Download Circum-Arctic mantle structure and long

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Supplementary Material for
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Circum-Arctic mantle structure and long-wavelength topography since the
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Jurassic
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Shephard, G. E., Flament, N., Williams, S., Seton, M., Gurnis, M., and Müller, R.D.
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Supplementary Methods
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Absolute reference frames and Net Lithospheric Rotation (NLR)
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The hybrid absolute plate reference frame of Seton et al. (2012) (case C2) is
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based on a moving Indian/Atlantic hotspot model (O’Neill et al., 2005) for times
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younger than 100 Ma and on a True Polar Wander (TPW)-corrected
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palaeomagnetic model (Steinberger and Torsvik, 2008) for older times (Table 2).
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The use of the hybrid absolute plate motion of O’Neill et al. (2005) and
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Steinberger and Torsvik (2008) implies NLR in excess of 0.4°/Myr between ~40-
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60, 65-80, 110-115 and 180-215 Ma (Figure S13). NLR is large at present-day in
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a Pacific hotspot reference frame (~ 0.44°/Myr HS3, Conrad and Behn, 2010)
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and geologically recent NLR (since ~ 50 Ma) has an overall westward direction
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with
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~0.11+_0.03°/Myr) depending on reconstructions (e.g. Ricard et al., 1991;
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Becker, 2006; Torsvik et al., 2010). While a component of NLR throughout time
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may be real, increasing uncertainty of the plate reconstruction back in time may
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result in unrealistically large NLR, especially concerning the velocities of the
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large plates comprising Panthalassa. Our plate models are constructed with
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continuously closing plates (Gurnis et al., 2012), which allow us to define global
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surface velocity fields through time and to calculate the NLR implied by a given
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reference frame as in Torsvik et al. (2010) and Alisic et al. (2012).
estimated
rates
previously
ranging
between
1.5-9 cm/year
(or
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We used three approaches to minimize NLR from the absolute reference frame in
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our geodynamic model cases (Tables 2 and S3); (i) computing and removing the
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NLR from the plate reconstruction (case C3), (ii) including a low-viscosity
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asthenosphere to decouple the lithosphere from the sub-asthenospheric mantle
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(cases C2 and C8) and (iii) changing the absolute reference frame by using the
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finite rotations from the moving hotspot reference frame of Torsvik et al. (2008)
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rather than that of O’Neill et al. (2005) for ages younger than 70 Ma (models C1,
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C4, C5 as well as C6-C8). We also change the absolute motion of the Pacific
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during the Cenozoic by changing the poles of rotation between east and west
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Antarctica (from Cande et al. [2000] to Granot et al. [2013]). The resultant NLR
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for this latter absolute plate motion model (C1, C4-C8) is < 0.4°/Myr for all times,
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although it is slightly more elevated for the last 20 Ma (~ 0.18°/Myr) than the
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previous reference frame (O’Neill et al., 2005; Steinberger and Torsvik, 2008:
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~0.12°/Myr; C2, Table 2, Fig. S13).
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In addition to differences in the absolute reference frame we explored different
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mantle parameters including viscosity profile, initial slab depth, slab dip and
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basal layer density (Figs. S3, S4, S6-8, S10-15, Table S3). We find that changes in
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dynamic topography are small and do not affect our main conclusions. Rates of
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dynamic topography for alternative cases C3-C5 are usually in the order of ±5
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m/Myr from those of C1 (Table S1, S2), and are compatible with the geological
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constraints presented in the main text (see Figs. 7e-h). Notably, under Eurasia,
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alternative cases C3-C5 (Figs. S10) predict a similar two-slab configuration
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(Mongol-Okhotsk slab to the west and north-eastern Panthalassa slab to the
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east) to those of C1 but with locations offset by ± 5° longitude (10° to the east for
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slab (m) in C5, though the use of a depth-dependent viscosity was not ideal, see
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below). Case C4, illustrates that increasing the slab dip does not significantly
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change the results.
