I've found the snail study:
Page not found | Physics
And what do you know? Same reason it doesn't work for aquatic organisms - limestone.
Can I point you to the salient sentence?
[url]No webpage found at provided URL: This is that at the time the living organism laid down its carbon into the structure which would later be analyzed, the carbon-14 laid down was an accurate reflection of the amount of carbon-14 in the atmosphere. This assumption holds very well for trees and other land plants. Recently, A. S. Riggs of the United States Geological Survey has reported an instance where the assumption was not true, and where radiocarbon dating gave misleading results.
The significance of Riggs' work is that scientists must take care to be sure that their experiments on carbon dating are done with materials for which the assumption just mentioned is justified. This is that at the time the living organism laid down its carbon into the structure which would later be analyzed, the carbon-14 laid down was an accurate reflection of the amount of carbon-14 in the atmosphere. This assumption holds very well for trees and other land plants. Recently, A. S. Riggs of the United States Geological Survey has reported an instance where the assumption was not true, and where radiocarbon dating gave misleading results.
The significance of Riggs' work is that scientists must take care to be sure that their experiments on carbon dating are done with materials for which the assumption just mentioned is justified. []This is that at the time the living organism laid down its carbon into the structure which would later be analyzed, the carbon-14 laid down was an accurate reflection of the amount of carbon-14 in the atmosphere. This assumption holds very well for trees and other land plants. Recently, A. S. Riggs of the United States Geological Survey has reported an instance where the assumption was not true, and where radiocarbon dating gave misleading results.
The significance of Riggs' work is that scientists must take care to be sure that their experiments on carbon dating are done with materials for which the assumption just mentioned is justified. This is that at the time the living organism laid down its carbon into the structure which would later be analyzed, the carbon-14 laid down was an accurate reflection of the amount of carbon-14 in the atmosphere. This assumption holds very well for trees and other land plants. Recently, A. S. Riggs of the United States Geological Survey has reported an instance where the assumption was not true, and where radiocarbon dating gave misleading results.
The significance of Riggs' work is that scientists must take care to be sure that their experiments on carbon dating are done with materials for which the assumption just mentioned is justified.