Table 1 Spectral features identified on the studied micro and macrofossils and their importance.
I | II | III | IV | V | VI |
|---|---|---|---|---|---|
450 nm | 900–1200 nm | 1400 nm | 1900 nm | 2100–2200 nm | 2330–2350 nm |
This spectral feature is indicative of the presence of Fe impurities/coating due to the electronic transition. This spectral feature is resulted due to charge transfer process of elements which enter into the fossil shells. So, it is an indicator of primary shell characteristics | This feature is used to distinguish different Fe oxides and hydroxides. The wavelength of the features vary from 900 nm (hematite), 1000 nm (goethite), 1010 nm (limonite) and 1200 nm (siderite). The depth and width of the feature is also important criteria along with the mineral to distinguish different minerals. It is deeper and narrower for hematite and wider for mineral like siderite. The wavelength of absorption minima of the feature shifts from lower to higher wavelength from hematite to goethite. This spectral feature is related to post depositional set-up | The feature is resulted due to the stretching vibration of OH bond. It is a signature of primary shell feature | The feature indicates free H2O molecule. The presence of this feature and the depth and width of the feature may indicate the degree of diagenesis happened in the shell (i.e. with better compaction and intense recrystallization, the depth of the feature is reduced)31,32. It is a signature of primary shell feature | This feature is indicative of metal-OH vibrational overtone. Presences of clay minerals on the outer shell surface are responsible for these absorption features | This feature is resulted due to vibration of carbonate bond. One of the prominent vibrational features of calcite. It is an indicator of primary shell characteristics |