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In addition to C1-C5 and in the interests of illustrating the main suite of
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parameters tested (see also Flament et al., 2014) we present an extended set of
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eight cases (C1-C8) in Figs. S14 and S15. These figures illustrate our
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investigation of the effect of rheological parameters on lower mantle structure
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and our selection of a set of parameters for C1 by visual comparison between
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predicted mantle temperature and seismic tomography along arbitrary cross-
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sections. For example, C6 and C8 both include a linear increase in viscosity for
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the lower mantle; looking under Eurasia (Fig. S15) in case C6, which has a higher
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density basal layer, the predicted volume of slabs is systematically too small,
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whereas in case C8, which has a lower density basal layer and asthenosphere,
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slabs are significantly offset compared to seismic tomography. C7, which also has
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a lower basal density over-predicts the amount of slab material and has
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dominant upwellings. Under North America (50°N, Figure S14) the alternative
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cases are similar to each other and to seismic tomography (no qualitatively “best”
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case, though C8 seems to under-predict slab volumes at this location). We
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therefore opted for a dense basal layer and a layered viscosity structure, with no
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depth-dependent viscosity in the lower mantle for reference case C1. Note that
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the influence of alternative parameters on the pattern of dynamic topography
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(right panels of Figs. S14 and S15) is small; our main conclusions are largely
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unaffected by parameter selection.
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Supplementary References
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Alisic, L., Gurnis, M., Stadler, G., Burstedde, C., and Ghattas, O., 2012, Multi-scale
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dynamics and rheology of mantle flow with plates. Journal of Geophysical
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Research, v.117 doi:10.29/2012JB009234
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Ballance, P.F., 1993, in South Pacific Sedimentary Basins v.2 of Sedimentary
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Basins of the Word P.F., Balance (Ed) Elsevier Amsterdam p.93-110.
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Becker, T.W., 2006, On the effect of temperature and strain-rate dependent
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viscosity on global mantle flow, net rotation, and plate-driving forces.
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Geophysical Journal International v.167 p.943-957.
90
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Cande, S.C., Stock J.M., Müller, R.D. and Ishihara, T., 2000, Cenozoic motion
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between East and West Antarctica, Nature v.404 p.145-150.
93
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Conrad, C.P. and Behn, M.D., 2010, Constraints on lithosphere net rotation and
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asthenospheric viscosity from global mantle flow models and seismic anisotropy.
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Geochemistry, Geophysics and Geosystems v.11 doi:10.1029/2009GC002970
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Granot, R., Cande, S.C., Stock, J.M., and Damaske, D., 2013, Revised Eocene-
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Oligocene kinematics for the West Antarctic rift system. Geophysical Research
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Letters v.40 p.279-284.
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Gurnis, M., Turner, M., Zahirovic, S., DiCaprio, L., Spasojevic, S., Müller, R., Boyden,
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J., Seton, M., Manea, V., and Bower, D., 2012, Plate Tectonic Reconstructions with
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Continuously Closing Plates. Computers and Geosciences, v. 38 p. 35-42.
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Flament, N., Gurnis, M., Williams, S., Seton, M., Skogseid, J., Heine, C and Müller,
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R.D. 2014. Topographic asymmetry of the South Atlantic from global models of
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mantle flow and lithospheric stretching. Earth and Planetary Science Letters v.
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387, p. 107-119.
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O'Neill, C., Müller, R.D., and Steinberger, B., 2005, On the Uncertainties in Hotspot
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Reconstructions, and the Significance of Moving Hotspot Reference Frames:
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Geochemistry, Geophysics, Geosystems, v. 6 doi:10.1029/2004GC000784.
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Ricard, Y., Doglioni, C., and Sabadini, R., 1991, Differential rotation between
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lithosphere and mantle. A consequence of lateral mantle viscosity variations.
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Journal of Geophysical Research v.96 p.8407-8415.
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Seton, M., Müller, R.D., Zahirovic, S., Gaina, C., Torsvik, T.H., Shephard, G., Talsma,
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A., Gurnis, M., Turner, M., Maus, S., and Chandler, M., 2012 Global continental and
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ocean basin reconstructions since 200 Ma. Earth-Science Reviews v.113 p.212-
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270 doi:10.1016/j.earscirev.2012.03.002
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Steinberger, B., and Torsvik, T., 2008. Absolute plate motions and true polar
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wander in the absence of hotspot tracks. Nature v.452 p.620–624.
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doi:10.1038/nature06842.
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Sutherland, R., 1995, The Australia-Pacific boundary and Cenozoic plate motions
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in the SW Pacific: Some constraints from Geosat data. Tectonics v.14 p.819-831.
