The Nounan Formation in north-central Utah thickens northward from 696 feet near Causey Dam to 1147 feet at High Creek in the Bear River Range, and northwestward to 1149 feet at Dry Canyon in Wellsville Mountain. The basal contact of the Nounan Formation is sharp, but dolomite extends irregularly downward into limestones of the Bloomington Formation as much as 6 feet. The Nounan Formation is divided into three members based on lithologic characters: (1) a lower member composed of dark, medium-crystalline dolomite; (2) a middle member composed of white, coarse-crystalline dolomite with tongues of dark dolomite; and (3) an upper member of interbedded light and dark dolomites and limestones with local arenites and sandy carbonates. The lower member was deposited in a high-energy, shallow-marine subtidal to intertidal environment. Evidence includes sets of low-angle cross stratification (dunes), oncolites, oolites, and rip-up clasts. The middle member forms distinctive ledges and cliffs. The presence of thinly laminated algal stromatolites and relict structures seen also in the lower member indicate a subtidal to intertidal environment similar to that inferred for the lower member. The white color and coarse crystallinity may have resulted from recrystallization of the dark, finer grained dolomite that comprises the lower member. The upper member is characterized by lithologic variability. Thicknesses of limestone are greatest in the north, and decrease to only a few feet in the south. Quartz and other terrigenous minerals are scattered at intervals throughout the upper member, with a marker of sandy (arenaceous) dolomites at the base and near the middle and an increase of sand near the top also. The upper contact, with quartz-rich arenites (subarkosic quartzites) of the Worm Creek Member of tho St. Charles Formation, is gradational overall, but is sharp and planar in each section and readily located. In the upper member, algal mats trapped a varying but overall increasing influx of quartz and feldspar, probably in shallow subtidal environments, and vertically stacked hemispheroids suggest that depositional conditions may have included intertidal. Virtually all of the dolomite in the Nounan Formation must have formed by replacement of lime sediments by downward-moving high-magnesium brines. It is that these brines originated in restricted, shallow, subtidal evaporating basins, such as the Great Bahama Banks today, and associated supratidal flats. Lateral changes from limestone to dolomite overall and also in individual beds of the upper member indicate that the brines travelled laterally as well as vertically, and dolomitization may have been limited as much by prior diagenetic alteration and cementation as by the volume, concentration, and proximity of the brine itself.

The Swan Peak Formation in southeastern Idaho and north-central Utah is a sedimentary unit consisting of orthoquartzite, sandstone, siltite, shale, and limestone. The formation is divisible into three members, and the lower two members each are divisible into two informal lithologic subunits. The lower member consists of a lower subunit of gray, calcareous sandy siltite composed of subangular to subrounded quartz grains cemented by quartz overgrowths, calcite, or iron oxide, and an upper subunit of black shale with minor interbedded silty quartzose sandstone and biomicrite (limestone). The middle member consists of a lower subunit of interbedded pale green shale and yellowish brown silty orthoquartzite and an upper subunit of purple orthoquartzite. The brown orthoquartzite consists of well-sorted, well-rounded very fine sand- to silt-sized quartz grains cemented by quartz overgrowths which are in optical continuity with the grains they surround. The purple orthoquartzite consists of wellsorted, well-rounded, very fine to medium sand-sized quartz grains cemented by quartz overgrowths and hematite. Hematite gives the rock its purple color. gydroxylapatite is locally abundant. The upper member is an orthoquartzite consisting of very fine to medium sand-sized, well-sorted, well-rounded quartz grains cemented by quartz overgrowths. The gastropod Murchisonia (Hormotoma) sp., the first body fossil found in the upper member, is reported. Previous work has shown that the upper member of the Swan Peak Formation and the Eureka Quartzite are similar in lithology, stratigraphy, and trace fossils. The Eureka Quartzite in the Newfoundland Range is a very fine to medium sand-sized, well-sorted, well-rounded orthoquartzite cemented predominantly by quartz overgrowths, locally by dolomite. The petrographic similarities of the two units, shown in the present study, strengthens their proposed correlation. High percentages of well rounded, polycrystalline and undulatory extinction quartz show that source areas for the Eureka Quartzite and Swan Peak Formation probably were immature sandstones or quartzites of Cambrian or Precambrian age, and./or exposed igneous or metamorphic rocks. The source for most of the sand probably was the Northwest Montana Uplift, although local sources along the Uinta Uplift undoubtedly played a minor role in supplying hydroxylapatite to the middle member and fine-grained elastics to the lower member.

