Deriving geological contact geometry from potential field data
Hernan Ugalde 1 2 William A. Morris 11 MAGGIC, School of Geography and Earth Sciences, McMaster University, Hamilton, Ontario L8S 4K1, Canada.
2 Corresponding author. Email: ugaldeh@mcmaster.ca
Exploration Geophysics 41(1) 40-50 https://doi.org/10.1071/EG09032
Submitted: 16 July 2009 Accepted: 14 December 2009 Published: 19 February 2010
Abstract
The building process of any geological map involves linking sparse lithological outcrop information with equally sparse geometrical measurements, all in a single entity which is the preferred interpretation of the field geologist. The actual veracity of this interpretative map is partially dependent upon the frequency and distribution of geological outcrops compounded by the complexity of the local geology. Geophysics is commonly used as a tool to augment the distribution of data points, however it normally does not have sufficient geometrical constraints due to: a) all geophysical inversion models being inherently non-unique; and b) the lack of knowledge of the physical property contrasts associated with specific lithologies. This contribution proposes the combined use of geophysical edge detection routines and ‘three point’ solutions from topographic data as a possible approach to obtaining geological contact geometry information (strike and dip), which can be used in the construction of a preliminary geological model. This derived geological information should first be assessed for its compatibility with the scale of the problem, and any directly observed geological data. Once verified it can be used to help constrain the preferred geological map interpretation being developed by the field geologist. The method models the contacts as planar surfaces. Therefore, it must be ensured that this assumption fits the scale and geometry of the problem. Two examples are shown from folded sequences at the Bathurst Mining Camp, New Brunswick, Canada.
Key words: Bathurst Mining Camp, potential fields, 3D modelling, topography.
Acknowledgements
This article is the outcome of substantial work done by the authors at the BMC, both with Neil Rogers and Cees van Staal, who have been providing the guidelines on the geology of the area. Funding for this project has been provided by the Targeted Geosciences Initiative 3 (TGI-3) from Natural Resources Canada (NRCAN), the New Brunswick Department of Mines, and an NSERC Discovery Grant to WAM. We thank the editor and reviewers (P. Schmidt, M. Thomas and a third anonymous reviewer) for valuable comments and suggestions that really improved the manuscript.
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