The Houtman Sub basin is an under-explored region of the northern Perth Basin, offshore Western Australia. Only three wells have been drilled in the southern part of the sub-basin, while the northern part remains an exploration frontier. Adjacent areas of the Perth Basin are proven hydrocarbon provinces with a long and continuing history of exploration, discovery and production. New seismic reflection data, obtained by Geoscience Australia in 2014–15 (GA-349) under the Australian government's precompetitive data acquisition program, has been used to reassess the tectonic evolution, structural architecture, major depositional phases and petroleum prospectivity of this frontier basin. Interpretation of these data has enabled mapping of the Moho, basement, pre-rift sequences and major syn rift sequences, along with the creation of a 3D geological model covering the survey area. As a result, this study has significantly reduced the level of exploration risk in the northern Houtman Sub-basin. Seismic interpretation, integrated with potential field modelling, shows a large variation in crustal structure beneath the study area. Beneath the central part of the northern Houtman Sub-basin continental crust is highly extended to hyperextended (<5 km thick), while further east, beneath the Bernier Platform, continental crust remains greater than 25 km thick. This extreme change in crustal thickness occurred along a major fault zone, marking the eastern boundary of the northern Houtman Sub-basin. Located outboard, along the western margin of the northern Houtman Sub-basin, is a zone of volcanic seaward-dipping reflector sequences, defining the volcanic province of the Wallaby Saddle. Regional correlation of the seismic stratigraphy across the northern Perth Basin has enabled the development of a new tectonostratigraphic framework for the Houtman Sub basin. The depocentre includes up to 16 km of a Permian–Cretaceous succession underlain by a 2–3 km thick section of pre-rift (?Paleozoic) sediments. The Permian syn rift succession is confined to a series of large half graben that are controlled by basement-involved faults that separate the northern Houtman Sub-basin from the Bernier Platform. This succession is up to 10 km thick and was mapped throughout the inboard part of the new seismic grid. A prominent unconformity at the top of the Permian syn-rift sequence is overlain by a thick (up to 1800 m) and regionally extensive seismic sequence interpreted as the Lower Triassic Kockatea Shale. The thickness of the Triassic succession (i.e. Kockatea, Woodada and Lesueur formations) ranges from about 1 km in the inboard part of the basin to up to 5 km outboard. The Late Triassic to Jurassic succession is thickest (up to 4 km) in the outboard part of the basin and is interpreted to contain sequences corresponding to the Eneabba, Cattamarra, Cadda and Yarragadee formations. An Early Cretaceous depocentre was mapped in southwestern part of the study area, and is interpreted to be a Parmelia Group equivalent. Comparison with the adjacent hydrocarbon producing regions of the northern Perth Basin highlights the likely presence of multiple petroleum source, reservoir and seal units. Potential source rocks consist of Permian to Jurassic marine and non marine carbonaceous shale and coal, the most prospective of these is the marine Triassic Kockatea Shale, especially if the organic-rich Hovea Member is present. In addition, multiple reservoir and seal intervals are likely to be present throughout the thick Permian, Triassic, Jurassic and Lower Cretaceous successions.

A high-resolution multibeam echosounder (MBES) dataset covering over 279,000 km2 was acquired in the southeastern Indian Ocean to assist the search for Malaysia Airlines Flight 370 (MH370) that disappeared on 8 March 2014. The data provided an essential geospatial framework for the search and is the first large-scale coverage of MBES data in this region. Here we report on geomorphic analyses of the new MBES data, including a comparison with the Global Seafloor Geomorphic Features Map (GSFM) that is based on coarser resolution satellite altimetry data, and the insights the new data provide into geological processes that have formed and are currently shaping this remote deepsea area. Our comparison between the new MBES bathymetric model and the latest global topographic/bathymetric model (SRTM15_plus) reveals that 62% of the satellite-derived data points for the study area are comparable with MBES measurements within the estimated vertical uncertainty of the SRTM15_plus model (± 100 m). However, > 38% of the SRTM15_plus depth estimates disagree with the MBES data by > 100 m, in places by up to 1900 m. The new MBES data show that abyssal plains and basins in the study area are significantly more rugged than their representation in the GSFM, with a 20% increase in the extent of hills and mountains. The new model also reveals four times more seamounts than presented in the GSFM, suggesting more of these features than previously estimated for the broader region. This is important considering the ecological significance of high-relief structures on the seabed, such as hosting high levels of biodiversity. Analyses of the new data also enabled sea knolls, fans, valleys, canyons, troughs, and holes to be identified, doubling the number of discrete features mapped. Importantly, mapping the study area using MBES data improves our understanding of the geological evolution of the region and reveals a range of modern sedimentary processes. For example, a large series of ridges extending over approximately 20% of the mapped area, in places capped by sea knolls, highlight the preserved seafloor spreading fabric and provide valuable insights into Southeast Indian Ridge seafloor spreading processes, especially volcanism. Rifting is also recorded along the Broken Ridge – Diamantina Escarpment, with rift blocks and well-bedded sedimentary bedrock outcrops discernible down to 2400 m water depth. Modern ocean floor sedimentary processes are documented by sediment mass transport features, especially along the northern margin of Broken Ridge, and in pockmarks (the finest-scale features mapped), which are numerous south of Diamantina Trench and appear to record gas and/or fluid discharge from underlying marine sediments. The new MBES data highlight the complexity of the search area and serve to demonstrate how little we know about the vast areas of the ocean that have not been mapped with MBES. The availability of high-resolution and accurate maps of the ocean floor can clearly provide new insights into the Earth's geological evolution, modern ocean floor processes, and the location of sites that are likely to have relatively high biodiversity. <b>Citation:</b> Kim Picard, Brendan P. Brooke, Peter T. Harris, Paulus J.W. Siwabessy, Millard F. Coffin, Maggie Tran, Michele Spinoccia, Jonathan Weales, Miles Macmillan-Lawler, Jonah Sullivan, Malaysia Airlines flight MH370 search data reveal geomorphology and seafloor processes in the remote southeast Indian Ocean, <i>Marine Geology</i>, Volume 395, 2018, Pages 301-319, ISSN 0025-3227, https://doi.org/10.1016/j.margeo.2017.10.014.

