[GPlates-discuss] plotting relative plate velocities

Tue Sep 20 13:22:28 AEST 2016

Hi Christoph and Christian,

Thanks for looking into this issue, and thanks for bringing it up.

Christoph, I found it a little difficult to reproduce exactly what you were doing, but I think I got there. I’ve got a few papers now that are associated with a specific plate reconstruction model, so Zahirovic et al. itself is not specific enough for me to figure out. I am assuming it’s our 2014 paper on Southeast Asia.

I used the kinematics tool in GPlates with the following setup (and loaded the 2014 rotation file):

[cid:image001.png at 01D21342.078C9A30]

Under settings:

[cid:image002.png at 01D21342.078C9A30]

(Make sure you click Apply, then Close).

I get something like this, which is similar to the trends you observe:

[cid:image003.png at 01D21342.078C9A30]

If I do the same, but load in our recent plate reconstructions (Muller et al., 2016, AREPS – also attached), then I get something more geodynamically reasonable:

[cid:image004.png at 01D21342.078C9A30]

You can see the comparisons also in the CSV files that I attach. The differences are due to the rotations of Arabia relative to Africa, but more-so the rotations of Eurasia relative to North America, and then how that links back up to the absolute reference frame. We did detect that problem a while back, and we removed a few of the rotations. This usually happens when you have magnetic anomaly identifications that are very close temporally, which can introduce sudden changes in plate motion that are not geodynamically feasible. You can explore that in more detail in a paper by Iaffaldano et al. (2014)<http://onlinelibrary.wiley.com/doi/10.1002/2014GC005309/abstract>.

In our older models we have these rotations for Eurasia:

301 47.9   65.38  138.44  -10.96  101 !EUR-NAM Gaina et al. 2002

301 53.3   63.07  144.26  -12.82  101 !EUR-NAM Gaina et al. 2002

301 55.9   56.17  145.06  -13.24  101 !EUR-NAM Gaina et al. 2002

301 68.7   54.45  147.06  -15.86  101 !EUR-NAM Gaina et al. 2002

In our new models, we have these rotations for Eurasia (you can see the ~53 Ma rotation has been removed):

301 47.9   65.38  138.44  -10.96  101 !EUR-NAM @REF Gaina_++_2002 @DOI"10.1016/S0012-821X(02)00499-5" (21o)

301 55.9   56.17  145.06  -13.24  101 !EUR-NAM @REF Gaina_++_2002 @DOI"10.1016/S0012-821X(02)00499-5" (25y)

301 68.7   60.38  146.96  -16.33  101 !EUR-NAM @REF Barnett-Moore_++_(in review)

For Arabia, we had these rotations:

503  0.0    0.0    0.0    0.0  701 !ARB-AFR Arabia-Nubia (Africa)

503 10.9   26.1   23.1   -3.86  701 !ARB-AFR Royer et.al 1998

503 20.6   30.9   17.5   -6.32  701 !ARB-AFR Royer et.al 1998

503 600.0   30.9   17.5   -6.32  701 !ARB-AFR

Now Arabia’s motions are:

503  0.0    0.0    0.0    0.0  709 !ARA-SOM Arabia-Somalia

503  2.6   23.67   22.21   -0.939  709 !ARA-SOM @REF Fournier_++_2010 @DOI"10.1029/2008JB006257", @CHRONID"C2An.1y"

503  3.6   21.28   28.5   -1.619  709 !ARA-SOM @REF Fournier_++_2010 @DOI"10.1029/2008JB006257", @CHRONID"C2An.3o"

503  6.0   25.46   25.41   -2.398  709 !ARA-SOM @REF Fournier_++_2010 @DOI"10.1029/2008JB006257", @CHRONID"C3An.1y"

503  8.8   22.56   27.71   -3.985  709 !ARA-SOM @REF Fournier_++_2010 @DOI"10.1029/2008JB006257", @CHRONIS"C4Ay"

503 11.0   23.88   26.66   -4.74  709 !ARA-SOM @REF Fournier_++_2010 @DOI"10.1029/2008JB006257", @CHRONID"C5n.2o"

503 16.0   25.85   25.4   -6.853  709 !ARA-SOM @REF Fournier_++_2010 @DOI"10.1029/2008JB006257", @CHRONID"C5Cn.1y"

503 17.5   26.1   22.98   -7.283  709 !ARA-SOM @REF Fournier_++_2010 @DOI"10.1029/2008JB006257", @CHRONID"C5Do"

