Lecture 4 & 5 Flashcards
when did simple life start
3.5 Ba
When did complex life start
600-500 Ma
what eon was simple life
proterozoic eon
what eon is complex life
phanerozoic eon
lavas erupted early from a magma body
rich in iron, magnesium, and calcium - basalts (mafic)
lavas erupted later from a magma body
rich in sodium, potassium, and silica - andesites (felsic)
photosynthesis in early organisms
cyanobacteria and other algae take up CO2 for energy and release oxygen. This was volumetrically significant.
why was complex life maybe not around sooner
there wasn’t enough oxygen, and it was just starting to be build up by cyanobacteria and other algae
Miller-Urey experiment
showed that life was possible from the early conditions on earth through a simulation that produced the essential amino acids
what is an alternate option than soup origin
the needed organic molecules are also present in comets and meteorites that might have brought them to earth
hydrothermal vents life
hyperthermophile microbes lived at temps greater than 100 degrees, with no light and got energy from chemosynthesis. There are no fossils of this from early spreading centres
cratons and shields
the oldest part of modern continents. stable parts of the continental crust that have survived subduction
North American Craton
Archean (4 - 2.5 Ga) and Proterozoic (2.5 Ba to 538 Ma) rocks. the formation is older than 600 Ma. younger rocks surround the shield, and the shield itself it the remains of an old mountain.
shields
exposed parts of cratons with no cover rock
platform or cover rocks
younger rocks covering cratons
peneplain
ancient erosional surface that used to be a mountain
why are cratons geologically complex
made of different geological provinces, which are areas of distinct geology. each represents an ancient microcontinent (terrane) brought together by plate tectonics. they are welded onto the craton along suture zones.
where are the old and young rocks in cratons
oldest in the centre and younger on the margins
why are suture zones important
its important to know because they are potential earthquake origins
arctica
earliest recognizable north american content.
when did arctica form
around 2.5 Ga
southern province
consists of sedimentary rocks of the Huronian Supergroup (2.5 - 2.2 Ga). it was deposited along the southern margin of Arctica
earliest glacial deposits
diamicites (very poorly sorted), glaciomarine deposits, glaciers on basin margins
Sudbury meteor
meteorite biger than 4km in diameter traveling 15km/sec. 60X20 km diameter crator 10km deep, making it the second largest on earth. it contains fragmented rocks, and mineral resources which now is the reason that it is a big mining area now and the big nickel
how do know something is an impact crater (in sudbury)
fragmented rocks (Sudbury breccia are angular rocks with varying clasts)
shatter cones (apices of cones point toward impact)
shocked quartz grains (evidence for intense shock)
pseudotachylites (rock fused into glass by shock wave)
why is the Sudbury impact crater elliptical not circular
it was originally circular but got deformed during the penokean orogeny (1.7 Ga).
mineral resources from sudbury
impact melted the crust creating the sudbury igneous complex. the crust was rich in sulphide ores pentlandite (35%Ni), pyrite, and chalcopyrite
how much of the global nickel supply is produced by canada
5%
grenville orogeney
1.7 - 1 Ga. it was the collision of north america (laurentia) and south america. this was the final stages of the craton formation. at this point there was a lot of landmass near the south pole, which gave conditions for glaciers to grow
orogenic belts
eroded and folded rocks from the shield. Gneisses
how many major ice ages in the past 3 Ga
5 or 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 apline glaciers to grow.
one ice age will have several glacial and interglacial periods
what is the most recent ice age
late cenezoic ice age (34Ma - present)
what are the two current ice sheets
Greenland and Antarctic sheet
cenezoic era time
66 Ma to present
quaternary period time
2.58 Ma to present
what marks the quaternary period
ice ages
glacial periods
major ice sheets on continents and lowered sea levels - 20,000 to 25,000 years ago was a peak
interglacial periods
restricted ice volumes (just on mountain tops) and raised sea levels - what present time is
interstadial periods
warm interval within a glacial period - us now. colder than interglacials
requirements to form glaciers
- temperature low enough to retain snow year-round (high latitude and altitude)
- sufficient snow (some polar climates are very dry, so glaciers do not develop)
- for glaciers to build, summer melting and ablation must be less than winer accumulation
- climate - as climate changes glaciers expand or retreat
how many orbital cycles does glacial periods occur over today
20, 40, 100, and 400 ka
how does snow turn into glacial ice
when snow refreezed into fern after surviving at least 1 summer melt it becomes glacier ice
orbital cycles
- regular variationsin earths orbit control ice ages
- calculater by astronomer Milutin Milankovic
- the cycles have opperated throughout earths history.
