GEOL 325: Stratigraphy

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GEOL 325 Stratigraphy Sedimentary
BasinsUniversity of South CarolinaSpring 2005
Professor Chris Kendall EWS 304 kendall_at_sc.edu
777.2410
Professor Dave Barbeau EWS 406 dbarbeau_at_geol.sc.e
du 777.5162
Instructional Assistant Liz Baresch EWS 403
baresch_at_geol.sc.edu 777.3353
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Glacial, Aeolian Lake Depositional Systems

• Driver for Base Level Change, a Marker of same,
  Hydrocarbon Sink

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Lecture Series Overview

• sediment production
• types of sediment and sedimentary rocks
• sediment transport and deposition
• depositional systems
• stratigraphic architecture and basins
• chrono-, bio-, chemo-, and sequence stratigraphy
• Earth history

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Sedimentary rocks are the product of the
creation, transport, deposition, and diagenesis
of detritus and solutes derived from pre-existing
rocks.
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Sedimentary rocks are the product of the
creation, transport, deposition, and diagenesis
of detritus and solutes derived from pre-existing
rocks.
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Depositional Systems

• depositional system assemblage of multiple
  process-related sedimentary facies assemblages,
  commonly identified by the geography in which
  deposition occurs.
• EX nearshore depositional system, deep marine
  depositional system, glacial depositional system,
  fluvial depositional system
• NB depositional systems are
• modern features
• used to interpret ancient sedimentary successions

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Types of Depositional Systems

• marine ? ocean, sea
• terrestrial ? land
• transitional ? part land, part ocean

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Types of Depositional Systems

• marine ? ocean, sea
• terrestrial ? land
• transitional ? part land, part ocean

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Terrestrial Depositional Systems

• fluvial
• alluvial fan
• glacial
• eolian
• lacustrine
• playa

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Terrestrial Depositional Systems

• fluvial
• alluvial fan
• glacial
• eolian
• lacustrine
• playa

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Lecture Outline

• Some more terrestrial depositional systems
• Glacial
• Aeolian
• Lacustrian
• Each are considered in terms of-
• Critical stratigraphic signals of that system
• Setting Geomorphologic tectonic
• Dominant sedimentary processes
• Facies
• Subdividing surfaces
• Lithology
• Sedimentary Structures
• Geometries Constricted
• Fauna Flora

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GLACIERSAND GLACIATION
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Glacial Systems

• Critical stratigraphic signals of system?
• Geomorphologic tectonic setting
• Dominant sedimentary processes
• Facies
• Subdividing surfaces
• Lithology
• Sedimentary structures
• Geometries Confined versus open
• Fauna flora

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Simplified Glacial Systems signals

• Sediment signal a mix of
• Glacial carried dumped moraines
• Water born fluvial sediment
• Lacustrian varves
• Aeolian loess
• Erosion
• U-shaped valleys
• Eroded rock surface
• Grooved
• Plucked
• Striated
• Base level changes in sea level.

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Glacial Setting
Currently forms 10 of earthss surface,
Pleistocene reached 30, but in Pre Cambrian
could have reached 100

• Develop where all of annual snow doesnt melt
  away in warm seasons
• Polar regions
• Heavy winter snowfall e.g. Washington State
• High elevations e.g. even equator
• 85 in Antarctica
• 10 in Greenland

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GLACIERS OUTLINE

• Theory of Glacial Ages
• Glaciers- Location, Formation Movement
• Distribution of Glaciers
• Types of Glaciers
• Formation Growth of Glaciers
• Movement of Valley Glaciers
• Movement of Ice Sheets
• Glacial Erosion
• Erosional Landscapes of Alpine Glaciation
• Erosional Landscapes of Continental Glaciation

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GLACIERS OUTLINE

• Glacial Deposition
• Moraines
• Outwash
• Glacial Lakes Varves
• Effects of Past Glaciations
• Glacial Ages
• Direct Effects of Past Glaciations in North
  America
• Indirect Effects of Past Glaciations
• Evidence for Older Glaciations

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Adelie Penguins Taking a Dive
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GLACIER

• Glaciation is a major process in landscape change
• A body of ice
• Formed on land
• Recrystallization of snow
• Evidence of movement
• Alpine glaciation found in mountainous regions
• Continental glaciation large continental areas
• Products of glaciation include fertile plains of
  Northern Hemisphere!

