rotations (Fig. 3b, Anomalies M2o to C33o, marked with filled black circles). Red stars denote the initiation points
of the displayed flowlines. For uncertainties on selected flowline locations see Fig. 4. Dashed red flowlines delineate the expected location of FZs using interpolation between
the rotation parameters of Anomalies M0y and C34y. Blue lines mark the oldest conjugate anomalies formed along the fossil spreading axes (black dashed lines) (Cande et
al., 1988; Cande and Rabinowitz, 1978). Arrows show the expected position of the flowlines based on the gravity data. Gray shaded area demarcates a sliver of transferred
crust (Sandwell et al., 2014).
Although geomagnetic reversal-related anomalies are the most
prominent magnetic signature of the oceanic crust, past changes in
the strength of the dipolar geomagnetic field are also recorded, resulting in globally correlatable wiggles within geomagnetic chrons
(Bouligand et al., 2006; Cande and Kent, 1992; Granot et al., 2012;
Pouliquen et al., 2001). Two globally traceable magnetic anomalies from the CNS (Granot et al., 2012) are used here to define
internal ages within the South Atlantic quiet zones: the oldest is
a long-wavelength wiggle (Anomaly Q2, 108 ± 1 Myr ago) and the
youngest (Anomaly Q1, 92 ± 1 Myr ago) is a short-wavelength wiggle, which is followed by subdued magnetic anomalies toward the
younger end of the quiet zones. The ages (and uncertainties) of
these anomalies are based on the ages of the oldest sediments that
were drilled in the Central Atlantic Ocean (Granot et al., 2012).
We have picked the location of these CNS magnetic anomalies and
combined them with fracture zone (FZ) locations to compute internal rotation parameters for the superchron period. We complement
these two rotations with a new set of picks for Anomalies M2o,
M0y, C34y and C33o. From these finite rotations we derive stage
rotations that constrain the relative motion of South America and
Africa at 5 to 15 Myr intervals between 124 and 79 Myr ago. We
then discuss the evolution of seafloor spreading in the South Atlantic and conclude with the geodynamic and paleooceanographic
implications of our results.
2. Data and methods
We constrain South America–Africa motion by using magnetic
anomaly picks and FZ traces found south of the Tristan da Cunha
FZ, where both quiet zones are fully preserved (Figs. 1, 2 and
S1). Locations of FZs were selected from the satellite gravity
map (version 23) of Sandwell et al. (2014). Magnetic anomaly
data were obtained from the National Geophysical Data Center
(NGDC) and contain both shipboard and aeromagnetic (Project
MAGNET) profiles. The locations of the reversal-related anomalies
were picked based on forward modeling whereas the location of
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R. Granot, J. Dyment / Earth and Planetary Science Letters 414 (2015) 156–163
Fig. 2. Magnetic anomaly profiles used in this study. Location of Anomalies Q2 and Q1 are shown with arrows. The profiles are located between FZs to prevent tectonic
complications at segment ends.
the geomagnetic intensity-related anomalies were determined by
comparison against profiles from other oceanic basins (Granot et
al., 2012). We identified Anomalies Q1 and Q2 within each quiet
zone by (1) tracing the general, long wavelength shape of the magnetic profiles and (2) picking their exact locations by correlation
of the short wavelength signal. We note that tectonic-related features (e.g., buried seamounts, variability in the basalt iron content,
undetected small offsets of the spreading centers, etc.) may alter
the shape of the anomalies enough to locally mask the intensityrelated signal. We therefore assigned conservative data uncertainties of 4 km and 5 km to the magnetic and FZ picks, respectively,
to account for these difficulties while computing the finite rotation
parameters.
Finite rotation parameters were calculated by implementing the
statistical routines of Kirkwood et al. (1999) and Royer and Chang
(1991). We define the location of six anomalies (M2o, M0y, Q2,
Q1, C34y and C33o, Supplementary Table S1), and together with
FZ crossings we calculate a set of finite rotation parameters (poles
and angles), with their 95% uncertainty intervals (Fig. 3a and Table 1). From the finite rotations we compute five stage poles that
describe the evolution of relative motions between the two plates
throughout most of the Cretaceous.
