Which map type specifically shows thickness of a stratigraphic interval by isopach contours?

• A. Bedrock Map
• B. Isopach Map
• C. Topographic Map
• D. Isoplets

Answer: (B)

Mapping how thick a sedimentary interval is across an area uses lines that connect points of equal thickness, called isopach contours. An isopach map collects thickness measurements from boreholes, cores, or measured sections and draws contour lines where the thickness is the same, revealing where the interval thickens or thins. This focused depiction specifically communicates stratigraphic thickness, which is different from bedrock maps that show rock types, or topographic maps that depict surface elevation and terrain shape. While lines of equal value (isopleths) exist for various properties, the term isopach is the standard and precise label for thickness of a stratigraphic interval.