Chevron fold in <a href="https://en.wikipedia.org/wiki/Upper_Carboniferous" class="extiw" title="en:Upper Carboniferous">Upper Carboniferous</a> shales, Hagen-Vorhalle, Germany
<a href="//commons.wikimedia.org/wiki/User:Jo_weber" class="mw-redirect" title="User:Jo weber">Jo Weber</a>
CC BY-SA 3.0
<span class="int-own-work" lang="en">Own work</span>