Magee, C orcid.org/0000-0001-9836-2365 and Jackson, CA-L (2021) Can we relate the surface expression of dike-induced normal faults to subsurface dike geometry? Geology, 49 (4). pp. 366-371. ISSN 0091-7613
Abstract
Many igneous dikes do not reach the surface, instead triggering normal faulting and graben formation in overlying rock. The surface expression of these dike-induced faults provides important records of active and ancient diking. For example, surface measurements of graben half-widths have been used to estimate dike upper-tip depths by projecting faults straight downdip, whereas extension measured at the surface across dike-induced fault pairs (i.e., their cumulative heave) is considered a proxy for dike thickness. We use three-dimensional seismic reflection data to test how the surface expression of two buried dike-induced faults relates to dike geometry. The dike-induced faults are nonplanar, suggesting fault dips should not be assumed constant when using graben half-widths to estimate dike depth. Multiple displacement maxima occur across the dike-induced faults, but rarely at their lower or upper tips, suggesting they formed through linkage of isolated faults that nucleated between the dike and free surface. Fault heave is greatest where these subsurface displacement maxima occur, meaning the cumulative heave of the dike-induced fault pair measured at the syn-faulting free surface underestimates their total extension and poorly reflects dike thickness. Our results imply that at-surface analyses of dike-induced fault geometry cannot be used to estimate key dike parameters without a priori knowledge of fault structure and kinematics or host rock lithological variations.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | Copyright © 2021 Geological Society of America. This is an author produced version of an article published in Geology. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | dike swarms; dikes; displacements; faults; geometry; grabens; intrusions; kinematics; normal faults; reflection; seismic attributes; systems |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst of Geophysics and Tectonics (IGT) (Leeds) |
Funding Information: | Funder Grant number NERC (Natural Environment Research Council) NE/R014086/1 |
Depositing User: | Symplectic Publications |
Date Deposited: | 02 Oct 2020 14:51 |
Last Modified: | 25 Nov 2021 01:38 |
Status: | Published |
Publisher: | Geological Society of America |
Identification Number: | 10.1130/G48171.1 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:166049 |