The Johnnie Formation is subdivided into five distinct members that are mapped areally for the first time in order to decipher the structurally complex geology within a portion of the Northwest Spring Mountains. Distinctive quartzite and dolomite beds serve as boundaries between the members. The sediments of the Johnnie Formation and overlying Stirling Quartzite were deposited in a nearshore environment in the Cordilleran miogeosyncline which persisted during most of the Paleozoic Era in this part of the Basin and Range Province. Folding and thrusting during the late Mesozoic Laramide Orogeny are responsible for the complex local and regional structural relationships. Two large recumbent folds and related smaller folds represent the earliest effects of deformation; this period of intense folding was accompanied by the development of the Johnnie Thrust, a regional thrust fault which is probably located near the base of the Johnnie Formation, above which the overlying beds have been displaced several miles to the southeast. This interpretation is different from that of T.B. Nolan (1929) who originally described the Johnnie Thrust as occurring at the contact between the Stirling Quartzite and Johnnie Formation. Later or synchronous deformation by right-lateral displacement along the Las Vegas Valley Shear Zone is reflected in the change of trend of cleavage and fold axes in the recumbent folds. Gentle folding unaffected by movement on the shear zone followed. Present deformation is probably continuing along normal faults which have been active since early Tertiary time. This faulting is responsible for the steep topography that has triggered a significant gravity slide involving a large block of Stirling Quartzite which rests with stratigraphic and structural discordance on the lower Johnnie Formation.