Divergent Plate Divergent Plate BoundariesBoundaries

Lithologic AssociationsLithologic Associations

Global Patterns of Global Patterns of DivergenceDivergence

Doming continental Doming continental lithospherelithosphere

What Processes are Illustrated?What Geologic Features would be Preserved?

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?

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?

Additional Processes Additional Processes Accompanying Collapse of the Accompanying Collapse of the

DomeDome

►WeatheringWeathering► ErosionErosion►DepositionDeposition

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?

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?

Lithosphere Subsides Below Sea Lithosphere Subsides Below Sea LevelLevel

►Modern Linear Seas: Red Sea, Dead Sea, Persian GulfModern Linear Seas: Red Sea, Dead Sea, Persian Gulf►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?

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 subside margins cool, become more dense and subside – continental shelves– continental shelves

►What kinds of sediments would you expect?What kinds of sediments would you expect?

From Doming to Rifting to From Doming to Rifting to DriftingDrifting

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

Evidence of Rifting – Palisades Evidence of Rifting – Palisades SillSill

Palisades Sill – lower contactPalisades Sill – lower contact

Evidence of Relief – Evidence of Relief – “Fanglomerates”“Fanglomerates”

Evidence of Relief - ArkoseEvidence of Relief - Arkose

Rift Basins – Closed Drainage - Rift Basins – Closed Drainage - LakesLakes