Talundilly, Western Queensland, Australia: Geophysical and petrological evidence for an 84 km-large impact structure and an Early Cretaceous impact cluster

The Talundilly Structure, southwestern Queensland, Australia, is represented on 2D seismic reflection transects as a major seismic anomaly disrupting the consistent 'C' seismic-stratigraphic horizon above the early Cretaceous Bulldog Wallumbilla Formation throughout the Eromanga Basin. The seismic anomalous zone, estimated at 84 km in diameter from the maximum extent of horizon disruption, coincides with a prominent aeromagnetic (TMI) high which is centrally located within a near-circular seismic anomaly of the 'C' horizon. The structure consists of a raised central area, with radial faults extending from the central high, an annular synform with disrupted seismic elements dipping at low angles towards the central uplift, and an outer faulted rim. Cuttings from the Talundilly-1 well, drilled ~ 30 km northwest from the central high, contain quartz grains with planar deformation features (PDF) indicative of shock metamorphism. The age of the structure, as determined from seismic correlation and sparse palynology, post-dates the 'C' seismic horizon and is determined as approximately 125 Ma, coinciding with a marine transgression. Correlation of seismic profiles suggest that the Talundilly impact structure is a possible twin of the Tookoonooka impact structure, dated as 125 ± 1 Ma and located 328 km to the south.