Which type of log indicates the arrangement of the formation strata?

The gamma log is the correct choice because it provides critical information about the arrangement of geological strata. The gamma ray logging technique measures the natural radioactivity of the formation, primarily due to the presence of potassium, uranium, and thorium. Different types of rocks emit varying levels of gamma radiation, which allows for the differentiation between various strata based on their radioactivity signatures.

In a typical geological formation, clay-rich formations emit higher gamma radiation compared to sandstones or carbonates, which usually have lower radioactivity. By plotting this data, one can visualize the vertical arrangement of different layers of rock, making it an invaluable tool for understanding the subsurface geology and stratigraphy.

Understanding the arrangement of strata is essential for various applications, including groundwater management, hydrocarbon exploration, and mineral extraction, as it influences porosity, permeability, and overall resource potential.