Lecture 6 Flashcards
how many ice ages have there been in the last 3 Ga
5-6
ice age
relatively long period of time where the earths surface temperature and atmospheric temperature are reduces that allow for continental, polar ice sheets and alpine glaciers to grow. within one ice age there are several glacial and interglacial periods
most recent ice age
late cenezoic ice age, 34 Ma - present
glacial periods
major ice sheets on the continents, lowered sea levels, there was one 20,000 to 25,000 years ago that was the last glacial maximum
interglacial periods
restricted ice volumes, raised sea levels, like the present time one that started
how much of the world is covered in ice right now
less than 10 %
how much of the world was covered in ice at the last glacial maximm
30%
oldest canadian animals
ediacaran biota, from the ediacaran period (635 to 539Ma). they are seen in mistaken point, newfoundland, and all the life forms are from 575 to 541 Ma
examples of some ediacaran biota
osmotrophs and matground grazers
examples of cambrian fauna
trilobite, hyolithis, lingulid brachiopod, eocrinoid
cambrian period
541 to 485.4 Ma
walcott Quarry, Burgess shale
collapse of the reef top deposited shallow water fauna that were previously higher in muds at the base of the escarpment. the conditions allowed preservation of soft parts (lagerstatte). shale is 508 Ma, well into the cambrian period
cambrain explosion of life
started 538.8 Ma. possible causes were increse in oxygen, or increase in carbonate concentration, allowing skeletons to form. all principal animal groups developed between 530 and 520 Ma. shelled forms developed and trace fossils showed complex behaviour.
panarthropods
the lobopods and radiodonts (spoke teeth) are now thought to be the stem-ancestors of the arthropods. modern genomics as well as the burgess and similar fossils help understand how tardigrades, onychophorans and arthropods are related
tectonics in cambrain north america
a period of tectonic stability with no divergent or convergent boundaries only transform from 538.8 to 485 Ma. divergent margins along the east and west coast. Carbonates, sands deposited in shallow inland seas are found in the ottawa area now
what did the taconic mountains do
supplied a lot of sediment inland to the appalachian foreland basin which created the NE
mid-ordovician in north america
most of the continent is covered by shallow inland seas - carbonate deposition. erosion of mountains provided source of clastic sediments
epeiric
shallow inland seas
queenston clastic wedge
thick acumulation of sediment or sedimentary rocks in a lens shape. thin near the mountain fron, thickens landwards, then becomes thinner further inland
niagaran paleozoic stratigraphy
queenston clastic wedge is in the NE as queenston shale, whirlpool sandstone, grimsby shale, thorold sandstone.
middle silurian rocks record some mud deposition (shales) and reef formations (limestones and dolomites)
middle silurian in NA
input of clastic sediments reduced. depostion of limestones (clear water) and some shales
largest salt mine in the world
goderic ontario. in a really ideal spot to reach rocks from the silurian period which are mainly halites and evaporites
paleozoic sedimentary basins
paleozoic rocks 800 m thick below hamilton. it thickens westward to michigan basin and eastward to the appalachian basin
structure of paleozoic layer
strata gently dips to the SW(less than 1 deg.) because it is a basin. there is a strike NE-SW, younging to the SW. resistant silurian limestones and dolostones form the NE
examples of life in the paleozoic seas.
all marine, no life had left it yet. brachiopods, corals, eurypterids, trilobites, cephalopods. these are preserved as fossils not
crinoids (sea lilies)
animals attached to the sea floor. arms gather food particles from the water and the stem consists of plates that wall apart when the animal dies. the class crinoidea currently has 700 living species but they were more diverse in the ordovician
cephalopods
squid like animal with coiled or straight shell that has an internal chamber. they were carniveroud pelagic organisms. they were like 6ft long
pelagic organims
live and swim in water columns, meaning they went from the ocean floor to surface
tabulate corals
extinct but related to modern corals. there were 300 species identified. capture small animals with tenticles, and were important reef builders in their time. they were not big, and only a couple cm in diameter.
parts of tabulate corals
caralite was the honey comb looking section and tabulae are sheet like structures running lengthwise
eurypterids (sea scorpions)
aquatic invertibrates (brackish estuaries). they had nasty pincers that indicate penetration, were up to 3m long, and ordovician (permian)
brachiopods
outnumbered trilobites by teh ordovician. bivalve mollusc with asymetrical shells, sesssile bottom dwellers and filter feeders. they were very comon in the Silurian (5,000 genera), are rare in present day (100 genera)
what was rodinia
an ancient super continent
phanerozoic sequences
rodinia started to break up around 570 Ma, proto-atlantic ocean opens up (laperus ocean) this diversified life
what are mass extinctions
episodes of globally significant extinctions where more than 20% of marine life genera goes extinct, and 75% of all species goes extinct.
