Nankoweap Butte, just to the southeast of the confluence of Nankoweap Creek and its major northern branch, displays the folded Kwagunt and Sixtymile Formations, uppermost sedimentary rock units of the Chuar Group and Grand Canyon Supergroup; folding is identified as the Chuar Syncline, formed by crustal extension and normal faulting on the Butte Fault about 740 million years ago.