Micro-FTIR Spectroscopic Imaging of ~1,900 Ma Stromatolitic Chert

Abstract

Micro-Fourier transform infrared (FTIR) spectroscopic imaging analyses nondestructively revealed micrometer to millimeter-scale distributions of organic and inorganic functional groups in Proterozoic stromatolitic chert containing prokaryotic fossils from similar to 1,900 Ma Gunflint Formation. CH3-/CH-(2) absorbance ratios (R-3/2) indicate a bacterial origin, but not Archaea, of most carbonaceous matter in the chert as well as in the microfossils themselves. However, the characterizations or the stromatolitic chert also show that R-3/2 value of carbonaceous matter existing with carbonates could be overestimated or underestimated. This technique is useful for searching and characterizing rapidly the organic matter in terrestrial and extraterrestrial samples at the micrometer to millimeter scale, and may provide useful information on the affinities of microfossils in the chert.