Faults, especially Normal January 18, 2005
Free Write 10 Minutes How did you feel at Natural Bridges? Successful? Fear? On task? Bored? Confused? Did you feel clear on what you were being asked to do and why we asked you to do it?
Know These Terms Footwall vs. Hanging wall Fault plane vs. Fault zone vs. Shear zone Offset: –Normal vs. thrust/reverse vs. strike-slip vs. oblique –Heave and throw –True vs. apparent
Fault vs. Fault zone vs. Shear Zone
Micro to Macro Faults
Oblique Slip
They gotta terminate somewhere…
Normal Fault Terms Scarp Offset stratigraphy on maps and in drill cores Triangular Facets Offset streams Two models - Horsts and Grabins Termination
Outcrop Patterns of Faults
Drill Core Patterns of Faults
Outcrops of Scarps
Atila Ayden at long, small offset normal fault.
Length Vs. Offset of faults
Grabin Shape Models
Space Problem Illustrated
Space Problem - Rollover Anticlines
Normal Fault Folds - Roll-over Anticlines and Synclines
Detachment Faults
Normal fault scarp with indurated breccia Breccia on normal fault. Quaternary Klamath Lake Ore. Note colluvial deposit against fault scarp. Smoother areas of fault show finer gouge that has not been weathered out from between breccia-size fragments.
Normal Scarp in the Andes (Glenn Wallace)
Slickenlines on hanging wall. Note brecciated textures above and below slickenlined gouge face.
Indurated breccia on detachment surface. Note coarse lineation parallel to pen.
Tectonic Environments of Normal Faulting Continental Rifting Oceanic Spreading Ridges - Mid Ocean Basins Sedimentary Basins - Compaction and gravitational collapse Pull-apart basins - TRANSTENSION
Continent Rifting
Continental regional extension - Basin and Range is unique.
B&R topography
Flatirons (triangular facets)
Detachment surface in Whipple Mtns. Gneissic basement complex below. Young volcanic rocks and scraps of basement above.
Cross Section by Eric Frost, San Diego State University
Ridges of the World
Mid- Atlantic Ridge
Sedimentary Basins Gravitational Shelf Collapse
Sample Seismic Line
A word about transtension
Pull -apart basins on transform margins