Three exposures of the Noonday Dolomite in the Clark Mountain thrust complex were studied extensively. Several sections were measured. Local accumulations of orthoquartzite within the dolomite were examined and described. The Noonday in the dark Mountain area is divided into four units and correlated withtthe units originally described by Hazzard (1937) from the southern Nopah Range. The Noonday in the study area represents the eastern feather edge of the formation and defines the eastern end of the Late Precambrian Amargosa Aulacogen, The Noonday represents a short period of quiet shallow subtidal to intertidal stromatolitic sedimentation. The quartzite bodies are interpreted as the filling of a young karst topography by the initial transgression of the overlying Johnnie Formation.