Geophysical correlation is based on the direct or indirect sampling of physical properties of distinct rock units together with qualitative and quantitative interpretation of geophysical data to provide spatial models of these rock units. In addition, the identification of major structural discontinuities from geophysical data has to be integrated into an overall model, including deformation and lithological correlations.
Unequivocal lithological identification, and therefore correlation, on the basis of measured or inferred geophysical properties is not generally possible. Commonly the range of physical properties associated with a particular rock unit will overlap that of other unrelated units. A further problem is that measured surface properties need to be adjusted for the effects of temperature and pressure to infer geophysical parameters at depth. Nevertheless, some rock units do have a sufficiently distinctive string of physical properties to generate a particular geophysical signature so that integrated analysis of the potential field and seismic data can suggest some models of (Precambrian) basement distribution and indicate possible styles of deformation.
Figures & Tables
This second and completely revised edition of Special Report No. 6 provides a comprehensive review and report of work earned out since 1975. It emphasizes the relationship between, and the correlation of, the units in to which the Precambrian rocks of England, Ireland, Scotland, Wales and the Channel Islands have been divided The chapters also provide a comprehensive bibliography of the work on which the correlations have been based.