a string indicating what kind of age should be plotted.
If x has class UPb, type could be one of
either t.75, t.68 (default), t.76 or
t.conc
pch
(optional) plot character
verticals
boolean flag indicating if the horizontal lines of
the CAD should be connected by vertical lines
xlab
x-axis label
colmap
an optional string with the name of one of R's
built-in colour palettes (e.g., heat.colors, terrain.colors,
topo.colors, cm.colors), which are to be used for plotting data
of class detritals.
col
colour to give to single sample datasets (i.e. not of
class detritals)