The ages of the Cenozoic anomalies follow the geomagnetic polarity timescale of Ogg (2012). The ages of the Mesozoic anomalies
(M-sequence) are less certain. We adopt 121 Myr old as the age
for Anomaly M0y and 124 Myr old as the age for Anomaly M2o
(He et al., 2008; Malinverno et al., 2012). We note that the choice
of the Mesozoic timescale affects only the calculated spreading
rates and tectonic inferences for the period bounded between
Anomalies M2o and Q2, since Anomalies Q2 and Q1 were independently dated (Granot et al., 2012).
3. Finite rotations
The six finite rotations and their uncertainty ellipses are shown
in Fig. 3. The rotations and their covariance matrices are presented
in Table 1. Generally, the locations of the poles are well-defined
and their positions form a clear trend. The values of the statistical
parameter κ̂ (Royer and Chang, 1991) are near one (Table 1) in-
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Fig. 3. Kinematics of the South Atlantic Ocean. a, Finite rotation poles with their 95% confidence limits. Dashed red line corresponds to the 95% confidence limits for the
solution calculated on the basis of data obtained south of the Rio Grande FZ. b, Stage poles for South America–Africa displacements. Poles are shown for South America
(red) and Africa (green). c, Spreading rates between South America and Africa along the Rio Grande FZ synthetic flowlines (blue). Gray bars show 95% confidence intervals.
Bars along the abscissa show chrons. Gray line shows spreading rates that are based on Mesozoic (Nürnberg and Müller, 1991) and Cenozoic (Cande et al., 1988) kinematic
solutions, with interpolated spreading rates for the CNS. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this
article.)
Table 1
Finite rotations and covariance matrices for the relative motion of Africa (fixed) and South America. The covariance matrix is given by the formula κ̂1 ∗
Age
(Ma)
Mag. ano.
Lat.
(◦ N)
Long.
(◦ E)
Angle
(◦ )
κ̂
79.9
83.6
92.0
108.0
120.6
124.0
C33r
C34
Q1
Q2
M0y
M2o
62.47
61.98
60.84
62.17
53.55
52.16
326.08
325.32
323.50
319.83
324.36
324.90
30.94
33.48
38.58
47.35
52.75
53.86
0.59
1.19
0.69
1.41
0.87
2.33
a
b
c
d
e
f
7.73
6.45
18.93
491.62
51.66
38.17
−4.31
−3.61
−14.70
−531.78
−58.28
−45.92
−4.83
−4.01
−15.72
−653.66
−64.08
−48.62
4.77
5.48
14.84
579.8
74.76
60.63
3.69
3.77
14.23
709.15
75.82
60.91
4.26
3.83
16.17
874.31
83.10
64.60
dicating that the uncertainty assigned to the data points used to
calculate the solutions were reasonable.
The identification of anomalies within the quiet zones is not
straightforward and requires special care. We validate the kinematic solution of Anomaly Q1 by re-calculating the rotation parameters by including magnetic picks from an additional spreading
segment located between the Bode Verde and Rio de Janeiro FZs,
for which there are sufficient data on both flanks (Fig. 1). A recent update of the satellite-derived world gravity field (Sandwell
et al., 2014) unraveled conjugate tectonic features of pseudofaults
and a sliver of transferred crust within this spreading segment
(Fig. 1). This suggests that an episode of northward ridge propagation possibly related to the Tristan hot spot activity has affected
the crust located ∼100 km west of the (soon to be failed) spreading axis. To avoid the possibility of a biased kinematic solution, we
have limited our identifications of Anomaly Q1 to the region located south of the tectonically-affected crust. The new solution is
identical to the one constrained solely by the southern spreading
segments, but it is better defined (Fig. 3a), confirming the Q1 identifications. The identifications and kinematic solution of Anomaly
Q2 are less certain (Table 1) due to its long wavelength nature
and the general tendency for strong and varied wiggles within
the middle part of the quiet zones (Granot et al., 2012). Although
less reliable, the Q2 solution provides a useful constraint on the
!a b c "
bd e
c e f
∗ 10−7 rad2 .
Points
Segs.
63
58
33
26
28
31
7
7
7
4
4
4
relative motion between the plates for the middle part of the superchron.