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Torsvik, T., Steinberger, B., Gurnis, M., and Gaina, C., 2010. Plate tectonics and net
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lithosphere rotation over the past 150 My. Earth and Planetary Science Letters
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v.291 p.106-112.
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Supplementary Figures
Supplementary Figure Captions
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Figure S1. 180-30 Ma evolution of the plate reconstruction (Shephard et al.,
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2013 with a modified reference frame, Table 2) assimilated in the mantle flow
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models. The absolute reference frame used here is that of case C1. Reconstructed
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plate boundaries (black lines with teeth located on overriding plate), coastlines
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(dark grey lines), continental lithosphere (grey polygons) and ages of oceanic
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lithosphere (see colour scale) are shown, as well as velocities (black arrows).
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Major plates and oceans labeled as AM Amerasia Basin, AFR Africa, CCR Cache
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Creek oceanic plate, EUR Eurasia, GRN Greenland, FAR Farallon, IZA Izanagi,
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MOK Mongol-Okhostk, NAM North America, SAO South Anuyi Oceans.
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Orthographic projection centered on 30°W. Additional reconstruction ages are
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shown in Fig. 2.
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Figure S2. Top panels, maps of predicted time-dependent temperature field
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from case C1 at 1000 km depth. Bottom panels, maps of predicted present-day
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temperature field for case C1 at different depths from 500 km to the near the
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core-mantle boundary (CMB ~2900 km). Slabs labeled as in text and Figs. 3-5.
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Present-day coastlines superimposed in black for reference. Cold material (T <
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0.45) is inferred to represent subducted lithosphere whereas hot material
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represents upwelling from the thermal boundary layer along the CMB.
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Figure S3. Predicted present-day mantle temperature field for cases C3-C5 at
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different depths from 500 km to near the core-mantle boundary. Present-day
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coastlines superimposed in black for reference. Cold material (T < 0.45) is
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inferred to represent subducted lithosphere whereas hot material represents
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upwelling from the thermal boundary layer along the CMB. Slabs labeled as in
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text and Figs. 3-5 and S6-S8, S10.
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Figure S4. Predicted time-dependent mantle temperature for cases C3-C5 at
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1000 km depth. Present-day coastlines superimposed in black for reference. Cold
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material (T < 0.45) is inferred to represent subducted lithosphere whereas hot
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material represents upwelling from the thermal boundary layer along the CMB.
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Figure S5. Predicted time-dependent mantle temperature for cases C1 and C2
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(Table 2) and comparison to seismic tomography for the present-day. As in
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Figure 3 but for a cross-section at 50°N latitude across NAM (130-30°W).
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Inferred slabs from this vertical cross-section result from subduction along the
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north-eastern margin of Panthalassa (a, c, d) and along the intra-oceanic
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subduction zone of the Wrangellia Superterrane (b).
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Figure S6. Predicted evolution of mantle temperature for cases C3, C4 and C5
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(Table S3) and comparison to seismic tomography for the present-day. Top
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panels, orthographic projection of cross-section at 50°N latitude across NAM
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(130-30°W) superimposed on location of subduction zones and predicted
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present-day temperature at ~1500 km depth. Inferred slabs from this vertical
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cross-section correspond largely to subduction along the north-eastern margin
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of Panthalassa and along the intra-oceanic subduction zone of the Wrangellia
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Superterrane. Panels in green box show seismic velocity anomalies for three
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tomography models with 0.45 mantle temperature contours overlain for cases
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C3 (green), C4 (black) and C5 (purple).
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Figure S7. Predicted time-dependent mantle temperature for cases C3, C4 and
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C5 (Table S3) and comparison to seismic tomography for the present-day. As in
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Figure S6 but for a cross-section at 30°N latitude across NAM.
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Figure S8. Predicted time-dependent mantle temperature for cases C3, C4 and
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C5 (Table S3) and comparison to seismic tomography for the present-day. As in
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Figure S6 but for a cross-section at 40°W latitude under Greenland (40-90°N). At
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150 Ma, two subducting slabs are captured in case C3, 75°N and 85°N, and a
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single slab at 75°N is clearly imaged in cases C4 and C5 with a second smeared
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slab under 85°N. The difference in location and dip of subducting slabs at this
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fixed vertical cross-section is a function of absolute reference frames used (Table
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S3).
