Seafloor Mapping of the South-east Region and Adjacent Waters : AUSTREA-2 Cruise Report: South-east of Tasmania and Southern Macquarie Ridge

In January/February 2000, the Australian Geological Survey Organisation (AGSO)
completed a 2S-day seabed swath-mapping and geophysical survey off south and
south-east Tasmania and south of Macquarie Island for the National Oceans Office
and Environment Australia. The survey, which is named AUSTREA-2 and designated
as AGSO Cruise 223, used the 8S-m French oceanographic and geoscience research
vessel N/O L 'Atalante, which departed Hobart on January IS and arrived in Bluff,
New Zealand, on February 9. The survey covered about 10,200 km and mapped about
140,000 km2 of seabed. The initial impetus for the work was to map the foot-of-slope
position in several areas to support definition of Australia's legal Continental Shelf
under the United Nations Convention on the Law of the Sea. A significant additional
but complementary aspect was to support marine zone planning and management, and
assessment of seabed living and non-living (petroleum and mineral) resources, as an
important step towards implementation of Australia's Oceans Policy and Australia's
Marine Science and Technology Plan, and, in particular, the development of the
South-east Regional Marine Plan by the National Oceans Office.
Geophysical data collected included Simrad EM12D swath bathymetry and
backscatter, 6-channel GI-gun seismic, 3.S kHz sub-bottom profiling, and gravity and
magnetic profiles. This was augmented by a suite of oceanographic data, such as
seawater temperature, and both current and salinity depth profiles. Weather and sea
conditions were highly favourable, particularly in the more southern latitudes.
Occasional periods of rough weather resulted in higher noise levels, but did not
seriously affect acquisition, and data quality was generally excellent.
The work conducted off Tasmania was mostly to fill in and extend previous swath
coverage, and map the foot-of-slope along the eastern margin of the South Tasman
Rise. It highlighted features such as the major development of slope canyons down
the eastern Tasmanian margin, and the complex character of the Cascade Seamount
and other seamounts adjacent to the South Tasman Rise.
The work conducted over the southern Macquarie Ridge Complex highlighted
features such as: a high-relief axial valley adjoining the deep Hjort Trench; the
broadening to the south of the submerged Hjort Ridge, east of the Hjort Trench; the
development of seafloor spreading tectonic fabric across the Hjort Ridge summit; and
the presence of a linear trough/ridge feature that obliquely truncates the southern end
of the Hjort Trench and adjoining axial valley.
A full set of shipboard maps are held by the National Oceans Office and AGSO, and
copies of the digital data are stored at AGSO. All data from the survey will be
managed jointly by AGSO and the National Oceans Office.

2000年1-2月，澳大利亚地质调查组织（AGSO）为国家海洋局和澳大利亚环境部完成了一项为期25天的海底条带测绘与地球物理调查，调查区域位于塔斯马尼亚南部、东南部及麦夸里岛以南。该调查名为AUSTREA-2，编号为AGSO Cruise 223，使用法国海洋与地球科学研究船N/O L'Atalante（85米级），该船于1月15日从霍巴特出发，2月9日抵达新西兰布拉夫。调查覆盖约10200公里，测绘约140000平方公里海底。此项工作的最初动因是在多个区域测绘坡脚位置，以支持依据《联合国海洋法公约》界定澳大利亚的合法大陆架。另一重要且互补的目标是为海洋区划规划与管理、海底生物与非生物（石油和矿产）资源评估提供支持，这是澳大利亚海洋政策及海洋科技计划实施的关键一步，尤其助力国家海洋局制定东南区域海洋计划。

采集的地球物理数据包括Simrad EM12D条带测深与反向散射数据、6道GI枪地震数据、3.5 kHz浅地层剖面测量数据，以及重力与磁力剖面数据。此外还补充了一系列海洋学数据，如海水温度、海流及盐度深度剖面。天气和海况极为有利，尤其是在更南的纬度区域。偶尔出现的恶劣天气导致噪声水平升高，但未严重影响数据采集，数据质量总体优异。

塔斯马尼亚附近开展的工作主要是填补并扩展此前的条带覆盖区域，以及测绘南塔斯曼隆起东缘的坡脚。该工作突出了塔斯马尼亚东缘斜坡峡谷的大规模发育、喀斯喀特海山及邻近南塔斯曼隆起的其他海山的复杂特征等。

麦夸里海脊复合体南部的调查工作则凸显了以下特征：与深海约尔特海沟相邻的高起伏轴谷；约尔特海沟以东的淹没约尔特海脊向南扩展变宽；约尔特海脊顶部存在海底扩张构造组构；以及斜向截断约尔特海沟南端及相邻轴谷的线性槽/脊特征。

全套船载地图由国家海洋局和AGSO持有，数字数据副本存储于AGSO。调查的所有数据将由AGSO和国家海洋局联合管理。