1. 3D Modeling of Fault-Growth Monoclines NATCHANAN DOUNGKAEW

2. GOAL To create the 3D models of the monoclines located at  the Walnut Canyon ( The Indian Shelter)  The Slaughter Canyon The models would provide geometric constraints such as :  Thicknesses, Orientations and Widths of the monoclines  Orientations and densities of the fractures The constraints will be used in the boundary element and finite element models

3. Background A monocline is a step-like fold in rock strata consisting of a zone of steeper dip within an otherwise horizontal or gently-dipping sequence. It formed during upward propagation of an extensional fault in basement into an overlying cover sequence. http://bc.outcrop.org/GEOL_B10/Dlecture9.html

4. Method Part I : Field Study  Visited a monocline located at the tip of Fault E in Slaughter Canyon and the Indian Shelter at Walnut Canyon at Carlsbad, New Mexico Took pictures for the 3D modelling Mapped the outcrops, recorded changes in facies and fractures dip and dip direction in ArcMap Used a laser range finder to located relative locations in horizontal and vertical axes and azimuthal distances

5. Method Part II : 3D Modelling Created 3D Models in Agisoft Photoscan Exported as DEM files and Orthophotos to ArcScene Digitized the fractures on the 3D models for fracture density analysis

6. Result The Final 3D models : The Indian Shelter - The monocline developed over shelfward dipping normal fault -Contains Syndepositional ( faulting happened simultaneously with sediment deposition) fractures and faults -Sandstone in Indian Shelter thicken in a shelfward direction N s Basin Area where coulomb stress present

7. Result The Final 3D models : The Indian Shelter

8. Result The Final 3D models : The Fault E Monocline -Fault E tips out below a growth monocline -The exposure is located further from the fault center compared to the exposure of the fault on the west. -The monocline is grown in a shallow subsurface during the deposition of sediments - the fault ceased by the end of deposition of siliciclastics above E W

9. Result The Final 3D models : The Fault E Monocline

10. Conclusion During the formation of folding, the rocks must have been brittle, allowing the fractures to form The orientation of the fractures varies along the monoclines The fracture density is greatest at the hinge zone, and decreases as the distance from the hinge line increases.