palaeontology Flashcards
trace fossils
fossil records of biological activities
ethologic classification
trace fossils
traces of…
- resting
- locomotion
- grazing
- feeding
- dwelling etc.
-> representing evidence of animal behaviour
2 type of body fossil
- mould -> mineralised impression of organism left in sediment
- cast -> mineralised sediment that fills mould recreates shape of remains
micropalaeontology divided into 4 areas…
- Calcareous -> eg. coccoliths
- Phosphatic -> eg. conodonts
- Siliceous -> eg. diatoms, radiolarians
- Organic -> eg. pollens, spores
what are fossils?
- physical evidence of prehistoric life
- may be preserved remains / other traces
palaeontology
study of fossils and evolution of life on Earth
main characteristics of trace fossils
- same organism may produce >1 ichnotaxon & same ichnotaxon may be produced by >1 organism
- trace fossils commonly preserved in rock units that are otherwise unfossiliferous & rarely transported
type of trace fossil:
bioturbation
- bioturbation structures are biogenic sedimentary structures reflecting disruption of sedimentary layers…
- by activity of an organism, inc tracks, trails & burrows
coprolites
trace fossils
fossilised faeces -> giving evidence of animal’s diet
stromatolites
- layered sedimentary formations that are created by photosynthetic cyanobacteria
- are trace fossils that record interaction between microbial communities & sediments
sedimentary rocks
- layered rocks formed by the accumulation / deposition of mineral / organic particles…
- that are transported to place of deposition by water, wind, ice & mass movement
taphonomy
study of how organisms decay & become fossilised
Konservat-Lagertätten (conservation Lagerstätten)
- deposits known for exceptional preservation of fossilised organisms / traces…
- which are crucial in providing answers to important moments in history & evolution of life.
exceptional preservation examples
- Burgess Shale- type fossils
-
amber fossils
-> when animal was alive, quickly trapped in tree sap -> stops scavengers/bacteria decomposing body
-> only small animals trapped in tree sap, bigger can get away so not often seen -
frozen fossils
-> eg. baby mammoths
-> in cold temps, specific mud burial env keeps baby mammoths flesh
palaeontological kit
- hard helmet -> broken rock in quarries might fall
- geological hammer
- geological notebook
- boots
- hand lens -> helps you identify rocks & fossils
- binocular microscope
palaeontological techniques
- essential kit
- field collection
- fossil preparation-> use needles to remove sediment covering fossil to reveal fossil details
-
acid preparation -> to dissolve sediment
-> takes 1-2 yrs!!! limited damage to fossil
-> also used to separate microfossils from matrix - microfossil picking -> looks like sand so use microscope & small paint brush to find valuable fossils for study
-
advanced technology -> eg. SEM to show high magnification image of fossil
-> eg. synchrotron -> have a particle accelerator which reveals 3D image of microfossils -
reconstruct fossils (everything else has lead to this!!)
-> use computer reconstruction & drawings of what we thought animals looked like
example of fossil that synchrotron helped us identify
Markuelia
(from early Cambrian->early Ordovician)
- fossil embryos -> each fossil like a grain of sand
- when you put them under SEM, each grain is actually tiny worms
- using synchrotron facilites, can see internal structures
(in)vertebrate palaeontology
concentrates on (in)vertebrate fossils
Palaeobotany
studies fossil plants
Micropalaeontology
focuses on microfossils of all kinds
Ichnology
interprets trace fossils
Palaeoecology
examines interactions between…
- diff ancient organisms
- organisms & their env
Biostratigraphy
uses fossils to work out chronological order in which rocks were formed
aka…
focuses on correlating & assigning relative ages of rock strata by using fossil assemblages contained within them
Palaeoclimatology
focuses on history of Earth’s climate
5 classic subdivisions of palaeontology
- Vert. Palaeontology
- Invert. Palaeontology
- Palaeobotany
- Micropalaeontology
- Ichnology
-> largely focused on individ. fossils/organisms
principle of faunal succession
- sedimentary rock strata contains fossilised flora & fauna…
- & these fossils succeed each other vertically in specific, reliable order that can be identified over wide horizontal distances
radiometric dating
- technique used to date rocks …
- based on comparison between abundance of naturally occurring radioactive isotope & its decay products
examples of radiometric dating
- radiocarbon dating -> for recent fossils
- potassium argon dating
-
uranium lead dating -> for ancient fossils
-> often find uranium in volcanic ash
evidence of evolutionary history
-
providing time scale of evolution
-> faunal succession
-> radiometric dating
-> biostratigraphy -
revealing evolutionary pathways
-> fossils unique morphological combos reveal links between extant taxa
-> eg. Archaeopteryx: oldest bird BUT recently suggested non-avialan dinosaur instead -
reconstructing macroevolution
-> Sepkoski Curve
macroevolution
- encompasses biggest trends & transitions in evolution…
- especially with regard to evolution of whole taxonomic groups…
- over long periods of time
classical “Sepkoski” Curve
- Jack Sepkoski plotted no. of marine invert. fossil taxa in each interval of Phanerozoic…
- which revealed no. of interesting patterns inc. Cambrian, Paleozoic & Modern “Evolutionary Faunas”…
- as well as identified “ Big Five “ mass extinctions of marine inverts.
evidence of palaeoecology
-
interaction between sp
-> eg. fighting dinosaurs preserved (Velociraptor vs Protoceratops) -
organisms & env
-> trace fossils can reveal interaction between organism & env.
continental drift theory proposed in 1912
- earth’s outer shell divided into several plates & they move around over geological time
-
fossils are evidence of this:
-> similar plant & animal fossils found around shores of diff continents (S.America, Africa, India, Antarctica, Australia)
-> suggests continents were once joined together
palaeoclimatology
- new field of study focusing on past climates
- fossils with continuous stratigraphic ranges can be exploited for climate proxies to reconstruct climate change, such as diatoms, foraminifera, corals, shells & pollens
- most widely used method based on variations in oxygen isotope composition of biogenic marine carbonate, from which the broad pattern of change in marine temps has been reconstructed
evidence of env changes
-
plate tectonics
-> similar fossils found around shores of continents suggest they were once joined - palaeoclimatology
