STRUCTURE AND STRATIGRAPHY OF THE CEDUNA TERRACE REGION, GREAT AUSTRALIAN BIGHT BASIN

1979 ◽  
Vol 19 (1) ◽  
pp. 53 ◽  
Author(s):  
A. R. Fraser ◽  
L. A. Tilbury
Keyword(s):  
Upper Cretaceous ◽  
Single Channel ◽  
South Australia ◽  
Magnetic Data ◽  
The West ◽  
Petroleum Potential ◽  
Northern Margin ◽  
Gravity And Magnetic ◽  
Gravity And Magnetic Data ◽  
Great Australian Bight

The Ceduna Terrace is a bathymetric feature covering some 70,000 sq km, in the continental slope of South Australia. Its most gently sloping part lies between the 500 and 2500m isobaths, and is underlain by the main depocentre of the Great Australian Bight Basin.A systematic interpretation of the region has been made, based on 17,000 km of multi-channel seismic data from Shell surveys, 8000 km of single-channel seismic, gravity and magnetic data from the BMR Continental Margins Survey, and 6000 km of gravity and magnetic data from surveys by Lamont-Doherty Geological Observatory. Seismic ties were made to the wells Potoroo-1 and Platypus-1.Mapping of the key seismic horizons confirms the picture of the basin as a sedimentary wedge, more than 10 km thick, extending from the edge of the shelf to the continental rise. Three important unconformities can be mapped over a wide area and tied to Potoroo-1 well-a basement reflector separating Lower Proterozoic crystalline rocks of the Gawler Craton from an overlying, block-faulted sequence of mainly Lower to mid-Cretaceaus sediments; an unconformity at the base of an Upper Cretaceous sequence which includes a major prograded unit in the west; and a break-up unconformity at the base of a Tertiary marine transgressive sequence, that, in turn, is overlain by marine carbonate deposits. Widespread shallow marine sediments are believed to exist in the west of the basin, in both the Lower and Upper Cretaceous sequences.Structure is dominated by normal, west to NW trending, down-to-the-south faults, many of which are synsedimentary. Fault displacements are greatest beneath the shelf-break, where basement has been downthrown 5 to 6 km. Farther south, synsedimentary faulting has resulted in a marked thickening of both Upper and Lower Cretaceous sequences.The basin has been barely explored for hydrocarbons. Regional seismic coverage is good, but drilling in the main part of the basin is limited to one well on the northern margin. The petroleum potential of the western half of the basin is rated as good, in view of the interpreted existence of abundant marine source beds and the recognition of situations favourable for generation, migration and entrapment of hydrocarbons.

Petroleum potential of the offshore southern Carnarvon Basin—insights from new Geoscience Australia data

2011 ◽  
Vol 51 (2) ◽  
pp. 746
Author(s):  
Irina Borissova ◽  
Gabriel Nelson
Keyword(s):  
Seismic Data ◽  
Source Rocks ◽  
Magnetic Data ◽  
Long Distance ◽  
Potential Field Data ◽  
Petroleum Potential ◽  
Gravity And Magnetic ◽  
Gravity And Magnetic Data ◽  
Insight Into ◽  
Carnarvon Basin

In 2008–9, under the Offshore Energy Security Program, Geoscience Australia (GA) acquired 650 km of seismic data, more than 3,000 km of gravity and magnetic data, and, dredge samples in the southern Carnarvon Basin. This area comprises the Paleozoic Bernier Platform and southern part of the Mesozoic Exmouth Sub-basin. The new seismic and potential field data provide a new insight into the structure and sediment thickness of the deepwater southernmost part of the Exmouth Sub-basin. Mesozoic depocentres correspond to a linear gravity low, in water depths between 1,000–2,000 m and contain between 2–3 sec (TWT) of sediments. They form a string of en-echelon northeast-southwest oriented depressions bounded by shallow-dipping faults. Seismic data indicates that these depocentres extend south to at least 24°S, where they become more shallow and overprinted by volcanics. Potential plays in this part of the Exmouth Sub-basin may include fluvio-deltaic Triassic sandstone and Lower–Middle Jurassic claystone source rocks sealed by the regional Early Cretaceous Muderong shale. On the adjoining Bernier Platform, minor oil shows in the Silurian and Devonian intervals at Pendock–1a indicate the presence of a Paleozoic petroleum system. Ordovician fluvio-deltaic sandstones sealed by the Silurian age marine shales, Devonian reef complexes and Miocene inversion anticlines are identified as potential plays. Long-distance migration may contribute to the formation of additional plays close to the boundary between the two provinces. With a range of both Mesozoic and Paleozoic plays, this under-explored region may have a significant hydrocarbon potential.

