| The western end of Glen Canyon is located near Lees Ferry. The Colorado River canyon cuts through a large structural fold in the rock, called the Echo Cliffs Monocline, exposing shales of the Chinle Formation (stratigraphically beneath the sandstones of the Glen Canyon Group exposed upriver in Glen Canyon). The Chinle Formation consists of shale, mudstone and sandstone formed from muddy sediments deposited by river systems (fluvial environments) in the Late Triassic Period. Fossil logs and stumps preserved in some of the Chinle's Petrified Forest Member show that tropical monsoonal existed in the region when the sediments were deposited (Anderson and others, 2000; Dubiel and others, 1991). |
