Modern cool-water siliciclastic/carbonate sediments, lacepede shelf South Australia
- Univ. of Adelaide (Australia)
- Queen's Univ., Kingston, Ontario (Canada)
- 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-; CODEN: AABUD
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 75:3; Conference: Annual meeting of the American Association of Petroleum Geologists (AAPG), Dallas, TX (United States), 7-10 Apr 1991; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
Similar Records
Paleoecology of cool-water, subtidal cycles in mid-cenozoic limestones, Eucla Platform, Southern Australia
Complex-mixing dolomitization of supratidal deposits, Ambergris Cay, Belize, Central America
Related Subjects
CONTINENTAL SHELF
SEDIMENTS
STRATIGRAPHY
DEPOSITION
MINERALOGY
SOUTH AUSTRALIA
BATHYMETRY
LITHOLOGY
PALEONTOLOGY
PLEISTOCENE EPOCH
QUARTZ
QUATERNARY PERIOD
SEISMIC SURVEYS
AUSTRALASIA
AUSTRALIA
CENOZOIC ERA
CONTINENTAL MARGIN
DEVELOPED COUNTRIES
GEOLOGIC AGES
GEOLOGY
GEOPHYSICAL SURVEYS
MINERALS
OXIDE MINERALS
SURVEYS
580000* - Geosciences