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Geomorphology and evolution of the gigantic Murray canyons on the Australian southern margin

Hill, PJ; De Deckker, Patrick; Exon, N.F.

Description

The Murray canyons are a group of deeply incised submarine canyons on a steep 400 km section of the continental slope off Kangaroo Island, South Australia. Some of the canyons are amongst the largest on Earth. The canyons, some 80 km long, descend from the shelf edge to the abyssal plain 5200 m deep. Sprigg Canyon, the deepest and one of the largest, has walls 2 km high. The thalwegs of the larger canyons are concave in profile, steepest on the upper continental slope (15-30°), with about 4°...[Show more]

dc.contributor.authorHill, PJ
dc.contributor.authorDe Deckker, Patrick
dc.contributor.authorExon, N.F.
dc.date.accessioned2015-12-13T22:27:04Z
dc.identifier.issn0812-0099
dc.identifier.urihttp://hdl.handle.net/1885/73775
dc.description.abstractThe Murray canyons are a group of deeply incised submarine canyons on a steep 400 km section of the continental slope off Kangaroo Island, South Australia. Some of the canyons are amongst the largest on Earth. The canyons, some 80 km long, descend from the shelf edge to the abyssal plain 5200 m deep. Sprigg Canyon, the deepest and one of the largest, has walls 2 km high. The thalwegs of the larger canyons are concave in profile, steepest on the upper continental slope (15-30°), with about 4° gradient on the mid slope, then level out on the lower slope to merge with the 1° continental rise. Between canyons, the continental slope is slightly convex to linear with a gradient of about 5-6°. Canyon walls commonly slope at 15-22°. The passive continental margin narrows to 65 km at the Murray canyons and links the Bight and Otway Basins. West-northwest-trending Jurassic-Cretaceous rift structures control the irregular shape of the central canyons. At the western end, large box canyons, 1 km deep, are incised into thick sediments of the Ceduna Sub-basin. Formed by headscarp erosion, some of these canyons have coalesced by canyon capture. The upper parts of most canyons are cut into Cretaceous sediments and in some places are floored by basement rocks. Large deep-water holes, spaced about 5 km apart and up to several hundred metres deep, along the outlet channels of the larger and steeper canyons were probably gouged by turbidity currents resulting from major slope failures at the shelf edge, but may be sites of fluid discharges. Quaternary turbidites were deposited on the abyssal plain more than 100 km from the foot of slope. Canyon downcutting has been episodic since the latest Cretaceous, with peak activity since the Oligocene due to strong glacioeustatic fluctuations and cycles. Canyon development occurred during lowstands and early in transgressions when sediment input at the shelf edge was usually highest. The timing of canyon development is linked to major unconformities in adjacent basins, with downcutting events recorded or inferred during the early Paleocene, Middle Eocene, Early Oligocene, Oligocene/Miocene transition (ca 24 Ma), Middle Miocene (ca 14 Ma) and latest Miocene-Pleistocene. The early phases involved siliciclastic sediments only, while post-Early Eocene canyon cutting was dominated by biogenic carbonates generated on the shelf and upper continental slope. The Murray River dumped its sediment load directly into Sprigg Canyon during extreme lowstands of the Late Pleistocene when the Lacepede Shelf was mostly dry land.
dc.publisherBlackwell Publishing Ltd
dc.sourceAustralian Journal of Earth Sciences
dc.subjectKeywords: submarine canyon; Australasia; Australia; Eastern Hemisphere; World Bight Basin; Continental margin; Geomorphology; Lacepede Shelf; Multibeam sonar; Murray canyons; Murray River; Otway Basin; Piston core; Submarine canyon; Turbidites
dc.titleGeomorphology and evolution of the gigantic Murray canyons on the Australian southern margin
dc.typeJournal article
local.description.notesImported from ARIES
local.description.refereedYes
local.identifier.citationvolume52
dc.date.issued2005
local.identifier.absfor040601 - Geomorphology and Regolith and Landscape Evolution
local.identifier.absfor040313 - Tectonics
local.identifier.ariespublicationMigratedxPub3825
local.type.statusPublished Version
local.contributor.affiliationHill, PJ, Geoscience Australia
local.contributor.affiliationDe Deckker, Patrick, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationExon, N.F., Geoscience Australia
local.description.embargo2037-12-31
local.bibliographicCitation.startpage117
local.bibliographicCitation.lastpage136
local.identifier.doi10.1080/08120090500100085
dc.date.updated2015-12-11T08:27:37Z
local.identifier.scopusID2-s2.0-22944484995
CollectionsANU Research Publications

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