4. Stage rotations
To evaluate the predictive quality of the new finite rotations we
calculate stage rotations (Fig. 3b) and generate synthetic flowlines
(Figs. 1 and 4) that, ideally, should trace the actual position of FZs.
Indeed, the southern flowlines (north of the Falkland-Agulhas and
Gough FZs) trace their positions within uncertainties (Fig. 4). Similarly, north of the Ascension FZ, in the northern part of the South
Atlantic Ocean and in the Equatorial Atlantic Ocean (Figs. 1 and 4),
the synthetic flowlines trace the actual location of FZs. Altogether,
these results indicate that the kinematic solutions presented here
are robust, even for the Cretaceous quiet zones.
In contrast to the southern and northern sections of the spreading system, there is a growing misfit between the FZs and the
synthetic flowlines on the African flank between (and including)
the Rio Grande and Ascension FZs. The misfit starts at Anomaly Q1
and grows to about 100 km towards Anomaly Q2 (Figs. 1 and 4).
This one-sided misfit could have resulted from an asymmetric
spreading episode that would have taken place between Anomalies Q2 (or possibly before) and Q1, whereby eastward migration of
the ridge there would have led to more lithosphere on the South
American flank. Alternatively, the misfit might have formed due to
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Fig. 4. Oblique Mercator projections (Anomaly C34y pole, 325◦ N, 62◦ E) of selected FZs. Synthetic flowlines (red) are based on new stage poles (Fig. 3b). Dashed red lines
show interpolated flowlines; green lines are flowlines computed assuming internal motion within Africa; purple lines are flowlines assuming internal motion within South
America; and light blue lines are flowlines assuming asymmetric spreading (70 percent of lithosphere created on the South American plate between Q2 and Q1). Details of
the parameters used are given in the text. Confidence intervals for the locations of Q1 and Q2 are shown. Arrows show the expected positions of the flowlines based on the
gravity data.
a missing plate boundary that straddled the Rio Grande FZ or a
nearby FZ, cutting through either of the two continents.
Kinematic simulations (Fig. 4) enable us to choose the most
suitable of the three possible tectonic scenarios. First, for the flowlines to fit the FZs of the African flank due to continental deformation within the African plate, it is necessary to have an internal African rift that could be described by a 1.3◦ rotation over a
345◦ E/15◦ S pole. In such a scenario, the misfit between the synthetic flowlines and the FZs of the African flank is indeed reduced,
but it introduces an unacceptable misfit to their conjugate FZs
located on the South American flank (Fig. 4, green lines). Furthermore, this scenario would require an unrealistic opening motion
within Africa (∼110 km of N–S opening near the East African
Rift). This prediction is not supported by geological observations
(Heine et al., 2013; Moulin et al., 2010) and we thus consider it
unlikely.
Introducing ∼106 km of dextral strike slip motion along the
Rio Grande FZ and further west within the South American Plate
(−1◦ rotation over a 306◦ E/79◦ N pole) provides a better fit to the
flowlines of the African flank while not affecting the fit to the
South American FZs (Fig. 4, purple lines). Importantly, the region
where the Rio Grande FZ meets the South American continent is
considered to be a deformed zone that might have accommodated
some (tens of kilometers) strike slip motion in the Cretaceous
(Eagles, 2007; Moulin et al., 2010; Torsvik et al., 2009).
Alternatively, asymmetry in seafloor spreading may have been
fueled by the proximity to the active Tristan da Cunha hotspot
(Rohde et al., 2013), resulting in an eastward migration of the
ridge axis. We modeled asymmetric seafloor spreading by assigning roughly 70 percent crustal accretion on the South American
flank between Anomalies Q2 and Q1. We assigned 60 percent
asymmetry for the spreading segment confined between the Bode
Verde and Rio de Janeiro FZs due to the ridge propagator and capture of transferred crust there (Sandwell et al., 2014). Asymmetric
seafloor spreading helps to fit (yet not perfectly) the FZs of the
African flank without affecting the South American fit while still
complying with the location of the anomalies (Fig. 4, blue lines).
