Date of Award:

1989

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Geology

Advisor/Chair:

Peter T. Kolesar

Abstract

Six major generations of dolomite are present within the Cambrian Langston Formation in the Wellsville Mountains and Bear River Range of northern Utah. Identification of dolomite generations and delineation of their relative sequences are based on normal light petrography, cathodoluminescence, staining, chemistry, inferred burial history, and deformation features. The earliest stage is believed to be Middle to Late Cambrian in age. The presence of dolomite rhombs and dolomitized echinoid fragments and peloids suggests that this stage probably formed under sabkha reflux conditions. Extensive nonferroan, polymodal, nonplanar ("xenotopic") dolomite formed next under confined mixing zone conditions. A succeeding generation of pervasive ferroan, polymodal, nonplanar dolomite formed upon exposure to evolved confined mixing zone waters or fluids derived from basin compaction. Subsequent neomorphism of these two nonplanar stages to nonferroan and ferroan saddle dolomites occurred with increased burial. The final stage of dolomitization is confined to dolomite-filled veins and an orthodolospar probably fanned from fluids associated with Tertiary Basin and Range faulting. Thus, there are at least six major types of dolomite within the Langston Formation. Spatial distribution and intensity of the early-formed dolomite facies, as revealed by fence diagrams, are postulated to be functions of changes in permeability, hydrodynamic dispersion, water chemistry, and concomitant variations in length of the induction ix stages.

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