Structural cross-section based on the Mt Isa deep seismic transect

Abstract

The Mt Isa deep seismic transect images a regional detachment surface and basement-cutting faults associated with Mesoproterozoic, east – west shortening in the Mt Isa Inlier, Queensland. New mapping along the trace of the transect is combined with interpretations of seismic-reflection data to derive a structural cross-section for the top 12 km of the crust. A regional detachment surface is imaged beneath the eastern half of the inlier leading to a fold and thrust belt interpretation for this region, where supracrustal units were decoupled from basement and translated west or northwest. The detachment is imaged across most of the Eastern Fold Belt in the reflection data, and it emerges as a series of thrust faults along the western margin of this belt. This detachment is cross-cut by reverse faults related to a regional, basement-involved style of deformation that involved the entire inlier. Shortening in the Western Fold Belt is dominantly east-vergent and was accommodated by a complex interplay of local thrusts, folds and reverse faults.

Key words:

• Mt Isa
• Proterozoic
• seismic reflection
• structural geology
• Tewinga Detachment

Acknowledgements

I would like to acknowledge the conscientious efforts of the Geoscience Australia land seismic crew who produced, collected and processed the reflection data used in this study.