Occurrence and formation of dolomite in organic-rich continental margin sediments

Journal Article · Fri Nov 01 04:00:00 EST 1985 · Am. Assoc. Pet. Geol., Bull.; (United States)

OSTI ID:5875645

Baker, P A; Burns, S J

Dolomite is presently forming at rates less than 500 m/m.y. in continental margin marine sediments having organic carbon contents greater than 0.5 wt. %. At higher sedimentation rates, the dolomite content of the sediments is greatly diluted. At lower organic carbon content, the pore-water chemistry precludes dolomite formation. The reactants for dolomite formation have the following sources: magnesium supplied from overlying seawater, calcium supplied by the dissolution of calcium carbonate, and carbon supplied from carbonate dissolution and organic carbon oxidation. The rate of dolomite formation appears to be limited by the rate of calcium carbonate dissolution. This rate can be quantitatively calculated from the magnesium diffusional and advective fluxes. Conversely, in ancient sediments the depth and timing of dolomite formation can be calculated from the amount of dolomite and the sedimentation rate. In dolomite-rich sediments these calculations demonstrate that most of the dolomite formed within a few tens of meters of the sea floor within the zone of microbial sulfate reduction. Such dolomites have negative values of delta/sup 13/C. In dolomite-poor sediments dolomite may form at greater burial depth, below the zone of sulfate reduction, resulting in positive values of delta/sup 13/C. The distribution coefficient of strontium in dolomite has been determined to have an average value of 0.06. Using this value, predicted strontium contents for submarine dolomites range from 150 ppm in dolomite-rich sections to 1,290 ppm in dolomite-poor sections.

• Research Organization: Duke University, Department of Geology, Durham, NC
• OSTI ID: 5875645
• Journal Information: Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 69:11; ISSN AAPGB
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580400* -- Geochemistry-- (-1989)
ALKALINE EARTH METAL COMPOUNDS
ALKALINE EARTH METALS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON
CARBON 13
CARBON COMPOUNDS
CARBON ISOTOPES
CARBONATE MINERALS
CARBONATES
CHEMISTRY
CONTINENTAL MARGIN
DOLOMITE
ELEMENTS
EVEN-ODD NUCLEI
GEOCHEMISTRY
GEOLOGY
ISOTOPE RATIO
ISOTOPES
LIGHT NUCLEI
MAGNESIUM
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
METALS
MINERALOGY
MINERALS
NONMETALS
NUCLEI
ORIGIN
OXYGEN COMPOUNDS
SEAS
SEDIMENTATION
SEDIMENTS
STABLE ISOTOPES
STRONTIUM
SURFACE WATERS