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THEORY OF GLACIAL AGES

• Ice more extensive in the past than today
• Last episode peaked 21,000 years ago
• Louis Agassiz popularized
• Recognized an extensive ice sheet in Europe
• Recognized an extensive ice sheet in North
  America
• Recognized Alpine glaciation
• Recognized Continental glaciation

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Yosemite - Glacial Valley
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Types of Glaciers

• Valley glacier
• Ice sheet
• Ice cap

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Denali National Park, Mt. McKinley center - Alaska
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Types of Glaciers

• Valley glacier
• Ice sheet
• Ice cap

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Ice Sheets
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Types of Glaciers

• Valley glacier
• Ice sheet
• Ice cap

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Ice Caps - Iceland
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Formation and Growth of Glaciers

• Snow to firn to glacier ice
• Wastage (or ablation)
• Melting, evaporation,
• Calving into icebergs
• Glacial Budgets
• Negative budget- Receding glacier
• Positive budget- Advancing glacier
• Zone of accumulation Zone of wastage
• Snow line- divides the zones
• Terminus- movement reflects budget

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Accumulation Ablation of Ice
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Consolidation of Snow Flakes with Time
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Formation and Growth of Glaciers

• Snow to firn to glacier ice
• Wastage (or ablation)
• Melting, evaporation,
• Calving into icebergs
• Glacial Budgets
• Negative budget- Receding glacier
• Positive budget- Advancing glacier
• Zone of accumulation Zone of wastage
• Snow line- divides the zones
• Terminus- movement reflects budget

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Formation and Growth of Glaciers

• Snow to firn to glacier ice
• Wastage (or ablation)
• Melting, evaporation,
• Calving into icebergs
• Glacial Budgets
• Negative budget- Receding glacier
• Positive budget- Advancing glacier
• Zone of accumulation Zone of wastage
• Snow line- divides the zones
• Terminus- movement reflects budget

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Antarctica Margin Glacier
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Formation of Glacial-Marine Sediment by Ice
Rafting
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Antarctic - Ross Ice Shelf
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Formation and Growth of Glaciers

• Snow to firn to glacier ice
• Wastage (or ablation)
• Melting, evaporation,
• Calving into icebergs
• Glacial Budgets
• Negative budget- Receding glacier
• Positive budget- Advancing glacier
• Zone of accumulation Zone of wastage
• Snow line- divides the zones
• Terminus- movement reflects budget

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Glacial Balance
Maps - Cascade Glacier - Washington
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South Cascade Glacier, WashingtonGlacier Melt
Recession
1957
1980
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Movement of Glaciers

• Avalanche movement from high snow accumulations
• Valley Glaciers
• Gravity driving force
• Sliding along its base -basal sliding
• Internal flowage- plastic flow
• Rigid zone
• Crevasses may form here
• Ice sheets
• Move downward outward from central high

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Denali National Park - Alaska
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Avalanche Colorado
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Avalanche Dog - Switzerland
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Movement of Glaciers

• Avalanche movement from high snow accumulations
• Valley Glaciers
• Gravity driving force
• Sliding along its base -basal sliding
• Internal flowage- plastic flow
• Rigid zone
• Crevasses may form here
• Ice sheets
• Move downward outward from central high

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FlowVelocityin aValleyGlacier
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Glacier Movement
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Diving Ice, Byrd Glacier - Antarctica.
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Glacial Erosion

• Under glacier
• Abrasion plucking
• Bedrock polished striated
• Rock flour washes out of glacier
• Polishing and rounding
• Sheep Rocks
• Striations- scratches grooves on rock
• Above glacier
• Frost wedging takes place
• Erosion by glaciers steepens slopes

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Plucking Abrasion Beneath Ice
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Glacial Abrasion - Maine
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Glacial Scarring Of Bedrock - Findelen
Glacier Switzerland - Matterhorn In Background
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Roche Moutone Ice Sheet Plucking
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Stoss Lee Plucking Yale Glacier
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Erosional Landscapes Associated with Alpine
Glaciation

• Glacial valleys
• U-shaped valleys
• Hanging valleys
• Truncated spurs
• Triangular facets
• Rock -basin lakes (tarns)
• Rounded knobs- rouche moutonnees

