Download The Middle Paleozoic World - Age of the Fishes and the land Plants

The Middle Paleozoic World
- Great changes in the Earth Systems –
Orogenic Events
Jarðsaga 1
- Saga Lands og Lífs –
Ólafur Ingólfsson
Development of the continents during
the Middle Paleozoic
• Avalonia and Baltica collide with
Laurentia, causing the build-up of the
Appalachian Mt´s and the
Scandinavian mountain chain.
• Subsequent erosion led to thick
sedimentary accumulations and the
deposition of the “Old Red Sandstone”
in areas that were close to the
Equator.
• Chemical weathering rates on land
increase dramatically due to spread of
terrestrial vegetation.
Major developments of life during
the Silurian and Devonian time
• Life
diversified rapidly after the
Ordovician mass extinction and surpassed
the Ordovician adaptive radiation
• The broad, shallow epicontinental seas
of the Silurian and Devonian were
optimal environments for development
of life
• In the tropical zone, a diverse
community of organisms built
reefs larger than any that had
formed during early Paleozoic
times
Major developments of life during Silurian
and Devonian...
• More advanced predators, including
jawed fishes, arrived on the scene
• Land habitats were progressively
colonized. Plants were restricted to
marshes in the Silurian, but were
forming large forests by Late
Devonian
• The first known insects and the
first vertebrate animals on land are
also of Devonian age
Falling CO2 in the atmosphere
Development of soils accelerates in
the Middle Paleozoic
Baltica on a
collision corse
with Laurentia
since
Ordovicium...
Silurian configuration of continents
http://jan.ucc.nau.edu/~rcb7/global_history.html
The Avalonian-Acadian-Caledonian
Orogeny
Europe (the Baltic
Plate) collides
with Northern
Laurentia, and
Avalonia collides
with southern
Laurentia during
the Silurian and
Devonian.
http://www.science.ubc.ca/~eoswr/lithoprobe/slide.html
The Acadian
Orogeny in N
America
• The rivers deposited the huge
Catskill Delta. The delta was made up
of conglomerates closest to the
mountains, and gradually graded into
sands, then shales further away and
eventually turbidites. These deposits
now make up the Catskill Mountains in
southeastern New York.
• By the late Silurian, the small
continent of Avalon was
approaching N. America A
shallow sea covered the
interior of the N. American
continent.
• The continent-continent
collision lasted approximately
30 My.
• As the Acadian mountains
rose, large rivers coursed
down their western slopes,
spreading sand and gravel
across the region.
The Acadian orogeny
The Acadian Orogeny was the result of collision of
Europe with northern portions of Laurentia and added
another permanent terrane to the eastern cratonic margin
This collision:
- overprinted Taconian metamorphic ages
- intruded abundant granite
- built another high eastern mountain range that shed
another clastic wedge that coarsens to the east called
the Catskill clastic wedge;
- the Catskill redbeds are the North American mirror
image of the Old Red Sandstone in Great Britain
formed in northwestern Europe's Caledonian Orogeny
- the tectonic unit composed of Laurentia and Europe
was called Laurussia – The Supercontinent of Pangea
was in the making...
The Appalachian
Mts
Appalchian geology
The Appalachians are a orogenic belt developed along the
eastern margin of the North American craton
The Appalachinas are
constructed by a series
of events, including
rifting apart of Rondina
Supercontinent;
sedimentation in an
ocean; closure of the
ocean by subduction; and
later collision between
two continental plates...
Satellite picture of the Appalachians
Geological terrains shaped by the
Acadian-Caledonian orogeny
The
Appalachians
Hills and ridges
History of the mountains
About 750 million years ago, the Rodina
supercontinent began to pull apart
because of expansion of the continental
crust. 540 million years ago, the
continental crust split into pieces that
drifted apart. Seawater spread into low
areas between crustal plates and, in time,
formed new oceans.
The extent of Oceans
about 480 million years
ago. The present-day
United States is
outlined in white, and
the equator shown as a
dashed yellow line.
History of the
mountains...