The Middle Cambrian Ute Formation was studied in the Bear River Range and the Wellsville Mountains of north-central Utah and southeastern Idaho. The depositional textures and sedimentary structures found within the rocks were compared with similar modern sediments and ancient rocks to determine depositional environments, paleogeography, and diagenetic alterations. The rocks of the Ute Formation were divided into five basic types. These five rock types were formed within four identifiable lithofacies: 1) elastic marine shelf; 2) carbonate marine shelf; 3) agitated shoal; and 4) quiet-water shoal. The sequence of elastic and carbonate sediments is believed to have been deposited in a shallow, subtidal environment. Clastic sediments from the east and northwest periodically prograded over the carbonate sequences. A major regression marks the base of the Ute Formation. This was followed by a series of transgressions and regressions, until a major transgression occurred near the end of the deposition of the Ute. Paleomagnetic and faunal evidence suggest the study area was within 10° of the equator during the Middle Cambrian. Clay mineralogy of insoluble residues indicates a humid, tropical climate. Primary diagenetic features are compaction, micritization, and cementation. Secondary diagenetic changes include the inversion of high-magnesium calcite to low-magnesium calcite, aggrading neomorphism, stylolitization, fracturing, and calcite infilling. Partial dolomitization of grains and/or matrix is believed to result from the release of magnesium due to the decomposition of magnesium-rich, organic matter. The formation of a lens-shaped body of dolostone may have resulted from dolomitization by a magnesium-rich fluid circulating along faults.

The Mississippian (Kinderhookian-Osagean) Lodgepole Formation contains a diverse fossil assemblage. Taxa present include brachiopods, crinoids, gastropods, cephalopods, trilobites and corals. Corals and associated fauna were collected from four localities within the Bear River Range. These are, from north to south, Beirdneau Hollow, Spring Hollow, Leatham Hollow and Porcupine Dam. The well-preserved tabulate and rugose (compound and solitary) corals exhibit a high degree of morphologic variability. The colonial corals of the Lodgepole Formation (particularly Lithostrotionella, Syringopora) exhibit a morphologic gradient from platy to hemispherical forms. The six morphologic categories of colonial corals discussed in this study are identified by mean corallus diameter/corallum height ratios, by the corallite growth direction, and by the shape of the base of the colony. Type I corals have an average mean diameter/height ratio of 3.4; corallites are directed laterally away from the flat base. Type I corals are interpreted to have been adapted to offshore, quiet-water conditions. Type II corals are flattened hemispheres; they have an average mean diameter/height ratio of 4.1. Corallites are directed radially (i.e., with vertical as well as a lateral component) away from the flat colony base. Type II corals are interpreted in this study to have been adapted to shallow, moderately-turbulent environments in which vertical growth was inhibited. Type III corals have an average mean diameter/height ratio of 3.9 and are similar to Type II corals in all respects but one, namely that there is an absence of corallites on the crown of the corallum. This feature is called balding and is interpreted in this study to have been the result of desiccation and subsequent death of coral polyps. Type III corals are thus interpreted to have inhabited very shallow water wherein subaerial exposure of the crown of the corallum occurred during periods of exceptionally low tides. Type IV corals are dome-shaped or slightly-flattened hemispheres; they have an average mean diameter/height ratio of 2.3. Corallites are directed radially away from the flat base. Type IV corals are interpreted to have inhabited a depth zone intermediate between that of Type II corals (within or barely below tidal range) and Type I corals (near or below wave base). The average mean diameter/height ratio of Type V corals is 1.7. Corallites are directed almost entirely vertically away from the rounded-to-conical colony base. Type V corals are interpreted to have inhabited areas where sedimentation rates were sufficiently high to encourage vertical growth to the virtual exclusion of lateral growth. Type VI corals are composite corals, consisting of combinations of hemispherical forms and platy forms. This morphologic type is characterized by a change in the direction of growth during the astogenetic development of colony. The combinations of varying growth forms presumably reflect fluctuations in sedimentation rate.