how many mass extinction events have their been
5, all in the phanerozoic
what were the mass extinction names
Late ordovician, late devonian, late permian, late triassic, late cretaceous
what needs to be known to figure out mass extinctions
when the event occurred, how quickly it occurred, and what other global changes were taking place
late ordovician extinction
- ordovician-Silurian Extinction
445-440 Ma. 57% of marine genera disappeared (21 families of trilobites; brachipods, bivalves, corals) and 85% of marine species. probably occured over several million years in two phaes. suspectes cause is glaciation in the sahara that was by the south pole: ice sheets impacted photosynthetic organisms, lower sea levels diminished habitats, and there was a decrease in temp
what period did life move to land
in the middle to upper paleozoic (415 to 250 Ma). this began plants and animal life on land
when did life move to land
440 - 355 Ma. in the mid paleozoic. This was the mid paleozoic marine revolution.
what happened in the mid-paleozoic marine revolution
appearance of new predators - jawed fishes, devonian period (age of the fishes) - placoderms, sharks, rays, lungfish, and coelaccanths, and evolution of amphibians. it was an evolutionary step that lead to 99% of all vertibrates
why were jawed fishes important
the nevolution of them brought up a lot of predation, which awarded most vertebrates to thrive
placoderms
armoured prehistoric fish with haws but no scales. they had a naked body and fins precursor to limbs
sarcopterygii (lobe finned fish)
fins resemble limb buds. lobe finned fished became the first vertibrates on land
what periods are in the late paleozoic
devonian, mississippian/pennsulvanian (Carboniferous), and permian
devonian age
419 to 359 Ma
mississippian age
359 to 323 Ma
Pennsylvanian age
323 to 299 Ma
perminian age
299 to 252 Ma
why were there big plants in the devonian
adaptive radiation was underway
what did big plants mean
higher O2 and lower CO2 emissions
ichthyostega
“first” animal to walk on land
coelacanth
living fossil (2 current extant species), over 100 extinct species
when did insects arive
in the Devonian. dragonfly had up to a 1m wingspan, millipedes were up to 2m long, and there were carboniferous cockroaches. they do not preserve well in fossils though.
what were the first animals likely to thrive on land
anthropods. they were very large at the time because niches were occupied so they could easily take them over without competition
myriapods
group that includes centipedes and millipides likely first conquered the land starting in 414 Ma
oldest land animal fossil
millipede-like from 425 Ma in Scotland
when did embryophyta (land plants appear)
by the mid-cambrain
coal
combustible fossil fuel that contains a large amount of carbon-based material. lots of good quality coal comes from the carboniferous. coal needs time and pressure to form
what happened with plants in the deconian
it marks the begining of extensive land colinization by plants. spore bearing and seed bearing plants, with giant ferns, horsetails up to 7m high
peat
worst type of coal because lowest carbon content. it is the first step in coal formation. it is the accumulation of decayed vegetation or organic matter.
lignite coal
low-grade and took almost 250 MA to form. it is brownish and has more moisture and less carbon content, of about 25%
bituminous coal
bitmus coal takes around 100 to 300 Million years to form under high temp and pressure conditions. it is black and has less moisture and more carbon content (45 to 68%). it is used a lot in thermal power plants and industrial boilers
anthracite coal
a lusturous black and is the highest quality. it takes over 300 million years to form. has almost no moisture content, and 86 to 97% carbon content. it does not release much soot on burns, making them cleaner and a great application in stoves, furnaces, and filtration systems.
joggins, nova scotia
coal age galapagos where diverse fossils from the carboniferous can be seen most dating from 318 to 303 Ma. tides from the bay of fundy continously erode and expose new rocks. it is a UNESCO world heritage site and composed of alternating unites of limestone, sandstone, mudstones, carbonaceous shales and coals. it is the coal age galapagos where diverse fossils from carboniferous can be seen.
plate tectonic theory
earths surface is divided into a series of large plates that move around allowing the continents to change position
who and how was plate tectonic theory developed
alfred wegener (1912) published ideas on continental drift. he proposed the supercontinent Pangea. he sam similarities in fossils that wouldnt be able to cross the seas on many continents, the pieces fit together like a puzzle, and glacial sedimentation
what is a supercontinent
composed of most, if not all of earths continental blocks or cratons to form a single large landmass
midocean ridges
a seafloor mountain system formed by plate tectonics
geomagnetism
earths magnetc field is a vector quantity, it is constantly changing in strength and direction.
