Polar lipids of archaebacteria in sediments and petroleums.

Glycerol tetraethers with head-to-head isoprenoid 40-carbon chains that are typical of archaebacteria, in particular of methanogens, were identified in the polar lipids of sediments and petroleums. These structures are at least partially preserved in the subsurface beyond the stage of petroleum formation. Their identification provides further evidence that a significant part of geological organic matter derives from the lipids of membranes of microorganisms.