The Middle Cambrian Spence Shale Member contains meter-scale, shallowing-up cycles (parasequences) and record approximately 360 ky of deposition. These meter-scale cycles are nested within transgressive systems tracts (TST) and highstand systems tracts (HST) which reflect different stages of a lower-order, higher-magnitude sea-level excursion. Fossil assemblages are located in stratigraphic positions within the Spence Shale Member that can be predicted on the basis of sequence architecture. The cycle architecture, taphonomy, and geochemistry of the Spence parasequences confirm synthetic sections and theoretical models of meter-scale cycles developed in other studies. Delineation of meterscale cycles, based on taphonomic and sedimentologic criteria, allows high-resolution (100-500 ky) correlation. This study also documented the Cambrian existence of the Tooele and Arco Arches and aided in further understanding paleoenvironmental conditions within the Spence Shale Member.

The Lower Middle Cambrian Langson Formation was studied in the xi Bear River Range of north-central Utah and southeasternmost Idaho and the Wellsville Mountains of north-central Utah. The depositional textures and sedimentary structures preserved within the rocks were compared with characteristics of similar modern sediments and ancient rock to determine environments of deposition, paleogeography, diagenetic alteration and pattern of dolomitization. The rocks of the Langston Formation were divided into eleven different rock types. These eleven rock types were formed within four recognizable lithofacies: 1) upper peritidal; 2) inner carbonate shelf; 3) inner clastic shelf; and 4) outer clastic shelf. The general depositional environment is inferred to have been a shall ow subtidal to subaerial carbonate shoal complex. Clastic sediments from the east and north or northwest periodically prograded over the carbonate complex during times of relatively slow subsidence. The deposition of the Langston Formation mudrocks and carbonates occurred during the first Cambrian grand cycle. Eogenetic diagenetic features include birdseye structures, relict evaporite structures, fibrous rim cement, compaction, and the begining of dolomitization. Mesogenetic diagenesis is characterized by dolomitization and pressure solution. Telogenetic diagenesis is limited to fracturing and calcite infilling. Dolomitization is believed to have resulted mainly from downward reflux of hypersaline brines, as indicated by relict evaporite structures, zoned dolomite rhombs, and a general association of dolomite with upper peritidal facies. The hypersaline brines formed in the upper peritidal environment, and percolated downward through underlying porous sediments. The greater density of the hypersaline brines displaced less-dense interstitial fluids. These brines were periodically diluted by normal marine water or fresh water.