palaeoenvironmental reconstruction Flashcards
who published a model in the 1970s?
John Imbrie
what did John Imbrie’s model demonstrate?
- link between isolation changes and global sea ice vol
what did Imbrie’s model suggest?
- chemical composition of G. bullies shells reflects composition of ocean water, effected by waxing and waning of N hemisphere ice sheets
- shells are fossilised down-core
- variation in G.bulloides matches modelled insolation changes
when was the existence of Greenland ice cap confirmed?
end of C19th
properties of Antarctic ice sheet
- ~4.5 km thick
- preserves record of snowfall through quaternary
- formed 35 mil y/a
properties of Greenland ice sheet
- ~3m thick
- formed 18 mil y/a
what is the oldest continental ice core?
Antarctica is 800,000 y/o
age of Greenland ice core
130,000 y/o
what do ice records provide?
- high res. of annual snow bands
- analysis of the ice and the air bubbles trapped inside
- provides records of ppt chemical composition temp
- greenhouse gas conc
- insight into how the earth system operates over time
size of ice cores
10 cm diameter but up to 3km long, can be cored by hand up to 40 cm
what is used to explain the timing of glacial-interglacial cycle?
solar forcing
types of instrumental records
remote sensing
meteorology
how is longer term perspective provided?
by proxy data from a range of palaeoenvironmental archives
what is an isotope?
variation of a given chemical element which differ in their neutron number
what are radioactive isotopes?
they decay over time
stable isotopes
do not decay, present in earth system in different quantities
18O
8 protons, 10 neutrons, heavy O2
what is a depleted O2?
less 18O so lower/ more -ve
what is enriched O2?
more 18O so higher/ more +ve
examples of biological proxies
plants and animals can indicate temp, salinity and moisture
why are biological proxies useful?
limited evolutionary change in quaternary period so taxonomy is strong
what is chironomid analysis?
- diverse group of non-biting midges
- ~1200 palaeoarctic species
- require temp, nutrient, pH and O2 conditions
what is dendroclimatology?
- climate info in tree rings
- absolute dating
- spatially extensive, often fossilised
- stable
what is geochronology?
provides a framework to estimate:
timing
duration
rate
-ves of dating techniques
- only suitable in specific environments
- all have specific time intervals over which they operate
- dependence on geological laws- the law of superstition
- all techniques vary on terms of their accuracy = uncertainty
