High Resolution Calibration and Correlation of the Permian-Triassic Boundary
Interval Across the Panthalassic Ocean
Charles M. Henderson
Department of Geoscience, University of Calgary, Calgary, AB, Canada
Global correlation of the Permian-Triassic Boundary
Interval (PTBI) demands the innovative use of numerous chronocorrelation approaches. The type area for the PTBI at Meishan, South China, was located at the mouth of the Paleotethys Ocean where carbonate with diverse biota was deposited in a tropical setting. Correlation in the region is largely achieved using conodonts and when cross-calibrated with geochronologic ages, the average zone duration in the Changhsingian Stage was about 500,000 years. However, close to the PTB in the latest Changhsingian the zonal duration decreases to about 60,000 years. It has yet to be determined whether this reflects true increase in evolutionary rates or an artifact of exceedingly detailed study and possible taxonomic over-splitting. One test is to determine how well these zones correlate with other regions like northwest Pangea on the opposite side of the Panthalassic Ocean, including the Opal Creek section in the Front Ranges of the southern Canadian Rocky Mountains. The Opal Creek section is punctuated by major unconformities and one Upper Permian sequence is less than 30 cm thick. Furthermore, the Upper Permian portion is difficult to correlate because of profound provincialism. The overlying transgressive silty-shale interval near the PTB, however, can be correlated closely with Meishan by comparing a tripartite series of events and because climate-change presumably broke-down provincialism boundaries. The most negative point on the carbon-isotopic excursion is bracketed by an extinction event bed below and the biostratigraphic
boundary
defined by Hindeodus parvus above, at both locations, but the intervening zonation is not identical. The high-resolution calibration of these events is the key to characterizing the significant differences associated with the end-Permian extinction in these widely separated regions.
AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas