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Plate-tectonic reconstructions predict part of the Hawaiian hotspot tract to be preserved in the Bering Sea

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We use plate reconstructions to show that parts of the Hawaiian hotspot track of ca. 80 90 Ma age could be preserved in the Bering Sea. Based on these reconstructions, the Hawaiian hotspot was beneath the Izanagi plate before ca. 83 Ma. Around that time, the part of the plate carrying the hotspot track was transferred to the Kula plate. After 75 80 Ma the Hawaiian hotspot underlay the Pacific plate. Circa 40 55 Ma, subduction initiated in the Aleutian Trench. Part of the Kula plate was attached to the North American plate and is preserved as the oceanic part of the Bering Sea. We show that for a number of different plate reconstructions and a variety of assumptions covering hotspot motion, part of the hotspot track should be preserved in the Bering Sea. The predicted age of the track depends on the age of Aleutian subduction initiation. We speculate that Bowers and Shirshov Ridges were formed by paleo-Hawaiian hotspot magmatism.
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GEOLOGY, May 2007 407
Geology, May 2007; v. 35; no. 5; p. 407–410; doi: 10.1130/G23383A.1; 2 fi gures; Data Repository item 2007098.
© 2007 The Geological Society of America. For permission to copy, contact Copyright Permissions, GSA, or editing@geosociety.org.
1GSA Data Repository item 2007098, informa-
tion on the construction of past plate boundaries,
Table DR1 (relevant fi nite plate rotation parameters)
and Figure DR1 (magnetic anomalies in the Bering
Sea region), is available online at www.geosociety.
org/pubs/ft2007.htm, or on request from editing@
geosociety .org or Documents Secretary, GSA, P.O.
Box 9140, Boulder, CO 80301, USA.
INTRODUCTION
Age-progressive, intraplate volcanism along
the Hawaiian-Emperor Chain (Pacifi c plate) led
Wilson (1963) to fi rst suggest a causal relation-
ship with an upwelling from deep inside Earth
(later called “mantle plume”) that is overridden
by a moving plate. However, the Hawaiian-
Emperor Chain ends at the Aleutian subduction
zone. Its northernmost part, north of, and pos-
sibly including, the Detroit seamount, aged 76–
81 Ma (Keller et al., 1995; Duncan and Keller,
2004), and oceanic basalts from accretionary
complexes in eastern Kamchatka (Portnyagin
et al., 2006), may have formed through chan-
neling of plume material to the ridge (Tarduno
et al., 2003), hence a corresponding track may
have formed on the Izanagi and Kula plates. It is
not clear whether parts of the hotspot track are
preserved beyond the subduction zone.
The ocean basin in the Bering Sea north of
the Aleutian Trench is usually interpreted as a
captured remnant of the Kula plate, which has
for the most part been subducted (Scholl et al.,
1975, 1986). Hence, it may have preserved older
parts of the Hawaiian hotspot track. Their exis-
tence and identifi cation could give important
insights about the age and earlier history of the
Hawaiian hotspot, thus further constraining the
nature of mantle plumes.
In this paper, we show that plate-tectonic
reconstructions (Fig. 1) yield a predicted hot-
spot track through the oceanic part of the Bering
Sea. It is possible that two ridges in this basin,
Shirshov and Bowers (Fig. 2), were originally
formed by the Hawaiian hotspot. However, a
hotspot track origin contrasts with other inter-
pretations for the formation of the ridges (e.g.,
Cooper et al., 1992; Baranov et al., 1991). We
therefore commence with a brief review of the
tectonic setting and conclude on a somewhat
speculative note how what is proposed here may
be reconciled with geologic evidence.
REGIONAL TECTONIC SETTING
OF SHIRSHOV AND BOWERS RIDGES
IN THE BERING SEA
Based on the age of oldest volcanic activity,
the Aleutian Arc is believed to have formed at
ca. 40–55 Ma (Scholl et al., 1987; Jicha et al.,
2006). The ocean fl oor to the north is prob-
ably a piece of captured Kula plate; most of
this plate subducted beneath continental crust
from Kamchatka to the Bering Shelf (Scholl
et al., 1975, 1986). Cooper et al. (1987b) sug-
gested that large structural depressions fi lled
with deformed sedimentary prisms beneath
the continental slopes are remnants of ancient
trenches. Probably Cenozoic crust formed due
to backarc extension in the Komandorsky and
possibly Bowers Basins ( Cooper et al., 1987a,
1992; Baranov et al., 1991).
Only undated arc-type volcanic rocks have
been dredged from Bowers Ridge (Cooper et al.,
1987a). Thus the ages of formation of Shirshov
and Bowers Ridges are unknown. Bowers Ridge
is bordered on its convex side by a sediment-fi lled
trench (Ludwig et al., 1971). Seismic, magnetic,
and gravity data support its interpretation as a
volcanic arc at a fossil subduction zone (Kienle,
1971). Trench sediments were deposited and sub-
sequently deformed probably during the Ceno-
zoic (Marlow et al., 1990). Shirshov Ridge is
characterized by thick sediments along its eastern
ank and steep scarps on its western side (Rabino-
witz and Cooper, 1977). Various concepts of its
uncertain origin are reviewed by Baranov et al.
(1991). Rock dredgings on Shirshov Ridge recov-
ered basalts, gabbros, and other datable rocks
(Baranov et al., 1991). An 40Ar/39Ar (plagioclase)
age 27.8 ± 1.1 Ma was determined for an andesite
(Cooper et al., 1987a). No oceanic-island basalts
are known to have been recovered from these
ridges (D. Scholl, 2000, personal commun.).
These fi ndings and interpretations do not exclude
the possibility that the ridges were fabricated out
of pre-existing structures of a different nature. We
speculate that a hotspot track localized the later
Bowers and Shirshov Ridges.
PACIFIC PLATE-TECTONIC
RECONSTRUCTIONS
Reconstructions of relative plate motions
(Table DR1 in the GSA Data Repository1) and
geometries in the Pacifi c Ocean Basin are based
on marine magnetic anomalies. In order to fi nd
the location of the plates within the Pacifi c
Ocean Basin relative to the plates surround-
ing it, and to plot them on a map with latitudes
and longitudes, these reconstructions must be
embedded in a suitable absolute reference frame.
A fi xed-hotspot reference frame has frequently
been used (e.g., Duncan and Clague, 1985).
However, there are a number of indications that
the Hawaiian hotspot has moved and was farther
north in the geologic past. These include analy-
ses of plate circuits (e.g., Raymond et al., 2000),
sedimentological evidence (Parés and Moore,
2005), numerical models (e.g., Steinberger et al.,
2004), and paleomagnetic data (e.g., Tarduno
and Cottrell, 1997; Tarduno et al., 2003). The
latter indicate that the Hawaiian hotspot was
at ~30–35° N at 75–80 Ma and had moved to
close to its present latitude at the time of the
Hawaiian-Emperor bend. True polar wander
(e.g., Besse and Courtillot, 2002) appears not
to have contributed more than a few degrees of
latitude change (Tarduno and Smirnov, 2001),
regardless of whether it is computed in a fi xed-
hotspot reference frame or a mantle reference
frame that considers hotspot motion (Torsvik
et al., 2006). We determine the best-fi tting
Pacifi c plate motion assuming a hotspot motion
that is broadly consistent with numerical mod-
els for Hawaiian and Louisville hotspot motion
(Koppers et al., 2004) and paleomagnetic data.
*E-mail: bernhard.steinberger@ngu.no.
Plate-tectonic reconstructions predict part of the Hawaiian hotspot
track to be preserved in the Bering Sea
Bernhard Steinberger* Center for Geodynamics, Geological Survey of Norway, Leiv Eirikssons vei 39,
Carmen Gaina N-7491 Trondheim, Norway
ABSTRACT
We use plate reconstructions to show that parts of the Hawaiian hotspot track of ca. 80–
90 Ma age could be preserved in the Bering Sea. Based on these reconstructions, the Hawaiian
hotspot was beneath the Izanagi plate before ca. 83 Ma. Around that time, the part of the plate
carrying the hotspot track was transferred to the Kula plate. After 75–80 Ma the Hawaiian
hotspot underlay the Pacifi c plate. Circa 40–55 Ma, subduction initiated in the Aleutian
Trench. Part of the Kula plate was attached to the North American plate and is preserved as
the oceanic part of the Bering Sea. We show that for a number of different plate reconstruc-
tions and a variety of assumptions covering hotspot motion, part of the hotspot track should
be preserved in the Bering Sea. The predicted age of the track depends on the age of Aleutian
subduction initiation. We speculate that Bowers and Shirshov Ridges were formed by paleo-
Hawaiian hotspot magmatism.
Keywords: Hawaii, hotspots, plate motion, Kula plate, Bering Sea, Bowers Ridge.
408 GEOLOGY, May 2007
We assume the Hawaiian hotspot moved 13°
southward and 3° eastward between 90 and
47 Ma, and 2° southward and 2° eastward since
47 Ma, and the Louisville hotspot has moved
10° eastward and 4° southward since 120 Ma,
all at constant speed. Optimization procedure
and age data from both hotspot tracks are the
same as in Koppers et al. (2004), who showed
that new radiometric age data are consistent
with relative hotspot motion as assumed here.
Results are included in Table DR1 (see foot-
note 1). Note that the Pacifi c plate motion is
thus determined independent of the global
plate circuit and Indo-Atlantic hotspot tracks.
Pacifi c plate rotation rates before 83 Ma are
from Duncan and Clague (1985), i.e., fi nite
rotations at 100 and 150 Ma were corrected
for inferred hotspot motion since 83 Ma. Con-
struction of plate boundaries is detailed in the
GSA Data Repository (see footnote 1).
Figure 1 shows reconstructions for this case:
The Hawaiian hotspot fi rst (top left panel)
occupied an intraplate location on the Izanagi
plate, which moved northwestward at a speed
of >10 cm/yr. After ca. 100 Ma, Pacifi c plate
motion also had a northward component: The
Izanagi-Pacifi c boundary moved northward,
approaching the Hawaiian hotspot at ~8 cm/yr.
At 100 Ma, the hotspot was ~14° north of the
plate boundary, at 90 Ma ~7°. It is more uncer-
tain where the Izanagi-Farallon boundary was,
and hence whether the track was emplaced on
crust formed at the Izanagi-Pacifi c or Izanagi-
Farallon spreading center. In the fi rst case, it is
estimated that the track formed at 100–90 Ma
on 35–17.5 m.y. old crust (now 135–107.5 m.y.
old), based on an Izanagi-Pacifi c half spread-
ing rate of ~0.4 degrees/m.y. as extrapolated
from isochrons. In the second case, crustal age
would be younger. We consider it possible, but
unlikely, that part of the track for part of the
time was on the Farallon plate.
During the reorganization of plate bound-
aries in the North Pacifi c at ca. 83 Ma, the Kula
plate formed from older pre-existing crust of the
Izanagi, Farallon, and possibly Pacifi c plates, pre-
sumably incorporating the entire Hawaiian hot-
spot track. At ca. 78 Ma, the northward-moving
ridge crossed over the hotspot; subsequently a
track was created on the Pacifi c plate, and the
track on the Kula plate was carried northward. At
ca. 40–55 Ma, subduction began in the Aleutians,
and the oceanic crust of the Bering Sea Basin,
being a fragment of the Kula plate, became part
of the North American plate at that time. For bet-
ter visibility, we plot tracks regardless of location
(black on North American, gray on Pacifi c plate
for ages older than 78 Ma, in Fig. 1).
DISCUSSION
Plate-tectonic reconstructions of the Pacifi c
region imply that the Hawaiian hotspot was
located beneath the Izanagi and Kula plates
10˚ N
20˚ N
30˚ N
40˚ N
50˚ N
60˚ N
110
120
130
140
90
100
110
120
10˚ N
20˚ N
30˚ N
40˚ N
50˚ N
60˚ N
80
90
100
110
80
90
100
80
90
100
110
80
90
60
70
80
90
80
90
100
110
140˚ E 160˚ E 180˚ 160˚ W 140˚ W
10˚ N
20˚ N
30˚ N
40˚ N
50˚ N
60˚ N
80
90
100
50
60
70
80
90
90
100
80
140˚ E 160˚ E 180˚ 160˚ W 140˚ W
80
90
80
90
100
90
10
20
30
40
50
60
70
90
100
80
90
104 Ma
Izanagi
Farallon
Pacific
88 Ma
Kula / Izanagi
Farallon
Pacific
72 Ma
Kula
Pacific
56 Ma
Kula
Pacific
40 Ma
Kula
Pacific
North American
Present
Pacific
North American
Okhotsk
Eur-
asian
inferred from marine magnetic anomalies
Plate boundaries at time indicated
~ 4 Myr earlier
~ 4 Myr later
Other intra-Pacific plate boundaries
Selected other plate boundaries
10 cm/yr (at 45º N)
Assumed location of Hawaiian hotspot Computed hotspot track:
IZAKUL at 83 Ma, KULNAM at 47 Ma
IZAKUL at 93 Ma, KULNAM at 47 Ma
IZAKUL at 73 Ma, KULNAM at 47 Ma
IZAKUL at 83 Ma, KULNAM at 54 Ma
IZAKUL at 83 Ma, KULNAM at 40 Ma
Isochrons at 120 Ma
Isochrons at 84 Ma
Figure 1. Plate reconstruction explaining how part of the Hawaiian hotspot track could have
become preserved in the Bering Sea. Arrows indicate plate velocities. Computed hotspot
tracks are shown on Pacifi c plate for ages younger than 78 Ma, and on Izanagi-Kula–North
American plate for ages older than 78 Ma, with ages indicated in Ma. 88 Ma: Black arrows
on Kula/Izanagi plate are Izanagi plate velocities, gray arrows are Kula plate velocities. Kula-
Pacifi c relative motion before 67.7 Ma was assumed to be as in the interval 67.7–55.9 Ma.
72 Ma and 56 Ma: Black, light gray, and dark gray lines are for change from Izanagi to Kula
plate motion at different times, as indicated. 40 Ma and present: Continuous, dashed, and
dotted lines are for transfer from Kula to North American plate as indicated; track extension
onto Pacifi c shown as gray dashed line. Tracks are shown on North American plate regard-
less of whether this part was on Kula plate before; only in this case (i.e., in the Bering Sea)
it may correspond to a real hotspot track. Reconstructed isochrons at 120 Ma and 84 Ma
enable comparison with magnetic anomalies. They are shown as lines of the same kind as
hotspot tracks for the same cases. They are plotted regardless of location but could only
be preserved if located in the Bering Sea. IZA—Izanagi plate; KUL—Kula plate; NAM—North
American plate.
GEOLOGY, May 2007 409
prior to ca. 75–80 Ma. Part of the track pro-
duced during that time could still be preserved
in the Bering Sea near Bowers and Shirshov
Ridges, provided that its ocean crust was part of
the Kula plate and became attached to the North
American plate ca. 55–40 Ma. We estimate that
the preserved part would be ~80–90 m.y. old.
Figure 2 shows a close-up look at the predicted
present-day location of that part of the track.
The geologic evidence that Bowers Ridge was
a volcanic arc in the Tertiary could mean that
the proximity of predicted track and observed
ridges is pure coincidence. Shirshov and Bowers
Ridges may be structurally unrelated (Rabino-
witz, 1974). Following Cooper et al. (1992), a
strike-slip zone roughly north-south in direc-
tion may have formed at the location of a pre-
existing oceanic plateau after subduction was
initiated in the eastern part of the Aleutian Arc,
and subsequently, the separate Shirshov and
Bowers Ridges developed from the originally
continuous and straight strike-slip zone. We
suggest here that the supposed oceanic plateau
has been part of the Hawaiian hotspot track.
The predicted tracks depend on a number of
assumptions, each uncertain to some degree.
1. Motion of hotspots in the Pacifi c Ocean
Basin: In our reference case (black continu-
ous lines in Figs. 1 and 2), the Hawaiian hot-
spot moved southward relative to the Louisville
hotspot. Hence the predicted track is consider-
ably farther north than for fi xed Pacifi c hotspots
(squares in Fig. 2); in the latter case it passes
through Komandorsky and Bowers Basins
instead of the Aleutian Basin. This offset comes
from relative motion between hotspots; pre-
dicted tracks for coherently moving hotspots are
the same as for fi xed hotspots.
2. Motion of hotspots in the African hemi-
sphere: Results also depend on the estimated
motion of the Tristan and Reunion hotspots
over the past 47 Ma. Their motion is likely to
be smaller, as discussed in Steinberger et al.
(2004), and hence has a smaller effect on the
predicted hotspot track: The track with dia-
monds in Figure 2 was computed with African
plate motion in a fi xed-hotspot reference frame
instead of moving hotspots. A number of further
computations with fi xed and moving hotspots
gave overall similar results.
