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Understanding the relative motion between the Pacific plate and its neighboring plates in the Paleogene has important consequences for deciphering the relationship between absolute and relative plate motions in the Pacific Ocean basin, the history of circum-Pacific subduction, and the cause of the Hawaiian-Emperor bend (HEB). We quantitatively model the Farallon/ Vancouver-Pacific-Antarctic seafloor spreading history from 67 to 33 Ma based on a compre- hensive synthesis of magnetic anomaly and fracture identifications. We find a well-constrained increase from 75 ± 5 mm/yr to 101 ± 5 mm/yr in Pacific-Farallon full spreading rates between 57.6 Ma and 55.9 Ma, followed by a stepwise increase to 182 ± 2 mm/yr from 49.7 to 40.1 Ma. The increases in Pacific-Farallon spreading rates are not accompanied by any statistically sig- nificant change in spreading direction. The 57.6–55.9 Ma surge of Pacific-Farallon spreading reflects an eastward acceleration in Farallon plate motion, as it precedes west Pacific subduction initiation and is not associated with any significant change in Pacific-Antarctic spreading. We interpret the increase in Pacific-Farallon spreading rates after ca. 50 Ma as a consequence of further acceleration in Farallon plate motion. We find no indication of a major change in Pacific plate absolute motion at this time. Our model suggests that changes in relative motion direction between the Pacific and Farallon and Pacific and Antarctic plates were insignificant around the formation time of the HEB (ca. 47.5 Ma), and the bend is largely a consequence of Hawaiian hotspot motion, which ceased rapid motion after 47 Ma.
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GEOLOGY
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Volume 43
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Revision of Paleogene plate motions in the Pacific and implications
for the Hawaiian-Emperor bend
Nicky M. Wright, R. Dietmar Müller, Maria Seton, and Simon E. Williams
EarthByte Group, School of Geosciences, University of Sydney, Sydney, NSW 2006, Australia
ABSTRACT
Understanding the relative motion between the Pacific plate and its neighboring plates in
the Paleogene has important consequences for deciphering the relationship between absolute
and relative plate motions in the Pacific Ocean basin, the history of circum-Pacific subduction,
and the cause of the Hawaiian-Emperor bend (HEB). We quantitatively model the Farallon/
Vancouver-Pacific-Antarctic seafloor spreading history from 67 to 33 Ma based on a compre-
hensive synthesis of magnetic anomaly and fracture identifications. We find a well-constrained
increase from 75 ± 5 mm/yr to 101 ± 5 mm/yr in Pacific-Farallon full spreading rates between
57.6 Ma and 55.9 Ma, followed by a stepwise increase to 182 ± 2 mm/yr from 49.7 to 40.1 Ma.
The increases in Pacific-Farallon spreading rates are not accompanied by any statistically sig-
nificant change in spreading direction. The 57.6–55.9 Ma surge of Pacific-Farallon spreading
reflects an eastward acceleration in Farallon plate motion, as it precedes west Pacific subduc-
tion initiation and is not associated with any significant change in Pacific-Antarctic spreading.
We interpret the increase in Pacific-Farallon spreading rates after ca. 50 Ma as a consequence
of further acceleration in Farallon plate motion. We find no indication of a major change in
Pacific plate absolute motion at this time. Our model suggests that changes in relative motion
direction between the Pacific and Farallon and Pacific and Antarctic plates were insignificant
around the formation time of the HEB (ca. 47.5 Ma), and the bend is largely a consequence of
Hawaiian hotspot motion, which ceased rapid motion after 47 Ma.
INTRODUCTION
The Hawaiian-Emperor bend (HEB) was tra-
ditionally interpreted as a relict of a large change
in absolute plate motion in the context of the
fixed hotspot hypothesis, but this interpretation
has been questioned (e.g., Norton, 1995; Chan-
dler et al., 2012; Tarduno, 2007). Recent dates
of the age of the HEB indicate that the arcu-
ate region of the Hawaiian-Emperor Seamount
Chain (e.g., Daikakuji and Yuryaku seamounts;
Fig. 1A) formed at ca. 47.5 Ma (O’Connor et al.,
2013) and initial stages of the bend formed at ca.
50 Ma (near the Kimmei seamount) (O’Connor
et al., 2013; Sharp and Clague, 2006). This age
is ~3 m.y. younger than the onset of the regional
Eocene plate reorganization (Whittaker et al.,
2007). Analyses of paleolatitudes from paleo-
magnetic versus hotspot track data (Tarduno
et al., 2003), mantle flow models (e.g., Stein-
berger et al., 2004), the relative motion between
the Hawaii and Louisville hotspots (O’Connor
et al., 2013), and predictions of the Hawaiian-
Emperor Seamount Chain from plate circuits
(e.g., Cande et al., 1995; Doubrovine and Tar-
duno, 2008) all point to the time dependence of
Hawaiian plume motion as a major contributing
factor to the HEB. Tarduno et al. (2009) explic-
itly suggested that the HEB may reflect mantle
plume dynamics in the absence of a major
change in plate motion. However, Koivisto et al.
(2014) proposed that paleolatitude differences
of the Emperor seamounts can be explained by
true polar wander, although this explanation was
questioned by analysis of paleomagnetic data
(Tarduno, 2007). Koivisto et al. (2014) sug-
gested that the HEB can be explained by a plate
reorganization, an idea reinforced by Barckhau-
sen et al. (2013), who concluded the HEB is
coincident with a major acceleration in Pacific-
Farallon spreading rates. Most published models
for relative plate motions in the Pacific Ocean
basin lack uncertainties, and studies that provide
uncertainties (e.g., Rowan and Rowley, 2014)
rely on long stages (e.g., ~7 m.y.), making it dif-
ficult to assess the significance and timing of any
given tectonic event. Here we present revised
relative plate motions with uncertainties for
the Pacific Ocean basin during the Paleogene.
Using a quantitative approach, we combine and
analyze an unprecedented number of magnetic
anomaly and fracture zone identifications from
the eastern and southern Pacific Ocean basin
spreading centers, i.e., the Pacific-Farallon/Van-
couver ridge and the Pacific-Antarctic Ridge
(Fig. 1). This four-plate analysis allows us to
relate relative motion between plates to absolute
plate motions (i.e., plate motion with respect to
the underlying mantle), considering that the two
are tightly connected, and test the plate reorgani-
zation hypothesis for the formation of the HEB.
METHODOLOGY
Rotation poles were obtained using the
method of Royer and Chang (1991). Magnetic
anomaly identifications are based on a compila-
tion (by Seton et al., 2014), which uses a self-
consistent set of magnetic identifications with
identical attributes (i.e., chron and anomaly end)
(Fig. 1). Ages attributed to chrons are based on
the time scale of Cande and Kent (1995). Frac-
ture zone interpretations are based on Matthews
et al. (2011). Assigned uncertainties of the mag-
netic lineations are 6.9 km (Pacific-Antarctic)
and 7.8 km (Pacific-Farallon/Vancouver), and
fracture zones are 5 km (Müller et al., 1991).
We derive finite rotations for the Pacific-Ant-
arctic seafloor spreading history between chron
30o (67.6 Ma) and chron 21o (47.9 Ma) and rely
on well-constrained published rotations (Croon
et al., 2008) for more recent times. In addition,
we compute half-stage rotations for the Pacific-
Farallon and Pacific-Vancouver seafloor spread-
ing histories between chron 31y (67.7 Ma) and
chron 13y (33.1 Ma), as finite rotations cannot
be directly calculated due to subduction of the
former Farallon and Vancouver plates. We rely
on magnetic identifications north of the Pioneer
Fracture Zone (Fig. 1B) for Pacific-Vancouver
spreading, and south of the Murray Fracture
Zone (Fig. 1C) for Pacific-Farallon spread-
ing, based on the location of the former Van-
couver plate boundary (Atwater, 1989). The
Pacific-Farallon/Vancouver half-stage rotation
poles were transformed into stage poles and
finite Euler poles based on assumed symmetric
spreading and standard statistical techniques.
All stage spreading rates and directions repre-
sent the mean for a given tectonic stage.
RESULTS
Our results produce well-constrained Pacific-
Farallon/Vancouver half-stage rotations, reflect-
ing the abundant magnetic identifications and
well-defined fracture zones on the Pacific plate
(Fig. 1). We express all spreading rates derived
from half-stage rotations as full spreading rates
to enable a straightforward comparison with
spreading rates derived from finite reconstruc-
tion poles (e.g., Pacific-Antarctic rotations). Our
Pacific-Farallon full spreading rates initially
increased from 75 ± 5 mm/yr at 57.6 Ma (chron
26y) to 101 ± 5 mm/yr at 55.9 Ma (chron 25y)
(Fig. 2). This initial increase at 55.9 Ma was fol-
lowed by a further stepwise increase in spread-
ing rates, from 118 ± 6 mm/yr to 182 ± 2 mm/
yr, between 49.7 Ma (chron 22o) and 40.1 Ma
(chron 18n.2o) (Fig. 2). The increases in Pacific-
Farallon spreading rates were not accompanied
by a statistically significant change in spreading
direction (Fig. 2). These results are not strongly
dependent on the time scale used: based on the
time scale of Ogg (2012), we observe a signifi-
cant increase in spreading rate at ca. 57 Ma from
68 ± 4 mm/yr to 78 ± 5 mm/yr, followed by an
increase at ca. 49 Ma from 77 ± 2 mm/yr to 106
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doi:10.1130/G36303.1
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Published online 27 March 2015
© 2015 Geological Society of America. For permission to copy, contact editing@geosociety.org.
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± 5 mm/yr (Fig. 2). We also find similar increases
in spreading rate when we consider asymmetric
spreading (Fig. DR2 in the GSA Data Reposi-
tory1). The initial increase in spreading precedes
the previously suggested ages of spreading
increase, ca. 53 Ma (chron 24; Rowan and Row-
1
GSA Data Repository item 2015156, additional
details on our methodology and results, is available
online at www.geosociety.org/pubs/ft2015.htm, or
on request from editing@geosociety.org or Docu-
ments Secretary, GSA, P.O. Box 9140, Boulder, CO
80301, USA.
ley, 2014) and ca. 47 Ma (chron 21; Barckhau-
sen et al., 2013; Cande and Haxby, 1991). We
find a similar trend in Pacific-Vancouver spread-
ing rates; however, we observe a large change in
spreading direction at 52.4 Ma (chron 24n.1y)
(Fig. 2). This reflects the break-up of the Faral-
lon plate to form the Vancouver plate, and is well
supported by the clockwise direction implied by
fracture zone trends, e.g., the Mendocino Frac-
ture Zone (Fig. 1B). Our model produces well-
constrained Pacific-Antarctic finite rotations,
and finds a significant decrease in Pacific-Ant-
arctic spreading rate and direction at ca. 53 Ma
(42 ± 17 mm/yr to 31 ± 5 mm/yr), and a further
decrease at 47.9 Ma (to 17 ± 5 mm/yr) (Fig. 2).
In contrast, we do not find a significant change
in Pacific-Antarctic spreading direction or rate
between ca. 61 and 56 Ma (Fig. 2).
DISCUSSION
Paleocene Farallon Plate Acceleration
We attribute the increase in Pacific-Farallon
spreading rates between ca. 58 Ma and ca. 56
Ma to an increase in the absolute speed of Faral-
lon plate motion rather than a change in Pacific
plate motion. If a major change in Pacific abso-
lute motion had occurred at this time, we would
also expect to see a corresponding signifi-
cant change in spreading direction or rates for
Pacific-Antarctic relative motions; however, no
such changes are observed (Fig. 2). The accel-
eration in Farallon plate motion during this time
period roughly marks the end of the Laramide
orogeny from ca. 60 Ma (Saleeby, 2003). The
Laramide orogeny has been linked with flat-
slab subduction (Atwater, 1989; Saleeby, 2003),
170°E 180° 170°W 160°W
20°N
30°N
40°N
50°N
160°W 150°W 140°W 130°W
40°N
50°N
150°W 140°W 130°W 120°W
10°N
20°N
30°N
150°W 140°W 130°W
30°S
20°S
10°S
170°E
170°E
180° 170°W
60°S
55°S
170°W 160°W160°W 150°W 140°W 130°W
70°S
65°S
ANT
PAC
BEL
NZ
MBL
Antarctic
Pitman FZ
Pitman FZ
Pacific
Austral FZ
Marquesas FZ
Galapagos FZ
Murray FZ
Molokai FZ
Clarion FZ
Clipperton FZ
Pacific
Pacific
Mendocino FZ
Pioneer FZ
Pacific
Sedna FZ
Surveyor FZ
JDF
Daikakuji
Kimmei
ca. 50 Ma
Yuryaku
Hawaiian Island Chain
Emperor Seamounts
Mendocino FZ
Murray FZ
ca. 47.5 Ma
Bend
Hawaiian-Emperor
Bend
E
F
AB
C
D
13y 24n.1y 26o
18n.2o 24n.3o 27o
20o 25y
28y
21o 25m 30o
22o 26y 31y
Chrons
AB
CD
EF
0
50
100
150
200
Stage rate [mm/yr]
35404550556065
Age [Ma]
PAC−ANT Croon et al. (2008)
A
PAC-FAR
PAC-VAN
PAC-VAN/FAR
13y
18n2o
20o
21o
22o
24n1y
24n3o
25y
26y
26o
27o
28y
30o
31y
18n2o
20o
21o
22o
24n1y
25y
26y
27o
28y
−60
−30
0
30
60
90
120
Spreading direction [°]
35404550556065
Age [Ma]
PAC−ANT
Croon et al. (2008)
B
PAC-FAR
PAC-VAN
PAC-VAN/FAR
Figure 1. Overview of the Pacific Ocean basin. A: Hawaiian-Emperor Seamount Chain, includ-
ing key seamounts identified by O’Connor et al. (2013) and Sharp and Clague (2006). Note that
the age for Kimmei is based on interpolation. Flowlines, magnetic identifications used in our
analysis, and fracture zones (FZ; observed in gravity anomaly), are shown in the northeastern
Pacific (B) (Pacific-Vancouver/Farallon). C: The central-North Pacific (Pacific-Farallon). D: The
South Pacific (Pacific-Farallon). E: The Pacific plate (Pacific-Antarctic). F: The Antarctic plate
(Pacific-Antarctic). Flowlines and symbols corresponding with magnetic identification times
are plotted at the east (dark blue, triangles) and west (magenta, diamonds) ridge-transform in-
tersections. JDF—Juan de Fuca plate; NZ—New Zealand; MBL—Marie Byrd Land (Antarctica);
PAC—Pacific plate; ANT—Antarctic plate; BEL—Bellingshausen plate.
Figure 2. A: Full spreading rate and 95% un-
certainty. B: Spreading direction and 95% un-
certainty. Spreading systems include Pacific-
Farallon (PAC-FAR) (dark gray) (also in Ogg,
2012; in orange), Pacific-Vancouver (PAC-
VAN; dotted light gray), and Pacific-Antarctic
(PAC-ANT; light gray). Chrons in the time
scales of Cande and Kent (1995; black) and
Ogg (2012; orange) are shown. Spreading
parameters and uncertainties prior to 40.1
Ma are from Croon et al. (2008) (vertical
lines). Prior to 52.4 Ma, Vancouver was part
of the Farallon plate (VAN/FAR). Rates were
calculated on the Molokai Fracture Zone (FZ)
(PAC-FAR), Mendocino FZ (PAC-VAN), and
Pitman FZ (PAC-ANT). The Hawaiian-Em-
peror bend (HEB) formed between ca. 50 Ma
and ca. 42 Ma; the arcuate region formed at
47.5 Ma (shaded background).
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possibly caused by an increased buoyancy of
the oceanic crust due to subduction of oceanic
plateaus (i.e., Shatsky and Hess conjugates)
on the Farallon plate (Liu et al., 2010). Cessa-
tion of Laramide deformation has been linked
to rapid steepening of the subducting Farallon
slab (Saleeby, 2003) or slab removal (Hum-
phreys et al., 2003). Alternatively, it is proposed
that closure of the Mezcalera and Angayucham
basins (i.e., by westward movement of North
America and west-dipping subduction beneath
the arcs) by 55 Ma resulted in terrane accretion
(e.g., Siletzia and Metchosin terranes; Sigloch
and Mihalynuk, 2013) and development of east-
dipping Farallon subduction. In both cases, we
expect an increase in Farallon absolute motion,
either from steepening of the subducting slab or
development of east-dipping subduction.
Farallon Plate Breakup and Vancouver
Plate Formation
We suggest that the increase in Farallon
absolute plate motion between ca. 58 Ma and
ca. 56 Ma would have led to elevated intraplate
stress, triggering its breakup and Vancouver
plate formation at ca. 52 Ma, given that the Far-
allon plate already satisfied the main condition
for instability of oceanic plates, a plate width
larger than the radius of the Earth (Morra et al.,
2012). We find a slight decrease from 101 to 93
mm/yr in Pacific-Farallon spreading rates at ca.
52 Ma (Fig. 2), synchronous with the timing
of Farallon plate fragmentation. A decrease in
Pacific-Farallon spreading rates is an expected
consequence of Farallon plate breakup, due to
the trench-parallel shortening of the Farallon
slab, reducing the slab-pull force. This contrasts
with work by Rowan and Rowley (2014), who
found an increase in Pacific-Farallon spreading
rates at ca. 53 Ma, from 65–97 mm/yr (depen-
dent on spreading asymmetry) to ≥150 mm/yr;
however, the difference in their spreading rates
is likely a consequence of their ~10-m.y.-long
stage intervals, compared to our smaller stages.
Eocene Farallon Plate Acceleration
Pacific-Farallon full spreading rates increased
stepwise from ~118 to 180 mm/yr between 49.7
and 40.1 Ma, while Pacific-Antarctic spreading
rates decreased slowly and spreading direc-
tions rotated counterclockwise by ~22° (Fig.
2), expressed by fracture zone bends (Fig. 1).
We suggest that this increase in Pacific-Farallon
spreading rates is driven by an eastward accel-
eration in Farallon absolute plate motion as the
Pacific-Farallon ridge approached the trench,
since younger oceanic lithosphere may subduct
as much as twice as fast as older oceanic litho-
sphere (Goes et al., 2008). The gradual increase
in Pacific-Farallon spreading rates initiating at
49.7 Ma corresponds to the time of inception of
the HEB, ca. 50 Ma (O’Connor et al., 2013), and
is in contrast with the Barckhausen et al. (2013)
suggestion of a singular increase in half-spread-
ing rates from 43 to 89 mm/yr at 47.5 Ma, and
the Rowan and Rowley (2014) spreading rate
increase at ca. 53 Ma.
The subduction of the Izanagi-Pacific ridge
prior to 50 Ma along the western Pacific basin
has been associated with initiating a major plate
reorganization event in the Pacific basin (Whit-
taker et al., 2007; Seton et al., 2015). If this
were due to a substantial westward acceleration
of the Pacific absolute motion due to western
Pacific subduction initiation, we would expect
a significant acceleration of Pacific-Antarctic
spreading rates. We find a decrease in Pacific-
Antarctic spreading rates during this time (Fig.
2), suggesting that any change in Pacific abso-
lute motion at this time was relatively minor.
Instead, the reorganization may have been
driven by the changing plate boundary forces
in the western Pacific (from ridge push to slab
pull) and the change in mantle flow pattern due
to the complete subduction of the Izanagi plate
(Seton et al., 2015).
Implications for the Hawaiian-Emperor Bend
The distinct kink in Vancouver-Pacific frac-
ture zones (e.g., Mendocino and Surveyor
Fracture Zones) accompanying Farallon plate
fragmentation at chron 24 (ca. 52 Ma; Fig.
1B) is related to the reorientation of spreading
geometries related to rift propagation (Caress
et al., 1988), rather than the HEB and a change
in Pacific plate motion. Contemporaneous seg-
ments of Pacific-Farallon fracture zones (e.g.,
Molokai and Clarion Fracture Zones; see Figs.
1C and 1D) preserve linear geometries, suggest-
ing that Pacific-Farallon plate motion is a reli-
able indicator of steady relative plate motion
during this time. Furthermore, a rapid change
in Pacific plate motion would also be expressed
as a simultaneous change in Pacific-Antarctic
motion; however, this is not observed (Fig. 2).
Plate velocity diagrams constructed for the
time of formation of the HEB (47.5 Ma) can be
used to clarify plate motion changes surround-
ing this event. We combine our Pacific-Farallon
relative motions (in the time scales of Cande
and Kent [1995] and Ogg [2012]) with indepen-
dently derived Pacific absolute motion models:
(1) a geodynamic forward-based model (Butter-
worth et al., 2014) (Fig. 3A), (2) a Pacific hotspot
model corrected for the southward motion of
the Hawaiian hotspot (WK08-D; Chandler et
al., 2012) (Fig. 3B), and (3) a smoothed Pacific
absolute plate motion model uncorrected for
Hawaiian hotspot drift (WK08-A; Wessel and
Kroenke, 2008) (Fig. 3C). Regardless of the time
scale used, all models suggest an acceleration in
Farallon plate absolute motion (Fig. 3), which
includes a minor clockwise change. This may
be attributed to the detachment of the Vancou-
ver plate at ca. 52 Ma, causing slab pull forces
associated with the South American trench to
become more dominant. Both Chandler et al.
(2012; WK08-D; Fig. 3B) and Butterworth et al.
(2014) (Fig. 3A) suggested a slight deceleration
in Pacific absolute motion around the forma-
tion time of the HEB, with little accompanying
change in direction (4° clockwise and 5° coun-
terclockwise, respectively). Wessel and Kroenke
(2008; WK08-A; Fig. 3C) implied a 31° coun-
terclockwise change and acceleration in Pacific
plate absolute motion, in order to reproduce the
HEB without attempting to separate absolute
plate motion change from plume motion. This
suggests that the HEB is largely due to the ces-
sation of the rapid southward motion of the
Hawaiian hotspot around the formation time
of the HEB (Tarduno et al., 2003), rather than
a large change in Pacific absolute motion or a
basin-wide plate reorganization event.
The lack of statistically significant change in
Pacific-Farallon spreading directions, combined
with a significant increase in Pacific-Farallon
FAR
CK95
A
FAR
PAC
Abs
PAC
Abs
GTS2012
CK95
GTS2012
CK95
GTS2012
FAR
PAC
Abs
WK08-D
B
FAR
PAC
Abs
Butterworth et al., 2014 WK08-A
C
FAR
PAC
Abs
FAR
PAC
Abs
50 mm/yr
58.5 - 53 Ma
53 - 47.5 Ma
47.5 - 42 Ma
31°
31°
Figure 3. Plate velocity diagrams surrounding the formation of the Hawaiian-Emperor bend
(HEB) (47.5 Ma) based on relative Pacific (PAC)-Farallon (FAR) motion (solid line, with uncer-
tainty shaded) in the time scales of Cande and Kent (1995; CK95) and Ogg (2012; GTS2012),
Pacific absolute (abs) motion (solid line), and Farallon absolute motion (dashed line). A: Pa-
cific absolute motion from Butterworth et al. (2014). B: Pacific absolute motion from model
WK08-D (Chandler et al., 2012). C: Pacific absolute motion from model WK08-A (Wessel and
Kroenke, 2008). Uncertainties in all parts are derived from a similar time period in this study.
All velocities were calculated at the paleo-ridge along the Murray Fracture Zone.
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GEOLOGY
spreading rates and a gradual deceleration of
Pacific-Antarctic spreading rates, suggests that
there was no major change in Pacific plate abso-
lute motion around the formation time of the
HEB (47.5 Ma). The increase in Pacific-Faral-
lon spreading rates can be attributed to changes
in Farallon plate absolute motion. Our analysis
supports the scenario that the rapid southward
motion of the Hawaiian hotspot until ca. 47 Ma
is responsible for the HEB, rather than a change
in Pacific absolute motion.
ACKNOWLEDGMENTS
We thank M. Croon, S. Cande, and J. Stock for
making their Hellinger plate reconstruction input
files available to us. We also thank Charles DeMets
and four anonymous reviewers for comments that
significantly improved this manuscript. This research
was funded by Australian Research Council grants
FL0992245 and DP0987713.
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Manuscript received 23 September 2014
Revised manuscript received 25 February 2015
Manuscript accepted 3 March 2015
Printed in USA
GSA DATA REPOSITORY
Revision of Paleogene plate motions in the Pacific and implications for the Hawaiian-Emperor
bend
N. M. Wright, R. D. Müller, M. Seton, S. E. Williams
Methodology
Data compilation
We rely on magnetic identifications compiled by Seton et al. (2014) and fracture zone crossings
determined by Matthews et al. (2011). Specifically, for our Pacific-Farallon reconstructions we rely
on magnetic identifications from Atwater and Severinghaus (1989), Barckhausen et al. (2013),
Cande and Haxby (1991), Cande et al. (1995), Caress et al. (1988), Elvers et al. (1967), Munschy et
al. (1996), and Vacquier et al. (1961). For our Pacific-Antarctic reconstruction, we rely on Cande et
al. (1995) and Wobbe et al. (2012).
All magnetic identifications compiled by Seton et al. (2014) are standardized to the Gee and Kent
(2007) timescale. We cite such ages as Cande and Kent (1995), from which the Cenozoic portion of
the Gee and Kent (2007) magnetic timescale is based. We identify chrons based on their young (y),
old (o), and middle (m) ends.
Reconstruction method
Uncertainty analysis
We assign a 5 km uncertainty to fracture zone identifications (Müller et al., 1991). Since our
magnetic identifcation compilation is based on different navigation methods, including celestial
navigation (i.e. for pre-1970 data), we rely on the dispersion of magnetic identifications in assigning
their uncertainty value (Gaina et al., 1998). This uncertainty value is found by (1) initially finding
the best fitting rotations for all data (magnetic and fracture zone crossings); (2) applying these
rotations only to magnetic crossings with an assigned initial uncertainty (10 km); (3) calculating the
harmonic mean of the quality factor 𝜅 (i.e. 𝜅!
avg
!), based the 𝜅 values of each magnetic anomaly set;
and (4) determining the 1-sigma standard error (𝜎) of the magnetic data, based on 𝜎=𝜎!/!𝜅!
avg
!,
which we assign as our magnetic uncertianty. For Pacific-Farallon/Vancouver rotations, we find
𝜅avg$$of 1.6 and $𝜎$of 7.8 km. For Pacific-Antarctic rotations, we find we find 𝜅avg$$of 2.1 and $𝜎$of
6.9 km.
Half’-stage rotations
Half-stage rotation poles and uncertainties were obtained based on preserved magnetic lineations on
the Pacific plate and Hellinger’s (1981) best-fitting method, implemented by Chang (1987, 1988)
and Royer and Chang (1991). We derived Pacific-Farallon half-stage rotation poles and 95%
uncertainties (Fig. DR1A) between chron 13y (33.058 Ma) and chron 24n.1y (52.364 Ma) (Table
DR1, Table DR2), based on magnetic identifications south of the Murray Fracture Zone. We derive
Vancouver-Pacific rotations and 95% uncertainties (Fig. DR1B) between chron 13y (33.058 Ma)
and chron 24n.1y (52.364 Ma) (Table DR1, Table DR2) based on magnetic identifications north of
the Mendocino Fracture Zone. We derive Pacific-Farallon/Vancouver rotations (i.e. pre-Vancouver
plate formation) and 95% uncertainties (Fig. DR1) between chron 24n.1y (52.364 Ma) and chron
31y (67.735 Ma) (Table DR1, Table DR2). Our obtained half-stage rotations are independent of
Nazca plate formation (e.g. at ~23 Ma; Barckhausen et al., 2008), as this spreading occurred prior to
Farallon plate breakup and we derive half-stage rotations only.
Figure DR1: Rotation poles and their corresponding 95% uncertainty regions, for A. Farallon-Pacific
spreading (half-stage poles); B. Vancouver-Pacific spreading (half-stage poles). C. Pacific-Antarctic (finite
poles). Labels denote chrons used for computation.
Table DR1: Chron and ages of half-stage rotations for Farallon-Pacific, Vancouver-Pacific, and
Farallon/Vancouver-Pacific spreading. Ages are from Cande and Kent (1995)
!
Plates
Chron
Age (Ma)
Farallon - Pacific
13y
-
18n.2o
33.058
-
40.130
18n.2o
-
20o
40.130
-
43.789
20o
-
21o
43.789
-
47.906
21o
-
22o
47.906
-
49.714
22o
-
24n.1y
49.714
-
52.364
Vancouver - Pacific
13y
-
18n.2o
33.058
-
40.130
18n.2o
-
21o
40.130
-
47.906
21o
-
22o
47.906
-
49.714
21o
-
24n.1y
49.714
-
52.364
Farallon/Vancouver
- Pacific
24n.1y
-
25y
52.364
-
55.904
25y
-
26y
55.904
-
57.554
26y
-
27o
57.554
-
61.276
27o
-
28y
61.276
-
62.499
28y
-
31y
62.499
-
67.735
Table DR2: Farallon-Pacific (FAR-PAC), Vancouver-Pacific (VAN-PAC), and Farallon/Vancouver-Pacific
(FAR/VAN-PAC) half-stage rotation and covariance matrices
Plates
Chron
Lat
(+ °N)
Long
(+ °E)
Angle
(deg)
𝜿
dF
N
s
r
a
b
c
d
e
f
g
FAR-PAC
13y - 18n.2o
-57.206
-119.683
5.796
0.24
51
76
11
208.82
8.49
8.83
0.24
11.90
0.27
1.90
10-7
18n.2o - 20o
-75.751
-90.302
2.765
0.30
51
74
10
172.34
10.45
9.08
-3.62
10.32
-3.58
2.94
10-7
20o - 21o
-59.482
-117.813
2.653
0.35
76
107
14
215.39
6.08
4.57
-1.72
4.95
-1.51
1.52
10-7
21o - 22o
-64.069
-111.485
0.954
0.99
105
138
15
105.87
3.20
2.11
-0.15
2.81
-0.24
0.68
10-7
22o - 24n.1y
-68.840
-104.776
1.147
3.19
57
80
10
17.86
6.18
3.79
-1.45
4.61
-1.30
1.61
10-7
VAN-PAC
13y - 18n.2o
-72.935
38.385
7.125
0.44
66
85
8
149.22
1.50
62.31
-80.15
30.99
-55.53
106.40
10-7
18n.2o 21o
-71.865
39.600
6.217
1.41
49
66
7
34.78
0.84
50.59
-59.96
21.29
-37.24
74.96
10-7
21o 22o
-71.145
37.555
1.319
2.32
35
52
7
15.06
0.66
78.03
-89.57
23.54
-47.23
107.24
10-7
21o - 24n.1y
-71.810
36.938
1.454
0.91
25
40
6
27.34
1.05
82.19
-93.96
36.53
-62.02
114.18
10-7
FAR/VAN-
PAC
24n.1y - 25y
-58.818
-119.609
1.591
0.60
71
96
11
118.99
6.58
4.17
-1.88
4.50
-1.51
1.65
10-7
25y 26y
-61.494
-118.605
0.571
1.49
118
151
15
79.16
3.32
1.62
-1.70
2.15
-1.30
1.74
10-7
26y - 27o
-63.787
-117.523
1.177
0.87
87
114
12
99.97
6.28
3.34
-3.36
3.46
-2.31
2.87
10-7
27o - 28y
-52.581
-127.173
0.374
1.51
89
118
13
58.90
6.26
3.48
-3.34
3.36
-2.26
2.81
10-7
28y 31y
-72.402
-102.630
1.881
0.61
122
145
10
198.70
4.84
2.05
-2.95
2.81
-2.01
2.82
10-7
Variables 𝜅,𝑎,𝑏,𝑐,𝑑,𝑒 and 𝑓are in radians. 𝜅 is the estimated quality factor, dF is number of degrees of
freedom, N is the number of datapoints, s is the number of great circle segments, r is the total misfit
The covariance matrix is defined as:!𝐶𝑜𝑣 𝑢=!
!
!!
𝑎𝑏𝑐
𝑏𝑑𝑒
𝑐𝑒𝑓
The quality factor 𝜅 value indicates whether our assigned uncertainties are relatively correct (𝜅 = 1),
overestimated (𝜅 >> 1) or underestimated (𝜅 << 1). Our 𝜅 values varied between 0.24 and 3.19 for
our derivations (Table DR2). We chose to retain our assigned uncertainties. We transformed these
‘half’-stage rotation poles into stage poles (assuming symmetrical spreading) and derived finite
rotation poles using ADDPLUS (Kirkwood et al., 1999). To assess our rotations, we visualised our
finite rotations as flowlines using GPlates (Boyden et al., 2011).
We present our Farallon-Pacific spreading velocities in Cande and Kent (1995) (Fig. DR2A, B) and
Ogg (2012) (Fig DR2C, D). We find a well-constrained increase in spreading rate at ca. 57 - 56 Ma
in both timescales. To account for the long term spreading asymmetry of the East-Pacific rise (EPR)
and its ancestor, Pacific-Farallon ridge (Rowan and Rowley, 2014), we additionally calculate full
stage rotations based on two spreading asymmetry cases: 1) ‘best-fitting’ asymmetry, with a
Pacific:Farallon spreading asymmetry of 44:56 for all stages (Rowan and Rowley, 2014), and 2)
maximum likely asymmetry, with a Pacific:Farallon spreading asymmetry of 36:64 for stages
before chron 24, and 44:56 for stages since chron 24 (Rowan and Rowley, 2014) (Fig DR2). A
comparison with the ‘best-fit’ rotation poles from Rowan and Rowley (2014) demonstrates a similar
overall trend, although we find an earlier increase in Pacific-Farallon spreading rates due to our
smaller stage rotations.
Figure DR2: Comparison of Pacific-Farallon spreading velocities in A and B: Cande and Kent (1995)
(‘CK95’) and C and D: Ogg (2012) (‘GTS2012’). Stage rates have been calculated based on symmetrical
spreading (black), ‘best-fit’ asymmetry (yellow), and maximum likely asymmetry (red). A comparison is
provided based on Rowan and Rowley’s (2014) preferred rotations poles.
Due to the sensitivity of the use of Hellinger’s (1981) method in half-stage cases, significant
differences in boundary segment trends (e.g. due to propagating ridges and transform faults) will
result in a non-Gaussian distribution. We verify the distribution by plotting both histograms of the
residual distribution (by stage) and normal quantile plots (qq plot; for combined dataset from all
stages). If the data residuals are normally distributed, all points on a qq plot should lie on a straight
line. We find a Gaussian distribution of our residuals for all half-stage rotations (Fig. DR3), and an
approximately linear distribution in qq plots (Fig. DR4).
50
100
150
200
Stage rate [mm/yr]
65
70
75
80
85
90
Spreading direction [°]
35404550556065
Age [Ma]
13y
18n2o
20o
21o
22o
24n1y
24n3o
25y
26y
27o
28y
13y
18n2o
20o
21o
22o
24n1y
24n3o
25y
26y
27o
28y
31y
Rowan and Rowley (2014)
‘best-fit’ asymmetry
maximum likely asymmetry
symmetrical spreading
GTS2012
35404550556065
Age [Ma]
CK95
A
B
C
D
Figure DR3: Histograms of weighted residual distributions from Farallon-Pacific and Farallon/Vancouver-
Pacific half-stage rotations (blue) and Vancouver-Pacific half-stage rotations (orange).
Figure DR4: qq-plots based on combined Farallon-Pacific, Vancouver-Pacific and Farallon/Vancouver-
Pacific half-stage poles, based on the full dataset, magnetic anomaly data only, and fracture zone data only.
−5 −4 −3 −2 −1 01 2 3 4 5
−5
−4
−3
−2
−1
0
1
2
3
4
5
Normal Score
Weighted residual
FZ + Mag Mag only FZ only
−5 −4 −3 −2 −1 01 2 3 4 5
−5
−4
−3
−2
−1
0
1
2
3
4
5
Normal Score
Weighted residual
−5 −4 −3 −2 −1 01 2 3 4 5
−5
−4
−3
−2
−1
0
1
2
3
4
5
Normal Score
Weighted residual
Finite rotations
Finite rotation poles were obtained based on preserved magnetic lineations on the Antarctic and
Pacific plates. We derive Pacific-Antarctic finite rotations and 95% uncertainties (Fig. DR1C)
between chron 21o (47.906 Ma) and chron 30o (67.610 Ma) (Table DR3, Table DR4). We rely on
Croon et al. (2008) for spreading rates and uncertainties for times since chron 20o (43.789 Ma).
Table DR3: Chron and ages of finite rotations for Pacific-Antarctic spreading. Ages are from Cande and
Kent (1995)
!
!
!
Table DR4: Finite rotations and covariance matrix for Pacific-Antarctic spreading
Chron
Lat
(+ °N)
Long
(+ °E)
Angle
(deg)
𝜿
df
N
s
r
a
b
c
d
e
f
g
21o
74.431
-48.544
38.176
0.37
37
56
8
100.11
0.24
0.05
0.37
0.02
0.08
0.62
10-5
24n.3o
73.474
-52.081
40.105
0.21
19
38
8
92.60
0.49
0.06
0.79
0.03
0.09
1.34
10-5
25m
72.627
-54.727
41.142
0.36
18
35
7
49.40
0.87
0.16
1.21
0.06
0.22
1.76
10-5
26o
72.317
-54.189
42.531
0.67
23
48
11
34.20
0.35
0.02
0.55
0.02
0.02
0.93
10-5
27o
71.348
-54.157
45.498
1.25
31
44
5
24.78
1.84
-0.21
3.00
0.04
-0.33
5.00
10-5
30o
68.941
-56.694
49.007
2.76
16
31
6
5.79
4.95
-0.26
7.47
0.06
-0.40
11.39
10-5
Variables 𝜅,𝑎,𝑏,𝑐,𝑑,𝑒 and 𝑓are in radians. 𝜅 is the estimated quality factor, dF is number of degrees of
freedom, N is the number of datapoints, s is the number of great circle segments, r is the total misfit
The covariance matrix is defined as:!𝐶𝑜𝑣𝑢=!
!
!!
𝑎𝑏𝑐
𝑏𝑑𝑒
𝑐𝑒𝑓
Our final 𝜿 values range from 0.21 to 2.76 (Table DR4), indicating we have overestimated
uncertainties (e.g. chron 30o) and underestimated uncertainties (e.g. chron 21o). We find a
Gaussian distribution of our residuals (Figure DR5), and a linear distribution in our qq-plots
(Figure DR6).
Chron
Age (Ma)
21o
47.906
24n.3o
53.347
25m
56.1475
26o
57.911
27o
61.276
30o
67.610
Figure DR5: Histograms of weighted residual distribution from Pacific-Antarctic rotations
Figure DR6: qq-plots based for Pacific-Antarctic rotations, based on the full dataset, magnetic anomaly
data only, and fracture zone data only.
0
5
10
15
20
Number of samples
−5 −4 −3 −2 −1 012345
Weighted residuals
21o
0
5
10
15
20
Number of samples
−5 −4 −3 −2 −1 012345
Weighted residuals
24n.3o
0
5
10
15
20
Number of samples
−5 −4 −3 −2 −1 012345
Weighted residuals
25o
0
5
10
15
20
Number of samples
−5 −4 −3 −2 −1 012345
Weighted residuals
26o
0
5
10
15
20
Number of samples
−5 −4 −3 −2 −1 012345
Weighted residuals
27o
0
5
10
15
20
Number of samples
−5 −4 −3 −2 −1 012345
Weifghted residuals
30o
0
5
10
15
20
Number of samples
−5 −4 −3 −2 −1 012345
Weighted residuals
33y
Weighted residual
Weighted residual
FZ + Mag Mag only FZ only
Normal Score
Normal ScoreNormal Score
−5
−4
−3
−2
−1
0
1
2
3
4
5
−5
−4
−3
−2
−1
0
1
2
3
4
5
Weighted residual
−5 −4 −3 −2 −1 01 2 3 4 5 −5 −4 −3 −2 −1 01 2 3 4 5 −5 −4 −3 −2 −1 01 2 3 4 5
−5
−4
−3
−2
−1
0
1
2
3
4
5
95% uncertainty ellipses
Figure DR7 displays the velocity arrows and uncertainty ellipses for each
Farallon/Vancouver-Pacific half-stage described in the text. Gravity is from Sandwell and
Smith (2009), plate boundaries are from Bird (2003), and magnetic identifications are from
Matthews et al. (2011). Chrons include: 13y (33.058 Ma; peach), 18n.2o (40.103 Ma; green),
20o (43.789 Ma; orange), 21o (47.906 Ma; light blue), 22o (49.714 Ma; purple), 24n.1y
(52.364 Ma; dark red), 25y (55.904 Ma; dark blue), 26y (57.554 Ma; gold), 27o (61.276 Ma;
pink), 28y (62.499 Ma; black) and 31y (67.735 Ma; pale yellow).
Figure DR8 displays the velocity arrows and uncertainty ellipses for Pacific-Antarctic
spreading, based on full stages. Accordingly, the velocity arrows will be twice as long as the
half-stage arrows, and will not align with the equivalent chron associated with each stage
rotation. Chrons include: 21o (47.906 Ma; light blue), 24n.3o (53.347 Ma; dark red), 25m
(56.1475 Ma; off-white), 26o (57.911 Ma; gold), 27o (61.276 Ma; pink), and 30o
(67.610 Ma; yellow).
175˚W
175˚W
170˚W
170˚W
165˚W
165˚W
160˚W
160˚W
155˚W
155˚W
150˚W
150˚W
145˚W
145˚W
140˚W
140˚W
135˚W
135˚W
130˚W
130˚W
125˚W
125˚W
120˚W
120˚W
115˚W
115˚W
110˚W
110˚W
105˚W
105˚W
40˚S40˚S
35˚S35˚S
30˚S30˚S
25˚S25˚S
20˚S20˚S
15˚S15˚S
10˚S10˚S
S5˚S
0˚ 0˚
5˚N 5˚N
10˚N 10˚N
15˚N 15˚N
20˚N 20˚N
25˚N 25˚N
30˚N 30˚N
35˚N 35˚N
40˚N 40˚N
45˚N 45˚N
50˚N 50˚N
55˚N 55˚N
B. Mendocino FZ
C. Murray FZ
D. Molokai FZ
E. Clarion FZ
F. Clipperton FZ
G. Marqueasas FZ
A. Sedna and Surveyor FZs
North
America
H. Austral FZ
Figure DR7: Overview of regions in sections A - H
164˚W
164˚W
162˚W
162˚W
160˚W
160˚W
158˚W
158˚W
156˚W
156˚W
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142˚W
142˚W
140˚W
140˚W
42˚N 42˚N
44˚N 44˚N
46˚N 46˚N
48˚N 48˚N
50˚N 50˚N
52˚N 52˚N
0200 400
km
Figure DR7A: Sedna and Surveyor Fracture Zones
28y
31y
27o 26y 25y
22o
21o
18n.2o
13y
Sedna FZ
13y
18n.2o
18n.2o
21o
22o
24n.1y
24n.1y
22o
25y
26y
27o
28y
31y
Surveyor FZ
13y
164˚W
164˚W
162˚W
162˚W
160˚W
160˚W
158˚W
158˚W
156˚W
156˚W
154˚W
154˚W
152˚W
152˚W
150˚W
150˚W
148˚W
148˚W
146˚W
146˚W
144˚W
144˚W
142˚W
142˚W
140˚W
140˚W
138˚W
138˚W
136˚W
136˚W
134˚W
134˚W
132˚W
132˚W
130˚W
130˚W
36˚N 36˚N
38˚N 38˚N
40˚N 40˚N
42˚N 42˚N
44˚N 44˚N
46˚N 46˚N
Figure DR7B: Mendocino Fracture Zone
0200
km
400
28y
31y 27o 26y
25y
24n.1y
22o
22o
24n.1y
25y
26y
28y 27o
21o
21o
18n.2o
18n.2o
13y
Mendocino FZ
31y
13y
Pioneer FZ
Surveyor FZ
31y 25y
26y
28y 27o
154˚W
154˚W
152˚W
152˚W
150˚W
150˚W
148˚W
148˚W
146˚W
146˚W
144˚W
144˚W
142˚W
142˚W
140˚W
140˚W
138˚W
138˚W
136˚W
136˚W
134˚W
134˚W
132˚W
132˚W
130˚W
130˚W
128˚W
128˚W
126˚W
126˚W
28˚N 28˚N
30˚N 30˚N
32˚N 32˚N
34˚N 34˚N
36˚N 36˚N
0200 400
km
Figure DR7C: Murray Fracture Zone
28y
31y 27o 26y 25y
24n.1y
22o
25y
26y
28y27o
21o
20o
20o
18n.2o
Murray FZ
31y
154˚W
154˚W
152˚W
152˚W
150˚W
150˚W
148˚W
