Posted: Feb 07, 2017 1:54 pm
Indeed, I've used the differential 13C carbon content of organisms in the past, to allow us to determine whether or not they had a trophic link to C3 or C4 plants, courtesy of the fact that the difference is amplified in consumers of those plants, and amplified further in predators on those consumers. So, differential 13C content is also useful in determining the likely diet of various fossil organisms.
But as you've noted above, differential 13C content is also useful in other areas. One area in which I've seen it applied, is the "Snowball Earth" hypothesis for the Neoproterozoic. During periods of hyperglaciation in the Neoproterozoic, photosynthesis was effectively shut down, and enrichment of the atmosphere with 13C came to a halt, which correlates with the isotopic signature of carbonate sediments deposited during the requisite hyperglaciation eras. Once volcanoes increased the atmospheric CO2 content to the point where heat retention melted the ice, photosynthesis restarted among surviving micro-organisms, and 13C enrichment of the atmosphere restarted, resulting in changes of isotopic signature in carbonate sediments deposited during the thermal retention eras.
There's a nice Scientific American article on the Neoproterozoic, which you can download for free here.
Oh, and as for creationist notions that everything from the Cambrian to the Quaternary was deposited by their fantasy "global flood", can they explain why there are no Precambrian mammals? Only according to their ridiculous assertions, any stratum earlier than the Cambrian pre-dated their fantasy "global flood", and according to their ridiculous mythology, there were humans and other mammals alive at that time. Except that oops, there weren't. For most of the Precambrian, fossils consist of micro-organisms, with the first multicellular eukaryotes appearing around 1200 MYa, and the most sophisticated organisms prior to the Cambrian being the Ediacaran Halucigenia and allies. Nothing even remotely resembling a mammal appears in those strata.
But as you've noted above, differential 13C content is also useful in other areas. One area in which I've seen it applied, is the "Snowball Earth" hypothesis for the Neoproterozoic. During periods of hyperglaciation in the Neoproterozoic, photosynthesis was effectively shut down, and enrichment of the atmosphere with 13C came to a halt, which correlates with the isotopic signature of carbonate sediments deposited during the requisite hyperglaciation eras. Once volcanoes increased the atmospheric CO2 content to the point where heat retention melted the ice, photosynthesis restarted among surviving micro-organisms, and 13C enrichment of the atmosphere restarted, resulting in changes of isotopic signature in carbonate sediments deposited during the thermal retention eras.
There's a nice Scientific American article on the Neoproterozoic, which you can download for free here.
Oh, and as for creationist notions that everything from the Cambrian to the Quaternary was deposited by their fantasy "global flood", can they explain why there are no Precambrian mammals? Only according to their ridiculous assertions, any stratum earlier than the Cambrian pre-dated their fantasy "global flood", and according to their ridiculous mythology, there were humans and other mammals alive at that time. Except that oops, there weren't. For most of the Precambrian, fossils consist of micro-organisms, with the first multicellular eukaryotes appearing around 1200 MYa, and the most sophisticated organisms prior to the Cambrian being the Ediacaran Halucigenia and allies. Nothing even remotely resembling a mammal appears in those strata.