Silica diagenesis in Monterey Formation: controls and application

Conference · Fri May 01 04:00:00 EDT 1987 · AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States)

OSTI ID:5993149

Kablanow, II, R I

The factors controlling diagenesis of biogenic silica (opal-A to opal-CT to quartz) in the Monterey Formation of California has been an ongoing subject of study. The accepted concept proposes that a high detrital content inhibits the opal-A to opal-CT reaction, whereas it accelerates the opal-CT to quartz reaction. Others have suggested that clay minerals directly influence the rate of silica transformation by the adsorption of silica from solution. It is proposed that the primary control on silica diagenesis is the thermal regime of the basin. Important variables which influence the temperature development include time, sediment accumulation rate, burial depth, porosity, thermal conductivity, temperature of silica phase change, and heat flow. The Miocene Monterey Formation had fairly rapid sedimentation rates which produced a thick section of fine-grained sediments (up to 13,000 ft, 4 km, in the Salinas basin). As these sediments underwent progressive burial, both compaction and silica transformation reduced porosity, resulting in an increase in thermal conductivity. To simulate the thermal, depositional, and diagenetic events, detailed thermal models were used. These models clearly reflect the difference in the geologic history observed between the Huasna, Pismo, and Salinas basins. The thermal models used in this study strongly confirm that silica diagenesis is primarily dependent on the temperature structure of a basin and that any catalytic influence which detrital minerals may have on silica diagenesis is a second-order effect and does not alter the regional reaction boundaries. These models can also be used as powerful tools in hydrocarbon exploration by providing a clearer picture of the thermal development of the basin.

• Research Organization: NC Programming, Coulterville, CA
• OSTI ID: 5993149
• Report Number(s): CONF-870606-
• Conference Information: Journal Name: AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States) Journal Volume: 71:5
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
CALIFORNIA
CENOZOIC ERA
CHALCOGENIDES
DIAGENESIS
FEDERAL REGION IX
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FORMATIONS
MATURATION
MINERAL RESOURCES
MINERALS
NORTH AMERICA
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PETROLEUM DEPOSITS
RESERVOIR ROCK
RESOURCES
SILICA
SILICON COMPOUNDS
SILICON OXIDES
TERTIARY PERIOD
USA