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Figure S9. Predicted evolution of mantle temperature for cases C1 and C2 (Table
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S3) and comparison to seismic tomography for the present-day. As in Figure 3
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but for a cross-section at 60°N longitude under Siberia (90-180°E). Inferred slabs
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within this cross-section correspond largely to subduction of the Izanagi Plate
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along the north-western margin of Panthalassa (p).
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Figure S10. Predicted time-dependent mantle temperature since initial
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conditions for cases C3, C4 and C5 (Table S3) and comparison to seismic
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tomography for the present-day. As in Figure S6 but for a cross-section at 60°N
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latitude under northern Eurasia (0-100°E). Inferred slabs within this cross-
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section largely result from subduction along the northern margin of the Mongol-
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Okhotsk Ocean (m) and along the northwestern margin of Panthalassa (p). Note
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that case C3 has an initial slab depth to 1750 km (Table S3) as opposed to the
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alternative cases, which are to 1210 km.
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Figure S11. Air-loaded surface dynamic topography for cases C3-C5 between
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170-0 Ma, as in Figure 6. Stars indicate location of selected reconstructed Arctic
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points as in Fig. 1. Orthographic projection centered on 30°W.
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Figure S12. Predicted evolution of dynamic topography for cases C3-C5 at
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selected circum-Arctic locations grouped into four geographic regions between
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170-0 Ma (based on the plate reconstruction). The colours of the plotted lines
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match the colours of the stars in Fig.1, and solid for C3, thick for C4 and dashed
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for C5. Note the broad subsidence predicted for most locations from 170 Ma to
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between ~70-50 Ma followed by slowed subsidence or uplift to present day.
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Values are detailed further in Table S2. Air-loaded results shown for all locations
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except for Lomonosov Ridge and Barents Sea which are water-loaded.
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Figure S13. Evolution of Net Lithospheric Rotation (NLR) for the five main
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reconstructions used herein (Table 2, S3), and present-day NLR calculated from
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reference frame HS3, based on Pacific hotspots (0.44°/Myr). NLR evolution was
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computed in 1 Myr increments, which is the interval at which boundary
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conditions are defined for the geodynamic models. Conrad and Behn (2010)
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proposed that 60% of HS3 (0.26°/Myr) is the geodynamically reasonable limit
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for NLR. Larger NLR from the reconstructions likely reflects the motion of large,
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fast-moving plates of Panthalassa, for which the reconstruction uncertainty is
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large before 83.5 Ma. NLR computed using the same relative plate motions as in
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Seton et al. (2012) and the absolute reference frame of Doubrovine et al. (2012)
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is shown for reference in green. The peak amplitudes at ~80 Ma for DBV is larger
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than in Fig. 9 of Doubrovine et al. (2012) that showed NLR computed in 10 Myr
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incrmenets. Other small differences may also arise due to different Pacific plate
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boundaries and the use of a Pacific plate circuit via Antarctica (Seton et al., 2012;
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Shephard et a;., 2013) rather than via the Lord Howe Rise (Doubrovine et al.,
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2012).
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Figure S14. Left panels, predicted present-day mantle temperature for cases C1-
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C8 (Tables 2, S3) and comparison to seismic tomography, middle panels. Details
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are as in Figs. 3 and S5, this location is at 50°N latitude across NAM (130-30°W).
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Right panels show the evolution of dynamic topography for the North American
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region illustrating the similarity between models despite variation in the
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predicted lower mantle structure.
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Figure S15. As in Figure S14. Left panels, predicted present-day mantle
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temperature for cases C1-C8 (Tables 2, S3) and comparison to seismic
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tomography for the present-day, middle panels. This location is at 60°N latitude
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across Eurasia (0-100°E). Right panels show the evolution of dynamic
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topography for the Barents Sea region illustrating the similarity between models
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despite variation in the predicted lower mantle structure.
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Table S1: Evolution of air-loaded dynamic topography (*except for Barents Sea and Lomonosov Ridge which are water-loaded) and its
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rate of change at selected circum-Arctic locations through time for our preferred case C1. The time intervals between ~170, ~100, ~50
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and 0 Ma were chosen to capture the main changes in dynamic topography trends and are to be used as a guide in conjunction with
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Figure 7. Note that shorter wavelength subsidence or uplift or changes in rates may occur within these intervals (see main text and Fig.
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7)..
