1. n. [Geology]

The thickness of a bed or rock body after correcting for the dip of the bed or body and the deviation of the well that penetrates it. The values of true stratigraphic thickness in an area can be plotted and contours drawn to create an isopach map.

See: attitude,  bed,  contour,  isochore,  isopach,  stratigraphy,  true vertical thickness