Foraminiferal Colouration Index

The Foraminiferal Colouration Index [1][2] (FCI) is a tool for assessing the thermal alteration of organic matter buried in sedimentary rock.

It uses temperature-controlled colour changes in the organic cement of agglutinated foraminifera (microfossils) to estimate thermal alteration.

The FCI values 0 to 10 are indicated below: Agglutinated foraminifera have a long geological history spanning the Paleozoic, Mesozoic, and Cenozoic.

[1] The FCI is therefore an indicator of temperatures required to initiate petroleum generation (oil window).

Raman spectroscopy (an analytical tool for fingerprinting molecules) has confirmed that organic cement is present in fossil agglutinated foraminifera.

Foraminiferal Colouration Index (FCI) - Example of thermal alteration colours (FCI 2 - 6) in agglutinated foraminifera from an oil well.