Multicycle Holocene dolomite in cool-water carbonate sediments Lacepede Shelf, South Australia

Conference · Fri Mar 01 04:00:00 EST 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:5904472

Bone, Y ^[1]; James, N P ^[2]; Kyser, T K ^[3]

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1. Univ. of Adelaide (Australia)
2. Queen's Univ., Kingston, Ontario (Canada)
3. Univ. of Saskatchewan, Saskatoon (Canada)

Modern carbonate sediments on the Lacepede Shelf contain up to 10% dolomite particles, as either single rhombs or clusters. The rhombs vary from sharply edged crystals and nonabraded to slightly worn to completely rounded rhombs. These groups probably represent different times of formation and transportation during Holocene glacioeustatic sea-level changes. The abraded aggregates that are loosely cemented by calcite occasionally have pristine rhombs attached. Color varies from transparent and colorless or light orange to dark red, without apparent pattern. Cathodoluminescence shows distinctive zoning, analogous to nearby mid-Cenozoic dolomites. Similarly the dolomite is Ca-rich (43 mole % Mg). It occurs within bryozoan-bivalve sediments that are a mixture of relict and modern bioclastic components, across the entire shelf, from siliciclastic sediments debouching from the Murray River to completely carbonate sediments at the shelf edge. Greatest concentrations are fund adjacent to seafloor highs, sites of abundant bryozoan, sponge, and coralline algae growth. Stable isotope values, however, are compatible with precipitation from seawater, similar to those of associated living brachiopods and Mg-rich bryozoans. Sr isotopes confirm the time of formation as modern, unlike the mid-Cenozoic time of formation for similar Tertiary dolomites. These multicycle rhombs and rhomb clusters may therefore be the nucleii for epitaxial precipitation of dolomite either on the modern sea floor or later during burial.

• OSTI ID: 5904472
• Report Number(s): CONF-910403--
• Conference Information: Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Journal Volume: 75:3
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AGE ESTIMATION
ALKALINE EARTH ISOTOPES
AUSTRALASIA
AUSTRALIA
CARBONATE MINERALS
CARBONATE ROCKS
CENOZOIC ERA
CONTINENTAL MARGIN
CONTINENTAL SHELF
CRYSTAL STRUCTURE
CRYSTALLOGRAPHY
DEVELOPED COUNTRIES
DOLOMITE
GEOLOGIC AGES
GEOLOGY
GRAIN SIZE
ISOTOPE DATING
ISOTOPES
MICROSTRUCTURE
MINERALOGY
MINERALS
PRECIPITATION
QUATERNARY PERIOD
ROCKS
SEDIMENTARY ROCKS
SEPARATION PROCESSES
SIZE
SOUTH AUSTRALIA
STRATIGRAPHY
STRONTIUM ISOTOPES