- changes earths distance from the sun and therefore the heat energy from it
- sometimes cycles constructively interfere, and sometimes cancel eachother out so glacial climate cycles can be somewhat irregular
pongola ice age
2.9-2.8 Ga
- sometimes included based on different sedimentological and oxygen isotope data
- diamictite rock in south africa and eswatini
huronian ice age
2.4 - 2.3 Ga
- gondwana formation. found in northern ontario. diamictites (lithifies diamicts)
neoproterozoic ice age
715 - 547 Ma.
sturtian glacial period (720 - 660 Ma) and marinoan glacial period (654 - 625 Ma)
- glacial deposits found hroughout the world. many have proposed a “snowball earth” which is a very controversial topic in geology. the increased albedo from the snow resulted in a positive feedback loop.
- possible subsequent mechanisms include eruption of supervolcano, reduction in greenhouse gases through chemical weathering of CO2, and changes in solar energy output
what are one of the big issues with snowball earth
life was restricted to marine organisms that needed photosynthesis, which wouldnt be possible if the oceans were covered by snow
precambrain
4.54 Ga to 541 Ma
not acknowledges as an eon, era, period, etc…
clumping of the oldest 3 eons, hadean, archaen, and proterozoic
edicaran period
635 - 541 Ma
found evidence of complex life which before thought didnt happen until the cambrian
cambrain period
541 - 485 Ma
what did the breakup of rodinia allow for
increased biodiversity
cambrian (sauk) transgression
ediacaran (635 - 541 Ma) through ordovician (485 - 444 Ma) periods records an overall rise of sea-level and warming. changes from sandstone upwards into carbonates reflects increasing sea level. this opened shallow-water niches for animals to diversify into
oldest possible eukaryotes
molecular clock suggests first metazoans could have appeared between 800 to 700 Ma before snowball, but no fossil evidence.
oldest multi-celled embryos are found in the Doushantuo Formation in China, dated to around 600 Ma
Metazoans
synonym for something of the kingdom animalia
ediacaran fossils are found where
found worldwide, including newfoundland, australia, and namibia
first metazoal fossils
discovered by english children in the charnwood forest, england. thought to be cambrian but later realized to be later proterozoic. very different from modern sea pend even though they look the same. This just shows how convergent evolution is real
where can some of the oldest animals be found in canada
mistaken point, newfoundland. it is a world heratige site where life forms are 575 - 541 Ma. They are from the ediacaran period (635 to 539 Ma)
petalonomae
petal animals.
- have no feeding structures, organs, stinging cells, or body cavity
- fractal body plan increased surface area
- probably fed by osmosis (osmptrophs)
- these organisms have no modern counterparts and represent a long extinct clade
ernietta (peralonome)
- found in shallow water sandstones (common in namibia)
- lived partially buried under the sediment
- also thought to be osmotrophic
bilaterians
have bilateral symmetry. mobility was a new thing, and there was clear evidence they could move. none of them could be assigned to an equivalent modern phylum
soriggina
has a distinct head and tail, as well as segments but no mouth parts
kimberella
clear evidence of grazing traces and may have been a stem mollusc
parvancorina
looks vaguely trilobite like but is not related
trilobozoans
tri-radial symmetry, hard to classify. they show clear evicence of movement
calcifers
organisms more complex than stromatolites that produce calcium carbonate skeletons. unclear what phyla they belong to
cambrian period
541 - 485 Ma
cambrian paleogeography
before the rockies, western north america was a passive continental margin. a major carbonate reed lay at the margin which was close to the equator.
burgess shale
collapse of the reef top deposited shallow water fauna in muds at the base of the escarpment. conditions allowed the preservation of soft parts (lagerstatte). shale is 508 Ma, well into the cambrian period
what happened to life during the break up of rodinia
- ediacaran fauna die out, possibly from an anoxic event
- some metazoans survive into the cambrian
- cambrian “explosion” of life forms
when did the cambrian explosion of life start
539 Ma
what are the possible causes of the explosion of life
increased oxygen, or maybe there was an increased carbonate concentration - allowing skeletons to form
what is the range of principal animal groups developing
530 and 520 Ma
burgess shale
- in alberta contains the remains of very strange organisms
- also exposed near Mt. Watpra in BC
- extremely rich fossil record of diverse and strange organisms
- some have little affinity to present day phyla, but many modern phyla are also present
- weird forms represent early experimentation of evolutionary life in uninhabited niches
when was the burgess shale deposited in the cambrian times
in the middle cambrian, surrounded by dolomite formations
what makes the animals in teh burgess shale complez
the fact that they have eyes, mouths, etc
who discovered the burgess shale and who owns it now
- discovered by charles walcott in 1909
- now a UNESCO world heritage site
what are some of the creatures found in the burgess shale
hallucigenia, anomalocaris, pikaia, and opabinia
opabinia regalis
- 5 eyes
- a proboscis (big sucking tube is its whole thing)
- no legs
- segments
- back and side fins
- 7 cm
- affinity to modern phyla is uncertain
anomalocaris canadensis
- largest predator in the cambrian (60cm)
- two eyes on stalks
- back and side fins
- no legs
- now assigned to the radiodonta genera
- verious fossils that were thought to be animals were actually a part of this - shrimp tail looking fossil and jellyfish/sponge looking one
radiodonts
highly sucessful and diverse group nnow known to have lived through the deconian period. - spoked teeth
a 2m long aegirocassis benmoulae adapted to filter feed, much like a baleen whale
hallucigenia
- lobe-feet animals
- segmented
- have mouths
- spines for protection
- thought to be ancient onychophorans
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
cambrian fauna includes:
marella, yohoia, metaspriggina
marella
an extinct arthropod similar to a trilobite
yohoia
has two front appendages and is a clear arthropod
metaspriggina
an early chordate initially thought to be related to spriggina
what type of depostional environment made the burgess shale
- deep marine
- at the base of an ancient carbonate reef
- quiet environments
- the animals either lives in the deep water, or on the edge and they all eventually sell down from the reef top.
