Abstract

The Hurricane Cliffs tongue is proposed as an informal name for a thin (0–30 feet thick) carbonate unit interbedded with clastics and evaporites in the uppermost (Woods Ranch) member of the Toroweap Formation of Lower Leonardian age in northwest Arizona. The carbonate unit represents several brief pulses of marine transgression from west to east during the generally regressive phase of late Toroweap deposition.

The western or more marine facies is dominated by packstones and wackestones containing the shells of a single species of the genus Schizodus. Oolites, often Schizodus-bearing, are also present and appear to be localized along several faults in the area. More nearshore facies represented by aphanitic dolomite are often petroliferous and may show varying degrees of siiicification.

To the east and south, intertidal and supratidal facies appear as stromatolites and gypsum deposits with associated sandstone. The gypsum appears to have been deposited in a coastal sabkha environment. Contorted and gnarlybedded sands are associated with the supratidal deposits, and appear to have formed as a result of syndepositional or post-depositional gypsum removal. This interpretation is supported by the presence of deformation features in the sand and of the stringers of texturally similar sand interbedded with gypsum where gypsum is found in thick sequence. Dune sands prograded over the sabkha deposits in the east.

The contact of the Toroweap with the overlying Kaibab Limestone in some localities shows channels cut into the Toroweap sands. In other areas, angular blocks of Kaibab are found embedded in the contorted Toroweap sandstones, further evidence of gypsum removal and resulting collapse of surrounding rock.