Diatomaceous oozes

The dominant clay mineral at high latitudes is chlorite. In addition to ice rafting, lithogenous materials are transported in the polar oceans by rivers and winds. Polar seas are also characterized by diatomaceous oozes due to the occurrence of upwelling supported by divergence at 60°N and 60°S. 

The neritic sediments surroimding the continent of Antarctica are dominated by glacial marine deposits. Divergence at 60°S causes oceanic upwelling, which transports cold, nutrient-rich waters to the euphotic zone. Since diatoms are the dominant phytoplankton, diatomaceous oozes encircle Antarctica between the latitudes 50° and 70°S. 

In the deep-water Black Sea basins, the sediments of the Middle Pleistocene are represented by clayey diatomaceous oozes and silts with three diatom assemblages the upper and lower assemblages are marine and brackish-water, while the middle assemblage contains numerous freshwater cryophilic species [7]. 

With respect to their composition, the deep-water Karangatian deposits are represented by clayey diatomaceous oozes with a rich assemblage of thermophilic marine diatoms dominated by the characteristic tropical species Thalassiosira oestrupii [1]. 

Reconstituted ion chromatogram (RIC) from gc-ms analysis of the ketones and carboxylic acids (as methyl esters) of a Pliocene diatomaceous ooze from Walvis Ridge (DSDP 75-532-21-2). Peak assignments numbered peaks are n-alkanoic acids solid pea k s lab e 11 e d 6,... 

Midchain ketones and sterol ethers. Figure 3 shows the upper part of a Total Ion Current (TIC) trace obtained from a TLC fraction of an extract of the Namibian Shelf diatomaceous ooze. Long midchain ketones and sterolethers together with a series of wax esters were shown to be present in this fraction (9 ). The sterolethers are composed of common A -sterol moieties and Cg and Cg alkyImoieties(I). 

Figure 3. Upper part of total ion current trace of a TLC fraction of Namibian Shelf diatomaceous ooze sediment extract.

Loliolides and dihydroactinidiolide. Although loliolides as such occur in living systems the recently discovered sedimentary loliolides (XV, XVI, XVII) isolated from Namibian Shelf diatomaceous ooze are thought to be compounds which have been generated by very early stage diagenetical pathways from carotenoids in the oxic zone of the water column (32). 

The electronic spectra of the native pigment (5=393,l=640nm), isolated from a Miocene shale of the Sisquoc formation (California. 24), and numerous diatomaceous oozes from the Gulf of Cali-fornia T20). and its copper chelate (5=395, I=606nm) match authentic DOMPP-a and CuDOMPP-a, respectively. 

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