Carbon and oxygen isotopic composition of carbonate fluorapatite in the Monterey Formation

Conference · Tue May 01 00:00:00 EDT 1990 · AAPG Bulletin (American Association of Petroleum Geologists); (USA)

OSTI ID:6677241

Leather, J M; Emanuele, G; Kastner, M ^[1]

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1. Scripps Institute of Oceanography, La Jolla, CA (USA)

Studies from organic-rich continental margins have indicated that carbonate fluorapatite (CFA) forms at or just below the sediment surface and, therefore, may record paleoceanography. To investigate this possibility, CFA from the Miocene Monterey Formation in the Santa Maria (SM) and Santa Barbara (SB) basins was analyzed for {delta}{sup 13}C{sub c} and {delta}{sup 18}O{sub c} in the lattice-bound carbonate ion and for {delta}{sup 18}O{sub P} in the phosphate ion. In contrast to modern continental margins, these sections are characterized by low sedimentation rates, but contain high (<5 to >20%) organic carbon contents (possibly related to anoxic bottom-water conditions ). The CFA isotopic data display a more restricted range than the data for dolomites from the same sections. The SM CFA {delta}{sup 13}C{sub c} ({minus}6.7 to {minus}3.4% PDB) and {delta}{sup 18}O{sub c} ({minus}7.8 to {minus}3.5% PDB) values are more depleted than the SB CFA {delta}{sup 13}C{sub c} ({minus}2.5 to 1.8% PDB) and {delta}{sup 18}O{sub c} ({minus}2.9 to 0.9% PDB) values. The {delta}{sup 18}O{sub p} values (15.4 to 20.9 % SMOW) are strongly correlated with the {delta}{sup 18}O{sub c} values and suggest that both record the same diagenetic environment. The content of lattice-bound carbonate in SM CFA (2 {plus minus} 1%) is also lower than in SB CFA (3.5 {plus minus} 1%). The CFA data suggest an early paleoenvironmental or diagenetic signal overprinted by later deeper burial diagenesis, especially in the SM basin where deeper burial and/or greater geothermal gradients were experienced. In addition, within each site there are inverse relationships between {delta}{sup 13}C{sub c} and {delta}{sup 18}o{sub c} and between {delta}{sup 13}C{sub c} and the amount of lattice-bound carbonate that allow various diagenetic environments to be distinguished.

• OSTI ID: 6677241
• Report Number(s): CONF-900605-; CODEN: AABUD
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (USA), Vol. 74:5; Conference: Annual convention and exposition of the American Association of Petroleum Geologists, San Francisco, CA (USA), 3-6 Jun 1990; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
58 GEOSCIENCES
CALIFORNIA
PETROLEUM DEPOSITS
SOURCE ROCKS
DIAGENESIS
APATITES
CARBON 13
CONTINENTAL MARGIN
GEOLOGIC FORMATIONS
OXYGEN 18
CARBON ISOTOPES
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FEDERAL REGION IX
GEOLOGIC DEPOSITS
ISOTOPES
LIGHT NUCLEI
MINERAL RESOURCES
MINERALS
NORTH AMERICA
NUCLEI
OXYGEN ISOTOPES
PHOSPHATE MINERALS
RESOURCES
STABLE ISOTOPES
USA
020200* - Petroleum- Reserves
Geology
&amp; Exploration
580000 - Geosciences