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Xeropreservation of Functionalized Lipid Biomarkers in Hyperarid Soils in the Atacama Desert

Authors :
Mary Beth Wilhelm
Alfonso F Davila
Jennifer L Eigenbrode
Mary N Parenteau
Linda L Jahnke
Xiao-Lei Liu
Roger E Summons
James J Wray
Brian N Stamos
Shane S O'Reilly
Amy Williams
Source :
Organic Geochemistry. 103
Publication Year :
2016
Publisher :
United States: NASA Center for Aerospace Information (CASI), 2016.

Abstract

Our understanding of long-term organic matter preservation comes mostly from studies in aquatic systems. In contrast, taphonomic processes in extremely dry environments are relatively understudied and are poorly understood. We investigated the accumulation and preservation of lipid biomarkers in hyperarid soils in the Yungay region of the Atacama Desert. Lipids from seven soil horizons in a 2.5 meter vertical profile were extracted and analyzed using GC-MS ( Gas Chromatography-Mass Spectrometry) and LC-MS (Liquid Chromatography-Mass Spectrometry). Diagnostic functionalized lipids and geolipids were detected and increased in abundance and diversity with depth. Deeper clay units contain fossil organic matter (radiocarbon dead) that has been protected from rainwater since the onset of hyperaridity. We show that these clay units contain lipids in an excellent state of structural preservation with functional groups and unsaturated bonds in carbon chains. This indicates that minimal degradation of lipids has occurred in these soils since the time of their deposition between more than 40,000 and up to 2 million years ago. The exceptional structural preservation of biomarkers is likely due to the long-term hyperaridity that has minimized microbial and enzymatic activity, a taphonomic process we term xeropreservation (i.e. preservation by drying). The degree of biomarker preservation allowed us to reconstruct major changes in ecology in the Yungay region that reflect a shift in hydrological regime from wet to dry since the early Quaternary. Our results suggest that hyperarid environments, which comprise 7.5 percent of the continental landmass, could represent a rich and relatively unexplored source of paleobiological information on Earth.

Details

Language :
English
ISSN :
01466380
Volume :
103
Database :
NASA Technical Reports
Journal :
Organic Geochemistry
Notes :
NNX15AM17G, , NNA13AA90A, , NNX15BB01A
Publication Type :
Report
Accession number :
edsnas.20180001603
Document Type :
Report
Full Text :
https://doi.org/10.1016/j.orggeochem.2016.10.015