Ehleringer JR, Buchmann N, Flanagan LB (2000) Carbon isotope ratios
in belowground carbon cycle processes.
Dunton, Schell and co-workers from Alaska, Texas and the Soviet Academy of Sciences in Leningrad have now extended the known zooplankton gradient--the range over which its carbon isotope ratio
changes--from the eastern Beaufor t Sea down to the Bering Sea and eastward into the Soviet East Siberian Sea.
Two years ago, after discovering widely fluctuating carbon isotope ratios
in rocks from that so-called Neoproterozoic era, Paul F.
To determine if these inclusions were actually biological in origin, the researchers looked at 15 different samples of Farrel Quartzite and determined their stable carbon isotope ratios
These processes could well produce a small rise in plant carbon isotope ratios
, which might be traceable in animal and human consumers (Heaton 1999; Hamilton et al.
Furthermore, less material is needed to do a cholesterol analysis; only about 50 billionths of a gram gives reliable carbon isotope ratios
Stable carbon isotope ratios
as indicators of prehistoric human diet.
All in all, carbon isotope ratios
suggest the environment back then was mostly grassy savanna.
Carbon isotope ratios
in almost all drill cores from the area reveal that calcite deposits above the present water table are depleted in the carbon-13 isotope -- an indication that the water table has not changed much since the deposits formed.
Research also compared the carbon isotope ratios
of Paranthropus teeth with the teeth of other grazing mammals living at the same time and in the same area, like ancestral zebras, hippos, warthogs and pigs.
Fogel & Tuross (2003) compared carbon isotope ratios
of individual amino acids from the collagen of prehistoric human hunter-gatherers and maize agriculturalists with those obtained from herbivore bone collagen and modern plants.
Ambrose analyzed stable carbon isotope ratios
in the soil in which the bones of 36 Ardipithecus individuals were found.