Which method is described as the best and cheapest to estimate the thickness of unit Ps?

• A. Seismic reflection
• B. Structural analysis
• C. Drilling
• D. Radiometric dating

Answer: (B)

The main idea is to use field geometry to measure how thick a layer is without needing expensive equipment. When a unit has clear, exposed top and bottom boundaries and the rocks are dipping at a known angle, you can lay out a cross-section perpendicular to the layering. By measuring the distance between the top and bottom contacts along that cross-section, you obtain the true thickness. If the dip isn’t steep, the measurements along the surface can be readily corrected to the vertical thickness with simple trigonometry, and multiple outcrops can be averaged for reliability. This approach relies on basic field mapping and geometry, so it’s inexpensive and often sufficient, especially for well-exposed, relatively uniform units. Seismic reflection, drilling, and radiometric dating provide valuable data in other contexts, but they’re more costly or not directly tied to thickness measurements in a straightforward way.