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Carbonate Deposition in the Great Salt Lake, Utah
Robert Baskin (1) & Paul Wright (2)University of Utah, Salt Lake City, Utah 84112. [email protected] Sciences, National Museum of Wales, Cardiff, UK ([email protected])
mailto:[email protected]:[email protected]:[email protected]:[email protected] -
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50 kms
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Carozzis1962 sediment map
based on Eardley 1938
Because it is the largest
lacustrine carbonate systemtoday
Because it is a natural
laboratory for understanding
carbonate deposition in a
dryland rift setting
Because there has been no
integrated study of the
sedimentary system
Why study it?
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4
Great Salt Lake- Key Facts
Area: 4400km2present
Drainage: Three ephemeral rivers fromwestern side; main rivers on the east.
Water Depth: 4.45m average (10mmaximum)
Climate: Arid to Semi-arid
Wave Base: Approx 4m
Chemocline: intermittent, affected byNorth Arm flow
Lake Type: Hypersaline-Saline (13-25%salinity)
Setting: Intracontinental rift
Fauna: Brine shrimp, brine fly larvae.
Sediments: extensive microbialites, ooliticsands. Halite precipitation in the NorthArm.
2003
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The current deposystem is very young and it is unclear how this
might be preserved to enter the stratigraphic record
In broad terms it fits well with the big picture model forcarbonate deposition in an arid rift setting, but with critical and
subtle tectonic controls on sediment production and distribution
We can develop some simple facies models but shoreline
diversity still not fully assessed
Most of the lake is currently within wave base
The specific hydrology of this shallow lake favours carbonateproduction over very large areas, with limited terrigenous
dilution and carbonate production related to groundwater inflow
(cf many other carbonate lakes).
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Structure
Various sources
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Closed basin hydrological model
From Renaut R & Gierlowski-Kordesch 2010, Facies Models 4,ed. By N P James & R W Dalrymple, Geoscience Canada
The Great Salt Lake
receives:-
66% from runoff
31% from direct
precipitation.
3% recharge from
groundwater
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Major catchments and river
inflows (Baskin et al 2002)
Terrigenous sedimentation is largelylocalised in the northwest allowing
carbonates to dominate most of the
lake
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From Harris P M et al. 2012 Bull. AAPG, 97, 27-
60
270m fall in 4kyrdue to breaching and
climate change
The current deposystem is
young!
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Modified from Harris P M et al. 2012 Bull. AAPG, 97, 27-60
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How well does the GSL today correspond to this model?
How well does the GSL today correspond to this model?
Dryland rift carbonate model
Hanging wall ramp margin
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500m
Shore line deposition: Bridger Bay = oolitic and
microbial (reflective) shorelines
Microbial mounds
Oolitic shore
Prevailing
wind
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Rippled ooliticsand flat
intraclasts
Oolite dunes
Oolitic
nebkha
Intraclast zone
Oolitic bars
Littoral-supralittoral facies
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Importance ofstable substrates
Oolitic shore
Microbial
mounds
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Pop-corn faciesaragonitic crusts shed off microbialites
pop corn berm
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PROGRADATIONAL WALTHERIAN
Supralittoralfacies aeolian oolitic sands, rooted,
larger dunes rarely preserved
platy intraclast rudstones
planar laminated oolitic, intraclasticgrainstones
small scale cross-bedding in ooliticgrainstones
microbial bioherms locally developed,partially truncated
popcornaragonite & ooid grainstones,peloidal
wave rippled oolitic grainstone -packstone
laminated, organic-richaragonite muds
Eulittoralfacies
Sub-littoralfacies
Profundalfacies
Based on southern arm of GSL
0
4m
Possible stratigraphic product
Analogue
Upper Triassic, SW England; Milroy & Wright 2002
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Restriction in the North Arm shows the fate of the carbonate
system when the lake begins to dry out -
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NON-WALTHERIAN,
lake evaporates
will be reducedin thickness dueto evaporation
tepees, truncated,brecciated bioherms
injected muds,selenite
displacive evaporitein saline mud flatfacies; dolomite?
dry mud flat facies
,
Based on northern arm of GSL
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Supralittoralfacies aeolian oolitic sands, rooted,
larger dunes rarely preserved
platy intraclast rudstones
planar laminated oolitic, intraclasticgrainstones
small scale cross-bedding in ooliticgrainstones
microbial bioherms locally developed,partially truncated
popcornaragonite & ooid grainstones,peloidal
wave rippled oolitic grainstone -packstone
laminated, organic-rich
aragonite muds
Eulittoralfacies
Sub-
littoralfacies
Profundalfacies
Based on southern arm of GSL
0
4m
Difficult to assess
Sub-littoral Zone
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Except when the lake dries out - 1964
Edge of rift
Perhaps 1000 km2of
stromatolites/microb
ial mounds in lake.
Sid d CHIRP l btl i t hi
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Side scan sonar and CHIRP surveys reveal subtle microtopographic
control by small faults on bioherm distribution and sediment
accumulation
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VE=70
The bioherm clusters extend
in dip direction of >400m
and much further in strike
direction - given typical
average outcrop constraints
it is highly unlikely thisrelationship to small faults
would be detected
Microbialite bioherm
fault
Sediment covered trough
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Stromatolitic Thrombolitic
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Arid rift carbonate model
Pyramid Lake10% groundwater fed.but 66% of Cacomes from thermal waters
Mono Lake
Carbonate production focussed
around Ca-rich vents producingsub-lacustrine mounds
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Larger buildups around faults occur but are not common andhave not been studied
from Colman et al.
2002
Colman et al. 2002
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Model Based on Current Great Salt Lake
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Aragonitic oolitic sand, bison hoof prints and snow
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The current deposystem is very young and it is unclear how this might be
preserved to enter the stratigraphic record
In broad terms it fits well with the big picture model for carbonate deposition
in an arid rift setting, but with critical and subtle tectonic controls on
sediment production and distribution
We can develop some simple facies models but shoreline diversity still notfully assessed
Most of the lake is currently within wave base
The specific hydrology of this shallow lake favours carbonate production oververy large areas, with limited terrigenous dilution and carbonate production
related to groundwater inflow (cf many other carbonate lakes).
Conclusions
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Moody and withdrawn, the lake unites a haunting loveliness to a raw
desolateness. Dale L Morgan, 1947: The Great Salt Lake
Thanks to BG Group for supporting RBs research