Boneyard Hollow is a small canyon in <a href="https://en.wikipedia.org/wiki/Dolliver_Memorial_State_Park" class="extiw" title="w:Dolliver Memorial State Park">Dolliver Memorial State Park</a>, just south of <a href="https://en.wikipedia.org/wiki/Fort_Dodge,_Iowa" class="extiw" title="w:Fort Dodge, Iowa">Fort Dodge, Iowa</a>.  The upper part of the canyon wall is <a href="https://en.wikipedia.org/wiki/sandstone" class="extiw" title="w:sandstone">sandstone</a> with clear <a href="https://en.wikipedia.org/wiki/cross-bedding" class="extiw" title="w:cross-bedding">cross-bedding</a>.  This sits on top of impermiable <a href="https://en.wikipedia.org/wiki/mudstone" class="extiw" title="w:mudstone">mudstone</a>, the surface of which is very wet because of water seeping out of the base of the sandstone layer.  All of the rocks are <a href="https://en.wikipedia.org/wiki/Pennsylvanian_(geology)" class="extiw" title="w:Pennsylvanian (geology)">Pennsylvanian</a>, some of the northernmost exposures of the the <a href="https://en.wikipedia.org/wiki/Cherokee_Group" class="extiw" title="w:Cherokee Group">Cherokee Group</a>.
<a href="//commons.wikimedia.org/wiki/User:Douglas_W._Jones" title="User:Douglas W. Jones">Douglas W. Jones</a>
<span class="int-own-work" lang="en">Own work</span>