While it has been a little break over the summer on this blog, I have nevertheless been able to make a few updates related to the geological time color palettes (see this link for the original post). I have added the GTS2004 palettes (epochs and ages) and also the SEPM95 timescale. The color palettes (or *.cpt files) are designed for use with the Generic Mapping Tools (GMT) but can also be loaded in GPlates. On cpt-city, other formats are also available:
Both palettes are still incomplete and require the extension back in geological time or adding eons or epochs. You can find the files on my BitBucket repository (https://bitbucket.org/chhei/gmt-cpts/). Any contribution to extend the individual files or add new timescales (or formats such as for QGIS) will be greatly appreciated!
The color palettes I described in my recent post can also be used with GPlates to color loaded features. Here are three examples which use the static polygon dataset which comes with GPlates. The first is using the GTS2012 chronostratigraphic time scale to color the static polygons by epoch and fill the polygons:
The world colored by geological epoch, filling the static polygons.
The second is just using the same data set and color the line features by geological era:
Coloring the polygons by era in GTS2012 colors.
And the last is a bit Bauhaus-y by coloring everything in black and white according to the Gee & Kent geomagnetic polarity time scale (not that this would make a lot of sense, but as we can do it…):
The world in normal polarity and reverse polarity according to the Gee & Kent geomagnetic polarity timescale (using the filled static polygons).
That planet looks way to boring – hemispherical view of the Earth with the static polygons colored according to a normal (white) and reverse (black) geomagnetic polarity. Again using the Gee & Kent 2007 timescale.
In order to color loaded features by age (and timescale) just add the colorpalettes to the “Draw style” settings (Features -> Manage colouring) like this:
The geological age color palettes can be added to the Draw style (Manage colouring).
Once the new colour palettes are available, they can be assigned to the individual layers either through the layer window or through “Features -> “Manage colouring” .
Such a color assignment is very helpful if you want to make maps in vectorgraphics illustrations by hand and you only have a few polygons to color in. It becomes a massive pain, however, if you want to automate map making, for example, when generating a sequence of paleo-tectonic maps using GMT. So what is needed here is to have that color information not locked up in an image file or as unstructured text, but rather as data file where an RGB value is assigned to a stage/period/eon (as categorical color palette) so that one can use this information in other applications – such as GMT or GPlates, but potentially also QGIS or ArcGIS or Inkscape/GIMP/Photoshop.
The same goes for information about magnetic polarity chrons which are used in plate tectonic reconstructions – a simple assignment of normal/reverse magnetisation to either white or black colors using a certain geomagnetic polarity timescale.
Here are some examples of how the color scales look like when plotted with GMT’s psscale:
GTS 2012 – Eons
GTS 2012 – Eras
GTS 2012 – stages
And the geomag timescale plotted is here:
Snapshot of Gee and Kent (2007) magnetic polarities plotted using the GeeK07.cpt file
I have made a set of CPT files (available as Git repository on my BitBucket site) for the GTS 2012, GTS 2004, and Exxon 88 geological time scales as well as the Gee and Kent (2007) geomagnetic polarity time scale. The files are available under a Creative Commons Share-Alike Attribution License. A zip archive of the data can be downloaded directly through this link. The files should also be incorporated into the fantastic CPT-CITY website over the next weeks.
If you feel like contributing to this work, just fork the Git repository or send me text snippets for the color scales by email.
GMT5‘s psxy offers a nice feature which lets the user designate fronts on a line segment basis – for example if you have a number of normal faults and subduction zone line segments in a multi-segment file, you can give each line a different symbol, depending on to which side the fault dips (left or right in line direction).
for the Juan de Fuca plate subducting under NorthAmerica. With the new header, psxy will now plot a triangle (+t) with a 3pt size (3p) to the right side (+r) of the front, fronts being separated by 0.45cm. And this is how it looks on a Robinson map centered on the dateline, generated with:
Here’s the relevant snippet from the psxy man page for the use of -Sf in segment headers:
-Sf front. -Sfgap/size[+l|+r][+b+c+f+s+t][+ooffset]. Supply distance gap between symbols and symbol size.
If gap is negative, it is interpreted to mean the number of symbols along the front instead. Append +l
or BD+r) to plot symbols on the left or right side of the front [Default is centered]. Append +type to
specify which symbol to plot: box, circle, fault, slip, or triangle. [Default is fault]. Slip means
left-lateral or right-lateral strike-slip arrows (centered is not an option). Append +ooffset to offset
the first symbol from the beginning of the front by that amount . Note: By placing -Sf options in the
segment header you can change the front types on a segment-by-segment basis.