GPlates Tutorial SE Asia Use Case
Contents
1. Ma D K 44 D gt O Type AR Name Q RS Plate ID Valid time gt from to Clicked geometry Feature collection e GB XY wy Si View 3D Globe 100 dat 0 36 lon 103 28 Mouse lat 19 86 lon 166 84 off globe Clicked Selected Topology Sections Feature type Plate ID Name Clicked geometry Begin End Present day geometry lat lon Figure 5 GPlates interface centered on SE Asia Since we want to have a closer look to SE Asia it is useful to zoom in to that region There are different ways to zoom in and out By mouse wheel up and down By using the Zoom Slider which is located at the right hand side of the globe Fig 6 gt zoom in or out by dragging the slider up or down using the mouse By using the set zoom percent field which is located beneath the globe Fig 6 gt enter percentage directly by click into the text field type a value 100 1000 and press enter By using the and keys and the 1 key to reset to 100 By using the Zoom tool located beneath the drag tool on the left hand side of the interface Fig 6 Once the tool is selected simply click to Zoom in 0 00 Gma p i gt as View 3D Globe He 316 8 lat 0 19 lon 113 28 Mouse lat 9 32 lon 88 09 Clicked Selected Topology Sections Feature type Plate ID Name Clicked geometry Begin End Present day geometry lat lon Figure 6 Di2. 180 0000 B i 4 SS eae tall OK Cancel O eee Figure 10 How to set Raster Surface Extent After you have changed the Camera Position you should be able to see the seismic tomography for the SE Asian region Fig 11 Time 0 00 Ma gt K DD Time 50 00 Ma D oa 4 b gt B Figure 11 Seismic tomography of the SE Asian Region with the raster surface extent set A Tomography model is Montelli06_S at 0 Ma B Tomography model is MITP08 at 50 Ma We want to use seismic tomography to find an hypothesised slab window beneath Sundaland in the late Cretaceous Early Tertiary A subduction zone can be seen in seismic tomography pictures as a anomalous fast area blue areas in our figures because the subducted Slab is colder and denser than the surrounding mantle A slab window can be seen as a break in the fast subducted slab The slab window is thought to have opened approximately between 70Ma and 43Ma and can be observed in different models at depths representative of these times Because the raster images change their pixels according to the reconstruction time we can animate the seismic tomography through time For the time dependent raster sets that already exist for SE Asia we can animate a period from 189 Ma to present day in 1 My time steps To animate the changes in seismic tomography through time we use the Animation Slider at the top of the interface To start the
3. GPlates Tutorial SE Asia Use Case Ee FG www gplates org Tutorial The aim of this tutorial is to acquaint you with GPlates It will help you to learn how to work with GPlates by focussing on the region of SE Asia as an example The first thing you have to do if you want to use GPlates is download it from the GPlates Download page http www gplates org download html and install it on your computer Download the GPlates User Manual as well in addition to this tutorial http www gplates org user manual If you want to work with GPlates you need data There is a Data Bundle for Beginners on the EarthByte website Download the Data Bundle for Beginners from http www earthbyte org Resources earthbyte gplates html After you ve downloaded GPlates and the data bundle start GPlates What you will see is the Main Window Fig 1 ane lt GPlates Current Feature Plate ID Valid time from to Clicked geometry Feature collection F ow X sf ge te View 3D Globe E 100 lat 0 36 lon 103 28 Mouse lat 31 87 lon 166 50 off globe O Clicked Selected Topology Sections Feature type Plate ID Name Clicked geometry Begin End Present day geometry lat lon A Figure 1 Main Window of GPlates You will learn what it contains and can do in the course of this tutorial To start working with GPlates load the files from your Data Bundle for Begin
4. able Fig 15 The Create Feature Window will pop up fig 18 First you will be asked to select a feature type gt Select Unclassified Feature for the slab window G Create Feature Feature type gpmi PassiveContinentalBoundary gpmi PseudoFault gpmil Roughness gpmi Seamount gpmi SedimentThickness gpmi SpreadingAsymmetry gpmI SpreadingRate gpmi Stress gpmi SubductionZone gpmi Suture gpmi TerraneBoundary gpmi Topography gpmi TopologicalClosedPlateBoundary gpmi Transform gpmi TransitionalCrust gpmi UnclassifiedFeature gpmi Unconformity gpmi UnknownContact gpmi Volcano ee O Previous Next Cancel Create Figure 18 Create Feature Window Click Next Leave the default setting for the geometry s purpose Fig 19 You have to give your feature a Plate ID It has to be the ID of the plate your feature is located on In our case the slab window is on the Eurasian Plate Type 301 for Plate ID which is the Eurasian Plate ID You have to give your feature a time of appearance and disappearence In our example Fig 19 we digitized the slab window at 70Ma Select 70Ma for Begin For End you can either tick Distant Future if you don t know exactly when it disappeared or select an End time For our slab window tick Distant Future Give ita name Create Feature Assign geometry to property Centre line Outline Which property best Unclassified miscellaneous indicates the geometry s purpose Basic prope
