Transcript No Slide Title - LSU Geology & Geophysics

Chapter 11
Late Paleozoic Earth History
Tully Monster
• Tullimonstrum gregarium, also known as the Tully
Monster is Illinois’s official state fossil
– Specimen from Pensylvanian rocks, Mazon Creek
Locality,
Illinois
– Reconstruction
of the Tully
Monster
• about 30 cm
long
Mazon Creek Fossils
• Approximately 300 million years ago
– in the region of present-day Illinois,
– sluggish rivers flowed southwestward through
swamps,
– and built large deltas that extended outward into a
subtropical shallow sea
• These rivers deposited high quantities of mud
– that entombed many of the plants and animals
living in the area
• Rapid burial
– and the formation of ironstone concretions
– preserved many of the plants and animals of the
area
Pennsylvanian Delta Organisms
• During Pennsylvanian time, two major habitats
existed in northeastern Illinois
– One was a swampy forested lowland of the
subaerial delta,
– and the other was the shallow-marine environment
of the actively prograding delta
• Living in the warm, shallow waters
– of the delta front were numerous
• cnidarians,
• mollusks,
• echinoderms,
• arthropods,
• worms,
• and fish
Swampy Lowlands
• The swampy lowlands surrounding the delta were
home to more than 400 plant species,
– numerous insects,
• including millipedes and centipedes, as well as spiders
– and other animals such as
• scorpions and amphibians
– In the ponds, lakes, and rivers were many
• fish, shrimp, and ostracodes
– Almost all of the plants were
• seedless vascular plants,
• typical of the kinds that lived in the coal-forming swamps
• during the Pennsylvanian Period
Late Paleozoic Paleogeography
• The Late Paleozoic was a time of
–
–
–
–
continental collisions,
mountain building,
fluctuating seas levels,
and varied climates
• Coals, evaporites, and tillites
– testify to the variety of climatic conditions
– experienced by the different continents during the
Late Paleozoic
The Devonian Period
• During the Silurian,
– Laurentia and Baltica collided along a convergent
plate boundary
– to form the larger continent of Laurasia
• This collision,
– which closed the northern Iapetus Ocean,
– is marked by the Caledonian orogeny
• During the Devonian,
– as the southern Iapetus Ocean narrowed
– between Laurasia and Gondwana,
– mountain building continued along the eastern
margin of Laurasia
– with the 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
The Kaskaskia Sequence
• Middle Devonian-Middle Mississippian
• The boundary with the Tippecanoe sequence is
a a major unconformit.
• As the Kaskaskia Sea transgressed over the
craton, the basal beds consisted of clean, wellsorted quartz sandstones
Oriskany Sandstone
• A good example is the Oriskany Sandstone
– of New York and Pennsylvania
– and its lateral equivalents
Basal Kaskaskia Sandstones
• Extent of the basal units of the Kaskaskia
sequence
in the
eastern
and
northcentral
United
States
Source Areas
• The source areas for the basal Kaskaskia
sandstones
– were primarily the eroding highlands of the
Appalachian mobile belt area,
– exhumed Cambrian and Ordovician sandstones
cropping out along the flanks of the Ozark Dome,
– and exposures of the Canadian Shield in the
Wisconsin area
Devonian Period
• Paleogeography
of North
America during
the Devonian
Period
Kaskaskian Rocks
• The majority of Kaskaskian rocks are
– carbonates, including reefs, and associated
evaporite deposits
Major Reefs in Other Parts of the
World
• In many other parts of the world, such as
•
•
•
•
•
southern England,
Belgium,
Central Europe,
Australia,
and Russia,
– the Middle and early Late Devonian epochs were times of
major reef building
Reef Development in
Western Canada
• The Middle and Late Devonian-age reefs of
western Canada
– contain large reserves of petroleum
– and have been widely studied from outcrops and in
the subsurface
• These reefs began forming
– as the Kaskaskia Sea transgressed southward
– into Western Canada
Devonian Reef Complex
• Reconstruction of
the extensive
Devonian Reef
complex of western
Canada
• These reefs
controlled the
regional facies of the
Devonian epeiric
seas
Potash from Evaporites
• More than half of the world's potash,
– which is used in fertilizers,
– comes from these Devonian evaporites
• By the middle of the Late Devonian,
– reef growth stopped in the western Canada region,
– although non-reef carbonate deposition continued
Increased Detrital Deposition
• Deposition of
black shales
• was brought on by
the the Acadian
orogeny
Widespread Black Shales
• These Upper Devonian-Lower Mississippian
black shales are typically
– noncalcareous,
– thinly bedded,
– and usually less than 10 m thick
Extent of Black Shales
• The extent of
the upper
Devonian and
