Abstract

Stratigraphic and facies analysis of the Toroweap Formation have yielded reliable indicators of the paleogeographic conditions that existed in northern Arizona during the Permian. Four depositional environments have been recognized that are based on definitive facies. The four environments and their respective facies laterally from west to east are: 1) Open Marine: skeletal packstone and wackestone, pelletal wackestone, 2) Restricted marine: aphanitic lime mudstone, dolomite mudstone, and quartzose dolomite, 3) Sabkha: gypsum, horizontal and contorted sandstone, 4) Eolian dune: cross-bedded sandstone.

During Permian time a marine transgression encroached upon coastal and continental sabkhas, eventually drowning a large eolian dune field in its eastward advance across northern Arizona, depositing the Toroweap Formation. Eventually the sea slowly withdrew westward and thick westward prograding sabkha and dune facies were deposited over older marine carbonates. Desert conditions prevailed at the eastern edge of the sea as it oscillated east-and westward across northern Arizona. Eolian dunes with south dipping foresets were formed by trade winds blowing toward a paleo-equator which lay to the south of Arizona during the Permian. Extensive coastal and continental sabkhas formed between the restricted marine carbonate deposits characterized by bivalves and gastropods were replaced by shallow open marine carbonates with brachiopods, bryozoans, corals and crinoids. Westward regression was reversed by a rapid marine transgression that resulted in formation of the extensive Kaibab Limestone across the older sabkhas and dune fields of the Toroweap and Coconino formations.