The organic geochemistry of glycerol dialkyl glycerol tetraether lipids: A review

Glycerol dialkyl glycerol tetraether (GDGT) lipids are membrane lipids which were long thought to be synthesized mainly by archaea, organisms thought to be limited to extreme environments. Analysis of environmental samples over the last decade has shown, however, that their structural diversity and sources are much wider than anticipated and that they occur ubiquitously in a wide range of environments, such as oceans and lakes, and their (sub) surface sediments, as well as soils. Several GDGTs have been unambiguously identified and can be used as biomarker lipids, since they are preserved in immature sediments < 140 Ma. Close examination of the distributions has led to the discovery that GDGTs might be used as proxies for certain environmental parameters, such as the input of soil organic matter to marine environments, soil pH, air temperature and sea and lake water temperature. Here, we review the progress made over the last decade in the analysis, occurrence and recognition of sources of GDGTs, their applications as biomarker lipids, and the development and application of proxies based on their distributions. (C) 2012 Elsevier Ltd. All rights reserved.