3. Motion of Kula and Izanagi plates: During
the Cretaceous superchron (118–83 Ma), marine
magnetic anomalies are absent, and the oldest
well-recognized isochron for the Kula-Pacifi c
boundary is 67.7 Ma, although older magnetic
anomalies (70–80 Ma) have been recognized
by Rea and Dixon (1983) and Mammerickx and
Sharman (1988). Black and gray arrows, and
black, light gray, and dark gray lines in Figure 1
(black, orange, and blue in Fig. 2) are for three
possible spreading history scenarios with change
from Izanagi to Kula plate motion at 83, 93, or
73 Ma, and illustrate uncertainties in azimuth of
the predicted hotspot track. With the scenario of
Cooper et al. (1992), a north-south hotspot track
orientation would be most suitable to explain the
geometry of Shirshov and Bowers Ridges.
4. Initiation of subduction in the Aleutians:
An older track is predicted for an earlier time of
the Bering Sea becoming attached to the North
American plate. This track would have formed
on older ocean fl oor. In our plate motion model,
the Izanagi-Farallon-Pacifi c triple junction was
captured on the Kula plate at 84 Ma, and thus
could be preserved east of the hotspot track in
the Bering Sea. If spreading at this triple junc-
tion had continued for a few million years after
84 Ma, magnetic anomalies of chron 34 and pos-
sibly 33 could be preserved there. The predicted
location and orientation of these isochrons rela-
tive to the hotspot track matches approximately
with the location and orientation of the most
prominent, approximately north-south–oriented
magnetic seafl oor lineations in the Aleutian
Basin (Cooper et al., 1976) (Fig. DR1; see foot-
note 1) relative to Shirshov and Bowers Ridges.
Magnetic lineations in the southern part of the
Bering Sea could have formed along the Pacifi c-
Farallon spreading ridge, i.e., the northern con-
tinuation of the Pacifi c-Chinook spreading ridge
preserved in the Emperor Trough south of the
Aleutian Trench, as proposed by Rea and Dixon
(1983). Older crustal ages, such as in the inter-
pretation of Cooper et al. (1976), would require
earlier subduction initiation in the Aleutian Arc
than assumed here.
5. Plate motion in the Bering Sea: Our
reconstructions assume that the Bering Sea has
moved with the North American plate after 40–
54 Ma. However, motion along strike-slip faults
in Alaska may have accommodated westward
motion of the Bering Sea relative to the stable
North American plate (Cooper et al., 1992).
This would move the hotspot track computed
for a moving Hawaiian hotspot toward Shirshov
and Bowers Ridges and would move predicted
84 Ma isochrons toward the clearest magnetic
160˚ E 170˚ E 180˚ 170˚ W
50˚ N
60˚ N
90
95
100
90
95
85
90
85
90
85
90
80
85
90
80
IZAKUL at 73 Ma at 73 Ma at 73 Ma at 83 Ma at 93 Ma
KULNAM at 54 Ma at 40 Ma at 47 Ma at 47 Ma at 47 Ma
African plate motion in fixed-hotspot reference frame (Torsvik et al., 2006)
Pacific plate motion in fixed-hotspot reference frame (Duncan and Clague, 1985)
African and Pacific plate motion in fixed-hotspot reference frame
Emperor
Chain
Kamchatka
Komandorsky
Basin
Shirshov
Ridge
Bowers
Ridge
Bowers
Basin
Aleutian Trench
Aleutian
Basin
Bering Shelf
-1200 m
-1800 m
Figure 2. Computed Hawaiian hotspot tracks in the Bering Sea for different plate motion and
reference frame scenarios. Depth contours are shown at sea level, –1200 m and –1800 m
(Smith and Sandwell, 1997). Black line with tick marks (reference case), and colored lines
with tick marks are computed with change from Izanagi to Kula plate motion and transfer
from Kula to North American plate as indicated, and Pacifi c and African plate motions in
the moving hotspot reference frame. Red line with diamonds is computed with African plate
motion in the fi xed (instead of moving) hotspot reference frame after 47 Ma; black line with
squares is computed with Pacifi c plate motion in the fi xed (instead of moving) hotspot ref-
erence frame before 47 Ma; red line with triangles is computed with both (see Table DR1
[see footnote 1]); otherwise as reference case. Further explanation is given with Figure 1.
IZA—Izanagi plate; KUL—Kula plate; NAM—North American plate.
410 GEOLOGY, May 2007
seafl oor lineations, which are somewhat east
and north of Bowers Ridge. This motion may
be a tectonic extrusion driven by Kula–North
American convergence (Scholl and Stevenson,
1991), similar to present-day Anatolia. Amounts
of motion are, however, diffi cult to quantify.
A hotspot track crossing the Bering Sea is
a prediction based on current knowledge of
plate and hotspot motions. This prediction is
made regardless of fi xed or moving hotspots;
the preserved part of the track is predicted to be
younger, and farther to the east, for faster south-
ward motion of the Hawaiian hotspot relative
to the Louisville hotspot. A relation with Shir-
shov and Bowers Ridges is plausible although
speculative. We expect that our prediction will
motivate further work, which may corroborate
our proposed relation.
ACKNOWLEDGMENTS
We thank David Scholl for very detailed infor-
mation about tectonic setting and regional geology,
Susanne Buiter for in-depth comments on lithosphere
dynamics, and Ulrich Christensen, Vic DiVenere,
Robert Duncan, Tim Redfi eld, Trond Torsvik, and an
anonymous reviewer for further helpful comments.
Figures are produced with Generic Mapping Tools
graphics (Wessel and Smith, 1998).
