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Line 19: + − − [[file:evaluating-top-and-fault-seal_fig10-19.png|thumb|{{figure number|10-19}}See text for explanation.]] − − Shale-rich gouge zones can create impermeable barriers. The following figure, a normal fault in Jurassic and Triassic sediments near Lilstock, U.K., shows a gouge zone approximately [[length::5 m]] thick. The gouge consists predominantly of ductile shales and marls as well as small amounts of brittle limestones. Faults with similar shale-rich gouge in producing fields create seals. + + + Line 51:
Line 51: − − [[file:evaluating-top-and-fault-seal_fig10-21.png|thumb|{{figure number|10-21}}See text for explanation.]]
How fault zones affect seal (view source)
Revision as of 16:14, 31 January 2014
, 16:14, 31 January 2014merged article in
The following figure is an example of smear gouge along a normal fault found in a sequence of Permian-Carboniferous sand and shales near Lynemouth, U.K. Ductile, light gray shales have been incorporated in the fault zone as a continuous layer sourced from a bed in the footwall (upper left). Similarly, a bed of coal (black) in the footwall and sandstone in the hanging wall have been incorporated as discontinuous fragments in the fault zone. The coal, however, is intensely fractured, reflecting brittle rather than ductile deformation.
The following figure is an example of smear gouge along a normal fault found in a sequence of Permian-Carboniferous sand and shales near Lynemouth, U.K. Ductile, light gray shales have been incorporated in the fault zone as a continuous layer sourced from a bed in the footwall (upper left). Similarly, a bed of coal (black) in the footwall and sandstone in the hanging wall have been incorporated as discontinuous fragments in the fault zone. The coal, however, is intensely fractured, reflecting brittle rather than ductile deformation.
[[file:evaluating-top-and-fault-seal_fig10-19.png|thumb|{{figure number|10-19}}See text for explanation.]]
Both brittle sands and coals as well as ductile shales are incorporated in the fault zone. The mechanism of gouge formation is much more complex than a simple “smearing” of ductile shales into the fault zone. Although faults exhibit a complete spectrum of behavior from brittle to ductile, interbedded sand-shale sequences with strong ductility contrast commonly exhibit this transitional behavior.
Both brittle sands and coals as well as ductile shales are incorporated in the fault zone. The mechanism of gouge formation is much more complex than a simple “smearing” of ductile shales into the fault zone. Although faults exhibit a complete spectrum of behavior from brittle to ductile, interbedded sand-shale sequences with strong ductility contrast commonly exhibit this transitional behavior.
[[file:evaluating-top-and-fault-seal_fig10-20.png|thumb|{{figure number|10-20}}See text for explanation.]]
[[file:evaluating-top-and-fault-seal_fig10-20.png|thumb|{{figure number|10-20}}See text for explanation.]]
Shale-rich gouge zones can create impermeable barriers. The following, a normal fault in Jurassic and Triassic sediments near Lilstock, U.K., shows a gouge zone approximately [[length::5 m]] thick. The gouge consists predominantly of ductile shales and marls as well as small amounts of brittle limestones. Faults with similar shale-rich gouge in producing fields create seals.
==Example: spectrum of gouge compositions==
[[file:evaluating-top-and-fault-seal_fig10-21.png|thumb|{{figure number|10-21}}See text for explanation.]]
Fault gouge can range from sand rich to shale rich. The following figure shows three fault zones exhibiting a spectrum of sand-shale ratios. The table below describes the position of the three faults, their sequences and characteristics, and their location.
Fault gouge can range from sand rich to shale rich. The following figure shows three fault zones exhibiting a spectrum of sand-shale ratios. The table below describes the position of the three faults, their sequences and characteristics, and their location.
| Jurassic, Kilve, U.K.
| Jurassic, Kilve, U.K.
|}
|}
==See also==
==See also==