Figure 2

⁴⁰Ar/³⁹Ar age spectrum and normal isochron plot obtained by the stepwise heating analysis of groundmass sample, P2-Lrl. C17004: Laboratory-ID. The error in the age spectrum shows 1 sigma error. Closed circles in the isochron plot are derived from plateau steps while open circles are not. Plateau age and isochron age from the plateau steps correspond well.