1 As we get into the spring and early summer, we see increased 



2 levels of pristane in the sediments, but for the most part these are 



3 short-lived concentrations. When we go through a whole seasonal cycle, 



4 we basically see concentrations of pristane back to original winter 



5 levels. 



6 Presumably this is not a degradation phenomenon, I don't think it 



7 is. I think this is just basically a depositional and erosional 



8 phenomenon, and we're seeing a cycle here of the deposition of pristane. 



9 Again, this is linked to the dynamics of the study area, but there 



10 is some seasonality in the biogenic imprint on the sediments. There is 



11 also some seasonality in the distribution of tarball materials. 



12 This will be the only gas chromatogram I show, and I need it 



13 support the next slide. The overall distributions of hydrocarbons, 



14 there are several components. If you look at these peaks above this 



15 baseline, we are looking at hydrocarbons which are sourced in 



16 terrigenous plant materials, plant waxes. 



17 These are primarily the odd-chain carbons and alkanes, normal 



18 alkanes. Underneath this distribution is something called the UCM, the 



19 unresolved complex mixture. This is a distribution associated generally 



20 with fossil fuel material, degraded petroleum. 



21 A composite source, composite material would have plant material 



22 and some UCM. There are some chromatograms and some samples from the 



23 bank which basically just contain the biogenic plant waxes, not much of 



24 the degraded petroleum material. 



25 There is a distribution which looks very much like tarballs. In 



26 this chromatogram we don't have the odd carbon preference, we have 



27 basically a smooth distribution of hydrocarbons with some UCM. 



28 This is very characteristic of petroleum or a tarball material. 



29 If you look at these three groups, group A, groups B and C, I'll try to 



30 explain the next slide. 



31 One of the conclusions that we found in studies of the 



32 hydrocarbons on the bank are that a lot of the hydrocarbon distributions 



33 are composites of several different source materials. 



79 



