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level: RADIOCARBON

Questions and Answers List

level questions: RADIOCARBON

Question	Answer
radiocarbon is produced from	cosmic rays
Radiocarbon decays over time (14C) half life of	5730 years
14C of atmospheric CO2 has varied over time (cosmic rays). This why we need to..	Need to calibrate 14C measured against age
The bomb spike (spike in 14C) is usefull	because the spike is represented in all material of that age and acts as a great tracer
Suess effect ?	depletion in d14C due to input of large amounts of fossil fuel derived CO2 (contains not 14C) (occurred before bomb spike due to burning of fossil fuels, 1950s)
The deeper ocean carbon is not conneted to atmosphere and is hence	14C depleted
Difference in radiocarbon of atmosphere and ocean --> Marine reservoir effect: between 400-800 yrs – have to compensate for this, were probably different in the past. What is the marine reservoir effect?	carbon taken up by a marine organism is older than a terrestrial organism as deeper waters are not in contact with the atmosphere
Amount of radiocarbon in deep ocean (old) is much ....than in the surface ocean	lower
Compare radiocarbon of biomarker lipids from surface sediments with surface waters...	if they have same composition, they are from surface waters, if lipids are more depleted they originate from bottom waters and made them there
Age difference between biomarker lipid (organic) and foram proxies (inorganic) due to ??	lateral transport -> causes age offsets
biomarker lipids have different offsets due to ...	degradation & transport
we like to avoid sight where ... is a big factor	lateral transport
Age of terrestrial lipids exported by rivers to the marine environment reveals the turnover and export of the soil organic carbon pool because	they are much younger and have higher d14C (fatty acids even more so that lignin phenols)
Compound specific radiocarbon is laborious and not sensitive. Need large amounts of material and long work up procedure.	Need atleast 50ug, but improvement is being made
Compound specific radiocarbon can be used to elucidate the age of a biomarker and particularly its origine e.g. ..... ?	local vs laterally transported? depth in watercolumn (Was it in contact with atmosphere? Surface ocean? Deep ocean?)? Influx from land?