Fracture-Controlled Karsted Carbonate Platform Tops, Rattlesnake Canyon, Guadalupe Mountains, New Mexico, U.S.A.
J.A. Toni Simo1, Jana M. Van Alstine1, Dave Hunt2, Conxita Taberner3,
John Thurmond2, and Leonardo Piccoli1
1 University of Wisconsin, Madison, WI
2 Norsk Hydro, Oil & Energy, Bergen, Norway
3 Shell International Exploration and Production, The Hague, Netherlands
Permian shelf strata equivalent to the Capitan reef are cut by closely spaced steep syndepositional faults that dip basinward and landward in Rattlesnake Canyon, Guadalupe Mountains, New Mexico, USA. Integrated LIDAR and field mapping and GPR profiles enable reconstruction of 3D variability in sedimentary package thicknesses across faults. These variations illustrate the synsedimentary nature of the faults, timing of fault movement, and the control of the faults on rock fabric distribution. The faults extend the height of the exposure (180 m) and moved multiple times during their development; in general, movement was dip-slip, but occasionally motion reversed and pop-up structures were created. Faults cut through mostly lithified shelf carbonates and poorly lithified sandstones. Groundwater preferentially flowed through these fractures during multiple sea level lowerings and polycyclic paleocavern systems developed. The faults have irregular margins and the rock affected by dissolution shows a vertical pinch (<1m) and swell (up to 30 m) geometry, a reflection of the multiphase deformation-dissolution. Clasts from different stratigraphic levels suggest that paleocaves were open and had a vertical relief of at least 25 m during time of deposition. The paleocaverns are filled mainly with sediments deposited during Capitan time such as limestones, limestone breccias (with a microspar, spar, siltstone or sandstone matrix), reworked and remnant breccias, and dolomitic siltstone–sandstone breccias. GPR profiles across faults and paleocaverns allows for identification of GPR-facies typical of cave fills. Combining GPR profiles with velocities calculated from GPR CMP's and handheld sonic probe, we can use the Rattle Snake fault system as an analog to seismically identified fractures and fills, and improve their recognition and reservoir characteristics.