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Erosional Landforms Mountain Glaciers
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Glacial Valleys - Innsbruck Alps
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Byrd Glacier - Antarctica
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Milford Sound - NZ
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Mount Everest Himalayas, Nepal
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Erosional Landscapes Associated with Alpine
Glaciation

• Cirque- at head of valley glacier
• Rock steps
• Rock basin lakes
• Horn
• Arete- sharp ridge

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Cirque in the Canadian Rockies
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Cutaway View of Cirque Forming
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Lake District UK - Arête
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Arête - MountLogan Yukon
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Erosional Landscapes Associated with Continental
Glaciation

• Grooved striated bedrock
• Grooves may be channels
• Rounded hills mountains

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Glacial Grooves Kellys Island
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Glacial Grooves Appalachian Trail
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Glacial Sediments

• Facies of continental glacial settings
• Grounded Ice Facies
• Glaciofluvial facies
• Glacial lacustrine facies
• Facies of proglacial lakes
• Facies of periglacial lakes
• Cold-climate periglacial facies
• Facies of marine glacial settings
• Proximal facies
• Continental Shelf facies
• Deepwater facies

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Glacial Deposition

• Till
• Unsorted debris in fine matrix
• Erratic
• Moraine- body of till
• Lateral Moraine
• Medial Moraine- where tributaries join
• End moraine-
• Terminal
• Recessional
• Ground moraine
• Drumlin

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Various Moraines
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Lateral Medial Moraines - Alaska
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Twenty Mile Medial Moraine
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Medial, Lateral other Moraines
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Robinson Tumbling Glacier Brit. Columbia
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Ground and End Moraines
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End Moraines-Long Island and Cape Cod
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Drumlin - Wisconsin
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Drumlin Formation Below Ice Cap
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Drumlins Chile
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Drumlins Form Beneath Ice Sheets
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Two Origins of Kettles, Kames Eskers, and Outwash
Plains.
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Glacial Deposition

• Outwash
• Stream-deposited sediment
• sorted
• Braided streams typical
• Esker
• Kettle
• Glacial lakes
• Varves

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Esker North East Washington
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Depositional Features of Receding Ice
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Glacial Outwash Pavement Iceland
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Kettles Central Chile
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Glacial Terminus - Argentina
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End Moraine in Sea
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Fjord Glacier Terminus
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Ice Rafting into the Atlantic
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Clearwater Lakes - Quebec - Asteroid Impacts Ice E
roded Lakes
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Glacial Lakes - Ireland
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Varves
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Varves
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Glacial Sediments
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Glaciation Subdividing Surfaces
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Glacial Sediments

• Facies of continental glacial settings
• Grounded Ice Facies
• Glaciofluvial facies
• Glacial lacustrine facies
• Facies of proglacial lakes
• Facies of periglacial lakes
• Cold-climate periglacial facies
• Facies of marine glacial settings
• Proximal facies
• Continental Shelf facies
• Deepwater facies

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Past Glacial Periods

• Pre-Cambrian at end of Neoproterozoic eon
• End of the Ordovician
• Late Carboniferous (Pennsylvanian through
  Permian
• Pleistocene

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Glacial Periods
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The Snowball Earth

• During last ice age max, 21,000 years ago, North
  America Europe covered by glaciers over 2
  kilometers thick, sea level dropped 120 meters.
  Global chill land sea ice covered 30 t of
  Earth, more than at other times in last 500
  million years
• Near end of Neoproterozoic eon (1000-543 million
  years ago), glaciation immediately preceded first
  appearance of recognizable animal life some 600
  million years ago

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Paul Hoffman Daniel Schrag - Snowball Earth

• Sun abruptly cooled or Earth tilted on its axis
  or experienced an orbital blip that reduced solar
  warmth or carbon dioxide increased?
• ice sheets covered continents seas froze almost
  to equator, events that occurred at least twice
  between 800 million 550 million years ago
• Each glacial period lasted millions of years
  ended under extreme greenhouse conditions.
  Climate shocks triggered evolution of
  multicellular animal life, challenge long-held
  assumptions regarding the limits of global change