A large multibeam echo sounder (MBES) dataset (710, 000 km2, inclusive of transit data) was acquired in the SE Indian Ocean to assist the search for Malaysia Airlines Flight 370 (MH370). Here, we present the results of a geomorphic analysis of this new data and compare with the Global Seafloor Geomorphic Features Map (GSFM) that is based on coarser resolution satellite-derived bathymetry data. The analyses show that abyssal plains and basins are significantly more rugged than their representation in the GSFM, with a 20% increase in the extent of hills and mountains. The new model also reveals four times more seamounts than presented in the GSFM, suggesting a greater number of these features than previously estimated for the broader region and indeed globally. This is important considering the potential ecological significance of these high-relief structures. Analyses of the new data also enabled knolls, fans, valleys, canyons, troughs and holes to be identified, doubling the number of discrete features mapped and revealing the true geodiversity of the deep ocean in this area. This high-resolution mapping of the seafloor also provides new insights into the geological evolution of the region, both in terms of structural, tectonic, and sedimentary processes. For example, sub-parallel ridges extend over approximately 20% of the area mapped and their form and alignment provide valuable insight into Southeast Indian Ridge seafloor spreading processes. Rifting is recorded along the Broken Ridge – Diamantina Escarpment, with rift blocks and well-bedded sedimentary bedrock exposures discernible down to 2,400 m water depth. Ocean floor sedimentary processes are represented in sediment mass transport features, especially along and north of Broken Ridge, and pockmarks (the finest-scale features mapped) south of Diamantina Trench. The new MBES data highlight the complexity of the search area and serve to demonstrate how little we know about the 85-90% of the ocean floor that has not been mapped with this technology. The availability of high-resolution and accurate maps of the ocean floor can clearly provide new insights into the Earth’s geological evolution, modern ocean floor processes, and the location of sites that are likely to have relatively high biodiversity. Poster presented the 2017 American Geophysical Union, Fall Meeting

On behalf of Australia, the Australian Transport Safety Bureau (ATSB) is leading search operations for missing Malaysian airlines flight MH370 in the Southern Indian Ocean. Geoscience Australia provided advice, expertise and support to the ATSB to facilitate bathymetric surveys, which were undertaken to provide a detailed map of the sea floor topography to aid navigation during the underwater search. Bathymetric data was acquired by multibeam sonar mounted on the hull of multiple vessels (GA survey reference: GA-4421, GA-4422 & GA-4430). Bathymetric surveys were conducted from June 2014 to February 2017, collecting over 710,000 square kilometres of data in the search area and along transit lines (to and from the search area). This dataset allows exploration of the seafloor topography through an optimal resolution compilation of tiles across the search and transit areas of the Southern Indian Ocean. The dataset is overlain on a hillshade created from the Optimal resolution bathymetry data. The hillshade was created with the parameters of point illumination azimuth at 45 degrees and altitude of 45 degrees.

This web service contains marine geospatial data held by Geoscience Australia. It includes bathymetry and backscatter gridded data plus derived layers, bathymetry coverage information, bathmetry collection priority and planning areas, marine sediment data and other derived products. It also contains the 150 m and optimal resolution bathymetry, 5 m sidescan sonar (SSS) and synthetic aperture sonar (SAS) data collected during phase 1 and 2 marine surveys conducted by the Governments of Australia, Malaysia and the People's Republic of China for the search of Malaysian Airlines Flight MH370 in the Indian Ocean. This web service allows exploration of the seafloor topography through the compilation of multibeam sonar and other marine datasets acquired.

This web service contains marine geospatial data held by Geoscience Australia. It includes bathymetry and backscatter gridded data plus derived layers, bathymetry coverage information, bathmetry collection priority and planning areas, marine sediment data and other derived products. It also contains the 150 m and optimal resolution bathymetry, 5 m sidescan sonar (SSS) and synthetic aperture sonar (SAS) data collected during phase 1 and 2 marine surveys conducted by the Governments of Australia, Malaysia and the People's Republic of China for the search of Malaysian Airlines Flight MH370 in the Indian Ocean. This web service allows exploration of the seafloor topography through the compilation of multibeam sonar and other marine datasets acquired.

This web service contains marine geospatial data held by Geoscience Australia. It includes bathymetry and backscatter gridded data plus derived layers, bathymetry coverage information, bathmetry collection priority and planning areas, marine sediment data and other derived products. It also contains the 150 m and optimal resolution bathymetry, 5 m sidescan sonar (SSS) and synthetic aperture sonar (SAS) data collected during phase 1 and 2 marine surveys conducted by the Governments of Australia, Malaysia and the People's Republic of China for the search of Malaysian Airlines Flight MH370 in the Indian Ocean. This web service allows exploration of the seafloor topography through the compilation of multibeam sonar and other marine datasets acquired.