Lagoonal Evaporite Formation
Two depositional types
1) Lake / Completely Enclosed Basin
2) Restricted Basin
with near permanent connection to open sea
bullseye precipitation
pattern
tear-drop precipitation
pattern
- Seawater becomes landlocked
- Precipitation of standing water body (with evaporation)
- Carbonate precipitation near the sea = abundant i.e. ooids
- 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
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
1) Dead Sea
Landlocked evaporative basin
2. Late summer - Salty water evaporates
--> forms thin evaporite crust halite ~ Salena
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