Absolute (m, top
Barents Sea and adjacent region
panels) and
Fennoscandia
Barents Sea*
Svalbard
Franz Josef Land
change in
dynamic
topography
(m/Myr, bottom
panels,
coloured/italic)
~170 Ma
329.6
10.2
223.9
-57.6
~100 Ma
~50 Ma
0 Ma
33.0
-482.7
-285.9
-463.6
-213.4
-640.1
-522.9
-608.7
-465.2
-501.8
-159.8
Rate 170-100 Ma -4.3
-350.3
-7.1
-7.4
-4.6
-5.9
-2.8
-3.1
5.9
1.2
2.2
South Greenland
East Greenland
West Greenland
Rate 100-50 Ma -4.7
Rate 50-0 Ma 1.1
Greenland
North Greenland
~170 Ma
~100 Ma
354.2
667.0
475.1
633.4
-113.7
329.6
181.8
164.9
-537.3
-223.6
-245.9
-417.3
-696.7
-543.6
-476.7
-660.2
~50 Ma
0 Ma
Rate 172-100 Ma
Rate 100-50 Ma
-6.8
-4.9
-4.3
-6.8
-8.1
-10.6
-8.2
-11.2
Rate 50-0 Ma
-3.3
Siberia
-6.5
-4.7
-5.0
Siberian Traps
East Siberia
Lomonosov Ridge*
Taimyr Peninsula
~170 Ma
-660.7
-850.0
-247.8
-530.9
-808.9
-620.6
~100 Ma
-491.8
~50 Ma
0 Ma
-903.6
-565.3
-946.0
-1071.7
-690.2
-454.6
-823.3
-1085.4
-608.6
Rate 170-100 Ma
2.4
Rate 100-50 Ma
Rate 50-0 Ma
~100 Ma
-1.3
-5.2
-1.3
-0.3
1.7
Banks Island
Ellesmere Island
-0.8
-1.4
-0.8
2.3
2.5
North America and Canadian Arctic Islands
Slave Craton
~170 Ma
-8.1
North Slope
2.6
-262.0
-27.6
123.9
-1095.2
-884.1
-801.4
-428.7
~50 Ma
-733.6
0 Ma
-677.9
-441.4
-804.6
-601.1
-728.9
-677.2
-815.6
Rate 170-100 Ma
-15.9
-9.0
-11.2
-8.0
Rate 100-50 Ma
7.0
4.0
-0.1
-5.8
Rate 50-0 Ma
6.0
1.6
2.6
-1.8
267
268
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Table S2: Evolution of air-loaded dynamic topography (* except for Barents Sea and Lomonosov Ridge which are water-loaded) and its
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rate of change at selected circum-Arctic locations through time for three alternative cases, separated by commas in order of C3, C4, C5.
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The time intervals between ~170, ~100, ~50 and 0 Ma were chosen to capture the main changes in dynamic topography trends and are
272
to be used as a guide in conjunction with Figure S12. Note that shorter wavelength subsidence or uplift or changes in rates may occur
273
within these intervals (see main text and Figs. 7 and S11, S12).
