Permian Extinction: The Origin of Specious Geological Events

first_imgThe Permian extinction – one of the most dramatic events in the history of life on Earth, in which some 90% of species went extinct – lay people assume scientists can back up this story with evidence from geology and fossils, but where is it?  Whatever happened at the prime site in South Africa, from which the story has been extrapolated to all other continents, is now being interpreted as a “nonevent” by four geologists.    Robert Gastaldo and two geology colleagues from Colby College in Maine, and geologist Johann Neveling from Pretoria, studied the Permian-Triassic boundary in the Karoo Basin of South Africa and published a paper in Geology this month,1 titled, “The terrestrial Permian-Triassic boundary event bed is a nonevent.”  This region has been ground zero for stories of the greatest mass extinction in geological history.  Since it now appears that the area does not show an isochronous (same-time) sequence of strata followed by a recovery of vertebrate biodiversity, the linchpin of the story appears undermined.  The authors are calling for “critical reevaluation” of “South African models for the response of terrestrial ecosystems to the perturbation in the marine realm.”  But that’s not all they think needs reevaluation.  Their ending discussion bears attention:In the Bethulie area and elsewhere, the event bed is used as the criterion for the terrestrial expression of the Permian-Triassic boundary event recorded in the marine realm (Ward et al., 2005).  Its unique character and presumed synchroneity within the Bethulie area (Fig. 3A), across the basin (Ward et al., 2000; Smith and Ward, 2001), and in the Southern Hemisphere (Retallack et al., 2003) have resulted in various models of extinction (Ward et al., 2005) and recovery (Smith and Botha, 2005; Botha and Smith, 2006) of the vertebrate fauna in response to climatic aridification.  The sedimentological features of the aerially restricted and stratigraphically confined heterolithic units do not support an interpretation of extensive playa lake formation (Smith and Ward, 2001, and others) or an isochronous marker bed that delimits the terrestrial expression of the paleontologically defined boundary.  Rather, the field relationships and suite of sedimentological features support deposition within floodplain avulsion channel systems (Slingerland and Smith, 2004), each of which has undergone weak pedogenesis.  Our study demonstrates that the laminated (laminite) beds are nonsynchronous (Fig. 3B), not isochronous, as contended by Ward et al.  (2005).  Approximately 10 m of stratigraphic section separate the exposures of the heterolithic beds on the Bethel and Heldenmoed farms, over a distance of [less than] 1 km.  In addition, neither laminated interval can be traced laterally for more than a few hundred meters, let alone traced regionally (kilometers) or across the basin.  Hence, extrapolation of the laminated interval to other continents as the terrestrial expression of the Permian-Triassic boundary event is imprudent.    The claims of rapid vertebrate recovery within [less than] 100 k.y. following the extinction event (Smith and Botha, 2005; Botha and Smith, 2006) also must be called into question (Fig. 3).  The interval used to speculate on the recovery is on the eastern side of the valley (Fig. 2F; Botha and Smith, 2006, their Fig. 1) beneath the Permian-Triassic boundary as recognized on the western side of the valley.  Hence, the diversification patterns reported by Smith and Botha (2005) and Botha and Smith (2006) are between the two stratigraphically distinct laminated intervals and may reflect Late Permian originations, rather than Early Triassic recovery.This appears to completely mix up the story of a Permian extinction event followed by rapid evolution.  Gastaldo has reproduced a PDF file of this paper at his Colby College web page.1.  Gastaldo, Neveling, Clark and Newbury, “The terrestrial Permian-Triassic boundary event bed is a nonevent,” Geology, March 2009 (37:3), pp. 199-202, doi:10.1130/G25255A.1. Well, isn’t this an upset.  How much lag time will it take to change the textbooks and documentaries?  The BBC, Nova and other evolution-drunk interpreters of science have treated the Permian extinction as solid fact.  The goods were right there, in the Karoo Basin, for anyone to see.  Whoops….    This announcement goes to show that rocks and layers do not interpret themselves.  They are placed in a prior philosophical framework first, then the stories and animations follow.  Notice how an interpretation at one site was extrapolated to the whole world.  How can such sweeping generalities be justified?  These geologists, bless their hearts, understate the lesson here: “extrapolation of the laminated interval to other continents as the terrestrial expression of the Permian-Triassic boundary event is imprudent,” they said.  How about “reckless”? (07/02/2007).    We’re still suffering from the consequences of the bad assumptions by early geologists (especially the Charlie & Charlie partners in crime, Lyell and Darwin, 07/25/2008).  Science is supposed to be progressing toward better and better knowledge of nature, but when it comes to geologists and their tales of earth history, it’s hard to follow the lead of a staggering Dar-wino with a hangover (01/02/2007, 05/15/2008).(Visited 13 times, 1 visits today)FacebookTwitterPinterestSave分享0last_img