5. animation press the Play button The animation will start in the past and end at present day If you want to stop the animation press Pause same button as Play By using the Fast Forward and the Rewind buttons you can watch the reconstruction in small steps By pressing the Fast Forward Rewind button once you can adjust the current reconstruction time by one timestep forwards backwards You can also use shortcut Keys Ctrl CMD I forwards Ctrl CMD Shift I backwards By keeping the button pressed or the shortcut keys held down you can move forwards backwards faster In the Animation Dialog fig 12 you can adjust the start and the end time for your reconstruction To access this click Reconstruction menu and select Configure Animation Animate Range Ma Use Main Window Animate from 140 00 4 gt es Ma Use Main Window Sir ee to 0 00 fa gt with an increment of 1 00 M per frame 4 Reverse the Animation by swapping the start and end times Options fa Frames per second 5 00 V Finish animation exactly on end time __ Loop _ Close this dialog when animation starts Playback Current time 0 00 B Ma Kl Reset D Play Close Figure 12 Animation Dialog For our data you can choose any start time between 189 to 1 Ma In the Animation Dialog fig 12 you can also adjust the frames per second and the increment per frame Default setti
6. diting tool has been selected Fig 16 shows the digitized slab window after Move Vertex has been selected Each vertex dot can now be moved If you want to add a vertex select Insert Vertex and click on the line at the spot you want to add a dot You can move the new vertex later if you don t like the position If you want to remove a vertex select Remove Vertex and click on the dot you would like to remove Once you are happy with the shape of your slab window you export it in a format GMT can read To export a feature the Digitization Tool has to be selected Click Export beneath the Geometry Table Fig 15 The Export Coordinates Window Fig 17 will open and ask you to choose a format the coordinate order and a destination Choose the Generic Mapping Tools GMT format Make sure the Coordinate order is Latitude Longitude Choose a destination and a name and click Export Export Coordinates Format Format Generic Mapping Tools GMT Ke The geometry will be exported in a format suitable for use in GMT scripts Coordinate order Latitude Longitude 4 M Include additional terminating point for polygon Destination Export To File Clipboard slabwindowsGPlates Montelli06 S70Ma_ Browse OOE T Figure 17 The export Coordinates window Ifyou want to load the feature in GPlates later again you have to create a new feature To create a new feature click Create Feature beneath the Geometry T
7. f Southeast Asia comprising the Malay Peninsula Borneo Java Sumatra and the surrounding islands SLAB WINDOWS Slab windows form as a result of spreading ridges intersecting subduction zones When ridges are subducted the down going plates continue to diverge yet due to an absence of ocean water to cool the upwelling asthenosphere and form new oceanic crust the plates no longer continue to grow and a gap develops and widens Seismic tomography enables us to visualise slab windows from present day and past subduction SEISMIC TOMOGRAPHY Seismic tomography is a method for imaging the Earth s interior revealing regions of past and present subduction and hot mantle upwellings It involves establishing how fast seismic waves elastic waves travel through the mantle for example seismic waves generated by earthquakes This information 1s then used to infer regions of anomalously hot or cold material anomalous is judged as deviating from a global reference model As the speed of seismic waves travelling through the mantle is influenced by temperature velocity can be used as a proxy for temperature fast velocities cold material slow velocities hot material However mantle composition also affects the speed of wave propagation and therefore establishing correlations between velocities and mantle structures is not simple The Importing Rasters data bundle includes 2 sequences of regional time dependent raster images show
