...the same day were all the fountains of the great deep broken up, and the windows of heaven were opened. Genesis 7:11
"Exposures of the South Fork Fault system (SFFS) extend for over 
35 km along the South Fork Shoshone River, southwest of Cody, Wyoming, and 30 km northwest up the western flank of Rattlesnake Mountain anticline, a basement-involved Laramide uplift.
Earlier research has demonstrated the presence of
tightly-folded sedimentary rocks,
tear faults,
a triangle zone
and other thin-skinned geometries along the leading edge of the allochthonous slide mass, typical of overthrust belts.
Transport was to the southeast, down a relatively flat slope (< 5o), in
early to middle Eocene time, approximately coeval with the Heart Mountain Fault system (HMFS) (Blackstone, 1985).
Well data, seismic data and surface exposures indicate the system detaches in the lower Jurassic Sundance Formation and/or the underlying Jurassic Gypsum Spring Formation.
The SFFS consists of nearly 1250 m of Jurassic through Tertiary strata, volcanic deposits, and possibly, several earlier-emplaced HMFS carbonate blocks.
Movement between 5 km and 10 km to the southeast spread the allochthonous mass over an area exceeding 1400 km2 (Clarey, 1990, 2008).
---The SFFS broke into several pieces during transport bounded by tear faults above the detachment in Jurassic rocks, segregating deformation in each segment (Clarey, 1990).
The area comprising the compressional “toe” of the allochthonous slide mass is exposed along the South Fork Shoshone River valley (Clarey, 1990). This area has been intensely drilled for oil exploration, and contains excellent exposures of tightly-folded strata.
Transport along the SFFS placed Jurassic through Eocene rocks on a possible bedding plane detachment in the Cretaceous Cody Shale and cutting across the Eocene Willwood Formation.The area west of the Hardpan fault shows a simple ramp geometry, placing Jurassic through Eocene rocks on an apparent detachment surface in the Upper Cretaceous Frontier Formation.
The Cody Shale at this location was eroded away, leaving the Frontier Formation exposed at the surface, prior to SFFS emplacement.
Published geologic maps in this area, and adjacent to the Castle fault, show folding and cross-cutting of the Eocene Willwood Formation, suggesting that the Willwood was involved in the SFFS and was transported along with the Mesozoic section beneath (Pierce and Nelson, 1969).
The conditions described by Heard and Rubey are similar to the conditions present for the SFFS.
The upper plate is approximately 1250 m thick, and composed of predominantly Jurassic through Upper Cretaceous shale-rich units, with 20-25 m of gypsum-anhydrite in the Gypsum Spring Formation to serve as the detachment.
All that may have been required for movement of the SFFS was for something to “trigger” the action, starting the slide.
Late Flood erosion by rapidly receding waters probably removed significant overburden and exposed lower Paleozoic rocks near the HMFS break-away.
Similarly-exposed volcanic centers near the break-away likely initiated the explosive movement of the HMFS, as envisioned by Beutner and Gerbi (2005).
Rapid loading, by the emplacement of the HMFS, may have been the trigger to initiate movement on the SFFS. Catastrophic emplacement of over 500 m of Ordovician through Mississippian carbonates, and unknown amounts of Absaroka volcanic deposits, on exposed Mesozoic and Tertiary rocks near the SFFS break-away.
In summary, the SFFS exhibits all the requirements of a high fluid-pressure system emplaced rapidly:
(1) it has a primary detachment surface in the Jurassic strata, rich in 
gypsum-anhydrite;
(2) it has a fluid generation mechanism in the dehydration reaction to anhydrite, which simultaneously raised the internal fluid pressure to near lithostatic and decreased the aggregate strength;
(3) it has the rapid emplacement of the HMFS to serve as the “triggering” process, initiating movement down the 3-5o slope by loading on the rear of the system; and
(4) it has a toe detachment in the Cody Shale to maintain high fluid pressure during transport along the leading edge of the system.
The discovery of a SFFS break-away fault, denuded zone, and detachment surface (analogous to the HMFS) further supports a model of catastrophic emplacement.
Field relations indicate transport on the SFFS and the HMFS during the early to middle Eocene (late or post-Flood). Both fault systems exhibit a consistent transport direction to the southeast, have bedding plane detachments, and have ramps placing older sediments on Eocene-age units.
Stage 1 Late or post-Flood volcanic activity caused the recently exposed rocks comprising the HMFS to separate along a break-away fault and catastrophically slide southeast, transporting large carbonate blocks such as Logan Mountain to the southeast. Rattlesnake Mountain apparently served as a buttress during emplacement the HMFS, splitting off the southern edge of the HMFS, and transporting it in a more southerly direction.
Stage 2 Rapid loading by the carbonate blocks and volcanic rocks of the HMFS served as a kinetic “trigger” for the SFFS as it rifted along its incipient break-away fault.
This rear loading, combined with the high fluid pressure and loss in cohesive strength from dehydration reactions in the Jurassic gypsum-rich layers, allowed transport to the southeast, possibly at the rate of a superfault (> 0.1 m/s) (Spray, 1997).
Movement on the SFFS caused “piggy-back” style transport of several of the carbonate blocks of the HMFS, transporting Logan and Sheep Mountain farther southeast.
The SFFS moved predominantly southeast, approximately parallel to the major tear faults. The end of Stage 2 left the tectonically denuded zones largely exposed for both the SFFS and the HMFS.
Stage 3 Deposition of additional Absaroka volcanic units quickly buried both denuded surfaces, preserving the planar SFFS break-away fault and the HMFS break-away fault (Pierce, 1987b).
Much of the SFFS and HMFS were covered with younger Absaroka volcanic rocks and the Deer Creek slide mass (Malone, 1994, 1995, 1996).
Completion of Stage 3, and the end of Absaroka volcanism, left the northwestern Wyoming region exposed to further withdrawal of the remaining Flood waters and weathering and erosion, resulting in the topography that is observed today .
Final Conclusions:
All data suggest overthrust faults like the SFFS and HMFS moved rapidly."
Timothy L. Clarey, PhD
