Text-book syncline. It is a pleasure to look at it!

The antyclinal is characterized by having a convex shape towards the upper part. This is because the youngest materials that make up the fold are located in the upper part, while the oldest ones form the core. There are occasions when we cannot determine the age of the materials, and in these cases, it is better to name this structure as antiform.

On the other hand, we have the synclinal fold. Its main characteristic is to be concave towards the upper part. This is because the youngest materials are found in the core, while the oldest ones form the lower part. Similarly to the anticlinal fold, if we do not know the age of the materials, it is better to name this structure as synform.

In summary, both the anticlinal fold and the synclinal fold are types of folds in the Earth's crust, but their shape and arrangement of materials vary depending on whether the ages of the strata involved can be determined. When the age is uncertain, the terms antiform and synform are used to describe these structures.