Absolute (m, top
Barents Sea and adjacent region
panels) and
Fennoscandia
Barents Sea*
Svalbard
Franz Josef Land
change in
dynamic
topography
(m/Myr, bottom
panels,
coloured/italic)
~170 Ma
156.5, 363.1, 251.7
-33.4, -158.0, 26.7
223.3, 274.6, 162.0
-5.6, 53.9, -28.7
~100 Ma
57.1, 115.6, 110.0
-506.5, -368.2, -336.7
-216.0, -210.9, -206.9
-490.0, -391.1, -407.6
~50 Ma
-233.4, -144.8, -263.4
-994.8, -598.0, -868.4
-695.2, -482.7, -658.0
-875.9, -590.3, -796.7
0 Ma
-371.3, -139.0, -598.9
-968.6, -382.3, -1016.9
-733.3, -540.3, -883.1
-817.5, -548.8, -868.0
Rate 170-100 Ma -1.4, -3.5, -2.0
-6.8, -1.2, -5.3
-6.3, -6.9, -5.3
-7.1, -6.3, -5.4
Rate 100-50 Ma -5.8, -5.3, -7.5
-9.7, -4.7, -9.0
-9.6, -5.5, -9.0
-7.7, -4.1, -7.8
0.5, 4.2, -3.0*
-0.8*, -1.1*, -4.5
1.2, 0.8, -1.4*
*uplift from 15Ma
*uplift from 9 and 3
*uplift from 15Ma
Rate 50-0 Ma -2.8, 0.1, -6.7
Ma respectively
Greenland
North Greenland
South Greenland
East Greenland
West Greenland
~170 Ma
298.8, 378.7, 252.4
534.0, 620.9, -463.5
316.2, 476.9, 347.2
540.3, 589.7, 422.9
~100 Ma
-21.2, -42.5, -45.6
418.8, 358.7, 333.3
226.0, 244.6, 224.1
303.4, 200.2, 180.4
~50 Ma
-613.6, -451.0, -605.1
-71.5, -151.9, -274.7
-197.2, -167.7, -311.7
-292.9, -354.1, -489.3
0 Ma
-847.4, -804.8, -957.7
-513.7, -584.4, -791.2
-572.0, -448.9, -770.0
-690.9, -730.5, -902.8
Rate 172-100 Ma
-4.6, -6.0, -4.3
-1.6, -3.7, -1.9
-1.2, -3.3, -1.8
-3.4, -5.6, -3.5
Rate 100-50 Ma
-11.8, -8.3, -11.2
-9.8, -10.4, -12.2
-8.5, -8.4, -10.7
-11.9, -11.3, -13.4
Rate 50-0 Ma
-4.7, -6.9, -7.1
-8.8, -8.4, -10.3
-7.5, -5.5, -9.2
-8.0, -7.3, -8.3
Siberian Traps
East Siberia
Lomonosov Ridge*
Taimyr Peninsula
~170 Ma
-714.4, -471.4, -588.0
-810.8, -653.9, -748.1
-93.1, -60.8, -158.3
-451.2, -300.7, -371.5
~100 Ma
-771.9, -456.3, -568.9
-1099.5, -875.7, -1024.2
-923.2, -707.9, -754.7
-825.0, -546.4, -656.2
Siberia
~50 Ma
-835.8, -487.7, -549.6
-1086.6, -915.9, -1024.3
-1451.8, -1057, -1356.3
-1012.0, -707.4, -933.3
0 Ma
-645.7, -363.8, -588.0
-796.6, -773.7, -821.9
-1348.2, -1230.3 -
-806.6, -573.4, -759.3
1435.0
Rate 170-100 Ma -0.8, 0.2, 0.3
Rate 100-50 Ma -1.3, -0.6, 0.4
Rate 50-0 Ma 3.8, 2.4, -0.8
-4.1, -3.2, -3.9
-11.9,-9.2, -8.5
-5.3, -3.5, -4.1
0.3, 0.8, 0.0
-10.6, -7.1, -12.0
-3.7, -3.2, -5.5
5.8, 2.8, 4.0
2.1, -3.3, -1.6*
4.1, 2.6, 3.5
*uplift from 30 Ma
North America and Canadian Arctic Islands
Slave Craton
North Slope
Banks Island
Ellesmere Island
~170 Ma
221.8, -41.2, -177.1
37.4, -191.5, -278.0
219.1, -6.8, -96.0
210.7, 184.1, 82.0
~100 Ma
-896.0, -1097.2, -
-930.3, -885.3, -906.7
-624.1, -749.9, -712.4
-339.3, -352.2, -348.6
1160.4
~50 Ma
-901.7, -836.8, -998.0
-841.0, -768.0, -857.7
-988.1, -879.7, -1044.8
-873.1, -697.1, -874.8
0 Ma
-452.5, -561.2, -606.8
-613.4, -660.0, -817.0
-730.0, -795.2, -850.0
-911.4, -938.0, -1013.1
Rate 170-100 Ma
-16.0, -15.1, -14.0
-12.8, -9.9, -9.0
-12.0, -10.6, -8.8
-7.9, -7.7, -6.2
Rate 100-50 Ma
-0.1, 5.3, 3.2
1.8, 2.4, 1.0
-7.3, -2.6, -6.6
-10.7, -7.0, -10.5
Rate 50-0 Ma
9.0, 5.4, 7.8
4.6, 2.1, 0.8
5.2, 1.7, 3.9
-0.8*, -4.7, -2.8*
*uplift from 9 and
10Ma respectively.
