Modern cool-water siliciclastic/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:5751150

Bone, Y; Gostin, V ^[1]; James, N P ^[2]; Von der Borch, C C ^[3]

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1. Univ. of Adelaide (Australia)
2. Queen's Univ., Kingston, Ontario (Canada)
3. Flinders Univ., Bedford Park (Australia)

The Lacepeded Shelf is a 130 km {times} 100 km open embayment along the southern passive continental margin of Australia. The shelf includes the mouth of the River Murray - Australia's largest drainage system- the extensive arcuate Coorong strand, the 50-70 m deep and flat plateau of the shelf proper, the nonrimmed shelf break, and the upper slope to depths of 200 m. The shelf bathymetry is locally interrupted by seafloor highs, reflecting the underlying rugged terrain of deformed Precambrian and early Paleozoic bedrock in the west and Tertiary limestones and Quaternary dunes in the east. The late Pleistocene/Holocene sediment blanket is formed by discrete sedimentary facies. Quartz sands cover a significant cross-shelf zone opposite the river mouth, with current generated offsets. High-resolution seismic profiles reveal buried lowstand channels. The mid-shelf is an area of conspicuously coarse-grained, mud-free loose sediments composed of variable amounts of bryozoans and bivalves. The shelf break and upper slop bryozoan sands are similar, apart from species differences, from 40 to 100 m, with an increase in mud below 100 m. The seafloor highs are sites of prolific bryozoan, calcareous algae, sponge, and bivalve growth, the skeletons of which are shed onto the shelf. Bryozoan distribution is moderated by water depth and substrate type. Most forms are low-Mg calcite to high-Mg calcite, but two major groups are aragonitic. Distribution of these different mineralogical types is important for later diagenesis. Both terrigenous clastic and carbonate sediments are a mixture of relict and modern components, depending upon location, and reflect Holocene glacio-eustatic sea-level changes.

• OSTI ID: 5751150
• 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
AUSTRALASIA
AUSTRALIA
BATHYMETRY
CENOZOIC ERA
CONTINENTAL MARGIN
CONTINENTAL SHELF
DEPOSITION
DEVELOPED COUNTRIES
GEOLOGIC AGES
GEOLOGY
GEOPHYSICAL SURVEYS
LITHOLOGY
MINERALOGY
MINERALS
OXIDE MINERALS
PALEONTOLOGY
PLEISTOCENE EPOCH
QUARTZ
QUATERNARY PERIOD
SEDIMENTS
SEISMIC SURVEYS
SOUTH AUSTRALIA
STRATIGRAPHY
SURVEYS