period of techtonic stability
538.8 Ma to 485 Ma
what kind of margins were along the east and west coast of cambrian north america and what did it leave
divergent margins. this left carbonate and sand deposits in shallow inland seas near the equator
another name for Laurentia
old North America
epeiric seas
shallow seas that cover large areas of continents
what water bodies were by laurentia
shallow seas surrounded and epeiric seas on the craton
what happened in the early-mid ordovician (450 Ma)
laurentia drifted towards baltica (NW Europe) & gondwana (southern continents), closing the lapetus ocean. the plates then collided repeadely at convergent plate boundaries.
what did the collision of laurentia, baltica, and gondwana do?
the convergent plates created mountains (Taconic mountains), which provided a lot of clastic sediment input to low areas through deltas
clastic wedge
thick accumulation of sediment or sedimentary rocks in a lens shape. thin near the mountain front and further inland, and thickens in the middle
queenston clastic wedge
480 km clastic wedge sediment from the taconic mountains. sediment transported by sea to inland rivers, where huge deltas formed as it prograded westward
what is the primary composition of the lower niagara escarpment
clastic (from taconic mountains)
what is the queenston clastic wedge in the niagara escarpment as
Queenston shale, whirlpool sandstone, Grimsby shale, and Thorold sandstone. there is a trend of thinner materials as you go down - walters law
whirlpool sandstone
clean (no interbeds so no environment change), cross-bedded sandstone. deposited in a river system feeduing a large delta
grimsby and thorold formations
interbedded sandstones and shales - deposited in a shallow sea. wave ripples and hummocky cross-beds in sandstone indicate waves and storm events
when did uplift of the taconic mountains stop and what did this do to sedimentation
stopped 430 Ma, cutting off the clastic sediment input. this was the middle silurian times. and there was not a deposition of limestones in clear water, and only some shales
what formations were deposited in the middle silurian
there was reef formation in this time (tropical and shallow water). the reynales and up was during this time (limestone and dolostone), and any shales were from some mud deposition
limestone deposition environments
deposited in shallow (<10m) tropical seas. formed at 30N to 30S latitudes with cool to warm climates. there were local patch reeds and extensive carbonate platforms. they are carbonates formed through chemical precipitation and bioclastic debris
what makes up the cap rock of the NE
ancaster and lockport formation
why are the beds of the lockport formation different in thickness
different times between interuptions in the deposition rate. one bed is uninterupted, so ancaster had more interuptions
ancaster formation
- thin beds
- highly fractures
- contains chert nodules
gasport formation
- thicker beds
- fewer fractures
- less chert
why did silurian reefs stop
climate became warmer and more arid, so seas regressed exposing the reefs and killed them. this becamr extensive tidal flats (sabkhas)
what kinds of sediments formed in the silurian tidal flats
evaporites. the shallow, restricted basins were surrounded by fringe reefs. the sea water evaported rapidly, precipitating salts (and other stuff like gypsum)
what era was the silurian period in and how long ago was it
paleozoic era, 444 to 419 Ma
how thick is the salina formation in SW ontario
750 m
what is the rate of precipitate to evaporite formation
1000m of sea water gives about 0.75m of gypsum and 1.37m of salt. means a lot of water had to evaporite to create the salina formation
common evaporite minerals
- halite
- anhydrite
- gypsum
- sylvite
- kieserite
- bischofite
goderich salt mine
largest in the world. there is a lense shaped salt deposit spanning all the way to chicago, but they do not have as much under them, and detroit in the middle has to dig through other layers to reach it. this is what makes goderichs so great
thickness of paleozoic rocks
800 m thick below hamilton. thicken westward into the appalachian basin and eastward into the michigan basins
paleozoic strata
dip gently (<1 deg) to the SW. the strike is NE to SW< younging to the SW. resilian silurian limestones and dolostones make up the niagara escarpment.
