Paleobiogeochemistry

Description

The Palaeobiogeochemistry Group at RSES investigates the co-evolution of life and environments on early Earth. Using the most advanced analytical tools, our laboratory specializes in the detection of traces of molecular fossils (biomarkers) in sedimentary rocks up to two billion years old. The lab currently holds the record for the oldest known abiogenic as well as genuine biogenic molecules. We combine biological information from the structure and isotopic composition of molecular fossils with data from sedimentology, microfossils and inorganic geochemical proxies to reconstruct ancient microbial ecosystems and to elucidate Precambrian environmental cataclysms. Some themes are:

Early life on Earth

  • What is the tempo and mode of evolution of complex life on Earth? When did modern, crown group eukaryotes first appear, what was the impact of the evolution of predatory single celled eukaryotes and what triggered the emergence of active and motile animal life?
  • How did life thrive and evolve in the enigmatic ferrous oceans that dominated Earth’s middle age between 1.8 and 0.8 billion years ago?
  • Where microorganisms involved in the formation of the giant sedimentary zinc and lead sulfide deposits in northern Australia more than 1.6 billion years ago?  
  • What are the causes and biological consequences of the massive carbon isotopic excursions in the Neoproterozoic?
  • How did live survive during the Sturtian and Marinoan Snowball Earth / Jormungand glaciations, and what were the biological consequences of these massive ice ages? 
  • How did the emergence of filter feeding, borrowing and predatory animals impact Neoproterozoic ecosystems and geochemical cycles?

Life in extreme environments

  • Lipid chemistry, metagenomics and proteomics of modern hypersaline Lake Tyrrell, and comparison with 800 million years old hypersaline ecosystems from the Centralian Superbasin.

Biomarkers and Archaeology

  • Using biomarkers, we also study the former content of ancient clay pots and reconstruct the impact of first human settlement on the ecology of remote Pacific islands.

Publications

(1) Pawlowska, M. M., Butterfield N. J. and Brocks J. J. (2013) Lipid taphonomy in the Proterozoic and the effect of microbial mats on biomarker preservation. Geology, 41:103–106.
Based on new technology, we present a revision of the Precambrian biomarker record, revealing unusual patterns and offering a controversial hypothesis about their origins (Brocks corresponding author).

 (2) Narasingarao P., Podell S., Ugalde J. A., Brochier-Armanet C., Emerson J. B., Brocks, J. J., Heidelberg, K. B., Banfield, J. B. and Allen, E. E. (2012) De novo metagenomic assembly reveals abundant novel major lineage of Archaea in hypersaline microbial communities, The ISME Journal [Nature family journal] 6, 81-93.   
We report the discovery of an entire new class of organisms, the ‘Nanohaloarchaea’. Brocks is the Australian CI of this international project investigating the microbiology of saline Lake Tyrrell in Victoria.

(3)  Brocks J. J., and Banfield J. (2009) Unravelling ancient microbial history using community proteogenomics and lipid geochemistry. Nature Reviews Microbiology, 7, 601-609.  
In this invited Opinon article published in a Nature family journal, we describe our vision about the future of biomarker geochemistry in light of the environmental genomic and proteomic revolution.

(4)  Rasmussen B., Fletcher I. R., Brocks J. J., and Kilburn M. R. (2008) Reassessing the first appearance of eukaryotes and cyanobacteria. Nature, 455, 1101 - 1104.
We pioneer the measurement of organic carbon isotopes at the micron scale and open the possibility that biological oxygen production may have evolved as late as 2.5 billion years ago.

 (5)  Brocks J. J., Love G. D., Summons R. E., Knoll A. H., Logan G. A., and Bowden S. A. (2005) Biomarker evidence for green and purple sulfur bacteria in an intensely stratified Paleoproterozoic sea. Nature, 437, 866-870.   
At 1.6 billion years, we describe the oldest clearly indigenous biomarkers. They describe an unusual, entirely microbial ecosystem dominated by green and purple sulfur bacteria, leading to the ‘Purple Ocean’ hypothesis.

(6) Brocks J. J. and Summons R. E. (2004) Sedimentary hydrocarbons, biomarkers for early life. In Treatise on Geochemistry, Vol. 8 - Biogeochemistry (ed. H. D. Holland and K. K. Turekian), pp. 63-115. Elsevier.                 
The Treatise on Geochemistry in 10 volumes is regarded as the most important reference work in geochemistry. All contributions are by leaders in the field and were by invitation only.

 (7)  Pearson A., Budin M., and Brocks J. J. (2003) Phylogenetic and biochemical evidence for sterol synthesis in the bacterium Gemmata obscuriglobusProceedings of the National Academy of Sciences,100, 15352–15357.
Using a pioneering, combined biomarker-genomic approach, we demonstrate that sterol biosynthesis was laterally transferred between bacteria and eukaryotes early in Earth history, a discovery of deciding significance for molecular and evolutionary biology.

(8) Brocks J. J., Buick R., Summons R. E., and Logan G. A. (2003) A reconstruction of Archean biological diversity based on molecular fossils from the 2.78 - 2.45 billion year old Mount Bruce Supergroup, Hamersley Basin, Western Australia. Geochimica et Cosmochimica Acta,67, 4321-4335.
Most downloaded research article in Geochimica et Cosmochimica Acta (GCA) in the year 2004 in discipline organic geochemistry. GCA is the highest ranking geochemical journal.

(9)  Brocks J. J., Buick R., Logan G. A., and Summons R. E. (2003) Composition and syngeneity of molecular fossils from the 2.78 - 2.45 billion year old Mount Bruce Supergroup, Pilbara Craton, Western Australia.Geochimica et Cosmochimica Acta, 67, 4289-4319.
Second most downloaded research article in GCA in the year 2004 in discipline organic geochemistry. Possibly the most detailed investigation of a Precambrian (> 542 Myrs) hydrocarbon assemblage.

 (10) Brocks J. J., Logan G. A., Buick R., and Summons R. E. (1999) Archean molecular fossils and the early rise of eukaryotes. Science, 285, 1033-1036.

Seminal work that initiated the renewed search for the oldest molecular fossils of early life. Selected byScience as a top-ten ‘Scientific breakthrough of the year’ (Science, 286, p. 2239).

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