Which geological structure involves older rock formations situated at the core?

The correct answer is the anticline. An anticline is a type of geological structure characterized by a convex-upward fold, where the oldest rock layers are situated at the core or center of the fold. This occurs during tectonic processes where compressional forces push the rock layers upward and create a dome-like shape. As the layers are folded upwards, the younger rock strata are found on the periphery, while the older, more established layers are exposed at the center.

In contrast, a syncline is a folded structure that is concave upward, which means it has the youngest rocks at the core. A fault zone refers to a region where rock fractures or displacements have occurred, but it does not specifically relate to the arrangement of rock ages. A rift valley is formed due to the pulling apart of tectonic plates, resulting in a downward displacement of the land, which also does not involve the layering of rock ages in a folding structure like an anticline does. Thus, identifying an anticline emphasizes the significance of rock age stratification in geological formations.