Sediment compaction and magnetotelluric data in the Eromanga Basin

Abstract

Magnetotelluric data obtained in the Eromanga Basin can be interpreted using one-dimensional models to describe plane layers consistent with geological mapping. Interpretations are based on the results of non-linear inversions generating a minimum least-squares error between the observations and the model. However there is no statistical justification for selecting highly complex starting models. In particular adequate solutions can be generated using models based on 2, 3 or 4 layers over basement; additional layers defining fine structure can only be retained using external geological constraints. Solutions based on random starting models suggest gradations in resistivity (1?4 ohm m) consistent with sediment compaction. Major discontinuities in all models (4?30 ohm m) are assumed to indicate a basement contact at depths of 7?8 km.