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SnowballEarth- Rocky cliffs along Namibia's
Skeleton Coast.
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SnowballEarth- Drop Stones
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Ice Polished Rock - Permian Australia
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Causes of Glacial Ages

• Precession Wobble in Earths axis
• Tilt From Plane of Earths axis
• Eccentric Path of Earth Around Sun
• Volcanic dust
• CO2 Release
• Continental position
• Sliding of West Antarctic Ice Sheet

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Precession - Wobble - Tilt From Plane - Eccentric
Path of Earth Around Sun
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Effects of Past Glaciation

• Glacial ages
• Direct effects in North America
• Scoured much of Canada
• Cut Great Lakes
• Deposited till flattened Midwest
• Extensive alpine glaciation in mountains

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PleistoceneIceSheetExtentEurope
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The Draining of Lake Missoula Giant Ripples
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Iceberg Antarctic
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Adelie Penguins - Jumping Back
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Glacial Systems - Conclusions

• Signal extremes in local climate sea level
  position
• Stratigraphic markers of glacial events
• Source of tillite (pebbles larger fragments
  supported in fine-grained matrix ) deposited from
  glaciers.
• Massive tillite inferred deposited below ice
  sheets or dropping from marine supported ice in
  submarine setting
• Banded tillite may be deposited by ice sheets
• Laminites common in lakes (Varve), Loess dust on
  land
• Supraglacial pro-glacial deposits with
  stratified conglomerates sandstone
• U Shaped valleys glacial striae
• Mountain glaciation could be source of much
  downslope fluvial sediment

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Simplified Conclusions Glacial Systems

• Sediment signal a mix of
• Glacial carried dumped moraines
• Water born fluvial sediment
• Lacustrian varves
• Aeolian loess
• Erosion
• U-shaped valleys
• Eroded rock surface
• Grooved
• Plucked
• Striated
• Base level changes in sea level.

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AEOLIANAND DESERTS
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Sandy Desert N. Africa Going
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Aeolian System Desert Coast

• Distribution of Aeolian systems Holocene
  Ancient
• Deserts Transport Depositional Sytems Wind
  Fluvial Action
• Deposits of Modern Deserts
• Dunes
• Interdunes
• Sheet Sands
• Aeolian Systems
• Bounding Surfaces
• Ancient Deposits

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Simplified Desert Systems signals

• Sediment signal a mix of
• Aeolian sediment dunes and sheets
• Water born intermittent fluvial sediment
• Playas and lakes
• Aeolian loess
• Erosion
• Water table Stokes Surfaces marks limit
• Incised valleys
• Gravel remnants
• Rock pavements
• Ventifacts
• Base level changes in ground water level.

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Desert

• Region with low precipitation
• Usually less than 25 cm rain per year
• Distribution
• Most related to descending air
• Belts at 30 degrees North South latitude
• Rain shadow of mountains
• Great distance from oceans
• Tropical coasts beside cold ocean currents
• Polar desserts

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Earth'sGeneralCirculation
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Word Map of Arid Semiarid Climates
Prevailing Winds
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Deserts of the World
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Deserts Dune Factories
Common characteristics-

• Lack of through-flowing streams
• Internal drainage
• Local base levels
• Desert thunderstorms
• Flash floods
• Mudflows

Dominated by water transportation
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Deserts Depositional Systems
Dunes fed by water transported sediment

• Margin rimmed by incised seasonal streams (Wadiis
  or Arroyo)
• In turn flanked by alluvial fans and rock
  pavements or bajada
• Intermittent drainage supplying sediment
• Dunes
• Playas

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Grand Canyon, South Side - Arizona
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Bajada PedimentAlluvialFans -Namibia
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Alluvial fans Death Valley
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Salt Pan Alluvial Fans Death Valley
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Playa Alluvial fans Death Valley
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Rain Shadow Deserts
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Sediment Source - Deserts Coasts

• Abundant sediment supply (sand, silt)
• Favorable wind regimes
• Grain transport in wind
• Transport populations resultant deposits
• i. Traction (deflation pavements)
• ii. Saltation (sand dunes)
• iii. Suspension (loess)
• III. Subenvironments of eolian dune systems

Dominated by water transportation
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Wind Erosion and Transportation

• Sand
• Moves along ground- saltation
• Sandstorms
• Sandblasting up to 1 meter
• Ventifact
• Deflation
• Blowout
• Dust storms

