A SEQUENCE STRATIGRAPHIC ANALYSIS OF MIXED CARBONATE – EVAPORITIC DEPOSITION IN THE HARRISBURG MEMBER OF THE PERMIAN AGED KAIBAB FORMATION, NORTHERN ARIZONA AND SOUTHERN UTAH

The Kaibab Formation is a carbonate system that outcrops across the Grand Canyon Region of northern Arizona and southwestern Utah, and is part of a 3^rd order sequence representing the Leonardian and Guadaloupian series of the upper Permian. The Kaibab Formation was deposited on a broad shallow shelf of the Grand Canyon Embayment. It consists of the Fossil Mountain Member, deposited during a transgression representing open marine conditions overlain by the Harrisburg Member, deposited during a regression representing a sabkha-like, evaporitic environment. A disconformity separates the Permian Kaibab Formation from the overlying Triassic Moenkopi Formation and scattered lenses of fluvial deposits.

Fourteen stratigraphic sections were measured across northern Arizona and southwestern Utah, allowing for the relatively high-resolution regional correlation of four limestone beds within the Harrisburg Member that have been interpreted as four 4^th order sequences (K1-K4). Sequence K1 contains a dolomitic skeletal wackestone at its base with faunas closely related to those of the underlying Fossil Mountain Member and grades upward into a mudstone; it also represents the first beginning of the 3^rd order regression of the Kaibab Sea. The HST of K2 is represented by a dolomitic mudstone interbedded with thin chert layers. Sequence K3 contains a massive mudstone overlain by a disconformity due to subaerial exposure during the FSST represented by angular chert and mudstone clasts in a fine sand matrix. The K4 LST contains red and yellow clays and silts. The HST marks a significant flooding surface and a return of marine faunas, represented by a dolomitic skeletal wackestone-to-packstone containing chertified gastropod fossils. K4 is absent in most localities due to the overlying Triassic unconformity and the present erosional cycle. Facies of the Harrisburg Member are divided into east and west phases. The eastern facies consist of mixed carbonate and clastic deposition. Downdip, the western facies indicate a distinct change to evaporitic conditions, represented by thick gypsum deposits. Further petrographic analysis verifies deposition on a broad carbonate shelf and provides information on the complex diagenetic history of the primary and secondary chert of the Harrisburg Member of the Kaibab Formation.