Multichannel seismic survey sonobuoy refraction survey and ...

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Also, 18 sites were chosen dredging from the single-channel seismic' data, but only 9
sites were actually dredged. Many of the remaining sites had to be abandoned due to the
alteration of arrival time in Suva by about 12 hours ahead of schedule. The latitudes and
longitudes and water depths of the dredge sites arc given in Appendix C and the locations are
shown in Figures 2(a) and 2(c). A short preliminary description of the dredge samples recovered
are given in Appendix I).
CONCLUSIONS AND RECOMMENDATIONS
Except for dredging, the programme was completed as planned. The area surveyed -
between Tongatapu and latitude 23° 30' on tile southern part of the Tonga Platform - appears to
have sufficient thicknesses and areal extent of sedimentary rocks below the seabed to constitute
an area of potential for accumulation of petroleum. The presence of possible reefal buildups is
confirmed by this survey. Also, it is likely that there are many fault and stratigraphic traps.
The multichannel seismic data after proper processing together with sonobuoy refraction
data may indicate the presence of more reefal buildups. It is recommended that a thorough
interpretation of all the data gathered during the present survey, i.e. multichannel seismic,
single-channel seismic, gravity, magnetic and sonobuoy refraction data be made in conjunction
with the results of the source rock investigation team of USGS which will visit Tonga in the
near future, be made to assess properly the petroleum potential of the surveyed area
WORK REMAINING
Data reduction and computer processing of all data gathered during the survey in Menlo
Park, California, by the Marine Geology Processing Centre of U.S. Geological Survey. The
processed multichannel and single-channel data are to be displayed in a 9-inch Mylar base
transparency. Processed gravity and magnetic data are also to be displayed on a 9-inch Mylar
base transparency at the same horizontal scale i.e. with the same shot-point spacing, so that the
available sets of data can be readily pasted together for interpretation.
REFERENCES
Dupont, J. in press: Morphologie et structures superficielles de l'arc insulaire des Tonga-
Kermadec, in Equipe de Geologie-Geophysique du Centre ORSTOM de Noumea.
Contribution a l'etude geodynamique du Sud-Ouest Pacifique. Travaux et Documents de
PORSTOM No. ___. 20pp.