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Manuscript received 21 September 2006
Revised manuscript received 13 December 2006
Manuscript accepted 29 December 2006
Printed in USA
... As in Steinberger and Gaina (2007) Moving hot spots (4 tracks) Torsvik et al. (2010) Note: Differ from all other frames because the Pacific (based on Steinberger & Gaina, 2007) and Indo-Atlantic frames have been computed separately (O'Neill et al., 2005; smooth version; see also Torsvik et al., 2008): We thus infer plate circuits between the Pacific and Indo-Atlantic realms from the two independent reference frames As in Steinberger and Gaina (2007 Geochemistry, Geophysics, Geosystems . The 70-to 100-Ma interval in between is linearly interpolated and thus smoothed. ...
... As in Steinberger and Gaina (2007) Moving hot spots (4 tracks) Torsvik et al. (2010) Note: Differ from all other frames because the Pacific (based on Steinberger & Gaina, 2007) and Indo-Atlantic frames have been computed separately (O'Neill et al., 2005; smooth version; see also Torsvik et al., 2008): We thus infer plate circuits between the Pacific and Indo-Atlantic realms from the two independent reference frames As in Steinberger and Gaina (2007 Geochemistry, Geophysics, Geosystems . The 70-to 100-Ma interval in between is linearly interpolated and thus smoothed. ...
... The Hawaiian-Emperor and Louisville volcanic chain tracks can be used to determine the motion of the Pacific plate independently relative to the mantle (e.g., Steinberger & Gaina, 2007;Torsvik et al., 2008Torsvik et al., , 2010, Table 1). But these two volcanic chains are also incorporated in the construction of the GMHRF that uses relative plate circuits to link the Pacific realm to the Indo-Atlantic realm. ...
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.
... The Izanagi/Kula plate was moving northward, such that eruptions at the ridge should have formed seamount chains on the Izanagi/Kula plate as well. It is possible that the Shirshov plateau was formed during the eruption of Meiji, whereas the Bowers plateau formed together with Detroit [25]. These two plateaus should also have MORB affinities. ...
... At~85 Ma, the plume was attracted southward to a spreading center (to 19°N, Fig. 1a), leading to large eruptive volumes and more depleted compositions. This is consistent with plate reconstructions using GPlates and previous results [4,14,25] which suggest that the Hawaiian plume was near the northern Pacific spreading centers at~85 Ma. Similar to our model, previous authors proposed that the southward movement of the plume may have started at the Bowers Ridges in the Bering Sea [25]. ...
... This is consistent with plate reconstructions using GPlates and previous results [4,14,25] which suggest that the Hawaiian plume was near the northern Pacific spreading centers at~85 Ma. Similar to our model, previous authors proposed that the southward movement of the plume may have started at the Bowers Ridges in the Bering Sea [25]. Plate reconstruction shows that the Hawaiian plume may have started to interact with the Pacific-Izanagi/Kula spreading ridge at~90 Ma ago [14]. ...
Article
Full-text available
The history of the Hawaiian hotspot is of enduring interest in studies of plate motion and mantle flow, and has been investigated by many using the detailed history of the Hawaiian-Emperor Seamount chain. One of the unexplained aspects of this history is the apparent offset of several Emperor seamounts from the Hawaii plume track. Here we show that the volcanic migration rates of the Emperor seamounts based on existing data are inconsistent with the drifting rate of the Pacific plate, and indicate northward and then southward “absolute movements” of the seamounts. Numerical modeling suggests that attraction and capture of the upper part of the plume by a moving spreading ridge led to variation in the location of the plume’s magmatic output at the surface. Flow of the plume material towards the ridge led to apparent southward movement of Meiji. Then, the upper part of the plume was carried northward until 65 Ma ago. After the ridge and the plume became sufficiently separated, magmatic output moved back to be centered over the plume stem. These changes are apparent in variations in the volume of seamounts along the plume track. Chemical and isotopic compositions of basalt from the Emperor Seamount chain changed from depleted (strong mid-ocean ridge affinity) in Meiji and Detroit to enriched (ocean island type), supporting declining influence from the ridge. Although its surface expression was modified by mantle flow and by plume-ridge interactions, the stem of the Hawaiian plume may have been essentially stationary during the Emperor period.
... Marine magnetic data of the Aleutian Basin ( Figure 2) shows a set of roughly north-south-trending magnetic anomalies (see, e.g., Figure 4 in Cooper et al., 1992, or Figure DR1 in the supporting information of Steinberger & Gaina, 2007). These anomalies were initially correlated with the Early Cretaceous M1-M13 sequence (Cooper et al., 1976), that is, ∼128-138 Ma (Ogg et al., 2016). ...
... Later, Cooper et al. (1992) cautioned that this age determination remains uncertain. Steinberger and Gaina (2007) tentatively suggested that the most prominent north-south-oriented magnetic lineations in the eastern part of the basin may correspond to chron 34 (~84 Ma) to chron 32 (~71 Ma). Although no definitive correlation with the magnetic polarity timescale has been made, the north-south-trending anomalies are generally interpreted as being formed by seafloor spreading (Cooper et al., 1976(Cooper et al., , 1992Scheirer et al., 2016;Scholl, 2007;Steinberger & Gaina, 2007). ...
... Steinberger and Gaina (2007) tentatively suggested that the most prominent north-south-oriented magnetic lineations in the eastern part of the basin may correspond to chron 34 (~84 Ma) to chron 32 (~71 Ma). Although no definitive correlation with the magnetic polarity timescale has been made, the north-south-trending anomalies are generally interpreted as being formed by seafloor spreading (Cooper et al., 1976(Cooper et al., , 1992Scheirer et al., 2016;Scholl, 2007;Steinberger & Gaina, 2007). In addition to the main set of N-S-trending anomalies, several enigmatic NE-SW oriented magnetic anomalies were traced on the northwest of the Aleutian Basin, interpreted by Cooper et al. (1992) to have formed in a Cenozoic back-arc spreading center. ...