503 19.7   26.46   21.66   -7.83  709 !ARA-SOM @REF Fournier_++_2010 @DOI"10.1029/2008JB006257", @CHRONID"C6no"

503 231.0   26.46   21.66   -7.83  709 !ARA-SOM

So the take-home message is that you should be using the latest plate reconstructions. The most recent model with evolving plate topologies is the AREPS Muller et al. (2016) model:

http://www.earthbyte.org/ocean-basin-evolution-and-global-scale-plate-reorganization-events-since-pangea-breakup/

A more recent model with some changes in the India-Eurasia and eastern Tethys region is here:

http://www.sciencedirect.com/science/article/pii/S0012825216302872

I recommend the AREPS model as it has the evolving plate topologies bundled, while in the other one we only provide the resolved topologies exported as GMT/SHP files. Hope that helps.

Cheers,

Sabin

--
DR SABIN ZAHIROVIC | Postdoctoral Research Associate
School of Geosciences | Faculty of Science

THE UNIVERSITY OF SYDNEY
Rm 403, Madsen Building F09 | The University of Sydney | NSW | 2006
M +61 416 775 589 P +61 2 9351 3625
E sabin.zahirovic at sydney.edu.au<mailto:sabin.zahirovic at sydney.edu.au> | W http://www.earthbyte.org<http://www.earthbyte.org/> | R http://www.researchgate.net/profile/Sabin_Zahirovic
F https://www.facebook.com/earthbyte | T https://twitter.com/EarthByteGroup
Faculty contact for the Society of Exploration Geophysicists (SEG) - Member # 283117

Most recent publications:

Zahirovic, S., Matthews, K.J., Flament, N., Müller, R.D., Hill, K.C., Seton, M. and Gurnis, M., (In Press), Tectonic evolution and deep mantle structure of the eastern Tethys since the latest Jurassic, Earth Science Reviews<http://www.sciencedirect.com/science/article/pii/S0012825216302872>, doi: 10.1016/j.earscirev.2016.09.005.

Zahirovic, S., N. Flament, R. D. Müller, M. Seton, and M. Gurnis (In Press), Large fluctuations of shallow seas in low-lying Southeast Asia driven by mantle flow, Geochemistry, Geophysics, Geosystems<https://www.researchgate.net/publication/306088667_Large_fluctuations_of_shallow_seas_in_low-lying_Southeast_Asia_driven_by_mantle_flow>, doi: 10.1002/2016GC006434.

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On 19/09/2016, 11:54 PM, "GPlates-discuss on behalf of Christian.Heine at shell.com" <gplates-discuss-bounces at mailman.sydney.edu.au on behalf of Christian.Heine at shell.com> wrote:

    Christoph,

    > I used the Zahirovic et al. model to extract plate velocities. I tried to

    > create plots with relative plate movements, and followed the instructions

    > from the tutorial.

    This (https://docs.google.com/document/d/1xUHGu1N-nirc9t2srspdSOsmx0jrRsrBoJgWw5Ge0bI/pub) one?

    [snip]

    > Here my first plot, it shows convergence of Arabia and Eurasia. (It's

    > based on an India-Eurasia-Convergence plot Sabin was kind enough to

    > share, and which I could reproduce, too)

    Attached my version which looks slightly similar but doesn't have the spikes at 27/16 Ma. This is for a point close to Kuweit.

    > Looks great, but has these two excursions at 27 & 16 Ma, which I find

    > geologically difficult. Is this an artifact? How would you deal with it?

    You haven't mentioned whether you use a single point or the velocity domain points to achieve this. I think in the latter case, what could happen (and lead to the spikes) is if a plate boundary moves across your velocity domain point for a very short amount of time and you hence pick up velocities from a separate plate there.

    Depending on what you're trying to do it might be easier to digitise your points as 'standard' features and then use them for input for a new 'Calculated velocity fields' layer (simply add a new layer in the layer mgr) instead of the velocity domain points.

    > Second, I tried to do the same plot for Arabia and India. Unfortunately

    > sth went wrong here, and in the .xy export files it shows the wrong plate

    > IDs. I tried it several times, but don't get it to work. Any idea is

    > appreciated. Thanks and cheers,

    Could be the same issue as above. Using the kinematics tool I can happily make vel magnitude vs time plots for ARA-IND. Try digitising a point and export vels from there.

    HTH,

    Christian

    --

      Christian Heine, Ph.D.

      Upstream - Opportunity Identification (UPX/N/OH)

      Shell Intl. Exploration and Production B.V.

      Carel van Bylandtlaan 5 | C05-01-B33

      2596 HP Den Haag, The Netherlands

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