Transcript Ch 11 ppt

Chapter 11
Late Paleozoic Earth History
Appalachians are built
North America is formed
Catskill Delta in NY is deposited
Coal formation is widespread
Limited transgression; reefs and basins
Supercontinent forms
Climate change occurs
Gondwana Continental
Glaciers
• Gondwana continued moving over the South
Pole
• Major glacial episodes:
Late Mississippian to Early Permian
• Continental glaciers
profoundly affected the world's biota
and global sea level changes
Continental glaciers or ice Sheets are
always over land masses!
Continental Collisions
• Collisions between continents
– formation of supercontinent Pangaea by the
end of the Permian,
– mountain building
– influenced oceanic and atmospheric
circulation patterns
• By the end of the Paleozoic,
– widespread arid and semiarid conditions
had prevailed over much of Pangaea
The Devonian Period
• During the Silurian (early paleozoic),
– Laurentia and Baltica collided
– larger continent of Laurasia
• Northern Iapetus Ocean closed:
Caledonian orogeny
• During the Devonian,
– Southern Iapetus Ocean narrowed
between Laurasia and Gondwana,
Acadian orogeny
Paleogeography of the World
• For the Late Devonian Period
Paleogeography of the World
• For the Early Carboniferous Period
Paleogeography of the World
• For the Late Carboniferous Period
Paleogeography of the World
• For the Late Permian Period
Evidence of Acadian Orogeny:
“Old Red Sandstone”
Reddish Fluvial Sediments formed during the
Devonian Age
• The erosion of the resulting highlands from
the Acadian Orogeny
– provided Old Red Sandstone
– covered large areas of northern Europe
– and eastern North America
• Evidence: the Catskill Delta, Scotland
and others
Catskill Delta red sandstone beds
are exposed in NY/PA
Old Red Sandstone in Europe
• Scotland
Catskill Delta Clastic Wedge
Devonian Rocks of New York
• The Devonian rocks of New York are
among the best studied on the continent
• A cross section of the Devonian strata
– clearly reflects an eastern source for the
Catskill facies
• from the Acadian Highlands
• These clastic rocks can be traced
– from eastern Pennsylvania,
• where the coarse clastics are approximately 3 km
thick,
– to Ohio,
• where the deltaic facies are only about 100 m thick
• and consist of cratonic shales and carbonates
Avalonia: microcontinent on the move
composed of
– coastal parts of New England,
– southern New Brunswick,
– Nova Scotia,
– eastern Newfoundland,
– southeastern Ireland,
– Wales, England,
--Belgium and Northern France
**later rifting took this land to present
locations
Acadian Orogeny
Acadian Orogeny
Acadian Orogeny
2800 feet of sediment on eastern margin
• Marcellus Shale
Devonian marine
facies
• Natural gas
reserves
Before Pangaea….
• Uniform global climate
• reefs,
• evaporites,
• and red beds,
– throughout the world,
The Carboniferous Period:
Mississippian & Pennsylvanian
• The advance and retreat of Gondwana’s
polar glaciers
– produced global changes in sea level
– and affected sedimentation pattern on the
cratons
• As Gondwana moved northward
– it first collided with Laurasia
• during the Early Carboniferous
– and continued suturing with it during the rest
of the Carboniferous
Closing of the Iapetus Ocean
• The Taconic, Caledonian, and Acadian
orogenies
– were all part of the same Paleozoic orogenic
event
– closing of the Iapetus Ocean
• Laurentia and Baltica became sutured as
Laurasia
Paleogeography of the World
• For the Early Carboniferous Period
Paleogeography of the World
• For the Late Carboniferous Period
Gondwana/Laurasia Collision
• Evidence:
Ouachita Mountains of Oklahoma
– Late Carboniferous and Early Permian
• By the end of the Carboniferous,
– the various continental landmasses were fairly
close together
– as Pangaea began taking shape
Paleogeography of the World
• For the Late Permian Period
Carboniferous Coal Basins
• The Carboniferous coal basins of
– eastern North America,
– western Europe,
• all lay in the equatorial zone,
– where rainfall was high and temperatures
were consistently warm
• The absence of strong seasonal growth rings
– in fossil plants from these coal basins
– is indicative of such a climate
What Are Cyclothems?
• A cyclical pattern of alternating marine
and nonmarine strata
– Characteristic of Pennsylvanian rocks
– usually in areas of low relief
U.S. Coal Deposits
• The age of the coals in the midwestern states and
the
Appalachian
region are
mostly
Pennsylvanian
• whereas
those in the
west are
mostly
Cretaceous
and
Cenozoic
Cyclothem
• Columnar section of a complete cyclothem
Pennsylvanian
Coal Bed
• Pennsylvanian coal
bed, West Virginia
• part of a cyclothem
Coal-Forming Swamp
• Reconstruction of the environment of a
Pennsylvanian coal-forming swamp
The Okefenokee Swamp
• in Georgia, is a modern coal-forming environment,
similar to
those
occurring
during the
Pennsylvania
n Period
Pennsylvanian Period
• Paleogeography
of North America
during the
Pennsylvanian
Period
Modern coal forming environments
•
•
•
•
the Mississippi delta,
the Okefenokee Swamp, Georgia
the Florida Everglades,
and the Dutch lowlands
– similar to those that existed during the
Pennsylvanian Period
The Permian
Permian Period
• Paleogeography
of North America
during the
Permian Period
Restricted Absaroka Sea
– west Texas and
southern New
Mexico,
• lagoonal
environments,
• reef environments,
• and open-shelf
environments
• Permian Basins
form
Permian Reefs and Basins
Capitan Limestone Reef
Reconstruction
• Reconstruction
Middle Permian
Capitan
Limestone reef
environment
• brachiopods,
corals,
bryozoans and
large glass
sponges
Pangaea Surrounded
• An enormous single ocean,
– Panthalassa,
– surrounded Pangaea and
– spanned Earth from pole to pole
– arid and semiarid conditions were widespread
over Pangaea
• The mountain ranges produced by
– the Alleghenian, and Ouachita orogenies
– created rain shadows
The stage is set for Earth’s
greatest mass extinction