Color-coding Gplates geometry exports in gmt plot?

I am trying to plot isochrons that are exported from Gplates at several reconstructed times in my GMT maps, and I want to color code the isochrons based on their age. I know this info is in the Gplates export files, and I was hoping GMT would automatically figure it out when I supply a cpt using -C in gmt plot, ie something like:

gmt plot $isochrons -W0.005i,dashed -C$isochron_age_color.cpt -V

but this does not seem to work, they are all black. Looking at the Gplates exports, I see that the age is in the header row of each isochron in the isochron export file, but there is no Z column in the rows of lat lons for the isochron trace. Is there a way to indicate that the Z column should be taken from the header row in a certain position? For example, here is an isochron from one of the exports:

@D701|40|Seton_etal_2020_Isochrons.gpmlz|Zahirovic_etal_2022_OptimisedMantleRef_and_NNRMantleRef.rot|833|gpml:Isochron|IC|55.9|-999|“TASMAN SEA, LORD HOWE RISE-AUSTRALIA ANOMALY 25y ISOCHRON CG <identity”|GPlates-930671a3-e10c-4836-a3ab-72c6bebf7a3c|801|99|1|1423|25|5|37
151.911907382949 -44.5998189313693
152.718229716401 -45.3964628557164
152.532681479465 -45.6466035012743
153.053169106557 -46.3532948491846
152.910040550203 -46.6248766351768
153.138201981277 -46.8378356026436
154.263569422899 -47.6760773660758

The age of this particular example (55.9) is bolded in the header row but its a bit hard to see.

Many thanks for the help.

  • Peter

In an abstract answer, yes, that must be possible. But I suspect it has to be done with the help of the -a option and I never felt at easy with using it. On the other hand, with the Julia wrapper that is trivial (now even more after a small improvement).

Using the isochrons of Gplates and that French attribute that seems to store the isochrons age, asimple plot can be done with (but strange things are happening with the East Pacific isochrons).

Using GMT

julia> D = gmtread("C:\\programs\\gplates\\GeoData\\FeatureCollections\\Isochrons\\Shapefile\\Seton_etal_2020_Isochrons.shp");

julia> viz(D, Z="att=FROMAGE", C=makecpt(0, 170), coast=true)

1 Like

Fromage. French attribute. Love it.


Hi Joaquim,
Thanks for the suggestion, I have never used the Julia wrapper, I will look into that along with the -a option.

Cheesily simple:

gmt plot -JH15 -B -Rd -Cage.cpt Muller_etal_AREPS_2016_Isochrons/reconstructed_100Ma.gmt -aZ=FROMAGE -png test

(just quickly exported a single snapshot from GPlates for 100 Ma - replace with your own cpt and input file).

Note that this relies on the OGR-GMT format output (which you’ve used) that maps the metadata attributes to fields in the segment headers (see here for details and the usage of the aspatial option in plot).