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Lagoonal Evaporite Formation (2) Restricted Basin (with near permanent…
Lagoonal Evaporite Formation
Two depositional types
1) Lake / Completely Enclosed Basin
bullseye precipitation
pattern
Seawater becomes
landlocked
Precipitation
of standing water body (with evaporation)
Evaporite facies form bullseye
Carbonates around edge (precipitate easiest)
Gypsum layer
Halite (last to precipitate in centre)
Porous barrier
- allows seawater to leach into circular water body
2) Restricted Basin
with near permanent connection to open sea
tear-drop precipitation
pattern
Carbonate precipitation near the sea
= abundant i.e. ooids
Seawater leaks into basin
Gypsum deposit
in central basin
Halite
precipitates in
most distal parts
only (hypersaline & away from marine influence)
2)
Larnaca Salt Lake, Cyprus
Coastal evaporative basin open to sea
- local evaporation
1. Winter storms / surge
- Water enters basin via porous sands
2. Late summer
- Salty water evaporates
--> forms thin evaporite crust halite ~ Salena
1) Dead Sea
Landlocked evaporative basin
Pull-apart basin
Subsided basin
formed as 2 faults form an area of crustal extension
Water flowed in
draining the desert surrounding the basin
well below sealevel
Strong evaporation
due to hot arid climate
Evaporites = anhydrite
primarily
precipitate directly from seawater
form at ends of basin esp
Dead sea complication
Erosion older Miocene Evaporites
(included amongst base rocks )
makes water even more salty
Limited water supply
Northern river source limited
damming
overabstraction for agriculture
Water level dropping annually