At and just above the contact with undeformed strata of the underlying Aztec Siltstone, the Metschel Tillite is deformed into textbook, imbricately stacked, soft-sediment thrust sheets up to 15 metres (49 ft) thick.
These thrust sheets were caused by the north-eastward advance of grounded ice into a glaciomarine setting during a Late Paleozoic icehouse glacial epoch.
These sedimentary strata contain calcrete, fining-upward cycles, red beds, rootlet horizons, mudcracks, and conchostracan fossils, which indicates that they were deposited in floodplains and channels of rivers and streams.
In addition, abundant fossil fish were excavated from near the top of the Aztec Siltstone, including Bothriolepis, Groenlandaspis, and Turinia gondwana.
[7][8] The Wellner Coal Measures at Mount Ritchie contain abundant Permian leaf, root, petrified wood, and other plant fossils.