Supporting Information for
Tectonic interaction between India and Arabia since the Jurassic reconstructed
from marine geophysics, ophiolite geology, and seismic tomography
Carmen Gaina 1, Douwe J.J. van Hinsbergen 2, and Wim Spakman 1,2
1 Centre
for Earth Evolution and Dynamics - CEED, University of Oslo, Sem Sælands vei 24, NO-0316 Oslo,
Norway
2 Department
of Earth Sciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, The Netherlands
* Corresponding author, ph:+ 47 2285 6042, fax: 47 2285 5101, email: carmen.gaina@geo.uio.no
Contents of this file
A. Description of kinematic reconstructions and associated files
B. Supplementary information regarding the tomography models, Figures S1 and S2, and Movies
S1 and S2
A.
I. Kinematic Reconstructions
We include in the Supplementary Material digital files (rotation (.rot) and GIS shape files (.gpml))
that can be used to reproduce kinematic reconstructions described in section 4. The .gpml files
define the line features and polygons of the reconstruction, and the .rot file defines the rotation
parameters through time. It is possible to build deforming topologies by using the topology tool and
combining independently moving line features, but for clarity, we have refrained from doing so in
this reconstruction.
These files can be uploaded in the freeware program GPlates (http://www.gplates.org). The .rot file
describes the finite rotations of tectonic blocks identified and used in this paper. The names in
the .rot file corresponds to the names of features in the .gpml file.
Note that we have a new model for the reconstruction of Afghanistan-Pakistan and eastern Oman
and this has been merged with other published reconstructions as follows:
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1. India-Asia plate circuit, with updates in this paper (Table 1), modified from: van Hinsbergen
et al (2011a)
2. Tibet, central Asia, and Indochina: van Hinsbergen et al. (2011b),
3. Arabia-Asia collision and reconstruction of Iran: McQuarrie and van Hinsbergen (2013)
4. Greater India Basin reconstruction: van Hinsbergen, et al., (2012)
There are five different .rot files given with this reconstruction. These all give the same relative
motions of features within the India-Asia collision zone, but are in different absolute reference
frames:
A. Siberia-fixed frame (India-Asia_Sibfixed-frame.rot);
B. paleomagnetic reference frame (India-Asia_pmag-frame.rot), which corresponds to the
Global Apparent Polar Wander Path (GAPWaP) of Torsvik et al. (2012). Please note: this
frame places the continents relative to the spin axis, but is NOT corrected for true polar
wander. Do NOT use this frame to reconstruct India-Asia motion relative to the mantle!
C. the hybrid mantle reference frame (India-Asia_hybrid-frame.rot), which consists of the
Indo-Atlantic moving hotspot frame of Torsvik et al. (2008) for times younger than 100 Ma,
and the true-polar wander corrected paleomagnetic reference frame of Steinberger and
Torsvik (2008) for times older than 100 Ma.
D. the slab-fitted mantle reference frame of van der Meer et al. (2010), which corresponds to
the True Polar Wander-corrected paleomagnetic reference frame of Steinberger and Torsvik
(2010) adjusted in longitude to optimize the connection of subduction zones in plate
reconstructions to corresponding slabs in seismic tomographic images of the lower mantle
(India-Asia_slab-frame.rot).
E. the Global Moving Hotspot Reference Frame of Doubrovine et al. (2012). This reference
frame goes back to 124 Ma, and is a global moving hotspot frame back to the late
Cretaceous, and an Indo-Atlantic frame before that.
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To view these files in GPlates, take the following steps: (a) Download the attached files; (b) Open
GPlates; (c) Go to File>Manage Feature collections; (d) In the Manage
Feature collections screen, click 'open file' and open the .gpml and one of the .rot files; (e) In the top
left of the screen one can type the age one wishes to view (this
reconstruction goes from 65 Ma to 0 Ma, with the notion that pre-50 Ma deformation of Tibet is not
reconstructed. The 65-50 Ma interval is included to illustrate the size of Greater India, under the
assumption of a 50 Ma Greater India-Asia collision) and one can move back and forth in time (1
Ma steps) with the arrows next to the ‘Time’ bar. One can also press 'play' and see the entire movie
of the reconstruction; (f) if one clicks on the green Africa-with-black-arrow logo on the left hand
side of the screen, one can select every item on the screen. On the top right hand side one will see
the name and the code of the item one selected. The rotation parameters of every file are described
in the .rot files that are included. For further instructions on how to modify the reconstruction or add
to it, we refer the reader to the manual that comes with the program.
Columns in the rotation files
2.1 Column 1: Plate ID of the feature, as defined in India-Asia.gpml
2.2 Column 2: Begin/End age
2.3 Column 3: latitude of the Euler pole
2.4 Column 4: longitude of the Euler pole
2.5 Column 5: angle of rotation around the Euler pole, until the ages as defined in column 1, since the age defined in
column 1 of the previous line
2.6 Column 6: name of the feature
Reference frames are defined at the bottom of the file, where rotation of ‘401’ (i.e. Siberia) is defined relative to 000
(i.e. the mantle).
B.