Two Cretaceous fossil spreading axes dated by magnetic anomalies
to be active prior (Cande and Rabinowitz, 1978) and after (Cande
et al., 1988) the CNS are indeed found on the current South American flank (Fig. 1), supporting the scenario that seafloor spreading
asymmetry must have started before and continued after the CNS,
with a preferentially eastward motion of the spreading axis, i.e.,
more lithosphere accreted to the South American flank. Moreover,
R. Granot, J. Dyment / Earth and Planetary Science Letters 414 (2015) 156–163
161
Fig. 5. Plate reconstructions and global bottom water temperatures. Plate reconstructions are shown at Anomalies Q2, 108 ± 1 Myr ago (a), Q1, 92 ± 1 Myr ago (b), and
C34y, 83.6 Myr ago (c). South America is fixed. Contours correspond to 1000- and 2000-m isobaths. The geometry of the mid-ocean ridges are constrained only where we
have magnetic anomaly picks (Fig. 1) and interpolated elsewhere. d, Benthic foraminifera oxygen isotopic data from Friedrich et al. (2012). Arrow delineates the initiation of
cooling of global deep-water masses.
gravity scars located within the South American quiet zone may
preserve evidence for the abandoned spreading center that was left
behind when the ridge migrated eastward (Pérez-Díaz and Eagles,
2014).
To conclude, our new rotations suggest that up to ∼100 km of
dextral motion has been accommodated within the South American Plate, west of Rio Grande FZ, after 121 Myr ago (Anomaly
M0y). Additionally, the central part of the South Atlantic was probably formed with some degree of asymmetric seafloor spreading resulting in preferential accumulation of crust to the South
American Plate. The exact amount of internal dextral deformation within South America depends on the magnitude of asymmetric seafloor spreading and therefore still remains uncertain.
Finally, the excellent fit of our flowlines to the actual position
of FZs on crust younger than Anomaly Q1 (Figs. 1 and 4) implies that internal continental deformation must have stopped
by 92 Myr ago, in agreement with geological observations from
Africa and South America (Heine et al., 2013; Moulin et al., 2010;
Torsvik et al., 2009).
5. Geodynamic implications
The new kinematic solutions presented here provide important constraints on the relative motions between Africa and South
America during their final stages of separation. The close proximity of the early rotation poles (Fig. 3b) to the Equatorial Atlantic implies that a slow rotational motion governed the equatorial area while the continents were still partly attached (Fig. 5).
Applying linear interpolation between the different rotations, our
plate reconstructions indicate that the transition from rift to drift
(breakup) took place at around 99 ± 1 Myr, assuming rigidity of
both plates. Independent palaeomagnetic data indicate that a vir-
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R. Granot, J. Dyment / Earth and Planetary Science Letters 414 (2015) 156–163
tual geomagnetic pole standstill of South America ended at around
100 Myr ago and was followed by a westward drift of the continent (Somoza and Zaffarana, 2008). This finding supports the
∼100 Myr timing for the final breakup between Africa and South
America. Rapid northward migration of the stage rotation poles after Anomaly Q2 (Fig. 3b) reveals a major plate reorganization of
the South Atlantic spreading system. This change in plate motion
has previously been linked to a supposedly global plate reorganization event at around 105–100 Myr, possibly triggered by the dynamics of subduction and mantle plumes (Matthews et al., 2012).
Our new reconstructions provide an alternative explanation suggesting that the plate motion reorganization in the South Atlantic
coincided with the final separation of South America and Africa.
Seafloor spreading rates increased steadily from slow rates (full
spreading rate of 20 mm/yr along the Rio Grande FZ) before the
CNS and peaked at intermediate rates (77 mm/yr, Fig. 3c) immediately after the superchron. Motion has decreased to intermediate
spreading rates (40 mm/yr) towards 60 Myr ago (Cande et al.,
1988). Interestingly, spreading rate has peaked some 20 Myr after the completion of separation of the plates. A similar tectonic
pattern, i.e. reorientation of relative plate motion direction and an
increase followed by a delayed decrease in spreading rates, occurred in the Northeast Atlantic during and after the breakup of
Greenland from Europe (Gaina et al., 2009). These two examples
suggest that the development of plate motions during (and up to
20 Myr after) the transition from rift to drift might be influenced
by the mechanical setting of the rift zone and not governed solely
by far-field (i.e., subduction-related) forces.
