The Messinian Salinity Crisis - Home: Earth and...
Transcript of The Messinian Salinity Crisis - Home: Earth and...
Miocene Milieu‘Musings on the Messinian Salinity Crisis’
USSP 2010 Science Party
Outline
• Introduction: the Miocene
• Background: the Messinian Salinity Crisis– When, where & the evidence
• The hypotheses: how did it happen?– The controversies
• The implications: who cares about the MSC?– Global impact & the hydrologic budget
The Miocene
A brief introduction
The Miocene
Zachos et al.
(2001)
Antarctica
partially
glaciated
fully glaciated
Vegetation
closed forest (C3)
open land (C3)
open grassland (C4)
Period
early
middle
lateMio
cen
e Fauna
↑ dominance of
grazing species
[CO₂]
≈600 ppmv
fluctuations
≈300 ppmv
Introduction
Changing glaciation
↕ NADW
formationMessinian
Salinity
Crisis
Humid
conditions
Upwelling
cycles –
trade winds
Southern Source Water
Strong
monsoonal
Systems
Changing glaciation
Moving
continents
The Messinian Salinity Crisis
Some background
Messinian Salinity CrisisBackground
Italy
Precession Minimum
Precession Maximum
Composite
Mediterranean
stratigraphy
Pre- and post- event
deposits:
Sapropels and marls –
precession cyclicity
Messinian Salinity
Crisis deposits:
Evaporites followed by
brackish fauna
What caused the MSC?
Two, main hypotheses
DesiccationHow did it happen?
Proposed by Hsü et al. (1973)
Reflooding
Deposition of
~25 m salt
Deposition of
~25 m salt
2500 m of salt
DesiccationHow did it happen?
Hsü et al. (1973)
DesiccationHow did it happen?
Hsü et al. (1973)
Feasible scenario?
100 cycles needed & each takes 10
ka +
= 1 Ma to accumulate salt deposits
Actually deposited in 450 ka
No Desiccation
Normal marine salinity
Siphoning event
Hypersaline: GYPSUM
Betic Corridor closed
Hypersaline: HALITE
Riffian Corridor closed
Hyposaline: brackish
Straits of Gibraltar open
Normal marine salinity
How did it happen?
Age (Ma) Lithology Salinity (g l-1) Hypothesis
Two-way (anti-estuarine) flow
through Gibraltar
Gypsum and brackish water
sediments – periodic freshwater
input & Atlantic incursions
Deposition of halite – no outflow,
some inflow
Persistent Atlantic inflow during
gypsum formation – no outflow
or small-scale outflow
Two-way (anti-estuarine) flow
through both Morocco & Spain
Atlantic water siphoned through Morocco
– outflow funnelled through Spain
Spanish gateway shut – two-way flow
through Morocco – reduced outflow
• Gateway analysis
• Evidence from the basins
Will we ever know the truth?
How did it happen?
But why should we care?
...pursuing knowledge for the sake of knowledge?...
• Total desiccation = 5 m global sea level rise
• Climate: drier Med region & amplification of seasonal temps
Impact of desiccation
Implications
Surface air temperature: the effect of desiccating the Mediterranean basin
• Deep source hypothesis: Nordic Sease.g. Reid et al. (1979)
• Shallow source hypothesis: NA Sub-tropical gyree.g. McCartney & Mauritzen (2001), Bower et al. (2002)
Outflow and global THCImplications
HadCM3 5m depth HadCM3 2730m depth
• Sensitive & high-resolution process studies
Studying hydrologic budgetsImplications
?
• Aydin Cicek, Ministry of environment and forestry of Turkey.Climate change mitigation
• Harald Poigner, Alfred Wegener Institute, Germany. Antarctic near-shore biogeochemistry: trace metals in bivalves
• Iuliana Vasiliev, Utrecht University, Netherlands. Palaeomagnetism & inorganic geochemistry
• Kate ‘Tug’ Olde, Kingston University London, UK. Dinocysts as palaeo-proxies during the Cretaceous greenhouse climate
• Robin Topper, Utrecht University, Netherlands. Modelling of the Messinian Salinity Crisis using 87Sr/86Sr
• Ruža Ivanović, University of Bristol, UK. Mediterranean-Atlantic exchange: Nd geochemistry & GCM modelling
The TeamThe Miocene Team