title: Branched aliphatic alkanes with quaternary substituted carbon atoms in modern and ancient geologic samples.
abstract: A pseudohomologous series of branched aliphatic alkanes with a quaternary substituted carbon atom (BAQCs, specifically 2,2-dimethylalkanes and 3,3- and 5,5-diethylalkanes) were identified in warm (65 degrees C) deep-sea hydrothermal waters and Late Cretaceous black shales. 5,5-Diethylalkanes were also observed in modern and Holocene marine shelf sediments and in shales spanning the last 800 million years of the geological record. The carbon number distribution of BAQCs indicates a biological origin. These compounds were observed but not identified in previous studies of 2.0 billion- to 2.2 billion-year-old metasediments and were commonly misidentified in other sediment samples, indicating that BAQCs are widespread in the geological record. The source organisms of BAQCs are unknown, but their paleobiogeographic distribution suggests that they have an affinity for sulfides and might be nonphotosynthetic sulfide oxidizers.
authors.affiliation: Departments of Earth and Environmental Sciences and Chemistry, University of Illinois, Chicago, IL 60607, USA. fkenig@uic.edu
authors.forename: Fabien
authors.initials: F
authors.lastname: Kenig
authors.forename: Dirk-Jan H
authors.initials: DJ
authors.lastname: Simons
authors.forename: David
authors.initials: D
authors.lastname: Crich
authors.forename: James P
authors.initials: JP
authors.lastname: Cowen
authors.forename: Gregory T
authors.initials: GT
authors.lastname: Ventura
authors.forename: Tatiana
authors.initials: T
authors.lastname: Rehbein-Khalily
authors.forename: Todd C
authors.initials: TC
authors.lastname: Brown
authors.forename: Ken B
authors.initials: KB
authors.lastname: Anderson
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D002852:Chromatography, Ion Exchange / Q000379:methods; D008401:Gas Chromatography-Mass Spectrometry; D019015:Geologic Sediments / Q000032:analysis*; D055593:Geological Phenomena; D005844:Geology; D012623:Seawater / Q000032:analysis; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods
chemical_list: D000473:Alkanes; C033245:pentadecane