Gravity and magnetic interpretation of the Deer Lake basin, Newfoundland

1984 ◽  
Vol 21 (1) ◽  
pp. 10-18 ◽  
Author(s):  
H. G. Miller ◽  
J. A. Wright
Keyword(s):  
Magnetic Data ◽  
Lake Basin ◽  
Magnetic Interpretation ◽  
Seismic Surveys ◽  
Reflection And Refraction ◽  
Gravity And Magnetic ◽  
Refraction Seismic ◽  
Gravity And Magnetic Data ◽  
Gravity And Magnetic Interpretation ◽  
Total Sediment

Detailed reconnaissance gravity surveys in the Deer Lake Carboniferous basin have been conducted using a station spacing of 2.5 km. The digitized aeromagnetic data for the basin were reduced to a 1:253 440 scale composite map. These two data bases were used to determine the configuration of major features and the total sediment thickness at various locations in the basin. Preliminary seismic results from reflection and refraction seismic surveys planned on the basis of these results are discussed. Modelling of gravity and magnetic data indicates that the Humber syncline contains approximately 1.2 km of sediments underlain on the west by rocks similar to the Long Range Complex. The eastern limb of the syncline is underlain by rocks similar to the Gull Pond Igneous Suite. The Howley Formation is deduced to be approximately 1.5 km thick and floored by rocks similar to the Topsails Igneous Suite.

scholarly journals Marine geophysical investigations offshore East Greenland

1983 ◽  
Vol 115 ◽  
pp. 93-100
Author(s):  
H.C Larsen
Keyword(s):  
Seismic Data ◽  
Seismic Refraction ◽  
Magnetic Data ◽  
Seismic Profiles ◽  
East Greenland ◽  
Gravity And Magnetic ◽  
Marine Gravity ◽  
Refraction Seismic ◽  
Regional Project ◽  
Gravity And Magnetic Data

During August and September 1982 a marine geophysical survey was conducted on the East Greenland Shelf. The survey was part of the ongoing regional project NAD (Larsen & Andersen, 1982; Andersen et al., 1981; Risum, 1980; Larsen & Thorning, 1980). In all 2794 km of 30-fold multi-channel seismic data and marine gravity and magnetic data were acquired (fig. 33). The object of the NAD programme is to acquire regional coverage of aeromagnetic, multichannel seismic refiection, seismic refraction (sonobuoy), marine gravity and magnetic data of the East Greenland Shelf between latitudes 60° N and 78°N. Aeromagnetic data comprising 63000 line kilometres were acquired in 1979 (Larsen & Thorning, 1980) and 5000 km of marine geophysical data were acquired in 1980 and 1981 (Larsen & Andersen, 1982; Andersen et al., 1981). This year the final data for the project were collected. Thus, a total of 7800 km of multi-channel refiection seismic data and 50 sonobuoy refraction seismic profiles of 20 to 70 km length have been acquired (fig. 33). In addition, marine gravity and magnetics were run at most lines.

Kowanyama deep refraction seismic survey

1989 ◽  
Vol 20 (2) ◽  
pp. 303
Author(s):  
B.M. Haines ◽  
B.A. McConachie
Keyword(s):  
Gravity Data ◽  
Seismic Refraction ◽  
Cost Effective ◽  
Seismic Survey ◽  
Magnetic Data ◽  
Gravity And Magnetic ◽  
Refraction Seismic ◽  
Intermediate Section ◽  
Cape York ◽  
Gravity And Magnetic Data

The Carpentaria Basin in the west/central portion of Cape York Peninsula is largely unexplored for petroleum, and there is an apparent ambiguity in the basement depths interpreted from gravity and aeromagnetic data. It was decided that deep seismic refraction surveys at a variety of sites should prove cost-effective in defining the geologic model for the basin. Of particular interest is the possible existence of a north-south trending elongate infrabasin inferred qualitatively from a strong gravity low shown Figure 1. Results of the refraction work indicate that the magnetic and gravity data suggestive of the presence of an infrabasin are probably related to lithological variations within basement. Furthermore, it is improbable that the thickness of the sedimentary pile anywhere within the area of investigation exceeds 1100 metres. Basement velocities are high, from 5500m/sec to 6200m/sec, typical of fresh igneous and/or metamorphic lithologies. Carbonates could not be totally excluded on the basis of these velocities alone, but are improbable in view of the gravity and magnetic data. At some locations there is evidence for the presence of an intermediate section of higher velocity within the sedimentary sequence. This is thought to be quite thin, and possibly representative of the Toolebuc Formation.

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.

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