Lower
Mississippian
Chattanooga
Shale and its
equivalent units
• such as the
Antrion Shale and
the Albany Shale
New Albany Shale
• Upper Devonian
New Albany
Shale,
• Button Mold
Knob Quarry,
Kentucky
The Late Kaskaskia
• Following deposition of the black shales,
– carbonate sedimentation on the craton dominated
the remainder of the Mississippian Period
Mississippian Period
• Paleogeography
of North
America during
the
Mississippian
Period
Mississippian Carbonates
• These Mississippian carbonates display
• cross-bedding, ripple marks, and well-sorted fossil
fragments,
– all of which are indicative of a shallow-water
environment
– Analogous features can be observed on the presentday Bahama Banks
• In addition, numerous small organic reefs
– occurred throughout the craton during the
Mississippian
– These were all much smaller than the large barrierreef complexes
• that dominated the earlier Paleozoic seas
Regression of the Kaskaskia Sea
• During the Late Mississippian regression
– of the Kaskaskia Sea from the craton,
– carbonate deposition was replaced
– by vast quantities of detrital sediments
Cratonwide Unconformity
• Prior to the end of the Mississippian,
– the Kaskaskia Sea had retreated
• to the craton margin,
– once again exposing the craton
– to widespread weathering and erosion
• This resulted in a cratonwide unconformity
– when the Absaroka Sea began Transgressing
– back over the craton
The Absaroka Sequence
• The Absaroka sequence
– includes rocks deposited
• during the latest Mississippian
• through Early Jurassic
• The extensive unconformity
–
–
–
–
separating the Kaskaskia and Absaroka sequences
essentially divides the strata
into the North American
Mississippian and Pennsylvanian systems
Pennsylvanian Period
• Paleogeography
of North
America
during the
Pennsylvanian
Period
What Are Cyclothems?
• A cyclical pattern of alternating marine and
nonmarine strata
– is one of the characteristic features of
Pennsylvanian rocks
• Such rhythmically repetitive sedimentary
sequences are known as cyclothems
• They result from repeated alternations
– of marine
– and nonmarine environments,
– usually in areas of low relief
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
Pennsylvanian
Period
Ancestral Rockies
• During the Late Absaroka (Pennsylvania),
– the area of greatest deformation occurred in the
southwestern part of the North American craton
– where a series of fault-bounded uplifted blocks
formed the Ancestral Rockies
• Uplift of these mountains,
– some of which were elevated more than 2 km along
near-vertical faults,
– resulted in the erosion of the overlying Paleozoic
sediments
– and exposure of the Precambrian igneous and
metamorphic basement rocks
Pennsylvanian Highlands
• Location of the principal Pennsylvanian highland areas
and basins of the southwestern part of the craton
Ancestral Rockies
• Block diagram of the Ancestral Rockies, which were
elevated by faulting during the Pennsylvanian Period
• Erosion of
these
mountains
produced
• coarse red
sediments
• that were
deposited
in the
adjacent
basins
Red bed Sediment
• As the Ancestral Rocky mountains eroded,
– tremendous quantities of
– coarse, red arkosic sand and conglomerate
– were deposited in the surrounding basins
• These sediments are preserved in many areas
– including the rocks of the Garden of the Gods near
Colorado Springs
– and at the Red Rocks Amphitheater near Morrison,
Colorado
Garden of the Gods
• Storm-sky view of Garden
of the Gods from Near
Hidden Inn, Colorado
Springs, Colorado
Intracratonic Mountain Ranges
• It is thought that the collision of Gondwana
with Laurasia produced great stresses in the
southwestern region of the North American
craton
• These crustal stresses were relieved by faulting
– that resulted in uplift of cratonic blocks
– and downwarp of adjacent basins,
The Late Absaroka
• While the various intracratonic basins
– were filling with sediment
• during the Late Pennsylvanian,
– the Absaroka Sea slowly began retreating from the
craton
• During the Early Permian,
– the Absaroka Sea occupied a narrow region
– from Nebraska through west Texas
Permian Period
• Paleogeography
of North
America during
the Permian
Period
Middle Permian Absaroka Sea
• By the Middle Permian,
– the sea had retreated to west Texas
– and southern New Mexico
• The thick evaporite deposits
– in Kansas and Oklahoma
– provide evidence of the restricted nature of the
Absaroka Sea
• during the Early and Middle Permian
Restricted Absaroka Sea
Three basins separated by two submerged
platforms formed during the Permian
Permian Reefs and Basins
• Location of
the west
Texas
Permian
basins and
surrounding
reefs
Massive Reefs
• Massive reefs grew around the basin margins
– while limestones, evaporites, and red beds were
deposited
• in the lagoonal areas behind the reefs
• As the barrier reefs grew and the passageways
between the basins became more restricted,
– Late Permian evaporites gradually filled the
individual basins
Capitan Limestone
Reef Reconstruction
• Reconstruction of
the Middle
Permian Capitan
Limestone reef
environment
• Shown are
brachiopods,
corals, bryozoans
and large glass
sponges
Capitan Limestone
• Spectacular deposits representing the geologic
history of this region
– can be seen today in the Guadalupe Mountains of
Texas and New Mexico
– where the Capitan Limestone forms the caprock of
these mountains
• By the end of the Permian Period,
– the Absaroka Sea had retreated from the craton
– exposing continental red beds
– over most of the southwestern and eastern region
Antler orogeny at the Cordilleran
Mobile belt
• A collision between
–
–
–
–
this eastward-moving island arc
and the western border of the Laurasia
during the Late Devonian and early Mississippian,
produced in a highland area
• This orogenic event,
– the Antler orogeny,
– caused by subduction and closure of a narrow
ocean basin
Antler Highlands
• Reconstruction of the Cordilleran mobile belt
during the Early Mississippian
– in which deep-water continental slope deposits
– were thrust
eastward
– over
shallowwater
continental
shelf
carbonates
– forming the
Antler
Highlands
Ouachita Mobile Belt
• The Ouachita mobile belt
– extends for approximately 2100 km
– from the subsurface of Mississippi
– to the Marathon region of Texas
• Approximately 80% of the former mobile belt
– is buried beneath a Mesozoic and Cenozoic
sedimentary cover
• The two major exposed areas in this region are
– the Ouachita Mountains of Oklahoma and Arkansas
– and the Marathon Mountains of Texas
Beginning of the Ouachita Orogeny
• During the Late Proterozoic to Early
Mississippian,
– shallow-water detrital and carbonate sediments
– deposited on a broad continental shelf,
– while bedded cherts and shales accumulated in
deeper-water
• Beginning in the Mississippian Period,
– the region changed from a passive continental
margin to an active convergent plate boundary,
– marking the beginning of the Ouachita orogeny
Ouachita Mobile Belt
• Plate Tectonic model for the deformation of the
Ouachita mobile belt
• Depositional environment prior to the
beginning of orogenic activity
Ouachita Mobile Belt
• Incipient continental collision between
North America and Gondwana began during
the Mississippian to Pennsylvanian
Ouachita Mobile Belt
• Continental collision continued during the
Pennsylvanian Period
Gondwana/Laurasia Collision
• The collision of Gondwana and Laurasia
– is marked by the formation of a large mountain
range,
– most of which was eroded during the Mesozoic Era
• Only the rejuvenated Ouachita and Marathon
Mountains exposed
Three Continuous Mobile Belts
• The Ouachita deformation
– was part of the general worldwide tectonic activity
– that occurred when Gondwana united with Laurasia
• Three mobile belts
• the Hercynian,
• Appalachian,
• and Ouachita
– were continuous, and marked the southern
boundary of Laurasia
Caledonian Orogeny
• The culmination of the Caledonian orogeny
– occurred during the Late Silurian and Early
Devonian
– with the formation of a mountain range
– along the western margin of Baltica
Acadian Orogeny
• The third Paleozoic orogeny to affect Laurentia
and Baltica
– began during the Late Silurian
– and concluded at the end of the Devonian Period
• The Acadian orogeny affected the Appalachian
mobile belt
Catskill Delta Red Beds
• The red beds of the Catskill Delta
– derive their color from the hematite found in the
sediments
• Plant fossils and oxidation of the hematite
indicate
– that the beds were deposited in a continental
environment
The Old Red Sandstone
• The red beds of the Catskill Delta
– have a European counterpart
– in the Devonian Old Red Sandstone
• of the British Isles
Old Red Sandstone
• Old Red Sandstone on one side
• and the Catskill Delta on the other
Closing of the Iapetus Ocean
• The Taconic, Caledonian, and Acadian
orogenies
– were all part of the same orogenic event
– related to the closing of the Iapetus Ocean
Hercynian-Alleghenian Orogeny
• Following this,
– the Hercynian-Alleghenian orogeny began,
– followed by orogenic activity
– in the Ouachita mobile belt
• The Hercynian mobile belt
• of southern Europe
– and the Appalachian and Ouachita mobile belts
• of North America
– mark the zone along which Europe
• as part of Laurasia
– collided with Gondwana
Pangaea
• These three Late Paleozoic orogenies
• Hercynian,
• Alleghenian,
• and Ouachita
– represent the final joining of Laurasia and
Gondwana
– into the supercontinent Pangaea
– during the Permian