22-2/F52-8/3-6

22-1/D51-16/3

do not sell until 01 May 1997 22-2/E52-06/1-3 Contour interval: 10

A pilot project conducted in October 1991, from Rig Seismic (AGSO Survey 104), utilising the continuous geochemical tracer [CGT] capability, showed that theanalyses of oceanic waters for light hydrocarbon content provides a useful method for characterising pollutants from various sources (BMR Research Newsletter, 16). The offshore Sydney component of Survey 104 was conducted between Botany Bay and North Head. Light hydrocarbon anomalies were detected from each of the three deepwater ocean outfalls operated by the Water Board. The results suggested that the molecular compositions of different hydrocarbon mixtures may be useful indicators of hydrocarbon 'sources' mixed together in the coastal zone. A reprint of the BMR Research Newsletter article of the pilot survey is reproduced in Figure 1.1. The usefulness of the CGT equipment, demonstrated during that pilot project, resultedin an additional survey (Survey 112), conducted on Rig Seismic during September/October 1992 (Heggie et al., 1992), which combined scientific staff from AGSO and the Water Board (Sydney). Scientific activities on Survey 112 included: (i)seafloor sampling, to gather environmental baseline information on the nutrient and contaminant (heavy metals and organochlorines) status of sediments, and also sedimentology of the nearshore region and, (ii) water column analyses, comprising approximately 500 line-km of CGT data (light hydrocarbons in seawater complemented with temperature, salinity, dissolved oxygen and pH) collected in the vicinity of the deepwater ocean outfalls. The purposes of this Record are to: (i) provide a description of the edited hydrographic (temperature and salinity), oxygen and pH data and, (ii) combine these data with some of the light hydrocarbon (DHD) data. Sediment and DHD data collected during Survey 112 are addressed in other AGSO Records (Heggie et al., 1993a; Heggie et al., I993b). A separate part of Survey 112, conducted with scientific staff from Sydney University, the NSW Geological Survey and the Ocean Sciences Institute, between Newcastle and Wollongong provides a regional context for thoseobservations focussed about Sydney. The preliminary results of that part of Survey 112 are included in Bickford and Heggie et al. (1993).

Legacy product - no abstract available

Seismic Test Survey conducted by the Bureau of Mineral Resources, Geology andGeophysics (BMR) (now Australian Geological Survey Organisation (AGSO)) during the early part of 1989. The objective of the survey was to test the suitability of the seismicreflection technique for proposed regional deep reflection seismic lines in the Gunnedah Basin and Cobar Basin. The major emphasis of the test survey was to assess the feasibility of acquiring shallow and deep seismic reflections in order to examine various geologicalmodels of bounding faults and basin structure. The survey acquired data from five sites in the Gunnedah Basin and three sites inthe Cobar Basin. The quality of data in the deeper part of the sections, i.e. 6-15 seconds (TWT), varied from very good to excellent. Seismic reflections in the sedimentary part ofthe succession were, in general, very poor, but some surprisingly good seismic reflectionevents were obtained below the Pilliga Sandstone in the Gunnedah Basin. The test survey indicated that the deep seismic reflection technique in theGunnedah Basin and Cobar Basin would provide data that would be of assistance in developing new geological models, and an understanding of fault geometries and basinstructure, and would assist the exploration for mineral and petroleum resources in the future.

Resources, Geology & Geophysics (now Australian Geological Survey Organisation (AGSO))conducted a seismic reflection, seismic crustal refraction and gravity survey in southeastern Queensland from August to November 1986. The primary objective of the survey was to complete seismic reflection coverage in the Dalby-Toowoomba area between Traverse 14 and Traverse 16 recorded during the BMR S.E. Queensland seismic survey in 1984. Secondary objectives, subject to survey progressincluded recording additional seismic reflection data east of Traverse 16 (1984) over the Beenleigh Block south of Brisbane, and a 100 km of seismic reflection data south of Mitchellover a deep crustal seismic reflection feature delinated on Traverse 14 (1984) centred at SP4030. Overall the survey objectives would allow the completion of a continuous deepcrustal seismic reflection profile of 1110 km length across southern Queensland, the basis of a lithospheric transect study in the southern region of Queensland. The survey obtained a total of 181 km of 6-16 fold CMP seismic reflection data in theBeenleigh, Darling Downs and Mitchell areas, using the Sercel SN368 seismic acquisition system. Both the primary and secondary objectives were achieved, although equipmentfailures were a major problem in causing decreased production rates. Gravity observations were made at 360m intervals along all traverses. The record presents operational information on the seismic reflection survey and preliminary sections of seismic traverses.

