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Marine geophysical investigations in the new Caledonialoyalty Islands-New Hebrides area
204
MARINE GEOPHYSICAL INVESTIGATIONS IN THE NEW CALEDONIALOYALTY ISLANDS-NEW HEBRIDES AREA
B.D. JOHNSON’,
D.M. HENRY’,
L.V. HAWKINS
and B.M. LARUE3
’ School
of Earth Sciences, Macquarie University, North Ryde, N.S. W. (Australia) ’ School of Applied Geology, University of New South Wales, Kensington, N.S. W. (Australia) 3 O.R.S.T.O.M., Noumea (New Caledonia)
Magnetic, bathymetric and seismic reflection data have been obtained in the New Caledonian-Loyalty Islands-New Hebrides region under a joint program involving the University of New South Wales and O.R.S.T.O.M., Noumea. The purpose of this investigation was to examine the structural framework of the region and to elucidate further the tectonic history of this part of Melanesia. The present paper concentrates on the Loyalty Islands trend. Correlation of magnetic and bathymetric traverses indicate that this trend is a continuous feature from 18”S, 164% to 27’S, 171% in an arc which touches the junction of the New Hebrides Trench and the Hunter Fracture Zone. Consistent features in the magnetic profiles are described and model solutions for the magnetic anomalies, assuming two-dimensionality, are presented. The solutions indicate that the trend is an ancient volcanic island arc with the associated, and now inactive, trench to the west. Examples of seismic data are presented and described and correlation of events is attempted on 2-way times. A more complete discussion of seismic sections awaits reliable velocity determination.
A QUALITATIVE STRUCTURAL INTERPRETATION ANOMALIES IN THE SOUTHWEST PACIFIC AREA
OF SOME MAGNETIC
A. LAPOUILLE and B. LARUE 0. R.S. T.O.M., Noumea (New Caledonia) D.M. Henry (Australia)
School
of Applied
Geology,
University
of New South
Wales, Sydney,
N.S. W
One map is presented illustrating results of measurements of total magnetic field from surveys carried out during 1970 to 1972 by Office de la Recherche Scientifique et Technique Outre-Mer (New Caledonia) and the University of New South Wales in the southwest Pacific Ocean, from 12”s to 28% and 158”E to 178”E. This map is a structural illustration deduced from correlations of anomalies from one profile to another. It displays the main features of the regional
MARINE GEOPHYSICAL INVESTIGATIONS IN THE NEW CALEDONIALOYALTY ISLANDS-NEW HEBRIDES AREA
B.D. JOHNSON’,
D.M. HENRY’,
L.V. HAWKINS
and B.M. LARUE3
’ School
of Earth Sciences, Macquarie University, North Ryde, N.S. W. (Australia) ’ School of Applied Geology, University of New South Wales, Kensington, N.S. W. (Australia) 3 O.R.S.T.O.M., Noumea (New Caledonia)
Magnetic, bathymetric and seismic reflection data have been obtained in the New Caledonian-Loyalty Islands-New Hebrides region under a joint program involving the University of New South Wales and O.R.S.T.O.M., Noumea. The purpose of this investigation was to examine the structural framework of the region and to elucidate further the tectonic history of this part of Melanesia. The present paper concentrates on the Loyalty Islands trend. Correlation of magnetic and bathymetric traverses indicate that this trend is a continuous feature from 18”S, 164% to 27’S, 171% in an arc which touches the junction of the New Hebrides Trench and the Hunter Fracture Zone. Consistent features in the magnetic profiles are described and model solutions for the magnetic anomalies, assuming two-dimensionality, are presented. The solutions indicate that the trend is an ancient volcanic island arc with the associated, and now inactive, trench to the west. Examples of seismic data are presented and described and correlation of events is attempted on 2-way times. A more complete discussion of seismic sections awaits reliable velocity determination.
A QUALITATIVE STRUCTURAL INTERPRETATION ANOMALIES IN THE SOUTHWEST PACIFIC AREA
OF SOME MAGNETIC
A. LAPOUILLE and B. LARUE 0. R.S. T.O.M., Noumea (New Caledonia) D.M. Henry (Australia)
School
of Applied
Geology,
University
of New South
Wales, Sydney,
N.S. W
One map is presented illustrating results of measurements of total magnetic field from surveys carried out during 1970 to 1972 by Office de la Recherche Scientifique et Technique Outre-Mer (New Caledonia) and the University of New South Wales in the southwest Pacific Ocean, from 12”s to 28% and 158”E to 178”E. This map is a structural illustration deduced from correlations of anomalies from one profile to another. It displays the main features of the regional