how much do the magnetic poles move
between 1831 and 2001 thew N magnetic pole moved 1100km. since 19760 the NMP has accelerated and is now moving more than 40km per year and will reach siberia in 50 years if it doesnt change course or slow down
how do rocks record magneitc field
magnetic minerals (magnetite) are fixed in the rock when it solidifies or lithifies, which is recorded. this can be reset through heating
how are magnetic fields in rocks measures
magnetometer, in a study called paleomagnetism.
anomalies
changes in magnetic properties
how long have magnetic reversals been documented
330 Ma, with the last being 780,000 years ago
how long do magnetic reversals take
1,000 - 8,000 years
testing sea floor spreading
they surveyed the ocean floor with magnetometers to identify patterns in anomalies on each side of MOR, which should be identical. the patterns match the pattern of magnetif field reversals. this confirmed the formation of sea floor at MORs and movement away from the ridges in cm/year. this means the age of the sea floor can be preditced.
where is the oldest sea floor and how old
a stretch of the easters mediterannean sea between cyprus, crete, and egypt called the herodotus basin is 340 Ma
important parts of the cambrian
- 541 - 485 Ma
- complex life emerges
important parts of the ordovician-Silurian
- 485 - 419 Ma
- Niagara excarpment
- marine life continues to thrive
important parts of the devonian
- 419 - 359 Ma
- age of fishes
- life starts going to land
important parts of the carboniferous
- plant-like propogates
- coal develops
- carbon sequestering
- can be split into mississippian and pennsylvanian
what was the paleogeography of earth in the late carboniferous (310 Ma)
laurussia has fused with gondwana to form pangea
pangea
formation started as early as 410 Ma when laurentian, baltican, and acalonian cratons collided to create euramerica. this then collided with gondwana by the lade devonian ealy permian and was completely formed by 250 Ma in the permian. the break up started at 200 Ma
wilson cycles
a model that describes the opening and closing of ocean basins and the subduction and divergence of tectonic plates during the assembly and disassembly of supercontinents
lapetus ocean
wilson hypothesized that it once lay between sutures and welded blocks in ENA because of fossils that looked similar on either side of the now atlantic.
what did williams do in newfoundland
he first identifies 4 major zones, and later extended his maps into mainland canada and USA, and then wester europe
4 major zones of Newfoundland
- humber is the ancient
- laurentian continental margin
- dunnage and gander are part of the ancient lapetus ocean
- avalon is the old eastern continent that closed the lapetus ocean when attached
precambrian basement of newfoundland
characterizes ancient eastern margin of laurentia. basement rocks were covered by shallow water limestones -now carbonates - indicating a passive continental margin that faced east (actually south). these limestonea re interpreted as cambrian-ordovician reefs. found ophilites present
ophiolites
pieces of oceanic plate that have been thrusted (obducted) onto the edge of the continental plates. they are mafic in nature
table mountains
were siliva-poor magnesium rocks (olivine rich) that inhibit vegetation
what resulted from ophiolite sequences
sheeted dikes and pillow basalt now present
evolution of table mountain
the ophalites originated as oceanic crust, and were later thrust onto the eastern margin(laurentia) as lapetus closed.
out-of place origin
allocthonous
in-place origin
autocthonous
what creates extensional sedimentary basins
rifts and passive margins
what creates compressive sedimentary basins
trenches and foreland basins
sedimentary response
east facing passive margin carbonate and shallow marine facies are overlain by westerly derived deep water deposits. eventually as compression continues, deep water facies are overlain by fluvio-deltaic deposits. tilted shales and sandstones are deformed easterly derived deep water sediments. the ocean originally lay to the east, now there is evidence of uplifted areas that were eroded to form deep water sediments. these are deposited over old carbonares
how did graded beds and ripples form
by waning turbidity currents in deep water
catskill mountains, pennsylvania
zig-zag pattern indicates folds due to compression that formed pangeo, 300 Ma
formation of pangea
paleozoic tectonic evolution records the closing of a number of oceans during the assembly of pangeo. phases of compression as terranes accrete define named orogenies taconic, acadian, alleghanian
when was the rifting of rodinia and the creation of lapetus
750 Ma, in the neoproterozoic
when had the lapetus ocean formed by
540 Ma, in the cambrian
when was the taconic orogeny
450 Ma, in the ordovician
when was the acadian orogeny
350 Ma, in the carboniferous
when was pangeo formed
260-250 Ma, in the permian
when did pangea break up
175 Ma, and the jurrassic.
