MARY C. RABBITT GSA HISTORY AND PHILOSOPHY OF GEOLOGY DIVISION AWARD: TED IRVING’S GREAT IDEA OF APPEALING TO BOTH PALEOMAGNETIC AND PALEOCLIMATIC RESULTS TO SUPPORT CONTINENTAL DRIFT

Alfred Wegener correctly realized the importance of measuring continental drift. He thought geodesy would yield such measurements, and encouraged attempts to measure Greenland’s purported eastward drift relative to Europe. However, geodetic techniques in Wegener’s time were inadequate to measure decadal separation of the two landmasses, approximately 2 cm per year, 3 orders of magnitude less than Wegener’s estimate. Paleomagnetism offered another method of measurement, and using paleomagnetism to test drift was a great idea; paleomagnetists could measure drift over millions and millions of years. Although Mercanton (1926) argued that Australian had been in higher latitudes during the Permian based on his paleomagnetic analysis of one sample, paleomagnetic testing of continental drift did not get off the ground until after WW II when two British groups, one housed at Cambridge (Runcorn, Hospers, Irving, and Creer) and the other at Manchester (Blackett, Clegg, Almond, and Stubbs) developed an APW path for Great Britain, and Irving (1954, 1956) found that India had drifted northward relative to Asia. Runcorn and others measured rocks in the Grand Canyon and surrounding area. Runcorn (1955) first argued that the North American results were sufficiently similar to those from Great Britain, favored polar wander, and rejected continental drift. Irving, having obtained a paleopole from Tasmania, which was far from roughly coeval paleopoles from elsewhere, rejected Runcorn’s analysis, and drew two APW paths to explain the North American and European results. Irving (1956) had the great idea of combining paleoclimatic and paleomagnetic results to argue for continental drift. Turning to Köppen and Wegener’s 1924 Die Klimate der Geologishen Vorseit, he further showed inconsistencies between paleomagnetic and paleoclimate findings could not be removed without postulation of continental drift.