White Ledges Formation

The White Ledges Formation is a geologic formation that crops out in central Arizona, US. Detrital [zircon geochronology] establishes a maximum age for the formation of 1726 million years, in the Statherian period of the Precambrian. The formation is typical of quartzites deposited around 1650 million years ago in the southwestern part of Laurentia, the ancient core of the North American continent.

Description

The White Ledges Formation consists of of orthoquartzite. The quartzite is cut by small reverse faults dipping to the north. It is the lowest member of the Hess [Canyon Group] and is disconformably overlain by the Yankee Joe Formation. It overlies and interfingers with the Redmond Formation, which has been radiometrically dated as 1657 ± 3 million years old, and it contains detrital zircons dated to not less than 1726 million years old.
The White Ledges Formation is thought to be sediments deposited in a nearshore tidal and fluvial environment. Together with other formations in the region, it records a long-lived tectonic margin along southern Laurentia through much of the Proterozoic This helps geologists reconstruct the assembly and breakup of supercontinents during this interval of time.

History of investigation

The beds making up the formation were first noted by N.H. Darton in 1925, who assigned them to the Pinal Schist. The White Ledges Formation was first designated by D.E. Livingston in 1969 in his doctoral dissertation and named for the White Ledges, a set of quartzite ridges along the Salt [River (Arizona)|Salt River] canyon north of Globe, Arizona.