Tectono-Geomorphic Mapping of Neotectonic Bedrock Structures Using Topobathymetric Modelling and Near-Surface Geophysics (Prince Edward County, Ontario, Canada)

Davies, Ethan, T

Please use this identifier to cite or link to this item: http://hdl.handle.net/11375/32497

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DC Field	Value	Language
dc.contributor.advisor	Boyce, Joseph, I	-
dc.contributor.advisor	Peace, Alexander, L	-
dc.contributor.author	Davies, Ethan, T	-
dc.date.accessioned	2025-10-08T19:21:54Z	-
dc.date.available	2025-10-08T19:21:54Z	-
dc.date.issued	2025	-
dc.identifier.uri	http://hdl.handle.net/11375/32497	-
dc.description.abstract	The causes of recurrent, low to moderate magnitude (≤ 4 Nuttli Magnitude – MN) intraplate seismicity in Southern Ontario are not well understood. Neotectonic faults and pop-up structures have been identified in Prince Edward County (PEC), but their links to underlying basement-fault zones and regional seismicity is uncertain. Tectono-geomorphic mapping and near-surface geophysics were conducted in this study on the Long Point peninsula (PEC) to investigate possible neotectonic structures. A high-resolution (2 m) digital topobathymetric model (TBM) was constructed by combining a LiDAR (Light Detection and Ranging) derived terrain model with multi-beam sonar bathymetric data. Six bedrock fault zones and > 30 pop-up structures were identified in the TBM, including a distinct, low relief (< 2 m) bedrock ridge (Gravelly Bay Fault Zone - GBFZ) that crosscuts late Pleistocene (ca. 12 ka) drumlin features. Ground-penetrating radar profiles reveal localized thrust faulting, block rotations and increased fracture density within the fault damage zone. The GBFZ is aligned with a NNW-trending magnetic lineament in Lake Ontario, indicating a coincident fault or shear zone in underlying Precambrian basement. Fault mechanisms for the GBFZ could include glaciotectectonic thrusting of bedrock, post-glacial isostatic unloading and reactivation of favourably oriented faults under the current intraplate stress field. The spatial coincidence of the GBFZ with basement magnetic lineaments suggests that the fault zone is structurally inherited from a fault or shear zone in the underlying Mesoproterozoic basement. The Picton and Salmon Point faults are also located over NE-trending aeromagnetic lineaments, indicating ‘tectonic templating’ of Paleozoic faults by underlying Precambrian basement structures. Further geophysical and field structural studies are underway in PEC to determine the fault mechanisms and possible linkages to recurrent seismicity in Southern Ontario.	en_US
dc.language.iso	en	en_US
dc.subject	Neotectonics	en_US
dc.subject	Southern Ontario	en_US
dc.subject	Prince Edward County	en_US
dc.subject	LiDAR	en_US
dc.subject	Topobathymetric Modelling	en_US
dc.subject	Basement Fault Reactivation	en_US
dc.title	Tectono-Geomorphic Mapping of Neotectonic Bedrock Structures Using Topobathymetric Modelling and Near-Surface Geophysics (Prince Edward County, Ontario, Canada)	en_US
dc.title.alternative	Tectono-Geomorphic Mapping of Neotectonic Bedrock Structures	en_US
dc.type	Thesis	en_US
dc.contributor.department	Earth Sciences	en_US
dc.description.degreetype	Thesis	en_US
dc.description.degree	Master of Science (MSc)	en_US
dc.description.layabstract	Damaging earthquakes often occur where tectonic plates converge at the edges of continents and are pushing against each other, compressing the Earth’ crust. Damaging earthquakes can also occur in the interior of continents, due to plate tectonic forces transmitted from the continental margins (so-called ‘intraplate’ earthquakes). In Southern Ontario, Canada, small to moderate intraplate earthquake events occur often, but their geological origins are not well understood. In Prince Edward County (PEC), in eastern Ontario, geological studies have found evidence for recent (‘neotectonic’) faults and folds (pop-up structures) in bedrock that may be linked to clusters of earthquakes activity. The earthquakes are centred over ancient faults in the Precambrian (> 1 billion-year-old) basement rocks, which suggest that these older structures are being ‘rejuvenated’ by plate tectonic forces. The region is a unique location to study modern neotectonic faults, as the surface soils and glacial sediments are very thin, allowing for detailed mapping and investigation of the exposed Paleozoic (~ 450-million-year-old) bedrock. Previous work in PEC relied on low-resolution aerial photographs and field mapping to identify neotectonic structures. To build on this previous work, a model of the Earth’s surface and underwater relief (known as a ‘topobathymetric model’ - TBM) was created in this study using newly available technology: LiDAR (Light Detection and Ranging) topographic elevations and bathymetry (water depth) data available for eastern Ontario. The TBM was employed to map bedrock surface structures across PEC, including pop-up structures and faults. A well-exposed fault (the Gravelly Bay Fault Zone — GBFZ) was further investigated using geophysical surveys (ground penetrating radar, gravity, magnetic surveys) to analyse its subsurface characteristics. The magnetic survey results show the fault zone is rooted in the Precambrian shield rocks underlying the Paleozoic cover, which have acted as a ‘tectonic template’, controlling fault development. The GBFZ cuts glacial landforms (e.g. drumlins) and surface sediments of the last Ice Age, confirming that the fault is a post-glacial (< 13,000 years) neotectonic bedrock fault. Future work in PEC will examine the relations between bedrock fault zones and earthquake clusters in Southern Ontario to better understand seismic risk and fault mechanisms.	en_US
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