<p> A study of 230 samples of porcelanite and siliceous mudstone from a single stratigraphic section containing all three silica phases in the Sisquoc and Monterey formations, Casmalia Hills, California, tested established models of silica diagenesis. Analysis of composition, silica phase, and d<sub> 101</sub>-spacing using combined EDS/XRF and XRD documented a broad distribution of opal-CT d<sub>101</sub>-spacing values rather than a linear progression for any particular compositional range predicted by prior studies. The data from this thesis study strongly suggest that other variables (e.g., carbonate, organic matter) besides burial depth/temperature and normalized silica:detritus ratios are critical to diagenetic ordering and that the opal-CT d<sub>101 </sub>-spacing and silica content of a single sample cannot be used as a geothermometer. Instead, the maximum opal-CT d<sub>101</sub>-spacing in a set of samples for any normalized silica:detritus ratio in a stratigraphic interval may be useful to determine the minimum temperature or maximum burial depth reached prior to tectonic uplift.</p>
| Identifer | oai:union.ndltd.org:PROQUEST/oai:pqdtoai.proquest.com:1569587 |
| Date | 02 December 2014 |
| Creators | Ijeoma, Idu Opral C. |
| Publisher | California State University, Long Beach |
| Source Sets | ProQuest.com |
| Language | English |
| Detected Language | English |
| Type | thesis |
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