46 
Fig. 39: Gas-chromatograms of 4 Nigerian crude oils (same as in Figure 36), showing 
relatively high concentrations of pristane (peak at 5.1 minutes). 
As with Oleanane, Gammacerane, contains a hexacyclic E-ring and can be observed in the 
191-mass-chromatogram, following the same fragmentation pattern as the hopanes. This 
compound indicates mainly marine sources of crude oils. It is found in higher concentrations 
(up to about 50% in relation to hopane) in the African Angola Cabinda - and Nemba crudes, 
and in Kongo - and Gabon crude oils (Figure 40). 
40 42 44 46 48 min 50 40 42 44 46 48 rrin 50 
Fig. 40: Hopanes of Angola Cabinda - and Nemba crude (above), Kongo Djeno - and Gabon 
Mandji crude (below). Gammacerane: peak at 48.4 minutes.