Legacy product - no abstract available

Legacy product - no abstract available

Christmas Island lies about 1600 km north-north west of Australia's Northwest Cape and approximately 350 km south of Java in the northern part of the Wharton basin (IndianOcean). Recently Australia declared a 200 mile Fisheries Zone around the island andAGSO was asked to assess seabed morphology, sediment thickness and offshore mineralresources in this area. In February 1992 RAT "Rig Seismic" carried out a detailed survey ofthe region, providing relevant data for the required assessment. Eight seismic profiles wereacquired on this cruise, totalling about 2000 km, and almost twice as much bathymetricdata was recorded. In conjunction with seismic and bathymetic data collected by otherinstitutions, our data provides a good coverage of the area, which enabled us to compile anew bathymetric map and to produce the first sediment thickness map. Among the published bathymetric maps only three cover the Christmas Island area: 1)published by Udintsev (Geophysical Atlas of the Indian Ocean, 1975; 1:5,000 000), 2) byMammerickx et al. (1976, 1:5,000 000) and 3) 1:10,000 000 General BathymetricCompilation (GEBCO) map, published by the International Oceanographic Service (1982).All published bathymetric maps were compiled in the end of the 1970s and the beginningof the 1980s, and all of them were based on processing analog records of water depths andwere drafted manually. Moreover, most of the data for map compilation were collectedusing a sextant, and only a very limited using satellite navigation. The amount and quality of data collected by the end of the 1970s allowed the production ofthe fairly accurate 1:5,000 000 and 1:10,000 000 maps of the Indian Ocean listed above,however a lot of smaller features, such as individual seamounts, are missing on those maps.Insufficient data coverage led to broad extrapolation of bathymetric trends, sometimesderived purely from magnetic lineation pattern (Fig.1). To the east of Christmas Island thelack of information is particularly evident: all the maps differ in their interpretation of this area. New high quality data collected by "Rig Seismic", and digital water depths obtained fromthe USA National Geophysical Data Bank (NGDC), were used for compilation of a newrevised version of the bathymetric map on the Christmas Island area in a 1:1,000 000 scale.The new map (to be published in AGSO's Offshore Resources Map Series) contains a lotmore detail on the complex bathymetry of the area, and gives a more realistic picture ofseamount distribution and the structure of the Java Trench and Java's outer-arc ridge. Theamount of added information can be clearly deduced from comparison of Fig.1 and Fig.2.The time scale used in this report is that of McDougall (1974) and Fanoon et al. (1993).

Legacy product - no abstract available

Legacy product - no abstract available

The Australian Territory of Christmas Island, a raised atoll with a population of about 2000 people, lies on oceanic crust about 1600 km north- north west of Australia's Northwest Cape, and 350 km south of western most Java (Fig. 1). The Australian Cocos-Keeling Islands group is 1000 km further west. Christmas Island resembles a 'T', with its stem running east-west (Fig. 4), has an area of 140 km2, and is up to 20 km across. Australia has declared a 200 mile fisheries zone around Christmas Island. The island is on the Indo-Australian Plate, which is moving 'north at about 7cm/year, and is being uplifted on the bulge in front of the Java Trench 150km to the north. It has the form of a plateau at 200-300 m above sea level,bounded by a series of sea cliffs and terraces. The plateau slopes to the south; the highest point is Murray's Hill (361 m) on the western end of the island. The natural vegetation is tropical rain forest. The island is at the eastern end of the submarine Christmas Rise, which extends south-south west for 700 km (Fig. 1). The Java Trench to the north is more than 6500 m deep, and the abyssal plains around the Christmas Rise are 5000-6000 m deep. The rise sits on oceanic crust of presumed LateCretaceous age, and both it and the pedestal of the island consist largely of volcanics. On the island the volcanics are overlain by Eocene limestone, and an extensive Miocene limestone which is associated with extensive phosphate deposits. These deposits produced nearly 1,000,000 tonnes a year of phosphate rock until 1987 when mining ceased. Mining resumed at asmaller scale in 1991. In early 1991, the Australian Department of Foreign Affairs and Trade requested BMR to undertake a study of the non-living seabed resources of the area around Christmas Island, as an aid to seabed boundary delimitation negotiations. This work arose from the request, and started in January 1992, using RV. Rig Seismic. A cruise narrative is provided in Appendix 7

Legacy product - no abstract available

Legacy product - no abstract available

The Christmas Island Geographic Information System (CIGIS) is a collection of spatial data, viewing and analysis tools dealing with Christmas Island, Indian Ocean. The data include orthophotography, topographic, mining, cultural and environmental features of the island. This work is part of ongoing service to the Department of Transport and Regional Services.

The Christmas Island Geographic Information System (CIGIS) is a collection of spatial data, viewing and analysis tools dealing with Christmas Island, Indian Ocean. The data includes orthophotography, topographic, mining, cultural and environmental features of the island. This work is part of an ongoing service to the Territories West of the Attorney General's Department.