Dissertation/Thesis Abstract

A test of diagenetic ordering in siliceous lithofacies, monterey formation, southwestern Casmalia Hills, Santa Maria Basin, California
by Ijeoma, Idu Opral C., M.S., California State University, Long Beach, 2014, 161; 1569587
Abstract (Summary)

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 101-spacing using combined EDS/XRF and XRD documented a broad distribution of opal-CT d101-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 d101 -spacing and silica content of a single sample cannot be used as a geothermometer. Instead, the maximum opal-CT d101-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.

Indexing (document details)
Advisor: Behl, Richard J.
Commitee: Holk, Gregory, Hummel, Greg
School: California State University, Long Beach
Department: Geological Sciences
School Location: United States -- California
Source: MAI 54/01M(E), Masters Abstracts International
Source Type: DISSERTATION
Subjects: Geology, Sedimentary Geology, Geochemistry
Keywords: Casmalia hills, D101-spacing, Monterey formation, Santa maria basin, Silica diagenesis, opal-CT
Publication Number: 1569587
ISBN: 9781321357516
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