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SUMMARY:Searching for the earliest signs of cellular life on Earth - Marti
 n Brasier\, Department of Earth Sciences\, University of Oxford
DTSTART:20130312T163000Z
DTEND:20130312T173000Z
UID:TALK39492@talks.cam.ac.uk
CONTACT:Dr. Alex Liu
DESCRIPTION:The rover Curiosity is currently exploring for signs of life i
 n ancient lakes and stream beds on Mars.  Back here on Earth\, molecular e
 vidence is being taken to suggest that major innovations in the biosphere\
 , notably the origins of life\, of cyanobacteria\, and green algae\, could
  each have taken place within ‘terrestrial’ settings (e.g.\, springs\,
  lakes\, rivers\, soils). Rather less plausibly\, Ediacara–type biotas h
 ave recently been heralded as terrestrial lichens. So what is the potentia
 l for developing a respectable fossil record from non-marine rocks of Prot
 erozoic to Archaean age?\n\nCritical investigation into the early terrestr
 ial fossil record is long overdue\, not least because such deposits are hi
 ghly sensitive environmental indicators that may hold clues to the early p
 hosphorus\, carbon and oxygen cycles. Precambrian habitats of this kind se
 em also to have been highly conducive to early diagenesis of the sediment 
 surface. Hence early river\, lake and shoreline deposits could contain a w
 ealth of information about the evolution of early cellular life. But decod
 ing this record requires careful and critical contextual analysis using hi
 gh resolution techniques\, of the kind now becoming available.\n\nThis tal
 k will review collaborative research at Oxford into remarkable cellular pr
 eservation within very early terrestrial and shoreline settings\, using te
 chniques including FIB TEM and nanoSIMS (UWA\, Bergen and Boston with D. W
 acey\, M. Kilburn\, N. McLoughlin\, P. Strother)\, and synchrotron (DLS Ha
 rwell with R. Garwood\, and PSI\, Villingen with B. Schirmeister and P. Do
 noghue). These techniques are being used by us to explore 3D morpho- and b
 iogeochemical mapping of early assemblages found within 1000 Ma ‘open’
 \, phosphogenic  lake ecosystems\, as well as 1200 Ma ‘closed’\, sulfi
 dic lake ecosystems of Scotland (e.g.\, Strother et al. 2011)\; 1900 Ma mi
 crobes from shoreline conglomerates of the Gunflint chert in Canada (e.g.\
 , Wacey et al. 2012)\; c.2900 Ma fluvial conglomerates of Witwatersrand in
  South Africa (with Lawrence Robb)\; the earliest (~3460-3430 Ma) preserve
 d land and beach deposits (Strelley Pool chert\, Wacey et al. 2011)\; and 
 the controversial but fascinating Apex chert (e.g.\, Brasier 2002\, 2012).
 \n	\n\nBrasier\, M.D.\, Green\, O.R.\, Jephcoat\, A.P.\, Kleppe\, A.K.\, V
 an Kranendonk\, M.J.\,  Lindsay\, J.F.\, Steele\, A. & Grassineau\, N.V. 2
 002. Questioning the evidence  for Earth's oldest fossils. Nature 416\, 76
 -81\n\nBrasier\, M.D.\, Green\, O.R.\, Lindsay\, J.F.\,  McLoughlin\, N.\,
  Stoakes\, C.A.\, Brasier\,  A.T. and Wacey\, D. (2012). Geology and putat
 ive microfossil assemblage of  the c. 3460 Ma ‘Apex chert’¸ Chinaman 
 Creek\, Western Australia – A Field  and Petrographic Guide. Geological 
 Survey of Western Australia\, 60pp.\n\nStrother\, P.K.\, Battison\, L.\, B
 rasier\, M.D. and Wellman\, C.H. (2011). Earth’s earliest 	non-marine eu
 karyotes. Nature\, 473\, 505–509.\n\nWacey\, D.\, Kilburn\, M.\, Saunder
 s\, M.\, Cliff\, J. and Brasier\, M.D. (2011). 	Microfossils of sulphur-me
 tabolizing cells in 3.4-billion-year-old rocks of Western Australia. Natur
 e Geoscience \, 4\, 698-702.\n\nWacey\, D.\, Menon\, S.\, Green\, L.\, Ger
 stmann\, D.\, Kong\, C.\, McLoughlin\, N.\, Sanders\, M. and Brasier\, M.D
 . (2012). Taphonomy of very ancient microfossils from the ∼3400 Ma Strel
 ley Pool Formation and ∼1900 Ma Gunflint Formation: New insights using a
  focused ion beam. Precambrian Research\, 220/221\, 234-250.\n
LOCATION:Harker 1 seminar room\, Department of Earth Sciences
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