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Amalgamation of Silt Smears on Normal Faults at Outcrop Scale
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, Fifth International Conference on Fault and Top Seals, Sep 2019, Volume 2019, p.1 - 5
Abstract
Presentation examines the role of silt smear amalgamation in low permeability fault-rock generation for two different siliciclastic sequences in New Zealand. Data for outcrop-scale normal faults indicate that the geometries and occurrence of smears is highly variable. In sequences where silt smear is common, fault rock is primarily derived from fine-grained beds in the wall rock with frequent smear amalgamation. In these cases published algorithms may provide useful measures of fault-seal potential. In sequences where smear of silt beds is not ubiquitous and the thickness of smears is highly irregular, smears are only rarely amalgamated. In such cases the majority of fault rock appears to be generated by cataclastic processes and existing algorithms may not accurately describe the contribution of low-permeability wall rock to fault zones. The distinction of these two smear models is key for fault-seal analysis and is partly attributed to sequence architecture and silt-bed composition, where higher phyllosilicate content is associated with greater smearing.