Paleomapping Manual

Back to the Mapping Form

Back to the Fossil Distribution

Paleomapping Manual

How to make Paleotectonic/Fossil Distribution Maps:

Introduction
Enter Data into the Form
Zoom and Recenter
Download TIF and PS Files
Bugs
You Want Your Rotation Data Here Too?
What if...
Credits

	1. Introduction The paleo plate tectonic mapping service lets you interactively create plate tectonic maps of any area in the world of a specified age. The data of 197 plate fragments and terranes and their movement parameters is used, to calculate the maps. The movement can be calculated relative to one of three major reference frames, one magnetic frame by Harrison & Lindh (1982) and two hotspot frames (Cox & Hart, 1986; Mueller et. al., 1993). The maps are calculated online, and displayed after a few seconds (calculation may take up to 2 minutes depending on the options you chose and the number of people online). You can recenter the maps by clicking the preferred map center with your mouse, and zoom into it by choosing a zoom factor. GMT (Generic Mapping Tools) is used to plot maps in various projections.

	2. Enter Data into the Form The following paragraphs describe how to modify the fields in this form.
	2a. Age In this box you specify the age in My (million years) for the reconstruction. You may enter any age, as long as it's <= 150.0 My. Although you could, it doesn't make sense to enter more than 1 digit after the decimal point, since the data are not precise enough for more detailed reconstructions. For more information about the blocks, terranes and rotations used for the reconstruction, please see the reference information. You may also enter ages < 0.0 My. What that means is explained in the What if... section of this manual.

	2b. Boundaries This part lets you define the area you want to be plotted. Specify boundaries by longitude and latitude in decimal degrees. Hence 30.5 equals 30 degree 30 minutes. You can't choose an area which covers more that 360 degrees in longitudinal or more than 180 degrees in latitudinal direction. Please note, that since the plates are moving, the plate constellation of an area today will not be the same as in the past. That means, if you plot a 50My reconstruction of the area which would show India today, you won't find India on the reconstruction anymore. It will have moved out of the boundaries of your map. Therefore, it is suggested to plot a map of global scale first, to find out where your area of interst moved. Then it's much easier to specify boundaries.

	2c. Annotation and Gridline Intervals Here you can set frame annotations of the map and the intervals for the gridlines. Simply type a degree value into each box. As in the boundaries boxes, the degrees are given as decimals, hence 30.5 equals 30 degree 30 minutes. Note: If you don't want any annotations and/or gridlines, enter a dash "-" into the appropriate box.

	2d. Frame Type For your plot you may choose between two different frame types. One is a simple line, with small annotation marks. This works best for most polar projections. The other type is a thick black/white alternating frame. Just choose the one you like better.

	2e. Plate Fragments Check the box to plot the plate fragments into the map. You may choose just outlines, or opt to fill the fragments in the color specified by the menu next to the appropriate box.

	2f. Plot and Label DSDP/ODP-sites If you want DSDP and/or ODP sites to be plotted in your map, check the appropriate boxes. If you don't plot sites, you can't label them. DSDP sites will allways be plotted as red dots, ODP sites will appear green. All sites will be shown in their reconstructed location. Sites won't appear, if their location didn't exist at the time of reconstruction (if you find sites appearing where they obviously shouldn't be, please notify me). Currently we have entered all DSDP sites and ODPs up to site 997. We're still working on adjustments of the labels. You'll notice, that some are already done, but many of them still plot over each other. This can't be avoided on global maps of course, but at higher resolutions we're still trying to get a better adjustment.

	2g. Plot Magnetic Lineations If you want to plot magnetic lineations, check this box. Lineations will be shown as black lines in their reconstructed position. In most areas the reconstructions work well. There are some areas in the pacific, where we still have to separate lineations onto their proper plates. You might find some inconsistencies there.

