20 radiometric dating

Question 1

The rate of decay of a parent nuclide into its daughter nuclide has a non-linear relationship with the number of parent nuclide present at all times. T or F

Answer 1

False. the rate of decat of a parent nuclide into its daughter nuclide is always proportional to the number of parent nuclides present at all times

Question 2

Describe in your own words Isochrone dating

Answer 2

1) several samples are collected from the same geographical site
2) separation and isotopic analysis of Sr delivers (Sr 87 / Sr 86 )t
3) Sr and Rb concentrations are determined by IDMS to calculate (87Rb / 86 Sr) t abundances
4) ratios are plotted against each other
5) slope of the regression line gives the age of the rock

Question 3

what is not affected by heat gravity, magnetic field, chem reactions?

Answer 3

Half-life / decay of a nucleus (an answer from tutorial)

Question 4

Describe radiocarbon dating.

Answer 4

neutrons from cosmic rays react with nitrogen in the atmosphere
carbon is quickly oxidised to CO2
CO2 is assimilated by plants through photosynthesis and enters the food chain
ratio of 14C to natural C is a constant in the losing organism because you can lose it when breathing out and gain it from breathing it
14C starts to decay when an organism dies

Question 5

What is used to do radiocarbon dating? Provide the full acronym

Answer 5

Accelerator Mass spec

Question 6

How does Accelerator Mass spec work?

Answer 6

See NB

Question 7

What is in the y-axis, y-intercept, slope and x-axis of the isochrone graph?

Answer 7

y-axis = (87Sr/86Sr)t 
x-axis = (87Rb/86Sr)t
y-intercept = (87Sr/86Sr)0
slope = radiometric age = closure age (time pt at which the mineral solidified

Question 8

Describe the implications of atmospheric 14C / 12C variation.

Answer 8

Variations due to:
natural isotope fractionation
solar flare activity affects cosmic neutron influx
need to correct these using tree dating where u can calibrate 14C / 12C against the tree rings.
problematic because of fluctuation

Question 9

Describe bomb peak dating.

Answer 9

Nuclear tests were done after 1950s. If there was a lot of 14C / 12C found in the painting, it means that it must have been made after 1950s which means that its a fake artefact.