The
Taconic
Orogeny
The
Acadian
Orogeny
About 470 million years
ago, the motion of the
crustal plates changed, and
the continents began
moving toward each other.
As the plates moved closer
together, fragments of
oceanic crust, islands, and
other continental masses
collided with the eastern
margin of ancestral North
America.
And the story continued...
The ocean continued to shrink
until, about 300 million years
ago (The Carboniferous), the
continents that were ancestral
to North America and Africa
collided. Huge masses of rocks
were pushed west-ward along
the margin of North America
and piled up to finish forming
the mountains that we now know
as the Appalachians.
The Birth of a Mountain: http://pubs.usgs.gov/gip/birth/birth.pdf
Diagrammatic history of major
continents
The Plutons of Appalachia
As blocks of continental crust rode
across one another, some rocks
became so hot that they melted.
When molten rock remains deep
below ground, it cools and
crystallizes to form bodies of rock
that arecalled igneous plutons. Some
plutons are now exposed at the land
surface due to erosion of overlying
rock. The plutons are composed of
granite and similar rocks. Plutons
are scattered throughout the
Southern Appalachians like plums in
a pudding.
Granites
Banded granite from New
Hampshire
A xenolith of older
basalt in younger
granite. Acadia National
Park, Maine
Dykes and sills
Basaltic dykes that cut
through older metamorphised rocks. Acadia
National Park, Maine
An example of the tectonics
of the Appalachians
The collision of continental plates is also
expressed in the rocks by tectonic
displacements, folds and faults. One
place where the effects of the faulting
can be seen is in Cades Cove in the Great
Smoky Mountains National Park. In a
normal sequence, younger rocks are
deposited on top of older ones. However,
in Cades Cove, the limestone that makes
up the floor of the cove is younger than
the rocks in the surrounding mountains.
The older rocks of the surrounding
mountains moved over the lime-stone on a
low-angle fault
Roadside geology
Landscape shaped by faulting
Many faults have been
identified throughout
the Southern
Appalachian Mountains
and the Valley and Ridge
province. Huge masses of
rock moved along these
faults for distances of
60 miles or more.
Geology and history...
Faults act as channels for migration
of fluids and were a key factor in
localizing gold in certain zones.
In 1829, newspaper articles
described vast riches of gold in
Cherokee land in North Georgia.
Thousands of miners quickly
flocked to the area with dreams of
quick riches. They washed gravel
from banks of the streams to
search for gold.
The Trail of Tears
The frenzy caused by the discovery of gold hastened
the removal of the Cherokees by a forced march to
Oklahoma during the winter of 1837–38. More than onethird of the Cherokee people who started the march
died along the way, on what is now known as the Trail of
Tears
Another story of geology and history...
The Black Hills
The Black Hills
are the surface
expression of an
dome, that rose
up in connection
with the
creation of the
Rocky Mountains
early in the
Cenozoic Era
See: Stanley, pg. 252
The Black Hills Dome
Paleozoic and Mesozoic strata flank crystalline Archean rocks that
erosion has exposed in the centre of the dome. The Black Hills contain
one of the worlds richest gold occurrances. The gold comes from
Archean rocks that were metamorphised in early Proterozoic times. The
gold probably precipitated from warm fluids or gases percolating
through cracks and faults...
The gold of the Black Hillls
The region was the homeland of Sioux
Indians who had been given the land by the
Fort Laramie Treaty in 1851. The uncovering
of gold in the Black Hills in 1874 caused an
onrush of settkers, which were forbidden to
entry under treaty terms with the Sioux .
General Custer and his
crave for gold
In 1876, general Custer, seeking fame as an
Indian killer and fortune as a prospector for
gold, led his men into the most devastating
defeat ever suffered by the US army at the
hands of the Indians. 269 soldiers were killed by
the Sioux in the battle at Little Big Horn.
The Homestake Gold Mine
More than 1 billion USD worth of gold has been mined in the Homestake
mine, opened in 1876, in the Black Hills. It is still one of the richest
gold mines in the world...
See: Stanley, pg. 333
Geology sets the pattern...