Our kinematic model has tectonics implications for the South
and Equatorial Atlantic Basins. The new stage poles suggest
that, until the middle of the CNS, the relative motions between
South America and Africa were slower than previously expected
(Nürnberg and Müller, 1991) (Fig. 3c). Since the apparent overall
overlap between the continents in the Equatorial Atlantic, as is evident from the rotation parameters of Anomalies M2o and M0y, is
similar to that suggested by previous studies (Moulin et al., 2010;
Nürnberg and Müller, 1991), our results imply that internal deformation lasted longer than previously expected, probably until
roughly 100 Myr ago and no later than 92 Myr ago. This age stands
in general agreement with geological observations from the rift
zones of Africa (Fairhead et al., 2013; Heine et al., 2013).
The seaward edge of the Aptian salt basins found along the
Brazilian and Angola–Congo–Gabon margins have been used by
Torsvik et al. (2009) as fixed conjugate isochrons for 112 Myr
time. Linear interpolation between our M0y and Q2 finite rotations
brings these basins to match at 116 Myr ago. We note that although it seems that the age of breakup of the basins is somewhat
older than previously assumed, our model is not well constrained
for that period of time.
Finally, the opening of the Equatorial Atlantic Gateway had a
profound effect on the Cretaceous climate (Frank and Arthur, 1999;
MacLeod et al., 2011), yet current magnetic anomaly-based kinematic models have failed to match the timing of the opening to geological observations. Our new reconstruction model suggests that
the final clearing of the continent–ocean boundaries in the Equatorial Atlantic Ocean was completed by 95 ± 1 Myr, followed by the
opening of the gateway (Fig. 5). The initial deep-water circulation
might have been restricted by the dynamically uplifted seafloor
(Flament et al., 2014) and the major FZs (Jones et al., 1995) found
in the Equatorial Atlantic. During that stage, the northern section
of the South Atlantic Basin was already rather wide (500–800 km),
and therefore we believe that the seamount chains resulting from
the volcanic activity at Tristan hotspot had only a minor impact
on water circulation. An increase in water exchanges between the
Atlantic basins developed progressively, while the oceanic crust
within the gateway continued to age and deepen. As a result, a
major reorganization of oceanic circulation patterns emerged, leading to circulation system similar to that of the modern Atlantic
Ocean, where north–south flow of intermediate and deep-water
dictates water-mass and heat exchanges (Frank and Arthur, 1999).
Oxygen isotopic signatures of benthic foraminifera from different
oceanic basins (Friedrich et al., 2012) (Fig. 5d) show that a global
cooling of bottom water started at about 92 Myr and continued
progressively until ∼80 Myr.
6. Conclusions
Magnetic anomalies and FZ locations from the southern and
central South Atlantic are used to construct a set of six rotation
parameters that provide new constraints on the relative plate motion between South America and Africa during the Cretaceous. The
rotations are consistent with the pattern of magnetic anomalies
found in other parts of the basin (for Anomaly Q1) and fracture
zone locations.
The rotations presented here indicate that Lower Cretaceous
slow spreading rates have gradually increased and peaked at intermediate spreading rates shortly after the CNS, followed by a
decrease in spreading rates. A change in the direction of relative
motions between the two plates took place in the middle of the
CNS, at around 100 Ma. This event generally coincided with the
time of final separation between the plates, and hence might be
linked with the final transition into complete drift motion. Misfit
of synthetic flowlines in the central South Atlantic indicates that
internal strike-slip deformation within the South American Plate
(at around the Rio Grande FZ) has lasted until roughly 92 Myr
ago. This process was probably active in conjugation with seafloor
asymmetry. Finally, the results indicate, without taking a-priori assumptions, that the separation of the plates was later than previously thought. This in-turn seems to agree with the global deepwater isotopic signature that suggest an age of roughly 95–90 Myr
for the establishment of deep water exchange across the Equatorial
gateway.
Acknowledgements
This work was supported by the European Union Seventh
Framework Programme (FP7/2007–2013) under grant agreement
n◦ 320496 (GEOPLATE). We thank Nicolas Flament, an anonymous
reviewer and the Editor for their constructive comments. Chris
Heine is thanked for his comments on the early version of this
manuscript. This is IPGP contribution 3606.
Appendix A. Supplementary material
Supplementary material related to this article can be found online at http://dx.doi.org/10.1016/j.epsl.2015.01.015.
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