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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 5. (May)

First Page: 931

Last Page: 931

Title: Oxygenated Versus Dysaerobic Depositional Environments, Upper Monterey Formation, California: ABSTRACT

Author(s): Frances M. Govean

Article Type: Meeting abstract


Massive and laminated diatomites are the two principal rock types that compose the upper Monterey Formation and reflect deposition under varying oxygen levels. Laminated units are characterized by greenish to yellowish hues, high organic content, lack of burrowing, specific foraminiferal faunas, and good preservation. Massive diatomites are predominantly white to orange in color, are bioturbated, and have high moldic porosity. The foraminifers differ from those found in the laminated units.

A third lithologic type, indistinctly laminated diatomite, occurs predominantly as yellow-gray homogeneous horizons alternating with olive-gray, partly burrowed, laminated bands. The foraminifera are a mixture of the faunas found in the laminated and massive units.

Dysaerobic or aerated conditions at the sediment-water interface during deposition can be interpreted by (1) foraminiferal taxa, (2) sediment color and texture, and (3) trace fossil assemblages.

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