	2h. Plot Present Day Shorelines If you check this box, present day shorelines will be printed onto the plate fragments. Parts of the shorelines will be moved with the fragments, as the continents break up. Be sure to choose a color for the shorelines, which contrasts to the color of the plate fragments, if you chose to color them. Please note, that the shorelines are just plotted to illustrate present day locations. The plotted shorelines have nothing to do with actually existing shorelines during the reconstructed timestep. Those were very different from todays existing shorelines.

	2i. Map Projections GMT, the program package the maps are plotted with, offers a wide range of map projections. The most important of them are implemented here. Most commonly used projections are Mercator, Mollweide, Orthographic or Equidistant. To make a polar plot, try the Orthographic projection. For more information on special projections, please refer to the GMT manual or other sources on this subject (i.e. Frederick Pearson: Map Projections: Theory and Applications, CRC Press).

	2j. Reference Frames and Fixed Plates As all plates are moving on the earths surface, their motions are described relative to each other. However, to determine their absolute motion it is necessary to define a latitudinal global reference frame. There are several possibilities for reference frames. The two most important ones are implemented here: Magnetic reference frames, relative to paleo-pole positions determined from the continents Hotspot reference frames, relative to hotspots. Depending on the magnetic pole positions and hotspots, slightly different reference frames can be constructed for different hotspots and paleo-poles. Implemented are 3 published frames: Magnetic Ref. Frame - paleo-poles in Northamerica (Harrison and Lindh (1982)) Hotspot Ref. Frame 1 - published by Cox and Hart (1986) Hotspot Ref. Frame 2 - published by Mueller et al. (1993) For more information on reference frames, please consult the reference information. Besides using reference frames, it can be useful to observe how plates move relative to each other. To accomplish this, it is possible to keep one major plate fixed in its present position, while everything else moves relative to it. Just choose the plate you want to be kept fixed from the list. Please note, that in this case paleolatitudinal positions of the fragments are far from being correct.

	2k. Plotting Data from a Fossil Distribution Map Instead of plotting all DSDP/ODP sites, you can plot data you obtained from the Fossil Distribution Map. To get this data plotted, simply check the apropriate box and enter the job number which was displayed with your distribution map. Positive sites (sites which contained the fossil you searched for) and negative sites will be displayed and labeled as selected by the checkboxes. "Positive Sites" are sites, where the searched fossil or combination of fossils were found. "Negative Sites" in contrast are sites, where the fossil(s) were not found. Be careful! The fact, that the specific fossil wasn't found doesn't mean it does not occur in the hole. The bearing layers might just not have been sampled. Check the rangecharts and fossil distribution charts for clues on this. Note that checking the "Sites from a previous Job"-box disables regular DSDP/ODP site plotting. ATTENTION! Mapping data is stored for about one hour only! This is the case for disribution data too, hence you will only be able to plot those data into paleo maps for about one hour after you generated the distribution map. Replot the distribution map if necessary.

	3. Zoom and Recenter After you have created a reconstruction, you may select a new map center by clicking the preferred position on the map with your mouse. A new map with that center will be calculated. You may also choose a zoom factor, to display a more detailed map. A zoom factor of 2 means that the extension of the map boundaries will be reduced by this factor, maintaining the map center you pointed on. No other parameters can be changed here. It is recommended that you find out about the exact area you want to plot by zooming first, and then go back to the form and enter the final boundaries. This way you will need a minimum of trial and error.

