Influence of depositional environments on origin of secondary carbonates and diagenesis of organic matter, Tertiary basinal units, La Honda basin, Santa Cruz Mountains, California
A comparative study of authigenic carbonates formed in five organic-rich, deep-water units of the La Honda basin indicates that sedimentation rate and degree of bottom-water oxygenation ultimately controlled the timing, chemical environment, mineralogy, and rate of authigenic carbonate formation. Additionally, sedimentation rate and oxygenation of bottom water governed the sequence of diagenetic chemical environments, the degree of preservation of organic matter, and the source bed potential of the basinal units. The conditions necessary for the preservation of organic matter and the development of potentially good source rocks were variable. However, the occurrence of anaerobic bottom waters was the critical element in the development of excellent source rocks (i.e., Twobar Shale Member, Lambert Shale) regardless of the rate of sedimentation or the rate of primary productivity. In contrast, in basinal units characterized by oxygenated bottom waters, high rates of sedimentation, and high rates of primary productivity (Monterey Formation and Santa Cruz Mudstone Member), rapid burial of organic matter promoted highly anaerobic diagenetic environments which decreased the rate of organic matter decomposition, thereby producing units with good potential source rocks.
- Research Organization:
- Swiss Federal Institute of Technology, Zurich
- OSTI ID:
- 6085553
- Report Number(s):
- CONF-890404-
- Journal Information:
- AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States), Vol. 73:3; Conference: AAPG annual convention with DPA/EMD Divisions and SEPM, San Antonio, TX, USA, 23 Apr 1989
- Country of Publication:
- United States
- Language:
- English
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