8. fferent ways of utilizing the Zoom tool Now you can see SE Asia Fig 6 B Current Feature Type a Name Plate ID Valid time from to Clicked geometry Feature collection eleme p If you want to get detailed information on one feature e g Sumatra you can select it using the Choose feature tool from the tool palette 3 4 from the top by pressing f For our next step we don t need all of the files we just loaded anymore and we want to hide those we need later again To unload save files or hide files we use the Manage Feature Collection Window Fig 7 Select Manage Feature Collection Dialog from the File Menu Or use the Shortcut Ctrl CMD M ANOO Manage Feature Collections Manage the feature collections which are loaded in the application File Name File Format Layer Types Actions 1 Global_EarthByte_GPlates_PresentDay_Ridges_20091015 dat PLATES4 line wm A Za cy 2 Global_EarthByte_GPlates_PresentDay_lIsochrons_20091015 PLATES4 line em A A B fz A 3 Global_EarthByte_GPlates_Coastlines_20091014 dat PLATES4 line wm i Bee A 4 Global_EarthByte_GPlates_PresentDay_COBs_20091007 dat PLATES4 line wm LA 2 j Hga Open File Save All Close Figure 7 The manage feature collection Dialog with all dat files loaded As you can see all features are selected ticked Fig 7 If we don t want to unload a file because we are going to need it later again we can
9. g to re orient the globe Shift drag to rotate the globe A Figure 3 All dat files from the Data Bundle for Beginners loaded The features are coloured by Plate ID Fig 3 Change the colours to Feature Age Feature Type and Single Colour Select Layers Menu from the menu bar Select Manage Colouring Try how it changes if you choose Feature Age Feature Type or Single Colour Fig 4 0 OO lt gt Manage Colouring Feature Collection All 34 Use Global Colour Scheme Plate ID Single Colour Feature Age Feature Type Group by Region v Show Thumbnails Close Figure 4 How to select a different colouring scheme You can individually change the colours for each feature layer You cannot see SE Asia our region of interest yet To change the camera position to the region of SE Asia make sure the Drag Globe tool is activated You can do this by either selecting the tool on the top left of the interface with the mouse or pressing d Fig 5 You can now change the camera position by clicking on the globe and dragging it or using the up down left and right keys f lt Select any other tool and try dragging the globe by pressing Ctrl Command on Macintosh Computers Try also to adjust the camera position by pressing Ctrl Command on Macintosh L and entering the coordinates for Sumatra in the window that will pop up GPlates Current Feature a amp Time 0 00
10. ics of Cenozoic and Mesozoic plate motions Reviews of Geophysics vol 36 1 27 78 1998 Montelli R G Nolet F A Dahlen and G Masters A catalogue of deep mantle plumes New results from finite frequency tomography Geochem Geophys Geosyst vol 7 11 2006 Muller R D M Sdrolias C Gaina B Steinberger and C Heine Long term sea level fluctuations driven by ocean basin dynamics Science vol 319 p 1357 1362 2008 Richards S G Lister and B Kennett A slab in depth Three dimensional geometry and evolution of the Indo Australian Plate Geochem Geophys Geosyst vol 8 12 2007 Whittaker J M R D Muller M Sdrolias and C Heine Sunda Java trench kinematics slab window formation and overriding plate deformation since the Cretaceous Earth Planet Sci Lett vol 255 p 445 457 2007
11. ing seismic tomography These images were generated from the seismic tomography model PRI SO5 Montelli et al 2006 and model MIT P08 Li et al 2008 Although seismic tomography is a method for imaging the structure of the present day mantle by establishing a relationship between slab depth and slab age i e when the slab was being subducted at the surface NOT the age of the oceanic crust we can use tomography data to learn about past subduction zones By examining the relationship between subducted materials sinking velocity and its current depth we can make estimates about the age of subducted material Table 1 displays the corresponding depth of the age coded tomography slices Depth Slice km Age Ma 40 P1224 o 1404 Table 1 Age depth relationship for tomography slices based on Lithgow Bertelloni and Richards 1998 You can load Time dependent Raster Sequences which are raster images whose pixels change according to the reconstruction time Presently GPlates can only open jpg files If you want to load your own time dependent raster set make sure Each image is a jpg file All files are named name time jpg The time numbers are integer time in Ma Example Montelli06_P 3 jpg Montelli06_P 4 jpg Montelli06_P 5 jpg etc For our region of interest time dependent raster sets already exists The seismic tomography data shows the mantle structure at different depths which are assumed to re
12. just untick it so that it can t be seen on the globe anymore but is still loaded Untick the coastlines We don t need all the other files anymore so we can unload them If we want to save them before we unload them we have different options Save saves the file using the current name Save As saves the file using a new name Ifyou want to save your file pick one option Save a Copy saves a copy of the file with a different name Unload your file after you saved it by clicking on the unload item A Eject unloads the file Your Manage Feature Collection Dialog should now look like this Fig 8 AO Manage Feature Collections Manage the feature collections which are loaded in the application File Name File Format Layer Types Actions 1 Global_EarthByte_GPlates_Coastlines_20091014 dat PLATES4 line 0e W g A q Open File A Save All Figure 8 The Manage Feature Collection Dialog with unticked coastline file Loading Time dependent Raster Sequences For the next exercise you will need to download a set of raster images You can download these images from the Earthbyte website http www earthbyte org Resources GPlates tutorials Importing Rast ers SampleData importing rasters zip We will now be using a combination of regional time dependent rasters and reconstructable data sets to reveal an assumed Late Cretaceous Early Tertiary slab window beneath Sundaland Whittaker et al 2007 a region o