148˚W
146˚W
146˚W
144˚W
144˚W
142˚W
142˚W
140˚W
140˚W
138˚W
138˚W
136˚W
136˚W
134˚W
134˚W
132˚W
132˚W
130˚W
130˚W
128˚W
128˚W
126˚W
126˚W
124˚W
124˚W
122˚W
122˚W
18˚N 18˚N
20˚N 20˚N
22˚N 22˚N
24˚N 24˚N
26˚N 26˚N
28˚N 28˚N
30˚N 30˚N
0200 400
km
Figure DR7D: Molokai Fracture Zone
28y
31y 27o
26y 25y 24n.1y 22o
22o
24n.1y
25y
26y
28y
27o
21o
21o
20o
20o
18n.2o
18n.2o
13y
Molokai FZ
31y
150˚W
150˚W
148˚W
148˚W
146˚W
146˚W
144˚W
144˚W
142˚W
142˚W
140˚W
140˚W
138˚W
138˚W
136˚W
136˚W
134˚W
134˚W
132˚W
132˚W
130˚W
130˚W
128˚W
128˚W
126˚W
126˚W
124˚W
124˚W
122˚W
122˚W
10˚N 10˚N
12˚N 12˚N
14˚N 14˚N
16˚N 16˚N
18˚N 18˚N
20˚N 20˚N
0200 400
km
Figure DR7E: Clarion Fracture Zone
28y
31y 27o
26y 25y
24n.1y 22o
22o
24n.1y
25y
26y
27o
21o
21o
20o
20o 18n.2o
18n.2o
13y
Clarion FZ
28y
31y
150˚W
150˚W
148˚W
148˚W
146˚W
146˚W
144˚W
144˚W
142˚W
142˚W
140˚W
140˚W
138˚W
138˚W
136˚W
136˚W
134˚W
134˚W
132˚W
132˚W
130˚W
130˚W
128˚W
128˚W
126˚W
126˚W
2˚S 2˚S
0˚ 0˚
2˚N 2˚N
4˚N 4˚N
6˚N 6˚N
8˚N 8˚N
10˚N 10˚N
0200 400
km
Figure DR7F: Clipperton Fracture Zone
28y
31y 27o 26y 25y 24n.1y 22o
22o
24n.1y
25y
26y
28y 27o
21o
21o
20o
20o
18n.2o
18n.2o 13y
Clipperton FZ
148˚W
148˚W
146˚W
146˚W
144˚W
144˚W
142˚W
142˚W
140˚W
140˚W
138˚W
138˚W
136˚W
136˚W
134˚W
134˚W
132˚W
132˚W
130˚W
130˚W
128˚W
128˚W
18˚S 18˚S
16˚S 16˚S
14˚S 14˚S
12˚S 12˚S
10˚S 10˚S
8˚S 8˚S
6˚S 6˚S
Figure DR7G: Marquesas Fracture Zone
0200 400
km
22o
21o 20o
18n.2o
13y
Marquesas FZ
20o
22o
21o
154˚W
154˚W
152˚W
152˚W
150˚W
150˚W
148˚W
148˚W
146˚W
146˚W
144˚W
144˚W
142˚W
142˚W
140˚W
140˚W
138˚W
138˚W
136˚W
136˚W
134˚W
134˚W
132˚W
132˚W
130˚W
130˚W
34˚S 34˚S
32˚S 32˚S
30˚S 30˚S
28˚S 28˚S
26˚S 26˚S
24˚S 24˚S
22˚S 22˚S
20˚S 20˚S
18˚S 18˚S
Figure DR7H: Austral Fracture Zone
0200 400
km
26y 25y 24n.1y 22o
22o
24n.1y
25y
21o
21o
20o
20o
18n.2o
18n.2o
13y
Austral FZ
164˚W
162˚W
160˚W
160˚W
158˚W
158˚W
156˚W 156˚W
154˚W
154˚W
152˚W
152˚W
150˚W
148˚W
146˚W
144˚W
78˚S
78˚S
76˚S
76˚S
76˚S
74˚S
74˚S
72˚S
72˚S
70˚S
70˚S
68˚S
0 100 200
km
21o
21o
24n.3o
24n.3o
25m
25m
26o
26o
27o 27o
30o
Figure DR8: Pitman Fracture Zone with velocity arrows and 95% uncertainties
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!
... The Pacific plate can be directly linked through regional plate circuits to the Indo-Atlantic realm only for the last 83.5 Ma (Figure 3a), but debates continue about the best relative motion pathway (Steinberger et al., 2004;Wright et al., 2015). Before 83.5 Ma, the Pacific plate was surrounded by subduction zones that cannot be directly connected with the rest of the relative motion chain. ...
... Similarly, the Pacific plate motion path also changes at 47 Ma in GMHRF-2 (compare red and green lines in Figure 5b), but the modeled southward hot spot drift is larger in this GMHRF and the Emperor Chain is lengthened by~1,200 km. Both models suggest a straightforward Matthews et al. (2016) where the Pacific plate is linked via Marie Byrd Land/West Antarctica (Wright et al., 2015), and then through East Antarctica to Africa. The predicted tracks plot west of the Emperor Chain but all indicate a plate motion change at around 50 Ma. ...
... Based on refinements of their model B ; Figure 3b), HEB is clearly predicted from both fixed and moving Indo-Atlantic hot spot frames (curves marked MHS-C and FHS-C in Figure 5d). New plate circuits between the Pacific Plate and Marie Byrd Land/West Antarctica (Wright et al., 2015), but more importantly revised plate circuits between West and East Antarctica (Granot et al., 2013 model extended beyond~40 Ma)-as implemented in Matthews et al. (2016)-predicts the HEB even more pronouncedly (curves marked MHS-E and FHS-E in Figure 5d). The HEB is therefore clearly predicted by a plate motion change from Indo-Atlantic hot spots in both fixed and moving hot spot reference frames, and with two different plate circuit models. ...
Article
We have devised a new absolute Late Jurassic‐Cretaceous Pacific plate model using a fixed hot spot approach coupled with paleomagnetic data from Pacific large igneous provinces (LIPs) while simultaneously minimizing plate velocity and net lithosphere rotation (NR). This study was motivated because published Pacific plate models for the 83.5‐ to 150‐Ma time interval are variably flawed, and their use affects modeling of the entire Pacific‐Panthalassic Ocean and interpretation of its margin evolution. These flaws could be corrected, but the revised models would imply unrealistically high plate velocities and NR. We have developed three new Pacific realm models with varying degrees of complexity, but we focus on the one that we consider most realistic. This model reproduces many of the Pacific volcanic paths, modeled paleomagnetic latitudes fit well with direct observations, plate velocities and NR resulting from the model are low, and all reconstructed Pacific LIPs align along the surface‐projected margin of the Pacific large low shear wave velocity province. The emplacement of the Shatsky Rise LIP at ~144 Ma probably caused a major plate boundary reorganization as indicated by a major jump of the Pacific‐Izanagi‐Farallon triple junction and a noteworthy change of the Pacific‐Izanagi seafloor spreading direction at around chron M20 time.
