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THE UTILITY OF LIPID BIOMARKERS AS PALEOENVIRONMENTAL INDICATORS

¹ Woods Hole Oceanographic Institute, Department of Marine Chemistry and Geochemistry, Woods Hole, Massachusetts 02543, USA aolcott@whoi.edu

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The goal of many geologists is to determine and understand the environmental conditions under which sediments were deposited. Paleontologists can use the known physiological, biological, and environmental limitations of flora and fauna found within a sedimentary unit to help elucidate the paleoenvironment in which those organisms once lived. As powerful as this tool is, however, there are limitations. In the Archean and Proterozoic, most organisms were microscopic, unmineralized, and morphologically simple prior to the radiation of metazoans. This means that, unlike the Phanerozoic, the preservation of fossils is relatively rare in the Precambrian, and hence, determining their biological affinity is often difficult. Additionally, many macroscopic organisms can live over a broad range of temperatures, so it can be difficult to pinpoint relatively small changes in climate using traditional paleontology. Finally, macroscopic organisms do not usually live in extreme environments, but waters too anoxic, sulfidic, acidic, basic, or saline for them can still support microorganisms. In fact, almost every type of environment on Earth, no matter how extreme, hosts microbial communities. Exploring these sorts of extreme environments can be of special interest, as environmental change is often cited as the impetus behind faunal turnover or mass extinctions (e.g., Hallam, 1987, 1989; Burger and Lynch, 1995; Jablonski and Sepkoski, 1996; Patzkowsky et al., 1997; Droser et al., 2000; Wignall, 2001; Brenchley et al., 2003).

The identification of lipid biomarkers can be a powerful technique to augment traditional paleontology. This branch of organic geochemistry involves the isolation and identification of geolipids, the preserved remnant of molecules originally synthesized by organisms. All living organisms produce lipids, primarily as components of their cellular membranes. These hydrophobic compounds are . . . [Full Text of this Article]