19 Salt Tectonics.ppt - West Virginia...
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Salt Tectonics Topics w Salt Deposition w Salt Movement w Diapir Structures w Imaging w Link to faulting Composition of Salt Domes w Mostly halite w Also gypsum or anhydrite w Often interbedded and folded Gypsum, Ca(SO 4 ).2H 2 0 Halite, NaCl Salt Deposition Bonneville Salt Flats, Utah Restricted marine basins Unusual Properties of Salt compared to Clastic rocks •Salt density= 2 g/ cm 3 •Salt undergoes no compaction •Mechanically weak - viscous •Shale Density •Initial Density = 1.8 g/ cm 3 ( 40% water) •Final Density = 2.4 g/ cm 3 ( after water is expelled) Density vs burial curve Density, kg/m 3 Depth, m
Transcript of 19 Salt Tectonics.ppt - West Virginia...
Salt Tectonics Topics
w Salt Deposition
w Salt Movement
w Diapir Structures
w Imaging
w Link to faulting
Composition of Salt Domesw Mostly halite
w Also gypsum or anhydrite
w Often interbedded and folded
Gypsum, Ca(SO4).2H20 Halite, NaCl
Salt Deposition
Bonneville Salt Flats, Utah
Restricted marine basins
Unusual Properties of Salt compared to Clastic rocks
•Salt density= 2 g/ cm3
•Salt undergoes no compaction
•Mechanically weak - viscous
•Shale Density
•Initial Density = 1.8 g/ cm3 ( 40% water)
•Final Density = 2.4 g/ cm3 (after water is expelled)
Density vsburial curve
Density, kg/m3
Dep
th, m
Relative Strength of Salt and Rock
Salt
Lab model of the rise of a diaper driven by buoyancy
Salt at the Surface
Salt Glacier - Iran
Salt Structures -Iran
Gulf of MexicoGulf of Mexico – US platforms in 2012
Gulf of MexicoSalt
Variety of Salt Structures
Jackson and Talbot, 1991
3D Seismic Interpretation of Salt Structures
Internal flow of salt
Jackson et al. 1990
Internal structure of diapirs from centrifuge experiments
6 Mechanisms for Salt Movement (halokinesis)
Main Classes of Diapirs
Active rise of salt
Passive: Salt keeps up with sedimentation
Reactive: Response to extension
Reactive: Response to thrusting
Fossen, 2010
Detection of Salt Domes
w Gravity surveys
• Find gravity lows
• Low density
w Seismic Imaging
GM-SYS™ Profile model of salt structure integrating seismic reflection, FTG gravity, and magnetic data (EarthExplorer, 2009).
Gravity
Geosoft GmsYs-3D model of a salt body embedded in a 3D density volume (Earth Explorer, 2009)_
Seismic Image of a Salt DomeSalt edges are hard to see Rootless Salt- Gulf of Mexico
AAPG Explorer, 2013
Diapir movement and extension Sandbox ExperimentRelationship between salt dome and normal faulting
http://www.beg.utexas.edu/indassoc/agl/animations/AGL95-MM-001/index.html
GUGLIELMO, G., Jr., , B. C. VENDEVILLE, D. D. SCHULTZ-ELA, and M. P. A. JACKSONBureau of Economic Geology, The University of Texas at Austin,
Sand box model ofa diaper in an extensional setting
Normal fault-diapirrelationship
Hughes, 1968
Cypress Creek Field
Gulf Coast
Diapir in a contractional setting
Extension Above Salt DiapirEkofisk Formation
W E
Late Cretaceous
Shallow Sea Continued regional subsidence Rising sea level Active phytoplankton growth
Late Cretaceous: Ekofisk FormationDanish North Sea
8kmCI = 30ms
Time
Salt Domes Pierce the Strata
Fractures around Salt Domes
Ant-Tracking displaying radial fracture pattern around salt domes
8km
Salt moves up, sediment moves down
Salt movement affects sediment thicknessOnce the salt is gone, unusual
structures remain
Salt Traps Salt is the best sealw Examples of Petroleum Salt Provinces
• Gulf of Mexico
• North Sea
• Middle East
La Popa Basin, MexicoZagros Mts., Iran
Salt Structures vs. Tectonic Structures
•Caused by movement of salt, not by plate boundary stresses
•Often linked to sedimentation
•Often localized by tectonic structures
•Both upwards movement of salt and salt withdrawal cause deformation