... Koivisto et al. (2014) suggested that the H-E bend can be explained by a plate reorganization, e.g., a major acceleration in Pacific-Farallon spreading rates around 49-40.1 Ma. However, based on a comprehensive synthesis of magnetic anomaly and fracture identifications, Wright et al. (2015) found that increases in Pacific-Farallon spreading rates are not accompanied by any statistically significant change in spreading direction. The changes in relative motion direction between the Pacific and Farallon plates, and the Pacific and Antarctic plates, were insignificant around the formation time of the H-E bend. ...
... Reorganization of Pacific-Farallon spreading occurred in the earliest Eocene around 55 Ma with a significant increase in spreading rate from 118 ± 6 mm/yr to 182 ± 2 mm/yr between 49.7 and 40.1 Ma. This is thought to be a result of an increase in Farallon plate motion, rather than a change in motion of the Pacific plate (Wright et al., 2015). Simultaneously, in the south Pacific, along the Austral Fracture zone, there is a significant 93 mm/yr increase in spreading rate between chron 25y (55.9 Ma) and 20o (43.8 Ma). ...
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The Hawaiian-Emperor volcanic chain (H-E chain) is located in the middle of the North Pacific Ocean. It extends from northwest to southeast, including two segments, the older Emperor chain and the younger Hawaiian chain between which is a 60o change in strike, here termed the H-E bend. The H-E chain is the clearest and most intensively researched hot spot track in terms of plate motion, mantle plumes, tectonics, geochemical evolution, and lithospheric studies. However, debates on the formation of the H-E chain, in particular the H-E bend, concerning its origin in hot spot drift and/or Pacific plate motion change, have been ongoing for several decades. In this paper, we review current understanding and ideas concerning this debate and suggest ways forward. So far, neither hot spot southerly drift nor Pacific plate motion change can perfectly account for the geometry and progression of the H-E chain. In this review, we put forward a joint model where these two competing processes together can reasonably explain the evolution of the H-E chain and the H-E bend. In addition, we proposed three stages for formation of the H-E chain, including: 1) A ridge-plume interaction stage: Meiji~Detroit seamounts and a possible subducted section; 2) A combination of hot spot-Pacific plate motion: South of Detroit seamount ~ H-E bend; and 3) Pacific plate motion with a fixed hot spot: Hawaiian volcanic chain. In addition, any plate movement at the surface must be balanced by motion deeper in the mantle. Therefore, we consider that the surface Pacific plate motion and the state of deep mantle plume at 47–55 Ma are not totally separated but co-evolved. Furthermore, reconstructions of the Pacific plate and its boundaries should be considered if Hawaiian hot spot motion makes great contributions to the formation of the H-E chain. Nevertheless, establishing the causal links between these events and their underlying dynamic triggers requires further, more comprehensive work.
... In the northern Pacific, an about twofold increase in spreading rate at C22-C20 time has been noted by others (Barckhausen et al., 2013;Wright et al., 2015). This spreading rate increase coincides with the prominent change in orientation in the Hawaiian-Emperor seamount chain (Hawaiian-Emperor bend [HEB]), whose date has been recently updated to~47 Ma (O'Connor et al., 2013;Torsvik et al., 2017;Wessel et al., 2006). ...
... This spreading rate increase coincides with the prominent change in orientation in the Hawaiian-Emperor seamount chain (Hawaiian-Emperor bend [HEB]), whose date has been recently updated to~47 Ma (O'Connor et al., 2013;Torsvik et al., 2017;Wessel et al., 2006). The HEB was originally explained by a change in absolute motion of the Pacific plate over a fixed hot spot, but later on, several authors argued that it resulted from a slowing southward motion of the Hawaiian hot spot (Norton, 1995;Tarduno et al., 2003;Wright et al., 2015). Torsvik et al. (2017), however, recently concluded that both a southward shift of the Hawaiian hot spot and a change in Pacific plate motion direction are necessary to explain the HEB. ...
... The highest quality K-Ar radiometric age data from mugearite and hawaiite from conglomerate pebbles above the Reef Hole basement yield an age of 27.6 ± 0.6 Ma 26,27 . This compares well with 40 Ar/ 39 Ar ages of 27.5 ± 1.2 Ma and 27.6 ± 0.9 Ma on shield phase samples recovered from subsequent dredging 28 . Grommé and Vine 29 sampled thirteen of the Midway lavas, applying only partial alternating field demagnetization on about one half of the samples. ...
... If the Louisville plume was only slowly moving while the Hawaiian plume was moving rapidly southward, this difference should be preserved as a change in distance between the volcanic edificies comprising the two hotspots tracks. Continued efforts to improve the age assignments of the Hawaiian-Emperor and Louisville Seamounts through 40 Ar/ 39 Ar radiometric analysis 20,21,28 allows this analysis (see Hawaii-Louisville seamount distances, in Methods). We select eight seamount pairs where the ages are within 3 m.y. ...
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Controversy surrounds the fixity of both hotspots and large low shear velocity provinces (LLSVPs). Paleomagnetism, plate-circuit analyses, sediment facies, geodynamic modeling, and geochemistry suggest motion of the Hawaiian plume in Earth's mantle during formation of the Emperor seamounts. Herein, we report new paleomagnetic data from the Hawaiian chain (Midway Atoll) that indicate the Hawaiian plume arrived at its current latitude by 28 Ma. A dramatic decrease in distance between Hawaiian-Emperor and Louisville chain seamounts between 63 and 52 Ma confirms a high rate of southward Hawaiian hotspot drift (~47 mm yr-1), and excludes true polar wander as a relevant factor. These findings further indicate that the Hawaiian-Emperor chain bend morphology was caused by hotspot motion, not plate motion. Rapid plume motion was likely produced by ridge-plume interaction and deeper influence of the Pacific LLSVP. When compared to plate circuit predictions, the Midway data suggest ~13 mm yr-1 of African LLSVP motion since the Oligocene. LLSVP upwellings are not fixed, but also wander as they attract plumes and are shaped by deep mantle convection.
... In the context of this mechanism, additional processes (such as the reactivation of crustal structures and/or the reorganization of the crustal stress field) must be invoked to explain the timing of pulses of volcanic activity. Interestingly, the bend in the Hawaii-Emperor seamount change suggests a global reorganization of plate motions at roughly ∼47 Ma (e.g., Wright et al., 2015); while this is speculative, in the context of this model this global change may have reorganized the stress field in our study region and allowed for the migration of melt to the surface (e.g., Southworth et al., 1993). This would mean that the lithospheric geometry seen today may have been established in the Jurassic (producing the initial episode of magmatism) and may have changed little since that time. ...
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... The Hawaii-Emperor Bend shows relatively low ( 25 km) e T in the whole chain. The e T of the Hawaiian section of the HESC increase gradually eastwards, coinciding with the age-progression of volcanism (O'Connor et al., 2013;Wright et al., 2015). We can observe a similar eastward increasing e T over the Louisville seamount chain, with the highest e T at the present location of the hot spot (Figure 4a). ...
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In this chapter we will focus primarily on the promise and limitations of the ocean crust as a recor- der of geomagnetic field variations, emphasizing the record of past geomagnetic field variations recorded in anomalies (and therefore in source magnetization) on timescales of 103 years (excursions) to 104–106 (reversals) and 107–108 (superchrons). We review the origin of the magnetization in the various crustal source layers responsible for lineated magnetic anomalies and conclude by mentioning some appli- cations to deciphering how oceanic crust formed and by speculating on future directions. The chapter is based mostly on published literature that appeared since the last major review of ocean crust magnetiza- tion by Smith (1990).
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