13. lick Choose Select age grid jpegs from the Importing _Rasters data bundle This is a global raster sequence Therefore the fields must be reset to 90 180 90 180 Spend some time reconstructing the raster sequence using the Animation and or Time controls you can see how old the oceanic crust is in various areas of the world We will now compare the location of the slab window that you inferred from seismic tomography to the location where the youngest oceanic crust and hence the crust adjacent to the spreading ridge is being subducted beneath Sundaland for simplification we will assume that the spreading ridge 1s positioned at the centre of the youngest oceanic crust Figure 21 In other words we will be comparing our slab window with the approximate location of the slab window inferred from a plate kinematic reconstruction Note youngest crust is coloured red AOO lt gt GPlates C Current Feature Time 60 00 ma D IK 44 gt ene T CU A Plate ID Valid time from to Clicked geometry Feature collection __ View 3D Globe RA 100 lat 0 00 lon 110 Mouse lat 18 43 lon 160 00 off globe i Selected Topology Sections ha Feature type Plate ID Name Clicked geometry Begin End en R lt 1 ff Figure 21 60 Ma reconstruction of ocean floor ages and present day coastlines Notice that the youngest oceanic crust and hence the spreading ridge is converging wi
14. ners Click on the File Menu in the menu bar Select Open Feature Collection gt a dialog window will appear Select the file Global_EarthByte_GPlates_Coastlines_20091014 dat from your data bundle gt Coastlines will appear on the grey globe in the Main Window Fig 2 ane gt GPlates z Current Feature g Time 0 00 Gma p K 4 D meee eee Plate ID Valid time from to Clicked geometry Feature collection wi k KOR ch Gry o gt h lt x on a q 2 a y g q g ne SS Ho he be o i 100 8 lat 0 89 lon 8 28 Mouse lat 59 99 lon 84 53 View 3D Globe Clicked Selected Topology Sections Feature type Plate ID Name Clicked geometry Begin End Present day geometry lat lon Figure 2 Coastlines Load the other dat files from your data bundle as well by clicking on Open Feature Collection in the File Menu again and selecting the remaining files you can open all files at once if you select all of them by pressing Ctrl Fig 3 LA OO GPlates C Current Feature ga Time 0 00 Gma P KKI 4 Db p0 TCTC aly Plate ID Valid time from to Clicked geometry Feature collection A x of View 3D Globe B 100 lat 0 89 lon 8 28 Mouse lat 15 23 lon 21 88 Clicked Selected Topology Sections Feature type Plate ID Name Clicked geometry Begin End Present day geometry lat lon Dra
15. ngs are 140 Ma for the start time and 0 Ma for the end time of the animation 5 frames per second 1 Ma increment per frame Ifyou want your animation to start at present day and go back in time you can choose Reverse the Animation from the Animation Dialog To find our slab window we don t need our animation to start at 140 Ma Change the start time for the animation to 80 Ma and the end time to 30 Ma Try to find the slab window in the different rasters fig 13 Figure 13 Slab window in the Montelli06_S model at 70Ma left 56Ma middle and 43 Ma right New Features GPlates provides the opportunity to create new features We want to digitise our slab window create a new feature and export it in a format that can be used in other programs e g GMT To digitize our slab window we need the Digitisation Tools from the Tool Palette on the left hand side of the globe Digitise new Polyline Geometry open polygon J Digitise new Mulit Point aiiis Geometry Digitise new Polygon Geometry Depending on which kind of feature you want to create you need a certain geometry For our slab window we choose the Polygon Tool Click on the polygon button to select the tool After a digitisation tool has been selected every mouse click creates a new vertex To digitize the position of our slab window we choose an oval shape The slab window opened approximately beneath the Sunda Java Trench and extended to the north so it i
