code: def plot_gc(poles, color='g', fignum=1):
      
      for pole in poles:
          pmagplotlib.plot_circ(fignum, pole, 90., color)
docs: plots a great circle on an equal area projection
      Parameters
      ____________________
      Input
         fignum : number of matplotlib object
         poles : nested list of [Dec,Inc] pairs of poles
         color : color of lower hemisphere dots for great circle - must be in form: 'g','r','y','k',etc.
                 upper hemisphere is always cyan