Figure 2. Raman spectra from a fossil feather preserved in amber and from a carbonised compression fossil.

Amber matrix, epoxy resin and fossil feather each had a distinct spectral signature. Near-identical spectra were collected from the fossil feathers and from the Green River Formation sediment. Yellow bars indicate locations where peaks are expected in spectra from carotenoids (see Fig. 1), showing that evidence for carotenoid pigmentation was not recovered from AMNH DR-14-32 (feather in amber) or USNM 584927 (compression fossil). Spectra have been baseline-corrected and smoothed. Spectral intensities have been normalized against the minimum and maximum values. Epoxy was only around the outside of the amber matrix, as oriented in the image, and not above and below the amber.