II. Seismic tomography
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The tomography images presented in this study (main manuscript - Fig 11, Supplementary files S1
and S2 and Movies 1, 2) are from model P06 of Amaru (2007). Model P06 has invariably been used
in scientific publications under the name UU-P07 (e.g. van der Meer et al. 2010, 2012, van
Benthem et al. 2013), which we will also use here. Model UU-P07 is created with the same
tomographic technique as that of Bijwaard et al. (1998). UU-P07 is based on an inversion of ~19.4
million P-wave travel times originating from an extended EHB data set (Engdahl et al. 1998)
covering the years 1964-2004. Data were selected from the 445,000 earthquakes in this database
leading to 7.9 million regional P arrivals, 9.7 million teleseismic P, pP and pwP arrivals and 1.5
million PcP, PKPab, PKPbc, PKPdf and PKiKP phases. In addition ~155,000 travel time
observations from local networks in the Euro-Mediterranean region were included and ~85,000 data
were picked from regional teleseismic experiments in Europe, as well as ~120,000 travel time picks
from networks in the western United States (see Amaru, 2007, for details).
The Earth was parameterized by an irregular cell grid of non-overlapping cells based on the
methodology of Spakman and Bijwaard (2001). Lateral cell size varies from 0.5o in well-sampled
regions to 10o in poorly sampled parts of the mantle. Cell thickness varies from 10 km in the crust,
to 35-60 km in upper mantle, to 100-200 km in the lower mantle. In total ~600,000 cells constitute
the tomographic model. The tomographic inversion solves jointly for seismic wave speed anomalies
with respect to the 1-D reference model ak135 (Kennett et al.,1995), relocation vectors of
earthquake clusters, and station statics. Testing with many combination of amplitude and second
derivative regularization led to selection the preferred model UU-P07. Model UU-P07 can be
considered as an update of model BSE of Bijwaard et al. (1998) using more than two times more
data and using two times more cells for mapping mantle structure.
For comparison, in Movies 1 and 2 we also present tomographic results from model S40RTS
(Ritsema et al. 2011). This S-wave velocity model is completely independent from UU-P06 because
of the data used (data derived from various S-waves) and because of the complete different
tomographic technique which is based on mantle parameterization with global base functions
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(spherical harmonics) instead of the local cell parameterization used for UU-P07. This
independence in data and imaging technique implies that if anomaly patterns are visible in both
models, albeit at a different resolution and detail, the actual existence of imaged mantle structure is
assured.
The high-velocity anomaly below the East Somali Basin at a depth of ~800-1400 km is visible in
both UU-P07 and S40RTS (Movies 1 and 2) although with different resolution and model
amplitude error causing different image distortion in the tomographic image of, what we have
called, the Carlsberg slab.
In addition to this positive comparison we show in Auxiliary Material Figure 1 results from various
resolution tests with synthetic velocity models consisting of well-separated velocity anomaly blocks
of lateral size of 5o or 6o. The original positions of these blocks are indicated with black contour
lines which can have an irregular shape as these large blocks are constructed from several smaller
cells of the underlying cell grid. The synthetic velocity anomalies assigned are +/- 5% in an
alternating pattern (laterally and in depth). The seismic ray paths used for the actual data inversion
are used in the synthetic tests for computing synthetic travel time data. Next, after adding Gaussian
noise to the synthetic data, the same tomographic equations are used to invert the synthetic data for
the synthetic block-model. The result is depicted with color contouring.
Model resolution increases from the top of the lower mantle downward to depths of 2000 km.
Although the amplitude response in the inversion is typically 50%-60% of the input values, the
block patterns are well resolved except in the top of the lower mantle in south of the region (note
that a block size of 5o corresponds to ~460 km, at a depth of ~1000 km, and ~370 km at a depth of
2000 km). We conclude from tests (A.M. Figure 1) that the spatial resolution is sufficient to image
anomalies with spatial dimensions at, or larger than the synthetic block sizes used. Together with
the positive match of Carlsberg slab images between models UU-P07 and S40RTS, this provides a
solid tomography basis for our interpretation of the Carlsberg slab anomaly.
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Figure S1. Sensitivity tests results from 4 different synthetic block models. The models differ in
characteristic block size (degrees; last number in lower-left label) and block position (black contour
lines). Input values for synthetic anomalies are +/- 5%. Generally the amplitudes are systematically
underestimated (~50%) as a result of lack of resolution caused by lack of data and regularization
(damping) of the tomographic inversion. The organization of the panels is on depth only, which
increases from left to right and from top to bottom.
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Figure S2. Map view of tomographic models UU-P07 and S40RTS at three different depths
(including the ones selected in Fig. 11). Interpreted slab contours as shown in Fig. 12.
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Movie 1. Map view movie from the surface to 2500 km of P-wave velocity model UU-P07 and Swave velocity S40RTS. The reference velocity model for UU-P07 is ak135 (Kennett et al. 1995)
and PREM (Dziewonski and Anderson 1981). Note that the contouring limits are a function of
depth derived from the temperature-seismic velocity scaling of Goes et al. (2004).
Movie 2. Movie of tomographic cross-sections showing models UU-P07 and S40RTS. The red line
in the geographic map above the mantle sections is the profile along which the section is computed
from the tomographic models. Longitude, latitude, azimuth and arc-length for each section are
given in the map above the tomographic section. The map-inset shows the profile on a larger scale
map.
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