Automatic 3-D interpretation of potential field data using analytic signal derivatives

Geophysics ◽  
1997 ◽  
Vol 62 (1) ◽  
pp. 87-96 ◽  
Author(s):  
Nicole Debeglia ◽  
Jacques Corpel
Keyword(s):  
Signal Amplitude ◽  
Vertical Gradient ◽  
Analytic Signal ◽  
Magnetic Data ◽  
Practical Implementation ◽  
Potential Field Data ◽  
Gravity And Magnetic ◽  
Second Derivatives ◽  
Gravity And Magnetic Data ◽  
Derivatives Of

A new method has been developed for the automatic and general interpretation of gravity and magnetic data. This technique, based on the analysis of 3-D analytic signal derivatives, involves as few assumptions as possible on the magnetization or density properties and on the geometry of the structures. It is therefore particularly well suited to preliminary interpretation and model initialization. Processing the derivatives of the analytic signal amplitude, instead of the original analytic signal amplitude, gives a more efficient separation of anomalies caused by close structures. Moreover, gravity and magnetic data can be taken into account by the same procedure merely through using the gravity vertical gradient. The main advantage of derivatives, however, is that any source geometry can be considered as the sum of only two types of model: contact and thin‐dike models. In a first step, depths are estimated using a double interpretation of the analytic signal amplitude function for these two basic models. Second, the most suitable solution is defined at each estimation location through analysis of the vertical and horizontal gradients. Practical implementation of the method involves accurate frequency‐domain algorithms for computing derivatives with an automatic control of noise effects by appropriate filtering and upward continuation operations. Tests on theoretical magnetic fields give good depth evaluations for derivative orders ranging from 0 to 3. For actual magnetic data with borehole controls, the first and second derivatives seem to provide the most satisfactory depth estimations.

3D inversion modeling of joint gravity and magnetic data based on a sinusoidal correlation constraint

2019 ◽  
Vol 16 (4) ◽  
pp. 519-529
Author(s):  
Xiu-He Gao ◽  
Sheng-Qing Xiong ◽  
Zhao-Fa Zeng ◽  
Chang-Chun Yu ◽  
Gui-Bin Zhang ◽  
...  
Keyword(s):  
Magnetic Data ◽  
3D Inversion ◽  
Gravity And Magnetic ◽  
Gravity And Magnetic Data

Application of gravity and magnetic methods to assess geological hazards and natural resource potential in the Mosida Hills, Utah County, Utah

Geophysics ◽  
2000 ◽  
Vol 65 (5) ◽  
pp. 1514-1526 ◽  
Author(s):  
Alvin K. Benson ◽  
Andrew R. Floyd
Keyword(s):  
Gravity Data ◽  
Magnetic Data ◽  
Geological Hazards ◽  
Mafic Lava ◽  
Subsurface Geology ◽  
Gravity And Magnetic ◽  
Geophysical Surveys ◽  
Utah County ◽  
Gravity And Magnetic Data ◽  
Hills Area

Gravity and magnetic data were collected in the Mosida Hills, Utah County, Utah, at over 1100 stations covering an area of approximately 58 km2 (150 mi2) in order to help define the subsurface geology and assess potential geological hazards for urban planning in an area where the population is rapidly increasing. In addition, potential hydrocarbon traps and mineral ore bodies may be associated with some of the interpreted subsurface structures. Standard processing techniques were applied to the data to remove known variations unrelated to the geology of the area. The residual data were used to generate gravity and magnetic contour maps, isometric projections, profiles, and subsurface models. Ambiguities in the geological models were reduced by (1) incorporating data from previous geophysical surveys, surface mapping, and aeromagnetic data, (2) integrating the gravity and magnetic data from our survey, and (3) correlating the modeled cross sections. Gravity highs and coincident magnetic highs delineate mafic lava flows, gravity lows and magnetic highs reflect tuffs, and gravity highs and magnetic lows spatially correlate with carbonates. These correlations help identify the subsurface geology and lead to new insights about the formation of the associated valleys. At least eight new faults (or fault segments) were identified from the gravity data, whereas the magnetic data indicate the existence of at least three concealed and/or poorly exposed igneous bodies, as well as a large ash‐flow tuff. The presence of low‐angle faults suggests that folding or downwarping, in addition to faulting, played a role in the formation of the valleys in the Mosida Hills area. The interpreted location and nature of concealed faults and volcanic flows in the Mosida Hills area are being used by policy makers to help develop mitigation procedures to protect life and property.

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