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Sand Movement
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Deflation in Wisconsin
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Brice Canyon - Utah
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Arches National Park Utah
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Wind Erosion and Transportation

• Dust storms
• Sand
• Moves along ground- saltation
• Sandstorms
• Sandblasting up to 1 meter
• Ventifact
• Deflation
• Blowout

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Wind Action

• Strong in desert because
• Low humidity
• Great temperature ranges
• More effective because of lack of vegetation
• Effective erosion in deserts because sediment is
  dry

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Wind Erosion and Transportation

• Sand
• Moves along ground- saltation
• Sandstorms
• Sandblasting up to 1 meter
• Ventifact
• Deflation
• Blowout
• Dust storms

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Blow Out!
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Wind Erosion and Transportation

• Sand
• Moves along ground- saltation
• Sandstorms
• Sandblasting up to 1 meter
• Ventifact
• Deflation
• Blowout
• Dust storms

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Red Sea Dust Storm
RedSeaDustStorm
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North Africa - Sea Dust Storm
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Wind Erosion and Transportation

• Dust storms
• Wind-blown dust accumulates in the deep ocean
  floor at a rate of 0.6 x 1014 g/year.

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Chinese Loess Gobi Desert
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Loess from Scandinavia in Europe
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Loess
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Wind Deposition

• Loess
• Gravel Pavements
• Desert varnish petroglyphs
• Sand Dunes
• Well-sorted, well-rounded sand grains
• Slip face
• Angle of repose
• Wind ripples

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Desert Pavement Formation
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Wind Deposition

• Loess
• Gravel Pavements
• Desert varnish petroglyphs
• Sand Dunes
• Well-sorted, well-rounded sand grains
• Slip face
• Angle of repose
• Wind ripples

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Gravel Pavement Arizonan Desert
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Wind Deposition

• Loess
• Gravel Pavements
• Desert varnish petroglyphs
• Sand Dunes
• Well-sorted, well-rounded sand grains
• Slip face
• Angle of repose
• Wind ripples

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Dune Field Death Valley
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Barchan Dunes - Jordan
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Zion National Park - Utah
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Wind Deposition

• Loess
• Gravel Pavements
• Desert varnish petroglyphs
• Sand Dunes
• Well-sorted, well-rounded sand grains
• Slip face
• Angle of repose
• Wind ripples

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Sand Movement
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Dune Evolution
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Hierarchies exhibited by aeolian and associated
sediments

• Grains
• Ripples
• Dunes
• Interdune unconfined sheets
• Confined bodies of wadii channel fills
• Playa unconfined sheets of heterogenous chemical,
  wind and water transported clastic sediments

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Mechanisms of Aeolian Transportation

• Rolling 2-4 mm
• Surface creep
• 20-25 of sand moves by grains shifted by
  impacting saltating grains lt 2 mm
• Suspension fine sand, silt, clay
• Grains 0.1 mm are most easily moved by wind
  mostly gt 2 m above the ground surface

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Mice Tracks RipplesWhite Sands, NM
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Ripples on Dune
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Wind Deposition

• Types of dunes
• Barchan
• Transverse dune
• Parabolic dune
• Longitudinal dune

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Salt Pan West Texas, El Capitan
LONGITUDINAL
BARCHAN
PARABOLIC
TRANSVERSE
STAR
BARCHINOID
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TifernineDuneField-AlgeriaSahara
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Transverse Barchans - Namibia
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Barchan Dunes Atacama Desert Peru
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NamibianDesert-DunesInselbergs
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Sand Dune Types
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StarDunes-LibyaEgypt
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North Africa - Sea Dust Storm
Star Dunes Namibia
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Dune Character Classification
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DomeDunes-SaudiArabia-EmptyQuarter
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Parabolic Gypsum Dunes White Sands, NM
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Formation of Wind Shadows Around an Obstacle
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Wind Shadow White Sands, NM
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SandDuneCrossing Road
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Dune Encroaching On The Forest
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Evolution of Dune Structure
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Parallel Dunes-SaudiArabia-EmptyQuarter
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Linear Dunes Eureka Valley - California
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Sahara Barchans Camels
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Navajo Sandstone
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Salt Pans Parallel Dunes Simpson Desert -
Central Australia
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Cross-bedded Navaho Sandstone
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NavajoSandstone
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Quaternary of UAE Stokes Surface
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NavajoSandstone
Base level change punctuates the sandstone with
erosion surfaces!
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NavajoSandstone
Base level change punctuates the sandstone with
erosion surfaces!
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NavajoSandstone
Base level change punctuates the sandstone with
erosion surfaces!
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NavajoSandstone
Base level change punctuates the sandstone with
erosion surfaces!
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NavajoSandstone
The sandstone progrades to left with deposition
on slip faces of dune!
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Navaho Sandstone Zion National Park
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Formation of Pediments
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Arid Landscape Evolution
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Salt Pan Alluvial Fans Death Valley
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Desert Features in S.W. United States

