Salt tectonics Flashcards
What is the link between salt deposition and climate or structural events?
Salt deposition is often related to early oceanic rifting and higher tempretures
Evaporation cycle
Increasing in evaporation / salinity
-Clay
-Limestone
-Dolomite
-Anhydrite
-Halite
-Potassium salt
Types of basins for deposition of evaporites
Type 1: Closed shallow basin with an exposed barrier (5-10 km) and open marine
Type 2:Isolated basin with restricted influx of water where theres a difference in sea-level.
There is variation of the thickness of the evaporites depending on where you are in the basin. Basin is a lot lower than open marine, and the basin deeper.
Why do we have salt structures in Denmark?
Missing
What causes deformation of salt structures?
load of deposition of top of the structure.
Sometimes the salt deposition will slide, if theres enough pressure it can act like a liquid
Material properties of salt
Wet salt has no strength
With dry salt strength decreases with depth (Due to temperature increasing with depth)
Porosity and density of salt?
Does not change depending on the depth this means:
At low depth salt is dense, and as the depth increases it will become lighter than the rock above it causing it to move upward.
It is not however, enough to create the upward movement: If salt cannot deform depositions above, it won’t flow upward
Trusheim model
Model for explaining the formation of a salt structure that is buoyancy driven
Subsidence and salt structures
Subsidence around a salt structure starts far away, and the more uplift happens for the salt structure, the subsidence will move closer
Yield point / Weld point
Pre-salt sediments touching cover sediments
Turtle formation
Anticline of sediments, not formed by compression, but due to removing salt. This causes several yield points across the bottom. We need an extension of the cover sediments
Active, passive and reactive diapirism
Active: Deforms cover sediments on their way to the top.
Passive: It does not deform, there’s no deformation of sediments around it. There’s no cover sediments.
Reactive: Reacts to deformation of sediments around it causing upward movement.
Reactive extension of cover sediments
Thinskinned extension
Contraction
Deposition on top of a preexisting diapir, the diapir gets reactivated through compression of the salt from both sides, this creates a teardrop diapir
Forway closure
Fold causing the salt to not go further up, upside down cup
