anticline

n. rock structure which descends downward on either side of a central axis (Geology)

In structural geology, an anticline is a fold that is convex up or to the youngest beds. On a geologic map, anticlines are usually recognized by a sequence of rock layers that are progressively older toward the center of the fold because the uplifted core of the fold is preferentially eroded to a deeper stratigraphic level relative to the topographically lower flanks. The strata dip away from the center, or crest, of the fold.
See more at Wikipedia.org...

A convex fold in rock, the central part of which contains the oldest section of rock. See also syncline.