Sedimeitfology,geochemistry and discriminant analysis in the engineering geological investigation of damsites,Lower Gordon Area,Tasmania

Application of sedimentological, geochemical and discriminant analysis techniques to the engineering geological investigation of damsites assists in understanding the variation of rock types, stratal correlation, porosity, folding and faulting, through studying the history of depositional and diagenetic environments.

Factor analysis (Rao & Naqvi, 1977) resulted in the proposal of a tidal depositional model consisting of subtidal, shoal, bar, intertidal and supratidal carbonate environments, and channels and dune‐and‐flat terrigenous environments. Discriminant analysis has now been employed to extend the paleo‐environmental model laterally. Samples (142) from four new drill holes were examined, and the data compared with the earlier data by a discriminant analysis technique. The results confirm our pre‐existing model of a prograding tidal complex.

Regional correlation of depositional environments of strata shows an anticlinal structure. Faulting in the sequence is indicated by secondary dolomitisation, breccia‐tion and stfatal discontinuities. The secondary dolomites replaced both limestones and sandstones in the sequence. The amount of porosity is related to depositional facies and dolomitisation. It is possible to understand the hydrologic regime with the aid of regional structure, depositional and diagenetic facies, and porosity.

Because this factor and discriminant analysis technique intensively uses information from each length of drill core, the possibility exists of more confident interpretation of new data from less extensive drilling, with consequent saving in cost.