On the west coast of the Auckland province in the North Island, New Zealand, basalts occur which on stratigraphic evidence appear to lie close to the climatically defined Pliocene-Pleistocene boundary. Samples of basalt from two localities have been dated by the potassium-argon method and yield concordant ages of 2.4 to 2.6 million years. Basalts, from one locality, that are younger than the base of the Pleistocene give dates of 2.4