I am seeking a word to describe horizontal lines (1D) cut parallel to the (mean) ground surface. The context I need it for is a plot of some variable along a horizontal line at a specific depth below the ground. 

In geology, vertical sections (2D) are called cross-sections, but there is no other word for horizontal sections (happy to be proved wrong!). Vertical profiles (1D) are also called sections as well in some cases, but there is no word I can think of for a horizontal profile. 

Isoline, cut line, horizontal profile, something else?