Download Pangea Breaks Up!

Divergent Plate
Boundaries
Lithologic Associations
Global Patterns of Divergence
Doming continental lithosphere
What Processes are Illustrated?
What Geologic Features would be Preserved?
Processes Accompanying Doming
► Normal
Faulting
► Earthquakes
► Volcanism
► What is the source
of the magma?
► Based on this
source, what type
of volcanism would
you expect?
The Dome Collapses – Rift Valleys,
Horsts, Grabens and Half Grabens
In Addition to the Faulting and Volcanism,
What Other Processes would Operate Here?
What types of rocks would you expect?
Additional Processes Accompanying
Collapse of the Dome
► Weathering
► Erosion
► Deposition
Additional Processes Accompanying
Collapse of the Dome
► How
much weathering would you expect in
this setting?
► What would be the composition of the
sediment?
► How much modification of sediment would
take place during transport?
► What textures would you expect?
► What patterns of deposition would you
expect?
As Lithosphere Stretches
► Lithosphere
thins
► Mafic magma is added intrusively and
extrusively
► What happens to the density of the
lithosphere?
► Why?
► What happens to the buoyancy of the
lithosphere?
► What is the result of this?
Lithosphere Subsides Below Sea Level
► Modern
Linear Seas: Red Sea, Dead Sea, Persian Gulf
► What would be the geologic record of this?
► What happens to the tectonic activity on the edges of
the continents?
From Rifting to Drifting
► Passive
Margins of Continents drift away from axis
of tectonic activity - Mid-Ocean Ridge (MOR)
► As distance from MOR increases, continental
margins cool, become more dense and subside –
continental shelves
► What kinds of sediments would you expect?
From Doming to Rifting to Drifting
Example of Rift Lithologic Association
► Mesozoic
rift basins up and down the
Eastern Seaboard
► Igneous and Sedimentary record in rift
basins
Evidence of Rifting – Palisades Sill
Palisades Sill – lower contact
Evidence of Relief – “Fanglomerates”
Evidence of Relief - Arkose
Rift Basins – Closed Drainage - Lakes