Print this pageFracture Controlled Platform Margins, Implications in the Evolution of Karst Processes: From Approach from a 3-D View
Gemma Labrana1, David Hunt2, and Juan José Pueyo1
1Geochemistry and Petrology, Universitat de Barcelona, Barcelona, Spain
2Carbonate Research, Norsk Hydro, Oil & Energy, Bergen, Norway
Paleocave systems controlled by faults and fractures record more efficient and widespread karst development. The focus of study are two faults which cut the Permian strata platform in Yates Formation, Guadalupe Mountains, Rattlesnake Canyon, New Mexico, USA, and are overlaid by shelf carbonates of the Tansill Formation. The Yates Formation consists of sandstone and carbonate siltstone/grainstone alternations. At the top of the Yates Formation a set of fractures related to syndepositional faulting were the major controls for preferential karst initial development.
Field and petrography observations support that caves are mainly filled with sediments deposited during Capitan time, such as limestone boulders and breccias (with microspar and sparry calcite cements and siltstone and/or sandstone matrix), reworked and remnant breccias, and dolomitic siltstone-sandstone breccias.
3D detailed mapping has proven essential to determine the distribution of breccia deposits, fracture distribution, limits of the caves, as well as the irregular boundaries of both studied faults due to karstic dissolution. The main capability of this mapping workflow is the development of a self-methodology for the generation of multivaluated surfaces using Microstation and Gocad software.
Dissolution features observed in the lower part of the Tansill Formation suggest that first Tansill stages of karst development were mainly matrix controlled. Faults and fractures at the top of the underlying Upper Yates sediments acted as sinkholes that evolved into vertical open passages (up to 100 m height). Lateral dissolution extensions (up to 20 m away from the cave vertical walls) are found to follow specific stratigraphic levels containing pisoid and fusulinid grainstones. This indicates that the original rock properties played a significant role in the development of lateral cavities.
AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas