Barnett fractures active in reverse faulting regime
Fractures expected to slip (red) and not slip (black) during hydraulic fracture stimulation of a horizontal well in the Barnett Shale, Fort Worth Basin, Texas. Fractures are from an image log. Stress conditions are from Lund Snee and Zoback (2016), except that a hypothetical strongly reverse faulting stress state is considered. Unlike in case of normal and/or strike-slip faulting, bedding planes (horizontal fractures, colored green) may be possible to make slip in this stress state. This figure is from Zoback and Lund Snee (2018).
Barnett fractures active in normal/strike-slip faulting regime
Fractures expected to slip (red) and not slip (black) during hydraulic fracture stimulation of a horizontal well in the Barnett Shale, Fort Worth Basin, Texas. Fractures are from an image log. Stress conditions are from Lund Snee and Zoback (2016). Note that horizontal fractures (bedding planes, colored green) are impossible to make slip in this stress state, except in cases of extremely high ambient pore pressure, which would cause the Mohr circle to shrink. This figure is from Zoback and Lund Snee (2018).
Redbeds above the basal unconformity
Redbed conglomerates sitting just above the unconformity at the top of the Paleozoic succession, north of Cedar Ridge, Huntington Valley, Nevada. These rocks lack Cenozoic volcanic detritus and their youngest zircon are Triassic in age. The depositional age is probably late Cretaceous or early Cenozoic, but it's uncertain. This is the record of what was sitting at the earth's surface following Mesozoic, Sevier-era shortening. It's overlain by the Eocene Elko Formation.
Thunderstorm over the Ruby Mountains
Standing at the top of Cedar Ridge looking east across Huntington Valley toward the Ruby Mountains.
Tuff of Dixie Creek, Huntington Valley, Nevada
Squaw Mountain, Huntington Valley, Nevada
Squaw Mountain, in the background, is an Eocene subvolcanic intrusion associated with the ignimbrite flare-up volcanic front that propagated southward through the United States Cordillera between ~55–21 Ma. We dated a sample at Squaw Mountain to 37.6±0.7 Ma.
South Island, New Zealand
Piñon Range, Nevada
Looking southeast from Huntington Valley toward the Piñon Range. Cedar Ridge is visible on the left. The middle-ground and foreground are west-dipping Eocene tuff of Dixie Creek unconformably overlain by the thin cliffs of the Oligocene tuff of Hackwood Ranch.
Smithy Creek fault, South Island, New Zealand
See Lund Snee et al. (2014) for a detailed study of this fault zone and its implications for the Alpine Fault interface between the Australian and New Zealand plates.
Stewart Island, New Zealand
University of Otago, New Zealand
Southern Alps, South Island, New Zealand
Looking east from near Okarito, New Zealand, across the Alpine Fault, to the Southern Alps. Mount Cook is the highest peak, near the right side.
Okarito, New Zealand
Fiordland, New Zealand
3D photogrammetry of the Smithy Creek fault
Annotated images extracted from a 3D whole-outcrop photo stitch depicting the principal slip zone, fault core, and damage zone of the Smithy Creek fault, South Island, New Zealand (from Lund Snee et al., 2014).