Article
Full-text available
The Eocene (~50‐45 Ma) major absolute plate motion change of the Pacific plate forming the Hawaii‐Emperor bend is thought to result from inception of Pacific plate subduction along one of its modern western trenches. Subduction is suggested to have started either spontaneously, or result from subduction of the Izanagi‐Pacific mid‐ocean ridge, or from subduction polarity reversal after collision of the Olyutorsky arc that was built on the Pacific plate with NE Asia. Here we provide a detailed plate‐kinematic reconstruction of back‐arc basins and accreted terranes in the northwest Pacific region, from Japan to the Bering Sea, since the Late Cretaceous. We present a new tectonic reconstruction of the intra‐oceanic Olyutorsky and Kronotsky arcs, which formed above two adjacent, oppositely‐dipping subduction zones at ~85 Ma within the north Pacific region, during another Pacific‐wide plate reorganization. We use our reconstruction to explain the formation of the submarine Shirshov and Bowers Ridges, and show that if marine magnetic anomalies reported from the Aleutian Basin represent magnetic polarity reversals, its crust most likely formed in an ~85‐60 Ma back‐arc basin behind the Olyutorsky arc. The Olyutorsky arc was then separated from the Pacific plate by a spreading ridge, so that the ~55‐50 Ma subduction polarity reversal that followed upon Olyutorsky‐NE Asia collision initiated subduction of a plate that was not the Pacific. Hence, this polarity reversal may not be a straightforward driver of the Eocene Pacific plate motion change, whose causes remain enigmatic.
... 14D27612.one-pager.xls printed at 18-10-2016 (16:21) ArArCALC v2.7.0 --Beta Version ...
... 14D28186.one-pager.xls printed at 18-10-2016 (16:21) ArArCALC v2.7.0 --Beta Version ...
... These reconstructions can be categorized into two main groups, those with reference to the hotspots in the Pacific realm and those in the Indo-Atlantic realm. In the Pacific realm, assuming fixed or moving hotspots, the Pacific Plate motion is inferred by fitting the age and the geometry of hotspot tracks in the Pacific 6,35 . These models suggest a substantial change of Pacific Plate motion at the time of the HEB. ...
Article
Full-text available
A drastic change in plate tectonics and mantle convection occurred around 50 Ma as exemplified by the prominent Hawaiian–Emperor Bend. Both an abrupt Pacific Plate motion change and a change in mantle plume dynamics have been proposed to account for the Hawaiian–Emperor Bend, but debates surround the relative contribution of the two mechanisms. Here we build kinematic plate reconstructions and high-resolution global dynamic models to quantify the amount of Pacific Plate motion change. We find Izanagi Plate subduction, followed by demise of the Izanagi–Pacific Ridge and Izu–Bonin–Mariana subduction initiation alone, is incapable of causing a sudden change in plate motion, challenging the conventional hypothesis on the mechanisms of Pacific Plate motion change. Instead, Palaeocene slab pull from Kronotsky intraoceanic subduction in the northern Pacific exerts a northward pull on the Pacific Plate, while its Eocene demise leads to a sudden 30–35° change in plate motion, accounting for about half of the Hawaiian–Emperor Bend. We suggest the Pacific Plate motion change and hotspot drift due to plume dynamics could have contributed nearly equally to the formation of the Hawaiian–Emperor Bend. Such a scenario is consistent with available constraints from global plate circuits, palaeomagnetic data and geodynamic models.
... The oldest surface portion of the Hawaiian-Emperor chain, the Meiji Guyot (older than 81 Ma) and Detroit Seamount (76 to 81 Ma) (11) are about to subduct into the Kamchatka Trench (Fig. 1). But whether the older parts of the seamount chain, particularly the plume head, also subducted into the deep mantle or stayed on Earth's surface is debated (12)(13)(14). ...
Article
The Hawaiian-Emperor seamount chain that includes the Hawaiian volcanoes was created by the Hawaiian mantle plume. Although the mantle plume hypothesis predicts an oceanic plateau produced by massive decompression melting during the initiation stage of the Hawaiian hot spot, the fate of this plateau is unclear. We discovered a megameter-scale portion of thickened oceanic crust in the uppermost lower mantle west of the Sea of Okhotsk by stacking seismic waveforms of SS precursors. We propose that this thick crust represents a major part of the oceanic plateau that was created by the Hawaiian plume head ~100 million years ago and subducted 20 million to 30 million years ago. Our discovery provides temporal and spatial clues of the early history of the Hawaiian plume for future plate reconstructions.
... However, if one or more hot spots have moved over geologic time, then the problem requires additional constraints. To date, the only models that include hot spot motions have relied on mantle convection predictions of plume behavior (Steinberger & O'Connell, 1998) or some idealized representation of hot spot motion, based on such models (Steinberger & Gaina, 2007). Such flow models strongly depend on rheological parameters and the history of past plate motions, as well as assumptions about the mantle's heterogeneous density structure at past times. ...
... Moreover, the curvatures in the Caribbean-Colombian region might be related to the eastward indentation of the Caribbean Oceanic Plateau (Kerr & Tarney, 2005;Whattam & Stern, 2015). Although it is needed to be further studied, the oceanic plateau subduction with the Kula Plate might have generated the Aleutian Arc ( Figure 1; Steinberger & Gaina, 2007). Therefore, multiple slab rollback, jointly working with buckling and indentation, has proven to be an important geodynamic process for generating huge oroclines (Moresi et al., 2014). ...
