The Middle Cambrian Ute Formation includes some 200 m of cyclically alternating carbonates and mud rocks. These are arranged in eight to nine, meter-scale, shallowing-upwards packages, representing deposition under predominantly subtidal conditions. The packages consist of vertical sequences of shale, silty limestone, oncolitic packstone, and oolitic grainstone that exhibit little variance in this general pattern. Small-scale unconformities separate the packages. The inferred depositional environment consists of an intrashelf basin that has a peritidal platform near its margins. The craton, which supplied most of the terrigenous sediment, was situated to the south (Cambrian orientation), and located near the equator. One cycle includes a stromatolite biostrome that is distributed across more than 1500 km2 in northern Utah and southern Idaho. Stromatolites range from mound-like to club-shaped to columnar and reach up to 2 min vertical dimension, and 0.15 min diameter. These large columnar structures were apparently established just basinward of an oolitic shoal. These ancient stromatolites, which are in many ways similar to those stromatolites recently reported from the Bahamas, contain many clues that suggest that they grew in normal marine conditions. These findings require a rethinking of the commonly held belief that Phanerozoic columnar stromatolites are indicators of restricted, hypersaline conditions. Analysis of several orders of laminae in Ute Formation stromatolites indicates periodicity in accumulation from which yearly accumulation rates may be inferred. Values obtained for growth rate range from 4.39-4.88 cm/yr. Such rates of accumulation are in accord with those documented for ancient stromatolites from the Bitter Springs Formation. Thus, even considering the occurrence of hiatal surfaces within the stromatolites, the duration of the columnar-stromatolite horizon probably encompasses 10-2 - 10-3 yr. The biostrome's position in the sequence of cycles and the changes in stromatolite morphology across depositional dip suggest that the biostrome may be essentially isochronous across its outcrop area and, thus, may be viewed as a bioevent horizon. The stromatolites also contribute to a better understanding of the paleogeography of the study area during the Middle Cambrian by providing information on relative energy levels and flow directions. (212 pages)

This thesis demonstrates that geological setting, depositional facies, open system flux of hot basinal brines and descending of shallow waters have a strong impact on the distribution of the diagenetic alterations within continental and paralic/shallow marine sandstones which in turn control the quality and heterogeneities of the reservoirs. Geological setting controls the mineralogical and textural maturity of sandstone, whereas depositional facies control the pore water chemistry (marine, brackish or meteoric), sedimentary texture and sand body geometry. Eogenetic alterations in the fluvial deposits are dominated by precipitation of infiltrated clays, kaolinitization of detrital silicates, whereas the shallow marine deposits are dominated by precipitation of early calcite and kaolinite. Conversely mesogenetic alterations are dominated by clay minerals transformation, quartz overgrowths and Ferroan- carbonates, barite and anhydrite. Flux of hot basinal brines is evidenced by precipitation of mesogenetic minerals that lack of internal sources (e.g. barite, anhydrite and ferroan carbonate cements), which is evidenced by: (1) restricted occurrence of these minerals in downthrown blocks. (2) The high fluid inclusion homogenization temperatures (Th) of quartz overgrowths (Th &gt; 110-139°C), and carbonate cements (T &gt; 80-140°C), which also have light δ18OV-PDB(-17.6‰ to -6.7‰). Flux of hot basinal brines is further evidenced by occurrence of saddle Fe-dolomite along stylolites. Fluid inclusion microthermometry further revealed a dramatic shift in pore- water chemistry from NaCl dominated brines during precipitation of quartz overgrowths to NaCl-CaCl2 dominated brines during cementation by Fe-dolomite. Presence of mixed brine (NaCl+CaCl2) systems in the fluid inclusions suggests flux of descending waters, which have circulated in the overlying carbonate-evaporite successions. The restricted occurrence of oil- filled inclusion to quartz overgrowths and methane to Fe-carbonate cements suggest migration of oil during precipitation by quartz and migration of methane during precipitation by Fe- carbonate cements. The extensive mesogenetic cements in the down thrown blocks is attributed to flux of basinal brines along deep seated faults, i.e. open system diagenesis. Integration of fluid inclusion microthermometry, isotopes, Raman spectrometry and thermal tectonic evolution of basins are essential techniques for unraveling the evolution of basinal fluids, cementation conditions and relative timing of hydrocarbons migration. / <p>Errata: Felaktigt disputationsdatum på spikbladet.</p>