What map shows areal variations in facies of a given stratigraphic unit?

• A. Facies map
• B. Isofacial map
• C. Isopach map
• D. Facies distribution map

Answer: (D)

Mapping lateral changes in sedimentary facies within a single stratigraphic unit is about showing where different facies types occur across the area. A facies distribution map does exactly that—it charts which facies appear where, revealing how environments change in space and how facies are arranged relative to one another. This makes it the best choice for illustrating areal variations in facies. It differs from an isopach map, which shows thickness variations, and from an isofacies map, which focuses on the extent of one particular facies type rather than the full mix of facies present.