16. present certain ages in the past To load the Time dependent Raster Sequence Select Open Time dependent Raster Sequences from the File Menu gt A finder window will pop up Select the jpg file and click Choose For this exercise we will be using the Montelli tomography model The importing Rasters databundle also contains the MITP08 model so feel free to try it out also The raster image will appear but will stretch over the whole globe Fig 9 ATA GPlates Current Feature Name Plate ID Valid time from to Clicked geometry Feature collection View 3D Globe R 100 dat 15 05 lon 91 47 Mouse lat 30 91 lon 74 15 Clicked Selected Topology Sections Feature type Plate ID Name Clicked geometry Begin End Present day geometry lat lon Figure 9 GPlates interface with a Raster Jpg loaded To define the region of SE Asia select Set Raster Surface Extent form the Layers Menu Fig 10 A window will appear and ask you for the lower left and upper right coordinates of your region of interest For the SE Asia data the Upper right coordinates are 30 lat and 130 lon Lower left coordinates are 20 lat and 80 lon Set Raster Surface Extent s ia Set the latitude and longitude extent of the raster image Use the Tab key to cycle through the fields Upper right Latitude 90 0000 Longitude 180 0000 f y Lower left Latitude 90 0000 R Longitude
17. rties Plate ID 301 8 Begin time of appearance 70 00 Ma D Distant Past End time of disappearance 0 00 Ma V Distant Future Name SlabwindowMontelli06_S70Ma Previous Next Cancel Create Ne O S Figure 19 Create Feature Dialog This is where most of the features attributes are set Click Next Select Create a new Feature Collection Fig 20 Click Create G Create Feature Add feature to collection Choose the feature collection to which the new feature should be added lt Create a new Feature Collection gt Previous gt Next Cancel Create Figure 20 Creating a new feature collection You ve created a new feature but it hasn t been saved yet Open your Manage Feature Collection Dialog And save the feature as a dat file by clicking the Save As button This is just an example using one tomography model If you would like to compare the different models go back to step 8 and load a new set of time dependant rasters from the folder called MIT P08 GPlates can further be employed to compare the location of the slab window inferred from seismic tomography with its location inferred from other data sources for example plate tectonic reconstructions We will now load in EarthByte s time dependent crustal age sequence from the Importing Rasters data bundle Select Open Time dependent Raster Sequences from the File Menu gt A finder window will pop up Select the jpg file and c
18. s helpful to see the coastline again Select the coastlines in your Manage Feature Collection Dialog again Because we want them to change position through time we need to load a rotation file as well The rotation file contains Longitude Latitude and the angle of rotation for each plate Select the file Global_EarthByte_GPlates_Rotation_20091015 rot from your data bundle Set the Reconstruction Time to 70 Ma and start digitizing the slab window Figure 14 Slab window Your slab window should look approximately like in the figure above Fig 14 The coordinates of each vertex can be seen in the New Geometry Table on the right hand side of the globe fig 15 New Geometry Mo lt lp Coordinates Lat Lon 3 1640 109 4917 4 1812 109 5694 5 3565 109 0196 6 6128 107 9951 8 1876 106 2501 9 3728 104 7297 10 0858 103 5225 10 6414 102 2298 10 8799 100 6959 10 7209 99 6523 10 4032 98 7742 9 5311 98 0772 8 5033 97 7887 7 5570 97 8175 X 5 9058 98 6613 v _ y Clear Export Feature ieee Create Feature i Figure15 Geometry in Lat and Lon of newly digitised slab window Fig 15 shows the coordinates for the digitized slab window in Fig 14 Ifyou don t like the shape you can move the vertexes ad new vertexes or delete those you don t like using the editing tools from the tool palette Gy q Move Vertex Insert Vertex Remove Vertex Figure16 Digitised slab window after e
19. th western most Sundaland Rotate the globe to centre on Sundaland and use the Time controls to jump to 60 Ma How does your digitised slab window compare to the location of subduction of the Wharton Ridge and hence the kinematically inferred slab window If you would like to learn more about how seismic tomography is being used to constrain the location of the Wharton Ridge and slab window beneath Sundaland during the Late Cretaceous to Early Tertiary see Fabian et al 2010 That s the end of today s exercises By now you should be familiar with using the GPlates interface to manipulate files containing a diverse range of geological data The functions and abilities that you have learned today are just a few of GPlates repertoire and advanced tutorials on such topics as manipulating Paleomagnetic data creating your own rotations and using velocity meshes are also available on the EarthByte website http www earthbyte org Resources earthbyte auscope html REFERENCES Fabian T J M Whittaker and R D Muller Ground truthing proposed slab window formation beneath Sundaland using Seismic Tomography ASEG PESA 2010 International Geophysical Conference and Exhibition Sydney Australia August 22 4 26 Li C R D van der Hilst E R Engdahl S Burdick A new global model for P wave speed variations in Earth s mantle Geochem Geophys Geosyst vol 9 5 2008 Lithgow Bertelloni C and M Richards The dynam
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