This format description is designed to assist users of AGSO digital seismic data. In general the standard descriptions have been adhered to as specified by Barry et. al. (Recommended Standardsfor Digital Tape Formats, Geophysics, vol 40, No 2 (April 1975) pp 344-352). Trace header mnemonics for many of the entries are as per used by CogniSeis in their DISCO software package, others have been defined by AGSO. Variations to the standard trace header descriptions (bytes 1-180) are as follows. TRACED has expanded codes which are applicable to unstacked data eg. reformatted field data. Static corrections and delays are defined to account for the field acquisition system. In addition to the standard entries a number of optional entries are also used. Some of these arecreated by DISCO and others relate to AGSO data acquisition and processing. The most importantof these are SHOT or SPN. Please note that for AGSO data released prior to 1993, a pseudo shot point number was used (SPN) as opposed to processing shot number (SHOT). The SPN was an assigned number generated from the stack data set and usually started at 100. This number has no direct relationship to the original field shot number (FFID) or processing shot number (SHOT) and may be considered to be a re-sequenced CDP. Therefore the first SPN on a line may not occur at fall fold but the first live stack trace. To relate this vintage data to original field data either 141-11) if present, must be used or time values from the headers must be used. Its use was historical and primarily for the purposes of producing shot point maps which could be related to a section. Its use has been discontinued from 01993 and replaced by SHOT which in most cases will be identical to FFID. Exceptions occur when the line has been merged for acquisition or processing reasons and SHOT numbers have been re-sequenced to obtain a continuous numbering sequence. The convention used for the SHOT annotation position is the mid-point of the source and the firstactive channel. Therefore the ship antenna position, which is Rig Seismic's firing navigation referencepoint, is corrected to relate to this point for all final navigation data. Field data polarity is maintained throughout the processing sequence. The convention for AGSOdata is that a compression wave is plotted as negative. Some data sets may include bathymetry and geophysical data such as magnetics and gravity. These are also corrected to the mid-point location.

In early 1994, the Australian Geological Survey Organisation (AGSO) will use the multibeam sonarsystem of the French research vessel l'Atalante for 35 days mapping of 200 000 lcm2 of the continental margin (southern Otway Basin, Sore11 Basin, South Tasman Rise) and the adjacentabyssal plain. The cruise will start in Wellington on 16 January and finish in Adelaide on 27 February. Data will be recorded on the transits, as well as near Tasmania. The SIMRAD EM12D system provides bathymetric maps and acoustic imagery in real time, and can map an area alongeach track up to 20 km wide at a speed of 10 knots. The maps will define batliymetry and surface texture with a degree of accuracy and rate of coverage unobtainable in any other way. In addition we will record 6 channel seismic reflection, magnetic, gravity and bathymetric profiles. Thismapping of an area three times that of Tasmania will help to clarify the region's structural pattern and tectonic history, largely controlled by the separation of Australia and Antarctica about 40million years ago. We will also map large-scale sedimentary structures and patterns to help elucidate Tertiary sedimentary history, and morphology to help define Australia's Legal Continental Shelf for the day when Australia ratifies the Law of the Sea Convention (expected within a coupleof years). The region's geological history bears on the history of the entire southern margin of Australia. This margin is already a major producer of petroleum from the Upper Cretaceous and Paleocene sequences in the Gippsland Basin, and has encouraging exploration results in several other basins.The Otway Basin, in particular, is the scene of major recent offshore gas discoveries in the Cretaceous sequence. The very accurate bathymetric maps and sonar images arising from thissurvey will provide an unequalled source of structural information of great value to AGSO and the petroleum exploration industry. The mapping of the fault patterns that come to the surface on the continental margin, believed to be part of a large, NNW to NW trending strike-slip system that firstformed in the Early Cretaceous, will lead to much better understanding of fault geometry. It also will aid the planning of future AGSO seismic reflection programs, aimed at mapping deep structurealong the margin. The mapping of the abyssal plain to the west will bear closely on the breakup history of Australiaand Antarctica. It is generally believed that Late Cretaceous and Cainozoic spreading took place along north-south fracture zones that are clearly visible in satellite altimetry data, but also there isevidence of earlier, probably Early Cretaceous, oceanic crust in which the fracture patterns trend northwestward. Swath-mapping imagery will give us more detail of trends, and also locate goodsites for sampling basalts for dating and geochemical examination. In addition, it is uncertain howfar continental blocks extend out onto the plain, and the mapping of all blocks will enable future sampling is properly targeted to resolve this important scientific question. The mapping of rocky outcrops, sedimentary structures, and sedimentary patterns will be invaluablein planning a forthcoming AGSO seafloor sampling cruise. This sampling will target Cretaceous, Paleocene and Eocene rocks to provide information on the pre-separation history of the margin, oceanic basalts to elucidate the spreading history, and Oligocene and younger sediments to provideinformation on changes in oceanic circulation and climate as Australia moved steadily north from Antarctica.

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).