Continental drift through hundreds of
millions of years sets the stage for the
patterns of human settlement, travel,
transportation routes, history etc
Most of Earth’s gold, silver and
coppermines are located on Precambrian
shields
A worthwhile visit to
the Appalchians...
A visit to the Tertiary in Iceland
The Acadian-Caledonian Orogeny
The Baltic plate collides with the Laurentia plate
during the Devonian, causing the Caledonian orogeny.
The Caledonian Orogeny
Caledonian Orogeny: Continental collision involving North America
and Europe led to mountain building and associated sedimentation
across most of Ireland, Wales, northern England, Scotland and
Norway. This orogeny is parallel in timing and cause to the Acadian
Orogeny of the northern Appalachians during the Devonian. A large
landmass--the so-called Old Red Continent--resulted with sediment
accumulation around the uplifted mountains.
Caledonian Orogeny: The mountain-building event that occurred
when England and Scotland collided around 430 million years ago.
Prior to the orogeny, Scotland formed part of the continent of
Laurentia and England formed part of the continents of Avalonia
and Baltica. Between these continents lay an ocean called the
Iapetus. Plate tectonics caused the continents to move towards
each other, closing the ocean.
Geology of Scotland
http://www.scottishgeology.com/regional_geology/map_regions.html
The Caledonian in Scotland
The Caledonian Orogeny
deformed and folded various
older sedimentary rocks,
which were also metamorphosed, with the recrystalisation of sandstones to
quartzites and mudstones to
slates. There was also the
intrusion of granite magama,
derived from the actual
partial melting of rocks lower
within the crust, where the
heat and deformation caused
by the continental collision,
was most intense.
Scandinavian mountains: Caledonian
orogeny
Fennoscandia
roughly corresponds to the
crystalline Baltic
Shield, comprised
mainly by either
reworked Archean
rocks or Lower
Proterozoic
basement.
Main Scandinavian stage of Caledonian orogeny is known to
be Middle to Late Silurian age.
Formation of the Scandinavian
Mountains during the
Caledonian orogeny
Skoðið þessa vefsíðu frá
háskólanum í Tromsö –
mjög fróðleg um myndun
fjalla almennt og í Noregi
sérstaklega:
http://www.ig.uit.no/~kaarek/geology_intro/mountains.swf
The Red Continent
The Old Red Sandstone
The Old Red Sandstone, in contrast to the typical formations of
the Devonian, is largely a continental formation, laid down in
freshwater and on land as a result of the erosion of the highlands
of the Silurian period. It is very thick in Scotland (> 10 km) and
contains a large assemblage of well-preserved fossils, particularly
of the Devonian fishes.
Formation of the Old Red Sandstone
The ORS was deposited between Late Silurian and Early Carboniferous, between ca. 420-320 MY, as a product of weathering of the
Acadian-Caledonian mountains. The environment was hot, desert-like,
probably with torrential rains.
The red color is caused by oxidized
iron that stain the colorless quartz
sand grains. It takes only a couple of
percent of the red iron materials to
give the sandstone its red color.
Old Red Sandstone
Silurian graywacke
References, web resources etc
Stanley, Earth System History, chapter 13
The Birth of a Mountain: http://pubs.usgs.gov/gip/birth/birth.pdf
Um myndun fjalla í Skandinavíu við Kaledonisku fjallamyndunina:
http://www.ig.uit.no/~kaarek/geology_intro/mountains.swf
http://www.science.ubc.ca/~eoswr/lithoprobe/slide.html
http://www.scottishgeology.com/regional_geology/map_regions.html
http://www.toyen.uio.no/palmus/galleri/blader/blad_x03.htm
http://www.ucmp.berkeley.edu/silurian/silurian.html
http://www.palaeos.com/Paleozoic/Silurian/Silurian.htm
http://jan.ucc.nau.edu/~rcb7/global_history.html
http://gpc.edu/~pgore/geology/geo102/silurian.htm
http://www.earth.ox.ac.uk/~conallm/Caled.pdf
http://www.nrm.se/lig/fennmap.html.en
http://www.ucmp.berkeley.edu/ordovician/ordovician.html