Reassessing the Holleford impact structure: Applying modern techniques to a classic Canadian crater

Impact cratering is a ubiquitous geological process affecting all planetary bodies with a solid surface. Despite advances in impact crater classification and confirmation, there still exists a disparity in impact evidence quality and type for newly confirmed versus previously established sites. Many known structures lack modern re-evaluation using contemporary criteria for confirming an impact site, including the Holleford structure in southern Ontario, Canada. This thesis revisits the ~2 km diameter, buried, simple crater, providing the first detailed analysis of the Holleford hole 2 drill core since the late 1960s. Through core logging, petrographic analysis and the use of modern techniques, this study further confirms an impact origin for Holleford and emphasizes the importance of re-evaluating previously established structures. This study uses electron backscatter diffraction to reassess microstructures in accessory minerals. Shock microstructures identified as {-111} twins in titanite, a feature which previous studies have hypothesized to be diagnostic of shock deformation at pressures between 12-17 GPa, were observed in one Holleford sample. Shock pressures for drill hole 2 were constrained to below 20 GPa, due to the absence of shock microstructures in zircon. These findings not only reinforce an impact origin for Holleford but also highlight a form of shock evidence that could be valuable in the confirmation of small, old impact structures, where impact evidence may have been erased, altered or did not develop due to low shock pressures. Small, old impact structures, like Holleford, are rare and unusual in the geologic record, and the outcomes of this thesis provide a foundation for future investigations. Similar reassessments of older structures and archived samples are encouraged to uncover hidden evidence of Earth’s impact record and to ensure consistent standards of impact characterization across Earth’s impact cratering record.

Department dc:contributor.department

Geological Sciences and Geological Engineering

Year dc:date.issued

2026

Author dc:creator

• McConnell-Radford, Emer

Advisor dc:contributor.supervisor

• Spencer, Christopher

• Impact cratering
• EBSD
• Titanite
• Shock metamorphism
• Deformation twinning

Statement dc:rights

• Attribution-NonCommercial-NoDerivatives 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by-nc-nd/4.0/

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1974/36042

OAI identifier oai:identifier

oai:queensu.scholaris.ca:1974/36042