Article
Oroclines are map‐view deformation of Earth's crust resulting from bending of quasi‐linear elements. The Central Asian Orogenic Belt (CAOB) is one of the largest and long‐lived accretionary orogens in the world and mainly consists of the Kazakhstan and Tuva–Mongolian oroclines. However, the mechanism of the oroclines is still in debate. Therefore, in this paper, we combine some investigation of high bathymetric relief resistance to subduction, review oroclinal bending models of the Kazakhstan Orocline, and propose a tentative model that involves asymmetric rollback in response to seamounts subduction and accretion, followed by bending associated with the convergence of the Siberian and Tarim cratons. Moreover, the role of pinning due to seamount and ridge subduction is probably more important than the convergence of continents in the CAOB. This model is compatible with the occurrence of seamounts, the spatial migration of intra‐oceanic arcs, and the development of multiple rollback processes during amalgamation of Eurasia. However, only geochemical and geochronological data will enable definition of the seamounts in CAOB so far, without much matching structural data. So we need more work to understand seamounts subduction and accretion as well as orocline bending in CAOB.
... Recent studies on global plate motion and reconstruction revealed a global-scale plate reorganization event at 105-100 Ma, which (1) influenced the relative motion at all of the major spreading systems where oceanic crust is preserved at present-day, (2) modified the pre-existing continental tectonic regimes along many of the major convergent margins, and (3) modified lithospheric stress patterns in continental regions far from convergent margins (Matthews et al., 2012;Müller et al., 2016). Interestingly for this paper, an abrupt change of the Pacific Plate (a part of the so-called Paleo-Pacific Plate) motion from westward to northwestward occurred at this time (Fig. 13), as well confirmed by a significant reorientation of the Pacific hotspot trails (Engebretson, 1985;Duncan and Clague, 1985;Koppers et al., 2001;Steinberger and Gaina, 2007;Wessel and Kroenke, 2008;Matthews et al., 2012;Müller et al., 2016). As a result, the motion of the northern Izanagi Plate (a part of the so-called Paleo-Pacific Plate), which was subducting beneath the Eurasian Plate, dramatically changed from roughly NW to more NNW at this time after it got a northward component form the Pacific Plate. ...
Article
Full-text available
Version 3.1 of the Generic Mapping Tools (GMT) has been released. More than 6000 scientists worldwide are currently using this free, public domain collection of UNIX tools that contains programs serving a variety of research functions. GMT allows users to manipulate (x,y) and (x,y,z) data, and generate PostScript illustrations, including simple x-y diagrams, contour maps, color images, and artificially illuminated, perspective, and/or shaded-relief plots using a variety of map projections (see Wessel and Smith [1991] and Wessel and Smith [1995], for details.). GMT has been installed under UNIX on most types of workstations and both IBM-compatible and Macintosh personal computers.
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Major improvements in Late Cretaceous-early Tertiary Pacific-Antarctica plate reconstructions, and new East-West Antarctica rotations, allow a more definitive test of the relative motion between hotspots using global plate circuit reconstructions with quantitative uncertainties. The hotspot reconstructions, using an updated Pacific-hotspot kinematic model, display significant misfits of observed and reconstructed hotspot tracks in the Pacific and Indian Oceans. The misfits imply motions of 5-80 mm/yr throughout the Cenozoic between the African-Indian hotspot group and the Hawaiian hotspot. Previously recognized misfits between reconstructed Pacific plate paleomagnetic poles and those of other plates might be accounted for within the age uncertainty of the paleomagnetic poles, and non-dipole field contributions. We conclude that the derived motion of the Hawaiian hotspot relative to the Indo-Atlantic hotspots between 61 Ma and present is a robust result. Thus, the Pacific hotspot reference frame cannot be considered as fixed relative to the deep mantle. The bend in the Hawaiian-Emperor Seamount chain at 43 Ma resulted from a speedup in the absolute motion of the Pacific plate in a westward direction during a period of southward migration of the hotspot. The relationship between the hotspot motion and plate motion at Hawaii suggests two possible scenarios: an entrainment of the volcanic sources in the asthenosphere beneath the rapidly moving plate while the hotspot source drifted in a plate-driven counterflow deeper within the mantle, or drift of the hotspot source which was independent of the plate motion, but responded to common forces, producing synchronous changes in hotspot and plate motion during the early Tertiary.
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Article
It is noted that different physicists and geologists have in recent years espoused not less than four groups of theories of the physical behavior of the Earth's interior. Recent observations of submarine geology, heat, and rock magnetism have tended to support some form of continental drift rather than the older concept of a rigid earth.The Hawaiian Islands are one of seven, parallel, linear chains of islands and seamounts in the Pacific Ocean of Tertiary to Recent age. Their nature had previously been explained in terms of a series of volcanoes along parallel faults. Horizontal shear motion along these faults was supposed to be extending them southeasterly.The inadequacies of this explanation are pointed out. If there are convection currents in the Pacific region and if the upper parts of these cells move faster than the central parts, sources of lava within the slower moving cores could give rise to linear chains of progressively older volcanic piles such as the Hawaiian Islands. This view is shown to be compatible with seismic observations and age determinations.
