1. n. [Geology]
A contour that connects points of equal thickness. Commonly, the isopachs, or contours that make up an isopach map, display the stratigraphic thickness of a rock unit as opposed to the true vertical thickness. Isopachs are true stratigraphic thicknesses; i.e., perpendicular to bedding surfaces.
See: contour, contour interval, contour map, formation, isochore, reservoir, stratigraphy, true stratigraphic thickness, true vertical thickness