Citation

Exon, N.F., Hill, P.J., Lafoy, Y., Burch, G.J., Post, A., Heine, C., Quilty, P.G., Howe, R. & Taylor, L., 2004. The Geology of the Kenn Plateau Off Northeast Australia: Results of Southern Surveyor Cruise SS5/2004 (Geoscience Australia Cruise 270). Record  2005/004. Geoscience Australia, Canberra.

Abstract

In the Late Cretaceous, the Kenn Plateau was part of the Maryborough Basin to the west and the Capricorn Basin to the north. It separated from Australia from the earliest Paleocene to the Middle Eocene by moving northeastward overall along the Cato Fault Zone and rotating 45 degrees anticlockwise. The West Bellona Fracture Zone splays off the Cato Fracture Zone and separates the western part of the plateau, with west to northwest trending structures, from the eastern part of the plateau, with northeast trending structures. The northeast trending structures correspond in trend to the fracture zones in the oceanic crust of the northern Tasman Basin, indicating that they have a common origin. The Kenn Plateau consists of about 140,000 km sq of thinned continental crust and it is surrounded by ocean basins, largely floored by oceanic crust, to the north, west and south. To the east are the limestone banks of the Early Miocene Lord Howe hotspot chain. A geoscience survey by R.V. Southern Surveyor in 2004 showed that the plateau is highly complex, consisting of basement ridges, intervening troughs, and the Oligocene hotspot volcanoes of the Tasmantid chain in the west. On this survey, multibeam-sonar swath-bathymetry was recorded continuously, and 3090 km of multichannel seismic data and magnetic data were also recorded. In addition, twelve dredge hauls recovered sedimentary rocks, many of which have been dated micropaleontologically as Eocene and younger. Rifting of the pre-existing continental basement rocks, and the overlying Mesozoic siliciclastic sedimentary rocks, thinned the crust, and formed Late Cretaceous and Cainozoic rift basins that trend ENE overall. The thinning led to subsidence, but this was complicated by Early Oligocene and Early Miocene volcanic heating and build-ups, and Eocene compression. Overall, subsidence has averaged ~50 m/m.yr. since the Early Oligocene. Three major sequences occur. The lowermost is the most poorly understood, but appears to consist of up to 2500 m of Upper Cretaceous and Lower Paleocene siliciclastic sediments deposited in the troughs. These detrital sediments grade into marine limestones, both upward and into basinal areas. Unconformably overlying the earlier sequence is a few hundred metres of Middle and Upper Eocene chalk, some of it highly siliceous, with the silica apparently derived from radiolarians. Compression during the Eocene formed anticlines in the troughs in places. Faults generally show major displacement only in the Cretaceous to Eocene sequences. Above another unconformity is a draped Oligocene to Recent sequence of chalk, containing few siliceous microfossils. It is relatively thin and often sits directly on basement on the highs, but is up to 700 m thick in the troughs. Virtually the entire area is blanketed in calcareous pelagic ooze. The Oligocene volcanic edifices of the Tasmantid chain formed at 30-34 Ma, earlier than the calculated onset of carbonate build-up of about 15-30 Ma. Erosion had probably removed most of the volcanic edifice above sea level before build-ups started to form. Cool water carbonates apparently formed here first (30 Ma) and somewhat later on the Marion Plateau (25 Ma), perhaps because the Kenn Plateau seamounts subsided beneath the sea earlier than did the Marion Plateau with its thicker continental crust. Limestone ages suggest that average reefal growth rates were 40-110 m/m.yr. Reefal growth kept up on some seamounts until the present day, but not on others. The Kenn Plateau, as expected, appears to have little petroleum resource potential. However, its varied environments reefs, slopes of basement rocks, volcanics, limestone and soft sediments, and bathyal ridges and deepwater troughs may well be significant environmentally.
Google map showing geographic bounding box with values North bound -21.0 East bound 159.0 West bound 154.0 South bound -26.0
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Product Type/Sub Type

dataset - GA Publication - Record

Constraints

license
Creative Commons Attribution 3.0 Australia Licence

IP Owner

Commonwealth of Australia (Geoscience Australia)

Author(s)

Date (publication)

2004

Product Type

dataset

Topic Category

geoscientificInformation

Keywords

GA Publication
Record
seismics
marine
geology
Earth Sciences

Resource Language

English

Resource Character Set

utf8

Resource Security Classification

unclassified

Geographic Extent

North bound
-21.0
East bound
159.0
West bound
154.0
South bound
-26.0

Lineage

Unknown

Digital Transfer Options

onLine

DISTRIBUTION Format

pdf

Distributor

Role
distributor
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address

Metadata File Identifier

a05f7892-c392-7506-e044-00144fdd4fa6

Metadata Standard Name

ANZLIC Metadata Profile: An Australian/New Zealand Profile of AS/NZS ISO 19115:2005, Geographic information - Metadata

Metadata Standard Version

1.1

Metadata Date Stamp

2004-12-09

METADATA SECURITY CLASSIFICATION

unclassified

Metadata Contact

Role
pointOfContact
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address
Downloads
For information on acquiring this product,
please contact the Geoscience Australia Sales Centre via:

fax:
+61 2 6249 9960; or
phone:
1800 800 173 (within Australia);
 
+61 2 6249 9966 (outside Australia).

Please note that support hours are 9 am to 5 pm weekdays