Article
The general aspects of the structural evolution of the Aleutian-Bering Sea region can be described in terms of plate tectonics. Involved in this model is the formation of the Aleutian Ridge in latest Cretaceous or earliest Tertiary time. The ridge is presumed to have formed in response to a southward relocation in the convergence zone of the Pacific oceanic plate, a shift away from the Beringian continental margin connecting Alaska and Siberia to an oceanic location at the Aleutian Trench. Prior to the formation of the ridge, Pacific crust is presumed to have directly underthrust the northeast-trending Koryak-Kamchatka coast. The middle and late Mesozoic eugeosynclinal or thalassogeosynclinal masses that underlie this segment of the Pacific fold belt are highly deformed, thrust faulted, and intruded by ultramafic bodies-characteristics that can be ascribed to the mechanical and magmatic consequence of plate underthrusting. This model implies a similar orogenic process for the formation of the stratigraphically and structurally similar Mesozoic rocks underlying the northeast-trending continental margin of southern Alaska. Less intense underthrusting may have occurred along the northwest-trending Pribilof segment of the Beringian margin connecting Alaska and Siberia. This margin may have been more parallel to the approximate direction of relative motion between the oceanic and continental plates. Nonetheless, fold belts, possibly intruded by ultramafic masses, formed along this segment of the Beringian continental margin in Late Cretaceous and perhaps earliest Tertiary time. The folds have since subsided below sea level-their eroded tops presently underlying as much as 3 km of virtually undeformed Cenozoic deposits. Our model relates pre- and postorogenic deposits underlying the Beringian margin and adjacent coast to the time of formation of the Aleutian Ridge, which marked the cessation of continental underthrusting and the beginning of island-arc underthrusting. Our model also implies that the ridge formed near or at its present location and that oceanic crust of late Mesozoic age underlies the Aleutian Basin of the Bering Sea. Since formation of the ridge this basin has received from 2 to 10 km of sedimentary fill. Although the model we suggest broadly explains the observed changes in tectonic style, magmatic history, and sedimentation for the Aleutian-Bering Sea region, it also implies that thousands of kilometers of oceanic crust underthrust the Kamchatka, Beringian, and Alaskan margins between Late Triassic and Late Cretaceous time, and hundreds of kilometers underthrust the Aleutian Ridge in Cenozoic time. The enormous masses of pelagic and volcanic offscrapings that would be indicative of extensive or long-term crustal underthrusting are not apparent as mappable units. Thus, while our model may be stylistically adequate, it paradoxically predicts quantities of rocks and structures that we are not able to find. Presumably they have been subducted.
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Radioisotopic dating of subaerial and submarine volcanic and plutonic rocks from the Aleutian Island Arc provides insight into the timing of arc formation in the middle Eocene. Twenty-eight 40Ar/39Ar ages constrain the duration of arc magmatism to the last 46 m.y. Basaltic lavas from the Finger Bay volcanics, the oldest exposed rocks in the arc, gave an isochron age of 37.4 � 0.6 Ma, which is 12–17 m.y. younger than a widely cited age of 55–50 Ma. Three main pulses of arc-wide magmatism occurred at 38–29, 16–11, and 6–0 Ma, which coincide with periods of intense magmatism in other western Pacific island arcs. Using the geochronology and volumetric estimates of crust generated and eroded over the last 46 m.y., we calculate a time-averaged magma production rate for the entire arc that exceeds previous estimates by almost an order of magnitude.
Article
Orogenesis in the Aleutian Bering Sea region would create an expansive new area of Pacific-rim mountain belts. The region itself formed about 55 Ma as a consequence of the suturing of a single exotic fragment of oceanic crust---Aleutia---to the Pacific's Alaskan-Siberian margin. A massive overlap assemblage of the igneous crust of the Aleutian Arc and the thick sedimentary masses of the Aleutian Basin have since accumulated above the captured basement terrane of Aleutia. Future closure of the Aleutian Bering Sea region, either northward toward the continent or southward toward the Aleutian Arc, would structurally mold new continental crust to the North American plate. The resulting ``Beringian orogen'' would be constructed of a collage of suspect terranes. Although some terranes would include exotic crustal rocks formed as far as 5000 km away, most terranes would be kindred or cotetonic blocks composed of the overlap assemblage and of relatively local (100 1000 km) derivation. The Aleutian Bering Sea perspective bolsters the common supposition that, although disrupted and smeared by transcurrent faulting, examples of kindred assemblages should exist, and perhaps commonly, in ocean-rim mountain belts.
Article
Geophysical and regional geologic data provide evidence that parts of the oceanic crust in the abyssal basins of the Bering Sea have been created or altered by crustal extension and back-arc spreading. These processes have occurred during and since early Eocene time when the Aleutian Ridge developed and isolated oceanic crust within parts of the Bering Sea. The crust in the Aleutian Basin, previously noted as presumably Early Cretaceous in age (M1–M13 anomalies), is still uncertain. Some crust may be younger. Vitus arch, a buried 100- to 200-km-wide extensionally deformed zone with linear basement structures and geophysical anomalies, crosses the entire west central Aleutian Basin. We suggest that the arch and the inferred fracture zones in the Aleutian Basin are early Cenozoic structures related to the early entrapment history of the Bering Sea. These structures lie on trend with known early Cenozoic structures near the Bowers-Shirshov-Aleutian ridge junction and on the Beringian continental margin (with possible continuation into Alaska); the structures may have coeval and cogenetic(?) histories for early Cenozoic and possibly younger times. Cenozoic deformation within parts of the Bering Sea region is principally extensional, although the total amount of extension is not known. As examples, the Komandorsky basin formed by back-arc seafloor spreading, the Aleutian Ridge has been extensively sheared, and extensional block faulting is common. Sedimentary basins of the Bering shelf have formed by extension associated with wrench faulting. The Cenozoic deformation throughout the Bering Sea region probably results from the interaction of major lithospheric plates and associated regional strike-slip faults. We present models for the Bering Sea over the past 55 m.y. that show oceanic plate entrapment, back-arc faulting and spreading along Vitus arch, breakup of the oceanic crust in the Aleutian Basin at fracture zones, and back-arc spreading in Bowers Basin.