Tag Archives: GMT5

Updated geological time scale color palettes

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:

The gradients on cpt-city are usually available in each of the following file formats:

  • Generic Mapping Tools, GMT (cpt)
  • CSS3 gradients (c3g)
  • GIMP (ggr)
  • Gnuplot palette files (gpf)
  • POV-Ray colour map headers (inc)
  • PaintShop Pro’s native format (having the extension PspGradient), which can also be read by Photoshop (psp)
  • The SAO format DS9 (sao)
  • Scalar vector graphics gradients (svg)

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!

Plate boundaries for GMT5’s psxy

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).

I have taken Peter Bird’s plate boundary file  and added these plotting instructions to the indivdual plate boundary line segment headers, for example:

> JF\NA by Peter Bird 1999
> -Sf0.45/3p+t+r

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:

pscoast -Rg -JN180/22 -Dl -A5000 -V -G200 -K -Y4 > Bird_PlateBoundaries.ps
psxy -J -R PB2002_boundaries.gmt -W0.5p,red -O -Sf0.25/3p -Gred -Ba30:."Bird's 2003 Plate Boundaries" >> Bird_PlateBoundaries.ps

Plate boundaries plotted using GMT5’s psxy and fronts specified on line header segments

The file can be downloaded here (please make sure you cite Peter Bird’s paper as original source of the data!). The file is released under the same license as the original data.

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 [0]. Note: By placing -Sf options in the
segment header you can change the front types on a segment-by-segment basis.