• Colorado Plateau
• Mostly flat-lying sedimentary beds
• Plateaus, mesas, buttes
• Monoclines
• Hogback cuesta

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Desert Features in S.W. United States

• Basin and Range Province
• Mountains valleys bounded by faults
• Alluvial fans bajada
• Playa lake playa
• Pediment
• Parallel retreat of slope

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Brice Canyon- Utah
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Some characteristics of deserts

• Stream channels normally dry
• covered with sand gravel
• Narrow canyons with vertical walls
• Resistance of rocks to weathering
• Desert topography typically steep and angular

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Aeolian Sediment - Critical Character

• Aeolian sediments evidenced by x-bedding with
  high angle (30-34 degrees)
• Horizontal thin laminae common locally
• Sand rounded and frosted
• Quartz coated by iron oxide suggests hot arid
  and/or seasonally humid climate (exceptions)
• Well Sorted often unimodal but if bimodal two
  populations present
• Silt and clay minimal

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Aeolian Sediment - Critical Character

• Small large scale cross bedding, with multiple
  orientations within horizontal bedding
• Grains in laminae well sorted, especially finer
  sizes, sharp differences in size between lamina
• Size ranges from silt (60 mu) to coarse (2mm)
• Max size transported by wind 1 cm but rare
  grains over 5 mm
• Larger grains (0.5 - 1.mm) often well rounded
• Sands free of clay and clay drapes rare
• Uncemented sands have frosted surfaces
• Mica usually absent

Rules of thumb - Glennie1970
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Aeolian sediment interpretation

• Analyse sedimentology internal architecture
  with outcrop, cores and downhole imaging
• Identify seperate single aggradational units
  bounded by regional deflation surfaces
  (deep-scoured to flat surfaces)
• Genetic models from cyclic recurrence in facies
• Aggradation characterises near- continuous
  accumulation
• Internal facies evolution related to differences
  in sediment budget moving water table
• Palaeosols provide evidence of climate change

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Conclusions - Desert Systems - Simplified

• Sediment signal a mix of
• Aeolian sediment dunes and sheets
• Water born intermittent fluvial sediment
• Playas and lakes
• Aeolian loess
• Erosion
• Water table Stokes Surfaces marks limit
• Incised valleys
• Gravel remnants
• Rock pavements
• Ventifacts
• Base level changes in ground water level.

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The End
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LAKE AND ORGANICS
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Lakes Are Ephemeral
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Lacustrian Systems

• Critical characteristics of system?
• Geomorphologic tectonic setting
• Dominant sedimentary processes
• Facies
• Subdividing surfaces
• Lithology
• Sedimentary structures
• Geometries Confined versus open
• Fauna flora

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Lake Systems Simplified Signals

• Sediment signal a mix of
• Lake Center sheets and incised unconfined
  turbidite cycles
• Margins marked by alluvial fans fluvial
  sediment
• Reducing setting that favors organic preservation
• Signal cycles in order from
• Clastics organics
• Limestone organics
• Evaporites organics
• Base level changes in ground water level
• Origin of large lakes
• Continental break up
• Continental collision
• Sags on craton

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Significance of Lake Systems

• Signal extremes in local climate geochemistry
• Stratigraphic markers (Organics trap radioactive
  minerals)
• Major source of hydrocarbons along Atlantic
  Margins
• Major source of oil shale gas in western USA
  Canada
• Major source of
• Trona (Hydrated Sodium Bicarbonate Carbonate)
• Borax (Hydrated Sodium Borate)
• Sulfohalite (Na6ClF(SO4)2)
• Hanksite (Sodium Potassium Sulfate Carbonate
  Chloride)

