Citation

Dickens, G., Exon, N.F., Holdway, D., Lafoy, Y., Auzende, J., Dunbar, G. & Summons, R.E., 2001. Quaternary Sediment Cores from the Southern Fairway Basin on the Northern Lord Howe Rise (Tasman Sea). Record  2001/031. AGSO-Geoscience Australia, Canberra.

Abstract

Thick packages of Cretaceous and Tertiary sediment with numerous diapirs fill the Southern Fairway Basin (SFB) on the Lord Howe Rise (LHR). A bottom-simulating reflector (BSR) also extends across much of this basin, perhaps indicating substantial amounts of CH4 as gas hydrate and free gas. As part of the ZoNiCo 5 survey, run on behalf of the New Caledonian government, 13 piston cores were taken by the RV L'Atalante in 1999 to assess the gas and petroleum potential of the SFB. Specifically, the cores were recovered to document the nature of sediment, pore water and gas in the shallow sedimentary section. The 13 cores, from 1250 to 2753 m below sea level (mbsl) and between 405 and 758 cm long, contain stiff nannofossil ooze. If average regional sedimentation rates apply (10 m/my), the maximum age at the bottom of cores is less than 800,000 years. The sediment typically grades from greyish orange at the top, to very pale orange in the middle, and then to either yellowish grey, very light grey or white at the bottom. Thin black horizons, presumably composed of pyrite, also occur. The changes in colour are related to variations in magnetic susceptibility (MS) and pore water SO42-. Pale and grey zones generally have low MS punctuated by MS highs, and low pore water SO42- concentrations. Methane was detected in most sediment samples, although at trace levels. The presence of ethane, propane and higher hydrocarbons suggests that gases in the SFB have a thermogenic component. With the available data, the best explanation for colour, MS and SO42- profiles is that Fe has been remobilised under anoxic conditions. Ferric iron in solid oxyhydroxide phases and SO42- in pore waters have been converted to dissolved ferrous iron and sulphide. Some of this iron and sulphur has then re-precipitated as pyrite or magnetite (the MS spikes). The overall process may be driven by CH4 from underlying gas hydrate deposits. Upward fluxes of CH4, perhaps of thermogenic origin, induce anaerobic CH4 oxidation in shallow sediment, a process that consumes SO42-. As a consequence, unexpectedly shallow redox fronts occur in the SFB. However, longer cores with less-oxidised sediment and additional analyses are needed to understand sediment, water and gas in this region.
Google map showing geographic bounding box with values North bound -22.0 East bound 166.0 West bound 161.0 South bound -27.0
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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)

2001

Product Type

dataset

Topic Category

geoscientificInformation

Keywords

GA Publication
Record
stratigraphy
geology
hydrocarbons
petroleum reserves
marine survey
Earth Sciences

Resource Language

English

Resource Character Set

utf8

Resource Security Classification

unclassified

Geographic Extent

North bound
-22.0
East bound
166.0
West bound
161.0
South bound
-27.0

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-b619-7506-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

2001-07-13

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