SILICA DIAGENESIS IN THE SANTA CRUZ MUDSTONE (UPPER MIOCENE) LA HONDA BASIN, CALIFORNIA
Published:January 01, 1990
D. El-Sabbagh, Dames Moore, R.E. Garrison, 1990. "SILICA DIAGENESIS IN THE SANTA CRUZ MUDSTONE (UPPER MIOCENE) LA HONDA BASIN, CALIFORNIA", Geology and Tectonics of the Central California Coastal Region, San Francisco to Monterey, Robert E. Garrison, H. Gary Greene, Karen R. Hicks, Gerald E. Weber, Thomas L. Wright
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Opal-CT is the only diagenetic silica phase present in the Santa Cruz Mudstone within a 16 Km long area extending from the city of Santa Cruz north to Davenport, California. The d(101)-spacing values of opal-CT range from 4.11 Angstroms in outcrops within the city of Santa Cruz area, to 4.06 Angstroms in outcrops north of Santa Cruz. Associated with the decrease in d-spacings, the morphology of crystallites making up rosettes of opal-CT (lepispheres) varies from feathery in high d-spacing samples to spiny in low d-spacing samples. The extent of silica diagenesis in the Santa Cruz Mudstone suggests the unit...