Permalink : http://hdl.handle.net/2115/38434

KEYWORDS : Mass Extinction;End-Permian;Smithian;Carbon isotopes

Improvements in biostratigraphic and radiometric dating, combined with palynological and palaeoecological studies of the same sections, have allowed the relative timing of ecosystem destruction during the end-Permian crisis to be determined in the past few years. The extinction is revealed to be neither synchronous nor instantaneous but instead reveals a protracted crisis. This is especially the case for terrestrial floral communities that show the onset of floral changes prior to the marine mass extinction, but a final extinction after the marine event making a total duration for the terrestrial extinctions of a few hundred thousand years. In the oceans the radiolarians provide the only detailed record of the fate of planktonic communities and these undergo a phase of stress and final extinction before the marine benthos. The initial phase of the aftermath is characterized by a globally-distributed, low diversity biota and, in shallow, equatorial settings, by the precipitation of Precambrian-like anachronistic carbonates. These are well developed during low points in the δ13C record and may be related to super-saturated anoxic waters. Few groups radiate in the Early Triassic and those that did suffered a second mass extinction event late in the Smithian Stage, around 2 million years after the end-Permian event. Only during the ensuing Spathian are there clear signs of uninterrupted recovery.