Following this, he published a seminal paper with Bob Parker, which employed Euler's Fixed Point Theorem, in conjunction with magnetic anomalies and earthquakes to determine a precise mathematical theory on plate tectonics. This work was published some 3–4 months after the same work had been carried out by Jason Morgan at Princeton. Allegations were subsequently made suggesting that McKenzie was at Morgan's spring AGU talk where he presented his plate tectonics work. Later in 1968 he went to Princeton where he found that he and Morgan had solved two or three problems using identical mathematics in exactly the same way – plate tectonics was one, another was the thermal structure of the oceans and another was looking at earthquake mechanisms in a different way to seismologists.