RESOLVING PANGEA RECONSTRUCTIONS WITH NEW PALEOMAGNETIC RESULTS FROM LATE PERMIAN – EARLY TRIASSIC IGNEOUS ROCKS IN NORWAY AND ARGENTINA

It has been noted repeatedly in the last 35 years that Permian reconstructions of the Atlantic-bordering continents in conventional Pangea fits (e.g., Bullard et al., 1965, Pangea-A type fits) are not well supported by the available paleomagnetic results. While it is widely recognized that the Atlantic Ocean opened from a Pangea-A configuration, rather different Permo-triassic configurations have been proposed that accommodate the paleopoles much better. These so-called Pangea-B and Pangea-C fits have the Gondwana continents in a much more easterly position with respect to Laurussia, such that the northwest coast of South America in Colombia and Venezuela was adjacent to the Appalachian coast of North America or farther east near the Mediterranean margin of Europe. The morphing of Pangea-B into Pangea-A would then have taken place along a 3500 km-long dextral megashear in Permo-triassic times. Besides these tectonic solutions to the problem, questions have been raised about the geocentric axial dipole hypothesis, which is so central for paleomagnetism. And lastly, nagging doubts that the paleomagnetic results may be less reliable, in that they do not perfectly reflect the ancient magnetic field, have not gone away. In an attempt to improve upon the available data, especially for the time interval of 270 – 230 Ma where the discrepancy between Laurussia and Gondwana poles is the greatest, we have studied ignimbrite flows (Puesto Viejo Fm., 265 – 240 Ma) from Argentina and late-stage dikes from the Oslo Graben (250 – 235 Ma) in Norway. A third and useful result has previously been published for the Esterel volcanics in France (270 – 258 Ma). The new results allow a Pangea-A fit to be constructed without significant (and impossible) overlap of the continental areas of Eurasia and Gondwana for the latest Permian – Early Triassic. North America, when positioned according to mid-Permian paleopoles from sedimentary rocks also is snuggled tightly into the Pangea-A type fit; moreover, a new Euler pole (78.6N, 161.9E, 31 degrees) for the fit of North America w.r.t. Europe brings nearly the same outcome. This implies that there is no longer any need to invoke a Pangea-B fit for latest Permian times; moreover, if Pangea-B existed in Late Carboniferous – Early Permian times, it likely had morphed into Pangea A before the end of the mid-Permian.