divergent plate boundaries lithologic associations
Post on 15-Jan-2016
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Divergent Plate Divergent Plate BoundariesBoundaries
Lithologic AssociationsLithologic Associations
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Global Patterns of Global Patterns of DivergenceDivergence
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Doming continental Doming continental lithospherelithosphere
What Processes are Illustrated?What Geologic Features would be Preserved?
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Processes Accompanying Processes Accompanying DomingDoming
► Normal FaultingNormal Faulting► EarthquakesEarthquakes► VolcanismVolcanism► What is the source What is the source
of the magma?of the magma?► Based on this Based on this
source, what type source, what type of volcanism of volcanism would you expect?would you expect?
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The Dome Collapses – Rift The Dome Collapses – Rift Valleys, Horsts, Grabens and Valleys, Horsts, Grabens and
Half GrabensHalf Grabens
In Addition to the Faulting and Volcanism,What Other Processes would Operate Here?
What types of rocks would you expect?
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Additional Processes Additional Processes Accompanying Collapse of the Accompanying Collapse of the
DomeDome
►WeatheringWeathering► ErosionErosion►DepositionDeposition
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Additional Processes Additional Processes Accompanying Collapse of the Accompanying Collapse of the
DomeDome►How much weathering would you How much weathering would you
expect in this setting?expect in this setting?►What would be the composition of the What would be the composition of the
sediment?sediment?►How much modification of sediment How much modification of sediment
would take place during transport?would take place during transport?►What textures would you expect?What textures would you expect?►What patterns of deposition would you What patterns of deposition would you
expect?expect?
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As Lithosphere StretchesAs Lithosphere Stretches►Lithosphere thinsLithosphere thins►Mafic magma is added intrusively and Mafic magma is added intrusively and
extrusivelyextrusively►What happens to the density of the What happens to the density of the
lithosphere?lithosphere?►Why?Why?►What happens to the buoyancy of the What happens to the buoyancy of the
lithosphere?lithosphere?►What is the result of this?What is the result of this?
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Lithosphere Subsides Below Sea Lithosphere Subsides Below Sea LevelLevel
►Modern Linear Seas: Red Sea, Dead Sea, Persian Modern Linear Seas: Red Sea, Dead Sea, Persian GulfGulf
►What would be the geologic record of this?What would be the geologic record of this?►What happens to the tectonic activity on the edges What happens to the tectonic activity on the edges
of the continents?of the continents?
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From Rifting to DriftingFrom Rifting to Drifting
► Passive Margins of Continents drift away from Passive Margins of Continents drift away from axis of tectonic activity - Mid-Ocean Ridge axis of tectonic activity - Mid-Ocean Ridge (MOR) (MOR)
► As distance from MOR increases, continental As distance from MOR increases, continental margins cool, become more dense and margins cool, become more dense and subside – continental shelvessubside – continental shelves
► What kinds of sediments would you expect?What kinds of sediments would you expect?
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From Doming to Rifting to From Doming to Rifting to DriftingDrifting
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Example of Rift Lithologic Example of Rift Lithologic AssociationAssociation
►Mesozoic rift basins up and down the Mesozoic rift basins up and down the Eastern SeaboardEastern Seaboard
► Igneous and Sedimentary record in rift Igneous and Sedimentary record in rift basinsbasins
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Evidence of Rifting – Palisades Evidence of Rifting – Palisades SillSill
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Palisades Sill – lower contactPalisades Sill – lower contact
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Evidence of Relief – Evidence of Relief – “Fanglomerates”“Fanglomerates”
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Evidence of Relief - ArkoseEvidence of Relief - Arkose
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Rift Basins – Closed Drainage - Rift Basins – Closed Drainage - LakesLakes