	4. Download TIFF and PS Files It is possible to download copies of the maps in Postscript and TIFF format for further use. Simply click the link to download the file. Calculated maps are stored for about 1 hour on the server (no guarantee). Please note that the downloaded Postscript files are zip-compressed! You need to expand them (use unzip, pkzip, WinZip or Stuffit Expander depending on your machine), before you can load them into Corel or Illustrator. Postscript files are in color, and can be printed on any Postscript printer. Some Programs are able to process Postscriptfiles. We have had good experience with Corel Draw Versions 5.0 and later on Computers running Windows (3.11, 95 or NT). Corel Draw allows you to import the files, and store them in vector format. This offers the possibility of completely modifying and reworking the files in the most convenient way, maintaining very high quality. I don't know if there are other programs which allow PS to vector conversion other than Corel Draw. I would be very interested to become to know other possibilities, if someone found any. If you are a Mac User, I'd suggest you use Adobe Illustrator to edit the postscript files. However, many people find Illustrator difficult to use. The only possibility I know to convert the postscript file into a vector format is to try to find somebody with Corel Draw, who can save the imported file in CGM-format. Be sure to use the "standard" option. In most cases, these files can be opened in Mac Programs such as Canvas or MacDraw as well. For Canvas and many other programs, it may be important to change the filetype with ResEdit or FileBuddy to CGMF. Also - be sure you have loaded the necessary CGM-filter to interpret the file. You can load the filter with Canvas by pressing the space-bar during startup, and selecting the filter in the upcoming menu. You might also want to transform the PS-file to a bitmap using GhostScript. GS offers various output formats, like PCX, TIFF, BMP and others. It's available on the web for most platforms like Unix, Windows, Mac, OS/2, so there shouldn't be a problem to aquire a copy. Just ask one of the www-search-machines. If none of these work for you, try the TIFF-file. This is a 300 dpi black/white LZW-compressed TIFF. Unfortunately not all graphics programs support TIFF compression formats, but an uncompressed picture would be more than 1MB in size, and hard to download (GEOMAR's internet connection so far is not part of the so called data-superhighway). However, this TIFF file was sucessfully loaded with Photoshop, Corel Photopaint and several other applications.

	5. Bugs Although in general everything works about well, there are several known bugs and errors I'm still working on to fix: the displayed map is sometimes collapsed to a thick vertical line after clicking for a new center. in fill-fragments mode, fragments at the poles are not filled properly in some projection modes (this usually is due to the nature of some projections). in fill_fragments mode, somtimes non-fragmant areas are filled as well, after zooming into a map. Try to move the map a little bit. This sometimes fixes the problem. many site labels overlap each other (we're working on fixing this, since it's just a matter of manpower).

	6. You Want Your Rotation Data Here Too? If you have other datasets with paleo plate tectonic data of other ages, or just data you think does a better fit, I'd be happy to try to incorporate it into this site as an optional rotation set. The program I use reads an ASCII rotation file with the following data: Plate - Reference Plate - Interval_Start - Interval_End - Lon_Euler_Pole - Lat_Euler_Pole - Rotation_Angle - Comment Email me and we can work it out. Thank you!

	7. What if... ... plate motions continue the way they do today? (This is the bonus section for you folks who read the manual) They probably wont do that but of course nobody knows. However, you can (just for fun) calculate an estimation on that here. If you enter a negative number into the "Age" section, a "view into the future" will be calculated, based on the average plate motions of the last 1My. For example if you enter "-2.0", the plates will move two times the opposite motion, they did the last 1My. You will see where we're all about to be in approximately 2My. Be aware, that this isn't even fiction, it's pure nonsense, because the calculation doesn't check for collisions of plates, nor subduction or spreading rates. It just stupidly calculates the motions. But - it's fun! Try 50 My, and see India drifting deep into the Asian continent, or Australia, overrunning the Philipines about to crash into China. Check out, where it's safe to buy property and where it's better to sell now, because in a few My this will be part of a nice new orogene. But again: Don't take this serious!.

	8. Credits At this point, I wish to thank some people, without whom this service would not have been possible to set up: The makers of GMT (Generic Mapping Tools) Paul Wessel and Walter H.F. Smith. If you want to know more about GMT, a free package of comandline driven graphics and mapping applications, please refer to the GMT website. Martin Weinelt for lots of help with the setup of the perl scripts. Actually this mapping script is a strongly modified version of his Online Map Creation.