The morphometry of small volcanic shields on Venus is used to assess stratigraphic relationships and the thickness of regional volcanic plains. Comparison of shield width and height in three different regions supports the interpretation that plains with shields form a distinctive stratigraphic unit (Psh) that is subsequently embayed and flooded by younger regional plains with wrinkle ridges (Pwr), leaving lava shield kipukas among the plains near the contact. Differences in shield morphometry in the two units show that Pwr averages less than ~150 m in these three embayed areas, and where the underlying shields disappear, the minimum thickness of Pwr is likely to be in excess of ~400 m. This technique can be applied elsewhere on Venus in order to provide improved estimates of the total volume of regional plains. ¿ 1999 American Geophysical Union