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SUMMARY:The end-Permian mass extinction from a high southern palaeolatitud
 e perspective - Prof. Chris Fielding\, University of Nebraska
DTSTART:20191015T110000Z
DTEND:20191015T120000Z
UID:TALK120853@talks.cam.ac.uk
CONTACT:37221
DESCRIPTION:The dominant view of the continental biosphere at the close of
  the Permian asserts high concentrations of atmospheric aerosols and CO2 r
 elated to eruption of magmas from large igneous provinces\, abrupt and sev
 ere warming\, aridity\, extensive loss of vegetation\, and consequent chan
 ges in depositional systems. Most work on the continental record of the en
 d-Permian mass extinction (EPME) has been carried out in low-paleolatitude
  locations\, hence the extent to which earth surface systems at high paleo
 latitudes were impacted remains unresolved. We document a multi-disciplina
 ry dataset focused on the relatively continuous paleo-continental margin s
 uccession of the Sydney Basin\, Australia\, constrained by a suite of high
 -resolution absolute ages from tuffs and relative dating via palynostratig
 raphy. We identify a complex record of floral extinctions and replacements
  from the latest Permian to earliest Triassic reflected by plant macro- an
 d microfossil assemblages. We constrain the major turnover in the terrestr
 ial vegetation in the Sydney Basin to ~410 kyrs before the Permo-Triassic 
 Boundary (PTB). Moreover\, this floral change occurred ~370 kyrs before th
 e marine extinction interval\, concurrent with the onset of the primary ex
 trusion phase of Siberian Trap magmatism. The biotic collapse was decouple
 d from regional environmental parameters. Specifically\, there is insubsta
 ntial change in fundamental fluvial style through the Permian–Triassic t
 ransition\, insignificant reorganization of the depositional surface\, no 
 evidence of abrupt aridification\, and only transient change in chemical i
 ndices of weathering. Fining-upward fluvial cycles of the Permian are typi
 cally capped by thick coal beds\; in contrast\, those of the lowermost Tri
 assic lack coals but are capped by mudrocks retaining abundant organic mat
 ter and monotypic phytoplankton assemblages typical of stratified aqueous 
 conditions. Our data suggest that the high southern paleolatitude biota re
 sponded to a series of environmental thresholds within a long-term trend o
 f intensifying seasonality from the Lopingian to the Olenekian that were d
 riven by far-field processes. Among these\, the influence of Siberian Trap
  volcanism is implicated by the detection of enhanced nickel concentration
 s around the continental EPME.
LOCATION:Tilley Lecture Theatre\, Department of Earth Sciences\, Downing S
 ite
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