ASBOG Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

The correct choice is the type of fold known as an anticline, which is defined by its characteristic shape where the limbs of the fold close upward toward the fold axis. In an anticline, the oldest rock layers are typically found at the core of the fold, and the strata dip away from the center, creating an arch-like structure. This formation is a result of compressional forces that cause the rock layers to bend upwards.

The terminology associated with folds helps to further understand the structure: while “syncline” describes a fold where the limbs dip toward the fold axis, creating a trough, “synform” is a broader category referring to any fold with limbs that close upward, without specifying which layer is oldest. Antiformal structures also relate to broader fold concepts but do not specifically designate the upward closing characteristic that defines an anticline. Thus, the defining features of an anticline—limbs that close upward and the location of the oldest rocks—clearly align with the description provided in the question.