The Chuar Syncline is a doubly plunging fold, which means that along the hingeline within the axis of the syncline, beds in some areas (Nankoweap Canyon) dip toward the south, and in other areas (Lava Chuar Canyon), beds dip toward the north.

The Unkar Group lies unconformably upon deeply eroded granites, gneisses, pegmatites, and schists of the Vishnu Basement Rocks.

The Nankoweap and Sixtymile formations together with the Chuar and Unkar groups comprise the Grand Canyon Supergroup.

The thin beds and laminations of it are crinkled in a manner that reflects slumping of the member toward the axis of the Chuar Syncline.

[5][8] The Upper Member of the Sixtymile Formation, which is about 12 m (39 ft), consists of fine-grained fluvial and fanglomeratic sandstone that grades abruptly into sandy conglomerate toward the axis of the syncline.

Massive weathering maroon conglomerate is present in the lower part of the Upper Member.

The transition beds and the basal laminated red sandstone of the Sixtymile Formation lack any fragmental or exotic debris, unlike the overlying strata.

[5][6][8] The strata of the Sixtymile Formation records the accumulation of sediments adjacent to an active fault scarp.

The sandstones and siltstones of the Lower Member are inferred to have accumulated within a lake occupying a basin formed by subsidence of the Chuar Syncline.

The Upper Member consists of fine-grained fluvial and fanglomeratic sandstone and conglomerate that were deposited by a stream that once flowed along the trough of the Chuar Syncline.

[5][6][8] In 2000, the radiometric dating of volcanic ash within the uppermost Walcott Member of the Chuar Group, 1 m (3.3 ft) below the base of the Sixtymile Formation provided a maximum age for its deposition.

[9] However, in 2018, the dating of detrital zircons by Karl Karlstrom[1] established that the Sixtymile Formation as being Cambrian in age, between 520 and 509 million years old.

Thus, the Sixtymile Formation accumulated in lacustrine, fluvial, and shallow marine environment and are preserved within narrow, fault-controlled basins contemporaneous with the accumulation strata of the lower Tonto Group in the western Grand Canyon and Lake Mead regions.