Evidence for intra-plate seismicity from spring-carbonate mound springs in the Kati Thanda-Lake Eyre region, South Australia: implications for groundwater discharge from the Great Artesian Basin

The relationship between fault structures and Great Artesian Basin (GAB) spring occurrence has rarely been discussed in relation to intra-plate seismicity. This is despite the occurrence of mound springs in the southwest portion of the GAB in South Australia being previously linked with the occurrence of faulting and the many studies concerning the role that tectonics plays in the formation and ongoing maintenance of spring activity. This study examines the correlation between seismicity and spring occurrences within the southwestern GAB, as well as field evidence for the relationship between ongoing spring activity and intra-plate seismicity. It was found that spring formation within the southwestern GAB is correlated with an interpreted northwest-southeast, left-lateral transpressional shear zone that is related to the Adelaide Fold Belt underlying the GAB. The influence of seismicity at these sites is implied through the propagation of deformation structures and lineaments concordant with interpreted underlying regional structures. In zones of reactivation, these structures and lineaments develop networks that readily form conduits for the migration of groundwater. Consequently, the spring-carbonate-depositing springs of the southwestern GAB have potential as a record for intra-plate tectonic activity associated with the northern portion of the underlying Adelaide Fold Belt. The work presented here re-enforces the importance of considering the effect that faulting has on groundwater flow paths and interconnectivity with either overlying or underlying aquifers within the southwestern GAB.