274
275
276
277
Table S3: Acronyms and alternative model details referred to in this study.
Name/Acronym
Base plate
Absolute reference frame (prior
Net Lithospheric rotation
Viscosity profile*
reconstruction
to NLR correction)
(NLR) correction
Initial slab depth
Slab dip
Basal layer density
C3
Shephard et al. (2013)
Moving hotspots 0-100 Ma
Removed from plate
1,1,1,100
(O’Neill et al., 2005)
reconstruction. Minimal NLR
TPW-corrected palaeomagnetic
remaining (<0.1°/Myr, Fig.
100-200 Ma (Steinberger and
S13).
1750 km
45° (<660 km) then 90°
Torsvik, 2008)
+3.6%
C4
Shephard et al. (2013)
Moving hotspots 0-70 Ma
Minimized from plate
1,1,1,100
(Torsvik et al., 2008)
reconstruction (NLR
TPW-corrected palaeomagnetic
<0.4°/Myr, Fig. S13) and by
105-200 Ma (Steinberger and
using new poles of rotation
Torsvik, 2008; interpolation
for E-W Antarctica (Granot et 58° (<425 km) then 90°
between 70-105 Ma)
al., 2013) $
1210 km
+3.6%
C5
Shephard et al. (2013)
Moving hotspots 0-70 Ma
Minimized from plate
1,1,1,10  100
C6
C7
Shephard et al. (2013)
Shephard et al. (2013)
(Torsvik et al., 2008) and TPW-
reconstruction (NLR
1210km
corrected palaeomagnetic 105-
<0.4°/Myr, Fig. S13) and by
200 Ma (Steinberger and Torsvik,
using new poles of rotation
2008) (interpolation between 70-
for E-W Antarctica (Granot et
105 Ma)
al., 2013)$
+1.7%
Moving hotspots 0-70 Ma
Minimized from plate
1,1,1, 10  100
(Torsvik et al., 2008)
reconstruction (NLR
1210km
TPW-corrected palaeomagnetic
<0.4°/Myr, Fig. S13) and by
45°
105-200 Ma (Steinberger and
using new poles of rotation
+3.6%
Torsvik, 2008; interpolation
for E-W Antarctica (Granot et
between 70-105 Ma)
al., 2013) $
Moving hotspots 0-70 Ma
Minimized from plate
1,1,1,100
(Torsvik et al., 2008)
reconstruction (NLR
1210km
TPW-corrected palaeomagnetic
<0.4°/Myr, Fig. S13) and by
45°
45°
C8
Shephard et al. (2013)
105-200 Ma (Steinberger and
using new poles of rotation
+1.7%
Torsvik, 2008; interpolation
for E-W Antarctica (Granot et
between 70-105 Ma)
al., 2013) $
Moving hotspots 0-70 Ma
Minimized from plate
1,0.1,1, 10  100
(Torsvik et al., 2008) and TPW-
reconstruction (NLR
1210km
corrected palaeomagnetic 105-
<0.4°/Myr, Fig. S13) and by
45°
200 Ma (Steinberger and Torsvik,
using new poles of rotation
+1.7%
2008) (interpolation between 70-
for E-W Antarctica (Granot et
105 Ma)
al., 2013).$ Minimized in the
lower mantle by the lowviscosity asthenosphere in
the dynamic model.
278
$
Granot et al. (2013) describes motion in the West Antarctic Rift System from Chron 18o (40.13 Ma) until around Chron 8o (26.5 Ma,
279
Cande et al., 2000; Granot et al., 2013). A plate boundary likely existed between East and West Antarctic earlier in the Cenozoic, though
280
the timing of extension is poorly constrained (Cande et al., 2000; Cande and Stock, 2004). For times earlier than Chron 18o we model
281
extension within the West Antarctic Rift System using the C18o pole of rotation from Granot et al. (2013) but with a larger angle to
282
minimize the amount of deformation implied in New Zealand, which is considered to be tectonically quiescent during this period
283
(Ballance, 1993; Sutherland, 1995).
284
285
* Factor applied to reference viscosity (1021 Pa s) for mantle above 160 km (lithosphere), between 160 and 310 km (asthenosphere),
286
between 310 and 410 km (upper mantle) and below 670 km (lower mantle). The “” symbol indicates that the viscosity linearly
287
increases with depth between the two listed values.