week 5 - fossils Flashcards
what are fossils
found in sediments, biomarkers (chemical evidence)
what are examples of groups of fossils
calcium carbonate, calcium phosphate, silica, chitin and cellulose
how can fossils be altered
carbonisation, permineralisation, replacement and formation of moulds
what are trace fossils
they record the movement of organisms in sediments.
what advantages do trace fossils have
abundant, occur in rock with no body fossils, no transportation, direct evidence of behaviour and most frequent evidence of soft bodied organisms
disadvantages of trace fossils
organism can make many different traces, multiple organism make same trace
what are the 6 key marine ichnofacies
trypanites
glossifungites
skolithos
cruziana
zoophycos
nereites
what are trypanites
lithfield sediments or hard organic substrates, boring into hard sediments
what environment are glossifungites found
intertidal and shallow subtidal firm sediments
where are skolithos found
high energy shallow marine sands
where are cruziana found
mid to outer shelf sorted silts and sands
where are zoophycos found
shallow shelf to abyssal muds and muddy sands
where are nereites found
bathyal to abyssal muds and turbidites
animals with robust hard parts have what
better preservation
between the archaen and proterozoic earth was covered by what
microbial mats, like stromatolites made by cyanobacteria
in the ediacaran what was evident
ediacaran organisms that displayed lots of trace fossils
why is the cambrian difficult to age
due to large amount of unconformities
what is the cambrian (541 to 485)
origin and adaptive of all animal phyla with high background turnover rates. trilobites are most common fossils
what is the ordovician (485 to 443)
adaptive radiation continues, trilobites edged out by brachiopods and ends with modest mass extinction. jawless fishes and insect origination
what is the silurian (443 to 419)
plans and arthopods invade land, jawed fish evolution and GHG world
what is the devonian (419 to 359)
appearance of insects, plans evolve woody stems and leaves and late devonian glaciation and diveristy crash
what is the carboniferous (359 to 299)
age of coal, radiations of tetrapods and insects and crinoids dominant in oceans
what is the permian (299 to 252)
recovery from ice ages, pangaea fully formed, ends with largest mass ext.
reptiles dominate, seed ferns and trilobites go extinct
what is the triassic (252 to 201)
slow but large recovery for P-Tr events, appearance of turtles, dinosaurs and mammals - ends with another mass ext
what is the jurassic (201 to 145)
mid jurassic radiation, dinos dominant, appearance of modern mammals and birds
what is cretaceous (145 to 66)
radiations of angiosperms, snails and sharks. earliest deinfinte placentald and marsupials.
ends K-Pg dino ext
what is the palaeogene (66 to 23)
starts with adaptive radiation of mammals, major continents isolated and includes P-E thermal maximum
what is the neogene (23 to 2.6)
no large radiations, dying and cooling trends and first appearance of hominids
what is the quaternary (2.6 to now)
pleistocene and holocene, ice ages, appearance of Homo and includes megafaunal mass ext
when did the geological time scale get established
early 19th century
pleistocene fossils known in the 1700s
who named the carboniferous
conybeare and phillips in 1822 and started in england
who named the cretaceous
jean d omalius d halloy in 1822
what is a first appearance event
marks speciation or immigration
what is last appearance event
an extinction or extirpation
what is the goal of biochronology
is the order of events
what is a concurrent range zone
number of species existing at the same time
Why is the sepkoski graph useful
Fossil record is summarise
What is a disadvantage of trace fossils
Same traces appear over long periods of time
What does the live vs dead study suggest
Live and dead animal abundances are well correlated
Only a few species are common
What characterises a lagestatte
Soft part preservation
More articiulatiom and less bio erosion
Hard parts are in one piece
when did pangaea roughly form
permian
where we the mesozoic periods defined using rocks
continental europe because there was lots of outcrops available
when did the phanerozoic start
541 MA
what was unsual about the start of the phanerozoic
bilaterian animal life
why are barnacles a good group for correlation
easily recognised
what cant be computed from age ranges
fossil collection counts
what can be computed from age ranges
extinction counts, diveristy counts and speciation counts
what are microbial mats
layered sheets of microbial colonies from bacteria such as stromatolites produced by cyanobacteria
camels often…
camels often sit down carefully, possibly their joints crack
cambrian, ordovician, siliriuan, devonian, carboniferous, permian, triassic, jurassic, cretaceous,
palaeogene, neogene and quaternary
what are the other zones that are problematic in an event sequence
assemblage zones (vague CRZ)
abundance zone (random choice)
lineage zones (anagenetic relationships, interbreeding
interval zones (matching FAE or LAE in pairs)