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Lake Geomorphologic Tectonic Setting
Temporary features forming 1 of earthss land
surface, filling-

• Major rifted, faulted (Break-up) continental
  terrains E. Africa
• Major final fill of foreland basin Caspian
  Aral
• Continental sags Victoria, Kenya, Uganda, and
  Eyre
• Glacial features including
• Moraine damming and/or ice scouring Great Lakes
  
• Ice damming
• Landslides or mass movements
• Volcanic activity including
• Lava damming
• Crater explosion and collapse Crater Lake
• Deflation by wind scour or damming by wind blown
  sand - Fayum
• Fluvial activity including
• Oxbow lakes
• Levee lakes,
• Delta barrier island entrapment

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Lake Tanganyika
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Lake Tanganyika
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Lake Tanganyika

• Lake levels have varied historical and earlier
• Fossil and living stromatolites abundant around
  the margins of Lake Tanganyika, Africa provides a
  source of paleolimnologic and paleoclimatic
  information for the late Holocene
• late Holocene carbonates suggests that the
  surface elevation of the lake has remained near
  the outlet level, with only occasional periods of
  closure
• In past the lake draw down encouraged evaporites

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Lakes formed between splitting continents
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Restricted Entrances To Sea
Isolated linear Belt of interior drainage
Regional Drainage Away From Margin
Organic Rich Lake Fill
Arid Tropics Air System
Wide Envelope of surrounding continents
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Lakes flanking Major Mountain Chains
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Caspian and the Arral Sea

• Bodies of fresh to saline water trapped on craton
  behind major mountain chains
• Tend to act as traps to clastics, carbonates and
  evaporitic sediments
• Climatic change is recorded in the record of the
  sediment fill
• Water draw down encourages evaporites

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Caspian
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Aral Sea
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Great Lakes
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Great Lakes

• Bodies of fresh water trapped on glacially
  scoured depressions on craton behind glacial
  moraines
• Act as traps to clastic sediments
• Climatic change is recorded in record of sediment
  fill
• Water draw down encourages precipitates

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Lake Constance - Switzerland
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Ice Dammed Lake Alaska
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Lake Response to Stratification
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Lake Sedimentary facies

• Sedimentary signal like that of a foreshortened
  Marine setting
• Narrow shores with beaches and deltas
• Finer sediments and turbidites fill the lake
  center

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Lake Sedimentary facies

• Presence of freshwater fossils
• Lake sediments commonly better sorted than
  fluvial and periglacial sediments
• May (or may not) display a tendency toward fining
  upward and inward towards the basin center
• Lake sediments are predominantly fine grained
  sediments either siliciclastic muds but may be
  carbonate sediments and evaporates
• Typical sequence may produced as the lake dries
  up with a coarsening upward sequence from
  laminated shales, marls and limestones to rippled
  and cross-bedded sandstone and possibly
  conglomerates
• Lake sediment fill often shows cyclic alternation
  of laminae
• Varves produced by seasonal variations in
  sediment supply and lake circulation which
  changes the chemistry of the lakes

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Lacustrian sedimentary geometries

• Shore marked by linear beaches
• Coarse to fine slope
• Deeper water lake laminae and turbidites
• Eclectic clastic and evaporitic sedments

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GreenRiver Lake
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Green River Lake Fill
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Green River Systems Facies
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Green River Section
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Green River Section
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Green River Section
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Green River Fauna Flora
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East African Lake Margin
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Green River Section
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Mono Lake
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Lake Eyre - Australia
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Death Valley - Panorama
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Salt Pan West Texas, El Capitan
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Conclusions - Lake Systems

• Sediment signal a mix of
• Lake Center sheets and incised unconfined
  turbidite cycles
• Margins marked by alluvial fans fluvial
  sediment
• Reducing setting that favors organic preservation
• Signal cycles in order from
• Clastics organics
• Limestone organics
• Evaporites organics
• Base level changes in ground water level
• Origin of large lakes
• Continental break up
• Continental collision
• Sags on craton

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Lakes Are Ephemeral
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End of the Lecture

• Lets go for lunch!!!