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SUMMARY:Microfossil and model constraints on the global climate during the
  Cambrian ‘explosion’ - Tom Hearing - University of Leicester
DTSTART:20181126T173000Z
DTEND:20181126T183000Z
UID:TALK109891@talks.cam.ac.uk
CONTACT:Ben Johnson
DESCRIPTION:The Neoproterozoic/Phanerozoic transition was characterised by
  one of the most fundamental phases in the evolution of life on Earth: the
  radiation and diversification of metazoans. The increasing abundance\, mo
 bility and mineralisation of early animals had profound consequences for E
 arth’s physical environment and geochemical cycles.\n\nHowever\, our und
 erstanding of the co-evolution of the physical environment and the biosphe
 re throughout the Ediacaran/Cambrian radiation of animals is hampered by s
 ubstantial uncertainties in global palaeogeography and palaeoclimate. Eart
 h surface temperatures during this interval are particularly poorly constr
 ained.\n\nThe stable oxygen isotope ratios (δ 18 O) is perhaps the most w
 idely used proxy for quantitatively constraining Phanerozoic ocean tempera
 tures. In particular\, the δ 18 O data held in the biomineralised parts o
 f foraminifera\, molluscs\, brachiopods and conodonts are routinely used t
 o investigate palaeoenvironmental questions. Indeed\, there is a near-cont
 inuous δ 18 O record back to the Early Ordovician. \n\nThe notable dearth
  of δ 18 O data in the Cambrian Period coincides with the global establis
 hment of animal-rich ecosystems\, and in part arises from a lack of tradit
 ionally targeted fossils in this interval.\n\nPhosphatic ‘small shelly f
 ossils’ (SSFs) provide a novel alternative source of biomineral δ 18 O 
 data\, but need to be carefully screened to exclude diagenetically altered
  specimens. Oxygen isotope data from well-preserved SSFs suggest that the 
 Cambrian was a greenhouse interval in Earth’s climate history. This is c
 onsistent with the available geological (sedimentological) evidence\, incl
 uding palaeogeographically widespread carbonate and evaporite deposits. \n
 \nTaking these δ 18 O data in concert with general circulation climate mo
 dels (GCMs) of the early Cambrian Period\, suggests that the early\nCambri
 an climate was comparable to later\, and better understood\, Phanerozoic g
 reenhouse climate states such as those of the late Mesozoic and early Ceno
 zoic.
LOCATION: Harker 1\, Department of Earth Sciences\, Downing Street
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