text: Stable carbon isotope composition is another widely used proxy for interpreting paleoenvironment conditions. The Surface temperature fluctuation from the Paleocene to Miocene has been established based on carbon isotope data from foraminifera in Antarctic region. The organic matter preserved in sediments records paleoecosystems, and its carbon isotope composition has been also utilized to reconstruct paleoclimatic evolution. For example, Rogers and Koons (1969) have reported that the carbon isotope ratios, derived from organic matter in Quaternary marine sediments in the Gulf of Mexico, correlate well with Pleistocene climate changes.
  Chen et al. (2011) have documented ancient climate fluctuations since the last glacial maximum based on soil samples in Tibet. Other sources for organic carbon isotope used as proxies for paleoenvironment reconstruction include lacustrine deposits for lake level variations, fossilized vertebrates for precipitation fluctuations, oil shales for paleoecological and paleoclimate conditions.